Magnetic susceptibility of metallic and nonmetallic expanded fluid cesium

Abstract

In this paper the first magnetic-susceptibility results for a fluid metal are reported, which cover a wide range of expansion between the normal melting point and conditions near the critical point. Measurements have been performed for fluid Cs at saturation conditions up to 1680\ifmmode^\circ\else\textdegree\fi{}C and 98 bar, that is 70\ifmmode^\circ\else\textdegree\fi{}C below the critical temperature. In the expanded liquid state, the mass susceptibility first decreases slightly, followed by a strong rise with increasing expansion by almost a factor of 5. A pronounced paramagnetic maximum is observed near 1600\ifmmode^\circ\else\textdegree\fi{}C, corresponding to about double the critical density and a dc conductivity of about ${10}^{3}$ ${\ensuremath{\Omega}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ This susceptibility enhancement indicates that the metal-nonmetal transition in fluid Cs might be of the Mott-Hubbard type. In the nonmetallic-dense-vapor phase, the susceptibility data give direct evidence for the existence of a high amount of diamagnetic molecular associations, like ${\mathrm{Cs}}_{2}$ molecules.