Spatiotemporal reaction kinetics of an ultrafast photoreaction pathway visualized by time-resolved liquid x-ray diffraction

Tae Kyu Kim, Maciej Lorenc, Jae Hyuk Lee, Manuela Lo Russo, Joonghan Kim, Marco Cammarata, Qingyu Kong, Sylvie Noel, Anton Plech, Michael Wulff, Hyotcherl Ihee

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42 Citations (Scopus)

Abstract

We have studied the reaction dynamics for Hgl2 in methanol by using time-resolved x-ray diffraction (TRXD). Although numerous time-resolved spectroscopic studies have provided ample information about the early dynamics of Hgl2, a comprehensive reaction mechanism in the solution phase spanning from picoseconds up to microseconds has been lacking. Here we show that TRXD can provide this information directly and quantitatively. Picosecond optical pulses triggered the dissociation of Hgl2, and 100-ps-long x-ray pulses from a synchrotron probed the evolving structures over a wide temporal range. To theoretically explain the diffracted intensities, the structural signal from the solute, the local structure around the solute, and the hydrodynamics of bulk solvents were considered in the analysis. The results in this work demonstrate that the determination of transient states in solution is strongly correlated with solvent energetics, and TRXD can be used as an ultrafast calorimeter. It also is shown that a manifold of structural channels can be resolved at the same time if the measurements are accurate enough and that global analysis is applied. The rate coefficients for the reactions were obtained by fitting our model against the experimental data in one global fit including all q-values and time delays. The comparison between all putative reaction channels confirms that two-body dissociation is the dominant dissociation pathway. After this primary bond breakage, two parallel channels proceed. Transient HgI associates nongeminately with an iodine atom to form HgI2, and I2 is formed by nongeminate association of two iodine atoms.

Original languageEnglish
Pages (from-to)9410-9415
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number25
DOIs
Publication statusPublished - 2006 Jun 20

All Science Journal Classification (ASJC) codes

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