The dynamic structure factor, S(Q,E), of liquid lithium (T=475 K) has been determined by inelastic x-ray scattering (IXS) in the momentum transfer region (Q = 1.4-110 nm-1). These data allow to observe how, in a simple liquid, a phonon-like collective mode evolves towards the single particle dynamics. As a function of Q, one finds: i) at low Q's, a sound mode with a positive dispersion of the sound velocity, ii) at intermediate Q's, excitations whose energy oscillates similarly to phonons in the crystal Brillouin zones, and iii) at high Q's, the S(Q,E) approaches a Gaussian shape, indicating that the single particle dynamics has been reached.
@article{arxiv.cond-mat/9911021,
title = {Phonon-like and single particle dynamics in liquid lithium},
author = {T. Scopigno and U. Balucani and A. Cunsolo and C. Masciovecchio and G. Ruocco and F. Sette and R. Verbeni},
journal= {arXiv preprint arXiv:cond-mat/9911021},
year = {2009}
}