Vibrational promotion of electron transfer

By using laser methods to prepare specific quantum states of gas-phase nitr ic oxide molecules, we examined the role of vibrational motion in electron transfer to a molecule from a metal surface free from the complicating infl uence of solvation effects. The signature of the electron transfer process is a highly efficient multiquantum vibrational relaxation event, where the nitrogen oxide loses hundreds of kilojoules per mole of energy on a subpico second time scale. These results cannot be explained simply on the basis of Franck-Condon factors. The large-amplitude vibrational motion associated;w ith molecules in high vibrational states strongly modulates the energetic d riving force of the electron transfer reaction. These results show the impo rtance of molecular vibration in promoting electron transfer reactions, a c lass of chemistry important to molecular electronics devices, solar energy conversion, and many biological processes.