PRECISION STARK SPECTROSCOPY OF SODIUM - IMPROVED VALUES FOR THE IONIZATION LIMIT AND BOUND-STATES

We report results of a combined theoretical and experimental investigation that uses Stark spectroscopy of high-lying Rydberg states to measure accurately zero-field atomic parameters. Improved values for the binding energies of the 11 2S, 12 2S, and 10(2)D states of sodium are presented. These results are combined with previous data in a global least-squares fit to obtain improved quantum-defect parameters for the sodium 2S and 2D manifolds. Using previous precision optical data, the present results, and the quantum-defect expansion, we obtain an improved value for the ionization limit of neutral sodium: E(ion) = 41449.451(2) cm-1. The consequences of the improved ionization energy on the quantum-defect expansion parameters of the 2P states are also discussed and values are obtained from fits to the available data.