Optical control of electrons during electron transfer.

The dynamics of electron transfer reactions in solution can be controlled with the use of a sequence of femtosecond laser pulses. In the charge transfer to solvent (CTTS) reaction of sodide (Na-) in tetrahydrofuran, an initial light pulse launched the CTTS reaction, ejecting an electron into either an immediate or a solvent-separated Na0:solvated electron contact pair. A second pulse was used to excite the electrons in the contact pairs, and a third pulse monitored the amount of Na- produced through the back electron transfer. Excitation of the electrons in immediate contact pairs shut off the back electron transfer, whereas excitation of the electrons in solvent-separated pairs both enhanced and hindered the back electron transfer.