Recent improvements in instrumentation and data analysis for soft X-ray spectromicroscopy and spectro-ptychography have made significant advances in spatial resolution and sensitivity. These improvements are providing researchers with new tools to contribute to solving real world technological issues as well as making fundamental discoveries. This presentation will give an overview of the performance of current instrumentation, report on exciting advances taking place in soft X-ray spectro-ptychography, and outline opportunities for in situ and operando studies. Spectro-ptychography studies of the magnetism of individual magnetosomes in magnetotactic bacteria by X-ray magnetic circular dichroism (XMCD). Results for 2D and 3D chemical analysis of polymer-electrolyte fuel cells will be presented.

Research performed at the Advanced Light Source, funded by DoE, BES, and at the Canadian Light Source, funded by CFI, NSERC, U. Saskatchewan, Saskatchewan, WEDC, NRC and the CIHR. The SHARP code used for ptychographic data analysis was developed by the Center for Applied Mathematics for Energy Research Applications (CAMERA) at LBNL, led by Jamie Sethian, in collaboration with Uppsala University .

Imaging live cells at a resolution higher than achieved using optical microscopy is a challenge. Ultra-fast coherent diffractive imaging¹ with X-ray free-electron lasers (XFELs) has the potential to achieve sub-nanometer resolution on micron-sized living cells². Our container-free injection method can introduce a beam of live cyanobacteria into the micron-sized focus of the Linac Coherent Light Source (LCLS) to record diffraction patterns from individual cells, with low noise at high hit rates³. We used iterative phase retrieval^4-6 to derive two-dimensional projection images directly from the diffraction patterns. Synthetic X-ray Nomarski images⁷, calculated from the complex-valued reconstructions, show cells in a similar manner to what one would expect to see using a Nomarski microscope, only at higher resolution than currently available. In a first experiment, we collected diffraction patterns to 33-46 nm full-period resolution, and reconstructed the exit wave front to 76 nm resolution³. In a second experiment, we demonstrate that it is indeed possible to record diffraction data to nanometer resolution on live cells with an intense, ultra-short X-ray pulse as predicted earlier^2,3. These results are encouraging, and future developments to the XFELs and improvements to the X-ray area-detectors will bring sub-nanometer resolution reconstructions of living cells within reach.

We thank the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the European Research Council, the Röntgen-Ångström Cluster, and Stiftelsen Olle Engkvist Byggmästare for supporting this work.

References

1. Neutze, R., Wouts, R., van der Spoel, D., Weckert, E. & Hajdu, J. Potential for biomolecular imaging with femtosecond X-ray pulses. Nature406, 752-757 (2000).

2. Bergh, M. et al. Feasibility of imaging living cells at subnanometer resolutions by ultrafast X-ray diffraction. Q. Rev. Biophys. 41, 181-204 (2008).

3. van der Schot, G. et al. Imaging single cells in a beam of live cyanobacteria with an X-ray laser. Nat. Commun. 6, 5704 (2015).

4. Gerchberg, R.W. & Saxton, W.O. Practical Algorithm for Determination of Phase from Image and Diffraction Plane Pictures. Optik35, 237-246 (1972).

5. Fienup, J.R. Reconstruction of an Object from Modulus of Its Fourier-Transform. Opt. Lett.3, 27-29 (1978).

6. Luke, D.R. Relaxed averaged alternating reflections for diffraction imaging. Inverse Probl.21, 37-50 (2005).

7. Paganin, D. et al. X-ray omni microscopy. J. Microsc.214, 315-327 (2004).

[1] P. Guttmann et al., Nature Photonics 6 (2012), 25-29

[2] K. Henzler et al., Nano Letters 13 (2013), 824-828

[3] G. Schneider et al., Nature Methods 7 (2010), 985-987

[4] E. Hummel et al., PLoS ONE 7 (12) (2012), e53293

[5] S. Kapishnikov et al., PNAS (2012) DOI: 10.1073/pnas.1118120109

[6] C. Hagen et al., J. Struct. Biol. 177 (2012), 193-201

[7] FCO J. Chichon et al., J. Struct. Biol. 177 (2012), 202-211

[8] D. Drescher et al., Nanoscale 5 (2013), 9193-9198

Ultrafast Dynamics in Magnetic Systems

Gerhard Grübel

DESY and The Hamburg Centre for Ultrafast Imaging (CUI)

Hamburg, Germany

Understanding ultrafast magnetization Dynamics on the nano-scale is a forefront problem in modern magnetism research with direct impact on the quest for faster and smaller storage devices. Probing the magnetization element-specifically and on the nanometer lenght-scale is a pre-requisite when probing technologically relevant material systems with complex composition.

X-ray free electron laser (FEL) sources with their unique properties delivering ultrashort and super intense soft X-ray pulses allow for the first time to address magnetization dynamics on the relevant time-and lenght scales.

We present recent results obtained on multi-domain Co/Pt magnetic multilayer samples with perpendicular magnetic anisotropy, pumped with short IR and THZ pulses. As a probe we use small angle X-ray scattering from the magnetic domains which, via X-ray magnetic circular dichroism at the Co M-edge, allows us to simultaneously obtain information on the magnitude of the local magnetization amd the characteristic lenght scale of the domains. The FEL sources FLASH at DESY (Hamburg) and FERMI at ELECTRA (Trieste) were used at a wavelenght of 20.8 nm corresponding to the CO M-edge.