Characteristic X-Ray Production in theMShell ofNd60,Sm62,Gd64,Tb65,Dy66, andHo67by 25- to 100-keV Protons

Characteristic $M$-shell x rays produced when protons of 25- to 100-keV energy are stopped in thick targets of ${}_{60}{}^{}{}_{}{}^{}\mathrm{Nd}$, ${}_{62}{}^{}{}_{}{}^{}\mathrm{Sm}$, ${}_{64}{}^{}{}_{}{}^{}\mathrm{Gd}$, ${}_{65}{}^{}{}_{}{}^{}\mathrm{Tb}$, ${}_{66}{}^{}{}_{}{}^{}\mathrm{Dy}$, and ${}_{67}{}^{}{}_{}{}^{}\mathrm{Ho}$ have been observed by proportional-counter detection. The energy of the x rays ($M_a$) varied from 980 to 1360 eV. The quantities obtained in the experiment were the thick-target yields (x rays per proton) and estimates of the x-ray production and ionization cross sections. With a fluorescence yield of 0.01, the ionization cross sections fall between ${10}^{-24\mathrm{}}$ and ${10}^{-21\mathrm{}}$ ${\mathrm{cm}}^2$.