HCO+ and ionization structure observed by ALMA
Y. Aikawa,1 Gianni Cataldi,2 Y. Yamato,1 Kenji Furuya,2 and MAPS team1
Departmen of Astronomy, University of Tokyo, Japan
2
National Astronomical Observatory, Japan
We observed HCO+(J=1−0) and H13CO+ (J=1−0) emission towards the five protoplanetarydisks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480 as part of the MAPS
project[1][2]. HCO+ is detected and mapped at 0.3” resolution in all five disks, while H13CO+
is detected (SNR >6σ ) towards GM Aur and HD 163296 and tentatively detected (SNR >3σ )towards the other disks by a matched filter analysis. Inside a radius of R∼100 au, the HCO+
column density is flat or shows a central dip. At outer radii ( ≳100 au), the HCO+ column
density decreases outwards, while the column density ratio of HCO+/CO is mostly in therange of ∼10−5−10−4 . We derived the HCO+ abundance in the warm CO-rich layer, where
HCO+ is expected to be the dominant molecular ion. At R≳100 au, the HCO+ abundance is ∼3×10−11−3×10−10 , which is consistent with a template disk model with X-ray ionization. At
the smaller radii, the abundance decreases inwards, which indicates that the ionization degree
is lower in denser gas, especially inside the CO snow line, where the CO-rich layer is in the
midplane. Comparison of template disk models with the column densities of HCO+, N2H+,
and N2D+ indicates that the midplane ionization rate is ≳10−18 s−1 for the disks around IM Lup,
AS 209, and HD 163296. We also find hints of an increased HCO+ abundance around thelocation of dust continuum gaps in AS 209, HD 163296, and MWC 480.
We also plan to show the summary of molecular column densities obtained in MAPS projectand some model results for discussions in the poster session.

Figure: (a)Radial distributions of column densities of CO, HCO+, N2H+, and N2D+ in IM
Lup derived from MAPS project. (b) Distributions of CO and HCO+ in a tempate disk model.
References[1]
Aikawa, Y., Cataldi, G., Yamato, Y. and MAPS team (2021) “Molecules with ALMA at Planet-forming
Scales (MAPS) XIII: HCO+ and disk ionization structure”, ApJS, in press[2]
Oberg, K.I., Guzman, V.V., Walsh, C., Aikawa, Y., Bergin, E.A. and MAPS team (2021) “Moleculeswith ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights”, ApJS in pressTesting Dust-Surface Formation Model of Prebiotic Molecule CH3NCO
in Star-Forming Cores Sagittarius B2 (M) and (N)M. Araki,1 Y. Ohno,1,2 K. Izuoka,1T. Oyama,2 S. Takano, 3 N. Kuze, 4 Y. Sumiyoshi,5 K. Tsukiyama1
1

Faculty of Science Division I, Tokyo University of Science, Japan
2
RIKEN, Japan
3
College of Engineering, Nihon University, Japan
4
Department of Materials and Life Sciences, Sophia University, Japan
5
Faculty of Science and Technology, Gunma University, Japan
Origin of organic molecules on Earth is discussed to be interstellar clouds, because comets
carried molecules produced in clouds. Methyl isocyanate CH3NCO is presumably one of thedelivered organic molecules at the primitive earth. This molecule was firstly detected in the the(N) core of the Galactic Center star-forming region Sagittarius (Sgr) B2 [1]. Recently, thetheoretical studies have suggested that this molecule is formed on dust surface in molecular
cloud [2]. If that is the case, CH3NCO abundantly desorbs from dust surface as hot gas in acentral region of a star-forming core and slightly exists in an outer region as cold gas.
To examine an outer region of a star-forming core, we observed the (M) core in Sgr B2 withthe 45-m telescope of Nobeyama Radio Observatory. Rotational transitions of CH3NCO werefirstly detected in this region. The abundance ratio and the rotational temperature are derived
to be [CH3NCO]/[HNCO] = 0.03 ± 0.01 and Trot = 28 ± 6 K, respectively.
To examine temperature and distribution of CH3NCO, the archival data toward the (N1) coreof Sgr B2 observed by ALMA were investigated in the 94–113 GHz region. Considering
intensity maps and velocity structures, a compact distribution having a clumpy toroidal
structure was firstly imaged by CH3NCO showing high temperature of ~60 K, as shown in Fig.
1. These results suggest a hot and abundant condition of this molecule in the central region of
the core. Hence, CH3NCO and/or its precursors are likely to be produced on dust surface.

Figure 1: The integrated intensity map of the JKa,Kc =111,10–101,9 line of CH3NCO (a) and its position velocity
map (b). The illustration in (a) shows an expected toroidal structure. The map (b) is sampled in the red squareof (a).

References[1]

Halfen et al., 2015, ApJL, 812, L5.

[2]e.g., Majumdar et al., 2018, MNRAS, 473, L59.

Complex organic molecules detected in twelve high mass star forming regions with
ALMA
Giseon Baek,1 Jeong-Eun Lee,1 Tomoya Hirota2,3, Kee-Tae Kim4
and KaVA Star-Formation Science Working Group1
School of Space Research, Kyung Hee University, Korea
2
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), Japan3
Department of Astronomical Sciences, SOKENDAI (The Graduate University for Advanced
Studies), Japan
4
Korea Astronomy and Space Science Institute (KASI), Korea
Recent astrochemical models and experiments have explained that complex organic
molecules (COMs; molecules composed of six or more atoms) are produced on the dust grain
mantles in cold and dense gas in prestellar cores [1]. However, the chemical networks and theroles of physical conditions on chemistry are not still understood well. To address thisquestion, hot cores in high mass young stellar objects are great laboratories due to their strong
emissions and larger samples than those of low-mass counterparts. In addition, CH3OH
masers, which have been mostly found in high mass star forming regions, can provide
constraints due to their very specific emerging conditions. We investigate the chemical
diversity in richness and complexity of twelve high mass star forming regions using the
ALMA band 6 observations. They are associated with 44/95 GHz class I and 6.7 GHz class II
CH3OH masers, implying that the active accretion processes are ongoing [2][3]. For thesepreviously unresolved regions, 63 continuum peaks are detected. Among them, we found 28
cores emitting COMs and specified 10 cores associated with 6.7 GHz Class II CH3OH masers.
We identified up to 19 COMs including oxygen- and nitrogen-bearing molecules and theirisotopologues in a core and derived their abundances. We found that (1) oxygen-bearing
molecules appear to be richer in abundance and more complex in molecular structures thanthose of nitrogen-bearing species, (2) COMs detection rate steeply grows with the gas column
density, above the threshold of ~1024cm-2, which can be attributed to the effective COMs
formation in dense cores, and (3) cores associated with class II CH3OH maser tend to emit
larger number of COMs. Therefore, from our analysis, we conclude that the chemical
diversity among hot cores could be originated by the degree of the accretion of each source aswell as different physical conditions of cores.
References

[1]
[2]
[3]

K. Öberg & E. A. Bergin, 2021, PhR, 893, 1
J.-H. Kang, D.-Y. Byun, K.-T. Kim et al. 2016, ApJS, 227, 17
B. Hu, K. M. Menten, Y. Wu et al. 2016, ApJ, 833, 18

Can grain-surface chemistry explain the surprisingly low C/CO ratio in the HD 32297
debris disk?
G. Cataldi,1,2 Y. Wu,3 A. Brandeker4 , N. Ohashi5, A. Moór6 et al.
1

2

National Astronomical Observatory of Japan, Japan
Department of Astronomy, Graduate School of Science, The University of Tokyo, Japan3
Department of Astronomy & Astrophysics, University of Toronto, Canada
4
Department of Astronomy, Stockholm University, Sweden
5
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan, R.O.C.
6
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungary

Debris disks are analogues of the solar system’s asteroid and Kuiper belt. They consist of
kilometer-sized rocky or icy bodies (“exocomets”) that continuously collide and produce dust.
However, in recent years observations of CO emission have shown that some of these objects
also contain substantial amounts of gas [e.g. 1]. Like the dust, this gas is probably producedby collisions of cometary bodies. It is important to understand the nature of this gas for anumber of reasons. For example, the gas allows us to study the composition of the exocomets[e.g. 2]. Furthermore, the gas might be accreted by planets, thereby changing theiratmospheric composition [3].
The A-type main sequence star HD 32297 (age of 15-30 Myr) hosts a debris disk with a highCO mass. Since CO is quickly photo-dissociated by the interstellar radiation field, it has beensuggested that CO is shielded by neutral carbon atoms that are produced by thephoto-dissociation [4]. This would allow a large CO mass to accumulate from the collisional
destruction of icy exocomets. In order to test this scenario, we observed neutral C emission
with ALMA towards HD 32297 [5].
In order to interpret our observations, we set up a simple model where CO is produced fromcometary bodies and destroyed by the interstellar field, taking into account CO self-shielding
and shielding by neutral C. We find that the observed C/CO ratio can only be explained if 1)
the CO production rate is uncomfortably high and 2) C is removed from the system on a shorttime scale by an unknown process. We hypothesize that grain surface chemistry might solve
this puzzle: C and O atoms might accrete onto dust grains and re-form CO, which is thanre-released to the gas phase. This would provide an additional CO source and a C sink,therefore explaining the surprisingly low C/CO ratio. However, a more detailed examination
with the help of grain surface chemistry experts is needed in order to assess whether this is arealistic scenario.
References
[1]
[2]
[3]
[4]
[5]

Moór, A., Curé, M., Kóspál, Á., et al. 2017, ApJ, 849, 123
Matrà, L., Wilner, D. J., Öberg, K. I., et al. 2018, ApJ, 853, 147
Kral, Q., Davoult, J., & Charnay, B., 2020, Nature Astronomy, 4, 769
Kral, Q., Marino, S., Wyatt, M. C., Kama, M., & Matrà, L. 2019, MNRAS, 489, 3670
Cataldi, G., Wu, Y., Brandeker, A., et al. 2020, ApJ, 892, 99

The GUAPOS project: A comprehensive study of peptide-like bond molecules
L. Colzi,1,2 V. M. Rivilla,1,2 M. T. Beltrán2, I. Jiménez-Serra1, and C. Mininni3
1

Centro de Astrobiología, Consejo Superior de Investigaciones Cientifícas (CSIC), Spain
2
Osservatorio Astrofisico di Arcetri, Istituto Nazionale di Astrofisica (INAF), Italy
3
Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica (INAF), Italy
Complex organic molecules (COMs), i.e. molecules containing carbon with 6 or more atoms,
have been detected ubiquitously in the interstellar medium (ISM) towards low- and high-massstar-forming regions (e.g. [1]). Among prebiotic COMs, those containing peptide-like bonds(NCO backbone) are of great interest because they can participate in the link of amino acids
forming proteins (e.g. [2]).
Here I present a study of HNCO, HC(O)NH2, CH3NCO, CH3C(O)NH2, CH3NHCHO (Fig. 1)
towards the chemically rich hot core G31.41+0.31, where these molecules have been
observed together for the first time in the disk of our Galaxy, outside the Galactic Centre([3]). This work is part of the GUAPOS (G31 Unbiased ALMA sPectral Observational
Survey) project, which is a sensitive spectral survey conducted with the ALMA (Atacama
Large Millimeter/submillimetre Array) observatory towards the star-forming region
G31.41+0.31, covering the whole Band 3, that is from 84 to 116 GHz, and with an angularresolution of 1.2’’ (~750 au, see [4]).
From the comparison with other sources, we find that molecular abundance ratios towards
different sources are found to be consistent between them within one order of magnitude,
regardless of the physical properties (e.g. different masses and luminosities), or the source
position throughout the Galaxy. Correlations have also been found between the abundances ofthese molecules. These results suggest that all these species are formed on grain surfaces inearly evolutionary stages of molecular clouds, and that they are subsequently released back to
the gas-phase through thermal desorption or shock-triggered desorption.

Formamide
Acetamide
Isocyanic acid

Methyl isocyanate

N-methylformamide

Figure 1: G31.41+0.31 at 8 μm (IRAC4, Spitzer space telescope, left panel) and ALMA 0.2’’ resolution
integrated emission maps at 1.4 mm of HC(O)NH2 (right panel, see [3]). The blue stars indicate theposition of protostars that are forming within this region. In the bottom the chemical structure of thepeptide-like bond molecules studied are shown.

References
[1]
[2]
[3]
[4]

B. McGuire, 2021, eprint arXiv:2109.13848
R. Pascal, L. Boiteau, & A. Commeyras, A. 2005, ed. P. Walde (Springer Berlin Heidelberg), 69–122
L. Colzi, V. M. Rivilla, M. T. Beltrán et al. 2021, A&A, 653, A129
C. Mininni, M. T. Beltrán, V. M. Rivilla, 2020, A&A, 644, A84

Non-thermal desorption of ice mantles:
cosmic rays desorption of complex organic molecules
E. Dartois1, M. Chabot2, V. Wakelam3, H. Rothard4, P. Boduch4, A. Domaracka4, B. Augé5, J.
Rojas2
1
Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Saclay, 91405 Orsay(France)
2
IJCLab, CNRS/IN2P3, Université Paris-Saclay, 91405 Orsay (France)
3
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, 33615 Pessac, (France)
4
CIMAP-CIRIL-GANIL, Normandie Université, ENSICAEN, UNICAEN, CEA, CNRS, 14000
Caen (France)
5
IPAG,CNRS, Université Grenoble Alpes, 38000 Grenoble (France)
Determining experimentally the magnitude of interstellar grain mantles accretion anddesorption mechanisms is mandatory for astrophysical models to constrain and predict gas
and solid phase chemical evolutions. Irradiation by cosmic rays have been simulated
experimentally using high energy ions. The ice mantles phase transformation and sputtering
yields for released species were monitored simultaneously by infrared spectroscopy and mass
spectrometry. The dominant ice mantle species, can be effciently sputtered by cosmic rays. In
this talk, the sputtering yield and its evolution as a function of ice mantle thickness for highenergy ions will be discussed in the context of astrophysical environments. Cosmic rays
penetrating deep into dense clouds provide a major sputtering mechanism to desorb theobserved complex organic molecules (COMs) built over the lifetime of dense clouds, whenmany other mechanisms fail at releasing them effciently from cold grains. We focused ourstudy on the sputtering effciency of two complex organic molecules that are observed either ininterstellar dense clouds ice mantles directly by infrared spectroscopy (CH3OH), or observedin the gas phase by millimetre telescopes (CH3COOCH3). The sputtering was measured for
different ice matrices dominated by water ice or carbon dioxide ices.
A large fraction of COMs desorbs as intact molecules with a proportion corresponding to thetime dependent bulk composition of the ice mantles, the latter evolving with time due to thesecondary photons VUV photolysis and CR ice mantle radiolysis. The astrophysical cases inrelation with these experiments will be discussed.
References[1] Dartois, E., Chabot, M., Bacmann, A. et al., accepted in Astronomy and Astrophysics. (2020).
[2] Dartois, E., Chabot, M., Id Barkach, T., et al., Astronomy & Astrophysics, 627, A55 (2019).
[3] Dartois, E., Chabot, M., Id Barkach, T., et al., Astronomy & Astrophysics, 618, A173 (2018).
[4] Dartois, E., Augé, B., Rothard, H. et al. NIMB, 365, 472 (2015).
[5] Mejia, C., de Barros, A. L. F., Seperuelo Duarte, E. et al., Icarus , 250, 222 (2015).
[6] Dartois, E., Augé, B., Boduch, P. et al., Astronomy and Astrophysics, 576, A125 (2015).
[7] Dartois, E., Ding, J. J., de Barros, A. L. F. et al., Astronomy and Astrophysics, 557, A97 (2013).

Nitrogen inclusion in organic dust in novae revealed by laboratory synthesis ofQuenched Nitrogen-included Carbonaceous Composite (QNCC)
I. Endo,1 I. Sakon,1 T. Onaka,2,1 Y. Kimura,3 S. Kimura,4 S. Wada,4 L. A. Helton,5 R. M. Lau,6
Y. Kebukawa,7 Y. Muramatsu,8 N. O. Ogawa,9 N. Ohkouchi,9 M. Nakamura,10 and
S. Kwok11
1

Department of Astronomy, University of Tokyo, Japan, 2Department of Physics, Meisei
University, Japan, 3Institute of Low Temperature Science, Hokkaido University, Japan, 4The
University of Electro-Communications, Japan, 5SOFIA Science Center/NASA Ames ResearchCenter, USA, 6Institute of Space and Astronautical Science, Japan Aerospace Exploration
Agency, Japan, 7Faculty of Engineering, Yokohama National University, Japan, 8Graduate
School of Engineering, University of Hyogo, Japan, 9 Biogeochemistry Program, Japan
Agency for Marine-Earth Science and Technology, Japan, 10Physics Laboratory and Instituteof Quantum Science, Nihon University, Japan, 11Department of Earth, Ocean & Atmospheric
Science, The University of British Columbia, Canada
The unidentified infrared (UIR) bands have been widely observed in various astrophysicalenvironments. They consist of a series of emission features arising from aromatic and/or
aliphatic C-C and C-H bonds in the near- to mid-infrared wavelength range[1] and therefore,
their carriers are thought to be related to organics. Although the carriers must be a major
constituent of the Galaxy, our knowledge of their properties is still limited. Dusty classicalnovae are valuable to investigate the formation process of dust because of their highoccurrence. Past studies have shown that the UIR bands in novae are characterized by thepresence of a broad 8µm feature [2,3].
We have succeeded to synthesize Quenched Nitrogen-included Carbonaceous Composite,laboratory organics whose infrared properties cane reproduce the UIR bands in novae. QNCC
is synthesized by quenching plasma produced from nitrogen gas and hydrocarbon solids. Thissynthesis method qualitatively mimic a possible formation process of organics in thecircumstellar environment of novae, where nitrogen-rich novae wind react with pre-existing
carbonaceous dust. Based on the infrared and X-ray analyses of QNCC, we found that QNCC
show the presence of amine structure, which can contribute to the broad 8µm feature
characterizing the UIR bands in novae. QNCC is at present the best laboratory analog oforganic dust formed in circumstellar environments of dusty classical novae[4].
References
[1]
[2]
[3]
[4]

L. J. Allamandola et al. 1989, ApJS, 71, 773
A. L. Helton et al. 2011, in EAS Publications Series, Vol. 46
I. Sakon et al. 2016, ApJ, 817, 145
I. Endo et al. 2021, ApJ, 917, 103

A systematic computational study of radical—radical reactions on interstellar ice
surfaces
J. Enrique-Romero,1,2 A. Rimola,2 and C. Ceccarelli1
1Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble(IPAG), 38000 Grenoble, France
2Departament de Química, Universitat Autònoma de Barcelona, Bellaterra, 08193,
Catalonia, Spain
Understanding how insterstellar complex organic molecules (iCOMs) are formed anddestroyed is of high importance to predict the ultimate organic complexity reached in theinterstellar medium (ISM) ([1], [2]). Two paradigms are invoked in the literature. Both argue
that simple molecules and atoms are hydrogenated on the interstellar grain surfaces during thecold prestellar phase. Following this first step, one paradigm assumes that iCOMs appear as aresult of gas-phase chemical processes, whereas the other predicts that radical-radical
reactivity on the grain surfaces is the major responsible for the observed chemical complexity.
The latter has profited of much popularity among astrochemical models in the last years, eventhough some basic assumptions of the paradigm are still a topic of debate. Among them, theradical-radical reactivity assumption, which is extremely difficult to quantify experimentally.
We propose a complementary and, sometimes, alternative method: theoretical quantum
chemical calculations, which can provide a precious atomistic perspective from which to
study such processes (e.g. [3], [4], [5]).
In this contribution, we present our recent systematic quantum chemical study on the surface
reactivity of several radical pairs. Some of the studied systems are CH3 + X and HCO + X (X
= CH3, HCO, NH2, CH2OH and CH3O). According to observational evidences, the icy
mantles that cover interstellar dust grains are dominated by water ([6]). We, therefore, use twocluster-like ice models consisting on 18 and 33 water molecules to simulate the grain surface
where the radical-radical reaction occurs. We then study the reactivity of the above biradical
systems by means of static quantum chemical calculations to obtain the potential energy
surfaces of several complex species and the approximate efficiency of the different reaction
product channels. We found that many reactions leading to iCOMs have non negligible
activation barriers and that the transfer of a hydrogen atom from a radical acting as a donnor
to its partner, acting as an acceptor are important competitive processes. The occurrence of
one process or the other could entirely depend on the relative orientation of the radicals upon
encounter, namely on the water ice structure and interaction with the two radicals. These
results indicate that the fraction of iCOMs generated in the current astrochemical models iscertainly overestimated since (i) it is assumed that reactions always occur and (ii) thecompetitive reactions are not included.
References
[1]
[2]
[3]
[4]
[5]
[6]

E. Herbst. & E. F. Van Dishoeck, 2009, ARA&A 47, p. 427-480
C. Ceccarelli, S. Viti, N. Balucani, et al., 2018, MNRAS 476(1), p. 1371-1383.
A. Rimola, D. Skouteris, N. Balucani, et al., 2018, ACS Earth and Space Chemistry 2(7), 720-734.
J. Enrique-Romero, A. Rimola, C. Ceccarelli, et al., 2019, ACS Earth Space Chem. 3(10), p. 2158-2170
J. Enrique-Romero, C. Ceccarelli, A. Rimola, et al., 2021, A&A (in press).
A. A. Boogert, P. A. Gerakines, & D. C. Whittet, 2015, ARA&A 53, p. 541-581.

The energy dissipation process of hydrogenation reactions of atomic nitrogen on water
ice surfaces
S. Ferrero,1 S. Pantaleone,2 P. Ugliengo2, M. Sodupe1 and A. Rimola1
1

Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia,
Spain
2
Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria 7, 10125, Torino,
Italy

In the colder (10-20K) regions of interstellar medium, the icy surfaces of interstellar grains
serve as solid state supports for chemical reactions[1][2]. Among the plausible roles of thesesurfaces, that of third body is advocated, in which the formation energy of surface reactions
can be dissipated among the grain causing the stabilization of the product[3]. This energy
dissipation process is poorly understood at the atomic scale and it can have a tremendous
impact on astrochemical surface processes like chemical desorption and diffusion[4][5].
In this work, we studied the formation of NH3 via successive H-addition to atomic nitrogen on
crystalline and amorphous ice surfaces. We first characterized the potential energy surfaces of
the hydrogenation reactions and possible competitive processes (i.e., H abstractions) using
static quantum chemical calculations. Subsequently, the partitioning of the nascent energy
released by the hydrogenation reactions between the newly formed species and the surface has
been elucidated by means of ab initio molecular dynamics (AIMD) simulations.
Results indicate that the H-additions on N are largely favorable reactions at 10 K, being
barrierless and exhibiting large negative reaction energies, as opposed to the competitive Habstractions, which are either endothermic or present high activation energies. AIMD
simulations show that such favorable nascent energies are, in large part, quickly absorbed by
the ice surfaces and their dissipation can be accelerated by mechanisms involving an H
exchange between the surface and the newly formed species (Figure 1).

Figure 1: H3O(+) NH2(-) complex formation on an amorphous ice surface.

References
[1]
[2]
[3]
[4]
[5]

A. Potapov.& M. McCoustra, 2021, Int Rev Phys Chem, 40(2), 299-364 .
G. Vidali 2013 Chem Rev 113(12), 8762–8782 .
T. Hama & N. Watanabe 2013 Chem Rev 113(12), 8783-8839 .
S. Pantaleone et al. 2020 ApJ 897, 56 .
S. Pantaleone et al. 2021 ApJ 917, 49 .

Photon Stimulated Desorption from interstellar ice analogs: recent results usingsynchrotron radiation.
J.-H. Fillion,1 R. Dupuy,1R. Basalgète,1 G. Féraud,1 C. Romanzin,2 L. Philippe,1 T. Putaud,1 V.
Baglin,3 R. Cimino,4 X. Michaut,1 and M. Bertin1
1

Sorbonne Université, Observatoire de Paris, Université PSL, CNRS-LERMA, Paris, France
2
Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, Orsay, France
3
CERN, Genève, Switzerland
4
Laboratori Nazionali di Frascati (LNF)-INFN, Frascati, Italy

Photon Stimulated Desorption (PSD) processes play a key role in the exchanges between thegas and solid phases of cold regions of the interstellar medium, where a lot of molecules are
expected to freeze out on dust grains with the temperature forbidding their thermal escape.
These processes have been used to explained otherwise puzzling gas phase observations ofsimple molecules like CO in dense cores or cold H2O in outer parts of protoplanetary disks.
They are also invoked as ways to get complex organic molecules (COMs) presumably formedon grains into the gas phase. Second, photon-induced desorption of residual molecules
adsorbed on the cryogenic parts of accelerators such as the LHC can be a limiting factor for
their vacuum performances. Desorption rates and mechanisms, especially in the submonolayer regime, can therefore be of particular interest in this case.
I will present an approach to study PSD of condensed films of molecules of astrophysicalinterest at cryogenic temperatures, using synchrotron radiation. Recent results obtained in the
VUV and soft X-ray ranges will be presented. In the VUV, we will focus on the PSD from
Amorphous Solid Water (ASW) and discuss experimental results evidencing two major
desorption mechanisms [1], [2]. Quantitative desorption yields from acetonitrile CH3CN inpure and mixed samples will be also presented [3]. In the soft X-ray range, results obtained at
the K-edge of Oxygen atoms will be discussed in the context of protoplanetary disks, first in
the case of pure H2O [4], CO [5], CH3OH [6] samples and secondly in the case H2O-rich andCO-rich samples containing CH3OH [7].
References[1]
J.-H Fillion, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, T. Putaud, V. Baglin, R. Cimino, P. MarieJeanne, P Jeseck, X. Michaut & M. Bertin. ACS : Earth and Space Chemistry, 2021 under review[2]
R. Dupuy; M. Bertin, G. Féraud, X. Michaut, P. Marie-Jeanne, P. Jeseck, L. Philippe, V. Baglin, R.
Cimino, C. Romanzin, J.-H. Fillion, PRL 2021, 126, 156001.
[3]
R. Basalgete , A. Jesus Ocana , G. Féraud , C. Romanzin, L. Philippe ,X. Michaut , J.-H. Fillion & M.
Bertin APJ, 2021, ApJ accepted for publication.
[4]
R. Dupuy, M. Bertin, G. Féraud, M. Hassenfratz, X. Michaut, T. Putaud, L. Philippe, P. Jeseck, M.
Angelucci, R. Cimino, V. Baglin, C. Romanzin & J.-H. Fillion, Nature Astronomy 2018, 2, 796.
[5]
R. Dupuy, M. Bertin, G. Féraud, C. Romanzin, T. Putaud, L. Philippe, X. Michaut, P. Jeseck, R. Cimino,
V. Baglin & J.-H. Fillion, 2021 PCCP, 23, 15965[6]
R. Basalgète, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, X. Michaut, J. Michoud, L. Amiaud,
A. Lafosse, J.-H. Fillion & M. Bertin, 2021 A&A 647, A35[7]
R. Basalgète, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, X. Michaut, J. Michoud, L. Amiaud,
A. Lafosse, J.-H. Fillion & M. Bertin, 2021 A&A 647, A36

Development of Cavity Enhanced Absorption Spectrometer
Aiming to Measure Optical Absorption Bands of Interstellar Molecules
I. Fukuda,1 T. Sato,1 M. Araki,1 T. Oyama,2 S. Hoshino,1 K. Tsukiyama1
1

Faculty of Science Division I, Tokyo University of Science, Japan
2
RIKEN, Japan

Diffuse Interstellar Bands (DIBs) are mysterious unidentified absorption bands detected
optically in diffuse clouds. DIBs are presumed to be electronic transitions of large organic
molecules. Identification of their origins allows us to unveil a wide variety of chemicalcomposition of space, because approximately 600 DIBs have been found so far [1]. However,at present only the five bands were assigned to the fullerene cation C60+ [2] and the other bands
are not identified yet.
To reveal DIB carriers, comparative studies of astronomically observed bands with laboratory
spectra are required. However, a covering range of a high-resolution laboratory spectrometer isgenerally narrow, although DIBs disperse over a wide range. A wide-band spectrometer can bea powerful tool to identify these bands.
Cavity enhanced absorption spectroscopy is possible to widely measure a high-resolution
spectrum [3]. This method enables us to achieve a very long optical path length, because whitelight introduced in between two high reflectivity mirrors reciprocates more than ten thousand
times. Based on these advantages, this spectrometer is suitable to measure DIB-candidate
molecules produced in laboratory. In this study, we developed this spectrometer thatsimultaneously covers the 60-nm range by using the 1200 lines/mm grating. As a demonstrationof sensitivity, the fifth CH stretching overtones (v' = 6) of methyl acetate (a) and ethyl acetate(b) were detected for the first time, as shown in Fig. 1. Additionally, we also detected methanol
produced via saponification of methyl acetate by sodium hydroxide (c3). As a next step, weplan to install a hollow-cathode discharge system to produce DIB-candidate ion and radical oflarge organic molecule.

Figure 1: Cavity-enhanced absorption spectrometer (left) and the observed spectra. (a) v' = 6 of methyl
acetate. (b) v' = 6 of ethyl acetate. (c1) v' = 4 of pure methanol. (c2) v' = 5 of pure methyl acetate. (c3) mixtureof methyl acetate with methanol produced by saponification of methyl acetate. The sample pressure wasadjusted in the range of 0.020 – 156 Torr depending on the peak intensities.

References[1][3]e.g., Fan et al. 2019, ApJ, 878, 151.
[2]
Oyama & Araki, 2020, J. Spectrosc. Soc. Jpn., 69, 144.

Campbell et al. 2015, Nature, 523, 322

Microwave Spectroscopy of Isothiazole
Hoga Furukawa,1 Kaori Kobayashi,1Maria A. Zdanovskaia, Brian J, Esselman,2 R. Claude Woods,2 Robert J. McMahon22

1

2

Department of Physics, University of Toyama, Japan
Department of Chemistry, University of Wisconsin–Madison, USA

Five-membered ring structure are found in some amino acids. In addition, five-memberedring cyanocyclopentadiene has been identified toward TMC-1 [1]. Therefore isothiazole(C3H3NS) is a potential interstellar molecule of five-membered ring with two adjacent hetero
atoms, nitrogen and sulfur. Previous studies of microwave spectroscopy have been conducted
below 35 GHz including information on the dipole moment, isotopologues, and the Zeemanneffect [2-4]. The a-axis and b-axis components of the dipole moment are doubled by 1.1 D
and 2.2 D, respectively. Information on higher frequency range is essential for future
detection.
In this study, microwave spectroscopy of isothiazole was performed in the 40-360 GHz
region at room temperature at the University of Toyama and University of Wisconsin–
Madison. The assignment was based on the frequency prediction using molecular constantsfrom previous high-resolution infrared studies [5,6]. The spectra were analyzed by using
AABS package.[7] Figure 1 shows an example. Over 2000 lines were assigned and analyzed
using Watson’s A-reduced Hamiltonian.

Figure 1: The spectrum and the frequency prediction of isothiazole.

References[1] M.C. McCarthy, K.L.K. Lee, R.A. Loomis, A.M. Burkhardt, C.N. Shingledecker, S.B. Charnley, M.A.
Cordiner, E. Herbst, S. Kalenskii, E.R. Willis, C. Xue, A.J. Remijan, B.A. McGuire, Nat. Astron. 5 (2021) 176–
180.
[2] J.H. GRIFFITHS, A. WARDLEY, V.E. WILLIAMS, N.L. OWEN, J. SHERIDAN, Nature. 216 (1967)
1301–1301.
[3] J. Wiese, D.H. Sutter, Zeitschrift Für Naturforsch. A. 35 (1980) 712–722.
[4] J. Gripp, U. Kretschmer, H. Dreizler, The 33S Nuclear Hyperfine Structure in the Rotational Spectrum ofIsothiazole, Zeitschrift Für Naturforsch. A. 49 (1994) 1059–1062.
[5] F. Hegelund, R. Wugt Larsen, R.A. Aitken, H. Kraus, F.M. Nicolaisen, M.H. Palmer, Mol. Phys. 102 (2004)
1583–1595.
[6] F. Hegelund, R.W. Larsen, R.A. Aitken, M.H. Palmer, J. Mol. Struct. 780–781 (2006) 45–56.
[7] Z.Kisiel, L.Pszczolkowski, I.R.Medvedev, M.Winnewisser, F.C.De Lucia, E.Herbst, J.Mol.Spectrosc. 233,
(2005) 231-243.

Quantifying the chemical desorption of H2S and PH3from water ice surface
K. Furuya,1 Y. Oba,2 and T. Shimonishi31

National Astronomical Observatory of Japan
Institute of Low Temperature Science, Hokkaido University
3
Center for Transdisciplinary Research, Niigata University2

Non-thermal desorption of molecules from icy grain surfaces is required to explain molecularline observations in the cold gas of star-forming regions [1]. Chemical desorption is one of the
non-thermal desorption processes, and is caused by the energy released by chemical reactions;after an exothermic surface reaction, the part of excess energy goes into products' translationalenergy in perpendicular direction to the surface, leading to desorption. The desorption
probability of product species, especially from water ice surfaces, is not well determined. This
limits our understanding of the interplay between gas-phase and ice surface chemistry.
In this work, we constrained the desorption probability of H2S and PH3 per reaction event on
porous amorphous solid water (ASW) by numerically simulating previous laboratory
experiments of chemical desorption [2,3]. Adopting the microscopic kinetic Monte-Carlo
method, we found that the desorption probability of H2S and PH3 from porous ASW perhydrogen addition event of the precursor species are 3±1.5 % and 4±2 %, respectively.
These probabilities are consistent with a theoretical model of chemical desorption in theliterature, if around 7 % of energy released by the reactions goes into the translational
excitation of the products. As a bi-product, we also found that around 70 % (40 %) ofadsorption sites for atomic H on porous ASW should have the binding energy lower than~300 K (~200 K).

Figure 1: Total abundance of H2S and HS on porous ASW normalized by the initial H2S abundance asfunctions of the H atom exposure time in our best-fit model. Square symbols indicate the experiments by[2] and [3].

References
[1]
[2]
[3]

R. T. Garrod, R. V. Wakelam, & E. Herbst, 2007, A&A, 467, 1103
H. Oba, T. Tomaru, A. Kouchi, & N. Watanabe, 2019, ApJ, 874, 124
T. Nguyen, Y. Oba, T. Shimonishi, A. Kouchi, & N. Watanabe, 2020, ApJL, 898, L52

Formation of phosphorus monoxide (PO) in the interstellar medium: insights fromquantum-chemical and kinetic calculations
J. García de la Concepción,1 Cristina Puzzarini,2 Vincenzo Barone3, Izaskun Jiménez-Serra1
and Octavio Roncero.4
1
Centro de Astrobiologia (CSIC-INTA), Ctra. de Ajalvir Km. 4, Torrej´on de Ardoz, 28850
Madrid, Spain
2
Department of Chemistry “Giacomo Ciamician”, University of Bologna, Via F. Selmi 2,
Bologna, 40126, Italy
3
Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa, 56126, Italy
4
Instituto de F´ısica Fundamental (IFF), C.S.I.C., Serrano 123, 28006 Madrid, Spain
In recent years, phosphorus monoxide (PO) –an important molecule for prebiotic chemistry–has been detected in star-forming regions and in the comet 67P/Churyumov-Gerasimenko [1].
These studies have revealed that, in the interstellar medium, PO is systematically the mostabundant P-bearing species, with abundances that are ∼1-3 times greater than those derived
for phosphorus nitride (PN), the second most abundant P-containing molecule. The reason
why PO is more abundant than PN remains still unclear. Experimental studies withphosphorus in the gas phase are not available. Therefore, the reactivity of atomic phosphorus
needs to be investigated using reliable computational tools. To this end, state-of-the-art
quantum-chemical computations have been employed to evaluate accurate reaction rates andbranching ratios for the P + OH → PO + H and P + H2O → PO + H2 reactions in theframework of a master equation approach based on ab-initio transition state theory. While thereaction of atomic phosphorus in its ground state with water is not a relevant source of PO
because of emerged energy barriers, the P + OH reaction represents an important formationroute of PO in the interstellar medium[2].

Figure 1. Singlet (blue profile) and triplet (red profile) potential energy surfaces (ZPE-corrected energies)
for the formation of PO from OH + P

References[1]
K. Altwegg et al. 2016, Sci Adv, 2:e1600285.
[2]
J. García de la Concepción, C. Puzzarini, V. Barone, I. Jiménez-Serra & O. Roncero. 2021, ApJ,
arXiv:2108.08530 [astro-ph.GA].

Cold chemistry in hot cores:
Non-diffusive grain-surface chemistry and its role in forming complex organic moleculesin star-forming regions
R. T. Garrod,1,2 M. Jin,1 and E. Herbst1,2
1
2

Department of Chemistry, University of Virginia, USA
Department of Astronomy, University of Virginia, USA

Reactions on dust-grain surfaces are responsible for the production of many importantinterstellar molecules, including gas-phase H2, grain-surface ice species such as water,
ammonia and methanol, and arguably some of the most complex molecules detected in starforming regions. However, our view of the temperature dependence of this chemistry has
recently been changing. A major driver in this shift is the gas-phase detection of complex
organic molecules (COMs) such as methyl formate in cold pre-stellar cores. These detections
have pushed back the astronomical clock on COM production, to a time much earlier than thewarm proto-stellar stage in which they are usually detected (albeit in much greater abundance).
Experimental evidence also suggests that COMs may be formed on very cold surfaces (~10K), through mechanisms that do not require thermal diffusion of the reactants. Past models
that rely solely on diffusive reaction mechanisms now appear inadequate.
I will discuss new modeling treatments [1,2] that adopt a more comprehensive framework forgrain-surface and ice-mantle chemistry, allowing reactants to meet in a variety of ways that do
not rely solely on diffusion. This allows COMs to form as the ice mantles grow, while
processing of the ices by external and cosmic-ray-induced UV fields can also lead to COM
production. The period when the water-dominated ices desorb from the grains (Fig. 1, dashedlines) also allows trapped radicals to meet and react on the warm ice surfaces, prior todesorption. Gas-phase chemistry can further enhance COM production in some cases. In
combination, these processes allow COMs to form over a range of temperatures, through avariety of mechanisms. I will discuss the implications of this new picture of COM chemistry.

Figure 1: Net rates (arb. units) of molecular formation/destruction (green/blue), summed over all chemicalphases (gas + surface + ice), from the collapse of a cold core through its evolution to a hot molecular core.

References[1][2]

M. Jin & R. T. Garrod, ApJS, 249, 26
R. T. Garrod et al., ApJS (accepted), https://arxiv.org/abs/2110.09743

Application of the Tight Binding GFN2-xTB Method to Model Large Interstellar
Amorphous Icy Grains
A. Germain,1 L. Tinacci,2 C. Ceccarelli2 and P. Ugliengo1
1

Dip. Di Chimica, Università degli studi di Torino, Italy
2
CNRS (IPAG), Université de Grenoble, France

Interstellar grains are made of a silicate core covered by a mantle of several layers ofamorphous ice. In the gas-phase of dense molecular clouds chemical species freeze onto thegrain and can diffuse on its surface, react to give interstellar more complex molecules andultimately desorb back to the gas-phase. Hence, the study of interstellar grains is an importantpart for understanding the chemical evolution in time of the Interstellar Medium (ISM). Thereis still no consensus in the Astrochemistry community on how to model these icy grains at
atomistic level with the requisite of treating the hydrogen bond interaction and otherimportant components accurately. Furthermore, the grain should be large enough to be
representative of the variability present in the ISM, which renders impractical the adoption ofplain DFT methods. Also, the adopted method should, not only be relatively fast, but also
applicable to study the interaction of large interstellar molecules with the grain itself. Force
fields are not the proper solution, due to the parametrization specific for each considered
species, breaking the universality of the approach. To fill in the above requested, we resort toa newly developed semi-empirical quantum mechanical method based on the tight binding
DFT approach called GFN2-xTB1 and a universal force field method called GFN-FF2, bothdeveloped by the Grimme’s group at the Bonn University. We present the methodology tobuild a water cluster model up to 1000 H2O molecules and to characterize its structural andelectrostatic potential surface (EPS) as a free grain (Fig. 1). Then, NH3 was chosen as
relevant interstellar molecule to compute its binding energy (BE) at more than 150 different
grain sites to characterize the BE distribution which revealed a bimodal distribution.

a)b)

Figure 1: a) Structure and b) EPS of the GFN2-xTB water cluster model (1000 H2O)

References[1][2]

C. Bannwarth, S. Ehlert, S. Grimme, J. Chem. Theory Comput. 2019, 15, 1652-1671
S. Spicher, S. Grimme, Angew. Chem. Int. Ed. 2020, 59, 15665-15673

Experimental measurement of the absorption cross section of dangling OH bonds inwater ice
T. Hama,1 T. Nagasawa,1 T. Hasegawa, and N. Numadate1
1

Komaba Institute for Science, The University of Tokyo, Meguro, Tokyo 153- 8902, Japan

Recent astronomical observations have revealed water (H2O) ice to be ubiquitous in space.
For example, it is the most abundant solid component in interstellar molecular clouds and theouter cold part of protoplanetary disks. Its ubiquity makes it essential to clarify the physics
and chemistry of ice to further our understanding of the formation of stars and planetarysystems, including our solar system [1].
Key infrared (IR) features related to interstellar ice are signals at 3720 and 3696 cm−1 from
dangling OH bonds, which have respectively been assigned to the free OH stretch modes oftwo- and three-coordinated H2O molecules at the surface of ice [2, 3]. Because dangling OH
bonds reflect the porosity of ice and serve as catalytic sites for adsorption and chemical
reactions, they have been intensely studied in many fields including interstellar chemistry [4,5]. Despite much active research, the absorption cross section, a fundamental optical constant,of dangling OH bonds remains unknown. This hampers the quantification of dangling OH
bonds from IR spectra of ice.
Recently, we developed an experimental setup for in situ infrared multiple-angle incidence
resolution spectrometry (IR-MAIRS) in low-temperature, ultrahigh-vacuum conditions [6].
IR-MAIRS is a spectroscopic method combining oblique incidence transmission
measurements and multivariate analysis to retrieve both pure in-plane (IP) and out-of-plane(OP) vibration spectra for a thin sample, which was originally developed for quantitative
molecular orientation analysis of organic thin films without the use of optical parameters [6,7]. In this study, we report our recent challenge to measure the absorption cross section of
dangling OH bonds of water ice using IR-MAIRS [8].
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

T. Hama, & N. Watanabe, 2013, Chem. Rev. 113, 8783.
Buch, V., & Devlin, J. P. 1991, J. Chem. Phys., 94, 4091.
Devlin, J. P., & Buch, V. 1995, J. Phys. Chem., 99, 16534.
Noble, J. A., Michoulier, E., Aupetit, C., & Mascetti, J. 2020, Astron. Astrophys., 644, 1.
Maté, B, Satorre, M., & Escribano, R. 2021, Phys. Chem. Chem. Phys., 23, 9532.
T. Hama, A. Ishibashi, A. Kouchi, N. Watanabe, N. Shioya, T. Shimoaka, & T. Hasegawa, 2020, J. Phys.
Chem. Lett. 11, 7857.
Hasegawa, T., & Shioya, N. 2020, Bull. Chem. Soc. Jpn., 93, 1127.
T. Nagasawa, R. Sato, N. Numadate, N. Shioya, T. Shimoaka, T. Hasegawa, & T. Hama, submitted.

Cloudlet capture model for the origin of asymmetry
in the molecular emission in TMC-1A
Tomoyuki Hanawa
Center for Frontier Science
Chiba University
Protostars are associated with protoplanetary disks and are surrounded by infalling envelopes.
The gas accretion from the envelope is thought to be more or less symmetric around therotation axis of the disk. However, some young protostars show highly asymmetric features in
the molecular emission lines. Blue-shifted component is much stronger than red-shited one in
the CS emission line in TMC-1A harboringIRAS 04365+2535, Class I protostar in Taurus.
The asymmetry may indicate that we are observing the capture of a cloudlet. We examine thispossibility based on hydrodynamical simulations in which a cloudlet accretes and collides thepre-existing disk. The orbital plane of the cloudlet is inclined to the disk. This model explains
several features such as (1) the asymmetry in the infalling gas, (2) a partial lack in the disk,and (3) apparently slow infall velocity. We discuss the implications of our hypothesis that thegas accretion onto protostar may be successive but sporadic captures of cloudlets rather thancontinuous flow.

The measuring the formation of products from reaction at low temperatures using
chirped pulse Fourier transform spectroscopy in uniform flows
B. M. Hays, T. Guillaume, D. Gupta, I. R. Cooke, O. Abdelkader Khedaoui, M. Drissi, T. S.
Hearne and I. R. Sims
IPR (Institut de Physique de Rennes) - UMR 6251, Univ Rennes, F-35000 Rennes, France.
The formation of complex molecules in the interstellar medium often proceeds at very low
temperatures. Predicting the formation mechanisms of these molecules depends heavily on
experimental measurements of the rates of reaction at low temperatures. While experiments
are available to measure these rates at low temperatures using the CRESU (French acronym
for Reaction Kinetics in Uniform Supersonic Flow) technique, the products of these reactions
and their branching ratios are usually not measured. This leaves a large gap in astrochemical
kinetics databases concerning the product branching ratios of reactions.
The CPUF (Chirped Pulse in Uniform Flow) combines the revolutionary chirped pulse
Fourier spectroscopy technique with the CRESU environment, using rotational spectroscopy
to unambiguously identify the products of reaction at low temperatures. A new chirped pulse
Fourier transform millimeter wave spectrometer was adapted to continuous uniform flow
apparatus available in Rennes. The products of fast CN radical reactions with ethane andacetylene were directly observed in the uniform flow, showing proof of concept results fromthis instrument.
The Fourier transform spectra were heavily affected by the buffer gas used in the CRESU
technique in interesting ways. This provided a unique opportunity to explore intermolecular
dynamics between the buffer gas and other molecules, specifically the elastic and inelastic
scattering of these species. HCN and HNC spectra were compared in the low temperature He
environments, where the collisional excitation of these two molecules were found to be very
different, especially at low temperatures relevant to molecular clouds. Finally, the CPUF
apparatus was extended to sample the uniform flow using a newly developed secondary
expansion chamber, where the product branching ratios could be measured from reaction.
Future developments will allow for the CPUF technique to be extended to even colder
temperatures and more molecular systems.

Submillimeter H2O masers in high-mass star-forming regions
T. Hirota1
1

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Japan

Molecular masers have been employed to investigate dynamical structures of circumstellar
disks and outflows in young stellar objects (YSOs). In particular, some representative
centimeter radio lines such as the 1.6 GHz OH, 6.7 GHz CH3OH, and 22 GHz H2O masers arewidely used for high resolution interferometric observations. In contrast, higher frequency
masers have not been well studied until recent developments with ALMA (Atacama Large
Millimeter/submillimeter Array).
Here we will present observational results of submillimeter H2O masers toward high-massstar-forming regions. We will review recent progress of our ALMA observations of submillimeter H2O lines toward the nearest high-mass YSO, Source I in Orion KL [e.g. 1,2],
which shows a rotating outflow driven from the Keplerian disk. We will also show tentative
results from ALMA observations of the 321 GHz H2O masers toward high-mass YSO
samples associated with the 22 GHz H2O masers observed with VERA (VLBI Exploration ofRadio Astrometry) [e.g. 3]. We find that the higher excitation 321 GHz H2O masers are in
general co-located with those of the 22 GHz H2O masers while in some sources they are
emitted from inner part of the outflows traced by the 22 GHz masers. The results suggest thatmultiple maser lines at different excitation conditions can be unique probes of physical andchemical properties of high density and temperature regions in the close vicinity to high-mass
YSOs associated with disk/outflow systems.
(a)

(b)

(c)

Figure 1: (a) Moment 0 map of the 321 GHz (102,9 - 93,6) H2O maser (color) and ALMA Band 10
continuum emission (contour) toward a high-mass YSO Orion Source I [1,2]. (b) Spectrum of the 321 GHz
H2O maser toward Source I [1,2]. (c) Moment 0 map of the 321 GHz H2O maser (gray), VLA 22 GHz
continuum (contour), and positions of the 22 GHz (61,6 - 52,3) H2O maser (cross) toward a high-mass YSOS255 NIRS3 [3].

References
[1]
[2]
[3]

T. Hirota, M. N. Machida, Y. Matsushita, et al., in proc. of IAUS 336, “Astrophysical Masers: Unlocking
the Mysteries of the Universe”, ed. A. Tarchi, M. J. Reid, and P. Castangia (Cambridge University Press,
Cambridge, 2018), p. 207.
T. Hirota, M. K. Kim, Y. Kurono, and M. Honma 2014, ApJL, 782, L28.
T. Hirota, R. Cesaroni, L. Moscadelli, et al. 2021, A&A, 647, A23.

Energetic processes caused by sub-keV electrons impacting on H2O+CO ice mixtures
C.-H. Huang1, C-Y Lee1, Jr-Yao Lee1, C. Cecchi-Pestellini2, A. Ciaravella2, A.
Jiménez-Escobar2, L.-C. Hsiao1, N.-E. Sie1, and Y.-J. Chen1
1

2

Department of Physics, National Central University, Taiwan
INAF - Osservatorio Astronomico di Palermo, P.za Parlamento 1, 90134 Palermo, Italy

The irradiation of molecules in condensed water is an important process in the chemistry of awide variety of astronomical environments. An important component of interstellar ices iscarbon monoxide, and consequently, a number of experiments have been performed in
mixtures of such species with water [1, 2].
In this work, we use middle-range electrons (200-1000 eV) to study the radiation induced
chemistry in H2O + CO ice mixtures. We derive destruction and production cross-sections ofparent molecules and products, and for the case of CO being the desorption cross-section. Welabel the products observed after irradiation with energetic electrons from IR spectra (Figure 1)
to understand the mechanisms and kinetics associated with the relevant reactions. A
comparison is made with the results of experiments performed using different processing
sources, such as X-ray, UV and hydrogenation. Finally, we discuss the difference ofdesorption relevant depths [3] between in the present case and that of a pure CO ice.

Figure 1: Assignment of products in irradiated H2O:CO ice mixture. From bottom to top are spectrum in
200, 400, 600, 800, and 1000 eV experiments.

References
[1]

[2]
[3]

Jiménez-Escobar, A., Chen, Y. J., Ciaravella, A., Huang, C.H., Micela, G., & Cecchi-Pestellini, C. 2016,
ApJ, 820(1),25
Watanabe, N., Mouri, O., Nagaoka, A., Chigai, T., Kouchi,A., & Pirronello, V. 2007, ApJ, 668(2), 1001.
R. Dupuy, M. Haubner, B. Henrist, J.-H. Fillion, & V.Baglin. 2020, JAP 128, 175304.

Water-promoted formation of methyl formate from methanol via methoxymethanolon iceA. Ishibashi,1 H. Hidaka,1 Y. Oba,1 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science/Hokkaido University, Japan

Methyl formate (MF; HCOOCH3) is abundantly found in various astronomical objects,
including cold molecular clouds [1]. Because of a good correlation with MF in observations,methanol, which is a primordial organic molecule on interstellar dust, is thought to be parent
molecule. However, the results of laboratory experiments on the photolysis of pure methanol
solid did not to explain the MF abundances astronomically observed [2, 3]. Recently, laboratory
observation of ice dust analogue indicated that methanol would contact water ice at the dust
surface rather than being as pure solid [4]. Therefore, the effect of H2O on the MF formation
should be considered as well as the photolysis of methanol. To study the details of the MF
formation mechanism, small amounts of products and those radical precursors on the ice surface
need to be monitored, which is difficult with conventional methods, such as FT-IR. Therefore,
we newly developed highly sensitive nondestructive detection method, so-called Cs+ ion
pickup method [5], to monitor products and radicals, and performed the experiments for thephotolysis of methanol (0.3 ML) on ice [6].
Analysis of the reaction products from the photolysis showed the formation of
methoxymethanol (MM; CH3OCH2OH) and MF as the main components. This result wasdifferent from the UV photolysis of pure methanol solids, in which CH2OH-derived molecules
such as ethylene glycol (EG; HOCH2CH2OH) and ethanol were mainly produced. This MF
generation is well consistent with cosmic MF observations. To clarify the reaction process of
MM and MF, the irradiation time dependence of the signal intensities of trace reaction products
such as CH3O and/or CH2OH, MM, MF, and OH was measured (Figure 1). A sequential
behavior such as CH3OH → CH3O and/or CH2OH → MM → MF was observed, indicating
found that MF was efficiently generated by photodissociation of MM. In addition, from the factthat MM is the main product on ice among the C2H6O2 isomers, it is considered that theformation of CH3O was promoted by the abstraction reaction from methanol by the OH radical
generated by the photolysis of H2O.

Figure 1: Variations in the signal intensities of surface species generated during UV irradiation to the sampleof CH3OH (0.3 ML) on ASW (10 ML) at 10 K. Pickup signals of MF, MM, CH3O and/or CH2OH, and OH
which are photoproducts.

References
[1]
[2]
[3]
[4]
[5]
[6]

T. Soma et al. Astrophys. J. 854, 116 (2018).
K. Öberg et al. Astron. Astrophys. 504, 891–913 (2009).
D. Paardekooper et al. Astron. Astrophys. 592, A67 (2016).
A. Kouchi et al. Astrophys. J. 918, 45 (2021).
H. Kang, Bull. Korean Chem. Soc. 32, 389 (2011).
A. Ishiabshi et al. Astrophys. J. Lett. 921, L13 (2021).

Development of a high-sensitivity and non-destructive detection system for trace
amounts of adsorbates on ice
A. Ishibashi,1 H. Hidaka,1 Y. Oba,1 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science/Hokkaido University, Japan

Molecular evolution on the surface of interstellar ice dust is important. In particular, theinformation of radical is crucial for understanding the formation process of complex organic
molecule. Although many experiments have been performed [1], the detection of trace
adsorbates like radicals is still difficult with conventional experimental methods due to the lackof sensitivity and thus little is known about behavior of such species on the ice surfaces.
Recently, we newly developed highly-sensitivity and non-destructive mass analysis
apparatus for trace amounts of adsorbates on the amorphous solid water (ASW) surface. Basedon a design in literature [2], we constructed an apparatus composed of a Cs+ ion gun andQuadrupole Mass Spectrometer (QMS) in an ultra-high vacuum chamber. Using that, adsorbed
species X (Mass: M) on ASW substrate were picked up with Cs+ ion and mass-analyzed by the
QMS as Cs-X+ (Mass: 133 + M). As a result of various improvements, we have succeeded in
detecting the trace of radicals adsorbates on ASW surface. As shown in Figure 1, we canmonitor the behavior of OH radical on ASW upon the photolysis of H2O.

Figure 1: Variations in the pickup signal intensity of OH radical generated by ASW (10 ML) during UV
irradiation at 10 K.

References[1][2]

T. Hama & N. Watanabe, 2013, Chem. Rev. 113, 8783-8839.
H. Kang, 2011, Bull. Korean Chem. Soc. 32, 389-398.

Workshop on Interstellar Matter 2021
Book of Abstracts

17-19 November 2021

Institute of Low Temperature Science,
Hokkaido University, JAPANProgram
In Japan Standard Time (UTC+9)

17th, Wed.
9:00-9:05 Opening remarks: Naoki Watanabe (Hokkaido University, Japan)
Morning Session 1

Chair: Tomoya Hirota

9:05-9:45 Brett McGuire (Massachusetts Institute of Technology, USA) Invited"The PAH Revolution: Cold, Dark Carbon at the Earliest Stages of Star Formation"
9:45-10:05 Yuki Okoda (The University of Tokyo, Japan)"Compact Distributions of N-bearing species and HCOOH in the Protostellar Source
B335"
10:05-10:25 Giseon Baek (Kyung Hee University, Korea)"Complex organic molecules detected in twelve high mass star forming regions withALMA"
10:25-10:40 Coffee break
Morning Session 2

Chair: Brett McGuire

10:40-11:00 Zwei Zhang (RIKEN, Japan)"Hot Disk Chemistry in Massive Star forming Regions"
11:00-11:20 Takashi Shimonishi (Niigata University, Japan)"ALMA Discovery of Chemical Complexity at the Edge of our Galaxy"
11:20-11:40 Nadia Murillo (RIKEN, Japan)"Studying the factors that determine multiplicity and chemical complexity in Perseus"
11:40-12:00 Hideko Nomura (NAOJ, Japan)"Formation of complex organic molecules through ice mantle reactions"12:00-14:00 Lunch
Afternoon Session 1

Chair: Germán

Molpeceres

14:00-14:20 Victor Manuel Rivilla Rodriguez (CSIC/INTA, Spain)"Molecular precursors of the RNA-world in the interstellar medium"
14:20-14:40 Laura Colzi (CSIC/INTA, Spain)"The GUAPOS project: A comprehensive study of peptide-like bond molecules"
14:40-15:00 Albert Rimola (Universitat Autònoma de Barcelona, Spain)"Quantum Chemical Simulations to Unveil the Interstellar Grain Surface Chemistry.
Insights at an Atomistic Scale"
15:00-16:30 Poster session
Afternoon Session 2

Chair: Thanja Lamberts

16:30-17:10 Germán Molpeceres (Universität Stuttgart, Germany) Invited"Machine Learning Meets Surface Astrochemistry"
17:10-17:30 Stephan Schlemmer (Universität zu Köln, Germany)"MissIons: Missing Ions in Laboratory"
17:30-17:50 Frederik Doktor S. Simonsen (Aarhus Universitet, Denmark)"Formation of water ice clusters on graphite"
17:50-18:00 Coffee breakAfternoon Session 3

Chair: Kensei Kitajima

18:00-18:40 Brian Hays (Université de Rennes 1, France) Invited"The measuring the formation of products from reaction at low temperatures using
chirped pulse Fourier transform spectroscopy in uniform flows"
18:40-19:00 Cristina Puzzarini (Universitá di Bologna, Italy)

"Theory and Experiment for Elucidating Chemical Evolution in Space"
19:00-19:20 Jesús Antonio Lique-Urrutia (Universtitat Autònoma de Barcelona, Spain)"Glycolaldehyde Formation on Interstellar Water Ice Surfaces. A Computational
Quantum Chemical Approach"

18th, Thu.
Morning Session 1

Chair: Kenji Furuya

9:00-9:40 Rob Garrod (University of Virginia, USA) Invited"Cold chemistry in hot cores: Non-diffusive grain-surface chemistry and its role informing complex organic molecules in star-forming regions"9:40-10:20 Masashi Tsuge (Hokkaido University, Japan) Invited"Icy grains are not spherical nor ellipsoidal"
10:20-10:40 Y. L. Yang (University of Virginia, USA)
"Chemistry of Embedded Disks in Perseus: Prevalent Complex Organic Molecules andShock-excited Sulfur-bearing Molecules"
10:40-12:20 Poster session
12:20-14:00 Lunch
Afternoon Session 1

Chair: W.M.C. Sameera

14:00-14:20 Izaskun Jimenez-Serra (CSIC/INTA, Spain)"Formation, Abundance Distribution and Evolution of Complex Organic Molecules inStarless/Pre-stellar Cores"
14:20-14:40 Juan García de la Concepción (Centro de Astrobiología, Spain)"Formation of phosphorus monoxide (PO) in the interstellar medium: insights fromquantum-chemical and kinetic calculations"14:40-15:00 Joan Enrique Romero (Universite Grenoble Alpes, France)"A systematic computational study of radical−radical reactions on interstellar ice
surfaces"
15:00-15:20 Ni-En Sie (National Central University, Taiwan)"The thickness and UV absorption effect on UV photolysis of CH4 ice"
15:20-16:30 Poster session
Afternoon Session 2

Chair: Yuri Aikawa

16:30-16:50 Thanja Lamberts (Universiteit Leiden, The Netherlands)"Carbon atom addition reactions in interstellar ices: How to marry laboratory andcomputational chemistry"
16:50-17:10 Aurèle Germain (Università degli studi di Torino, Italy)"Application of the Tight Binding GFN-xTB Method to Model Large Interstellar
Amorphous Icy Grains"
17:10-17:30 Stefano Ferrero (Universitat Autònoma de Barcelona, Spain)"The energy dissipation process of hydrogenation reactions of atomic nitrogen on water
ice surfaces"
17:30-17:50 Coffee breakAfternoon Session 3

Chair: Masashi Tsuge

17:50-18:30 Jean-Hugues Fillion (LERMA - Sorbonne Université et Obserbatoire de Paris,
France) Invited"Photon Stimulated Desorption from interstellar ice analogs: recent results usingsynchrotron radiation"
18:30-19:10 Emmanuel Dartois (Institut des sciences moléculaires d'Orsay, France)
Invited"Non-thermal desorption of ice mantles: cosmic rays desorption of complex organicmolecules"
19:10-19:30 Kenji Furuya (NAOJ, Japan)"Quantifying the chemical desorption of H2S and PH3 from water ice surface"

19th, Fri.
Morning Session 1

Chair: Ralf Kaiser

9:00-9:40 Susanna Widicus Weaver (University of Wisconsin-Madison, USA) Invited"The role of UV photolysis and thermal processing in interstellar ice chemistry"
9:40-10:00 Atsuki Ishibashi (Hokkaido University, Japan)"Water-promoted formation of methyl formate from methanol via methokxymethanolon ice"10:00-10:20 Zhen-Dong Sun (Shandong University, China)"Calculation of the ortho-para conversion rate of gaseous methanol by the internal axis
method"10:20-10:40 Coffee break
Morning Session 2

Chair: Kaori Kobayashi

10:40-11:20 Ralf Kaiser (University of Hawaii, USA) Invited"An Aromatic Universe - Low Temperature Molecular Mass Growth Processes to
Polycyclic Aromatic Hydrocarbons (PAHs)"
11:20-12:00 Shogo Tachibana (The University of Tokyo, Japan) Invited"Hayabusa2 returned samples from C-type near-Earth asteroid (162173) Ryugu:
Preliminary report of initial analysis"
12:00- Concluding remarks: Nami Sakai (RIKEN, Japan)

Posters
In Japan Standard Time (UTC+9)
17th Wed. 15:00-16:30
18th Thu. 10:40-12:20, 15:20-16:30
1. Yuri Aikawa (The University of Tokyo, Japan)"HCO+ and ionization structure observed by ALMA"
2. Mitsunori Araki (Tokyo University of Science)"Testing Dust-Surface Formation Model of Prebiotic Molecule CH3NCO in Star-Forming
Cores Sagittarius B2 (M) and (N)"
3. Gianni Cataldi (NAOJ, Japan)"Can grain-surface chemistry explain the surprisingly low C/CO ratio in the HD 32297
debris disk?"
4. Izumi Endo (The University of Tokyo, Japan)"Nitrogen inclusion in organic dust in novae revealed by laboratory synthesis ofQuenched Nitrogen-included Carbonaceous Composite (QNCC)"
5. Izuru Fukuda (Tokyo University of Science, Japan)"Development of Cavity Enhanced Absorption Spectrometer Aiming to Measure Optical
Absorption Bands of Interstellar Molecules"
6. Tetsuya Hama (The University of Tokyo, Japan)"Experimental measurement of the absorption cross section of dangling OH bonds inwater ice"
7. Tomoyuki Hanawa (Chiba University)"Cloudlet capture model for the origin of asymmetric molecular line emissions from inthe young stellar objects"
8. Tomoya Hirota (NAOJ, Japan)"Submillimeter H2O masers in high-mass star-forming regions"9. Hoga Furukawa (University of Toyama, Japan)"Microwave spectroscopy of isothiazole"
10. Chao-Hui Huang (National Central University, Taiwan)"Energetic processes caused by sub-keV electrons impacting on H2O+CO ice mixtures"
11. Hyeon-Deuk Kim (Kyoto University, Japan)"Anomalous Properties of Condensed Hydrogen Molecules under Extreme
Thermodynamic Conditions Revealed by the Non-Empirical Quantum Molecular
Dynamic Simulation Method"
12. Kensei Kitajima (Hokkaido University, Japan)"A new electrochemical property of ice: negative charge transport triggered by reactionsof surface OH radicals with electrons"
13. Beatrice Kulterer (University of Bern, Switzerland)"Mono-deuterated methanol in prestellar cores"
14. Signe Kyrkjebø (Aarhus University, Denmark)"Early stages of water cluster growth observed with low-temperature scanningtunnelling microscopy"
15. Berta Martínez-Bachs (Universitat Autònoma de Barcelona, Spain)"Computational Investigation on the Potential Energy Surface of the Formation Route ofFormamide from Reaction between NH2 and H2CO on Interstellar Water Ice Surface"
16. Ayane Miyazaki (Hokkaido University, Japan)"Detection of photodesorption OH radicals from H2O ice surface by visible light"
17. T. Nagasawa (The University of Tokyo, Japan)"An infrared spectroscopic approach towards understanding the orientation of dangling
OH bonds on amorphous solid water"
18. Yoichi Nakai (RIKEN, Japan)"Methanol production via interactions of low-energy CH3+ ions with ASW surface:experimental investigation of ion-surface reactions"19. Thanh Nguyen (Hokkaido University, Japan)"Experimental and computational studies on the physicochemical behavior of phosphine
induced by reactions with H and D atoms on interstellar ice grains"
20. Shota Notsu (RIKEN, Japan)"X-ray-induced chemistry of water and related molecules in low-mass protostellar
envelopes"
21. Naoki Numadate (The University of Tokyo, Japan)"First direct detection of OH radicals photodesorbed from liquid organic surface by using
laser-induced fluorescence technique"
22. Satoshi Ohashi (RIKEN, Japan)"FAUST III. Misaligned rotations of the envelope, outflow, and disks in the multiple
protostellar system of VLA 1623$-$2417"
23. Kunihiro Okada (Sophia University, Japan)"Experimental study toward the measurements of rotational state dependence ofinterstellar ion-polar molecule reactions at low temperatures"
24. Yoko Oya (The University of Tokyo, Japan)"Chemical Differentiation and its Relation with the Physical Structures in Disk-Forming
Regions of Young Low-Mass Protostellar Sources"
25. Anshika Pandey (Banaras Hindu University, India)"Formation of 3-Pyrolline in Interstellar Space: A Computational Study"
26. Akant Vats (Banaras Hindu University, India)"DFT study on hydrogenated and deuterated derivatives of interstellar fullerenes"
27. Jessica Perrero (Universtitat Autònoma de Barcelona, Spain)"Formation of acetaldehyde on mixed-ice grain surfaces"
28. P. V. G. M. Rathnayake (The University of Sydney, Australia)"PyQMMM for modelling chemical processes in the interstellar medium"29. Eri Saiga (The University of Tokyo, Japan)"Star Formation Feedback to a Parent Cloud: The Elias 29 Case"
30. Nami Sakai (RIKEN, Japan)"Measurements of Microwave Spectra of Methanol Isotopologues in ALMA Band 6
Frequency Range"
31. R. Sato (The University of Tokyo, Japan)"Development of the RHEED apparatus for in situ structural analysis of water ices in lowtemperature and ultrahigh vacuum conditions"
32. Richard Schömig (Universität Stuttgart, Germany)"A Theoretical, Neural-Network Assisted Study of Methane Formation under
Astrophysical Conditions"
33. Taha Selim (Radboud University, The Netherlands)"Unraveling Molecular Collisions in Protoplanetary Disks"
34. Bethmini Senevirathne (University of Gothenburg, Sweden)"H and D diffusion on interstellar water ices"
35. Atsuki Ishibashi (Hokkaido University, Japan)"Development of a high-sensitivity and non-destructive detection system for trace
amounts of adsorbates on ice"
36. Satyam Srivastav (Banaras Hindu Univ, India)"Interstellar Branched Chain Molecules"
37. Kotomi Taniguchi (NAOJ, Japan)"Nitrile Chemistry in a Disk Structure around the G24.78+0.08 A1 Hyper-compact HII
region"38. Lorenzo Tinacci (Univerisitè Grenoble Alpes, France)"A New Approach to the Compute Accurate Binding Energy Distribution of Molecules at
Ice Interstellar Grain Models: the Case of NH3"

39. Takuto Tomaru (Hokkaido University, Japan)"STM and Non-Contact-AFM observation of Si(111) by a self-made Qplus sensor at low
temperatures"
40. Masashi Tsuge (Hokkaido University, Japan)"Diffusive hydrogenation of CO embedded in amorphous solid water at temperature up
to 70 K"
41. Masashi Tsuge (Hokkaido University, Japan)"Ortho-to-para nuclear spin conversion of H2 on interstellar bare grain analogues"
42. Withdraw
43. Yoshimasa Watanabe (Shibaura Institute of Technology, Japan)"Development of Spectrometer Using Superconductor Mixer Receiver (SUMIRE)"
44. Tomohiro Yoshida (NAOJ, Japan)"A new measurement method of isotopologue ratios in protoplanetary disks: a casestudy of the 12CO/13CO ratio in the TW Hya disk"
45. Yichen Zhang (RIKEN, Japan)"Multi-tracer Observations for Multi-scale Accretion Structures in Massive Star
Formation"
46. Shaoshan Zeng (RIKEN, Japan)"Inventory of Nitrogen-bearing organics towards G+0.693-0.027"
47. Akemi Tamanai (RIKEN, Japan)"Experimental Molecular Emission Spectroscopy of Ethylene Oxide in ALMA Band 6"

Oral Presentations

The PAH Revolution: Cold, Dark Carbon at the Earliest Stages of Star Formation
Brett A. McGuire1,2
1

Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
2
National Radio Astronomy Observatory, Charlottesville, VA, USA

Polycyclic Aromatic Hydrocarbons (PAHs) have been implicated as a large reservoir ofreactive carbon in the interstellar medium since the 1980s. PAHs have been widely
attributed as the carriers of the unidentified infrared bands where their aggregate vibrationalemission spectra are extremely well matched to the observed line signals. Only in the lastyear have individual PAHs been detected in the ISM for the first time [1–3], however,allowing us to begin to investigate the detailed chemical pathways for the formation anddestruction of these molecules. In this talk, I will discuss our detections of PAH molecules
via their rotational transitions using Green Bank Telescope observations of TMC-1 from the
GOTHAM collaboration [4]. I will discuss the efforts to model the chemistry of these PAHs,
the necessity of complementary laboratory kinetics work such as the elegant single-collision
studies being carried out by R. Kaiser and co-workers [5], our application of novel machinelearning approaches to exploring the chemical inventory in TMC-1 [6], and finally thebenefits of unbiased reaction screening studies in the laboratory with Microwave Spectral
Taxonomy [7, 8].
References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

B. McGuire et al. 2021, Science 371, 1265
A. Burkhardt et al. 2021, ApJL 908, L11
J. Cernicharo et al. 2021, A&A 649, L15
B. McGuire et al. 2020, ApJL 900, L10
S. Doddipatla et al. 2021, Science Advances 7, eabd4044
K. Lee et al. 2021, ApJL 917, L6
M. McCarthy & B. McGuire 2021, JPCA 125, 3231
M. McCarthy et al. 2020, JPCA 124, 5170

Compact Distributions of N-bearing species and HCOOH
in the Protostellar Source B335
Y. Okoda,1 Y. Oya,1 M. Imai1, N. Sakai2, Y. Watanabe3, A. López-Sepulcre4,
and S. Yamamoto1
1

Physics, The University of Tokyo, JapanRIKEN Cluster for Pioneering Research, Japan
3
Materials Science and Engineering, College of Engineering, Shibaura Institute ofTechnology, Japan4
Univ. Grenoble Alpes, CNRS, IPAG, FranceInstitut de Radioastronomie Millimétrique, France
2

References[1] Imai, M., Sakai, N., Oya, Y., etal. 2016, ApJL, 830, L37[2] Colzi, L., Rivilla, V.~M.,
Beltrán, M.~T., et al. 2021, AAP,
653, A129[3] Okoda, Y., Oya, Y., Abe, S.,
Komaki, A., et al. 2021,
arXiv:2110.00150[4] Csengeri, T., Belloche, A.,
Bontemps, S., et al. 2019, AAP,
632, A57

Rotation temperature and Dust temperature [K]Molecular-line distributions around newly born protostars provide us an important clue tounderstanding chemical processes as well as physical structures such as a disk/envelope or an
outflow. B335 is a Bok globule harboring the Class 0 protostellar source (Tbol=37 K), IRAS
19347+0727, whose distance is reported to be 90-120 pc. A number of Complex Organic
Molecule (COM) lines were detected in the vicinity of the protostar with ALMA (Atacama
Large Millimeter/submillimeter Array), and hence, this source contains a hot corino at a few
10 au scale [1].
We have conducted ALMA observations toward this source at a high spatial resolution of ~3
au. The CH3OH and CH2DOH line emission have an extended distribution with the radius of~10 au around the protostar. In contrast, the N-bearing molecular lines, NH2CHO and HNCO,
show a more compact distribution within a radius of ~6 au or less. These characteristicfeatures have been reported for other sources [2][3]. Interestingly, the HCOOH lines show asimilar distribution to the N-bearing molecular lines, despite being an O-bearing species. This
trend has also been seen in a high-mass source [4]. We derive the rotation temperature aroundthe protostar under the assumption of the LTE condition using multiple lines each for CH3OH,
CH2DOH, NH2CHO, and HCOOH. Figure 1 shows the temperature distribution along the
disk/envelope system. The temperature is derived to be ~250 K at the continuum peak, anddecreases with increasing the distance from it. The derived temperatures in the vicinity of theContinuum
protostar within 3 au are all
CH₃OH
300
CH₂DOHsimilar. However, it depends
NH₂CHO
HCOOH
on molecules at 6 au. This250
may suggest the complex
structure of the disk/envelope
200
system. Further works are in
progress.
150
100

50

5 au
0
-0.2

-0.15

-0.1

-0.05

Beam size
0

0.05

0.1

0.15

0.2

Angular offset [arcsec]

Figure 1: The blue, yellow, green, and orange marks represent therotation temperatures derived from the CH3OH, CH2DOH, NH2CHO,
and HCOOH lines, respectively, along the disk/envelope system. The
vertical bars indicate the error bars. The purple line represents the dust
continuum distribution.

Complex organic molecules detected in twelve high mass star forming regions with
ALMA
Giseon Baek,1 Jeong-Eun Lee,1 Tomoya Hirota2,3, Kee-Tae Kim4
and KaVA Star-Formation Science Working Group1
School of Space Research, Kyung Hee University, Korea
2
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), Japan3
Department of Astronomical Sciences, SOKENDAI (The Graduate University for Advanced
Studies), Japan
4
Korea Astronomy and Space Science Institute (KASI), Korea
Recent astrochemical models and experiments have explained that complex organic
molecules (COMs; molecules composed of six or more atoms) are produced on the dust grain
mantles in cold and dense gas in prestellar cores [1]. However, the chemical networks and theroles of physical conditions on chemistry are not still understood well. To address thisquestion, hot cores in high mass young stellar objects are great laboratories due to their strong
emissions and larger samples than those of low-mass counterparts. In addition, CH3OH
masers, which have been mostly found in high mass star forming regions, can provide
constraints due to their very specific emerging conditions. We investigate the chemical
diversity in richness and complexity of twelve high mass star forming regions using the
ALMA band 6 observations. They are associated with 44/95 GHz class I and 6.7 GHz class II
CH3OH masers, implying that the active accretion processes are ongoing [2][3]. For thesepreviously unresolved regions, 63 continuum peaks are detected. Among them, we found 28
cores emitting COMs and specified 10 cores associated with 6.7 GHz Class II CH3OH masers.
We identified up to 19 COMs including oxygen- and nitrogen-bearing molecules and theirisotopologues in a core and derived their abundances. We found that (1) oxygen-bearing
molecules appear to be richer in abundance and more complex in molecular structures thanthose of nitrogen-bearing species, (2) COMs detection rate steeply grows with the gas column
density, above the threshold of ~1024cm-2, which can be attributed to the effective COMs
formation in dense cores, and (3) cores associated with class II CH3OH maser tend to emit
larger number of COMs. Therefore, from our analysis, we conclude that the chemical
diversity among hot cores could be originated by the degree of the accretion of each source aswell as different physical conditions of cores.
References

[1]
[2]
[3]

K. Öberg & E. A. Bergin, 2021, PhR, 893, 1
J.-H. Kang, D.-Y. Byun, K.-T. Kim et al. 2016, ApJS, 227, 17
B. Hu, K. M. Menten, Y. Wu et al. 2016, ApJ, 833, 18

Hot Disk Chemistry in Massive Star Forming Regions
Z. E. Zhang1, Y. Zhang1, K. Tanaka2, Y. Kawashima1, P. C. Stancil3, B. H. Yang3, N.
Balakrishnan4, and N. Sakai1
1Star and Planet Formation Lab, RIKEN, Japan
2Department of Astrophysical and Planetary Sciences, University of Colorado, USA
3Department of Physics and Astronomy, University of Georgia, USA
4Department of Chemistry, University of Nevada, USA

During the embedded phase of massive star formation, the surrounding materials of protostars
experience vigorous physics and chemistry, resulting in intense physical conditions, such as
high temperature and density. As a consequence, various high excitation molecular lines havebeen detected and used to probe the physical properties of these massive protostellar systems(e.g., Orion Source I [1][2]). Recent ALMA observations have unveiled the unusual structureof the inner region of IRAS 16547–4247 (an O-type binary protostellar object) withrovibrationally excited “hot-disk” tracing molecules, e.g., NaCl, SiS, and H2O [3]. We present
non-local thermal equilibrium (NLTE) analysis of the detected species to constrain thephysical properties of this circumbinary system. The effects of physical conditions (e.g.,temperature, density, and radiation) on the excitation of these detected molecules are exploredwith NLTE modeling. Furthermore, we discuss the unique chemistry for refractory species
and sulfur in the massive star forming regions. Such study is essential to the evaluation of thepotential of these rovibrationally excited molecules as “disk-tracers”, as well as to theinvestigation of detailed physical and chemical structures of massive protostars.

Figure 1: Integrated intensity maps of emission lines overlaid with the 1.3 mm continuum emission. The
velocity maps for representative molecules are attached in grayscale.

References[1] Tachibana, S. et al. 2019, ApJL, 875, 2, L29.
[2] Wright, M. et al. 2020, ApJ, 880, 2, 155.
[3] Tanaka, K. et al. 2020, ApJL, 900, 2, L2.

ALMA Discovery of Chemical Complexity at the Edge of our Galaxy
T. Shimonishi,1 N. Izumi,2 K. Furuya3, and C. Yasui4
1Center for Transdisciplinary Research, Niigata University, Japan
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
3
National Astronomical Observatory of Japan, Japan
4
National Astronomical Observatory of Japan, California Office, USA
2Interstellar chemistry in low metallicity environments is crucial to understand chemical
processes in the past metal-poor universe. Here we report the first detection of a hot molecularcore in the extreme outer Galaxy, which is an excellent laboratory to study star formation andinterstellar medium in a Galactic low-metallicity environment [1]. The target star-forming
region, WB89-789, is located at the galactocentric distance of 19 kpc. Our ALMA
observations have detected a variety of carbon-, oxygen-, nitrogen-, sulfur-, andsilicon-bearing species, including complex organic molecules (COMs) containing up to nine
atoms, towards a warm (>100 K) and compact (<0.03 pc) region associated with a protostar(~8x10^3 Lsun) (Fig.1). Deuterated species such as HDO, HDCO, D2CO, and CH2DOH are
also detected. A comparison of fractional abundances of COMs relative to CH3OH between
the outer Galactic hot core and an inner Galactic counterpart shows a remarkable similarity.
The presence of a great molecular complexity in a primordial environment of the extreme
outer Galaxy suggests that the interstellar condition to form the chemical complexity might
exist from the early history of the Universe.

Figure 1: Examples of ALMA submillimeter spectrum (up) and molecular line distributions (bottom) for a
newly-discovered hot molecular core in the extreme outer Galaxy [1].

References[1]

T. Shimonishi, N. Izumi, K. Furuya, & C. Yasui, 2021, ApJ, in press,

arXiv/astro-ph: 2109.11123.

Studying the factors that determine multiplicity and chemical complexity in Perseus
N. M. Murillo,1 and N. Sakai1
1Star and Planet Formation Laboratory, RIKEN, Japan

Star formation involves a wide range of physical and chemical processes. To fullycomprehend and build a picture of star formation and evolution, we need to understand howeach process influences the final outcome. While models provide some insight into thisquestion, observational constraints are needed to fully understand this topic.
Two aspects of protostellar systems that are of interest are their multiplicity and chemicalcomplexity. Multiple protostars are common at all stages and masses of star formation. The
chemical complexity of protostellar systems significantly varies among systems. A curious
observational occurrence in low-mass star formation is that almost all, if not all, chemicallycomplex systems are multiple protostellar systems (e.g., IRAS16293, NGC1333 IRAS4), but
not all multiple protostellar systems are chemically complex (e.g., VLA1623, L1448 N). In
addition, within multiple protostellar systems the chemical complexity can vary among
components.
Observations of protostellar systems from molecular cloud to disk scales are needed to study
which physical and chemical processes determine multiplicity, chemical complexity, andwhether there is a relation between both. A large sample including multiple and single
protostellar systems is necessary to obtain statistically significant results. The Perseus
molecular cloud (d ~ 300pc) is ideal for such studies, given the extensive available data which
covers dust continuum, molecular lines, and magnetic fields for a range of scales.
In this talk, a large sample of Perseus protostellar systems observed with the Nobeyama 45m
Telescope, Atacama Pathfinder EXperiment (APEX), and Atacama Large
Millimeter/submillimeter Array (ALMA) will be presented. Our observations trace scales
from molecular cloud to the protostellar envelope (few 100 AU). The spectral set-up includes
a range of molecular species that can trace gas distribution, kinematics and temperature
toward each protostellar system to study the impact of heating, mass, and accretion on
multiplicity and chemical complexity. Further information from smaller scales is obtained
from previous studies. Our results suggest that multiplicity is determined by mass, while howthat mass is accumulated may be related to chemical complexity.

Formation of complex organic molecules through ice mantle reactions
C.-E. Wei1, H. Nomura2, P. Theulé3, and C. Walsh4
1

EPS Department, Tokyo Institute of Technology, Japan
Divison of Science, National Astronomical Observatory of Japan, Japan
3
Laboratory of Astrophysics of Marseille, Aix-Marseille Université, France
2
School of Physics and Astronomy, University of Leeds, UK
2

Recent solar system exploration missions, such as Rosetta mission, have found various
complex molecules in solar system objects. Some of these materials are thought to be pristineand produced before the solar system objects are formed. Meanwhile, recent development inastronomical observations, for example, by ALMA, as well as in chemical model calculations
have brought us new knowledge on formation of complex organic molecules inprotoplanetary disks, natal place of planet formation [1][2][3].
In interstellar clouds it is believed that complex organic molecules are mainly formed throughgrain surface reactions. Meanwhile, laboratory experiments suggest that ice mantle reactions
can proceed in certain conditions, and produce more complex species [4]. In this work wehave constructed a formula of mantle reaction rate based on the recent laboratory experiments
which show ice chemistry proceeding through the thermal process inside the ice bulk. Also,
we introduced the obtained reaction rates to chemical reaction network with three phasemodel including gas-phase, grain surface, and ice mantle reactions. We performed model
calculations with different physical conditions, which show that the mantle reactions canproceed efficiently when the temperature is higher than ~120K.
In addition, we adopt some physical conditions of protoplanetary disks in early evolution
phase, taking account of the temperature increase caused by FU Ori type outbursts, andinvestigate the effect on formation rate of COMs via mantle reactions. We especially focus on
the formation rates of the materials detected on the comet 67P/Churyumov-Gerasimenko in
the Rosetta mission, and found that the mass accretion rate of 10-5 solar mass per year isrequired in order to produce the ammonium carbamate found in the comet 67P/C-G efficiently
at comet forming region in protoplanetary disks [5].

References

[1]
[2]
[3]
[4]
[5]

C. Walsh, T.J. Millar, H. Nomura et al. 2014, A&A 563, A33.
C. Walsh, R. Loomis, K. Oberg et al. 2016, ApJL 823, L10.
C. Walsh 2015, EAS Publication Series 75-76, 315.
P. Ghesquière, A. Ivlev, J. A. Noble, and P. Theulé, 2018, A&A 614, A107.
C.-E.. Wei, 2019, PhD Thesis.

Molecular precursors of the RNA-world in the interstellar medium
V. M. Rivilla,1 et al.
1

Centro de Astrobiología (CSIC-INTA), Department of Astrophysics, Madrid, Spain
2
Osservatorio Astrofisico di Arcetri, Florence, Italy

The question of the origin of Life has intrigued human beings for centuries. We still do notunderstand how simple molecules combine together to form large molecules essential for livingorganisms. Recent prebiotic experiments, based on the RNA-world hypothesis for the origin ofLife, have suggested that the three basic macromolecular systems (nucleic acids, proteins andlipids) could have formed from relatively simple precursors. The detection of some of thesemolecules in space, thanks to the unprecedented capabilities of current astronomical facilities,
has opened a new window for Astrobiology from the Astrochemical point of view.
In this talk I will present an overview of the most recent results of a ultradeep unbiased spectral
survey towards the Galactic Center molecular cloud G+0.693-0.027 with the Yebes 40m and thethe IRAM 30m telescopes. Among the more than 120 molecules detected, we have discovered in
the last three years 9 new interstellar species towards this cloud (see Figure 1). These molecules
include key precursors of RNA nucleotides such as hydroxylamine [1] (NH2OH) or
cyanomethanimine [2] (HNCHCN), proteins, such as ethyl isocyanate [3] (C2H5NCO), andlipids, such as ethanolamine [4] (NH2CH2CH2OH). This amazing chemical complexity, whichmight be only the tip of the iceberg, means that interstellar chemistry offers an extremely richfeedstock for triggering prebiotic chemistry.

Figure 1: New interstellar molecules detected towards the molecular cloud G+0.693-0.027 using a deep
unbiased spectral survey conducted with the Yebes 40m and IRAM 30m telescope.

References[1] V. M. Rivilla, et al. 2020c, The Astrophysical Journal Letters, 899, id.L28
V.M. Rivilla et al. 2019b, Monthly Notices of the Royal Astronomical Society Letters, 483, p.L114-L119

[2]
[3]
[4]

L. F. Rodríguez-Almeida, Astronomy & Astrophysics, 654, id.L1
V. M. Rivilla, et al. 2021a, PNAS, 118, id. 2101314118

The GUAPOS project: A comprehensive study of peptide-like bond molecules
L. Colzi,1,2 V. M. Rivilla,1,2 M. T. Beltrán2, I. Jiménez-Serra1, and C. Mininni3
1

Centro de Astrobiología, Consejo Superior de Investigaciones Cientifícas (CSIC), Spain
2
Osservatorio Astrofisico di Arcetri, Istituto Nazionale di Astrofisica (INAF), Italy
3
Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica (INAF), Italy
Complex organic molecules (COMs), i.e. molecules containing carbon with 6 or more atoms,
have been detected ubiquitously in the interstellar medium (ISM) towards low- and high-massstar-forming regions (e.g. [1]). Among prebiotic COMs, those containing peptide-like bonds(NCO backbone) are of great interest because they can participate in the link of amino acids
forming proteins (e.g. [2]).
Here I present a study of HNCO, HC(O)NH2, CH3NCO, CH3C(O)NH2, CH3NHCHO (Fig. 1)
towards the chemically rich hot core G31.41+0.31, where these molecules have been
observed together for the first time in the disk of our Galaxy, outside the Galactic Centre([3]). This work is part of the GUAPOS (G31 Unbiased ALMA sPectral Observational
Survey) project, which is a sensitive spectral survey conducted with the ALMA (Atacama
Large Millimeter/submillimetre Array) observatory towards the star-forming region
G31.41+0.31, covering the whole Band 3, that is from 84 to 116 GHz, and with an angularresolution of 1.2’’ (~750 au, see [4]).
From the comparison with other sources, we find that molecular abundance ratios towards
different sources are found to be consistent between them within one order of magnitude,
regardless of the physical properties (e.g. different masses and luminosities), or the source
position throughout the Galaxy. Correlations have also been found between the abundances ofthese molecules. These results suggest that all these species are formed on grain surfaces inearly evolutionary stages of molecular clouds, and that they are subsequently released back to
the gas-phase through thermal desorption or shock-triggered desorption.

Formamide
Acetamide
Isocyanic acid

Methyl isocyanate

N-methylformamide

Figure 1: G31.41+0.31 at 8 μm (IRAC4, Spitzer space telescope, left panel) and ALMA 0.2’’ resolution
integrated emission maps at 1.4 mm of HC(O)NH2 (right panel, see [3]). The blue stars indicate theposition of protostars that are forming within this region. In the bottom the chemical structure of thepeptide-like bond molecules studied are shown.

References
[1]
[2]
[3]
[4]

B. McGuire, 2021, eprint arXiv:2109.13848
R. Pascal, L. Boiteau, & A. Commeyras, A. 2005, ed. P. Walde (Springer Berlin Heidelberg), 69–122
L. Colzi, V. M. Rivilla, M. T. Beltrán et al. 2021, A&A, 653, A129
C. Mininni, M. T. Beltrán, V. M. Rivilla, 2020, A&A, 644, A84

Quantum Chemical Simulations to Unveil the Interstellar Grain Surface Chemistry.
Insights at an Atomistic Scale
A. Rimola,1 J. Enrique-Romero,1,2 S. Ferrero,1 J.A. Luque-Urrutia,1 B. Martínez-Bachs,1 J.
Perrero,1,3 C. Ceccarelli,2 N. Balucani,4 and P. Ugliengo3
1

QuantumGrain, Departament de Química, Universitat Autònoma de Barcelona, 08193
Bellaterra, Catalonia, Spain
2
Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d'Astrophysique de Grenoble(IPAG), 38000 Grenoble, France
3
Dipartimento di Chimica and Nanostructured Interfaces and Surfaces (NIS) Centre,
Università degli Studi di Torino, via P. Giuria 7, 10125, Torino, Italy
4
Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto
8, 06123 Perugia, Italy
The Universe is molecularly rich [1]. Its chemical diversity and complexity is reflected by themore than 250 molecular species detected in the gaseous phase by means of radioastronomy[2] and the different solid-state phases in the form of dust grains [3]. The presence of the gasphase molecules cannot be explained uniquely by reactions taking place in the gas phase but
chemical reactions occurring on the surfaces of grains are essential to rationalize theinterstellar chemistry. However, combining astronomical observations with astrochemical
modelling and laboratory experiments is not enough to fully unveil the grain surface
chemistry and its contribution to the chemistry of space because they hold some intrinsic
limitations [4,5,6]. Quantum chemical simulations can partly alleviate this as they provide
reliable, quantitative atomic-scale information (structure, energetics, and dynamics) of
chemical processes taking place on the surface of grains, this way allowing us to determine
the actual role of the grains on them, that is, as chemical catalysts, reactant concentrator
and/or third bodies. This contribution aims to present some of the potentialities of current
state-of-the-art computations developed in the QuantumGrain group to obtain unique andfundamental information that help improving our know-how on the grain surface chemistry.
To this end, examples on the modelling of realistic grain surfaces for ices and silicates [7], on
simulations dealing with the adsorption of astrochemically-relevant species [8] and withchemical reactions forming ethanol from CCH reacting with water ice [9], and finally on thefate of the extra energy released in an exothermic reaction (here the H2 formation, [10]) will
be presented.

References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]

E.F. van Dishoeck, 2014, Farady Disc. 168, 9.
B.A. McGuire, 2018, ApJS 239, 17.
P. Ehrenfreund, & S.B. Charnley, 2000, ARA&A 38, 427.
P. Caselli, & C. Ceccarelli, 2012, A&AR 20, 1.
H.M. Cuppen, C. Walsh, T. Lamberts, et al., 2017, Space Sci. Rev. 212, 1.
A. Potapov, & M. McCoustra 2021, Int. Rev. Phys. Chem. 40, 299.
A. Rimola, S. Ferrero, A. Germain, M. Corno, & P. Ugliengo, 2021, Minerals 11, 26.
S. Ferrero, L. Zamirro, C. Ceccarelli, A. Witzel, A. Rimola, & P. Ugliengo, 2020, ApJ 904, 11.
J. Perrero, J. Enrique-Romero, B. Martínez-Bachs, et al., submitted to ACS Earth Space Chem.
S. Pantaleone, J. Enrique-Romero, C. Ceccarelli, et al., 2021, ApJ 917, 49.

Machine Learning Meets Surface Astrochemistry
G. Molpeceres1
1Institute for Theoretical Chemistry University of Stuttgart Pfaffenwaldring 55, 70569
Stuttgart, Germany

Surface reactions play a vital role in the chemistry occurring on interstellar mediums (ISM).
In particular, under the cold conditions of a molecular cloud (~10-20 K), adsorbates (atoms,
radicals and molecules) accrete, diffuse, react and desorb on top of ice-covered dust grains [1].
The chemical composition of these ices is varied and depends on the cloud's evolutionary
stage, e.g. water ice dominates the early stages [2]. At the same time, CO and CO2 areprevalent in later stages. Moreover, interstellar ices are usually amorphous, presenting a wide
range of binding sites for adsorbates to perform the aforementioned processes [2]. It appears
evident that, given the complexity of the substrates, the dynamics of adsorbates on interstellar
ices are essentially non-local, meaning that a particular process depends significantly on thebinding site under consideration. This condition imposes a constraint on computational
studies of interstellar surface chemistry, requiring extensive sampling and considerablyincreasing the computational cost for constructing reliable models. Several approaches are
employed in the literature to reduce this cost, i.e. cluster models [3], periodic models, [4]QM/MM models [5] and recently, machine-learned models [6]. In this contribution, I will
present our recent efforts in the application of neural-network potentials [7] to surface
astrochemistry, putting the focus on the simulation of:
1. Adsorption and desorption (calculation of sticking coefficients and desorption rate
constants) [6];2. Diffusion (estimation of diffusion coefficients and hopping rate constants) [8];3. Reaction (chemical desorption vs energy dissipation) [9].
References[1]
Cuppen, H.M. et al. Space Sci. Rev. 212, 1-58 (2017).
[2]
Boogert, A.C.A., Gerakines, P.A. & Whittet, D.C.B. Annu. Rev. Astron. Astrophys. 53, 541–581 (2015).
[3]
Shimonishi, T., Nakatani, N., Furuya, K. & Hama, T. Astrophys. J. 855, 27 (2018), Bovolenta, G. et al.
Mol. Astrophys. 21, 100095 (2020).
[4]
Ferrero, S. et al. Astrophys. J. 904, 11 (2020).
[5]
Molpeceres, G. & Kästner, J. Phys. Chem. Chem. Phys. 22, 7552–7563 (2020), Sameera, W.M.C. et al.
J. Phys. Chem. A 125, 387–393 (2021), Duflot, D., Toubin, C. & Monnerville, M. Front. Astron. Sp. Sci. 8, 24(2021).
[6]
Molpeceres, G., Zaverkin, V. & Kästner, J. Mon. Not. R. Astron. Soc. 499, 1373–1384 (2020),
Molpeceres, G., Zaverkin, V., Watanabe, N. & Kastner, J. Astron. Astrophys. 648, A84 (2021).
[7]
Zaverkin, V. & Kästner, J. J. Chem. Theory Comput. 16, 5410–5421 (2020).
[8]
Zaverkin, V., Molpeceres, G. & Kästner, J. Mon. Not. R. Astron. Soc., Submitted.
[9]
Schömig, R., Kästner, J. and Molpeceres, G. In preparation.

MissIons: Missing Ions in Laboratory
S. Schlemmer,1 O. Asvany1 and S. Thorwirth1
1I. Physikalisches Institut, Universität zu Köln, Germany

Ions play a key role in the chemical evolution of our universe. The process of star and planet
formation is tightly connected to the presence and abundance of these species. Their spectra
are diagnostic tools for various astrophysical environments and their temporal evolution.
However, laboratory spectra of most ions relevant to astrophysics are not available. Moreover,predicted spectra from ab-initio theory are not nearly accurate enough to guide astrophysicalsearches. Therefore, laboratory spectra of molecular ions are needed.
We will report on progress towards recording high-resolution spectra from the microwave tovisible range using our unique and innovative light induced reactions (LIR) methods in ion
traps [1]. It is molecule specific through mass selection, many orders of magnitude moresensitive and less complex due to buffer gas cooling as compared to conventional methods.
Examples concern the molecule first observed in space, CH + [2] but also ions which can play
an important role in the chemical development producing more complex species, e.g., C3H+
[3] and C3H2+ [4]. For many reasons H3+ is the corner stone in ion chemistry. It gives away its
proton to most other species. As a result, protonation of more complex species, like methanol,
could be another key towards the formation of complex organic species, molecules which areobserved with today’s telescopes but how they come into existence is under debate. We will
discuss the tools to record the spectra and to understand the relevant reactions in thelaboratory.
References
[1]
[2]
[3]
[4]

B.A. McGuire, O. Asvany, S. Brünken, and S. Schlemmer, Nature Review Physics (2020) 2, 402–410.
J.L. Doménech, P. Jusko, S. Schlemmer et al., Astrophys. J., 857, (2018)Art. No. 61.
S. Brünken, L. Kluge, A. Stoffels, et al., Astrophys. J., Lett., (2014) 783, Art. No. L4.
C.R. Markus, O. Asvany, T. Salomon et al. Phys. Rev. Lett. (2020) 124, 233401.

Formation of water ice clusters on graphite
Frederik Doktor S. Simonsen, Signe Kyrkjebø, Richard Balog and Liv Hornekær

Center for Interstellar Catalysis (InterCat) & Department of Physics and Astronomy, Aarhus University, Denmark

Prashant Srivastava and Karina Morgenstern

Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Germany

In cold regions of the interstellar medium (ISM) icy mantles may form on the surface of cold
dust grains and act as heterogeneous catalysts for the formation of complex organic molecules(COMs) [1].
In recent years the “onion model”, which describes icy mantles as thick layered structures ofpolar molecules underneath apolar molecules, has been challenged by several groups, e.g.
[2][3]. Arguments are made for partly ice-covered grains with exposed bare grain surfaces
which themselves are complex and porous structures, stressing the importance of the grain-ice
interface. The structure of the grains and their ices will likely impact the COM production as
diffusion, adsorption and possible reaction barrier characteristics are influenced [4].
Here we examine sub-monolayer water ice formation on highly oriented pyrolytic graphite(HOPG), using a low-temperature scanning tunnelling microscope (LT-STM) functioning at 5
K. Sub-monolayer amounts of water were deposited onto an HOPG surface kept at ≈ 40 K.
Presented in Figure 1 is an example of water ice clusters grown at 40 K via moleculardeposition on the HOPG surface. We argue for diffusion limited aggregation (DLA) [5]growth which is visible from the fractal structure of the clusters, both near step edges and forindividual nucleation sites.
DLA leads to low densities and an amorphous and porous structure which with growth may
form the reputed amorphous solid water of icy grain mantles.
Finally, water was deposited at varying surface temperatures, offering a unique look into nonheat-treated water ice clusters formed under slightly different, but controlled, conditions.

Figure 1: LT-STM image of water ice clusters on HOPG (4.5 V, 15 pA). The image shows a cluster on theterrasse of HOPG and aggregation of water along a step-edge on the HOPG surface.

References
[1]
[2]
[3]
[4]
[5]

Abplanalp, M. J., & Kaiser, R. I. (2019), PCCP 21(31), pp. 16949-16980
Rosu-Finsen, A., et al. (2016). PCCP 18(46), 31930-31935.
Potapov, A., Jäger, C., & Henning, T. (2020). PRL, 124(22), 221103.
Karssemeijer, L. J. et al. (2013), ApJ 781(1), 16
Witten Jr, T. A., & Sander, L. M. (1981), PRL 47(19), 1400

The measuring the formation of products from reaction at low temperatures using
chirped pulse Fourier transform spectroscopy in uniform flows
B. M. Hays, T. Guillaume, D. Gupta, I. R. Cooke, O. Abdelkader Khedaoui, M. Drissi, T. S.
Hearne and I. R. Sims
IPR (Institut de Physique de Rennes) - UMR 6251, Univ Rennes, F-35000 Rennes, France.
The formation of complex molecules in the interstellar medium often proceeds at very low
temperatures. Predicting the formation mechanisms of these molecules depends heavily on
experimental measurements of the rates of reaction at low temperatures. While experiments
are available to measure these rates at low temperatures using the CRESU (French acronym
for Reaction Kinetics in Uniform Supersonic Flow) technique, the products of these reactions
and their branching ratios are usually not measured. This leaves a large gap in astrochemical
kinetics databases concerning the product branching ratios of reactions.
The CPUF (Chirped Pulse in Uniform Flow) combines the revolutionary chirped pulse
Fourier spectroscopy technique with the CRESU environment, using rotational spectroscopy
to unambiguously identify the products of reaction at low temperatures. A new chirped pulse
Fourier transform millimeter wave spectrometer was adapted to continuous uniform flow
apparatus available in Rennes. The products of fast CN radical reactions with ethane andacetylene were directly observed in the uniform flow, showing proof of concept results fromthis instrument.
The Fourier transform spectra were heavily affected by the buffer gas used in the CRESU
technique in interesting ways. This provided a unique opportunity to explore intermolecular
dynamics between the buffer gas and other molecules, specifically the elastic and inelastic
scattering of these species. HCN and HNC spectra were compared in the low temperature He
environments, where the collisional excitation of these two molecules were found to be very
different, especially at low temperatures relevant to molecular clouds. Finally, the CPUF
apparatus was extended to sample the uniform flow using a newly developed secondary
expansion chamber, where the product branching ratios could be measured from reaction.
Future developments will allow for the CPUF technique to be extended to even colder
temperatures and more molecular systems.

Theory and Experiment for Elucidating Chemical Evolution in Space
C. Puzzarini1
1

Department of Chemistry “Giacomo Ciamician”, University of Bologna, Italy

Understanding the chemical evolution of the universe is one of the main aims of
Astrochemistry, with the starting point being the knowledge whether a molecule is present in
the astronomical environment under consideration and, if so, its abundance. In this context,
molecular spectroscopy plays the central role. The astronomical observation of thespectroscopic features of a given molecule is the definitive, unequivocal proof of its presencein the astronomical environment under consideration, with the overwhelming majority of gasphase chemical species being discovered via their rotational signatures.
Among the goals of astrochemistry, the detection of prebiotic COMs in astrophysicalenvironments is fundamental in view of possibly understanding the origin of life. While theevidence for molecular complexity in the universe is undisputed, there is still much to beunderstood about what prebiotic molecules are present and how they are formed in the
typically cold and (largely) collision free environment of the interstellar medium. By meansof selected examples, it will be shown that: (i) the interplay of experiment and theory in thefield of rotational spectroscopy is a powerful tool in astrochemistry [1-3]; (ii) state-of-the-art
computational approaches allow for deriving formation pathways able to explain themolecular abundances derived from astronomical observations [3-5]; (iii) a rationalization ofinterstellar chemistry in terms of class of reactions might be a feasible way [5].
References
[1]
[2]
[3]
[4]
[5]

C. Puzzarini & V. Barone, 2020, PCCP 22, 6507.
C. Puzzarini, 2020, Proc. IAU 15(S350), 65.
C. Puzzarini, 2020, Front. Astron. Space Sci. 7, 19.
C. Puzzarini et al., 2020, MNRAS 496, 4298.
J. Lupi, C. Puzzarini & V. Barone, 2020, ApJL 903, L35.

Glycolaldehyde Formation on Interstellar Water Ice Surfaces. A
Computational Quantum Chemical Approach
J. A. Luque-Urrutia, A. Rimola
1

Departament de Química, Universitat Autònoma de Barcelona, Spain

Astrochemists of diverse disciplines aim to unfold the intricate chemicalmechanisms that occur in space to get insight on one of the primordial questions
we have today: what is the origin of life? To evolve from dead chemical matter
into living beings, there are some essential chemical compounds that must bepresent for that to occur, such as amino acids [1] and complex sugars [2].
Focusing on sugars, glucose is one of the main targets. However, its presence
has not been confirmed in space while this is indeed the case of its closest
relative, glycolaldehyde (GLA, HOCH2CHO) [3]. In this contribution, we
present results dedicated to GLA formation on surfaces of interstellar water ice
adopting the formose reaction, 2·H2CO → GLA, and its radical derivation H2CO
+ CHO* + H* → GLA. Reactions in the gas phase (i.e., absence of water ice)have been used for a benchmarking study, in which CCSD(T) results werecompared with those obtained at the more approximated DFT theory level. With
the latter, calculations of the GLA formation reactions have been carried out oncluster models for water ice (see Figure 1), in which the energy features of thereactions (i.e., reaction energy and activation energies) are provided.
Additionally, simulations also help us to understand the role of the ice surface
in this synthetic route.

Figure 1: Glycolaldehyde formation by reaction of HCO with H2CO followed by H addition
simulated on a cluster model mimicking the surfaces of interstellar of water ice.
[1] Ehrenfreund, P.; Charnley, S. B. 2000 ARA&A 38, p. 427-83.
[2] Woods, P.M.; Slater, B.; Raza, Z.; Viti, S.; Brown, W.A.; Burke, D.J. 2013 ApJ, 777, p. 90.
[3] Jørgensen J.K.; Favre, C.; Bisschop, S.E.; Bourke, T.L.; Dishoek, E.F.; Schmalz, M. 2012
ApJL 757 L4.

Cold chemistry in hot cores:
Non-diffusive grain-surface chemistry and its role in forming complex organic moleculesin star-forming regions
R. T. Garrod,1,2 M. Jin,1 and E. Herbst1,2
1
2

Department of Chemistry, University of Virginia, USA
Department of Astronomy, University of Virginia, USA

Reactions on dust-grain surfaces are responsible for the production of many importantinterstellar molecules, including gas-phase H2, grain-surface ice species such as water,
ammonia and methanol, and arguably some of the most complex molecules detected in starforming regions. However, our view of the temperature dependence of this chemistry has
recently been changing. A major driver in this shift is the gas-phase detection of complex
organic molecules (COMs) such as methyl formate in cold pre-stellar cores. These detections
have pushed back the astronomical clock on COM production, to a time much earlier than thewarm proto-stellar stage in which they are usually detected (albeit in much greater abundance).
Experimental evidence also suggests that COMs may be formed on very cold surfaces (~10K), through mechanisms that do not require thermal diffusion of the reactants. Past models
that rely solely on diffusive reaction mechanisms now appear inadequate.
I will discuss new modeling treatments [1,2] that adopt a more comprehensive framework forgrain-surface and ice-mantle chemistry, allowing reactants to meet in a variety of ways that do
not rely solely on diffusion. This allows COMs to form as the ice mantles grow, while
processing of the ices by external and cosmic-ray-induced UV fields can also lead to COM
production. The period when the water-dominated ices desorb from the grains (Fig. 1, dashedlines) also allows trapped radicals to meet and react on the warm ice surfaces, prior todesorption. Gas-phase chemistry can further enhance COM production in some cases. In
combination, these processes allow COMs to form over a range of temperatures, through avariety of mechanisms. I will discuss the implications of this new picture of COM chemistry.

Figure 1: Net rates (arb. units) of molecular formation/destruction (green/blue), summed over all chemicalphases (gas + surface + ice), from the collapse of a cold core through its evolution to a hot molecular core.

References[1][2]

M. Jin & R. T. Garrod, ApJS, 249, 26
R. T. Garrod et al., ApJS (accepted), https://arxiv.org/abs/2110.09743

Icy grains are not spherical nor ellipsoidal
M. Tsuge,1 A. Kouchi,1 T. Hama,2 Y. Oba,1 S. Okuzumi,3 S.-i. Sirono,4 M. Momose,5
N. Nakatani,6 K. Furuya,7 T. Shimonishi,8 T. Yamazaki,1 H. Hidaka,1 Y. Kimura,1K.-i. Murata,1 S. Tachibana,9 and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University Japan
2
Komaba Institute for Science, The University of Tokyo, Japan3
Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Japan
4
Earth and Environmental Sciences, Nagoya University, Japan, Japan
5
College of Science, Ibaraki University, Japan
6
Department of Chemistry, Tokyo Metropolitan University, Japan
7
National Astronomical Observatory of Japan, Japan
8
Center for Transdisciplinary Research, Niigata University, Japan
9
UTokyo Organization for Planetary and Space Science, The University of Tokyo, Japan
In the astrochemical community, it has been assumed, without experimental validations, thatices on grains in molecular clouds and proto-planetary disks are formed by homogeneous
layers regardless of their composition or crystallinity (Figure 1A). To verify this assumption,
we investigated the H2O deposition onto refractory substrates and the crystallization of
amorphous ices (H2O, CO2, and CO) using an ultra-high-vacuum transmission electron
microscope [1]. Upon heating the samples deposited at 10 K, which are uniform layer ofamorphous H2O (a-H2O) on refractory substrates, amorphous CO on a-H2O, and amorphous
CO2 on a-H2O, we found that the uniform thin films of a-H2O and amorphous CO became
three-dimensional islands of polyhedral crystals while amorphous CO2 became a thin film of
nano-crystalline CO2 covering a-H2O. Our observations indicate that crystal morphologies
greatly depend on not only the ice composition but also the substrate material. Using
experimental data and the crystallization timescale of amorphous ices, we conclude that icy
grains in molecular clouds and proto-planetary disks are not spherical nor ellipsoidal; in
molecular clouds, a-H2O covered the refractory grain uniformly, CO2 nano-crystals wereembedded in a-H2O, and a polyhedral CO crystal was attached to a-H2O at temperatures as
low as 10 K (Figure 1B); in proto-planetary disks, one thin CO2 I crystal on a-H2O (1C) or
one ice I crystal on organics (1D). Important implications for the chemical evolution ofmolecules, non-thermal desorption, collision of icy grains, and sintering will be presented.

Figure 1: The schematic of icy grains (cross-section): (A) spherical onion-like grain as hitherto assumed,(B) in molecular clouds (T ~10 K), (C) in proto-planetary disks (T > 32 K), and (D) in proto-planetary disks(T > 88 K). Respective colors show the chemical compositions: red—core; yellow—refractory material;
green—CO2; light blue—a-H2O; dark blue—CO.

Reference[1]

Kouchi, A., Tsuge, M., Hama, T., et al. 2021, ApJ, 918, 45

Chemistry of Embedded Disks in Perseus: Prevalent Complex Organic Molecules andShock-excited Sulfur-bearing Molecules
Y.-L. Yang1, Z. Zhang2, and N. Sakai2
1

2

Department of Astronomy, University of Virginia, USAStar and Planet Formation Laboratory, Center for Pioneering Research, RIKEN, Japan

In recent years, observations discover several embedded protostars that have developed
complex organic chemistry in the disk-forming region. Recent observations also show potential
signs of planet formation in these young disks, hinting at a stronger chemical link between the
protostellar cores and planetary systems. While observations start to find rich spectra of COMsin embedded protostars, only a few observations attempt to statistically constrain theabundances of COMs at embedded protostars and their relationships to star formation
processes. With the PEACHES survey, an unbiased chemistry survey of embedded protostars
in the Perseus molecular cloud, we have begun to systematically characterize the COMs in the
disk-forming regions[1] in addition to simple molecules, such as SO and SO2[2]. The majorityof young protostars in Perseus have COMs. For the COM-rich protostars, their column densities
of COMs correlate between species, hinting at similar chemistry for the protostars in Perseus.
Particularly, the abundance of CH3OH tightly correlates with that of CH3CN (Figure 1 left);however, a direct chemical link between these two molecules has not been firmly
established. Protostellar properties, such as bolometric luminosity and bolometric temperature,
have little impact on the occurrence of COMs. While emission of COMs concentrates on theembedded disk or the inner envelope, the emission of SO and SO2 appears asymmetric in a few
sources. I will discuss the origin of these asymmetry which serendipitously corresponds tomajor changes of polarization near the edge of disks (Figure 1 right). I will also discuss ourplan to understand the origin of COMs using JWST, which is accepted to the Cycle 1 GO
program.

Figure 1: Left: The normalized column density correlation between CH3OH and CH3CN in the PEACHES
sample. Right: The SO2 emission of Per-ebb 50 compared to the linear polarization fraction. The white line
indicates the disk direction, while the red and blue arrows show the outflow direction.

References[1] Y.-L. Yang, N. Sakai, Y. Zhang, et al., 2021, ApJ, 910, 20.
[2] Z. Zhang, Y.-L. Yang, Y. Zhang, et al. 2021, in prep.

Formation, Abundance Distribution and Evolution of Complex Organic Molecules inStarless/Pre-stellar Cores
Izaskun Jimenez-Serra1, Anton I. Vasyunin2, Andres Megias-Toledano1, Silvia Spezzano3,
Paola Caselli3, Giuliana Cosentino4, and Serena Viti5
1

Centro de Astrobiologia (CSIC-INTA), Ctra. de Torrejon a Ajalvir km 4, 28850, Torrejon deArdoz, Spain
2
3

Ural Federal University, Kuybysheva st. 48, 620002, Ekaterinburg, Russian Federation

Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748, Garching,
Germany
45Chalmers University of Technology, SE41296, Gothenburg, Sweden

University of Leiden, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands

Observations carried out toward starless and pre-stellar cores have revealed that complex
organic molecules (COMs) are prevalent in these objects (Vastel et al. 2014; Jimenez-Serra etal. 2019; Scibelli et al. 2020). However, it remains unclear what chemical processes are
involved in COM formation and at what stage in dense core evolution complex organics form.
In this contribution, we will present high-sensitivity observations carried out toward theL1517B and L1498 starless cores. These cores are believed to be at earlier evolutionary stages
than the well-known L1544 pre-stellar core, also studied in COM emission by our group.
Similarly to what we found in L1544, small O-bearing molecules and N-bearing species areenhanced by factors ∼4-14 toward the outer shells of L1498 and L1517B. However, unlike
L1544, large O-bearing COMs such as CH3CHO, CH3OCH3 or CH3OCHO are not detected
within our sensitivity limits - comparable to the ones obtained for L1544. Surprisingly, Nbearing organics are more abundant toward the outer shells of L1498 and L1517B than in
L1544. We have carried out a detailed modelling of the formation of O-bearing and N-bearing
COMs in L1498 and L1517B following the model of Vasyunin et al. (2017), which considers
both the chemical reactive desorption of COM precursors and their subsequent gas-phasechemistry yielding COMs. The distribution of the COM abundances predicted for L1498 andL1517B nicely matches our observations for both O-bearing and N-bearing COMs in thesecores, and reveal that the differences observed between the complex organic content in L1498,
L1517B and L1544 are due to the different physical structure of these cores, which in turn is aconsequence of their evolution. From our results we conclude that while N-bearing COMs
form early in dense core evolution, O-bearing COMs form at a later stage when enough CO
has catastrophically depleted onto the surface of dust grains. These results have been
published recently in Jimenez-Serra et al. (2021).
References
[1]
[2]
[3]
[4]

Vastel, C., Ceccarelli, C., Lefloch, B., & Bachiller, R. ApJ, 2014, 795L, 2V
Jimenez-Serra, I., et al. ApJ, 2016, 830L, 6J
Scibelli & Shirley, ApJ, 2020, 891, 73S
Jimenez-Serra, I., et al. ApJ, 2021, 917, 44J

Formation of phosphorus monoxide (PO) in the interstellar medium: insights fromquantum-chemical and kinetic calculations
J. García de la Concepción,1 Cristina Puzzarini,2 Vincenzo Barone3, Izaskun Jiménez-Serra1
and Octavio Roncero.4
1
Centro de Astrobiologia (CSIC-INTA), Ctra. de Ajalvir Km. 4, Torrej´on de Ardoz, 28850
Madrid, Spain
2
Department of Chemistry “Giacomo Ciamician”, University of Bologna, Via F. Selmi 2,
Bologna, 40126, Italy
3
Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa, 56126, Italy
4
Instituto de F´ısica Fundamental (IFF), C.S.I.C., Serrano 123, 28006 Madrid, Spain
In recent years, phosphorus monoxide (PO) –an important molecule for prebiotic chemistry–has been detected in star-forming regions and in the comet 67P/Churyumov-Gerasimenko [1].
These studies have revealed that, in the interstellar medium, PO is systematically the mostabundant P-bearing species, with abundances that are ∼1-3 times greater than those derived
for phosphorus nitride (PN), the second most abundant P-containing molecule. The reason
why PO is more abundant than PN remains still unclear. Experimental studies withphosphorus in the gas phase are not available. Therefore, the reactivity of atomic phosphorus
needs to be investigated using reliable computational tools. To this end, state-of-the-art
quantum-chemical computations have been employed to evaluate accurate reaction rates andbranching ratios for the P + OH → PO + H and P + H2O → PO + H2 reactions in theframework of a master equation approach based on ab-initio transition state theory. While thereaction of atomic phosphorus in its ground state with water is not a relevant source of PO
because of emerged energy barriers, the P + OH reaction represents an important formationroute of PO in the interstellar medium[2].

Figure 1. Singlet (blue profile) and triplet (red profile) potential energy surfaces (ZPE-corrected energies)
for the formation of PO from OH + P

References[1]
K. Altwegg et al. 2016, Sci Adv, 2:e1600285.
[2]
J. García de la Concepción, C. Puzzarini, V. Barone, I. Jiménez-Serra & O. Roncero. 2021, ApJ,
arXiv:2108.08530 [astro-ph.GA].

A systematic computational study of radical—radical reactions on interstellar ice
surfaces
J. Enrique-Romero,1,2 A. Rimola,2 and C. Ceccarelli1
1Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble(IPAG), 38000 Grenoble, France
2Departament de Química, Universitat Autònoma de Barcelona, Bellaterra, 08193,
Catalonia, Spain

Understanding how insterstellar complex organic molecules (iCOMs) are formed anddestroyed is of high importance to predict the ultimate organic complexity reached in theinterstellar medium (ISM) ([1], [2]). Two paradigms are invoked in the literature. Both argue
that simple molecules and atoms are hydrogenated on the interstellar grain surfaces during thecold prestellar phase. Following this first step, one paradigm assumes that iCOMs appear as aresult of gas-phase chemical processes, whereas the other predicts that radical-radical
reactivity on the grain surfaces is the major responsible for the observed chemical complexity.
The latter has profited of much popularity among astrochemical models in the last years, eventhough some basic assumptions of the paradigm are still a topic of debate. Among them, theradical-radical reactivity assumption, which is extremely difficult to quantify experimentally.
We propose a complementary and, sometimes, alternative method: theoretical quantum
chemical calculations, which can provide a precious atomistic perspective from which to
study such processes (e.g. [3], [4], [5]).
In this contribution, we present our recent systematic quantum chemical study on the surface
reactivity of several radical pairs. Some of the studied systems are CH3 + X and HCO + X (X
= CH3, HCO, NH2, CH2OH and CH3O). According to observational evidences, the icy
mantles that cover interstellar dust grains are dominated by water ([6]). We, therefore, use twocluster-like ice models consisting on 18 and 33 water molecules to simulate the grain surface
where the radical-radical reaction occurs. We then study the reactivity of the above biradical
systems by means of static quantum chemical calculations to obtain the potential energy
surfaces of several complex species and the approximate efficiency of the different reaction
product channels. We found that many reactions leading to iCOMs have non negligible
activation barriers and that the transfer of a hydrogen atom from a radical acting as a donnor
to its partner, acting as an acceptor are important competitive processes. The occurrence of
one process or the other could entirely depend on the relative orientation of the radicals upon
encounter, namely on the water ice structure and interaction with the two radicals. These
results indicate that the fraction of iCOMs generated in the current astrochemical models iscertainly overestimated since (i) it is assumed that reactions always occur and (ii) thecompetitive reactions are not included.
References
[1]
[2]
[3]
[4]
[5]
[6]

E. Herbst. & E. F. Van Dishoeck, 2009, ARA&A 47, p. 427-480
C. Ceccarelli, S. Viti, N. Balucani, et al., 2018, MNRAS 476(1), p. 1371-1383.
A. Rimola, D. Skouteris, N. Balucani, et al., 2018, ACS Earth and Space Chemistry 2(7), 720-734.
J. Enrique-Romero, A. Rimola, C. Ceccarelli, et al., 2019, ACS Earth Space Chem. 3(10), p. 2158-2170
J. Enrique-Romero, C. Ceccarelli, A. Rimola, et al., 2021, A&A (in press).
A. A. Boogert, P. A. Gerakines, & D. C. Whittet, 2015, ARA&A 53, p. 541-581.

P35

The thickness and UV absorption effect on UV photolysis of CH4 ice
Ni-En Sie, 1 Yi-Xiang Peng,1 Ying-Hsuan Chen,1 Jr-Yao Lee,1 Chun-Yi Lee,1
Chao-Hui Huang,1 and Yu-Jung Chen1
1

Department of Physics, National Central University, Taiwan

The secondary UV light induced by cosmic rays has been seen as a dominant energetic source
impinging on the ice mantles in the region of cold dense clouds and interstellar medium(ISM), contributing to the photodesorption of solid molecules. Among the ice mantle, CH4 is
one of the most abundant ice observed, and the UV irradiation of CH4 ice is widely interesting.
The UV emission spectra of microwave-discharged hydrogen-flow lamp (MDHL) generated
in the laboratory has an analogous profile as the simulated one[1, 2]. In addition, theconfiguration of MDHL is influential on the photodepletion and photodesorption[3, 4], andthis effect is molecule dependent since the absorption cross-section should be considered. The
Ly-α (121.6 nm) photon plays a vital role in MDHL spectra, and the CH4 ice also has a largest
absorption around at Ly-α in the range of 114-170 nm. As long as the ice thickness becomes
thicker, the absorption ratio increases but saturates at a certain thickness.
In this study, we investigate the photodepletion as well as photodesorption in threecharacteristic topics: thickness effect, light effect, and deposition temperature effect. We
performed three different configurations of MDHL to investigate the destruction cross-sectionof CH4 as a function of thickness from 50 to 400 ML (1 ML = 1015 molecules cm–2), and thecontribution from Ly-α line and H2 emission band are defined. The depletion seems to be
thickness dependent, but if we calculate the absorbed photons rather than incident photons,
the destruction cross-section in different MDHL configurations have a great similarity. The
photodesorption is also independent of the ice thickness, confirming that the process happensin the top layers.

Figure 1: The MDHL spectra of 3 configurations and the absorption cross-section of solid CH4.

References

1.
2.
3.
4.

[1]
[2]
[3]
[4]

Gredel, R., et al., ApJ, 1989. 347: p. 289-293.
Cruz-Diaz, G.A., et al., A&A, 2014. 562: p. A120.
Chen, Y.-J., et al., ApJ, 2014. 781: p. 15.
Sie, N.-E., et al., ApJ, 2019. 874(1): p. 35.

Theoretical study of adsorption energies of molecules oninterstellar ice surfaces
D. Duflot1, M. Monnerville1, C. Toubin1

1 Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molcules,
F-59000 Lille, France

The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH,
H2O, CH3, NH3) on hexagonal crystalline and amorphous ice clusters were obtained via
classical molecular dynamics and electronic structure methods. The geometry and binding
energies were calculated using a QMHigh:QMLow hybrid method on model clusters. Moreaccurate binding energies were also refined via single point Coupled Cluster calculations.
Most species, except carbon atom, physisorb on the surface, leading to rather small binding
energies. Amorphous ices are characterized by slightly stronger binding energies than the
crystalline phase. A major result of this work is to also access the dispersion of the binding
energies since a variety of adsorption sites is explored. The interaction energies thus obtained
may serve to feed or refine astrochemical model. The present methodology could be easily
extended to other types of surfaces and larger adsorbates.

Figure 1 : NH3 adsorption optimized geometry on ice surface

References[1] Duflot D., Toubin C., Monnerville M., Front. Astron. Space Sci., 8 (2021) 24.

Carbon atom addition reactions in interstellar ices:
How to marry laboratory and computational chemistry
T. Lamberts1,2 and collaborators
1

Theoretical Chemistry, Leiden Institute of Chemistry, Leiden University, The Netherlands
2
Leiden Observatory, Leiden University, The Netherlands

I will focus on surface reactions of carbon atoms on amorphous solid water (ASW) ices,
mimicking the icy mantle covering the micron-sized dust grains in the interstellar medium. In
the translucent stage of a molecular cloud, carbon is predominantly present in its atomic form
C(3P0) [1] and even in dense regions it is likely more abundant than typically thought [2,3].
Moreover, already in 2001 carbon atoms additions have been proposed to lead to the formationof complex organics [4]. Therefore, a carbon atom beam source was installed at the Leiden
Laboratory for Astrophysics [5], successfully demonstrating that methane can be formed fromexperiments of C + H on ASW [6]. In this talk I will discuss three new projects:
1. The interaction of atomic carbon with water has been extensively studied, bothexperimentally and theoretically [e.g., 7, 8], but particularly puzzling is the different
chemical behaviour in the gas phase versus in condensed phases. I will provide a
detailed explanation of the formation of formaldehyde from carbon atoms withamorphous solid water within a theoretical framework, supported by tailoredexperiments [9].
2. I will touch upon the reactions of carbon atoms with molecular hydrogen and show thatan intricate interplay of reactions can lead to the formation of methane, even when H
atoms are not present. I will discuss this both from an experimental and computational
point-of-view and link the various intermediates to other recent studies [10].
3. Finally, I will show that the reactivity with H2 and H2O does not restrict the formationof complex organics, and in fact the reaction between C and CO occurs so rapidly thatketene and acetaldehyde can be formed in the presence of H atoms [11].
References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]

Van Dishoeck and Black, 1988, ApJ 334, 771
M.G. Burton et al., 2015, ApJ 811, 13
Bisbas et al., 2019, MNRAS 485, 3097
Charnley et al., 2001 SAA, 57, 685
Qasim et al., 2020, RSI 91, 054501
Qasim et al., 2020 NatAs 4, 781
Schreiner et al., 2006, CPC 7, 880
Shimonishi et al., 2018 ApJ 855, 27
Molpeceres et al., 2021 JPCL subm.
Lamberts et al., 2021 ApJ subm.
Fedoseev et al., 2021 ApJ subm.

Application of the Tight Binding GFN2-xTB Method to Model Large Interstellar
Amorphous Icy Grains
A. Germain,1 L. Tinacci,2 C. Ceccarelli2 and P. Ugliengo1
1

Dip. Di Chimica, Università degli studi di Torino, Italy
2
CNRS (IPAG), Université de Grenoble, France

Interstellar grains are made of a silicate core covered by a mantle of several layers ofamorphous ice. In the gas-phase of dense molecular clouds chemical species freeze onto thegrain and can diffuse on its surface, react to give interstellar more complex molecules andultimately desorb back to the gas-phase. Hence, the study of interstellar grains is an importantpart for understanding the chemical evolution in time of the Interstellar Medium (ISM). Thereis still no consensus in the Astrochemistry community on how to model these icy grains at
atomistic level with the requisite of treating the hydrogen bond interaction and otherimportant components accurately. Furthermore, the grain should be large enough to be
representative of the variability present in the ISM, which renders impractical the adoption ofplain DFT methods. Also, the adopted method should, not only be relatively fast, but also
applicable to study the interaction of large interstellar molecules with the grain itself. Force
fields are not the proper solution, due to the parametrization specific for each considered
species, breaking the universality of the approach. To fill in the above requested, we resort toa newly developed semi-empirical quantum mechanical method based on the tight binding
DFT approach called GFN2-xTB1 and a universal force field method called GFN-FF2, bothdeveloped by the Grimme’s group at the Bonn University. We present the methodology tobuild a water cluster model up to 1000 H2O molecules and to characterize its structural andelectrostatic potential surface (EPS) as a free grain (Fig. 1). Then, NH3 was chosen as
relevant interstellar molecule to compute its binding energy (BE) at more than 150 different
grain sites to characterize the BE distribution which revealed a bimodal distribution.

a)b)

Figure 1: a) Structure and b) EPS of the GFN2-xTB water cluster model (1000 H2O)

References[1][2]

C. Bannwarth, S. Ehlert, S. Grimme, J. Chem. Theory Comput. 2019, 15, 1652-1671
S. Spicher, S. Grimme, Angew. Chem. Int. Ed. 2020, 59, 15665-15673

The energy dissipation process of hydrogenation reactions of atomic nitrogen on water
ice surfaces
S. Ferrero,1 S. Pantaleone,2 P. Ugliengo2, M. Sodupe1 and A. Rimola1
1

Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia,
Spain
2
Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria 7, 10125, Torino,
Italy

In the colder (10-20K) regions of interstellar medium, the icy surfaces of interstellar grains
serve as solid state supports for chemical reactions[1][2]. Among the plausible roles of thesesurfaces, that of third body is advocated, in which the formation energy of surface reactions
can be dissipated among the grain causing the stabilization of the product[3]. This energy
dissipation process is poorly understood at the atomic scale and it can have a tremendous
impact on astrochemical surface processes like chemical desorption and diffusion[4][5].
In this work, we studied the formation of NH3 via successive H-addition to atomic nitrogen on
crystalline and amorphous ice surfaces. We first characterized the potential energy surfaces of
the hydrogenation reactions and possible competitive processes (i.e., H abstractions) using
static quantum chemical calculations. Subsequently, the partitioning of the nascent energy
released by the hydrogenation reactions between the newly formed species and the surface has
been elucidated by means of ab initio molecular dynamics (AIMD) simulations.
Results indicate that the H-additions on N are largely favorable reactions at 10 K, being
barrierless and exhibiting large negative reaction energies, as opposed to the competitive Habstractions, which are either endothermic or present high activation energies. AIMD
simulations show that such favorable nascent energies are, in large part, quickly absorbed by
the ice surfaces and their dissipation can be accelerated by mechanisms involving an H
exchange between the surface and the newly formed species (Figure 1).

Figure 1: H3O(+) NH2(-) complex formation on an amorphous ice surface.

References
[1]
[2]
[3]
[4]
[5]

A. Potapov.& M. McCoustra, 2021, Int Rev Phys Chem, 40(2), 299-364 .
G. Vidali 2013 Chem Rev 113(12), 8762–8782 .
T. Hama & N. Watanabe 2013 Chem Rev 113(12), 8783-8839 .
S. Pantaleone et al. 2020 ApJ 897, 56 .
S. Pantaleone et al. 2021 ApJ 917, 49 .

Photon Stimulated Desorption from interstellar ice analogs: recent results usingsynchrotron radiation.
J.-H. Fillion,1 R. Dupuy,1R. Basalgète,1 G. Féraud,1 C. Romanzin,2 L. Philippe,1 T. Putaud,1 V.
Baglin,3 R. Cimino,4 X. Michaut,1 and M. Bertin1
1

Sorbonne Université, Observatoire de Paris, Université PSL, CNRS-LERMA, Paris, France
2
Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, Orsay, France
3
CERN, Genève, Switzerland
4
Laboratori Nazionali di Frascati (LNF)-INFN, Frascati, Italy

Photon Stimulated Desorption (PSD) processes play a key role in the exchanges between thegas and solid phases of cold regions of the interstellar medium, where a lot of molecules are
expected to freeze out on dust grains with the temperature forbidding their thermal escape.
These processes have been used to explained otherwise puzzling gas phase observations ofsimple molecules like CO in dense cores or cold H2O in outer parts of protoplanetary disks.
They are also invoked as ways to get complex organic molecules (COMs) presumably formedon grains into the gas phase. Second, photon-induced desorption of residual molecules
adsorbed on the cryogenic parts of accelerators such as the LHC can be a limiting factor for
their vacuum performances. Desorption rates and mechanisms, especially in the submonolayer regime, can therefore be of particular interest in this case.
I will present an approach to study PSD of condensed films of molecules of astrophysicalinterest at cryogenic temperatures, using synchrotron radiation. Recent results obtained in the
VUV and soft X-ray ranges will be presented. In the VUV, we will focus on the PSD from
Amorphous Solid Water (ASW) and discuss experimental results evidencing two major
desorption mechanisms [1], [2]. Quantitative desorption yields from acetonitrile CH3CN inpure and mixed samples will be also presented [3]. In the soft X-ray range, results obtained at
the K-edge of Oxygen atoms will be discussed in the context of protoplanetary disks, first in
the case of pure H2O [4], CO [5], CH3OH [6] samples and secondly in the case H2O-rich andCO-rich samples containing CH3OH [7].
References[1]
J.-H Fillion, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, T. Putaud, V. Baglin, R. Cimino, P. MarieJeanne, P Jeseck, X. Michaut & M. Bertin. ACS : Earth and Space Chemistry, 2021 under review[2]
R. Dupuy; M. Bertin, G. Féraud, X. Michaut, P. Marie-Jeanne, P. Jeseck, L. Philippe, V. Baglin, R.
Cimino, C. Romanzin, J.-H. Fillion, PRL 2021, 126, 156001.
[3]
R. Basalgete , A. Jesus Ocana , G. Féraud , C. Romanzin, L. Philippe ,X. Michaut , J.-H. Fillion & M.
Bertin APJ, 2021, ApJ accepted for publication.
[4]
R. Dupuy, M. Bertin, G. Féraud, M. Hassenfratz, X. Michaut, T. Putaud, L. Philippe, P. Jeseck, M.
Angelucci, R. Cimino, V. Baglin, C. Romanzin & J.-H. Fillion, Nature Astronomy 2018, 2, 796.
[5]
R. Dupuy, M. Bertin, G. Féraud, C. Romanzin, T. Putaud, L. Philippe, X. Michaut, P. Jeseck, R. Cimino,
V. Baglin & J.-H. Fillion, 2021 PCCP, 23, 15965[6]
R. Basalgète, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, X. Michaut, J. Michoud, L. Amiaud,
A. Lafosse, J.-H. Fillion & M. Bertin, 2021 A&A 647, A35[7]
R. Basalgète, R. Dupuy, G. Féraud, C. Romanzin, L. Philippe, X. Michaut, J. Michoud, L. Amiaud,
A. Lafosse, J.-H. Fillion & M. Bertin, 2021 A&A 647, A36

Non-thermal desorption of ice mantles:
cosmic rays desorption of complex organic molecules
E. Dartois1, M. Chabot2, V. Wakelam3, H. Rothard4, P. Boduch4, A. Domaracka4, B. Augé5, J.
Rojas2
1
Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Saclay, 91405 Orsay(France)
2
IJCLab, CNRS/IN2P3, Université Paris-Saclay, 91405 Orsay (France)
3
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, 33615 Pessac, (France)
4
CIMAP-CIRIL-GANIL, Normandie Université, ENSICAEN, UNICAEN, CEA, CNRS, 14000
Caen (France)
5
IPAG,CNRS, Université Grenoble Alpes, 38000 Grenoble (France)
Determining experimentally the magnitude of interstellar grain mantles accretion anddesorption mechanisms is mandatory for astrophysical models to constrain and predict gas
and solid phase chemical evolutions. Irradiation by cosmic rays have been simulated
experimentally using high energy ions. The ice mantles phase transformation and sputtering
yields for released species were monitored simultaneously by infrared spectroscopy and mass
spectrometry. The dominant ice mantle species, can be effciently sputtered by cosmic rays. In
this talk, the sputtering yield and its evolution as a function of ice mantle thickness for highenergy ions will be discussed in the context of astrophysical environments. Cosmic rays
penetrating deep into dense clouds provide a major sputtering mechanism to desorb theobserved complex organic molecules (COMs) built over the lifetime of dense clouds, whenmany other mechanisms fail at releasing them effciently from cold grains. We focused ourstudy on the sputtering effciency of two complex organic molecules that are observed either ininterstellar dense clouds ice mantles directly by infrared spectroscopy (CH3OH), or observedin the gas phase by millimetre telescopes (CH3COOCH3). The sputtering was measured for
different ice matrices dominated by water ice or carbon dioxide ices.
A large fraction of COMs desorbs as intact molecules with a proportion corresponding to thetime dependent bulk composition of the ice mantles, the latter evolving with time due to thesecondary photons VUV photolysis and CR ice mantle radiolysis. The astrophysical cases inrelation with these experiments will be discussed.
References[1] Dartois, E., Chabot, M., Bacmann, A. et al., accepted in Astronomy and Astrophysics. (2020).
[2] Dartois, E., Chabot, M., Id Barkach, T., et al., Astronomy & Astrophysics, 627, A55 (2019).
[3] Dartois, E., Chabot, M., Id Barkach, T., et al., Astronomy & Astrophysics, 618, A173 (2018).
[4] Dartois, E., Augé, B., Rothard, H. et al. NIMB, 365, 472 (2015).
[5] Mejia, C., de Barros, A. L. F., Seperuelo Duarte, E. et al., Icarus , 250, 222 (2015).
[6] Dartois, E., Augé, B., Boduch, P. et al., Astronomy and Astrophysics, 576, A125 (2015).
[7] Dartois, E., Ding, J. J., de Barros, A. L. F. et al., Astronomy and Astrophysics, 557, A97 (2013).

Quantifying the chemical desorption of H2S and PH3from water ice surface
K. Furuya,1 Y. Oba,2 and T. Shimonishi31

National Astronomical Observatory of Japan
Institute of Low Temperature Science, Hokkaido University
3
Center for Transdisciplinary Research, Niigata University2

Non-thermal desorption of molecules from icy grain surfaces is required to explain molecularline observations in the cold gas of star-forming regions [1]. Chemical desorption is one of the
non-thermal desorption processes, and is caused by the energy released by chemical reactions;after an exothermic surface reaction, the part of excess energy goes into products' translationalenergy in perpendicular direction to the surface, leading to desorption. The desorption
probability of product species, especially from water ice surfaces, is not well determined. This
limits our understanding of the interplay between gas-phase and ice surface chemistry.
In this work, we constrained the desorption probability of H2S and PH3 per reaction event on
porous amorphous solid water (ASW) by numerically simulating previous laboratory
experiments of chemical desorption [2,3]. Adopting the microscopic kinetic Monte-Carlo
method, we found that the desorption probability of H2S and PH3 from porous ASW perhydrogen addition event of the precursor species are 3±1.5 % and 4±2 %, respectively.
These probabilities are consistent with a theoretical model of chemical desorption in theliterature, if around 7 % of energy released by the reactions goes into the translational
excitation of the products. As a bi-product, we also found that around 70 % (40 %) ofadsorption sites for atomic H on porous ASW should have the binding energy lower than~300 K (~200 K).

Figure 1: Total abundance of H2S and HS on porous ASW normalized by the initial H2S abundance asfunctions of the H atom exposure time in our best-fit model. Square symbols indicate the experiments by[2] and [3].

References
[1]
[2]
[3]

R. T. Garrod, R. V. Wakelam, & E. Herbst, 2007, A&A, 467, 1103
H. Oba, T. Tomaru, A. Kouchi, & N. Watanabe, 2019, ApJ, 874, 124
T. Nguyen, Y. Oba, T. Shimonishi, A. Kouchi, & N. Watanabe, 2020, ApJL, 898, L52

The role of UV photolysis and thermal processing in interstellar ice chemistry
Susanna Widicus Weaver,1 Katarina Yocum, Perry Gerakines, and Stefanie Milam
1

Department of Chemistry, University of Wisconsin-Madison, USA

It has been shown through both laboratory and observational studies that direct and cosmicray induced UV photodissociation drives a complex network of chemistry in interstellar ices.
Astrochemical models have demonstrated that gradual heating of these UV-processed icesduring star formation can lead to a wide variety of complex organic molecules. Additionalmodeling and observational studies have shown that these molecules are likely incorporated
into protoplanetary disks and participate in the chemistry of planet formation. These
processes could therefore serve as molecular starting points for prebiotic chemistry in theuniverse. Our observations of the chemistry of star-forming regions have shown that there is
wide variation in the chemical compositions of hot cores, and that methanol photodissociation
on icy grains may be the key process feeding the formation of larger prebiotic molecules. To
test possible chemical routes in interstellar ices, we have built a novel laboratory experimentthat couples the traditional tools of ice studies – FTIR spectroscopy and mass spectrometry –with the structure specificity of rotational spectroscopy. Such measurements can provide the“ground truth” to guide observations of star- and planet-forming zones. In this talk I will
present both the observational and laboratory studies and discuss these results in the context
of prebiotic astrochemistry.

Water-promoted formation of methyl formate from methanol via methoxymethanolon iceA. Ishibashi,1 H. Hidaka,1 Y. Oba,1 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science/Hokkaido University, Japan

Methyl formate (MF; HCOOCH3) is abundantly found in various astronomical objects,
including cold molecular clouds [1]. Because of a good correlation with MF in observations,methanol, which is a primordial organic molecule on interstellar dust, is thought to be parent
molecule. However, the results of laboratory experiments on the photolysis of pure methanol
solid did not to explain the MF abundances astronomically observed [2, 3]. Recently, laboratory
observation of ice dust analogue indicated that methanol would contact water ice at the dust
surface rather than being as pure solid [4]. Therefore, the effect of H2O on the MF formation
should be considered as well as the photolysis of methanol. To study the details of the MF
formation mechanism, small amounts of products and those radical precursors on the ice surface
need to be monitored, which is difficult with conventional methods, such as FT-IR. Therefore,
we newly developed highly sensitive nondestructive detection method, so-called Cs+ ion
pickup method [5], to monitor products and radicals, and performed the experiments for thephotolysis of methanol (0.3 ML) on ice [6].
Analysis of the reaction products from the photolysis showed the formation of
methoxymethanol (MM; CH3OCH2OH) and MF as the main components. This result wasdifferent from the UV photolysis of pure methanol solids, in which CH2OH-derived molecules
such as ethylene glycol (EG; HOCH2CH2OH) and ethanol were mainly produced. This MF
generation is well consistent with cosmic MF observations. To clarify the reaction process of
MM and MF, the irradiation time dependence of the signal intensities of trace reaction products
such as CH3O and/or CH2OH, MM, MF, and OH was measured (Figure 1). A sequential
behavior such as CH3OH → CH3O and/or CH2OH → MM → MF was observed, indicating
found that MF was efficiently generated by photodissociation of MM. In addition, from the factthat MM is the main product on ice among the C2H6O2 isomers, it is considered that theformation of CH3O was promoted by the abstraction reaction from methanol by the OH radical
generated by the photolysis of H2O.

Figure 1: Variations in the signal intensities of surface species generated during UV irradiation to the sampleof CH3OH (0.3 ML) on ASW (10 ML) at 10 K. Pickup signals of MF, MM, CH3O and/or CH2OH, and OH
which are photoproducts.

References
[1]
[2]
[3]
[4]
[5]
[6]

T. Soma et al. Astrophys. J. 854, 116 (2018).
K. Öberg et al. Astron. Astrophys. 504, 891–913 (2009).
D. Paardekooper et al. Astron. Astrophys. 592, A67 (2016).
A. Kouchi et al. Astrophys. J. 918, 45 (2021).
H. Kang, Bull. Korean Chem. Soc. 32, 389 (2011).
A. Ishiabshi et al. Astrophys. J. Lett. 921, L13 (2021).

Calculation of the ortho-para conversion rate of gaseous methanol by the internal axis
methodZ.-D. Sun and L.-S. Ma
School of Physics, Shandong University, China
School of Physics and Electrical Engineering, Kashi University, China
In astrophysics and astrochemistry, the ortho-para conversion rate is an important parameter
which is related to the ortho-to-para population ratio (OPR) and the nuclear-spin temperatureof nuclear-spin isomers of molecules in the interstellar medium (ISM) [1]. The methanol(CH3OH) molecule is a major source of interstellar organic species due to its abundance in the
ISM. Although conversion rate of nuclear-spin isomers in gaseous methanol has been
experimentally measured recently [2], the quantum calculation of the ortho-para conversion
rate of methanol molecules in the gas phase, the conversion mechanism in the nuclear-spin
isomers conversion of methanol, and the most probable gateways of spin conversion inmethanol have not yet theoretically studied by the internal axis method (IAM) that is aclassical method commonly used by many researchers.
In molecular physics, methanol is one of the simplest asymmetric-top molecules withhindered internal rotation (i.e. torsion) [3]. Methanol does not rotate around the overallrotational symmetry axis but the methyl (CH3) group axis. In the IAM, the CH3-group and the
OH-group in methanol relatively rotate in the opposite directions with each other, and thecoupling of the angular momenta between torsion and overall rotation in the Hamiltonian ofmethanol can therefore be completely separated from each other. In accordance with Pauli’s
principle in quantum mechanics, the identical nuclei in the methyl group produce a specific
type of nuclear spin isomers of the ortho-CH3OH and para-CH3OH in methanol. In this study,
we have developed a theoretical model by the IAM for the description of isomer conversions
by molecular collisions in gaseous methanol. The model is based on the quantum-relaxation
theory confirmed to be valid for the standard nuclear-spin isomers based on the molecularrotational states [4]. The expressions of the ortho-para state-mixing strengths induced byintramolecular nuclear-spin−nuclear-spin and nuclear-spin−rotation interactions in methanol
have been analytically deduced and numerically calculated. We found that the ortho-parastates-mixings and ortho-para conversion can be induced by both of these two intramolecular
hyperfine interactions whereas the nuclear-spin−rotation interaction plays a major role. The
conversion rates at room temperature low pressures over eight ortho-para level pairs havebeen calculated to be closely to the measured values and the most probable gateways of spin
conversion in methanol by collision-induced population transfers are found.
Acknowledgements

We express sincere thanks to P. L. Chapovsky for valuable guidance and discussions with us when
he visited our laboratory. This work was jointly supported by the National Natural Science Foundation ofChina (Grants No. 91536105, No. 11174186, and No. 11074147) and the Tianshan Scholar Program andthe FY2021 JSPS Invitational Fellowship for Research in Japan in a short-term program (S21002).

References

[1]
[2]
[3]
[4]

T. Hama & N. Watanabe, 2013, Chem. Rev. 113, 8783.
Z.-D. Sun, M. Ge, & Y. Zheng, 2015, Nat. Commun. 6:6877.
Z.-D. Sun, F. Matsushima, S. Tsunekawa, & K. Takagi, 2000, J. Opt. Soc. Am. B 17, 2068.
P. L. Chapovsky, 1991, Phys. Rev. A 43, 3624.

An Aromatic Universe - Low Temperature Molecular Mass Growth Processes to Polycyclic
Aromatic Hydrocarbons (PAHs)
Ralf I. Kaiser1,2
12Department of Chemistry, University of Hawaii at Manoa, Honolulu HI 96822, USA
W.M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa,
Honolulu HI 96822, USA

Polycyclic aromatic hydrocarbons (PAHs) represent key molecular building blocks leading tocarbonaceous nanoparticles identified in combustion systems and extraterrestrial environments.
However, the understanding of their formation and growth has remained elusive. Here, we
present evidence based on laboratory data combined with electronic structure calculations on
fundamental mass growth processes of PAHs in the gas phase via ring expansion and ringannulation. Key reaction pathways operate at ultralow temperatures such as at 10 K as present incold molecular clods like TMC-1 synthesizing PAHs at least from two to five six memberedrings such as naphthalene, anthracene, phenanthrene, triphenylene, [4]-helicene, and [5]-helicene.
These elementary reactions are rapid, have no entrance barriers, and synthesize PAHs via
van-der-Waals complexes and submerged barriers. This facile route to complex PAHs signifies a
critical shift in the perception that PAHs can be only formed at high-temperature combustion andcircumstellar conditions providing a detailed understanding of the low temperature chemistry
through untangling elementary reactions on the most fundamental level. An outlook is alsopresented on the synthesis of PAHs in low temperature, hydrocarbon-dominated ices in deep
space and in the outer Solar System upon interaction with (non)-ionizing radiation; theseprocesses are driven by non-adiabatic reaction dynamics and low lying triplet states of acetylene
leading to PAHs as complex as coronene. Overall, these mechanisms eventually lead tographene-type PAHs and two dimensional nanostructures providing an exciting view about thetransformation of carbon in our universe.
References

L. Zhao et al. Pyrene Synthesis in Circumstellar Envelopes and its Role in the Formation of 2D
Nanostructures. Nature Astron. 2, 413-419 (2018).
L. Zhao et al. Low-Temperature Formation of Polycyclic Aromatic Hydrocarbons in Titan’s Atmosphere.
Nature Aston. 2, 973-979 (2018).
L. Zhao, R.I. Kaiser, B. Xu, U. Ablikim, W. Lu, M. Ahmed, M. Evseev, E. K. Bashkirov, V.N. Azyazov,
M.V. Zagidullin, A.N. Morozov, A.H. Howlader, S.F. Wnuk, A.M. Mebel, D. Joshi, G. Veber, F. R.
Fischer, Gas Phase Synthesis of [4]-Helicene. Nature Commun. 10, 1510 (2019).
L. Zhao et al. Molecular Mass Growth through Ring Expansion in Polycyclic Aromatic Hydrocarbons via
Radical-Radical Reactions. Nature Commun. 10, 3689 (2019).
L. Zhao et al., A Unified Mechanism on the Formation of Acenes, Helicenes, and Phenacenes in the Gas
Phase. Angewandte Chemie – International Edition 59, 4051-4056 (2020).
S. Doddipatla et al., Low-temperature Gas-phase Formation of Indene in the Interstellar Medium, Science
Advances, 7, eabd4044 (2021).
R.I. Kaiser, N. Hansen, An Aromatic Universe – A Physical Chemistry Perspective, J. Chem. Phys. A,
Invited Perspective 125, 3826-3840 (2021).
L. Zhao et al., Gas Phase Synthesis of Benzene via the Propargyl Radical Self Reaction. Science
Advances 7, eabf0360 (2021).

Hayabusa2 returned samples from C-type near-Earth asteroid (162173) Ryugu:
Preliminary report of initial analysis
S. Tachibana,1, 2 H. Yurimoto,3 T. Nakamura,4 T. Noguchi,5 R. Okazaki,6 H. Yabuta,7 H.
Naraoka,6 K. Sakamoto,2 S. Watanabe,8 Y. Tsuda,2 and the Hayabusa2 initial analysis team
1

UTOPS, University of Tokyo, Japan
Institute of Space and Astronautical Science, JAXA, Japan
3
Dept. Natural History Sciences, Hokkaido University, Japan
4
Dept. Earth Science, Tohoku University, Japan
5
Div. Earth and Planetary Sciences, Kyoto University, Japan
6
Dept. Earth and Planetary Sciences, Kyushu University, Japan
7
Earth and Planetary Systems Science Program, Hiroshima University, Japan
8
Dept. Earth and Planetary Sciences, Nagoya University, Japan
2

JAXA’s Hayabusa2 spacecraft returned the sample from C-type (carbonaceous) near-Earthasteroid (162173) Ryugu in December 2020. The total weight of samples collected from two
surface locations of the asteroid exceeds 5 grams, which is the largest ever from deep space.
The Hayabusa2 project has begun a year-long analysis of returned samples on a priority basis(initial analysis). In order to unravel the nature of C-type asteroid and the origin and evolutionof Solar System, the Hayabusa2 initial analysis team consists of six sub-teams focusing on 1)
chemistry (elements and isotopes), 2) petrology and mineralogy of coarse grains (mm-sizedgrains referred as ‘Stone’), 3) petrology and mineralogy of fine grains (<100 μm-sized grains
referred as ‘Sand’), 4) volatiles, 5) insoluble organic matter (macromolecular organics), and6) soluble organic matter (organic molecules).
After six-month initial description inside clean chambers at Institute of Space andAstronautical Science (ISAS), JAXA, ~6 % of the samples (0.3 g out of total 5 g) was
allocated to the initial analysis team and has been investigated since June 2021. Twenty-two
particles were individually photographed, weighed, and spectroscopically described without
exposure to air at ISAS in advance of allocation to the team. Most of individual particles are
one to a few millimeter in size except for a centimeter-sized grain obtained during the second
landing at Ryugu. Along with the individual particles, ten sets of aggregate samples,consisting of grains with <1 mm diameter, were allocated to the team. The aggregate samples
range from 0.3 to 38.8 mg.
We will present current status of initial analysis and discuss some preliminary results at theworkshop.

Poster Presentations

P1

HCO+ and ionization structure observed by ALMA
Y. Aikawa,1 Gianni Cataldi,2 Y. Yamato,1 Kenji Furuya,2 and MAPS team1
Departmen of Astronomy, University of Tokyo, Japan
2
National Astronomical Observatory, Japan
We observed HCO+(J=1−0) and H13CO+ (J=1−0) emission towards the five protoplanetarydisks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480 as part of the MAPS
project[1][2]. HCO+ is detected and mapped at 0.3” resolution in all five disks, while H13CO+
is detected (SNR >6σ ) towards GM Aur and HD 163296 and tentatively detected (SNR >3σ )towards the other disks by a matched filter analysis. Inside a radius of R∼100 au, the HCO+
column density is flat or shows a central dip. At outer radii ( ≳100 au), the HCO+ column
density decreases outwards, while the column density ratio of HCO+/CO is mostly in therange of ∼10−5−10−4 . We derived the HCO+ abundance in the warm CO-rich layer, where
HCO+ is expected to be the dominant molecular ion. At R≳100 au, the HCO+ abundance is ∼3×10−11−3×10−10 , which is consistent with a template disk model with X-ray ionization. At
the smaller radii, the abundance decreases inwards, which indicates that the ionization degree
is lower in denser gas, especially inside the CO snow line, where the CO-rich layer is in the
midplane. Comparison of template disk models with the column densities of HCO+, N2H+,
and N2D+ indicates that the midplane ionization rate is ≳10−18 s−1 for the disks around IM Lup,
AS 209, and HD 163296. We also find hints of an increased HCO+ abundance around thelocation of dust continuum gaps in AS 209, HD 163296, and MWC 480.
We also plan to show the summary of molecular column densities obtained in MAPS projectand some model results for discussions in the poster session.

Figure: (a)Radial distributions of column densities of CO, HCO+, N2H+, and N2D+ in IM
Lup derived from MAPS project. (b) Distributions of CO and HCO+ in a tempate disk model.
References[1]
Aikawa, Y., Cataldi, G., Yamato, Y. and MAPS team (2021) “Molecules with ALMA at Planet-forming
Scales (MAPS) XIII: HCO+ and disk ionization structure”, ApJS, in press[2]
Oberg, K.I., Guzman, V.V., Walsh, C., Aikawa, Y., Bergin, E.A. and MAPS team (2021) “Moleculeswith ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights”, ApJS in press

P2

Testing Dust-Surface Formation Model of Prebiotic Molecule CH3NCO
in Star-Forming Cores Sagittarius B2 (M) and (N)M. Araki,1 Y. Ohno,1,2 K. Izuoka,1T. Oyama,2 S. Takano, 3 N. Kuze, 4 Y. Sumiyoshi,5 K. Tsukiyama1
1

Faculty of Science Division I, Tokyo University of Science, Japan
2
RIKEN, Japan
3
College of Engineering, Nihon University, Japan
4
Department of Materials and Life Sciences, Sophia University, Japan
5
Faculty of Science and Technology, Gunma University, Japan
Origin of organic molecules on Earth is discussed to be interstellar clouds, because comets
carried molecules produced in clouds. Methyl isocyanate CH3NCO is presumably one of thedelivered organic molecules at the primitive earth. This molecule was firstly detected in the the(N) core of the Galactic Center star-forming region Sagittarius (Sgr) B2 [1]. Recently, thetheoretical studies have suggested that this molecule is formed on dust surface in molecular
cloud [2]. If that is the case, CH3NCO abundantly desorbs from dust surface as hot gas in acentral region of a star-forming core and slightly exists in an outer region as cold gas.
To examine an outer region of a star-forming core, we observed the (M) core in Sgr B2 withthe 45-m telescope of Nobeyama Radio Observatory. Rotational transitions of CH3NCO werefirstly detected in this region. The abundance ratio and the rotational temperature are derived
to be [CH3NCO]/[HNCO] = 0.03 ± 0.01 and Trot = 28 ± 6 K, respectively.
To examine temperature and distribution of CH3NCO, the archival data toward the (N1) coreof Sgr B2 observed by ALMA were investigated in the 94–113 GHz region. Considering
intensity maps and velocity structures, a compact distribution having a clumpy toroidal
structure was firstly imaged by CH3NCO showing high temperature of ~60 K, as shown in Fig.
1. These results suggest a hot and abundant condition of this molecule in the central region of
the core. Hence, CH3NCO and/or its precursors are likely to be produced on dust surface.

Figure 1: The integrated intensity map of the JKa,Kc =111,10–101,9 line of CH3NCO (a) and its position velocity
map (b). The illustration in (a) shows an expected toroidal structure. The map (b) is sampled in the red squareof (a).

References[1]

Halfen et al., 2015, ApJL, 812, L5.

[2]e.g., Majumdar et al., 2018, MNRAS, 473, L59.

P3

Can grain-surface chemistry explain the surprisingly low C/CO ratio in the HD 32297
debris disk?
G. Cataldi,1,2 Y. Wu,3 A. Brandeker4 , N. Ohashi5, A. Moór6 et al.
1

2

National Astronomical Observatory of Japan, Japan
Department of Astronomy, Graduate School of Science, The University of Tokyo, Japan3
Department of Astronomy & Astrophysics, University of Toronto, Canada
4
Department of Astronomy, Stockholm University, Sweden
5
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan, R.O.C.
6
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungary

Debris disks are analogues of the solar system’s asteroid and Kuiper belt. They consist of
kilometer-sized rocky or icy bodies (“exocomets”) that continuously collide and produce dust.
However, in recent years observations of CO emission have shown that some of these objects
also contain substantial amounts of gas [e.g. 1]. Like the dust, this gas is probably producedby collisions of cometary bodies. It is important to understand the nature of this gas for anumber of reasons. For example, the gas allows us to study the composition of the exocomets[e.g. 2]. Furthermore, the gas might be accreted by planets, thereby changing theiratmospheric composition [3].
The A-type main sequence star HD 32297 (age of 15-30 Myr) hosts a debris disk with a highCO mass. Since CO is quickly photo-dissociated by the interstellar radiation field, it has beensuggested that CO is shielded by neutral carbon atoms that are produced by thephoto-dissociation [4]. This would allow a large CO mass to accumulate from the collisional
destruction of icy exocomets. In order to test this scenario, we observed neutral C emission
with ALMA towards HD 32297 [5].
In order to interpret our observations, we set up a simple model where CO is produced fromcometary bodies and destroyed by the interstellar field, taking into account CO self-shielding
and shielding by neutral C. We find that the observed C/CO ratio can only be explained if 1)
the CO production rate is uncomfortably high and 2) C is removed from the system on a shorttime scale by an unknown process. We hypothesize that grain surface chemistry might solve
this puzzle: C and O atoms might accrete onto dust grains and re-form CO, which is thanre-released to the gas phase. This would provide an additional CO source and a C sink,therefore explaining the surprisingly low C/CO ratio. However, a more detailed examination
with the help of grain surface chemistry experts is needed in order to assess whether this is arealistic scenario.
References
[1]
[2]
[3]
[4]
[5]

Moór, A., Curé, M., Kóspál, Á., et al. 2017, ApJ, 849, 123
Matrà, L., Wilner, D. J., Öberg, K. I., et al. 2018, ApJ, 853, 147
Kral, Q., Davoult, J., & Charnay, B., 2020, Nature Astronomy, 4, 769
Kral, Q., Marino, S., Wyatt, M. C., Kama, M., & Matrà, L. 2019, MNRAS, 489, 3670
Cataldi, G., Wu, Y., Brandeker, A., et al. 2020, ApJ, 892, 99

P4

Nitrogen inclusion in organic dust in novae revealed by laboratory synthesis ofQuenched Nitrogen-included Carbonaceous Composite (QNCC)
I. Endo,1 I. Sakon,1 T. Onaka,2,1 Y. Kimura,3 S. Kimura,4 S. Wada,4 L. A. Helton,5 R. M. Lau,6
Y. Kebukawa,7 Y. Muramatsu,8 N. O. Ogawa,9 N. Ohkouchi,9 M. Nakamura,10 and
S. Kwok11
1

Department of Astronomy, University of Tokyo, Japan, 2Department of Physics, Meisei
University, Japan, 3Institute of Low Temperature Science, Hokkaido University, Japan, 4The
University of Electro-Communications, Japan, 5SOFIA Science Center/NASA Ames ResearchCenter, USA, 6Institute of Space and Astronautical Science, Japan Aerospace Exploration
Agency, Japan, 7Faculty of Engineering, Yokohama National University, Japan, 8Graduate
School of Engineering, University of Hyogo, Japan, 9 Biogeochemistry Program, Japan
Agency for Marine-Earth Science and Technology, Japan, 10Physics Laboratory and Instituteof Quantum Science, Nihon University, Japan, 11Department of Earth, Ocean & Atmospheric
Science, The University of British Columbia, Canada
The unidentified infrared (UIR) bands have been widely observed in various astrophysicalenvironments. They consist of a series of emission features arising from aromatic and/or
aliphatic C-C and C-H bonds in the near- to mid-infrared wavelength range[1] and therefore,
their carriers are thought to be related to organics. Although the carriers must be a major
constituent of the Galaxy, our knowledge of their properties is still limited. Dusty classicalnovae are valuable to investigate the formation process of dust because of their highoccurrence. Past studies have shown that the UIR bands in novae are characterized by thepresence of a broad 8µm feature [2,3].
We have succeeded to synthesize Quenched Nitrogen-included Carbonaceous Composite,laboratory organics whose infrared properties cane reproduce the UIR bands in novae. QNCC
is synthesized by quenching plasma produced from nitrogen gas and hydrocarbon solids. Thissynthesis method qualitatively mimic a possible formation process of organics in thecircumstellar environment of novae, where nitrogen-rich novae wind react with pre-existing
carbonaceous dust. Based on the infrared and X-ray analyses of QNCC, we found that QNCC
show the presence of amine structure, which can contribute to the broad 8µm feature
characterizing the UIR bands in novae. QNCC is at present the best laboratory analog oforganic dust formed in circumstellar environments of dusty classical novae[4].
References
[1]
[2]
[3]
[4]

L. J. Allamandola et al. 1989, ApJS, 71, 773
A. L. Helton et al. 2011, in EAS Publications Series, Vol. 46
I. Sakon et al. 2016, ApJ, 817, 145
I. Endo et al. 2021, ApJ, 917, 103

P5

Development of Cavity Enhanced Absorption Spectrometer
Aiming to Measure Optical Absorption Bands of Interstellar Molecules
I. Fukuda,1 T. Sato,1 M. Araki,1 T. Oyama,2 S. Hoshino,1 K. Tsukiyama1
1

Faculty of Science Division I, Tokyo University of Science, Japan
2
RIKEN, Japan

Diffuse Interstellar Bands (DIBs) are mysterious unidentified absorption bands detected
optically in diffuse clouds. DIBs are presumed to be electronic transitions of large organic
molecules. Identification of their origins allows us to unveil a wide variety of chemicalcomposition of space, because approximately 600 DIBs have been found so far [1]. However,at present only the five bands were assigned to the fullerene cation C60+ [2] and the other bands
are not identified yet.
To reveal DIB carriers, comparative studies of astronomically observed bands with laboratory
spectra are required. However, a covering range of a high-resolution laboratory spectrometer isgenerally narrow, although DIBs disperse over a wide range. A wide-band spectrometer can bea powerful tool to identify these bands.
Cavity enhanced absorption spectroscopy is possible to widely measure a high-resolution
spectrum [3]. This method enables us to achieve a very long optical path length, because whitelight introduced in between two high reflectivity mirrors reciprocates more than ten thousand
times. Based on these advantages, this spectrometer is suitable to measure DIB-candidate
molecules produced in laboratory. In this study, we developed this spectrometer thatsimultaneously covers the 60-nm range by using the 1200 lines/mm grating. As a demonstrationof sensitivity, the fifth CH stretching overtones (v' = 6) of methyl acetate (a) and ethyl acetate(b) were detected for the first time, as shown in Fig. 1. Additionally, we also detected methanol
produced via saponification of methyl acetate by sodium hydroxide (c3). As a next step, weplan to install a hollow-cathode discharge system to produce DIB-candidate ion and radical oflarge organic molecule.

Figure 1: Cavity-enhanced absorption spectrometer (left) and the observed spectra. (a) v' = 6 of methyl
acetate. (b) v' = 6 of ethyl acetate. (c1) v' = 4 of pure methanol. (c2) v' = 5 of pure methyl acetate. (c3) mixtureof methyl acetate with methanol produced by saponification of methyl acetate. The sample pressure wasadjusted in the range of 0.020 – 156 Torr depending on the peak intensities.

References[1][3]e.g., Fan et al. 2019, ApJ, 878, 151.
[2]
Oyama & Araki, 2020, J. Spectrosc. Soc. Jpn., 69, 144.

Campbell et al. 2015, Nature, 523, 322

P6

Experimental measurement of the absorption cross section of dangling OH bonds inwater ice
T. Hama,1 T. Nagasawa,1 T. Hasegawa, and N. Numadate1
1

Komaba Institute for Science, The University of Tokyo, Meguro, Tokyo 153- 8902, Japan

Recent astronomical observations have revealed water (H2O) ice to be ubiquitous in space.
For example, it is the most abundant solid component in interstellar molecular clouds and theouter cold part of protoplanetary disks. Its ubiquity makes it essential to clarify the physics
and chemistry of ice to further our understanding of the formation of stars and planetarysystems, including our solar system [1].
Key infrared (IR) features related to interstellar ice are signals at 3720 and 3696 cm−1 from
dangling OH bonds, which have respectively been assigned to the free OH stretch modes oftwo- and three-coordinated H2O molecules at the surface of ice [2, 3]. Because dangling OH
bonds reflect the porosity of ice and serve as catalytic sites for adsorption and chemical
reactions, they have been intensely studied in many fields including interstellar chemistry [4,5]. Despite much active research, the absorption cross section, a fundamental optical constant,of dangling OH bonds remains unknown. This hampers the quantification of dangling OH
bonds from IR spectra of ice.
Recently, we developed an experimental setup for in situ infrared multiple-angle incidence
resolution spectrometry (IR-MAIRS) in low-temperature, ultrahigh-vacuum conditions [6].
IR-MAIRS is a spectroscopic method combining oblique incidence transmission
measurements and multivariate analysis to retrieve both pure in-plane (IP) and out-of-plane(OP) vibration spectra for a thin sample, which was originally developed for quantitative
molecular orientation analysis of organic thin films without the use of optical parameters [6,7]. In this study, we report our recent challenge to measure the absorption cross section of
dangling OH bonds of water ice using IR-MAIRS [8].
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

T. Hama, & N. Watanabe, 2013, Chem. Rev. 113, 8783.
Buch, V., & Devlin, J. P. 1991, J. Chem. Phys., 94, 4091.
Devlin, J. P., & Buch, V. 1995, J. Phys. Chem., 99, 16534.
Noble, J. A., Michoulier, E., Aupetit, C., & Mascetti, J. 2020, Astron. Astrophys., 644, 1.
Maté, B, Satorre, M., & Escribano, R. 2021, Phys. Chem. Chem. Phys., 23, 9532.
T. Hama, A. Ishibashi, A. Kouchi, N. Watanabe, N. Shioya, T. Shimoaka, & T. Hasegawa, 2020, J. Phys.
Chem. Lett. 11, 7857.
Hasegawa, T., & Shioya, N. 2020, Bull. Chem. Soc. Jpn., 93, 1127.
T. Nagasawa, R. Sato, N. Numadate, N. Shioya, T. Shimoaka, T. Hasegawa, & T. Hama, submitted.

P7

Cloudlet capture model for the origin of asymmetry
in the molecular emission in TMC-1A
Tomoyuki Hanawa
Center for Frontier Science
Chiba University
Protostars are associated with protoplanetary disks and are surrounded by infalling envelopes.
The gas accretion from the envelope is thought to be more or less symmetric around therotation axis of the disk. However, some young protostars show highly asymmetric features in
the molecular emission lines. Blue-shifted component is much stronger than red-shited one in
the CS emission line in TMC-1A harboringIRAS 04365+2535, Class I protostar in Taurus.
The asymmetry may indicate that we are observing the capture of a cloudlet. We examine thispossibility based on hydrodynamical simulations in which a cloudlet accretes and collides thepre-existing disk. The orbital plane of the cloudlet is inclined to the disk. This model explains
several features such as (1) the asymmetry in the infalling gas, (2) a partial lack in the disk,and (3) apparently slow infall velocity. We discuss the implications of our hypothesis that thegas accretion onto protostar may be successive but sporadic captures of cloudlets rather thancontinuous flow.

P8

Submillimeter H2O masers in high-mass star-forming regions
T. Hirota1
1

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Japan

Molecular masers have been employed to investigate dynamical structures of circumstellar
disks and outflows in young stellar objects (YSOs). In particular, some representative
centimeter radio lines such as the 1.6 GHz OH, 6.7 GHz CH3OH, and 22 GHz H2O masers arewidely used for high resolution interferometric observations. In contrast, higher frequency
masers have not been well studied until recent developments with ALMA (Atacama Large
Millimeter/submillimeter Array).
Here we will present observational results of submillimeter H2O masers toward high-massstar-forming regions. We will review recent progress of our ALMA observations of submillimeter H2O lines toward the nearest high-mass YSO, Source I in Orion KL [e.g. 1,2],
which shows a rotating outflow driven from the Keplerian disk. We will also show tentative
results from ALMA observations of the 321 GHz H2O masers toward high-mass YSO
samples associated with the 22 GHz H2O masers observed with VERA (VLBI Exploration ofRadio Astrometry) [e.g. 3]. We find that the higher excitation 321 GHz H2O masers are in
general co-located with those of the 22 GHz H2O masers while in some sources they are
emitted from inner part of the outflows traced by the 22 GHz masers. The results suggest thatmultiple maser lines at different excitation conditions can be unique probes of physical andchemical properties of high density and temperature regions in the close vicinity to high-mass
YSOs associated with disk/outflow systems.
(a)

(b)

(c)

Figure 1: (a) Moment 0 map of the 321 GHz (102,9 - 93,6) H2O maser (color) and ALMA Band 10
continuum emission (contour) toward a high-mass YSO Orion Source I [1,2]. (b) Spectrum of the 321 GHz
H2O maser toward Source I [1,2]. (c) Moment 0 map of the 321 GHz H2O maser (gray), VLA 22 GHz
continuum (contour), and positions of the 22 GHz (61,6 - 52,3) H2O maser (cross) toward a high-mass YSOS255 NIRS3 [3].

References
[1]

[2]
[3]

T. Hirota, M. N. Machida, Y. Matsushita, et al., in proc. of IAUS 336, “Astrophysical Masers: Unlocking
the Mysteries of the Universe”, ed. A. Tarchi, M. J. Reid, and P. Castangia (Cambridge University Press,
Cambridge, 2018), p. 207.
T. Hirota, M. K. Kim, Y. Kurono, and M. Honma 2014, ApJL, 782, L28.
T. Hirota, R. Cesaroni, L. Moscadelli, et al. 2021, A&A, 647, A23.

P9

Microwave Spectroscopy of Isothiazole
Hoga Furukawa,1 Kaori Kobayashi,1Maria A. Zdanovskaia, Brian J, Esselman,2 R. Claude Woods,2 Robert J. McMahon22

1

2

Department of Physics, University of Toyama, Japan
Department of Chemistry, University of Wisconsin–Madison, USA

Five-membered ring structure are found in some amino acids. In addition, five-memberedring cyanocyclopentadiene has been identified toward TMC-1 [1]. Therefore isothiazole(C3H3NS) is a potential interstellar molecule of five-membered ring with two adjacent hetero
atoms, nitrogen and sulfur. Previous studies of microwave spectroscopy have been conducted
below 35 GHz including information on the dipole moment, isotopologues, and the Zeemanneffect [2-4]. The a-axis and b-axis components of the dipole moment are doubled by 1.1 D
and 2.2 D, respectively. Information on higher frequency range is essential for future
detection.
In this study, microwave spectroscopy of isothiazole was performed in the 40-360 GHz
region at room temperature at the University of Toyama and University of Wisconsin–
Madison. The assignment was based on the frequency prediction using molecular constantsfrom previous high-resolution infrared studies [5,6]. The spectra were analyzed by using
AABS package.[7] Figure 1 shows an example. Over 2000 lines were assigned and analyzed
using Watson’s A-reduced Hamiltonian.

Figure 1: The spectrum and the frequency prediction of isothiazole.

References[1] M.C. McCarthy, K.L.K. Lee, R.A. Loomis, A.M. Burkhardt, C.N. Shingledecker, S.B. Charnley, M.A.
Cordiner, E. Herbst, S. Kalenskii, E.R. Willis, C. Xue, A.J. Remijan, B.A. McGuire, Nat. Astron. 5 (2021) 176–
180.
[2] J.H. GRIFFITHS, A. WARDLEY, V.E. WILLIAMS, N.L. OWEN, J. SHERIDAN, Nature. 216 (1967)
1301–1301.
[3] J. Wiese, D.H. Sutter, Zeitschrift Für Naturforsch. A. 35 (1980) 712–722.
[4] J. Gripp, U. Kretschmer, H. Dreizler, The 33S Nuclear Hyperfine Structure in the Rotational Spectrum ofIsothiazole, Zeitschrift Für Naturforsch. A. 49 (1994) 1059–1062.
[5] F. Hegelund, R. Wugt Larsen, R.A. Aitken, H. Kraus, F.M. Nicolaisen, M.H. Palmer, Mol. Phys. 102 (2004)
1583–1595.
[6] F. Hegelund, R.W. Larsen, R.A. Aitken, M.H. Palmer, J. Mol. Struct. 780–781 (2006) 45–56.
[7] Z.Kisiel, L.Pszczolkowski, I.R.Medvedev, M.Winnewisser, F.C.De Lucia, E.Herbst, J.Mol.Spectrosc. 233,
(2005) 231-243.

P10

Energetic processes caused by sub-keV electrons impacting on H2O+CO ice mixtures
C.-H. Huang1, C-Y Lee1, Jr-Yao Lee1, C. Cecchi-Pestellini2, A. Ciaravella2, A.
Jiménez-Escobar2, L.-C. Hsiao1, N.-E. Sie1, and Y.-J. Chen1
1

2

Department of Physics, National Central University, Taiwan
INAF - Osservatorio Astronomico di Palermo, P.za Parlamento 1, 90134 Palermo, Italy

The irradiation of molecules in condensed water is an important process in the chemistry of awide variety of astronomical environments. An important component of interstellar ices iscarbon monoxide, and consequently, a number of experiments have been performed in
mixtures of such species with water [1, 2].
In this work, we use middle-range electrons (200-1000 eV) to study the radiation induced
chemistry in H2O + CO ice mixtures. We derive destruction and production cross-sections ofparent molecules and products, and for the case of CO being the desorption cross-section. Welabel the products observed after irradiation with energetic electrons from IR spectra (Figure 1)
to understand the mechanisms and kinetics associated with the relevant reactions. A
comparison is made with the results of experiments performed using different processing
sources, such as X-ray, UV and hydrogenation. Finally, we discuss the difference ofdesorption relevant depths [3] between in the present case and that of a pure CO ice.

Figure 1: Assignment of products in irradiated H2O:CO ice mixture. From bottom to top are spectrum in
200, 400, 600, 800, and 1000 eV experiments.

References
[1]

[2]
[3]

Jiménez-Escobar, A., Chen, Y. J., Ciaravella, A., Huang, C.H., Micela, G., & Cecchi-Pestellini, C. 2016,
ApJ, 820(1),25
Watanabe, N., Mouri, O., Nagaoka, A., Chigai, T., Kouchi,A., & Pirronello, V. 2007, ApJ, 668(2), 1001.
R. Dupuy, M. Haubner, B. Henrist, J.-H. Fillion, & V.Baglin. 2020, JAP 128, 175304.

P11

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ÿ

P12

A new electrochemical property of ice: negative charge transport triggered byreactions of surface OH radicals with electrons
K. Kitajima1, Y. Nakai2, W. M. C. Sameera1, M. Tsuge1, A. Miyazaki1, H. Hidaka1,
A. Kouchi1, and N. Watanabe1
12Institute of Low Temperature Science, Hokkaido University, Japan
Radioactive Isotope Physics Laboratory, RIKEN Nishina Center, JapanThe electrochemical behavior of water ice is of particular interest in astrophysicalchemistry and atmospheric chemistry. Much research has shown that the ice can be a p-typesemiconductor due to the conduction of excess protons along the hydrogen bonds. In contrast
to positive charges, the conductivity of negative charges due to the relay of hydroxide ions(OH−) in ice has not been verified. We have recently observed the negative charge
conductivity of ice simultaneously exposed to UV and electrons at temperatures below 50 K
[1]. The phenomenon can be explained by the following processes: (1) production of OH
radicals on ice surface by UV irradiation, (2) electron attachment to OH radicals, and (3) the
produced OH− induce the sequence of proton abstraction from surrounding H2O. To confirm
the above processes, we additionally measured the density of surface OH radicals using anovel technique, a combination of photostimulated desorption and resonance-enhanced
multiphoton ionization [2].
Figure 1(a) shows the temporal variation of the negative currents through H2O ice at 10 K.
One can see the increase in negative currents during simultaneous exposure to UV andelectrons. A transient peak initially formed by electron irradiation may be attributed to theleakage of electrons through pores or cracks in ice. Meanwhile, as shown in Figure 1(b), thedensity of surface OH radicals decrease upon electron exposure. The results suggest that thesurface OH radicals are consumed via electron attachment to the radicals to produce OH−. We
consider that the negative currents are subsequently induced by the relay of OH− in ice at low
temperatures.

Figure 1 (a) Temporal variation in negative currents through H2O ice at 10 K upon repetitive UV irradiation
with continuous exposure to electrons. (b) Temporal variation in OH radical densities on ice at 10 K upon
repetitive electron irradiation with continuous exposure to UV.

References[1][2]

N. Watanabe, W.M.C. Sameera, H. Hidaka, A. Miyazaki, A. Kouchi, 2019, CPL, 737, 136820.
K. Kitajima, Y. Nakai, W.M.C. Sameera, M. Tsuge, A. Miyazaki, H. Hidaka, A. Kouchi, N. Watanabe,
2021, JPCL, 12, 704.

P13

Mono-deuterated methanol in prestellar cores
B. M. Kulterer,1 M. N. Drozdovskaya,1 S. Antonellini,2 C. Walsh,3 and T. J. Millar4
1

Center for Space and Habitability/University of Bern, Switzerland
2
Department, Institution/University, France
3
School of Physics and Astronomy/University of Leeds, United Kingdom
4
Astrophysics Research Center, School of Mathematics and Physics/Queen’s University
Belfast, UK
Mono-deuterated methanol is thought to form during the prestellar core stage of starformation. Variations in the CH2DOH/CH3OD ratio suggest that its formation is strongly
dependent on the surrounding cloud conditions. Thus it is a potential tracer of the physicalconditions before the onset of star formation.
A single-point physical model descriptive of a prestellar core is coupled to chemical models
to investigate potential formation pathways towards deuterated methanol at the prestellar
stage and discussed in context with observational findings [1]. The implementation of an
abstraction scheme [2] leads to the efficient formation of methyl-deuterated methanol, butlacks sufficient formation of hydroxyl-deuterated methanol.
This leads to the conclusion that CH3OD is most likely formed at a later evolutionary stage,
potentially from H/D exchange in warm ices between D2O (or HDO) and CH3OH.
Our results suggest that the ratio of CH2DOH/CH3OD is therefore not an appropriate tracer ofthe physical conditions during the prestellar stage, but might be better suited as a tracer of ice
heating.

Figure 1: Ratio of CH2DOH/CH3OD over a grid of core ages and dust temperatures descriptive of theprestellar phase as obtained with three different chemical networks [1]. The gray, dashed line indicates thestatistically expected value of 3, the solid, black line indicates the lower limit derived from observations [3].

References
[1]
[2]
[3]

B. M. Kulterer et al., 2021, submitted to: ACS Earth and Space Chemistry
H. Hidaka et al., 2009, ApJ, 702, 291
L. Bizzocchi et al., 2014, A&A, 569, 27

P14

Early stages of water cluster growth observed with low-temperature scanning tunnelling
microscopy
Signe Kyrkjebø,1,2 Frederik Doktor S. Simonsen,1 Richard Balog,1,2 Liv Hornekær1,2
1

Center for Interstellar Catalysis and the Department of Physics and Astronomy
2
Interdisciplinary Nanoscience Center
Aarhus University, Denmark

Water ice is known to form on carbonaceous dust grains in the interstellar medium [1], but thestructural morphology of icy grains including their chemical activity is still underinvestigation.
It has recently been shown that water molecules are mobile at temperatures down to 25 K on
highly-oriented pyrolytic graphite (HOPG), suggesting that ice may grow via clustering rather
than layer-by-layer [2]. However, realistic interstellar grains are not pristine and are likely
terminated by various functional groups, which may further affect ice formation [3].
We have studied the initial stages of ice formation on HOPG and O-terminated HOPG, as
dust grain analogues, using low-temperature scanning tunneling microscopy (LT-STM). Data
reveal that step-edges and O-functional groups act as nucleation sites for ice formation. The
size, fractal structure, and porosity of nanometer size water clusters are found to be strongly
dependent on the sample temperature.

Figure 1: LT-STM image of water ice clusters on O-HOPG. It: 4 pA, Vt: 4.5 V.

References
[1]
[2]
[3]

van Dishoeck, E. F. et al., Chem. Rev. 113, 9043 (2013)
Rosu-Finsen, A. et al., Phys. Chem. Chem. Phys. 18, 31930 (2016)
Kyrkjebø, S. et al., Carbon. 174, 396 (2021)

P15

Computational Investigation on the Potential Energy Surface of the Formation Route ofFormamide from Reaction between NH2 and H2CO on Interstellar Water Ice Surface
Berta Martínez-Bachs, Albert Rimola
Departament de Química, Universitat Autònoma de Barcelona, Catalonia, Spain
Formamide has a key role in prebiotic chemistry as it is the simplest molecule containing thefour most important atoms from a biological point of view: hydrogen, carbon, nitrogen andoxygen. But also, because it is the simplest molecule containing the amide bond O-C-NH, thegroup that join amino acids forming peptides [1]–[3]. Since it was first detected and due to its
importance, different pathways leading to its interstellar formation has been studied
considering both the gas-phase scenario and on ices of dust grains[2]–[4]. In the present
contribution, computational simulations based on quantum chemical calculations arepresented, focusing on the energetics of the NH2CHO formation from reaction of NH2 with
H2CO (a channel proposed to occur in the gas phase [3]) on water ice surfaces. To model thewater ice surfaces, a periodic approach has been adopted, in which both a crystalline and an
amorphous model has been used. Different DFT functionals have been employed to obtainaccurate energy values for the mechanistic steps involved in the reaction.

Figure 1: Potential Energy Surface and optimized structures of the stationary points of the studied reaction
on the amorphous slab model. Values are in kJ/mol. Bare values correspond to those at B3LYP-D3(BJ), inbrackets to those at PBE-D3(BJ) and in square brackets to those at M06-2X-D3. Atom color legend: red, O;
blue, N; green, C white, H.

References
[1]
[2]
[3]
[4]

C. Ceccarelli et al, 2017, ApJ 850, 176.
A. Rimola et al, 2018, ACS Earth Space Chem. 2, 7, 720.
V. Barone et al., 2015, Mon. Not. R. Astron. Soc. Lett. 453, 1, L31.
J. Enrique-Romero et al., 2019, ACS Earth Space Chem. 3, 10, 2158.

P16

Detection of photodesorption OH radicals from H2O ice surface by visible lightAyane Miyazaki1, Naoki Watanabe1, W. M. C. Sameera1, Yoichi Nakai2,
Masashi Tsuge1, Testuya Hama3, Hiroshi Hidaka1, Akira Kouchi1
1 Institute of Low Temperature Science, Hokkaido University, Japan
2

Nishina Center, RIKEN, Japan

3 Komaba Institute for Science, The University of Tokyo, Japan

There are various molecules including complex organic molecules in interstellar molecular
clouds. Surface reactions involving radicals on interstellar ice-dust grain play an importantrole in chemical evolution because they are indispensable for the formation of complex
interstellar molecules [1,2]. In order to understand the details of the molecular formation on
the surface of dust, it is necessary to clarify the behavior of radicals on the surface. However,the detection of radicals on ice surface has intrinsic experimental difficulties.
In this study, we investigated behavior of OH radicals on the ice surface. Because they canbe easily produced by photolysis of ice and would greatly contribute to the formation ofcomplex molecules or those precursors. Using the combination of photo-stimulated
desorption and resonance-enhanced multiphoton ionization, we have first succeeded inmonitoring OH radicals on ice [3]. The results of the experiments indicate thatphotodesorption of OH radicals are induced by one photon absorption at 532 nm, which istransparent for gaseous OH radical as well as for water ice. I present the details on the
behavior of OH radicals and adsorption sites on water ice [4,5].
References[1] R. T. Garrod, S. L. W. Weaver, E. Herbst, 2008, Astrophys. J. 682, 283.
[2] K. I. Öberg, Chem. Rev. 2016, 116, 17, 9631–9663.
[3] A. Miyazaki, N. Watanabe, W. M. C. Sameera1, Y. Nakai, M. Tsuge, T. Hama, H. Hidaka1, A. Kouchi, Phys.
Rev. A 102, 052822 (2020).
[4] N. Watanabe and M. Tsuge, 2020, J. Phys. Soc. Jpn. 89, 051015.
[5] M. Tsuge and N. Watanabe, 2021, Acc. Chem. Res. 54, 471.

P17

An infrared spectroscopic approach towards understanding the orientation of dangling OH
bonds on amorphous solid water
1
T. Nagasawa, T. Hasegawa1 N. Numadate,1 T. Hama1
1

Komaba Institute for Science, The University of Tokyo, JapanThe surface reaction on amorphous solid water (ASW) is the key to figuring out thechemical processes in interstellar molecular clouds, where stars and planets are being born [1].
Macroscopic properties of ASW such as heat transfer coefficient [2], surface potential [3]have progressively become understood through intensive research. By contrast, ourunderstanding about the microscopic structure of ASW is still at an early stage. For example,
there is almost no experimental study about the molecular orientation in ASW, which is a key
factor to control the physicochemical properties of organic thin films [4], due to the lack of
direct measurement technique. Recently, we built an experimental apparatus for low
temperature ultrahigh vacuum infrared multiple-angle incidence resolution spectrometry (IRMAIRS [4][5]. IR–MAIRS is a spectroscopic method combining oblique incidencetransmission measurements and multivariate analysis to retrieve both pure (in-plane; IP) IP
and (out-of-plane; OP) OP vibration spectra for a thin sample. The method has the uniqueadvantage that the average molecular orientation is determined by comparing the IP to OPband intensity ratio spectra on the absorbance scale. In this research, we report our recent IRMAIRS results for dangling OH bands in ASW at 10 to 90 K. It is found that the averageorientation angle of dangling OH bonds exhibit a drastic ice temperature dependence in therange of 10 to 90 K. The detailed results are presented in the poster.

Figure: (left) Schematic illustration of IR-MAIRS. IR–MAIRS: Typical single-beam spectra
measured at an angle of incidence of 45° at various polarization angles from 0° to 90° in 15°
steps, and then extracting the IP and OP spectra by multivariate analysis.
(right) Molecular orientation analysis based on IR-MAIRS. The average orientation angle ofmolecules is determined by comparing the ratio of absorbance both IP and OP spectra.
References

[1]
[2]
[3]
[4]
[5]

T. Hama, N. Watanabe, 2013, Chem. Rev 113, 12, 8783-8839.
A. Kouchi, 1994, J. Japanese Society of Snow and Ice, Vol.56 No.1 63-70.
C. Bu, J. Shi, U. Raut, E. Mitchell & R. Baragiola, 2015, J.Chem.Phys 142, 134702.
T. Hasegawa & N. Shioya, 2020, Bull. Chem. Soc. Jpn 93, 1127-1138.
T. Hama, A. Ishibashi, A. Kouchi, N. Watanabe, N. Nobuya, T. Shimoaka & T Hasegawa, 2020, J. Phys.
Chem. Lett 11, 7857-7866.

P18

Methanol production via interactions of low-energy CH3+ ions with ASW surface:experimental investigation of ion-surface reactions
Y. Nakai1, H. Hidaka2, and N. Watanabe2
1

RIKEN Nishina Center for Accelerator-Based Science, RIKEN, Japan
2
Institute of Low Temperature Science, Hokkaido University, Japan

Various neutral and ion species have been observed in molecular clouds, despite their very
low temperatures. To understand how molecules evoluve, many chemical processes have been
proposed. In gas phase, ion-molecule reactions have been always considered to play animportant role. However, the abundances of some molecules such as water and methanol
molecules cannot be explained only by the gas-phase reactions. Consequently, reactions
between neutral radicals and neutral species on an icy grain surface have been proposed as theother essential pathways and it has been experimentally confirmed that reactions of hydrogenatoms adsorbed on an ice surface are essential for productions of hydrogen, water, methanol,and so on [1, 2]. Besides pure gas-phase and surface reactions, it is reasonably inferred thatprocesses triggered by interactions of gas-phase ions with an ice mantle play some role inmolecular evolution. In this context, the experiments of energetic ion bombardment to an ice
containing other primordial molecules have been performed for a long time. In contrast, little
is known about the interactions between low-energy ions and an ice surface, while molecular
cations have been simply considered to recombine with negative charge (electrons) on an ice
surface in theoretical models [3, 4]. However, it is not clear how electrons exist on icy grains,
and thus it is also unclear if cation-electron recombination immediately occurs or not.
In fact, the reactions of very-low-energy ions with an icy surface have been theoretically
proposed as new non-energetic reaction pathways [5, 6]. Since an icy grain can be regarded asa huge molecular cluster, reactions of ions with an icy grain surface would occur without
reaction barriers as ion-molecule reactions. For example, the quantum chemical calculation
predicted that the reaction of a CH3+ ion with a water ice surface spontaneously produces amethanol molecule [5]. Despite recent theoretical progress, no experimental study for lowenergy ion reactions with ice surface have been performed due to experimental difficulties in
obtaining enough reaction products for their detection using conventional methods such as
infrared absorption spectroscopy. Accordingly, we have newly developed an experimental
setup to enable us detecting trace amounts of reaction products. Using this setup, we have
performed the experiments for production of methanol through the reaction of low-energy
CH3+ ions with a water ice surface. The CH3+ ions with their energies as low as or lower than
~10 eV impinged on an amorphous solid water (ASW) prepared on an Al substrate around 10
K. Reaction products by CH3+ irradiation were monitored through pick-up reaction method by
Cs+ ions at several tens eV [7, 8]. After CH3+ irradiation, methanol molecules on the ASW
were observed as the theoretical study suggested.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

T. Hama and N. Watanabe, 2013, Chem. Rev., 113, 8783
N. Watanabe and A. Kouchi, 2008, Prog. Surf. Sci., 83, 439.
C. Walsh, T. J. Millar, and H. Nomura, 2013, ApJL 766, L23.
A. Rimola, C. Ceccarelli, N. Balucani, and P. Ugliengo, 2021, frontiers in Astron. Space Sci., 8, 655405.
D. E. Woon, 2011, ApJ, 728, 44.
D. E. Woon, 2021, Acc. Chem. Res., 54, 490.
H. Kang, 2011, Bull. Korean Chem. Soc., 32, 389.
A. Ishibashi, ApJL, to be published.

P19

Experimental and computational studies on the physicochemical behavior of phosphine
induced by reactions with H and D atoms on interstellar ice grains
T. Nguyen,1 Y. Oba,1, W.M.C. Sameera1, A. Kouchi1, and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University,
N19W8, Sapporo, Hokkaido, Japan

Phosphine (PH3) is an important molecule for the chemistry of phosphorus (P-) bearing species
in the interstellar medium (ISM). Interstellar PH3 is thought to primarily form on icy grains,
where several surface processes may occur during and after its formation. To better understandthe physicochemical behavior of PH3 on ice grains in dense molecular clouds, we performedexperimental and computational studies on the reactions of phosphine with H and D atoms at
low temperatures. We found that phosphine and its deuterated isotopologue PD3 are released
into the gas phase from ice surfaces via chemical desorption. We confirmed that H-D
substitution reactions of PH3 and D-H substitution reactions of PD3 occurred following
reactions with D and H atoms, respectively, at 10 K on icy surface. Because the activation
barrier for the abstraction of H and D atoms from phosphine is ~1500 K, quantum tunnelingshould play a role at low temperatures. On the other hand, the D-H substitution reactions of PD3
was slightly faster than the H-D substitution reactions of PH3, meaning that the rates of the HD and D-H substitution reactions are not constrained by tunneling reactions but rather by otherelementary processes such as atoms diffusion on ice.

P20

X-ray-induced chemistry of water and related molecules in low-mass protostellar
envelopes
Shota Notsu,1 Ewine F. van Dishoeck,2,3 Catherine Walsh,4 Arthur D. Bosman,5 and Hideko
Nomura6
1

Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Japan
2
Leiden Observatory, Faculty of Science, Leiden University, The Netherlands
3
Max-Planck-Institut für Extraterrestrische Physik (MPE), Germany
4
School of Physics and Astronomy, University of Leeds, UK
5
Department of Astronomy, University of Michigan, USA
6
Division of Science, National Astronomical Observatory of Japan, Japan

Water is a key molecule in star and planet forming regions. Recent water line observations
toward several low-mass protostars suggest low water gas fractional abundances (<10^-6) in
the inner warm envelopes (r<100 au). Water destruction by X-ray radiation has been proposed
to influence the water abundances in these regions, but the detailed chemistry, including thenature of alternative oxygen carriers, is not yet understood. In our study [1], we calculated thechemical composition of low-mass Class 0 protostar envelopes using a detailed gas-grainchemical reaction network including X-ray induced chemical reactions. We aimed tounderstand the impact of X-ray radiation on the composition of low-mass protostar envelopes,
focusing specifically on water the related oxygen bearing species.
On the basis of our calculations [1], the protostar X-ray luminosity has a strong effect on thewater gas abundances, both within and outside the water snowline (T<100K, r<100 au).
Outside the water snowline, the water gas abundance increases with X-ray luminosities, due
to X-ray-induced photodesorption of water ice. Inside the water snowline, water maintains ahigh abundance of 10^-4 for low X-ray luminosities, with water and CO dominant oxygen
carriers. For high X-ray luminosities (>10^30 erg/s), the water gas abundances significantly
decrease just inside the water snowline (down to ~10^-8–10^-7) and in the innermost regionswith T >250K (~10^-6). For these cases, the fractional abundances of molecular and atomic
oxygen gas reach <10^-4 within the water snowline, and they become the dominant oxygen
carriers. In the presence of strong X-ray fields, gas-phase water molecules within the water
snowline are mainly destroyed with ion-molecule reactions and X-ray-induced
photo-dissociation. In addition, the fractional abundances of HCO+ and CH3OH, which havebeen considered to be tracers of the water snowline, significantly increase and decrease within
the water snowline, respectively, as the X-ray fluxes become larger. These X-ray effects arelarger in envelope models with lower number densities. Future molecular line observations
for protostars (using e.g., ALMA, ngVLA) will access the regions around protostars wheresuch X-ray induced chemistry is effective.
References[1]

Notsu. S., et al., 2021, A&A, 650, A180

P21First direct detection of OH radicals photodesorbed from liquid organic surface
by using laser-induced fluorescence technique
N. Numadate,1 S. Saito,2 and T. Hama1,3
1

Komaba Institute for Science, The University of Tokyo, Japan
Department of Chemistry, Tokyo University of Science, Japan3
Department of Basic Science, The University of Tokyo, Japan2

The 5th assessment report of the Intergovernmental Panel on Climate Change provides thataerosols contribute the largest uncertainty of the Earth’s changing energy budget and thisshould be evaluated in order to understand climate change [1]. Especially, interfacial reactionsat atmospheric aerosols and sea surface are of increasing importance because these interfaces
occupy a great deal of reaction fields on the Earth. Recently, photochemical reactions ofsurfactant organic compounds such as fatty acids that cover the top surfaces of aerosols andsea have attracted much attention. For example, it had been believed that gaseous and liquid
nonanoic acids (NA) do not absorb ultraviolet – visible radiation (> 295 nm). However,
Rossignol et al. found that NA at the air-water interface absorbs the ultraviolet, and thencomplex organic compounds were produced, which eventually act as aerosol precursors [2].
Although the photochemical reaction mechanism of NA is still poorly understood, it has beensuggested that OH radicals are a primary photoproduct in the ultraviolet photolysis of NA at
the interface [2, 3].
CH3(CH2)7COOH + hν (> 295 nm) → CH3(CH2)7CO + OH?
OH radical is one of the most important chemical species in atmospheric chemistry andquantum yields of OH radical formation are needed to incorporate the interfacial reactions
into atmospheric models. However, even direct measurements of desorption of OH radicals inphotolysis of liquid NA have not been achieved yet.
We have developed an instrument for direct detection of photodesorbed OH radicals in theultraviolet photolysis of liquid NA by using laser-induced fluorescence (LIF) technique.
Liquid NA was put on a silicon substrate in a low vacuum chamber (1 – 100 Pa) andirradiated with a pulsed 213 nm Nd:YAG laser. OH radicals desorbed from the NA surface
were excited by a second harmonic 282 nm dye laser, and OH-LIF at 315 nm was detected bya photomultiplier tube.
OH (X2Π, v = 0) + hν (282 nm) → OH (A2Σ, v = 1) → OH (X2Π, v = 1) + hν (315 nm)
In order to verify that the detected OH radicals were desorbed from liquid NA surface notformed from gaseous NA, we measured OH-LIF intensities as a function of the delay time
between the two lasers, changing a distance between the dye laser and the Si substrate.
Moreover, we performed single shot experiments to clarify that OH radicals were originatedfrom parent NA molecules on the liquid surface not from photoproducts.
In the workshop, we will show our new experimental setup for the photolysis of liquidorganics and detection of photodesorbed OH radicals using the LIF technique.
References[1] Intergovernmental Panel on Climate Change (IPCC), Fifth Assessment Report (2017).
[2] Rossignol et al., Science 353, 699 (2016).
[3] Vaida, Science 353, 650 (2016).

P22

FAUST III. Misaligned rotations of the envelope, outflow, and disks
protostellar system of VLA 1623$-$2417

in the multiple

S. Ohashi,1 C. Codella,2 N. Sakai,1 C. Chandler,3 C. Ceccarelli,4 S. Yamamoto5, and
FAUST team
1

RIKEN cluster for pioneering research, Japan
2
Osservatorio Astrofisico di Arcetri, Italy
3
National Radio Astronomy Observatory, USA
4
CNRS, IPAG, Univ. Grenoble Alpes, France
5
Department of Physics, The University of Tokyo, Japan
We report a study of the low-mass Class-0 multiple system VLA 1623AB in the Ophiuchus
star-forming region, using H$^{13}$CO$^+$ ($J=3-2$), CS ($J=5-4$), and CCH ($N=3-2$)
lines as part of the ALMA Large Program FAUST. The analysis of the velocity fields
revealed the rotation motions on a wide range of scales in the envelope and the outflows(about 2000 au down to 50 au). We further investigated the rotation of the circum-binary
VLA 1623A disk as well as the VLA 1623B disk.
We found that the minor axis of the circum-binary disk of VLA 1623A is misaligned byabout 12 degrees with respect to the rotation axis of the large-scale outflow and the envelope.
In contrast, the minor axis of the circum-binary disk is parallel to the large-scale magnetic
field according to previous dust polarization observations, suggesting that the misalignment
may be caused by the different directions of the envelope rotation and the magnetic field.
The outflow rotation shows a constant angular momentum with a mean specific angularmomentum of about 100 au km s$^{-1}$.
The launching radius is estimated to be $5-16$ au, suggesting that the outflow is launchedfrom the VLA 1623A1 disk rather than the circum-binary disk.
Furthermore, we detected for the first time a velocity gradient associated with rotation toward
the VLA 16293B disk. The velocity gradient is opposite to the one from the large-scaleenvelope, outflow, and circum-binary disk. The origin of its opposite velocity gradient is also
discussed.
References[1]

Ohashi et al. submitted to ApJ

P23

Experimental study toward the measurements of rotational state dependence ofinterstellar ion-polar molecule reactions at low temperatures
K. Okada, 1 Y. Murayama, 1 N. Kimura, 2 and K. Sakimoto 1
1

2

Department of Materials & Life Sciences, Sophia University, Tokyo, JapanRIKEN, Atomic, Molecular & Optical Physics Laboratory, Wako, Saitama, Japan

Recent astronomical observations have revealed the details of chemical composition in starforming regions and molecular clouds. However, the chemical processes in those regions havenot been fully understood using the existing chemical models with available data on relevant
reaction rate constants [1]. This is because the temperature dependence of the gas-phase ionmolecule reactions in the range of low to intermediate temperatures (10 - 200 K) and theirreaction branching ratio remain unknown. Thus, we have been developing a new experimental
apparatus to measure the reaction temperature dependence of ion-polar molecule reactions at
low temperatures [2, 3].
We report on an experimental study of the rotational cooling effect on the reaction rate
constant of Ca+ + CH3F → CaF+ + CH3 at low translational temperatures as a performance
test of a new experimental apparatus. Combining a cold helium buffer gas cell with a wavy
Stark velocity filter provides us with rotationally and translationally cooled polar molecules,
we could compare the reaction rate constants measured at two different gas cell temperatures,
namely the room temperature and about 30 K. The translational temperatures of the velocityselected molecules were set in the range of approximately 10 to 40 K. The rotational level
distribution of the velocity-selected CH3F molecules was determined by numericalsimulations of the velocity filtering and was used to calculate the rotationally-averaged
capture rate constants with the Perturbed Rotational State (PRS) theory [2]. Comparing to theresults obtained under the condition of room temperature gas cell, we observed a notable
increase in the reaction rate constant at low buffer-gas temperatures. This clearly shows astrong rotational state dependence of the rate constant at low translational temperatures.
(c)1|Vs| = 0.8 kV
TPM = 12(3) K+

ln[V(Ca )]

0.98
0.96
0.94

|Vs| = 2.0 kV
TPM = 24(5) K

0.92
0.9

0

500

1000

1500

reaction time (s)Figure 1 Fluorescence images of Ca+ Coulomb crystals before (a) and after (b) the Ca+ + CH3F → CaF+ +CH3 reactions. (c) A decay curve of the relative number of Ca+ ions due to the reactions between Ca+ andthe velocity-selected CH3F measured at two different translational temperatures of CH3F extracted from thehelium buffer gas cell at about 30 K (He pressure 80 Pa, UV laser detuning −40 MHz).

References[1] N. Sakai et al., 2014, Nature 507, 78.
[2] K. Okada, K. Sakimoto, Y. Takada, and H. A. Schuessler, 2020, J. Chem. Phys. 153, 124305.
[3] K. Okada, Y. Takada, M. Wada, and H. A. Schuessler, 2017, Rev. Sci. Instrum. 88, 083106.

P24

Chemical Differentiation and its Relation with the Physical Structuresin Disk-Forming Regions of Young Low-Mass Protostellar Sources
Y. Oya1,2

and S. Yamamoto1,2

1

2

Department of Physics, The University of Tokyo, Japan
Research Center for the Early Universe, The University of Tokyo, JapanTo understand the chemical origin of the Solar system, the chemical evolution along thestar/planet formation is a key issue. Extensive observational studies have so for demonstrated
a chemical diversity in young low-mass protostellar sources [e.g. 1, 2, 3]. Furthermore,chemical differentiations in the vicinity of the protostars have recently been reported (Figure1). This suggests that molecular distribution is sensitive to a change in the physical conditions
associated with disk formation. Some kinds of molecular lines are therefore prospected towork as molecular markers to highlight particular structures of disk forming regions.
Sulfur-bearing species, for instance OCS and H2CS, especially seem good tracers.
Conversely, detailed physical characterization is essential for elucidating the chemical
evolution occurring there. It has recently been recognized that some molecular lines tend to
trace the mid-plane of a disk/envelope system and others its surface [e.g. 4]. The traced
kinematic structure may differ among these molecular emissions, and thus, their carefulanalyses are essential for further observational studies in disk forming regions. Machinelearnings may help us to disentangle the observed structures.
In this presentation, we would like to report recent progresses in delineating the chemicaldifferentiation and the physical structures in disk forming regions of young protostellar
sources (IRAS 16293-2422 A, L483, B335, etc.) with ALMA.

Figure 1: Chemical differentiation in disk forming regions of young low-mass protostellar sources withdifferent chemical characteristics.

References
[1]
[2]
[3]
[4]

Cazaux et al., 2003, ApJL, 593, 51.
Bottinelli et al., 2004, ApJL, 617, 69.
Sakai and Yamamoto, 2013, ChRv, 113, 8981.
Podio et al., 2020, A&A, 642, L7.

P25

Formation of 3-Pyrolline in Interstellar Space: A Computational Study
A. Pandey,1 A. Pathak,2 and K. A. P. Singh2
1

Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, India

2

Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, India

Complex organic molecules (COMs) are thought to form on icy dust grains in the earliest
phase of star formation. Interstellar detection of the straight-chain (n-propyl cyanide,n−C3H7CN) and branched-chain (i-propyl cyanide, i−C3H7CN) molecules toward the starforming region, Sgr B2(N2) has attracted attention to study the formation mechanism ofCOMs [1]. The first detection of COM strongly hints the existence of other linear and ringshaped molecules, which are prebiotic and building block of proteins.
Through computational methods, we suggest new possible formation and destruction
pathways of branched aliphatic molecule to aromatic compounds in space. We computed
binding energy, enthalpies of formation of several species. We also calculate the kinetic dataof reactions and other spectroscopic information in order to understand the chemical evolution
and formation of aromatic compounds to be present in the Interstellar medium (ISM).

References[1]

A. Belloche, R.T. Garrod, H.S.P. Müller, K.M. Menten,Sci. 345, 158 (2014)[2]

E.E. Etim, P. Gorai, Das. Ankan, E. Arunan, Eur. Phys. J. D (2017) 71: 86[3]

F. J. Lovas, J. M. Hollis, Anthony J. Remijan,P. R. Jewell,The Astrophysical Journal, 645: L137–L140,
2006 July 10[4]

J. Cernicharo1 , N. Marcelino, M. Agúndez , C. Bermúdez , C. Cabezas , B. Tercero , J. R.Pardo, A&A
642, L8 (2020)[5]

R. T. Garrod, A. Belloche, H. S. P. Müller, K. M. Menten , A&A 601, A48 (2017)

P34

H and D diffusion on interstellar water ices
B. Senevirathne,1 S. Andersson,2 and G. Nyman2
1

Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden
2
SINTEF Materials and Chemistry, P.O. Box 4760, NO-7465 Trondheim, Norway

Studies of surface diffusion of atoms on interstellar ices are a popular topic in the field of
Astrochemistry. These chemical processes occur at very low temperatures (e.g., around 10K). At
low temperatures, quantum tunneling becomes a dominant factor deciding the diffusion throughbarriers [1]. Therefore, quantum tunneling must be taken into account in calculating rate
constants. Here, I discuss the single H and D atom diffusion on crystalline (Ih) and amorphous
ice surfaces (ASW). The harmonic transition state theory was used to calculate the rate constants,
and the Wigner tunneling correction was employed as well as a tunneling correction based on the
Eckart potential to address the tunneling effect. The adaptive kinetic Monte Carlo method wasapplied to analyze the random walk trajectories [2]. A range of diffusion coefficients were foundat low temperatures [3].

Figure 1: A map of local minima on a crystalline ice surface (left) and on an ASW surface (right). The blue
dots are the local minima and the red and blue are O and H atoms of the water molecules. There are 59 local
minima on the Ih surface and 30 local minima on the ASW surface.

References

[1]
[2]
[3]

B. Senevirathne, S. Andersson, F. Dulieu, G. Nyman, 2017, Mol. Astrophys. 6, 59.
L. Xu, G. Henkelman, 2008, J. Chem. Phys. 129, 114104.
B. Senevirathne, S. Andersson, G. Nyman, In preparation.

P26

DFT study on hydrogenated and deuterated derivatives of interstellar fullerenes
A. Vats,1 A. Pathak1
1

Department of Physics, Institute of Science, Banaras Hindu University, India+

The credible detection of C60, C70 and C60 in astronomical environments enables the searchfor other fullerene molecules and their derivatives (Zhang et al. 2017). The high reaction rates
of fullerenes with atomic H, the most abundant element in the universe, suggest thedominance of their hydrogeneted forms (Garcίa-Hernández et al. 2010 ), which can go
through deuterium enrichment as well (Cataldo et al. 2009c).
Here, we present theoretical infrared (IR) spectra and standard enthalpy of formation forneutral and singly ionized C60Hm, C60Dm, C70Hn and C70Dn using Density Functional
Theory (DFT). The calculated IR spectra is then compared with observations.

References[1] Cataldo F., Strazzulla G., Iglesias-Groth S., 2009c, MNRAS, 394, 615[2] García-Hernández D. A., Manchado A., García-Lario P., Stanghellini L.,Villaver E.,
Shaw R. A., Szczerba R., Perea-Calderón J. V., 2010, ApJ,724, L39[3] Zhang Y., Sadjadi S., Hsia C.-H., Kwok S., 2017, ApJ, 845, 76

P27

Formation of acetaldehyde on mixed-ice grain surfaces
J. Perrero,1,2 P. Ugliengo,2 and A. Rimola1
1

Universitat Autònoma de Barcelona, Departament de Química, E-08193, Bellaterra, SPAIN
2Università degli Studi di Torino, Dipartimento di Chimica, I-10125, Torino, ITALYInterstellar complex organic molecules (iCOMs) are defined as compounds with ≥6 atoms, inwhich at least one is carbon. [1] Since their discovery in star-forming regions, they have been
gaining increasing interest, as they can be considered the precursors of more complex
molecules, which can have biological relevance. [2] However, understanding how iCOMs areformed is still a matter of debate, as it is supposed that both gas-phase and on-grain chemistry
are needed for their synthesis. [3], [4] Acetaldehyde is one of the most detected species,
therefore its formation routes are of paramount interest in astrochemical models. [5]In the gas phase, CH3CHO appears to be efficiently synthesized from ethanol and from ethyl
radical. [5], [6] On the surface, radical-radical recombinations are preferred, for being
barrierless, even though the orientation of the fragments has a crucial role and side reactions
like H-abstraction may take place. [7], [8] We investigated a new reaction pathway for theformation of acetaldehyde, namely CH3 + CO(ice), where the CO is a component of the ice
surface. Our H2O:CO amorphous model contains 25% of carbon monoxide and was chosen to
avoid H-abstraction reactions. We found that the reaction, in the case to follow a LangmuirHinshelwood mechanism, exhibits a high energy barrier to be surmountable in interstellar
conditions, but when adopting a Eley-Rideal mechanism it is barrierless. Subsequenthydrogenation step is found to be barrierless depending on the orientation of the two radicals.
Thus, we suggest this pathway to form acetaldehyde to be likely when a CH3 radical comingfrom the gas phase lands on a CO-rich region in icy surfaces.

Figure 1: Reactant (R), transition state (TS), and product (P) of the reaction of CH3 with a CO molecule ofthe (001) surface cut from our H2O:CO amorphous ice model. Fragments involved in the reaction are
represented as balls and sticks. Colour code: gray, H; brown, C; red, O. Distances are in Å.

References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

E. Herbst, 2017, Int. Rev. Phys. Chem. 36, 287.
C. Ceccarelli, P. Caselli, F. Fontani, et al., 2017, ApJ 850, 176.
N. Balucani, C. Ceccarelli, & V. Taquet, 2015, MNRAS 449, L16.
R.T. Garrod, S.L.W. Weaver, & E. Herbst, 2008, ApJ, 682, 283.
F.Vazart, C. Ceccarelli, N. Balucani, & D. Skouteris, 2020, MNRAS 499, 5547.
D. Skouteris, N. Balucani, C. Ceccarelli, et al., 2018, ApJ, 854, 135.
J. Enrique-Romero, A. Rimola, C. Ceccarelli, et al., 2019, ACS Earth Space Chem 3, 2158.
T. Lamberts, M.N. Markmeyer, F.J. Kolb, & J.Kastner, 2019, ACS Earth Space Chem 3, 958.

P28

PyQMMM for modelling chemical processes in the interstellar medium
P. V. G. M. Rathnayake,1 W. M. C. Sameera,2 and N. Watanabe2
1School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
2
Institute of Low Temperature Science, Hokkaido University, N19-W8, Kita-ku, Sapporo,
Hokkaido 060-0819, Japan.

We have developed PyQMMM; [1] a Python-based interfacing software for subtractive
quantum mechanics/molecular mechanics (QM/MM) calculations with the AMOEBA09
polarizable force field. PyQMMM enables calculating large molecular systems, such as
interstellar ices, using the ONIOM(QM:MM) [2-7] method at a low computational cost. We
have used PyQMMM, employing the ONIOM(QM:AMOEBA09) method, to calculate thebinding energy of SH and OH radicals on amorphous solid water (ASW). A range of binding
energies was obtained for SH radical (0.10-0.36 eV) and OH radical (0.21-0.52 eV) on ASW.
Computed average binding energies, 0.22 eV of SH and 0.36 eV of OH, suggested that the SH
radical binding on ASW is weak compared to that of OH. We have also rationalized themechanism for the reaction between OH anion and CO2 in ice using the ONIOM(wB97XD:AMOEBA09) calculations. The computed reaction mechanism showed a very low energy
path, giving rise to HO-C(O)-OH and OH anion is recovered during the reaction. Thus, for
implications in astrochemistry, we propose that OH anions in interstellar ices can react with themolecules trapped in ices to synthesize organic molecules. These examples evidence that the
PyQMMM is a user-friendly strategy to study chemical processes in the interstellar medium.
References[1] P. V. G. M. Rathnayake, W. M. C. Sameera, Naoki Watanabe. (In preparation).
[2] W. M. C. Sameera, B. Senevirathne, S. Andersson, M. Al-lbadi, H. Hidaka, A. Kouchi, G. Nyman, N.
Watanabe. J. Phy. Chem. A, 2021, 125, 1, 387–393.
[3] W. M. C. Sameera, F. Maseras, J. Chem. Info. Model. 2018, 58, 1828-1835.
[4] W. M. C. Sameera, B. Senevirathne, S. Andersson, F. Maseras, G. Nyman, J. Phy. Chem. C, 2017, 121,
15223-15232.
[5] L. W. Chung, W. M. C. Sameera, R. Ramozzi, A. J. Page, M. Hatanaka, G. P. Petrova, T. V. Harris, X.
Li, Z. Ke, F. Liu, H-B. Li, L. Ding and K. Morokuma, Chem. Rev. 2015, 115, 5678-5796.
[6] W. M. C. Sameera, F. Maseras, WIREs Comput. Mol. Sci., Wiley-VCH, 2012, 2, 375-380.
[7] W. M. C. Sameera, F. Maseras, Phys. Chem. Chem. Phys., 2011, 13, 10520-10526

P29

Star Formation Feedback to a Parent Cloud: The Elias 29 Case
E. Saiga,1 Y. Oya,1 A. Miottello,2 C. Ceccarelli,3 C. Codella,4 C. Chandler,5N. Sakai,6 S. Yamamoto,1 and FAUST Team Members
1Department of Physics, University of Tokyo, Japan
2European Southern Observatory, Germany
3Université Grenoble Alpes, IPAG, France
4INAF, Osservatorio Astrofisico di Arcetri, Italy
5National Radio Astronomy Observatory, USA
6RIKEN Cluster for Pioneering Research, Japan

Elias 29 is a low-mass Class I protostar in the ρ-Ophiuchi molecular cloud complex.
According to the recent ALMA observation, a compact component (∼50 au) associated to theprotostar is abundant in SO and SO2, while deficient in CS and organic molecules such as
CCH and CH3OH [1]. On the other hand, a southern ridge component apart from the protostar
by 500 au is mainly traced by CS and H13CO+. For these interesting features, this source isselected in the ALMA large program FAUST (Fifty AU STudy of the chemistry in the disk/
envelope system of Solar-like protostars).
To further characterize this source, we have studied an outflow/jet around the protostar andthe star formation feedback to a parent cloud by using the chemical diagnostic power of
FAUST. Main results are as follows. (1) We have detected the C18O (2-1) and SO (65-54)
emission at a spatial resolution of 70 au, and found that they trace an outflow cavity on a 2000
au scale for the first time. (2) We have detected a compact component in the SO emission at
the eastern side of the protostar. Since the SO emission is often recognized as a shock tracer,
this component is likely attributed to a bow shock caused by a protostellar jet.
(3) We have found a relatively low DCO+/HCO+
ratio in the southern ridge. In particular, the ratio
is as low as 0.0029 at the interaction position
between the outflow and the ridge. Thus, this low
ratio would originate from the outflow interaction.
(4) We have evaluated the rotation temperaturearound Elias 29 by using the SO (65-54) andSO (66-55) emission and identified the relatively
high temperature at the position of the bow shock
Figure 1: The rotation temperature around and the interaction region.
the protostar. The highest temperature isobserved at the protostar position. The hightemperature at the eastern side of the
protostar is attributed to the bow shock andthat at the southern side to the interaction
between the outflow and the ridge.

References[1] Oya et al., 2019, ApJ, 881, 112

This study reveals a chemical change associated toa small-scale (∼100 au scale) dynamic interaction
between the Class I outflow/jet structure and thesurrounding cloud material, i.e., the southernridge.

P30

Measurements of Microwave Spectra of Methanol Isotopologues
in ALMA Band 6 Frequency Range
T. Oyama,1 A. Tamanai,1 Y. Ohno,1,2 S. Zeng,1 Y. Watanabe,1,3 T. Sakai,4 R. Nakatani,1and N. Sakai1
1

Cluster for Pioneering Research, RIKEN, Japan
Department of Chemistry, Tokyo University of Science, Japan
3
Materials Science and Engineering, College of Engineering,Shibaura Institute of Technology
4
Graduate School of Informatics and Engineering, The University of Electro-Communications
2

In radio astronomy, accurate rest frequencies of molecular transitions are indispensable forsecure identification of molecular species and accurate analyses of Doppler shifts caused bymotions of the target sources. In observations, we have seriously realized the importance of
the accurate rest frequencies of molecular transitions [cf; 1-4]. By strong lines, we can discussgas motions in detail, and can set the velocity of the target system to the Solar system. As
demonstrated in many sources, velocity analysis not only tells us kinematics of the system but
also excitation condition of the gas on the corresponding position [cf; 5]. Accurate restfrequencies of lines are therefore indispensable for such astronomical studies.
Methanol is a fundamental saturated-organic molecule and known to be abundant in star
forming regions. It is thought to be formed on grain surface through hydrogenation reactionsof adsorbed CO molecule. Since methanol can be a parent of more complex organic
molecules (COMs), tracing it’s abundance along protoplanetary-disk formation is importantto understand origin of the chemical complexity in the Solar system. Especially isotopic
ratios of molecules tell us critical information about their formation pathways. With these inmind, we have measured rotation spectra of methanol isotopologues by using SUMIRE(Emission type microwave spectrometer developed in RIKEN, [6]) in the frequency range
corresponding to ALMA Band 6 (215-265 GHz). A portion of the results will be presented.
References
[1]
[2]
[3]
[4]
[5]
[6]

N. Sakai, O. Saruwatari, T. Sakai, S. Takano, and S. Yamamoto 2010 A&A, 512, A31
N. Sakai, S. Shuro, T. Sakai, S. Shiba, Y. Sumiyoshi, Y. Endo, and Y. Yamamoto 2013, JCPA, 117, 9831
T. Soma, N. Sakai, Y. Watanabe, and Y. Yamamoto 2018, ApJ, 854, 116
Y. Shibayama, Y. Watanabe, Y. Oya, N. Sakai, et al. 2021, ApJ, 918, 32
N. Sakai, T. Sakai, T. Hirota, Y. Watanabe, et al. 2014, Natur., 507, 78
Y. Watanabe, Y. Chiba, T. Sakai, A. Tamanai, R. Suzuki, and N. Sakai 2021, PASJ, 73, 372.

P31

Development of the RHEED apparatus for in situ structural analysis ofwater ices in low-temperature and ultrahigh vacuum conditions
R. Sato,1 S. Taniguchi,1 N. Numadate,1 and T. Hama1
1

Komaba Institute for Science, The University of Tokyo, Meguro, Tokyo 153- 8902, Japan

Water (H2O) ice is a ubiquitous material for all of us, which has been also found to exist incold regions of the Universe. In interstellar molecular clouds, the birth places for stars andplanets, water ice is the dominant solid component, and chemical reactions occurring on theice surface are expected to contribute greatly to the evolution of interstellar molecules [1].
Due to its cryogenic environment in interstellar molecular clouds, it has been regarded thatinterstellar water ice is mostly in amorphous forms. However, Hama et al. recently reported
for the first time that ice with a long-range ordered crystalline structure can be formed even at
cryogenic temperatures by preparing a H2O/Ne matrix at 6 K in a vacuum environment andheating it to 11~12 K to sublimate Ne [2]. They determined the crystallinity only by infrared(IR) spectroscopy, whereas IR spectroscopy has a problem that Ice Ic (cubic) and Ice Ih(hexagonal) cannot be distinguished. Therefore, further structural analysis by diffraction is
crucial.
In this research, we report on the development of the experimental apparatus necessary to
identify the crystal structure of ice surfaces. Specifically, an Al vacuum chamber isevacuated at the base pressure of 10-7 Pa. An Al substrate is mounted on the cold head of aclosed-cycle He refrigerator, which is cooled down to 6 K for water vapor deposition. The
structure of vapor-deposited ice is then analyzed by RHEED (Reflection High Energy
Electron Diffraction). The RHEED patterns are projected onto a fluorescent screen. Figure 1
shows the present view of the RHEED apparatus in the laboratory. We will report moredetails of the experimental setup and present some preliminary RHEED data.

Figure 1: The present view of the RHEED apparatus

References[1]
T. Hama, & N. Watanabe, 2013, Chem. Rev. 113, 8783−8839[2]
T. Hama, S. Ishizuka, T. Yamazaki, Y. Kimura, A. Kouchi, N. Watanabe, T. Sugimoto, & V. Pirronello,
2017, Phys. Chem. Chem. Phys. 19, 17677−17684

P32

A Theoretical, Neural-Network Assisted Study of Methane Formation under
Astrophysical Conditions
R. Schömig,1 G. Molpeceres,1 and J. Kästner1
1

Institute for Theoretical Chemistry, University of Stuttgart, Germany

Dense molecular clouds are cold regions (~10-20 K) in the interstellar medium (ISM) that
accommodate dust grains coated with ice, usually amorphous. The chemical components of
those ices are H2O, CO, CO2, CH3OH, etc. with strongly fluctuating compositions. Thesesurfaces play a central role in the chemistry of the ISM and therefore in the evolution ofmolecular clouds, acting as templates of atoms, radicals and molecules, to meet on top ofthem [1]. Additionally these ices help to dissipate the energy of the reactions occurring on
them. Hence, these surfaces enable the synthesis of a variety of chemical compounds thatwould not be accessible by gas phase reactions alone. In this work, we studied the formationof CH4 by investigating the reaction of a CH3 radical with H on the surface of amorphoussolid water (ASW). Among the things we analyzed is the energy redistribution vs chemicaldesorption [2, 3]. A periodic model of ASW was used to mimic the reaction. As a first step,
we have obtained the binding energy (BE) distribution of CH3 on the surface with values
between -500 and -4000 K. The reaction was modeled by placing CH3 on binding sites withhigh, medium and low BEs for both axial and planar orientation of the CH3 radical on thesurface. Later, hydrogen atoms have been placed spherically around the CH3 radical to sample
many possible trajectories. Subsequently, molecular dynamics simulations for the reaction
were carried out at a temperature of 10 K. The potential driving the dynamics is a neuralnetwork potential trained on DFT energies and forces [4, 5]. We have found that the initialorientation of the CH3 radical hardly plays any role on the reaction. On the contrary, we foundhuge differences in the evolution of the reaction as a function of the CH3 binding site and theinitial orientation of the H with respect to the methyl radical.

Figure 1: Trajectory of the hydrogen atom approaching the methyl radical to form methane during the MD
simulation in increments of 2 fs per hydrogen frame.

References

[1]
[2]
[3]
[4]
[5]

Cuppen, H., Walsh, C., Lamberts, T., et al. 2017, Space Sci. Rev. 212, 1
Garrod, R. T., Wakelam, V., Herbst, E. 2007, Astron & Astrophys. 467, 1103
Pantaleone, S., Enrique-Romero, J., Ceccarelli, C., et al. 2021, Astrophys. J. 917, 49
Molpeceres, G., Zaverkin, V., & Kästner, J. 2020, Mon. Not. R. Astron. Soc. 499, 1373
Zaverkin, V., & Kästner, J. 2020, J. Chem. Theory Comput. 16, 5410

P33

H and D diffusion on interstellar water ices
B. Senevirathne,1 S. Andersson,2 and G. Nyman2
1

Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden
2
SINTEF Materials and Chemistry, P.O. Box 4760, NO-7465 Trondheim, Norway

Studies of surface diffusion of atoms on interstellar ices are a popular topic in the field of
Astrochemistry. These chemical processes occur at very low temperatures (e.g., around 10K). At
low temperatures, quantum tunneling becomes a dominant factor deciding the diffusion throughbarriers [1]. Therefore, quantum tunneling must be taken into account in calculating rate
constants. Here, I discuss the single H and D atom diffusion on crystalline (Ih) and amorphous
ice surfaces (ASW). The harmonic transition state theory was used to calculate the rate constants,
and the Wigner tunneling correction was employed as well as a tunneling correction based on the
Eckart potential to address the tunneling effect. The adaptive kinetic Monte Carlo method wasapplied to analyze the random walk trajectories [2]. A range of diffusion coefficients were foundat low temperatures [3].

Figure 1: A map of local minima on a crystalline ice surface (left) and on an ASW surface (right). The blue
dots are the local minima and the red and blue are O and H atoms of the water molecules. There are 59 local
minima on the Ih surface and 30 local minima on the ASW surface.

References

[1]
[2]
[3]

B. Senevirathne, S. Andersson, F. Dulieu, G. Nyman, 2017, Mol. Astrophys. 6, 59.
L. Xu, G. Henkelman, 2008, J. Chem. Phys. 129, 114104.
B. Senevirathne, S. Andersson, G. Nyman, In preparation.

Development of a high-sensitivity and non-destructive detection system for trace
amounts of adsorbates on ice
A. Ishibashi,1 H. Hidaka,1 Y. Oba,1 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science/Hokkaido University, Japan

Molecular evolution on the surface of interstellar ice dust is important. In particular, theinformation of radical is crucial for understanding the formation process of complex organic
molecule. Although many experiments have been performed [1], the detection of trace
adsorbates like radicals is still difficult with conventional experimental methods due to the lackof sensitivity and thus little is known about behavior of such species on the ice surfaces.
Recently, we newly developed highly-sensitivity and non-destructive mass analysis
apparatus for trace amounts of adsorbates on the amorphous solid water (ASW) surface. Basedon a design in literature [2], we constructed an apparatus composed of a Cs+ ion gun andQuadrupole Mass Spectrometer (QMS) in an ultra-high vacuum chamber. Using that, adsorbed
species X (Mass: M) on ASW substrate were picked up with Cs+ ion and mass-analyzed by the
QMS as Cs-X+ (Mass: 133 + M). As a result of various improvements, we have succeeded in
detecting the trace of radicals adsorbates on ASW surface. As shown in Figure 1, we canmonitor the behavior of OH radical on ASW upon the photolysis of H2O.

Figure 1: Variations in the pickup signal intensity of OH radical generated by ASW (10 ML) during UV
irradiation at 10 K.

References[1][2]

T. Hama & N. Watanabe, 2013, Chem. Rev. 113, 8783-8839.
H. Kang, 2011, Bull. Korean Chem. Soc. 32, 389-398.

P36

Branched Chain Molecules in Interstellar Medium
S. Srivastav,1 M. Sil,2 P. Gorai,3 A. Das,2 A. Pathak,1
1

Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, India
Indian Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata, 700084,
West Bengal, India
3
Department of Space, Earth & Environment, Chalmers University of Technology, SE-412 96
Gothenburg, Sweden
2

Interstellar detection of the straight-chain (n-propyl cyanide, n−C3H7CN) and branched-chain(i-propyl cyanide, i−C3H7CN) molecules toward the star-forming region, Sgr B2(N2) has
attracted attention to study the formation mechanism and chemical evolution of branchedcarbon-chain molecules. These moleules are the precursors of biologically relevant prebiotic
molecules, i.e., amino acids. In this light, we consider n-butyl cyanide and higher-orderbranched chain molecule, t-butyl cyanide from the C5H9N isomeric group. We employ gasgrain chemical model to study the chemical evolution of these species. We predict newformation and destruction pathways which could lead to more insight into the formation anddestruction schemes of complex organic branched chain molecules in space. Quantum
chemical calculations such as binding energy, enthalpy of formation, reaction enthalpies,
activation barrier, dipole moments, and other spectroscopic information assist to study thechemical evolution and examine the possibility of detecting higher-order branched-chain
molecules in high-mass star-forming regions.

References:
1. Garrod, R. T., Belloche, A., M ̈uller, H. S. P., & Menten,K. M. 2017, A&A, 601, A48
2. Belloche, A., Garrod, R. T., M ̈uller, H. S. P., & Menten,K. M. 2014, Science, 345, 1584
3. Das, A., Sahu, D., Majumdar, L., & Chakrabarti, S. K.2016, MNRAS, 455, 540
4. Das, A., & Chakrabarti, S. K. 2011, MNRAS, 418, 545

P37

Nitrile chemistry in a disk structure around the G24.78+0.08 hyper-compact HII region
K. Taniguchi,1 K. Tanaka,2,1 Y. Zhang,3 R. Fedriani,4 J. C. Tan,4,5 S. Takakuwa,6
F. Nakamura,1,7 M. Saito,1,7 L. Majumdar,8 and E. Herbst5,91

National Astronomical Observatory of Japan, Japan
Center for Astrophysics and Space Astronomy, University of Colorado Boulder, USA
3
Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Japan
4
Department of Space, Earth & Environment, Chalmers University of Technology, Sweden
5
Department of Astronomy, University of Virginia, USA
6
Department of Physics and Astronomy, Kagoshima University, Japan
7
Department of Astronomical Science, SOKENDAI, Japan
8
School of Earth and Planetary Science, NISER, India
9
Department of Chemistry, University of Virginia, USA
2

Complex nitrile species, such as CH3CN and HC3N, have been usually detected in disks
around T Tauri stars and Herbig Ae stars (e.g., [1]). The Molecules with ALMA at Planetforming Scale (MAPS) [2] Large Program reveals that CH3CN and HC3N trace different layers of these disks; HC3N traces upper and warmer layers compared to CH3CN [3]. Thus, it isuseful for investigating physical conditions of disks to observe different nitrile species. However, only CH3CN lines have been used as typical disk tracers around massive stars (M > 8Msun) so far, and the nitrile chemistry in disks around such massive stars is still unrevealed yet.
We have analyzed Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 6 Band 6
data toward the hyper-compact HII region G24.78+0.08 A1 (hereafter G24 HC HII region). A
current protostellar mass is derived to be ~20 Msun by the SED fitting. Two vibrationallyexcited lines of HC3N (v7=2, J=24-23, l= 0 and l= 2e) have been detected from this HC HII
region. The spatial distribution and position-velocity (P-V) diagram of the HC3N line (l=2e)
are similar to those of the vibrationally-excited CH3CN line (v8=1, JK,l =126,1-116,1). The
CH3CN lines were confirmed to trace the molecular disk in the G24 HC HII region [4]. These
results suggest that the HC3N emission traces the molecular disk around the G24 HC HII region previously identified by CH3CN.
Using the 13CH3CN (J=13K-12K, K=0-6) and HC13CCN (J=26-25) lines, we have derived theN(13CH3CN)/N(HC13CCN) column density ratios at the two positions around the G24 HC HII
region, which we name “HC HII region” and “Molecular Peak”, respectively. The
N(13CH3CN)/N(HC13CCN) ratios are derived to be ~3.0-3.5. If there are no effects of the 13C
isotopic fractionation in each molecule (e.g., [5]) and the selective photodissociation of
13
CH3CN and HC13CCN, the N(13CH3CN)/N(HC13CCN) ratio is expected to reflect theCH3CN/HC3N abundance ratio. We compare these N(13CH3CN)/N(HC13CCN) ratios to theCH3CN/HC3N abundance ratio in disks around T Tauri stars and Herbig Ae stars [3], asshown in Figure 1. The N(13CH3CN)/N(HC13CCN) ratios around the G24 HC HII region are
more than an order of magnitude higher than the CH3CN/HC3N abundance ratios in the otherdisks (~0.03-0.11). The higher N(13CH3CN)/N(HC13CCN) ratios around G24 suggest that theCH3CN/HC3N abundance ratios in the disk around the massive star are higher than thosearound the other disks.
Another possible interpretation of the much high N(13CH3CN)/N(HC13CCN) ratios around theG24 HC HII region is that the column density ratios do not reflect the CH3CN/HC3N abun-dance ratios. In fact, the integrated-intensity ratios of the vibrationally-excited lines of
CH3CN and HC3N, which have almost same upper-state energies (~770 K), are derived to be~ 0.5-1.5 around the G24 HC HII region. These integrated-intensity ratios are still higher than
the abundance ratios in disks around T Tauri stars and Herbig Ae stars. Thus, it is most likelythat the CH3CN/HC3N abundance ratios around the G24 HC HII region are higher than thosein the other disks around the lower-mass stars.
The high CH3CN/HC3N ratios around the G24 HC HII region imply the thermal desorption ofCH3CN in the hot dense region, and efficient destruction of HC3N by the UV radiation andreactions with ions (e.g., H3+) in the ionized region. The former is supported by the fact thatthe derived excitation temperatures of CH3CN (~ 330 K) around the G24 HC HII region aremuch higher than its sublimation temperature. This is different from a suggestion that thephoto-evaporation is important in disks around T Tauri stars and Herbig Ae stars. The higher
UV photodissociation rate of HC3N compared to CH3CN [6] can destroy both HC3N and
HC13CCN efficiently, which should increase the CH3CN/HC3N abundance ratios and theN(13CH3CN)/N(HC13CCN) ratios. In summary, the nitrile chemistry around the massive star is
likely different from that in the disks around T Tauri stars and Herbig Ae stars.

Figure 1: Comparisons of the CH3CN/HC3N abundance ratio among disks with different stellar masses.

References

[1]
[2]
[3]
[4]
[5]
[6]

J. B. Bergner, V. G. Guzman, K. I. Öberg, et al., 2018, ApJ, 857, 69.
K. I. Öberg, V. V. Guzman, C. Walsh, et al., 2021 (in press) arXiv:2109.06268
J. D. Ilee, C. Walsh, A. S. Booth, et al., 2021 (in press) arXiv:2109.06319
L. Moscadelli, R. Cesaroni, M. T. Beltrán, 2021, A&A, 650, A142.
K. Taniguchi, H. Ozeki, M. Saito, 2017, ApJ, 846, 46.
R. Le Gal, M. T. Brady, K. I. Öberg, et al., 2019, ApJ, 886, 86.

P38

A New Approach to Compute the Accurate Binding Energy Distribution of Molecules
at Ice Interstellar Grain Models: the Case of NH3
L. Tinacci,1,2 A. Germain,2 S. Pantaleone2,3, S. Ferrero2,4, C. Ceccarelli1 and P. Ugliengo2
1

IPAG, CNRS, Univ. Grenoble Alpes, France
Dip. di Chimica, Univ. degli studi di Torino, Italy
3
Dip. di Chimica, Biologia e Biotecnologie, Univ. di Perugia, Italy
4Dip. di Quimica, Univ. Autonoma de Barcelona, Spain
2

In the denser (≥104 cm-3) and colder (≤20 K) regions of the interstellar medium (ISM), submicron sized dust grains are covered by several layers of H2O-dominated ices [1]. The
composition and thickness of these ices is governed by whether molecules and atoms remain
glued to the grain surfaces or not and whether they can move on the surfaces and scan them,so to meet other species and react. On the other hand, in warmer regions, these interstellar
ices can (partially) sublimate and enriched the gas of its components. The ice-gas interactionis, therefore, a hugely important process that determines the chemical composition of theISM. The basic quantity that rules all these processes is the binding energy (BE) of thespecies to the interstellar ice surface. It is thus not an exaggeration to affirm that the BE ofinterstellar atoms and molecules is a small quantity with a huge impact. So far, with very
few exceptions, astrochemical models have assumed single values for each species BE. In
this work, we present a new and robust computational strategy to evaluate BEs bytheoretical computations on a novel amorphous solid water (ASW) cluster [2]. This cluster
exhibits a large number of adsorption sites where NH3 (our test molecules) can be adsorbed.
The BEs are computed through the ONIOM [3] approach using a QM:QM layer envisaging
xTB-GFN2 [4] as the low method and DLNPO-CCSD(T) [5] as the high level method. The
generality of xTB-GFN2 as a low-level method allows to treat a large variety of interstellar
species, at variance with the adoption of ad hoc force fields as currently done in theliterature. As a first study and astrochemically important case, we applied this new
methodology, to derive the BE distribution of ammonia, computed on about 160 different
adsorptions shown in the right figure. Machine learning clustering analysis is performed andfurther the two clusters found were fitted by Maxwell-Boltzmann distributions, which reflect
the different nature of the possible bonds of NH3 on ASW. Particularly important is the lowenergy end of the BE distribution, which has an unexpected impact on some astrochemical
situations, like protoplanetary disks.

Figure 1: NH3 ZPE corrected BE Distribution

References

[1]
[2]
[3]
[4]
[5]

A. Boogert, et al., ARRA 2015, 53, 541
A. Germain, et al., to be submitted
S. Dapprich, et al., J. Mol. Struct. 1999, 462, 1-21
C. Bannwarth, et al., J. Chem. Theory & Comp. 2019, 15(3), 1652-1671
Y. Guo, et al., J. Chem. Phys. 2018, 148, 011101

P39

STM and Non-Contact-AFM observation of Si(111)by a self-made qPlus sensor at low temperatures
T. Tomaru, H. Hidaka, A. Kouchi, N. Watanabe
Institute of Low Temperature Science /Hokkaido University

In recent years, many laboratory experiments have been performed to simulate chemical
reactions on the surfaces of interstellar ice dust. In those experiments, amorphous ices wereformed by water vapor deposition onto the low-temperature substrate under an ultra-highvacuum condition as an analogue of ice dust. The morphology of such amorphous ices
strongly depends on the various experimental conditions like deposition angle, growth rate,
and the deposition temperature when ices were formed. Because the morphology would affectchemical processes occurring on the surface, direct observation of ice morphology isessentially important to understand the simulation experiments appropriately. Therefore, toobserve the surface morphology of amorphous ice under various formation conditions, we aredeveloping a new device. To perform nondestructive real-space measurements of thenanoscale structure of the amorphous ice surface, an ultra-high vacuum low-temperaturescanning probe microscope (SPM: INFINITY, Scienta Omicron) with a non-contact atomic
force microscope (nc-AFM) mode is used. Although this device is powerful tool for our
purpose, the probe generally used in this type of SPM, named qPlus sensor, is not sufficiently
sharp for measuring the fine surface structure of amorphous ice. Therefore, the ultra-sharp
qPlus sensor (the tip curvature radius of ~ 1 nm) is required. In this presentation, we introduce
the present status of the production of the ultra-sharp qPlus sensor.
For a Si cantilever, which is conventional type of the SPM probe, many commercial
products with the ultra-sharp shape are available because the manufacturing technology with a
tip curvature radius of ~ 1 nm is well established. Therefore, we tried to construct the ultrasharp qPlus sensor by using the tip of an ultra-sharp Si cantilever instead of the conventional
tungsten wire tip. As the tentative production, the qPlus sensor using the tip of an inexpensive
Si cantilever (the tip curvature radius of ~ 10 nm) was produced. To test the self-made qPlus
sensor, STM (scanning tunneling microscope) and nc-AFM measurements of Si(111)-7×7
were conducted. Figure 1 shows the results of observations at 10 K using (a) Pt/Ir tip for STM
and (b) the self-made qPlus sensor for STM and nc-AFM. We confirmed that the self-madeqPlus sensor could obtain the Si(111)-7×7 structure in STM and AFM.

Figure.1 (a)STM image scanned by Pt/Ir tip at 10 K. (b) Image scanned by the self-made qPlus sensor at 10
K. The upper and lower sides are nc-AFM and STM images, respectively. Scan areas of both images are 20
nm×20 nm.

P40

Diffusive hydrogenation of CO embedded in amorphous solid waterat temperature up to 70 K
M. Tsuge, H. Hidaka, A. Kouchi, and N. Watanabe
Institute of Low Temperature Science, Hokkaido University, Japan
Surface processes on interstellar dust grains have an important role in the chemical evolution
in molecular clouds. Hydrogenation reactions on ice surfaces have been extensively studied
and are known to occur at low temperatures mostly below 20 K [1,2]. In contrast, information
about the chemical processes of molecules within an ice mantle is lacking. In this work, weinvestigated diffusive hydrogenation reactions of carbon monoxide (CO) embedded inamorphous solid water (ASW) as a model case and discovered that the hydrogenation of CO
efficiently proceeds to yield H2CO and CH3OH even above 20 K when CO is buried beneath
ASW [3].
In our experiments, layered ice samples were prepared by depositing water molecules oversolid CO (~5 monolayers, MLs), in which the thickness of ASW layer was varied from 1 to
80 MLs. The temperature of layered ice sample was set within the range 10–70 K for H-atom
irradiation. Depletion of CO and formation of H2CO and CH3OH were monitored by thereflection absorption infrared spectrometry.
Figure 1 shows the experimental result for a layered ice at 20 K; in the IR spectrum (leftpanel), depletion of CO and formation of H2CO and CH3OH are clearly seen, and time
variation of column densities are plotted on the right panel. For the ASW layer with 20 MLs,
temperature dependence was investigated, and it was found that CO hydrogenation efficiency
is enhanced by elevating temperatures from 10 to 20 K and that CO hydrogenation occurred
even at temperatures up to ~70 K. Another series of experiments performed by varying the
thickness of the ASW layer (at 20 K) revealed that hydrogenation of CO occurs when CO isfully buried under the ASW layer. The experimental results suggest that H atoms diffuse
through the cracks of ASW and have a sufficient residence time to react with embedded CO.
Cracks collapse at elevated temperatures but the occurrence of hydrogenation reactions meansthat the cracks would not completely disappear and remain large enough for penetration byhydrogen atoms. Considering the H-atom fluence in the laboratory and molecular clouds, wesuggest that the penetration of H atom and its reactions within the ice mantle occur inastrophysical environments.
H-atom fluence / atoms cm−2
(A)

H2CO
CH3OH

4

2

Layered ice(20ML ASW on CO)

0
H2O

−2

−4

CO
2200

2000

1800

1600

1400

Wavenumber / cm−1

1200

1000

Column density / 1015 molecules cm−2

ΔAbsorbance / 10−3

6

5.0×1017

0.0
1.5

1.0×1018

1.5×1018

(B)

1.0
0.5
0.0

H2CO
CH3OH
CO

−0.5
−1.0
0

50

100

150

200

250

H-atom irradiation Time / minFigure 1: (A) Infrared difference spectrum after 180 min H-atom irradiation on a layered sample with 20
MLs ASW on 5 MLs CO. (B) Variations in column densities with H-atom irradiation time.

References

[1]
[2]
[3]

Watanabe, N., Shiraki, T., & Kouchi, A. 2003, ApJL, 588, L121
Fuchs, G. W., Cuppen, H. M., Ioppolo, S., et al. 2009, A&A, 505, 629
Tsuge, M., Hidaka, H., Kouchi, A., Watanabe, N. 2020, ApJ, 900, 187

P41

Ortho-to-para nuclear spin conversion of H2 on interstellar bare grain analogues
M. Tsuge,1 T. Namiyoshi,1 K. Furuya,2 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University, Japan
2
National Astronomical Observatory of Japan, JapanThe H2 molecule has two nuclear spin isomers: ortho and para isomers. The energy difference
between ortho and para state is as large as 14.7 meV (~170 K), and the nuclear spin
conversion between these states is forbidden in the gaseous phase. Therefore, these isomers
are often considered different species. The ortho-to-para ratio (OPR) is known to affectchemical evolution as well as gas dynamics in space. To understand the meaning of H2 OPR
determined from astronomical observations, the mechanisms that change the OPR should beclarified. In contrast to the gaseous phase mechanisms, in which spin exchange reactions with
protons and hydrogen atoms alter OPR, little has been known about H2 nuclear spin
conversion (NSC) on astrophysically relevant surfaces. In this work, we investigated the H2
NSC on interstellar bare grain analogues: silicate and carbonaceous materials [1,2].
In our experiments, time evolution of H2 OPR on the surfaces was traced by using a
combination of temperature-programmed desorption (TPD) and resonance-enhanced
multiphoton ionization (REMPI) methods. H2 with OPR = 3 was deposited onto amorphousMg2SiO4 or amorphous diamond-like carbon film kept at 10–18 K, TPD was initiated after
certain waiting times after deposition, and desorbing ortho and para isomers were selectively
ionized by the REMPI method and detected by a time-of-flight mass spectrometer.
The NSC time constants obtained for the surfaces of astronomical grain analogues [1–3]are plotted as a function of temperature in Figure 1. In each case, the NSC time constants
became smaller as temperature increases. This temperature dependence indicates that surface
phonons play an important role in the energy dissipation process associated with the H2 NSC.
Using a simple model considering collision rate of gaseous H2 with grain surfaces, sticking
probability, NSC time constant, and sublimation timescale of adsorbed H2, we found that theH2 NSC process especially on bare silicate grain surface is efficient to reduce the gaseous H2
OPR within astronomically meaningful timescale.

NSC time constant (s)

10000

DLC
ASW
Silicate

1000

100

8

10

12

14

16

18

Temperature (K)Figure 1: The plot of temperature dependence of the NSC time constants for amorphous diamond-likecarbon (DLC, blue triangle) [1], amorphous solid water (ASW, black square) [3], and amorphous-Mg2SiO4(silicate, red circle) [2].

References

[1]
[2]
[3]

Tsuge, M., T. Namiyoshi, K. Furuya, et al. 2021, ApJ, 908, 234
Tsuge, M., Kouchi, A., & Watanabe, N. 2021, ApJ, in press, https://arxiv.org/abs/2109.12734
Ueta, H., Watanabe, N., Hama, T., & Kouchi, A. 2016, PhRvL, 116, 253201

P43

Development of Spectrometer Using Superconductor Mixer
Receiver (SUMIRE)
Y. Watanabe,1,2 A. Tamanai,2 T. Sakai,3 T, Oyama,2 R. Nakatani, 2 Y. Chiba,4 and N. Sakai2
1

Department of Material Science, Shibaura Institute of Technology, Japan
2
RIKEN, Japan
3
Graduate School of Informatics and Engineering, The University ofElectro-Communications,, Japan
4
Department of Physics, The University of Tokyo, Japan

Thanks to the high sensitivity and high spatial resolution of ALMA, many unidentified
molecular lines have been detected in various sources [e.g., 1-3]. In order to identify theselines, it is essential to measure the rest frequencies of the molecular transition lines accurately.
For the molecular spectroscopy in the submillimeter wavelength in a laboratory, we have beendeveloping an emission-type molecular spectrometer by using state-of-art radio astronomical
technics (Figure 1) [4]. The spectrometer is equipped with a 200 cm glass cylinder cell, an
ALMA-type cartridge heterodyne receiver with 2SB SIS mixers in the 230 GHz bandcorresponding to ALMA Band 6, and wide-band digital autocorrelation spectrometer XFFTS.
By using the four 2.5 GHz digital spectrometers, a total instantaneous bandwidth of the 2SB
SIS receiver of 8GHz can be covered with a frequency resolution of 88.5 kHz. Recently, weapplied anti-reflection grooves on the surface of the gas cell windows and receiver window to
reduce reflection. As a result, the standing wave seen on the measured spectra is greatly
improved, and the system noise temperature is decreased from 300-400 K to 90-300 K. In
addition, we are now fabricating a new cartridge receiver that covers the radio frequency from
275 – 500 GHz corresponding to the ALMA Band 7 and 8 receivers. With this receiver, weplan to measure higher-J transition lines of methanol, and its isotopologues, including D, 13C,
17
O, and 18O.

Figure 1: A block diagram of the SUMIRE system.

References

1]
Y. Watanabe, et al. “Discovery of Striking Difference of Molecular-emission-line Richness in the Potential
Proto-binary System NGC 2264 CMM3”, 2017, ApJ, 847, 108[2]M. Imai, et al., “Discovery of a Hot Corino in the Bok Globule B335”, 2016, ApJ, 830, L37

[3]A. Belloche, et al., “Re-exploring Molecular Complexity with ALMA (ReMoCA): interstellar detection ofurea” 2019, A&A, 628, A10[4]
Y. Watanabe, et al., “Spectrometer Using superconductor MIxer Receiver (SUMIRE) for laboratory
submillimeter spectroscopy”, 2021, PASJ, 73, 372-393.

P44

A new measurement method of isotopologue ratios in protoplanetary disks: a case studyof the 12CO/13CO ratio in the TW Hya disk
T. Yoshida,1, 2 H. Nomura,1, 2 K. Furuya,2 T. Tsukagoshi2 and S. Lee2
1Department of Astronomical Science, The Graduate University for Advanced Studies,
SOKENDAI, Japan
2National Astronomical Observatory of Japan
Isotope ratio is a powerful tool to investigate the material origin and evolution from molecular
clouds to planetary systems. For instance, the ratio of deuterium to hydrogen can be used as a
tracer of material formed in a low-temperature environment, permitting us to study the origin
of water on the Earth. The oxygen isotope ratios have an anomaly in the solar system, whichis considered to reflect mass-independent fractionation of the carbon monoxide (CO)molecule in the pre/early stage of the solar system formation [1]. To explain the isotopic
compositions in planetary systems, physicochemical models of molecular clouds andprotoplanetary disks have been proposed.
Despite its importance, however, the observational constraint is difficult especially in
protoplanetary disks. The molecular gas in protoplanetary disks is observed in emission lines.
Since isotopologue ratios often reach tens and handreds, it is common that rarer isotopologueemission becomes too weak to be detected. In contrast, when the rarer isotopologue line isbright enough, the main isotopologue line (center) becomes optically thick, which makes
column density measurement impossible. However, the lines broaden due to thermal motion
in general, which makes line wings optically thin. Therefore, we have a chance to measure theisotopologue ratios by observing the multiple isotopologue line wings.
We present that the isotopologue ratios in protoplanetary disks can be practically measured
using the line wings, assuming high velocity resolution observations with Atacama Large
Millimeter/submillimeter Array (ALMA). Detailed disk models are used for proof of themethod. Moreover, we analyzed archival ALMA observations of the 12CO 3-2 and 13CO 3-2

lines toward a protoplanetary disk around a T Tauri star, TW Hya. The 12CO/13CO ratio in
the outer disk (R~60-100 au) was estimated to be 23 6, which is extremely smaller than the
canonical interstellar value of 69 6 [2]. This could imply that a volatile C/O ratio larger thanunity promotes an isotope exchange reaction between the carbon ions and the CO molecules,
making 13CO richer. Indeed, such a high C/O ratio has been suggested in previous
observations of hydrocarbon species [3]. In addition, it is also suggested that the 12CO/13CO
ratio is enhanced beyond a radius of 120 au with a lower limit of ~100, although the origin is
unclear.
References
[1]
[2]
[3]

K. I. Öberg & E. A. Bergin, 2021, Phys. Rep., 893, 1
T. L. Wilson, 1999, Rep. Prog. Phys., 62, 143
E. A. Bergin, 2016, ApJ, 831, 101

P45

Multi-tracer Observations for Multi-scale Accretion Structures in Massive Star
Formation
Y. Zhang,1 K. Tanaka, 2,3 N. Sakai 1, and J. Tan 4,5
1

RIKEN, Japan
Center for Astrophysics and Space Astronomy, University of Colorado, US
3 NAOJ, Japan
4 Department of Space, Earth & Environment, Chalmers University of Technology, Sweden
5 Department of Astronomy, University of Virginia, US
2

How massive forming stars accrete material from their surrounding dense clouds are still
unclear. Growing observational evidences have shown disk-mediated accretion is a viablemechanism to form massive stars. However, disks in massive star formation, as it contains
material in drastically different physical and chemical conditions, cannot be effectively traced
by any single type of tracers.
Our recent high-resolution ALMA observations have shown that, in addition to typical hot-coremolecular lines, a group of “hot-disk” line can exclusively trace the disks around massive
forming stars, including gaseous refractory molecules such as SiO, NaCl, and high upper stateenergy transitions of a few simple molecules such as H2O [1,2]. Furthermore, recombinationlines are important in tracing the innermost disk which has been ionized by the forming massive
star, supplementary to the molecular tracers for the neutral disk [3,4].
Here we report another case study using ALMA observations to reveal the complex multi-scaleaccretion structures around massive young star G35.20-0.74 (Zhang et al. in prep.). The
molecular line emissions such as SO2, H2CO, and CH3OH show rotational structures aroundthe main sources, with SO2 emission further traces two spiral arm structures in the fragmented
disk perturbed by a forming binary system, as well as the inner and faster-rotating materials
around the primary. The innermost region is photoionized with its kinematics revealed by thehydrogen recombination lines. This study agains shows the importance of using different
molecular lines and recombination lines to trace different components of the accretion structures,in order to obtain the full picture of the accretion process in massive star formation.
References
[1]
[2]
[3]
[4]

Y. Zhang, J. Tan, N. Sakai, et al. 2019, ApJ, 873, 73
K. Tanaka, Y. Zhang, T. Hirota, et al. 2020, ApJL, 900, L2
Y. Zhang, J. Tan, K. Tanaka, et al. 2019, Nat. Astro. 3. 517
Y. Zhang, K. Tanaka, V. Rosero, et al. 2019, ApJL, 886, L4

P46

Inventory of Nitrogen-bearing organics towards G+0.693-0.027
S. Zeng,1 L.F. Rodríguez-Almeida,2 V.M. Rivilla,2 I. Jiménez-Serra2 et al.
1

Star and Planet Formation Laboratory, Cluster for Pioneering Research, RIKEN, Japan
2
Centro de Astrobiología (CSIC-INTA), Department of Astrophysics, Spain

Among over 250 molecules discovered in the ISM, nitrogen-bearing (N-bearing) species areof interest as many likely play a crucial role in prebiotic chemistry and thus essential for the
emergence of life. In the last two decades, a great effort has been put in order to explore thelevel of molecular complexity of N-bearing species and the corresponding chemical processes.
With sensitive unbiased spectral surveys towards the quiescent Galactic Centre molecular
cloud G+0.693-0.027, we present in this talk the temporary (still evolving) census ofN-bearing species[1], including the first detection of vinylamine (C2H3NH2) [2] and ethyl
isocyanate (C2H5NCO)[3] in the ISM. We compared the derived abundance with respect to
H2 to those obtained towards other interstellar sources. We also discussed the possible
chemical routes, in gas-phase and/or on the grain surface, of the interstellar synthesis of theseN-bearing molecules along with their prebiotic relevance. This study have allowed us to better
understand the chemical complexity and diversity of N-bearing species in extreme
environments and provided observational constraints for chemical models and laboratory
studies in terms of investigating the chemical processes at work in space.

References

[1]
[2]
[3]

S. Zeng, I. Jiménez-Serra, V.M. Rivilla et al. 2018, MNRAS, 478, 2962
S. Zeng, I. Jiménez-Serra, V.M. Rivilla et al. 2021, ApJL, 920, L27
L. F. Rodríguez-Almeida, I. Jiménez-Serra, V.M. Rivilla et al. 2021, ApJL, 912, L11

P47

Experimental Molecular Emission Spectroscopy of Ethylene Oxide in ALMA Band 6
A. Tamanai,1 Y. Watanabe,2 T. Sakai,3 R. Nakatani,1 S. Zeng,1 S. Yamamoto,4 and N. Sakai1
1 Cluster for Pioneering Research, RIKEN, Japan
2Material Science and Engineering, Shibaura Institute of Technology, Japan3

Department of Engineering Science, The University of Electro-Communications, Japan
4Department of physics, The University of Tokyo, Japan

New discoveries related to astrochemistry in mm and sub-mm frequency ranges haveprovided us fruitful information on valuable chemical properties of organic compounds.
Thanks to the highly sensitive ALMA telescope, it has become possible to detect very
complex interstellar organic molecules than ever before [1-4]. Emission and absorption lines
from each molecule obtained from observations give us a clue to understand the chemical
pathways from simple molecules to complex molecules including the essential molecules oflife.
Either or both of theoretically calculated and experimentally measured emission spectra areapplied for interpretation of observed molecular lines in general. One of major problems
concerning molecular survey is that an insufficient supply of experimentally measured data
sets for both organic and inorganic compounds in millimeter and submillimeter frequency
ranges. To solve this problem, we have set up the emission type molecular spectroscope forastronomically relevant materials in the frequency range between 216 GHz and 264 GHz(ALMA Band 6). Superconductor-Insulator-Superconductor (SIS) mixer for ~230 GHz band
mounted on the ALMA-type cartridge receiver as a heterodyne apparatus (SUMIRE) isapplied in this measurement (details in [3]).
In here, we introduce our experimental broadband and high-resolution spectroscopic
apparatus as well as a measured ethylene oxide (C 2H4O) which has been detected in highmass star forming regions such as the galactic center source Sgr B2 (N) [5], hot molecular
clouds DR21 (OH), NGC7538 [6] and low-mass protostar IRAS 16293-2422 [7]. In
consequence, 677 peaks due to rotational transitions have been detected. Molecularparameters including predicted transition frequencies, rotational constants, and centrifugal
distortion constants were derived by making use of a least-squares analysis and selfdeveloped SUMIRE data analysis code, Aqualious for both C2H4O and 13C2H4O. 256 peaks
and 108 peaks were assigned as contributions from C2H4O and 13C2H4O rotational transitions,
respectively. In addition, we compared our experimental outcomes with the data sets in
Cologne Database for Molecular Spectroscopy (CDMS) [8] and previous works [9-10].
Thereby our results are in good agreement with previously obtained data. This also
demonstrates the reliability of our experimental results.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]

Y. Oya & S. Yamamoto, 2020, ApJ 904, 185.
B.A. McGuire, C.L. Brogan, T.R. Hunter, A.J.Remijan, G.A. Blake et al., 2018, ApJ 863, L35.
Y. Watanabe, N. Sakai, A. López-Sepulcre, T. Sakai, T. Hirota et al., 2017, ApJ 847, 108.
N. Sakai, T. Sakai, T., Hirota, Y. Watanabe, C. Ceccarelli et al., 2014, Nature 507, 78.
J.E. Dickens, W.M. Irvine, M. Ohishi, M. Ikeda, S. Ishikawa, 1997, ApJ 489, 753.
M. Ikeda, M. Ohishi, A. Nummelin, J.E. Dickens, P. Bergman et al., 2001, ApJ 560, 792.
J.M. Lykke, A. Coutens, J.K. Jøgensen, M.H.D. van der Wiel, R.T. Garrod et al., 2017, A&A 597, A53.
C.P. Endres, S. Schlemmer, P. Schilke, J. Stutzki, H.S.P. Müller, 2016, J. Mol. Spectrosc. 327, 95.
R.A. Creswell & R.H. Schwendeman, 1974, Chem Phys L 27, 521.
C. Hirose, 1974, B Chem Soc Jpn 47, 1311.

Formation, Abundance Distribution and Evolution of Complex Organic Molecules inStarless/Pre-stellar Cores
Izaskun Jimenez-Serra1, Anton I. Vasyunin2, Andres Megias-Toledano1, Silvia Spezzano3,
Paola Caselli3, Giuliana Cosentino4, and Serena Viti5
1

Centro de Astrobiologia (CSIC-INTA), Ctra. de Torrejon a Ajalvir km 4, 28850, Torrejon deArdoz, Spain
2
3

Ural Federal University, Kuybysheva st. 48, 620002, Ekaterinburg, Russian Federation

Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748, Garching,
Germany
45Chalmers University of Technology, SE41296, Gothenburg, Sweden

University of Leiden, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands

Observations carried out toward starless and pre-stellar cores have revealed that complex
organic molecules (COMs) are prevalent in these objects (Vastel et al. 2014; Jimenez-Serra etal. 2019; Scibelli et al. 2020). However, it remains unclear what chemical processes are
involved in COM formation and at what stage in dense core evolution complex organics form.
In this contribution, we will present high-sensitivity observations carried out toward theL1517B and L1498 starless cores. These cores are believed to be at earlier evolutionary stages
than the well-known L1544 pre-stellar core, also studied in COM emission by our group.
Similarly to what we found in L1544, small O-bearing molecules and N-bearing species areenhanced by factors ∼4-14 toward the outer shells of L1498 and L1517B. However, unlike
L1544, large O-bearing COMs such as CH3CHO, CH3OCH3 or CH3OCHO are not detected
within our sensitivity limits - comparable to the ones obtained for L1544. Surprisingly, Nbearing organics are more abundant toward the outer shells of L1498 and L1517B than in
L1544. We have carried out a detailed modelling of the formation of O-bearing and N-bearing
COMs in L1498 and L1517B following the model of Vasyunin et al. (2017), which considers
both the chemical reactive desorption of COM precursors and their subsequent gas-phasechemistry yielding COMs. The distribution of the COM abundances predicted for L1498 andL1517B nicely matches our observations for both O-bearing and N-bearing COMs in thesecores, and reveal that the differences observed between the complex organic content in L1498,
L1517B and L1544 are due to the different physical structure of these cores, which in turn is aconsequence of their evolution. From our results we conclude that while N-bearing COMs
form early in dense core evolution, O-bearing COMs form at a later stage when enough CO
has catastrophically depleted onto the surface of dust grains. These results have been
published recently in Jimenez-Serra et al. (2021).
References
[1]
[2]
[3]
[4]

Vastel, C., Ceccarelli, C., Lefloch, B., & Bachiller, R. ApJ, 2014, 795L, 2V
Jimenez-Serra, I., et al. ApJ, 2016, 830L, 6J
Scibelli & Shirley, ApJ, 2020, 891, 73S
Jimenez-Serra, I., et al. ApJ, 2021, 917, 44J

An Aromatic Universe - Low Temperature Molecular Mass Growth Processes to Polycyclic
Aromatic Hydrocarbons (PAHs)
Ralf I. Kaiser1,2
12Department of Chemistry, University of Hawaii at Manoa, Honolulu HI 96822, USA
W.M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa,
Honolulu HI 96822, USA

Polycyclic aromatic hydrocarbons (PAHs) represent key molecular building blocks leading tocarbonaceous nanoparticles identified in combustion systems and extraterrestrial environments.
However, the understanding of their formation and growth has remained elusive. Here, we
present evidence based on laboratory data combined with electronic structure calculations on
fundamental mass growth processes of PAHs in the gas phase via ring expansion and ringannulation. Key reaction pathways operate at ultralow temperatures such as at 10 K as present incold molecular clods like TMC-1 synthesizing PAHs at least from two to five six memberedrings such as naphthalene, anthracene, phenanthrene, triphenylene, [4]-helicene, and [5]-helicene.
These elementary reactions are rapid, have no entrance barriers, and synthesize PAHs via
van-der-Waals complexes and submerged barriers. This facile route to complex PAHs signifies a
critical shift in the perception that PAHs can be only formed at high-temperature combustion andcircumstellar conditions providing a detailed understanding of the low temperature chemistry
through untangling elementary reactions on the most fundamental level. An outlook is alsopresented on the synthesis of PAHs in low temperature, hydrocarbon-dominated ices in deep
space and in the outer Solar System upon interaction with (non)-ionizing radiation; theseprocesses are driven by non-adiabatic reaction dynamics and low lying triplet states of acetylene
leading to PAHs as complex as coronene. Overall, these mechanisms eventually lead tographene-type PAHs and two dimensional nanostructures providing an exciting view about thetransformation of carbon in our universe.
References

L. Zhao et al. Pyrene Synthesis in Circumstellar Envelopes and its Role in the Formation of 2D
Nanostructures. Nature Astron. 2, 413-419 (2018).
L. Zhao et al. Low-Temperature Formation of Polycyclic Aromatic Hydrocarbons in Titan’s Atmosphere.
Nature Aston. 2, 973-979 (2018).
L. Zhao, R.I. Kaiser, B. Xu, U. Ablikim, W. Lu, M. Ahmed, M. Evseev, E. K. Bashkirov, V.N. Azyazov,
M.V. Zagidullin, A.N. Morozov, A.H. Howlader, S.F. Wnuk, A.M. Mebel, D. Joshi, G. Veber, F. R.
Fischer, Gas Phase Synthesis of [4]-Helicene. Nature Commun. 10, 1510 (2019).
L. Zhao et al. Molecular Mass Growth through Ring Expansion in Polycyclic Aromatic Hydrocarbons via
Radical-Radical Reactions. Nature Commun. 10, 3689 (2019).
L. Zhao et al., A Unified Mechanism on the Formation of Acenes, Helicenes, and Phenacenes in the Gas
Phase. Angewandte Chemie – International Edition 59, 4051-4056 (2020).
S. Doddipatla et al., Low-temperature Gas-phase Formation of Indene in the Interstellar Medium, Science
Advances, 7, eabd4044 (2021).
R.I. Kaiser, N. Hansen, An Aromatic Universe – A Physical Chemistry Perspective, J. Chem. Phys. A,
Invited Perspective 125, 3826-3840 (2021).
L. Zhao et al., Gas Phase Synthesis of Benzene via the Propargyl Radical Self Reaction. Science
Advances 7, eabf0360 (2021).

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K(PK)L-H(SÿJÿI)*]+KJ*](ÿR*M(KQ)I(H-IJKÿLRSP(KSR)*ÿ\)KH(ÿ[(MN((*ÿ&bÿQ)I(H-I(SÿNGRHGÿMG(ÿH)*O(*MR)*JIÿL(*SRM'ÿ\-*HMR)*JIÿMG()K'ÿHJ**)MÿPK)ORL(%ÿÿÿ
FG(ÿUVWXY,ÿQ(MG)LÿGJSÿS-HH(SS\-II'ÿK(PK)L-H(LÿOJKR)-Sÿ(`P(KRQ(*MJIÿ)[S(KOJMR)*Sÿ
NRMG)-MÿJ*'ÿQ)L(IÿP)M(*MRJIÿJ*Lÿ(QPRKRHJIÿPJKJQ(M(KÿS-HGÿJSÿT/ZÿMG(ÿKJLRJIÿLRSMKR[-MR)*ÿ\-*HMR)*S_ÿLR\\-SR)*ÿH)(\\RHR(*MS_ÿORSH)SRM'ÿJ*LÿSGR\MSÿ)\ÿMG(ÿ&+&ÿOR[KJMR)*JIÿ\K(d-(*H'ÿR*ÿ
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S-P(KHKRMRHJIÿG'LK)](*Sÿaoc%ÿFG(ÿM(QP(KJM-K(ÿJ*LÿL(*SRM'ÿN(K(ÿ*(O(KÿJLk-SM(Lÿ)KÿSHJI(LÿR*ÿJ*'ÿ)\ÿMG(S(ÿSRQ-IJMR)*S%ÿpIIÿMG(ÿJ[)O(+Q(*MR)*(LÿS-HH(SS\-IÿJ]K((Q(*MSÿNRMGÿMG(ÿ(`P(KRQ(*MJIÿK(S-IMSÿR*ÿMG(ÿ\JK+LR\\(K(*MÿOJKR)-SÿPGJS(SÿJ*LÿMG(KQ)L'*JQRHÿSMJM(SÿL(Q)*SMKJM(ÿMGJMÿMG(ÿUVWXY,ÿQ(MG)Lÿ*)Mÿ)*I'ÿK(\I(HMSÿMG(ÿK(JIÿMG(KQ)L'*JQRHÿSMJM(Sÿ)\ÿG'LK)](*ÿS'SM(QSÿJMÿMG(ÿSJQ(ÿM(QP(KJM-K(ÿJ*LÿL(*SRMR(SÿJSÿMG(ÿ(`P(KRQ(*MJIÿOJI-(Sÿ[-MÿJIS)ÿS-HH(SS\-II'ÿK(PK)L-H(SÿMG(ÿJPPK)PKRJM(ÿR*M(KQ)I(H-IJKÿR*M(KJHMR)*ÿP)M(*MRJIÿNGRHGÿ(SS(*MRJII'ÿR*\I-(*H(SÿMG(ÿMG(KQ)L'*JQRHÿPK)P(KMR(S%ÿÿÿf*ÿMGRSÿPK(S(*MJMR)*_ÿN(ÿNRIIÿK(P)KMÿ)-KÿH)QP-MJMR)*JIÿK(S-IMSÿ(SP(HRJII'ÿ\)H-SR*]ÿ)*ÿMG(ÿIJM(SMÿH)QP-MJMR)*JIÿ\R*LR*]Sÿ)*ÿMG(ÿMN)ÿ(`MK(Q(ÿMG(KQ)L'*JQRHÿH)*LRMR)*SqÿT/ZÿMG(ÿL(H(I(KJM(LÿIRd-RLÿL'*JQRHSÿR*L-H(Lÿ['ÿH)QP)*(*M+L(P(*L(*MÿS-P(KH))IR*]ÿR*ÿG'LK)](*ÿJ*LÿL(-M(KR-Qÿ
d-J*M-QÿQR̀M-K(SÿJMÿI)NÿM(QP(KJM-K(_ÿJ*LÿTbZÿMG(ÿLRSMR*HMÿQ)I(H-IJKÿL'*JQRHSÿLRORLR*]ÿIRd-RLÿIR.(ÿJ*Lÿ]JS+IR.(ÿS-P(KHKRMRHJIÿG'LK)](*SÿJMÿGR]G(KÿM(QP(KJM-K(ÿMGJ*ÿMG(ÿHKRMRHJIÿM(QP(KJM-K(ÿTgg$Z%ÿf*ÿMG(ÿ\)KQ(K_ÿN(ÿH)QP-MJMR)*JII'ÿ\)-*LÿMGJMÿMG(ÿL'*JQRHSÿ)\ÿMG(ÿd-J*M-Qÿ&b+,bÿ
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A new electrochemical property of ice: negative charge transport triggered byreactions of surface OH radicals with electrons
K. Kitajima1, Y. Nakai2, W. M. C. Sameera1, M. Tsuge1, A. Miyazaki1, H. Hidaka1,
A. Kouchi1, and N. Watanabe1
12Institute of Low Temperature Science, Hokkaido University, Japan
Radioactive Isotope Physics Laboratory, RIKEN Nishina Center, JapanThe electrochemical behavior of water ice is of particular interest in astrophysicalchemistry and atmospheric chemistry. Much research has shown that the ice can be a p-typesemiconductor due to the conduction of excess protons along the hydrogen bonds. In contrast
to positive charges, the conductivity of negative charges due to the relay of hydroxide ions(OH−) in ice has not been verified. We have recently observed the negative charge
conductivity of ice simultaneously exposed to UV and electrons at temperatures below 50 K
[1]. The phenomenon can be explained by the following processes: (1) production of OH
radicals on ice surface by UV irradiation, (2) electron attachment to OH radicals, and (3) the
produced OH− induce the sequence of proton abstraction from surrounding H2O. To confirm
the above processes, we additionally measured the density of surface OH radicals using anovel technique, a combination of photostimulated desorption and resonance-enhanced
multiphoton ionization [2].
Figure 1(a) shows the temporal variation of the negative currents through H2O ice at 10 K.
One can see the increase in negative currents during simultaneous exposure to UV andelectrons. A transient peak initially formed by electron irradiation may be attributed to theleakage of electrons through pores or cracks in ice. Meanwhile, as shown in Figure 1(b), thedensity of surface OH radicals decrease upon electron exposure. The results suggest that thesurface OH radicals are consumed via electron attachment to the radicals to produce OH−. We
consider that the negative currents are subsequently induced by the relay of OH− in ice at low
temperatures.

Figure 1 (a) Temporal variation in negative currents through H2O ice at 10 K upon repetitive UV irradiation
with continuous exposure to electrons. (b) Temporal variation in OH radical densities on ice at 10 K upon
repetitive electron irradiation with continuous exposure to UV.

References[1][2]

N. Watanabe, W.M.C. Sameera, H. Hidaka, A. Miyazaki, A. Kouchi, 2019, CPL, 737, 136820.
K. Kitajima, Y. Nakai, W.M.C. Sameera, M. Tsuge, A. Miyazaki, H. Hidaka, A. Kouchi, N. Watanabe,
2021, JPCL, 12, 704.

Mono-deuterated methanol in prestellar cores
B. M. Kulterer,1 M. N. Drozdovskaya,1 S. Antonellini,2 C. Walsh,3 and T. J. Millar4
1

Center for Space and Habitability/University of Bern, Switzerland
2
Department, Institution/University, France
3
School of Physics and Astronomy/University of Leeds, United Kingdom
4
Astrophysics Research Center, School of Mathematics and Physics/Queen’s University
Belfast, UK
Mono-deuterated methanol is thought to form during the prestellar core stage of starformation. Variations in the CH2DOH/CH3OD ratio suggest that its formation is strongly
dependent on the surrounding cloud conditions. Thus it is a potential tracer of the physicalconditions before the onset of star formation.
A single-point physical model descriptive of a prestellar core is coupled to chemical models
to investigate potential formation pathways towards deuterated methanol at the prestellar
stage and discussed in context with observational findings [1]. The implementation of an
abstraction scheme [2] leads to the efficient formation of methyl-deuterated methanol, butlacks sufficient formation of hydroxyl-deuterated methanol.
This leads to the conclusion that CH3OD is most likely formed at a later evolutionary stage,
potentially from H/D exchange in warm ices between D2O (or HDO) and CH3OH.
Our results suggest that the ratio of CH2DOH/CH3OD is therefore not an appropriate tracer ofthe physical conditions during the prestellar stage, but might be better suited as a tracer of ice
heating.

Figure 1: Ratio of CH2DOH/CH3OD over a grid of core ages and dust temperatures descriptive of theprestellar phase as obtained with three different chemical networks [1]. The gray, dashed line indicates thestatistically expected value of 3, the solid, black line indicates the lower limit derived from observations [3].

References

[1]
[2]
[3]

B. M. Kulterer et al., 2021, submitted to: ACS Earth and Space Chemistry
H. Hidaka et al., 2009, ApJ, 702, 291
L. Bizzocchi et al., 2014, A&A, 569, 27

Early stages of water cluster growth observed with low-temperature scanning tunnelling
microscopy
Signe Kyrkjebø,1,2 Frederik Doktor S. Simonsen,1 Richard Balog,1,2 Liv Hornekær1,2
1

Center for Interstellar Catalysis and the Department of Physics and Astronomy
2
Interdisciplinary Nanoscience Center
Aarhus University, Denmark

Water ice is known to form on carbonaceous dust grains in the interstellar medium [1], but thestructural morphology of icy grains including their chemical activity is still underinvestigation.
It has recently been shown that water molecules are mobile at temperatures down to 25 K on
highly-oriented pyrolytic graphite (HOPG), suggesting that ice may grow via clustering rather
than layer-by-layer [2]. However, realistic interstellar grains are not pristine and are likely
terminated by various functional groups, which may further affect ice formation [3].
We have studied the initial stages of ice formation on HOPG and O-terminated HOPG, as
dust grain analogues, using low-temperature scanning tunneling microscopy (LT-STM). Data
reveal that step-edges and O-functional groups act as nucleation sites for ice formation. The
size, fractal structure, and porosity of nanometer size water clusters are found to be strongly
dependent on the sample temperature.

Figure 1: LT-STM image of water ice clusters on O-HOPG. It: 4 pA, Vt: 4.5 V.

References
[1]
[2]
[3]

van Dishoeck, E. F. et al., Chem. Rev. 113, 9043 (2013)
Rosu-Finsen, A. et al., Phys. Chem. Chem. Phys. 18, 31930 (2016)
Kyrkjebø, S. et al., Carbon. 174, 396 (2021)

Carbon atom addition reactions in interstellar ices:
How to marry laboratory and computational chemistry
T. Lamberts1,2 and collaborators
1

Theoretical Chemistry, Leiden Institute of Chemistry, Leiden University, The Netherlands
2
Leiden Observatory, Leiden University, The Netherlands

I will focus on surface reactions of carbon atoms on amorphous solid water (ASW) ices,
mimicking the icy mantle covering the micron-sized dust grains in the interstellar medium. In
the translucent stage of a molecular cloud, carbon is predominantly present in its atomic form
C(3P0) [1] and even in dense regions it is likely more abundant than typically thought [2,3].
Moreover, already in 2001 carbon atoms additions have been proposed to lead to the formationof complex organics [4]. Therefore, a carbon atom beam source was installed at the Leiden
Laboratory for Astrophysics [5], successfully demonstrating that methane can be formed fromexperiments of C + H on ASW [6]. In this talk I will discuss three new projects:
1. The interaction of atomic carbon with water has been extensively studied, bothexperimentally and theoretically [e.g., 7, 8], but particularly puzzling is the different
chemical behaviour in the gas phase versus in condensed phases. I will provide a
detailed explanation of the formation of formaldehyde from carbon atoms withamorphous solid water within a theoretical framework, supported by tailoredexperiments [9].
2. I will touch upon the reactions of carbon atoms with molecular hydrogen and show thatan intricate interplay of reactions can lead to the formation of methane, even when H
atoms are not present. I will discuss this both from an experimental and computational
point-of-view and link the various intermediates to other recent studies [10].
3. Finally, I will show that the reactivity with H2 and H2O does not restrict the formationof complex organics, and in fact the reaction between C and CO occurs so rapidly thatketene and acetaldehyde can be formed in the presence of H atoms [11].
References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]

Van Dishoeck and Black, 1988, ApJ 334, 771
M.G. Burton et al., 2015, ApJ 811, 13
Bisbas et al., 2019, MNRAS 485, 3097
Charnley et al., 2001 SAA, 57, 685
Qasim et al., 2020, RSI 91, 054501
Qasim et al., 2020 NatAs 4, 781
Schreiner et al., 2006, CPC 7, 880
Shimonishi et al., 2018 ApJ 855, 27
Molpeceres et al., 2021 JPCL subm.
Lamberts et al., 2021 ApJ subm.
Fedoseev et al., 2021 ApJ subm.

Glycolaldehyde Formation on Interstellar Water Ice Surfaces. A
Computational Quantum Chemical Approach
J. A. Luque-Urrutia, A. Rimola
1

Departament de Química, Universitat Autònoma de Barcelona, Spain

Astrochemists of diverse disciplines aim to unfold the intricate chemicalmechanisms that occur in space to get insight on one of the primordial questions
we have today: what is the origin of life? To evolve from dead chemical matter
into living beings, there are some essential chemical compounds that must bepresent for that to occur, such as amino acids [1] and complex sugars [2].
Focusing on sugars, glucose is one of the main targets. However, its presence
has not been confirmed in space while this is indeed the case of its closest
relative, glycolaldehyde (GLA, HOCH2CHO) [3]. In this contribution, we
present results dedicated to GLA formation on surfaces of interstellar water ice
adopting the formose reaction, 2·H2CO → GLA, and its radical derivation H2CO
+ CHO* + H* → GLA. Reactions in the gas phase (i.e., absence of water ice)have been used for a benchmarking study, in which CCSD(T) results werecompared with those obtained at the more approximated DFT theory level. With
the latter, calculations of the GLA formation reactions have been carried out oncluster models for water ice (see Figure 1), in which the energy features of thereactions (i.e., reaction energy and activation energies) are provided.
Additionally, simulations also help us to understand the role of the ice surface
in this synthetic route.

Figure 1: Glycolaldehyde formation by reaction of HCO with H2CO followed by H addition
simulated on a cluster model mimicking the surfaces of interstellar of water ice.
[1] Ehrenfreund, P.; Charnley, S. B. 2000 ARA&A 38, p. 427-83.
[2] Woods, P.M.; Slater, B.; Raza, Z.; Viti, S.; Brown, W.A.; Burke, D.J. 2013 ApJ, 777, p. 90.
[3] Jørgensen J.K.; Favre, C.; Bisschop, S.E.; Bourke, T.L.; Dishoek, E.F.; Schmalz, M. 2012
ApJL 757 L4.

Computational Investigation on the Potential Energy Surface of the Formation Route ofFormamide from Reaction between NH2 and H2CO on Interstellar Water Ice Surface
Berta Martínez-Bachs, Albert Rimola
Departament de Química, Universitat Autònoma de Barcelona, Catalonia, Spain

Formamide has a key role in prebiotic chemistry as it is the simplest molecule containing thefour most important atoms from a biological point of view: hydrogen, carbon, nitrogen andoxygen. But also, because it is the simplest molecule containing the amide bond O-C-NH, thegroup that join amino acids forming peptides [1]–[3]. Since it was first detected and due to its
importance, different pathways leading to its interstellar formation has been studied
considering both the gas-phase scenario and on ices of dust grains[2]–[4]. In the present
contribution, computational simulations based on quantum chemical calculations arepresented, focusing on the energetics of the NH2CHO formation from reaction of NH2 with
H2CO (a channel proposed to occur in the gas phase [3]) on water ice surfaces. To model thewater ice surfaces, a periodic approach has been adopted, in which both a crystalline and an
amorphous model has been used. Different DFT functionals have been employed to obtainaccurate energy values for the mechanistic steps involved in the reaction.

Figure 1: Potential Energy Surface and optimized structures of the stationary points of the studied reaction
on the amorphous slab model. Values are in kJ/mol. Bare values correspond to those at B3LYP-D3(BJ), inbrackets to those at PBE-D3(BJ) and in square brackets to those at M06-2X-D3. Atom color legend: red, O;
blue, N; green, C white, H.

References
[1]
[2]
[3]
[4]

C. Ceccarelli et al, 2017, ApJ 850, 176.
A. Rimola et al, 2018, ACS Earth Space Chem. 2, 7, 720.
V. Barone et al., 2015, Mon. Not. R. Astron. Soc. Lett. 453, 1, L31.
J. Enrique-Romero et al., 2019, ACS Earth Space Chem. 3, 10, 2158.

The PAH Revolution: Cold, Dark Carbon at the Earliest Stages of Star Formation
Brett A. McGuire1,2
1

Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
2
National Radio Astronomy Observatory, Charlottesville, VA, USA

Polycyclic Aromatic Hydrocarbons (PAHs) have been implicated as a large reservoir ofreactive carbon in the interstellar medium since the 1980s. PAHs have been widely
attributed as the carriers of the unidentified infrared bands where their aggregate vibrationalemission spectra are extremely well matched to the observed line signals. Only in the lastyear have individual PAHs been detected in the ISM for the first time [1–3], however,allowing us to begin to investigate the detailed chemical pathways for the formation anddestruction of these molecules. In this talk, I will discuss our detections of PAH molecules
via their rotational transitions using Green Bank Telescope observations of TMC-1 from the
GOTHAM collaboration [4]. I will discuss the efforts to model the chemistry of these PAHs,
the necessity of complementary laboratory kinetics work such as the elegant single-collision
studies being carried out by R. Kaiser and co-workers [5], our application of novel machinelearning approaches to exploring the chemical inventory in TMC-1 [6], and finally thebenefits of unbiased reaction screening studies in the laboratory with Microwave Spectral
Taxonomy [7, 8].
References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

B. McGuire et al. 2021, Science 371, 1265
A. Burkhardt et al. 2021, ApJL 908, L11
J. Cernicharo et al. 2021, A&A 649, L15
B. McGuire et al. 2020, ApJL 900, L10
S. Doddipatla et al. 2021, Science Advances 7, eabd4044
K. Lee et al. 2021, ApJL 917, L6
M. McCarthy & B. McGuire 2021, JPCA 125, 3231
M. McCarthy et al. 2020, JPCA 124, 5170

Detection of photodesorption OH radicals from H2O ice surface by visible lightAyane Miyazaki1, Naoki Watanabe1, W. M. C. Sameera1, Yoichi Nakai2,
Masashi Tsuge1, Testuya Hama3, Hiroshi Hidaka1, Akira Kouchi1
1 Institute of Low Temperature Science, Hokkaido University, Japan
2

Nishina Center, RIKEN, Japan

3 Komaba Institute for Science, The University of Tokyo, Japan

There are various molecules including complex organic molecules in interstellar molecular
clouds. Surface reactions involving radicals on interstellar ice-dust grain play an importantrole in chemical evolution because they are indispensable for the formation of complex
interstellar molecules [1,2]. In order to understand the details of the molecular formation on
the surface of dust, it is necessary to clarify the behavior of radicals on the surface. However,the detection of radicals on ice surface has intrinsic experimental difficulties.
In this study, we investigated behavior of OH radicals on the ice surface. Because they canbe easily produced by photolysis of ice and would greatly contribute to the formation ofcomplex molecules or those precursors. Using the combination of photo-stimulated
desorption and resonance-enhanced multiphoton ionization, we have first succeeded inmonitoring OH radicals on ice [3]. The results of the experiments indicate thatphotodesorption of OH radicals are induced by one photon absorption at 532 nm, which istransparent for gaseous OH radical as well as for water ice. I present the details on the
behavior of OH radicals and adsorption sites on water ice [4,5].
References[1] R. T. Garrod, S. L. W. Weaver, E. Herbst, 2008, Astrophys. J. 682, 283.
[2] K. I. Öberg, Chem. Rev. 2016, 116, 17, 9631–9663.
[3] A. Miyazaki, N. Watanabe, W. M. C. Sameera1, Y. Nakai, M. Tsuge, T. Hama, H. Hidaka1, A. Kouchi, Phys.
Rev. A 102, 052822 (2020).
[4] N. Watanabe and M. Tsuge, 2020, J. Phys. Soc. Jpn. 89, 051015.
[5] M. Tsuge and N. Watanabe, 2021, Acc. Chem. Res. 54, 471.

Machine Learning Meets Surface Astrochemistry
G. Molpeceres1
1Institute for Theoretical Chemistry University of Stuttgart Pfaffenwaldring 55, 70569
Stuttgart, Germany

Surface reactions play a vital role in the chemistry occurring on interstellar mediums (ISM).
In particular, under the cold conditions of a molecular cloud (~10-20 K), adsorbates (atoms,
radicals and molecules) accrete, diffuse, react and desorb on top of ice-covered dust grains [1].
The chemical composition of these ices is varied and depends on the cloud's evolutionary
stage, e.g. water ice dominates the early stages [2]. At the same time, CO and CO2 areprevalent in later stages. Moreover, interstellar ices are usually amorphous, presenting a wide
range of binding sites for adsorbates to perform the aforementioned processes [2]. It appears
evident that, given the complexity of the substrates, the dynamics of adsorbates on interstellar
ices are essentially non-local, meaning that a particular process depends significantly on thebinding site under consideration. This condition imposes a constraint on computational
studies of interstellar surface chemistry, requiring extensive sampling and considerablyincreasing the computational cost for constructing reliable models. Several approaches are
employed in the literature to reduce this cost, i.e. cluster models [3], periodic models, [4]QM/MM models [5] and recently, machine-learned models [6]. In this contribution, I will
present our recent efforts in the application of neural-network potentials [7] to surface
astrochemistry, putting the focus on the simulation of:
1. Adsorption and desorption (calculation of sticking coefficients and desorption rate
constants) [6];2. Diffusion (estimation of diffusion coefficients and hopping rate constants) [8];3. Reaction (chemical desorption vs energy dissipation) [9].
References[1]
Cuppen, H.M. et al. Space Sci. Rev. 212, 1-58 (2017).
[2]
Boogert, A.C.A., Gerakines, P.A. & Whittet, D.C.B. Annu. Rev. Astron. Astrophys. 53, 541–581 (2015).
[3]
Shimonishi, T., Nakatani, N., Furuya, K. & Hama, T. Astrophys. J. 855, 27 (2018), Bovolenta, G. et al.
Mol. Astrophys. 21, 100095 (2020).
[4]
Ferrero, S. et al. Astrophys. J. 904, 11 (2020).
[5]
Molpeceres, G. & Kästner, J. Phys. Chem. Chem. Phys. 22, 7552–7563 (2020), Sameera, W.M.C. et al.
J. Phys. Chem. A 125, 387–393 (2021), Duflot, D., Toubin, C. & Monnerville, M. Front. Astron. Sp. Sci. 8, 24(2021).
[6]
Molpeceres, G., Zaverkin, V. & Kästner, J. Mon. Not. R. Astron. Soc. 499, 1373–1384 (2020),
Molpeceres, G., Zaverkin, V., Watanabe, N. & Kastner, J. Astron. Astrophys. 648, A84 (2021).
[7]
Zaverkin, V. & Kästner, J. J. Chem. Theory Comput. 16, 5410–5421 (2020).
[8]
Zaverkin, V., Molpeceres, G. & Kästner, J. Mon. Not. R. Astron. Soc., Submitted.
[9]
Schömig, R., Kästner, J. and Molpeceres, G. In preparation.

Studying the factors that determine multiplicity and chemical complexity in Perseus
N. M. Murillo,1 and N. Sakai1
1Star and Planet Formation Laboratory, RIKEN, Japan

Star formation involves a wide range of physical and chemical processes. To fullycomprehend and build a picture of star formation and evolution, we need to understand howeach process influences the final outcome. While models provide some insight into thisquestion, observational constraints are needed to fully understand this topic.
Two aspects of protostellar systems that are of interest are their multiplicity and chemicalcomplexity. Multiple protostars are common at all stages and masses of star formation. The
chemical complexity of protostellar systems significantly varies among systems. A curious
observational occurrence in low-mass star formation is that almost all, if not all, chemicallycomplex systems are multiple protostellar systems (e.g., IRAS16293, NGC1333 IRAS4), but
not all multiple protostellar systems are chemically complex (e.g., VLA1623, L1448 N). In
addition, within multiple protostellar systems the chemical complexity can vary among
components.
Observations of protostellar systems from molecular cloud to disk scales are needed to study
which physical and chemical processes determine multiplicity, chemical complexity, andwhether there is a relation between both. A large sample including multiple and single
protostellar systems is necessary to obtain statistically significant results. The Perseus
molecular cloud (d ~ 300pc) is ideal for such studies, given the extensive available data which
covers dust continuum, molecular lines, and magnetic fields for a range of scales.
In this talk, a large sample of Perseus protostellar systems observed with the Nobeyama 45m
Telescope, Atacama Pathfinder EXperiment (APEX), and Atacama Large
Millimeter/submillimeter Array (ALMA) will be presented. Our observations trace scales
from molecular cloud to the protostellar envelope (few 100 AU). The spectral set-up includes
a range of molecular species that can trace gas distribution, kinematics and temperature
toward each protostellar system to study the impact of heating, mass, and accretion on
multiplicity and chemical complexity. Further information from smaller scales is obtained
from previous studies. Our results suggest that multiplicity is determined by mass, while howthat mass is accumulated may be related to chemical complexity.

An infrared spectroscopic approach towards understanding the orientation of dangling OH
bonds on amorphous solid water
1
T. Nagasawa, T. Hasegawa1 N. Numadate,1 T. Hama1
1

Komaba Institute for Science, The University of Tokyo, JapanThe surface reaction on amorphous solid water (ASW) is the key to figuring out thechemical processes in interstellar molecular clouds, where stars and planets are being born [1].
Macroscopic properties of ASW such as heat transfer coefficient [2], surface potential [3]have progressively become understood through intensive research. By contrast, ourunderstanding about the microscopic structure of ASW is still at an early stage. For example,
there is almost no experimental study about the molecular orientation in ASW, which is a key
factor to control the physicochemical properties of organic thin films [4], due to the lack of
direct measurement technique. Recently, we built an experimental apparatus for low
temperature ultrahigh vacuum infrared multiple-angle incidence resolution spectrometry (IRMAIRS [4][5]. IR–MAIRS is a spectroscopic method combining oblique incidencetransmission measurements and multivariate analysis to retrieve both pure (in-plane; IP) IP
and (out-of-plane; OP) OP vibration spectra for a thin sample. The method has the uniqueadvantage that the average molecular orientation is determined by comparing the IP to OPband intensity ratio spectra on the absorbance scale. In this research, we report our recent IRMAIRS results for dangling OH bands in ASW at 10 to 90 K. It is found that the averageorientation angle of dangling OH bonds exhibit a drastic ice temperature dependence in therange of 10 to 90 K. The detailed results are presented in the poster.

Figure: (left) Schematic illustration of IR-MAIRS. IR–MAIRS: Typical single-beam spectra
measured at an angle of incidence of 45° at various polarization angles from 0° to 90° in 15°
steps, and then extracting the IP and OP spectra by multivariate analysis.
(right) Molecular orientation analysis based on IR-MAIRS. The average orientation angle ofmolecules is determined by comparing the ratio of absorbance both IP and OP spectra.
References

[1]
[2]
[3]
[4]
[5]

T. Hama, N. Watanabe, 2013, Chem. Rev 113, 12, 8783-8839.
A. Kouchi, 1994, J. Japanese Society of Snow and Ice, Vol.56 No.1 63-70.
C. Bu, J. Shi, U. Raut, E. Mitchell & R. Baragiola, 2015, J.Chem.Phys 142, 134702.
T. Hasegawa & N. Shioya, 2020, Bull. Chem. Soc. Jpn 93, 1127-1138.
T. Hama, A. Ishibashi, A. Kouchi, N. Watanabe, N. Nobuya, T. Shimoaka & T Hasegawa, 2020, J. Phys.
Chem. Lett 11, 7857-7866.

Methanol production via interactions of low-energy CH3+ ions with ASW surface:experimental investigation of ion-surface reactions
Y. Nakai1, H. Hidaka2, and N. Watanabe2
1

RIKEN Nishina Center for Accelerator-Based Science, RIKEN, Japan
2
Institute of Low Temperature Science, Hokkaido University, Japan

Various neutral and ion species have been observed in molecular clouds, despite their very
low temperatures. To understand how molecules evoluve, many chemical processes have been
proposed. In gas phase, ion-molecule reactions have been always considered to play animportant role. However, the abundances of some molecules such as water and methanol
molecules cannot be explained only by the gas-phase reactions. Consequently, reactions
between neutral radicals and neutral species on an icy grain surface have been proposed as theother essential pathways and it has been experimentally confirmed that reactions of hydrogenatoms adsorbed on an ice surface are essential for productions of hydrogen, water, methanol,and so on [1, 2]. Besides pure gas-phase and surface reactions, it is reasonably inferred thatprocesses triggered by interactions of gas-phase ions with an ice mantle play some role inmolecular evolution. In this context, the experiments of energetic ion bombardment to an ice
containing other primordial molecules have been performed for a long time. In contrast, little
is known about the interactions between low-energy ions and an ice surface, while molecular
cations have been simply considered to recombine with negative charge (electrons) on an ice
surface in theoretical models [3, 4]. However, it is not clear how electrons exist on icy grains,
and thus it is also unclear if cation-electron recombination immediately occurs or not.
In fact, the reactions of very-low-energy ions with an icy surface have been theoretically
proposed as new non-energetic reaction pathways [5, 6]. Since an icy grain can be regarded asa huge molecular cluster, reactions of ions with an icy grain surface would occur without
reaction barriers as ion-molecule reactions. For example, the quantum chemical calculation
predicted that the reaction of a CH3+ ion with a water ice surface spontaneously produces amethanol molecule [5]. Despite recent theoretical progress, no experimental study for lowenergy ion reactions with ice surface have been performed due to experimental difficulties in
obtaining enough reaction products for their detection using conventional methods such as
infrared absorption spectroscopy. Accordingly, we have newly developed an experimental
setup to enable us detecting trace amounts of reaction products. Using this setup, we have
performed the experiments for production of methanol through the reaction of low-energy
CH3+ ions with a water ice surface. The CH3+ ions with their energies as low as or lower than
~10 eV impinged on an amorphous solid water (ASW) prepared on an Al substrate around 10
K. Reaction products by CH3+ irradiation were monitored through pick-up reaction method by
Cs+ ions at several tens eV [7, 8]. After CH3+ irradiation, methanol molecules on the ASW
were observed as the theoretical study suggested.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

T. Hama and N. Watanabe, 2013, Chem. Rev., 113, 8783
N. Watanabe and A. Kouchi, 2008, Prog. Surf. Sci., 83, 439.
C. Walsh, T. J. Millar, and H. Nomura, 2013, ApJL 766, L23.
A. Rimola, C. Ceccarelli, N. Balucani, and P. Ugliengo, 2021, frontiers in Astron. Space Sci., 8, 655405.
D. E. Woon, 2011, ApJ, 728, 44.
D. E. Woon, 2021, Acc. Chem. Res., 54, 490.
H. Kang, 2011, Bull. Korean Chem. Soc., 32, 389.
A. Ishibashi, ApJL, to be published.

Experimental and computational studies on the physicochemical behavior of phosphine
induced by reactions with H and D atoms on interstellar ice grains
T. Nguyen,1 Y. Oba,1, W.M.C. Sameera1, A. Kouchi1, and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University,
N19W8, Sapporo, Hokkaido, Japan

Phosphine (PH3) is an important molecule for the chemistry of phosphorus (P-) bearing species
in the interstellar medium (ISM). Interstellar PH3 is thought to primarily form on icy grains,
where several surface processes may occur during and after its formation. To better understandthe physicochemical behavior of PH3 on ice grains in dense molecular clouds, we performedexperimental and computational studies on the reactions of phosphine with H and D atoms at
low temperatures. We found that phosphine and its deuterated isotopologue PD3 are released
into the gas phase from ice surfaces via chemical desorption. We confirmed that H-D
substitution reactions of PH3 and D-H substitution reactions of PD3 occurred following
reactions with D and H atoms, respectively, at 10 K on icy surface. Because the activation
barrier for the abstraction of H and D atoms from phosphine is ~1500 K, quantum tunnelingshould play a role at low temperatures. On the other hand, the D-H substitution reactions of PD3
was slightly faster than the H-D substitution reactions of PH3, meaning that the rates of the HD and D-H substitution reactions are not constrained by tunneling reactions but rather by otherelementary processes such as atoms diffusion on ice.

Formation of complex organic molecules through ice mantle reactions
C.-E. Wei1, H. Nomura2, P. Theulé3, and C. Walsh4
1

EPS Department, Tokyo Institute of Technology, Japan
Divison of Science, National Astronomical Observatory of Japan, Japan
3
Laboratory of Astrophysics of Marseille, Aix-Marseille Université, France
2
School of Physics and Astronomy, University of Leeds, UK
2

Recent solar system exploration missions, such as Rosetta mission, have found various
complex molecules in solar system objects. Some of these materials are thought to be pristineand produced before the solar system objects are formed. Meanwhile, recent development inastronomical observations, for example, by ALMA, as well as in chemical model calculations
have brought us new knowledge on formation of complex organic molecules inprotoplanetary disks, natal place of planet formation [1][2][3].
In interstellar clouds it is believed that complex organic molecules are mainly formed throughgrain surface reactions. Meanwhile, laboratory experiments suggest that ice mantle reactions
can proceed in certain conditions, and produce more complex species [4]. In this work wehave constructed a formula of mantle reaction rate based on the recent laboratory experiments
which show ice chemistry proceeding through the thermal process inside the ice bulk. Also,
we introduced the obtained reaction rates to chemical reaction network with three phasemodel including gas-phase, grain surface, and ice mantle reactions. We performed model
calculations with different physical conditions, which show that the mantle reactions canproceed efficiently when the temperature is higher than ~120K.
In addition, we adopt some physical conditions of protoplanetary disks in early evolution
phase, taking account of the temperature increase caused by FU Ori type outbursts, andinvestigate the effect on formation rate of COMs via mantle reactions. We especially focus on
the formation rates of the materials detected on the comet 67P/Churyumov-Gerasimenko in
the Rosetta mission, and found that the mass accretion rate of 10-5 solar mass per year isrequired in order to produce the ammonium carbamate found in the comet 67P/C-G efficiently
at comet forming region in protoplanetary disks [5].

References

[1]
[2]
[3]
[4]
[5]

C. Walsh, T.J. Millar, H. Nomura et al. 2014, A&A 563, A33.
C. Walsh, R. Loomis, K. Oberg et al. 2016, ApJL 823, L10.
C. Walsh 2015, EAS Publication Series 75-76, 315.
P. Ghesquière, A. Ivlev, J. A. Noble, and P. Theulé, 2018, A&A 614, A107.
C.-E.. Wei, 2019, PhD Thesis.

X-ray-induced chemistry of water and related molecules in low-mass protostellar
envelopes
Shota Notsu,1 Ewine F. van Dishoeck,2,3 Catherine Walsh,4 Arthur D. Bosman,5 and Hideko
Nomura6
1

Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Japan
2
Leiden Observatory, Faculty of Science, Leiden University, The Netherlands
3
Max-Planck-Institut für Extraterrestrische Physik (MPE), Germany
4
School of Physics and Astronomy, University of Leeds, UK
5
Department of Astronomy, University of Michigan, USA
6
Division of Science, National Astronomical Observatory of Japan, Japan

Water is a key molecule in star and planet forming regions. Recent water line observations
toward several low-mass protostars suggest low water gas fractional abundances (<10^-6) in
the inner warm envelopes (r<100 au). Water destruction by X-ray radiation has been proposed
to influence the water abundances in these regions, but the detailed chemistry, including thenature of alternative oxygen carriers, is not yet understood. In our study [1], we calculated thechemical composition of low-mass Class 0 protostar envelopes using a detailed gas-grainchemical reaction network including X-ray induced chemical reactions. We aimed tounderstand the impact of X-ray radiation on the composition of low-mass protostar envelopes,
focusing specifically on water the related oxygen bearing species.
On the basis of our calculations [1], the protostar X-ray luminosity has a strong effect on thewater gas abundances, both within and outside the water snowline (T<100K, r<100 au).
Outside the water snowline, the water gas abundance increases with X-ray luminosities, due
to X-ray-induced photodesorption of water ice. Inside the water snowline, water maintains ahigh abundance of 10^-4 for low X-ray luminosities, with water and CO dominant oxygen
carriers. For high X-ray luminosities (>10^30 erg/s), the water gas abundances significantly
decrease just inside the water snowline (down to ~10^-8–10^-7) and in the innermost regionswith T >250K (~10^-6). For these cases, the fractional abundances of molecular and atomic
oxygen gas reach <10^-4 within the water snowline, and they become the dominant oxygen
carriers. In the presence of strong X-ray fields, gas-phase water molecules within the water
snowline are mainly destroyed with ion-molecule reactions and X-ray-induced
photo-dissociation. In addition, the fractional abundances of HCO+ and CH3OH, which havebeen considered to be tracers of the water snowline, significantly increase and decrease within
the water snowline, respectively, as the X-ray fluxes become larger. These X-ray effects arelarger in envelope models with lower number densities. Future molecular line observations
for protostars (using e.g., ALMA, ngVLA) will access the regions around protostars wheresuch X-ray induced chemistry is effective.
References[1]

Notsu. S., et al., 2021, A&A, 650, A180

First direct detection of OH radicals photodesorbed from liquid organic surface
by using laser-induced fluorescence technique
N. Numadate,1 S. Saito,2 and T. Hama1,3
1

Komaba Institute for Science, The University of Tokyo, Japan
Department of Chemistry, Tokyo University of Science, Japan3
Department of Basic Science, The University of Tokyo, Japan2

The 5th assessment report of the Intergovernmental Panel on Climate Change provides thataerosols contribute the largest uncertainty of the Earth’s changing energy budget and thisshould be evaluated in order to understand climate change [1]. Especially, interfacial reactionsat atmospheric aerosols and sea surface are of increasing importance because these interfaces
occupy a great deal of reaction fields on the Earth. Recently, photochemical reactions ofsurfactant organic compounds such as fatty acids that cover the top surfaces of aerosols andsea have attracted much attention. For example, it had been believed that gaseous and liquid
nonanoic acids (NA) do not absorb ultraviolet – visible radiation (> 295 nm). However,
Rossignol et al. found that NA at the air-water interface absorbs the ultraviolet, and thencomplex organic compounds were produced, which eventually act as aerosol precursors [2].
Although the photochemical reaction mechanism of NA is still poorly understood, it has beensuggested that OH radicals are a primary photoproduct in the ultraviolet photolysis of NA at
the interface [2, 3].
CH3(CH2)7COOH + hν (> 295 nm) → CH3(CH2)7CO + OH?
OH radical is one of the most important chemical species in atmospheric chemistry andquantum yields of OH radical formation are needed to incorporate the interfacial reactions
into atmospheric models. However, even direct measurements of desorption of OH radicals inphotolysis of liquid NA have not been achieved yet.
We have developed an instrument for direct detection of photodesorbed OH radicals in theultraviolet photolysis of liquid NA by using laser-induced fluorescence (LIF) technique.
Liquid NA was put on a silicon substrate in a low vacuum chamber (1 – 100 Pa) andirradiated with a pulsed 213 nm Nd:YAG laser. OH radicals desorbed from the NA surface
were excited by a second harmonic 282 nm dye laser, and OH-LIF at 315 nm was detected bya photomultiplier tube.
OH (X2Π, v = 0) + hν (282 nm) → OH (A2Σ, v = 1) → OH (X2Π, v = 1) + hν (315 nm)
In order to verify that the detected OH radicals were desorbed from liquid NA surface notformed from gaseous NA, we measured OH-LIF intensities as a function of the delay time
between the two lasers, changing a distance between the dye laser and the Si substrate.
Moreover, we performed single shot experiments to clarify that OH radicals were originatedfrom parent NA molecules on the liquid surface not from photoproducts.
In the workshop, we will show our new experimental setup for the photolysis of liquidorganics and detection of photodesorbed OH radicals using the LIF technique.
References[1] Intergovernmental Panel on Climate Change (IPCC), Fifth Assessment Report (2017).
[2] Rossignol et al., Science 353, 699 (2016).
[3] Vaida, Science 353, 650 (2016).

FAUST III. Misaligned rotations of the envelope, outflow, and disks
protostellar system of VLA 1623$-$2417

in the multiple

S. Ohashi,1 C. Codella,2 N. Sakai,1 C. Chandler,3 C. Ceccarelli,4 S. Yamamoto5, and
FAUST team
1

RIKEN cluster for pioneering research, Japan
2
Osservatorio Astrofisico di Arcetri, Italy
3
National Radio Astronomy Observatory, USA
4
CNRS, IPAG, Univ. Grenoble Alpes, France
5
Department of Physics, The University of Tokyo, Japan
We report a study of the low-mass Class-0 multiple system VLA 1623AB in the Ophiuchus
star-forming region, using H$^{13}$CO$^+$ ($J=3-2$), CS ($J=5-4$), and CCH ($N=3-2$)
lines as part of the ALMA Large Program FAUST. The analysis of the velocity fields
revealed the rotation motions on a wide range of scales in the envelope and the outflows(about 2000 au down to 50 au). We further investigated the rotation of the circum-binary
VLA 1623A disk as well as the VLA 1623B disk.
We found that the minor axis of the circum-binary disk of VLA 1623A is misaligned byabout 12 degrees with respect to the rotation axis of the large-scale outflow and the envelope.
In contrast, the minor axis of the circum-binary disk is parallel to the large-scale magnetic
field according to previous dust polarization observations, suggesting that the misalignment
may be caused by the different directions of the envelope rotation and the magnetic field.
The outflow rotation shows a constant angular momentum with a mean specific angularmomentum of about 100 au km s$^{-1}$.
The launching radius is estimated to be $5-16$ au, suggesting that the outflow is launchedfrom the VLA 1623A1 disk rather than the circum-binary disk.
Furthermore, we detected for the first time a velocity gradient associated with rotation toward
the VLA 16293B disk. The velocity gradient is opposite to the one from the large-scaleenvelope, outflow, and circum-binary disk. The origin of its opposite velocity gradient is also
discussed.
References[1]

Ohashi et al. submitted to ApJ

Experimental study toward the measurements of rotational state dependence ofinterstellar ion-polar molecule reactions at low temperatures
K. Okada, 1 Y. Murayama, 1 N. Kimura, 2 and K. Sakimoto 1
1

2

Department of Materials & Life Sciences, Sophia University, Tokyo, JapanRIKEN, Atomic, Molecular & Optical Physics Laboratory, Wako, Saitama, Japan

Recent astronomical observations have revealed the details of chemical composition in starforming regions and molecular clouds. However, the chemical processes in those regions havenot been fully understood using the existing chemical models with available data on relevant
reaction rate constants [1]. This is because the temperature dependence of the gas-phase ionmolecule reactions in the range of low to intermediate temperatures (10 - 200 K) and theirreaction branching ratio remain unknown. Thus, we have been developing a new experimental
apparatus to measure the reaction temperature dependence of ion-polar molecule reactions at
low temperatures [2, 3].
We report on an experimental study of the rotational cooling effect on the reaction rate
constant of Ca+ + CH3F → CaF+ + CH3 at low translational temperatures as a performance
test of a new experimental apparatus. Combining a cold helium buffer gas cell with a wavy
Stark velocity filter provides us with rotationally and translationally cooled polar molecules,
we could compare the reaction rate constants measured at two different gas cell temperatures,
namely the room temperature and about 30 K. The translational temperatures of the velocityselected molecules were set in the range of approximately 10 to 40 K. The rotational level
distribution of the velocity-selected CH3F molecules was determined by numericalsimulations of the velocity filtering and was used to calculate the rotationally-averaged
capture rate constants with the Perturbed Rotational State (PRS) theory [2]. Comparing to theresults obtained under the condition of room temperature gas cell, we observed a notable
increase in the reaction rate constant at low buffer-gas temperatures. This clearly shows astrong rotational state dependence of the rate constant at low translational temperatures.
(c)1|Vs| = 0.8 kV
TPM = 12(3) K+

ln[V(Ca )]

0.98
0.96
0.94

|Vs| = 2.0 kV
TPM = 24(5) K

0.92
0.9

0

500

1000

1500

reaction time (s)Figure 1 Fluorescence images of Ca+ Coulomb crystals before (a) and after (b) the Ca+ + CH3F → CaF+ +CH3 reactions. (c) A decay curve of the relative number of Ca+ ions due to the reactions between Ca+ andthe velocity-selected CH3F measured at two different translational temperatures of CH3F extracted from thehelium buffer gas cell at about 30 K (He pressure 80 Pa, UV laser detuning −40 MHz).

References[1] N. Sakai et al., 2014, Nature 507, 78.
[2] K. Okada, K. Sakimoto, Y. Takada, and H. A. Schuessler, 2020, J. Chem. Phys. 153, 124305.
[3] K. Okada, Y. Takada, M. Wada, and H. A. Schuessler, 2017, Rev. Sci. Instrum. 88, 083106.

Compact Distributions of N-bearing species and HCOOH
in the Protostellar Source B335
Y. Okoda,1 Y. Oya,1 M. Imai1, N. Sakai2, Y. Watanabe3, A. López-Sepulcre4,
and S. Yamamoto1
1

Physics, The University of Tokyo, JapanRIKEN Cluster for Pioneering Research, Japan
3
Materials Science and Engineering, College of Engineering, Shibaura Institute ofTechnology, Japan4
Univ. Grenoble Alpes, CNRS, IPAG, FranceInstitut de Radioastronomie Millimétrique, France
2

References[1] Imai, M., Sakai, N., Oya, Y., etal. 2016, ApJL, 830, L37[2] Colzi, L., Rivilla, V.~M.,
Beltrán, M.~T., et al. 2021, AAP,
653, A129[3] Okoda, Y., Oya, Y., Abe, S.,
Komaki, A., et al. 2021,
arXiv:2110.00150[4] Csengeri, T., Belloche, A.,
Bontemps, S., et al. 2019, AAP,
632, A57

Rotation temperature and Dust temperature [K]Molecular-line distributions around newly born protostars provide us an important clue tounderstanding chemical processes as well as physical structures such as a disk/envelope or an
outflow. B335 is a Bok globule harboring the Class 0 protostellar source (Tbol=37 K), IRAS
19347+0727, whose distance is reported to be 90-120 pc. A number of Complex Organic
Molecule (COM) lines were detected in the vicinity of the protostar with ALMA (Atacama
Large Millimeter/submillimeter Array), and hence, this source contains a hot corino at a few
10 au scale [1].
We have conducted ALMA observations toward this source at a high spatial resolution of ~3
au. The CH3OH and CH2DOH line emission have an extended distribution with the radius of~10 au around the protostar. In contrast, the N-bearing molecular lines, NH2CHO and HNCO,
show a more compact distribution within a radius of ~6 au or less. These characteristicfeatures have been reported for other sources [2][3]. Interestingly, the HCOOH lines show asimilar distribution to the N-bearing molecular lines, despite being an O-bearing species. This
trend has also been seen in a high-mass source [4]. We derive the rotation temperature aroundthe protostar under the assumption of the LTE condition using multiple lines each for CH3OH,
CH2DOH, NH2CHO, and HCOOH. Figure 1 shows the temperature distribution along the
disk/envelope system. The temperature is derived to be ~250 K at the continuum peak, anddecreases with increasing the distance from it. The derived temperatures in the vicinity of theContinuum
protostar within 3 au are all
CH₃OH
300
CH₂DOHsimilar. However, it depends
NH₂CHO
HCOOH
on molecules at 6 au. This250
may suggest the complex
structure of the disk/envelope
200
system. Further works are in
progress.
150
100

50

5 au
0
-0.2

-0.15

-0.1

-0.05

Beam size
0

0.05

0.1

0.15

0.2

Angular offset [arcsec]

Figure 1: The blue, yellow, green, and orange marks represent therotation temperatures derived from the CH3OH, CH2DOH, NH2CHO,
and HCOOH lines, respectively, along the disk/envelope system. The
vertical bars indicate the error bars. The purple line represents the dust
continuum distribution.

Chemical Differentiation and its Relation with the Physical Structuresin Disk-Forming Regions of Young Low-Mass Protostellar Sources
Y. Oya1,2

and S. Yamamoto1,2

1

2

Department of Physics, The University of Tokyo, Japan
Research Center for the Early Universe, The University of Tokyo, JapanTo understand the chemical origin of the Solar system, the chemical evolution along thestar/planet formation is a key issue. Extensive observational studies have so for demonstrated
a chemical diversity in young low-mass protostellar sources [e.g. 1, 2, 3]. Furthermore,chemical differentiations in the vicinity of the protostars have recently been reported (Figure1). This suggests that molecular distribution is sensitive to a change in the physical conditions
associated with disk formation. Some kinds of molecular lines are therefore prospected towork as molecular markers to highlight particular structures of disk forming regions.
Sulfur-bearing species, for instance OCS and H2CS, especially seem good tracers.
Conversely, detailed physical characterization is essential for elucidating the chemical
evolution occurring there. It has recently been recognized that some molecular lines tend to
trace the mid-plane of a disk/envelope system and others its surface [e.g. 4]. The traced
kinematic structure may differ among these molecular emissions, and thus, their carefulanalyses are essential for further observational studies in disk forming regions. Machinelearnings may help us to disentangle the observed structures.
In this presentation, we would like to report recent progresses in delineating the chemicaldifferentiation and the physical structures in disk forming regions of young protostellar
sources (IRAS 16293-2422 A, L483, B335, etc.) with ALMA.

Figure 1: Chemical differentiation in disk forming regions of young low-mass protostellar sources withdifferent chemical characteristics.

References
[1]
[2]
[3]
[4]

Cazaux et al., 2003, ApJL, 593, 51.
Bottinelli et al., 2004, ApJL, 617, 69.
Sakai and Yamamoto, 2013, ChRv, 113, 8981.
Podio et al., 2020, A&A, 642, L7.

Formation of 3-Pyrolline in Interstellar Space: A Computational Study
A. Pandey,1 A. Pathak,2 and K. A. P. Singh2
1

Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, India

2

Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, India

Complex organic molecules (COMs) are thought to form on icy dust grains in the earliest
phase of star formation. Interstellar detection of the straight-chain (n-propyl cyanide,n−C3H7CN) and branched-chain (i-propyl cyanide, i−C3H7CN) molecules toward the starforming region, Sgr B2(N2) has attracted attention to study the formation mechanism ofCOMs [1]. The first detection of COM strongly hints the existence of other linear and ringshaped molecules, which are prebiotic and building block of proteins.
Through computational methods, we suggest new possible formation and destruction
pathways of branched aliphatic molecule to aromatic compounds in space. We computed
binding energy, enthalpies of formation of several species. We also calculate the kinetic dataof reactions and other spectroscopic information in order to understand the chemical evolution
and formation of aromatic compounds to be present in the Interstellar medium (ISM).

References[1]

A. Belloche, R.T. Garrod, H.S.P. Müller, K.M. Menten,Sci. 345, 158 (2014)[2]

E.E. Etim, P. Gorai, Das. Ankan, E. Arunan, Eur. Phys. J. D (2017) 71: 86[3]

F. J. Lovas, J. M. Hollis, Anthony J. Remijan,P. R. Jewell,The Astrophysical Journal, 645: L137–L140,
2006 July 10[4]

J. Cernicharo1 , N. Marcelino, M. Agúndez , C. Bermúdez , C. Cabezas , B. Tercero , J. R.Pardo, A&A
642, L8 (2020)[5]

R. T. Garrod, A. Belloche, H. S. P. Müller, K. M. Menten , A&A 601, A48 (2017)