Soft X-ray Absorption Spectroscopy is a powerful probe of the valence electronic structure in transition metal complexes and compounds, in particular due to the narrow bandwidth and the direct transition from the 2p core-hole to the 3d-derived states that determines the valence electronic structure; chemical state, spin, and symmetry. Although electron detection is often a preferred detection mode of XAS in the soft x-ray regime due its higher (Auger) yields, fluorescence detection has been widely adopted for its ability to probe deeper into the bulk, non-conductive samples, and more flexible environments in general. Fluorescence is also the preferred choice in most in-situ and pump-probe (time-resolved) studies. However, fluorescence (radiative) decay does not provide the true absorption cross-section due to a number well established (i.e. self absorption and saturation) and lesser known (i.e. state-dependent transition probabilities) distorsions. As has been shown recently, by detecting partial fluorescence yields from inner core-level emission lines (i.e. 3s-&gt;2p, or Lgamma), distortions from state-dependent transitions can be avoided. Moreover, the detection of emission from another element than the one that is resonantly excited (e.g. oxygen when exciting a dissolved transition metal ion in solution), results in an inverse partial fluorescence yield (IPFY) that is undistorted by state-dependent decay probabilities and saturation effects. We have recently commissioned a new soft X-ray Emission Spectrometer based on an energy-dispersive Transition Edge Sensor (TES) array that has an resolution of 1.5 eV (with a future target of 0.5eV) that can simultaneously measure all energies from 200 eV to 1200 eV. This detection allows complete separation all three PFY regions directly. In this presentation, we will present a selection of standards and examples where we have simultaneously measured the 3d2p, 3s2p, and iPFY signals along with the Total Fluorescence Yield as well a the Total Electron Yield, to experimentally map out trends in the X-ray Absorption Profile as a function of detection channel. This will be be discussed together with spectral simulations based on atomic multiplet calculations. The broader impact of the ability to measure all yields simultaneously beyond diagnostic advantages will also be discussed.

Undistorted fluorescence yield detected soft x-ray absorption spectroscopy: Direct detection of outer (3d->2p), inner (3s->2p) and inverse partial fluorescence yield using TES based spectrometers

253rd National Meeting (2017)

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