Intensity Anomalies and Perturbations in the CN Bands

The rotational structures of the 0,0 violet and the 9,4 red CN bands, developed by CHCl₃ in active nitrogen, are measured on plates from the first and second orders of a 30-ft. grating. The rotational constants of the b²Σ,v=0 and the a²Σ,v=4 states are in good agreement with the previously published values; those for the v=9²Π state are B_^'₉^=1.5312±0.0008 cm^-1, D_^'₉^=7.408±0.002×10^-6 cm^-1. The A-doubling in this state, except for four perturbations, can be represented by use of the constants p₀=+0.01597 and q₀=-0.00080. The value γ^'=+0.021 is determined for the spin doubling in the b²Σ,v=0 state. Four perturbations are found at K=4,7,11, and 15 for b²Σ; extra P and R lines separated from the main lines by Δν=-0.352 cm^-1,+0.938 cm^-1,+1.177 cm^-1, and +1.212 cm^-1, respectively, appear in both the 0,0 and 0,1 bands of the violet system. In the red system, shifts of the right amount and direction in the lines Q₁[31/2], R₁[71/2], P₁[71/2], R₂[101/2], P₂[101/2], and Q₂[151/2] confirm the assumption that rotational levels of ²Π,v=9, perturb those of b²Σ,v=0, and that the perturbations occur for the K and J values indicated. (Brackets denote upper state J.) The values of the perturbation matrix elements are obtained for the various levels. Some anomalies of the R branch band lines in the range 23-29 of K^' values in the 0,0 violet band are mentioned.The mechanism responsible for the enhancements of the main and extra lines of the 0,0 violet band is discussed. Collisions involving interstate transfer (²Π→a²Σ) evidently occur, or are enhanced, at each perturbed level; and rapid redistribution of molecules among rotational levels by collisions must also occur. Where spin doublets are resolvable in the violet bands, rotational redistribution occurs without change of spin direction.