Hyperfine structure in the sequence of sodium S states

The hyperfine structure for the 6, 7 and 8 2 S 1/2 states of 23 Na was measured by optical double-resonance techniques. The states were populated by step-wise excitation using two CW dye lasers. For the dipole interaction constant a, a(6 2 S 1/2 ) = 37.5(2) MHz, a(7 2 S 1/2 )=20.9(1) MHz, a(8 2 S 1/2 )=12.85(10) MHz. were obtained. Theoretical calculations of the hyperfine structure were performed for the 3-8 2 S 1/2 states using many-body perturbation techniques. When polarization as well as certain correlation effects are included in the calculation, an agreement with the experimental values within 2% is obtained