Excitations in liquid 4He beyond the roton

The dynamic structure factors S(Q,E) for liquid 4He at saturated vapor pressure was measured by inelastic neutron scattering for wave vectors Q between 1.9 and 2.8 angstrom -1. The temperature dependence is studied for Q = 2.3 angstrom -1. The sharp phonon-roton peak gradually disappears with increasing temperature, while the scattering at higher energies is nearly temperature independent. The experimental results are compared with the density-quasiparticle interpretation introduced by Glyde and Griffin, and with a model describing the hybridization with the multiparticle excitations