title: Time-resolved synchrotron diffraction and theoretical studies of very short-lived photo-induced molecular species.
abstract: Definitive experimental results on the geometry of fleeting species are at the time of writing still limited to monochromatic data collection, but methods for modifications of the polychromatic Laue data to increase their accuracy and their suitability for pump-probe experiments have been implemented and are reviewed. In the monochromatic experiments summarized, excited-state conversion percentages are small when neat crystals are used, but are higher when photoactive species are embedded in an inert framework in supramolecular crystals. With polychromatic techniques and increasing source brightness, smaller samples down to tenths of a micrometre or less can be used, increasing homogeneity of exposure and the fractional population of the excited species. Experiments described include a series of transition metal complexes and a fully organic example involving excimer formation. In the final section, experimental findings are compared with those from theoretical calculations on the isolated species. Qualitative agreement is generally obtained, but the theoretical results are strongly dependent on the details of the calculation, indicating the need for further systematic analysis.
authors.affiliation: Chemistry Department, University at Buffalo, State University of New York, Buffalo, NY 14260-3000, USA. coppens@buffalo.edu
authors.forename: Philip
authors.initials: P
authors.lastname: Coppens
authors.forename: Jason
authors.initials: J
authors.lastname: Benedict
authors.forename: Marc
authors.initials: M
authors.lastname: Messerschmidt
authors.forename: Irina
authors.initials: I
authors.lastname: Novozhilova
authors.forename: Tim
authors.initials: T
authors.lastname: Graber
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Ivan
authors.initials: I
authors.lastname: Vorontsov
authors.forename: Stephan
authors.initials: S
authors.lastname: Scheins
authors.forename: Shao-Liang
authors.initials: SL
authors.lastname: Zheng
mesh_terms: D003198:Computer Simulation; D018360:Crystallography, X-Ray; D054018:Lasers, Excimer; D008027:Light; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D010777:Photochemistry; D017356:Synchrotrons; D013997:Time Factors; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D008670:Metals