Laser-Induced Fluorescence Studies of Molecular Dynamics

Abstract

The vibronic rovibronic fluoresence excitation spectra of biacetyl, methylglyoxal, and pentanedione have been recorded for the excited singlet state of each molecule. In particular, the fluorescence of biacetyl in a molecular beam has been shown to exhibit the quantum beat effect in the time-resolved fluoresence. By the use of a simple, perturbation theory-derived analysis and also a more complicated, simulation-based method, the effective densities of the triplet states involved in the beat phenomena and the mean interaction energies for singlet-triplet state coupling have been determined.

The dissociation of ClCn and cyanogen at 193 nm by the use of an ArF laser has been investigated. The nascent rovibronic energy distributions were obtained by a simple laser-induced fluoresence method, and the angular and velocity distributions of the recoiling photofragments determined by the use of a unique, multichannel photomultiplier array for each individual internal energy state. The internal energy distributions show cold vibrational state distributions and hot rotational state distributions, while the translational energy distributions are very hot. The preliminary data for the angular distributions indicate an isotropic profile, which is the expected result for a predissociating molecule. Extensive details on the construction of the photomultiplier array are included, along with the necessary computer programs and electronics for the experiments.