Inelastic X-ray scattering determination of the dynamic structure factor of liquid lithium

We present new inelastic X-ray scattering data for the dynamic structure fa ctor S(Q,omega) of liquid lithium collected at two different temperatures ( T = 475 K and T = 600 K) and in a wide range of exchanged wave-vectors (Q = 1 nm(-1) to Q = 110 nm(-1)). The analysed Q range covers the transition fr om collective to single-particle regimes. The spectra have been put on an a bsolute scale using its first sum rules, and the result obtained has been t ested on diffraction data and novel molecular dynamic results. A relaxation fingerprint is observed at low wave-vectors (the so-called positive disper sion of the apparent sound speed), while at higher Q the single particle be haviour gradually emerges.