Stochastic dynamics in liquid potassium as explored by polarized neutron scattering

The coherent Sc(Q, ω) and single particle Ss(Q, ω) dynamic structure factors which contribute to the low-energy spectrum of molten potassium are separated by means of neutron polarization analysis. The linewidth and amplitude of the single-particle spectra follow an apparent Fickian behavior with a diffusion coefficient well below the value found by macroscopic means. Once this is accounted for, the results are found to conform with predictions made from kinetic theory. In contrast, the available theoretical recipes to account for the coherent quasielastic intensity are seen to be semiquantitative, at best.