High-Momentum-Transfer Neutron-Liquid-Helium Scattering bose Condensation

Abstract

Neutron inelastic scattering with high momentum transfers was used to probe the single-particle motions in liquid $^{4}\mathrm{He}$ at temperatures ranging from 4.2 to 1.27\ifmmode^\circ\else\textdegree\fi{}K. The observed scattered neutron distributions below ${T}_{\ensuremath{\lambda}}$ are consistent with a two-component model of liquid helium involving condensation into a zero-momentum ground state. A fractional condensate density of (7.4\ifmmode\pm\else\textpm\fi{}1.5)% and an average kinetic energy per particle of 14.1\ifmmode\pm\else\textpm\fi{}0.6\ifmmode^\circ\else\textdegree\fi{}K for helium at 1.27\ifmmode^\circ\else\textdegree\fi{}K is deduced from a comparison of the experimental results with a theory for high-energy neutron-liquid-He scattering.