抄録
Fluid alkali metals are typical examples of materials whose electronic structures depend strongly on the thermodynamic state of the system. The most striking manifestation of this state dependence is the metal - nonmetal transition which occurs when the dense liquid evaporates to the dilute vapour or when the fluid is expanded by heating to its liquid - vapour critical point. The paper discusses equation of state data, electrical, and optical properties, and neutron scattering measurements of S ( Q) and S ( Q, ω) with special emphasis on the change in these properties in the metal - nonmetal transition region. The shape of S ( Q, ω) changes considerably on approaching the transition from the high - density liquid side, indicating a change in the interparticle interaction and the molecular structure. S (Q, ω) of rubidium in the density range between the melting point density and three times the critical density is characterized by the existence of well defined acoustic - phonon - like collective density excitations at high momentum transfer, whereas S (Q, ω) at a density of about twice the critical density is consistent with excitations of an optic - type mode in which two species tend to move in opposite directions.
