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High Resolution Spectroscopy of the Carbon K Edge in Polymers with a Doppler Tuned X-Ray Spectrometer

X-rays emitted by fast ion beams can be Doppler tuned by variation of the observation angle. With X-ray detectors collimated to a narrow acceptance angle high resolution spectroscopy of absorption structures of gaseous or solid absorbers can be performed. This novel technique seems useful in the soft X-ray region (e.g. K absorption edges of carbon to oxygen) where conventional (crystal or grating at grazing incidence) monochromators suffer from low transmission and moderate energy resolution. We studied the performance of a Doppler tuned X-ray monochromator in the carbon K region using 7.5 to 11.5 MeV carbon beams excited by gas or beam foil collisions. With X-ray detectors collimated to 1° angular acceptance the calculated monochromator band width at the carbon K edge of polymer foil absorbers becomes ¿E < 0.1 eV for 7.5 MeV beam energy. The purpose of our measurements is the study of the near structure (position, width and structural details) of the carbon K edge in polymers at high resolution as a function of chemical composition.