LEED intensity analysis of the (1 × 5) reconstruction of Ir(100)

A new LEED structural analysis is carried out for the (1 × 5) reconstruction of Ir(100). It is based on a recent set of experimental I–V curves obtained with a computer-controlled video camera. Special attention is paid to reproducibility and reliability, and an R?factor analysis is now included. The previously preferred structure (a buckled top layer that is quasi-hexagonally close-packed and involves bridge sites) is confirmed with minor positional adjustments comparable to the uncertainty of the method. The other structural models that have been examined can clearly be rejected.     

The surface reconstructions of the (100) crystal faces of iridium,platinum and gold: I. Experimental observations and possible structural models

The structures of the reconstructed Ir(100), Pt(100) and Au(100) surfaces have been investigated. Low energy electron diffraction (LEED) patterns are analyzed and LEED intensity versus energy data are measured. A variety of structures is observed by LEED: Ir(100) exhibits a relatively simple (1 × 5) pattern; Pt(100) shows a series of closely related patterns, a typical representative of which has a $\text{(}\text{14}\text{1}\text{?1}\text{5}\text{)}$ structure; Au(100) usually exhibits a c(26 × 68) pattern, often inaccurately described in the literature as a (20 × 5) pattern. The reconstruction of Au(111) is also considered for comparison. Various plausible structural models are discussed, while laser simulation is used to lessen the number of these models. The analysis is completed in a companion paper where LEED intensity calculations are reported to determine the atomic locations.     

Orientation and bonding of ethylene and ethylidyne on Pt(111) by means of near-edge x-ray absorption fine structure spectroscopy

Near-edge X-ray absorption fine structure (NEXAFS) spectra have been measured for ethylene chemisorbed on Pt(111) at 90 and 300 K. From the polarization dependence of the spectra at 90 K, ethylene is found to lie down with a π bond to the surface. The spectra collected at 300 K indicate a CC bond normal to the surface in ethylidyne, and a SCF Xα calculation was carried out to assign the K-edge transitions in this species. The ethylidyne carboncarbon bond (which is nominally a single bond) appears to be shorter (≈0.03 A) than that for chemisorbed ethylene.     

FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.