Photo-Initiated Ion-Molecular Reactions in Size-Selected Clusters.

During the grant period, this work has focused on two research areas zero electron kinetic energy ZEKE spectroscopy experiments on mass-selected cluster anions in which a halide ion C1 or I is solvated with a known number of rare gas atoms, and stimulated Raman pumping of negative ions. Negative ion ZEKE spectroscopy is a high resolution laser photodetachment experiment which yields information on the vibrational and electronic spectroscopy of both the anion cluster and the neutral species formed by photodetachment. By performing this experiment on a series of clusters ArnI, for example, one learns how the stepwise solvation of the halide ion affects the anion and neutral energetics and spectroscopy. We have measured ZEKE spectra of ArnC1, ArnBr, ArnI, and XenI clusters. In all cases, we obtain high quality intermolecular potentials for the diatomic neutral and anionic i.e. n1 clusters, and learn about the how the spin-orbit levels of the neutral halogen atom are perturbed by the rare gas atom. We have also performed stimulated Raman pumping in C2, the first such observation for a molecular negative ion.