Apparatus for in situ x-ray absorption fine structure studies on catalyticsystems in the energy range 1000 eV < E < 3500 eV

A new apparatus for in situ x-ray absoprtion fine structure measurements in the medium energy range of 1000-3500 eV has been developed. Measurements c an be performed in a gaseous environment (max. pressure 1 bar) at temperatu res ranging from 80 to 750 K. Pre-treatments can be performed at 5 bar and 750 K in the same cell, after which XAFS measurements can be done without e xposing the sample to ambient air. In a modular set-up several detector sys tems can be used: fluorescence detection using a gas proportional counter, a photodiode or a microstrip detector. All detectors are highly integrated into the cell, gaining solid angle for detection. Electron yield detection can be used simultaneously using conversion electron yield or total electro n yield. The performance of the new apparatus is demonstrated by a study of the K edge of Al in Zeolite Beta. The Al content is as low as 2 wt%. It wi ll be shown that octahedral framework Al is formed while adding gaseous wat er at room temperature after ammonia removal (at 450 degrees C) of an NH4-B eta. (C) 2000 American Institute of Physics. [S0034-6748(00)03209-3].