Collective excitations in liquid rubidium

Abstract

The dynamical structure factor $S(q,\ensuremath{\omega})$ 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 $S(q,\ensuremath{\omega})$ in the range of momentum transfer 0.174-2.750 ${\mathrm{\AA{}}\mathrm{A}}^{\ensuremath{-}1}$. For $q\ensuremath{\ge}2.750$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$, both one- and two-relaxation-time Gaussian models reproduce the experimental data very well.