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Literatura académica sobre el tema "Atomes neutres"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Atomes neutres"

Atiyah, M. F. y N. S. Manton. "Complex geometry of nuclei and atoms". International Journal of Modern Physics A 33, n.º 24 (30 de agosto de 2018): 1830022. http://dx.doi.org/10.1142/s0217751x18300223.

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We propose a new geometrical model of matter, in which neutral atoms are modelled by compact, complex algebraic surfaces. Proton and neutron numbers are determined by a surface’s Chern numbers. Equivalently, they are determined by combinations of the Hodge numbers, or the Betti numbers. Geometrical constraints on algebraic surfaces allow just a finite range of neutron numbers for a given proton number. This range encompasses the known isotopes.

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Naghiyev, T. G. "Neutron-alpha reactions in nano α-Si3N4 particles by neutrons". Modern Physics Letters A 36, n.º 24 (10 de agosto de 2021): 2150181. http://dx.doi.org/10.1142/s0217732321501819.

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Computer modeling was applied to the study of [Formula: see text] transmutations in [Formula: see text] nanoparticles under the influence of neutrons at different energies. The modeling was separately performed for each Si and N atoms in the [Formula: see text] nanoparticles and the effect of neutrons on transmutations was investigated. The simulations were conducted individually for each stable isotope due to different effective cross-section of the probability of transmutation in the different types of isotopes of silicon and nitrogen atoms. Effective cross-section spectra of [Formula: see text] transmutation in Si and N atoms were comparatively studied.

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Mason, T. E. y A. D. Taylor. "Neutron Scattering in Materials Research". MRS Bulletin 24, n.º 12 (diciembre de 1999): 14–16. http://dx.doi.org/10.1557/s0883769400053665.

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With materials of ever-increasing complexity becoming key elements of the technologies underpinning industrial and economic development, there is an ongoing need for tools that reveal the microscopic origins of physical, electrical, magnetic, chemical, and biological properties. Neutron scattering is one such powerful tool for the study of the structure and dynamics of materials. Neutrons are well suited to this purpose for several reasons:∎ Neutrons are electrically neutral, leading to penetration depths of centimeters and thereby enabling in situ studies.∎ Neutron cross sections exhibit no regular dependence on atomic number and are similar in magnitude across the periodic table, giving rise to sensitivity to light elements in the presence of heavier ones.∎ Certain large differences in isotopic scattering cross sections (e.g., hydrogen to deuterium, H/D) make neutrons especially useful for the study of light atoms in materials.∎ The range of momentum transfer available allows probing of a broad range of length scales (0.1–105 Å), important in many different materials and applications.∎ Thermal and “cold” (longer-wavelength) neutrons cover a range of energies sufficient to probe a wide range of lattice or magnetic excitations, “slow” dynamic processes such as polymer chain reptation, and so forth.∎ Neutrons have magnetic moments and are thus uniquely sensitive probes of magnetic interactions.∎ Neutrons can be polarized, allowing the cross sections (magnetic and non-magnetic) to be separated.∎ The simplicity of the magnetic and nuclear interactions makes interpretation of results straightforward.

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Morris, Elizabeth M. y J. David Cooper. "Density measurements in ice boreholes using neutron scattering". Journal of Glaciology 49, n.º 167 (2003): 599–604. http://dx.doi.org/10.3189/172756503781830403.

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AbstractThis paper describes the use of a neutron probe to measure detailed stratigraphy in ice and snow. The Wallingford neutron probe, developed for measurement of soil moisture, consists of an annular radioactive source of fast neutrons around the centre of a cylindrical detector for slow (thermal) neutrons. In snow and ice, the fast neutrons lose energy by scattering from hydrogen atoms, and the number of slow neutrons arriving at the detector (the count rate) is related to the density of the medium. Calibration equations for count rate as a function of snow density and borehole diameter have been derived. Snow-density profiles from boreholes obtained using the probe show that, despite the smoothing produced by the neutron-scattering process, annual variations in density can be resolved. The potential contribution of the neutron probe to improvements in mass-balance monitoring is discussed.

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Roberts, Joyce A. "The Manuel Lujan Jr. Neutron Scattering Center". MRS Bulletin 22, n.º 9 (septiembre de 1997): 42–46. http://dx.doi.org/10.1557/s0883769400033996.

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In October 1986, the neutron scattering facility at Los Alamos National Laboratory became a national user facility and a formal user program was initiated in 1988. In July 1989, this facility was dedicated as the Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) in honor of the long-term Congress representative from New Mexico. The Lujan Center, part of the Los Alamos Neutron Science Center (LANSCE), is a pulsed spallation neutron source equipped with time-of-flight neutron-scattering spectrometers for condensed-matter research. Neutron scattering is a powerful technique for probing the microscopic structure of condensed matter. The energies and wavelengths of thermal neutrons closely match typical excitation energies and interatomic distances in solids and liquids. Because neutrons have no charge, they penetrate bulk samples of material to give precise information on the positions and motions of individual atoms. The magnetic moment of a neutron interacts with unpaired electrons, making neutrons ideal for probing microscopic magnetic properties. Because neutron-scattering cross sections do not vary monotonically with the atomic number of the scattering nucleus, neutrons and x-rays can provide complementary structural information. This technique is particularly effective for structural problems in polymer and biological studies because hydrogen and deuterium scatter neutrons strongly but with different cross sections.

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Dlougach, Eugenia, Mikhail Shlenskii y Boris Kuteev. "Neutral Beams for Neutron Generation in Fusion Neutron Sources". Atoms 10, n.º 4 (25 de noviembre de 2022): 143. http://dx.doi.org/10.3390/atoms10040143.

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Neutral beam injection is supposed to be the main source of high-energy particles, driving non-inductive current and generating primary neutrons in fusion neutron sources design based on tokamaks. Numerical simulation of high-energy particles’ thermalization in plasma and fusion neutron emission is calculated by novel dedicated software (NESTOR code). The neutral beam is reproduced statistically by up to 109 injected particles. The beam efficiency and contribution to primary neutron generation is shown to be dependent on the injection energy, input current, and plasma temperature profile. A beam-driven plasma operation scenario, specific for FNS design, enables the fusion rate and neutron generation in plasma volume to be controlled by the beam parameters; the resultant primary neutron yield can be efficiently boosted in plasma maintained at a relatively low temperature when compared to ‘pure’ fusion reactors. NESTOR results are applicable to high-precision nuclear and power balance estimations, neutron power loads distribution among tokamak components, tritium generation in hybrid reactors, and for many other tasks critical for FNS design.

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Pylypchuk, Ie V., V. O. Kovach, Anna V. Iatsyshyn, O. V. Farrakhov, V. N. Bliznyuk y V. O. Kutsenko. "Immobilization of boronic acid derivative onto the magnetic Gd-containing composites". IOP Conference Series: Earth and Environmental Science 1049, n.º 1 (1 de junio de 2022): 012014. http://dx.doi.org/10.1088/1755-1315/1049/1/012014.

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Abstract Aiming to develop new magnetic materials for neutron shielding applications, B- and Gd-containing magnetic nanoparticles were synthesized. Following bottom-up synthetic approach, core-shell Fe 3 O 4/Gd 2 O 3 nanocomposite particles were synthesized at the first stage. In the next stage, magnetic core-shell particles were modified with amino groups followed by grafting onto their surface of the boronic acid derivative. Such a multifunctional material, containing both boron (B) and gadolinium (Gd) atoms is a promising candidate for developing films and membranes, strongly interacting with neutrons. Due to the presence of boronic acids and bound to the indicator (Alizarin Red S), the material can induce color changes while immersed in sugar-containing solutions. Such a feature enables a possibility to estimate the number of boron atoms left after interaction with neutrons, thus allowing to check composite neutron-capture recourse.

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Liebschner, Dorothee, Pavel V. Afonine, Nigel W. Moriarty, Paul Langan y Paul D. Adams. "Evaluation of models determined by neutron diffraction and proposed improvements to their validation and deposition". Acta Crystallographica Section D Structural Biology 74, n.º 8 (24 de julio de 2018): 800–813. http://dx.doi.org/10.1107/s2059798318004588.

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The Protein Data Bank (PDB) contains a growing number of models that have been determined using neutron diffraction or a hybrid method that combines X-ray and neutron diffraction. The advantage of neutron diffraction experiments is that the positions of all atoms can be determined, including H atoms, which are hardly detectable by X-ray diffraction. This allows the determination of protonation states and the assignment of H atoms to water molecules. Because neutrons are scattered differently by hydrogen and its isotope deuterium, neutron diffraction in combination with H/D exchange can provide information on accessibility, dynamics and chemical lability. In this study, the deposited data, models and model-to-data fit for all PDB entries that used neutron diffraction as the source of experimental data have been analysed. In many cases, the reported R work and R free values were not reproducible. In such cases, the model and data files were analysed to identify the reasons for this mismatch. The issues responsible for the discrepancies are summarized and explained. The analysis unveiled limitations to the annotation, deposition and validation of models and data, and a lack of community-wide accepted standards for the description of neutron models and data, as well as deficiencies in current model refinement tools. Most of the issues identified concern the handling of H atoms. Since the primary use of neutron macromolecular crystallography is to locate and directly visualize H atoms, it is important to address these issues, so that the deposited neutron models allow the retrieval of the maximum amount of information with the smallest effort of manual intervention. A path forward to improving the annotation, validation and deposition of neutron models and hybrid X-ray and neutron models is suggested.

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Lucas, G. E., G. R. Odette y A. F. Rowcliffe. "Innovations in Testing Methodology for Fusion Reactor Materials Development". MRS Bulletin 14, n.º 7 (julio de 1989): 29–35. http://dx.doi.org/10.1557/s0883769400062138.

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The successful development of fusion power critically depends on structural materials which can maintain their integrity and dimensional stability in an extremely hostile service environment involving high temperatures and heat fluxes, corrosive media, high stresses, and intense fluxes of neutrons. Neutron irradiation results in a variety of mechanical, physical, and chemical property changes that are collectively referred to as radiation effects. The primary sources of damage are neutron-induced atomic displacements and transmutation products.High-energy neutrons produce primary recoil atoms (PKAs) with energies ranging from less than 1 keV to more than 100 keV. The energetic PKAs create a cascade of additional displacements. About 10% of the displaced atoms survive cascade recombination as isolated vacancies and self-interstitials or small clusters of these defects. The mobile defects migrate to pre-existing sinks such as grain boundaries and dislocations, or cluster to form a variety of extended defects such as voids (vacancies) or faulted dislocation loops (interstitials).

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Meilleur, Flora, Leighton Coates, Matthew Cuneo, Andrey Kovalevsky y Dean Myles. "The Neutron Macromolecular Crystallography Instruments at Oak Ridge National Laboratory: Advances, Challenges, and Opportunities". Crystals 8, n.º 10 (11 de octubre de 2018): 388. http://dx.doi.org/10.3390/cryst8100388.

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The IMAGINE and MaNDi instruments, located at Oak Ridge National Laboratory High Flux Isotope Reactor and Spallation Neutron Source, respectively, are powerful tools for determining the positions of hydrogen atoms in biological macromolecules and their ligands, orienting water molecules, and for differentiating chemical states in macromolecular structures. The possibility to model hydrogen and deuterium atoms in neutron structures arises from the strong interaction of neutrons with the nuclei of these isotopes. Positions can be unambiguously assigned from diffraction studies at the 1.5–2.5 Å resolutions, which are typical for protein crystals. Neutrons have the additional benefit for structural biology of not inducing radiation damage to protein crystals, which can be critical in the study of metalloproteins. Here we review the specifications of the IMAGINE and MaNDi beamlines and illustrate their complementarity. IMAGINE is suitable for crystals with unit cell edges up to 150 Å using a quasi-Laue technique, whereas MaNDi provides neutron crystallography resources for large unit cell samples with unit cell edges up to 300 Å using the time of flight (TOF) Laue technique. The microbial culture and crystal growth facilities which support the IMAGINE and MaNDi user programs are also described.

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Tesis sobre el tema "Atomes neutres"

Schlosser, Nicolas. "Etude et réalisation de micro-pièges dipolaires optiques pour atomes neutres". Phd thesis, Université Paris Sud - Paris XI, 2001. http://tel.archives-ouvertes.fr/tel-00001195.

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Les atomes neutres piégés sont des candidats potentiels pour
l'implémentation de portes logiques quantiques. Dans ce contexte, cette étude
porte sur la réalisation d'un piège dipolaire optique de si petite taille qu'il
ne puisse contenir qu'un atome unique. Pour cela, il est nécessaire de
focaliser très fortement un laser à l'endroit où l'on désire capturer les
atomes. L'expérience s'articule donc autour d'un objectif de microscope de
grande ouverture numérique, entièrement conçu et réalisé au laboratoire. Cette
optique est utilisée pour faire focaliser un laser au centre d'un piège
magnéto-optique, réservoir d'atomes froids alimentant le piège dipolaire ainsi
créé.

Le dispositif d'observation des atomes piégés est basé sur le même objectif,
qui collecte, avec une grande efficacité, la fluorescence des atomes piégés et
en fait l'image sur une caméra CCD ou une photodiode à avalanche. La résolution
spatiale du dispositif utilisant la caméra permet d'obtenir une image des
atomes capturés, alors que l'on utilise la rapidité de la photodiode à
avalanche pour les études de la dynamique du piège avec une bonne résolution
temporelle.

Après une description détaillée de ce dispositif expérimental, nous montrons
qu'il est possible de réaliser des micro-pièges dipolaires optiques, de
quelques microns cube et contenant une dizaine d'atomes. L'étude de la
dynamique de chargement et de la durée de vie de ces pièges révèle également la
présence de processus de collisions à deux corps. Nous montrons ensuite qu'en
diminuant le taux de chargement il est possible d'observer, en temps réel, un
atome unique piégé pendant quelques secondes. Dans ce régime, un processus de
"blocage collisionnel" limite ce nombre d'atome à un. Pour finir, nous
décrirons la mise en place d'un double piège dipolaire, dans lequel on peut
piéger un atome unique dans chaque site. Ce dispositif ouvre la voie vers
l'étude de l'interaction entre atomes piégés individuellement.

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Beugnon, Jérôme. "Contrôle de l'état interne d'un atome unique piégé et expériences d'interférences à deux photons : vers l'information quantique avec des atomes neutres". Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00185446.

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Les atomes neutres sont de bons candidats pour la réalisation de protocoles d'information quantique. Cette thèse présente des expériences effectuées dans cette perspective sur des atomes individuels de rubidium piégés dans des pinces optiques de taille microscopique. Ces pinces sont obtenues en focalisant un faisceau laser sur une taille inférieure à un micromètre. Nous montrons que l'on peut contrôler l'état de chaque atome individuellement en faisant des transitions Raman à deux photons entre deux niveaux hyperfins de l'état fondamental. Nous observons des oscillations de Rabi entre ces deux niveaux à des fréquences pouvant atteindre plusieurs mégaHertz. Nous étudions aussi la cohérence de ce système par des expériences de franges de Ramsey et d'écho de spin. Des temps de cohérence de plusieurs dizaines de millisecondes sont mesurés. De plus, dans le but de manipuler des atomes dans un registre quantique, nous démontrons le déplacement d'une pince optique contenant un atome et le transfert de celui-ci d'une pince dans une autre sans perte de cohérence ni chauffage. Finalement, en vue de réaliser l'intrication conditionnelle de deux atomes, nous étudions l'émission de photons par ces atomes piégés. Nous montrons que ces atomes sont des sources de photons uniques déclenchables efficaces et nous décrivons l'observation d'interférences à deux photons entre deux photons uniques émis par deux atomes voisins indépendants. Ces interférences quantiques prouvent l'indiscernabilité des photons émis par chaque atome.

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Kara, Abdelkader. "Contribution à l'étude expérimentale et théorique de la diffusion élastique d'atomes neutres par des surfaces périodiques et des surfaces avec des défauts isolés". Lille 1, 1985. http://www.theses.fr/1985LIL10031.

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L'étude expérimentale des surfaces de Cu par diffraction d'hélium à basse énergie permet de déterminer un potentiel d'interaction atome-surface. On peut déterminer la densité électronique en surface. Développement d'un formalisme de diffusion d'atomes neutres par les surfaces avec défauts isolés. La solution exacte est décrite sous forme de série de perturbation. En prenant une distribution aléatoire de défauts, les sections efficaces de diffusion calculées au 2ème ordre de perturbation pour des lacunes sur Cu(100) et Cu(110) et des atomes d'hydrogène adsorbés sur Cu(110) sont comparables a celles mesurées.

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Kissami, Abdelhamid. "Etude des sections efficaces d'excitation (desexcitation) et des profils des raies par des atomes neutres et ionises". Orléans, 1990. http://www.theses.fr/1990ORLE2030.

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Le travail entrepris a consiste en la realisation d'un programme numerique capable de calculer le profil des raies spectrales dans les plasmas, dans le cadre de l'approximation semi classique. Afin d'atteindre cet objectif plusieurs etapes ont ete franchies. La premiere consiste a calculer les sections efficaces d'excitation et desexcitation puis d'integrer l'ensemble sur une distribution maxwellienne dans l'espace des vitesses. La seconde etape a trait au calcul de la partie atomique du profil de raie (force de raie), qui est obtenue a partir d'une nouvelle technique fondee sur l'approximation coulombienne, dont le calcul de l'element de matrice radial est base sur des series recurrentes aisement calculables s'etendant a des domaines non hydrogenoides ainsi qu'aux niveaux de rydberg. La partie angulaire qui ne depend que du mode de couplage a ete programmee en utilisant les coefficients 6-j pour n'importe quel mode de couplage pur. En troisieme partie, la partie collisionnelle, du profil des raies est obtenue de maniere quasi-exacte par un calcul original des fonctions electroniques dipolaires et quadrupolaires. Cette methode s'avere etre une alternative bien superieure a toutes les formes empiriques, tel que le facteur de gaunt, utilisees habituellement. Les codes numeriques realises rendent possible le calcul des parametres d'elargissement d'un bon nombre de raies spectrales non tabulees jusqu'a present. Finalement ce logiciel permet un progres tres sensible, notamment par sa simplicite et sa vitesse d'execution par rapport a toutes les methodes de calcul utilisees actuellement et donne des resultats au moins aussi precis que les meilleurs calculs publies en bon accord avec la plupart des experiences fiables

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Loisel, Jean-Philippe. "Réalisation de sources lasers à l'état solide et observation du phénomène LIAD : application au développement d'une horloge optique à atomes neutres d'argent". Versailles-St Quentin en Yvelines, 2010. http://www.theses.fr/2010VERS0062.

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Les possibilités remarquables offertes par les techniques de refroidissement laser et de piégeage ont permis des avancées significatives dans le domaine des standards de fréquence à base d'atomes neutres. Parmi les différents systèmes permettant d'accéder à des valeurs de stabilité et précision élevés, l'atome d'argent est considéré comme l'un des candidats les plus prometteurs comme standard optique de fréquence. Cette thèse traite du développement d'une horloge basée sur des atomes neutres d'Ag. La transition 4d105s2 S1/2 > 4d95s2 2D5/2 dans l'Argent peut fournir une référence de fréquence pour les raisons suivantes : le niveau métastable 2D5/2, qui se relaxe par émission d'un photon quadripolaire électrique à 330. 5 nm, possède une durée de vie estimée à 0. 2 s, correspondant à une largeur de raie naturelle très faible de 0. 8 Hz. Il est par conséquent possible de bénéficier d'un long temps d'interaction pour le dispositif de fontaine atomique. De plus, cet état est accessible par une transition à 2 photons à 661. 2 nm, permettant d'éliminer l'effet Doppler du 1er ordre. Comme aspect technique important, la fréquence nécessaire pour la transition d'horloge et celle pour le refroidissement des atomes d'argent (raie D2 à 328 nm) peut être obtenue avec le même cristal de NdYLF (émission possible à 1322 nm/1312 nm). Ce travailde thèse détaille la réalisation de s sources nécessaires au refroidissement des atomes d'argent et à la transition d'horloge à l'aide d'un cristal de NdYLF pompé par diode et par deux étapes de doublage de fréquence intracavité. Par ailleurs, le phénomène LIAD y est présenté comme un compromis intéressant dans la conception d'une horloge atomique optique
The remarkable capabilities of laser cooling and trapping techniques for neutral atoms have led to great advances in the field of neutral atom-based frequency standards. Among the several atomic systems affording excellent prospects of high stability and accuracy in the optical region, the silver atom is regarded as one of the most promising candidates for an optical frequency standard. This thesis deals with the development of a clock based on neutral silver atoms. The Ag 4d105s2 S1/2 > 4d95s2 2D5/2 transition provides an attractive reference frequency for the following reasons : the 2D5/2 metastable level, which decays by emission of electric quadrupole radiation at 330. 5 nm, has an estimated lifetime of 0. 2 s, corresponding to an ultralow natural linewidth of only 0. 8 Hz. It’s therefore possible therefore to benefit from the long interaction time in an atomic fountain setup. Furthermore, the long-lived state is accessible with a two-photon transition at 661. 2 nm, providing a first-order Doppler-free interaction with atoms of all velocities. As an important technical aspect, the frequency needed to drive the clock transition and to cool the silver atoms (D2 line at 328 nm) can be provided by the same crystal Nd:YLF enable to generate both 1322 nm and 1312 nm. This work details especially the realization of the laser sources for both cooling silver atoms and driving the clock transition by diode-pumped Nd-YLF crystal and intracavity frequency doubling operation in two steps (second and fourth harmonic generation). In addition, the Lignt Induced Atomic Desorption (LIAD) phenomenon is described and observed as an interesting compromise in the case of an optical atomic clock conception

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Petitjean, Luc. "Étude théorique et expérimentale des collisions entre atomes de Rydberg et cibles neutres (atomique ou moléculaire) à énergie thermique : transferts résonnants d'énergie interne". Paris 11, 1985. http://www.theses.fr/1985PA112108.

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Cette thèse reporte une étude des propriétés collisionnelles des atomes de Rydberg avec des cibles neutres (atomique ou moléculaire). Ces collisions sont décrites dans le cadre de l'Approximation d'Impact (AI). Des méthodes permettant l'évaluation du facteur de forme de la transition atomique, étape clé dans le calcul d'une section efficace, sont proposées et discutées. Celles-ci autorisent de nombreuses confrontations avec les résultats expérimentaux. Les sections efficaces de dépeuplement total d'états de Rydberg du rubidium par des perturbateurs moléculaires (N2, CO, NH₃, ND₃) sont mesurées et comparées aux valeurs prédites par l'AI. L'influence des moments multipolaires de la molécule ainsi que celui d'autres paramètres physiques importants (le défaut d’énergie de la réaction, par exemple) sont clairement établies. Dans le cas des molécules dipolaires, le dépeuplement total est principalement dû au transfert quasi-résonnant d'énergie où l'énergie interne (atomique ou rotationnelle) perdue par l'un des partenaires de la collision est gagnée par l'autre. Enfin, notre approche théorique est étendue aux états moins excités et comparée à des résultats expérimentaux
This thesis reports a study of the collisional behavior of atomic Rydberg states with atomic and molecular targets. These collisions are described within the frame of the Impulse Approximation (IA). Methods for the evaluation of the atomic form factor, the key step in the derivation of the cross-section, are proposed and discussed allowing numerous comparisons with experimental data. The quenching cross-sections of high rubidium Rydberg states by molecular perturbers (N₂, CO, NH₃, ND₃) are measured and compared to IA predictions. The influence of the molecular multipole moment as well as of ether relevant physical parameters (energy balance of the reaction) are clearly stated. In the case of dipole molecules the total depopulation is mainly governed by near-resonant energy transfer where the internal energy (atomic or rotational) lest by one colliding partner is gained by the ether. Finally, our theoretical approach is tentatively extended to low-lying excited states and compared to experimental results

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Haas, Florian. "Creation of entangled states of a set of atoms in an optical cavity". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00968861.

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In this thesis, we demonstrate the creation and characterization of multiparticle entangled states of neutral atoms with the help of a high finesse cavity. Our experimental setup consists of a fibre-based high finesse cavity above the surface of an atom chip. It allows us to prepare an ensemble of 87Rb atoms with well-defined atom number. The atoms are trapped in a single antinode of an intracavity standing wave dipole trap and are therefore all equally coupled to the cavity mode. We present a scheme based on a collective, quantum non-destructive (QND) measurement and conditional evolution to create symmetric entangled states and to analyze them at the single-particle level by directly measuring their Husimi Q function. We use this method to create and characterize W states of up to 41 atoms. From the tomography curve of the Q function, we reconstruct the symmetric part of the density matrix via different reconstruction techniques and obtain a fidelity of 0.42. Furthermore, we have devised an entanglement criterion which only relies on comparing two populations of the density matrix. We use it to infer the degree of multiparticle entanglement in our experimentally created states and find that the state with highest fidelity contains at least 13 entangled particles. In addition, we show preliminary results on experiments to count the atom number inside a cavity in the QND regime and to create entangled states via quantum Zeno dynamics.

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Garnier, Philippe. "Etude de l'interaction entre l'exosphère de Titan et la magnétosphère kronienne, à l'aide des données de l'expérience MIMI (Magnetosphere Imaging Instrument) à bord de Cassini". Phd thesis, Toulouse 3, 2007. http://thesesups.ups-tlse.fr/109/.

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Le plus gros satellite de Saturne, Titan, voit son atmosphère dense en azote bombardée par les ions énergétiques de la magnétosphère, en raison de l'absence de champ magnétique intrinsèque significatif. Des réactions d'échange de charge entre les neutres froids de l'exosphère (plus haute région atmosphérique) et ces ions énergétiques créent alors des atomes énergétiques neutres (ENAs). L'instrument INCA (Ion and Neutral Camera), l'un des trois instruments de l'expérience MIMI (Magnetosphere Imaging Instrument) à bord de la sonde Cassini en orbite autour de Saturne, permet d'imager ces neutres comme des photons et de mesurer leur flux, et fournit ainsi un diagnostic précieux de l'interaction entre Titan et le magnétosphère kronienne. Notre travail de thèse a consisté, en premier lieu, à modéliser l'exosphère de Titan, en considérant à la fois des profils thermiques et non thermiques. Un modèle de calcul de flux d'ENAs a été, en second lieu, développé, comparé aux observations, et enrichi par une étude des processus d'absorption des ENAs. Nous avons ensuite réalisé une analyse statistique des données de l'expérience MIMI durant les traversées d'orbite et survols de Titan. Enfin, une application au satellite de glace Rhéa a permis de fournir des conditions limites pour l'existence de son éventuelle exosphère
The largest satellite of Saturn, Titan, has a nitrogen-rich atmosphere directly bombarded by magnetospheric energetic ions, due to its lack of a significant intrinsic magnetic field. Charge-exchange collisions between the cold neutrals of its exosphere (the upper part of the atmosphere) and the energetic ions from Saturn's magnetosphere produce then energetic neutral atoms (ENAs). The Ion and Neutral Camera (INCA), one of the three sensors that comprise the Magnetosphere Imaging Instrument (MIMI) on the Cassini spacecraft orbiting around Saturn, images these neutrals like photons, measures their fluxes and provides a powerful diagnostic of the interaction between Titan and the kronian magnetosphere. Our work during this PhD thesis was first to model the Titan exosphere, with both thermal and non thermal profiles. An ENA flux calculation model was then developed, compared to observations and completed with a study of the ENA absorption mechanisms. We have also performed a statistical analysis of the MIMI data during the Titan flybys and orbit crossings. Finally, an application on the icy satellite Rhea allowed to infer upper limits for its eventual exosphere

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Mekkaoui, Mohamed. "Transport des atomes et des molécules dans les plasmas fluctuants de bord des machines de fusion". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4784/document.

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La fusion thermonucléaire est l'une des candidates favorites a la production d'énergie au courant de ce siècle. Parmi les défi que nous pose cette discipline, on note la turbulence au bord des machine de fusion et l'interaction plasma paroi. En effet nous avons montre que les fluctuations turbulentes affectent le transport des particules neutres et le rayonnement qui leur est associe. En particulier, sont affectes les neutres lents (dont le libre parcours moyen est de l'ordre de la longueur de corrélation des fluctuations), comme les molécules et les atomes d´impuretés pulvérises a la parois. Cette conclusion nous a conduit a inclure ces fluctuations dans le code de transport EIRENE utilise pour le dimensionnement de la machine ITER. Il a aussi été montre qu'en moyenne les fluctuations favorisent la pénétration des neutres dans le plasma
Edge plasma of tokamaks manifests high level of fluctuations amplitude (>50%). It has been demonstrated that such a fluctuations affect significantly the transport of neutral particles, and in particular the slow particles as molecules and sputtered impurities. That is their penetration depth in the plasma is enhanced in the average. Then turbulent fluctuations are now implemented in the monte carlo transport code EIRENE used for the design of ITER

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Leite, Carlos Alberto Faria. "Desaceleração e manipulação de átomos neutros". Universidade de São Paulo, 1992. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-26082014-153955/.

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O trabalho trata da desaceleração de feixes de átomos neutros de Sódio, pela técnica de sintonia Zeeman. O processo de desaceleração é estudado em detalhes e demonstrado com a utilização de um único laser. É feito o estudo do seguimento adiabático do átomo em relação ao campo magnético e demonstrada sua importância no processo de produção de fluxos intensos de átomos lentos. A posição em que os átomos param foi modificada, através da mudança do perfil do campo magnético onde os átomos se movimentam, levando-os para uma região de fácil acesso. A forma peculiar da distribuição espacial dos átomos ao atingirem o repouso é explicada e, finalmente, é estudada a focalização dos átomos, através de um campo magnético hexapolar, e o aprisionamento de átomos em uma armadilha magnética
This work describes the deceleration a sodium atoms beam by means of the Zeeman tuning technique. The deceleration process is studied in details and its demonstration is made using a single laser. We have studied and present the adiabatic following of the atoms along the magnetic field and its relevance to produce slow, high density, flux of neutral atoms. The atoms\' stopping position was varied, by changing the magnetic field profile, in a way to produce slows atoms outside the solenoid. The peculiar shape of the atomic spatial distribution of atoms at rest is explained, the focusing of atoms though a hexapole magnetic field is studied and the trapping of atoms in a magnetic trap is demonstrated

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Libros sobre el tema "Atomes neutres"

1964-, Newbury Nathan, Wieman C. E y American Association of Physics Teachers., eds. Trapping of neutral atoms. College Park, MD: American Association of Physics Teachers, 1998.

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Atomic hydrogen in the local universe. Groningen, The Netherlands: Rijksuniversiteit Groningen, 2000.

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P, Ozerov Ruslan, ed. Magnetic Neutron Diffraction. Boston, MA: Springer US, 1995.

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The neutron and the bomb: A biography of Sir James Chadwick. Oxford: Oxford University Press, 1997.

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Smarandache, Florentin. Neutrosophic physics: More problems, more solutions, collection of papers. Hanko, Finland: North-European Scientific Publishers, 2010.

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Mohd Nor bin Md Yusuf. The interaction of fast neutral atoms with metal surfaces. [s.l.]: typescript, 1989.

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Janot, Christian, Winfried Petry, Dieter Richter y Tasso Springer, eds. Atomic Transport and Defects in Metals by Neutron Scattering. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71007-0.

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DeLay, Glen Clark. Neutron placement with proton and positon. Lawndale, CA: DeLay's Printing, 2004.

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Unified field theory: Atomic nuclei, neutron stars, and black holes. Cookeville, TN: Tennessee Tech Printing Services Press, 2007.

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United States. National Aeronautics and Space Administration., ed. Surface conversion techniques for low energy neutral atom imagers: Final report. [Washington, DC: National Aeronautics and Space Administration, 1995.

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Capítulos de libros sobre el tema "Atomes neutres"

Averyn, Viktar S. "Short Refresher of Radiobiology". En Nuclear and Radiological Emergencies in Animal Production Systems, Preparedness, Response and Recovery, 13–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 2021. http://dx.doi.org/10.1007/978-3-662-63021-1_2.

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AbstractThe atoms are built up of a nucleus, containing positive (protons) and neutral (neutrons) particles, surrounded by negative particles (electrons), circulating around the “atomic orbit”. The number of the protons in the nucleus is giving the atomic number of the element (usually labelled as “Z”), and the sum of the neutrons and protons in the nucleus is giving the atomic or mass number of the element (usually labelled as “A”). The number in the electrons in the atomic orbit is always equal to the number of protons in the nucleus. However, as the mass of the electrons is almost equal to zero, they do not influence the whole atomic mass.

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Michaud, Georges, Georges Alecian y Jacques Richer. "Neutron Stars". En Atomic Diffusion in Stars, 259–70. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-19854-5_14.

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Radzig, Alexandre A. y Boris M. Smirnov. "Energetics of Neutral Atoms". En Springer Series in Chemical Physics, 87–120. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82048-9_5.

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Vorburger, A. y P. Wurz. "Lunar Atmosphere, Energetic Neutral Atoms". En Encyclopedia of Lunar Science, 1–6. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-05546-6_221-1.

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Missimer, J. "Neutral Currents in Muonic Atoms". En Fundamental Interactions in Low-Energy Systems, 115–25. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4967-9_7.

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Radzig, Alexandre A. y Boris M. Smirnov. "Spectroscopic Characteristics of Neutral Atoms". En Springer Series in Chemical Physics, 147–257. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82048-9_7.

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Aspect, Alain. "Laser Manipulation of Neutral Atoms". En NATO ASI Series, 193–206. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4899-1576-4_9.

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Metcalf, Harold J. y Peter van der Straten. "Magnetic Trapping of Neutral Atoms". En Graduate Texts in Contemporary Physics, 137–48. New York, NY: Springer New York, 1999. http://dx.doi.org/10.1007/978-1-4612-1470-0_10.

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Metcalf, Harold J. y Peter van der Straten. "Optical Traps for Neutral Atoms". En Graduate Texts in Contemporary Physics, 149–64. New York, NY: Springer New York, 1999. http://dx.doi.org/10.1007/978-1-4612-1470-0_11.

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Eichler, Hans Joachim, Jürgen Eichler y Oliver Lux. "Laser Transitions in Neutral Atoms". En Lasers, 65–76. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-99895-4_4.

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Actas de conferencias sobre el tema "Atomes neutres"

Bergeman, Thomas y Harold Metcalf. "Magnetic trapping of neutral atoms". En International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.wf6.

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Magnetic trapping of laser-cooled neutral atoms has been demonstrated at NBS and is progressing in other laboratories. Confinement of any object requires exchanging kinetic for potential energy, and for neutral atoms, this necessarily derives from shifts of internal energy levels. This is implemented through the force experienced by the atomic magnetic moment in a carefully designed, highly inhomogeneous field. Since magnetic fields of convenient strength can shift atomic energy levels by only a few gigahertz (temperature ≌ 0.1 K), neutral atom traps are very shallow and must be loaded with very cold atoms. We present some motivations for using magnetic traps and then discuss the constraints and optimal configurations of various arrangements. For example, no trap can be isotropic. Next we discuss both the classical and quantum mechanical motions of trapped atoms. These motions are important for at least two reasons: First, several schemes under study for further cooling depend on knowing the position and velocity of the atoms, as well as the vector field at each point along the orbit. Second, magnetic traps depend on the atomic moment remaining aligned with the field as the atom orbits in the trap, and this precludes rapid motion through a low-field region.

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Chu, Steven, Mark Kasevich, Kathryn Moler, Erling Riis y David Weiss. "Future of neutral atom clocks". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.wh1.

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The measurement on energy levels suitable for time standards can be made more precise with the use of neutral atom manipulation techniques. We have created a fountain of atoms where the measurement time of atoms in ballistic free-fall can be on the order of a fraction of a second. With these long measurement times, the linewidth of the transition between the ground state hyperfine transition of sodium was measured to be 2 Hz. Transitions in the optical frequency range could then have Q's of 1014 to 1015. In addition to creating high Q resonances, it is desirable to have a continuous, high density fountain of atoms. Towards this end, we have constructed an "atomic funnel" capable of creating a cold, high flux stream of atoms suitable for injection into a continuous atomic fountain. In the first embodiment of the funnel, the brightness of the atomic beam (defined as the number of atoms per second/( ΔvxΔvyΔvz) was increased by a factor of 3 × 103. With more recent improvements for both funneling more atoms from the hot atomic beam and better use of polarization gradient cooling to launch the atoms, we will describe how to improve the brightness enhancement by another four orders of magnitude.

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Oates, Chris, Zeb Barber, Jason Stalnaker, Chad Hoyt, Yann Le Coq y Leo Hollberg. "Optical Atomic Clocks Based Upon Neutral Atoms". En Laser Science. Washington, D.C.: OSA, 2007. http://dx.doi.org/10.1364/ls.2007.ltuh3.

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Ketterle, Wolfgang. "Recent Advances in Bose-Einstein Condensation". En The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.plen1.

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The observation of Bose-Einstein condensation (BEC) in dilute atomic gases was the realization of many long-standing goals: (1) to cool neutral atoms into the ground state of the system, thus exerting ultimate control over the motion and position of atoms limited only by Heisenberg's uncertainty relation; (2) to generate a coherent sample of atoms all occupying the same quantum state (this was subsequently used to realize an atom laser, a device which generates coherent matter waves); and (3) to create a quantum fluid with properties quite different from the quantum liquids He-3 and He-4. This provides a test-ground for many-body theories of the dilute Bose gas which were developed many decades ago, but never tested experimentally.

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Ido, T., M. M. Boyd, A. D. Ludlow, T. Zelevinsky, S. Blatt, S. M. Foreman, M. Notcutt y J. Ye. "Optical atomic clocks based on ultracold neutral strontium atoms". En International Quantum Electronics Conference, 2005. IEEE, 2005. http://dx.doi.org/10.1109/iqec.2005.1561161.

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Phillips, William D. "Laser cooling, stopping, and magnetic trapping of neutral atoms". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.wv3.

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A thermal atomic Na beam is opposed by a resonantly tuned laser beam. The radiation pressure decelerates and compresses the thermal velocity distribution, bringing the average velocity to zero and reducing the width from ~1000 m/s to a few tens of m/s or less.1 The density of stopped atoms is > 106/cm3 within a bandwidth of a few m/ s. These densities and velocities are suitable for trapping by a number of proposed optical and magnetic traps. Using these stopped atoms, we have demonstrated the first electromagnetic trapping of neutral atoms. The trap, a magnetic quadrupole formed by two separated, coaxial, opposed current loops, confines the atoms by virtue of the force exerted on the Na magnetic dipole moment by the inhomogeneous magnetic field. The time constant for exponential decay of the atomic population in the trap is 0.83(7) s and is limited mainly by collisions with fast background gas atoms. The maximum velocity of atoms contained in the trap is 3.5 m/s, corresponding to a maximum energy of 17 mK.

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Maruyama, Ippei, Osamu Kontani, Shohei Sawada, Osamu Sato, Go Igarashi y Masayuki Takizawa. "Evaluation of Irradiation Effects on Concrete Structure: Background and Preparation of Neutron Irradiation Test". En ASME 2013 Power Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/power2013-98114.

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Methods for assessing the soundness of concrete exposed to irradiation are being developed within the framework of a project of the Nuclear Regulation Authority (NRA) “Japan Ageing Management Program for System Safety”. This paper presents the background of this project and recent research works. The major reason for deterioration of concrete under irradiation conditions is expansion of aggregate due to neutron and gamma-ray irradiation. Dislocation of atoms in covalent structures of aggregate minerals, and resultant lattice constant change and alteration to amorphous phase are produced by fast neutrons. In addition, through electronic exertion, some energy deposition is accumulated as permanent distortion/strain in atomic structures. Other effects are also summarized. We plan to conduct a neutron irradiation test from May 2013. In selecting mix proportions and concrete components for the irradiation test program, sample size as a function of capsule size and gamma-heating, cement type, and aggregate size and type are determined based on preliminary experiments.

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Holmgren, D. E. y D. F. Prelewitz. "Sodium core-excited fluorescence enhancement by charge transfer". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.thpo19.

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We have demonstrated a technique which enhances emission lines of core-excited Na transitions occurring in a hollow-cathode discharge. The technique should apply to other alkali atoms and could help in identifying the core-excited visible spectra of heavier alkali atoms. In our experiment, stored population is produced by the discharge in the Na-ion metastable level 2p53s J = 2. A pulsed dye laser is used to transfer this population to a higher ion level of the 2p53p configuration. Core-excited neutral atoms are subsequently produced by an exothermic charge transfer from ground neutrals to the enhanced parent 2p53p ion population. We observe enhanced fluorescence (2 to 3 times above background levels) from neutral 2p53s3d, 2p53s4s, and possibly 2p53p2 configurations when the metastable ion population is transferred to higher ion levels.

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Yanli, Xiong, Qiu Xiaopeng, Liu Shuhuan, Li Zhuoqi, Liu Shuangying, Ma Yong, Song Ci y Han Ning. "Simulation and Analysis of 4H-SiC-Based PiN Fast Neutron Detector With Polyethylene Converter Using Geant4". En 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-92268.

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Abstract When detecting fast neutrons, generally select materials with high hydrogen content, such as polyethylene and lithium hydride. It’s known that polyethylene is widely used and has high detect efficiency. Therefore, this paper uses Geant4 software to simulate 4H-SiC-based PiN fast neutron detector with polyethylene converter of varies thickness. With the increase of converter thickness, the conversion efficiency of 1–14MeV monoenergetic fast neutron will first increase and then decrease. By analysing the trend of conversion efficiency, the thickness is determined as 1000um. Then, the 1MeV, 2MeV, 4MeV and 8MeV monoenergetic neutrons and typical fats neutron source: Am-Be neutron source are simulated under the thickness of 1000um convertor, the particle types and energy distribution to the sensitive volume and the energy deposition of particles in the sensitive region are also obtained. Through the analysis of recoil proton energy spectrum, the relationship between incident neutron energy and recoil proton energy are studied. Also, through the analysis of PKA (primary knocked-out atoms) energy spectrum, we found that the main reactions in epi-layer are 28Si(n,n’) 28Si, 12C(n,n’) 12C, 28Si(n,α) 25Mg, 28Si(n,p) 28Al, etc. It is found that heavy ions such as C and Si produced by neutrons in sensitive volume account for a large proportion. The above research finally helps to investigate the deposit energy in the epi-layer.

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Gattobigio, G. L., F. Michaud, G. Labeyrie, T. Pohl y R. Kaiser. "Long Range Interactions Between Neutral Atoms". En NON-NEUTRAL PLASMA PHYSICS VI: Workshop on Non-Neutral Plasmas 2006. AIP, 2006. http://dx.doi.org/10.1063/1.2387926.

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Informes sobre el tema "Atomes neutres"

Ків, Арнольд Юхимович, Володимир Миколайович Соловйов y Sergey A. Tomilin. Formation of Si precipitates іn neutron irradiated Al. Видавничий відділ КДПУ, 2001. http://dx.doi.org/10.31812/0564/1027.

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Transmutation reactions are the unique way to get a large concentration of Silicon atoms in Aluminum lattice, and just in substitutional positions. Appearing Silicon atoms in Aluminum lattice instead of Aluminum atoms leads to arising of mechanical stresses. This factor is the keystone of the model, which allows to explain the main peculiarities of Si precipitate creation in Aluminum irradiated by thermal neutrons. First, we shall describe the qualitative peculiarities of the model. Then we shall perform some quantitative estimates. At last the model will be discussed and compared with experimental data.

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Holden, T., J. Root y R. Hosbons. CWI1988-Andi-12 Neutron Diffraction of Axial Residual Strains in the Vicinity of a Girth Weld. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), abril de 1988. http://dx.doi.org/10.55274/r0011390.

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Recent research has shown that neutron diffraction is a practical non-destructive method for determining residual strains in the vicinity of a girth weld in line pipe. The basis of the technique is that the distance between planes of atoms is used as a miniature, directional, internal strain gauge, just as for X-ray measurements. However, the penetration of neutrons into metals ls from 1000 to 10,000 times greater than that of X-rays, so that measurements may easily be made throughout the thickness of steel pipe including the region of the weld itself. The purpose of the present measurements was to characterize the axial residual strains remaining in linepipe after two pieces had been joined with a girth weld. This report summarizes the measurements of the axial residual strains in each of two pipes of thickness 11 and 16 mm at the 6:00, 1:30 and 10:00 positions.

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Hill, C. Summary Report of the Third Research Coordination Meeting on Data for Atomic Processes of Neutral Beams in Fusion Plasma. IAEA Nuclear Data Section, junio de 2022. http://dx.doi.org/10.61092/iaea.twqe-92hz.

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10 experts in the field of atomic collisional physics and neutral beam modelling for magnetic confinement fusion devices, together with IAEA Staff met online from 24 – 26 November 2021 for the Third Research Coordination Meeting of the IAEA Coordinated Research Project (CRP) F43023: Data for Atomic Processes of Neutral Beams in Fusion Plasma. They described progress since the previous project meeting in February 2019, discussed open issues and reviewed the coordinated research and code comparison activities conducted as part of the CRP. The proceedings of the meeting are summarized in this report.

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Hill, Christian. Data for Atomic Processes of Neutral Beams in Fusion Plasma. IAEA Nuclear Data Section, febrero de 2019. http://dx.doi.org/10.61092/iaea.19hv-wzn5.

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12 experts in the field of atomic collisional physics and neutral beam modelling for magnetic confinement fusion devices, together with IAEA staff met at IAEA Headquarters 19 – 21 February 2019 for the Second Research Coordination Meeting of an IAEA Coordinated Research Project on Data for Atomic Processes of Neutral Beams in Fusion Plasma. They described progress with their research since the previous project meeting in June 2017, discussed open issues and made plans for continued coordinated research and code comparison during the remaining years of the project. The proceedings of the meeting are summarized in this report.

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Pritchard, David E. y Wolfgang Ketterle. Experiments with Trapped Neutral Atoms. Fort Belvoir, VA: Defense Technical Information Center, marzo de 1996. http://dx.doi.org/10.21236/ada306690.

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Ketterle, Wolfgang. Experiments With Trapped Neutral Atoms. Fort Belvoir, VA: Defense Technical Information Center, enero de 2010. http://dx.doi.org/10.21236/ada514076.

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Ketterle, Wolfgang. Experiments with Trapped Neutral Atoms. Fort Belvoir, VA: Defense Technical Information Center, agosto de 2000. http://dx.doi.org/10.21236/ada381427.

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Saffman, Mark y Thad Walker. Quantum Logic With Cold Neutral Atoms. Fort Belvoir, VA: Defense Technical Information Center, agosto de 2006. http://dx.doi.org/10.21236/ada454801.

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Lee, Jongmin, Michael J. Martin, Yuan-Yu Jau, Ivan H. Deutsch y Grant W. Biedermann. A new approach to entangling neutral atoms. Office of Scientific and Technical Information (OSTI), noviembre de 2016. http://dx.doi.org/10.2172/1333520.

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Phillips, William D. Laser Cooling and Trapping of Neutral Atoms. Fort Belvoir, VA: Defense Technical Information Center, julio de 1992. http://dx.doi.org/10.21236/ada253537.

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