He3-Limited Drift of Charge Carriers in SuperfluidHe4(0.3<T<1.0°K)

Measurements were made of the mobility of positive and negative charge carriers in ${\mathrm{He}}^4$, for ${\mathrm{He}}^3$ impurity concentrations ranging from 10 to 1800 ppm and temperatures in the range $0.3<T<\mathrm{}1.0\mathrm{}°$K. The excess inverse mobility $\frac{e}{\mu }-\frac{e}{{\mu }_0}$ was everywhere found to vary linearly with concentration, as expected. For negative carriers, the data are well explained by a hardsphere scattering model with a collision radius of 21 Å. For positive carriers, the polarization-deficit potential proposed by Bowley and Lekner gives reasonable agreement with experiment, provided a collision radius of 7.0 Å is assumed.