Series formulas for the spectrum of atomic sodium (Na i)

The available data on the energy levels of Na i yield Ritz quantum-defect formulas predicting all one-electron (nl) levels with an uncertainty of ± 0.03 cm−1 with respect to the 3s2S1/2 ground level. Such formulas are given here for the ns through ni series as expressions for the quantum defect δ in inverse even powers of n − δ0, with δ0 constant for each nl series. These formulas are usually more convenient for calculations than the formulas in powers of n − δ and core-polarization formulas given previously. Term differences or quantum defects predicted by the ns through nh formulas are compared with a number of more recent experimental determinations in the range n = 13–41.