Distribution of Energy on a Molecular Time Scale

The molecular time scale may be taken to start at 10 14 s following energy absorption (see Sect. 2.2.3). At this time, H atoms begin to vibrate and most OH in water radiolysis is formed through the ion-molecule reaction H20+ + H20 H30+ + OH. Dissociation of excited and superexcited states, including delayed ionization, also should occur in this time scale. The subexcitation electron has not yet thermalized, but it should have established a quasi-stationary spectrum its mean energy is expected to be around a few tenths of an eV. 

The foregoing analysis was for gas-phase water radiolysis. Similar estimates may be made for the condensed phases and for other media when the relevant yields and energetics become progressively available. On the whole, these species will gradually thermalize and become available for track reactions. Such reactions are greatly influenced by track structure, which is taken up in the following section. 

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