Characteristic X-Ray Production in theMVShell in Ytterbium by 30-100-keV Protons

Abstract

Characteristic $M$-shell x rays produced when protons of 30-100-keV energy are stopped in a thick target of ytterbium were observed by proportional-counter detection. By use of an aluminum absorber, radiation originating from the filling of $M_{\mathrm{V}}$-subshell vacancies can be isolated. Thick-target yields of the $M_{\mathrm{V}}$-shell and $(M_{\mathrm{I}}+M_{\mathrm{II}}+M_{\mathrm{III}}+M_{\mathrm{IV}})$-shell x rays were measured separately. With extrapolated values of the fluorescence yield (0.06), the mass absorption coefficient (1500 ${\mathrm{cm}}^2$/g) and the stopping power, estimates of the ionization cross section for the ${\mathrm{M}}_{\mathrm{v}}$ shell have been made (neglecting contributions from other subshells by Coster-Kroning transitions). These vary from 6×${10}^{-26\mathrm{}}$ ${\mathrm{cm}}^2$ at 30 keV to 2×${10}^{-22\mathrm{}}$ ${\mathrm{cm}}^2$ at 100 keV.