Phenomenon of the time-reversal-violating photon polarization plane   rotation by a gas placed to an electric field
  T-odd P-odd phenomenon of the photon polarization plane rotation (circular dichroism) is considered for an atomic (molecules) gas placed to an electric field. The expression for the T non-invariant polarizability of an atom (molecule) placed to an electric field is obtained. It is shown that the T-odd plane rotation angle increases when the interaction energy of an atom (molecule) with an electric field is the same order as the opposite parity levels spacing. 
Vladimir G. Baryshevsky