Keywords
Chemical kinetics, interstellar medium, low temperatures, rate coefficients
Definition
By neutral-neutral reactions, we mean those chemical reactions that occur in collisions between atomic or molecular species that carry no electrical charge. Because of the extremely low gas densities that characterize even the densest regions of the interstellar medium, it is only necessary in this environment to consider bimolecular reactions that occur in binary collisions. The crucial properties that are sought in kinetic experiments are the rate coefficient and its dependence on temperature, denoted by k(T), and, in cases where two or more sets of products are possible, the branching ratio – that is, the fractions of the overall reaction that proceed via different channels. For a bimolecular reaction, say A + B → C + D, the rate of the loss of A may be written as −d[A]/dt = k(T) [A][B], where the square brackets denoted concentrations, usually expressed in cm−3 so that the units of k(T)...
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References and Further Reading
Bell MT, Softley TP (2009) Ultracold molecules and ultracold chemistry, Mol Phys 107:99
Canosa A, Goulay F, Sims IR, Rowe BR (2008) Gas phase reactive collisions at very low temperature: Recent experimental advances and perspectives. In Smith IWM (ed) Low temperatures and cold molecules. Imperial College Press, London
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Smith, I.W.M. (2011). Neutral-Neutral Reactions. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11274-4_1051
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DOI: https://doi.org/10.1007/978-3-642-11274-4_1051
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