Rotationally resolved Fano effect of HI molecules: An experimental study using coherent vacuum-ultraviolet radiation

An experiment studying the influence of molecular rotation in HI on photoelectron-spin polarization is presented. The experiment is highly wavelength selective since a laser-based vacuum-ultraviolet-radiation source with a bandwidth of 0.5×${10}^{\mathrm{-}4}$ nm is applied to produce circularly polarized light. Although in the Fano effect the kinetic energy of the photoelectrons is not analyzed, rotational structure is resolved via narrow-band excitation of autoionization resonances. The photoelectron-spin polarization is found to be strongly affected by the rotational substructure, leading to changes in both magnitude and sign for different rotational lines.