A HIGH-RESOLUTION INTERFEROMETER FOR USE WITH SYNCHROTRON RADIATION

We present the first results from a new instrument which is designed to work at very high resolution in the infrared spectral region but whose principles can be used in the VuV/soft-X-ray region. The instrument is based on an interferometer. For the VUV/soft-X-ray region the beamsplitting is achieved by wavefront division which takes advantage of the spatial coherence of synchrotron radiation. Normally the highest frequency in the spectrum from an interferometer is determined by the sampling frequency, which has to be at least twice that of the highest frequency in the spectrum. We show that this can be avoided if the spectral range is deliberately restricted by a grating or by the use of an undulator. In this case the interferograms contain a known and restricted range of frequencies which lead to an unambiguous assignment during the Fourier processing required to generate the spectrum.