关键词: 电子转移, 外电场, 苯正离子自由基, 电子转移矩阵元, 从头算

Abstract: Based on the semiclassical theory of electron transfer, quantum chemical calcula-tions at HF/DZP level were performed for the study of intramolecular electron transfer between parallel benzene and benzene cation radical. After the geometric optimizations of the donor and the acceptor, a linear reaction coordinate ξ was introduced to determine the transition state. The variation principle applied to the two diabatic states and Koopmans theorem used in the calculation of molecular orbital transition energy, were invoked to evaluate the electron transfer matrix element V_AB. The exponential falloff of V_AB with increasing d, the distance between the center of the donor and that of the acceptor, was discussed. The influence of external electric field on the exothermicity of the electron transfer was investigated with d=0.6 nm, and then the rate constant k of the intramolecular gas-phase electron transfer was estimated for different values of the external electric field strength.

Key words: Electron transfer, External electric field, Benzene cation radical, Electron trans-fer matrix element, Ab initio