A reinvestigation of the c3Π-X1Σ+ (0-0) absorption band of carbon monoxide

The forbidden c(3)II-X(1)Sigma(+) (0-0) absorption band of carbon monoxide has been reinvestigated under different pressure conditions using the 10.7-m VUV spectrograph at Meudon. Overlap with the allowed (CII)-I-1-X(1)Sigma(+) (0-0) band at lower transition energy has been taken into account. We have identified a new rotational branch corresponding to an S-type branch and extended the analysis to both higher and lower J. An analysis of the band structure and the low J transition lines suggests that the band gains its intensity predominantly as a result of an interaction of the c(3)II state with a (1)Sigma(+) state, most likely the C(1)Sigma(+) (nu = 0) state. Molecular constants have been obtained for the c(3)II state that are in reasonable agreement with those previously published. The apparently anomalous small value for the centrifugal distortion constant is explained by a homogeneous perturbation with the k(3)II valence state. (C) 2000 Academic Press.