Photoemission studies of chiral metal surfaces using circularly polarized synchrotron radiation

In an attempt to measure classical circular dichroism (CD) in the photoemission of electrons from a solid surface, valence-band photoemission from clean and adsorbate-covered chiral metal surfaces has been investigated using circularly polarized synchrotron radiation. An experimental geometry was used whereby q, the polarization of the radiation, k, the wave vector of the photoemitted electrons, and n, the surface normal, were coplanar. It was anticipated that by doing this, so-called CDAD (circular dichroism in the angular distribution) effects associated with chiral photoemission geometries would be decoupled from classical CD arising from the difference in absorption cross-section for left and right circularly polarized light of electrons in energy states associated with R and S kinks. However, from the magnitude of the effects observed, it is evident that any classical CD features in the photoelectron spectrum arising from kinks, including photoemission from surface states or resonances, are swamped by other dichroic effects. We conclude that final-state effects in the diffraction of photoelectrons dominate the intensity of all peaks observed in angle-resolved photoemission from chiral, single crystal, metal surfaces using circularly polarized photons.