INELASTIC X-RAY-SCATTERING STUDY OF SOLID AND LIQUID LI AND NA

We present the first measurements of the dynamic structure factor of l ithium and sodium in the liquid and solid phases, in the intermediate- q regime. The overall shape of the response function is little changed on melting, implying that it is not determined by the long range orde r of the ion cores. Conversely, fine structure, observed in the Li dat a, disappears on melting, and is attributed to band-structure-induced transitions. At small q, the plasmon lifetime and dispersion remain un changed on melting.