Eur. Phys. J. D (2015) 69: 225
https://doi.org/10.1140/epjd/e2015-60207-4

Regular Article

Measurement of a false electric dipole moment signal from ¹⁹⁹Hg atoms exposed to an inhomogeneous magnetic field

¹ ETH Zürich, Institute for Particle Physics, 8093 Zürich, Switzerland
² Paul Scherrer Institute (PSI), 5232 Villigen-PSI, Switzerland
³ Hans Berger Department of Neurology, Jena University Hospital, 07747 Jena, Germany
⁴ Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
⁵ LPC Caen, ENSICAEN, Université de Caen Basse-Normandie, CNRS/IN2P3, Caen, France
⁶ Marian Smoluchowski Institute of Physics, Jagiellonian University, 30–059 Cracow, Poland
⁷ Institut Laue-Langevin, Grenoble, France
⁸ Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH, UK
⁹ Physics Department, University of Fribourg, 1700 Fribourg, Switzerland
¹⁰ Institut für Physik, Johannes–Gutenberg–Universität, 55128 Mainz, Germany
¹¹ LPSC, Université Grenoble Alpes, CNRS/IN2P3, Grenoble, France
¹² Henryk Niedwodniczański Institute for Nuclear Physics, 31–342 Cracow, Poland
¹³ Instituut voor Kern – en Stralingsfysica, University of Leuven, 3001 Leuven, Belgium
¹⁴ CSNSM, Université Paris Sud, CNRS/IN2P3, Orsay Campus, France

^a Present address: University of Washington, Seattle WA, USA.
^b Present address: Max-Planck-Institute of Quantum Optics, Garching, Germany.
^c Present address: LPSC, Grenoble, France.
^d Present address: Hauptstrasse 60, 4455 Zunzgen, Switzerland.
^e On leave from INRNE, Sofia, Bulgaria.
^f On leave from PNPI, St. Petersburg, Russia.
^g e-mail: kermaidic@lpsc.in2p3.fr
^h Present address: Rilkeplatz 8/9, 1040 Vienna, Austria.
ⁱ Present address: Michigan State University, East-Lansing, USA.
^j Deceased.
^k e-mail: rebreyend@lpsc.in2p3.fr

Received: 31 March 2015
Received in final form: 31 July 2015
Published online: 6 October 2015

Abstract

We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for ¹⁹⁹Hg atoms contained in a volume permeated with aligned magnetic and electric fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.