Spectroscopy of Na2 Using Laser-Induced Fluorescence

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 ${\mathrm{(X}}^1{\Sigma }_g^{+}{\mathrm{\hspace{0.17em}-\hspace{0.17em}B}}^1{\Pi }_u)$ blue‐green band system. Altogether, 19 different fluorescence progressions have been identified and assigned $\upsilon$ , $J$ 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.