Date/Time
Date(s) - Jul 15 2019
11:00 AM - 12:30 PM
Location
Sycamore Room, Building 40, room 195
Category(ies)
John J. Rehr
Adjunct Professor of Photon Science, SLAC
and
Dept. of Physics, University of Washington
Seattle, WA 98195-1560
I Introduction to X-ray Spectroscopy Theory
II Real-space Green’s function Theory and FEFF
There has been dramatic progress both in calculations and the interpretation of x-ray and electron spectroscopies, ranging from x-ray absorption spectra (XAS) and inelastic x-ray scattering (IXS) to electron energy loss spectra (EELS). Using modern synchrotron radiation x-ray sources, these spectroscopies have become powerful probes of complex materials ranging from catalysts and minerals to bio-structures and aqueous solutions. Combined with modern theory, these spectroscopies now permit an interpretation in terms of the structural, electronic, magnetic and vibrational properties of a system. This Lecture series aims to summarize these theoretical developments.
Lecture I presents an introduction to x-ray spectroscopy theory, starting with a qualitative, phenomenological discussion of both x-ray absorption fine structure (XAFS) and near-edge structure (XANES). We then present an overview of various quantitative approaches using approximations ranging from density functional theory and quantum chemistry methods to quasi-particle methods and the Bethe-Salpeter equation.
Lecture II is devoted to a more detailed treatment of the multiple-scattering approach used in the x-ray spectroscopy and excited state electronic structure codes FEFF [1,2]. This approach is based on real-space Green’s function techniques, rather than wave-functions and other approximations that considerably speed up calculations for systems throughout the periodic table. The approach used in FEFF also builds in key many-body effects and relativistic corrections.
Subsequent lectures will treat the theory at a more advanced level: Lecture III covers many-body effects and inelastic losses, and Lecture IV real-time approaches.
[1] J. J. Rehr, J. J. Kas, M. P. Prange, A. P. Sorini, Y. Takimoto, F. Vila,
Comptes Rendus Physique 10, 548 (2009).
[2] J. J. Rehr and R. C. Albers, Rev. Mod. Phys. 72, 621 (2000).
