Accurate spectroscopic calculations of 21 electronic states of ClO radical including transition properties

• 21 states exist but 9 are repulsive for the lowest two dissociation limits.
• PECs obtained by the MRCI + Q are extrapolated to the CBS limit.
• Core-valence correlation and scalar relativistic corrections are included.
• Spectroscopic parameters of 12 bound states are obtained.
• Franck-Condon factors and radiative lifetimes are calculated.

The potential energy curves were calculated for the 21 states (X2Π, A2Π, 32Π, 42Π, 52Π, 12Σ+, 22Σ+, 32Σ+, 12Σ−, 22Σ−, 32Σ−, 12Δ, 22Δ, 32Δ, 12Φ, 14Σ+, a4Σ−, 24Σ−, 14Π, 24Π and 14Δ), which originated from the two lowest dissociation channels of ClO radical. The calculations were done for internuclear separations approximately from 0.08 to 1.10 nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV5Z basis set. Of these 21 states, the 14Π, 24Π, 32Δ, 42Π, 52Π, 12Φ, 32Σ+, 14Δ and 24Σ− states are repulsive. The 12Δ, 12Σ−, 14Σ+, 22Σ−, 12Σ+, 22Σ+, 22Δ and 32Σ− states are very weakly bound. Only the A2Π state has one barrier. The avoided crossing exists between the A2Π and the 32Π state. However, the avoided crossing does not generate any double wells. Core- valence correlation correction was accounted for at the level of an aug-cc-pCVQZ basis set. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pVQZ basis set. All the potential energy curves were extrapolated to the complete basis set limit. The spectroscopic parameters were determined. The 12Σ−, 22Σ−, 32Σ− and 14Σ+ states may be very difficult to be detected in an experiment, since each of these Λ-S states has only one or two vibrational states. The Franck-Condon factors and radiative lifetimes were calculated for several low vibrational levels of the A2Π - X2Π, 32Π - a4Σ−, 22Δ - a4Σ− and 32Σ− - 12Σ− transitions. The spin-orbit coupling effect on the spectroscopic parameters of the X2Π, A2Π, 32Π, a4Σ− and 22Σ+ states were discussed. The spectroscopic properties reported here can be expected to be reliably predicted ones.

The PECs are calculated for the 21 states originating from the lowest two dissociation channels of ClO radical using the CASSCF method, which is followed by the icMRCI approach. Of the 21 states, the 14Π, 24Π, 32Δ, 42Π, 52Π, 12Φ, 32Σ+, 14Δ and 24Σ− states are repulsive. The 12Δ, 12Σ−, 14Σ+, 22Σ−, 12Σ+, 22Σ+, 22Δ and 32Σ− states are very weakly bound. Only the A2Π state has one barrier. The avoided crossing is found between the A2Π and the 32Π state, but no double wells are yielded. Core-valence correlation and scalar relativistic corrections are accounted for. All the PECs are extrapolated to the CBS limit. The spectroscopic parameters of all the bound states are determined. The 12Σ−, 22Σ−, 32Σ− and 14Σ+ states may be very hard to be observed in an experiment, since each of the four electronic states has only one or two vibrational states. The Franck-Condon factors and radiative lifetimes are calculated for several low vibrational levels of the A2Π - X2Π, 32Π - a4Σ−, 22Δ - a4Σ− and 32Σ− - 12Σ− transitions.Figure optionsDownload as PowerPoint slide