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

## TL;DR

This paper calculates and compares rotational line strengths for the CN violet band, revealing significant perturbations and demonstrating good agreement with experimental spectra from Fourier transform spectroscopy.

## Contribution

It introduces a method using eigenvectors of Hund's case (a) matrices to compute line strengths, highlighting perturbation effects in the (5,4) band.

## Key findings

- Larger than expected perturbation effects observed in the (5,4) band.
- Good agreement between calculated and experimental spectra.
- Method effectively captures perturbation influences on line strengths.

## Abstract

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