MUTUAL ANGLE AND ENERGY-DISTRIBUTIONS NEAR IONIZATION THRESHOLDS FOR ELECTRON-ION COLLISIONS

Angular correlations between the escaping electrons after ionising collisions between an electron and single-, double- and triple-charged hydrogenic ions have been examined in the vicinity of the ionisation thresholds. Numerical investigations indicate, within a restricted classical model, an increasing spread of the mutual-angle distribution with an increase of the ion charge, but do not reveal the total disappearance of all angular correlations for an ion nuclear charge Z>or=3, as predicted by Rau (1971, 1976). The increase in the total spread of the mutual angle with the nuclear charge has been fitted by a Z0.56 power law. Dependence of the angular spread on the total energy has been examined for e-Li2+ and excellent agreement with the analytical prediction of Vinkalns and Gailitis (1967) has been obtained. The final energy distribution generally appears to be uniform. It deviates from this simple behaviour when Z>or=3. The relation between the regular non-uniform distributions and those suggested by Temkin (1974) and Rau has been discussed.