Belyaev, S. T.
2016-06-15
We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.
Bose-Einstein Condensation in the Relativistic Ideal Bose Gas
Grether, M.; Llano, M. de; Baker, George A. Jr.
2007-11-16
The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.
Bose-Einstein condensation in the relativistic ideal Bose gas.
Grether, M; de Llano, M; Baker, George A
2007-11-16
The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.
Numerical simulation of polariton Bose gas thermalization
NASA Astrophysics Data System (ADS)
Kartsev, P. F.; Kuznetsov, I. O.
2016-08-01
In this work, we present the numerical simulation of the process a Bose gas thermalization and the formation of the condensate. Our approach is based on kinetic equations and “Fermi's golden rule” in the incoherent approximation. Direct summation of terms is performed using GPGPU OpenCL parallel code using AMD Radeon HD 7970.
Canonical Bose gas simulations with stochastic gauges.
Drummond, P D; Deuar, P; Kheruntsyan, K V
2004-01-30
A technique to simulate the grand canonical ensembles of interacting Bose gases is presented. Results are generated for many temperatures by averaging over energy-weighted stochastic paths, each corresponding to a solution of coupled Gross-Pitaevskii equations with phase noise. The stochastic gauge method used relies on an off-diagonal coherent-state expansion, thus taking into account all quantum correlations. As an example, the second-order spatial correlation function and momentum distribution for an interacting 1D Bose gas are calculated.
Excitation picture of an interacting Bose gas
Kira, M.
2014-12-15
Atomic Bose–Einstein condensates (BECs) can be viewed as macroscopic objects where atoms form correlated atom clusters to all orders. Therefore, the presence of a BEC makes the direct use of the cluster-expansion approach–lucrative e.g. in semiconductor quantum optics–inefficient when solving the many-body kinetics of a strongly interacting Bose. An excitation picture is introduced with a nonunitary transformation that describes the system in terms of atom clusters within the normal component alone. The nontrivial properties of this transformation are systematically studied, which yields a cluster-expansion friendly formalism for a strongly interacting Bose gas. Its connections and corrections to the standard Hartree–Fock–Bogoliubov approach are discussed and the role of the order parameter and the Bogoliubov excitations are identified. The resulting interaction effects are shown to visibly modify number fluctuations of the BEC. Even when the BEC has a nearly perfect second-order coherence, the BEC number fluctuations can still resolve interaction-generated non-Poissonian fluctuations. - Highlights: • Excitation picture expresses interacting Bose gas with few atom clusters. • Semiconductor and BEC many-body investigations are connected with cluster expansion. • Quantum statistics of BEC is identified in terms of atom clusters. • BEC number fluctuations show extreme sensitivity to many-body correlations. • Cluster-expansion friendly framework is established for an interacting Bose gas.
Stability of a unitary Bose gas.
Fletcher, Richard J; Gaunt, Alexander L; Navon, Nir; Smith, Robert P; Hadzibabic, Zoran
2013-09-20
We study the stability of a thermal (39)K Bose gas across a broad Feshbach resonance, focusing on the unitary regime, where the scattering length a exceeds the thermal wavelength λ. We measure the general scaling laws relating the particle-loss and heating rates to the temperature, scattering length, and atom number. Both at unitarity and for positive a<λ we find agreement with three-body theory. However, for a<0 and away from unitarity, we observe significant four-body decay. At unitarity, the three-body loss coefficient, L(3) proportional λ(4), is 3 times lower than the universal theoretical upper bound. This reduction is a consequence of species-specific Efimov physics and makes (39)K particularly promising for studies of many-body physics in a unitary Bose gas.
Calorimetry of a Bose-Einstein-condensed photon gas.
Damm, Tobias; Schmitt, Julian; Liang, Qi; Dung, David; Vewinger, Frank; Weitz, Martin; Klaers, Jan
2016-04-19
Phase transitions, as the condensation of a gas to a liquid, are often revealed by a discontinuous behaviour of thermodynamic quantities. For liquid helium, for example, a divergence of the specific heat signals the transition from the normal fluid to the superfluid state. Apart from liquid helium, determining the specific heat of a Bose gas has proven to be a challenging task, for example, for ultracold atomic Bose gases. Here we examine the thermodynamic behaviour of a trapped two-dimensional photon gas, a system that allows us to spectroscopically determine the specific heat and the entropy of a nearly ideal Bose gas from the classical high temperature to the Bose-condensed quantum regime. The critical behaviour at the phase transition is clearly revealed by a cusp singularity of the specific heat. Regarded as a test of quantum statistical mechanics, our results demonstrate a quantitative agreement with its predictions at the microscopic level.
Calorimetry of a Bose-Einstein-condensed photon gas
NASA Astrophysics Data System (ADS)
Damm, Tobias; Schmitt, Julian; Liang, Qi; Dung, David; Vewinger, Frank; Weitz, Martin; Klaers, Jan
2016-04-01
Phase transitions, as the condensation of a gas to a liquid, are often revealed by a discontinuous behaviour of thermodynamic quantities. For liquid helium, for example, a divergence of the specific heat signals the transition from the normal fluid to the superfluid state. Apart from liquid helium, determining the specific heat of a Bose gas has proven to be a challenging task, for example, for ultracold atomic Bose gases. Here we examine the thermodynamic behaviour of a trapped two-dimensional photon gas, a system that allows us to spectroscopically determine the specific heat and the entropy of a nearly ideal Bose gas from the classical high temperature to the Bose-condensed quantum regime. The critical behaviour at the phase transition is clearly revealed by a cusp singularity of the specific heat. Regarded as a test of quantum statistical mechanics, our results demonstrate a quantitative agreement with its predictions at the microscopic level.
Theory of a Nearly Two-Dimensional Dipolar Bose Gas
2016-05-11
A TRIDENT SCHOLAR PROJECT REPORT NO. 453 Theory of a Nearly Two-Dimensional Dipolar Bose Gas by Midshipman 1/C Michael A. Woulfe...approved for public release and sale; its distribution is unlimited. U.S.N.A. --- Trident Scholar project report; no. 453 (2016) THEORY OF A...YYYY) 05-11-2016 2. REPORT TYPE 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Theory of a Nearly Two-Dimensional Dipolar Bose Gas 5a
Degenerate Bose gas without anomalous averages
NASA Astrophysics Data System (ADS)
Bobrov, V. B.; Trigger, S. A.; Schram, P. P.
2016-11-01
Theory of a weakly non-ideal Bose gas in the canonical ensemble is developed without assumption of the C-number representation of the creation and annihilation operators with zero momentum. Instead of this assumption, we use the assumption on the C-number nature of the density operator N0 = a† 0a0 with zero momentum. It is shown that the pole of the “density-density” Green function (DDGF), as well as the pole of the single-particle Green function (SPGF), exactly coincide with the Bogoliubov phonon-roton spectrum of excitations for both assumptions. This spectrum, as is known confirmed by many neutron and x-ray experimental measurements of the dynamic structure factor in He II, is straightly related to the DDGF. At the same time, we show that in the other case under consideration, when neither N0 nor a† 0 and a0 are C-numbers, a gap can exist in SPGF. This gap in SPGF excitations is straightly related to the density of particles in the “condensate”. Therefore, the spectra of excitations for the DDGF and SPGF in the last case under consideration are different, in contrast to the Bogoliubov-type theory where these spectra are identical.
Nonequilibrium States of a Quenched Bose Gas
NASA Astrophysics Data System (ADS)
Ling, Hong; Kain, Ben
2014-05-01
Yin and Radzihovsky [Phys. Rev. A 88, 063611 (2014)] recently developed a self-consistent extension of a Bogoliubov theory, in which the condensate number density, nc, is treated as a mean field that changes with time in order to analyze a JILA experiment by Makotyn et al. [Nature Physics doi:10.1038/nphys2850 (2014)] on a 85Rb Bose gas following a deep quench to a large scattering length. We apply this theory to construct a set of closed equations that highlight the role of dnc/dt, which is to induce an effective interaction between quasiparticles. We show analytically that such a system supports a steady state characterized by a constant condensate density and a steady but periodically changing momentum distribution, whose time average is described exactly by the generalized Gibbs ensemble. We discuss how the dnc/dt-induced effective interaction, which cannot be ignored on the grounds of the adiabatic approximation for modes near the gapless Goldstone mode, can affect experimentally measurable quantities such as Tan's contact. This work is supported in part by the US Army Research Office under Grant No. W911NF-10-1-0096 and in part by the US National Science Foundation under Grant No. PHY11-25915.
Hydrodynamic modes of a one-dimensional trapped Bose gas
Fuchs, J.N.; Leyronas, X.; Combescot, R.
2003-10-01
We consider two regimes where a trapped Bose gas behaves as a one-dimensional (1D) system. In the first one the Bose gas is microscopically described by 3D mean-field theory, but the trap is so elongated that it behaves as a 1D gas with respect to low-frequency collective modes. In the second regime we assume that the 1D gas is truly 1D and that it is properly described by the Lieb-Liniger model. In both regimes we find the frequency of the lowest compressional mode by solving the hydrodynamic equations. This is done by making use of a method which allows us to find analytical or quasianalytical solutions of these equations for a large class of models approaching very closely the actual equation of state of the Bose gas. We find an excellent agreement with the recent results of Menotti and Stringari obtained from a sum-rule approach.
First and second sounds in a degenerate Bose gas
NASA Astrophysics Data System (ADS)
Dmytruk, I.; Svidzynskiy, A.; Shygorin, P.
2017-06-01
In this work the propagation of sound waves in a degenerate quantum gas is considered. We modify the Wang Chang and Uhlenbeck method for description of the sounds in a Maxwell gas for the case of a degenerate quantum gas. Using this approach, we constructed a dispersion relation for sound waves in a condensed Bose gas at finite temperatures, and calculate the velocities of first and second sounds in the first approximation. The possibility of the theoretical investigation for sound damping is discussed.
Esteve, J; Trebbia, J-B; Schumm, T; Aspect, A; Westbrook, C I; Bouchoule, I
2006-04-07
We report in situ measurements of density fluctuations in a quasi-one-dimensional 87Rb Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot-noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected "bunching" for an ideal Bose gas. At high density, the measured fluctuations are strongly reduced compared to the ideal gas case. We attribute this reduction to repulsive interatomic interactions. The data are compared with a calculation for an interacting Bose gas in the quasicondensate regime.
Anisotropic Expansion of a Thermal Dipolar Bose Gas.
Tang, Y; Sykes, A G; Burdick, N Q; DiSciacca, J M; Petrov, D S; Lev, B L
2016-10-07
We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the postexpansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.
Anisotropic Expansion of a Thermal Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Tang, Y.; Sykes, A. G.; Burdick, N. Q.; DiSciacca, J. M.; Petrov, D. S.; Lev, B. L.
2016-10-01
We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the postexpansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.
Percolation analysis of a disordered spinor Bose gas
NASA Astrophysics Data System (ADS)
Nabi, Sk Noor; Basu, Saurabh
2016-06-01
We study the effects of an on-site disorder potential in a gas of spinor (spin-1) ultracold atoms loaded in an optical lattice corresponding to both ferromagnetic and antiferromagnetic spin-dependent interactions. Starting with a disordered spinor Bose-Hubbard model (SBHM) on a two-dimensional square lattice, we observe the appearance of a Bose glass phase using the fraction of the lattice sites having finite superfluid order parameter and non integer local densities as an indicator. A precise distinction between three different types of phases namely, superfluid, Mott insulator and Bose glass is done via a percolation analysis thereby demonstrating that a reliable enumeration of phases is possible at particular values of the parameters of the SBHM. Finally, we present the phase diagram based on the above information for both antiferromagnetic and ferromagnetic interactions.
Anisotropic superfluidity in a dipolar Bose gas.
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Anisotropic Superfluidity in a Dipolar Bose Gas
Ticknor, Christopher; Wilson, Ryan M.; Bohn, John L.
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Casimir force induced by an imperfect Bose gas.
Napiórkowski, Marek; Piasecki, Jarosław
2011-12-01
We present a study of the Casimir effect in an imperfect (mean-field) Bose gas contained between two infinite parallel plane walls. The derivation of the Casimir force follows from the calculation of the excess grand-canonical free energy density under periodic, Dirichlet, and Neumann boundary conditions with the use of the steepest descent method. In the one-phase region, the force decays exponentially fast when distance D between the walls tends to infinity. When the Bose-Einstein condensation point is approached, the decay length in the exponential law diverges with critical exponent ν(IMP) = 1, which differs from the perfect gas case where ν(P) = 1/2. In the two-phase region, the Casimir force is long range and decays following the power law D(-3), with the same amplitude as in the perfect gas.
Fast thermalization and Helmholtz oscillations of an ultracold Bose gas.
Papoular, D J; Pitaevskii, L P; Stringari, S
2014-10-24
We analyze theoretically the transport properties of a weakly interacting ultracold Bose gas enclosed in two reservoirs connected by a constriction. We assume that the transport of the superfluid part is hydrodynamic, and we describe the ballistic transport of the normal part using the Landauer-Büttiker formalism. Modeling the coupled evolution of the phase, atom number, and temperature mismatches between the reservoirs, we predict that Helmholtz (plasma) oscillations can be observed at nonzero temperatures below Tc. We show that, because of its strong compressibility, the Bose gas is characterized by a fast thermalization compared to the damping time for plasma oscillations, accompanied by a fast transfer of the normal component. This fast thermalization also affects the gas above Tc, where we present a comparison to the ideal fermionic case. Moreover, we outline the possible realization of a superleak through the inclusion of a disordered potential.
Momentum Distribution in the Unitary Bose Gas from First Principles.
Comparin, Tommaso; Krauth, Werner
2016-11-25
We consider a realistic bosonic N-particle model with unitary interactions relevant for Efimov physics. Using quantum Monte Carlo methods, we find that the critical temperature for Bose-Einstein condensation is decreased with respect to the ideal Bose gas. We also determine the full momentum distribution of the gas, including its universal asymptotic behavior, and compare this crucial observable to recent experimental data. Similar to the experiments with different atomic species, differentiated solely by a three-body length scale, our model only depends on a single parameter. We establish a weak influence of this parameter on physical observables. In current experiments, the thermodynamic instability of our model from the atomic gas towards an Efimov liquid could be masked by the dynamical instability due to three-body losses.
Vortices in a highly rotating Bose condensed gas
NASA Astrophysics Data System (ADS)
Coddington, I. R.
Superfluids, with their dissipationless flow and exotic topologies, have puzzled researchers in diverse fields of physics for almost a century. One of the hallmark features of superfluids is their response to rotation, which requires the fluid to be pierced by an array quantized singularities or vortices. Over the past few years, vortices and the lattices they organize into have become one of the major fields of experimental research with dilute gas Bose-Einstein condensates. This thesis explores the physics of vortices and vortex lattices in the dilute gas Bose-Einstein condensate while drawing connections to other superfluid systems. In addition to characterizing several equilibrium vortex effects, this work also studies several excitations. By removing atoms from the rotating condensate with a tightly focused, resonant laser, the density can be locally suppressed, creating aggregate vortices containing many units of circulation. These so called "giant vortices" offer insight into the dynamical stability of density defects in this system. Using similar techniques we can excite and directly image Tkachenko waves in the vortex. These low frequency modes are a consequence of the small but nonvanishing elastic shear modulus of the vortex-filled superfluid. Finally, by working at extremely high rotations we can create a Bose-Einstein condensates in the lowest Landau level. In this regime, which requires rotation rates greater than 99% of the centrifugal limit for a harmonically trapped gas, we are able to observe several expected and unexpected shifts in the physical properties of the condensate. In conclusion the dilute gas Bose-Einstein condensates offers a rich system in which to study vortex physics, and explore dynamical effects common to all rotating superfluids.
Neutral gas dynamics in fireballs
Stenzel, R. L.; Ionita, C.; Schrittwieser, R.
2011-06-01
Fireballs are local discharge phenomena on positively biased electrodes in partially ionized plasmas. Electrons, energized at a double layer, heat neutral gas which expands. The gas pressure exceeds the plasma pressure, hence becomes important to the stability and transport in fireballs. The flow of gas moves the electrode and sensors similar to a mica pendulum. Flow speed and directions are measured. A fireball gun has been developed to partially collimate the flow of hot gas and heat objects in its path. New applications of fireballs are suggested.
Dynamics of impurities in ultracold Bose gas
NASA Astrophysics Data System (ADS)
Shchadilova, Yulia; Grusdt, Fabian; Rubtsov, Alexey; Demler, Eugene
2015-05-01
A system of an impurity immersed in a Bose-Einstein condensate (BEC) exhibits the polaronic effect, which is known to be an ubiquitous phenomenon in a wide range of physical systems including semiconductors, doped Mott insulators, and high-Tc superconductors. Recent analysis of the BEC-polaron problem showed that existing analytical approaches do not provide reliable results in the experimentally relevant range of parameters when tested against Monte Carlo (MC) simulations. In this contribution we demonstrate that the description of polarons at finite momentum can be done by employing an analytical class of wavefunctions based on the correlated Gaussian ansatz (CGWs). We show that CGWs show excellent agreement with known MC results for the polaron binding energy for a wide range of interactions. We discuss the properties of the polarons and atomic mixtures in systems of ultracold atoms in which polaronic effects can be observed with current experimental technology. Our CGWs predicts a specific pattern of correlations between host atoms that can be measured in time-of-flight experiments. Department of Physics, Harvard University.
Gas cell neutralizers (Fundamental principles)
Fuehrer, B.
1985-06-01
Neutralizing an ion-beam of the size and energy levels involved in the neutral-particle-beam program represents a considerable extension of the state-of-the-art of neutralizer technology. Many different mediums (e.g., solid, liquid, gas, plasma, photons) can be used to strip the hydrogen ion of its extra electron. A large, multidisciplinary R and D effort will no doubt be required to sort out all of the ''pros and cons'' of these various techniques. The purpose of this particular presentation is to discuss some basic configurations and fundamental principles of the gas type of neutralizer cell. Particular emphasis is placed on the ''Gasdynamic Free-Jet'' neutralizer since this configuration has the potential of being much shorter than other type of gas cells (in the beam direction) and it could operate in nearly a continuous mode (CW) if necessary. These were important considerations in the ATSU design which is discussed in some detail in the second presentation entitled ''ATSU Point Design''.
Anisotropic superfluidity in a dipolar Bose gas
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2010-11-04
A quintessential feature of superfluidity is the ability to support dissipationless flow, for example, when an object moves through a superfluid and experiences no drag. This, however, only occurs when the object is moving below a certain critical velocity; when it exceeds this critical velocity it dissipates energy into excitations of the superfluid, resulting in a net drag force on the object and the breakdown of superfluid flow. In many superfluids, such as dilute Bose-Einstein condensates (BECs) of atoms with contact interactions, this critical velocity is simply the speed of sound in the system, where the speed of sound is set by the density and the s-wave scattering length of the atoms. However, for other superfluids, such as liquid {sup 4}He, this is not the case. In {sup 4}He, the critical velocity is set by a roton mode, corresponding to a peak in the static structure factor of the system at some finite, non-zero momentum, with a characteristic velocity that is considerably less than the speed of sound in the liquid. This feature has been verified experimentally via measurements of ion-drift velocity in the fluid, thereby providing insight into the detailed structure of the system. Interestingly, a roton-like feature was predicted to exist in the dispersion relation of a quasi-two-dimensional (q2D) dipolar BEC (DBEC) [16], or a BEC with dipole-dipole interactions. However, unlike the dispersion of {sup 4}He, the disperSion of a DBEC is highly tunable as a function of the condensate density or dipole-dipole interaction (ddi) strength. Additionally, the DBEC is set apart from liquid {sup 4}He in that its interactions depend on how the dipoles are oriented in space. Thus, the DBEC provides an ideal system to study the effects that anisotropies have on the bulk properties of a superfluid, such as the critical velocity. Here we consider a DBEC in a quasi-two-dimensional (q2D) geometry and allow for the dipoles to be polarized at a nonzero angle into the plane
Ground state of a resonantly interacting Bose gas
Diederix, J. M.; Heijst, T. C. F. van; Stoof, H. T. C.
2011-09-15
We show that a two-channel mean-field theory for a Bose gas near a Feshbach resonance allows for an analytic computation of the chemical potential, and therefore the universal constant {beta}, at unitarity. To improve on this mean-field theory, which physically neglects condensate depletion, we study a variational Jastrow ansatz for the ground-state wave function and use the hypernetted-chain approximation to minimize the energy for all positive values of the scattering length. We also show that other important physical quantities such as Tan's contact and the condensate fraction can be directly obtained from this approach.
Equilibrium state of a trapped two-dimensional Bose gas
Rath, Steffen P.; Yefsah, Tarik; Guenter, Kenneth J.; Cheneau, Marc; Desbuquois, Remi; Dalibard, Jean; Holzmann, Markus; Krauth, Werner
2010-07-15
We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional {sup 87}Rb Bose gas and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in situ measurements and quantum Monte Carlo simulations, which we attribute to a nonlinear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time of flight, taking advantage of their self-similarity in a two-dimensional expansion.
Two-step condensation of the charged Bose gas.
Delgado, R L; Bargueño, P; Sols, F
2012-09-01
The condensation of the spinless ideal charged Bose gas in the presence of a magnetic field is revisited. The conventional approach is extended to include the macroscopic occupation of excited kinetic states lying in the lowest Landau level, which plays an essential role in the case of large magnetic fields. In that limit, signatures of two diffuse phase transitions (crossovers) appear in the specific heat. In particular, at temperatures lower than the cyclotron frequency, the system behaves as an effectively one-dimensional free boson system, with the specific heat equal to 1/2Nk(B) and a gradual condensation at lower temperatures.
On the Ground-State Energy and Local Pressure of an Inhomogeneous Bose Gas
NASA Astrophysics Data System (ADS)
Bobrov, V. B.; Trigger, S. A.
2017-01-01
The exact expression for the average kinetic energy of an inhomogeneous Bose gas in the ground state is obtained as a functional of the inhomogeneous density of the Bose-Einstein condensate. The result is based on existence of the off-diagonal long-range order in the single-particle density matrix for systems with a Bose-Einstein condensate. This makes it possible to avoid the use of anomalous averages. On this basis, the explicit expressions for the ground-state energy and the local pressure of an inhomogeneous Bose gas are derived within the self-consistent Hartree-Fock approximation.
Localization of weakly interacting Bose gas in quasiperiodic potential
NASA Astrophysics Data System (ADS)
Ray, Sayak; Pandey, Mohit; Ghosh, Anandamohan; Sinha, Subhasis
2016-01-01
We study the localization properties of weakly interacting Bose gas in a quasiperiodic potential. The Hamiltonian of the non-interacting system reduces to the well known ‘Aubry-André model’, which shows the localization transition at a critical strength of the potential. In the presence of repulsive interaction we observe multi-site localization and obtain a phase diagram of the dilute Bose gas by computing the superfluid fraction and the inverse participation ratio. We construct a low-dimensional classical Hamiltonian map and show that the onset of localization is manifested by the chaotic phase space dynamics. The level spacing statistics also identify the transition to localized states resembling a Poisson distribution that are ubiquitous for both non-interacting and interacting systems. We also study the quantum fluctuations within the Bogoliubov approximation and compute the quasiparticle energy spectrum. Enhanced quantum fluctuation and multi-site localization phenomenon of non-condensate density are observed above the critical coupling of the potential. We briefly discuss the effect of the trapping potential on the localization of matter wave.
NASA Astrophysics Data System (ADS)
Mehedi Faruk, Mir; Sazzad Hossain, Md.; Muktadir Rahman, Md.
2016-02-01
The changes in characteristics of Bose condensation of ideal Bose gas due to an external generic power law potential U=\\sumi=1dci\\vert xi/ai\\vertni are studied carefully. Detailed calculation of Kim et al. (J. Phys. Condens. Matter 11 (1999) 10269) yielded the hierarchy of condensation transitions with changing fractional dimensionality. In this manuscript, some theorems regarding specific heat at constant volume CV are presented. Careful examination of these theorems reveal the existence of hidden hierarchy of the condensation transition in trapped systems as well.
Quench dynamics of a strongly interacting resonant Bose gas
NASA Astrophysics Data System (ADS)
Yin, Xiao; Radzihovsky, Leo
2015-03-01
We explore the dynamics of a resonant Bose gas following its quench to a strongly interacting regime near a Feshbach resonance. For such deep quenches, we utilize a self-consistent dynamic mean-field approximation and find that after an initial regime of many-body Rabi-like oscillations between the condensate and finite-momentum quasiparticle pairs, at long times, the gas reaches a prethermalized nonequilibrium steady state. We explore the resulting state through its broad stationary momentum distribution function, that exhibits a power-law high momentum tail. We study the associated enhanced depletion, quench-rate dependent excitation energy, Tan's contact, structure function and radio frequency spectroscopy. We find these predictions to be in a qualitative agreement with recent experiments We acknowledge the supported by the NSF through DMR-1001240 on this research.
Superfluidity and phase transitions in a resonant Bose gas
Radzihovsky, Leo; Weichman, Peter B.; Park, Jae I.
2008-10-15
The atomic Bose gas is studied across a Feshbach resonance, mapping out its phase diagram, and computing its thermodynamics and excitation spectra. It is shown that such a degenerate gas admits two distinct atomic and molecular superfluid phases, with the latter distinguished by the absence of atomic off-diagonal long-range order, gapped atomic excitations, and deconfined atomic {pi}-vortices. The properties of the molecular superfluid are explored, and it is shown that across a Feshbach resonance it undergoes a quantum Ising transition to the atomic superfluid, where both atoms and molecules are condensed. In addition to its distinct thermodynamic signatures and deconfined half-vortices, in a trap a molecular superfluid should be identifiable by the absence of an atomic condensate peak and the presence of a molecular one.
Bose gas with generalized dispersion relation plus an energy gap
NASA Astrophysics Data System (ADS)
Solis, M. A.; Martinez, J. G.; Garcia, J.
We report the critical temperature, the condensed fraction, the internal energy and the specific heat for a d-dimensional Bose gas with a generalized dispersion relation plus an energy gap, i.e., ɛ =ɛ0 for k = 0 and ɛ =ɛ0 + Δ +csks , for k > 0 , where ℏk is the particle momentum, ɛ0 the lowest particle energy, cs a constant with dimension of energy multiplied by a length to the power s > 0 . When Δ > 0 , a Bose-Einstein critical temperature Tc ≠ 0 exists for any d / s >= 0 at which the internal energy shows a peak and the specific heat shows a jump. The critical temperature and the specific heat jump increase as functions of the gap but they decrease as functions of d / s . Thermodynamic properties are ɛ0 independent since this is just a reference energy. For Δ = 0 we recover the results reported in Ref. [1]. V. C. Aguilera-Navarro, M. de Llano y M. A. Solís, Eur. J. Phys. 20, 177 (1999). We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.
Superfluid density of a spin-orbit-coupled Bose gas
NASA Astrophysics Data System (ADS)
Zhang, Yi-Cai; Yu, Zeng-Qiang; Ng, Tai Kai; Zhang, Shizhong; Pitaevskii, Lev; Stringari, Sandro
2016-09-01
We discuss the superfluid properties of a uniform, weakly interacting Bose-Einstein condensed gas with spin-orbit coupling, realized recently in experiments. We find a finite normal fluid density ρn at zero temperature which turns out to be a function of the Raman coupling. In particular, the entire fluid becomes normal at the transition point from the zero momentum to the plane wave phase, even though the condensate fraction remains finite. We emphasize the crucial role played by the breaking of Galilean invariance and by the gapped branch of the elementary excitations whose contribution to various sum rules is discussed explicitly. Our predictions for the superfluid density are successfully compared with the available experimental results based on the measurement of the sound velocities.
Dynamics of a finite temperature Bose gas in atomtronic devices
NASA Astrophysics Data System (ADS)
Colussi, Victor; Holland, Murray; Anderson, Dana Z.
2014-05-01
We investigate the problem of modeling atomtronic devices that utilize the nonequilibrium dynamics of a finite temperature Bose-condensed gas placed underneath an atom chip to mimic the properties of classical circuit elements. Our model consists of the full dynamics of the condensate and thermal cloud. The thermal cloud is treated semiclassically, in the spirit of the ZNG method (Zaremba, Nikuni and Griffin.) However, we develop a novel procedure to account for collisions between the condensate and thermal cloud which evaluates collision rates directly. We present the results of this model compared to two experiments: the atomtronic battery and transistor [arXiv:1208.3109v2]. Also presented are predictions for more complex circuit elements. This work is funded by the NSF Physics Frontier Center at JILA and by the Air Force Office of Scientific Research.
The production of neutral kaons in Z0 decays and their Bose-Einstein correlations
NASA Astrophysics Data System (ADS)
Akers, R.; Alexander, G.; Allison, J.; Ametewee, K.; Anderson, K. J.; Arcelli, S.; Asai, S.; Axen, D.; Azuelos, G.; Ball, A. H.; Barberio, E.; Barlow, R. J.; Bartoldus, R.; Batley, J. R.; Beaudoin, G.; Beck, A.; Beck, G. A.; Beeston, C.; Behnke, T.; Bell, K. W.; Bella, G.; Bentvelsen, S.; Berlich, P.; Bethke, S.; Biebel, O.; Bloodworth, I. J.; Bock, P.; Bosch, H. M.; Boutemeur, M.; Braibant, S.; Bright-Thomas, P.; Brown, R. M.; Buijs, A.; Burckhart, H. J.; Bürgin, R.; Burgard, C.; Capdevielle, N.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlesworth, C.; Charlton, D. G.; Chu, S. L.; Clarke, P. E. L.; Clayton, J. C.; Clowes, S. G.; Cohen, I.; Conboy, J. E.; Cooke, O. C.; Cuffiani, M.; Dado, S.; Dallapiccola, C.; Dallavalle, G. M.; Darling, C.; de Jong, S.; Del Pozo, L. A.; Deng, H.; Dittmar, M.; Dixit, M. S.; Do Couto E Silva, E.; Duboscq, J. E.; Duchovni, E.; Duckeck, G.; Duerdoth, I. P.; Dunwoody, U. C.; Edwards, J. E. G.; Elcombe, P. A.; Estabrooks, P. G.; Etzion, E.; Evans, H. G.; Fabbri, F.; Fabbro, B.; Fanti, M.; Fath, P.; Fierro, M.; Fincke-Keeler, M.; Fischer, H. M.; Fischer, P.; Folman, R.; Fong, D. G.; Foucher, M.; Fukui, H.; Fürtjes, A.; Gagnon, P.; Gaidot, A.; Gary, J. W.; Gascon, J.; Geddes, N. I.; Geich-Gimbel, C.; Gensler, S. W.; Gentit, F. X.; Geralis, T.; Giacomelli, G.; Giacomelli, P.; Giacomelli, R.; Gibson, V.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Gingrich, D. M.; Goodrick, M. J.; Gorn, W.; Grandi, C.; Gross, E.; Hagemann, J.; Hanson, G. G.; Hansroul, M.; Hargrove, C. K.; Hart, P. A.; Hauschild, M.; Hawkes, C. M.; Heflin, E.; Hemingway, R. J.; Herten, G.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Hilse, T.; Hobson, P. R.; Hochman, D.; Homer, R. J.; Honma, A. K.; Howard, R.; Hughes-Jones, R. E.; Igo-Kemenes, P.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Jones, M.; Jones, R. W. L.; Jovanovic, P.; Jui, C.; Karlen, D.; Kanzaki, J.; Kawagoe, K.; Kawamoto, T.; Keeler, R. K.; Kellogg, R. G.; Kennedy, B. W.; King, B.; King, J.; Kirk, J.; Kluth, S.; Kobayashi, T.; Kobel, M.; Koetke, D. S.; Kokott, T. P.; Komamiya, S.; Kowalewski, R.; Kress, T.; Krieger, P.; von Krogh, J.; Kyberd, P.; Lafferty, G. D.; Lafoux, H.; Lahmann, R.; Lai, W. P.; Lauber, J.; Layter, J. G.; Leblanc, P.; Lee, A. M.; Lefebvre, E.; Lellouch, D.; Leroy, C.; Letts, J.; Levinson, L.; Lloyd, S. L.; Loebinger, F. K.; Long, G. D.; Lorazo, B.; Losty, M. J.; Lou, X. C.; Ludwig, J.; Luig, A.; Mannelli, M.; Marcellini, S.; Markus, C.; Martin, A. J.; Martin, J. P.; Mashimo, T.; Matthews, W.; Mättig, P.; Maur, U.; McKenna, J.; McMahon, T. J.; McNab, A. I.; Meijers, F.; Merritt, F. S.; Mes, H.; Michelini, A.; Middleton, R. P.; Mikenberg, G.; Miller, D. J.; Mir, R.; Mohr, W.; Montanari, A.; Mori, T.; Morii, M.; Müller, U.; Nellen, B.; Nijjhar, B.; O'Neale, S. W.; Oakham, F. G.; Odorici, F.; Ogren, H. O.; Oldershaw, N. J.; Oram, C. J.; Oreglia, M. J.; Orito, S.; Palmonari, F.; Pansart, J. P.; Patrick, G. N.; Pearce, M. J.; Phillips, P. D.; Pilcher, J. E.; Pinfold, J.; Plane, D. E.; Poffenberger, P.; Poli, B.; Posthaus, A.; Pritchard, T. W.; Przysiezniak, H.; Redmond, M. W.; Rees, D. L.; Rigby, D.; Rison, M. G.; Robins, S. A.; Robinson, D.; Rodning, N.; Roney, J. M.; Ros, E.; Rossi, A. M.; Rosvick, M.; Routenburg, P.; Rozen, Y.; Runge, K.; Runolfsson, O.; Rust, D. R.; Sasaki, M.; Sbarra, C.; Schaile, A. D.; Schaile, O.; Scharf, F.; Scharff-Hansen, P.; Schenk, P.; Schmitt, B.; Schröder, M.; Schultz-Coulon, H. C.; Schütz, P.; Schulz, M.; Schwick, C.; Schwiening, J.; Scott, W. G.; Settles, M.; Shears, T. G.; Shen, B. C.; Shepherd-Themistocleous, C. H.; Sherwood, P.; Siroli, G. P.; Skillman, A.; Skuja, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Sobie, R.; Söldner-Rembold, S.; Springer, R. W.; Sproston, M.; Stahl, A.; Starks, M.; Stegmann, C.; Stephens, K.; Steuerer, J.; Stockhausen, B.; Strom, D.; Szymanski, P.; Tafirout, R.; Takeda, H.; Takeshita, T.; Taras, P.; Tarem, S.; Tecchio, M.; Teixeira-Dias, P.; Tesch, N.; Thomson, M. A.; Tousignant, O.; Towers, S.; Tscheulin, M.; Tsukamoto, T.; Turcot, A. S.; Turner-Watson, M. F.; Utzat, P.; van Kooten, R.; Vasseur, G.; Vikas, P.; Vincter, M.; Wagner, A.; Wagner, D. L.; Ward, C. P.; Ward, D. R.; Ward, J. J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, P.; Wells, P. S.; Wermes, N.; Wilkens, B.; Wilson, G. W.; Wilson, J. A.; Winterer, V.-H.; Wlodek, T.; Wolf, G.; Wotton, S.; Wyatt, T. R.; Yeaman, A.; Yekutieli, G.; Yurko, M.; Zacek, V.; Zeuner, W.; Zorn, G. T.
1995-09-01
The production of neutral kaons in e+e- annihilation at centre-of-mass energies in the region of the Z0 mass and their Bose-Einstein correlations are investigated with the OPAL detector at LEP. A total of about 1.26×106 Z0 hadronic decay events are used in the analysis. The production rate of K0 mesons is found to be 1.99±0.01±0.04 per hadronic event, where the first error is statistical and the second systematic. Both the rate and the differential cross section for K0 production are compared to the predictions of Monte Carlo generators. This comparison indicates that the fragmentation is too soft in both Jetset and Herwig. Bose-Einstein correlations in K{s/0}K{s/0} pairs are measured through the quantity Q, the four momentum difference of the pair. A threshold enhancement is observed in K{s/0}K{s/0} pairs originating from a mixed sample ofK^0 bar K^0 and K0K0 (bar K^0 bar K^0) pairs. For the strength of the effect and for the radius of the emitting source we find values of λ=1.14±0.23±0.32 and R 0=(0.76±0.10±0.11) fm respectively. The first error is statistical and the second systematic.
Kinetics of a bose gas in harmonic traps: nonergodic behavior
NASA Astrophysics Data System (ADS)
Geist, Wolfgang; You, Li; Kennedy, Brian
1997-11-01
The quantum Boltzmann equation describes kinetics of a degenerate quantum gas. For applications to a trapped Bose gas, it takes the following form *be1 fracdn_idt&=& sum_j,k,lδ (ɛi +ɛj -ɛk -ɛl )*g(i,j,k,l) &&(; n_k*n_l*(1+n_i)*(1+n_j)-n_i*n_j*(1+n_l)*(1+n_k)) * with ni the average number of particles in the state i of the three dimension al harmonic trap labelled by quantum numbers (i_x,i_y,i_z). The delta function ensures energy conservation and the matrix element g(i,j,k,l) is a two-body scattering matrix element which includes an overlap integral of the fou r harmonic oscillator eigenstates associated with the states i,j,k and l. Previous studies of this equation (M.Holland, J.Williams, K.Coakley, J.Cooper, Phys.Rev.A,55,3670, (1996)), (C W Gardiner and P Zoller, Phys.Rev.A(1997)) assume an ergodic approximation (degenerate energy states have equal particle numbers) in order to simplify numerical simula tions. In this study we include a limited number of low lying states without making the ergodic assumption. Interesting nonergodic effects will be reported, and comparisons between the ergodic and nonergodic kinetics will be made.
Surface Region of Superfluid Helium as an Inhomogeneous Bose-Condensed Gas
NASA Astrophysics Data System (ADS)
Griffin, A.; Stringari, S.
1996-01-01
We present arguments that the low density surface region of self-bounded superfluid 4He systems is an inhomogeneous dilute Bose gas, with almost all of the atoms occupying the same single-particle state at T = 0. Numerical evidence for this complete Bose-Einstein condensation was first given by the many-body variational calculations of 4He droplets by Lewart, Pandharipande, and Pieper in 1988 [Phys. Rev. B 37, 4950 (1988)]. We show that the low density surface region can be treated rigorously using a generalized Gross-Pitaevskii equation for the Bose order parameter.
Interacting Bose gas confined in a Kronig-Penney potential
NASA Astrophysics Data System (ADS)
Rodríguez, O. A.; Solís, M. A.
We analyze the effect of the 1D periodic Kronig-Penney potential, composed of barriers of width b and separated a distance a, over an interacting Bose gas. At T = 0 , the Gross-Pitaevskii equation is solved analytically in terms of the Jacobi elliptic functions for repulsive or attractive interaction between bosons. By applying the boundary conditions for periodic solutions as well as the normalization of the wave function, we arrive to a set of nonlinear equations from which we obtain the density profile and the chemical potential of the condensate as a function of the particle momentum. The profiles for attractive and repulsive interactions are compared with that of the non-interacting case. For attractive interaction we are able to observe a pronounced spatial localization in the middle of every two barriers. We reproduce the well known results when the Kronig-Penney potential becomes a Dirac Comb. We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.
Quantum hydrodynamics in dilute-gas Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Engels, Peter
2012-10-01
The peculiar dynamics of superfluids are a fascinating research topic. Since the first generation of a dilute gas Bose-Einstein condensate (BEC) in 1995, quantum degenerate atomic gases have taken the investigation of quantum hydrodynamics to a new level. The atomic physics toolbox has grown tremendously and now provides unique and powerful ways to explore nonlinear quantum systems. As an example, pioneering results have recently revealed that the counterflow between two superfluids can be used as a well controlled tool to access the rich dynamics of vector systems. New structures, such as beating dark-dark solitons which only exist in multicomponent systems and have never been observed before, can now be realized in the lab for the first time. Furthermore, the field of nonlinear quantum hydrodynamics is entering new regimes by exploiting Raman dressing as a tool to directly modify the dispersion relation. This leads to the generation of spin-orbit coupled BECs, artificial gauge fields, etc. that are currently receiving tremendous interest due to their parallels to complex condensed-matter systems. Studies of quantum hydrodynamics help to develop a profound understanding of nonlinear quantum dynamics, which is not only of fundamental interest but also of eminent importance for future technological applications, e.g. in telecommunication applications using optical solitons in fibers. This talk will showcase some ``classic'' hallmark results and highlight recent advances from the forefront of the field.
Vortex patterns in moderately rotating Bose-condensed gas
NASA Astrophysics Data System (ADS)
Imran, Mohd; Ahsan, M. A. H.
2017-02-01
Using exact diagonalization, we investigate the many-body ground state for regular vortex patterns in a rotating Bose-condensed gas of N spinless particles, confined in a quasi-two-dimensional harmonic trap and interacting repulsively via finite-range Gaussian potential. The N-body Hamiltonian matrix is diagonalized in given subspaces of quantized total angular momentum L z , to obtain the lowest-energy eigenstate. Further, the internal structure of these eigenstates is analyzed by calculating the corresponding conditional probability distribution. Specifically, the quantum mechanically stable as well as unstable states in a co-rotating frame are examined in the moderately rotating regime corresponding to angular momenta 4N≤slant {L}z< 5N for N = 16 bosons. In response to externally impressed rotation, the patterns of singly quantized vortices are formed, shaping into canonical polygons with a central vortex at the trap center. The internal structure of unstable states reveals the mechanism of entry, nucleation and pattern formation of vortices with structural phase transition, as the condensate goes from one stable vortical state to the other. The stable polygonal vortex patterns having discrete p-fold rotational symmetry with p = 5 and p = 6 are observed. The hexagonal vortex pattern with p = 6 symmetry is a precursor to the triangular vortex lattice of singly quantized vortices in the thermodynamic limit. For unstable states, quantum melting of vortex patterns due to uncertainty in positions of individual vortices, is also briefly discussed.
Bose-Einstein condensation in an ultra-hot gas of pumped magnons.
Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard
2014-03-11
Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.
Collective modes of a one-dimensional trapped atomic Bose gas at finite temperatures
NASA Astrophysics Data System (ADS)
Hu, Hui; Xianlong, Gao; Liu, Xia-Ji
2014-07-01
We theoretically investigate collective modes of a one-dimensional (1D) interacting Bose gas in a harmonic tras at finite temperatures, by using a variational approach and the local density approximation. We find that the temperature dependence of collective mode frequencies is notably different in the weakly and strongly interacting regimes. Therefore, the experimental measurement of collective modes could provide a sensitive probe for different quantum phases of a 1D trapped Bose gas, realized by tuning the interatomic interaction strength and temperature. Our prediction on the temperature dependence of the breathing mode frequency is in good qualitative agreement with an earlier experimental measurement for a weakly interacting 1D Bose gas of rubidium-87 atoms in harmonic traps [Moritz et al., Phys. Rev. Lett. 91, 250402 (2003), 10.1103/PhysRevLett.91.250402].
Ultrarelativistic Bose-Einstein gas on Lorentz symmetry violation
NASA Astrophysics Data System (ADS)
de Sales, J. A.; Costa-Soares, T.; Vasquez Otoya, V. J.
2012-11-01
In this paper, we study the effects of Lorentz Symmetry Breaking on the thermodynamic properties of ideal gases. Inspired by the dispersion relation coming from the Carroll-Field-Jackiw model for Electrodynamics with Lorentz and CPT violation term, we compute the thermodynamics quantities for a Boltzmann, Fermi-Dirac and Bose-Einstein distributions. Two regimes are analyzed: the large and the small Lorentz violation. In the first case, we show that the topological mass induced by the Chern-Simons term behaves as a chemical potential. For Bose-Einstein gases, a condensation in both regimes can be found.
Single-particle spectral density of a Bose gas in the two-fluid hydrodynamic regime
Arahata, Emiko; Nikuni, Tetsuro; Griffin, Allan
2011-11-15
In Bose superfluids, the single-particle Green's function can be directly related to the superfluid velocity-velocity correlation function in the hydrodynamic regime. An explicit expression for the single-particle spectral density was originally written down by Hohenberg and Martin in 1965, starting from the two-fluid equations for a superfluid. We give a simple derivation of their results. Using these results, we calculate the relative weights of first and second sound modes in the single-particle spectral density as a function of temperature in a uniform Bose gas. We show that the second sound mode makes a dominant contribution to the single-particle spectrum in a relatively high-temperature region. We also discuss the possibility of experimental observation of the second sound mode in a Bose gas by photoemission spectroscopy.
1/N-expansion for the critical temperature of the Bose gas
NASA Astrophysics Data System (ADS)
Hryhorchak, O.; Pastukhov, V.
2017-06-01
We revised the large-N expansion for a three-dimensional Bose system with short-range repulsion in normal phase. Particularly, for the model potential that is characterised only by the s-wave scattering length a the full numerical calculations of the critical temperature in the 1/N -approximation as a function of the gas parameter an1/3 are performed. Additionally to the well-known result in the dilute limit we estimated analytically the leading-order strong-coupling behavior of the Bose-Einstein condensation transition temperature. It is shown that the critical temperature shift of the non-ideal Bose gas grows at small an1/3 , reaches some maximal value and then falls down becoming negative.
Momentum-Space Correlations of a One-Dimensional Bose Gas.
Fang, Bess; Johnson, Aisling; Roscilde, Tommaso; Bouchoule, Isabelle
2016-02-05
Analyzing the noise in the momentum profiles of single realizations of one-dimensional Bose gases, we present the experimental measurement of the full momentum-space density correlations ⟨δn_{p}δn_{p^{'}}⟩, which are related to the two-body momentum correlation function. Our data span the weakly interacting region of the phase diagram, going from the ideal Bose gas regime to the quasicondensate regime. We show experimentally that the bunching phenomenon, which manifests itself as super-Poissonian local fluctuations in momentum space, is present in all regimes. The quasicondensate regime is, however, characterized by the presence of negative correlations between different momenta, in contrast to the Bogolyubov theory for Bose condensates, predicting positive correlations between opposite momenta. Our data are in good agreement with ab initio calculations.
Equation of state and contact of a strongly interacting Bose gas in the normal state
Liu, Xia -Ji; Mulkerin, Brendan; He, Lianyi; Hu, Hui
2015-04-27
Here, we theoretically investigate the equation of state and Tan's contact of a nondegenerate three-dimensional Bose gas near a broad Feshbach resonance, within the framework of large-N expansion. Our results agree with the path-integral Monte Carlo simulations in the weak-coupling limit and recover the second-order virial expansion predictions at strong interactions and high temperatures. At resonance, we find that the chemical potential and energy are significantly enhanced by the strong repulsion, while the entropy does not change significantly. With increasing temperature, the two-body contact initially increases and then decreases like T^{–1} at large temperature, and therefore exhibits a peak structure at about 4T_{c0}, where T_{c0} is the Bose-Einstein condensation temperature of an ideal, noninteracting Bose gas. These results may be experimentally examined with a nondegenerate unitary Bose gas, where the three-body recombination rate is substantially reduced. In particular, the nonmonotonic temperature dependence of the two-body contact could be inferred from the momentum distribution measurement.
Distribution of Zeros and the Equation of State. IV ---Ideal Bose-Einstein Gas---
NASA Astrophysics Data System (ADS)
Ikeda, K.
1982-09-01
The ideal Bose-Einstein gas is investigated on the basis of the fundamental concept of the distribution of zeros of the grand partition function on the complex z(= activity) plane. For this gas there are no zeros; but poles play essentially the same role as zeros from an analytical point of view, and are distributed on the part of the positive real axis from λ-3(>0) to +∞, where λ=h(2π mkT)-1/2. The distribution function of poles is calculated, and the function-theoretical structure of the equation of state is discussed. The Bose-Einstein condensation (especially the continuity of the slope of the p-v isotherm at the condensation point and the continuity of the specific heat at the transition temperature) is examined from the point of view of the distribution of poles. From the same point of view the two-dimensional and one-dimensional ideal Bose-Einstein gases are treated. Finally, the n-dimensional (n≥ 4) ideal Bose-Einstein gas is discussed, and it is shown that for n≥ 5 the specific heat is discontinuous at the transition temperature.
Equation of state and contact of a strongly interacting Bose gas in the normal state
Liu, Xia -Ji; Mulkerin, Brendan; He, Lianyi; ...
2015-04-27
Here, we theoretically investigate the equation of state and Tan's contact of a nondegenerate three-dimensional Bose gas near a broad Feshbach resonance, within the framework of large-N expansion. Our results agree with the path-integral Monte Carlo simulations in the weak-coupling limit and recover the second-order virial expansion predictions at strong interactions and high temperatures. At resonance, we find that the chemical potential and energy are significantly enhanced by the strong repulsion, while the entropy does not change significantly. With increasing temperature, the two-body contact initially increases and then decreases like T–1 at large temperature, and therefore exhibits a peak structuremore » at about 4Tc0, where Tc0 is the Bose-Einstein condensation temperature of an ideal, noninteracting Bose gas. These results may be experimentally examined with a nondegenerate unitary Bose gas, where the three-body recombination rate is substantially reduced. In particular, the nonmonotonic temperature dependence of the two-body contact could be inferred from the momentum distribution measurement.« less
Quantized vortices in the ideal bose gas: a physical realization of random polynomials.
Castin, Yvan; Hadzibabic, Zoran; Stock, Sabine; Dalibard, Jean; Stringari, Sandro
2006-02-03
We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.
Stability spectroscopy of rotons in a dipolar Bose gas
NASA Astrophysics Data System (ADS)
Corson, John P.; Wilson, Ryan M.; Bohn, John L.
2013-05-01
We study the stability of a quasi-one-dimensional dipolar Bose-Einstein condensate that is perturbed by a weak lattice potential along its axis. Our numerical simulations demonstrate that systems exhibiting a roton-maxon structure destabilize readily when the lattice wavelength equals either half the roton wavelength or a low roton subharmonic. We apply perturbation theory to the Gross-Pitaevskii and Bogoliubov-de Gennes equations to illustrate the mechanisms behind the instability threshold. The features of our stability diagram may be used as a direct measurement of the roton wavelength for quasi-one-dimensional geometries.
Stability Spectroscopy of Rotons in a Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Corson, John; Wilson, Ryan; Bohn, John
2013-05-01
We study the stability of a quasi-one-dimensional dipolar Bose-Einstein condensate that is perturbed by a weak lattice potential along its axis. Our numerical simulations demonstrate that systems exhibiting a roton-maxon structure destabilize readily when the lattice wavelength equals either half the roton wavelength or a low roton subharmonic. We apply perturbation theory to the Gross-Pitaevskii and Bogoliubov de Gennes equations to illustrate the mechanisms behind the instability threshold. The features of our stability diagram are a novel signature of roton physics, and their experimental observation would constitute a direct measurement of the roton wavelength for quasi-one-dimensional geometries.
Onset of thermalization in a 1D Bose gas
NASA Astrophysics Data System (ADS)
Riou, Jean-Felix; Reinhard, Aaron W.; Adams, Laura; Weiss, David S.
2011-05-01
There has been considerable theoretical debate about how nearly integrable many-body quantum systems approach thermal equilibrium. Experiments on one dimensional Bose gases in optical lattices may shed light on this issue. We have studied the time evolution of momentum distributions of Rb clouds initially prepared in ``quantum Newton's cradle'' states [T. Kinoshita, T. Wenger and David S. Weiss, ``A quantum Newton's Cradle,'' Nature 440, 900 (2006)]. The measured evolution rates are found to depend on density and lattice depth. In order to isolate the part of the approach to equilibrium due to atom-atom interactions, it has been necessary to quantify, experimentally and theoretically, the contributions of various heating and loss processes to these rates.
Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms
NASA Astrophysics Data System (ADS)
Turlapov, A. V.; Kagan, M. Yu
2017-09-01
The physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: on one hand, neither long-range order nor Bose condensation may appear in infinite uniform 2D systems at finite temperature, on the other hand this does not prohibit superfluidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with the highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Unique from other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated, as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.
Non-equilibrium dynamics of an impurity in the one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Robinson, Neil; Konik, Robert
2015-03-01
In recent years, the out-of-equilibrium dynamics of interacting many-body quantum systems have attracted much attention. Integrable quantum models have played an important role in understanding the role of local conservation laws in the relaxation of observables, explaining unusual experimental observations in the one-component Bose gas. We study the non-equilibrium dynamics of ``impurity'' wave packets containing a single boson propagating in the one-component Bose gas. Utilizing the integrability of the multi-component Lieb-Liniger model and recent results from the algebraic Bethe ansatz, we compute the time-evolution of the density profile of the ``impurity'' in the cases where the bosons is of the same or different species as the background gas. Our method, based upon numerically solving the Bethe ansatz equations and evaluating the Lehmann spectral representation for local observables, allows us to reach long times with high numerical precision. By comparing results from the two-component Lieb-Liniger model to the one-component Bose gas we can comment on the role of distinguishability in the dynamics of impurities in integrable models.
Measuring the Edwards-Anderson order parameter of the Bose glass: A quantum gas microscope approach
NASA Astrophysics Data System (ADS)
Thomson, S. J.; Walker, L. S.; Harte, T. L.; Bruce, G. D.
2016-11-01
With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system, and use it to simulate the density distributions seen in single-shot fluorescence microscopy. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments which will allow further properties of the Bose glass to be measured.
Ohashi, Y.; Kitaura, M.; Matsumoto, H.
2006-03-15
We investigate a strongly correlated Bose gas in an optical lattice. Extending the standard-basis operator method developed by Haley and Erdoes to a boson Hubbard model, we calculate excitation spectra in the superfluid phase, as well as in the Mott insulating phase, at T=0. In the Mott phase, the excitation spectrum has a finite energy gap, reflecting the localized character of atoms. In the superfluid phase, the excitation spectrum is shown to have an itinerant-localized dual structure, where the gapless Bogoliubov mode (which describes the itinerant character of superfluid atoms) and a band with a finite energy gap coexist. We also show that the rf-tunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluid-insulator transition.
Dynamical density-density correlations in the one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Caux, Jean-Sébastien; Calabrese, Pasquale
2006-09-01
The zero-temperature dynamical structure factor of the one-dimensional Bose gas with delta-function interaction (Lieb-Liniger model) is computed as a function of momentum and frequency using a hybrid theoretical/numerical method based on the exact Bethe-ansatz solution. This allows one to interpolate continuously between the weakly coupled Thomas-Fermi and strongly coupled Tonks-Girardeau regimes. The results should be experimentally accessible with Bragg spectroscopy.
Quantum and thermal fluctuations in a Raman spin-orbit-coupled Bose gas
NASA Astrophysics Data System (ADS)
Chen, Xiao-Long; Liu, Xia-Ji; Hu, Hui
2017-07-01
We theoretically study a three-dimensional weakly interacting Bose gas with Raman-induced spin-orbit coupling at finite temperature. By employing a generalized Hartree-Fock-Bogoliubov theory with Popov approximation, we determine a complete finite-temperature phase diagram of three exotic condensation phases (i.e., the stripe, plane-wave, and zero-momentum phases), against both quantum and thermal fluctuations. We find that the plane-wave phase is significantly broadened by thermal fluctuations. The phonon mode and sound velocity at the transition from the plane-wave phase to the zero-momentum phase are thoughtfully analyzed. At zero temperature, we find that quantum fluctuations open an unexpected gap in sound velocity at the phase transition, in stark contrast to the previous theoretical prediction of a vanishing sound velocity. At finite temperature, thermal fluctuations continue to significantly enlarge the gap, and simultaneously shift the critical minimum. For a Bose gas of 87Rb atoms at the typical experimental temperature, T =0.3 T0 , where T0 is the critical temperature of an ideal Bose gas without spin-orbit coupling, our results of gap opening and critical minimum shifting in the sound velocity are qualitatively consistent with the recent experimental observation [Ji et al., Phys. Rev. Lett. 114, 105301 (2015), 10.1103/PhysRevLett.114.105301].
Laboratory simulation of cometary neutral gas ionization
NASA Technical Reports Server (NTRS)
Chang, Tsuey-Fen; Rahman, H. U.; White, R. S.
1989-01-01
The laboratory simulation of the interaction of the solar wind with a comet is used to study the cometary neural gas ionization. The experiment is carried out in the UCR T-1 facility with an ice ball as the comet model. Photographs and data are taken with a variety of values of the solar wind velocity, interplanetary magnetic field (IMF), and comet configurations. The results show that the cometary neutral gas ionization depends on both the velocity of the solar wind and the interplanetary magnetic field. The plasma cloud surrounding the comet is visible only when the solar wind velocity and IMF are both above certain minimum values. This velocity dependent phenomena is explained by Alfven's critical ionization velocity effect. The critical magnetic field may be explained by assuming two stream lower hybrid instability as a triggering mechanism for the ionization of the neutral gas by plasma flow. Critical upper and lower limits for the magnetic field, required by anomalous ionization, are also derived that satisfy the experimental observations.
Experiments on a one-dimensional Bose gas: Thomas Fermi to Tonks-Girardeau
NASA Astrophysics Data System (ADS)
Wenger, Trevor
A set of experiments was performed on a one-dimensional Bose gas system. A 3D Bose-Einstein condensate of 87Rb atoms was formed in an all-optical trap. The BEC was then loaded into a 2D optical lattice that consists of an array of parallel 1D tubes. Measurements of the energy, cloud size, and local pair correlation function probe the properties of the gas from the weak coupling to strong coupling (Tonks-Girardeau) limit. The characteristic property of fermionization of the wave functions was observed in the TG limit. Another experiment was done to probe the nature on non-equilibrium 1D Bose gases. This integrable system, when placed in a non-equilibrium momentum distribution, was found not to thermalize on the time scale of our experiment (hundreds of trap oscillations or thousands of collisions). This is in stark contrast to the 3D case, which thermalizes on the order of 3 trap oscillations.
Isobars of an ideal Bose gas within the grand canonical ensemble
Jeon, Imtak; Park, Jeong-Hyuck; Kim, Sang-Woo
2011-08-15
We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an N{sup -1/3} or N{sup -1/4} power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N{>=}14 393. In particular, for the Avogadro's number of particles, the volume expands discretely about 10{sup 5} times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.
Isobars of an ideal Bose gas within the grand canonical ensemble
NASA Astrophysics Data System (ADS)
Jeon, Imtak; Kim, Sang-Woo; Park, Jeong-Hyuck
2011-08-01
We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an N-1/3 or N-1/4 power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N≥14393. In particular, for the Avogadro’s number of particles, the volume expands discretely about 105 times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.
Optimum criteria of an irreversible quantum Brayton refrigeration cycle with an ideal Bose gas
NASA Astrophysics Data System (ADS)
Wang, Hao; Liu, Sanqiu; He, Jizhou
2008-11-01
An irreversible cycle model of the quantum Brayton refrigeration cycle is established, in which finite-time processes and irreversibility in the two adiabatic processes are taken into account. On the basis of the thermodynamic properties of an ideal Bose gas, by using the optimal control-theory, the mathematical expressions for several important performance parameters, such as the coefficient of performance, power input and cooling load, are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of a Bose-Brayton refrigeration cycle are obtained and analyzed. Furthermore, some optimal operating regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail.
Correlation dynamics during a slow interaction quench in a one-dimensional Bose gas.
Bernier, Jean-Sébastien; Citro, Roberta; Kollath, Corinna; Orignac, Edmond
2014-02-14
We investigate the response of a one-dimensional Bose gas to a slow increase of its interaction strength. We focus on the rich dynamics of equal-time single-particle correlations treating the Lieb-Liniger model within a bosonization approach and the Bose-Hubbard model using the time-dependent density-matrix renormalization group method. For short distances, correlations follow a power law with distance with an exponent given by the adiabatic approximation. In contrast, for long distances, correlations decay algebraically with an exponent understood within the sudden quench approximation. This long distance regime is separated from an intermediate distance one by a generalized Lieb-Robinson criterion. At long times, in this intermediate regime, bosonization predicts that single-particle correlations decay following a stretched exponential, an unconventional behavior. We develop here an intuitive understanding for the propagation of correlations, in terms of a generalized light cone, applicable to a large variety of systems and quench forms.
Spontaneously Broken Gauge Symmetry in a Bose Gas with Constant Particle Number
NASA Astrophysics Data System (ADS)
Schelle, A.
The interplay between spontaneously broken gauge symmetries and Bose-Einstein condensation has long been controversially discussed in science, since the equations of motion are invariant under phase transformations. Within the present model, it is illustrated that spontaneous symmetry breaking appears as a non-local process in position space, but within disjoint subspaces of the underlying Hilbert space. Numerical simulations show that it is the symmetry of the relative phase distribution between condensate and non-condensate quantum fields which is spontaneously broken when passing the critical temperature for Bose-Einstein condensation. Since the total number of gas particles remains constant over time, the global U(1)-gauge symmetry of the system is preserved.
Critical temperature of a Rashba spin-orbit-coupled Bose gas in a harmonic trap
NASA Astrophysics Data System (ADS)
Hu, Hui; Liu, Xia-Ji
2012-01-01
We investigate theoretically Bose-Einstein condensation of an ideal, trapped Bose gas in the presence of Rashba spin-orbit coupling. Analytic results for the critical temperature and condensate fraction are derived based on a semiclassical approximation to the single-particle-energy spectrum and density of states and are compared with exact results obtained by explicitly summing discrete energy levels for a small number of particles. We find a significant decrease of the critical temperature and of the condensate fraction due to finite spin-orbit coupling. For a large coupling strength and a finite number of particles N, the critical temperature scales as N2/5 and N2/3 in three and two dimensions, respectively, contrasted to the predictions of N1/3 and N1/2 in the absence of spin-orbit coupling. Finite-size corrections in three dimensions are also discussed.
Coherence-enhanced imaging of a degenerate Bose-Einstein gas.
Sadler, L E; Higbie, J M; Leslie, S R; Vengalattore, M; Stamper-Kurn, D M
2007-03-16
We present coherence-enhanced imaging, an in situ technique that uses Raman superradiance to probe the spatial coherence of an ultracold gas. Applying this technique, we identify the coherent portion of an inhomogeneous degenerate (87)Rb gas and obtain a spatially resolved measurement of the first-order spatial correlation function. We find that the decay of spin gratings is enhanced in high density regions of a Bose-Einstein condensate, and ascribe the enhancement to collective atom-atom scattering. Further, we directly observe spatial inhomogeneities that arise generally in the course of extended-sample superradiance.
Probing the Quantum State of a 1D Bose Gas Using Off-Resonant Light Scattering
Sykes, A. G.; Ballagh, R. J.
2011-12-30
We present a theoretical treatment of coherent light scattering from an interacting 1D Bose gas at finite temperatures. We show how this can provide a nondestructive measurement of the atomic system states. The equilibrium states are determined by the temperature and interaction strength, and are characterized by the spatial density-density correlation function. We show how this correlation function is encoded in the angular distribution of the fluctuations of the scattered light intensity, thus providing a sensitive, quantitative probe of the density-density correlation function and therefore the quantum state of the gas.
Ground state and excitations of a Bose gas: From a harmonic trap to a double well
Japha, Y.; Band, Y. B.
2011-09-15
We determine the low-energy properties of a trapped Bose gas split in two by a potential barrier over the whole range of barrier heights and asymmetry between the wells. For either weak or strong coupling between the wells, our two-mode theory yields a two-site Bose-Hubbard Hamiltonian with the tunneling, interaction, and bias parameters calculated simply using an explicit form of two mode functions. When the potential barrier is relatively low, most of the particles occupy the condensate mode and our theory reduces to a two-mode version of the Bogoliubov theory, which gives a satisfactory estimate of the spatial shape and energy of the lowest collective excitation. When the barrier is high, our theory generalizes the standard two-site Bose-Hubbard model into the case of asymmetric modes, and correctly predicts a full separation of the modes in the limit of strong separation of the wells. We provide explicit analytic forms for the number squeezing and coherence as a function of particle number and temperature. We compare our theory to other two-mode theories for bosons in a double well and discuss their validity in different parameter regimes.
Entanglement pre-thermalization in a one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Kaminishi, Eriko; Mori, Takashi; Ikeda, Tatsuhiko N.; Ueda, Masahito
2015-12-01
An isolated quantum system often shows relaxation to a quasi-stationary state before reaching thermal equilibrium. Such a pre-thermalized state was observed in recent experiments in a one-dimensional Bose gas after it had been coherently split into two. Although the existence of local conserved quantities is usually considered to be the key ingredient of pre-thermalization, the question of whether non-local correlations between the subsystems can influence pre-thermalization of the entire system has remained unanswered. Here we study the dynamics of coherently split one-dimensional Bose gases and find that the initial entanglement combined with energy degeneracy due to parity and translation invariance strongly affects the long-term behaviour of the system. The mechanism of this entanglement pre-thermalization is quite general and not restricted to one-dimensional Bose gases. In view of recent experiments with a small and well-defined number of ultracold atoms, our predictions based on exact few-body calculations could be tested in experiments.
NASA Astrophysics Data System (ADS)
Shimada, Masashi; Tynan, George R.; Cattolica, Robert
2007-02-01
The spatial distribution of neutral gas temperature and total pressure have been measured for pure N2, He/5%N2 and Ar/5%N2 in an inductively coupled plasma (ICP) reactor, and a significant rise in the neutral gas temperature has been observed. When thermal transpiration is used to correct total pressure measurements, the total pressure remains constant regardless of the plasma condition. Neutral pressure is depleted due to the pressure balance when the plasma pressure (mainly electron pressure) becomes comparable to the neutral pressure in high density plasma. Since the neutral gas follows the ideal gas law, the neutral gas density profile was obtained from the neutral gas temperature and the corrected neutral pressure measurements. The results show that the neutral gas density at the centre of the plasma chamber (factor of 2-4 ×) decreases significantly in the presence of a plasma discharge. Significant spatial variation in neutral gas uniformity occurs in such plasmas due to neutral gas heating and pressure balance.
Neutral gas measurements of comet Halley from Vega 1
NASA Technical Reports Server (NTRS)
Keppler, E.; Afonin, V. V.; Dyachkov, A. V.; Curtis, C. C.; Ero, J., Jr.
1986-01-01
The neutral gas experiment (ING) aboard the Vega 1 spacecraft detected cometary gas within a distance of 60,000 km from the nucleus of comet Halley. A preliminary inspection of the data permits an analysis of the variation in neutral gas density. Fine structure was detected in the spatial disribution of lower-mass species.
Stepwise Bose-Einstein Condensation in a Spinor Gas
NASA Astrophysics Data System (ADS)
Frapolli, C.; Zibold, T.; Invernizzi, A.; Jiménez-García, K.; Dalibard, J.; Gerbier, F.
2017-08-01
We observe multistep condensation of sodium atoms with spin F =1 , where the different Zeeman components mF=0 ,±1 condense sequentially as the temperature decreases. The precise sequence changes drastically depending on the magnetization mz and on the quadratic Zeeman energy q (QZE) in an applied magnetic field. For large QZE, the overall structure of the phase diagram is the same as for an ideal spin-1 gas, although the precise locations of the phase boundaries are significantly shifted by interactions. For small QZE, antiferromagnetic interactions qualitatively change the phase diagram with respect to the ideal case, leading, for instance, to condensation in mF=±1 , a phenomenon that cannot occur for an ideal gas with q >0 .
Stepwise Bose-Einstein Condensation in a Spinor Gas.
Frapolli, C; Zibold, T; Invernizzi, A; Jiménez-García, K; Dalibard, J; Gerbier, F
2017-08-04
We observe multistep condensation of sodium atoms with spin F=1, where the different Zeeman components m_{F}=0,±1 condense sequentially as the temperature decreases. The precise sequence changes drastically depending on the magnetization m_{z} and on the quadratic Zeeman energy q (QZE) in an applied magnetic field. For large QZE, the overall structure of the phase diagram is the same as for an ideal spin-1 gas, although the precise locations of the phase boundaries are significantly shifted by interactions. For small QZE, antiferromagnetic interactions qualitatively change the phase diagram with respect to the ideal case, leading, for instance, to condensation in m_{F}=±1, a phenomenon that cannot occur for an ideal gas with q>0.
Photon recoil momentum in a Bose-Einstein condensate of a dilute gas
NASA Astrophysics Data System (ADS)
Avetisyan, Yu A.; Malyshev, V. A.; Trifonov, E. D.
2017-04-01
We develop a ‘minimal’ microscopic model to describe a two-pulse-Ramsey-interferometer-based scheme of measurement of the photon recoil momentum in a Bose-Einstein condensate of a dilute gas (Campbell et al 2005 Phys. Rev. Lett. 94 170403). We exploit the truncated coupled Maxwell-Schrödinger equations to elaborate the problem. Our approach provides a theoretical tool to reproduce essential features of the experimental results. Additionally, we calculate the quantum-mechanical mean value of the recoil momentum and its statistical distribution that provides a detailed information about the recoil event.
Cooperative scattering measurement of coherence in a spatially modulated Bose gas
Lu Bo; Vogt, Thibault; Liu Xinxing; Xu Xu; Zhou Xiaoji; Chen Xuzong
2011-05-15
Correlations of a Bose gas released from an optical lattice are measured using superradiant scattering. Conditions are chosen so that, after initial incident light pumping at the Bragg angle for diffraction, superradiant scattering into the Bragg diffracted mode is preponderant due to matter-wave amplification and mode competition. A temporal analysis of the superradiant scattering gain reveals periodical oscillations and damping due to the initial lack of coherence between lattice sites. Such damping is used for characterizing first-order spatial correlations in our system with a precision of one lattice period.
Two- and three-body contacts in the unitary Bose gas
NASA Astrophysics Data System (ADS)
Fletcher, Richard J.; Lopes, Raphael; Man, Jay; Navon, Nir; Smith, Robert P.; Zwierlein, Martin W.; Hadzibabic, Zoran
2017-01-01
In many-body systems governed by pairwise contact interactions, a wide range of observables is linked by a single parameter, the two-body contact, which quantifies two-particle correlations. This profound insight has transformed our understanding of strongly interacting Fermi gases. Using Ramsey interferometry, we studied coherent evolution of the resonantly interacting Bose gas, and we show here that it cannot be explained by only pairwise correlations. Our experiments reveal the crucial role of three-body correlations arising from Efimov physics and provide a direct measurement of the associated three-body contact.
Coherence properties of a two-dimensional trapped Bose gas around the superfluid transition
Plisson, T.; Allard, B.; Salomon, G.; Aspect, A.; Bourdel, T.; Holzmann, M.; Bouyer, P.
2011-12-15
We measure the momentum distribution of a two-dimensional trapped Bose gas and observe the increase of the range of coherence around the Berezinskii-Kosterlitz-Thouless (BKT) transition. We quantitatively compare our observed profiles to both a Hartree-Fock mean-field theory and quantum Monte Carlo simulations. In the normal phase, the momentum distribution is observed to sharpen well before the phase transition. This behavior is partially captured in a mean-field approach, in contrast to the physics of the BKT transition.
Momentum-Resolved Observation of Thermal and Quantum Depletion in a Bose Gas
NASA Astrophysics Data System (ADS)
Chang, R.; Bouton, Q.; Cayla, H.; Qu, C.; Aspect, A.; Westbrook, C. I.; Clément, D.
2016-12-01
We report on the single-atom-resolved measurement of the distribution of momenta ℏk in a weakly interacting Bose gas after a 330 ms time of flight. We investigate it for various temperatures and clearly separate two contributions to the depletion of the condensate by their k dependence. The first one is the thermal depletion. The second contribution falls off as k-4, and its magnitude increases with the in-trap condensate density as predicted by the Bogoliubov theory at zero temperature. These observations suggest associating it with the quantum depletion. How this contribution can survive the expansion of the released interacting condensate is an intriguing open question.
Non-equilibrium scale invariance and shortcuts to adiabaticity in a one-dimensional Bose gas
Rohringer, W.; Fischer, D.; Steiner, F.; Mazets, I. E.; Schmiedmayer, J.; Trupke, M.
2015-01-01
We present experimental evidence for scale invariant behaviour of the excitation spectrum in phase-fluctuating quasi-1d Bose gases after a rapid change of the external trapping potential. Probing density correlations in free expansion, we find that the temperature of an initial thermal state scales with the spatial extension of the cloud as predicted by a model based on adiabatic rescaling of initial eigenmodes with conserved quasiparticle occupation numbers. Based on this result, we demonstrate that shortcuts to adiabaticity for the rapid expansion or compression of the gas do not induce additional heating. PMID:25867640
NASA Astrophysics Data System (ADS)
Arahata, E.; Nikuni, T.
2013-05-01
We study sound propagation in a Bose-condensed gas confined in a highly elongated harmonic trap at finite temperatures. Our analysis is based on Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of Gross-Pitaevskii equation for the condensate and the kinetic equation for a thermal cloud. We extend ZNG formalism to deal with a highly-anisotropic trap potential, and use it to simulate sound propagation in the two fluid hydrodynamic regime. We use the trap parameters for the experiment that has reported second sound propagation. Our simulation results show that propagation of two sound pulses corresponding to first and second sound can be observed in an intermediate temperature.
Nonuniversal Equation of State of the Two-Dimensional Bose Gas.
Salasnich, L
2017-03-31
For a dilute two-dimensional Bose gas the universal equation of state has a logarithmic dependence on the s-wave scattering length. Here we derive nonuniversal corrections to this equation of state, taking account of finite-range effects of the interatomic potential. Our beyond-mean-field analytical results are obtained performing dimensional regularization of divergent zero-point quantum fluctuations within the finite-temperature formalism of functional integration. In particular, we find that in the grand canonical ensemble the pressure has a nonpolynomial dependence on the finite- range parameter and it is a highly nontrivial function of chemical potential and temperature.
Finite Size Effect on the Specific Heat of a Bose Gas in Multi-filament Cables
NASA Astrophysics Data System (ADS)
Guijarro, G.; Solís, M. A.
2016-05-01
The specific heat for an ideal Bose gas confined in semi-infinite multi-filament cables is analyzed. We start with a Bose gas inside a semi-infinite tube of impenetrable walls and finite rectangular cross section. The internal filament structure is created by applying to the gas two, mutually perpendicular, finite Kronig-Penney delta potentials along the tube cross section, while particles are free to move perpendicular to the cross section. The energy spectrum accessible to the particles is obtained and introduced into the grand potential to calculate the specific heat of the system as a function of temperature for different values of the periodic structure parameters such as the cross-section area, the wall impenetrability, and the number of filaments. The specific heat as a function of temperature shows at least two maxima and one minimum. The main difference with respect to the infinite case is that the peak associated with the BE condensation becomes a smoothed maximum, namely there is not a jump in the specific heat derivative, whose temperature no longer represents a critical point.
Thermodynamic behavior of a one-dimensional Bose gas at low temperature
NASA Astrophysics Data System (ADS)
De Rosi, Giulia; Astrakharchik, Grigori E.; Stringari, Sandro
2017-07-01
We show that the chemical potential of a one-dimensional (1D) interacting Bose gas exhibits a nonmonotonic temperature dependence which is peculiar of superfluids. The effect is a direct consequence of the phononic nature of the excitation spectrum at large wavelengths exhibited by 1D Bose gases. For low temperatures T , we demonstrate that the coefficient in T2 expansion of the chemical potential is entirely defined by the zero-temperature density dependence of the sound velocity. We calculate that coefficient along the crossover between the Bogoliubov weakly interacting gas and the Tonks-Girardeau gas of impenetrable bosons. Analytic expansions are provided in the asymptotic regimes. The theoretical predictions along the crossover are confirmed by comparison with the exactly solvable Yang-Yang model in which the finite-temperature equation of state is obtained numerically by solving Bethe-ansatz equations. A 1D ring geometry is equivalent to imposing periodic boundary conditions and arising finite-size effects are studied in detail. At T =0 we calculated various thermodynamic functions, including the inelastic structure factor, as a function of the number of atoms, pointing out the occurrence of important deviations from the thermodynamic limit.
Level density of a bose gas and extreme value statistics.
Comtet, A; Leboeuf, P; Majumdar, Satya N
2007-02-16
We establish a connection between the level density of a gas of noninteracting bosons and the theory of extreme value statistics. Depending on the exponent that characterizes the growth of the underlying single-particle spectrum, we show that at a given excitation energy the limiting distribution function for the number of excited particles follows the three universal distribution laws of extreme value statistics, namely, the Gumbel, Weibull, and Fréchet distributions. Implications of this result, as well as general properties of the level density at different energies, are discussed.
Strong correlation effects in a two-dimensional Bose gas with quartic dispersion
NASA Astrophysics Data System (ADS)
Radić, Juraj; Natu, Stefan S.; Galitski, Victor
2015-06-01
Motivated by the fundamental question of the fate of interacting bosons in flat bands, we consider a two-dimensional Bose gas at zero temperature with an underlying quartic single-particle dispersion in one spatial direction. This type of band structure can be realized using the NIST scheme of spin-orbit coupling [Y.-J. Lin, K. Jiménez-Garcia, and I. B. Spielman, Nature (London) 471, 83 (2011), 10.1038/nature09887], in the regime where the lower-band dispersion has the form ɛk˜kx4/4 +ky2+... , or using the shaken lattice scheme of Parker et al. [C. V. Parker, L.-C. Ha, and C. Chin, Nat. Phys. 9, 769 (2013), 10.1038/nphys2789]. We numerically compare the ground-state energies of the mean-field Bose-Einstein condensate (BEC) and various trial wave functions, where bosons avoid each other at short distances. We discover that, at low densities, several types of strongly correlated states have an energy per particle (ɛ ), which scales with density (n ) as ɛ ˜n4 /3 , in contrast to ɛ ˜n for the weakly interacting Bose gas. These competing states include a Wigner crystal, quasicondensates described in terms of properly symmetrized fermionic states, and variational wave functions of Jastrow type. We find that one of the latter has the lowest energy among the states we consider. This Jastrow-type state has a strongly reduced, but finite, condensate fraction, and true off-diagonal long-range order, which suggests that the ground state of interacting bosons with quartic dispersion is a strongly correlated condensate reminiscent of superfluid helium-4. Our results show that even for weakly interacting bosons in higher dimensions, one can explore the crossover from a weakly coupled BEC to a strongly correlated condensate by simply tuning the single-particle dispersion or density.
Quantum Joule-Thomson effect in a saturated homogeneous Bose gas.
Schmidutz, Tobias F; Gotlibovych, Igor; Gaunt, Alexander L; Smith, Robert P; Navon, Nir; Hadzibabic, Zoran
2014-01-31
We study the thermodynamics of Bose-Einstein condensation in a weakly interacting quasihomogeneous atomic gas, prepared in an optical-box trap. We characterize the critical point for condensation and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. Finally, we observe the quantum Joule-Thomson effect, namely isoenthalpic cooling of an (essentially) ideal gas. In our experiments this cooling occurs spontaneously, due to energy-independent collisions with the background gas in the vacuum chamber. We extract a Joule-Thomson coefficient μJT>10(9) K/bar, about 10 orders of magnitude larger than observed in classical gases.
Quantum Joule-Thomson Effect in a Saturated Homogeneous Bose Gas
NASA Astrophysics Data System (ADS)
Schmidutz, Tobias F.; Gotlibovych, Igor; Gaunt, Alexander L.; Smith, Robert P.; Navon, Nir; Hadzibabic, Zoran
2014-01-01
We study the thermodynamics of Bose-Einstein condensation in a weakly interacting quasihomogeneous atomic gas, prepared in an optical-box trap. We characterize the critical point for condensation and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. Finally, we observe the quantum Joule-Thomson effect, namely isoenthalpic cooling of an (essentially) ideal gas. In our experiments this cooling occurs spontaneously, due to energy-independent collisions with the background gas in the vacuum chamber. We extract a Joule-Thomson coefficient μJT>109 K /bar, about 10 orders of magnitude larger than observed in classical gases.
NASA Astrophysics Data System (ADS)
Boudjemâa, Abdelâali; Guebli, Nadia
2017-10-01
Using the time-dependent Hartree–Fock–Bogoliubov approach, where the condensate is coupled with the thermal cloud and the anomalous density, we study the equilibrium and the dynamical properties of three-dimensional quantum-degenerate Bose gas at finite temperature. Effects of the anomalous correlations on the condensed fraction and the critical temperature are discussed. In uniform Bose gas, useful expressions for the Bogoliubov excitations spectrum, the first and second sound, the condensate depletion and the superfluid fraction are derived. Our results are tested by comparing the findings computed by quantum Monte Carlo simulations. We present also a systematic investigation of the collective modes of a Bose condensate confined in an external trap. Our predictions are in qualitative agreement with previous experimental and theoretical results. We show in particular that our theory is capable of explaining the so-called anomalous behavior of the m=0 mode.
Generation and exploration of the Spin-Orbit coupled Bose gas
NASA Astrophysics Data System (ADS)
Pan, Jian-Wei
2013-03-01
To generate an artificial gauge field with ultracold quantum gas becomes a very hot topic in last few years and will continue to be attractive for ultracold atomic and condensed matter physics in the coming future. Many interesting and important topics such as Fractional Quantum Hall effect, Spin-orbit coupling and Topological insulator are connected to this topic very closely. Here we present our recent experimental progress of the synthesized gauge potential and the spin-orbit coupled Bose-Einstein condensate (BEC) in optical dipole trap. Raman coupling technique and a bias magnetic field is applied to tune the structure of the gauge potential and spin-orbit coupling. Several fundamental properties of spin-orbit coupled BEC is experimentally studied including the properties of collective dipole oscillation, the stability of excited dressed state, the critical temperature of spin-orbit coupled Bose gas and the formation of magnetic order during evaporative cooling. These studies enrich the knowledge of this field and further explorations are also in planning.
Nondissipative drag of superflow in a two-component Bose gas
Fil, D.V.; Shevchenko, S.I.
2005-07-15
A microscopic theory of a nondissipative drag in a two-component superfluid Bose gas is developed. The expression for the drag current in the system with the components of different atomic masses, densities, and scattering lengths is derived. It is shown that the drag current is proportional to the square root of the gas parameter. The temperature dependence of the drag current is studied and it is shown that at temperature of order or smaller than the interaction energy the temperature reduction of the drag current is rather small. A possible way of measuring the drag factor is proposed. A toroidal system with the drag component confined in two half-ring wells separated by two Josephson barriers is considered. Under certain condition such a system can be treated as a Bose-Einstein counterpart of the Josephson charge qubit in an external magnetic field. It is shown that the measurement of the difference of number of atoms in two wells under a controlled evolution of the state of the qubit allows one to determine the drag factor.
Stoner ferromagnetism in a thermal pseudospin-1/2 Bose gas.
Radić, Juraj; Natu, Stefan S; Galitski, Victor
2014-10-31
We compute the finite-temperature phase diagram of a pseudospin-1/2 Bose gas with contact interactions, using two complementary methods: the random-phase approximation and self-consistent Hartree-Fock theory. We show that the spin-dependent interactions, which break the (pseudo-) spin-rotational symmetry of the Hamiltonian, generally lead to the appearance of a magnetically ordered phase at temperatures above the superfluid transition. In three dimensions, we predict a normal easy-axis (easy-plane) ferromagnet for sufficiently strong repulsive (attractive) interspecies interactions, respectively. The normal easy-axis ferromagnet is the bosonic analog of Stoner ferromagnetism known in electronic systems. For the case of interspecies attraction, we also discuss the possibility of a bosonic analog of the Cooper-paired phase. This state is shown to significantly lose in energy to the transverse ferromagnet in three dimensions, but is more energetically competitive in lower dimensions. Extending our calculations to a spin-orbit-coupled Bose gas with equal Rashba and Dresselhaus-type couplings (as recently realized in experiment), we investigate the possibility of stripe ordering in the normal phase. Within our approximations, however, we do not find an instability towards stripe formation, suggesting that the stripe order melts below the condensation temperature, which is consistent with the experimental observations of Ji et al. [Ji et al., Nat. Phys. 10, 314 (2014)].
Quantum sine-Gordon dynamics on analogue curved spacetime in a weakly imperfect scalar Bose gas
NASA Astrophysics Data System (ADS)
Volkoff, T. J.; Fischer, Uwe R.
2016-07-01
Using the coherent state functional integral expression of the partition function, we show that the sine-Gordon model on an analogue curved spacetime arises as the effective quantum field theory for phase fluctuations of a weakly imperfect Bose gas on an incompressible background superfluid flow when these fluctuations are restricted to a subspace of the single-particle Hilbert space. We consider bipartitions of the single-particle Hilbert space relevant to experiments on ultracold bosonic atomic or molecular gases, including, e.g., restriction to high- or low-energy sectors of the dynamics and spatial bipartition corresponding to tunnel-coupled planar Bose gases. By assuming full unitary quantum control in the low-energy subspace of a trapped gas, we show that (1) appropriately tuning the particle number statistics of the lowest-energy mode partially decouples the low- and high-energy sectors, allowing any low-energy single-particle wave function to define a background for sine-Gordon dynamics on curved spacetime and (2) macroscopic occupation of a quantum superposition of two states of the lowest two modes produces an analogue curved spacetime depending on two background flows, with respective weights continuously dependent on the corresponding weights of the superposed quantum states.
Bose-Einstein Condensation in a Dilute Gas; the First 70 Years and Some Recent Experiments
NASA Astrophysics Data System (ADS)
Cornell, E. A.; Wieman, C. E.
Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of ``How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why?'' We will review some of our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging.
Lorentz-violating effects in the Bose-Einstein condensation of an ideal bosonic gas
NASA Astrophysics Data System (ADS)
Casana, Rodolfo; da Silva, Kleber A. T.
2015-03-01
We have studied the effects of Lorentz-violation in the Bose-Einstein condensation (BEC) of an ideal boson gas, by assessing both the nonrelativistic and ultrarelativistic limits. Our model describes a massive complex scalar field coupled to a CPT-even and Lorentz-violating background. We first analyze the nonrelativistic case, at this level by using experimental data, we obtain upper-bounds for some LIV parameters. In the sequel, we have constructed the partition function for the relativistic ideal boson gas which to be able of a consistent description requires the imposition of severe restrictions on some LIV coefficients. In both cases, we have demonstrated that the LIV contributions are contained in an overall factor, which multiplies almost all thermodynamical properties. An exception is the fraction of the condensed particles.
Hydrodynamic versus collisionless dynamics of a one-dimensional harmonically trapped Bose gas
NASA Astrophysics Data System (ADS)
De Rosi, Giulia; Stringari, Sandro
2016-12-01
By using a sum-rule approach we investigate the transition between the hydrodynamic and the collisionless regime of the collective modes in a one-dimensional (1D) harmonically trapped Bose gas. Both the weakly interacting gas and the Tonks-Girardeau limits are considered. We predict that the excitation of the dipole compression mode is characterized in the high-temperature collisionless regime by a beating signal of two different frequencies (ωz and 3 ωz ), while in the high-temperature collisional regime, the excitation consists of a single frequency (√{7 }ωz ). This behavior differs from the case of the lowest breathing mode whose excitation consists of a single frequency (2 ωz ) in both regimes. Our predictions for the dipole compression mode open promising perspectives for the experimental investigation of collisional effects in 1D configurations.
Critical behavior of the ideal-gas Bose-Einstein condensation in the Apollonian network.
de Oliveira, I N; dos Santos, T B; de Moura, F A B F; Lyra, M L; Serva, M
2013-08-01
We show that the ideal Boson gas displays a finite-temperature Bose-Einstein condensation transition in the complex Apollonian network exhibiting scale-free, small-world, and hierarchical properties. The single-particle tight-binding Hamiltonian with properly rescaled hopping amplitudes has a fractal-like energy spectrum. The energy spectrum is analytically demonstrated to be generated by a nonlinear mapping transformation. A finite-size scaling analysis over several orders of magnitudes of network sizes is shown to provide precise estimates for the exponents characterizing the condensed fraction, correlation size, and specific heat. The critical exponents, as well as the power-law behavior of the density of states at the bottom of the band, are similar to those of the ideal Boson gas in lattices with spectral dimension d(s)=2ln(3)/ln(9/5)~/=3.74.
NASA Astrophysics Data System (ADS)
Lo Gullo, Nicola; Dell'Anna, Luca
2015-12-01
We study the spreading of density-density correlations and the Loschmidt echo, after different sudden quenches in an interacting one-dimensional Bose gas on a lattice, also in the presence of a superimposed aperiodic potential. We use a time dependent Bogoliubov approach to calculate the evolution of the correlation functions and employ the linked cluster expansion to derive the Loschmidt echo.
Emergent structure in a dipolar Bose gas in a one-dimensional lattice
Wilson, Ryan M.; Bohn, John L.
2011-02-15
We consider an ultracold dipolar Bose gas in a one-dimensional lattice. For a sufficiently large lattice recoil energy, such a system becomes a series of nonoverlapping Bose-Einstein condensates that interact via the long-range dipole-dipole interaction (ddi). We model this system via a coupled set of nonlocal Gross-Pitaevskii equations (GPEs) for lattices of both infinite and finite extent. We find significantly modified stability properties in the lattice due to the softening of a discrete roton-like mode, as well as ''islands'' in parameter space where biconcave densities are predicted to exist and that only exist in the presence of the other condensates on the lattice. We solve for the elementary excitations of the system to check the dynamical stability of these solutions and to uncover the nature of their collapse. By solving a coupled set of GPEs exactly on a full numeric grid, we show that this emergent biconcave structure can be realized in a finite lattice with atomic {sup 52}Cr.
Ultra-cold dilute gas Bose-Fermi mixture with ^87Rb and ^40K
NASA Astrophysics Data System (ADS)
Goldwin, J.; Olsen, M. L.; Inouye, S.; Jin, D. S.
2003-05-01
Sympathetic cooling experiments with Bose-Fermi mixtures offer a way to cool Fermi gases to quantum degeneracy with relatively little loss in atom number, as well as offering interesting new systems for study with the control and precision typical of atomic physics experiments. Here we report on the sympathetic cooling of fermionic ^40K with bosonic ^87Rb. We first trap and cool ^87Rb atoms in a two-species MOT together with ^40K. After loading into a purely magnetic quadrupole configuration trap, the gas is transferred mechanically nearly a meter to a Ioffe-Pritchard type magnetic trap in an ultra-high vacuum cell. radio-frequency induced evaporation of the ^87Rb atoms results in pure Bose-Einstein condensates of ˜ 2× 10^5 atoms. In the process ^40K atoms are cooled by virtue of thermal contact with the ^87Rb reservoir resulting in cooling of ^40K, with ˜ 1 × 10^4 atoms at temperatures below 100 nK. We present results from the experiment demonstrating the efficiency of the cooling, and describe ongoing investigations into the limits of the cooling and the strong inter-species interactions in the mixture. Finally, future directions for the experiment are discussed.
Thermodynamics of the Noninteracting Bose Gas in a Two-Dimensional Box
NASA Astrophysics Data System (ADS)
Li, Heqiu; Guo, Qiujiang; Jiang, Ji; Johnston, David C.
Bose-Einstein condensation (BEC) of a noninteracting Bose gas of N particles in a two-dimensional (2D) box with Dirichlet boundary conditions is studied. Confirming previous work, we find that BEC occurs at finite N at low temperatures T without the occurrence of a phase transition. We further show that the crossover temperature between weak and strong increases in BEC upon cooling is TE ~ 1 / log (N) at fixed area per boson, so in the thermodynamic limit there is no significant BEC in 2D at finite T. Calculations of thermodynamic properties versus T and area A are presented, including Helmholtz free energy, entropy S, pressure p, ratio of p to the energy density U / A , heat capacity at constant area CV and at constant pressure Cp, isothermal compressibility κT and thermal expansion coefficient αp, obtained using both the grand canonical ensemble (GCE) and canonical ensemble (CE) formalisms. The GCE formalism gives acceptable predictions for S, p, p / (U / A) , κT and αp at large N, T and A, but fails when N is small or BEC is significant, whereas the CE formalism gives accurate results even at low T and/or A where BEC occurs.
Kosterlitz-Thouless Transition of the Quasi-Two-Dimensional Trapped Bose Gas
Holzmann, Markus; Krauth, Werner
2008-05-16
We use quantum Monte Carlo methods to compute the density profile, the nonclassical moment of inertia, and the condensate fraction of an interacting quasi-two-dimensional trapped Bose gas with up to N{approx}5x10{sup 5} atoms and parameters closely related to recent experiments. We locate the Kosterlitz-Thouless temperature T{sub KT} and discuss intrinsic signatures of the onset of superfluidity in the density profile. Below T{sub KT}, the condensate fraction is macroscopic even for our largest systems and decays only slowly with system size. We show that the thermal population of excited states in the transverse direction changes the two-dimensional density profile noticeably in both the normal and the superfluid phase.
Spin squeezing of a dipolar Bose gas in a double-well potential
NASA Astrophysics Data System (ADS)
Tan, Qing-Shou; Lu, Hai-Yan; Yi, Su
2016-01-01
The spin-squeezing dynamics of a quasi-one-dimensional dipolar Bose gas trapped in a double-well potential is studied by employing the method of the multiconfigurational time-dependent Hartree for bosons. We find that optimal squeezing generated by the dipolar interaction can be improved over the one-axis twisting limit, and this squeezing is much stronger than that obtained by the contact interaction. Moreover, natural orbital-related squeezing can be controlled by the direction of the dipole moment, which provides control for storing the optimal spin squeezing. The origin of the squeezing as well as the relationship between spin squeezing and the two-order correlation function are also discussed.
Thermodynamic Properties of a Trapped Bose Gas:. a Diffusion Monte Carlo Study
NASA Astrophysics Data System (ADS)
Datta, S.
We investigate the thermodynamic properties of a trapped Bose gas of Rb atoms interacting through a repulsive potential at low but finite temperature (kBT < μ < Tc) by Quantum Monte Carlo method based upon the generalization of Feynman-Kac method1-3 applicable to many-body systems at T=0 to finite temperatures. In this paper, we report temperature variation of condensation fraction, chemical potential, density profile, total energy of the system, release energy, frequency shifts and moment of inertia within the realistic potential model (Morse type) for the first time by diffusion Monte Carlo technique. The most remarkable success was in achieving the same trend in the temperature variation of frequency shifts as was observed in JILA4 for both m=2 and m=0 modes. For other things, we agree with the work of Giorgini et al.,5 Pitaevskii et al.6 and Krauth.7
Quenched Dynamics of the Momentum Distribution of the Unitary Bose Gas
NASA Astrophysics Data System (ADS)
Ancilotto, Francesco; Rossi, Maurizio; Salasnich, Luca; Toigo, Flavio
2015-12-01
We study the quenched dynamics of the momentum distribution of a unitary Bose gas under isotropic harmonic confinement within a time-dependent density functional approach based on our recently calculated Monte Carlo bulk equation of state. In our calculations the inter-atomic s-wave scattering length of the trapped bosons is suddenly increased to a very large value and the real-time evolution of the system is studied. Prompted by the very recent experimental data of 85Rb atoms at unitarity (Makotyn et al. in Nat Phys 10:116, 2014) we focus on the momentum distribution as a function of time. Our results suggest that at low momenta, a quasi-stationary momentum distribution is reached after a long transient, contrary to what found experimentally for large momenta which equilibrate on a time scale shorter than the one for three body losses.
Spatial Nonlocal Pair Correlations in a Repulsive 1D Bose Gas
Sykes, A. G.; Davis, M. J.; Kheruntsyan, K. V.; Gangardt, D. M.; Viering, K.; Raizen, M. G.
2008-04-25
We analytically calculate the spatial nonlocal pair correlation function for an interacting uniform 1D Bose gas at finite temperature and propose an experimental method to measure nonlocal correlations. Our results span six different physical realms, including the weakly and strongly interacting regimes. We show explicitly that the characteristic correlation lengths are given by one of four length scales: the thermal de Broglie wavelength, the mean interparticle separation, the healing length, or the phase coherence length. In all regimes, we identify the profound role of interactions and find that under certain conditions the pair correlation may develop a global maximum at a finite interparticle separation due to the competition between repulsive interactions and thermal effects.
Two-dimensional dynamics of expansion of a degenerate Bose gas
NASA Astrophysics Data System (ADS)
Mazets, Igor E.
2012-11-01
Expansion of a degenerate Bose gas released from a pancakelike trap is numerically simulated under the assumption of separation of the motion in the plane of the loose initial trapping and the motion in the direction of the initial tight trapping. The initial conditions for the phase fluctuations are generated using the extension to the two-dimensional case of the description of the phase noise by the Ornstein-Uhlenbeck stochastic process. The numerical simulations, taking into account both the finite size of the two-dimensional system and the atomic interactions, which cannot be neglected on the early stage of expansion, did not reproduce the scaling law for the peaks in the density fluctuation spectra experimentally observed by Choi, Seo, Kwon, and Shin [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.125301 109, 125301 (2012)]. The latter experimental results may thus require an explanation beyond our current assumptions.
Reentrant behavior of the breathing-mode-oscillation frequency in a one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Gudyma, A. Iu.; Astrakharchik, G. E.; Zvonarev, Mikhail B.
2015-08-01
Exciting temporal oscillations of the density distribution is a high-precision method for probing ultracold trapped atomic gases. Interaction effects in their many-body dynamics are particularly puzzling and counter-intuitive in one spatial dimension (1D) due to enhanced quantum correlations. We consider 1D quantum Bose gas in a parabolic trap at zero temperature and explain, analytically and numerically, how oscillation frequency depends on the number of particles, their repulsion, and the trap strength. We identify the frequency with the energy difference between the ground state and a particular excited state. This way we avoided resolving the dynamical evolution of the system, simplifying the problem immensely. We find an excellent quantitative agreement of our results with the data from the Innsbruck experiment [Science 325, 1224 (2009), 10.1126/science.1175850].
Off-diagonal long-range order, cycle probabilities, and condensate fraction in the ideal Bose gas.
Chevallier, Maguelonne; Krauth, Werner
2007-11-01
We discuss the relationship between the cycle probabilities in the path-integral representation of the ideal Bose gas, off-diagonal long-range order, and Bose-Einstein condensation. Starting from the Landsberg recursion relation for the canonic partition function, we use elementary considerations to show that in a box of size L3 the sum of the cycle probabilities of length k>L2 equals the off-diagonal long-range order parameter in the thermodynamic limit. For arbitrary systems of ideal bosons, the integer derivative of the cycle probabilities is related to the probability of condensing k bosons. We use this relation to derive the precise form of the pik in the thermodynamic limit. We also determine the function pik for arbitrary systems. Furthermore, we use the cycle probabilities to compute the probability distribution of the maximum-length cycles both at T=0, where the ideal Bose gas reduces to the study of random permutations, and at finite temperature. We close with comments on the cycle probabilities in interacting Bose gases.
Determination of exospheric neutral gas temperatures
NASA Technical Reports Server (NTRS)
Mauersberger, K.; Nier, A. O.; Kayser, D. C.; Potter, W. E.; Engebretson, M. J.
1976-01-01
The Atmosphere Explorer satellites (AE-C, -D, and -E) were initially placed into highly elliptical orbits with perigees around 140 km and apogees of 4000 km. As a result of such an orbital geometry, measurements of neutral constituents at high altitudes represent mainly vertical changes in densities. The influence of horizontal density gradients on measurements above 400 km is small. Under geomagnetically quiet conditions, the density profiles can be used to derive scale-height temperatures of the exosphere. The open-source neutral mass spectrometer (OSS) flown on all three AE-satellites measured neutral constituents such as N2, O, and N well above 400 km. The temperatures derived from scale heights show a good agreement among the constituents and the expected close correlation with the F10.7-cm solar flux. Satellites with highly elliptical orbits provide the opportunity to measure simultaneously both densities and temperatures.
Hybrid simulation of neutral gas interacting with a plasma
NASA Astrophysics Data System (ADS)
Karney, C. F. F.; Stotler, D. P.; Braams, B. J.
1997-08-01
Plasma in contact with a material surface is neutralized and recycled as a gas that in turn interacts with the plasma. The neutral gas may be in a kinetic regime (long mean free path) in some regions and in a fluid regime (short mean free path) elsewhere. In order to model this situation, we imagine the neutral gas as the superposition of two populations, one fluid and one kinetic, with transfer terms coupling the two populations. We model these populations by coupling together a plasma fluid code, B2.5,(B. J. Braams, Radiative Divertor Modelling for ITER and TPX, Contrib. Plasma Phys. 36), 276-281 (1996) and a neutral Monte Carlo code, Degas 2.footnote D. P. Stotler and C. F. F. Karney, Neutral Gas Transport Modeling with Degas 2, Contrib. Plasma Phys. 34, 392-397 (1994). The coupling terms conserve mass, momentum, and energy, and are chosen so that fluid neutrals are converted to kinetic neutrals where their mean free path is long and vice versa. In this scheme, self collisions are never a dominant term in the Monte Carlo code may be treated by a simplified BGK model.
FK-DLR properties of a quantum multi-type Bose-gas with a repulsive interaction
NASA Astrophysics Data System (ADS)
Suhov, Y.; Stuhl, I.
2014-08-01
The paper extends earlier results from Suhov and Kelbert ["FK-DLR states of a quantum Bose-gas with a hardcore interaction," arXiv:1304.0782] and Suhov et al. ["Shift-invariance for FK-DLR states of a 2D quantum Bose-gas," arXiv:1304.4177] about infinite-volume quantum bosonic states (FK-DLR states) to the case of multi-type particles with non-negative interactions. (An example is a quantum Widom-Rowlinson model.) Following the strategy from Suhov and Kelbert and Suhov et al., we establish that, for the values of fugacity z ∈ (0, 1) and inverse temperature β > 0, finite-volume Gibbs states form a compact family in the thermodynamic limit. Next, in dimension two we show that any limit-point state (an FK-DLR state in the terminology adopted in Suhov and Kelbert and Suhov et al.) is translation-invariant.
Disordered spin dependent interactions in a spinor (S=1) Bose gas: A percolation analysis
NASA Astrophysics Data System (ADS)
Nabi, Sk. Noor; Basu, Saurabh
2016-05-01
We study the effect of disorder in the spin dependent interaction of a spinor Bose Hubbard model. We apply mean field theory and observe the presence of Bose glass phase by computing the superfluid order parameter and compressibility. The extent of different types of phase is computed via a percolation analysis for phase diagram corresponding to antiferromagnetic interactions.
Disordered spin dependent interactions in a spinor (S=1) Bose gas: A percolation analysis
Nabi, Sk. Noor; Basu, Saurabh
2016-05-23
We study the effect of disorder in the spin dependent interaction of a spinor Bose Hubbard model. We apply mean field theory and observe the presence of Bose glass phase by computing the superfluid order parameter and compressibility. The extent of different types of phase is computed via a percolation analysis for phase diagram corresponding to antiferromagnetic interactions.
Mora, Christophe; Castin, Yvan
2009-05-08
We consider the grand potential {omega} of a two-dimensional weakly interacting homogeneous Bose gas at zero temperature. Building on a number-conserving Bogoliubov method for a lattice model in the grand canonical ensemble, we calculate the next order term as compared to the Bogoliubov prediction, in a systematic expansion of {omega} in powers of the parameter measuring the weakness of the interaction. Our prediction is in very good agreement with recent Monte Carlo calculations.
Modeling of neutral gas dynamics in high-density plasmas
NASA Astrophysics Data System (ADS)
Canupp, Patrick Wellington
This thesis describes a physical model of chemically reactive neutral gas flow and discusses numerical solutions of this model for the flow in an inductively coupled plasma etch reactor. To obtain these solutions, this research develops an efficient, implicit numerical method. As a result of the enhanced numerical stability of the scheme, large time steps advance the solution from initial conditions to a final steady state in fewer iterations and with less computational expense than simpler explicit methods. This method would incorporate suitably as a module in currently existing large scale plasma simulation tools. In order to demonstrate the accuracy of the numerical technique, this thesis presents results from two simulations of flows that possess theoretical solutions. The first case is the inviscid flow of a gas through a converging nozzle. A comparison of the numerical solution to isentropic flow theory shows that the numerical technique capably captures the essential flow features of this environment. The second case is the Couette flow of a gas between two parallel plates. The simulation results compare well with the exact solution for this flow. After establishing the accuracy of the numerical technique, this thesis discusses results for the flow of chemically reactive gases in a chlorine plasma etch reactor. This research examines the influence of the plasma on the neutral gas and the dynamics exhibited by the neutral gas in the reactor. This research finds that the neutral gas temperature strongly depends on the rate at which inelastic, electron-impact dissociation reactions occur and on atomic chlorine wall recombination rates. Additionally, the neutral gas Aow in the reactor includes a significant mass flux of etch product from the wafer surface. Resolution of these effects is useful for neutral gas simulation. Finally, this thesis demonstrates that continuum fluid models provide reasonable accuracy for these low pressure reactor flows due to the fact
Black hole thermodynamics as seen through a microscopic model of a relativistic Bose gas
NASA Astrophysics Data System (ADS)
Skákala, Jozef; Shankaranarayanan, S.
2016-02-01
Equations of gravity when projected on spacetime horizons resemble Navier-Stokes equation of a fluid with a specific equation of state [T. Damour, Surface effects of black hole physics, in Proc. M. Grossman Meeting (North Holland, 1982), p. 587, T. Padmanabhan, Phys. Rev. D 83 (2011) 044048, arXiv:gr-qc/1012.0119, S. Kolekar and T. Padmanabhan, Phys. Rev. D 85 (2011) 024004, arXiv:gr-qc/1012.5421]. We show that this equation of state describes massless ideal relativistic gas. We use these results, and build an explicit and simple molecular model of the fluid living on the Schwarzschild and Reissner-Nordström black hole horizons. For the spin zero Bose gas, our model makes two predictions: (i) The horizon area/entropy is quantized as given by Bekenstein’s quantization rule, (ii) The model explains the correct type of proportionality between horizon area and entropy. However, for the physically relevant range of parameters, the proportionality constant is never equal to 1/4.
Bose-Einstein Condensation in a Dilute Gas:. the First 70 Years and Some Recent Experiments
NASA Astrophysics Data System (ADS)
Cornell, E. A.; Wieman, C. E.
2003-04-01
Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of "How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why?" We will review some of our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging.
Resonance glow of the neutral interplanetary gas
NASA Astrophysics Data System (ADS)
Scherer, Horst
2000-05-01
The neutral hydrogen, embedded in the partially ionized local interstellar medium, can enter deeply into the heliosphere with the interstellar wind flow. While entering into the heliosphere it suffers from intense charge-exchange interactions with the solar wind protons. This charge-exchange leads to a fractional depletion of the interstellar hydrogen atoms inside the heliosphere and modulates their velocity and temperature distribution. The resulting thermodynamical conditions of the interstellar hydrogen inside the heliosphere are described by two kinetic density models. The first model by Wu & Judge specially takes into account the influence on hydrogen due to solar photo ionization and solar gravitation and leads to appropriate results in the solar vicinity. The second model by Osterbart & Fahr takes into account the plasma interaction effects near the solar wind shock region and near the heliopause. Hence, this model gives more realistic results for the hydrogen properties far away from the Sun. Besides these theoretical modelings of the interplanetary hydrogen, measurements of the interplanetary hydrogen HI-Lyman-Alpha resonance glow were performed and attempts have been made to deduce the relevant thermodynamical parameter of the neutral interstellar hydrogen by analyzing these glow data. Two radiation transport models will be discussed which are used to analyze the interplanetary hydrogen HI-Lyman-Alpha resonance glow data. First, the "optically thin" approximation which is used very often in the literature because of its simple numerical handling. Unfortunately, this model has a very limited region of validity. The second radiation transport model by Scherer & Fahr introduces the exact redistribution function which takes into account the local thermodynamical conditions of the scattering agent, like density, bulk velocity and temperature of the neutral interplanetary hydrogen. Also it takes into account the actually observed solar HI-Lyman-Alpha emission
Modeling of modification experiments involving neutral-gas release
Bernhardt, P.A.
1983-01-01
Many experiments involve the injection of neutral gases into the upper atmosphere. Examples are critical velocity experiments, MHD wave generation, ionospheric hole production, plasma striation formation, and ion tracing. Many of these experiments are discussed in other sessions of the Active Experiments Conference. This paper limits its discussion to: (1) the modeling of the neutral gas dynamics after injection, (2) subsequent formation of ionosphere holes, and (3) use of such holes as experimental tools.
Microcanonical finite-size scaling of an ideal Bose gas in a box
NASA Astrophysics Data System (ADS)
Wang, Honghui; He, Jizhou; Wang, Jianhui
2017-01-01
We derive an exact recursive scheme to determine exactly the microcanonical partition function of a finite Bose system. Such a recursive approach is identical to that previously obtained within the context of counting statistics. Within the exact microcanonical ensemble, we study microcanonical finite-size scaling behaviors of condensate fraction and specific heat around the critical energy ɛ c for the finite ideal Bose system. We show that the microcanonical scaling functions governing the various critical behaviors are universal in the ideal Bose-Einstein condensates.
NASA Astrophysics Data System (ADS)
Bera, Sangita; Lekala, Mantile Leslie; Chakrabarti, Barnali; Bhattacharyya, Satadal; Rampho, Gaotsiwe Joel
2017-09-01
'We study the condensate fluctuation and several statistics of weakly interacting attractive Bose gas of 7 Li atoms in harmonic trap. Using exact recursion relation we calculate canonical ensemble partition function and study the thermal evolution of the condensate. As 7 Li condensate is associated with collapse, the number of condensate atom is truly finite and it facilitates to study the condensate in mesoscopic region. Being highly correlated, we utilize the two-body correlated basis function to get the many-body effective potential which is further used to calculate the energy levels. Taking van der Waals interaction as interatomic interaction we calculate several quantities like condensate fraction
Quantum states of dark solitons in the 1D Bose gas
NASA Astrophysics Data System (ADS)
Sato, Jun; Kanamoto, Rina; Kaminishi, Eriko; Deguchi, Tetsuo
2016-07-01
We present a series of quantum states that are characterized by dark solitons of the nonlinear Schrödinger equation (i.e. the Gross-Pitaevskii equation) for the one-dimensional Bose gas interacting through the repulsive delta-function potentials. The classical solutions satisfy the periodic boundary conditions and we simply call them classical dark solitons. Through exact solutions we show corresponding aspects between the states and the solitons in the weak coupling case: the quantum and classical density profiles completely overlap with each other not only at an initial time but also at later times over a long period of time, and they move together with the same speed in time; the matrix element of the bosonic field operator between the quantum states has exactly the same profiles of the square amplitude and the phase as the classical complex scalar field of a classical dark soliton not only at the initial time but also at later times, and the corresponding profiles move together for a long period of time. We suggest that the corresponding properties hold rigorously in the weak coupling limit. Furthermore, we argue that the lifetime of the dark soliton-like density profile in the quantum state becomes infinitely long as the coupling constant approaches zero, by comparing it with the quantum speed limit time. Thus, we call the quantum states quantum dark soliton states.
Nonlinear quantization of a degenerate charged Bose gas in an external Coulomb trap
Reinisch, Gilbert
2004-09-01
We consider a degenerate charged Bose-Coulomb gas populating several discrete stationary boson bound states that are located in a spherical-symmetrical central Coulombian potential. Each such state is defined, through appropriate boundary conditions and normalization, by a so-called 'nonlinear eigenstate' that is actually a solution of the coupled (linear) stationary Schroedinger-like Gross-Pitaevskii differential equation and the (nonlinear) Poisson equation. The corresponding eigenvalues allow us to define the energies of these degenerate boson states, much like the Koopmans orbital energy in atomic physics. This theory applies surprisingly well (compared with the corresponding Hartree-Fock results) to spherical-symmetrical s orbital states in atomic physics (i.e., bosonlike restricted orbital states where the additional spin degree of freedom is already integrated out). Finally the superposition of two such stationary nonlinear eigenstates is investigated and given a semiclassical physical significance similar to a Thomas-Fermi approach. The resulting concepts apply particularly well (namely within an average 1% error bar with respect to spectroscopic data) to the 1s{sup 2}-2s{sup 2} orbital states of the 3{<=}Z{<=}9 atomic subsystems.
Real-space mean-field theory of a spin-1 Bose gas in synthetic dimensions
NASA Astrophysics Data System (ADS)
Hurst, Hilary M.; Wilson, Justin H.; Pixley, J. H.; Spielman, I. B.; Natu, Stefan S.
2016-12-01
The internal degrees of freedom provided by ultracold atoms provide a route for realizing higher dimensional physics in systems with limited spatial dimensions. Nonspatial degrees of freedom in these systems are dubbed "synthetic dimensions." This connection is useful from an experimental standpoint but complicated by the fact that interactions alter the condensate ground state. Here we use the Gross-Pitaevskii equation to study the ground-state properties of a spin-1 Bose gas under the combined influence of an optical lattice, spatially varying spin-orbit coupling, and interactions at the mean-field level. The associated phases depend on the sign of the spin-dependent interaction parameter and the strength of the spin-orbit field. We find "charge"- and spin-density-wave phases which are directly related to helical spin order in real space and affect the behavior of edge currents in the synthetic dimension. We determine the resulting phase diagram as a function of the spin-orbit coupling and spin-dependent interaction strength, considering both attractive (ferromagnetic) and repulsive (polar) spin-dependent interactions, and we provide a direct comparison of our results with the noninteracting case. Our findings are applicable to current and future experiments, specifically with 87Rb, 7Li, 41K, and 23Na.
Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Singh, Vijay Pal; Weitenberg, Christof; Dalibard, Jean; Mathey, Ludwig
2017-04-01
We investigate the superfluid behavior of a two-dimensional (2D) Bose gas of 87Rb atoms using classical field dynamics. In the experiment by R. Desbuquois et al. [Nat. Phys. 8, 645 (2012), 10.1038/nphys2378], a 2D quasicondensate in a trap is stirred with a blue-detuned laser beam along a circular path around the trap center. Here, we study this experiment from a theoretical perspective. The heating induced by stirring increases rapidly above a velocity vc, which we define as the critical velocity. We identify the superfluid, the crossover, and the thermal regime by a finite, a sharply decreasing, and a vanishing critical velocity, respectively. We demonstrate that the onset of heating occurs due to the creation of vortex-antivortex pairs. A direct comparison of our numerical results to the experimental ones shows a good agreement, if a systematic shift of the critical phase-space density is included. We relate this shift to the absence of thermal equilibrium between the condensate and the thermal wings, which were used in the experiment to extract the temperature. We expand on this observation by studying the full relaxation dynamics between the condensate and the thermal cloud.
Relaxation dynamics of the one-dimensional Bose gas via the coordinate Bethe ansatz
NASA Astrophysics Data System (ADS)
Davis, Matthew; Zill, Jan; Wright, Tod; Kheruntsyan, Karen; Gasenzer, Thomas
2015-05-01
Recently there has been significant progress in understanding the nature of relaxation in closed quantum systems following a disturbance. Many of the theoretical results have been obtained through the study of models that can be mapped to non-interacting systems, or via approximate numerical methods. We instead utilise the symbolic evaluation of matrix elements between the coordinate Bethe-ansatz eigenstates of the Lieb-Liniger model to simulate quenches of the one-dimensional Bose gas for up to N = 5 particles. We consider a range of scenarios, including quenches of the interaction strength to both repulsive and attractive values, and the application of momentum kicks in analogy to the quantum Newton's cradle experiment of Ref.. Our approach allows us to compare the time-evolving nonequilibrium correlation functions to their diagonal-ensemble (infinite-time-average) values. We find evidence of relaxation to the diagonal ensemble following a quench to repulsive interactions, and most of our results for relaxed-state correlations agree with recent generalized thermodynamic Bethe-ansatz calculations. However, our results for local third-order correlations differ markedly from the predictions of these generalized ensembles.
Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Karl, Markus; Gasenzer, Thomas
2017-09-01
Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross–Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent η ≃ -3 and, related to this, a large dynamical exponent z≃ 5 are identified. The corresponding power-law decay is found to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phase-ordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifying far-from-equilibrium scaling dynamics with each other. In particular, a close connection between the anomalous scaling exponent η, introduced in a quantum-field theoretic approach, and conservation-law induced scaling in classical phase-ordering kinetics is revealed. Moreover, the relation to superfluid turbulence as well as to driven stationary systems is discussed.
NASA Astrophysics Data System (ADS)
Heller, Sigmund; Strunz, Walter T.
2010-12-01
Stochastic field equations represent a powerful tool to describe the thermal state of a trapped Bose gas. Often, such approaches are confronted with the old problem of an ultraviolet catastrophe, which demands a cutoff at high energies. In Heller and Strunz (2009 J. Phys. B: At. Mol. Opt. Phys. 42 081001) we introduce a quantum stochastic field equation, avoiding the cutoff problem through a fully quantum approach based on the Glauber-Sudarshan P-function. For a close link to actual experimental setups, the theory is formulated for a fixed particle number and thus based on the canonical ensemble. In this work the derivation and the non-trivial numerical implementation of the equation is explained in detail. We present applications for finite Bose gases trapped in a variety of potentials and show results for ground state occupation numbers and their equilibrium fluctuations. Moreover, we investigate spatial coherence properties by studying correlation functions of various orders.
Quantum particle-number fluctuations in a two-component Bose gas in a double-well potential
Zin, Pawel; Oles, Bartlomiej; Sacha, Krzysztof
2011-09-15
A two-component Bose gas in a double-well potential with repulsive interactions may undergo a phase separation transition if the interspecies interactions outweigh the intraspecies ones. We analyze the transition in the strong interaction limit within the two-mode approximation. Numbers of particles in each potential well are equal and constant. However, at the transition point, the ground state of the system reveals huge fluctuations of numbers of particles belonging to the different gas components; that is, the probability for observation of any mixture of particles in each potential well becomes uniform.
The neutral gas content of post-merger galaxies
NASA Astrophysics Data System (ADS)
Ellison, Sara L.; Fertig, Derek; Rosenberg, Jessica L.; Nair, Preethi; Simard, Luc; Torrey, Paul; Patton, David R.
2015-03-01
Measurements of the neutral hydrogen gas content of a sample of 93 post-merger galaxies are presented, from a combination of matches to the ALFALFA.40 data release and new Arecibo observations. By imposing completeness thresholds identical to that of the ALFALFA (Arecibo Legacy Fast ALFA) survey, and by compiling a mass-, redshift- and environment-matched control sample from the public ALFALFA.40 data release, we calculate gas fraction offsets (Δfgas) for the post-mergers, relative to the control sample. We find that the post-mergers have H I gas fractions that are consistent with undisturbed galaxies. However, due to the relative gas richness of the ALFALFA.40 sample, from which we draw our control sample, our measurements of gas fraction enhancements are likely to be conservative lower limits. Combined with comparable gas fraction measurements by Fertig et al. in a sample of galaxy pairs, who also determine gas fraction offsets consistent with zero, we conclude that there is no evidence for significant neutral gas consumption throughout the merger sequence. From a suite of 75 binary merger simulations we confirm that star formation is expected to decrease the post-merger gas fraction by only 0.06 dex, even several Gyr after the merger. Moreover, in addition to the lack of evidence for gas consumption from gas fraction offsets, the observed H I detection fraction in the complete sample of post-mergers is twice as high as the controls, which suggests that the post-merger gas fractions may actually be enhanced. We demonstrate that a gas fraction enhancement in post-mergers, relative to a stellar mass-matched control sample, would indeed be the natural result of merging randomly drawn pairs from a parent population which exhibits a declining gas fraction with increasing stellar mass.
Beau, Mathieu; Savoie, Baptiste
2014-05-15
In this paper, we rigorously investigate the reduced density matrix (RDM) associated to the ideal Bose gas in harmonic traps. We present a method based on a sum-decomposition of the RDM allowing to treat not only the isotropic trap, but also general anisotropic traps. When focusing on the isotropic trap, the method is analogous to the loop-gas approach developed by Mullin [“The loop-gas approach to Bose-Einstein condensation for trapped particles,” Am. J. Phys. 68(2), 120 (2000)]. Turning to the case of anisotropic traps, we examine the RDM for some anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes. For such models, we bring out an additional contribution in the local density of particles which arises from the mesoscopic loops. The close connection with the occurrence of generalized-Bose-Einstein condensation is discussed. Our loop-gas-like approach provides relevant information which can help guide numerical investigations on highly anisotropic systems based on the Path Integral Monte Carlo method.
NASA Astrophysics Data System (ADS)
Kocharovsky, V. V.; Scully, Marlan O.; Zhu, Shi-Yao; Suhail Zubairy, M.
2000-02-01
A nonequilibrium approach to the dynamics and statistics of the condensate of an ideal N-atom Bose gas cooling via interaction with a thermal reservoir using the canonical ensemble is developed. We derive simple analytical expressions for the canonical partition function and equilibrium distribution of the number of atoms in the ground state of a trap under different approximations, and compare them with exact numerical results. The N-particle constraint associated with the canonical ensemble is usually a burden. In the words of Kittel, ``in the investigation of the Bose-Einstein...laws it is very inconvenient to impose the restriction that the number of particles in the subsystem shall be held constant.'' But in the present approach, based on the analogy between a second-order phase transition and laser threshold behavior, the N-particle constraint makes the problem easier. We emphasize that the present work provides another example of a case in which equilibrium (detailed balance) solutions to nonequilibrium equations of motion provide a useful supplementary approach to conventional statistical mechanics. We also discuss some dynamical and mesoscopic aspects of Bose-Einstein condensation. The conclusion is that the present analytical (but approximate) results, based on a nonequilibrium approach, are in excellent agreement with exact (but numerical) results. The present analysis has much in common with the quantum theory of the laser.
NASA Astrophysics Data System (ADS)
Girardeau, M. D.
1998-07-01
A recent paper of Gardiner [Phys. Rev. A 56, 1414 (1997)] introduces a particle-number-conserving Bogoliubov method for the excitation spectrum of a Bose-condensed gas, for use in theories of recently experimentally produced trapped atomic Bose condensates. Gardiner's approach is compared and contrasted with the 1959 Girardeau-Arnowitt theory [Phys. Rev. 113, 755 (1959)], to which it is closely related and which is also fully number conserving. The number-conserving Bogoliubov quasiparticle operators of the Girardeau-Arnowitt theory satisfy Bose commutation relations exactly so long as states with the condensate totally depleted are neglected, whereas those of Gardiner satisfy Bose commutation relations only in an approximation that deteriorates progressively as the condensate is depleted.
Gas-liquid chromatography of fecal neutral steriods.
Gerhardt, K O; Gehrke, C W; Rogers, I T; Flynn, M A; Hentges, D J
1977-05-21
A method is described for the analysis of fecal neutral steriods with a dual-column gas-liquid chromatography (GLC) system. After saponification of the fecal slurry, the neutral steroids were extracted with hexane. The GLC separation of the compounds and quantitation were achieved by simultaneous injection of the derivatized and derivatized aliquots of the extract onto dual colmuns under identical conditions. The neutral steroids of interest were than identified by matching the retention times with those of known standards, and identification was confirmed by use of an interfaced GLC high-resolution mass spectrometry system. The detection limit was 0.003 mg of steroid/g of fecal slurry. The pricision of the method is illustrated by a relative standard diviation of 2-10% and a recovery of neutral steroids from 73-96%. The method was applied to the determination of fecal neutral steroids in a "High protein diet in colon cancer study". A considerably larger level of coprostanone than of coprostanol was observed. Data on neutral steroids in fecal samples from subjects on different diets are the subject of a separate publication.
Metastable quantum phase transitions in a periodic one-dimensional Bose gas. II. Many-body theory
Kanamoto, R.; Carr, L. D.; Ueda, M.
2010-02-15
We show that quantum solitons in the Lieb-Liniger Hamiltonian are precisely the yrast states. We identify such solutions with Lieb's type II excitations from weak to strong interactions, clarifying a long-standing question of the physical meaning of this excitation branch. We demonstrate that the metastable quantum phase transition previously found in mean-field analysis of the weakly interacting Lieb-Liniger Hamiltonian [Phys. Rev. A 79, 063616 (2009)] extends into the medium- to strongly interacting regime of a periodic one-dimensional Bose gas. Our methods are exact diagonalization, finite-size Bethe ansatz, and the boson-fermion mapping in the Tonks-Girardeau limit.
Rezende, Sergio M.
2009-09-01
A magnon gas in a film of yttrium iron garnet driven by microwave radiation exhibits Bose-Einstein condensation (BEC) when the driving power exceeds a critical value. We show that the nature and the critical exponents of the BEC transition change dramatically if the BEC magnons are significantly coupled to the zone-center magnons. The theoretical results explain the diverse behavior of the order parameter inferred from the experimental data for the light scattering and the microwave emission from the BEC observed with coherent and incoherent microwave pumping.
Mott-insulator transition in a two-dimensional atomic Bose gas.
Spielman, I B; Phillips, W D; Porto, J V
2007-02-23
Cold atoms in periodic potentials are versatile quantum systems for implementing simple models prevalent in condensed matter theory. Here we realize the 2D Bose-Hubbard model by loading a Bose-Einstein condensate into an optical lattice, and study the resulting Mott insulator. The measured momentum distributions agree quantitatively with theory (no adjustable parameters). In these systems, the Mott insulator forms in a spatially discrete shell structure which we probe by focusing on correlations in atom shot noise. These correlations show a marked dependence on the lattice depth, consistent with the changing size of the insulating shell expected from simple arguments.
Observational Constraints on a Pluto Torus of Circumsolar Neutral Gas
NASA Astrophysics Data System (ADS)
Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Smith, H. T.; Bagenal, F.; Brown, L. E.; Elliott, H. A.; Haggerty, D. K.; Horanyi, M.; Krimigis, S. M.; Kusterer, M. B.; Lisse, C. M.; McComas, D. J.; Piquette, M. R.; Sidrow, E. J.; Strobel, D. F.; Szalay, J.; Vandegriff, J. D.; Zirnstein, E.; Ennico Smith, K.; Olkin, C.; Weaver, H. A., Jr.; Young, L. A.; Stern, S. A.
2015-12-01
We present the concept of a neutral gas torus surrounding the Sun, aligned with Pluto's orbit, and place observational constraints based primarily on comparison of New Horizons (NH) measurements with a 3-D Monte Carlo model adapted from analogous satellite tori surrounding Saturn and Jupiter. Such a torus, or perhaps partial torus, should result from neutral N2 escaping from Pluto's exosphere. Unlike other more massive planets closer to the Sun, neutrals escape Pluto readily owing, e.g., to the high thermal speed relative to the escape velocity. Importantly, escaped neutrals have a long lifetime due to the great distance from the Sun, ~100 years for photoionization of N2 and ~180 years for photoionization of N, which results from disassociated N2. Despite the lengthy 248-year orbit, these long e-folding lifetimes may allow an enhanced neutral population to form an extended gas cloud that modifies the N2 spatial profile near Pluto. These neutrals are not directly observable by NH but once ionized N2+ or N+ are picked up by the solar wind, reaching ~50 keV, making these pickup ions (PUIs) detectable by NH's Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. PEPSSI observations analyzed to date may constrain the N2 density; the remaining ~95% of the encounter data, scheduled for downlink in August along with similarly anticipated data from the Solar Wind Around Pluto (SWAP) experiment, should help determine the Pluto outgassing rates. Measurements from SWAP include the solar wind speed, a quantity that greatly enhances PUI studies by enabling us to directly account for the PUI distribution's sensitive dependence on plasma speed. Note that anomalous cosmic ray Si observed at Voyager is overabundant by a factor of ~3000 relative to interstellar composition. This might be related to "outer source" PUIs, but the fact that N2 and Si are indistinguishable in many instruments could mean that N2 is actually driving this apparent Si discrepancy.
NASA Astrophysics Data System (ADS)
Pires, M. O. C.; de Passos, E. J. V.
2017-02-01
We develop the Hartree-Fock-Bogoliubov theory at finite temperature for Bose gas trapped in the two-dimensional optical lattice with the on-site energy low enough that the gas presents superfluid properties. We obtain the condensate density as function of the temperature neglecting the anomalous density in the thermodynamics equation. The condensate fraction provides two critical temperature. Below the temperature T_{C1}, there is one condensate fraction. Above two condensate fractions merger up to the critical temperature T_{C2}. At temperatures larger than T_{C2}, the condensate fraction is null and, therefore, the gas is normal fluid. We resume by a finite-temperature phase diagram where three domains can be identified: the normal fluid, the superfluid with one stable condensate fraction and the superfluid with two condensate fractions being unstable one of them.
Application of the Lagrangian variational method to a one-dimensional Bose gas in a dimple trap
NASA Astrophysics Data System (ADS)
Sakhel, Roger R.; Sakhel, Asaad R.
2017-05-01
We present an application of the Lagrangian variational method (LVM) to study the small-oscillation dynamics and ground-state properties of an interacting Bose gas in a one-dimensional dimple trap, for the first time. For this purpose, a Gaussian wavefunction ansatz—rich in variational parameters—is used for the analytical solutions of the equations of motion resulting from the LVM. The results of LVM are found to agree well with those due to the numerical Crank-Nicolson method. The strength of this method is shown to reveal details hidden in the wavefunction and its dynamics that are otherwise hard to obtain numerically or even experimentally. In this regard, the important role that the wavefunction-width plays in determining the properties of a trapped Bose gas is manifested. Via this method, the dependence of the breathing-mode frequency on the interactions, width of wavefunction, and dimple trap parameters, is demonstrated. A significant result is that in the ‘width-space’ of the wavefunction, the LVM yields a differential equation that describes the motion of a fictitious particle in an effective potential whose shape is by analogy similar to that of an interatomic interaction potential.
P-wave superfluid in a quasi-two-dimensional dipolar Bose-Fermi quantum gas mixture
NASA Astrophysics Data System (ADS)
Kain, Ben; Ling, Hong
2013-03-01
The p-wave (px + ipy) superfluid has attracted significant attention in recent years mainly because its vortex core supports a Majorana fermion which, due to its non-Abelian statistics, can be explored for implementing topological quantum computation (TQC). Mixing in bosons may lead to p-wave pairing in a Fermi gas. In a dipolar condensate, the dipole-dipole interaction represents a control knob inaccessible to nondipolar Bosons. Thus, mixing dipolar bosons with fermions opens up new possibilities. We consider a mixture of a spin-polarized Fermi gas and a dipolar Bose-Einstein condensate in a quasi-two-dimensional trap setting. We take the Hartree-Fock-Bogoliubov mean-field approach and develop a theory for studying the stability of the mixture and estimating the critical temperature of the p-wave superfluid. We use this theory to identify the experimentally accessible parameter space in which the mixture is stable against phase separation and the p-wave superfluid pairing can be resonantly enhanced. An enhanced p-wave superfluid order parameter can make the fault tolerant TQC less susceptible to thermal fluctuations. This work aims to stimulate experimental activity in creating dipolar Bose-Fermi mixtures. This work is supported by the US National Science Foundation and the US Army Research Office
NASA Astrophysics Data System (ADS)
Krieg, Jan; Strassel, Dominik; Streib, Simon; Eggert, Sebastian; Kopietz, Peter
2017-01-01
We use the functional renormalization group (FRG) to derive analytical expressions for thermodynamic observables (density, pressure, entropy, and compressibility) as well as for single-particle properties (wave-function renormalization and effective mass) of interacting bosons in two dimensions as a function of temperature T and chemical potential μ . We focus on the quantum disordered and the quantum critical regime close to the dilute Bose gas quantum critical point. Our approach is based on a truncated vertex expansion of the hierarchy of FRG flow equations and the decoupling of the two-body contact interaction in the particle-particle channel using a suitable Hubbard-Stratonovich transformation. Our analytic FRG results extend previous analytical renormalization-group calculations for thermodynamic observables at μ =0 to finite values of μ . To confirm the validity of our FRG approach, we have also performed quantum Monte Carlo simulations to obtain the magnetization, susceptibility, and correlation length of the two-dimensional spin-1 /2 quantum X Y model with coupling J in a regime where its quantum critical behavior is controlled by the dilute Bose gas quantum critical point. We find that our analytical results describe the Monte Carlo data for μ ≤0 rather accurately up to relatively high temperatures T ≲0.1 J .
FK-DLR properties of a quantum multi-type Bose-gas with a repulsive interaction
Suhov, Y.; Stuhl, I.
2014-08-01
The paper extends earlier results from Suhov and Kelbert [“FK-DLR states of a quantum Bose-gas with a hardcore interaction,” http://arxiv.org/abs/arXiv:1304.0782 ] and Suhov et al. [“Shift-invariance for FK-DLR states of a 2D quantum Bose-gas,” http://arxiv.org/abs/arXiv:1304.4177 ] about infinite-volume quantum bosonic states (FK-DLR states) to the case of multi-type particles with non-negative interactions. (An example is a quantum Widom–Rowlinson model.) Following the strategy from Suhov and Kelbert and Suhov et al., we establish that, for the values of fugacity zϵ(0, 1) and inverse temperature β > 0, finite-volume Gibbs states form a compact family in the thermodynamic limit. Next, in dimension two we show that any limit-point state (an FK-DLR state in the terminology adopted in Suhov and Kelbert and Suhov et al.) is translation-invariant.
Neutral Gas and Ion Measurements by the CONTOUR Mission
NASA Technical Reports Server (NTRS)
Mahaffy, Paul R.; Niemann, Hasso B. (Technical Monitor)
2002-01-01
The Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Comet Nucleus Tour (CONTOUR) Mission will measure the chemical and isotopic composition of neutral and ion species in the coma of comet Encke and the subsequent targets of this mission. Currently the second target of this mission is comet Schwassmann-Wachmann 3. This neutral gas and ion data together with complementary data from the dust analyzer and the imaging spectrometer is designed to allow a broad characterization of the molecular and elemental composition of each cometary nucleus. These experiments enable the study of the of the likely variations in chemical conditions present in different regions of the early solar nebula where the comets formed. With these experiments we will also test ideas about cometary contributions of organics, water, and other volatiles to the inner planets. The CONTOUR NGIMS data set from multiple comets is expected to provide an important extension of to the only other detailed in situ data set from a close flyby of a nucleus, that from Halley. CONTOUR will extend this measurement of an Oort cloud comet to the class of short period comets thought to originate in the Kuiper belt. This data will complement the detailed measurements to be carried out at a single nucleus by the Rosetta Mission.
NASA Astrophysics Data System (ADS)
Lin, Bihong; Chen, Jincan
2008-05-01
An irreversible model of the Carnot cryogenic refrigeration cycle working with an ideal Bose or Fermi gas is established, which is composed of two irreversible adiabatic and two isothermal processes. The effects of the quantum degeneracy of the working substance, the irreversibility of the finite-rate heat transfer between the working fluid and the heat reservoirs, and the internal irreversibility in two adiabatic processes on the optimum performance characteristics of the quantum refrigeration cycle are analyzed. The performance characteristics of the cycle in strong and weak gas degeneracy cases are discussed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Some optimum criteria are given.
Jacqmin, Thibaut; Armijo, Julien; Bouchoule, Isabelle; Berrada, Tarik; Kheruntsyan, Karen V.
2011-06-10
We report on local, in situ measurements of atom number fluctuations in slices of a one-dimensional Bose gas on an atom chip setup. By using current modulation techniques to prevent cloud fragmentation, we are able to probe the crossover from weak to strong interactions. For weak interactions, fluctuations go continuously from super- to sub-Poissonian as the density is increased, which is a signature of the transition between the subregimes where the two-body correlation function is dominated, respectively, by thermal and quantum contributions. At stronger interactions, the super-Poissonian region disappears, and the fluctuations go directly from Poissonian to sub-Poissonian, as expected for a ''fermionized'' gas.
Jacqmin, Thibaut; Armijo, Julien; Berrada, Tarik; Kheruntsyan, Karen V; Bouchoule, Isabelle
2011-06-10
We report on local, in situ measurements of atom number fluctuations in slices of a one-dimensional Bose gas on an atom chip setup. By using current modulation techniques to prevent cloud fragmentation, we are able to probe the crossover from weak to strong interactions. For weak interactions, fluctuations go continuously from super- to sub-Poissonian as the density is increased, which is a signature of the transition between the subregimes where the two-body correlation function is dominated, respectively, by thermal and quantum contributions. At stronger interactions, the super-Poissonian region disappears, and the fluctuations go directly from Poissonian to sub-Poissonian, as expected for a "fermionized" gas.
Phases of a two-dimensional bose gas in an optical lattice.
Jiménez-García, K; Compton, R L; Lin, Y-J; Phillips, W D; Porto, J V; Spielman, I B
2010-09-10
Ultracold atoms in optical lattices realize simple condensed matter models. We create an ensemble of ≈60 harmonically trapped 2D Bose-Hubbard systems from a 87Rb Bose-Einstein condensate in an optical lattice and use a magnetic resonance imaging approach to select a few 2D systems for study, thereby eliminating ensemble averaging. Our identification of the transition from superfluid to Mott insulator, as a function of both atom density and lattice depth, is in excellent agreement with a universal state diagram [M. Rigol, Phys. Rev. A 79 053605 (2009)] suitable for our trapped system. In agreement with theory, our data suggest a failure of the local density approximation in the transition region.
Loading and compression of a single two-dimensional Bose gas in an optical accordion
NASA Astrophysics Data System (ADS)
Ville, J. L.; Bienaimé, T.; Saint-Jalm, R.; Corman, L.; Aidelsburger, M.; Chomaz, L.; Kleinlein, K.; Perconte, D.; Nascimbène, S.; Dalibard, J.; Beugnon, J.
2017-01-01
The experimental realization of two-dimensional (2D) Bose gases with a tunable interaction strength is an important challenge for the study of ultracold quantum matter. Here we report on the realization of an optical accordion creating a lattice potential with a spacing that can be dynamically tuned between 11 and 2 μ m . We show that we can load ultracold 87Rb atoms into a single node of this optical lattice in the large spacing configuration and then decrease nearly adiabatically the spacing to reach a strong harmonic confinement with frequencies larger than ωz/2 π =10 kHz. Atoms are trapped in an additional flat-bottom in-plane potential that is shaped with a high resolution. By combining these tools we create custom-shaped uniform 2D Bose gases with tunable confinement along the transverse direction and hence with a tunable interaction strength.
Quenching to unitarity: Quantum dynamics in a 3D Bose gas
NASA Astrophysics Data System (ADS)
Sykes, Andrew; Corson, John; D'Incao, Jose; Koller, Andrew; Bohn, John; Rey, Ana Maria; Hazzard, Kaden; Greene, Chris
2014-03-01
We study the dynamics of a zero temperature Bose condensate following a sudden quench of the scattering length from noninteracting to unitarity (infinite scattering length). In this talk we discuss how a qualitative understanding of the dynamics can be built up by understanding few-body physics under the same dynamical scenario. We calculate the coherent evolution of the momentum distribution, particularly focusing on the time dependence of the contact. By comparing the results to a many-body mean-field calculation, we gauge the qualitative and quantitative accuracy of this approach. We then discuss the results of a three-body calculation, in which loss dynamics occurs due to three-body recombination. One the key results of this work indicates that loss dynamics takes place over a much longer timescale than the coherent dynamics. This exciting result supports the idea that meta-stable degenerate unitary Bose gases may be experimentally observable in such a non-equilibrium scenario.
Condensate fraction in a 2D Bose gas measured across the Mott-insulator transition.
Spielman, I B; Phillips, W D; Porto, J V
2008-03-28
We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical lattice and measure the condensate fraction as a function of lattice depth, crossing from the superfluid to the Mott-insulating phase. We quantitatively identify the location of the superfluid to normal transition by observing when the condensed fraction vanishes. Our measurement agrees with recent quantum Monte Carlo calculations for a finite-sized 2D system to within experimental uncertainty.
Ramsey Interferometry Using the Zeeman Sublevels in a Spin-2 Bose Gas
NASA Astrophysics Data System (ADS)
Sadgrove, Mark; Eto, Yujiro; Sekine, Sawako; Suzuki, Hirosuke; Hirano, Takuya
2013-09-01
We perform atom interferometry using the Zeeman sublevels of a spin-2 Bose--Einstein condensate of 87Rb. The observed fringes are strongly peaked, and fringe repetition rates higher than the fundamental Ramsey frequency are found in agreement with a simple theory based on spin rotations. With a suitable choice of initial states, the interferometer could function as a useful tool for magnetometry and studies of spinor dynamics in general.
Liu, Xia-Ji Hu, Hui
2014-12-15
We theoretically investigate first and second sound of a two-dimensional (2D) atomic Bose gas in harmonic traps by solving Landau’s two-fluid hydrodynamic equations. For an isotropic trap, we find that first and second sound modes become degenerate at certain temperatures and exhibit typical avoided crossings in mode frequencies. At these temperatures, second sound has significant density fluctuation due to its hybridization with first sound and has a divergent mode frequency towards the Berezinskii–Kosterlitz–Thouless (BKT) transition. For a highly anisotropic trap, we derive the simplified one-dimensional hydrodynamic equations and discuss the sound-wave propagation along the weakly confined direction. Due to the universal jump of the superfluid density inherent to the BKT transition, we show that the first sound velocity exhibits a kink across the transition. These predictions might be readily examined in current experimental setups for 2D dilute Bose gases with a sufficiently large number of atoms, where the finite-size effect due to harmonic traps is relatively weak.
NASA Astrophysics Data System (ADS)
Berman, Oleg L.; Kezerashvili, Roman Ya.
2016-06-01
The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel transition metal dichalcogenide (TMDC) layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity, and critical temperature are obtained for different TMDC materials. It is shown that in the Bogoliubov approximation, the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component exciton system. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for a two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the two-component exciton system in a TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.
Experimental and numerical studies of neutral gas depletion in an inductively coupled plasma
NASA Astrophysics Data System (ADS)
Shimada, Masashi
The central theme of this dissertation is to explore the impact of neutral depletion and coupling between plasma and neutral gas in weakly ionized unmagnetized plasma. Since there have been few systematic studies of the mechanism which leads to non-uniform neutral distribution in processing plasmas, this work investigated the spatial profiles of neutral temperature and pressure experimentally, and the mechanism of resulting neutral depletion by simulation. The experimental work is comprised of neutral temperature measurements using high resolution atomic spectroscopy and molecular spectroscopy, and neutral pressure measurements considering thermal transpiration. When thermal transpiration effects are used to correct the gas pressure measurements, the total pressure remains constant regardless of the plasma condition. Since the neutral gas follows the ideal gas law, the neutral gas density profile is also obtained from the measured neutral gas temperature and the corrected pressure measurements. The results show that neutral gas temperature rises close to ˜ 900 [K], and the neutral gas density at the center of plasma chamber has a significant (factor of 2-4x) decrease in the presence of a plasma discharge. In numerical work, neutral and ion transport phenomena were simulated by a hybrid-type direct simulation Monte Carlo (DSMC) method of one dimensional (1D) electrostatic plasma to identify the mechanism of the neutral gas density depletion in Ar/N2 mixtures. The simulation reveals that the neutral depletion is the result of the interplay between plasma and neutral gas, and a parametric study indicates that neutral depletion occurs mainly due to gas heating and pressure balance for the typical condition of plasma processing. In high density plasma sources (Te ≈ 2-5 eV, ne ≈ 1011-1012 cm-3) where the plasma pressure becomes comparable to neutral pressure, total pressure (neutral pressure and plasma pressure) is conserved before and after the discharge. Therefore
Kochereshko, Vladimir P.; Durnev, Mikhail V.; Besombes, Lucien; Mariette, Henri; Sapega, Victor F.; Askitopoulos, Alexis; Savenko, Ivan G.; Liew, Timothy C. H.; Shelykh, Ivan A.; Platonov, Alexey V.; Tsintzos, Simeon I.; Hatzopoulos, Z.; Savvidis, Pavlos G.; Kalevich, Vladimir K.; Afanasiev, Mikhail M.; Lukoshkin, Vladimir A.; Schneider, Christian; Amthor, Matthias; Metzger, Christian; Kamp, Martin; Hoefling, Sven; Lagoudakis, Pavlos; Kavokin, Alexey
2016-01-01
Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling. PMID:26822483
NASA Astrophysics Data System (ADS)
Kochereshko, Vladimir P.; Durnev, Mikhail V.; Besombes, Lucien; Mariette, Henri; Sapega, Victor F.; Askitopoulos, Alexis; Savenko, Ivan G.; Liew, Timothy C. H.; Shelykh, Ivan A.; Platonov, Alexey V.; Tsintzos, Simeon I.; Hatzopoulos, Z.; Savvidis, Pavlos G.; Kalevich, Vladimir K.; Afanasiev, Mikhail M.; Lukoshkin, Vladimir A.; Schneider, Christian; Amthor, Matthias; Metzger, Christian; Kamp, Martin; Hoefling, Sven; Lagoudakis, Pavlos; Kavokin, Alexey
2016-01-01
Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling.
Choi, S; Dunjko, V; Zhang, Z D; Olshanii, M
2015-09-11
Using a time-dependent modified nonlinear Schrödinger equation (MNLSE)-where the conventional chemical potential proportional to the density is replaced by the one inferred from Lieb-Liniger's exact solution-we study frequencies of the collective monopole excitations of a one-dimensional Bose gas. We find that our method accurately reproduces the results of a recent experimental study [E. Haller et al., Science 325, 1224 (2009)] in the full spectrum of interaction regimes from the ideal gas, through the mean-field regime, through the mean-field Thomas-Fermi regime, all the way to the Tonks-Giradeau gas. While the former two are accessible by the standard time-dependent NLSE and inaccessible by the time-dependent local density approximation, the situation reverses in the latter case. However, the MNLSE is shown to treat all these regimes within a single numerical method.
Excitation dynamics in a lattice Bose gas within the time-dependent Gutzwiller mean-field approach
Krutitsky, Konstantin V.; Navez, Patrick
2011-09-15
The dynamics of the collective excitations of a lattice Bose gas at zero temperature is systematically investigated using the time-dependent Gutzwiller mean-field approach. The excitation modes are determined within the framework of the linear-response theory as solutions of the generalized Bogoliubov-de Gennes equations valid in the superfluid and Mott-insulator phases at arbitrary values of parameters. The expression for the sound velocity derived in this approach coincides with the hydrodynamic relation. We calculate the transition amplitudes for the excitations in the Bragg scattering process and show that the higher excitation modes make significant contributions. We simulate the dynamics of the density perturbations and show that their propagation velocity in the limit of week perturbation is satisfactorily described by the predictions of the linear-response analysis.
Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap
NASA Astrophysics Data System (ADS)
Straatsma, C. J. E.; Colussi, V. E.; Davis, M. J.; Lobser, D. S.; Holland, M. J.; Anderson, D. Z.; Lewandowski, H. J.; Cornell, E. A.
2016-10-01
We study the monopole (breathing) mode of a finite temperature Bose-Einstein condensate in an isotropic harmonic trap recently developed by Lobser et al. [Nat. Phys. 11, 1009 (2015), 10.1038/nphys3491]. We observe a nonexponential collapse of the amplitude of the condensate oscillation followed by a partial revival. This behavior is identified as being due to beating between two eigenmodes of the system, corresponding to in-phase and out-of-phase oscillations of the condensed and noncondensed fractions of the gas. We perform finite temperature simulations of the system dynamics using the Zaremba-Nikuni-Griffin methodology [J. Low Temp. Phys. 116, 277 (1999), 10.1023/A:1021846002995], and find good agreement with the data, thus confirming the two mode description.
Rezende, Sergio M.
2009-05-01
Strong experimental evidences of the formation of quasiequilibrium Bose-Einstein condensation (BEC) of magnons at room temperature in a film of yttrium iron garnet (YIG) excited by microwave radiation have been recently reported. Here we present a theory for the dynamics of the magnon gas driven by a microwave field far out of equilibrium that provides rigorous support for the formation of a BEC of magnons in a YIG film magnetized in the plane. We show that if the microwave driving power exceeds a threshold value the nonlinear magnetic interactions create cooperative mechanisms for the onset of a phase transition leading to the spontaneous generation of quantum coherence and magnetic dynamic order in a macroscopic scale. The theoretical results agree with the experimental data for the intensity and the decay rate of the Brillouin light scattering from the BEC as a function of power and for the microwave emission from the uniform mode generated by the confluence of BEC magnon pairs.
Transport of a Bose gas in 1D disordered lattices at the fluid-insulator transition.
Tanzi, Luca; Lucioni, Eleonora; Chaudhuri, Saptarishi; Gori, Lorenzo; Kumar, Avinash; D'Errico, Chiara; Inguscio, Massimo; Modugno, Giovanni
2013-09-13
We investigate the momentum-dependent transport of 1D quasicondensates in quasiperiodic optical lattices. We observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. In the limit of nondisordered lattices the observations suggest a contribution of quantum phase slips to the dissipation. We identify a set of critical disorder and interaction strengths for which such critical momentum vanishes, separating a fluid regime from an insulating one. We relate our observation to the predicted zero-temperature superfluid-Bose glass transition.
Exponents of the spectral functions and dynamical structure factor of the 1D Lieb-Liniger Bose gas
NASA Astrophysics Data System (ADS)
Carmelo, J. M. P.; Sacramento, P. D.
2016-06-01
We study the (k , ω) -plane finite-energy line shape of the zero-temperature one-boson removal spectral function (ω < 0) , one-boson addition spectral function (ω > 0) , and charge dynamical structure factor (ω > 0) of the 1D Lieb-Liniger Bose gas with repulsive boson interaction c > 0. Our analysis of the problem focuses on the line shape at finite excitation energies in the vicinity of these functions spectrum upper (ω < 0) or lower (ω > 0) threshold. Specifically, we derive the exact momentum, interaction, and density dependences of the exponents controlling such a line shape in each of the N = 1 , 2 , 3 , … momentum subdomains k ∈ [(N - 1) 2 πn , N 2 πn ] . Here n = N / L is the boson density, N the boson number, and L the system length. In the thermodynamic limit considered in our study nearly all spectral weight of the dynamical correlation functions is for large values of n / c contained in the N = 1 momentum subdomain k ∈ [ 0 , 2 πn ] . As n / c decreases a small fraction of that weight is transferred to the remaining set of N = 2 , 3 , 4 , … momentum subdomains, particularly to the N = 2 subdomain. In the case of the momentum subdomain k ∈ [ 0 , 2 πn ] , our exact results agree with those of previous studies. For that subdomain the above exponents are plotted as a function of the momentum for several n / c values. Our derivation of the line shapes of the three dynamical correlation functions relies on the use of a simplified form of the pseudofermion dynamical theory of the fermionic 1D Hubbard model suitably modified in this paper for the 1D Bose gas.
Einstein, Bose and Bose-Einstein Statistics
NASA Astrophysics Data System (ADS)
Wali, Kameshwar C.
2005-05-01
In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8πυ^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8πυ^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.
Role of neutral gas in scrape-off layer tokamak plasma
Bisai, N.; Jha, R.; Kaw, P. K.
2015-02-15
Neutral gas in scrape-off layer of tokamak plasma plays an important role as it can modify the plasma turbulence. In order to investigate this, we have derived a simple two-dimensional (2D) model that consists of electron continuity, quasi-neutrality, and neutral gas continuity equations using neutral gas ionization and charge exchange processes. Simple 1D profile analysis predicts neutral penetration depth into the plasma. Growth rate obtained from the linear theory has been presented. The 2D model equations have been solved numerically. It is found that the neutral gas reduces plasma fluctuations and shifts spectrum of the turbulence towards lower frequency side. The neutral gas fluctuation levels have been presented. The numerical results have been compared with Aditya tokamak experiments.
Neutral Gas Outside the Disks of Local Group Galaxies
NASA Astrophysics Data System (ADS)
Lockman, Felix J.
2017-03-01
Of the three kinds of neutral gas found outside the stellar disks of Local Group galaxies, only the products of interaction, like the Magellanic Stream, have a clearly understandable origin. Both the high-velocity clouds and the faint H I between M31 and M33 remain a mystery. New observations of the region between M31 and M33 with the Green Bank Telescope show that the H I there resides in clouds with a size and mass similar to that of dwarf galaxies, but without stars. These clouds might be products of an interaction, or condensations in the hot circumgalactic medium of M31, but both these models have difficulties. The prevalence of clouds like this in the Local Group remains to be determined.
Equation of state of a polarized Fermi gas in the Bose-Einstein-condensate limit
Alzetto, F.; Leyronas, X.
2010-04-15
We present a theoretical study of the BEC-BCS crossover in the Bose-Einstein-condensate (BEC) regime in the case of an unequal number of fermions of two species. We take full account of the composite nature of the dimers made of fermions. In the limit of low densities, we calculate the ground-state energy of the system, or equivalently the chemical potentials of each species, as well as the one-particle gap and the energy of an 'impurity' immersed in a Fermi sea. For the chemical potentials we go up to order (density){sup 4/3}. The results found involve the exact atom-dimer a{sub AD} and dimer-dimer a{sub DD} scattering lengths and therefore include the three- and four-body problems in the many-body problem. We briefly comment on the importance of the different mean-field corrections for recent experiments.
Half-quantum vortex molecules in a binary dipolar Bose gas.
Shirley, Wilbur E; Anderson, Brandon M; Clark, Charles W; Wilson, Ryan M
2014-10-17
We study the ground state phases of a rotating two-component, or binary, Bose-Einstein condensate, wherein one component possesses a large permanent magnetic dipole moment. A variety of nontrivial phases emerge in this system, including a half-quantum vortex (HQV) chain phase and a HQV molecule phase, where HQVs bind at short distances. We attribute these phases to the development of a minimum in the HQV interaction potential, which emerges without coherent coupling or attractive interactions between the components. Thus, we show that the presence of dipolar interactions in this system provides a unique mechanism for the formation of HQV molecules and results in a rich ground state phase diagram.
Quenching to unitarity: Quantum dynamics in a three-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Sykes, A. G.; Corson, J. P.; D'Incao, J. P.; Koller, A. P.; Greene, C. H.; Rey, A. M.; Hazzard, K. R. A.; Bohn, J. L.
2014-02-01
We study the dynamics of a zero-temperature Bose condensate following a sudden quench of the scattering length from noninteracting to unitarity (infinite scattering length). We apply three complementary approaches to understand the momentum distribution and loss rate. First, using a time-dependent variational ansatz for the many-body state, we calculate the dynamics of the momentum distribution. Second, we demonstrate that, at short times and large momenta compared to those set by the density, the physics can be understood within a simple, analytic two-body model. We make a quantitative prediction for the evolution of Tan's contact and find features in the momentum distribution that are absent in equilibrium. Third, we study three-body loss at finite density under the same dynamic scenario. We find lifetimes that are long compared to the saturation times of large-momentum modes, and we relate this result to the three-body inelasticity parameter.
Observation of a Rosensweig Instability and Stable Quantum Droplets in a Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Pfau, Tilman; Ferrier Barbut, Igor; Kadau, Holger; Schmitt, Matthias; Wenzel, Matthias
2016-05-01
Ferrofluids show unusual hydrodynamic effects due to the magnetic nature of their constituents. For increasing magnetization a classical ferrofluid undergoes a Rosensweig instability and creates self-organized ordered surface structures or droplet crystals. We observe a related instability in a Bose-Einstein condensate with strong dipolar interactions resulting in surprisingly stable droplet crystals. We find that quantum fluctuations which are the origin of genuine quantum many-body effects cannot be neglected and provide a stabilizing mechanism. We study experimentally individual stable quantum droplets containing about 800 atoms which are expected to collapse at the mean-field level due to the essentially attractive interaction. By systematic measurements on individual droplets we demonstrate quantitatively that quantum fluctuations stabilize them against the mean-field collapse. We observe in addition interference of several droplets indicating that this stable many-body state is phase coherent.
NASA Astrophysics Data System (ADS)
Gavrilik, A. M.; Mishchenko, Yu. A.
2014-11-01
We establish the relation of the second virial coefficient of a recently proposed (μ ˜,q ) -deformed Bose gas model [A. M. Gavrilik and Yu. A. Mishchenko, Ukr. J. Phys. 58, 1171 (2013)] to the interaction and compositeness parameters when either of these factors is taken into account separately. When the interaction is dealt with, the deformation parameter becomes linked directly to the scattering length and the effective radius of interaction (in general, to scattering phases). The additionally arising temperature dependence is a feature absent in the deformed Bose gas model within the adopted interpretation of the deformation parameters μ ˜ and q . Here the problem of the temperature dependence is analyzed in detail and its possible solution is proposed.
Gavrilik, A M; Mishchenko, Yu A
2014-11-01
We establish the relation of the second virial coefficient of a recently proposed (μ[over ̃],q)-deformed Bose gas model [A. M. Gavrilik and Yu. A. Mishchenko, Ukr. J. Phys. 58, 1171 (2013)] to the interaction and compositeness parameters when either of these factors is taken into account separately. When the interaction is dealt with, the deformation parameter becomes linked directly to the scattering length and the effective radius of interaction (in general, to scattering phases). The additionally arising temperature dependence is a feature absent in the deformed Bose gas model within the adopted interpretation of the deformation parameters μ[over ̃] and q. Here the problem of the temperature dependence is analyzed in detail and its possible solution is proposed.
NASA Astrophysics Data System (ADS)
Peletminskii, A. S.; Peletminskii, S. V.; Slyusarenko, Yu V.
2017-07-01
We study a many-body system of interacting fermionic atoms of two species that are in thermodynamic equilibrium with their condensed heteronuclear bound states (molecules). In order to describe such an equilibrium state, we use a microscopic approach that involves the Bogoliubov model for a weakly interacting Bose gas and approximate formulation of the second quantization method in the presence of bound states of particles elaborated earlier by the authors. This microscopic approach is valid at low temperatures, when the average kinetic energy of all the components in the system is small in comparison with the bound state energy. The coupled equations, which relate the chemical potentials of fermionic components and molecular condensate density, are obtained within the proposed theory. At zero temperature, these equations are analyzed both analytically and numerically, attracting the relevant experimental data. We find the conditions at which a condensate of heteronuclear molecules coexists in equilibrium with degenerate components of a Fermi gas. The ground state energy and single-particle excitation spectrum are found. The boundaries of the applicability of the developed microscopic approach are analyzed.
Transport of an interacting Bose gas in 1D disordered lattices
D'Errico, C.; Chaudhuri, S.; Gori, L.; Kumar, A.; Lucioni, E.; Tanzi, L.; Inguscio, M.; Modugno, G.
2014-08-20
We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass transition.
NASA Astrophysics Data System (ADS)
Parisi, L.; Giorgini, S.
2017-02-01
We present a theoretical study based upon quantum Monte Carlo methods of the Bose polaron in one-dimensional systems with contact interactions. In this instance of the problem of a single impurity immersed in a quantum bath, the medium is a Lieb-Liniger gas of bosons ranging from the weakly interacting to the Tonks-Girardeau regime, whereas the impurity is coupled to the bath via a different contact potential, producing both repulsive and attractive interactions. Both the case of a mobile impurity, having the same mass as the particles in the medium, and the case of a static impurity with infinite mass are considered. We make use of numerical techniques that allow us to calculate the ground-state energy of the impurity, its effective mass, and the contact parameter between the impurity and the bath. These quantities are investigated as a function of the strength of interactions between the impurity and the bath and within the bath. In particular, we find that the effective mass rapidly increases to very large values when the impurity gets strongly coupled to an otherwise weakly repulsive bath. This heavy impurity hardly moves within the medium, thereby realizing the "self-localization" regime of the Landau-Pekar polaron. Furthermore, we compare our results with predictions of perturbation theory valid for weak interactions and with exact solutions available when the bosons in the medium behave as impenetrable particles.
NASA Astrophysics Data System (ADS)
Hanai, R.; Littlewood, P. B.; Ohashi, Y.
2016-05-01
We theoretically investigate a Bose-condensed exciton gas out of equilibrium. Within the framework of the combined BCS-Leggett strong-coupling theory with the non-equilibrium Keldysh formalism, we show how the Bose-Einstein condensation (BEC) of excitons is suppressed to eventually disappear, when the system is in the non-equilibrium steady state. The supply of electrons and holes from the bath is shown to induce quasi-particle excitations, leading to the partial occupation of the upper branch of Bogoliubov single-particle excitation spectrum. We also discuss how this quasi-particle induction is related to the suppression of exciton BEC, as well as the stability of the steady state.
NASA Astrophysics Data System (ADS)
Wali, Kameshwar C.
2005-04-01
In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8πυ^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8πυ^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.
Three-dimensional modeling of the neutral gas depletion effect in a helicon discharge plasma
NASA Astrophysics Data System (ADS)
Kollasch, Jeffrey; Schmitz, Oliver; Norval, Ryan; Reiter, Detlev; Sovinec, Carl
2016-10-01
Helicon discharges provide an attractive radio-frequency driven regime for plasma, but neutral-particle dynamics present a challenge to extending performance. A neutral gas depletion effect occurs when neutrals in the plasma core are not replenished at a sufficient rate to sustain a higher plasma density. The Monte Carlo neutral particle tracking code EIRENE was setup for the MARIA helicon experiment at UW Madison to study its neutral particle dynamics. Prescribed plasma temperature and density profiles similar to those in the MARIA device are used in EIRENE to investigate the main causes of the neutral gas depletion effect. The most dominant plasma-neutral interactions are included so far, namely electron impact ionization of neutrals, charge exchange interactions of neutrals with plasma ions, and recycling at the wall. Parameter scans show how the neutral depletion effect depends on parameters such as Knudsen number, plasma density and temperature, and gas-surface interaction accommodation coefficients. Results are compared to similar analytic studies in the low Knudsen number limit. Plans to incorporate a similar Monte Carlo neutral model into a larger helicon modeling framework are discussed. This work is funded by the NSF CAREER Award PHY-1455210.
Fedichev, Petr O; Fischer, Uwe R
2003-12-12
We propose an experimental scheme to observe the Gibbons-Hawking effect in the acoustic analog of a (1+1)-dimensional de Sitter universe, produced in an expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level system created at the center of the trap, an atomic quantum dot interacting with phonons, observes a thermal Bose distribution at the de Sitter temperature.
A new apparatus for studies of quantized vortex dynamics in dilute-gas Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Newman, Zachary L.
The presence of quantized vortices and a high level of control over trap geometries and other system parameters make dilute-gas Bose-Einstein condensates (BECs) a natural environment for studies of vortex dynamics and quantum turbulence in superfluids, primary interests of the BEC group at the University of Arizona. Such research may lead to deeper understanding of the nature of quantum fluid dynamics and far-from-equilbrium phenomena. Despite the importance of quantized vortex dynamics in the fields of superfluidity, superconductivity and quantum turbulence, direct imaging of vortices in trapped BECs remains a significant technical challenge. This is primarily due to the small size of the vortex core in a trapped gas, which is typically a few hundred nanometers in diameter. In this dissertation I present the design and construction of a new 87Rb BEC apparatus with the goal of studying vortex dynamics in trapped BECs. The heart of the apparatus is a compact vacuum chamber with a custom, all-glass science cell designed to accommodate the use of commercial high-numerical-aperture microscope objectives for in situ imaging of vortices. The designs for the new system are, in part, based on prior work in our group on in situ imaging of vortices. Here I review aspects of our prior work and discuss some of the successes and limitations that are relevant to the new apparatus. The bulk of the thesis is used to described the major subsystems of the new apparatus which include the vacuum chamber, the laser systems, the magnetic transfer system and the final magnetic trap for the atoms. Finally, I demonstrate the creation of a BEC of ˜ 2 x 106 87Rb atoms in our new system and show that the BEC can be transferred into a weak, spherical, magnetic trap with a well defined magnetic field axis that may be useful for future vortex imaging studies.
NASA Astrophysics Data System (ADS)
Matsui, Kei; Ikenaga, Noriaki; Sakudo, Noriyuki
2015-09-01
We investigate the mechanism of the sterilization with plasma-excited neutral gas that uniformly sterilizes both the space and inner wall of the reactor chamber at atmospheric pressure. Only reactive neutral species such as plasma-excited gas molecules and radicals are separated from the plasma and sent to the reactor chamber for chemical sterilization. The plasma source gas uses humidified mixture of nitrogen and oxygen. Geobacillus stearothermophilus spores and tyrosine which is amino acid are treated by the plasma-excited neutral gas. Shape change of the treated spore is observed by SEM, and chemical modification of the treated tyrosine is analyzed by HPLC. As a result, the surface of the treated spore shows depression. Hydroxylation and nitration of tyrosine are shown after the treatment. For these reasons, we believe that the sterilization with plasma-excited neutral gas results from the deformation of spore structure due to the chemical modification of amino acid.
NASA Astrophysics Data System (ADS)
Duan-Liang, Xiao; Meng-Yun, Lai; Xiao-Yin, Pan
2016-01-01
We investigate the thermodynamic properties of an ideal charged Bose gas confined in an anisotropic harmonic potential and a constant magnetic field. Using an accurate density of states, we calculate analytically the thermodynamic potential and consequently various intriguing thermodynamic properties, including the Bose-Einstein transition temperature, the specific heat, magnetization, and the corrections to these quantities due to the finite number of particles are also given explicitly. In contrast to the infinite number of particles scenarios, we show that those thermodynamic properties, particularly the Bose-Einstein transition temperature depends upon the strength of the magnetic field due to the finiteness of the particle numbers, and the collective effects of a finite number of particles become larger when the particle number decreases. Moreover, the magnetization varies with the temperature due to the finiteness of the particle number while it keeps invariant in the thermodynamic limit N → ∞. Project supported by the National Natural Science Foundation of China (Grant No. 11375090), and the K. C. Wong Magna Foundation of Ningbo University, China.
NASA Astrophysics Data System (ADS)
Wahl, Christian; Brausemann, Rudolf; Schmitt, Julian; Vewinger, Frank; Christopoulos, Stavros; Weitz, Martin
2016-12-01
Bose-Einstein condensation is a phenomenon well known for material particles as cold atomic gases, and this concept has in recent years been extended to photons confined in microscopic optical cavities. Essential for the operation of such a photon condensate is a thermalization mechanism that conserves the average particle number, as in the visible spectral regime can be realized by subsequent absorption re-emission processes in dye molecules. Here we report on the status of an experimental effort aiming at the extension of the concept of Bose-Einstein condensation of photons towards the vacuum ultraviolet spectral regime, with gases at high-pressure conditions serving as a thermalization medium for the photon gas. We have recorded absorption spectra of xenon gas at up to 30 bar gas pressure of the 5p^6-5p^56s transition with a wavelength close to 147 nm. Moreover, spectra of ethylene noble gas mixtures between 158 and 180 nm wavelength are reported.
Kovalev, Vadim Mikhailovich; Tse, Wang-Kong
2017-09-01
We develop a microscopic theory for the relaxation dynamics of an optically pumped two-level system (TLS) coupled to a bath of weakly interacting Bose gas. Using Keldysh formalism and diagrammatic perturbation theory, expressions for the relaxation times of the TLS Rabi oscillations are derived when the boson bath is in the normal state and the Bose-Einstein condensate (BEC) state. We apply our general theory to consider an irradiated quantum dot coupled with a boson bath consisting of a two-dimensional dipolar exciton gas. When the bath is in the BEC regime, relaxation of the Rabi oscillations is due to both condensate and non-condensate fractions of the bath bosons for weak TLS-light coupling and dominantly due to the non-condensate fraction for strong TLS-light coupling. Our theory also shows that a phase transition of the bath from the normal to the BEC state strongly influences the relaxation rate of the TLS Rabi oscillations. The TLS relaxation rate is approximately independent of the pump field frequency and monotonically dependent on the field strength when the bath is in the low-temperature regime of the normal phase. Phase transition of the dipolar exciton gas leads to a non-monotonic dependence of the TLS relaxation rate on both the pump field frequency and field strength, providing a characteristic signature for the detection of BEC phase transition of the coupled dipolar exciton gas. © 2017 IOP Publishing Ltd.
Satyendranath Bose: Co-Founder of Quantum Statistics
ERIC Educational Resources Information Center
Blanpied, William A.
1972-01-01
Satyendranath Bose was first to prove Planck's Law by using ideal quantum gas. Einstein credited Bose for this first step in the development of quantum statistical mechanics. Bose did not realize the importance of his work, perhaps because of peculiar academic settings in India under British rule. (PS)
Desbuquois, Rémi; Yefsah, Tarik; Chomaz, Lauriane; Weitenberg, Christof; Corman, Laura; Nascimbène, Sylvain; Dalibard, Jean
2014-07-11
We present a general "fit-free" method for measuring the equation of state (EoS) of a scale-invariant gas. This method, which is inspired from the procedure introduced by Ku et al. [Science 335, 563 (2012)] for the unitary three-dimensional Fermi gas, provides a general formalism which can be readily applied to any quantum gas in a known trapping potential, in the frame of the local density approximation. We implement this method on a weakly interacting two-dimensional Bose gas across the Berezinskii-Kosterlitz-Thouless transition and determine its EoS with unprecedented accuracy in the critical region. Our measurements provide an important experimental benchmark for classical-field approaches which are believed to accurately describe quantum systems in the weakly interacting but nonperturbative regime.
Fiber Bragg grating-based temperature sensor for neutral gas in capacitively coupled plasmas
NASA Astrophysics Data System (ADS)
Liu, Zigeng; Han, Daoman; Zhang, Xinpu; Liu, Yongxin; Peng, Wei; Wang, Younian
2016-11-01
A fiber Bragg grating (FBG) has been utilized in capacitively coupled plasmas (CCP) for thermometry of neutral gas. We studied the effects of high frequency and low frequency power on radial distribution of neutral gas temperature. The result shows that the neutral gas temperature increases with increasing high frequency power. However, the presence of low frequency power will decrease the neutral gas temperature. Particularly, we eliminated the effect of ion bombardment on temperature measurement by studying axial distribution near plasma-sheath boundary. With features of immune to electromagnetic interference, high precision, and spatial resolving power, the FBG is a commendable candidate for CCP or other radio-frequency plasmas thermometry in both laboratory and industry.
NASA Astrophysics Data System (ADS)
Plata, J.
2006-07-01
The effect of magnetic-field modulation on a Fermi gas of atoms in the BCS-BEC crossover is studied analytically. Recent experimental findings on the system response to a sinusoidal variation of the field are explained. Specifically, the dissociation processes induced by the modulation in the Bose-Einstein condensate regime are described. The role played by the frequency, amplitude, and application time of the perturbation in the emergence of the observed behavior is clarified. The results uncover also the relevance of the detuning from the Feshbach resonance to the appearance of particular spectral features. The applicability of the field modulation as a spectroscopic tool for probing the crossover is discussed.
Gas utilization in TFTR (Tokamak Fusion Test Reactor) neutral beam injectors
Kamperschroer, J.H.; Gammel, G.M.; Kugel, H.W.; Grisham, L.R.; Stevenson, T.N.; von Halle, A.; Williams, M.D.
1987-08-01
Measurements of gas utilization in a test TFTR neutral beam injector have been performed to study the feasibility of running tritium neutral beams with existing ion sources. Gas consumption is limited by the restriction of 50,000 curies of T/sub 2/ allowed on site. It was found that the gas efficiency of the present long-pulse ion sources is higher than it was with previous short-pulse sources. Gas efficiencies were studied over the range of 35 to 55%. At the high end of this range the neutral fraction of the beam fell below that predicted by room temperature molecular gas flow. This is consistent with observations made on the JET injectors, where it has been attributed to beam heating of the neutralizer gas and a concomitant increase in conductance. It was found that a working gas isotope exchange from H/sub 2/ to D/sub 2/ could be accomplished on the first beam shot after changing the gas supply, without any intermediate preconditioning. The mechanism believed responsible for this phenomenon is heating of the plasma generator walls by the arc and a resulting thermal desorption of all previously adsorbed and implanted gas. Finally, it was observed that an ion source conditioned to 120 kV operation could produce a beam pulse after a waiting period of fourteen hours by preceding the beam extraction with several hi-pot/filament warm-up pulses, without any gas consumption. 18 refs., 7 figs., 2 tabs.
Finite-momentum superfluidity and phase transitions in a p-wave resonant Bose gas
Choi, Sungsoo; Radzihovsky, Leo
2011-10-15
We study a degenerate two-species gas of bosonic atoms interacting through a p-wave Feshbach resonance as, for example, realized in a {sup 85}Rb-{sup 87}Rb mixture. We show that, in addition to a conventional atomic and a p-wave molecular spinor-1 superfluidity at large positive and negative detunings, respectively, the system generically exhibits a finite-momentum atomic-molecular superfluidity at intermediate detuning around the unitary point. We analyze the detailed nature of the corresponding phases and the associated quantum and thermal phase transitions.
Density form factors of the 1D Bose gas for finite entropy states
NASA Astrophysics Data System (ADS)
De Nardis, J.; Panfil, M.
2015-02-01
We consider the Lieb-Liniger model for a gas of bosonic δ-interacting particles. Using Algebraic Bethe Ansatz results we compute the thermodynamic limit of the form factors of the density operator between finite entropy eigenstates such as finite temperature states or generic non-equilibrium highly excited states. These form factors are crucial building blocks to obtain the thermodynamic exact dynamic correlation functions of such physically relevant states. As a proof of principle we compute an approximated dynamic structure factor by including only the simplest types of particle-hole excitations and show the agreement with known results.
Understanding of Neutral Gas Transport in the Alcator C-Mod Tokamak Divertor
D.P. Stotler; C.S. Pitcher; C.J. Boswell; B. LaBombard; J.L. Terry; J.D. Elder; S. Lisgo
2002-05-07
A series of experiments on the effect of divertor baffling on the Alcator C-Mod tokamak provides stringent tests on models of neutral gas transport in and around the divertor region. One attractive feature of these experiments is that a trial description of the background plasma can be constructed from experimental measurements using a simple model, allowing the neutral gas transport to be studied with a stand-alone code. The neutral-ion and neutral-neutral elastic scattering processes recently added to the DEGAS 2 Monte Carlo neutral transport code permit the neutral gas flow rates between the divertor and main chamber to be simulated more realistically than before. Nonetheless, the simulated neutral pressures are too low and the deuterium Balmer-alpha emission profiles differ qualitatively from those measured, indicating an incomplete understanding of the physical processes involved in the experiment. Some potential explanations are examined and opportunities for future exploration a re highlighted. Improvements to atomic and surface physics data and models will play a role in the latter.
Localized collapse and revival of coherence in an ultracold Bose gas
McGuirk, J. M.; Zajiczek, L. F.
2011-01-15
We study the collapse and revival of coherence induced by dipolar spin waves in a trapped gas of {sup 87}Rb atoms. In particular, we observe spatially localized collapse and revival of Ramsey fringe contrast and show how the pattern of coherence depends on the strength of the spin-wave excitation. We find that the spatial character of the coherence dynamics is incompatible with a simple model based only on position-space overlap of wave functions. We show that this phenomenon requires a full phase-space description of the atomic spin using a quantum Boltzmann transport equation, which highlights spin-wave-induced coherent spin currents and the ensuing dynamics they drive.
Advanced neutral gas diagnostics for magnetic confinement devices
NASA Astrophysics Data System (ADS)
Wenzel, U.; Kremeyer, T.; Schlisio, G.; Marquardt, M.; Pedersen, T. S.; Schmitz, O.; Mackie, B.; Maisano-Brown, J.; the W7-X team
2017-09-01
For the study of particle exhaust in nuclear fusion devices the neutral pressure must be measured in strong magnetic fields. We describe as an example the neutral pressure gauges in the Wendelstein 7-X stellarator. Two types are used: hot cathode ionization gauges (or ASDEX pressure gauges) and Penning gauges. We show some results from the first experimental campaign. The main problems were runtime effects and the failure of some ASDEX pressure gauges. To improve the reliability we integrated a new LaB6 electron emitter into the ASDEX pressure gauges. In addition, a special Penning gauge without permanent magnets was developed in order to operate Penning gauges near the plasma edge. These new pressure gauges will be used in the upcoming campaign of Wendelstein 7-X.
Neutral gas heating via non-resonant optical lattices
NASA Astrophysics Data System (ADS)
Cornella, Barry Michael
The influence of intense optical lattices on atoms or molecules offers a particularly useful method for energy and momentum deposition into a non-resonant gas. In this investigation, a proof-of-concept experiment was conducted to validate high intensity pulsed optical lattices as a means of creating high temperature gases for a myriad of aerospace, basic physics, and nanotechnology applications. Traditional methods for creating these flows have either involved altering the chemical composition of the initial gas sample through combustion or ionization or relied on laser resonant interactions with internal energy modes through laser pyrolysis. Due to its non-resonant nature, the use of optical lattices might be beneficial compared to existing methods since it provides an arbitrary, localized, high temperature gas that is tunable and does not introduce unwanted chemical species or high ionization concentrations. As an intermediate step toward verifying optical lattice gas heating, a coherent Rayleigh-Brillouin scattering (CRBS) study was also performed to verify the presented methodology. CRBS is a gas diagnostic technique used for non-intrusive probing of gas thermodynamic properties. In addition to the experimental investigation, a complementary numerical study was conducted using a direct simulation Monte Carlo approach. The numerical study used a modified version of SMILE to predict the gas phenomena within the strong optical potential fields. The goal of substantiating optical lattice heating was accomplished by detecting the acoustic wave generated from the heated volume. The magnitude of the resulting acoustic wave was shown to vary with the optical lattice phase velocity, peaking on the order of the gas' most probable speed. The trend with lattice velocity is consistent with both theory and the numerical study and eliminates other possible heating mechanisms such as laser-induced ionization or molecular dissociation. Limitations for the investigated heating
Investigation of the Neutral Gas Pressure Effect on the Metal Resistive Bolometer
Zhang, D.; Giannone, L.; Piechotka, M.; Windisch, T.; Klinger, T.; Grulke, O.; Stark, A.
2008-03-19
The bolometer system planned for W7-X consists mainly of metal (Au) resistive detector arrays. All the detectors are exposed to neutral gas environment. The thin bolometer foil used for detecting the radiated power loss may be sensitive to the neutral gas pressure due to the strain gauge effect. Recently, a prototype of this kind of bolometer camera consisting of 12 channels has been installed on the cylindrical plasma device VINETA in order to investigate the influences of the neutral gas pressure on the bolometer signals. Experiments are carried out for Ar-discharges under different gas pressure conditions. It is found that the pressure effect of the neutral gas can make considerable contributions, thus inducing non-negligible errors of the results in most of the investigated cases. Using the VINETA plasmas (Ar, T{sub e}<10 eV, n{sub e}<10{sup -19} m{sup -3}) as examples, the paper demonstrates and discusses how to minimize the neutral gas effects, especially in the data analysis process. The radiated power and the radiation intensity profile obtained in helicon discharges are presented.
Greig, A. Charles, C.; Boswell, R. W.
2016-01-15
Rovibrational spectroscopy band fitting of the nitrogen (N{sub 2}) second positive system is a technique used to estimate the neutral gas temperature of N{sub 2} discharges, or atomic discharges with trace amounts of a N{sub 2} added. For mixtures involving argon and N{sub 2}, resonant energy transfer between argon metastable atoms (Ar*) and N{sub 2} molecules may affect gas temperature estimates made using the second positive system. The effect of Ar* resonance energy transfer is investigated here by analyzing neutral gas temperatures of argon-N{sub 2} mixtures, for N{sub 2} percentages from 1% to 100%. Neutral gas temperature estimates are higher than expected for mixtures involving greater than 5% N{sub 2} addition, but are reasonable for argon with less than 5% N{sub 2} addition when compared with an analytic model for ion-neutral charge exchange collisional heating. Additional spatiotemporal investigations into neutral gas temperature estimates with 10% N{sub 2} addition demonstrate that although absolute temperature values may be affected by Ar* resonant energy transfer, spatiotemporal trends may still be used to accurately diagnose the discharge.
Method and apparatus for confinement of ions in the presence of a neutral gas
Peurrung, Anthony J.; Barlow, Stephan E.
1999-01-01
The present invention is an apparatus and method for combining ions with a neutral gas and flowing the mixture with a radial flow component through a magnetic field so that the weakly ionized gas is confined by the neutral gas. When the weakly ionized gas is present in sufficient density, a weakly ionized non-neutral plasma is formed that may be trapped in accordance with the present invention. Applications for a weakly ionized non-neutral plasma exploit the trap's ability to store and manipulate ionic species in the presence of neutral gas. The trap may be connected to a mass spectrometer thereby permitting species identification after a fixed period of time. Delicate and/or heavy particles such as clusters may be held and studied in a "gentle" environment. In addition, the trap can provide a relatively intense, low-energy source of a particular ion species for surface implantation or molecular chemistry. Finally, a long trap may permit spectroscopy of unprecedented accuracy to be performed on ionic species.
Method and apparatus for confinement of ions in the presence of a neutral gas
Peurrung, A.J.; Barlow, S.E.
1999-08-03
The present invention is an apparatus and method for combining ions with a neutral gas and flowing the mixture with a radial flow component through a magnetic field so that the weakly ionized gas is confined by the neutral gas. When the weakly ionized gas is present in sufficient density, a weakly ionized non-neutral plasma is formed that may be trapped in accordance with the present invention. Applications for a weakly ionized non-neutral plasma exploit the trap`s ability to store and manipulate ionic species in the presence of neutral gas. The trap may be connected to a mass spectrometer thereby permitting species identification after a fixed period of time. Delicate and/or heavy particles such as clusters may be held and studied in a ``gentle`` environment. In addition, the trap can provide a relatively intense, low-energy source of a particular ion species for surface implantation or molecular chemistry. Finally, a long trap may permit spectroscopy of unprecedented accuracy to be performed on ionic species. 4 figs.
Investigation of accelerated neutral atom beams created from gas cluster ion beams
NASA Astrophysics Data System (ADS)
Kirkpatrick, A.; Kirkpatrick, S.; Walsh, M.; Chau, S.; Mack, M.; Harrison, S.; Svrluga, R.; Khoury, J.
2013-07-01
A new concept for ultra-shallow processing of surfaces known as accelerated neutral atom beam (ANAB) technique employs conversion of energetic gas cluster ions produced by the gas cluster ion beam (GCIB) method into intense collimated beams of coincident neutral gas atoms having controllable average energies from less than 10 eV per atom to beyond 100 eV per atom. A beam of accelerated gas cluster ions is first produced as is usual in GCIB, but conditions within the source ionizer and extraction regions are adjusted such that immediately after ionization and acceleration the clusters undergo collisions with non-ionized gas atoms. Energy transfer during these collisions causes the energetic cluster ions to release many of their constituent atoms. An electrostatic deflector is then used to eliminate charged species, leaving the released neutral atoms to still travel collectively at the same velocities they had as bonded components of their parent clusters. Upon target impact, the accelerated neutral atom beams produce effects similar to those normally associated with GCIB, but to shallower depths, with less surface damage and with superior subsurface interfaces. The paper discusses generation and characterization of the accelerated neutral atom beams, describes interactions of the beams with target surfaces, and presents examples of ongoing work on applications for biomedical devices.
The Effects of Neutral Gas Release on Vehicle Charging: Experiment and Theory
NASA Astrophysics Data System (ADS)
Walker, D. N.; Amatucci, W. E.; Bowles, J. H.; Fernsler, R. F.; Siefring, C. L.; Antoniades, J. A.; Keskinen, M. J.
1998-11-01
This paper describes an experimental and theoretical research effort related to the mitigation of spacecraft charging by Neutral Gas Release (NGR). The Space Power Experiments Aboard Rockets programs (SPEAR I and III) [Mandel et al., 1998; Berg et al., 1995] and other earlier efforts have demonstrated that NGR is an effective method of controlling discharges in space. The laboratory experimentswere conducted in the large volume Space Physics Simulation Chamber (SPSC) at the Naval Research Laboratory (NRL). A realistic near-earth space environment can be simulated in this device for whichminimumscalingneeds to be performedtorelate the data to space plasma regimes. This environment is similar to that encountered by LEO spacecraft, e.g., the Space Station, Shuttle, and high inclination satellites. The experimental arrangement consists of an aluminum cylinder which can be biased to high negative voltage (0.4 kV
Efficiencies of gas neutralizers for multi-MeV beams of light negative ions
Grisham, L.R.; Post, D.E.; Johnson, B.M.; Jones, K.W.; Barette, J.; Kruse, T.H.; Tserruya, I.; Da-Hai, W.
1981-11-01
Measurements are reported of the neutral and charged particle fractions produced by running beams of Li/sup -/, C/sup -/, O/sup -/, and Si/sup -/ at energies up to 7 MeV through gas cells of N/sub 2/, Ar, or CO/sub 2/. We discuss the implications of these measurements for the design of neutralizers to produce high energy light atom beams for heating or current drive in tokamaks.
Interactions between anionic and neutral bromine and rare gas atoms
Buchachenko, Alexei A.; Grinev, Timur A.; Wright, Timothy G.; Viehland, Larry A.
2008-02-14
High-quality, ab initio potential energy functions are obtained for the interaction of bromine atoms and anions with atoms of the six rare gases (Rg) from He to Rn. The potentials of the nonrelativistic {sup 2}{sigma}{sup +} and {sup 2}{pi} electronic states arising from the ground-state Br({sup 2}P)-Rg interactions are computed over a wide range of internuclear separations using a spin-restricted version of the coupled cluster method with single and double excitations and noniterative correction to triple excitations [RCCSD(T)] with an extrapolation to the complete basis set limit, from basis sets of d-aug-cc-pVQZ and d-aug-cc-pV5Z quality. These are compared with potentials derived previously from experimental measurements and ab initio calculations. The same approach is used also to refine the potentials of the Br{sup -}-Rg anions obtained previously [Buchachenko et al., J. Chem. Phys. 125, 064305 (2006)]. Spin-orbit coupling in the neutral species is included both ab initio and via an atomic approximation; deviations between two approaches that are large enough to affect the results significantly are observed only in the Br-Xe and Br-Rn systems. The resulting relativistic potentials are used to compute anion zero electron kinetic energy photoelectron spectra, differential scattering cross sections, and the transport coefficients of trace amounts of both anionic and neutral bromine in the rare gases. Comparison with available experimental data for all systems considered proves a very high precision of the present potentials.
Fetal response to neutral gas and liquid media for intraamniotic distension.
Fauza, D O; Rawn, J; Fishman, S J
1999-04-01
This study was aimed at comparing the effects of a neutral liquid and a neutral gas used as intraamniotic media on umbilical blood flow, O2 delivery, blood pressure, acid-base status, and electrolytes in the fetus at escalating intraamniotic pressures. Eight fetal lambs underwent invasive monitoring of common umbilical blood flow, blood pressure, blood gases, sodium, and hematocrit, as intraamniotic pressure was raised from 0 to 30 mm Hg. The animals were divided equally in two groups depending on the intraamniotic medium used (group I, warmed saline and group II, air). Maternal systemic blood pressure, O2 saturation, and temperature were kept constant. In each group, a threshold level of intraamniotic pressure was evident, above which there was a significant decrease in the common umbilical artery blood flow, with concomitant fetal hypoxemia and hypercarbia. This intraamniotic pressure threshold was 20 mm Hg in group I (saline), but only 15 mm Hg in group II (air). Although both a neutral liquid and a neutral gas can safely be used as intraamniotic media, a neutral liquid medium allows for a wider range of safe intrauterine working pressure (0 to 20 mm Hg), as compared with a neutral gas (0-15 mm Hg).
Measurement of neutral gas temperature in a 13.56 MHz inductively coupled plasma
Jayapalan, Kanesh K.; Chin, Oi Hoong
2015-04-24
Measuring the temperature of neutrals in inductively coupled plasmas (ICP) is important as heating of neutral particles will influence plasma characteristics such as the spatial distributions of plasma density and electron temperature. Neutral gas temperatures were deduced using a non-invasive technique that combines gas actinometry, optical emission spectroscopy and simulation which is described here. Argon gas temperature in a 13.56 MHz ICP were found to fall within the range of 500 − 800 K for input power of 140 − 200 W and pressure of 0.05 − 0.2 mbar. Comparing spectrometers with 0.2 nm and 0.5 nm resolution, improved fitting sensitivity was observed for the 0.2 nm resolution.
A general model for Io's neutral gas clouds. I - Mathematical description
NASA Technical Reports Server (NTRS)
Smyth, W. H.; Combi, M. R.
1988-01-01
A general mathematical formalism for calculating the physical properties of any of Io's neutral gas clouds (Na, K, O, S, SO2) is presented. The dynamical effects of both the gravitational fields of Io and Jupiter and solar radiation pressure are included, in addition to the many complex space- and time-dependent interactions that occur between the neutral clouds and the plasma torus. The importance of this new model in studying both the plasma conditions prevalent in the inner planetary magnetosphere and the nature of Io's local atmosphere is discussed. A numerical method for evaluating the physical properties of the neutral clouds using the new model is described.
The interstellar tunnel of neutral-free gas toward Beta Canis Majoris
Welsh, B.Y. )
1991-06-01
Using high-resolution sodium absorption observations of early-type stars to determine the distribution of neutral interstellar gas in the direction of the star Beta CMa, the contours of a large feature in the local interstellar medium, some 50 pc in diameter and 300 pc long, that appears to be virtually free of neutral gas have been mapped. This rarefied 'interstellar tunnel' is an extension of a region of very low gas density surrounding the sun called the Local Bubble, which may well have been formed by the interaction of expanding interstellar cavities produced by multiple supernova events. This large region of unusually low gas density will be a prime area for study in the soft X-ray and EUV spectral regions. 21 refs.
The interstellar tunnel of neutral-free gas toward Beta Canis Majoris
NASA Technical Reports Server (NTRS)
Welsh, Barry Y.
1991-01-01
Using high-resolution sodium absorption observations of early-type stars to determine the distribution of neutral interstellar gas in the direction of the star Beta CMa, the contours of a large feature in the local interstellar medium, some 50 pc in diameter and 300 pc long, that appears to be virtually free of neutral gas have been mapped. This rarefied 'interstellar tunnel' is an extension of a region of very low gas density surrounding the sun called the Local Bubble, which may well have been formed by the interaction of expanding interstellar cavities produced by multiple supernova events. This large region of unusually low gas density will be a prime area for study in the soft X-ray and EUV spectral regions.
Trace organic compounds in rain—II. Gas scavenging of neutral organic compounds
NASA Astrophysics Data System (ADS)
Ligocki, Mary P.; Leuenberger, Christian; Pankow, James F.
Concurrent rain and air sampling was conducted for seven rain events in Portland, Oregon during February through to April of 1984. Concentration data are presented for a number of neutral organic compounds for both the rain-dissolved phase and the atmospheric gas phase. The ambient temperature averaged 8°C. Measured gas scavenging ratios ranged from 3 for tetrachloroethene to 10 5 for dibutylphthalate, and were generally 3-6 times higher than those calculated from Henry's Law constant ( H) values at 25°C taken from the literature. This discrepancy was due to the inappropriateness of applying 25°C H data at 5-10°C. Indeed, excellent agreement between the measured and predicted gas scavenging ratios was found for several polycyclic aromatic hydrocarbons for which temperature-dependent H data were available. These results demonstrate that equilibrium between rain and the atmospheric gas phase is attained for non-reactive neutral organic compounds.
Neutral Gas Properties of Extremely Isolated Early-type Galaxies
NASA Astrophysics Data System (ADS)
Ashley, Trisha; Marcum, Pamela M.; Fanelli, Michael N.
2017-04-01
We present the results of single-dish atomic hydrogen (H i) observations of six highly isolated early-type galaxies. These objects are a representative subset of galaxies previously studied at optical wavelengths and selected to be separated by at least 2.5 Mpc from companions brighter than M V = -16.5 mag. Each galaxy was observed with a single pointing using the NRAO Green Bank Telescope L-band receiver. Five of these systems were strongly detected in H i. These five galaxies exhibit H i profiles with a range of properties: single Gaussian-like peaks, separate double peaks, and double horn-like profiles. The four bluest galaxies (B-V < 0.54) all contain significant gas with H i masses ranging from 1.1 × 108 to 1.4 × 109.
An apparatus for immersing trapped ions into an ultracold gas of neutral atoms.
Schmid, Stefan; Härter, Arne; Frisch, Albert; Hoinka, Sascha; Denschlag, Johannes Hecker
2012-05-01
We describe a hybrid vacuum system in which a single ion or a well-defined small number of trapped ions (in our case Ba(+) or Rb(+)) can be immersed into a cloud of ultracold neutral atoms (in our case Rb). This apparatus allows for the study of collisions and interactions between atoms and ions in the ultracold regime. Our setup is a combination of a Bose-Einstein condensation apparatus and a linear Paul trap. The main design feature of the apparatus is to first separate the production locations for the ion and the ultracold atoms and then to bring the two species together. This scheme has advantages in terms of stability and available access to the region where the atom-ion collision experiments are carried out. The ion and the atoms are brought together using a moving one-dimensional optical lattice transport which vertically lifts the atomic sample over a distance of 30 cm from its production chamber into the center of the Paul trap in another chamber. We present techniques to detect and control the relative position between the ion and the atom cloud.
Transport in a field aligned magnetized plasma/neutral gas boundary: the end of the plasma
NASA Astrophysics Data System (ADS)
Cooper, Christopher Michael
The objective of this dissertation is to characterize the physics of a boundary layer between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. A series of experiments are performed at the Enormous Toroidal Plasma Device (ETPD) at UCLA to study this field aligned Neutral Boundary Layer (NBL) at the end of the plasma. A Lanthanum Hexaboride (LaB6) cathode and semi-transparent anode creates a magnetized, current-free helium plasma which terminates on a neutral helium gas without touching any walls. Probes are inserted into the plasma to measure the basic plasma parameters and study the transport in the NBL. The experiment is performed in the weakly ionized limit where the plasma density (ne) is much less than the neutral density (nn) such that ne/nn < 5%. The NBL is characterized by a field-aligned electric field which begins at the point where the plasma pressure equilibrates with the neutral gas pressure. Beyond the pressure equilibration point the electrons and ions lose their momentum by collisions with the neutral gas and come to rest. An electric field is established self consistently to maintain a current-free termination through equilibration of the different species' stopping rates in the neutral gas. The electric field resembles a collisional quasineutral sheath with a length 10 times the electron-ion collision length, 100 times the neutral collision length, and 10,000 times the Debye length. Collisions with the neutral gas dominate the losses in the system. The measured plasma density loss rates are above the classical cross-field current-free ambipolar rate, but below the anomalous Bohm diffusion rate. The electron temperature is below the ionization threshold of the gas, 2.2 eV in helium. The ions are in thermal equilibrium with the neutral gas. A generalized theory of plasma termination in a Neutral Boundary Layer is applied to this case using a two-fluid, current-free, weakly ionized transport model. The electron
Disorder, three body interaction and Bose glass phase in a spinor atomic gas in an optical lattice
NASA Astrophysics Data System (ADS)
Nabi, Sk Noor; Basu, Saurabh
2016-10-01
We study the effects of disorder on the spin dependent interaction term of a spinor Bose Hubbard model with a three body interaction potential. The signature of the Bose glass (BG) phase is observed by computing the fraction of the lattice sites having finite superfluid (SF) order parameter and non integer occupation densities. We obtain the phase diagram both for the antiferromagnetic (AF) and ferromagnetic (F) cases via a percolation analysis. In the AF case, the BG phase intervenes between the odd-even Mott insulating (MI) lobes (for example, the lobes corresponding to occupation densities, n=1 and (n=2) but not between the even-odd MI lobes. In the ferromagnetic case, the presence of the BG phase is observed between all the MI lobes irrespective of them being even or odd. The BG phase almost destroys the first MI lobe while the MI phase looks more stable than the SF phase both in the AF and F cases due to the presence of the three body interactions.
Neutral gas jet in a low velocity shock front at the boundary of the Draco Nebula
Kalberla, P.W.M.; Herbstmeier, U.; Mebold, U.
1984-11-01
Twenty-one cm line observations with the Westerbork Synthesis Radio Telescope of a dust and molecular filament at the boundary of the Draco Nebula reveal a jet like neutral hydrogen feature funneling through an outlet in the low velocity shock front at the interface between the Draco Nebula and the surrounding gas. The jet like feature is apparently connected with a high velocity filament at VLSR -180 km/sec. It is suggested that soft X-ray emission observed in the area is thermal bremsstrahlung produced by the deceleration of high velocity gas in galactic gas.
An enhancement of plasma density by neutral gas injection observed in SEPAC Spacelab-1 experiment
NASA Technical Reports Server (NTRS)
Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Kubota, S.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.; Williamson, P. R.
1985-01-01
An enhancement of plasma density observed during a neutral gas injection in Space Experiments with Particle Accelerators by the Space Shuttle/Spacelab-1 is presented. When a plume of nitrogen gas was injected from the orbiter into space, a large amount of plasma was detected by an onboard plasma probe. The observed density often increased beyond the background plasma density and was strongly dependent on the attitude of the orbiter with respect to the velocity vector. This effect has been explained by a collisional interaction between the injected gas molecules and the ionospheric ions relatively drifting at the orbital speed.
Neutral gas heating and ion transport in a constricted plasma flow
NASA Astrophysics Data System (ADS)
Ho, Teck Seng; Charles, Christine; Boswell, Rod
2017-08-01
Ion-neutral charge exchange collisions are demonstrated to be the dominant heating mechanism in a weakly ionised ˜1 Torr Ar capacitively coupled radiofrequency plasma flowing through a cylinder. In this rarefied regime, thermal conduction is ineffective. The neutral gas temperature is significantly higher in the plasma bulk than in the plasma sheath due to different plasma parameters and ion transport behaviours in these regions. This study is achieved in a computational fluid dynamics and plasma simulation, and is applicable to similar plasmas at different pressures and physical scales.
Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density
Surrey, Elizabeth; Porton, Michael
2011-09-26
The application of neutral beams to future power plant devices (DEMO) is dependent on achieving significantly improved electrical efficiency and the most promising route to achieving this is by implementing a photoneutralizer in place of the traditional gas neutralizer. A corollary of this innovation would be a significant reduction in the background gas density through which the beam is transported between the accelerator and the neutralizer. This background gas is responsible for the space charge neutralization of the beam, enabling distances of several metres to be traversed without significant beam expansion. This work investigates the sensitivity of a D{sup -} beam to reduced levels of space charge compensation for energies from 100 keV to 1.5 MeV, representative of a scaled prototype experiment, commissioning and full energy operation. A beam transport code, following the evolution of the phase space ellipse, is employed to investigate the effect of space charge on the beam optics. This shows that the higher energy beams are insensitive to large degrees of under compensation, unlike the lower energies. The probable degree of compensation at low gas density is then investigated through a simple, two component beam-plasma model that allows the potential to be negative. The degree of under-compensation is dependent on the positive plasma ion energy, one source of which is dissociation of the gas by the beam. The subsequent space charge state of the beam is shown to depend upon the relative times for equilibration of the dissociation energy and ionization by the beam ions.
Cornell, Eric A; Wieman, Carl E
2002-06-17
Bose-Einstein condensates of dilute gases offer a rich field to study fundamental quantum-mechanical processes, manipulation of the speed at which light propogates, observation of atomic pair-formation and superfluidity, or even simulating white dwarf stars. Still more radical applications are on the horizon. However, their initial creation was a masterpiece of experimental physics. After an initial process of laser cooling (which itself won its developers the 1997 Nobel Prize), atoms in a magnetic-optical trap must be safely transferred into a purely magnetic trap, where the condensation process begins at 170 nK and 20 nK a pure condensate of 2000 atoms could be created. More astonishingly, Wieman and Cornell showed these low temperatures could be achieved in "bench scale" equipment rather than the massive pieces normally demanded by cryoscience. For their 1995 discovery of this new state of matter, they were awarded the 2001 Nobel Prize in Physics.
NASA Astrophysics Data System (ADS)
Jain, P.; Bradley, A. S.; Gardiner, C. W.
2007-08-01
We study an experimentally realizable system containing stable black hole white hole acoustic horizons in toroidally trapped Bose-Einstein condensates—the quantum de Laval nozzle. We numerically obtain stationary flow configurations and assess their stability using Bogoliubov theory, finding both in hydrodynamic and nonhydrodynamic regimes there exist dynamically unstable regions associated with the creation of positive and negative energy quasiparticle pairs in analogy with the gravitational Hawking effect. The dynamical instability takes the form of a two mode squeezing interaction between resonant pairs of Bogoliubov modes. We study the evolution of dynamically unstable flows using the truncated Wigner method, which confirms the two mode squeezed state picture of the analogue Hawking effect for low winding number.
NASA Astrophysics Data System (ADS)
Arahata, Emiko; Nikuni, Tetsuro
2013-03-01
We study sound propagation in Bose-condensed gases in a highly elongated harmonic trap at finite temperatures. This problem is studied within the framework of the Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of a generalized Gross-Pitaevskii equation for the condensate and a kinetic equation for the thermal cloud. We extend the ZNG formalism to deal with a highly anisotropic trap potential and use it to simulate sound propagation using the trap parameters corresponding to an experiment on sound pulse propagation at finite temperature. We focus on the high-density two-fluid hydrodynamic regime, and explore the possibility of observing first- and second-sound pulse propagation. The results of numerical simulation are compared with analytical results derived from linearized ZNG hydrodynamic equations. We show that the second-sound mode makes the dominant contribution to condensate motion at relatively high temperature, while the first-sound mode makes an appreciable contribution.
Collective modes of a one-dimensional trapped Bose gas in the presence of the anomalous density
NASA Astrophysics Data System (ADS)
Boudjemâa, Abdelâali
2016-11-01
We study the collective modes of a one-dimensional harmonically trapped Bose-Einstein condensate in the presence of the anomalous density using the time-dependent Hartree-Fock-Bogoliubov theory. Within the hydrodynamic equations, we derive analytical expressions for the mode frequencies and the density fluctuations of the anomalous density which constitutes the minority component at very low temperature and feels an effective external potential exerted by the majority component, i.e., the condensate. On the other hand, we numerically examine the temperature dependence of the breathing mode oscillations of the condensate at finite temperature in the weak-coupling regime. At zero temperature, we compare our predictions with available experimental data, theoretical treatments, and Monte carlo simulations in all interaction regimes and the remaining hindrances are emphasized. We show that the anomalous correlations have a non-negligible role on the collective modes at both zero and finite temperatures.
Alfalfa discovery of the nearby gas-rich dwarf galaxy LEO P. V. Neutral gas dynamics and kinematics
Bernstein-Cooper, Elijah Z.; Pardy, Stephen A.; Cannon, John M. E-mail: spardy@astro.wisc.edu; and others
2014-08-01
We present new H I spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our H I images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The H I morphology is slightly elongated along the optical major axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V {sub c} =15 ± 5 km s{sup –1}. Within the H I radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ≳15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature components in the neutral ISM of Leo P; the cold and warm components have characteristic velocity widths of 4.2 ± 0.9 km s{sup –1} and 10.1 ± 1.2 km s{sup –1}, corresponding to kinetic temperature upper limits of ∼1100 K and ∼6200 K, respectively. The cold H I component is unresolved at a physical resolution of 200 pc. The highest H I surface densities are observed in close physical proximity to the single H II region. A comparison of the neutral gas properties of Leo P with other extremely metal-deficient (XMD) galaxies reveals that Leo P has the lowest neutral gas mass of any known XMD, and that the dynamical mass of Leo P is more than two orders of magnitude smaller than any known XMD with comparable metallicity.
Collision of an Arched Plasma-Filled Flux Rope with a Target Cloud of Initially Neutral Gas
NASA Astrophysics Data System (ADS)
Wongwaitayakornkul, Pakorn; Bellan, Paul M.
2015-11-01
The Caltech solar loop experiment apparatus had been used to create an arched plasma-filled flux rope that expands to collide with a pre-injected initially-neutral gas. We investigated such a situation in two regimes: (i) plasma made by heavy gas impacting a much lighter neutral gas cloud and (ii) a light-gas plasma impacting much heavier neutral gas. The neutral gas became ionized immediately upon impact. In regime (i), multiple shock layers were formed in the target cloud; these magnetized collisionless shocks are relevant to solar physics as such shocks develop ahead of Coronal Mass Ejections and occur in Co-rotating Interaction Regions. In regime (ii), plasma expansion was inhibited. In both cases, fast camera images, magnetic probe measurements, and spectroscopy data will be reported. The analysis of plasma and shock expansion, as well as associated density and temperature changes, will be presented.
The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission
NASA Astrophysics Data System (ADS)
Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent; Johnson, Christopher S.; Kellogg, James; Kimvilakani, Patrick; Lefavor, Matthew; Hengemihle, Jerome; Jaeger, Ferzan; Lyness, Eric; Maurer, John; Melak, Anthony; Noreiga, Felix; Noriega, Marvin; Patel, Kiran; Prats, Benito; Raaen, Eric; Tan, Florence; Weidner, Edwin; Gundersen, Cynthia; Battel, Steven; Block, Bruce P.; Arnett, Ken; Miller, Ryan; Cooper, Curt; Edmonson, Charles; Nolan, J. Thomas
2015-12-01
The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution Mission (MAVEN) is designed to measure the composition, structure, and variability of the upper atmosphere of Mars. The NGIMS complements two other instrument packages on the MAVEN spacecraft designed to characterize the neutral upper atmosphere and ionosphere of Mars and the solar wind input to this region of the atmosphere. The combined measurement set is designed to quantify atmosphere escape rates and provide input to models of the evolution of the martian atmosphere. The NGIMS is designed to measure both surface reactive and inert neutral species and ambient ions along the spacecraft track over the 125-500 km altitude region utilizing a dual ion source and a quadrupole analyzer.
The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission
NASA Technical Reports Server (NTRS)
Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent; Kellogg, James; Jaeger, Ferzan; Raaen, Eric; Tan, Florence
2014-01-01
The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution Mission (MAVEN) is designed to measure the composition, structure, and variability of the upper atmosphere of Mars. The NGIMS complements two other instrument packages on the MAVEN spacecraft designed to characterize the neutral upper atmosphere and ionosphere of Mars and the solar wind input to this region of the atmosphere. The combined measurement set is designed to quantify atmosphere escape rates and provide input to models of the evolution of the martian atmosphere. The NGIMS is designed to measure both surface reactive and inert neutral species and ambient ions along the spacecraft track over the 125-500 km altitude region utilizing a dual ion source and a quadrupole analyzer.
Properties of clusters in the gas phase: V. Complexes of neutral molecules onto negative ions
Keesee, R.G.; Lee, N.; Castleman, A.W. Jr.
1980-09-01
Ion--molecules association reactions of the form A/sup -/(B)/sub n1/-+B=A/sup -/(B)/sub n/ were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl/sup -/, I/sup -/, and NO/sub 2//sup -/ with n ranging from one to three or four, and onto SO/sub 2//sup -/ and SO/sub 3//sup -/ with n equal to one; and (2) carbon dioxide onto Cl/sup -/, I/sup -/, NO/sub 2//sup -/, CO/sub 3//sup -/, and SO/sub 3//sup -/ with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions. For any given ion, the relative order of the addition enthalpies among the neutrals was found to be dependent on the polarizabilities of the neutrals and on the covalency in the ion-neutral bond. Dispersion of charge via covalent bonding was found to affect significantly the succeeding clustering steps.
Asymptotic theory of neutral stability curve of the Couette flow of vibrationally excited gas
NASA Astrophysics Data System (ADS)
Grigor'ev, Yu N.; Ershov, I. V.
2016-06-01
The asymptotic theory of neutral stability curve of the supersonic plane Couette flow of vibrationally excited gas is constructed. The system of two-temperature viscous gas dynamics equations was used as original mathematical model. Spectral problem for an eighth order linear system of ordinary differential equations was obtained from the system within framework of classical theory of linear stability. Transformations of the spectral problem universal for all shear flows were carried along the classical Dunn — Lin scheme. As a result the problem was reduced to secular algebraic equation with a characteristic division on “inviscid” and “viscous” parts which was solved numerically. The calculated neutral stability curves coincide in limits of 10% with corresponding results of direct numerical solution of original spectral problem.
Three-Dimensional Neutral Transport Simulations of Gas Puff Imaging Experiments
D.P. Stotler; D.A. DIppolito; B. LeBlanc; R.J. Maqueda; J.R. Myra; S.A. Sabbagh; S.J. Zweben
2003-09-19
Gas Puff Imaging (GPI) experiments are designed to isolate the structure of plasma turbulence in the plane perpendicular to the magnetic field. Three-dimensional aspects of this diagnostic technique as used on the National Spherical Torus eXperiment (NSTX) are examined via Monte Carlo neutral transport simulations. The radial width of the simulated GPI images are in rough agreement with observations. However, the simulated emission clouds are angled approximately 15 degrees with respect to the experimental images. The simulations indicate that the finite extent of the gas puff along the viewing direction does not significantly degrade the radial resolution of the diagnostic. These simulations also yield effective neutral density data that can be used in an approximate attempt to infer two-dimensional electron density and temperature profiles from the experimental images.
Neutral gas laser: a tool for sensing atmospheric species by infrared absorption
NASA Astrophysics Data System (ADS)
Wormhoudt, Joda C.; Kebabian, Paul L.
1994-07-01
In the spectroscopic analysis of atmospheric composition, there is a continuing need for stable and reproducible mid-infrared light sources. The neutral rare gas lasers offer several important benefits, in the many cases where one of their lines coincides with an absorption line of an atmospheric species to be observed. As atomic spectral lines, they are not subject to the drift and aging effects seen in diode lasers. Furthermore, the Zeeman effect provides up to a few tenths of a wavenumber of tunability, which can be an advantage over molecular lasers (such as CO2) which can only be tuned by line selection. We present observations in applications of neutral rare gas lasers to measurements of CO, N2O and CH4, and discuss possible applications to a variety of other species, including formaldehyde, methanol, hydrazine, water vapor, and the methyl radical.
Digital image analysis of four-frame holographic plasma and neutral gas interferograms
Mastin, G.A.; Allen, G.R.
1985-01-01
Diagnostic interferograms characterizing the dynamics of plasma and neutral in the anode-cathode gap of magnetically insulated transmission lines (MITL) are well suited for digital image analysis. The presence of plasma or a neutral gas near the cathode surface produces bending of a pattern of background fringes on the interferogram; the fringes would be straight and uniformly spaced in the absence of such a perturbation. Because the fringes are periodic, we can perform a Fast Fourier Transform (FFT) and extract the phase of the dominant spatial frequency component of the fringe pattern. The fringe phase shift is proportional to the plasma electron or neutral gas density. Futhermore, the location of the plasma-cathode interface can be estimated from the interferogram so that electron density as a function of distance from the cathode surface can be computed. This report introduces the technical problem, examines the image analysis algorithm and presents diagnostic interferogram analysis results. The ability to reliably extract and estimate quantitative parameters from interferograms via digital image analysis is emphasized. This image analysis technique is applicable to a broad class of interferograms where a background fringe pattern is distorted by the refractive index of a plasma or gas.
A Ring with a Spin: Superfluidity in a toroidal Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Ramanathan, Anand Krishnan
2011-12-01
Superfluidity is a remarkable phenomenon. Superfluidity was initially characterized by flow without friction, first seen in liquid helium in 1938, and has been studied extensively since. Superfluidity is believed to be related to, but not identical to Bose-Einstein condensation, a statistical mechanical phenomena predicted by Albert Einstein in 1924 based on the statistics of Satyendra Nath Bose, where bosonic atoms make a phase transition to form a Bose-Einstein condensate (BEC), a gas which has macroscopic occupation of a single quantum state. Developments in laser cooling of neutral atoms and the subsequent realization of Bose-Einstein condensates in ultracold gases have opened a new window into the study of superfluidity and its relation to Bose-Einstein condensation. In our atomic sodium BEC experiment, we studied superfluidity and dissipationless flow in an all-optical toroidal trap, constructed using the combination of a horizontal "sheet"-like beam and vertical "ring"-like beam, which, like a circuit loop, allows flow around the ring. On inducing a single quantum of circulation in the condensate, the smoothness and uniformity of the toroidal BEC enabled the sustaining of a persistent current lasting 40 seconds, limited by the lifetime of the BEC due to background gas pressure. This success set the stage for further experiments studying superfluidity. In a first set of experiments, we studied the stability of the persistent current by inserting a barrier in the flow path of the ring. The superflow stopped abruptly at a barrier strength such that the local flow velocity at the barrier exceeded a critical velocity, which supported decay via the creation of a vortex-antivortex pair. Our precise control in inducing and arresting superflow in the BEC is a first step toward studying other aspects of superfluidity, such as the effect of temperature and dimensionality. This thesis discusses these experiments and also details partial-transfer absorption imaging, an
Competition between Bose-Einstein Condensation and Spin Dynamics.
Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B
2016-10-28
We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.
NASA Astrophysics Data System (ADS)
Rubin, Martin; Toth, Gabor; Tenishev, Valeriy; Fougere, Nicolas; Huang, Zhenguang
2016-07-01
Comets are surrounded by an extended gas and dust coma. Neutral particles are continuously ionized by solar irradiation and then picked-up by the solar wind. This leads to a complex interaction between the neutral gas coma and the solar wind, which changes over the course of the comet's orbit around the Sun. The European Space Agency's Rosetta spacecraft has been in orbit around comet 67P/Churyumov-Gerasimenko since August 2014. Rosetta carries several instruments to investigate the comet's nucleus and surrounding neutral gas coma and plasma. Part of the payload is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) that consists of two mass spectrometers and a pressure sensor. ROSINA was designed to measure the neutral gas abundance and composition and low energy ions in the coma in situ. ROSINA observations have shown that the coma is very heterogeneous both in total density and composition of the neutral gas. This heterogeneity is driven in large part by the complex shape of the nucleus and the varying illumination conditions associated with the comet's rotation. In this presentation we will show the time-dependent distribution of the major volatiles around the comet constrained by ROSINA observations. Furthermore we will investigate the impact of the highly non-symmetric neutral gas coma on the interaction of the solar wind with the comet.
Ground-state phases of the spin-orbit-coupled spin-1 Bose gas in a toroidal trap
NASA Astrophysics Data System (ADS)
Wang, Ji-Guo; Xu, Liang-Liang; Yang, Shi-Jie
2017-09-01
We consider the spin-1 Bose-Einstein condensates with the isotropic Rashba spin-orbit coupling in a two-dimensional toroidal trap. Three types of striped phases are found in a nonrotational system, i.e., the stripe phase with the periodic density modulation along the azimuthal direction, the stripe phase with the periodic density modulation along both the azimuthal and the radial directions, and the stripe phase with the periodic density modulation along the radial direction. By adding the rotation, the condensates occupy the mF=0 component for small rotational frequency, while they occupy both the mF=1 and mF=-1 components for large rotational frequency when both the relative interaction and the spin-orbit coupling are weak. For the stronger relative interaction and spin-orbit coupling, the vortices of the system are elongated along the radial direction and linked one after another. As the rotational frequency further increases, the density evolves from the elongated effect of the vortices into a laminar vortex ring.
Si II mapping of the neutral gas ring in the Galactic center - Evidence for dust destruction
NASA Technical Reports Server (NTRS)
Herter, T.; Gull, G. E.; Megeath, S. T.; Rowlands, N.; Houck, J. R.
1989-01-01
The distribution of Si II emission in the Galactic center has been measured and found to extend beyond 4 pc from the center. The observed forbidden Si II 34.8 micron line, which is thermally excited by H I and H2 collisions, originates from the photodissociation region formed in the neutral gas ring surrounding the ionized core. Two peaks in the Si II emission are found, one lying 20 arcsec northeast of Sgr A-asterisk along the Galactic plane and the other located about 80 arcsec north of Sgr A-asterisk. The latter peak is located beyond the northern arm seen in the ionized gas. The ratio of Si II to dust mass density varies in the ring, indicating changes in the gas-to-dust ratio. The mass density of Si II and dust are anticorrelated, indicating that Si II tracks the destruction of dust.
Gas-Phase Oxidation of Neutral Basic Residues in Polypeptide Cations by Periodate.
Pilo, Alice L; Bu, Jiexun; McLuckey, Scott A
2016-12-01
The gas-phase oxidation of doubly protonated peptides containing neutral basic residues to various products, including [M + H + O](+), [M - H](+), and [M - H - NH3](+), is demonstrated here via ion/ion reactions with periodate. It was previously demonstrated that periodate anions are capable of oxidizing disulfide bonds and methionine, tryptophan, and S-alkyl cysteine residues. However, in the absence of these easily oxidized sites, we show here that systems containing neutral basic residues can undergo oxidation. Furthermore, we show that these neutral basic residues primarily undergo different types of oxidation (e.g., hydrogen abstraction) reactions than those observed previously (i.e., oxygen transfer to yield the [M + H + O](+) species) upon gas-phase ion/ion reactions with periodate anions. This chemistry is illustrated with a variety of systems, including a series of model peptides, a cell-penetrating peptide containing a large number of unprotonated basic sites, and ubiquitin, a roughly 8.6 kDa protein. Graphical Abstract ᅟ.
Asymptotic theory of neutral stability of the Couette flow of a vibrationally excited gas
NASA Astrophysics Data System (ADS)
Grigor'ev, Yu. N.; Ershov, I. V.
2017-01-01
An asymptotic theory of the neutral stability curve for a supersonic plane Couette flow of a vibrationally excited gas is developed. The initial mathematical model consists of equations of two-temperature viscous gas dynamics, which are used to derive a spectral problem for a linear system of eighth-order ordinary differential equations within the framework of the classical linear stability theory. Unified transformations of the system for all shear flows are performed in accordance with the classical Lin scheme. The problem is reduced to an algebraic secular equation with separation into the "inviscid" and "viscous" parts, which is solved numerically. It is shown that the thus-calculated neutral stability curves agree well with the previously obtained results of the direct numerical solution of the original spectral problem. In particular, the critical Reynolds number increases with excitation enhancement, and the neutral stability curve is shifted toward the domain of higher wave numbers. This is also confirmed by means of solving an asymptotic equation for the critical Reynolds number at the Mach number M ≤ 4.
Gas-Phase Oxidation of Neutral Basic Residues in Polypeptide Cations by Periodate
NASA Astrophysics Data System (ADS)
Pilo, Alice L.; Bu, Jiexun; McLuckey, Scott A.
2016-12-01
The gas-phase oxidation of doubly protonated peptides containing neutral basic residues to various products, including [M + H + O]+, [M - H]+, and [M - H - NH3]+, is demonstrated here via ion/ion reactions with periodate. It was previously demonstrated that periodate anions are capable of oxidizing disulfide bonds and methionine, tryptophan, and S-alkyl cysteine residues. However, in the absence of these easily oxidized sites, we show here that systems containing neutral basic residues can undergo oxidation. Furthermore, we show that these neutral basic residues primarily undergo different types of oxidation (e.g., hydrogen abstraction) reactions than those observed previously (i.e., oxygen transfer to yield the [M + H + O]+ species) upon gas-phase ion/ion reactions with periodate anions. This chemistry is illustrated with a variety of systems, including a series of model peptides, a cell-penetrating peptide containing a large number of unprotonated basic sites, and ubiquitin, a roughly 8.6 kDa protein.
Abdullaev, F.Kh.; Garnier, J.
2004-11-01
The collective oscillations of one-dimensional (1D) repulsive Bose gas with external harmonic confinement in two different regimes are studied. The first regime is the mean-field regime when the density is high. The second regime is the Tonks-Girardeau regime when the density is low. We investigate the resonances under periodic modulations of the trap potential and the effective nonlinearity. Modulations of the effective nonlinear coefficient result from modulations of the atomic scattering length by the Feshbach resonance method or variations of the transverse trap frequency. In the mean-field regime we predict bistability in the nonlinear oscillations of the condensate. In the Tonks-Girardeau regime the resonance has the character of a linear parametric resonance. In the case of rapid strong modulations of the nonlinear coefficient we find analytical expressions for the nonlinearity managed soliton width and the frequency of the slow secondary oscillations near the fixed point. We confirm the analytical predictions by direct numerical simulations of the 1D Gross-Pitaevskii equation and the effective nonlinear Schroedinger equation with quintic nonlinearity and trap potential.
Sakhel, Asaad R.; Qashou, Saleem I.; Sakhel, Roger R.; Ghassib, Humam B.
2010-12-15
The static fluctuation approximation (SFA) is applied to compute the thermodynamic properties of a trapped two-dimensional (2D) interacting hard-sphere (HS) Bose gas in the weakly and strongly interacting regime. A mean-field approach involving a variational wave function is used to compute the mean-field energy as a function of temperature for each harmonic oscillator (HO) state plugged into the SFA technique. In the variational approach, a parameter {alpha} is introduced into the harmonic oscillator wave function in order to take into account the changes in the width when the repulsive interactions between the bosons are increased. In the weakly interacting regime, below the critical temperature, the total energy of all HO states (evaluated by our model) matches the noninteracting result very well. However, beyond the critical temperature, we 'fit' our energies to the classical limit for 2D bosons in a trap by using a suitably proposed weighting function. We compare our results to earlier results of mean-field theory. Further, we evaluate the density matrix arising from correlations between the HO orbitals.
Discrete clouds of neutral gas between the galaxies M31 and M33.
Wolfe, Spencer A; Pisano, D J; Lockman, Felix J; McGaugh, Stacy S; Shaya, Edward J
2013-05-09
Spiral galaxies must acquire gas to maintain their observed level of star formation beyond the next few billion years. A source of this material may be the gas that resides between galaxies, but our understanding of the state and distribution of this gas is incomplete. Radio observations of the Local Group of galaxies have revealed hydrogen gas extending from the disk of the galaxy M31 at least halfway to M33. This feature has been interpreted to be the neutral component of a condensing intergalactic filament, which would be able to fuel star formation in M31 and M33, but simulations suggest that such a feature could also result from an interaction between both galaxies within the past few billion years (ref. 5). Here we report radio observations showing that about 50 per cent of this gas is composed of clouds, with the rest distributed in an extended, diffuse component. The clouds have velocities comparable to those of M31 and M33, and have properties suggesting that they are unrelated to other Local Group objects. We conclude that the clouds are likely to be transient condensations of gas embedded in an intergalactic filament and are therefore a potential source of fuel for future star formation in M31 and M33.
Energetic neutral atoms from a trans-Europa gas torus at Jupiter.
Mauk, B H; Mitchell, D G; Krimigis, S M; Roelof, E C; Paranicas, C P
2003-02-27
The space environments--or magnetospheres--of magnetized planets emit copious quantities of energetic neutral atoms (ENAs) at energies between tens of electron volts to hundreds of kiloelectron volts (keV). These energetic atoms result from charge exchange between magnetically trapped energetic ions and cold neutral atoms, and they carry significant amounts of energy and mass from the magnetospheres. Imaging their distribution allows us to investigate the structure of planetary magnetospheres. Here we report the analysis of 50-80 keV ENA images of Jupiter's magnetosphere, where two distinct emission regions dominate: the upper atmosphere of Jupiter itself, and a torus of emission residing just outside the orbit of Jupiter's satellite Europa. The trans-Europa component shows that, unexpectedly, Europa generates a gas cloud comparable in gas content to that associated with the volcanic moon Io. The quantity of gas found indicates that Europa has a much greater impact than hitherto believed on the structure of, and the energy flow within, Jupiter's magnetosphere.
Gas-phase structures and thermochemistry of neutral histidine and its conjugated acid and base.
Riffet, Vanessa; Bouchoux, Guy
2013-04-28
Extensive exploration of the conformational space of neutral, protonated and deprotonated histidine has been conducted at the G4MP2 level. Theoretical protonation and deprotonation thermochemistry as well as heats of formation of gaseous histidine and its ionized forms have been calculated at the G4 level considering either the most stable conformers or an equilibrium population of conformers at 298 K. These theoretical results were compared to evaluated experimental determinations. Recommended proton affinity and protonation entropy deduced from these comparisons are PA(His) = 980 kJ mol(-1) and ΔpS(His) ∼ 0 J mol(-1) K(-1), thus leading to a gas-phase basicity value of GB(His) = 947.5 kJ mol(-1). Similarly, gas phase acidity parameters are ΔacidH(o)(His) = 1373 kJ mol(-1), ΔacidS(His) ∼ 10 J mol(-1) K(-1) and ΔacidG(o)(His) = 1343 kJ mol(-1). Computed G4 heats of formation values are equal to -290, 265 and -451 kJ mol(-1) for gaseous neutral histidine and its protonated and deprotonated forms, respectively. The present computational data correct, and complete, previous thermochemical parameter estimates proposed for gas-phase histidine and its acido-basic properties.
A Pre-ionization System to Limit Neutral Gas in a Compact Toroid Injector
NASA Astrophysics Data System (ADS)
Allfrey, Ian; Roche, Thomas; Matsumoto, Tadafumi; Garate, Eusebio; Gota, Hiroshi; Asai, Tomohiko; the TAE Team
2016-10-01
Fusion plasmas require long lifetimes and high temperatures, both of which are limited by particle loss, among other factors. Therefore, refueling a long-lived advanced beam-driven field-reversed configuration (FRC) plasma in C-2U is necessary, and injecting a supersonic compact toroid (CT) is an effective means of introducing particles into the FRC core. However, neutral gas that trails the CT into the target chamber cools the FRC. Pre-ionization (PI) system assists the break down between electrodes of the CT injector (CTI), so the amount of introduced gas can be lowered by up to a factor of two, effectively increasing the ionization fraction; thus, reducing the amount of neutral gas in the system. Additionally, the PI decreases the delay in CTI breakdown so a highly reproducible operation is achievable. The PI system consists of a fast, high voltage, pulse discharge circuit coupled to a Teflon insulated semi-rigid coaxial cable inserted into the CTI. System details and experimental data will be presented, in addition to issues such as the introduction of impurities and pre-ionizer lifetime.
NASA Technical Reports Server (NTRS)
Hedin, A. E.; Hinton, B. B.; Schmitt, G. A.
1972-01-01
The gas-surface interaction effects observed by the quadrupole mass spectrometer are described, and the technique developed to account for them in determining ambient neutral densities is summarized. The total ion current and the ion currents for ions with molecular weights 2, 4, 16, 28, and 32 are sampled for 1.125 sec once every 9.216 sec, for 258 sec out of a 368 sec cycle. An equation is given for the number density of any constituent in the ion source region, and source density data are discussed. The mass 28 background gas is considered to be CO rather than N2, and a CO model is developed. A quasi-equilibrium model of the atomic oxygen interactions is constructed, and a set of surface parameters is determined which provides a reasonable fit to the mass 16 and 32 source densities consistent with the predicted ambient atomic oxygen.
Bose Polarons in the Strongly Interacting Regime
NASA Astrophysics Data System (ADS)
Hu, Ming-Guang; Van de Graaff, Michael J.; Kedar, Dhruv; Corson, John P.; Cornell, Eric A.; Jin, Deborah S.
2016-07-01
When an impurity is immersed in a Bose-Einstein condensate, impurity-boson interactions are expected to dress the impurity into a quasiparticle, the Bose polaron. We superimpose an ultracold atomic gas of 87Rb with a much lower density gas of fermionic 40 impurities. Through the use of a Feshbach resonance and radio-frequency spectroscopy, we characterize the energy, spectral width, and lifetime of the resultant polaron on both the attractive and the repulsive branches in the strongly interacting regime. The width of the polaron in the attractive branch is narrow compared to its binding energy, even as the two-body scattering length diverges.
Detection of cold gas releases in space via low energy neutral atom imaging
McComas, D.J.; Funsten, H.O.; Moore, K.R.; Scime, E.E.; Thomsen, M.F.
1993-01-01
Low energy neutral atoms (LENAs) are produced in space plasmas by charge exchange between the ambient magnetospheric plasma ions and cold neutral atoms. Under normal conditions these cold neutrals come from the terrestrial geocorona, a shroud of few-ev hydrogen atoms surrounding the Earth. As a consequence of this charge exchange, it has become possible to remotely image many regions of the magnetosphere for the first time utilizing recently developed LENA imaging technology. In addition to the natural hydrogen geocorona, conventional explosions and maneuvering thruster firings can also introduce large amounts of cold gas into the space environment. In this paper we examine whether such potentially clandestine activities could also be remotely observed for the first time via LENA imaging. First, we examine the fluxes of LENAs produced in the space environment from a conventional explosion. Then we review the present state of the art in the emerging field of LENA detection and imaging. Recent work has shown that LENAs can be imaged by first converting the neutrals to ions with ultra-thin (10s of [Angstrom]) foils and then electrostatically analyzing these newly created ions to reject the large (>10[sup 10] cm[sup [minus]2] [sup [minus]1]) UV background to which the low energy detectors are sensitive. We conclude that the sensitivities for present LENA imager designs may be just adequate for detecting some man-made releases. With additional improvements in LENA detection capabilities, this technique could become an important new method for monitoring for conventional explosions, as well as other man-made neutral releases, in the space environment.
Detection of cold gas releases in space via low energy neutral atom imaging
McComas, D.J.; Funsten, H.O.; Moore, K.R.; Scime, E.E.; Thomsen, M.F.
1993-04-01
Low energy neutral atoms (LENAs) are produced in space plasmas by charge exchange between the ambient magnetospheric plasma ions and cold neutral atoms. Under normal conditions these cold neutrals come from the terrestrial geocorona, a shroud of few-ev hydrogen atoms surrounding the Earth. As a consequence of this charge exchange, it has become possible to remotely image many regions of the magnetosphere for the first time utilizing recently developed LENA imaging technology. In addition to the natural hydrogen geocorona, conventional explosions and maneuvering thruster firings can also introduce large amounts of cold gas into the space environment. In this paper we examine whether such potentially clandestine activities could also be remotely observed for the first time via LENA imaging. First, we examine the fluxes of LENAs produced in the space environment from a conventional explosion. Then we review the present state of the art in the emerging field of LENA detection and imaging. Recent work has shown that LENAs can be imaged by first converting the neutrals to ions with ultra-thin (10s of {Angstrom}) foils and then electrostatically analyzing these newly created ions to reject the large (>10{sup 10} cm{sup {minus}2} {sup {minus}1}) UV background to which the low energy detectors are sensitive. We conclude that the sensitivities for present LENA imager designs may be just adequate for detecting some man-made releases. With additional improvements in LENA detection capabilities, this technique could become an important new method for monitoring for conventional explosions, as well as other man-made neutral releases, in the space environment.
Interactions Between Neutral Gas Clouds and Plasma Near the icy satellites of Jupiter and Saturn.
NASA Astrophysics Data System (ADS)
Burger, M. H.
2007-05-01
Neutral gas clouds associated with icy satellites are intimately tied to the magnetospheric plasma in which they are formed and reside. Plasma interactions can create the clouds, remove material from them, and make it possible for us to observe them. At Europa, for example, energetic ions incident on the icy surface eject hydrogen and oxygen formed from the dissociation of water (Johnson et al. 1982). The hydrogen escapes, but the O2remains gravitationally bound, forming an atmosphere. This atmosphere then interacts with the thermal plasma in Jupiter's magneotpshere: the O2is dissociated by the electrons resulting in emissions from atomic oxygen which have been observed by HST and Cassini (Hall et al. 1995; Hansen et al. 2005). Charge exchange with magnetospheric ions and electron-impact ionization removes atoms and molecules from Europa's atmosphere and exosphere, and contributes fresh ions to the plasma (Saur et al. 1998; Shematovich et al 2005). At Enceladus, where 150-300 kg/s of H2O gas is supplied by the south pole plume (Hansen et al. 2006; Burger et al. 2007), charge exchange reactions between the plasma and H2O produce fresh pickup ions which slow and deflect the plasma (Tokar et al. 2006; Pontius and Hill 2006) and induce perturbations in Saturn's magnetic field (Dougherty et al. 2006; Khurana et al. 2006). The neutrals created in these charge exchange reactions either escape from Saturn entirely or are redistributed throughout the inner magnetosphere forming gas clouds which have been observed by HST and Cassini (Johnson et al. 2006). I will describe the interaction processes between the neutral atoms and molecules in icy satellite atmospheres and exospheres, and discuss differences between the processes imporant in Jupiter's magnetosphere, where the plasma content is greater than the neutral content, and Saturn's magnetosphere, which is dominated by neutrals. References: Burger et al., JGR, 2007, in press. Dougherty et al., Science, 311, 1406, 2006
Satyendra Nath Bose and nanophotonics
NASA Astrophysics Data System (ADS)
Gaponenko, Sergey V.
2014-01-01
This paper is devoted to the 90th anniversary of the 1924 publication of the seminal paper by Bose titled "Planck's law and the hypothesis on light quanta" (Zeitschrift für Physik 26, 178-181). The paper has been the cornerstone quantum statistical physics. Remarkably, the very starting idea is the discreteness of phase space expressed in the form of the density of states. Bose considered equilibrium electromagnetic radiation as gas of photons and, therefore, introduced the photon density of states notion into the physics though without using directly the term "density of states." Today, engineering photon density of states to modify light-matter interaction in nanostructures including both spontaneous emission and spontaneous scattering of photons constitutes the solid part of nanophotonics.
Tracing neutral FeI gas evaporating from exocomets in the beta Pictoris disk
NASA Astrophysics Data System (ADS)
Welsh, Barry; Montgomery, Sharon Lynn; DeMark, Richard; Price, Joshua
2016-01-01
Absorption variability due to the evaporating gas from comet-like bodies on their grazing approach towards a parent star has now been observed in over a dozen A-type stellar systems. Ground based observations of the resultant replenished gas have routinely been performed using high resolution spectroscopy of the CaII-K (3933Å) and NaI (5890Å) circumstellar absorption lines, especially towards the well-known exoplanet bearing Beta Pictoris stellar system. Here we present a preliminary study of the neutral FeI (3860Å) circumstellar absorption line observed towards Beta Pictoris using data in the ESO Data Archive obtained over the 2003 to 2014 timeframe. This spectral line samples neutral gas with an ionization potential < 7.9eV and from a sample of 15 observations we show 5 examples in which high velocity absorption features (Vhelio > +35 km s-1) have, for the first time, been simultaneously detected in both the FeI and CaII line profiles. Such absorption features can be associated with liberated exocomet gas which seems to be preferentially observed at circumstellar disk velocities of +35 to +45 km s-1. Additional absorption features with velocities > 100 km s-1 in the FeI line profile have also been observed on two occasions. Our data supports the recent findings of Kiefer et al (2014) in which at least two families of exocomets exist with distinctly different circumstellar gas disk velocities, both residing within~ 1 AU from the central star.
Tracing the neutral gas environments of young radio AGN with ASKAP
NASA Astrophysics Data System (ADS)
Allison, J. R.; Sadler, E. M.; Moss, V. A.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B. T.; McConnell, D.; Sault, R. J.; Whiting, M. T.
2016-02-01
At present neutral atomic hydrogen (H I) gas in galaxies at redshifts above {z ˜ 0.3} (the extent of 21 cm emission surveys in individual galaxies) and below {z ˜ 1.7} (where the Lyman-\\alpha line is not observable with ground-based telescopes) has remained largely unexplored. The advent of precursor telescopes to the Square Kilometre Array will allow us to conduct the first systematic radio-selected 21 cm absorption surveys for H I over these redshifts. While H I absorption is a tracer of the reservoir of cold neutral gas in galaxies available for star formation, it can also be used to reveal the extreme kinematics associated with jet-driven neutral outflows in radio-loud active galactic nuclei. Using the six-antenna Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder, we have demonstrated that in a single frequency tuning we can detect H I absorption over a broad range of redshifts between z = 0.4 and 1.0. As part of our early science and commissioning program, we are now carrying out a search for absorption towards a sample of the brightest GPS and CSS sources in the southern sky. These intrinsically compact sources present us with an opportunity to study the circumnuclear region of recently re-started radio galaxies, in some cases showing direct evidence of mechanical feedback through jet-driven outflows. With the sensitivity of the full ASKAP array we will be able to study the kinematics of atomic gas in a few thousand radio galaxies, testing models of radio jet feedback well beyond the nearby Universe.
Neutral gas outflows in nearby [U]LIRGs via optical NaD feature
NASA Astrophysics Data System (ADS)
Cazzoli, S.; Arribas, S.; Maiolino, R.; Colina, L.
2016-05-01
We studied the properties of the neutral gas in a sample of 38 local luminous and ultra luminous infrared galaxies ([U]LIRGs, 51 individual galaxies at z ≤ 0.09), which mainly covers the less explored LIRG luminosity range. This study is based on the analysis of the spatially integrated and spatially resolved spectra of the NaDλλ 5890, 5896 Å feature obtained with the integral field unit (IFU) of VIMOS at the Very Large Telescope. Analyzing spatially integrated spectra, we find that the contribution of the stars to the observed NaD equivalent width is small (<35%) for about half of the sample, and therefore this feature is dominated by inter stellar medium (ISM) absorption. After subtracting the stellar contribution, we find that the pure-ISM integrated spectra generally show blueshifted NaD profiles, indicating neutral gas outflow velocities, V, in the range 65-260 km s-1. Excluding the galaxies with powerful AGNs, V shows a dependency with the star formation rate (SFR) of the type V ∝ SFR0.15, which is in rather good agreement with previous results. The spatially resolved analysis could be performed for 40 galaxies, 22 of which have neutral gas velocity fields dominated by noncircular motions with signatures of cone-like winds. However, a large number of targets (11/40) show disk rotation signatures. Based on a simple model, we found that the wind masses are in the range 0.4-7.5 × 108 M⊙, reaching up to ~3% of the dynamical mass of the host. The mass rates are typically only ~0.2-0.4 times the corresponding global SFR indicating that, in general, the mass loss is too small to slow down the star formation significantly. In the majority of cases, the velocity of the outflowing gas is not sufficient to escape the host potential well and, therefore, most of the gas rains back into the galaxy disk. On average V/vesc is higher in less massive galaxies, confirming that the galaxy mass has a primary role in shaping the recycling of gas and metals. The
NASA Astrophysics Data System (ADS)
Mandell, M. J.; Jongeward, G. A.; Cooke, D. L.; Raitt, W. J.
1998-01-01
The Space Power Experiment Aboard Rockets (SPEAR) 3 experiment was launched on March 15, 1993, to test grounding devices for negative payloads. In this paper we review two aspects of the high-altitude flight data and compare them with preflight predictions. The SPEAR 3 neutral gas release experiment studied a grounding mechanism observed on previous flights during attitude control system (ACS) firings. Preflight calculations using Paschen law physics generalized to three dimensions predicted that the high rate gas release (about one order of magnitude below normal ACS) would reduce the rocket potential to within 200-300 V of plasma ground. The flight data is well fit by a value of -225V. Orientation relative to Earth's magnetic field had no effect on the floating potential or grounding operations but had a large effect on the portion of the current collected by the boom. We compare these flight measurements with preflight calculations made with the DynaPAC computer code.
Properties of clusters in the gas phase. V - Complexes of neutral molecules onto negative ions
NASA Technical Reports Server (NTRS)
Keesee, R. G.; Lee, N.; Castleman, A. W., Jr.
1980-01-01
Ion-molecules association reactions of the form A(-)(B)n-1 + B = A(-)(B)n were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl(-), I(-), and NO2(-) with n ranging from one to three or four, and onto SO2(-) and SO3(-) with n equal to one; and (2) carbon dioxide onto Cl(-), I(-), NO2(-), CO3(-), and SO3(-) with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions.
Infrared Action Spectroscopy of Low-Temperature Neutral Gas-Phase Molecules of Arbitrary Structure
NASA Astrophysics Data System (ADS)
Yatsyna, Vasyl; Bakker, Daniël J.; Salén, Peter; Feifel, Raimund; Rijs, Anouk M.; Zhaunerchyk, Vitali
2016-09-01
We demonstrate a technique for IR action spectroscopy that enables measuring IR spectra in a background-free fashion for low-temperature neutral gas-phase molecules of arbitrary structure. The method is exemplified experimentally for N -methylacetamide molecules in the mid-IR spectral range of 1000 - 1800 cm-1 , utilizing the free electron laser FELIX. The technique involves the resonant absorption of multiple mid-IR photons, which induces molecular dissociation. The dissociation products are probed with 10.49 eV vacuum ultraviolet photons and analyzed with a mass spectrometer. We also demonstrate the capability of this method to record, with unprecedented ease, mid-IR spectra for the molecular associates, such as clusters and oligomers, present in a molecular beam. In this way the mass-selected spectra of low-temperature gas-phase dimers and trimers of N -methylacetamide are measured in the full amide I-III range.
NASA Astrophysics Data System (ADS)
Stone, Shane W.; Yelle, Roger; Mahaffy, Paul; Benna, Mehdi; Elrod, Meredith K.; Bougher, Stephen W.; MAVEN
2016-10-01
The MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) measures composition and variability of neutral and ionic species in the Martian upper atmosphere, allowing us to calculate neutral temperatures from roughly 130 km to 300 km above the surface. Over the past two years at Mars, NGIMS has collected an extensive and useful data set that covers much of the Martian thermosphere and exosphere. We use new, improved algorithms for the most accurate determination of densities from the NGIMS data. We use the densities of inert species (specifically CO2, Ar, and N2) along with a hydrostatic equilibrium model to infer the temperature profile and its uncertainty. Uncertainties include the errors in the density measurements, unknown upper boundary conditions, and horizontal variations in the atmosphere. Our calculations reveal diurnal temperature variations of up to 90 K and maximum latitudinal temperature variations of 130 K. These fluctuations in temperature in the upper atmosphere are surprising because they are significantly larger than those predicted by the latest 3D general circulation models for Mars.
NASA Astrophysics Data System (ADS)
Bzowski, Maciej; McComas, David; Galli, Andre; Kucharek, Harald; Wurz, Peter; Sokol, Justyna M.; Schwadron, Nathan; Heirtzler, David M.; Kubiak, M. Marzena A.; Möbius, Eberhard; Fuselier, Stephen; Swaczyna, Paweł; Leonard, Trevor; Park, Jeewoo
2016-07-01
The large-scale structure of the heliosphere is governed by the interaction of the partly ionized, magnetized interstellar gas and the magnetized, fully ionized solar wind, structured in heliolatitude. Determining factors of this interaction are the density and flow velocity of interstellar gas relative to the Sun, the Mach number of this flow and the strength and inclination of the interstellar magnetic field to the flow vector at the interstellar side, and the magnitude of dynamic pressure of solar wind and the strength of its embedded magnetic field at the solar side. As a result of charge exchange interactions operating in the boundary region between the heliosphere and interstellar matter, a new population of neutral atoms is created, in addition to the population of unperturbed interstellar neutral gas. Both of these populations penetrate deep inside the heliosphere, where they can be sampled by the first space probe dedicated to observations of the heliosphere and its immediate surroundings by means of neutral atoms: the Interstellar Boundary Explorer (IBEX). Due to distortion of the heliosphere from axial symmetry, the secondary population of interstellar neutrals, created via charge exchange between the plasma flowing past the heliopause and the unperturbed pristine neutral interstellar gas, appears to be coming from a different direction than the unperturbed interstellar neutral flow. These two directions should be coplanar with the plane defined by the local interstellar magnetic field and the flow direction of the unperturbed gas. IBEX provides an unprecedented opportunity to study and interpret these relations. The IBEX science team have recently accomplished important milestones in researching the primary and secondary populations of interstellar gas and their relation to the local interstellar magnetic fields. First, the temperature and velocity vector of the inflowing interstellar neutral gas has been determined with unprecedented robustness based
NASA Astrophysics Data System (ADS)
Yuan, Quan; Ma, Guangcai; Xu, Ting; Serge, Bakire; Yu, Haiying; Chen, Jianrong; Lin, Hongjun
2016-10-01
Poly-/perfluoroalkyl substances (PFASs) are a class of synthetic fluorinated organic substances that raise increasing concern because of their environmental persistence, bioaccumulation and widespread presence in various environment media and organisms. PFASs can be released into the atmosphere through both direct and indirect sources, and the gas/particle partition coefficient (KP) is an important parameter that helps us to understand their atmospheric behavior. In this study, we developed a temperature-dependent predictive model for log KP of PFASs and analyzed the molecular mechanism that governs their partitioning equilibrium between gas phase and particle phase. All theoretical computation was carried out at B3LYP/6-31G (d, p) level based on neutral molecular structures by Gaussian 09 program package. The regression model has a good statistical performance and robustness. The application domain has also been defined according to OECD guidance. The mechanism analysis shows that electrostatic interaction and dispersion interaction play the most important role in the partitioning equilibrium. The developed model can be used to predict log KP values of neutral fluorotelomer alcohols and perfluor sulfonamides/sulfonamidoethanols with different substitutions at nitrogen atoms, providing basic data for their ecological risk assessment.
Modeling the neutral gas and dust coma of Comet 1P/Halley
NASA Astrophysics Data System (ADS)
Rubin, Martin; Tenishev, Valeriy M.; Combi, Michael R.; Hansen, Kenneth C.; Gombosi, Tamas I.; Altwegg, Kathrin; Balsiger, Hans
2010-05-01
The neutral gas environment of a comet is largely influenced by dissociation of parent molecules created at the surface of the comet and collisions of all the involved species. We compare the results from a kinetic model of the neutral cometary environment with measurements from the Neutral Mass Spectrometer (NMS) and the Dust Impact Detection System (DIDSY) onboard the Giotto spacecraft which flew-by at comet 1P/Halley in 1986. We further show that our model is in good agreement to measurements obtained by the International Ultraviolet Explorer (IUE), sounding rocket experiments, and the International Halley Watch (IHW). The model solves the Boltzmann equation with a Direct Simulation Monte Carlo technique [Tenishev et al. (2008, Astrophys. J., 685, 659-677)] by tracking trajectories of gas molecules and dust grains under the influence of the comet's weak gravity field with momentum exchange among particles modeled in a probabilistic manner. The cometary nucleus is considered to be the source of dust and the parent species (in our model: H2O, CO, H2CO, CO2, CH3OH, C2H6, C2H4, C2H2, HCN, NH3, and CH4) in the coma. Subsequently our model also tracks the corresponding dissociation products (H, H2, O, OH, C, CH, CH2, CH3, N, NH, NH2, C2, C2H, C2H5, CN, and HCO). This work has been supported by JPL subcontract 1266313 under NASA grant NMO710889, NASA planetary atmospheres program grant NNX09AB59G, grant AST-0707283 from the NSF Planetary Astronomy program, and the Swiss National Science Foundation.
Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.
2016-04-07
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum,more » the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.« less
Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.
2016-04-07
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.
NASA Astrophysics Data System (ADS)
Robinson, Neil J.; Caux, Jean-Sébastien; Konik, Robert M.
2016-04-01
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. When the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton's cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.
Observing the Interstellar Neutral He Gas Flow with a Variable IBEX Pointing Strategy
NASA Astrophysics Data System (ADS)
Leonard, T.; Moebius, E.; Bzowski, M.; Fuselier, S. A.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee, M. A.; McComas, D. J.; Schwadron, N.; Wurz, P.
2015-12-01
The Interstellar Neutral (ISN) gas flow can be observed at Earth's orbit due to the motion of the solar system relative to the surrounding interstellar gas. Since He is minimally influenced by ionization and charge exchange, the ISN He flow provides a sample of the pristine interstellar environment. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. IBEX is a Sun-pointing spinning spacecraft with energetic neutral atom (ENA) detectors observing perpendicular to the spacecraft spin axis. Due to the Earth's orbital motion around the Sun, it is necessary for IBEX to perform spin axis pointing maneuvers every few days to maintain a sunward pointed spin axis. The IBEX operations team has successfully pointed the spin axis in a variety of latitude orientations during the mission, including in the ecliptic during the 2012 and 2013 seasons, about 5 degrees below the ecliptic during the 2014 season, and recently about 5 degrees above the ecliptic during the 2015 season, as well as optimizing observations with the spin axis pointed along the Earth-Sun line. These observations include a growing number of measurements near the perihelion of the interstellar atom trajectories, which allow for an improved determination of the ISN He bulk flow longitude at Earth orbit. Combining these bulk flow measurements with an analytical model (Lee et al. 2012 ApJS, 198, 10) based upon orbital mechanics improves the knowledge of the narrow ISN parameter tube, obtained with IBEX, which couples the interstellar inflow longitude, latitude, speed, and temperature.
NASA Astrophysics Data System (ADS)
Provornikova, E.; Izmodenov, V. V.; Lallement, R.
2012-04-01
Charge-transfer is the main process linking neutrals and charged particles in the interaction regions of neutral (or partly ionized) gas with a plasma. In this paper we illustrate the importance of charge-transfer with respect to the dynamics and the structure of neutral gas-plasma interfaces. We consider the following phenomena: (1) the heliospheric interface - region where the solar wind plasma interacts with the partly-ionized local interstellar medium (LISM) and (2) neutral interstellar clouds embedded in a hot, tenuous plasma such as the million degree gas that fills the so-called ``Local Bubble". In (1), we discuss several effects in the outer heliosphere caused by charge exchange of interstellar neutral atoms and plasma protons. In (2) we describe the role of charge exchange in the formation of a transition region between the cloud and the surrounding plasma based on a two-component model of the cloud-plasma interaction. In the model the cloud consists of relatively cold and dense atomic hydrogen gas, surrounded by hot, low density, fully ionized plasma. We discuss the structure of the cloud-plasma interface and the effect of charge exchange on the lifetime of interstellar clouds. Charge transfer between neutral atoms and minor ions in the plasma produces X-ray emission. Assuming standard abundances of minor ions in the hot gas surrounding the cold interstellar cloud, we estimate the X-ray emissivity consecutive to the charge transfer reactions. Our model shows that the charge-transfer X-ray emission from the neutral cloud-plasma interface may be comparable to the diffuse thermal X-ray emission from the million degree gas cavity itself.
Inhibition of Coherence in Trapped Bose-Einstein Condensates
Imamoglu, A.; Lewenstein, M.
1997-03-01
We analyze the dependence of the collapse and revival of many-atom coherence of a trapped Bose-Einstein condensate on the trap potential, dimensionality of the gas, and atom number fluctuations. We show that in a class of experimentally relevant systems the collapse time vanishes in the limit of a large number of atoms, implying that the trapped Bose gas cannot sustain a well-defined quantum phase. {copyright} {ital 1997} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Huang, Z.; Toth, G.; Gombosi, T. I.; Jia, X.; Rubin, M.; Hansen, K. C.; Fougere, N.; Bieler, A. M.; Shou, Y.; Altwegg, K.; Combi, M. R.; Tenishev, V.
2015-12-01
The neutral and plasma environment is critical in understanding the interaction of comet Churyumov-Gerasimenko (CG), the target of the Rosetta mission, and the solar wind. To serve this need and support the Rosetta mission, we develop a 3-D four fluid model, which is based on BATS-R-US within the SWMF (Space Weather Modeling Framework) that solves the governing multi-fluid MHD equations and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. This model incorporates different mass loading processes, including photo and electron impact ionization, charge exchange, dissociative ion-electron recombination, and collisional interactions between different fluids. We simulate the near nucleus plasma and neutral gas environment near perihelion with a realistic shape model of CG and compare our simulation results with Rosetta observations.
NASA Astrophysics Data System (ADS)
Mahé, Jérôme; Gaigeot, Marie-Pierre; Bakker, Daniël; Jaeqx, Sander; Rijs, Anouk
2016-06-01
Within the past two decades, action vibrational spectroscopy has become an almost routine experimental method to probe the structures of molecules and clusters in the gas phase (neutral and ions). Such experiments are mainly performed in the 1000-4000 wn fingerprint regions. Though successful in many respects, these spectral domains can be however restrictive in the information provided, and sometimes reach limitations for unravelling structures without ambiguity. In a collaborative work with the group of Dr A.M. Rijs (FELIX laboratory, Radbout University, The Netherlands) we have launched a new strategy where the far-IR/Tera-Hertz domain (100-800 wn domain) is experimentally probed for neutral gas phase molecules. Our group in Paris apply finite temperature DFT-based molecular dynamics (DFT-MD) simulations in order to unravel the complex signatures arising in the far-IR domain, and provide an unambiguous assignment both of the structural conformation of the gas phase molecules (taking into account the experimental conditions) and an understanding of the spectral signatures/fingerprints. We will discuss our experimental and theoretical investigations on two neutral peptides in the 100-800 wn far-IR spectral domain, i.e. Z-Ala6 and PheGly dipeptide, that represent two systems which definitive conformational assignment was not possible without the far IR signatures. We will also present our very recent results on the Phe-X peptide series, where X stands for Gly, Ala, Pro, Val, Ser, Cys, combining experiments and DFT-MD simulations, providing a detailed understanding of the vibrational fingerprints in the far-IR domain. In all exemples, we will show how DFT-MD simulations is the proper theoretical tool to account for vibrational anharmonicities and mode couplings, of prime importance in the far-IR domain. References : J. Mahé, S. Jaeqx, A.M. Rijs, M.P. Gaigeot, Phys. Chem. Chem. Phys., 17 :25905 (2015) S. Jaeqx, J. Oomens, A. Cimas, M.P. Gaigeot, A.M. Rijs, Angew
Prediction of a neutral noble gas compound in the triplet state.
Manna, Debashree; Ghosh, Ayan; Ghanty, Tapan K
2015-05-26
Discovery of the HArF molecule associated with H-Ar covalent bonding [Nature, 2000, 406, 874-876] has revolutionized the field of noble gas chemistry. In general, this class of noble gas compound involving conventional chemical bonds exists as closed-shell species in a singlet electronic state. For the first time, in a bid to predict neutral noble gas chemical compounds in their triplet electronic state, we have carried out a systematic investigation of xenon inserted FN and FP species by using quantum chemical calculations with density functional theory and various post-Hartree-Fock-based correlated methods, including the multireference configuration interaction technique. The FXeP and FXeN species are predicted to be stable by all the computational methods employed in the present work, such as density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2), coupled-cluster theory (CCSD(T)), and multireference configuration interaction (MRCI). For the purpose of comparison we have also included the Kr-inserted compounds of FN and FP species. Geometrical parameters, dissociation energies, transition-state barrier heights, atomic charge distributions, vibrational frequency data, and atoms-in-molecules properties clearly indicate that it is possible to experimentally realize the most stable state of FXeP and FXeN molecules, which is triplet in nature, through the matrix isolation technique under cryogenic conditions.
Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density
NASA Astrophysics Data System (ADS)
Chaplin, Vernon H.; Bellan, Paul M.
2016-08-01
We describe some notable aspects of the light emission and afterglow properties in pulsed, high-density ( 1018-1020 m-3 ) argon inductively coupled discharges initiated following fast gas injection. The plasma was created in a long, narrow discharge tube and then expanded downstream of the radiofrequency (RF) antenna into a large chamber. Fast camera images of the expanding plasma revealed a multi-phase time-dependent emission pattern that did not follow the ion density distribution. Dramatic differences in visible brightness were observed between discharges with and without an externally applied magnetic field. These phenomena were studied by tracking excited state populations using passive emission spectroscopy and are discussed in terms of the distinction between ionizing and recombining phase plasmas. Additionally, a method is presented for inferring the unknown neutral gas pressure in the discharge tube from the time-dependent visible and infrared emission measured by a simple photodiode placed near the antenna. In magnetized discharges created with fast gas injection, the downstream ion density rose by Δni˜1018 m-3 in the first ˜100 μs after the RF power was turned off. The conditions conducive to this afterglow density rise are investigated in detail, and the effect is tentatively attributed to pooling ionization.
Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphere
NASA Astrophysics Data System (ADS)
Gogoberidze, G.; Voitenko, Y.; Poedts, S.; De Keyser, J.
2014-03-01
We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion thermal effect is highly reduced by the Coulomb collisions and can be ignored for the chromospheric FB-type instabilities. In contrast, the destabilizing electron thermal effect is important and causes a significant reduction of the neutral drag velocity triggering the instability. The resulting threshold velocity is found as function of chromospheric height. Our results indicate that the FB-type instabilities are still less efficient in the global chromospheric heating than the Joule dissipation of the currents driving these instabilities. This conclusion does not exclude the possibility that the FB-type instabilities develop in the places where the cross-field currents overcome the threshold value and contribute to the heating locally. Typical length-scales of plasma density fluctuations produced by these instabilities are determined by the wavelengths of unstable modes, which are in the range 10-102 cm in the lower chromosphere and 102-103 cm in the upper chromosphere. These results suggest that the decimetric radio waves undergoing scattering (scintillations) by these plasma irregularities can serve as a tool for remote probing of the solar chromosphere at different heights.
On the oxygen abundance of neutral gas in I ZW 18.
NASA Astrophysics Data System (ADS)
Pettini, M.; Lipman, K.
1995-05-01
Whether the H II regions of dwarf emission line galaxies are self-polluted by the nucleosynthetic products of massive stars remains an open question, despite recent claims to the contrary. We show that the finding by Kunth and collaborators that the neutral interstellar medium of I Zw 18 has a metallicity one order of magnitude lower than that of the ionized gas is highly uncertain. The range of possible values of (O/H) admitted by the saturated O I absorption line used in their analysis is very large, spanning a factor of ~1000. We suggest that future observations of the intrinsically weaker S II λ1256 multiplet offer the best prospects for measuring the true degree of metal enrichment of this dwarf galaxy.
Quantum phase transition of a Bose gas in a lattice with a controlled number of atoms per site
NASA Astrophysics Data System (ADS)
Du, Xu
2005-05-01
We have studied the superfluid-Mott insulator quantum phase transition [1] of a gas of ^87Rb atoms in an optical lattice. We are able to prepare the gas with a controllable number of one, two, or three atoms per lattice site, as verified with photoassociation spectroscopy. We measure momentum distributions using standard time-of-flight imaging techniques. These are similar to those of ref. [1], and exhibit narrow peaks at moderate lattice strengths. We find that the width of these peaks increases for lattice heights greater than about 13 times the recoil energy [2], and we observe interesting differences in this behavior, depending on the number of atoms per site. The data suggest that the quantum phase transition occurs at higher lattice strength with larger site occupation. We acknowledge the support of this work by the R. A. Welch Foundation, The N. S. F., and the D.O.E. Quantum Optics Initiative. [1] Markus Greiner et al., Nature 415, 39 (2002). [2] Thilo St"oferle et al., Phys. Rev. Lett. 92, 130403 (2004).
Diagnosing the Neutral Interstellar Gas Flow at 1 AU with IBEX-Lo
NASA Astrophysics Data System (ADS)
Möbius, E.; Kucharek, H.; Clark, G.; O'Neill, M.; Petersen, L.; Bzowski, M.; Saul, L.; Wurz, P.; Fuselier, S. A.; Izmodenov, V. V.; McComas, D. J.; Müller, H. R.; Alexashov, D. B.
2009-08-01
Every year in fall and spring the Interstellar Boundary Explorer (IBEX) will observe directly the interstellar gas flow at 1 AU over periods of several months. The IBEX-Lo sensor employs a powerful triple time-of-flight mass spectrometer. It can distinguish and image the O and He flow distributions in the northern fall and spring, making use of sensor viewing perpendicular to the Sun-pointing spin axis. To effectively image the narrow flow distributions IBEX-Lo has a high angular resolution quadrant in its collimator. This quadrant is employed selectively for the interstellar gas flow viewing in the spring by electrostatically shutting off the remainder of the aperture. The operational scenarios, the expected data, and the necessary modeling to extract the interstellar parameters and the conditions in the heliospheric boundary are described. The combination of two key interstellar species will facilitate a direct comparison of the pristine interstellar flow, represented by He, which has not been altered in the heliospheric boundary region, with a flow that is processed in the outer heliosheath, represented by O. The O flow distribution consists of a depleted pristine component and decelerated and heated neutrals. Extracting the latter so-called secondary component of interstellar neutrals will provide quantitative constraints for several important parameters of the heliosheath interaction in current global heliospheric models. Finding the fraction and width of the secondary component yields an independent value for the global filtration factor of species, such as O and H. Thus far filtration can only be inferred, barring observations in the local interstellar cloud proper. The direction of the secondary component will provide independent information on the interstellar magnetic field strength and orientation, which has been inferred from SOHO SWAN Ly- α backscattering observations and the two Voyager crossings of the termination shock.
NASA Astrophysics Data System (ADS)
Vergely, J.-L.; Valette, B.; Lallement, R.; Raimond, S.
2010-07-01
Aims: 3D tomography of the interstellar dust and gas may be useful in many respects, from the physical and chemical evolution of the interstellar medium itself to foreground decontamination of the cosmic microwave background, or various studies of the environments of specific objects. However, while spectral data cubes of the galactic emission become increasingly precise, the information on the distance to the emitting regions has not progressed as well and relies essentially on the galactic rotation curve. Our goal here is to bring more precise information on the distance to nearby interstellar dust and gas clouds within 250 pc. Methods: We apply the best available calibration methods to a carefully screened set of stellar Strömgren photometry data for targets possessing a Hipparcos parallax and spectral type classification. We combine the derived interstellar extinctions and the parallax distances for about 6000 stars to build a 3D tomography of the local dust. We use an inversion method based on a regularized Bayesian approach and a least squares criterion, optimized for this specific data set. We apply the same inversion technique to a totally independent set of neutral sodium absorption data available for about 1700 target stars. Results: We obtain 3D maps of the opacity and the distance to the main dust-bearing clouds within 250 pc and identify in those maps well-known dark clouds and high galactic more diffuse entities. We calculate the integrated extinction between the Sun and the cube boundary and compare this with the total galactic extinction derived from infrared 2D maps. The two quantities reach similar values at high latitudes, as expected if the local dust content is satisfyingly reproduced and the dust is closer than 250 pc. Those maps show a larger high latitude dust opacity in the North compared to the South, reinforcing earlier evidences. Interestingly the gas maps do not show the same asymmetry, suggesting a polar asymmetry of the dust to gas
NASA Astrophysics Data System (ADS)
Benna, Mehdi; Mahaffy, Paul R.; Elrod, Meredith
2015-04-01
The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution (MAVEN) Mission is designed to characterize the source region of escaping atoms in the upper atmosphere and ionosphere of Mars. The NGIMS instrument is a quadrupole analyzer with a mass rang of 2-150 Da. It utilizes a dual ion source in order to measure both surface reactive neutrals (using the Open Source Neutral mode - OSN), inert neutrals (using the Closed Source Neutral mode - CSN), and thermal ions (using the Open Source Ion mode - OSI) at altitudes below 500 km.In the first few months of the MAVEN mission, NGIMS alternated on sequential orbits between measurement sequences that focus on fully characterizing neutral species (using the CSN/OSN modes) and ions (using the CSN/OSI modes). The collected data revealed the substantial structure present in both neutral and ion densities with spatial scales of hundreds of kilometers along the spacecraft track. The data also brought to light the sharp contrast between the day side and night side atmospheric profiles of neutrals and ions in both total density and relative abundance.
Jayapalan, Kanesh K. Chin, Oi-Hoong
2014-04-15
The axial and radial magnetic field profiles in a 13.56 MHz (radio frequency) laboratory 6 turn planar coil inductively coupled plasma reactor are simulated with the consideration of the effect of neutral gas heating. Spatially resolved electron densities, electron temperatures, and neutral gas temperatures were obtained for simulation using empirically fitted electron density and electron temperature and heuristically determined neutral gas temperature. Comparison between simulated results and measured fields indicates that neutral gas heating plays an important role in determining the skin depth of the magnetic fields.
NASA Astrophysics Data System (ADS)
Jayapalan, Kanesh K.; Chin, Oi-Hoong
2014-04-01
The axial and radial magnetic field profiles in a 13.56 MHz (radio frequency) laboratory 6 turn planar coil inductively coupled plasma reactor are simulated with the consideration of the effect of neutral gas heating. Spatially resolved electron densities, electron temperatures, and neutral gas temperatures were obtained for simulation using empirically fitted electron density and electron temperature and heuristically determined neutral gas temperature. Comparison between simulated results and measured fields indicates that neutral gas heating plays an important role in determining the skin depth of the magnetic fields.
A Field-Reversed Configuration Plasma Translated into a Neutral Gas Atmosphere
NASA Astrophysics Data System (ADS)
Sekiguchi, Jun'ichi; Asai, Tomohiko; Takahashi, Tsutomu; Ando, Hirotoshi; Arai, Mamiko; Katayama, Seri; Takahashi, Toshiki
2014-10-01
A field-reversed configuration (FRC) is a compact toroid dominantly with poloidal magnetic field. Because of its simply-connected configuration, an FRC can be translated axially along a gradient of guide magnetic field, and trapped in a confinement region with quasi-static external magnetic field. FRC translation experiments have been performed several facilities. Translation speed of those translated FRCs is comparable with super-Alfvenic speed of approximately 200 km/s. In this experiments, FRC translation has been performed on the FAT (FRC Amplification via Translation) facility. Achieved translation speed in the case of translation into a confinement chamber maintained as the vacuum state is in the range from 130 to 210 km/s. On the other hand, FRC translation into a statically filled deuterium gas atmosphere has also been performed. In the case of translation into filled neutral gas, FRC translation speed is approximately 80 km/s and the separatrix volume has extremely expanded compared with the case of a vacuum state. The phenomenon suggests the presence of regeneration process of translation kinetic energy back into the internal plasma energy during the translation process. This work was partially supported by ``Nihon University Symbolic Project.'' The authors gratefully acknowledge contributions from Nac Image Technology Inc. on the fast camera measurements.
NASA Astrophysics Data System (ADS)
Tagawa, Masahito; Kimoto, Yugo; Yokota, Kumiko; Ohira, Junki; Watanabe, Daiki; Nishimura, Hiroaki
The reaction mechanism of atomic oxygen (AO) in low Earth orbit (LEO) with spacecraft materials has been studied by ground-based experiments using laser-detonation hyperthermal beam source, which enables to accelerate the electrically neutral AO up to 8 km/s. However, the beam conditions in the laser-detonation sources could not fully duplicate the AO environment in space. The difference in beam condition including side products leads to the different material responses. The light emission from the laser-induced oxygen plasma may affect the erosion of ultraviolet (UV)-sensitive materials. However, the light emission could also be used as a diagnostic tool to understand the molecular processes in plasma. In this presentation, extreme ultraviolet (EUV) emission from the laser-induced plasma during AO test was evaluated by the flat field EUV spectrometer. Many emission lines between 25-40 nm originated from OII and OIII were observed from the laser-induced oxygen plasma. This result suggested multiple-charged O ions are generated in the laser-induced plasma. Promotion of oxygen dissociation effect by adding Ar in the target gas was explained by the energy transfer processes from Ar to O2 in the plasma. From the viewpoint of reducing the side products in the AO exposure tests, a method to reduce the EUV emission will also be investigated. These results could be used for establishing more accurate ground-based natural gas simulations on the space environmental effect of materials.
NASA Astrophysics Data System (ADS)
Solís, Miguel A.; Sevilla, Francisco J.; Fortes, Mauricio; de Llano, Manuel
2002-03-01
Cooper pair formation is studied in a 2D electron gas interacting pairwise through a finite-range, separable interfermion potential in wavevector space V_ kk^' =-(v_0/L^2)g_kg_k^' , where L^2 is the system area, v0 >= 0 the interaction strength, g_k≡ (1+k^2/k_0^2)-1/2 with k0 the inverse interaction range. The interaction strength v0 is eliminated [1] in favor of the (positive) binding energy B2 of an electron pair in vacuum under the same interfermion interaction. For finite range, i.e., 1/k_0>0, we report numerical calculations of the gap, the critical temperature and the chemical potential as functions of B2 and 1/k_0. For k_0= ∞ or zero-range (viz., a delta potential well) we recover at T=0 the well-known Miyake [2] results. Finally, the gap-to-Tc ratio is exhibited as a function of B2 and compared with other calculations as well as with empirical values for cuprate superconductors. [1] S.K. Adhikari, M. Casas, A. Puente, A. Rigo, M. Fortes, M.A. Solís, M. de Llano, A.A. Valladares and O. Rojo, Phys. Rev. B 62, 8671 (2000). [2] K. Miyake, Prog. Theor. Phys. 69, 1794 (1983). We thank UNAM-DGAPA-PAPIIT # IN102198 and CONACyT # 27828E for partial support.
Ground state energy of the δ-Bose and Fermi gas at weak coupling from double extrapolation
NASA Astrophysics Data System (ADS)
Prolhac, Sylvain
2017-04-01
We consider the ground state energy of the Lieb–Liniger gas with δ interaction in the weak coupling regime γ \\to 0 . For bosons with repulsive interaction, previous studies gave the expansion {{e}\\text{B}}≤ft(γ \\right)≃ γ -4{γ3/2}/3π +≤ft(1/6-1/{π2}\\right){γ2} . Using a numerical solution of the Lieb–Liniger integral equation discretized with M points and finite strength γ of the interaction, we obtain very accurate numerics for the next orders after extrapolation on M and γ. The coefficient of {γ5/2} in the expansion is found to be approximately equal to -0.001 587 699 865 505 944 989 29 , accurate within all digits shown. This value is supported by a numerical solution of the Bethe equations with N particles, followed by extrapolation on N and γ. It was identified as ≤ft(3\\zeta (3)/8-1/2\\right)/{π3} by G Lang. The next two coefficients are also guessed from the numerics. For balanced spin 1/2 fermions with attractive interaction, the best result so far for the ground state energy has been {{e}\\text{F}}≤ft(γ \\right)≃ {π2}/12-γ /2+{γ2}/6 . An analogue double extrapolation scheme leads to the value -\\zeta (3)/{π4} for the coefficient of {γ3} .
Metal enrichment of the neutral gas of blue compact dwarf galaxies: the compelling case of Pox 36
NASA Astrophysics Data System (ADS)
Lebouteiller, V.; Kunth, D.; Thuan, T. X.; Désert, J. M.
2009-02-01
Context: Evidence has grown over the past few years that the neutral phase of blue compact dwarf (BCD) galaxies may be metal-deficient as compared to the ionized gas of their H ii regions. These results have strong implications for our understanding of the chemical evolution of galaxies, and it is essential to strengthen the method, as well as to find possible explanations. Aims: We present the analysis of the interstellar spectrum of Pox 36 with the Far Ultraviolet Spectroscopic Explorer (FUSE). Pox 36 was selected because of the relatively low foreground gas content that makes it possible to detect absorption-lines weak enough that unseen components should not be saturated. Methods: Interstellar lines of H i, N i, O i, Si ii, P ii, Ar i, and Fe ii are detected. Column densities are derived directly from the observed line profiles except for H i, whose lines are contaminated by stellar absorption, thus needing the stellar continuum to be removed. We used the TLUSTY models to remove the stellar continuum and isolate the interstellar component. The best fit indicates that the dominant stellar population is B0. The observed far-UV flux agrees with an equivalent number of ~300 B0 stars. The fit of the interstellar H i line gives a column density of 1020.3±0.4 cm-2. Chemical abundances were then computed from the column densities using the dominant ionization stage in the neutral gas. Our abundances are compared to those measured from emission-line spectra in the optical, probing the ionized gas of the H ii regions. Results: Our results suggest that the neutral gas of Pox 36 is metal-deficient by a factor ~7 as compared to the ionized gas, and they agree with a metallicity of ≈1/35 Z_⊙. Elemental depletion is not problematic because of the low dust content along the selected lines of sight. In contrast, the ionized gas shows a clear depletion pattern, with iron being strongly depleted. Conclusions: The abundance discontinuity between the neutral and ionized phases
Condensate fluctuations of interacting Bose gases within a microcanonical ensemble.
Wang, Jianhui; He, Jizhou; Ma, Yongli
2011-05-01
Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.
Condensate fluctuations of interacting Bose gases within a microcanonical ensemble
Wang Jianhui; He Jizhou; Ma Yongli
2011-05-15
Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.
Bose-Einstein condensate strings
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lake, Matthew J.
2015-02-01
We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schrödinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue, though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.
Guiberteau, E.; Bonhomme, G.; Zoheir, C.
1995-12-31
We present here the first results obtained from the modelling of a pulsed glow discharge in nitrogen, taking into account the heat transfer to the neutral gas. The aim of modelling is to optimize the plasma process in a nitriding reactor. The iron sample to be nitrided forms the cathode of the glow discharge at low pressure (100 to 200 Pa). The reactor uses two disks of diameter 50 mm as electrodes with a 40 mm gap. It works in a pulsed regime (cycle period varies from 10 to 100 ms) with a discharge duration which can be varied from 0.5 to 10 ms. Experimental studies have been carried out using emission spectroscopy resolved in space (1 mm) and time (1 {mu}s), under various discharge and post-discharge durations. These studies have shown the important effect of energy transfer from the discharge to the neutral gas. In fact this transfer produces an expansion of the negative glow observed when the post-discharge duration is decreased. A realistic modelling should thus be performed bearing in mind that the neutral gas behaves not as a thermostat. Consequently the thermal and hydrodynamic evolution of the neutral gas must be considered in the whole modelling.
Three-body physics in quenched unitary Bose gases
NASA Astrophysics Data System (ADS)
D'Incao, Jose P.; Sykes, Andrew G.; Corson, John P.; Koller, Andrew P.; Greene, Chris H.; Rey, Ana M.; Hazzard, Kaden R. A.; Bohn, John L.
2014-05-01
A degenerate Bose gas, quenched to unitarity, displays rapid losses that are attributed to three-body recombination. The rate at which this occurs is an item of keen interest in producing and probing a unitary Bose gas. In this work we explore the three-body physics relevant for unitary Bose gases using the hyperspherical adiabatic representation and determine the population of Efimov states formed during the quench and their subsequent decay rate by assuming a local interaction model in which a harmonic potential mimics the finite density of other particles. Our findings, consistent with experiments at JILA, indicate that the three-body loss time scales are generally longer than the system's equilibration time, therefore bolstering this scheme as an efficient route to create and explore the dynamics of unitary Bose gases. Supported by National Science Foundation, AFOSR-MURI, ARO-MURI, NDSEG and NRC.
ERIC Educational Resources Information Center
Sudarshan, E. C. G.
1975-01-01
Describes a four page paper written by S. Bose who helped found quantum statistics. The consequences of the paper to modern physics are presented. Contrasted are the scientific relationships of Einstein, Dirac, and Bose. (GH)
ERIC Educational Resources Information Center
Sudarshan, E. C. G.
1975-01-01
Describes a four page paper written by S. Bose who helped found quantum statistics. The consequences of the paper to modern physics are presented. Contrasted are the scientific relationships of Einstein, Dirac, and Bose. (GH)
A Neutral Gas Jet in a Low Velocity Shock Front at the Boundary of the Draco Nebula
NASA Technical Reports Server (NTRS)
Kalberla, P. W. M.; Herbstmeier, U.; Mebold, U.
1984-01-01
Twenty-one cm line observations with the Westerbork Synthesis Radio Telescope of a dust and molecular filament at the boundary of the Draco Nebula reveal a jet like neutral hydrogen feature funneling through an outlet in the low velocity shock front at the interface between the Draco Nebula and the surrounding gas. The jet like feature is apparently connected with a high velocity filament at VLSR = -180 km/sec. It is suggested that soft X-ray emission observed in the area is thermal bremsstrahlung produced by the deceleration of high velocity gas in galactic gas.
The Neutral Gas Desorption and Breakdown on a Metal-Dielectric Junction Immersed in a Plasma
NASA Technical Reports Server (NTRS)
Vayner, Boris; Galofaro, Joel; Ferguson, Dale; Lyons, Valerie J. (Technical Monitor)
2002-01-01
New results are presented of an experimental study and theoretical analysis of arcing on metal-dielectric junctions immersed in a low-density plasma. Two samples of conventional solar arrays have been used to investigate the effects of arcing within a wide range of neutral gas pressures, ion currents, and electron number densities. All data (except video) were obtained in digital form that allowed us to study the correlation between external parameters (plasma density, additional capacitance, bias voltage, etc) and arc characteristics (arc rate, arc current pulse width and amplitude, gas species partial pressures, intensities of spectral lines, and so on). Arc sites were determined by employing a video-camera, and it is shown that the most probable sites for arc inception are trip le-junctions, even though some arcs were initiated in gaps between cells. The effect of surface conditioning (decrease of arc rate due to outgassing) was clearly demonstrated. Moreover, a considerable increase in arc rate due to absorption of molecules from atmospheric air has been confirmed. The analysis of optical spectra (240-800 nm) reveals intense narrow atomic lines (Ag, H) and wide molecular bands (OH, CH, SiH, SiN) that confirm a complicated mechanism of arc plasma generation. The rate of plasma contamination due to arcing was measured by employing a mass-spectrometer. These measurements provided quite reliable data for the development of a theoretical model of plasma contamination, In conclusion, the arc threshold was increased to above 350 V (from 190 V) by keeping a sample in vacuum (20 micronTorr) for seven days. The results obtained are important for the understanding of the arc inception mechanism, which is absolutely essential for progress toward the design of high voltage solar arrays for space applications.
Song, Yixuan; Hagen, David A; Qin, Shuang; Holder, Kevin M; Falke, Kyle; Grunlan, Jaime C
2016-12-21
Layer-by-layer (LbL) assembled polymer-clay multilayer thin films are known to provide transparent and flexible gas barrier. In an effort to further lower the oxygen transmission rate (OTR) of these nanobrick wall thin films, sodium chloride was introduced into montmorillonite (MMT) suspension as an "indifferent electrolyte". At pH 6.5 the amphoteric edge sites of MMT have a neutral net charge, and a moderate concentration of NaCl effectively shields the charge from neighboring platelets, allowing van der Waals forces to attract the edges to one another. This edge-to-edge bonding creates a much more tortuous path for diffusing oxygen molecules. An eight-bilayer (BL) polyethylenimine (PEI)/MMT multilayer coating (∼50 nm thick), assembled with 5 mM NaCl in the aqueous clay suspension, exhibited an order of magnitude reduction in oxygen permeability (∼4 × 10(-20) cm(3)·cm/(cm(2)·Pa·s)) relative to its salt-free counterpart. This result represents the best barrier among polymer-clay bilayer systems, which is also lower than SiOx or AlxOy thin films. At higher NaCl concentration, the strong charge screening causes edge-to-face bonding among MMT nanoplatelets, which leads to misalignment in assembled films and increased OTR. This "salty-clay" strategy provides an efficient way to produce better multilayer oxygen barrier thin films by altering ionic strength of the MMT suspension. This simple modification reduces the number of layers necessary for high gas barrier, potentially making these multilayer films interesting for commercial packaging applications.
A Tetrapositive Metal Ion in the Gas Phase: Thorium(IV) Coordinated by Neutral Tridentate Ligands
Gong, Yu; Hu, Han-Shi; Tian, Guoxin; Rao, Linfeng; Li, Jun; Gibson, John K.
2013-07-01
ESI of 1:1 mixtures of Th(ClO₄)₄ and ligand TMOGA in acetonitrile resulted in the observation of the TMOGA supported tetracation, Th(L)₃⁴⁺, in the gas phase. Three TMOGA ligands are necessary to stabilize the tetrapositive thorium ion; no Th(L)₂⁴⁺ or Th(L)₄⁴⁺ was observed. Theoretical calculations reveal that the Th(L)₃⁴⁺ complex possesses C₃ symmetry with the thorium center coordinated by nine oxygen atoms from three ligands, which forms a twisted TPP geometry. Actinide compounds with such a geometry feature a nine-coordinate chiral actinide center. The Th-L binding energy and bond orders of Th(L)n⁴⁺ decrease as the coordination number increases, consistent with the trend of concurrently increasing Th-O distances. The Th-O bonding is mainly electrostatic in nature, but the covalent interactions are not negligible. CID of the Th(L)₃⁴⁺ complex mainly resulted in charge reduction to form Th(L)₂(L-86)³⁺oss of neutral TMOGA was not observed. The protic ligand methanol stabilized only tri- and dications of ligated thorium. The intensity of the Th(L)₃⁴⁺ peak was reduced as the percentage of water increased in the Th(ClO₄)₄/TMOGA solution.
NASA Technical Reports Server (NTRS)
Niemann, H. B.; Kasprzak, W. T.; Hedin, A. E.; Spencer, N. W.; Hunten, D. M.
1980-01-01
The neutral gas composition and density in the thermosphere of Venus is being measured with a quadrupole mass spectrometer on the Pioneer Venus orbiter. Data are obtained near periapsis once per day approximately 150-250 km above the surface. The principal gases in the thermosphere are CO2, CO, N2, O, N, and He. Atomic oxygen is the major constituent above 155 km on the dayside and also on the nightside up to 180 km when helium becomes the major constituent. The average values of CO2, CO, N2, O, and N remain nearly constant during day and night, but an abrupt change occurs across the terminator from a high dayside value to a low nightside value. The helium density varies in the opposite way, and a distinct bulge was observed at night near the morning terminator. The data have been used as the basis of an empirical model. Large orbit to orbit variations in densities were also observed on the nightside, suggesting perhaps strong turbulent motion in the atmosphere below. Kinetic temperatures inferred from scale heights are approximately 285 K on the dayside and 110 K at night. The average global temperature obtained from the model is 199 K.
NASA Technical Reports Server (NTRS)
Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.
2001-01-01
This work examines the accuracy of plasma neutral temperature estimates by fitting the rotational band envelope of different diatomic species in emission. Experiments are performed in an inductively coupled CF4 plasma generated in a Gaseous Electronics Conference reference cell. Visible and ultraviolet emission spectra are collected at a power of 300 W (approximately 0.7 W/cc) and pressure of 30 mtorr. The emission bands of several molecules (CF, CN, C2, CO, and SiF) are fit simultaneously for rotational and vibrational temperatures and compared. Four different rotational temperatures are obtained: 1250 K for CF and CN, 1600 K for CO, 1800 K for C2, and 2300 K for SiF. The vibrational temperatures obtained vary from 1750-5950 K, with the higher vibrational temperatures generally corresponding to the lower rotational temperatures. These results suggest that the different species have achieved different degrees of equilibration between the rotational and vibrational modes and may not be equilibrated with the translational temperatures. The different temperatures are also related to the likelihood that the species are produced by ion bombardment of the surface, with etch products like SiF, CO, and C2 having higher temperatures than species expected to have formed in the gas phase.
Investigating the Neutral-Gas Manometers in the Wendelstein 7-X Experimental Fusion Reactor
NASA Astrophysics Data System (ADS)
Maisano-Brown, Jeannette; Wenzel, Uwe; Sunn-Pederson, Thomas
2017-01-01
The neutral-gas manometer is a powerful diagnostic tool used in the Wendelstein 7-X stellarator, a magnetized fusion experiment located in Germany. The Wendelstein, produced at a cost of 1.2 billion euros, and 20 years in the making, had its first experimental results in Winter 2016. Initial findings exceeded expectations but further study is still necessary. The particular instrument we examined was a hot-cathode ionization gauge, critical for attaining a quality in-vessel environment and a stable plasma. However, after the winter operation of Wendelstein, we found that some of the gauges had failed the six-second (maximum) plasma runs. Wendelstein is on track for 30-minute operations within three years, so it has become of utmost importance to scrutinize gauge design claims. We therefore subjected the devices to high magnetic field, input current, and temperature, as well as to long operational periods. Our results confirmed that the manometer cannot survive a 30-minute run. Though our findings did motivate promising recommendations for design improvement and for further experimentation so that the gauge can be ready for upcoming operations in Summer 2017 and eventual installment in ITER, the International Thermonuclear Experimental Reactor, currently under construction. This research was graciously supported by the Max Planck Institute and the MIT-Germany Initiative.
Mixed-dimensional Bose polaron
NASA Astrophysics Data System (ADS)
Loft, Niels Jakob Søe; Wu, Zhigang; Bruun, G. M.
2017-09-01
A new generation of cold atom experiments trapping atomic mixtures in species-selective optical potentials opens up the intriguing possibility to create systems in which different atoms live in different spatial dimensions. Inspired by this, we investigate a mixed-dimensional Bose polaron consisting of an impurity particle moving in a two-dimensional (2D) layer immersed in a 3D Bose-Einstein condensate (BEC), using a theory that includes the mixed-dimensional vacuum scattering between the impurity and the bosons exactly. We show that similarly to the pure 3D case, this system exhibits a well-defined polaron state for attractive boson-impurity interaction that evolves smoothly into a mixed-dimensional dimer for strong attraction, as well as a well-defined polaron state for weak repulsive interaction, which becomes overdamped for strong interaction. We furthermore find that the properties of the polaron depend only weakly on the gas parameter of the BEC as long as the Bogoliubov theory remains a valid description for the BEC. This indicates that higher-order correlations between the impurity and the bosons are suppressed by the mixed-dimensional geometry in comparison to a pure 3D system, which led us to speculate that the mixed-dimensional polaron has universal properties in the unitarity limit of the impurity-boson interaction.
NASA Astrophysics Data System (ADS)
Wongwaitayakornkul, Pakorn; Bellan, Paul; Li, Hui; Li, Shengtai
2016-10-01
Shocks occur in the co-rotating interaction regions just beyond the solar corona, in the corona during CME events, and when the solar wind impacts Earth's magnetosphere. The Caltech solar loop experiment investigates shock physics by creating an arched plasma-filled flux rope that expands to collide with a pre-injected, initially-neutral gas. We focus the investigation on the situation of a heavy-gas plasma (Argon) impacting a much lighter neutral gas cloud (Hydrogen). The neutral gas target cloud ionizes immediately upon being impacted and plasma-induced shock waves propagate in the target cloud away from the impact region. Analysis of data from magnetic probes, Langmuir probes, a fast camera, and spectroscopic measurements will be presented. The measurements suggest that a thin, compressed, ionized layer of hydrogen is formed just downstream of the Argon plasma loop and that thin, supersonic shocks form further downstream and propagate obliquely away from the plasma loop. Numerical simulation of an ideal MHD plasma is underway to enable comparison of the measurements with the predictions of MHD theory.
Predicted signatures of rotating Bose-Einstein Condensates
Butts, D.A.; Rokhsar, D.S.
1999-01-01
Superfluids are distinguished from normal fluidsby theirpeculiar response1 to rotation: circulating flow in superfuid helium2,3,astrongly coupled Bose liquid, can appear only as quantized vortices4-6.The newly created Bose-Einstein condensates7,9--clouds of millions ofultracold, weakly interacting alkali-metal atoms that occupy a singlequantum state Doffer the possibility of investigating superuidity in theweak-coupling regime. An outstanding question is whether Bose-Einsteincondensates exhibit a mesoscopic quantum analogue of the macroscopicvortices in superfluids, and what its experimental signature would be.Here we report calculations of the low-energy states of a rotating,weakly interacting Bose gas. We find a succession of transitions betweenstab reement with observations5 of rotating super-fluid helium, astrong-coupling superfuid. Counterintuitively, the angular momentum perparticle is not quantized. Some angular momenta are forbidden,corresponding to asymmetrical unstablestates that provide a physicalmechanism for the entry of vorticity into the condensate.
The neutral gas extent of galaxies as derived from weak intervening Ca ii absorbers
NASA Astrophysics Data System (ADS)
Richter, P.; Krause, F.; Fechner, C.; Charlton, J. C.; Murphy, M. T.
2011-04-01
We present a systematic study of weak intervening Ca ii absorbers at low redshift (z < 0.5), based on the analysis of archival high-resolution (R ≥ 45 000) optical spectra of 304 quasars and active galactic nuclei observed with VLT/UVES. Along a total redshift path of Δz ≈ 100 we detected 23 intervening Ca ii absorbers in both the Ca ii H & K lines, with rest frame equivalent widths Wr,3934 = 15-799 mÅ and column densities log N(Ca ii) = 11.25-13.04 (obtained by fitting Voigt-profile components). We obtain a bias-corrected number density of weak intervening Ca ii absorbers of {d{N}/dz=0.117 ± 0.044} at ⟨zabs⟩ = 0.35 for absorbers with log N(Ca ii) ≥ 11.65 (Wr,3934 ≥ 32 mÅ). This is 2.6 times the value obtained for damped Lyman α absorbers (DLAs) at low redshift. All Ca ii absorbers in our sample show associated absorption by other low ions such as Mg ii and Fe ii; 45 percent of them have associated Na i absorption. From ionization modelling we conclude that intervening Ca ii absorption with log N(Ca ii) ≥ 11.5 arises in DLAs, sub-DLAs and Lyman-limit systems (LLS) at H i column densities of log N(H i) ≥ 17.4. Using supplementary H i information for nine of the absorbers we find that the Ca ii/H i ratio decreases strongly with increasing H i column density, indicating a column-density-dependent dust depletion of Ca. The observed column density distribution function of Ca ii absorption components follows a relatively steep power law, f(N) ∝ N - β, with a slope of - β = -1.68, which again points towards an enhanced dust depletion in high column density systems. The relatively large cross section of these absorbers together with the frequent detection of Ca ii absorption in high-velocity clouds (HVCs) in the halo of the Milky Way suggests that a considerable fraction of the intervening Ca ii systems trace (partly) neutral gas structures in the halos and circumgalactic environment of galaxies (i.e., they are HVC analogs). Based on the recently
NASA Astrophysics Data System (ADS)
Huang, Zhenguang; Tóth, Gábor; Gombosi, Tamas I.; Jia, Xianzhe; Rubin, Martin; Fougere, Nicolas; Tenishev, Valeriy; Combi, Michael R.; Bieler, Andre; Hansen, Kenneth C.; Shou, Yinsi; Altwegg, Kathrin
2016-05-01
The neutral and plasma environment is critical in understanding the interaction of the solar wind and comet 67P/Churyumov-Gerasimenko (CG), the target of the European Space Agency's Rosetta mission. To serve this need and support the Rosetta mission, we have developed a 3-D four-fluid model, which is based on BATS-R-US (Block-Adaptive Tree Solarwind Roe-type Upwind Scheme) within SWMF (Space Weather Modeling Framework) that solves the governing multifluid MHD equations and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. This model incorporates different mass loading processes, including photoionization and electron impact ionization, charge exchange, dissociative ion-electron recombination, and collisional interactions between different fluids. We simulated the plasma and neutral gas environment near perihelion in three different cases: an idealized comet with a spherical body and uniform neutral gas outflow, an idealized comet with a spherical body and illumination-driven neutral gas outflow, and comet CG with a realistic shape model and illumination-driven neutral gas outflow. We compared the results of the three cases and showed that the simulations with illumination-driven neutral gas outflow have magnetic reconnection, a magnetic pileup region and nucleus directed plasma flow inside the nightside reconnection region, which have not been reported in the literature.
NASA Astrophysics Data System (ADS)
Shuman, Nicholas S.; Viggiano, Albert A.; Johnsen, Rainer
2013-05-01
We have studied the dependence of several ion-ion mutual neutralization (MN) reactions on helium density in the range from 1.6 × 1016 to 1.5 × 1017 cm-3 at 300 K, using the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The rate coefficients of the reactions Ar+ + Br2-, Ar+ + SF6-, and Ar+ + C7F14- were found to be independent of gas density over the range studied, in disagreement with earlier observations that similar MN reactions are strongly enhanced at the same gas densities. The cause of the previous enhancement with density is traced to the use of "orbital-motion-limit" theory to infer ion densities from the currents collected by ion-attracting Langmuir probes in a region where it is not applicable.
Shuman, Nicholas S.; Viggiano, Albert A.; Johnsen, Rainer
2013-05-28
We have studied the dependence of several ion-ion mutual neutralization (MN) reactions on helium density in the range from 1.6 Multiplication-Sign 10{sup 16} to 1.5 Multiplication-Sign 10{sup 17} cm{sup -3} at 300 K, using the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The rate coefficients of the reactions Ar{sup +}+ Br{sub 2}{sup -}, Ar{sup +}+ SF{sub 6}{sup -}, and Ar{sup +}+ C{sub 7}F{sub 14}{sup -} were found to be independent of gas density over the range studied, in disagreement with earlier observations that similar MN reactions are strongly enhanced at the same gas densities. The cause of the previous enhancement with density is traced to the use of 'orbital-motion-limit' theory to infer ion densities from the currents collected by ion-attracting Langmuir probes in a region where it is not applicable.
Montero-Campillo, M Merced; Mora-Diez, Nelaine; Lamsabhi, Al Mokhtar
2010-09-23
The thermodynamic stability of the 89 isomers of the eight-carbon-atom compound perfluorooctane sulfonate (PFOS) in their neutral and anionic forms has been studied in the gas phase, n-octanol, and water using density functional theory (B3LYP/6-311+G(d,p)). The gas-phase calculations are compared with previous semiempirical and partial ab initio studies; the calculations in water and n-octanol are reported for the first time. The results obtained indicate that the thermodynamic stability assessment of this family of persistent organic pollutants is independent of the environment and type of species (neutral or anionic) considered and that it is important to consider other PFOSs outside of the 83-89 set, which is the most frequently studied.
Schowalter, Steven J.; Dunning, Alexander J.; Chen, Kuang; Puri, Prateek; Schneider, Christian; Hudson, Eric R.
2016-01-01
Sympathetic cooling of trapped ions through collisions with neutral buffer gases is critical to a variety of modern scientific fields, including fundamental chemistry, mass spectrometry, nuclear and particle physics, and atomic and molecular physics. Despite its widespread use over four decades, there remain open questions regarding its fundamental limitations. To probe these limits, here we examine the steady-state evolution of up to 10 barium ions immersed in a gas of three-million laser-cooled calcium atoms. We observe and explain the emergence of nonequilibrium behaviour as evidenced by bifurcations in the ion steady-state temperature, parameterized by ion number. We show that this behaviour leads to the limitations in creating and maintaining translationally cold samples of trapped ions using neutral-gas sympathetic cooling. These results may provide a route to studying non-equilibrium thermodynamics at the atomic level. PMID:27511602
Marcalo, Joaquim; Gibson, John K.
2009-08-10
An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.
NASA Astrophysics Data System (ADS)
Marçalo, Joaquim; Gibson, John K.
2009-09-01
An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.
Khrapak, S. A.; Klumov, B. A.; Huber, P.; Thomas, H. M.; Ivlev, A. V.; Morfill, G. E.; Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N.; Petrov, O. F.; Fortov, V. E.; Malentschenko, Yu.; Volkov, S.
2011-05-20
Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. The evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify the main factors responsible for the observed behavior.
Marçalo, Joaquim; Gibson, John K
2009-11-12
An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.
NASA Astrophysics Data System (ADS)
Nandan Gupta, Devki
2013-11-01
We study the effect of laser-induced double-ionization of a helium gas (with inhomogeneous density profile) on vacuum electron acceleration. For enough laser intensity, helium gas can be found doubly ionized and it strengthens the divergence of the pulse. The double ionization of helium gas can defocus the laser pulse significantly, and electrons are accelerated by the front of the laser pulse in vacuum and then decelerated by the defocused trail part of the laser pulse. It is observed that the electrons experience a very low laser-intensity at the trailing part of the laser pulse. Hence, there is not much electron deceleration at the trailing part of the pulse. We found that the inhomogeneity of the neutral gas reduced the rate of tunnel ionization causing less defocusing of the laser pulse and thus the electron energy gain is reduced.
Atomtronics with Ultracold Bose Gases
NASA Astrophysics Data System (ADS)
Ott, Herwig
Neutral atom systems can exhibit similar transport properties like solid state devices. For instance, a neutral atom current is induced by a difference in chemical potential very much in the same way as a voltage drives an electric current. Employing Bose-Einstein condensed atomic gases allows observing superfluid transport phenomena, thus drawing connections to superconductivity. With help of light fields, the atomic current can additionally be guided in engineered potential landscapes in which one can also incorporate tunneling junctions. Eventually, the different components and elements can be integrated in atomtronic circuits which shed light on fundamental transport properties of many-body quantum systems. In this talk, I will present two fundamental atomtronic devices. The first is the observation of negative differential conductivity, which occurs at a multimode tunneling junction for ultracold atoms. The second is the appearance of a DC Josephson current in a biased tunneling junction, which features bistable transport characteristics. I will discuss the prospects of these basic elements for more complex atomtronic circuits.
Fox, A; Morgan, S L; Hudson, J R; Zhu, Z T; Lau, P Y
1983-02-18
Several improvements in the preparation of alditol acetates of neutral and amino sugars and in the preparation of glass capillary columns for their separation are described. Modifications in sample preparation permitted the simultaneous processing of multiple samples and eliminated extraneous background peaks. Efficient and inert columns were tailor-made for the separation of alditol acetates of neutral and amino sugars by leaching glass capillaries with aqueous hydrochloric acid and dynamically coating with SP-2330.
Tan, Cheng-Yan; /Fermilab
2010-03-01
The neutralization of H{sup -} beam with a gas like Xe is an important part of low energy beam transport (LEBT). It is well known that choppers which use an electric field when placed in the LEBT strongly affects the neutralization of H{sup -}. The question then naturally arises as to whether a magnetic chopper has a better neutralization time than an electric chopper. To answer this question, a simple 1-space, 1 time drift-diffusion model of H{sup -} beam in Xe gas has been used to calculate the neutralization times for the following scenarios: (a) a region initially cleared of Xe+ ions with an electric field but partially neutralized outside, (b) a region within and outside the chopper which is initially partially neutralized.
Basic Mean-Field Theory for Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Kevrekidis, P. G.; Frantzeskakis, D. J.; Carretero-González, R.
The phenomenon of Bose-Einstein condensation, initially predicted by Bose [1] and Einstein [2, 3] in 1924, refers to systems of particles obeying the Bose statistics. In particular, when a gas of bosonic particles is cooled below a critical transition temperature T c , the particles merge into the Bose-Einstein condensate (BEC), in which a macroscopic number of particles (typically 103 to 106) share the same quantum state. Bose-Einstein condensation is in fact a quantum phase transition, which is connected to the manifestation of fundamental physical phenomena, such as superfluidity in liquid helium and superconductivity in metals (see, e.g., [4] for a relevant discussion and references). Dilute weakly-interacting BECs were first realized experimentally in 1995 in atomic gases, and specifically in vapors of rubidium [5] and sodium [6]. In the same year, first signatures of Bose-Einstein condensation in vapors of lithium were also reported [7] and were later more systematically confirmed [8]. The significance and importance of the emergence of BECs has been recognized through the 2001 Nobel prize in Physics [9, 10]. During the last years there has been an explosion of interest in the physics of BECs. Today, over fifty experimental groups around the world can routinely produce BECs, while an enormous amount of theoretical work has ensued.
Noise thermometry with two weakly coupled Bose-Einstein condensates.
Gati, Rudolf; Hemmerling, Börge; Fölling, Jonas; Albiez, Michael; Oberthaler, Markus K
2006-04-07
Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.
Composite fermion basis for M-component Bose gases
NASA Astrophysics Data System (ADS)
Skogvoll, V.; Liabøtrø, O.
2017-10-01
The composite fermion (CF) formalism produces wave functions that are not always linearly independent. This is especially so in the low angular momentum regime in the lowest Landau level, where a subclass of CF states, known as simple states, gives a good description of the low energy spectrum. For the two-component Bose gas, explicit bases avoiding the large number of redundant states have been found. We generalize one of these bases to the M-component Bose gas and prove its validity. We also show that the numbers of linearly independent simple states for different values of angular momentum are given by coefficients of q-multinomials.
Analytical approach to relaxation dynamics of condensed Bose gases
Escobedo, Miguel; Pezzotti, Federica; Valle, Manuel
2011-04-15
Research Highlights: > Time evolution of perturbations from equilibrium in a condensed Bose gas is studied. > Just below the critical temperature the perturbations vanish algebraically. > Anisotropic perturbations are unstable. > At very low temperature perturbations decay exponentially. - Abstract: The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.
NASA Astrophysics Data System (ADS)
Moebius, E.; Bochsler, P. A.; Bzowski, M.; Fuselier, S. A.; Heirtzler, D.; Hlond, M.; Kubiak, M.; Kucharek, H.; Lee, M. A.; Leonard, T.; McComas, D. J.; Saul, L. A.; Schwadron, N. A.; Sokol, J.; Wurz, P.
2013-05-01
The Interstellar Boundary Explorer (IBEX) observes the interstellar neutral gas flow tra-jectories at their perihelion in Earth's orbit every year from December through late March, when the Earth moves into the oncoming flow. Surprisingly, the initial quantita-tive analysis resulted in a somewhat different interstellar flow vector with noticeably lower speed than obtained previously. In comparison with astronomical observations of the flow vectors of neighboring interstellar clouds, this result locates the solar system within the Local Interstellar Cloud (LIC), contrary to the previous determination, which indicated values between the LIC and the G-Cloud. This year, the fifth season is being accumulated, providing a database over increasing solar activity and with varying view-ing strategies. These recurring observations of the interstellar flow pattern and its spatial distribution allow us to consolidate the derived physical conditions of the surrounding interstellar medium. We can also track variations in the flow at 1 AU that may arise from solar cycle related changes in ionization and radiation pressure for H and explore any other variations of the neutral gas flow. Based on the angular distributions in latitude and longitude, the neutral flow observations also indicate the presence of a secondary compo-nent for most of the species, which most probably stems from charge exchange with ions in the outer heliosheath. We will review our observations and discuss implications for the LIC and its interaction with the heliosphere in the light of a growing data set and improv-ing analysis techniques.
Oscillons in coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Su, Shih-Wei; Gou, Shih-Chuan; Liu, I.-Kang; Bradley, Ashton S.; Fialko, Oleksandr; Brand, Joachim
2015-02-01
Long-lived, spatially localized, and temporally oscillating nonlinear excitations are predicted by numerical simulation of coupled Gross-Pitaevskii equations. These oscillons closely resemble the time-periodic breather solutions of the sine-Gordon equation but decay slowly by radiating Bogoliubov phonons. Their time-dependent profile is closely matched with solutions of the sine-Gordon equation, which emerges as an effective field theory for the relative phase of two linearly coupled Bose fields in the weak-coupling limit. For strong coupling the long-lived oscillons persist and involve both relative and total phase fields. The oscillons decay via Bogoliubov phonon radiation that is increasingly suppressed for decreasing oscillon amplitude. Possibilities for creating oscillons are addressed in atomic gas experiments by collision of oppositely charged Bose-Josephson vortices and direct phase imprinting.
Rotons in Interacting Ultracold Bose Gases
Cormack, Samuel C.; Schumayer, Daniel; Hutchinson, David A. W.
2011-09-30
In three dimensions, noninteracting bosons undergo Bose-Einstein condensation at a critical temperature, T{sub c}, which is slightly shifted by {Delta}T{sub c}, if the particles interact. We calculate the excitation spectrum of interacting Bose systems, {sup 4}He and {sup 87}Rb, and show that a roton minimum emerges in the spectrum above a threshold value of the gas parameter. We provide a general theoretical argument for why the roton minimum and the maximal upward critical temperature shift are related. We also suggest two experimental avenues to observe rotons in condensates. These results, based upon a path-integral Monte Carlo approach, provide a microscopic explanation of the shift in the critical temperature and also show that a roton minimum does emerge in the excitation spectrum of particles with a structureless, short-range, two-body interaction.
NASA Astrophysics Data System (ADS)
Yamada, Hiromasa; Yamagishi, Yusuke; Sakakita, Hajime; Tsunoda, Syuichiro; Kasahara, Jiro; Fujiwara, Masanori; Kato, Susumu; Itagaki, Hirotomo; Kim, Jaeho; Kiyama, Satoru; Fujiwara, Yutaka; Ikehara, Yuzuru; Ikehara, Sanae; Nakanishi, Hayao; Shimizu, Nobuyuki
2016-01-01
To understand the mechanism of turbulent enhancement phenomena of a neutral gas flow containing plasma ejected from the nozzle of plasma equipment, the schlieren optical method was performed to visualize the neutral gas behavior. It was confirmed that the turbulent starting point became closer to the nozzle exit, as the amplitude of discharge voltage (electric field) increased. To study the effect of electric field on turbulent enhancement, two sets of external electrodes were arranged in parallel, and the gas from the nozzle was allowed to flow between the upper and lower electrodes. It was found that the neutral gas flow was bent, and the bending angle increased as the amplitude of the external electric field increased. The results obtained using a simple model analysis roughly coincide with experimental data. These results indicate that momentum transport from drifted ions induced by the electric field to neutral particles is an important factor that enhances turbulence.
Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers
Maingi, R.
1992-08-01
The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles.
NASA Astrophysics Data System (ADS)
Moebius, E.; Bzowski, M.; Drews, C.; Frisch, P. C.; Fuselier, S. A.; Galli, A.; Gloeckler, G.; Kubiak, M. A.; Kucharek, H.; Lee, M. A.; Leonard, T.; McComas, D. J.; Park, J.; Schwadron, N.; Swaczyna, P.; Sokol, J. M.; Wood, B. E.; Wurz, P.
2015-12-01
The Sun's motion relative to the surrounding interstellar medium leads to an interstellar neutral (ISN) wind through the heliosphere that is moderately depleted by ionization. This situation allows remote sensing of the ISN through resonant scattering of solar UV and in-situ sampling, first via pickup ions (PUI) and most recently with direct neutral atom imaging. PUI observations have revealed the gravitational focusing cone of interstellar He and Ne as well as the composition of high ionization potential elements. After the first direct ISN He observations with Ulysses GAS, the Interstellar Boundary Explorer (IBEX) observes with high collecting power the ISN flow trajectories very close to their perihelion in Earth's orbit for H, He, O, and Ne from December through March. Meanwhile, IBEX has recorded seven years of ISN observations, with changing solar activity and varying viewing strategies. These recurring and remarkably repeatable observations allow us to consolidate the derived physical parameters and some key compositional aspects of the interstellar medium. IBEX observations provide a very precise relation between ISN flow longitude and speed via the hyperbolic trajectory equation, but with larger uncertainties separately for longitude and speed. Recent concerted studies have led to a velocity vector that is consistent between IBEX and Ulysses, with a substantially higher temperature than found previously. The fact that the IBEX He and O ISN observations contain a substantial secondary neutral contribution adds complexity to the quantitative analysis of the physical interstellar medium parameters. However, their discovery also provides invaluable insight into the interstellar plasma interaction in the outer heliosheath, which is shaped strongly by the interstellar magnetic field. The longitude range of the IBEX observations limits the precision of the ISN velocity vector. The IBEX collection power and its sensitivity to the Earth's magnetosphere limit
Two-component Bose gases under rotation
Bargi, S.; Kaerkkaeinen, K.; Christensson, J.; Reimann, S. M.; Kavoulakis, G. M.; Manninen, M.
2008-04-04
We examine the formation of vortices in a one- and two-component gas of bosonic atoms in a harmonic trap that is set rotating. Both the mean-field Gross-Pitaevskii approach, and the numerical diagonalization method are employed. For a two-component Bose gas, we show that beside the well-known coreless vortices of single quantization, the interatomic interactions between the two species may lead to coreless vortices of multiple quantization. We furthermore comment on the geometries of the interlaced vortex patterns. In the limit of weak interactions, we finally demonstrate a number of exact results.
NASA Astrophysics Data System (ADS)
Maffucci, D. M.; Woon, D. E.; Herbst, E.
2017-05-01
Using updated electronic structures, we employ a variety of kinetic theories to calculate the reaction rate constants for neutral-neutral chemical reactions between sulfur- and chlorine-containing molecules observed in the atmosphere of Venus.
A new technique for in situ measurement of the composition of neutral gas in interplanetary space
NASA Technical Reports Server (NTRS)
Gruntman, Michael A.
1993-01-01
Neutral atoms in interplanetary space play an important role in many processes relevant to the formation and evolution of the Solar System. An experimental approach is proposed for in situ atom detection based on the conversion of neutral atoms to negative ions at a specially prepared sensitive surface. Negative ions are subsequently analyzed and detected in an essentially noise-free mode. The use of the technique for in situ study of the composition of neutral interstellar atoms is considered. It is shown that interstellar H, D, and O atoms and possibly H2 molecules can be measured by the proposed technique. The experiment can be performed from a high-apogee Earth-orbiting satellite or from a deep space probe. Possible applications of the technique are discussed.
A SEARCH FOR CO-EVOLVING ION AND NEUTRAL GAS SPECIES IN PRESTELLAR MOLECULAR CLOUD CORES
Tassis, Konstantinos; Hezareh, Talayeh; Willacy, Karen
2012-11-20
A comparison between the widths of ion and neutral molecule spectral lines has been recently used to estimate the strength of the magnetic field in turbulent star-forming regions. However, the ion (HCO{sup +}) and neutral (HCN) species used in such studies may not be necessarily co-evolving at every scale and density, and thus, may not trace the same regions. Here, we use coupled chemical/dynamical models of evolving prestellar molecular cloud cores including non-equilibrium chemistry, with and without magnetic fields, to study the spatial distribution of HCO{sup +} and HCN, which have been used in observations of spectral line width differences to date. In addition, we seek new ion-neutral pairs that are good candidates for such observations, because they have similar evolution and are approximately co-spatial in our models. We identify three such good candidate pairs: HCO{sup +}/NO, HCO{sup +}/CO, and NO{sup +}/NO.
Effects of neutral gas releases on electron beam injection from electrically tethered spacecraft
NASA Technical Reports Server (NTRS)
Winglee, R. M.
1990-01-01
The presence of high neutral densities at low altitudes and/or during thruster firings is known to modify the spacecraft potential during active electron beam injection. Two-dimensional (three velocity) particle simulations are used to investigate the ionization processes including the neutral density required, the modification of the spacecraft potential, beam profile and spatial distribution of the return current into the spacecraft. Three processes are identified: (1) beam-induced ionization, (2) vehicle-induced ionization, and (3) beam plasma discharge. Only in the first two cases does the beam propagate away with little distortion.
NASA Astrophysics Data System (ADS)
Shuman, Nicholas S.; Miller, Thomas M.; Johnsen, Rainer; Viggiano, Albert A.
2014-01-01
We report thermal rate coefficients for 12 reactions of rare gas cations (Ne+, Ar+, Kr+, Xe+) with halide anions (Cl-, Br-, I-), comprising both mutual neutralization (MN) and transfer ionization. No rate coefficients have been previously reported for these reactions; however, the development of the Variable Electron and Neutral Density Attachment Mass Spectrometry technique makes it possible to measure the difference of the rate coefficients for pairs of parallel reactions in a Flowing Afterglow-Langmuir Probe apparatus. Measurements of 18 such combinations of competing reaction pairs yield an over-determined data set from which a consistent set of rate coefficients of the 12 MN reactions can be deduced. Unlike rate coefficients of MN reactions involving at least one polyatomic ion, which vary by at most a factor of ˜3, those of the atom-atom reactions vary by at least a factor 60 depending on the species. It is found that the rate coefficients involving light rare-gas ions are larger than those for the heavier rare-gas ions, but the opposite trend is observed in the progression from Cl- to I-. The largest rate coefficient is 6.5 × 10-8 cm3 s-1 for Ne+ with I-. Rate coefficients for Ar+, Kr+, and Xe+ reacting with Br2- are also reported.
Shuman, Nicholas S; Miller, Thomas M; Johnsen, Rainer; Viggiano, Albert A
2014-01-28
We report thermal rate coefficients for 12 reactions of rare gas cations (Ne(+), Ar(+), Kr(+), Xe(+)) with halide anions (Cl(-), Br(-), I(-)), comprising both mutual neutralization (MN) and transfer ionization. No rate coefficients have been previously reported for these reactions; however, the development of the Variable Electron and Neutral Density Attachment Mass Spectrometry technique makes it possible to measure the difference of the rate coefficients for pairs of parallel reactions in a Flowing Afterglow-Langmuir Probe apparatus. Measurements of 18 such combinations of competing reaction pairs yield an over-determined data set from which a consistent set of rate coefficients of the 12 MN reactions can be deduced. Unlike rate coefficients of MN reactions involving at least one polyatomic ion, which vary by at most a factor of ∼3, those of the atom-atom reactions vary by at least a factor 60 depending on the species. It is found that the rate coefficients involving light rare-gas ions are larger than those for the heavier rare-gas ions, but the opposite trend is observed in the progression from Cl(-) to I(-). The largest rate coefficient is 6.5 × 10(-8) cm(3) s(-1) for Ne(+) with I(-). Rate coefficients for Ar(+), Kr(+), and Xe(+) reacting with Br2 (-) are also reported.
Spatially Periodic Structures of an Atomic Bose-Einstein Condensate
Rozanov, N.N.
2005-06-15
The conditions providing the formation of periodic vortex lattices of an interference nature in an atomic Bose-Einstein condensate (i.e., in the absence of rotation of the condensate) are determined. Spatially periodic exact solutions of the nonlocal nonlinear Schroedinger equation (the generalized Gross-Pitaevskii equation) that describes the Bose-Einstein condensate of a dilute gas of alkali metal atoms with due regard for the nonlocality of interatomic interactions are obtained in the form of a set of two or three plane waves. It is shown that periodic vortex lattices can be produced in interference experiments with a Bose-Einstein condensate of a dilute gas of alkali metal atoms.
Multiple condensed phases in attractively interacting Bose systems
NASA Astrophysics Data System (ADS)
Männel, M.; Morawetz, K.; Lipavský, P.
2010-03-01
We investigate a Bose gas with finite-range interaction using a scheme to eliminate unphysical processes in the T-matrix approximation. In this way the corrected T-matrix becomes suitable to calculate properties below the critical temperature. For attractive interaction, an Evans-Rashid transition occurs between a quasi-ideal Bose gas and a Bardeen-Cooper-Schrieffer-like phase with a gap dispersion. The gap decreases with increasing density and vanishes at a critical density where the single-particle dispersion becomes linear for small momenta, indicating Bose-Einstein condensation. The investigation of the pressure shows, however, that the mentioned quantum phase transitions might be inaccessible due to a preceding first-order transition.
El-Sherbini, Th.M.
2005-03-17
This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.
Monte Carlo modeling of neutral gas and dust in the coma of Comet 1P/Halley
NASA Astrophysics Data System (ADS)
Rubin, Martin; Tenishev, Valeriy M.; Combi, Michael R.; Hansen, Kenneth C.; Gombosi, Tamas I.; Altwegg, Kathrin; Balsiger, Hans
2011-06-01
The neutral gas environment of a comet is largely influenced by dissociation of parent molecules created at the surface of the comet and collisions of all the involved species. We compare the results from a kinetic model of the neutral cometary environment with measurements from the Neutral Mass Spectrometer and the Dust Impact Detection System onboard the Giotto spacecraft taken during the fly-by at Comet 1P/Halley in 1986. We also show that our model is in good agreement with contemporaneous measurements obtained by the International Ultraviolet Explorer, sounding rocket experiments, and various ground based observations. The model solves the Boltzmann equation with a Direct Simulation Monte Carlo technique (Tenishev, V., Combi, M., Davidsson, B. [2008]. Astrophys. J. 685, 659-677) by tracking trajectories of gas molecules and dust grains under the influence of the comet's weak gravity field with momentum exchange among particles modeled in a probabilistic manner. The cometary nucleus is considered to be the source of dust and the parent species (in our model: H 2O, CO, H 2CO, CO 2, CH 3OH, C 2H 6, C 2H 4, C 2H 2, HCN, NH 3, and CH 4) in the coma. Subsequently our model also tracks the corresponding dissociation products (H, H 2, O, OH, C, CH, CH 2, CH 3, N, NH, NH 2, C 2, C 2H, C 2H 5, CN, and HCO) from the comet's surface all the way out to 10 6 km. As a result we are able to further constrain cometary the gas production rates of CO (13%), CO 2 (2.5%), and H 2CO (1.5%) relative to water without invoking unknown extended sources.
NASA Technical Reports Server (NTRS)
Hollenbach, D. J.; Watson, D. M.; Townes, C. H.; Dinerstein, H. L.; Hollenbach, D.; Lester, D. F.; Werner, M.; Storey, J. W. V.
1983-01-01
The 3P1 - 3P2 fine structure line emission from neutral atomic oxygen at 63 microns in the vicinity of the galactic center was mapped. The emission is extended over more than 4' (12 pc) along the galactic plane, centered on the position of Sgr A West. The line center velocities show that the O I gas is rotating around the galactic center with an axis close to that of the general galactic rotation, but there appear also to be noncircular motions. The rotational velocity at R is approximately 1 pc corresponds to a mass within the central pc of about 3 x 10(6) solar mass. Between 1 and 6 pc from the center the mass is approximately proportional to radius. The (O I) line probability arises in a predominantly neutral, atomic region immediately outside of the ionized central parsec of out galaxy. Hydrogen densities in the (O I) emitting region are 10(3) to 10(6) cm(-3) and gas temperatures are or = 100 K. The total integrated luminosity radiated in the line is about 10(5) solar luminosity, and is a substantial contribution to the cooling of the gas. Photoelectric heating or heating by ultraviolet excitation of H2 at high densities (10(5) cm(-3)) are promising mechanisms for heating of the gas, but heating due to dissipation of noncircular motions of the gas may be an alternative possibility. The 3P1 - 3P0 fine structure line of (O III) at 88 microns toward Sgr A West was also detected. The (O III) emission comes from high density ionized gas (n 10(4) cm(-3)), and there is no evidence for a medium density region (n 10(3) cm(-3)), such as the ionized halo in Sgr A West deduced from radio observations. This radio halo may be nonthermal, or may consist of many compact, dense clumps of filaments on the inner edges of neutral condensations at R or = 2 pc.
Modeling the Neutral Gas and Plasma Environment of Jupiter's Moon Europa
NASA Astrophysics Data System (ADS)
Rubin, Martin; Tenishev, Valeriy; Hansen, Kenneth; Jia, Xianzhe; Combi, Michael; Gombosi, Tamas
Jupiter's moon Europa has a thin gravitationally bound neutral atmosphere, which is mostly created through sputtering of high-energy ions impacting on its icy surface. The interaction of Europa with the Jovian magnetosphere is simulated using the magnetohydrodynamics (MHD) model BATSRUS. We start from the model by Kabin et al. [JGR, Vol. 104, No. A9, (1999)], which accounts for the exospheric mass loading, ion-neutral charge exchange, and ion-electron recombination. The derived magnetic field topology and plasma speeds are used to calculate the Lorentz force for our test particle Monte Carlo model. We use this model to simulate Europa's plasma and neutral environment by tracking particles created on the moon's surface by sputtering or sublimation, through dissociation and/or ionization in the atmosphere, or entering the system from Jupiter's magnetosphere as high energy ions. Neutral particle trajectories are followed by solving the equation of motion in Europa's gravity field whereas the ion population is additionally subject to the Lorentz force. We will show preliminary results of this work with application to the missions to the Jupiter system currently under consideration by NASA (JEO) and ESA (JGO).
Upper-Thermospheric Observations and Neutral-Gas Dynamics at High Latitudes During Solar Maximum.
1987-01-01
thermosphere is sensitive, vary vith solar activity. These variations effect the global ...While solar - flare effects are of practical importance, the solar phenomenon that routinely controls upper- thermospheric dynamics is the low-energy plasma...Mechanisms in the Thermosphere 2.3.4 Global - Thermospheric Neutral Winds 2.4 Perturbations From the Mean Thermospheric State 2.4.1 Variations in Solar
2015-01-07
two noble gases (e.g., Ar and Kr) are added to an upstream inlet to create an Ar+/Kr+/e− plasma as described above. Downstream, a single gas that...Ne+ dominated plasma in the same manner. Alternatively, two rare gases instead of one may be added downstream, each through a separate mass flow meter...reducing the fraction of He+ in the plasma. Either one or two neutral attaching gases (CCl4 (Sigma Aldrich) to yield Cl−, CF2Br2 (Sigma Aldrich) to
NASA Astrophysics Data System (ADS)
Doyle, Scott; Gibson, Andrew; Boswell, Roderick; Charles, Christine; Dedrick, James
2016-09-01
Over the past few decades there has been a growing interest in the development compact sources of electric propulsion. In this study the effect of driving the `Pocket Rocket' radio-frequency electrothermal microthruster with non-sinusoidal voltage waveforms, consisting of multiple harmonics of 13.56 MHz, is investigated using the Hybrid Plasma Equipment Model (HPEM). The results are compared to previous experiments and simulation results using CFD-ACE+ to investigate the potential to generate an increased neutral gas temperature and density in the source. The authors gratefully acknowledge M. Kushner of the University of Michigan for the use of the Hybrid Plasma Equipment Model (HPEM).
New look at thermodynamics of gas and at clusterization
NASA Astrophysics Data System (ADS)
Maslov, V. P.
2008-12-01
In the paper, by using the example of a rigorous formulation and rigorous proof of the Maxwell distribution, estimates for the distribution in dependence of the parameter N (the number of particles) are established. Further, the problem concerning the creation of dimers in classical gas is regarded as an analog of Bose condensation, and estimates for the lower level of the analog of Bose condensation are proved. The relationship between this level and the theory of “capture” in the scattering problem corresponding to interaction in the form of Lennard-Jones potential is clarified. The equation of state of a nonideal gas as a result of pairwise interaction of particles in the Lennard-Jones and Kihara models is derived. New quantum equations for the transfer of neutral gas consisting of particles with evenly and oddly many neutrons in capillaries and nanotubes are also presented.
NASA Astrophysics Data System (ADS)
Grcevich, Jana; Berger, Sabrina; Putman, Mary E.; Eli Goldston Peek, Joshua
2016-01-01
Several interesting compact neutral hydrogen clouds were found in the GALFA-HI (Galactic Arecibo L-Band Feed Array HI) survey which may represent undiscovered dwarf galaxy candidates. The continuation of this search is motivated by successful discoveries of Local Volume dwarfs in the GALFA-HI DR1. We identify additional potential dwarf galaxies from the GALFA-HI DR1 Compact Cloud Catalog which are indentified as having unexpected velocities given their other characteristics via the bayesian analysis software BayesDB. We also present preliminary results of a by-eye search for dwarf galaxies in the GALFA-HI DR2, which provides additional sky coverage. Interestingly, one particularly compact cloud discovered during our dwarf galaxy search is spatially coincident with an Algol-type variable star. Although the association is tentative, Algol-type variables are thought to have undergone significant gas loss and it is possible this gas may be observable in HI.
Critical properties of weakly interacting Bose gases as modified by a harmonic confinement
NASA Astrophysics Data System (ADS)
Reyes-Ayala, I.; Poveda-Cuevas, F. J.; Seman, J. A.; Romero-Rochín, V.
2017-07-01
The critical properties of the phase transition from a normal gas to a Bose-Einstein condensate (superfluid) of a harmonically confined Bose gas are addressed with the knowledge of an equation of state of the underlying homogeneous Bose fluid. It is shown that while the presence of the confinement trap arrests the usual divergences of the isothermal compressibility and heat capacities, the critical behavior manifests itself now in the divergence of derivatives of the mentioned susceptibilities. This result is illustrated with a mean-field like model of an equation of state for the homogeneous particle density as a function of the chemical potential and temperature of the gas. The model assumes the form of an ideal Bose gas in the normal fluid while in the superfluid state a function is proposed such that, both, asymptotically reaches the Thomas-Fermi solution of a weakly interacting Bose gas at large densities and low temperatures and, at the transition, matches the critical properties of the ideal Bose gas. With this model we obtain the global thermodynamics of the harmonically confined gas, from which we analyze its critical properties. We discuss how these properties can be experimentally tested.
Neutral-pion-decay gamma rays from the Galaxy and the interstellar gas content
NASA Technical Reports Server (NTRS)
Stecker, F. W.
1973-01-01
Knowledge of the total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated here using the latest accelerator data on neutral pion production in p-p interactions up to about 1500 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 plus or minus 0.23) times 10 to the -25th power/sec, consistent with the observed upper limit of 1.6 times 10 to the -25th power/sec.
Bai Bo; Sawin, Herbert H.; Cruden, Brett A.
2006-01-01
The neutral gas temperature of fluorocarbon plasmas in a remote toroidal transformer-coupled source was measured to be greater than 5000 K, under the conditions of a power density greater than 15 W/cm{sup 3} and pressures above 2 torr. The rovibrational bands of C{sub 2} molecules (swan bands, d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) were fitted to obtain the rotational temperature that was assumed to equal the translational temperature. This rotational-translational temperature equilibrium assumption was supported by the comparison with the rotational temperature of second positive system of added N{sub 2}. For the same gas mixture, the neutral gas temperature is nearly a linear function of plasma power, since the conduction to chamber wall and convection are the major energy-loss processes, and they are both proportional to neutral gas temperature. The dependence of the neutral gas temperature on O{sub 2} flow rate and pressure can be well represented through the power dependence, under the condition of constant current operation. An Arrhenius type of dependence between the etching rate of oxide film and the neutral gas temperature is observed, maybe indicating the importance of the pyrolytic dissociation in the plasma formation process when the temperature is above 5000 K.
Zhou, Xiaoji; Xu, Xu; Yin, Lan; Liu, W M; Chen, Xuzong
2010-07-19
We propose a new method of detecting quantum coherence of a Bose gas trapped in a one-dimensional optical lattice by measuring the light intensity from Raman scattering in cavity. After pump and displacement process, the intensity or amplitude of scattering light is different for different quantum states of a Bose gas, such as superfluid and Mott-Insulator states. This method can also be useful to detect quantum states of atoms with two components in an optical lattice.
Kinetic Modeling of the Neutral Gas, Ions, and Charged Dust in Europa's Exosphere
NASA Astrophysics Data System (ADS)
Tenishev, V.; Borovikov, D.; Rubin, M.; Jia, X.; Combi, M. R.
2015-12-01
The interaction of the Jovian magnetosphere with Europa has been a subject of active research during the last few decades both through in-situ and remote sensing observations as well as theoretical considerations. Linking the magnetosphere and the moon's surface and interior, Europa's exosphere has become one of the primary objects of study in the field. Understanding the physical processes occurring in the exosphere and its chemical composition is required for the understanding of the interaction between Europa and Jupiter. Europa's surface-bound exosphere originates mostly from ion sputtering of the water ice surface. Minor neutral species and ions of exospheric origin are produced via photolytic and electron impact reactions. The interaction of the Jovian magnetosphere and Europa affects the exospheric population of both neutrals and ions via source and loss processes. Moreover, the Lorentz force causes the newly created exospheric ions to move preferably aligned with the magnetic field lines. Contrary to the ions, heavier and slow-moving charged dust grains are mostly affected by gravity and the electric field component of the Lorentz force. As a result, escaping dust forms a narrow tail aligned in the direction of the convection electric field. Here we present results of a kinetic model of the neutral species (H2O, OH, O2, O, and H), ions (O+, O2+, H+, H2+, H2O+, and OH+), and neutral and charged dust in Europa's exosphere. In our model H2O and O2 are produced via sputtering and other exospheric neutral and ions species are produced via photolytic and electron impact reactions. For the charged dust we compute the equilibrium grain charge by balancing the electron and ion collecting currents according to the local plasma flow conditions at the grain's location. For the tracking of the ions, charged dust, and the calculation of the grains' charge we use plasma density and velocity, and the magnetic field derived from our multi-fluid MHD model of Europa
Quantum Phase Diffusion of a Bose-Einstein Condensate
Lewenstein, M.; You, L. |
1996-10-01
We discuss the quantum properties of the Bose-Einstein condensate of a dilute gas of atoms in a trap. We show that the phase of the condensate undergoes quantum diffusion which can be detected in far off-resonant light scattering experiments. {copyright} {ital 1996 The American Physical Society.}
Bose gases, Bose–Einstein condensation, and the Bogoliubov approximation
Seiringer, Robert
2014-07-15
We review recent progress towards a rigorous understanding of the Bogoliubov approximation for bosonic quantum many-body systems. We focus, in particular, on the excitation spectrum of a Bose gas in the mean-field (Hartree) limit. A list of open problems will be discussed at the end.
NASA Astrophysics Data System (ADS)
Gardiner, S. A.; Morgan, S. A.
2007-04-01
We describe a number-conserving approach to the dynamics of Bose-Einstein condensed dilute atomic gases. This builds upon the works of Gardiner [Phys. Rev. A 56, 1414 (1997)] and Castin and Dum [Phys. Rev. A 57, 3008 (1998)]. We consider what is effectively an expansion in powers of the ratio of noncondensate to condensate particle numbers, rather than inverse powers of the total number of particles. This requires the number of condensate particles to be a majority, but not necessarily almost equal to the total number of particles in the system. We argue that a second-order treatment of the relevant dynamical equations of motion is the minimum order necessary to provide consistent coupled condensate and noncondensate number dynamics for a finite total number of particles, and show that such a second-order treatment is provided by a suitably generalized Gross-Pitaevskii equation, coupled to the Castin-Dum number-conserving formulation of the Bogoliubov-de Gennes equations. The necessary equations of motion can be generated from an approximate third-order Hamiltonian, which effectively reduces to second order in the steady state. Such a treatment as described here is suitable for dynamics occurring at finite temperature, where there is a significant noncondensate fraction from the outset, or dynamics leading to dynamical instabilities, where depletion of the condensate can also lead to a significant noncondensate fraction, even if the noncondensate fraction is initially negligible.
NASA Astrophysics Data System (ADS)
Wang, Zhen; Xie, Zhiyong; Möller, Axel; Mi, Wenying; Wolschke, Hendrik; Ebinghaus, Ralf
2014-10-01
Total 58 high volume air samples were collected in Büsum, Germany, from August 2011 to October 2012 to investigate air concentrations of 12 per- and polyfluoroalkyl substances (PFASs) and their gas/particle partitioning. The total concentration (vapor plus particle phases) of the 12 PFASs (ΣPFASs) ranged from 8.6 to 155 pg/m3 (mean: 41 pg/m3) while fluorotelomer alcohols 8:2 (8:2 FTOH) dominated all samples accounting for 61.9% of ΣPFASs and the next most species were 10:2 FTOH (12.7%). Air mass back trajectory analysis showed that atmospheric PFASs in most samples were from long range atmospheric transport processes and had higher ratios of 8:2 to 6:2 FTOH compared to the data obtained from urban/industrial sources. Small portion of particle PFASs in the atmosphere was observed and the average percent to ΣPFASs was 2.0%. The particle-associated fractions of different PFASs decreased from perfluorooctane sulfonamidoethanols (FOSEs) (15.5%) to fluorotelomer acrylates (FTAs) (7.6%) to perfluorooctane sulfonamides (FOSAs) (3.1%) and FTOHs (1.8%), indicating the functional group obviously influenced their gas/particle partitioning. For neutral compounds with acid dissociation constant (pKa) > 7.0 (i.e., FTOHs, FOSEs and FOSAs), a significant log-linear relationship was observed between their gas/particle partition coefficients (KSP) and vapor pressures (pºL), suggesting the gas/particle partitioning of neutral PFASs agreed with the classical logKSP-logpºL relation. Due to the pKa values of 6:2 and 8:2 FTA below the typical environmental pH conditions, they mainly exist as ionic form in aerosols, and the corrected logKSP (neutral form) were considerably lower than those of FTOHs, FOSEs and FOSAs with similar vapor pressures. Considering the strong partitioning potential to aqueous phases for ionic PFASs at higher pH values, a need exists to develop a model taking account of the ad/absorption mechanism to the condensed phase of aerosols for ionizable PFASs (e
Asymmetry between protons and proton holes in gas-phase neutralization reactions
NASA Astrophysics Data System (ADS)
Stillinger, Frank H.; Weber, Thomas A.
Energy distribution functions have been computed for neutral water molecules produced by reactive collisions of H5O2+ with OH-, and of H3O+ with H3O2-. The potential energy hypersurface was approximated by the polarization model, and 500 classical trajectories were generated by computer for each reaction. The translational and the rotational-vibrational excitation energy distributions differ qualitatively for the two cases, thereby demonstrating an asymmetry under proton, proton-hole interchange between reactant clusters. The mean excitation energies for product molecules of anionic origin are found to be greater in both cases than those of cationic origin.
Reduction of gas flow into a hollow cathode ion source for a neutral beam injector
NASA Astrophysics Data System (ADS)
Tanaka, Shigeru; Akiba, Masato; Arakawa, Yoshihiro; Horiike, Hiroshi; Sakuraba, Junji
1982-07-01
Experimental studies have been made on the reduction of the gas flow rate into ion sources which utilize a hollow cathode. The electron emitter of the hollow cathode was a barium oxide impregnated porous tungsten tube. The hollow cathode was mounted to a circular or a rectangular bucket source and the following results were obtained. There was a tendency for the minimum gas flow rate for the stable source operation to decrease with increasing orifice diameter of the hollow cathode up to 10 mm. A molybdenum button with an appropriate diameter set in front of the orifice reduced the minimum gas flow rate to one half of that without button. An external magnetic field applied antiparallel to the field generated by the heater current stabilized the discharges and reduced the minimum gas flow rate to one half of that without field. Combination of the button and the antiparallel field reduced the minimum gas flow rate from the initial value (9.5 Torr 1/s) to 2.4 Torr 1/s. The reason for these effects was discussed on the basis of the theory for arc starvation.
Effects of neutral gas collisions on the power transmission factor at the divertor sheath
NASA Astrophysics Data System (ADS)
Futch, A. H.; Hill, D. N.; Jong, R. A.; Porter, G. D.; Matthews, G. F.; Buchenauer, D.
1992-03-01
We show that charge-exchange and other ion-neutral collisions can reduce the power transmission factor of the plasma sheath, thereby lowering the ion impact energy and target plate sputtering. The power transmission factor relates the heat flux reaching the divertor target to the surface: Delta= Q(sub surf)/n(sub e)T(sub e)C(sub s). Experimental data from the D3-D tokamak suggest that Delta could be as low as 2-3 near the region of peak divertor particle flux, instead of the 7-8 expected from usual sheath theory. Several effects combine to allow ion-neutral interactions to be important in the divertor plasma sheath. The shallow angle of incidence of the magnetic field (1-3 degrees in D3-D) leads to the spatial extension of the sheath from approximately (pi)i approximately = 1 mm normal to the plate to several centimeters along the field lines. Ionization reduces the sheath potential, and collisions reduce the ion impact energy.
NASA Astrophysics Data System (ADS)
Ichimura, K.; Fukumoto, M.; Islam, M. M.; Islam, M. S.; Shimizu, K.; Fukui, K.; Ohuchi, M.; Nojiri, K.; Terakado, A.; Yoshikawa, M.; Ezumi, N.; Sakamoto, M.; Nakashima, Y.
2016-11-01
In the divertor simulation experiments in the GAMMA 10/PDX tandem mirror, pressure of the neutral gas was investigated by using a fast ionization gauge. The gauge was absolutely calibrated for hydrogen gas by using a capacitance manometer. Change of the gauge sensitivity due to the magnetic field of GAMMA 10/PDX was also evaluated. The typical gas pressure measured in detached plasma experiments was 0.1-10 Pa. The degree of plasma detachment determined from the reduction of heat flux was enhanced as the gas pressure increases. Rapid increase of the gas pressure under the plasma flow was also observed.
Bose-Einstein condensation on closed Robertson-Walker spacetimes
NASA Astrophysics Data System (ADS)
Trucks, M.
1998-12-01
In this letter we summarize our analysis of Bose-Einstein condensation on closed Robertson-Walker spacetimes. In a previous work we defined an adiabatic KMS state on the Weyl-algebra of the free massive Klein-Gordon field [M. Trucks, M. Keyl, Phys. Lett. B 399 (1997) 223, M. Trucks, Commun. Math. Phys. 197 (1998) 387]. This state describes a free Bose gas on Robertson-Walker spacetimes. We use this state to analyze the possibility of Bose-Einstein condensation on closed Robertson-Walker spacetimes. We take into account the effects due to the finiteness of the spatial volume and show that they are not relevant in the early universe. Furthermore we show that a critical radius can be defined. The condensate disappears above the critical radius.
Bose-Einstein condensation of photons in an optical microcavity.
Klaers, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin
2010-11-25
Bose-Einstein condensation (BEC)-the macroscopic ground-state accumulation of particles with integer spin (bosons) at low temperature and high density-has been observed in several physical systems, including cold atomic gases and solid-state quasiparticles. However, the most omnipresent Bose gas, blackbody radiation (radiation in thermal equilibrium with the cavity walls) does not show this phase transition. In such systems photons have a vanishing chemical potential, meaning that their number is not conserved when the temperature of the photon gas is varied; at low temperatures, photons disappear in the cavity walls instead of occupying the cavity ground state. Theoretical works have considered thermalization processes that conserve photon number (a prerequisite for BEC), involving Compton scattering with a gas of thermal electrons or photon-photon scattering in a nonlinear resonator configuration. Number-conserving thermalization was experimentally observed for a two-dimensional photon gas in a dye-filled optical microcavity, which acts as a 'white-wall' box. Here we report the observation of a Bose-Einstein condensate of photons in this system. The cavity mirrors provide both a confining potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped, massive bosons. The photons thermalize to the temperature of the dye solution (room temperature) by multiple scattering with the dye molecules. Upon increasing the photon density, we observe the following BEC signatures: the photon energies have a Bose-Einstein distribution with a massively populated ground-state mode on top of a broad thermal wing; the phase transition occurs at the expected photon density and exhibits the predicted dependence on cavity geometry; and the ground-state mode emerges even for a spatially displaced pump spot. The prospects of the observed effects include studies of extremely weakly interacting low-dimensional Bose gases and
NASA Astrophysics Data System (ADS)
Appleton, P. N.; Charmandaris, V.; Gao, Yu; Jarrett, Tom; Bransford, M. A.
2003-03-01
We present new high-resolution H I observations of the disk of the collisional infrared luminous (LIR=2.2×1011Lsolar) galaxy NGC 1144, which reveal an apparent large-scale azimuthal and kinematic segregation of neutral hydrogen relative to the molecular gas distribution. Even among violently collisional galaxies, the CO/H I asymmetry in NGC 1144 is unusual, both in the inner regions and in the outer disk. We suggest that we are observing Arp 118 at a special moment, shortly after a high-speed collision between NGC 1144 and its elliptical companion NGC 1143. H I emission with an average molecular fraction fmol<0.5 is observed on one side (northwest) of the rotating disk of NGC 1144, while the other side (southeast) is dominated by dense molecular complexes in which fmol is almost unity. The interface region between the warm- and cool-cloud dominated regions lies on a deep spiral-like dust lane that we identify as a shock wave responsible for the relative shift in the dominance of H I and H2 gas. A strong shock being fed by diffuse H I clouds with unusually large (>400 km s-1) rotational velocities can explain (1) the CO/H I asymmetries, (2) a large velocity jump (185 km s-1) across the arm as measured by H I absorption against a radio bright continuum source that straddles the arm, and (3) the asymmetric distribution of star formation and off-nuclear molecular gas resulting from likely streaming motions associated with the strong shock. The new results provide for the first time a coherent picture of Arp 118's many peculiarities and underline the potentially complex changes in the gas phase that can accompany large gravitational perturbations of gas-rich galaxies.
The neutral dust and gas in the radio galaxy 3C 305
NASA Astrophysics Data System (ADS)
Jackson, N.; Beswick, R.; Pedlar, A.; Cole, G.; Leahy, J. P.; Holloway, A. J.; Sparks, W. B.; Axon, D.
3C305 is a nearby radio galaxy which shows strong warping of the stellar disk and a dust lane running almost parallel to the jet axis. We present and discuss HST and radio studies of the dust and gas which strongly constrain the geometry of this system, and explore the line ionization mechanism (photoionization/ jet-induced shocks) using emission line diagnostic ratios.
Jayapalan, Kanesh K.; Chin, Oi-Hoong
2012-09-15
The H mode transition and maintenance currents in a 13.56 MHz laboratory 6 turn planar coil inductively coupled plasma (ICP) reactor are simulated for low pressure argon discharge range of 0.02-0.3 mbar with neutral gas heating and at ambient temperature. An experimentally fitted 3D power evolution plot for 0.02 mbar argon pressure is also shown to visualize the effects of hysteresis in the system. Comparisons between simulation and experimental measurements show good agreement in the pressure range of 0.02-0.3 mbar for transition currents and 0.02-0.1 mbar for maintenance currents only when neutral gas heating is considered. This suggests that neutral gas heating plays a non-negligible role in determining the mode transition points of a rf ICP system.
Coagulation of charged microparticles in neutral gas and charge-induced gel transitions.
Ivlev, A V; Morfill, G E; Konopka, U
2002-11-04
Coagulation of charged particles was studied using the mean-field Smoluchowski equation. The coagulation equation was generalized for the case of a conserved system of charged particles. It was shown that runaway cluster growth (gelation) solutions exist if the charge-dipole (induced) interaction of clusters is included. When clusters are in thermal equilibrium with the ambient gas, the charge-dipole interaction dramatically enhances the aggregation process and considerably increases the likelihood of a gelation transition.
NASA Astrophysics Data System (ADS)
Bergeson, Scott; Lyon, Mary
2016-05-01
We report measurements of the ion velocity distribution in an ultracold neutral plasma derived from a dense, cold Rydberg gas in a MOT. The Rydberg atoms are excited using a resonant two-step excitation pathway with lasers of 4 ns duration. The plasma forms spontaneously and rapidly. The rms width of the ion velocity distribution is determined by measuring laser-induced fluorescence (LIF) of the ions. The measured excitation efficiency is compared with a Monte-Carlo wavefunction calculation, and significant differences are observed. We discuss the conditions for blockaded Rydberg excitation and the subsequent spatial ordering of Rydberg atom domains. While the blockade interaction is greater than the Rabi frequency in portions of the atomic sample, no evidence for spatial ordering is observed. This research is supported in part by the Air Force Office of Scientific Research (Grant No. FA9950-12- 0308) and by the National Science Foundation (Grant No. PHY-1404488).
NASA Astrophysics Data System (ADS)
Zhang, Xiaoping; Cheng, Shuai
2017-10-01
Intramolecular halogen atom coordinated H transfer reaction in the gas phase dissociation of protonated dichlorvos derivatives has been explored by electrospray ionization tandem mass spectrometry. Upon collisional activation, protonated dichlorvos underwent dissociation reaction via cleavage of the P-O bond to give reactive ion-neutral complex (INC) intermediate, [dimethoxylphosphinoylium + dichloroacetaldehyde]. Besides direct dissociation of the complex, intramolecular chlorine atom coordinated H transfer reaction within the complex takes place, leading to the formation of protonated dimethyl chlorophosphate. To investigate the fragmentation mechanism, deuterium-labeled experiments and several other halogen-substituted (Br and F) analogs of dichlorvos were prepared and evaluated, which display a similar intramolecular halogen transfer. Density functional theory (DFT)-based calculations were performed and the computational results also support the mechanism. [Figure not available: see fulltext.
NASA Astrophysics Data System (ADS)
Zhang, Xiaoping; Cheng, Shuai
2017-07-01
Intramolecular halogen atom coordinated H transfer reaction in the gas phase dissociation of protonated dichlorvos derivatives has been explored by electrospray ionization tandem mass spectrometry. Upon collisional activation, protonated dichlorvos underwent dissociation reaction via cleavage of the P-O bond to give reactive ion-neutral complex (INC) intermediate, [dimethoxylphosphinoylium + dichloroacetaldehyde]. Besides direct dissociation of the complex, intramolecular chlorine atom coordinated H transfer reaction within the complex takes place, leading to the formation of protonated dimethyl chlorophosphate. To investigate the fragmentation mechanism, deuterium-labeled experiments and several other halogen-substituted (Br and F) analogs of dichlorvos were prepared and evaluated, which display a similar intramolecular halogen transfer. Density functional theory (DFT)-based calculations were performed and the computational results also support the mechanism.
Khriachtchev, Leonid; Lignell, Antti; Raesaenen, Markku
2005-08-08
The (NgHNg){sup +} cations (Ng=Ar and Kr) produced via the photolysis of HF/Ar, HF/Kr, and HBr/Kr solid mixtures are studied, with emphasis on their decay mechanisms. The present experiments provide a large variety of parameters connected to this decay phenomenon, which allows us to reconsider various models for the decay of the (NgHNg){sup +} cations in noble-gas matrices. As a result, we propose that this phenomenon could be explained by the neutralization of the solvated protons by electrons. The mechanism of this neutralization reaction probably involves tunneling of an electron from an electronegative fragment or another trap to the (NgHNg){sup +} cation. The proposed electron-tunneling mechanism should be considered as a possible alternative to the literature models based on tunneling-assisted or radiation-induced diffusion of protons in noble-gas solids. As a novel experimental observation of this work, the efficient formation of HArF molecules occurs at 8 K in a photolyzed HF/Ar matrix. It is probable that the low-temperature formation of HArF involves local tunneling of the H atom to the Ar-F center, which in turn supports the locality of HF photolysis in solid Ar. In this model, the decay of (ArHAr){sup +} ions and the formation of HArF molecules observed at low temperatures are generally unconnected processes; however, the decaying (ArHAr){sup +} ions may contribute to some extent to the formation of HArF molecules.
The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M 8)
NASA Astrophysics Data System (ADS)
Damiani, F.; Bonito, R.; Prisinzano, L.; Zwitter, T.; Bayo, A.; Kalari, V.; Jiménez-Esteban, F. M.; Costado, M. T.; Jofré, P.; Randich, S.; Flaccomio, E.; Lanzafame, A. C.; Lardo, C.; Morbidelli, L.; Zaggia, S.
2017-08-01
Aims: We present a spectroscopic study of the dynamics of the ionized and neutral gas throughout the Lagoon nebula (M 8), using VLT-FLAMES data from the Gaia-ESO Survey. The new data permit exploration of the physical connections between the nebular gas and the stellar population of the associated star cluster NGC 6530. Methods: We characterized through spectral fitting emission lines of Hα, [N II] and [S II] doublets, [O III], and absorption lines of sodium D doublet, using data from the FLAMES-Giraffe and UVES spectrographs, on more than 1000 sightlines toward the entire face of the Lagoon nebula. Gas temperatures are derived from line-width comparisons, densities from the [S II] doublet ratio, and ionization parameter from Hα/[N II] ratio. Although doubly-peaked emission profiles are rarely found, line asymmetries often imply multiple velocity components along the same line of sight. This is especially true for the sodium absorption, and for the [O III] lines. Results: Spatial maps for density and ionization are derived, and compared to other known properties of the nebula and of its massive stars 9 Sgr, Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing flux. The detailed velocity fields across the nebula show several expanding shells, related to the cluster NGC 6530, the O stars 9 Sgr and Herschel 36, and the massive protostar M 8East-IR. The origins of kinematical expansion and ionization of the NGC 6530 shell appear to be different. We are able to put constrains on the line-of-sight (relative or absolute) distances between some of these objects and the molecular cloud. The data show that the large obscuring band running through the middle of the nebula is being compressed by both sides, which might explain its enhanced density. We also find an unexplained large-scale velocity gradient across the entire nebula. At larger distances, the transition from ionized to neutral gas is studied using the sodium lines. Based on observations
Beams of fast neutral atoms and molecules in low-pressure gas-discharge plasma
Metel, A. S.
2012-03-15
Fast neutral atom and molecule beams have been studied, the beams being produced in a vacuum chamber at nitrogen, argon, or helium pressure of 0.1-10 Pa due to charge-exchange collisions of ions accelerated in the sheath between the glow discharge plasma and a negative grid immersed therein. From a flat grid, two broad beams of molecules with continuous distribution of their energy from zero up to e(U + U{sub c}) (where U is voltage between the grid and the vacuum chamber and U{sub c} is cathode fall of the discharge) are propagating in opposite directions. The beam propagating from the concave surface of a 0.2-m-diameter grid is focused within a 10-mm-diameter spot on the target surface. When a 0.2-m-diameter 0.2-m-high cylindrical grid covered by end disks and composed of parallel 1.5-mm-diameter knitting needles spaced by 4.5 mm is immersed in the plasma, the accelerated ions pass through the gaps between the needles, turn inside the grid into fast atoms or molecules, and escape from the grid through the gaps on its opposite side. The Doppler shift of spectral lines allows for measuring the fast atom energy, which corresponds to the potential difference between the plasma inside the chamber and the plasma produced as a result of charge-exchange collisions inside the cylindrical grid.
Lo, C. C.; Lang, V.; George, R. E.; Morton, J. J. L.; Tyryshkin, A. M.; Lyon, A.; Bokor, J.; Schenkel, T.
2011-04-20
We have measured the electrically detected magnetic resonance of donor-doped silicon field-effect transistors in resonant X- (9.7 GHz) and W-band (94 GHz) microwave cavities. The two-dimensional electron gas (2DEG) resonance signal increases by two orders of magnitude from X- to W-band, while the donor resonance signals are enhanced by over one order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the 2DEG is the main mechanism giving rise to the spin resonance signals.
Spacelab 2 Upper Atmospheric Modification experiment over Arecibo. I - Neutral gas dynamics
NASA Technical Reports Server (NTRS)
Bernhardt, P. A.; Kashiwa, B. A.; Tepley, C. A.; Noble, S. T.
1988-01-01
The Orbital Maneuvering Subsystem engines of the Space Shuttle were used to inject H2, CO2, H2O and other combustion products into the upper atmosphere over the Arecibo Observatory. Images of the airglow enhancements that resulted from chemical reactions between the exhaust gases and the F-layer plasma showed that the exhaust vapor trail came to rest 80 km downstream from the center of the burn. A computer simulation of the gas dynamics shows that the region of the burn was dominated by a 'snow plow' effect sweeping out a corridor in the atmosphere and collisionally heating the injected vapors.
Ring structure of a neutral gas cloud studied in a one-dimensional expansion into space
NASA Technical Reports Server (NTRS)
Davidson, R. E.
1972-01-01
A one dimensional treatment of the expansion of a gas cloud of uncharged particles into vacuum is discussed. It is determined that the whole cloud does not change from continuum to free molecular flow at the same time. Some regions of the cloud make the transition sooner than others. An explanation of the ring structure observed during barium cloud experiments is presented using this conclusion. An analysis of the velocity distributions for the two kinds of flow yields a velocity distribution for the whole cloud that exhibits ring structure.
Renewable Doesn’t Mean Carbon Neutral: Emerging Greenhouse Gas Inventory Challenge
2009-06-17
Renewable” energy purchases produced via combustion of: – Biomass / biogas – Biofuels – Biomass portion of MSW FES-East Conference – June 17...and materials), such as: – Biomass , wood, and wood waste – Landfill gas / biogas – Biofuels (B100, E100) – Biofuel component of mixed fuels (B20, E85...included in Scope 1 or 2 emissions – P.85 - Biofuels fall under “renewable energy ” CCAR, General Reporting Protocol, Version 3 (April 2008) – P.41
Renewable Doesn’t Mean Carbon Neutral: Emerging Greenhouse Gas Inventory Challenge
2009-05-06
produced via combustion of: – Biomass / biogas – Biofuels – Biomass portion of MSW E2S2 Conference – May 06, 20096National Defense Center for Energy and...and wood waste – Landfill gas / biogas – Biofuels (B100, E100) – Biofuel component of mixed fuels (B20, E85) “Renewable” energy purchases... Biofuels fall under “renewable energy ” CCAR, General Reporting Protocol, Version 3 (April 2008) – P.41 – Lack of international consensus on biogenic
Using custom potentials to access quantum Hall states in rotating Bose gases
NASA Astrophysics Data System (ADS)
Morris, Alexis G.; Feder, David L.
2007-03-01
The exact ground states of zero-temperature rotating Bose gases confined in quasi-two-dimensional harmonic traps are studied numerically, for small numbers of alkali atoms. As the rotation frequency increases, the interacting Bose gas undergoes a series of transitions from one quantum Hall state to another. We have investigated the possibility of facilitating access to specific quantum Hall states through the addition of customized potentials to the existing trapping potential. For the right choice of potential, we show that creation of predetermined quantum Hall states in rotating Bose gases should be possible using current experimental setups. (Research supported by NSERC, iCORE and CFI)
High-speed digital holography for neutral gas and electron density imaging
Granstedt, E. M.; Thomas, C. E.; Kaita, R.; Majeski, R.; Baylor, L. R.; Meitner, S. J.; Combs, S. K.
2016-05-15
An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.
Smoothed MHD equations for numerical simulations of ideal quasi-neutral gas dynamic flows
NASA Astrophysics Data System (ADS)
Popov, Mikhail V.; Elizarova, Tatiana G.
2015-11-01
We introduce a mathematical model and related numerical method for numerical modeling of ideal magnetohydrodynamic (MHD) gas flows as an extension of previously known quasi-gasdynamic (QGD) equations. This approach is based on smoothing, or averaging of the original MHD equation system over a small time interval that leads to a new equation system, named quasi-MHD, or QMHD system. The QMHD equations are closely related to the original MHD system except for additional strongly non-linear dissipative τ-terms with a small parameter τ as a factor. The τ-terms depend on the solution itself and decrease in regions with the small space gradients of the solution. In this sense the QMHD system could be regarded as an approach with adaptive artificial dissipation. The QMHD is a generalization of regularized (or quasi-) gas dynamic equation system suggested in last three decades. In the QMHD numerical method the evolution of all physical variables is presented in a non-split divergence form. Divergence-free evolution of the magnetic field provides by using a constrained transport method based on Faraday's law of induction. Accuracy and convergence of the QMHD method is verified on a wide set of standard MHD tests including the 3D Orszag-Tang vortex flow.
High-speed digital holography for neutral gas and electron density imaging.
Granstedt, E M; Thomas, C E; Kaita, R; Majeski, R; Baylor, L R; Meitner, S J; Combs, S K
2016-05-01
An instrument was developed using digital holographic reconstruction of the wavefront from a CO2 laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1-25 μs pulses from a continuous-wave CO2 laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.
Two characteristic temperatures for a Bose-Einstein condensate of a finite number of particles
Idziaszek, Z.; Rzazewski, K.
2003-09-01
We consider two characteristic temperatures for a Bose-Einstein condensate, which are related to certain properties of the condensate statistics. We calculate them for an ideal gas confined in power-law traps and show that they approach the critical temperature in the limit of large number of particles. The considered characteristic temperatures can be useful in the studies of Bose-Einstein condensates of a finite number of atoms indicating the point of a phase transition.
Bose-Einstein condensation on a manifold with non-negative Ricci curvature
Akant, Levent Ertuğrul, Emine Tapramaz, Ferzan Turgut, O. Teoman
2015-01-15
The Bose-Einstein condensation for an ideal Bose gas and for a dilute weakly interacting Bose gas in a manifold with non-negative Ricci curvature is investigated using the heat kernel and eigenvalue estimates of the Laplace operator. The main focus is on the nonrelativistic gas. However, special relativistic ideal gas is also discussed. The thermodynamic limit of the heat kernel and eigenvalue estimates is taken and the results are used to derive bounds for the depletion coefficient. In the case of a weakly interacting gas, Bogoliubov approximation is employed. The ground state is analyzed using heat kernel methods and finite size effects on the ground state energy are proposed. The justification of the c-number substitution on a manifold is given.
NASA Technical Reports Server (NTRS)
Koga, J. K.; Lin, C. S.; Winglee, R. M.
1989-01-01
Injections of nonrelativistic electron beams from an isolated equipotential conductor into a uniform background of plasma and neutral gas were simulated using a 2-D electrostatic particle code. The ionization effects on spacecraft charging are examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. In the spacecraft wake, the background electrons accelerated towards the charged spacecraft produce an enhancement of secondary electrons and ions. Simulations run for longer times indicate that the spacecraft potential is further reduced and short wavelength beam-plasma oscillations appear. The results are applied to explain the spacecraft charging potential measured during the SEPAC experiments from Spacelab 1.
NASA Astrophysics Data System (ADS)
Jiao, Qian; Zhao, Yinghe; Zhu, Ming; Lu, Nanyao; Gao, Yu; Zhang, Zhi-Yu
2017-05-01
We present a statistical study of the [C i] (3P1 \\to 3P0), [C i] (3P2 \\to 3P1) lines (hereafter [C i] (1-0) and [C i] (2-1), respectively) and the CO(1-0) line for a sample of (ultra-)luminous infrared galaxies ((U)LIRGs). We explore the correlations between the luminosities of CO(1-0) and [C i] lines, and find that {L}{CO(1-0)}\\prime correlates almost linearly with both {L}[{{C} {{I}}](1-0)}\\prime and {L}[{{C} {{I}}](2-1)}\\prime , suggesting that [C i] lines can trace total molecular gas mass, at least for (U)LIRGs. We also investigate the dependence of {L}[{{C} {{I}}](1-0)}\\prime /{L}{CO(1-0)}\\prime , {L}[{{C} {{I}}](2-1)}\\prime /{L}{CO(1-0)}\\prime , and {L}[{{C} {{I}}](2-1)}\\prime /{L}[{{C} {{I}}](1-0)}\\prime on the far-infrared color of 60-to-100 μm, and find non-correlation, a weak correlation, and a modest correlation, respectively. Under the assumption that these two carbon transitions are optically thin, we further calculate the [C i] line excitation temperatures, atomic carbon masses, and mean [C i] line flux-to-H2 mass conversion factors for our sample. The resulting {{{H}}}2 masses using these [C i]-based conversion factors roughly agree with those derived from {L}{CO(1-0)}\\prime and CO-to-H2 conversion factor. Based on Herschel observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Curran, S. J.; Whiting, M. T.
2012-11-10
From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.
NASA Astrophysics Data System (ADS)
Noterdaeme, P.; Petitjean, P.; Ledoux, C.; Srianand, R.
2009-10-01
We present the results of a search for damped Lyman-α (DLA) systems in the Sloan Digital Sky Survey II (SDSS), Data Release 7. We use a fully automatic procedure to identify DLAs and derive their column densities. The procedure is checked against the results of previous searches for DLAs in SDSS. We discuss the agreements and differences and show the robustness of our procedure. For each system, we obtain an accurate measurement of the absorber's redshift, the H I column density and the equivalent width of associated metal absorption lines, without any human intervention. We find 1426 absorbers with 2.15 < z < 5.2 with log N(H I) ≥ 20, out of which 937 systems have log N(H I) ≥ 20.3. This is the largest DLA sample ever built, made available to the scientific community through the electronic version of this paper. In the course of the survey, we discovered the intervening DLA with highest H I column density known to date with log N(H I) = 22.0±0.1. This single system provides a strong constraint on the high-end of the N(H I) frequency distribution now measured with high accuracy. We show that the presence of a DLA at the blue end of a QSO spectrum can lead to important systematic errors and propose a method to avoid them. This has important consequences for the measurement of the cosmological mass density of neutral gas at z ~ 2.2 and therefore on our understanding of galaxy evolution over the past 10 billion years. We find a significant decrease of the cosmological mass density of neutral gas in DLAs, Ω_g^DLA, from z = 4 to z = 2.2, consistent with the result of previous SDSS studies. However, and contrary to other SDSS studies, we find that Ω_g^DLA(z = 2.2) is about twice the value at z = 0. This implies that Ω_g^DLA keeps decreasing at z < 2.2. Catalog is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/1087
NASA Technical Reports Server (NTRS)
De Boer, K. S.; Fitzpatrick, E. L.; Savage, B. D.
1985-01-01
Weak absorption lines of C I, O I, Mg I, Mg II, Si I, Si II, P I, Cl I, Cr II, Mn II, Fe I, Ni II, Zn II, CO and C2 are detected in neutral gas in front of the 30 Doradus H II region by IUE spectra of R 136. The Large Magellanic Cloud abundances from the absorption lines are a factor of 2 or 3 below those of the Milky Way, in agreement with emission line study results. Neutral gas density and temperature are estimated from the observed excitation and ionization to be about 300/cu cm and 100 K, respectively; this implies a gas pressure of 30,000/cu cm K.
Davidson, R.C.; Chao, E.H.
1996-07-01
This paper investigates theoretically the heating and nonlinear expansion of a nonneutral electron plasma due to elastic collisions with constant collision frequency {nu}{sub {ital en}} between the plasma electrons and a background neutral gas. The model treats the electrons as a strongly magnetized fluid ({omega}{sub {ital pe}}{sup 2}/{omega}{sub {ital ce}}{sup 2}{lt}1) immersed in a uniform magnetic field {ital B}{sub 0}{ital {bold {cflx e}}}{sub {ital z}}. The model also assumes an axisymmetric plasma column ({partial_derivative}/{partial_derivative}{theta}=0) with negligible axial variation ({partial_derivative}/{partial_derivative}{ital z}=0), and that the process of heat conduction is sufficiently fast that the electrons have relaxed through electron-electron collisions to a quasi-equilibrium state with scalar pressure {ital P}({ital r},{ital t})={ital n}({ital r},{ital t}){ital T}, and isothermal temperature {ital T}. Assuming that the electrons undergo elastic collisions with infinitely massive background gas atoms, global energy conservation is used to calculate the electron heating rate, {ital dT}({ital t})/{ital dt}, as the plasma column expands on a time scale {tau}{sub {ital diff}}{approximately}({omega}{sub {ital pe}}{sup 2}{nu}{sub {ital en}}/{omega}{sub {ital ce}}{sup 2} ){sup {minus}1}, and the electrostatic potential energy decreases. Coupled dynamical equations that describe the nonlinear evolution of the mean-square column radius {ital r}{sup 2}{sub 0}({ital t}) and electron temperature {ital T}({ital t}) are derived and solved numerically. {copyright} {ital 1996 American Institute of Physics.}
Bose-Einstein condensation in binary mixture of Bose gases
Tran Huu Phat; Le Viet Hoa; Nguyen Tuan Anh Nguyen Van Long
2009-10-15
The Bose-Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall-Jackiw-Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments.
NASA Astrophysics Data System (ADS)
Gilchrist, B. E.; Bonifazi, C.; Bilén, S. G.; Raitt, W. J.; Burke, W. J.; Stone, N. H.; Lebreton, J. P.
During the reflight of the first electrodynamic Tethered Satellite System (TSS-1R) mission, the unplanned separation of the tether at the Orbiter end resulted in the highest tether current during the mission. In the moments just prior to the tether separation with 19.7 km of tether deployed and a generated electromotive force (EMF) of 3482 V, currents reaching approximately 0.97 A were shunted through the tether to the Orbiter electrical ground, which was in contact with the ionosphere primarily through its main engine surfaces. This current level was nearly twice as large as observed during any nominal operating period. As the failure point of the tether entered into the ambient plasma, the current increased to 1.1 A and maintained this level even after the break for approximately 75 s. The principal surprise in these results was that the broken end of the tether, with only a few short strands of copper wire, could support higher currents than the much larger Orbiter conducting surface areas. Analysis of possible current enhancement mechanisms revealed that only a gas-enhanced electrical discharge, providing an electron emission source, was plausible. Ground plasma chamber tests confirmed this analysis. The TSS-1R results thus represent the highest electron current emission from a neutral plasma source yet demonstrated in a space plasma. This is of interest for current collection processes in general and plasma contactor development in particular.
NASA Astrophysics Data System (ADS)
Noterdaeme, P.; Petitjean, P.; Carithers, W. C.; Pâris, I.; Font-Ribera, A.; Bailey, S.; Aubourg, E.; Bizyaev, D.; Ebelke, G.; Finley, H.; Ge, J.; Malanushenko, E.; Malanushenko, V.; Miralda-Escudé, J.; Myers, A. D.; Oravetz, D.; Pan, K.; Pieri, M. M.; Ross, N. P.; Schneider, D. P.; Simmons, A.; York, D. G.
2012-11-01
We present the first results from an ongoing survey for damped Lyman-α systems (DLAs) in the spectra of z > 2 quasars observed in the course of the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey (SDSS) III. Our full (non-statistical) sample, based on Data Release 9, comprises 12 081 systems with log N(H i) ≥ 20, out of which 6839 have log N(H i) ≥ 20.3. This is the largest DLA sample ever compiled, superseding that from SDSS-II by a factor of seven. Using a statistical sub-sample and estimating systematics from realistic mock data, we probe the N(H i) distribution at ⟨z⟩ = 2.5. Contrary to what is generally believed, the distribution extends beyond 1022 cm-2 with a moderate slope of index ≈-3.5. This result matches the opacity-corrected distribution observed at z = 0 surprisingly well. The cosmological mass density of neutral gas in DLAs is found to be ωgdla ≈ 10-3, evolving only mildly over the past 12 billion years. Table 3 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/547/L1
Diffusion dynamics in the disordered Bose Hubbard model
NASA Astrophysics Data System (ADS)
Wadleigh, Laura; Russ, Philip; Demarco, Brian
2016-05-01
We explore the dynamics of diffusion for out-of-equilibrium superfluid, Mott insulator, and Bose glass states using an atomic realization of the disordered Bose Hubbard (DBH) model. Dynamics in strongly correlated systems, especially far from equilibrium, are not well understood. The introduction of disorder further complicates these systems. We realize the DBH model--which has been central to our understanding of quantum phase transitions in disordered systems--using ultracold Rubidium-87 atoms trapped in a cubic disordered optical lattice. By tightly focusing a beam into the center of the gas, we create a hole in the atomic density profile. We achieve Mott insulator, superfluid, or Bose glass states by varying the interaction and disorder strength, and measure the time evolution of the density profile after removing the central barrier. This allows us to infer diffusion rates from the velocities at the edge of the hole and to look for signatures of superfluid puddles in the Bose glass state. We acknowledge funding from NSF Grant PHY 15-05468, NSF Grant DGE-1144245, and ARO Grant W911NF-12-1-0462.
D-dimensional Bose gases and the Lambert W function
NASA Astrophysics Data System (ADS)
Tanguay, J.; Gil, M.; Jeffrey, D. J.; Valluri, S. R.
2010-12-01
The applications of the Lambert W function (also known as the W function) to D-dimensional Bose gases are presented. We introduce two sets of families of logarithmic transcendental equations that occur frequently in thermodynamics and statistical mechanics and present their solution in terms of the W function. The low temperature T behavior of free ideal Bose gases is considered in three and four dimensions. It is shown that near condensation in four dimensions, the chemical potential μ and pressure P can be expressed in terms of T through the W function. The low T behavior of one- and two-dimensional ideal Bose gases in a harmonic trap is studied. In 1D, the W function is used to express the condensate temperature, T_C, in terms of the number of particles N; in 2D, it is used to express μ in terms of T. In the low T limit of the 1D hard-core and the 3D Bose gas, T can be expressed in terms of P and μ through the W function. Our analysis allows for the possibility to consider μ, T, and P as complex variables. The importance of the underlying logarithmic structure in ideal quantum gases is seen in the polylogarithmic and W function expressions relating thermodynamic variables such as μ, T, and P.
Thermodynamic equivalence of two-dimensional imperfect attractive Fermi and repulsive Bose gases
NASA Astrophysics Data System (ADS)
Napiórkowski, Marek; Piasecki, Jarosław
2017-06-01
We consider two-dimensional imperfect attractive Fermi and repulsive Bose gases consisting of spinless point particles whose total interparticle interaction energy is represented by a N2/2 V with a =-aF≤0 for fermions and a =aB≥0 for bosons. We show that, in spite of the attraction, the thermodynamics of a d =2 imperfect Fermi gas remains well defined for 0 ≤aF≤a0=h2/2 π m , and is exactly the same as the one of the repulsive imperfect Bose gas with aB=a0-aF . In particular, for aF=a0 one observes the thermodynamic equivalence of the attractive imperfect Fermi gas and the ideal Bose gas.
Bose polaron problem: Effect of mass imbalance on binding energy
NASA Astrophysics Data System (ADS)
Ardila, L. A. Peña; Giorgini, S.
2016-12-01
By means of quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T =0 . The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to 40K impurities in a gas of 87Rb atoms, we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.
Evolution and dynamical properties of Bose-Einstein condensate dark matter stars
NASA Astrophysics Data System (ADS)
Madarassy, Eniko J. M.; Toth, Viktor T.
2015-02-01
Using recently developed nonrelativistic numerical simulation code, we investigate the stability properties of compact astrophysical objects that may be formed due to the Bose-Einstein condensation of dark matter. Once the temperature of a boson gas is less than the critical temperature, a Bose-Einstein condensation process can always take place during the cosmic history of the Universe. Because of dark matter accretion, a Bose-Einstein condensed core can also be formed inside massive astrophysical objects such as neutron stars or white dwarfs, for example. Numerically solving the Gross-Pitaevskii-Poisson system of coupled differential equations, we demonstrate, with longer simulation runs, that within the computational limits of the simulation the objects we investigate are stable. Physical properties of a self-gravitating Bose-Einstein condensate are examined both in nonrotating and rotating cases.
Transport of ultracold Bose gases beyond the Gross-Pitaevskii description
Ernst, Thomas; Paul, Tobias; Schlagheck, Peter
2010-01-15
We explore atom-laser-like transport processes of ultracold Bose-condensed atomic vapors in mesoscopic waveguide structures beyond the Gross-Pitaevskii mean-field theory. Based on a microscopic description of the transport process in the presence of a coherent source that models the outcoupling from a reservoir of perfectly Bose-Einstein condensed atoms, we derive a system of coupled quantum evolution equations that describe the dynamics of a dilute condensed Bose gas in the framework of the Hartree-Fock-Bogoliubov approximation. We apply this method to study the transport of dilute Bose gases through an atomic quantum dot and through waveguides with disorder. Our numerical simulations reveal that the onset of an explicitly time-dependent flow corresponds to the appearance of strong depletion of the condensate on the microscopic level and leads to a loss of global phase coherence.
Performance analysis and parametric optimum criteria of an irreversible Bose-Otto engine
NASA Astrophysics Data System (ADS)
Wang, Hao; Liu, Sanqiu; He, Jizhou
2009-04-01
An irreversible cycle model of a Bose-Otto engine is established, in which finite time thermodynamic processes and the irreversibility result from the nonisentropic compression and expansion processes are taken into account. Based on the model, expressions for the power output and efficiency of the Bose-Otto engine are derived. On the basis of the thermodynamic properties of ideal Bose gas, the effects of the irreversibility and the compression ratio of the two isochoric processes on the performance of the Bose-Otto engine are revealed and some important performance parameters are optimized. Furthermore, some optimal operating regions including those for the power output, efficiency, and the temperatures of the cyclic working substance at two important state points are determined and evaluated. Finally, several special cases are discussed in detail.
Coherent tunneling of atoms from Bose-condensed gases at finite temperatures
NASA Astrophysics Data System (ADS)
Luxat, David L.; Griffin, Allan
2002-04-01
Tunneling of atoms between two trapped Bose-condensed gases at finite temperatures is explored using a many-body linear-response tunneling formalism similar to that used in superconductors. To lowest order, the tunneling currents can be expressed quite generally in terms of the single-particle Green's functions of isolated Bose gases. A coherent first-order tunneling Josephson current between two atomic Bose-Einstein condensates is found, in addition to coherent and dissipative contributions from second-order condensate-noncondensate and noncondensate-noncondensate tunneling. Our work is a generalization of Meier and Zwerger, who recently treated tunneling between uniform atomic Bose gases. We apply our formalism to the analysis of an out-coupling experiment induced by light wave fields, using a simple Bogoliubov-Popov quasiparticle approximation for the trapped Bose gas. For tunneling into the vacuum, we recover the results of Japha, Choi, Burnett, and Band, who recently pointed out the usefulness of studying the spectrum of out-coupled atoms. In particular, we show that the small tunneling current of noncondensate atoms from a trapped Bose gas has a broad spectrum of energies, with a characteristic structure associated with the Bogoliubov quasiparticle u2 and v2 amplitudes.
Bose-Einstein condensation of quasi-equilibrium magnons at room temperature under pumping.
Demokritov, S O; Demidov, V E; Dzyapko, O; Melkov, G A; Serga, A A; Hillebrands, B; Slavin, A N
2006-09-28
Bose-Einstein condensation is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose-Einstein condensation, one can either decrease the temperature or increase the density of bosons. It has been predicted that a quasi-equilibrium system of bosons could undergo Bose-Einstein condensation even at relatively high temperatures, if the flow rate of energy pumped into the system exceeds a critical value. Here we report the observation of Bose-Einstein condensation in a gas of magnons at room temperature. Magnons are the quanta of magnetic excitations in a magnetically ordered ensemble of magnetic moments. In thermal equilibrium, they can be described by Bose-Einstein statistics with zero chemical potential and a temperature-dependent density. In the experiments presented here, we show that by using a technique of microwave pumping it is possible to excite additional magnons and to create a gas of quasi-equilibrium magnons with a non-zero chemical potential. With increasing pumping intensity, the chemical potential reaches the energy of the lowest magnon state, and a Bose condensate of magnons is formed.
NASA Astrophysics Data System (ADS)
Miyagawa, Y.; Tanaka, M.; Ikeyama, M.; Nakao, S.; Choi, J.; Miyagawa, S.
2006-01-01
The plasma behavior inside of a PET bottle has been simulated under the condition of plasma immersed ion implantation and deposition (PIII&D) using the simulation software "PEGASUS". The software uses the "PIC-MCCM" module for the plasma analysis and the "DSMCM" module for the gas flow field analysis. DSMCM gives densities, velocities, fluxes, temperatures and pressures of each neutral species such as the fed gas species and radicals. By coupling PIC-MCCM with DSMCM simulation, the plasma behavior in the flowing Ar gas and N2 gas has been simulated. The gas was injected from the tip of the gas inlet which was inserted into the center of the bottle. The base gas pressure was 1-50 Pa and a positive pulse voltage (maximum voltage = 0.1-1 kV) was applied to the center rod. A two-dimensional cylindrical coordinate system was used. Time evolution of the spacial distribution was obtained for densities of electrons, N2+ ions, N2∗ radicals and N atoms in N2 gas, and Ar+ ions, Ar∗ and Ar∗(4s) radicals in Ar gas. Time evolution of the particle flux and the energy flux of electrons and ions on the target surface was also obtained.
Solitonic vortices in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Tylutki, M.; Donadello, S.; Serafini, S.; Pitaevskii, L. P.; Dalfovo, F.; Lamporesi, G.; Ferrari, G.
2015-04-01
We analyse, theoretically and experimentally, the nature of solitonic vortices (SV) in an elongated Bose-Einstein condensate. In the experiment, such defects are created via the Kibble-Zurek mechanism, when the temperature of a gas of sodium atoms is quenched across the BEC transition, and are imaged after a free expansion of the condensate. By using the Gross-Pitaevskii equation, we calculate the in-trap density and phase distributions characterizing a SV in the crossover from an elongated quasi-1D to a bulk 3D regime. The simulations show that the free expansion strongly amplifies the key features of a SV and produces a remarkable twist of the solitonic plane due to the quantized vorticity associated with the defect. Good agreement is found between simulations and experiments.
Gotti, Roberto; Fiori, Jessica; Mancini, Francesca; Cavrini, Vanni
2005-09-01
Nitromusks used as fragrances in a variety of personal-care products, cleansers, and domestic deodorants, including incense sticks, are neutral nitro aromatic compounds; some of these have been reported as photosensitizers. In this work, their analysis was performed by capillary electrophoresis (CE) in a methanol-based background electrolyte (BGE). In particular, a 10 mM solution of citric acid in methanol was used; under these conditions the strong suppression of the electroosmotic flow favored the use of negatively charged surfactants as additives for the anodic migration of the studied analytes. To this end, sodium taurodeoxycholate (TDC) was supplemented at high concentration (190 mM) to the organic background electrolyte (BGE), showing strong indication of the ability to give micelle-like aggregates. Since nitromusks are characterized by the presence of a nitroaromatic ring with low charge density, their association with TDC aggregates can be ascribed to donor-acceptor interactions. Separation of musk xylene, musk ketone, and the banned musk moskene and musk ambrette was obtained under full nonaqueous BGE; the addition of relatively small water percentages (15% v/v) was found to be useful in improving the separation of pairs of adjacent peaks. Under optimized conditions (190 mM sodium TDC in methanol-water, 85-15 v/v containing citric acid 10 mM) the system was applied to the analysis of nitromusks in incense sticks extracted with methanol. The results were compared with those obtained by the analysis of the same samples using gas chromatography with mass detector. The expected different selectivity of separation obtained using the two techniques can be useful in the unambiguous determination of the analytes; furthermore, a substantial accord of the preliminary quantitative results achieved with the two methods was assumed as the confirmation of the potential reliability of CE performed with high percentage of organic solvent.
Gas-Phase Oxidation of Cm+ and Cm2+ -- Thermodynamics of neutral and ionized CmO
Gibson, John K; Haire, Richard G.; Santos, Marta; Pires de Matos, Antonio; Marcalo, Joaquim
2008-12-08
Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm+ and Cm2+; parallel studies were carried out with La+/2+, Gd+/2+ and Lu+/2+. Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M+-O](M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO+ with dienes, and the second ionization energies, IE[MO+](M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO2+ ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO]= 6.4+-0.2 eV; IE[CmO+]= 15.8+-0.4 eV; D[Cm-O]= 710+-45 kJ mol-1; D[Cm+-O]= 670+-40 kJ mol-1; and D[Cm2+-O]= 342+-55 kJ mol-1. Estimates for the M2+-O bond energies for M = Cm, La, Gd and Lu are all intermediate between D[N2-O]and D[OC-O]--i.e., 167 kJ mol-1< D[M2+-O]< 532 kJ mol-1 -- such that the four MO2+ ions fulfill the thermodynamic requirement for catalytic O-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO2+, LaO2+, GdO2+ and LuO2+ dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO2+ ion appeared during the reaction of Cm+ with O2 when the intermediate, CmO+, was not collisionally cooled -- although its formation is kinetically and/or thermodynamically unfavorable, CmO2+ is a stable species.
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
NASA Astrophysics Data System (ADS)
Huang, Zhenguang; Toth, Gabor; Gombosi, Tamas; Jia, Xianzhe; Rubin, Martin; Fougere, Nicolas; Tenishev, Valeriy; Combi, Michael; Bieler, Andre; Hansen, Kenneth; Shou, Yinsi; Altwegg, Kathrin
2016-04-01
The neutral and plasma environment is critical in understanding the interaction of the solar wind and comet 67P/Churyumov-Gerasimenko (CG), the target of the European Space Agency's Rosetta mission. In this study, we have developed a 3-D four-fluid model, which is based on BATS-R-US (Block-Adaptive Tree Solarwind Roe-type Upwind Scheme) within SWMF (Space Weather Modeling Framework) that solves the governing multi-fluid MHD equations and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. We simulated the plasma and neutral gas environment of comet CG with SHAP5 model near perihelion and we showed that the plasma environment in the inner coma region have some new features: magnetic reconnection in the tail region, a magnetic pile-up region on the nightside, and nucleus directed plasma flow inside the nightside reconnection region.
NASA Technical Reports Server (NTRS)
Telesco, C. M.; Davidson, J. A.; Werner, M. W.
1995-01-01
Maps are presented for 10, 20, and 30 micrometers of the central 60' X 90' (RA X Dec) of the galaxy made at approximately 4' resolution with the MSFC bolometer array. The maps are the first to show the thermal emission from dust particles in both the ionized cavity and the neutral-gas ring with high sensitivity and an angular resolution as good as several arcsec.
Bose glass and Mott glass of quasiparticles in a doped quantum magnet.
Yu, Rong; Yin, Liang; Sullivan, Neil S; Xia, J S; Huan, Chao; Paduan-Filho, Armando; Oliveira, Nei F; Haas, Stephan; Steppke, Alexander; Miclea, Corneliu F; Weickert, Franziska; Movshovich, Roman; Mun, Eun-Deok; Scott, Brian L; Zapf, Vivien S; Roscilde, Tommaso
2012-09-20
The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a 'Bose glass'. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum. Here we report the observation of a Bose glass of field-induced magnetic quasiparticles in a doped quantum magnet (bromine-doped dichloro-tetrakis-thiourea-nickel, DTN). The physics of DTN in a magnetic field is equivalent to that of a lattice gas of bosons in the grand canonical ensemble; bromine doping introduces disorder into the hopping and interaction strength of the bosons, leading to their localization into a Bose glass down to zero field, where it becomes an incompressible Mott glass. The transition from the Bose glass (corresponding to a gapless spin liquid) to the Bose-Einstein condensate (corresponding to a magnetically ordered phase) is marked by a universal exponent that governs the scaling of the critical temperature with the applied field, in excellent agreement with theoretical predictions. Our study represents a quantitative experimental account of the universal features of disordered bosons in the grand canonical ensemble.
The effect of adiabaticity on strongly quenched Bose Einstein Condensates
NASA Astrophysics Data System (ADS)
Ling, Hong; Kain, Ben
2015-05-01
We study the properties of a Bose-Einstein condensate following a deep quench to a large scattering length during which the condensate fraction nc changes with time. We construct a closed set of equations that highlight the role of the adiabaticity or equivalently, dnc/dt, the rate change of nc, which is to induce an (imaginary) effective interaction between quasiparticles. We show analytically that such a system supports a steady state characterized by a constant condensate density and a steady but periodically changing momentum distribution, whose time average is described exactly by the generalized Gibbs ensemble. We discuss how the nc -induced effective interaction, which cannot be ignored on the grounds of the adiabatic approximation for modes near the gapless Goldstone mode, can significantly affect condensate populations and Tan's contact for a Bose gas that has undergone a deep quench. In particular, we find that even when the Bose gas is quenched to unitarity, nc(t) does not completely deplete, approaching, instead, to a steady state with a finite condensate fraction. ITAMP, Harvard-Smithsonian Center for Astrophysics; KITP, University of Santa Barbara.
Internal Josephson effects in spinor dipolar Bose-Einstein condensates
Yasunaga, Masashi; Tsubota, Makoto
2010-02-15
We theoretically study the internal Josephson effect, which is driven by spin-exchange interactions and magnetic dipole-dipole interactions, in a three-level system for spin-1 Bose-Einstein condensates, obtaining novel spin dynamics. We introduce single spatial mode approximations into the Gross-Pitaevskii equations and derive the Josephson-type equations, which are analogous to tunneling currents through three junctions between three superconductors. From an analogy with two interacting nonrigid pendulums, we identify unique varied oscillational modes, called the 0-{pi}, 0-running, running-running, 2n{pi} and running-2{pi}, single nonrigid pendulum, and two rigid pendulums phase modes. These Josephson modes in the three states are expected to be found in real atomic Bose gas systems.
Landau criterion for an anisotropic Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Yu, Zeng-Qiang
2017-03-01
In this work we discuss the Landau criterion for anisotropic superfluidity. To this end we consider a pointlike impurity moving in a uniform Bose-Einstein condensate with either interparticle dipole-dipole interaction or Raman-induced spin-orbit coupling. In both cases we find that the Landau critical velocity vc is generally smaller than the sound velocity in the moving direction. Beyond vc, the energy dissipation rate is explicitly calculated via a perturbation approach. In the plane-wave phase of a spin-orbit-coupled Bose gas, the dissipationless motion is suppressed by the Raman coupling even in the direction orthogonal to the recoil momentum. Our predictions can be tested in the experiments with ultracold atoms.
Sideband Rabi spectroscopy of finite-temperature trapped Bose gases
NASA Astrophysics Data System (ADS)
Allard, Baptiste; Fadel, Matteo; Schmied, Roman; Treutlein, Philipp
2016-04-01
We use Rabi spectroscopy to explore the low-energy excitation spectrum of a finite-temperature Bose gas of rubidium atoms across the phase transition to a Bose-Einstein condensate (BEC). To record this spectrum, we coherently drive the atomic population between two spin states. A small relative displacement of the spin-specific trapping potentials enables sideband transitions between different motional states. The intrinsic nonlinearity of the motional spectrum, mainly originating from two-body interactions, makes it possible to resolve and address individual excitation lines. Together with sensitive atom counting, this constitutes a feasible technique to count single excited atoms of a BEC and to determine the temperature of nearly pure condensates. As an example, we show that for a nearly pure BEC of N =800 atoms the first excited state has a population of less than five atoms, corresponding to an upper bound on the temperature of 30 nK .
Bose polarons in the strongly interacting regime
NASA Astrophysics Data System (ADS)
Kedar, Dhruv; Hu, Ming-Guang; van de Graaff, Michael; Corson, John; Cornell, Eric; Jin, Deborah
2016-05-01
Impurities immersed in and interacting with a Bose-Einstein condensate (BEC) are predicted to form quasiparticle excitations called Bose polarons. I will present experimental evidence of Bose polarons in cold atoms obtained using radio-frequency spectroscopy to measure the excitation spectrum of fermionic K-40 impurities interacting with a BEC of Rb-87 atoms. We use an interspecies Feshbach resonance to tune the interactions between the impurities and the bosons, and we take data in the strongly interacting regime.
Nonlinear Dynamics of Bose-Einstein Condensates with Long-Range Interactions
Wunner, G.; Cartarius, H.; Fabcic, T.; Koeberle, P.; Main, J.; Schwidder, T.
2008-11-13
The motto of this paper is: Let's face Bose-Einstein condensation through nonlinear dynamics. We do this by choosing variational forms of the condensate wave functions (of given symmetry classes), which convert the Bose-Einstein condensates via the time-dependent Gross-Pitaevskii equation into Hamiltonian systems that can be studied using the methods of nonlinear dynamics. We consider in particular cold quantum gases where long-range interactions between the neutral atoms are present, in addition to the conventional short-range contact interaction, viz. gravity-like interactions, and dipole-dipole interactions. The results obtained serve as a useful guide in the search for nonlinear dynamics effects in numerically exact quantum calculations for Bose-Einstein condensates. A main result is the prediction of the existence of stable islands as well as chaotic regions for excited states of dipolar condensates, which could be checked experimentally.
NASA Astrophysics Data System (ADS)
Ostrikov, K. N.; Denysenko, I. B.; Tsakadze, E. L.; Xu, S.; Storer, R. G.
2002-11-01
This article presents the results on the diagnostics and numerical modeling of low-frequency (approx460 KHz) inductively coupled plasmas generated in a cylindrical metal chamber by an external flat spiral coil. Experimental data on the electron number densities and temperatures, electron energy distribution functions, and optical emission intensities of the abundant plasma species in low/intermediate pressure argon discharges are included. The spatial profiles of the plasma density, electron temperature, and excited argon species are computed, for different rf powers and working gas pressures, using the two-dimensional fluid approach. The model allows one to achieve a reasonable agreement between the computed and experimental data. The effect of the neutral gas temperature on the plasma parameters is also investigated. It is shown that neutral gas heating (at rf powers[greater-than-or-equal, slanted]0.55 kW) is one of the key factors that control the electron number density and temperature. The dependence of the average rf power loss, per electron-ion pair created, on the working gas pressure shows that the electron heat flux to the walls appears to be a critical factor in the total power loss in the discharge.
NASA Astrophysics Data System (ADS)
Thayer, Jeffrey; Hsu, Vicki
2015-04-01
The high-latitude regions of Earth’s upper atmosphere are strongly influenced by plasma-neutral interactions. These interactions couple electrodynamic processes of the ionosphere with hydrodynamic processes of the more abundant thermosphere neutral gas, consequently connecting the high-latitude upper atmosphere to distant regions of the geoplasma environment. This produces a complex spatial and temporal interplay of competing processes that results in a myriad of physical and chemical responses and a rich array of neutral and plasma morphologies that constitute the high-latitude thermosphere and ionosphere. The altitude extent from the lower thermosphere to the upper ionosphere (90km - 1000km) can be considered Earth’s space-atmosphere interaction region - likened to the solar chromosphere’s interaction region where radiative processes and hydrodynamic waves from the dense lower atmosphere produce a cold lower boundary that quickly transitions over a few 100 kilometers to neutral and plasma temperatures that are five times hotter. A thousand or more kilometers further in altitude, Earth's upper atmosphere becomes a hot, collisionless, geomagnetically controlled protonosphere whose neutral and plasma population originates from the thermosphere and ionosphere. A grand challenge in the study of Earth’s interaction region is how the collision-dominated thermosphere/ionosphere system exchanges energy, mass and momentum with the collisionless magnetosphere. This talk will focus primarily on collision-dominated processes of the high-latitude ionosphere and the electromagnetic energy transfer processes that lead to frictional heating of ions and neutrals, and plasma instability phenomenon that leads to extreme electron heating. Observations of the ionosphere response to these processes will be illustrated using incoherent scatter radar measurements. Relevance to the solar chromosphere will be identified where appropriate and outstanding issues in Earth
Polymer Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Castellanos, E.; Chacón-Acosta, G.
2013-05-01
In this work we analyze a non-interacting one-dimensional polymer Bose-Einstein condensate in a harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose-Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for λ2 up to ≲10-16 m2. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles.
Spezia, Riccardo; Salpin, Jean-Yves; Cimas, Alvaro; Gaigeot, Marie-Pierre; Song, Kihyung; Hase, William L.
2012-07-01
In this paper we report different theoretical approaches to study the gas-phase unimolecular dissociation of the doubly-charged cation [Ca(urea)]{sup 2+}, in order to rationalize recent experimental findings. Quantum mechanical plus molecular mechanical (QM/MM) direct chemical dynamics simulations were used to investigate collision induced dissociation (CID) and rotational-vibrational energy transfer for Ar{sup +} [Ca(urea)]{sup 2+} collisions. For the picosecond time-domain of the simulations, both neutral loss and Coulomb explosion reactions were found and the differences in their mechanisms elucidated. The loss of neutral urea subsequent to collision with Ar occurs via a shattering mechanism, while the formation of two singly-charged cations follows statistical (or almost statistical) dynamics. Vibrational-rotational energy transfer efficiencies obtained for trajectories that do not dissociate during the trajectory integration were used in conjunction with RRKM rate constants to approximate dissociation pathways assuming complete intramolecular vibrational energy redistribution (IVR) and statistical dynamics. This statistical limit predicts, as expected, that at long time the most stable species on the potential energy surface (PES) dominate. These results, coupled with experimental CID from which both neutral loss and Coulomb explosion products were obtained, show that the gas phase dissociation of this ion occurs by multiple mechanisms leading to different products and that reactivity on the complicated PES is dynamically complex. (authors)
NASA Astrophysics Data System (ADS)
Rocker, G.; Feulner, P.; Scheuerer, R.; Zhu, L.; Menzel, D.
1990-06-01
In order to investigate the modification of excitation and decay of core holes by condensation and adsorption in the simplest possible cases, as well as the coupling to atomic motion, we have studied the Ar2p and Kr3d excitation regions in Ar and Kr mono- and multilayers on Ru(001). Using synchrotron radiation from BESSY (Berlin), total and Auger electron yields and yields of desorbing ions and neutrals, as function of photon energy, as well as decay electron spectra for specific primary excitations have been measured. The main results are: Multilayers: Energies for resonant core excitations are shifted to higher values by 0.6 to 1 eV compared to free atoms; for Kr, surface (smaller shifts) and bulk excitations can be distinguished. Autoionization and normal Auger spectra are clearly different, as in the gas phase. Besides desorption of neutral atoms as in the valence region, singly and doubly charged ions as well as ionic clusters are desorbed. Monolayers: The shift of resonant excitation energies relative to the gas phase is smaller than for condensed layers. Decay spectra for resonant and non-resonant excitations are identical, as for strongly coupled chemisorbates, proving that charge exchange with the metal is fast compared to core decay. As in the valence region, only neutral atoms desorb. The results shed light on the screening and charge transfer behaviour and on the mechanisms of stimulated desorption which are operative in them.
Free-free absorption of infrared radiation in collisions of electrons with neutral rare-gas atoms
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
A relationship between the inverse bremsstrahlung absorption cross section and the electron neutral momentum transfer cross section has been utilized to determine the infrared free-free continuum absorption coefficient for the negative ions of helium, neon, argon, krypton, and xenon. The values of the momentum transfer cross section for this calculation have been obtained from experimental measurements. Analytical expressions for the absorption coefficient have also been developed. From the results of this calculation, it is possible to determine the absorption coefficient per unit electron density per neutral atom for temperatures in the range from 2500 to 25,000 K. The results are compared with those from tabulations of previous calculations and those computed from theoretical values of the phase shifts for the elastic scattering of electrons by neutral atoms.
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Collision of Bose Condensate Dark Matter structures
Guzman, F. S.
2008-12-04
The status of the scalar field or Bose condensate dark matter model is presented. Results about the solitonic behavior in collision of structures is presented as a possible explanation to the recent-possibly-solitonic behavior in the bullet cluster merger. Some estimates about the possibility to simulate the bullet cluster under the Bose Condensate dark matter model are indicated.
Bose-Einstein condensation of light: general theory.
Sob'yanin, Denis Nikolaevich
2013-08-01
A theory of Bose-Einstein condensation of light in a dye-filled optical microcavity is presented. The theory is based on the hierarchical maximum entropy principle and allows one to investigate the fluctuating behavior of the photon gas in the microcavity for all numbers of photons, dye molecules, and excitations at all temperatures, including the whole critical region. The master equation describing the interaction between photons and dye molecules in the microcavity is derived and the equivalence between the hierarchical maximum entropy principle and the master equation approach is shown. The cases of a fixed mean total photon number and a fixed total excitation number are considered, and a much sharper, nonparabolic onset of a macroscopic Bose-Einstein condensation of light in the latter case is demonstrated. The theory does not use the grand canonical approximation, takes into account the photon polarization degeneracy, and exactly describes the microscopic, mesoscopic, and macroscopic Bose-Einstein condensation of light. Under certain conditions, it predicts sub-Poissonian statistics of the photon condensate and the polarized photon condensate, and a universal relation takes place between the degrees of second-order coherence for these condensates. In the macroscopic case, there appear a sharp jump in the degrees of second-order coherence, a sharp jump and kink in the reduced standard deviations of the fluctuating numbers of photons in the polarized and whole condensates, and a sharp peak, a cusp, of the Mandel parameter for the whole condensate in the critical region. The possibility of nonclassical light generation in the microcavity with the photon Bose-Einstein condensate is predicted.
NASA Astrophysics Data System (ADS)
Sugimura, Natsuhiko; Igarashi, Yoko; Aoyama, Reiko; Shibue, Toshimichi
2017-10-01
An energy-decomposition analysis clarified the physical origins that change in gas-phase unimolecular proton-transfer reactions via ion-neutral complexes of the 2-butanol radical ion and protonated 2-ethoxypropane ion. In the bond cleavage and new bond-formation parts of the reaction coordinates, exchange and polarization energies provide a major source of the attraction. In the ion-neutral complex-formation part of the reaction coordinate, different major attractive sources, dispersion, and electrostatic energies were observed. The physical origins of weak interaction in the ion-neutral complexes were affected by the local charges and distances between the ion moieties and the neutral moieties.
NASA Astrophysics Data System (ADS)
Volciuc, O.; Monaico, E.; Enachi, M.; Ursaki, V. V.; Pavlidis, D.; Popa, V.; Tiginyanu, I. M.
2010-11-01
Porous InP membranes have been prepared by anodization of InP wafers with electron concentration of 1 × 10 17 cm -3 and 1 × 10 18 cm -3 in a neutral NaCl electrolyte. The internal surfaces of pores in some membranes were modified by electrochemical deposition of gold in a pulsed voltage regime. Photoluminescence and photosensitivity measurements indicate efficient light trapping and porous surface passivation. The photoluminescence and electrical resistivity of the membranes are sensitive to the adsorption of H 2 and CO gas molecules. These properties are also influenced by the deposition of Au nanoparticles inside the pores.
Wei, H. L.; Cao, J. Y.; Rao, J.; Lei, G. J.; Jiang, S. F.; Liu, H.; Yu, L. M.; Xie, W. M.; Li, M.; Yang, X. F.; Zou, G. Q.; Lu, D. L.; Duan, X. R.
2012-02-15
The discharge gas pressure is a key factor to influence the extracted current of ion source. In this paper, the dependence of extracted current on discharge gas pressure was investigated in detail at different arc discharge currents. The discharge gas pressure with a very broad range (0.1 Pa-2.7 Pa) was scanned for the first time. It is turned out that, with the increasing of discharge gas pressure, the extracted current increases and the arc voltage decreases at different arc currents; however, when the discharge gas pressure exceeds a certain value, the extracted current decreases. For the same discharge gas pressure, the higher the arc current, the higher the arc voltage and the extracted current are. The arc efficiency was also calculated, and its dependence on gas pressure was almost the same with the dependence of extracted current on gas pressure, but at the same discharge gas pressure, the lower the arc current, the higher the arc efficiency is and the lower the extracted current is.
NASA Technical Reports Server (NTRS)
Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia
2016-01-01
Current observational evidence suggests that the star formation rate (SFR)efficiency of neutral atomic hydrogen gas measured in damped Ly(alpha) systems (DLAs) at z approx. 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS)relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z approx. 1, z approx. 2, and z approx. 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies' outskirts. We find that the SFR efficiency of H I gas at z > 1 is approx. 1%-3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.
NASA Technical Reports Server (NTRS)
Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia
2016-01-01
Current observational evidence suggests that the star formation rate (SFR)efficiency of neutral atomic hydrogen gas measured in damped Ly(alpha) systems (DLAs) at z approx. 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS)relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z approx. 1, z approx. 2, and z approx. 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies' outskirts. We find that the SFR efficiency of H I gas at z > 1 is approx. 1%-3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.
Quantum Monte Carlo method for the Bose-Hubbard model with harmonic confining potential.
Kato, Yasuyuki; Kawashima, Naoki
2009-02-01
We study the Bose-Hubbard model with an external harmonic field, which is effective for modeling a cold atomic Bose gas trapped in an optical lattice. We modify the directed-loop algorithm to simulate large systems efficiently. As a demonstration we carry out the simulation of a system consisting of 1. 8 x 10{5} particles on a 64{3} lattice. These numbers are comparable to those in the pioneering experimental work by Greiner [Nature (London) 415, 39 (2002)]. Furthermore, we observe coherence between two superfluid spheres separated by a Mott insulator region in a "wedding-cake" structure.
Bose-Einstein condensate on a persistent-supercurrent atom chip
NASA Astrophysics Data System (ADS)
Imai, Hiromitsu; Inaba, Kensuke; Tanji-Suzuki, Haruka; Yamashita, Makoto; Mukai, Tetsuya
2014-09-01
A Bose-Einstein condensate was achieved in a stable magnetic trap on a persistent-supercurrent atom chip with a superconducting closed-loop circuit. We determined precisely the shape of the magnetic trapping potential by systematically controlling the persistent supercurrent. The condensation was verified by time-of-flight imaging and by atom number decay measurements. The measured decay rates agreed quantitatively with numerical simulations on the three-body loss process assuming all of the atoms to be a condensate. We also discuss the feasibility of creating a quasi-one-dimensional Bose gas on our atom chip.
Superfluid-insulator transition of two-dimensional disordered Bose gases
NASA Astrophysics Data System (ADS)
Saliba, Joseph; Lugan, Pierre; Savona, Vincenzo
2014-09-01
We study the two-dimensional weakly repulsive Bose gas at zero temperature in the presence of correlated disorder. Using large-scale simulations, we show that the low-energy Bogoliubov cumulative density of states remains quadratic up to a critical disorder strength, beyond which a power law with disorder-dependent exponent β <2 sets in. We associate this threshold behavior with the transition from superfluid to Bose glass, and compare the resulting mean-field phase diagram with scaling laws and the Thomas-Fermi percolation threshold of the mean-field density profile.
NASA Astrophysics Data System (ADS)
Adhikari, S. K.; de Llano, M.; Sevilla, F. J.; Solís, M. A.; Valencia, J. J.
2007-03-01
We contrast four distinct versions of the BCS-Bose statistical crossover theory according to the form assumed for the electron-number equation that accompanies the BCS gap equation. The four versions correspond to explicitly accounting for two-hole-(2h) as well as two-electron-(2e) Cooper pairs (CPs), or both in equal proportions, or only either kind. This follows from a recent generalization of the Bose-Einstein condensation (GBEC) statistical theory that includes not boson-boson interactions but rather 2e- and also (without loss of generality) 2h-CPs interacting with unpaired electrons and holes in a single-band model that is easily converted into a two-band model. The GBEC theory is essentially an extension of the Friedberg-Lee 1989 BEC theory of superconductors that excludes 2h-CPs. It can thus recover, when the numbers of 2h- and 2e-CPs in both BE-condensed and non-condensed states are separately equal, the BCS gap equation for all temperatures and couplings as well as the zero-temperature BCS (rigorous-upper-bound) condensation energy for all couplings. But ignoring either 2h- or 2e-CPs it can do neither. In particular, only half the BCS condensation energy is obtained in the two crossover versions ignoring either kind of CPs. We show how critical temperatures Tc from the original BCS-Bose crossover theory in 2D require unphysically large couplings for the Cooper/BCS model interaction to differ significantly from the Tcs of ordinary BCS theory (where the number equation is substituted by the assumption that the chemical potential equals the Fermi energy).
NASA Astrophysics Data System (ADS)
Dorfner, F.; Heidrich-Meisner, F.
2016-06-01
We study properties of the single-site reduced density matrix in the Bose-Bose resonance model as a function of system parameters. This model describes a single-component Bose gas with a resonant coupling to a diatomic molecular state, here defined on a lattice. A main goal is to demonstrate that the eigenstates of the single-site reduced density matrix have structures that are characteristic for the various quantum phases of this system. Since the Hamiltonian conserves only the global particle number but not the number of bosons and molecules individually, these eigenstates, referred to as optimal modes, can be nontrivial linear combinations of bare eigenstates of the molecular and boson particle number. We numerically analyze the optimal modes and their weights, the latter giving the importance of the corresponding state, in the ground state of the Bose-Bose resonance model. We find that the single-site von Neumann entropy is sensitive to the location of the phase boundaries. We explain the structure of the optimal modes and their weight spectra using perturbation theory and via a comparison to results for the single-component Bose-Hubbard model. We further study the dynamical evolution of the optimal modes and of the single-site entanglement entropy in two quantum quenches that cross phase boundaries of the model and show that these quantities are thermal in the steady state. For our numerical calculations, we use the density-matrix renormalization group method for ground-state calculations and time evolution in a Krylov subspace for the quench dynamics as well as exact diagonalization.
NASA Astrophysics Data System (ADS)
Hill, Matthew Eric; Kollmann, Peter; McNutt, Ralph L.; Smith, H. Todd; Bagenal, Fran; Brown, Lawrence E.; Elliott, Heather A.; Haggerty, Dennis K.; Horanyi, Mihaly; Krimigis, Stamatios M.; Kusterer, Martha; Lisse, Carey M.; McComas, David J.; Piquette, Marcus; Strobel, Darrell; Szalay, Jamey; Vandegriff, Jon; Zirnstein, Eric; Ennico, Kimberly; Olkin, Cathy B.; Weaver, Harold A.; Young, Leslie A.; Stern, S. A.
2015-11-01
The energetic particle environment at Pluto has been unknown, and little modeled, until this year’s historic encounter by the New Horizon (NH) spacecraft on 14 July 2015. The first energetic particle observations, made with the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument, were downlinked in August 2015. There are variations in the intensities of suprathermal (~3-30 keV/nucleon) ions that are associated with a combination of the position of the spacecraft relative to Pluto, the look direction of PEPSSI, and (potentially) temporal evolution in the system. We present the results of the near encounter with Pluto, to as close as ~11.6 Rp (1 Rp = 1187 km), which, early analysis shows, include large intensity variations associated with Pluto. We also present the concept of a neutral gas torus surrounding the Sun, aligned with Pluto’s orbit, and place observational constraints on it based primarily on comparison of NH measurements with a 3-D Monte Carlo model adapted from analogous satellite tori surrounding Saturn and Jupiter. Such a torus, or perhaps partial torus, could result from neutral N2 escaping from Pluto’s exosphere. Unlike other more massive planets, gaseous neutrals escape Pluto readily via Jeans escape (i.e., owing to the high thermal speed relative to the escape velocity). These neutrals are not directly observable by NH but, once ionized to N2+ or N+ via photolysis or charge exchange, are picked up by the solar wind, ultimately reaching ~50 keV or more, making these pickup ions detectable by PEPSSI. This work was supported by NASA's New Horizons project.
Pairing and condensation in a resonant Bose-Fermi mixture
NASA Astrophysics Data System (ADS)
Fratini, Elisa; Pieri, Pierbiagio
2010-05-01
We study by diagrammatic means a Bose-Fermi mixture, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and, for vanishing boson densities, coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.
Robustness of discrete semifluxons in closed Bose-Hubbard chains
NASA Astrophysics Data System (ADS)
Gallemí, A.; Guilleumas, M.; Martorell, J.; Mayol, R.; Polls, A.; Juliá-Díaz, B.
2016-07-01
We present the properties of the ground state and low-energy excitations of Bose-Hubbard chains with a geometry that varies from open to closed and with a tunable twisted link. In the vicinity of the symmetric π-flux case the system behaves as an interacting gas of discrete semifluxons for finite chains and interactions in the Josephson regime. The energy spectrum of the system is studied by direct diagonalization and by solving the corresponding Bogoliubov-de Gennes equations. The atom-atom interactions are found to enhance the presence of strongly correlated macroscopic superpositions of semifluxons.
Superfluidity of a nonequilibrium Bose-Einstein condensate of polaritons
Wouters, Michiel; Savona, Vincenzo
2010-02-01
We study theoretically superfluidity in a driven-dissipative Bose gas out of thermal equilibrium, and discuss the relation with conventional superfluids. We show how the superfluid behavior is characterized by a dramatic increase in the lifetime of a quantized vortex and point out the influence of the spatial geometry of the condensate. We apply our study to a condensate of polaritons in a semiconductor microcavity, whose properties can be directly inferred from optical spectroscopy. We propose three different experimental schemes to measure the vorticity of the polariton condensate.
Topological Superfluid in a Fermi-Bose Mixture with a High Critical Temperature
NASA Astrophysics Data System (ADS)
Wu, Zhigang; Bruun, G. M.
2016-12-01
We show that a 2D spin-polarized Fermi gas immersed in a 3D Bose-Einstein condensate constitutes a very promising system for realizing a px+i py superfluid. The fermions attract each other via an induced interaction mediated by the bosons, and the resulting pairing is analyzed with retardation effects fully taken into account. This is further combined with Berezinskii-Kosterlitz-Thouless (BKT) theory to obtain reliable results for the superfluid critical temperature. We show that both the strength and the range of the induced interaction can be tuned experimentally, which can be used to make the critical temperature approach the maximum value allowed by general BKT theory. Moreover, this is achieved while keeping the Fermi-Bose interaction weak so that three-body losses are small. Our results show that realizing a topological superfluid with atomic Fermi-Bose mixtures is within experimental reach.
Probing the Bose glass-superfluid transition using quantum quenches of disorder
NASA Astrophysics Data System (ADS)
Meldgin, Carolyn; Ray, Ushnish; Russ, Philip; Chen, David; Ceperley, David M.; Demarco, Brian
2016-07-01
The disordered Bose-Hubbard model--a paradigm for strongly correlated and disordered bosonic systems--is central to our understanding of quantum phase transitions. Despite extensive theoretical work on the disordered Bose-Hubbard model, little is known about the impact of temperature, the dynamical behaviour of quantum phases, and how equilibrium is affected during quantum phase transitions. These issues are critically important to applications such as quantum annealing and electronics based on quantum phase transitions. Here, we use a quantum quench of disorder in an ultracold lattice gas to dynamically probe the superfluid-Bose glass quantum phase transition at non-zero temperature ( Fig. 1). By measuring excitations generated during the quench, we provide evidence for superfluid puddles in the Bose glass phase and produce a superfluid-Bose glass phase diagram consistent with completely constrained, finite temperature, and equilibrium quantum Monte Carlo simulations. The residual energy from the quench, which is an efficacy measure for optimization through quantum annealing, is unchanged for quench times spanning nearly a hundred tunnelling times.
NASA Technical Reports Server (NTRS)
Savage, Blair D.; Cardelli, Jason A.; Bruhweiler, Frederick C.; Smith, Andrew M.; Ebbets, Dennis C.
1991-01-01
Observations of ultraviolet interstellar absorption lines toward Xi Persei obtained with the echelle mode of the Goddard High-Resolution Spectrograph (GHRS) aboard the HST at a resolution of 3.5 km/s are presented. The data for O I, C II, Mg II, S II, Fe II, Si II, Mn II, and Zn II are converted into representations of apparent column density per unit velocity, Na(v), over the velocity range from -30 to +40 km/s. The profiles for ions that are the dominant state of ionization in neutral clouds permit a study of the variation of element abundance with velocity caused by changes in the gas phase depletion in the different absorbing regions situated toward Xi Per. In the denser portions of the diffuse clouds, heavy element depletions are very large. However, in absorbing components near -5 and +25 km/s, the depletions are less severe, with a nearly solar gas phase abundance ratio being found for the gas in the +25 km/s component. The measurements confirm that the GHRS is well suited for diagnostic spectroscopy of interstellar gas.
Neutral particle beam intensity controller
Dagenhart, William K.
1986-01-01
A neutral beam intensity controller is provided for a neutral beam generator in which a neutral beam is established by accelerating ions from an ion source into a gas neutralizer. An amplitude modulated, rotating magnetic field is applied to the accelerated ion beam in the gas neutralizer to defocus the resultant neutral beam in a controlled manner to achieve intensity control of the neutral beam along the beam axis at constant beam energy. The rotating magnetic field alters the orbits of ions in the gas neutralizer before they are neutralized, thereby controlling the fraction of neutral particles transmitted out of the neutralizer along the central beam axis to a fusion device or the like. The altered path or defocused neutral particles are sprayed onto an actively cooled beam dump disposed perpendicular to the neutral beam axis and having a central open for passage of the focused beam at the central axis of the beamline. Virtually zero therough 100% intensity control is achieved by varying the magnetic field strength without altering the ion source beam intensity or its species yield.
Ultracold Bose gases: From the Gross-Pitaevskii to the fractional quantum Hall regime
NASA Astrophysics Data System (ADS)
Bhongale, Satyan Gopal
Ultra-cold Bose gases present an ideal environment for the study of many-body physics. These systems can be prepared under various experimental conditions with precise control. Techniques like Feshbach resonances allow us to dynamically tune the inter atomic interaction, from strongly attractive to a strongly repulsive one. In the first part of the thesis, we study the weakly interacting Bose gas in connection with the dynamics of an atom laser. Here we propose a possible optical pumping model for loading the reservoir of a continuous wave atom laser. The finite temperature effects like phase diffusion require a thorough understanding of the kinetic regime of the dilute Bose gas. In this respect, we develop a non-Markovian quantum kinetic theory and thereby show the emergence of different time scales for correlation and subsequent relaxation to an equilibrium states. Using numerical simulations, we also predict the damping rates and frequencies of collective modes. In the second part, we study the strongly correlated regime where the interaction energy is greater than any other (single particle) energy scale of the problem. Here, in the presence of a Feshbach interaction we predict the generation of novel strongly correlated paired states. Such states while similar to the one observed in a 5/2 fractional quantum hall effect, are unique in symmetry to the Bose gas system.
Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases.
Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh
2016-12-01
We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z^{*}, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for z
Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases
NASA Astrophysics Data System (ADS)
Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh
2016-12-01
We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z*, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for z
Bose-Einstein Condensation in low dimensionality
NASA Astrophysics Data System (ADS)
Nho, Kwangsik; Landau, D. P.
2006-03-01
Using path integral Monte Carlo simulation methods[1], we have studied properties of Bose-Einstein Condensates harmonically trapped in low dimemsion. Each boson has a hard-sphere potential whose core radius equals its corresponding scattering length. We have tightly confined the motion of trapped particles in one or more direction by increasing the trap anisotropy in order to simulate lower dimensional atomic gases. We have investigated the effect of both the temperature and the dimemsionality on the energetics and structural properties such as the total energy, the density profile, and the superfluid fraction. Our results show that the physics of low dimensional bosonic systems is very different from that of their three dimensional counterparts[2]. The superfluid fraction for a quasi-2D boson gas decreases faster than that for both a quasi-1D system[3] and a true 3D system with increasing temperature. The superfluid fraction decreases gradually as the two-body interaction strength increases although it shows no noticable dependence for both a quasi-1D system and a true 3D system. [1] K. Nho and D. P. Landau, Phys. Rev. A. 70, 53614 (2004).[2] N. D. Mermin and H. Wagner, Phys. Rev. Lett. 22, 1133 (1966);1.5inP. C. Hohenberg, Phys. Rev. 158, 383 (1967).[3] K. Nho and D. Blume, Phys. Rev. Lett. 95, 193601 (2005).
Three-dimensional distribution of the ISM in the Milky Way galaxy. III. The total neutral gas disk
NASA Astrophysics Data System (ADS)
Nakanishi, Hiroyuki; Sofue, Yoshiaki
2016-02-01
We present newly obtained three-dimensional gaseous maps of the Milky Way Galaxy: H I, H2, and total-gas (H I plus H2) maps, which were derived from the H I and 12CO(J = 1-0) survey data and rotation curves based on the kinematic distance. The H I and H2 face-on maps show that the H I disk is extended to a radius of 15-20 kpc and its outskirts are asymmetric to the Galactic center, while most of the H2 gas is distributed inside the solar circle. The total gas mass within a radius of 30 kpc amounts to 8.0 × 109 M⊙, 89% and 11% of which are H I and H2, respectively. The vertical slices show that the outer H I disk is strongly warped and the inner H I and H2 disks are corrugated. The total gas map is advantageous for tracing spiral structures from the inner to outer disk. Spiral structures such as the Norma-Cygnus, the Perseus, the Sagittarius-Carina, the Scutum-Crux, and the Orion arms are more clearly traced in the total gas map than ever. All the spiral arms are well explained by logarithmic spiral arms with pitch angles of 11°-15°. The molecular fraction of the total gas is high near the Galactic center and decreases with Galactocentric distance. The molecular fraction is also locally enhanced at the spiral arms compared with the inter-arm regions.
NASA Astrophysics Data System (ADS)
Auerbach, David; Aspenleiter, Julia; Volmer, Dietrich A.
2014-09-01
Differential ion mobility spectrometry (DMS) coupled to mass spectrometry is increasingly used in both quantitative analyses of biological samples and as a means of removing background interferences for enhanced selectivity and improved quality of mass spectra. However, DMS separation efficiency using dry inert gases often lacks the required selectivity to achieve baseline separation. Polar gas-phase modifiers such as alcohols are therefore frequently employed to improve selectivity via clustering/declustering processes. The choice of an optimal modifier currently relies on trial and error experiments, making method development a tedious activity. It was the goal of this study to establish a means of CV prediction for compounds using a homologous series of alcohols as gas-phase modifiers. This prediction was based on linear regression of compensation voltages of two calibration runs for the alcohols with the lowest and the highest molecular weights and readily available descriptors such as proton affinity and gas phase acidity of the modifier molecules. All experiments were performed on a commercial quadrupole linear ion trap mass spectrometer equipped with a DMS device between electrospray ionization source and entrance quadrupole lens. We evaluated our approach using a homologous series of 4-alkylbenzoic acids and a selection of 23 small molecules of high chemical diversity. Predicted CV values typically deviated from the experimentally determined values by less than 0.5 V. Several test compounds changed their ion mobility behavior for the investigated gas phase modifiers (e.g., from type B to type A) and thus could thus not be evaluated.
Recent developments in Bose-Einstein condensation
Kalman, G.
1997-09-22
This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.
Forming a Bose-Einstein Condensate
2014-09-26
This sequence of false-color images shows the formation of a Bose-Einstein condensate in the Cold Atom Laboratory prototype at NASA Jet Propulsion Laboratory as the temperature gets progressively closer to absolute zero.
Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.
2013-03-15
We present high-resolution, optical images (BVI + H{alpha}) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z {approx}2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our H{alpha} images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed H{alpha} emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions.
NASA Technical Reports Server (NTRS)
Combi, Michael R.
2004-01-01
In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important.
Interactions of neutral and singly charged keV atomic particles with gas-phase adenine molecules
NASA Astrophysics Data System (ADS)
Alvarado, Fresia; Bari, Sadia; Hoekstra, Ronnie; Schlathölter, Thomas
2007-07-01
KeV atomic particles traversing biological matter are subject to charge exchange and screening effects which dynamically change this particle's effective charge. The understanding of the collision cascade along the track thus requires a detailed knowledge of the interaction dynamics of radiobiologically relevant molecules, such as DNA building blocks or water, not only with ionic but also with neutral species. We have studied collisions of keV H+, He+, and C+ ions and H0, He0, and C0 atoms with the DNA base adenine by means of high resolution time-of-flight spectrometry. For H0 and H+ we find qualitatively very similar fragmentation patterns, while for carbon, strong differences are observed when comparing C0 and C+ impact. For collisions with He0 and He+ projectiles, a pronounced delayed fragmentation channel is observed, which has not been reported before.
Atomic Phase Conjugation From a Bose Condensate
1996-07-01
Schrödinger equation that we use in this paper is not the Gross - Pitaevskii nonlinear Schrödinger equation familiar in the description of Bose conden...dipole- dipole interaction as local, so that our nonlinear Schrödinger equation is itself local, just like the Gross - Pitaevskii equation. However, the...dynamics of a Bose condensate is described by the Gross - Pitaevskii nonlinear Schrödinger equation [15], in which the nonlinearity results from short
Bose-Einstein condensates in rotating lattices.
Bhat, Rajiv; Holland, M J; Carr, L D
2006-02-17
Strongly interacting bosons in a two-dimensional rotating square lattice are investigated via a modified Bose-Hubbard Hamiltonian. Such a system corresponds to a rotating lattice potential imprinted on a trapped Bose-Einstein condensate. Second-order quantum phase transitions between states of different symmetries are observed at discrete rotation rates. For the square lattice we study, there are four possible ground-state symmetries.
NASA Astrophysics Data System (ADS)
Stroe, Andra; Oosterloo, Tom; Röttgering, Huub J. A.; Sobral, David; van Weeren, Reinout; Dawson, William
2015-09-01
CIZA J2242.8+5301 (z = 0.188, nicknamed `Sausage') is an extremely massive (M200 ˜ 2.0 × 1015 M⊙), merging cluster with shock waves towards its outskirts, which was found to host numerous emission line galaxies. We performed extremely deep Westerbork Synthesis Radio Telescope H I observations of the `Sausage' cluster to investigate the effect of the merger and the shocks on the gas reservoirs fuelling present and future star formation (SF) in cluster members. By using spectral stacking, we find that the emission line galaxies in the `Sausage' cluster have, on average, as much H I gas as field galaxies (when accounting for the fact cluster galaxies are more massive than the field galaxies), contrary to previous studies. Since the cluster galaxies are more massive than the field spirals, they may have been able to retain their gas during the cluster merger. The large H I reservoirs are expected to be consumed within ˜0.75-1.0 Gyr by the vigorous SF and active galactic nuclei activity and/or driven out by the outflows we observe. We find that the star formation rate (SFR) in a large fraction of H α emission line cluster galaxies correlates well with the radio broad-band emission, tracing supernova remnant emission. This suggests that the cluster galaxies, all located in post-shock regions, may have been undergoing sustained SFR for at least 100 Myr. This fully supports the interpretation proposed by Stroe et al. and Sobral et al. that gas-rich cluster galaxies have been triggered to form stars by the passage of the shock.
NASA Astrophysics Data System (ADS)
Watson, Valerie J.; Nieto Delgado, Cesar; Logan, Bruce E.
2013-11-01
Commercially available activated carbon (AC) powders from different precursor materials (peat, coconut shell, coal, and hardwood) were treated with ammonia gas at 700 °C to improve their performance as oxygen reduction catalysts in neutral pH solutions used in microbial fuel cells (MFCs). The ammonia treated ACs exhibited better catalytic performance in rotating ring-disk electrode tests than their untreated precursors, with the bituminous based AC most improved, with an onset potential of Eonset = 0.12 V (untreated, Eonset = 0.08 V) and n = 3.9 electrons transferred in oxygen reduction (untreated, n = 3.6), and the hardwood based AC (treated, Eonset = 0.03 V, n = 3.3; untreated, Eonset = -0.04 V, n = 3.0). Ammonia treatment decreased oxygen content by 29-58%, increased nitrogen content to 1.8 atomic %, and increased the basicity of the bituminous, peat, and hardwood ACs. The treated coal based AC cathodes had higher maximum power densities in MFCs (2450 ± 40 mW m-2) than the other AC cathodes or a Pt/C cathode (2100 ± 1 mW m-2). These results show that reduced oxygen abundance and increased nitrogen functionalities on the AC surface can increase catalytic performance for oxygen reduction in neutral media.
NASA Astrophysics Data System (ADS)
Camacho, J. F.; Ruden, E. L.; Domonkos, M. T.; Schmitt-Sody, A.; Lucero, A.
2014-10-01
A Mach-Zehnder imaging interferometer, operating with 1064-nm and 532-nm wavelength beams from a short-pulse laser and a frequency-doubled branch, respectively, has been designed and built to simultaneously measure plasma free electron and neutral gas densities profiles within a laser-triggered spark gap switch with a 5-mm gap. The switch will be triggered by focusing a separate 532-nm or 1064-nm laser pulse along the gap's axis to trigger low-jitter breakdown. Illuminating the gap transverse to this axis, the diagnostic will generate interferograms for each wavelength, which will then be numerically converted to phase-shift maps. These will be used to calculate independent line-integrated free electron and neutral density profiles by exploiting their different frequency dispersion curves. The density profiles themselves, then, will be calculated by Abel inversion. Details of the interferometer's design will be presented along with density data obtained using a variety of fill gasses at various pressures. Other switch parameters will be varied as well in order to characterize more fully the performance of the switch.
Jeong, Mijeong Lee; Zahn, Michael; Trinh, Thao; Brooke, Fay A; Ma, Wenwen
2008-01-01
A sample cleanup procedure has been developed to remove coextractives that interfere with pesticide residue analysis of a dietary ingredient (Product B), an extract consisting of Scutellaria baicalensis and Acacia catechu. Samples were extracted using 1% acetic acid in acetonitrile, followed by solid-phase extraction and analysis by capillary gas chromatography with mass spectrometry in the selective-ion monitoring mode. Neutral alumina (alumina N) was found to be the most effective sorbent to remove coextractives from Product B; other materials that were tested but failed to remove interference were graphitized carbon black/primary-secondary amine (PSA), octadecylsilane (C18), Florisil, Oasis MCX, and strong anion exchange-PSA. The method was specifically developed for Product B, which was spiked with 41 organochlorine and organophosphorus pesticides, and resulted in the recovery of 80 to 120% at U.S. Pharmacopeia limits (0.06 to 4 microg/g) for the majority of the pesticides.
NASA Astrophysics Data System (ADS)
Benna, Mehdi; Yelle, Roger; Grebowsky, Joseph; Fox, Jane L.; Mahaffy, Paul
2016-07-01
We report the results of the observations of the ionosphere of Mars by the Neutral Gas and Ion Mass Spectrometer (NGIMS). These observations were conducted during the first two years of the Mars Atmosphere and Volatile Evolution mission (MAVEN), which also cover a full Martian year. The NGIMS observations revealed the spatial and temporal structures in the density distributions of major and several minor ion species (H_2^+, H_3^+, He^+, O_2^+, C^+, CH^+, N^+, NH^+, O^+, OH^+, H_2O^+, H_3O^+, N_2^+/CO^+, CO^+/HOC^+/N_2H^+, NO^+, HNO^+, O_2^+, HO_2^+, Ar^+, ArH^+, CO_2^+, and OCOH^+). Dusk/dawn and day/night asymmetries in the density distributions were also observed for nearly all ion species. Additionally, NGIMS revealed the presence of a persistent metal layer below 140 km. This layer was accessible for measurement during the MAVEN's "deep-dip" campaigns.
Yeliseyev, Y. N.
2013-03-19
It is shown that the frequencies of Trivelpiece-Gould (TG) modes in non-neutral plasma can get into the low-frequency range due to the Doppler shift caused by plasma rotation in crossed fields. TG modes interact with the ion modes that leads to plasma instability. In paper the frequency spectrum of 'cold' electron plasma completely filling a waveguide and containing small density fraction of ions of background gas is determined numerically. For ions the kinetic description is used. Oscillations having azimuthal number m= 2 are considered. In this case both low- and upper-hybrid TG modes get into the low-frequency range. The spectrum consists of families of 'modified' ion cyclotron (MIC) modes and electron TG modes with the frequencies equal to hybrid frequencies with the Doppler shift. The growth rates of upper-hybrid modes are much faster than the growth rates of low-hybrid and MIC modes.
watts, Christopher
2010-01-31
The grant funded a three year project to investigate the role of Alfvén waves as a possible mechanism heating plasmas, with relevance to solar coronal heating. Evidence suggests that there is strong coupling between the solar photosphere, corona and solar wind through Alfvén wave interaction with the neutral gas particles. A laboratory experimental and solar observational plan was designed to investigate in detail this interaction. Although many of the original research goals were met, difficulties in detecting the Alfvén wave signature meant that much of the research was stymied. This report summaries the work during the grant period, the challenges encountered and overcome, and the future research directions.
Benoit, Michael; Klaus, David
2005-01-01
Space flight has been shown to affect various bacterial growth parameters. It is proposed that weightlessness allows the cells to remain evenly distributed, consequently altering the chemical makeup of their surrounding fluid, and hence indirectly affecting their physiological behaviour. In support of this argument, ground-based studies using clinostats to partially simulate the quiescent environment attained in microgravity have generally been successful in producing bacterial growth characteristics that mimic responses reported under actual space conditions. A novel approach for evaluating the effects of reduced cell sedimentation is presented here through use of Escherichia coli cultures genetically modified to be neutrally buoyant. Since clinorotation would not (or would only minimally) affect cell distribution of this already near-colloidal cell system, it was hypothesized that the effects on final population density would be eliminated relative to a static control. Gas-vesicle-producing E. coli cultures were grown under clinostat and static conditions and the culture densities at 60 h were compared. As a control, E. coli that do not produce gas vesicles, but were otherwise identical to the experimental strain, were also grown under clinostat and static conditions. As hypothesized, no significant difference was observed in cell populations at 60 h between the clinorotated and static gas-vesicle-producing E. coli cultures, while the cells that did not produce gas vesicles showed a mean increase in population density of 10.5 % (P = 0.001). These results further suggest that the lack of cumulative cell sedimentation is the dominant effect of space flight on non-stirred, in vitro E. coli cultures.
NASA Technical Reports Server (NTRS)
1991-01-01
The object was to conduct large scale simulations of electron beams injected into space. The study of active injection of electron beams from spacecraft is important since it provides valuable insight into beam-plasma interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw return current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional particle simulations with collisional processes included are used to show how these different and often coupled processes can be utilized to enhance beam propagation from the spacecraft. To understand the radical expansion of mechanism of an electron beam from a highly charged spacecraft, two dimensional particle in cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge buildup at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.
NASA Astrophysics Data System (ADS)
Ruzic, D. N.; Juliano, D. R.
1992-12-01
The DEGAS neutral atom transport code was used to simulate helium pumping and D/T throughput in ITER. The sensitivity of the simulation to two different reflection models, four transmission probabilities from the exit of the simulation to the pump (0.0625, 0.125, 0.1875 and 0.250), and a 2-D model versus a 3-D model were analyzed. The variation in reflection model changes the densities in the duct and the recycling of D/T by a factor of 1.6. The variation in the transmission probabilities affects these same quantities by a factor of 2.5. The dimensionality of the simulation affects the density profile in the duct. A transmission probability from the exit of the DEGAS simulation to the pump of 0.110 to 0.125 was calculated from the ITER reference drawings. Using this quantity and the DEGAS results, an exhaust rate of 112 to 127 moles/h is predicted, implying that the reference pumping systems may be larger than necessary by a factor of 2.
NASA Technical Reports Server (NTRS)
Winglee, Robert M.
1991-01-01
The objective was to conduct large scale simulations of electron beams injected into space. The study of the active injection of electron beams from spacecraft is important, as it provides valuable insight into the plasma beam interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional (three velocity) particle simulations with collisional processes included are used to show how these different and often coupled processes can be used to enhance beam propagation from the spacecraft. To understand the radial expansion mechanism of an electron beam injected from a highly charged spacecraft, two dimensional particle-in-cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge build-up at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.
Interactions of neutral and singly charged keV atomic particles with gas-phase adenine molecules
Alvarado, Fresia; Bari, Sadia; Hoekstra, Ronnie; Schlathoelter, Thomas
2007-07-21
KeV atomic particles traversing biological matter are subject to charge exchange and screening effects which dynamically change this particle's effective charge. The understanding of the collision cascade along the track thus requires a detailed knowledge of the interaction dynamics of radiobiologically relevant molecules, such as DNA building blocks or water, not only with ionic but also with neutral species. We have studied collisions of keV H{sup +}, He{sup +}, and C{sup +} ions and H{sup 0}, He{sup 0}, and C{sup 0} atoms with the DNA base adenine by means of high resolution time-of-flight spectrometry. For H{sup 0} and H{sup +} we find qualitatively very similar fragmentation patterns, while for carbon, strong differences are observed when comparing C{sup 0} and C{sup +} impact. For collisions with He{sup 0} and He{sup +} projectiles, a pronounced delayed fragmentation channel is observed, which has not been reported before.
NASA Astrophysics Data System (ADS)
Nestingen-Palm, David; Stanimirović, Snežana; González-Casanova, Diego F.; Babler, Brian; Jameson, Katherine; Bolatto, Alberto
2017-08-01
We investigate spatial variations of turbulent properties in the Small Magellanic Cloud (SMC) by using neutral hydrogen (H i) observations. With the goal of testing the importance of stellar feedback on H i turbulence, we define central and outer SMC regions based on the star formation rate (SFR) surface density, as well as the H i integrated intensity. We use the structure function and the velocity channel analysis to calculate the power-law index (γ) for both underlying density and velocity fields in these regions. In all cases, our results show essentially no difference in γ between the central and outer regions. This suggests that H i turbulent properties are surprisingly homogeneous across the SMC when probed at a resolution of 30 pc. Contrary to recent suggestions from numerical simulations, we do not find a significant change in γ due to stellar feedback as traced by the SFR surface density. This could be due to the stellar feedback being widespread over the whole of the SMC, but more likely due to a large-scale gravitational driving of turbulence. We show that the lack of difference between central and outer SMC regions cannot be explained by the high optical depth H I.
Experiments on hydrodynamic transport in ultra-cold bose gasses
NASA Astrophysics Data System (ADS)
Koller, S. B.
2012-09-01
At temperatures near the absolut zero, a gas, here atomic sodium vapour, with high enough density cannot be described as tiny balls moving around as in classical physics. Since the temperature is low, the atoms are so slow that the matterwave of each atom starts to extend over the size of the atom and even over the interatomic distance. Therefore, they start to interfere like waves. Quantum mechanics start to dominate the physics in this regime. Further, depending on the sort of atoms (bosons or fermions) the atoms prefer to be in the same state or avoid to be in the same state. In the case of bosons as in the thesis, if the temperature is lowered to sub micro Kelvin temperature, a new state of matter appears after a phase transition - a macroscopic, standing wave, the Bose-Einstein condensate. This leads to a new phenomena: superfluidity - frictionless flow, second sound, vorticity and coherent scattering effects to name a few. The atoms are trapped in a elongated trap as in most of the experiments in ultra cold gasses. Usually experiments are done in a regime where the atoms seldomly collide with each other while travelling from one end to the other end of the cloud. In this experiment, however, the atoms collide many times with each other when they oscillate in the trap. This means that the cloud is hydrodynamic and leads to a very different behaviour. Two different sound waves (first and second sound), heat conduction, and collisional dominated transport can be observed in this case. The fact that the gas is weakly interacting allows comparison with current theory. At very low temperatures as in the experiments described in the thesis, the Bose character strongly alters the collisions of the atoms. The outcome of the collision does not only depend on the colliding atoms, but also on the atoms near by in phase space. The experiments outlined in this thesis cover some aspects of physics involved. Vortices have been created and observed in the Bose
Microcanonical fluctuations of the condensate in weakly interacting Bose gases
Idziaszek, Zbigniew
2005-05-15
We study fluctuations of the number of Bose condensed atoms in a weakly interacting homogeneous and trapped gases. For a homogeneous system we apply the particle-number-conserving formulation of the Bogoliubov theory and calculate the condensate fluctuations within the canonical and the microcanonical ensembles. We demonstrate that, at least in the low-temperature regime, predictions of the particle-number-conserving and traditional, nonconserving theory are identical, and lead to the anomalous scaling of fluctuations. Furthermore, the microcanonical fluctuations differ from the canonical ones by a quantity which scales normally in the number of particles, thus predictions of both ensembles are equivalent in the thermodynamic limit. We observe a similar behavior for a weakly interacting gas in a harmonic trap. This is in contrast to the trapped, ideal gas, where microcanonical and canonical fluctuations are different in the thermodynamic limit.
NASA Astrophysics Data System (ADS)
Kharga, Digvijay; Inotani, Daisuke; Hanai, Ryo; Ohashi, Yoji
2017-08-01
We theoretically investigate normal-state properties of a gas mixture of single-component bosons and fermions with a hetero-nuclear Feshbach resonance. Including strong hetero-pairing fluctuations associated with the Feshbach resonance, we calculate single-particle density of states, as well as the spectral weight at various interaction strengths. For this purpose, we employ an improved T-matrix approximation (TMA), where the bare Bose Green's function in the non-selfconsistent TMA self-energy is modified so as to satisfy the Hugenholtz-Pines relation at the Bose-Einstein condensation (BEC) temperature TBEC. In the unitary regime at TBEC, we show that hetero-pairing fluctuations couple Fermi atomic excitations with Fermi molecular excitations, as well as with Bose atomic excitations. Although a similar coupling phenomenon by pairing fluctuations is known to give a pseudo-gapped density of states in the unitary regime of a two-component Fermi gas, such a dip structure is found to not appear even in the unitary limit of a Bose-Fermi mixture. It only appears in the strong-coupling regime. Instead, a spectral peak along the molecular dispersion appears in the spectral weight. We also clarify how this coupling phenomenon is seen in the Bose channel. Since a hetero-nuclear Feshbach resonance, as well as the formation of Bose-Fermi molecules, have been realized, our results would be useful for the study of strong-coupling properties of this unique quantum gas.
Reed, M.H. . Dept. of Geological Sciences)
1993-04-01
Fluid inclusions in quartz and sphalerite of epithermal veins containing galena, sphalerite and chalcopyrite with silver sulfides and electrum commonly have salinities of 2 to 10 weight percent NaCl equivalent. Examples include Bohemia, OR, Comstock, NV, and Creede, CO. Salinities in such base metal-rich systems are apparently greater than those in gold-adularia, base metal-poor systems such as Sleeper, NV, Republic, WA, and Hishikare, Kyushu. Saline epithermal fluids are commonly assumed to have been derived from saline magmatic brines, from local host formations, as has been suggested for Creede, or from evaporative concentration (boiling) of more dilute meteoric ground water. Another possibility, which may be the most common origin, is reaction of wall rocks with magmatic gas condensates rich in HCl and sulfuric acid. A mixture of one part Augustine Volcanic gas condensate in 10 parts cold ground water has a pH of 0.7 and the dominant cation is H[sup +] by a factor of 10[sup 4]. Calculated reaction of this condensate mixture with andesite at 300 C to a water/rock ratio (w/r) of 4.6 yields an NaCl-dominated fluid with a total salinity of 2.1 wt %. and pH 3.7. Further reaction, to w/r 0.14 yields a fluid salinity of 2.6 wt % and pH of 5.7; this fluid is in equilibrium with a propylitic alteration assemblage. Aqueous sulfide accumulates during the rock reaction as sulfate is reduced to sulfide when ferrous iron is oxidized to ferric iron. Sulfide concentration in the latter fluid is 32 ppm, far exceeding sulfate concentration. In the overall reaction, hydrogen ion is exchanged for base cations (including base metals) and sulfate is reduced to sulfide.
Neutral and ionised gas around the post-red supergiant IRC +10 420 at AU size scales
NASA Astrophysics Data System (ADS)
Oudmaijer, R. D.; de Wit, W. J.
2013-03-01
Context. IRC +10 420 is one of the few known massive stars in rapid transition from the red supergiant phase to the Wolf-Rayet or luminous blue variable phase. Aims: The star has an ionised wind and using the Brγ line we assess the mass-loss on spatial scales of ~1 AU. Methods: We present new VLT Interferometer AMBER data which are combined with all other AMBER data present in the literature. The final dataset covers a position angle range of ~180° and baselines up to 110 m. The spectrally dispersed visibilities, differential phases and line flux are conjointly analysed and modelled. We also present the first AMBER/FINITO observations which cover a larger wavelength range and allow us to observe the Na i doublet at 2.2 μm. The data are complemented by X-Shooter data, which provide a higher spectral resolution view. Results: The Brγ emission line and the Na i doublet are both spatially resolved. After correcting the AMBER data for the fact that the lines are not spectrally resolved, we find that Brγ traces a ring with a diameter of 4.18 mas, in agreement with higher spectral resolution data. We consider a geometric model in which the Brγ emission emerges from the top and bottom rings of an hour-glass shaped structure, viewed almost pole-on. It provides satisfactory fits to most visibilities and differential phases. The fact that we detect line emission from a neutral metal like Na i within the ionised region, a very unusual occurrence, suggests the presence of a dense pseudo-photosphere. Conclusions: The ionised wind can be reproduced with a polar wind, which could well have the shape of an hour-glass. Closer in, the resolved Na i emission is found to occur on scales barely larger than the continuum. This fact and that many yellow hypergiants exhibit this comparatively rare emission hints at the presence of a "Yellow" or even "White Wall" in the Hertzsprung-Russell diagram, preventing them from visibly evolving to the blue. Based on observations at ESO, and in
Ghosh, Ayan; Manna, Debashree; Ghanty, Tapan K
2016-04-28
A novel class of interesting insertion compounds obtained through the insertion of a noble gas atom into the heavier pnictides have been explored by various ab initio quantum chemical techniques. Recently, the first neutral noble gas insertion compounds, FXeY (Y = P, N), were theoretically predicted to be stable; the triplet state was found to be the most stable state, with a high triplet-singlet energy gap, by our group. In this study, we investigated another noble gas inserted compound, FNgY (Ng = Kr and Xe; Y = As, Sb and Bi), with a triplet ground state. Density functional theory (DFT), second order Møller-Plesset perturbation theory (MP2), coupled-cluster theory (CCSD(T)) and multi-reference configuration interaction (MRCI) based techniques have been utilized to investigate the structures, stabilities, harmonic vibrational frequencies, charge distributions and topological properties of these compounds. These predicted species, FNgY (Ng = Kr and Xe; Y = As, Sb and Bi) are found to be energetically stable with respect to all the probable 2-body and 3-body dissociation pathways, except for the 2-body channel leading to the global minimum products (FY + Ng). Nevertheless, the finite barrier height corresponding to the saddle points of the compounds connected to their respective global minima products indicates that these compounds are kinetically stable. The structural parameters, energetics, and charge distribution results as well as atoms-in-molecules (AIM) analysis suggest that these predicted molecules can be best represented as F(-)[(3)NgY](+). Thus, all the aforementioned computed results clearly indicate that it may be possible to experimentally prepare the most stable triplet state of FNgY molecules under cryogenic conditions through a matrix isolation technique.
Cannon, John M.; Most, Hans P.; Skillman, Evan D.; Weisz, Daniel R.; Warren, Steven R.; Cook, David; Dolphin, Andrew E.; Kennicutt, Robert C.; Lee, Janice; Seth, Anil; Walter, Fabian E-mail: skillman@astro.umn.edu E-mail: warren@astro.umn.edu E-mail: adolphin@raytheon.com E-mail: jlee@obs.carnegiescience.edu E-mail: walter@mpia.de
2011-07-01
We present new multi-configuration Very Large Array H I spectral line observations of the M81 group dwarf irregular post-starburst galaxy DDO 165. The H I morphology is complex, with multiple column density peaks surrounding a large region of very low H I surface density that is offset from the center of the stellar distribution. The bulk of the neutral gas is associated with the southern section of the galaxy; a secondary peak in the north contains {approx}15% of the total H I mass. These components appear to be kinematically distinct, suggesting that either tidal processes or large-scale blowout have recently shaped the interstellar medium (ISM) of DDO 165. Using spatially resolved position-velocity maps, we find multiple localized high-velocity gas features. Cross-correlating with radius-velocity analyses, we identify eight shell/hole structures in the ISM with a range of sizes ({approx}400-900 pc) and expansion velocities ({approx}7-11 km s{sup -1}). These structures are compared with narrow- and broadband imaging from the Kitt Peak National Observatory and the Hubble Space Telescope (HST). Using the latter data, recent works have shown that DDO 165's previous 'burst' phase was extended temporally ({approx}>1 Gyr). We thus interpret the high-velocity gas features, H I holes, and kinematically distinct components of the galaxy in the context of the immediate effects of 'feedback' from recent star formation (SF). In addition to creating H I holes and shells, extended SF events are capable of creating localized high-velocity motion of the surrounding interstellar material. A companion paper connects the energetics from the H I and HST data.
NASA Astrophysics Data System (ADS)
Israel, F. P.; Rosenberg, M. J. F.; van der Werf, P.
2015-06-01
In this paper we present fluxes in the [ CI ] lines of neutral carbon at the centers of some 76 galaxies with far-infrared luminosities ranging from 109 to 1012L⊙, as obtained with the Herschel Space Observatory and ground-based facilities, along with the line fluxes of the J = 7-6, J = 4-3, J = 2-112CO, and J = 2-113CO transitions. With this dataset, we determine the behavior of the observed lines with respect to each other and then investigate whether they can be used to characterize the molecular interstellar medium (ISM) of the parent galaxies in simple ways and how the molecular gas properties define the model results. In most starburst galaxies, the [ CI ] to 13CO line flux ratio is much higher than in Galactic star-forming regions, and it is correlated to the total far-infrared luminosity. The [ CI ] (1-0)/12CO (4-3), the [ CI ] (2-1)/12CO (7-6), and the [ CI ] (2-1)/(1-0) flux ratios are correlated, and they trace the excitation of the molecular gas. In the most luminous infrared galaxies (LIRGs), the ISM is fully dominated by dense (n( H2) = 104-105 cm-3) and moderately warm (Tkin ≈ 30 K) gas clouds that appear to have low [C°]/[CO] and [13CO]/[12CO] abundances. In less luminous galaxies, emission from gas clouds at lower densities becomes progressively more important, and a multiple-phase analysis is required to determine consistent physical characteristics. Neither the 12CO nor the [ CI ] velocity-integrated line fluxes are good predictors of molecular hydrogen column densities in individual galaxies. In particular, so-called X( [ CI ]) conversion factors are not superior to X( 12CO) factors. The methods and diagnostic diagrams outlined in this paper also provide a new and relatively straightforward means of deriving the physical characteristics of molecular gas in high-redshift galaxies up to z = 5, which are otherwise hard to determine.
Vortices in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Haljan, Paul C.
2004-05-01
Since the advent of Bose-Einstein condensation in the dilute alkalis, there has been considerable interest in observing effects in atomic condensates akin to the hallmark effects associated with superfluidity and superconductivity. In particular, the study of quantized vortices and vortex lattices represents an important connection between the traditional ``super" systems such as liquid Helium and this new atomic system. This thesis explores some of the first vortex experiments in a condensate of magnetically trapped Rubidium-87. Single vortex lines and rings are created using a wavefunction engineering technique, which is an ideal starting point to study the dynamical behavior of vortices within the condensate. An entirely different approach of ``intrinsic nucleation" has been developed to create rapidly rotating condensates with large amounts of vorticity. A novel variation of forced evaporation is used to simultaneously cool and spin up an ultracold gas. In this way, condensates can be formed that are rotating in excess of 95% of the centrifugal limit and contain large, extraordinarily regular lattices of well over 100 vortices. Direct detection of the vortex cores makes it possible to study the microscopic structure of the vortex arrangements both at equilibrium and under dynamical conditions where severe applied stresses distort the lattice far from its equilibrium configuration. In conclusion, the techniques developed in this work have helped to open up a new area of rotating condensate physics and, in the future, may lead to regimes of extreme rotation and quantum Hall physics. This work was performed at the University of Colorado, Boulder, under the supervision of Prof. Eric A. Cornell.
THE GEOMETRY EFFECTS OF AN EXPANDING UNIVERSE ON THE DETECTION OF COOL NEUTRAL GAS AT HIGH REDSHIFT
Curran, S. J.
2012-03-20
Recent high-redshift surveys for 21 cm absorption in damped Ly{alpha} absorption systems (DLAs) take the number of published searches at z{sub abs} > 2 to 25, the same number as at z{sub abs} < 2, although the detection rate at high redshift remains significantly lower (20% compared to 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21 cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low-redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low- and high-redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21 cm detections in DLAs can be accounted for by the geometry effects of an expanding universe. That is, as yet there is no evidence of the spin temperature of gas-rich galaxies evolving with redshift.
Role of ion-neutral complexes during acid-catalyzed dehydration of ethanol in the gas phase
Bouchoux, G.; Hoppilliard, Y. )
1990-12-05
Acid-catalyzed dehydration of ethanol in the gas phase has been studied both theoretically and experimentally. Molecular orbital calculations have been done at the MP3/6-31G*//6-31G* level with correction of the zero-point vibrational energy. Protonated ethanol, 1 is predicted to isomerize easily into the C{sub 2}H{sub 4} {hor ellipsis} H {hor ellipsis} OH{sub 2}{sup +} complex, 2 (activation energy 120 kJ/mol). This result is in agreement with the observation of a near statistical hydrogen exchange preceding the dehydration reaction 1 {yields} C{sub 2}H{sub 4} + H{sub 3}O{sup +}. In the case of the water-solvated ion C{sub 2}H{sub 5}OH{sub 2} {hor ellipsis} OH{sub 2}{sup +}, 5, isomerization into a proton-bound complex C{sub 2}H{sub 4} {hor ellipsis} H{sub 5}O{sub 2}{sup +}, 6, needs a larger amount of energy (ca. 180 kJ/mol). Again the calculations agree with experiments: the important activation energy for the process 5 {yields} 6 prevents hydrogen exchanges and ethene elimination. Extension of these calculations to higher systems is discussed.
Cheng, Chin-Min; Walker, Harold W; Bigham, Jerry M
2007-01-01
A number of agricultural and engineering uses for fixated flue gas desulfurization (FGD) material exist; however, the potential for leaching of hazardous elements has limited widespread application and the processes controlling the leaching of this material are poorly understood. In this study, a flow-through rotating-disk system was applied to elucidate the relative importance of bulk diffusion, pore diffusion, and surface chemical reaction in controlling the leaching of fixated FGD material under pH conditions ranging from 2.2 to 6.8. Changing the hydrodynamics in the rotating disk system did not affect the leaching kinetics at both pH 2.2 and 6.8, indicating that bulk diffusion was not the kinetic-limiting step. Application of the shrinking core model (SCM) to the data suggested a surface reaction-controlled mechanism, rather than a pore diffusion mechanism. The leaching of fixated FGD material increased with decreasing pH, suggesting it can be described by a combination of an intrinsic hydration reaction and a proton-promoted dissolution reaction. X-ray diffraction (XRD) and elemental composition analyses before and after leaching suggests that for most elements a number of solid phases controlled the leaching process.
Data is presented showing the progress made towards the development of a new automated system combining solid phase extraction (SPE) with gas chromatography/mass spectrometry for the single run analysis of water samples containing a broad range of acid, base and neutral compounds...
Data is presented showing the progress made towards the development of a new automated system combining solid phase extraction (SPE) with gas chromatography/mass spectrometry for the single run analysis of water samples containing a broad range of acid, base and neutral compounds...
Yin, Shi; Wang, Zhechen; Bernstein, Elliot R
2013-04-07
Reaction of CO with H2 on neutral FemSn clusters in a fast flow reactor is investigated both experimentally and theoretically. Single photon ionization at 118 nm is used to detect neutral cluster distributions through time of flight mass spectrometry. FemSn clusters are generated through laser ablation of a mixed iron-sulfur target in the presence of a pure helium carrier gas. A strong size dependent reactivity of (FeS)m clusters toward CO is characterized. The reaction FeS + CO → Fe + OCS is found for the FeS cluster, and the association product Fe2S2CO is observed for the Fe2S2 cluster. Products Fe2S2(13)COH2 and Fe2S2(13)COH4 are identified for reactions of (13)CO and H2 on Fe2S2 clusters: this suggests that the Fe2S2 cluster has a high catalytic activity for hydrogenation reactions of CO to form formaldehyde and methanol. Density functional theory (DFT) calculations are performed to explore the potential energy surfaces for the two reactions: Fe2S2 + CO + 2H2 → Fe2S2 + CH3OH; and Fe2S2 + CO + H2 → Fe2S2 + CH2O. A barrierless, thermodynamically favorable pathway is obtained for both catalytic processes. Catalytic cycles for formaldehyde and methanol formation from CO and H2 on a Fe2S2 cluster are proposed based on our experimental and theoretical investigations. The various reaction mechanisms explored by DFT are in good agreement with the experimental results. Condensed phase iron sulfide, which contains exposed Fe2S2 units on its surface, is suggested to be a good catalyst for low temperature formaldehyde/methanol synthesis.
Domain walls and bubble droplets in immiscible binary Bose gases
NASA Astrophysics Data System (ADS)
Filatrella, G.; Malomed, Boris A.; Salerno, Mario
2014-10-01
The existence and stability of domain walls (DWs) and bubble-droplet (BD) states in binary mixtures of quasi-one-dimensional ultracold Bose gases with inter- and intraspecies repulsive interactions is considered. Previously, DWs were studied by means of coupled systems of Gross-Pitaevskii equations (GPEs) with cubic terms, which model immiscible binary Bose-Einstein condensates (BECs). We address immiscible BECs with two- and three-body repulsive interactions, as well as binary Tonks-Girardeau (TG) gases, using systems of GPEs with cubic and quintic nonlinearities for the binary BEC, and coupled nonlinear Schrödinger equations with quintic terms for the TG gases. Exact DW solutions are found for the symmetric BEC mixture, with equal intraspecies scattering lengths. Stable asymmetric DWs in the BEC mixtures with dissimilar interactions in the two components, as well as of symmetric and asymmetric DWs in the binary TG gas, are found by means of numerical and approximate analytical methods. In the BEC system, DWs can be easily put in motion by phase imprinting. Combining a DW and anti-DW on a ring, we construct BD states for both the BEC and TG models. These consist of a dark soliton in one component (the "bubble"), and a bright soliton (the "droplet") in the other. In the BEC system, these composite states are mobile, too.
NASA Astrophysics Data System (ADS)
Lebouteiller, V.; Péquignot, D.; Cormier, D.; Madden, S.; Pakull, M. W.; Kunth, D.; Galliano, F.; Chevance, M.; Heap, S. R.; Lee, M.-Y.; Polles, F. L.
2017-06-01
Context. The neutral interstellar medium of galaxies acts as a reservoir to fuel star formation. The dominant heating and cooling mechanisms in this phase are uncertain in extremely metal-poor star-forming galaxies. The low dust-to-gas mass ratio and low polycyclic aromatic hydrocarbon abundance in such objects suggest that the traditional photoelectric effect heating may not be effective. Aims: Our objective is to identify the dominant thermal mechanisms in one such galaxy, I Zw 18 (1/30Z⊙), assess the diagnostic value of fine-structure cooling lines, and estimate the molecular gas content. Even though molecular gas is an important catalyst and tracer of star formation, constraints on the molecular gas mass remain elusive in the most metal-poor galaxies. Methods: Building on a previous photoionization model describing the giant H ii region of I Zw 18-NW within a multi-sector topology, we provide additional constraints using, in particular, the [C ii] 157 μm and [O i] 63 μm lines and the dust mass recently measured with the Herschel Space Telescope. Results: The heating of the H i region appears to be mainly due to photoionization by radiation from a bright X-ray binary source, while the photoelectric effect is negligible. Significant cosmic ray heating is not excluded. Inasmuch as X-ray heating dominates in the H i gas, the infrared fine-structure lines provide an average X-ray luminosity of order 4 × 1040 erg s-1 over the last few 104 yr in the galaxy. The upper limits to the [Ne v] lines provide strong constraints on the soft X-ray flux arising from the binary. A negligible mass of H2 is predicted. Nonetheless, up to 107 M⊙ of H2 may be hidden in a few sufficiently dense clouds of order ≲5 pc (≲0.05'') in size. Regardless of the presence of significant amounts of H2 gas, [C ii] and [O i] do not trace the so-called "CO-dark gas", but they trace the almost purely atomic medium. Although the [C ii]+[O i] to total infrared ratio in I Zw 18 is similar to
Bose polarons: Dynamical decay and RF signatures
NASA Astrophysics Data System (ADS)
Corson, John; Bohn, John
2016-05-01
Interactions of a single impurity with a quantum many-body environment are known to alter the character of the impurity, thereby forming a ``quasiparticle''. The condensed matter tradition often identifies quasiparticles as poles of a Green function in the complex plane, a notion whose sophistication sometimes obscures the underlying physics. The problem of a single quantum impurity in a Bose condensate, or Bose polaron, is an illustrative example where the meaning of the impurity Green function, and hence the quasiparticle itself, becomes especially transparent. Using direct diagonalization in a truncated Hilbert space, we examine the dynamical evolution and quasiparticle decay of the repulsive Bose polaron. This approach also allows us to simulate RF spectroscopy across a Feshbach resonance and outside the linear regime, as well as account for motional and thermal effects in a harmonic trap.
NASA Astrophysics Data System (ADS)
Hanish, D. J.; Meurer, G. R.; Ferguson, H. C.; Zwaan, M. A.; Heckman, T. M.; Staveley-Smith, L.; Bland-Hawthorn, J.; Kilborn, V. A.; Koribalski, B. S.; Putman, M. E.; Ryan-Weber, E. V.; Oey, M. S.; Kennicutt, R. C., Jr.; Knezek, P. M.; Meyer, M. J.; Smith, R. C.; Webster, R. L.; Dopita, M. A.; Doyle, M. T.; Drinkwater, M. J.; Freeman, K. C.; Werk, J. K.
2006-09-01
We derive observed Hα and R-band luminosity densities of an H I-selected sample of nearby galaxies using the SINGG sample to be l'Hα=(9.4+/-1.8)×1038 h70 ergs s-1 Mpc-3 for Hα and l'R=(4.4+/-0.7)×1037 h70 ergs s-1 Å-1 Mpc-3 in the R band. This R-band luminosity density is approximately 70% of that found by the Sloan Digital Sky Survey. This leads to a local star formation rate density of log(ρ˙SFR [Msolar yr-1 Mpc-3])=-1.80+0.13-0.07(random)+/-0.03(systematic)+log(h70) after applying a mean internal extinction correction of 0.82 mag. The gas cycling time of this sample is found to be tgas=7.5+1.3-2.1 Gyr, and the volume-averaged equivalent width of the SINGG galaxies is EW(Hα)=28.8+7.2-4.7 Å (21.2+4.2-3.5 Å without internal dust correction). As with similar surveys, these results imply that ρ˙SFR(z) decreases drastically from z~1.5 to the present. A comparison of the dynamical masses of the SINGG galaxies evaluated at their optical limits with their stellar and H I masses shows significant evidence of downsizing: the most massive galaxies have a larger fraction of their mass locked up in stars compared with H I, while the opposite is true for less massive galaxies. We show that the application of the Kennicutt star formation law to a galaxy having the median orbital time at the optical limit of this sample results in a star formation rate decay with cosmic time similar to that given by the ρ˙SFR(z) evolution. This implies that the ρ˙SFR(z) evolution is primarily due to the secular evolution of galaxies, rather than interactions or mergers. This is consistent with the morphologies predominantly seen in the SINGG sample.
Rosenberg, M. J. F.; Van der Werf, P. P.; Israel, F. P.; Meijerink, R.; Aalto, S.; Armus, L.; Díaz-Santos, T.; Charmandaris, V.; Evans, A. S.; Fischer, J.; Gao, Y.; González-Alfonso, E.; Greve, T. R.; Harris, A. I.; Henkel, C.; Isaak, K. G.; and others
2015-03-10
(Ultra) luminous infrared galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 μm) luminosities (L {sub LIRG} > 10{sup 11} L {sub ☉} and L {sub ULIRG} > 10{sup 12} L {sub ☉}). The Herschel Comprehensive ULIRG Emission Survey (PI: van der Werf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (10{sup 11} L {sub ☉} ≤ L {sub IR} ≤ 10{sup 13} L {sub ☉}). With the Herschel Space Observatory, we observe [C II] 157 μm, [O I] 63 μm, and [O I] 145 μm line emission with Photodetector Array Camera and Spectrometer, CO J = 4-3 through J = 13-12, [C I] 370 μm, and [C I] 609 μm with SPIRE, and low-J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [O I] 63 μm emission line is self absorbed. Comparing the CO excitation to the InfraRed Astronomical Satellite 60/100 μm ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [C II], [Si II], [O I], and [C I] lines in the objects with the highest far IR fluxes, but do not observe this for CO 4 ≤ J {sub upp} ≤ 13. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J = 1-0 linewidth, and the active galactic nucleus (AGN) contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important.
NASA Astrophysics Data System (ADS)
Rhee, Jonghwan; Lah, Philip; Chengalur, Jayaram N.; Briggs, Frank H.; Colless, Matthew
2016-08-01
We present the results of H I spectral stacking analysis of Giant Metrewave Radio Telescope (GMRT) observations targeting the Cosmological Evolution Survey (COSMOS) field. The GMRT data cube contains 474 field galaxies with redshifts known from the zCOSMOS-bright 10 k catalogue. Spectra for the galaxies are co-added and the stacked spectrum allows us to make a ˜3σ measurement of the average H I mass. Using this average H I mass, along with the integral optical B-band luminosity of the galaxies and the luminosity density of the COSMOS field, a volume normalization is applied to obtain the cosmic H I mass density (ΩH I). We find a cosmic H I mass density of ΩH I = (0.42 ± 0.16) × 10-3 at z ˜ 0.37, which is the highest redshift measurement of ΩH I ever made using H I spectral stacking. The value we obtained for ΩH I at z ˜ 0.37 is consistent with that measured from large blind 21-cm surveys at z = 0, as well as measurements from other H I stacking experiments at lower redshifts. Our measurement, in conjunction with earlier measurements, indicates that there has been no significant evolution of H I gas abundance over the last 4 Gyr. A weighted mean of ΩH I from all 21-cm measurements at redshifts z ≲ 0.4 gives ΩH I = (0.35 ± 0.01) × 10-3. The ΩH I measured (from H I 21-cm emission measurements) at z ≲ 0.4 is, however, approximately half that measured from damped Lyman-α absorption (DLA) systems at z ≳ 2. Deeper surveys with existing and upcoming instruments will be critical to understand the evolution of ΩH I in the redshift range intermediate between z ˜ 0.4 and the range probed by DLA observations.
NASA Astrophysics Data System (ADS)
Rosenberg, M. J. F.; van der Werf, P. P.; Aalto, S.; Armus, L.; Charmandaris, V.; Díaz-Santos, T.; Evans, A. S.; Fischer, J.; Gao, Y.; González-Alfonso, E.; Greve, T. R.; Harris, A. I.; Henkel, C.; Israel, F. P.; Isaak, K. G.; Kramer, C.; Meijerink, R.; Naylor, D. A.; Sanders, D. B.; Smith, H. A.; Spaans, M.; Spinoglio, L.; Stacey, G. J.; Veenendaal, I.; Veilleux, S.; Walter, F.; Weiß, A.; Wiedner, M. C.; van der Wiel, M. H. D.; Xilouris, E. M.
2015-03-01
(Ultra) luminous infrared galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 μm) luminosities (L LIRG > 1011 L ⊙ and L ULIRG > 1012 L ⊙). The Herschel Comprehensive ULIRG Emission Survey (PI: van der Werf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (1011 L ⊙ <= L IR <= 1013 L ⊙). With the Herschel Space Observatory, we observe [C II] 157 μm, [O I] 63 μm, and [O I] 145 μm line emission with Photodetector Array Camera and Spectrometer, CO J = 4-3 through J = 13-12, [C I] 370 μm, and [C I] 609 μm with SPIRE, and low-J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [O I] 63 μm emission line is self absorbed. Comparing the CO excitation to the InfraRed Astronomical Satellite 60/100 μm ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [C II], [Si II], [O I], and [C I] lines in the objects with the highest far IR fluxes, but do not observe this for CO 4 <= J upp <= 13. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J = 1-0 linewidth, and the active galactic nucleus (AGN) contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
A Simple Model of Bose-Einstein Condensation of Interacting Particles
NASA Astrophysics Data System (ADS)
Poluektov, Yu. M.
2017-03-01
A simple model of Bose-Einstein condensation of interacting particles is proposed. It is shown that in the condensate state the dependence of thermodynamic quantities on the interaction constant does not allow an expansion in powers of the coupling constant. Therefore, it is impossible to pass to the Einstein model of condensation in an ideal Bose gas by means of a limiting passage, setting the interaction constant to zero. The account for the interaction between particles eliminates difficulties in the description of condensation available in the model of an ideal gas, which are connected with the fulfillment of thermodynamic relations and an infinite value of the particle number fluctuation in the condensate phase.
Quantum phase transitions of atom-molecule Bose mixtures in a double-well potential.
Relaño, A; Dukelsky, J; Pérez-Fernández, P; Arias, J M
2014-10-01
The ground state and spectral properties of Bose gases in double-well potentials are studied in two different scenarios: (i) an interacting atomic Bose gas, and (ii) a mixture of an atomic gas interacting with diatomic molecules. A ground state second-order quantum phase transition is observed in both scenarios. For large attractive values of the atom-atom interaction, the ground state is degenerate. For repulsive and small attractive interaction, the ground state is not degenerate and is well approximated by a boson coherent state. Both systems depict an excited state quantum phase transition. In both cases, a critical energy separates a region in which all the energy levels are degenerate in pairs, from another region in which there are no degeneracies. For the atomic system, the critical point displays a singularity in the density of states, whereas this behavior is largely smoothed for the mixed atom-molecule system.
Bose-Einstein condensation in low dimensional systems with deformed bosons
NASA Astrophysics Data System (ADS)
Algin, Abdullah; Olkun, Ali
2017-08-01
We study the low and high temperature thermostatistical properties of a deformed boson gas constructed by the bosonic intermediate-statistics particles confined in low spatial dimensions. Many of the deformed thermodynamical functions of the system such as internal energy and entropy are investigated by means of some elements of the Fibonacci calculus. Particular emphasis is given to a careful analysis on low dimensional systems of such deformed bosons, and the conditions under which the Bose-Einstein condensation would occur in such systems are discussed. We show that low dimensional systems with deformed bosons exhibit the Bose-Einstein condensation for values of the model deformation parameters (p , q) greater than one. We also study possible anyonic behavior of the model for high temperatures. The results obtained in this work reveal that the present deformed boson gas model can be used for modeling nonlinear behavior of systems with quasiparticles encountered in several areas of research particularly in quantum science.
Bose-Einstein condensation. Twenty years after
Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; Malomed, B. A.; Mihalache, D.
2015-02-23
The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.
Bolte, Jens; Kerner, Joachim
2016-04-15
In this paper we investigate Bose-Einstein condensation into the one-particle ground state in interacting quantum many-particle systems on graphs. We extend previous results obtained for particles on an interval and show that even arbitrarily small repulsive two-particle interactions destroy the condensate in the one-particle ground state present in the non-interacting Bose gas. Our results also cover singular two-particle interactions, such as the well-known Lieb-Liniger model, in the thermodynamic limit.
Energy dependent 3-body loss in out-of-equilibrium 1D Bose gases
NASA Astrophysics Data System (ADS)
Zundel, Laura; Xia, Lin; Wilson, Joshua; Riou, Jean-Felix; Weiss, David
2015-05-01
We measure the three-body loss of out-of-equilibrium one-dimensional (1D) Bose gases and find that it depends strongly on the average energy of the distribution. The theory of three-body loss in 1D gas experiments is incomplete due to the challenge of calculating how correlations evolve. We present an empirical model based on energy dependent correlations and show that it reproduces the data.