Photoelectron circular dichroism: Chiral asymmetry in the angular distribution of electrons emitted by (+)-S-carvone.

The technique of photoelectron circular dichroism (PECD) is introduced and illustrated by the presentation of results obtained for the C 1s core ionization of (+)-S-carvone enantiomers. Using circularly polarized ionizing radiation, large chiral effects in the angular distribution of photoelectrons emitted from a dilute, randomly oriented gas phase sample can be detected. This effect is predicted in the pure electric dipole approximation and is expected to be quite general. The forward-backward asymmetry regularly exceeds 10%, as demonstrated here for the carbonyl C 1s photoemission of carvone. Calculations are presented that reveal a pronounced dependence of this effect on molecular conformation. In the case of carvone the PECD associated with the C 1s electron localized at the carbonyl group varies with orientation of the isopropenyl tail group at the opposite end of the molecule. Comparisons of calculations with experiment confirm the molecular configuration and permit inferences to be drawn concerning the relative conformer populations in the experimental sample.