New Results on the B2Σ+, b4Σ−, and X2Π States of PO

Abstract

An extensive study of the β system of the PO molecule has been carried out. The rotational analysis of 23 bands has yielded the constants of the ν = 0–9 levels of the B2Σ+ state and of the ν = 0–11 levels of the X2Π state with a precision higher than previous measurements. The spin coupling constant, Aν, evaluated for the 12 levels of X2Π is found to follow the equation Aν = 224.03 + 0.18ν–0.013ν2. The perturbations observed in the B2Σ (ν = 6 and 7) levels have been interpreted as being caused by a 4Σ− state and the B′2Π state. A deperturbation calculation has been carried out to evaluate the molecular constants of the PO molecule in the 4Σ− state. Several new bands were also observed; some of these belong to the β and B′–X systems and others are left unassigned.