A new cascade-decoupling technique has been used to measure hyperfine intervals (in MHz) of the following excited $S$ states of alkali-metal atoms: ${\mathrm{K}}^{39}\left(6\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)46\mathrm{}\pm 2$; ${\mathrm{K}}^{41}\left(6\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)26\mathrm{}\pm 2$; ${\mathrm{Rb}}^{85}\left(7\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)270\mathrm{}\pm 10$; ${\mathrm{Rb}}^{85}\left(8\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)135\mathrm{}\pm 15$; ${\mathrm{Rb}}^{87}\left(7\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)565\mathrm{}\pm 60$; ${\mathrm{Rb}}^{87}\left(8\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)290\mathrm{}\pm 20$; ${\mathrm{Cs}}^{133}\left(8\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)680\mathrm{}\pm 120$; and ${\mathrm{Cs}}^{133}\left(9\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)405\mathrm{}\pm 30$.

• Received 17 March 1972

DOI:https://doi.org/10.1103/PhysRevA.6.529