Reliability of Herman–Wallis factors for Raman spectroscopy of Q-branch molecular transitions

The centrifugal force in a rotating molecule influences the intensity of spectral lines. This effect is quantified by the so-called Herman–Wallis factor, but its calculation is rather involved and the result is uncertain for Q-branch Raman transitions. This Letter discusses the reliability of various predictions by means of an experimental proof based on coherent anti-Stokes Raman scattering from H2 molecules.