The isotope shifts in the resonance lines 4${\mathit{s}}_{1/2}$→4${\mathit{p}}_{1/2,3/2}$ in Ca ii have been measured for the isotopes ${}_{}{}^{40\mathrm{-}48}{}_{}{}^{}\mathrm{Ca}$ by fast-ion-beam collinear laser spectroscopy. Atomic many-body perturbation theory was then used to calculate the electronic factor for the field shift, giving F=-285(3) MHz/${\mathrm{fm}}^2$. The estimate of the uncertainty in F is based on the agreement at the level of 1% for the 4s and 4p hyperfine structures obtained using the same wave functions which include core polarization and pair correlation to all orders. The theoretical value is in excellent agreement with the result F=-283(6) MHz/${\mathrm{fm}}^2$ obtained from a King-plot procedure combining the experimental isotope shifts with earlier data. In combination with the electron scattering data for the isotope pair ${}_{}{}^{40,48}{}_{}{}^{}\mathrm{Ca}$, the present results are used to extract a set of δ〈${\mathit{r}}^2$〉 values for all the isotopes, independent of the muonic data and earlier optical isotope-shift measurements.

• Received 25 October 1991

DOI:https://doi.org/10.1103/PhysRevA.45.4675