An inelastic X-ray investigation on the collective inelastic dynamics of molten NaCl revealed the remarkable result that the acoustic-like dynamics is similar to the dispersion of liquid sodium. One interpretation could be that the cation movement is decoupled from the anion "background" at high frequencies or equivalent at short wavelengths. This anomalous behaviour should be reflected in the single particle motion of the cations. The aim of the experiment is to determine the Q-dependent broadening of the quasielastic line steming from the sodium diffusion in molten NaBr to confirm the anomalous behaviour of the cations with rising momentum transfer.