THEORY OF CORE-RESONANT IONIZATION

We present the theory of photoelectron energy spectra in two-electron atoms strongly driven by a field near resonance with the ionic core. W e show that the unavoidable simultaneous excitation of the atomic reso nance transition and the ever present a.c. Stark shifts leads to rich structure in the spectrum not predictable by simplified models. We pre sent quantitative results for calcium which illustrate the theory and also pertain to ongoing experiments.