ELECTRON-MOBILITY AND MULTIPLE-SCATTERING EFFECTS IN DENSE METHANOL GAS

The electron drift mobility mu has been measured in sub- and supercrit ical methanol (CH3OH) gas in the temperature range 393 less than or eq ual 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(2 1) cm(-3). The ''zero-field'' density-normalized mobility (mu n) shows a strong density dependence at low gas densities, which cannot be des cribed by the multiple scattering theory for electrons in a disordered medium of polar molecules as given by Polischuk. The anomalous densit y 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 criticall y the effect of changes in the electron dispersion law due to the long -range electron-dipole interaction. Finally the observed anion mobilit ies are briefly discussed in connection with current theoretical appro aches.