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AP483 Optics & Electronics Seminar presents Ultrafast X-ray diffraction imaging with Free Electron Lasers

Ultrafast X-ray diffraction imaging with Free Electron Lasers
Monday, January 14, 2019 - 4:15pm
Spilker 232
Taisia Gorkhover, Project Scientist (SLAC)
Abstract / Description: 

The advent of X-ray Free Electron Lasers (FELs) opens the door for unprecedented studies on non-crystallin nanoparticles with high spatial and temporal resolutions. In the recent past, ultrafast X-ray imaging studies with intense, femtosecond short FEL pulses have elucidated hidden processes in individual fragile specimens, which are inaccessible with conventional imaging techniques. Examples include airborne soot particle formation [1], metastable states in the synthesis of metal nanoparticles [2] and transient vortices in superfluid quantum systems [3] . Theoretically, ultrafast coherent diffraction X-ray imaging (CDI) could achieve atomic resolution in combination with sub-femtosecond temporal precision. Currently, the spatial resolution of ultrafast X-ray CDI is limited to several nanometers due to a combination of several factors such as X-ray photon flux, image imperfections and ultimately, sample damage [4] .

In this talk, I will present several experimental studies, which address these limitations and/or demonstrate the potential of ultrafast CDI. In the first part of the talk, I will report on a novel "in-flight" holographic method which overcomes the phase problem and paves the way for high-resolution X-ray imaging in presence of noise and image imperfections [5]. The second part will focus on potential applications of ultrafast X-ray CDI such as visualization of irreversible light-induced dynamics at the nanoscale with nanometer and sub-femtosecond resolutions [6]. In the third part, I will present world's first diffraction images of heavy atom nanoparticles recorded with isolated soft X-ray attosecond pulses. The study indicates that the combination of the optimal pulse length and X-ray energy can significantly deviate from linear models and control over transient resonances might be an efficient pathway for the improvement of spatial resolution [7] .

In summary, ultrafast CDI is a powerful method for studies of transient non-equilibrium dynamics at the nanoscale. The increasing number of X-ray FEL facilities, and the constant improvement in accelerator and X-ray focusing technology will broaden our capabilities to observe transient states of matter. This development will have a significant impact on research fields such as catalysis, nanophotonics, matter under extreme conditions, light-matter interactions and biological studies.

[1] Loh, N. D. et al. Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight. Nature 486, 513–517 (2012).
[2] Barke, I. et al. The 3D-architecture of individual free silver nanoparticles captured by X-ray scattering. Nat. Commun. 6, (2015):6187.
[3] Gomez, L. F. et al. Shapes and vorticities of superfluid helium nanodroplets. Science 345, 906–909 (2014).
[4] Aquila, Andrew, et al., The linac coherent light source single particle imaging road map., Structur. Dyn. 2.4 (2015): 041701
[5] Gorkhover,T. et al., Femtosecond and nanometre visualization of structural dynamics in superheated nanoparticles. Nat. Phot. 10, (2016):93.
[6] Gorkhover,T.,et al., Femtosecond X-ray Fourier holography imaging of free-flying nanoparticles. Nat. Phot. 12.3, (2018): 150.
[7] Kuschel, S., et al, in prep.