A sensitivity study of the neutral-neutral reactions C + C3 and C + C5 in cold dense interstellar clouds

Abstract

Chemical networks used for models of interstellar clouds contain many reactions, some of them with poorly determined rate coefficients and/or products. In this work, we report a method for improving the predictions of molecular abundances using sensitivity methods and ab initio calculations. Based on the chemical network osu.2003, we used two different sensitivity methods to determine the most important reactions as a function of time for models of dense cold clouds. Of these reactions, we concentrated on those between C and C3 and between C and C5, both for their effect on specific important species such as CO and for their general effect on large numbers of species. We then used ab initio and kinetic methods to determine an improved rate coefficient for the former reaction and a new set of products, plus a slightly changed rate coefficient for the latter. Putting our new results in a pseudo-time-dependent model of cold dense clouds, we found that the abundances of many species are altered at early times, based on large changes in the abundances of CO and atomic C. We compared the effect of these new rate coefficients/products on the comparison with observed abundances and found that they shift the best agreement from 3e4 yr to (1-3)e5 yr.

References in corpus (4)

• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• The effect of uncertainties on chemical models of dark clouds
• Chemistry in Protoplanetary Disks: A Sensitivity Analysis

Cited by in corpus (8)

• Sensitivity analyses of dense cloud chemical models
• Carbon isotopic fractionation in molecular clouds
• Gas-grain model of carbon fractionation in dense molecular clouds
• A high resolution study of complex organic molecules in hot cores
• Reaction Studies of Neutral Atomic $\mathrm{C}$ with ${\mathrm{H}}_3^{+}$ using a Merged-Beams Apparatus
• Temperature Dependent Product Yields for the Spin Forbidden Singlet Channel of the C(3P) + C2H2 Reaction
• Sensitivity Analysis of Aromatic Chemistry to Gas-Phase Kinetics in a Dark Molecular Cloud Model
• The EDIBLES Survey. VII. A survey of C2 and C3 in interstellar clouds