Collision-energy-resolved penning ionization electron spectroscopy of p-benzoquinone: Study of electronic structure and anisotropic interaction with He*(2³S) metastable atoms

The electronic structure of p-benzoquinone (PBQ) was analyzed on the basis of anisotropic interaction around the molecule and the anisotropic electron density distribution of molecular orbitals (MO) to be ionized. The different collision energy dependence of partial Penning ionization cross sections (CEDPICS) upon collision with metastable atoms was used for the study. Attractive interactions were found for in-plane and out-plane directions, while repulsive interactions were found around CH bonds and the benzenoid ring. An extra band that shows negative CEDPICS was observed in Penning ionization electron spectrum.