Theoretical spectroscopy of the NO radical. III. Λ doubling and predissociation in the C 2Π state

Abstract

The Λ doubling of the C 2Π state of NO is calculated by considering the heterogeneous couplings (spin–orbit and rotational angular momentum) between the C 2Π and the first three 2Σ+ states plus the homogeneous interaction of the C 2Π with the B 2Π state. All wave functions and energies result from highly correlated configuration interaction wave functions. A transformation from the adiabatic to the diabatic basis is performed by employing the radial coupling between the two 2Π states. The perturbation matrix is solved in the diabatic basis and leads directly to the eigenvectors and eigenvalues of the Λ components. It is found that for J≥3/2 the Λ components are completely mixed and can therefore not be labeled according to their Ω values any more. Vibrational averaging leads to a calculated value of 0.019 cm−1 (J=0.5, v=0) compared to the measured value of 0.016 cm−1 for the Λ doubling. The predissociation process of the C 2Π state is calculated in the adiabatic basis; the mechanism is found to be caused solely by the spin–orbit interaction with the a 4Π state.