title: Photolysis of Br2 in CCl4 studied by time-resolved X-ray scattering.
abstract: A time-resolved X-ray solution scattering study of bromine molecules in CCl(4) 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 micros after dissociation. The relaxation of hot Br(2)(*) 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 Br(2)(*) 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 A.
authors.affiliation: Synchrotron Soleil, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Kong
authors.forename: Jae Hyuk
authors.initials: JH
authors.lastname: Lee
authors.forename: Manuela
authors.initials: M
authors.lastname: Lo Russo
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Kim
authors.forename: Maciej
authors.initials: M
authors.lastname: Lorenc
authors.forename: Marco
authors.initials: M
authors.lastname: Cammarata
authors.forename: Savo
authors.initials: S
authors.lastname: Bratos
authors.forename: Thomas
authors.initials: T
authors.lastname: Buslaps
authors.forename: Veijo
authors.initials: V
authors.lastname: Honkimaki
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
authors.forename: Michael
authors.initials: M
authors.lastname: Wulff
mesh_terms: D001966:Bromine / Q000737:chemistry*; D002251:Carbon Tetrachloride / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008027:Light; D008958:Models, Molecular; D010782:Photolysis; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014965:X-Rays
chemical_list: D012997:Solvents; D002251:Carbon Tetrachloride; D001966:Bromine