Rings among the rotons : measurements of the vortex nucleation rate for negative ions whose drift velocities are limited by roton emission.

Allum, D. R. and McClintock, Peter V. E. (1978) Rings among the rotons : measurements of the vortex nucleation rate for negative ions whose drift velocities are limited by roton emission. Journal de Physique, Colloq. pp. 174-175. ISSN 0302-0738

Abstract

We have measured vortex ring nucleation rates nu for negative ions moving in He II under the influence of electric fields 0.8 < E < 12 kV/cm, for temperatures 0.4 < T < 0.6 K and a pressure of 25 bar. For E > 5 kV/cm, the experimental data are well described by a theory due to Bowley. An anomalous dependence of nu on T found at lower lower E is attributed to the influence of isotopic impurities.