• Bulletin of the Korean Chemical Society
• /
• 제23권11호
• /
• pp.1553-1559
• /
• 2002

Calculations are presented for the molecule HC2N and its geometrical isomers. The structures, harmonic frequencies and dipole moments are reported. The potential energy surface of the [H,C,C,N] system is investigated in detail, and the transition states, intermediate complexes, and the energies of barrier for the isomerization and dissociation reactions are computed in order to determine the reaction paths and to estimate the stability of the isomers. The barriers of isomerization among HCCN, HCNC and HNCC are computed to be rather large and dissociations of these molecules are highly endothermic, indicating that these molecules are kinetically stable. The association reactions HC + CN→HCCN, HC + NC→HCNC, and HN + CC →HNCC are barrierless and very exothermic, suggesting that they may be considered as efficient means of producing the HCCN and the isomers in the laboratory and in interstellar space.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.65.1-65.1
• /
• 2013

Icy dust particles in interstellar clouds are considered to play a catalytic role in molecular evolution in space. Atoms and simple molecules constituting the ice mantles of dust particles may be transformed into more complex molecules under the irradiation of UV and cosmic rays. This seminar will present our recent study results for chemistry of ice surfaces, with the emphases on the mechanistic features of elementary reactions and the implications for interstellar molecular evolution. The types of reactions studied include molecule diffusion in ice, proton and hydroxide transfers, and some UV-induced reactions wih astrobiological relevance.

• 천문학회지
• /
• 제26권2호
• /
• pp.99-101
• /
• 1993

We have searched for the 2 mm transitions of $H_2COH^+(2_{02}-1_{01})$ and $H_2\;^{13}CO(2_{02} - 1_{01},\; 2_{12}-1_{11},\;and\;2_{11}-1_{10})$ toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14 m telescope. None of the transitions have been detected except the $H_2\;^{13}CO$ transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion $(H_2COH^+)$, which are close to the abundances expected from ion-molecule chemistry.

• Bulletin of the Korean Chemical Society
• /
• 제23권12호
• /
• pp.1737-1743
• /
• 2002

We have studied the dynamics of energy-rich hydrogen molecules produced on a graphite surface through H(g) + H(ad)/C(gr) → $H_2$ + C(gr) at thermal conditions mimicking the interstellar medium using a classical trajectory procedure. The recombination reaction of gaseous H atom at 100 K and the adsorbed H atom on the interstellar graphite grains at 10 K efficiently takes place on a subpicosecond time scale with most of the reaction exothermicity depositing in the product vibration, which leads to a strong vibrational population inversion. The molecules produced in nearly end-on geometry where H(g) is positioned below H(ad) rotate clockwise and are more highly rotationally excited. but in low-lying vibrational levels. The rotational axis of most of the molecule rotating clockwise is tilted from the surface normal by more than 30°, the intensity peaking at 35°. The molecules produced when H(ad) is close to the surface rotate counter-clockwise and are weakly rotationally excited, but highly vibrationally excited. These molecules tend to align their rotational axes parallel to the surface. The number of molecules rotating clockwise is eight times larger than that rotating counter-clockwise.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2009년도 제38회 동계학술대회 초록집
• /
• pp.394-394
• /
• 2010

Ammonium ion (${NH_4}^+$) was suggested as the origin of interstellar $6.85\;{\mu}m$ band. Early study, in which organic molecule and water ice film mixtures were photolyzed so that organic acids could be produced, explained the generation of ${NH_4}^+$ from the reaction of photogenerated organic acid and ammonia ($NH_3$). However, the observed abundance of organic acids or their counter-anions are not so high in interstellar ice and not enough to protonate $NH_3$ into ${NH_4}^+$ in the observed level. Because of the shortage in photogenerated organic acids, the candidate of acid which protonates $NH_3$ should be modified. Here, we prepare $NH_3/H_2O$ binary mixtures and photolyze them with vacuum ultraviolet (VUV, peak at 10.6 and 10.0 eV). We find the ammonium ion (${NH_4}^+$) from photolyzed mixture by using low energy sputtering (LES) and reflection absorption IR spectroscopy (RAIRS). As a hydronium ($H_3O^+$) can be produced by UV irradiation and protonate bases, ${NH_4}^+$ may be formed from the reaction of photogenerated $H_3O^+$ and $NH_3$. We show the generation of ${NH_4}^+$ without any kind of organic molecules or acids, and it may explain the relatively high abundance of ${NH_4}^+$ compared to the counter-anions or organic acids in interstellar ice.

• 천문학회지
• /
• 제26권1호
• /
• pp.65-72
• /
• 1993

Using the Daeduk Radio Telescope, we have observed $J=1\rightarrow0$ transitions of 1$^{12}CO,\;^{13}CO\;and\;C^{18}O$ toward OMC-l. The column densities of $1\~5\times10^{17}\;cm^{-2}\;and\;1\~3\times10^{16}\;cm^{-2}$ have been derived, for $^{13}CO$ and $C^{18}O$, respectively, in the $11'\times11'$ region centered at Orion - KL. The double isotope ratio $[^{13}CO]/[C^{18}O]$ was found to be larger than the cosmic abundance ratio by factors of $2\~10$ which may result from the chemical fractionation effect.

• 한국대기환경학회:학술대회논문집
• /
• 한국대기환경학회 2003년도 춘계학술대회 논문집
• /
• pp.163-164
• /
• 2003

Reaction dynamics plays an essential role in understanding the microscopic mechanism of elementary chemical processes at the molecular level. Detailed studies of the reactions of atomic species such as hydrogen and second-row atoms with small closed-shell molecules have provided important insights into hydrocarbon synthesis, combustion, interstellar space and atmospheric chemistry. Despite its mechanistic significance, however, the investigations of atom-radical reaction dynamics are quite scarce in comparison to the extensive studies of atom-molecule reactions. (omitted)

• 천문학회지
• /
• 제27권1호
• /
• pp.55-60
• /
• 1994

The 3mm transitions to CO, $^{13}CO,\;CS,\;HCO^+$, and HCN have been observed toward the compact HII regions in W58 using the 14m Daeduk Radio Telescope (DRT). Some of the observed lines show high-velocity wings resulted from outflowing materials of the compact HII regions. We derive the beam averaged column densities of the observed species and compare their relative abundances. The $HCO^+$ abundance appears to be smaller by about an order of magnitude than those of 'typical' quiet molecular clouds. CS may be a good reference molecule in comparing relative abundances in different physical conditions.

• 천문학회지
• /
• 제26권1호
• /
• pp.73-78
• /
• 1993

We have mapped the $C_3H_2\;2_{12}-1_{01}$ transition line toward the Sgr A molecular cloud on a 1' grid spacing and derived $C_3H_2$ column densities of $3\~7\times10^{14}\;cm^{-2}$ for molecular clouds of Sgr A. The fractional abundances of $C_3H_2$ relative to $H_2$ are obtained to be $3\~6\times10^{-9}$, which are slightly lower than that for the cold dark cloud TMC-1 but are enhanced by factors of 5-60 compared to those for Sgr B2 and the Orion extended ridge. We also estimate from the $C_3H_2$ column densities total masses of $\~10^6\; M_\bigodot$ for two clouds (M - 0.13 - 0.08 and M - 0.02 - 0.07), which are thought to be close to the virial equilibrium. We suggest that the large abundance of $C_3H_2$ in Sgr A may be partly due to the activities of the Galactic center.

• Journal of Astronomy and Space Sciences
• /
• 제21권4호
• /
• pp.243-248
• /
• 2004

FUSE(Far Ultraviolet Spectroscopic Explorer)를 이용해 7개의 초기형 별 방향에 존재하는 CO 흡수선을 관측했다. BEFS(Berkeley Extreme and Far-ultraviolet Spectrometer)로 관측한 54개의 초기형 별들 중에서 이번 논문에서는 시선방향으로 1개의 성간운만 존재하는 7개의 별(HD 37903, HD 97991, HD 149881, HD 156110, HD 164794, HD 214080, HD 219188)들을 선택해서 분석했다. CO 분자의 분석을 위해 자외선 영역에서 수소분자의 흡수선에 의해 가려지지 않는 E-X(0-0)($1076{\AA}$) 흡수선이 있는지 확인했으며 그 결과 3개의 별 방향에 존재하는 성간운에 대해서 CO 흡수선이 있는 것을 발견했다. 그 흡수선의 분석을 통해 성간운에 존재하는 CO의 기둥밀도를 구했고, 이번 논문에서의 결과와 이전에 구했던 수소분자의 기둥밀도로부터 CO분자와 수소분자 사이의 비율(CO to $H_2$ ratio)을 계산할 수 있었다.