Influence of spatial degeneracy on rotational spectroscopy: Three-wave mixing and enantiomeric state separation of chiral molecules.

Pulse flip angles are calculated for three-wave mixing, three-state cycles of chiral molecules to produce optimized free induction decay amplitudes proportional to the enantiomeric excess of a sample and to produce optimized degrees of state-specific enantiomeric separation. The calculations account for the spatial degeneracy of the levels involved and the resulting inhomogeneous distribution of transition dipole moments. Cycles of transitions that include R followed by Q followed by P branch transitions display only modest reductions of the calculated optimal signals compared to those calculated if every M component was optimally polarized. Transition cycles P-Q-R are only slightly worse, while the Q-Q-Q cycles are much worse, increasingly so, as the rotational total quantum number is increased.