L-subshell ionization of heavy elements by carbon and nitrogen ions of energy 0.4–1.8 MeV/amu

L-shell x-ray production and subshell ionization cross sections have been measured for 0.4–1.8-MeV/amu carbon and nitrogen ions for selected heavy elements with 72≤${\mathit{Z}}_2$≤90. The results are compared with the predictions of the ECPSSR theory [perturbed-stationary-state (PSS) theory with energy-loss (E), Coulomb deflection (C), and relativistic (R) corrections] describing both direct ionization and electron-capture processes and the semiclassical approximation (SCA) calculations for direct ionization. For both theories significant deviations are found for ${\mathit{L}}_2$-subshell ionization in the low-energy range. The multiple ionization of outer shells was studied by comparing L x-ray intensity ratios measured for heavy ions and protons. The ionization probabilities of the ${\mathit{N}}_4$ subshell at zero impact parameter was extracted from these data. Measured ionization probabilities are compared with the predictions of the SCA theory and the ‘‘geometrical model.’’ The influence of multiple ionization on the measured L-subshell cross sections is discussed.