Energy shifts ofKx-ray lines for different chemical compounds of Ru, Pr, and Yb

The energy shifts of $K{\alpha }_2$, $K{\alpha }_1$, $K{\beta }_3$, $K{\beta }_1$, and $K{\beta }_2$ x rays were measured for the following Ru, Pr, and Yb compounds: Ru, Ru(C${\mathrm{O}}_2$)${\mathrm{Cl}}_2$, Ru${\mathrm{O}}_2$, [Ru${\left(\mathrm{N}{\mathrm{H}}_3\right)}_4$OHCl]Cl · 2${\mathrm{H}}_2$O, and Ru${\mathrm{F}}_3$; Pr, Pr${\mathrm{C}}_2$, ${\mathrm{Pr}}_2$ ${\mathrm{O}}_3$, PrFe${\mathrm{O}}_3$, ${\mathrm{Pr}}_6$ ${\mathrm{O}}_{11}$, Pr${\mathrm{O}}_2$, CsPr${\mathrm{F}}_5$, and ${\mathrm{Cs}}_2$Pr${\mathrm{F}}_6$, Yb, Yb${\mathrm{F}}_3$, and ${\mathrm{Yb}}_2$ ${\mathrm{O}}_3$. The results are compared with free-ion relativistic self-consistent-field calculations. The measurements bear out the dominant role of the $4f$ electrons in energy shifts between the trivalent and tetravalent Pr and the divalent and trivalent Yb. In Yb the full free-ion value is observed, while in Pr the free-ion value appears to be attenuated by a factor of 0.4, presumably owing to covalency. In all cases the relation of the x-ray energy shift to the Mössbauer isomer shift is discussed.