Parity and nuclear spin symmetry are approximate symmetries, which for many primary processes in molecular spectroscopy and kinetics lead to almost exact constants of the motion [1-3]. The violation of these symmetries leads to very slow primary processes such as the time dependence of parity or nuclear spin symmetry, which can be observed, in principle, by the generation of exotic quantum superposition states for instance of two different enantiomers [4], which would also provide access to the measurement of the parity violating energy difference ∆_pvE between the ground states of the enantiomers, predicted to be very small in the sub-eV range, but not yet confirmed experimentally (refs. [1-5] and references cited therein). ClSSCl is chiral and has been investigated in this context predicting a ∆_pvE of about 0.17 feV [6], making it suitable for such experiments.

The symmetric isotopomer ³⁵Cl³²S³²S³⁵Cl is chiral with two enantiomers, each of which has also two nuclear spin isomers (ortho and para). Recent microwave spectroscopy has indicated ‘forbidden’ microwave transition between these nuclear spin isomers [7]. ClSSCl is thus a unique example to study the two time dependent processes of nuclear spin symmetry and parity violation for the first time ever. We report quantum dynamical simulations demonstrating these phenomena in detail. We shall also discuss the general concept of preparing a quantum system in an exotic superposition ’chameleon state’ with a time dependent spectrum but constant energy eigenstate populations [1].

[1] M. Quack, G. Seyfang, G.Wichmann, Adv. Quant. Chem., 2020, 81, 51-104.
[2] M. Quack, Fundamental Symmetries and Symmetry Violations from High Resolution Spectroscopy, chapter 18 in ‚Handbook of High-Resolution Spectroscopy‘, Vol. 1, pages 659- 722, M. Quack, and F.
Merkt, Eds., Wiley Chichester, 2011, ISBN-13: 978-0-470-06653-9.
[3] R. Marquardt and M. Quack Eds. Molecular Spectroscopy and Quantum Dynamics, Elsevier, Amsterdam, 2020, ISBN: 9780128172346
[4]  M. Quack, Chem. Phys. Letters., 1986, 132, 147.
[5]  M. Quack and G. Seyfang, Tunnelling and Parity Violation in Chiral and Achiral Molecules: Theory and High-resolution Spectroscopy, chapter 6 in ‚Tunnelling in Molecules: Nuclear Quantum Effects from Bio to Physical Chemistry‘, J. Kästner, and S. Kozuch Eds. The Royal Society of Chemistry, Cambridge, 2021, pages 192-244, ISBN: 978-1-78801-870-8
[6] R. Berger, M. Gottselig, M. Quack and M. Willeke, Angew. Chem. Int. Ed., 2001, 40, 4195–4198.
[7] H. Kanamori, Z.T. Dehghani, A. Mizoguchi and Y. Endo, Phys. Rev. Lett., 2017, 119, 173401-1 -173401.-5.