Achieving atomistic understanding of solvation dynamics from X-ray free-electron laser measurements

Wednesday, April 6, 2016 - 3:00pm

Speaker: Kasper, Kjaer, PULSE

Program Description

The efficiency, selectivity, and rate of chemical reactions depend critically on the reaction environment. Solvation, the local organization of the solvent molecules around a solute, plays a central role in the description of condensed phase chemical properties. The influence of the solvent on the solute structure and reaction dynamics has been extensively studied within the field of chemical physics. However, the atomistic picture of solvation dynamics has hitherto been difficult to elucidate experimentally, since studies of solvation dynamics have relied on experimental methods that are not directly sensitive to intermolecular atomic structure, such as optical spectroscopies.

Over the last five years we have conducted a range of femtosecond X-ray Diffuse Scattering (XDS) experiments at the Linear Coherent Light Source (LCLS), investigating the excited state dynamics of molecules in solution. For all conducted experiments we have seen a significant contribution to the XDS signal arising from the solvation dynamics of the excited molecular system, happening on the sub- to few picosecond timescale. By simulating XDS signal directly from Molecular Mechanics and Quantum Mechanical / Molecular Mechanics calculations, we have been able to model our data, and unambiguously determine the underlying atomistic origins of the solvation dynamics.

This talk will provide an overview of the classes of solvation dynamics observed over the first five years of XDS measurements at the LCLS, discuss their origin, and how future experiments at the LCLS could improve our atomistic understanding of solvation further.

Achieving atomistic understanding of solvation dynamics from X-ray free-electron laser measurements
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