Line strengths for fine- and hyperfine-resolved electric-quadrupole rotation-vibration transitions in Hund’s case b molecules

We report the derivation of line-strength formulae for fine- and hyperfine-resolved electric-quadrupole rotation–vibration transitions in Hund's case b molecules using the formalism of spherical tensor algebra. These expressions may serve in the analysis of spectra of linear molecules, in particular diatomic molecules such as H2, N2 and their ions, which are of current interest in precision spectroscopy.