Possible influence of thermal rotons on vortex nucleation by negative ions in pressurised He II below 1K

Abstract

A new technique has been developed for measuring the nucleation rate nu of negatively charged vortex rings in HeII when the temperature T, pressure P and electric field E are such that the bare-ion drift velocity is limited principally by roton emission. For P=25 bar, E=7.9*10⁵ V m^-1 and 0.77 exp(-6.2/T) was obtained, which suggests that the magnitude of nu may be closely related to the thermal roton density.