For the nf (l=3) series of Na-2, 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 39 478.75 +/- 0.04 cm(-1) as previously reported, but rather 39 478.101 +/- 0.013 cm(-1), implying a molecular ion dissociation energy of D-0(0)(Na-2(+))=7914.038 +/- 0.014 cm(-1).