| 1. |
- Miteva, Tsveta, et al.
(författare)
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The All-Seeing Eye of Resonant Auger Electron Spectroscopy : A Study on Aqueous Solution Using Tender X-rays
- 2018
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 9:15, s. 4457-4462
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and Auger electron spectroscopies are demonstrated to be powerful tools to unravel the electronic structure of solvated ions. In this work for the first time, we use a combination of these methods in the tender X-ray regime. This allowed us to address electronic transitions from deep core levels, to probe environmental effects, specifically in the bulk of the solution since the created energetic Auger electrons possess large mean free paths, and moreover, to obtain dynamical information about the ultrafast delocalization of the core-excited electron. In the considered exemplary aqueous KCl solution, the solvated isoelectronic K+ and Cl- ions exhibit notably different Auger electron spectra as a function of the photon energy. Differences appear due to dipole-forbidden transitions in aqueous K+ whose occurrence, according to the performed ab initio calculations, becomes possible only in the presence of solvent water molecules.
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| 2. |
- Norman, Patrick, et al.
(författare)
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Simulating X-ray Spectroscopies and Calculating Core-Excited States of Molecules
- 2018
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Ingår i: Chemical Reviews. - : AMER CHEMICAL SOC. - 0009-2665 .- 1520-6890. ; 118:15, s. 7208-7248
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Forskningsöversikt (refereegranskat)abstract
- During the past decade, the research field of computational X-ray spectroscopy has witnessed an advancement triggered by the development of advanced synchrotron light sources and X-ray free electron lasers that in turn has enabled new sophisticated experiments with needs for supporting theoretical investigations. Following a discussion about fundamental conceptual aspects of the physical nature of core excitations and the concomitant requirements on theoretical methods, an overview is given of the major developments made in electronic-structure theory for the purpose of simulating advanced X-ray spectroscopies, covering methods based on density-functional theory as well as wave function theory. The capabilities of these theoretical approaches are illustrated by an overview of simulations of selected linear and nonlinear X-ray spectroscopies, including X-ray absorption spectroscopy (XAS), X-ray natural circular dichroism (XNCD), X-ray emission spectroscopy (XES), resonant inelastic X-ray scattering (RIXS), and X-ray two-photon absorption (XTPA).
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| 3. |
- Orms, Natalie, et al.
(författare)
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Characterizing Bonding Patterns in Diradicals and Triradicals by Density-Based Wave Function Analysis : A Uniform Approach
- 2018
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 14:2, s. 638-648
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Tidskriftsartikel (refereegranskat)abstract
- Density-based wave function analysis enables unambiguous comparisons of the electronic structure computed by different methods and removes ambiguity of orbital choices. We use this tool to investigate the performance of different spin flip methods for several prototypical diradicals and triradicals. In contrast to previous calibration studies that focused on energy gaps between high- and low spin-states, we focus on the properties of the underlying wave functions, such as the number of effectively unpaired electrons. Comparison of different density functional and wave function theory results provides insight into the performance of the different methods when applied to strongly correlated systems such as polyradicals. We show that canonical molecular orbitals for species like large copper-containing diradicals fail to correctly represent the underlying electronic structure due to highly non-Koopmans character, while density-based analysis of the same wave function delivers a clear picture of the bonding pattern.
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