2015: Measurement of a false electric dipole moment signal from 199Hg atoms exposed to an inhomogeneous magnetic field

Eur. Phys. Jour. D 69, (2015)

Afach S, Baker CA, Ban G, Bison G, Bodek K, Chowdhuri Z, Daum M, Fertl M, Franke B, Geltenbort P, Green K, van der Grinten MGD, Grujic Z, Harris PG, Heil W, Hélaine V, Henneck R, Horras M, Iaydjiev P, Ivanov SN, Kasprzak M, Kermaïdic Y, Kirch K, Knowles P, Koch HC, Komposch S, Kozela A, Krempel J, Lauss B, Lefort T, Lemière Y, Mtchedlishvili A, Naviliat-Cuncic O, Pendlebury JM, Piegsa FM, Pignol G, Prashant PN, Quéméner G, Rebreyend D, Ries D, Roccia S, Schmidt-Wellenburg P, Severijns N, Weis A, Wursten E, Wyszynski G, Zejma J, Zenner J, Zsigmond G




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.