Delocalisation of electrons in dense helium gas by external electric field

Abstract

A theory of the sharp increase of the electron mobility as a function of the external field in dense helium gas is proposed. Low mobility of thermalised electrons is shown to be caused by their localisation in bubbles. Free electrons as well as bound ones are supposed to exist in the gas. As the external field increases free electrons are heated and redistribution of the numbers of free and bound electrons occurs. The fraction of free electrons and experimentally measured drift velocity rise steeply. In high fields the drift velocity attains its gas-kinetic value.