L-shell ionization studies of Pb and Bi with alpha particles.

Abstract

Ionization cross sections for the L subshells of Pb and Bi by \ensuremath{\alpha}-particle bombardment (2.2--8.2 MeV) have been determined from the experimental data and the currently available radiative transition probabilities, fluorescence yields, and Coster-Kronig factors. The measured ionization cross sections and their ratios are compared with the results of ECPSSR calculations [ECPSSR denotes perturbed-stationary-state (PSS) theory with energy-loss (E), Coulomb deflection (C), and relativistic (R) corrections]. The measured individual cross sections for ${\mathit{L}}_{1}$ and ${\mathit{L}}_{2}$ subshells deviated in opposite directions from the theory, whereas their sum shows good agreement. The ${\mathit{L}}_{3}$ and total ionization cross sections obtained from the data also show good agreement with the ECPSSR theory. The ionization cross-section ratios ${\mathrm{\ensuremath{\sigma}}}_{\mathit{L}1}$/${\mathrm{\ensuremath{\sigma}}}_{\mathit{L}2}$ and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{L}3}$/${\mathrm{\ensuremath{\sigma}}}_{\mathit{L}2}$ show large deviations from the ECPSSR theory. The experimental x-ray production cross-section ratios are found to be in better agreement with the theoretical results obtained from using ECPSSR ionization cross sections and the decay yield data of Xu and Xu [J. Phys. B 25, 695 (1992)] rather than those obtained from using the decay yield data of Krause [J. Phys. Chem. Ref. Data 8, 307 (1979)]. The x-ray production cross sections, however, are in better agreement with the theoretical results obtained from using the decay yield data of Krause. The measured centroid energy of the L\ensuremath{\gamma} lines of Pb shows large deviations at high projectile energy, whereas for Bi large deviations are found at the low-energy region.