Determination of molecular constants of the X3Σg− state of O2

From the absorption lines assigned to the B - X, 2-7 band of O 2 in the KrF laser spectrum, new molecular constants of v = 7(X) are obtained. The term values, T v , for v =0-3 recently determined by Raman spectroscopy are modified to render them consistent with those obtained by UV spectroscopy for v= 11-18, 4 and 7. This modification, based on the theoretical energy formulas of fine structure levels of 3 Σ, is numerically justified by the new T 7 value and also by the set of spectroscopic constants of X 3 Σ g - obtained.