Electron mobility and multiple scattering effects in dense methanol gas

The electron drift mobility mu has been measured in sub- and supercritical methanol (CH3OH) gas in the temperature range 393 less than or equal to T less than or equal to 573 K and in the number density range 1.67 x 10(19) less than or equal to n less than or equal to 3.60 x 10(21) cm(-3). The ''zero-field'' density-normalized mobility (mu n) shows a strong density dependence at low gas densities, which cannot be described by the multiple scattering theory for electrons in a disordered medium of polar molecules as given by Polischuk. The anomalous density dependence of mu n can be explained almost quantitatively by taking into account correlations between the dipole scatterers in a nonideal gas. Both effects lead finally to the localization of excess electrons in CH3OH. In connection with these observations, we discuss critically the effect of changes in the electron dispersion law due to the long-range electron-dipole interaction. Finally the observed anion mobilities are briefly discussed in connection with current theoretical approaches.