Mobility of Positive and Negative Charges inHe3at the Critical Point

Measurements of the mobility of positive and negative charges in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ critical region are reported. The experimental data show that for the two probes there is a definite lowering of the mobility at the critical point. However, within the limits of our approach to the critical point ($\frac{\Delta T}{T_c}\simeq 6\times {10}^{-4\mathrm{}}$; $\frac{\Delta p}{p_c}\simeq 3\times {10}^{-5\mathrm{}}$), no evidence of dramatic decrease in the mobility is observed. The decrease in the mobility is $\approx 30\%$ for either probes; however, the influence of the critical phenomena on the shape of the mobility curve differs for the two probes probably because the positive and negative carriers differ in their effective radius. Some indication of the correct value of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ critical temperature is also reported.