Interferometric measurements on $\lambda 7182(5s6p{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\to 5s6s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{})$ and $\lambda 7276(5s6p{}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}\to 5s6s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{})$ of In II indicate that the separations of the state $5s6s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ follow the interval rule to within the experimental error (approximately 0.05 percent). Perturbations by neighboring states are negligible and there are no effects for this state due to the known electric quadrupole moment of the nucleus. The results indicate that the assumption of a nuclear magnetic moment is very successful in accounting for the observed relative separations.

• Received 24 June 1938

DOI:https://doi.org/10.1103/PhysRev.54.446