• Capturing Transient Electronic and Molecular Structures in Liquids by Picosecond X-Ray Absorption Spectroscopy
    W. Gawelda, V.T. Pham, A. El Nahhas, M. Kaiser, Y. Zaushitsyn, S.L. Johnson, D. Grolimund, R. Abela, A. Hauser, C. Bressler and M. Chergui
    American Institute of Physics Conference Proceedings, 882 (2007), p31-36
    DOI:10.1063/1.2644425 | unige:4058 | Abstract | Article PDF
We describe an advanced setup for time-resolved x-ray absorption fine structure (XAFS) Spectroscopy with picosecond temporal resolution. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of the Swiss Light Source (SLS). The setup is applied to measure the short-lived high-spin geometric structure of photoexcited aqueous Fe(bpy)3 at room temperature.
  • Structural Determination of a Short-lived Iron(II) Complex by Picosecond X-ray Absorption Spectroscopy
    W. Gawelda, V.-T. Pham, M. Benfatto, Y. Zaushitsyn, M. Kaiser, D. Grolimund, S.L. Johnson, R. Abela, A. Hauser, C. Bressler and M. Chergui
    Physical Review Letters, 98 (2007), p57401
    DOI:10.1103/PhysRevLett.98.057401 | unige:3198 | Abstract | Article PDF | Article PS (gzipped)
Structural changes of the iron(II)-tris-bipyridine ([FeII(bpy)3]2+) complex induced by ultrashort pulse excitation and population of its short-lived (≤0.6  ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x-ray-absorption near-edge structure and extended x-ray-absorption fine structure spectroscopy features delivers an Fe-N bond elongation of 0.2 Å in the quintet state compared to the singlet ground state.



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