Kinetic energy of He atoms in liquid He-4-He-3 mixtures

Abstract

Deep inelastic neutron scattering measurements on liquid He-3-He-4 mixtures in the normal phase have been performed on the VESUVIO spectrometer at the ISIS pulsed neutron source at exchanged wave vectors of about qsimilar or equal to120.0 Angstrom(-1). The neutron Compton profiles J(y) of the mixtures were measured along the T=1.96 K isotherm for He-3 concentrations, x, ranging from 0.1 to 1.0 at saturated vapor pressures. Values of kinetic energies <T> of He-3 and He-4 atoms as a function of x, <T>(x), were extracted from the second moment of J(y). The present determinations of <T>(x) confirm previous experimental findings for both isotopes and, in the case of He-3, a substantial disagreement with theory is found. In particular <T>(x) for the He-3 atoms is found to be independent of concentration yielding a value <T>(3)(x=0.1)similar or equal to12 K, much lower than the value suggested by the most recent theoretical estimates of approximately 19 K.