Volume 133, 2006

The temperature-dependence of rapid low temperature reactions: experiment, understanding and prediction

Abstract

Despite the success of the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) method in measuring rate coefficients for neutral–neutral reactions of radicals down close to the very low temperatures prevalent in dense interstellar clouds (ISCs), there are still many reactions of potential importance in the chemistry of these objects for which there have been no measurements of low temperature rate coefficients. One important class of reactions is that between atomic and molecular free radicals and unsaturated hydrocarbons; that is, alkynes and alkenes. Based on semi-empirical arguments and correlations of ‘room temperature’ rate coefficients, k(298 K), for reactions of this type with the difference between the ionisation energy of the alkyne/alkene and the electron affinity of the radical, we suggest which reactions between the radicals, C(3P), O(3P), N(4S), CH, C2H and CN, and carbon chain molecules (Cn) and cyanopolyynes (HC2nCN and NCC2nCN) are likely to be fast at the temperature of dense ISCs. These reactions and rate coefficients have been incorporated into a purely gas-phase model (osu2005) of ISC chemistry. The results of these calculations are presented and discussed.

Article information

Article type
Paper
Submitted
17 Jan 2006
Accepted
08 Feb 2006
First published
21 Jun 2006

Faraday Discuss., 2006,133, 137-156

The temperature-dependence of rapid low temperature reactions: experiment, understanding and prediction

I. W. M. Smith, A. M. Sage, N. M. Donahue, E. Herbst and D. Quan, Faraday Discuss., 2006, 133, 137 DOI: 10.1039/B600721J

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