O-2(-) ION MOBILITY IN COMPRESSED HE AND NE GAS

We report measurements of the drift mobility of O-2(-) ions in dense H e and Ne gas (in the temperature range 45 < T < 330 K spanning a range of gas densities from dilute gas up to liquid values. Measurements ha ve been carried out by means of the pulsed photoinjection technique. I ons are produced by resonant electron attachment to O-2 impurities. In the low-density region the experimental results show a strong tempera ture dependence, in disagreement with the prediction of classical kine tic theory even though realistic interaction potentials are considered . On the other side of the density range, the ionic mobility in Ne see ms to be explainable in terms of a hydrodynamic model including electr ostriction effects.