• 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, , 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, , 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 in the quintet state compared to the singlet ground state.



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