MULTIEXCITATION SCATTERING BY SUPERFLUID HE-4

High-resolution inelastic neutron scattering results for the multiphon on component of S(q,omega) for superfluid He-4 at T=1.35 K at saturate d vapour pressure (SVP), 10 bars and 20 bars are presented. The result s exhibit marked structure, with numerous sharp features whose intensi ties and positions depend strongly on momentum transfer and change app reciably with pressure. Some of these features clearly correspond to t wo-roton, roton-plus-maxon and two-maxon processes.