Calculation of the inelastic-light-scattering spectrum in He4 in the two-body approximation

We describe calculations of the inelastic-light-scattering spectrum for frequencies of the order of up to several times the roton frequency. The calculations are based on the two-body approximation in a theoretical description of the fluid due to Manousakis and Pandharipande. On the basis of earlier results we calculate only the contribution arising from quasiparticle anharmonicities in the spectrum and take full account of the strong dependence of the three-quasiparticle coupling on the magnitudes and directions of the momenta of the quasiparticles, which is implied by the two-body approximation. The results are compared with recent experimental results. At high energies, the calculated spectrum is in most respects consistent with the experimental one. We discuss the possible origins of the remaining discrepancies.