Isotope shifts and hyperfine structure of the4s2S01−4s4pP11transition in calcium isotopes

Isotope shifts and hyperfine structure splittings of the CaI resonance line ($4s^2{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-4s4p{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$, $\lambda =422.7\mathrm{}$ nm) have been measured for all calcium isotopes between ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, including the short-lived isotope ${}_{}{}^{47}{}_{}{}^{}\mathrm{Ca}$ ($T_{\frac{1}{2}}=4.54\mathrm{}$ d). Resonance fluorescence was observed in a well-collimated atomic beam of calcium excited by a narrow band tunable continuous-wave dye laser. Combining the result with muonic x-ray data for the stable isotopes, accurate values for the changes of mean square charge radii of the Ca nuclei are obtained, in addition to information on electromagnetic moments from the measured hyperfine structure constants. The influence of ground state correlations (represented by quadrupole and octupole mean square deformations) on the observed peculiar variation of the Ca charge radii is discussed as well as the relation to the droplet model and to a mixed ${\left(f_{\frac{7}{2}}\right)}^n$ model.