Deep inelastic neutron scattering from liquid 4He

The author performed an extensive series of high-resolution deep in-elastic neutron-scattering measurements on liquid 4He at a number of high-momentum transfers for several temperatures and densities in both the normal and superfluid phases. The primary goal of these measurements was to obtain information on the momentum distribution of liquid 4He. The shape of the momentum distribution of liquid 2He in the superfluid phase is a fundamental interest since, according to our present theoretical understanding of superfluidity in bulk 4He, a δ-function singularity at p = 0 should exist due to the Bose condensate. A secondary goal, motivated by the momentum-distribution studies, was to investigate the nature of the corrections to the Impulse Approximation, called final state effects (FSE), in deep inelastic neutron scattering from liquid 4He. The observed Compton profiles, whose shape depends on both the underlying momentum distribution and FSE, were analyzed. Results provide strong evidence for a narrow component in the momentum distribution of the superfluid phase corresponding to the Bose condensate