Bibliografie tematiche / Helium Superfluid

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Letteratura scientifica selezionata sul tema "Helium Superfluid"

Autore: Grafiati
Pubblicato: 21 settembre 2024

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Articoli di riviste sul tema "Helium Superfluid"

1

BRUSOV, PETER, e PAVEL BRUSOV. "NOVEL SOUND PHENOMENA IN IMPURE SUPERFLUIDS". International Journal of Modern Physics B 20, n. 03 (30 gennaio 2006): 355–80. http://dx.doi.org/10.1142/s021797920603322x.

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In the last decade, new techniques for producing impure superfluids with unique properties have been developed. This new class of systems includes superfluid helium confined to aerogel, HeII with different impurities, superfluids in Vycor glasses, and watergel. These systems exhibit very unusual properties including unexpected acoustic features. We discuss the sound properties of these systems and show that sound phenomena in impure superfluids are modified from those in pure superfluids. We calculate the coupling between temperature and pressure oscillations for impure superfluids and show that this coupling increases significantly. This leads to the existence in impure superfluids of such unusual sound phenomena as slow "pressure" waves and fast "temperature" waves. This also decreases the threshold values for nonlinear processes as compared to pure superfluids. Sound conversion, which has been observed in pure superfluids only by high intensity waves should be observed at moderate sound amplitude in impure superfluids. Cerenkov emission of second sound by first sound (which has never been observed in superfluids) could be observed in impure superfluids. Even the nature of the sound modes in impure superfluids turns out to be changed. We have also derived for the first time the nonlinear hydrodynamic equations for superfluid helium in aerogel.
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2

HIRSCH, J. E. "KINETIC ENERGY DRIVEN SUPERCONDUCTIVITY AND SUPERFLUIDITY". Modern Physics Letters B 25, n. 29 (20 novembre 2011): 2219–37. http://dx.doi.org/10.1142/s0217984911027613.

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The theory of hole superconductivity proposes that superconductivity is driven by lowering of quantum kinetic energy and is associated with expansion of electronic orbits and expulsion of negative charge from the interior to the surface of superconductors and beyond. This physics provides a dynamical explanation of the Meissner effect. Here we propose that similar physics takes place in superfluid helium 4. Experimental manifestations of this physics in 4 He are the negative thermal expansion of 4 He below the λ point and the "Onnes effect", the fact that superfluid helium will creep up the walls of the container and escape to the exterior. The Onnes effect and the Meissner effect are proposed to originate in macroscopic zero point rotational motion of the superfluids. It is proposed that this physics indicates a fundamental inadequacy of conventional quantum mechanics.
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3

OWCZAREK, ROBERT. "KNOTTED VORTICES AND SUPERFLUID PHASE TRANSITION". Modern Physics Letters B 07, n. 23 (10 ottobre 1993): 1523–26. http://dx.doi.org/10.1142/s0217984993001557.

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In this letter, studies of knotted vortex structures in superfluid helium are continued. A model of superfluid phase transition (λ-transition) is built in this framework. Similarities of this model to the two-dimensional Ising model are shown. Dependence of specific heat of superfluid helium on temperature near the λ point is explained.
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4

SATO, Akio. "Superfluid Helium Cryogenics." TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan) 28, n. 6 (1993): 304–15. http://dx.doi.org/10.2221/jcsj.28.304.

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5

Sato, Yuki, e Richard Packard. "Superfluid helium interferometers". Physics Today 65, n. 10 (ottobre 2012): 31–36. http://dx.doi.org/10.1063/pt.3.1749.

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6

Tilley, John. "Superfluid helium 3". Contemporary Physics 32, n. 5 (settembre 1991): 339–40. http://dx.doi.org/10.1080/00107519108223708.

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7

Gessner, Oliver, e Andrey F. Vilesov. "Imaging Quantum Vortices in Superfluid Helium Droplets". Annual Review of Physical Chemistry 70, n. 1 (14 giugno 2019): 173–98. http://dx.doi.org/10.1146/annurev-physchem-042018-052744.

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Free superfluid helium droplets constitute a versatile medium for a diverse range of experiments in physics and chemistry that extend from studies of the fundamental laws of superfluid motion to the synthesis of novel nanomaterials. In particular, the emergence of quantum vortices in rotating helium droplets is one of the most dramatic hallmarks of superfluidity and gives detailed access to the wave function describing the quantum liquid. This review provides an introduction to quantum vorticity in helium droplets, followed by a historical account of experiments on vortex visualization in bulk superfluid helium and a more detailed discussion of recent advances in the study of the rotational motion of isolated, nano- to micrometer-scale superfluid helium droplets. Ultrafast X-ray and extreme ultraviolet scattering techniques enabled by X-ray free-electron lasers and high-order harmonic generation in particular have facilitated the in situ detection of droplet shapes and the imaging of vortex structures inside individual, isolated droplets. New applications of helium droplets ranging from studies of quantum phase separations to mechanisms of low-temperature aggregation are discussed.
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8

Kawasaki, Shinsuke, e Takahiro Okamura. "Cryogenic design for a high intensity ultracold neutron source at TRIUMF". EPJ Web of Conferences 219 (2019): 10001. http://dx.doi.org/10.1051/epjconf/201921910001.

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The TUCAN (TRIUMF Ultra-Cold Advanced Neutron) collaboration has been developing a source of high-intensity ultra-cold neutrons for use in a neutron electric dipole search. The source is composed of a spallation neutron source and a superfluid helium ultra-cold neutron converter, surrounded by a cold moderator. The temperature of the superfluid helium needs to be maintained at approximately 1.0 K to suppress up-scattering by phonons. The Kapitza conductance and the heat transport by the superfluid helium are key parameters which need to be well characterized. We have therefore investigated them in first experiments. Current efforts are directed at optimizing the design of the helium cryostat.
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OWCZAREK, ROBERT. "KNOTTED VORTICES AND FERMIONIC EXCITATIONS IN BULK SUPERFLUID HELIUM". Modern Physics Letters B 07, n. 21 (10 settembre 1993): 1383–86. http://dx.doi.org/10.1142/s0217984993001429.

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In the present paper, knotted and linked vortices in superfluid helium were considered, following ideas presented in Ref. 1. The conclusion is that fermionic excitations could exist in bulk superfluid helium filled by knotted and linked vortex filaments.
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Korostyshevskyi, O., C. K. Wetzel, D. M. Lee e V. V. Khmelenko. "Enhanced luminescence of oxygen atoms in solid molecular nitrogen nanoclusters". Low Temperature Physics 50, n. 9 (1 settembre 2024): 722–32. http://dx.doi.org/10.1063/10.0028138.

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We studied luminescence accompanied an injection of the nitrogen-helium gas mixture after passing discharge into dense cold helium gas. Initially, when the experimental beaker was filled with superfluid helium and the nitrogen-helium gas was injected into bulk superfluid helium at T ≈ 1.5 K, the dominant band in the emission spectra was the α-group of nitrogen atoms. At these conditions, the nanoclusters of molecular nitrogen with high concentrations of stabilized nitrogen atoms were formed. When superfluid helium was evaporated from the beaker and the temperature at the bottom of the beaker was increased to T ≈ 20 K, we observed a drastic change in the luminescence spectra. The β-group of oxygen atoms was dominated in the luminescence spectra, and the emission of the α-group became small. At high temperatures (T ≈ 20 K), most of the nitrogen atoms recombine on the surface of N2 nanoclusters with the formation of excited nitrogen molecules. We explained the effect of the enhancement of β-group emission by effective energy transfer from excited nitrogen molecules to the stabilized impurity oxygen atom inside N2 nanoclusters.
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Più fonti

Tesi sul tema "Helium Superfluid"

1

Matthias, John Robert. "Quantum evaporation from superfluid helium". Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390167.

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2

Rorai, Cecilia. "Vortex reconnection in superfluid helium". Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7868.

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2010/2011
La presente tesi concerne la modellizzazione e simulazione numerica, attraverso l'equazione di Gross-Pitaevskii (chiamata anche equazione di Schroedinger non lineare), della dinamica dei vortici quantistici nell'elio superfluido e in particolare del fenomeno della riconnessione. La riconnessione si verifica qualora due vortici approssimativamente antiparalleli, si intersecano e si scambiano le estremità. Questo fenomeno è stato osservato sperimentalmente e risulta essere una caratteristica essenziale della turbolenza quantistica.
XXIII Ciclo
1983
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3

Boatwright, Adrian Lional. "Molecular behaviour in superfluid helium clusters". Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478961.

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4

Blancafort, Jorquera Miquel. "Theoretical reaction and relaxation dynamics in superfluid helium nanodroplets". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668116.

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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.
Les nanogotes d’heli superfluid (HeNDs) són matrius inerts i nanoreactors ideals a baixa temperatura (0.37 K). Això ha atret l’atenció de químics doncs permeten realitzar espectroscopia d’altra resolució, estudiar la reactivitat i sintetitzar en condicions especials. L’estudi teòric de la dinàmica de processos en HeND ha estat possible tan sols fa cinc anys i, tot i el seu interès, n’hi ha molt pocs estudis. L’objectiu d’aquesta tesi és contribuir a la recerca en aquesta àrea. El Capítol 1 descriu les propietats de l’heli, la història de la superfluïdesa i les propietats i aplicacions de les HeNDs. La teoria del funcional de la densitat (DFT) i l’extensió de la mateixa depenent del temps (TDDFT), els principals funcionals per HeNDs i els mètodes numèrics es presenten al Capítol 2. Els següents capítols contenen els estudis originals d’aquesta tesi. En el Capítol 3 s’investiga la captura de Ne en una HeND on l’àtom es tracta clàssicament. El mecanisme, els intercanvis d’energia i moment angular i la formació de vòrtexs s’han analitzat àmpliament. Aquest és el primer anàlisi rigorós de la influència del moment angular en la captura i formació de vòrtexs. El Capítol 4 descriu la formació de Ne2/Ne-Ne en HeND tractant ambdós àtoms clàssicament. El mecanisme, bescanvis d’energia i moment angular i formació de vòrtexs també s’han estudiat. És el segon estudi sobre reaccions bimoleculars en HeNDs. Els Capítols 3 i 4 complementen i amplien dues investigacions del nostre grup on els àtoms es van tractar quànticament amb moment angular zero. En els propers dos capítols es consideren les relaxacions rotacional i vibracional utilitzant enfocs quàntics híbrids. El Capítol 5 correspon al primer estudi teòric de la relaxació rotacional de molècules en HeNDs, i s’han considerat varis isòtops de H2 i excitacions inicials i mides de nanogota. El Capítol 6 detalla la influència de la separació energètica vibracional, interacció molècula-heli i mida de nanogota en la relaxació vibracional en HeNDs, agafant com a referència el sistema I2@(4He)100. És el primer cop que s’examina l’efecte d’aquestes propietats clau. Els Capítols 7 i 8 presenten les principals conclusions i un resum en català, respectivament.
Las nanogotas de helio superfluido (HeNDs) son matrices inertes y nanoreactores ideales a baja temperatura (0.37 K). Esto ha atraído a los químicos pues posibilitan realizar espectroscopia de alta resolución, así como estudiar de la reactividad y síntesis en condiciones especiales. La dinámica teórica de procesos en HeND ha sido posible tan sólo hace cinco años y, a pesar de su interés, todavía hay muy pocos estudios. Esta tesis pretende contribuir a la investigación en esta área. El Capítulo 1 describe las propiedades del helio, la superfluidez y las propiedades y aplicaciones de las HeNDs. La teoría del funcional de la densidad (DFT) y su extensión dependiente del tiempo (TDDFT), los principales funcionales para HeNDs y los métodos numéricos se presentan en el Capítulo 2. Los siguientes capítulos contienen los estudios originales de esta tesis. En el Capítulo 3 se investiga la captura de Ne en una HeND donde el átomo se trata clásicamente. El mecanismo microscópico, intercambios de energía y momento angular y formación de vórtices se han analizado ampliamente. Este es el primer análisis detallado de la influencia del momento angular en la captura y la formación de vórtices. El Capítulo 4 describe la formación de Ne2/Ne-Ne en HeND tratando ambos átomos clásicamente. El mecanismo, intercambios de energía y momento angular y formación de vórtices también se han estudiado. Los Capítulos 3 y 4 complementan y amplían dos investigaciones de nuestro grupo donde los átomos se trataron cuánticamente con momento angular cero. En los dos capítulos siguientes se estudian las relajaciones rotacional y vibracional utilizando enfoques cuánticos híbridos. El Capítulo 5 corresponde al primer estudio teórico de la relajación rotacional de moléculas en HeNDs, y se han considerando varios isótopos de H2, excitaciones iniciales y tamaños de nanogota. El Capítulo 6 detalla la influencia de la separación energética, interacción molécula-helio y tamaño de nanogota en la relajación vibracional en HeND, habiéndose tomando como referencia el sistema I2@(4He)100. Es la primera vez que se examina el efecto de estas propiedades clave en la dinámica. Los Capítulos 7 y 8 presentan las principales conclusiones y un resumen en catalán, respectivamente.
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5

Bryan, Matthew S. "Inelastic Neutron Scattering of Nanoconfined Superfluid Helium". Thesis, Indiana University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10842052.

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The dynamics of liquid 4He confined in a mesoporous powder FSM-16 are reported in this dissertation, including the roton linewidth, excitation spectrum, and Compton profile. With an ordered triangular lattice structure, FSM-16 is a high surface area porous glass with hexagonal pores a few nanometers in diameter. Neutron backscattering results examined the roton linewidth as a function of temperature. Observed linewidths in confinement are consistent with the theoretical and experimental results of the bulk liquid. The temperature-filling phase diagram was explored at intermediate fillings and low temperatures. The maxon and roton excitations are used as indicators of density for a thin-film that transitions into a three dimensional confined fluid. The resulting excitation spectrum at low fillings does not correspond to the bulk liquid at any pressure. The deep inelastic neutron scattering results found an enhanced single particle kinetic energy, with full pore and thin film liquid deviating from the bulk momentum distribution in shape.

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6

Lorenson, Claude Pierre. "Dynamical properties of superfluid turbulence /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726339902566.

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7

Cregan, Robert Fraser. "Defects on the free surface of superfluid helium". Thesis, University of Exeter, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261949.

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8

Feng, Cheng. "Superfluid helium droplets : from spectroscopy to magnetic nanoparticles". Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32439.

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This project applies superfluid helium droplets in two big areas: spectroscopy and nanoparticles formation. Helium droplets, consisted of more than 103 helium atoms, provide a non-friction and very cold (~0.37 K) environment for clusters/nanoparticles growth, which offers unique advantages as a medium in applications of both spectroscopy and nanostructures formation. By sequentially adding NaCl and water molecules, the dissolution process of NaCl in water can be experimentally studied for the first time. This is achieved by recording the infra-red spectra of NaCl(H2O)n (1 ≤ n ≤ 7) complexes in O-H stretching region in combination with ab initio calculations. In particular, two bands have been assigned to dissolution of NaCl in water. The existence of quantum vortices in helium droplets has been firmly evident from spherical Ag nanoparticles formed in a chain. Quantum vortices provide a new route for the formation of one-dimensional nanostructures, which has been exploited in the fabrication of novel nanowires. Finally the pioneering work on the fabrication of both antiferromagnetic and ferromagnetic nanomaterials is reported for the first time, taking Cr and Ni as examples respectively. It is found that we can force ferromagnetic ordering in magnetic materials in superfluid helium. In particular, antiferromagnetic chromium has been discovered to convert to ferromagnetic, and the magnetism of ferromagnetic materials can have hugely enhanced magnetic moments that are close to the theoretical limit. This will have potential for applications in biomedical science, data storage and energy efficient technologies in the longer term.
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Ohya, Masayoshi. "Stability of superconducting magnets cooled by superfluid helium". Kyoto University, 2006. http://hdl.handle.net/2433/143795.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(エネルギー科学)
甲第12421号
エネ博第128号
新制||エネ||32(附属図書館)
24257
UT51-2006-J412
京都大学大学院エネルギー科学研究科エネルギー応用科学専攻
(主査)教授 塩津 正博, 教授 宅田 裕彦, 助教授 白井 康之
学位規則第4条第1項該当
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Coppens, François M. G. J. "Ultrafast quantum dynamics of doped superfluid helium nanodroplets". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30145/document.

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Dans cette thèse, nous étudions deux aspects de la dynamique d'impuretés atomiques interagissant avec des nanogouttes d'hélium superfluide (He) : la photo-excitation d'alcalins sur une nanogoutte et le dopage de nanogouttes contenant des tourbillons (vortex) quantiques avec des atomes de gaz rares. Nous utilisons la théorie de la fonctionnelle de la densité d'hélium ainsi que sa version dépendante du temps pour en faire la description théorique. Le premier aspect a été effectué dans le cadre d'une collaboration avec des expérimentateurs sur la photo-excitation du rubidium (Rb). Les alcalins sont une sonde très intéressante des gouttelettes d'hélium car ils résident dans leur zone de surface, où il a été prédit qu'un taux de condensation de Bose-Einstein de 100% était possible en raison d'une densité inférieure à celle de l'hélium superfluide. Nos simulations montrent que les états excités 5p et 6p désorbent à des échelles de temps très différentes, séparées par 2 ordres de grandeur (~100 ps et ~1 ps pour 5p et 6p respectivement). Ces résultats sont en accord avec ceux de l'expérience pompe-sonde à l'échelle femtoseconde qui a étudié la photodesorption d'atomes de Rb. Cependant, dans nos simulations, l'excitation vers 5pPi_{3/2} aboutit à un exciplexe RbHe lié à la surface, contrairement à l'expérience où RbHe est éjecté. L'introduction de la relaxation de spin de Pi_{3/2} à Pi_{1/2} nous a permis de résoudre ce désaccord, l'exciplexe RbHe ayant alors assez d'énergie pour désorber. Le deuxième aspect concerne une investigation purement théorique inspirée par les travaux récents de Gomez et Vilesov et al., où les tourbillons quantiques étaient visualisés en dopant les nanogouttes d'hélium avec des atomes d'argent, puis en les faisant atterrir en douceur (soft landing) sur un écran de carbone. Les images au microscope électronique montrent de longs filaments d'agrégats d'atomes d'argent qui s'étaient accumulés le long des coeurs des vortex. La formation de réseaux de tourbillons quantiques à l'intérieur de nanogoutelettes dopées par du xénon est également mise en évidence par diffraction de rayons X qui montrent des pics de Bragg caractéristiques d'agrégats de xénon piégés dans les coeurs des vortex. Nous avons d'abord étudié des collisions frontales entre un atome de xénon, héliophile, et une nanogoutte de 1000 héliums, et comparé les résultats à ceux d'une étude précédente sur le même processus avec le césium (Cs), qui est héliophobe. Dans le cas de Xe une «boule de neige» se forme autour de lui quand il entre dans la nanogoutte, et il lui faut beaucoup plus d'énergie qu'au Cs pour qu'il puisse en ressortir. Quand il le fait, il emporte des héliums avec lui, contrairement au Cs. Nous avons ensuite simulé des collisions entre Ar/Xe et des nanogouttes d'hélium superfluides pour différentes vitesses initiales et paramètres d'impact afin de déterminer leur section efficace de capture. Ces simulations ont ensuite été répétées pour des gouttelettes hébergeant un vortex quantique. On observe que l'impact des impuretés induit de grandes déformations de flexion et de torsion de la ligne de vortex, allant jusqu'à la génération d'ondes de Kelvin hélicoïdales qui se propagent le long du coeur du vortex. Ar/Xe est bien finalement capturé par le vortex, mais pas dans son coeur. Nous avons également découvert que l'existence d'un réseau de 6 lignes de vortex dont les noyaux sont remplis d'atomes d'Ar donne une rigidité accrue à la nanogoutte qui permet de stabiliser le système nano-goutte + vortex même à de faibles vitesses angulaires. Nos simulations impliquant des nanogouttes d'hélium comportant des tourbillons quantiques ouvrent la voie à d'autres investigations sur des nanogouttes hébergeant un ensemble de vortex, en collision avec de multiples impuretés
In this thesis we investigate two aspects of the dynamics of atomic impurities interacting with superfluid helium (He) nanodroplets, namely the photo-excitation of alkalis on a nanodroplet and the doping process of nanodroplets hosting quantised vortices with noble gas atoms. For the theoretical investigations we use He density functional theory and its time-dependent version. The first aspect involves a joint experimental and theoretical collaboration that focusses on the photo-excitation of the alkali rubidium (Rb). Alkalis are a very interesting probe of He droplets since they reside in their surface region, where it has been argued that almost 100% Bose-Einstein condensation could be achieved due to a density that is lower than in bulk superfluid He. In our simulations we find that states excited to the 5p and 6p manifold desorb at very different timescales, separated by 2 orders of magnitude (~100 ps and ~1 ps for 5p and 6p respectively). This is in good agreement with experimental results where the desorption behaviour of photo-excited Rb atoms is determined using a femtosecond pump-probe scheme. However, in our simulations excitation to the 5pPi_{3/2}-state results in a surface-bound RbHe exciplex, contrary to the experimental case where the RbHe exciplex desorbs from the droplets surface. Introducing spin-relaxation from Pi_{3/2} to Pi_{1/2} into the simulations, the RbHe exciplex is able to desorb from the droplet's surface, which resolves this contradiction. The second aspect concerns a purely theoretical investigation that is inspired by recent work of Gomez and Vilesov et al., where quantised vortices were visualised by doping He nanodroplets with silver atoms, subsequently "soft landing" them on a carbon screen. Electron-microscope images show long filaments of silver atom clusters that accumulated along the vortex cores. Also the formation of quantum-vortex lattices inside nanodroplets is evidenced by using X-ray diffractive imaging to visualise the characteristic Bragg patterns from xenon (Xe) clusters trapped inside the vortex cores. First, head-on collisions between heliophilic Xe and a He nanodroplet made of 1000 He atoms are studied. The results are then compared with the results of a previous study of an equivalent kinematic case with cesium (Cs), which is heliophobic. Xe acquires a "snowball" of He around itself when it traverses the droplet and much more kinetic energy is required before Xe is able to pierce the droplet completely. When it does, it takes away some He with it, contrary to the Cs case. Next, collisions between argon (Ar)/Xe and pristine superfluid He nanodroplets are performed for various initial velocities and impact parameters to determine the effective cross-section for capture. Finally, the simulations are then repeated for droplets hosting a single quantised vortex line. It is observed that the impact of the impurities induces large bending and twisting excitations of the vortex line, including the generation of helical Kelvin waves propagating along the vortex core. We conclude that Ar/Xe is captured by the quantised vortex line, although not in its core. Also we find that a He droplet, hosting a 6-vortex line array whose cores are filled with Ar atoms, results in added rigidity to the system which stabilises the droplets at low angular velocities. Our simulations involving droplets hosting quantum vortices open the way to further investigations on droplets hosting an array of vortices, involving multiple impurities
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Libri sul tema "Helium Superfluid"

1

Slenczka, Alkwin, e Jan Peter Toennies, a cura di. Molecules in Superfluid Helium Nanodroplets. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-94896-2.

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United States. National Aeronautics and Space Administration., a cura di. Superfluid Helium Tanker (SFHT) Study. [Denver, Colo.?]: Martin Marietta Astronautics Group, Space Systems, 1988.

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Vollhardt, Dieter. The superfluid phases of helium 3. London: Taylor & Francis, 1990.

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Volovik, G. E. Exotic properties of superfluid 3 He. Singapore: World Scientific, 1992.

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Center, Ames Research, a cura di. Temperature rise in superfluid helium pumps. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.

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1942-, Wölfle Peter, a cura di. The superfluid phases of helium 3. Mineola, New York: Dover Publications, Inc., 2013.

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Sciver, Steven W. Van. Final technical report on superfluid helium dynamics. [Madison, Wis.]: Nuclear Engineering & Engineering Physics, Univeristy of Wisconsin, 1990.

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J, DiPirro M., e Ames Research Center, a cura di. Superfluid Helium On-Orbit Transfer (SHOOT) operations. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.

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J, DiPirro M., e Ames Research Center, a cura di. Superfluid Helium On-Orbit Transfer (SHOOT) operations. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.

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Lyndon B. Johnson Space Center., a cura di. Superfluid Helium Tanker Study (SFHT): Program progress report. Sunnyvale, CA: Lockheed Missiles & Space Co., Inc., 1989.

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Capitoli di libri sul tema "Helium Superfluid"

1

Schmitt, Andreas. "Superfluid Helium". In Introduction to Superfluidity, 7–31. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07947-9_2.

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Schlaghaufer, Florian, Johannes Fischer e Alkwin Slenczka. "Electronic Spectroscopy in Superfluid Helium Droplets". In Topics in Applied Physics, 179–240. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-94896-2_5.

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Abstract (sommario):
AbstractElectronic spectroscopy has been instrumental in demonstrating the properties of helium droplets as a cryogenic matrix for molecules. The electronic spectrum of glyoxal, which was one of the first molecules investigated in helium droplets by means of electronic spectroscopy, showed two features that provided convincing evidence that the droplets were superfluid. These were free rotation and the distinct shape of the phonon side band which could be directly assigned to the characteristic dispersion curve of a superfluid. On closer examination, however, details such as increased moments of inertia and a spectral response on the droplet size distribution revealed unexpected features of microsolvation in the superfluid helium. In the course of studying many different molecules, it has become clear that electronic spectroscopy in helium droplets provides insight into the detailed effects of microsolvation. These in turn lead to numerous questions regarding the interaction with the superfluid which are discussed in this chapter. In addition, the influence of microsolvation in helium droplets on van der Waals clusters generated inside helium droplets are discussed. Finally, the effect of helium solvation on unimolecular or bimolecular elementary chemical reactions is evaluated in comparison with corresponding experiments in the gas phase. Particular focus of this article lies on the spectral features related to helium solvation which are not yet fully understood.
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Fiszdon, W. "Waves in Superfluid Helium". In Nonlinear Waves in Real Fluids, 273–334. Vienna: Springer Vienna, 1991. http://dx.doi.org/10.1007/978-3-7091-2608-0_8.

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Eberhardt, Ralph N., e John P. Gille. "Superfluid Helium Onorbit Resupply". In Advances in Cryogenic Engineering, 311–20. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-0639-9_38.

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Minier, Vincent, Roger-Maurice Bonnet, Vincent Bontems, Thijs de Graauw, Matt Griffin, Frank Helmich, Göran Pilbratt e Sergio Volonte. "Superfluid Helium Cryostat Customisation". In Inventing a Space Mission, 213–29. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60024-6_9.

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Zhang, Jie, Yunteng He, Lei Lei, Yuzhong Yao, Stephen Bradford e Wei Kong. "Electron Diffraction of Molecules and Clusters in Superfluid Helium Droplets". In Topics in Applied Physics, 343–79. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-94896-2_8.

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AbstractIn an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed “serial single molecule electron diffraction imaging” (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation. With two features combined, the process constitutes a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this chapter, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of monomer-doped droplets, small cluster and nanocluster -doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the “proof-of-concept” one step further.
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Sato, Y., E. Hoskinson e R. E. Packard. "Josephson Effects in Superfluid Helium". In Fundamentals and Frontiers of the Josephson Effect, 765–810. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20726-7_19.

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Zudin, Yuri B. "Heat Transfer in Superfluid Helium". In Non-equilibrium Evaporation and Condensation Processes, 297–320. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13815-8_13.

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Vinen, W. F. "Fifty Years of Superfluid Helium". In Advances in Cryogenic Engineering, 1–14. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-0639-9_1.

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Lappe, Tim. "Superfluid Helium: The Volovik Lessons". In Experimental Search for Quantum Gravity, 15–19. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-64537-7_3.

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Atti di convegni sul tema "Helium Superfluid"

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McAuslan, D. L., G. I. Harris, E. Sheridan e W. P. Bowen. "Superfluid Helium Optomechanics". In CLEO: QELS_Fundamental Science. Washington, D.C.: OSA, 2014. http://dx.doi.org/10.1364/cleo_qels.2014.fw3b.6.

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Domenikos, G. R., P. Bitsikas e E. Rogdakis. "Thermodynamic Modelling of Superfluid Stirling Cryocoolers". In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10077.

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Abstract The aim of this paper is to describe and thermodynamically model cryogenic Stirling refrigerators, using Helium in its different forms as the working medium. Helium has unique properties at cryogenic temperatures forming a superfluid. The cryogenic Stirling refrigerators with Helium at such low temperatures make use of the properties of this superfluid nature of Helium, thus they are referred to as Superfluid Stirling Refrigerators (SSR). To make use of these remarkable properties of superfluid helium a different version of Stirling refrigerator is used where superleaks are introduced in the pistons in order to let the superfluid part flow freely but constrain the normal fluid. This cooling procedure has an upper temperature limit as it is based on the superfluidity of helium, hence all the workings of this cycle must be well below the Lambda line. In addition, different models are needed and are used for the different isotopes of helium as their atomic spin nature is different and therefore their behavior at temperatures near absolute zero. In this study of SSR cryocoolers great care is being given towards the thermodynamic behavior of the entire system and working media, as well as different designs of the apparatus.
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Yabuzaki, T., A. Fujisaki, K. Sano, T. Kinoshita e Y. Takahashi. "Laser spectroscopy in superfluid helium". In Thirteenth International conference on atomic physics (ICAP-13). AIP, 1993. http://dx.doi.org/10.1063/1.43783.

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Harris, G. I., D. L. McAuslan, C. Baker, Y. Sachkou, E. Sheridan, Z. Duan e W. P. Bowen. "Optomechanics with Superfluid Helium-4". In CLEO: Applications and Technology. Washington, D.C.: OSA, 2015. http://dx.doi.org/10.1364/cleo_at.2015.jth5b.2.

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Minowa, Yosuke, Kensuke Kokado, Shota Aoyagi e Masaaki Ashida. "Quantum vortex visualization in superfluid helium". In Optical Manipulation and Structured Materials Conference, a cura di Takashige Omatsu, Hajime Ishihara, Keiji Sasaki e Kishan Dholakia. SPIE, 2020. http://dx.doi.org/10.1117/12.2573515.

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Lee, D. M. "The Discovery of Superfluid Helium-3". In Proceedings of the 29th International Conference on Low Temperature Physics (LT29). Journal of the Physical Society of Japan, 2023. http://dx.doi.org/10.7566/jpscp.38.011001.

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Harris, J. G. E., A. D. Kashkanova, A. B. Shkarin, C. D. Brown, S. Garcia, K. Ott e J. Reichel. "Quantum optomechanics experiments in superfluid helium". In Conference on Coherence and Quantum Optics. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/cqo.2019.tu2b.1.

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MASON, P., D. PETRAC, D. ELLEMAN, T. WANG, H. JACKSON, D. COLLINS, P. COWGILL e J. GATEWOOD. "The Spacelab 2 superfluid helium experiment". In 24th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-143.

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Nishigaki, K. "Observation of cavitation in superfluid helium". In ADVANCES IN CRYOGENIC ENGINEERING: Proceedings of the Cryogenic Engineering Conference - CEC. AIP, 2002. http://dx.doi.org/10.1063/1.1472163.

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Kaiser, G. "Thermo-Mechanical Pumps for Superfluid Helium". In ADVANCES IN CRYOGENIC ENGEINEERING: Transactions of the Cryogenic Engineering Conference - CEC. AIP, 2004. http://dx.doi.org/10.1063/1.1774788.

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Rapporti di organizzazioni sul tema "Helium Superfluid"

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Packard, Richard. Josephson Acoustic Radiation in Superfluid Helium. Fort Belvoir, VA: Defense Technical Information Center, maggio 1994. http://dx.doi.org/10.21236/ada279809.

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Packard, Richard. Josephson Acoustic Radiation in Superfluid Helium. Fort Belvoir, VA: Defense Technical Information Center, maggio 1995. http://dx.doi.org/10.21236/ada294424.

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Miller, Roger E. Superfluid Helium Droplet Spectroscopy Equipment Development. Fort Belvoir, VA: Defense Technical Information Center, gennaio 2003. http://dx.doi.org/10.21236/ada413202.

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Greene, G. L., e S. Lamoreaux. Production and storage of ultra cold neutrons in superfluid helium. Office of Scientific and Technical Information (OSTI), dicembre 1998. http://dx.doi.org/10.2172/334304.

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Ghosh, A. K., W. B. Sampson, S. W. Kim, D. Leroy, L. R. Oberli e M. N. Wilson. Stability measurements on cored cables in normal and superfluid helium. Office of Scientific and Technical Information (OSTI), luglio 1998. http://dx.doi.org/10.2172/638203.

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Lanou, Robert E. ,. Jr. Particle Detection in Superfluid Helium: R&D for Low Energy Solar Neutrinos. Office of Scientific and Technical Information (OSTI), marzo 2006. http://dx.doi.org/10.2172/878465.

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