States behaving like autoionizing states can be selectively induced by laser radiation into one of the continuum spin channels in the photoionization of polarized excited alkaki atoms. As a result of destructive or constructive interference between the direct ionization channel and those introduced by the dressing laser radiation, the cross section of this specific spin component is completely suppressed or enhanced, while leaving the other spin channel unaffected. The $q$ parameter which determines the line shape of the Fano-type resonance can be resonantly tuned as a function of the dressing laser frequency.

• Received 3 December 1982

DOI:https://doi.org/10.1103/PhysRevA.27.1713