The rotationally resolved 1 3Σg+ ← 1 3Σu+ transition in Na2 studied by resonant two-photon ionization in a molecular beam

The 1 3Σg+ ← 1 3Σu+ band system of the sodium dimer has been studied with rotational resolution in a supersonic molecular beam. The laser excited triplet-triplet transitions have been monitored by observation of the resonantly enhanced ionization of Na2 (1 3Σg+) induced by the light of a second laser. The molecular constants for the observed vibrational levels of both triplet states are derived from the experiment and compared with the results of ab initio calculations.