Mobility of O2− ions in supercritical Ar: Experiment and molecular dynamics simulations

A new analysis and new molecular dynamics (MD) simulations of the measurements of the mobility [mu]i of O2- ions in dense supercritical Ar gas are reported. [mu]i shows a marked dependence on the distance from the critical temperature Tc. A mobility dip appears as a function of the gas density and its maximum value occurs below the critical density. The locus of points of maximum mobility dip in the P-T plane appears on the extrapolation of the coexistence curve into the single-phase region. MD simulations quantitatively reproduce the mobility dip near Tc.