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Interference between extrinsic and intrinsic losses in x-ray absorption fine structure

Campbell, L; Hedin, Lars LU ; Rehr, JJ and Bardyszewski, W (2002) In Physical Review B 65(6). p.1-13
Abstract
The interference between extrinsic and intrinsic losses in x-ray absorption fine structure (XAFS) is treated within a Green's-function formalism, without explicit reference to final states. The approach makes use of a quasiboson representation of excitations and perturbation theory in the interaction potential between electrons and quasibosons. These losses lead to an asymmetric broadening of the main quasiparticle peak plus an energy-dependent satellite in the spectral function. The x-ray absorption spectra (XAS) is then given by a convolution of an effective spectral function over a one-electron cross section. It is shown that extrinsic and intrinsic losses tend to cancel near excitation thresholds, and correspondingly, the strength in... (More)
The interference between extrinsic and intrinsic losses in x-ray absorption fine structure (XAFS) is treated within a Green's-function formalism, without explicit reference to final states. The approach makes use of a quasiboson representation of excitations and perturbation theory in the interaction potential between electrons and quasibosons. These losses lead to an asymmetric broadening of the main quasiparticle peak plus an energy-dependent satellite in the spectral function. The x-ray absorption spectra (XAS) is then given by a convolution of an effective spectral function over a one-electron cross section. It is shown that extrinsic and intrinsic losses tend to cancel near excitation thresholds, and correspondingly, the strength in the main peak increases. At high energies, the theory crosses over to the sudden approximation. These results thus explain the observed weakness of multielectron excitations in XAS. The approach is applied to estimate the many-body corrections to XAFS, beyond the usual mean-free path, using a phasor summation over the spectral function. The asymmetry of the spectral function gives rise to an additional many-body phase shift in the XAFS formula. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Fysicumarkivet F:780
in
Physical Review B
volume
65
issue
6
pages
1 - 13
publisher
American Physical Society
external identifiers
  • wos:000173879700019
  • scopus:0036471901
ISSN
1550-235X
DOI
10.1103/PhysRevB.65.064107
language
English
LU publication?
yes
id
7444eaf5-400d-4bd2-bf3b-0dfaa4062918 (old id 910175)
date added to LUP
2008-01-17 13:17:46
date last changed
2017-03-26 04:08:42
@article{7444eaf5-400d-4bd2-bf3b-0dfaa4062918,
  abstract     = {The interference between extrinsic and intrinsic losses in x-ray absorption fine structure (XAFS) is treated within a Green's-function formalism, without explicit reference to final states. The approach makes use of a quasiboson representation of excitations and perturbation theory in the interaction potential between electrons and quasibosons. These losses lead to an asymmetric broadening of the main quasiparticle peak plus an energy-dependent satellite in the spectral function. The x-ray absorption spectra (XAS) is then given by a convolution of an effective spectral function over a one-electron cross section. It is shown that extrinsic and intrinsic losses tend to cancel near excitation thresholds, and correspondingly, the strength in the main peak increases. At high energies, the theory crosses over to the sudden approximation. These results thus explain the observed weakness of multielectron excitations in XAS. The approach is applied to estimate the many-body corrections to XAFS, beyond the usual mean-free path, using a phasor summation over the spectral function. The asymmetry of the spectral function gives rise to an additional many-body phase shift in the XAFS formula.},
  author       = {Campbell, L and Hedin, Lars and Rehr, JJ and Bardyszewski, W},
  issn         = {1550-235X},
  keyword      = {Fysicumarkivet F:780},
  language     = {eng},
  number       = {6},
  pages        = {1--13},
  publisher    = {American Physical Society},
  series       = {Physical Review B},
  title        = {Interference between extrinsic and intrinsic losses in x-ray absorption fine structure},
  url          = {http://dx.doi.org/10.1103/PhysRevB.65.064107},
  volume       = {65},
  year         = {2002},
}