The diffuse v = 4 and 5 vibrational levels of the B 1Σ+ Rydberg state of carbon monoxide

Two new diffuse bands in the VUV absorption spectrum of carbon monoxide at 105.6 and 103.0 nm have been identified. Their spectral characteristics are consistent with B 1Σ+ (v = 4, 5) ← X 1Σ+ (v = 0) 12C16O assignments, with band origins at 94 700 ± 120 cm−1 and 97 050 ± 150 cm−1 and predissociation linewidths of ≈350 and 450 cm−1, respectively. These upper state vibrational levels occur in the ‘avoided crossing region’ of the 3sσ, B Rydberg state and the repulsive part of the D′ 1Σ+ valence state potential energy surface.