Structure and forces in expanded liquid cesium

The paper presents a neutron diffraction investigation of the static structure factor S(Q) of liquid cesium expanded by heating toward conditions close to its liquid-vapor critical point. The experiment was designed to obtain the isothermal density derivative of 5(Q) which is related to the triplet correlation function. The data give the first information on the density-dependent changes in the interatomic forces as the metal-nonmetal transition is approached in the expanded liquid. In particular, the results provide direct experimental evidence for the limitation of the uniform fluid model.