Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: Poster: New Instruments and Methods

CPP 11.8: Poster

Montag, 14. März 2011, 17:30–19:30, P2

Time-resolved soft X-ray Absorption Spectroscopy of Soluted Coordination Chemistry Compounds on a Microjet — •Alexander Kothe¹, Kai F. Hodeck¹, Chris J. Milne², Frank van Mourik³, Kathrin M. Lange¹, Majed Chergui³, and Emad F. Aziz^1,4 — ¹Helmholtz Zentrum Berlin — ²Ecole Polytechnique Federale de Lausanne — ³Paul Scherrer Institut — ⁴FU Berlin

Investigation of the spin cross-over of coordination chemistry compounds in solution permits the study of the fundamental intramolecular processes in the absence of intermolecular effects. Time-resolved soft x-ray absorption spectroscopy (XAS) gives the opportunity to investigate especially the electronic and spin structure of molecular states and their dynamics. On a sub-fs scale this was achieved by means of dark channel fluorescence yield (DCFY), where L-edge XAS on FeCl₃ revealed the upper limit of 1-1.5 fs for the electron transfer to the solvent. Moreover we currently establish a system of ps-laser pump and L-edge XAS as a probe at BESSY. For this experiment we use [FeII(bpy)₃]2+ dissolved in water. Light of 532 nm wavelength excites a metal-to-ligand-charge-transfer state, which leads to an ultrafast spin change from singlet to quintet. The latter has a lifetime of 650 ps. Using a 23 µm microjet, the setup allows to constantly renew or cycle the sample. Besides circumventing sample damage, this gives direct access to the sample in vacuum for high repetition rate fluorescence yield measurements. This experiment opens the door for investigations of the dynamics of the charge transfer in heme proteins and other bio-chemical systems in solutions under real conditions.