Positive-Ion Trapping on Vortex Lines in Rotating He II

Abstract

The direct trapping of positive He ions on quantized vortex lines in rotating He II has been observed at temperatures below 0.7 K. Trapping lifetimes have been measured between 0.1 and 0.7 K, and agree with models of thermal escape and charge loss from vortex motion. An ion radius of 7.7\ifmmode\pm\else\textpm\fi{}0.1 \AA{} is found.