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arXiv · 1604.06829

Particle-hole cumulant approach for inelastic losses in x-ray spectra

J. J. Kas·J. J. Rehr·J. B. Curtis
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Abstract

Inelastic losses in core level x-ray spectra arise from many-body excitations, leading to broadening and damping as well as satellite peaks in x-ray photoemission (XPS) and x-ray absorption (XAS) spectra. Here we present a practical approach for calculating these losses based on a cumulant representation of the particle-hole Green's function, a quasi-boson approximation, and a partition of the cumulant into extrinsic, intrinsic and interference terms. The intrinsic losses are calculated using real-time, time-dependent density functional theory while the extrinsic losses are obtained from the GW approximation of the photo-electron self-energy and the interference terms are approximated. These effects are included in the spectra using a convolution with an energy dependent particle-hole spectral function. The approach elucidates the nature of the spectral functions in XPS and XAS and explains the significant cancellation between extrinsic and intrinsic losses. Edge-singularity effects in metals are also accounted for. Illustrative results are presented for the XPS and XAS for both weakly and more correlated systems.

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J. J. Kas, J. J. Rehr, J. B. Curtis. 2016-04-22. Particle-hole cumulant approach for inelastic losses in x-ray spectra. https://doi.org/10.1103/physrevb.94.035156

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