Collective excitations in liquid rubidium

Abstract

The dynamical structure factor $S(q,\omega )$ for liquid rubidium obtained from recent neutron inelastic scattering experiments as well as from molecular dynamics calculations has been analyzed on the basis of Mori's memory-function approach. It has been found that the double Gaussian memory function with two distinct relaxation times gives an excellent representation of the experimental data on $S(q,\omega )$ in the range of momentum transfer 0.174-2.750 ${\mathrm{\AA }\mathrm{A}}^{-1\mathrm{}}$. For $q\ge 2.750$ ${\mathrm{\AA }}^{-1\mathrm{}}$, both one- and two-relaxation-time Gaussian models reproduce the experimental data very well.