Parity nonconservation in the radiative recombination of electrons with heavy hydrogen-like ions

The parity nonconservation effect on the radiative recombination of electrons with heavy hydrogen-like ions is studied. Calculations are performed for the recombination into the 21S0 state of helium-like thorium and gadolinium, where, due to the near-degeneracy of the opposite-parity 21S0 and 23P0 states, the effect is strongly enhanced. Two scenarios for possible experiments are studied. In the first scenario, the electron beam is assumed to be fully polarized while the H-like ions are unpolarized, and the polarization of the emitted photons is not detected. In the second scenario, the linearly polarized photons are detected in an experiment with unpolarized electrons and ions. Corresponding calculations for the recombination into the 23P0 state are presented as well.