The energetics and dynamics of free radicals, ions, and clusters. Progress report, August 1, 1991--March 31, 1992

Abstract

The structure and energetics of free radicals, ions, and clusters have been investigated by photoelectron photoion coincidence (PEPICO) and analyzed with ab initio molecular orbital and statistical theory RRKM calculations. In these experiments, molecules are prepared in a molecular beam so that their internal as well as translational energies are cooled to near O K. The coincidence condition between energy analyzed electrons and their corresponding ions insures that the ions are energy selected. The primary experimental information includes ionization and fragment ion appearance energies, and the ion time of flight (TOF) distributions. The latter are obtained by using the energy selected electron as a start signal and the ion as the stop signal. These types of experiments allow us to measure the ion dissociation rates in the 10{sup 4} to 10{sup 7} sec {sup {minus}1} range. Such ions are commonly referred to a metastable ions. In addition, the TOF peak widths are related to the release of translational energy in the ion dissociation process. Perhaps the most important advance during the past year has been in the study of cluster photoionization. We have developed an experimental method for differentiating similar mass cluster ions based on the kinetic energy of the ions measured by TOF.