4f sigma excitation in slow Kr-Kr and Kr-Xe collisions

Krypton L-shell vacancy production in slow Kr-Kr and Kr-Xe collisions has been investigated both experimentally and theoretically. Impact-parameter-dependent vacancy production rates have been obtained for 0.7 to 3.0 MeV Kr-Kr collisions and for 0.7 to 1.4 MeV Kr-Xe collisions by performing ion-x-ray coincidence measurements. Absolute total Kr L cross sections have been determined for 0.7 to 3.0 MeV Kr-Kr collisions. The experimental data of the present work as well as the total cross sections measured previously by earlier workers have been theoretically analysed. Model calculations have been performed for 4fσ excitation via 4fphi-4fdelta-4fπ-4fσ rotational coupling and for direct 4fσ ionisation. The theoretical results corresponding to rotationally induced 4fσ excitation are in good agreement with the experimental data for collision energies below about 2 MeV. (author)