Multiple photon excitation of adsorbed toluene by KrF laser

Abstract

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.

The Photolysis of Aromatic Hydrocarbons Adsorbed on the Surfaces of Cosmic Dust Grains

“…This gives rise to desorption of individual molecules and/or molecular clusters, while desorption of molecules from a single-layer coating occurs in accordance with the theoretical mechanism. The subsequent photodissociation of the desorbed particles is analogous to the gas-phase process [22]. Under the conditions of the ISM, multi-layer coatings consisting of many molecular components predominate.…”

“…In our current study, we have considered another factor influencing the photostability of a number of adsorbed molecules. A series of laboratory experiments on the photostability of adsorbed molecules of the simplest aromatic hydrocarbons, such as benzene [20], chlorobenzene [21], and toluene [22] have been carried out in the Chemistry Department of Moscow State University using powerful UV laser radiation. It was established in these experiments that adsorbed molecules are much more stable than their gas-phase analogs, due to the transfer of the excess internal energy of the photoexcited molecule to the substrate via rapid intramolecular relaxation.…”