Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight

Abstract

The morphology of micrometre−size particulate matter is of critical importance in fields ranging from toxicology to climate science, yet these properties are surprisingly difficult to measure in the particles' native environment. Electron microscopy requires collection of particles on a substrate; visible light scattering provides insufficient resolution; and X−ray synchrotron studies have been limited to ensembles of particles. Here we demonstrate an in situ method for imaging individual sub−micrometre particles to nanometre resolution in their native environment, using intense, coherent X−ray pulses from the Linac Coherent Light Source free−electron laser. We introduced individual aerosol particles into the pulsed X−ray beam, which is sufficiently intense that diffraction from individual particles can be measured for morphological analysis. At the same time, ion fragments ejected from the beam were analysed using mass spectrometry, to determine the composition of single aerosol particles. Our results show the extent of internal dilation symmetry of individual soot particles subject to non−equilibrium aggregation, and the surprisingly large variability in their fractal dimensions. More broadly, our methods can be extended to resolve both static and dynamic morphology of general ensembles of disordered particles. Such general morphology has implications in topics such as solvent accessibilities in proteins, vibrational energy transfer by the hydrodynamic interaction of amino acids, and large−scale production of nanoscale structures by flame synthesi

Nonsequential two-photon absorption from the K shell in solid zirconium

“…This process requires knowledge of the particle shape and size. Both size and shape can in principle be obtained from the inversion of the diffraction image using single-particle coherent x-ray diffraction imaging techniques [25,26], while the photon number is extracted from the integrated intensity of the diffraction pattern. This leaves the temporal pulse shape as the largest uncertainty.…”

Ultrafast Charge Rearrangement and Nuclear Dynamics upon Inner-Shell Multiple Ionization of Small Polyatomic Molecules

“…The availability of the first hard x-ray FEL, the Linac Coherent Light Source (LCLS) [2], enabled proof-ofprinciple imaging experiments on single nanoscale particles [3][4][5][6] and nanocrystals [7][8][9], and triggered dedicated radiation damage studies [8,9]. In parallel, measurements aimed at understanding the behavior of simple systems such as isolated atoms [10][11][12], diatomic molecules [13][14][15], and small rare gas clusters [16] were conducted.…”

Macromolecular structures probed by combining single-shot free-electron laser diffraction with synchrotron coherent X-ray imaging

“…Hence, a multimodal approach judiciously combining such complimentary characteristics is essential, and opens up new capabilities of X-ray structural investigation. In this paper, we demonstrate combined use of tomographic 3D imaging by rotating the same sample, more pertinent with synchrotron X-rays, and single-shot imaging of small specimens at radiation damage unlimited resolution, uniquely available with femtosecond X-ray laser pulses from the XFEL, to gain structural insights from inhomogenous samples 43,44 . We propose that the combined applications of synchrotron X-rays and XFELs demonstrated in this work can establish a unique path to seamlessly perform ab initio structure analysis of non-resembling structures within cells, organelles and macromolecular complexes, from micron-scale architectures to nano-scale details.…”