The argon-ion laser lines at 4658, 4727, 4765, 4880, 4965, 5017, and 5145 Å are each found to excite one or more resonance fluorescence series of the Na2 (X 1Σg+ - B 1Πu) blue-green band system. Altogether, 19 different fluorescence progressions have been identified and assigned υ, J quantum numbers. The absolute wavenumbers of many of these emission lines have been measured interferometrically using a Fabry-Perot etalon crossed with a Bass-Kessler type spectrograph. A revised set of spectroscopic constants has been determined for both the upper and lower states which reproduce the observed term energies to better than 0.1 cm-1 on the average. Using these improved spectroscopic data, potential curves have been constructed for the B and X states of Na2 by the Rydberg-Klein-Rees method. These potential curves are used in turn to compute Franck-Condon factors for the Na2 B-X band system.