Measurement of the Hyperfine Structure of the5S122State ofNa23by Two-Step Excitation Using Two cw Dye Lasers

Abstract

We report a direct measurement of the hyperfine splitting of the $5{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ state in sodium using a two-step excitation of an atomic beam with two cw tunable dye lasers. The linewidth obtained is 24 MHz and we measure a hyperfine splitting $\Delta \nu \left(5\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=159\mathrm{}\pm 6$ MHz, in good agreement with the theoretical value.