Spectroscopic Signatures of the Dynamical Hydrophobic Solvation Shell Formation

  • When a hydrophilic solute in water is suddenly turned into a hydrophobic species, for instance, by photoionization, a layer of hydrated water molecules forms around the solute on a time scale of a few picoseconds. We study the dynamic buildup of the hydration shell around a hydrophobic solute on the basis of a time-dependent dielectric continuum model. Information about the solvent is spectroscopically extracted from the relaxation dynamics of a test dipole inside a static Onsager sphere in the nonequilibrium solvent. The growth process is described phenomenologically within two approaches. First, we consider a time-dependent thickness of the hydration layer that grows from zero to a finite value over a finite time. Second, we assume a time-dependent complex permittivity within a finite layer region around the Onsager sphere. The layer is modeled as a continuous dielectric with a much slower fluctuation dynamics. We find a time-dependent frequency shift down to the blue of the resonant absorption of the dipole, together with a dynamically decreasing line width, as compared to bulk water. The blue shift reflects the work performed against the hydrogen-bonded network of the bulk solvent and is a directly measurable quantity. Our results are in agreement with an experiment on the hydrophobic solvation of iodine in water.

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Metadaten
Author:Henning Kirchberg, Peter Nalbach, Christian Bressler, Michael Thorwart
DOI:https://doi.org/10.1021/acs.jpcb.8b11885
ISSN:1520-6106
Parent Title (English):The Journal of Physical Chemistry B
Document Type:Article
Language:English
Date of Publication (online):2020/02/24
Year of first Publication:2019
Publishing Institution:Westfälische Hochschule Gelsenkirchen Bocholt Recklinghausen
Release Date:2020/02/25
Volume:123
Issue:9
First Page:2106
Last Page:2113
Departments / faculties:Fachbereiche / Wirtschaft und Informationstechnik Bocholt
Licence (German):License LogoEs gilt das Urheberrechtsgesetz

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