Recent experimental and theoretical developments towards the observation of parity violation (PV) effects in molecules by spectroscopy

Abstract

Parity violation (PV) at the molecular level is known to be responsible for a tiny energy difference between the two enantiomers of a chiral molecule. This parity violation energy difference (PVED) has not yet been detected by experiment. In the last few years, the search for PV effects in molecules has made important steps ahead for several reasons. On one hand, very accurate infra-red spectroscopy measurements were performed by metrologists on bromochlorofluoromethane (CHFClBr) with a 10 Hz accuracy, which so far is the most precise. On the other hand, relativistic calculations were used for the evaluation of DeltaE(PV) allowing for a screening of favorable molecules for future measurements. The synthesis of such chiral molecules with high parity violation effects is currently being investigated. In memory of Professor Jean-Bernard Robert.

Quantum stochastic resonance in parity violating chiral molecules

“…Electroweak quantum chemistry calculations predict the PVED to be between 10 À13 and 10 À21 eV [8][9][10][11] but no conclusive energy difference has been reported, for instance, in experimental spectroscopic studies of the CHBrClF molecule reaching an energy resolution of about 10 À15 eV. 12 It is however noticeable the experimental results of Wang et al 13,14 in which a chiral discriminating phase transition without conformational changes was obtained at temperature 77-300 K for D/L-alanine and valine. It was interpreted as a manifestation of the PVED and related to the phase transition postulated by Salam.…”

Molecular collisions in ultracold atomic gases

“…There is interest in producing a quantum gas of 6 Li 7 Li in its ground rovibronic state in an ultracold mixture of 6 Li and 7 Li atoms. In order to stabilize the molecular cloud against two-body trap losses induced by the reactive process (15), the remaining atomic 7 Li would have to be removed quickly after ground-state molecule production, so that just the two-species fermionic mixture of 6 Li 7 Li(v = 0, j = 0) molecules and 6 Li atoms is left in the trap. The 6 Li cloud could be removed as well, but it might be advantageous to keep it in the trap.…”

“…High-resolution spectroscopy on cold molecules may allow the measurement of fundamental physical properties such as the electric dipole moment of the electron [13], the energy differences between enantiomers [14,15] and the time-dependence of the fine-structure constant [16]. In addition, since molecules have a much richer energy level structure than atoms, they offer many new possibilities for quantum control.…”

An alternative route to detect parity violating energy differences through Bose–Einstein condensation of chiral molecules

“…[4][5][6][7][8][9][10][11][12][13][14] However, no conclusive energy difference has been reported, for example, in experimental spectroscopic studies of the CHBrClF molecule reaching an energy resolution of about 10 À15 eV. 15,16 The importance of this symmetry-breaking in molecules is twofold: (i) at a fundamental level, the intrinsic chiral nature which is present in some molecules should reflect the underlying interaction containing pseudoscalar magnitudes such as those appearing in the weak interaction; and (ii) it could be intimately related to the origin of homochirality, that is, the almost exclusive one-handedness of the chiral molecules found in living systems, e.g. L-amino acids and D-sugars, this being one of the most fascinating open problems which links fundamental physics with the biochemistry of life.…”