Design and optimization of a parallel spectrometer for ultra-fast X-ray science

Abstract

In the present work, different varied line space (VLS) and reflection zone plate (RZP) gratings are analyzed for their suitability in low-signal femtosecond soft X-ray spectroscopy. The need for high efficiency suggests a straightened focal line whose sharpness and residual curvature will determine the quality. One- and two-dimensional VLS structures feature an attractive trade-off between a sufficient optical performance and a strongly relaxed fabrication, due to moderate line densities which are easily accessible by e-beam lithography. Based on fanned-out RZP arrays, their continuous limit version is identified to generate an almost perfect focal line however, with an aberration level three orders of magnitude better than for the VLS gratings and well below the diffraction limit over large acceptance angles.

Probing the oxidation state of transition metal complexes: a case study on how charge and spin densities determine Mn L-edge X-ray absorption energies

“… 22 , 44 , 45 X-ray fluorescence from the sample mainly consists of Mn L α,β emission at ∼640 eV from the solute and of O K α at ∼525 eV from the solvent. Dispersion with our RZP spectrometer, optimized for high transmission, 46 is essential for separating the weak Mn L α,β signal of the dilute Mn samples from the overwhelming O K α background. The energy of the photons incident on the liquid sample is scanned stepwise over the Mn L absorption edge, where at each step the Mn L α,β partial fluorescence is detected.…”

X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

“…The PFY signal was detected using a reflection zone-plate (RZP) spectrometer with an energy bandwidth of 20 eV, (Fig. 1) [24,38] where for the first time a new-generation 3-dimensional laterally depth-graded RZP was implemented. Using a RZP allows to discriminate the O K emission from the Mn L emission especially for systems in aqueous solutions [24].…”

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers

“…In the case of PFY-XAS on the Mn L-edge, the RZPs have been optimized to separate the Mn L α,β (3d $\to$ 2p) fluorescence at ∼637 eV subsequent to Mn L-edge (2p $\to$ 3d) absorption [Fig. 1(a)] from the O K α -edge fluorescence at 525 eV with a bandwidth of 20 eV (FWHM) 31 . In a previous proof of principle experiment, using an ionic Mn model system in aqueous solution (Mn concentration, ∼500 mM), we have demonstrated the viability of the concept for collecting PFY-XAS at an XFEL source at physiological temperature and pressure 16,22 .…”