Low-Temperature Heat Capacities of Gallium, Cadmium, and Copper

The heat capacities of gallium, cadmium, and copper have been measured from 0.1 or 0.2°K to 4.2°K. The experimental data for copper suggest that the measurements are accurate to within 3% at 0.1°K and to within 1% at temperatures above 0.2°K. In the superconducting state both gallium and cadmium show the typical deviations from the BCS law of corresponding states. The nuclear quadrupole contribution to the heat capacity of gallium was observed in the normal state but not in the superconducting state. The absence of this contribution in the superconducting state state can be used to set an approximate lower limit of 60 sec for the spin-lattice relaxation time at 0.25°K. For cadmium ${\theta }_0=209.0\mathrm{}\pm 2.3°$K, in reasonable agreement with the value calculated from the elastic constants.