Coupled-states model calculations of L-subshell ionisation probabilities for Ne on Yb, Pt collisions

The deviation from first-order perturbation theory in the description of the impact parameter dependence of L-subshell ionisation probabilities has been estimated by model calculations for 0.9 MeV amu-1 Ne on Yb and Pt collisions. The applied model takes into account the strong distortion of the L shell by solving a truncated set of coupled equations which describe the time evolution of the L-substate amplitudes. According to the model the subshell couplings lead to a large reduction of the L1-subshell ionisation probabilities, but they alter the L3 probabilities to a lesser extent. As a result the crossing of the probability curves predicted by the relativistic first-order theory at small impact parameters disappears. The possibilities of further improvements in the theoretical description are discussed. (author)