Plasmons in Liquid Rb at Elevated Temperatures Studied by Inelastic X-ray Scattering

Inelastic X-ray scattering measurements have been carried out to investigate the energy and line width of plasmons in liquid Rb at elevated temperatures (300 and 500 °C). The plasmon energy decreases with increasing temperature, which can reasonably be explained by the decrease in valence electron density. However, the plasmon energy takes values lower than those predicted from the electron gas model. We calculate plasmon energies in the long-wavelength limit under these conditions and show that an effect of ionic structure, which is described by the liquid structure factor, is essential to reproduce the experimental results. We calculate the plasmon line widths and compare them with the experimental values, which also indicates the importance of the effect of ionic structure.