Forbidden Transitions in Diatomic Molecules: Iii. New and Absorption Bands of the Oxygen Molecule

Two new forbidden transitions of the O 2 molecule have been found. They give rise to very faint absorption bands overlapping the much stronger forbidden [Formula: see text] bands previously described. The upper states are identified as [Formula: see text] and 3 Δ u respectively, both of which arise from the same electron configuration as the known states [Formula: see text] and [Formula: see text]. For the [Formula: see text] state the following vibrational and rotational constants have been determined: T e = 36678.9 1 , ω e = 650.4 9 , ω e x e = 17.03 6 , ω e y e = −0.105 6 , ω e z e = −0.0074 4 , B e = 0.826 1 , α e = 0.020 5 , γ e = −0.00083 0 cm. −1 , γ e = 1.597 × 10 −5 cm. The constants are based on the assumption of a certain vibrational numbering which may have to be revised (increased). For the 3 Δ u state the data are quite fragmentary and only two rotational constants, B 5 = 0.817 7 , B 6 = 0.791 5 , and one vibrational quantum, [Formula: see text], have been determined. The bands of the [Formula: see text] system are very close to those of the [Formula: see text] system and represent in all probability the analogue in free O 2 of the diffuse triplet bands of Wulf, Finkelnburg, and Steiner ascribed to O 4 . The positions of the new [Formula: see text] and 3 Δ u states agree closely with those predicted by Moffitt. Almost half of the unidentified features of the spectrum of the nightglow agree within 5 Å with the predicted positions of emission bands of the [Formula: see text] system.