Probing aqueous ions with non-local Auger relaxation

• Published in: Physical chemistry chemical physics : PCCP Vol. 24; no. 15; pp. 8661 - 8671
• Main Authors: Gopakumar, Geethanjali, Muchová, Eva, Unger, Isaak, Malerz, Sebastian, Trinter, Florian, Öhrwall, Gunnar, Lipparini, Filippo, Mennucci, Benedetta, Céolin, Denis, Caleman, Carl, Wilkinson, Iain, Winter, Bernd, Slavíček, Petr, Hergenhahn, Uwe, Björneholm, Olle
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 13.04.2022; The Royal Society of Chemistry
• Subjects: Aluminum; Atom and Molecular Physics and Optics; Atom- och molekylfysik och optik; Autoionization; Chemistry; Decay; Fysik; Liquid phases; Molecular dynamics; Molecular structure; Natural Sciences; Naturvetenskap; Physical Sciences; Signal processing; Sodium; Solvents
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d2cp00227b

Non-local analogues of Auger decay are increasingly recognized as important relaxation processes in the condensed phase. Here, we explore non-local autoionization, specifically Intermolecular Coulombic Decay (ICD), of a series of aqueous-phase isoelectronic cations following 1s core-level ionization. In particular, we focus on Na , Mg , and Al ions. We unambiguously identify the ICD contribution to the K-edge Auger spectrum. The different strength of the ion-water interactions is manifested by varying intensities of the respective signals: the ICD signal intensity is greatest for the Al case, weaker for Mg , and absent for weakly-solvent-bound Na . With the assistance of calculations and molecular dynamics simulations, we provide a microscopic understanding of the non-local decay processes. We assign the ICD signals to decay processes ending in two-hole states, delocalized between the central ion and neighbouring water. Importantly, these processes are shown to be highly selective with respect to the promoted water solvent ionization channels. Furthermore, using a core-hole-clock analysis, the associated ICD timescales are estimated to be around 76 fs for Mg and 34 fs for Al . Building on these results, we argue that Auger and ICD spectroscopy represents a unique tool for the exploration of intra- and inter-molecular structure in the liquid phase, simultaneously providing both structural and electronic information.