The Current Image of the Fundamental Asymmetry of Time and Space in Molecular Dynamics

Martin Quack

ETH Zurich, Switzerland

The traditional image of time and space in molecular dynamics pictured them in two equivalent mirror image forms each, with a space inverted and a time reversed system being equivalent to the original systems before taking the mirror image. In technical terms this corresponds to the symmetry under space inversion and time reversal in the dynamical system. Symmetries can furthermore be related to conservation laws and ‘nonobservables’ . The inversion symmetry of space, for instance, corresponds to parity conservation. Since the discovery of parity violation 50 years ago in nuclear and high energy physics, we know that the mirror image of a molecule does not exactly correspond to the physically realized enantiomer, or ‘mirror image isomer’, thus the real image shows a slight asymmetry, which also is observable as a slight energy difference between enantiomers of chiral molecules.

The spectroscopic observation of the small parity violating energy difference D_pvE between the two enantiomers of a chiral molecule predicted within the framework of the standard model of high energy physics remains one of the greatest challenges of current molecular physics with possible consequences also for biomolecular evolution [1-3].

A possible, very difficult spectroscopic experiment has been proposed by us about two decades ago [4,5].The first requirement for such an experiment is the analysis of rovibrationally resolved optical(infrared or visible or ultraviolet) spectra of chiral molecules and the experimental breakthrough achieving this goal arose from work in our group around 1995(see refs 1-3 for reviews). A major theoretical breakthrough occurred about at the same time , when we discovered that earlier estimates for D_pvE were too low by one to two orders of magnitude for the prototype molecules H₂O₂ and H₂S₂ and also other chiral molecules [6-8]. This striking result has in the meantime been reconfirmed by a variety of other quantum chemical techniques and from other theoretical groups and can be considered reliable (for a recent review see [1-3]). Still the predicted energy differences remain very small; in the Attohartree range 10^–18 E_h to 10^–15 E_h or 2.6 pJ mol^–1 to 2.6 nJ mol^–1 is fairly typical, depending on the molecule. The corresponding spectroscopic challenge is substantial. In the lecture we shall report about current experimental and theoretical work of the Zurich group (see also [9,10]) also in relation to work of other groups. If time permits we will also discuss possible CPT tests according to our scheme [1,11]. This, indeed, would lead to a completely revised image of time and space asymmetries in physics and chemistry.

References:

1. M. Quack, in Modelling Molecular Structure and Reactivity in Biological Systems, Proc. 7th WATOC Congress , Capetown 2005, edited by K. Naidoo, J. Brady, M. Field, J. Gao, and M. Hann (Royal Society of Chemistry, Cambridge, 2006), pp. 3 - 38.

2. M. Quack and J. Stohner, Chimia 59, 530-538 (2005).

3. M. Quack, Angew. Chem. Int. Ed. (Engl.) 114, 4618-4630 (2002).

4. M. Quack, Chem. Phys. Lett. 132, 147-153 (1986).

5. M. Quack, Angew. Chem. Int. Ed. (Engl.) 28, 571-586 (1989).

6. A. Bakasov, T. K. Ha, and M. Quack, in Chemical Evolution, Physics of the Origin and Evolution of Life, Proc. of the 4th Trieste Conference (1995), edited by J. Chela-Flores and F. Raulin (Kluwer Academic Publishers, Dordrecht, 1996), pp. 287-296.

7. A. Bakasov, T. K. Ha, and M. Quack, J. Chem. Phys. 109, 7263-7285 (1998).

8. R. Berger and M. Quack, J. Chem. Phys. 112 (7), 3148-3158 (2000).

9. R. Berger, G. Laubender, M. Quack, A. Sieben, J. Stohner, and M. Willeke, Angew. Chem. Int. Ed. (Engl.) 44, 3623-3626 (2005).

10. M. Quack and M. Willeke, J. Phys. Chem. A 110, 3338-3348 (2006).

11. M. Quack,chapter 27 in Femtosecond Chemistry, Proc. Berlin Conf. Femtosecond Chemistry, Berlin (March 1993), edited by J. Manz and L. Woeste (Verlag Chemie, Weinheim, 1995), pp. 781-818.