M-shell x-ray production by 0.6-3.0-MeV 3He+ ions in tantalum, osmium, gold, bismuth, and thorium.

Abstract

M-shell x-ray production cross sections in $_{73}\mathrm{Ta}$, $_{76}\mathrm{Os}$, $_{79}\mathrm{Au}$, $_{83}\mathrm{Bi}$, and $_{90}\mathrm{Th}$ bombarded by $^{3}\mathrm{He}^{+}$ ions of energy 0.6--3.0 MeV are reported. The data are compared with the predictions of the semiclassical and the first-order Born approximations and the calculations of the perturbed-stationary-state (PSS) theory that accounts for energy-loss (E), Coulomb deflection (C), and relativistic (R) effects (ECPSSR). The ECPSSR theory gives the best description of the measured cross sections, although a systematical underestimation of the data is observed in the low-velocity region. For tantalum, uncertainties of the available M-shell Coster-Kronig factors and fluorescence yields are indicated, as they have been noted previously for ${\mathit{Z}}_{2}$\ensuremath{\approxeq}74 elements, bombarded by protons and $^{4}\mathrm{He}$ ions [Pajek et al., Phys. Rev. A 42, 261 (1990); 42, 5298 (1990)]. Using average M-shell fluorescence yields \ensuremath{\omega}${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{M}}$, we have obtained the scaled M-shell ionization cross sections, which were highly universal as a function of projectile velocity scaled to the mean M-shell orbital velocity. Finally, comparing our previously measured M x-ray production cross sections for $^{4}\mathrm{He}^{+}$ ions with the present data for $^{3}\mathrm{He}^{+}$ ions---taken at the same velocities---we try to test a description of the Coulomb deflection effect within the ECPSSR theory.