Photoexcitation of an autoionizing resonance in the presence of off-diagonal relaxation

We discuss the theory of photoexcitation of an autoionizing resonance. We solve a set of coupled stochastic integrodifferential equations which are based on the Fano model for autoionization, but which include the effects of weak elastic collisions, weak or strong laser excitation, and finite laser bandwidth. We determine the exact photoelectron spectrum and give formulas for spectral peak positions and widths. Redistributive scattering is evident, as are various effects normally associated only with transitions between discrete levels. Under certain conditions symmetries and fixed points of the electron spectrum can be predicted.