Techniques for inelastic X-ray spectroscopy with mu eV-resolution

We introduce a novel type of spectrometer that provides a mu eV bandpass to gether with a tunability over a few meV. The technique relies on nuclear re sonant scattering (Mossbauer effect) of synchrotron radiation at the 14.4-k eV resonance of Fe-57. Energy tuning is achieved by the Doppler effect in h igh-speed rotary motion. The resonantly scattered monochromatic radiation i s extracted by a polarization filtering technique or by spatial separation due to the "nuclear lighthouse effect". (C) 1999 Elsevier Science B.V. All rights reserved.