M-shell ionization of atoms by C, N, and O ions

M-shell ionization in selected heavy atoms (Au, Bi, Th and U) by energetic Cq+, Nq+ and Oq+, ions of different charge states (q=1–6) has been studied in the energy range 0.1–2 MeV/amu. The measurements were performed using target thicknesses allowing ion charge equilibration in the target. Derived equilibrium M-shell ionization cross sections are compared with the theoretical predictions based on the semiclassical (SCA) and the PWBA approximations for direct ionization and the OBK approximation for the electron capture, as well as the ECPSSR theory including the corrections for higher-order effects. Substantial contribution of the electron capture caused by the ion charge equilibration is observed for high energies. The influence of the multiple ionization in M-, N- and O-shells on measured cross sections is discussed.