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100 Picosecond Diffraction Catches Structural Transients of Laser-Pulse Triggered Switching in a Spin-Crossover Crystal

Authors

  • Prof. Eric Collet,

    Corresponding author
    1. Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
    • Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
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  • Dr. Maciej Lorenc,

    1. Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
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  • Dr. Marco Cammarata,

    1. European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France)
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  • Dr. Laurent Guérin,

    1. European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France)
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  • Dr. Marina Servol,

    1. Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
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  • Dr. Antoine Tissot,

    1. Institut de Chimie Moléculaire et Matériaux d'Orsay, UMR-CNRS 8182, University Paris-Sud 11, 91405 Orsay Cedex (France)
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  • Dr. Marie-Laure Boillot,

    1. Institut de Chimie Moléculaire et Matériaux d'Orsay, UMR-CNRS 8182, University Paris-Sud 11, 91405 Orsay Cedex (France)
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  • Prof. Hervé Cailleau,

    1. Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
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  • Prof. Marylise Buron-Le Cointe

    1. Institut de Physique de Rennes, UMR 6251 UR1-CNRS, Bat 11 A Campus de Beaulieu, University Rennes 1, 35042 Rennes Cedex (France), Fax: (+33) 223-23-65-32
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Abstract

We study by 100 picosecond X-ray diffraction the photo-switching dynamics of single crystal of the orthorhombic polymorph of the spin-crossover complex [(TPA)Fe(TCC)]PF6, in which TPA=tris(2-pyridyl methyl)amine, TCC2−=3,4,5,6-Cl4-Catecholate2−. In the frame of the emerging field of dynamical structural science, this is made possible by using optical pump/X-ray probe techniques, which allow following in real time structural reorganization at intra- and intermolecular levels associated with the change of spin state in the crystal. We use here the time structure of the synchrotron radiation generating 100 picosecond X-ray pulses, coupled to 100 fs laser excitation. This study has revealed a rich variety of structural reorganizations, associated with the different steps of the dynamical process. Three consecutive regimes are evidenced in the time domain: 1) local molecular photo-switching with structural reorganization at constant volume, 2) volume relaxation with inhomogeneous distribution of local temperatures, 3) homogenization of the crystal in the transient state 100 µs after laser excitation. These findings are fundamentally different from those of conventional diffraction studies of long-lived photoinduced high spin states. The time-resolution used here with picosecond X-ray diffraction probes different physical quantities on their intrinsic time-scale, shedding new light on the successive processes driving macroscopic switching in a functionalized material. These results pave the way for structural studies away from equilibrium and represent a first step toward femtosecond crystallography.

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