Neutron inelastic scattering from liquid helium three

Abstract

The neutron scattering from liquid helium 3 at 0.63K, and at its saturated vapour pressure, has been measured using the IN5 time-of-flight spectrometer situated on the cold source of the high flux reactor. The measurements, which cover momentum transfers between 1.0 and 2.5 AA^-1 and energy transfers between 0.5 and 4.0 meV, show that the scattering has a broad spectrum without the well defined excitations found in superfluid liquid ⁴He. The maxima of the spectra are at energies of less than 1.0 meV for wavevectors below 1.8 AA^-1 but then increase in energy to 3.0 meV at the largest wavevector transfers. The results are compared with calculations based on variants of the random phase approximation. The comparison suggests that it is necessary to include in the calculation the self-energy of the single-particle states and the effect of the multi-particle excitations.