Synchrotron-based multiple-beam FTIR chemical imaging of a multi-layered polymer in transmission and reflection: towards cultural heritage applications
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IRENI (infrared environmental imaging) is a recently commissioned Fourier transform infrared (FTIR) chemical imaging beamline at the Synchrotron Radiation Center in Madison, WI, USA. This novel beamline extracts 320 mrad of radiation, horizontally, from one bending magnet. The optical transport separates and recombines the beam into 12 parallel collimated beams to illuminate a commercial FTIR microspectrometer (Bruker Hyperion 3000) equipped with a focal plane array detector where single pixels in the detector image a projected sample area of either 0.54×0.54 μm2 or 2×2 μm2, depending in the measurement geometry. The 12 beams are partially overlapped and defocused, similar to wide-field microscopy, homogeneously illuminating a relatively large sample area compared to single-beam arrangements. Both transmission and reflection geometries are used to examine a model cross section from a layered polymer material. The compromises for sample preparation and measurement strategies are discussed, and the chemical composition and spatial definition of the layers are distinguished in chemical images generated from data sets. Deconvolution methods that may allow more detailed data analysis are also discussed.
KeywordsCultural Heritage Point Spread Function Chemical Image Reflection Geometry Integration Window
This work was supported by the US National Science Foundation under awards CHE-0832298, CHE-1112433 and DMR-0619759, the Research Growth Initiative of the University of Wisconsin-Milwaukee, and is based on research conducted at the Synchrotron Radiation Center, University of Wisconsin-Madison, which is supported by the National Science Foundation under award DMR-0537588 and by the University of Wisconsin- Milwaukee and the University of Wisconsin-Madison.
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