Collision energy resolved Penning ionization electron spectroscopy of p-penzoquinone

Kohji Okamura, Hideo Yamakado, and Koichi Ohno
(Department of Chemistry, Graduate School of Science, Tohoku University)

In order to probe anisotropic interaction potentials between target molecules and metastable He*(23S) atoms, we have measured collision energy dependence of partial Penning ionization cross sections upon collision with He*(23S). We have studied p-benzoquinone as a target molecule, whose assignment of the ultraviolet photoelectron spectra were studied by many investigators. The unambiguous assignment only for the most loosely bound electrons is proposed by D. Dougherty and S. P. McGlynn, that is based on the vibronic characteristics of the various ionization events and on the differential sensitivities of these events to chemical substitution on the benzenoid ring. In the present work we make an empirical assignment of the whole region of the HeI photoelectron spectra of p-benzoquinone by comparing with conjugated carbonyl compounds (acrolein and maleic anhydride) of which anisotropic interaction potentials had been investigated in our previous work.