On the thermodynamics of quantum liquids

The thermodynamic characteristics of liquid 4He and 3He are determined in the temperature range where effects of the particle statistics can be neglected. Experimental data are used to determine the kinetic energies K40(n) and K30(n) of liquid 4He and 3He as functions of density n at T = 0 to an accuracy corresponding to small exchange effects. The potential energies V40(n) and V30(n) are indistinguishable to high accuracy and depend linearly on n. The kinetic energies K are inversely proportional to the atomic mass M, so that K40(n)≅(3/4)K30(n). A diffusion model of quantum nondegenerate liquids is proposed for liquid 4He. A detailed comparison of theory and experiments reveals the existence of quantum scaling. With a suitable temperature scale, it is possible to obtain reduced thermodynamic characteristics of the quantum nondegenerate liquids that depend weakly on the density of the medium and the particle statistics.