Symmetrization Method for Enhancement of Digital ESDIAD Measurements: Increased Resolution for Study of Adsorbate Bond Directions

摘要

A new data smoothing method for distinguishing the symmetrical features of digital ESDIAD patterns has been developed. The method is based on the assumption that ESDIAD patterns from adsorbed molecules on an 'n-fold' symmetric single crystal should in principle contain the same 'n-fold' symmetry, although in some cases this may be below the detection limit. The symmetrization method is applied to real ESDIAD data with the expected enhancement of the azimuthal symmetry of the ESDIAD pattern. Two strenuous tests have been devised to determine the reliability of the method: (i) quantitative comparison of azimuthal symmetry elements in the digital ESDIAD pattern with the substrate symmetry as determined by digital LEED in the same apparatus; (ii) qualitative comparison of physically-meaningful symmetry elements with non-physical symmetries. It is also shown in model calculations that the symmetrization procedure is effective in removing systematic noise from digital ESDIAD data. Keywords: Electron stimulated desorption; Ion angular distribution; Spectroscopy; Crystallographic symmetries; Chemisorption; Carbon monoxide; Crystals; Low energy electron diffraction; Platinum (111). Reprints. (AW)