Mobile electrons on a solid hydrogen surface.

We have verified the existence of the mobile electrons on the surface of solid H(2) and reached electron mobilities up to 6.5 m(2)/Vs. We have found that the deposition of a He film on the H(2) surface suppresses the mobility, which in addition shows interesting oscillatory behavior as a function of the film thickness. We explain the decrease in the mobility by the electron scattering from the He gas atoms, the surface waves (ripplons) and from the density fluctuations in the uppermost He monolayer. The scattering from the density fluctuations is a direct measure of K(2), the two-dimensional compressibility of the uppermost He monolayer, and causes the oscillatory behavior of the mobility.