Journal article
Observing Solvation Dynamics with Simultaneous Femtosecond X-ray Emission Spectroscopy and X-ray Scattering
Department of Physics, Technical University of Denmark1
Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark2
European XFEL3
Paul Scherrer Institute4
SLAC National Accelerator Laboratory5
Hungarian Academy of Sciences6
Lund University7
Department of Chemistry, Technical University of Denmark8
European Synchrotron Radiation Facility9
In liquid phase chemistry dynamic solute solvent interactions often govern the path, ultimate outcome, and efficiency of chemical reactions. These steps involve many-body movements on subpicosecond time scales and thus ultrafast structural tools capable of capturing both intramolecular electronic and structural changes, and local solvent structural changes are desired.
We have studied the intra- and intermolecular dynamics of a model chromophore, aqueous [Fe(bpy)3]2+, with complementary X-ray tools in a single experiment exploiting intense XFEL radiation as a probe. We monitored the ultrafast structural rearrangement of the solute with X-ray emission spectroscopy, thus establishing time zero for the ensuing X-ray diffuse scattering analysis.
The simultaneously recorded X-ray diffuse scattering atterns reveal slower subpicosecond dynamics triggered by the intramolecular structural dynamics of the photoexcited solute. By simultaneous combination of both methods only, we can extract new information about the solvation dynamic processes unfolding during the first picosecond (ps).
The measured bulk solvent density increase of 0.2% indicates a dramatic change of the solvation shell around each photoexcited solute, confirming previous ab initio molecular dynamics simulations. Structural changes in the aqueous solvent associated with density and temperature changes occur with similar to 1 ps time constants, characteristic for structural dynamics in water.
This slower time scale of the solvent response allows us to directly observe the structure of the excited solute molecules well before the solvent contributions become dominant.
Language: | English |
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Year: | 2016 |
Pages: | 1158-1168 |
ISSN: | 15205207 and 15206106 |
Types: | Journal article |
DOI: | 10.1021/acs.jpcb.5b12471 |
ORCIDs: | Haldrup, Kristoffer , Dohn, Asmus Ougaard , Kjær, Kasper Skov , Møller, Klaus Braagaard , Pápai, Mátyás Imre and Nielsen, Martin Meedom |