The nuclear Schiff moment

Full text: Parity and time invariance violating (P,T-odd) nuclear forces produce P,T-odd nuclear moments. These moments can induce electric dipole moments (EDMs) in atoms through the mixing of electron wave functions of opposite parity. In diamagnetic atoms the nuclear Schiff moment induces an EDM. Previously the interaction with the Schiff moment has been defined for a point-like nucleus No problems arise with the calculation of the electron matrix element of this interaction as long as the electrons are considered to be non-relativistic. However, a more realistic model obviously involves a nucleus of finite-size and relativistic electrons. We have calculated the finite nuclear-size and relativistic corrections to the Schiff moment. The relativistic corrections originate from the electron wave functions and are incorporated into a 'nuclear' moment, which we call the local dipole moment. For 199Hg these corrections amount to 25%. We have found that the natural generalization of the electrostatic potential of the Schiff moment for a finite-size nucleus corresponds to an electric field distribution which, inside the nucleus, is well approximated as constant and directed along the nuclear spin, and outside the nucleus is zero