Ultracold gas shows 'lopsided' properties

CERN Multimedia

2002-01-01

"Duke University researchers have created an ultracold gas that has the startling property of bursting outward in a preferred direction when released. According to the researchers, studying the properties of the "lopsided" gas will yield fundamental insights into how matter holds itself together at the subatomic level" (1 page).

Evidence of Antiblockade in an Ultracold Rydberg Gas

Science.gov (United States)

Amthor, Thomas; Giese, Christian; Hofmann, Christoph S.; Weidemüller, Matthias

2010-01-01

We present the experimental observation of the antiblockade in an ultracold Rydberg gas recently proposed by Ates et al. [Phys. Rev. Lett. 98, 023002 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.023002]. Our approach allows the control of the pair distribution in the gas and is based on a strong coupling of one transition in an atomic three-level system, while introducing specific detunings of the other transition. When the coupling energy matches the interaction energy of the Rydberg long-range interactions, the otherwise blocked excitation of close pairs becomes possible. A time-resolved spectroscopic measurement of the Penning ionization signal is used to identify slight variations in the Rydberg pair distribution of a random arrangement of atoms. A model based on a pair interaction Hamiltonian is presented which well reproduces our experimental observations and allows one to deduce the distribution of nearest-neighbor distances.

High-Flux Ultracold-Atom Chip Interferometers, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — ColdQuanta's ultimate objective is to produce a compact, turnkey, ultracold-atom system specifically designed for performing interferometry with Bose-Einstein...

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

Energy Technology Data Exchange (ETDEWEB)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan); Qamar, Sajid [Department of Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan)

2011-09-15

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

International Nuclear Information System (INIS)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid; Qamar, Sajid

2011-01-01

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Disordered ultracold atomic gases in optical lattices: A case study of Fermi-Bose mixtures

International Nuclear Information System (INIS)

Ahufinger, V.; Sanchez-Palencia, L.; Kantian, A.; Sanpera, A.; Lewenstein, M.

2005-01-01

We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, 'dirty' superfluids, disordered metallic phases, and phases involving quantum percolation

Illustration of Babinet's principle with ultracold atoms

OpenAIRE

Reinhard, Aaron; Riou, Jean-Félix; Zundel, Laura A.; Weiss, David S.

2013-01-01

We demonstrate Babinet's principle by the absorption of high intensity light from dense clouds of ultracold atoms. Images of the diffracted light are directly related to the spatial distribution of atoms. The advantages of employing Babinet's principle as an imaging technique are that it is easy to implement and the detected signal is large. We discuss the regimes of applicability of this technique as well as its limitations.

Ultracold atoms in one-dimensional optical lattices approaching the Tonks-Girardeau regime

International Nuclear Information System (INIS)

Pollet, L.; Rombouts, S.M.A.; Denteneer, P.J. H.

2004-01-01

Recent experiments on ultracold atomic alkali gases in a one-dimensional optical lattice have demonstrated the transition from a gas of soft-core bosons to a Tonks-Girardeau gas in the hard-core limit, where one-dimensional bosons behave like fermions in many respects. We have studied the underlying many-body physics through numerical simulations which accommodate both the soft-core and hard-core limits in one single framework. We find that the Tonks-Girardeau gas is reached only at the strongest optical lattice potentials. Results for slightly higher densities, where the gas develops a Mott-like phase already at weaker optical lattice potentials, show that these Mott-like short-range correlations do not enhance the convergence to the hard-core limit

Superconducting microtraps for ultracold atoms

International Nuclear Information System (INIS)

Hufnagel, C.

2011-01-01

Atom chips are integrated devices in which atoms and atomic clouds are stored and manipulated in miniaturized magnetic traps. State of the art fabrication technologies allow for a flexible design of the trapping potentials and consequently provide extraordinary control over atomic samples, which leads to a promising role of atom chips in the engineering and investigation of quantum mechanical systems. Naturally, for quantum mechanical applications, the atomic coherence has to be preserved. Using room temperature circuits, the coherence time of atoms close to the surface was found to be drastically limited by thermal current fluctuations in the conductors. Superconductors offer an elegant way to circumvent thermal noise and therefore present a promising option for the coherent manipulation of atomic quantum states. In this thesis trapping and manipulation of ultracold Rubidium atoms in superconducting microtraps is demonstrated. In this connection the unique properties of superconductors are used to build traps based on persistent currents, the Meissner effect and remanent magnetization. In experiment it is shown, that in superconducting atom chips, thermal magnetic field noise is significantly reduced. Furthermore it is demonstrated, that atomic samples can be employed to probe the properties of superconducting materials. (author) [de

Spatially resolved photoionization of ultracold atoms on an atom chip

International Nuclear Information System (INIS)

Kraft, S.; Guenther, A.; Fortagh, J.; Zimmermann, C.

2007-01-01

We report on photoionization of ultracold magnetically trapped Rb atoms on an atom chip. The atoms are trapped at 5 μK in a strongly anisotropic trap. Through a hole in the chip with a diameter of 150 μm, two laser beams are focused onto a fraction of the atomic cloud. A first laser beam with a wavelength of 778 nm excites the atoms via a two-photon transition to the 5D level. With a fiber laser at 1080 nm the excited atoms are photoionized. Ionization leads to depletion of the atomic density distribution observed by absorption imaging. The resonant ionization spectrum is reported. The setup used in this experiment is suitable not only to investigate mixtures of Bose-Einstein condensates and ions but also for single-atom detection on an atom chip

Manipulating beams of ultra-cold atoms with a static magnetic field

International Nuclear Information System (INIS)

Rowlands, W.J.; Lau, D.C.; Opat, G.I.; Sidorov, A.I.; McLean, R.J.; Hannaford, P.

1996-01-01

The preliminary results on the deflection of a beam of ultra-cold atoms by a static magnetic field are presented. Caesium atoms trapped in a magneto-optical trap (MOT) are cooled using optical molasses, and then fall freely under gravity to form a beam of ultra-cold atoms. The atoms pass through a static inhomogeneous magnetic field produced by a single current-carrying wire, and are deflected by a force dependent on the magnetic substate of the atom. A schematical diagram of the experimental layout for laser trapping and cooling of cesium atom is given. The population of atoms in various magnetic substates can be altered by using resonant laser radiation to optically pump the atoms. The single-wire deflection experiment described can be considered as atomic reflexion from a cylindrical magnetic mirror; the underlying principles and techniques being relevant to the production of atomic mirrors and diffraction gratings. 16 refs., 10 figs

Light-induced gauge fields for ultracold atoms

Science.gov (United States)

Goldman, N.; Juzeliūnas, G.; Öhberg, P.; Spielman, I. B.

2014-12-01

Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle—the graviton—that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms ‘feeling’ laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials—both Abelian and non-Abelian—in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

Light-induced gauge fields for ultracold atoms

International Nuclear Information System (INIS)

Goldman, N; Juzeliūnas, G; Öhberg, P; Spielman, I B

2014-01-01

Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle—the graviton—that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms ‘feeling’ laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials—both Abelian and non-Abelian—in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms. (review article)

Measuring the One-Particle Excitations of Ultracold Fermionic Atoms by Stimulated Raman Spectroscopy

International Nuclear Information System (INIS)

Dao, T.-L.; Georges, Antoine; Dalibard, Jean; Salomon, Christophe; Carusotto, Iacopo

2007-01-01

We propose a Raman spectroscopy technique which is able to probe the one-particle Green function, the Fermi surface, and the quasiparticles of a gas of strongly interacting ultracold atoms. We give quantitative examples of experimentally accessible spectra. The efficiency of the method is validated by means of simulated images for the case of a usual Fermi liquid as well as for more exotic states: specific signatures of, e.g., a d-wave pseudogap are clearly visible

Towards quantum magnetism with ultracold atoms

International Nuclear Information System (INIS)

Weld, David M; Ketterle, Wolfgang

2011-01-01

At ICAP we presented the efforts and progress at MIT towards using ultracold atoms for the realization of various forms of quantum magnetism. These efforts include a study of fermions with strong repulsive interactions in which we obtained evidence for a phase transition to itinerant ferromagnetism, the characterization of cold atom systems by noise measurements, and a new adiabatic gradient demagnetization cooling scheme which has enabled us to realize temperatures of less than 350 picokelvin and spin temperatures of less than 50 picokelvin in optical lattices. These are the lowest temperatures ever measured in any physical system.

Ultracold fermions with repulsive interactions

Directory of Open Access Journals (Sweden)

Ketterle W.

2013-08-01

Full Text Available An ultracold Fermi gas with repulsive interaction has been studied. For weak interactions, the atomic gas is metastable, and the interactions were characterized by obtaining the isothermal compressibility from atomic density profiles. For stronger interactions (kFa ≈ 1, rapid conversion into Feshbach molecules is observed. When the conversion rate becomes comparable to the Fermi energy divided by η, the atomic gas cannot reach equilibrium without forming pairs. This precludes the predicted transition to a ferromagnetic state (Stoner transition. The absence of spin fluctuations proves that the gas stays paramagnetic. In free space, a Fermi gas with strong short-range repulsion does not exist because of the rapid coupling to molecular states.

Holographic method for site-resolved detection of a 2D array of ultracold atoms

Science.gov (United States)

Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

2016-08-01

We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

Ultracold atoms for precision measurement of fundamental physical quantities

CERN Multimedia

CERN. Geneva

2003-01-01

Cooling and trapping of neutral atoms has been one of the most active fields of research in physics in recent years. Several methods were demonstrated to reach temperatures as low as a few nanokelvin allowing, for example, the investigation of quantum degenerate gases. The ability to control the quantum degrees of freedom of atoms opens the way to applications for precision measurement of fundamental physical quantities. Experiments in progress, planned or being considered using new quantum devices based on ultracold atoms, namely atom interferometers and atomic clocks, will be discussed.

Quantum phases of low-dimensional ultra-cold atom systems

Science.gov (United States)

Mathey, Ludwig G.

2007-06-01

In this thesis we derive and explore the quantum phases of various types of ultracold atom systems, as well as their experimental signature. The technology of cooling, trapping and manipulating ultracold atoms has advanced in an amazing fashion during the last decade, which has led to the study of many-body effects of atomic ensembles. We first consider atomic mixtures in one dimension, which show a rich structure of phases, using a Luttinger liquid description. We then go on to consider how noise correlations in time-of-flight images of one-dimensional systems can be used to draw conclusions about the many-body state that they're in. Thirdly, we consider the quantum phases of Bose-Fermi mixtures in optical lattices, either square lattices or triangular lattices, using the powerful method of functional renormalization group analysis. Lastly, we study the phases of two-coupled quasi-superfluids in two dimensions, which shows unusual phases, and which could be used to realize the Kibble-Zurek mechanism, i.e. the generation of topological defects by ramping across a phase transition, first proposed in the context of an early universe scenario.

Coupling ultracold atoms to a superconducting coplanar waveguide resonator

OpenAIRE

Hattermann, H.; Bothner, D.; Ley, L. Y.; Ferdinand, B.; Wiedmaier, D.; Sárkány, L.; Kleiner, R.; Koelle, D.; Fortágh, J.

2017-01-01

We demonstrate coupling of magnetically trapped ultracold $^87$Rb ground state atoms to a coherently driven superconducting coplanar resonator on an integrated atom chip. We measure the microwave field strength in the cavity through observation of the AC shift of the hyperfine transition frequency when the cavity is driven off-resonance from the atomic transition. The measured shifts are used to reconstruct the field in the resonator, in close agreement with transmission measurements of the c...

Non-destructive Faraday imaging of dynamically controlled ultracold atoms

DEFF Research Database (Denmark)

Gajdacz, Miroslav; Pedersen, Poul Lindholm; Mørch, Troels

2013-01-01

We describe an easily implementable method for non-destructive measurements of ultracold atomic clouds based on dark field imaging of spatially resolved Faraday rotation. The signal-to-noise ratio is analyzed theoretically and, in the absence of experimental imperfections, the sensitivity limit...

A hybrid system of a membrane oscillator coupled to ultracold atoms

Science.gov (United States)

Kampschulte, Tobias

2015-05-01

The control over micro- and nanomechanical oscillators has recently made impressive progress. First experiments demonstrated ground-state cooling and single-phonon control of high-frequency oscillators using cryogenic cooling and techniques of cavity optomechanics. Coupling engineered mechanical structures to microscopic quantum system with good coherence properties offers new possibilities for quantum control of mechanical vibrations, precision sensing and quantum-level signal transduction. Ultracold atoms are an attractive choice for such hybrid systems: Mechanical can either be coupled to the motional state of trapped atoms, which can routinely be ground-state cooled, or to the internal states, for which a toolbox of coherent manipulation and detection exists. Furthermore, atomic collective states with non-classical properties can be exploited to infer the mechanical motion with reduced quantum noise. Here we use trapped ultracold atoms to sympathetically cool the fundamental vibrational mode of a Si3N4 membrane. The coupling of membrane and atomic motion is mediated by laser light over a macroscopic distance and enhanced by an optical cavity around the membrane. The observed cooling of the membrane from room temperature to 650 +/- 230 mK shows that our hybrid mechanical-atomic system operates at a large cooperativity. Our scheme could provide ground-state cooling and quantum control of low-frequency oscillators such as levitated nanoparticles, in a regime where purely optomechanical techniques cannot reach the ground state. Furthermore, we will present a scheme where an optomechanical system is coupled to internal states of ultracold atoms. The mechanical motion is translated into a polarization rotation which drives Raman transitions between atomic ground states. Compared to the motional-state coupling, the new scheme enables to couple atoms to high-frequency structures such as optomechanical crystals.

Floquet Engineering of Correlated Tunneling in the Bose-Hubbard Model with Ultracold Atoms.

Science.gov (United States)

Meinert, F; Mark, M J; Lauber, K; Daley, A J; Nägerl, H-C

2016-05-20

We report on the experimental implementation of tunable occupation-dependent tunneling in a Bose-Hubbard system of ultracold atoms via time-periodic modulation of the on-site interaction energy. The tunneling rate is inferred from a time-resolved measurement of the lattice site occupation after a quantum quench. We demonstrate coherent control of the tunneling dynamics in the correlated many-body system, including full suppression of tunneling as predicted within the framework of Floquet theory. We find that the tunneling rate explicitly depends on the atom number difference in neighboring lattice sites. Our results may open up ways to realize artificial gauge fields that feature density dependence with ultracold atoms.

Extended Hubbard models for ultracold atoms in optical lattices

International Nuclear Information System (INIS)

Juergensen, Ole

2015-01-01

In this thesis, the phase diagrams and dynamics of various extended Hubbard models for ultracold atoms in optical lattices are studied. Hubbard models are the primary description for many interacting particles in periodic potentials with the paramount example of the electrons in solids. The very same models describe the behavior of ultracold quantum gases trapped in the periodic potentials generated by interfering beams of laser light. These optical lattices provide an unprecedented access to the fundamentals of the many-particle physics that govern the properties of solid-state materials. They can be used to simulate solid-state systems and validate the approximations and simplifications made in theoretical models. This thesis revisits the numerous approximations underlying the standard Hubbard models with special regard to optical lattice experiments. The incorporation of the interaction between particles on adjacent lattice sites leads to extended Hubbard models. Offsite interactions have a strong influence on the phase boundaries and can give rise to novel correlated quantum phases. The extended models are studied with the numerical methods of exact diagonalization and time evolution, a cluster Gutzwiller approximation, as well as with the strong-coupling expansion approach. In total, this thesis demonstrates the high relevance of beyond-Hubbard processes for ultracold atoms in optical lattices. Extended Hubbard models can be employed to tackle unexplained problems of solid-state physics as well as enter previously inaccessible regimes.

Extended Hubbard models for ultracold atoms in optical lattices

Energy Technology Data Exchange (ETDEWEB)

Juergensen, Ole

2015-06-05

In this thesis, the phase diagrams and dynamics of various extended Hubbard models for ultracold atoms in optical lattices are studied. Hubbard models are the primary description for many interacting particles in periodic potentials with the paramount example of the electrons in solids. The very same models describe the behavior of ultracold quantum gases trapped in the periodic potentials generated by interfering beams of laser light. These optical lattices provide an unprecedented access to the fundamentals of the many-particle physics that govern the properties of solid-state materials. They can be used to simulate solid-state systems and validate the approximations and simplifications made in theoretical models. This thesis revisits the numerous approximations underlying the standard Hubbard models with special regard to optical lattice experiments. The incorporation of the interaction between particles on adjacent lattice sites leads to extended Hubbard models. Offsite interactions have a strong influence on the phase boundaries and can give rise to novel correlated quantum phases. The extended models are studied with the numerical methods of exact diagonalization and time evolution, a cluster Gutzwiller approximation, as well as with the strong-coupling expansion approach. In total, this thesis demonstrates the high relevance of beyond-Hubbard processes for ultracold atoms in optical lattices. Extended Hubbard models can be employed to tackle unexplained problems of solid-state physics as well as enter previously inaccessible regimes.

Ultracold atoms and the Functional Renormalization Group

International Nuclear Information System (INIS)

Boettcher, Igor; Pawlowski, Jan M.; Diehl, Sebastian

2012-01-01

We give a self-contained introduction to the physics of ultracold atoms using functional integral techniques. Based on a consideration of the relevant length scales, we derive the universal effective low energy Hamiltonian describing ultracold alkali atoms. We then introduce the concept of the effective action, which generalizes the classical action principle to full quantum status and provides an intuitive and versatile tool for practical calculations. This framework is applied to weakly interacting degenerate bosons and fermions in the spatial continuum. In particular, we discuss the related BEC and BCS quantum condensation mechanisms. We then turn to the BCS-BEC crossover, which interpolates between both phenomena, and which is realized experimentally in the vicinity of a Feshbach resonance. For its description, we introduce the Functional Renormalization Group approach. After a general discussion of the method in the cold atoms context, we present a detailed and pedagogical application to the crossover problem. This not only provides the physical mechanism underlying this phenomenon. More generally, it also reveals how the renormalization group can be used as a tool to capture physics at all scales, from few-body scattering on microscopic scales, through the finite temperature phase diagram governed by many-body length scales, up to critical phenomena dictating long distance physics at the phase transition. The presentation aims to equip students at the beginning PhD level with knowledge on key physical phenomena and flexible tools for their description, and should enable to embark upon practical calculations in this field.

Quantum information entropies of ultracold atomic gases in a ...

Indian Academy of Sciences (India)

bosonic systems and a ≃ 1.982 and b = 1 for ideal fermionic systems. These results obey the entropic uncertainty relation given by Beckner, Bialynicki-Birula and Myceilski. Keywords. Ultracold atomic gases; information entropy; foundations of quantum mechanics. PACS Nos 67.85.−d; 89.70.Cf; 03.65.Ta. 1. Introduction.

Superexchange-mediated magnetization dynamics with ultracold alkaline-earth atoms in an optical lattice

International Nuclear Information System (INIS)

Zhu Shaobing; Qian Jun; Wang Yuzhu

2017-01-01

Superexchange and inter-orbital spin-exchange interactions are key ingredients for understanding (orbital) quantum magnetism in strongly correlated systems and have been realized in ultracold atomic gases. Here we study the spin dynamics of ultracold alkaline-earth atoms in an optical lattice when the two exchange interactions coexist. In the superexchange interaction dominating regime, we find that the time-resolved spin imbalance shows a remarkable modulated oscillation, which can be attributed to the interplay between local and nonlocal quantum mechanical exchange mechanisms. Moreover, the filling of the long-lived excited atoms affects the collapse and revival of the magnetization dynamics. These observations can be realized in state-dependent optical lattices combined with the state-of-the-art advances in optical lattice clock spectroscopy. (paper)

Microscopic description and simulation of ultracold atoms in optical resonators

International Nuclear Information System (INIS)

Niedenzu, W.

2012-01-01

Ultracold atoms in optical resonators are an ideal system to investigate the full quantum regime of light-matter interaction. Microscopic insight into the underlying processes can nowadays easily be obtained from numerical calculations, e.g. with Monte Carlo wave function simulations. In the first part we discuss cold atoms in ring resonators, where the modified boundary conditions significantly alter the dynamics as compared to the standing-wave case. Quantum jumps induce momentum correlations and entanglement between the particles. We observe strong non-classical motional correlations, cooling and entanglement heralded by single photon measurements. For deeply trapped particles the complex system Hamiltonian can be mapped onto a generic optomechanical model, allowing for analytical microscopic insight into the dynamics. The rates of cavity-mediated correlated heating and cooling processes are obtained by adiabatically eliminating the cavity field from the dynamics and can be directly related to the steady-state momentum correlation coefficient. The second part is devoted to cooling and self-organisation of a cold gas in a transversally pumped standing-wave resonator, in which the atoms are directly illuminated by a laser beam. Above a certain critical laser intensity the atoms order in a specific pattern, maximising light scattering into the cavity. The particles thus create and sustain their own trap. We derive a nonlinear Fokker-Planck equation for the one-particle distribution function describing the gas dynamics below and above threshold. This kinetic theory predicts dissipation-induced self-organisation and q-Gaussian velocity distributions in steady state. (author)

Permanent magnetic lattices for ultracold atoms and quantum degenerate gases

International Nuclear Information System (INIS)

Ghanbari, Saeed; Kieu, Tien D; Sidorov, Andrei; Hannaford, Peter

2006-01-01

We propose the use of periodic arrays of permanent magnetic films for producing magnetic lattices of microtraps for confining, manipulating and controlling small clouds of ultracold atoms and quantum degenerate gases. Using analytical expressions and numerical calculations we show that periodic arrays of magnetic films can produce one-dimensional (1D) and two-dimensional (2D) magnetic lattices with non-zero potential minima, allowing ultracold atoms to be trapped without losses due to spin flips. In particular, we show that two crossed layers of periodic arrays of parallel rectangular magnets plus bias fields, or a single layer of periodic arrays of square-shaped magnets with three different thicknesses plus bias fields, can produce 2D magnetic lattices of microtraps having non-zero potential minima and controllable trap depth. For arrays with micron-scale periodicity, the magnetic microtraps can have very large trap depths (∼0.5 mK for the realistic parameters chosen for the 2D lattice) and very tight confinement

Scattering amplitude of ultracold atoms near the p-wave magnetic Feshbach resonance

International Nuclear Information System (INIS)

Zhang Peng; Naidon, Pascal; Ueda, Masahito

2010-01-01

Most of the current theories on the p-wave superfluid in cold atomic gases are based on the effective-range theory for the two-body scattering, where the low-energy p-wave scattering amplitude f 1 (k) is given by f 1 (k)=-1/[ik+1/(Vk 2 )+1/R]. Here k is the incident momentum, V and R are the k-independent scattering volume and effective range, respectively. However, due to the long-range nature of the van der Waals interaction between two colliding ultracold atoms, the p-wave scattering amplitude of the two atoms is not described by the effective-range theory [J. Math. Phys. 4, 54 (1963); Phys. Rev. A 58, 4222 (1998)]. In this paper we provide an explicit calculation for the p-wave scattering of two ultracold atoms near the p-wave magnetic Feshbach resonance. We show that in this case the low-energy p-wave scattering amplitude f 1 (k)=-1/[ik+1/(V eff k 2 )+1/(S eff k)+1/R eff ] where V eff , S eff , and R eff are k-dependent parameters. Based on this result, we identify sufficient conditions for the effective-range theory to be a good approximation of the exact scattering amplitude. Using these conditions we show that the effective-range theory is a good approximation for the p-wave scattering in the ultracold gases of 6 Li and 40 K when the scattering volume is enhanced by the resonance.

Detecting Friedel oscillations in ultracold Fermi gases

Science.gov (United States)

Riechers, Keno; Hueck, Klaus; Luick, Niclas; Lompe, Thomas; Moritz, Henning

2017-09-01

Investigating Friedel oscillations in ultracold gases would complement the studies performed on solid state samples with scanning-tunneling microscopes. In atomic quantum gases interactions and external potentials can be tuned freely and the inherently slower dynamics allow to access non-equilibrium dynamics following a potential or interaction quench. Here, we examine how Friedel oscillations can be observed in current ultracold gas experiments under realistic conditions. To this aim we numerically calculate the amplitude of the Friedel oscillations which are induced by a potential barrier in a 1D Fermi gas and compare it to the expected atomic and photonic shot noise in a density measurement. We find that to detect Friedel oscillations the signal from several thousand one-dimensional systems has to be averaged. However, as up to 100 parallel one-dimensional systems can be prepared in a single run with present experiments, averaging over about 100 images is sufficient.

Formation of Ultracold Molecules

Energy Technology Data Exchange (ETDEWEB)

Cote, Robin [Univ. of Connecticut, Storrs, CT (United States)

2016-01-28

Advances in our ability to slow down and cool atoms and molecules to ultracold temperatures have paved the way to a revolution in basic research on molecules. Ultracold molecules are sensitive of very weak interactions, even when separated by large distances, which allow studies of the effect of those interactions on the behavior of molecules. In this program, we have explored ways to form ultracold molecules starting from pairs of atoms that have already reached the ultracold regime. We devised methods that enhance the efficiency of ultracold molecule production, for example by tuning external magnetic fields and using appropriate laser excitations. We also investigates the properties of those ultracold molecules, especially their de-excitation into stable molecules. We studied the possibility of creating new classes of ultra-long range molecules, named macrodimers, thousand times more extended than regular molecules. Again, such objects are possible because ultra low temperatures prevent their breakup by collision. Finally, we carried out calculations on how chemical reactions are affected and modified at ultracold temperatures. Normally, reactions become less effective as the temperature decreases, but at ultracold temperatures, they can become very effective. We studied this counter-intuitive behavior for benchmark chemical reactions involving molecular hydrogen.

Effects of mode profile on tunneling and traversal of ultracold atoms through vacuum-induced potentials

Science.gov (United States)

Badshah, Fazal; Irfan, Muhammad; Qamar, Sajid; Qamar, Shahid

2016-04-01

We consider the resonant interaction of an ultracold two-level atom with an electromagnetic field inside a high-Q micromaser cavity. In particular, we study the tunneling and traversal of ultracold atoms through vacuum-induced potentials for secant hyperbolic square and sinusoidal cavity mode functions. The phase time which may be considered as an appropriate measure of the time required for the atoms to cross the cavity, significantly modifies with the change of cavity mode profile. For example, switching between the sub and superclassical behaviors in phase time can occur due to the mode function. Similarly, negative phase time appears for the transmission of the two-level atoms in both excited and ground states for secant hyperbolic square mode function which is in contrast to the mesa mode case.

EDITORIAL: Focus on Cold and Ultracold Molecules FOCUS ON COLD AND ULTRACOLD MOLECULES

Science.gov (United States)

Carr, Lincoln D.; Ye, Jun

2009-05-01

Cold and ultracold molecules are the next wave of ultracold physics, giving rise to an exciting array of scientific opportunities, including many body physics for novel quantum phase transitions, new states of matter, and quantum information processing. Precision tests of fundamental physical laws benefit from the existence of molecular internal structure with exquisite control. The study of novel collision and reaction dynamics will open a new chapter of quantum chemistry. Cold molecules bring together researchers from a variety of fields, including atomic, molecular, and optical physics, chemistry and chemical physics, quantum information science and quantum simulations, condensed matter physics, nuclear physics, and astrophysics, a truly remarkable synergy of scientific explorations. For the past decade there have been steady advances in direct cooling techniques, from buffer-gas cooling to cold molecular beams to electro- and magneto-molecular decelerators. These techniques have allowed a large variety of molecules to be cooled for pioneering studies. Recent amazing advances in experimental techniques combining the ultracold and the ultraprecise have furthermore brought molecules to the point of quantum degeneracy. These latter indirect cooling techniques magnetically associate atoms from a Bose-Einstein condensate and/or a quantum degenerate Fermi gas, transferring at 90% efficiency highly excited Fano-Feshbach molecules, which are on the order of 10 000 Bohr radii in size, to absolute ground state molecules just a few Bohr across. It was this latter advance, together with significant breakthroughs in internal state manipulations, which inspired us to coordinate this focus issue now, and is the reason why we say the next wave of ultracold physics has now arrived. Whether directly or indirectly cooled, heteronuclear polar molecules offer distinct new features in comparison to cold atoms, while sharing all of their advantages (purity, high coherence

Ultracold atoms in optical lattices simulating quantum many-body systems

CERN Document Server

Lewenstein, Maciej; Ahufinger, Verònica

2012-01-01

Quantum computers, though not yet available on the market, will revolutionize the future of information processing. Quantum computers for special purposes like quantum simulators are already within reach. The physics of ultracold atoms, ions and molecules offer unprecedented possibilities of control of quantum many body systems and novel possibilities of applications to quantum information processing and quantum metrology. Particularly fascinating is the possibility of usingultracold atoms in lattices to simulate condensed matter or even high energy physics.This book provides a complete and co

Few-particle quantum magnetism with ultracold atoms

Energy Technology Data Exchange (ETDEWEB)

Murmann, Simon

2015-11-25

This thesis reports on the deterministic preparation of magnetically ordered states in systems of few fermionic atoms. We follow the concept of quantum simulation and use {sup 6}Li atoms in two different hyperfine states to mimic the behavior of electrons in a solidstate system. In a first experiment, we simulate the two-site Hubbard model by using two atoms in an isolated double-well potential. We prepare the two-particle ground state of this model with a fidelity exceeding 90%. By introducing strong repulsive interactions, we are able to realize a pure spin model and describe the energy spectrum with a two-site Heisenberg Hamiltonian. In a second experiment, we realize Heisenberg spin chains of up to four atoms in a single strongly-elongated trapping potential. Here, the atoms self-align along the potential axis due to strong repulsive interactions. We introduce two novel measurement techniques to identify the state of the spin chains and thereby confirm that we can deterministically prepare antiferromagnetic ground-state systems. This constitutes the first observation of quantum magnetism with fermionic atoms that exceeds nearest-neighbor correlations. Both the double-well system and the spin chains can be seen as building blocks of larger ground-state spin systems. Their deterministic preparation therefore opens up a new bottom-up approach to the experimental realization of quantum many-body systems with ultracold atoms.

Ultrafast electron diffraction using an ultracold source

Directory of Open Access Journals (Sweden)

M. W. van Mourik

2014-05-01

Full Text Available The study of structural dynamics of complex macromolecular crystals using electrons requires bunches of sufficient coherence and charge. We present diffraction patterns from graphite, obtained with bunches from an ultracold electron source, based on femtosecond near-threshold photoionization of a laser-cooled atomic gas. By varying the photoionization wavelength, we change the effective source temperature from 300 K to 10 K, resulting in a concomitant change in the width of the diffraction peaks, which is consistent with independently measured source parameters. This constitutes a direct measurement of the beam coherence of this ultracold source and confirms its suitability for protein crystal diffraction.

Measurement of Spectral Functions of Ultracold Atoms in Disordered Potentials

Science.gov (United States)

Volchkov, Valentin V.; Pasek, Michael; Denechaud, Vincent; Mukhtar, Musawwadah; Aspect, Alain; Delande, Dominique; Josse, Vincent

2018-02-01

We report on the measurement of the spectral functions of noninteracting ultracold atoms in a three-dimensional disordered potential resulting from an optical speckle field. Varying the disorder strength by 2 orders of magnitude, we observe the crossover from the "quantum" perturbative regime of low disorder to the "classical" regime at higher disorder strength, and find an excellent agreement with numerical simulations. The method relies on the use of state-dependent disorder and the controlled transfer of atoms to create well-defined energy states. This opens new avenues for experimental investigations of three-dimensional Anderson localization.

First-principles many-body theory for ultra-cold atoms

International Nuclear Information System (INIS)

Drummond, Peter D.; Hu Hui; Liu Xiaji

2010-01-01

Recent breakthroughs in the creation of ultra-cold atoms in the laboratory have ushered in unprecedented changes in physical science. These enormous changes in the coldest temperatures available in the laboratory mean that many novel experiments are possible. There is unprecedented control and simplicity in these novel systems, meaning that quantum many-body theory is now facing severe challenges in quantitatively understanding these new results. We discuss some of the new experiments and recently developed theoretical techniques required to predict the results obtained.

Predicting scattering properties of ultracold atoms : Adiabatic accumulated phase method and mass scaling

NARCIS (Netherlands)

Verhaar, B.J.; Kempen, van E.G.M.; Kokkelmans, S.J.J.M.F.

2009-01-01

Ultracold atoms are increasingly used for high-precision experiments that can be utilized to extract accurate scattering properties. This results in a stronger need to improve on the accuracy of interatomic potentials, and in particular the usually rather inaccurate inner-range potentials. A

Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond

Science.gov (United States)

Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

2017-12-01

Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.

Scattering resonances of ultracold atoms in confined geometries

International Nuclear Information System (INIS)

Saeidian, Shahpoor

2008-01-01

Subject of this thesis is the investigation of the quantum dynamics of ultracold atoms in confined geometries. We discuss the behavior of ground state atoms inside a 3D magnetic quadrupole field. Such atoms in enough weak magnetic fields can be approximately treated as neutral point-like particles. Complementary to the well-known positive energy resonances, we point out the existence of short-lived negative energy resonances. The latter originate from a fundamental symmetry of the underlying Hamiltonian. We drive a mapping of the two branches of the spectrum. Moreover, we analyze atomic hyperfine resonances in a magnetic quadrupole field. This corresponds to the case for which both the hyperfine and Zeeman interaction, are comparable, and should be taken into account. Finally, we develop a general grid method for multichannel scattering of two atoms in a two-dimensional harmonic confinement. With our approach we analyze transverse excitations/deexcitations in the course of the collisional process (distinguishable or identical atoms) including all important partial waves and their couplings due to the broken spherical symmetry. Special attention is paid to suggest a non-trivial extension of the CIRs theory developed so far only for the single-mode regime and zero-energy limit. (orig.)

Scattering resonances of ultracold atoms in confined geometries

Energy Technology Data Exchange (ETDEWEB)

Saeidian, Shahpoor

2008-06-18

Subject of this thesis is the investigation of the quantum dynamics of ultracold atoms in confined geometries. We discuss the behavior of ground state atoms inside a 3D magnetic quadrupole field. Such atoms in enough weak magnetic fields can be approximately treated as neutral point-like particles. Complementary to the well-known positive energy resonances, we point out the existence of short-lived negative energy resonances. The latter originate from a fundamental symmetry of the underlying Hamiltonian. We drive a mapping of the two branches of the spectrum. Moreover, we analyze atomic hyperfine resonances in a magnetic quadrupole field. This corresponds to the case for which both the hyperfine and Zeeman interaction, are comparable, and should be taken into account. Finally, we develop a general grid method for multichannel scattering of two atoms in a two-dimensional harmonic confinement. With our approach we analyze transverse excitations/deexcitations in the course of the collisional process (distinguishable or identical atoms) including all important partial waves and their couplings due to the broken spherical symmetry. Special attention is paid to suggest a non-trivial extension of the CIRs theory developed so far only for the single-mode regime and zero-energy limit. (orig.)

Numerical methods for atomic quantum gases with applications to Bose-Einstein condensates and to ultracold fermions

NARCIS (Netherlands)

Minguzzi, A.; Succi, S.; Toschi, F.; Tosi, M.P.; Vignolo, P.

2004-01-01

The achievement of Bose–Einstein condensation in ultra-cold vapours of alkali atoms has given enormous impulse to the study of dilute atomic gases in condensed quantum states inside magnetic traps and optical lattices. High-purity and easy optical access make them ideal candidates to investigate

Quantum versus classical statistical dynamics of an ultracold Bose gas

International Nuclear Information System (INIS)

Berges, Juergen; Gasenzer, Thomas

2007-01-01

We investigate the conditions under which quantum fluctuations are relevant for the quantitative interpretation of experiments with ultracold Bose gases. This requires to go beyond the description in terms of the Gross-Pitaevskii and Hartree-Fock-Bogoliubov mean-field theories, which can be obtained as classical (statistical) field-theory approximations of the quantum many-body problem. We employ functional-integral techniques based on the two-particle irreducible (2PI) effective action. The role of quantum fluctuations is studied within the nonperturbative 2PI 1/N expansion to next-to-leading order. At this accuracy level memory integrals enter the dynamic equations, which differ for quantum and classical statistical descriptions. This can be used to obtain a classicality condition for the many-body dynamics. We exemplify this condition by studying the nonequilibrium evolution of a one-dimensional Bose gas of sodium atoms, and discuss some distinctive properties of quantum versus classical statistical dynamics

Observation of electric quadrupole transitions to Rydberg nd states of ultracold rubidium atoms

NARCIS (Netherlands)

Tong, D.; Farooqi, S.M.; Kempen, van E.G.M.; Pavlovic, Z.; Stanojevic, J.; Coté, R.; Eyler, E.E.; Gould, P.L.

2009-01-01

We report the observation of dipole-forbidden, but quadrupole-allowed, one-photon transitions to high-Rydberg states in Rb. Using pulsed uv excitation of ultracold atoms in a magneto-optical trap, we excite 5s¿nd transitions over a range of principal quantum numbers n=27–59. Compared to

Trapping ultracold gases near cryogenic materials with rapid reconfigurability

Energy Technology Data Exchange (ETDEWEB)

Naides, Matthew A.; Turner, Richard W.; Lai, Ruby A.; DiSciacca, Jack M.; Lev, Benjamin L. [Departments of Applied Physics and Physics and Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)

2013-12-16

We demonstrate an atom chip trapping system that allows the placement and high-resolution imaging of ultracold atoms within microns from any ≲100 μm-thin, UHV-compatible material, while also allowing sample exchange with minimal experimental downtime. The sample is not connected to the atom chip, allowing rapid exchange without perturbing the atom chip or laser cooling apparatus. Exchange of the sample and retrapping of atoms has been performed within a week turnaround, limited only by chamber baking. Moreover, the decoupling of sample and atom chip provides the ability to independently tune the sample temperature and its position with respect to the trapped ultracold gas, which itself may remain in the focus of a high-resolution imaging system. As a first demonstration of this system, we have confined a 700-nK cloud of 8 × 10{sup 4} {sup 87}Rb atoms within 100 μm of a gold-mirrored 100-μm-thick silicon substrate. The substrate was cooled to 35 K without use of a heat shield, while the atom chip, 120 μm away, remained at room temperature. Atoms may be imaged and retrapped every 16 s, allowing rapid data collection.

Sympathetic cooling in a rubidium cesium mixture: Production of ultracold cesium atoms

International Nuclear Information System (INIS)

Haas, M.

2007-01-01

This thesis presents experiments for the production of ultracold rubidium cesium mixture in a magnetic trap. The long-termed aim of the experiment is the study of the interaction of few cesium atoms with a Bose-Einstein condensate of rubidium atoms. Especially by controlled variation of the cesium atom number the transition in the description of the interaction by concepts of the one-particle physics to the description by concepts of the many-particle physics shall be studied. The rubidium atoms are trapped in a magneto-optical trap (MOT) and from there reloaded into a magnetic trap. In this the rubidium atoms are stored in the state vertical stroke f=2,m f =2 right angle of the electronic ground state and evaporatively cooled by means of microwave-induced transitions into the state vertical stroke f=1,m f =1] (microwave cooling). The cesium atoms are also trppaed in a MOT and into the same magnetic trap reloaded, in which they are stored in the state vertical stroke f=4,m f =4 right angle of the electronic ground state together with rubidium. Because of the different hyperfine splitting only rubidium is evaporatively cooled, while cesium is cooled jointly sympathetically - i.e. by theramal contact via elastic collisions with rubidium atoms. The first two chapters contain a description of interatomic interactions in ultracold gases as well as a short summary of theoretical concepts in the description of Bose-Einstein condensates. The chapters 3 and 4 contain a short presentation of the methods applied in the experiment for the production of ultracold gases as well as the experimental arrangement; especially in the framework of this thesis a new coil system has been designed, which offers in view of future experiments additionally optical access for an optical trap. Additionally the fourth chapter contains an extensive description of the experimental cycle, which is applied in order to store rubidium and cesium atoms together into the magnetic trap. The last chapter

Superfluidity and BCS-BEC crossover of ultracold atomic Fermi gases in mixed dimensions

Science.gov (United States)

Zhang, Leifeng; Chen, Qijin

Atomic Fermi gases have been under active investigation in the past decade. Here we study the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas in the presence of mixed dimensionality, in which one component is confined on a 1D optical lattice whereas the other is free in the 3D continuum. We assume a short-range pairing interaction and determine the superfluid transition temperature Tc and the phase diagram for the entire BCS-BEC crossover, using a pairing fluctuation theory which includes self-consistently the contributions of finite momentum pairs. We find that, as the lattice depth increases and the lattice spacing decreases, the behavior of Tc becomes very similar to that of a population imbalance Fermi gas in a simple 3D continuum. There is no superfluidity even at T = 0 below certain threshold of pairing strength in the BCS regime. Nonmonotonic Tc behavior and intermediate temperature superfluidity emerge, and for deep enough lattice, the Tc curve will split into two parts. Implications for experiment will be discussed. References: 1. Q.J. Chen, Ioan Kosztin, B. Janko, and K. Levin, Phys. Rev. B 59, 7083 (1999). 2. Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin, Phys. Rev. Lett. 97, 090402(2006). Work supported by NSF of China and the National Basic Research Program of China.

Detecting high-density ultracold molecules using atom–molecule collision

International Nuclear Information System (INIS)

Chen, Jun-Ren; Kao, Cheng-Yang; Chen, Hung-Bin; Liu, Yi-Wei

2013-01-01

Utilizing single-photon photoassociation, we have achieved ultracold rubidium molecules with a high number density that provides a new efficient approach toward molecular quantum degeneracy. A new detection mechanism for ultracold molecules utilizing inelastic atom–molecule collision is demonstrated. The resonant coupling effect on the formation of the X 1 Σ + g ground state 85 Rb 2 allows for a sufficient number of more deeply bound ultracold molecules, which induced an additional trap loss and heating of the co-existing atoms owing to the inelastic atom–molecule collision. Therefore, after the photoassociation process, the ultracold molecules can be investigated using the absorption image of the ultracold rubidium atoms mixed with the molecules in a crossed optical dipole trap. The existence of the ultracold molecules was then verified, and the amount of accumulated molecules was measured. This method detects the final produced ultracold molecules, and hence is distinct from the conventional trap loss experiment, which is used to study the association resonance. It is composed of measurements of the time evolution of an atomic cloud and a decay model, by which the number density of the ultracold 85 Rb 2 molecules in the optical trap was estimated to be >5.2 × 10 11 cm −3 . (paper)

D-state Rydberg electrons interacting with ultracold atoms

Energy Technology Data Exchange (ETDEWEB)

Krupp, Alexander Thorsten

2014-10-02

This thesis was established in the field of ultracold atoms where the interaction of highly excited D-state electrons with rubidium atoms was examined. This work is divided into two main parts: In the first part we study D-state Rydberg molecules resulting from the binding of a D-state Rydberg electron to a ground state rubidium atom. We show that we can address specific rovibrational molecular states by changing our laser detuning and thus create perfectly aligned axial or antialigned toroidal molecules, in good agreement with our theoretical calculations. Furthermore the influence of the electric field on the Rydberg molecules was investigated, creating novel states which show a different angular dependence and alignment. In the second part of this thesis we excite single D-state Rydberg electrons in a Bose-Einstein condensate. We study the lifetime of these Rydberg electrons, the change of the shape of our condensate and the atom losses in the condensate due to this process. Moreover, we observe quadrupolar shape oscillations of the whole condensate created by the consecutive excitation of Rydberg atoms and compare all results to previous S-state measurements. In the outlook we propose a wide range of further experiments including the proposal of imaging a single electron wavefunction by the imprint of its orbit into the Bose-Einstein condensate.

Transport, atom blockade, and output coupling in a Tonks-Girardeau gas

International Nuclear Information System (INIS)

Rutherford, L.; McCann, J. F.; Goold, J.; Busch, Th.

2011-01-01

Recent experiments have demonstrated how quantum-mechanical impurities can be created within strongly correlated quantum gases and used to probe the coherence properties of these systems [S. Palzer, C. Zipkes, C. Sias, and M. Koehl, Phys. Rev. Lett. 103, 150601 (2009).]. Here we present a phenomenological model to simulate such an output coupler for a Tonks-Girardeau gas that shows qualitative agreement with the experimental results for atom transport and output coupling. Our model allows us to explore nonequilibrium transport phenomena in ultracold quantum gases and leads us to predict a regime of atom blockade, where the impurity component becomes localized in the parent cloud despite the presence of gravity. We show that this provides a stable mixed-species quantum gas in the strongly correlated limit.

Ultracold Dipolar Gases in Optical Lattices

OpenAIRE

Trefzger, C.; Menotti, C.; Capogrosso-Sansone, B.; Lewenstein, M.

2011-01-01

This tutorial is a theoretical work, in which we study the physics of ultra-cold dipolar bosonic gases in optical lattices. Such gases consist of bosonic atoms or molecules that interact via dipolar forces, and that are cooled below the quantum degeneracy temperature, typically in the nK range. When such a degenerate quantum gas is loaded into an optical lattice produced by standing waves of laser light, new kinds of physical phenomena occur. These systems realize then extended Hubbard-type m...

Rydberg-atom formation in strongly correlated ultracold plasmas

International Nuclear Information System (INIS)

Bannasch, G.; Pohl, T.

2011-01-01

In plasmas at very low temperatures, the formation of neutral atoms is dominated by collisional three-body recombination, owing to the strong ∼T -9/2 scaling of the corresponding recombination rate with the electron temperature T. While this law is well established at high temperatures, the unphysical divergence as T→0 clearly suggests a breakdown in the low-temperature regime. Here, we present a combined molecular dynamics Monte Carlo study of electron-ion recombination over a wide range of temperatures and densities. Our results reproduce the known behavior of the recombination rate at high temperatures, but reveal significant deviations with decreasing temperature. We discuss the fate of the kinetic bottleneck and resolve the divergence problem as the plasma enters the ultracold, strongly coupled domain.

Tunable superconducting resonators with integrated trap structures for coupling with ultracold atomic gases

Energy Technology Data Exchange (ETDEWEB)

Ferdinand, Benedikt; Wiedmaier, Dominik; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Bothner, Daniel [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands)

2016-07-01

We intend to investigate a hybrid quantum system where ultracold atomic gases play the role of a long-living quantum memory, coupled to a superconducting qubit via a coplanar waveguide transmission line resonator. As a first step we developed a resonator chip containing a Z-shaped trapping wire for the atom trap. In order to suppress parasitic resonances due to stray capacitances, and to achieve good ground connection we use hybrid superconductor - normal conductor chips. As an additional degree of freedom we add a ferroelectric capacitor making the resonators voltage-tunable. We furthermore show theoretical results on the expected coupling strength between resonator and atomic cloud.

Itinerant ferromagnetism in an atomic Fermi gas: Influence of population imbalance

International Nuclear Information System (INIS)

Conduit, G. J.; Simons, B. D.

2009-01-01

We investigate ferromagnetic ordering in an itinerant ultracold atomic Fermi gas with repulsive interactions and population imbalance. In a spatially uniform system, we show that at zero temperature the transition to the itinerant magnetic phase transforms from first to second order with increasing population imbalance. Drawing on these results, we elucidate the phases present in a trapped geometry, finding three characteristic types of behavior with changing population imbalance. Finally, we outline the potential experimental implications of the findings.

Fast, High-Precision Optical Polarization Synthesizer for Ultracold-Atom Experiments

Science.gov (United States)

Robens, Carsten; Brakhane, Stefan; Alt, Wolfgang; Meschede, Dieter; Zopes, Jonathan; Alberti, Andrea

2018-03-01

We present a technique for the precision synthesis of arbitrary polarization states of light with a high modulation bandwidth. Our approach consists of superimposing two laser light fields with the same wavelength, but with opposite circular polarizations, where the phase and the amplitude of each light field are individually controlled. We find that the polarization-synthesized beam reaches a degree of polarization of 99.99%, which is mainly limited by static spatial variations of the polarization state over the beam profile. We also find that the depolarization caused by temporal fluctuations of the polarization state is about 2 orders of magnitude smaller. In a recent work, Robens et al. [Low-Entropy States of Neutral Atoms in Polarization-Synthesized Optical Lattices, Phys. Rev. Lett. 118, 065302 (2017), 10.1103/PhysRevLett.118.065302] demonstrated an application of the polarization synthesizer to create two independently controllable optical lattices which trap atoms depending on their internal spin state. We use ultracold atoms in polarization-synthesized optical lattices to give an independent, in situ demonstration of the performance of the polarization synthesizer.

Dark states and interferences in cascade transitions of ultracold atoms in a cavity

International Nuclear Information System (INIS)

Arun, R.; Agarwal, G.S.

2002-01-01

We examine the competition among one- and two-photon processes in an ultracold, three-level atom undergoing cascade transitions as a result of its interaction with a bimodal cavity. We show parameter domains where two-photon transitions are dominant, and we also study the effect of two-photon emission on the mazer action in the cavity. The two-photon emission leads to the loss of detailed balance and therefore we obtain the photon statistics of the cavity field by the numerical integration of the master equation. The photon distribution in each cavity mode exhibits sub- and super-Poissonian behaviors depending on the strength of atom-field coupling. The photon distribution becomes identical to a Poisson distribution when the atom-field coupling strengths of the modes are equal

Classical and quantum analysis of one-dimensional velocity selection for ultracold atoms

International Nuclear Information System (INIS)

Fox, J K; Kim, H A; Mishra, S R; Myrskog, S H; Jofre, A M; Segal, L R; Kim, J B; Steinberg, A M

2005-01-01

We discuss a velocity selection technique for obtaining cold atoms, in which all atoms below a certain energy are spatially selected from the surrounding atom cloud. Velocity selection can in some cases be more efficient than other cooling techniques for the preparation of ultracold atom clouds in one dimension. With quantum mechanical and classical simulations and theory we present a scheme using a dipole force barrier to select the coldest atoms from a magnetically trapped atom cloud. The dipole and magnetic potentials create a local minimum which traps the coldest atoms. A unique advantage of this technique is the sharp cut-off in the velocity distribution of the sample of selected atoms. Such a non-thermal distribution should prove useful for a variety of experiments, including proposed studies of atomic tunnelling and scattering from quantum potentials. We show that when the rms size of the atom cloud is smaller than the local minimum in which the selected atoms are trapped, the velocity selection technique can be more efficient in one dimension than some common techniques such as evaporative cooling. For example, one simulation shows nearly 6% of the atoms retained at a temperature 100 times lower than the starting condition

Thermalization and Prethermalization in an ultracold Bose Gas

International Nuclear Information System (INIS)

Kuhnert, M.

2013-01-01

Atom chips consist of microscopic current carrying structures that generate magnetic trapping potentials for ultracold neutral atoms. These atom chips provide a high design flexibility of possible trap geometries, making the creation of highly anisotropic trapping potentials feasible. The resulting magnetic traps are characterized by a high isolation from the environment and are used to create degenerate, one-dimensional (1d) Bose gases. On typical experimental time scales, these 1d Bose gases can be described as practically closed quantum many-body systems. By applying a rapid quantum quench, the many-body system is brought out of thermal equilibrium and the resulting dynamics are studied via the statistical properties of matter-wave interference measurements. These measured quantum statistical distributions reveal that thermalization of this effectively integrable 1d Bose gas happens in a two-step process. First, the system rapidly dephases to a prethermalized state, characterized by thermal-like correlation properties, which are still distinctly different from the true thermal equilibrium state. Second, on a much longer time scale, the measured distribution functions indicate a further decay to the true thermal equilibrium state. Furthermore, by studying a highly non-equilibrium system via matter-wave interferometry, the underlying multimode dynamics, characterizing one-dimensional quantum systems, are revealed. This thesis shows that these dynamics are essential in establishing the prethermalized state and that its properties are defined by the quantum shot noise of the splitting process. In conclusion, this work aims at improving the understanding of quantum thermalization processes in integrable and nearly-integrable systems in the 1d and 1d/3d crossover regimes. Apparently, the general paths to thermal equilibrium in nearly-integrable systems are indirect and complex. This work provides an in depth experimental study of the relaxation dynamics of a highly

Symmetry breaking in small rotating clouds of trapped ultracold Bose atoms

International Nuclear Information System (INIS)

Dagnino, D.; Barberan, N.; Riera, A.; Osterloh, K.; Lewenstein, M.

2007-01-01

We study the signatures of rotational and phase symmetry breaking in small rotating clouds of trapped ultracold Bose atoms by looking at rigorously defined condensate wave function. Rotational symmetry breaking occurs in narrow frequency windows, where energy degeneracy between the lowest energy states of different total angular momentum takes place. This leads to a complex condensate wave function that exhibits vortices clearly seen as holes in the density, as well as characteristic local phase patterns, reflecting the appearance of vorticities. Phase symmetry (or gauge symmetry) breaking, on the other hand, is clearly manifested in the interference of two independent rotating clouds

Conjugate gradient minimisation approach to generating holographic traps for ultracold atoms.

Science.gov (United States)

Harte, Tiffany; Bruce, Graham D; Keeling, Jonathan; Cassettari, Donatella

2014-11-03

Direct minimisation of a cost function can in principle provide a versatile and highly controllable route to computational hologram generation. Here we show that the careful design of cost functions, combined with numerically efficient conjugate gradient minimisation, establishes a practical method for the generation of holograms for a wide range of target light distributions. This results in a guided optimisation process, with a crucial advantage illustrated by the ability to circumvent optical vortex formation during hologram calculation. We demonstrate the implementation of the conjugate gradient method for both discrete and continuous intensity distributions and discuss its applicability to optical trapping of ultracold atoms.

Experimental apparatus for overlapping a ground-state cooled ion with ultracold atoms

Science.gov (United States)

Meir, Ziv; Sikorsky, Tomas; Ben-shlomi, Ruti; Akerman, Nitzan; Pinkas, Meirav; Dallal, Yehonatan; Ozeri, Roee

2018-03-01

Experimental realizations of charged ions and neutral atoms in overlapping traps are gaining increasing interest due to their wide research application ranging from chemistry at the quantum level to quantum simulations of solid state systems. In this paper, we describe our experimental system in which we overlap a single ground-state cooled ion trapped in a linear Paul trap with a cloud of ultracold atoms such that both constituents are in the ?K regime. Excess micromotion (EMM) currently limits atom-ion interaction energy to the mK energy scale and above. We demonstrate spectroscopy methods and compensation techniques which characterize and reduce the ion's parasitic EMM energy to the ?K regime even for ion crystals of several ions. We further give a substantial review on the non-equilibrium dynamics which governs atom-ion systems. The non-equilibrium dynamics is manifested by a power law distribution of the ion's energy. We also give an overview on the coherent and non-coherent thermometry tools which can be used to characterize the ion's energy distribution after single to many atom-ion collisions.

Quantum many-body dynamics of ultracold atoms in optical lattices

Energy Technology Data Exchange (ETDEWEB)

Kessler, Stefan

2014-04-15

Ultracold atoms can be trapped in periodic intensity patterns of light created by counterpropagating laser beams, so-called optical lattices. In contrast to its natural counterpart, electrons in a solid state crystal, this man-made setup is very clean and highly isolated from environmental degrees of freedom. Moreover, to a large extent, the experimenter has dynamical control over the relevant system parameters: the interaction between atoms, the tunneling amplitude between lattice sites, and even the dimensionality of the lattice. These advantages render this system a unique platform for the simulation of quantum many-body dynamics for various lattice Hamiltonians as has been demonstrated in several experiments by now. The most significant step in recent times has arguably been the introduction of single-site detection of individual atoms in optical lattices. This technique, based on fluorescence microscopy, opens a new doorway for the study of quantum many-body states: the detection of the microscopic atom configuration. In this thesis, we theoretically explore the dynamics of ultracold atoms in optical lattices for various setups realized in present-day experiments. Our main focus lies on aspects that become experimentally accessible by (realistic extensions of) the novel single-site measurement technique. The first part deals with the expansion of initially confined atoms in a homogeneous lattice, which is one way to create atomic motion in experiments. We analyze the buildup of spatial correlations during the expansion of a finitely extended band insulating state in one dimension. The numerical simulation reveals the creation of remote spin-entangled fermions in the strongly interacting regime. We discuss the experimental observation of such spin-entangled pairs by means of a single-site measurement. Furthermore, we suggest studying the impact of observations on the expansion dynamics for the extreme case of a projective measurement in the spatial occupation

Quantum many-body dynamics of ultracold atoms in optical lattices

International Nuclear Information System (INIS)

Kessler, Stefan

2014-01-01

Ultracold atoms can be trapped in periodic intensity patterns of light created by counterpropagating laser beams, so-called optical lattices. In contrast to its natural counterpart, electrons in a solid state crystal, this man-made setup is very clean and highly isolated from environmental degrees of freedom. Moreover, to a large extent, the experimenter has dynamical control over the relevant system parameters: the interaction between atoms, the tunneling amplitude between lattice sites, and even the dimensionality of the lattice. These advantages render this system a unique platform for the simulation of quantum many-body dynamics for various lattice Hamiltonians as has been demonstrated in several experiments by now. The most significant step in recent times has arguably been the introduction of single-site detection of individual atoms in optical lattices. This technique, based on fluorescence microscopy, opens a new doorway for the study of quantum many-body states: the detection of the microscopic atom configuration. In this thesis, we theoretically explore the dynamics of ultracold atoms in optical lattices for various setups realized in present-day experiments. Our main focus lies on aspects that become experimentally accessible by (realistic extensions of) the novel single-site measurement technique. The first part deals with the expansion of initially confined atoms in a homogeneous lattice, which is one way to create atomic motion in experiments. We analyze the buildup of spatial correlations during the expansion of a finitely extended band insulating state in one dimension. The numerical simulation reveals the creation of remote spin-entangled fermions in the strongly interacting regime. We discuss the experimental observation of such spin-entangled pairs by means of a single-site measurement. Furthermore, we suggest studying the impact of observations on the expansion dynamics for the extreme case of a projective measurement in the spatial occupation

From few to many. Ultracold atoms in reduced dimensions

International Nuclear Information System (INIS)

Wenz, Andre Niklas

2013-01-01

This thesis reports on experimental studies exploring few and many-body physics of ultracold Bose and Fermi gases with reduced dimensionality. These experiments illustrate the versatility and great amount of control over the particle number, the interaction and other degrees of freedom, like the spin, that these generic quantum systems offer. In the first part of this thesis, we use quasi one-dimensional few-particle systems of one to ten fermionic atoms to investigate the crossover from few to many-body physics. This is achieved by measuring the interaction energy between a single impurity atom in a state vertical stroke ↓ right angle which repulsively interacts with an increasing number of majority atoms in a state vertical stroke ↑ right angle. We find that the system quickly approaches the results from the many-body theory, which describes the behavior of a single impurity immersed in a Fermi sea of an infinite number of majority particles. The second part of this thesis presents studies of the time evolution of a bosonic F=1 spinor BEC of 87 Rb atoms. In this system, we investigate the emergence and coarsening of ferromagnetic spin textures from initially unmagnetized samples. While the ferromagnetic domains grow, we observe the development of a spin space anisotropy which is in agreement with the predicted phase-diagram. The last part of this thesis presents our first steps towards the investigation of phase coherence of quasi two-dimensional quantum gases in the crossover from bosonic molecules to fermionic atoms.

From few to many. Ultracold atoms in reduced dimensions

Energy Technology Data Exchange (ETDEWEB)

Wenz, Andre Niklas

2013-12-19

This thesis reports on experimental studies exploring few and many-body physics of ultracold Bose and Fermi gases with reduced dimensionality. These experiments illustrate the versatility and great amount of control over the particle number, the interaction and other degrees of freedom, like the spin, that these generic quantum systems offer. In the first part of this thesis, we use quasi one-dimensional few-particle systems of one to ten fermionic atoms to investigate the crossover from few to many-body physics. This is achieved by measuring the interaction energy between a single impurity atom in a state vertical stroke ↓ right angle which repulsively interacts with an increasing number of majority atoms in a state vertical stroke ↑ right angle. We find that the system quickly approaches the results from the many-body theory, which describes the behavior of a single impurity immersed in a Fermi sea of an infinite number of majority particles. The second part of this thesis presents studies of the time evolution of a bosonic F=1 spinor BEC of {sup 87}Rb atoms. In this system, we investigate the emergence and coarsening of ferromagnetic spin textures from initially unmagnetized samples. While the ferromagnetic domains grow, we observe the development of a spin space anisotropy which is in agreement with the predicted phase-diagram. The last part of this thesis presents our first steps towards the investigation of phase coherence of quasi two-dimensional quantum gases in the crossover from bosonic molecules to fermionic atoms.

Universal Three-Body Physics in Ultracold KRb Mixtures

DEFF Research Database (Denmark)

Wacker, L. J.; Jørgensen, N. B.; Birkmose, Danny Matthiesen

2016-01-01

Ultracold atomic gases have recently become a driving force in few-body physics due to the observation of the Efimov effect. While initially observed in equal mass systems, one expects even richer few-body physics in the mass-imbalanced case. In previous experiments with ultracold mixtures of pot...

Realization of the manipulation of ultracold atoms with a reconfigurable nanomagnetic system of domain walls.

Science.gov (United States)

West, Adam D; Weatherill, Kevin J; Hayward, Thomas J; Fry, Paul W; Schrefl, Thomas; Gibbs, Mike R J; Adams, Charles S; Allwood, Dan A; Hughes, Ifan G

2012-08-08

Planar magnetic nanowires have been vital to the development of spintronic technology. They provide an unparalleled combination of magnetic reconfigurability, controllability, and scalability, which has helped to realize such applications as racetrack memory and novel logic gates. Microfabricated atom optics benefit from all of these properties, and we present the first demonstration of the amalgamation of spintronic technology with ultracold atoms. A magnetic interaction is exhibited through the reflection of a cloud of (87)Rb atoms at a temperature of 10 μK, from a 2 mm × 2 mm array of nanomagnetic domain walls. In turn, the incident atoms approach the array at heights of the order of 100 nm and are thus used to probe magnetic fields at this distance.

Lattice-Assisted Spectroscopy: A Generalized Scanning Tunneling Microscope for Ultracold Atoms.

Science.gov (United States)

Kantian, A; Schollwöck, U; Giamarchi, T

2015-10-16

We propose a scheme to measure the frequency-resolved local particle and hole spectra of any optical lattice-confined system of correlated ultracold atoms that offers single-site addressing and imaging, which is now an experimental reality. Combining perturbation theory and time-dependent density matrix renormalization group simulations, we quantitatively test and validate this approach of lattice-assisted spectroscopy on several one-dimensional example systems, such as the superfluid and Mott insulator, with and without a parabolic trap, and finally on edge states of the bosonic Su-Schrieffer-Heeger model. We highlight extensions of our basic scheme to obtain an even wider variety of interesting and important frequency resolved spectra.

Quantifying, characterizing, and controlling information flow in ultracold atomic gases

International Nuclear Information System (INIS)

Haikka, P.; McEndoo, S.; Maniscalco, S.; De Chiara, G.; Palma, G. M.

2011-01-01

We study quantum information flow in a model comprised of a trapped impurity qubit immersed in a Bose-Einstein-condensed reservoir. We demonstrate how information flux between the qubit and the condensate can be manipulated by engineering the ultracold reservoir within experimentally realistic limits. We show that this system undergoes a transition from Markovian to non-Markovian dynamics, which can be controlled by changing key parameters such as the condensate scattering length. In this way, one can realize a quantum simulator of both Markovian and non-Markovian open quantum systems, the latter ones being characterized by a reverse flow of information from the background gas (reservoir) to the impurity (system).

Observation of Spin Polarons in a Tunable Fermi Liquid of Ultracold Atoms

Science.gov (United States)

Zwierlein, Martin

2009-05-01

We have observed spin polarons, dressed spin down impurities in a spin up Fermi sea of ultracold atoms via tomographic RF spectroscopy. Feshbach resonances allow to freely tune the interactions between the two spin states involved. A single spin down atom immersed in a Fermi sea of spin up atoms can do one of two things: For strong attraction, it can form a molecule with exactly one spin up partner, but for weaker interaction it will spread its attraction and surround itself with a collection of majority atoms. This spin down atom dressed with a spin up cloud constitutes the spin- or Fermi polaron. We have observed a striking spectroscopic signature of this quasi-particle for various interaction strengths, a narrow peak in the spin down spectrum that emerges above a broad background. The spectra allow us to directly measure the polaron energy and the quasi-particle residue Z. The polarons are found to be only weakly interacting with each other, and can thus be identified with the quasi-particles of Landau's Fermi liquid theory. At a critical interaction strength, we observe a transition from spin one-half polarons to spin zero molecules. At this point the Fermi liquid undergoes a phase transition into a superfluid Bose liquid.

Low-energy-spread ion bunches from a trapped atomic gas

NARCIS (Netherlands)

Reijnders, M.P.; Kruisbergen, van P.A.; Taban, G.; Geer, van der S.B.; Mutsaers, P.H.A.; Vredenbregt, E.J.D.; Luiten, O.J.

2009-01-01

We present time-of-flight measurements of the longitudinal energy spread of pulsed ultracold ion beams, produced by near-threshold ionization of rubidium atoms captured in a magneto-optical atom trap. Well-defined pulsed beams have been produced with energies of only 1 eV and a root-mean-square

Strategic Applications of Ultra-Cold Atoms

Science.gov (United States)

2008-03-07

Peer-Reviewed Conference Proceeding publications (other than abstracts): “Laser cooling in anisotropic traps”, M. Vengalattore, R.S. Conroy, M. Prentiss...IEEE Cat. No. 04CH37598. Piscataway, NJ, IEEE, 2004, 1 pp. “Guiding of light in an ultracold, anisotropic medium”, M. Vengalattore and M. Prentiss, in...molecules the rotational dynamics imposes significantly larger Rabi frequencies than would otherwise be expected, but within this limitation, a full

Mixtures of ultracold atoms and the quest for ultracold molecules

International Nuclear Information System (INIS)

Weidemueller, M.

2000-08-01

A cold atomic gas formed by two different species represents an intriguing system for a deeper understanding of atom-atom interactions at ultralow temperatures. We present experiments on a mixture of atomic lithium and cesium which are of particular interest regarding the formation of heteronuclear molecules on the one hand, and the prospects for sympathetic cooling of atomic gases through mutual thermalization on the other hand. A first series of experiments on interaction in presence of a near-resonant light field is performed in a two-species magneto-optical trap. The collisional properties of the lithium-cesium mixture are investigated through detailed analysis of trap-loss processes induced by the trap light. Photoassociation in an additional near-resonant laser field yields high-resolution spectra of the excited Cs 2 dimers, but shows no unambiguous indication of LiCs molecule formation. A second series of experiments on pure ground-state collisional properties utilizes an optical dipole trap formed by light that is detuned extremely far below atomic resonance (quasi-electrostatic trap). Storage times of many minutes are achieved in a particularly simple and versatile setup for both atomic species. Cooling of cesium through evaporation and thermalization by elastic collisions is observed. The evolution of temperature and particle number is compared with model simulations of evaporative cooling. Direct laser cooling of trapped cesium in the absolute energetic ground state is demonstrated. Homonuclear spin-changing collisions of ground-state cesium and lithium atoms are analyzed, and first evidence for pure ground-state collisions between atoms of different species is found. Based on the current achievements, prospects for future experiments are discussed. (orig.)

Trapping and interactions of an ultracold gas of Cs2 molecules

International Nuclear Information System (INIS)

Mark, M.; Kraemer, T.; Herbig, J.; Waldburger, P.; Naegerl, H.C.; Chin, C.; Grimm, R.

2005-01-01

Full text: We investigate dynamics and interactions of Cs 2 dimers in a CO2-laser dipole trap. Starting with a Bose-Einstein condensate (BEC) of 2.2 x 10 5 Cs atoms, we create ultracold molecules in a single, weakly bound quantum state by sweeping the magnetic field across a narrow Feshbach resonance. When the molecules are created in free space, the conversion efficiency exceeds 30 %, yielding up to 50000 molecules. In our trapping experiments, about 6000 ultracold Cs 2 dimers are prepared in the optical trap at a temperature of 200 nK. We transfer the trapped molecules from the initial molecular state to other molecular states by following avoided crossings. We find two magnetically tunable resonances in collisions between the molecules for one of the molecular states. We interpret these Feshbach-liKEX resonances as being induced by Cs 4 bound states near the molecular scattering continuum. Further, we have discovered a new molecular state with very large orbital angular momentum of l = 8. This state is very weakly coupled to one of the initial molecular states. We use the associated avoided crossing as a molecular beam splitter to realize a molecular Ramsey-type interferometer. Refs. 2 (author)

Tunable spin-orbit coupling for ultracold atoms in two-dimensional optical lattices

Science.gov (United States)

Grusdt, Fabian; Li, Tracy; Bloch, Immanuel; Demler, Eugene

2017-06-01

Spin-orbit coupling (SOC) is at the heart of many exotic band structures and can give rise to many-body states with topological order. Here we present a general scheme based on a combination of microwave driving and lattice shaking for the realization of two-dimensional SOC with ultracold atoms in systems with inversion symmetry. We show that the strengths of Rashba and Dresselhaus SOC can be independently tuned in a spin-dependent square lattice. More generally, our method can be used to open gaps between different spin states without breaking time-reversal symmetry. We demonstrate that this allows for the realization of topological insulators with nontrivial spin textures closely related to the Kane-Mele model.

Repulsive atomic gas in a harmonic trap on the border of itinerant ferromagnetism.

Science.gov (United States)

Conduit, G J; Simons, B D

2009-11-13

Alongside superfluidity, itinerant (Stoner) ferromagnetism remains one of the most well-characterized phases of correlated Fermi systems. A recent experiment has reported the first evidence for novel phase behavior on the repulsive side of the Feshbach resonance in a two-component ultracold Fermi gas. By adapting recent theoretical studies to the atomic trap geometry, we show that an adiabatic ferromagnetic transition would take place at a weaker interaction strength than is observed in experiment. This discrepancy motivates a simple nonequilibrium theory that takes account of the dynamics of magnetic defects and three-body losses. The formalism developed displays good quantitative agreement with experiment.

Mean-field description of ultracold bosons on disordered two-dimensional optical lattices

International Nuclear Information System (INIS)

Buonsante, Pierfrancesco; Massel, Francesco; Penna, Vittorio; Vezzani, Alessandro

2007-01-01

In the present communication, we describe the properties induced by disorder on an ultracold gas of bosonic atoms loaded into a two-dimensional optical lattice with global confinement ensured by a parabolic potential. Our analysis is centred on the spatial distribution of the various phases, focusing particularly on the superfluid properties of the system as a function of external parameters and disorder amplitude. In particular, it is shown how disorder can suppress superfluidity, while partially preserving the system coherence. (fast track communication)

The formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics

Energy Technology Data Exchange (ETDEWEB)

Dulieu, O [Laboratoire Aime Cotton, CNRS, Bat. 505, Univ Paris-Sud 11, F-91405 Orsay Cedex (France); Gabbanini, C [Istituto per i processi chimico-fisici del C.N.R., Via Moruzzi 1, 56124 Pisa (Italy)], E-mail: olivier.dulieu@lac.u-psud.fr, E-mail: carlo@ipcf.cnr.it

2009-08-15

Progress on research in the field of molecules at cold and ultracold temperatures is reported in this review. It covers extensively the experimental methods to produce, detect and characterize cold and ultracold molecules including association of ultracold atoms, deceleration by external fields and kinematic cooling. Confinement of molecules in different kinds of traps is also discussed. The basic theoretical issues related to the knowledge of the molecular structure, the atom-molecule and molecule-molecule mutual interactions, and to their possible manipulation and control with external fields, are reviewed. A short discussion on the broad area of applications completes the review.

Comparing and contrasting nuclei and cold atomic gases

DEFF Research Database (Denmark)

Zinner, Nikolaj Thomas; Jensen, Aksel Stenholm

2013-01-01

The experimental revolution in ultracold atomic gas physics over the past decades has brought tremendous amounts of new insight to the world of degenerate quantum systems. Here we compare and contrast the developments of cold atomic gases with the physics of nuclei since many concepts, techniques......, and nomenclatures are common to both fields. However, nuclei are finite systems with interactions that are typically much more complicated than those of ultracold atomic gases. The similarities and differences must therefore be carefully addressed for a meaningful comparison and to facilitate fruitful......, interactions, and relevant length and energy scales of cold atoms and nuclei. Next we address some attempts in nuclear physics to transfer the concepts of condensates in nuclei that can in principle be built from bosonic alpha-particle constituents. We also consider Efimov physics, a prime example of nuclear...

Strongly-correlated ultracold atoms in optical lattices

International Nuclear Information System (INIS)

Dao, Tung-Lam

2008-01-01

This thesis is concerned with the theoretical study of strongly correlated quantum states of ultra-cold fermionic atoms trapped in optical lattices. This field has grown considerably in recent years, following the experimental progress made in cooling and controlling atomic gases, which has led to the observation of the first Bose-Einstein condensation (in 1995). The trapping of these gases in optical lattices has opened a new field of research at the interface between atomic physics and condensed matter physics. The observation of the transition from a superfluid to a Mott insulator for bosonic atoms paved the way for the study of strongly correlated phases and quantum phase transitions in these systems. Very recently, the investigation of the Mott insulator state of fermionic atoms provides additional motivation to conduct such theoretical studies. This thesis can be divided broadly into two types of work: - On the one hand, we have proposed a new type of spectroscopy to measure single-particle correlators and associated physical observables in these strongly correlated states. - On the other hand, we have studied the ground state of the fermionic Hubbard model under different conditions (mass imbalance, population imbalance) by using analytical techniques and numerical simulations. In a collaboration with J. Dalibard and C. Salomon (LKB at the ENS Paris) and I. Carusotto (Trento, Italy), we have proposed and studied a novel spectroscopic method for the measurement and characterization of single particle excitations (in particular, the low energy excitations, namely the quasiparticles) in systems of cold fermionic atoms, with energy and momentum resolution. This type of spectroscopy is an analogue of angular-resolved photoemission in solid state physics (ARPES). We have shown, via simple models, that this method of measurement can characterize quasiparticles not only in the 'conventional' phases such as the weakly interacting gas in the lattice or in Fermi

Conversion of a Degenerate Fermi Gas of 6Li Atoms to a Molecular BEC

International Nuclear Information System (INIS)

Strecker, K.E.; Partridge, G.B.; Kamar, R.I.; Jack, M.W.; Hulet, R.G.

2005-01-01

Atomic Feshbach resonances have recently been used to produce a strongly interacting Fermi gas, where the BCS/BEC crossover can be explored. We have used both narrow and broad Feshbach resonances to convert a quantum degenerate Fermi gas of 6Li atoms into an ultracold gas of Li2 molecules. For the narrow resonances, the molecules are formed by coherent adiabatic passage through the resonance. We find that 50% of the atoms are converted to molecules. Furthermore, the lifetime of these molecules was measured to be surprisingly long, 1 s. We will discuss these measurements in the context of the present theoretical understanding. Molecules can also be formed using static fields near the broad Feshbach resonance. The lifetime of these molecules is again long, and sufficient to enable their evaporation to a Bose-Einstein condensate. Phase contrast images of the molecular condensate are presented. The BCS/BEC crossover may be explored by starting with a pure molecular condensate on the low-field side of the Feshbach resonance, and adiabatically changing the field to any final value around resonance. We combine this ability with optical spectroscopy on a bound-bound molecular transition to probe the nature of the many-body wavefunction in the crossover regime

Ground States of Ultracold Spin-1 Atoms in a Deep Double-Well Optical Superlattice in a Weak Magnetic Field

International Nuclear Information System (INIS)

Zheng Gong-Ping; Qin Shuai-Feng; Wang Shou-Yang; Jian Wen-Tian

2013-01-01

The ground states of the ultracold spin-1 atoms trapped in a deep one-dimensional double-well optical superlattice in a weak magnetic field are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic condensates. The transition between the singlet state and nematic state is observed for the antiferromagnetic interaction atoms, which can be realized by modulating the tunneling parameter or the quadratic Zeeman energy. An experiment to distinguish the different spin states is suggested. (general)

Pulse length of ultracold electron bunches extracted from a laser cooled gas

Directory of Open Access Journals (Sweden)

J. G. H. Franssen

2017-07-01

Full Text Available We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps but hot (∼104 K electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K and ultrafast (∼25 ps electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales.

Magnetic-Field Dependence of Raman Coupling Strength in Ultracold "4"0K Atomic Fermi Gas

International Nuclear Information System (INIS)

Huang Liang-Hui; Wang Peng-Jun; Meng Zeng-Ming; Peng Peng; Chen Liang-Chao; Li Dong-Hao; Zhang Jing

2016-01-01

We experimentally demonstrate the relation of Raman coupling strength with the external bias magnetic field in degenerate Fermi gas of "4"0K atoms. Two Raman lasers couple two Zeeman energy levels, whose energy splitting depends on the external bias magnetic field. The Raman coupling strength is determined by measuring the Rabi oscillation frequency. The characteristics of the Rabi oscillation is to be damped after several periods due to Fermi atoms in different momentum states oscillating with different Rabi frequencies. The experimental results show that the Raman coupling strength will decrease as the external bias magnetic field increases, which is in good agreement with the theoretical prediction. (paper)

Expansion of an ultracold Rydberg plasma

Science.gov (United States)

Forest, Gabriel T.; Li, Yin; Ward, Edwin D.; Goodsell, Anne L.; Tate, Duncan A.

2018-04-01

We report a systematic experimental and numerical study of the expansion of ultracold Rydberg plasmas. Specifically, we have measured the asymptotic expansion velocities, v0, of ultracold neutral plasmas (UNPs) which evolve from cold, dense samples of Rydberg rubidium atoms using ion time-of-flight spectroscopy. From this, we have obtained values for the effective initial plasma electron temperature, Te ,0=mionv02/kB (where mion is the Rb+ ion mass), as a function of the original Rydberg atom density and binding energy, Eb ,i. We have also simulated numerically the interaction of UNPs with a large reservoir of Rydberg atoms to obtain data to compare with our experimental results. We find that for Rydberg atom densities in the range 107-109 cm-3, for states with principal quantum number n >40 , Te ,0 is insensitive to the initial ionization mechanism which seeds the plasma. In addition, the quantity kBTe ,0 is strongly correlated with the fraction of atoms which ionize, and is in the range 0.6 ×| Eb ,i|≲ kBTe ,0≲2.5 ×|Eb ,i| . On the other hand, plasmas from Rydberg samples with n ≲40 evolve with no significant additional ionization of the remaining atoms once a threshold number of ions has been established. The dominant interaction between the plasma electrons and the Rydberg atoms is one in which the atoms are deexcited, a heating process for electrons that competes with adiabatic cooling to establish an equilibrium where Te ,0 is determined by their Coulomb coupling parameter, Γe˜0.01 .

Moller Polarimetry with Atomic Hydrogen Targets

International Nuclear Information System (INIS)

Chudakov, Eugene; Luppov, V.

2012-01-01

A proposal to use polarized atomic hydrogen gas as the target for electron beam polarimetry based on the Moller scattering is described. Such a gas, stored in an ultra-cold magnetic trap, would provide a target of practically 100% polarized electrons. It is conceivable to reach a ∼0.3% systematic accuracy of the beam polarimetry with such a target. Feasibility studies for the CEBAF electron beam have been performed

Realizing analogues of color superconductivity with ultracold alkali atoms

International Nuclear Information System (INIS)

O'Hara, K M

2011-01-01

A degenerate three-component Fermi gas of atoms with identical attractive interactions is expected to exhibit superfluidity and magnetic order at low temperature and, for sufficiently strong pairwise interactions, become a Fermi liquid of weakly interacting trimers. The phase diagram of this system is analogous to that of quark matter at low temperature, motivating strong interest in its investigation. We describe how a three-component gas below the superfluid critical temperature can be prepared in an optical lattice. To realize an SU(3)-symmetric system, we show how pairwise interactions in the three-component atomic system can be made equal by applying radiofrequency and microwave radiation. Finally, motivated by the aim to make more accurate models of quark matter, which have color, flavor and spin degrees of freedom, we discuss how an atomic system with SU(2)xSU(3) symmetry can be achieved by confining a three-component Fermi gas in the p-orbital band of an optical lattice potential.

From ultracold Fermi Gases to Neutron Stars

Science.gov (United States)

Salomon, Christophe

2012-02-01

Ultracold dilute atomic gases can be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. We have developed a general method to probe with high precision the thermodynamics of locally homogeneous ultracold Bose and Fermi gases [1,2,3]. This method allows stringent tests of recent many-body theories. For attractive spin 1/2 fermions with tunable interaction (^6Li), we will show that the gas thermodynamic properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. First, we focus on the finite-temperature Equation of State (EoS) of the unpolarized unitary gas. Surprisingly, the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory [3] and we localize the superfluid phase transition. A detailed comparison with theories including recent Monte-Carlo calculations will be presented. Moving away from the unitary gas, the Lee-Huang-Yang and Lee-Yang beyond-mean-field corrections for low density bosonic and fermionic superfluids are quantitatively measured for the first time. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. [4pt] [1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010) [0pt] [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010) [0pt] [3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett. 106, 215303 (2011)

Light crystals for ultracold quantum degenerate bosonic gases

International Nuclear Information System (INIS)

Arimondo, E.

2009-01-01

Full text follows. The experimental realization of quantum degenerate states in ultracold atomic gases has opened the possibility to realize few body systems isolated from external perturbations and at temperatures close to absolute zero. Under these conditions counterintuitive phenomena characteristic of the quantum mechanical evolution may be assessed experimentally. Matter quantum-mechanical waves inside periodic potentials investigated in solid-state physics, where electrons propagate within a crystal lattice. Interfering laser beams create a light-induced spatial periodic potential for ultracold atoms called an 'optical lattice'. Atoms hopping between the lattice periodic potential minima emulate the motion of electrons in a crystal. The creation of one-, two-, and three-dimensional periodic structures in which atoms can be trapped and accelerated, with the possibility of switching or modulating the lattice at will, gives a great flexibility. In addition atomic physicists can tune the lattice's geometry, the rate of hopping, and the push and pull between atoms within the light crystals. So they hope to map the various behaviors of solid-state models. On the basis of the research work performed at Pisa, several processes of quantum mechanics evolution within a spatial periodic potential and associated to the solid-state physics will be presented

Ultracold neutrons

International Nuclear Information System (INIS)

Steenstrup, S.

Briefly surveys recent developments in research work with ultracold neutrons (neutrons of very low velocity, up to 10 m/s at up to 10 -7 eV and 10 -3 K). Slow neutrons can be detected in an ionisation chamber filled with B 10 F 3 . Very slow neutrons can be used for investigations into the dipole moment of neutrons. Neutrons of large wave length have properties similar to those of light. The limit angle for total reflection is governed by the wave length and by the material. Total reflection can be used to filter ultracold neutrons out of the moderator material of a reactor. Total reflection can also be used to store ultracold neutrons but certain problems with storage have not yet been clarified. Slow neutrons can be made to lose speed in a neutron turbine, and come out as ultracold neutrons. A beam of ultracold neutrons could be used in a neutron microscope. (J.S.)

Exciton induced directed motion of unconstrained atoms in an ultracold gas

Science.gov (United States)

Leonhardt, K.; Wüster, S.; Rost, J. M.

2017-03-01

We demonstrate that through localised Rydberg excitation in a three-dimensional cold atom cloud atomic motion can be rendered directed and nearly confined to a plane, without spatial constraints for the motion of individual atoms. This enables creation and observation of non-adiabatic electronic Rydberg dynamics in atoms accelerated by dipole-dipole interactions under natural conditions. Using the full l = 0, 1 m=0,+/- 1 angular momentum state space, our simulations show that conical intersection crossings are clearly evident, both in atomic position information and excited state spectra of the Rydberg system. Hence, flexible Rydberg aggregates suggest themselves for probing quantum chemical effects in experiments on length scales much inflated as compared to a standard molecular situation.

Dissociation and decay of ultracold sodium molecules

International Nuclear Information System (INIS)

Mukaiyama, T.; Abo-Shaeer, J.R.; Xu, K.; Chin, J.K.; Ketterle, W.

2004-01-01

The dissociation of ultracold molecules was studied by ramping an external magnetic field through a Feshbach resonance. The observed dissociation energies directly yielded the strength of the atom-molecule coupling. They showed nonlinear dependence on the ramp speed. This was explained by a Wigner threshold law which predicts that the decay rate of the molecules above threshold increases with the density of states. In addition, inelastic molecule-molecule and molecule-atom collisions were characterized

Quantum optics with ultracold quantum gases: towards the full quantum regime of the light-matter interaction

International Nuclear Information System (INIS)

Mekhov, Igor B; Ritsch, Helmut

2012-01-01

Although the study of ultracold quantum gases trapped by light is a prominent direction of modern research, the quantum properties of light were widely neglected in this field. Quantum optics with quantum gases closes this gap and addresses phenomena where the quantum statistical natures of both light and ultracold matter play equally important roles. First, light can serve as a quantum nondemolition probe of the quantum dynamics of various ultracold particles from ultracold atomic and molecular gases to nanoparticles and nanomechanical systems. Second, due to the dynamic light-matter entanglement, projective measurement-based preparation of the many-body states is possible, where the class of emerging atomic states can be designed via optical geometry. Light scattering constitutes such a quantum measurement with controllable measurement back-action. As in cavity-based spin squeezing, the atom number squeezed and Schrödinger cat states can be prepared. Third, trapping atoms inside an optical cavity, one creates optical potentials and forces, which are not prescribed but quantized and dynamical variables themselves. Ultimately, cavity quantum electrodynamics with quantum gases requires a self-consistent solution for light and particles, which enriches the picture of quantum many-body states of atoms trapped in quantum potentials. This will allow quantum simulations of phenomena related to the physics of phonons, polarons, polaritons and other quantum quasiparticles. (topical review)

High-resolution imaging of ultracold fermions in microscopically tailored optical potentials

International Nuclear Information System (INIS)

Zimmermann, B; Mueller, T; Meineke, J; Esslinger, T; Moritz, H

2011-01-01

We report on the local probing and preparation of an ultracold Fermi gas on the length scale of one micrometer, i.e. of the order of the Fermi wavelength. The essential tool of our experimental setup is a pair of identical, high-resolution microscope objectives. One of the microscope objectives allows local imaging of the trapped Fermi gas of 6 Li atoms with a maximum resolution of 660 nm, while the other enables the generation of arbitrary optical dipole potentials on the same length scale. Employing a two-dimensional (2D) acousto-optical deflector, we demonstrate the formation of several trapping geometries, including a tightly focused single optical dipole trap, a 4x4 site 2D optical lattice and an 8 site ring lattice configuration. Furthermore, we show the ability to load and detect a small number of atoms in these trapping potentials. A site separation down to one micrometer in combination with the low mass of 6 Li results in tunneling rates that are sufficiently large for the implementation of Hubbard models with the designed geometries.

Moeller polarimetry with atomic hydrogen targets

International Nuclear Information System (INIS)

Chudakov, E.; Luppov, V.

2005-01-01

A novel proposal of using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Moeller scattering is discussed. Such a target of practically 100% polarized electrons could provide a superb systematic accuracy of about 0.5% for beam polarization measurements. Feasibility studies for the CEBAF electron beam have been performed. (orig.)

Competition between Final-State and Pairing-Gap Effects in the Radio-Frequency Spectra of Ultracold Fermi Atoms

International Nuclear Information System (INIS)

Perali, A.; Pieri, P.; Strinati, G. C.

2008-01-01

The radio-frequency spectra of ultracold Fermi atoms are calculated by including final-state interactions affecting the excited level of the transition and compared with the experimental data. A competition is revealed between pairing-gap effects which tend to push the oscillator strength toward high frequencies away from threshold and final-state effects which tend instead to pull the oscillator strength toward threshold. As a result of this competition, the position of the peak of the spectra cannot be simply related to the value of the pairing gap, whose extraction thus requires support from theoretical calculations

Generalized quantum mean-field systems and their application to ultracold atoms

International Nuclear Information System (INIS)

Trimborn-Witthaut, Friederike Annemarie

2011-01-01

Strongly interacting many-body systems consisting of a large number of indistinguishable particles play an important role in many areas of physics. Though such systems are hard to deal with theoretically since the dimension of the respective Hilbert space increases exponentially both in the particle number and in the number of system modes. Therefore, approximations are of considerable interest. The mean-field approximation describes the behaviour in the macroscopic limit N→∞, which leads to an effective nonlinear single-particle problem. Although this approximation is widely used, rigorous results on the applicability and especially on finite size corrections are extremely rare. One prominent example of strongly interacting many-body systems are ultracold atoms in optical lattices, which are a major subject of this thesis. Typically these systems consist of a large but well-defined number of particles, such that corrections to the mean-field limit can be systematically studied. This thesis is divided into two parts: In the first part we study generalized quantum mean-field systems in a C * -algebraic framework. These systems are characterized by their intrinsic permutation symmetry. In the limit of infinite system size, N→∞, the intensive observables converge to the commutative algebra of weak * -continuous functions on the single particle state space. To quantify the deviations from the meanfield prediction for large but finite N, we establish a differential calculus for state space functions and provide a generalized Taylor expansion around the mean-field limit. Furthermore, we introduce the algebra of macroscopic fluctuations around the mean-field limit and prove a quantum version of the central limit theorem. On the basis of these results, we give a detailed study of the finite size corrections to the ground state energy and establish bounds, for both the quantum and the classical case. Finally, we restrict ourselves to the subspace of Bose

Two-stage crossed beam cooling with ⁶Li and ¹³³Cs atoms in microgravity.

Science.gov (United States)

Luan, Tian; Yao, Hepeng; Wang, Lu; Li, Chen; Yang, Shifeng; Chen, Xuzong; Ma, Zhaoyuan

2015-05-04

Applying the direct simulation Monte Carlo (DSMC) method developed for ultracold Bose-Fermi mixture gases research, we study the sympathetic cooling process of 6Li and 133Cs atoms in a crossed optical dipole trap. The obstacles to producing 6Li Fermi degenerate gas via direct sympathetic cooling with 133Cs are also analyzed, by which we find that the side-effect of the gravity is one of the main obstacles. Based on the dynamic nature of 6Li and 133Cs atoms, we suggest a two-stage cooling process with two pairs of crossed beams in microgravity environment. According to our simulations, the temperature of 6Li atoms can be cooled to T = 29.5 pK and T/TF = 0.59 with several thousand atoms, which propose a novel way to get ultracold fermion atoms with quantum degeneracy near pico-Kelvin.

Functional renormalization and ultracold quantum gases

International Nuclear Information System (INIS)

Floerchinger, Stefan

2010-01-01

Modern techniques from quantum field theory are applied in this work to the description of ultracold quantum gases. This leads to a unified description of many phenomena including superfluidity for bosons and fermions, classical and quantum phase transitions, different dimensions, thermodynamic properties and few-body phenomena as bound state formation or the Efimov effect. The non-perturbative treatment with renormalization group flow equations can account for all known limiting cases by solving one single equation. It improves previous results quantitatively and brings qualitatively new insights. As an example, new quantum phase transitions are found for fermions with three spin states. Ultracold atomic gases can be seen as an interesting model for features of high energy physics and for condensed matter theory. The research reported in this thesis helps to solve the difficult complexity problem in modern theoretical physics. (orig.)

Thermodynamics of ultracold Fermi gases

International Nuclear Information System (INIS)

Nascimbene, Sylvain

2010-01-01

Complex Hamiltonians from condensed matter, such as the Fermi-Hubbard model, can be experimentally studied using ultracold gases. This thesis describes a new method for determining the equation of state of an ultracold gas, making the comparison with many-body theories straightforward. It is based on the measurement of the local pressure inside a trapped gas from the analysis of its in situ image. We first apply this method to the study of a Fermi gas with resonant interactions, a weakly-interacting 7 Li gas acting as a thermometer. Surprisingly, none of the existing many-body theories of the unitary gas accounts for the equation of state deduced from our study over its full range. The virial expansion extracted from the high-temperature data agrees with the resolution of the three-body problem. At low temperature, we observe, contrary to some previous studies, that the normal phase behaves as a Fermi liquid. Finally we obtain the critical temperature for superfluidity from a clear signature on the equation of state. We also measure the pressure of the ground state as a function of spin imbalance and interaction strength - measure directly relevant to describe the crust of neutron stars. Our data validate Monte-Carlo simulations and quantify the Lee-Huang-Yang corrections to mean-field interactions in low-density fermionic or bosonic superfluids. We show that, in most cases, the partially polarized normal phase can be described as a Fermi liquid of polarons. The polaron effective mass extracted from the equation of state is in agreement with a study of collective modes. (author)

Sympathetic cooling in a rubidium cesium mixture: Production of ultracold cesium atoms; Sympathetisches Kuehlen in einer Rubidium-Caesium-Mischung: Erzeugung ultrakalter Caesiumatome

Energy Technology Data Exchange (ETDEWEB)

Haas, M.

2007-07-01

This thesis presents experiments for the production of ultracold rubidium cesium mixture in a magnetic trap. The long-termed aim of the experiment is the study of the interaction of few cesium atoms with a Bose-Einstein condensate of rubidium atoms. Especially by controlled variation of the cesium atom number the transition in the description of the interaction by concepts of the one-particle physics to the description by concepts of the many-particle physics shall be studied. The rubidium atoms are trapped in a magneto-optical trap (MOT) and from there reloaded into a magnetic trap. In this the rubidium atoms are stored in the state vertical stroke f=2,m{sub f}=2 right angle of the electronic ground state and evaporatively cooled by means of microwave-induced transitions into the state vertical stroke f=1,m{sub f}=1] (microwave cooling). The cesium atoms are also trppaed in a MOT and into the same magnetic trap reloaded, in which they are stored in the state vertical stroke f=4,m{sub f}=4 right angle of the electronic ground state together with rubidium. Because of the different hyperfine splitting only rubidium is evaporatively cooled, while cesium is cooled jointly sympathetically - i.e. by theramal contact via elastic collisions with rubidium atoms. The first two chapters contain a description of interatomic interactions in ultracold gases as well as a short summary of theoretical concepts in the description of Bose-Einstein condensates. The chapters 3 and 4 contain a short presentation of the methods applied in the experiment for the production of ultracold gases as well as the experimental arrangement; especially in the framework of this thesis a new coil system has been designed, which offers in view of future experiments additionally optical access for an optical trap. Additionally the fourth chapter contains an extensive description of the experimental cycle, which is applied in order to store rubidium and cesium atoms together into the magnetic trap. The

The Pauli potential in relation to the differential virial theorem with application to experiments on ultracold atomic gases of fermions

International Nuclear Information System (INIS)

March, N.H.

2008-08-01

In early work by the writer introducing the Pauli potential VP (r) into density functional theory, the relation of VP (r) to the, as yet unknown, single-particle kinetic energy density functional was emphasized. Here, because of ongoing experiments on ultracold atomic gases of fermions, an explicit expression for the first derivative of VP (r) for an arbitrary number of closed shells generated by harmonic confinement is derived in terms of the spherically symmetric particle density n(r) and the confining potential. (author)

Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas

International Nuclear Information System (INIS)

Palestini, F.; Perali, A.; Pieri, P.; Strinati, G. C.

2010-01-01

Physical properties of an ultracold Fermi gas in the temperature-coupling phase diagram can be characterized by the contact intensity C, which enters the pair-correlation function at short distances and describes how the two-body problem merges into its surrounding. We show that the local order established by pairing fluctuations about the critical temperature T c of the superfluid transition considerably enhances the contact C in a temperature range where pseudogap phenomena are maximal. Our ab initio results for C in a trap compare well with recently available experimental data over a wide coupling range. An analysis is also provided for the effects of trap averaging on C.

Photodissociation of ultracold diatomic strontium molecules with quantum state control.

Science.gov (United States)

McDonald, M; McGuyer, B H; Apfelbeck, F; Lee, C-H; Majewska, I; Moszynski, R; Zelevinsky, T

2016-07-07

Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold (88)Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

Negative-Mass Instability of the Spin and Motion of an Atomic Gas Driven by Optical Cavity Backaction

Science.gov (United States)

Kohler, Jonathan; Gerber, Justin A.; Dowd, Emma; Stamper-Kurn, Dan M.

2018-01-01

We realize a spin-orbit interaction between the collective spin precession and center-of-mass motion of a trapped ultracold atomic gas, mediated by spin- and position-dependent dispersive coupling to a driven optical cavity. The collective spin, precessing near its highest-energy state in an applied magnetic field, can be approximated as a negative-mass harmonic oscillator. When the Larmor precession and mechanical motion are nearly resonant, cavity mediated coupling leads to a negative-mass instability, driving exponential growth of a correlated mode of the hybrid system. We observe this growth imprinted on modulations of the cavity field and estimate the full covariance of the resulting two-mode state by observing its transient decay during subsequent free evolution.

Trapping hydrogen atoms from a neon-gas matrix: a theoretical simulation.

Science.gov (United States)

Bovino, S; Zhang, P; Kharchenko, V; Dalgarno, A

2009-08-07

Hydrogen is of critical importance in atomic and molecular physics and the development of a simple and efficient technique for trapping cold and ultracold hydrogen atoms would be a significant advance. In this study we simulate a recently proposed trap-loading mechanism for trapping hydrogen atoms released from a neon matrix. Accurate ab initio quantum calculations are reported of the neon-hydrogen interaction potential and the energy- and angular-dependent elastic scattering cross sections that control the energy transfer of initially cold atoms are obtained. They are then used to construct the Boltzmann kinetic equation, describing the energy relaxation process. Numerical solutions of the Boltzmann equation predict the time evolution of the hydrogen energy distribution function. Based on the simulations we discuss the prospects of the technique.

Ultracold Atoms in a Square Lattice with Spin-Orbit Coupling: Charge Order, Superfluidity, and Topological Signatures

Science.gov (United States)

Rosenberg, Peter; Shi, Hao; Zhang, Shiwei

2017-12-01

We present an ab initio, numerically exact study of attractive fermions in square lattices with Rashba spin-orbit coupling. The ground state of this system is a supersolid, with coexisting charge and superfluid order. The superfluid is composed of both singlet and triplet pairs induced by spin-orbit coupling. We perform large-scale calculations using the auxiliary-field quantum Monte Carlo method to provide the first full, quantitative description of the charge, spin, and pairing properties of the system. In addition to characterizing the exotic physics, our results will serve as essential high-accuracy benchmarks for the intense theoretical and especially experimental efforts in ultracold atoms to realize and understand an expanding variety of quantum Hall and topological superconductor systems.

Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

International Nuclear Information System (INIS)

Haendel, S.; Marchant, A. L.; Wiles, T. P.; Hopkins, S. A.; Cornish, S. L.

2012-01-01

We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of 85 Rb and 87 Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum. To maintain excellent optical access to the region surrounding the surface, magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally, we demonstrate the loading of a hybrid optical-magnetic trap with 87 Rb and the creation of Bose-Einstein condensates via forced evaporative cooling close to the dielectric surface.

Collisional Cooling of Light Ions by Cotrapped Heavy Atoms.

Science.gov (United States)

Dutta, Sourav; Sawant, Rahul; Rangwala, S A

2017-03-17

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter ^{39}K^{+} ions, created by ionizing ^{39}K atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier ^{85}Rb atoms in a MOT, exhibit a longer trap lifetime than without the localized ^{85}Rb MOT atoms. A similar cooling of trapped ^{85}Rb^{+} ions by ultracold ^{133}Cs atoms in a MOT is also demonstrated in a different experimental configuration to validate this mechanism of ion cooling by localized and centered ultracold neutral atoms. Our results suggest that the cooling of ions by localized cold atoms holds for any mass ratio, thereby enabling studies on a wider class of atom-ion systems irrespective of their masses.

Measurement of optical Feshbach resonances in an ideal gas.

Science.gov (United States)

Blatt, S; Nicholson, T L; Bloom, B J; Williams, J R; Thomsen, J W; Julienne, P S; Ye, J

2011-08-12

Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the optical Feshbach resonance effect in an ultracold gas of bosonic (88)Sr. A systematic measurement of three resonances allows precise determinations of the optical Feshbach resonance strength and scaling law, in agreement with coupled-channel theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. Optical Feshbach resonance could be used to control atomic interactions with high spatial and temporal resolution.

Measurement of Optical Feshbach Resonances in an Ideal Gas

International Nuclear Information System (INIS)

Blatt, S.; Nicholson, T. L.; Bloom, B. J.; Williams, J. R.; Thomsen, J. W.; Ye, J.; Julienne, P. S.

2011-01-01

Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the optical Feshbach resonance effect in an ultracold gas of bosonic 88 Sr. A systematic measurement of three resonances allows precise determinations of the optical Feshbach resonance strength and scaling law, in agreement with coupled-channel theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. Optical Feshbach resonance could be used to control atomic interactions with high spatial and temporal resolution.

Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms.

Science.gov (United States)

Leung, V Y F; Pijn, D R M; Schlatter, H; Torralbo-Campo, L; La Rooij, A L; Mulder, G B; Naber, J; Soudijn, M L; Tauschinsky, A; Abarbanel, C; Hadad, B; Golan, E; Folman, R; Spreeuw, R J C

2014-05-01

We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold (87)Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation.

Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms

Energy Technology Data Exchange (ETDEWEB)

Leung, V. Y. F. [Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, PO Box 94485, 1090 GL Amsterdam (Netherlands); Complex Photonic Systems (COPS), MESA Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede (Netherlands); Pijn, D. R. M.; Schlatter, H.; Torralbo-Campo, L.; La Rooij, A. L.; Mulder, G. B.; Naber, J.; Soudijn, M. L.; Tauschinsky, A.; Spreeuw, R. J. C., E-mail: r.j.c.spreeuw@uva.nl [Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, PO Box 94485, 1090 GL Amsterdam (Netherlands); Abarbanel, C.; Hadad, B.; Golan, E. [Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Be' er Sheva 84105 (Israel); Folman, R. [Department of Physics and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Be' er Sheva 84105 (Israel)

2014-05-15

We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold {sup 87}Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation.

Theory of superfluidity and drag force in the one-dimensional Bose gas

NARCIS (Netherlands)

Cherny, A.Y.; Caux, J.-S.; Brand, J.

2012-01-01

The one-dimensional Bose gas is an unusual superfluid. In contrast to higher spatial dimensions, the existence of non-classical rotational inertia is not directly linked to the dissipationless motion of infinitesimal impurities. Recently, experimental tests with ultracold atoms have begun and

Limit Cycles and Chaos via Quasi-periodicity in Two Coupled Ensembles of Ultra-cold Atoms.

Science.gov (United States)

Patra, Aniket; Yuzbashyan, Emil; Altshuler, Boris

We study the dynamics of two mesoscopic ensembles of ultra-cold two level atoms, which are collectively coupled to an optical cavity and are being pumped incoherently to the excited state. Whereas the time independent steady states are well understood, little is known about the time dependent ones. We explore and categorize various time dependent steady states, e.g. limit cycles and chaotic behavior. We draw a non-equilibrium phase diagram indicating different steady-state behaviors in different parts of the parameter space. We discuss the synchronization of the two ensembles in the time dependent steady states. We also show the onset of chaos via quasi-periodicity. The rich time dependent steady-state behavior, especially the existence of chaos, opens up possibilities for several engineering applications. Supported in part by the University and Louis Bevier Graduate Fellowship.

Experiments with cold hydrogen atoms

International Nuclear Information System (INIS)

Leonas, V.B.

1981-01-01

Numerous investigations of atomic processes in Waseous phase on the surface with participation of ''cold'' hydrogen atoms, made during the last years, are considered. The term ''cold atom'' means the range of relative collision energies E<10 MeV (respectively 'ultracold ' atoms at E< or approximately 1 MeV) which corresponds to the range of temperatures in tens (units) of K degrees. Three main ranges of investigations where extensive experimental programs are realized are considered: study of collisional processes with hydrogen atom participation, hydrogen atoms being of astrophysical interest; study of elastic atom-molecular scattering at superlow energies and studies on the problem of condensed hydrogen. Hydrogen atoms production is realized at dissociation in non-electrode high-frequency or superhigh-frequency discharge. A method of hydrogen quantum generator and of its modifications appeared to be rather an effective means to study collisional changes of spin state of hydrogen atoms. First important results on storage and stabilization of the gas of polarized hydrogen atoms are received

Ultra-cold molecule production

International Nuclear Information System (INIS)

Ramirez-Serrano, Jamie; Chandler, David W.; Strecker, Kevin; Rahn, Larry A.

2005-01-01

The production of Ultra-cold molecules is a goal of many laboratories through out the world. Here we are pursuing a unique technique that utilizes the kinematics of atomic and molecular collisions to achieve the goal of producing substantial numbers of sub Kelvin molecules confined in a trap. Here a trap is defined as an apparatus that spatially localizes, in a known location in the laboratory, a sample of molecules whose temperature is below one degree absolute Kelvin. Further, the storage time for the molecules must be sufficient to measure and possibly further cool the molecules. We utilize a technique unique to Sandia to form cold molecules from near mass degenerate collisions between atoms and molecules. This report describes the progress we have made using this novel technique and the further progress towards trapping molecules we have cooled

Formation of ultracold NaRb Feshbach molecules

International Nuclear Information System (INIS)

Wang, Fudong; He, Xiaodong; Li, Xiaoke; Zhu, Bing; Chen, Jun; Wang, Dajun

2015-01-01

We report the creation of ultracold bosonic 23 Na 87 Rb Feshbach molecules via magneto-association. By ramping the magnetic field across an interspecies Feshbach resonance (FR), at least 4000 molecules can be produced out of the near degenerate ultracold mixture. Fast loss due to inelastic atom–molecule collisions is observed, which limits the pure molecule number, after residual atoms removal, to 1700. The pure molecule sample can live for 21.8(8) ms in the optical trap, long enough for future molecular spectroscopy studies toward coherently transferring to the singlet ro-vibrational ground state, where these molecules are stable against chemical reaction and have a permanent electric dipole moment of 3.3 Debye. We have also measured the Feshbach molecule’s binding energy near the FR by the oscillating magnetic field method and found these molecules have a large closed-channel fraction. (paper)

Observation of symmetry-protected topological band with ultracold fermions

Science.gov (United States)

Song, Bo; Zhang, Long; He, Chengdong; Poon, Ting Fung Jeffrey; Hajiyev, Elnur; Zhang, Shanchao; Liu, Xiong-Jun; Jo, Gyu-Boong

2018-01-01

Symmetry plays a fundamental role in understanding complex quantum matter, particularly in classifying topological quantum phases, which have attracted great interests in the recent decade. An outstanding example is the time-reversal invariant topological insulator, a symmetry-protected topological (SPT) phase in the symplectic class of the Altland-Zirnbauer classification. We report the observation for ultracold atoms of a noninteracting SPT band in a one-dimensional optical lattice and study quench dynamics between topologically distinct regimes. The observed SPT band can be protected by a magnetic group and a nonlocal chiral symmetry, with the band topology being measured via Bloch states at symmetric momenta. The topology also resides in far-from-equilibrium spin dynamics, which are predicted and observed in experiment to exhibit qualitatively distinct behaviors in quenching to trivial and nontrivial regimes, revealing two fundamental types of spin-relaxation dynamics related to bulk topology. This work opens the way to expanding the scope of SPT physics with ultracold atoms and studying nonequilibrium quantum dynamics in these exotic systems. PMID:29492457

Polyatomic Trilobite Rydberg Molecules in a Dense Random Gas.

Science.gov (United States)

Luukko, Perttu J J; Rost, Jan-Michael

2017-11-17

Trilobites are exotic giant dimers with enormous dipole moments. They consist of a Rydberg atom and a distant ground-state atom bound together by short-range electron-neutral attraction. We show that highly polar, polyatomic trilobite states unexpectedly persist and thrive in a dense ultracold gas of randomly positioned atoms. This is caused by perturbation-induced quantum scarring and the localization of electron density on randomly occurring atom clusters. At certain densities these states also mix with an s state, overcoming selection rules that hinder the photoassociation of ordinary trilobites.

Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System

Science.gov (United States)

Mann, Niklas; Bakhtiari, M. Reza; Pelster, Axel; Thorwart, Michael

2018-02-01

We consider a hybrid quantum many-body system formed by a vibrational mode of a nanomembrane, which interacts optomechanically with light in a cavity, and an ultracold atom gas in the optical lattice of the out-coupled light. The adiabatic elimination of the light field yields an effective Hamiltonian which reveals a competition between the force localizing the atoms and the membrane displacement. At a critical atom-membrane interaction, we find a nonequilibrium quantum phase transition from a localized symmetric state of the atom cloud to a shifted symmetry-broken state, the energy of the lowest collective excitation vanishes, and a strong atom-membrane entanglement arises. The effect occurs when the atoms and the membrane are nonresonantly coupled.

Universal relations of an ultracold Fermi gas with arbitrary spin-orbit coupling

Science.gov (United States)

Jie, Jianwen; Qi, Ran; Zhang, Peng

2018-05-01

We derive the universal relations for an ultracold two-component Fermi gas with a spin-orbit coupling (SOC) ∑α,β =x ,y ,zλα βσαpβ , where px ,y ,z and σx ,y ,z are the single-atom momentum and Pauli operators for pseudospin, respectively, and the SOC intensity λα β could take an arbitrary value. We consider the system with an s -wave short-range interspecies interaction, and ignore the SOC-induced modification for the value of the scattering length. Using the first-quantized approach developed by Tan [S. Tan, Phys. Rev. Lett. 107, 145302 (2011), 10.1103/PhysRevLett.107.145302], we obtain the short-range and high-momentum expansions for the one-body real-space correlation function and momentum distribution function, respectively. For our system these functions are a 2 ×2 matrix in the pseudospin basis. We find that the leading-order (1 /k4 ) behavior of the diagonal elements of the momentum distribution function, i.e., n↑↑(k ) and n↓↓(k ) , are not modified by the SOC. However, the SOC can significantly modify the large-k behaviors of the distribution difference δ n (k ) ≡n↑↑(k ) -n↓↓(k ) as well as the nondiagonal elements of the momentum distribution function, i.e., n↑↓(k ) and n↓↑(k ) . In the absence of the SOC, the leading order of δ n (k ) , n↑↓(k ) , and n↓↑(k ) is O (1 /k6) . When SOC appears, it can induce a term on the order of 1 /k5 for these elements. We further derive the adiabatic relation and the energy functional. Our results show that the SOC can induce an additional term in the energy functional, which describes the contribution from the SOC to the total energy. In addition, the form of the adiabatic relation for our system is not modified by the SOC. Our results are applicable for the systems with any type of single-atom trapping potential, which could be either diagonal or nondiagonal in the pseudospin basis.

Metal powder production by gas atomization

Science.gov (United States)

Ting, E. Y.; Grant, N. J.

1986-01-01

The confined liquid, gas-atomization process was investigated. Results from a two-dimensional water model showed the importance of atomization pressure, as well as delivery tube and atomizer design. The atomization process at the tip of the delivery tube was photographed. Results from the atomization of a modified 7075 aluminum alloy yielded up to 60 wt pct. powders that were finer than 45 microns in diameter. Two different atomizer designs were evaluated. The amount of fine powders produced was correlated to a calculated gas-power term. An optimal gas-power value existed for maximized fine powder production. Atomization at gas-power greater than or less than this optimal value produced coarser powders.

One-Dimensional Rydberg Gas in a Magnetoelectric Trap

International Nuclear Information System (INIS)

Mayle, Michael; Hezel, Bernd; Lesanovsky, Igor; Schmelcher, Peter

2007-01-01

We study the quantum properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap which is superimposed by a homogeneous electric field. Trapped Rydberg atoms can be created in long-lived electronic states exhibiting a permanent electric dipole moment of several hundred Debye. The resulting dipole-dipole interaction in conjunction with the radial confinement is demonstrated to give rise to an effectively one-dimensional ultracold Rydberg gas with a macroscopic interparticle distance. We derive analytical expressions for the electric dipole moment and the required linear density of Rydberg atoms

Fast switching of alkali atom dispensers using laser-induced heating

International Nuclear Information System (INIS)

Griffin, P.F.; Weatherill, K.J.; Adams, C.S.

2005-01-01

We show that by using an intense laser source to locally heat an alkali atom dispenser, one can generate a high flux of atoms followed by fast recovery (<100 ms) of the background pressure when the laser is extinguished. For repeated heating pulses a switch-on time for the atomic flux of 200 ms is readily attainable. This technique is suited to ultracold atom experiments using simple ultrahigh vacuum (UHV) chambers. Laser-induced heating provides a fast repetition of the experimental cycle, which, combined with low atom loss due to background gas collisions, is particularly useful for experiments involving far-off resonance optical traps, where sufficient laser power (0.5-4 W) is readily available

Atom interferometry with trapped Bose-Einstein condensates: impact of atom-atom interactions

International Nuclear Information System (INIS)

Grond, Julian; Hohenester, Ulrich; Mazets, Igor; Schmiedmayer, Joerg

2010-01-01

Interferometry with ultracold atoms promises the possibility of ultraprecise and ultrasensitive measurements in many fields of physics, and is the basis of our most precise atomic clocks. Key to a high sensitivity is the possibility to achieve long measurement times and precise readout. Ultracold atoms can be precisely manipulated at the quantum level and can be held for very long times in traps; they would therefore be an ideal setting for interferometry. In this paper, we discuss how the nonlinearities from atom-atom interactions, on the one hand, allow us to efficiently produce squeezed states for enhanced readout and, on the other hand, result in phase diffusion that limits the phase accumulation time. We find that low-dimensional geometries are favorable, with two-dimensional (2D) settings giving the smallest contribution of phase diffusion caused by atom-atom interactions. Even for time sequences generated by optimal control, the achievable minimal detectable interaction energy ΔE min is of the order of 10 -4 μ, where μ is the chemical potential of the Bose-Einstein condensate (BEC) in the trap. From these we have to conclude that for more precise measurements with atom interferometers, more sophisticated strategies, or turning off the interaction-induced dephasing during the phase accumulation stage, will be necessary.

s-wave elastic scattering of antihydrogen off atomic alkali-metal targets

International Nuclear Information System (INIS)

Sinha, Prabal K.; Ghosh, A. S.

2006-01-01

We have investigated the s-wave elastic scattering of antihydrogen atoms off atomic alkali-metal targets (Li, Na, K, and Rb) at thermal energies (10 -16 -10 -4 a.u.) using an atomic orbital expansion technique. The elastic cross sections of these systems at thermal energies are found to be very high compared to H-H and H-He systems. The theoretical models employed in this study are so chosen to consider long-range forces dynamically in the calculation. The mechanism of cooling suggests that Li may be considered to be a good candidate as a buffer gas for enhanced cooling of antihydrogen atoms to ultracold temperature

Quantum Fluctuations of Vortex Lattices in Ultracold Gases

OpenAIRE

Kwasigroch, M. P.; Cooper, N. R.

2012-01-01

We discuss the effects of quantum fluctuations on the properties of vortex lattices in rapidly rotating ultracold atomic gases. We develop a variational method that goes beyond the Bogoliubov theory by including the effects of interactions between the quasiparticle excitations. These interactions are found to have significant quantitative effects on physical properties even at relatively large filling factors. We use our theory to predict the expected experimental signatures of quantum fluctu...

Single-atom detection on a chip: from realization to application

Energy Technology Data Exchange (ETDEWEB)

Stibor, A; Bender, H; Kuehnhold, S; Fortagh, J; Zimmermann, C; Guenther, A, E-mail: aguenth@pit.physik.uni-tuebingen.d [CQ Center for Collective Quantum Phenomena and their Applications, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2010-06-15

In this paper, we describe the preparation and detection of ultracold atoms on a microchip with single-atom sensitivity. The detection scheme is based on multi-photon ionization of atoms and the subsequent guiding of the generated ions by ion optics to a channel electron multiplier. We resolve single atoms with a detection efficiency above 60%. The detector is suitable for real-time observations of static and dynamic processes in ultracold quantum gases. Although the ionization is destructive, sampling a small subset of the atomic distribution is sufficient for the determination of the desired information. We take full high-resolution spectra of ultracold atoms by ionizing only 5% of the atoms. Using an additional microwave near 6.8 GHz, the detection scheme becomes energy, position and state selective. This can be used for in situ determination of the energy distribution and temperature of atom clouds inside the trap and applied for future correlation measurements.

Magnetic-field gradiometer based on ultracold collisions

Science.gov (United States)

Wasak, Tomasz; Jachymski, Krzysztof; Calarco, Tommaso; Negretti, Antonio

2018-05-01

We present a detailed analysis of the usefulness of ultracold atomic collisions for sensing the strength of an external magnetic field as well as its spatial gradient. The core idea of the sensor, which we recently proposed in Jachymski et al. [Phys. Rev. Lett. 120, 013401 (2018), 10.1103/PhysRevLett.120.013401], is to probe the transmission of the atoms through a set of quasi-one-dimensional waveguides that contain an impurity. Magnetic-field-dependent interactions between the incoming atoms and the impurity naturally lead to narrow resonances that can act as sensitive field probes since they strongly affect the transmission. We illustrate our findings with concrete examples of experimental relevance, demonstrating that for large atom fluences N a sensitivity of the order of 1 nT/√{N } for the field strength and 100 nT/(mm √{N }) for the gradient can be reached with our scheme.

Radio frequency acceleration and manipulation of ultra-cold electron bunches

NARCIS (Netherlands)

Franssen, J.G.H.; Vredenbregt, E.J.D.; Luiten, O.J.

2016-01-01

We are developing an ultra-fast and ultra-cold electron source based on a grating magneto optical trap, RF acceleration and RF (de-) compression techniques. The electrons will be created by near-threshold, femtosecond photoionization of a laser-cooled and trapped gas. The electron cloud is extracted

Preparation of a pure molecular quantum gas.

Science.gov (United States)

Herbig, Jens; Kraemer, Tobias; Mark, Michael; Weber, Tino; Chin, Cheng; Nägerl, Hanns-Christoph; Grimm, Rudolf

2003-09-12

An ultracold molecular quantum gas is created by application of a magnetic field sweep across a Feshbach resonance to a Bose-Einstein condensate of cesium atoms. The ability to separate the molecules from the atoms permits direct imaging of the pure molecular sample. Magnetic levitation enables study of the dynamics of the ensemble on extended time scales. We measured ultralow expansion energies in the range of a few nanokelvin for a sample of 3000 molecules. Our observations are consistent with the presence of a macroscopic molecular matter wave.

Electric-field-modified Feshbach resonances in ultracold atom–molecule collision

International Nuclear Information System (INIS)

Cheng Dong; Li Ya; Feng Eryin; Huang Wuying

2017-01-01

We present a detailed analysis of near zero-energy Feshbach resonances in ultracold collisions of atom and molecule, taking the He–PH system as an example, subject to superimposed electric and magnetic static fields. We find that the electric field can induce Feshbach resonance which cannot occur when only a magnetic field is applied, through couplings of the adjacent rotational states of different parities. We show that the electric field can shift the position of the magnetic Feshbach resonance, and change the amplitude of resonance significantly. Finally, we demonstrate that, for narrow magnetic Feshbach resonance as in most cases of ultracold atom–molecule collision, the electric field may be used to modulate the resonance, because the width of resonance in electric field scale is relatively larger than that in magnetic field scale. (paper)

Optical trapping and Feshbach spectroscopy of an ultracold Rb-Cs mixture

International Nuclear Information System (INIS)

Pilch, K.

2009-01-01

We investigate quantum-mechanical interactions between ultracold rubidium and cesium in an optical trap at temperatures of a few micro kelvin. Our results provide, on the one hand, an experimental key to understand the collisional properties and, on the other hand, a tool to control the interspecies interactions. By performing loss measurements we locate several Feshbach resonances, which provide insight into the energy structure of weakly bound RbCs molecules near the dissociation threshold and allow for the production of such heteronuclear Feshbach molecules. In the future we will transfer these loosely-bound molecules into the absolute internal ground state. The availability of ultracold heteronuclear ground state molecules will open the door to investigate phenomena associated with ultracold polar quantum gases. In our new experimental set-up we are able to trap and cool rubidium and cesium atoms in their lowest internal states. First we load both species into a two-color magneto-optical trap, having full control over the single-species atom number. We extend the technique of degenerate Raman-sideband cooling to a two-color version, which is able to simultaneously cool and polarize both rubidium and cesium. Thereafter we load the atoms into a levitated crossed optical dipole trap. Because of the presence of the gradient magnetic field the trap is highly state selective and consequently provides perfect spin-polarization of the sample. Furthermore, a coincidence of the magnetic-moment-to-mass ratios of the two species allows for simultaneous levitation of both, which assures an almost perfect spatial overlap between the species. We perform Feshbach spectroscopy in two dierent spin channels of the mixture within a magnetic field ranging from 20 to 300 Gauss. In the lowest spin combination of the species we locate 23 interspecies Feshbach resonances, while in a higher spin mixture we find 2 resonances. The high number of resonances found within this range of

An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms

NARCIS (Netherlands)

Flores, A.S.; Mishra, H.P.; Vassen, Wim; Knoop, S.

2017-01-01

We report on the realization of an ultracold (<25 μK) mixture of rubidium (87Rb) and metastable triplet helium (4He) in an optical dipole trap. Our scheme involves laser cooling in a dual-species magneto-optical trap, simultaneous MW- and RF-induced forced evaporative cooling in a quadrupole

Soliton Trains Induced by Adaptive Shaping with Periodic Traps in Four-Level Ultracold Atom Systems

International Nuclear Information System (INIS)

Djouom Tchenkoue, M. L.; Welakuh Mbangheku, D.; Dikandé, Alain M.

2017-01-01

It is well known that an optical trap can be imprinted by a light field in an ultracold-atom system embedded in an optical cavity, and driven by three different coherent fields. Of the three fields coexisting in the optical cavity there is an intense control field that induces a giant Kerr nonlinearity via electromagnetically-induced transparency, and another field that creates a periodic optical grating of strength proportional to the square of the associated Rabi frequency. In this work elliptic-soliton solutions to the nonlinear equation governing the propagation of the probe field are considered, with emphasis on the possible generation of optical soliton trains forming a discrete spectrum with well defined quantum numbers. The problem is treated assuming two distinct types of periodic optical gratings and taking into account the negative and positive signs of detunings (detuning above or below resonance). Results predict that the competition between the self-phase and cross-phase modulation nonlinearities gives rise to a rich family of temporal soliton train modes characterized by distinct quantum numbers. (paper)

Soliton Trains Induced by Adaptive Shaping with Periodic Traps in Four-Level Ultracold Atom Systems

Science.gov (United States)

Djouom Tchenkoue, M. L.; Welakuh Mbangheku, D.; Dikandé, Alain M.

2017-06-01

It is well known that an optical trap can be imprinted by a light field in an ultracold-atom system embedded in an optical cavity, and driven by three different coherent fields. Of the three fields coexisting in the optical cavity there is an intense control field that induces a giant Kerr nonlinearity via electromagnetically-induced transparency, and another field that creates a periodic optical grating of strength proportional to the square of the associated Rabi frequency. In this work elliptic-soliton solutions to the nonlinear equation governing the propagation of the probe field are considered, with emphasis on the possible generation of optical soliton trains forming a discrete spectrum with well defined quantum numbers. The problem is treated assuming two distinct types of periodic optical gratings and taking into account the negative and positive signs of detunings (detuning above or below resonance). Results predict that the competition between the self-phase and cross-phase modulation nonlinearities gives rise to a rich family of temporal soliton train modes characterized by distinct quantum numbers.

The production and storage of ultracold neutrons

Energy Technology Data Exchange (ETDEWEB)

Yoshiki, Hajime [Kure University, Hiroshima (Japan); Shimizu, Hirohiko; Sakai, Kenji [and others

1998-01-01

The electric dipole measurement done on the ultracold neutron till now shows that its quantity is minute, not more than 10{sup -25}e.cm. It is purpose of this particular research program to produce such very slow neutrons, or so-cold ultracold neutrons in great quantity. Then, it was investigated what was the ultracold neutron important for, how is the ultracold neutron made, and how is very pure superfluid liquid helium made. As a result of these investigations, it was found that the validity of ultracold neutron production by superfluid liquid helium was established, that its efficiency is high enough to improve the neutron electric dipole moment detection sensitivity by at least one order of magnitude, and so forth. (G.K.)

Ultracold molecules: vehicles to scalable quantum information processing

International Nuclear Information System (INIS)

Brickman Soderberg, Kathy-Anne; Gemelke, Nathan; Chin Cheng

2009-01-01

In this paper, we describe a novel scheme to implement scalable quantum information processing using Li-Cs molecular states to entangle 6 Li and 133 Cs ultracold atoms held in independent optical lattices. The 6 Li atoms will act as quantum bits to store information and 133 Cs atoms will serve as messenger bits that aid in quantum gate operations and mediate entanglement between distant qubit atoms. Each atomic species is held in a separate optical lattice and the atoms can be overlapped by translating the lattices with respect to each other. When the messenger and qubit atoms are overlapped, targeted single-spin operations and entangling operations can be performed by coupling the atomic states to a molecular state with radio-frequency pulses. By controlling the frequency and duration of the radio-frequency pulses, entanglement can be either created or swapped between a qubit messenger pair. We estimate operation fidelities for entangling two distant qubits and discuss scalability of this scheme and constraints on the optical lattice lasers. Finally we demonstrate experimental control of the optical potentials sufficient to translate atoms in the lattice.

Diatomic molecules in ultracold Fermi gases - Novel composite bosons

OpenAIRE

Petrov, D. S.; Salomon, C.; Shlyapnikov, G. V.

2005-01-01

We give a brief overview of recent studies of weakly bound homonuclear molecules in ultracold two-component Fermi gases. It is emphasized that they represent novel composite bosons, which exhibit features of Fermi statistics at short intermolecular distances. In particular, Pauli exclusion principle for identical fermionic atoms provides a strong suppression of collisional relaxation of such molecules into deep bound states. We then analyze heteronuclear molecules which are expected to be for...

Numerical methods for atomic quantum gases with applications to Bose-Einstein condensates and to ultracold fermions

International Nuclear Information System (INIS)

Minguzzi, A.; Succi, S.; Toschi, F.; Tosi, M.P.; Vignolo, P.

2004-01-01

The achievement of Bose-Einstein condensation in ultra-cold vapours of alkali atoms has given enormous impulse to the study of dilute atomic gases in condensed quantum states inside magnetic traps and optical lattices. High-purity and easy optical access make them ideal candidates to investigate fundamental issues on interacting quantum systems. This review presents some theoretical issues which have been addressed in this area and the numerical techniques which have been developed and used to describe them, from mean-field models to classical and quantum simulations for equilibrium and dynamical properties. After an introductory overview on dilute quantum gases, both in the homogeneus state and under harmonic or periodic confinement, the article is organized in three main sections. The first concerns Bose-condensed gases at zero temperature, with main regard to the properties of the ground state in different confinements and to collective excitations and transport in the condensate. Bose-Einstein-condensed gases at finite temperature are addressed in the next section, the main emphasis being on equilibrium properties and phase transitions and on dynamical and transport properties associated with the presence of the thermal cloud. Finally, the last section is focused on theoretical and computational issues that have emerged from the efforts to drive gases of fermionic atoms and boson-fermion mixtures deep into the quantum degeneracy regime, with the aim of realizing novel superfluids from fermion pairing. The attention given in this article to methods beyond standard mean-field approaches should make it a useful reference point for future advances in these areas

Strongly correlated quantum fluids: ultracold quantum gases, quantum chromodynamic plasmas and holographic duality

OpenAIRE

Adams, Allan; Carr, Lincoln D.; Schafer, Thomas; Steinberg, Peter; Thomas, John E.

2012-01-01

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These sy...

Association of atoms into universal dimers using an oscillating magnetic field.

Science.gov (United States)

Langmack, Christian; Smith, D Hudson; Braaten, Eric

2015-03-13

In a system of ultracold atoms near a Feshbach resonance, pairs of atoms can be associated into universal dimers by an oscillating magnetic field with a frequency near that determined by the dimer binding energy. We present a simple expression for the transition rate that takes into account many-body effects through a transition matrix element of the contact. In a thermal gas, the width of the peak in the transition rate as a function of the frequency is determined by the temperature. In a dilute Bose-Einstein condensate of atoms, the width is determined by the inelastic scattering rates of a dimer with zero-energy atoms. Near an atom-dimer resonance, there is a dramatic increase in the width from inelastic atom-dimer scattering and from atom-atom-dimer recombination. The recombination contribution provides a signature for universal tetramers that are Efimov states consisting of two atoms and a dimer.

Advances in ultracold collisions: Experimentation and theory

International Nuclear Information System (INIS)

Weiner, J.

1995-01-01

Collisions between optically cooled and trapped atoms have been the subject of intensive investigation since early proposals discussed their novel features and key importance to the achievement of a gaseous ensemble in a single quantum state. Progress in both experimentation and theory has accelerated rapidly over the last three years, and two reviews, one emphasizing theory and the other, experiments, recount the state of the art published up to about the midpoint of 1993. The purpose of this chapter is to update continuing lines of research set forth in these and earlier works and to relate new results, establishing novel directions for investigation that have appeared in the literature. Two principal questions motivate research into the nature of ultracold collisions: (1) what new phenomena arise when collisionally interacting particles also exchange photons with modes of the radiation field and (2) what are the important two-body collisional heating mechanisms and how can they be overcome in order to achieve the temperature and density conditions appropriate for Bose-Einstein condensation (BEC)? In fact these two questions are not mutually exclusive, and one of the most notable developments in the past year, relevant to both, has been the demonstration of optical control of two-body ultracold collisional processes. Other important issues touching, on one or both of these questions are the magnitude and sign of the scattering length in s-wave collisions between species in various well-defined quantum states, progress in high-resolution trap loss and photoassociation spectroscopy, and application of optical cooling and compression to atomic beams. 58 refs., 21 figs

Storage ring to investigate cold unidimensional atomic collisions

International Nuclear Information System (INIS)

Marcassa, L. G.; Caires, A. R. L.; Nascimento, V. A.; Dulieu, O.; Weiner, J.; Bagnato, V. S.

2005-01-01

In this paper we employ a circulating ring of trapped atoms, that we have named the atomotron, to study cold collisions. The atomotron is obtained from a conventional magneto-optical trap when the two pairs of normally retroreflecting Gaussian laser beams in the x-y plane are slightly offset. Circulating stable atomic orbits then form a racetrack geometry in this plane. The circulating atom flux behaves similarly to an atomic beam with an average tangential velocity much greater than the transverse components, and is therefore suitable for one-dimensional atomic collision studies. Using the atomotron, we have investigated the polarization dependence of ultracold photoassociation collisions between Rb atoms circulating in the racetrack. The ability to investigate collisions in ultracold circulating atomic rings reveals alignment and orientation properties that are averaged away in ordinary three-dimensional magneto-optical trap collision processes

From rotating atomic rings to quantum Hall states.

Science.gov (United States)

Roncaglia, M; Rizzi, M; Dalibard, J

2011-01-01

Considerable efforts are currently devoted to the preparation of ultracold neutral atoms in the strongly correlated quantum Hall regime. However, the necessary angular momentum is very large and in experiments with rotating traps this means spinning frequencies extremely near to the deconfinement limit; consequently, the required control on parameters turns out to be too stringent. Here we propose instead to follow a dynamic path starting from the gas initially confined in a rotating ring. The large moment of inertia of the ring-shaped fluid facilitates the access to large angular momenta, corresponding to giant vortex states. The trapping potential is then adiabatically transformed into a harmonic confinement, which brings the interacting atomic gas in the desired quantum-Hall regime. We provide numerical evidence that for a broad range of initial angular frequencies, the giant-vortex state is adiabatically connected to the bosonic ν = 1/2 Laughlin state.

Absorption imaging of a quasi-two-dimensional gas: a multiple scattering analysis

International Nuclear Information System (INIS)

Chomaz, L; Corman, L; Yefsah, T; Desbuquois, R; Dalibard, J

2012-01-01

Absorption imaging with quasi-resonant laser light is a commonly used technique for probing ultra-cold atomic gases in various geometries. In this paper, we investigate some non-trivial aspects of this method when applying the method to in situ diagnosis of a quasi-two-dimensional (2D) gas. Using Monte Carlo simulations we study the modification of the absorption cross-section of a photon when it undergoes multiple scattering in the gas. We determine the variations of the optical density with various parameters, such as the detuning of the light from the atomic resonance and the thickness of the gas. We compare our results to the known 3D result (the Beer-Lambert law) and outline the specific features of the 2D case. (paper)

Nonlinear dynamics of ultracold gases in double-well lattices

International Nuclear Information System (INIS)

Yukalov, V I; Yukalova, E P

2009-01-01

An ultracold gas is considered, loaded into a lattice, each site of which is formed by a double-well potential. Initial conditions, after the loading, correspond to a nonequilibrium state. The nonlinear dynamics of the system, starting with a nonequilibrium state, is analysed in the local-field approximation. The importance of taking into account attenuation, caused by particle collisions, is emphasized. The presence of this attenuation dramatically influences the system dynamics

Inflow of atomic gas fuelling star formation

DEFF Research Database (Denmark)

Michałowski, M. J.; Gentile, G.; Hjorth, Jeppe

2016-01-01

Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation in these ga......Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation...... in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion....

Experimental investigation of the dynamics in a strongly interacting Fermi gas : collective modes and rotational properties

International Nuclear Information System (INIS)

Riedl, S.

2009-01-01

This thesis explores the dynamics in an ultracold strongly interacting Fermi gas. Therefore we perform measurements on collective excitation modes and rotational properties of the gas. The strongly interacting gas is realized using an optically trapped Fermi gas of 6 Li atoms, where the interactions can be tuned using a broad Feshbach resonance. Our measurements allow to test the equation of state of the gas, study the transition from hydrodynamic to collisionless behavior, reveal almost ideal hydrodynamic behavior in the nonsuperfluid phase, investigate the lifetime of angular momentum, and show superfluidity through the quenching of the moment of inertia. (author)

Noble gas atoms as chemical impurities in silicon

International Nuclear Information System (INIS)

Tkachev, V.D.; Mudryi, A.V.; Minaev, N.S.

1984-01-01

The behaviour of noble gas atoms implanted in silicon is studied by the luminescence method. The energy position of Moessbauer-type luminescence bands with zero-phonon lines 1.0148, 1.0120, 1.0097, 1.0048 eV and others connected with implanted atoms of neon, helium, argon, krypton, respectively, indicates the formation of deep energy levels in the forbidden gap of silicon. Implantation of the noble gas isotopes confirms their participation in formation processes of the luminescence centers in silicon. The temperature range of existence and the symmetry of defects incorporating the noble gas atoms are found. It is noted that noble gas atoms form impurity complexes with deep energy levels and their behaviour in crystals does not differ from that of main doped or residual technological impurity atoms. (author)

Optical ferris wheel for ultracold atoms

Science.gov (United States)

Franke-Arnold, S.; Leach, J.; Padgett, M. J.; Lembessis, V. E.; Ellinas, D.; Wright, A. J.; Girkin, J. M.; Ohberg, P.; Arnold, A. S.

2007-07-01

We propose a versatile optical ring lattice suitable for trapping cold and quantum degenerate atomic samples. We demonstrate the realisation of intensity patterns from pairs of Laguerre-Gauss (exp(iℓө) modes with different ℓ indices. These patterns can be rotated by introducing a frequency shift between the modes. We can generate bright ring lattices for trapping atoms in red-detuned light, and dark ring lattices suitable for trapping atoms with minimal heating in the optical vortices of blue-detuned light. The lattice sites can be joined to form a uniform ring trap, making it ideal for studying persistent currents and the Mott insulator transition in a ring geometry.

On the theory of ultracold neutrons scattering by Davydov solitons

International Nuclear Information System (INIS)

Brizhik, L.S.

1984-01-01

Elastic coherent scattering of ultracold neutrons by Davydov solitons in one-dimensional periodic molecular chains without account of thermal oscillations of chain atoms is studied. It is shown that the expression for the differential cross section of the elastic neutron scattering by Davydov soliton breaks down into two components. One of them corresponds to scattering by a resting soliton, the other is proportional to the soliton velocity and has a sharp maximum in the direction of mirror reflection of neutrons from the chain

Time-Dependent Impurity in Ultracold Fermions: Orthogonality Catastrophe and Beyond

Directory of Open Access Journals (Sweden)

Michael Knap

2012-12-01

Full Text Available The recent experimental realization of strongly imbalanced mixtures of ultracold atoms opens new possibilities for studying impurity dynamics in a controlled setting. In this paper, we discuss how the techniques of atomic physics can be used to explore new regimes and manifestations of Anderson’s orthogonality catastrophe (OC, which could not be accessed in solid-state systems. Specifically, we consider a system of impurity atoms, localized by a strong optical-lattice potential, immersed in a sea of itinerant Fermi atoms. We point out that the Ramsey-interference-type experiments with the impurity atoms allow one to study the OC in the time domain, while radio-frequency (RF spectroscopy probes the OC in the frequency domain. The OC in such systems is universal, not only in the long-time limit, but also for all times and is determined fully by the impurity-scattering length and the Fermi wave vector of the itinerant fermions. We calculate the universal Ramsey response and RF-absorption spectra. In addition to the standard power-law contributions, which correspond to the excitation of multiple particle-hole pairs near the Fermi surface, we identify a novel, important contribution to the OC that comes from exciting one extra particle from the bottom of the itinerant band. This contribution gives rise to a nonanalytic feature in the RF-absorption spectra, which shows a nontrivial dependence on the scattering length, and evolves into a true power-law singularity with the universal exponent 1/4 at the unitarity. We extend our discussion to spin-echo-type experiments, and show that they probe more complicated nonequilibirum dynamics of the Fermi gas in processes in which an impurity switches between states with different interaction strength several times; such processes play an important role in the Kondo problem, but remained out of reach in the solid-state systems. We show that, alternatively, the OC can be seen in the energy-counting statistics

Quantum coherent tractor beam effect for atoms trapped near a nanowaveguide

Science.gov (United States)

Sadgrove, Mark; Wimberger, Sandro; Nic Chormaic, Síle

2016-01-01

We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold 23Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry. PMID:27440516

Ultracold molecules for the masses: Evaporative cooling and magneto-optical trapping

Science.gov (United States)

Stuhl, B. K.

While cold molecule experiments are rapidly moving towards their promised benefits of precision spectroscopy, controllable chemistry, and novel condensed phases, heretofore the field has been greatly limited by a lack of methods to cool and compress chemically diverse species to temperatures below ten millikelvin. While in atomic physics these needs are fulfilled by laser cooling, magneto-optical trapping, and evaporative cooling, until now none of these techniques have been applicable to molecules. In this thesis, two major breakthroughs are reported. The first is the observation of evaporative cooling in magnetically trapped hydroxyl (OH) radicals, which potentially opens a path all the way to Bose-Einstein condensation of dipolar radicals, as well as allowing cold- and ultracold-chemistry studies of fundamental reaction mechanisms. Through the combination of an extremely high gradient magnetic quadrupole trap and the use of the OH Λ-doublet transition to enable highly selective forced evaporation, cooling by an order of magnitude in temperature was achieved and yielded a final temperature no higher than 5mK. The second breakthrough is the successful application of laser cooling and magneto-optical trapping to molecules. Motivated by a proposal in this thesis, laser cooling of molecules is now known to be technically feasible in a select but substantial pool of diatomic molecules. The demonstration of not only Doppler cooling but also two-dimensional magneto-optical trapping in yttrium (II) oxide, YO, is expected to enable rapid growth in the availability of ultracold molecules—just as the invention of the atomic magneto-optical trap stimulated atomic physics twenty-five years ago.

Use of ultracold neutrons for condensed-matter studies

Energy Technology Data Exchange (ETDEWEB)

Michaudon, A.

1997-05-01

Ultracold neutrons have such low velocities that they are reflected by most materials at all incident angles and can be stored in material bottles for long periods of time during which their intrinsic properties can be studied in great detail. These features have been mainly used for fundamental-physics studies including the detection of a possible neutron electric dipole moment and the precise determination of neutron-decay properties. Ultracold neutrons can also play a role in condensed-matter studies with the help of high-resolution spectrometers that use gravity as a strongly dispersive medium for low-velocity neutrons. Such studies have so far been limited by the low intensity of existing ultracold-neutron sources but could be reconsidered with more intense sources, which are now envisaged. This report provides a broad survey of the properties of ultracold neutrons (including their reflectivity by different types of samples), of ultracold-neutron spectrometers that are compared with other high-resolution instruments, of results obtained in the field of condensed matter with these instruments, and of neutron microscopes. All these subjects are illustrated by numerous examples.

Use of ultracold neutrons for condensed-matter studies

International Nuclear Information System (INIS)

Michaudon, A.

1997-05-01

Ultracold neutrons have such low velocities that they are reflected by most materials at all incident angles and can be stored in material bottles for long periods of time during which their intrinsic properties can be studied in great detail. These features have been mainly used for fundamental-physics studies including the detection of a possible neutron electric dipole moment and the precise determination of neutron-decay properties. Ultracold neutrons can also play a role in condensed-matter studies with the help of high-resolution spectrometers that use gravity as a strongly dispersive medium for low-velocity neutrons. Such studies have so far been limited by the low intensity of existing ultracold-neutron sources but could be reconsidered with more intense sources, which are now envisaged. This report provides a broad survey of the properties of ultracold neutrons (including their reflectivity by different types of samples), of ultracold-neutron spectrometers that are compared with other high-resolution instruments, of results obtained in the field of condensed matter with these instruments, and of neutron microscopes. All these subjects are illustrated by numerous examples

Towards experimental quantum-field tomography with ultracold atoms.

Science.gov (United States)

Steffens, A; Friesdorf, M; Langen, T; Rauer, B; Schweigler, T; Hübener, R; Schmiedmayer, J; Riofrío, C A; Eisert, J

2015-07-03

The experimental realization of large-scale many-body systems in atomic-optical architectures has seen immense progress in recent years, rendering full tomography tools for state identification inefficient, especially for continuous systems. To work with these emerging physical platforms, new technologies for state identification are required. Here we present first steps towards efficient experimental quantum-field tomography. Our procedure is based on the continuous analogues of matrix-product states, ubiquitous in condensed-matter theory. These states naturally incorporate the locality present in realistic physical settings and are thus prime candidates for describing the physics of locally interacting quantum fields. To experimentally demonstrate the power of our procedure, we quench a one-dimensional Bose gas by a transversal split and use our method for a partial quantum-field reconstruction of the far-from-equilibrium states of this system. We expect our technique to play an important role in future studies of continuous quantum many-body systems.

High-speed cinematography of gas-metal atomization

Energy Technology Data Exchange (ETDEWEB)

Ting, Jason [ALCOA Specialty Metals Division, 100 Technical Drive, Alcoa Center, PA 15069 (United States)]. E-mail: jason.ting@alcoa.com; Connor, Jeffery [Material Science Engineering Department, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Ridder, Stephen [Metallurgical Processing Group, NIST, 100 Bureau Dr. Stop 8556, Gaithersburg, MD 20899 (United States)

2005-01-15

A high-speed cinematographic footage of a 304L stainless steel gas atomization, recorded at the National Institute of Standard and Technology (NIST), was analyzed using a discrete Fourier transform (DFT) algorithm. The analysis showed the gas atomization process possesses two prominent frequency ranges of melt oscillation (pulsation). A low-frequency oscillation in the melt flow occurring between 5.41 and 123 Hz, with a dominant frequency at 9.93 Hz, was seen in the recirculation zone adjacent to the melt orifice. A high-frequency melt oscillation range was observed above 123 Hz, and was more prominent one melt-tip-diameter downstream in the melt atomization image than upstream near the melt tip. This high-frequency range may reflect the melt atomization frequency used to produce finely atomized powder. This range also included a prominent high frequency at 1273 Hz, which dominated in the image further away downstream from the melt tip. This discrete high-frequency oscillation is most probably caused by the aeroacoustic ''screech'' phenomenon, intrasound (<20 kHz), a result of the atomizing gas jets undergoing flow resonance. It is hypothesized that this discrete intrinsic aeroacoustic tone may enhance melt breakup in the atomization process with evidence of this fact in the melt images.

High-speed cinematography of gas-metal atomization

International Nuclear Information System (INIS)

Ting, Jason; Connor, Jeffery; Ridder, Stephen

2005-01-01

A high-speed cinematographic footage of a 304L stainless steel gas atomization, recorded at the National Institute of Standard and Technology (NIST), was analyzed using a discrete Fourier transform (DFT) algorithm. The analysis showed the gas atomization process possesses two prominent frequency ranges of melt oscillation (pulsation). A low-frequency oscillation in the melt flow occurring between 5.41 and 123 Hz, with a dominant frequency at 9.93 Hz, was seen in the recirculation zone adjacent to the melt orifice. A high-frequency melt oscillation range was observed above 123 Hz, and was more prominent one melt-tip-diameter downstream in the melt atomization image than upstream near the melt tip. This high-frequency range may reflect the melt atomization frequency used to produce finely atomized powder. This range also included a prominent high frequency at 1273 Hz, which dominated in the image further away downstream from the melt tip. This discrete high-frequency oscillation is most probably caused by the aeroacoustic ''screech'' phenomenon, intrasound (<20 kHz), a result of the atomizing gas jets undergoing flow resonance. It is hypothesized that this discrete intrinsic aeroacoustic tone may enhance melt breakup in the atomization process with evidence of this fact in the melt images

Rapid prototyping of versatile atom chips for atom interferometry applications.

Science.gov (United States)

Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

2016-05-01

We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

International Nuclear Information System (INIS)

Marschner, Karel; Musil, Stanislav; Dědina, Jiří

2015-01-01

A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH 4 in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l −1 and 1.0 ng l −1 , respectively. - Highlights: • We optimized and compared two hydride atomizers for atomic fluorescence spectrometry. • Miniature diffusion flame and flame-in-gas-shield atomizer were optimized. • The limit of detection for arsenic was 1.0 ng l −1

Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

Energy Technology Data Exchange (ETDEWEB)

Marschner, Karel, E-mail: karel.marschner@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Albertov 8, 128 43 Prague (Czech Republic); Musil, Stanislav; Dědina, Jiří [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

2015-07-01

A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH{sub 4} in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l{sup −1} and 1.0 ng l{sup −1}, respectively. - Highlights: • We optimized and compared two hydride atomizers for atomic fluorescence spectrometry. • Miniature diffusion flame and flame-in-gas-shield atomizer were optimized. • The limit of detection for arsenic was 1.0 ng l{sup −1}.

Non-abelian geometrical quantum gate operation in an ultracold strontium gas

Science.gov (United States)

Leroux, Frederic

The work developed in this PhD thesis is about geometric operation on a single qubit. If the external control parameters vary slowly, the quantum system evolves adiabatically in a sub-space composed of two degenerate eigenstates. After a closed loop in the space of the external parameters, the qubit acquires a geometrical rotation, which can be described by a unitary matrix in the Hilbert space of the two-level system. To the geometric rotation corresponds a non-Abelian gauge field. In this work, the qubit and the adiabatic geometrical quantum gates are implemented on a cold gas of atomic Strontium 87, trapped and cooled at the vicinity of the recoil temperature. The internal Hilbert space of the cold atoms has for basis the dressed states issued from the atom-light interaction of three lasers within a tripod configuration.

Cold atoms close to surfaces

DEFF Research Database (Denmark)

Krüger, Peter; Wildermuth, Stephan; Hofferberth, Sebastian

2005-01-01

Microscopic atom optical devices integrated on atom chips allow to precisely control and manipulate ultra-cold (T atoms and Bose-Einstein condensates (BECs) close to surfaces. The relevant energy scale of a BEC is extremely small (down to ... be utilized as a sensor for variations of the potential energy of the atoms close to the surface. Here we describe how to use trapped atoms as a measurement device and analyze the performance and flexibility of the field sensor. We demonstrate microscopic magnetic imaging with simultaneous high spatial...

Hofstadter's butterfly energy spectrum of ultracold fermions on the two-dimensional triangular optical lattice

International Nuclear Information System (INIS)

Hou Jingmin; Lu Qingqing

2009-01-01

We study the energy spectrum of ultracold fermionic atoms on the two-dimensional triangular optical lattice subjected to a perpendicular effective magnetic field, which can be realized with laser beams. We derive the generalized Harper's equations and numerically solve them, then we obtain the Hofstadter's butterfly-like energy spectrum, which has a novel fractal structure. The observability of the Hofstadter's butterfly spectrum is also discussed

Interactions of Ultracold Impurity Particles with Bose-Einstein Condensates

Science.gov (United States)

2015-06-23

AFRL-OSR-VA-TR-2015-0141 INTERACTIONS OF ULTRACOLD IMPURITY PARTICLES WITH BOSE- EINSTEIN CONDENSATES Georg Raithel UNIVERSITY OF MICHIGAN Final...SUBTITLE Interactions of ultracold impurity particles with Bose- Einstein Condensates 5a. CONTRACT NUMBER FA9550-10-1-0453 5b. GRANT NUMBER 5c...Interactions of ultracold impurity particles with Bose- Einstein Condensates Contract/Grant #: FA9550-10-1-0453 Reporting Period: 8/15/2010 to 2/14

Cold and ultracold molecules: science, technology and applications

International Nuclear Information System (INIS)

Carr, Lincoln D; DeMille, David; Krems, Roman V; Ye Jun

2009-01-01

This paper presents a review of the current state of the art in the research field of cold and ultracold molecules. It serves as an introduction to the focus issue of New Journal of Physics on Cold and Ultracold Molecules and describes new prospects for fundamental research and technological development. Cold and ultracold molecules may revolutionize physical chemistry and few-body physics, provide techniques for probing new states of quantum matter, allow for precision measurements of both fundamental and applied interest, and enable quantum simulations of condensed-matter phenomena. Ultracold molecules offer promising applications such as new platforms for quantum computing, precise control of molecular dynamics, nanolithography and Bose-enhanced chemistry. The discussion is based on recent experimental and theoretical work and concludes with a summary of anticipated future directions and open questions in this rapidly expanding research field.

Gas lasers applied atomic collision physics, v.3

CERN Document Server

McDaniel, E W

1982-01-01

Applied Atomic Collision Physics, Volume 3: Gas Lasers describes the applications of atomic collision physics in the development of many types of gas lasers. Topics covered range from negative ion formation in gas lasers to high-pressure ion kinetics and relaxation of molecules exchanging vibrational energy. Ion-ion recombination in high-pressure plasmas is also discussed, along with electron-ion recombination in gas lasers and collision processes in chemical lasers.Comprised of 14 chapters, this volume begins with a historical summary of gas laser developments and an overview of the basic ope

Refined potentials for rare gas atom adsorption on rare gas and alkali-halide surfaces

Science.gov (United States)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1985-01-01

The utilization of models of interatomic potential for physical interaction to estimate the long range attractive potential for rare gases and ions is discussed. The long range attractive force is calculated in terms of the atomic dispersion properties. A data base of atomic dispersion parameters for rare gas atoms, alkali ion, and halogen ions is applied to the study of the repulsive core; the procedure for evaluating the repulsive core of ion interactions is described. The interaction of rare gas atoms on ideal rare gas solid and alkali-halide surfaces is analyzed; zero coverage absorption potentials are derived.

Development of indigenous laboratory scale gas atomizer for producing metal powders

International Nuclear Information System (INIS)

Khan, K.K.; Qasim, A.M.; Ahmed, P.

2011-01-01

Gas atomization is one of the methods for production of clean metal powders at relatively moderate cost. A laboratory scale gas atomizer was designed and fabricated indigenously to produce metal powders with a batch capacity of 500 g of copper (Cu). The design includes several features regarding fabrication and operation to provide optimum conditions for atomization. The inner diameter of atomizing chamber is 440 mm and its height is 1200 mm. The atomizing nozzle is of annular confined convergent type with an angle of 25 degree. Argon gas at desired pressure has been used for atomizing the metals to produce relatively clean powders. A provision has also been made to view the atomization process. The indigenous laboratory scale gas atomizer was used to produce tin (Sn) and copper (Cu) powders with different atomizing gas pressures ranging from 2 to 10 bar. The particle size of different powders produced ranges from 40 to 400 im. (author)

Optical Studies of Strong Coupling and Recombination in Ultracold Neutral Plasmas

International Nuclear Information System (INIS)

Killian, Thomas C.

2004-01-01

The ultracold atoms and plasmas research group at Rice University uses a combination of atomic and plasma physics techniques to create neutral plasmas that are orders of magnitude colder than have ever been studied before. Through this work, we probe the basic plasma physics of this exotic regime. During the past year, the major components of a new experiment were completed. We demonstrated a powerful new diagnostic, optical imaging of the plasma, which led to a paper that was published in Physical Review Letters. (Figure A, Phys. Rev. Lett. 92, 143001 (2004)) This was the central feature of my DOE Junior Faculty Award proposal. DOE funding has been used to support one postdoctoral researcher, multiple graduate students, the principle investigator, apparatus construction, and normal laboratory expenses

Analytical results for the time-dependent current density distribution of expanding ultracold gases after a sudden change of the confining potential

Science.gov (United States)

Boumaza, R.; Bencheikh, K.

2017-12-01

Using the so-called operator product expansion to lowest order, we extend the work in Campbell et al (2015 Phys. Rev. Lett 114 125302) by deriving a simple analytical expression for the long-time asymptotic one-body reduced density matrix during free expansion for a one-dimensional system of bosons with large atom number interacting through a repulsive delta potential initially confined by a potential well. This density matrix allows direct access to the momentum distribution and also to the mass current density. For initially confining power-law potentials we give explicit expressions, in the limits of very weak and very strong interaction, for the current density distributions during the free expansion. In the second part of the work we consider the expansion of ultracold gas from a confining harmonic trap to another harmonic trap with a different frequency. For the case of a quantum impenetrable gas of bosons (a Tonks-Girardeau gas) with a given atom number, we present an exact analytical expression for the mass current distribution (mass transport) after release from one harmonic trap to another harmonic trap. It is shown that, for a harmonically quenched Tonks-Girardeau gas, the current distribution is a suitable collective observable and under the weak quench regime, it exhibits oscillations at the same frequencies as those recently predicted for the peak momentum distribution in the breathing mode. The analysis is extended to other possible quenched systems.

Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

Science.gov (United States)

Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

1988-01-01

The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Hybrid quantum systems of ions and atoms

OpenAIRE

Sias, Carlo; Köhl, Michael

2014-01-01

In this chapter we review the progress in experiments with hybrid systems of trapped ions and ultracold neutral atoms. We give a theoretical overview over the atom-ion interactions in the cold regime and give a summary of the most important experimental results. We conclude with an overview of remaining open challenges and possible applications in hybrid quantum systems of ions and neutral atoms.

Physics with Ultracold and Thermal Neutron Beams

International Nuclear Information System (INIS)

None

2004-01-01

The final report is broken into 5 segments, reflecting research conclusions reached during specific time periods: 1991-1997, 1997-1999, 1999-2000, 2000-2001, and 2001-2002. The first part of the work reported was carried out at the 2 Mw research reactor of the Rhode Island Nuclaer Science Center (RJNSC). Chosen for study was the slow phase separation in mixtures of oil and water in the presence of a surfactant, and the structural features of an oil layer during the slow build-up from the gas phase. The results of these measurements, as well as studies of the capillary wave properties of oil/surfactant/water interfaces are described. The second part of the work was performed at the neutron reflection facilities of the Intennse Pulsed Neutron Source at Argonne and of the NBSR reactor at NIST. At Argonne, the uniaxial magnetic order of an Fe/CR superlattice was investigated, while the experiments at NIST studied the swelling behavior of ordered thin films of diblock copolymers when they were exposed to solvent vapors. The third part of the work was concerned with the storage properties of ultracold neturons in a trap. New experiments on spectral evolution during storage, using the UCN source of the Institut Laue-Langevin were able to be run. Subsequent periods focussed on the ultracold neutrons work, spin valve multilayer systems, and pseudo-partial wetting

Atomic rubidium, the workhorse of theoretical collision physics

NARCIS (Netherlands)

Verhaar, B.; van Kempen, E.; Kokkelmans, S.J.J.M.F.

2008-01-01

Since the first realizations of Bose-Einstein condensates in ultracold atomic gases in 1995, the 85Rb and 87Rb atomic species have acted as the workhorses of experimental developments in this field. Parallel to and partly preceding this work the same isotopes figured also as workhorses for

Damping of electron center-of-mass oscillation in ultracold plasmas

International Nuclear Information System (INIS)

Chen, Wei-Ting; Witte, Craig; Roberts, Jacob L.

2016-01-01

Applying a short electric field pulse to an ultracold plasma induces an electron plasma oscillation. This manifests itself as an oscillation of the electron center of mass around the ion center of mass in the ultracold plasma. In general, the oscillation can damp due to either collisionless or collisional mechanisms, or a combination of the both. To investigate the nature of oscillation damping in ultracold plasmas, we developed a molecular dynamics model of the ultracold plasma electrons. Through this model, we found that depending on the neutrality of the ultracold plasma and the size of an applied DC electric field, there are some parameter ranges where the damping is primarily collisional and some primarily collisionless. We conducted experiments to compare the measured damping rate with theory predictions and found them to be in good agreement. Extension of our measurements to different parameter ranges should enable studies for strong-coupling influence on electron-ion collision rates.

Atomic physics precise measurements and ultracold matter

CERN Document Server

Inguscio, Massimo

2013-01-01

Atomic Physics provides an expert guide to two spectacular new landscapes in physics: precision measurements, which have been revolutionized by the advent of the optical frequency comb, and atomic physics, which has been revolutionized by laser cooling. These advances are not incremental but transformative: they have generated a consilience between atomic and many-body physics, precipitated an explosion of scientific and technological applications, opened new areas of research, and attracted a brilliant generation of younger scientists. The research is advancing so rapidly, the barrage of applications is so dazzling, that students can be bewildered. For both students and experienced scientists, this book provides an invaluable description of basic principles, experimental methods, and scientific applications.

A compound parabolic concentrator as an ultracold neutron spectrometer

Energy Technology Data Exchange (ETDEWEB)

Hickerson, K.P., E-mail: hickerson@gmail.com; Filippone, B.W., E-mail: bradf@caltech.edu

2013-09-01

The design principles of nonimaging optics are applied to ultracold neutrons (UCN). In particular a vertical compound parabolic concentrator (CPC) that efficiently redirects UCN vertically into a bounded spatial volume where they have a maximum energy mga that depends only on the initial phase space cross sectional area πa{sup 2} creates a spectrometer which can be applied to neutron lifetime and gravitational quantum state experiments. -- Highlights: • Nonimaging optics is applied to ultracold neutrons. • A novel ultracold neutron spectrometer is discussed. • New uses may include a neutron lifetime experiment.

A compound parabolic concentrator as an ultracold neutron spectrometer

International Nuclear Information System (INIS)

Hickerson, K.P.; Filippone, B.W.

2013-01-01

The design principles of nonimaging optics are applied to ultracold neutrons (UCN). In particular a vertical compound parabolic concentrator (CPC) that efficiently redirects UCN vertically into a bounded spatial volume where they have a maximum energy mga that depends only on the initial phase space cross sectional area πa 2 creates a spectrometer which can be applied to neutron lifetime and gravitational quantum state experiments. -- Highlights: • Nonimaging optics is applied to ultracold neutrons. • A novel ultracold neutron spectrometer is discussed. • New uses may include a neutron lifetime experiment

Interaction of antihydrogen with ordinary atoms and solid surfaces

Energy Technology Data Exchange (ETDEWEB)

Froelich, Piotr, E-mail: piotr.froelich@kvac.uu.se; Voronin, Alexei [P.N. Lebedev Physical Institute (Russian Federation)

2012-12-15

The characteristic features of cold atom-antiatom collisions and antiatom-surface interactions are discussed and illustrated by the results for hydrogen-antihydrogen scattering and for quantum reflection of ultracold antihydrogen from a metallic surface. We discuss in some detail the case of spin-exchange in ultracold H-bar - H collisions, exposing the interplay of Coulombic, strong and dispersive forces, and demonstrating the sensitivity of the spin-exchange cross sections to hypothetical violations of Charge-Parity-Time (CPT) symmetry.

Pump-probe study of the formation of rubidium molecules by ultrafast photoassociation of ultracold atoms

Science.gov (United States)

McCabe, David J.; England, Duncan G.; Martay, Hugo E. L.; Friedman, Melissa E.; Petrovic, Jovana; Dimova, Emiliya; Chatel, Béatrice; Walmsley, Ian A.

2009-09-01

An experimental pump-probe study of the photoassociative creation of translationally ultracold rubidium molecules is presented together with numerical simulations of the process. The formation of loosely bound excited-state dimers is observed as a first step toward a fully coherent pump-dump approach to the stabilization of Rb2 into its lowest ground vibrational states. The population that contributes to the pump-probe process is characterized and found to be distinct from a background population of preassociated molecules.

Kinetics of heterogeneous nucleation of gas-atomized Sn-5 mass%Pb droplets

International Nuclear Information System (INIS)

Li Shu; Wu Ping; Zhou Wei; Ando, Teiichi

2008-01-01

A method for predicting the nucleation kinetics of gas-atomized droplets has been developed by combining models predicting the nucleation temperature of cooling droplets with a model simulating the droplet motion and cooling in gas atomization. Application to a Sn-5 mass%Pb alloy has yielded continuous-cooling transformation (CCT) diagrams for the heterogeneous droplet nucleation in helium gas atomization. Both internal nucleation caused by a catalyst present in the melt and surface nucleation caused by oxidation are considered. Droplets atomized at a high atomizing gas velocity get around surface oxidation and nucleate internally at high supercoolings. Low atomization gas velocities promote oxidation-catalyzed nucleation which leads to lower supercoolings. The developed method enables improved screening of atomized powders for critical applications where stringent control of powder microstructure is required

Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap

International Nuclear Information System (INIS)

Yi, W.; Duan, L.-M.

2006-01-01

We map out the detailed phase diagram of a trapped ultracold Fermi gas with population imbalance across a wide Feshbach resonance. We show that under the local density approximation, the properties of the atoms in any (anisotropic) harmonic traps are universally characterized by three dimensionless parameters: the normalized temperature, the dimensionless interaction strength, and the population imbalance. We then discuss the possible quantum phases in the trap, and quantitatively characterize their phase boundaries in various typical parameter regions

Interatomic interaction effects on second-order momentum correlations and Hong-Ou-Mandel interference of double-well-trapped ultracold fermionic atoms

Science.gov (United States)

Brandt, Benedikt B.; Yannouleas, Constantine; Landman, Uzi

2018-05-01

Identification and understanding of the evolution of interference patterns in two-particle momentum correlations as a function of the strength of interatomic interactions are important in explorations of the nature of quantum states of trapped particles. Together with the analysis of two-particle spatial correlations, they offer the prospect of uncovering fundamental symmetries and structure of correlated many-body states, as well as opening vistas into potential control and utilization of correlated quantum states as quantum-information resources. With the use of the second-order density matrix constructed via exact diagonalization of the microscopic Hamiltonian, and an analytic Hubbard-type model, we explore here the systematic evolution of characteristic interference patterns in the two-body momentum and spatial correlation maps of two entangled ultracold fermionic atoms in a double well, for the entire attractive- and repulsive-interaction range. We uncover quantum-statistics-governed bunching and antibunching, as well as interaction-dependent interference patterns, in the ground and excited states, and interpret our results in light of the Hong-Ou-Mandel interference physics, widely exploited in photon indistinguishability testing and quantum-information science.

Ab initio theory of noble gas atoms in bcc transition metals.

Science.gov (United States)

Jiang, Chao; Zhang, Yongfeng; Gao, Yipeng; Gan, Jian

2018-06-18

Systematic ab initio calculations based on density functional theory have been performed to gain fundamental understanding of the interactions between noble gas atoms (He, Ne, Ar and Kr) and bcc transition metals in groups 5B (V, Nb and Ta), 6B (Cr, Mo and W) and 8B (Fe). Our charge density analysis indicates that the strong polarization of nearest-neighbor metal atoms by noble gas interstitials is the electronic origin of their high formation energies. Such polarization becomes more significant with an increasing gas atom size and interstitial charge density in the host bcc metal, which explains the similar trend followed by the unrelaxed formation energies of noble gas interstitials. Upon allowing for local relaxation, nearby metal atoms move farther away from gas interstitials in order to decrease polarization, albeit at the expense of increasing the elastic strain energy. Such atomic relaxation is found to play an important role in governing both the energetics and site preference of noble gas atoms in bcc metals. Our most notable finding is that the fully relaxed formation energies of noble gas interstitials are strongly correlated with the elastic shear modulus of the bcc metal, and the physical origin of this unexpected correlation has been elucidated by our theoretical analysis based on the effective-medium theory. The kinetic behavior of noble gas atoms and their interaction with pre-existing vacancies in bcc transition metals have also been discussed in this work.

Making ultracold molecules in a two color pump-dump photoassociation scheme using chirped pulses

OpenAIRE

Koch, Christiane P.; Luc-Koenig, Eliane; Masnou-Seeuws, Françoise

2005-01-01

This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A {\\bf 70}, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in t...

Using Three-Body Recombination to Extract Electron Temperatures of Ultracold Plasmas

International Nuclear Information System (INIS)

Fletcher, R. S.; Zhang, X. L.; Rolston, S. L.

2007-01-01

Three-body recombination, an important collisional process in plasmas, increases dramatically at low electron temperatures, with an accepted scaling of T e -9/2 . We measure three-body recombination in an ultracold neutral xenon plasma by detecting recombination-created Rydberg atoms using a microwave-ionization technique. With the accepted theory (expected to be applicable for weakly coupled plasmas) and our measured rates, we extract the plasma temperatures, which are in reasonable agreement with previous measurements early in the plasma lifetime. The resulting electron temperatures indicate that the plasma continues to cool to temperatures below 1 K

Many-body physics using cold atoms

Science.gov (United States)

Sundar, Bhuvanesh

Advances in experiments on dilute ultracold atomic gases have given us access to highly tunable quantum systems. In particular, there have been substantial improvements in achieving different kinds of interaction between atoms. As a result, utracold atomic gases oer an ideal platform to simulate many-body phenomena in condensed matter physics, and engineer other novel phenomena that are a result of the exotic interactions produced between atoms. In this dissertation, I present a series of studies that explore the physics of dilute ultracold atomic gases in different settings. In each setting, I explore a different form of the inter-particle interaction. Motivated by experiments which induce artificial spin-orbit coupling for cold fermions, I explore this system in my first project. In this project, I propose a method to perform universal quantum computation using the excitations of interacting spin-orbit coupled fermions, in which effective p-wave interactions lead to the formation of a topological superfluid. Motivated by experiments which explore the physics of exotic interactions between atoms trapped inside optical cavities, I explore this system in a second project. I calculate the phase diagram of lattice bosons trapped in an optical cavity, where the cavity modes mediates effective global range checkerboard interactions between the atoms. I compare this phase diagram with one that was recently measured experimentally. In two other projects, I explore quantum simulation of condensed matter phenomena due to spin-dependent interactions between particles. I propose a method to produce tunable spin-dependent interactions between atoms, using an optical Feshbach resonance. In one project, I use these spin-dependent interactions in an ultracold Bose-Fermi system, and propose a method to produce the Kondo model. I propose an experiment to directly observe the Kondo effect in this system. In another project, I propose using lattice bosons with a large hyperfine spin

High precision optical spectroscopy and quantum state selected photodissociation of ultracold 88Sr2 molecules in an optical lattice

Science.gov (United States)

McDonald, Mickey

2017-04-01

Over the past several decades, rapid progress has been made toward the accurate characterization and control of atoms, epitomized by the ever-increasing accuracy and precision of optical atomic lattice clocks. Extending this progress to molecules will have exciting implications for chemistry, condensed matter physics, and precision tests of physics beyond the Standard Model. My thesis describes work performed over the past six years to establish the state of the art in manipulation and quantum control of ultracold molecules. We describe a thorough set of measurements characterizing the rovibrational structure of weakly bound 88Sr2 molecules from several different perspectives, including determinations of binding energies; linear, quadratic, and higher order Zeeman shifts; transition strengths between bound states; and lifetimes of narrow subradiant states. Finally, we discuss measurements of photofragment angular distributions produced by photodissociation of molecules in single quantum states, leading to an exploration of quantum-state-resolved ultracold chemistry. The images of exploding photofragments produced in these studies exhibit dramatic interference effects and strongly violate semiclassical predictions, instead requiring a fully quantum mechanical description.

Effects of gas liquid ratio on the atomization characteristics of gas-liquid swirl coaxial injectors

Science.gov (United States)

Kang, Zhongtao; Li, Qinglian; Zhang, Jiaqi; Cheng, Peng

2018-05-01

To understand the atomization characteristics and atomization mechanism of the gas-liquid swirl coaxial (GLSC) injector, a back-lighting photography technique has been employed to capture the instantaneous spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of gas liquid ratio (GLR) on the spray pattern, Sauter mean diameter (SMD), diameter-velocity distribution and mass flow rate distribution were analyzed and discussed. The results show that the atomization of the GLSC injector is dominated by the film breakup when the GLR is small, and violent gas-liquid interaction when the GLR is large enough. The film breakup dominated spray can be divided into gas acceleration region and film breakup region while the violent gas-liquid interaction dominated spray can be divided into the gas acceleration region, violent gas-liquid interaction region and big droplets breakup region. The atomization characteristics of the GLSC injector is significantly influenced by the GLR. From the point of atomization performance, the increase of GLR has positive effects. It decreases the global Sauter mean diameter (GSMD) and varies the SMD distribution from a hollow cone shape (GLR = 0) to an inverted V shape, and finally slanted N shape. However, from the point of spatial distribution, the increase of GLR has negative effects, because the mass flow rate distribution becomes more nonuniform.

A quantum trampoline for ultra-cold atoms

Science.gov (United States)

Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Bordé, Ch. J.; Aspect, A.; Bourdel, T.; Bouyer, P.

2010-01-01

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. This scheme permits simultaneously the compensation of gravity and coherent splitting/recombination of the matter waves. It results in high-contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We characterize our atom interferometer and use it to measure the acceleration of gravity.

Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

Science.gov (United States)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1986-01-01

The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Spatial noise correlations of a chain of ultracold fermions: A numerical study

International Nuclear Information System (INIS)

Luescher, Andreas; Laeuchli, Andreas M.; Noack, Reinhard M.

2007-01-01

We present a numerical study of noise correlations, i.e., density-density correlations in momentum space, in the extended fermionic Hubbard model in one dimension. In experiments with ultracold atoms, these noise correlations can be extracted from time-of-flight images of the expanding cloud. Using the density-matrix renormalization group method to investigate the Hubbard model at various fillings and interactions, we confirm that the noise correlations contain full information on the most important fluctuations present in the system. We point out the importance of the sum rules fulfilled by the noise correlations and show that they yield nonsingular structures beyond the predictions of bosonization approaches. Noise correlations can thus serve as a universal probe of order and can be used to characterize the many-body states of cold atoms in optical lattices

Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system

Science.gov (United States)

Jöckel, Andreas; Faber, Aline; Kampschulte, Tobias; Korppi, Maria; Rakher, Matthew T.; Treutlein, Philipp

2015-01-01

Sympathetic cooling with ultracold atoms and atomic ions enables ultralow temperatures in systems where direct laser or evaporative cooling is not possible. It has so far been limited to the cooling of other microscopic particles, with masses up to 90 times larger than that of the coolant atom. Here, we use ultracold atoms to sympathetically cool the vibrations of a Si3N4 nanomembrane, the mass of which exceeds that of the atomic ensemble by a factor of 1010. The coupling of atomic and membrane vibrations is mediated by laser light over a macroscopic distance and is enhanced by placing the membrane in an optical cavity. We observe cooling of the membrane vibrations from room temperature to 650 ± 230 mK, exploiting the large atom-membrane cooperativity of our hybrid optomechanical system. With technical improvements, our scheme could provide ground-state cooling and quantum control of low-frequency oscillators such as nanomembranes or levitated nanoparticles, in a regime where purely optomechanical techniques cannot reach the ground state.

General Atomic's radioactive gas recovery system

International Nuclear Information System (INIS)

Mahn, J.A.; Perry, C.A.

1975-01-01

General Atomic Company has developed a Radioactive Gas Recovery System for the HTGR which separates, for purposes of retention, the radioactive components from the non-radioactive reactor plant waste gases. This provides the capability for reducing to an insignificant level the amount of radioactivity released from the gas waste system to the atmosphere--a most significant improvement in reducing total activity release to the environment. (U.S.)

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus

International Nuclear Information System (INIS)

Teichmann, M.

2007-09-01

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between 6 Li and 7 Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules

Science.gov (United States)

Huang, Jiayu; Liu, Shu; Zhang, Dong H.; Krems, Roman V.

2018-04-01

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Cucurbit[6]uril: A Possible Host for Noble Gas Atoms.

Science.gov (United States)

Pan, Sudip; Mandal, Subhajit; Chattaraj, Pratim K

2015-08-27

Density functional and ab initio molecular dynamics studies are carried out to investigate the stability of noble gas encapsulated cucurbit[6]uril (CB[6]) systems. Interaction energy, dissociation energy and dissociation enthalpy are calculated to understand the efficacy of CB[6] in encapsulating noble gas atoms. CB[6] could encapsulate up to three Ne atoms having dissociation energy (zero-point energy corrected) in the range of 3.4-4.1 kcal/mol, whereas due to larger size, only one Ar or Kr atom encapsulated analogues would be viable. The dissociation energy value for the second Ar atom is only 1.0 kcal/mol. On the other hand, the same for the second Kr is -0.5 kcal/mol, implying the instability of the system. The noble gas dissociation processes are endothermic in nature, which increases gradually along Ne to Kr. Kr encapsulated analogue is found to be viable at room temperature. However, low temperature is needed for Ne and Ar encapsulated analogues. The temperature-pressure phase diagram highlights the region in which association and dissociation processes of Kr@CB[6] would be favorable. At ambient temperature and pressure, CB[6] may be used as an effective noble gas carrier. Wiberg bond indices, noncovalent interaction indices, electron density, and energy decomposition analyses are used to explore the nature of interaction between noble gas atoms and CB[6]. Dispersion interaction is found to be the most important term in the attraction energy. Ne and Ar atoms in one Ng entrapped analogue are found to stay inside the cavity of CB[6] throughout the simulation at 298 K. However, during simulation Ng2 units in Ng2@CB[6] flip toward the open faces of CB[6]. After 1 ps, one Ne atom of Ne3@CB[6] almost reaches the open face keeping other two Ne atoms inside. At lower temperature (77 K), all the Ng atoms in Ngn@CB[6] remain well inside the cavity of CB[6] throughout the simulation time (1 ps).

Resonance ionization spectroscopy: Counting noble gas atoms

International Nuclear Information System (INIS)

Hurst, G.S.; Payne, M.G.; Chen, C.H.; Willis, R.D.; Lehmann, B.E.; Kramer, S.D.

1981-01-01

The purpose of this paper is to describe new work on the counting of noble gas atoms, using lasers for the selective ionization and detectors for counting individual particles (electrons or positive ions). When positive ions are counted, various kinds of mass analyzers (magnetic, quadrupole, or time-of-flight) can be incorporated to provide A selectivity. We show that a variety of interesting and important applications can be made with atom-counting techniques which are both atomic number (Z) and mass number (A) selective. (orig./FKS)

Detection of gas atoms with carbon nanotubes

Science.gov (United States)

Arash, B.; Wang, Q.

2013-01-01

Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

Atomic Quantum Simulations of Abelian and non-Abelian Gauge Theories

CERN Multimedia

CERN. Geneva

2014-01-01

Using a Fermi-Bose mixture of ultra-cold atoms in an optical lattice, in a collaboration of atomic and particle physicists, we have constructed a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum link models which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows investigations of string breaking as well as the real-time evolution after a quench in gauge theories, which are inaccessible to classical simulation methods. Similarly, using ultracold alkaline-earth atoms in optical lattices, we have constructed a quantum simulator for U(N) and SU(N) lattice gauge theories with fermionic matter based on quantum link models. These systems share qualitative features with QCD, including chiral symmetry breaking and restoration at non-zero temperature or baryon density. Unlike classical simulations, a quantum ...

Generating a picokelvin ultracold atomic ensemble in microgravity

International Nuclear Information System (INIS)

Wang, Lu; Ma, Zhao-Yuan; Zhang, Peng; Chen, Xu-Zong

2013-01-01

Applying the direct Monte Carlo simulation (DSMC) method developed for a cold atom system, we study the evaporative cooling process in tilted optical dipole traps with a magnetic field gradient-induced over-levitation or merely a gravitational force. We propose a two-stage decomposed evaporative cooling process in a microgravity environment, and suggest that quantum degeneracy can be obtained at a few picokelvins with several thousand atoms. (paper)

Role of Feshbach resonances in enhancing the production of deeply bound ultracold LiRb molecules with laser pulses

Science.gov (United States)

Gacesa, Marko; Ghosal, Subhas; Côté, Robin

2010-03-01

We investigate the possibility of forming deeply bound LiRb molecules in a two-color photoassociation experiment. Ultracold ^6Li and ^87Rb atoms colliding in the vicinity of a magnetic Feshbach resonance are photoassociated into an excited electronic state. A wavepacket is then formed by exciting a few vibrational levels of the excited state and allowed to propagate. We calculate the time-dependent overlaps between the wave packet and the lowest vibrational levels of the ground state. After the optimal overlap is obtained we use the second laser pulse to dump the wave packet and efficiently populate the deeply bound ro-vibrational levels of ^6Li^87Rb in the ground state. The resulting combination of Feshbach-optimized photoassociation (FOPA) with the time-dependent pump-dump approach will produce a large number of stable ultracold molecules in the ground state. This technique is general and applicable to other systems.

SO(3) "Nuclear Physics" with ultracold Gases

Science.gov (United States)

Rico, E.; Dalmonte, M.; Zoller, P.; Banerjee, D.; Bögli, M.; Stebler, P.; Wiese, U.-J.

2018-06-01

An ab initio calculation of nuclear physics from Quantum Chromodynamics (QCD), the fundamental SU(3) gauge theory of the strong interaction, remains an outstanding challenge. Here, we discuss the emergence of key elements of nuclear physics using an SO(3) lattice gauge theory as a toy model for QCD. We show that this model is accessible to state-of-the-art quantum simulation experiments with ultracold atoms in an optical lattice. First, we demonstrate that our model shares characteristic many-body features with QCD, such as the spontaneous breakdown of chiral symmetry, its restoration at finite baryon density, as well as the existence of few-body bound states. Then we show that in the one-dimensional case, the dynamics in the gauge invariant sector can be encoded as a spin S = 3/2 Heisenberg model, i.e., as quantum magnetism, which has a natural realization with bosonic mixtures in optical lattices, and thus sheds light on the connection between non-Abelian gauge theories and quantum magnetism.

Anisotropic relaxation dynamics in a dipolar Fermi gas driven out of equilibrium

DEFF Research Database (Denmark)

Aikawa, K.; Frisch, A.; Mark, M.

2014-01-01

We report on the observation of a large anisotropy in the rethermalization dynamics of an ultracold dipolar Fermi gas driven out of equilibrium. Our system consists of an ultracold sample of strongly magnetic $^{167}$Er fermions, spin-polarized in the lowest Zeeman sublevel. In this system, elastic...

High-precision multiband spectroscopy of ultracold fermions in a nonseparable optical lattice

Science.gov (United States)

Fläschner, Nick; Tarnowski, Matthias; Rem, Benno S.; Vogel, Dominik; Sengstock, Klaus; Weitenberg, Christof

2018-05-01

Spectroscopic tools are fundamental for the understanding of complex quantum systems. Here, we demonstrate high-precision multiband spectroscopy in a graphenelike lattice using ultracold fermionic atoms. From the measured band structure, we characterize the underlying lattice potential with a relative error of 1.2 ×10-3 . Such a precise characterization of complex lattice potentials is an important step towards precision measurements of quantum many-body systems. Furthermore, we explain the excitation strengths into different bands with a model and experimentally study their dependency on the symmetry of the perturbation operator. This insight suggests the excitation strengths as a suitable observable for interaction effects on the eigenstates.

Gas Atomization of Aluminium Melts: Comparison of Analytical Models

Directory of Open Access Journals (Sweden)

Georgios Antipas

2012-06-01

Full Text Available A number of analytical models predicting the size distribution of particles during atomization of Al-based alloys by N2, He and Ar gases were compared. Simulations of liquid break up in a close coupled atomizer revealed that the finer particles are located near the center of the spray cone. Increasing gas injection pressures led to an overall reduction of particle diameters and caused a migration of the larger powder particles towards the outer boundary of the flow. At sufficiently high gas pressures the spray became monodisperse. The models also indicated that there is a minimum achievable mean diameter for any melt/gas system.

Exotic pairing in 1D spin-3/2 atomic gases with SO(4 symmetry

Directory of Open Access Journals (Sweden)

Yuzhu Jiang

2015-06-01

Full Text Available Tuning interactions in the spin singlet and quintet channels of two colliding atoms could change the symmetry of the one-dimensional spin-3/2 fermionic systems of ultracold atoms while preserving the integrability. Here we find a novel SO(4 symmetry integrable point in the spin-3/2 Fermi gas and derive the exact solution of the model using the Bethe ansatz. In contrast to the model with SU(4 and SO(5 symmetries, the present model with SO(4 symmetry preserves spin singlet and quintet Cooper pairs in two sets of SU(2⊗SU(2 spin subspaces. We obtain full phase diagrams, including the Fulde–Ferrel–Larkin–Ovchinnikov like pair correlations, spin excitations and quantum criticality through the generalized Yang–Yang thermodynamic equations. In particular, various correlation functions are calculated by using finite-size corrections in the frame work of conformal field theory. Moreover, within the local density approximation, we further find that spin singlet and quintet pairs form subtle multiple shell structures in density profiles of the trapped gas.

Trapped atoms along nanophotonic resonators

Science.gov (United States)

Fields, Brian; Kim, May; Chang, Tzu-Han; Hung, Chen-Lung

2017-04-01

Many-body systems subject to long-range interactions have remained a very challenging topic experimentally. Ultracold atoms trapped in extreme proximity to the surface of nanophotonic structures provides a dynamic system combining the strong atom-atom interactions mediated by guided mode photons with the exquisite control implemented with trapped atom systems. The hybrid system promises pair-wise tunability of long-range interactions between atomic pseudo spins, allowing studies of quantum magnetism extending far beyond nearest neighbor interactions. In this talk, we will discuss our current status developing high quality nanophotonic ring resonators, engineered on CMOS compatible optical chips with integrated nanostructures that, in combination with a side illuminating beam, can realize stable atom traps approximately 100nm above the surface. We will report on our progress towards loading arrays of cold atoms near the surface of these structures and studying atom-atom interaction mediated by photons with high cooperativity.

Radio frequency selective addressing of localized atoms in a periodic potential

International Nuclear Information System (INIS)

Ott, H.; De Mirandes, E.; Ferlaino, F.; Roati, G.; Tuerck, V.; Modugno, G.; Inguscio, M.

2004-01-01

We study the localization and addressability of ultracold atoms in a combined parabolic and periodic potential. Such a potential supports the existence of localized stationary states and we show that applying a radio frequency field allows us to selectively address atoms in these states. This method is used to measure the energy and momentum distribution of the atoms in the localized states. We also discuss possible extensions of this scheme to address and manipulate atoms in single lattice sites

An approach to spin-resolved molecular gas microscopy

Science.gov (United States)

Covey, Jacob P.; De Marco, Luigi; Acevedo, Óscar L.; Rey, Ana Maria; Ye, Jun

2018-04-01

Ultracold polar molecules are an ideal platform for studying many-body physics with long-range dipolar interactions. Experiments in this field have progressed enormously, and several groups are pursuing advanced apparatus for manipulation of molecules with electric fields as well as single-atom-resolved in situ detection. Such detection has become ubiquitous for atoms in optical lattices and tweezer arrays, but has yet to be demonstrated for ultracold polar molecules. Here we present a proposal for the implementation of site-resolved microscopy for polar molecules, and specifically discuss a technique for spin-resolved molecular detection. We use numerical simulation of spin dynamics of lattice-confined polar molecules to show how such a scheme would be of utility in a spin-diffusion experiment.

Cold atoms in a cryogenic environment

International Nuclear Information System (INIS)

Haslinger, S.

2011-01-01

The idea of quantum information processing attracts increasingly interest, where a complex collection of quantum objects and quantum bits are employed to find the ideal building blocks for quantum information systems. Hybrid quantum systems are therefore promising objects as they countervail the particular drawbacks of single quantum objects. Based on superconducting resonator technology, microwave coplanar waveguides provide a well suited interconnection for photons and solid-state quantum bits (qubits), extensively investigated in recent years. Since a quantum memory is presently missing in those electrical accessible circuit cavity quantum devices, connecting the fast processing in a solid sate device to the exceptional long coherence times in atomic ensembles, the presented work is focused to establish the technological foundations for the hybridization of such quantum systems. The microwave photons stored in a superconducting high finesse microwave resonator are therefore an ideal connection between the atom and the solid state quantum world. In the last decade, the miniaturization and integration of quantum optics and atomic physics manipulation techniques on to a single chip was successfully established. Such atom chips are capable of detailed quantum manipulation of ultra-cold atoms and provide a versatile platform to combine the manipulation techniques from atomic physics with the capability of nano-fabrication. In recent years several experiments succeeded in realization of superconducting atom chips in cryogenic environments which opens the road for integrating super-conductive microwave resonators to magnetically couple an atomic ensemble to photons stored in the coplanar high finesse cavity. This thesis presents the concept, design and experimental setup of two approaches to establish an atomic ensemble of rubidium atoms inside a cryogenic environment, based on an Electron beam driven alkali metal atom source for loading a magneto optical trap in a

Stability of gas atomized reactive powders through multiple step in-situ passivation

Science.gov (United States)

Anderson, Iver E.; Steinmetz, Andrew D.; Byrd, David J.

2017-05-16

A method for gas atomization of oxygen-reactive reactive metals and alloys wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a protective reaction film on the atomized particles. The present invention is especially useful for making highly pyrophoric reactive metal or alloy atomized powders, such as atomized magnesium and magnesium alloy powders. The gaseous reactive species (agents) are introduced into the atomization spray chamber at locations downstream of a gas atomizing nozzle as determined by the desired powder or particle temperature for the reactions and the desired thickness of the reaction film.

The charge imbalance in ultracold plasmas

International Nuclear Information System (INIS)

Chen, Tianxing; Lu, Ronghua; Guo, Li; Han, Shensheng

2016-01-01

Ultracold plasmas are regarded as quasineutral but not strictly neutral. The results of charge imbalance in the expansion of ultracold plasmas are reported. The calculations are performed by a full molecular-dynamics simulation. The details of the electron velocity distributions are calculated without the assumption of electron global thermal equilibrium and Boltzmann distribution. Spontaneous evolutions of the charge imbalance from the initial states with perfect neutrality are given in the simulations. The expansion of outer plasma slows down with the charge imbalance. The influences of plasma size and parameters on the charge imbalance are discussed. The radial profiles of electron temperature are given for the first time, and the self-similar expansion can still occur even if there is no global thermal equilibrium. The electron disorder induced heating is also found in the simulation.

The charge imbalance in ultracold plasmas

Energy Technology Data Exchange (ETDEWEB)

Chen, Tianxing; Lu, Ronghua, E-mail: lurh@siom.ac.cn; Guo, Li; Han, Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2016-09-15

Ultracold plasmas are regarded as quasineutral but not strictly neutral. The results of charge imbalance in the expansion of ultracold plasmas are reported. The calculations are performed by a full molecular-dynamics simulation. The details of the electron velocity distributions are calculated without the assumption of electron global thermal equilibrium and Boltzmann distribution. Spontaneous evolutions of the charge imbalance from the initial states with perfect neutrality are given in the simulations. The expansion of outer plasma slows down with the charge imbalance. The influences of plasma size and parameters on the charge imbalance are discussed. The radial profiles of electron temperature are given for the first time, and the self-similar expansion can still occur even if there is no global thermal equilibrium. The electron disorder induced heating is also found in the simulation.

Visualization of Atomization Gas Flow and Melt Break-up Effects in Response to Nozzle Design

Energy Technology Data Exchange (ETDEWEB)

Anderson, Iver; Rieken, Joel; Meyer, John; Byrd, David; Heidloff, Andy

2011-04-01

Both powder particle size control and efficient use of gas flow energy are highly prized goals for gas atomization of metal and alloy powder to minimize off-size powder inventory (or 'reverb') and excessive gas consumption. Recent progress in the design of close-coupled gas atomization nozzles and the water model simulation of melt feed tubes were coupled with previous results from several types of gas flow characterization methods, e.g., aspiration measurements and gas flow visualization, to make progress toward these goals. Size distribution analysis and high speed video recordings of gas atomization reaction synthesis (GARS) experiments on special ferritic stainless steel alloy powders with an Ar+O{sub 2} gas mixture were performed to investigate the operating mechanisms and possible advantages of several melt flow tube modifications with one specific gas atomization nozzle. In this study, close-coupled gas atomization under closed wake gas flow conditions was demonstrated to produce large yields of ultrafine (dia.<20 {mu}m) powders (up to 32%) with moderate standard deviations (1.62 to 1.99). The increased yield of fine powders is consistent with the dual atomization mechanisms of closed wake gas flow patterns in the near-field of the melt orifice. Enhanced size control by stabilized pre-filming of the melt with a slotted trumpet bell pour tube was not clearly demonstrated in the current experiments, perhaps confounded by the influence of the melt oxidation reaction that occurred simultaneously with the atomization process. For this GARS variation of close-coupled gas atomization, it may be best to utilize the straight cylindrical pour tube and closed wake operation of an atomization nozzle with higher gas mass flow to promote the maximum yields of ultrafine powders that are preferred for the oxide dispersion strengthened alloys made from these powders.

Production and spectroscopy of ultracold YbRb* molecules

International Nuclear Information System (INIS)

Nemitz, Nils

2008-11-01

This thesis describes the formation of electronically excited but translationally cold molecules formed from rubidium atoms and two isotopes of ytterbium ( 176 Yb and 174 Yb) by means of photoassociation. The experiments were performed in a combined MOT with 10 9 rubidium atoms and 2.10 6 ytterbium atoms at temperatures of less than 1 mK. Photoassociation lines were found by trap loss spectroscopy throughout a wavelength range of 2 nm near the 795 nm D1 transition in rubidium. The majority of lines belong to two vibrational series in the excited YbRb * molecule, converging on a system of a ground state ytterbium atom and an excited rubidium atom. The strong variation of line strength between different vibrational lines is explained through the Franck-Condon principle. An improved version of the Leroy-Bernstein equation was used to extract the leading dispersion coefficient of the potential from the vibrational progression. Most of the observed lines show a resolved rotational structure as expected from a basic quantum mechanical model. The series terminates with the third or forth rotational component due to the ground state centrifugal barrier.The measured rotational constants agree very well with calculations based on the C 6 coefficient. The discovery of a splitting of the rotational components into subcomponents indicates an uncommon angular momentum coupling described by Hund's case. Variations in the depth of the subcomponents indicates a similar splitting in the ground state, with the energies of the substates based on the alignment of the rubidium atom's magnetic dipole moment relative to the angular momentum carried by an approaching ytterbium atom. This creates an additional ground state barrier, partially suppressing some of the subcomponents. Using a rate equation model developed for this purpose, a maximum formation rate of 2.5.10 6 molecules per second was calculated over the volume of the entire trap. The work presented here is an important step on

Exploiting Universality in Atoms with Large Scattering Lengths

International Nuclear Information System (INIS)

Braaten, Eric

2012-01-01

The focus of this research project was atoms with scattering lengths that are large compared to the range of their interactions and which therefore exhibit universal behavior at sufficiently low energies. Recent dramatic advances in cooling atoms and in manipulating their scattering lengths have made this phenomenon of practical importance for controlling ultracold atoms and molecules. This research project was aimed at developing a systematically improvable method for calculating few-body observables for atoms with large scattering lengths starting from the universal results as a first approximation. Significant progress towards this goal was made during the five years of the project.

Quantum information entropies of ultracold atomic gases in a ...

Indian Academy of Sciences (India)

The position and momentum space information entropies of weakly interacting trapped atomic Bose–Einstein condensates and spin-polarized trapped atomic Fermi gases at absolute zero temperature are evaluated. We find that sum of the position and momentum space information entropies of these quantum systems ...

Characterization of a scintillating lithium glass ultra-cold neutron detector

Energy Technology Data Exchange (ETDEWEB)

Jamieson, B.; Rebenitsch, L.A.; Hansen-Romu, S.; Mammei, R.; Martin, J.W. [University of Winnipeg, Department of Physics, Winnipeg (Canada); Lauss, B. [Paul Scherrer Institute, Laboratory for Particle Physics, Villigen (Switzerland); Lindner, T. [TRIUMF, Vancouver (Canada); University of Winnipeg, Department of Physics, Winnipeg (Canada); Pierre, E. [TRIUMF, Vancouver (Canada); Osaka University, Research Centre for Nuclear Physics, Osaka (Japan)

2017-01-15

A {sup 6}Li-glass-based scintillation detector developed for the TRIUMF neutron electric dipole moment experiment was characterized using the ultra-cold neutron source at the Paul Scherrer Institute (PSI). The data acquisition system for this detector was demonstrated to perform well at rejecting backgrounds. An estimate of the absolute efficiency of background rejection of 99.7±0.1% is made. For variable ultra-cold neutron rate (varying from < 1 kHz to approx. 100 kHz per channel) and background rate seen at the Paul Scherrer Institute, we estimate that the absolute detector efficiency is 89.7{sup +1.3}{sub -1.9}%. Finally a comparison with a commercial Cascade detector was performed for a specific setup at the West-2 beamline of the ultra-cold neutron source at PSI. (orig.)

A momentum filter for atomic gas

International Nuclear Information System (INIS)

Xiong, Wei; Zhou, Xiaoji; Yue, Xuguang; Zhai, Yueyang; Chen, Xuzong

2013-01-01

We propose and demonstrate a momentum filter for atomic gas-based on a designed Talbot–Lau interferometer. It consists of two identical optical standing-wave pulses separated by a delay equal to odd multiples of the half Talbot time. The one-dimensional momentum width along the long direction of a cigar-shaped condensate is rapidly and greatly purified to a minimum, which corresponds to the ground state energy of the confining trap in our experiment. We find good agreement between theoretical analysis and experimental results. The filter is also effective for non-condensed cold atoms and could be applied widely. (paper)

Exotic superfluidity and pairing phenomena in atomic Fermi gases in mixed dimensions.

Science.gov (United States)

Zhang, Leifeng; Che, Yanming; Wang, Jibiao; Chen, Qijin

2017-10-11

Atomic Fermi gases have been an ideal platform for simulating conventional and engineering exotic physical systems owing to their multiple tunable control parameters. Here we investigate the effects of mixed dimensionality on the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas with a short-range pairing interaction, while one component is confined on a one-dimensional (1D) optical lattice whereas the other is in a homogeneous 3D continuum. We study the phase diagram and the pseudogap phenomena throughout the entire BCS-BEC crossover, using a pairing fluctuation theory. We find that the effective dimensionality of the non-interacting lattice component can evolve from quasi-3D to quasi-1D, leading to strong Fermi surface mismatch. Upon pairing, the system becomes effectively quasi-two dimensional in the BEC regime. The behavior of T c bears similarity to that of a regular 3D population imbalanced Fermi gas, but with a more drastic departure from the regular 3D balanced case, featuring both intermediate temperature superfluidity and possible pair density wave ground state. Unlike a simple 1D optical lattice case, T c in the mixed dimensions has a constant BEC asymptote.

Universal Behavior of Pair Correlations in a Strongly Interacting Fermi Gas

International Nuclear Information System (INIS)

Kuhnle, E. D.; Hu, H.; Liu, X.-J.; Dyke, P.; Mark, M.; Drummond, P. D.; Hannaford, P.; Vale, C. J.

2010-01-01

We show that short-range pair correlations in a strongly interacting Fermi gas follow a simple universal law described by Tan's relations. This is achieved through measurements of the static structure factor which displays a universal scaling proportional to the ratio of Tan's contact to the momentum C/q. Bragg spectroscopy of ultracold 6 Li atoms from a periodic optical potential is used to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We calibrate our Bragg spectra using the f-sum rule, which is found to improve the accuracy of the structure factor measurement.

Ultracold and very cold neutron facility in KUR

International Nuclear Information System (INIS)

Kawabata, Yuji; Utsuro, Masahiko

1992-01-01

The present status of the ultracold and very cold neutron facility installed in the Kyoto University Reactor (KUR) is described in this presentation. It consists of a VCN (very cold neutrons) guide tube, a VCN bender and a supermirror neutron turbine. The guide tube extracts VCN from a liquid deuterium cold neutron source in a graphite thermal column and the neutron turbine converts VCN to UCN (ultracold neutrons). As for the utilization of the present facility, VCN radiography and an UCN gravity spectrometer are shown for the practical examples of the research with VCN and UCN. (author)

Influence of electron evaporative cooling on ultracold plasma expansion

International Nuclear Information System (INIS)

Wilson, Truman; Chen, Wei-Ting; Roberts, Jacob

2013-01-01

The expansion of ultracold neutral plasmas (UCP) is driven primarily by the thermal pressure of the electron component and is therefore sensitive to the electron temperature. For typical UCP spatial extents, evaporative cooling has a significant influence on the UCP expansion rate at lower densities (less than 10 8 /cm 3 ). We studied the effect of electron evaporation in this density range. Owing to the low density, the effects of three-body recombination were negligible. We modeled the expansion by taking into account the change in electron temperature owing to evaporation as well as adiabatic expansion and found good agreement with our data. We also developed a simple model for initial evaporation over a range of ultracold plasma densities, sizes, and electron temperatures to determine over what parameter range electron evaporation is expected to have a significant effect. We also report on a signal calibration technique, which relates the signal at our detector to the total number of ions and electrons in the ultracold plasma

xGASS: total cold gas scaling relations and molecular-to-atomic gas ratios of galaxies in the local Universe

Science.gov (United States)

Catinella, Barbara; Saintonge, Amélie; Janowiecki, Steven; Cortese, Luca; Davé, Romeel; Lemonias, Jenna J.; Cooper, Andrew P.; Schiminovich, David; Hummels, Cameron B.; Fabello, Silvia; Geréb, Katinka; Kilborn, Virginia; Wang, Jing

2018-05-01

We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic hydrogen (H I) gas content of 1179 galaxies selected only by stellar mass (M⋆ = 109-1011.5 M⊙) and redshift (0.01 new Arecibo observations of 208 galaxies, for which we release catalogues and H I spectra. In addition to extending the GASS H I scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, Rmol, for the subset of 477 galaxies observed with the IRAM 30 m telescope. We find that atomic gas fractions keep increasing with decreasing stellar mass, with no sign of a plateau down to log M⋆/M⊙ = 9. Total gas reservoirs remain H I-dominated across our full stellar mass range, hence total gas fraction scaling relations closely resemble atomic ones, but with a scatter that strongly correlates with Rmol, especially at fixed specific star formation rate. On average, Rmol weakly increases with stellar mass and stellar surface density μ⋆, but individual values vary by almost two orders of magnitude at fixed M⋆ or μ⋆. We show that, for galaxies on the star-forming sequence, variations of Rmol are mostly driven by changes of the H I reservoirs, with a clear dependence on μ⋆. Establishing if galaxy mass or structure plays the most important role in regulating the cold gas content of galaxies requires an accurate separation of bulge and disc components for the study of gas scaling relations.

Manipulating Atoms with Light Achievements and Perspectives

CERN Multimedia

CERN. Geneva

2006-01-01

During the last few decades spectacular progress has been achieved in the control of atomic systems by light. It will be shown how it is possible to use the basic conservation laws in atom-photon interactions for polarizing atoms, for trapping them, for cooling them to extremely low temperatures, in the microkelvin, and even in the nanokelvin range. A review will be given of recent advances in this field and of new applications, including atomic clocks with very high relative stability and accuracy, atomic interferometers allowing precise measurement of rotation speeds and gravitational fields, the realization of new states of matter such as Bose-Einstein condensates, matter waves and atom lasers, ultracold molecules. New perspectives opened by these results will be also briefly discussed.

Entanglement between two spatially separated atomic modes

Science.gov (United States)

Lange, Karsten; Peise, Jan; Lücke, Bernd; Kruse, Ilka; Vitagliano, Giuseppe; Apellaniz, Iagoba; Kleinmann, Matthias; Tóth, Géza; Klempt, Carsten

2018-04-01

Modern quantum technologies in the fields of quantum computing, quantum simulation, and quantum metrology require the creation and control of large ensembles of entangled particles. In ultracold ensembles of neutral atoms, nonclassical states have been generated with mutual entanglement among thousands of particles. The entanglement generation relies on the fundamental particle-exchange symmetry in ensembles of identical particles, which lacks the standard notion of entanglement between clearly definable subsystems. Here, we present the generation of entanglement between two spatially separated clouds by splitting an ensemble of ultracold identical particles prepared in a twin Fock state. Because the clouds can be addressed individually, our experiments open a path to exploit the available entangled states of indistinguishable particles for quantum information applications.

Linear spin waves in a trapped Bose gas

International Nuclear Information System (INIS)

Nikuni, T.; Williams, J.E.; Clark, C.W.

2002-01-01

An ultracold Bose gas of two-level atoms can be thought of as a spin-1/2 Bose gas. It supports spin-wave collective modes due to the exchange mean field. Such collective spin oscillations have been observed in recent experiments at JILA with 87 Rb atoms confined in a harmonic trap. We present a theory of the spin-wave collective modes based on the moment method for trapped gases. In the collisionless and hydrodynamic limits, we derive analytic expressions for the frequencies and damping rates of modes with dipole and quadrupole symmetry. We find that the frequency for a given mode is given by a temperature-independent function of the peak density n, and falls off as 1/n. We also find that, to a very good approximation, excitations in the radial and axial directions are decoupled. We compare our model to the numerical integration of a one-dimensional version of the kinetic equation and find very good qualitative agreement. The damping rates, however, show the largest deviation for intermediate densities, where one expects Landau damping--which is unaccounted for in our moment approach--to play a significant role

Dependences of the van der Waals atom-wall interaction on atomic and material properties

International Nuclear Information System (INIS)

Caride, A.O.; Klimchitskaya, G.L.; Mostepanenko, V.M.; Zanette, S.I.

2005-01-01

The 1%-accurate calculations of the van der Waals interaction between an atom and a cavity wall are performed in the separation region from 3 nm to 150 nm. The cases of metastable He * and Na atoms near metal, semiconductor, and dielectric walls are considered. Different approximations to the description of wall material and atomic dynamic polarizability are carefully compared. The smooth transition to the Casimir-Polder interaction is verified. It is shown that to obtain accurate results for the atom-wall van der Waals interaction at short separations with an error less than 1% one should use the complete optical-tabulated data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. The obtained results may be useful for the theoretical interpretation of recent experiments on quantum reflection and Bose-Einstein condensation of ultracold atoms on or near surfaces of different kinds

Passivation and alloying element retention in gas atomized powders

Science.gov (United States)

Heidloff, Andrew J.; Rieken, Joel R.; Anderson, Iver E.

2017-12-05

A method for gas atomization of a titanium alloy, nickel alloy, or other alumina (Al.sub.2O.sub.3)-forming alloy wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a passivation reaction film on the atomized particles wherein the reaction film retains a precursor halogen alloying element that is subsequently introduced into a microstructure formed by subsequent thermally processing of the atomized particles to improve oxidation resistance.

Hyperfine structure of 2Σ molecules containing alkaline-earth-metal atoms

Science.gov (United States)

Aldegunde, Jesus; Hutson, Jeremy M.

2018-04-01

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

Critical radius and critical number of gas atoms for cavities containing a Van der Waals gas

International Nuclear Information System (INIS)

Coghlan, W.A.; Mansur, L.K.

1983-01-01

The effect of gas on void nucleation and growth is particularly important for structural materials in fusion reactors because of the high production of helium by neutron-induced transmutation reactions. Gas reduces the critical radius for bias driven growth and there is a critical number of gas atoms, n/sub g/*, at which the critical radius is reduced essentially to zero. The significance of this is that the time interval to the accumulation of n/sub g/* gas atoms may determine the time to the onset of bias driven swelling where n/sub g/* is large. In previous papers these critical quantities were given for an ideal gas. Recently, we presented the results for a Van der Waals gas. Here the derivation of these relations is presented and further results of calculations are given. At low temperatures (high pressures) the results depart from those of the ideal gas, with the critical number affected more strongly than the critical radius. Comparisons are made with earlier calculations

Submicron Positioning of Single Atoms in a Microcavity

International Nuclear Information System (INIS)

Nussmann, Stefan; Hijlkema, Markus; Weber, Bernhard; Rohde, Felix; Rempe, Gerhard; Kuhn, Axel

2005-01-01

The coupling of individual atoms to a high-finesse optical cavity is precisely controlled and adjusted using a standing-wave dipole-force trap, a challenge for strong atom-cavity coupling. Ultracold Rubidium atoms are first loaded into potential minima of the dipole trap in the center of the cavity. Then we use the trap as a conveyor belt that we set into motion perpendicular to the cavity axis. This allows us to repetitively move atoms out of and back into the cavity mode with a repositioning precision of 135 nm. This makes it possible to either selectively address one atom of a string of atoms by the cavity, or to simultaneously couple two precisely separated atoms to a higher mode of the cavity

Laser-Cooled Ions and Atoms in a Storage Ring

International Nuclear Information System (INIS)

Kleinert, J.; Hannemann, S.; Eike, B.; Eisenbarth, U.; Grieser, M.; Grimm, R.; Gwinner, G.; Karpuk, S.; Saathoff, G.; Schramm, U.; Schwalm, D.; Weidemueller, M.

2003-01-01

We review recent experiments at the Heidelberg Test Storage Ring which apply advanced laser cooling techniques to stored ion beams. Very high phase-space densities are achieved by three-dimensional laser cooling of a coasting 9 Be + beam at 7.3 MeV. Laser-cooled, trapped Cs atoms are used as an ultracold precision target for the study of ion-atom interactions with a 74 MeV beam of 12 C 6+ ions.

Observation of Resonant Effects in Ultracold Collisions between Heteronuclear Feshbach Molecules

Science.gov (United States)

Ye, Xin; Wang, Fudong; Zhu, Bing; Guo, Mingyang; Lu, Bo; Wang, Dajun

2016-05-01

Magnetic field dependent dimer-dimer collisional losses are studied with ultracold 23 Na87 Rb Feshbach molecules. By ramping the magnetic field across the 347.8 G inter-species Feshbach resonance and removing residual atoms with a magnetic field gradient, ~ 8000 pure NaRb Feshbach molecules with a temperature below 1 μK are produced. By holding the pure molecule sample in a crossed optical dipole trap and measuring the time-dependent loss curves under different magnetic fields near the Feshbach resonance, the dimer-dimer loss rates with respect to the atomic scattering length a are mapped out. We observe a resonant feature at around a = 600a0 and a rising tail at above a = 1600a0 . This behavior resembles previous theoretical works on homonuclear Feshbach molecule, where resonant effects between dimer-dimer collisions tied to tetramer bound states were predicted. Our work shows the possibility of exploring four-body physics within a heteronuclear system. We are supported by Hong Kong RGC General Research Fund no. CUHK403813.

A device for simultaneous spin analysis of ultracold neutrons

Energy Technology Data Exchange (ETDEWEB)

Afach, S. [Institute for Particle Physics, ETH Zuerich, Zuerich (Switzerland); Paul Scherrer Institute, Villigen-PSI (Switzerland); Jena University Hospital, Hans Berger Department of Neurology, Jena (Germany); Ban, G.; Lefort, T.; Lemiere, Y.; Naviliat-Cuncic, O.; Quemener, G. [Universite de Caen, CNRS/IN2P3, LPC Caen ENSICAEN, Caen (France); Bison, G.; Chowdhuri, Z.; Daum, M.; Henneck, R.; Lauss, B.; Mtchedlishvili, A.; Schmidt-Wellenburg, P.; Zsigmond, G. [Paul Scherrer Institute, Villigen-PSI (Switzerland); Bodek, K.; Rawlik, M.; Rozpedzik, D.; Zejma, J. [Jagiellonian University, Marian Smoluchowski Institute of Physics, Cracow (Poland); Fertl, M.; Franke, B.; Kirch, K.; Komposch, S. [Institute for Particle Physics, ETH Zuerich, Zuerich (Switzerland); Paul Scherrer Institute, Villigen-PSI (Switzerland); Geltenbort, P. [Institut Laue-Langevin, Grenoble (France); Grujic, Z.D.; Kasprzak, M.; Weis, A. [University of Fribourg, Physics Department, Fribourg (Switzerland); Hayen, L.; Severijns, N.; Wursten, E. [Katholieke Universiteit Leuven, Instituut voor Kernen Stralingsfysica, Leuven (Belgium); Helaine, V. [Paul Scherrer Institute, Villigen-PSI (Switzerland); Universite de Caen, CNRS/IN2P3, LPC Caen ENSICAEN, Caen (France); Kermaidic, Y.; Pignol, G.; Rebreyend, D. [Universite Grenoble Alpes, CNRS/IN2P3, LPSC, Grenoble (France); Kozela, A. [Henryk Niedwodniczanski Institute for Nuclear Physics, Cracow (Poland); Krempel, J.; Piegsa, F.M. [Institute for Particle Physics, ETH Zuerich, Zuerich (Switzerland); Prashanth, P.N. [Paul Scherrer Institute, Villigen-PSI (Switzerland); Katholieke Universiteit Leuven, Instituut voor Kernen Stralingsfysica, Leuven (Belgium); Ries, D. [Paul Scherrer Institute, Villigen-PSI (Switzerland); Jena University Hospital, Hans Berger Department of Neurology, Jena (Germany); Roccia, S. [Universite Paris Sud, CNRS/IN2P3, CSNSM, Orsay campus (France); Wyszynski, G. [Institute for Particle Physics, ETH Zuerich, Zuerich (Switzerland); Jagiellonian University, Marian Smoluchowski Institute of Physics, Cracow (Poland)

2015-11-15

We report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components. The device was developed in the framework of the neutron electric dipole moment experiment at the Paul Scherrer Institute. Individual parts and the entire newly built system have been characterised with ultracold neutrons. The gain in statistical sensitivity obtained with the simultaneous spin analyser is (18.2 ± 6.1) % relative to the former sequential analyser under nominal running conditions. (orig.)

Localization of Cold Atoms in State-Dependent Optical Lattices via a Rabi Pulse

International Nuclear Information System (INIS)

Horstmann, Birger; Duerr, Stephan; Roscilde, Tommaso

2010-01-01

We propose a novel realization of Anderson localization in nonequilibrium states of ultracold atoms in an optical lattice. A Rabi pulse transfers part of the population to a different internal state with infinite effective mass. These frozen atoms create a quantum superposition of different disorder potentials, localizing the mobile atoms. For weakly interacting mobile atoms, Anderson localization is obtained. The localization length increases with increasing disorder and decreasing interaction strength, contrary to the expectation for equilibrium localization.

A Michelson interferometer for ultracold neutrons

International Nuclear Information System (INIS)

Steyerl, A.; Malik, S.S.; Steinhauser, K.A.; Berger, L.

1979-01-01

We propose a neutron Michelson Interferometer installed within a focussing 'gravity diffractometer' for ultracold neutrons. In this arrangement the expected interference pattern depends only on the well-defined vertical component of neutron wavevector. Possible applications of such an interferometer are discussed. (orig.)

Matter-wave localization in disordered cold atom lattices.

Science.gov (United States)

Gavish, Uri; Castin, Yvan

2005-07-08

We propose to observe Anderson localization of ultracold atoms in the presence of a random potential made of atoms of another species or spin state and trapped at the nodes of an optical lattice, with a filling factor less than unity. Such systems enable a nearly perfect experimental control of the disorder, while the possibility of modeling the scattering potentials by a set of pointlike ones allows an exact theoretical analysis. This is illustrated by a detailed analysis of the one-dimensional case.

Laser-Cooled Ions and Atoms in a Storage Ring

Energy Technology Data Exchange (ETDEWEB)

Kleinert, J.; Hannemann, S.; Eike, B.; Eisenbarth, U.; Grieser, M.; Grimm, R.; Gwinner, G.; Karpuk, S.; Saathoff, G.; Schramm, U.; Schwalm, D.; Weidemueller, M., E-mail: m.weidemueller@mpi-hd.mpg.de [Max-Planck-Insitut fuer Kernphysik (Germany)

2003-03-15

We review recent experiments at the Heidelberg Test Storage Ring which apply advanced laser cooling techniques to stored ion beams. Very high phase-space densities are achieved by three-dimensional laser cooling of a coasting {sup 9}Be{sup +} beam at 7.3 MeV. Laser-cooled, trapped Cs atoms are used as an ultracold precision target for the study of ion-atom interactions with a 74 MeV beam of {sup 12}C{sup 6+} ions.

Magnetic resonance studies of atomic hydrogen gas at low temperatures

International Nuclear Information System (INIS)

Hardy, W.N.; Morrow, M.; Jochemsen, R.; Statt, B.W.; Kubik, P.R.; Marsolais, R.M.; Berlinsky, A.J.; Landesman, A.

1980-01-01

Using a pulsed low temperature discharge in a closed cell containing H 2 and 4 He, we have been able to store a low density (approximately 10 12 atoms/cc) gas of atomic hydrogen for periods of order one hour in zero magnetic field and T=1 K. Pulsed magnetic resonance at the 1420 MHz hyperfine transition has been used to study a number of the properties of the gas, including the recombination rate H + H + 4 He→H 2 + 4 He, the hydrogen spin-exchange relaxation rates, the diffusion coefficient of H in 4 He gas and the pressure shift of the hyperfine frequency due to the 4 He buffer gas. Here we discuss the application of hyperfine frequency shifts as a probe of the H-He potential, and as a means for determining the binding energy of H on liquid helium

Tonks-Girardeau and super-Tonks-Girardeau states of a trapped one-dimensional spinor Bose gas

International Nuclear Information System (INIS)

Girardeau, M. D.

2011-01-01

A harmonically trapped, ultracold, one-dimensional (1D) spin-1 Bose gas with strongly repulsive or attractive 1D even-wave interactions induced by a three-dimensional (3D) Feshbach resonance is studied. The exact ground state, a hybrid of Tonks-Girardeau (TG) and ideal Fermi gases, is constructed in the TG limit of infinite even-wave repulsion by a spinor Fermi-Bose mapping to a spinless ideal Fermi gas. It is then shown that in the limit of infinite even-wave attraction this same state remains an exact many-body eigenstate, now highly excited relative to the collapsed generalized McGuire-cluster ground state, showing that the hybrid TG state is completely stable against collapse to this cluster ground state under a sudden switch from infinite repulsion to infinite attraction. It is shown to be the TG limit of a hybrid super-Tonks-Girardeau (STG) state, which is metastable under a sudden switch from finite but very strong repulsion to finite but very strong attraction. It should be possible to create it experimentally by a sudden switch from strongly repulsive to strongly attractive interaction, as in the recent Innsbruck experiment on a spin-polarized bosonic STG gas. In the case of strong attraction, there should also exist another STG state of much lower energy, consisting of strongly bound dimers, a bosonic analog of a recently predicted STG state which is an ultracold gas of strongly bound bosonic dimers of fermionic atoms, but it is shown that this STG state cannot be created by such a switch from strong repulsion to strong attraction.

Gas atomization of Cu-modified AB5 metal hydride alloys

International Nuclear Information System (INIS)

Young, K.; Ouchi, T.; Banik, A.; Koch, J.; Fetcenko, M.A.; Bendersky, L.A.; Wang, K.; Vaudin, M.

2011-01-01

Research highlights: → The gas atomization process together with a hydrogen annealing process was demonstrated on AB5 alloys. → The method was found to be effective in restoring the original cycle life sacrificed by the incorporation of copper in the alloy formula as a means of improving the low temperature performance of AB 5 alloys. → The new process also improves high rate, low temperature, and charge retention performances for both Cu-free and Cu-containing AB 5 alloys. - Abstract: Gas atomization together with a hydrogen annealing process has been proposed as a method to achieve improved low-temperature performance of AB 5 alloy electrodes in Ni/MH batteries and restore the original cycle life which was sacrificed by the incorporation of copper in the alloy formula. While the gas atomization process reduces the lattice constant aspect ratio c/a of the Cu-containing alloys, the addition of a hydrogen annealing step recovers this property, although it is still inferior to the conventionally prepared annealed Cu-free alloy. This observation correlates very well with the cycle life performance. In addition to extending the cycle life of the Cu-containing metal hydride electrode, processing by gas atomization with additional hydrogen annealing improves high-rate, low-temperature, and charge retention performances for both Cu-free and Cu-containing AB 5 alloys. The degradation mechanisms of alloys made by different processes through cycling are also discussed.

Editorial: Focus on Atom Optics and its Applications

Science.gov (United States)

Schmidt-Kaler, F.; Pfau, T.; Schmelcher, P.; Schleich, W.

2010-06-01

Frequency stability of optical lattice clocks Jérôme Lodewyck, Philip G Westergaard, Arnaud Lecallier, Luca Lorini and Pierre Lemonde Ultracold quantum gases in triangular optical lattices C Becker, P Soltan-Panahi, J Kronjäger, S Dörscher, K Bongs and K Sengstock Cold atoms near superconductors: atomic spin coherence beyond the Johnson noise limit B Kasch, H Hattermann, D Cano, T E Judd, S Scheel, C Zimmermann, R Kleiner, D Koelle and J Fortágh Focusing a deterministic single-ion beam Wolfgang Schnitzler, Georg Jacob, Robert Fickler, Ferdinand Schmidt-Kaler and Kilian Singer Tuning the structural and dynamical properties of a dipolar Bose-Einstein condensate: ripples and instability islands M Asad-uz-Zaman and D Blume Double-resonance lineshapes in a cell with wall coating and buffer gas Svenja Knappe and Hugh G Robinson Transport and interaction blockade of cold bosonic atoms in a triple-well potential P Schlagheck, F Malet, J C Cremon and S M Reimann Fabrication of a planar micro Penning trap and numerical investigations of versatile ion positioning protocols M Hellwig, A Bautista-Salvador, K Singer, G Werth and F Schmidt-Kaler Laser cooling of a magnetically guided ultracold atom beam A Aghajani-Talesh, M Falkenau, V V Volchkov, L E Trafford, T Pfau and A Griesmaier Creation efficiency of nitrogen-vacancy centres in diamond S Pezzagna, B Naydenov, F Jelezko, J Wrachtrup and J Meijer Top-down pathways to devices with few and single atoms placed to high precision Jessica A Van Donkelaar, Andrew D Greentree, Andrew D C Alves, Lenneke M Jong, Lloyd C L Hollenberg and David N Jamieson Enhanced electric field sensitivity of rf-dressed Rydberg dark states M G Bason, M Tanasittikosol, A Sargsyan, A K Mohapatra, D Sarkisyan, R M Potvliege and C S Adams

Reactive Collisions and Interactions of Ultracold Dipolar Atoms

Science.gov (United States)

2014-10-29

Kotochigova Department of Physics, Temple University, Philadelphia, PA 19122-6082 I. COLLISIONAL INTERACTIONS OF RARE- EARTH MAGNETIC ATOMS The breakthroughs...technologies, it was not previously implemented, possibly owing to the misconception that molecular ions predominantly undergo charge-exchange reactions leading

Collapse and revival oscillations as a probe for the tunneling amplitude in an ultracold Bose gas

International Nuclear Information System (INIS)

Wolf, F. Alexander; Hen, Itay; Rigol, Marcos

2010-01-01

We present a theoretical study of the quantum corrections to the revival time due to finite tunneling in the collapse and revival of matter-wave interference after a quantum quench. We study hard-core bosons in a superlattice potential and the Bose-Hubbard model by means of exact numerical approaches and mean-field theory. We consider systems without and with a trapping potential present. We show that the quantum corrections to the revival time can be used to accurately determine the value of the hopping parameter in experiments with ultracold bosons in optical lattices.

Specific Adaptation of Gas Atomization Processing for Al-Based Alloy Powder for Additive Manufacturing

Energy Technology Data Exchange (ETDEWEB)

Anderson, Iver [Ames Lab., Ames, IA (United States); Siemon, John [Alcoa Inc., Pittsburgh, PA (United States)

2017-06-30

The charge for each gas atomization experiment was provided by Alcoa and consisted of cast blocks cut into 1 inch by 1 inch square rods of the chosen aluminum alloys. The atmosphere in the melting chamber and connected atomization system was evacuated with a mechanical pump prior to backfilling with ultrahigh purity (UHP grade) Ar. The melt was contained in a bottom tapped alumina crucible with an alumina stopper rod to seal the exit while heating to a pouring temperature of 1000 – 1400°C. When the desired superheat was reached, the stopper rod was lifted and melt flowed through pour tube and was atomized with Ar from a 45-22-052-409 gas atomization nozzle (or atomization die), having a jet apex angle of 45 degrees with 22 cylindrical gas jets (each with diameter of 1.32 mm or 0.052 inches) arrayed around the axis of a 10.4 mm central bore. The Ar atomization gas supply regulator pressure was set to produce nozzle manifold pressures for the series of runs at pressures of 250-650 psi. Secondary gas halos of Ar+O₂ and He also were added to the interior of the spray chamber at various downstream locations for additional cooling of the atomized droplets, surface passivation, and to prevent coalescence of the resulting powder.

Quantum Optics 6 - Quantum Engineering of Atoms and Photons - Conference Materials

International Nuclear Information System (INIS)

2005-01-01

The conference organized by Center for Theoretical Physics, Institute of Physics and Warsaw University, sponsored by European Science Foundation, was held in Krynica (120 km south-east of Cracow), Poland, June 13-18 2005. This was the sixth conference of the cycle, the previous one was held in Koscielisko, Poland in 2001. This time the main subject of the conference was: Quantum Engineering of Atoms and Photons. The meeting was focused on the physics of ultracold quantum gases, which without doubts determines the frontiers of the modern atomic, molecular and optical physics. Special attention was also be given to quantum information processing, both from theoretical and experimental point of view, including possible realizations in ultracold quantum gases. The conference consisted of invited lectures and a poster session. Competition for the best poster was held, sponsored by Journal of Optics B and Journal of Physics B - for more on this, including the results of the competition visit. (author)

Luther-Emery Phase and Atomic-Density Waves in a Trapped Fermion Gas

International Nuclear Information System (INIS)

Gao Xianlong; Rizzi, M.; Polini, Marco; Tosi, M. P.; Fazio, Rosario; Campo, V. L. Jr.; Capelle, K.

2007-01-01

The Luther-Emery liquid is a state of matter that is predicted to occur in one-dimensional systems of interacting fermions and is characterized by a gapless charge spectrum and a gapped spin spectrum. In this Letter we discuss a realization of the Luther-Emery phase in a trapped cold-atom gas. We study by means of the density-matrix renormalization-group technique a two-component atomic Fermi gas with attractive interactions subject to parabolic trapping inside an optical lattice. We demonstrate how this system exhibits compound phases characterized by the coexistence of spin pairing and atomic-density waves. A smooth crossover occurs with increasing magnitude of the atom-atom attraction to a state in which tightly bound spin-singlet dimers occupy the center of the trap. The existence of atomic-density waves could be detected in the elastic contribution to the light-scattering diffraction pattern

Ultracold Fermi and Bose gases and Spinless Bose Charged Sound Particles

Directory of Open Access Journals (Sweden)

Minasyan V.

2011-10-01

Full Text Available We propose a novel approach for investigation of the motion of Bose or Fermi liquid (or gas which consists of decoupled electrons and ions in the uppermost hyperfine state. Hence, we use such a concept as the fluctuation motion of “charged fluid particles” or “charged fluid points” representing a charged longitudinal elastic wave. In turn, this elastic wave is quantized by spinless longitudinal Bose charged sound particles with the rest mass m and charge e 0 . The existence of spinless Bose charged sound particles allows us to present a new model for description of Bose or Fermi liquid via a non-ideal Bose gas of charged sound particles . In this respect, we introduce a new postulation for the superfluid component of Bose or Fermi liquid determined by means of charged sound particles in the condensate, which may explain the results of experiments connected with ultra-cold Fermi gases of spin-polarized hydrogen, 6 Li and 40 K, and such a Bose gas as 87 Rb in the uppermost hyperfine state, where the Bose- Einstein condensation of charged sound particles is realized by tuning the magnetic field.

Forward and backward scattering experiments in ultra-cold Rubidium atoms

DEFF Research Database (Denmark)

Kampel, Nir Shlomo

project, we have studied coherent forward scattering in the form of a memory experiment. In such an experiment we convert the input light pulse to an atomic excitation, and at a later time convert back the atomic excitation into the retrieved light pulse. In the first project, we investigate the source...

Exploring strategies for the production of ultracold RbYb molecules in conservative traps

Energy Technology Data Exchange (ETDEWEB)

Bruni, Cristian

2015-07-14

Within the scope of this thesis, the production of ultracold molecules at a temperature of a few μK with various isotopes of rubidium (Rb) and ytterbium (Yb) was examined by means of photoassociation spectroscopy and magnetic Feshbach resonances in combined conservative traps. The long-term goal of this experiment is the production of ultracold RbYb molecules in the rovibronic ground state. It was possible to produce electronically excited {sup 87}Rb {sup 176}Yb molecules in a novel hybrid trap (HT) at a combined temperature of 1.7 μK by means of 1-photon photoassociation close to the Rb D1 line at 795 nm. This HT takes advantage of the different magnetic properties of Rb and Yb and allows for independent trapping and manipulation of the atomic species. It combines an Ioffe-Pritchard type magnetic trap for Rb and a near-resonant optical dipole trap for Yb. The excited molecular {sup 2}Π{sub 1/2} state could be characterized further extending previous works in a combined MOT and vibrational levels reaching binding energies up to E{sub b}=-h x 2.2 THz could be assigned by trap-loss spectroscopy. Almost every detected vibrational state consists of two resonances that could be assigned to the molecular analogue of the hyperfine structure of {sup 87}Rb. An important experimental observation is a decrease in hyperfine splitting with increasing binding energy of a vibrational level. For the deepest found vibrational state the hyperfine splitting amounts only 70 % of the atomic value (817 MHz) which emphasizes a gradual passage from weakly to tightly bound molecules. Furthermore, detailed attempts were undertaken to induce magnetic Feshbach resonances in {sup 85}Rb and different Yb isotopes, especially {sup 171}Yb in a crossed optical dipole trap at 1064 nm at temperatures of 10 μK. For this purpose, a homogeneous magnetic field was applied and scanned in small steps over the range of 495 G ∼ 640 G. Unfortunately, our efforts were without success. Additionally, well

Many-body pairing in a two-dimensional Fermi gas

Energy Technology Data Exchange (ETDEWEB)

Neidig, Mathias

2017-05-24

This thesis reports on experiments conducted in a single layer, quasi two-dimensional, two-component ultracold Fermi gas in the strongly interacting regime. Ultracold gases can be used to simulate key aspects of more complicated systems like for example cuprates which show high-T{sub c} superconductivity. The momentum distribution of a sample of bosonic dimers in a quasi-2D square lattice geometry was measured to obtain the coherence properties. For shallow lattices, sharp peaks in the momentum distribution, indicating coherence, were observed at zero momentum as well as at positive and negative lattice momenta along each axis. For deeper lattices, heating impeded the ability to prepare a Mott-insulator. A spatially resolved radio-frequency spectroscopy was employed for a quasi-2D Fermi gas in the normal phase throughout the BEC-BCS crossover. The interaction induced energy shifts were measured in the strongly interacting region where they can be on the order of the Fermi energy and thus the local resolution is crucial. Furthermore, the onset of pairing in the strongly interacting region was measured as a function of temperature and it was shown that the fraction of free atoms decreases faster than expected from thermal non-interacting theory. At last, the pairing gap was measured using an imbalanced sample. On the BEC side it was found to be in very good agreement with two-body physics as expected. In the strongly interacting regime, however, a deviation from two-body physics indicates that here many-body effects play a role and thus further studies are required.

Penning ionization cross sections of excited rare gas atoms

International Nuclear Information System (INIS)

Ukai, Masatoshi; Hatano, Yoshihiko.

1988-01-01

Electronic energy transfer processes involving excited rare gas atoms play one of the most important roles in ionized gas phenomena. Penning ionization is one of the well known electronic energy transfer processes and has been studied extensively both experimentally and theoretically. The present paper reports the deexcitation (Penning ionization) cross sections of metastable state helium He(2 3 S) and radiative He(2 1 P) atoms in collision with atoms and molecules, which have recently been obtained by the authors' group by using a pulse radiolysis method. Investigation is made of the selected deexcitation cross sections of He(2 3 S) by atoms and molecules in the thermal collisional energy region. Results indicate that the cross sections are strongly dependent on the target molecule. The deexcitation probability of He(2 3 S) per collision increases with the excess electronic energy of He(2 3 S) above the ionization potential of the target atom or molecule. Another investigation, made on the deexcitation of He(2 1 P), suggests that the deexcitation cross section for He(2 1 P) by Ar is determined mainly by the Penning ionization cross section due to a dipole-dipole interaction. Penning ionization due to the dipole-dipole interaction is also important for deexcitation of He(2 1 P) by the target molecules examined. (N.K.)

Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas

Science.gov (United States)

Adams, Allan; Carr, Lincoln D.; Schaefer, Thomas; Steinberg, Peter; Thomas, John E.

2013-04-01

The last few years have witnessed a dramatic convergence of three distinct lines of research concerned with different kinds of extreme quantum matter. Two of these involve new quantum fluids that can be studied in the laboratory, ultracold quantum gases and quantum chromodynamics (QCD) plasmas. Even though these systems involve vastly different energy scales, the physical properties of the two quantum fluids are remarkably similar. The third line of research is based on the discovery of a new theoretical tool for investigating the properties of extreme quantum matter, holographic dualties. The main goal of this focus issue is to foster communication and understanding between these three fields. We proceed to describe each in more detail. Ultracold quantum gases offer a new paradigm for the study of nonperturbative quantum many-body physics. With widely tunable interaction strength, spin composition, and temperature, using different hyperfine states one can model spin-1/2 fermions, spin-3/2 fermions, and many other spin structures of bosons, fermions, and mixtures thereof. Such systems have produced a revolution in the study of strongly interacting Fermi systems, for example in the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover region, where a close collaboration between experimentalists and theorists—typical in this field—enabled ground-breaking studies in an area spanning several decades. Half-way through this crossover, when the scattering length characterizing low-energy collisions diverges, one obtains a unitary quantum gas, which is universal and scale invariant. The unitary gas has close parallels in the hydrodynamics of QCD plasmas, where the ratio of viscosity to entropy density is extremely low and comparable to the minimum viscosity conjecture, an important prediction of AdS/CFT (see below). Exciting developments in the thermodynamic and transport properties of strongly interacting Fermi gases are of broad

Magnetic field modification of ultracold molecule-molecule collisions

International Nuclear Information System (INIS)

Tscherbul, T V; Suleimanov, Yu V; Aquilanti, V; Krems, R V

2009-01-01

We present an accurate quantum mechanical study of molecule-molecule collisions in the presence of a magnetic field. The work focuses on the analysis of elastic scattering and spin relaxation in collisions of O 2 ( 3 Σ g - ) molecules at cold (∼0.1 K) and ultracold (∼10 -6 K) temperatures. Our calculations show that magnetic spin relaxation in molecule-molecule collisions is extremely efficient except at magnetic fields below 1 mT. The rate constant for spin relaxation at T=0.1 K and a magnetic field of 0.1 T is found to be as large as 6.1x10 -11 cm -3 s -1 . The magnetic field dependence of elastic and inelastic scattering cross sections at ultracold temperatures is dominated by a manifold of Feshbach resonances with the density of ∼100 resonances per Tesla for collisions of molecules in the absolute ground state. This suggests that the scattering length of ultracold molecules in the absolute ground state can be effectively tuned in a very wide range of magnetic fields. Our calculations demonstrate that the number and properties of the magnetic Feshbach resonances are dramatically different for molecules in the absolute ground and excited spin states. The density of Feshbach resonances for molecule-molecule scattering in the low-field-seeking Zeeman state is reduced by a factor of 10.

Strong dependence of ultracold chemical rates on electric dipole moments

International Nuclear Information System (INIS)

Quemener, Goulven; Bohn, John L.

2010-01-01

We use the quantum threshold laws combined with a classical capture model to provide an analytical estimate of the chemical quenching cross sections and rate coefficients of two colliding particles at ultralow temperatures. We apply this quantum threshold model (QT model) to indistinguishable fermionic polar molecules in an electric field. At ultracold temperatures and in weak electric fields, the cross sections and rate coefficients depend only weakly on the electric dipole moment d induced by the electric field. In stronger electric fields, the quenching processes scale as d 4(L+(1/2)) where L>0 is the orbital angular-momentum quantum number between the two colliding particles. For p-wave collisions (L=1) of indistinguishable fermionic polar molecules at ultracold temperatures, the quenching rate thus scales as d 6 . We also apply this model to pure two-dimensional collisions and find that chemical rates vanish as d -4 for ultracold indistinguishable fermions. This model provides a quick and intuitive way to estimate chemical rate coefficients of reactions occuring with high probability.

Stability of a fully magnetized ferromagnetic state in repulsively interacting ultracold Fermi gases

International Nuclear Information System (INIS)

Cui Xiaoling; Zhai Hui

2010-01-01

We construct a variational wave function to study whether a fully polarized Fermi sea of ultracold atoms is energetically stable against a single spin flip. Our variational wave function contains short-range correlations at least to the same level as Gutzwiller's projected wave function. For the Hubbard lattice model and the continuum model with pure repulsive interaction, we show that a fully polarized Fermi sea is generally unstable even for infinite repulsive strength. By contrast, for a resonance model, the ferromagnetic state is possible if the s-wave scattering length is positive and sufficiently large and the system is prepared to be orthogonal to the molecular bound state. However, we cannot rule out the possibility that more exotic correlations can destabilize the ferromagnetic state.

Ultra-cold molecules in an atomic Bose-Einstein condensate

Science.gov (United States)

Wynar, Roahn Helden

2000-08-01

This thesis is about photoassociation of Bose-condensed 87Rb. Most importantly we report that state selected 87Rb2 molecules were created at rest in a condensate of 87Rb using two-photon photoassociation. Additionally, we have identified three weakly bound states of the 87Rb2 S+u3 , potential for the |1, -1> + |1, - 1> collisional channel. The binding energies of these states are 529.4 +/- .07, 636.0094 +/- .0012, and 24.24 +/- .01 MHz respectively. We have also carried out a detailed study of the density dependence of the shift and width of the two-photon lineshape. This shift and width is modeled using the theory of Bohn and Julienne [34] and in addition to the precise measurement of binding energy we also report the first measurement of an atom molecule scattering length, aam, which we conclude is -180 +/- 150 a0, and the inelastic collision rate, Kinel dependent coherent coupling between atoms and molecules. This theory yields two coupled equations, one for the evolution of atomic condensate amplitude and one for the evolution of molecular condensate amplitude. The nature of the atomic-molecular condensate evolution is shown to depend on six, model parameters including the coherent coupling, given by cn . The other five parameters can be interpreted as light-shifts and incoherent loss rates. We present a calculation intended to estimate the values of these six parameters for the 87Rb - 87Rb 2 system. Based on the results of this calculation we identify two locations in the 87Rb2 spectrum where coherent transfer of population from atomic condensate to molecular condensate is plausible. Finally, we examine the credibility of the theoretical model used to estimate the six parameters used by the mean field theory. By comparing the measured Stark shifts of two-color resonances with predictions based on our theoretical model we conclude that the model is satisfactory for the v = 37 level of the S+u3 potential. This work also describes the experimental details of

Atom history, from intuitive ideas to reality

International Nuclear Information System (INIS)

Radvanyi, P.

2007-01-01

This book gathers the ground scientific texts that have stood out as milestones in the way scientists have built their understanding of the atom over centuries. From the very intuitive ideas of Greek philosophers to the most recent results on ultra-cold atoms, via the discovery of natural radioactivity or the existence of the neutron, about 55 articles written by prestigious physicists have been organized into 16 chapters. Each chapter being dedicated to a topic such as molecules, spectroscopy, electrons, X-rays, atom mass, artificial radioactivity..., begins with a commentary that draws the scientific context of that time, describes the links between the articles and highlights the importance of the discoveries. (A.C.)

Numerical and experimental modelling of back stream flow during close-coupled gas atomization

OpenAIRE

Motaman, S; Mullis, AM; Borman, DJ; Cochrane, RF; McCarthy, IN

2013-01-01

This paper reports the numerical and experimental investigation into the effects of different gas jet mis-match angles (for an external melt nozzle wall) on the back-stream flow in close coupled gas atomization. The Pulse Laser Imaging (PLI) technique was applied for visualising the back-stream melt flow phenomena with an analogue water atomizer and the associated PLI images compared with numerical results. In the investigation a Convergent–Divergent (C–D) discrete gas jet die at five differe...

Atom loss resonances in a Bose-Einstein condensate.

Science.gov (United States)

Langmack, Christian; Smith, D Hudson; Braaten, Eric

2013-07-12

Atom loss resonances in ultracold trapped atoms have been observed at scattering lengths near atom-dimer resonances, at which Efimov trimers cross the atom-dimer threshold, and near two-dimer resonances, at which universal tetramers cross the dimer-dimer threshold. We propose a new mechanism for these loss resonances in a Bose-Einstein condensate of atoms. As the scattering length is ramped to the large final value at which the atom loss rate is measured, the time-dependent scattering length generates a small condensate of shallow dimers coherently from the atom condensate. The coexisting atom and dimer condensates can be described by a low-energy effective field theory with universal coefficients that are determined by matching exact results from few-body physics. The classical field equations for the atom and dimer condensates predict narrow enhancements in the atom loss rate near atom-dimer resonances and near two-dimer resonances due to inelastic dimer collisions.

Determination of the Axial-Vector Weak Coupling Constant with Ultracold Neutrons

International Nuclear Information System (INIS)

Liu, J.; Mendenhall, M. P.; Carr, R.; Filippone, B. W.; Hickerson, K. P.; Perez Galvan, A.; Russell, R.; Holley, A. T.; Hoagland, J.; VornDick, B.; Back, H. O.; Pattie, R. W. Jr.; Young, A. R.; Bowles, T. J.; Clayton, S.; Currie, S.; Hogan, G. E.; Ito, T. M.; Makela, M.; Morris, C. L.

2010-01-01

A precise measurement of the neutron decay β asymmetry A 0 has been carried out using polarized ultracold neutrons from the pulsed spallation ultracold neutron source at the Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report A 0 =-0.119 66±0.000 89 -0.00140 +0.00123 , from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon g A /g V =-1.275 90 -0.00445 +0.00409 .

Manipulation of ultracold atoms in dressed adiabatic radio-frequency potentials

DEFF Research Database (Denmark)

Lesanovsky, Igor; Hofferberth, S.; Schmiedmayer, Jörg

2006-01-01

We explore properties of atoms whose magnetic hyperfine sublevels are coupled by an external magnetic radio frequency (rf) field. We perform a thorough theoretical analysis of this driven system and present a number of systematic approximations which eventually give rise to dressed adiabatic radio...... frequency potentials. The predictions of this analytical investigation are compared to numerically exact results obtained by a wave packet propagation. We outline the versatility and flexibility of this class of potentials and demonstrate their potential use to build atom optical elements such as double...... wells, interferometers, and ringtraps. Moreover, we perform simulations of interference experiments carried out in rf induced double-well potentials. We discuss how the nature of the atom-field coupling mechanism gives rise to a decrease of the interference contrast....

Photon-Induced Spin-Orbit Coupling in Ultracold Atoms inside Optical Cavity

Directory of Open Access Journals (Sweden)

Lin Dong

2015-05-01

Full Text Available We consider an atom inside a ring cavity, where a plane-wave cavity field together with an external coherent laser beam induces a two-photon Raman transition between two hyperfine ground states of the atom. This cavity-assisted Raman transition induces effective coupling between atom’s internal degrees of freedom and its center-of-mass motion. In the meantime, atomic dynamics exerts a back-action to cavity photons. We investigate the properties of this system by adopting a mean-field and a full quantum approach, and show that the interplay between the atomic dynamics and the cavity field gives rise to intriguing nonlinear phenomena.

Thermoelectric transport and Peltier cooling of cold atomic gases

Science.gov (United States)

Grenier, Charles; Kollath, Corinna; Georges, Antoine

2016-12-01

This brief review presents the emerging field of mesoscopic physics with cold atoms, with an emphasis on thermal and 'thermoelectric' transport, i.e. coupled transport of particles and entropy. We review in particular the comparison between theoretically predicted and experimentally observed thermoelectric effects in such systems. We also show how combining well-designed transport properties and evaporative cooling leads to an equivalent of the Peltier effect with cold atoms, which can be used as a new cooling procedure with improved cooling power and efficiency compared to the evaporative cooling currently used in atomic gases. This could lead to a new generation of experiments probing strong correlation effects of ultracold fermionic atoms at low temperatures.

Production and spectroscopy of ultracold YbRb{sup *} molecules

Energy Technology Data Exchange (ETDEWEB)

Nemitz, Nils

2008-11-15

This thesis describes the formation of electronically excited but translationally cold molecules formed from rubidium atoms and two isotopes of ytterbium ({sup 176}Yb and {sup 174}Yb) by means of photoassociation. The experiments were performed in a combined MOT with 10{sup 9} rubidium atoms and 2.10{sup 6} ytterbium atoms at temperatures of less than 1 mK. Photoassociation lines were found by trap loss spectroscopy throughout a wavelength range of 2 nm near the 795 nm D1 transition in rubidium. The majority of lines belong to two vibrational series in the excited YbRb{sup *} molecule, converging on a system of a ground state ytterbium atom and an excited rubidium atom. The strong variation of line strength between different vibrational lines is explained through the Franck-Condon principle. An improved version of the Leroy-Bernstein equation was used to extract the leading dispersion coefficient of the potential from the vibrational progression. Most of the observed lines show a resolved rotational structure as expected from a basic quantum mechanical model. The series terminates with the third or forth rotational component due to the ground state centrifugal barrier.The measured rotational constants agree very well with calculations based on the C{sub 6} coefficient. The discovery of a splitting of the rotational components into subcomponents indicates an uncommon angular momentum coupling described by Hund's case. Variations in the depth of the subcomponents indicates a similar splitting in the ground state, with the energies of the substates based on the alignment of the rubidium atom's magnetic dipole moment relative to the angular momentum carried by an approaching ytterbium atom. This creates an additional ground state barrier, partially suppressing some of the subcomponents. Using a rate equation model developed for this purpose, a maximum formation rate of 2.5.10{sup 6} molecules per second was calculated over the volume of the entire trap. The

Investigations of Laser Pumped Gas Cell Atomic Frequency Standard

National Research Council Canada - National Science Library

Volk, C. H; Camparo, J. C; Frueholz, R. P

1981-01-01

Recently it has been suggested that the performance characteristics of a rubidium gas cell atomic frequency standard might be improved by replacing the standard rubidium discharge lamp with a single mode laser diode...

Atomic iodine production in a gas flow by decomposing methyl iodide in a dc glow discharge

International Nuclear Information System (INIS)

Mikheyev, P A; Shepelenko, A A; Voronov, A I; Kupryaev, Nikolai V

2002-01-01

The production of atomic iodine for an oxygen - iodine laser is studied by decomposing methyl iodide in a dc glow discharge in a vortex gas flow. The concentration of iodine atoms in discharge products was measured from the atomic iodine absorption of the radiation of a single-frequency tunable diode laser at a wavelength of 1.315 μm. Atomic iodine concentrations sufficient for the operation of an oxygen - iodine laser were obtained. The concentration of atomic iodine amounted to 3.6 x 10 15 cm -3 for a pressure of the carrying argon gas of 15 Torr. The discharge stabilisation by a vortex gas flow allowed the glow discharge to be sustained in a strongly electronegative halogen-containing gas mixture for pressures up to 20 Torr. (active media)

Magnetic-field-driven localization of light in a cold-atom gas.

Science.gov (United States)

Skipetrov, S E; Sokolov, I M

2015-02-06

We discover a transition from extended to localized quasimodes for light in a gas of immobile two-level atoms in a magnetic field. The transition takes place either upon increasing the number density of atoms in a strong field or upon increasing the field at a high enough density. It has many characteristic features of a disorder-driven (Anderson) transition but is strongly influenced by near-field interactions between atoms and the anisotropy of the atomic medium induced by the magnetic field.

Optimization study of ultracold neutron sources at TRIGA reactors using MCNP

International Nuclear Information System (INIS)

Pokotilovskij, Yu.N.; Rogov, A.D.

1997-01-01

Monte Carlo simulation for the optimization of ultracold and very cold neutron sources for TRIGA reactors is performed. The calculations of thermal and cold neutron fluxes from the TRIGA reactor for different positions and configurations of a very cold solid methane moderator were performed with using the MCNP program. The production of neutrons in the ultracold and very cold energy range was calculated for the most promising final moderators (converters): very cold solid deuterium and heavy methane. The radiation energy deposition was calculated for the optimized solid methane-heavy methane cold neutron moderator

Long-range interactions of excited He atoms with ground-state noble-gas atoms

KAUST Repository

Zhang, J.-Y.; Qian, Ying; Schwingenschlö gl, Udo; Yan, Z.-C.

2013-01-01

The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition

Attosecond Time Delay in Photoionization of Noble-Gas and Halogen Atoms

Directory of Open Access Journals (Sweden)

Liang-Wen Pi

2018-02-01

Full Text Available Ultrafast processes are now accessible on the attosecond time scale due to the availability of ultrashort XUV laser pulses. Noble-gas and halogen atoms remain important targets due to their giant dipole resonance and Cooper minimum. Here, we calculate photoionization cross section, asymmetry parameter and Wigner time delay using the time-dependent local-density approximation (TDLDA, which includes the electron correlation effects. Our results are consistent with experimental data and other theoretical calculations. The asymmetry parameter provides an extra layer of access to the phase information of the photoionization processes. We find that halogen atoms bear a strong resemblance on cross section, asymmetry parameter and time delay to their noble-gas neighbors. Our predicted time delay should provide a guidance for future experiments on those atoms and related molecules.

High-resolution internal state control of ultracold 23Na87Rb molecules

Science.gov (United States)

Guo, Mingyang; Ye, Xin; He, Junyu; Quéméner, Goulven; Wang, Dajun

2018-02-01

We report the full internal state control of ultracold 23Na87Rb molecules, including vibrational, rotational, and hyperfine degrees of freedom. Starting from a sample of weakly bound Feshbach molecules, we realize the creation of molecules in single hyperfine levels of both the rovibrational ground and excited states with a high-efficiency and high-resolution stimulated Raman adiabatic passage. This capability brings broad possibilities for investigating ultracold polar molecules with different chemical reactivities and interactions with a single molecular species. Moreover, starting from the rovibrational and hyperfine ground state, we achieve rotational and hyperfine control with one- and two-photon microwave spectroscopy to reach levels not accessible by the stimulated Raman transfer. The combination of these two techniques results in complete control over the internal state of ultracold polar molecules, which paves the way to study state-dependent molecular collisions and state-controlled chemical reactions.

Microstructural and magnetic behavior of nanostructured soft alloys prepared by mechanical grinding and gas atomization

International Nuclear Information System (INIS)

Marin, P.; Lopez, M.; Garcia-Escorial, A.; Lieblich, M.

2007-01-01

Nanocrystalline powder of Fe-Si-B-Cu-Nb has been obtained by means of mechanical milling of the corresponding nanocrystalline ribbons. Gas atomization technique has been used to minimize the magnetic hardening due to stress effects observed in ball-milled samples. Fe-Si-B-Cu-Nb and Fe-Si nanocrystalline samples have been prepared by gas atomization. The aim of our work is to analyse the particle size dependence of coercivity in this nanostructured alloys and to show the analogies and differences between ball-milled and gas atomized samples

Radio-Frequency-Controlled Cold Collisions and Universal Properties of Unitary Bose Gases

Science.gov (United States)

Ding, Yijue

This thesis investigates two topics: ultracold atomic collisions in a radio-frequency field and universal properties of a degenerate unitary Bose gas. One interesting point of the unitary Bose gas is that the system has only one length scale, that is, the average interparticle distance. This single parameter determines all properties of the gas, which is called the universality of the system. We first introduce a renormalized contact interaction to extend the validity of the zero-range interaction to large scattering lengths. Then this renormalized interaction is applied to many-body theories to determined those universal relations of the system. From the few-body perspective, we discuss the scattering between atoms in a single-color radio-frequency field. Our motivation is proposing the radio-frequency field as an effective tool to control interactions between cold atoms. Such a technique may be useful in future experiments such as creating phase transitions in spinor condensates. We also discuss the formation of ultracold molecules using radio-freqency fields from a time-dependent approach.

The Coldest Place in the Universe: Probing the Ultra-cold Outflow and Dusty Disk in the Boomerang Nebula

Science.gov (United States)

Sahai, R.; Vlemmings, W. H. T.; Nyman, L.-Å.

2017-06-01

Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is the coldest known object in the universe, with a massive high-speed outflow that has cooled significantly below the cosmic background temperature. Our new CO 1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow, out to ≳120,000 au. We find that in the ultra-cold outflow, the mass-loss rate (\\dot{M}) increases with radius, similar to its expansion velocity (V)—taking V\\propto r, we find \\dot{M}\\propto {r}0.9{--2.2}. The mass in the ultra-cold outflow is ≳ 3.3 M ⊙, and the Boomerang’s main-sequence progenitor mass is ≳ 4 M ⊙. Our high angular resolution (˜ 0\\buildrel{\\prime\\prime}\\over{.} 3) CO J = 3-2 map shows the inner bipolar nebula’s precise, highly collimated shape, and a dense central waist of size (FWHM) ˜1740 au × 275 au. The molecular gas and the dust as seen in scattered light via optical Hubble Space Telescope imaging show a detailed correspondence. The waist shows a compact core in thermal dust emission at 0.87-3.3 mm, which harbors (4{--}7)× {10}-4 M ⊙ of very large (˜millimeter-to-centimeter sized), cold (˜ 20{--}30 K) grains. The central waist (assuming its outer regions to be expanding) and fast bipolar outflow have expansion ages of ≲ 1925 {years} and ≤slant 1050 {years}: the “jet-lag” (I.e., torus age minus the fast-outflow age) in the Boomerang supports models in which the primary star interacts directly with a binary companion. We argue that this interaction resulted in a common-envelope configuration, while the Boomerang’s primary was an RGB or early-AGB star, with the companion finally merging into the primary’s core, and ejecting the primary’s envelope that now forms the ultra-cold outflow.

Geometric phase effects in ultracold chemistry

Science.gov (United States)

Hazra, Jisha; Naduvalath, Balakrishnan; Kendrick, Brian K.

2016-05-01

In molecules, the geometric phase, also known as Berry's phase, originates from the adiabatic transport of the electronic wavefunction when the nuclei follow a closed path encircling a conical intersection between two electronic potential energy surfaces. It is demonstrated that the inclusion of the geometric phase has an important effect on ultracold chemical reaction rates. The effect appears in rotationally and vibrationally resolved integral cross sections as well as cross sections summed over all product quantum states. It arises from interference between scattering amplitudes of two reaction pathways: a direct path and a looping path that encircle the conical intersection between the two lowest adiabatic electronic potential energy surfaces. Illustrative results are presented for the O+ OH --> H+ O2 reaction and for hydrogen exchange in H+ H2 and D+HD reactions. It is also qualitatively demonstrated that the geometric phase effect can be modulated by applying an external electric field allowing the possibility of quantum control of chemical reactions in the ultracold regime. This work was supported in part by NSF Grant PHY-1505557 (N.B.) and ARO MURI Grant No. W911NF-12-1-0476 (N.B.).

Manipulating ultracold polar molecules with microwave radiation: The influence of hyperfine structure

International Nuclear Information System (INIS)

Aldegunde, J.; Hutson, Jeremy M.; Ran Hong

2009-01-01

We calculate the microwave spectra of ultracold 40 K 87 Rb alkali-metal dimers, including hyperfine interactions and in the presence of electric and magnetic fields. We show that microwave transitions may be used to transfer molecules between different hyperfine states, but only because of the presence of nuclear quadrupole interactions. Hyperfine splittings may also complicate the use of ultracold molecules for quantum computing. The spectrum of molecules oriented in electric fields may be simplified dramatically by applying a simultaneous magnetic field.

Photo-associative ionization in ultracold sodium atoms

International Nuclear Information System (INIS)

Bagnato, V.; Marcassa, L.; Tsao, C.; Wang, Y.; Weiner, J.

1993-01-01

We study photo-associative ionization (PAI) for sodium atoms held in a magneto-optical trap (T < 1 mK). The process is investigated using one and two laser frequencies. For a single color PAI, we measure the rate constant as a function of light intensity and the result is compared with calculation based on semiclassical Bloch equation theory. The measured rate constant appears to saturate sooner than theory. In the two-color PAI (TCPAI) we investigate individual steps of the process. Different combinations of laser frequencies prepare different populations in each of the hyperfine ground state and the contribution of each one in this collisional process is investigated. The comparison with theory allows a fairly clear understanding of PAI and TCPAI

Dynamic of cold-atom tips in anharmonic potentials

Science.gov (United States)

Menold, Tobias; Federsel, Peter; Rogulj, Carola; Hölscher, Hendrik; Fortágh, József

2016-01-01

Background: Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion. Results: Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time. In agreement with theory, the first measurements show that particle interactions and anharmonic motion have a significant impact on the tip dynamics. Conclusion: Our findings will be crucial for the realization of high-sensitivity force spectroscopy with cold-atom tips and could possibly allow for the development of advanced spectroscopic techniques such as Q-control. PMID:28144505

Virtual states, halos and resonances in three-body atomic and nuclear systems

International Nuclear Information System (INIS)

Frederico, T.; Yamashita, M.T.; Tomio, L.

2009-01-01

By considering nuclear and ultracold trapped atomic systems, we review the trajectory of Efimov excited states in the complex plane by changing the two-body scattering lengths and one three-body scale. This article is based on the presentation by T. Frederico at the Fifth Workshop on Critical Stability, Erice, Sicily. (author)

Atomic and molecular hydrogen gas temperatures in a low-pressure helicon plasma

Science.gov (United States)

Samuell, Cameron M.; Corr, Cormac S.

2015-08-01

Neutral gas temperatures in hydrogen plasmas are important for experimental and modelling efforts in fusion technology, plasma processing, and surface modification applications. To provide values relevant to these application areas, neutral gas temperatures were measured in a low pressure (radiofrequency helicon discharge using spectroscopic techniques. The atomic and molecular species were not found to be in thermal equilibrium with the atomic temperature being mostly larger then the molecular temperature. In low power operation (measurements near a graphite target demonstrated localised cooling near the sample surface. The temporal evolution of the molecular gas temperature during a high power 1.1 ms plasma pulse was also investigated and found to vary considerably as a function of pressure.

Fermionic Collective Excitations in a Lattice Gas of Rydberg Atoms

International Nuclear Information System (INIS)

Olmos, B.; Gonzalez-Ferez, R.; Lesanovsky, I.

2009-01-01

We investigate the many-body quantum states of a laser-driven gas of Rydberg atoms confined to a large spacing ring lattice. If the laser driving is much stronger than the van der Waals interaction among the Rydberg atoms, these many-body states are collective fermionic excitations. The first excited state is a spin wave that extends over the entire lattice. We demonstrate that our system permits us to study fermions in the presence of disorder although no external atomic motion takes place. We analyze how this disorder influences the excitation properties of the fermionic states. Our work shows a route towards the creation of complex many-particle states with atoms in lattices.

Effects of N2 mixed gas atomization on electrochemical properties of Mm(Ni,Co,Mn,Al)5.0 alloy powder

International Nuclear Information System (INIS)

Yanagimoto, K.; Sunada, S.; Majima, K.; Sawada, T.

2004-01-01

N 2 gas, N 2 -Ar mixed gas and Ar gas atomization followed by acid surface treatment was applied to improve electrochemical properties of AB 5 type hydrogen storage alloy powder. The shape of Ar atomized powder was spherical and it changed to be irregular with increasing N 2 content of mixed gas. Irrespective of gas kinds, electrodes of atomized powder showed the same discharge capacity as cast-pulverized powder under auxiliary electrical conductivity by nickel powder addition. Without nickel powder, however, N 2 atomized powder showed the best electrochemical properties as well as gas activation behavior. By the combination process of N 2 gas atomization and acid surface treatment, it was considered that irregular shape of N 2 atomized powder promoted electrical conductivity of electrodes and catalytic nickel concentrated surface layer was formed to increase the hydrogen storage rapidity

Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases

Directory of Open Access Journals (Sweden)

Antonello Sindona

2015-03-01

Full Text Available The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.

Diffusion of Magnetized Binary Ionic Mixtures at Ultracold Plasma Conditions

Science.gov (United States)

Vidal, Keith R.; Baalrud, Scott D.

2017-10-01

Ultracold plasma experiments offer an accessible means to test transport theories for strongly coupled systems. Application of an external magnetic field might further increase their utility by inhibiting heating mechanisms of ions and electrons and increasing the temperature at which strong coupling effects are observed. We present results focused on developing and validating a transport theory to describe binary ionic mixtures across a wide range of coupling and magnetization strengths relevant to ultracold plasma experiments. The transport theory is an extension of the Effective Potential Theory (EPT), which has been shown to accurately model correlation effects at these conditions, to include magnetization. We focus on diffusion as it can be measured in ultracold plasma experiments. Using EPT within the framework of the Chapman-Enskog expansion, the parallel and perpendicular self and interdiffusion coefficients for binary ionic mixtures with varying mass ratios are calculated and are compared to molecular dynamics simulations. The theory is found to accurately extend Braginskii-like transport to stronger coupling, but to break down when the magnetization strength becomes large enough that the typical gyroradius is smaller than the interaction scale length. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-16-1-0221.

Sub-Doppler temperature measurements of laser-cooled atoms using optical nanofibres

International Nuclear Information System (INIS)

Russell, Laura; Daly, Mark J; Chormaic, Síle Nic; Deasy, Kieran; Morrissey, Michael J

2012-01-01

We present a method for measuring the average temperature of a cloud of cold 85 Rb atoms in a magneto-optical trap using an optical nanofibre. A periodic spatial variation is applied to the magnetic fields generated by the trapping coils and this causes the trap centre to oscillate, which, in turn, causes the cloud of cold atoms to oscillate. The optical nanofibre is used to collect the fluorescence emitted by the cold atoms, and the frequency response between the motion of the centre of the oscillating trap and the cloud of atoms is determined. This allows us to make measurements of cloud temperature both above and below the Doppler limit, thereby paving the way for nanofibres to be integrated with ultracold atoms for hybrid quantum devices

Coherent and non coherent atom optics experiment with an ultra-narrow beam of metastable rare gas atoms

International Nuclear Information System (INIS)

Grucker, J.

2007-12-01

In this thesis, we present a new type of atomic source: an ultra-narrow beam of metastable atoms produced by resonant metastability exchange inside a supersonic beam of rare gas atoms. We used the coherence properties of this beam to observe the diffraction of metastable helium, argon and neon atoms by a nano-transmission grating and by micro-reflection-gratings. Then, we evidenced transitions between Zeeman sublevels of neon metastable 3 P 2 state due to the quadrupolar part of Van der Waals potential. After we showed experimental proofs of the observation of this phenomenon, we calculated the transition probabilities in the Landau - Zener model. We discussed the interest of Van der Waals - Zeeman transitions for atom interferometry. Last, we described the Zeeman cooling of the supersonic metastable argon beam ( 3 P 2 ). We have succeeded in slowing down atoms to speeds below 100 m/s. We gave experimental details and showed the first time-of-flight measurements of slowed atoms

Lamb-Dicke spectroscopy of atoms in a hollow-core photonic crystal fibre

Science.gov (United States)

Okaba, Shoichi; Takano, Tetsushi; Benabid, Fetah; Bradley, Tom; Vincetti, Luca; Maizelis, Zakhar; Yampol'skii, Valery; Nori, Franco; Katori, Hidetoshi

2014-01-01

Unlike photons, which are conveniently handled by mirrors and optical fibres without loss of coherence, atoms lose their coherence via atom–atom and atom–wall interactions. This decoherence of atoms deteriorates the performance of atomic clocks and magnetometers, and also hinders their miniaturization. Here we report a novel platform for precision spectroscopy. Ultracold strontium atoms inside a kagome-lattice hollow-core photonic crystal fibre are transversely confined by an optical lattice to prevent atoms from interacting with the fibre wall. By confining at most one atom in each lattice site, to avoid atom–atom interactions and Doppler effect, a 7.8-kHz-wide spectrum is observed for the 1S0−3P1(m=0) transition. Atoms singly trapped in a magic lattice in hollow-core photonic crystal fibres improve the optical depth while preserving atomic coherence time. PMID:24934478

Light absorption during alkali atom-noble gas atom interactions at thermal energies: a quantum dynamics treatment.

Science.gov (United States)

Pacheco, Alexander B; Reyes, Andrés; Micha, David A

2006-10-21

The absorption of light during atomic collisions is treated by coupling electronic excitations, treated quantum mechanically, to the motion of the nuclei described within a short de Broglie wavelength approximation, using a density matrix approach. The time-dependent electric dipole of the system provides the intensity of light absorption in a treatment valid for transient phenomena, and the Fourier transform of time-dependent intensities gives absorption spectra that are very sensitive to details of the interaction potentials of excited diatomic states. We consider several sets of atomic expansion functions and atomic pseudopotentials, and introduce new parametrizations to provide light absorption spectra in good agreement with experimentally measured and ab initio calculated spectra. To this end, we describe the electronic excitation of the valence electron of excited alkali atoms in collisions with noble gas atoms with a procedure that combines l-dependent atomic pseudopotentials, including two- and three-body polarization terms, and a treatment of the dynamics based on the eikonal approximation of atomic motions and time-dependent molecular orbitals. We present results for the collision induced absorption spectra in the Li-He system at 720 K, which display both atomic and molecular transition intensities.

Laser diagnostics of the energy spectrum of Rydberg states of the lithium-7 atom

Energy Technology Data Exchange (ETDEWEB)

Zelener, B. B., E-mail: bobozel@mail.ru; Saakyan, S. A.; Sautenkov, V. A.; Manykin, E. A.; Zelener, B. V.; Fortov, V. E. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2015-12-15

The spectra of excited lithium-7 atoms prepared in a magneto-optical trap are studied using a UV laser. The laser diagnostics of the energy of Rydberg atoms is developed based on measurements of the change in resonance fluorescence intensity of ultracold atoms as the exciting UV radiation frequency passes through the Rydberg transition frequency. The energies of various nS configurations are obtained in a broad range of the principal quantum number n from 38 to 165. The values of the quantum defect and ionization energy obtained in experiments and predicted theoretically are discussed.

On a magnet configuration for confining ultracold neutrons

International Nuclear Information System (INIS)

Abov, Yu.G.; Vasil'ev, V.V.; Vladimirskij, V.V.; Krupchitskij, P.A.; Rissukhin, V.K.

1977-01-01

A magnetic system for experiments on the ultracold neutron confinement is described. The magnetic field calculation results are given. They make it possible to select the geometric places of points in which the neutron depolarization may appear and to suggest the way for diminishing the depolarization

Influence of the atomic mass of the background gas on laser ablation plume propagation

DEFF Research Database (Denmark)

Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

2008-01-01

A combination of time-of-flight ion probe measurements and gas dynamical modeling has been used to investigate the propagation of a laser ablation plume in gases of different atomic/molecular weight. The pressure variation of the ion time-of-flight was found to be well described by the gas...... dynamical model of Predtechensky and Mayorov (Appl. Supercond. 1:2011, 1993). In particular, the model describes how the pressure required to stop the plume in a given distance depends on the atomic/molecular weight of the gas, which is a feature that cannot be explained by standard point......-blast-wave descriptions of laser ablation plume expansion in gas....

Subwavelength Localization of Atomic Excitation Using Electromagnetically Induced Transparency

Directory of Open Access Journals (Sweden)

J. A. Miles

2013-09-01

Full Text Available We report an experiment in which an atomic excitation is localized to a spatial width that is a factor of 8 smaller than the wavelength of the incident light. The experiment utilizes the sensitivity of the dark state of electromagnetically induced transparency (EIT to the intensity of the coupling laser beam. A standing-wave coupling laser with a sinusoidally varying intensity yields tightly confined Raman excitations during the EIT process. The excitations, located near the nodes of the intensity profile, have a width of 100 nm. The experiment is performed using ultracold ^{87}Rb atoms trapped in an optical dipole trap, and atomic localization is achieved with EIT pulses that are approximately 100 ns long. To probe subwavelength atom localization, we have developed a technique that can measure the width of the atomic excitations with nanometer spatial resolution.

Making ultracold molecules in a two-color pump-dump photoassociation scheme using chirped pulses

International Nuclear Information System (INIS)

Koch, Christiane P.; Luc-Koenig, Eliane; Masnou-Seeuws, Francoise

2006-01-01

This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A, 70, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in the ground triplet state. We discuss (i) broad-bandwidth dump pulses which maximize the probability to form molecules while creating a broad vibrational distribution as well as (ii) narrow-bandwidth pulses populating a single vibrational ground state level, bound by 113 cm -1 . The use of chirped pulses makes the two-color scheme robust, simple, and efficient

Controlling interactions between highly magnetic atoms with Feshbach resonances.

Science.gov (United States)

Kotochigova, Svetlana

2014-09-01

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

An improved model of fission gas atom transport in irradiated uranium dioxide

Science.gov (United States)

Shea, J. H.

2018-04-01

The hitherto standard approach to predicting fission gas release has been a pure diffusion gas atom transport model based upon Fick's law. An additional mechanism has subsequently been identified from experimental data at high burnup and has been summarised in an empirical model that is considered to embody a so-called fuel matrix 'saturation' phenomenon whereby the fuel matrix has become saturated with fission gas so that the continued addition of extra fission gas atoms results in their expulsion from the fuel matrix into the fuel rod plenum. The present paper proposes a different approach by constructing an enhanced fission gas transport law consisting of two components: 1) Fick's law and 2) a so-called drift term. The new transport law can be shown to be effectively identical in its predictions to the 'saturation' approach and is more readily physically justifiable. The method introduces a generalisation of the standard diffusion equation which is dubbed the Drift Diffusion Equation. According to the magnitude of a dimensionless Péclet number, P, the new equation can vary from pure diffusion to pure drift, which latter represents a collective motion of the fission gas atoms through the fuel matrix at a translational velocity. Comparison is made between the saturation and enhanced transport approaches. Because of its dependence on P, the Drift Diffusion Equation is shown to be more effective at managing the transition from one type of limiting transport phenomenon to the other. Thus it can adapt appropriately according to the reactor operation.

Computer simulation of void formation in residual gas atom free metals by dual beam irradiation experiments

International Nuclear Information System (INIS)

Shimomura, Y.; Nishiguchi, R.; La Rubia, T.D. de; Guinan, M.W.

1992-01-01

In our recent experiments (1), we found that voids nucleate at vacancy clusters which trap gas atoms such as hydrogen and helium in ion- and neutron-irradiated copper. A molecular dynamics computer simulation, which implements an empirical embedded atom method to calculate forces that act on atoms in metals, suggests that a void nucleation occurs in pure copper at six and seven vacancy clusters. The structure of six and seven vacancy clusters in copper fluctuates between a stacking fault tetrahedron and a void. When a hydrogen is trapped at voids of six and seven vacancy, a void can keep their structure for appreciably long time; that is, the void do not relax to a stacking fault tetrahedron and grows to a large void. In order to explore the detailed atomics of void formation, it is emphasized that dual-beam irradiation experiments that utilize beams of gas atoms and self-ions should be carried out with residual gas atom free metal specimens. (author)

Bloch oscillations of ultracold atoms and measurement of the fine structure constant

International Nuclear Information System (INIS)

Clade, P.

2005-10-01

From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technique of Bloch oscillations, which allows us to transfer a large number of recoils to atoms. A velocity sensor, based on velocity selective Raman transition, enables us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 10 -9 , in conjunction with a careful study of systematic effects (5 10 -9 ), has led us to a determination of alpha with an uncertainty of 6.7 10 -9 : α -1 (Rb) = 137.03599878 (91). This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry. (author)

Recent results from the chemistry of recoiling carbon and silicon atoms: The interplay between hot atom chemistry and gas kinetics

International Nuclear Information System (INIS)

Gaspar, P.P.; Garmestani, K.; Ferrieri, R.A.; Wolf, A.P.

1990-01-01

Recent results from the chemistry of recoiling carbon and silicon atoms illustrate the power of an experimental approach to the solution of complex mechanistic problems that combines the study of the reactions of recoiling atoms with conventional gas kinetic techniques. Included will be the reactions of 11 C atoms with anisole, addressing the question whether an aromatic pi-electron system can compete as a reactive site with carbon-hydrogen bonds

All-optical spinor Bose-Einstein condensation and the spinor dynamics-driven atom laser

Science.gov (United States)

Lundblad, Nathan Eric

Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature---a phenomenon known as Bose-Einstein condensation---has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial ('spinor BEC'), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO2 laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin

Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment

Science.gov (United States)

Williams, Jason; D'Incao, Jose; Chiow, Sheng-Wey; Yu, Nan

2015-05-01

Precision atom interferometers (AI) in space promise exciting technical capabilities for fundamental physics research, with proposals including unprecedented tests of the weak equivalence principle, precision measurements of the fine structure and gravitational constants, and detection of gravity waves and dark energy. Consequently, multiple AI-based missions have been proposed to NASA, including a dual-atomic-species interferometer that is to be integrated into the Cold Atom Laboratory (CAL) onboard the International Space Station. In this talk, I will discuss our plans and preparation at JPL for the proposed flight experiments to use the CAL facility to study the leading-order systematics expected to corrupt future high-precision measurements of fundamental physics with AIs in microgravity. The project centers on the physics of pairwise interactions and molecular dynamics in these quantum systems as a means to overcome uncontrolled shifts associated with the gravity gradient and few-particle collisions. We will further utilize the CAL AI for proof-of-principle tests of systematic mitigation and phase-readout techniques for use in the next-generation of precision metrology experiments based on AIs in microgravity. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Ultracold neutron detectors based on {sup 10}B converters used in the qBounce experiments

Energy Technology Data Exchange (ETDEWEB)

Jenke, Tobias, E-mail: tjenke@ati.ac.at [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); Cronenberg, Gunther; Filter, Hanno [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); Geltenbort, Peter [Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Klein, Martin [Physikalisches Institut Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg (Germany); Lauer, Thorsten [FRM II, TU München, Lichtenbergstraße 1, 85748 Garching (Germany); Mitsch, Kevin [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); Saul, Heiko [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); FRM II, TU München, Lichtenbergstraße 1, 85748 Garching (Germany); Seiler, Dominik [Physik Department, TU München, James-Franck-Straße, 85748 Garching (Germany); Stadler, David [Physikalisches Institut Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg (Germany); Thalhammer, Martin [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); Abele, Hartmut, E-mail: abele@ati.ac.at [Atominstitut TU Wien, Stadionallee 2, 1020 Wien (Austria); Physikalisches Institut Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg (Germany); Physik Department, TU München, James-Franck-Straße, 85748 Garching (Germany)

2013-12-21

Gravity experiments with very slow, so-called ultracold neutrons connect quantum mechanics with tests of Newton's inverse square law at short distances. These experiments face a low count rate and hence need highly optimized detector concepts. In the frame of this paper, we present low-background ultracold neutron counters and track detectors with micron resolution based on a {sup 10}B converter. We discuss the optimization of {sup 10}B converter layers, detector design and concepts for read-out electronics focusing on high-efficiency and low-background. We describe modifications of the counters that allow one to detect ultracold neutrons selectively on their spin-orientation. This is required for searches of hypothetical forces with spin–mass couplings. The mentioned experiments utilize a beam-monitoring concept which accounts for variations in the neutron flux that are typical for nuclear research facilities. The converter can also be used for detectors, which feature high efficiencies paired with high spatial resolution of 1–2μm. They allow one to resolve the quantum mechanical wave function of an ultracold neutron bound in the gravity potential above a neutron mirror.

Casimir interaction between gas media of excited atoms

International Nuclear Information System (INIS)

Sherkunov, Yury

2007-01-01

The retarded dispersion interaction (Casimir interaction) between two dilute dielectric media at high temperatures is considered. The excited atoms are taken into account. It is shown that the perturbation technique cannot be applied to this problem due to divergence of integrals. A non-perturbative approach based on kinetic Green functions is implemented. We consider the interaction between two atoms (one of them is excited) embedded in an absorbing dielectric medium. We take into account the possible absorption of photons in the medium, which solves the problem of divergence. The force between two plane dilute dielectric media is calculated at pair interaction approximation. We show that the result of quantum electrodynamics differs from the Lifshitz formula for dilute gas media at high temperatures (if the number of excited atoms is significant). According to quantum electrodynamics, the interaction may be either attractive or repulsive depending on the temperature and the density numbers of the media

Ultracold fermion race is on

International Nuclear Information System (INIS)

Hulet, R.

1999-01-01

At the quantum level, particles behave very differently depending on whether their spin angular momentum is an integer or a half-integer. Half-integer spin particles are known as fermions, and include all the constituents of atoms: electrons, protons and neutrons. Bosons, on the other hand, are particles with integer spin, such as photons. Atoms are fermions if they are composed of an odd number of particles, like helium-3 or lithium-6. If they have an even number of constituents, like hydrogen, helium-4 or lithium-7, they are known as bosons. Fermions and bosons behave in profoundly different ways under certain conditions, especially at low temperatures. Four years ago, physicists created a Bose condensate, a quantum degenerate gas of bosons. Now the race is on to do the same with fermions. Deborah Jin's group at the US National Institute of Standards and Technology (NIST) and the University of Colorado has cooled a fermion gas to the lowest temperature yet (B DeMarco 1999 Phys. Rev. Lett. 82 4208). And John Thomas and co-workers at Duke University have set a new record for the length of time that fermions can be trapped using lasers (K O'Hara 1999 Phys. Rev. Lett. 82 4204). In this article the author describes the latest advances in the race to create a quantum degenerate gas of fermions. (UK)

Phase diagrams for an ideal gas mixture of fermionic atoms and bosonic molecules

DEFF Research Database (Denmark)

Williams, J. E.; Nygaard, Nicolai; Clark, C. W.

2004-01-01

We calculate the phase diagrams for a harmonically trapped ideal gas mixture of fermionic atoms and bosonic molecules in chemical and thermal equilibrium, where the internal energy of the molecules can be adjusted relative to that of the atoms by use of a tunable Feshbach resonance. We plot...... diagrams obtained in recent experiments on the Bose-Einstein condensation to Bardeen-Cooper-Schrieffer crossover, in which the condensate fraction is plotted as a function of the initial temperature of the Fermi gas measured before a sweep of the magnetic field through the resonance region....

Scattering resonances in a low-dimensional Rashba-Dresselhaus spin-orbit coupled quantum gas

Science.gov (United States)

Wang, Su-Ju; Blume, D.

2017-04-01

Confinement-induced resonances allow for the tuning of the effective one-dimensional coupling constant. When the scattering state associated with the ground transverse mode is brought into resonance with the bound state attached to the energetically excited transverse modes, the atoms interact through an infinitely strong repulsion. This provides a route to realize the Tonks-Girardeau gas. On the other hand, the realization of synthetic gauge fields in cold atomic systems has attracted a lot of attention. For instance, bound-state formation is found to be significantly modified in the presence of spin-orbit coupling in three dimensions. This motivates us to study ultracold collisions between two Rashba-Dresselhaus spin-orbit coupled atoms in a quasi-one-dimensional geometry. We develop a multi-channel scattering formalism that accounts for the external transverse confinement and the spin-orbit coupling terms. The interplay between these two single-particle terms is shown to give rise to new scattering resonances. In particular, it is analyzed what happens when the scattering energy crosses the various scattering thresholds that arise from the single-particle confinement and the spin-orbit coupling. Support by the NSF is gratefully acknowledged.

Multiphoton Ionization of Laser Cooled Lithium

OpenAIRE

Steinmann, Jochen

2007-01-01

Reaction microscopes enable kinematically complete measurements of atomic and molecular fragmentation. An ultracold atomic target is usually provided by a supersonic gas jet. The apparatus developed in the course of this thesis for the first time combines the principle of the reaction microscope with a magneto-optical trap. This allows for the preparation of lithium atoms in the sub-mK range. Being a three-electron system, its simple atomic structure makes lithium a model system of great topi...

Universality and Quantum Criticality of the One-Dimensional Spinor Bose Gas

Science.gov (United States)

PâÅ£u, Ovidiu I.; Klümper, Andreas; Foerster, Angela

2018-06-01

We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point. Remarkably, in the Tonks-Girardeau regime, the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices.

Measurements of an ablator-gas atomic mix in indirectly driven implosions at the National Ignition Facility.

Science.gov (United States)

Smalyuk, V A; Tipton, R E; Pino, J E; Casey, D T; Grim, G P; Remington, B A; Rowley, D P; Weber, S V; Barrios, M; Benedetti, L R; Bleuel, D L; Bradley, D K; Caggiano, J A; Callahan, D A; Cerjan, C J; Clark, D S; Edgell, D H; Edwards, M J; Frenje, J A; Gatu-Johnson, M; Glebov, V Y; Glenn, S; Haan, S W; Hamza, A; Hatarik, R; Hsing, W W; Izumi, N; Khan, S; Kilkenny, J D; Kline, J; Knauer, J; Landen, O L; Ma, T; McNaney, J M; Mintz, M; Moore, A; Nikroo, A; Pak, A; Parham, T; Petrasso, R; Sayre, D B; Schneider, M B; Tommasini, R; Town, R P; Widmann, K; Wilson, D C; Yeamans, C B

2014-01-17

We present the first results from an experimental campaign to measure the atomic ablator-gas mix in the deceleration phase of gas-filled capsule implosions on the National Ignition Facility. Plastic capsules containing CD layers were filled with tritium gas; as the reactants are initially separated, DT fusion yield provides a direct measure of the atomic mix of ablator into the hot spot gas. Capsules were imploded with x rays generated in hohlraums with peak radiation temperatures of ∼294  eV. While the TT fusion reaction probes conditions in the central part (core) of the implosion hot spot, the DT reaction probes a mixed region on the outer part of the hot spot near the ablator-hot-spot interface. Experimental data were used to develop and validate the atomic-mix model used in two-dimensional simulations.

Cold atomic gas in the inner Galaxy

International Nuclear Information System (INIS)

Garwood, R.W.; Dickey, J.M.

1989-01-01

A new set of 21 cm H I absorption spectra were obtained toward 21 compact continuum sources in the Galactic plane is presented. The 21 cm line velocity-averaged absorption coefficient as a function of Galactocentric distance is calculated. The result for distances within 2 kpc of the sun agrees with the local value found from absorption toward pulsars of 5-7 km/s/kpc. Overall, the absorption coefficient decreases to about half of its local value inside a Galactocentric radius of about 4 kpc. This decrease is shown to be primarily due to an increase in the mean line-of-sight distance between absorbing atomic clouds. Thus, the cool phase of the atomic gas is less abundant in the inner Galaxy than at the solar circle. The absorption spectra are similar in appearance to existing (C-12)O spectra. The spectral regions which show H I absorption also show CO emission. 43 references

Universal structure of a strongly interacting Fermi gas

Energy Technology Data Exchange (ETDEWEB)

Kuhnle, Eva; Dyke, Paul; Hoinka, Sascha; Mark, Michael; Hu Hui; Liu Xiaji; Drummond, Peter; Hannaford, Peter; Vale, Chris, E-mail: cvale@swin.edu.au [ARC Centre of Excellence for Quantum Atom Optics, Swinburne University of Technology, Hawthorn 3122 (Australia)

2011-01-10

This paper presents studies of the universal properties of strongly interacting Fermi gases using Bragg spectroscopy. We focus on pair-correlations, their relationship to the contact C introduced by Tan, and their dependence on both the momentum and temperature. We show that short-range pair correlations obey a universal law, first derived by Tan through measurements of the static structure factor, which displays a universal scaling with the ratio of the contact to the momentum C/q. Bragg spectroscopy of ultracold {sup 6}Li atoms is employed to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We show that calibrating our Bragg spectra using the f-sum rule leads to a dramatic improvement in the accuracy of the structure factor measurement. We also measure the temperature dependence of the contact in a unitary gas and compare our results to calculations based on a virial expansion.

Characterization of atomic spin polarization lifetime of cesium vapor cells with neon buffer gas

Science.gov (United States)

Lou, Janet W.; Cranch, Geoffrey A.

2018-02-01

The dephasing time of spin-polarized atoms in an atomic vapor cell plays an important role in determining the stability of vapor-cell clocks as well as the sensitivity of optically-pumped magnetometers. The presence of a buffer gas can extend the lifetime of these atoms. Many vapor cell systems operate at a fixed (often elevated) temperature. For ambient temperature operation with no temperature control, it is necessary to characterize the temperature dependence as well. We present a spin-polarization lifetime study of Cesium vapor cells with different buffer gas pressures, and find good agreement with expectations based on the combined effects of wall collisions, spin exchange, and spin destruction. For our (7.5 mm diameter) vapor cells, the lifetime can be increased by two orders of magnitude by introducing Ne buffer gas up to 100 Torr. Additionally, the dependence of the lifetime on temperature is measured (25 - 47 oC) and simulated for the first time to our knowledge with reasonable agreement.

Highly versatile atomic micro traps generated by multifrequency magnetic field modulation

International Nuclear Information System (INIS)

Courteille, Ph W; Deh, B; Fortagh, J; Guenther, A; Kraft, S; Marzok, C; Slama, S; Zimmermann, C

2006-01-01

We propose the realization of custom-designed adiabatic potentials for cold atoms based on multimode radio frequency radiation in combination with static inhomogeneous magnetic fields. For example, the use of radio frequency combs gives rise to periodic potentials acting as gratings for cold atoms. In strong magnetic field gradients, the lattice constant can be well below 1 μm. By changing the frequencies of the comb in time the gratings can easily be propagated in space, which may prove useful for Bragg scattering atomic matter waves. Furthermore, almost arbitrarily shaped potentials are possible such as disordered potentials on a scale of several 100 nm or lattices with a spatially varying lattice constant. The potentials can be made state selective and, in the case of atomic mixtures, also species selective. This opens new perspectives for generating tailored quantum systems based on ultracold single atoms or degenerate atomic and molecular quantum gases

Laser manipulation of atomic and molecular flows

Science.gov (United States)

Lilly, Taylor C.

The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques. The characteristics of these laser-based flow manipulations suggest that they may augment, or be superior to, such traditional electro-mechanical methods as ionic flow control, shock tubes, and small scale wind tunnels. In this study, methodology was developed for investigating laser flow manipulation techniques, and testing their feasibility for a number of aerospace, basic physics, and micro technology applications. Theories for laser-atom and laser-molecule interactions have been under development since the advent of laser technology. The theories have yet to be adequately integrated into kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the realm of ultra-cold atomic physics. This goal was realized in the present study. A representative numerical investigation, of laser-based neutral atomic and molecular flow manipulations, was conducted using near-resonant and non-resonant laser fields. To simulate the laser interactions over a range of laser and flow conditions, the following tools were employed: a custom collisionless gas particle trajectory code and a specifically modified version of the Direct Simulation Monte Carlo statistical kinetic solver known as SMILE. In addition to the numerical investigations, a validating experiment was conducted. The experimental results showed good agreement with the numerical simulations when experimental parameters, such as finite laser line width, were taken into account. Several areas of interest were addressed: laser induced neutral flow steering, collimation, direct flow acceleration, and neutral gas heating. Near-resonant continuous wave laser, and non-resonant pulsed laser, interactions with cesium and nitrogen were simulated. These simulations showed trends and some limitations associated with these interactions, used for flow

Experimental testing of the dispersion law of ultracold neutrons

International Nuclear Information System (INIS)

Bondarenko, I.V.; Krasnoperov, A.V.; Frank, A.I.; Geltenbort, P.; Hoghoj, P.; Klein, A.G.; Cimmino, A.; Masalovich, S.V.; Nosov, V.G.

1998-01-01

Experiment on testing the generally accepted laws on ultracold neutron dispersion is described. The experiment is based on search of displacement lines of a neutron interference filter resonance by variation of neutrons rapidity component, parallel to the filter surface. The first results testify to the presence of statistically meaningful effect

Interaction effects on dynamic correlations in noncondensed Bose gases

NARCIS (Netherlands)

Bezett, A.; Van Driel, H. J.; Mink, M. P.; Stoof, H. T C; Duine, R. A.

2014-01-01

We consider dynamic, i.e., frequency-dependent, correlations in noncondensed ultracold atomic Bose gases. In particular, we consider the single-particle correlation function and its power spectrum. We compute this power spectrum for a one-component Bose gas, and we show how it depends on the

Robust mesoscopic superposition of strongly correlated ultracold atoms

International Nuclear Information System (INIS)

Hallwood, David W.; Ernst, Thomas; Brand, Joachim

2010-01-01

We propose a scheme to create coherent superpositions of annular flow of strongly interacting bosonic atoms in a one-dimensional ring trap. The nonrotating ground state is coupled to a vortex state with mesoscopic angular momentum by means of a narrow potential barrier and an applied phase that originates from either rotation or a synthetic magnetic field. We show that superposition states in the Tonks-Girardeau regime are robust against single-particle loss due to the effects of strong correlations. The coupling between the mesoscopically distinct states scales much more favorably with particle number than in schemes relying on weak interactions, thus making particle numbers of hundreds or thousands feasible. Coherent oscillations induced by time variation of parameters may serve as a 'smoking gun' signature for detecting superposition states.

Quantum measurement-induced dynamics of many-body ultracold bosonic and fermionic systems in optical lattices

Science.gov (United States)

Mazzucchi, Gabriel; Kozlowski, Wojciech; Caballero-Benitez, Santiago F.; Elliott, Thomas J.; Mekhov, Igor B.

2016-02-01

Trapping ultracold atoms in optical lattices enabled numerous breakthroughs uniting several disciplines. Coupling these systems to quantized light leads to a plethora of new phenomena and has opened up a new field of study. Here we introduce an unusual additional source of competition in a many-body strongly correlated system: We prove that quantum backaction of global measurement is able to efficiently compete with intrinsic short-range dynamics of an atomic system. The competition becomes possible due to the ability to change the spatial profile of a global measurement at a microscopic scale comparable to the lattice period without the need of single site addressing. In coherence with a general physical concept, where new competitions typically lead to new phenomena, we demonstrate nontrivial dynamical effects such as large-scale multimode oscillations, long-range entanglement, and correlated tunneling, as well as selective suppression and enhancement of dynamical processes beyond the projective limit of the quantum Zeno effect. We demonstrate both the breakup and protection of strongly interacting fermion pairs by measurement. Such a quantum optical approach introduces into many-body physics novel processes, objects, and methods of quantum engineering, including the design of many-body entangled environments for open systems.

Chemical reactivity of the compressed noble gas atoms and their ...

Indian Academy of Sciences (India)

Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study ...

Multi-quantum excitation in optically pumped alkali atom: rare gas mixtures

Science.gov (United States)

Galbally-Kinney, K. L.; Rawlins, W. T.; Davis, S. J.

2014-03-01

Diode-pumped alkali laser (DPAL) technology offers a means of achieving high-energy gas laser output through optical pumping of the D-lines of Cs, Rb, and K. The exciplex effect, based on weak attractive forces between alkali atoms and polarizable rare gas atoms (Ar, Kr, Xe), provides an alternative approach via broadband excitation of exciplex precursors (XPAL). In XPAL configurations, we have observed multi-quantum excitation within the alkali manifolds which result in infrared emission lines between 1 and 4 μm. The observed excited states include the 42FJ states of both Cs and Rb, which are well above the two-photon energy of the excitation laser in each case. We have observed fluorescence from multi-quantum states for excitation wavelengths throughout the exciplex absorption bands of Cs-Ar, Cs-Kr, and Cs-Xe. The intensity scaling is roughly first-order or less in both pump power and alkali concentration, suggesting a collisional energy pooling excitation mechanism. Collisional up-pumping appears to present a parasitic loss term for optically pumped atomic systems at high intensities, however there may also be excitation of other lasing transitions at infrared wavelengths.

Excited Atoms and Molecules in High Pressure Gas Discharges

International Nuclear Information System (INIS)

Vuskovic, L.; Popovic, S.

2003-01-01

Various types of high-pressure non-thermal discharges are increasingly drawing attention in view of many interesting applications. These, partially ionized media in non-equilibrium state, tend to generate complex effects that are difficult to interpret without a detailed knowledge of elementary processes involved. Electronically excited molecules and atoms may play an important role as intermediate states in a wide range of atomic and molecular processes, many of which are important in high-pressure discharges. They can serve also as reservoirs of energy or as sources of high energy electrons either through the energy pooling or through superelastic collisions. By presenting the analysis of current situation on the processes involving excited atoms and molecules of interest for high-pressure gas discharges, we will attempt to draw attention on the insufficiency of available data. In the same time we will show how to circumvent this situation and still be able to develop accurate models and interpretations of the observed phenomena

Quasi-energy of ultracold neutrons

International Nuclear Information System (INIS)

Frank, A.I.; Nosov, V.G.

1992-01-01

A solution is found to the problem of the propagation of a neutron beam transmitted through a periodically acting high-speed chopper. It is a generalization of the Moshinsky's problem of the evolution of a plane wave in the right half-space after an ideal absorber at the origin of coordinates has been instantaneously removed. The energy spectrum of transmitted neutrons is found to be discrete and corresponding to their quasi-energy. Interference of the states corresponding to different satellite lines leads to a complex spatial pattern with typical beats. A number of experiments with ultracold neutrons are suggested and discussed. 12 refs.; 1 fig

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

Energy Technology Data Exchange (ETDEWEB)

Teichmann, M

2007-09-15

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

A Portable Source of Lattice-Trapped and Ultracold Strontium (PLUS), Phase II

Data.gov (United States)

National Aeronautics and Space Administration — We propose to demonstrate the portable source of lattice-trapped, ultracold strontium (PLUS) designed during Phase I. The device uses simplified and robust...

Interfacial-Bonding-Regulated CO Oxidation over Pt Atoms Immobilized on Gas-Exfoliated Hexagonal Boron Nitride

KAUST Repository

Liu, Xin; Zhu, Hongdan; Linguerri, Roberto; Han, Yu; Chambaud, Gilberte; Meng, Changgong

2017-01-01

We compared the electronic structure and CO oxidation mechanisms over Pt atoms immobilized by both B-vacancies and N-vacancies on gas-exfoliated hexagonal boron nitride. We showed that chemical bonds are formed between the B atoms associated

Time-dependent analysis of tunneling effect in the formation of ultracold molecules via photo-association of laser-cooled atoms

International Nuclear Information System (INIS)

Vatasescu, M.; Masnou-Seeuws, F.

2002-01-01

The paper contains a time-dependent investigation of the tunneling effect observed in the photo-association spectrum of Cs 2 and attributed to the 0 g - (6s,6p 3/2 ) double well. When by photo-association of two cold cesium atoms a vibrational level of the outer well is populated, tunneling is an efficient mechanism for transferring the population to the inner well (R 0 ), where spontaneous emission may lead to formation of cold molecules in low vibrational levels of the a 3 Σ u + (6s,6s) electronic state. This tunneling effect is analyzed by wave packets propagation, first considering the double well potential alone, and following a packet made by a superposition of states initially located at large distances. Characteristic times for the vibration dynamics, corresponding to a beating phenomenon between the two wells, to partial 'revival' at large distances, and to maxima in the population localized in the inner well are reported and discussed. Second, we simulate the two-channels a 3 Σ u + (6s,6s) → 0 g - (6s,6p 3/2 ) photo-association at detuning around 2.9 cm -1 : the inner well can be populated either by the excitation of a vibrational level of the external well (resonant excitation), or by tuning the photo-association laser at the energy of the inner well level which displays tunneling (''off-resonance excitation''). In the first case the photo-association is efficient, while the tunneling probability is small; in the second, the tunneling probability is large, so that despite the poor efficiency of the photo-association process, more population can be transferred to the inner well. This second choice is shown to be very sensitive to the laser intensity, which could be used to control the population of the inner well and hence the formation of ultracold molecules in low vibrational levels. (authors)

Self-bound droplets of a dilute magnetic quantum liquid

Science.gov (United States)

Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

2016-11-01

Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 108 times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

A portable source of lattice-trapped and ultracold strontium (PLUS), Phase I

Data.gov (United States)

National Aeronautics and Space Administration — We propose to design and demonstrate a portable source of lattice-trapped, ultracold strontium (PLUS). The device uses simplified and robust techniques for loading...

Continuous all-optical deceleration of molecular beams and demonstration with Rb atoms

Science.gov (United States)

Long, Xueping; Jayich, Andrew; Campbell, Wesley

2017-04-01

Ultracold samples of molecules are desirable for a variety of applications, such as many-body physics, precision measurement and quantum information science. However, the pursuit of ultracold molecules has achieved limited success: spontaneous emission into many different dark states makes it hard to optically decelerate molecules to trappable speed. We propose to address this problem with a general optical deceleration technique that exploits a pump-dump pulse pair from a mode-locked laser. A molecular beam is first excited by a counter-propagating ``pump'' pulse. The molecular beam is then driven back to the initial ground state by a co-propagating ``dump'' pulse via stimulated emission. The delay between the pump and dump pulse is set to be shorter than the excited state lifetimes in order to limit decays to dark states. We report progress benchmarking this stimulated force by accelerating a cold sample of neutral Rb atoms.

Band structure engineering for ultracold quantum gases in optical lattices

International Nuclear Information System (INIS)

Weinberg, Malte

2014-01-01

the same system maps onto a quantum spin-1/2 XY model. Owing to the quantum nature of the pseudospins, geometrical frustration leads to a highly degenerate ground state which can result in exotic valence bond spin-liquid phases. First signatures of an order-by-disorder effect emerge in this regime. A complementary approach to the manipulation of the band structure is investigated in a honeycomb potential. By rotating the quantization field of the system, the statedependent energy offset between the twofold atomic basis of the hexagonal Bravais lattice can be adjusted. This purposeful breaking of inversion symmetry enables the continuous opening of an energy gap at the Dirac points of the honeycomb band structure. In addition, a striking influence of the band gap onto the lifetimes for atoms in the first excited energy band is observed. In the last part of the thesis, both experimental manipulation techniques are discussed with respect to future applications for ultracold quantum gases in non-cubic optical lattices.

Intertwined and vestigial order with ultracold atoms in multiple cavity modes

Science.gov (United States)

Gopalakrishnan, Sarang; Shchadilova, Yulia E.; Demler, Eugene

2017-12-01

Atoms in transversely pumped optical cavities "self-organize" by forming a density wave and emitting superradiantly into the cavity mode(s). For a single-mode cavity, the properties of this self-organization transition are well characterized both theoretically and experimentally. Here, we explore the self-organization of a Bose-Einstein condensate in the presence of two cavity modes—a system that recently was realized experimentally [Léonard et al., Nature (London) 543, 87 (2017), 10.1038/nature21067]. We argue that this system can exhibit a "vestigially ordered" phase in which neither cavity mode exhibits superradiance but the cavity modes are mutually phase locked by the atoms. We argue that this vestigially ordered phase should generically be present in multimode cavity geometries.

Fermi-Dirac gas of atoms in a box with low adiabatic invariant

International Nuclear Information System (INIS)

Vlad, V.I.; Inonescu-Pallas, N.

2004-06-01

Quantum degenerate Fermi-Dirac gas of atoms, confined in a cubic box, shows an energy spectrum, which is discrete and strongly dependent on the atomic mass number, A at , box geometry and temperature, for low product of A at and the adiabatic invariant, TV 1/3 , i.e. on γ = A at TV 1/3 . The present study compares the total number of particles and the total energy obtained by summing up the contributions of a finite number of states, defined by the values of γ, to the widespread approximations of the corresponding integrals. The sums show simple calculation algorithms and more precise results for a large interval of values of γ. A new accurate analytic formula for the chemical potential of the Fermi-Dirac quantum gas is also given. (author)

Theory of a Nearly Two-Dimensional Dipolar Bose Gas

Science.gov (United States)

2016-05-11

order to be published, he sent the paper to Einstein to translate it. The other contributing scientist is world famous physicist Albert Einstein , maybe...mechanical state, a Bose- Einstein condensate (BEC), where the atoms cease to behave like distinguishable entities, and instead form a single macroscopic...model in both three- and two-dimensional geometries. 15. SUBJECT TERMS Bose Einstein condensation, ultracold physics, condensed matter, dipoles 16

Orbital alignment effects in near-resonant Rydberg atoms-rare gas collisions

International Nuclear Information System (INIS)

Isaacs, W.A.; Morrison, M.A.

1993-01-01

Recent experimental and theoretical studies of near-resonant energy transfer collisions involving rare-gas atoms and alkali or alkaline earth atoms which have been initially excited to an aligned state via one or more linearly polarized rasters have yielded a wealth of insight into orbital alignment and related effects. We have extended this inquiry to initially aligned Rydberg states, examining state-to-state and alignment-selected cross sections using quantum collision theory augmented by approximations appropriate to the special characteristics of the Rydberg state (e.g., the quasi-free-electron model and the impulse approximation)

Progress in atomizing high melting intermetallic titanium based alloys by means of a novel plasma melting induction guiding gas atomization facility (PIGA)

Energy Technology Data Exchange (ETDEWEB)

Gerling, R.; Schimansky, F.P.; Wagner, R. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung

1994-12-31

For the production of intermetallic titanium based alloy powders a novel gas atomization facility has been put into operation: By means of a plasma torch the alloy is melted in a water cooled copper crucible in skull melting technique. To the tap hole of the crucible, a novel transfer system is mounted which forms a thin melt stream and guides it into the gas nozzle. This transfer system consists of a ceramic free induction heated water cooled copper funnel. Gas atomization of {gamma}-TiAl (melting temperature 1400 C) and Ti{sub 5}Si{sub 3} (2130 C) proved the possibility to produce ceramic free pre-alloyed powders with this novel facility. The TiAl powder particles are spherical; about 20 wt.% are smaller than 45 {mu}m. The oxygen and copper pick up during atomization do not exceed 250 and 35 {mu}g/g respectively. The Ti{sub 5}Si{sub 3} powder particles are almost spherical. Only about 10 wt.% are <45 {mu}m whereas the O{sub 2} and Cu contamination is also kept at a very low level (250 and 20 {mu}g/g respectively). (orig.)

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

Energy Technology Data Exchange (ETDEWEB)

Teichmann, M

2007-09-15

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

Fundamental Interactions for Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment

Science.gov (United States)

D'Incao, Jose P.; Willians, Jason R.

2015-05-01

Precision atom interferometers (AI) in space are a key element for several applications of interest to NASA. Our proposal for participating in the Cold Atom Laboratory (CAL) onboard the International Space Station is dedicated to mitigating the leading-order systematics expected to corrupt future high-precision AI-based measurements of fundamental physics in microgravity. One important focus of our proposal is to enhance initial state preparation for dual-species AIs. Our proposed filtering scheme uses Feshbach molecular states to create highly correlated mixtures of heteronuclear atomic gases in both their position and momentum distributions. We will detail our filtering scheme along with the main factors that determine its efficiency. We also show that the atomic and molecular heating and loss rates can be mitigated at the unique temperature and density regimes accessible on CAL. This research is supported by the National Aeronautics and Space Administration.

Precision spectroscopy with ultracold 87Rb2 triplet molecules

International Nuclear Information System (INIS)

Strauss, Christoph

2011-01-01

In this thesis I report precision spectroscopy with ultracold 87 Rb 2 triplet molecules where we use lasers to couple the states in different molecular potentials. We study in detail states of the a 3 sum + u and (1) 3 sum + g potentials. These states are of great importance for transferring weakly bound molecules to the ro-vibrational triplet ground state via states of the excited potential. As most experiments start from molecules in their X 1 sum + g ground state, the triplet states were hard to access via dipole transitions and remained largely unexplored. The measurements presented in this thesis are the first detailed study of diatomic 87 Rb 2 molecules in these states. Our experiments start with an ultracold cloud of 87 Rb atoms. We then load this cloud into an optical lattice where we use a magnetic Feshbach resonance at 1007.4 G to perform a Feshbach association. After we have removed all unbound atoms, we end up with a pure sample of weakly bound Feshbach molecules inside the optical lattice. The optical lattice prevents these molecules from colliding with each other which results in molecular lifetimes on the order of a few hundred milliseconds. In the first set of experiments, we use a laser coupling the Feshbach state to the excited (1) 3 sum + g triplet state to map out its low-lying vibrational (v = 0.. 15), rotational, hyperfine, and Zeeman structure. The experimental results are in good agreement with calculations done by Marius Lysebo and Prof. Leif Veseth. We then map out in detail the vibrational, rotational, hyperfine, and Zeeman structure of the a 3 sum + u triplet ground state using dark state spectroscopy with levels in the (1) 3 sum + g potential as an intermediate state. In this scheme we are able to access molecules in triplet states because our Feshbach state has strong triplet character. Interestingly, it happens that some deeply bound states which belong to the X 1 sum + g potential are close to levels in the a 3 sum + u potential. In

A novel apparatus for the investigation of material properties for the storage of ultracold neutrons

International Nuclear Information System (INIS)

Brys, T.; Daum, M.; Fierlinger, P.; Geltenbort, P.; George, D.; Gupta, M.; Henneck, R.; Heule, S.; Horvat, M.; Kasprzak, M.; Kirch, K.; Kohlik, K.; Negrazus, M.; Pichlmaier, A.; Straumann, U.; Vrankovic, V.; Wermelinger, C.

2005-01-01

We have built a novel apparatus for the investigation of materials for the storage of ultracold neutrons. Neutrons are filled into a storage volume, confined at the bottom by a magnetic field, at the top by gravity and at the sides by the slit-less sample surface under investigation. For different beryllium and diamond-like carbon samples, storage times up to 200s were obtained at room temperature. The corresponding loss parameters η for ultracold neutrons varied between 4.2 and 6.8x10 -4 per wall collision

Excitation of surface waves of ultracold neutrons on absorbing trap walls as anomalous loss factor

International Nuclear Information System (INIS)

Bokun, R.Ch.

2006-01-01

One analyzed probability of excitation of surface waves of ultracold neutrons in terms of a plane model consisting of three media: vacuum, a finite depth neutron absorbing substance layer and a neutron reflecting substrate. One demonstrated the absence of the mentioned surface waves in terms of the generally accepted model of two media: vacuum contiguous to the plane surface of a substance filled half-space. One pointed out the effect of the excited surface waves of ultracold neutrons on the increase of their anomalous losses in traps [ru

Fidelity for kicked atoms with gravity near a quantum resonance.

Science.gov (United States)

Dubertrand, Rémy; Guarneri, Italo; Wimberger, Sandro

2012-03-01

Kicked atoms under a constant Stark or gravity field are investigated for experimental setups with cold and ultracold atoms. The parametric stability of the quantum dynamics is studied using the fidelity. In the case of a quantum resonance, it is shown that the behavior of the fidelity depends on arithmetic properties of the gravity parameter. Close to a quantum resonance, the long-time asymptotics of the fidelity is studied by means of a pseudoclassical approximation introduced by Fishman et al. [J. Stat. Phys. 110, 911 (2003)]. The long-time decay of fidelity arises from the tunneling out of pseudoclassical stable islands, and a simple ansatz is proposed which satisfactorily reproduces the main features observed in numerical simulations.

Ultracold fermion cooling cycle using heteronuclear Feshbach resonances

DEFF Research Database (Denmark)

Morales, M. A.; Nygaard, Nicolai; Williams, J. E.

2005-01-01

We consider an ideal gas of Bose and Fermi atoms in a harmonic trap, with a Feshbach resonance in the interspecies atomic scattering that can lead to the formation of fermionic molecules. We map out the phase diagram for this three-component mixture in chemical and thermal equilibrium. Considering...... adiabatic association and dissociation of the molecules, we identify a possible cooling cycle, which in ideal circumstances can yield an exponential increase of the phase-space density....

Production and manipulation of wave packets from ultracold atoms in an optical lattice

DEFF Research Database (Denmark)

Pedersen, Poul Lindholm; Gajdacz, Miroslav; Winter, Nils

2013-01-01

of the system. The modulation technique also allows for a controllable transfer (deexcitation) of atoms from such wave packets to a state bound by the lattice. Thus, it acts as a beam splitter for matter waves that can selectively address different bands, enabling the preparation of atoms in localized states...

The Use of an Air-Natural Gas Flame in Atomic Absorption.

Science.gov (United States)

Melucci, Robert C.

1983-01-01

Points out that excellent results are obtained using an air-natural gas flame in atomic absorption experiments rather than using an air-acetylene flame. Good results are obtained for alkali metals, copper, cadmium, and zinc but not for the alkaline earths since they form refractory oxides. (Author/JN)

Multiplicity dependence of matrix-induced frequency shifts for atomic transitions of the group 12 metals in rare gas solids

International Nuclear Information System (INIS)

Laursen, S.L.; Cartland, H.E.

1991-01-01

Atomic resonances of the group 12 metal atoms, Hg, Cd, and Zn, undergo frequency shifts from the gas phase atomic line when trapped in rare gas matrices of Ar, Kr, and Xe at 12 K. As expected, the shifts are approximately linear in polarizability of the rare gas, but the slope of this line depends on whether the transition in question is 1 P 1 left-arrow 1 S 0 or 3 P 1 left-arrow 1 S 0 . Thus the matrix-induced frequency shift is dependent on the singlet or triplet nature of the excited state as well as on the matrix material. This dependence on multiplicity is discussed in terms of interactions between the excited-state atomic orbitals and the matrix. The results are compared to matrix studies of other metals and to related gas-phase work on diatomic van der Waals complexes of group 12 metals with rare gases

Realistic Rashba and Dresselhaus spin-orbit coupling for neutral atoms

International Nuclear Information System (INIS)

Campbell, D. L.; Spielman, I. B.; Juzeliunas, G.

2011-01-01

We describe a new class of atom-laser coupling schemes which lead to spin-orbit-coupled Hamiltonians for ultracold neutral atoms. By properly setting the optical phases, a pair of degenerate pseudospin (a linear combination of internal atomic) states emerge as the lowest-energy eigenstates in the spectrum and are thus immune to collisionally induced decay. These schemes use N cyclically coupled ground or metastable internal states. We focus on two situations: a three-level case and a four-level case, where the latter adds a controllable Dresselhaus contribution. We describe an implementation of the four-level scheme for 87 Rb and analyze its sensitivity to typical laboratory noise sources. Last, we argue that the Rashba Hamiltonian applies only in the large intensity limit since any laser coupling scheme will produce terms nonlinear in momentum that decline with intensity.

Inhomogeneous spectral moment sum rules for the retarded Green function and self-energy of strongly correlated electrons or ultracold fermionic atoms in optical lattices

International Nuclear Information System (INIS)

Freericks, J. K.; Turkowski, V.

2009-01-01

Spectral moment sum rules are presented for the inhomogeneous many-body problem described by the fermionic Falicov-Kimball or Hubbard models. These local sum rules allow for arbitrary hoppings, site energies, and interactions. They can be employed to quantify the accuracy of numerical solutions to the inhomogeneous many-body problem such as strongly correlated multilayered devices, ultracold atoms in an optical lattice with a trap potential, strongly correlated systems that are disordered, or systems with nontrivial spatial ordering such as a charge-density wave or a spin-density wave. We also show how the spectral moment sum rules determine the asymptotic behavior of the Green function, self-energy, and dynamical mean field when applied to the dynamical mean-field theory solution of the many-body problem. In particular, we illustrate in detail how one can dramatically reduce the number of Matsubara frequencies needed to solve the Falicov-Kimball model while still retaining high precision, and we sketch how one can incorporate these results into Hirsch-Fye quantum Monte Carlo solvers for the Hubbard (or more complicated) models. Since the solution of inhomogeneous problems is significantly more time consuming than periodic systems, efficient use of these sum rules can provide a dramatic speed up in the computational time required to solve the many-body problem. We also discuss how these sum rules behave in nonequilibrium situations as well, where the Hamiltonian has explicit time dependence due to a driving field or due to the time-dependent change in a parameter such as the interaction strength or the origin of the trap potential.

Taming light with cold atoms

International Nuclear Information System (INIS)

Vestergaard Hau, Lene

2002-01-01

Much of the extraordinary progress of developments in communication (e-mail, and/or internet) has been achieved due to improvements in optical communication. This paper describes a new approach which could improve the speed of communication. The ability to stop light in its tracks by passing it through a cloud of ultracold atoms could lead to new techniques for optical storage. The described slow-light experiments have triggered new physics both on the experimental and theoretical fronts. The cold atom system allows the steepest possible refractive index profiles, and therefore the most dramatic effects, as Doppler effects are eliminated. Furthermore, cold atoms provide maximum flexibility in the choice of beam geometry. This is important for the storage and retrieval of multiple pulses of optical information in an atomic medium, as it would allow individual pulses to be selectively addressed. Slow and stopped light have many potential applications in optical communication and processing, including optical information storage, ultra-sensitive optical switches, and optical delay lines. It could also be used in quantum-information processing, in which quantum-mechanical information is used for computing and communication purposes. On a very different front, slow light provides us with a totally new way of probing the unusual properties of Bose-Einstein condensates

Building one molecule from a reservoir of two atoms.

Science.gov (United States)

Liu, L R; Hood, J D; Yu, Y; Zhang, J T; Hutzler, N R; Rosenband, T; Ni, K-K

2018-05-25

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Universal Borromean Binding in Spin-Orbit-Coupled Ultracold Fermi Gases

Directory of Open Access Journals (Sweden)

Xiaoling Cui

2014-08-01

Full Text Available Borromean rings and Borromean binding, a class of intriguing phenomena as three objects are linked (bound together while any two of them are unlinked (unbound, widely exist in nature and have been found in systems of biology, chemistry, and physics. Previous studies have suggested that the occurrence of such a binding in physical systems typically relies on the microscopic details of pairwise interaction potentials at short range and is, therefore, nonuniversal. Here, we report a new type of Borromean binding in ultracold Fermi gases with Rashba spin-orbit coupling, which is universal against short-range interaction details, with its binding energy only dependent on the s-wave scattering length and the spin-orbit-coupling strength. We show that the occurrence of this universal Borromean binding is facilitated by the symmetry of the single-particle dispersion under spin-orbit coupling and is, therefore, symmetry selective rather than interaction selective. The state is robust over a wide range of mass ratios between composing fermions, which are accessible by Li-Li, K-K, and K-Li mixtures in cold-atom experiments. Our results reveal the importance of single- particle spectral symmetry in few-body physics and shed light on the emergence of new quantum phases in a many-body system with exotic few-body correlations.

A high resolution ion microscope for cold atoms

International Nuclear Information System (INIS)

Stecker, Markus; Schefzyk, Hannah; Fortágh, József; Günther, Andreas

2017-01-01

We report on an ion-optical system that serves as a microscope for ultracold ground state and Rydberg atoms. The system is designed to achieve a magnification of up to 1000 and a spatial resolution in the 100 nm range, thereby surpassing many standard imaging techniques for cold atoms. The microscope consists of four electrostatic lenses and a microchannel plate in conjunction with a delay line detector in order to achieve single particle sensitivity with high temporal and spatial resolution. We describe the design process of the microscope including ion-optical simulations of the imaging system and characterize aberrations and the resolution limit. Furthermore, we present the experimental realization of the microscope in a cold atom setup and investigate its performance by patterned ionization with a structure size down to 2.7 μ m. The microscope meets the requirements for studying various many-body effects, ranging from correlations in cold quantum gases up to Rydberg molecule formation. (paper)

Attosecond time delays in the photoionization of noble gas atoms studied in TDLDA

International Nuclear Information System (INIS)

Magrakvelidze, Maia; Chakraborty, Himadri; Madjet, Mohamed

2015-01-01

We perform time-dependent local density functional calculations of the quantum phase and time delays of valence photoionization of noble gas atoms. Results may be accessed by XUV-IR interferometric metrology. (paper)

Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions

Science.gov (United States)

Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

2013-04-01

Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Hollow cathode discharges with gas flow: numerical modelling for the effect on the sputtered atoms and the deposition flux

International Nuclear Information System (INIS)

Bogaerts, Annemie; Okhrimovskyy, Andriy; Baguer, Neyda; Gijbels, Renaat

2005-01-01

A model is developed for a cylindrical hollow cathode discharge (HCD), with an axial gas flow (entering through a hole in the cathode bottom). The model combines a commercial computational fluid dynamics program 'FLUENT' to compute the gas flow, with home-developed Monte Carlo and fluid models for the plasma behaviour. In this paper, we focus on the behaviour of the sputtered atoms, and we investigate how the gas flow affects the sputtered atom density profiles and the fluxes, which is important for sputter deposition. The sputtered atom density profiles are not much affected by the gas flow. The flux, on the other hand, is found to be significantly enhanced by the gas flow, but in the present set-up it is far from uniform in the radial direction at the open end of the HCD, where a substrate for deposition could be located

Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

International Nuclear Information System (INIS)

Perali, A.; Palestini, F.; Pieri, P.; Strinati, G. C.; Stewart, J. T.; Gaebler, J. P.; Drake, T. E.; Jin, D. S.

2011-01-01

Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T c , and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T c .

Transfer coefficients in ultracold strongly coupled plasma

Science.gov (United States)

Bobrov, A. A.; Vorob'ev, V. S.; Zelener, B. V.

2018-03-01

We use both analytical and molecular dynamic methods for electron transfer coefficients in an ultracold plasma when its temperature is small and the coupling parameter characterizing the interaction of electrons and ions exceeds unity. For these conditions, we use the approach of nearest neighbor to determine the average electron (ion) diffusion coefficient and to calculate other electron transfer coefficients (viscosity and electrical and thermal conductivities). Molecular dynamics simulations produce electronic and ionic diffusion coefficients, confirming the reliability of these results. The results compare favorably with experimental and numerical data from earlier studies.

Research using ultracold neutrons at the ILL

International Nuclear Information System (INIS)

Steyerl, A.

1990-01-01

In this talk I will make no effort to give an exhaustive, detailed description of the well-published results of recent work with ultracold neutrons (UCN) at the ILL. Instead, there will be a biased selection of some topics in which author happens to be most interested, though in some cases as a spectator from a considerable distance than as an actor. The selection includes the recent lifetime experiment using a Fomblin-coated bottle, the continuing search for an electric dipole moment of the neutron and some ideas on high precision neutron optics experiments

An ultracold neutron storage bottle for UCN density measurements

Energy Technology Data Exchange (ETDEWEB)

Bison, G.; Burri, F.; Daum, M. [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Kirch, K. [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Institute for Particle Physics, Eidgenössische Technische Hochschule (ETH), Zürich (Switzerland); Krempel, J. [Institute for Particle Physics, Eidgenössische Technische Hochschule (ETH), Zürich (Switzerland); Lauss, B., E-mail: bernhard.lauss@psi.ch [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Meier, M. [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Ries, D., E-mail: dieter.ries@psi.ch [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Institute for Particle Physics, Eidgenössische Technische Hochschule (ETH), Zürich (Switzerland); Schmidt-Wellenburg, P.; Zsigmond, G. [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland)

2016-09-11

We have developed a storage bottle for ultracold neutrons (UCNs) in order to measure the UCN density at the beamports of the Paul Scherrer Institute's (PSI) UCN source. This paper describes the design, construction and commissioning of the robust and mobile storage bottle with a volume comparable to typical storage experiments (32 L) e.g. searching for an electric dipole moment of the neutron.

Observation of two-orbital spin-exchange interactions with ultracold SU(N)-symmetric fermions

Science.gov (United States)

Scazza, F.; Hofrichter, C.; Höfer, M.; de Groot, P. C.; Bloch, I.; Fölling, S.

2014-10-01

Spin-exchanging interactions govern the properties of strongly correlated electron systems such as many magnetic materials. When orbital degrees of freedom are present, spin exchange between different orbitals often dominates, leading to the Kondo effect, heavy fermion behaviour or magnetic ordering. Ultracold ytterbium or alkaline-earth ensembles have attracted much recent interest as model systems for these effects, with two (meta-) stable electronic configurations representing independent orbitals. We report the observation of spin-exchanging contact interactions in a two-orbital SU(N)-symmetric quantum gas realized with fermionic 173Yb. We find strong inter-orbital spin exchange by spectroscopic characterization of all interaction channels and demonstrate SU(N = 6) symmetry within our measurement precision. The spin-exchange process is also directly observed through the dynamic equilibration of spin imbalances between ensembles in separate orbitals. The realization of an SU(N)-symmetric two-orbital Hubbard Hamiltonian opens the route to quantum simulations with extended symmetries and with orbital magnetic interactions, such as the Kondo lattice model.

Spin-orbit coupling in ultracold Fermi gases of 173Yb atoms

Science.gov (United States)

Song, Bo; He, Chengdong; Hajiyev, Elnur; Ren, Zejian; Seo, Bojeong; Cai, Geyue; Amanov, Dovran; Zhang, Shanchao; Jo, Gyu-Boong

2017-04-01

Synthetic spin-orbit coupling (SOC) in cold atoms opens an intriguing new way to probe nontrivial topological orders beyond natural conditions. Here, we report the realization of the SOC physics both in a bulk system and in an optical lattice. First, we demonstrate two hallmarks induced from SOC in a bulk system, spin dephasing in the Rabi oscillation and asymmetric atomic distribution in the momentum space respectively. Then we describe the observation of non-trivial spin textures and the determination of the topological phase transition in a spin-dependent optical lattice dressed by the periodic Raman field. Furthermore, we discuss the quench dynamics between topological and trivial states by suddenly changing the band topology. Our work paves a new way to study non-equilibrium topological states in a controlled manner. Funded by Croucher Foundation and Research Grants Council (RGC) of Hong Kong (Project ECS26300014, GRF16300215, GRF16311516, and Croucher Innovation Grants).

Dimensional BCS-BEC crossover in ultracold Fermi gases

Energy Technology Data Exchange (ETDEWEB)

Boettcher, Igor

2014-12-10

We investigate thermodynamics and phase structure of ultracold Fermi gases, which can be realized and measured in the laboratory with modern trapping techniques. We approach the subject from a both theoretical and experimental perspective. Central to the analysis is the systematic comparison of the BCS-BEC crossover of two-component fermions in both three and two dimensions. A dimensional reduction can be achieved in experiments by means of highly anisotropic traps. The Functional Renormalization Group (FRG) allows for a description of both cases in a unified theoretical framework. In three dimensions we discuss with the FRG the influence of high momentum particles onto the density, extend previous approaches to the Unitary Fermi Gas to reach quantitative precision, and study the breakdown of superfluidity due to an asymmetry in the population of the two fermion components. In this context we also investigate the stability of the Sarma phase. For the two-dimensional system scattering theory in reduced dimension plays an important role. We present both the theoretically as well as experimentally relevant aspects thereof. After a qualitative analysis of the phase diagram and the equation of state in two dimensions with the FRG we describe the experimental determination of the phase diagram of the two-dimensional BCS-BEC crossover in collaboration with the group of S. Jochim at PI Heidelberg.

Ultra-cold WIMPs relics of non-standard pre-BBN cosmologies

CERN Document Server

Gelmini, Graciela B

2008-01-01

We point out that in scenarios in which the Universe evolves in a non-standard manner during and after the kinetic decoupling of weakly interacting massive particles (WIMPs), these relics can be much colder than in standard cosmological scenarios (i.e. can be ultra-cold), possibly leading to the formation of smaller first objects in hierarchical structure formation scenarios.

Depolarization of ultracold neutrons during their storage in material bottles

International Nuclear Information System (INIS)

Serebrov, A.P.; Lasakov, M.S.; Vassiljev, A.V.; Krasnoschekova, I.A.; Rudnev, Yu.P.; Fomin, A.K.; Varlamov, V.E.; Geltenbort, P.; Butterworth, J.; Young, A.R.; Pesavento, U.

2003-01-01

The depolarization of ultracold neutrons (UCN) during their storage in traps has been investigated. The neutron spin-flip probability for the materials studied amounts to ∼(1-2)x10 -5 per collision and does not depend on the temperature. The possible connection between the phenomenon of UCN depolarization and that of anomalous losses is discussed

Depolarization of ultracold neutrons during their storage in material bottles

Energy Technology Data Exchange (ETDEWEB)

Serebrov, A.P.; Lasakov, M.S.; Vassiljev, A.V.; Krasnoschekova, I.A.; Rudnev, Yu.P.; Fomin, A.K.; Varlamov, V.E.; Geltenbort, P.; Butterworth, J.; Young, A.R.; Pesavento, U

2003-07-14

The depolarization of ultracold neutrons (UCN) during their storage in traps has been investigated. The neutron spin-flip probability for the materials studied amounts to {approx}(1-2)x10{sup -5} per collision and does not depend on the temperature. The possible connection between the phenomenon of UCN depolarization and that of anomalous losses is discussed.

Spatially distributed multipartite entanglement enables EPR steering of atomic clouds

Science.gov (United States)

Kunkel, Philipp; Prüfer, Maximilian; Strobel, Helmut; Linnemann, Daniel; Frölian, Anika; Gasenzer, Thomas; Gärttner, Martin; Oberthaler, Markus K.

2018-04-01

A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.

Long-range interactions of excited He atoms with ground-state noble-gas atoms

KAUST Repository

Zhang, J.-Y.

2013-10-09

The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.

Ionization Spectroscopic Measurement of nP Rydberg Levels of 87Rb Cold Atoms

Science.gov (United States)

Li, Yufan; Zaheeruddin, Syed; Zhao, Dongmei; Ma, Xinwen; Yang, Jie

2018-05-01

We created an ultracold plasma via the spontaneous ionization of cold dense Rydberg atoms of 87Rb in a magneto-optical trap (MOT), and measured the nS1/2 (n = 50-80), nP1/2 (n = 16-23), nP3/2 (n = 16-98), and nD5/2 (n = 49-96) Rydberg levels by detecting the electrons in the ultracold plasma. By fitting the energy levels of Rydberg states, the first ionization potential of 33690.950(11) cm-1 and the quantum defects of S, P, and D orbitals were obtained. The absolute transition energies of nS1/2 (n = 66-80), nP1/2 (n = 16-23), nP3/2 (n = 16-98), and nD5/2 (n = 58-96) states of 87Rb, as well as the quantum defects for p1/2 and p3/2 series, are given for the first time.

Matter-wave interferometry in a double well on an atom chip

DEFF Research Database (Denmark)

Schumm, Thorsten; Hofferberth, S.; Andersson, L. M.

2005-01-01

Matter-wave interference experiments enable us to study matter at its most basic, quantum level and form the basis of high-precision sensors for applications such as inertial and gravitational field sensing. Success in both of these pursuits requires the development of atom-optical elements...... that can manipulate matter waves at the same time as preserving their coherence and phase. Here, we present an integrated interferometer based on a simple, coherent matter-wave beam splitter constructed on an atom chip. Through the use of radio-frequency-induced adiabatic double-well potentials, we...... demonstrate the splitting of Bose-Einstein condensates into two clouds separated by distances ranging from 3 to 80 μm, enabling access to both tunnelling and isolated regimes. Moreover, by analysing the interference patterns formed by combining two clouds of ultracold atoms originating from a single...

Ghost imaging with atoms

Science.gov (United States)

Khakimov, R. I.; Henson, B. M.; Shin, D. K.; Hodgman, S. S.; Dall, R. G.; Baldwin, K. G. H.; Truscott, A. G.

2016-12-01

Ghost imaging is a counter-intuitive phenomenon—first realized in quantum optics—that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a ‘ghost’ image. Here we report the realization of ghost imaging using massive particles instead of photons. In our experiment, the two beams are formed by correlated pairs of ultracold, metastable helium atoms, which originate from s-wave scattering of two colliding Bose-Einstein condensates. We use higher-order Kapitza-Dirac scattering to generate a large number of correlated atom pairs, enabling the creation of a clear ghost image with submillimetre resolution. Future extensions of our technique could lead to the realization of ghost interference, and enable tests of Einstein-Podolsky-Rosen entanglement and Bell’s inequalities with atoms.

The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems

Science.gov (United States)

Strinati, Giancarlo Calvanese; Pieri, Pierbiagio; Röpke, Gerd; Schuck, Peter; Urban, Michael

2018-04-01

This report addresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance. The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient

Magnetic trapping of buffer-gas-cooled chromium atoms and prospects for the extension to paramagnetic molecules

International Nuclear Information System (INIS)

Bakker, Joost M; Stoll, Michael; Weise, Dennis R; Vogelsang, Oliver; Meijer, Gerard; Peters, Achim

2006-01-01

We report the successful buffer-gas cooling and magnetic trapping of chromium atoms with densities exceeding 10 12 atoms per cm 3 at a temperature of 350 mK for the trapped sample. The possibilities of extending the method to buffer-gas cool and magnetically trap molecules are discussed. To minimize the most important loss mechanism in magnetic trapping, molecules with a small spin-spin interaction and a large rotational constant are preferred. Both the CrH ( 6 Σ + ground state) and MnH ( 7 Σ + ) radicals appear to be suitable systems for future experiments

Dynamic effect of collision failure of phase in gas of cold dark atoms

International Nuclear Information System (INIS)

Il'ichev, L.V.

2005-01-01

In a gas of slow atoms exhibiting the effect of coherent population trapping (CPT) on the sublevels of the ground state in a spatially nonuniform light field, rare collisions destroying the CPT state initiate the irreversible exchange of momentum between radiation and atoms. This exchange is manifested as an additional force that acts on the particles. The force is of geometric origin, being determined only by the structure of the field of local CPT states. When this force is not masked by the standard collision change in atomic momentum, the observation of the kinetics of the particles may provide information on the physics of the collisions [ru

Plasma effective field theory advertised, then illustrated by e, p, H-atom gas

International Nuclear Information System (INIS)

Brown, L.S.

2001-01-01

The first part is a lightning fast overview of the application of ideas of modern effective quantum field theory (which originated in elementary particle theory) to plasma physics. An exhaustive account is presented in a long report with L. G. Yaffe which contains all the details set out in a self-contained and pedagogical fashion. The second part shows how the low temperature but dilute limit of the partition function at two-loop order describes a gas of electrons, protons, and hydrogen atoms in their ground state. Hydrogen atoms emerge automatically from the general framework which does not begin with any explicit consideration of atoms. (orig.)

Quantum dynamics of atoms in a resonator-generated optical lattice

International Nuclear Information System (INIS)

Maschler, C.; Ritsch, H.

2005-01-01

Full text: We investigate the quantum motion of coherently driven ultracold atoms in the field of a damped high-Q optical cavity mode. The laser field is chosen far detuned from the atomic transition but close to a cavity resonance, so that spontaneous emission is strongly suppressed but a coherent field builds up in the resonator by stimulated scattering. On one hand the shape of the atomic wave function determines the field dynamics via the magnitude of the scattering and the effective refractive index the atoms create for the mode. The mode intensity on the other hand determines the optical dipole force on the atoms.The system shows rich atom-field dynamics including self organization, self-trapping, cooling or heating. In the limit of deep trapping we are able to derive a system of closed, coupled equations for a finite set of atomic expectation values and the field. This allows us to determine the self-consistent ground state of the system as well as the eigenfrequencies and damping rates for excitations. To treat several atoms in more detail we introduce the Bose-Hubbard model. This allows us to investigate several aspects of the quantum motion of the atoms inside the cavity. (author)

Atomizing industrial gas-liquid flows – Development of an efficient hybrid VOF-LPT numerical framework

International Nuclear Information System (INIS)

Ström, Henrik; Sasic, Srdjan; Holm-Christensen, Olav; Shah, Louise Jivan

2016-01-01

Highlights: • Modelling of turbulent atomizing gas-liquid flows in real industrial devices. • A combined VOF-LPT framework with statistical coupling. • Regions of separated and dispersed multiphase flow treated simultaneously. • Statistical model based on a limited amount of highly resolved VOF data. - Abstract: Atomizing gas-liquid flows are used in industrial applications where high interphase heat and mass transfer rates and good mixing are of primary importance. Today, there is no single mathematical framework available to predict the entire liquid breakup process at an acceptable computational cost for a typical problem of industrial size. In this work, we develop a volume-of-fluid (VOF) framework that is combined with Lagrangian particle tracking (LPT) to take advantage of the respective strengths of these two approaches. The two frameworks are coupled via a statistical model that enables a transition from the VOF to the LPT formulation using input data about the primary breakup process obtained from detailed VOF simulations in dedicated switching zones. LPT-to-VOF transitions are handled directly by analyzing the proximity of LPT parcels to larger VOF structures. The combined framework is specifically designed to accommodate situations where atomization occurs in several locations simultaneously and when separated and dispersed turbulent gas-liquid flows co-exist in the same industrial unit. The procedure in which the statistical model is derived is presented and discussed, its performance is verified and the computational efficiency of the combined VOF-LPT model is assessed. Finally, the application of the coupled framework to the simulation of an industrial gas-liquid mixer with four separate atomization regions is presented.

Test of the fast thin-film ferromagnetic shutters for ultracold neutrons

International Nuclear Information System (INIS)

Pokotilovskij, Yu.N.; Novopol'tsev, M.I.; Geltenbort, P.

2008-01-01

Test of thin-film ferromagnetic shutters of two types for ultracold neutrons has been performed. The first type is based on neutron reflection from the sequence of successively placed thin ferromagnetic layers with oppositely directed magnetization. The second one is based on neutron refraction in ferromagnetic foils inserted in the beam

Probing Efimov discrete scaling in an atom-molecule collision

Science.gov (United States)

Shalchi, M. A.; Yamashita, M. T.; Hadizadeh, M. R.; Garrido, E.; Tomio, Lauro; Frederico, T.

2018-01-01

The discrete Efimov scaling behavior, well known in the low-energy spectrum of three-body bound systems for large scattering lengths (unitary limit), is identified in the energy dependence of an atom-molecule elastic cross section in mass-imbalanced systems. That happens in the collision of a heavy atom with mass mH with a weakly bound dimer formed by the heavy atom and a lighter one with mass mL≪mH . Approaching the heavy-light unitary limit, the s -wave elastic cross section σ will present a sequence of zeros or minima at collision energies following closely the Efimov geometrical law. Our results, obtained with Faddeev calculations and supplemented by a Born-Oppenheimer analysis, open a perspective to detecting the discrete scaling behavior from low-energy scattering data, which is timely in view of the ongoing experiments with ultracold binary mixtures having strong mass asymmetries, such as lithium and cesium or lithium and ytterbium.

Collision-induced polarizabilities of inert gas atoms

International Nuclear Information System (INIS)

Clarke, K.L.; Madden, P.A.; Buckingham, A.D.

1978-01-01

The use of polarizability densities to calculate collision-induced polarizabilities is investigated. One method for computing polarizabilities of inert gas diatoms employs atomic polarizability densities from finite-field Hartree-Fock calculations, together with classical equations for the polarization of dielectrics. It is shown that this model gives inaccurate values for both the local fields and the local response to non-uniform fields. An alternative method incorporating the same physical effects is used to compute the pair polarizabilities to first order in the interatomic interaction. To first order the pair contribution to the trace of the polarizability is negative at short range. The calculated anisotropy does not differ significantly from the DID value, whereas the polarizability density calculation gives a substantial reduction in the anisotropy. (author)

Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

DEFF Research Database (Denmark)

Abu-Samha, Mahmoud; Madsen, Lars Bojer

2011-01-01

We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The cal......We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses....... The calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

Regimes of spray formation in gas-centered swirl coaxial atomizers

Energy Technology Data Exchange (ETDEWEB)

Sivakumar, D.; Kulkarni, V. [Indian Institute of Science, Department of Aerospace Engineering, Bangalore (India)

2011-09-15

Spray formation in ambient atmosphere from gas-centered swirl coaxial atomizers is described by carrying out experiments in a spray test facility. The atomizer discharges a circular air jet and an axisymmetric swirling water sheet from its coaxially arranged inner and outer orifices. A high-speed digital imaging system along with a backlight illumination arrangement is employed to record the details of liquid sheet breakup and spray development. Spray regimes exhibiting different sheet breakup mechanisms are identified and their characteristic features presented. The identified spray regimes are wave-assisted sheet breakup, perforated sheet breakup, segmented sheet breakup, and pulsation spray regime. In the regime of wave-assisted sheet breakup, the sheet breakup shows features similar to the breakup of two-dimensional planar air-blasted liquid sheets. At high air-to-liquid momentum ratios, the interaction process between the axisymmetric swirling liquid sheet and the circular air jet develops spray processes which are more specific to the atomizer studied here. The spray exhibits a periodic ejection of liquid masses whose features are dominantly controlled by the central air jet. (orig.)

Diamond-like carbon coated ultracold neutron guides

International Nuclear Information System (INIS)

Heule, S.; Atchison, F.; Daum, M.; Foelske, A.; Henneck, R.; Kasprzak, M.; Kirch, K.; Knecht, A.; Kuzniak, M.; Lippert, T.; Meier, M.; Pichlmaier, A.; Straumann, U.

2007-01-01

It has been shown recently that diamond-like carbon (DLC) with a sp 3 fraction above 60% is a better wall coating material for ultracold neutron applications than beryllium. We report on results of Raman spectroscopic and XPS measurements obtained for diamond-like carbon coated neutron guides produced in a new facility, which is based on pulsed laser deposition at 193 nm. For diamond-like carbon coatings on small stainless steel substrates we find sp 3 fractions in the range from 60 to 70% and showing slightly increasing values with laser pulse energy and pulse repetition rate

Collisions of halogen (2P) and rare gas (1S) atoms

International Nuclear Information System (INIS)

Becker, C.H.

1978-12-01

Differential cross sections I (THETA) at several collision energies measured in crossed molecular beam experiments are reported for several combinations of halogen atoms ( 2 P) scattered off rare gas-rare gas atoms ( 1 S 0 ), namely, F + Ne, F + Ar, F + Kr, F + Xe, C1 + Xe. The scattering is described by an elastic model appropriate to Hund's case c coupling. With the use of this model, the X 1/2, I 3/2, and II 1/2 interaction potential energy curves are derived by fitting calculated differential cross sections, based on analytic representations of the potentials, to the data. The F - Xe X 1/2 potential shows a significant bonding qualitatively different than for the other F-rare gases. The I 3/2 and II 1/2 potentials closely resemble the van der Waals interactions of the one electron richer ground state rare gas-rare gas systems. Coupled-channel scattering calculations are carried out for F + Ar, F + Xe, and C1 + Xe using the realistic potential curves derived earlier. The results justify the use of the elastic model, and give additional information on intramultiplet and intermultiplet transitions. The transitions are found to be governed by the crossing of the two Ω = 1/2 potentials in the complex plane. The measured I (theta) and I (THETA) derived from the coupled-channel computations show small oscillations or perturbations (Stueckelberg oscillations) though quantitative agreement is not obtained.The nature of the anomalous F - Xe X 1/2 potential is discussed as is the approximation of a constant spin orbit coupling over the experimentally accessible range of internuclear distances for these open shell molecules. 55 references

An endoscopic detector for ultracold neutrons

Energy Technology Data Exchange (ETDEWEB)

Goeltl, L.; Fertl, M.; Kirch, K. [Paul Scherrer Institute, Laboratory for Particle Physics, Villigen-PSI (Switzerland); Institute for Particle Physics, Zuerich (Switzerland); Chowdhuri, Z.; Henneck, R.; Lauss, B.; Mtchedlishvili, A.; Schmidt-Wellenburg, P.; Zsigmond, G. [Paul Scherrer Institute, Laboratory for Particle Physics, Villigen-PSI (Switzerland); Gray, F. [Regis University, Denver, CO (United States); Lefort, T. [Universite de Caen, CNRS/IN2P3, Laboratoire de Physique Corpusculaire, Caen (France)

2013-01-15

A new versatile detector for ultracold neutrons (UCN) has been built and operated which combines multi-pixel photon counters and GS10 lithium-doped scintillators. Such detectors can be very small and can be used to monitor UCN inside storage vessels or guides with negligible influence (of order 10{sup -6}) on the UCN intensity itself. We have shown that such detectors can be used in a very harsh radiation environment of up to 200Gy/h via the addition of a 4m long quartz light guide in order to place the radiation-sensitive photon counters outside the hot zone. Additionally we have measured the UCN storage times in situ in this harsh environment. (orig.)

Possible Many-Body Localization in a Long-Lived Finite-Temperature Ultracold Quasineutral Molecular Plasma

Science.gov (United States)

Sous, John; Grant, Edward

2018-03-01

We argue that the quenched ultracold plasma presents an experimental platform for studying the quantum many-body physics of disordered systems in the long-time and finite energy-density limits. We consider an experiment that quenches a plasma of nitric oxide to an ultracold system of Rydberg molecules, ions, and electrons that exhibits a long-lived state of arrested relaxation. The qualitative features of this state fail to conform with classical models. Here, we develop a microscopic quantum description for the arrested phase based on an effective many-body spin Hamiltonian that includes both dipole-dipole and van der Waals interactions. This effective model appears to offer a way to envision the essential quantum disordered nonequilibrium physics of this system.

Recent developments in trapping and manipulation of atoms with adiabatic potentials

Science.gov (United States)

Garraway, Barry M.; Perrin, Hélène

2016-09-01

A combination of static and oscillating magnetic fields can be used to ‘dress’ atoms with radio-frequency (RF), or microwave, radiation. The spatial variation of these fields can be used to create an enormous variety of traps for ultra-cold atoms and quantum gases. This article reviews the type and character of these adiabatic traps and the applications which include atom interferometry and the study of low-dimensional quantum systems. We introduce the main concepts of magnetic traps leading to adiabatic dressed traps. The concept of adiabaticity is discussed in the context of the Landau-Zener model. The first bubble trap experiment is reviewed together with the method used for loading it. Experiments based on atom chips show the production of double wells and ring traps. Dressed atom traps can be evaporatively cooled with an additional RF field, and a weak RF field can be used to probe the spectroscopy of the adiabatic potentials. Several approaches to ring traps formed from adiabatic potentials are discussed, including those based on atom chips, time-averaged adiabatic potentials and induction methods. Several proposals for adiabatic lattices with dressed atoms are also reviewed.

Trapping and Evolution Dynamics of Ultracold Two-Component Plasmas

International Nuclear Information System (INIS)

Choi, J.-H.; Knuffman, B.; Zhang, X. H.; Povilus, A. P.; Raithel, G.

2008-01-01

We demonstrate the trapping of a strongly magnetized, quasineutral ultracold plasma in a nested Penning trap with a background field of 2.9 T. Electrons remain trapped in this system for several milliseconds. Early in the evolution, the dynamics are driven by a breathing-mode oscillation in the ionic charge distribution, which modulates the electron trap depth. Over longer times scales, the electronic component undergoes cooling. Trap loss resulting from ExB drift is characterized

Magnetic trapping of buffer-gas-cooled chromium atoms and prospects for the extension to paramagnetic molecules

Energy Technology Data Exchange (ETDEWEB)

Bakker, Joost M [Humboldt Universitaet zu Berlin, Institut fuer Physik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Stoll, Michael [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany); Weise, Dennis R [Universitaet Konstanz, Fachbereich Physik, 78457 Constance (Germany); Vogelsang, Oliver [Universitaet Konstanz, Fachbereich Physik, 78457 Konstanz (Germany); Meijer, Gerard [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany); Peters, Achim [Humboldt Universitaet zu Berlin, Institut fuer Physik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2006-10-14

We report the successful buffer-gas cooling and magnetic trapping of chromium atoms with densities exceeding 10{sup 12} atoms per cm{sup 3} at a temperature of 350 mK for the trapped sample. The possibilities of extending the method to buffer-gas cool and magnetically trap molecules are discussed. To minimize the most important loss mechanism in magnetic trapping, molecules with a small spin-spin interaction and a large rotational constant are preferred. Both the CrH ({sup 6}{sigma}{sup +} ground state) and MnH ({sup 7}{sigma}{sup +}) radicals appear to be suitable systems for future experiments.

Atomic and molecular physics in the gas phase

International Nuclear Information System (INIS)

Toburen, L.H.

1990-09-01

The spatial and temporal distributions of energy deposition by high-linear-energy-transfer radiation play an important role in the subsequent chemical and biological processes leading to radiation damage. Because the spatial structures of energy deposition events are of the same dimensions as molecular structures in the mammalian cell, direct measurements of energy deposition distributions appropriate to radiation biology are infeasible. This has led to the development of models of energy transport based on a knowledge of atomic and molecular interactions process that enable one to simulate energy transfer on an atomic scale. Such models require a detailed understanding of the interactions of ions and electrons with biologically relevant material. During the past 20 years there has been a great deal of progress in our understanding of these interactions; much of it coming from studies in the gas phase. These studies provide information on the systematics of interaction cross sections leading to a knowledge of the regions of energy deposition where molecular and phase effects are important and that guide developments in appropriate theory. In this report studies of the doubly differential cross sections, crucial to the development of stochastic energy deposition calculations and track structure simulation, will be reviewed. Areas of understanding are discussed and directions for future work addressed. Particular attention is given to experimental and theoretical findings that have changed the traditional view of secondary electron production for charged particle interactions with atomic and molecular targets

Metal-Insulator Transition Revisited for Cold Atoms in Non-Abelian Gauge Potentials

International Nuclear Information System (INIS)

Satija, Indubala I.; Dakin, Daniel C.; Clark, Charles W.

2006-01-01

We discuss the possibility of realizing metal-insulator transitions with ultracold atoms in two-dimensional optical lattices in the presence of artificial gauge potentials. For Abelian gauges, such transitions occur when the magnetic flux penetrating the lattice plaquette is an irrational multiple of the magnetic flux quantum. Here we present the first study of these transitions for non-Abelian U(2) gauge fields. In contrast to the Abelian case, the spectrum and localization transition in the non-Abelian case is strongly influenced by atomic momenta. In addition to determining the localization boundary, the momentum fragments the spectrum. Other key characteristics of the non-Abelian case include the absence of localization for certain states and satellite fringes around the Bragg peaks in the momentum distribution and an interesting possibility that the transition can be tuned by the atomic momenta

Localization of atomic excitation beyond the diffraction limit using electromagnetically induced transparency

Science.gov (United States)

Miles, J. A.; Das, Diptaranjan; Simmons, Z. J.; Yavuz, D. D.

2015-09-01

We experimentally demonstrate the localization of excitation between hyperfine ground states of 87Rb atoms to as small as λ /13 -wide spatial regions. We use ultracold atoms trapped in a dipole trap and utilize electromagnetically induced transparency (EIT) for the atomic excitation. The localization is achieved by combining a spatially varying coupling laser (standing wave) with the intensity dependence of EIT. The excitation is fast (150 ns laser pulses) and the dark-state fidelity can be made higher than 94% throughout the standing wave. Because the width of the localized regions is much smaller than the wavelength of the driving light, traditional optical imaging techniques cannot resolve the localized features. Therefore, to measure the excitation profile, we use an autocorrelation-like method where we perform two EIT sequences separated by a time delay, during which we move the standing wave.

Xenon gas field ion source from a single-atom tip

Science.gov (United States)

Lai, Wei-Chiao; Lin, Chun-Yueh; Chang, Wei-Tse; Li, Po-Chang; Fu, Tsu-Yi; Chang, Chia-Seng; Tsong, T. T.; Hwang, Ing-Shouh

2017-06-01

Focused ion beam (FIB) systems have become powerful diagnostic and modification tools for nanoscience and nanotechnology. Gas field ion sources (GFISs) built from atomic-size emitters offer the highest brightness among all ion sources and thus can improve the spatial resolution of FIB systems. Here we show that the Ir/W(111) single-atom tip (SAT) can emit high-brightness Xe+ ion beams with a high current stability. The ion emission current versus extraction voltage was analyzed from 150 K up to 309 K. The optimal emitter temperature for maximum Xe+ ion emission was ˜150 K and the reduced brightness at the Xe gas pressure of 1 × 10-4 torr is two to three orders of magnitude higher than that of a Ga liquid metal ion source, and four to five orders of magnitude higher than that of a Xe inductively coupled plasma ion source. Most surprisingly, the SAT emitter remained stable even when operated at 309 K. Even though the ion current decreased with increasing temperature, the current at room temperature (RT) could still reach over 1 pA when the gas pressure was higher than 1 × 10-3 torr, indicating the feasibility of RT-Xe-GFIS for application to FIB systems. The operation temperature of Xe-SAT-GFIS is considerably higher than the cryogenic temperature required for the helium ion microscope (HIM), which offers great technical advantages because only simple or no cooling schemes can be adopted. Thus, Xe-GFIS-FIB would be easy to implement and may become a powerful tool for nanoscale milling and secondary ion mass spectroscopy.

Polarization of stable and radioactive noble gas nuclei by spin exchange with laser pumped alkali atoms

International Nuclear Information System (INIS)

Calaprice, F.; Happer, W.; Schreiber, D.

1984-01-01

The nuclei of noble gases can be strongly polarized by spin exchange with sufficiently dense optically pumped alkali vapors. Only a small fraction of the spin angular momentum of the alkali atoms is transferred to the nuclear spin of the noble gas. Most of the spin angular momentum is lost to translational angular momentum of the alkali and noble gas atoms about each other. For heavy noble gases most of the angular momentum transfer occurs in alkali-noble-gas van der Waals molecules. The transfer efficiency depends on the formation and breakup rates of the van der Waals molecules in the ambient gas. Experimental methods to measure the spin transfer efficiencies have been developed. Nuclei of radioactive noble gases have been polarized by these methods, and the polarization has been detected by observing the anisotropy of the radioactive decay products. Very precise measurements of the magnetic moments of the radioactive nuclei have been made. 12 references, 9 figures

Probe Knots and Hopf Insulators with Ultracold Atoms

Science.gov (United States)

Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, L.-M.

2018-01-01

Knots and links are fascinating and intricate topological objects. Their influence spans from DNA and molecular chemistry to vortices in superfluid helium, defects in liquid crystals and cosmic strings in the early universe. Here we find that knotted structures also exist in a peculiar class of three-dimensional topological insulators—the Hopf insulators. In particular, we demonstrate that the momentum-space spin textures of Hopf insulators are twisted in a nontrivial way, which implies the presence of various knot and link structures. We further illustrate that the knots and nontrivial spin textures can be probed via standard time-of-flight images in cold atoms as preimage contours of spin orientations in stereographic coordinates. The extracted Hopf invariants, knots, and links are validated to be robust to typical experimental imperfections. Our work establishes the existence of knotted structures in Hopf insulators, which may have potential applications in spintronics and quantum information processing. D.L.D., S.T.W. and L.M.D. are supported by the ARL, the IARPA LogiQ program, and the AFOSR MURI program, and supported by Tsinghua University for their visits. K.S. acknowledges the support from NSF under Grant No. PHY1402971. D.L.D. is also supported by JQI-NSF-PFC and LPS-MPO-CMTC at the final stage of this paper.

Gas atomization processing of tin and silicon modified LaNi₅ for nickel-metal hydride battery applications

Energy Technology Data Exchange (ETDEWEB)

Ting, Jason [Iowa State Univ., Ames, IA (United States)

1999-02-12

Numerous researchers have studied the relevant material properties of so-called AB₅ alloys for battery applications. These studies involved LaNi₅ substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relationship between gas atomization processes, powder particle solidification phases, and hydrogen absorption properties of ultra fine (< 25 μm) atomized powders with high surface area for enhanced battery performance. Concurrently, development of a gas atomization nozzle that is more efficient than all current designs is needed to increase the yield of ultrafine AB₅ alloy powder for further processing advantage. Gas atomization processing of the AB₅ alloys was demonstrated to be effective in producing ultrafine spherical powders that were resilient to hydrogen cycling for the benefit of improving corrosion resistance in battery application. These ultrafine powders benefited from the rapid solidification process by having refined solute segregation in the microstructure of the gas atomized powders which enabled a rapid anneal treatment of the powders. The author has demonstrated the ability to produce high yields of ultrafine powder efficiently and cost effectively, using the new HPGA-III technology. Thus, the potential benefits of processing AB₅ alloys using the new HPGA technology could reduce manufacturing cost of nickel-metal hydride powder. In the near future, the manufacture of AB₅ alloy powders could become a continuous and rapid production process. The economic benefit of an improved AB₅ production process may thereby encourage the use of nickel-metal hydride rechargeable batteries in electrical vehicle

Distribution and kinematics of atomic and molecular gas inside the solar circle

NARCIS (Netherlands)

Marasco, A.; Fraternali, F.; van der Hulst, J. M.; Oosterloo, T.

2017-01-01

The detailed distribution and kinematics of the atomic and the CO-bright molecular hydrogen in the disc of the Milky Way inside the solar circle are derived under the assumptions of axisymmetry and pure circular motions. We divide the Galactic disc into a series of rings, and assume that the gas in

Stability investigation of a high number density Pt1/Fe2O3 single-atom catalyst under different gas environments by HAADF-STEM

Science.gov (United States)

Duan, Sibin; Wang, Rongming; Liu, Jingyue

2018-05-01

Catalysis by supported single metal atoms has demonstrated tremendous potential for practical applications due to their unique catalytic properties. Unless they are strongly anchored to the support surfaces, supported single atoms, however, are thermodynamically unstable, which poses a major obstacle for broad applications of single-atom catalysts (SACs). In order to develop strategies to improve the stability of SACs, we need to understand the intrinsic nature of the sintering processes of supported single metal atoms, especially under various gas environments that are relevant to important catalytic reactions. We report on the synthesis of high number density Pt1/Fe2O3 SACs using a facial strong adsorption method and the study of the mobility of these supported Pt single atoms at 250 °C under various gas environments that are relevant to CO oxidation, water–gas shift, and hydrogenation reactions. Under the oxidative gas environment, Fe2O3 supported Pt single atoms are stable even at high temperatures. The presence of either CO or H2 molecules in the gas environment, however, facilitates the movement of the Pt atoms. The strong interaction between CO and Pt weakens the binding between the Pt atoms and the support, facilitating the movement of the Pt single atoms. The dissociation of H2 molecules on the Pt atoms and their subsequent interaction with the oxygen species of the support surfaces dislodge the surface oxygen anchored Pt atoms, resulting in the formation of Pt clusters. The addition of H2O molecules to the CO or H2 significantly accelerates the sintering of the Fe2O3 supported Pt single atoms. An anchoring-site determined sintering mechanism is further proposed, which is related to the metal–support interaction.

Photoionization and cold collision studies using trapped atoms

International Nuclear Information System (INIS)

Gould, P.L.

1996-01-01

The authors have used laser cooling and trapping techniques to investigate photoionization and cold collisions. With laser-trapped Rb, they have measured the photoionization cross section from the first excited (5P) level by observing the photoionization-induced loss rate of neutral atoms from the trap. This technique has the advantage that it directly measures the photoionization rate per atom. Knowing the ionizing laser intensity and the excited-state fraction, the measured loss rate gives the absolute cross section. Using this technique, the Rb 5P photoionization cross section at ∼400 nm has been determined with an uncertainty of 9%. The authors are currently attempting to extend this method to the 5D level. Using time-ordered pulses of diode-laser light (similar to the STIRAP technique), they have performed very efficient two-photon excitation of trapped Rb atoms to 5D. Finally, they will present results from a recent collaboration which combines measurements form conventional molecular spectroscopy (single photon and double resonance) with photoassociation collisions of ultracold Na atoms to yield a precise (≤1 ppm) value for the dissociation energy of the X Σ g+ ground state of the Na 2 molecule

Spectroscopic and Kinetic Measurements of Alkali Atom-Rare Gas Excimers

Science.gov (United States)

2009-11-04

vapors – Exciplex molecules absorb over much greater bandwidth • Control of inherent high optical gain to minimize ASE and optimize laser oscillation... Exciplex assisted diode Pumped Alkali Laser (XPAL) • Education of a future generation of laser scientists VG09-227-2 Physical Sciences Inc. Novel Approach...This new laser exploits the optical properties of weakly-bound alkali/rare-gas exciplexes for pumping the 2P1/2, 3/2 alkali atomic excited states 4

Progress towards magnetic trapping of ultra-cold neutrons

CERN Document Server

Huffman, P R; Butterworth, J S; Coakley, K J; Dewey, M S; Dzhosyuk, S N; Gilliam, D M; Golub, R; Greene, G L; Habicht, K; Lamoreaux, S K; Mattoni, C E H; McKinsey, D N; Wietfeldt, F E; Doyle, J M

2000-01-01

We report progress towards magnetic trapping of ultra-cold neutrons (UCN) in preparation for a neutron lifetime measurement. UCN will be produced by inelastic scattering of cold (0.89 nm) neutrons in a reservoir of superfluid sup 4 He and confined in a three-dimensional magnetic trap. As the trapped neutrons decay, recoil electrons will generate scintillations in the liquid He, which should be detectable with nearly 100% efficiency. This direct measure of the number of UCN decays vs. time can be used to determine the neutron beta-decay lifetime.

Manipulating Neutral Atoms in Chip-Based Magnetic Traps

Science.gov (United States)

Aveline, David; Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Yu, Nan; Kohel, James

2009-01-01

Several techniques for manipulating neutral atoms (more precisely, ultracold clouds of neutral atoms) in chip-based magnetic traps and atomic waveguides have been demonstrated. Such traps and waveguides are promising components of future quantum sensors that would offer sensitivities much greater than those of conventional sensors. Potential applications include gyroscopy and basic research in physical phenomena that involve gravitational and/or electromagnetic fields. The developed techniques make it possible to control atoms with greater versatility and dexterity than were previously possible and, hence, can be expected to contribute to the value of chip-based magnetic traps and atomic waveguides. The basic principle of these techniques is to control gradient magnetic fields with suitable timing so as to alter a trap to exert position-, velocity-, and/or time-dependent forces on atoms in the trap to obtain desired effects. The trap magnetic fields are generated by controlled electric currents flowing in both macroscopic off-chip electromagnet coils and microscopic wires on the surface of the chip. The methods are best explained in terms of examples. Rather than simply allowing atoms to expand freely into an atomic waveguide, one can give them a controllable push by switching on an externally generated or a chip-based gradient magnetic field. This push can increase the speed of the atoms, typically from about 5 to about 20 cm/s. Applying a non-linear magnetic-field gradient exerts different forces on atoms in different positions a phenomenon that one can exploit by introducing a delay between releasing atoms into the waveguide and turning on the magnetic field.

Effect of lattice-gas atoms on the adsorption behaviour of thioether molecules.

Science.gov (United States)

Pan, Yi; Yang, Bing; Hulot, Catherine; Blechert, Siegfried; Nilius, Niklas; Freund, Hans-Joachim

2012-08-21

Using STM topographic imaging and spectroscopy, we have investigated the adsorption of two thioether molecules, 1,2-bis(phenylthio)benzene and (bis(3-phenylthio)-phenyl)sulfane, on noble and transition metal surfaces. The two substrates show nearly antipodal behaviour. Whereas complexes with one or two protruding centres are observed on Au(111), only flat and uniform ad-structures are found on NiAl(110). The difference is ascribed to the possibility of the thioethers to form metal-organic complexes by coordinating lattice-gas atoms on the Au(111), while only the pristine molecules adsorb on the alloy surface. The metal coordination in the first case is driven by the formation of strong Au-S bonds and enables the formation of characteristic monomer, dimer and chain-like structures of the thioethers, using the Au atoms as linkers. A similar mechanism is not available on the NiAl, because no lattice gas develops at this surface at room temperature. Our work demonstrates how surface properties, i.e. the availability of mobile ad-species, determine the interaction of organic molecules with metallic substrates.

Experimental study of single-electron loss by Ar+ ions in rare-gas atoms

Science.gov (United States)

Reyes, P. G.; Castillo, F.; Martínez, H.

2001-04-01

Absolute differential and total cross sections for single-electron loss were measured for Ar+ ions on rare-gas atoms in the laboratory energy range of 1.5 to 5.0 keV. The electron loss cross sections for all the targets studied are found to be in the order of magnitude between 10-19 and 10-22 cm2, and show a monotonically increasing behaviour as a function of the incident energy. The behaviour of the total single-electron loss cross sections with the atomic target number, Zt, shows different dependences as the collision energy increases. In all cases the present results display experimental evidence of saturation in the single-electron loss cross section as the atomic number of the target increases.

Spectroscopy with cold and ultra-cold neutrons

Directory of Open Access Journals (Sweden)

Abele Hartmut

2015-01-01

Full Text Available We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first method, which uses the R×B drift effect to disperse charged particles in a uniformly curved magnetic field, allows to study neutron β-decay. We aim for a precision on the 10−4 level. The second method that we refer to as gravity resonance spectroscopy (GRS allows to test Newton’s gravity law at short distances. At the level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, limits on dark energy chameleon fields are improved by several orders of magnitude.

Pyrolysis gas chromatographic atomic emission detection for sediments, coals and other petrochemical precursors

Energy Technology Data Exchange (ETDEWEB)

Seeley, J.A.; Zeng, Y.D.; Uden, P.C.; Eglinton, T.I.; Ericson, I. (Massachusetts University, Amherst, MA (USA). Dept. of Chemistry)

1992-09-01

On-line flash pyrolysis coupled to a capillary gas chromatograph for the characterization of marine sediments, coals and other heterogeneous solid samples is described. A helium microwave-induced plasma is used for chromatographic detection by atomic emission spectrometry. Simultaneous multi-element detection is achieved with a photodiode array detector. The optical path of the gas chromatographic atomic emission detector is purged with helium, allowing simultaneous, sensitive detection of atomic emission from sulfur 181 nm, phosphorous 186 nm, arsenic 189 nm, selenium 196 nm and carbon 193 nm. Several sediment and coal samples have been analysed for their carbon, nitrogen, sulfur, oxygen, phosphorous, arsenic and selenium content. Qualitative information indicating the occurrence and distribution of these elements in the samples can be used to gauge the relative stage of diagenetic evolution of the samples and provide information on their depositional environment. In some instances the chromatographic behaviour of the compounds produced upon pyrolysis is improved through on-line alkylation. This on-line derivatization is achieved by adding liquid reagents to the pyrolysis probe or by adding liquid reagents to the pyrolysis probe or by adding solid reagents either to the solid sample or by packing the reagent in the injection port of the chromatograph.

Dynamics of gas-surface interactions atomic-level understanding of scattering processes at surfaces

CERN Document Server

Díez Muniño, Ricardo

2013-01-01

This book gives a representative survey of the state of the art of research on gas-surface interactions. It provides an overview of the current understanding of gas surface dynamics and, in particular, of the reactive and non-reactive processes of atoms and small molecules at surfaces. Leading scientists in the field, both from the theoretical and the experimental sides, write in this book about their most recent advances. Surface science grew as an interdisciplinary research area over the last decades, mostly because of new experimental technologies (ultra-high vacuum, for instance), as well as because of a novel paradigm, the ‘surface science’ approach. The book describes the second transformation which is now taking place pushed by the availability of powerful quantum-mechanical theoretical methods implemented numerically. In the book, experiment and theory progress hand in hand with an unprecedented degree of accuracy and control. The book presents how modern surface science targets the atomic-level u...

Nucleation and microstructure development in Cr-Mo-V tool steel during gas atomization

Science.gov (United States)

Behúlová, M.; Grgač, P.; Čička, R.

2017-11-01

Nucleation studies of undercooled metallic melts are of essential interest for the understanding of phase selection, growth kinetics and microstructure development during their rapid non-equilibrium solidification. The paper deals with the modelling of nucleation processes and microstructure development in the hypoeutectic tool steel Ch12MF4 with the chemical composition of 2.37% C, 12.06 % Cr, 1.2% Mo, 4.0% V and balance Fe [wt. %] in the process of nitrogen gas atomization. Based on the classical theory of homogeneous nucleation, the nucleation temperature of molten rapidly cooled spherical particles from this alloy with diameter from 40 μm to 600 μm in the gas atomization process is calculated using various estimations of parameters influencing the nucleation process - the Gibbs free energy difference between solid and liquid phases and the solid/liquid interfacial energy. Results of numerical calculations are compared with experimentally measured nucleation temperatures during levitation experiments and microstructures developed in rapidly solidified powder particles from the investigated alloy.

Quantum Simulation of the Hubbard Model Using Ultra-Cold Atoms

Science.gov (United States)

2008-11-01

Hubbard model. The SU(3) Hubbard model has been proposed as a model system for studying different phases of matter expected to occur in quantum...chromodynamics (QCD): the color superconducting phase and the formation of baryons . Our initial investigations have focused on understanding three-body...density quark matter described by quantum chromodynamics . We have been investigating the stability of the 3-state Fermi gas with respect to decay due

Novel Fe-based nanocrystalline powder cores with excellent magnetic properties produced using gas-atomized powder

Science.gov (United States)

Chang, Liang; Xie, Lei; Liu, Min; Li, Qiang; Dong, Yaqiang; Chang, Chuntao; Wang, Xin-Min; Inoue, Akihisa

2018-04-01

FeSiBPNbCu nanocrystalline powder cores (NPCs) with excellent magnetic properties were fabricated by cold-compaction of the gas-atomized amorphous powder. Upon annealing at the optimum temperature, the NPCs showed excellent magnetic properties, including high initial permeability of 88, high frequency stability up to 1 MHz with a constant value of 85, low core loss of 265 mW/cm3 at 100 kHz for Bm = 0.05 T, and superior DC-bias permeability of 60% at a bias field of 100 Oe. The excellent magnetic properties of the present NPCs could be attributed to the ultrafine α-Fe(Si) phase precipitated in the amorphous matrix and the use of gas-atomized powder coated with a uniform insulation layer.

The King model for electrons in a finite-size ultracold plasma

Energy Technology Data Exchange (ETDEWEB)

Vrinceanu, D; Collins, L A [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Balaraman, G S [School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2008-10-24

A self-consistent model for a finite-size non-neutral ultracold plasma is obtained by extending a conventional model of globular star clusters. This model describes the dynamics of electrons at quasi-equilibrium trapped within the potential created by a cloud of stationary ions. A random sample of electron positions and velocities can be generated with the statistical properties defined by this model.

Light-pressure-induced nonlinear dispersion of a laser field interacting with an atomic gas

International Nuclear Information System (INIS)

Grimm, R.; Mlynek, J.

1990-01-01

We report on detailed studies of the effect of resonant light pressure on the optical response of an atomic gas to a single monochromatic laser field. In this very elementary situation of laser spectroscopy, the redistribution of atomic velocities that is induced by spontaneous light pressure leads to a novel contribution to the optical dispersion curve of the medium. This light-pressure-induced dispersion phenomenon displays a pronounced nonlinear dependence on the laser intensity. Moreover, for a given intensity, its strength is closely related to the laser beam diameter. As most important feature, this light-pressure-induced dispersion displays an even symmetry with respect to the optical detuning from line center. As a result, the total Doppler-broadened dispersion curve of the gas can become asymmetric, and a significant shift of the dispersion line center can occur. In addition to a detailed theoretical description of the phenomenon, we report on its experimental investigation on the λ=555.6 nm 1 S 0 - 3 P 1 transition in atomic ytterbium vapor with the use of frequency-modulation spectroscopy. The experimental findings are in good quantitative agreement with theoretical predictions

Investigation of an alternating current plasma as an element selective atomic emission detector for high-resolution capillary gas chromatography and as a source for atomic absorption and atomic emission spectrometry

Science.gov (United States)

Ombaba, Jackson M.

This thesis deals with the construction and evaluation of an alternating current plasma (ACP) as an element-selective detector for high resolution capillary gas chromatography (GC) and as an excitation source for atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES). The plasma, constrained in a quartz discharge tube at atmospheric pressure, is generated between two copper electrodes and utilizes helium as the plasma supporting gas. The alternating current plasma power source consists of a step-up transformer with a secondary output voltage of 14,000 V at a current of 23 mA. The device exhibits a stable signal because the plasma is self-seeding and reignites itself every half cycle. A tesla coil is not required to commence generation of the plasma if the ac voltage applied is greater than the breakdown voltage of the plasma-supporting gas. The chromatographic applications studied included the following: (1) the separation and selective detection of the organotin species, tributyltin chloride (TBT) and tetrabutyltin (TEBT), in environmental matrices including mussels (Mvutilus edullus) and sediment from Boston Harbor, industrial waste water and industrial sludge, and (2) the detection of methylcyclopentadienyl manganesetricarbonyl (MMT) and similar compounds used as gasoline additives. An ultrasonic nebulizer (common room humidifier) was utilized as a sample introduction device for aqueous solutions when the ACP was employed as an atomization source for atomic absorption spectrometry and as an excitation source for atomic emission spectrometry. Plasma diagnostic parameters studied include spatial electron number density across the discharge tube, electronic, excitation and ionization temperatures. Interference studies both in absorption and emission modes were also considered. Figures of merits of selected elements both in absorption and emission modes are reported. The evaluation of a computer-aided optimization program, Drylab GC, using

Atomization process for metal powder

International Nuclear Information System (INIS)

Lagutkin, Stanislav; Achelis, Lydia; Sheikhaliev, Sheikhali; Uhlenwinkel, Volker; Srivastava, Vikas

2004-01-01

A new atomization process has been developed, which combines pressure and gas atomization. The melt leaves the pressure nozzle as a hollow thin film cone. After the pre-filming step, the melt is atomized by a gas stream delivered by a ring nozzle. The objectives of this investigation are to achieve a narrow size distribution and low specific gas consumption compared to conventional gas atomization techniques. Both lead to a higher efficiency and low costs. Tin and some alloys have been atomized successfully with this technique. The mass median diameters from different experiments are between 20 and 100 μm. Sieving analysis of the tin powder shows close particle size distributions

Collisional energy dependence of molecular ionization by metastable rare gas atoms

International Nuclear Information System (INIS)

Martin, R.M.; Parr, T.P.

1979-01-01

The collisional energy dependence of several molecular total ionization cross sections by metastable rare gas atoms was studied over the thermal energy region using the crossed molecular beam time-of-flight method. Results are reported for the collision systems He, Ne, and Ar ionizing the geometric isomers cis- and trans-dichloroethylene and ortho- and para-dichlorobenzene. The He ionization cross sections oscillate about an energy dependence of E/sup -1/2/ over the energy range 0.004--1.0 eV, and the Ar*+para-dichlorobenzene cross section oscillates about an energy dependence of E/sup -2/5/ over the energy range 0.011--0.64 eV. The remaining systems are characterized by ''bent'' E/sup -m/ dependences with m values of 0.56--0.70 at low energies changing to 0.07--0.29 at higher energies. Comparison with the slopes of the He* systems and the Ar*+para-dichlorobenzene system shows that the ''bent'' and ''oscillating'' energy dependences are similar except for the form of the cross section functions at the lowest energies. No systematic differences are found between the cross section energy dependences for ionization of different geometric isomers or for ionization by the different metastable rare gas atoms

Small angle elastic scattering of electrons by noble gas atoms

International Nuclear Information System (INIS)

Wagenaar, R.W.

1984-01-01

In this thesis, measurements are carried out to obtain small angle elastic differential cross sections in order to check the validity of Kramers-Kronig dispersion relations for electrons scattered by noble gas atoms. First, total cross sections are obtained for argon, krypton and xenon. Next, a parallel plate electrostatic energy analyser for the simultaneous measurement of doubly differential cross section for small angle electron scattering is described. Also absolute differential cross sections are reported. Finally the forward dispersion relation for electron-helium collisions is dealt with. (Auth.)

Some aspects of the interaction of photons and electrons with rare gas atoms

International Nuclear Information System (INIS)

Westerveld, W.B.

1979-01-01

Processes for excitation in rare gas atoms are described, due to absorption of photons and bombardment with electrons. The differences and similarities between excitation by absorption of light (spectroscopy) and by electron impact (collision physics) are qualified. Oscillator strengths from the self-absorption of resonance radiation in rare gases are determined. The excitation of 2'P and 3'P states of helium by electrons has been studied by observing excitation cross sections and polarization fractions obtained from XUV radiation. A description is given of a recently completed apparatus to study inelastic electron-atom scattering processes by coincidence techniques. An introduction is given to the theory which relates the parameters describing an excited state of an atom to the angular distribution of the radiation emitted in the decay of the excited state. (Auth.)

Comparative investigation of pure and mixed rare gas atoms on coronene molecules.

Science.gov (United States)

Rodríguez-Cantano, Rocío; Bartolomei, Massimiliano; Hernández, Marta I; Campos-Martínez, José; González-Lezana, Tomás; Villarreal, Pablo; Pérez de Tudela, Ricardo; Pirani, Fernando; Hernández-Rojas, Javier; Bretón, José

2017-01-21

Clusters formed by the combination of rare gas (RG) atoms of He, Ne, Ar, and Kr on coronene have been investigated by means of a basin-hopping algorithm and path integral Monte Carlo calculations at T = 2 K. Energies and geometries have been obtained and the role played by the specific RG-RG and RG-coronene interactions on the final results is analysed in detail. Signatures of diffuse behavior of the He atoms on the surface of the coronene are in contrast with the localization of the heavier species, Ar and Kr. The observed coexistence of various geometries for Ne suggests the motion of the RG atoms on the multi-well potential energy surface landscape offered by the coronene. Therefore, the investigation of different clusters enables a comparative analysis of localized versus non-localized features. Mixed Ar-He-coronene clusters have also been considered and the competition of the RG atoms to occupy the docking sites on the molecule is discussed. All the obtained information is crucial to assess the behavior of coronene, a prototypical polycyclic aromatic hydrocarbon clustering with RG atoms at a temperature close to that of interstellar medium, which arises from the critical balance of the interactions involved.

Transport of Gas-Phase Anthropogenic VOCs to the Remote Troposphere During the NASA ATom Mission

Science.gov (United States)

Hornbrook, R. S.; Apel, E. C.; Hills, A. J.; Asher, E. C. C.; Emmons, L. K.; Blake, D. R.; Blake, N. J.; Simpson, I. J.; Barletta, B.; Meinardi, S.; Montzka, S. A.; Moore, F. L.; Miller, B. R.; Sweeney, C.; McKain, K.; Wofsy, S. C.; Daube, B. C.; Commane, R.; Bui, T. V.; Hanisco, T. F.; Wolfe, G. M.; St Clair, J. M.; Ryerson, T. B.; Thompson, C. R.; Peischl, J.; Ray, E. A.

2017-12-01

The NASA Atmospheric Tomography (ATom) project aims to study the impact of human-produced air pollution on greenhouse gases and on chemically reactive gases in the atmosphere. During the first two deployments, ATom-1 and ATom-2, which took place August 2016 and February 2017, respectively, a suite of trace gas measurement instruments were deployed on the NASA DC-8 which profiled the atmosphere between 0.2 and 13 km from near-pole to near-pole around the globe, sampling in the most remote regions of the atmosphere over the Arctic, Pacific, Southern, and Atlantic Oceans. Volatile organic compounds (VOCs) with a range of lifetimes from days to decades quantified using the Trace Organic Gas Analyzer (TOGA), Whole Air Sampler (WAS) and Programmable Flask Packages (PFPs) demonstrate a significant impact on the remote atmosphere from urban and industrial sources. Comparisons between the transport and fate of pollutants during Northern Hemisphere summer and winter will be presented. Observations of the distributions of anthropogenic VOCs will be compared with simulations using the Community Atmosphere Model with chemistry (CAM-chem).

Atom-dimer scattering in a heteronuclear mixture with a finite intraspecies scattering length

Science.gov (United States)

Gao, Chao; Zhang, Peng

2018-04-01

We study the three-body problem of two ultracold identical bosonic atoms (denoted by B ) and one extra atom (denoted by X ), where the scattering length aB X between each bosonic atom and atom X is resonantly large and positive. We calculate the scattering length aad between one bosonic atom and the shallow dimer formed by the other bosonic atom and atom X , and investigate the effect induced by the interaction between the two bosonic atoms. We find that even if this interaction is weak (i.e., the corresponding scattering length aB B is of the same order of the van der Waals length rvdW or even smaller), it can still induce a significant effect for the atom-dimer scattering length aad. Explicitly, an atom-dimer scattering resonance can always occur when the value of aB B varies in the region with | aB B|≲ rvdW . As a result, both the sign and the absolute value of aad, as well as the behavior of the aad-aB X function, depends sensitively on the exact value of aB B. Our results show that, for a good quantitative theory, the intraspecies interaction is required to be taken into account for this heteronuclear system, even if this interaction is weak.

Ultracold neutron source at the PULSTAR reactor: Engineering design and cryogenic testing

Energy Technology Data Exchange (ETDEWEB)

Korobkina, E., E-mail: ekorobk@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, 2500 Stinson Drive, Box 7909, Raleigh, NC 27695 (United States); Medlin, G. [Department of Physics, North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States); Wehring, B.; Hawari, A.I. [Department of Nuclear Engineering, North Carolina State University, 2500 Stinson Drive, Box 7909, Raleigh, NC 27695 (United States); Huffman, P.R.; Young, A.R. [Department of Physics, North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States); Beaumont, B. [Department of Physics, North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Palmquist, G. [Department of Physics, North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States)

2014-12-11

Construction is completed and commissioning is in progress for an ultracold neutron (UCN) source at the PULSTAR reactor on the campus of North Carolina State University. The source utilizes two stages of neutron moderation, one in heavy water at room temperature and the other in solid methane at ∼40K, followed by a converter stage, solid deuterium at 5 K, that allows a single down scattering of cold neutrons to provide UCN. The UCN source rolls into the thermal column enclosure of the PULSTAR reactor, where neutrons will be delivered from a bare face of the reactor core by streaming through a graphite-lined assembly. The source infrastructure, i.e., graphite-lined assembly, heavy-water system, gas handling system, and helium liquefier cooling system, has been tested and all systems operate as predicted. The research program being considered for the PULSTAR UCN source includes the physics of UCN production, fundamental particle physics, and material surface studies of nanolayers containing hydrogen. In the present paper we report details of the engineering and cryogenic design of the facility as well as results of critical commissioning tests without neutrons.

Densification behavior of gas and water atomized 316L stainless steel powder during selective laser melting

Science.gov (United States)

Li, Ruidi; Shi, Yusheng; Wang, Zhigang; Wang, Li; Liu, Jinhui; Jiang, Wei

2010-04-01

The densification during selective laser melting (SLM) process is an important factor determining the final application of SLM-part. In the present work, the densifications under different processing conditions were investigated and the densification mechanisms were elucidated. It was found that the higher laser power, lower scan speed, narrower hatch spacing and thinner layer thickness could enable a much smoother melting surface and consequently a higher densification. The gas atomized powder possessed better densification than water atomized powder, due to the lower oxygen content and higher packing density of gas atomized powder. A large number of regular-shaped pores can be generated at a wider hatch spacing, even if the scanning track is continuous and wetted very well. The densification mechanisms were addressed and the methods for building dense metal parts were also proposed as follows: inhibiting the balling phenomenon, increasing the overlap ratio of scanning tracks and reducing the micro-cracks.

An ultra-cold neutron source at the MLNSC

International Nuclear Information System (INIS)

Bowles, T.J.; Brun, T.; Hill, R.; Morris, C.; Seestrom, S.J.; Crow, L.; Serebrov, A.

1998-01-01

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have carried out the research and development of an Ultra-Cold Neutron (UCN) source at the Manuel Lujan Neutron Scattering Center (MLNSC). A first generation source was constructed to test the feasibility of a rotor source. The source performed well with an UCN production rate reasonably consistent with that expected. This source can now provide the basis for further development work directed at using UCN in fundamental physics research as well as possible applications in materials science

An ultra-cold neutron source at the MLNSC

Energy Technology Data Exchange (ETDEWEB)

Bowles, T.J.; Brun, T.; Hill, R.; Morris, C.; Seestrom, S.J. [Los Alamos National Lab., NM (United States); Crow, L. [Univ. of Rhode Island, Kingston, RI (United States); Serebrov, A. [Petersburg Nuclear Physics Inst. (Russian Federation)

1998-11-01

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have carried out the research and development of an Ultra-Cold Neutron (UCN) source at the Manuel Lujan Neutron Scattering Center (MLNSC). A first generation source was constructed to test the feasibility of a rotor source. The source performed well with an UCN production rate reasonably consistent with that expected. This source can now provide the basis for further development work directed at using UCN in fundamental physics research as well as possible applications in materials science.

Quantum levitation of nanoparticles seen with ultracold neutrons

Energy Technology Data Exchange (ETDEWEB)

Nesvizhevsky, V. V., E-mail: nesvizhevsky@ill.eu [Institut Laue-Langevin (France); Voronin, A. Yu. [Lebedev Institute (Russian Federation); Lambrecht, A.; Reynaud, S. [Laboratoire Kastler-Brossel, CNRS, ENS, UPMC (France); Lychagin, E. V.; Muzychka, A. Yu.; Strelkov, A. V. [Joint Institute for Nuclear Research (Russian Federation)

2013-09-15

Analyzing new experiments with ultracold neutrons (UCNs) we show that physical adsorption of nanoparticles/nanodroplets, levitating in high-excited states in a deep and broad potential well formed by van der Waals/Casimir-Polder (vdW/CP) forces results in new effects on a cross-road of the fields of fundamental interactions, neutron, surface and nanoparticle physics. Accounting for the interaction of UCNs with nanoparticles explains a recently discovered intriguing so-called 'small heating' of UCNs in traps. It might be relevant to the striking conflict of the neutron lifetime experiments with smallest reported uncertainties by adding false effects there.

Quantum levitation of nanoparticles seen with ultracold neutrons

International Nuclear Information System (INIS)

Nesvizhevsky, V. V.; Voronin, A. Yu.; Lambrecht, A.; Reynaud, S.; Lychagin, E. V.; Muzychka, A. Yu.; Strelkov, A. V.

2013-01-01

Analyzing new experiments with ultracold neutrons (UCNs) we show that physical adsorption of nanoparticles/nanodroplets, levitating in high-excited states in a deep and broad potential well formed by van der Waals/Casimir-Polder (vdW/CP) forces results in new effects on a cross-road of the fields of fundamental interactions, neutron, surface and nanoparticle physics. Accounting for the interaction of UCNs with nanoparticles explains a recently discovered intriguing so-called “small heating” of UCNs in traps. It might be relevant to the striking conflict of the neutron lifetime experiments with smallest reported uncertainties by adding false effects there

How can we probe the atom mass currents induced by synthetic gauge fields?

Science.gov (United States)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Dicke superradiance as nondestructive probe for the state of atoms in optical lattices

Science.gov (United States)

ten Brinke, Nicolai; Schützhold, Ralf

2016-04-01

We present a proposal for a probing scheme utilizing Dicke superradiance to obtain information about ultracold atoms in optical lattices. A probe photon is absorbed collectively by an ensemble of lattice atoms generating a Dicke state. The lattice dynamics (e.g., tunneling) affects the coherence properties of that Dicke state and thus alters the superradiant emission characteristics - which in turn provides insight into the lattice (dynamics). Comparing the Bose-Hubbard and the Fermi-Hubbard model, we find similar superradiance in the strongly interacting Mott insulator regime, but crucial differences in the weakly interacting (superfluid or metallic) phase. Furthermore, we study the possibility to detect whether a quantum phase transition between the two regimes can be considered adiabatic or a quantum quench.

Speciation analysis of arsenic by selective hydride generation- cryotrapping-atomic fluorescence spectrometry with flame-in-gas- shield atomizer: Achieving extremely low detection limits with inexpensive instrumentation

Czech Academy of Sciences Publication Activity Database

Musil, Stanislav; Matoušek, Tomáš; Currier, J. M.; Stýblo, M.; Dědina, Jiří