Optical transitions for 2D electrons at the solid hydrogen – vapor interface

Details of the problem of “vertical” transitions between discrete levels of 2D electrons on the surface of liquid (solid) dielectrics in the presence of a gas over this surface (their own vapors or artificially produced combinations such as solid hydrogen-gaseous helium) are discussed. The structure of the interaction of an electron with a gaseous medium, where the so-called scattering length appears to depend on the gas density, is determined. The role of Van der Waals forces, which attract gas atoms to the dielectric surface, is shown. A notion of quasi-2D electron bound states on gas atoms is introduced. The experimental data concerning the effect of the gas on the frequencies of optical transitions for 2D electrons over the surface of solid hydrogen are discussed using this information.