High-resolution laser spectroscopy has been performed on an atomic beam of natural erbium isotopes. The isotope shift in the 582.7 nm transitions [${4\mathrm{f}}^{12}$${6\mathrm{s}}^2$(${\mathrm{}}^3$${\mathrm{H}}_6$)→${4\mathrm{f}}^{12}$(${\mathrm{}}^3$${\mathrm{H}}_6$)66(${\mathrm{}}^3$${\mathrm{P}}_1^0$)J=7] for the pairs of ${}_{}{}^{162}{}_{}{}^{}$,164,166,167,168,170Er I was obtained with an accuracy of about 4 MHz. Relative changes of mean-square nuclear charge radii δ〈$r^2$〉 for these isotopes were thus deduced. The isotope shift in ${}_{}{}^{167}{}_{}{}^{}\mathrm{Er}$, obtained from the well-resolved hyperfine components, shows similar even-odd staggering effect in δ〈$r^2$〉 found in the nearby elements.

• Received 27 August 1986

DOI:https://doi.org/10.1103/PhysRevC.35.1574