Radiofrequency Spectrum of Indium. Nuclear Spin ofIn113

The atomic beam methods of studying the radiofrequency spectra of atoms in the ground state has been applied to indium. Lines characterized by the transitions $\Delta F=0\mathrm{}$, $\Delta m=\pm 1$, were observed, in magnetic fields ranging from 3000 to 7000 gauss, for ${\mathrm{In}}^{113}$ as well as for ${\mathrm{In}}^{115}$. The experiments give conclusive evidence that the nuclear spin of ${\mathrm{In}}^{113}$ is 9/2 and that its moment is positive, the same as that of ${\mathrm{In}}^{115}$. The ratio of the hyperfine separation of the ground state of ${\mathrm{In}}^{115}$ to that of ${\mathrm{In}}^{113}$ was found to be 1.00224±0.00010. This is also the ratio of the magnetic moments of the two isotopes. A h.f.s. value of (11413±3) ${10}^6$ cycles/sec. and a nuclear moment of 5.49±0.04 nuclear magnetons were found for ${\mathrm{In}}^{115}$