Oral 1

The evolution of ice mantles during the star formation process: an IceAge JWST studyof Chamaeleon I
J. A. Noble,1 for the IceAge team2
1
Physics of the Interactions of Ions and Molecules (PIIM) laboratory, CNRS/Aix-Marseille
Université, France
2
PI M. K. McClure and co-PI H. Linnartz, Leiden Observatory, Leiden; co-PI A. C. A. Boogert,
Institute for Astronomy/InfraRed Telescope Facility, Honolulu
Icy grain mantles are the main reservoir for volatile elements in star-forming regions. The IceAge
Early Release Science program [1,2] on the James Webb Space Telescope proposes to observe
infrared spectra of objects at various stages of star formation, from dense cloud to protoplanetary
disk. By observing Chamaeleon I – a representative low-mass star-forming region containing
objects at each of these stages – we aim to trace the evolution of pristine and complex ice
chemistry that accompanies the physical evolution of the objects. The dense cloud was observed
using the NIRCam, NIRSpec and MIRI instruments in summer 2022, providing high spectral
resolution (R~1500-3000) and sensitivity (S/N>100) infrared spectra from 2.5 to 13 μm of two
highly extincted background stars (Av < 100) and additional L and M band spectra towards
hundreds more field stars. In this talk, we will present the first results of the IceAge program: acomplete ice inventory towards observed lines of sight, including derived column densities for
expected ice species as well as the first detection of several species along lines of sight in aquiescent cold core [3]. We will also present some more recent advances and give perspectives forthe rest of the IceAge program, with a particular focus on the NIRCam observations that permit
mapping the spatial distribution of ices down to ~20-50 au with the aim of identifying the onset ofice formation.

Figure 1: Star-forming region Chamaeleon I, imaged by the JWST NIRCam instrument.[4]References[1]
http://jwst-iceage.org/[2]
M. McClure, J. Bailey, T. Beck, A. C. A. Boogert, W. Brown, P. Caselli., J. Chiar, E. Egami, H. J. Fraser, R.
Garrod, K. D. Gordon, S. Ioppolo, I. Jimenez-Serra, J. Jorgensen, L. E. Kristensen, H. Linnartz, M. McCoustra, N.
Murillo, J. A. Noble, K. Oberg, M. E. Palumbo, Y. J. Pendleton, K. M. Pontoppidan, E. F. van Dishoeck. & S. Viti
“IceAge: Chemical Evolution of Ices during Star Formation” 2017, JWST cycle 0 ERS Accepted Proposal 1309,
arxiv: 2017jwst.prop.1309M[3]
M. K. McClure, W. R. M. Rocha, K. M. Pontoppidan, N. Crouzet, L. E. U. Chu, E. Dartois, T. Lamberts, J. A.
Noble, Y. J. Pendleton, G. Perotti, D. Qasim, M. G. Rachid, Z. L. Smith, F. Sun, T. L. Beck, A. C. A. Boogert, W. A.
Brown, P. Caselli, S. B. Charnley, H. M. Cuppen, H. Dickinson, M. N. Drozdovskaya, E. Egami, J. Erkal, H. Fraser, R.
T. Garrod, D. Harsono, S. Ioppolo, I. Jiménez-Serra, M. Jin, J. K. Jørgensen, L. E. Kristensen, D. C. Lis, M. R. S.
McCoustra, B. A. McGuire, G. J. Melnick, K. I. Öberg, M. E. Palumbo, T. Shimonishi, J. A. Sturm, E. F. van
Dishoeck & H. Linnartz “An IceAge JWST inventory of dense molecular cloud ices” 2023, Nature Astronomy, doi:
10.1038/s41550-022-01875-w[4]
Press release 23/01/23 23 https://esawebb.org/news/weic2303/ Image Credit: NASA, ESA, CSA, and M.
Zamani (ESA/Webb); Science: M. K. McClure (Leiden Observatory), F. Sun (Steward Observatory), Z. Smith (Open
University), and the Ice Age ERS Team.

https://esawebb.org/news/weic2303/

Oral 2Icy Origin of Complex Molecules in Embedded Protostars
Y.-L. Yang1 and The CORINOS Team
1

Star and Planet Formation Laboratory, Cluster for Pioneering Research, RIKEN, Japan

In recent years, the increasing detection of gas-phase complex organic molecules (COMs) inClass 0/I protostars highlights the extensive chemical evolution at the onset of star and planet
formation. Recent ALMA surveys found ~40% protostars without detectable gaseous COMs
[1]. It is thus unclear whether most protostars undergo the similar chemical evolution,
resulting in formation of COMs. Most COMs are thought to form in the ice mantles
covering dust grains. Therefore, constraining the ice composition in embedded protostars
would provide the smoking gun evidence to answer the origin of chemical diversity ingas-phase measurements. Ice measurements had been limited by low-resolution and limited
sensitivity until JWST, which can probe ices at a spatial scale comparable to that by ALMA
with unprecedented sensitivity. In this talk, I will present the results of the CORINOS
program, which aims to map the ice distribution toward a sample of protostars chosen to
represent ranges of complex chemistry and thermal structure using JWST/MIRI. I will sharethe ice analysis toward a Class 0 protostar, IRAS 15398-3359 [2], where we detect ice
absorption of H2O, CO2, CH3OH, CH4, and NH3 as well as signatures of organic ice,including HCOOH, H2CO, C2H5OH, CH3CHO, CH3COOH, and HCOOCH3. The ice
abundance will be compared with the abundance of gas-phase COMs surveyed by ALMA,
compiling a complete chemical budget of ice and gas. I will also present preliminary results of
the observations of the remaining sources. The data of the CORINOS program show striking
details on the ice absorption as well as the protostellar structure, demonstrating the prospectof understanding organic chemical evolution from protostars to planets.

Figure 1: MIRI MRS spectrum of IRAS 15398-3359, showing various ice absorption features detected at
the highest fidelity achieved to date.

References[1][2]

Y.-L. Yang, N. Sakai, Y. Zhang, et al. 2021, ApJ, 910, 20
Y.-L. Yang, J. D. Green, K. M. Pontoppidan, et al. 2023, ApJL, 941, L13

Oral 3

Molecules in Outflow Shocked Regions: JWST meets ALMAY. Okoda,1 Y. Yang,1 N. Sakai1, and CORINOS team members
1

RIKEN Cluster for Pioneering Research, JapanHow low-mass protostars at the earliest stage grow has still been veiled. As one approachto this problem, we study shock regions in the outflow structure of IRAS 15398-3359 byusing some molecular lines observed with JWST (James Webb Space Telescope) and ALMA
(Atacama Large Millimeter/submillimeter Array).
IRAS 15398-3359 is a Class 0 protostellar source (Tbol = 44 K) in the Lupus 1 molecular
cloud (d= 156 pc). In the previous studies (e.g., [1][2][3][4]), some molecular lines, such as
H2CO, CS, and 12CO etc, were found to trace the outflow structure extending from thenortheast to southwest axis, which is almost parallel to the plane of the sky. The rotationally
supported disk was detected in the SO emission, which is perpendicular to the outflow
direction. The protostellar mass was estimated to be 0.007 solar mass on the assumption of a
Keplerian rotation [5]. Based on the dust continuum data, the envelope mass was reported to
be much larger, 0.5-1.2 solar mass[6][7], and hence, IRAS 15398-3359 should be a very
young source.
CORINOS have conducted the JWST observation toward this source, and have detected thesouthern part of the outflow structure with the mid-infrared instrument (MIRI) [8]. The MIRI
image shows the three shell structures and the front shock (Fig.1a). We compare the structure
to molecular-line distributions observed with ALMA. The H2CO and CS lines show the shellstructures corresponding to those in the MIRI image, and the 12CO line traces the whole
structure including the front shock. We determine the outflow direction of P.A 235 degree,
based on the structure in the MIRI image, which is slightly different from the outflow
direction near the protostar (P.A 220 [5] and 230 degrees [1]). Furthermore, we detect eightlines of H2 with JWST, mainly tracing the southern part of the outflow near the protostar (Fig.
1b). Assuming the LTE condition, we derive the temperature and the column density map tobe ~700-800 K and ~1019 cm-2, respectively. Comparing between the distributions of H2 andthose of the molecular lines (H2CO, CS, and 12CO), we find that the three molecular lines
show a weak emission where the H2 lines are enhanced with the high temperature. In theshock regions of the outflow cavity, the temperature is estimated to be 46-126 K when the H2
density is assumed to be 106 cm-2, by using the three H2CO lines observed with ALMA. Our
results suggest an episodic outflow ejecting with precession.
(a) MIRI(b) H₂ (S1)

(P.A. 235°)

Figure 1: (a) MIRI image with
JWST. Red cross mark shows
the continuum peak. Dottedlines represent the shellstructures and the front shock.
The box with orange dottedlines corresponds to the areain the panel (b). (b) Integrated
intensity map of H2 (S1).
Black cross mark shows thecontinuum peak.

References[1] Y. Oya, et al. 2014, ApJ, 795, 152 [2] Y. Okoda et al. 2020, ApJ, 900, 40 [3] Y. Okoda et al. 2021, ApJ, 910,
11 [4] M.M.Vazzano et al. 2021, A&A, 648, A41 [5] Y. Okoda, 2018, ApJL, 864, L25 [6] L.E. Kristensen et al.
2012, A&A 542, A8 [7] Jes K. Jørgensen et al. 2013, ApJL, 779, L22 [8] Y. Yang, 2022, ApJL, 941, L13

Oral 4

Exploiting Molecular Beams and Surface Science Studies to Untangle the Formation ofComplex Organics in Deep Space - From Nanoparticles to Interstellar Ices
Ralf I. Kaiser1,2
1

Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
2 W.M. keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA

Ice coated interstellar nanoparticles have emerged as molecular factories in the synthesis of(aromatic) hydrocarbons and of complex, biorelevant organics in cold molecular clouds and instar forming regions. An detailed understanding of the fundamental reaction mechanisms leading
to these organics in deep space requires new knowledge not only on the formation of thesenanoparticles (carbonaceous, silicates, sulfides) from the bottom up via elementary gas phasereactions, but also on the processing of low temperature ices by (non)ionizing radiation present
even deep inside cold molecular clods. Extensive gas phase and condensed phase (ices) physicalchemistry laboratory experiments have been at the center of attention in providing thisknowledge. This talk provides an overview on recent molecular beams experiments (gas phase)and surface science studies (ice chemistry) of particular importance in deciphering theunderlying reaction dynamics and kinetics leading to fundamental molecular building blocks ofinterstellar nanoparticles and to complex organics of astrobiological significance and concludes
with new developments in this field. The gas-phase studies have culminated in the preparationof planar (2D) and bent (3D) polycyclic aromatic hydrocarbons (corannulene [1], coronene [2],C40 nanobowls [3], helicenes [4-6]) involving multifaceted reaction mechanisms [7] asfundamental molecular building blocks of graphenes, fullerenes, and nanotubes; surface
science experiments advanced to an understanding of the non-equilibrium chemistry leading toC1-C6 complex organics (alcohols, aldehydes/ketones, carboxylic acids, sugars) connected to theOrigin of Life theme [8-15]
References[1] L. Zhao et al., PCCP, 23, 5740 (2021).
[2] S. Goettl et al., JACS, (2023).
[3] L.B. Tuli, Nat. Commun., 14, 1527 (2023).
[4] R.I. Kaiser, PCCP, 24, 25077 (2022).
[5] L. Zhao et al., Angew Chemie Int. Ed., 59, 4051 (2020).
[6] L. Zhao et al., Nat. Commun., 10, 1510 (2019).
[7] R.I. Kaiser et al., JPCA, 125, 3826 (2021).
[8] J. Wang et al., Sci. Adv., eadg1134 (2023).
[9] J.H. Marks et al., Angew Chemie Int. Ed., 62, e202218645 (2023).
[10] J.H. Marks et al., PNAS, 119, e2217329119 (2022).
[11] S.K. Singh et al., Nat. Comm., 13, 375 (2022).
[12] C. Zhu et al., PNAS 119, e2111938119 (2022).
[13] A.M. Turner et al., ACR, 53, 2791 (2020).
[14] N.F. Kleimeier et al., Chem, 6, 1 (2020).
[15] N.F. Kleimeier et al, JACS, 143, 14009 (2021).

Oral 5

Electronic Spectroscopy of Polycyclic Aromatic Hydrocarbons in solid para-Hydrogen
I. Weber1 and Y.-P. Lee1,21

Dept. Applied Chemistry and Center for Emergent Functional Matter Science, National Yang-Ming Chiao Tung
University, Taiwan
2
Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Taiwan

Polycyclic aromatic hydrocarbons (PAH) and their heteroatom-substituted, protonated,hydrogenated, and cationic derivatives are commonly considered as the carriers of theunidentified infrared (UIR) bands and as promising candidates for the carriers of the diffuse
interstellar bands (DIB), [1] absorption bands in the UV/VIS to near-IR region. However,despite the large number of known DIB (well over 200 up to today), only the
buckminsterfullerene cation C60+ has been confirmed as the carrier of two DIB at 9577.5 and9632.7 Å on the basis of its laboratory spectrum. [2,3]Para-hydrogen (p-H2) has frequently been employed as a matrix host for IR spectroscopy of
PAH, PANH, and their protonated and hydrogenated derivatives; the IR absorption spectra
exhibit only small shifts relative to the gas-phase, in line with the “softness” of solid p-H2.
Over the past years, we have recorded the dispersed fluorescence and fluorescence excitation
spectra of various PAH with 10 to 42 carbon atoms as well as a small number of protonatedand hydrogenated PAH and PANH, to assess the properties of p-H2 as a matrix host forelectronic spectroscopy and its potential to provide laboratory reference spectra forcomparison to observations. We find a generally good agreement with previously literature
data, indicating a rather small but consistent redshift of <100 cm−1 relative to the gas phase
due to the matrix environment.
In our contribution, we discuss advantages and disadvantages of p-H2 as a matrix host forelectronic spectroscopy by providing experimental data and spectra simulated based on
quantum-chemical calculations for three examples: the 1-hydronaphthyl radical (1-C10H9),
which has been extensively studied in the gas phase and in solid Ne, and the two large PAH
peri-hexabenzocoronene (peri-HBC, C42H18) and ovalene (C32H14). Our work on 1-C10H9
demonstrates the good agreement of the p-H2 data with previous work and the comparablyeasy accessibility of hydrogenated (and protonated) PAH in p-H2, but also shows the stronger
influence of p-H2 on spectral line positions compared to Ne. We observed the D1–D0 origin at
18881 cm−1 giving a matrix shift of 68 cm−1; for Ne, a blue shift of ~13 cm−1 can be inferredfrom the work of Garkusha et al. [4] Peri-HBC has rarely been studied before. We provide afirst full assignment of the vibrational structure of the fluorescence emission and excitation
spectra centered around the S1–S0 origin band located ~22075 cm−1 in solid p-H2. Ovalene has
been discussed as potential DIB carrier and a system exhibiting anomalous fluorescence fromhigher excited singlet states. Combining experiment and theory, we found, however, that thelowest excited singlet state (S1) was previously assigned erroneously; we report thefluorescence emission and excitation spectra as well as fluorescence lifetimes of the true S1state.
References

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

A. G. G. M. Tielens, 2008, Ann. Rev. Astron. Astrophys. 46, 289.
E. K. Campbell, M. Holz, P. & J. P. Maier, 2015, Nature 523, 322.
E. K. Campbell, M. Holz, J. P. Maier, P. Gerlich, G. A. H. Walker & D. Bohlender, 2016, ApJ 822, 17.
I. Garkusha, A. Nagy, J. Fulara, M. F. Rode, A. L. Sobolewski & J. P. Maier, 2013, JPCA 117, 351.

Oral 6

Experimental measurement for absorption cross section of two-coordinated dangling
OH bonds on the surface of amorphous ice at 20 K
T. Hasegawa, H. Yanagisawa, T. Nagasawa, N. Numadate and T. Hama
Graduate School of Arts and Science, Komaba Institute for Science/UTokyo, Japan
In cold and dense interstellar clouds, amorphous water (H2O) is abundant and forms icy dust
grains [1]. Infrared (IR) spectra of amorphous water prepared at low temperatures show two
weak absorption peaks at 3696 cm-1 and 3720 cm-1 in laboratory experiments. These areassigned to "dangling OH bonds", which are the free OH stretching modes of 3-coordinated(one H doner and two H acceptors; 3dOH) and 2-coordinated (one H donor and one H
acceptor; 2dOH) H2O on the ice surface, respectively [2]. Dangling OH bonds reflect thesurface structure of ice and act as a chemical reaction site on the ice surface. Recently, theJames Webb Space Telescope, a high sensitivity infrared telescope in space launched in 2021,
detected possible dangling OH feature for amorphous icy dust grains in an interstellar cloud,
where stars and planets will form [3]. With the absorption cross section for dangling OH
bonds, the number density can be calculated from the observed absorbance, which leads us tounderstanding the surface structure of interstellar ices [4]. In this study, we measured thenumber densities of 2dOH and 3dOH on amorphous ice at 20 K using infrared multiple-angle
incidence resolution spectrometry (IR-MAIRS). IR-MAIRS is a technique combining oblique
incidence transmit measurements and multiple variation analysis to obtain pure out-of-plane(OP) and in-plane (IP) spectra. Figure 1 shows the OP and IP spectra of amorphous water at
20 K before and after the deposition of carbon monoxide (CO). Both 2dOH and 3dOH
features appeared and quenched after CO exposure at 20 K. At the same time new peaks
appeared at around 2152
and 2139 cm-1, which areassigned to the CO
stretching vibration bands
for CO molecules adsorbed
at dangling OH bonds andhydrogen-bondedOHbonds [5]. Assuming thatthe amount of the COmolecules adsorbed at
dangling OH bonds to fully
quench the two peaks
corresponds to the column
densities of 3dOH and
2dOH, the absorption cross Figure 1. OP and IP spectra of amorphous ice vapor deposited at 20
section for 2dOH is K before (A) and after (B) CO exposure.
estimated much smaller
than that for 3dOH.
References[1] T. Hama & N. Watanabe, Chemical Reviews 113, 8783–8839 (2013).
[2] V. Buch & J. P. Devlin, The Journal of Chemical Physics 94(5), 1, 4091-4092 (1991).
[3] M. K. McClure et al., Nature astronomy 7, 431-443 (2023).
[4] T. Nagasawa et al., The Astrophysical Journal Letters 923, L3 (8pp) (2021).
[5] S. Matsuda et al., Chemistry Letters 47(4), 468-471 (2018).

Oral 7

Exploring the Mysteries of CO Ices: Weak Interactions and Vibrational Energy
Relaxation
B.C. Ferrari,1 M. van Hemert,1 J. Meyer,1 and T. Lamberts1
1

Leiden Institute of Chemistry, Leiden University, Leiden 2300 RA, The Netherlands

One of the largest fractions of interstellar ice and gas, carbon monoxide, still remains
shrouded in mystery. In particular, models still fail to accurately reproduce the observed iceto-gas ratio of CO without adding unrealistic tweaks to the models. We previously
investigated the binding energy of CO on CO ices, where we found a rather large number of
weak binding sites [1]. These weak sites, if incorporated within models, could reduce thediscrepancy between observations and models [2]. Additionally, non-thermal desorption
mechanisms are being scrutinized to understand their role in non-destructively desorbing
molecules. One such novel mechanism speculated by experiments is vibrationally-induced
desorption.
Recently, infrared-induced desorption of interstellar CO ice analogs was experimentally
performed [3]. However, for it to explain the gas-phase CO abundance, we need to understandthe mechanism behind the desorption. We studied the vibrational energy relaxation (VER) of
CO ices, with a particular aim of unraveling how desorption could be induced. We find that
CO has an extremely slow classical VER timescale and that vibrational to translational energy
conversion is extremely inefficient. Furthermore, we do not observe any desorption within the4700 simulations that we carried out. These results suggest that possible explanations for thedesorption seen experimentally are: (i) quantum effects that are not captured by the classicalsimulations, or (ii) surface or local heating.

References[1]
Ferrari, Brian C., et al. "Floating in Space: How to Treat the Weak Interaction between CO Molecules inInterstellar Ices." ACS Earth and Space Chemistry (2023).
[2]
Cazaux, S., et al. "CO Depletion: A microscopic perspective." The Astrophysical Journal 849.2 (2017):80.
[3]Santos, J. C., et al. "Resonant infrared irradiation of CO and CH3OH interstellar ices." Astronomy &Astrophysics 672 (2023): A112.

Oral 8Heterogeneous catalysis in space: CH3OH formation via Fischer-Tropsch reactions. A
computational approach.
G. Pareras,1 V. Cabedo,2 M. McCoustra,2 and A. Rimola1
1

Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia,
Spain.
2
Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt
University, Edinburgh, EH14 4AS, Scotland.

Gas-phase chemistry under extreme conditions, characterized by low densities andtemperatures, poses significant challenges. The presence of interstellar grains plays a crucialrole in facilitating the formation of molecules that cannot naturally emerge in the gaseous phase.
Interstellar grains are believed to enhance the interaction between reactive species, promoting
reactions on their surfaces, and mitigate the energy excess of highly exothermic reactions.
However, their function as chemical catalysts, offering low activation energy pathways toaccelerate reaction rates, remains less explored.
Nevertheless, various materials with catalytic properties can be found in interstellar
environments, including refractory grains containing transition metals abundant in space. In
this study, we present novel mechanistic insights into the synthesis of methanol (CH3OH) via
the Fischer-Tropsch process under astrophysical conditions. We employ single-atom iron (Fe)containing silica surfaces as heterogeneous catalysts in an interstellar context. Our approach
involves quantum chemical calculations considering extended periodic surfaces to identify
stationary points and transition states, ultimately constructing reaction potential energy
surfaces. Additionally, we conduct binding energy and kinetic calculations based on the Rice–Ramsperger–Kassel–Marcus (RRKM) scheme to assess the catalytic capability of these grains
and place these reaction processes within the framework of astrochemistry.
Our mechanistic investigations demonstrate the feasibility of astrocatalysis in astrophysicalenvironments. While the proposed process is thermodynamically highly exergonic, it exhibits
kinetic barriers necessitating an activation energy to proceed. Furthermore, our kinetic
calculations underscore the strong temperature dependence of this reaction process, withtunnelling effects being insignificant across the involved energetic barriers. These findings shedlight on the presence of CH3OH in various regions where current models struggle to explain its
observed abundance. Moreover, the revelation of astrocatalysis introduces an entirely new
spectrum of synthetic pathways, sparking chemical evolution in space.

Figure 1. Representation of the surface model and the catalytic cycle under study.

Oral 9

Atomistic insight into molecular processes on interstellar ice analogs
T. Lamberts1,2 Niels Munch Mikkelsen3, Mie Andersen3, Joan Enrique-Romero1
1

Theoretical Chemistry, Leiden Institute of Chemistry, Leiden University, The Netherlands
2
Leiden Observatory, Leiden University, The Netherlands
3
Aarhus Institute of Advanced Studies, Aarhus University, Denmark

The darkness observed between the stars on a clear night sky is far from empty, in fact a hidden
chemical world thrives. The focus of my group is primarily on the cold, dense molecular medium
where surface reactions orchestrate the build-up of ‘dirty’ ices, forming a molecular mantle covering
the micron-sized dust grains.
Species accrete, diffuse, and react on the surface after which they can evaporate back into the gas
phase. The interplay between these processes dictates the composition of icy mantles, along with
where and whether or not they are astronomically observable, either in the solid or gas phase. Withthe use of computational chemistry, we aim to contribute to an atomistic understanding of therelevant surface processes and untangle the web of reactions within realistic, amorphous ices.
In this presentation specifically I will shine light on the creation, structure, and accompanying
spectroscopy of H2O:CO2 ice mixtures, on the types of bonding the CN radical can undergo on H2O
and CO ices, and on the potential implications thereof for interstellar surface chemistry.

Oral 10

Next-generation cosmic ice models for the JWST Era
C. N. Shingledecker1
1

Department of Physics & Astronomy, Benedictine College, USA

The key role of grain-surface processes for accurately simulating interstellar chemistry has
long been known [1]; however, the importance of modelling processes occurring within dust
grain ice mantles has only been fully realized in the last decade or so [2,3]. This new
appreciation for solid-phase chemistry has been largely motivated by an extensive body oflaboratory astrochemical studies, which have conclusively demonstrated the rich array ofcomplex molecules that can form at very low temperatures [4-6]. More recently, data from the
newly-launched James Webb Space Telescope has already revealed that even in regions
previously thought to have been COM-poor, there exists a hidden reservoir of COMs withincosmic ice, which are unlikely to have been formed primarily via gas-phase reactions [7].
Substantial progress in treating cosmic ice chemistry is likely needed before simulations will
be able to reliably replicate such observational results, and in this talk, I review some of ourrecent work along these lines, as well as present preliminary results from two projects that
represent promising breakthroughs in how grain-surface chemistry is simulated in
astrochemical models.

References

1.
[1]
T. I. Hasegawa, E. Herbst, C. M. Leung, Models of gas-grain chemistry in dense interstellar clouds withcomplex organic molecules. The Astrophysical Journal Supplement Series. 82, 167–195 (1992).
[2]
R. T. Garrod, A Three-phase Chemical Model of Hot Cores: The Formation of Glycine. The
Astrophysical Journal. 765, 60 (2013).
[3]
C. N. Shingledecker, T. Lamberts, J. C. Laas, A. Vasyunin, E. Herbst, J. Kästner, P. Caselli, Efficient
Production of S8 in Interstellar Ices: The Effects of Cosmic-Ray-driven Radiation Chemistry and Nondiffusive
Bulk Reactions. ApJ. 888, 52 (2020).
[4] R. I. Kaiser, K. Roessler, Theoretical and Laboratory Studies on the Interaction of Cosmic-Ray Particles
with Interstellar Ices. I. Synthesis of Polycyclic Aromatic Hydrocarbons by a Cosmic-Ray-Induced Multicenter
Mechanism. The Astrophysical Journal. 475, 144–154 (1997).
[5]
P. D. Holtom, C. J. Bennett, Y. Osamura, N. J. Mason, R. I. Kaiser, A combined experimental andtheoretical study on the formation of the amino acid glycine (NH2CH2COOH) and its isomer (CH3NHCOOH)
in extraterrestrial ices. The Astrophysical Journal. 626, 940 (2005).
[6]
R. L. Hudson, M. H. Moore, J. P. Dworkin, M. P. Martin, Z. D. Pozun, Amino Acids from Ion-IrradiatedNitrile-Containing Ices. Astrobiology. 8, 771–779 (2008).
[7] Y.-L. Yang, J. D. Green, K. M. Pontoppidan, J. B. Bergner, L. I. Cleeves, N. J. E. II, R. T. Garrod, M. Jin,
C. H. Kim, J. Kim, J.-E. Lee, N. Sakai, C. N. Shingledecker, B. Shope, J. J. Tobin, E. F. van Dishoeck,
CORINOS. I. JWST/MIRI Spectroscopy and Imaging of a Class 0 Protostar IRAS 15398–3359. ApJL. 941, L13(2022).

Oral 11

A framework for incorporating binding energy distributions in astrochemical models
K. Furuya,11National Astronomical Observatory of Japan, JapanOne of the most severe limitations of the current astrochemical models is that only a single
type of binding site is considered, although laboratory and quantum chemical studies havefound that there are multiple types of binding sites with different potential energy depths [e.g.,1, 2]. On a surface with multiple types of binding sites, adsorbed species can be trapped insites with a deep potential, increasing the resident time of the adsorbed species. On the other
hand, species can be populated in shallow potential sites, activating thermal hopping and thus
two-body reactions even at low temperatures, where thermal hopping from deeper sites is not
activated. Such behavior cannot be described by the conventional rate equation method [3, 4].
I present a framework for incorporating binding energy distributions in gas-ice astrochemical
models as a natural extension of the conventional rate equation method. I developed a simple
method to estimate the probability distribution function for the occupation of binding sites
with different potential energy depths, assuming a quasi-steady state. By using hopping anddesorption rates weighted by the probability distribution functions, the effect of binding
energy distribution is incorporated into the rate equation method without increasing thenumber of ordinary differential equations to be solved. This method was found to be accurate
and computationally efficient and enables us to consider binding energy distributions even fora large gas-ice chemical network, which contains hundreds of different icy species. The
impact of the binding energy distribution on the interstellar chemistry will be discussed
quantitatively.

References[1] Amiaud, L., Dulieu, F., Fillion, J. H., Momeni, A., & Lemaire, J. L. 2007, JChPh, 127, 144709[2] Tinacci, L., Germain, A., Pantaleone, S., et al. 2022, ACS Earth and Space Chemistry, 6, 1514
[3] Hasegawa, T. I., Herbst, E., & Leung, C. M. 1992, ApJS, 82, 167[4] Hasegawa, T. I., & Herbst, E. 1993, MNRAS, 263, 589

Oral 12       +!,+#+0)#,+#%)'#+%,,.+,+" '*,)
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 1/56813-%)41881!9;+01>)4)"/31-5/665156)8:8)    Oral 13

Surface chemical properties of interstellar grains. Insights from quantum chemical
simulations
A. Rimola,1 N. Bancone,1,2 J. Enrique-Romero,1,3 S. Ferrero,1 H. Kakkar,1 B. MartínezBachs,1 E. Mates-Torres,1 G. Pareras,1 J. Perrero1,2
1

Department de Química, Universitat Autònoma de Barcelona, 08193, Catalonia, Spain
2
Dipartimento di Chimica, Università degli Stduy di Torino, 10125, Torino, Italy
3
Leiden Institute of Chemistry, Leiden University, Leiden 2300 RA, The Netherlands

There is clear evidence that dust grain particles are central players contributing to thechemical inventory of the Universe. However, the exact role played by the grains is still not
well understood and hard to unveil in a “rule-of-thumb” fashion: with the research progress
made, the role of grains appears to be case-dependent. Grains are usually referred to as
catalysts, a concept attributed in a generic sense, meaning that their presence allows thereactions to evolve, which is not the case in their absence. However, by dissecting this generalidea of catalysis, for the case of ices, one can realize that, rather than being actual chemical
catalysts (i.e., bodies that activate the reactants and provide alternative routes with lower
energy requirements) they are more like reactant concentrators/suppliers [1,2,3,4] and/or thirdbodies that absorb the large extra energies released in chemical reactions (hence stabilizing
the newly formed products) [5,6]. Thus, for a paradox, the capability of water ices to act aschemical catalysts is limited due to their relatively chemical inertness. In contrast, chemical
catalytic properties can be found in interstellar refractory materials (e.g., silicates, ironsulfides, metallic grains…) due to the presence of transitions metals (e.g., Fe, Ni) that can
activate the reactants [7,8]. In this contribution, different paradigmatic roles exerted by grains(ices and refractories) in different chemical reactions of astrochemical interest will be shown,which have been discerned thanks to the unique capabilities of quantum chemical simulationsat providing exclusive atomic-scale information.

References

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

S. Ferrero, L. Zamirri, C. Ceccarelli, A. Witzel, A. Rimola, & P. Ugliengo, 2021, ApJ, 904, 11.
J. Perrero, J. Enrique-Romero, S. Ferrero, et al., 2022, ApJ, 938, 158.
J. Enrique-Romero, A. Rimola, C. Ceccarelli, et al., 2022, ApJS, 259, 39.
J. Perrero, J. Enrique-Romero, B. Martínez-Bavhs et al., 2022, ACS Earth Space Chem., 6, 496.
S. Pantaleone, J. Enrique-Romero, C. Ceccarelli, et al., 2021, ApJ., 917, 49.
S. Ferrero, S. Pantaleone, C. Ceccarelli, et al., ApJ, 944, 142.
V. Cabedo, J. Llorca, J. M. Trigo-Rodriguez, A. Rimola, 2021, A&A, 650, A160.
M. Serra-Peralta, C. Domínguez-Dalmases, A. Rimola, 2022, Phys. Chem. Chem. Phys., 24, 28381.

Oral 14

Dissolution process of forsterite coexisting with interstitial water
Y. Kobayashi, T. Ikeda-Fukazawa
Department of Applied Chemistry, Meiji University, Japan
Inclusions of liquid water have been found in the samples collected from the carbonaceous
asteroid Ryugu [1]. Though the origin of water is not conclusive, the deposited ice on mineral
dust grains in interstellar molecular clouds could be a potential cause. In interstellar molecular
clouds, mineral dust grains are covered with amorphous ice mantles [2]. The major componentof the mineral dust grains is forsterite (Mg2SiO4) in glassy state [3], which is considered toundergo a mineral evolution through various processes to be a crystalline state in planets.
Although most water molecules desorb from the mineral grains with heating during theformation of protoplanetary disk, residues can be confined in the grain boundaries as aninterstitial water. The interstitial water of forsterite has unique properties. Kubo et al. [4] foundthat the interstitial water of glassy forsterite has higher density than that of ordinary water andexists as liquid state at high temperatures above the boiling point. However, the mechanisms of
the structural change of the interstitial water have not yet been well understood. In this study,
molecular dynamics (MD) calculations were performed to investigate the effects of thicknessof water layer on structure of interstitial water and forsterite.
MD calculations were performed using the MXDORTO program developed by Kawamura [5].
Fundamental orthorhombic cells consisting of 484–3311 H2O and 1176 Mg2SiO4 (forsterite in
crystalline or glassy states) were used as the initial structures. The thicknesses of water layer d
between the forsterite phases were controlled with the number of H2O to be 1–6 nm at the initialstructure. The MD code was run with an NTP ensemble at 280–670 K. The pressure was kept
at 0.1 MPa. The structure was analyzed using the equilibrated states. For the comparison, thepure water system consisting of 360 H2O was also calculated.
Dissolutions of Mg and Si from the glassy forsterite toward interstitial water were observed attemperatures above 280 K for the system with d > 1 nm. The dissolved Mg exists as MgO6Hx
unit and forms Mg(OH)2 crystal by collisions of the MgO6Hx units in water layer [4]. The
dissolved Si maintained tetrahedral SiO4 structure due to the strong Si–O bond.
For crystalline forsterite, in contrast, no dissolution of Mg and Si was observed at temperatures
below 610 K. Only Mg dissolved at temperatures above 630 K for the system with d < 1.5 nm.
The dissolution of Mg generates a defect on the surface of crystalline forsterite. The distortionof structure around the defects might promote an additional dissolution of Mg. The dissolution
occurs for the systems with d < 1.5 nm, because the density of water increases as the thicknessof the water layer decreases. The result suggests that the dense structure of interstitial water has
an effect to enhance the decomposition of crystalline forsterite. Since the number of dissolved
Mg was extremely small, the formation of Mg(OH)2 crystal was not observed in the calculation
period of the present study (3.0 ns).
References
[1]
[2]
[3]
[4]
[5]

T. Nakamura et al., 2023, Science 379, 8671.
J. M. Greenberg & J. I. Hage, 1990, ApJ 361, 260.
T. Henning, 2010, Annu. Rev. Astron. Astrophys. 48, 1.
A. Kubo, J. Nishizawa, & T. Ikeda-Fukazawa, 2022, Chem. Phys. Lett. 805, 139932.
K. Kawamura, MXDORTO, 1996, Japan Chemistry Program Exchange 029.

Oral 15

Chemical Evolution in Turbulent Disks: Stochastic Effect by UV photons
T. Suzuki,1 K. Furuya,2 Y. Aikawa,1 T. Shibata,2 and M. Liton31

2

Department of Astronomy, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japa
3
School of Earth and Planetary Sciences, National Institute of Science Education andResearch, Jatni 752050, Odisha, India
4
Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai
400094, India

Whether the complex organic molecules (COMs) detected within the disk are inherited
directly from the protostellar stage or are chemically processed within the disk itself remains a
topic of debate. Our research aims to shed light on this debate by studying the chemical
evolution of COMs in these dynamic environments. First, we trace the grain motion(advection, turbulent diffusion, radial drift, and vertical settling) of individual dust particles
for 106 yrs on a physical structure model of a protoplanetary disk[1]. Next, we solve a gas-ice
chemical reaction network along the trajectories and obtain the temporal evolution ofmolecular abundances.
Our findings underscore the pivotal role of UV flux in the formation of COMs within
turbulent disks. The journey of each grain particle, marked by its unique thermal and UV
exposures, results in diverse chemical evolutionary among grains even if the cumulative UV
dose is same. Contrary to the hypotheses of past research[1], there is not a direct
proportionality between the abundance of COMs and cumulative UV exposure. High UV
exposure convert oxygen into CO2, diminishing the abundances of oxygen-bearing COMs.
Nitrogen, however, is not locked into certain species, leading to the high abundances ofCOMs, even under intense UV exposure. Notably, a threshold UV fluence of around 500 [G0* years] signals the decline of COMs with oxygen, mirroring the reduction trend of the major
source of radical, i.e. CH3OH. Since COM abundances depend on the stochastic evolution ofphysical parameters, grains ended up in a similar disk radius will show significant diversity of
COM composition.

Figure 1: Abundance of COMs containing at least one O (excluding CH3OH) and COMs
containing at least one N, after 106 years of turbulent motion. The horizontal axis represents
cumulative UV exposure.
References[1] Ciesla, F. J., & Sandford, S. A. 2012, Science, 336, 452

QUIJOTE: Q-band Ultrasensitive Inspection Journey to
the Obscure TMC-1 Environment.
The chemical complexity of a cold dark cloud
J. Cernicharo

Dpt. of Molecular Astrophysics. IFF-CSIC (Spain)

e-mail: jose.cernicharo@csic.es

I will present the recent results obtained with the QUIJOTE line survey of the cold dark core
TMC-1. The observations have been carried out with the YEBES 40m radio telescope in the Qband. A new set of receivers have been installed in the telescope within the frame of the ERC
synergy Nanocosmos project that allows to cover the whole 31-50 GHz band in dual
polarization with a spectral resolution of 38.15 kHz. The sensitivity achieved so far varies
between 0.08 and 0.20 mK, and allows to search for new molecules in a line by line (nostacking) detection procedure. These new data have permitted to detect many protonatedspecies of abundant molecules, several sulfur-bearing species, cycles (benzyne,
cyclopentadiene, indene), radicals, and long hydrocarbon chains. I will show the present
chemical models we have performed to explain the chemistry of these species and in particular
the possible reactions leading to the formation of these cycles. We suggest that a bottom-up
approach starting with reactions of simple radicals, such as propargyl and the vinyl radical,
with vinyl and allyl acetylene and other hydrocarbons could reproduce satisfactorily well theobserved abundances. None of the new molecules found in TMC-1 are detected towards the
carbon-rich evolved star IRC+10216.
Finally, I will show the SANCHO project which is devoted to the study of the spatial
distribution of these molecules around TMC-1 with a sensitivity never achieved so far (4 mK).

Oral 17

Modeling Maser Activity of Organic Molecules toward Sgr B2
C. Xue,1 A. Remijan,2 A. Faure,3 B. McGuire1
1

Department of Chemistry, Massachusetts Institute of Technology, USA
2
National Radio Astronomy Observatory, USA
3
Universit ́e Grenoble Alpes, CNRS, France

Single-dish observations have revealed that the Sagittarius B2 molecular cloud at the Galactic
Center hosts maser emission from several organic molecules, including CH2NH [1], HNCNH[2], and HCOOCH3 [3]. However, the lack of spatial information for these new maser species
has prevented us from assessing their excitation conditions and pumping mechanisms. In thispresentation, we introduce a cutting-edge tool for modeling and fitting the maser signals,
leveraging non-LTE radiative transfer models and Bayesian statistics. This MCMC approachenables us to quantitatively assess the physical conditions of maser clumps under varying
continuum background radiation levels. Our analyses suggest reference conditions for a gas
clump to achieve the necessary population inversion for maser action, specifically a kinetic
temperature of ~30 K, a gas density of ~104 cm-3, and a molecular column density of
1016-1017 cm-2 in the context of collisional pumped CH3OH maser. In addition, the recent
interferometric observations conducted with both ALMA and VLA enable us to compare thespatial origins and compact extents of maser emissions from several molecular species. We
find a close spatial relationship between the 5.29 GHz CH2NH maser and the 4.36 GHz
CH3NH2 maser with the 84 GHz CH3OH maser, supporting a shared collisional pumping
mechanism.

References
[1]
[2]
[3]

A. Faure, A. J. Remijan, K. Szalewicz, & L. Wiesenfeld, 2014, ApJ 783, 72.
R. A. Loomis, D. P. Zaleski, A. L. Steber, et al. 2013, ApJL 765, L9.
A. Faure, F. Lique, & A. J. Remijan, 2018, The Journal of Physical Chemistry Letters 9, 3199.

Oral 18

The chemistry in the starburst galaxy NGC 253 from the ALCHEMI survey
N. Harada,1 S. Martin,2 J. Mangum,3 and ALCHEMI collaboration
1Division of Science, National Astronomical Observatory of Japan
2Joint ALMA Observatory/European Southern Observatory
3National Radio Astronomy Observatory

Intense star formation, or starburst, characterizes the important phase of the galaxy evolution.
Much is unknown about the properties of the interstellar medium (ISM) when the starburst is
taking place, and when it is about to cease from the feedback. Astrochemistry is a useful tool
to study these ISM properties.
By taking an advantage of the excellent capabilities of ALMA, we conducted a spectral line
survey called ALCHEMI in the nearby starburst galaxy NGC 253 as a part of Cycle 5 ALMA
large program. It covers most of ALMA Bands 3-7 that allowed the detection 1500
transitions.
Our results show that the central region of NGC 253 has at least three orders of magnitude
higher cosmic-ray ionization rates than that in dense clouds in the Galactic disk[1,2,3]. We
also found that the outskirts of the central molecular zone host intersections of galaxy orbits,
and can be used as a laboratory of shock chemistry. We found that methanol, HNCO,
HOCO+, and OCS are species that are enhanced in these regions[4,5,6]. From a statisticalanalysis on 150 integrated-intensity images using principal component analysis, we were able
to identify the chemistry between young super star clusters and more developed ones.

Figure 1: (Left) Selected velocity-integrated images and (right) spectra obtained from the ALCHEMI
survey.

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

N. Harada et al. (2021) ApJ, 923, 24
J. Holdship et al. (2022) ApJ 931, 89
E. Behrens et al. (2022) ApJ 939, 119
K.-Y. Huang et al. (2023) A&A, 675, 151
N. Harada et al. (2022) ApJ 938, 80
N. Harada et al. (2023) submitted to ApJ

Oral 19

From lab to space: An integrated rotational spectroscopy–quantum chemistry strategy
C. Puzzarini1
1

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

Understanding the chemical evolution of the interstellar medium is one of the main aims ofastrochemistry, and one of the biggest challenges (see Figure 1). The starting point for thedevelopment of astrochemical models is the knowledge whether a molecule is present in theastronomical environment considered and, if so, its abundance [1]. In this scenario, rotational
spectroscopy plays a crucial role because most of the molecular species have been detectedthanks to their rotational signatures. These, in turn, are accurately obtained from laboratory
spectroscopy studies that are increasingly assisted by quantum-chemical calculations, also inthe derivation of molecular abundances [2-6]. The subsequent step is understanding thechemical evolution: how the detected molecules were formed and how they can further react[1]. Accurate computational approaches play a fundamental role in this respect [7-10].
In this presentation, by means of a few selected examples taken from the work done in mylaboratory, I will address: (i) the interplay of experiment and theory in the field of rotational
spectroscopy in support of astronomical observations; (ii) the exploitation of state-of-the-art
computational approaches to derive non-LTE molecular abundances and formation pathways
able to explain molecular detections.

Figure 1: Chemical evolution – the required steps for the chemical characterization of a molecular cloud.

References[1] C. Puzzarini, 2020, Front. Astron. Space Sci. 7, 19.
[2] M. Melosso, L. Bizzocchi, H. Gazzeh, F. Tonolo, J.-C. Guillemin, S. Alessandrini, V. M. Rivilla, L. Dore, V.
Barone, & C. Puzzarini, 2022, Chem. Comm. 58, 2750.
[3] V. M. Rivilla, L. Colzi, I. Jimenez-Serra, J. Martín-Pintado, A. Megías, M. Melosso, L. Bizzocchi, A. L.pezGallifa, A. Mart.nez-Henares, S. Massalkhi, B. Tercero, P. de Vicente, J.-C. Guillemin, J. G. de la Concepcion,
F. Rico-Villas, S. Zeng, S. Martín, M. A. Requena-Torres, F. Tonolo, S. Alessandrini, L. Dore, V. Barone, & C.
Puzzarini, 2022, ApJ 929, L11.
[4] D. Alberton, L. Bizzocchi, N. Jiang, M. Melosso, V. M. Rivilla, A. Pietropolli Charmet, B.M. Giuliano, P.
Caselli, C. Puzzarini, S. Alessandrini, L. Dore, I. Jiménez-Serra, & J. Martín-Pintado, 2022, A&A 669, A93.
[5] C. Puzzarini, S. Alessandrini, L. Bizzocchi, & M. Melosso, 2023, Faraday Discuss. 245, 309.
[6] F. Tonolo, L. Bizzocchi, V.M. Rivilla, F. Lique, M. Melosso, & C. Puzzarini, 2023, MNRAS, accepted.
[7] J. García de la Concepción, C. Puzzarini, V. Barone, I. Jiménez-Serra, & O. Roncero, 2021, ApJ 922, 169.
[9] P. Recio, S. Alessandrini, G. Vanuzzo, G. Pannacci, A. Baggioli, D. Marchione, A. Caracciolo, V.J. Murray,
P. Casavecchia, N. Balucani, C. Cavallotti, C. Puzzarini, & V. Barone, 2022, Natur. Chem. 14, 1405.
[10] H. Ye, S. Alessandrini, & C. Puzzarini, 2023, MNRAS 525, 1158.

Oral 20

Stability of diatomic carbon anion C2- in interstellar clouds:
a time-resolved laboratory spectroscopy in a cryogenic ion storage ring
Y. Nakano,1 M. Iizawa,1.2 S. Kuma,2 N. Kimura,2KC. Chartkunchand,2 S. Harayama,2,3 T. Azuma 2
1

Department of Physics, Rikkyo University, Tokyo, Japan
2
AMO Physics Laboratory, RIKEN, Saitama, Japan3
Department of Physics, Saitama University, Saitama, JapanThe diatomic carbon C2 is one of the most studied molecules as the simplest systemhaving a C-C bond, and so are their ionic species C2+ and C2-. In astronomical observation, theA-X absorption line of neutral C2 has been detected in the near-infrared spectrum of aluminous blue hypergiant Cyg OB2 No. 12. [1,2] On the other hand, C2+ and C2- are yet
undetected so far, and their relevance to the C2 abundance and chemical reaction network is
not fully elucidated.
In this work, we carried out high-resolution rovibrational spectroscopy of C2- in acryogenic ion storage ring RICE. [3] The photo-detachment spectrum in the 537.63 – 568.18
nm wavelength region (17600 – 18600 cm-1) exhibited a lot of unassigned absorption lines,
which were not ascribed to the known A-X and B-X transitions. Interestingly, these lines may
or may not appear depending on how these C2- ions are produced in ion sources. Taking theunique advantage of the storage ring experiment, we analyzed the temporal evolution of thephoto-detachment spectrum and identified a millisecond-order autodetachment process of C2-.
[4]. The possible origins of these lines and their effect on the stability and reactivity of C2- ininterstellar clouds will be discussed.

Fig1. A part of the C2- photo-detachment spectra recorded at different storage times.
[1] S.P. Souza and B.L. Lutz, ApJL 216, L49 (1977).
[2] S. Hamano et al., ApJ 881, 143 (2019) .
[3] Y. Nakano et al., Rev. Sci. Instr. 88, 033110 (2017).
[4] M. Iizawa et al., J. Phys. Soc. Jpn 91, 084302 (2022).

Oral 21

Possible observation of linear H3+ in the laboratory
Ryo Ui, Saki Imaizumi, and Hajime Tanuma
Department of Physics, Tokyo Metropolitan University, Japan
H3+ was discovered by J. J. Thomson in 1911 in the laboratory with a mass spectroscopic
method, determined its structure by T. Oka in 1980 with infrared spectroscopy, and observed
as an interstellar molecule by T. Oka in 1996. Now, we regard H3+ as one of the most criticalspecies in interstellar clouds because many complex molecules are produced via the reaction
involving H3+ [1].
We performed the ion mobility measurements after injecting H2+ into a drift tube filled withnormal H2 gas at the liquid nitrogen temperature of 77 K using a very low-temperature drift
tube mass spectrometer [2]. The following ion-molecule reaction produces H3+ in the gas
phase [3]:H2+ + H2 → H3+ + H
This is one of the important reactions that produce H3+ in molecular clouds, and it has been
investigated in laboratories. We measured the arrival time spectra of H3+ at various H2 gaspressures and electric field strengths in the drift tube to obtain the reduced mobility of H3+ in
H2 gas at 77K.
Arrival time spectra of H3+ surprisingly split two components in weak electric fields. As themobility of molecular ions depends on their molecular structure, we consider that two peaks
correspond to two isomers, namely triangle and linear structures of H3+. The ground state of
H3+ has a triangle structure confirmed with spectroscopic observation, and theoretical
calculations proposed the first excited triplet state with a linear structure [4]. However, theenergy of this triplet state is too high to be produced in the low-energy collision of H2+ with
H2. Then the meta-stable linear structure in the electronic ground state will be the candidate.
If this interpretation is correct, this result might be the first observation of linear H3+ ions inexperiments.
References
[1]
[2]
[3]
[4]

T. Oka, 2013, Chem. Rev. 113, 8738.
H. Tanuma et al., 2000, Rev. Sci. Instrum. 71, 2019.
M. T. Bowers et al., 1969, J. Chem. Phys. 50, 4787.
A. Aguado et al., 2021, Phys. Chem. Chem. Phys. 23, 7735.

Oral 22

Pushing Astrochemistry into the Solar System through Mission Science
Danna Qasim
Southwest Research Institute, San Antonio, TX, USA 78238
In the past decade, astrochemistry has experienced an explosion of rich data from revolutionary
observatories (ALMA, JWST), advances in experimental laboratory techniques, and thedevelopment of state-of-the-art computational calculations and models. Despite this remarkable
growth, the value of this field to very relevant and neighboring fields of astronomy is not fully
appreciated. Notably, as multimillion to multibillion-dollar space missions venture our solar
system, the limited involvement of astrochemists in such missions has hindered the planetaryscience community's access to the insights of astrochemistry in interpreting solar system data.
In this talk, I outline strategies undertaken at Southwest Research Institute to bridge the gap
between interstellar and solar system chemistry. This includes plans to conduct pure interstellar
chemistry experiments, notably atom chemistry, and initiatives to connect interstellar and solar
system chemistry. These strategies will act as the foundations for the bigger goal of enhancing
the visibility and value of astrochemistry among numerous solar system missions.

Oral 23

Methanol production through irradiation of low-energy CH3+ ions on an ice surface at
low temperature
Y. Nakai 1, W. M. C. Sameera 2, 3, K. Furuya 4, H. Hidaka 2, A. Ishibashi 2, and N. Watanabe 2
1

2

RIKEN Nishina Center for Accelerator-based Science, Japan
Institute of Low Temperature Science, Hokkaido University, Japan3
Department of Chemistry, University of Colombo, Sri Lanka
4
National Astronomical Observatory of Japan, JapanTo understand a variety of chemical species in molecular clouds, theoretical and experimental
studies have been intensively performed. In a gas phase, it has been considered that ionmolecule reactions are indispensable. On the other hand, in a solid phase, it has been
experimentally confirmed that reactions of hydrogen atoms adsorbed on an icy grain surface
are essential for productions of hydrogen, water, methanol, and so on. Furthermore, reactionsof other heavier radicals adsorbed on an ice surface attract many interests. Besides thesereactions, recent theoretical investigations have suggested molecular formation throughreactions of low-energy ions with an ice surface. In contrast to the theoretical investigations,little experimental investigations have been done because of difficulties in detecting the trace
amount of reaction products with conventional methods. We have developed an experimental
apparatus to sensitively detect those reaction products and performed experiments for thereactions of low-energy molecular ions with an ice surface. The CH3+ ions in the energy rangeof several electron volts impinged on an ice surface around 10 K. The reaction products on thesurface were detected using pick-up reaction method by Cs+ ions at ~40 eV. After CH3+
irradiation, methanol molecules were observed as the theoretically suggested. In addition, we
also investigated ice-temperature dependence of methanol production. Little temperaturedependence of detected methanol intensities was observed in the temperature range 12–60 K.
We will also touch the results of our ab-initio molecular dynamics simulation with NVT
ensemble and astrochemical model simulation in our presentation.

Oral 24

Formation of Sodium-bearing species in the interstellar medium
E. Herbst,1 K. Acharyya,2 and D. E. Woon3
1

Departments of Chemistry and Astronomy, University of Virginia, USA
2
Planetary Sciences Division, Physical Research Laboratory, India
3
Department of Chemistry, University of Illinois at Urbana-Champaign, USA

Sodium-bearing species such as NaCl in the gas-phase have been observed in an assortmentof stellar atmospheres and interstellar environments. [1],[2] However, their detection in
relatively low-temperature regions has yet to be made. Here we emphasize NaCl via both
gas-phase and grain-surface chemistry under assorted interstellar conditions. Two types ofnumerical gas-grain simulations have been run: models under isothermal conditions attemperatures from 10 K to 800 K with varied intervals, and three-phase warm-up models thatconsist of an initial isothermal collapse at 10 K, a warm-up phase, in which temperaturereaches 200 K with varied intervals, and lastly a hot-core phase. The surfaces of dust grains
contain water-ice using a base cluster of 17H2O. Desorption and barriers against diffusion
were calculated with Gaussian 09 using B3LYP density functional theory. We found thatfor isothermal models over a broad parameter space, the fractional abundances of gaseous
NaCl and NaOH can reach above 2 x 10(-10) and approximately 1 x 10(-10) respectively,
which may be in the detection range of observational facilities such as ALMA and JWST.
For warm-up models, we found that if we consider sodium-bearing molecules to be
co-desorbed with water ice, then gaseous NaCl can reach a sufficiently large abundance fordetection to be possible. However, more experiments and quantum calculations are needed
to constrain the relevant reaction rates in our simulations better.

References[1][2]

J. Cernicharo & M. Guélin, 1987, A&A 183, L10.
S. N.Milam, A. J. Apponi, N.J. Woolf, & L. M. Ziurys, 2007, ApJ

668, L131.

Oral 25

Overview of ALMA Large Project FAUST(Fifty AU STudy of the chemistry in the disk/envelope system of Solar-like protostars)
Y. Oya,1 C. Ceccarelli,2 C. Codella,3 C. Chandler,4 N. Sakai,5 S. Yamamoto,6and FAUST members
1

Yukawa Institute for Theoretical Physics, Kyoto University, Japan
2
Universite Grenoble Alpes, CNRS, IPAG, France
3
INAF, Osservatorio Astrofisico di Arcetri, Italy
4
National Radio Astronomy Observatory, USA
5
RIKEN, Japan
6
SOKENDAI, Japan

A huge variety of planetary systems has been discovered in recent decades, and it likely
related to the early history of their formation. Meanwhile, it has been recognized that
protostellar cores show chemical diversity, especially in the composition of organic species.
For instance, two distinct cases are well known: hot corino sources are rich in intestellar
complex organic molecules (iCOMs), while warm carbon-chain chemistry (WCCC) sources
are rich in unsaturated hydrocarbons. They are still unclear whether such a chemical
diversity is seen in disk-forming regions (~50 au scale) and what kinds of molecular species
are delivered into disks from envelope gas (~2000 au scale).
To tackle with the above problems, our ALMA large program ‘FAUST’ (P.I. S. Yamamoto)focuses on the early history of Solar-type protostars and their chemical diversity on a 50 au
scale, where planets are expected to be formed. The main goal of this project is to revealand quantify the variety of chemical composition of the disk/envelope system. We observed
thirteen young (Class 0-I) protostellar sources as representatives of the chemical diversity
observed on larger scales to obtain a homogeneous database of thousands of images fromdifferent lines and species. The analysis of this huge database is in progress (1) todisentangle the components of the 50-2000 au disk/envelope system, (2) to characterize theorganic complexity in each source, (3) to probe their ionization structure, and (4) to measure
their molecular deuteration. We are going to present the overview compiling the results in
13 sources.

Oral 26

ALMA Observations of the Young Bursting Star V883 Ori:
Chemistry of Complex Organic Molecules in the Protoplanetary Disk
Y. Yamato1, S. Notsu1, 2, Y. Aikawa1, Y. Okoda2, H. Nomura3, and N. Sakai2
1
2

Department of Astronomy, Graduate School of Science, The University of Tokyo, Japan
Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Japan
3
Division of Science, National Astronomical Observatory of Japan, Japan

Complex organic molecules (COMs), potential precursors of prebiotic molecules, are key tounderstanding the chemical evolution from the interstellar medium to planetary systems. Recent
interferometric observations suggest that COMs are abundant in the warm inner envelopes aroundlow-mass protostars. However, complex organic chemistry in protoplanetary disks, the immediatebirthplace of planets, is still poorly understood because COMs are frozen out and thus hidden fromview in archetypal disks [1].
Recent ALMA detections of thermally sublimated COMs in the warm disk around the young burstingstar V883 Ori have opened a new window to probe the complex organic chemistry in protoplanetarydisks [2][3]. We will present our new observations of COMs toward V883 Ori in ALMA Band 3 at
an angular resolution of ~0.3” (or ~120 au). We detected ten oxygen-bearing COMs including 13C
isotopologues in the disk. We measured the abundance ratios of COMs with respect to CH3OH andthe isotopic ratios (12C/13C and D/H) of COMs for the first time in a protoplanetary disk. The
abundances of COMs are systematically higher than those in the warm envelopes of IRAS
16293-2422. The 12C/13C ratios of different COMs are consistently lower (~20-30) than the canonical
ISM ratio (~69). The upper limits of COM D/H ratios (< 0.01) are also lower than those in IRAS
16293-2422. These high abundances of COMs and peculiar isotopic ratios could be explained by theefficient (re-)formation of COMs on the lukewarm dust grain surfaces from the 13C-enriched CO due
to the exchange reaction with 13C+.

References
[1]
[2]
[3]

Öberg, K. I., Facchini, S., & Anderson, D. E., 2023, ARA&A, 61, 287
van 't Hoff, M. L. R., et al., 2018, ApJL, 864, 23
Lee, J.-E., et al., 2019, NatAs, 3, 314

Oral 27

Photochemistry of Sulfur-species in ice mantles
G. M. Muñoz Caro,1 R. Martín-Doménech,1 H. Carrascosa,1 C. González-Díaz,1
B.
Escribano,1 C. del Burgo,1 A. Fuente,1 Y.-J. Chen,2 A. Ciaravella,3 A. Jiménez-Escobar,3 C.
Cecchi-Pestellini,3 S. Cazaux4 and P. Caselli5
Centro de Astrobiología (CAB), INTA-CSIC, Spain
Department of Physics, National Central University, Taiwan
3
Osservatorio Astronomico di Palermo, INAF, Italy
4
Faculty of Aerospace Engineering, Delft University of Technology, The Netherlands
5
Max Planck Institute for Extraterrestrial Physics, Germany
1

2

Sulfur chemistry is a trending topic in Astrochemistry. Several S-species are commonly detected in the gas
toward interstellar and circumstellar environments, such as SO2, SO, CS, OCS, H2S, C2S and H2CS, but
their total observed abundance in the dense interstellar medium is more than one order of magnitude lower
than the sulfur cosmic abundance. Refractory sulfur in dust grains is summoned to account for the
S-depletion in dense clouds and protoplanetary disks. This refractory form of sulfur, however, remains amistery. Laboratory experiments involving irradiation of H2S in the ice, theoretical models, and thedetection of S2, S3 and S4 in comet 67P during the Rosetta mission, suggest that S-chains is a potential
source of refractory sulfur in the dust.
Figure 1 displays the thermal desorption of an irradiated H2S ice sample [1]. Each mass over charge(m/z) value corresponds to the molecular ion of a species or to a fragment of a larger species. The
desorption temperatures of Sx molecules are indicated by the solid vertical lines, while dashed lines indicate
the desorption of H2Sx species. Apart from the molecular ion of each species, the m/z values of the main
fragments used to confirm the presence of these species are displayed.
A brief overview of experiments mimicking the photochemistry of H2S and other S-bearing species in
the ice will be presented. We use the experimental data and modeling to interpret the observational results.
The study of S-species in the ice serves to prepare the observations of refractory sulfur and to interpret thegas phase observations accounting for the desorption of S from the ice. In addition to thermal desorption
when the dust temperature is high enough, other mechanisms were proposed for the release of solid
S-species to the gas phase, among them are chemical desorption [2] and photodesorption [3] . The lattermechanism will also be discussed in our presentation.

Figure 1: Desorption of S-photoproducts during warm-up of a previously UV-irradiated H2S ice layer,
adapted from [1].

References[1]
S. Cazaux, H. Carrascosa, G. M. Muñoz Caro, P. Caselli, A. Fuente, D. Navarro-Almaida, & P.
Riviére-Marichalar “Photoprocessing of H2S on dust grains. Building S chains in translucent clouds and comets”,
2022, A&A 657, A100
[2]
Y. Oba, T. Tomaru, T. Lamberts, A. Kouchi, & N. Watanabe ¨An infrared measurement of chemicaldesorption from interstellar ice analogues¨, 2018, Nat. Astron. 2, 228[3]
A. Fuente, J. R. Goicoechea, J. Pety, R. Le Gal, R. Martín-Doménech, P. Gratier, V. Guzmán, E. Roueff, J.
C. Loison, G. M. Muñoz Caro, V. Wakelam, M. Gerin, P. Riviére-Marichalar, Th. Vidal ¨First detection ofinterstellar S2H¨, 2017, ApJL 851, L49

Oral 28

VUV photodesorption of H2S ices
Yen-Yu Hsu1, Guillermo M. Muñoz Caro2, Yu-Jung Chen1
1

Department of Physics, National Central University, Taiwan
2
Centro de Astrobiología (INTA-CSIC), Spain

Hydrogen sulfide (H2S), one of the most abundant sulfur-bearing species detected in theinterstellar medium (ISM), can be considered a precursor to certain biochemical molecules.
Within the dense clouds, the significant energetic source stems from the secondary vacuum
ultraviolet (VUV) field generated by the interaction of cosmic rays with molecular hydrogen.
Oba et al. (2018) conducted measurements of chemical desorption caused by H atom
incidents and speculated that it should surpass VUV photodesorption [1].
In this study, we investigated the VUV-induced desorption of H2S ices and assessed theimpact of structural factors by depositing ices at two different temperatures, 13 K and 70 K
(both of which were subsequently irradiated at 13 K). Our findings indicate that amorphous
H2S ice deposited at 13 K exhibited a higher depletion cross-section and VUV-induced
desorption yield compared to crystalline ice deposited at 70 K. Moreover, the VUVphotodesorption yield of H2S ice was influenced by both energy transfer length and surface
purity of H2S [2]. The VUV photodesorption yield measured in this study was found to becomparable to the chemical desorption yield measured through hydrogenation, especiallywhen both values are applied to simulate conditions in dense cloud environments.

Figure 1: VUV photodesorption yield for different initial column densities as a function of remainingcolumn density of H2S ice.

References[1][2]

Y. Oba, T. Tomaru, T. Lamberts et al., 2018, Nat Astron 2, 228.
N.-E. Sie, G. M. Muñoz Caro, Z.-H. Huang et al., 2019, ApJ 874, 35.

Oral 29

Chemical pathways of Methyl Mercaptan (CH3SH) with Hydrogen atoms on Interstellar
Ice
T. Nguyen,1 Y. Oba,1, W.M.C Sameera1,2, A. Kouchi, and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University, N19W8, Kita-ku, Sapporo,Japan
2
University of Colombo, Colombo, Sri Lanka
There have been about 30 sulfur (S)-bearing species identified in the interstellar medium(ISM). Since the observed abundance of S-bearing species in the gas phase is lower than thecosmic abundance of S1, it is often considered that there might be a source of “missing S" oninterstellar grains. Based on an assumption that physico-chemical processes of S-bearing
species on interstellar grains would be a key to constrain their presence in the ISM, several
laboratory studies have been performed and our understanding has been significantly
improved on the surface processes of S-bearing species at low temperatures2,3. In the present
study, we shed light on the behavior of other S-bearing species, methyl-mercaptan (CH3SH),
via chemical reactions of CH3SH and H atoms without external energies on interstellar ices at
low temperatures (typically 10 K) using experimental and computational methods.
We found that chemical reactions of CH3SH with H atoms proceeded via multiple channels:
CH3SH + H  CH3 + H2S, CH3S + H2, or CH2SH + H2. The major channel was thedissociation of C-S bond in CH3SH with the activation barrier of 0.05 eV on amorphous solid
water, eventually resulting in the formation of methane (CH4) by further hydrogenation toCH34. The hydrogen abstraction channels lead to the formation of CH3S and CH2SH radicals,
and further hydrogenation to these radicals would result in the formation of CH3SH again.
Chemical desorption of CH3SH was not positively identified via these processes, implying thepresence of other processes for the desorption of CH3SH from interstellar grains at low
temperatures.
References[1]. V. Wakelam, A. Castets, C. Ceccarelli, et al. A&A, 2004, 413, 60[2]. A. Jiménez-Escobar, & G. M. Muñoz Caro, A&A, 2011, 536, A91[3]. Y. Oba, T. Tomaru, T. Lamberts, A. Kouchi, N. Watanabe, Nat. Astron. 2018, 2, 228-232[4]. T. Nguyen, Y. Oba, W. M. C. Sameera, K. Furuya, A. Kouchi, N. Watanabe, ApJ, 2023, 944(2), 219.

Oral 30

Chemical evolution from the interstellar medium to the solar system: Insight from theanalysis of asteroidal materials
Y. Oba1
Institute of Low Temperature Science, Hokkaido University, Japan
More than 180 interstellar molecules have been identified by radio telescopes, and recently,
the presence of interstellar molecules having more than 10 atoms such as glycolamide(NH2C(O)CH2OH) and propanol (C3H7OH) has often been reported in literature [1,2].
Although the presence of further complex interstellar molecules may be detected in future
astronomical observations, it is still widely accepted that interstellar molecules have muchless complex structures compared to molecules in the solar system. Since all materials present
in the solar system should have their ultimate origin in the interstellar medium (ISM) where it
was born, it is straightforward to consider that the relatively simple interstellar molecules
should have become more complex through the evolution from the ISM to the solar system.
Organic molecules in carbonaceous meteorites have been regarded as a good target forunderstanding the “end member” of chemical evolution in space since they are the mostpristine solar system materials that can be analyzed in the laboratory. Moreover, the recent
great successes in the recovery of materials from carbonaceous asteroids Ryugu and Bennu
should provide researchers precious opportunities to analyze the most primordial solar system
materials without terrestrial contamination [3,4].
The initial analysis of the Ryugu samples detected various kinds of organic molecules such asamino acids and nucleobase, which provides strong evidence for the presence of suchbiologically relevant molecules in extraterrestrial environments [5,6]. In this talk, I would liketo show further findings on the organic contents in the samples recovered from Ryugu. In
addition, several potential pathways for the formation of organic molecules inasteroids/meteorites will be discussed based on the distribution of organics in those materials
and laboratory experiments.
References
[1]
[2]
[3]
[4]
[5]
[6]

V. M. Rivilla, et al., 2023, ApJL, 953, L23.
I. Jimenez-Serra et al., 2022, A&A, 663, A181.
S. Tachibana et al., 2022, Science, 375, 1011.
D. S. Lauretta et al., 2022, Science, 377, 285.
H. Naraoka et al., 2023, Science, 379, eabn9033.
Y. Oba et al., 2023, Nature Communications, 14, 1292.

Poster 1

Intensity-calibrated molecular spectroscopy and determination of intrinsic line intensity
Sμ2 for CH2DOH
T. Oyama,1 Y. Watanabe,1,2 T. Sakai,3 S. Yamamoto,4 A. Tamanai,1 S. Zeng,1 and N. Sakai1
1

RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
2
Materials Science and Engineering, College of Engineering, Shibaura Institute ofTechnology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan
3
Graduate School of Informatics and Engineering, The University of Electro-Communications,
Chofu, Tokyo 182-8585, Japan
4
Research Center for the Early Universe, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,
Tokyo 113-0033, Japan
Isotopic fractionation in molecules is known as one of the powerful tools to trace themolecular evolution during the Solar system. Among various interstellar species, methanol is
the most abundant saturated-organic molecule and is known as an important species to form
more complex organic molecules in interstellar clouds. Observing isotope fractionation ratiosof methanol is especially useful to reveal reaction pathways of such organic molecules [e.g., 1,
2]. Despite its importance, current spectroscopic information is not enough to determine theirabundances accurately even for the methanol isotopologues. For example, CH2DOH
significantly suffers from the uncertainty of intrinsic line intensities (Sμ2) due to their floppy
nature. Although Sμ2 of each transition line is a critical parameter to derive accurate column
density and temperature of the molecular gas, they are not easy to be evaluated theoreticallyfor the asymmetric-top asymmetric-frame isotopologue. With our emission-type spectrometer,
SUMIRE [3], using technique developed for radio astronomical observations, we can now
derive Sμ2 and transition frequency for various isotopologues of methanol by laboratory
spectroscopy in the millimeter-wave region from 216 GHz to 264 GHz [4,5]. In the b-typetransitions of CH2DOH, significant systematic errors were found between theoretical andexperimental Sμ2 for three torsional sub-state, e0, e1 and o1 as shown in Figure 1. This study
will enable us to trace deuterium fractionation of COMs along the star formation.

Figure 1: Ratios between the Sμ2 values derived in this study and those listed in the JPL
database for the b-type Q-branches in CH2DOH.
References[1] N. Sakai, S. Takano, T. Sakai, S. Shiba, Y. Sumiyoshi, Y. Endo, and S. Yamamoto, 2013, JPCA, 117, 9831.
[2] B. Parise, C. Ceccarelli, A.G.G.M. Tielens, A. Castets, E. Caux, B. Lefloch, and S. Maret, 2006, A&A, 453,
949.
[3] Y. Watanabe, Y. Chiba, T. Sakai, A. Tamanai, R. Suzuki, and N. Sakai, 2021, PASJ, 73, 372.
[4] Y. Ohno, T. Oyama, A. Tamanai, S. Zeng, Y. Watanabe, R. Nakatani, T. Sakai, and N. Sakai, 2022, ApJ, 932,
101.
[5] T. Oyama, Y. Ohno, A. Tamanai, Y. Watanabe, S. Yamamoto, T. Sakai, S. Zeng, R. Nakatani, and N. Sakai,
2023, ApJ, accepted.

Poster 2

Microwave spectroscopy of CH2Cl2
Manamu Kobayashi1, Kaori Kobayashi1, Brian J. Esselman2
1
University of Toyama
2
Department of Chemistry, University of Wisconsin-Madison. USA
Dichloromethane (CH2Cl2) is a known organic solvent and atmospheric molecule. In
recent studies, there are two astronomy-related reports of CH2Cl2. In 2008, it was reported
that the Phoenix Mars lander collected three soil samples and confirmed the presence ofCH2Cl2[1]. In 2010, Navarro-González et al. found CH2Cl2 in Martian soil which had
been previously considered to be terrestrial contaminant.[2].
So far, studies have been conducted to obtain laboratory molecular data on CH2Cl2. For
example, in 1952, Myers and Gwinn measured the microwave spectra of seven isotopic
species of CH2Cl2 and determined the dipole moment and the chlorine nuclear quadrupole
coupling constants [3]. In 1981, Gerry measured microwave spectrum of CH2Cl2 up to J
= 80 to get centrifugal distortion constants [4]. Later, Tullini measured far-infrared spectrain the region between 10 and 75 cm-1, and assigned rotational transitions [5].
However, the current available data do not possess sufficient accuracy. Therefore, we
performed measurement and analysis to provide sufficiently accurate rest frequencies. In
this study, we used microwave spectroscopy to measure and analyze the spectrum ofCH2Cl2 to improve the data. The frequency region from 50 to 750 GHz was measured
with a measurement error of 50 kHz at the University of Toyama and at the University of
Wisconsin-Madison. More than 7000 transition frequencies were assigned up to J = 99
and K = 5. As a result, the parameters that were determined in this study were therotational constant and centrifugal distortion constants. We plan to extend the range of K
values.
References[1]S.P. Kounaves, B.L. Carrier, G.D. O’neil, S.T. Stroble, & M.W. Claire, 2014, Icarus, 229, 206.
[2]R. Navarro-González, E. Vargas, J. De La Rosa, A.C. Raga, & C.P. McKay, 2010, J Geophys Res, 115,
E12010[3] R.J. Myers & W.D. Gwinn, 1952, J Chem Phys, 20, 1420.
[4] R.W. Davis, A.G. Robiette, & M.C.L. Gerry, 1981, J Mol Spectrosc, 85, 399.
[5]F. Tullini, G.D. Nivellini, M. Carlotti, & B. Carli, 1989, J Mol Spectrosc, 138, 355.

Poster 3

The microwave spectroscopy of trans-ethyl methyl ether
F. Kidono and K. Kobayashi,
Department of Physics/University of Toyama, Japan
1.Introduction
Trans-ethyl methyl ether (CH3CH2OCH3) is the next simplest ether structure after dimethyl
ether (CH3OCH3), and dimethyl ether has been observed in many spectra as an interstellar
molecule. It was identified in Orion KL [1]. The rotational structure of this molecule is verymuch complicated because it has two internal rotors and there are many low-lying vibrational
excited states. One rotational level splits into 5 sublevels (AA, AE, EA, EE1, and EE2). In alaboratory microwave study, Hayashi and Kuwada measured in the frequency range of 8.5 34 GHz, and gave molecular constants, dipole moment, and the molecular structure [2]. In
addition, past study, K. Kobayashi and her collaborators analyzed this molecule in the firstskeletal torsional excited state [3], ν29 = 1 excited torsional state [4] and determined twentytwo molecular parameters composed of rotational constants, centrifugal distortion constants,
internal rotation parameters and internal rotation tunneling parameters for the ground state,
and three torsional states were also reanalyzed [5]. In this study, we extended and analyzed
microwave spectra, providing effective molecular parameters of the AA sublevel in the
ground state, and low-lying vibrational excited states.
2.Experiment
All the measurements were made using our conventional frequency modulation spectrometerin the frequency range of 330 - 360 GHz. The experiment was carried out at room temperature.
3.Results
The observed spectra were analyzed together with our previous 202 - 330 GHz data. Over
2500 transitions were newly assigned and analyzed over 6000 transitions in total. The highest
J and K values of each vibrational states were 98, and 22 in the ground state, 98, and 19 in theskeletal torsional excited state, 99, and 16 in the C-CH3 torsional excited state, and 98, and 17
in the O-CH3 torsional excited state, respectively. We plan to further assign and analyze othersub-levels in the future.
References
[1]
[2]
[3]
[4]
[5]

G.W. Fuchs, U. Fuchs, T.F. Giesn, and F. Wyrowski, Astronomy & Astrophysics 444, (2005) 521-530
M. Hayashi, K. Kuwada, J. Mol. Struct. 28, (1975) 147-161
K. Kobayashi, T. Matsui, N. Mori, S. Tsunekawa, N. Ohashi, J.Mol.Spectrosc. 251 (2008) 301-304
K. Kobayashi, T. Matsui, S, Tsunekawa, N, Ohashi, J.Mol.Spectrosc. 255 (2009) 164-171
K. Kobayashi, Y. Sakai, S. Tsunekawa, T. Miyamoto, M. Fujitake, J.Mol.Spectrosc. 321 (2016) 63-77

Poster 4

Development of a merged-beam apparatus to study the interstellar ion-neutral reactions
R. Takemasa,1 M. Hamaguchi,1 Y. Hachiyama,1 H. Tamaru,1 K. Yoden,1 R. Imai,1R. Ota,1 T. Kurihara,1 Y. Shiina,1 and Y. Nakano1
1

Department of Physics, Rikkyo University, Japan

Experimental determination of ion-neutral reaction cross sections and their internal state
dependence is crucial to understanding interstellar gas-phase chemistry. A merged-beamexperiment is capable of measuring the energy-dependent reaction cross-sections by merging
the ion and neutral beams collinearly at low center-of-mass collision energies. We plan to
conduct a merged-beam experiment on state-selective low-energy collisions of interstellar
molecular ions with neutral atoms such as H, D, C, and O at 10 — 100 meV region.
An overview of the experiment is shown in Fig.1. The neutral beam of the ground-state
atoms is produced by laser photo-detachment of a negative ion beam extracted from theduoplasmatron ion source, which generates about 100 nA of negative ions by a two-stage
discharge process. The photo-detachment is done by an 808 nm laser diode array in a
multi-reflection cavity. A cold-cathode PIG ion source is also under development for the
production of molecular ion beams. The two beams are merged and mass-analyzed byelectrostatic deflectors at the entrance and exit of the merged section.

Fig1.

Overview of the merged-beam apparatus

Poster 5

Development of far ultraviolet light source using laser-produced plasma
S. Tamaki,1 S. Igawa,1 H. Ohnishi,1 Y. Shiina,1 Y. Nakano, 1
1Department of Physics, Rikkyo University, Japan

In the photodissociation region of interstellar space, photoionization, dissociation, andisomerization occur due to the far-ultraviolet light (100-200 nm) from stars. Our goal is toquantitatively understand the reaction dynamics and measure rate constants. Laser-produced
plasmas are expected to be a compact FUV light source. We have obtained emission spectrafrom plasmas of four different metal targets (Al, Fe, Cu, and Inconel (Ni/Cr/Fe)), which show
characteristic profiles in the wavelength range 100-200 nm. From the intensity ratios of theobtained spectra, the electron temperature of the plasma was estimated to be 6.4 eV by using
the Boltzmann Plot method. The obtained emission spectra were also compared with spectral
simulations (Fig.1). In addition, a dedicated off-axis parabolic mirror was developed tocollimate the light emitted from the plasma and incident on the monochromator. As a result,
the FUV light intensity detected after passing through the monochromator was about 10⁷
photons/pulse, an amplification of about 35 times (Fig.2). We plan to experimentally study
the interaction of FUV light with polycyclic aromatic hydrocarbons (PAHs), which have few
data on photoionization cross sections and reaction branching ratios among molecules in thephotodissociation region, PAH molecules have high vapor pressure, and we are currently
developing a mechanism to vaporize and pulse PAH molecules. We have also developed amechanism for discharging the pulsed gas to induce a gas-phase reaction. The reaction routes
that occur in this discharge are of interest for astrochemistry as possible growth pathways for
PAHs [2]. In this presentation, we will report on the comparison of emission spectra obtained
from the four targets with simulations, as well as the specifications of the developed off-axis
parabolic mirror and future prospects.

Fig1. Emission spectrum and simulation of Al [1]Fig2. Spectrum change by mirror [1]Spectra from plasma produced by irradiating an
Al target with a 532 nm pulsed laser

References[1]

H. Ohnishi, S. Tamaki, Y. Shiina, Y. Nakano; Generation of collimated far-ultraviolet (FUV) light using
the laser-produced metal plasma. J. Appl. Phys. 134, 013103 (2023)[2] Lemmens, A.K., Rap, D.B., Thunnissen, J.M.M. et al. Polycyclic aromatic hydrocarbon formation
chemistry in a plasma jet revealed by IR-UV action spectroscopy. Nat Commun 11, 269 (2020).

Poster 6

A new approach for reaction rate measurements of cold ion-polar molecule reactions
K. Urata1, N. Kimura2, K. Sakimoto1, K. Okada1
1

Department of Materials and Life Sciences, Sophia University, Japan
2
Atomic, Molecular and Optical Physics Lab., RIKEN, Japan

Low-energy ion–polar-molecule reactions are important chemical processes in interstellar
matter. However, due to experimental difficulties, the reaction rate constants have not been
sufficiently measured at low temperatures. In this context, we have been working on thereaction rate measurements of cold ion-polar molecule reactions by combining velocityselected polar molecules and sympathetically cooled ions in a linear Paul trap [1].
Additionally, we have proposed a new approach that combines buffer-gas cooling of trappedions in a cryogenic ion trap with a wavy Stark velocity filter [2, 3]. As a proof-of-principle
experiment for this new approach, we measured the electronic state-dependent reaction-rate
constants of Ca+(2S1/2, 2D3/2) + CH3F → CaF+ + CH3 at a translational temperature of about
110 K [3]. In addition, the rotational cooling effect on the rate constants was also observed by
implementing a cryogenic buffer gas cell for the rotational cooling of polar molecules.
Recently, we also measured the rate constants of Ca+(2S1/2, 2D3/2) + C2H5OH at a translationaltemperature of about 90 K. Since this new approach can be applied to various ion-polar
molecule reactions over wide ranges of translational and rotational temperatures of molecularions and polar molecules, we have been constructing a new experimental setup based on thisnew measurement method by combining a wavy Stark velocity filter and a cryogenic linear
octupole rf ion trap (Fig.1). In this poster presentation, we will present the recent results on
the reaction rate measurements on cold ion-polar molecule reactions as well as the status of
the new experimental setup.

Figure 1: Wavy Stark velocity filter–cryogenic octupole ion trap apparatus with a storage ion source.

References[1] K. Okada et al. 2013 Phys. Rev. A 87, 043427; K. Okada et al. 2020 J. Chem. Phys. 153, 124305[2] K. Okada et al. 2017 Rev. Sci. Instrum. 88, 083106[3] K. Okada et al. 2022 J. Phys. Chem. A 126, 4881

Poster 7

Collisional excitation and collision-induced dissociation of astrochemically relevantmolecules by ion impacts
M. Nakamura
Physics Laboratory, College of Science and Technology Nihon University, JapanThe collision-induced dissociation (CID) of small molecules by ion impacts such as
X+ + AB → X+ + A + B
plays an important role in the chemical evolution in molecular clouds [1-3]. Here we present atheoretical work on the energy transfer and fragmentation of molecules by ion impacts at
hyperthermal energies. The classical trajectory (CT) calculation and the sudden-limit model[4,5] are applied to estimate the energy transfer from translational to internal degrees of
freedom. Figure 1 represents the calculated excitation spectrum of CO molecule by proton
impacts at the collision energy E=27 eV. The model predicts the energy-transfer from thetranslational to the internal degrees of freedom with less efficiency. The threshold energy for
CID of CO molecule by ion impacts is calculated. The results are listed in Table I. When the
projectile is much lighter than the target, the spectator model works well. The probability of
CID depends strongly on the orientation angle at the moment of the contact. The CID takes
place predominantly when an ion hits the molecule either perpendicular or parallel to themolecular axis. Calculation and analysis would be extended to other astrochemically relevantmolecules.
Table I: Threshold energy (eV) for the collision-induced dissociation of CO by ion impacts obtained withthe classical trajectory calculation and with the spectator model.
.
ProjectileCT
Spectator
calculation
Model
60
59
H+
D+
41
31
+
He
29
17
C+
35
7

Figure 1: Calculated excitation spectrum of CO molecule by proton impact with incident energy of 27 eV.
The black (red) curve is the result obtained with the classical trajectory (sudden limit model).

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

W. Roberge and A. Dalgarno, Astrophysical Journal, 255, 176-180 (1982)
R.S. Wood et al. Journal of Chemical Physics, 69, 4487- 4494 (1978)
C. Stopera et al, Journal of Chemical Physics, 136,054304 (2012)
A. Ichimura and M. Nakamura, Physical Revie. A 69, 022716 (2004)
M. Nakamura, Journal of Physical Society of Japan, 91, 054301 (2022)

Poster 8

Electron discharge chemistry in exoplanetary CO2-rich atmospheres
A. Jiménez-Escobar,1 A. Ciaravella,1 C. Cecchi-Pestellini,1 , F. Piazzese,2 , and G. D’amato2
1

2

Istituto Nazionale di Astrofisica (INAF-OAPa), Italy
Dipartimento di chimica, Università degli Studi di Palermo, Italy

Electrical processes are expected to be a common process on planets. Lightning has been
observed on Jupiter [1], Saturn [2], Uranus [3], Neptune [4], it is also possible in theatmospheres of Mars and Titan. Electrical processes may be crucial to increase chemicalcomposition in prebiotic atmospheres.
In the present work we simulate the chemistry induced by electrical processes in CO2 richatmospheres. We study the influence of small amounts of NH3 on the chemical network ofthese atmospheric analogues.
We irradiate a CO2:NH3 (10:1) gas mixture at a pressure of 20 mbar. The gas composition
was measured in real time by mass spectrometry and the ionized fraction was monitored by
UV spectroscopy during the electrical discharge. UV spectroscopy highlights opticalphenomena such as self-absorption, which could obscure a fraction of the emitted spectrum.
The residue formed after electrical processing of each gas mixture was compared andanalyzed by IR spectroscopy.
We found that abiotic processes such as electrical discharge are capable of producing organic
compounds. The solid residue formed in the gas phase and deposited is strongly influenced by
the presence of small amounts of NH3.
References[1] Cook, A. F., Duxbury, T. C., and Hunt, G. E. 1979. Nature 280, 794.
[2] Warwick, J.W., Pearce, J.B., Evans, D.R., et al. 1981, Science 212 4491.
[3] Zarka, B.M. Pedersen, J. 1983 Geophys. Res. 88(A11), 9007–9018.
[4] Gurnett, D. A., Kurth, W. S., Cairns, I. H., Granroth, L. J. 1990, J. Geophys. Res. 95, 20967.

Poster 9

Impurity contribution to photoabsorption of saturated fatty acids andits implications to tropospheric chemistry
T. Hama,1 S. Saito,1 N. Numadate,1 H. Teraoka,1 S. Enami,2 and H. Kobayashi1
1

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

Saturated fatty acids are abundant surfactants in oceans andsea sprays, in which they concentrate at interfaces. Recent
laboratory studies have reported that irradiating liquidsaturated fatty acids with ultraviolet (UV) wavelengths
longer than 295 nm produce various volatile organic
compounds, which enhance marine aerosol formation byacting as precursors [1]. UV absorption spectra of liquidsaturated fatty acids exhibit a weak shoulder absorption band
centered at 270 nm and extending to 330 nm, in addition to
the main band at around 210 nm, due to a singlet-singlet (S0S1) n→π* transition (Fig. 1). Various origins have been
proposed for shoulder absorption, e.g., carboxylate anions, asinglet-triplet (S0-T1) n→π* spin-forbidden transition ofneutral molecules, and the formation of cyclic dimers [2].
However, no consensus has yet been reached, despite over
90 years of investigation [3].
The present study of the absorption of wavelengths longer Fig. 1. UV absorption spectrathan 250 nm by nonanoic acid [CH3(CH2)7COOH], a and absorption cross sections ofrepresentative fatty acid present in the sea-surface liquid nonanoic acid at room
microlayer, demonstrates that the weak absorption band temperature. (A) UV absorption
originates from trace amounts of impurities (0.1% at most) spectra of nonanoic acid: (a)intrinsically contained in nonanoic acid reagents (Fig. 1). reported by Rossignol et al. [1]for a commercial sample (purity,
We developed a unique recrystallization purification system 97%) and measured here for aand purified commercial nonanoic acid by 15 commercial sample (purity,
recrystallizations. As a result, the absorption band at >98.0%) (b) before and (c) after
250−330 nm completely disappeared (Fig. 1A). The recrystallization. Optical pathabsorption cross section at 295 nm (1.3 × 10−23 cm2) was lengths were 10 mm. (B) The
found to be three orders of magnitude smaller than those corresponding calculated
typical for atmospherically relevant organic molecules such absorption cross sections [3].
as formaldehyde (H2CO, 4.4 × 10−20 cm2), acetaldehyde(CH3CHO, 4.3 × 10−20 cm2), and acetone (CH3(CO)CH3, 3.4 × 10−20 cm2) at 295 nm (1 nmaverage) in the gas phase [2]. Our results show that purified fatty acids are photochemicallyinert in the troposphere, in contrast to previous predictions. This study also suggests that moreaccurate evaluation about the effects of impurities is required for scientific research. This isparticularly important in research of photochemical systems because impurities andcontaminants can act as photosensitizers when they are selectively excited by photons.
References
[1]
[2]
[3]

S. Rossignol et al., 2016, Science, 353, 699.
S. Saito et al., 2023, Science Advances 9, eadj6438.
O. Hartleb, 1931, Strahlentherapie, 39, 442.

Poster 10

Chemical Composition of Interstellar Amorphous Silicate Dust
H. Enomoto,1 and A. Takigawa1
1

Department of Earth and Planetary Science, The University of Tokyo, Japan

Absorption features at ~10 µm and ~18 µm of interstellar dust indicate the majority ofinterstellar silicate dust is amorphous and the upper limit to the fraction of crystalline silicatesin the diffuse interstellar medium is 2.2 ± 0.2 % by mass [1, 2]. Synthetic optical constants
such as “astronomical silicate” [3] and “interstellar dust” [4] have been widely used in theinterpretation of observational data. These optical properties, however, do not represent realsolid materials because they are arbitrarily synthesized from the combination of theobservation and laboratory data. Various dust analogs have been produced in laboratories[e.g., 5, 6] but still cannot replace the astronomical silicates. Thus, the nature of amorphoussilicate dust in the circumstellar and interstellar environments, such as chemical compositionand structure, cannot be derived from discussions using astronomical silicates.
In this study, we conducted gaseous condensation experiments of dust analog nanoparticles inthe system of Na-Al-Ca-Mg-Fe-Ni-Si-O using the induction thermal plasma (ITP) system(JEOL TP-40020NPS, [7]). The chemical compositions of the starting materials are shown in
Table 1. The products were analyzed by XRD (Rigaku RINT-2100), FT-IR (JASCO
FT/IR-4200), and EPMA (JEOL JXA-8530F) and partly observed by TEM (JEOL JEM-2800).
We report IR spectral dependence on the chemical compositions of amorphous silicates anddiscuss the chemical composition of interstellar silicates by comparing the experimental
products with astronomical silicates and observations.
Table 1: Chemical Composition of the Starting Material

References

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

F. Kemper, W. J. Vriend, & A. G. G. M. Tielens, 2004, ApJ 609(2), 826.
F. Kemper, W. J. Vriend, & A. G. G. M. Tielens, 2005, ApJ 633, 534.
B. T. Draine & H. M. Lee,1984, 1984, ApJ 285, 89.
V. Ossenkopf, Th. Henning, & J. S. Mathis, 1992, A&A 261, 567.
H. Mutschke, B. Begemann, J. Dorschner, et al., 1998, A&A 333, 188.
J. Dorschner, B. Begemann, H. Mutschke, et al., 1995, A&A 300, 503.
T.H. Kim, A. Takigawa, A. Tsuchiyama, et al., 2021, A&A 656, A42.

Poster 11

Kinetic isotope effects in high-temperature evaporation in protoplanetary disks
S. Inada,1 and S. Tachibana1
1

Department of Earth and Planetary Science, University of Tokyo, Japan

Interstellar dust grains are building blocks of planetary materials but are likely to be thermallyprocessed in protoplanetary disks before they accrete to form planets. The most intensive
processing in inner hot regions of disks results in vaporization of dust grains, and theirchemical compositions are significantly altered when they are partially vaporized. The
metal-bearing molecules (e.g., SiO, AlO and NaCl) observed in a high mass young protostar
candidate (Orion Source I) are likely to be the molecules evaporated from dust [1-3].
Evaporation is a kinetic process that governs the timescales of such solid-vapor partitioning
and thus is important in understanding chemical evolution of planetary materials. Kinetic
isotope effects (KIEs) associated with evaporation lead to isotopic fractionation of theresidual phase, providing information about evaporation experienced by extraterrestrial
samples. For example, calcium-, aluminum-rich inclusions (CAIs) with igneous textures
found in chondrites show enrichment of heavy isotopes of Mg and Si, which is attributed toevaporative isotopic fractionation in the protosolar disk [4]. The KIE in evaporation can betheoretically predicted by the ratio of the thermal velocity of the evaporating molecules, i.e.,the square root of their inverse mass ratio. However, experimentally determined KIEs areusually smaller than the theoretical prediction [5,6].
In this study, we newly formulated the KIE in evaporation by using the expression of theevaporation rate based on conventional transition state theory (CTST) [7,8]. We found that
the KIE in evaporation at the high-temperature limit is expressed by the square root of theinverse ratio of the reduced mass for the motion along the reaction coordinate at the transition
state. This result is consistent with the theory previously proposed for KIEs in generalchemical reactions [9] and explains the experimental KIEs in evaporation smaller than theconventional prediction. By considering the motion along the reaction coordinate as vibration
with an imaginary frequency, we further evaluated the KIE in evaporation using normal-mode
vibration analyses for the transition state. The result suggested that the KIE is smaller than theconventional prediction when the activation barrier exists for the bond dissociation. Thissuggests that the different degrees of KIEs of metallic iron and silicates obtained byexperiments might indicate the presence of an activation barrier for the dissociation of anionic bond that originates from the avoided crossing of potential energy curves.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]

T. Hirota et al., 2017, Nature Astronomy 1, 0146
S. Tachibana et al., 2019, ApJ 875, L29
A. Ginsburg et al., 2019 ApJ 872 54.
L. Grossman et al., 2008, GCA 72, 3001.
M. Yamada, S. Tachibana, H. Nagahara, & K. Ozawa, 2006, Planet. Space Sci. 54, 1096.
F. M. Richter, P. E. Janney, R. A. Mendybaev, A. M. Davis, & M. Wadhwa, 2007, GCA 71, 5544
E. Mortensen & H. Eyring, 1960, J. Phys. Chem. 64, 846.
S. Inada, T. Hama, & S. Tachibana, J. Chem. Phys., in revision.
J. Bigeleisen, 1949, J. Chem. Phys. 17, 675.

Poster 12

Development and preliminary results of the low-temperature gas evaporation method tounderstand nucleation conditions of water ice and related materials
Yuki Kimura, Tomoya Yamazaki, Yuga Yashima, Shoichi Mori,
Fumiaki Saito, and Akira Kouchi
Institute of Low Temperature Science, Hokkaido University, Japan
In our previous studies, we have shown that the key factors governing nucleation from the gas
phase are the melting point depression of nanoparticles and sticking probability (dimer
formation) [1,2]. In long years, nucleation theory has been known to be completely unable toexplain the results of experiments and molecular dynamics simulations. In contrast, we haveclarified that the latest nucleation theory can explain experimental results by using
appropriately determined sticking probabilities and surface free energies of nanoparticles asphysical parameters [1], and by including chemical potential differences that consider the
nucleation pathway [2].
To understand the nucleation processes of ice, we developed a low-temperature gas
evaporation method to determine the sticking probability and surface free energy ofnanoparticles of ice. The gas evaporation method has been used to make nanoparticles ofrefractory materials through homogeneous nucleation during the cooling process of hightemperature vapor generated by heating and evaporating the starting material [3]. By
applying interferometry to this method, two physical quantities (surface free energy andsticking probability), which are essential for understanding the nucleation process, can beobtained. In addition, infrared spectral measurements can reveal the nucleation pathways.
The low-temperature nucleation chamber has a double-tube structure. The inner chamber,where ice nucleation takes place, is filled with neon gas to reduce the mean free path andcooled by liquid nitrogen. The evaporation source was also cooled with liquid nitrogen. The
space between the inner and outer chambers is evacuated to thermally insulate them andprevent condensation.
Water vapor generated by heating and sublimating ice in the low-temperature nucleationchamber is cooled by neon gas, and after becoming supersaturated, it undergoes homogeneous
nucleation to form nanoparticles. This process was observed in situ using a doublewavelength Mach-Zehnder laser interferometer and an infrared spectral system. Theinterferometer can quantitatively determine the temperature and concentration fields from
evaporation to nucleation. The infrared system can investigate the changes in the crystal
structure of water and ice particles during the nucleation process.
In the experiment, the interferometer succeeded in capturing the moment of nucleation, andthe infrared system also succeeded in capturing the temporal change in absorption intensity.
This means that the nucleation process of ice nanoparticles from water vapor was captured.
This achievement is expected to lead to the construction of a nucleation model that can predict
the state of ice dust formation that repeatedly sublimated and condensed in the primordial
solar nebula 4.6 billion years ago.
References
[1]
[2]
[3]

Y. Kimura, K. K. Tanaka et al., 2017, Science Advances 3, e1601992.
S. Ishizuka, Y. Kimura et al., 2018, Nature Communications 9, 3820.
C. Kaito, 1978, Japanese Journal of Applied Physics 17, 601.

Poster 13

Returned sample from carbonaceous asteroid Ryugu and its astrochemical implications
S. Tachibana1,2 and N. Sakai3
1

UTOPS, Univ. Tokyo, Japan, 2ISAS, JAXA, Japan, 3Star and Planet Formation Laboratory,
RIKEN Cluster for Pioneering Research, JapanThe Hayabusa2-returned C-type asteroid Ryugu samples [1] are the chemically most pristinematerial in the Solar System as they have not been exposed to terrestrial conditions [e.g., 2-9].
The Ryugu samples have the bulk elemental compositions similar to those of the Sun and CI
chondrites, which are the chemically most primitive meteorites [1], suggesting that Ryugu
formed from the Solar System’s original elemental ingredients without experiencing
elemental fractionation except for highly volatile elements such as H, C, N, and noble gases.
The carbon abundance of the bulk Ryugu samples ranges from 3.2 to 6.8 wt % [2, 5, 8, 9],which is similar to that in CI chondrites and among the highest in the meteorite samples.
About 2/3 of this carbon is in organic matter [1]. The organic matter in Ryugu records themolecular evolution from the Sun’s parent molecular cloud chemistry to the asteroidal
aqueous alteration [e.g. 7-9]. The Ryugu samples contain organic matter having hydrogen
and/or nitrogen isotopic compositions highly enriched/depleted in D and 15N [7]. These
distinct isotope compositions of macromolecular organics may have been inherited from thechemistry in the Sun’s parent molecular cloud or the cold outer Solar System.
The N/C ratio of the Ryugu’s macromolecular organic matter ranges from 0.01 to 0.035 [5].
Thosee N/C ratios of the Ryugu’s macromolecular organic matter are within the range of
thoseN/C ratios found inof insoluble organic matter (IOM) in carbonaceous chondrites andthose inof organic particles from comet 67P/Churyumov-Gerasimenko [e.g., 10]. It is thus
suggested that the macromolecular organics with the N/C ratio lower than the solar N/C ratio
was present with those having the high N/C ratios in the Sun’s protoplanetary disk, and theorganics with the lower N/C ratio was incorporated into the Ryugu’s parent body and comet
67P/Churyumov-Gerasimenko [10].
We review the results of Ryugu sample analysis and discuss the evolution of organic matter inthe early Solar System by comparing with the recent radio and infrared observations ofprotostars and protoplanetary disks.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]

S. Tachibana et al. (2022) Science
T. Yokoyama et al. (2022) Science
T. Nakamura et al. (2022) Science
T. Noguchi et al. (2023) Nature Astronomy
R. Okazaki et al. (2022) Science
R. Okazaki et al. (2022) Science Advances
H. Yabuta et al. (2023) Science
H. Naraoka et al. (2023) Science
Y. Oba et al. (2023) Nature Communications
S. Tachibana & N. Sakai, Elements, in press.

Poster 14

Infrared spectra of isomers of protonated and hydrogenated phenanthridine isolated insolid para-hydrogen
Yi-Shan Chung1, Man-Lin Yang1, Jun-Ying Feng1 and Yuan-Pern Lee1,21Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming
Chiao Tung University, 1001, Ta-Hsueh Rood, Hsinchu 300093, Taiwan
2

Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung
University, 1001, Ta-Hsueh Rood, Hsinchu 300093, Taiwan
e-mail: cindy40232@gmail.com and yplee@nycu.edu.tw

Abstract
Large polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic nitrogen
heterocycles (PANH) have been proposed to be potential carriers responsible for theunidentified infrared (UIR) emission bands in the interstellar medium.1 The nitrogen atom in
PANH induces a blue shift of the CC-stretching mode of the PAH, occurring around 6.3 μm. In
addition to PANH, several protonated polycyclic aromatic hydrocarbons (H+PAH) and thecorresponding nitrogen heterocycles (H+PANH) also exhibit blue shifts.2 Therefore, the CCstretching band of the H+PANH might agree better with the UIB band at 6.2 μm and H+PANH
might be potential candidates that contribute to the UIR bands.
We report the infrared (IR) spectra of two isomers of protonated phenanthridine(H+C13H9N) and seven isomers of mono-hydrogenated phenanthridine (HC13H9N), produced
upon electron-bombardment of a mixture of phenanthridine (C13H9N) and para-hydrogen (pH2) during matrix deposition at 3.2 K. IR spectra of protonated species C13H9NH+ and 4H+C13H9N were observed. In addition to the hydrogenation on the N atom of C13H9N to form
C13H9NH, mono-hydrogenation at six carbon sites to form 1-, 2-, 3-, 7-, 9-, and 10-HC13H9N,
respectively, were also observed. To confirm the spectral identification of hydrogenatedphenanthridine, additional experiments on a C13H9N/Cl2/p-H2 matrix were performed; thematrix was irradiated at 365 nm to generate Cl atoms, followed by IR irradiation to generate H
atoms via Cl + H2 (v = 1) → HCl + H. The H atoms thus generated propagated throughout thematrix and reacted with C13H9N via quantum tunneling. In these experiments, six hydrogenatedphenanthridine species, except the one hydrogenated at the carbon site 3, were clearly observed.
Spectral groupings were achieved according to the behaviors of lines upon secondary photolysis
at various wavelengths, chosen according to the vertical electronic transitions of various
isomers of HC13H9N predicted with the TD-B3LYP/6-311++G(d,p) method. The spectral
assignments were supported via comparison of the experimental results with the vibrationalwavenumbers and IR intensities of possible isomers predicted with the B3LYP/6-311++G(d,p)
method. All spectra of H+C13H9N and HC13H9N are new.
For H+C13H9N, major observed lines are at 2.95, 6.22 and 12.53 μm; the CC-stretching
band of C13H9NH+ was observed at 6.22 μm, blue shifted from that of the corresponding PAH,
10-C14H11+. For HC13H9N, major lines were observed at 13.43, 13.16, and 13.55 μm for
C13H9NH, 9-HC13H9N, and 2-HC13H9N, respectively. Based on the overall spectral pattern,these protonated and hydrogenated species are unlikely to be the carriers of the UIR bands,
characterized by emission bands near 3.3, 6.2, 7.7, 8.6, 11.2, and 12.0 μm.
References[1][2]

A. Leger, J. L. Puget, Astron. Astrophys., 137, L5-L8 (1984).
H. A. Galue, O. Pirali, J. Oomens, Astron. Astrophys., 517 (2010).

Poster 15

Photochemistry of six-membered hydrocarbons in solid parahydrogen
J. Miyazaki,1,2 S. Y. Toh,2 B. Moore,2 P. Djuricanin,2 and T. Momose2
1

2

Department of Natural Sciences, Tokyo Denki University, Japan
Department of Chemistry, The University of British Columbia, Canada

Photochemical reactivities of cyclic hydrocarbons are interested in natural sciences, biologicalsciences, and astrochemistry, because the investigation of these ring molecules give us theuseful information about the noble or unstable species formation and chemical reactions. In
particular, since polycyclic aromatic hydrocarbons (PHAs) are one of the potential candidates
for the carrier of diffuse interstellar bands (DIB) [1-3], it is important to understand the UV
photochemical behavior of PHAs because interstellar molecules are constantly exposed tostrong UV radiation. In this study, we investigate the photochemistry of six-memberedhydrocarbons: benzene (Bz) [4], one of the simplest and most widely studied aromatichydrocarbons, and 1,3-cyclohexadiene (1,3-CHD) [5] and 1,4-cyclohexadiene (1,4-CHD) [6],two double bonding at different position in ring, trapped in solid parahydrogen by a joint useof Fourie transform infrared spectroscopy and density functional theory (DFT) calculations,aiming to compare the photochemical stability, reactivity and photochemical products among
three molecules. The mixture of hydrocarbons and parahydrogen were condensed on the cold
substrate (4.2 K) cooled down by closed-cycle GM refrigerator. The sample was them
irradiated by 193 nm photons of an ArF pulsed laser, and photoproducts were detected by and
FT-IR spectrometer. In order to confirm the spectral assignment of reactants and products,
DFT calculations were also performed. In the IR spectra of 1,4-CHD in solid parahydrogen
after ArF laser irradiation, we observed peaks of 1,3-CHD and Bz as photoproducts. Further
irradiation using ArF, we observed the cyclohexadienyl radical, hexatriene derivatives, andsmall photofragment molecules. Comparing with the photochemical behavior of three sixmembered hydrocarbons, the photochemical products and reactions mechanism of threemolecules will be discussed.

References

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

G. P. Van der Zwet & L. J. Allamandola, 1985, A&A. 146, 76−80.
A. Leǵer & L. d’Hendecourt, 1985, A&A. 146, 81−85.
M. K. Crawford, A. G. G. M. Tielens, & L. J. Allamandola, 1985, ApJ. 293, L45−L48.
S. Y. Toh, P. Djuricanin, T. Momose, & J. Miyazaki, 2015, J. Phys. Chem. A, 119, 2683−2691
J. Miyazaki, S. Y. Toh, B. Moore, P. Djuricanin & T. Momose, 2021, J. Mol. Struct., 1224, 128986
J. Miyazaki, S. Y. Toh, B. Moore, P. Djuricanin & T. Momose, in preparation

Poster 16

Quantitative analysis for the branching ratio of CH3O and CH2OH radicals formed from
CH3OH + OH reaction on ice surface
A. Ishibashi,1 H. Hidaka,1 W. M. C. Sameera,1, 2 Y. Oba,1 and N. Watanabe1
1Institute of Low Temperature Science/Hokkaido University, Japan
2Department of Chemistry/University of Colombo, Sri Lanka

Complex organic molecules (COMs) with CH3O incorporated into their structure, such as methyl
formate (HCOOCH3) and dimethyl ether (CH3OCH3), have been found in various astronomical objects
including cold molecular clouds. For these COMs formation, radical reactions on the surface ofinterstellar dust would play an important role. Recent experiment suggested that the surface reaction of
methanol and OH formed promotes the formation of CH3O-bearing COMs on ice [1]. That is, of thefollowing two reactions, the branch to CH3O radical formation would be the major.
CH3OH + OH ˢ CH3O and/or CH2OH + H2OHowever, while this reaction in the gas phase has been extensively studied [2, 3], little information isavailable for that on ice surfaces. Since information of branching ratios is needed for constructing betterchemical evolution models, we measured the branching ratio of CH3O and CH2OH produced by CH3OH+ OH reaction on water ice surface at 10 K.
For trace radical detection, we used a newly developed high-sensitive “Ion Pickup” apparatus. In thismethod, low-energy Cs+ ions (~20 eV) nondestructively pickup adsorbates on the ice surface. The
adsorbate was then detected as a Cs+-molecule complex in a quadrupole mass spectrometer, and its
mass number was obtained by subtracting the Mass 133 of Cs [1, 4]. Thanks to our various
improvements, this apparatus has a sensitivity of ~0.0001-0.001 ML, which is much higher thanconventional methods like FT-IR.
The experimental procedure of present study is shown in Figure 1. We first prepared OH radicals on
ice surface by UV irradiation at 30 K, where most H atom did not remain on the surface. Then, after
UV was turned off, the reaction was triggered by depositing methanol on the ice at 10 K. The radicals
formed by this procedure were monitored using Ion Pickup. We also performed experiments withisotopologues (CH3OD and CD3OH) to distinguish the products of CH3O and CH2OH. Quantitative
analysis shown the branching ratio (CH3O/CH2OH) of 4.3 ± 0.6 (i.e., CH3O ~ 80 %) [5].

Figure 1: Experimental procedure for the reaction of methanol and OH on ice surface

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

A. Ishiabshi et al., Astrophys. J. Lett. 921, L13 (2021).
R. J. Shannon et al., Nat. Chem. 5, 745-749 (2013).
A. Canosa, Proc. Int. Astron. Union. 15, 35−40 (2019).
H. Kang, Bull. Korean Chem. Soc. 32, 389 (2011).
A. Ishiabshi et al. Accepted in Astrophys. J. (2023). dio: 10.48550/arXiv.2309.10351.

Poster 17

Laboratory development for the study of interstellar surface chemistry
C. Suwannajak,1 N. Tanakul,1 W. Jaikla,1 S. Homnan,2 P. Wongkummoon,1,2
M. Jitvisate,3 T. Phimsen,4 P. Nimmanpipug,5 A. Leckngam,1 and S. Rimjaem2
12

National Astronomical Research Institute of Thailand (Public Organization), Thailand
Department of Physics and Materials Science, Faculty of Science, Chiang Mai University,
Thailand3
School of Physics, Suranaree University of Technology, Thailand
4
Synchrotron Light Research Institute (Public Organization), Thailand
5
Department of Chemistry, Faculty of Science, Chiang Mai University, Thailand

It is suggested that interstellar complex organic molecules (COMs) may give rise to thechemical complexity on planetary surface. These COMs are proposed to be formed on the ice
surface of dust grains in molecular clouds. We present the experimental apparatus designed
for simulating the environments of the interstellar clouds to study the chemical process
underlying the formation of these COMs. The apparatus includes a main ultra-high vacuum
chamber with 10-10 mbar base-pressure. The experiments will be conducted by feeding gas
into the chamber through gas deposition lines, onto the liquid nitrogen-cooled substrate toform an interstellar ice analog. The ice will be irradiated by VUV, with a source equipped tothe chamber. Then, mass spectroscopy and FTIR spectroscopy will be used to identified thechemical products. Finally, we present the progress of the manufacturing process as well as
the development plan of the apparatus.

Poster 18

Visible light-induced photodesorption of OH radicals adsorbed on water ice surface
Ni-En Sie,1 Masashi Tsuge,1 Yoichi Nakai,2 W.M.C. Sameera,1,3 and Naoki Watanabe1
1Institute of Low Temperature Science, Hokkaido University, Japan
2
Radioactive Isotope Physics Laboratory, RIKEN Nishina Center, Japan3
Department of Chemistry, University of Colombo, Sri Lanka
In cold interstellar medium, the OH radical would be one of the most predominant reactive
species on ice dust because it is readily produced by the photolysis of H2O or surface reactionof H and O atoms. At low temperatures, OH radicals can take part in various chemical
activities on the ice dust surfaces, while once they are released from the surface, gas phasechemistry like O2 formation can be enhanced [1]. However, because the OH radical is highly
reactive and thus easily consumed by reactions with other adsorbates at higher temperatures,its thermal desorption as intact may hardly happen. Instead, the photodesorption induced by
UV and X-ray photons, which often follow the photodissociation of H2O, has been
investigated for a long time. In contrast, visible light has not been considered as the trigger ofphotodesorption, because both isolated water molecules and OH radicals are transparent in avisible region. Recently, we observed the photodesorption of OH radical on water ice at 532
nm through combining photostimulated desorption (PSD) and resonance-enhanced
multiphoton ionization (REMPI), the PSD-REMPI method [2]. According to quantum
chemical calculation, the absorption of 532 nm photons is triggered by the OH strongly
bonded with surrounding H2O through three hydrogen bonds, indicating that thephotodesorption strongly depends on the adsorption sites of OH on the water ice surface.
In this study, we extended the wavelength of visible light in the range of 410 to 700 nm tomeasure the photodesorption efficiency of OH radicals on ice surface, which would becontributed by the population of OH adsorption sites and the photodesorption cross section.
The multiplication of the population and cross section represents the effective cross section
for each wavelength, which was found to explain the trend of photodesorption efficiency as afunction of wavelength very well.

Figure 1: The schematic diagram of OH radicals photodesorb from water ice surface by the visible light.

References

[1]
[2]

Chaparro et al., A&A, 537, A138 (2012)
Miyazaki et al., Physical Review A, 102, 052822 (2020)

Poster 19

Laboratory studies on the infrared emission spectra of fullerene C60 thin films
T. Wakabayashi,1 H. Suzuki,1 M. Hatanaka,2 and T. Kodama3
1

Department of Chemistry, Kindai University, Japan2
Department of Chemistry, Keio University, Japan
3
Kanagawa Institute of Technology, Japan

Fullerene C60 has been detected in interstellar objects at late stages of the stellar evolution,such as post asymptotic giant branch (post-AGB) stars, protoplanetary nebulae (PPNe),
planetary nebulae (PNe), reflection nebulae, and young stellar objects (YSOs) [1-3]. It isnatural to consider that the relative intensity of multiple emission bands of a single molecularspecies in the infrared (IR) spectra can be exploited as a probe for vibrational temperature ofan ensemble of the molecules. Concerning C60, variations are observed for the relative
intensity of bands for four IR-active vibrational modes of T1u symmetry. The thermal emission
mechanism [1] and the UV-induced fluorescent mechanism [2] are proposed. However, theobservations do not simply follow either mechanism. There must be another factor to be taken
into considerations.
We have conducted laboratory studies on the measurement of IR emission spectra of fullerene
C60 at elevated temperatures. Using a commercial FTIR spectrometer, power spectra of heatedsamples of a thin film of C60 deposited on a KBr slab were recorded in a range of 300–400 K.
Theoretical simulations were performed under the assumption of Boltzmann distributions ofmolecules in vibrationally excited states up to seven vibrational quanta. Figure 1 depicts animage of contribution of vibrationally excited molecules to the IR emission of bands for T1u
modes of C60 at ambient temperature.

Figure 1: The simulated IR emission intensity of four vibrational T1u modes of the fullerene C60 molecule.
Contributions from vibrationally excited states including 46 fundamentals and their overtones andcombinations with excitations up to seven vibrational quanta are taken into considerations.

References[1]
J. Cami, J. Bernard-Salas, E. Peeters, & S. E. Malek, 2010, Science 329, 1180.
[2]
K. Sellgren, M. W. Werner, J. G. Ingalls, J. D. T. Smith, T. M. Carleton, & C. Joblin, 2010, ApJ. 722, L54.
[3]
J. Bernard-Salas, J. Cami, E. Peeters, A. P. Jones, E. R. Micelotta, & M. A. T. Groenwegen, 2012, ApJ
757, 41.

Poster 20

A Laboratory-Demonstrated Model that Explains the Galactic Extended Red Emission:
Graphene Exposed to Far-ultraviolet Light
Sheng-Lung Chou1, Wen-Bing Shih2, Min-Zhen Yang2, Tzu-Ping Huang1, Shu-Yu Lin2,
Meng-Yeh Lin1, Wen-Jian Huang1, Yin-Yu Lee1, Yuan-Pern Lee2, Yu-Jong Wu1,2
12

National Synchrotron Radiation Research Center, Taiwan
Department of Applied Chemistry, National Yang Ming Chiao Tung University, Taiwan

Extended red emission (ERE) is a broad feature in spectral region 500~900 nm commonly
observed in a wide range of circumstellar and interstellar environments [1]. Although theobservational constraints for ERE are well established, definitive identifications of the carriers
and associated processes complying these constraints remain unanswered. We report aplausible two-step model involving far-UV irradiated single-layer graphene (SLG),
considered as large polycyclic aromatic hydrocarbons, to meet these constraints and supported
by laboratory experiments. The far-UV-treated SLG, producing structural defects andgraphene quantum dots, showed photoluminescence excitation spectrum extending from farUV to UV–visible region, hence meeting the requirements of far-UV light and high photonconversion efficiency. Furthermore, a photoluminescence band shifted from ~585 nm to ~750
nm for high-dose-exposed SLG agrees with the observed red shift of the ERE band in regions
under a greater far-UV radiation density [2,3]References[1] A. N. Witt & T. S.-Y. Lai, 2020, Astrophys. Space Sci. 365, 58[2] S.-L. Chou, M.-Y. Lin, S.-Y. Lin, W.-J. Huang, T.-P. Huang, Y.-C. Lee, & Y.-J. Wu, 2020, ApJ 901, 103.
[3] S.-L. Chou, W.-B. Shih, M.-Z. Yang, T.-P. Huang, S.-Y. Lin, M.-Y. Lin, W.-J. Huang, C. M. Chu, W.-Y. W,
Y.-Y. Lee, Y.-P. Lee, & Y.-J. Wu, 2023, ApJ 944, 18

Poster 21

In situ electron diffraction analysis of stacking sequences in ice I
under interstellar conditions
R. Sato,1 S. Taniguchi,1 N. Numadate,1 and T. Hama1
1

Graduate School of Arts and Sciences, The University of Tokyo, Japan

Infrared (IR) observations toward interstellar molecular clouds reveal that water ice without along-range ordered structure (amorphous water) is the dominant solid component in icy dust
grains. At high temperatures, amorphous water is crystallized into ice I, which consists ofstable hexagonal ice Ih, metastable cubic ice Ic, and their mixed structure. Although themorphology of water ice affects the reactivity of chemical reactions in icy dust grains [1], theselection rule of those different ice structures is not completely understood yet.
In laboratory, interstellar ice analogues are usually prepared by deposition of a water vapor
onto a cold substrate (vapor-deposition). Crystallinity of water ice depends not only on thetemperature of a substrate but also on the deposition rate of a water vapor [2]. Recently, theformation of crystalline ice is reported even at extremely low temperatures by a methodarranged from vapor-deposition (for details, see ref. [3]). However, because the previous
study [3] analyzed the ice only by IR spectroscopy, the amount of cubic or hexagonal stacking
sequences in the ice is still unknown. In situ diffraction analysis is crucial to determine theextent of stacking sequences in ice I.
By using newly developed reflection high-energy electron diffraction (RHEED), we foundthat the amount of hexagonal stacking sequences in the ice I formed by the new method at 13
K was lower than that in the ice I prepared by annealing vapor-deposited amorphous water at
143 K (Fig. 1) [4]. The formation of less hexagonal stacking sequences in ice I at higher
supercooling degree is qualitatively in line with the study of cubic ice Ic formation by usingclassical thermodynamics theory [5]. In the session, we will introduce further information
about the experiment and its astrophysical implications.

Figure 1: RHEED images of ice I obtained by the new method at 13 K (left), and ice I obtained byannealing vapor-deposited amorphous water at 143 K (right).

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

T. Hama, & N. Watanabe, 2013, Chem. Rev. 113, 8783.
A. Kouchi, T. Yamamoto, T. Kozasa, T. Kuroda, & J. M. Greenberg, 1994, A&A. 290, 1009.
T. Hama, S. Ishizuka, T. Yamazaki, Y. Kimura, A. Kouchi, N. Watanabe, T. Sugimoto, & V. Pirronello,
2017, Phys. Chem. Chem. Phys. 19, 17677.
R. Sato, S. Taniguchi, N. Numadate, & T. Hama, 2023, J. Chem. Phys. 158, 211101.
T. Takahashi, 1982, J. Cryst. Growth. 59, 441.

Poster 22

Atomic force microscopy measurement of local contact potential difference ofamorphous solid water deposited at 15 and 100 K
H. Hidaka, T. Tomaru, and N. Watanabe
1Institute of Low Temperature Science, Hokkaido University, JapanIcy dust particles, which are mineral nanoparticles covered with an amorphous ice mantle
primarily composed of H2O, play an important role in chemical evolution in space. This isbecause the surface of icy dust surface facilitates a variety of molecular syntheses involving
processes such as adsorption, diffusion, reaction and desorption of atoms and molecules [1, 2].
However, it is difficult to say that our understanding of the amorphous solid water (ASW) is
sufficiently comprehensive.
ASW films formed by vapor deposition onto a cold surface are known to have negative
surface potentials due to spontaneous polarization, which varies depending on the temperatureand film thickness [3,4]. However, the mechanisms underlying this polarization, responsible
for the surface potentials, remain unclear. Although previous studies that used Kelvin probe
measurements have proposed the polarization model of ASW named tilted dipole model, thedirect evidence confirming accuracy of this model has not been obtained yet due to limitationof spatial resolution. To overcome this limitation in spatial resolution, we used FM-AFM tomeasure variations in the negative surface voltage of ASW with nanoscale resolution
depending on the surface structures.
We conducted measurements on two types of ASW formed by water vapor deposition at 15
and 100K on a Si (111) 7×7 substrate in ultra-high vacuum conditions. The topographic
images of the surface structure showed temperature dependence, attributed to the differencesin diffusion length of water molecules on the surface until reaching stabilization at themeasurement temperature. We also measured the local contact potential difference between
probe tip and 400 measurement points set on ASW surface within a 200 nm x 200 nm are,respectively. On both ASW surfaces, the local contact potential difference varied at eachmeasurement point without correlation with local thickness (topographic height). Thissuggests that this polarization phenomenon cannot simply attributed to the thickness of ASW
but depends on the local structure. Our observations with nanoscale resolution imply that thetilted dipole model is a plausible representation of the spontaneous polarization of ASW.

References

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

T. Hama and N. Watanabe, Chem. Rev., 2013, 113, 8783-8839.
E. Herbst and E. F. van Dishoeck, Annu. Rev. Astron. Astrophys., 2009, 47, 427-280.
M. J. Iedema, M. J. Dresser, D. L. Doering, J. B. Rowland, W. P. Hess, A. A. Tsekouras, J. P. Cowin,
1998, J. Phys. Chem. B, 102, 9203-9214.
C. Bu, J. Shi, U. Raut, E. H. Mitchell, R. A. Baragiola, 2015, J. Chem. Phys., 142, 134702.

Poster 23

Preliminary study of radiation-induced morphological alteration to water ice (Ih)
Y. Nakano,1 Y. Kimura,1 T. Yamazaki1, and Y. Sasaki2
1

Institute of Low Temperature Science, Hokkaido University, Japan
2
Screen Holdings Co., Ltd., Kyoto 612-8486, Japan

A large fraction of amorphous solid water is expected to be crystalline phase in protoplanetarydisks (PPDs) [1]. Two variant crystal structures of the water ice are potentially formed aroundthe snow line at PPDs: hexagonal ice (Ih), which is produced above 150 K by condensation ofwater vapor and/or above 140 K by annealing of amorphous solid water (ASW), and cubic ice(Ic), which is produced above 130 K by condensation of water vapor and/or 130 to 140 K byannealing of ASW [2], depend on the temperature of the snow line.
Cosmic rays from a central star irradiate the upper layer of a PPD where gas and dust aredecomposed and altered by the high-energy solar wind [3]. The consequence of the radiolysis
depends on the physical state and the composition of the dust. In the case of crystalline water,tiny-cavities are formed due to immediate clustering of myriad vacancies generated bydiffusion of hydrogen and oxygen atoms from their lattice sites, which are a direct result of
the electron-induced radiolysis of water ice [4]. The tiny-cavities produced by radiolysis canserve as additional surface on the water ices.
It is widely supposed that the surface of water ice works as a catalysis for gas-solid phasechemistry in interstellar environments [5]. To understand radiation-induced alterations towater ice, we observed a time-evolution of tiny-cavities in water ice (Ih) with a liquid-celltransmission electron microscopy (LC-TEM). Figure 1 shows a moment of the timeevolutions of tiny-cavities in the ices around −15 ℃ obtained by a 200 keV TEM (JEM2100F). The tiny-cavities were discerned their shapes at the beginning of the observation andthen clearly recognized in a period of the observation due to a simultaneous disappearance ofthe mother ice body. We found that the size, the shape, and the evolution path of the tinycavities were changed depend on the thickness of the mother ices that was estimated from 17
to 500 nm.
Figure 1: Bright field TEM images of
selected frames in each video of tiny-cavities
evolution in ice Ih encapsulated between
electron-transparent SiN windows. The
relative dark fields correspond to ice at a
range of the estimated thickness 17 to 35 nm
for (a) and 70 to 150 nm for (b). The relative
bright fields are possibly filled with gas
generated by the radiolysis of the ice.

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

M. Min, et al. 2016, A&A, 593, A11.
D.V. Mifsud, et al. 2022, Eur. Phys. J. D, 76, 87.
L. Klarmann, C.W. Ormel, & C. Dominik, 2018, A&A, 618, L1.
P.N.T. Unwin, & J. Muguruma, 1971, J. Appl. Phys., 42, 3640.
R.A. Carmack, Tribbett, P.D. & M.J. Loeffler, 2023, ApJ., 942, 1

Poster 24

In situ cryogenic transmission electron microscopy observation on the formation ofhydrogen-ordered hexagonal ices and its astrophysical implications
T. Yamazaki,1 A. Kouchi,1 K. Murata,1 H. Katsuno,1 H. Nada,2 T. Hama,3 and Y. Kimura1
1

Institute of Low Temperature Science, Hokkaido University, Japan
2
Faculty of Engineering, Tottori University, Japan
2
Komaba Institute for Science, The University of Tokyo, Japan

Water ice is ubiquitous in molecular clouds, protoplanetary disks, and icy bodies of the outersolar system. In addition to the formation of various molecules on water ice in molecular
clouds, water ice also has an important role for the formation of planetesimals in
protoplanetary disks. It is therefore essential to clarify how the ice exist (e.g., phase) undersuch low-temperature and low-pressure environments. To investigate the ice under suchenvironment, here we developed ultra-high vacuum cryogenic transmission electron
microscopy [1] and observed water ice and its structural changes [2].
Two types of ice, cubic ice I (ice Ic) and hexagonal ice I (ice Ih), were observed whileannealing under the microscope. First, ice was deposited on the 5 nm amorphous SiNx
membrane by controlling the partial pressure of H2O at 140 K for ice Ic, and 150 K for ice Ih.
Then, the ice was annealed at 83-130 K for ice Ic and 120-150 K for ice Ih. During annealing,
electron diffraction patterns were acquired to investigate its structural changes.
Many diffraction spots in the electron diffraction patterns appeared with time, some of them
do not belong to either ice Ic or ice Ih. To determine the origin of these diffraction spots, we
calculated the d-spacings and diffraction intensities of several ice polymorphs that form underthe experimental conditions. Then we found that the possible origin of these diffraction spots
was hydrogen-ordered phases, that the ice Ic or Ih having specific hydrogen positions. We
plan to discuss the formation of these ice phases and their impacts on chemical and physicalevolution in a planetary system.

Figure 1: Examples of a TEM image of initial water ice sample of ice Ic crystals (left) and an electron
diffraction pattern with a diffraction spot not observed in ordinary ice Ic and Ih (right). The TEM image
was taken immediately after the start of annealing (1 min later), and the electron diffraction pattern was
acquired by annealing at 130 K for 342 min. The arrowhead on the right indicates the diffraction spotcorresponding to d-spacing of 6.4 Å, which is not observed in ordinary ice.

References[1] A. Kouchi, Y. Kimura, K. Kitajima, H. Katsuno, H. Hidaka, Y. Oba, M. Tsuge, T. Yamazaki, K. Fujita, T.
Hama, Y. Takahashi, S. Nakatsubo, N. Watanabe, 2021, Front. Chem. 9, 799851.
[2]
A. Kouchi, T. Yamazaki, H. Katsuno, H. Nada, T. Hama, Y. Kimura, 2023, Chem. Phys. 572, 111966.

Poster 25

Nuclear quantum effect in the phase transition between Ice VII and ice X
K. Kuwahata and M.Tachikawa
Yokohama City University, Japan
Water is one of the most abundant and essential substances on Earth, playing a critical role in thediversity of nature and natural phenomena, including the existence of life. Despite being composedof a single molecule, H2O, ice is a complex substance with 17 different stable structures. As a result,
it is an important model for studying hydrogen modeling[1]. At room temperature and pressure
between 2 and 60 GPa, ice VII is a stable crystalline phase, where the oxygen atoms form a bodycentered cubic structure, with the hydrogen atoms being delocalized between the two oxygen atoms(Fig. 1(a)). Infrared spectroscopy has confirmed that above 60 GPa, ice VII undergoes a phasetransition to ice X, in which the hydrogen atoms lie midway between the two oxygens[2]. Although
the phase transition from ice VII to ice X is a change in the symmetry of the hydrogen atom, thebehavior of the hydrogen atom is still unknown due to the difficulty of conducting neutron
diffraction experiments under high-pressure conditions. To address the gap, this study uses the path
integral molecular dynamics method (PIMD), which can treat the nuclear quantum effect, totheoretically clarify the behavior of hydrogen atoms in the phase transition from ice VII to ice X.
We conducted three types of PIMD simulations to study the impact of the nuclear quantum effect:
the simulation for hydrogen atoms (QM(H)), for deuterium atoms (QM(D)), and the classicalsimulation without nuclear quantum effect (CL). To analyze the phase transition, we used thedifference in distance between the two oxygen atoms and the hydrogen atom (𝛿𝛿OH ) as a guide. At alattice constant of 2.9 Å, the hydrogen atoms in the CL simulation were found to be localized on
one oxygen atom, while in the QM(H) and QM(D) simulations, the hydrogen atoms weredelocalized, and the distribution at 𝛿𝛿OH = 0 Å was increased. Across all simulations at a lattice
constant of 2.9 Å, the distribution displayed two peaks, indicating the phase was ice VII. Upon
reducing the lattice constant to 2.78 Å, the distribution in QM(H) displayed only one peak,suggesting that the nuclear quantum effect promotes the phase transition. Futher details will bepresented in a poster.

Figure 1: The structure of ice VII (a), distribution of 𝛿𝛿OH at a lattice constant of 2.90 Å (b) and 2.78 Å (b)[1] C. G. Salzmann, J. Chem. Phys., 150, 06091 (2019)[2] K. Aoki, H. Yamawaki, M. Sakashita, and H. Fujihisa, Phys. Rev. Let. 76, 5, (1996)

Poster 26

The cold path to saturation:hydrogenation of cyanoacetylene towards ethyl cyanide in dark molecular clouds
M.T. Raaphorst,1 A.L.M. Lamberts1,2
1

Leiden Institute of Chemistry, Leiden University, the Netherlands
2
Leiden Observatory, Leiden University, the Netherlands

Cyanoacetylene (HC3N) is a nitrogen-bearing carbon chain that is ubiquitous in the ISM.
Once it is formed in the gas phase, it is thought to freeze out on the icy grain mantles in dense
molecular clouds. Atop the ice it could react with a number of available chemical species, butlittle it known about the surface reactivity of HC3N, in part because of experimental
difficulties. In this work we present a computational investigation of the hydrogenation of
HC3N under interstellar conditions. We have performed DFT and CCSD(T)-F12 calculations
to obtain the energy profiles of various hydrogenation pathways. Based on activation andreaction energies of the gas phase reactions, the most favourable pathways lead to vinyl
cyanide and ethyl cyanide, which have also been detected in the ISM. Additionally we present
some first results on the interaction of HC3N with H2O ice clusters. The next step is to obtain
the energy profiles for the HC3N hydrogenation on an H2O ice cluster, and to investigate thekinetics of the reactions. This will indicate whether HC3N can hydrogenate to form saturated
species on ice grains in the ISM.

Poster 27

Rovibrational transitions in HCl due to collisions with H2: spin-free andhyperfine-resolved transitions
D. Hoffman,1 J. Taylor,1 T. J. Price,1,2 Robert C. Forrey,2 B. H. Yang,3 P. C. Stancil,3 Z. E.
Zhang,4 and N. Balakrishnan51Department of Physics, Penn State University, United States
2
Department of Mathematics and Technology, Alvernia University, United States
3
Department of Physics and Astronomy, University of Georgia, United States
4
Star and Planet Formation Lab, RIKEN, Japan
5
Department of Chemistry and Biochemistry, University of Nevada, United States
Hydrogen chloride (HCl) is a key repository of chlorine in the interstellar medium. Accurate
determinations of its abundance is critical to assessing the chlorine elemental abundance andconstraining stellar nucleosynthesis models. To aid in modeling recent and future
observations of HCl rovibrational spectra, we present cross sections and rate coefficients forcollisions between HCl and molecular hydrogen. Transitions between rovibrational states of
HCl are considered for temperatures ranging from 10 to 3000 K. Cross sections are computed
using a full dimensional quantum close-coupling (CC) method and a reduced dimensionality
coupled-states (CS) approach. The CS results, benchmarked against the CC results, are usedwith a recoupling approach to calculate hyperfine-resolved rate coefficients for rovibrationaltransitions of HCl induced by H2. The rate coefficients will allow for a better determination of
the HCl abundance in the interstellar medium and an improved understanding of interstellar
chlorine chemistry. We demonstrate the utility of the new rate coefficients in a
non-thermodynamic equilibrium radiative transfer model applied to observations of HClrovibrational transitions in a circumstellar envelope.

Poster 28   "  ! 
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,0',0*(0(4*,(55$4(&47&,$.2$4$/(6(456170'(456$0'6+((81.76,101)/1.(&7.$452(&,(5,0'(05(&.17'5 '(6(4/,0,0* 9+(6+(4 $ 52(&,(5 ,5 )41;(0 1061 6+( *4$,0 574)$&(5 14 )4(( ,0 6+( *$5 2+$5(19$'$:55$4(757$..:2418,'('$55,0*.(21,068$.7(519(8(46+(24('1/,0$06$/142+1750(551),&:*4$,05*,8(54,5(61$',564,%76,101)5,6(5$0'8$.7(506,.0195(8(4$.*4$,0/1'(.5+$8($22($4(',0.,6(4$674(%766+(:.$&-$&1/24(+(05,8(2+:5,&$.$0'5:56(/$6,&$.'(5&4,26,10(&(06.:$0$761/$6,&241&('74(615,/7.$6(4($.,56,&,&:*4$,05+$5%((04(.($5('"#+,5&1'($..1957561%7,.'72/1'(.51)$/142+175,&(7261$61/5$0'615,/7.$6($.$4*(8$4,(6:1)
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#(0-%+#&"+*/+,,'$"*%/"("/0-%./-+*+)1

Poster 29

Insights into the Third-Body Role of Interstellar Water Ices Mantles in Formamide
Formation Route
B. Martínez-Bachs,1 G. Pareras,1 J. Enrique-Romero,2 and A. Rimola1
1

Universitat Autònoma de Barcelona, Departament de Química, 08193 Bellaterra, Spain
2
Leiden Institute of Chemistry, Leiden, University, Leiden 2300 RA, The Netherlands

Ice mantles covering dust particles provide a solid-state support for chemical reactions in theInterstellar Medium. Such water ice surfaces can act as third bodies by absorbing the energy
released by surface reactions [1]. Indeed, the ability of ice mantles to absorb the energy released
by surface reactions is a crucial factor that will determine the fate of the newly formed species.
These species can either remain adsorbed on the ices or be desorbed and ejected into the gas
phase, as is commonly assumed by astrochemical models [2-4]. In this contribution, we analyze
the third-body role of water ice mantles for a particular reaction: the radical-radical coupling
between NH2 and HCO leading to the formation of formamide. This mechanism presents a low
energy barrier and is largely exothermic [5]. Its potential energy surface has been characterized
on an amorphous water ice model using static quantum chemical methods. Ab initio molecular
dynamics simulations have been performed to elucidate how the nascent reaction energy is
dissipated through the amorphous water ice model. Results indicate that the energy release by
the reaction is effectively absorbed and dissipated by water ices, and therefore, the energy
reaming on the newly formed formamide is not large enough to cause its ejection into the gasphase.

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

A. Potapov and M. McCoustra, 2021, Int. Rev. Phys. Chem., 40, 299.
S. Pantaleone et al., 2020, Astrophys. J., 897, 56.
S. Pantaleone et al., 2021, Astrohpys. J., 917, 49.
S. Ferrero et al., 2023, Astrophys. J., 944.2, 142.
J. Enrique-Romero et al., 2019, ACS Earth Space Chem., 3, 2158.

Poster 30

Cracking the Puzzle of CO2 Formation on Interstellar Ices
G. Molpeceres, 1 J. Enrique-Romero, 2 and Y. Aikawa.1
1

2

Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113
0033, Japan

Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, PO Box 9502, 2300
RA Leiden, The Netherlands

The formation of an ice layer on top of interstellar dust grains is a central topic in astrochemistry.
The chemical composition of interstellar ices varies over time [1], and the dominance of polar
or apolar fractions in them is important for several surface properties, like adsorption, diffusion
or reaction. Among the most abundant components of interstellar ice we find H2O, CO, CH3OH
or CO2, to give some examples. These molecules can be formed in situ on interstellar ices, as itis the case of H2O or CH3OH, or can land on the ices after formation in the gas, like CO.
Experiments show that CO2 mainly forms via surface reactions (see, for example [2]), e.g. theCO + OH à CO2 + H reaction. In this talk I will review our recent calculations on such reaction[3]. I will cover the reactivity on a CO and H2O ice, showing that the reaction does not proceed
directly in neither of them. In reality, the reaction stops at the very stable HOCO radical that
may be later transformed into CO2 via a H abstraction reaction. The H2O ice is found to be abetter substrate for the formation of HOCO, which can be behind the higher abundance of thepolar component of CO2 found in astronomical observations, in comparison with the apolar one[4].

Figure 1: Stationary points in the potential energy surface for the CO + OH à CO2 + H reaction on water(left) and CO ice (right).

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

Boogert, A.C.A., Gerakines, P.A., Whittet, D.C.B., 2015, Ann. Rev. Astron. Astrophys. 53, 541–581.
Oba, Y., Watanabe. N., Kouchi. A., et al., 2023, Astrophys. J., 712, 2, L174–L178.
Molpeceres, G., Enrique-Romero, J., Aikawa, Y. 2023, Astron. Astrophys, 677, A39.
McClure, M.K., Rocha, W.R.M., Pontoppidan, K.M. et al., 2023, Nature Astron 7, 431–443.

Poster 31

Studying shell structure in CO outflows in the eDisk survey
A. Feeney-Johansson1
1Department of Astronomy, The University of Tokyo, Japan

In star formation, jet and outflows play a key role, as they extract angular momentum fromthe protostar-disk system while injecting energy and momentum into the surrounding cloudand envelope [1]. In many sources, evidence for variation in the mass-loss rate of the
protostar is seen, most commonly in the form of series of knots along the axis of the jet,which are thought to be caused by internal shocks in the jet due to variations in the jet velocity.
Since the accretion rate and mass-loss rate of protostars are thought to be closely related,these variations in mass-loss rate are therefore thought to trace variations in the accretion rateof the protostar. As well as knots in the jet, variation in the mass-loss rate has been seen in theform of wide-angle shell structures in molecular outflows, such as in the HH 46/47 outflow,which are believed to trace the entrainment of ambient gas by a series of outbursts in awide-angle wind from the protostar and disk[2][3].
We take advantage of the high-resolution 12CO data obtained in the ALMA Large Program“eDisk” to search for similar shell structures in molecular outflows from low-mass protostars.
Out of the 19 sources, 6 sources seem to show some level of shell structure in their outflows
similar to that seen in previous studies. For three of these source: CB68, GSS30 IRS3, andIRAS32, we were able to fit the shell structure seen with a model which assumes that theshells are caused by previous outbursts in the outflow which entrained ambient gas, as wasseen in HH46/47. In CB68, shell models fitted to the data suggest two previous outbursts
occurred ~160 yrs ago and ~300 years ago respectively. In Figure 1, the position-velocity
diagram along the axis of the outflow shows the two shell models which were fitted. For theother 3 sources, where shell structure was detected, it wasn’t possible to fit the shells observedwith the entrained ambient gas model, and so alternative explanations are required for the
structure detected.

Figure 1: The position-velocity diagram along the outflow axis of CB68 showing the two shell models
fitted to the data, tracing the outbursts launched ~160 years ago (red) and ~300 years ago (orange).

References

[1]
[2]
[3]

Frank A. et al., 2014, Protostars and Planets VI (University of Arizona Press), p.451-474
Zhang, Y., Arce H. G., Mardones D. et al., 2019, ApJ, 883, 1.
Lee, C.-F., Mundy, L. G., Reipurth, B., Ostriker, E., Stone, J. M., 2000, ApJ, 542, 925

Poster 32

ALMA Unbiased Spectral Line Survey of an Organic-poor High-mass Protostar
in the Large Magellanic Cloud
T. Shimonishi,1 H. Kaneko,1 Y. Aikawa,2 Y. Nishimura,2Y. Watanabe,3 N. Sakai,4 T. Onaka,2 and S. Yamamoto5,6
1

Institute of Science and Technology, Niigata University
Department of Astronomy, The University of Tokyo, Japan
3
College of Engineering, Shibaura Institute of Technology, Japan
4
RIKEN Cluster for Pioneering Research, Japan
5
Department of Physics, The University of Tokyo, Japan
6
Research Center for the Early Universe, The University of Tokyo, Japan2

Because cosmic metallicity is increasing in time with the evolution of the Universe,
understanding interstellar chemistry in low metallicity environments is crucial to unveil
chemical processes in past metal-poor galaxies and the early Milky Way Galaxy.
We here present a high-sensitivity spectral line survey towards a high-mass protostellar object
located in a nearby low-metallicity galaxy, the Large Magellanic Cloud (LMC). The survey
was conducted by the Atacama Large Millimeter/submillimeter Array (ALMA). The
frequency coverage of the survey is from 333 to 364 GHz and the spatial resolution is about
0.4 arcseconds, which corresponds to 0.1 pc at the distance of the LMC. The target source,
ST11, is reported to harbor a hot molecular core [1].
As a result of the spectral line survey, we have obtained a high-quality wide-band
submillimeter spectral and continuum data for this low-metallicity high-mass protostar. Its
physical and chemical characterstics are investigated in detail using the detected various
molecular lines. The high gas density (>10^6), high temperature (>100 K), and small source
size (<0.1 pc) observed in ST11 suggest that its physical characteristics are consistent withthose of known normal-metallicity hot cores in the inner Galaxy. However, unlike typical hot
cores, the source does not show any emission line of complex organic molecules such as
CH3OH even after the stacking analysis of multiple lines. Only small organic molecules suchas H2CO are detected. On ther other hand, inorganic molecules such as SO and SO2 areabundantly detected in the source. Several hydrogen recombination lines are also detected.
In this poster, we present the results of the initial analysis of the spectral line survey, anddiscuss the nature of this organic-poor high-mass protostar.
References[1]

T. Shimonishi, T. Onaka, A. Kawamura, & Y. Aikawa, 2016, ApJ 827, 72.

Poster 33

Millimeter emission in the methanol maser flare source G24.33+0.14
T. Hirota1,2, Maser Monitoring Organization (M2O)31

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Japan
2
The Graduate University for Advanced Studies, SOKENDAI, Japan3
https://www.masermonitoring.com

In September 2019, a sudden brightening of the 6.7 GHz methanol maser line (methanol
maser flare) was reported for the high-mass young stellar object (HMYSO) G24.33+0.14. It issuggested that this event would be caused by a transient mass accretion burst event in
HMYSOs as reported for other HMYSOs, S255IR NIRS3, NGC6334I-MM1, and G358.930.03-MM1. Among them, G24.33+0.14 seems to be a unique case because it has been
identified a past maser flare event with an interval of 8-year. In the case of another recent
methanol maser flare event in G358.93-0.03-MM1, several methanol transitions from
centimeter to submillimeter wavelengths also showed flare activities. To study timevariability of methanol maser lines at millimeter wavelengths in G24.33+0.14, we conducted
target-of-opportunity (ToO) observations using the Atacama Large Millimeter/submillimeter
Array (ALMA) as a director's discretionary time (DDT) [1]. We observed the millimeter
continuum and molecular lines at Band 6 (217-230 GHz) toward G24.33+0.14 in the pre-flarephase in August 2016 (Cycle 3) and the mid-flare phase in September 2019 (Cycle 6 DDT) at
resolutions of about 300 milliarcseconds.
We identified 3 continuum sources in G24.33+0.14, where the brightest source, C1, is
associated with the 6.7 GHz maser emission. The continuum sources show only marginalincreases in flux density with a mean flux ratio (Cycle 6/Cycle 3) of 1.16. In addition, we also
compared the total 26 millimeter transitions from 13 molecular species between the Cycle 3
and Cycle 6 data and found similar levels of flux differences of ~12%. Considering the flux
calibration accuracy of ALMA, 10%, these differences would not be significant. On the otherhands, we investigated 8 methanol lines identified in our observing band including a 13C
isotopologue and a torsionally excited transition and found an average flux ratio (Cycle
6/Cycle 3) of 1.23+/-0.13. There is a possible tendency that the higher excitation lines show alarger flux increase in Cycle 6. If this systematic trend is real, it would suggest radiative
heating close to the central HMYSO caused by the accretion event which could expand thesize of the emission region and/or change the excitation conditions.

Figure 1: A sample spectrum of G24.33+0.14 [1].

References[1]

T. Hirota, Wolak, P, Hunter, T. R., et al. 2022, PASJ, 74, 1234.

Poster 34

50 au-scale Chemical Composition of R CrA IRS7B-a: FAUST
Y. Watanabe,1 Y. Oya,2 L. Podio, 3 S. Yamamoto, 4 and FAUST members
1

Department of Material Science, Shibaura Institute of Technology, Japan
2
Yukawa Institute for Theoretical Physics, Kyoto University, Japan
2
INAF, Osservatorio Astrofisico di Arcetri, Itaryn
2
The Graduate University for Advanced Studies SOKENDAI, JapanThe diversity of chemical compositions among Solar-like protostars has been recognized byrecent high angular resolution and high sensitivity observations of ALMA. R CrA IRS7B is a
low-mass protostar in the Class 0/I stage in Corona Australis (d = 152 pc: Galli et al. 2020).
The protostar is thought to be strongly irradiated by a Herbig Ae star R CrA at a distance ofabout 4000 au from IRS7B-a. In fact, the temperature of extended molecular gas component
around the protostar is estimated to be about 50 K, which is higher than that of typical dense
molecular clouds, by H2CO observation with APEX and SMA (Lindberg et al. 2012).
Moreover, CCH and CN, which are characteristic molecular species in the photodissociation
region, are strongly detected at the protostar position by spectral line survey observations
ASTE and APEX telescopes (Watanabe et al. 2012, Lindberg et al. 2014).
We have observed the protostar IRS7B at a scale of 50 au, as one of 13 target sources of
ALMA large program FAUST (Fifty AU STudy of the chemistry in the disk/envelope systemof solar-like protostars). The ALMA observation detected two continuum sources as Ohashi
et al. (2023) reported. SO and C18O are associated with the strongest continuum peak IRS7Ba and show a rotation motion of a Keplerian disk. On the other hand, the emission lines of
CH3OH and CS are weakly detected and no complex organic molecules (COMs) found in Hot
Corinos are detected at IRS7B-a. One possible origin of the deficiency of COMs is that theformation of COMs is suppressed due to inefficient adsorption of molecules under the hightemperature environment by strong UV radiation during the starless phase. Moreover, wefound that carbon-bearing sulfur molecules, such as CS, H2CS, and OCS are deficient in
IRS7B-a compared with a typical Hot Corino source IRAS 16293-2422 while the abundanceof SO2 relative to SO is similar to each other. In this poster, we will discuss the chemical
characteristics in this source at a scale of 50 au.
References
[1]
[2]
[3]
[4]
[5]

P.A.B. Galli et al., 2020, A&A, 634, A98.
J. Lindberg et al., 2012, A&A, 548, 24.
J. Lindberg et al., 2015, A&A, 584, 28.
N. Ohashi et al., 2023, ApJ, 951, 8.
Y. Watanabe et al., 2012, ApJ, 745, 126.

Poster 35

Amides inventory towards the G+0.693-0.027 molecular cloud1

S. Zeng,1 et al.
Star and Planet Formation Laboratory, RIKEN, Japan

Interstellar amides, species that contain peptide-like bond, have attracted significant attentions
as they are potential precursors for a wide variety of organics essential to life. However,detection of several amides from the same regions are still relatively sparse and they aremostly biased towards the physical conditions of star-forming regions (e.g. [1-3]. The
chemical networks that include amides may therefore lack of further constraints to elucidate
the chemical link between these species and the interplay with the physical conditions
especially at earliest stage of star formation.
In this talk I will report the detection of a series of amide species, including HC(O)NH2,
CH3C(O)NH2, CH3NHCHO, and NH2C(O)NH2 towards the chemically rich Galactic Centre
molecular cloud G+0.693-0.027 [4]. From the comparison with other sources as well as works
from laboratory experiments and chemical models, we find constant abundance ratios
independently of the evolutionary stages, suggesting that amides related chemistry is triggeredin early evolutionary stages of molecular cloud and remain unaffected by the warm-up phaseduring the star formation process.

Figure 1: Amides species detected towards the molecular cloud G+0.693-0.027 as a result of the deep
unbiased spectral survey conducted with the Yebes 40m and IRAM 30m telescope.

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

Colzi L., et al., 2021, A&A, 653, A129
Ligterink N. F. W., et al., 2020, ApJ, 901, 37
Ligterink N. F. W., et al., 2022, ACS Earth and Space Chemistry, 6, 455
Zeng S., et al. 2023, MNRAS, 523, 1448

Poster 36

Detection of 13C17O line emission in the disk around the young outbursting protostar
V883 Ori by ALMA observations
S. Notsu,1,2 T. Tsukagoshi,3 H. Nomura,4 T. Hirota,4 M. Honda,5 E. Akiyama,6 A. S. Booth,7C. Walsh,8 T. J. Millar,9 S. Lee,10 J. Lee,11 Y. Yamato,1 Y. Aikawa,1 Y. Okoda,2 N. Sakai,2
1

2
Department of Astronomy, The University of Tokyo, Japan
Star and Planet Formation
3
4
Laboratory, RIKEN, Japan
Ashikaga University, Japan
National Astronomical
5
6
Observatory Japan, Japan
Okayama University of Science, Japan
Niigata Institute of7
Technology, Japan
Harvard-Smithsonian Center for Astrophysics, USA 8University of
9Leeds, UK
Queen’s University Belfast, UK 10Korea Astronomy and Space Science
Institute, Korea 11Seoul National University, Korea

Understanding the spatial distribution of gas and mass evolution in protoplanetary disks are
essential for elucidating the formation and evolution processes of planetary systems.
Therefore, a lot of statistical observations of the disk gas distribution using 13C16O and12C18O emission lines have been carried out (e.g., [1]). However, if these emission lines are
optically thick, the disk gas mass will be underestimated. Here, by using the 13C17O
emission line, which is the rarest and thus most optically thin among the stable carbon
monoxide isotope species, it becomes possible to measure the gas mass with higher precision,
including disk midplane. In recent ALMA observations, the 13C17O emission line was
detected for the first time in two protoplanetary disks (HD 163296: [2]; HL Tau: [3]), and theestimated disk masses are about 2-10 times heavier than those estimated from previous
12C18O emission line observations. In this presentation, we report the detection of the
13C17O J=3−2 emission line by ALMA observations (Band 7 (~0.9 mm), spatial resolution:~0.3-0.4”) in the disk around the Class I protostar V883 Ori, a typical young outbursting FU
Ori type star. We found that the 13C17O line emission has ring-like distribution within thedisk surrounding the optically thick dust emission (radius r~40 au) near the protostar, similar
to the 12C17O line emission line obtained in past observations ([4]). In addition, the 13C17O
line emission extends further to the outside of the disk (r~200 au) compared with H2O andCH3OH line emission (r~80 au). We derived the column density and the total gas surface
distributions in the disk radial direction, and discuss the gas to dust mass ratio G/D, Toomre Q
values (= Index of gravitational stability in the disk), and 12C/13C isotope ratio in the V883
Ori disk. We also conduct the comparative discussion of the 12C/13C ratio between CO (thisstudy) and complex organic molecules (Yamato, Notsu et al. in prep.).
References

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

A. Miotello et al. 2017, A&A, 599, A113.
A. Booth et al. 2019, ApJL, 882, L31.
A. Booth & J. Ilee. 2020, MNRAS, 493, L108.
J. Tobin, 2023, Nature, 615, 227.

Poster 37

Complex Carbon Isotope Fractionation in a Protoplanetary Disk
T. C. Yoshida,1,2 H. Nomura,1,2 K. Furuya,1 T. Tsukagoshi,3 R. Teague,4 C. Law5, S. Lee6, K.
Öberg7, C. Rab8,9, and R. Loomis10
1

National Astronomical Observatory of Japan
Graduate University for Advanced Studies (SOKENDAI), Japan
3
Ashikaga University, Japan
4
Depertment of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute ofTechnology, USA
5
Depertment of Astronomy, University of Virginia, USA
6
Korea Astronomy and Space Science Institute (KASI), Republic of Korea
7
Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA
8
University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München,
Germany
9Max-Planck-Institute fur Extraterrestrische Physik, Germany
10
National Radio Astronomy Observatory, USA
2

Chemical information is vital to understanding material evolution during planetary systemformation. Specifically, isotopologue ratios are of interest because they could conserve theformation history of molecules, linking the planetary system bodies and their birthenvironment, protoplanetary disks. Hereafter, we focus on the carbon isotope ratio, 12C/13C, inthe gas phase of the nearest protoplanetary disk around TW Hya. Recent measurement
suggests that significant carbon isotope fractionation occurred in this disk while the 12C/13C
ratio in the local interstellar medium (ISM) is ~70. Zhang et al. (2017) and Yoshida et al.
(2022) found significantly low 12C18O/13C18O and 12CO/13CO of 20-40. On the other hand,
H12CN/H13CN is estimated to be ~86 by Hily-Blant et al. (2019).
In this talk, we present the first spatially-resolved detection of 13CN with the Atacama Large
Millimeter/sub-millimeter Array. By combining archival 12CN observations, we derived the12
CN/13CN ratio to be ~70 with non-local thermal equilibrium (non-LTE) modeling.
Additionally, we found tentative evidence of a dip of 12CN/13CN at ~100 au, where the ratio
decreases to ~50.
Different molecules exhibit different carbon isotopologue ratios in the TW Hya disk. In termsof the molecular column densities, the main carbon carrier in the gas phase is CO. Therefore,
if the bulk carbon isotope ratio is the same as the ISM value, there are significant amount of
hidden 12C in the solid phase. This might be caused by an isotope exchange reaction between
CO and carbon ions under the environment where the carbon-to-oxygen ratio (C/O) is larger
than unity in the past. The higher isotopologue ratios found in other molecules would be
explained by the isotope exchange reaction and/or vertical variation of the C/O ratio. Indeed,
our non-LTE modeling implies that the CN line traces the disk atmosphere rather than near
the midplane where CO isotopologue measurement traces. This study sheds light on complex
carbon isotope fractionation patterns, requesting a more detailed understanding of the isotope
chemistry.
References
[1]
[2]
[3]

Zhang et al., 2017, Nat. Astron., 1, 0130
Yoshida et al., 2022, ApJ, 932, 126
Hily-Blant et al., 2019, A&A, 632, L12

Poster 38

Molecular Formation in Low-Metallicity Hot Cores
Y. Sobhy, 1 H. Nomura,2 T. Yamamoto,3 and O.M. Shalabeia1,41

Department of Astronomy, Space Science and Meteorology, Cairo University, Egypt
2
Division of Science, National Astronomical Observatory of Japan, Japan
3
Institute of Low Temperature Science, Hokkaido University, Japan
4
Faculty of Navigation Science and Space Technology, Beni-Suef University, Egypt

The chemical complexity in low-metallicity hot cores has been confirmed by observations.
We investigate the effect of varying different physical parameters, such as temperature,density and cosmic ray ionization rate (CRIR), on the molecular abundance evolution in the
low-metallicity hot cores using UMIST gas-phase chemical model. CRIR has the strongest
effect on the molecular abundances. The resulted molecular abundances were divided into
three categories with different trends in time evolution. We compare our results with theobservations of hot cores in Large Magellanic Cloud (LMC). Our model fits the best with theobservations at a time around 105 years after the evaporation of ices and at the CRIR of
1.36×10−16 s−1. The resulted abundances of the oxygen-bearing Complex Organic Molecules(COMs), such as CH3OH, HCOOCH3 and CH3OCH3, don’t fit with observations in the same
physical condition and may locate in different physical environment. Our results suggest thatinvestigating the CRIR value is crucial in predicting the molecular evolution in the LMC hot
cores.

Poster 39

Theoretical investigation of the formation pathways of (Z)-1,2-ethenediol andglyceraldehyde
JC. Del Valle1, P. Redondo2, J. Kästner1 and G. Molpeceres3
1

2

Institute for Theoretical Chemistry, University of Stuttgart, Germany
Computational Chemistry Group, Departamento de Química Física y Química Inorgánica,
Facultad de Ciencias, Universidad de Valladolid, Spain
3
Department of Astronomy, Graduate School of Science, The University of Tokyo, JapanThe origin of life in our planet is one of the holy grails of chemistry [1]. Regions between
stars are hypothesized to have furnished prebiotic molecules to Earth, which further
developed into life-bearing compounds. The RNA-world hypothesis proposes that early lifeon Earth was based on the versatility of RNA molecules to both hold information and act as
catalysts [2]. Glyceraldehyde, a key precursor in the RNA-world chemical scheme, is
proposed to be formed from (Z)-1,2-ethenediol, detected towards the G+0.693-0.027
molecular cloud located in the galactic center [2].
A set of reactions leading to formation of (Z)-1,2-ethenediol and its evolution toglyceraldehyde both in the gas phase and on grain surface has been considered. We model
grain surface reactions using a two-water molecule cluster model. We report possible
formation pathways of (Z)-1,2-ethenediol from simple radical species and discard enolizationof glycolaldehyde. The addition of the OH radical to vinyl alcohol furnishes two stablespecies, that following H-insertion and abstraction reactions, yield cis-ethyleneglycol and (Z)1,2-ethenediol under ISM conditions. Formation of L and D-glyceraldehyde is also proved
successful from (Z)-1,2-ethenediol and glycolaldehyde.
This work provides an efficient and cost-effective view of the formation of key prebiotic
species in the RNA-world scheme. Further work on the OH addition to vinylol is currently
been performed, focusing on the improvement of the ice-slab and its relationship with thestereoselectivity of the formation of 1,2-ethenediol.

References
[1]
[2]
[3]

Burrows, C.J. Acc. Chem. Res. 2017, 50, 3, 445
Gilbert, W. Origin of life: The RNA world. Nature 319, 618 (1986).
Rivilla, V.M. et al 2022 ApJL 929 L11

Poster 40

Chemistry of Forming Molecular Clouds: Comparison with Molecular Absorption Lines
Y. Komichi,1 Y. Aikawa,1 K. Iwasaki,2 and K. Furuya
1

2

Department of Astronomy, the University of Tokyo, Japan
Division of Science, National Astronomical Observatory of Japan, Japan

Molecular clouds are formed by the compression of atomic gas by interstellar shockwaves.
This process is intensively studied using MHD simulations in recent years (e.g. [1]). Whilethese studies include the formation and destruction of major coolants (e.g. O atom, C+, andCO), they do not include less abundant molecules (e.g. carbon-chains) that are observed andused for chemical diagnosis of molecular clouds. So far more than a hundred molecularspecies are detected in interstellar clouds, and their abundances and spatial distributions areused to investigate the physical conditions and evolutionary stage of clouds.
We aim to fully understand the chemistry in the molecular cloud formation process, including
the less abundant molecules for the chemical diagnosis. In the present study, we investigate
the chemistry in the shock-compressed layer of Av ≤ a few mag, which corresponds to diffuse
clouds, as a first step. We perform 3D MHD simulations of converging atomic gas flow. We
analyze the results to derive the 1D mean flow, along which we solve the detailed chemical
reaction network. Compared with previous studies on 1D shock model of cloud formation (e.g.
[2], [3]), we cover a wider range of shock parameters such as initial gas density, velocity, andthe angle between the gas flow and magnetic field.
We derive the column densities of various species such as HCO+ and C3H2 along the mean
flows and compare them with the observations of molecular absorption lines of diffuse clouds
observed toward field stars and quasars (e.g. [4]). The column densities vary among the shock
parameters, depending on density structures of post-shock regions and timescales of Av. Theyshow reasonable agreement with the observations. We also investigate the dependence ofchemistry on cosmic-ray ionization rate, elemental abundance, and PAHs.
References

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

Iwasaki, K., Tomida, K., Inoue, T., & Inutsuka, S. 2019, ApJ, 873, 6
Bergin, E. A., Hartmann, L. W., Raymond, J. C., & Ballesteros-Paredes, J. 2004, ApJ, 612, 921
Hassel, G. E., Herbst, E., & Bergin, E. A. 2010, A&A, 515, A66
Riquelme, D., Bronfman, L., Mauersberger, R., et al. 2018, A&A, 610, A43,

Poster 41

From Stardust to Life: Decoding the Role of Ionic Minerals on the Formation ofPrebiotic Molecules
E. Mates-Torres,1 and A. Rimola1
1

Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia,
Spain

Interstellar grains and cometary and meteoritic seeds have undoubtedly been found to be key
for the formation of interstellar simple and complex organic molecules (iCOMs) [1]. To thisdate, over 200 molecular species have been identified in our galaxy and beyond [2]. Many
studies have focused on identifying the effect that the interstellar bodies play on the formation
process of these molecules; however, computational studies have mainly focused on the roleof the icy surfaces that usually surround them, for at initial stages of planetary formation,these have been shown to provide surface sites where primordial molecules adsorb, diffuse
and eventually react.
In our study, the vast diversity of materials present in the currently analysed stellar objects
and the predicted presence of liquid water and exposed mineral surfaces in the latter stages ofplanetary evolution [3] led us to assess how the solid surface of interstellar, cometary andmeteoritic grains interact with the molecular species in the interstellar medium. While theformer are usually composed of silicates and pyroxenes of different compositions, ca. 275
different minerals have been found to constitute the latter two [4]. In order to thoroughly
study this variety of surface compositions and interacting molecular species, we propose anovel and unexplored approach to automatically investigate, using state-of-the-art quantum
chemistry simulations, how most molecules in the observed universe interact with the known
surface compositions. This thorough analysis will lay down the path to rationalise theabundance of certain molecular species in meteoritic samples, as well as provide a foundation
for the investigation of how very complex molecular species, such as amino acids and sugars,
are formed along the planetary formation stages.

References[1]
Molpeceres, G.; Rimola, A.; Ceccarelli, C.; Kästner, J.; Ugliengo, P.; Maté, B. MNRAS 2019, 482, 5389–
5400.
[2] McGuire, B. A., Astrophys. J., Suppl. Ser. 2022, 259, 51.
[3] Muneishi, K. et al., Meteorit. Planet. Sci. 2021, 56, 195–205.
[4] Rubin, A. E., Meteorit. Planet. Sci. 1997, 32, 231–247.

Poster 42

Gas-Grain Model for Carbon Isotope Fractionation of COMs in Star-Forming Cores
R. Ichimura,1,2 H. Nomura,1,2 and K. Furuya1
1

2

Division of Science, National Astronomical Observatory of Japan
Department of Astronomical Science, The Graduate University for Advanced Studies,
SOKENDAI

Understanding the isotopic composition of ice molecules in star-forming cores is a powerfultool for investigating the origin of organic molecules in solar system objects. Recent
high-resolution ALMA observations have measured the carbon isotopic ratios (12C/13C) of
Complex Organic Molecules (COMs) in the Class 0 low-mass protostellar object IRAS
16293-2422B. The measured isotopic values are comparable to the average values in the local
interstellar medium or show lower values, that is enriched in 13C. Several model calculations ,observations, and laboratory experiments suggest that COMs are formed on the dust grainsurface during star-formation. However, there are no model calculations of carbon isotope
fractionations of COMs, and the origin of observed fractionations is not well understood.
In this study, we use a physical model of a star-forming core undergoing gravitational
contraction, and performing chemical reaction network calculations considering three phases:
the gas phase, the grain surface, and the ice mantle. And then we systematically investigate
the carbon isotopic fractionations of COMs including formation of icy COMs prior to starformation and subsequent their sublimation into the gas phase following star formation.
Before the protostar formation, the 12C/13C ratios of icy small carbon species exhibit bimodal
profile: the derivative species from CO are slightly enriched in 13C, while those succeededfrom C and C+ are depleted in 13C owing to isotope exchange reactions. Icy COMs,
originating from simpler species, also show this bimodality or deviation from it due to mixing.
Sublimated COMs reflect the 12C/13C ratios of their icy counterparts. However, parts ofCOMs originate from radical and ionised species at higher temperature (T > 20 K), whichchange the 12C/13C ratios of the molecules from that of their ice in the prestellar phase.
Eventually, in our base model COMs exhibit more fractionated rather than the observed value.
The additional Eley-Rideal (ER) reactions, which is a grain surface reaction having occurredat shorter timescales relative to isotope exchange reactions, lead to formation of COMs
originated from less fractionated atomic carbon.
Consequently, the ER reactions mitigates isotope fractionation, and roughly reproduces thenon-fractionated observed values. Nonetheless, further investigation is necessary to reproduce
the observed values more comprehensively.

Poster 43

The impact of high-mass protostellar accretion bursts on the physical conditions in the
ISM in high-mass star forming regions
R.Burns,1 N. Sakai,1 and O. Bayandina2
1

RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198,
Japan
2
INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

High-mass protostellar accretion bursts are rare and energetic events which drive increased
radiation. Due to the scarcity of studied events their impact on the surrounding ISM is notwell documented. However, very recently a handful of accretion events have been
investigated and clear evidence of the effects of irradiation has been observed in both the
10-1000 AU regions within the disk of the accreting protostars, out to influencing the physicalconditions of other protostars 1000s of AU away. In this contribution we present evidence of
the affects of high-mass protostellar bursts on the ISM regions of high-mass star formation.