Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source

Rupp, Daniela; Monserud, Nils C.; Langbehn, Bruno; Sauppe, Mario; Zimmermann, Julian; Ovcharenko, Yevheniy; Möller, Thomas; Frassetto, Fabio; Poletto, Luca; Trabattoni, Andrea; Calegari, Francesca; Nisoli, M.; Sander, Katharina; Peltz, Christian; Vrakking, Marc J. J.; Fennel, Thomas; Rouzée, Arnaud

doi:10.1038/s41467-017-00287-z

Cited by 88 publications

(83 citation statements)

References 52 publications

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“…A recent XFEL based wide angle x-ray scattering study of Ag nano-particles enabled the reconstruction of their three-dimensional shapes [36]. Very recently, wide angle scattering from He droplets in the XUV regime has been studied [39].…”

Section: Oblate and Prolate Shapes Of Rotating Dropletsmentioning

confidence: 99%

Shapes of rotating superfluid helium nanodroplets

et al. 2017

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Rotating superfluid He droplets of approximately 1 μm in diameter were obtained in a free nozzle beam expansion of liquid He in vacuum and were studied by single-shot coherent diffractive imaging using an x-ray free electron laser. The formation of strongly deformed droplets is evidenced by large anisotropies and intensity anomalies (streaks) in the obtained diffraction images. The analysis of the images shows that, in addition to previously described axially symmetric oblate shapes, some droplets exhibit prolate shapes. Forward modeling of the diffraction images indicates that the shapes of rotating superfluid droplets are very similar to their classical counterparts, giving direct access to the droplet angular momenta and angular velocities. The analyses of the radial intensity distribution and appearance statistics of the anisotropic images confirm the existence of oblate metastable superfluid droplets with large angular momenta beyond the classical bifurcation threshold.3

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Section: Oblate and Prolate Shapes Of Rotating Dropletsmentioning

confidence: 99%

Shapes of rotating superfluid helium nanodroplets

et al. 2017

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“…Speaking of molecular characterization, it should also be possible to use strong electrostatic deflections to separate doped and undoped nanodroplets, which is important for emerging applications aiming at structural analysis of embedded molecules by x-ray, EUV, and electron pulses [15,[58][59][60].…”

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confidence: 99%

Oriented Polar Molecules Trapped in Cold Helium Nanodropets: Electrostatic Deflection, Size Separation, and Charge Migration

et al. 2019

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Helium nanodroplets doped with polar molecules are studied by electrostatic deflection. This broadly applicable method allows even polyatomic molecules to attain sub-Kelvin temperatures and nearly full orientation in the field. The resulting intense force from the field gradient strongly deflects even droplets with tens of thousands of atoms, the most massive neutral systems studied by beam "deflectometry." We use the deflections to extract droplet size distributions.Moreover, since each host droplet deflects according to its mass, spatial filtering of the deflected beam translates into size filtering of neutral fragile nanodroplets. As an example, we measure the dopant ionization probability as a function of droplet radius and determine the mean free path for charge hopping through the helium matrix. The technique will enable separation of doped and neat nanodroplets and size-dependent spectroscopic studies. * Present address: Modern Electron, Bellevue, WA 98007, USA Introduction.-If the internal and relative motion of molecules is cooled into the sub-Kelvin range, it becomes possible to observe and steer their reactions with precision, to determine their physical parameters and structures with high accuracy, and to use external fields to finely control their motion and orientation [1-4]. For example, buffer-gas cooling [5] can be employed as an entryway to electrostatic guiding and ultracold trapping [6,7], merged beams enable exploration of chemical reactions in the quantum regime [8], and Stark deflection of small molecules in a supersonic beam can be used to spatially separate their low rotational states and conformers [9].While high level of control has been demonstrated for individual small molecules, pursuing it for larger polyatomic systems becomes increasingly demanding [10]. Their rotational spectra are more congested, their degrees of freedom are less efficiently and uniformly cooled by nozzle expansion [10,11], and their higher masses reduce the deflection.A powerful tool to cool and study molecules of a wide range of sizes is "helium nanodroplet isolation" [12][13][14][15][16]. Molecules are entrapped and transported by a beam of 4 He N nanodroplets generated by expansion of helium gas through a cryogenic nozzle. Nanodroplets cool by evaporation upon exiting the nozzle, reaching an internal temperature of only T 0 =370 mK and turning superfluid. This temperature is set by the surface binding energy of helium atoms [17,18] and has been verified, as has the onset of superfluidity, by rotational spectroscopy of entrapped molecules [12]. When the droplet beam passes through one or more vapor-filled cells, atoms and molecules are readily picked up, cooled by heat transfer to the helium matrix (evaporation of surface helium atoms promptly brings the complex back to T 0 ), and carried along by the droplet beam.This method is unique in being applicable to a variety of molecules and atoms: essentially all that is required for embedding is the availability of ~10 -6 -10 -4 mbar of vapor. Its other key feature...

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“…Only recently, lab-based single-shot CDI of single Helium nanodroplets could be demonstrated with a laser-driven table-top high-harmonic generation (HHG) source [12]. Besides marking a breakthrough regarding accessibility, laser-based sources open unprecedented conceptual opportunities for CDI applications.…”

Section: Introductionmentioning

confidence: 99%

“…Note that, despite limitations regarding pulse duration, seeded FELs can provide widely adjustable multi-color beams, even with accurate phase control [14]. HHG-based multi-color scattering patterns have already been shown to enable the single-shot characterization of optical properties of non-reproducible targets [12]. Most importantly, because of the opportunity to provide intense pulses with durations comparable to the coherence times of XUV excitations, XUV-CDI with HHG sources (or appropriately seeded FELs) is expected to open unprecedented routes to monitor and temporally probe quantum coherent dynamics in excited nanostructures.…”

Section: Introductionmentioning

confidence: 99%

Quantum coherent diffractive imaging

et al. 2020

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Coherent diffractive imaging (CDI) has enabled the structural analysis of individual free nanoparticles in a single shot and offers the tracking of their light induced dynamics with unprecedented spatial and temporal resolution. The retrieval of structural information from scattering images in CDI experiments is so far mostly based on the assumption of classical scattering in linear response. For strong laser fields and in particular for resonant excitations, both the linear and the classical description may no longer be valid as population depletion and stimulated emission become important. Here we develop a density matrix-based scattering model in order to include such quantum effects in the local medium response and explore the transition from linear to non-linear CDI for the resonant scattering from Helium nanodroplets. We find substantial departures from the linear response case already for experimentally reachable pulse parameters and show that non-linear spatio-temporal excitation dynamics results in rich features in the scattering, leading to the proposal of quantum coherent diffractive imaging as a promising novel branch in strong-field XUV and x-ray physics.

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Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source

Cited by 88 publications

References 52 publications

Shapes of rotating superfluid helium nanodroplets

Shapes of rotating superfluid helium nanodroplets

Oriented Polar Molecules Trapped in Cold Helium Nanodropets: Electrostatic Deflection, Size Separation, and Charge Migration

Quantum coherent diffractive imaging

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