ChemInform Abstract: Photodissociaton of Simple Molecules in the Gas Phase

ChemInform ◽  
2010 ◽  
Vol 32 (47) ◽  
pp. no-no
Author(s):  
Hiroyasu Sato
Keyword(s):  
Gas Phase ◽  
Simple Molecules

scholarly journals Ices in star forming regions

1997 ◽  
Vol 178 ◽  
pp. 45-60 ◽  
Author(s):  
A.G.G.M. Tielens ◽  
D.C.B. Whittet
Keyword(s):  
Ir Spectra ◽  
Gas Phase ◽  
Molecular Cloud ◽  
Oxidation Reactions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Interstellar Ice ◽  
Simple Molecules ◽  
Absorption Features ◽  
Cloud Material

IR spectra of sources associated with molecular cloud material show a variety of absorption features attributed to simple molecules, such as H2O, CO, CH3OH, CO2, CH4, and OCS in icy grain mantles. These identifications are reviewed. These molecules are formed through accretion and reaction of gas phase species on grain surfaces. The high abundance of CH3OH and CO2 point towards the importance of hydrogenation and oxidation reactions in this process. Observations also show that thermal outgassing is of great importance for the composition of interstellar ice mantles. Both these processes are discussed in some detail.

scholarly journals The role of atom tunneling in gas-phase reactions in planet-forming disks

2019 ◽  
Vol 627 ◽  
pp. A45 ◽  
Author(s):  
J. Meisner ◽  
I. Kamp ◽  
W.-F. Thi ◽  
J. Kästner
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Reaction Rate ◽  
Tunneling Effect ◽  
Gas Phase Reactions ◽  
Disk Model ◽  
Reaction Rate Constants ◽  
T Tauri ◽  
Simple Molecules ◽  
The Impact

Context. Chemical Gas-phase reactions of simple molecules have been recently revised to include atom tunneling at very low temperatures. This paper investigates the impact of the increased reaction rate constant due to tunneling effects on planet-forming disks. Aims. Our aim is to quantify the astrophysical implications of atom tunneling for simple molecules that are frequently used to infer disk structure information or to define the initial conditions for planet (atmosphere) formation. Methods. We quantify the tunneling effect on reaction rate constants by using H2 + OH → H2O + H as a scholarly example in comparison to previous UMIST2012 rate constants. In a chemical network with 1299 reactions, we identify all chemical reactions that could show tunneling effects. We devise a simple formulation of reaction rate constants that overestimates tunneling and screen a standard T Tauri disk model for changes in species abundances. For those reactions found to be relevant, we find values of the most recent literature for the rate constants including tunneling and compare the resulting disk chemistry to the standard disk model(s), a T Tauri and a Herbig disk. Results. The rate constants in the UMIST2012 database in many cases already capture tunneling effects implicitly, as seen in the curvature of the Arrhenius plots of some reactions at low temperature. A rigorous screening procedure identified three neutral-neutral reactions where atom tunneling could change simple molecule abundances. However, by adopting recent values of the rate constants of these reactions and due to the layered structure of planet-forming disks, the effects are limited to a small region between the ion-molecule dominated regime and the ice reservoirs where cold (<250 K) neutral-neutral chemistry dominates. Abundances of water close to the midplane snowline can increase by a factor of two at most compared to previous results with UMIST2012 rates. Observables from the disk surface, such as high excitation (>500 K) water line fluxes, decrease by 60% at most when tunneling effects are explicitly excluded. On the other hand, disk midplane quantities relevant for planet formation such as the C-to-O ratio and also the ice-to-rock ratio are clearly affected by these gas-phase tunneling effects.

Coordination of Some Simple Molecules onto W(CO)5in the Gas Phase

1993 ◽  
Vol 66 (12) ◽  
pp. 3618-3626 ◽  
Author(s):  
Motohiro Jyo-o ◽  
Hideki Takeda ◽  
Kenji Omiya ◽  
Yo-ichi Ishikawa ◽  
Shigeyoshi Arai
Keyword(s):  
Gas Phase ◽  
Simple Molecules

Gas-phase reactivity of the vinyl cation towards simple molecules. Hydrogen and methane

1986 ◽  
Vol 72 (1-2) ◽  
pp. 137-144 ◽  
Author(s):  
Simonetta Fornarini ◽  
Roberto Gabrielli ◽  
Maurizio Speranza
Keyword(s):  
Gas Phase ◽  
Vinyl Cation ◽  
Simple Molecules

scholarly journals The Environment of High-Mass Young Stellar Objects

1992 ◽  
Vol 150 ◽  
pp. 259-264
Author(s):  
Jean-Pierre Maillard ◽  
George F. Mitchell
Keyword(s):  
Gas Phase ◽  
Massive Star ◽  
Young Stellar Objects ◽  
High Mass ◽  
Phase Detection ◽  
Giant Molecular Clouds ◽  
General Phenomenon ◽  
Stellar Objects ◽  
New Class ◽  
Simple Molecules

Using high-resolution infrared CO spectroscopy new results have been obtained on the environment of high-mass young stellar objects (YSOs). In particular, a new class of neutral, warm and dense outflows has been discovered. The infrared outflows appear a general phenomenon of the activity of high-mass YSOs. With well-defined and often multiple velocities they seem to correspond to episodic and violent mass-loss events from the central source. In addition, a shell of warm, quiescent gas, is formed near the massive star. All these dynamical elements influence the chemistry inside the giant molecular clouds. Beside CO in solid and in gas phase, detection in the infrared has been attempted of simple molecules like CH4, C2H2, H2O and ion H3+ toward few of these sources.

Photodissociation of Simple Molecules in the Gas Phase

2001 ◽  
Vol 101 (9) ◽  
pp. 2687-2726 ◽  
Author(s):  
Hiroyasu Sato
Keyword(s):  
Gas Phase ◽  
Simple Molecules
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