K-shell ionization in (0.2–1.75)MeV/u Fe, Co+Cr and Fe+Cu collisions

K-shell ionization cross-sections and mean vacancy sharing probabilities measured in the near-symmetric collision systems Fe, Co, Cu+Cr and Fe+Cu at 0.2–1.75MeV/u energies are reported. Beams of 56Fe, 59Co and 63Cuq+ ions (3⩽q⩽12) delivered by the Van de Graaff tandem accelerator of NIPNE Bucharest were used. The cross-section values have been corrected for multiple ionization in the outer (L,M) shells by using the energy and yield shift method. Mean ionization probabilities per electron in the outer shells have been estimated. Calculations in the Briggs model, using SCA with relativistic hydrogenic wave functions and binding energy corrections, could explain the 2pσ-molecular orbital ionization cross-sections at higher energies (⩾1MeV/u). The vacancy sharing results show that predictions of the two-state coupling Demkov–Meyerhof model are less fulfilled at higher energies (⩾1.5MeV/u).