Instrument description

The KMC-2 XANES is a dedicated endstation to investigate the short-range environment around selected atomic species in condensed matter by X-ray Absorption Spectroscopy. This end-station provides possibility for EXAFS, XANES and X-ray fluorescence measurements at-air. The detector system consists of three ionization chambers, Si-PIN photodiode, energy-dispersive detector (Bruker X-Flash 6|60) and scintillation counter. The experimental setup allows for a parallel monitoring of the transmitted through the sample X-ray beam intensity as well as for fluorescence yield measurements. This end-station is permanently attached to the KMC-2 beamline providing medium photon flux between 4000 eV and 15000 eV and linear photon polarization, necessary to exploit the potential of X-ray absorption spectroscopy.

List of publications
Station data
Monochromator KMC-2
Experiment in vacuum no
Temperature range 293 K
Detector Bruker X-Flash 6|60, 3 ionization chambers, Si-PIN photodiodes
Manipulators Huber goniometer
Beam intensity stabilization MOSTAB electronics (accuracy 0.3%)
Microfocusing > 5 μm
Micro-EXAFS, micro-fluorescen limited / no mapping
Maximum sample size unlimited
Control system PC-based BESSY monochromator control system EMP/2
Data-acquisition computer Personal computer, measurement bus-extension, OS/2-operating system
Data-acquisition software Windows-NT, RADICON RDPW software



Instrument application

X-ray Absorption Spectroscopy (XAS) is a powerful structural technique to investigate the short-range environment around selected atomic species in condensed matter. While scanning the x-ray energy impinging onto the sample, a core level photoelectron is generated. This is scattered by the surroundings matter producing interference effects visible in the absorption cross-section and usually referred to as x-ray absorption fine structure (XAFS). The process itself is general and therefore fundamental to study structural properties in materials like:
•    liquids, molecular solutions, liquid crystals;
•    single- and poly-crystalline materials;
•    amorphous and highly disordered solids;
•    molecules and macromolecules containing metallic atoms or partially substituted with heavy atoms.
The energy range 4.0 keV < E < 15 keV is sufficient for K-edge studies of elements in the range 21 < Z < 36 and L-edge studies of elements in the range 49 < Z < 83. The sample thicknesses for experiments are in the µm range for transmission experiments. However, thin film and/or dilute systems studies are still possible in fluorescence mode.