The atomic-beam magnetic-resonance method has been used to determine the hyperfine-structure interaction constants of 68-min ${\mathrm{Ga}}^{68}$. Measurements performed in both the ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ electronic ground state and the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ first excited state give the results: ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$, $\mathrm{}\left|a\right|=11.716\mathrm{}\pm 0.010$ Mc/sec; ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$, $\mathrm{}\left|a\right|=1.660\mathrm{}\pm 0.010$ Mc/sec, $\mathrm{}\left|b\right|=10.276\mathrm{}\pm 0.017$ Mc/sec, $\frac{b}{a}<0\mathrm{}$. The small value of the magnetic dipole interaction constant results in an inversion of the hyperfine-structure energy levels in the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ state. In descending order, the levels for an assumed positive-moment diagram are $F=\frac{3}{2}, \frac{5}{2}, \mathrm{and} \frac{1}{2}$.

The uncorrected nuclear moments calculated from these measurements and from known constants of the stable gallium isotopes are $\left|{\mu }_I\right|=0.01172\mathrm{}\pm 0.00006$ nm, $\mathrm{}\left|Q\right|=0.0313\mathrm{}\pm 0.0016$ b. The stated uncertainty in the magnetic moment is large enough to include the effect of a possible hyperfine-structure anomaly. The dipole and quadrupole moments have opposite signs.

• Received 2 March 1962

DOI:https://doi.org/10.1103/PhysRev.127.529