M-shell x-ray production cross sections in Pb have been measured using 58-82 MeV Ni q+ (q = 5, 6) ions and those in Bi by 1-5 MeV protons and 58-82 MeV Ni q+ ions (q = 5, 6). The experimental results have been compared with the predictions of the planewave Born approximation (PWBA) and with the calculations of the perturbed stationary state theory (ECPSSR) accounting for the energy loss (E), Coulomb deflection (C) and relativistic (R) effects. The present results of proton impact on bismuth have also been compared with the experimental data available from other investigations. To the best of our knowledge, the M-shell x-ray production cross sections in Pb and Bi by Ni-ion impact are reported here for the first time. Good agreement of the present results with the predictions of the ECPSSR theory has been observed for the total M x-ray cross sections in Bi due to proton impact while discrepancies to a factor of 1.5-2.5 in the case of total M x-ray cross sections have been observed between the present experimental and theoretical (PWBA and ECPSSR, respectively) results for Pb and Bi in the case of Ni-ion impact. These discrepancies between the experimental and theoretical results could be attributed to the effect of multiple ionization on the x-ray emission probabilities. If the modified value of the average fluorescence yield accounting for the outer-shell multiple ionization is used, the theoretical results of total M-shell x-ray cross sections based on the PWBA theory show fair agreement with the experimental results (within experimental uncertainties) while the ECPSSR theory is found to underestimate the experimental results by about 40% for both Pb and Bi in the case of Ni-ion impact. Furthermore, the Mαβ, Mγ and (M 3 O 1,4,5 + M 2 N 4 ) x-ray cross sections have been evaluated experimentally for both Pb and Bi. The comparison of these results with the corresponding theoretical estimates have been done only for Pb as the emission rates for various M x-ray transitions of Bi are not available in the literature. The comparison of the Mαβ cross sections show fair agreement with the PWBA-based theoretical values, while there are discrepancies of a factor of 10 and 20 in the cases of Mγ and (M 3 O 1,4,5 + M 2 N 4 ) x-ray transitions.

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Abstract. The L X-ray production cross sections in gold by 60 to 72 MeV 0 5 ÷ ions and 58 to 87 MeV Ni s-t-ions have been measured. The L-subshell ionization cross sections derived from these experimental results have been compared with the direct ionization theories viz. plane wave Born approximation (PWBA) theory and modified perturbed-stationary-state theory with energy loss, Coulomb deflection and relativistic effects (MECPSSR). A new procedure has been described to account for the

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