Picosecond Multiphoton Laser Photolysis and Spectroscopy of Liquid Benzenes

Measurement of transient absorption spectra by means of ps laser has been one of the most useful methods to investigate photophysical and photochemical primary processes. The high peak power of the ps pulse, however, induces easily nonlinear phenomena such as multiphoton excitation as well as multiphoton ionization and decomposition of molecules. Therefore, it is possible by using this ps multiphoton laser photolysis to excite or ionize various kinds of neat liquids and investigate the transient species by time-resolved absorption measurements. We have already demonstrated the measurements of excimer formation processes by 355 nm two photon excitation of neat benzene1 and solvated electron formation processes by 266 nm multiphoton excitation of water and alcohols.2 Solvated electron formation in liquids has been studied by means of ps pulse radiolysis as well as by ps laser ionization of solute molecule in the liquid solvent. Comparison of the results of these investigations with those of the 266 nm multiphoton ionization of pure liquids will be an interesting problem. In this report, results of investigations on the mechanism of excimer formation in neat benzene and alkyl substituted benzenes induced by multiphoton excitation will be given.