Dynamics of vibrationally excited van der Waals complex: Stimulated-emission-pumping laser-induced-fluorescence spectroscopy of the anisole⋅Ar complex

Abstract

The stimulated-emission-pumping laser-induced-fluorescence technique was applied to investigate the dynamics of vibrationally excited states of van der Waals complexes, anisole-d0⋅Ar and anisole-d3⋅Ar, produced in the supersonic expansion. In this technique, the complex excited to a specific vibrational state by stimulated-emission pumping is detected by measuring the laser-induced-fluorescence excitation spectrum with an appropriate delay to probe the vibrational relaxation or predissociation. Five vibrational states, 18b1, 6a1, 121, 16a2, and 11, of the complexes were investigated. Main results obtained in this study are (1) The vibrational excitation of one of 11, 16a2, and 121 gives hot bands in the laser-induced-fluorescence excitation spectrum due to the anisole monomer produced by vibrational predissociation. (2) Excitation of 18b1, whose energy is below the dissociation threshold, does not lead to vibrational relaxation of the complexes. (3) Excitation of 6a1 causes the predissociation into vibrationally cold monomers. (4) The predissociation is completed within 300 ns, the shortest available delay time between the stimulated-emission pumping and probe pulse.