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- Gopakumar, Geethanjali, 1992-, et al.
(author)
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Probing Aqueous Ions with Non-local Auger Relaxation
- 2022
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:15, s. 8661-8671
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Journal article (peer-reviewed)abstract
- The decay of core holes is often regarded as a local process, but in some systems, it involves the autoionization of neighbouring atoms or molecules. Here, we explore such non-local autoionization (Intermolecular Coulombic Decay, ICD) of surrounding molecules upon 1s ionization of aqueous-phase Na+, Mg2+ and Al3+ ions. The three ions are isoelectronic but differ in the strength of the ion-water interactions which is manifested in experimental Auger electron spectra by varying intensities. While for strongly interacting Mg2+ and Al3+ the non-local decay is observed, for weakly bound Na+ no signal was measured. Combined with theoretical simulations we provide a microscopic understanding of the non-local decay processes. We assigned the ICD to decay processes ending with two-hole states delocalized between the central ion and neighbouring water. The ICD process is also shown to be highly selective with respect to water molecular orbitals. The ICD lifetime was estimated to be around 40 fs for Mg and 20 fs for Al. Auger spectroscopy thus represents a novel tool for exploring molecules in the liquid phase, providing simultaneously structural and electronic information.
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- Gopakumar, G., et al.
(author)
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Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions
- 2023
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In: Nature Chemistry. - : Nature Publishing Group. - 1755-4330 .- 1755-4349. ; 15:10, s. 1408-1414
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Journal article (peer-reviewed)abstract
- Biomolecular radiation damage is largely mediated by radicals and low-energy electrons formed by water ionization rather than by direct ionization of biomolecules. It was speculated that such an extensive, localized water ionization can be caused by ultrafast processes following excitation by core-level ionization of hydrated metal ions. In this model, ions relax via a cascade of local Auger–Meitner and, importantly, non-local charge- and energy-transfer processes involving the water environment. Here, we experimentally and theoretically show that, for solvated paradigmatic intermediate-mass Al3+ ions, electronic relaxation involves two sequential solute–solvent electron transfer-mediated decay processes. The electron transfer-mediated decay steps correspond to sequential relaxation from Al5+ to Al3+ accompanied by formation of four ionized water molecules and two low-energy electrons. Such charge multiplication and the generated highly reactive species are expected to initiate cascades of radical reactions. [Figure not available: see fulltext.]
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