Surface X-ray dichroism of rare-earths

The two-dimensional nature of surface adsorbate layers of rare earth atoms and of epitaxial interfaces of rare earths on Si(111)-7 x 7 is reflected in the axial symmetry of the local field at the rare earth site. The induced splitting of the ground state of the rare earth is probed by linear polarized X-ray absorption spectroscopy (XAS), which exhibits strong dichroism.