Ultrafast laser-pump x-ray probe measurements of solvated transition metal complexes

摘要

Ultrafast laser pump-x-ray absorption fine structure (XAFS) probespectra of Fe(CN)(,4-solvated in water have been measured using table-topultrafast laser driven plasma x-ray sources. The principles of XAFS have beendiscussed extensively in the literature 1, 2. Close to the x-ray absorption edge,in the region of x-ray absorption near edge structure (XANES), large electrons cattering cross sections cause intense modulations and favor multiplephoto electron scattering events with several atoms. This, in principle, permitsthe measurements of not just metal-ligand distances but also bond angles. Asshown in Figure 2 and in the literature 3, 4, the modulation depth for highly symmetric molecules can reach 100% of the absorption edge jump. At higher x-ray energies. corre sponding to the region of Extended X-ray Absorption Fine Structure (EXAFS) 11J, spectra are determined by single scattering events between the x-ray absorbing atom and surrounding atoms. Thus, the EXAFS spectra are a measure of the first-order atomic pair correlation function, whichcan be approximated by Fourier-transforming the EXAFS spectrum.