X-ray line shapes of metals: Exact solutions of a final-state interaction model

Abstract

By means of model calculations for an independent-electron metal, we obtain exact line shapes for the photon absorption, emission, and photoemission spectra of core states, including electronic relaxation. In all cases we find an x-ray edge anomaly. For the absorption and emission spectra this anomaly is superposed on a continuum resembling Elliott exciton theory. We display how the spectra evolve from the exciton limit to the free-electron limit as the final-state interaction strength is decreased or the Fermi energy increased. We compare the spectra obtained for different final-state interactions and find that different types of interactions produce different spectral shapes. Away from threshold the absorption and emission profiles show an enhancement of the free-electron result, as predicted by the screened-exciton theory. Our results offer potential explanations for ͑i͒ incompatibilities between threshold exponents and exponents extracted from other data, ͑ii͒ the occurrence of nearly symmetric x-ray photoemission lines, and ͑iii͒ the lack of mirror symmetry of absorption and emission edges.

Spatiotemporal Spread of Fermi-edge Singularity as Time Delayed Interaction and Impact on Time-dependent RKKY Type Coupling

“…Its universal many-body behaviour has made FES an important testing ground for a multitude of many-body techniques over more than 50 years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Experimental and theoretical evidence started with absorption and emission spectra in metals and semiconductors [20][21][22][23][24][25][26][27][28], and extended then to nanostructured systems and atomic gases [50][51][52][53][54][55].…”