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Title: Hydration shell effects in the relaxation dynamics of photoexcited Fe-II complexes in water

Abstract

We study the relaxation dynamics of photoexcited Fe-II complexes dissolved in water and identify the relaxation pathway which the molecular complex follows in presence of a hydration shell of bound water at the interface between the complex and the solvent. Starting from a low-spin state, the photoexcited complex can reach the high-spin state via a cascade of different possible transitions involving electronic as well as vibrational relaxation processes. By numerically exact path integral calculations for the relaxational dynamics of a continuous solvent model, we find that the vibrational life times of the intermittent states are of the order of a few ps. Since the electronic rearrangement in the complex occurs on the time scale of about 100 fs, we find that the complex first rearranges itself in a high-spin and highly excited vibrational state, before it relaxes its energy to the solvent via vibrational relaxation transitions. By this, the relaxation pathway can be clearly identified. We find that the life time of the vibrational states increases with the size of the complex (within a spherical model), but decreases with the thickness of the hydration shell, indicating that the hydration shell acts as an additional source of fluctuations.

Authors:
; ; ; ;  [1];  [2];  [3];  [2]
  1. I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg (Germany)
  2. (Germany)
  3. The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg (Germany)
Publication Date:
OSTI Identifier:
22419934
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; HIGH SPIN STATES; HYDRATION; PATH INTEGRALS; RELAXATION; SOLVENTS; SPIN; VIBRATIONAL STATES; WATER

Citation Formats

Nalbach, P., Achner, A. J. A., Frey, M., Grosser, M., Thorwart, M., The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Bressler, C., and European XFEL GmbH, Notkestraße 85, 22607 Hamburg. Hydration shell effects in the relaxation dynamics of photoexcited Fe-II complexes in water. United States: N. p., 2014. Web. doi:10.1063/1.4890528.
Nalbach, P., Achner, A. J. A., Frey, M., Grosser, M., Thorwart, M., The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Bressler, C., & European XFEL GmbH, Notkestraße 85, 22607 Hamburg. Hydration shell effects in the relaxation dynamics of photoexcited Fe-II complexes in water. United States. doi:10.1063/1.4890528.
Nalbach, P., Achner, A. J. A., Frey, M., Grosser, M., Thorwart, M., The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Bressler, C., and European XFEL GmbH, Notkestraße 85, 22607 Hamburg. Mon . "Hydration shell effects in the relaxation dynamics of photoexcited Fe-II complexes in water". United States. doi:10.1063/1.4890528.
@article{osti_22419934,
title = {Hydration shell effects in the relaxation dynamics of photoexcited Fe-II complexes in water},
author = {Nalbach, P. and Achner, A. J. A. and Frey, M. and Grosser, M. and Thorwart, M. and The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg and Bressler, C. and European XFEL GmbH, Notkestraße 85, 22607 Hamburg},
abstractNote = {We study the relaxation dynamics of photoexcited Fe-II complexes dissolved in water and identify the relaxation pathway which the molecular complex follows in presence of a hydration shell of bound water at the interface between the complex and the solvent. Starting from a low-spin state, the photoexcited complex can reach the high-spin state via a cascade of different possible transitions involving electronic as well as vibrational relaxation processes. By numerically exact path integral calculations for the relaxational dynamics of a continuous solvent model, we find that the vibrational life times of the intermittent states are of the order of a few ps. Since the electronic rearrangement in the complex occurs on the time scale of about 100 fs, we find that the complex first rearranges itself in a high-spin and highly excited vibrational state, before it relaxes its energy to the solvent via vibrational relaxation transitions. By this, the relaxation pathway can be clearly identified. We find that the life time of the vibrational states increases with the size of the complex (within a spherical model), but decreases with the thickness of the hydration shell, indicating that the hydration shell acts as an additional source of fluctuations.},
doi = {10.1063/1.4890528},
journal = {Journal of Chemical Physics},
number = 4,
volume = 141,
place = {United States},
year = {Mon Jul 28 00:00:00 EDT 2014},
month = {Mon Jul 28 00:00:00 EDT 2014}
}
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