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

被引:97
作者
Campbell, L [1 ]
Hedin, L
Rehr, JJ
Bardyszewski, W
机构
[1] Univ Washington, Dept Phys, Seattle, WA 98195 USA
[2] Lund Univ, Dept Phys, S-22362 Lund, Sweden
[3] MPIFKF, D-70569 Stuttgart, Germany
[4] Inst Theoret Phys, Dept Phys, PL-00681 Warsaw, Poland
关键词
D O I
10.1103/PhysRevB.65.064107
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
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.
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收藏
页码:641071 / 6410713
页数:13
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