Direct Surface Structure Determination with Photoelectron Diffraction

The Study of Surface Structures by Photoelectron Diffraction and Auger Electron Diffraction

“…21 and also discussed by Barton and Shirley. 25 This more correct form for vibrational attenuation involves a factor Wj"rr of the form: 21 (8) where aJ(T) = < (Llkj • uY> is a thermal average of the projection of the atomic displacement Uj as measured with respect to the emitter onto the direction of the change in wave vector produced by the scattering Llkj • Thus, each scatterer in a photoelectron diffraction experiment is sensitive to a different type of vibrational displacement, varying from no effects for forward scattering, to small effects for small-angle scattering associated with components of Uj perpendicular to the emitter-scatterer axis, to maximum effects for backscattering associated with components of u j along this axis. By contrast, in SEXAFS, it is only the along-axis components that contribute.…”

“…99 Several photoelectron diffraction studies have been made of this system,14,15,19,21,25,99 including both scanned-angle and scanned-energy measurements, and we will consider a few of these. Higher-energy scanned-angle XPD measurements have been made for this system by Connelly et al (Fig.…”

“…Finally, it requires more-complex theoretical calculations in that scattering phase shifts and other nonstructural parameters have to be generated for all of the energies in a scan. 8 ,19-22 However, an advantage in scanned-energy work is that Fourier transform (FT) methods can be used to estimate the path-length differences for various strong scatterers. 8 ,20-22 A key element in either photoelectron or Auger electron diffraction is the energy dependence of the relevant elastic-scattering factors.…”

Photoelectron Diffraction and Synchrotron Radiation

“…It should be pointed out here that Fourier methods were successfully applied to the analysis of energy-scanned photoelectron diffraction data [35] (see below), where the intensity modulations are created by the energy-dependent interference effects along a fixed direction. The new approach represents thus an extension of this technique to include all emission angles.…”

Curved-wave-front corrections for photoelectron scattering

“…To construct the scattered wave, we multiply each incoming partial wave by (6) ' .. The sum of t may be stopped at t max when all higher partial waves have negligible amplitude, ITt(k)1 -0, 1 > tmax~ At the angle resolved .…”