Collision-energy-resolved Penning ionization electron spectroscopy of toluene and chlorotoluenes

Abstract

Stereodynamics in ionization of toluene and o-, p-chlorotoluenes by collision with He*(23S) metastable atoms were investigated by two-dimensional collision-energy/electron-energy-resolved Penning ionization electron spectroscopy. Anisotropic interactions around the molecule were studied by the collision energy dependence of partial ionization cross-sections (CEDPICS) as well as model potential calculations, and shielding effect by the methyl group was observed in CEDPICS for ionization from Cl lone-pair orbitals of o- chlorotoluene. Attractive interaction with He*(23S) around the π orbital region was found to be larger for toluene rather than o-, p- chlorotoluenes. Exterior electron density (EED) calculation of partial ionization cross-sections in Penning ionization and negative CEDPICS for ionization band observed in ca. 4 eV in electron energy indicated that π-2π+1 shake-up state was observed in Penning ionization electron spectroscopy of toluene.