Dynamic structure factor in liquid cesium on the basis of time-scale invariance of relaxation processes

The dynamic structure factor $S(k,\omega)$ in liquid cesium near the melting point at $T=308\,$K is studied by means of Zwanzig–Mori's memory function formalism. The spectra of $S(k,\omega)$ are calculated on the basis of the idea of time-scale invariance of relaxation processes in liquid metals, which appeared on the fourth relaxation level. The obtained spectra of $S(k,\omega)$ are compared with the results of the inelastic neutron scattering measurement. For the description of memory effects we use the statistical presentation about the non-Markovity parameter $\varepsilon_{1}(k,\omega)$. We find that collective excitations at the low wave vector values have a non-Markovian nature.