Complex organic chemistry in star-forming regions
A. Coutens1
1Department of Physics and Astronomy, University College London, UK

Complex organic molecules may play a key role in the emergence of life. They are detected invarious astrophysical environments (e.g., low- and high-mass star-forming regions, prestellar
cores, outflows, comets). In particular, they are found to be highly abundant in the warm inner
regions of protostars, where planets are expected to form. These molecules may survive
during the star formation process and be incorporated into asteroids and comets, which coulddeliver them to planetary embryos through impacts.
The formation mechanisms of complex organic molecules are however debated. Observations
and chemical modelling are helpful to constrain how these species form. In particular,
measurements of isotopic fractionation (especially deuteration) and relative abundance ratios
of isomers or related species can help to distinguish between different routes. The detection ofless abundant isotopologues and isomers can, however, be difficult. With the Atacama Large(Sub-)Millimeter Array (ALMA), it is now possible to detect them. The Protostellar
Interferometric Line Survey (PILS) is a large spectral survey of the solar-type protostar IRAS
16293-2422 carried out with ALMA [1]. In the framework of this program, the deuterated
forms of formamide (NH2CHO) and glycolaldehyde (CH2OHCHO) were detected for the
first time [1,2]. Ethylene oxide (C2H4O) and propanal (CH3CH2CHO), the isomers ofacetaldehyde (CH3CHO) and acetone (CH3COCH3) respectively, were also found for the
first time towards a low-mass protostar [3]. In the first part of this talk, I will present theresults of these recent studies and I will discuss the possible formation pathways of these
species.
In the second part, I will show the results obtained with the gas-grain chemical code UCL
Chem to constrain the formation pathways of a few complex O-bearing species (e.g.,
glycolaldehyde, ethylene glycol, methyl formate) detected in various star-forming regions [4].

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

J. K. Jørgensen, M. H. D. van der Wiel, A. Coutens et al., 2016, A&A in press
A. Coutens, J. K. Jørgensen, M. H. D. van der Wiel et al., 2016, A&A 590, L6
J. M. Lykke, A. Coutens, J. K. Jørgensen et al., submitted to A&A
V. M. Rivilla, M. T. Beltran, R. Cesaroni, et al. 2016, A&A in press

Exploring Molecular-Cloud formation with OH 18 cm transition
Y. Ebisawa,1 N. Sakai,2 Y. Watanabe,1 K. Menten3 and S. Yamamoto1
1

Department of Physics, The University of Tokyo, Japan
Star and Planet Formation Laboratory, RIKEN, Japan
3
Max-Planck-Institut für Radioastronome, Germany

2

Recently, we found that the OH 18 cm transition can be used as an excellent
thermometer of the molecular gas in a wide range of the H2 density from 102 -107 cm-2([1] Ebisawa et al. 2015). The OH 18 cm transition consists of the four hyperfine
components, and their relative intensities are sensitive to the gas kinetic temperature.
For instance, we found a clear absorption feature of the 1612 MHz line against thecosmic microwave background (CMB) toward the translucent cloud eastward of Heiles
Cloud 2 (HCL2). By using the statistical equilibrium analysis, we determined the gas
kinetic temperature to be 53-60 K in this source, which is apparently higher than that ofdense cores. This method was also applied to the dark molecular cloud L134N and thephotodissociation region of the rho-Ophiuchi molecular cloud, and the existence of thewarm molecular gas surrounding the dense cores were revealed. All these results
suggest that the OH 18 cm transition traces a new class of warm molecular gas, which ispossibly related to the formation processes of molecular clouds.
Then, we applied this technique to the outstanding straight structure in the northern partof HCL2 to explore its origin (Figure 1 left). Interestingly, we detected the 1720 MHz
line in absorption toward the straight structure (Figure 1 right). According to our
statistical equilibrium analysis, the 1720 MHz line absorption traces a dense and cold
(Tk < 30 K) part of the cloud surrounded by a warm envelope gas. Combined analysesof OH, 13CO and C18O suggest that the straight structure would be formed bycompression of a warm envelope gas extending to the southwestern part of HCL2.
These results demonstrate that the OH 18 cm transition can be used to study
molecular-cloud formation.

Figure 1: (left) The integrated intensity map of 13CO (J=1-0) (color) and C18O (J=1-0) (contours) in HCL2.
(right) Spectra of the OH 18 cm transition observed toward TMC-1FN (white circle in the left panel).

References[1] Y. Ebisawa, H. Inokuma, N. Sakai, et al. 2015, ApJ, 815, 13

Deuterium Fractionation in the Earliest Stages of High-Mass Star Formation
T. Sakai,1 K. Furuya,2, P. Sanhueza,3 N. Sakai,4
T. Hirota,3 Y. Aikawa,2, Y. Watanabe,5 J. Foster,6
J. Jackson7, S. Yamamoto5
1
The University of Electro-Communications, Japan
2
University of Tsukuba, Japan
3
National Astronomical Observatory of Japan, Japan
4
RIKEN, Japan
5
The University of Tokyo, Japan
6
Yale University, USA
7
The University of Newcastle, Australia
High-mass stars release a huge amount of energy to interstellar space by outflows, UV
radiation, stellar winds and supernovae, so that high-mass stars play important roles in
evolution of galaxies. Understanding high-mass star formation is one of the most important
issues for astronomy. For the purpose, it is crucial to understand the initial conditions,because expected initial conditions are different among the current proposed models ofhigh-mass star formation (turbulent core accretion model and competitive accretion model).
To investigate the initial conditions of high-mass star formation, we focus on the deuterium
fractionation of molecules.
Recently, we conducted a molecular line survey, including DNC J=1-0 and HN13C J=1-0,
toward the candidates of high-mass starless clumps, which were recently identified by
Herschel observations (Traficante et al. 2015), by using the Nobeyama Radio Observatory 45
m telescope. Then, we found that there is diversity of DNC/HNC ratio among the observed
sources, although the temperature of the sources is as low as about 10 K. By comparing theobservational results with the chemical model calculation results, we suggest that the diversity
of DNC/HNC ratio could be due to the diversity of the formation timescale of dense cores.
In addition, we investigate how the chemical composition of hot cores depends on theinitial physical conditions. We compared the chemical composition of the hot core in the
Infrared dark cloud G34.43+00.24 MM3 (T. Sakai et al. 2013) with that of the other hot cores.
Then, we found that the D2CO/CH3OH abundance ratio of the G34.43+00.24 MM3 hot coreis higher than that of the Orion KL hot core. We suggest that the difference in
D2CO/CH3OH ratio is due to the difference in the initial conditions (i.e. timescale of coldstarless phase). We also discuss how the abundances of complex organic molecules in hot
cores depend on the initial physical conditions.
References[1][2]

Traficante et al. 2015, MNRAS, 451, 3089.
T. Sakai et al. 2013, ApJ, 775, L31.

Formation and isotope fractionation of interstellar ices, and their delivery to a forming
disk
K. Furuya1
1

Center for Computational Sciences, University of Tsukuba, JapanThe level of isotope fractionation in molecules provides insights into their formation
environments and how they formed [e.g., 1, 2]. In this presentation, we present results from aseries of astrochemical simulations from molecular clouds to forming circumstellar disks,considering isotope fractionation mechanisms and a layered ice structure [3, 4, 5]. Our main
focus is placed on deuterium fractionation, while, if time allows, we will also discuss nitrogenisotope fractionation. In our models, icy molecules are mostly formed in the prestellar stages,
and they are delivered to a disk or (partly) destroyed en route into the disk via thermal andstellar UV processing. The processing modifies the level of isotope fractionation in icy
molecules. The numerical results are compared with observational studies of objects at
various evolutionary stages.

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

Caselli, P., & Ceccarelli, C., “Our astrochemical heritage”, 2012, ARA&A, 20, 56
Willacy, K., Alexander, C., & Ali-Dib, M., et al., “The Composition of the Protosolar Disk and theFormation Conditions for Comets”, 2015, Space Sci Rev, 197, 151
Furuya, K., Aikawa, Y., Hincelin, U., et al., “Water deuteration and ortho-to-para nuclear spin ratio of H2
in molecular clouds formed via the accumulation of HI gas”, 2015, A&A, 584, 124
Furuya, K., van Dishoeck, E.F., & Aikawa, Y., “Reconstructing the history of water ice formation from
HDO/H2O and D2O/HDO ratios in protostellar cores”, 2016, A&A, 586, 127
Furuya, K., Drozdovskaya, M. N., Visser, R., et al., “Water delivery from cores to disks: deuteration as aprobe of the prestellar inheritance of H2O”, 2016, submitted to A&A

Dynamic assembly of cometary ices in protoplanetary disk midplanes
M. N. Drozdovskaya1, C. Walsh1, E. F. van Dishoeck1, K. Furuya1,
U. Marboeuf2, A. Thiabaud2, D. Harsono3, and R. Visser4
1

2

Leiden Observatory, Leiden University, The Netherlands
Center for Space and Habitability, Universität Bern, Switzerland
3
Heidelberg University, Germany
4
European Southern Observatory, Germany

Protoplanetary disk midplanes harbor the largest reservoir of icy dust grains that will beincorporated into planetary embryos and comets. The chemical content of these midplane icesoriginates in the prestellar phase and is shaped during the dynamic transport towards the disk
upon the onset of collapse, as shown by means of a sophisticated physicochemical model [1,2]. In this talk, results for two protoplanetary disks, one grown predominantly via viscous
spreading and another via pure infall, will be shown. The models predict that the amount of
CO2 can increase during infall via the grain-surface reaction of OH with CO, which isenhanced by photodissociation of H2O ice. Complex organic ices can be produced atabundances as high as a few % of H2O ice at large disk radii (R > 30 AU) at the expense of
CH3OH ice, meaning that current Class II disc models may be underestimating the complex
organic content. These simulations immediately imply that planet population synthesis
models may underestimate the amount of CO2 and overestimate CH3OH ices in planetesimals
by disregarding chemical processing between the cloud and disk phases. The model results
are used to derive the C/O and C/N ratios as a function of radius in midplanes of embedded
disks and are predicted to differ between the gas and solid phases. The two ice ratios show
little variation beyond the inner 10 AU and both are nearly solar in the case of pure infall (Fig.
1), but both are sub-solar when viscous spreading dominates. These models highlight theimportance of dynamics and chemistry in the embedded phase of star and planet formation forthe chemical budget of comets and planetary building blocks.

Figure 1: The midplane C/O and C/N ratios as a function of disc radius (R) in the gaseous (coral coloredlines) and solid (turquoise colored lines) phases at the end of the simulation (2.46×105 yr after the onset ofcollapse) for the infall-dominated disk. The locations of some snowlines are marked. The grey curves withdots and stars are the ratios in the gaseous and solid phases, respectively, as calculated with abundances ofsimple volatiles only (namely H2O, CO, CO2, CH3OH, CH4, N2 and NH3 only).

References[1]
M.N. Drozdovskaya, C. Walsh, R. Visser, D. Harsono, E.F. van Dishoeck, 2014, MNRAS 445, 913.
[2]
M.N. Drozdovskaya, C. Walsh, E.F. van Dishoeck, K. Furuya, U. Marboeuf, A. Thiabaud, D. Harsono, R.
Visser, 2016, MNRAS 462, 977.

How to measure snowlines and C/O ratio distributions in protoplanetary disks using
infrared spectroscopic observations
S. Notsu,1 H. Nomura,2 M. Honda3, C. Walsh4
1Department of Astronomy, Graduate School of Science, Kyoto University, Japan
2Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Japan
3Department of Physics, School of Medicine, Kurume University, Japan
4Leiden Observatory, Leiden University, The Netherlands
Protoplanetary disks are active environment for the creation of simple molecules (e.g., H2O,
CO, CO2, HCN) and complex organic molecules (COMs). The emission lines of these simple
molecules from disks are detected by the infrared spectroscopic observations using Spitzer
space telescope and large ground-based telescopes like VLT, Keck (e.g., [1])Since protoplanetary disks rotate with Keplerian velocity, the emissions from disks havecharacteristic profiles due to doppler shift. Analyzing the profiles of lines, we will obtain theinformation on the distance from the central star of the line emitting regions. We havecalculated the chemical structure of protoplanetary disks and H2O line profiles, and haveproposed the method to locate the position of the H2O snowline in the disk midplane using
high-dispersion spectroscopic observations. We have found that the H2O lines with small
Einstein A coefficients and relatively high upper state energies are dominated by emission
from the disk region inside the H2O snowline, and thus their profiles potentially contain
information which can be used to locate the position of the H2O snowline.[2][3].
It is thought that difference in snowlines of oxygen- and carbon-bearing molecules, such as
H2O, CO, CO2, HCN, will result in systematic variations in the C/O ratio both in the gas andice [4] [5]. In addition, the C/O ratio of atmosphere of some exoplanets (e.g., Hot Jupiter)
were estimated by recent studies [6]. Therefore, the planet forming regions could be confined
through comparing the radial distributions of C/O ratio in disks and those of planetaryatmospheres.
In this study, we developed our calculations of disk chemical structures, and investigated theabundance distributions of simple molecules. We then calculated various line profiles ofsimple molecules from disks. We found that through investigating the profiles of various
molecular lines with various Einstein A coefficients and upper state energies, we can confine
C/O ratio distributions in disks. For example, HCN lines from a Herbig Ae disk in 14µm band
reflect gas distributions of the outer disk. In contrast, HCN lines in 3µm bands reflect those of
the inner disk surface. We also discuss the possibility to measure such molecular lines with
future near- and mid-infrared spectroscopic observations.
References
[1]
[2]
[3]
[4]
[5]
[6]

K.M. Pontoppidan, C. Salyk, G. A. Blake et al. 2010, ApJ, 720, 887
S. Notsu, H. Nomura, D. Ishimoto et al., 2016a, ApJ, 827, 113
S. Notsu, H. Nomura, D. Ishimoto et al., 2016b, in prep.
K. M. Pontoppidan, C. Salyk, G. A. Blake et al., 2014, PPVI, Univ. of Arizona Press, 363
C. Eistrup, C. Walsh, E. F. van Dishoeck, 2016, A&A in press, arXiv:1607.06710
N. Madhusudhan, 2012, ApJ, 758, 36

CO observations toward debris disk candidates with ALMA/ASTE
A. Higuchi,1 H. Kobayashi,2 D. Ishihara, 2 S. Watanabe, 2 A. Sato, 3 M. Momose, 3
1

2

RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602,
Japan
3
College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito, 310-8512, Japan

From the recent survey of gaseous debris disks, 10 debris disks with gas have been discovered.
Our aim is to understand the origin of the gas in debris disk; (1) primordial: the remnant gasof protoplanetary disks[1], and (2) secondary: sublimation of dust grains[2].
We present the results of CO(2–1) and CO(3-2) observations toward debris disk
candidates made with ALMA and ASTE. We search for CO gas in debris disk candidates
identified by AKARI[3]. In addition, we analyzed ALMA archival data of CO line emission ofdebris disk candidates. Comparing physical properties and velocity structures of CO emissionin our sample with the famous debris disk of Beta Pic[4], we discussed the origin of origin of
the gas in debris disk.
References
[1]
[2]
[3]
[4]

K{¥'o}sp{¥'a}l, {¥'A}., Mo{¥'o}r, A., Juh{¥'a}sz, A., et al. 2013, ApJ, 776, 77
Kobayashi, H., Watanabe, S.-i., Kimura, H., & Yamamoto, T. 2008, icarus, 195, 871
Ishihara, D., Takeuchi, N., Kobayashi, H., et al. 2016, arXiv:1608.04480
Dent, W.R.F., Wyatt, M.C., Roberge, A., et al. 2014, Science, 343, 1490

Precise determination of the isotopic ratios of HC3Nin the massive star-forming region Sgr B2(M)Takahiro Oyama,1 Rin Abe,1 Ayane Miyazaki,1 Mitsunori Araki,1 Shuro Takano,2Nobuhiko Kuze,3 Yoshihiro Sumiyoshi,4 Koichi Tsukiyama,1 and Yasuki Endo5
1

Department of Chemistry, Tokyo University of Science, Japan
Department of Physics, College of Engineering, Nihon University, Japan3
Department of Materials and Life Sciences, Sophia University, Japan
4
Division of Pure and Applied Science, Graduate School of Scienceand Technology, Gunma University, Japan
5
Department of Applied Chemistry, National Chiao Tung University, Taiwan
2

Isotopic ratio is a critical parameter in understanding galactic chemical evolution. In particular,
C isotopic ratio of an organic molecule reflects its formation mechanism. In the present study,
we observed the simplest cyanopolyyne HC3N and its isotopomers in the massive star-forming
region Sgr B2(M) with Nobeyama 45 m radio telescope. Fig. 1 shows the observed peaks of
the J = 10−9 transition. The column density and the rotational temperature of HC3N were
determined to be 1.6 10 cm−2 and 163 K, respectively. The ratios of the column densities
for the 13C isotopomers were derived to be [H13CCCN]:[HC13CCN]:[HCC13CN] = 1:
04(4):1.01(4), where the rotational temperature was fixed to that of HC3N. The ratios are almost
the same. It is considered that the 13C isotope exchange reactions do not contribute to makeslight difference between the column densities of the three 13C isotopomers in the relatively
warm region Sgr B2(M). Therefore, we concluded that there is no isotopic fractionation for the
specific carbon atoms in HC3N. We also observed the transitions in the vibrational excited statesof HC3N. The rotational temperature of 352 K determined was obviously different from that ofthe vibrational ground state.
13

In addition, we observed the peak of the J = 10−9 transition of HC315N as shown in Fig. 1. The
N/15N ratio was tentatively determined to be ~99 in Sgr B2(M), which agrees with that
estimated by Adande et al (123.8 37.1) [1]. It is considered that this ratio reflects differenceof nucleosynthesis processes between 14N and 15N atoms.

4

H13CCCN

HCCCN

HC13CCN
HCC13CN

2

88.2

≈

0

90.6
90.8
Frequency/GHz

91.0

Brightness temperature TB/K

6

J = 10−9≈Brightness temperature TB/K

14

0.2

C2H5CN
10010−909

HCCC15NJ = 10−9

0.1
0.0
88.30
88.35
Frequency/GHz

Figure 1: The J = 10‒9 transitions of HC3N observed toward Sgr B2(M) with Nobeyama radio
telescope. Left panel: the lines of HCCCN, H13CCCN, HC13CCN and HCC13CN. Right panel:
the line of HCCC15N.
Reference: [1] G. R. Adande and L. M. Ziurys, ApJ, 744, 194 (2012).

A survey of near-infrared diffuse interstellar bands
S. Hamano,1 N. Kobayashi,2 H. Kawakita,1 K. Takenaka,3 and WINERED team1

Laboratory of Infrared High-resolution Spectroscopy, Kyoto Sangyo University, Japan
2
Institute of Astronomy, School of Science, University of Tokyo, Japan3
Department of Physics, Faculty of Science, Kyoto Sangyo University, Japan

Diffuse interstellar bands (DIBs) are ubiquitous absorption lines in the spectra of thereddened stars, which originate from foreground interstellar clouds. Although the carriersof most DIBs have not been successfully identified yet, they are considered to arise fromthe gas-phase carbonaceous molecules, such as fullerenes, polycyclic aromatichydrocarbons (PAHs) and carbon-chain molecules [1]. The observational studies of DIBs
may play an important role toward the understanding of the properties and chemistry oflarge organic molecules in interstellar medium.
To identify their carriers and investigate their interstellar properties, we are conducting thefirst comprehensive survey of the DIBs in near-infrared (NIR) wavelength range, where
the ionized large molecules, such as PAHs and fullerenes, are considered tohave absorption bands. The data have been collected with the NIR high-resolution(R=28,000) spectrograph WINERED, which offers a high sensitivity in the wavelength
coverage of 0.91-1.36 micron. We successfully found a number of new NIR DIBs, some ofwhich are detected at the wavelengths close to the peaks of the absorption bands of PAH
cations [2]. In addition, the high transmittance of the NIR wavelength range enables us to
explore the environmental dependence of the DIB carriers in the dusty environment [3]. We
will present some results obtained in this survey and future prospects.

Figure 1: Upper panel: The spectra obtained with WINERED. The DIBs (thick lines) are detected only inthe reddened object (lower spectrum). Lower panel: The model spectrum of telluric absorption lines.

References
[1]
[2]
[3]

E. K. Campbell, M. Holz, D. Gerlich, J. P. Maier, 2015 Nature 523, 322
S. Hamano, N. Kobayashi, S. Kondo et al., 2015, ApJ 800, 137 .
S. Hamano, N. Kobayashi, S. Kondo et al., 2016, ApJ 821, 42 .

Grain Surface Pathways to Complex Organic Molecule Formation
S. Ioppolo,1 K.-J. Chuang,2 G. Fedoseev,2 E. F. van Dishoeck,3 and H. Linnartz2
1

Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7
6AA, UK
2
Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513,
NL-2300 RA Leiden, the Netherlands
3
Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands

Complex organic molecules (COMs) have been identified in a number of distinct interstellar
environments, characterized by radically different physical conditions, e.g., hot cores of lowand high-mass protostars as well as cold dense molecular clouds [1]. Although gas-phase
COM formation channels may be particularly important in hot cores, they cannot fully explain
the presence of complex species in cold regions. Recent laboratory studies showed that COMs
form effectively at low temperatures (10-30 K) in the solid state, i.e., on icy grains, typicallyfollowing a non-energetic (atom-addition) or energetic (X-rays, VUV photons, ions, andelectrons) trigger. So far, such studies have been mostly performed for one of the twoprocesses. For decades, surface complex molecule formation has been thought to be induced
largely by energetic processing. Very recently, my co-workers and I gave the first laboratory
evidence that the building blocks of sugars, fats, and proteins can be formed through nonenergetic surface reactions under dark molecular cloud conditions [2, 3]. During my talk, I
will review the most recent laboratory work carried out at the Sackler Laboratory for
Astrophysics in Leiden (Netherlands). Particularly, I will qualitatively and quantitatively
discuss both the relative importance and the cumulative effect of atom-addition and VUVirradiation on the surface formation of complex species at 15 K [4, 5]. Results will be linked
to current astronomical observations.

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

E. Herbst & E. F. van Dishoeck 2009, ARAA 47, 427.
G. Fedoseev, H. M. Cuppen, S. Ioppolo, T. Lamberts & H. Linnartz 2015, MNRAS 448, 1288.
K.-J. Chuang, G. Fedoseev, S. Ioppolo, E. F. van Dishoeck & H. Linnartz 2016, MNRAS 455, 1702.
G. Fedoseev, K.-J. Chuang, E. F. van Dishoeck, S. Ioppolo & H. Linnartz 2016, MNRAS 460, 4297.
K.-J. Chuang, G. Fedoseev, S. Ioppolo, E. F. van Dishoeck & H. Linnartz 2016, submitted to MNRAS.

Laboratory Simulation of Chemical Reactions on Pluto
Yu-Jong Wu,1,2,* Chih-Hao Chin,1 Meng-Chen Liu,1 and Sian-Cong Chen1
1

Scientific Research Division, National Synchrotron Radiation Research Center, Taiwan
2
Department of Chemistry, National Chiao Tung University, Taiwan
E-mail:yjwu@nsrrc.org.tw

Stern et al. [1] used the Hubble Space Telescope with the Cosmic Origins Spectrograph(HST-COS) to record ultraviolet reflectance spectra of Pluto at two rotational phases. An
absorption feature between 210 and 240 nm with an absorption maximum near 222 nm wasfound in the 95º longitude of Pluto. Because most nitriles and/or large hydrocarbons have UV
absorptions in this spectral region, they suggested that complex molecules may exist on thesurface of Pluto. In our previous works, we recorded the UV absorption spectrum of electronbombarded CH4 diluted in solid N2 at 10 K [2]. The observed spectrum revealed a bandwithin the 310–200 nm region, centered at 260 nm and with a shoulder near 220 nm. We
further studied the UV spectra of electron-bombarded pure solid N2 [3], C2H2 [4], and C2H4 [5]in solid N2 at 10 K, but all the recorded spectra showed no significant features near 220 nm.
The temperature on Pluto’s surface ranges from 33 K to 55 K, which means that laboratory
simulations of chemical reactions at 10 K might be improper. The current work presents a
study of electron irradiated CH4:N2 ices during deposition at various temperatures. IR spectra
show formation of N3 and CH3 radicals at low temperatures while only nitrile species wereobserved at higher deposition temperatures. This was attributed to radical recombination
enabled by diffusion at the higher temperatures. UV absorption spectrum of electron
irradiated samples at 44K, depicted in Fig. 1, shows a feature that compares well with the
Pluto spectrum observed by Stern et al [1]. This along with the IR based identifications
implies that nitriles exist on Pluto's surface [6].

Figure 1: Ultraviolet (UV) absorption spectra of electron-bombarded CH4/N2 matrix samples during
deposition at (A) 10 K, (B) 20 K, (C) 33 K, (D) 44 K. (E) The inverted HST-COS Pluto spectrum [1].

References[1] S. A. Stern, et al, 2012, A J, 143, 22.
[2] Y.-J. Wu, H.-F. Chen, S.-J. Chuang, & T.-P. Huang, 2013, ApJ 768, 83.
[3] Y.-J. Wu, H.-F. Chen, S.-J. Chuang, & T.-P. Huang, 2013, ApJ, 779, 40.
[4] Y.-J. Wu, S.-J. Chuang, S.-C. Chen, & T.-P. Huang, 2014, ApJS. 212, 7.
[5] H.-F. Chen, S.-C. Chen, M.-C. Liu, T.-P. Huang, & Y.-J. Wu, 2015, ApJ. 804, 36.
[6] C.-H. Chin, S.-C. Chen, M.-C. Liu, T.-P. Huang, & Y.-J. Wu, 2016, ApJS, 224, 17.

Formation of Complex Organic Molecules on Interstellar Grain Surfaces. Insights from
Periodic Quantum Chemical Simulations
A. Rimola,1 J. Enrique-Romero,1 C. Ceccarelli,2 N. Balucani,3 and P. Ugliengo4
1

Departament de Química, Universitat Autònoma de Barcelona, Catalonia, Spain
2
CNRS, IPAG, Université Grenoble Alpes, France
3
Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Italy
4
Dipartimento di Chimica, Università di Torino, Italy

About 200 molecular species were detected in the ISM. Some of them are complex organic
molecules (COMs), molecules with more than 6 atoms containing one or multiple C atoms.
Some COMs can reach a certain degree of complexity and can have a prebiotic relevance.
Knowing whether COMs contributed or not to the chemical evolution needed for the
emergence of life is one of the open questions in the origin of life studies. Two classes ofmodels are invoked to explain the interstellar synthesis of COMs. One advocates formation ofCOMs on the grain surfaces [1, 2], in which dissociation of frozen hydrogenated species gives
radicals, which in turn recombine to form COMs. The other postulates that they form via gasphase reactions [3, 4], in which the frozen hydrogenated species desorb into the gas phase andreact with other gaseous species to form COMs through a series of gas-phase processes. The
problem in knowing which of the two models is correct and in which conditions each model isapplicable mostly comes from a dramatic lack of experimental and theoretical data of gasphase and on-surface reactions. This communication focuses on the formation of several
COMs by recombination of their precursor radicals (e.g., CH3 + HCO  CH3CHO; CH2OH+ HCO  HOCH2CHO, and others) on grain surfaces by means of quantum chemical
simulations. Surfaces are based on a periodic approach of a slab model consisting of H2O
mixed with CO (Figure 1). Results indicate that, in addition to radical recombination, otherprocesses are competitive reactive channels. The occurrence of these processes depends on
several factors such as the nature of the radical recombination, the proximity of the reactantsor the capability of the radicals to transfer their H atoms [5].
CH3

HCO
CO

H2O

CO

H2O

Figure 1: Surface slab model employed to simulate the recombination of radical species on surfaces. In thiscase the CH3 and HCO radicals are adsorbed on the surface model.

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

K. I. Öberg, 2016, Chem. Rev. Article ASAP, DOI: 10.1021/acs.chemrev.5b00694 .
R. T. Garrod, S. L. W. Weaver, E. Herbst, 2008, ApJ, 682, 283.
P. Caselli, T. I. Hasegawa, E. Herbst, 1993, ApJ, 408, 548.
V. Taquet, E. S. Wirström, S. B. Charnley, 2016, ApJ, 821, 46.
J. Enrique-Romero, A. Rimola, N. Balucani, C. Ceccarelli, 2016, MNRAS, 459, L6.

Instanton Theory: Prediction of Rate Constants for Astrochemical Reactions
J. Kästner,1 L. Song,1 T. Lamberts,1 J. Meisner,1 S. Álvarez-Barcia1
1

Institute for Theoretical Chemistry, University of Stuttgart, Germany

Simulations of reaction rates including quantum tunneling of atoms complement measurements and help to interpret data. An appropriate rate theory must be accurate enough to provide reliable predictions, but efficient enough to allow for computationally intensive electronic structure calculations at large enough structural models. Instanton theory, based on Feynman path integrals, matches these requirements [1]. It provides the dominant tunneling path ata given temperature or energy.
We have used it to calculate rate constants for a number of reactions of astrochemical interest
both in the gas phase and on surfaces. Examples are:H2 + OH⟶ H2 O + H[2]++NH3 + H2 ⟶ NH4 + H[3]
HNCO + H ⟶ NH2CO[4]
C2H2 + H ⟶ C2H3
[5]
C2H4 + H ⟶ C2H5
[5]
Models of surface reactions need to include the interplay between reactions and diffusion.

Figure 1: Tunneling path (instanton path) of the reaction HNCO + H ⟶ NH2CO on a surface of amorphous solid water [4]. The path is colored from the reactant side (red) to the product side (blue).

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

J. Meisner and J. Kästner, 2016, Angew. Chem. Int. Ed. 55, 5400
S. Álvarez-Barcia, M.-S. Russ, J. Meisner and J. Kästner 2016 Faraday Discuss.
DOI 10.1039/c6fd00096g
J. Meisner and J. Kästner, 2016, J. Chem. Phys. 144, 174303
L. Song and J. Kästner, 2016, submitted
H. Kobayashi, H. Hidaka, T. Lamberts, T. Hama, H. Kawakita, J. Kästner and N. Watanabe, 2016, submitted

Tunneling reaction rate constants on a surface:a case study of H + H2O2 → H2O + OH
T. Lamberts1 and J. Kästner1
1

Institute for Theoretical Chemistry, University of Stuttgart, Germany

In the dense and cold regions of the Interstellar Medium (ISM), water is known to be formedon the surface of dust grains via sequential hydrogenation of O, O2, or O3. The full water
surface reaction network consists of ∼ 15 reactions and depending on density, temperature andH, H2, O abundance of the interstellar region, different reaction pathways towards theformation of water are important [1]. In the most dense regions, the absolute amount ofoxygen becomes sufficiently high for the following reaction pathway to contributesignificantly to the formation of H2O and OH:
O (+O) → O2 (+H)→ HO2 (+H)→H2O2 (+H)→H2O + OH.
The final step in this reaction route has been reported to have a large activation barrier. It has
been studied experimentally on the surface at low temperatures and a kinetic isotope effect
was found [2]. This indicates the importance of tunneling yielding it efficient even at 15 K.
Furthermore, the detections and non-detections of H2O2 in a diverse sample of sources indifferent environments gave rise to the conclusion that the production of peroxide is very
sensitive to temperature. The production of peroxide was taken into account by rescaling thereaction rate according to experimental data [3, 4]. Quantitatively rescaling rates is, however,not trivial for reactions that are deeply embedded in a reaction network.
Therefore, we present a theoretical study of the reaction H + H2O2 → H2O + OH within theframework of studying tunneled reactions on a surface. Calculations are performed using a
DFT functional benchmarked to CCSD(T)-F12 single-point energies. Rate constants arecalculated with instanton theory. We present activation barriers and rate constants for threedifferent cases: the gas-phase reaction, the gas-phase reaction with several spectator H2O
molecules (small clusters) and we show how to extend these to studying the reaction on a
crystalline water surface using a QM/MM method.

Figure 1: Example of a transition state structure on a water surface, the colored atoms are part of the QM
region, whereas the gray lines represent water molecules described on an MM level.

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

T. Lamberts, X. de Vries, & H. M. Cuppen, 2014, Far. Disc. 168, 327
Y. Oba, K. Osaka, N. Watanabe, T. Chigaia, & A. Kouchia, 2014, Far. Disc. 168, 185
F. Du, B. Parise, & P. Bergman, 2012, A&A 538, A91
B. Parise, P. Bergman, & K. Menten, 2014, Far. Disc. 168, 349

Investigations on IR spectra of astronomically important species using the parahydrogen matrix-isolation technique
M. Tsuge,1 K. Haupa,1 and Y.-P. Lee1, 2
1

Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung
University, Taiwan
2
Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan

Two types of methods using para-hydrogen (p-H2) matrix isolation were employed to prepare
species that might be important in astronomy. These species were characterized with infrared(IR) absorption.
(1) The bombardment of p-H2 with electrons produces H3+ and H via H2 + e− → H2+ + 2e− andH2+ + H2 → H3+ + H reactions. Proton transfer from H3+ to species of interest produces
mainly protonated and mono-hydrogenated species trapped in a p-H2 matrix. This method has
been applied to produce protonated polycyclic aromatic hydrocarbons (designated H+PAH)
and some small molecules. The protonated PAH are potential carriers of the unidentified
infrared emission (UIR) bands in interstellar media. Our previous work on protonated pyrene
and coronene [1−3] indicates that, as the size of aromatic ring increases, the spectral shifts of
IR bands point the direction toward the positions of the UIR bands. When we extended thework to protonated ovalene (7-C32H15+), we found a close resemblance between the laboratory
IR spectrum and the UIR emission bands, indicating that H+PAH can contribute to the UIR
emission and protonated ovalene might be an important member of the interstellar PAH
inventory [4]. The IR spectra of mono-hydrogenated ovalene 7-C32H15 were also identified forthe first time.
(2) The N/O chemical network is important in understanding the formation mechanism ofamino acids in dark interstellar clouds. We present the results of IR studies on the H +HONO reactions in solid p-H2 at 3.3 K. Isolated HONO molecules were irradiated with lightat 355 nm from a Nd:YAG laser. The photoproduct OH radicals react readily with nearby pH2 to produce H2O and mobile H atoms. A few hours after irradiations, we observed
absorption lines of products of hydrogenation of HONO: hydroxyl nitroxide HON(O)H,dihydroxyloamino radical HONOH, and dihydroxyl amine HONHOH. The spectral
assignments were based on comparison with calculated vibrational wavenumbers and IR
intensities, and were further confirmed with the observed isotopic ratios for D/H and N15/N14
species that were in agreements with predicted values. The formation mechanism including
tunneling reactions of H + HONO and other secondary reactions will be discussed. The
presented results show some new reaction paths which might lead to formation of prebiotic
molecules in the dust grains in interstellar medium.

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

M. Bahou, P. Das, Y.-F. Lee, Y.-J. Wu, & Y.-P. Lee, 2014, Phys. Chem. Chem. Phys. 16, 2200.
M. Bahou, Y.-J. Wu, & Y.-P. Lee, 2013, J. Phys. Chem. Lett. 4, 1989.
M. Bahou, Y.-J. Wu, & Y.-P. Lee, 2014, Angew. Chem. Int. Ed. 53, 1021.
M. Tsuge, M. Bahou, Y.-J. Wu, L. Allamandola & Y.-P. Lee, 2016, Astrophys. J. 825, 96.

High-resolution and high-accuracy infrared spectra of interstellar methylamine in thegas phase
Z.-D. Sun,1,2 S.-D. Qi,1 L.-S. Ma,1 R. M. Lees,3 and L.-H. Xu3
1

2

School of Physics, Shandong University, China
School of Physics and Electrical Engineering, Kashgar University, China
3
Department of Physics, University of New Brunswick, Canada

The study of the rotational and vibrational spectra of molecules in the interstellar medium isparticularly useful to elucidate the physical conditions and chemical contents and evolutionsof these interstellar gases. The spectrsocopic study of methylamine (CH3NH2) in thelaboratory has been directly led to the valuable application to the detection of CH3NH2 earlier
in 1974 [1] and recently in 2011 [2] in the Universe. In fact, the spectra of CH3NH2 are richand highly crowded due to the two coupled large-amplitude internal motions of torsion andinversion which can be caused in collisions with He and H2 in a molecular cloud. Furthermore,
the Universe has a very wide range of astrophysical sources, and the astrophysicalobservations now are increased in resolution and in sensitivity by ALMA (Atacama Large
Millimeter Array), HIFI (Heterodyne Instrument for the Far Infrared), and FAST (Fivehundred-meter Aperture Spherical radio Telescope), which greatly need more and precisely
expanded laboratory databases of CH3NH2. However, since the first report about seventy
years ago at low resolution of 1 cm-1 and an accuracy of about 0.1 cm-1 [3], the high-accuracy
infrared spectra in the CN vibrationally stretching band of CH3NH2 have just recently beenstudied by the technique of Lamb-dip saturated absorption spectrum by us for just a set of 43
saturation dips primarily in the C−N stretching Q-branch region in only two sub-states [4].
Currently, we have systematically expanded our sub-Doppler measurement to this band of
gaseous CH3NH2 over a wider range of transitions in P-, Q-, and R-branch. More than 200
Lamb-dip signals in 27 sub-states have been observed individually at a spectral resolution of
0.4 MHz and the transition frequencies of them have been determined with an accuracy of0.1 MHz. Our current experimental results constitute a high-accuracy spectral database in
the important 9−11 micrometer region for various theoretical and experimental studies andapplications to CH3NH2 for astrophysical and astrochemical communities.
Acknowledgements
We express our thanks to Prof. N. Ohashi for providing a list of calculated ground-state energies. This
research was partially supported by the NSFC (Grants No. 11174186 and 91536105), the Tianshan Scholar
Program and the JSPS BRIDGE Fellowship Program (BR161302). L.H.X and R.M.L acknowledge financial
support from the NSERC.

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

N. Kaifu, et al., 1974. Astrophys. J. 191, L135.
S. Muller, A. Beelen, & M. Guelin, 2011, Astron. Astrophys, 535, A103.
A. P. Gray & R. C. Lord, 1957, J. Chem. Phys. 26, 690.
Z.-D. Sun, R. M. Lees, & L.-H. Xu, 2010, J. Chem. Phys. 132, 194310.

Recent Advances in Our Understanding of the Molecular Complexity in Astronomical
Environments.
A. Remijan,1
1North American ALMA Regional Center, National Radio Astronomy Observatory,
Charlottesville, Virginia, United States

Over the past several years, observations of a variety of astronomical environments has led tothe detection and characterization of new molecular species as well as to a better
understanding of the physical and chemical conditions of these regions. Molecular material is
now found in a host of Galactic and extragalactic environments and has been used as tracers
of a variety of conditions including but certainly not limited to, PDRs, XDRs, shocks, diffusegas, dense gas, HMCs and UC HII regions. In the era of large single dish telescopes andbroadband interferometric arrays, we are truly getting a chemical picture of the universe. This
presentation will look at the recent advances our team has made in the detection of new
astronomical molecules and how these new detections are driving better and more complex
theories of large molecule formation in astronomical environments. Included in thispresentation will be the first astronomical observation of a chiral molecule detected towards
the high mass star forming region SgrB2N [1]. Figure 1 shows the detection of propyleneoxide (CH3CHCH2O) (reproduced from [1])Figure. 1: Observations of the 1(1,0) – 1(0,1) (Parkes), 2(1,1) – 2(0,2) (GBT), and 3(1,2) – 3(0,3) (GBT)transitions of propylene oxide, in absorption, toward the Galactic center.

References[1]

McGuire et al. 2016, Science, 352, 6292, 1449

Multi-scale polarization, chemistry and kinematics in the Pipe nebula
F. O. Alves1, J. M. Girart2, P. Caselli1, G. A. P. Franco3, J. Soler4, G. Busquet2, F. P. Santos5,
H. Wiesemeyer6, C. Juárez2 and P. Frau7
1

Max Planck Institute for Extraterrestrial Physics, Germany
2
Institut de Ciències de l’Espai (CSIC-IEEC), Spain
3
Departamento de Física, Universidade Federal de Minas Gerais, Brazil
4
Institute d’Astrophysique Spatiale, CNRS, France
5
Department of Physics and Astronomy, Northwestern University, USA
6
Max Planck Institute for Radio Astronomy, Germany
7
Institut d’Estudis Espacials de Catalunya, Spain
Our team is involved in multi-wavelength observations of the Pipe nebula across several
spatial scales and my goal is to present the most relevant results of this investigation. A recent
comparison between Planck submm data and optical data has proven that polarization byemission and absorption are remarkably consistent [1]. Both techniques show an orderedmagnetic field that may be the result of the interaction between two clouds [2, 3]. We are also
investigating the ionization properties of the Pipe through observations of several species such
as DCO+ and H13CO+. Preliminary results point to an unusually high ionization fraction andtherefore a tighter coupling between matter and magnetic field.
I will also present results of a chemical survey that reveals a close correlation between
deuteration in the cores and visual extinction [4]. One particular core, FeSt 1-457, shows
chemical differentiation and polarization levels consistent with a starless core [5,6]. Finally, I
will present ALMA observations toward B59, the only active core in the Pipe. Our data show
impressive substructure in dust and molecular emission, suggesting that a centrifugal barrier
may be the key mechanism regulating the kinematics of a young stellar object.

Figure 1: The left panel shows a comparison between the Planck polarization (drapery pattern) and opticalpolarization (black segments) in the Pipe nebula. The right panel shows optical (blue segments), nearinfrared (red segments) and submm polarization (green segments) in the prestellar core FeSt 1-457.

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

J. Soler, F. O. Alves, F. Boulanger et al., 2016, submitted.
F. O. Alves, G. A. P. Franco, & J. M. Girart, 2008, A&A 486, L13
P. Frau, J. M. Girart, F. O. Alves et al., 2015, A&A 574, L6
P. Frau, M., J. M. Girart, & M. Beltrán, 2012, A&A 537, L9
C. Juárez, J. M. Girart, P. Frau et al., 2016, submitted.
F. O. Alves, P. Frau, J. M. Girart et al., 2014, A&A 569, L1

HI-to-H2 Transitions in Galaxy Star-Forming Regions
Amiel Sternberg
Sackler School of Physics and Astronomy, Tel Aviv University, Israel
I will describe new analytic theory for the atomic to molecular (HI-to-H2) transitions, and thebuild-up of atomic-hydrogen (HI) gas columns in star-forming clouds, based on fundamental
physics principles. I will discuss my general-purpose formula for the total HI columns
produced by photodissociation in optically thick media, valid for beamed or isotropic
radiation fields, the weak- to strong-field limits, gradual to sharp HI-to-H2 transitions, and forarbitrary metallicity. The analytic theory is validated with detailed numerical radiativetransfer computations. The general theory may be broadly used for interpreting 21 cm
studies of individual Galactic sources and global galaxy properties, and may also be
incorporated intohydrodynamics simulations.

References
[1]
[2]
[3]

A. Sternberg, F. Le Petit, E. Roueff, & J. Le Bourlot, 2014, ApJ, 790, 100
S. Bialy, A. Sternberg, M.-Y. Lee, F. Le Petit. & E. Roueff, 2015, ApJ, 809, 122
S. Bialy, & A. Sternberg, 2016, ApJ, 822, 83

The Detection and Synthesis of Large and Very Large Interstellar Molecules
E. Herbst1
1

Departments of Chemistry and Astronomy, University of Virginia, USA

Interstellar molecules with six or more atoms are often referred to as “complex” organic
molecules, or COMs, even though they are certainly not complex by the standards of organic
chemistry [1]. Better adjectives to describe these molecules are “large” and “very large.”
The large molecules are those with up to 13 atoms in size, whereas the “very large” molecules
include PAH’s and, more specifically, fullerenes. The large organic molecules can be
subdivided into unsaturated carbon chains and more terrestrial-like species similar to solventsin the terrestrial organic laboratory. Until recently, it was thought that the different classesof large molecules belonged to different sources based on the dominant mode of synthesis.
New observations however have thrown this dichotomy into disarray, and new theoretical andlaboratory results have shown that the synthesis of large and very large molecules can occur
via a variety of methods under different conditions. These different mechanisms, including
a variety of gas-phase and grain-surface reactions, will be discussed. The rebirth ofneutral-neutral chemistry, outbursts, and grain bombardment by cosmic rays will beemphasized, as will possible syntheses of very large molecules [2,3].
How can we observe larger molecules than seen up to now? The relative merits of rotational,
vibrational, and electronic spectroscopy will be discussed. One advantage of rotational
spectroscopy is that the spectral frequencies are directly related to the geometry of themolecule. To detect molecules with significantly more than 13 atoms will probably require
lower frequency observations that customary these days because of larger moments of inertia.
Difficulties in observing molecules at lower frequencies require larger surface areas, such as
will be available with the Square Kilometer Array (SKA) and the extended/refurbished Very
Large Array (VLA). Infrared spectroscopy can also be of use despite atmospheric opacity.
The new James Webb Space Telescope will be launched within a year, and allow infrared
astronomers to search for less abundant molecules albeit with a not very high spectral
resolution. The SOFIA aircraft has much higher spectral resolution, but may be limited tomore abundant species. Finally, the use of visible and UV spectroscopy, which probe
electronic transitions, is probably limited to diffuse clouds or borders of denser regions. In asense, observations in the visible have already been undertaken and have given us the diffuse
interstellar bands, which are still mainly unassigned.
References[1]
E. Herbst & E. F. van Dishoeck, 2009, ARAA, 47, 2009
[2]
N. Balucani, C. Ceccarelli, & V. Taquet, 2015, MNRAS, 449, L16[3]
V. Taquet, E. S. Wirtstrom, & S. B. Charnley, 2016, ApJ, 821, 46

On the Chemistry of Hydrides of N Atoms and O+ Ions
Z. Awad,1,2 S. Viti,2 and D. A. Williams2
1

Astronomy, Space Science, & Meteorology Department, Faculty of Science, Cairo University,
Egypt
2
Physics and Astronomy Department, University College London, UK

Previous work by various authors has suggested that the detection by Herschel/HIFI ofnitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be
accounted for by gas-phase chemical models. In this paper we investigate the role of surface
reactions on dust grains in diffuse regions, and we find that formation of the hydrides by
surface reactions on dust grains with efficiency comparable to that for H 2 formation
reconciles models with observations of nitrogen hydrides. However, similar surface reactions
do not contribute significantly to the hydrides of O + ions detected by Herschel/HIFI that arepresent along many sight lines in the Galaxy. The O + hydrides can be accounted for by
conventional gas-phase chemistry either in diffuse clouds of very low density with normal
cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydridechemistry in dense dark clouds appears to be dominated by gas-phase ion–molecule reactions.

Figure 1: The main routes in the gas-phasechemistry forming hydrides of N and O + . Diagrams
modified from [1] and [2].

Figure 2: The time evolution of the fractional
abundances of all the hydrides in the Reference
Model (RM) with (top) and without (bottom)
surface reactions.

References[1]
Hollenbach, D., Kaufman, M. J., Neufeld, D., Wolfire, M., & Goicoechea, J. R. 2012, ApJ 754, 105[2] Le Gal, R., Hily-Blant, P., & Faure, A. 2014, in SF2A-2014: Proceedings of the Annual meeting of theFrench Society of Astronomy and Astrophysics, ed. J. Ballet, F. Martins, F. Bournaud, R. Monier, & C. Reyle ,p.397–401

New Methods in Molecular Spectroscopy:
Cologne Center for THz Spectroscopy
O. Asvany1, S. Brünken1, Pavol Jusko1, S. Thorwirth1,
C. Endres1,2, F. Lewen1 and S. Schlemmer1
1

2

I. Physikalisches Institut, Universität zu Köln, Germany
Max-Planck Institute for Extraterrestrial Physics, Garching, Germany

The Cologne Center for THz Spectroscopy invites guests to use a wide variety of instruments
to obtain spectra from the far-infrared to the mid-infrared region. Spectra of complex organic
molecules (COMs) are recorded in several conventional absorption spectrometers in order to
identify them in observations of the ALMA, Herschel and SOFIA telescopes. Driving
questions in this area of research are, e.g., up to which molecular complexity do these species
grow in the interstellar environment and how can they be formed under the prevailing low
pressure and temperature conditions.
Apart from these traditional spectroscopy tools, new instruments are built in the Cologne
laboratories to improve the sensitivity, frequency coverage and spectral resolution, inparticular to allow the study of radicals and ions which shall be found in future observations.
We present a 75-110 GHz emission spectrometer which is operated at room temperature. An
immediate bandwidth of 2.5 GHz is recorded with this instrument at a noise temperature of
only several hundred Kelvin. Apart from its high sensitivity new features will be discussed. A
chirped pulse spectrometer has been constructed not only to record broad band spectra but inparticular to determine rate coefficients for inelastic and reactive collisions.
The method of light induced reactions (LIR) has been developed over the last 20 years in ourgroup in order to record spectra of mass selected, cold molecular ions which are stored in ion
traps. Compared to traditional absorption spectroscopy in discharge cells the sensitivity of ourdevices is increased by many orders of magnitude. The spectral resolution is high enough topredict THz spectra at sub-MHz accuracy which is sufficient to identify those ions inastronomical observations [1]. Changing the population of the rotational states andinterrogating them by LIR in double resonance experiments leads to predictions of THz
transition frequencies at the 10-9 level [2], which challenge observations [3]. The ion trap
instrument FELion allows to record spectra of cold ions over a range of 250 – 3200 cm-1. Thisapproach allows the identification of isomers and conformers of the molecular species
selected by mass spectrometry. Moreover, identifying the vibrational bands of more complex
molecular ions challenges quantum chemical predictions [4] and is used as a basis forhigh-resolution studies in order to find those molecules in space [5].
References[1]
S. Brünken, O. Sipilä, E.T. Chambers, J. Harju, P. Caselli, O. Asvany, C.E. Honingh, T. Kamiński, K.M.
Menten, J. Stutzki, and S. Schlemmer, An age of at least 1 Myr for a dense cloud core forming Sun-like stars,
Nature, 516, 219–221 (2014).
[2]
P. Jusko, O. Asvany, A.-C. Wallerstein, S. Brünken, S. Schlemmer, Two photon rotational action
spectroscopy of cold OH- at 1 ppb accuracy, Phys.Rev.Lett. 112 (2014) 253005.
[3]
S. Brünken, L. Kluge, A. Stoffels, O. Asvany, and S. Schlemmer, Laboratory Rotational Spectrum ofl-C3H+ and Conformation of its Astronomical Detection, ApJ 783 (2014) L4.
[4]
O. Asvany, P. Kumar, I. Hegemann, B. Redlich, S. Schlemmer and D. Marx, Understanding the LIR
Infrared Spectrum of Bare CH 5+, Science 309, 1219-1222 (2005)[5]
O. Asvany, K.M.T. Yamada, S. Brünken, A. Potapov, S. Schlemmer, Experimental Ground State
Combination Differences of CH5+, Science 347 (2015) 1346-1349

A laboratory experiment of interstellar molecular reactions
at RIKEN Cryogenic Electrostatic ring (RICE)
Y. Nakano1, Y. Enomoto1, T. Masunaga1, S. Menk1, P. Bertier1,2, and T. Azuma1,3
1

AMO Physics Laboratory, RIKEN, Japan
Institut de Physique Nucléaire de Lyon, Université de Lyon,
Université de Lyon 1, CNRS/IN2P3, France
3
Department of Physics, Tokyo Metropolitan University, Japan2

A laboratory experiment of the interstellar molecular reactions is being developed at RIKEN cryogenic
electrostatic ring (RICE). The RICE, shown in Figure 1, provides a novel opportunity to store atomic andmolecular ion beams in a closed orbit under variable ambient temperatures (4-300 K). By injecting two
different beams into the RICE at a low relative velocity to each other, the slow collision of interstellar
molecules is reproduced in a cryogenic environment. The first cryogenic operation of the RICE wassuccessfully performed in 2014 August, and a rotational laser spectroscopy of cold molecular ions is ongoingat 4 K.
Currently, an experimental setup for the neutral beam injection is under preparation. This aims to study thereaction of H3+ ions with C and O atoms, namely,
H3+ + C => CH+ + H2
H3+ + O => OH+ + H2
as the starting point of the C-H and O-H series molecular evolution in space. The rate and branching ratio foreach reaction path will be investigated as a function of the collision energy and environment temperatures.

Figure 1: The photograph of the RIKEN Cryogenic Electrostatic ring (RICE); the copper-made electrostatic
elements of the ring (center), the vacuum vessel with cryoheads (left), and the injection beamline (right).

References[1]
Y. Nakano, et al., J. Phys. Conf. Ser. 388, 142027 (2012).

Unveiling subsurface hydrogen-bond structure of crystalline ice
T. Sugimoto,1,2 Y. Otsuki,1 T. Ishiyama,3 A. Morita,4,5
K. Watanabe,1 and Y. Matsumoto1
1

Department of Chemistry, Graduate School of Science, Kyoto University, Japan.
2
3

4
5

JST Precursory Research for Embryonic Science and Technology, Japan.

Graduate School of Science and Engineering, University of Toyama, Japan.

Department of Chemistry, Graduate School of Science, Tohoku University, Japan.

Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Japan.
Determinations of structural reconstruction and molecular orientation at surfaces ofubiquitous water ice are challenging due to the inherent difficulty in probing surfaces of thefragile and insulating material through traditional experimental approaches. Because buried
subsurface structures govern the physicochemical properties of topmost surfaces [1],unveiling the subsurface structures is of crucial importance for an ultimate understanding ofvarious heterogeneous ice-surface processes vastly taking place on earth and in the universe.
For the basal face of crystalline ice Ih, we have tackled this problem with a non-invasive
surface-sensitive method of sum-frequency generation (SFG) vibrational spectroscopy withstate-of-the-art phase detection [2] in combination with molecular dynamics simulations andab initio quantum calculations [3].
Here we demonstrate that the SFG spectra of isotope-diluted crystalline ice Ih are highly
sensitive to the symmetry breaking of inter-bilayer hydrogen bonds at subsurface. The
observed Imχ(2) spectrum for the hydrogen bonded OH-stretch vibration of HDO ice Ih(0001)
at 120 K shows positive and negative peaks at lower and higher frequencies, respectively. Asa H-bond that connects neighbouring molecules becomes stronger, the frequency of local OHstretch vibration involved in the H-bond decreases [4]. Therefore, our result suggests that theOH oscillators pointing toward the bulk (negative peak) form weaker H-bond than thosepointing toward the surface (positive peak). From the analysis of the observed spectra, we will
discuss that, in contrast to the bulk, the strength of hydrogen bond strongly depends on theorientation of water molecules at subsurface due to asymmetric librational fluctuation and thecorporative nature of hydrogen bond.
References[1]I. E. L. Stephens et al., 2011, J. Am. Chem. Soc. 133, 5485.
[2]T. Sugimoto, N. Aiga, Y. Otsuki, K. Watanabe, & Y. Matsumoto, 2016, Nature. Phys.doi:10.1038/nphys3820.
[3]T. Ishiyama, H. Takahashi, & A. Morita, 2012, J. Phys. Chem. Lett. 3, 3001.
[4]B. A. Zilles, & W. B. Person, 1983, J. Chem. Phys. 79, 65.

Analogs of interstellar carbonaceous dust:
processing by electron bombardment and theoretical modeling
V. J. Herrero, G. Molpeceres, B. Maté, V. Timón,
M. Jiménez Redondo and I. Tanarro
Instituto de Estructura de la Materia (IEM-CSIC), Serrano 123, 28006 Madrid, Spain

Observational evidence, based on IR absorption spectra, indicates that interstellar (IS)carbonaceous dust in the diffuse interstellar medium is largely made of some sort ofhydrogenated amorphous carbon (abbreviated HAC o a-C:H). Observations also show that themost prominent spectroscopic feature associated with the aliphatic component of IS
carbonaceous dust (the 3.4 m absorption band) disappears in dense molecular clouds,
although the details of the destruction mechanism are not entirely clear. The effects of cosmic
rays, which can reach the interior of dense clouds, on the carriers of this feature, have been
investigated in this work by irradiating HAC samples with 5 keV electrons. High energetic
electrons had proved previously [1] to have similar effects to MeV ion beams of different
species tested in laboratory, which are usually accepted as good analogs of cosmic rays [2].
The HAC deposits were grown by plasma enhanced chemical vapor deposition (PECVD) in
inductively coupled RF discharges of CH4/He mixtures. The estimated effects are found to besmall and are not enough to explain the disappearance of the 3.4 m band in dense clouds.
On the other hand, two alternative models of the structure of the carbonaceous dust analogs
can be found at present in the literature. One of them favors a solid made by small aromaticislands linked by aliphatic chains [3], whereas the other proposes large polyaromatic
structures with small aliphatic substituents at the edges [4]. Theoretical models of amorphous
HAC solids, based on the mentioned competing structures [3,4], have been constructed by ourgroup using Density Functional Theory (DFT), and their calculated IR spectra have been
compared to those of a-C:H samples generated by PECVD. The deposition conditions wereselected to obtain a-C:H films with a variable proportion of aliphatic and aromatic structures.
The results suggest that the estimation of the hydrogen contents and the aliphatic/aromatic
ratios of a-C:H samples, using just literature IR band strengths advanced by some authors [5],is difficult and might be not reliable.

References[1] B. Maté et al. 2016, ApJ, in press.
[2] M. Godard et al., 2011, A&A, 529, A146
[3] E. Dartois et al. 2005, A&A, 432, 895, ibid 2007, 463, 635[4] M. Steglich et al. 2013, ApJSS, 208, 26[5] J. E. Chiar et al. 2013, ApJ, 770, 78.

Modification of the physico-chemical properties of interstellar organic analogues by UVirradiation.
L. Piani1, S. Tachibana1, T. Hama2, I. Sugawara1, H. Tanaka2,3, Y. Kimura2, Y. Oba2, A.
Miyake4, J. Matsuno4, A. Tsuchiyama4, H. Yurimoto1 and A. Kouchi2.
1

Department of Natural History Sciences, Hokkaido University, Japan.
2
Institute of Low Temperature Science, Hokkaido University, Japan.
3
Astronomical Institute, Tohoku University, Sendai 980-8578, Japan.
4
Division of Earth and Planetary Science, Kyoto University, Japan.

In the interstellar medium (ISM), photochemical reactions in ice lead to the formation ofrelatively complex organic molecules [1]. These molecules are among the potential building
blocks of our solar system and could be the precursors of a part of the organic matter found incomets and meteorites. However, it is not clear how the organic ice formed in the ISM may
have evolved through temperature increase and irradiations by UV-photons and cosmic rays
until their incorporation into the Solar System objects.
The experimental apparatus PICACHU developed at Hokkaido University was used to
produce molecular cloud organic analogues and study their evolution through UV-irradiation.
Typical ISM gases (H2O, CH3OH, NH3, or CH4,) are deposited onto the faces of a refrigerated
substrate (~12 K) and simultaneously irradiated by UV under high vacuum. The organic
residues that remain after the sublimation of volatiles are thus analogues of the organic matter
formed in the dense and cold molecular clouds. In this study, we are characterizing theseresidues before and after UV photoprocessing at room temperature in order to simulate theiralteration in diffuse clouds or protoplanetary disks, in which, the UV photon flux andtemperature are higher than those in the dense molecular cloud [2].
By irradiating the residues with UV doses corresponding to short residence durations in
diffuse cloud (≤104 yrs), significant changes occurred in the morphological and physicalproperties of the organic residues [3]. They became highly porous and more rigid, and containamorphous nanoparticles similar to organic nanoglobules found in chondrites, IDPs andcometary samples. UV-photoprocessing of molecular cloud organics derived from D-rich icesseems thus to be a possible pathway to form D-rich amorphous nanoparticles.
According to the empirical formula of [4], the viscoelastic properties of the UV-irradiatedorganic residues would favor the merging of grains coated by organics after collision in
protoplanetary disks. However, the organic coating might also reduce the growth efficiency ofaggregates because the viscoelastic nature of organic coating could strengthen the grain-grain
connections and make the dust aggregates brittle.
UV-irradiation in the diffuse clouds or in the outermost part of the protoplanetary disks thus
has a strong influence on the evolution of the precursor organic compounds of protoplanetarydisks.
References[1] Greenberg 2002. Surf. Sci. 500, 793–822.
[2] Jenniskens et al. 1993. Astron. Astrophys. 273, 583–600.
[3] Piani et al. 2016. LPSC, Abstract #1715.
[4] Wada et al. 2013. Astron. Astrophys. 559, A62 (1-8).

Infrared spectra of potential interstellar molecules: protonated PANH and OCS
M. Tsuge,1 C.-Y. Tseng,1 and Y.-P. Lee1,21Department of Applied Chemistry, National Chiao Tung University, Taiwan
2
Instritute of Molecular Sciences, Academia Sinica, Taiwan

The infrared emission from many astronomical objects is dominated by the unidentified
infrared (UIR) emission bands, which are characterized by main features at 3.3, 6.2, 7.7, 8.6,
and 11.2 μm. Because these features are characteristic of the CH stretching, CC stretching,
and CH bending modes of aromatic compounds, polycyclic aromatic hydrocarbons (PAHs)
were proposed to be possible emitters. The nitrogen containing PAHs, known as polycyclicaromatic nitrogen heterocycles (PANHs), might be responsible for the 6.2-μm feature of UIRbands because the N atom induces a blue shift to the CC stretching modes of pure PAHs near
6.3 μm [1]. The existence of protonated PANHs is expected because of the large proton
affinity at the nitrogen site of PANHs.
We have developed a new method to investigate the infrared spectra of protonated PAHs
using electron bombardment during deposition of a PAH/para-H2 mixture at 3.2 K [2]. The
electron bombardment of para-H2 produces H3+, which subsequently react with PAH to form
protonated PAH (H+PAH). We have applied this method to PAHs up to ovalene (C32H14) toobtain infrared spectra of protonated species with narrow lines and excellent signal-to-noise
ratio [3]. In this work, we extended our investigation to quinoline and isoquinoline (C9H7N)
as a first step toward the study of protonated PANHs. The IR spectra of protonated quinoline
and isoquinoline (C9H7NH+) are characterized by features originating from NH stretching, CC
stretching, and CH(NH) bending modes. Agreement between observed spectra of C9H7NH+
and the UIR emission spectrum is unsatisfactory, most probably because the size of molecule
is too small; in the case of H+PAH, features close to the UIR bands were observed for only
large H+PAH such as protonated ovalene (C32H15+). However, the blue shifts of the CC
stretching bands of protonated quinolone and isoquinoline from the corresponding H+PAH,
protonated naphthalene (C10H9+), are clearly observed. IR spectra of mono-hydrogenatedquinoline and isoquinoline (C9H7NH∙) radicals, with hydrogen atom attached on the N atom,
were also identified for the first time.
We also applied this method to small molecules such as OCS, which has been postulated toexist in the ISM. The OCS molecule has two possible protonation sites, leading to isomers
HOCS+ and HSCO+. Both HOCS+ and HSCO+ have been observed with microwave
spectroscopy [5], but only the OH stretching mode of HOCS+ has been identified with gasphase IR spectroscopy [6]. We identified three IR absorption lines of HOCS+ at 2945.9 (ν1),
1875.3 (ν2), and 1041.9 (ν3) cm−1 and two of HSCO+ at 2506.9 (ν1) and 2074.2 (ν2) cm−1.
Absorption lines of t-HOCS at 3563.4, 1394.8, and 1199.0 cm−1 were also identified for the
first time. Assignments were achieved according to expected chemistry, comparison between
experimental spectra and theoretical predictions, and isotopic substitutions. The large red shiftof the ν1 of HOCS+ is attributed to partial proton sharing between OCS and H2.
References
[1]
[2]
[3]
[4]
[5]

E. Peeters, S. Hony, C. Van Kerckhoven, et al. 2002, A&A 390, 1089.
M. Bahou, P. Das, Y.-F. Lee, Y.-J. Wu, & Y.-P. Lee 2014, PCCP, 16, 2200.
For example, M. Tsuge, M. Bahou, Y.-J. Wu, L. Allamandola & Y.-P. Lee 2016, ApJ, 825, 96.
M. C. McCarthy, & P. Thaddeus 2007, JChPh, 127, 221104.
T. Nakanaga, & T. Amano 1987, Mol. Phys., 61, 313.

Formation of high-density amorphous ice by matrix sublimation method
A. Kouchi,1 T. Hama,1 Y. Kimura,1 H. Hidaka,1 R. Escribano,2 and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University, Japan
2
Instituto de Estructura de la Materia, IEM-CSIC, Spain

Various methods for the preparation of amorphous ice have been developed to investigate therelationship between its structure and method of formation (Fig.1). However, unknown amorphous
ice may still be discovered through new formation method.
A new method for the formation of amorphous ice has been developed. First, CO-rich ice mixture(CO:H2O ice) was deposited at around 10 K. Then, ice mixture was warmed-up. After the
sublimation of CO matrix at around 35 K, amorphous ice remained. We observed these process by
ultra-high vacuum transmission electron microscope and Fourier transform infrared spectrometer.
The amorphous ice formed shows highly porous texture, but it is high-density form similar tohigh-density amorphous ice formed under high pressure. The high-density amorphous ice is stable
up to 140 K, where it transforms directly to ice Ic.

Figure 1: Schematic temperature-density diagram for the formation of amorphous ices. The starting materials areshown in rounded rectangles, formation routes as arrows with name of methods, and products in rectangles.

References[1]

A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano & N. Watanabe, 2016, Chem. Phys. Lett., 658, 287.

Simulations of CH4/H2O ices as models for TNOs
R. Escribano,1 B. Maté,1 G. Molpeceres,1 P.C. Gómez,2 and M.A. Satorre3
1

2

Instituto de Estructura de la Materia, IEM-CSIC, Madrid, Spain
Departamento de Química-Física I, Universidad Complutense, Unidad Asociada UCM-CSIC,
Madrid, Spain
3
Centro de tecnologías Físicas, Universitat Politècnica de València, UPV, Alcoi, Spain

The arrival of the New Horizons mission to the limits of the solar system has provided new
and exciting data on the distant objects found there. Among these data, infrared spectra on a
range of locations of the surface of Pluto and Charon have shown the variety of compositionof different spots. The spectra reveal the general abundance of CH4 ice in Pluto, mixed with
CO, N2 and other hydrocarbons, and also the presence of H2O at some specific points [1].
The observed spectra cover the near-infrared range, 1.1 to 2.5 μm. Our goal in this work is tomake theoretical models for mixtures of ices with various compositions and predict theirspectra, aiming to match the New Horizons observations. In a first stage, we are focused on
mixtures of CH4 and H2O (see Figure). Previous experimental work of our group in this field
consisted in the measurement of optical constants and band strengths of CH4/C2H6 in the nearand mid-IR regions [2]. The methodology employed in this work consists in generating
amorphous mixtures of the desired composition by means of a molecular dynamics andoptimizing their structure searching for the minimum of their potential energy surface. This
structure is taken to calculate the harmonic vibrational spectrum, and as a starting point for amolecular dynamics simulation, which will yield also the prediction of the near-IR spectrum.
All calculations are carried out by means of Materials Studio software [3], using the Density
Functional Theory method, with GGA-PBE functionals and Grimme D2 dispersion correction.

Figure : Relaxed amorphous structure for a 5:1 CH4/H2O mixture.

References
[1]
[2]
[3]

W.M. Grundy et al. Science, 351, 1283, 2016.
G. Molpeceres et al., Astrophys. J, 825:156, 2016.
S.J. Clark, M.D. Segall, C.J. Pickard, et al., Z. Krist. 220, 567, 2005.

Infrared spectra of ice mixtures: Methane/Ethylene
Germán Molpeceres1(*), Miguel Angel Satorre2, Juan Ortigoso1, Carlos Millán2, Rafael
Escribano1, Víctor Herrero1, Isabel Tanarro1, Ramón Luna2, Belén Maté11

Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, 28006 Madrid, Spain
2
Escuela Politécnica Superior de Alcoy, UPV, 03801 Alicante, Spain)

Ethylene, a product of energetic processing of methane ices [1] is known to be an astromoleculepresent in our solar system [2]. In addition, methane is thought to be the most abundant ofhydrocarbons among those present in the surface of transneptunian objects (TNOs) [3]. Recently, the
New Horizons mission has provided abundant data of Pluto’s surface, and assignment of several
spectroscopic features associated with planetary ices is required.
In the present work, the second of a series dedicated to astrophysical relevant mixtures[4], a full setof spectroscopic data from 6000 cm-1 (1.6m) to 800 cm-1 (12.5m) has been obtained of ice mixturesat 30K of CH4/C2H4 in several proportions, namely 100/0, 75/25, 50/50, 25/75 and 0/100. Band
displacements, band strengths and imaginary and real components of the complex refractive index
have been determined for these materials in the spectral window under consideration. Along with thespectroscopic features, density and visible refractive index of these ices have also been measured.
For the study of the subtle spectroscopic effects arising from the mixtures with respect to the purespecies, we have built several theoretical models at the DFT level using the CASTEP code [5].
Simulation cells are randomly built using Montecarlo simulations and then, molecules in the cell arerelaxed until a minimum in the potential energy surface of the system is reached. Infrared spectra arecomputed at this minimum.
From our experiments we observe a deviation in several factors such as band positions and bandstrengths with respect to the pure species, as expected from previous works [6]. Band displacements
follow the trend expected for methane, in which a dilution in a non polar environment displaces themethane vibrations to lower wavenumbers with an increase in the wavenumbers of the second
molecule. An abrupt decrease of the density of ethylene in comparison with previous diffractometricmeasurements has also been observed [7]. Band strengths for methane also behave as in our previous
work, leading to decays in the total band strength with the dilution. However, for ethylene,
strengthening and weakening have been observed for different bands, leading to a complex
interpretation in which atomistic calculations play an important role.

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

Bennett, C.J., Jamieson, C.S, Osamura, Y., Kaiser, R.I, Astrophys. J. 653 2006. 792–811
Gladstone, G.R., Stern, S.A., Ennico, K., Olkin, C.B et al. Science 351 2016. 1280
Cruikshank, D.P., Grundy, W.M., DeMeo, F.E., Buie, M.W. Icarus 246, 2015. 82–92.
Molpeceres, G., Satorre, M.A., Ortigoso, J., Millán, C., Escribano, R., Maté, B. Astrophys. J. 825. 2016 156
Clark, S.J., Segall, M.D., Pickard, C.J., Hasnip, P.J. et al Z. Krist 220 2005. 567–570
Quirico, E., Schmidt, B., Icarus 127 1997. 354–378
van Nes, G.J.H., Vos, A. Acta Crystallogr. Sect. B 35 1979. 2593–2601

The OC-HOCO Complex: Identification and Implications for ISM Chemistry
Y. Yarnall1, F. Azari1, K. Stelmach1, P. Cooper1, O. Gadzhiev2 and A. Masunov3
1

Department of Chemistry and Biochemistry, George Mason University, USA
Department of Chemistry, N.I. Lobachevsky State University of Nizhny Novgorod, Russia
3
Department of Chemistry & NanoScience Technology Center, University of Central Florida,
USA
2

Abstract
Water (H2O) and carbon monoxide (CO) are two of the most abundant molecular constituentsof ices that accrete onto dust grains in the interstellar medium (ISM) [1]. Irradiation of suchices increases the chemical complexity of the ISM through generation of molecules such ascarbon dioxide (CO2), formaldehyde (H2CO), and methanol (CH3OH) [2]. While the study ofsuch ices in the laboratory can easily identify end products, reaction mechanisms are often muchharder to determine experimentally in ices. The reactions of reactive intermediates can,however, be investigated by using a combination of matrix-isolation spectroscopy andtheoretical chemistry.
In the present work, we identified the formation of an OC-HOCO complex in argon matrices
using infrared spectroscopy. The complex is formed in the matrix after deposition of adischarged dilute mixture of H2O and CO in argon at 6 K.

Figure 1: The structure of the OC-HOCO complex as was determined at the CCSD/cc-pVTZ theory level. Bond
lengths and bond angles are given in Å and degrees, respectively.

The proposed mechanism of formation involves the reaction between a hydroxyl (OH) radical
and CO, and so should also occur in the irradiated CO/H2O ices. This reactive intermediate is
likely a key participant in the formation of CO2 in CO-rich ices through a proton-transfer
reaction resulting in HCO and CO2 production.
OC-HOCO  HCO + CO2
The OH/2CO potential energy surface has been investigated theoretically and shows that theexothermic decomposition of the OC-HOCO to CO2 is likely. This previously unrecognizedcomplex could be an important intermediate in the formation of CO2 in CO-rich ices.
References[1] L. J. Allamandola, M. P. Bernstein, S. A. Sandford, & R. L. Walker, 1999, Space Sci. Rev., 90, 219.
[2] M. H. Moore, R. Khanna, B. Donn. 1991, JGR-Planets, 96, 17541.

Structural transitions of amorphous ice during heating
A. Kinjo, R. Netsu, and T. Ikeda-Fukazawa
Department of Applied Chemistry, Meiji University, Japan
In molecular clouds, elements such as hydrogen, oxygen, carbon, and nitrogen deposit on dust
grains, and are transformed into amorphous H2O ice and other various molecules. Because themolecules undergo chemical evolutions through various processes on amorphous ice, theamorphous ice has an important role for the chemical evolutions in the universe. Vapor
deposition method is often used for formation of amorphous ice, because deposition process issimilar to the situation of amorphous ice formation in the universe. When water vapor isdeposited at a low temperature, high density amorphous ice (HDA) ice is formed [1]. HDA ice
is transforms into low density amorphous (LDA) ice with warming. However, the phasetransition dynamics is less conclusive because the structure of deposited amorphous ice
depends on various factors; deposited temperature, growth velocity, impurities, thermal history
after deposition, and so on. To investigate the effects of deposition temperature on phasetransition dynamics, we analyzed sublimation and structural changes of water with heatingprocess using mass spectrometry and infra-red (IR) spectroscopy.
Amorphous ice was prepared with vapor deposition of distilled and degassed water on asubstrate of oxygen-free copper at 42–100 K. The total pressure in the vacuum chamber was
about 2.0 × 10–4 Pa during the deposition. After deposition of amorphous ice, the substrate was
warmed to 180 K at a rate of 2 K/min. The IR spectra were measured using Shimadzu
IRPrestage-21 at 2 K intervals during warming. The mass spectra were measured by Pfeiffer
QME220.
From the analyses of mass spectra, the four steps of gas desorption was observed in thetemperature range of 42–140 K. For the sample from deposition at 42 K, for instance, theobserved gas-desorption temperatures are 70, 100, 110 and 126 K. The desorption temperature
decreases as the deposition temperature increases. From the temperature dependence of wave
number of O–H stretching modes in IR spectra, the crystallization point to cubic ice (Ic) andtransition point from Ic to hexagonal ice (Ih) are confirmed to be around 145 and 175 K,
respectively. Thus, the present result suggests that the five types of amorphous phases exist in
the temperature range of 42–140 K. The first phase at <~70 K and the second phase at ~70 < T< ~100 K are assigned to HDA and LDA ice, respectively [1]. The fifth phase at > 126 K is
probably attributed to a precursor of ice Ic due to glass transition of water [2]. The precursor
exists because the crystallization to ice Ic is inhibited. For the third and fourth phases observed
at ~100 < T < ~126 K, the assignments are less conclusive. However, the gas desorption
observed in this temperature range may be due to a collapse of pore structures, because wave
number of the O–H stretching mode in IR spectra increases with warming. This indicates thestrength of hydrogen bonds increases as the temperature rise.
References[1][2]

A. H. Narten, C. G. Venkatesh, and S. A. Rice, 1976, J. Chem. Phys. 64, 1106.
P. Jenniskens, and D. F. Blake, 1996, ApJ 473, 1104.

Measurements of surface profile of amorphous solid water by a non-contact atomic
force microscope
H. Hidaka,1 Y. Sugimoto,2 A. Kouchi1, and N. Watanabe1
12Institute of Low Temperature Science, Hokkaido University, Japan
Department of Advanced Materials Science, Graduate School of Frontier Science, The
University of Tokyo, Japan

Amorphous solid water (ASW) is abundant material of interstellar ice and is mainly present
so as to cover the interstellar dust grains which are mineral particles with sub-micron size.
The physical and chemical phenomena occurring on ASW surface are affected by the surface
profile, because the adsorption, the desorption and the diffusion processes of atoms andmolecules depend on the that profile. Therefore, the surface profile of ASW is one of theimportant information for understanding of the surface reactions on icy dust grains. However,the profile of ASW in nano-scale range depending on the growth conditions is still unknown.
Recently, we performed the real-space observations of surface profile of ASW formed by avapor deposition method by using non-contact atomic force microscope (NC-AFM) at 45 and
103 K. The low-temperature ultrahigh-vacuum NC-AFM which was built by incorporating aself-designed cooling system into JSPM-4500A (JEOL) was used in this study. Measured
ASW films were prepared on a cold Si(111)7 7 surface by a oblique deposition using aeffusive H2O beam collimated by a micro capitally plate. An injection angle of H2O beam tothe substrate was selected to be 60°.
Figure 1(A) and 1(B) show(A)(B)
surface profiles of ASW formed at
45 and 103K, respectively. The
ice thickness and growth rate ofthose samples are about 2 nm (54BL) and 1 pm/s, respectively. The
surface structure at 45K shows therelatively flat and uniform size
structure than that at 103K. Fromthe height profiles of Fig. 1(C)(C)
(D)
and 1(D) on the lines of Fig. 1(A)and 1(B), respectively, it is foundthat the surface roughness at 103K
sometimes exceeds 1 nm within
the ice thickness of 2 nm, whereas
the roughness almost falls within±0.5 nm at 45K.

Figure 1: Comparison of surface profile of ASW formed by theoblique deposition method at (A) 45 and (B) 103K. The image
size is 250 × 250 nm2. Thickness and deposition rates of both
samples are 2 nm and 1 pm/s, respectively. (C) and (D) Heightprofiles at solid lines in Fig.1 (A) and 1(B), respectively.

In this presentation, the formation
mechanisms of observed surface
profiles depending on growthtemperatures will be discussed.

Effects of ion adsorption on surface structure of amorphous ice
Norifumi Hara, Riku Togashi, Yu Kumagai, and Tomoko Ikeda-Fukazawa
Department of Applied Chemistry, Meiji University, Japan
In interstellar molecular clouds, various molecules (for instance, H2O, NH3, CO, CO2,and so on) are formed from elements such as H, C, O, and N [1]. Most of H2O exists as a thinshell of amorphous ice around dust grain. The molecules undergo chemical evolutions toorganic molecules through various processes on the surface of amorphous ice [2]. Thus, thesurface structure of amorphous ice is an important factor to understand the molecular
evolution of organic molecules in molecular clouds. To investigate the effects of adsorption of
ion on the surface structure of amorphous ice, the molecular dynamics (MD) calculations ofamorphous ice with NO3− and NH4+ were performed.
The MD calculations were performed using an atom-atom potential model,
KAWAMURA potential model [3]. The amorphous ice was prepared by quenching of a liquid
phase consisting of 2760 water molecules from 280 to 235 K with 2.5 K/fs in cooling rate.
After annealing at 235 K, the system was cooled to 10 K. The density of amorphous ice at 10
K was controlled with the time period of the annealing at 235 K. To equilibrate thefundamental cell, the MD code was run for 40 ps at 10 K. Then, an ion (NO3− or NH4+) was
put in a position, such the center of nitrogen in ion was at a distance of 0.5 nm from theoutermost hydrogen atom in surface. An infinite surface was simulated by replicating the cellin the directions parallel to the surface using periodic boundary conditions. The pressure was
kept at 0.1 MPa. The layer with 0.5 nm in thickness from the outmost atom was analyzed as
the surface layer.
The result shows that the atomic displacement parameters (ADP) of oxygen andhydrogen of water molecules in surface layer increase during the adsorption of NO3− andNH4+. The maximum value of ADP for surface with NH4+ is larger than that with NO3−. The
values are diminished with formation of hydrogen bonds with surrounding water molecules,
and gradually approach the values of pure amorphous ice without ions. For surface with NO3−,
three oxygen atoms of NO3− form hydrogen bonds with hydrogen atoms in dangling bonds ofwater on the surface layer. In the case of surface with NH4+, hydrogen atoms form hydrogenbonds with oxygen atoms of water molecule in the surface layer. When an ion is adsorbed,
surrounding water molecules rotate to form hydrogen bonds with the ion. Thus, therearrangement of water molecules occur even at low temperature. The result indicates that thethermal vibrations of water molecules are enhanced with adsorption and diffusion of ions on
the surface, and the effects depend on ion species. The effects of ion adsorption might haveimportant implications for surface reaction in interstellar molecular clouds.
References[1] A. Kouchi, T. Yamamoto, T. Kuroda, J. M. Greenberg, 1994, Astron. Astrophys. 290, 1009.
[2] N. Watanabe, A. Kouchi, 2008, Surface Science, 83, 439.
[3] N. Kumagai, K. Kawamura, T. Yokokawa, 1994, Mol. Simul. 12, 177.

Experiments on hydrogenation and deuteration of C2H2 and C2H4 on low temperature surfaces :formation mechanism of C2H6 with astronomical interest
H. Kobayashi,1,2 H. Hidaka,3 T. Hama,3 H. Kawakita,1 and N. Watanabe3
1

Koyama Astronomical Observatory, Kyoto Sangyo University, Japan
2
Kyoto Nijikoubou, LLP, Japan
3
Institute of Low temperature Science, Hokkaido University, Japan

Simple hydrocarbons, acetylene (C2H2), ethylene (C2H4) and ethane (C2H6) widely exist in various circumstancesin space. Although the gas phase C2H2 and C2H4 are detected in limited objects of interstellar medium (ISM, e.g.,[1,2]), C2H6 was not detected in the ISM yet. Observational bias might be a reason for this difference because thebands of these species in infrared region are greatly affected by severe telluric absorptions. Alternatively theobservational results may reflect the result of chemical evolution in ISM. Thus we performed quantitative
experiments providing a precious clue for understanding the evolution of these hydrocarbons. As previously
proposed, one of most important processes to form C2H6 is hydrogenation of C2H2 on low temperature surface(C2H2 -> C2H3 -> C2H4 -> C2H5 -> C2H6) [3, 4]. We conducted hydrogenation experiments of pure C2H2 andC2H4 solids (to compare our results with the previous studies [3, 4]) and those on amorphous solid water (ASW,
to reproduce the ISM condition) at 10K and 20K, respectively. Deuteration experiments of C2H2 and C2H4 on
ASW were also performed. All experiments were conducted by using laboratory setup for surface reaction ininterstellar environment (LASSIE) at Institute of Low Temperature Science, Hokkaido University [5].
Obtained effective reaction rate constants, which are defined by a reaction rate constant times a number densityof atomic hydrogen/deuterium adsorbed on the surface, are shown in Figure 1 with a result of CO hydrogenation
on ASW reported by Hidaka et al. [6]. At 10K, the difference in the effective hydrogenation reaction rate
constants between C2H2 and C2H4 was found to be a factor of ~3 on both pure solids and ASW samples, whereas
previous experimental studies [3, 4] reported that the hydrogenation rate of C2H4 is larger than that of C2H2 byorders of magnitude. The kinetic isotope effects of hydrogenation/deuteration are found to be very small in both
C2H2 and C2H4 reactions at 10 K. This significantly small kinetic isotope effect for tunneling reactions can be
explained as “diffusive reaction” where the reaction process is dominated by diffusion of H and D atoms on thesurface. At 20 K, the effective rate constants of deuteration became larger than those of the hydrogenation. This
unusual behavior would be attributable to the difference of the number densities of H and D atoms on thesurface.

Figure 1: Temperature dependences of theeffective reaction rate constants for the H
and D atom exposure for each sample(filled square with solid line; C2H2-ASW+ H, filled square with dashed line;
pure-C2H2 solid + H, filled circle withsolid line; C2H4-ASW + H, filled circle
with dashed line; pure C2H4 solid + H,
open square with solid line; C2H2-ASW +D, open circle with solid line; C2H4-ASW+ H, triangle; CO-ASW + H).

References[1] Bast, J. E., Lahuis, F., van Dishoeck, E. F., Tielens, A. G. G. M. 2013, A&A, 551, 118[2] Hinkle, K. H., Wallace, L., Richter, M. J., Cernicharo, J. 2008, Proc. IAU symp. 251, 2008[3] Hiraoka, K., Takayama, T., Euchi, A., Handa, H., Sato, T. 2000, ApJ, 532, 1029
[4] Bennet, J. E., and Mile, B. 1973, J.Chem.Soc, Faraday Trans. 1, 69, 1398
[5] Watanabe, N and Kouchi, A. 2002, ApJ, 571, L173
[6] Hidaka, H., Watanabe, N., Shiraki, T., Nagaoka, A., Kouchi, A. 2004, ApJ, 614, 1124

Negative catalytic effect of amorphous solid water on the hydrogen
abstraction from dimethyl ether with deuterium atoms at low temperatures
Y. Oba, N. Watanabe, and A. Kouchi
Institute of Low Temperature Science, Hokkaido University, JAPAN
Amorphous solid water (ASW) plays crucial roles in interstellar chemistry as a cold catalytic
surface for various chemical and physical processes. Previous studies reported that the surfaceof ASW lowers an activation barrier of some reactions such as tunneling hydrogen addition toformaldehyde [1]. In addition, some reactions of H and D atoms with molecules such as CO
were found to be enhanced on ASW at higher temperatures due to the longer residence timeof the atoms on ASW [2]. So, does ASW always act as a “positive” catalyst for chemical
reactions on interstellar grains? In the present poster, we will show experimental results on the“negative” catalytic effect of ASW on the quantum-tunneling hydrogen abstraction fromdimethyl ether (DME: CH3OCH3) by deuterium (D) atoms at low temperatures. By forming acomplex with water via a hydrogen bond, the C-H stretching band of DME shows a blue-shift
as a result of the C-H bond contraction [3], which may suppress the reaction compared to thatof pure solid DME with D atoms.
The experiments were performed in an apparatus named ASURA, which is mainly composedof an ultra-high vacuum chamber, an atomic source, and a FTIR. The base pressure of thereaction chamber is about 10-8 Pa. DME-H2O complex with the thickness of ~25 monolayers(1 monolayer = 1015 molecules cm-2) was produced by the vapor-deposition of the mixed gas(DME:H2O = 1:4) onto an Al substrate at 15 K. D atoms were produced by the dissociation ofD2 molecules in microwave-induced plasma and cooled to 100 K. The sample solid was
exposed to D atoms for up to 240 min at 15 K. Progress in reaction was monitored in-situ by
the FTIR. The reaction of pure solid DME (~10 monolayers) with D atoms was also
investigated under the same experimental conditions for comparison.
When pure solid DME was exposed to D atoms at 15 K, the formation of deuterated DME
was observed on the FTIR spectrum of the reaction product, which indicates the occurrence ofhydrogen (H)-D substitution of DME. We propose the successive H-abstraction and Daddition occurred as follows: (1) CH3OCH3 + D → CH2OCH3 + HD, (2) CH2OCH3 + D →CH2DOCH3. Since reaction (1) has a large activation barrier of ~3600 K in the gas phase [4],quantum-tunneling is required for the reaction to occur at 15 K.
When solid DME in the complex reacted with D atoms, the H-D substitution reactions also
occurred under the same experimental conditions. However, the reaction was more than 20
times slower than pure solid DME + D. This would be due to the strengthening of the C-H
bond, which is attributable to the formation of a complex with H2O via hydrogen bond.

References[1] D. E. Woon, Astrophys. J., 2002, 569, 541[2] Watanabe N. & Kouchi A., 2008, Prog. Surf. Sci., 83, 43[3] Barnes A. J. & Beech T. R., 1983, Chem. Phys. Lett., 94, 568[4] Saheb V.,J. Phys. Chem. A, 2015, 119, 4711

Photodesorption and CO2 formation induced by 157 nm irradiation to CO on water ice
S. Matsuda,1 M. Yamazaki,2 A. Harata,1 and A. Yabushita1
1Department of Molecular and Material Sciences, Kyushu University, Japan2
Department of Molecular Engineering, Kyoto University, Japan

Photodesorption of CO is suggested as a possible process which maintains a measurable
amount of gaseous CO in cold interstellar clouds, where thermal desorption is negligible.
Observations have indicated that the water-rich ice layer forms first on the grain and that most
CO ice is present on top of the water ice [1]. Previous study indicates that there are two typesof CO adsorption sites, free hydroxyl groups and oxygen atoms of surface coordinately
unsaturated water molecules [2]. UV-induced CO2 formation using CO/H2O binary ice wasreported [3]. However, the effect of adsorption states of CO on CO2 formation has not beenstudied. In this study, we have investigated 157 nm photodesorption of CO on water ice at 8
K by measuring the time-of-flight (TOF) spectra of CO (v=0) detected by (2+1) resonanceenhanced multiphoton ionization technique. Using the reflection absorption infrared (RAIR)
spectroscopy, adsorption sites of CO on water ice and photoproducts was measured.

0.006

1

Absorbance

CO signal intensity / arb.unit

Figure 1 shows typical TOF spectrum of CO from 0.15 ML CO on water ice at 8 K. Measured
spectrum could be characterized by a combination of three different Maxwell-Boltzmann
distributions. It was described by a fast component (A) with Ttrans = 1700 ± 300 K, a middle
component (B) with Ttrans = 450 ± 100 K and a slow component (C) with Ttrans = 100 ± 30 K.
The result indicates that there are three possible processes for photodesorption. Figure 2
shows RAIR spectra after 2, 6, 10 × 104 shots of 157 nm irradiation to 0.4 ML CO on water
ice at 8 K. The peak is attributed to CO2. CO2 was produced via the reaction of CO with OH
radical which was generated by photodissociation of water ice. In this presentation, we
evaluate the possible link between adsorption sites of CO and CO2 formation induced by 157
nm irradiation.

B
0
0

5

10

0.002

0.000

C

A

0.004

15

20

2400

Time of flight / s

Figure 1: TOF spectrum of photodesorbed CO(v=0) from 0.15 ML CO on water ice.

2360 2340 2320
Wavenumber / cm-1

2300

Figure 2: RAIR spectra measured after 2 (solid),
6 (dashed), 10(dotted) × 104 shots of 157 nm
irradiation to 0.4 ML CO on water ice.

References
[1]
[2]
[3]

2380

K. M. Pontoppidan et al., 2008, Astrophys. J., 678, 1005.
A. V. Rudakova et al., 2010, Opt. Spectrosc., 109, 708.
N. Watanabe and A. Kouchi, 2002, Astrophys. J., 567, 651.

Nuclear spin isomers of photodesorbed water from ice at 10 K
T. Hama,1 A. Kouchi,1 and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University, Japan

Recent astronomical observations have observed H2O in space. The ubiquity of H2O makes it
essential to clarify the chemistry of interstellar H2O to further our understanding of theformation of stars and planetary systems, including our solar system. [1]A key observable related to interstellar water chemistry is the abundance ratio of nuclear spinisomers (the ortho-to-para ratio, OPR), because it is a valuable tracer of the physical andchemical history of H2O. Cometary comae, and star- and planet-forming regions have of
OPRs for gaseous H2O (0.1–2.4), which are anomalously lower than the statistical value of 3.
The OPR of H2O in a comet has been considered a indicator that gives the past formation
temperature (30 K) of the ice nucleus in the solar nebula. The low OPR of interstellar H2O has
also been used to determine the formation temperature (<50 K) of water ice on cold
interstellar dust. However, the use of the OPR as a temperature probe requires the assumptionthat the OPR of H2O desorbed from ice is related to the ice temperature. However, the OPR of
H2O desorbed from ice remains poorly understood, especially at low temperatures, and theabove assumption has not been validated. Therefore, the significance of the OPR of water is
unknown and remains one of the most problematic issues in astronomy and planetaryscience. [2]The present study performed direct measurements of the OPR of water photodesorbed fromwater ice at 10 K. The photodesorbed water showed the statistical high-temperature OPR of 3,even when the ice is produced in situ by hydrogenation of O2, a known formation process ofinterstellar water. Our results indicate that the OPR did not reflect the formation temperatureof the ice (10 K, OPR = 0.3). Reinterpretation of previous observations is necessary and will
improve our understanding of interstellar chemistry, and the formation of the solar system andcomets. [3]References
[1]
[2]
[3]

E. F. van Dishoeck, & E. Herbst, D. A. Neufeld, 2013, Chem. Rev. 113, 9043.
T. Hama, & N. Watanabe, 2013, Chem. Rev. 113, 8783.
T. Hama, A. Kouchi, & N. Watanabe, 2016, Science 351, 65.

Temperature dependence of ortho-to-para conversion of H2 on amorphous solid waterat around 10 K
H. Ueta,1,2 N. Watanabe,1 T. Hama,1 A. Kouchi1
11

Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
2
National Institute for Material Science, Tsukuba, Ibaraki, Japanwatanabe@lowtem.hokudai.ac.jp

The ortho-to-para abundance ratio (OPR) of H2 is crucial for chemical evolution anddeuterium fractionation of molecules in molecular clouds, because H2 in the ortho-groundstate (J=1) is more energetic (and thus reactive) than that in the para-ground state (J=0) byapproximately 14.6 meV corresponding to 170 K, which is significantly higher than typicaltemperatures of molecular clouds. Since the radiative transformation of molecular nuclear
spins is forbidden in the gas phase, the OPRs of hydrogen molecule (H2) observed towardvarious astronomical objects have been often considered as tracers of chemical history of themolecule.
In the gas phase, spin-exchange reaction with either ionic or neutral hydrogens can alter the
OPR of H2. In contrast, little is known about how the nuclear spins behave on cosmic ice dust.
It was often assumed without the experimental evidences that the OPR of H2 formed on thecosmic dust surface is statistical value of 3. Recently, our group has tackled this issue
experimentally and found that the OPR of nascent H2 is 3 at the formation by H-H
recombination on cosmic ice dust [1]. In the preset study, using experimental techniques ofmolecular beam, photostimulated-desorption, and resonance-enhanced multiphoton ionization,
we measured the OPRs of H2 photodesorbed from amorphous solid water (ASW) at
temperatures around 10 K, which is an ice dust analogue. We demonstrated that the OPR of
H2 easily varies on ASW and that the rate of spin conversion from ortho to para steeply
increases from 2.4×10-4 to 1.6×10-3 s-1 within the very narrow temperature window of 9.5
to12 K and reach a plateau at temperatures above 12 K [2]. This temperature dependencecannot be explained solely by state-mixing models ever proposed [3]. The temperaturedependence of the conversion rate was very well represented by the power law of T7 where T
is the surface temperature. This indicates that the conversion rate at lower temperatures isdominated by the two-phonon energy dissipation process (Raman process) for the excessenergy (~14.6 meV) arising from the conversion, and at higher temperatures the rate may belimited by a spin-flip transition rate.
From the present and our previous results, astrochemical history of interstellar H2-OPR is
depicted as follows. When H2 molecule is produced by H-H recombination on cosmic ice dust,
the OPR of nascent H2 is 3 [1]. If the H2 is immediately desorbed at the formation, the OPR of
H2 released should be near 3. However, if H2 is trapped even for a short period on the ice dust
surface before desorption, the OPR at desorption strongly depends on the surface temperatureand duration of trapped.

References[1] Watanabe, N., Kimura, Y., Kouchi, A., Chigai, T., Hama, T., Pirronello, V., Astrophys. J.
Lett. 714, L233 (2010).
[2] Ueta, H., Watanabe, N., Hama, T., Kouchi, A., Phys. Rev. Lett. 116, 253201 (2016).
[3] Sugimoto, T., Fukutani, K., Nature Physics 7 307 (2011).

Sublimation dynamics and isotope fractionation of
crystalline- and amorphous-ice thin films
F. Kato,1 T. Sugimoto,1,2 K. Watanabe,1 and Y. Matsumoto1
1

Department of Chemistry, Graduate School of Science, Kyoto University, Japan
2

JST Precursory Research for Embryonic Science and Technology, Japan.

Ice sublimation is one of the most fundamental processes associated with growth of ice
particles and snow on earth and in the universe [1, 2]. In spite of the fundamental importanceof molecular level understanding of the sublimation process, little is known about mechanistic
details including isotope effects. It was recently reported that not only the translational degreeof freedom but also the rotational degree of freedom play key roles in the desorption processof water molecules, based on the comparison of sublimation rates of pure H2O, D2O andH218O ice [3]. However, the effects of neighboring water molecules on desorption process
have not been investigated, although water molecules at ice surfaces are strongly interacted
each other through hydrogen bonds.
Here, using temperature-programmed desorption (TPD) under ultra-high vacuum condition,
we have investigated the sublimation dynamics of H2O, HDO, and D2O from isotope mixed
crystalline-ice (CI) and amorphous-ice (AI) thin films, whose D to H ratio xD was
systematically controlled. For both CI and AI, desorption rate of each isotope becomes
smaller as the xD become increased (Fig. 1). This result indicates that desorption of watermolecules from ice surface is not a unimolecular process; neighboring water molecules indeed
affect the desorption rate. Based on the Arrhenius plots, we found that many-body cooperative
isotope effects appear at larger xD, especially in the pre-exponential factor of the desorption
rate rather than the activation energy of desorption. Additionally, we found the extraordinary
isotope fractionation of AI under and after the crystallization process at ~155 K. We will

HDO des. rate [ML/s]

discuss these results in details.
2.0
1.5
1.0
0.5

HDO from CI
D ratio xD
0.26
0.44
0.74
0.93

Figure 1: D to H ratio dependence of thedesorption rate of HDO molecules fromisotope mixed CI.

0.0
140

150
160
170
Temperature [K]References[1] N. Fray, & B. Schmitt, 2009, Planetary and Space Science 57, 2053.
[2] U. Nakaya, 1955, Journal of the Faculty of Science, Hokkaido University. Ser. 2, Physics 4, 341[3] J. A. Smith, F. E. Livingston, & S. M. George, 2003, J. Phys. Chem. B 107, 3871.

A theoretical study on physisorption states of non-metal adatom on graphene
Y. Kunisada and N. Sakaguchi
Center for Advanced Research of Energy and Materials,
Faculty of Engineering, Hokkaido University, Japan

Because of the low density of gases in cosmic space, molecular formation reaction can notrelease the heats of exothermal chemical reactions. On the other hand, if the chemical reaction
occurs on dust grain surfaces, heat of formation can be dissipated to substrates. Therefore,
dust grains are considered as one of the most important stages for various molecularformation reaction.[1] Dust grains are generally in low temperature condition. For instance,
the temperature of dense clouds is about 10 K. In these low temperature conditions,adsorbates cannot thermally diffuse because of its strong chemical bonding to substrates,
which indicates that the physisorbed adsorbates play an important role of chemical reaction
on dust grain. Therefore, in this study, we investigated the physisorption properties of nonmetal atoms on carbon materials.
In this study, we performed the first principles calculations based on density functional theory,
which is implemented in the plane-wave and projector-augmented wave method code, theVienna Ab-initio Simulation Package (VASP 5.3.3).[2-7] We applied a 550 eV cutoff to limit
the plane-wave basis set without compromising computational accuracy. A 5 × 5 × 1
Monkhorst–Pack special k-point grid [8] for the first Brillouin zone sampling and a Gaussian
smearing model of σ=0.05 eV was used. Moreover, we took the van der Waals interaction into
consideration with the non-local correlation functional rev-vdW-DF2 [9,10] to treat
pysisorption states on graphene accurately. We focused on the H, N, and P adsorption on 4 ×
4 graphene. The supercell was constructed with a 20 Å vacuum separation between slabs to
reduce the interaction between slabs.
At first, we studied the dependence of H adsorption energy on the H coverage. We considered
the H coverage of 0.02 to 1 ML. We found that the interaction between H atoms on graphene
is smaller than 1 meV with H-H distance of 10 Å. Therefore, in this study, we adopted 4x4graphene as substrates. The adsorption energies of H, N, P atoms on graphene correspond to80, 120, 130 meV, respectively. In the workshop, we will also report the diffusion propertiesof adsorbates on graphene.

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

T. Hama, & N. Watanabe 2013, Chem. Rev. 113, 8783.
G. Kresse & J. Hafner 1993, Phys. Rev. B, 47, 558.
G. Kresse & J. Hafner 1994, Phys. Rev. B, 49, 14251.
G. Kresse & J. Furthmüller 1996, Comput. Mater. Sci., 6, 15.
P.E. Blöchl 1994, Phys. Rev. B, 50, 17953.
G. Kresse & J. Furthmüller 1996, Phys. Rev. B, 54, 11169.
G. Kresse & D. Joubert 1999, Phys. Rev. B, 59, 1758.
H.J. Monkhorst & J.D. Pack 1976, Phys. Rev. B, 13, 5188.
I. Hamada 2014 Phys. Rev. B, 89, 121103(R).
Y. Kunisada & H. Kasai 2015, Phys. Chem. Chem. Phys., 17, 19625.

Theoretical study on dissociative recombination reaction of NH2+
T. Koyama, T. Akama, and T. Taketsugu
Department of Chemistry, Faculty of Science, Hokkaido University, JapanThe dissociative recombination (DR) reaction is a combination of an electron and a positive
molecular ion, which is followed by the dissociation into neutral molecules. The DR reaction
proceeds via the direct process or the indirect process. In the direct process, the molecule
system makes transitions directly from the electronic ground state of cation to the dissociative
excited state of neutral molecule after capturing an electron. In the indirect process, thistransition proceeds via Rydberg states. In the interstellar space, temperature and pressure is so
low that the DR reaction which proceeds with electrostatic attraction is very important.
We have studied the DR reactions of HCNH+ [1], H3O+ [2], and HD2O+ [3], using ab initio
molecular dynamics (AIMD) simulation with a surface hopping scheme, and discussed nonadiabatic dynamics and the branching mechanism. In the present study we investigate themechanism of the DR reaction of NH2+,
NH2+ + e- → [NH2]* → dissociation products.
While in the previous studies initial condition of AIMD simulation was determined byconservation of energy before and after the collision, in this study we aim to take electron
dynamics into account for the initial condition. The electron dynamics can be described byreal-time propagation of time-dependent density functional theory (RT-TDDFT).
For preparation of electron dynamics, geometry of positive molecular ion NH2+ was
optimized first by the B3LYP/cc-pVTZ method. Then, excited states of NH2 which areproduced after the collision were calculated by CASPT2 and TDDFT(B3LYP) with the ccpVTZ basis-set. The TDDFT result was very close to the highly accurate CASPT2 result, andso we decided to adopt TDDFT in the following. Because the indirect process needs the
Rydberg states, TDDFT calculation including Rydberg basis-set was also carried out. The
result of this calculation shows that Rydberg state lies at low level, indicating that thisreaction may proceed via the indirect process. Next, we will perform electron dynamics todetermine the initial distribution of electronic states just after the collision, and execute AIMD
simulation.

References
[1]
[2]
[3]

T. Taketsugu, A. Tajima, K. Ishii, & T. Hirano, 2004, ApJ 608, 323.
M. Kayanuma, T. Taketsugu, & K. Ishii, 2006, CPL 418, 511.
M. Kayanuma, T. Taketsugu, & K. Ishii, 2008, TCA 120, 191.

Electron dynamics described by real-time time-dependent Hartree-Fock and/or timedependent density functional theory (RT-TDHF/TDDFT) calculation
T. Akama and T. Taketsugu
Department of Chemistry, Faculty of Science, Hokkaido University, Japan

Electron dynamics, which is an ultrafast phenomenon occurring in attoseconds or
femtoseconds, was recently observed by experiments and has attracted much attention.
Electron dynamics is caused by change of external field of the intriguing system, such as lightor collision of molecules and electrons. Therefore, electron dynamics should play animportant role in reaction of interstellar matters which is sometimes concerned withelectronically excited states. To elucidate mechanism of electron dynamics, theoretical
calculation would be a powerful tool. Real-time propagation (RT) of time-dependent theories,
such as time-dependent Hartree-Fock (TDHF) method and time-dependent density functional
theory (TDDFT), have been applied to describing electron dynamics,.
In previous studies, electron dynamics described by RT-TDHF/TDDFT calculations wasanalyzed by the Fourier transform technique to obtain frequency-domain properties anddirectly through time evolution of molecular properties. In this study, we proposed short-time
Fourier transform (STFT) analysis for electron dynamics [1]. STFT is a time-frequency
analysis technique to provide time evolution of spectrum, which is called spectrogram. Figure
1 shows absorption spectrograms obtained by STFT analysis of RT-TDHF calculation offormaldehyde dimer as a model system. The STFT analysis of RT-TDHF calculation enables
us to directly observe the electron dynamics associated with the excited states.
Furthermore, the RT-TDHF/TDDFT approaches have limited applications because evaluationof the time evolution operator is computationally demanding. In this study, we developed anefficient time evolution method based on three-term recurrence relation (3TRR) [2]. 3TRR isderived by introducing transformation of the operator in time-dependent equation, such as
Hamiltonian. The 3TRR method achieved efficiency that is about four times faster thanconventional fourth-order Runge-Kutta method.

Figure 1: (a) Formaldehyde dimer model, in which two molecules are vertically arranged; (b) Absorption
spectrogram for z direction; (c) Absorption spectrogram for y direction.

References[1][2]

T. Akama & H. Nakai, 2010, JCP 132, 054104.
T. Akama, O. Kobayashi, & S. Nanbu, 2015, JCP 142, 204104.

Laser Spectroscopic Study of CaH B/B'(ν=10, 11) -X bands
Kyohei Watanabe1, Naoya Yoneyama1, Kanako Uchida1, Kaori Kobayashi1,
Fusakazu Matsushima1, Yoshiki Moriwaki1 and Stephen C. Ross2
1

2

Department of Physics/ University of Toyama, Japan
Department of Physics/ University of New Brunswick, Canada

Electric transitions of Calcium monohydride (CaH) have been found in sunspots and M
dwarf stars [1], and have been used to investigate them. Despite the long history of study ofthis molecule the first two exited 2Σ+ states, B/B’ and D2Σ+, have continued to pose challenges
for experiment and theory. The B/B’ state is formed by the avoided crossing between two
diabatic states and a non-bonding diabatic state, resulting in a double minimum potential
energy function. Martin calculated energy levels in Born-Oppenheimer approximation [2]. He
was able to perform a least-squares fitting to the available rovibronic data. The result was aset of empirically generated, but physically-constrained, potential energy curves for the X,
B/B’, D states. Carlsund-Levin et al. used updated versions of Martin’s potential but also
accounted for Martin’s R-dependent interaction
B/B' state
D state/cm-1
term in a coupled-channel (CC) calculation of the E30000
BO
CC/Expt. CC/Expt. BO
rovibronic energies [3]. In a bid to resolve
8
23
discrepancies in vibronic assignments of these states
722
we observed the rotational-resolved fluorescence21
620
spectrum of CaH.
19
518
In previous work, we observed four vibronic levels
174
and attributed them to B/B’ (ν=12, 13, 14 and 16)16325000 15
lying above the double-minimum potential energy
142
barrier, and five levels previously assigned to the D
13
12state [4], to the B/B’ state. In additional to this, we1
11
recently observed the B/B' (ν=10, 11) levels. Fig 1
100
9shows the vibrational levels of D and B/B’. The
CC/Expt. BO
8levels’ properties alternate strongly with vibrational
D state7
6
excitation and the new assignment brings the
520000
B/B' BO
4experimental vibronic structure into remarkably
B/B' CC
3
B/B' Expt.
good agreement with the CC calculation values of
D BO
2Carlsund-Levin.
D CC
Figure 1: Vibronic energy levels of the B/B’2Σ+ and D2Σ+states of CaH. Outer lines show values calculated in the
Born-Oppenheimer approximation [2]. Dotted lines in thecenter show the couple-channel (CC) calculated values [3].
Thick solid lines in the center show experimental values[4-7]. B/B' (ν=10, 11) are shown by the green lines.
Close lying levels are connected (in the center) to highlightinteractions between the B/B’2Σ+ and D2Σ+ states.

D Expt.

1
0
15000

References[1] C. M. Olmsted, Astrophys. J. 27, 66(1908).
[2] H. Martin, J. Chem. Phys. 88, 1797(1988).
[3] C. Carlsund-Levin et al., Scrinzi, Physica Scripta. 65, 306 (2002).
[4] K. Watanabe et al., Chem. Phys. Lett. 657, 1 (2016).
[5] A. Shayesteh, et al. J. Mol. Struct. 288, 46(2013).
[6] B. Grundström. Z. Phys. 75, 302 (1932).
[7] G. D. Bell et al. Physica Scripta, 20, 609(1979).

BO
CC/Expt.
B/B' state

A New Terahertz Emission Spectrometer at RIKEN
Y. Chiba,1 N. Sakai,2 Y. Ebisawa,1 K. Yoshida,1 T. Sakai, 3 Y. Watanabe,1 and S. Yamamoto1
1

Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
2
RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
3
Graduate School of Informatics and Engineering, The University of Electro-Communication,
Chofu, Tokyo 182-8585, Japan
In radioastronomy, rotational emission lines of molecules are extensively observed toinvestigate physical and chemical structures of target sources. For secure identification ofmolecules and accurate analyses of Doppler shifts caused by overall/internal motions of thetarget sources, accurate rest frequencies of molecular transitions are indispensable. Rest
frequencies of various molecules have been measured by spectroscopic studies in thelaboratory, and are tabulated in the spectral line catalogs with the aid of extrapolation basedon spectroscopic data analyses. However, their accuracies are sometimes insufficient for
identification of molecules and detailed discussions of the velocity structure of the sources,
which causes serious limitation and uncertainty in astrophysical and astrochemicalinterpretations. Hence, it is important to measure rest frequencies of the transitions used for
astronomical observations directly by the laboratory spectroscopy. Such an effort is more andmore important in the ALMA era, because even faint rotational spectral lines of various
isotopic species as well as those in vibrationally excited states, which have not been wellstudied in the laboratory, are readily observed, thanks to high sensitivity of ALMA.
With this in mind, we are constructing a new laboratory THz emission spectrometer at
RIKEN. A block diagram of the spectrometer is shown in Figure 1. We measure theemission of rotational transitions of molecules in the 2 m long glass cell by using thesuperconducting hot electron bolometer (HEB) mixer receiver, which has been developed for
the THz astronomical observations [1]. The HEB mixer is mounted on the ALMA-type
cartridge receiver system. The THz emission from the molecule is down-converted to the 1.01.6 GHz range, and is frequency-analyzed by the XFFTS spectrometer with the spectral
resolution of 0.8 MHz. We are now assembling the components toward test measurements.
At this moment, the frequency coverage is limited to 0.8 THz-0.9 THz and 1.3-1.5 THz. We
are planning to extend it to the lower frequencies by employing the SIS mixer receivers.

Figure 1: The block diagram of the spectrometer at RIKEN

References[1]
T. Soma, “Development of the HEB receiver for ground-based THz astronomical observations”, PhD
thesis, The University of Tokyo, 2015

Detections of long carbon chains CH3CCCCH, C6H, linear-C6H2 and C7H in the lowmass star forming region L1527
Mitsunori Araki,1 Shuro Takano,2 Nami Sakai,3 Satoshi Yamamoto,4 Takahiro Oyama,1Nobuhiko Kuze,5 Koichi Tsukiyama1
1

Department of Chemistry, Tokyo Univ. of Science, Japan2
Department of Physics, Nihon Univ., Japan
3
RIKEN, Japan
4
Department of Physics and Research Center for the Early Universe, Univ. of Tokyo, Japan
5
Department of Materials and Life Sciences, Sophia Univ., JapanLong carbon chains CH3CCCCH, C6H, l-C6H2, and C7H were detected in the low-mass star
forming region L1527, showing a warm carbon chain chemistry (WCCC), by using GreenBank 100 m telescope. The K = 0, 1, and 2 lines of the J = 11‒10 transition of CH3CCCCH
were detected, and the column density and the gas kinetic temperature were determined to be
5.6 × 1012 cm−2 and 20 K, respectively. The 2П1/2 state of C6H, locating 15.04 cm−1 higher
than the 2П3/2 state, was detected for the first time except for the circumstellar envelope
IRC+10216. The column densities of the 2П1/2 and 2П3/2 states of C6H in L1527 were derived
to be 1.6 × 1011 and 1.1 × 1012 cm−2, respectively, leading the temperature of 11 K between
the two states. In the present observations, the Ka = 0 line of para species of l-C6H2 wasdetected, although the detection was limited for the Ka = 1 line of ortho species so far except
for IRC+10216. The column densities of the ortho and para species of l-C6H2 wereindependently obtained to be 1.3 × 1011 and 0.6 × 1011 cm−2, respectively. C7H was detected
for the first time except for IRC+10216. The column density of C7H was estimated to be 6.2 ×1010 cm−2 from the J = 24.5‒23.5 and 25.5‒24.5 lines. These results of detections would
suggest that C7H and C6H2 are remarkably abundant species in L1527 although they are longcarbon chains. These species can be good probes of chemical composition for heavy
molecules in WCCC regions.

Figure 1: The J = 24.5‒23.5 and 25.5‒24.5 rotational transitions of C7H (21/2) observed by the GreenBank 100 m telescope .

Study of CH3CN in Diffuse Clouds by “Hot Axis Effect”
Mitsunori Araki,1 Shuro Takano,2 Yoshiaki Minami,1 Kei Niwayama,1 Nobuhiko Kuze,3Takahiro Oyama,1 Kazuhisa Kamegai,4 and Koichi Tsukiyama1
1

2

Department of Chemistry, Tokyo University of Science, Japan
Department of Physics, College of Engineering, Nihon University, Japan3
Department of Materials and Life Sciences, Sophia University, Japan
4
National Astronomical Observatory of Japan, JapanThe diffuse interstellar bands (DIBs) are optical absorption lines by molecules in diffuse
clouds. Initially observed more than 100 years ago, they still remain the longest standing
unsolved problem in spectroscopy and astrochemistry, although five DIBs have recently been
identified as due to fullerene ion C60+ [1]. Identifications of DIBs are important because they
can give us information on chemical composition in diffuse clouds. To further identify carrier
molecules of DIBs we have measured DIB candidate molecules produced in the laboratory tocompare their absorption spectra with astronomically observed DIB spectra. In this work, we
first present our latest results on the search for the thiophenoxy radical C6H5S, benzene
derivative, by using our cavity ringdown spectrometer [2]. We then present a new insight into
diffuse clouds. Molecules in diffuse clouds are collisionally heated and radiatively cooled. In
diffuse clouds the latter is dominant. Due to the spectroscopic selection rules, acetonitrile
CH3CN is cooled well for the end-over-end rotation but is not cooled for rotation around its
molecular axis, as shown in Figure 1. We made a model of this non-thermal rotation as “HotAxis Effect.” Based on this model, we estimated a rotational absorption spectrum of CH3CN
in the radio frequency region. By using Nobeyama 45 m radio telescope, the absorption lines
were searched in the diffuse clouds in front of the Orion IRc2 region and the radio continuum
source B0212+735 quasar. The upper limits of column densities of CH3CN toward Orion
IRc2 and B0212+735 were determined to be 2×1012 and 2×1013 cm−2, respectively. On theother hand, a possible absorption feature, as a disturbed feature around the K = 3, 2, 1, and 0lines, by Hot-axis effect for CH3CN was found in the spectrum toward Sgr B2 in the reported
line survey data [3], as shown in Figure 2.

J
CooledK
No Cooling
Permanent
Dipole Moment

Figure 1 (Left): Hot-axis effect for a symmetric-top molecule. The red dotted line is the hot-axis.
Figure 2 (Right): Absorption feature of K = 4 and a disturbed feature around the K = 3, 2, 1, and 0 lines by
Hot-axis effect for CH3CN in the spectrum of Ref. [3]. The black line is an observed profile, and green amode one.

References[1] Campbell et al., 2015, Nature 523, 322, Walker et al., 2015, ApJ 812, L8, Campbell et al., 2016, ApJ 822, 17.
[2] Araki et al., 2014, ApJ 148, 87. [3] Belloche et al., 2013, A&A 559, 47.

Computational Molecular Spectroscopy:
Fe-containing Molecules of Astrochemical Interest
Tsuneo Hirano,1 Umpei Nagashima,2 and Per Jensen3
1)
Ochanomizu University, Japan.
2)Foundation for Computational Science (FOCUS), Japan.
3)
Bergische Universität, Germany
The aim of Astrochemistry is to elucidate how molecules have evolved in space, i.e., todetermine which molecules are there and which reactions have formed them. More than 180
molecules have been detected already. Although Fe is known to have a large cosmic
abundance comparable to those of Mg and Si, the only iron-containing molecules detected in
the cosmic environment so far are FeH in sunspots [1], FeO toward Sgr B2 [2,3]，and
FeCN toward IRC +10216 [4]. In 1994, we made a preliminary ab initio calculation for
FeCO as a candidate for observation in interstellar space, but attempts to detect it in space
failed [5,6]. Then we started ab initio calculations on several Fe-containing molecules ofastrochemical interest, including FeC [7], FeN [8], FeS, FeNC [9], FeCN [10], FeOH [11,12],and FeCO [13 (electronic properties)]. We will report here recent progress of computational
molecular spectroscopy on Fe-containing molecules.
For FeCO, we have published a very accurate 3D potential energy surface [14], and reported
many ro-vibrational properties. The calculated rotational constant B0 deviates by only 0.03%
from experimental value. For FeCN, observed by the Ziurys group toward IRC +10216 [4],the electronic ground state was erroneously claimed to be 4∆i [4] simply because rotational
spectrum for the other electronic states was not observed in their laboratory. Our
MR-SDCI+Q calculations show that the 4∆i state is higher in energy than the 6∆i state by ca.
4000 cm-1.
FeOH is another possible interstellar molecule candidate, but neither laboratory experiments
nor space observations have been reported. Stimulated by IR cold-chemistry experiments on
FeO+ reactions by the Dieter Gerlich group [15], we have calculated the equilibrium
structures and energy levels of FeO, FeO+, and FeOH+. Presently, 3D PES calculations for
FeOH+ are in progress.
We hope these studies will be helpful for identification of more Fe-containing molecules inspace.
References.

[1] P.K. Caroll, P. McCormack, and S. O'Connor, Astrophys. J., 208, 903 (1976). [2] C.M. Walmsley, R.
Bachiller, G. Pineau des Forêts, and P. Schilke, Astrophys. J., 566, L109 (2002). [3] R.S. Furuya, C.M.
Walmsley, K. Nakanishi, P. Schilke, and R. Bachiller, A & A, 409, L21 (2003). [4] L.A.Zack, D.T. Halfen,
L.M. Ziurys, ApJ,Lett.,733,L36 (2011). [5] Y. Kasai and K. Obi, Y. Ohshima, Y. Endo, and K. Kawaguchi, J.
Chem. Phys.,103,90 (1995). [6] E. Kagi, Y. Kasai, H. Ungerechts, and K. Kawaguchi, Astrophys. J., 488, 766(1997). [7] S. S. Itono, T. Taketsugu, T. Hirano, and U. Nagashima, J. Chem. Phys., 115, 11213 (2001). [8]P.M. Scheridan, L.M. Ziurys, and T. Hirano, Astrophys. J., 593, L141 (2003). [9] T. Hirano, R. Okuda, U.
Nagashima, V. Špirko, and P. Jensen, J. Mol. Spectrosc., 236, 234 (2006). [10] T. Hirano, M. Amano, Y. Mitsui,
S. S. Itono, R. Okuda, U. Nagashima, and P. Jensen, J. Mol. Spectrosc., 243, 267 (2007). [11] T. Hirano, P.R.
Bunker, S. Patchkovskii, U. Nagashima, and P. Jensen, J. Mol. Spectrosc., 256, 45 (2009). [12] T. Hirano, U.
Nagashima, G. Winnewisser, and P. Jensen, J. Chem. Phys., 132, 094303 (2010). [13] Hirano, V. Derpmann, U.
Nagashima, and P. Jensen, J. Mol. Spectrosc. 263, 150 (2010). [14] T. Hirano and U. Nagashima, J. Mol.
Spectrosc. 314, 35 (2015). [15] D. Gerlich et al., private communication (2016).

A search for the HOCO radical in the massive star-forming region Sgr B2(M)Rin Abe,1 Ayane Miyazaki,1 Takahiro Oyama,1 Mitsunori Araki,1 Shuro Takano,2Nobuhiko Kuze,3 Yoshihiro Sumiyoshi,4 Koichi Tsukiyama,1 Yasuki Endo5
1

Department of Chemistry, Tokyo University of Science, Japan2

Department of Physics, College of Engineering, Nihon University, Japan3
Department of Materials and Life Science, Sophia University, Japan
4
Division of Pure and Applied Science, Graduated School of Science and Technology,
Gunma University, Japan
5

Department of Applied Chemistry, National Chiao Tung University, Taiwan

Despite importance of the origin of life, long lasting challenges to detect the simplest aminoacid glycine (H2NCH2COOH) in interstellar medium has not been successful. As a preliminary
step toward search for glycine, the detection of its precursor has received attention. It isconsidered that glycine is produced by a reaction of the HOCO radical and the aminomethyl
radical (CH2NH2) on interstellar grain surface [1]:HOCO + CH2NH2 → H2NCH2COOH.
(1)
HOCO is produced by the reaction of OH + CO → HOCO, and or HCOOH → HOCO + H.
However, HOCO and CH2NH2 have not been investigated in interstellar medium. Recently, we
determined the accurate molecular constants of HOCO [2]. Thus, accurate rest frequencies were
derived from the constants. In the present study, we carried out the observations of HOCO in
Sgr B2(M) with Nobeyama 45 m radio telescope, where Sgr B2(M) is a massive star-forming
region and almost all reported interstellar molecules are observed in this region. Although
HOCO could not be detected in Sgr B2(M) (Fig. 1), the upper limit of the column density wasderived to be 9.0×1012 cm−2 via the spectrum in the 88 GHz region by the rotational diagram
method [3]. If the reaction (1) is main process of the glycine production in this region, thecolumn density of glycine can be assumed to be comparable to that of HOCO [1]. This
assumption allows us to derive the upper limit of column density of glycine which is one or twoorder smaller than the reported ones [4-8].
HOCO
N = 202-101

J = 2.5-1.5

0.04
0.03

J = 1.5-0.5

0.02
0.01

*

0.00

44.22

44.23

44.24

frequency (GHz)

44.25

44.26

HOCO
N = 404-303

J = 4.5-3.5

0.04
0.03

He52β

J = 3.5-2.5

0.02
0.01
0.00

-0.01

-0.01
44.21

0.05
brightness temperature Tb (K)brightness temperature Tb (K)

0.05

88.43

*
88.44

88.45

88.46

88.47

88.48

frequency (GHz)

Fig. 1. The estimated lines of the J = 2.5−1.5, 1.5−0.5, 4.5−3.5 and 3.5−2.5 transitions (red), and theobservational results (black). The dips labeled by asterisks are absorption feature. Total ON times are 1.0 and
4.0 hours in the 44 and 88 GHz regions, respectively.
References [1] Woon et al., ApJ, 571, L177 (2002). [2] Oyama et al., JCP. 134, 174303 (2011). [3] Turner
et al., ApJS. 76, 617 (1991). [4] Belloche et al., A&A 482, 179 (2008). [5] Jones et al., MNRAS. 374, 579(2007). [6] Kuan et al., ApJS. 593, 848 (2003). [7] Canningham et al., MNRAS. 376, 1201 (2007). [8] Brown
et al., MNRAS. 186, 5 (1979).

Molecular-Cloud-Scale Chemical Composition:
Mapping Spectral Line Survey toward W3(OH)
Y. Nishimura,1 Y. Watanabe,1 N. Harada,2 T. Shimonishi,3,4
N. Sakai,5 Y. Aikawa,6 A. Kawamura,7 and S. Yamamoto1,8
1

Department of Physics, The University of Tokyo, Japan
Academia Sinica Institute of Astronomy and Astrophysics, Taiwan
3
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Japan
4
Astronomical Institute, Tohoku University, Japan
5
RIKEN, Japan
6
Center for Computational Sciences, The University of Tsukuba, Japan
7
National Astronomical Observatory of Japan, Japan
8
Research Center for the Early Universe, The University of Tokyo, Japan
2

In order to study a molecular-cloud-scale chemical composition, we have conducted amapping spectral line survey toward the Galactic molecular cloud W3(OH) with the NRO 45
m telescope. W3(OH) is one of the most active star forming regions in our Galaxy, lying on
the Perseus arm. We have observed the area of 16' × 16', which corresponds to 9.0 pc × 9.0 pc.
The observed frequency ranges are 87 − 91, 96 − 103, and 108 − 112 GHz. As a result, 8molecular species CCH, HCN, HCO+, HNC, CS, SO, C18O, and 13CO are identified in the
spectrum averaged over all the observed area. The spectral pattern is found to be different
from that of the hot core observed at a 0.17 pc resolution. We find the following
characteristics in the specially averaged spectrum: (1) Emission of the species concentrated
just around the star-forming core, such as CH3OH, HC3N, and CH3CCH, is fainter than the hotcore spectrum and (2) whereas emission of the species widely extended over the cloud, such
as CCH, is relatively stronger. The averaged spectrum is rather similar to the spectra observedin external galaxies such as M51 [1] and the Large Magellanic Cloud [2]. We have divided
the observed area into 5 sub-regions according to the integrated intensity of 13CO, and haveevaluated the contribution to the averaged spectrum from each sub-region. The sub-region
with the 13CO integrated intensity from 10 K km s−1 to 30 K km s−1, which does not involve thehot core, shows the most similar characteristics to the averaged spectrum. Hence, themolecular-cloud-scale averaged spectrum seems to represent the gas extended around thestar-forming core, rather than the core itself.

References[1][2]

Y. Watanabe, N. Sakai, K. Sorai, et al. 2014, ApJ, 788, 4 .
Y. Nishimura, T. Shimonishi, Y. Watanabe, et al. 2016, ApJ, 818, 161.

A line survey of the massive star-forming region
Sgr B2(M) in the 3 and 7 mm regions
Ayane Miyazaki,1 Takahiro Oyama,1 Rin Abe,1 Mitsunori Araki,1 Shuro Takano,2Nobuhiko Kuze,3 Yoshihiro Sumiyoshi,4 Koichi Tsukiyama,1 and Yasuki Endo5
1

Department of Chemistry, Tokyo University of Science, Japan
Department of Physics, College of Engineering, Nihon University, Japan3
Department of Materials and Life Sciences, Sophia University, Japan
4
Division of Pure and Applied Science, Graduate School of Scienceand Technology, Gunma University, Japan
5
Department of Applied Chemistry, National Chiao Tung University, Taiwan
2Line survey is an intensive investigation of chemical composition of a molecular cloud. The
galactic center region is still primitive for detail chemical composition. In the present study, we
carried out line survey of the massive star-forming region Sgr B2(M) in the 3 and 7 mm regionswith Nobeyama 45 m radio telescope. Especially the 7 mm region was firstly surveyed in thiscloud. Fig. 1 shows the observed peaks in the 3 and 7 mm regions. The J = 716−615 and 725−624transitions of HCOOCH3 were observed for the first time in Sgr B2(M). The column density
was determined to be 9.3 10 cm−2, where the rotational temperature was fixed at 23 K
reported by Cummins et al [1]. The lines of the J = 6−5 transition for CH3CCH were also
observed. The column density and the rotational temperature were determined to be 1.1 10
cm−2 and 38 K, respectively. In addition, the lines of CH313CCH were observed for the firsttime as an interstellar molecule. In the 7 mm region, the absorption lines of the J = 1−0transition were observed for 28SiO and 29SiO. Although both the components of the envelop of
Sgr B2(M) and the clouds in front of it were found for 28SiO, the former was only detected for
29
SiO. This difference is thought to be due to a higher 29Si/28Si ratio in Sgr B2(M).

Fig. 1: The observed peaks in the 3 mm and 7 mm regions with Nobeyama radio telescope. Upper
panel: 87.5~91.5 GHz. Middle panel: 99.6~103.6 GHz. Lower panel: 42.5~45.5 GHz.
Reference: [1] S. E. Cummins et al., ApJS, 60, 819 (1986).

Line Survey of Large Organic Molecules toward Orion IRc2
in the 73-89 GHz region
Yoshiaki Minami,1 Mitsunori Araki,1 Shuro Takano,2 Kei Niwayama,1 Nobuhiko Kuze,3Takahiro Oyama,1 Kazuhisa Kamegai,4 and Koichi Tsukiyama1
1

2

Department of Chemistry, Tokyo University of Science, Japan
Department of Physics, College of Engineering Nihon University, Japan3
Department of Materials and Life Sciences, Sophia University, Japan
4
National Astronomical Observatory of Japan, Japan

Orion cloud located distance at 440 pc (1400 ly) is the nearest massive star−forming region.
IRc2, which is an infrared star, is located at the center of this cloud and the region toward thisstar has been investigated so far. In this survey, we observed between 73 and 89 GHz byusing 45m telescope of the Nobeyama Radio Observatory (NRO), which has a narrow beam
size of ~20". As major examples, the 17 lines of methyl formate HCOOCH3, the 20 lines ofdimethyl ether CH3OCH3, and the 4 lines of the 13C isotopic species of acetonitrile CH313CN
were detected in this cloud.
Large saturated organic molecules, such as methyl formate, are often found in cores ofmassive star-forming regions. Methyl formate is one of the molecules responsible for many
rotational transitions in such regions. Thus, detection of the vibrational excited states ofmethyl formate can give us information of physical condition of molecules. The rotationallines of the vibrational excited states for methyl formate have been reported for vt = 1 and 2
by Kobayashi et al. [1] and Takano et al. [2], respectively. However, the number of the lines
on the vibrational excited states is still limited. In this survey, the 12 lines in the vt = 1 state
were newly detected.
The present observations show that the center of this cloud has a higher vibrationaltemperature than outside, because the narrow beam size of this telescope gives new lines ofthe vibrational exited state.

Figure 1 : Observed spectra of methyl formate toward Orion IRC2

References[1] Takano et al., PASJ, 64, 89 (2012)[2] Kobayashi et al., ApJ, 657, 17 (2007)

Spectral Line Survey Observations toward the Low-mass Star-forming Region L1527
with the Nobeyama 45-m Telescope
K. Yoshida1,2, T. Tokudome1, N. Sakai2, Y. Watanabe1, S. Takano3, and S. Yamamoto1
1

Department of Physics, The University of Tokyo, JapanThe Institute of Physical and Chemical Research (RIKEN), Japan3
Department of Physics, General Education, College of Engineering, Nihon University, Japan2

We have carried out spectral line survey observations toward the low-mass star-forming
region L1527 with the Nobeyama 45 m telescope in the 3 mm region. L1527 is a prototypical
Warm Carbon-Chain Chemistry (WCCC) source, which harbors various carbon-chain
molecules and their isomers in a dense and warm region (~1000 au) around the protostar [1].
In this spectral survey covering 80 GHz to 116 GHz, we have detected about 300 spectral
lines and have identified more than 60 molecules including minor isotopic species. In thispaper, we summarize the result of the line survey.
We have detected many carbon-chain molecules and their isomers. In particular, cyclic-C3Hand cyclic-C3H2 are found to be abundant in comparison with the other sources, resulting in
the first detection of c-C3D and c-13CCCH2 in cold clouds [2]. We have also detected thelines of cyclopropenone (c-C3H2O) and propynal (HCCCHO). We compare the chemicalcomposition of L1527 with those of the well-known hot corino source IRAS16293-2422 andthe starless core TMC-1. The chemical compositions of L1527 and IRAS16293-2422 are
exclusive to each other: the line survey observations toward IRAS16293-2422 shows rich
spectral lines of complex organic molecules and deficient carbon-chain molecules, while theL1527 survey shows an opposite trend [3]. On the other hand, column densities ofcarbon-chain molecules in L1527 are found to be well correlated with those in TMC-1. When
compared with TMC-1, longer carbon-chain molecules and N-bearing carbon-chain
molecules tend to be less abundant in L1527. This would be due to the difference in the
dynamical time scale of the molecular cloud cores.
NRO3mm_.eps ¬Figure 1: Spectral line survey toward L1527.

References
[1]
[2]
[3]

Sakai, N. et al. 2008, ApJ 672, 371
Yoshida, K. et al. 2015, ApJ 807, 66
Caux, E. et al. 2011, A&A 532, 23

Spectral Line Survey toward NGC 2264 CMM3 with ALMA
Y. Watanabe,1 N. Sakai,2 A. Lopez-Sepulcre,3 T. Sakai4 , T. Hirota,5
S. Liu, 6 Y. Su,6 and S. Yamamoto, 1
1

Depertment of Physics, The University of Tokyo, Japan
2
RIKEN
3
The University of Electro-Communications, Japan
4
Institut de Radioastronomie Millimetrique (IRAM), France
5
National Astronomical Observatory of Japan, Japan
6
Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan
NGC2264 CMM3 is a massive protostellar core associated with a very young outflow(Saruwatari et al. 2011). According to the theoretical prediction (Maury et al. 2009), a
protostar in this source will evolve into a main-sequence star with 8 Msun. In order to explore
the chemical composition of this high-mass protostellar candidate in the earliest evolutionary
phase, we conducted a spectral line survey with the Nobeyama 45 m telescope and the ASTE
10 m telescope in the 4, 3, and 0.8 mm bands (Watanabe et al. 2015). Carbon-chain molecules
are found to be abundant in this source, whereas saturated complex organic molecules and Sbearing molecules are deficient. This result confirms chemical youth of the source.
Recently, we conducted a spectral line survey in the 0.8 mm band toward NGC2264
CMM3 with ALMA at an angular resolution of 0.3”-0.9”. As the result, this source is found to
be a binary (A and B) separated by 660 au (Figure 1 Left). Furthermore, the binary issurrounded by 4 isolated continuum peaks, which are likely low-mass young stellar objects.
CMM3A is very rich in molecular lines, as shown in Figure 1 Right), and possesses a hot core.
On the other hand, CMM3B is rather deficient in molecular lines. This distinct chemicaldifferentiation would originate from the different ages and/or the different temperatures ofthese two sources. This result will give us an important constraint on the mechanism ofcluster/binary formation in this region.

Figure 1: (Left) Continuum map observed with ALMA in the 0.8 mm band around CMM3. (Right) Spectrain the CMM3A observed the ALMA (Top) and that observed with the ASTE 10 m telescope (Bottom).

References
[1]
[2]
[3]

Maury et al., 2009, A&A, 499, 175.
Saruwatari et al. 2011, ApJ, 729, 147.
Watanabe et al. 2015, ApJ, 809, 162.

Methanol maser survey observation with the Nobeyama 45 m telescope
Kazuaki Fukushima,1 Kaori Kobayashi,1 Tomoya Hirota,2
1

2Department of Physics, University of Toyama, Japan
National Astronomical Observatory of Japan and SOKENDAI (The Graduate University for
Advanced Studies), Japan

Circular polarization from methanol masers are observed in star-forming regions at several
frequencies (6.7 GHz etc.) [1, 2]. If this circular polarization is caused by the Zeeman effect,
it is possible to get information on magnetic field strength. It has been proposed thatmagnetic field is related to star formation closely and it will be a clue to understanding starformation by obtaining information on magnetic field in star-forming regions. For thispurpose, it is essential to know laboratory data of the Zeeman effect of methanol (or, g-factor)
so that the magnetic field can be deducted from the splitting of the observed methanol masers.
There is a preliminary study on the Zeeman effect of methanol. A series of transitions in the
25 GHz range were observed [3] and the results were applied to the different transitions. This
is not appropriate treatment and we have started laboratory measurements of methanoltransitions to determine gfactor to obtain Zeeman effect on any transitions.[4]It is generally expected that the splittings of methanol transitions are larger for low J, K
transitions. From this point of view, the 108 GHz transition, J, K = (0, 0)-(1, -1) (E sublevel)
is one of the most promising transitions. However, the observations of this transition werelimited and hence, we carried out a survey of 108 GHz methanol masers along with othertransitions at 95, 96, and 107 GHz by using Nobeyama 45 m telescope in April 2016. We
observed in total 36 high-mass star-forming regions associated with 6.7 GHz methanol masers.
We will discuss the comparison between the sources and the relative intensities of the 4transitions above.
References[1]
A. P. Sarma, 2012, Proc. IAU Sympos. No. 287, 41.
[2]W. H. T. Vlemmings, 2012, Proc. IAU Symp. No. 287, 31.
[3]
C .K. Jen, 1951, Phys. Rev. 81, 197.
[4]
K. Takagi, S. Tsunekawa, K. Kobayashi, T. Hirota, F. Matsushima, 2015, The Physical Society of Japan
70(2), 555, 2015-09-16

Analysis of Ice Absorption Features toward YSOs Candidates Using AKARI
T. Kimura,1 T. Onaka,1 I. Sakon1, T. Shimonishi2
1Department of Astronomy, University of Tokyo, Tokyo 113-0033, Japan,
2Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Miyagi
980-8578, Japan
We present a study of near- to mid-infrared spectra (2.5—12μm) of two galactic YSO
candidates, which have been discovered in serendipitous spectroscopy in the Galactic plane
using the slit-less mode of the InfraRed Camera (IRC) on board AKARI. These sources do notbelong to any known star-forming region. Absorption bands of molecular species, including
solid phase H2O, CO2, CO, and possibly gas phase CO, are seen in the spectra towards both
sources.Absorption bands of XCN, organics and silicates are also seen towards one of thesources.
We found that the column densities of the above detected species are large column densities ofthem, espacially for XCN. These results suggest that the objects are highly embedded class I
protostars or class II YSOs with an edge-on (i ~ 70°) disk[1]. However, their SEDs are
peculiar as class I or II YSOs since their peaks are located at around 4μm, while usual YSOs
show a peak at a much longer wavelength (Figure 1) [2,3]. Their spectral energy distributions(SED) are quite blue as YSOs and no FIR emission has been detected. They are similar to thatof class III YSOs, which do not show deep absorption bands of molecular species. Any
existing SED models of YSOs cannot well account for the entire infrared SEDs.
On the other hand, the presence of the XCN and organics and CO gas features and noapparent associated nebulosity in the regions suggest that they are not likely background stars.
In this presentation, we will discuss the properties of these objects and their physicalimplications.

Figure 1: IRC spectra (blue) and photometry (green) of Object 1 (left) and Object 2 (right). The spectrum of
Object 2 is reliable only at 3 - 5.5 µm because of overlaps by neighboring sources.

References[1]K. M. Pontoppidan, et al. 2008, ApJ 622, 463[2]
Megeath, S. T., et al. 2004, ApJS, 154, 367[3]Allen, L. E., et al. 2007, in Protostars and Planets V, ed. B. Reipurth, D. Jewitt, & K. Keli (Tucson, AZ:
Univ. Arizona Press), 361

The Effects of the Star-forming Environments on the Thermal and Chemical Evolutionof Protostellar Cores
Yichen Zhang,1,2 Jonathan C. Tan,3 Maria Drozdovskaya,4 Shuo Kong,3 Diego Mardones,2Guido Garay2
1

Star & Planet Formation Lab., RIKEN, Japan
2
Universidad de Chile, Chile
3
University of Florida, USA
4
Leiden University, Netherland

Stars form from clouds with wide ranges of surface densities. In the core accretion theory,
such initial and environmental conditions may affect the evolution of the protostars and theircores, which further affects the chemical conditions of these cores. We explore suchpossibility by constructing evolution models of stars forming from cores embedded indifferent star formation environments. Each evolutionary track is built from three initialconditions: environmental surface density (which sets the pressure on the core), initial coremass, and its initial rotation. The model self-consistently calculates the collapse of theenvelopes, growth of the accretion disks, gradually opening of the outflow cavities, andevolution of the protostars. We use continuum radiation transfer simulation to predict the dust
temperature profile inside the core and its time evolution. By coupling such a physical modelwith chemical simulations, we are able to further predict the distribution of the molecules
inside the protostellar core at a given evolutionary stage. The model shows that thestar-forming environment strongly affects the thermal and chemical conditions of the cores
which can be tested by observations. We present the preliminary results of our ALMA
observation of 8 massive cores/regions. While the focus of this project is on the(sub-)strucutres of the cores and filaments, it also reveals rich information on the chemical
conditions of these cores which are in different environments and evolutionary stages.

References

Shock heating of dusts and icy planetesimals due to bow shocks in protoplanetary disks
K. K. Tanaka1, M. Nagasawa2, H. Nomura 3, H. Miura4, T. Nakamoto3, H. Tanaka5 andT. Yamamoto1
1

Hokkaido University, Japan, 2Kurume University, Japan, 3Tokyo Institute of Technology,
Japan, 4Nagoya City University, Japan, 5Tohoku University, Japan

In protoplanetary disks, planetesimals grow to planets through mutual collisions andaccretions. The gravitational interactions among planetesimals increase the eccentricities of
their orbits. Especially, large planeteimals have high eccentric orbits and supersonicvelocities relative to the nebular gas. Small silicate particles in the nebular gas are heated andcould be melted by passages though the bow shocks of such planetesimals [1-3]. It is
proposed that the planetesimals perturbed by Jovian mean-motion resonances are thepromising source of shock waves that form chondrules in chondritic meteorites because theshocks give short-time-scale heating of dust grains appropriate for the formation ofchondrules [1]. In the previous studies on the planetesimal excitation, however, the velocities
obtained were at most 8 kms-1 in the asteroid belt, which is insufficient to account for theubiquitous existence of chondrules. Recently Nagasawa et al. [4] reexamined the effect ofJovian resonances, taking into account the secular resonance in the asteroid belt caused by thegravity of the gas disk. They found that the velocities of planetesimals relative to the gas disk
exceed 12 kms-1 and the heating region is restricted to a relatively narrowband (1.5-3.5 au).
These results suggest that chondrules were produced effectively in the asteroid region.
The planetesimal bow shocks also lead to heating of the planetesimal itself. Tanaka et al.
[5] presented that icy planetesimals with radii larger than 100 km suffer from significant
evaporation even outside the snow line. In [5], we focused on the oligarchic growth stage of
propoplanets, in which planetesimals have velocities of 1-5 kms-1 relative to the gas due tostirring by protoplanets. In this study, we investigate the evaporation of planetesimal in thestage of the formation of gas giant planets. In such a stage, the evaporation of planetesimalproceeds much more effectively because of the stronger shocks and the evaporation time ismuch shorter than the disk lifetime of 106 yr. The evaporated H2O vapor from the planetesimal
surface recondenses as it cools and form a large amount of icy fine grains. During theevaporation of icy planetesimals, the silicate dust is also expected to be released from theplanetesimal surface by the strong flow of the disk gas. This process provides a large amountof chondrule precursors. Our results may also relate to the origin of crystalline silicate
observed in various comets and protoplanetary disks. The planetesimal bow shocks also leadto chemical reactions among various evaporated molecules. We propose a possibility that we
can diagnose the shock heating and evaporation of icy planetesimals, using observations oflines of the molecules in the protoplanetary disks.
References[1] S. J. Weidenschilling, F. Marzari, & L. L. Hood, (1998), Sci. 279, 681.
[2] H. Miura, & T. Nakamoto, 2005, Icar., 175, 289[3] H. Miura, K. K. Tanaka, T. Yamamoto, T.Nakamoto, J. Yamada, & K. Tsukamoto, 2010, ApJ, 642[4] M. Nagasawa, K. K. Tanaka, H. Tanaka, T. Nakamoto, H. Miura, & T. Yamamoto, 2014, ApJL, 794:L7.
[5] K. K. Tanaka, T. Yamamoto, H. Tanaka, H. Miura, M. Nagasawa, & T. Nakamoto, 2013, ApJ, 764, 120.

Interstellar Dust Properties Revealed by Diffuse Galactic Light Measurements
K. Sano,1, 2 S. Matsuura,3 K. Tsumura,4 T. Arai,4 M. Shirahata,4 Y. Onishi 2, 5
1

2

Department of Astronomy, Graduate School of Science, The University of Tokyo, Japan
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan3
Department of Physics, School of Science and Engineering, Kwansei Gakuin University,
Japan
4
Frontier Research Institute for Interdisciplinary Science, Tohoku University, Japan
5
Department of Physics, Tokyo Institute of Technology, Japan

In this presentation, we constrain interstellar dust properties by observing diffuse Galactic
light (DGL). The DGL consists of scattered light and thermal emission from interstellar dust
grains illuminated by the interstellar radiation field. Therefore, the DGL measurement isuseful in constraining some properties of interstellar dust, such as size distribution, albedo,
and scattering asymmetry of dust grains.
In the diffuse interstellar medium, the DGL observation has been limited due to its faintness,particularly in the near-infrared wavelengths. We thus reanalyze all-sky maps obtained from
Diffuse Infrared Background Experiment (DIRBE) onboard the Cosmic Background Explorer(COBE) satellite in the four near-infrared bands (1.25, 2.2, 3.5, and 4.9 micron). As a result,
we succeed in detecting the near-infrared DGL as a component that linearly correlates withinterstellar 100 micron emission.
At 1.25 and 2.2 micron, our results are marginally consistent with the expected spectrum of
scattered light assuming a recent interstellar dust model. At 3.5 and 4.9 micron, thermal
emission from stochastic heating of very small grains and fluorescence of polycyclic aromatichydrocarbon (PAH) dominate the DGL. Compared with a recent thermal emission model inthe diffuse interstellar medium, we constrain the mass fraction of very small grains and PAH
to the total dust to be more than 2%.
We also find that the intensity ratios of DGL to 100 micron emission are higher toward low
Galactic latitudes at 1.25 and 2.2 micron. Since this trend is expected from forward scatteringcharacteristic of dust grains, we compare the obtained latitude dependence with the scattered
light model that takes into account the scattering asymmetry. The derived forward scatteringcharacteristic is stronger than that expected from the recent dust model. This may indicate thatsize or shape of the interstellar dust grain is different from the model prediction.

References
[1]
[2]
[3]

Sano et al. 2015, ApJ, 811, 77
Sano et al. 2016, ApJ, 818, 72
Sano et al. 2016, ApJL, 821, L11

Infalling-Rotaing Motion and Associated Chemical Change in the Envelopeof IRAS 16293-2422 Source A Studied with ALMA
Y. Oya,1 N. Sakai,2 A. López-Sepulcre,1,3 Y. Watanabe,1 C. Ceccarelli,4,5 B. Lefloch,4,5
C. Favre,4,5 and S. Yamamoto1
1

2

Department of Physics, The University of Tokyo, JapanThe Institute of Physical and Chemical Research (RIKEN), Japan
3
Institut de Radioastronomie Millimétrique (IRAM), France
4
Universite Grenoble Alpes, IPAG, France
5
CNRS, IPAG, France

We have analyzed rotational spectral line emission of OCS, CH3OH, HCOOCH3, and H2CS
observed toward the low-mass Class 0 protostellar source IRAS 16293-2422 Source A at a
sub-arcsecond resolution (~0”.6x0”.5) with ALMA[1]. Significant chemical differentiation isfound at a 50 au scale. The OCS line is found to well trace the infalling-rotating envelope inthis source. On the other hand, the CH3OH and HCOOCH3 distributions are found to beconcentrated around the inner part of the infalling-rotating envelope. The kinematic structureof the infalling-rotating envelope is well explained with a simple ballistic model, as in thecase of L1527 [2,3]. With this model, the radius of the centrifugal barrier (a half of thecentrifugal radius) and the protostellar mass are evaluated from the OCS data to be from 40 to
60 au and from 0.5 to 1.0 M⊙ , respectively, assuming the inclination angle of theenvelope/disk structure to be 60º (90º for the edge-on configuration). Although theprotostellar mass is correlated with the inclination angle, the radius of the centrifugal barrier
is not. This is the first indication of the centrifugal barrier of the infalling-rotating envelope ina hot corino source. CH3OH and HCOOCH3 may be liberated from ice mantles due to weakaccretion shocks around the centrifugal barrier, and/or due to protostellar heating. H2CS
emission seems to come from the disk component inside the centrifugal barrier in addition to
the envelope component. This study has further revealed that the centrifugal barrier plays acentral role not only in the formation of a rotationally-supported disk but also in the chemical
evolution from the envelope to the protoplanetary disk.
References
[1]
[2]
[3]

Oya, Y., Sakai, N., López-Sepulcre, A., et al. 2016, ApJ, 824, 88
Sakai, N., Sakai, T., Hirota, T., et al. 2014, Nature, 507, 78
Oya, Y., Sakai, N., Sakai, T., et al. 2014, ApJ, 795, 152

CO gas depletion and formation of organic molecules in protoplanetary disks
H. Nomura,1 T. Tsukagohi,2 K. Ryohei,3 D. Ishimoto,4,1 S. Okuzumi,1 T. Muto,5 K.D.
Kanagawa,6 S. Ida,1 C. Walsh,7,8 T.J. Millar,9 X.-N. Bai,10 M. Numata,11 P. Theule12
1

Tokyo Institute of Technology, 2Ibaraki University, 3NAOJ, 4Kyoto University, 5Kogakuin
University, 6University of Szcecin, 7Leiden University, 8University of Lees, 9Queen’s
University Belfast, 10CfA, 11University of Tokyo, 12Aix-Marseille Universite

Protoplanetary disks are the natal place of planets and ALMA observations are now revealing
the physical and chemical structure of planet forming regions in the disks. Understanding
chemical components of gas, dust and ice in the disks is essential to investigate the origins ofmaterials in the plants. In the talk, I shall report our recent ALMA Band 7 observations of CO
isotopologue lines from the protoplanetary disk around TW Hya. The result shows asignificant decrement in CO gas throughout the disk even inside the CO snowline, indicating
freeze-out of gas-phase CO onto grain surfaces and possible subsequent surface reactions toform larger molecules. Complex organic molecules could be efficiently produced in theobserved CO gas depleted regions. Actually, methanol has been detected towards the TW Hya,
whose abundance relative to water is consistent with that of comets in our Solar system.
In addition, we performed model calculations of formation of complex organic molecules inprotoplanetary disks, taking into account of thermal reactions including acid-based reactionsin ice based on laboratory experiments. The result suggests relatively effective formation ofsome nitrogen-bearing species, such as CH3NH2, NH2CHO, CH3NHCOOH, NH2COOH.

Figure 1: The CO gas column density profile (left) and the CO gas-to-dust ratio profile (right) in the
protoplanetary disk around TW Hya, derived from our ALMA observations..

References[1][2]

H. Nomura, T. Tsukaghoshi, K. Ryohei et al. 2016, ApJL, 819, L7
C. Walsh, R. Loomis, K. Oberg et al. 2016, ApJL 823, L10.

Spatial variations of PAH properties in M17 revealed by Spitzer/IRS spectral mapping
M. Yamagishi1, H. Kaneda2, D. Ishihara2, S. Oyabu2, T. Suzuki2, T. Onaka3, T. Nagayama4, T.
Umemoto5, T. Minamidani5, A. Nishimura2, M. Matsuo4, S. Fujita6, Y. Tsuda7, M. Kohno2,
and S. Ohashi3
1

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
2
Graduate School of Science, Nagoya University, Japan
3
Graduate School of Science, The University of Tokyo, Japan
4
Graduate School of Science and Engineering, Kagoshima University, Japan
5
Nobeyama Radio Observatory, Japan
6
Graduate School of Pure and Applied Sciences, University of Tsukuba, Japan
7
Graduate School of Science and Engineering, Meisei University, Japan

PAH (polycyclic aromatic hydrocarbon) emission features in mid-infrared spectra (e.g., 6.2,
7.7, 8.6, 11.3, 12.7 μm) are characteristic of PDRs (photo-dissociation regions). Past studies
have shown that the PAH interband ratios are useful probes of the PAH properties (e.g.,
degree of ionization, size, and edge structure). The PAH properties have been discussed basedon pencil-beam observations for many objects. In order to examine the effects of thesurrounding interstellar environment on the PAH properties in detail, however, spatiallyresolved observations are essential.
We analyzed Spitzer/IRS mid-infrared (5.5-14.5 μm) spectral mapping data of the Galactic
star-forming region M17 as well as the IRSF Brγ and Nobeyama 45-m 13CO (J=1-0) maps.
We decomposed the mid-infrared spectra using PAHFIT[1], and obtained spectral maps of the
PAH features. As a result, we find that the PAH emission features are bright in the region
between the HII region traced by Brγ and the molecular cloud traced by 13CO, supporting that
the PAH features originate from PDRs. We also find that the PAH7.7/PAH11.3 ratios are
independent to the distance from the M17 center (Fig.1), suggesting that the degree of PAH
ionization is mainly controlled by the local interstellar environment. Based on these results,
we examine the effects of the intense star-forming activity on the PAH properties in detail.

Figure 1: (a) PAH7.7/PAH11.3 interband ratio map. Contours are the 13CO integrated intensity. (b,c) Examplesof the mid-infrared spectra. The green, blue, and red curves indicate the best-fit models using PAHFIT.

References[1]

Smith, J. D. T., Draine, B. T., Dale, D. A., et al. 2007b, ApJ, 656, 770.

Chemistry in a forming protoplanetary disk: main accretion phase
H. Yoneda1, Y. Tsukamoto2, K. Furuya3, and Y. Aikawa3
1

Department of Planetology, Kobe University, Japan
2
Riken, Japan
3
Center for Computational Sciences, University of Tsukuba. Japan

Protostellar cores harbor rich chemistry: i.e. complex organic molecules (COMs) and carbon
chains. At the core center, a protostar and disk system are formed. Thus various molecules
currently observed in protostellar cores will eventually be incorporated into disk. The mainaccretion phase, in which a protostar accretes most of its mass from the envelope via
circumstellar disk, could also be an important transition phase for chemistry: from interstellar
matter to disk material. Due to the high mass accretion rate, the forming disk could be much
warmer than the Class II disk, and thus could enhance chemical reactions.
In this presentation, we report our numerical calculation of the molecular evolution[1] in aradiation-hydrodynamics model of star-forming core[2]. The model evolves from a cold (~ 10K) prestellar core to the main accretion phase in ~105 yr, which corresponds to Class 0 objects.
A rotationally-supported gravitationally unstable disk is formed around the protostar. We
extract the temporal variation of physical parameters of 103 SPH particles which end up in thedisk, and perform post-processing calculations of the gas-grain chemistry adopting a threephase model. Inside the disk, SPH particles migrate both inward and outward. Since asignificant fraction of volatiles such as CO can be trapped in the water-dominant ice in thethree-phase model, ice mantle composition depends not only on the current position in thedisk but also on whether the dust grain has ever migrated inside the water snow line. Stablemolecules such as H2O, CH4, NH3 and CH3OH are abundantly formed in the molecular cloud
before the onset of collapse and simply sublimated as the fluid parcels migrate inside thewater snow line. On the other hand, various molecules such as carbon chains and complex
organic molecules (COMs) are formed in the disk. COMs abundances sensitively depend on
the efficiency of photodissociation and diffusion of photofragments in bulk ice mantle. As for
S-bearing species, H2S is abundant in the collapse phase. In the warm regions in the disk, H2S
is sublimated to be destroyed, while SO, H2CS, OCS and SO2 become abundant.

References[1][2]

H. Yoneda et al, in prep.
Y. Tsukamoto, S.Z. Takahashi, M.N. Machida & S. Inutsuka, S. 2015, MNRAS, 446, 1175

Chemical Properties of Glycine rich sources
T. Suzuki,1 M. Ohishi1 , S. Masao3, T. Hirota2, Liton Majumdar4, and Valentine Wakelam4
1

Astronomy Data Center, NAOJ, Japan
Mizusawa VLBI Observatory, NAOJ, Japan
3
Nobeyama Radio Observatory, NAOJ, Japan
4
University of Bordeaux, France2

It is thought that early terrestrial life originated through chemical evolutions of organic
compounds on the primordial Earth surface. Some organic molecules would be included inthis process. However, it is still unknown if such organic molecules were formed on the Earthsurface. Ehrenfreund et al. (2002) estimated that comets would have delivered sufficientamounts of organic molecules to the Earth surface. If this is a case, organic molecules, such asamino acids, would exist in the extraterrestrial environment. The simplest amino acid, glycine
attracted attention of many scientists. Since glycine is detected in the comet (Altwegg 2016),
it must contributed to the Early Earth chemistry to form the very first life. In these days, thelatest telescope, ALMA, is expected to achieve the first detection of glycine. However, theformation process of glycine is poorly known. It would be essential to reveal which sources
are promising glycine sources for the future glycine surveys.
The essential formation process of glycine was investigated by our modelling. For thechemical processes, in addition to the reaction dataset of KIDA, gas phase and grain surface
formation processes of COMs by Garrod (2013) are included. We assumed that the physicalevolution of star-forming regions start from the extended and cold gas. After the formation of
the dense core, the gas and dust temperatures were raised to release the frozen species on thegrain surface. With this model, we succeeded to explain almost observed COMs towards
G10.47+0.03 (not only CH3OH, CH3OCH3, HCOOCH3, CH3COCH3, but also N-bearing
species such as NH2CHO, CH2CHCN, CH3NH2, and CH2NH).
We confirmed that the radical-radical reaction of HOCO + CH2NH2 is the most efficient
formation process to glycine. These radicals are formed via the hydrogen subtraction processfrom HCOOH and CH3NH2 by other radical species. For the formation process of CH3NH2,
we reached to the same conclusion with Theule et al.(2011): the hydrogenation process to
HCN is so rapid that almost HCN and CH2NH are converted to CH3NH2. While CH2NH issuggested as the precursor of CH3NH2, it is formed via the reaction of “NH + CH3” in the gas
phase, and do not directly connected to CH3NH2. In the symposium, we will discuss thechemical properties of promising glycine rich sources from our modelling.

Figure1: Essential formation path to glycine
References
[1]
[2]
[3]

Ehrenfreund, P., et al., 2002, Rep. Prog. Phys. 65, 1427
Altwegg, K., et al, 2016, science, 2, id=e1600285
Garrod, R, T., 2013, ApJ,765, 60

Discovery of a Hot Corino in the Bok Globule B335
M. Imai,1 N. Sakai,2 Y. Oya1_, A. Lopez-Sepulcre1,3, Y. Watanabe1,S. Yamamoto1
1
2

Department of Physics, The University of Tokyo, JapanThe Institute of Physical and Chemical Research (RIKEN), Japan
3

Institut de Radioastronomic Millimetrique (IRAM), France

We report the first evidence of a hot corino in a Bok globule. This is based on the ALMA
observations in the 1.2 mm band toward the low-mass Class 0 protostar IRAS 19347+0727 in B335.
Saturated complex organic molecules (COMs), CH3CHO, HCOOCH3, and NH2CHO, are detected
in a compact region within a few 10 au around the protostar. Additionally, CH3OCH3, C2H5OH,
C2H5CN, and CH3COCH3 are tentatively detected. Carbon-chain related molecules, CCH andc-C3H2, are also found in this source, whose distributions are extended over a few 100 au scale. On
the other hand, sulfur-bearing molecules CS, SO, and SO2, have both compact and extended
components. Fractional abundances of the COMs relative to H2 are found to be comparable to thosein known hot-corino sources. Though the COMs lines are as broad as 5-8 km/s, they do not show
obvious rotation motion in the present observation. Thus, the COMs mainly exist in an infalling gas
to the protostar, or in a rotating disk (ring) much smaller than the synthesized beam (0’’58 x 0”52).

Figure 1: The continuum map and the moment 0 maps of HCOOCH3, NH2CHO, (CH3)2CO, CCH,
CS, and SO. The contours represent the continuum flux of 10, 20, 40, 80 sigma levels. Comparedwith the synthesized beam shown in the bottom left in each figure, distribution of COMs are notresolved.

Hot water molecule around Orion Source I
T. Hirota1,21Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Japan2
Department of Astronomical Sciences, SOKENDAI, Japan

We report ALMA observations of submillimeter H2O lines at bands 6, 7, 8 and 9 toward a
massive protostar candidate Source I in the Orion KL region. We detect in total seven H2Olines including vibrationally ground and excited (2=1) transitions at the highest upper stateenergy of ~3500 K. Their maps show compact structures associated with a close vicinity to
Source I (<200 au). The 321 GHz (102,9-93,6) and 658 GHz (2=1, 11,0-10,1) lines show
elongated structure along the northeast-southwest bipolar outflow[1,2]. On the other hand,higher excitation transitions such as 336 GHz (2=1, 52,3-61,6) and 232 GHz (2=1, 55,0-64,3)
lines show more compact structures[1], as shown in Figure 1.
All the H2O line maps show velocity gradients perpendicular to the bipolar outflow indicatingrotation motions about the outflow axis. We interpret that the 321 GHz and 658 GHz lines
trace the base of the bipolar outflow similar to the vibrationally excited SiO masers[3].
According to their brightness, the 321 GHz and 658 GHz lines are thought to be maser
emissions. In contrast, some of the other H2O lines could be explained via thermal excitation
emitted from a midplane of the edge-on hot (~3000 K) molecular gas disk rotating aroundSource I. Based on the spectral profiles and intensity maps of the detected lines, we will
discuss physical and dynamical properties of the hot molecular gas disk around Source I.

(b)
(a)

Figure 1: (a) Moment 0 (contour, integrated intensity) and 1 (color scale, peak velocity) maps of the 232
GHz H2O line. A cross indicates the position of Source I determined from the continuum emission peak.
(b) Observed (red) and model (green) spectra of the 232 GHz H2O line.

References
[1]
[2]
[3]

T. Hirota, M. K. Kim, Kurono, Y. & M. Honma 2014, ApJL, 782, L28.
T. Hirota, M. K. Kim, & M. Honma 2016, ApJ, 817, 168.
M. K. Kim, T. Hirota, M. Honma, et al. 2008, PASJ, 60, 991.

Chemistry of Cyanopolyynes in Hot Core Regions
K. Taniguchi,1,2 M. Saito,1,2 H. Ozeki,3 Y. Miyamoto,2 H. Kaneko,2 T. Minamidani,1,2
F. Nakamura,1,4 T. Hirota,1,4 K. Dobashi,5 T. Shimoikura5
1

2

Department of Astronomical Science, SOKENDAI, Japan
Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Japan3
Department of Environmental Science, Toho University, Japan
4
National Astronomical Observatory of Japan, Japan
5
Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Japan

Cyanopolyynes (HC2n+1N; n=1-5) are one of the representative series of carbon-chain molecules. Carbon-chain molecules are good indicators of starless and star-forming cores; carbonchain molecules are abundant in young starless cores and decrease as progress of the star formation processes[1]. However, two low-mass star forming cores where various carbon-chain
molecules are abundant were discovered, and these regions were named Warm Carbon Chain
Chemistry (WCCC) sources[2].
G12.89+0.49

We derived 13C isotopic fractionation of HC3N
toward G28.28-0.36 by observations of thethree 13C isotopologues with the Nobeyama 45m telescope. The abundance ratios are found tobe 1.0(±0.2):1.00:1.47(±0.17) for [H13CCCN] :[HC13CCN] : [HCC13CN]. The observational
results imply that the neutral-neutral reaction
between C2H2 and CN overwhelms other formation pathways, which is consistent with thechemical model calculation[3].

TA [K]

G28.28-0.36

HC5N

CH3OH
H2CO

CH3OH
SpriousFrequency [GHz]

CH3OH SO2 HC7N

HC5N
TA [K]On the other hand, there are few studies aboutcarbon-chain molecules in high-mass star forming regions, and our understanding is poor. We
then carried out observations toward hot coreswith the Nobeyama 45-m radio telescope, theGreen Bank 100-m telescope, and the Very
Large Array (VLA) in order to study chemicalmechanisms of carbon-chain molecules in hotcore regions.

CH3OH

HC5N

G12.89+0.49
G28.28-0.36
Frequency [GHz]

Figure 1. The spectra in two hot cores obtainedwith the Green Bank 100-m telescope.

We also detected HC7N toward 2 hot cores,
G28.28-0.36 and G12.89+0.49, with the GreenBank 100-m telescope at the time of writing the abstract (Figure 1). Our high-spatialresolution maps with the VLA toward G28.28-0.36 show that the spatial distributions of cyanopolyynes (HC3N, HC5N, and HC7N) are similar to that of CH3CN, which is a hot core tracer. Based on these observational results, we consider that there is a possibility that cyanopolyynes can be efficiently formed in hot core regions.
References
[1]
[2]
[3]

H. Suzuki et al., 1992, ApJ 392, 551
N. Sakai & S. Yamamoto, 2013, Chem. Rev., 113(12), 8981
J. F. Chapman et al., 2009, MNRAS, 394, 221