STUDY OF POLYCYCLIC AROMATIC-HYDROCARBONS IN THE SOLID-STATE BY COLLISION ENERGY-RESOLVED PENNING IONIZATION ELECTRON-SPECTROSCOPY

He(2(3)S) Penning ionization electron spectra (PIES) of chrysene (C18 H12), perylene (C20H12), and coronene (C24H12) in the solid state were studied. Collision energy dependence of partial ionization cross-sect ions (CEDPICS) of solid state samples was measured for the first time. The CEDPICS of those samples shows positive and negative slopes depen ding on the final ionic states. As common features, negative CEDPICS f or pi bands and positive CEDPICS for a bands were observed. This indic ates that the interactions between He(2(3)S) and those aromatic hydro carbons are attractive in the region where pi orbitals extend and are repulsive around the hydrogen atoms. (C) 1998 Elsevier Science B.V.