SPHERICALLY BENT SI ANALYSER CRYSTALS FOR RIXS WITH INTRENSIC RESOL OF 150 MEV

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. High-resolution RIXS is a highly promising technique for investigation of 3d and 4d transition metals in materials science and biology. RIXS at the 1s resonances with lowest incident energies (K pre-edges) is a very recent, exciting technique. We have constructed installed at BioCAT a high resolution spherical analyzer for emitted x-rays which uses a variety of Si and Ge crystals at 0.8 - 1.0 m Roland circle radius. A typical intrinsic energy resolution of this analyzer is about 1 eV (FWHM) and this limits overall experimental resolution. Improvement of this resolution to the order of ~200-300 meV should substantially increase the information content of the spectra. We will use beamtime to enhance resolution by adapting our instrument to accommodate crystals with a 2 m circular radius and to investigate the geometric limitations of our apparatus. By perfecting each aspect of the fabrication and by using the "anodic bonding" technique to bind the Si wafer to a spherical glass substrate, silicon bent analysers can provide the required resolution and such analysers have been successfuly produced by our collaborators for several K edges of 3d transition metals, enormously improving the potential energy resolution compared to the standard spherically bent analysers. Hence, we intend to use for the first time in our existing setup at BioCAT Si (551) spherically bent at 2 m. These enable analysis of photons with scattered energy roughly ranging from 8200 eV to 8500 eV - around Ni K-edge at 8333 eV - and with an overall resolution energy of 400-450 meV (FWHM) in experimental conditions.