Iodine termolecular recombination

The temjjerature dependence of in (6.13) is weak, and primarily arises from that of Q b. t,ab> t,am and / t,bm which decrease with temjjerature. The temperature dependence of C from Section IV B can enhance these changes. In the case of iodine termolecular recombination... 

The rapid formation of molecular iodine following the flash photolytic dissociation of CHgl has been observed by time-resolved mass spectrometry.60 This has been attributed to the reaction (20) rather than to slow termolecular recombination. The experimental difficulties associated with sampling by this technique have been discussed by Meyer.61 This reaction is further discussed in Section IX.D on reaction of I(52Py2) with alkyl iodides. 

A termolecular reaction step involves the simultaneous collision of three molecules, which is a much less likely event. An example is the recombination of iodine atoms in the gas phase to form iodine molecules. So much energy is released in forming the I—I bond that the molecule would simply fly apart as soon as it was formed if the event were a binary collision. A third atom or molecule is necessary to take away some of the excess energy. If iodine recombination takes place in the presence of a sufficiently high concentration of an inert gas such as argon, termolecular reactions... 

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