Neutron investigation of the ion dynamics in liquid mercury: Evidence for collective excitations

The ion dynamics of liquid mercury was investigated by inelastic neutron scattering. By exploiting an optimized high-resolution (?1 meV) experimental configuration, the dynamic response function was accurately measured. Collective excitations extending up to 0.6 Å21 were observed with an associated velocity of 2100 6 80 m?s. This value is notably greater than the sound velocity, but it is provided by a simple Bohm-Staver calculation. The latter finding emphasizes those electron-related features in the ion dynamics, which are common to systems as different as polyvalent and alkali metals.