Analysis of perturbations in the A2Π-X2Σ+ “Red” system of CN

Deperturbed vibration-rotation constants of the A²Π(v′ = 0 to 12) and X²Σ⁺(v″ = 0 to 8) states of CN are obtained. Specroscopic data from several sources are combined using a weighted, nonlinear least-squares fitting routine. The diagonalized effective Hamiltonian matrix contains as many as two ²Π and four ²Σ⁺ mutually interacting vibronic levels. Perturbations of A²Π by both X²Σ⁺ and B²Σ⁺ are treated simultaneously. The deperturbed constants and interaction matrix elements obtained provide a significantly more accurate representation of all perturbed and unperturbed observed lines than the previously reported values. The electronic factors of the spin-orbit and rotation-electronic perturbation matrix elements for the A ～ X and A ～ B interactions are determined and several previously unreported perturbations are detected and analyzed. Merged constants and Dunham coefficients are calculated; a detailed statistical treatment of the parameters and error estimates has also been carried out.