Multiexcitation scattering by superfluid4He

High-resolution inelastic neutron scattering results for the multiphonon component of S(q,ω) for superfluid4He at T=1.35 K at saturated vapour pressure (SVP), 10 bars and 20 bars are presented. The results exhibit marked structure, with numerous sharp features whose intensities and positions depend strongly on momentum transfer and change appreciably with pressure. Some of these features clearly correspond to two-roton, roton-plus-maxon and two-maxon processes.