Valence excited states of CH. I. Potential curves

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Abstract
Ab initio CI calculations have been performed over a wide range of internuclear distances (1.00–20.00 bohr) to obtain the potential curves for the first five valence excited states of CH; X2Π, a4Σ−1, A2Δ, B2Σ−, and C2Σ+. Results, with known experimental values in parentheses, are Re(X2Π) = 2.113 (2.116) bohr, Re(a4Σ−) = 2.053 bohr, Re(A2Δ) = 2.083(2.083) bohr, Re(B2Σ−) = 2.216(2.20) bohr, Re(C2Σ+) = 2.100(2.105) bohr; De(X2Π) = 3.51(3.63) eV, De(a4Σ−) = 2.84 eV, De(A2Δ) = 1.90(2.01) eV, De(B2Σ−) = 0.23(0.40) eV, and De(C2Σ+) = 0.78(0.94) eV. Potential maxima of heights 1284 and 3228 cm−1 are calculated for the B2Σ− and C2Σ+ states, respectively. These maxima are attributed to avoided curve crossings. The a4Σ− state, not observed experimentally, is estimated to lie between 0.62 and 0.76 eV above the X2Π state.