Electron mobility in dense Argon gas at several temperatures

We report measurements of electron mobility μ in Ar gas in a range below and above the critical point. μ is measured as a function of the electric field E for densities up to N < 100 × 10²⁶ m^-3, encompassing the critical density (N_c = 80.8 × 10²¹ m^-3), for T=142.8, 152.2, 177.3, and 199.7 K The data confirm the model proposed for the positive density effect observed in the zero-field density-normalized mobility μ₀N in Argon at T=162.7 K We observe that below the critical temperature T_c = 150.9 K the density effect is neither positive nor negative. This is consistent with the observation that at 90 K μ₀N shows a negative effect in contrast with its behavior at room temperature. The modified kinetic-theory model accurately describes the T, N, and E dependence of μN mainly by including a density dependent shift of the ground state energy of the electrons that affects the cross section.