Term Values and Molecular Parameters for CH and CH+

By using a model-independent statistical method, term values were determined for the rotational and vibrational levels of the X 2 Π, A 2 Δ, B 2 Σ - , and C 2 Σ + electronic states of CH, and the X 1 Σ + and A 1 Π 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 X 2 Π and B 2 Σ - states of CH and the A 1 Π and X 1 Σ + states of CH + , while the A 2 Δ and C 2 Σ + 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 X 2 Π ground state arises from interaction with the B 2 Σ - state. A discussion of the influence of the predissociation observed for the B 2 Σ - state on the X 2 Π Λ-doubling is also included. For CH + good agreement was found between observed and pure precession values of the X 1 Σ + - A 1 Π interaction matrix element.