Electron mobility maximum in near-critical argon gas

Measurements of the drift mobility it of excess electrons in dense argon ga s in proximity of the critical point of the liquid-vapor transition are rep orted. The density and electric field dependence of It at two temperatures fairly close to the critical point, namely T = 162.30 K (T/T-c approximate to 1.08) and T = 152.15 K (T/T-c approximate to 1.01) (T-c = 150.7 K) in a density range (0.5 less than or equal to N less than or equal to 14) atoms. nm(-3) (0.06 less than or equal to N/N-c less than or equal to 1.73), encom passing the critical region of Ar (N-c = 8.08 atoms.nm(-3)), are investigat ed. At the lower temperature a maximum of the zero-field density-normalized mobility mu N-0 was observed at the same density as observed in the liquid . A density-modified kinetic model describes well all features of mu in the gas phase, even at densities comparable to those of the liquid. It is argu ed that the electron scattering processes in the liquid phase can be descri bed in terms of kinetic theory rather than in terms of the usual deformatio n potential model.