Localized states in disordered mercury-xenon mixtures

Abstract

Optical absorption spectra in the energy range 2.0–5.5 eV have been obtained for thin films of Hg/Xe mixtures at 6 K in the concentration range X = 0.01–0.40 atomic fraction Hg. At low concentrations (X = 0.01–0.20) the films exhibit well-defined absorption peaks corresponding to trapped single Hg atoms and to Hg₂ diatomic molecules. A gradual transition to continuous absorption extending to low energies, which is due to larger molecular clusters, is exhibited at higher (X ≥ 0.10) metal concentrations. Charge-transfer excitations of the clusters account for the low-energy absorption tails.