Intravalence and Extravalence Excitations of the Ethylene Molecule in Liquid and Solid Rare Gas Matrices

In this paper we present the results of a spectroscopic study of the absorption spectra of ethylene and ethylene-Ji in liquid argon, liquid krypton, and solid krypton in the spectral region 2000-1400 A. The samples involved 1 cm thick doped liquids and 1 cm thick doped krypton crystal (doping level 1-10 ppm). The intravalence nature of the N→V transition was confirmed. On the basis of some general criteria based on vibrational structure, vibrational isotope effects, matrix shifts, and line broadening we were able to provide a definite identification of the lowest Rydberg state of ethylene and of ethylene-d₄ in solid krypton. The effect of the liquid-solid phase transition on the line broadening in the lowest Rydberg state was elucidated. We were also able to provide the first experimental observation of the n -2 impurity Wannier state originating from the molecular positive ion in liquid argon.