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Measurement and Investigation of the Xenon-129 electric dipole moment


The existence of electric dipole moments (EDMs) of atoms or the neutron is still an unresolved question which could indicate new physics beyond the standard model. EDMs could be a source of CP violation which is thought to be responsible for the different behavior of particles and antiparticles. That would explain the apparent matter-antimatter asymmetry in the universe.

The precession of co-located 3He/129Xe nuclear spins can be used as ultra-sensitive probe for non-magnetic spin interactions of type Δω ~ dXeE, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference Δω of their Larmor frequencies [1]. The measurement principle is based on simultaneously recording the free spin precession of 3He and 129Xe with liquid-helium-cooled SQUIDs. The experiment is being set up inside our magnetically shielded room. The envisioned measurement procedure includes

1. preparation of the polarized gas mixture outside of MSR;
2. a polarization-preserving transfer of the gases into the EDM cell;
3. an adiabatic spin rotation by rotating the field from transverse to vertical;
4. starting spin precession by non-adiabatic switching from vertical to transverse;
5. a long-term measurement of spin precession using LTc SQUID gradiometers.


F. Allmendinger, I. Engin, W. Heil, S. Karpuk, H.-J. Krause, B. Niederländer, A. Offenhäusser, M. Repetto, U. Schmidt, S. Zimmer, Measurement of the Permanent Electric Dipole Moment of the 129Xe Atom, Phys. Rev. A 100, 022505 (2019).

Partner: University of Mainz, University of Heidelberg, University of Groningen

Principal investigators: Prof. Werner Heil (Universität Mainz), Prof. Ulrich Schmidt (Universität Heidelberg)

Further information: project website

Status: active