Structure of the excitation spectrum of liquid [sup 4]He

Results of high-resolution measurements of the inelastic scattering of neutrons from normal and superfluid [sup 4]He are presented. A complicated structure of peaks corresponding to phonon-maxon-roton excitations is observed. At [ital T][lt][ital T][sub [lambda]], the scattering can be described by a narrow peak plus a wide component. The relative intensity of the narrow and wide components in the maxon-roton region follows the temperature dependence of density of the Bose condensate. Above [ital T][sub [lambda]], for the wave vectors [ital q][gt]0.65 A[sup [minus]1], only the wide component exists. In the long-wave region ([ital q][lt]0.65 A[sup [minus]1]), a considerable transformation of peaks with changing temperature occurs as well, although the two-component structure persists in the normal phase.