title: X-ray induced dimerization of cinnamic acid: Time-resolved inelastic X-ray scattering study.
abstract: A classic example of solid-state topochemical reactions is the ultraviolet-light induced photodimerization of α-trans-cinnamic acid (CA). Here, we report the first observation of an X-ray-induced dimerization of CA and monitor it in situ using nonresonant inelastic X-ray scattering spectroscopy (NRIXS). The time-evolution of the carbon core-electron excitation spectra shows the effects of two X-ray induced reactions: dimerization on a short time-scale and disintegration on a long time-scale. We used spectrum simulations of CA and its dimerization product, α-truxillic acid (TA), to gain insight into the dimerization effects. From the time-resolved spectra, we extracted component spectra and time-dependent weights corresponding to CA and TA. The results suggest that the X-ray induced dimerization proceeds homogeneously in contrast to the dimerization induced by ultraviolet light. We also utilized the ability of NRIXS for direct tomography with chemical-bond contrast to image the spatial progress of the reactions in the sample crystal. Our work paves the way for other time-resolved studies on chemical reactions using inelastic X-ray scattering.
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Juho
authors.initials: J
authors.lastname: Inkinen
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Niskanen
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Talka
authors.affiliation: ESRF - The European Synchrotron, CS 40220, F-38043 Grenoble Cedex 9, France.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Sahle
authors.affiliation: ESRF - The European Synchrotron, CS 40220, F-38043 Grenoble Cedex 9, France.
authors.forename: Harald
authors.initials: H
authors.lastname: Müller
authors.affiliation: Department of Chemistry, P.O. Box 55, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Leonid
authors.initials: L
authors.lastname: Khriachtchev
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Javad
authors.initials: J
authors.lastname: Hashemi
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Ali
authors.initials: A
authors.lastname: Akbari
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.affiliation: Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari