Potential-energy curves of the CH radical molecule under spin-orbit coupling

Potential energy curves for the ground and excited electronic states of the CH radical molecule were calculated employing spin-orbit multiconfiguration quasi-degenerate perturbation theory (SO-MCQDPT). The results of our present SO-MCQDPT calculation for the CH radical molecule indicate that the ground electronic state of X 2Π splits into lower X1 2Π1/2 and higher X2 2Π3/2Ω states. The excited electronic state of a 4Σ– splits into lower a1 4Σ–1/2 and higher a24Σ–3/2, and the excited electronic state of A 2Δ splits into lower A1 2Δ3/2 and higher A2 2Δ5/2. The spin-orbit splittings for the 2S+1Λ states X 2Π, a 4Σ–, and A 2Δ are determined to be 25.963, 0.016, and 0.992 cm–1, respectively. The splittings are in good agreement with the experimental data for X 2Π and A 2Δ , and there are no experimental data for a 4Σ–. The potential-energy curves for all calculated bound states of CH are fitted to an analytical potential-energy function in the large range of R = 0.06–0.55 nm, from which accurate spectroscopic parameters are derived. It is the first time that the eight Ω states (X1 2Π1/2, X2 2Π3/2, a1 4Σ–1/2, a2 4Σ–3/2, A1 2Δ3/2, A2 2Δ5/2, B2Σ–1/2, and C2Σ+1/2) generated from the five valence 2S+1 Λ states (X 2Π , a 4Σ–, A 2Δ, B 2Σ–, and C 2Σ+) among those dissociating up to H(2Sg)+C(1Dg) have been studied theoretically. In addition, the carbon atom was taken as an example to prove the validity of the SO-MCQDPT method. The agreement between calculated and observed spin-orbit coupling is vert good. PACS Nos.: 31.15.aj, 31.15.xh, 71.70.Ej