Scanning Transmission X-ray Microscopy with X-ray Fluorescence Detection at the XUV Beamline P04, PETRA III, DESY

The presented scanning transmission x-ray microscope (STXM), build on top of our existing modular platform (FlexIX) for high resolution imaging experiments, allows versatile investigations of different samples. The FlexIX endstation allows to switch between a Full Field and a STXM mode. For the STXM mode we use a spatialy resolved detector together with an energy dispersive detector, this allows to investigate the morphology and the chemical or elemental distribution of the sample simultaneous. The combination of the nanoscopy endstation and the XUV beamline P04 results in a powerful tool for investigations of life science samples.BMBF, 05K13UL1, Verbundprojekt 05K2013 - Hochauflösende Bildgebung: Hochauflösende Bildgebung im EUV- und weichen Röntgenbereich bei PETRA III und FLASH. Teilprojekt 1

Towards understanding excited state properties of organic molecules using time resolved soft X ray absorption spectroscopy

The extension of the pump probe approach known from UV VIS spectroscopy to very short wavelengths together with advanced simulation techniques allows a detailed analysis of excited state dynamics in organic molecules or biomolecular structures on a nanosecond to femtosecond time level. Optical pump soft X ray probe spectroscopy is a relatively new approach to detect and characterize optically dark states in organic molecules, exciton dynamics or transient ligand to metal charge transfer states. In this paper, we describe two experimental setups for transient soft X ray absorption spectroscopy based on an LPP emitting picosecond and sub nanosecond soft X ray pulses in the photon energy range between 50 and 1500 eV. We apply these setups for near edge X ray absorption fine structure NEXAFS investigations of thin films of a metal free porphyrin, an aggregate forming carbocyanine and a nickel oxide molecule. NEXAFS investigations have been carried out at the carbon, nitrogen and oxygen K edge as well as on the Ni L edge. From time resolved NEXAFS carbon, K edge measurements of the metal free porphyrin first insights into a long lived trap state are gained. Our findings are discussed and compared with density functional theory calculation

Calcium Valence-to-Core X-ray Emission Spectroscopy: A Sensitive Probe of Oxo Protonation in Structural Models of the Oxygen-Evolving Complex

Calcium is an abundant, nontoxic metal that finds many roles in synthetic and biological systems including the oxygen-evolving complex (OEC) of photosystem II. Characterization methods for calcium centers, however, are underdeveloped compared to those available for transition metals. Valence-to-core X-ray emission spectroscopy (VtC XES) selectively probes the electronic structure of an element’s chemical environment, providing insight that complements the geometric information available from other techniques. Here, the utility of calcium VtC XES is established using an in-house dispersive spectrometer in combination with density functional theory. Spectral trends are rationalized within a molecular orbital framework, and Kβ2,5 transitions, derived from molecular orbitals with primarily ligand p character, are found to be a promising probe of the calcium coordination environment. In particular, it is shown that calcium VtC XES is sensitive to the electronic structure changes that accompany oxo protonation in Mn3CaO4-based molecular mimics of the OEC. Through correlation to calculations, the potential of calcium VtC XES to address unresolved questions regarding the mechanism of biological water oxidation is highlighted

Increasing the sensitivity of micro X ray fluorescence spectroscopy through an optimized adaptation of polycapillary lenses to a liquid metal jet source

The combination of brilliant liquid metal jet sources LMJS and polycapillary lenses yields substantial advantages in the excitation efficiency of traces of transition metals by micro X ray fluorescence spectroscopy amp; 956;XRF and confocal amp; 956;XRF in the laboratory. We show, that it is possible to especially adapt the parameters of polycapillary lenses to achieve an optimized performance in transmission and exit focal spot size. Furthermore, we demonstrate an energy dependent influence of the source spot size on the effective transmission of the lenses, which increases with decreasing field of view of the polycapillary lenses. A measurement on a mussel foot cross section using a amp; 956;XRF setup with a specially designed polycapillary lens in combination with the LMJS shows a significant increase of the excitation efficiency for vanadium. A 24 times higher net peak fluorescence intensity for V K radiation is achieved resulting in well defined and detailed vanadium structures compared to measurements performed with a state of the art amp; 956;XRF setu

A laboratory spectrometer for high throughput X-ray emission spectroscopy in catalysis research

We have built a laboratory spectrometer for X-ray emission spectroscopy. The instrument is employed in catalysis research. The key component is a von Hamos full cylinder optic with Highly Annealed Pyrolytic Graphite (HAPG) as a dispersive element. With this very efficient optic, the spectrometer subtends an effective solid angle of detection of around 1 msr, allowing for the analysis of dilute samples. The resolving power of the spectrometer is approximately E/ΔE = 4000, with an energy range of ∼2.3 keV–10 keV. The instrument and its characteristics are described herein. Further, a comparison with a prototype spectrometer, based on the same principle, shows the substantial improvement in the spectral resolution and energy range for the present setup. The paper concludes with a discussion of sample handling. A compilation of HAPG fundamentals and related publications are given in a brief Appendix.EC/FP7/615414/EU/Spectroscopic Studies of N2 Reduction: From Biological to Heterogeneous Catalysis/N2RE

Scanning X-ray microscopy with large solid angle X-ray fluorescence detection at the XUV beamline P04, DESY

The presented scanning transmission X-ray microscope (STXM), built on top of a modular platform, combines soft X-ray transmission and fluorescence microscopy with high detection efficiency and high spatial resolution. The setups user concept as well as the large solid angle (> 1 sr) of the integrated Silicon-drift-detector are unique characteristics of this endstation. In combination with the soft X-ray beamline P04 at PETRA III (DESY), it delivers a new type of nanoscope, providing a high flexibility and very low acquisition times