Multiple photon excitation of adsorbed toluene by KrF laser

KrF laser-induced multiple photon dissociation and desorption of toluene condensed on fused silica have been studied using mass spectrometry. The three-photon (2-1) excitation of the molecule including its transition connected with laser stimulated emission was found to control this dissociation in all coverages as well as the ejection of single toluene molecules from the multilayer. Fragments were also produced in two successive steps of two-photon excitation that caused the release of toluene clusters from the adsorbed multilayer and the breaking of intramolecular bonds in the desorbed species. A mechanism of toluene and its cluster ejection has been proposed. The difference in the dynamics of the excited adsorbed and gaseous molecules has been discovered. The irradiation of the silica surface by KrF laser was found to lead to an increase of the local laser field acting on the adsorbed toluene of more than 50 times. (paper)