Charge inhomogeneity in an expanded fluid metal: X-ray Compton scattering observation

Abstract

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.

X‐Ray Compton Scattering Study of Liquid Sodium at Elevated Temperatures

“…The that corresponds to each experimental liquid density was derived by the linear interpolation with respect to r s from that at r s = 3.99 and 5, because the r s that corresponds to the experimental condition ranges from 4.09 to 4.42. CPs were derived from these s, as the procedure in the study by Matsuda et al [ 16 ] The CPs were broadened by the experimental momentum resolution and normalized to 1.…”

“…[ 34 ] The valence‐electron profile was derived by subtracting the theoretical core‐electron profiles from the CP. The procedure to derive a valence CP appears the study by Matsuda et al, [ 16 ] which is based on the analysis in the studies by Schülke et al [ 10,35 ] Here, the cutoff momentum was set to 1.0 a.u. beyond which the valence contribution is assumed to be 0.…”

“…We have thus far conducted X‐ray Compton experiments to measure the momentum distributions of electrons in fluid Rb [ 16 ] and observed the width of Compton profiles narrowed with volume expansion at a relatively higher density range (≈3.5 ρ c ), reflecting the decrease in the Fermi momentum, which is given by ( n denotes the electron density) in the electron gas model. [ 17 ] With further volume expansion, the observation revealed the narrowing of Compton profile was saturated, which leads to the discrepancy between the experimental Compton profile and that of the electron gas.…”

“…The observation indicates the existence of charge inhomogeneity in the spatial distribution of valence electrons in the fluid, being coupled with ionic density fluctuations. [ 4,16 ]…”

“…Motivated by these backgrounds and the previous observations for fluid Rb, [ 16 ] we have extended the measurements to other alkali element Na. In this article, we report the results of X‐ray Compton scattering experiments of liquid Na at elevated temperatures up to 1273 K.…”