Radiative corrections to parity-nonconserving transitions in atoms

The matrix element of a bound electron interacting with the nucleus through exchange of a Z boson is studied for the gauge-invariant case of 2s(1/2)-2p(1/2) transitions in hydrogenic ions. The QED radiative correction to the matrix element, which is -alpha/2pi in lowest order, is calculated to all orders in Zalpha using exact propagators. Previous calculations of the first-order binding correction are confirmed both analytically and by fitting the exact function at low Z. Consequences for the interpretation of parity nonconservation in cesium are discussed.