Journal of Physical Chemistry B, Vol.105, No.28, 6500-6506, 2001
Theory and control of thermal photoinduced electron transfer reactions in polyatomic molecules
The nature of the nascent vibrational distribution in the excited donor state in photoinduced electron transfer is shown to have a profound effect on the electron-transfer rate. In polyatomic molecules, excitation at wavelengths in the vicinity of the ground state to ground state excitation frequency may lead to significant cooling of the excited vibrational state distribution. This cooling is shown to lead to a slowing down of the electron-transfer rate. A theory for photoinduced electron transfer is developed to include the nonequilibrium nature of the excited donor vibrational distribution. The rate expression is shown to be the standard Golden rule thermal rate expression but at an effective temperature which depends on the ground electronic state temperature and the photoexcitation frequency. A simple numerical model is presented to demonstrate the cooling and control of the electron-transfer rate by variation of the excitation frequency.