Induced circular dichroism and spin polarization in the angular distribution of photoelectrons by optical properties of adsorbate systems

The influence of optical properties on photoelectron diffraction is considered in a very straightforward way. A general polarization vector of light is introduced in the calculation of the dipole transition matrix element in photoelectron diffraction theory. In a first step the radiation field of light outside and inside the solid is approximated macroscopically according to classical electrodynamics, respectively. Analytical expressions are derived within a real-angle representation of Fresnel equations to reveal the influence of reflection, refraction and absorption of light at the vacuum–solid boundary on the state of polarization of light. In particular, the circular dichroism in the angular distribution (CDAD) and the spin polarization of photoelectrons excited from adsorbed atoms at single crystal surfaces are discussed within the improved theory of photoelectron diffraction. It is shown that a complex refraction index of the substrate may cause strong CDAD and spin polarization along symmetry directions where no contributions are expected. As an example the system Ba/W(1 1 0) is considered in detail.