Interference between dielectronic and radiative recombination of Be-like highly charged ions

We perform a systematical study for the polarization of x rays emitted when a free electron is captured by Be-like highly charged ions theoretically. We focus on the dielectronic recombination of the J = 1/2 -> J = 1/2 transition and its polarization is zero due to axial symmetry. Including the interference between the dielectronic and radiative recombinations, the polarization changes dramatically when the electron energy crosses the resonant energy. By comparing the simulations with or without certain interactions, we found that the Breit interaction is not important even for very high-Z ions. For low-Z ions, the configuration interaction of the dielectronic recombination states affects the polarization greatly, while for high-Z ions the configuration interaction of the ground state of Be-like ions plays an important role.