Precision Stark spectroscopy of sodium 2P and 2D states

We report precision measurements of the energies of the Na 10 P-2, 11 2P, and 10 D-2 states and their fine-structure intervals. The P-state results bridge the gap between earlier high- and low-n measurements from other laboratories, thus facilitating calculation of quantum-defect parameters. Quantum-defect theory fits to all available data on Na are critically examined. Using the most reliable values at low, intermediate, and high n leads to a single set of four quantum-defect parameters that is useful over the entire range of n. Also, using the present P-state measurements, we extract a value of the ionization potential that is in exact agreement with our earlier determination. [S1050-2947(98)08308-5].