Term Values and Molecular Parameters for CH and CH+

Abstract

By using a model-independent statistical method, term values were determined for the rotational and vibrational levels of the X2Π, A2Δ, B2Σ-, and C2Σ+ electronic states of CH, and the X1Σ+ and A1Π states of CH+. Molecular parameters were obtained from a least squares fit to these term values. A method based on exact numerical diagonalization of the respective perturbation matrices yielded parameters for the X2Π and B2Σ- states of CH and the A1Π and X1Σ+ states of CH+, while the A2Δ and C2Σ+ states of CH had to be treated according to a polynomial model. In the case of CH several arguments indicate that the Λ-doubling of the X2Π ground state arises from interaction with the B2Σ- state. A discussion of the influence of the predissociation observed for the B2Σ- state on the X2Π Λ-doubling is also included. For CH+ good agreement was found between observed and pure precession values of the X1Σ+ - A1Π interaction matrix element.