Low-Temperature Specific Heat of LiquidHe3near the Saturated Vapor Pressure and at Higher Pressures

The specific heat of liquid ${\mathrm{He}}^3$ has been measured near the saturation vapor pressure in the range 0.085°K to 0.75°K, and at pressures up to the melting pressure between 0.12°K and 0.6°K. There is no evidence of a specific heat transition in the range of measurements. Near 0.1°K the specific heat near the saturated vapor pressure appears to tend linearly to zero at 0°K with a slope of 4.0±0.1 cal/mole-${\mathrm{deg}}^2$, providing evidence for regarding ${\mathrm{He}}^3$ as a Fermi liquid near this temperature with an effective excitation mass of (2.00±0.05) × the mass of a ${\mathrm{He}}^3$ atom. Entropies calculated with this linear extrapolation and with the assumption that no transition occurs below 0.085°K agree well with previous evaluations. Measurements at higher pressures show a negative dependence of specific heat on pressure above 0.16°K, but a positive dependence below this temperature, in contradistinction to the case of an ideal Fermi gas.