STRUCTURE INVESTIGATIONS OF XE-ADSORBATE LAYERS BY SPIN-POLARIZED LOW-ENERGY-ELECTRON DIFFRACTION .2. (ROOT-3X-ROOT-3)R30-DEGREES-XE PD(111) AND THE DILUTE PHASE OF XE PD(111)

The adsorbate systems (root 3 x root 3)R30 degrees-Xe/Pd(111) and the 'dilute' phase of Xe/Pd(111) were investigated with spin-polarized low -energy electron diffraction (SPLEED). Spin-polarized electrons from a GaAs source were scattered and the spin-dependent intensities were me asured. Comparative calculations were carried out by means of a relati vistic LEED program. The structure determination of (root 3 x root 3)R 30 degrees-Xe/Pd(111) yields a layer distance of 3.5+/-0.1 Angstrom, t he Xe atoms being adsorbed in hollow sites. In the 'dilute' phase of X e/Pd(111) the adsorbed Xe atoms occupy on-top sites with a Xe-Pd dista nce of 4.0+/-0.1 Angstrom without two-dimensional periodicity.