48 research outputs found
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Single-shot 3D coherent diffractive imaging of core-shell nanoparticles with elemental specificity.
We report 3D coherent diffractive imaging (CDI) of Au/Pd core-shell nanoparticles with 6.1 nm spatial resolution with elemental specificity. We measured single-shot diffraction patterns of the nanoparticles using intense x-ray free electron laser pulses. By exploiting the curvature of the Ewald sphere and the symmetry of the nanoparticle, we reconstructed the 3D electron density of 34 core-shell structures from these diffraction patterns. To extract 3D structural information beyond the diffraction signal, we implemented a super-resolution technique by taking advantage of CDI's quantitative reconstruction capabilities. We used high-resolution model fitting to determine the Au core size and the Pd shell thickness to be 65.0 ± 1.0 nm and 4.0 ± 0.5 nm, respectively. We also identified the 3D elemental distribution inside the nanoparticles with an accuracy of 3%. To further examine the model fitting procedure, we simulated noisy diffraction patterns from a Au/Pd core-shell model and a solid Au model and confirmed the validity of the method. We anticipate this super-resolution CDI method can be generally used for quantitative 3D imaging of symmetrical nanostructures with elemental specificity
An Online Dynamic Amplitude-Correcting Gradient Estimation Technique to Align X-ray Focusing Optics
High-brightness X-ray pulses, as generated at synchrotrons and X-ray free
electron lasers (XFEL), are used in a variety of scientific experiments. Many
experimental testbeds require optical equipment, e.g Compound Refractive Lenses
(CRLs), to be precisely aligned and focused. The lateral alignment of CRLs to a
beamline requires precise positioning along four axes: two translational, and
the two rotational. At a synchrotron, alignment is often accomplished manually.
However, XFEL beamlines present a beam brightness that fluctuates in time,
making manual alignment a time-consuming endeavor. Automation using classic
stochastic methods often fail, given the errant gradient estimates. We present
an online correction based on the combination of a generalized finite
difference stencil and a time-dependent sampling pattern. Error expectation is
analyzed, and efficacy is demonstrated. We provide a proof of concept by
laterally aligning optics on a simulated XFEL beamline
Single-shot 3D coherent diffractive imaging of core-shell nanoparticles with elemental specificity
We report 3D coherent diffractive imaging (CDI) of Au/Pd core-shell nanoparticles with 6.1 nm spatial resolution with elemental specificity. We measured single-shot diffraction patterns of the nanoparticles using intense x-ray free electron laser pulses. By exploiting the curvature of the Ewald sphere and the symmetry of the nanoparticle, we reconstructed the 3D electron density of 34 core-shell structures from these diffraction patterns. To extract 3D structural information beyond the diffraction signal, we implemented a super-resolution technique by taking advantage of CDI's quantitative reconstruction capabilities. We used high-resolution model fitting to determine the Au core size and the Pd shell thickness to be 65.0 +/- 1.0 nm and 4.0 +/- 0.5 nm, respectively. We also identified the 3D elemental distribution inside the nanoparticles with an accuracy of 3%. To further examine the model fitting procedure, we simulated noisy diffraction patterns from a Au/Pd core-shell model and a solid Au model and confirmed the validity of the method. We anticipate this super-resolution CDI method can be generally used for quantitative 3D imaging of symmetrical nanostructures with elemental specificity.111Ysciescopu
Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source
Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency