Experimental Ion Mobilities in LiquidHe3below 1°K

The low-field mobility of positive and negative ions in liquid ${\mathrm{He}}^3$ was measured using a time-of-flight technique for temperatures between 0.03 and 1°K and pressures of 27.9, 7.5, and less than 0.35 atm. Details of the experimental procedures as well as of the experimental apparatus and its construction are presented. The positive-ion mobility ${\mu }_{+}$ was found to be larger than the negative ${\mu }_{-}$, except at 27.9 atm above 0.3°K, where both are ∼0.036 ${\mathrm{cm}}^2$/V sec. By increasing the pressure, ${\mu }_{-}$ was observed to increase while ${\mu }_{+}$ decreased. Furthermore, ${\mu }_{-}$ was found to be a continuous function of the temperature, reproducible within 1% throughout the entire temperature range of the measurements, whereas ${\mu }_{+}$ presented hysteresis in a temperature range that was dependent on the pressure. Some typical mobility values are: The systematic error involved in the absolute value of the mobility is less than 10%. No theoretical calculation presently available correctly predicts ${\mu }_{-}$ or ${\mu }_{+}$.