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Title:IR spectroscopic studies on microsolvation of HCL by water
Author(s):Mani, Devendra
Contributor(s):Havenith, Martina; Schwaab, Gerhard; van der Meer, Lex; Redlich, Britta; Kaufmann, Matin; Dey, Arghya; Fischer, Theo; Schwan, Raffael
Subject(s):Matrix isolation (and droplets)
Abstract:Acid dissociation reactions are at the heart of chemistry. These reactions are well understood at the macroscopic level. However, a microscopic level understanding is still in the early stages of development. Questions such as \textit{‘how many \chem{H_2O} molecules are needed to dissociate one HCl molecule?’} have been posed and explored both theoretically and experimentally.$^{1-5}$ Most of the theoretical calculations predict that four \chem{H_2O} molecules are sufficient to dissociate one HCl molecule, resulting in the formation of a solvent separated \chem{H_3O}$^{+}$(\chem{H_2O})$_{3}$Cl$^{-}$ cluster.$^{1-3}$ IR spectroscopy in helium nanodroplets has earlier been used to study this dissociation process.$^{3-5}$ However, these studies were carried out in the region of O-H and H-Cl stretch, which is dominated by the spectral features of undissociated (HCl)$_{m}$-(\chem{H_2O})$_{n}$ clusters. This contributed to the ambiguity in assigning the spectral features arising from the dissociated cluster.$^{4,5}$ Recent predictions from Bowman’s group, suggest the presence of a broad spectral feature (1300-1360 \wn) for the \chem{H_3O}$^{+}$(\chem{H_2O})$_{3}$Cl$^{-}$ cluster, corresponding to the umbrella motion of \chem{H_3O}$^{+}$ moiety.$^{6}$ This region is expected to be free from the spectral features due to the undissociated clusters. In conjunction with the FELIX laboratory, we have performed experiments on the (HCl)$_{m}$(\chem{H_2O})$_{n}$ (m=1-2, n$\geq$4) clusters, aggregated in helium nanodroplets, in the 900-1700 \wn region. Mass selective measurements on these clusters revealed the presence of a weak-broad feature which spans between 1000-1450 \wn and depends on both HCl as well as \chem{H_2O} concentration. Measurements are in progress for the different deuterated species. The details will be presented in the talk. \\\textbf{References}: \textbf{1)} C.T. Lee et al., \textit{J. Chem. Phys.}, \textbf{104}, 7081 (1996). \textbf{2)} H. Forbert et al., \textit{J. Am. Chem. Soc.}, \textbf{133}, 4062 (2011). \textbf{3)} A. Gutberlet et al., \textit{Science}, \textbf{324}, 1545 (2009). \textbf{4)} S. D. Flynn et al., \textit{J. Phys. Chem. Lett.}, \textbf{1}, 2233 (2010). \textbf{5)} M. Letzner et al., \textit{J. Chem. Phys.}, \textbf{139}, 154304 (2013). \textbf{6)} J. M. Bowman et al., \textit{Phys. Chem. Chem. Phys.}, \textbf{17}, 6222 (2015).
Issue Date:2016-06-20
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2017-01-26

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