Ground-State Energy of LiquidHe3and LiquidHe4: Evaluation from the Sound-Propagation Data

Recent measurements on the pressure dependence of the sound velocity $c\left(P\right)\mathrm{}$ in liquid ${\mathrm{He}}^3$ and liquid ${\mathrm{He}}^4$ are employed for deriving the ground-state energy of these liquids as power series in the parameter $\frac{(\rho -{\rho }_0)}{{\rho }_0}$, where $\rho$ is the density of the liquid while ${\rho }_0$ is the value of $\rho$ at saturated vapor pressure. Results thus obtained are compared with the corresponding ones derived theoretically. The existence of an almost linear relationship between the variables $c$ and $\rho$, as observed by Aziz et al. on one hand and by Abraham et al. on the other, is discussed.