Ultraviolet photoelectron spectra of tetrahalogeno-p-benzoquinones and hexahalogenobenzenes in the solid state

Abstract

The electronic structures of tetrahalogeno-p-benzoquinones and hexahalogenobenzenes (C₆X₄O₂ and C₆X₆; X = Cl, Br and I) in the solid state were studied by means of ultraviolet photoelectron spectroscopy. The spectra of the chloro- and bromo-compounds resemble each other, while those of the iodo-compounds are different; these results suggest that the conduction band structures of the iodo-compounds are different from those of the other compounds. The ionization potential of tetraiodo-p-benzoquinone solid is unusually small compared with the value expected of the hexahalogenobenzenes. Its polarization energy is 3.0 eV, which is the largest value observed for organic solids.