COLLECTIVE DYNAMICS OF LIQUID POTASSIUM STUDIED BY INELASTIC NEUTRON-SCATTERING

Dispersion curves of collective excitations have been obtained from th e data on inelastic neutron scattering on liquid potassium at 340 and 550 K for the wave-vector transfer region of 1.0 less than or equal to Q less than or equal to 1.3 Angstrom(-1). Experimental points were de scribed in the frame of a model for longitudinal collective modes. In using the values of model parameters omega(E) and r(O), the shear modu lus and the high-frequency sound velocity have been evaluated. The lat ter seems to exceed the adiabatic sound velocity beyond the hydrodynam ic limit (Q > 0.1 Angstrom(-1)) near the melting point due to the effe cts of shear relaxation. This is the characteristic feature of liquid alkali metals.