Penning Ionization — The Outer Shape of Molecules

Important intermolecular interaction processes involving electron transfer, energy transfer, molecular collisions, and chemical reactions take place through a close contact of molecules, since a short-range interaction, such as an exchange-interaction, is responsible for most of the above processes. In order to elucidate such processes, it is interesting and seems almost necessary to study the outer characteristics of molecules by introducing an experimental probe which provides information on the frontier properties of molecules. As shown below in detail, Penning ionization electron spectroscopy (PIES) is a sensitive method for probing electron densities as well as potential energy surfaces at the very frontier of the molecule where the molecule is attacked by the reagent.