How Much Does Auger Spectroscopy Add to XAS? A Fisher-information Analysis of Core-Hole Dynamics in Ar+
Abstract
X-ray absorption spectroscopy (XAS) and resonant-Auger spectroscopy probe different stages of core-hole excitation and decay, but distinct spectra need not provide independent information about decay parameters. We quantify their complementarity for the Ar+ 2p→3d manifold using state-resolved atomic calculations and a two-parameter Fisher-information model. A common scale of primary autoionization rates sΓ and a selective spectator-pp rescaling ηpp both alter XAS linewidths. Their spectral responses are nearly collinear because the spectator-pp fraction varies weakly among populated intermediate states. We compare XAS with an effective, scan-integrated, normalized Auger spectrum defined on a final-state-energy coordinate, with fixed excitation weights and final-state widths. Within this reduced observable, the common rate scale cancels from the normalized branching fractions, while ηpp redistributes intensity among ionic final states. This cancellation is a property of the adopted model, not of photon-energy-resolved resonant-Auger spectroscopy generally. Under the reference count and resolution assumptions, XAS alone yields a Cramér-Rao lower bound (CRLB) corresponding to a 1.20% local fractional standard uncertainty in the excitation-weighted total natural width; adding Auger reduces this uncertainty by only 0.70%. In contrast, the uncertainty in the spectator-pp branching fraction falls by 99.19%, with similarly large gains for partial-rate scales. A generalized Fisher comparison gives a 123.5-fold improvement on the standard-deviation scale along the most enhanced information mode. Thus, the principal benefit of the complementary Auger observable is to resolve a nearly degenerate decay-channel decomposition rather than substantially refine the total natural width.
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BibTeX
@misc{saud2026much,
title = {{How Much Does Auger Spectroscopy Add to XAS? A Fisher-information Analysis of Core-Hole Dynamics in $Ar^+$}},
author = {Hadeel Hamid Saud},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.26234},
eprint = {2610.26234},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.26234},
}
RIS
TY - UNPB
TI - How Much Does Auger Spectroscopy Add to XAS? A Fisher-information Analysis of Core-Hole Dynamics in Ar^+
AU - Hadeel Hamid Saud
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.26234
UR - https://arxiv.org/abs/2610.26234
AB - X-ray absorption spectroscopy (XAS) and resonant-Auger spectroscopy probe different stages of core-hole excitation and decay, but distinct spectra need not provide independent information about decay parameters. We quantify their complementarity for the Ar^+ 2p→3d manifold using state-resolved atomic calculations and a two-parameter Fisher-information model. A common scale of primary autoionization rates s_Γ and a selective spectator-pp rescaling η_pp both alter XAS linewidths. Their spectral responses are nearly collinear because the spectator-pp fraction varies weakly among populated intermediate states. We compare XAS with an effective, scan-integrated, normalized Auger spectrum defined on a final-state-energy coordinate, with fixed excitation weights and final-state widths. Within this reduced observable, the common rate scale cancels from the normalized branching fractions, while η_pp redistributes intensity among ionic final states. This cancellation is a property of the adopted model, not of photon-energy-resolved resonant-Auger spectroscopy generally. Under the reference count and resolution assumptions, XAS alone yields a Cramér-Rao lower bound (CRLB) corresponding to a 1.20% local fractional standard uncertainty in the excitation-weighted total natural width; adding Auger reduces this uncertainty by only 0.70%. In contrast, the uncertainty in the spectator-pp branching fraction falls by 99.19%, with similarly large gains for partial-rate scales. A generalized Fisher comparison gives a 123.5-fold improvement on the standard-deviation scale along the most enhanced information mode. Thus, the principal benefit of the complementary Auger observable is to resolve a nearly degenerate decay-channel decomposition rather than substantially refine the total natural width.
ER -