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.
Author: | Henning Kirchberg, Peter Nalbach, Christian Bressler, Michael Thorwart |
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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): | Es gilt das Urheberrechtsgesetz |