Neutron scattering from liquid mixtures of 3He and 4He

Calculations have been made of the dynamic structure factor S(Q,#betta#) of liquid mixtures of 6%, 12%, 25%, 50% and 75% of 3He in 4He using a polarisation potential theory. The resulting spectra contain two principal features: 4He phonon-roton excitations and 3He quasiparticle-quasihole excitations. It is not however possible to describe the scattering quantitatively without taking account of the interference terms arising in the scattering. The frequencies of the well defined excitations are almost independent of concentration. (author)