Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


The broken mirror: Can parity violation in molecules finally be measured?


Scientists from the PRISMA⁺ Cluster of Excellence and the Helmholtz Institute Mainz propose a promising way to detect parity violation in molecules for the first time

Scientists have long tried to experimentally demonstrate a certain symmetry property of the weak interaction - parity violation - in molecules. So far, this has not been possible.

Schematic illustration of parity violation in a molecule containing two nuclear spins

©: Dr. John W. Blanchard

A new interdisciplinary effort led by a research group at the at the PRISMA⁺ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz (HIM) has now shown a realistic path to demonstrating this phenomenon.

The approach includes aspects of nuclear, elementary particle, atomic and molecular physics as well as nuclear magnetic resonance (NMR). “Molecular parity nonconservation in nuclear spin couplings” is published in the current issue of the journal Physical Review Research.

Symmetries are omnipresent - in space as well as in the world of molecules, atoms and elementary particles. The four fundamental forces (electromagnetism, gravity, and the strong and weak nuclear forces) also obey certain, perhaps seemingly abstract, symmetries.

From the Big Bang to the present day, existing symmetries were repeatedly broken. Symmetry and symmetry breaking are necessarily reflected in the physical processes and states that we can observe.

One of these symmetries is the mirror symmetry (symmetry with regard to reflection in space) – if it is broken, the researchers speak of parity violation. According to current knowledge, the weak interaction is the only one among the four fundamental forces that does not appear mirror-symmetrical:

Only in processes that are subject to this interaction do parity violations occur. "Since the weak interaction plays almost no role in our everyday experience – gravity and electromagnetism dominate here – the phenomenon of parity violation contradicts our normal idea and is therefore difficult to grasp," says Dr. John Blanchard, lead author of the study.

“Parity violation in the weak interaction was therefore only theoretically predicted in the 1950s and was discovered shortly afterwards in certain nuclear and elementary particle decays. Parity-violating processes have never been detected in molecules, although theoretical calculations predict that they should be there. Definitive evidence of such subtle effects is, so to speak, a holy grail of precision-measurement physics.”

Many attempts have been made to experimentally observe the effects of parity violation in molecules. One example is the interaction of the spins of different atomic nuclei in a molecule. In turn, these can in principle be detected and analyzed using nuclear magnetic resonance methods (NMR). While the team of scientists has already developed a promising approach to chiral molecules in a previous work (, their current publication focuses on simple molecules that consist of as few as two atoms.

First of all, they identify a special NMR measurement variable (a specific spin-spin coupling) on the basis of which the parity violation is shown and carry out complex theoretical analyses to calculate the expected effect within the molecule. These calculations were carried out in close collaboration with the co-author of the study, Prof. Mikhail G. Kozlov from the Nuclear Physics Institute in St. Petersburg, Russia, with whom the Mainz group has been working very successfully for many years.

Building on this, the scientists propose a special experiment that should be sensitive enough to detect the calculated signals: “The so-called ZULF (zero to ultra-low field) NMR method is an exotic technique that we were already using for dark matter successfully,” explains Prof. Dr. Dmitry Budker, also an author of the study. “It offers a system in which nuclear spins interact with each other more than with an external magnetic field. In this way, it enables the direct measurement of antisymmetric spin-spin couplings, which are cut off in conventional high-field NMR experiments.”

"Our results show an elegant way to quantitatively investigate the weak interaction in molecules and atomic nuclei," concludes Dr. Blanchard. "The results of our feasibility study are very promising – we hope to soon have experimental verification of molecular parity nonconservation."

Wissenschaftliche Ansprechpartner:

Prof. Dr. Dmitry Budker
Quantum, Atomic and Neutron Physics (QUANTUM)
Institute of Physics and PRISMA+ Cluster of Excellence
Johannes Gutenberg-University Mainz
55099 Mainz
Tel. +49 6131 39-29630

Dr. John W. Blanchard
Helmholtz Institute Mainz / Johannes Gutenberg-University Mainz
55099 Mainz
Tel.: +49 6131 39-29632


John W. Blanchard, Jonathan P. King, Tobias F. Sjolander, Mikhail G. Kozlov, Dmitry Budker Molecular parity nonconservation in nuclear spin couplings
Physical Review Research (Vol. 2, No. 2 - 023258, 01 June 2020)
DOI: 10.1103/PhysRevResearch.2.023258

Weitere Informationen:

Dr. Renée Dillinger-Reiter | idw - Informationsdienst Wissenschaft

More articles from Physics and Astronomy:

nachricht Black phosphorus-based van der Waals heterostructures for mid-infrared light-emission applications
13.07.2020 | Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, Chinese Academy

nachricht Robust high-performance data storage through magnetic anisotropy
13.07.2020 | Helmholtz-Zentrum Berlin für Materialien und Energie

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron cryo-microscopy: Using inexpensive technology to produce high-resolution images

Biochemists at Martin Luther University Halle-Wittenberg (MLU) have used a standard electron cryo-microscope to achieve surprisingly good images that are on par with those taken by far more sophisticated equipment. They have succeeded in determining the structure of ferritin almost at the atomic level. Their results were published in the journal "PLOS ONE".

Electron cryo-microscopy has become increasingly important in recent years, especially in shedding light on protein structures. The developers of the new...

Im Focus: The spin state story: Observation of the quantum spin liquid state in novel material

New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices

Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Latest News

Shedding light on the brown color of algae

14.07.2020 | Life Sciences

Color barcode becomes ISO standard

14.07.2020 | Information Technology

New substance library to accelerate the search for active compounds

14.07.2020 | Life Sciences

Science & Research
Overview of more VideoLinks >>>