Optical control of electrons during electron transfer

The dynamics of electron transfer reactions in solution can be controlled w ith the use of a sequence of femtosecond laser pulses. In the charge transf er to solvent (CTTS) reaction of sodide (Na-) in tetrahydrofuran, an initia l Light pulse Launched the CTTS reaction, ejecting an electron into either an immediate or a solvent-separated Na-o:solvated electron contact pair. A second pulse was used to excite the electrons in the contact pairs, and a t hird pulse monitored the amount of Na- produced through the back electron t ransfer. Excitation of the electrons in immediate contact pairs shut off th e back electron transfer, whereas excitation of the electrons in solvent-se parated pairs both enhanced and hindered the back electron transfer.