The Spectral Line Survey in TMC-1 -- Progress of the Data Analysis
Masatoshi. Ohishi
National Astronomical Observatory of Japan, Japan
E-mail: masatoshi.ohishi@nao.ac.jp

Cold dark interstellar clouds have been extensively studied as the formation sites of low-massstars and planetary systems since their identification to the interstellar molecular clouds in1970's. A variety of exotic chemical compounds found in molecular clouds, especially thosecontaining carbon atoms, attracted strong interests in connection with the formation of planetsand the origin of life in the universe. Recent radio and IR observations towards comets
collected important evidence that comets, 4.6 billion year-old fossil bodies of the proto-solarsystem nebula, keep molecular composition similar to that in cold dark clouds. Therefore, thechemical evolution in cold dark clouds is basically important as the initial process ofinterstellar matter evolution toward the planets, and, ultimately to life.
Chemical reactions in dark clouds are not yet fully understood, and many unknown molecules
might be synthesized in dark clouds. It is essential for understanding the chemical reactions indark clouds, therefore, to make an unbiased frequency survey that can detect all molecularlines, including unpredicted lines of unknown molecules.
Kaifu et al. [1] published a molecular spectral line survey data toward a dark cloud, thecyanopolyyne peak of TMC-1, in the frequency range between 8.8 and 50 GHz (see Figure 1),
using the 45-m mm-wave telescope of the Nobeyama Radio Observatory 1 . They detected 414
lines from 38 molecules. Most of the molecules are linear carbon chain species and theirderivatives, and there are only a few organic species such as CH3OH, CH3CHO, HCCCHO
and CH2CHCN. More saturated species, e.g., C2H5CN and HCOOCH3, were not detected.

Figure 1: A compressed atlas of the 8.8--50 GHz spectrum toward TMC-1 (cyanopolyyne peak).
1

Nobeyama Radio Observatory is an open-use facility for mm-wave astronomy, being
operated under the National Astronomical Observatory of Japan (NAOJ).

We have made detailed data analyses for the 29 species out of detected 58 species by utilizing
peak line temperatures that were obtained through the Gaussian fitting. The detected lines foreach molecule were analyzed assuming the LTE condition with the weight of 1/σ2 where σ isthe rms noise value at each line position. When available, we incorporated weaker hyper finecomponents in order to avoid the photon trapping effect. Figure 2 shows a comparison
between old column density values [2] and present values for several carbon chain species.

Figure 2: Comparison between old column density values and new values for several carbon chain species.

It is readily seen that the column density of C4H has lowered by about two orders ofmagnitude, which is consistent with the theoretical prediction by [3] on the abundance ratio of
C4H- to C4H. The abundances for C5H and C6H have been reversed, which is consistent withthe past reports. For HCnN molecules, the old and new values do not change significantly.
We will talk the detailed procedure of the analyses, excitation temperature variation vs.
number of carbon atoms, and derived isotope ratios, D/H, 13C/12C, and 15N/14N.
References[1]
Kaifu, N., Ohishi, M., Kawaguchi, K., Saito, S., Yamamoto, S., Miyaji, T., Miyazawa, K., Ishikawa, S.,
Noumaru, C., Harasawa, S., Okuda, M., & Suzuki, H. 2004, PASJ, 56, 69.
[2]
Ohishi, M., & Kaifu, N. 1998, J. Chem. Soc., Faraday Discussion, 109, 205.
[3]
Herbst, E., 2008, private communication.

Study of the L1551 pre-stellar core using the C18O(1-0) and H13CO+(1-0) line emission with
the Nobeyama 45 m telescope and Millimeter Array.
Aya Higuchi,1,2 Y.Kitamura3
1

Tokyo Institute of Technology, 2Nobeyama Radio Observatory, 3Department of Basic Space
ScienceInstitute of Space and Astronautical Science (ISAS) / Japan Aerospace Exploration
Agency (JAXA)
We carried out C18O(1-0) and H13CO+(1-0) line observations of the L1551 pre-stellar core
(L1551 MC) with the Nobeyama 45 m telescope and Millimter Array (NMA). The purpose ofthis study is to reveal the initial conditions for low-mass star formation. We obtained the C18O
and H13CO+ maps of the core with the 45 m telescope. The peak position of the C18O core isshifted by 60" to the center from that of the H13CO+ core. The radius , mass, and velocity
width of the core are 0.1 pc, 1 M◉, and 0.71 km s-1, respectively, in C18O, and 0.15 pc, 4 M◉,
and 0.47 km s-1, respectively, in H13CO+. Our model analysis derived the density profiles ofrho ~ r-1.3 and r-1.4 for the C18O and H13CO+ cores, respectively, which are flatter that thetheoretical prediction of r-2 for a star-forming core (Shu 1977[1]; Larson 1969[2]; Penston
1969[3]). In addition, we found that the C18O core has a velocity gradient along the NE-SW
direction, which can be interpreted as rotation, and that the velocity width of the core
increases toward the center. However, the NMA could not detect any compact component
within 0.05 pc from the core center in C18O. These results lead us to the conclusion that theL1551 MC has not yet evolved into a centrally concentrated star-forming core in spite of theage of 104-5 yr (Swift et al. 2005[4]). The ALMA can reveal the detailed density and velocity
structures of the interesting core..

Figure 1: (left) Total integrated intensity map of the H13CO+(1-0) emission (color and contours).
(right) Total integrated intensity map of the C18O(1-0) emission (color and contours). The contours with theintervals of 3σlevel start from the 3σlevels, where the 1σ noise levels are 0.05K and 0.1K in TA* for
H13CO+ core and C18O core, respectively.

References[1] Shu, F.~H.1977, Apj 214, 488[2] Larson, R.~B. 1969, MNRAS, 145, 271[3] Penston, M.~V.1969, MNRAS 144, 425[4] Swift, J.~J., Welch, W.~J., & Di Francesco, J. 2005, Apj, 620, 823

Nobeyama 45 m telescope legacy project: Line survey
Takano, S. (NRO), Aikawa, Y. (Kobe U.), Chen, V. (NTHU), Hirano, N. (ASIAA), Hirota, T. (NAOJ),
Kamegai, K. (U. Tokyo), Kobayashi K. (Toyama U.), Kohno, K. (U. Tokyo), Kuan, Y-J. (NTNU), Liu, S.Y. (ASIAA), Ohashi, N. (ASIAA), Ohishi, M. (NAOJ), Ozeki, H. (Toho U.), Sakai, N. (U. Tokyo), Sakai,T. (NRO), Shiba, S. (U. Tokyo), Su, Y.-N. (ASIAA), Sugimura, M. (U. Tokyo), Takahashi, S. (ASIAA),
Takakuwa, S. (ASIAA), Umemoto, T. (NRO), Wang, K.-S. (ASIAA), Yamada, M. (NAOJ), Yamamoto, S.
(U. Tokyo), Zhang, Q.-Z. (CfA)

Line surveys are of fundamental importance in astronomy not only for complete
understanding of chemical compositions in representative sources, but also for finding out
new observing tools probing interstellar medium and star formation. We started the line
surveys toward a few new type of sources with the Nobeyama 45 m telescope. The target
sources include the low-mass star forming region L1527, the shocked region of L1157,
infrared dark clouds G28, and external galaxies Arp 220, NGC 1068 and NGC 253. Mainlywith the new 3 mm receivers installed on the 45 m telescope [1], the frequency range from
84-115 GHz will be surveyed with much higher sensitivity than the previous observations.
The total observing time is expected to be about 1000 hours for four years. The results fromthe survey will be used for detailed studies on chemistry in each source, and will also provide
us with useful templates for planning the observing strategy with ALMA. The first year of
the line surveys was finished. We report the preliminary results.
L1527 is a very interesting object, because the abundances of carbon-chain molecules are
high, though this source is a low-mass star forming region [2]. We detected many lines
including high excitation lines of HC5N (e.g. J=41-40, upper state energy of 110 K), isotopic
species (D, 13C) of some carbon-chain molecules, and HCO.
In L1157, where interactions between an outflow and ambient clouds are prominent [3, 4], we
detected many lines including C34S, CH3CHO, and HCOOCH3. To study shock chemistry
and gas-grain interaction, these detections are rather important information. After ourobservations, we noticed that HCOOCH3 is independently detected with the IRAM 30m
telescope [5].
In G28 three interesting positions called mm1, mm4, and mm9 are selected. Toward mm1
and mm4 line wings were found in HCO+, HCN, SiO, CS, and CH3OH. These wings indicate
outflow activities. In addition, CH3CHO is detected only in mm1 and mm4. This molecule isone of the probable grain related species. Therefore CH3CHO may be evaporated from grain.
Based on these results, mm1 and mm4 are thought to be high-mass protostellar objects.
About galaxies we observed only Arp 220 in the first year. In Arp 220 wide absorption linesof ammonia have been detected [6]. We expected such absorption lines for other molecules,
which have low excitation lines at relatively low frequency region like ammonia. We tried tofind spectral lines of HNCO (21.98 GHz) and SO (30.00 GHz), but they were not detected at
the rms antenna noise temperature of 1.0 and 1.5 mK, respectively.
Many new lines were detected in L1527, L1157, and G28. We hope that these results will
become invaluable heritages of molecular line data.
References [1] Nakajima et al. 2008, PASJ, 60, 435. [2] Sakai et al. 2008, ApJ 672, 371. [3] Umemoto et al.
1992, ApJ 392, L83. [4] Mikami et al. 1992, ApJ 392, L87. [5] Arce et al. 2008, ApJ 681, L21. [6] Takano et al.
2005, PASJ 57, L29.

Gas and dust of asymptotic giant branch (AGB) stars and planetary nebulae (PNe)
M. Matsuura1,2
1

National Astronomical Observatory of Japan
2
University College London, UK

Recent infrared observations using the Spitzer Space Telescope, the Subaru
Telescope and the AKARI provided good opportunities to understand the mass andgas formed in evolved stars.
We first present the estimation of the total mass-loss
rate from all carbon-rich AGB stars in the Large Magellanic Cloud (LMC). AGB
stars are one of the important dust sources in the ISM of the LMC. Gas injection fromsupernovae is more important in the Bar region, than AGB stars. AGB stars are an
important gas contributor in the Disk.
We show some of the representative
spectra of AGB stars and PNe in the Galaxies in the Local Group, including the LMC,
and Galactic Globular Clusters (GC). Their spectra show a wide range and varieties ofmolecular and dust features. The strength of this molecular band tends to be stronger
towards the AGB stars at low metallicity. This can be explained, because at low
metallicity, the initial oxygen abundance is low, resulting in chemical processes being
more sensitive to carbon synthesized in AGB stars [1]. It appears that the dust
composition depends on both the stellar evolution stage and the metallicities of thegalaxies.
Finally, we show a wide-field-of-view (4’x7’) image of the Helix
Nebula in the molecular hydrogen lines. The Helix Nebula is one of the closest PNe(219 pc), and detailed studies within the nebula are possible. Molecular hydrogen isfound only in association with globules in the nebula. PDR models suggest that thesehydrogen molecules were formed during the AGB phase, and they survived over the
UV radiation field from the PN central star.
References[1]

Matsuura M., Zijlstra A.A., van Loon J.Th., et al., 2005, A&A, 434, 691

Properties of Interstellar PAHs in the Milky Way and in Nearby Galaxies
I. Sakon,1 T. Onaka, 1 H. Kaneda 2, Y. Okada 2, and T. Nakagawa 2
1

Department of Astronomy, Graduate School of Science, University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
2
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency,
3-1-1 Yoshinodai Sagamihara, Kanagawa 229-8510, Country
The ubiquitous infrared (UIR) bands are a family of emission bands that have been observed
ubiquitously in various astrophysical environments including planetary nebulae, reflection
nebulae, HII regions (see [1] for a review), general interstellar medium and cirrus clouds (e.g.,[2], [3], [4]) not just in our Galaxy but also in external galaxies (e.g., [5], [6]). It is widely
accepted that the carriers of these bands contain polycyclic aromatic hydrocarbons (PAHs;[7]) or PAH-like molecular groups (i.e. QCCs; [8]). Indeed, [9] has recently reported that theobserved UIR spectra are closely reproduced by a mixture of theoretically calculated infrared
spectra of PAHs with different size distribution, charge state and the precise chemicalcomposition of the contributing molecules. However, it still remains uncertain how we could
interpret the observed variations in the spectra of UIR bands and how we could understand theevolution of interstellar PAHs. For this purpose, close collaboration among the laboratory
experiments as well as the theoretical calculations on the infrared spectra of PAH relatedmaterials and the observations of UIR spectra in various environments are indispensable.
AKARI, the Japanese Infrared Satellite, has been playing an important role in this fieldpresenting a number of near- to mid-infrared spectra of ISM in our Galaxy and in nearby
galaxies. In this presentation I will introduce some of AKARI’s latest observational results
and their impacts on the studies of interstellar PAHs.

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

Tokunaga, A. T., 1997, ASP Conf. Ser. 124, p149
Mattila, K., et al. 1996, A&A, 315, L5
Tanaka, M., et al. 1996, PASJ, 48, L53
Onaka,T., et al. 2000, PASJ, Adv. in Sp.Res., 25, 2167
Lu, N., et al. 2003, ApJ, 588, 119
Kaneda, H., et al. 2005, ApJ, 632, L83
Allamandola, L.J., 1989, ApJS, 71, 733
Sakata, A., et al. 1984, ApJ, 287, L51
Cami, J., et al. 2007, Proc. of 4th Spitzer Science Center Conference, in press
Sakon et al., 2007, PASJ, 59, S483

How forms observed low-temperature crystalline silicate:Approach from laboratory experiments
Yuki KimuraInstitute of Low Temperature Science / Hokkaido University, Japan
Astronomical observations have shown the existence of abundant silicate grains aroundevolved stars in the infrared spectra. It has been realized that most of the silicate grains areamorphous phases based on the infrared features. In contrast, characteristic infrared features
attributed to Mg-rich crystalline silicates have been reported in limited number of evolvedstars with high mass loss rate (>10-5 Msun/yr) [1]. The fraction of the crystalline silicates,
particularly forsterite, is typically 10-15 % in the outflows with high mass loss rate ofasymptotic giant branch (AGB) stars [2]. During the formation of silicate grains, whether asilicate grain becomes crystalline or amorphous depends sensitively on its formation
conditions. To elucidate the crystallization condition of amorphous silicate, several
laboratory experiments have been attempted. It has been known that crystalline forsterite
grains are formed at a slower cooling rate (<~700 K/s: [3]) or by later annealing (~1000 K:[4]) of previously condensed amorphous grains. Crystallization has generally been discussed
on the basis of thermal annealing [5]. However, it seems to be unrealistic to find amechanism of partial annealing occurred only at the stars with high mass loss rate, because
the crystallization of silicate is very sensitive in temperature. In addition, some implicationsof low-temperature crystallization have been reported from the astronomical observation ofboth young and evolved stars [6-8]. Generally, the temperatures of the crystalline silicate
grains astronomically observed are at as low as 100-250 K. In contrast, warmed amorphoussilicates in a stationary circumstellar disk were observed [9]. Therefore, it can be consideredthat the crystallization of silicates may be not affected by thermal heating.
In this situation, I would like to propose that the astronomically observed crystalline
forsterite can be formed by direct condensation from the vapor phase of magnesium andsilicon oxide. It was found that the crystallinity, which was deduced from the shape of the 10
μm feature, of the circumstellar silicates could be determined by the balance between heatgeneration by Mg oxidation and heat dissipation due to radiation. In this case, later annealingof the silicate fraction or the use of a warm substrate for condensation of crystalline silicate is
unnecessary. In addition, to explain the existence of highly crystalline silicate grains (75% of
total silicate) observed in some silicate carbon stars, the possibility of low-temperature
crystallization is presented based on electron irradiation on amorphous Mg-silicate grains,because the environment of the envelope is very low in temperature for the crystallization ofsilicates due to annealing [10].
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]

A. Speck et al., 2000, A&A Suppl. Ser. 146, 437.
F. Molster & C. Kemper, 2005, Space Science Reviews 119, 3.
J. A. Tangeman, et al., 2001, Geophysical Research Letters 28, 2517.
Y. Kimura et al., 2007, Workshop on the Chronology of Meteorites and the Early Solar System, LPI
Contribution, No. 1374, p.90-91.
S. L. Hallenbeck, J. A. Nuth, Ш & P. L. Daukantas, 1998, Icarus 131, 198.
F. J. Molster, et al., 1999, Nature 401, 563.
T. K. Okamoto, et al., 2004, Nature 431, 660.
B. Merin, et al., 2007, ApJ 661, 361.
I. Yamamura, et al. “in Proc, 1st ISO workshop on Analytical Spectroscopy” eds. A. M. Heras, et al. (SP419, ESA, Noordwijk, 1997), p. 313-314.
F. J. Molster et al. 2001, A&A 366, 923.

The role of heterogeneous reactions in the origin and evolution of Titan’s atmosphere
Y. Sekine1 H. Imanaka2,3, S. Lebonnois3, B.N. Khare3, E.L.O. Bakes3, C.P. McKay5,
S. Sugita1, T. Matsui1
1

Dept. of Complexity Sci. & Engr., University of Tokyo, Japan
2 Dept. of Chemistry, University of Arizona, USA
3 SETI Institute, USA
4 Laboratoire de Météorologie Dynamique, CNRS/UPMC, France
5 Space Science Division, NASA Ames Research Center, USA
Titan, the largest moon of Saturn, has a thick atmosphere composed primary ofnitrogen and methane. More than 10 organic molecules and dense haze layers also have been
detected in Titan’s atmosphere [1]. The goal of this study is to understand why Titan’s
atmospheric composition is the current one and how the atmosphere has evolved during theage of solar system. In this study, we focused on the heterogeneous reactions on the surface oforganic aerosol, which forms haze layers in Titan’s atmosphere. We experimentallyinvestigated the heterogeneous reactions of atomic deuterium with Titan tholin (laboratory
analog of Titan’s aerosol) in a laboratory and determined the reaction probabilities of theheterogeneous reactions quantitatively [2]. By incorporating the reaction probabilities into a
photochemical model of Titan’s atmosphere, we evaluated the role of organic haze both in thechemical composition of the atmosphere and the hydrogen budget on Titan [3].
Our results suggest that the heterogeneous reactions significantly reduce theconcentrations of atomic hydrogen in the stratosphere and mesosphere. Low concentration of
atomic hydrogen enhances the concentrations of unsaturated complex organics and reduces
the concentrations of saturated hydrocarbons. These results show that Titan’s aerosols act asan efficient sink of atomic hydrogen (Figure 1). Such behavior of aerosol may keep thechemical composition of the Titan’s atmosphere to the current one, which is suitable forsynthesis of complex organic molecules. Furthermore, our results also suggest that theincrease in haze production induces further increase in the haze production in the atmosphere.
By taking into account this positive feedback in Titan’s atmosphere, we will discuss the roleof the heterogeneous reactions in the evolution of the atmosphere-surface system on Titan.

Figure 1: Schematic diagram of the fate of atomic hydrogen in Titan’s atmosphere. The organic aerosol acts
as a catalyst not only to remove highly reactive atomic hydrogen from the atmosphere but also to enhancethe efficient production of higher molecular-weight hydrocarbons in the atmosphere.

References
[1]
[2]
[3]

F. M. Flaser, et al., 2005, Science 308, 975
Y. Sekine et al., 2008, Icarus 194, 186
Y. Sekine et al., 2008, Icarus 194, 201

Reaction Dynamics in the Interstellar Medium - From Molecule Formation in the Gas
Phase to Interstellar Grains
Ralf I. Kaiser1
ralfk@hawaii.edu
1

Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA,The formation of molecules in extraterrestrial environments has fascinated scientists since thepioneering detection, in 1937-39, of CH, CH+, and CN in interstellar space. We now know ofat least 120 species, ranging in complexity from diatomics such as molecular hydrogen (H2) topolyatomics like the sugar glycolaldehyde (HOCH2CHO), benzene (C6H6), and cyanopentaacetylene (HC11N), which have been identified as gas-phase constituents of extraterrestrial
environments. Nevertheless, many facets of the question "How do these molecules arise?"remain unanswered or contentious. In searching for answers to this question, we also obtain
crucial information relevant to the chemistry of our immediate environment: the rules ofchemistry, after all, are universal, even when the conditions are very different.
This talk reviews recent developments on laboratory experiments to untangle how complex(astrobiologically important) molecules are formed in extraterrestrial ices (Solar System Ices,
ices on interstellar grains) and in the gas phase (ISM, atmospheres of planets and theirmoons). The experimental techniques utilized are surface scattering experiments at UHV conditions (< 5×10-11 torr) and crossed molecular beam studies under single collision conditions.
Implications to specific Solar System Environments like Kuiper Belt Objects and Saturn’ssatellite Titan are presented, too.

Figure 1: Images of the crossed molecular beams machine (left) and the surface scattering machine (right)
utilized to study bimolecular neutral-neutral reactions in the gas phase and the interaction of ionizing radiation with (icy) surfaces.

Experimental Studies of Molecule Formation on Astrophysical Surfaces at Low
Temperatures
V. Pirronello
DMFCI, Università di Catania, Sicily, Italy

Heterogeneous catalysis on dust grains has been proven to be very important for the chemicalenrichment of interstellar clouds through a relevant series of experiments performed byseveral groups in conditions and on surfaces close to realistic ones.
I will present results relative to species that need surfaces either to be synthesized or to beformed more efficiently than in the gas phase.
Attention will be paid to the mechanisms that might be involved.

Ice Surface Chemistry: Implication for Molecule Formation on Interstellar Dust
Particles

H. Kang, E. S. Moon, C. W. Lee
Department of Chemistry, Seoul National University, South Korea

Icy surfaces of interstellar dust particles are considered to play important roles in molecule
formation in space. This presentation will describe our recent investigations of chemistry of
ice surfaces with the emphases on the mechanistic features of elementary reactions and theimplication for molecular evolution on interstellar grains. The types of reactions include thediffusion of molecules, proton transfer through the hydrogen-bonded network of ice, andsimple acid-base reactions. Photoreaction of amine and carbon dioxide on ice surfaces leading
to the formation of glycine and its isomers as identified by in situ mass spectrometricdetection is also presented.

References[1][2]

H. Kang, 2005, Acc. Chem. Res. 38, 893.
Eui-Seong Moon, Chang-Woo Lee, Joon-Ki Kim, Seong-Chan Park, and H. Kang, 2008, J. Chem. Phys.,

128, 191101.

Quantum chemical studies of H + (H2O)n system as model of chemisorption on icy grain
Y. Osamura
Kanagawa Institute of Technology, Atsugi 243-0292, JapanThe reactions of hydrogen atom with various chemical species on icy grain are important
processes on the formation of hydrogenated molecules in interstellar medium. It would beinteresting to see the behavior of hydrogen atom both on ice surface and inside ice. Theinteraction between hydrogen atom and amorphous ice can be modeled as H + (H2O)n cluster
system in order to explore quantum chemically. We have calculated the structures andinteraction energies between hydrogen atom and water clusters with the hybrid density
functional method. We have used the B3LYP method with 6-311G(d,p) basis functions to
optimize the geometries of H…(H2O)n system for n=1~4. Table 1 shows the distance betweenhydrogen atom and oxygen atom of H2O and the stabilization energies depending on thenumber of water molecules. All interaction energies are calculated to be small (1~2 kJ mol-1)
and the distance between hydrogen atom and water clusters are shown to be ca. 2.5 Å. This
indicates that the interaction between hydrogen atom and water molecule is due to the weakvan der Waals attraction. When we look at the dependence of the number of water molecules
surrounding to a hydrogen atom, both the binding energies and the distances are found to benearly the same except the case of water dimer.
If one says that this type of interaction is physisorption, there might be a type ofchemisorption between H atom and H2O molecules. Nevertheless, H3O radical is energeticallyhigh species and spontaneously decompose to H + H2O. Since the energy of H3O molecule(69.0 kJ mol-1 relative to H + H2O) is higher than that of the transition state leading to OH +H2 (42.0 kJ mol-1), the chemical species H3O cannot be exist not only in gas phase but also in
solid or liquid phase. The transition states for hydrogen exchange reactions in H + (H2O)nclusters are calculated to be also high in energy.
Table 1. The interaction distances and interaction energies between H atom and H2O clusters.
----------------------------------------------------------------------------------------------------------nsystemH … O distancestabilization energy(Å)ΔE (kJ mol-1)----------------------------------------------------------------------------------------------------------1
H2O…H
2.38
0.9
2
(H2O)2…H
2.14
2.2
3(H2O)3…H
2.49
1.1
4(H2O)4…H
2.50
0.9-----------------------------------------------------------------------------------------------------------Negative ions in space
K. Kawaguchi
Department of Chemistry, Faculty of Science, Okayama University, Okayama
Existence of negative ions in space has been discussed for a long time. Although 15 positive
ions have been known in interstellar space, the first identification of the negative ion C6Hwas carried out quite recently(2006).
The late type carbon star IRC+10216 is well known to be one of the richest molecular source.
So far more than 53 molecular species were identified in IRC+10216. During spectral line
survey observations in the frequency region between 28 and 50 GHz by using the Nobeyama
45-m radio telescope, Kawaguchi et al.[1] found a series of unidentified lines with a spectral
pattern of a 1Σ linear molecule. The rotational constant was determined to be 1376.864 MHz.
Later, Aoki [2] carried out ab initio calculations to find a candidate to explain the magnitudeof the rotational constant and concluded that the C6H- anion is a probable candidate. In 2006,
McCarthy et al. [3] succeeded to detect the rotational lines of C6H- by laboratory millimeterwave spectroscopy and Fourier transform microwave (FT MW) spectroscopy and establishedthat the C6H- anion is the carrier of the unidentified species with the rotational constant.
Following to C6H-, the C4H-, C8H-, C3N- anions have been detected in IRC+10216 and othersources. The C8H- detection [4] and search for C10H- with the Nobeyama 45-m telescope will
be presented. Table 1 lists the electron affinities of the CnH (CnN) radicals and dipole
moments of CnH- (CnN-), where n=odd (for CnH) and n=even (for CnN) chain molecules are
not listed because of less abundances.
Table 1. Electron affinity(EA) of CnH(N), dipole moment (μ) of CnH(N)－, and column
density(N) in IRC+10216
(CnH)
n=2
4
6
8
10
(CnN) 1
3
5
EA of CnH 2.96
3.56
3.81 3.97
3.9
3.86
4.6
4.5 (eV)
5.9
8.2
10.4
12.7
0.6
3.1
5.2 (Debye)
μ of CnH－ 3.4
N of CnH 5000
2980
80
5.5
640
310
6 (×1012 cm-2)
N of CnH－ <0.4
0.71
6.9
2.6
<16
1.6
<1(×1012 cm-2)aRatio<1/12500 1/4200 1/12 1/2<40 1/194<1/6
a[anion]/[neutral]
We discuss about production reactions related to the observed abundances listed in Table 1
and spatial distributions of negative ions and neutral species in IRAC+10216. When we
consider star forming region like as Orion KL, above anions are expected to be less becauseof small abundances of carbon chain molecules. On the other hand, the positive ion HCO+ isabundant with a column density of 3 x1014 cm-1, so we will discuss about existence form ofnegative charge in star forming regions.
References[1] Kawaguchi,K., Kasai, Y., Ishikawa, S., Kaifu, N. 1995, PASJ, 47, 853[2] Aoki, K. 2000, Chem. Phys. Lett., 323, 55[3] McCarthy, M. C., Gottlieb, C. A., Gupta, H., & Thaddeus, P. 2006, ApJ, 652, L141
[4] Kawaguchi, et al. 2007, PASJ, 59, L57

Oxygen isotope anomalies of the Sun and the original environment of the Solar system
J.-E. Lee, 1 E. A. Bergin, 2 and J. R. Lyons 3
1

Department of Astronomy and Space Science/ Sejong University, Korea
2
Department of Astronomy/ The University of Michigan, USA
3
Department of Earth and Space Sciences/ University of California, USA

Most stars form in clusters [1] even though our star, the Sun, seems alone at present with theclosest stellar neighbor at 1.3 pc. It is not certain, however, whether the Sun formed in acluster or in isolation. Some memory of the environment where the Sun formed might exist
within the remnants of the formation of the Solar System. In this regard, primitive meteorites,
interplanetary dust particles, and comets have been considered as the best sources to search
for memory of conditions prior to and during formation, since they escaped from significant
physical and chemical processing and therefore may preserve some relic of interstellar
material. For instance, the inferred presence of short-lived radionuclides, especially 60Fe, inmeteorites [2] suggests that the Sun formed near a massive star, which went through the corecollapse of a supernova and provided the radionuclide to the solar nebula [3] or to the protosolar molecular cloud [4]. This possibility of the Sun formation in proximity to massive stars
is also supported by the prominent dearth of objects beyond the semi-major axes of theKuiper Belt, which might be caused by the dynamical truncation though stellar encounters[5][6] or by the external photoevaporation [7].
If the Sun formed in a cluster, as described above, the ultraviolet radiation field around theproto-Sun would have been enhanced by 4 to 5 orders of magnitude compared to the standard
local interstellar radiation field. Therefore, this enhanced radiation environment must havealso left some evidences in chemistry affected by photolysis. It has been discovered thatoxygen isotopes in calcium aluminum rich inclusions (CAIs) embedded in primitive
meteorites had different ratios from those seen in terrestrial rocks [8], where the oxygenisotopic fractionation depends on mass. Recent theories suggest this mass-independent
fractionation recorded in meteorites can be understood as a result from the isotopic-selective
photodissociation of CO, either in the Solar Nebula [9][10] or parent cloud [11]. The
photodissociation of CO is strongly coupled with the strength of the far-ultraviolet (FUV)
radiation field as well as the CO column density. The studying of oxygen isotope ratios in the
Solar system, therefore, will place strong constraints on its formation environment.
The oxygen isotope composition of the Sun is central to understanding the oxygen isotope
evolution of the Solar system as recorded in meteorites. Recent preliminary Genesis results[12] of the direct Solar wind measurements show that the Solar oxygen isotope ratios are
similar to the initial bulk values (δ18,17SMOW = -50 permil), i.e., isotopically light compared to
the Standard Mean Ocean Water (SMOW). However, the Solar wind isotope measurements inlunar metal grains have yielded dramatically different results; δ18,17SMOW = -50 permil in one
case [13] and δ18,17SMOW = +50 permil in the other [14].
Based on the CO self-shielding model in a collapsing low mass star forming cloud, we haveshowed that the Solar oxygen isotopic anomalies could vary depending on the strength of thesurrounding radiation field (G0) when the Sun formed [15]. When constrained by oxygenisotope anomalies measured in meteorites, comets, and the Solar wind (Genesis), our model
independently suggests that the Sun formed in the vicinity of massive stars, which isconsistent with other evidences such as short-lived radionuclides and the dynamical propertiesof planets and Kuiper Belt objects.

References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]

[13]
[14]
[15]

C. J. Lada & E. A. Lada 2003, ARA&A, 41, 57.
M Wadhwa, Y Amelin, A. M. Davis, G. W. Lugmair, B. Meyer, M. Gounelle, & S. J. Desch 2007, In
Protostars and Planets V, edited by Reipurth B., Jewitt D., and Kiel K. Univ. of Arizona, Tucson. pp. 835.
N. Ouellette, S. J. Desch, J. J. Hester, & L. A. Leshin 2005, In Chondrites and the Protoplanetary Disk,
edited by Krot A. N., Scott E. R. D., and Reipurth B. ASP. v.341 pp.527.
M. Gounelle 2006, New Astronomy Reviews, 50, 596.
G. Laughlin & F. C. Adams 1998, Astrophys. J. 508, L171.
S. Ida, J. Larwood, & A. Burkert 2000, Astrophys. J. 528, 351.
F. C. Adams, D. Hollenbach., G. Laughlin, & U. Gorti 2004, Astrophys. J., 611, 360.
R. N. Clayton, L. Grossman, & T. K. Mayeda 1973, Science, 182, 485.
R. N. Clayton 2002, Nature, 415, 860.
J. R. Lyons & E. D. Young 2005, Nature, 435, 317.
H. Yurimoto & K. Kuramoto 2004, Science, 305, 1763.
K. D. McKeegan , G. Jarzebinski., A. P. Kallio, P. H. Mao, C. D. Coath, T. Kunihiro, R. Wiens, J.
Allton, M. Callaway, M. Rodriguez, & D. S. Burnett 2008, A first look at oxygen in a Genesis
concentrator sample. Lunar Planet. Sci. XXXIX, #2020 (CD-ROM).
K. Hashizume & M. Chaussidon 2005, Nature, 434, 619.
T. R. Ireland, P. Holden, M. D. Norman, & J. Clarke 2006, Nature 440, 776.
J.-E. Lee, E. A. Bergin, & J. R. Lyons 2008, M&PS, in press.

Observations of deuterium-bearing molecules in star-forming regions
B. Parise 1
1

Max-Planck-Institut für Radioastronomie, Bonn, Germany

Despite the low deuterium abundance in the Universe (D/H ~ 1.5 x 10-5), high abundances of
deuterated molecules are detected in star-forming regions, with the abundance ratio of thedeuterated over the main isotopologues being higher than the cosmic abundance of deuteriumby several orders of magnitude. Particularly, the warm dense gas in hot cores around lowmass protostars is enriched in deuterated species, with even high observed abundances of
triply-deuterated species such as CD3OH ([1], see Figure 1). These deuterated molecules
provide valuable tools to probe the physical conditions occurring during star formation, as
well as the formation mechanisms of molecules. Deuteration is thought to be driven by thesmall energy differences between a deuterated species and the normal isotope. Because thetemperatures indicated by the fractionation are much lower than the present gas temperaturesin hot cores, the observed deuterations are thought to reflect a previous cold phase. Likely
these molecules formed during the preceding prestellar core phase -- either in the gas phase oron the grain surface -- and were stored in an ice mantle which evaporated once the YSO
heated its environment above the ice sublimation temperature.
In this talk, I will present observations of deuterium-bearing molecules in star forming
regions, and illustrate which constraints they bring to the understanding of the formation
processes of molecules. I will also underline the interaction with studies performed in thelaboratory.

Figure 1: Detection of CD3OH towards the low-mass protostar IRAS16293-2422. The abundance ratio
CD3OH/CH3OH is 13 orders of magnitude higher than the cosmic D/H ratio.

References[1]

B. Parise, A. Castets, E. Herbst et al., 2004, A&A 416, 159.

Molecular Signatures in Massive Star Forming Regions
S.-Y. Liu1
1

Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan, R.O.C.

Star formation processes not only reshape the physical environment of molecular clouds
but also alter the chemical composition in the clouds, such chemical evolution could inturn influence critical physical states of the clouds as well as determine the molecularinventory in the clouds. The chemical signature of different components at various stagesof star formation, therefore, is a result of complicated interplay between the chemical
processes in gas phase, on grain surfaces and the interactions between gas and grains.
Such effect may be particularly important for high-mass star forming regions, sincemassive star formation process can be very energetic and hence the interactions
presumably have more significant impacts, even at very early stages.
Rich molecular complexity has been demonstrated to exist in massive star forming
regions. For example, the so-called "hot molecular cores" are characterized by enhanced
abundances of complex and highly-saturated organic molecules, which is likely to be
resulted from surface reactions and/or UV-radiation, comic ray processing during thecollapse phase and mantle evaporation after the onset of central massive stars. However,
our understanding of the chemical condition for the precursors of high mass stars is still
far from complete. What are their unique chemical characteristics? Do they have any
molecular signature similar to the cold dark clouds? Or significant chemical evolution has
already occurred? In this contribution, I will review recent results from observations ofmassive star formation regions, with some emphasis over high angular resolution studies
with interferometric arrays.

Evidences of infalling gas onto the circumnuclear ring at the galactic center from SiO
and H13CO+ emission lines observation
Mamiko Sato1 and Masato Tsuboi, 1,2
1

2

Department of Astronomy, The University of Tokyo, Japan
Department of Basic Space ScienceInstitute of Space and Astronautical Science (ISAS) /Japan Aerospace Exploration Agency (JAXA)The central region of our Galaxy (Sgr A ) is the nearest galactic center harboring a massive
black hole [1,2]. The environment around Sgr A is a topic of interest to diverse fields. We
are interested in gas feeding from giant molecular clouds (GMC) within 10 pc of the Galactic
center to the Circumnuclear Ring/Disk (CND), which is presumable ”lay-down bay” ofinfalling gas toward Sgr A [3]. In order to reveal the mechanism, we observed the CND and
its surroundings in SiO and H13 CO+ lines using Nobeyama Millimeter Array (NMA). We
depict the CND clearly in both lines and some molecular streamers to the CND in only SiO
line including one new detection. The line intensity ratios at overlapping points of streamers
with the CND are higher (I(SiO)/I(H13 CO+) > 6) than the average of CND (2-4). This is astrong evidence indicating these streamers are connecting to the CND. Some components atthe outer region of the CND are also detected in both lines. We also estimate the rotation
velocity of the CND as 110 ±10 km s−1 and of just a bit outside from the CND as 93 ±14 km
s− 1 . The estimation of the rotation velocity in the distance range of 5-10 pc from the Sgr A
has a great meaning since there have been few report about the kinematic parameters at justoutside of the CND [3,4 and 5].

References[1] Genzel R, Eckart A, Ott T l and Eisenhauer F 1997 MNRAS 291 219-234[2] Ghez A M, Klein B L, Morris M and Becklin E E 1998 ApJ 509 678-686[3] Gusten R, Genzel R, Wright M C H, Jaffe D T, Stutzki J and Harris A 1987 ApJ 318 124-138[4] Schoedel R, Ott T, Genzel R, Eckart A, Mouawad N and Alexander T 2003 ApJ 596 1015-1034[5] Tsuboi M, Okumura S K and Miyazaki A 2006 JPhCS 54 16-21

AKARI’s view of interstellar matter in galaxies
T Nakagawa,11Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan

We review recent observational results on the interstellar matter in galaxies obtained by theJapanese infrared astronomical satellite AKARI.
AKARI was launched in February 2006 and started observations in May of the same year.
AKARI has a 68.5 cm cooled telescope together with two focal plane instruments, which haveimaging and spectroscopic capability in the wavelength range 2-180 μm. One of the mostimportant missions of AKARI was to make an all-sky survey in six bands in the mid- and farinfrared, and AKARI also made extensive observations of specific targets in pointed modes.
After liquid helium ran out in August 2007, AKARI has been making observations in thenear-infrared with mechanical cryocoolers.
AKARI made systematic observations of near-by galaxies. Wide spectral coverage of AKARI
enables us to deconvolve dust thermal emission in the far-infrared into two components:
warm dust, which traces recent star-formation activity, and cold dust, which traces generalinterstellar dust. The distribution of hot dust component shows wide variety among observed
galaxies, reflecting the difference of recent star-formation activity and distribution of heating
sources.
Another important aspect of AKARI observations is its capability of sensitive spectroscopic
observations in the near- and mid-infrared. Especially toward heavily obscured galaxies (e.g.
most of ultra luminous infrared galaxies), AKARI detected absorption features due to various
types of molecules. Observed absorption features show huge variety, reflecting the differenceof physical conditions of interstellar matter in various types of galaxies.
Some galaxies show wide CO absorption features around 4.6 μm, which indicates thepresence of hot (500-1000 K) molecular gas in these galaxies. These hot clouds could beheated by X-ray radiation from the central activity of the galaxies.
References
[1]
[2]
[3]

.

H. Murakami, et al., 2007, PASJ, 59, S369.
H. Kaneda, et al. 2007, PASJ, 59, S463
T. Suzuki, et al. 2007, PASJ, 59, S473

The simplest carbon growth mechanism by atomic carbon insertion reactions
and the source of DIB
Teruhiko Ogata and Yoshio Tatamitani
Department of Chemistry, Shizuoka University, Shizuoka 422-8529, Japan
Carbon growth reactions represent oneof the most fundamental chemical
processes. The simplest example is theatomic carbon insertion reaction (ACIR).
In ACIR, atomic carbon, :C, or its
precursors, :CCO and C3O2, jump into
the CC bond without cleaving the overall
structure. As a result, no side-products
are produced from this reaction (Figure1).

a) Potolysis of C3O2 [1a]O C C C O
C C + C C OhνC C O + CO
hν

C C O

hν

hν
-CO

(1)

C + 2CO
C

C C C

(2)

b) Ion + C3O2 reactions [1b,1c ]CnO+ + C3O2+

CnO2 + C3O2+

CnH6 + C3O2

Cn+3O3+

Cn+3O4+-2CO

Cn+3H6O2+

-2CO
-2CO

Cn+1O+ (n = 1-6)

(3)+
Cn+1O2 (n = 1-18)(4)+
Cn+1H6 (n = 1-4)(5)c) Discharge of C3O2 [ 2 ]n C3O2

C +CO +C2O +C3O +C4O +C5O +C6O +C7O +C8O +C9O (6)The mechanism of linear-carbond) Radiation-induced reaction in CO ice [ 3 ]monoxides formation, CnO (n = 2 - 9),
Cn+1O(X 3Σ −/ 1Σ+) (n = 1 - 4) (7)CnO(X 1Σ+/ 3Σ −) + C(3P /1D)
which is synthesized in the discharge of
C3O2, has been investigated based on thedetailed analyses of FTMW
Figure 1: Some linear-carbon-chain growths by atomicspectroscopic data [2]. The relative
carbon-insertion reactions.
abundances of the CnO products,
determined from their rotational spectrum intensities, agree with those for the CnO+ ions,which were known to be lengthened by successive mono-carbon insertions [1b]. The active
chemicals in the reaction system include only :C and :CCO. Moreover, since the observed
products consist exclusively of CnO, the reaction occurs via the ACIR mechanism (Figure 2).
C
C C C OC C C C O
Nearly all of the
C6O
C C C C C O
linear-carbonC
6
1
3
C C O
7
chain moleculesC
C2O
C C C OC C C C C O
Cdetected in
C8O
C
5
2
C
laboratories or inC
C C C C O
space, which are
C9O
available on Prof. Sucsessive mono carbon insertions
4C
Okabayashi’s
Figure 2: The proposed formation mechanism for CnO (n = 2 - 9) by atomic
homepage [4],carbon insertion reactions.
can be interpretedby this formation
mechanism. The exception is (c-H2C3)=C=C, which requires isomerization from (c-HC3)C≡CH.

ACIR is simple, as it only requires the presence of :C and a CC bond, and efficient due to its low
or zero activation energy. Hence, this reaction scheme is applicable to a wide-range of carbonbased processes, in particular, to ultra low temperature or incomplete combustion conditions [5].
It is commonly thought that long carbon chains and atomic carbon primarily exist in a relatively
diffuse part of the molecular cloud in space, which suggests that carbon chains are formed by
ACIR.
Based on the following evidence, we can also imagine that a huge amount of the atomic carbon
inserted clusters form a kind of “amorphous carbon” in interstellar space (reminiscent of thesource of DIBs):
1. “Amorphous carbon” can be formed by ACIR, which is the dominant reaction at ultra
low temperatures [5b].

2. While all “amorphous carbon” species have distinct structures from each other, theirstructures may be partially similar.
3. “Amorphous carbon” is black, implying that many absorption features fall in the UVvisible light region.
4. “Amorphous carbon” can withstand bombardment with ultraviolet photons in space.
Previous work has reported that the absorption curves for soots and quenched carbonaceouscomposites agree well to the absorption curves from interstellar extinction [6].
Presumably, “amorphous carbon” has a highly strained filled interior with many dangling
bonds. The possible structure and formation mechanism of “amorphous carbon” will be
proposed at the workshop.
References:[1] (a) K. D. Bayes, 1962, JACS, 84, 4077; (b) S. M. Schildcrout, et. al., 1970, JACS, 92, 251;(c) O.Bortolini, et al., 1999, Int. J. Mass Spectrom., 190/19, 171.
[2] (a) T. Ogata, et al., 1995, JACS, 117, 3593; (b) Y. Ohshima, et al., 1995, JCP, 102, 1493.
[3] C. S. Jamieson, A. M. Mebel, & R. I. Kaiser, 2006 , ApJ Supp. 163, 184.
[4] Prof. T. Okabayashi’s homepage, http://www.ipc.shizuoka.ac.jp/~sctokab/Okab.htm.
[5] (a) T. Ogata, et al., Proceedings of the Carbon2007 Conference, B083, Seattle, USA (2007); (b) Proceedingsof the Carbon2008 Conference, P0469, Nagano, Japan (2008).
[6] (a) A.T. Tokunaga and S. Wada, 1997, Adv. Space Res.,19, 1009; (b) Y. Kimura, T. Sato, and C. Kaito, 2004,
Carbon, 42, 33.

Ab initio molecular dynamics approach to dissociative recombination reactions
T. Taketsugu,1 Y. Kobayashi,1 A. Nakayama,1 T. Noro,1 M. Kayanuma,2 and K. Ishii3
1

Division of Chemistry, Graduate School of Science, Hokkaido University, Japan
Department of Chemistry, Graduate School of Science, Ochanomizu University, Japan3
Department of Chemical System Engineering, School of Engineering, The University ofTokyo, Japan2

The 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 mechanism or the indirect mechanism. In the direct mechanism, themolecular system makes transitions directly from the electronic ground state of cation to thedissociative state of neutral molecule after capturing an electron. In the indirect mechanism,
this transition proceeds via Rydberg states. In the interstellar medium, polyatomic ions areproduced through ion-molecule reactions, and the DR process is one of the possible ways ofneutralizing the ions. Through the DR reactions, polyatomic ions dissociate into different
combinations of neutral atoms/molecules, and the study of the branching ratios of the DR
reaction will help to understand the chemical evolution in interstellar clouds.
In order to examine the reaction mechanism and dynamics in the DR processes, we havedeveloped an ab initio molecular dynamics (AIMD) program code for excited-state dynamics,
including the Tully’s surface hopping algorithm for nonadiabatic transitions between
adiabatic electronic states. The code uses the adiabatic potential energy, energy gradients,
and nonadiabatic coupling terms at the state-averaged complete active space multiconfigurational SCF level, evaluated by the quantum chemistry program package, MOLPRO.
The code has been applied to DR reactions, HCNH+ + e- [1,2], H3O+ + e- [3], HD2O+ + e- [4],and CH3+ + e- to examine the tendency in the branching ratio of the dissociative products, andto investigate the dynamical processes with nonadiabatic transitions. In the application to
HCNH+ + e- [1], we found that (1) HNC and HCN are generated with almost the same ratio,(2) the products, CN + 2H, are also generated, and (3) the isomerization between HNC and
HCN can occur while the HCNH molecule descends through the electronic excited states. In
the second application [3], two Rydberg states and three valence states were included indynamics, the surface hopping was observed in the relatively early stage less than 30 fs inmost cases, and the rates of the respective dissociative products are estimated as (OH + 2H) :(H2O + H) : (OH + H2) : (O + H2 + H) = 0.87 : 0.10 : 0.015 : 0.015, while the corresponding
experimental rates were reported as 0.60 : 0.25 : 0.14 : 0.013. The rate of exothermic
products is small compared to the experimental ones, but the order in the ratio is reproduced.
In the third application [4], it was shown that the dominant products, OD + D + H, weregenerated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% oftrajectories, indicating that the release of a light fragment H is favored over the release of aheavy fragment D. This result is in conformity with the observation that there is a larger
amount of deuterium substituted species than the non-substituted species in the interstellar
space.
References[1] T. Taketsugu, A. Tajima, K. Ishii, & T. Hirano, 2004, ApJ 608, 323.
[2] K. Ishii, A. Tajima, T. Taketsugu, & K. Yamashita, 2006, ApJ 636, 927.
[3] M. Kayanuma, T. Taketsugu, & K. Ishii, 2006, Chem. Phys. Lett. 418, 511.
[4] M. Kayanuma, T. Taketsugu, & K. Ishii, 2008, Theor. Chem. Accounts 120, 191.

Atomic density dependence of formation of polycyclic aromatic hydrocarbon bymolecular dynamics simulation
A. Ito,1 H. Nakamura, 2 and J. Takahashi 3
1

Department of Physics, Graduate School of Science, Nagoya University, Japan
Department of Simulation Science, National Institute for Fusion Science, Japan3
Department of Current Legal Studies, Faculty of Law, Meiji Gakuin University, Japan2

We have been studying the formation and deformation processes of nano-carbon moleculesby use of molecular dynamics (MD) simulation. We deal here with the formation ofhydrocarbon dust in the interstellar space. The purpose of this study is to make clear thegrowth of hydrocarbon dust from carbon atoms, hydrogen atoms and their small molecules.
In the MD simulation, the carbon and hydrogen atoms were initially located at random in asimulation box under periodic boundary condition. Chemical interaction between atoms was
represented by the modified Brenner reactive empirical bond order potential [1] andtemperature was controlled by the Langevin thermostat regarded as background radiation.
As a simulation result, polycyclic aromatic hydrocarbons (PAH) occurred and the following
formation process was clarified. First, many carbon chain molecules occurred. Next, longcarbon chains made carbon rings with tentacle, which is called “octopus structure”. Finally,
the rings and tentacle were knitted into six-membered rings and then they were formed into
the PAH like a graphene. In addition, amorphous carbon did not appear.
This MD simulation treated high atomic density and short time scale. However, under theassumption that the collision number of molecules is in proportion to atomic density, thisformation process of PAH corresponds to a phenomenon for 300 year on the atomic densityof 100 atom/cc. The second point that requires clarification is whether this assumption is valid.
To clarify its point, we execute the MD simulations on deferent atomic densities and wecompare formation speeds.

Figure 1: Formation process. The gray and black spheres indicate carbon and hydrogen atoms,

respectively.
References[1]

A. Ito and H. Nakamura, Commun. Comput. Phys 4 (2008), 3, 592.

Shocked molecular gas in the foot point of the molecular loop near the Galactic Center
K. Torii,1 M. Fujishita, 1 N. Kudo, 1 A. Kawamura, 1 R. Matsumoto, 2
S. Nozawa, 3 K. Takahashi, 4 M. Machida, 5 and Y. Fukui, 1
1

Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya, Japan
2
Faculty of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan3
Department of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki, Japan
4
CFCA, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, Japan
5
Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya, JapanThe Central Molecular Zone (CMZ) of the Galaxy is characterized by high gas kinetic
temperature (~30-60K) and by high gas density (~104 cm-3). We found the loop like molecularfeatures 300 pc away from the Galactic Center, which have the same properties of CMZ at thegiant molecular cloud (GMC) in their foot point, and suggested that the loops and the GMC
are formed by magnetically buoyancy driven by Parker instability [1, 2]. It is expected that
there are shock fronts made by the slipping gases along the loop in the foot point. We report
the results of molecular line observations by using ASTE, Mopra, NANTEN2 telescopes
toward the GMC in the foot point of the loops in order to search for evidence of the shock.
We found more than ten clumps sizes of which 2-3 pc and masses of which ~1000 solar
masses in the GMC in CO(J=3-2,1-0) [Figure 1]. They show high excited emission in CO(R_3-2/1-0 ~ 1.0-1.5). The shapes of the spectra in these clumps have very broad velocity
dispersion (30-40 km/s) and wing like components [Figure 2]. These properties suggest theexistence of the shock. High excited CO emissions also support it. On the other hand, theemissions of 13CO and CI (3P1-3P0) are very weak and almost the same. The emission of CO(J=7-6) was not detected. We have estimated physical parameters in these clumps by using
LVG analysis. The results indicate that these regions have low-density (102-103 cm-3) andhigh-temperature (>100 K). Additionally, the model of shocked gas shows the consistent
results on temperature and density and indicates the shock velocity of 40-50 km/s [3].

Figure 1(left): The integrated intensity map of the foot point of the Galactic Loop in 12CO(J=3-2).
Fgiure 2(right): The spectra in each line toward the region inditated by circle in Figure 1.

References
[1]
[2]
[3]

Y. Fukui et al., 2006, Science 314, 106.
N. Parker, 1966, ApJ 145, 811
D. Hollenbach, C. McKee, 1989, ApJ 342, 306

Chemical Models of Hot Molecules at Shocks in Outflows
H. Nomura,1 and T.J. Millar 2
1

2

Department of Astronomy, Kyoto University, Japan
ARC, School of Mathematics and Physics, Queen’s University Belfast, U.K.

It is observationally known that outflows are associated with many young stars, and they arethought to originate from accretion disks around the stars. Meanwhile, molecular line
observations have shown that some molecules such as CH3OH and SiO are very abundant atshocks and/or clumps in outflows.
In this work we have constructed chemical models at shock fronts in outflows by calculatingtime-dependent gas-phase reactions which are initiated by evaporation of icy mantle
molecules on dust grains [1]. We have studied dependences of the chemical structure of O-,
N-, and S-bearing molecules at the shocks on different physical conditions to show that avariety of molecular abundance ratios can be obtained, owing to the dependence ofdissociation rates on gas temperature and of adsorption rates on dust temperature. Initialcondition, that is, physical properties in disks at the upstream of the outflow also affects theabundance ratios. Our results suggest that observations of molecular abundance ratios will
trace the physical structure and the chemical processes, especially gas-grain interactions, atshock in outflows.

Figure 1: Dependences of the molecular abundances at shock on the shock velocity (the gas temperature)(left), and on the time which the molecules spend in the disk after the icy mantle evaporation and before theoutflow launching (right). Some parent molecules (e.g., CH3OH, H2CO) and daughter species (e.g.,
CH3OCH3) are depleted at strong shock (left). Some N-bearing daughter species (e.g., HCN, CH3CN) areabundant if they move into the outflow after they spend enough time in the disk (right).

References[1]

H. Nomura & T.J. Millar 2004, A&A, 414, 409

Oxygen Isotopic Evolution in the Early Solar Nebula:Interpretation of the Small Oxygen Isotopic Variation of Chondrules
T. Fukui and K. Kuramoto
Department of Cosmosciences, Hokkaido University, Japan

Oxygen isotopic systematics observed in chondritic components provides important clues to
elucidate physical and chemical processes occurred in the early solar nebula. Chondrules haveO-isotopic composition similar to those of terrestrial materials with small variation. In
contrast, CAIs, the oldest minerals formed in the early solar nebula, have anomalously
16
O-rich composition [1]. A plausible explanation for the origin of the systematics isenhancement of 16O-poor H2O concentration in the initially 16O-rich inner solar nebula [2].
The 16O-poor H2O is produced by isotope-selective photodissociation of CO in the parent
molecular cloud and stored as icy mantle on silicate dust in the cold outer part of the nebula.
The ice-coated dust particles drift inward due to nebula gas drag [3] and releases water vapor
at the hot inner nebula. As a result, the 16O-poor H2O concentrates with time and the meanO-isotopic composition of the inner nebula evolves to be 16O-poor. This model is consistent
with the large variation between CAIs and chondrules, however, not likely to explain thesmall O-isotopic variation of chondrules because H2O concentration is expected to be
temporally and spatially heterogeneous during chondrule formation.
In this study, we suggest a process which is overlooked in the previous study and possibly
explains the small variation of chondrules; i.e., enhancement of silicate dust concentration in
the inner nebula. Collision experiment of the nebula dust analogous implies that the typicalsize of dust particles would be determined by the adhesive properties of them [4]. Because
silicate is less sticky than H2O ice, dust particles would be refined after evaporation of icy
mantle. The size of silicate dust is theoretically estimated to be ~ sub-millimeter, which isinterestingly comparable to that of typical chondrules. Such small dust particles are wellcoupled with the nebula gas motion and hardly drift inward. Thus concentration of silicate
dust would also be enhanced almost same degree as that of H2O in the inner nebula. The mostimportant consequence of this model is that, in case the concentration of H2O and silicate dust
is enhanced >~ 5 times larger than the solar abundance, the mean O-isotopic composition of
the inner nebula is almost determined as the weighted mean of O-isotopic composition of
H2O and silicate in the solar abundance ratio; i.e., independent for their concentration. Thissuggests that temporal and spatial variation of concentration of H2O little affects on the meanO-isotopic composition of the inner nebula as long as the enhancement is sufficiently large.
Numerical simulation on the evolution of concentration of H2O and silicate dust using typical
properties of observed protoplanetary disks confirms that such large enhancement is sustained
during chondrule formation in the inner nebula. Thus, the small O-isotopic variation ofchondrules would be reproduced in our model.
References
[1]
[2]
[3]
[4]

R. N. Clayton, 1993, Ann. Rev. Earth Planet. Sci. 21, 115.
H. Yurimoto & K. Kuramoto, 2004, Science 305, 1763.
Y. Nakagawa, M. Sekiya & C. Hayashi, 1986, Icarus 67, 375.
J. Blum, "Astrophysics of Dust", ed. A.N. Witt et al. (ASP Conf. Series, Vol. 309, 2004), p. 369.

Eects of Radionuclides on the Ionization State of Dense Cloud
Cores and Protoplanetary Disks
Toyoharu Umebayashi1 and Takenori Nakano2
1

Department of Physics, Yamagata University, Yamagata 990-8560, Japan2
5-6 Muramatsu-cho, Iwakura, Sakyo-ku, Kyoto 606-0034, Japan

We reinvestigate the ionization rates by radionuclides with the abundances in the primitive
solar nebula by adopting the revised data on nuclides, extending the decay processes, andsurveying radionuclides more extensively. Although the ionization rates by 232 Th, 235 U, and238
U have become at least 10 times the previous ones, the total ionization rate by the longlived radionuclides, 1 4 10;22s;1 per hydrogen molecule, is still mostly contributed by 40K.
Among the short-lived radionuclides which are extinct in the present solar system, 26 Al is thedominant ionization source with the rate (7 { 10) 10;19 s;1 , overwhelming the long-lived
nuclides. With the average interstellar abundance of 26 Al estimated from -ray observation of
the galactic plane, the ionization rate is 8 times smaller than this. In addition, 60 Fe and 36 Cl,
whose ionization rates with the abundances in the primitive solar nebula are at least 10 times
smaller than that of 26 Al, can be more ecient than the long-lived nuclides. In protoplanetarydisks the ionization rate by radionuclides depends sensitive on the growth and sedimentationof dust particles. Ionization by radionuclides is quite inecient when the mean dust size isgreater than about 1 cm. Using these ionization rates we investigate the ionization state forsome congurations of the clouds. We nd that in dynamically collapsing very dense cloud
cores the short-lived radionuclides are more ecient ionization source than cosmic rays whenthe mean pressure (H2 ) & 1 1014 cm;3 K. We improve the attenuation law of cosmic rays
in geometrically thin disks. Using this law we nd that the dead zones in protoplanetary disks
are signicantly larger than those obtained in the previous work.
:



n

T

Development of the Mid-Infrared High Dispersion Spectrograph (IRHS)
Y. Hirahara,1 T. Hirao, 1 T. Oka 1, H. Tokoro 2, N. Ebizuka, and K. Kawaguchi 3
1

Graduate School of Environmental Studies, Nagoya University, Japan
2
Nano-Optonics Research Institute, Japan3
Department of Chemistry, Okayama University, Japan

High-dispersion infrared observations are useful for the definite identification of molecularspecies in the interstellar medium (ISM) by their vibration-rotation transitions. According toradio wavelength observations, molecular transitions in the ISM are Doppler-broadened, withline widths of 2~20 km/s in typical high-mass star forming regions and circumstellar
envelopes of late type stars. Due to these broadenings, the wavelength resolving power R=λ/Δλ=15,000~150,000 is required for sensitive detection of the spectra. In order toachieve such a high resolution in infrared region, Fourier transform spectroscopy (FTS) has
usually been employed. In the mid-infrared region (8~13μm), however, the dominant noise
source is the background blackbody radiation, so multiplex property of FTS is no longer
advantageous toward fainter astronomical sources.
Recently, we have developed the “mid-InfraRed High dispersion Spectrograph” (IRHS), a
cryogenic échelle spectrometer designed for Nasmyth focus stage of NAOJ Subaru 8.2m
telescope, which operates at 8-13μm in wavelength with the resolving power λ/Δλ of>50,000 at 10μm. To reduce thermal radiation of the instrument, all optics of IRHS isarranged on the cold optical base plate (~30K) of the cryostat with the diameter of 80cm. In
order to achieve high dispersion, broad bandwidth, and high sensitivity, two key devices are
employed: a single crystal germanium immersion echelle grating (30×30×72mm) and a Si:As
IBC (Impurity Band Conductor) focal plane array (FPA) detector (412×512 pixels, unit pixel
size 30μm) operated at 5 K[1]. The most important key device, germanium immersion
échelle grating for collimated beam size of 28mmφ was fabricated by utilizing ultra precision
micro-grinding method coupled with “ELectrolytic In-process Dressing” (ELID) technique[2].
The immersion grating has 600 μm groove spacing with a 68.75° blaze angle. It is used invery high order, ranging from 332 at 13.5μm to 597 at 7.5 μm. In order to separate theéchelle orders by ~10 pixels on the Si:As array detector, the cross-disperser wheel employs
two first-order echelette gratings: a 100 grooves/mm with a 26.7° blaze angle for shortwavelength (7.5–10 μm) and a 61.97 grooves/mm with a 18.1° blaze angle for long
(10–13.5 μm). The spectral coverage is typically λ/15, which includes 32–56 échelleorders, depending on wavelength. Eight cross-disperser position angles give full continuous
coverage throughout 7.5–13.5 μm.
The optics on the spectrometer was aligned by using an attenuated CO2 laser as a light source.
In the alignment procedures at room temperature condition, an infrared bolometer camera was
replaced with the Si:As IBC FPA detector. Since the CO2 laser was operated in multi-mode
oscillation, simultaneous observation by using the FT-IR spectrometer (BioRad FTS-6000)
was necessary to assign the laser transitions. After the alignment, placing Si:As IBC arrayback to the original position, we examined the sensitivity tests of IRHS by recording theblackbody radiation around the 10.6 μm wavelength region at the room temperature (~300
K). It took approximately 3 seconds to saturate the Si:As IBC detector, which is wellcompared with our design specification and the full-well capacity of the detector. For the
check of the wavelength resolution, we observed the spacially diffracted light from the CO2
laser source by the #3000 sandpaper. Figure 1 shows the échelle image thus obtained of
IRHS in the region of 904 – 967 cm-1 (10.3-11.1μm in wavelength). The HWHM linewidth
for the most faintly observed P(20) laser transition to 0.018 cm-1, assuming that one pixel

corresponds to 0.0052 cm-1. The currently derived resolving power, ~50,000, is in an
excellent agreement with a design specification of our spectrograph.

411st
412nd
413rd

422nd
423rd

431st

Slow scanner readout direction

421st

432nd

Figure 1: The first échelle image of IRHS for the the CO2 laser, taken with Si:As IBC 512 x 412 FPA
detector cooled to 5.7K. The exposure time for each pixel is uniformly 0.17 second. The abscissa for
the image (412 pixels) represents direction for the fast scanner readout of the detector. The ordinate for theimage (512 pixels) represents the direction for slow scanner readout, and that for dispersion for the
cross-disperser. Diffraction orders for the Ge immersion grating separated by the cross-disperser are also
shown. The assignments for the dark spots for the CO2 laser are shown on the image. The backgroundstripes are due to the thermal emission on the room temperature. Note that the laser spots except for P(20)and probably P(26) are heavily saturated and the spot sizes for the laser lines are significantly larger than
the intrinsic resolution of the spectrograph, since the laser power during the measurement is stiil very high.

References[1]
H. Tokoro, M. Atarashi, M. Omori, T. Machida, S. Hirabayashi, H. Kobayashi, Y. Hirahara, T. Masuda,
N. Ebizuka, K. Kawaguchi, “Development of Mid-Infrared High Dispersion Spectrograph (IRHS) for the Subaru
Telescope", Proc. SPIE, 4841, 1016 (2003).
[2]
N. Ebizuka, S. Morita, Y. Yamagata, H. Omori, M. Wakaki, K. Kawaguchi, H. Kobayashi and Y.
Hirahara, “Development of Immersion Gratings for Near and Middle Infrared High Dispersion Spectrograph of
8.2 m Subaru Telescope”, Proc. SPIE 4837, 293 (2003).

Laboratory measurement of methyl formate (HCOO13CH3)
H. Tachi,1 and K. Kobayashi 1
1

Department of Physics, University of Toyama, JapanThe methyl formate molecule is one of the most known interstellar weeds. The figure 1
shows the structure of methyl foamte. In most cases, saturated organic molecules like methyl
formate have methyl group internal rotation which is equivalent to the vibrational mode of
torsion. The interaction between the rotation and the internal rotations causes the splitting of
the spectra. In addition, since the vibrational frequency of the torsion is usually low andvibrationally excited states are populated even at the room temperature, a great number oflines are observed but many lines remain unassigned. The progress of the laboratory
measurement could help assignment of the astronomical detection. Recently unidentifiedlines from Orion KL were assigned to this molecule in its torsionally excited state [1] basedon the previous microwave study.[2]

O
C

C
O

Fig. 1 The structure of methyl formate
Recently the production scheme of CCS was clarified using the observed abundance ratio of
isotopomers. It is quite indispensible to have rest frequencies of the isotopomers. Therefore
we report the current status of the microwave study on the isotopomer HCOO13CH3
anticipating for future detection. The first microwave study on this isotopomer was carriedout by Curl.[3]The experiment was carried out with our conventional source modulation microwave
spectrometer. The microwave radiation from the synthesizer is multiplied and detected with
the InSb bolometer. The 13C isotopomer was synthesized by the reaction of HCOOH and
13
CH3OH. The observation of spectra from 75 GHz without gap is under way. The
preliminary analysis will be given

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

K. Kobayashi, K. Ogata, S. Tsunekawa, & S. Takano, 2007, ApJ, L17
K. Ogata, H. Odashima, K. Takagi, & S. Tsunekawa,2004, J. Mol. Spectroscop., 225, 14
N. Sakai, M. Ikeda M. Morita, T. Sakai, S. Takano, Y. Osamura, & S. Yamamoto, 2007, ApJ 663, 1174.
R. F. Curl, 1959, J. Chem. Phys. 30, 1529 .

Laboratory FIR Spectroscopy of OD-, N2H+, H2D+
T. Yonezu,1 F. Matsushima, 1 T.Amano, 2 and Y. Moriwaki 1
1

2

Department of Physics/University of Toyama, Japan
Department of Chemistry/University of Waterloo, Canada

Rotational spectra of molecular ions which are important in interstellar chemistry are studied
with tunable far-infrared spectrometer. Frequency measurements of the rotational lines of OD-,
N2H+, and H2D+ in 1-5 THz region are reported.
As for OD-, the fundamental band transitions were studied by Rehfuss et. al. in 1986 [1], andlow-J rotational lines R(J) (J=1,2) were reported by Cazzoli et.al. [2,3]. We observed the lines
R(J) (J=1-2,4,5,7) (Fig.1). This work is an extension of our previous work of OH- [4]. The
molecular constants and the istope-independent Dunham parameters were obtained.

Figure 1: Tipical trace of J = 5←4 transition of 16OD- .

The molecular cation H2D+ and D2H+ are the isotopomers of H3+. Submillimeter-wave spectraof H2D+ and D2H+ were studied by Amano and Hirao in 2005 [5]. We have observed several
lines of H2D+ such as 211-110, 313-212, 202-101, and 212-111 (Fig.2). Among them, the detectionof 212-111 line in space has recently been reported. Our measured frequency will be useful toanalyze this observation.

Figure 2: J = 212←111 transition of H2D+.

Figure 3: J = 14←13 transition of N2H+.

An extended-negative discharge glow discharge cell was applied to observe some of themolecular cations. Rotational lines of N2H+, R(J) (J=13,15,20) were measured to confirm theability of this type of discharge cell (Fig.3).

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

B. D. Rehfuss, M. W. Crofton, T.Oka, 1986, J. Chem. Phys. 85, 1785.
G. Cazzoli, C. Puzzarini, 2005, J. Chem. Phys. 123, 041101-1-4.
G. Cazzoli, C. Puzzarini, 2006, Astrophys. J. 648, L79.
F. Matsushima, T. Yonezu, T. Okabe, K. Tomaru, & Y. Moriwaki, 2006, J. Mol. Spectrosc. 235, 261.
T. Amano, T.Hirao, 2005, J. Mol. Spectrosc. 233, 7.

Comparing Cloud Properties from Chemical Compositions of Cores
K. Hosaka 1, K. Sorai 1, and A. Habe 1
1

Department of Cosmoscinences, Hokkaido University, JapanThe chemical characteristics within dense cloud cores can reveal their evolution stage.
Because they have different production chemistries, the column densities of NH3, CCS canreveal the chemical characteristics in dense cores. So, N(CCS)/N(NH3) is a good indicator ofchemical evolution [1].
We observed CCS JN=21-10, NH3 (J, K) = (1, 1), (2, 2) lines toward molecular cores in the
Taurus Cloud Complex with the Hokkaido University Tomakomai 11 m Telescope.
Assuming LTE and Tk=10 K, we estimated column densities from our results. Figure 1 is a
distribution of column densities of CCS and NH3. Comparing this result with results of otherclouds (e.g. the Perseus Cloud Complex [2], the Pipe Nebula [3]), we can compare propertiesof these clouds from chemical compositions of cores. For example, from low column densityof NH3 in cores, the Pipe Nebula seems to be younger than the Taurus Cloud Complex.
Additionally, we found that N(CCS)/N(NH3(1, 1)) of our samples are lower in higher n(H2)from H13CO+ J=1-0 line observation [4]. So, we can say chemical evolution of cores is
consistent with physical evolution of cores.

Figure 1: N(CCS) and N(NH3(1, 1)) of Cores. Blue symbols show starless cores, orange and red symbols
show cores with stars, a green symbol shows an accreting core. Open triangles show upper limit of N(CCS).

References[1]
H. Suzuki, S. Yamamoto, M. Ohishi, N. Kaifu, S. Ishikawa, Y. Hirahara & S. Takano, 1992, ApJ, 392,
551.
[2] E. W. Rosolowsky, J. E. Pineda, J. B. Foster, M. A. Borkin, J. Kauffmann, P. Caselli, P. C. Myers & A. A.
Goodman, 2008, ApJS, 175, 509[3]J. M. Rathborne, C. J. Lada, A. A. Muench, J. F. Alves & M. Lombardi, 2008, ApJS, 174, 396.
[4]
T. Ohnishi, A. Mizuno, A. Kawamura, K. Tachihara & Y. Fukui, 2002, ApJ, 575, 950.

Water ice absorption map of Pipe Nebura
M.Tanaka1
1

National Astronomical Observatory of Japan

Interstellar water ice is one of important materials for interstellar chemistry. Water ice has
been observationally detected as an infrared absorption band at 3.07 μm in dark clouds. The
results of past observations show that the optical depth of water ice absorption (τice) is
quantitatively related to visual extinction (AV) as τice ~ 0 for AV < Ath and τice = q (AV - Ath) for
AV > Ath, where q is a constant and Ath is the threshold extinction which depends on the cloud([1],[2],[3],[4],[5]).
The observations of water ice absorption require background stars at the opposite side of darkclouds. This fact makes it difficult to obtain the continuous spatial distribution of water ice.
We employ an unprecedented method to obtain a water ice absorption map by utilizing
Galactic bulge stars as diffuse background light. The target dark cloud is Pipe Nebula whichis in the direction toward the bulge and at the distance of 130-160 pc from the earth ([6]).
Analyzed data were obtained with the Near-Infrared Spectrometer (NIRS) in the Infrared
Telescope in Space (IRTS) ([7]), which was optimized for observations of diffuse light. The
IRTS observation covered about half area of Pipe nebula.
The result of the detailed analysis shows that water ice absorption at Pipe nebula follows theAV-τice relation which mentioned above, i.e., τice is under detection at AV < Ath and τice islinearly correlated with the extinction at AV > Ath. The water ice map is compared with COemission maps obtained with NANTEN telescope ([8]). The result shows that the spatial
distribution of water ice is correlated with the dense part of molecular cloud. The relation of
τice with the strength of 12CO and 13CO emission shows the “threshold” effect similar to theAV-τice relation. We discuss quantitative relations and properties of water ice in Pipe nebula.

References[1] Whittet, D. C. B. et al., 1983, Nature, 303, 218[2] Whittet, D. C. B. et al., 1988, MNRAS, 233, 321[3] Whittet, D. C. B., Gerakines, P. A., Hough, J. H., & Shenoy, S. S., 2001, ApJ, 547, 872[4] Smith, R. G., Sellgren, K., & Brooke, T. Y., 1993, MNRAS, 263, 749[5] Murakawa, K., Tamura, M., & Nagata, T., 2000, ApJS, 128, 603[6] Alves, F. O. & Franco, G. A. P., 2007, A&A, 470, 597[7] Noda, M. et al., 1994, ApJ, 428, 363[8] Onishi, T. et al., 1999, PASJ, 51, 871

AKARI Observation of Interstellar Ice
Y. Aikawa1, AFSAS team1

Department of Earth and Planetary Sciences, Kobe University, Japan

In molecular clouds, a significant amount of Oxygen, Carbon and Nitrogen is in the form ofmolecule in ice mantle, such as H2O, CO, CO2, NH3 and CH3OH. These icy materials areformed by adsorption of gas-phase molecules onto grain surfaces and/or grain-surface
reactions of the adsorbed species (e.g. [1]). Molecular evolution in the gas phase and ice
mantle depends on the physical conditions such as temperature, density, and UV intensity. In
order to understand the chemical processes of interstellar matter, it is important to observe thecomposition of gas and ice in various conditions. Composition of ice has been investigated by
the absorption feature in the infrared. Spatial distribution of ice composition and its
dependence on physical conditions are less constrained than the gas-phase molecules, because
there are only a limited number of bright light sources behind or within the molecular clouds.
In addition, some important bands cannot be observed from the ground.
We are observing near-infrared (2.5-5micron) spectrum of background stars using AKARI
satellite. Compared with the ground-based telescopes and Spitzer Space Telescope, AKARI is
unique in enabling us to observe the full NIR wavelength region towards faint backgroundstars with < 14 mag at K band.
We will present preliminary results of our data analysis: spectrum of several backgroundstars behind Taurus molecular clouds and determination of spectrum type and visualextinction (i.e. the continuum spectrum) of each star.

References[1]

Y. Aikawa, V. Wakelam, E. Herbst & R.T. Garrod 2008, ApJ, 674, 984

AKARI observation of ice in protoplanetary disks
D. Kamuro 1, Y.Aikawa1 , Y.Itoh 1, H.Terada 2, AFSAS TEAM
1

2

Department of Earth and Planetary Science Kobe university , Japan
National Astronomical Observatory , Japan

In outer region (r > several AU) of protoplanetary disks, a significant amount of Carbon,
Nitrogen and Oxygen exists in the form of molecular ice such as H2O, CO, CO2, and NH3 on
the grain surface. These ices are raw material of comets, and would provide volatiles to form
the atmosphere of terrestrial planets. Observing the ice in protoplanetary disks alongevolutionary sequence (i.e. from Class 0 to Class II), we can investigate the composition andabundance of ice, and reveal chemical processes in planetary system formation.
We have carried out near-infrared (NIR) spectroscopic observation of protoplanetary disks
using AKARI satellite. The NIR wavelength region (2.5-5 micron) contains absorption
features of ices such as H2O, CO, CO2 and CH3OH. While ground-based telescopes andSpitzer Space Telescope have already detected ices in disks [1][2][3], AKARI is an uniquetelescope which enables us to observe the full NIR wavelength region towards low-mass
YSOs. We selected several edge-on disks around Class I-Class II YSOs, and detected several
ice absorption bands towards Class1 source IRAS04302+2247 and IRAS04368+2557(L1527)
in Taurus star forming region (Fig1). We derive the ice composition in these objects bycomparing the absorption feature with laboratory data (e.g. [4])Fig 1 : Our sample of AKARI spectra.This plot is Flux[mJy] vs wavelength [μm].
Left is IRAS04302+2247,right is IRAS04368+2557 (L1527).Especially,a deep H2O and CO2 iceabsorption seen these spectra.

References[1] H.Terada, 2007, ApJ 667:303-307[2] E.Furlun, 2008, ApJS 176:184-215[3] Thi, 2002, A&A 394, L27-L30[4] Oberg, 2007, A&A, 462, 1187-1198

Molecular Evolution in Star-Forming Cores:
From Prestellar Cores to Protostellar Cores
Y. Aikawa,1 V. Wakelam,2 R.T. Garrod3, E. Herbst4, N. Sakai5, S. Yamamoto5
1

Department of Earth and Planetary Sciences, Kobe University, Japan
2
Universite Bordeaux, France
3
Max-Planck-Institute fur Radioastronomie, Germany
4
Departments of Physics, Chemistry, and Astronomy,
The Ohio State University, USA
5
Department of Physics, University of Tokyo, Japan

We investigate the molecular abundances in protostellar cores by solving the gas-grainchemical reaction network[1]. As a physical model of the core, we adopt a result of onedimensional radiation-hydrodynamics calculation, which follows the contraction of an
initially hydrostatic prestellar core to form a protostellar core. Temporal variation ofmolecular abundances is solved in multiple infalling shells, which enable us to investigate thespatial distribution of molecules in the evolving core. The shells pass through the warm
region of T=10-100 K in several 104 yr and falls onto the central star in ~ 100 yr after they
enter the region of T > 100 K. We found that the complex organic species such as HCOOCH3
are formed mainly via grain-surface reactions at T ~ 20-40 K, and then sublimated to the gas
phase when the shell temperature reaches their sublimation temperatures (T>= 100 K).
Carbon-chain species are re-generated from sublimated CH4 via gas-phase and grain-surface
reactions [1][2]. HCO2+, which is recently detected towards L1527[3], are abundant at r=1002000 AU, and its column density reaches 1011 cm-2 in our model[1]. If a core is isolated andirradiated by interstellar UV radiation, photo-dissociation of water ice could produce higher
abundance of CO2, while complex species become less abundant, compared with the case ofembedded core in ambient clouds.
We are now extending the above model to multiply-deuterated species. Preliminary results
would be reported on the deuterated species.

References
[1]
[2]
[3]

Y. Aikawa, V. Wakelam, E. Herbst & R.T. Garrod 2008, ApJ, 674, 984
N. Sakai, T. Sakai, T. Hirota & S. Yamamoto 2008, ApJ, 672, 371
N. Sakai, T. Sakai, Y. Aikawa & S. Yamamoto 2008, ApJ, 675, L89

Structural effects of icy grain surfaces in CO hydrogenation at a low temperature
H. Hidaka, N. Miyauchi, A. Kouchi, and N. Watanabe
Institute of Low Temperature Science, Hokkaido University, JapanThe successive hydrogenation of CO (CO → H2CO → CH3OH) on the icy grain surface has
been perceived as an effective process for the formation of H2CO and CH3OH in molecular
clouds [1]. That process on amorphous sold water (ASW) has been investigated extensively
from several points of view (the dependences of temperature [1,2], ice compositions [3,4]). In
the present study, we focus on the structural effects of the ice surface on the hydrogenation of
CO at a low temperature, while the reactivity was compared between ASW and crystalline ice(CI) surface.
The top and bottom panels in Figure1 shows the IR absorption spectra of the initial samples
with the same amounts of CO deposited at 15 K and the variation in the absorption spectra ofthese samples during exposure to hydrogen atoms, respectively. The formation of H2CO andCH3OH with decreasing of CO was observed in both samples. The hydrogenation reaction on
ASW was found to be much faster than that on CI. The higher reactivity on ASW is attributed
to the enhancement of the number density of adsorbed hydrogen atoms due to larger surface
area of ASW compared to CI.

Figure 1: Initial IR adsorption spectra (top) and variations in the absorption spectra (bottom) with H atom
exposure for (a) CO on ASW and (b) CO on CI at 15 K, respectively. Peaks below and above the base line
represent a decrease and increase in the absorbance, respectively.

References[1] N. Watanabe and A. Kouchi, 2002, ApJ 571, L173.
[2] N. Watanabe, T. Shiraki, & A. Kouchi, 2003, ApJ 588, L121.
[3] N. Watanabe, A. Nagaoka, T. Shiraki, & A. Kouchi, 2004, ApJ 616, 638.
[4] N. Watanabe, A. Nagaoka, H. Hidaka, T. Shiraki, T. Chigai, & A. Kouchi, 2006, Planet. Space Sci. 54, 1107.

H-D substitution reactions of formaldehyde on icy grain surfaces at low temperatures
H. Hidaka, M. Watanabe, A. Kouchi, and N. Watanabe
Institute of Low Temperature Science, Hokkaido University, JapanThe high gas-phase abundance of deuterated molecules, H2CO-d1,2 and CH3OH-d1-3, havebeen observed in molecular clouds [1-3] and comet [4]. This deuterium fractionation ininterstellar molecules has been an interesting topic in interstellar chemistry. Although several
studies on the fractionation mechanism have been carried out by using pure gas phase models,
it is difficult to explain the deuterium fractionations of formaldehyde and methanol especiallyin multiply deuterated molecules. Recently, our group revealed the validity of surface
reactions in the formation of multiply deuterated methanol [5]. We believe that the surface
reaction on interstellar ice is a key process not only for the production of H2CO and CH3OH
but also for that of H2CO-d1,2 and CH3OH-d1-3. In this study, the formation of deuterated
formaldehyde on amorphous solid water (ASW) surface was investigated experimentally.
Experiments were performed by the exposure of H2CO and D2CO on ASW to D and H atoms
at low temperatures, respectively. Figure 1 shows the infrared (IR) absorption spectra ofinitial samples (top) and variations in IR absorption spectra (bottom) for (a) D atom exposureof H2CO on ASW and (b) H atom exposure of D2CO at 15 K, respectively. For D + H2CO,
H2CO was converted to HDCO and D2CO by the H-D substitution reactions. The addition
reactions (formation of deuterated methanol) were minor routes. On the other hand, for H +D2CO, the substitution reactions to produce HDCO and H2CO as well as the addition
reactions proceeded. We discuss formation processes for the deuterated formaldehyde on
ASW surface in the environment of molecular clouds.

Figure 1: Initial IR spectra (top) and variations in the IR spectra (bottom) for (a) D atom exposure of H2CO
on ASW and (b) H atom exposure of D2CO at 15 K, respectively.

References[1] L. Loinard et al., 2000, A&A 359, 1169.
[2] B. Parise et al., 2002, A&A 393, L49.
[3] B. Parise, et al., 2004, A&A 416, 159.
[4] J. Crovisier, et al., 2004, A&A 418, 1141.
[5] A. Nagaoka, N. Watanabe, & A. Kouchi, 2005, A&A 624, L29.

Effective rate constants for H-D substitution reactions in methanol on the surface at
10 K
A. Nagaoka1, N. Watanabe1, and A. Kouchi1
1

Institute of Low Temperature Science, Hokkaido University, JAPAN

Recent astronomical observations have discovered extreme deuterium enrichment ininterstellar formaldehyde and methanol [1-3]. The abundances of these deuterated
molecules are up to 4 orders of magnitude higher than the cosmic D/H ratio of 1.5×10-5. For
methanol molecules, even doubly and triply deuterated isotopologues have been detected in
the vicinity of low-mass protostars [2,3]. Deuterium fractionation in interstellar molecules
has long been a topic of interest in interstellar chemistry, and the fractionation processes inmolecular clouds have attracted attention from both astronomers and earth and planetaryscientists as a potential explanation for the high D fractionations observed in our solar
system. Since pure gas phase chemistry hardly reproduces the deuteration level offormaldehyde and methanol observed, the evaluation of the role of grain surface chemistry
in the deuterium fractionation was desirable. For methanol, we recently demonstrated thatthe H-D substitution reactions in methanol proceed efficiently on the ice surface at 10 K,
and that the surface substitution reaction is a key for the deuterium enrichment in molecular
clouds [4, 5]. However, the reaction rates of the surface substitution remained to be
determined.
To obtained the reaction rates of H-D substitution in (deuterated) methanol on the
cryogenic surfaces, solid CH3OH, CH2DOH, and CHD2OH were exposed to D atoms at 10
K. Deuteration levels increased in methyl group in all cases. The pseudo-first-order rates
for the reactions CH3OH + D → CH2OH + HD, CH2DOH + D → CHDOH + HD, and
CHD2OH + D →CD2OH + HD were estimated. The ratios of the reaction rates of thesecond and third reactions to the first reaction were 0.69 ± 0.11 and 0.52 ± 0.14,
respectively [6]. The difference in reaction rates is thought to be due to a secondary kinetic
isotope effect on the H-abstraction reaction from the methyl side by D atoms.

References[1] L. Loinard, A. Castets, C. Ceccarelli, A. G. G. M. Tielens, A. Faure, E. Caux, & G. Duvert, 2000, A&A,
359, 1169.
[2] B. Parise, A. Castets, E. Herbst, E. Caux, C. Ceccarelli, I. Mukhopadhyay, & A. G. G. M. Tielens, 2004,
A&A, 416, 159.
[3] B. Parise et al. 2002, A&A, 393, L49; B. Parise, C. Ceccarelli, A. G. G. M. Tielens, A. Castets, E. Caux, B.
Lefloch, & S. Maret, A&A, 2006, 453, 949.
W. A. Schutte, P. A. Gerakines, T. R. Geballe, E. F. van Dishoeck, & J. M. Greenberg, 1996, A&A, 309, 633[4] A. Nagaoka, N. Watanabe, & A. Kouchi, 2005, ApJ, 629, L24.
[5] N. Watanabe, 2006, in Astrochemistry, ed. D. C. Lis, G. A. Blake, & E. Herbst (Cambridge: Cambridge
Univ. Press), 415.
[6] A. Nagaoka, N. Watanabe, & A. Kouchi, 2007, J. Phys. Chem. A, 111, 3016.

Laboratory simulation of competition between hydrogenation and photolysis in thechemical evolution of H2O-CO ice mixtures
N. Watanabe1, O. Mouri1, A. Nagaoka1, T. Chigai1, A. Kouchi1, and V. Pirronello2
1

Institute of Low Temperature Science, Hokkaido University, JAPAN2
D.M.F.C.I., Universita` di Catania, Italy

Photolysis and hydrogenation of ice dust are important processes of chemical evolution inmolecular clouds. Phyotolysis has been studies experimentally by many researchers using
astrophysically-relevant ice-mixture and found to yield various molecules [e.g. 1,2].
Hydrogenation has been first proposed theoretically since 1980s [3] as a main formation routeof formaldehyde and methanol from a primordial CO molecule on ice dust. Recently, theseries of our experiments [4] have confirmed that this process efficiently proceeds due totunneling effect under the condition of quiescent molecular cloud where the temperature is as
low as 10 K. Experiments of photolysis and hydrogenation were performed separately bydifferent groups with their own experimental conditions. In addition, kinetic data such as rate
constants obtained are still not enough. It is very difficult not only to measure those data forsurface reactions but also to construct the models because reactions strongly depend on thesurface composition and morphology. Therefore, the relative importance of photolysis andhydrogenation in molecular clouds was not examined. To do so, the simulation experiments
for those processes under well controlled conditions were very desirable.
In the present study, photolysis and hydrogenation of H2O-CO binary ice mixtures (as theanalogues of the most primordial ice composition) at 10–50 K are investigated in order toquantitatively evaluate their relative importance in the chemical evolution of interstellar dust
icy mantles [5]. The dominant product of photolysis was CO2, with lower yields offormaldehyde, methanol, and formic acid, while only formaldehyde and methanol wereobtained by hydrogenation reactions. Hydrogenation has higher formation efficiencies andyields of formaldehyde and methanol than photolysis. However, the contribution of photolysis
should not be negligible for the formation of these molecules in molecular clouds, in contrast
to the previously reported results [2]. The simultaneous irradiation of binary ice mixtures withhydrogen atoms and UV photons resulted in relative abundances of CO2, formaldehyde,
methanol, and formic acid that are consistent with the observed abundances. Our results showthat the composition and structure of ice are crucial in the chemical evolution of ice mantles,
as much as the temperature and the type of irradiation.

References[1] L. J. Allamandola, S. A. Sandford, & G. J. Valero, 1988, Icarus, 76, 225.
[2] W. A. Schutte, P. A. Gerakines, T. R. Geballe, E. F. van Dishoeck, & J. M. Greenberg, 1996, A&A, 309,
633.
[3] e.g. S. B. Charnley, A. G. G. M. Tielens, & S. D. Rodgers, 1997, ApJ, 482, L203; A. G. G. M. Tielens, & D.
C. B. Whittet, 1997, in IAU Symp. 178, Molecules in Astrophysics, ed. E. F. van Dishoeck ( Dordrecht: Kluwer),45.
[4] e. g. N. Watanabe & A. Kouchi, 2002, ApJ, 571, L173.; N. Watanabe, A. Nagaoka, T. Shiraki, & A. Kouchi,
2004, ApJ, 616, 638.; N. Watanabe, 2006, in Astrochemistry, ed. D. C. Lis, G. A. Blake, & E. Herbst(Cambridge: Cambridge Univ. Press), 415.
[5] N. Watanabe, O. Mouri, A. Nagaoka, T. Chigai, A. Kouchi, and V. Pirronello, 2007, ApJ, 668, 1001.

Catalytic effect of amorphous solid water on surface reactions of hydrogen atoms atvery low temperatures
N. Watanabe1, H. Hidaka1, A. Nagaoka1, and A. Kouchi1
1

Institute of Low Temperature Science, Hokkaido University, JAPANThe role of amorphous solid water (ASW) in surface reactions of hydrogen atoms withmolecules was investigated. In the series of our experiments on hydrogenation (deuteration)of CO and O2 molecules [1-3], and H-D substitution in methanol [4], the comparison ofreactivities was made between on the surfaces of pure solid reactant molecules (i.e., puresolid CO, O2, and methanol) and ASW. It was found that the effective reaction rates areenhanced on the surface of ASW at relatively higher temperatures. This catalytic effect of
ASW would be due to the higher adsorption energy of hydrogen atom for ASW than thesurface of pure reactant solids and/or the modification of potential energy surfaces by watermolecules.
References[1] N. Watanabe, A. Nagaoka, T. Shiraki, & A. Kouchi, 2004, ApJ, 616, 638.
[2] N. Watanabe, A. Nagaoka, H. Hidaka, T. Shiraki, T. Chigai, & A. Kouchi, Planet. Space Sci. 2006, 54,
1107.
[3] Y. Oba et al. 2008, in preparation[4] N. Watanabe & A. Kouchi, 2008, submitted to Prog. Surf. Sci.

Formation of H2O by the H-addition to solid O2 on amorphous D2O ice
Y. Oba, N. Miyauchi, T. Chigai, H. Hidaka, N. Watanabe, and A. Kouchi
Institute of Low Temperature Science, Hokkaido University, JAPANINTRODUCTION
Water is the most abundant solid material in space, and has been observed in various
astrophysical environments, e.g., interstellar clouds. Nevertheless, the formation
mechanism(s) of water in interstellar clouds still remains understood. Since the formation ofwater molecules in the gas phase is revealed to be difficult to explain the observed abundance
in molecular clouds, it has been suggested that they could be synthesized by atomic reactionsof H and O on inorganic grains [1]. Recent studies have demonstrated that water (H2O) and its
oxygenated molecule, hydrogen peroxide (H2O2), were formed after hydrogen atom (H)exposure to pure solid oxygen molecules (O2) on a metal substrate at 10-28K [2,3].
It has been reported that the presence of an amorphous water ice enhances the reaction
rate and raises the reactive temperature for H-addition reaction to CO [4]. So in this study, we
conducted H-addition reactions to O2 on amorphous D2O ice, and compare the results withthose using pure solid O2.
EXPERIMENTAL
D2O with an ~30 monolayer (ML) was deposited onto an aluminum substrate at 10K
under ultra high vacuum conditions (~10-10 Torr), followed by a deposition of ~3 ML O2 onto
the D2O ice. After the deposition, the aluminum substrate was heated to up to 40K and
exposed to H atoms (100K) produced by a microwave-induced plasma. Products (H2O andH2O2) were monitored in situ by FTIR. As a counterpart experiment, pure ~10 ML O2 was
exposed to H atoms at 10-23K.
9column density (1014 molecules/cm2)

RESULTS AND DISCUSSIONAs the time of H-exposure to solid
O2 increases, H2O2 and H2O were formed(e.g. at 20K, Figure 1), being consistent
with previous studies using pure O2 [2,3].
However, it should be noted that thehydrogenation occurs even at 40K,
unlike pure O2 experiments [3]. This isprobably due to the higher sticking
coefficients of O2 molecules to an
amorphous D2O ice compared to those toaluminum substrate. Both temperaturedependence and effect of amorphous ice
for the reaction rate will also be
discussed in this presentation.

6

3
H2O
H2O2
0
1

10

Figure 1 Variations in column density of H2O
and H2O2 at 20K on amorphous D2O ice.

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

100

Exposure time (min)L.B. d’Hendecourt, L.J. Allamandola, & J.M. Greenberg, 1985, A&A 152, 130.
N. Miyauchi, H. Hidaka, T. Chigai, A. Nagaoka, N. Watanabe, & A. Kouchi, 2008, Chem. Phys. Lett.
456, 27.
S. Ioppolo, H.M. Cuppen, C. Romanzin, E.F. van Dishoeck, & H. Linnartz. 2008, ApJ, in press.
H. Hidaka, A. Kouchi, & N. Watanabe, 2007, J. Chem. Phys. 126, 204707.

Energy partitioning in H2 formation by photolysis of amorphous water ice
A. Yabushita, T. Hama, M. Yokoyama, and M. Kawasaki
Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan
In molecular clouds at temperatures below approximately 130 K, dust grains are covered withamorphous water ice mantles and thus photolysis of water ice plays an important role in grainchemistry. The formation of H2 from water ice is a process of fundamental importance inmolecular clouds and the outer solar system. H2 formation from hot H atoms produced byphotolysis of water ice involves two distinct mechanisms: endothermic hydrogen abstraction(HAB) and highly exothermic hydrogen recombination (HR).
HAB:
HR:

H + HOH → H2 + OH
H + H → H2

∆H = 0.6 eV∆H = −4.5 eV

(1)
(2)

Since these routes result in very different rovibrational distributions of the H2 product,
measurements of the H2 state distributions point directly to the respective formation
mechanism.
Formation of H2 molecules from amorphous solid water has been investigated at 100 K using
pulsed 157 nm laser radiation. We report the simultaneous measurement of kinetic androvibrational energy distributions of the H2 photoproduct. Two distinct mechanisms can be
identified as shown in reaction (1) and (2): Endothermic abstraction of a hydrogen atom from
H2O by a photolytically produced H-atom yields vibrationally cold H2 products, whereas
exothermic recombination of two H-atom photoproducts yields H2 molecules with a highly
excited vibrational distribution, non-Boltzmann rotational population distributions, andkinetic energies that decrease according to their depth of formation beneath the ice-vacuum
interface.
Table 1: Energy partitioning and relative population distribution in H2 from the photolysis ofamorphous water ice at 100 K. The tabulated data show the relative populations of products with v =2, 3 and 4, and their variation with J. HAB and HR denote endothermic hydrogen abstraction andhighly exothermic hydrogen recombination, respectively.

H2(v)
0
2
3
4

Relativevibrational
population
0.58
1
1.34

Vibrationalenergy (eV)Translationalenergy (eV)Rotationalenergy (eV)01.00 (22%)
1.48(33%)
1.88(42%)0.028
0.032(0.7%)
0.028(0.6%)
0.044(0.1%)

0.013
0.65(14%)0.54(12%)0.33(7%)

Energyabsorbed byice (eV)2.82(63%)
2.45(54%)2.25(50%)

Dominant
Mechanism
HAB
HR
HR
HR

References[1][2]

Yabushita, A.; Hama, T.; Iida, D.; Kawanaka, N.; Kawasaki, M.; Watanabe, N.; Ashfold, M. N. R.;
Loock, H.-P. Astrophys. J. 682, L69 (2008)
Yabushita, A.; Hama, T.; Iida, D.; Kawanaka, N.; Kawasaki, M.; Watanabe, N.; Ashfold, M. N. R.;
Loock, H.-P. J. Chem. Phys. 129, 044501 (2008)

Direct observation of OH formation in the photolysis of amorphous water
M. Kawasaki, T. Hama, M. Yokoyama, and A. Yabushita
Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan

Many interstellar dust grains are coated with an ice mantle, a major component of which isamorphous solid water (ASW) that is constantly exposed to photon, magnetospheric ions, thesolar wind and cosmic rays. When water ice is exposed to vacuum-ultraviolet radiation, thehydrogen-oxygen bond breaks followed by formation of OH, HO2, H2O2 and so on.
H2O(ice) + hν Æ H + OH

(1)

Tappe et al. [1] have reported the detection of rotationally excited OH by analyzing a 5-7 µm
infrared spectrum obtained with Spitzer Space Telescope toward the southeastern lobe of theyoung protostellar out flow HH 211. The origin of the highly excited emission is most likely
the photodissociation of H2O by the UV radiation generated in the terminal outflow shock of
HH 211.
Previous experiments on the photolysis of an amorphous ice focused on species formed on/in
ice, and did not investigate atoms and molecules released into the vacuum. Here we haveinvestigated OH radical desorption following 157 nm photodissociation of amorphous solid
water at 90 K. Ro-vibrational excited OH(v=0 and 1) radicals are directly detected with theresonance-enhanced multiphoton ionization technique. In addition, we discussed OH radical
desorption from photodissociation of H2O2 formed with 157 nm irradiation on ice as thesecondary process.

OH signal intensity / arb. unit

OH + OH Æ H2O2

P2

(2)

1

2
P14
O13

4
O21
S21

R1 3

2

1

1

P12

R124

237.55237.60237.65

Wavelength / nm
Figure 1: (upper) REMPI spectrum of OH(D2 Σ -- X2Π) and OH(32Σ- - X2Π), and (lower) Calculated
spectra of OH(D2 Σ -, v’=1 - X2Π, v”=0) (pale gray line) and OH(32Σ-, v’=0 - X2Π, v”=1) (dark grey line).

Reference[1]

Tappe, A.; Lada, C. J.; Black, J. H.; and Muench, A. A., Astrophys. J. 680, L117 (2008)

Translational and internal states of hydrogen molecules produced fromthe vacuum ultraviolet photodissociation of amorphous solid methanol
T. Hama, M. Yokoyama, A. Yabushita, and M. Kawasaki
Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan
Within water rich interstellar ices, methanol is typically observed and is often the mostabundant molecule after water. Because its abundance in some grain mantles varies between
0.05 and 0.50 relative to water, photolysis of methanol could be an appreciable source of theinterstellar H2 molecules.
CH3OH + hν

→ CH3O·+ H→ CH2(·)OH + H→ CH(‫)׃‬OH + H2
→ CH2(·)O·+ H2
H + H → H2
H + CH3OH →CH2(·)OH + H2
H + CH3OH →CH3O· + H2

∆H (kcal/mol)
104
92
71
19
-104
-8
1

Ea (kcal/mol)
0
9
14

(1)
(2)
(3)
(4)
(5)
(6)
(7)

We have investigated the mechanisms and dynamics of H2(v=0-5) production from the 157
nm (181 kcal/mol) photodissociation of amorphous solid methanol at 90 K with theresonance-enhanced multiphoton ionization technique. The hydrogen abstraction mechanism
from methanol parent molecule by the photolytically produced hydrogen atom, reactions (6)and (7), yields translatioanlly and internally cold H2(v=0 and 1) products. The molecularelimination processes, reactions (3) and (4), are the major sources of H2(v=2-5) products
while the contribution of the hydrogen recombination mechanism, reaction (5), is minor.

H2 signal intensity / arb. units

1.0(v = 3, J = 3)

(3, 13)(5, 3)(5, 13)

0.5

0.0
1.0

0.5

0.0
0

5

10

15

0

5

10

15

Time of flight / µs

Figure 1: Time-of-flight spectra of H2(v=3, J=3, 13) and H2(v=5, J=3, 13). These spectra are composedof four Maxwell-Boltzmann distributions with Ttrans = 5000, 1800, 700 and 100 K.