X-ray determinations of the liquid-structure factor and pair-correlation function ofHe4

Measurements of the intensity of Cu? alpha— x rays scattered from liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ as a function of temperature and pressure are used to determine the liquid-structure factor and pair-correlation function of the fluid. Data are reported for 1.16≤T≤3.5 K at the three densities 150.3, 162.5, and 171.0 kg/${\mathrm{m}}^3$. Earlier data of Robkoff and Hallock are reanalyzed and found to be in excellent agreement with our new results. The temperature dependence of the structure factor at fixed density is in good agreement with predictions based on the thermal population of rotons due to Reatto and co-workers.