Angular distribution of photoelectrons in resonant photoionization of polarized atoms

The angular distribution of photoelectrons produced by excitation of polarized atoms to autoionizing states is analysed. In particular, core-excited autoionizing states produced in absorption of synchrotron radiation by laser-pumped excited atoms are considered. A general expression for the angular distribution of arbitrarily oriented laser and synchrotron beams is obtained and further reduced to a simpler form for a particular geometry used in experiments. A case of an isolated autoionizing state (resonance) interacting with several continua is considered and parametrization of the observable parameters in the region of the resonance is discussed. Peculiarities of the circular dichroism in the region of autoionizing resonances are analysed. Formulae suitable for particular resonances with J<or=5/2 are presented and all parameters necessary for analysis of experimental angular distributions are tabulated. As examples, excitations of autoionizing 2p⁵3s3p and 2s3p² states in Na and 3p⁵3d4s4p states in Ca are considered. Theoretical angular distributions are compared with recent experimental data.