Effects of multiple ionization and intrashell coupling in L-subshell ionization by heavy ions

L-subshell ionization cross sections are extracted from measured Lα, Lβ, Lγ, Lγ₁, Lγ₂₃, and Lγ₄₄ x-ray production cross sections in thin targets of ₇₅Re, ₇₈Pt, and ₇₉Au bombarded by 4–8 MeV C³⁺ ions. For each projectile energy, using the fluorescence and Coster-Kronig yields recently recommended by Campbell with an amendment for multiple ionization effects, a mutually consistent set of ionization cross sections is extracted from Lα and six pairs of other L-line x-ray production cross sections. Extracted L₁-, L₂-, L₃-ionization cross sections are compared with the predictions of the ECPSSR theory—which accounts for the energy (E) loss and Coulomb (C) deflection of the projectile as well as for perturbed-stationary state (PSS) and relativistic (R) nature of L subshells—and its modification, ECUSAR-IS. In the ECUSAR-IS theory, the PSS effect is calculated with a united and separated atom (USA) treatment and the intrashell (IS) coupling is accounted for by multiplicative factors of Sarkadi and Mukoyama normalized so that the sum of L-subshell ECUSAR-IS cross sections equals ECUSAR L-shell ionization cross section without the IS correction. Further improvement of this theory to account for better wave functions in its evaluation is made by scaling it with ratios of Dirac-Hartree-Slater cross sections to the screened hydrogenic formulas used in the ECPSSR theory. Very good agreement is obtained with L₂ and L₃ ionization data. For the L₁ subshell, the data are in good agreement with the ECPSSR theory but are by factors of 2 to 3 above the results of its modifications.