Theory of coherent thermal photoinduced electron transfer reactions in polyatomic molecules

Abstract

The second order perturbation theory expression for the time dependent populations and rates of photoinduced electron transfer reactions has been previously derived by R.D. Coalson, D.G. Evans and A. Nitzan (J. chem. Phys., 101, 436 (1994)) and by M. Cho and R.J. Silbey (J. chem. Phys., 103, 595 (1995)). Here, we adapt these expressions for the study and analysis of the excitation laser frequency dependence of the time dependent populations and rates. Our model consists of a molecule with three electronic states, each supporting a manifold of harmonic internal vibrations of the molecule. In contrast to previous expectations, we find that in the region of significant absorption, the photoinduced electron transfer rate is almost independent of the frequency and the temporal width of the excitation laser. This conclusion implies that control of the excitation rate through the excitation laser frequency is possible only if external noise destroys the coherence of the excitation process.

Acknowledgement

This work was supported by grants of the Israel Science Foundation, the US Israel Binational Science Foundation and the German Israel Foundation for Basic Research.