Theoretical analysis of angular correlation between the photoelectron and subsequent polarized fluorescent photon in atomic photoionization

The angular correlation between the photoelectron and subsequent polarized fluorescent radiation measured in coincidence is analysed theoretically for atomic photoionization. Using the density matrix and statistical tensor formalism the general expression for the correlation function is obtained for an arbitrary polarized incident photon beam. The particular geometry of a recent experiment (Beyer et al., 1995) is considered and the parameters which determine the angular correlation are expressed in terms of photoionization amplitudes. It is demonstrated that the photoelectron- (polarized) fluorescence coincidence measurements reveal strong circular and linear dichroism. As an example the photoionization of Ca atoms near the 4p 2P3/2 threshold is calculated within the framework of multichannel quantum defect theory.