OBSERVATIONS OF THE 3(3D)3 SIGMA-G+ STATE OF NA2

The 3(3d)3Σg+ state of the Na2 molecule has been observed for the first time by perturbation-facilitated optical-optical double-resonance (PFOODR) excitation spectroscopy through A1Σu+ ∼ b3Πu mixed intermediate levels. The rotational structure and the fine-hyperfine splittings of the 33Σg+ ← b3Πu transitions are similar to the 43Σg+ ← b3Πu transitions of Na2. Absolute vibrational numbering of the 33Σg+ state was determined by comparing the experimental excitation intensities with the calculated Franck-Condon factors. Molecular constants and the RKR potential curve are also reported. A comparison of the molecular constants of all eight observed states dissociating to the same 3s + 3d asymptote with ab initio theory shows remarkably good agreement. © 1992.