  The measurement of electric dipole moment in storage rings can potentially
exceed the sensitivity of tests with neutral systems. The spin dynamics under
such conditions is described by the Bargmann-Michel-Telegdi equation. It can be
derived in the semiclassical approximation under several assumptions one of
which is the zero pseudoscalar bilinear. However, many promising extensions to
the standard model consider scalar-pseudoscalar couplings which assume nonzero
electron pseudoscalar. We re-derive the spin precession equation under
conditions that do not assume that pseudoscalar is zero. It leads to a
correction term that might be required for matching the storage ring
measurements with QFT evaluations.
