Kx-ray production in H-likeSi13+,S15+,andAr17+ions colliding with various atom and molecule gas targets at low collision energies

Abstract

K x rays have been observed in electron capture processes of H-like ${\mathrm{Si}}^{13+},$ ${\mathrm{S}}^{15+},$ and ${\mathrm{Ar}}^{17+}(1s)$ ions colliding with various atom and molecule gas targets over the collision energy of $1--70$ $\mathrm{keV}/u.$ These K x rays are the final results of cascade-down to the ground ${(1s}^{2})$ state from highly excited states formed through electron capture. It has been found that at low energies $(l10$ $\mathrm{keV}/u)$ the cross sections for the production of K x rays are nearly constant, and decrease slowly when the collision energy is increased. The cross sections also have been found to increase roughly with the inverse square of the ionization energy of the targets. It is also noted that the intensity ratios of the $K\ensuremath{\beta}$ line to the $K\ensuremath{\alpha}$ line increase slightly as the ionization energy of the target increases, suggesting that an electron is captured in different $(n/)$ states in different targets. These ratios are found to decrease slightly as the collision energy increases. The measured K x-ray production cross sections also have been compared with total electron-capture cross sections based upon an empirical formula, and it has been found that, on average, roughly two-third of total electron capture processes result in K x-ray emission, with the remaining one-third ending at the metastable state level after electron capture without emitting K x rays.