Time of flight measurement of recoil energy distributions from vibrationalpredissociation of van der Waals clusters

A velocity-resolved time-of-flight technique is used to quantify the recoil energy released in the vibrational predissociation of triplet state mixed van der Waals dimers which contain similar to 2000 to similar to 8000 cm(-1 ) of vibrational energy. The clusters consist of an aromatic molecule (pyra zine, pyrimidine, methylpyrazine, benzene, aniline, or toluene) and a partn er molecule (rare gas atom, diatomic, or polyatomic molecule). The resultin g recoil energy distributions peak near zero energy and are monotonically d ecreasing functions of energy. The fraction of initially available vibratio nal energy that appears as recoil energy is small. The average recoil energ y is not strongly dependent on the initial vibrational energy or the densit y of states of the aromatic donor. The results are discussed in relationshi p to cluster partner dependence, statistical models, classical trajectory c alculations, and collisional energy transfer experiments.