M-shell x-ray production cross sections in thick targets of Ir, Pt, and Pb by 0.4–2.2-MeVHe+4ions

M-shell x-ray production cross sections in thick targets of Ir, Pt, and Pb have been measured for ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions of energy from 0.4 to 2.2 MeV in steps of 0.1 MeV. The cross sections are compared with plane-wave Born approximation (PWBA) calculations and with perturbed-stationary-state calculations with energy-loss, Coulomb deflection, and relativistic corrections (ECPSSR). The present measurements, in general, agree well with the PWBA predictions at all energies, but agree with the ECPSSR theory only at projectile energies ≥1.5 MeV. The M-subshell x-ray cross sections are also calculated by a nonlinear (iterative) least-squares-fitting algorithm by extracting the relative line intensities of the experimentally observed spectra obtained with a Si(Li) detector. The subshell cross sections are compared with the scaled cross sections based on PWBA calculations. Good agreement is obtained for the case of $M_1$, $M_2$, and $M_4$, and a larger deviation is found for $M_3$ and $M_5$. The double nodal structure of the 3s-electron wave functions is confirmed, and the single inflection associated with the 3$p_{3/2}$-electron wave functions is not clearly visible in our data. The M-subshell cross-section ratios for $M_1$/($M_2$+$M_3$), $M_1$/($M_4$+$M_5$), and ($M_2$+$M_3$)/($M_4$+$M_5$) are also calcu- lated, compared with the PWBA and ECPSSR theories, and discussed.