Multireference configuration interaction study of the 21 low-lying states of the OF radical

- Effect of core-valence correlation and scalar relativistic corrections is included.
- PECs are extrapolated to the CBS limit.
- TDMs between two states and FC factors of some transitions are calculated.
- Spectroscopic properties and vibrational properties are evaluated.
- SOC effect on the spectroscopic parameters is discussed.

This paper calculated the potential energy curves of 21 Λ-S and 42 Ω states of the OF radical. The 21 Λ-S states were the X2Π, A2Σ−, B2Σ−, C2Δ, D2Σ+, E2Σ+, 22Π, a4Σ−, b4Δ, 24Σ−, 14Σ+, 14Π, 24Π, 32Σ+, 32Σ−, 32Π, 42Π, 52Π, 22Δ, 32Δ, and 12Φ, which arose from the first two dissociation limits. The 42 Ω states were generated from these Λ-S states. All the potential energy curves were calculated with the CASSCF method, which was followed by the icMRCI + Q approach. The 14Π, 24Π, 22Π, 42Π, 52Π, 32Σ+, and 32Δ states were repulsive whether the spin-orbit coupling effect included or not, but the A2Σ−, D2Σ+, 32Σ−, 22Δ, and 12Φ states became repulsive with the spin-orbit coupling effect included. Only the 16 Ω states were bound. With the spin-orbit coupling effect accounted for, the X2Π state was inverted among the bound states; the X2Π, a4Σ−, and E2Σ+ states were strongly bound; and the 32Π, b4Δ, B2Σ−, C2Δ, 24Σ−, and 14Σ+ states were very weakly bound. The spectroscopic and vibrational properties were determined. Franck-Condon factors of some transitions were evaluated. The spin-orbit coupling effect on the spectroscopic parameters and vibrational properties was discussed. It is very difficult to explore the X2Π, a4Σ−, and E2Σ+ states by observing the electronic transitions between them because all these strong transitions originating only from the highly-vibrational states of the X2Π or a4Σ− state. It is also very hard to detect the 32Π, b4Δ, B2Σ−, C2Δ, 24Σ−, and 14Σ+ states by observing the transitions originating from these states, because these states are very weakly bound and unstable, though some transitions originating from them are very strong. These results can well explain why the OF radical is very difficult to detect in a spectroscopic experiment by observing the electronic transitions between different states.

This work investigated the PECs of 21 Λ-S and 42 Ω states of the OF radical. The extrapolation, core-valence correlation and scalar relativistic corrections were included into the PEC calculations. Only the X2Π, 32Π, a4Σ-, B2Σ-, 24Σ-, 14Σ+, E2Σ+, b4Δ, and C2Δ states were bound when the SOC effect were included. Only the X2Π3/2, X2Π1/2, 32Π1/2, a4Σ-1/2, a4Σ-3/2, B2Σ-1/2, 24Σ-1/2, 24Σ-3/2, 14Σ+1/2, 14Σ+3/2, E2Σ+1/2, b4Δ1/2, b4Δ3/2, b4Δ5/2, b4Δ7/2, and C2Δ5/2 states were bound. For the nine bound Λ-S states, the X2Π state was inverted; the X2Π, a4Σ-, and E2Σ+ states were strongly bound; and the 32Π, b4Δ, B2Σ-, C2Δ, 24Σ-, and 14Σ+ states were very weakly bound, which were very difficult to observe. Almost all the strong transitions between the X2Π, a4Σ-, and E2Σ+ states originated only from the highly- vibrational states of X2Π or a4Σ- state, which made the detection of these transitions become very hard. The spectroscopic and vibrational properties were evaluated. The SOC effect on the spectroscopic parameters and vibrational states was very obvious for most Ω states. The X2Π and a4Σ- states could be detected by observing their rovibrational transitions. The spectroscopic parameters and vibrational properties obtained here can be expected to be reliably predicted ones and can be used for some guidelines to observe these states, in particular for the X2Π, a4Σ-, and E2Σ+ states PECs of the 12 Λ-S states arising from the first dissociation limit. 1-12Π; 2-a4Σ-; 3-A2Σ-; 4-B2Σ-; 5-b4Δ; 6-14Σ+;7-C2Δ; 8-D2Σ+; 9-14Π; 10-22Π; 11-24Σ-; 12-24Π. 88