OPTIMAL ATOMIC IMAGING BY PHOTOELECTRON HOLOGRAPHY

Several recent papers have dealt with the question of whether large-sc ale photoelectron diffraction data spanning a significant range in bot h angle and wavenumber can be analyzed as holograms so as to produce d irectly three-dimensional images of near-surface atomic structure. Dat a are thus taken over some volume in the photoelectron wavevector k-sp ace, and then transformed to obtained atomic images. In this work, we review four analysis methods proposed to date for deriving atomic posi tions directly from photoelectron diffraction data and consider the ap plication of them to theoretical diffraction patterns calculated from various single-scattering model clusters. This permits some general co nclusions as to domains of applicability and the optimization of k-spa ce sampling so as to minimize data acquisition time, while still assur ing atomic images that are free of coarse k-sampling aberrations. We c onclude that holographic imaging of atoms does not require exceedingly large photoelectron diffraction data sets, with a few thousand data p oints being a suitable minimum, and we also comment on the relative me rits of the four different imaging algorithms. (C) 1997 Elsevier Scien ce B.V.