Theory and analysis of sodium dimer Rydberg states observed by all-optical triple resonance spectroscopy

For the nf(l = 3) series of Na₂, quantum defects are calculated from theoretical values of the core quadrupole moment and polarizabilities. They compare favorably with those inferred from our preliminary report of high resolution all-optical triple resonance spectroscopy [Chem. Phys. Lett. 236, 553 (1995)] and from the full report of such spectra given here. The spectrum is the simplest when the higher intermediate state has J′ = 0 which requires a final state J = 1. We predict the stroboscopic effect should first occur when n = 52 for the nf series, as we observe, rather than at n = 69 for the np series. Our data thus confirm that the strongest series is the nf. Hence the ionization potential is not 39478.75 ± 0.04 cm^-1 as previously reported, but rather 39478.101 ± 0.013 cm^-1, implying a molecular ion dissociation energy of D⁰₀(Na⁺₂) = 7914.038 ± 0.014 cm^-1.