Augusta Bianca Ene

XAS measurements were performed at beamline E4 at the Hamburger Synchrotron Strahlungslabor (HASYLAB) under ambient conditions at 293 K. A Si(111) double crystal monochromator was used for measurements at the Cu K-edge (8.979 keV). The second monochromator crystal was tilted for optimal harmonic rejection. The energy resolution for the Cu K-edge energy is estimated to be 3.0 eV. The spectra were recorded in transmission mode with ionisation chambers filled with nitrogen. The individual pressures were adjusted to optimize the signal to noise ratio. Energy calibration was performed with a copper metal foil, which was measured simultaneously with the samples between the second and third ionisation chamber. To avoid errors in the XANES region due to small changes in the energy calibration between two measurements, all spectra were calibrated to the edge position of the copper foil. The solid samples were embedded in an oxygen-free cellulose matrix and pressed into pellets. Since the copper loading of the liquid ion exchanged samples was an order of magnitude lower than that of the solid state ion exchanged samples, only solid state ion exchanged Cu/HZSM5 samples were analyzed (ZSM500 and ZSM700). Data evaluation started with background absorption removal from the experimental absorption spectrum by subtracting a Victoreen-type polynomial. Due to several inflection points in the absorption edge, the threshold energy E0 was determined consistently by taking the energy at half the edge jump1,2. For copper metal, this procedure causes a shift of the energy scale in comparison with most published data by around 5 eV. Since all spectra were corrected in a consistent way, this shift does not lead to misinterpretations. To determine the smooth part of the spectrum, corrected for pre-edge absorption, a piecewise polynomial was used. It was adjusted in such a way that the low-R components of the resulting Fourier transform were minimal. After division of