X-ray Compton scattering measurements have been carried out for fluid rubidium (Rb) from near the melting point up to the critical regions. The electron kinetic energy (KE) was derived from the valence Compton profiles and its relative variation as a function of the fluid density was compared with that of the electron gas model. Reduction in the KE occurs more slowly than that predicted by the model as the fluid density decreases and an apparent deviation in the KE from the model is observed at the densities where the fluid is still metallic. These findings suggest that a fluctuation intrinsic to the low-density electron gas causes charge inhomogeneity in valence electrons in real fluid rubidium, being coupled with ionic density fluctuations.
We have measured the momentum distribution and renormalization factor Z k F in liquid and solid lithium by high-resolution Compton scattering. High-resolution data over a wide momentum range exhibit a clear feature of the renormalization and a sharp drop of momentum densities at the Fermi momentum k F. These results are compared with those computed by quantum Monte Carlo simulation performed both on a disordered crystal and a liquid exhibiting very good agreement. Asymptotic behavior of the experimental and theoretical momentum distributions are examined to estimate Z k F. The experimentally obtained Z k F = 0.43 +0.11 −0.01 for liquid Li and 0.54 +0.11 −0.02 for solid Li are in good agreement with theoretical results of 0.54 ± 0.01 and 0.64 ± 0.01, respectively.
The dynamic structure factor S(Q, E), where Q and E are momentum and energy transfer, respectively, has been measured for liquid Sb, using inelastic x-ray scattering. A modified damped harmonic oscillator model function was applied to analyse S(Q, E) of liquid Sb and also to that of liquid Bi by Inui et al (2015 Phys. Rev. B 92, 054206). The obtained excitation energy was in fairly good agreement with that predicted by ab initio molecular dynamics simulations on these liquid semi-metals. The excitation energy of the longitudinal acoustic mode in liquid Sb and liquid Bi exhibits flat-topped Q dependence whereas the lower excitation energy below the longitudinal acoustic excitation shows Q-gap behaviour. From the viscosity estimated from the Q-gap experimentally obtained, it is inferred that the lower energy excitation arises from the transverse acoustic excitation in the liquids.
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