Hyperfine Structure ofBi209

We have used the atomic-beam magnetic-resonance technique to improve and extend the measurements of Title and Smith on the hyperfine structure of the $\left(6\mathrm{}{p}^3\right) {}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{}$ ground state of ($I=\frac{9}{2}$). We measured the three zero-field hyperfine intervals and computed the octupole interaction constant. Our experimental results are ${\nu }_1(F=5\mathrm{}\to F=6)=2884.666\mathrm{}\left(2\right)\mathrm{}$, ${\nu }_2(F=4\mathrm{}\to F=5)=2171.419\mathrm{}\left(2\right)\mathrm{}$, and ${\nu }_3(F=3\mathrm{}\to F=4)=1584.502\mathrm{}\left(2\right)\mathrm{}$ MHz. From these values, we obtain for the hyperfine-interaction constants, corrected for the pseudo-octupole interactions due to perturbation by neighboring fine-structure levels $A=-446.937\mathrm{}\left(1\right)\mathrm{}$, $B=-305.067\mathrm{}\left(2\right)\mathrm{}$, and $C=0.0183\mathrm{}\left(1\right)\mathrm{}$ MHz. The assigned errors include only the experimental errors in the measurement of the three hyperfine intervals, and no estimate of the errors in the theoretical corrections has been made. We have also corrected the data of Lurio and Landman for the $\left(6\mathrm{}{p}^3\right){}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ metastable state of bismuth for these octupolelike interactions and have deduced a fairly consistent value for the one-electron octupole-interaction constant. From the average value of the octupole-interaction constant $c_{\frac{3}{2}}=0.0206\mathrm{}$ MHz we find that the nuclear magnetic octupole moment is $0.0086{\mu }_N\mathrm{b}$. This value is compared with the prediction of the shell model.