In this project in the Physical Chemistry Program of the Chemistry Division, Prof. Peter Siska of the University of Pittsburgh will study crossed molecular beam reactions involving noble gas atoms with other atoms or diatomic molecules. Specifically, Penning and associative ionization dynamics will be investigated using Penning ionization electron spectroscopy (PIES). Also included are theoretical studies of the scattering of metastable noble gases by atoms and molecules on a state-specific level. %%% When an electronically excited atom A* meets a molecule BC, the atom may lose its energy by a variety of pathways. In some circumstances the loss of the atom's energy results in the ejection of an electron from the intermediate molecular complex, leaving a positively charged ion, which may be ABC+, BC+, or AB+. Such processes are known by the name "Penning ionization" and have been used to elucidate the electronic or molecular structure of large organic molecules, adsorbates on metal surfaces, and even liquid surfaces. These applications are possible because Penning ionization is sensitive to the spatial extent and shape of individual molecular orbitals, that is, the molecule's electron clouds. In this project various reactions involving Penning ionization will be examined in order to answer some basic questions regarding the mechanism by which this process works.
