PICOSECOND PHOTOINDUCED FORMATION OF A RADICAL-CATION - CARS AND TRANSIENT ABSORPTION STUDIES OF 1,4-DIPHENYLBUTADIENE

We report the direct observation of the formation and stabilization of the radical cation of 1,4-diphenylbutadiene (DPB) in polar solvents ( acetonitrile, linear alcohols) by picosecond ''pump-probe'' and polari zation-sensitive resonant CARS (Coherent Anti-Stokes Raman Scattering) experiments. For the first time, we have observed the formation and s tabilization rate of the DPB radical cation which occurs on a 10-20 ps timescale. We confirm that the formation process is mainly monophoton ic. (C) 1997 Elsevier Science S.A.