Quadrupole moments of radium isotopes from the 7p 2 P 3/2 hyperfine structure in Ra II

The hyperfine structure and isotope shift of^221–226Ra and^212,214Ra have been measured in the ionic (Ra II) transition 7s ² S _1/2–7p ² P _3/2 (λ=381.4 nm). The method of on-line collinear fast-beam laser spectroscopy has been applied using frequency-doubling of cw dye laser radiation in an external ring cavity. The magnetic hyperfine fields are compared with semi-empirical and ab initio calculations. The analysis of the quadrupole splitting by the same method yields the following, improved values of spectroscopic quadrupole moments:Q _s (²²¹Ra)=1.978(7)b,Q _s (²²³Ra)=1.254(3)b and the reanalyzed valuesQ _s (²⁰⁹Ra)=0.40(2)b,Q _s (²¹¹Ra)=0.48(2)b,Q _s (²²⁷Ra)=1.58(3)b,Q _s (²²⁹Ra)=3.09(4)b with an additional scaling uncertainty of ±5%. Furthermore, theJ-dependence of the isotope shift is analyzed in both Ra II transitions connecting the 7s ² S _1/2 ground state with the first excited doublet 7p ² P _1/2 and 7p ² P _3/2.