Periodic Critical Velocities of Ions in Liquid Helium II. Temperature Dependence

Abstract

The behavior of positive- and negative-ion mobility in liquid helium as a function of the electric-field intensity has been investigated from 1.0 up to 2.3°K. Periodic discontinuities have been observed up to the $\lambda$ point, while within the limits of the present technique no discontinuity has been observed above $T_{\lambda }$. It has been confirmed that the velocity at which the discontinuity occurs is temperature-independent below 1.1°K, but above this point a striking temperature dependence is reported. Various theoretical models proposed to account for this phenomenon around 1°K are discussed, and are found to be unsatisfactory at higher temperatures.