The hyperfine structure of the metastable $\left(4\mathrm{}\mathrm{s}4p\right){}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ state of ${\mathrm{Zn}}^{67}$ and the metastable $\mathrm{}\left(3s3p\right)\mathrm{}{}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ states of ${\mathrm{Mg}}^{25}$ have been measured by the atomic beam magnetic-resonance technique. The magnetic dipole and electric quadrupole-coupling constants obtained from these measurements are: ${\mathrm{Zn}}^{67}\left({}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}\right)$, $A=531.987\mathrm{}\pm 0.005$ Mc/sec, $B=35.806\mathrm{}\pm 0.005$ Mc/sec; ${\mathrm{Mg}}^{25}\left({}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}\right)$, $A=-128.445\mathrm{}\pm 0.005$ Mc/sec, $B=16.009\mathrm{}\pm 0.005$ Mc/sec; ${\mathrm{Mg}}^{25}\left({}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\right)$, $A=-144.977\mathrm{}\pm 0.005$ Mc/sec, $B=-8.308\mathrm{}\pm 0.005$ Mc/sec. These results are compared in detail with the Breit-Wills and Casimir theory of two-electron hyperfine structure. The electric quadrupole moments of these nuclei are found to be: $Q\left({\mathrm{Zn}}^{67}\right)=0.16\mathrm{}\times {10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$, $Q\left({\mathrm{Mg}}^{25}\right)=0.22\mathrm{}\times {10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$. The quadrupole moment of ${\mathrm{Mg}}^{25}$ is shown to be in very good agreement with that value obtained from other experiments thru the use of the collective model in strong coupling. The detection of a beam of metastable ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ Mg atoms places a lower limit on the lifetime of this state of about ${10}^{-3\mathrm{}}$ sec.

• Received 28 November 1961

DOI:https://doi.org/10.1103/PhysRev.126.1768