Dynamical structure factor of an electron liquid. II

The dynamical structure factor $S(q,\omega )$ of an electron liquid at metallic densities is studied numerically on the basis of the quasi-one-pair excitation approximation obtained in the preceding paper. The spin-averaged local field correction $G\left(q\right)\mathrm{}$ is estimated numerically; the local field correction $C\left(q\right)\mathrm{}$ arising from only spin-antiparallel correlation is also estimated. It is pointed out that inclusion of short-range correlations is important for the quantitative estimation of the energy width of the quasiparticle $\Gamma \mathrm{}\left(p\right)\mathrm{}$ at metallic densities. Owing to the local field corrections and the energy width of the quasiparticle, the cutoff wave number $q_c$ estimated by the present theory is considerably reduced, compared with the random-phase approximation case. The spectral structure in $S(q,\omega )$ is numerically estimated from the wave number much smaller than $q_c$ up to the wave number twice as large as the Fermi wave number. The calculated plasmon dispersion around $q_c$ is in excellent agreement with the observed one for A1 in electron scattering experiments. In the intermediate wave-number region the calculated spectra of $S(q,\omega )$ reproduce distinctly a plasmonlike peak and a broad peak in good agreement with experimental observations. These characteristic features of $S(q,\omega )$ are ascribed to the striking damping effect of one-electron states originating from virtual plasmon emission under the influence of strong short-range correlations at metallic densities.