Spins of Thallium-197, -198m, -199, and -204, and the Hyperfine-Structure Splitting of Thallium-204

The nuclear angular momenta of four isotopes of thallium and the hyperfine-structure splitting of ${\mathrm{Tl}}^{204}$ in the ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ state have been measured by the atomic-beam magnetic resonance method. The results are: for 2.7-hr ${\mathrm{Tl}}^{197}$, $I=\frac{1}{2}$; for 1.8-hr ${\mathrm{Tl}}^{198m}$, $I=7\mathrm{}$; for 7.2-hr ${\mathrm{Tl}}^{199}$, $I=\frac{1}{2}$; for 4.1-yr ${\mathrm{Tl}}^{204}$, $I=2\mathrm{}$ and $\Delta \nu \left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)=732\mathrm{}\pm 5$ Mc/sec. The neutron-deficient isotopes are produced by alpha-particle bombardment of gold in the Berkeley 60-inch cyclotron; ${\mathrm{Tl}}^{204}$ is produced by neutron activation of metallic thallium samples.