DYNAMICS OF VIBRATIONALLY EXCITED VANDERWAALS COMPLEX - STIMULATED-EMISSION-PUMPING LASER-INDUCED-FLUORESCENCE SPECTROSCOPY OF THE ANISOLE.AR COMPLEX

The stimulated-emission-pumping laser-induced-fluorescence technique w as applied to investigate the dynamics of vibrationally excited states of van der Waals complexes, anisole-d0 . Ar and anisole-d3 . Ar, prod uced in the supersonic expansion. In this technique, the complex excit ed to a specific vibrational state by stimulated-emission pumping is d etected by measuring the laser-induced-fluorescence excitation spectru m with an appropriate delay to probe the vibrational relaxation or pre dissociation. Five vibrational states, 18b1, 6a1, 12(1), 16a2, and 1(1 ), of the complexes were investigated. Main results obtained in this s tudy are (1) The vibrational excitation of one of 1(1), 16a2, and 12(1 ) gives hot bands in the laser-induced-fluorescence excitation spectru m due to the anisole monomer produced by vibrational predissociation. (2) Excitation of 18b1, whose energy is below the dissociation thresho ld, does not lead to vibrational relaxation of the complexes. (3) Exci tation of 6a1 causes the predissociation into vibrationally cold monom ers. (4) The predissociation is completed within 300 ns, the shortest available delay time between the stimulated-emission pumping and probe pulse.