Roton-Limited Mobility of Ions in SuperfluidHe4

Abstract

We calculate the roton-limited mobility of ions in superfluid ${\mathrm{He}}^4$ for temperatures below ∼ 1.7°K. Taking, as a first approximation, a constant ion-roton transition-matrix element, which we treat as an adjustable parameter, we find good agreement with experiment for both positive and negative ions. This model calculation indicates that the most mobile of the recently discovered "exotic" negative carriers is a very light ion.