Injection and Thermalization of Hot Electrons in Solid, Liquid, and Gaseous Helium at Low Temperatures

Abstract

Thin-film cold-cathode emitters were used to inject electrons into solid helium, liquid helium under pressure, and gaseous helium at 4.2 and 20 °K. The cross section for the interaction of the injected quasifree electrons with the helium was deduced by use of an appropriate model for the thermalization of the electrons, and sundry other parameters of the quasifree state, such as its lifetime and collision frequency of the electron therein, were deduced. The cross section derived is within a factor of 2 of the value for the elastic scattering cross section for the isolated atom. The description of the scattering and thermalization process is dependent only on the helium atomic density and is independent of phase.