A new value for the nuclear magnetic moment of ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$ has been obtained: ${\mu }_{\mathrm{nucl}}\left({}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}\right)=4.2754\mathrm{}\left(5\right)\mathrm{}{\mu }_N$. This is two orders of magnitude more precise than the best previous (atomic beam) measurement. Major limitations of previous measurements were circumvented by a direct measurement of the moment in an electronically excited state (${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ of the ${\mathrm{Pr}}^{3+}$ ion in Ca${\mathrm{F}}_2$), where electronic contributions to the nuclear moment are only 3 parts in ${10}^4$.

• Received 10 June 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.636