Isotope shifts of $K$ x-ray transitions have been measured in several isotopes of Gd, Dy, Er, and Hf. The results of these observations, together with results of previously communicated measurements on Sn, Nd, Sm, W, Hg, Pb, and U, have been analyzed in terms of even nuclear charge moments. The dominant moment $\delta 〈r^2〉$ is listed for 26 isotope pairs. A comparison of the x-ray shifts with the optical isotope shifts furnishes in several cases the optical specific mass shifts. The difficulties of comparison with muonic x-ray isotope shifts are discussed.

• Received 8 July 1969

DOI:https://doi.org/10.1103/PhysRev.188.1919