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The angular dependence of the circular dichroism in photoemission from Pt(111) was investigated for excitation with VUV and soft X-ray radiation. VUV excitation was used to probe band structure and the circular dichroism for valence band emission. The measurements are compared to full relativistic single step photoemission calculations. XPS was used to investigate the circular dichroism in emission from the 4f core level. In this case, the dichroism is induced by photoelectron diffraction. First results from single step core level calculations are compared to the experimental observations. [ABSTRACT FROM AUTHOR]

The energy dependence of the circular dichroism in the angular distribution of photoelectrons (CDAD) was investigated from the shallow Cs 5p core levels. Cesium was prepared in a hexagonal ordered monolayer on W(110). The results are mainly influenced by scattering of the photoelectrons within the adlayer. At low energies, the behavior observed is described by means of a model that treats only the back-scattering of photoelectrons at the potential step between the adlayer and the substrate. It leads to a simple method determining the position of the monolayer with respect to the substrate. In this approach, the back-scattering model is matched with the measured energy dependence of the CDAD between hν = 21 eV and hν = 33 eV. This procedure yields reliable results already for a single observation angle of the photoelectron. The distance between cesium and tungsten was determined to be (2.2 ± 0.1) Å, which corresponds to the effective distance between the center of the adsorbed layer and the potential step between the layer and the substrate. Finally, the fitted result was proven to meet the complete angular dependence of the CDAD at different photon energies. [ABSTRACT FROM AUTHOR]

The observation of magnetic circular dichroism in the angular distribution of photoelectrons (MCDAD) from alkali and rare-gas films adsorbed on a thin remanently magnetized Co layer is reported. The observation of an antisymmetric MCDAD near normal emission for Co(0001)-Cs 5p semi core level is shown. The reversed magnetization leads to a mirror-image-like distribution. The second system under investigation, physisorbed Co(0001)-Xe 5p, does not give such an but shows significant differences in the MCDAD signal for both directions of magnetization, in particular in the m[sub j] substates of the p[sub 3/2] level. A magnetic coupling between Xe and Co is evident when we take results of spin-resolved photoemission into account. The observation of magnetic circular dichroism in the angular distribution of photoelectrons (MCDAD) from alkali and rare-gas films adsorbed on a thin remanently magnetized Co layer is reported. The observation of an antisymmetric MCDAD near normal emission for Co(0001)-Cs 5p semi core level is shown. The reversed magnetization leads to a mirror-image-like distribution. The second system under investigation, physisorbed Co(0001)-Xe 5p, does not give such an but shows significant differences in the MCDAD signal for both directions of magnetization, in particular in the m[sub j] substates of the p[sub 3/2] level. A magnetic coupling between Xe and Co is evident when we take results of spin-resolved photoemission into account. [ABSTRACT FROM AUTHOR]

A new approach for investigations of circular dichroism in the angular distribution of photoelectrons (CDAD) is presented. The image contrast using a photoemission line of a certain material is combined with imaging of the angular distribution pattern using a photoemission electron microscope (PEEM). CDAD can be used to investigate pure scattering information by means of the same instrument in microscopically selected regions on a surface. The experiment combines angle-resolved XPS imaging with the indirect mapping of the local environment of atoms by means of CDAD holography. In a conventional photoelectron diffraction or photoelectron holography experiment, it is necessary to move the sample and/or the detector; for example, a rotatable electron analyzer is used to map a full angular pattern. In the present approach, the diffraction plane is mapped for a certain kinetic energy of electrons in the backfocal plane. An imaging high-pass energy filter has been used in combination with the PEEM in order to acquire surface images and/or diffraction pattern maps. Direct photoemission from the W-4f core levels was observed at different photon polarization to obtain two images and two diffraction patterns of the W-4f emission line using light of opposite helicity. The agreement of calculations with the experimental result is satisfactory. This constitutes a very encouraging starting point for the use of the CDAD holography together with the PEEM technique providing mesoscopic and atomic as well as chemical resolution in microselected areas on solid surfaces. [ABSTRACT FROM AUTHOR]