Theory and Interpretation of x-ray spectra:XAS, EELS and RIXS: John Rehr

Title: Theory and Interpretation of x-ray spectra: XAS, EELS and RIXS
Speaker: Prof. John Rehr (University of Washington)
Abstract: In this review, we first briefly summarize the Real-space Green's function (RSGF) theory as applied in the FEFF codes for a number of x-ray spectra, including XAS, EELS, NRIXS and RIXS [1]. Next , we discuss some extensions that permit parameter-free calculations of the key ingredients and many-body effects in the theory, including the screened core-hole, self-energy, and Debye-Waller factors. We also discuss inelastic losses and satellites that account for the many-body amplitude factor S02, which are treated using a cumulant Green’s function technique [2] in terms of a convolution of the quasi-particle x-ray spectra and a spectral function that builds in extrinsic and intrinsic losses and interference [4]. Finally, we discuss high temperature extensions in the theory which permit calculations up to the warm dense matter regime [5], which are included in recently released update FEFF10 [6].

Suggested reading:
[1] JJR et al., Comptes Rendus Physique 10, 548 (2009). https://doi.org/10.1016/j.crhy.2008.0...
[2] J. Sky Zhou et al., Phys Rev B 97, 035137 (2018). https://doi.org/10.1103/PhysRevB.97.0...
[3] J. J. Kas, J. J. Rehr, and J. B. Curtis, Phys. Rev. B 94, 035156 (2016). https://doi.org/10.1103/PhysRevB.94.0...
[4] J.J. Kas and J. J. Rehr, Phys. Rev. Lett. 119, 176403 (2017). https://doi.org/10.1103/PhysRevLett.1...
[5] Tun S. Tan, J. J. Kas, and J. J. Rehr, Phys. Rev. B 104, 035144 (2021). https://doi.org/10.1103/PhysRevB.104....
[6] J. J. Kas et al., J. Synchrotron Rad. In press 2021, arXiv:2106.13334. https://arxiv.org/abs/2106.13334