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

Abstract

In this paper we present the results of a spectroscopic study of the absorption spectra of ethylene and ethylene‐d₄ in liquid argon, liquid krypton, and solid krypton in the spectral region 2000–1400 Å. 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 $\mathrm{N\to V}$ 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.