MOBILITY OF ALKALI-EARTH IONS IN SUPERFLUID-HELIUM

Alkali earth ions are utilized as microscopic probes in superfluid hel ium to study the roton limited mobility in the kinetic regime. A new i on source was used in the gas phase as well as inside the liquid heliu m (He-4). Drift velocities have been measured as a function of tile el ectrical drift field for He+, Ca+, Sr+, Ba+ and for Mg+ ions. Data for the latter ion were not available so far. The results of recent measu rements fit well into the picture extrapolated from the other ions.