User:Gerrit C. Groenenboom/Hönl-London factors

In spectroscopy Hönl-London factors give the dependence of line intensities on the rotational quantum numbers of molecules. Different sets of quantum numbers can be used to describe the rotation of molecules. For linear molecules these choices are known as Hund's cases. The expressions for the Hönl-London factors depend on this choice. The expressions in the 1925 publication of Hönl and London (in German) are applicable to one-photon transitions in Hund's case (a) diatomic molecules and symmetric top molecules.