Deperturbation analysis of an avoided crossing in the A1 v = 0 and B1 v = 0 states of WO

The (0,0) and (0,1) bands of the A1 – X0⁺ and B1 – X0⁺ transitions of tungsten monoxide (WO) have been recorded in high resolution using intracavity laser absorption spectroscopy techniques (ILS and ILS-FTS). Lines for all four abundant isotopologues, ¹⁸²WO, ¹⁸³WO, ¹⁸⁴WO, and ¹⁸⁶WO, are observed and have been rotationally analyzed and fit using a constrained-variables approach in PGOPHER. While these transitions have been previously described in the literature, this new analysis incorporates all four isotopologues and presents evidence for an avoided crossing interaction between the v = 0 vibrational levels of the A1 and B1 states. New values for spectroscopic constants that incorporate the perturbation interactions are presented and compared to literature results.