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Auger electron spectroscopy is an omnipresent experimental tool in many fields of fundamental research and applied science. The determination of the kinetic energies of the Auger electrons yields information about the element emitting the electron and its chemical environment at the time of emission. Here, we present an experimental approach to determine Auger spectra for emitter sites in the vicinity of a positive elementary charge based on electron-electron-electron and electron-electron-photon coincidence spectroscopy. We observe a characteristic redshift of the Auger spectrum caused by the Coulomb interaction with the charged environment. Our results are relevant for the interpretation of Auger spectra of extended systems like large molecules, clusters, liquids, and solids, in particular in high-intensity radiation fields which are nowadays routinely available, e.g., at x-ray free-electron laser facilities. The effect has been widely ignored in the literature so far, and some interpretations of Auger spectra from clusters might need to be revisited.
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http://dx.doi.org/10.1103/PhysRevLett.132.203002 | DOI Listing |
J Chem Phys
September 2025
Department of Chemistry, KU Leuven, B-3001 Leuven, Belgium.
We model Auger spectra using second-order Møller-Plesset perturbation (MP2) theory combined with complex-scaled basis functions. For this purpose, we decompose the complex MP2 energy of the core-hole state into contributions from specific decay channels and propose a corresponding equation-of-motion (EOM) method for computing the doubly ionized final states of Auger decay. These methods lead to significant savings in computational cost compared to our recently developed approaches based on coupled-cluster theory [F.
View Article and Find Full Text PDFPhys Chem Chem Phys
September 2025
DTU Chemistry, Technical University of Denmark, Kemitorvet Bldg. 207, 2800 Kongens Lyngby, Denmark.
A robust and computationally efficient methodology to compute Auger decay rates is presented that combines equation-of-motion coupled cluster singles and doubles two-particle Auger density matrices (also known as two-particle Dyson matrices) with precalculated bound-continuum integrals from atomic calculations, known as the one-center approximation. Illustrative applications include KLL Auger electron spectra (AES) of several small and medium-sized molecules.
View Article and Find Full Text PDFJ Phys Chem Lett
September 2025
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China.
Vibrationally resolved resonant Auger spectroscopy (RAS) on bound-continuum transitions enables highly sensitive probing of ultrafast dissociation in molecular core-excited states, where a distinct fragment band arises from Auger decay in dissociation fragments. Here, we theoretically investigate fragment band formation driven by ultrashort X-ray pulses. Unlike conventional molecular bands, fragment RAS peaks exhibit an insensitivity to strong X-ray Rabi oscillations.
View Article and Find Full Text PDFJ Phys Chem A
August 2025
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States.
Efficient and accurate computation of molecular Auger electron spectra for larger systems is limited by the rapid increase in the number of doubly ionized final states as the system size grows. In this work, we benchmark the application of multiconfiguration pair-density functional theory with a restricted active space (RAS) reference wave function for computing the carbon K-edge decay spectra of 20 organic molecules. Decay rates are computed within the one-center approximation.
View Article and Find Full Text PDFRapid Commun Mass Spectrom
October 2025
Federal Bureau of Investigation Laboratory, Quantico, Virginia, USA.
Rationale: This paper presents an in-depth evaluation of the laser diode thermal desorption (LDTD) device interfaced to a mass spectrometer and identifies the critical method parameters to evaluate when developing a new procedure.
Methods: Samples were solvent extracted and spotted in a 96-well plate. In the case of biological fluids, hydrolysis followed by solid phase extraction is required.