A 2+1 REMPI study of the E-X transition in CO. Indirect predissociations in the E 1Π state

Abstract In this study 2+1 resonance enhanced multiphoton spectra of the E 1 Π( v =1, 0)-X 1 Σ + ( v =0) transitions in 12 C 16 O, 13 C 16 O, 12 C 18 O and 13 C 18 O have been recorded in the laser wavelenght range, 210–216 nm, and rotationally analysed. Perturbations have been observed in both the e and f parity levels of the E 1 Π( v =1) state which have the characteristics of an indirect predissociation similar to the well-known accidental predissociation in the J e =31 level of 12 C 16 O (E 1 Π, v =0). The present results favour 3 Π valence perturbing state which is itself predissociated by a 3 Π repulsive state correlating to the lowest dissociation limit; C( 3 P)+O( 3 P). Lambda doubling constants for all four isotopes in both the v =0 and v =1 vibrational levels of the E 1 Π state have also been obtained.