Multiple Photon Processes in Molecules Induced by Picosecond UV Laser Pulses

Abstract

Multistep and multiple photon excitation of atoms and molecules by laser radiation makes a base for nonlinear laser photochemistry and their applications (see, e.g. [1,2]). Multiple photon processes dealing with vibrational and electronic excitation of molecules have been studied mainly in the gas phase when a comparatively long time of excitation and relaxation allows the use of nanosecond pulses. In condensed media at room temperature, due to a fast energy relaxation efficient multiple photon excitation is possible only when one applies laser pulses of picosecond duration. This approach has already resulted in the first successful experiments on multiquantum photochemistry of molecules in condensed media (aqueous solutions of nucleic acid bases [3,4], porphyrine [5]).