Short-Wavelength Collective Excitations in Liquid Rubidium Observed by Coherent Neutron Scattering

Abstract

The short-wavelength collective excitations in liquid rubidium at 320 K have been studied by coherent neutron scattering. For values of $\ensuremath{\kappa}=\frac{2\ensuremath{\pi}}{\ensuremath{\lambda}}$ up to 1.0 ${\mathrm{\AA{}}}^{\ensuremath{-}1}$, clear evidence of propagating modes was found from the shape of the scattering function $S(\ensuremath{\kappa}, \ensuremath{\omega})$ at constant values of $\ensuremath{\kappa}$. This result shows that the existence of such modes does not depend upon either quantum effects or low thermal population of the modes.