John Rehr (TIMES Lecture)

Date(s) - Jan 19 2017
1:00 PM - 2:30 PM

Sycamore Room, Building 40, room 195


X-ray Spectroscopy Theory Lecture

John Rehr

Adjunct Professor of Photon Science, SLAC


Dept of Physics, University of Washington



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),  inelastic x-ray scattering (IXS), and electron energy loss spectra (EELS). Using synchrotron radiation x-ray sources and modern electron microscope techniques, these spectroscopies have become powerful probes of complex materials ranging from catalysts and minerals to bio-structures and aqueous solutions, permitting an interpretation in terms of the structural, electronic, magnetic and vibrational properties.

In Lecture I, we present an introduction to x-ray spectroscopy theory, starting with a qualitative discussion of the phenomenology including both x-ray absorption fine structure (XAFS) and near-edge structure (XANES).  We then present an overview of various quantitative approaches and approximations, ranging from density functional theory and quasi-particle approaches to Bethe-Salpeter equation, atomic multiplets, and quantum chemistry methods.   Lecture II is devoted to the real-space approach used in the x-ray spectroscopy and electronic structure codes FEFF [1]. This approach is based on real-space Green’s function techniques, rather than wave-functions, which considerably speeds up calculations. The method also builds in key many-body effects and relativistic corrections.

Subsequent lectures in this series will include: III Inelastic losses and Many-body effects; and 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).