We report dynamical calculations for large-$q$ structure functions of liquid ${}^4\mathrm{He}$ at $T=1.6\mathrm{}$ and 2.3 K and compare those with recent MARI data. We extend those calculations far beyond the experimental range $q<~29$ ${\mathrm{\AA }}^{\mathrm{-}1}$ in order to study the approach of the response to its asymptotic limit for a system with interactions having a strong short-range repulsion. We find only small deviations from theoretical $1/q$ behavior, valid for smooth $V.\mathrm{}$ We repeat an extraction by Glyde et al. of cumulant coefficients from data which are invariably very well reproduced. We argue that fits determine the single atom momentum distribution, but express doubt as to the extraction of meaningful final state interaction parameters.

• Received 10 June 1997

DOI:https://doi.org/10.1103/PhysRevB.57.5347