ULTRAFAST EXPERIMENTS ON INTERMOLECULAR ELECTRON-TRANSFER IN THE BENZENE-BROMINE ATOM CHARGE-TRANSFER COMPLEX

Ultrafast pump - probe measurements have been made on the benzene - br omine atom charge transfer (CT) complex in CCl4 and cyclohexane soluti ons. Ultrafast optical excitation of the CT band of the complex yields an ion pair, which is comprised of a benzene cation and a bromide ani on. The rate of charge recombination between the bromide and the benze ne cation in the ion pair has been observed to be much faster than the rate of diffusion apart. The charge recombination rate is accelerated at high benzene concentrations as a result of the formation of a benz ene dimer cation - bromide ion pair which undergoes much faster charge recombination than the benzene cation - bromide ion pair.