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

Abstract

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 \ensuremath{\ge}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.