The manifestation of atomic and core resonances in photoelectron energy spectra of two-electron atoms is discussed in detail. An approach to the general problem of elimination of strongly coupled continua is presented and quantitative requirements for the validity of the theory are obtained. The theory is applied to calcium thus providing a theoretical interpretation of, and additional insight into, all features of an experiment by Walker et al. [Phys. Rev. Lett. 75, 633 (1995)].

• Received 30 August 1996

DOI:https://doi.org/10.1103/PhysRevA.55.2232