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Free keywords:
Contact ion pairs, charge transfer, core-level ionization, lithium chloride, lithium acetate, aqueous solution, autoionization, ETMD, liquid microjet
Abstract:
Ion pairing in electrolyte solutions remains a topic of discussion despite a long history of research. Very recently, nearest-neighbor mediated electronic deexcitation processes of core hole vacancies (Electron Transfer Mediated Decay, ETMD) were proposed to carry a spectral fingerprint of local solvation structure and in particular of contact ion pairs. Here, for the first time, we apply electron–electron coincidence detection to a liquid microjet, and record ETMD spectra of Li 1s vacancies in aqueous solutions of lithium chloride (LiCl) in direct comparison to lithium acetate (LiOAc). A change in the ETMD spectrum dependent on the electrolyte anion identity is observed for 4.5 M salt concentration. We discuss these findings within the framework of the formation and presence of contact ion pairs and the unique sensitivity of ETMD spectroscopy to ion pairing.
