Soft x-ray angle-resolved photoemission spectroscopy on Ag(001) : Band mapping, photon momentum effects, and circular dichroism

The (001) surface of silver (Ag) has been chosen as a simple and well known system for investigating the band mapping potential of angle-resolved photoemission spectroscopy in the soft x-ray energy range. Low temperature data of the valence band of Ag have been measured for four different high symmetry directions in reciprocal space. Furthermore, in order to determine the intrinsic limits of this technique, the issue of phonon-assisted nondirect transitions is addressed, both as a function of the measuring temperature and the incoming photon energy. The experimental data are directly compared with fully relativistic one-step model photoemission calculations. In particular, photon momentum transfer effects, which are often neglected in this energy regime, are discussed in detail. Finally, the experimental observation of circular dichroism in the angular distribution of the emitted photoelectrons allows for a comparison with the first calculated angle-resolved photoemission spectra showing this effect.