Regensburg 2007 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Dynamics of Molecular Systems

CPP 6.4: Vortrag

Montag, 26. März 2007, 15:15–15:30, H47

Investigation of the electronic structure of NH3 and ND3 in aqueous solution using x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) — •M. Weigand1, O. Fuchs1, M. Blum1, F. Maier1, E. Umbach1, L. Weinhardt2, M. Bär2, C. Heske2, M. Zharnikov3, M. Grunze3, and J. Denlinger41Universität Würzburg, Experimentelle Physik II, 97074 Würzburg — 2Dept. of Chem., University of Nevada, Las Vegas — 3Ang. Phys. Chemie, Uni Heidelberg — 4ALS, Berkeley

Soft x-ray spectroscopy of aqueous solutions at the carbon-, nitrogen- and oxygen-edge is a promising technique to investigate the electronic structure of biological systems in natural enviroment. Precise measurements require the use of a flow-through liquid cell to ensure thermodynamic equilibrium and to reduce beam-induced damage effects. Hitherto used Si3N4-windows denied access to the N-edge and showed contaminations limiting the viability of spectroscopy of solutions at the C- and O-edge. Using new ultra-thin SiC-membranes, the N-edge energy window is now open to measurements.

NH3 and ND3 provide an excellent test system to study the influence of H-bonds in aqueous solution, providing complementary information compared to the O-edge of H2O and D2O, which is currently in the focus of extensive investigations. XAS showed pronounced differences to the gas phase as well as strong isotopic effects, mirroring the behaviour of the water O-edge. RIXS results demonstrate excellent membrane properties and provide evidence of spectator and shake-up processes in NH3 solutions.

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