Rotational line strengths for the CN $B{}^2{\mathrm{\Sigma }}^{+}-X{}^2{\mathrm{\Sigma }}^{+}$ (5,4) band

Rotational line strengths, computed from eigenvectors of Hund’s case (a) matrix representations of the upper and lower Hamiltonians using Wigner-Witmer basis functions, show a larger than expected influence from the well known perturbation in the (5,4) band. Comparisons with National Solar Observatory experimental Fourier transform spectroscopy data reveal nice agreement of measured and predicted spectra. Keywords: Diatomic spectroscopy, rotational line strengths, H"onl-London factors, cyanide spectra violet band perturbations