Isotope Shifts ofKX Rays and Variations of Nuclear Charge Radii

The electronic $K{\alpha }_1$ isotope shifts have been studied for the following sets of isotopes: ${\mathrm{Sn}}^{116-124}$, ${\mathrm{Nd}}^{144-150}$, ${\mathrm{Sm}}^{148-154}$, ${\mathrm{Gd}}^{155-156-160}$, ${\mathrm{W}}^{182-184-186}$, ${\mathrm{Hg}}^{200-204}$, and ${\mathrm{Pb}}^{206-208}$. With the help of a curved-crystal spectrometer in the Cauchois geometry the relative wavelengths of fluorescently excited x rays for two enriched isotope samples were measured to a precision of ${10}^{-7\mathrm{}}$. The observed shifts, corrected for the normal and specific mass shifts, were compared with calculated shifts, taking into account the volume effect (adjusted for the dynamic quadrupole interaction), screening by the transition electron, and a term arising from the anomalous magnetic moment. The anomalies previously observed in the optical and muonic shifts are established with good accuracy by the present experiments.