Anisotropy of pump-probe absorption of the hydrated electron: A statistical model

摘要

A statistical model is presented to interpret the pump-probe absorption anisotropy of the hydrated electron. Its basic ingredient is the assumption of cascade-type deactivation processes between its excited p-states. The theory uses the correlation function formalism of nonlinear statistical mechanics. A number of technical problems are discussed: construction of a relaxation operator describing the cascade, solution of the corresponding Heisenberg equation of motion, calculation of various tensorial quantities, etc. According to this model, the presence of a cascade reduces the pump-probe dichroism, particularly if the p-state splitting is small. Very short cascade relaxation times of the order of 10 fs are required for that purpose. As the upper state of an s<->p transition is quasi-degenerate, the magic angle theories do not apply here. The similarity between the deactivation processes in excited electronic states of polyatomic molecules and of the hydrated electron is emphasized. (C) 1998 American Institute of Physics. [S0021-9606(98)51546-2]. [References: 48]