We present high resolution inelastic x-ray scattering measurements of the coherent dynamic structure factor $S(Q,\omega )$ of liquid lithium at momentum transfers $0.36\le Q\le 5{Å}^{-1\mathrm{}}$. The determined $S(Q,\omega )$ agrees much better with molecular dynamic simulations using the neutral pseudo-atom potential rather than the empty core potential. We observe a positive dispersion in the sound velocity confirming that in liquid lithium the longitudinal dynamics reaches a solid-like response at high frequencies.

• Received 5 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.1715