Properties ofHe4Near theγPhase

Abstract

The heat capacity of solid ${\mathrm{He}}^4$ was measured at several constant volumes in the vicinity of the $\gamma$ phase. The heat capacity of the $\alpha$ phase near the melting line was found to decrease exceptionally rapidly with decreasing molar volume, and the heat capacity of the $\gamma$ phase was found to increase with decreasing molar volume. The unusual behavior of the $\gamma$ phase is consistent with the existence of anomalous thermal excitations in this phase. The thermal expansion coefficient and the compressibility of the $\gamma$ phase were estimated. Their temperature dependences are consistent with the volume dependence of the heat capacity. The triple-point temperatures and the $\lambda$ temperature at the solid-liquid boundary were found to be 1.462, 1.773, and 1.763°K, respectively.