A 2+1 Rempi study of the E‐X transition in CO

Two‐photon E 1Π (v=1,0)–X 1Σ+ (v=0) resonant, three‐photon ionization spectra of the four isotopomers 12C16O, 13C16O, 12C18O, and 13C18O have been recorded over the laser wavelength range, 210–216 nm, using a time of flight mass spectrometer, and rotational analyzed. Both e and f parity levels of the E 1Π state have been observed and localized perturbations have been identified in the v=1 vibrational level. These perturbations, which occur in both parity levels, have the characteristics of an indirect predissociation similar to the well‐known accidental predissociation in the J=31 level of 12C16O(E 1Π, v=0). The present results favor a 3Π valence perturbing state which is itself predissociated by a 3Π repulsive state correlating to the lowest dissociation limit; C(3P)+O(3P).