The chemical evolution in a model of contracting cloud

Abstract

The evolution of the different chemical species are followed in a model of contracting interstellar cloud. The central density increases from n = 10 cme3 diffuse initial cloud model to a dense cloud with central density number of n 1 lo5 cmA3 after a time of 1.2 x lo7 yr. A network of 622 reactions has been involved. The chemistry of the cloud is integrated simultaneously with the hydrodynamic equations of contraction.The results predict that the different molecular species increase in abundance as the contraction proceeds. The species which enhance significantly are CO, HCO, CS and NO. The fractional abundances of many of the other molecular species increase distinctly with contraction, e.g. CH, GH, CN, SOz, COz, HzO, CZ, NHs, HCN, SO, OCS and SN. The transformation of the initial diffuse cloud model with small abundances of molecular species to a dense molecular cloud with enhancement of the different molecular species is confirmed. The results predict good agreements of our results with both the observations and other theoretical studies.

A Quantum Monte Carlo Study of the Reactions of CH with Acrolein

“…It is important to assess how the increased oxygen content of such fuels affects the absolute and relative concentrations of aldehydes emitted due to the use of biodiesels . The high reactivity of CH leads to its significant role in various fields of science including interstellar chemistry, combustion chemistry, and planetary atmospheres − with report of detection in the interstellar medium, − comets, stellar atmospheres, , and flames …”

Reaction Mechanism of CH + C3H6: A Theoretical Study

“…The methylidyne radical, CH plays an important role in various fields including combustion chemistry, , interstellar chemistry, , and planetary atmosphere chemistry . It has been detected in the interstellar medium, – comets, stellar atmospheres, , and flames .…”

H Atom Branching Ratios from the Reactions of CH with C2H2, C2H4, C2H6, and neo-C5H12 at Room Temperature and 25 Torr

“…The methylidene radical (CH) plays an important role in a variety of chemical environments, ranging from interstellar chemistry 1,2 through planetary atmospheres 3 to combustion chemistry. 4,5 The kinetics of CH removal are now well studied following extensive measurements by Lin and co-workers [6][7][8][9] and more recently by Smith and co-workers, 10,11 Taatjes and co-workers, 12-14 ourselves, [15][16][17][18] and others.…”

“…The methylidene radical (CH) plays an important role in a variety of chemical environments, ranging from interstellar chemistry , through planetary atmospheres to combustion chemistry. , The kinetics of CH removal are now well studied following extensive measurements by Lin and co-workers − and more recently by Smith and co-workers, , Taatjes and co-workers, − ourselves, − and others. − In general, CH reactions are characterized by fast barrierless insertion reactions forming an intermediate that rapidly decomposes to products, although there is debate as to the exact nature of the reaction mechanisms. − The absence of any pressure dependence in the removal kinetics of most reactions and the high rate coefficients show that stabilization and redissociation to form reagents are not competitive with dissociation of the intermediate to products.…”