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

Abstract

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 ∽2000 to ∽8000 cm−1 of vibrational energy. The clusters consist of an aromatic molecule (pyrazine, pyrimidine, methylpyrazine, benzene, aniline, or toluene) and a partner molecule (rare gas atom, diatomic, or polyatomic molecule). The resulting recoil energy distributions peak near zero energy and are monotonically decreasing functions of energy. The fraction of initially available vibrational energy that appears as recoil energy is small. The average recoil energy is not strongly dependent on the initial vibrational energy or the density of states of the aromatic donor. The results are discussed in relationship to cluster partner dependence, statistical models, classical trajectory calculations, and collisional energy transfer experiments.