Electron-mobility and Localization Effects In High-density Ne Gas

We report on the measurements of electron as well as ion mobility in neon gas at low temperature (close to the critical temperature) and up to very high density ( N almost-equal-to 180 X 10(20) cm-3). We have found evidence of localized electron states at densities larger than (90-100 X 10(20) cm-3. The transition from the region of quasifree states to that of coexisting quasifree and localized states takes place in a density range in fairly good agreement with the predictions of a simple bubble model. The mobility data of the quasifree electron are in disagreement with the actual multiple-scattering theory. The detailed calculation of the mean mobility in the high-density region where localization takes place is still an unsolved problem.