Fine Structure of Na4dD2Using High-Resolution Two-Photon Spectroscopy

Abstract

We have measured the fine-structure splitting of the $4d{}_{}{}^2{}_{}{}^{}D$ state of neutral sodium using high-resolution, cw, simultaneous two-photon excitation from the $3s{}_{}{}^2{}_{}{}^{}S$ ground state. Sodium atoms in an atomic beam were excited by a single-mode, cw, tunable dye laser, and the resonance was detected by monitoring the decay fluorescence from the excited state. The fine structure of the $4d{}_{}{}^2{}_{}{}^{}D$ state was well resolved and measured to be ${\Delta }_{\mathrm{fs}}=1025\mathrm{}\pm 6$ MHz.