Friday, March 10, 2006, 11:00 am — Bldg. 817, NSLS II Conference Room
nelastic x-ray scattering (IXS) spectroscopy is one of the major techniques for studying vibrational dynamics in solids, liquids, and biological molecules. X-ray monochromators and analyzers with meV-resolution and sub-meV are the main optical components of the IXS spectrometers.
Single-crystal and multiple-crystal techniques for the meV-monochromatization and the spectral analysis of x-rays have been developed during the last decades. These techniques have a basic general
property: the higher the required energy-resolution, the higher indexed Bragg reflections have to be used, and thus photons of higher energy E are needed. By this reason, photons with E > 20 keV are typically used in IXS experiments. This tendency is, however, in dissonance with the increasing demand for more spectral flux in IXS experiments and the fact that undulator based synchrotron radiation sources generate less photons in the high-energy spectral range. Using high-energy photons allows IXS spectroscopy only at high-energy machines like ESRF, APS, and SPring-8, but not at future powerful medium-energy facilities such as DIAMOND, SOLEIL, NSLS-II, etc., and future X-FELs.
To overcome these problems, a concept of an IXS spectrometer with meV and sub-meV resolution has been proposed for x-rays in the low-energy spectral range E < 10 keV [1]. It is based on a principle of monochromatization and spectral analysis, which exploits the effect of angular dispersion in asymmetric Bragg diffraction. One of its beneficial features is that higher energy-resolutions are achieved at lower(!) photon energies, typically E < 10 keV, a tendency, which is consistent with better performance of x-ray undulators at these energies.
I will discuss the concept of the monochromators and analyzers with sub-meV resolution for x-rays in the low-energy spectral range (E < 10 keV), the concept of the IXS spectrometer, and present results of the first experiments.
[1] Yu. V. Shvyd'ko. "X-ray optics. High En
Hosted by: John Hill
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