Penning Ionization of Cyclic Ethers by Collision with He*(2³S) Metastable Atoms

Abstract

Penning ionization of tetrahydropyran, tetrahydrofuran, 1,4-dioxane, and 1,3-dioxane upon collision with He*(23S) atoms was studied by collision-energy-resolved Penning ionization electron spectroscopy. In the studied energy range, the interaction potential around the oxygen atoms was found to be attractive and anisotropic depending on the in-plane and the out-of-plane access of He*, in good agreement with model potential calculations. Observed collision energy dependence of partial Penning ionization cross sections can be related to the molecular orbital of which ionization occurs and also to local interaction potentials where the electron distribution of the molecular orbital is mainly exposed to the outside. Effects of attractive interaction potentials around the oxygen atoms were found to depend on the stereochemical surroundings. Enhancement of PIES intensity was commonly found for C2s bands and some πCO bands of studied cyclic ethers. On the basis of these findings, assignments of ultraviolet photoelectron spectra were discussed.