Spin-orbit effects in gas-phase chemical reactions

1987 ◽  
Vol 87 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Paul J. Dagdigian ◽  
Mark L. Campbell
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Spin Orbit ◽  
Phase Chemical

scholarly journals Galactic Bulge PNe: Carbon molecules in oxygen-rich environments

2011 ◽  
Vol 7 (S283) ◽  
pp. 259-262
Author(s):  
Lizette Guzmán-Ramírez ◽  
Albert Zijlstra ◽  
Roisin Níchuimín ◽  
Krzysztof Gesicki ◽  
Eric Lagadec ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Planetary Nebulae ◽  
Galactic Bulge ◽  
Hydrocarbon Chains ◽  
Show Evidence ◽  
Low Mass ◽  
Carbon Molecules ◽  
Hydrocarbon Chemistry ◽  
Phase Chemical

AbstractGalactic bulge planetary nebulae show evidence of mixed chemistry with emission from both silicate dust and PAHs. This mixed chemistry is unlikely to be related to carbon dredge up, as third dredge-up is not expected to occur in the low mass bulge stars. We show that the phenomenon is widespread, and is seen in 30 nebulae out of our sample of 40. A strong correlation is found between strength of the PAH bands and morphology, in particular, the presence of a dense torus. A chemical model is presented which shows that hydrocarbon chains can form within oxygen-rich gas through gas-phase chemical reactions. We conclude that the mixed chemistry phenomenon occurring in the galactic bulge planetary nebulae is best explained through hydrocarbon chemistry in an UV-irradiated, dense torus.

Global minimum profile error (GMPE) – a least-squares-based approach for extracting macroscopic rate coefficients for complex gas-phase chemical reactions

2018 ◽  
Vol 20 (2) ◽  
pp. 1231-1239 ◽  
Author(s):  
Minh v. Duong ◽  
Hieu T. Nguyen ◽  
Tam V.-T. Mai ◽  
Lam K. Huynh
Keyword(s):  
Master Equation ◽  
Least Squares ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Global Minimum ◽  
Rate Coefficients ◽  
Gas Phase Reactions ◽  
Profile Error ◽  
Time Resolved ◽  
Phase Chemical

The new GMPE method was introduced to derive the macroscopic rate coefficients for complex gas-phase reactions from the time-resolved species profiles obtained from the master equation (ME) solutions.

scholarly journals Impact of PAH photodissociation on the formation of small hydrocarbons in the Orion Bar and the horsehead PDRs

2020 ◽  
Vol 497 (2) ◽  
pp. 2327-2339 ◽  
Author(s):  
M S Murga ◽  
M S Kirsanova ◽  
A I Vasyunin ◽  
Ya N Pavlyuchenkov
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Aromatic Hydrocarbons ◽  
Laboratory Experiments ◽  
Acetylene Molecule ◽  
Physical Conditions ◽  
Polycyclic Aromatic ◽  
Photodissociation Regions ◽  
Acetylene Production ◽  
Phase Chemical

ABSTRACT We study whether polycyclic aromatic hydrocarbons (PAHs) can be a weighty source of small hydrocarbons in photodissociation regions (PDRs). We modelled the evolution of 20 specific PAH molecules in terms of dehydrogenation and destruction of the carbon skeleton under the physical conditions of two well-studied PDRs, the Orion Bar, and the Horsehead nebula that represent prototypical examples of PDRs irradiated by ‘high’ and ‘low’ ultraviolet radiation field. PAHs are described as microcanonical systems. The acetylene molecule is considered as the main carbonaceous fragment of the PAH dissociation, as it follows from laboratory experiments and theory. We estimated the rates of acetylene production in gas phase chemical reactions and compared them with the rates of the acetylene production through the PAH dissociation. It is found that the latter rates can be higher than the former rates in the Orion Bar at AV < 1 and also at AV > 3.5. In the Horsehead nebula, the chemical reactions provide more acetylene than the PAH dissociation. The produced acetylene participate in the reactions of the formation of small hydrocarbons (C2H, C3H, C3H+, C3H2, C4H). Acetylene production via the PAH destruction may increase the abundances of small hydrocarbons produced in gas phase chemical reactions in the Orion Bar only at AV > 3.5. In the Horsehead nebula, the contribution of PAHs to the abundances of the small hydrocarbons is negligible. We conclude that the PAHs are not a major source of small hydrocarbons in both PDRs except some locations in the Orion Bar.

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