EXCESS ELECTRON-MOBILITY IN LOW-DENSITY CH3CN GAS - SHORT-LIVED DIPOLE-BOUND ELECTRON GROUND-STATES AS PRECURSORS OF LOCALIZED ELECTRON-STATES

We measured the mobility of excess electrons in the strongly polar ace tonitrile (CH3CN) gas at low densities as a function of density and te mperature by the pulsed Townsend method. We found an unexpected strong density dependence of the ''zero-field'' density-normalized mobility (mu n) that cannot be explained only by different multiple-scattering effects. We propose a transport process where short-lived dipole-bound electron ground states as quasilocalized states are involved. Finally we discuss the experimentally observed anion mobilities as a function of density and temperature according to current theoretical approache s.