Imaging the Shapes and Dynamics of Superfluid Helium Nanodroplets PDF Download

Author: Bruno Langbehn
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Alkwin Slenczka
Publisher: Springer Nature
ISBN: 303094896X
Category : Science
Languages : en
Pages : 590

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This open access book covers recent advances in experiments using the ultra-cold, very weakly perturbing superfluid environment provided by helium nanodroplets for high resolution spectroscopic, structural and dynamic studies of molecules and synthetic clusters. The recent infra-red, UV-Vis studies of radicals, molecules, clusters, ions and biomolecules, as well as laser dynamical and laser orientational studies, are reviewed. The Coulomb explosion studies of the uniquely quantum structures of small helium clusters, X-ray imaging of large droplets and electron diffraction of embedded molecules are also described. Particular emphasis is given to the synthesis and detection of new species by mass spectrometry and deposition electron microscopy.

Author: Aaron LaForge
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Abstract: We explore the light induced dynamics in superfluid helium nanodroplets with wide-angle scattering in a pump-probe measurement scheme. The droplets are doped with xenon atoms to facilitate the ignition of a nanoplasma through irradiation with near-infrared laser pulses. After a variable time delay of up to 800 ps, we image the subsequent dynamics using intense extreme ultraviolet pulses from the FERMI free-electron laser. The recorded scattering images exhibit complex intensity fluctuations that are categorized based on their characteristic features. Systematic simulations of wide-angle diffraction patterns are performed, which can qualitatively explain the observed features by employing model shapes with both randomly distributed as well as structured, symmetric distortions. This points to a connection between the dynamics and the positions of the dopants in the droplets. In particular, the structured fluctuations might be governed by an underlying array of quantized vortices in the superfluid droplet as has been observed in previous small-angle diffraction experiments. Our results provide a basis for further investigations of dopant-droplet interactions and associated heating mechanisms

Author: Camila Bacellar C Silveira
Publisher:
ISBN:
Category :
Languages : en
Pages : 107

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Helium nanodroplets are the smallest known objects exhibiting superfluidity, and they provide a unique cryogenic matrix for high-resolution spectroscopy and ultracold chemistry applications. The relatively simple electronic structure of helium atoms and the homogeneity of the quantum fluid clusters make them excellent model systems for the study of electronic structures and dynamics in complex systems and the emergence of collective phenomena. Coupled electronic-nuclear dynamics in laser-excited helium nanodroplets are studied in the time-domain in two distinctly different excitation regimes following either single XUV-photon excitation or strong-field ionization by a near-infrared (NIR) laser pulse. Femtosecond time- resolved XUV photoelectron spectroscopy and femtosecond time-resolved X-ray coherent diffractive imaging are employed to monitor electronic relaxation dynamics in neutral droplets and the emergence and evolution of a nanoplasma in strong-field ionized droplets, respectively. Electronically excited pure and doped He droplets are prepared using femtosecond XUV pump pulses produced by high-order harmonic generation. The excited states and subsequent relaxation dynamics are probed by ionization of transient species with a femtosecond UV probe- pulse. Pump-probe time delay-dependent photoelectron kinetic energy distributions are measured using velocity map imaging. In pure droplets excited with 23.7 eV, three dynamic pathways are identified: interband relaxation from the initially excited 1s3p,1s4p manifold to the 1s2p band, further relaxation within the 1s2p Rydberg band and rapid atomic reconfiguration involving formation of Rydberg-excited (Hen)* cores within the droplet. Ongoing efforts towards understanding energy- and charge-transfer mechanisms between the host droplets and dopant atoms are discussed. New high-harmonic generation schemes were implemented in order to directly access the lower 1s2p droplet resonances. Droplets doped with a small amounts of Kr and Ne atoms (ndopant/ndroplet

Author: Kasra Amini
Publisher: Royal Society of Chemistry
ISBN: 1837671141
Category : Science
Languages : en
Pages : 671

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Author: Grigori Volovik
Publisher: World Scientific
ISBN: 9814513989
Category : Science
Languages : en
Pages : 231

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This book discusses the unique properties of superfluid phases of 3He, the condensed matter with the outmost broken symmetry, which combine in a surprising way the properties of ordered magnets, liquid crystals and superfluids. The complicated vacuum state of these phases with a large number of fermionic and bosonic quasiparticles and topological objects remains the vacuum in modern quantum field theories. Some of the objects and physical phenomena in 3He have strong analogy with the neutrino, W-bosons, weak interactions, gravity, chiral anomaly, Quantum Hall Effect and fractional statistics. As an example of topological objects, the quantized vortices in 3He phases are discussed in detail, including singular and continuous vortices, half-quantum vortices, broken symmetry in the vortex core and phase transitions between the vortex states with different symmetry and topology.

Author: Julian Claudius Zimmermann
Publisher:
ISBN:
Category : Diffraction
Languages : en
Pages :

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Author: Miquel Blancafort Jorquera
Publisher:
ISBN:
Category :
Languages : en
Pages : 209

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The study of superfluid helium has been carried out mainly by physicists. In recent years, taking advantage of the potentialities presented by superfluid helium nanodroplets (HeNDs) as inert matrices at very low temperatures (0.37 K), the chemical community became involved in its application to high-resolution spectroscopy. More recently (early 2000s), this community began to be involved in research using HeNDs to investigate chemical reactivity in this quantum solvent. As for the theoretical studies on the dynamics of physicochemical processes in HeNDs, they have been possible about five years ago and the number of theoretical dynamics studies, despite their interest, is very scarce. The main objective of this thesis is to contribute to the development of the research in this area.To introduce the reader into the topic, Chapter 1 is divided into four sections: the first one describes the properties of helium, the second one considers the history of the discovery and research carried out on the superfluidity phenomenon, the third one outlines the properties of superfluid helium nanodroplets, and the last one gives an overview of the applications and fields of study implying HeNDs.The theoretical and numerical methods used to describe superfluid liquid helium are detailed in Chapter 2. In the first section attention has been paid on the density functional theory (DFT) and its time dependent extension for real-time simulations (TDDFT). The second section describes the main density functionals used and the third section is aimed to present the numerical methods employed to perform the TDDFT calculations.The following four chapters contain the original studies carried out in this thesis. The investigation of the capture process of a Ne atom by a HeND can be found in Chapter 3. Here, the atom is treated using classical mechanics and the influence of energy and angular momentum is examined for a wide set of initial conditions. The microscopic mechanism, energy and angular momentum exchanges and vortex formation have been extensively analysed. The present contribution corresponds to the first systematic analysis of the influence of angular momentum in the capture process and vortex formation.Chapter 4 represents a natural evolution from Chapter 3 and describes the formation of a neon dimer or neon adduct inside a superfluid helium nanodroplet, treating both atoms classically. Analogously as in the previous chapter, angular momentum has also been taken into consideration and the mechanism, energy an angular momentum exchanges and vortex formation are analysed. These two chapters complement and extend two previous investigations of our group where the Ne atoms were treated using standard quantum mechanics at zero angular momentum. The contents of Chapter 4 correspond to the second theoretical investigation on bimolecular reaction dynamics in HeNDs.The following two chapters use a full quantum hybrid approach to explore rotational and vibrational energy relaxation dynamics. Chapter 5 corresponds to the first theoretical study reported so far on the rotational energy relaxation dynamics of molecules in HeNDs. This process has been studied using several isotopes of the H2 molecule (fast rotors) and considering a set of initial excitations and nanodroplet sizes.The last investigation (Chapter 6) is centred on the study of the vibrational energy relaxation in HeNDs. Thus, the influence of the energy gap between the vibrational levels, molecule-helium interaction energy and nanodroplet size on the vibrational relaxation dynamics has been analysed, taking as a reference the I2@(4He)100 doped nanodroplet which was recently studied in our group. To the best of our knowledge it is the first time that the influence of these key factors has been examined.Finally, in Chapters 7 and 8 the main conclusions and a summary in Catalan are presented.

Author: Zhiming M. Wang
Publisher: Springer Science & Business Media
ISBN: 1461494729
Category : Technology & Engineering
Languages : en
Pages : 392

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Nanodroplets, the basis of complex and advanced nanostructures such as quantum rings, quantum dots and quantum dot clusters for future electronic and optoelectronic materials and devices, have attracted the interdisciplinary interest of chemists, physicists and engineers. This book combines experimental and theoretical analyses of nanosized droplets which reveal many attractive properties. Coverage includes nanodroplet synthesis, structure, unique behaviors and their nanofabrication, including chapters on focused ion beam, atomic force microscopy, molecular beam epitaxy and the "vapor-liquid- solid" route. Particular emphasis is given to the behavior of metallic nanodroplets, water nanodroplets and nanodroplets in polymer and metamaterial nanocomposites. The contributions of leading scientists and their research groups will provide readers with deeper insight into the chemical and physical mechanisms, properties, and potential applications of various nanodroplets.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 34

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The dynamics of electronically excited helium nanodroplets are studied by femtosecond time-resolved photoelectron imaging. EUV excitation into a broad absorption band centered around 23.8 eV leads to an indirect photoemission process that generates ultraslow photoelectrons. A 1.58 eV probe pulse transiently depletes the indirect photoemission signal for pump-probe time delays