Dipole-field contributions to geometric-phase-induced false electric-dipole-moment signals for particles in traps

It has been shown in an earlier publication [J. Pendlebury Phys. Rev. A 70, 032102 (2004)] that magnetic-field gradients applied to particles in traps can induce Larmor frequency shifts that may falsely be interpreted as electric-dipole moment signals. This study has now been extended to include nonuniform magnetic-field gradients due to the presence of a local magnetic dipole. It is found that, in the high orbit-frequency regime, .the magnitude of the shifts can be enhanced beyond the simple expectation of proportionality to the volume-averaged magnetic-field gradient <partial derivative B-z/partial derivative z >.