Polarization studies on the two-step radiative recombination of highly-charged, heavy ions

The radiative recombination of a free electron into an excited state of a bare, high-Z ion is studied, together with its subsequent decay, within the framework of the density matrix theory and Dirac's relativistic equation. Special attention is paid to the polarization and angular correlations between the recombination and the decay photons. In order to perform a systematic analysis of these correlations the general expression for the double-differential recombination cross section is obtained by making use of the resonance approximation. Based on this expression, detailed computations for the linear polarization of x-ray photons emitted in the (e, 2\gamma) two-step recombination of uranium ions U^92+ are carried out for a wide range of projectile energies.