Evidence for multiple scattering effects in the electron mobility in dense argon gas

Abstract

We report measurements of the electron drift mobility in dense argon gas over an extended range of densities, temperatures, and electric fields, supplementing our earlier work. The measurements confirm the validity of the heuristic model we previously developed by introducing multiple scattering effects in the classical kinetic theory description of the electron mobility in a dilute gas. We definitively show that, in the argon gas, because of the particular energy dependence of its electron-atom momentum-transfer scattering cross section, none of the multiple scattering effects we have identified in the past can be neglected if the mobility behavior is to be accurately rationalized over the whole investigated parameter range.

Figures (19)

• Figure 1: Density normalized mobility $\mu N$ as a function of the reduced electric field $E/N$ at $T=177.3\,$K for several densities $N$. From top: $N\, (10^{26}\, \hbox{m}^{-3}) =\,42.9,\,41.3,\,38.6,\,36.0,\,33.2,\,30.9,\,28.3,\,25.7,\,23.1.$ The arrow indicates the reduced electric field strength $(E/N)_\mathrm{max}$, at which $\mu N$ is maximum. ($1\,$mTd$\, = 10^{-24}\,\hbox{Vm}^2$).
• Figure 2: Density normalized mobility $\mu N$ as a function of the reduced electric field $E/N$ at $T=177.3\,$K for several densities $N$. From top: $N\, (10^{26}\, \hbox{m}^{-3}) =\,20.5,\, 18.0,\,15.4,\, 12.8,\, 10.3, \, 7.67, \, 5.10,\, 2.55.$ ($1\,$mTd$\, = 10^{-24}\,\hbox{Vm}^2$).
• Figure 3: Typical electron-atom scattering cross sections Wey88. Solid line: momentum-transfer cross section. Dashed line: total cross section. The Ramsauer-Townsend minimum occurs at an energy $\varepsilon_\mathrm{RT}\approx 230\,$meV.
• Figure 4: Comparison of the density dependence of the experimentally determined energy shift value $E_k$ for several temperatures with the theoretical prediction. The temperatures are: $T=142.6\,$K (triangles), $T=177.3\,$K (diamonds), and $T=199.7\,$K (circles). Solid line: Wigner-Seitz model Eq. (\ref{['eq:ekk0']}).
• Figure 5: Density dependence of the zero-field density-normalized mobility $\mu_0 N$ for $T=199.7\,$K (circles) and for $T=162.7\,$K (replotted anew from Ref. Bor92). Solid lines: prediction of the heuristic model using the theoretical prediction for $E_k(N)$, shown by the line in Fig. \ref{['fig:figure4']}.