Basic Concepts for Gas-Phase Chemical Reactions
This chapter describes fundamental physical aspects of gas-phase chemical reactions which are of particular importance in astrochemistry. Rate coefficients of chemical reactions are defined both in microscopic and macroscopic views. After summarizing important constraints required for chemical reactions in low-density and low-temperature conditions of interstellar clouds, ion–molecule reactions, neutral–neutral reactions, radiative association reactions, dissociative electron recombination reactions, photodissociation, and photoionization are described. Timescales for chemical reactions and that for chemical equilibrium are defined in relation to rate coefficients, which are often used in the later chapters.
KeywordsRate coefficients Gas-phase reactions Photodissociation Photoionization
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