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. Soft X-ray absorption spectroscopy (SXA) is a powerful tool for the investigation of the electronic structure of transition metals. In the last five years our group has made significant advances in the interpretation of metal L3,2-edges have been made allowing us to derive unique information about the electronic structure of transition metals. A significant restriction of the technique to date has been the necessity to perform these experiments in ultra high vacuum (UHV), which limits both the types of compounds which can be studied, and the form in which they can be studied. Compounds need to be both available in the solid-state, and need to not degrade when exposed to UHV. Recently, it has been demonstrated that it is possible to perform SXA in ambient pressure environments. The key element enabling this experiment was the advent of soft x-ray transparent SiN membranes capable of separating the beam line UHV from at atmospheric pressure sample environment. We have recorded the oxygen K absorption spectrum of liquid water as well as the L3,2 edge absorption spectra of a saturated solution of transition metals, under SPEAR2. With SPEAR2 these measurements were limited by the flux density at the sample position, which prevented us from expanding to non-saturated solutions. Similar studies have been performed at the ALS, and we wish to create the capability to perform these experiments also at SSRL. We propose with this LOI to explore whether the increased flux density of SPEAR3 is sufficient to perform soft x-ray absorption spectroscopy experiments on biologically relevant compounds in a solvent environment. We will start with small molecule Cu- and Fe- compounds dissolved in two different solvents, acetonitrile and water.
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