The nuclear magnetic moments of ${}_{}{}^{213}{}_{}{}^{}\mathrm{Ra}$ and ${}_{}{}^{225}{}_{}{}^{}\mathrm{Ra}$ have been measured at ISOLDE (isotope separator at the CERN synchrocyclotron) by observation of the Larmor precession of optically pumped atoms in a fast beam. The results ${\mu }_I$(${}^{213}$Ra)=0.6133(18)${\mu }_N$ and ${\mu }_1$${(\mathrm{}}^{225}$Ra)= -0.7338(15)${\mu }_N$ provide an accurate test of ab initio and semiempirical calculations from optical hyperfine structures in Ra i and Ra ii. .AE

• Received 3 April 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.771