The A(3Π1) state of ClF

The A((3)Pi(1)) state of ClF is studied (1) in emission from the beta(1(3)P(2)) ion-pair state in a high-pressure discharge, (2) from its role in perturbations of the B((3)Pi(0+)) and A'((3)Pi(2)) states, and (3) in direct absorption from the X((1)Sigma(+)) ground state. The last of these is obtained via a UV-labeling technique and represents the first observation of the A <-- X transition. The emission spectrum yields extensive assignments for the 0-4, 0-5, and 1-4 bands of beta --> A, with both e and f Lines identified. The well-known perturbation in upsilon = 7 of the B state is attributed to interaction with upsilon = 9 of A. A newly identified perturbation in B(6) involves coupling with A(8). The known perturbation in B(8) may involve A(11), but other assignments cannot be ruled out. Approximate potential curves are derived for all three valence states and used to compute the vibrational factors for the perturbations, permitting extraction of the electronic coupling strengths. The B-A coupling elements are within similar to 10% of expectations for rotation-electronic coupling within a Hund's case (a) (3)Pi manifold, but the strength of the perturbation between A(5) and A'(6) is only about 30% of predictions for this model, (C) 1999 Academic Press.