Hyperfine Structure Separation and Magnetic Moment ofK42

The atomic beam flop-in magnetic-resonance method has been employed to measure the hyperfine structure separation $\Delta \nu$ and the nuclear magnetic moment ${\mu }_I$ in the ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ electronic ground state of the 12.4-h potassium-42. The results are: $\Delta \nu \left({\mathrm{K}}^{42}\right)=1258.877\mathrm{}\left(4\right)\mathrm{}$ Mc/sec; ${\mu }_I\left({\mathrm{K}}^{42}\right)=-1.1395\mathrm{}\left(30\right)\mathrm{}$ nuclear magnetons (diamagnetic correction not included). With these values, estimates of the hyperfine structure anomaly with respect to other potassium isotopes can be made: ${}_{}{}^{39}{}_{}{}^{}\Delta _{}^{42}{}_{}{}^{}=+0.20\mathrm{}\left(25\right)\%$, ${}_{}{}^{40}{}_{}{}^{}\Delta _{}^{42}{}_{}{}^{}=-0.25\mathrm{}\left(25\right)\%$, ${}_{}{}^{41}{}_{}{}^{}\Delta _{}^{42}{}_{}{}^{}=+0.42\mathrm{}\left(25\right)\%$.