Photolysis of Br2 in CCl4 studied by time-resolved X-ray scattering

Qingyu Kong, Jae Hyuk Lee, Manuela Lo Russo, Tae Kyu Kim, MacIej Lorenc, Marco Cammarata, Savo Bratos, Thomas Buslaps, Veijo Honkimaki, Hyotcherl Ihee, Michael Wulff

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Abstract

A time-resolved X-ray solution scattering study of bromine molecules in CCl4 is presented as an example of how to track atomic motions in a simple chemical reaction. The structures of the photoproducts are tracked during the recombination process, geminate and non-geminate, from 100 ps to 10 s after dissociation. The relaxation of hot Br2 * molecules heats the solvent. At early times, from 0.1 to 10 ns, an adiabatic temperature rise is observed, which leads to a pressure gradient that forces the sample to expand. The expansion starts after about 10 ns with the laser beam sizes used here. When thermal artefacts are removed by suitable scaling of the transient solvent response, the excited-state solute structures can be obtained with high fidelity. The analysis shows that 30% of Br2 * molecules recombine directly along the X potential, 60% are trapped in the A/A′ state with a lifetime of 5.5 ns, and 10% recombine non-geminately via diffusive motion in about 25 ns. The Br - Br distance distribution in the A/A′ state peaks at 3.0 Å.

Original languageEnglish
Pages (from-to)252-260
Number of pages9
JournalActa Crystallographica Section A: Foundations of Crystallography
Volume66
Issue number2
DOIs
Publication statusPublished - 2010 Mar 1

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All Science Journal Classification (ASJC) codes

  • Structural Biology

Cite this

Kong, Q., Lee, J. H., Lo Russo, M., Kim, T. K., Lorenc, M., Cammarata, M., Bratos, S., Buslaps, T., Honkimaki, V., Ihee, H., & Wulff, M. (2010). Photolysis of Br2 in CCl4 studied by time-resolved X-ray scattering. Acta Crystallographica Section A: Foundations of Crystallography, 66(2), 252-260. https://doi.org/10.1107/S0108767309054993