Reactions of Halogen Atoms, Free Radicals, and Excited States

We have included in our article a survey of energy-transfer kinetics involving 

Note All second-order rate constants mentioned in this articie have units of cm molecule s third-order rate constants are in cm molecule- s . Strictly, to correlate with cm mol s, second-order rate constants should have units cm s b ause L = 6.02 x I0 mol however, the expressions more familiar to kineticists have been retained, in I ine with Volume 1. 

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Reactions of Halogen Atoms, Free Radicals, and Excited States... 

When an electric discharge is passed through a cold diatomic gas at low pressure it is partially dissociated into atoms in this way reasonable concentrations of O, H, D, N, halogen or other atoms can be produced in a chemically inert diluent. The recombination of these atoms, and their reaction with other molecules can be observed as the gas flows down a long tube. Many of the reactions produce molecules in excited electronic states the resulting chemiluminescence can be used to measure the concentration of atomic species as a function of distance, and hence time, down the tube. Dr Clyne describes this important technique, which has produced direct measurements of the rates of many exothermic reactions of atoms and free radicals at room temperature and below. The reverse of the recombination steps are, of course, the dissociation reactions whose kinetics at high temperatures were described in the first chapter if the ratio of forward and reverse rate constants is equal to the equilibrium constant, the temperature dependence of these rates can be deduced over very wide ranges of temperature. 

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