Extravalence molecular excitations in inert matrices

In this paper we present the results of an experimental study of extravalence excitations of molecular impurities in solid rare gases and in molecular host matrices. We report the absorption spectra of methyl iodide, benzene, ethylene, and acetylene in solid Ne, Ar, Kr, Xe, N₂, and CF₄ in thé spectral région 2000-1150 A. Spectroscopic evidence has been obtained for the observation of high (n -42) Wannier impurity states originating from a molecular positive ion. These molecular Wannier series yield spectroscopic information concerning the energetics of molecular photoionization in a dense medium. The large blue spectral shifts of the lowest extravalence molecular excitations in dense media can be rationalized in terms of central cell corrections to the n = \Wannier state, which are determined by the exciton binding energy.