Perturbative Form ofS(k,ω)for LiquidHe4: Basic Calculation and Results

Abstract

The dynamic form factor $S(k,\omega )$ for liquid ${\mathrm{He}}^4$ at $T=0\mathrm{}$°K is calculated by a straightforward perturbation technique, and the results are displayed graphically for $k\le 6.0$ ${\mathrm{\AA }}^{-1\mathrm{}}$. The dominant features of the single-excitation and multiphoton contributions are discussed and compared with those observed in neutron-scattering experiments. The reliability and accuracy of the computed form factor is studied with the aid of well-known sum rules and comparison with experimental data.