Parity Violation in Molecules

The fundamental symmetries and conservation laws are essential building blocks in our understanding of the physical-chemical world. If, as in the traditional theory of atoms and molecules, only the electromagnetic interaction is included, the symmetry with respect to space inversion is generally accepted. But if also the electroweak interaction is taken into account, a parity violating energy difference ΔPVE between the two enantiomers (R,S) of a chiral compound is obtained. This energy difference corresponds to a reaction enthalpy ΔPVH0ø for the stereomutation   R ⇔ S.
Theoretical calculations show that this parity violating energy difference is extremely small, in the order of 10-11 Jmol-1 [1-6]. The parity violating energy difference has been measured for atoms [7], but its experimental verification for molecules is still missing. Three different experimental methods have been proposed to measure ΔPVE for molecules.

References:

  1. A.Bakasov, T.K.Ha, and M.Quack, J.Chem. Phys. 109, 7263 (1998); R.Berger and M.Quack, J.Chem.Phys. 112, 3148 (2000)
  2. M.Quack and J.Stohner, Phys.Rev.Lett. 84, 3807, (2000) and J.Chem.Phys, 119, 11228 (2003)
  3. J.K.Laerdahl, P.Schwerdtfeger and H.M.Quiney, Phys.Rev.Lett. 84, 3811 (2000)
  4. R.Berger in ‘Relativistic Structure Theory, Part 2: Applications’, P.Schwerdtfeger (edt.), Theoret. and Comput. Chem. 14, 188 (2002)
  5. M.Quack, J.Stohner, and M.Willeke, Ann. Rev. Phys. Chem. 59, 741 (2008)
  6. M.Quack, ‘Fundamental Symmetries and Symmetry Violations from High-resolution Specttroscopy’, in Handbook of High-resolution Spectroscopy, Vol.1, pages 659 – 722, M.Quack and F.Merkt (eds.), Wiley, Chichester (2011)
  7. S.C.Bennet and C.Wiemann, Phys. Rev. Lett. 82, 2484 (1999)

Image and mirror image of the chiral moloecule CHFBrI

Parity violating energy difference ΔPVE for the ground and ΔPVE* for an excited state