Behavior of Ions and Quantized Vortex Rings of Low Energy in Helium II around 0.3°K

Quantized vortex rings of low energy down to 0.1 eV have been produced in specially purified liquid helium at 0.3°K and the deflection of rings of 0.15- to 0.5-eV energy in a transverse magnetic field measured. In the same apparatus the Hall mobility of positive ions has been measured at 0.3°K, yielding after extrapolation to zero electric field a value $\mu =3.0\mathrm{}\times {10}^4$ ${\mathrm{cm}}^2$ ${\mathrm{V}}^{-1\mathrm{}}$ ${\sec }^{-1\mathrm{}}$. The drift velocity of ions can reach 40 m ${\sec }^{-1\mathrm{}}$ before vortex rings are produced, also at 0.3°K.