Escape rates of electrons from the surface of liquid helium

Abstract

Electrons on the surface of liquid helium are confined to the plane of the surface by the image potential in the liquid. The confining field can be further increased by an external electric fild normal to the surface. If these potentials are sufficiently weak, electrons can escape from the surface. As an electron moves off of the surface the potential barrier includes additional contributions from the electrostatic field of the electrons remaining on the surface and their correlations. These contributions depend on the electron density. Electrons escape by thermal activation over the barrier at high temperatures and /or small external field. At low temperatures and/or high applied the electrons escape by quantum tunneling. We have measured the escape rate of electrons from the surface of liquid helium as a function of temperature and the electrostatic field normal to the surface. The results show the transition from thermal activation to tunneling and the increase in correlation energy with increasing density.