Trace chemical characterization using monochromatic X-ray undulator radiation

An efficient Johansson-type X-ray fluorescence spectrometer has been developed for advanced X-ray spectroscopic analysis with third-generation synchrotron radiation. K alpha and K beta X-ray fluorescence spectra for trace metals have been collected by a Ge(220) analyzing crystal with a Rowland radius of 1501 mm, under monochromatic X-ray excitation at the undulator beamline at the SPring-8. The energy resolution is similar to 10 eV for most of the K lines for 3d transition metals. In light of the greatly improved efficiency, as well as the excellent signal-to-background ratio, the relative and absolute detection limits achieved are 1 ppm and 1.2 ng of copper in a carbon matrix, respectively. The energy resolution of the present spectrometer permits the observation of some chemical effects in K beta spectra. It has been demonstrated that the changes in K beta(5) and K beta" intensity for iron and cobalt compounds can be used for the analysis of chemical states. Resonant X-ray fluorescent spectra are another important application of monochromatic excitation. In view of trace chemical characterization, the present spectrometer can be a good alternative to a conventional Si(Li) detector system when combined with highly brilliant X-rays.