Abstract

Among the possible processes which can occur after photo-excitation of diphenylpolyenes, direct photoionization and production of ion radicals has been observed using nanosecond tune resolution [1]. While the excitation wavelength was well below the photoionization threshold, it was unambigously shown, that in polar solvent direct formation of radical ion occur. In this communication we report for the first time, using subpicosecond time resolved degenerate CARS and transient absorption experiments, the observation of direct monophotonic ionization process under excitation at 300nm of 1,4-diphenyl-butadiene and trans-stilbene in polar solvents (acetonitrile, linear alcohols). The influence of other processes, such as solvent thermal cooling after IVR, on the formation and stabilisation rate will be discussed.

© 1996 IEEE