Optical isotopic shifts and hyperfine splittings for Yb

A cw tunable dye laser and atomic-beam techniques were used to determine the splittings and separations of the natural Yb isotopes for the 5556.5-Å, ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}-{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ transition. The resonant scattering was recorded with an instrumental resolution of 7 MHz full width at half-maximum, giving peak separations accurate to ±0.5 MHz. The hyperfine splittings were analyzed to yield values of -0.382(19)% for the hyperfine anomaly and 10.9 GHz/${\mathrm{fm}}^2$ for the field-shift constant; these agree with published values. The optical isotope shifts obtained, along with published electronic and muonic x-ray shifts, were analyzed to yield $\delta 〈r^2〉$ values and a specific mass shift in the range 200-300 MHz. This latter is considerably greater than is normally used for $6s^2-6s6p$ transitions. The model dependence of the isotopic-shift analysis was examined, and the hyperfine anomaly was compared with calculations based on Nilsson wave functions.