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

We report measurements of the drift mobility of O-2(-) ions in dense He 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 have been carried out by means of the pulsed photoinjection technique. Ionsare produced by resonant electron attachment to O-2 impurities. In the low-density region the experimental results show a strong temperature dependence, in disagreement with the prediction of classical kinetic theory even though realistic interaction potentials are considered. On the other side of the density range, the ionic mobility in Ne seems tobe explainable in terms of a hydrodynamic model including electrostriction effects.