Delayed cage effect

Figure 5 Illustration of solvent cage effect in delaying excited state thermal equilibration (reproduced with permission from J. Chem. Educ., 1983, 60, 797)...

A very fundamental difference between reactions in condensed matter and isolated molecular processes in the gas phase is the cage effect when a reaction or excitation process occurs in a cluster or in a condensed phase, the surrounding solvent molecules may prevent the separation of the reaction products or excited interacting species or delay such separation, confining the nascent species to the initial cage for an extended period of time. As in the work reviewed in subsection 1.3.2, this involves the interplay of dissociation and energy transfer. There, the emphasis was... 

Monchick [36, 273] has used the diffusion equation and radiation boundary conditions [eqns. (122) and (127)] to discuss photodissociative recombination probabilities. His results are similar to those of Collins and Kimball [4] and Noyes [269]. However, Monchick extended the analysis to probe the effect of a time delay in the dissociation of the encounter pair. It was hoped that such an effect would mimic the caging of an encounter pair. Since the cage oscillations have periods < 1 ps, and the diffusion equation is hardly adequate over such times (see Chap. 11, Sect. 2), this is a doubtful improvement. Nor does using the telegraphers equation (Chap. 11, Sect. 3.3) help significantly as it is only valid for times longer than a few picoseconds. 

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