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 ${\mathrm{In}}^{115}$

• Received 26 January 1942

DOI:https://doi.org/10.1103/PhysRev.61.459