Intensity Anomalies and Perturbations in the CN Bands

Abstract

The rotational structures of the 0,0 violet and the 9,4 red CN bands, developed by CH${\mathrm{Cl}}_3$ in active nitrogen, are measured on plates from the first and second orders of a 30-ft. grating. The rotational constants of the $b^2\Sigma ,v=0\mathrm{}$ and the $a^2\Sigma ,v=4\mathrm{}$ states are in good agreement with the previously published values; those for the $v=9^2\Pi$ state are $B_{}^{\prime }{}_9{}^{}=1.5312\mathrm{}\pm 0.0008$ ${\mathrm{cm}}^{-1\mathrm{}}$, $D_{}^{\prime }{}_9{}^{}=7.408\mathrm{}\pm 0.002\times {10}^{-6\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. The A-doubling in this state, except for four perturbations, can be represented by use of the constants $p_0=+0.01597\mathrm{}$ and $q_0=-0.00080\mathrm{}$. The value ${\gamma }^{\prime }=+0.021\mathrm{}$ is determined for the spin doubling in the $b^2\Sigma ,v=0\mathrm{}$ state. Four perturbations are found at $K=4,7,11, \mathrm{and} 15$ for $b^2\Sigma$; extra $P$ and $R$ lines separated from the main lines by $\Delta \nu =-0.352\mathrm{} {\mathrm{cm}}^{-1\mathrm{}},+0.938\mathrm{} {\mathrm{cm}}^{-1\mathrm{}},+1.177\mathrm{} {\mathrm{cm}}^{-1\mathrm{}}, \mathrm{and} +1.212\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, 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 $Q_1\left[3\mathrm{}\frac{1}{2}\right]$, $R_1\left[7\mathrm{}\frac{1}{2}\right]$, $P_1\left[7\mathrm{}\frac{1}{2}\right]$, $R_2\left[10\mathrm{}\frac{1}{2}\right]$, $P_2\left[10\mathrm{}\frac{1}{2}\right]$, and $Q_2\left[15\mathrm{}\frac{1}{2}\right]$ confirm the assumption that rotational levels of ${}_{}{}^2{}_{}{}^{}\Pi ,v=9\mathrm{}$, perturb those of $b^2\Sigma ,v=0\mathrm{}$, 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 $K^{\prime }$ values in the 0,0 violet band are mentioned.