The lowest-lying doublet electronic states of CoC – A theoretical study

Multiconfigurational SCF and second-order perturbation theory have been employed to study seven low-lying electronic states of the CoC molecule (X2Σ+, A2Δ, B2Φ, C2Φ, D2Π, E2Π, and F2Σ+). Three doublet electronic states have been described for the first time: B2Φ (R0 = 1.632 Å, T0 = 8950 cm−1, and ωe = 993 cm−1), C2Φ (R0 = 1.617 Å, T0 = 10455 cm−1, and ωe = 1159 cm−1), and D2Π (R0 = 1.618 Å, T0 = 10767 cm−1, and ωe = 1105 cm−1). The results support the previous assignment of the 13 000–14 500 cm−1 band to the E2Π state but, unlike previous suggestions, we identify the (8σ2)(3π4)(9σ1)(1δ3)(4π1) electronic configuration to be the most relevant for its description. We identify the experimentally observed [14.0]2Σ+ state as the F2Σ+ electronic state of CoC.