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1

Ground state properties of spin-alined atomic hydrogen  

NASA Technical Reports Server (NTRS)

Theoretical calculation of the ground state properties of spin-alined atomic hydrogen by the Monte Carlo method. The interatomic interaction, as described by the results of Kolos and Wolniewicz (1965), is made fit to a Morse potential form. An appropriate trail wavefunction is formed from the short-range part of the WKB solution for a pair of atoms interacting through a Morse potential.

Dugan, J. V., Jr.; Etters, R. D.

1973-01-01

2

Variable energy, high flux, ground-state atomic oxygen source  

NASA Technical Reports Server (NTRS)

A variable energy, high flux atomic oxygen source is described which is comprised of a means for producing a high density beam of molecules which will emit O(-) ions when bombarded with electrons; a means of producing a high current stream of electrons at a low energy level passing through the high density beam of molecules to produce a combined stream of electrons and O(-) ions; means for accelerating the combined stream to a desired energy level; means for producing an intense magnetic field to confine the electrons and O(-) ions; means for directing a multiple pass laser beam through the combined stream to strip off the excess electrons from a plurality of the O(-) ions to produce ground-state O atoms within the combined stream; electrostatic deflection means for deflecting the path of the O(-) ions and the electrons in the combined stream; and, means for stopping the O(-) ions and the electrons and for allowing only the ground-state O atoms to continue as the source of the atoms of interest. The method and apparatus are also adaptable for producing other ground-state atoms and/or molecules.

Chutjian, Ara (inventor); Orient, Otto J. (inventor)

1987-01-01

3

Photoabsorption by Ground-State Alkali-Metal Atoms  

Microsoft Academic Search

Principal-series oscillator strengths and ground-state photoionization cross sections are computed for sodium, potassium, rubidium, and cesium. The degree of polarization of the photoelectrons is also predicted for each atom. The core-polarization correction to the dipole transition moment is included in all of the calculations, and the spin-orbit perturbation of valence-p-electron orbitals is included in the calculations of the Rb and

Jon C. Weisheit

1972-01-01

4

Ultracold Heteronuclear Mixture of Ground and Excited State Atoms  

NASA Astrophysics Data System (ADS)

We report on the realization of an ultracold mixture of lithium atoms in the ground state and ytterbium atoms in an excited metastable (P23) state. Such a mixture can support broad magnetic Feshbach resonances which may be utilized for the production of ultracold molecules with an electronic spin degree of freedom, as well as novel Efimov trimers. We investigate the interaction properties of the mixture in the presence of an external magnetic field and find an upper limit for the background interspecies two-body inelastic decay coefficient of K2'<3×10-12 cm3/s for the P23 mJ=-1 substate. We calculate the dynamic polarizabilities of the Yb(P23) magnetic substates for a range of wavelengths, and find good agreement with our measurements at 1064 nm. Our calculations also allow the identification of magic frequencies where Yb ground and metastable states are identically trapped and the determination of the interspecies van der Waals coefficients.

Khramov, Alexander; Hansen, Anders; Dowd, William; Roy, Richard J.; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana; Gupta, Subhadeep

2014-01-01

5

Acceleration-induced radiative excitation of ground-state atoms  

NASA Astrophysics Data System (ADS)

We use elementary time-dependent perturbation theory, referred wholly to an inertial (laboratory) frame, to determine the probability that a semi-realistically modelled atom is promoted from the ground to an excited state, with the emission of a photon, when its nucleus is constrained to follow a classically prescribed trajectory including a finite interval of (arbitrary) acceleration between asymptotically uniform initial and final motions. In the formal limit where the proper acceleration ? is constant and lasts forever, we verify the Unruh effect, namely that the atom then behaves as if it had been exposed to black-body radiation at temperature TU = planck?/2?ckB. The point is that in virtue of its simplicity our formalism is reasonably adaptable, and its predictions free of objections like those often and rightly based on the unrealizable nature of strictly constant ? considered directly rather than as a limit.

Barton, G.; Calogeracos, A.

2008-04-01

6

Ground-state Hanle effect based on atomic alignment  

NASA Astrophysics Data System (ADS)

We have studied the ground-state Hanle effect (GSHE) excited by linearly polarized laser light on the D1 line of cesium atoms. We have solved algebraically the Liouville equation using the irreducible tensor formalism, and derive an analytical expression for the resonance line shapes in a magnetic field of arbitrary direction. The model predictions are in excellent agreement with experimental observations in various field geometries. Our model is valid for arbitrary F?F' transitions in the low-power limit. We discuss the relation between the GSHE and electromagnetically induced transparency or absorption. Our approach allows a full understanding of the mechanism of the GSHE and provides tools for quantifying the resonance contrast, a crucial parameter for metrological applications of level crossing resonances.

Breschi, Evelina; Weis, Antoine

2012-11-01

7

Gas flow dependence of ground state atomic oxygen in plasma needle discharge at atmospheric pressure  

Microsoft Academic Search

We present clear evidence that ground state atomic oxygen shows two patterns near a surface in the helium plasma needle discharge. Two-photon absorption laser-induced fluorescence spectroscopy, combined with gas flow simulation, was employed to obtain spatially-resolved ground state atomic oxygen densities. When the feed gas flow rate is low, the radial density peaks along the axis of the needle. At

Yukinori Sakiyama; Nikolas Knake; Daniel Schröder; Jörg Winter; Volker Schulz-von der Gathen; David B. Graves

2010-01-01

8

Ground state properties of solid and liquid spin-aligned atomic hydrogen  

NASA Technical Reports Server (NTRS)

Calculations of the ground state energy in the solid phase were performed with the aid of a variational approach. The Morse potential form of the atomic triple potential computed by Kolos and Wolniewicz (1965) was employed for the calculations. The ground state energies of both the liquid and solid phases of spin-aligned atomic hydrogen around the volume of the transition are presented in a graph.

Danilowicz, R. L.; Dugan, J. V., Jr.; Etters, R. D.

1976-01-01

9

Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State  

NASA Astrophysics Data System (ADS)

We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.

Kaufman, A. M.; Lester, B. J.; Regal, C. A.

2012-10-01

10

Lower bounds to energies for cusped-gaussian wavefunctions. [hydrogen atom ground state  

NASA Technical Reports Server (NTRS)

Calculations for the ground states of H, He, and Be, conducted by Steiner and Sykes (1972), show that the inclusion of a very small number of cusp functions can lead to a substantial enhancement of the quality of the Gaussian basis used in molecular wavefunction computations. The properties of the cusped-Gaussian basis are investigated by a calculation of lower bounds concerning the ground state energy of the hydrogen atom.

Eaves, J. O.; Walsh, B. C.; Steiner, E.

1974-01-01

11

Manipulation of a single molecule ground state by means of gold atom contacts  

NASA Astrophysics Data System (ADS)

Single gold adatoms were manipulated on a Au(1 1 1) surface with the tip of a scanning tunnelling microscope to contact selected peripheral ? bonds of a single Coronene molecule. Tunnelling electron spectroscopy and differential conductance mapping of the Au-Coronene complexes show how Coronene's electronic ground state is shifted down in energy as the function of the number of interacting Au atoms, demonstrating that a Coronene molecule can function like a single molecule counter. The number of interacting atoms can be counted by simply following the linear energy downshift of Coronene's ground state.

Manzano, C.; Soe, W. H.; Hliwa, M.; Grisolia, M.; Wong, H. S.; Joachim, C.

2013-11-01

12

The ground state properties of spin-aligned atomic hydrogen, deuterium, and tritium  

NASA Technical Reports Server (NTRS)

The internal energy, pressure, and compressibility of ground-state, spin-aligned atomic hydrogen, deuterium, and tritium are calculated assuming that all pair interactions occur via the atomic triplet (spin-aligned) potential. The conditions required to obtain atomic hydrogen and its isotopes in bulk are discussed; such a development would be of value in propulsion systems because of the light mass and energetic recombination of atomic hydrogen. Results show that atomic triplet hydrogen and deuterium remain gaseous at 0 K, and that tritium forms a liquid with a binding energy of approximately -0.75 K per atom at a molar volume of 130 cu cm per mole. The pair distribution function for these systems is calculated, and the predicted superfluid behavior of atomic triplet hydrogen and tritium is briefly discussed.

Etters, R. D.; Dugan, J. V., Jr.; Palmer, R. W.

1975-01-01

13

Electron capture in ground and excited states in proton-alkali-metal-atom collisions  

Microsoft Academic Search

The wave formulation of the impulse approximation has been applied to the case of electron capture into the ground, 2s and 2p excited states of hydrogen in collisions between protons and alkali-metal atoms sodium, potassium, rubidium and caesium. The transition matrix elements have been numerically calculated and used to determine the differential and integral cross sections for charge transfer for

K. B. Choudhury; D. P. Sural

1992-01-01

14

Helium AtomSCF-LCAO Calculation of the (1s)2 Ground State of the  

NSDL National Science Digital Library

Using a double-zeta basis of Slater-type orbitals [STOs], this Java applet calculates the single determinant singlet ground state 1s2 wavefunction of the helium atom. The doubly occupied orbital is expanded in terms of two basis functions, 1s and 1s`.

15

Lower bounds to energies for Gaussian wave functions: studies of the hydrogen-atom ground state  

Microsoft Academic Search

To test the possibility of extending lower bound energy determinations to molecules by the methods of Temple, Weinstein, and Stevenson and Crawford, lower bounds for the energy of the 1s ground state of the H atom are computed for Gaussian based wave functions, for which the calculation of the average value of the square of the Hamiltonian is not too

M E Schwartz

1967-01-01

16

Role of electronic excitations in ground-state-forbidden inelastic collisions between ultracold atoms and ions.  

PubMed

The role of electronic excitation in inelastic collisions between ultracold Ca atoms and Ba(+) ions, confined in a hybrid trap, is studied for the first time. Unlike previous investigations, this system is energetically precluded from undergoing inelastic collisions in its ground state, allowing a relatively simple experimental determination and interpretation of the influence of electronic excitation. It is found that while the electronic state of the ion can critically influence the inelastic collision rate, the polarizability mismatch of the neutral atom electronic states suppresses short-range collisions, and thus inelastic processes, involving electronically excited neutral atoms. As a result of these features, it is experimentally demonstrated that it is possible to mitigate inelastic collision loss mechanisms in these systems, marking an important step toward long-lived hybrid atom-ion devices. PMID:23368115

Sullivan, Scott T; Rellergert, Wade G; Kotochigova, Svetlana; Hudson, Eric R

2012-11-30

17

Role of Electronic Excitations in Ground-State-Forbidden Inelastic Collisions Between Ultracold Atoms and Ions  

NASA Astrophysics Data System (ADS)

The role of electronic excitation in inelastic collisions between ultracold Ca atoms and Ba+ ions, confined in a hybrid trap, is studied for the first time. Unlike previous investigations, this system is energetically precluded from undergoing inelastic collisions in its ground state, allowing a relatively simple experimental determination and interpretation of the influence of electronic excitation. It is found that while the electronic state of the ion can critically influence the inelastic collision rate, the polarizability mismatch of the neutral atom electronic states suppresses short-range collisions, and thus inelastic processes, involving electronically excited neutral atoms. As a result of these features, it is experimentally demonstrated that it is possible to mitigate inelastic collision loss mechanisms in these systems, marking an important step toward long-lived hybrid atom-ion devices.

Sullivan, Scott T.; Rellergert, Wade G.; Kotochigova, Svetlana; Hudson, Eric R.

2012-11-01

18

[Collisional energy transfer of the Rb (7 2D) state by ground state K atoms].  

PubMed

In the K-Rb vaper mixtures, the two-photon stepwise excitation of rubidium atoms from the ground state to the state Rb 7 2D is obtained by the use of a rubidium lamp and a cw dye laser. The cross sections for the collisional process Rb (7 2D) +K (4S) -->Rb (5S) +K (7S. 5D) have been measured by observation of the resulting fluorescence. The ratio of K (7S. 5D) to Rb7D fluorescence contains a contribution from K 7S<==>5D mixing. The contribution could effectively be subtracted out using a second experiment in which a potassium lamp and a cw dye laser were used to pump the K7S or 5D state, and the ratio of 7S to 5D or 5D to 7S fluorescence was monitored. The cross sections (in 10(-15)cm2) for Rb7D-->K7S. 5D excitation transfer are 25.8 +/- 10. 3 and 1.5 +/- 0.6 respectively. PMID:15806758

Shen, Y; Li, W

1997-08-01

19

Ground state of alkaline-earth fermionic atoms in one-dimensional optical lattices  

NASA Astrophysics Data System (ADS)

We studied the ground state of alkaline-earth-metal atoms confined in one-dimensional optical lattices modeled by the Kondo lattice model plus a quadratic confining potential. We considered the half-filling case and both ferromagnetic and antiferromagnetic interaction between the localized and delocalized atoms. We found Kondo insulator domains that always coexist with metallic and/or band insulator regions. We observed that the on-site delocalized-localized spin correlation remains constant in the insulating regions and used it to determine the state diagrams. Metallic regions were found for both ferromagnetic and antiferromagnetic couplings.

Silva-Valencia, J.; Souza, A. M. C.

2012-01-01

20

Atoms and quantum dots with a large number of electrons: The ground-state energy  

SciTech Connect

We compute the ground-state energy of atoms and quantum dots with a large number N of electrons. Both systems are described by a nonrelativistic Hamiltonian of electrons in a d-dimensional space. The electrons interact via the Coulomb potential. In the case of atoms (d=3), the electrons are attracted by the nucleus via the Coulomb potential. In the case of quantum dots (d=2), the electrons are confined by an external potential, whose shape can be varied. We show that the dominant terms of the ground-state energy are those given by a semiclassical Hartree-exchange energy, whose N{yields}{infinity} limit corresponds to Thomas-Fermi theory. This semiclassical Hartree-exchange theory creates oscillations in the ground-state energy as a function of N. These oscillations reflect the dynamics of a classical particle moving in the presence of the Thomas-Fermi potential. The dynamics is regular for atoms and some dots, but in general in the case of dots, the motion contains a chaotic component. We compute the correlation effects. They appear at the order NlnN for atoms, in agreement with available data. For dots, they appear at the order N.

Kunz, Herve; Rueedi, Rico [Institute of Theoretical Physics, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2010-03-15

21

Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium  

NASA Technical Reports Server (NTRS)

Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

Drachman, Richard J.

2006-01-01

22

Atomic-Beam Investigations of Electronic and Nuclear Ground States in the Rare-Earth Region  

Microsoft Academic Search

A number of radioactive isotopes in the rare-earth region have been investigated by using the atomic-beam magnetic-resonance technique. The total electronic angular momentum (J) and the atomic g value (gJ) have been determined for some low-lying levels in, Pm, Dy, Ho, and Er. These observations are consistent with the following ground-state assignments: Pmi-(4f)5(6s)2, 6H52; Dyi-(4f)10(6s)2, 5I8; Hoi-(4f)11(6s)2, 4I152; and Eri-(4f)12(6s)2,

Amado Y. Cabezas; Ingvar Lindgren; Richard Marrus

1961-01-01

23

Electromagnetically induced transparency in cold 85Rb atoms trapped in the ground hyperfine F = 2 state  

NASA Astrophysics Data System (ADS)

We report electromagnetically induced transparency (EIT) in cold 85Rb atoms, trapped in the lower hyperfine level F = 2, of the ground state 52S1/2 (Tiwari V B et al 2008 Phys. Rev. A 78 063421). Two steady-state ?-type systems of hyperfine energy levels are investigated using probe transitions into the levels F' = 2 and F' = 3 of the excited state 52P3/2 in the presence of coupling transitions F = 3 ? F' = 2 and F = 3 ? F' = 3, respectively. The effects of uncoupled magnetic sublevel transitions and coupling field's Rabi frequency on the EIT signal from these systems are studied using a simple theoretical model.

Tiwari, V. B.; Singh, S.; Rawat, H. S.; Singh, Manoranjan P.; Mehendale, S. C.

2010-05-01

24

ELECTRON IMPACT EXCITATION CROSS SECTIONS AND RATES FROM THE GROUND STATE OF ATOMIC CALCIUM  

Microsoft Academic Search

New R-matrix calculations are presented for electron excitation of atomic calcium. The target state expansion includes 22 states: 4s21S; 4snl1,3L, where nl is 3d, 4p, 5s, 5p, 4d and 4f; 3d4p1,3P,D,F; and 4p23P, 1D, 1S terms. The calculation is in LS coupling, and configuration interaction involving 3p subshell correlation is included. Electron impact excitation cross sections from the 4s2 ground

ANDY M. SAMSON; KEITH A. BERRINGTON

2001-01-01

25

Electron Impact Excitation Cross Sections and Rates from the Ground State of Atomic Calcium  

Microsoft Academic Search

New R-matrix calculations are presented for electron excitation of atomic calcium. The target state expansion includes 22 states: 4s21S; 4snl1,3L, where nl is 3d, 4p, 5s, 5p, 4d and 4f; 3d4p1,3P,D,F; and 4p23P, 1D, 1S terms. The calculation is in LS coupling, and configuration interaction involving 3p subshell correlation is included. Electron impact excitation cross sections from the 4s2 ground

Andy M. Samson; Keith A. Berrington

2001-01-01

26

Concentration of atomic population in any single-ground-state magnetic sublevel in alkali-metal vapors  

NASA Astrophysics Data System (ADS)

A scheme for concentrating a large fraction (~100%) of the alkali-metal atoms in an atomic vapor in any single magnetic sublevel of the ground state is developed. This is experimentally demonstrated in the 87Rb vapor. The atomic vapor is optically pumped to a high degree of spin polarization after which two radio-frequency ? pulses are applied to transfer the atomic population from the (2,2) or (2,-2) (F,MF) state to the (2,0) sublevel of the ground state. The resulting distribution is diagnosed using a microwave field tuned to the hyperfine transition (6834 MHz).

Bhaskar, N. D.

1993-06-01

27

s-wave elastic collisions between cold ground-state 87Rb atoms  

NASA Astrophysics Data System (ADS)

We have measured the elastic-scattering cross section of 87Rb atoms in the ||F=1,mF=-1> ground state at 25 ?K. The cross section is almost purely s wave at these temperatures and has a value of (5.4+/-1.3)×10-12 cm2. We have searched for the predicted Feshbach-type resonances in the elastic cross section [Tiesinga et al., Phys. Rev. A 46, 1167 (1992)] as a function of magnetic field. There are no resonances with a magnetic-field width >=2 G over a magnetic-field range of 15-540 G.

Newbury, N. R.; Myatt, C. J.; Wieman, C. E.

1995-04-01

28

A numerical study of the ground state and dynamics of atomic-molecular Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

In this paper, we numerically investigate the ground-state structure and dynamics of atomic-molecular Bose-Einstein condensates at zero temperature, which are modeled by coupled Gross-Pitaevskii equations (GPEs). To get the ground state, we evolve a gradient flow with discrete normalization numerically. To study the dynamics, we employ an efficient numerical method—the time-splitting Fourier pseudospectral method for solving the coupled GPEs. The proposed numerical methods have been numerically tested and employed in studying the mechanism on how an atomic condensate can be converted into an atomic-molecular mixture or a pure molecular condensate from an atomic condensate either in equilibrium or dynamically.

Jiang, Wei; Wang, Hanquan; Li, Xianggui

2013-11-01

29

Direct measurement of fine structure in the ground state of atomic carbon by laser magnetic resonance  

NASA Astrophysics Data System (ADS)

Laser magnetic resonance measurements of fine-structure intervals in the ground state of atomic carbon, which have made possible the detection of far infrared line emissions from C-12 in several interstellar sources, are reported. The 3P0 to 3P1 and 3P1 to 3P2 transitions in C-12 and C-13 atoms in a methane-fluorine atom flame were observed at 10 different optically pumped far infrared laser lines, and the C-12 fine structure intervals were determined from the combined data of all 10 lines and g-factors from the atomic beam experiments of Wolber et al. (1970). Interval spacings of 809.3446 (29) and 492.1623 (7) GHz are obtained for the 3P0-3P1 and 3P1-3P2 transitions, respectively. It is pointed out that the further detection of these transitions should lead to information regarding atomic abundances, isotope ratios, chemical fractionation effects, processes involving interstellar dust grains and the physical conditions of the interstellar medium

Saykally, R. J.; Evenson, K. M.

1980-06-01

30

Analysis of exchange energy at long range for states of alkali diatomic molecules correlating to two ground state atoms  

NASA Astrophysics Data System (ADS)

Recently experimentally-based asymptotic exchange energies ?VE between ground state atoms in Li2, Na2, K2, and NaK have been determined from spectroscopically-determined potential energy curves. These empirical results are shown to be well fit by the expression -CR?e-?R of Smirnov and Chibisov, where C is a positive constant and ? and ? can be readily calculated from the atomic ionization energies. The expression should be useful for estimating the exchange energy in other alkali dimers.

Zemke, Warren T.; Stwalley, William C.

1999-09-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

32

Particle-localized ground state of atom-molecule Bose-Einstein condensates in a double-well potential  

SciTech Connect

We study the effect of atom-molecule internal tunneling on the ground state of atom-molecule Bose-Einstein condensates in a double-well potential. In the absence of internal tunneling between atomic and molecular states, the ground state is symmetric, which has equal-particle populations in two wells. From the linear stability analysis, we show that the symmetric stationary state becomes dynamically unstable at a certain value of the atom-molecule internal tunneling strength. Above the critical value of the internal tunneling strength, the ground state bifurcates to the particle-localized ground states. The origin of this transition can be attributed to the effective attractive interatomic interaction induced by the atom-molecule internal tunneling. This effective interaction is similar to that familiar in the context of BCS-BEC crossover in a Fermi gas with Feshbach resonance. Furthermore, we point out the possibility of reentrant transition in the case of the large detuning between the atomic and molecular states.

Motohashi, Atsushi; Nikuni, Tetsuro [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)

2010-09-15

33

Ground-State Binding Energies of Substitutional Cu, Ag and Au Impurity Atoms in Ge1-xSix Crystals  

NASA Astrophysics Data System (ADS)

The ground-state binding energies of substitutional Cus,Ags and Aus impurity atoms in Ge1-xSix(0? ×? 0,3) have been determined on the basis of Hall measurements. It is shown that the averaged activation energies D E of all explored impurity levels in Ge1-x Six grow linearly with Si concentration in crystals. Random-alloy splitting of the ground-states of the impurities in the crystals is discussed. A conclusion is made due to multiplicity of possible acceptor states of substitutional atoms of this impurities in Ge1-xSix and Si.

Kyazimzade, R. Z.

1996-10-01

34

Scattering properties of ground-state spin-polarized atomic hydrogen  

NASA Astrophysics Data System (ADS)

In this paper, the scattering properties of ground-state spin-polarized atomic hydrogen (H?) are studied at 0 K using the Lippmann-Schwinger formalism. The total, diffusion and viscosity cross sections, as well as the S-wave scattering length, are calculated. The S-wave scattering cross section is found to be the most significant partial wave contributing to the total cross section at low energy. The contribution of the higher angular momentum waves, especially the D-wave (?=2), to the scattering increases with increasing relative momentum k. Our calculations are performed for three triplet-state potentials: Morse-type, Silvera and Born-Oppenheimer potentials. It is also noted that as k?0, the results of the Morse potential are larger than those of the Silvera and Born-Oppenheimer potentials. This is because of the exponential tail of the Morse potential which falls off more rapidly than the r-6 behavior of the Silvera and Born-Oppenheimer potentials. Also, the Morse potential is relatively shallower than the other two potentials. For high k, the Morse cross sections approach the corresponding Silvera cross sections. This is because these triplet-state potentials have almost the same short-range part. The total cross sections reflect the quantum oscillations arising from the diffraction caused by the repulsive short-range part of the potential. Our results are consistent with those obtained by other methods.

Joudeh, B. R.

2013-07-01

35

Electronic excitation of ground state atoms by collision with heavy gas particles  

NASA Technical Reports Server (NTRS)

Most of the important chemical reactions which occur in the very high temperature air produced around space vehicles as they enter the atmosphere were investigated both experimentally and theoretically, to some extent at least. One remaining reaction about which little is known, and which could be quite important at the extremely high temperatures that will be produced by the class of space vehicles now contemplated - such as the AOTV - is the excitation of bound electron states due to collisions between heavy gas particles. Rates of electronic excitation due to free electron collisions are known to be very rapid, but because these collisions quickly equilibrate the free and bound electron energy, the approach to full equilibrium with the heavy particle kinetic energy will depend primarily on the much slower process of bound electron excitation in heavy particle collisions and the subsequent rapid transfer to free electron energy. This may be the dominant mechanism leading to full equilibrium in the gas once the dissociation process has depleted the molecular states so the transfer between molecular vibrational energy and free electron energy is no longer available as a channel for equilibration of free electron and heavy particle kinetic energies. Two mechanisms seem probable in electronic excitation by heavy particle impact. One of these is the collision excitation and deexcitation of higher electronic states which are Rydberg like. A report, entitled 'Semi-Classical Theory of Electronic Excitation Rates', was submitted previously. This presented analytic expressions for the transition probabilities, assuming that the interaction potential is an exponential repulsion with a perturbation ripple due to the dipole-induced dipole effect in the case of neutral-neutral collisions, and to the ion-dipole interaction in the case of ion-neutral collisions. However the above may be, there is little doubt that excitation of ground state species by collision occurs at the point where the initial and final potentials cross, or at least come very close. Therefore, this mechanism would be applicable to the case where a gas is initially at very low temperature suddenly subjected to high energy heavy particle bombardment. This situation would model the measurement of excitation cross section by molecular beam techniques, for example. The purpose is to report values of cross sections and rate coefficients for collision excitation of ground state atoms estimated with the Landau-Zener transition theory and to compare results with measurement of excitation cross sections for a beam of Hydrogen atoms impacting Argon atom targets. Some very dubious approximations are used, and the comparison with measurement is found less than ideal, but results are at least consistent within order of magnitude. The same model is then applied to the case of N-N atom collisions, even though the approximations then become even more doubtful. Still the rate coefficients obtained are at least plausible in both magnitude and functional form, and as far as I am aware these are the only estimates available for such rate coefficients.

Hansen, C. Frederick

1993-01-01

36

Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions  

SciTech Connect

Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2’-bi-1,4,5,6-tetrahydro¬pyrimidine, H2bim = 2,2’-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2’-pyridyl)¬imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO• (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements for the reactions of Co and Fe complexes with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer: ?SºHAT = -30 ± 2 cal mol-1 K-1 for the two iron complexes and -41 ± 2 cal mol-1 K-1 for [CoII(H2bim)3]2+. The ?SºHAT for TEMPO + RuII(acac)2(py-imH) is much closer to zero, 4.9 ± 1.1 cal mol-1 K-1. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ?SºHAT. Calorimetry on TEMPOH + tBu3PhO• gives ?HºHAT = 11.2 ± 0.5 kcal mol-1 which matches the enthalpy predicted from the difference in literature solution BDEs. An evaluation of the literature BDEs of both TEMPOH and tBu3PhOH is briefly presented and new estimates are included on the relative enthalpy of solvation for tBu3PhO• vs. tBu3PhOH. The primary contributor to the large magnitude of the ground-state entropy |?SºHAT| for the metal complexes is vibrational entropy, ?Sºvib. The common assumption that ?SºHAT ? 0 for HAT reactions, developed for organic and small gas phase molecules, does not hold for transition metal based HAT reactions. The trend in magnitude of |?SºHAT| for reactions with TEMPO, RuII(acac)2(py-imH) << [FeII(H2bip)3]2+ = [FeII(H2bim)3]2+ < [CoII(H2bim)3]2+, is surprisingly well predicted by the trends for electron transfer half-reaction entropies, ?SºET, in aprotic solvents. ?SºET and ?SºHAT are both affected by ?Sºvib and vary significantly with the metal center involved. The close connection between ?SºHAT and ?SºET provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.

2009-03-10

37

Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions  

PubMed Central

Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2’-bi-1,4,5,6-tetrahydropyrimidine, H2bim = 2,2’-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2’-pyridyl)-imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO• (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements for the reaction of [CoII(H2bim)3]2+ with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer, ?41 ± 2 cal mol?1 K?1. This is even more negative than the ?SoHAT = ?30 ± 2 cal mol?1 K?1 for the two iron complexes and the ?SoHAT for RuII(acac)2(py-imH) + TEMPO, 4.9 ± 1.1 cal mol?1 K?1, as reported earlier. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ?SoHAT. Calorimetry on TEMPOH + tBu3PhO• gives ?HoHAT = ?11.2 ± 0.5 kcal mol?1 which matches the enthalpy predicted from the difference in literature solution BDEs. A brief evaluation of the literature thermochemistry of TEMPOH and tBu3PhOH supports the common assumption that ?SoHAT ? 0 for HAT reactions of organic and small gas-phase molecules. However, this assumption does not hold for transition metal based HAT reactions. The trend in magnitude of |?SoHAT| for reactions with TEMPO, RuII(acac)2(py-imH) << [FeII(H2bip)3]2+ = [FeII(H2bim)3]2+ < [CoII(H2bim)3]2+, is surprisingly well predicted by the trends for electron transfer half-reaction entropies, ?SoET, in aprotic solvents. This is because both ?SoET and ?SoHAT have substantial contributions from vibrational entropy, which varies significantly with the metal center involved. The close connection between ?SoHAT and ?SoET provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects.

Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.

2009-01-01

38

Vibrational Relaxation of Ground-State Oxygen Molecules With Atomic Oxygen and Carbon Dioxide  

NASA Astrophysics Data System (ADS)

Vertical water vapor profiles are key to understanding the composition and energy budget in the mesosphere and lower thermosphere (MLT). The SABER instrument onboard NASA's TIMED satellite measures such profiles by detecting H2O(?2) emission in the 6.8 ?m region. Collisional deactivation of vibrationally excited O2, O2(X3?-g, ? = 1) + H2O ? O2(X3?-g, ? = 0) + H2O(?2), is an important source of H2O(?2). A recent study has identified two other processes involving excited O2 that control H2O(?2) population in the MLT: (1) the vibrational-translational (V-T) relaxation of O2(X3?-g, ? = 1) level by atomic oxygen and (2) the V-V exchange between CO2 and excited O2 molecules [1]. Over the past few years SRI researchers have measured the atomic oxygen removal process mentioned above at room temperature [2] and 240 K [3]. These measurements have been incorporated into the models for H2O(?2) emission [1]. Here we report laboratory studies of the collisional removal of O2(X3?-g, ? = 1) by O(3P) at room temperature and below, reaching temperatures relevant to mesopause and polar summer MLT (~150 K). Instead of directly detecting the O2(X3?-g, ? = 1) population, a technically simpler approach is used in which the ? = 1 level of the O2(a1?g) state is monitored. A two-laser method is employed, in which the pulsed output of the first laser near 285 nm photodissociates ozone to produce atomic oxygen and O2(a1?g, ? = 1), and the pulsed output of the second laser detects O2(a1?g, ? = 1) via resonance-enhanced multiphoton ionization. With ground-state O2 present, owing to the rapid equilibration of the O2(X3?-g, ? = 1) and O2(a1?g, ? = 1) populations via the processes O2(a1?g, ? = 1) + O2(X3?-g, ? = 0) ? O2(a1?g, ? = 0) + O2(X3?-g, ? = 1), the information on the O2(X3?-g, ? = 1) kinetics is extracted from the O2(a1?g, ? = 1) temporal evolution. In addition, measurements of the removal of O2(X3?-g, ? = 1) by CO2 at room temperature will also be presented. This work is supported by the Johns Hopkins University, Applied Physics Laboratory, under grant 939991 (under NASA grant NAG5-13002). [1] Feofilov, A., Kutepov, A. A., Garcí­a-Comas, M., López-Puertas, M., Marshall, B. T., Gordley, L. L., Manuilova, R. O., Yankovsky, V. A., Pesnell, W. D., Goldberg, R. A., Petelina, S. V., and Russell III., J. M. 'SABER/TIMED Observations of Water Vapor in the Mesosphere: Retrieval Methodology and First Results'. Submitted to J. of Atmos. and Terrest. Phys., (2008). [2] Kalogerakis, K. S., Copeland, R. A., and Slanger, T. G., J. of Chem. Phys., 123, 194303, (2005). [3] Pejakovic, D. A., Campbell, Z., Kalogerakis, K. S., Copeland, R. A., and Slanger, T. G., Eos. Trans. AGU 85(47), Fall Meet. Suppl., Abstract SA41A-1032, (2004).

Saran, D. V.; Pejakovic, D. A.; Copeland, R. A.

2008-12-01

39

Ground state of a mixture of two species of fermionic atoms in a one-dimensional optical lattice  

SciTech Connect

In this paper, we investigate the ground-state properties of a mixture of two species of fermionic atoms in a one-dimensional optical lattice, as described by the asymmetric Hubbard model. The quantum phase transition from density wave to phase separation is investigated by studying both the corresponding charge order parameter and quantum entanglement. A rigorous proof that even for the single-hole doping case, the density wave is unstable to the phase separation in the infinite U limit, is given. Therefore, our results are quite instructive for both ongoing experiments on strongly correlated cold-atomic systems and traditional heavy fermion systems.

Gu Shijian; Fan Rui; Lin Haiqing [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Hong Kong (China)

2007-09-15

40

Correlated-Gaussian calculations of the ground and low-lying excited states of the boron atom  

SciTech Connect

Benchmark variational calculations of the four lowest {sup 2}P and {sup 2}S states of the boron atom (including the ground state) have been performed. The wave functions of the states have been expanded in terms of all-particle explicitly correlated Gaussian basis functions and the finite mass of the nucleus has been explicitly accounted for. Variational upper bounds for the nonrelativistic finite- and infinite-nuclear-mass energies of all considered states have been obtained with the relative convergence of the order of 10{sup -7}-10{sup -8}. Expectation values of the powers of the inter-particle distances and Dirac {delta} functions depending on those distances have also been computed. These calculations provide reference values that can be used to test other high-level quantum chemistry methods.

Bubin, Sergiy [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Adamowicz, Ludwik [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2011-02-15

41

Ground Levels and Ionization Energies for the Neutral Atoms  

National Institute of Standards and Technology Data Gateway

SRD 111 Ground Levels and Ionization Energies for the Neutral Atoms (Web, free access)   Data for ground state electron configurations and ionization energies for the neutral atoms (Z = 1-104) including references.

42

Integral cross sections for electron scattering by ground-state Ba atoms  

NASA Astrophysics Data System (ADS)

We have used the convergent close-coupling method and a unitarized first-order many-body theory to calculate integral cross sections for elastic scattering and momentum transfer, for excitation of the 5d2 1S, 6s6p 1P1, 6s7p 1P1, 6s8p 1P1, 6s5d 1D2, 5d2 1D2, 6s6d 1D2, 6p5d 1F3, 6s4f 1F3, 6p5d 1D2, 6s6p 3P0,1,2, 6s5d 3D1,2,3, and 6p5d 3D2 states, for ionization and for total scattering by electron impact on the ground state of barium at incident electron energies from 1 to 1000 eV. These results and all available experimental data have been combined to produce a recommended set of integral cross sections.

Fursa, D. V.; Trajmar, S.; Bray, I.; Kanik, I.; Csanak, G.; Clark, R. E. H.; Abdallah, J., Jr.

1999-12-01

43

Calculation of the ground-state energy and average distance between particles for the nonsymmetric muonic 3He atom  

NASA Astrophysics Data System (ADS)

A calculation of the ground-state energy and average distance between particles in the nonsymmetric muonic He3 atom is given. We have used a wave function with one free parameter, which satisfies boundary conditions such as the behavior of the wave function when two particles are close to each other or far away. In the proposed wave function, the electron-muon correlation function is also considered. It has a correct behavior for r12 tending to zero and infinity. The calculated values for the energy and expectation values of r2n are compared with the multibox variational approach and the correlation function hyperspherical harmonic method. In addition, to show the importance and accuracy of approach used, the method is applied to evaluate the ground-state energy and average distance between the particles of nonsymmetric muonic He4 atom. Our obtained results are very close to the values calculated by the mentioned methods and giving strong indications that the proposed wave functions, in addition to being very simple, provide relatively accurate values for the energy and expectation values of r2n , emphasizing the importance of the local properties of the wave function.

Eskandari, M. R.; Rezaie, B.

2005-07-01

44

Determination of the Ground-State Atomic Structures of Size-Selected Au Nanoclusters by Electron-Beam-Induced Transformation  

NASA Astrophysics Data System (ADS)

The equilibrium ground state atomic structures of nanoparticles are critical to understanding the relationship between their structure and functionality, e.g., in catalysis, and are the standard output of first principles and semiempirical theoretical treatments. We demonstrate a method of obtaining a stable population of the structural isomers of supported Au clusters from a metastable initial array via electron beam irradiation. Statistical investigation of size-selected Au clusters containing 923±23 atoms via aberration-corrected scanning transmission electron microscopy shows that virtually all of the icosahedral (Ih) clusters undergo structural transformations into decahedral (Dh) (primarily) or fcc isomers while Dh and FCC clusters generally retain their atomic structures after electron irradiation of each cluster individually for up to 400 s at a dose of 2.4×104e-/angstrom2/frame. Intermediate phases are often observed in the image series (videos) before the appearance of the new stable isomers, the relative structural populations of which can be controlled via the electron beam dose. The comprehensive results reported here should provide a valuable experimental reference for testing or refining potential models and for kinetic or dynamical treatments of the atomic configurations.

Wang, Z. W.; Palmer, R. E.

2012-06-01

45

Buckministerfullerene (C 60) encapsulated ground state atoms: semi-empirical approximate effective volume relations  

Microsoft Academic Search

An AM1 investigation of the molar volumes changes with values of Z for various atoms is investigated. Essentially all values for Z are decreasing according an exponential decay function for both cases of the complex atomic molar volumes, verses the molar radii computed (this is the so-called a0 value which is recommended radius which is 0.5Å larger than the radius

Abraham F. Jalbout; L. Türker

2003-01-01

46

The state dependence of the interaction of metastable rare gas atoms Rg*(ms3 P 2,3 P 0) (Rg=Ne, Ar, Kr, Xe) with ground state sodium atoms  

Microsoft Academic Search

Using crossed beams of metastable rare gas atoms Rg*(ms3 P 2,3 P 0) (Rg=Ne, Ar, Kr, Xe) and ground state sodium atoms Na(3 s 2 S 1\\/2), we have measured the energy spectra of electrons released in the respective Penning ionization processes at thermal collision energies. For Rg*(3 P 2)+Na(3 s), the spectra are quite similar for the different rare

S. Schohl; M. W. Müller; H. A. J. Meijer; M.-W. Ruf; H. Hotop; H. Morgner

1990-01-01

47

Rate constants for the reaction of ground state atomic oxygen with methanol  

Microsoft Academic Search

The reaction of O(³P) with methanol has been studied using the complementary discharge flow and flash photolysis techniques. In both cases, resonance fluorescence detection of atomic oxygen was employed. The discharge flow (DF) apparatus was used in a temperature range of 298--998 K while the flash photolysis (FP) apparatus was used in the overlapping range of 329--527 K. The apparent

David G. Keil; Tsuneo Tanzawa; Edward G. Skolni; R. Bruce Klemm; Joe V. Michael

1981-01-01

48

Evaluation of the CINDI-C/NOFS Ram Wind Sensor in a Ground State Atomic Oxygen Beam  

NASA Astrophysics Data System (ADS)

The Ram Wind Sensor (RWS) is a flow-through retarding potential analyzer equipped with an ionization source that is designed to measure the ram component of neutral particle energy. RWS and the Cross-track wind sensor (XTRK) function together as the Neutral Wind Meter (NWM) being developed for NASA's Coupled Ion-Neutral Dynamics Investigation (CINDI) that will enable in-situ measurements of the 3-D neutral wind field. The CINDI mission will be launched in late 2003 aboard the US Air Force's Communications/Navigation Outage Forecast System (C/NOFS) satellite. The efficiency, energy resolution, and angular variability of RWS are being tested in a ground state atomic oxygen (AO) beam facility at the University of Denver in order to simulate the space environment. The AO beam has energies variable from 4 eV to 1000 eV with a 1.5 eV FWHM energy distribution and fluxes on the order of 1012 atoms/cm2 s. The instrument being tested is mechanically identical to the CINDI flight instrument, but is equipped with pulse counting electronics to enable measurements in the low flux AO beam system. The results of these laboratory tests along with their implications for the precision, accuracy, and overall effectiveness of RWS and NWM will be presented.

Roddy, P. A.; Earle, G. D.; Stephen, T. M.; Heelis, R. A.

2003-04-01

49

The reaction of benzene with a ground state carbon atom, C({sup 3}P{sub j})  

SciTech Connect

The reaction between benzene and a single ground state carbon atom, C({sup 3}P{sub j}), which yields a C{sub 7}H{sub 5} radical without a barrier in the exit channel, has been studied using density functional theory (B3LYP), Moeller-Plesset perturbation theory, and the G2(B3LYP/MP2) and complete basis set (CBS) model chemistries. Comparing the computed reaction energies for the formation of various C{sub 7}H{sub 5} radicals with experimental data suggests that the 1,2-didehydrocycloheptatrienyl radical (15) is observed in crossed-beams experiments at collision energies between 2 and 12 kcal mol{sup -1}. The carbon atom attacks the {pi}-electron density of benzene and forms without entrance barrier a C{sub s} symmetric complex (17T) in which the carbon atom is bound to the edge of benzene. From 17T, the insertion of the C atom into a benzene CC bond to yield triplet cycloheptatrienylidene (9T) is associated with a much lower barrier than the insertion into a CH bond to give triplet phenylcarbene (7T). As both steps are strongly exothermic, high energy vinyl carbene rearrangements on the triplet C{sub 7}H{sub 6} potential energy surface provide pathways between 9T and 7T below the energy of separated reactants. In addition, intersystem crossing in the vicinity of 17T and 9T might give rise to singlet cycloheptatetraene (12S). The monocyclic seven-membered ring compounds 9T or 12S are precursors of the 1,2-didehydrocycloheptatrienyl radical: the dissociation of a CH bond {alpha} to the divalent carbon atom proceeds without an exit barrier, in agreement with experiment. In contrast, a direct carbon-hydrogen exchange reaction pathway analogous to the aromatic electrophilic substitution followed by rearrangement of phenylcarbyne (13) to 15 involves high barriers (39 kcal mol-1 with respect to separated reactants) and is thus not viable under the experimental conditions. (c) 2000 American Institute of Physics.

Bettinger, Holger F. [Institut fuer Organische Chemie, Universitaet Erlangen-Nuernberg, Henkestr. 42, D-91054 Erlangen, (Germany) [Institut fuer Organische Chemie, Universitaet Erlangen-Nuernberg, Henkestr. 42, D-91054 Erlangen, (Germany); Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States); Schleyer, Paul v. R. [Institut fuer Organische Chemie, Universitaet Erlangen-Nuernberg, Henkestr. 42, D-91054 Erlangen, (Germany) [Institut fuer Organische Chemie, Universitaet Erlangen-Nuernberg, Henkestr. 42, D-91054 Erlangen, (Germany); Schaefer, Henry F. III [Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)] [Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States); Schreiner, Peter R. [Institut fuer Organische Chemie, Universitaet Goettingen, Tammannstr. 2, D-37077 Goettingen, (Germany)] [Institut fuer Organische Chemie, Universitaet Goettingen, Tammannstr. 2, D-37077 Goettingen, (Germany); Kaiser, Ralf I. [Institute of Atomic and Molecular Sciences I, Section 4, Roosevelt Rd., 107 Taipei, Taiwan, Republic of China (China)] [Institute of Atomic and Molecular Sciences I, Section 4, Roosevelt Rd., 107 Taipei, Taiwan, Republic of China (China); Lee, Yuan T. [Institute of Atomic and Molecular Sciences I, Section 4, Roosevelt Rd., 107 Taipei, Taiwan, Republic of China (China)] [Institute of Atomic and Molecular Sciences I, Section 4, Roosevelt Rd., 107 Taipei, Taiwan, Republic of China (China)

2000-09-08

50

The state dependence of the interaction of metastable rare gas atoms Rg*(ms 3 P 2 , 3 P 0 ) (Rg=Ne, Ar, Kr, Xe) with ground state sodium atoms  

Microsoft Academic Search

Using crossed beams of metastable rare gas atoms Rg*(ms3P2,3P0) (Rg=Ne, Ar, Kr, Xe) and ground state sodium atoms Na(3s2S1\\/2), we have measured the energy spectra of electrons released in the respective Penning ionization processes at thermal collision energies. For Rg*(3P2)+Na(3s), the spectra are quite similar for the different rare gases, both in width and shape; they reflect attractive interactions in

S. Schohl; M. W. Müller; H. A. J. Meijer; M-W Ruf; H. Hotop; H. Morgner

1990-01-01

51

Time-resolved tunable diode laser absorption spectroscopy of excited argon and ground-state titanium atoms in pulsed magnetron discharges  

NASA Astrophysics Data System (ADS)

Time-resolved investigations of excited argon atom density and temperature and ground-state titanium atom density during high-power impulse magnetron sputtering (HiPIMS, repetition frequency 100 Hz) and direct current pulsed magnetron (repetition frequency 2.5 kHz) discharges (PMDs) in argon employing a titanium target were performed. Atom density and temperature were measured with the help of tunable diode laser absorption spectroscopy. Excited argon atoms form during the discharge pulse and again by three-body electron ion recombination in the afterglow. Similarly, the temperature of excited (metastable) argon atoms rises during the plasma on phase and again during the afterglow. The observed temporal evolution of the temperature is faster than expected from thermal conductivity considerations, which is taken as an indication that metastable and ground-state argon atoms are not in thermal equilibrium. The time dependence of titanium atoms can be explained by recombination and diffusion. The results provide new insights into the physics of PMDs.

Sushkov, V.; Do, H. T.; Cada, M.; Hubicka, Z.; Hippler, R.

2013-02-01

52

Calculation of the ground state energy of neutral atoms ( Z ? 54) by the algebraic variant of the Hartree-Fock method  

NASA Astrophysics Data System (ADS)

High-precision calculations of the ground-state energy of atoms He through Xe are performed in the algebraic approximation of the Hartree-Fock method. The orbital exponents of Slater-type basis functions are optimized using the second-order minimization methods, which allows the virial theorem to be fulfilled to within 10-15-10-17 for the first time. The energies of atoms calculated with rather limited basis sets are, in terms of accuracy, as good as the results obtained by using the numerical procedure for solving the Hartree-Fock equations.

Malykhanov, Yu. B.; Gorshunov, M. V.; Evseev, S. V.; Eremkin, I. N.; Chadin, R. M.

2013-03-01

53

Determination of the electronic structure of atoms and molecules in the ground state: Measurement of molecular hydrogen by high-resolution x-ray scattering  

NASA Astrophysics Data System (ADS)

The high-resolution x-ray-scattering technique is used to study the elastic scattering of atoms and molecules in the gas phase. The elastic squared form factor, which is the square of the Fourier transformation of the electron density distribution in position space and reveals the pure electronic structure of atoms and molecules in the ground state, of molecular hydrogen is measured at an incident photon energy of about 9889 eV and an energy resolution of about 70 meV. Although it is generally thought that the x-ray-scattering technique is identical to high-energy electron scattering, at least for elastic scattering these two techniques have an apparent difference, i.e., the pure electronic structure of a molecule in the ground state can be determined by x-ray scattering while it cannot be obtained by the high-energy electron impact method due to the interference between the scattering of separate nuclei and of the electrons in the target. The present experimental results match the theoretical calculations very well, which demonstrates that high-resolution x-ray scattering is a powerful tool to study the electronic structure of atoms and molecules in the ground state.

Liu, Ya-Wei; Mei, Xiao-Xun; Kang, Xu; Yang, Ke; Xu, Wei-Qing; Peng, Yi-Geng; Hiraoka, Nozomu; Tsuei, Ku-Ding; Zhang, Peng-Fei; Zhu, Lin-Fan

2014-01-01

54

Towards coherent manipulation of the ground states of single cesium atom confined in a microscopic far-off-resonance optical dipole trap  

NASA Astrophysics Data System (ADS)

This work deals with the cooling and trapping of single cesium (Cs) atoms in a large-magnetic-gradient magneto-optical trap (MOT) and the confinement of single Cs atoms in a far-off-resonance optical dipole trap (FORT). The experiment setup is based on two large-numerical-aperture lens assemblies which allow us to strongly focus a 1064-nm TEM00-mode Gaussian laser beam to a 1/e2 radius of ~ 2.3 ?m to form a microscopic FORT for isolating single atom with environment and to efficiently collect the laser-induced-fluorescence photons emitted by single atoms for detecting and recognizing single atom's internal state. We have tried both of "bottom-up" and "top-down" loading schemes to confine single atoms in the microscopic FORT. In the "bottom-up" scheme, we have successfully prepared single Cs atoms in the MOT and transferred it into FORT with a probability of almost 100%. In the "top-down" scheme, we have achieved ~ 74% of single atom loading probability in the FORT using light-assisted collisions induced by blue detuning laser and with prepared many Cs atoms in the MOT. The relaxation time in hyperfine level of ground state of trapped single Cs atom is measured to be ~5.4 s. To coherently manipulate atomic quantum bits (qubit) encoded in the clock states (mF = 0 states in Fg = 3 and 4 hyperfine levels) of single Cs atom via the two-photon simulated Raman adiabatic passage (STIRAP), we have prepared two phase-locked laser beams with a frequency difference of ~ 9.192 GHz by optically injecting an 852-nm master laser to lock the +1-order sideband of a 9-GHz current-modulated slave diode laser. The two phase-locked laser beams are used to drive STIRAP process in the ?-type three-level system consists of Cs |6S1/2 Fg = 4, mF = 0> and |6S1/2 Fg = 3, mF = 0< long-lived clock states and Cs |6S1/2 Fe = 4, mF = +1 > excited state with the single-photon detuning of ~ -20 GHz. Rabi flopping experiments are in progress.

Diao, Wenting; He, Jun; Liu, Bei; Wang, Junmin

2012-11-01

55

Models including electron correlation in relation to Fock's proposed expansion of the ground-state wave function of He-like atomic ions  

SciTech Connect

Here attention is first drawn to the importance of gaining insight into Fock's early proposal for expanding the ground-state wave function for He-like atomic ions in hyperspherical coordinates. We approach the problem via two solvable models, namely, (i) the s-term model put forth by Temkin [Phys. Rev. 126, 130 (1962)] and (ii) the Hookean atom model proposed by Kestner and Sinanoglu [Phys. Rev. 128, 2687 (1962)]. In both cases the local kinetic energy can be obtained explicitly in hyperspherical coordinates. Separation of variables occurs in both model wave functions, though in a different context in the two cases. Finally, a k-space formulation is proposed that should eventually result in distinctive identifying characteristics of Fock's nonanalyticities for He-like atomic ions when both electrons are close to the nucleus.

Glasser, M. L.; March, N. H.; Nieto, L. M. [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, ES-47011 Valladolid, Spain and Department of Physics, Clarkson University, Potsdam, New York 13699 (United States); Department of Physics, University of Antwerp, BE-2020 Antwerp, Belgium and Department of Theoretical Chemistry, University of Oxford, Oxford OX1 2JD (United Kingdom); Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, ES-47011 Valladolid (Spain)

2011-12-15

56

Crystalline beam ground state  

SciTech Connect

In order to employ molecular dynamics (MD) methods, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations using MD methods has been performed to obtain the equilibrium crystalline beam structure. The effect of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Schiffer et al. depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Li, Xiao-Ping [Rutgers Univ., Piscataway, NJ (United States). Dept. of Physics; Sessler, A.M. [Lawrence Berkeley Lab., CA (United States)

1993-06-11

57

Investigations of the ground-state hyperfine atomic structure and beta decay measurement prospects of {sup 21}Na with improved laser trapping techniques  

SciTech Connect

This thesis describes an experiment in which a neutral atom laser trap loaded with radioactive {sup 21}Na was improved and then used for measurements. The sodium isotope (half-life=22 sec) is produced on line at the 88in cyclotron at Lawrence Berkeley National Laboratory. The author developed an effective magnesium oxide target system which is crucial to deliver a substantive beam of {sup 21}Na to the experiment. Efficient manipulation of the {sup 21}Na beam with lasers allowed 30,000 atoms to be contained in a magneto-optical trap. Using the cold trapped atoms, the author measured to high precision the hyperfine splitting of the atomic ground state of {sup 21}Na. She measured the 3S{sub 1/2}(F=1,m=0)-3S{sub 1/2}(F=2,m=0) atomic level splitting of {sup 21}Na to be 1,906,471,870{+-}200 Hz. Additionally, she achieved initial detection of beta decay from the trap and evaluated the prospects of precision beta decay correlation studies with trapped atoms.

Rowe, Mary A.

1999-05-24

58

Quantum fluid dynamics approach for electronic structure calculation: application to the study of ground-state properties of rare gas atoms  

NASA Astrophysics Data System (ADS)

We explore the usefulness of a quantum fluid dynamics (QFD) approach for quantitative electronic structure calculations of many-electron systems. By combining QFD and density functional theory, a single time-dependent nonlinear QFD equation can be derived. The equation is further transformed into a diffusion-type form by an imaginary-time evolution method, whose asymptotic solution reaches a global minimum and the many-body ground-state wavefunction. The time-dependent generalized pseudospectral method is extended to solve the diffusion equation in spherical coordinates, allowing optimal and nonuniform spatial discretization and accurate and efficient solution of the diffusion function in space and time. The procedure is applied to the study of electronic energies, densities and other ground-state properties of noble gas atoms (He, Ne, Ar, Kr, Xe). The results are in good agreement with other best available values. The method offers a conceptually appealing and computationally practical procedure for the treatment of many-electron systems beyond the Hartree-Fock level.

Roy, Amlan K.; Chu, Shih-I.

2002-05-01

59

Existence of ground states of hydrogen-like atoms in relativistic QED II: The no-pair operator  

Microsoft Academic Search

We consider a hydrogen-like atom in a quantized electromagnetic field which is modeled by means of a no-pair operator acting in the positive spectral subspace of the free Dirac operator minimally coupled to the quantized vector potential. We prove that the infimum of the spectrum of the no-pair operator is an evenly degenerate eigenvalue. In particular, we show that the

Martin Könenberg; Oliver Matte; Edgardo Stockmeyer

2010-01-01

60

Photoelectron spectroscopy of O{sup -} at 266 nm: Ratio of ground- and excited-state atomic oxygen production and channel-resolved photoelectron anisotropy parameters  

SciTech Connect

The photodetachment dynamics of the atomic oxygen anion O{sup -} has been investigated at 266 nm (4.67 eV) by photoelectron detection in a crossed-beam experiment using a magnetic-bottle electron spectrometer. Taking explicit advantage of the Doppler shift imposed by the moving ion beam on the photoelectron energies, we report both the final-state branching ratio and photoelectron angular distributions. After photoabsorption at 266 nm, the formed electron-oxygen scattering state disintegrates, forming either the excited {sup 1}D or the ground {sup 3}P state of oxygen with a partition of {sup 1}D:{sup 3}P=0.32 {+-} 0.06. The detachment leading to the production of O({sup 3}P) shows an angular distribution of photoelectrons characterized by {beta}{sub P}=0.00 {+-} 0.10 mimicking a pure s-wave detachment, while the detachment into excited O({sup 1}D) occurs with {beta}{sub D}=-0.90{+-}0.10, giving direct evidence of interference between the outgoing s and d waves.

Domesle, C.; Jordon-Thaden, B.; Wolf, A. [Max-Planck-Institut fuer Kernphysik, DE-69117 Heidelberg (Germany); Lammich, L.; Pedersen, H. B. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Foerstel, M. [Max-Planck-Institut fuer Kernphysik, DE-69117 Heidelberg (Germany); Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, DE-85748 Garching (Germany); Hergenhahn, U. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, DE-85748 Garching (Germany)

2010-09-15

61

Existence of ground states of hydrogen-like atoms in relativistic quantum electrodynamics. II. The no-pair operator  

NASA Astrophysics Data System (ADS)

We consider a hydrogen-like atom in a quantized electromagnetic field which is modeled by means of a no-pair operator acting in the positive spectral subspace of the free Dirac operator minimally coupled to the quantized vector potential. We prove that the infimum of the spectrum of the no-pair operator is an evenly degenerate eigenvalue. In particular, we show that the bottom of its spectrum is strictly less than its ionization threshold. These results hold true, for arbitrary values of the fine-structure constant and the ultraviolet cut-off and for all Coulomb coupling constants less than the critical one of the Brown-Ravenhall model, 2/(2/? + ?/2). For Coulomb coupling constants larger than the critical one, we show that the quadratic form of the no-pair operator is unbounded below. Along the way we discuss the domains and operator cores of the semi-relativistic Pauli-Fierz and no-pair operators, for Coulomb coupling constants less than or equal to the critical ones.

Könenberg, Martin; Matte, Oliver; Stockmeyer, Edgardo

2011-12-01

62

Electric-field-induced magnetic quadrupole moment in the ground state of the relativistic hydrogenlike atom: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function  

NASA Astrophysics Data System (ADS)

We consider a Dirac one-electron atom placed in a weak, static, uniform electric field. We show that, to the first order in the strength of the perturbing field, the only magnetic multipole moment induced in the ground state of the atom is the quadrupole one. The tensorial structure of that moment is resolved. Using the Sturmian expansion of the generalized Dirac-Coulomb Green function [Szmytkowski, J. Phys. B 30, 825 (1997), 10.1088/0953-4075/30/4/007; Szmytkowski, J. Phys. B 30, 2747(E) (1997), 10.1088/0953-4075/30/11/023], we derive a closed-form expression for an E1?M2 cross-susceptibility of the atom in the ground state.

Szmytkowski, Rados?aw; Stefa?ska, Patrycja

2014-01-01

63

Modified Atoms-in-Molecules Model for Predicting Diatomic Ground and Excited-State Potential-Energy Curves. I. LiH, BeH, and BH  

Microsoft Academic Search

A model is proposed for the approximate calculation, starting with theoretical atoms-in-molecules-like composite functions (or linear combinations of valence bond structures) of potential-energy curves for ground and excited diatomic systems. The assumptions which define the model may be summarized as follows: (1) diatomic electronic eigenstates are represented by a linear combination of composite functions which, in their orbital approximation, are

Frank O. Ellison

1965-01-01

64

Multilevel Atomic Coherent States and Atomic Holomorphic Representation  

NASA Technical Reports Server (NTRS)

The notion of atomic coherent states is extended to the case of multilevel atom collective. Based on atomic coherent states, a holomorphic representation for atom collective states and operators is defined. An example is given to illustrate its application.

Cao, Chang-Qi; Haake, Fritz

1996-01-01

65

Change in total angular momentum within the z 3° titanium excited state induced by collisions with ground-state argon, neon, and helium atoms  

Microsoft Academic Search

Collisions that produce a change in the total angular momentum and quenching processes involving the triplet z 3° titanium excited level and noble gases have been studied by laser perturbation and time-resolved spectroscopy. Titanium atoms are produced in a hollow-cathode discharge, and the analysis of resonance and sensitized fluorescence light decays enable us to determine total-angular-momentum-changing (J-changing) and quenching cross

D. Dezert; V. Quichaud; D. Degout; A. Catherinot

1986-01-01

66

Hyperfine structure measurements in the ground states4 F 3\\/2,4 F 5\\/2 and4 F 7\\/2 of Ta181 with the atomic beam magnetic resonance method  

Microsoft Academic Search

Applying a recently developed evaporation technique for refractory elements the following results have been obtained for Ta181 in an atomic beam magnetic resonance experiment studying the hyperfine structure of 3 levels of the ground state multiplet4 F: 10050_2005_Article_BF01407256_TeX2GIFE1.gif begin{gathered} g_J (^4 F_{3\\/2} ) = 0.45024 (4) \\\\ Delta v (^4 F_{3\\/2} ;F = 5 leftrightarrow F = 4) = 1822.389

S. Büttgenbach; G. Meisel

1971-01-01

67

Change in total angular momentum within the z 3° titanium excited state induced by collisions with ground-state argon, neon, and helium atoms  

NASA Astrophysics Data System (ADS)

Collisions that produce a change in the total angular momentum and quenching processes involving the triplet z 3° titanium excited level and noble gases have been studied by laser perturbation and time-resolved spectroscopy. Titanium atoms are produced in a hollow-cathode discharge, and the analysis of resonance and sensitized fluorescence light decays enable us to determine total-angular-momentum-changing (J-changing) and quenching cross sections induced by collisions with helium, neon, and argon atoms. The thermally averaged J-changing cross section (z 3F ° i-->z 3F ° j) in units of 10-16 cm2 are ?¯4-->2=1.7+/-0.5, 0.7+/-0.06, 3.1+/-1 ?¯4-->3=11+/-2, 1.4+/-0.1, 11+/-1 ?¯3-->2=7+/-2, 2.2+/-0.3, 14+/-2, respectively, for helium, neon, and argon colliding partners. As for alkali-metal-noble-gas collisions, a pronounced minimum of the J-changing cross sections is obtained for the titanium (z 3F °)-neon collisions. Radiative destruction probabilities of the z 3F ° j (j=4,3,2) titanium sublevels have been measured also, and good agreement with accepted values is found.

Dezert, D.; Quichaud, V.; Degout, D.; Catherinot, A.

1986-12-01

68

Photoionization of the Zn@C60 endofullerene: Atom-fullerene ground-state orbital hybridization of d-d character  

NASA Astrophysics Data System (ADS)

A detailed theoretical study of the subshell photoionization of Zn endohedrally confined in C60 has been performed. The fullerene molecular core of sixty C^4+ ions is modeled by a classical jellium smearing, while the delocalized cloud of 240 carbon valence electrons, plus the encaged Zn atom placed at the center of the cage, are treated in the time-dependent local density approximation (TDLDA) [1]. A powerful hybridization of the Zn 3d state with the 2d orbital near the low end of C60 electronic band are unraveled. Cross sections for these hybrid states at both low photon energies, overwhelmed by electronic collective motions, and high energies of dominant single-electron behavior are presented. The results exhibit rich structures and are radically different from the cross sections of free atomic or free fullerene states participating in the hybridization process.[4pt] [1] M.E. Madjet et al., Phys. Rev. A 81, 013202 (2010).

Maser, Jaykob; Javani, Mohammad; de, Ruma; Madjet, Mohamed; Chakraborty, Himadri; Manson, Steve

2012-06-01

69

Ground-State of Water  

NASA Astrophysics Data System (ADS)

The study of the ground-state properties of molecular systems has long been the focus of both quantum chemists as well as physicists. In general, most of the calculational methods are dependent on the use of high-power computers to generate large basis states. Such schemes as the full-configuration-interaction method, coupled-pair functionals and its modification, Moller-Plesset perturbation theory as well as both the restricted and unrestricted Hartree-Fock schemes have been used not only for ground-state calculations but also to calculate electron correlation energies. In general such schemes are limited to those basis which are constructed from single Slatter determinant. Here we wish to study the ground-state of water as well as hydrogen fluoride using the recently developed canonical sequence scheme which is a calculational cousin of the Connected Moments Expansion of Cioslowski. Comparisons are then made with other methods [for example P.J. Knowles Chem. Phys. Lett. 134, 512 (1987)].

Saltzman, Emily; Carey, Mike; Fessatidis, Vassilios; Mancini, Jay D.; Bowen, Samuel P.

2002-03-01

70

Ground State of ^10Li  

Microsoft Academic Search

The neutron decay of ^10Li, produced in the fragmentation reaction of 80 MeV\\/nucleon ^18O + ^9Be was studied with the method of sequential neutron decay spectroscopy at 0^circ. The ^9Li fragments were detected in a silicon CsI(Tl) telescope and the neutrons in an array of 4 NE213 liquid scintillator detectors. The ground state resonance energy and spin of ^10Li is

S. Yokoyama; A. Azhari; J. Brown; T. Baumann; A. Galonsky; J. H. Kelley; R. A. Kryger; R. Pfaff; E. Ramakrishnan; P. Thirolf; M. Thoennessen

1996-01-01

71

Ground states of heavy electrons in metals  

Microsoft Academic Search

We briefly discuss experimental observations which imply that heavy electron ground states of different varieties exist. It seems possible that more sophisticated models than the Fermi liquid concept are necessary for a theoretical description of these ground states.

H. R. Ott; E. Felder; A. Bernasconi

1993-01-01

72

Simulations of Ground and Space-Based Oxygen Atom Experiments  

NASA Technical Reports Server (NTRS)

Fast, pulsed atomic oxygen sources are a key tool in ground-based investigations of spacecraft contamination and surface erosion effects. These technically challenging ground-based studies provide a before and after picture of materials under low-earth-orbit (LEO) conditions. It would be of great interest to track in real time the pulsed flux from the source to the surface sample target and beyond in order to characterize the population of atoms and molecules that actually impact the surface and those that make it downstream to any coincident detectors. We have performed simulations in order to provide such detailed descriptions of these ground-based measurements and to provide an assessment of their correspondence to the actual LEO environment. Where possible we also make comparisons to measured fluxes and erosion yields. To perform the calculations we use a detailed description of a measurement beam and surface geometry based on the W, pulsed apparatus at Montana State University. In this system, a short pulse (on the order of 10 microseconds) of an O/O2 beam impacts a flat sample about 40 cm downstream and slightly displaced &om the beam s central axis. Past this target, at the end of the beam axis is a quadrupole mass spectrometer that measures the relative in situ flux of 0102 to give an overall normalized erosion yield. In our simulations we use the Direct Simulation Monte Carlo (DSMC) method, and track individual atoms within the atomic oxygen pulse. DSMC techniques are typically used to model rarefied (few collision) gas-flows which occur at altitudes above approximately 110 kilometers. These techniques are well suited for the conditions here, and multi-collision effects that can only be treated by this or a similar technique are included. This simulation includes collisions with the surface and among gas atoms that have scattered from the surface. The simulation also includes descriptions of the velocity spread and spatial profiles of the O/O2 beam obtained from separate measurements. These computations use basic engineering models for the gas-gas and gas-surface scattering and focus on the influence of multi-collision effects. These simulations characterize many important quantities of interest including the actual flux of atoms that reach the surface, the energy distribution of this flux, as well as the direction of the velocity of the flux that strikes the surface. These quantities are important in characterizing the conditions which give rise to measured surface erosion. The calculations also yield time- snapshots of the pulse as it impacts and flows around the surface. These snapshots reveal the local environment of gas near the surface for the duration of the pulse. We are also able to compute the flux of molecules that travel downstream and reach the spectrometer, and we characterize their velocity distribution. The number of atoms that reach the spectrometer can in fact be influenced by the presence of the surface due to gas-gas collisions from atoms scattered h m the surface, and it will generally be less than that with the surface absent. This amounts to an overall normalization factor in computing erosion yields. We discuss these quantities and their relationship to the gas-surf$ce interaction parameters. We have also performed similar calculations corresponding to conditions (number densities, temperatures, and velocities) of low-earth orbit. The steady-state nature and lower overall flux of the actual space environment give rise to differences in the nature of the gas-impacts on the surface from those of the ground-based measurements using a pulsed source.

Minton, T. K.; Cline, J. A.; Braunstein, M.

2002-01-01

73

Radiofrequency-dressed-state potentials for neutral atoms  

Microsoft Academic Search

Potentials for atoms can be created by external fields acting on properties such as magnetic moment, charge, polarizability, or by oscillating fields that couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground and electronically excited states of an atom with light. Here, we present an extensive experimental analysis of potentials

S. Hofferberth; I. Lesanovsky; B. Fischer; J. Verdu; J. Schmiedmayer

2006-01-01

74

Coherent Transfer of Photoassociated Molecules into the Rovibrational Ground State  

SciTech Connect

We report on the direct conversion of laser-cooled {sup 41}K and {sup 87}Rb atoms into ultracold {sup 41}K{sup 87}Rb molecules in the rovibrational ground state via photoassociation followed by stimulated Raman adiabatic passage. High-resolution spectroscopy based on the coherent transfer revealed the hyperfine structure of weakly bound molecules in an unexplored region. Our results show that a rovibrationally pure sample of ultracold ground-state molecules is achieved via the all-optical association of laser-cooled atoms, opening possibilities to coherently manipulate a wide variety of molecules.

Aikawa, K.; Hayashi, M.; Oasa, K. [Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Akamatsu, D.; Kobayashi, J. [Institute of Engineering Innovation, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Naidon, P. [JST, ERATO, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Kishimoto, T. [Center for Frontier Science and Engineering, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Ueda, M. [JST, ERATO, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Inouye, S. [Institute of Engineering Innovation, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, ERATO, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)

2010-11-12

75

7/sup 2/D/sub 3/2/-7/sup 2/D/sub 5/2/ excitation transfer in rubidium induced in collisions with ground-state Rb and noble-gas atoms  

SciTech Connect

Cross sections for 7/sup 2/D/sub 3/2/bold-arrow-left-right7/sup 2/D/sub 5/2/ transfer in Rb, induced in collisions with He, Ne, Ar, and with ground-state Rb atoms, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a noble gas, was irradiated in a glass fluorescence cell with pulses of 660-nm radiation from a N/sub 2/-laser-pumped dye laser, populating one of the /sup 2/D states by two-photon absorption. The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated state. Relative intensities of the components yielded the cross sections for 7/sup 2/D mixing: Q(/sup 2/D/sub 3/2/..-->../sup 2/D/sub 5/2/) = 8.8, 6.5, 10.4, and 30; Q(/sup 2/D/sub 3/2/reverse arrow/sup 2/D/sub 5/2/) = 5.8, 4.0, 6.9, and 18, in units of 10/sup -14/ cm/sup 2/ for He, Ne, Ar, and Rb, respectively. Cross sections for the effective quenching of the /sup 2/D states were also determined.

Wolnikowski, J.; Atkinson, J.B.; Supronowicz, J.; Krause, L.

1982-05-01

76

Exact integral constraint requiring only the ground-state electron density as input on the exchange-correlation force - partial differential(V)(xc)(r)/partial differential(r) for spherical atoms.  

PubMed

Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell. PMID:19026052

March, N H; Nagy, A

2008-11-21

77

Ground water contamination in the United States  

SciTech Connect

This book demonstrates an exhaustive research effort into published reports and legal documents of which 344 are cited. From the literature, the authors selected 84 tables and 41 figures and maps, adding to the value of the collected body of information provided within the text. These summarize and graphically illustrate the 10 major ground water regions, population served by source and supply, US ground water use; ground water overdrafts; sources of ground water contamination; characteristics of domestic waste water; nitrate-nitrogen concentrations in ground water by state; pesticides found in ground water; general state land use profiles; states with significant coal mining waste water discharges, cattle feeding operations, and underground storage tank release incidents; costs of analysis; and state ground water quality standards. Radioactive waste and spent fuel generated as of 1983 are reported from the US Dept. of Energy's 1984 Inventory, Projections, and Characteristics, as are data collected by OTA and the League of Women Voters. The authors summarize reports issued by US Government Accounting Office, EPA, and others on other sources of ground water contamination, such as accidental leaks and spills, mining, atmospheric contaminants and acid rain. The authors provide the geographical extent of ground water contamination in a list that ranks major ground water pollution problems for each state as provided in EPA's State Ground-Water Program Summaries. Among those problems classified are oil and gas brine pits, underground storage tanks, injection wells, abandoned hazardous waste sites, and regulated hazardous waste sites.

Patrick, R.; Ford, E.; Quarles, J.

1987-01-01

78

Unfrustrated qudit chains and their ground states  

SciTech Connect

We investigate chains of d-dimensional quantum spins (qudits) on a line with generic nearest-neighbor interactions without translational invariance. We find the conditions under which these systems are not frustrated, that is, when the ground states are also the common ground states of all the local terms in the Hamiltonians. The states of a quantum spin chain are naturally represented in the matrix product states (MPS) framework. Using imaginary time evolution in the MPS ansatz, we numerically investigate the range of parameters in which we expect the ground states to be highly entangled and find them hard to approximate using our MPS method.

Movassagh, Ramis; Shor, Peter W. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Farhi, Edward; Goldstone, Jeffrey [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Nagaj, Daniel [Research Center for Quantum Information, Institute of Physics, Slovak Academy of Sciences, Bratislava (Slovakia); Osborne, Tobias J. [Institute for Advanced Study, Wissenschaftskolleg zu Berlin, Berlin (Germany)

2010-07-15

79

Quantum computation in the ground state of interacting fermions  

NASA Astrophysics Data System (ADS)

In measurement-based quantum computation (MBQC), an algorithm proceeds entirely by making projective measurements on successive qubits comprising some highly entangled `resource state.' While two-dimensional cluster states are known to be universal resources for MBQC, it has been proven that they cannot be the unique ground states of any two-body spin Hamiltonian. We show that a particular ground state of non-interacting fermions (equivalent to a many-body spin system) is formally equivalent to a cluster state, though only capable of simulating a limited set of quantum operations. In the presence of two-particle interactions, however, the ground state becomes a universal resource for MBQC. This result suggests that arbitrary quantum algorithms could be simulated fault-tolerantly simply by measuring a cold gas of interacting fermions, such as ultracold atoms in optical lattices.

Feder, David; Shlyapnikov, Gora

2010-03-01

80

Preparing and Probing Atomic Number States with an Atom Interferometer  

Microsoft Academic Search

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave

J. Sebby-Strabley; Marco Anderlini; Patricia Lee; Philip Johnson; William Phillips

2007-01-01

81

A facility to produce an energetic, ground state atomic oxygen beam for the simulation of the Low-Earth Orbit environment  

NASA Technical Reports Server (NTRS)

Because of the continuing commitment to activity in low-Earth orbit (LEO), a facility is under development to produce energetic atmospheric species, particularly atomic oxygen, with energies ranging from 5 to 80 eV. This relatively high flux facility incorporates an ion engine to produce the corresponding specie ion which is charge exchanged to produce a neutral atomic beam. Ion fluxes of around 10(exp 15) sec(exp -1) with energies of 20-70 eV have been achieved. A geometrically augmented inertially tethered charge exchanger (GAITCE) was designed to provide a large column depth of charge exchange gas while reducing the gas load to the low pressure portion of the atomic beam facility. This is accomplished using opposed containment jets which act as collisional barriers to the escape of the dense gas region formed between the jets. Leak rate gains to the pumping system on the order of 10 were achieved for moderate jet mass flows. This system provides an attractive means for the charge exchange of atomic ions with a variety of gases to produce energetic atomic beams.

Ketsdever, Andrew D.; Weaver, David P.; Muntz, E. P.

1994-01-01

82

On the Stable Ground State of Mackinawite  

NASA Astrophysics Data System (ADS)

Mackinawite is a layer type iron monosulfide (FeS) with stacked sheets of edge-sharing FeS4 tetrahedra. An important player in iron and sulfur cycles, mackinawite is one of the first-formed metastable iron sulfides in anoxic environments, transforming into greigite (Fe3S4) and pyrite (FeS2) minerals or elemental sulfur (S0) and iron (Fe0) depending on redox conditions. Mackinawite also affects the mobility and oxidation states of toxic metals such as As, Hg, and Se. The mineral, typically found as a nanoparticle, has been characterized experimentally. Its fundamental conducting and magnetic properties, however, are still controversial; e.g., whether mackinawite is metallic and whether it has magnetic order. Mackinawite is believed to be metallic and without magnetic ordering down at 4 K based on Mössbauer spectroscopy studies. We examined these two issues by applying plane-wave density functional theory (DFT) to FeS geometry optimization under different magnetic orderings. We found that antiferromagnetic ordering among the Fe atoms is the stable ground state of mackinawite. In this presentation, we shall discuss this result and how it relates to previous experimental work.

Kwon, K.; Refson, K.; Sposito, G.

2009-12-01

83

Langevin equation path integral ground state.  

PubMed

We propose a Langevin equation path integral ground state (LePIGS) approach for the calculation of ground state (zero temperature) properties of molecular systems. The approach is based on a modification of the finite temperature path integral Langevin equation (PILE) method (J. Chem. Phys. 2010, 133, 124104) to the case of open Feynman paths. Such open paths are necessary for a ground state formulation. We illustrate the applicability of the method using model systems and the weakly bound water-parahydrogen dimer. We show that the method can lead to converged zero point energies and structural properties. PMID:23738885

Constable, Steve; Schmidt, Matthew; Ing, Christopher; Zeng, Tao; Roy, Pierre-Nicholas

2013-08-15

84

Computing many-body wave functions with guaranteed precision: The first-order Møller-Plesset wave function for the ground state of helium atom  

NASA Astrophysics Data System (ADS)

We present an approach to compute accurate correlation energies for atoms and molecules using an adaptive discontinuous spectral-element multiresolution representation for the two-electron wave function. Because of the exponential storage complexity of the spectral-element representation with the number of dimensions, a brute-force computation of two-electron (six-dimensional) wave functions with high precision was not practical. To overcome the key storage bottlenecks we utilized (1) a low-rank tensor approximation (specifically, the singular value decomposition) to compress the wave function, and (2) explicitly correlated R12-type terms in the wave function to regularize the Coulomb electron-electron singularities of the Hamiltonian. All operations necessary to solve the Schrödinger equation were expressed so that the reconstruction of the full-rank form of the wave function is never necessary. Numerical performance of the method was highlighted by computing the first-order Møller-Plesset wave function of a helium atom. The computed second-order Møller-Plesset energy is precise to ~2 microhartrees, which is at the precision limit of the existing general atomic-orbital-based approaches. Our approach does not assume special geometric symmetries, hence application to molecules is straightforward.

Bischoff, Florian A.; Harrison, Robert J.; Valeev, Edward F.

2012-09-01

85

Ground Water Contamination in the United States  

Microsoft Academic Search

Ground water contamination is of increasing concern in the United States because about 50 percent of our drinking water comes from well water. The causes of contamination stem from both point sources and nonpoint sources. Since ground water moves slowly, the contaminant may affect only a small portion of an aquifer for a considerable period of time. Deleterious effects on

Veronica I. Pye; Ruth Patrick

1983-01-01

86

Ground-based laboratory atomic oxygen calibration experiments  

Microsoft Academic Search

Existing devices and analysis techniques for the monitoring of space and laboratory simulated Atomic Oxygen (AO) environments have been investigated and improved to enable more accurate and reliable measurement and calibration of AO flux and fluences than previously possible. This research was based on experimental work carried out in a ground based AO facility designed to simulate the low Earth

Jeremy Stephen Matcham

1998-01-01

87

Existence of Ground States of Hydrogen-Like Atoms in Relativistic QED I:. the Semi-Relativistic Pauli-Fierz Operator  

NASA Astrophysics Data System (ADS)

We consider a hydrogen-like atom in a quantized electromagnetic field which is modeled by means of the semi-relativistic Pauli-Fierz operator and prove that the infimum of the spectrum of the latter operator is an eigenvalue. In particular, we verify that the bottom of its spectrum is strictly less than its ionization threshold. These results hold true, for arbitrary values of the fine-structure constant and the ultraviolet cut-off as long as the Coulomb coupling constant is less than 2/?. For Coulomb coupling constants larger than 2/?, we show that the quadratic form of the Hamiltonian is unbounded below.

Könenberg, Martin; Matte, Oliver; Stockmeyer, Edgardo

88

Ground states of two-dimensional quasicrystals  

SciTech Connect

Necessary conditions for a quasicrystal to be a ground state are found within the framework of a tiling model (thermal fluctuations are supposed to be irrelevant). It is proven that a generic quasicrystal cannot be a ground state. Only very special quasicrystals are shown to survive: They must possess high rotational symmetry or the frequencies defining quasiperiodic properties must satisfy numerous rational constraints. A quasicrystal may be a ground state only if hexagons flipping under the infinitesimal phason shift are not isolated from one another but form rows or nets. Necessary and sufficient conditions for a (2,3) quasicrystal to be a ground state are found. All (2,4) quasicrystals satisfying the necessary conditions are classified. Stability of a quasicrystalline phase is discussed.

Burkov, S.E. (Landau Institute for Theoretical Physics, GSP-1, 117940 Moscow V-334 (USSR) Brookhaven National Laboratory, Upton, NY (USA))

1990-05-15

89

On the ground state of metallic hydrogen  

NASA Technical Reports Server (NTRS)

A proposed liquid ground state of metallic hydrogen at zero temperature is explored and a variational upper bound to the ground state energy is calculated. The possibility that the metallic hydrogen is a liquid around the metastable point (rs = 1.64) cannot be ruled out. This conclusion crucially hinges on the contribution to the energy arising from the third order in the electron-proton interaction which is shown here to be more significant in the liquid phase than in crystals.

Chakravarty, S.; Ashcroft, N. W.

1978-01-01

90

Preparation of a single-state atomic beam by optical pumping and radiative deflection  

SciTech Connect

A simple technique for producing a single-state sodium atomic beam is described. A single laser both optically pumps the F = 2 ground-state atoms into m/sub F/ = +2 and deflects the pumped atoms away from residual F = 1 atoms. Data demonstrating the technique are presented, and a practical design for an apparatus based on these principles is described.

Gould, P.L.; Ruff, G.A.; Martin, P.J.; Pritchard, D.E.

1987-08-01

91

Lattice QCD Beyond Ground States  

SciTech Connect

In this work, we apply black box methods (methods not requiring input) to find excited-state energies. A variety of such methods for lattice QCD were introduced at the 3rd iteration of the numerical workshop series. We first review a selection of approaches that have been used in lattice calculations to determine multiple energy states: multiple correlator fits, the variational method and Bayesian fitting. In the second half, we will focus on a black box method, the multi-effective mass. We demonstrate the approach on a toy model, as well as on real lattice data, extracting multiple states from single correlators. Without complicated operator construction or specialized fitting programs, the black box method shows good consistency with the traditional approaches.

Huey-Wen Lin; Saul D. Cohen

2007-09-11

92

Abundance of Ground States with Positive Parity  

SciTech Connect

We investigate analytically and numerically a random-matrix model for m fermions occupying {ell}{sub 1} single-particle states with positive parity and {ell}{sub 2} single-particle states with negative parity and interacting through random two-body forces that conserve parity. The single-particle states are completely degenerate and carry no further quantum numbers. We compare spectra of many-body states with positive and with negative parity. We show that in the dilute limit defined by m, {ell}{sub 1,2} {yields} {infinity} and ml {ell}{sub 1,2} {yields} 0, ground states with positive and negative parity occur with equal probability. Differences in the ground-state probabilities are, thus, a finite-size effect and are mainly due to different dimensions of the Hilbert spaces of either parity.

Papenbrock, T. F. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Weidenmueller, H. A. [Max-Planck Institut fur Kernphysik, Heidelberg, Germany

2008-01-01

93

Preponderance of Ground States with Positive Parity  

SciTech Connect

We investigate analytically and numerically a random-matrix model for m fermions occupying {ell}_1 single-particle states with positive parity and {ell}_2 single-particle states with negative parity and interacting through random two-body forces that conserve parity. The single-particle states are completely degenerate and carry no further quantum numbers. We compare spectra of many-body states with positive and with negative parity. We show that in the dilute limit defined by 1 << m << {ell}_1,{ell}_2, ground states with positive and with negative parity occur with equal probability. Differences in the ground-state probabilities are, thus, a finite-size effect and are mainly due to different dimensions of the Hilbert spaces of either parity.

Papenbrock, T. F. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Weidenmueller, H. A. [Max-Planck Institut fur Kernphysik, Heidelberg, Germany

2008-01-01

94

Coherent Transfer of Photoassociated Molecules into the Rovibrational Ground State  

NASA Astrophysics Data System (ADS)

Recently, there have been impressive advances in methods of creating ultracold molecules from ultracold atomic gases. One of the key technologies used there is Stimulated Raman Adiabatic Passage (STIRAP), which has been successfully used for transferring Feshbach molecules into the rovibrational ground state. Since STIRAP relies on quantum coherence, it is unclear if STIRAP is also useful for non-polarized sample, like photo-associated molecules in a magneto-optical trap. Here we report on the SITRAP transfer of weakly bound molecules produced by photoassociation (PA). Laser cooled 41K and 87Rb atoms were first photo-associated into loosely-bound molecules in the X^1? potential. Using v=41, J=1 level in the (3)^1? potential as an intermediate level, we succeeded in transferring molecules in the v=91, J=0 level into the absolute ground state (X^1?, v=0, N=0). High-resolution spectroscopy based on the coherent transfer revealed the hyperfine structure of both weakly-bound and tightly-bound molecules. Our results show that a pure sample of ultracold ground-state molecules is achieved via the all-optical association of laser-cooled atoms, opening possibilities to coherently manipulate a wide variety of molecules.[4pt] In collaboration with Kiyotaka Aikawa, Kohei Oasa, University of Tokyo; Masahito Ueda, University of Tokyo, JST, ERATO; Jun Kobayashi, University of Tokyo; and Tetsuo Kishimoto, University of Electro-Communications.

Inouye, Shin

2011-06-01

95

High harmonics generation from excited states of atomic lithium  

NASA Astrophysics Data System (ADS)

We present a calculation of the harmonics yield from the lithium atom exposed to an intense 3.5 µm mid-infrared laser pulse. Our calculation shows that a considerable increase of the yield of high harmonics generation (HHG) can be achieved if initially the atom is prepared in an excited 2p state. We show that this increase can be regarded as a resonant process due to appearance of a multiphoton resonance between the initial state and a quasienergy state. We also consider HHG from lithium prepared initially in a superposition of the ground and excited states.

Ivanov, I. A.; Kheifets, A. S.

2008-06-01

96

Collinear laser spectroscopy on the ground state and an excited state in neutral 55Mn  

NASA Astrophysics Data System (ADS)

Collinear laser spectroscopy was performed on an atomic beam of stable 55Mn. An ion beam of 55Mn+ was generated in an ion source, accelerated to 15 keV, and neutralized via charge-exchange reactions with a Na vapor. A long-lived metastable state of Mn i, near-resonantly populated in the charge-exchange process, was investigated via laser probing in addition to a laser excitation from the ground state in Mn i. The relative population of the Mn i metastable state compared to that of the ground state was found to be 0.7±0.3. A theoretical calculation, which included feeding to the ground state and the metastable state from higher-energy excited electronic states populated in the charge-exchange process, agreed with the present result. The deduced A and B hyperfine coupling constants agreed with literature values, where available.

Klose, A.; Minamisono, K.; Mantica, P. F.

2013-10-01

97

The Ground State Rotational Spectrum of Formaldehyde  

NASA Astrophysics Data System (ADS)

The ground state rotational spectrum has been measured from 1 to 2600 GHz. These new measurements together with the older ones have been fitted to a standard A-reduced Watson-type Hamiltonian. The accuracy of the rotational and centrifugal distortion (including some octic ones) constants has been notably improved. The experimental constants are compared to the ab initioones.

Bocquet, R.; Demaison, J.; Poteau, L.; Liedtke, M.; Belov, S.; Yamada, K. M. T.; Winnewisser, G.; Gerke, C.; Gripp, J.; Köhler, Th.

1996-05-01

98

The Ground State Rotational Spectrum of Formaldehyde  

Microsoft Academic Search

The ground state rotational spectrum has been measured from 1 to 2600 GHz. These new measurements together with the older ones have been fitted to a standardA-reduced Watson-type Hamiltonian. The accuracy of the rotational and centrifugal distortion (including some octic ones) constants has been notably improved. The experimental constants are compared to theab initioones.

R. Bocquet; J. Demaison; L. Poteau; M. Liedtke; S. Belov; K. M. T. Yamada; G. Winnewisser; C. Gerke; J. Gripp; Th. Köhler

1996-01-01

99

Ground State of the Double Exchange Model  

Microsoft Academic Search

We invesitgate the electronic correlation effect on the ground-state properties of the double exchange model for manganites by using a semiclassical approach and the slave-boson technique. It is shown that magnetic feild has a similar effect on the canted angle between manganese spins as doping concentration does, and the canted angle exhibits weak dependence on the Coulomb interaction. We have

Liang-Jian Zou; Qing-Qi Zheng; H. Q. Lin

1998-01-01

100

Creation of a six-atom 'Schrödinger cat' state.  

PubMed

Among the classes of highly entangled states of multiple quantum systems, the so-called 'Schrödinger cat' states are particularly useful. Cat states are equal superpositions of two maximally different quantum states. They are a fundamental resource in fault-tolerant quantum computing and quantum communication, where they can enable protocols such as open-destination teleportation and secret sharing. They play a role in fundamental tests of quantum mechanics and enable improved signal-to-noise ratios in interferometry. Cat states are very sensitive to decoherence, and as a result their preparation is challenging and can serve as a demonstration of good quantum control. Here we report the creation of cat states of up to six atomic qubits. Each qubit's state space is defined by two hyperfine ground states of a beryllium ion; the cat state corresponds to an entangled equal superposition of all the atoms in one hyperfine state and all atoms in the other hyperfine state. In our experiments, the cat states are prepared in a three-step process, irrespective of the number of entangled atoms. Together with entangled states of a different class created in Innsbruck, this work represents the current state-of-the-art for large entangled states in any qubit system. PMID:16319885

Leibfried, D; Knill, E; Seidelin, S; Britton, J; Blakestad, R B; Chiaverini, J; Hume, D B; Itano, W M; Jost, J D; Langer, C; Ozeri, R; Reichle, R; Wineland, D J

2005-12-01

101

Optical Atomic Clocks for Ground and Space Applications  

NASA Astrophysics Data System (ADS)

Optical atomic clocks on ground have now matured to a status where they compete favourably with the best caesium atomic clocks that realize the unit of time in the International System of Units (SI). Optical clocks can have orders of magnitude better short term stability than their radio-frequency counterparts. Even though optical clocks cannot realize the second in the SI better than the best caesium clocks (as long as the definition of the SI second is based on the caesium transition) they can realize the unperturbed center of a quantum transition with much better accuracy and stability. Optical atomic clocks now represent the most accurate measuring devices for applications in technology and basic science. Three alternative routes are followed by optical atomic clocks: In the first approach -the single ion clock -a single quantum absorber is trapped in a field-free region for virtually unlimited time. In neutral atom clocks a large number of atoms trapped in a light field can interrogated in parallel which allows for unprecedented high short-term stability. A very promising third avenue relies on ions where the quantum transition is read out by means of quantum logic techniques. This approach allows to use nearly ideal transitions that are otherwise not accessible. In the first part of this presentation the principles and status of the different types of clocks will be outlined using examples of the PTB's Y b+ single ion clock and the Sr neutral atom lattice clock. Particular emphasis is given to the application of such clocks for advanced applications in science and technology. A number of proposals has been made to utilize the superior properties of optical clocks also for novel science and applications in space and several attempts are under way to realize optical clocks for space applications. Thus, the second part of this contribution will deal with the special requirements for optical clocks in space and the associated similarities and differences of optical clocks for ground and space applications. Furthermore typical applications for optical space clocks for the different approaches will be given.

Riehle, Fritz

102

Atomic Fock state preparation using Rydberg blockade.  

PubMed

We use coherent excitation of 3-16 atom ensembles to demonstrate collective Rabi flopping mediated by Rydberg blockade. Using calibrated atom number measurements, we quantitatively confirm the expected ?N Rabi frequency enhancement to within 4%. The resulting atom number distributions are consistent with an essentially perfect blockade. We then use collective Rabi ? pulses to produce N=1, 2 atom number Fock states with fidelities of 62% and 48%, respectively. The N=2 Fock state shows the collective Rabi frequency enhancement without corruption from atom number fluctuations. PMID:24580449

Ebert, Matthew; Gill, Alexander; Gibbons, Michael; Zhang, Xianli; Saffman, Mark; Walker, Thad G

2014-01-31

103

Ground-State of Hydrogen Fluoride  

NASA Astrophysics Data System (ADS)

The study of the ground-state properties of molecular systems has long been the focus of both quantum chemists as well as physicists. In general, most of the calculational methods are dependent on the use of high-power computers to generate large basis states. Such schemes as the full-configuration-interaction method, coupled-pair functionals and its modification, Moller-Plesset perturbation theory as well as both the restricted and unrestricted Hartree-Fock schemes have been used not only for ground-state calculations but also to calculate electron correlation energies. In general such schemes are limited to those bases which are constructed from single Slatter determinant. Here we wish to study the ground-state of hydrogen fluoride(HF) using the recently developed canonical sequence scheme which is a calculational cousin of the Connected Moments Expansion of Cioslowski. Comparisons are then made with other methods [for example P.J. Knowles Chem. Phys. Lett. 134, 512 (1987)].

Bowen, Samuel P.; Fessatidis, Vassilios; Celi, Christina; Mancini, Jay D.

2001-03-01

104

Determination of Hyperfine Structure of Highly Excited S States in Alkali Atoms Using a CW Dye Laser.  

National Technical Information Service (NTIS)

The excited S states in alkali atoms cannot be populated by direct optical excitation of the ground state atoms. In order to reach the excited S states, which have the same parity as the ground state, either a cascade excitation, or a two-step excitation ...

P. Tsekeris R. Gupta W. Harper G. Belin S. Svanberg

1974-01-01

105

Preparing and Probing Atomic Number States with an Atom Interferometer  

SciTech Connect

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state.

Sebby-Strabley, J.; Brown, B. L.; Anderlini, M.; Lee, P. J.; Phillips, W. D.; Porto, J. V.; Johnson, P. R. [Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, Maryland 20899 (United States); Physics Program, American University, Washington D.C. 20016 (United States) and National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2007-05-18

106

Preparing and probing atomic number states with an atom interferometer.  

PubMed

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state. PMID:17677678

Sebby-Strabley, J; Brown, B L; Anderlini, M; Lee, P J; Phillips, W D; Porto, J V; Johnson, P R

2007-05-18

107

Ground-state energy of nuclear matter  

SciTech Connect

The low-density expansion of the ground-state energy for spin-dependent forces is given, through order k/sub F//sup 6/ for the ladder approximation and through order k/sub F//sup 6/lnk/sub F/ for the complete energy, in terms of derivatives with respect to the strength of the attractive part of the interaction defined by the Baker-Hind-Kahane potential. The ladder approximation is also computed by the numerical solution of the K-matrix equation. The resulting series gives a satisfactory representation of the energy at interesting densities. Using Pade extrapolation techniques, both in the density and in the attractive part of the interaction, we obtain the ground-state energy of nuclear matter.

Baker G.A. Jr.; Benofy, L.P.; Fortes, M.

1988-07-01

108

Landau Ground State on Riemannian Surfaces  

NASA Astrophysics Data System (ADS)

We study the ground state of a particle moving on an even-dimensional Riemannian manifold (M,g??) under the action of a nondegenerate magnetic field B?? in the hypothesis that the metric and the symplectic two-form provided by B, define a conformal Kähler structure on M. On a Riemannian surface the Hamiltonian \\[ H=\\frac{1}{2m\\sqrt{g}}\\left(-i\\hbar\\partial_\\mu - \\frac{e}{c} A_\\mu\\right) g^{\\mu \

Maraner, P.

109

Ground state of octahedral platinum hexafluoride  

NASA Astrophysics Data System (ADS)

All previously published nonrelativistic and scalar relativistic electronic structure calculations of platinum hexafluoride predict a paramagnetic distorted octahedral molecule with a triplet ground state. The four-component spin-free method also predicts a distorted octahedral molecule with longest axial Pt-F bond due to the Jahn-Teller effect. However, four-component Dirac molecular Hartree-Fock and density-functional theory (DFT) and the two-component zeroth-order regular approach (ZORA) including spin-orbit interaction calculations predict a diamagnetic octahedral molecule with a closed-shell ground state, which is in accordance with the observation of the F19 and P195t high-resolution nuclear magnetic resonance spectra and its undisturbed ir and Raman spectra of PtF6 . The excitation energies involving the d-d transitions are well calculated by performing time-dependent DFT calculations using the two-component ZORA method. Thus, its octahedral molecular structure with a closed-shell ground state is stabilized by the effect of a spin-orbit interaction.

Alvarez-Thon, Luis; David, J.; Arratia-Pérez, Ramiro; Seppelt, Konrad

2008-03-01

110

Photonic multiqubit states from a single atom  

SciTech Connect

We propose a protocol for the creation of photonic Greenberger-Horne-Zeilinger and linear cluster states emitted from a single atom--or ion--coupled to an optical cavity field. The method is based on laser pulses with different polarizations and exploits the atomic transition amplitudes to state-selectively achieve the desired transitions. The scheme lies within reach of current technology.

Li Ying [Centre for Quantum Technologies, National University of Singapore, Singapore 117543 (Singapore); Aolita, Leandro [ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, 08860 Castelldefels, Barcelona (Spain); Kwek, L. C. [Centre for Quantum Technologies, National University of Singapore, Singapore 117543 (Singapore); Institute of Advanced Studies (IAS), Nanyang Technological University, Singapore 639673 (Singapore); National Institute of Education, Nanyang Technological University, Singapore 637616 (Singapore)

2011-03-15

111

The polaron: Ground state, excited states, and far from equilibrium  

SciTech Connect

The authors describe a variational approach for solving the Holstein polaron model with dynamical quantum phonons on an infinite lattice. The method is simple, fast, extremely accurate, and gives ground and excited state energies and wavefunctions at any momentum k. The method can also be used to calculate coherent quantum dynamics for inelastic tunneling and for strongly driven polarons far from equilibrium.

Trugman, S.A. [Los Alamos National Lab., NM (United States). Theory Div.; Bonca, J. [Univ. of Ljubljana (Slovenia)]|[Jozef Stefan Inst., Ljubljana (Slovenia)

1998-12-01

112

Teleportation of an atomic momentum state  

SciTech Connect

In this paper, we propose a scheme for teleportating a superposition of atomic center-of-mass momentum states to a superposition of the cavity field using quantum controlled-NOT gate via atomic scattering in the Bragg regime and cavity quantum electrodynamics.

Qamar, Shahid [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad (Pakistan); Zhu Shiyao [Department of Physics, Hong Kong Baptist University, Hong Kong (China); Zubairy, M. Suhail [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Electronics, Quaid-i-Azam University, Islamabad (Pakistan)

2003-04-01

113

A solid-state atomic frequency standard  

Microsoft Academic Search

This paper describes a new class of frequency reference. The frequency source uses the same operating principle as a passive atomic frequency standard; however, the device is entirely solid-state, removing many cost and reliability issues associated with gas phase atomic clocks. More specifically, the \\

Christopher J. White; Ali Hajimiri

2005-01-01

114

Quantum States of Atoms and Molecules  

NSDL National Science Digital Library

Quantum States of Atoms and Molecules is an introduction to quantum mechanics as it relates to spectroscopy, the electronic structure of atoms and molecules, and molecular properties. A digital, living textbook, it provides opportunities not found in conventional textbooks opportunities that allow students to develop skills in information processing, critical thinking or analytical reasoning, and problem solving that are so important for success.

115

Minimal instances for toric code ground states  

NASA Astrophysics Data System (ADS)

A decade ago Kitaev's toric code model established the new paradigm of topological quantum computation. Due to remarkable theoretical and experimental progress, the quantum simulation of such complex many-body systems is now within the realms of possibility. Here we consider the question, to which extent the ground states of small toric code systems differ from local-unitary (LU)-equivalent graph states. We argue that simplistic (though experimentally attractive) setups obliterate the differences between the toric code and equivalent graph states; hence we search for the smallest setups on the square and triangular lattices, such that the quasilocality of the toric code Hamiltonian becomes a distinctive feature. To this end, a purely geometric procedure to transform a given toric code setup into a local-Clifford (LC)-equivalent graph state is derived. In combination with an algorithmic computation of LC-equivalent graph states, we find the smallest nontrivial setup on the square lattice to contain five plaquettes and 16 qubits; on the triangular lattice the number of plaquettes and qubits is reduced to four and nine, respectively.

Lang, Nicolai; Büchler, Hans Peter

2012-08-01

116

Quantum State Sharing of an Arbitrary Three-Atom State by Using Five-Atom Cluster State in Cavity QED  

NASA Astrophysics Data System (ADS)

We present a scheme for implementing the deterministic quantum state sharing of an arbitrary three-atom state by using a five-atom cluster state and a Bell-state in cavity QED. In the scheme, it does not involve Bell-state measurement and only needs to perform the single-atom measurements. Our scheme is not sensitive to both the cavity decay and the atom radiation, which is of importance in view of decoherence.

Nie, Yi-you; Xu, Yue; Li, Yuan-hua; Sang, Ming-huang

2014-04-01

117

Pyramidal atoms: Berylliumlike hollow states  

SciTech Connect

Based on the idea that four excited electrons arrange themselves around the nucleus in the corners of a pyramid in order to minimize their mutual repulsion, we present an analytical model of quadruply excited states. The model shows excellent comparison with ab initio results and provides a clear physical picture of the intrinsic motion of the four electrons. The model is used to predict configuration-mixing fractions and spectra of these highly correlated states.

Poulsen, Marianne Dahlerup; Madsen, Lars Bojer [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark)

2005-06-15

118

Antimatter Advances Include Trapped Antihydrogen in Its Ground State  

NASA Astrophysics Data System (ADS)

Three recent advances in antimatter physics show significant progress towards precision tests of fundamental symmetries. The first and primary focus of this talk is ATRAP's observation of five simultaneously trapped antihydrogen atoms per trial, confined for long enough to ensure that they are in their ground state.ootnotetextG. Gabrielse et al. (ATRAP Collaboration). Phys. Rev. Lett. 108, 113002 (2012). Large numbers of simultaneously trapped atoms are crucial if laser cooling and spectroscopy of antihydrogen at high levels of precision are to be achieved. Fundamental to this result is the careful control and characterization of the geometry and temperature of the large-number antiproton and positron plasmas from which antihydrogen is formed, along with enhanced event detection and cosmic ray background rejection techniques. A second advance, by the ALPHA collaboration, is a demonstration that smaller numbers of simultaneously trapped antihydrogen atoms can be ejected from a magnetic trap when microwaves flip the spin of the atoms.ootnotetextC. Amole et al. (ALPHA Collaboration). Nature 483, 439 (2012). A third advance is a direct measurement of the proton magnetic moment to 2.5 parts per million using a technique that can be directly applied to an antiprotonootnotetextJ. DiSciacca and G. Gabrielse. Phys. Rev. Lett. 108, 153001 (2012). to improve the precision with which the antiproton magnetic moment is measured by a factor of 1000.

Richerme, Phil

2012-06-01

119

Influence of vibrational continuum states on vibrational transitions among bound states of H2 molecule by H atom impact  

Microsoft Academic Search

The influence of coupling between vibrational bound and continuum states on vibrational transitions among bound states of H2 molecule in the electronic ground state caused by H atom impact is theoretically investigated by solving the vibrational close-coupling equations under the rotational IOS approximation. It is found that the coupling between the bound and continuum states causes a noticeable change in

K. Onda

1991-01-01

120

Ground-state structure and stability of dipolar condensates in anisotropic traps  

SciTech Connect

We study the Hartree ground state of a dipolar condensate of atoms or molecules in a three-dimensional anisotropic geometry and at T=0. We determine the stability of the condensate as a function of the aspect ratios of the trap frequencies and of the dipolar strength. We find numerically a rich phase space structure characterized by various structures of the ground-state density profile.

Dutta, O.; Meystre, P. [Department of Physics and College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States)

2007-05-15

121

Ground state of high-density matter  

NASA Technical Reports Server (NTRS)

It is shown that if an upper bound to the false vacuum energy of the electroweak Higgs potential is satisfied, the true ground state of high-density matter is not nuclear matter, or even strange-quark matter, but rather a non-topological soliton where the electroweak symmetry is exact and the fermions are massless. This possibility is examined in the standard SU(3) sub C tensor product SU(2) sub L tensor product U(1) sub Y model. The bound to the false vacuum energy is satisfied only for a narrow range of the Higgs boson masses in the minimal electroweak model (within about 10 eV of its minimum allowed value of 6.6 GeV) and a somewhat wider range for electroweak models with a non-minimal Higgs sector.

Copeland, ED; Kolb, Edward W.; Lee, Kimyeong

1988-01-01

122

Coherent control of atomic quantum states by single frequency-chirped laser pulses  

SciTech Connect

We present a scheme of population transfer between two metastable (ground) states of the {lambda} atom without considerable excitation of the atom using single frequency-chirped laser pulses. The physics of the process is generation of the 'trapped' superposition of the ground states by the laser pulse at sufficiently high laser peak intensity. The main conditions for realization of this regime are the following: The width of the transform-limited laser pulse envelope frequency spectrum (without chirp) must be smaller and the peak Rabi frequency of the pulse must be larger than the frequency interval between the two ground states of the {lambda} atom. During the frequency chirp, the laser pulse must first come into resonance with the transition from the initially occupied ground state to the excited state and after that with the transition between the excited and second initially empty ground states. In the case when the envelope frequency spectrum width (without chirp) of the pulse exceeds the frequency interval between the two ground states, we show a possibility of controllable generation of superposition of the ground states with a controllable excitation of the {lambda} atom.

Djotyan, G.P.; Bakos, J.S.; Soerlei, Zs.; Szigeti, J. [Research Institute for Particle and Nuclear Physics, XII. Konkoly Thege ut 29-33, P.O. Box 49, H-1525, Budapest (Hungary)

2004-12-01

123

Conformationally controlled chemistry: Excited state dynamics dictate ground state dissociation  

NASA Astrophysics Data System (ADS)

Ion imaging results show distinct photodissociation dynamics for propanal cations initially prepared in either the cis- or gauche- conformation, even though these differ only slightly in energy and there is a small barrier between them. The product kinetic energy distributions for the H elimination channels are bimodal, and the two peaks are readily assigned to propanoyl cation + H and hydroxyallyl cation + H. Ab initio multiple spawning dynamical calculations show that distinct ultrafast dynamics in the excited state leads to internal conversion to the ground state in isolated regions of the potential surface for the two conformers, and from these distinct regions, conformer interconversion does not effectively compete with dissociation.

Suits, Arthur; Kim, Myung-Hwa; Shen, Lei; Zhang, Bailin; Tao, Hongli; Martinez, Todd

2007-03-01

124

Cold Atom Optics on Ground and in Space  

Microsoft Academic Search

Microgravity is the ultimate laboratory environment for experiments in fundamental physics based on cold atoms. The talk will give a survey of recent activities on atomic quantum sensors and atom lasers. Inertial atomic quantum sensors are a promising and complementary technique for experiments in fundamental physics. Pioneering experiments at Yale [1,2] and Stanford [3] displayed recently the fascinating potential of

E. M. Rasel

2004-01-01

125

Ground-state energetics of helium and deuterium fermion fluids  

NASA Astrophysics Data System (ADS)

The method of correlated basis functions (CBF) is applied to the evaluation of the ground-state energy of atomic fermion fluids as a function of density. As a first step, liquid 3He in both unpolarized and fully polarized spin configurations is considered variationally, using Slater-Jastrow trial wave functions. Results are reported for a conventional analytic choice of the state-independent two-body correlation function f(r) and for the optimal f(r) determined by the solution of a suitable Euler equation. The Jastrow treatment is found to be inadequate in that (i) the energy expectation value lies above the experimental equilibrium energy by some 1.5 K, and (ii) the polarized phase is predicted to be more stable than the unpolarized one. For a given polarization, a correlated basis is formed by application of the assumed Jastrow correlation factor to the elements of a complete set of noninteracting-Fermi-gas Slater determinants. The exact ground-state energy may be developed in a perturbation expansion in the correlated basis, the leading term being the Jastrow energy expectation value. Considerable improvement on the Jastrow description of the unpolarized phase is achieved upon inclusion of the correlated two-particle-two-hole component of the second-order CBF perturbation correction. At the experimental equilibrium density, this contribution, which incorporates important momentum- and spin-dependent correlations, can amount to some 0.6-1.1 K [depending on the choice of f(r)]. The required correlated-basis matrix elements are calculated by Fermi hypernetted-chain (FHNC) techniques, crucial Pauli effects of the elementary diagrams being introduced through the FHNC/C algorithm. The Euler equation is approximated within the same framework. The momentum-space integrations in the second-order perturbation correction are evaluated by a Monte Carlo procedure. One may reasonably expect that further refinements of the CBF method will lead to an accurate microscopic description of the ground-state energetics of liquid 3He. Bulk atomic deuterium with all electronic spins aligned is treated at the same level of approximation as applied to helium. Three choices of nuclear-spin distribution are examined, with a single spin state present, or two or three equally populated nuclear spin states. The finite-density energy minimum is found to lie very close to zero energy in all three examples; a very precise many-body calculation will thus be needed to decide their liquid or gaseous nature at zero temperature under zero external pressure.

Krotscheck, E.; Smith, R. A.; Clark, J. W.; Panoff, R. M.

1981-12-01

126

Creating and probing coherent atomic states  

SciTech Connect

The authors present a brief review of recent experimental and theoretical time resolved studies of the evolution of atomic wavepackets. In particular, wavepackets comprising a superposition of very-high-lying Rydberg states which are created either using a short half-cycle pulse (HCP) or by rapid application of a DC field. The properties of the wavepackets are probed using a second HCP that is applied following a variable time delay and ionizes a fraction of the atoms, much like a passing-by ion in atomic collisions.

Reinhold, C.O.; Burgdoerfer, J. [Oak Ridge National Lab., TN (United States). Physics Div.]|[Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Frey, M.T.; Dunning, F.B. [Rice Univ., Houston, TX (United States)

1997-06-01

127

Ground-based investigations of atomic oxygen interactions with space station surfaces  

SciTech Connect

High strength to weight ratio fiber organic epoxy materials are primary candidates as structural members for Space Station construction but preliminary STS exposure experiments have shown that many of these materials experience extensive etching by oxygen atoms present in low earth orbit (LEO). Oxygen atoms colliding with ram directed surfaces have energies of 5 eV (due to 8 km/s orbital velocity) and produce etching rates of 0.1 micron/orbit, i.e., 10% of the incoming O-atom flux reacts with organic based surfaces causing surface recession; while ram surface reflected O-atoms (thermal), react with rates 3 to 4 times lower. In order to investigate this problem ground-based simulation and testing facilities have been developed which include a high kinetic energy O-atom source, a sample exposure chamber and a high sensitivity molecular beam apparatus. The sample exposure chamber is suited for surveying materials for their O-atom reactivity through weight loss measurements. The high sensitivity molecular beam apparatus will be used for determining reaction mechanisms through measurements of reaction product identity, translational and internal state of products, and angular distribution of reaction products. The O-atom source, based on the use of a laser sustained discharge, has demonstrated O-atom translational temperatures of 8 to 9000 K and is presently operating with 50% oxygen in argon using 500 watts of CO/sub 2/ laser power which is expected to produce velocities of 4 to 5 km/s. One hour exposures of kapton, two types of fiber glass epoxy materials, and MgF/sub 2/ coated optics have been accomplished and preliminary results indicate that the coated aluminium optics have very low reaction rates while kapton has the highest rate.

Cross, J.B.; Cremers, D.A.; Tucker, D.F.

1985-01-01

128

Towards the measurement of the ground-state hyperfine splitting of antihydrogen  

NASA Astrophysics Data System (ADS)

The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, which will consist of a superconducting cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of better than ˜ 10 - 6. The first preliminary measurements of the hyperfine transitions will start in 2011.

Juhász, Bertalan

2012-12-01

129

Is the ground state of Yang-Mills theory Coulombic?  

SciTech Connect

We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-Abelian Coulomb fields is found to have a good overlap with the ground state for all charge separations. In fact, the overlap increases as the lattice regulator is removed. This opens up the possibility that the Coulomb state is the true ground state in the continuum limit.

Heinzl, T.; Ilderton, A.; Langfeld, K.; Lavelle, M.; McMullan, D. [School of Mathematics and Statistics, University of Plymouth, Plymouth, PL4 8AA (United Kingdom); Lutz, W. [School of Mathematics and Statistics, University of Plymouth, Plymouth, PL4 8AA (United Kingdom); Institut fuer Theoretische Physik, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2008-08-01

130

Ground-based laboratory atomic oxygen calibration experiments  

NASA Astrophysics Data System (ADS)

Existing devices and analysis techniques for the monitoring of space and laboratory simulated Atomic Oxygen (AO) environments have been investigated and improved to enable more accurate and reliable measurement and calibration of AO flux and fluences than previously possible. This research was based on experimental work carried out in a ground based AO facility designed to simulate the low Earth orbit (LEO) AO space environment, an environment which contributes significantly to the degradation of spacecraft materials. Three types of AO measuring device, referred to as 'silver film', 'bulk polymer mass loss' and 'polymer overlay' devices, were used in the experiments and were based on the following principles for detection of AO, respectively: (1) The electrical resistivity characteristics of oxidising, thin silver films. (2) The mass loss of bulk polymeric materials. (3) The combination of both the above phenomena. In calibrating the responses of these devices upon exposure to AO, it was necessary to improve an existing technique to establish reference measurements of AO fluences based on the mass loss of the polymeric material 'Kapton-H'. Experiments showed that the most significant disturbance factor affecting accurate measurements of mass loss was atmospheric humidity, which was found to be responsible for a disturbance of 0.012(±0.002)mg per percent change in atmospheric humidity level for the particular samples used in this research. Experiments also revealed a novel technique which indicated the relative stability of conditions within a simulated AO environment by the ratio of mass losses of a set of polymeric test samples, including polyethylene, polytetrafluoroethylene and Kapton-H, described as a 'signature analysis technique'. Interactions occurring between AO and a variety of polyethylene related polymeric materials were shown to be influenced by the methods used to manufacture and process the polymers. This influence has been related to changes in polymeric material density and crystallinity. In addition, the limitations in protecting a polymeric material from AO erosion by insertion of fluorine into the side-chain group chemistry has been indicated. Of most significance to the development of polymer overlay devices was the discovery that the overlay material AO erosion yield was dependent upon the rate at which the polymer overlay material was sputter deposited. These devices were also shown to detect AO fluences that were linearly dependent upon the initial thickness of the overlay material up to certain thicknesses, beyond which the effects of overlay porosity or fracturing weakened the linear relationship. A novel method for analysing silver film device electrical resistances under AO exposure has been developed from a combination of existing fundamental theories concerning the electrical resistivity phenomena in thin metallic films. Validation of this analysis method revealed that experimental silver film data were consistently in disagreement with the existing theories due to a factor influencing the conduction electron mean free path length in the silver films. Final validation of this analysis technique was performed by comparing results derived from the same set of experimental silver film device data using the new technique and an example of a previous technique. It was confirmed that the novel analysis technique produced far more consistent values for the oxidation yield of silver, 3/pm0.5×10-24cm3.atom-1, than the previously used technique, 6/pm3×10- 24cm3.atom-1. The novel analysis technique has been demonstrated to be theoretically more accurate for the analysis of silver film resistance data than any previously applied theories.

Matcham, Jeremy Stephen

1998-12-01

131

Ground-state potentials for Co+/rare-gas interactions  

NASA Astrophysics Data System (ADS)

Spectroscopic constants (Re, ?e, De, D0) for the 3? ground-state potentials of the diatomic ions CoAr+, CoKr+, CoXe+, and CoRn+ are calculated using coupled-cluster theory, flexible basis sets, and relativistic ab initio pseudo-potentials for the heavy rare-gas atoms. This standard approach yields c. 90% of the measured interaction energies and overestimates the bond distances by c. 0?05 bohr. Bonding is shown to be intrinsically electrostatic. For the case of CoAr+, possible sources of error in the calculation are investigated by studying the effects of core correlation,scalar and spin-orbit relativistic effects, and basis set superposition errors. Correlating the 3s and 3p electrons in Co and the inclusion of scalar relativistic terms increase the bond strengths and decrease the equilibrium distance in CoAr+, while accounting for spin-orbit interaction and correction for the basis set superposition errors lead to the opposite effects. Including all these corrections, the theoretical predictions of the spectroscopic parameters for the 3?3 ground state of CoAr+ are (experimental values in parentheses) Re = 4?460 (4?509 ± 0?009) bohr; ?e = 198 cm-1; Do = 0±4874 (0?5097 ± 0?0006) eV.

Heinemann, Christoph

132

Partially autoionizing states of atomic oxygen  

NASA Technical Reports Server (NTRS)

The Rydberg states 3d' (3Po)2,1,0 and 3s'' (3Po)2,1,0 and the inner shell transition 2s 2p5 (3Po)2,1,0, which are forbidden to autoionize on the basis of LS coupling, were observed in emission spectroscopy and in autoionization spectra produced in the photoelectron spectrum of atomic oxygen.

Samson, J. A. R.; Petrosky, V. E.

1972-01-01

133

Atomic Schroedinger cat-like states  

SciTech Connect

After a short overview of the basic mathematical structure of quantum mechanics we analyze the Schroedinger's antinomic example of a living and dead cat mixed in equal parts. Superpositions of Glauber kets are shown to approximate such macroscopic states. Then, two-level atomic states are used to construct mesoscopic kittens as appropriate linear combinations of angular momentum eigenkets for j = 1/2. Some general comments close the present contribution.

Enriquez-Flores, Marco [Departamento de Fisica, Escuela Superior de Fisica y Matematicas, IPN Edificio 9, Unidad Profesional Adolfo Lopez Mateos, Mexico D.F. 07738 (Mexico); Rosas-Ortiz, Oscar [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, Mexico D.F. 01000 (Mexico); Departamento de Fisica, Cinvestav, A.P. 14-740, Mexico D.F. 07000 (Mexico)

2010-10-11

134

Ground state properties and applications of dipolar ultracold gases  

NASA Astrophysics Data System (ADS)

This thesis contains a study of ultracold paramagnetic atoms or polar molecules characterized by a long-range anisotropic dipolar interaction. We particularly focus on two aspects of ultracold dipolar gases. In the first problem the ground state properties of dipolar Bose-Einstein condensates (BEC) are investigated. This problem has gained importance due to recent experimental advances in achieving a condensate of Chromium atoms and ongoing research to produce quantum degenerate polar molecules. In the second problem, we consider possible applications of ultracold polar molecules to rotation sensing and interferometry. First, we concentrate on the interplay between the trapping geometry and dipole-dipole interaction for a polarized dipolar bosonic condensate. As the dipole dipole interaction is attractive along the polarized direction, the lowest energy state of the BEC is always a collapsed state. However by applying a trapping potential along the polarization direction it is possible to achieve a metastable dipolar BEC. By numerically solving the Gross-Pitaevskii equation, we show that below a critical interaction strength, a metastable state exists depending on the trapping geometry. We also show that a novel feature of dipolar BEC is the appearance of different structural metastable ground states for certain combinations of trapping geometry and particle number. Next, by mixing in single component fermions we show that dipolar BEC can be stabilized against collapse in pancake shaped or cylindrical traps. We also show that the excitation spectrum of the BEC may have a minimum for non-zero momentum, termed a "roton minimum". This minimum leads to a transition to stable or metastable density-wave states depending on the density of the bosons and boson-fermion interaction strength. In the second problem, we study a proposal for a large-angle coherent beam splitter for polar molecules. By taking into account the effect of a quasi-static external electric field on the rotational levels of the polarized molecules we show that it is possible to coherently split a stationary cloud of molecules into two counter-propagating components. We then investigate the effect of longitudinal acceleration on the transverse motion of the particles, assuming that the longitudinal motion of the molecules can be approximated classically by a wave packet with some mean velocity while the transverse motion is governed by quantum mechanics. We propose a particular time-dependent shape of acceleration to minimize the excitations in the transverse motion. Our theory is also applicable to the general case of particles moving along a circular guide with time-dependent longitudinal velocity. In addition, we include the effects of velocity fluctuations due to noise in the accelerating field.

Dutta, Omjyoti

135

Ground-State Properties of Superfluid Fermi Gas in Fourier-Synthesized Optical Lattices  

NASA Astrophysics Data System (ADS)

By employing the balance condition between the lattice potential and the interatomic interaction, we study the ground state solutions of superfluid Fermi gases in Fourier-synthesized (FS) optical lattices. The average energy of the ground state, the atoms number, and the atom density distribution of the Fermi system are analytically derived along the Bose—Einstein condensation (BEC) side to the Bardeen—Cooper—Schrieffer (BCS) side. We analyze the properties of ground state solutions at both the BEC limit and unitarity in FS optical lattices. It is found that the relative phase ? between the two lattice harmonics impacts greatly on the properties of the ground state of the superfluid Fermi gas. Especially in the BCS limit, when ? = ?/2, the average energy presents an exponential form with the increase of the potential depth of the lattice harmonics ?2. Meanwhile, there exits a minimal value. Moreover, due to the Fermi pressure, the atom density distribution at unitarity is more outstretched than that in the BEC limit. The average energy at unitarity is apparently larger than that in the BEC limit. The properties of the ground state solution exhibit very different behaviors when the system transits from the BEC side to the BCS side.

Chen, Yan; Zhang, Ke-Zhi; Wang, Xiao-Liang; Chen, Yong

2014-03-01

136

Interaction of Helium Rydberg State Atoms with Superfluid Helium  

NASA Astrophysics Data System (ADS)

The pair potentials between ground state helium and Rydberg He atoms are calculated by the full configuration interaction electronic structure method for both the electronic singlet and the triplet manifolds. The obtained pair potentials are validated against existing experimental molecular and atomic data. Most states show remarkable energy barriers at long distances ( Å), which can effectively stabilize He against the formation of He at low nuclear kinetic energies. Bosonic density functional theory calculations, based on the calculated pair potential data, indicate that the triplet ground state He reside in spherical bubbles in superfluid helium with a barycenter radius of 6.1 Å at the liquid saturated vapor pressure. The pressure dependency of the relative He absorption line blue shift in the liquid was obtained through both the statistical line broadening theory as well as the dynamic adiabatic following method. The pronounced difference between the results from the static and dynamic models is attributed to the dynamic Jahn-Teller effect that takes places in the electronically excited state within the dephasing time of 150 fs. Transient non-thermalized liquid surroundings near He may contribute to an artificial reduction in the absorption line blue shift by up to 30 cm.

Fiedler, Steven L.; Eloranta, Jussi

2014-03-01

137

Ground-state valency and spin configuration of the nickelates.  

NASA Astrophysics Data System (ADS)

The ab initio self-interaction-corrected local-spin-density approximation is used to study the electronic structure of both stoichiometric and non-stoichiometric nickelates. From total energy considerations it emerges that, in their ground-state, both LiNiO2, and NaNiO2 are insulators, with the Ni ion in the Ni^3+ low spin state (t2g^6eg^1) configuration. We find that the substitution of Li/Na atoms by divalent impurities, drives an equivalent number of Ni ions in the NiO2 layers from the JT-active trivalent low-spin state to the divalent JT-inactive state. We propose that an experimental study on MgxNa1-xNiO2 might clarify the role of Ni^2+ impurities with respect to the vanishing of long range orbital ordering in Li1-xNi1+xO2. (Work sponsored by the Laboratory Directed Research and Development Program (LDRD) program of ORNL (LP, GMS, TE), and by the DOE-OS through the Offices of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering (LP, GMS, TE). Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the Department of Energy under Contract No. DE-AC05-00OR22725.)

Petit, Leon; Stocks, George M.; Egami, Takeshi; Szotek, Zdzislawa; Temmerman, Walter M.

2006-03-01

138

Fisher-like atomic divergences: Mathematical grounds and physical applications  

NASA Astrophysics Data System (ADS)

Two different local divergence measures, the Fisher (FD) and the Jensen-Fisher (JFD) ones, are compared in this work by applying them to atomic one-particle densities in position and momentum spaces. They are defined in terms of the absolute and the relative Fisher information functionals. The analysis here afforded includes not only neutral atoms, but also singly-charged cations. The results are interpreted and justified according to (i) shell-filling patterns, (ii) short- and long-range behaviors of the atomic densities, and (iii) the value of the atomic ionization potential. The strengths of the FD measure, as compared to the JFD one, are emphasized.

Martín, A. L.; Angulo, J. C.; Antolín, J.

2013-11-01

139

Nanoscale atoms in solid-state chemistry.  

PubMed

We describe a solid-state material formed from binary assembly of atomically precise molecular clusters. [Co6Se8(PEt3)6][C60]2 and [Cr6Te8(PEt3)6][C60]2 assembled into a superatomic relative of the cadmium iodide (CdI2) structure type. These solid-state materials showed activated electronic transport with activation energies of 100 to 150 millielectron volts. The more reducing cluster Ni9Te6(PEt3)8 transferred more charge to the fullerene and formed a rock-salt-related structure. In this material, the constituent clusters are able to interact electronically to produce a magnetically ordered phase at low temperature, akin to atoms in a solid-state compound. PMID:23744780

Roy, Xavier; Lee, Chul-Ho; Crowther, Andrew C; Schenck, Christine L; Besara, Tiglet; Lalancette, Roger A; Siegrist, Theo; Stephens, Peter W; Brus, Louis E; Kim, Philip; Steigerwald, Michael L; Nuckolls, Colin

2013-07-12

140

On the ground state of Yang-Mills theory  

SciTech Connect

Highlights: > The ground state overlap for sets of meson potential trial states is measured. > Non-uniform gluonic distributions are probed via Wilson loop operator. > The locally UV-regulated flux-tube operators can optimize the ground state overlap. - Abstract: We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state overlap.

Bakry, Ahmed S., E-mail: abakry@physics.adelaide.edu.au [Special Research Center for the Subatomic Structure of Matter, Department of Physics, University of Adelaide, South Australia 5005 (Australia); Leinweber, Derek B.; Williams, Anthony G. [Special Research Center for the Subatomic Structure of Matter, Department of Physics, University of Adelaide, South Australia 5005 (Australia)

2011-08-15

141

Coherent structures in the ground state of the quantum Frenkel-Kontorova model  

SciTech Connect

We study the quantum ground state of the Frenkel-Kontorova model in the strongly nonlinear'' regime in which in the corresponding classical limit the coordinates of the atoms are distributed on Cantori.'' We identify (many) quasidegenerate configurations that contribute to the quantum ground state. When the characteristic quantum and classical energy scales are roughly equal (the intermediate'' quantum regime), we find, consistent with earlier numerical studies, that the standard map'' determining the coordinates in the classical ground state is renormalized to an effective sawtooth'' map, which determines the expectation values of the coordinates in the quantum ground state. We also discuss the dynamics of the model and estimate the characteristic time for various quantum tunneling effects.

Berman, G.P.; Bulgakov, E.N. (Center for Nonlinear Studies, MS-B258, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) Kirensky Institute of Physics, Research Educational Center for Nonlinear Processes at Krasnoyarsk Technical University, Theoretical Department at Krasnoyarsk State University, 660036, Krasnoyarsk (Russian Federation)); Campbell, D.K. (Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States))

1994-03-15

142

Ground states of spin-3 Bose-Einstein condensates for conserved magnetization  

SciTech Connect

We calculate the ground states and ground state phase diagrams of Bose-Einstein condensates of spin-3 atoms under the assumption of conserved magnetization. We especially concentrate on the ground states of a {sup 52}Cr condensate. In {sup 52}Cr the magnetic dipole-dipole interaction enables magnetization changing collisions, but in a strong magnetic field these are suppressed. In the calculation of the phase diagrams we neglect the contribution from the dipole-dipole interaction, but discuss its effects at the end of the paper. We show that the ground state of a {sup 52}Cr condensate does not seem to depend on whether or not the dipole-dipole interaction is taken into attention.

Maekelae, H.; Suominen, K.-A. [Department of Physics, University of Turku, FIN-20014 Turun yliopisto (Finland)

2007-03-15

143

Simulations of Ground and Space-Based Oxygen Atom Experiments  

NASA Technical Reports Server (NTRS)

A low-earth orbit (LEO) materials erosion scenario and the ground-based experiment designed to simulate it are compared using the direct-simulation Monte Carlo (DSMC) method. The DSMC model provides a detailed description of the interactions between the hyperthermal gas flow and a normally oriented flat plate for each case. We find that while the general characteristics of the LEO exposure are represented in the ground-based experiment, multi-collision effects can potentially alter the impact energy and directionality of the impinging molecules in the ground-based experiment. Multi-collision phenomena also affect downstream flux measurements.

Finchum, A. (Technical Monitor); Cline, J. A.; Minton, T. K.; Braunstein, M.

2003-01-01

144

Radio astronomical determination of ground state transition frequencies of CH  

NASA Technical Reports Server (NTRS)

From a comparison of the spectra of CH and other molecules toward the continuum source Cas A and four dark clouds, the ground state transition frequencies of CH have been determined and are reported. The relative errors in these frequencies are about twice as small as those obtained earlier by radio astronomical methods for the two main lines of ground state OH.

Rydbeck, O. E. H.; Ellder, J.; Sume, A.; Hjalmarson, A.; Irvine, W. M.

1974-01-01

145

Theory of Ground State Factorization in Quantum Cooperative Systems  

Microsoft Academic Search

We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective

Salvatore M. Giampaolo; Gerardo Adesso; Fabrizio Illuminati

2008-01-01

146

Calculations of ground-state properties of liquid ⁴He droplets  

Microsoft Academic Search

Quantum mechanical calculations of the ground states of droplets of N atoms of ⁴He are reported. The calculations have been made by the variational Monte Carlo Method for 4< or =N< or =728 and by the Green's function Monte Carlo method for 3< or =N< or =112. The energies, rms radii, and density distributions are reported; liquid-drop fits to the

V. R. Pandharipande; J. G. Zabolitzky; Steven Pieper; R. B. Wiringa; U. Helmbrecht

1983-01-01

147

Lossless anomalous dispersion and an inversionless gain doublet via dressed interacting ground states  

SciTech Connect

Transparent media exhibiting anomalous dispersion have been of considerable interest since Wang, Kuzmich, and Dogariu [Nature 406, 277 (2000)] first observed light propagate with superluminal and negative group velocities without absorption. Here, we propose an atomic model exhibiting these properties, based on a generalization of amplification without inversion in a five-level dressed interacting ground-state system. The system consists of a {Lambda} atom prepared as in standard electromagnetically induced transparency (EIT), with two additional metastable ground states coupled to the {Lambda} atom ground states by two rf-microwave fields. We consider two configurations by which population is incoherently pumped into the ground states of the atom. Under appropriate circumstances, we predict a pair of new gain lines with tunable width, separation, and height. Between these lines, absorption vanishes but dispersion is large and anomalous. The system described here is a significant improvement over other proposals in the anomalous dispersion literature in that it permits additional coherent control over the spectral properties of the anomalous region, including a possible 10{sup 4}-fold increase over the group delay observed by Wang, Kuzmich, and Dogariu.

Weatherall, James Owen [Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Department of Mathematical Sciences, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Department of Logic and Philosophy of Science, University of California Irvine, 3151 Social Science Plaza A, Irvine, California 92697 (United States); Search, Christopher P. [Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States)

2010-02-15

148

Atomic charge state determination by AFM  

Microsoft Academic Search

We investigated the charge state switching of individual gold and silver adatoms on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 Kelvin with oscillation amplitudes in the sub-ångstrom regime. Charging of a gold adatom by one electron charge increased the force on the AFM tip by a few piconewtons. Employing Kelvin

Leo Gross; Fabian Mohn; Peter Liljeroth; Jascha Repp; Franz Giessibl; Gerhard Meyer

2010-01-01

149

Ground water contamination in the United States  

Microsoft Academic Search

This book demonstrates an exhaustive research effort into published reports and legal documents of which 344 are cited. From the literature, the authors selected 84 tables and 41 figures and maps, adding to the value of the collected body of information provided within the text. These summarize and graphically illustrate the 10 major ground water regions, population served by source

R. Patrick; E. Ford; J. Quarles

1987-01-01

150

Gamow-Teller transitions from the 14N ground state to the 14C ground and excited states  

NASA Astrophysics Data System (ADS)

Gamow-Teller transitions from the 14N ground state to the 14C ground and excited states were investigated, based on the model of antisymmetrized molecular dynamics. The calculated strengths for the allowed transitions to the 0+, 1+, and 2+ states of 14C were compared with the experimental data measured by high-resolution charge-exchange reactions. The calculated GT transition to the 21+ state is strong while those to the 02,3+ and 22,3+ states having dominant 2?? excited configurations are relatively weak. The present calculation cannot describe the anonymously long lifetime of 14C, though the strength of the 14C ground state is somewhat suppressed because of the cluster (many-body) correlation in the ground states of 14C and 14N.

Kanada-En'yo, Yoshiko; Suhara, Tadahiro

2014-04-01

151

Colour polymeric paints research under atomic oxygen in flight and ground-based experiments  

NASA Astrophysics Data System (ADS)

Three types of colour coatings were tested to atomic oxygen resistance on ground-based and in-flight experiments. The epoxy enamels colouring change and significant mass losses are observed. The effect of atomic oxygen on silicone enamels almost does not change their colouring and mass. Protection of the epoxy enamels by a layer of silicone varnish increases paints resistance.

Chernik, V. N.; Naumov, S. F.; Sokolova, S. P.; Gerasimova, T. I.; Kurilyonok, A. O.; Poruchikova, Ju. V.; Novikova, V. A.

2003-09-01

152

Dissociative recombination of the ground state of N2(+)  

NASA Technical Reports Server (NTRS)

Large-scale calculations of the dissociative recombination cross sections and rates for the v = 0 level of the N2(+) ground state are reported, and the important role played by vibrationally excited Rydberg states lying both below and above the v = 0 level of the ion is demonstrated. The large-scale electronic wave function calculations were done using triple zeta plus polarization nuclear-centered-valence Gaussian basis sets. The electronic widths were obtained using smaller wave functions, and the cross sections were calculated on the basis of the multichannel quantum defect theory. The DR rate is calculated at 1.6 x 10 to the -7th x (Te/300) to the -0.37 cu cm/sec for Te in the range of 100 to 1000 K, and is found to be in excellent agreement with prior microwave afterglow experiments but in disagreement with recent merged beam results. It is inferred that the dominant mechanism for DR imparts sufficient energy to the product atoms to allow for escape from the Martian atmosphere.

Guberman, Steven L.

1991-01-01

153

Wave function microscopy of quasibound atomic states.  

PubMed

In the 1980s Demkov, Kondratovich, and Ostrovsky and Kondratovich and Ostrovsky proposed an experiment based on the projection of slow electrons emitted by a photoionized atom onto a position-sensitive detector. In the case of resonant excitation, they predicted that the spatial electron distribution on the detector should represent nothing else but a magnified image of the projection of a quasibound electronic state. By exciting lithium atoms in the presence of a static electric field, we present in this Letter the first experimental photoionization wave function microscopy images where signatures of quasibound states are evident. Characteristic resonant features, such as (i) the abrupt change of the number of wave function nodes across a resonance and (ii) the broadening of the outer ring of the image (associated with tunneling ionization), are observed and interpreted via wave packet propagation simulations and recently proposed resonance tunneling mechanisms. The electron spatial distribution measured by our microscope is a direct macroscopic image of the projection of the microscopic squared modulus of the electron wave that is quasibound to the atom and constitutes the first experimental realization of the experiment proposed 30 years ago. PMID:23683194

Cohen, S; Harb, M M; Ollagnier, A; Robicheaux, F; Vrakking, M J J; Barillot, T; Lépine, F; Bordas, C

2013-05-01

154

Wave Function Microscopy of Quasibound Atomic States  

NASA Astrophysics Data System (ADS)

In the 1980s Demkov, Kondratovich, and Ostrovsky and Kondratovich and Ostrovsky proposed an experiment based on the projection of slow electrons emitted by a photoionized atom onto a position-sensitive detector. In the case of resonant excitation, they predicted that the spatial electron distribution on the detector should represent nothing else but a magnified image of the projection of a quasibound electronic state. By exciting lithium atoms in the presence of a static electric field, we present in this Letter the first experimental photoionization wave function microscopy images where signatures of quasibound states are evident. Characteristic resonant features, such as (i) the abrupt change of the number of wave function nodes across a resonance and (ii) the broadening of the outer ring of the image (associated with tunneling ionization), are observed and interpreted via wave packet propagation simulations and recently proposed resonance tunneling mechanisms. The electron spatial distribution measured by our microscope is a direct macroscopic image of the projection of the microscopic squared modulus of the electron wave that is quasibound to the atom and constitutes the first experimental realization of the experiment proposed 30 years ago.

Cohen, S.; Harb, M. M.; Ollagnier, A.; Robicheaux, F.; Vrakking, M. J. J.; Barillot, T.; Lépine, F.; Bordas, C.

2013-05-01

155

Decay of the {sup 12}O ground state  

SciTech Connect

The previously measured decay of the ground state of {sup 12}O was reanalyzed based on new experimental and theoretical results for the ground state of {sup 11}N. In the previous analysis no evidence for diproton emission was found and the measured large decay width was inconsistent with sequential proton decay via the intermediate system of {sup 11}N. The recent results on {sup 11}N show evidence that the ground state of {sup 11}N is at substantially lower energy allowing for a consistent explanation of the two-proton decay of {sup 12}O in terms of sequential proton emission. {copyright} {ital 1998} {ital The American Physical Society}

Azhari, A.; Kryger, R.A.; Thoennessen, M. [National Superconducting Cyclotron Laboratory and Department of Physics Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)] [National Superconducting Cyclotron Laboratory and Department of Physics Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)

1998-10-01

156

Atomic charge state determination by AFM  

NASA Astrophysics Data System (ADS)

We investigated the charge state switching of individual gold and silver adatoms on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 Kelvin with oscillation amplitudes in the sub-ångstrom regime. Charging of a gold adatom by one electron charge increased the force on the AFM tip by a few piconewtons. Employing Kelvin probe force microscopy (KPFM) we also measured the local contact potential difference (LCPD) as a function of the tip height above differently charged adatoms. We observed that the LCPD is shifted depending on the sign of the charge and allows the discrimination of positively charged, neutral, and negatively charged atoms. [L. Gross, et al., Science 324, 1428 (2009)

Gross, Leo; Mohn, Fabian; Liljeroth, Peter; Repp, Jascha; Giessibl, Franz; Meyer, Gerhard

2010-03-01

157

Dimerized ground state in the one-dimensional spin-1 boson Hubbard model  

SciTech Connect

We have investigated the one-dimensional spin-1 boson Hubbard model with antiferromagnetic interactions using quantum Monte Carlo methods. We obtain the shapes of the two lowest Mott lobes and show that the ground state within the lowest Mott lobe is dimerized. The results presented here are relevant for optically trapped antiferromagnetic spin-1 bosons. An experimental signature of the dimerized ground state is modulated Bragg peaks in the noise distribution of the atomic cloud obtained after switching off the trap. These Bragg peaks are located at wave vectors corresponding to half-integer multiples of the reciprocal wave vector of the optical lattice.

Apaja, Vesa; Syljuaasen, Olav F. [Institut fuer Theoretische Physik, Johannes-Kepler Universitaet, A-4040 Linz (Austria); Nordita, Blegdamsvej 17, DK-2100, Copenhagen O (Denmark)

2006-09-15

158

Inhibition of TGF? signaling promotes ground state pluripotency.  

PubMed

Embryonic stem (ES) cells are considered to exist in a ground state if shielded from differentiation triggers. Here we show that FGF4 and TGF? signaling pathway inhibitors, designated R2i, not only provide the ground state pluripotency in production and maintenance of naïve ES cells from blastocysts of different mouse strains, but also maintain ES cells with higher genomic integrity following long-term cultivation compared with the chemical inhibition of the FGF4 and GSK3 pathways, known as 2i. Global transcriptome analysis of the ES cells highlights augmented BMP4 signaling pathway. The crucial role of the BMP4 pathway in maintaining the R2i ground state pluripotency is demonstrated by BMP4 receptor suppression, resulting in differentiation and cell death. In conclusion, by inhibiting TGF? and FGF signaling pathways, we introduce a novel defined approach to efficiently establish the ground state pluripotency. PMID:24036899

Hassani, Seyedeh-Nafiseh; Totonchi, Mehdi; Sharifi-Zarchi, Ali; Mollamohammadi, Sepideh; Pakzad, Mohammad; Moradi, Sharif; Samadian, Azam; Masoudi, Najmehsadat; Mirshahvaladi, Shahab; Farrokhi, Ali; Greber, Boris; Araúzo-Bravo, Marcos J; Sabour, Davood; Sadeghi, Mehdi; Salekdeh, Ghasem Hosseini; Gourabi, Hamid; Schöler, Hans R; Baharvand, Hossein

2014-02-01

159

Multidomain and ground state configurations of two-phase vesicles  

PubMed Central

A simple model is used to study the equilibrium of lipid domains on two-phase vesicles. Two classes of configurations are considered: multidomain and ground state configurations. For multidomain configurations, the vesicle has a finite number of identical lipid domains. For ground state configurations, the vesicle is fully phase separated into two coexisting domains. Whereas the volume enclosed by a vesicle with multidomains is fixed, the volume enclosed by a vesicle in a ground state is allowed to vary with the osmotic pressure. Guided by experimental observations, all domains are assumed to be spherical caps. In a multidomain configuration, the line tension is found to decrease with the number of domains present, with possible exceptions when the number of domains is very small. The importance of a critical osmotic pressure and a critical excess radius on ground state configurations is explored. Emphasis is placed on understanding the variations of these critical quantities with relevant parameters.

Maleki, Mohsen; Fried, Eliot

2013-01-01

160

Ground state asymptotics of a dilute, rotating gas  

NASA Astrophysics Data System (ADS)

We investigate the ground state properties of a gas of interacting particles confined in an external potential in three dimensions and subject to rotation around an axis of symmetry. We consider the Gross-Pitaevskii (GP) limit of a dilute gas. Analysing both the absolute and the bosonic ground states of the system, we show, in particular, their different behaviour for a certain range of parameters. This parameter range is determined by the question whether the rotational symmetry in the minimizer of the GP functional is broken or not. For the absolute ground state, we prove that in the GP limit a modified GP functional depending on density matrices correctly describes the energy and reduced density matrices, independent of symmetry breaking. For the bosonic ground state this holds true if and only if the symmetry is unbroken.

Seiringer, Robert

2003-09-01

161

Approximating the ground state of gapped quantum spin systems  

SciTech Connect

We consider quantum spin systems defined on finite sets V equipped with a metric. In typical examples, V is a large, but finite subset of Z{sup d}. For finite range Hamiltonians with uniformly bounded interaction terms and a unique, gapped ground state, we demonstrate a locality property of the corresponding ground state projector. In such systems, this ground state projector can be approximated by the product of observables with quantifiable supports. In fact, given any subset {chi} {contained_in} V the ground state projector can be approximated by the product of two projections, one supported on {chi} and one supported on {chi}{sup c}, and a bounded observable supported on a boundary region in such a way that as the boundary region increases, the approximation becomes better. Such an approximation was useful in proving an area law in one dimension, and this result corresponds to a multi-dimensional analogue.

Michalakis, Spyridon [Los Alamos National Laboratory; Hamza, Eman [NON LANL; Nachtergaele, Bruno [NON LANL; Sims, Robert [NON LANL

2009-01-01

162

Ground-state properties of the periodic Anderson model  

NASA Technical Reports Server (NTRS)

The ground-state energy, hybridization matrix element, local moment, and spin-density correlations of a one-dimensional, finite-chain, periodic, symmetric Anderson model are obtained by numerical simulations and compared with perturbation theory and strong-coupling results. It is found that the local f-electron spins are compensated by correlation with other f-electrons as well as band electrons leading to a nonmagnetic ground state.

Blankenbecler, R.; Fulco, J. R.; Gill, W.; Scalapino, D. J.

1987-01-01

163

Ground state description of bound polarons in parabolic quantum wires  

Microsoft Academic Search

:   The Feynman-Haken variational path integral theory is, for the first time, generalized to calculate the ground-state energy\\u000a of an electron coupled simultaneously to a Coulomb potential and to a longitudinal-optical (LO) phonon field in parabolic\\u000a quantum wires. It is shown that the polaronic correction to the ground-state energy is more sensitive to the electron-phonon\\u000a coupling constant than the Coulomb

Qinghu Chen; Yuhang Ren; Zhengkuan Jiao; Kelin Wang

1999-01-01

164

Theory of ground state factorization in quantum cooperative systems.  

PubMed

We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range. PMID:18518481

Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

2008-05-16

165

Where is the ground state of 10He?  

NASA Astrophysics Data System (ADS)

We investigated the ground state of 10He by using the method of analytic continuation in the coupling constant with a 8He+ n+ n model. We got a solution of a three-body cluster resonance near to the 8He+ n+ n threshold as the ground state. Its main component is two valence neutrons in the s-orbit ( [s {1}/{2}s {1}/{2}] 0+).

Aoyama, S.

2003-07-01

166

Ground State of the H3+ Molecular Ion: Physics Behind  

NASA Astrophysics Data System (ADS)

Five physics mechanisms of interaction leading to the binding of the H3+ molecular ion are identified. They are realized in a form of variational trial functions, and their respective total energies are calculated. Each of them provides subsequently the most accurate approximation for the Born-Oppenheimer (BO) ground state energy among (two-three-seven)-parametric trial functions being, correspondingly, H2-molecule plus proton (two variational parameters), H2+-ion plus H-atom (three variational parameters), and generalized Guillemin-Zener (seven variational parameters). These trial functions are chosen following a criterion of physical adequacy. They include the electronic correlation in the exponential form, exp(-r12), where - is a variational parameter. Superpositions of two different mechanisms of binding are investigated, and a particular one, which is a generalized Guillemin-Zener plus H2-molecule plus proton (ten variational parameters), provides the total energy at the equilibrium of E = -1.3432 au. The superposition of three mechanisms, generalized Guillemin-Zener plus (H2-molecule plus proton) plus (H2+-ion plus H) (14 parameters) leads to the total energy, which deviates from the best known BO energy to -0.0004 au, it reproduces two-three significant digits in exact, non-BO total energy. In general, our variational energy agrees in two-three-four significant digits with the most accurate results available at present as well as major expectation values.

Turbiner, A. V.; Lopez Vieyra, J. C.

2013-10-01

167

Ground state of the H3(+) molecular ion: physics behind.  

PubMed

Five physics mechanisms of interaction leading to the binding of the H3(+) molecular ion are identified. They are realized in a form of variational trial functions, and their respective total energies are calculated. Each of them provides subsequently the most accurate approximation for the Born–Oppenheimer (BO) ground state energy among (two–three–seven)-parametric trial functions being, correspondingly, H2-molecule plus proton (two variational parameters), H2(+)-ion plus H-atom (three variational parameters), and generalized Guillemin–Zener (seven variational parameters). These trial functions are chosen following a criterion of physical adequacy. They include the electronic correlation in the exponential form, exp(?r12), where ? is a variational parameter. Superpositions of two different mechanisms of binding are investigated, and a particular one, which is a generalized Guillemin–Zener plus H2-molecule plus proton (ten variational parameters), provides the total energy at the equilibrium of E = ?1.3432 au. The superposition of three mechanisms, generalized Guillemin–Zener plus (H2-molecule plus proton) plus (H2(+)-ion plus H) (14 parameters) leads to the total energy, which deviates from the best known BO energy to 0.0004 au, it reproduces two–three significant digits in exact, non-BO total energy. In general, our variational energy agrees in two–three–four significant digits with the most accurate results available at present as well as major expectation values. PMID:23581885

Turbiner, A V; Lopez Vieyra, J C

2013-10-01

168

Concentration for unknown atomic entangled states via cavity decay  

SciTech Connect

We present a physical scheme for entanglement concentration of unknown atomic entangled states via cavity decay. In the scheme, the atomic state is used as a stationary qubit and the photonic state as a flying qubit, and a close maximally entangled state can be obtained from pairs of partially entangled states probabilistically.

Cao Zhuoliang; Yang Ming [School of Physics and Material Science, Anhui University, Hefei, 230039 (China); Zhang Lihua [School of Physics and Material Science, Anhui University, Hefei, 230039 (China); Department of Physics, Anqing Teacher College, Anqing, 246011 (China)

2006-01-15

169

Homogeneous binary trees as ground states of quantum critical Hamiltonians  

SciTech Connect

Many-body states whose wave functions admit a representation in terms of a uniform binary-tree tensor decomposition are shown to obey power-law two-body correlation functions. Any such state can be associated with the ground state of a translationally invariant Hamiltonian which, depending on the dimension of the systems sites, involves at most couplings between third-neighboring sites. Under general conditions it is shown that they describe unfrustrated systems which admit an exponentially large degeneracy of the ground state.

Silvi, P. [International School for Advanced Studies (SISSA), Via Bonomea 265, I-34136 Trieste (Italy); Giovannetti, V. [NEST, Scuola Normale Superiore and Istituto di Nanoscienze-CNR, I-56127 Pisa (Italy); Montangero, S. [Institut fuer Quanteninformationsverarbeitung, Universitaet Ulm, D-89069 Ulm (Germany); Rizzi, M.; Cirac, J. I. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Fazio, R. [NEST, Scuola Normale Superiore and Istituto di Nanoscienze-CNR, I-56127 Pisa (Italy); Center for Quantum Technologies, National University of Singapore, 119077 (Singapore)

2010-06-15

170

Estimation of ground state pentaquark masses  

NASA Astrophysics Data System (ADS)

Permutation groups are applied to analyze the symmetries of multiquark systems and wave functions of pentaquark states are constructed systematically in the language of Yamanouchi basis. We estimate the mass of baryons in the constituent quark model with one-gluon-exchange interaction, assuming that baryons consist of the q3 component as well as the q4/line q pentaquark component.

Xu, K.; Ritjoho, N.; Srisuphaphon, S.; Yan, Y.

2014-04-01

171

Electronic excited-state energies from a linear response theory based on the ground-state two-electron reduced density matrix.  

PubMed

Ground-state two-particle reduced density matrices (2-RDMs) are used to calculate excited-state energy spectra. Solving the Schrodinger equation for excited states dominated by single excitations from the ground-state wavefunction requires the ground-state 2- and 3-RDMs. The excited states, however, can be obtained without a knowledge of the ground-state 3-RDM by two methods: (i) cumulant expansion methods which build the 3-RDM from the 2-RDM, and (ii) double commutator methods which eliminate the 3-RDM. Previous work [Mazziotti, Phys. Rev. A 68, 052501 (2003)] examined the accuracy of excited states extracted from ground-state 2-RDMs, which were calculated by full configuration interaction or the variational 2-RDM method. In this work we employ (i) advances in semidefinite programming to treat the excited states of water and hydrogen fluoride and chains of hydrogen atoms, and (ii) the addition of partial three-particle N-representability conditions to compute more accurate ground-state 2-RDMs. With the hydrogen chains we examine the metal-to-insulator transition as measured by the band gap (the difference between the ground-state and the first excited-state energies), which is difficult for excited-state methods to capture. PMID:18361556

Greenman, Loren; Mazziotti, David A

2008-03-21

172

High-speed ground transportation development outside United States  

SciTech Connect

This paper surveys the state of high-speed (in excess of 200 km/h) ground-transportation developments outside the United States. Both high-speed rail and Maglev systems are covered. Many vehicle systems capable of providing intercity service in the speed range 200--500 km/h are or will soon be available. The current state of various technologies, their implementation, and the near-term plans of countries that are most active in high-speed ground transportation development are reported.

Eastham, T.R. [Queen`s Univ., Kingston, Ontario (United Kingdom)

1995-09-01

173

Magnetic field induced lattice ground states from holography  

NASA Astrophysics Data System (ADS)

We study the holographic field theory dual of a probe SU(2) Yang-Mills field in a background (4 + 1)-dimensional asymptotically Anti-de Sitter space. We find a new ground state when a magnetic component of the gauge field is larger than a critical value. The ground state forms a triangular Abrikosov lattice in the spatial directions perpendicular to the magnetic field. The lattice is composed of superconducting vortices induced by the condensation of a charged vector operator. We perform this calculation both at finite temperature and at zero temperature with a hard wall cutoff dual to a confining gauge theory. The study of this state may be of relevance to both holographic condensed matter models as well as to heavy ion physics. The results shown here provide support for the proposal that such a ground state may be found in the QCD vacuum when a large magnetic field is present.

Bu, Yan-Yan; Erdmenger, Johanna; Shock, Jonathan P.; Strydom, Migael

2013-03-01

174

Electronic structure of azobenzene: ground and first excited singlet states  

Microsoft Academic Search

QMC techniques are used to obtain energies at selected points on the potential energy surfaces of a photoswitchable molecule, azobenzene (AB), along the torsion pathway (CNNC dihedral angle), in the ground and first excited singlet states. We study the excitation energies of well separable cis- and trans-conformers, and th Inst. Phys., Slovak Acad. Scie energy of the transition state located

Matus Dubecky; Rene Derian; Lubos Mitas; Ivan Stich

2010-01-01

175

Analytical ground state for the Jaynes-Cummings model with ultrastrong coupling  

SciTech Connect

We present a generalized variational method to analytically obtain the ground-state properties of the Jaynes-Cummings model with the ultrastrong coupling. An explicit expression for the ground-state energy, which agrees well with the numerical simulation in a wide range of the experimental parameters, is given. In particular, the introduced method can successfully solve this Jaynes-Cummings model with the positive detuning (the atomic resonant level is larger than the photon frequency), which cannot be treated in the adiabatical approximation and the generalized rotating-wave approximation. Finally, we also demonstrate analytically how to control the mean photon number by means of the current experimental parameters including the photon frequency, the coupling strength, and especially the atomic resonant level.

Zhang Yuanwei [State Key Laboratory of Quantum Optics and Quantum Optics Devices, College of Physics and Electronic Engineering, Shanxi University, Taiyuan 030006 (China); Institute of Theoretical Physics, Shanxi University, Taiyuan 030006 (China); Chen Gang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, College of Physics and Electronic Engineering, Shanxi University, Taiyuan 030006 (China); Department of Physics, Shaoxing University, Shaoxing 312000 (China); Yu Lixian; Liang Qifeng [Department of Physics, Shaoxing University, Shaoxing 312000 (China); Liang, J.-Q. [Institute of Theoretical Physics, Shanxi University, Taiyuan 030006 (China); Jia Suotang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, College of Physics and Electronic Engineering, Shanxi University, Taiyuan 030006 (China)

2011-06-15

176

First Measurements of Hollow Lithium States Produced by Triple Excitation of Laser-Excited Lithium Atoms  

Microsoft Academic Search

Hollow lithium atoms are usually formed(L. Kiernan et al., Phys. Rev. Lett. 72), 2359(1994). ^2Y. Azuma et al., Phys. Rev. Lett. 74, 3770(1995). ^3L. Journel et al., Phys. Rev. Lett. 76, 30(1996).-3 by simultaneous three electron excitations of lithium atoms in the ground state. Combining the use of a cw dye laser with the highly monochromatic beam of synchrotron radiation

Francois Wuilleumier; Denis Cubaynes; Segolene Diehl; Jean-Marc Bizau; Bruno Rouvellou; Loic Journel; Samir Al Moussalami; Nora Berrah; L. Voky; P. Faucher; A. Hibbert; T. J. Morgan; E. T. Kennedy; C. Blanchard; J. D. Bozek; A. S. Schlachter

1996-01-01

177

Solving Quantum Ground-State Problems with Nuclear Magnetic Resonance  

PubMed Central

Quantum ground-state problems are computationally hard problems for general many-body Hamiltonians; there is no classical or quantum algorithm known to be able to solve them efficiently. Nevertheless, if a trial wavefunction approximating the ground state is available, as often happens for many problems in physics and chemistry, a quantum computer could employ this trial wavefunction to project the ground state by means of the phase estimation algorithm (PEA). We performed an experimental realization of this idea by implementing a variational-wavefunction approach to solve the ground-state problem of the Heisenberg spin model with an NMR quantum simulator. Our iterative phase estimation procedure yields a high accuracy for the eigenenergies (to the 10?5 decimal digit). The ground-state fidelity was distilled to be more than 80%, and the singlet-to-triplet switching near the critical field is reliably captured. This result shows that quantum simulators can better leverage classical trial wave functions than classical computers

Li, Zhaokai; Yung, Man-Hong; Chen, Hongwei; Lu, Dawei; Whitfield, James D.; Peng, Xinhua; Aspuru-Guzik, Alan; Du, Jiangfeng

2011-01-01

178

Ground State Misidentification in Superconducting Qubits  

NASA Astrophysics Data System (ADS)

To achieve fault tolerant quantum computation, it is necessary to maximize measurement fidelity and minimize readout-induced measurement errors. A new protocol was developed to measure P1(|g>), the probability of measuring the excited state without exciting the qubit, while not including stray tunneling present in superconducting phase qubits. We have confirmed the expected trend in P1(|g>) with device temperature. We then compared P1(|g>) for phase qubits with different readout mechanisms and found that it is ˜3% for our dispersive readout scheme and ˜1.5% for our prior SQUID-based readout scheme. We have further applied microwave power to the flux bias and microwave drive lines to understand the source of this difference.

Wenner, James; Chen, Y.; Kelly, J.; Wang, H.; Lucero, E.; Chiaro, B.; Barends, R.; Lenander, M.; Mariantoni, M.; Megrant, A.; Neill, C.; O'Malley, P.; Roushan, P.; Sank, D.; Vainsencher, A.; White, T.; Yin, Y.; Zhao, J.; Cleland, A. N.; Martinis, John M.

2012-02-01

179

Nuclear Ground State Spins of the Francium Isotopes 208-213, 220-222Fr  

Microsoft Academic Search

The nuclear ground state spins of some francium isotopes have been measured using on-line atomic-beam magnetic resonance techniques. The following results have been obtained: 208Fr I = 7, 209Fr I = 9\\/2, 210Fr I = 6, 211Fr I = 9\\/2, 212Fr I = 5, 213Fr I = 9\\/2, 220Fr I = 1, 221Fr I = 5\\/2 and 222Fr I =

C. Ekström; S. Ingelman; G. Wannberg; M. Skarestad

1978-01-01

180

Preparation of multi-atom cluster state and teleportation of arbitrary two-atom state via thermal cavity  

NASA Astrophysics Data System (ADS)

We propose one cavity QED (CQED) scheme for generating an arbitrary 2-level-atom cluster state. Besides, by using a 4-atom cluster state as quantum channel, we propose another CQED scheme for teleporting any unknown two-atom state. In both schemes, the dynamics processes are essentially quite similar. The Rabi frequency of the classical driving field is much bigger than the detuning between the atoms and the cavity. Hence both schemes are insensitive to the cavity decay. The necessary time for implementation is much shorter than the Rydberg-atom lifespan, therefore atom decays do not need to be considered. Moreover, in the teleportation scheme the discrimination of the 16 mutually orthogonal 4-atom cluster states is transformed into the discrimination of single-atom product states, consequently the discrimination difficulty is degraded and the scheme is more easily implemented.

Zhang, Wen; Liu, Yi-min; Wang, Zhang-yin; Zhang, Zhan-jun

2008-09-01

181

Effect of adiabatic phonons on striped and homogeneous ground states  

NASA Astrophysics Data System (ADS)

The effects of adiabatic phonons on a spin-fermion model for high Tc cuprates are studied using numerical simulations. In the absence of electron-phonon interactions (EPI), stripes in the ground state are observed [C. Buhler, S. Yunoki, and A. Moreo, Phys. Rev. Lett. 84, 2690 (2000); Phys. Rev. B. 62, R3620 (2000)] for certain dopings while homogeneous states are stabilized in other regions of parameter space. Different modes of adiabatic phonons are added to the Hamiltonian: breathing, shear, and half-breathing modes. Diagonal and off-diagonal electron-phonon couplings are considered. It is observed that strong diagonal EPI generate stripes in previously homogeneous states, while in striped ground states an increase in the diagonal couplings tends to stabilize the stripes, inducing a gap in the density of states (DOS) and rendering the ground state insulating. The off-diagonal terms, on the other hand, destabilize the stripes creating inhomogeneous ground states with a pseudogap at the chemical potential in the DOS. The breathing mode stabilizes static diagonal stripes; while the half-breathing (shear) modes stabilize dynamical (localized) vertical and horizontal stripes. The EPI induces decoherence of the quasiparticle peaks in the spectral functions.

Yildirim, Yucel; Moreo, Adriana

2005-10-01

182

All-optical scheme for strongly enhanced production of a Bose-Einstein condensate of dipolar molecules in the vibronic ground state  

SciTech Connect

We consider two-color heteronuclear photoassociation of a dual-species Bose-Einstein condensate into a Bose-Einstein condensate of dipolar molecules in the J=1 vibronic ground state, where a free-ground laser couples atoms directly to the ground state and a free-bound laser couples the atoms to an electronically excited state. This problem raises an interest because heteronuclear photoassociation from atoms to near-ground-state molecules is limited by the small size of the target state. Nevertheless, the addition of the electronically excited state creates a second pathway for creating molecules in the vibronic ground state, leading to quantum interference between direct photoassociation and photoassociation via the excited molecular state, as well as a dispersivelike shift of the free-ground resonance position. Using LiNa as an example, these results are shown to depend on the detuning and intensity of the free-bound laser, as well as the semiclassical size of both molecular states. Whereas strong enhancement enables saturation of the free-ground transition, coherent conversion from a two-species condensate of atoms to a condensate of dipolar molecules in the vibronic ground state is only possible for a limited range of free-bound detunings near resonance.

Mackie, Matt [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Debrosse, Catherine [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Biology, Temple University, Philadelphia, Pennsylvania 19122 (United States)

2010-04-15

183

Ground-Laboratory to In-Space Atomic Oxygen Correlation for the PEACE Polymers  

NASA Astrophysics Data System (ADS)

The Materials International Space Station Experiment 2 (MISSE 2) Polymer Erosion and Contamination Experiment (PEACE) polymers were exposed to the environment of low Earth orbit (LEO) for 3.95 years from 2001 to 2005. There were forty-one different PEACE polymers, which were flown on the exterior of the International Space Station (ISS) in order to determine their atomic oxygen erosion yields. In LEO, atomic oxygen is an environmental durability threat, particularly for long duration mission exposures. Although space flight experiments, such as the MISSE 2 PEACE experiment, are ideal for determining LEO environmental durability of spacecraft materials, ground-laboratory testing is often relied upon for durability evaluation and prediction. Unfortunately, significant differences exist between LEO atomic oxygen exposure and atomic oxygen exposure in ground-laboratory facilities. These differences include variations in species, energies, thermal exposures and radiation exposures, all of which may result in different reactions and erosion rates. In an effort to improve the accuracy of ground-based durability testing, ground-laboratory to in-space atomic oxygen correlation experiments have been conducted. In these tests, the atomic oxygen erosion yields of the PEACE polymers were determined relative to Kapton H using a radio-frequency (RF) plasma asher (operated on air). The asher erosion yields were compared to the MISSE 2 PEACE erosion yields to determine the correlation between erosion rates in the two environments. This paper provides a summary of the MISSE 2 PEACE experiment; it reviews the specific polymers tested as well as the techniques used to determine erosion yield in the asher, and it provides a correlation between the space and ground-laboratory erosion yield values. Using the PEACE polymers' asher to in-space erosion yield ratios will allow more accurate in-space materials performance predictions to be made based on plasma asher durability evaluation.

Stambler, Arielle H.; Inoshita, Karen E.; Roberts, Lily M.; Barbagallo, Claire E.; de Groh, Kim K.; Banks, Bruce A.

2009-01-01

184

Emergent Structure of Multidislocation Ground States in Curved Crystals  

NASA Astrophysics Data System (ADS)

We study the structural features and underlying principles of multidislocation ground states of a crystalline spherical cap. In the continuum limit where the ratio of crystal size to lattice spacing W/a diverges, dislocations proliferate and ground states approach a characteristic sequence of structures composed of radial grain boundaries ("neutral scars"), extending radially from the boundary and terminating in the bulk. Employing a combination of numerical simulations and asymptotic analysis of continuum elasticity theory, we prove that an energetic hierarchy gives rise to a structural hierarchy, whereby dislocation number and scar number diverge as a/W?0 while scar length and dislocation number per scar become independent of lattice spacing. We characterize a secondary transition occurring as scar length grows, where the n-fold scar symmetry is broken and ground states are characterized by polydisperse, forked-scar morphologies.

Azadi, Amir; Grason, Gregory M.

2014-06-01

185

Josephson Junction with a Magnetic-Field Tunable Ground State  

NASA Astrophysics Data System (ADS)

We consider an asymmetric 0-? Josephson junction consisting of 0 and ? regions of different lengths L0 and L?. As predicted earlier this system can be described by an effective sine-Gordon equation for the spatially averaged phase ? so that the effective current-phase relation of this system includes a negative second harmonic ?sin?(2?). If its amplitude is large enough, the ground state of the junction is doubly degenerate ?=±?, where ? depends on the amplitudes of the first and second harmonics. We study the behavior of such a junction in an applied magnetic field H and demonstrate that H induces an additional term ?Hcos?? in the effective current-phase relation. This results in a nontrivial ground state tunable by magnetic field. The dependence of the critical current on H allows for revealing the ground state experimentally.

Goldobin, E.; Koelle, D.; Kleiner, R.; Mints, R. G.

2011-11-01

186

Emergent structure of multidislocation ground States in curved crystals.  

PubMed

We study the structural features and underlying principles of multidislocation ground states of a crystalline spherical cap. In the continuum limit where the ratio of crystal size to lattice spacing W/a diverges, dislocations proliferate and ground states approach a characteristic sequence of structures composed of radial grain boundaries ("neutral scars"), extending radially from the boundary and terminating in the bulk. Employing a combination of numerical simulations and asymptotic analysis of continuum elasticity theory, we prove that an energetic hierarchy gives rise to a structural hierarchy, whereby dislocation number and scar number diverge as a/W?0 while scar length and dislocation number per scar become independent of lattice spacing. We characterize a secondary transition occurring as scar length grows, where the n-fold scar symmetry is broken and ground states are characterized by polydisperse, forked-scar morphologies. PMID:24949777

Azadi, Amir; Grason, Gregory M

2014-06-01

187

Probing quantum frustrated systems via factorization of the ground state.  

PubMed

The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures. PMID:20867055

Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

2010-05-21

188

Protocol for Atomic Oxygen Testing of Materials in Ground-Based Facilities. No. 2  

NASA Technical Reports Server (NTRS)

A second version of standard guidelines is proposed for improving materials testing in ground-based atomic oxygen environments for the purpose of predicting the durability of the tested materials in low Earth orbit (LEO). Accompanying these guidelines are background information and notes about testing. Both the guidelines and the additional information are intended to aid users who wish to evaluate the potential hazard of atomic oxygen in LEO to a candidate space component without actually flying the component in space, and to provide a framework for more consistent atomic oxygen testing in the future.

Minton, Timothy K.

1995-01-01

189

Ground state alignment as a tracer of interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We demonstrate a new way of studying interplanetary magnetic field -- spectropolarimetry based on ground state alignment. Ground state alignment is a new promising way of sub-gausian magnetic fields in radiation-dominated environment. The polarization of spectral lines that are pumped by the anisotropic radiation from the sun is influenced by the magnetic alignment, which happens for sub-gausian magnetic field. As a result, the linear polarization becomes an excellent tracer of the embedded magnetic field. The method is illustrated by our synthetic obser- vation of the Jupiter's Io and comet Halley. A uniform density distribution of Na was considered and polar- ization at each point was then constructed. Both spa- tial and temporal variations of turbulent magnetic field can be traced with this technique as well. Instead of sending thousands of space probes, ground state alignment allows magnetic mapping with any ground telescope facilities equipped with spectrometer and polarimeter. For remote regions like the the boundary of interstellar medium, ground state alignment provides a unique diagnostics of magnetic field, which is crucial for understanding the physical processes such as the IBEX ribbons.

Yan, H.

2012-12-01

190

Rydberg States of Atoms and Molecules  

NASA Astrophysics Data System (ADS)

List of contributors; Preface; 1. Rydberg atoms in astrophysics A. Dalgarno; 2. Theoretical studies of hydrogen Rydberg atoms in electric fields R. J. Damburg and V. V. Kolosov; 3. Rydberg atoms in strong fields D. Kleppner, Michael G. Littman and Myron L. Zimmerman; 4. Spectroscopy of one- and two-electron Rydberg atoms C. Fabre and S. Haroche; 5. Interaction of Rydberg atoms with blackbody radiation T. F. Gallagher; 6. Theoretical approaches to low-energy collisions of Rydberg atoms with atoms and ions A. P. Hickman, R. E. Olson and J. Pascale; 7. Experimental studies of the interaction of Rydberg atoms with atomic species at thermal energies F. Gounand and J. Berlande; 8. Theoretical studies of collisions of Rydberg atoms with molecules Michio Matsuzawa; 9. Experimental studies of thermal-energy collisions of Rydberg atoms with molecules F. B. Dunning and R. F. Stebbings; 10. High-Rydberg molecules Robert S. Freund; 11. Theory of Rydberg collisions with electrons, ions and neutrals M. R. Flannery; 12. Experimental studies of the interactions of Rydberg atoms with charged particles J. -F. Delpech; 13. Rydberg studies using fast beams Peter M. Koch; Index.

Stebbings, R. F.; Dunning, F. B.

2011-03-01

191

Optimization of Initial State Vector in the Ground State Algorithm of Lattice Fermion Simulations  

NASA Astrophysics Data System (ADS)

Quantum simulation algorithm for the lattice fermions in the ground state is examined. Initial trial state is optimized using the unrestricted Hartree Fock solution. Convergence to the ground state average in the projection process is compared among several choices of the trial state. The optimized trial state provides a faster convergence for physical quantities as well as a better minus sign ratio in the sampling.

Furukawa, Nobuo; Imada, Masatoshi

1991-11-01

192

Ground state microstructure of a ferrofluid thin layer  

SciTech Connect

Using a fine weave of theoretical analysis and computer simulations, we found various aggregates of magnetic single-domain nanoparticles, which can form in a quasi-two-dimensional (q2D) ferrofluid layer at low temperatures. Our theoretical investigation allowed us to obtain exact expressions and their asymptotes for the energies of each configuration. Thus, for ferrofluid q2D layers it proved possible to identify the ground states as a function of the particle number, size, and other system parameters. Our suggested approach can be used for the investigation of ground state structures in systems with more complex interparticle interactions.

Prokopieva, T. A.; Danilov, V. A.; Kantorovich, S. S., E-mail: sofia@icp.uni-stuttgart.de [Ural State University (Russian Federation)

2011-09-15

193

Ground state properties of graphene in Hartree-Fock theory  

NASA Astrophysics Data System (ADS)

We study the Hartree-Fock approximation of graphene in infinite volume, with instantaneous Coulomb interactions. First we construct its translation-invariant ground state and we recover the well-known fact that, due to the exchange term, the effective Fermi velocity is logarithmically divergent at zero momentum. In a second step we prove the existence of a ground state in the presence of local defects and we discuss some properties of the linear response to an external electric field. All our results are non-perturbative.

Hainzl, Christian; Lewin, Mathieu; Sparber, Christof

2012-09-01

194

Conditional quantum phase gate between two 3-state atoms.  

PubMed

We propose a scheme for conditional quantum logic between two 3-state atoms that share a quantum data bus such as a single mode optical field in cavity QED systems, or a collective vibrational state of trapped ions. Making use of quantum interference, our scheme achieves successful conditional phase evolution without any real transitions of atomic internal states or populating the quantum data bus. In addition, it requires only common addressing of the two atoms by external laser fields. PMID:12689256

Yi, X X; Su, X H; You, L

2003-03-01

195

Dark entangled steady states of interacting Rydberg atoms.  

PubMed

We propose a scheme for rapid generation of high fidelity steady-state entanglement between a pair of atoms. A two-photon excitation process toward long-lived Rydberg states with finite pairwise interaction, a dark-state interference effect in the individual atoms, and spontaneous emission from their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly dependent on the Rydberg interaction strength. PMID:23909321

Rao, D D Bhaktavatsala; Mølmer, Klaus

2013-07-19

196

Dark Entangled Steady States of Interacting Rydberg Atoms  

NASA Astrophysics Data System (ADS)

We propose a scheme for rapid generation of high fidelity steady-state entanglement between a pair of atoms. A two-photon excitation process toward long-lived Rydberg states with finite pairwise interaction, a dark-state interference effect in the individual atoms, and spontaneous emission from their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly dependent on the Rydberg interaction strength.

Rao, D. D. Bhaktavatsala; Mølmer, Klaus

2013-07-01

197

Resonant two-photon ionization spectroscopy of jet-cooled UN: Determination of the ground state  

NASA Astrophysics Data System (ADS)

The optical transitions of supersonically cooled uranium nitride (UN) have been investigated in the range from 19 200 to 23 900 cm-1 using resonant two-photon ionization spectroscopy. A large number of bands have been observed, of which seven have been rotationally resolved and analyzed. All are found to arise from the same state, which is presumably the ground state of the molecule. From the analysis of the bands, the ground state has ? = 3.5, with a bond length of 1.7650(12) A?. Comparisons to the known isovalent molecules are made, and the variations in ground state configuration are explained in terms of the configurational reordering that occurs with changes in the nuclear and ligand charges. It is concluded that the UN molecule is best considered as a U3+N3- species in which the closed shell nitride ligand interacts with a U3+ ion. The ground state of the molecule derives from a U3+ ion in its 7s15f 2 atomic configuration.

Matthew, Daniel J.; Morse, Michael D.

2013-05-01

198

Tuning ground states and excitations in complex electronic materials  

SciTech Connect

Modern electronic materials are characterized by a great variety of broken-symmetry ground states and excitations. Their control requires understanding and tuning underlying driving forces of spin-charge-lattice coupling, critical to macroscopic properties and applications. We report representative model calculations which demonstrate some of the richness of the phenomena and the challenges for successful microscopic modeling.

Bishop, A.R.

1996-09-01

199

Ground-State Energy of a Dilute Fermi Gas.  

National Technical Information Service (NTIS)

A large assembly of identical fermions interacting via a repulsive two-body potential is considered, and a series expression for the ground-state energy is developed. All terms preceding those dependent on parameters of three (or more)-particle scattering...

R. F. Bishop

1972-01-01

200

Making Classical Ground State Spin Computing Fault-Tolerant.  

National Technical Information Service (NTIS)

We examine a model of classical deterministic computing in which the ground state of the classical system is a spatial history of the computation. This model is relevant to quantum dot cellular automata as well as to recent universal adiabatic quantum com...

D. Bacon I. Crosson K. R. Brown

2010-01-01

201

Ground state transition for the Heisenberg model with planar anisotropy  

Microsoft Academic Search

The Oguchi method is applied to the Heisenberg ferro- and antiferromagnet with single ion anisotropy for one, two and three dimensions. The obtained ground state magnetization exhibits transitions for the case of planar anisotropy, thus confirming already existing results obtained by other methods.

G. T. Cantieni; R. Schilling

1984-01-01

202

Ground state solutions of asymptotically linear fractional Schrödinger equations  

NASA Astrophysics Data System (ADS)

This paper is devoted to a time-independent fractional Schrödinger equation of the form (-?)su+V(x)u=f(x,u) in RN, where N >= 2, s ? (0, 1), (-?)s stands for the fractional Laplacian. We apply the variational methods to obtain the existence of ground state solutions when f(x, u) is asymptotically linear with respect to u at infinity.

Chang, Xiaojun

2013-06-01

203

Ferromagnetic Pairing Ground States on Two-Coupled Chains  

NASA Astrophysics Data System (ADS)

Recently, ferromagnetic superconductivity was discovered in ZrZn2, UGe2 and URhGe. Microscopic explanation of this phenomenon is a challenge in theoretical physics, but the problem is rather subtle and difficult, since we have to treat rotational symmetry breaking of spin and electron-pair condensation simultaneously. At the present stage, it is expected that a simple concrete model exhibiting both ferromagnetism and electron-pair condensation, even if it has somewhat artificial aspects, will shed some light on understanding of mechanisms of ferromagnetic superconductivity. Here we report an extended Hubbard model on two chains which has fullypolarized pairing ground states. The Hamiltonian consists of intra-chain electron-hopping, on-site repulsion, inter-chain charge attraction and inter-chain ferromagnetic interaction terms. The following is shown in our model. In the case where the on-site repulsion term is vanishing, the model has degenerate ground states in which electrons form spin triplet pairs, and thus the ground states exhibit electron-pair condensation but do not exhibit ferromagnetism. When the on-site repulsion is added, the model has the unique (up to spin degeneracy) ground state in which ferromagnetism and electron-pair condensation coexist. We also present an extension of the model to higher dimensional cases.

Tanaka, Akinori

2008-03-01

204

Ground states of the massless Derezinski-Gerard model  

SciTech Connect

We consider the massless Derezinski-Gerard model introduced by Derezinski and Gerard in 1999. We give a sufficient condition for the existence of a ground state of the massless Derezinski-Gerard model without the assumption that the Hamiltonian of particles has compact resolvent.

Ohkubo, Atsushi [Graduate School of Informatics, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)

2009-11-15

205

Slow-light probe of Fermi pairing through an atom-molecule dark state  

SciTech Connect

We consider the two-color photoassociation of a quantum degenerate atomic gas into ground-state diatomic molecules via a molecular dark state. This process can be described in terms of a {Lambda} level scheme that is formally analogous to the situation in electromagnetically induced transparency in atomic systems and therefore can result in slow-light propagation. We show that the group velocity of the light field depends explicitly on whether the atoms are bosons or fermions, as well as on the existence or absence of a pairing gap in the case of fermions, so that the measurement of the group velocity realizes a nondestructive diagnosis of the atomic state and the pairing gap.

Jing, H. [Department of Physics, Henan Normal University, Xinxiang 453007 (China); B2 Institute, Department of Physics and College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Deng, Y. [Department of Physics, Henan Normal University, Xinxiang 453007 (China); Meystre, P. [B2 Institute, Department of Physics and College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States)

2011-06-15

206

The benzene-argon ground-state intermolecular potential energy surface revisited.  

PubMed

The benzene-Ar ground-state S(0) intermolecular potential energy surface is evaluated using the coupled cluster singles and doubles model including connected triple corrections and the augmented correlation consistent polarized valence triple-zeta basis set extended with a set of 3s3p2d1f1g midbond functions. The surface is characterized by absolute minima of -390.1 cm(-1) where the argon atom is located on the benzene C(6) axis at distances of +/-3.536 A, and has a general shape close to the available ground-state S(0) and the first singlet S(1) and triplet T(1) excited-state surfaces. Using the potential, the intermolecular level structure of the complex is evaluated. The new intermolecular potential energy surface gives very accurate results and improves those previously available. PMID:19354204

Capelo, Silvia Bouzón; Fernández, Berta; Koch, Henrik; Felker, Peter M

2009-04-30

207

Effect of the repulsion interaction on the ground-state of the Kondo lattice model with a superlattice potential  

NASA Astrophysics Data System (ADS)

We investigate the ground-state of a new Kondo lattice model, where the free carriers interact repulsively between them and undergo an external superlattice potential. This model can be simulated with 171Yb atoms confined in optical lattices. We use the density matrix renormalization group method to evaluate the charge and spin gaps, and the structure factors. We found that the ground-state evolves from a Kondo spin liquid state to a charge-gapped antiferromagnetic state with zero spin gap, when the antiferromagnetic exchange increases. Also, we verify that the quantum critical point varies linearly with the repulsion and the exchange.

Silva-Valencia, J.; Franco, R.; Figueira, M. S.

2014-04-01

208

Transitions to Atomic Rydberg States Perturbed by Foreign Gases.  

NASA Astrophysics Data System (ADS)

Collisional interactions of neutral, ground state foreign gases with highly excited atomic states have been experimentally investigated. Transitions to Rydberg states of Na, Rb and Sr are pumped using a tunable dye laser and two-photon excitation techniques. States studied include the 4d('2)D(,J) and 5s('2)S(, 1/2) states of Na, the nd('2)D(,J) and ns('2)S(, 1/2) series of Rb and the 5snd ('1.3)D(,2) and 5sns ('1)S(,0) series of Sr. Absorption lineshapes were recorded while these transitions were collisionally perturbed by various foreign gases. Perturber gases included He, Ar, Kr, Xe and N(,2) at densities that range from 0.05 to 2.5 relative density. Lineshape parameters for energy shift and line broadening have been measured for Na and Rb transitions as functions of principal and angular momentum quantum numbers. The variations of these parameters were also measured as functions of perturber gas species and density. These results were related to the theory of Alekseev and Sobelman which models perturbed lineshapes in terms of independent elastic and inelastic collisional processes. Sr transitions yield more diverse results. For high Rydberg levels (n (GREATERTHEQ) 20) lineshape parameters and the Alekseev -Sobelman theory provide an adequate description of the interaction processes. Intermediate states (12 (LESSTHEQ) n (LESSTHEQ) 20) demonstrate enhanced inelastic processes due to energy level perturbations and complete lineshapes are required for analysis. Low lying transitions (6 (LESSTHEQ) n (LESSTHEQ) 10) have extended absorption lineshapes. Again complete lineshapes are necessary to account for the observed red-wing and satellite structures using the unified theory of Anderson and Talman.

Bruce, Douglas Maitland

209

Entanglement Concentration for Three-Atom W State via Introducing an Auxiliary Atom in Cavity QED  

Microsoft Academic Search

We present two physical schemes for concentrating three-atom W state based on the same interaction model which involves two\\u000a three-level atoms, a cavity field and a classical field. Both schemes introduce only one auxiliary atom. The first scheme\\u000a involves only one measurement. There is one more measurement on the auxiliary atom in the second scheme, but the interaction\\u000a time is

Li-Li Sun; Hong-Fu Wang; Shou Zhang

2011-01-01

210

Measurement-based quantum computer in the gapped ground state of a two-body Hamiltonian.  

PubMed

We propose a scheme for a ground-code measurement-based quantum computer, which enjoys two major advantages. First, every logical qubit is encoded in the gapped degenerate ground subspace of a spin-1 chain with nearest-neighbor two-body interactions, so that it equips built-in robustness against noise. Second, computation is processed by single-spin measurements along multiple chains dynamically coupled on demand, so as to keep teleporting only logical information into a gap-protected ground state of the residual chains after the interactions with spins to be measured are turned off. We describe implementations using trapped atoms or polar molecules in an optical lattice, where the gap is expected to be as large as 0.2 or 4.8 kHz, respectively. PMID:18764096

Brennen, Gavin K; Miyake, Akimasa

2008-07-01

211

Ground Control to Niels Bohr: Exploring Outer Space with Atomic Physics  

Microsoft Academic Search

We provided an introduction to transition state theory and the connections it provides between atomic and celestial physics. We include brief discussions of historical background, recent applications in space mission design, and current research efforts.

Mason A. Porter; Predrag Cvitanovic

2005-01-01

212

Necessary condition for an atom-positron bound state  

SciTech Connect

Following closely a technique due to Lieb [Phys. Rev. Lett. 52, 315 (1984)], a rigorous condition for an atom-positron bound state is derived in terms of the electrostatic Coulomb attractive potential between the positron and the atomic electrons. Further, it is demonstrated that for a joint electron-positron pair density distribution that is spherically symmetric around the nucleus in the positron and/or the electron coordinate, a bound state between a neutral atom and a positron is not possible.

Pathak, R.K. (Department of Physics, University of Poona, Pune-411 007, Maharashtra (India))

1994-06-01

213

Experimental Investigation of Excited-State Lifetimes in Atomic Ytterbium  

SciTech Connect

Lifetimes of 21 excited states in atomic Yb were measured using time-resolved fluorescence detection following pulsed laser excitation. The lifetime of the 4f{sup 14}5d6s {sup 3}D{sub 1} state, which is of particular importance for a proposed study of parity nonconservation in atoms, was measured to be 380(30) ns.

Bowers, C.J.; Budker, D.; Commins, E.D.; DeMille, D.; Freedman, S.J.; Nguyen, A.-T.; Shang, S.-Q.; /UC, Berkeley; Zolotorev, M.; /SLAC

2011-11-15

214

Toward coherent excitation: Development of a single-source pump for the rubidium hyperfine ground state doublet  

NASA Astrophysics Data System (ADS)

Coherent excitation is a phenomenon which, if achieved, could provide a new tool for the investigation of many fundamental questions in atomic physics and quantum optics. A design which could produce such coherences could lead to applications as varied as lasing without inversion and electromagnetically induced transparency. In this thesis, the basic theory concerning the generation of coherent superpositions of the ground states of atomic rubidium is reviewed. Next, the design, construction, and testing of a Littrow-style grating-tuned laser and a standing wave electro-optic modulator used in generating sidebands at the frequency matching the rubidium hyperfine ground state doublet are described. An experiment demonstrating simultaneous absorption by the Rb-85 F = 2 and Rb-85 F = 3 using a single laser as the pump is chronicled. An experiment to test coherences generated by this method of single-source pumping of the ground state doublet is proposed.

Tomme, Edward B.

1994-12-01

215

Variational Calculation of 4He Tetramer Ground and Excited States Using Realistic 4He-4He Potentials  

NASA Astrophysics Data System (ADS)

We calculated binding energies and wave functions of the 4He tetramer ground and excited states employing various realistic 4He-4He potentials which includes the currently most accurate one with the adiabatic, relativistic, QED and residual retardation corrections. We used our Gaussian expansion method (GEM) for ab initio variational calculations of few-body systems. We found that precisely the same shape of the short-range correlation ( r ij < 4Å) in the dimer appear in the ground and excited states of trimer and tetramer. The four kinds of the binding energies of the trimer and tetramer ground and excited states, and , for the different potentials exhibit perfect linear correlations over the range of binding energies relevant for 4He atoms; namely, six types of the generalized atomic Tjon lines were observed.

Hiyama, Emiko; Kamimura, Masayasu

2013-08-01

216

Energy transfer from PO excited states to alkali metal atoms in the phosphorus chemiluminescence flame  

PubMed Central

Phosphorus chemiluminescence under ambient conditions of a phosphorus oxidation flame is found to offer an efficient electronic energy transferring system to alkali metal atoms. The lowest resonance lines, 2P3 / 2,½?2S½, of potassium and sodium are excited by energy transfer when an argon stream at 80°C carrying potassium or sodium atoms intersects a phosphorus vapor stream, either at the flame or in the postflame region. The lowest electronically excited metastable 4IIi state of PO or the (PO[unk]PO)* excimer is considered to be the probable energy donor. The (PO[unk]PO)* excimer results from the interaction of the 4IIi state of one PO molecule with the ground 2IIr state of another. Metastability of the donor state is strongly indicated by the observation of intense sensitized alkali atom fluorescence in the postflame region.

Khan, Ahsan U.

1980-01-01

217

Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states  

SciTech Connect

We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasi-one-dimensional double-well potential within the two-site Bose-Hubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedinger-cat state to a separable Fock state through an atomic coherent regime. By diagonalizing the Bose-Hubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibility {alpha} of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the ground-state energy by employing the Hellmann-Feynman theorem. This result, together with a perturbative calculation of the ground-state energy, allows simple analytical formulas for F and {alpha} to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the Bose-Hubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the region where coherence is lost and self-trapping sets in.

Mazzarella, G.; Toigo, F. [Dipartimento di Fisica 'Galileo Galilei' and Consorzio Nazionale Interuniversitario per la Scienze Fisiche della Materia (CNISM), Universita di Padova, Via Marzolo 8, I-35122 Padova (Italy); Salasnich, L. [Dipartimento di Fisica 'Galileo Galilei' and Consorzio Nazionale Interuniversitario per la Scienze Fisiche della Materia (CNISM), Universita di Padova, Via Marzolo 8, I-35122 Padova (Italy); Istituto Nazionale di Ottica (INO) del Consiglio Nazionale delle Ricerche (CNR), via G. Sansone 1, I-50019 Sesto Fiorentino (Italy); Parola, A. [Dipartimento di Fisica e Matematica and CNISM, Universita dell'Insubria, Via Valleggio 11, I-22100 Como (Italy)

2011-05-15

218

Guidelines for ground motion definition for the eastern United States  

SciTech Connect

Guidelines for the determination of earthquake ground motion definition for the eastern United States are established here. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large- to great-sized earthquakes (M/sub s/ > 7.5) have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes has been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data have been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data, a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the safe shutdown earthquake (SSE). A new procedure for establishing the operating basis earthquake (OBE) is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors. 17 refs., figs., tabs.

Gwaltney, R.C.; Aramayo, G.A.; Williams, R.T.

1985-06-01

219

Boron aggregation in the ground states of boron-carbon fullerenes  

NASA Astrophysics Data System (ADS)

We present unexpected structural motifs for boron-carbon nanocages of the stoichiometries B12C48 and B12C50, based on first-principles calculations. These configurations are distinct from those proposed so far because the boron atoms are not isolated and distributed over the entire surface of the cages, but rather aggregate at one location to form a patch. Our putative ground state of B12C48 is 1.8 eV lower in energy than the previously proposed ground state and violates all the suggested empirical rules for constructing low-energy fullerenes. The B12C50 configuration is energetically even more favorable than B12C48, showing that structures derived from the C60 buckminsterfullerene are not necessarily magic sizes for heterofullerenes.

Mohr, Stephan; Pochet, Pascal; Amsler, Maximilian; Schaefer, Bastian; Sadeghi, Ali; Genovese, Luigi; Goedecker, Stefan

2014-01-01

220

A Note on the Ground State Energy of an Assembly of Interacting Electrons  

PubMed Central

The ground state energy of an assembly of charged particles of density ? imbedded in a continuum of charge of the other sign in an electrically neutral system is considered. Asymptotic formulae for the ground state energy of such systems are known in the high- and low-density regimes. An interpolation formula covering the entire density range is derived using the method of two-point Padé approximants. A phase transition from an electron lettice to an electron gas seems to occur at r3 ? 14, r3 being the radius of a sphere which, on the average, contains a single charge, in units of the Bohr radius of the electron in a hydrogen atom.

Isihara, Akira; Montroll, Elliott W.

1971-01-01

221

A note on the ground state energy of an assembly of interacting electrons.  

PubMed

The ground state energy of an assembly of charged particles of density rho imbedded in a continuum of charge of the other sign in an electrically neutral system is considered. Asymptotic formulae for the ground state energy of such systems are known in the high- and low-density regimes. An interpolation formula covering the entire density range is derived using the method of two-point Padé approximants. A phase transition from an electron lettice to an electron gas seems to occur at r(3) congruent with 14, r(3) being the radius of a sphere which, on the average, contains a single charge, in units of the Bohr radius of the electron in a hydrogen atom. PMID:16591957

Isihara, A; Montroll, E W

1971-12-01

222

Determination of the calcium ground state scattering length by photoassociation spectroscopy at large detunings  

NASA Astrophysics Data System (ADS)

Photoassociation spectroscopy was used to determine the s-wave scattering length of 40Ca atoms in their electronic ground state. Vibrational levels were observed in an extended range of up to 182 GHz below the dissociation limit 4s2 ^1S0 4s4p ^1P1. Thus, the frequency interval was nearly tripled, in which photoassociation was observed compared to previous measurements. The spectra were analyzed by means of quantum mechanical simulations. With the new data it was possible to resolve the discrepancy concerning the ground state scattering length presented in earlier publications [Phys. Rev. A 67, 043408 (2003); Eur. Phys. J. D 26, 155 (2003)]. An improved dipole-dipole coupling constant C_3? = 0.52306(20) × 103 cm-1 nm3 is obtained.

Vogt, F.; Grain, Ch.; Nazarova, T.; Sterr, U.; Riehle, F.; Lisdat, Ch.; Tiemann, E.

2007-07-01

223

High-order time expansion path integral ground state.  

PubMed

The feasibility of path integral Monte Carlo ground state calculations with very few beads using a high-order short-time Green's function expansion is discussed. An explicit expression of the evolution operator which provides dramatic enhancements in the quality of ground-state wave functions is examined. The efficiency of the method makes possible to remove the trial wave function and thus obtain completely model-independent results still with a very small number of beads. If a single iteration of the method is used to improve a given model wave function, the result is invariably a shadow-type wave function, whose precise content is provided by the high-order algorithm employed. PMID:20365502

Rota, R; Casulleras, J; Mazzanti, F; Boronat, J

2010-01-01

224

High-order time expansion path integral ground state  

NASA Astrophysics Data System (ADS)

The feasibility of path integral Monte Carlo ground state calculations with very few beads using a high-order short-time Green’s function expansion is discussed. An explicit expression of the evolution operator which provides dramatic enhancements in the quality of ground-state wave functions is examined. The efficiency of the method makes possible to remove the trial wave function and thus obtain completely model-independent results still with a very small number of beads. If a single iteration of the method is used to improve a given model wave function, the result is invariably a shadow-type wave function, whose precise content is provided by the high-order algorithm employed.

Rota, R.; Casulleras, J.; Mazzanti, F.; Boronat, J.

2010-01-01

225

Continuous Measurement Quantum State Tomography of Atomic Ensembles  

NASA Astrophysics Data System (ADS)

Quantum state tomography is a fundamental tool in quantum information processing tasks. It allows us to estimate the state of a quantum system by measuring different observables on many identically prepared copies of the system. Usually, one makes projective measurements of an "informationally complete" set of observables and repeats them enough times so that good estimates of their expectation values are obtained. This is, in general, a very time-consuming task that requires a large number of measurements. There are, however, systems in which the data acquisition can be done more efficiently. In fact, an ensemble of quantum systems can be prepared and manipulated by external fields while being continuously probed collectively, producing enough information to estimate its state. This provides a basis for continuous measurement quantum tomography, and is the main topic of this dissertation. This method, based on weak continuous measurement, has the advantage of being fast, accurate, and almost nonperturbative. In this work, we present a extensive discussion and a generalization of the protocol proposed in [1], which was experimentally achieved in [2] using cold cesium atoms. In this protocol, an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner so as to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time. To achieve this, we use two different estimation methods: the widely used maximum likelihood and the novel compressed sensing algorithms. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sub-levels of a large-spin alkali atom, 133Cs. We extend the applicability of the protocol in [1] to the more ambitious case of reconstruction of states in the full 16-dimensional electronic-ground subspace ( F = 3, F = 4), controlled by microwaves and radio-frequency magnetic fields. We give detailed derivations of all physical interactions, approximations, numerical methods, and fitting procedures, tailored to the realistic experimental setting. In addition, we numerically study the reconstruction algorithms and determine their applicability and appropriate use. Moreover, in collaboration with the lab of Prof. P. Jessen at the University of Arizona, we present an experimental demonstration of continuous measurement quantum tomography in an ensemble of cold cesium atoms with full control of its 16-dimensional Hilbert space. In this case, we show the exquisite level of control achieved in the lab and the excellent agreement between the theory discussed in this dissertation and the experimental results. This allows us to achieve fidelities > 95% for low complexity quantum states, and > 92% for arbitrary random states, which is a formidable accomplishment for a space of this size. To conclude this work, we study quantum tomography in an abstract system driven by random dynamics and show the conditions for high-fidelity estimation when a single parameter defines the dynamics of the system. This study helps elucidate the reconstruction algorithm and gives rise to interesting questions about the geometry of quantum states.

Riofrio Almeida, Carlos A.

226

Atom-by-atom quantum state control in adatom chains on a semiconductor.  

PubMed

The vertical manipulation of native adatoms on a III-V semiconductor surface was achieved in a scanning tunneling microscope at 5 K. Reversible repositioning of individual In atoms on InAs(111)A allows us to construct one-atom-wide In chains. Tunneling spectroscopy reveals that these chains host quantum states deriving from an adatom-induced electronic state and substantial substrate-mediated coupling. Our results show that the combined approach of atom manipulation and local spectroscopy is capable to explore atomic-scale quantum structures on semiconductor platform. PMID:19792811

Fölsch, Stefan; Yang, Jianshu; Nacci, Christophe; Kanisawa, Kiyoshi

2009-08-28

227

Ground state solutions for the nonlinear Schrödinger–Maxwell equations  

Microsoft Academic Search

In this paper we study the nonlinear Schrödinger–Maxwell equations{??u+V(x)u+?u=|u|p?1uin R3,???=u2in R3. If V is a positive constant, we prove the existence of a ground state solution (u,?) for 2p5. The non-constant potential case is treated for 3p5, and V possibly unbounded below. Existence and nonexistence results are proved also when the nonlinearity exhibits a critical growth.

Antonio Azzollini; A. Pomponio

2008-01-01

228

Relativistic ground state of a hydrogenlike molecular ion  

NASA Astrophysics Data System (ADS)

In this preliminary Brief Report we explore a method for examining relativistic effects in one-electron molecules that avoids the evaluation of multicenter integrals. Here the Dirac equation for a simplified version of the H2+ ion is solved exactly for the ground-state Schrödinger and Dirac energy levels. The model consists of representing the electron-proton Coulomb interaction as a projection operator onto a linear subspace of Hilbert space.

Glasser, M. L.

2014-05-01

229

Electronic Ground State Constants for Molecular Hydrogen and Hydrogen Deuteride  

Microsoft Academic Search

Observed rotational and rotational-vibrational transitions for molecular H2 and HD have been combined to produce best, non-linear least-squares fits to a set of self-consistent electronic ground state molecular constants for each molecule. For H2, the effects of pressure shifts have been included. Line centers, broadening coefficients and pressure shifts are given for some 35 observed lines from the 0-0 band

M. E. Mickelson

2005-01-01

230

Ground state and supersymmetry of generally covariant systems  

SciTech Connect

We discuss the extension of Gozzi's approach to supersymmetry, based on the ground state representation (GSR) for quantum mechanical systems. The approach leads directly to the supersymmetric extensions of generally covariant systems, whose Hamiltonian constraints H = 0 are naturally in their GSR form. The method is applied to several cases: relativistic particles interacting with external gauge and gravitational fields, strings, etc. copyright 1988 Academic Press, Inc.

Gamboa, J.; Zanelli, J.

1988-12-01

231

Ground-state energy and relativistic corrections for positronium hydride  

SciTech Connect

Variational calculations of the ground state of positronium hydride (HPs) are reported, including various expectation values, electron-positron annihilation rates, and leading relativistic corrections to the total and dissociation energies. The calculations have been performed using a basis set of 4000 thoroughly optimized explicitly correlated Gaussian basis functions. The relative accuracy of the variational energy upper bound is estimated to be of the order of 2x10{sup -10}, which is a significant improvement over previous nonrelativistic results.

Bubin, Sergiy; Varga, Kalman [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)

2011-07-15

232

Calculated ground-state properties of heavy nuclei  

Microsoft Academic Search

Ground-state distortions and single-particle corrections are calculated fornuclei with Z >= 68 and N >= 106 by use of the macroscopic-microscopic method as developed by Strutinsky. The microscopic part is calculated primarily by use of the folded Yukawa single-particle potential. Its parameters are redetermined to fit a actinide data. The modified oscillator potential is also used in some of the

P. Moeller; S. G. Nilsson; J. R. Nix

1974-01-01

233

Pure superposition states of atoms generated by a bichromatic elliptically polarized field  

SciTech Connect

We identify the specific polarizations for the two components of a bichromatic field, which produce pure superposition states of atoms with a specific magnetic quantum number m via coherent population trapping. The superposition states are composed of two Zeeman substates magnetic quantum number m of the two ground-state hyperfine levels with arbitrary angular momenta F{sub 1} and F{sub 2}. It is established that in the general case of m{ne}0, optical fields with elliptical polarizations are needed for the preparation of such a pure state. It is shown analitically that a unique advantage of the D1 line (over the D2 line) of alkali-metal atoms is the possibility that pure m-m states may be generated even if the excited-state hyperfine levels are not spectrally resolved.

Taichenachev, A. V.; Yudin, V. I. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Institute of Laser Physics SB RAS, Novosibirsk 630090 (Russian Federation); Velichansky, V. L.; Zibrov, S. A. [P. N. Lebedev Physical Institute RAS, Moscow 117924 (Russian Federation); Zibrov, A. S. [Physics Department, Harvard University and Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, 02138 (United States); P. N. Lebedev Physical Institute RAS, Moscow 117924 (Russian Federation)

2006-01-15

234

On the ground electronic states of copper silicide and its ions  

NASA Astrophysics Data System (ADS)

The low-lying electronic states of SiCu, SiCu+, and SiCu- have been studied using a variety of high-level ab initio techniques. As expected on the basis of simple orbital occupancy and bond forming for Si(s2p2)+Cu(s1) species, 2?r, 1?+, and 3?- states were found to be the ground electronic states for SiCu, SiCu+, and SiCu-, respectively; the 2?r state is not that suggested in most recent experimental studies. All of these molecules were found to be quite strongly bound although the bond lengths, bond energies, and harmonic frequencies vary slightly among them, as a result of the nonbonding character of the 2?-MO (molecular orbital) [composed almost entirely of the Si 3p-AO (atomic orbital)], the occupation of which varies from 0 to 2 within the 1?+, 2?r, and 3?- series. The neutral SiCu is found to have bound excited electronic states of 4?-, 2?, 2?+, and 2?i symmetry lying 0.5, 1.2, 1.8, and 3.2 eV above the 2?r ground state. It is possible but not yet certain that the 2?i state is, in fact, the ``B state'' observed in the recent experimental studies by Scherer, Paul, Collier, and Saykally.

Boldyrev, Alexander I.; Simons, Jack; Scherer, J. J.; Paul, J. B.; Collier, C. P.; Saykally, R. J.

1998-04-01

235

Hyperspherical Ground State Wave Functions for Nuclei with a > 4  

NASA Astrophysics Data System (ADS)

The general formulation of a technically advantageous method to find the ground state solution of the Schrödinger equation in configuration space for systems with the number of particles A greater than 4 is presented. The wave function is expanded in pair-correlated hyperspherical harmonics beyond the lowest-order approximation and then calculated in the Faddeev approach. A recent efficient recursive method to construct antisymmetric A-particle hyperspherical harmonics is used. The accuracy is tested for the bound-state energies of nuclei with A = 6 to 12 using the effective V4 potentials. The high quality of the obtained results becomes evident from a comparison with other approaches.

Barnea, Nir; Leidemann, Winfried; Orlandini, Giuseppina

236

Semiclassical study of the quenching of excited-state fluorine atom by hydrogen molecule - Comparison between reactive and nonreactive processes  

NASA Technical Reports Server (NTRS)

Semiclassical calculations are carried out for the quenching of excited-state fluorine atom by collinear collisions with hydrogen molecule. The overall quenching probability is the sum of two contributions: the reactive quenching probability associated with the formation of hydrogen fluoride and the nonreactive quenching probability leading to ground-state fluorine atom and hydrogen molecule. The reactive probability is greater in the threshold region of the collision energy, whereas the nonreactive probability dominates for energies above the threshold region.

Yuan, J.-M.; Skuse, B. M.; Jaffe, R. L.; Komornicki, A.; Morokuma, K.; George, T. F.

1980-01-01

237

Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation  

SciTech Connect

State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data.

Majumder, A.; Dikshit, B.; Bhatia, M. S.; Mago, V. K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2008-09-15

238

Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation  

NASA Astrophysics Data System (ADS)

State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data.

Majumder, A.; Dikshit, B.; Bhatia, M. S.; Mago, V. K.

2008-09-01

239

Tuning of the ground state in electron doped anthracene.  

PubMed

High quality bulk samples of anthracene (AN) doped with potassium (K) in 1?:?1 and 2?:?1 stoichiometries were successfully prepared by a method involving a room temperature solid-state mechanical diffusion process prior to intercalation reactions during heat treatment, and their physical properties were studied using both magnetic and optical measurements. The transfer of almost one electron from K to AN in K1(AN) was confirmed by SQUID and ESR measurements. A pronounced magnetic hump centered at 150 K associated with antiferromagnetic interactions was observed, which can most likely be interpreted in terms of on-site Coulomb repulsions of the Mott insulating states. Optical spectra of K1(AN) clearly showed the insulating states, as well as the electron occupation of the LUMO-derived band of AN. Our results demonstrated tuning of the ground state of a typical bulk hydrocarbon by alkali metal intercalation. PMID:24867585

Phan, Quynh T N; Heguri, Satoshi; Tanabe, Yoichi; Shimotani, Hidekazu; Nakano, Takehito; Nozue, Yasuo; Tanigaki, Katsumi

2014-07-14

240

Entanglement concentration for unknown atomic entangled states via entanglement swapping  

Microsoft Academic Search

An entanglement concentration scheme for unknown atomic entanglement states is proposed via entanglement swapping in cavity QED. Because the interaction used here is a large-detuned one between two driven atoms and a quantized cavity mode, the effects of the cavity decay and thermal field have been eliminated. These advantages can warrant the experimental feasibility of the current scheme.

Ming Yang; Yan Zhao; Wei Song; Zhuo-Liang Cao

2005-01-01

241

Entanglement concentration for unknown atomic entangled states via entanglement swapping  

SciTech Connect

An entanglement concentration scheme for unknown atomic entanglement states is proposed via entanglement swapping in cavity QED. Because the interaction used here is a large-detuned one between two driven atoms and a quantized cavity mode, the effects of the cavity decay and thermal field have been eliminated. These advantages can warrant the experimental feasibility of the current scheme.

Yang Ming; Zhao Yan; Song Wei; Cao Zhuoliang [Anhui Key Laboratory of Information Material and Devices, School of Physics and Material Science, Anhui University, Hefei 230039 (China)

2005-04-01

242

Aurora Borealis: stochastic cellular automata simulations of the excited-state dynamics of oxygen atoms.  

NASA Astrophysics Data System (ADS)

Emissions from the 1S and 1D excited states of atomic oxygen play a prominent role in creating the dramatic light displays (aurora borealis) seen in the skies over polar regions of the Northern Hemisphere. A probabilistic asynchronous cellular automaton model described previously has been applied to the excited-state dynamics of atomic oxygen. The model simulates the time-dependent variations in ground (3P) and excited-state populations that occur under user-defined probabilistic transition rules for both pulse and steady-state conditions. Although each trial simulation is itself an independent "experiment", deterministic values for the excited-state emission lifetimes and quantum yields emerge as limiting cases for large numbers of cells or large numbers of trials. Stochastic variations in the lifetimes and emission yields can be estimated from repeated trials.

Seybold, P. G.; Kier, L. B.; Cheng, C.-K.

1999-12-01

243

Observing Quantum Oscillation of Ground States in Single Molecular Magnet  

NASA Astrophysics Data System (ADS)

Single molecular magnets (SMMs) are among the potential systems for quantum memory and quantum information processing. Quantum coherence and oscillation are critical for these applications. The ground-state quantum coherence and Rabi oscillations of the SMM V15 ([V15IVAs6IIIO42(H2O)]6-) have been studied in this context. We have affirmatively measured at 2.4 K the Rabi quantum oscillations and coherence time T2 for the ground states of the V15 ion of collective spin S=1/2, in addition to confirming the previously reported results for the S=3/2 excited states. The oscillations of S=3/2 and S=1/2 states are of different frequencies, and so can be separately selected for purposive manipulations. T2 of 188±4ns (S=3/2) and 149±10ns (S=1/2) are much less than T1˜12?s and are further extendible via various approaches for qubit implementations.

Yang, Jiahui; Wang, Ya; Wang, Zixiang; Rong, Xing; Duan, Chang-Kui; Su, Ji-Hu; Du, Jiangfeng

2012-06-01

244

Transcription regulation and chromatin structure in the pluripotent ground state.  

PubMed

The use of mouse embryonic stem cells (ESCs) has provided invaluable insights into transcription and epigenetic regulation of pluripotency and self-renewal. Many of these insights were gained in mouse ESCs that are derived and maintained using serum, either on feeder cells or supplemented with the cytokine leukemia inhibitory factor (LIF). These 'serum' ESCs are in a metastable state characterized by the expression of many lineage-specifying genes. The use of two small-molecule kinase inhibitors (2i), targeting mitogen-activated protein kinase (MEK) and glycogen synthase kinase-3 (GSK3), has enabled derivation of mouse ESCs in defined serum-free conditions. These '2i' ESCs are more homogeneous in morphology and gene expression than serum ESCs, and are postulated to represent the ground state of pluripotency. Recent studies have shown that the epigenome and transcriptome of 2i and serum ESCs are markedly different, suggesting that these ESCs represent two distinct states of pluripotency regulated by different factors and pathways. There is growing evidence that the 2i ESCs closely parallel the early blastocyst cells of the inner cell mass (ICM) or even earlier stages, while serum cells possibly reflect later stages. In this review, we will focus on the difference in chromatin structure, transcription regulation and cell cycle regulation between ground state pluripotent 2i ESCs and serum ESCs, and compare to corresponding data in embryos if available. This article is part of a Special Issue entitled: Chromatin and epigenetic regulation of animal development. PMID:24096207

Marks, Hendrik; Stunnenberg, Hendrik G

2014-03-01

245

Anomalous Ground State of the Electrons in Nanoconfined Water  

NASA Astrophysics Data System (ADS)

Water confined on the scale of 20 Å, is known to have different transport and thermodynamic properties from that of bulk water, and the proton momentum distribution has recently been shown to have qualitatively different properties from that exhibited in bulk water. The electronic ground state of nanoconfined water must be responsible for these anomalies but has so far not been investigated. We show here for the first time, using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nanoconfined water system, Nafion, is so different from that of bulk water that the weakly electrostatically interacting molecule model of water is clearly inapplicable. We argue that this is a generic property of nanoconfinement. The present results demonstrate that the electrons, and hence the protons as well, of nanoconfined water are in a distinctly different quantum state from that of bulk water. Biological cell function must make use of the properties of this state and cannot be expected to be described correctly by empirical models based on the weakly interacting molecules model.

Reiter, G. F.; Deb, Aniruddha; Sakurai, Y.; Itou, M.; Krishnan, V. G.; Paddison, S. J.

2013-07-01

246

One-dimensional random-field Ising model: Gibbs states and structure of ground states  

SciTech Connect

We consider the random Gibbs field formalism for the ferromagnetic ID dichotomous random-field Ising model as the simplest example of a quenched disordered system. We prove that for nonzero temperatures the Gibbs state is unique for any realization of the external field. Then we prove that as T {l_arrow} 0, the Gibbs state converges to a limit, a ground state, for almost all realizations of the external field. The ground state turns out to be a probability measure concentrated on an infinite set of configurations, and we give a constructive description of this measure.

Bleher, P.M. [Indiana Univ.-Purdue Univ., Indianapolis, IN (United States); Ruiz, J. [CNRS, Marseille (France); Zagrebnov, V.A. [CNRS, Marseille (France)]|[Universite de la Mediterranee (France)

1996-09-01

247

Klf4 reverts developmentally programmed restriction of ground state pluripotency.  

PubMed

Mouse embryonic stem (ES) cells derived from pluripotent early epiblast contribute functionally differentiated progeny to all foetal lineages of chimaeras. By contrast, epistem cell (EpiSC) lines from post-implantation epithelialised epiblast are unable to colonise the embryo even though they express the core pluripotency genes Oct4, Sox2 and Nanog. We examined interconversion between these two cell types. ES cells can readily become EpiSCs in response to growth factor cues. By contrast, EpiSCs do not change into ES cells. We exploited PiggyBac transposition to introduce a single reprogramming factor, Klf4, into EpiSCs. No effect was apparent in EpiSC culture conditions, but in ground state ES cell conditions a fraction of cells formed undifferentiated colonies. These EpiSC-derived induced pluripotent stem (Epi-iPS) cells activated expression of ES cell-specific transcripts including endogenous Klf4, and downregulated markers of lineage specification. X chromosome silencing in female cells, a feature of the EpiSC state, was erased in Epi-iPS cells. They produced high-contribution chimaeras that yielded germline transmission. These properties were maintained after Cre-mediated deletion of the Klf4 transgene, formally demonstrating complete and stable reprogramming of developmental phenotype. Thus, re-expression of Klf4 in an appropriate environment can regenerate the naïve ground state from EpiSCs. Reprogramming is dependent on suppression of extrinsic growth factor stimuli and proceeds to completion in less than 1% of cells. This substantiates the argument that EpiSCs are developmentally, epigenetically and functionally differentiated from ES cells. However, because a single transgene is the minimum requirement to attain the ground state, EpiSCs offer an attractive opportunity for screening for unknown components of the reprogramming process. PMID:19224983

Guo, Ge; Yang, Jian; Nichols, Jennifer; Hall, John Simon; Eyres, Isobel; Mansfield, William; Smith, Austin

2009-04-01

248

Equatorial ground ice on Mars: Steady-state stability  

NASA Technical Reports Server (NTRS)

Current Martian equatorial surface temperatures are too warm for water ice to exist at the surface for any appreciable length of time before subliming into the atmosphere. Subsurface temperatures are generally warmer still and, despite the presence of a diffusive barrier of porous regolith material, it has been shown by Smoluchowski, Clifford and Hillel, and Fanale et al. that buried ground ice will also sublime and be lost to the atmosphere in a relatively short time. We investigate the behavior of this subliming subsurface ice and show that it is possible for ice to maintain at a steady-state depth, where sublimation and diffusive loss to the atmosphere is balanced by resupply from beneath by diffusion and recondensation of either a deeper buried ice deposits or ground water. We examine the behavior of equatorial ground ice with a numercial time-marching molecular diffusion model. In our model we allow for diffusion of water vapor through a porous regolith, variations in diffusivity and porosity with ice content, and recondensation of sublimed water vapor. A regolith containing considerable amounts of ice can still be very porous, allowing water vapor to diffuse up from deeper within the ice layer where temperatures are warmer due to the geothermal gradient. This vapor can then recondense nearer to the surface where ice had previously sublimed and been lost to the atmosphere. As a result we find that ice deposits migrate to find a steady-state depth, which represents a balance between diffusive loss to the atmosphere through the overlying porous regolith and diffusive resupply through a porous icy regolith below. This depth depends primarily on the long-term mean surface temperature and the nature of the geothermal gradient, and is independent of the ice-free porosity and the regolith diffusivity. Only the rate of loss of ground ice depends on diffusive properties.

Mellon, Michael T.; Jakosky, Bruce M.; Postawko, Susan E.

1993-01-01

249

Undeniable quantum state sharing with a five-atom cluster state in cavity QED  

NASA Astrophysics Data System (ADS)

We present an efficient scheme for undeniable five-party quantum state sharing(FQSTS) of an arbitrary single-atom state with a five-atom cluster state in cavity QED. The implementation of this scheme does not involve the joint-state measurement of multi-atoms, which makes it convenient in a practical application. The scheme is also insensitive to the cavity decay and the thermal field.

Yang, YuGuang; Xia, Juan; Jia, Xin; Zhang, Hua

2012-12-01

250

Deterministic production of N-photon states from a single atom-cavity system  

NASA Astrophysics Data System (ADS)

We propose a mechanism for producing N-photon states on demand leaking from a single-mode optical cavity interacting with a single atom and a laser pulse. The number of photons can be chosen because it is determined by the Zeeman substructure of the ground state of the atom and its initial state. The deterministic generation of traveling light of 1?n?2F photons is achieved, when a circularly polarized laser pulse completely transfers the atomic population between Zeeman sublevels of the ground hyperfine state F through far-detuned Raman scattering, thus producing linearly polarized cavity photons. We describe analytically the evolution of optical field taking into account the spontaneous losses and the cavity damping. We analyze the photon statistics showing that it is close to Poissonian light. We show also that this technique provides a deterministic source of a train of identical multiphoton states with a definite number of photons if a sequence of left- and right-circularly polarized laser pulses is applied. The scheme expands the possibilities for using complex internal states of light to transmit data.

Gogyan, A.; Guérin, S.; Leroy, C.; Malakyan, Yu.

2012-12-01

251

Magnetic State Selection in Atomic Frequency and Time Standards.  

National Technical Information Service (NTIS)

Atomic standards such as those based upon cesium and hydrogen rely upon magnetic state selection to obtain population inversion in the hyperfine transition levels. Use of new design approaches and improved magnetic materials has made it possible to fabric...

H. E. Peters

1981-01-01

252

Ground state of the time-independent Gross Pitaevskii equation  

NASA Astrophysics Data System (ADS)

We present a suite of programs to determine the ground state of the time-independent Gross-Pitaevskii equation, used in the simulation of Bose-Einstein condensates. The calculation is based on the Optimal Damping Algorithm, ensuring a fast convergence to the true ground state. Versions are given for the one-, two-, and three-dimensional equation, using either a spectral method, well suited for harmonic trapping potentials, or a spatial grid. Program summaryProgram title: GPODA Catalogue identifier: ADZN_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZN_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5339 No. of bytes in distributed program, including test data, etc.: 19 426 Distribution format: tar.gz Programming language: Fortran 90 Computer: ANY (Compilers under which the program has been tested: Absoft Pro Fortran, The Portland Group Fortran 90/95 compiler, Intel Fortran Compiler) RAM: From <1 MB in 1D to ˜10 MB for a large 3D grid Classification: 2.7, 4.9 External routines: LAPACK, BLAS, DFFTPACK Nature of problem: The order parameter (or wave function) of a Bose-Einstein condensate (BEC) is obtained, in a mean field approximation, by the Gross-Pitaevskii equation (GPE) [F. Dalfovo, S. Giorgini, L.P. Pitaevskii, S. Stringari, Rev. Mod. Phys. 71 (1999) 463]. The GPE is a nonlinear Schrödinger-like equation, including here a confining potential. The stationary state of a BEC is obtained by finding the ground state of the time-independent GPE, i.e., the order parameter that minimizes the energy. In addition to the standard three-dimensional GPE, tight traps can lead to effective two- or even one-dimensional BECs, so the 2D and 1D GPEs are also considered. Solution method: The ground state of the time-independent of the GPE is calculated using the Optimal Damping Algorithm [E. Cancès, C. Le Bris, Int. J. Quantum Chem. 79 (2000) 82]. Two sets of programs are given, using either a spectral representation of the order parameter [C.M. Dion, E. Cancès, Phys. Rev. E 67 (2003) 046706], suitable for a (quasi) harmonic trapping potential, or by discretizing the order parameter on a spatial grid. Running time: From seconds in 1D to a few hours for large 3D grids

Dion, Claude M.; Cancès, Eric

2007-11-01

253

Bound state spectrum of the triplet states in the Be atom  

NASA Astrophysics Data System (ADS)

The bound state spectrum of the low-lying triplet states in the Be atom is investigated. In particular, we perform accurate computations of the bound triplet S,P,D,F,G, H and I states in the Be atom. The results of these calculations are employed to draw the spectral diagram which contains the energy levels of the triplet states. Based on our computational results we can observe transitions from the low-lying bound states to the weakly-bound Rydberg states. For the 23S,33S and 43S states in the Be atom we also determine a number of bound states properties.

Frolov, Alexei M.; Ruiz, María Belén

2014-03-01

254

Hartree-Fock Ground State Phase Diagram of Jellium  

NASA Astrophysics Data System (ADS)

We calculate the ground state phase diagram of the homogeneous electron gas in three dimensions within the Hartree-Fock approximation and show that broken symmetry states are energetically favored at any density against the homogeneous Fermi gas state with isotropic Fermi surface. At high density, we find metallic spin-unpolarized solutions where electronic charge and spin density form an incommensurate crystal having more crystal sites than electrons. For rs?0, our solutions approach pure spin-density waves, whereas the commensurate Wigner crystal is favored at lower densities, rs?3.4. Decreasing the density, the system undergoes several structural phase transitions with different lattice symmetries. The polarization transition occurs around rs?8.5.

Baguet, L.; Delyon, F.; Bernu, B.; Holzmann, M.

2013-10-01

255

Basicity of coumarin derivatives in the ground and excited states  

SciTech Connect

The acid-base properties of coumarin luminophores are widely used for widening the optical spectrum generated by lasers. The aim of this work was a quantitative study of the proton-acceptor capacity of a series of substituted coumarins at the H-complex formation stage and during protonation, and also to evaluate the basicity of these compounds in the first excited singlet state. The compounds chosen were the 4- and 7-substituted coumarins, most widely used in laser technology. In the ground state the sensitivity of the carbonyl group to the effect of a substituent was twice as great in position 4 as in position 7; for the excited state the effect was reversed.

Ponomarev, O.A.; Mitina, V.G.; Vasina, E.R.; Yarmolenko, S.N.

1985-07-01

256

Hartree-Fock ground state phase diagram of jellium.  

PubMed

We calculate the ground state phase diagram of the homogeneous electron gas in three dimensions within the Hartree-Fock approximation and show that broken symmetry states are energetically favored at any density against the homogeneous Fermi gas state with isotropic Fermi surface. At high density, we find metallic spin-unpolarized solutions where electronic charge and spin density form an incommensurate crystal having more crystal sites than electrons. For r(s)?0, our solutions approach pure spin-density waves, whereas the commensurate Wigner crystal is favored at lower densities, r(s)?3.4. Decreasing the density, the system undergoes several structural phase transitions with different lattice symmetries. The polarization transition occurs around r(s)?8.5. PMID:24182285

Baguet, L; Delyon, F; Bernu, B; Holzmann, M

2013-10-18

257

Steady state of atoms in a resonant field with elliptical polarization  

SciTech Connect

We present a complete set of analytical and invariant expressions for the steady-state density matrix of atoms in a resonant radiation field with arbitrary intensity and polarization. The field drives the closed dipole transition with arbitrary values of the angular momenta J{sub g} and J{sub e} of the ground and excited state. The steady-state density matrix is expressed in terms of spherical harmonics of a complex direction given by the field polarization vector. The generalization to the case of broadband radiation is given. We indicate various applications of these results.

Taichenachev, A.V. [Laser Physics Laboratory, Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Tumaikin, A.M.; Yudin, V.I. [Institute of Laser Physics SD RAS, Lavrent'eva 13/1, Novosibirsk 630090 (Russian Federation); Nienhuis, G. [Huygens Laboratorium, University of Leiden, P. O. Box 9504, 2300 RA Leiden (Netherlands)

2004-03-01

258

Ground-state electronic structure of actinide monocarbides and mononitrides  

NASA Astrophysics Data System (ADS)

The self-interaction corrected local spin-density approximation is used to investigate the ground-state valency configuration of the actinide ions in the actinide monocarbides, AC (A=U,Np,Pu,Am,Cm) , and the actinide mononitrides, AN. The electronic structure is characterized by a gradually increasing degree of f electron localization from U to Cm, with the tendency toward localization being slightly stronger in the (more ionic) nitrides compared to the (more covalent) carbides. The itinerant band picture is found to be adequate for UC and acceptable for UN, while a more complex manifold of competing localized and delocalized f -electron configurations underlies the ground states of NpC, PuC, AmC, NpN, and PuN. The fully localized 5f -electron configuration is realized in CmC (f7) , CmN (f7) , and AmN (f6) . The observed sudden increase in lattice parameter from PuN to AmN is found to be related to the localization transition. The calculated valence electron densities of states are in good agreement with photoemission data.

Petit, L.; Svane, A.; Szotek, Z.; Temmerman, W. M.; Stocks, G. M.

2009-07-01

259

Lee-Yang Polynomials and Ground States of Spin Systems  

NASA Astrophysics Data System (ADS)

We obtain two kinds of results on the region in the space of the interactions of lattice systems where the Lee-Yang property holds (LY domain). First we show that the LY domain is related to interactions with exactly two ground states. Then we give a description of the full LY domain of an extended "plaquette model" analyzed by Lebowitz and Ruelle (Commun Math Phys 304:711-722, 2011). This allows us to prove a permanence property of the system, which we conjecture to hold in general.

Slawny, Joseph

2014-08-01

260

Lee-Yang Polynomials and Ground States of Spin Systems  

NASA Astrophysics Data System (ADS)

We obtain two kinds of results on the region in the space of the interactions of lattice systems where the Lee-Yang property holds (LY domain). First we show that the LY domain is related to interactions with exactly two ground states. Then we give a description of the full LY domain of an extended "plaquette model" analyzed by Lebowitz and Ruelle (Commun Math Phys 304:711-722, 2011). This allows us to prove a permanence property of the system, which we conjecture to hold in general.

Slawny, Joseph

2014-05-01

261

Ground State Properties of Fluxlines in a Disordered Environment  

NASA Astrophysics Data System (ADS)

A new numerical method to calculate exact ground states of multifluxline systems with quenched disorder is presented, which is based on the minimum cost flow algorithm from combinatorial optimization. We discuss several models that can be studied with this method including their specific implementations, physically relevant observables and results: (1) The N-line model with N fluxlines (or directed polymers) in a d-dimensional environment with point and/or columnar disorder and hard or soft-core repulsion; (2) the vortex glass model for a disordered superconductor in the strong screening limit; and (3) the sine-Gordon model with random pase shifts in the strong coupling limit.

Rieger, Heiko

1998-11-01

262

Ground State and Excitation Properties of Soft-Core Bosons  

NASA Astrophysics Data System (ADS)

We study the physics of soft-core bosons at zero temperature in two dimensions for a class of potentials that could be realised in experiments with Rydberg dressed Bose-Einstein condensates. We analyze the ground state properties of the system in detail and provide a complete description of the excitation spectra in both superfluid, supersolid and crystalline phase for a wide range of interaction strengths and densities. In addition we describe a method to extract the transverse gapless excitation modes in the phases with broken translational symmetry within the framework of path integral Monte Carlo methods.

Macrì, Tommaso; Saccani, Sebastiano; Cinti, Fabio

2014-05-01

263

Vibrational fundamentals and natural bond orbitals analysis of some tri-fluorinated benzonitriles in ground state.  

PubMed

The theoretical IR and Raman spectra of the 2,3,4-, 2,3,6-, 2,4,5- and 3,4,5-tri-fluorobenzonitrile molecules have been calculated by using the density functional method in the ground state. The rigorous normal coordinate analyses based upon both an empirical force field and quantum chemical calculations have been performed and the detailed vibrational assignment has been made on the basis of the calculated potential energy distributions (PEDs). A comparison of molecular geometries, atomic charges and vibrational fundamentals of these molecules has been reported. The effects of fluorination upon the geometries, atomic charges and vibrational frequencies of benzonitrile have been discussed. Several ambiguities and contradictions in the previously reported vibrational assignments have been clarified. In addition, the variation of Raman intensity with excitation frequency and with temperature has also been studied. PMID:21802350

Mukherjee, V; Singh, N P; Yadav, R A

2011-10-15

264

LETTER TO THE EDITOR: The stability of the ground state for positronic sodium  

NASA Astrophysics Data System (ADS)

The existence of a stable ground state for the exotic 0953-4075/31/6/003/img6 atom is demonstrated by using a modified version of the stochastic variational method to solve the Schrödinger equation for a positron and valence electron moving under the influence of a model potential. The model potential consists of the direct interaction between the positronium and the Hartree - Fock wavefunction for the alkali ion. The exchange potential between the valence electron and the core electrons is approximated with a local potential. The structure of positronic sodium is best described as a slightly stretched and polarized positronium atom orbiting the 0953-4075/31/6/003/img7 core at distances of the order of 10 - 0953-4075/31/6/003/img8. It is found that positronic sodium is stable against decay into 0953-4075/31/6/003/img9 with a binding energy of 0.000177 Hartree.

Ryzhikh, G.; Mitroy, J.; Varga, K.

1998-03-01

265

ELECTRONIC STRUCTURE FOR THE GROUND STATE OF T1H FROM RELATIVISTIC MULTICONFIGURATION SCF CALCULATIONS  

SciTech Connect

The dissociation curve for the ground state of TlH was computed using a relativistic {omega}-{omega} coupling formalism. The relativistic effects represented by the Dirac equation were introduced using effective potentials generated from atomic Dirac-Fock wave functions using a generalization of the improved effective potential formulation of Christiansen, Lee, and Pitzer. The multiconfiguration SCF treatment used is a generalization of the two-component molecular spinor formalism of Lee, Ermler, and Pitzer. Using a five configuration wave function we were able to obtain approximately 85% of the experimental dissociation energy. Our computations indicate that the bond is principally sigma in form, despite the large spin-orbit splitting in atomic thallium. Furthermore the bond appears to be slightly ionic (Tl{sup +}H{sup -}) with about 0.3 extra electron charge on the hydrogen.

Christiansen, P.A.; Pitzer, K.S.

1980-07-01

266

Effects of Rashba and Dresselhaus spin–orbit interactions on the ground state of two-dimensional localized spins  

NASA Astrophysics Data System (ADS)

Starting with the indirect exchange model influenced by the Rashba and the Dresselhaus spin–orbit interactions, we derive the Dzyaloshinskii–Moriya interaction of localized spins. The strength of the Dzyaloshinskii–Moriya interaction is compared with that of the Heisenberg exchange term as a function of atomic distance. Using the calculated interaction strengths, we discuss the formation of various atomic ground states as a function of temperature and external magnetic field. By plotting the magnetic field–temperature phase diagram, we present approximate phase boundaries between the spiral, Skyrmion and ferromagnetic states of the two-dimensional weak ferromagnetic system.

Oh, J. H.; Lee, K.-J.; Lee, Hyun-Woo; Shin, M.

2014-05-01

267

Electron holography at atomic dimensions -- Present state  

SciTech Connect

An electron microscope is a wave optical instrument where the object information is carried by an electron wave. However, an important information, the phase of the electron wave, is lost, because only intensities can be recorded in a conventional electron micrograph. Off-axis electron holography solves this phase problem by encoding amplitude and phase information in an interference pattern, the so-called hologram. After reconstruction, a rather unrestricted wave optical analysis can be performed on a computer. The possibilities as well as the current limitations of off-axis electron holography at atomic dimensions are discussed, and they are illustrated at two applications of structure characterization of {epsilon}-NbN and YBCO-1237. Finally, an electron microscope equipped with a Cs-corrector, a monochromator, and a Moellenstedt biprism is outlined for subangstrom holography.

Lehmann, M.; Lichte, H. [Technische Univ. Dresden (Germany). Inst. fuer Angewandte Physik] [Technische Univ. Dresden (Germany). Inst. fuer Angewandte Physik; Geiger, D.; Lang, G.; Schweda, E. [Univ. Tuebingen (Germany)] [Univ. Tuebingen (Germany)

1999-04-01

268

Term energies of 1s2nf high Rydberg states for the lithium atom  

NASA Astrophysics Data System (ADS)

Ionization potentials and quantum defects of 1s2nf bound states and their adjacent continuum states for the lithium atom are calculated with the R-matrix theory; then the quantum defect function (QDF) of the 1s2nf channel is obtained, which varies smoothly with the energy based on the quantum defect theory. The original QDF is calibrated from a more accurate literature value and used to calculate quantum defects, ionization potentials and term energies (relative to the 1s22s ground state) of 1s2nf high Rydberg states of the lithium atom. The term energies in this work are, on the whole, in good agreement with the experimental data in the literature.

Chen, Chao

2013-10-01

269

Realizing a Kondo-correlated state with ultracold atoms.  

PubMed

We propose a novel realization of Kondo physics with ultracold atomic gases. It is based on a Fermi sea of two different hyperfine states of one atom species forming bound states with a different species, which is spatially confined in a trapping potential. We show that different situations displaying Kondo physics can be realized when Feshbach resonances between the species are tuned by a magnetic field and the trapping frequency is varied. We illustrate that a mixture of 40K and 23Na atoms can be used to generate a Kondo-correlated state and that momentum resolved radio frequency spectroscopy can provide unambiguous signatures of the formation of Kondo resonances at the Fermi energy. We discuss how tools of atomic physics can be used to investigate open questions for Kondo physics, such as the extension of the Kondo screening cloud. PMID:24313499

Bauer, Johannes; Salomon, Christophe; Demler, Eugene

2013-11-22

270

On the topological ground state of E-infinity spacetime and the super string connection  

Microsoft Academic Search

There are at present a huge number of valid super string ground states, making the one corresponding to our own universe extremely hard to determine. Therefore it may come as quite a surprise that it is a rather simple undertaking to determine the exact topological ground state of E-infinity Cantorian spacetime theory. Similar to the ground state of the Higgs

M. S. El Naschie

2007-01-01

271

Ground states for a system of nonlinear Schrödinger equations with three wave interaction  

NASA Astrophysics Data System (ADS)

We consider a system of nonlinear Schrödinger equations with three wave interaction studying the existence of ground state solutions. In particular, we find a vector ground state, namely, a ground state (u1,u2,u3) such that ui?0 for all i=1,2,3.

Pomponio, A.

2010-09-01

272

Ground state of the dipolar Bose-Einstein condensate  

SciTech Connect

We present a variational method to study the ground state of the newly realized {sup 52}Cr dipolar Bose-Einstein condensate. Besides the usual contact potential term in the mean-field equation, there is an additional long-range and anisotropic dipole-dipole interaction potential. We develop an efficient Newton-Raphson's scheme to solve the condensate state. The solution shows a double-peak feature in the loosely confined dimension. Compared to the existing single-peak calculations, the double-peak solution has lower energy and reflects the distinct property of the dipole-dipole interaction. Our method is easy and efficient to use for future investigations of the dipolar systems.

Jiang, T. F.; Su, W. C. [Institute of Physics, National Chiao Tung University, Hsinchu, 300, Taiwan (China); Department of Civil Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan (China)

2006-12-15

273

Au42: a possible ground-state noble metallic nanotube.  

PubMed

A large hollow tubelike Au(42) is predicted as a new ground-state configuration based on the scalar relativistic density functional theory. The shape of this new Au(42) cluster is similar to a (5,5) single-wall gold nanotube, the two ends of which are capped by half of a fullerenelike Au(32). In the same way, a series of Au(n) (n = 37, 42, 47, 52, 57, 62, 67, 72, ..., Delta n = 5) tubelike structures has been constructed. The highest occupied molecular orbital-lowest unoccupied molecular orbital gaps suggested a significant semiconductor-conductor alternation in n is an element of [32,47]. Similar to the predictions and speculation of Daedalus [D. E. H. Jones, New Sci. 32, 245 (1966); E. Osawa, Superaromaticity (Kagaku, Kyoto, 1970), Vol. 25, pp. 854-863; Z. Yoshida and E. Osawa, Aromaticity Chemical Monograph (Kagaku Dojin, Kyoto, Japan, 1971), Vol. 22, pp. 174-176; D. A. Bochvar and E. G. Gal'pern, Dokl. Akad. Nauk SSSR 209, 610 (1973)], here a large hollow ground-state gold nanotube was predicted theoretically. PMID:19045114

Wang, Jing; Ning, Hua; Ma, Qing-Min; Liu, Ying; Li, You-Cheng

2008-10-01

274

Au42: A possible ground-state noble metallic nanotube  

NASA Astrophysics Data System (ADS)

A large hollow tubelike Au42 is predicted as a new ground-state configuration based on the scalar relativistic density functional theory. The shape of this new Au42 cluster is similar to a (5,5) single-wall gold nanotube, the two ends of which are capped by half of a fullerenelike Au32. In the same way, a series of Aun (n=37,42,47,52,57,62,67,72,..., ?n=5) tubelike structures has been constructed. The highest occupied molecular orbital-lowest unoccupied molecular orbital gaps suggested a significant semiconductor-conductor alternation in n?[32,47]. Similar to the predictions and speculation of Daedalus [D. E. H. Jones, New Sci. 32, 245 (1966); E. Osawa, Superaromaticity (Kagaku, Kyoto, 1970), Vol. 25, pp. 854-863 Z. Yoshida and E. Osawa, Aromaticity Chemical Monograph (Kagaku Dojin, Kyoto, Japan, 1971), Vol. 22, pp. 174-176 D. A. Bochvar and E. G. Gal'pern, Dokl. Akad. Nauk SSSR 209, 610 (1973)], here a large hollow ground-state gold nanotube was predicted theoretically.

Wang, Jing; Ning, Hua; Ma, Qing-Min; Liu, Ying; Li, You-Cheng

2008-10-01

275

The ground state rotational spectrum of SO 2F 2  

NASA Astrophysics Data System (ADS)

The analysis of the ground state rotational spectrum of SO 2F 2 [K. Sarka, J. Demaison, L. Margulès, I. Merke, N. Heineking, H. Bürger, H. Ruland, J. Mol. Spectrosc. 200 (2000) 55] has been performed with the Watson's Hamiltonian up to sextic terms but shows some limits due to the A and S reductions. Since SO 2F 2 is a quasi-spherical top, it can also be regarded as derived from an hypothetical XY 4 molecule. Thus we have developed a new tensorial formalism in the O(3)? Td? C2 v group chain (M. Rotger, V. Boudon, M. Loëte, J. Mol. Spectrosc. 216 (2002) 297]. We test it on the ground state of this molecule using the same experimental data (10 GHz-1 THz region, J up to 99). Both fits are comparable even if the formalisms are slightly different. This paper intends to establish a link between the classical approach and the tensorial formalism. In particular, our tensorial parameters at a given order of the development are related to the usual ones. Programs for spectrum simulation and fit using these methods are named C2 vTDS. They are freely available at the URL: http://www.u-bourgogne.fr/LPUB/c2vTDS.html.

Rotger, M.; Boudon, V.; Loëte, M.; Margulès, L.; Demaison, J.; Mäder, H.; Winnewisser, G.; Müller, H. S. P.

2003-12-01

276

The ground and first excited torsional states of methyl carbamate  

NASA Astrophysics Data System (ADS)

A global fit within experimental accuracy of microwave and millimeter-wave transitions in the ground and first excited torsional states of methyl carbamate (H 2NC(O)OCH 3) is presented. The data set consisting of 995 vt = 0 and 731 vt = 1 transition frequencies combines 1544 new measurements from Kharkov with previously published vt = 0 microwave lines. In this study the so-called "rho axis method" that treats simultaneously both A and E species of the ground and first excited torsional states is applied to the methyl carbamate data set for the first time. The final fit requires only 32 parameters to achieve a unitless weighted standard deviation for the whole fit of 0.89 for a total of 1726 transitions with rotational quantum numbers up to J ? 20 and Ka ? 10. The barrier to internal rotation of the methyl group obtained in this study, V3 = 359.141(24) cm -1, is in good agreement with previously published values but more accurate.

Ilyushin, V.; Alekseev, E.; Demaison, J.; Kleiner, I.

2006-11-01

277

Ground-state photoneutron reactions in /sup 15/N  

SciTech Connect

Photoneutron angular distributions were measured by time-of-flight techniques for the reaction /sup 15/N(..gamma..,n/sub 0/) /sup 14/N over the region of excitation energy from 15 to 25 MeV. Ground state cross sections were obtained by stepping the bremsstrahlung end point over the energy region of interest in 2 MeV intervals. By fitting the spectral data to a series of Legendre polynomials, angular distribution coefficients were extracted and interpreted on the basis of a simple single particle model. It appears that a large fraction of the photoabsorption strength leading to decays via the ground state channel is due to the formation of J/sup ..pi../ = (3/2)/sup +/, T = (1/2) states in /sup 15/N which decay by d-wave neutron emission. The data support an approximation of purely electric dipole absorption in the region measured. Some small amount of s-wave neutron emission interfering with the dominant p/sub 1/2/..-->..d/sub 3/2/ transition is consistent with an observed value for the a/sub 2//a/sub 0/ coefficient of -0.7 +- 0.2. The (..gamma..,n/sub 0/) cross section integrated between threshold and 30 MeV is estimated to represent about one-third of the total strength in the neutron channel. A state identified at 17.3 MeV is consistent in energy and composition with a theoretical prediction based on a shell model calculation using a residual interaction with a Soper mixture of exchange forces.

Watson, J.D.; Jury, J.W.; Kuo, P.C.; Davidson, W.F.; Sherman, N.K.; McNeill, K.G.

1983-02-01

278

Combined quantum-state preparation and laser cooling of a continuous beam of cold atoms  

SciTech Connect

We use two-laser optical pumping on a continuous atomic fountain in order to prepare cold cesium atoms in the same quantum ground state. A first laser excites the F=4 ground state to pump the atoms toward F=3 while a second {pi}-polarized laser excites the F=3{yields}F{sup '}=3 transition of the D{sub 2} line to produce Zeeman pumping toward m=0. To avoid trap states, we implement the first laser in a two-dimensional optical lattice geometry, thereby creating polarization gradients. This configuration has the advantage of simultaneously producing Sisyphus cooling when the optical lattice laser is tuned between the F=4{yields}F{sup '}=4 and F=4{yields}F{sup '}=5 transitions of the D{sub 2} line, which is important to remove the heat produced by optical pumping. Detuning the frequency of the second {pi}-polarized laser reveals the action of a mechanism improving both laser cooling and state-preparation efficiency. A physical interpretation of this mechanism is discussed.

Di Domenico, Gianni; Devenoges, Laurent; Dumas, Claire; Thomann, Pierre [Laboratoire Temps-Frequence, Universite de Neuchatel, Avenue de Bellevaux 51, CH-2009 Neuchatel (Switzerland)

2010-11-15

279

Electronic Ground State Constants for Molecular Hydrogen and Hydrogen Deuteride  

NASA Astrophysics Data System (ADS)

Observed rotational and rotational-vibrational transitions for molecular H2 and HD have been combined to produce best, non-linear least-squares fits to a set of self-consistent electronic ground state molecular constants for each molecule. For H2, the effects of pressure shifts have been included. Line centers, broadening coefficients and pressure shifts are given for some 35 observed lines from the 0-0 band through the 5-0 band of H2. HD constants are based on lines observed for bands from 1-0 through the 6-0 band. Research supported by the NASA Planetary Atmospheres Program Grant NAG5-11966 and by Denison University.

Mickelson, M. E.

2005-08-01

280

Unresolved Question of the He10 Ground State Resonance  

NASA Astrophysics Data System (ADS)

The ground state of He10 was populated using a 2p2n-removal reaction from a 59MeV/u Be14 beam. The decay energy of the three-body system, He8+n+n, was measured and a resonance was observed at E=1.60(25)MeV with a 1.8(4) MeV width. This result is in agreement with previous invariant mass spectroscopy measurements, using the Li11(-p) reaction, but is inconsistent with recent transfer reaction results. The proposed explanation that the difference, about 500 keV, is due to the effect of the extended halo nature of Li11 in the one-proton knockout reaction is no longer valid as the present work demonstrates that the discrepancy between the transfer reaction results persists despite using a very different reaction mechanism, Be14(-2p2n).

Kohley, Z.; Snyder, J.; Baumann, T.; Christian, G.; DeYoung, P. A.; Finck, J. E.; Haring-Kaye, R. A.; Jones, M.; Lunderberg, E.; Luther, B.; Mosby, S.; Simon, A.; Smith, J. K.; Spyrou, A.; Stephenson, S. L.; Thoennessen, M.

2012-12-01

281

Ground states of dispersion-managed nonlinear Schrodinger equation  

PubMed

An exact pulse for the parametrically forced nonlinear Schrodinger equation (NLS) is isolated. The equation governs wave envelope propagation in dispersion-managed fiber lines with positive residual dispersion. The pulse is obtained as a ground state of an averaged variational principle associated with the equation governing pulse dynamics. The solutions of the averaged and original equations are shown to stay close for a sufficiently long time. A properly adjusted pulse will therefore exhibit nearly periodic behavior in the time interval of validity of the averaging procedure. Furthermore, we show that periodic variation of dispersion can stabilize spatial solitons in a Kerr medium and one-dimensional solitons in the NLS with quintic nonlinearity. The results are confirmed by numerical simulations. PMID:11102097

Zharnitsky; Grenier; Turitsyn; Jones; Hesthaven

2000-11-01

282

Improved ground state rotational parameters of deuterium fluoride, DF  

NASA Astrophysics Data System (ADS)

The rotational spectrum of DF in the 1.3-3.3 THz frequency region has been observed by means of a tunable far-infrared spectrometer. The J + 1 ? J, with J = 1-4, rotational transitions of DF have been recorded with an accuracy of the order of 50-200 kHz. These measurements, in conjunction with the hyperfine components of the J = 1 ? 0 transition recently observed [Cazzoli and Puzzarini, J. Mol. Spectrosc. 231 (2005) 124-130] and the rotational transitions up to J = 47 [R.S. Ram, Z. Morbi, B. Guo, K.-Q. Zhang, P.F. Bernath, J. Vander Auwera, J.W.C. Johns, S.P. Davies, Astrophys. J. Suppl. Series 103 (1996) 247-254] consented to improve the ground state rotational parameters of DF.

Cazzoli, Gabriele; Puzzarini, Cristina; Tamassia, Filippo; Borri, Simone; Bartalini, Saverio

2006-02-01

283

Tuning the magnetic ground state of a triangular lattice system  

SciTech Connect

The anisotropic triangular lattice of the crednerite system Cu(Mn$_{1-x}$Cu$_{x}$)O$_{2}$ is used as a basic model for studying the influence of spin disorder on the ground state properties of a two-dimensional frustrated antiferromagnet. Neutron diffraction measurements show that the undoped phase (x=0) undergoes a transition to antiferromagnetic long-range order that is stabilized by a frustration-relieving structural distortion. Small deviation from the stoichiometric composition alters the magnetoelastic characteristics and reduces the effective dimensionality of the magnetic lattice. Upon increasing the doping level, the interlayer coupling changes from antiferromagnetic to ferromagnetic, while the structural distortion is fully suppressed. Concomitantly, the long-range magnetic order is gradually transformed into a two-dimensional order.

Garlea, Vasile O [ORNL; Savici, Andrei T [ORNL; Jin, Rongying [Louisiana State University

2011-01-01

284

Ground state and phase transitions in solid C sub 60  

SciTech Connect

A simple model is developed to describe the intermolecular interactions in solid C{sub 60}. The model correctly predicts the observed ground-state structure {ital Pa}{bar 3} and the first-order transition to the high-temperature fcc phase. The calculated transition temperature {ital T}{sub {ital c}}{similar to}270 K and its pressure dependence {ital dT}{sub {ital c}}/{ital dP}=11.5 K/kbar agree very well with recent experiments. Below {ital T}{sub {ital c}}, there exist nearly degenerate orientations that are separated by potential barriers of order {similar to}300 meV, leading to a glassy behavior with {ital T}{sub {ital g}}{similar to}90--130 K. It is suggested that similar orientational disorder exists in K{sub 3}C{sub 60} and other fullerides.

Lu, J.P.; Li, X.; Martin, R.M. (Department of Physics and Material Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))

1992-03-09

285

Dipolar Interaction and Magnetic Ordering Ground State in Mn12 Molecular Magnet  

Microsoft Academic Search

Here a direct calculation of the dipolar interaction in a single crystal Mn12, with all of Mn ions summed, shows that a transition between a ferromagnetic ground state and an antiferromagnetic ground state takes place where the dimension along the a(b) axis versus the dimension along the c axis reaches a certain critical value. It is shown that the ground

Hai-Qing Liu; Yun-Ping Wang

2005-01-01

286

Determination of Ground-Laboratory to In-Space Effective Atomic Oxygen Fluence for DC 93?500 Silicone  

NASA Technical Reports Server (NTRS)

The objective of this research was to calibrate the ground-to-space effective atomic oxygen fluence for DC 93-500 silicone in a thermal energy electron cyclotron resonance (ECR) oxygen plasma facility. Silicones, commonly used spacecraft materials, do not chemically erode with atomic oxygen attack like other organic materials but form an oxidized hardened silicate surface layer. Therefore, the effective atomic oxygen fluence in a ground test facility should not be determined based on mass loss measurements, as they are with organic polymers. A technique has been developed at the Glenn Research Center to determine the equivalent amount of atomic oxygen exposure in an ECR ground test facility to produce the same degree of atomic oxygen damage as in space. The approach used was to compare changes in the surface hardness of ground test (ECR) exposed DC 93-500 silicone with DC 93-500 exposed to low Earth orbit (LEO) atomic oxygen as part of a shuttle flight experiment. The ground to in-space effective atomic oxygen fluence correlation was determined based on the fluence in the ECR source that produced the same hardness for the fluence in-space. Nanomechanical hardness versus contact depth measurements were obtained for five ECR exposed DC 93-500 samples (ECR exposed for 18 to 40 hrs, corresponding to Kapton effective fluences of 4.2 x 10(exp 20) to 9.4 x 10(exp 20) atoms/sq cm, respectively) and for space exposed DC 93-500 from the Evaluation of Oxygen Interactions with Materials III (EOIM III) shuttle flight experiment, exposed to LEO atomic oxygen for 2.3 x 10(exp 20) atoms/sq cm. Pristine controls were also evaluated. A ground-to-space correlation value was determined based on correlation values for four contact depths (150, 200, 250, and 300 nm), which represent the near surface depth data. The results indicate that the Kapton effective atomic oxygen fluence in the ECR facility needs to be 2.64 times higher than in LEO to replicate equivalent exposure damage in the ground test silicone as occurred in the space exposed silicone.

deGroh, Kim K.; Banks, Bruce A.; Ma, David

2004-01-01

287

Ground States and Excited States in a Tunable Graphene Quantum Dot  

NASA Astrophysics Data System (ADS)

We prepare an etched gate tunable quantum dot in single-layer graphene and present transport measurement in this system. We extract the information of the ground states and excited states of the graphene quantum dot, as denoted by the presence of characteristic Coulomb blockade diamond diagrams. The results demonstrate that the quantum dot in single-layer graphene bodes well for future quantum transport study and quantum computing applications.

Wang, Lin-Jun; Cao, Gang; Tu, Tao; Li, Hai-Ou; Zhou, Cheng; Hao, Xiao-Jie; Guo, Guang-Can; Guo, Guo-Ping

2011-06-01

288

Ground-Laboratory to In-Space Effective Atomic-Oxygen Fluence Determined for DC 93-500 Silicone  

NASA Technical Reports Server (NTRS)

Surfaces on the leading edge of spacecraft in low Earth orbit (e.g., surface facing the velocity direction), such as on the International Space Station, are subject to atomic oxygen attack, and certain materials are susceptible to erosion. Therefore, ground-based laboratory testing of the atomic oxygen durability of spacecraft materials is necessary for durability assessment when flight data are not available. For accurate space simulation, the facility is commonly calibrated on the basis of the mass loss of Kapton (DuPont, Wilmington, DE) as a control sample for effective fluence determination. This is because Kapton has a well-characterized atomic oxygen erosion yield (E(sub y), in cubic centimeters per atom) in the low Earth orbit (LEO) environment. Silicones, a family of commonly used spacecraft materials, do not chemically erode away with atomic oxygen attack like other organic materials that have volatile oxidation products. Instead, silicones react with atomic oxygen and form an oxidized hardened silicate surface layer. Often the loss of methyl groups causes shrinkage of the surface skin and "mud-tile" crazing degradation. But silicones often do not lose mass, and some silicones actually gain mass during atomic oxygen exposure. Therefore, the effective atomic oxygen fluence for silicones in a ground-test facility should not be determined on the basis of traditional mass-loss measurements, as it is with polymers that erode. Another method for determining effective fluence needs to be employed for silicones. A new technique has been developed at the NASA Glenn Research Center for determining the effective atomic oxygen fluence for silicones in ground-test facilities. This technique determines the equivalent amount of atomic oxygen oxidation on the basis of changes in the surface-oxide hardness. The specific approach developed was to compare changes in the surface hardness of ground-laboratory-exposed DC93-500 silicone with DC93-500 exposed to LEO atomic oxygen as part of a shuttle flight experiment. The on-the-ground to in-space effective atomic oxygen fluence was determined on the basis of the Kapton effective fluence in the ground-laboratory facility that produced the same hardness for the fluence in space.

deGroh, Kim K.; Banks, Bruce A.; Ma, David

2005-01-01

289

Method for preparing two-atom entangled states in circuit QED and probing it via quantum nondemolition measurements  

NASA Astrophysics Data System (ADS)

We propose a probabilistic scheme to prepare a maximally entangled state between a pair of two-level atoms coupled to a leaking cavity mode in circuit QED, without requiring precise time control of the system evolution and initial atomic state. We show that the steady state of this dissipative system is a mixture of two parts, where the atoms are either in their ground state or in a maximally entangled one. Then, by applying a weak probe field to the cavity mode, we are able to discriminate those states without disturbing the atomic system, i.e., to perform a quantum nondemolition measurement via the cavity transmission. In this scheme, one has maximum cavity transmission only when the atomic system is in an entangled state, so that a single click in the detector is enough to be sure that the atoms are in a maximally entangled state. Our scheme relies on an interference effect as it happens in an electromagnetically induced transparency phenomenon so that it works even in the limit of a cavity decay rate much stronger than the atom-field coupling.

Rossatto, D. Z.; Villas-Boas, C. J.

2013-10-01

290

Estimation of ground and excited state dipole moments of some laser dyes  

NASA Astrophysics Data System (ADS)

The ground state ( ?g) and the excited state ( ?e) dipole moments of three laser dyes namely 2, 5-diphenyl-1, 3, 4- oxadiazole (PPD), 2, 2?-dimethyl-p-terphenyl (DMT) and 1, 3-diphenyl benzene (MT) were studied at room temperature in various solvents. The ground state dipole moments ( ?g) of all the three laser dyes were determined experimentally by Guggenheim method. The excited state dipole moments ( ?e) were estimated from Lippert's, Bakshiev's and Chamma Viallet's equations by using the variation of the Stokes shift with the solvent dielectric constant and refractive index. Ground and excited state dipole moments were evaluated by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was observed that dipole moment values of excited states ( ?e) were higher than corresponding ground state values ( ?g), indicating a substantial redistribution of the ?-electron densities in a more polar excited state for all the dyes investigated.

Biradar, D. S.; Siddlingeshwar, B.; Hanagodimath, S. M.

2008-03-01

291

Antiferromagnetic ground state in NpCoGe  

NASA Astrophysics Data System (ADS)

NpCoGe, the neptunium analog of the ferromagnetic superconductor UCoGe, has been investigated by dc magnetization, ac susceptibility, specific heat, electrical resistivity, Hall effect, 237Np Mössbauer spectroscopy, and local spin-density approximation (LSDA) calculations. NpCoGe exhibits an antiferromagnetic ground state with a Néel temperature TN?13 K and an average ordered magnetic moment =0.80?B. The magnetic phase diagram has been determined and shows that the antiferromagnetic structure is destroyed by the application of a magnetic field (?3 T). The value of the isomer shift suggests a Np3+ charge state (configuration 5f4). A high Sommerfeld coefficient value for NpCoGe (170 mJ mol-1 K-2) is inferred from specific heat. LSDA calculations indicate strong magnetic anisotropy and easy magnetization along the c axis. Mössbauer data and calculated exchange interactions support the possible occurrence of an elliptical spin-spiral structure in NpCoGe. The comparison with NpRhGe and uranium analogs suggests the leading role of 5f-d hybridization, the rather delocalized character of 5f electrons in NpCoGe, and the possible proximity of NpRuGe or NpFeGe to a magnetic quantum critical point.

Colineau, E.; Griveau, J.-C.; Eloirdi, R.; Gaczy?ski, P.; Khmelevskyi, S.; Shick, A. B.; Caciuffo, R.

2014-03-01

292

Transition state geometry in radical hydrogen atom abstraction  

NASA Astrophysics Data System (ADS)

The interatomic distances in the transition states of radical hydrogen atom abstraction reactions X•+HY ? XH+Y• determined by quantum chemical calculations are systematized and generalized. It is shown that depending on the reaction centre structure, these reactions can be subdivided into classes with the same X...Y interatomic distance in each class. The transition state geometries found by the methods of intersecting parabolas and intersecting Morse curves are also presented. The X...H...Y fragments are almost linear, the hydrogen atom position being determined by the reaction enthalpy. The effects of triplet repulsion, electronegativities and radii of X and Y atoms, the presence of adjoining ?-bonds, and steric effects on the X...Y interatomic distances are analyzed and characterized. The bibliography includes 62 references.

Denisov, Evgenii T.; Shestakov, Alexander F.; Denisova, Taisa G.

2012-12-01

293

Ground and lowest-lying electronic states of CoN. A multiconfigurational study.  

PubMed

The lowest-lying X1Sigma+, a3Phi, b3II, c5Delta, A1Phi, and B1II electronic states of CoN have been investigated at the ab initio MRCI and MS-CASPT2 levels, with extended atomic basis sets and inclusion of scalar relativistic effects. Among the singlet states, the A1Phi and B1II states have been described for the first time. Potential energy curves, excitation energies, spectroscopic constants, and bonding character for all states are reported. Comparison with other early transition-metal nitrides (ScN, TiN, VN, and CrN), isoelectronic (NiC) and isovalent (RhN and IrN) species has been made, besides analyzing the B1II <=> X1+ electronic transition in terms of Franck-Condon factors, Einstein coefficients, and radiative lifetimes. At both levels of theory, the following energetic order has been obtained: X1Sigma+, a3Phi, b3II, c5Delta, A1Phi, and B1II, with good agreement with experimental results. In contrast, previous DFT and MRCI calculations predicted the ground state to be the 5Delta state. PMID:17181357

Gobbo, João Paulo; Borin, Antonio Carlos

2006-12-28

294

Combined Film Catalog, 1972, United States Atomic Energy Commission.  

ERIC Educational Resources Information Center

A comprehensive listing of all current United States Atomic Energy Commission (USAEC) films, this catalog describes 232 films in two major film collections. Part One: Education-Information contains 17 subject categories and two series and describes 134 films with indicated understanding levels on each film for use by schools. The categories…

Atomic Energy Commission, Washington, DC.

295

Positron spectroscopy in atomic and solid state physics  

Microsoft Academic Search

Basic research problems in Atomic Physics with positrons (total cross sections, Ramsauer minima, positronium formation, selective ionization) and some benchmark measurements in Solid State Physics using positron annihilation (He-created nano-voids in Si, Oxygen precipitates in Si, low ? materials) are discussed.

G. P. Karwasz; R. S. Brusa; A. Zecca

2003-01-01

296

Towards the creation of Fock states of atoms  

NASA Astrophysics Data System (ADS)

Ultracold atoms have been successfully used to study numerous systems, previously unaccessible, but a precise control over the atom number of the sample still remains a challenge. This dissertation describes our progress towards achieving Fock states of atoms. The first three chapters cover the basic physics necessary to understand the techniques we use in our lab to manipulate atoms. We then summarize our experimental results from an earlier setup where we did two experiments. In the first experiment we compare the transport of cold atoms and a Bose Einstein Condensate (BEC) in a periodic potential. We find a critical potential height beyond which the condensate behavior deviates significantly from that of thermal atoms. In the second experiment we study the effect of periodic temporal kicks by a spatially periodic potential on a BEC in a quasi one dimensional trap. We observe a limit on the energy that the system can absorb from the kicks, which we conclude is due to the finite height of the trap rather than quantum effects. The majority of the dissertation discusses our experimental setup designed to produce Fock states. The setup is designed to use the method of laser culling to produce Fock states. We are able to create a BEC and transport it into a glass cell 25 cm away. We tried different innovative methods to reduce vibrations during transport before finally settling to a commercial air bearing translation stage. We create a high confinement one dimensional optical trap using the Hermite Gaussian TEM01 mode of a laser beam. Such a trap gives trapping frequencies comparable to an optical lattice and allows us to create a single one dimensional trap. We creating the TEM01 mode using an appropriate phase object (phase plate) in the path of a TEM00 mode beam. The method for producing the phase plate was very well controlled to obtain a good quality mode. Once the atoms are loaded into this one dimensional trap we can proceed to do laser culling to observe Sub-Poissonian number statistics and eventually create Fock states of few atoms. Finally, we describe a novel method to create a real time tunable optical lattice which would provide us with the ability of spatially resolved single atom detection.

Kelkar, Hrishikesh Vidyadhar

297

Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification  

Microsoft Academic Search

The effects of atomic oxygen on boron nitride, silicon nitride, solar cell interconnects used on the Intelsat 6 satellite, organic polymers, and MoSâ and WSâ dry lubricant have been studied in low Earth orbit (LEO) flight experiments and in our ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed in situ electrical resistance measurements

J. B. Cross; S. L. Koontz; E. H. Lan

1991-01-01

298

The Excitation of the Ground State of Helium to the 2(1)p State by Fast Electrons.  

National Technical Information Service (NTIS)

The first Born approximation is used to calculate the cross section for electron excitation of the ground state of helium to the 2(1)P state. Various ground- and excited-state wave functions are employed and the calculations are performed using both the l...

D. J. Kennedy A. E. Kingston

1967-01-01

299

Fragmented Metastable States Exist in an Attractive Bose-Einstein Condensate for Atom Numbers Well above the Critical Number of the Gross-Pitaevskii Theory  

NASA Astrophysics Data System (ADS)

It is well known that attractive condensates do not posses a stable ground state in three dimensions. The widely used Gross-Pitaevskii theory predicts the existence of metastable states up to some critical number NcrGP of atoms. It is demonstrated here that fragmented metastable states exist for atom numbers well above NcrGP. The fragments are strongly overlapping in space. The results are obtained and analyzed analytically as well as numerically. The implications are discussed.

Cederbaum, Lorenz S.; Streltsov, Alexej I.; Alon, Ofir E.

2008-02-01

300

From rotating atomic rings to quantum Hall states  

PubMed Central

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

Roncaglia, M.; Rizzi, M.; Dalibard, J.

2011-01-01

301

Correction method for obtaining the variationally best ground-state pair density  

SciTech Connect

We present a correction method for the pair density (PD) to get close to the ground-state one. The PD is corrected to be a variationally best PD within the search region that is extended by adding the uniformly scaled PDs to its elements. The corrected PD is kept N-representable and satisfies the virial relation rigorously. The validity of the present method is confirmed by numerical calculations of neon atom. It is shown that the root-mean-square error of the electron-electron interaction and external potential energies, which is a good benchmark for the error of the PD, is reduced by 69.7% without additional heavy calculations.

Higuchi, Masahiko; Higuchi, Katsuhiko [Department of Physics, Faculty of Science, Shinshu University, Matsumoto 390-8621 (Japan); Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan)

2011-10-15

302

Structural expansions for the ground state energy of a simple metal  

NASA Technical Reports Server (NTRS)

A structural expansion for the static ground state energy of a simple metal is derived. An approach based on single particle band structure which treats the electron gas as a non-linear dielectric is presented, along with a more general many particle analysis using finite temperature perturbation theory. The two methods are compared, and it is shown in detail how band-structure effects, Fermi surface distortions, and chemical potential shifts affect the total energy. These are of special interest in corrections to the total energy beyond third order in the electron ion interaction, and hence to systems where differences in energies for various crystal structures are exceptionally small. Preliminary calculations using these methods for the zero temperature thermodynamic functions of atomic hydrogen are reported.

Hammerberg, J.; Ashcroft, N. W.

1973-01-01

303

Ground-State Pressure of Quasi-2D Fermi and Bose Gases  

NASA Astrophysics Data System (ADS)

Using an ultracold gas of atoms, we have realized a quasi-two-dimensional Fermi system with widely tunable s-wave interactions nearly in a ground state. Pressure and density are measured. The experiment covers physically different regimes: weakly and strongly attractive Fermi gases and a Bose gas of tightly bound pairs of fermions. In the Fermi regime of weak interactions, the pressure is systematically above a Fermi-liquid-theory prediction, maybe due to mesoscopic effects. In the opposite Bose regime, the pressure agrees with a bosonic mean-field scaling in a range beyond simplest expectations. In the strongly interacting regime, measurements disagree with a purely 2D model. Reported data may serve for sensitive testing of theoretical methods applicable across different quantum physics disciplines.

Makhalov, Vasiliy; Martiyanov, Kirill; Turlapov, Andrey

2014-01-01

304

Table of experimental nuclear ground state charge radii: An update  

NASA Astrophysics Data System (ADS)

The present table contains experimental root-mean-square (rms) nuclear charge radii R obtained by combined analysis of two types of experimental data: (i) radii changes determined from optical and, to a lesser extent, K? X-ray isotope shifts and (ii) absolute radii measured by muonic spectra and electronic scattering experiments. The table combines the results of two working groups, using respectively two different methods of evaluation, published in ADNDT earlier. It presents an updated set of rms charge radii for 909 isotopes of 92 elements from 1H to 96Cm together, when available, with the radii changes from optical isotope shifts. Compared with the last published tables of R-values from 2004 (799 ground states), many new data are added due to progress recently achieved by laser spectroscopy up to early 2011. The radii changes in isotopic chains for He, Li, Be, Ne, Sc, Mn, Y, Nb, Bi have been first obtained in the last years and several isotopic sequences have been recently extended to regions far off stability, (e.g., Ar, Mo, Sn, Te, Pb, Po).

Angeli, I.; Marinova, K. P.

2013-01-01

305

Universality in Ground State Energy Distributions of Random Elastic Manifolds  

NASA Astrophysics Data System (ADS)

The distribution of ground state energies of elastic manifolds with random-bond disorder is studied numerically in (1+1), (1+2), (1+3), and (2+1) dimensions. (1+1) -dimensional manifolds, or directed polymers, are known to have in a ``single valley'' an energy distribution which is Gaussian close to the mean, and has stretched exponential low and high energy tails with the stretching exponents ?- = 1.6 and ?+ = 2.3 (J. A. Kim, M. A. Moore, and A. J. Bray, Phys. Rev. A 44), 2345 (1991).. With free or periodic boundary conditions, if the transverse height of the system is increased the ?-exponents vary continuosly and the energy distribution has an asymptotic cross-over to the Gumbel distribution of extreme statistics. For all the cases, including the (2+1)-dimensional random bond Ising domain wall one, it is found that the ?-exponents corresponding to a single-valley boundary condition are hyper-universal, close to those from (1+1) dimensions. This is in contrast to the scaling of the width of the distribution, characterized by the energy fluctuation exponent ? which depends on dimensionality. Acknowledgment: This work was performed under the auspices of the US Dept. of Energy at the University of California/Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48.

Seppälä, Eira T.; Kytölä, Kalle P.; Alava, Mikko J.

2002-03-01

306

Making classical ground-state spin computing fault-tolerant.  

PubMed

We examine a model of classical deterministic computing in which the ground state of the classical system is a spatial history of the computation. This model is relevant to quantum dot cellular automata as well as to recent universal adiabatic quantum computing constructions. In its most primitive form, systems constructed in this model cannot compute in an error-free manner when working at nonzero temperature. However, by exploiting a mapping between the partition function for this model and probabilistic classical circuits we are able to show that it is possible to make this model effectively error-free. We achieve this by using techniques in fault-tolerant classical computing and the result is that the system can compute effectively error-free if the temperature is below a critical temperature. We further link this model to computational complexity and show that a certain problem concerning finite temperature classical spin systems is complete for the complexity class Merlin-Arthur. This provides an interesting connection between the physical behavior of certain many-body spin systems and computational complexity. PMID:21230024

Crosson, I J; Bacon, D; Brown, K R

2010-09-01

307

Making classical ground-state spin computing fault-tolerant  

NASA Astrophysics Data System (ADS)

We examine a model of classical deterministic computing in which the ground state of the classical system is a spatial history of the computation. This model is relevant to quantum dot cellular automata as well as to recent universal adiabatic quantum computing constructions. In its most primitive form, systems constructed in this model cannot compute in an error-free manner when working at nonzero temperature. However, by exploiting a mapping between the partition function for this model and probabilistic classical circuits we are able to show that it is possible to make this model effectively error-free. We achieve this by using techniques in fault-tolerant classical computing and the result is that the system can compute effectively error-free if the temperature is below a critical temperature. We further link this model to computational complexity and show that a certain problem concerning finite temperature classical spin systems is complete for the complexity class Merlin-Arthur. This provides an interesting connection between the physical behavior of certain many-body spin systems and computational complexity.

Crosson, I. J.; Bacon, D.; Brown, K. R.

2010-09-01

308

Ground-state coding in partially connected neural networks  

NASA Technical Reports Server (NTRS)

Patterns over (-1,0,1) define, by their outer products, partially connected neural networks, consisting of internally strongly connected, externally weakly connected subnetworks. The connectivity patterns may have highly organized structures, such as lattices and fractal trees or nests. Subpatterns over (-1,1) define the subcodes stored in the subnetwork, that agree in their common bits. It is first shown that the code words are locally stable stares of the network, provided that each of the subcodes consists of mutually orthogonal words or of, at most, two words. Then it is shown that if each of the subcodes consists of two orthogonal words, the code words are the unique ground states (absolute minima) of the Hamiltonian associated with the network. The regions of attraction associated with the code words are shown to grow with the number of subnetworks sharing each of the neurons. Depending on the particular network architecture, the code sizes of partially connected networks can be vastly greater than those of fully connected ones and their error correction capabilities can be significantly greater than those of the disconnected subnetworks. The codes associated with lattice-structured and hierarchical networks are discussed in some detail.

Baram, Yoram

1989-01-01

309

Thermal Ground State in Yang-Mills Thermodynamics  

SciTech Connect

We derive an a useful priori estimate for the thermal ground state of deconfining phase of SU(2) Yang-Mills thermodynamics in four-dimensional, flat spacetime and discuss its implications. Upon a selfconsistent spatial coarse-graining over noninteracting, trivial-holonomy (BPS saturated)(anti)calorons of unit topological charge modulus an inert, adjoint scalar field |{phi}| and an effective pure-gauge configuration a{sub {mu}}{sup gs} emerge. The modulus |{phi}|>0 defines the maximal resolution in the coarse-grained theory and induces dynamical gauge-symmetry breaking. Thanks to perturbative renormalizability and the fact that |{phi}| can not absorb or emit energy-momentum the effective action is local and simple. The temperature dependence of the effective coupling is a consequence of thermodynamical consistency and describes the Coulomb screening of a static test charge due to short-lived monopole-antimonopole pairs. The latter occur unresolvably as small-holonomy excitations of (anti)calorons by the absorption of propagating fundamental gauge fields.

Hofmann, Ralf [ITP, Universitaet Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany)

2011-09-22

310

Regularities in molecular properties of ground state stable diatomics  

NASA Astrophysics Data System (ADS)

A simple relationship is reported between vibrational frequencies, bond lengths, and reduced masses for many families of stable, ground state diatomics: the frequency is proportional to the reciprocal of the product of the bond length and the square root of the reduced mass. This is demonstrated with each of the following related families: the alkali metal diatomics, the group 15 diatomics, the group 16 diatomics, the halogen diatomics, the alkali metal hydrides, the alkaline earth oxides, the group 14 oxides and their sulfides, the diatomics of carbon, of silicon and of germanium with group 16 elements, the hydrogen halides, the halides of lithium, of sodium, of potassium, of rubidium and of cesium, the chlorides of the alkali metals and of silver, and the polyatomic hydrides of groups 14 and 15. Although correlation coefficients of 0.99 or greater in each of the 21 families examined demonstrate the validity of the correlation, the deviations found are significantly larger than can be attributed to experimental uncertainties.

Zavitsas, Andreas A.

2004-06-01

311

Ground-state properties of neutron-rich Mg isotopes  

NASA Astrophysics Data System (ADS)

We analyze recently measured total reaction cross sections for 24-38Mg isotopes incident on 12C targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics (AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of 24-38Mg are then deduced from the measured reaction cross sections by fine tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for 24-36Mg, but still considerably underestimate them for 37,38Mg. The large matter radii suggest that 37,38Mg are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of deformation parameter is predicted by AMD. Large deformation is seen from 31Mg with N =19 to a drip-line nucleus 40Mg with N =28, indicating that both the N =20 and 28 magicities disappear. N dependence of neutron skin thickness is also predicted by AMD.

Watanabe, S.; Minomo, K.; Shimada, M.; Tagami, S.; Kimura, M.; Takechi, M.; Fukuda, M.; Nishimura, D.; Suzuki, T.; Matsumoto, T.; Shimizu, Y. R.; Yahiro, M.

2014-04-01

312

Ab initio study of ground and excited states of 6Li40Ca and 6Li88Sr molecules.  

PubMed

We present quantum-chemical calculations for the ground and some low-lying excited states of isolated LiCa and LiSr molecules using multi-state complete active space second-order perturbation theory (MS-CASPT2). The potential energy curves (PECs) and their corresponding spectroscopic constants, obtained at the spin-free (SF) and spin-orbit (SO) levels, agree well with available experimental values. Our SO-MS-CASPT2 calculation at the atomic limit (R = 100 a.u.) with the largest basis set reproduces experimental atomic excitation energies within 3% for both LiCa and LiSr. In addition, permanent dipole moments and transition dipole moments at the SF level are also obtained. Rovibrational calculations of the ground and selected excited states, together with the spontaneous emission rates, demonstrate that the formation of ultracold LiCa and LiSr molecules in low-lying vibrational levels of the electronic ground state may be possible. PMID:23697418

Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

2013-05-21

313

Generation of hyperentangled states between remote noninteracting atomic ions  

SciTech Connect

We propose a scheme of generating four-qubit hyperentangled states between a pair of remote noninteracting atomic ions with a {Lambda} configuration that are confined in Paul traps. These hyperentangled states, different from the normal entangled states that are entangled in a single degree of freedom, are entangled in both spin and motion degrees of freedom. In our proposal, the entanglement is first generated in spin degrees of freedom using linear optics and then transferred to the motion degree of freedom using a sequence of laser pluses, including the stimulated Raman carrier transitions and sideband transitions. The proposal is completed with regenerating entanglement in spin degrees of freedom using linear optics.

Hu Baolin [School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223001 (China); Zhan Youbang [School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223001 (China); CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China)

2010-11-15

314

Robustness of fractional quantum Hall states with dipolar atoms in artificial gauge fields  

SciTech Connect

The robustness of fractional quantum Hall states is measured as the energy gap separating the Laughlin ground state from excitations. Using thermodynamic approximations for the correlation functions of the Laughlin state and the quasihole state, we evaluate the gap in a two-dimensional system of dipolar atoms exposed to an artificial gauge field. For Abelian fields, our results agree well with the results of exact diagonalization for small systems but indicate that the large value of the gap predicted [Phys. Rev. Lett. 94, 070404 (2005)] was overestimated. However, we are able to show that the small gap found in the Abelian scenario dramatically increases if we turn to non-Abelian fields squeezing the Landau levels.

Grass, T. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Baranov, M. A. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); RRC ''Kurchatov Institute,'' Kurchatov Square 1, 123182 Moscow (Russian Federation); Lewenstein, M. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, Lluis Companys 23, E-08010 Barcelona (Spain)

2011-10-15

315

Ground-state magneto-optical resonances in cesium vapor confined in an extremely thin cell  

SciTech Connect

Experimental and theoretical studies are presented related to the ground-state magneto-optical resonance observed in cesium vapor confined in an extremely thin cell (ETC), with thickness equal to the wavelength of the irradiating light. It is shown that utilization of the ETC allows one to examine the formation of a magneto-optical resonance on the individual hyperfine transitions, thus distinguishing processes resulting in dark (reduced absorption) or bright (enhanced absorption) resonance formation. We report experimental evidence of bright magneto-optical resonance sign reversal in Cs atoms confined in an ETC. A theoretical model is proposed based on the optical Bloch equations that involves the elastic interaction processes of atoms in the ETC with its walls, resulting in depolarization of the Cs excited state, which is polarized by the exciting radiation. This depolarization leads to the sign reversal of the bright resonance. Using the proposed model, the magneto-optical resonance amplitude and width as a function of laser power are calculated and compared with the experimental ones. The numerical results are in good agreement with those of experiment.

Andreeva, C.; Cartaleva, S.; Petrov, L.; Slavov, D. [Institute of Electronics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko shosse 72, 1784 Sofia (Bulgaria); Atvars, A.; Auzinsh, M.; Blush, K. [Department of Physics and Institute of Atomic Physics and Spectroscopy, University of Latvia, 19 Rainis Boulevard, LV-1586 Riga (Latvia)

2007-12-15

316

Ground-state muon transfer from deuterium to 3He and 4He  

NASA Astrophysics Data System (ADS)

We have observed the deexcitation x-ray spectra of the exotic molecules (d?4He)* and (d?3He)* with good statistics and low background. From the time distributions of these x rays, we have directly determined the muon transfer rates from ground-state muonic deuterium atoms to helium nuclei. The obtained transfer rates in gaseous mixtures at ~30 K are ?d3He=(1.856+/-0.077)×108 s-1 to 3He, and ?d4He=(10.50+/-0.21)×108 s-1 to 4He. In liquid mixtures, we measured the muon transfer rates ?d3He=(2.77+/-0.73)×108 s-1 and ?d4He=(14.2+/-1.4)×108 s-1. These transfer rates have to be multiplied with the target density and the atomic helium concentration to obtain the ``effective transfer rates'' for a specific target composition. The expected isotopic effect between mixtures containing 3He and mixtures containing 4He, as well as with respect to the hydrogen-helium case, is clearly confirmed. A density effect was observed for both isotopic compositions. We investigated the widths and the energies of the intensity maxima of the observed energy spectra of the molecular x rays. From the comparison of the measured energy spectra with calculated ones, we conclude that decay from the rotational state J=1 of the muonic molecule dominates over decay from J=0 at the investigated experimental conditions.

Gartner, B.; Ackerbauer, P.; Breunlich, W. H.; Cargnelli, M.; Kammel, P.; King, R.; Lauss, B.; Marton, J.; Prymas, W.; Zmeskal, J.; Petitjean, C.; Augsburger, M.; Chatellard, D.; Egger, J.-P.; von Egidy, T.; Hartmann, F. J.; Kosak, A.; Mühlbauer, M.; Mulhauser, F.; Schaller, L. A.; Schellenberg, L.; Schneuwly, H.; Thalmann, Y.-A.; Tresch, S.; Werthmüller, A.

2000-07-01

317

Ground-Laboratory to In-Space Atomic Oxygen Correlation for the Polymer Erosion and Contamination Experiment (PEACE) Polymers  

NASA Technical Reports Server (NTRS)

The Materials International Space Station Experiment 2 (MISSE 2) Polymer Erosion and Contamination Experiment (PEACE) polymers were exposed to the environment of low Earth orbit (LEO) for 3.95 years from 2001 to 2005. There were 41 different PEACE polymers, which were flown on the exterior of the International Space Station (ISS) in order to determine their atomic oxygen erosion yields. In LEO, atomic oxygen is an environmental durability threat, particularly for long duration mission exposures. Although spaceflight experiments, such as the MISSE 2 PEACE experiment, are ideal for determining LEO environmental durability of spacecraft materials, ground-laboratory testing is often relied upon for durability evaluation and prediction. Unfortunately, significant differences exist between LEO atomic oxygen exposure and atomic oxygen exposure in ground-laboratory facilities. These differences include variations in species, energies, thermal exposures and radiation exposures, all of which may result in different reactions and erosion rates. In an effort to improve the accuracy of ground-based durability testing, ground-laboratory to in-space atomic oxygen correlation experiments have been conducted. In these tests, the atomic oxygen erosion yields of the PEACE polymers were determined relative to Kapton H using a radio-frequency (RF) plasma asher (operated on air). The asher erosion yields were compared to the MISSE 2 PEACE erosion yields to determine the correlation between erosion rates in the two environments. This paper provides a summary of the MISSE 2 PEACE experiment; it reviews the specific polymers tested as well as the techniques used to determine erosion yield in the asher, and it provides a correlation between the space and ground laboratory erosion yield values. Using the PEACE polymers asher to in-space erosion yield ratios will allow more accurate in-space materials performance predictions to be made based on plasma asher durability evaluation.

Stambler, Arielle H.; Inoshita, Karen E.; Roberts, Lily M.; Barbagallo, Claire E.; deGroh, Kim K.; Banks, Bruce A.

2011-01-01

318

Potential energy curves of M(np 2P)?RG(2&Pgr;) excited states and M+?RG ground states (M=Li, Na; RG=He, Ne)  

Microsoft Academic Search

It has been established for some time that the bond energies for any given valence p? excited state of Group 1 (2P) and Group 2 (1,3P) metal-atom\\/rare-gas (M?RG) van der Waals complexes tend to increase with the polarizability of the RG atom. It is also known that the binding energies of the corresponding M+?RG ground state ions are generally greater

Solomon Bililign; Maciej Gutowski; Jack Simons; W. H. Breckenridge

1994-01-01

319

Structure and vibrations of catechol in the S 1 state and ionic ground state  

Microsoft Academic Search

To determine structure and vibrations of catechol and d2-catechol (C6H4(OD)2) in the ionic ground state, MATI spectra as well as ab initio and DFT calculations are presented. The comparison of the experimentally observed vibrational frequencies with the calculated values leads to a complete assignment of all vibrations. CASSCF and DFT calculations predict a planar geometry of catechol in the S0

M. Gerhards; S. Schumm; C. Unterberg; K. Kleinermanns

1998-01-01

320

Ground States as Resources for Universal Measurement-Based Quantum Computing  

NASA Astrophysics Data System (ADS)

Measurement-based quantum computation (MBQC) requires a massively entangled resource state (such as a cluster state) as input. Experimental efforts towards generating such states have typically focused on performing global entangling operations on uncorrelated qubits. As the states that result from this type of procedure are not generally ground states, they are very sensitive to decoherence effects. A more robust resource would be one that is in fact a ground state of some Hamiltonian that exhibits a reasonably large energy gap between the ground state and the various excited states. We will discuss the possibility of finding simple two-body spin Hamiltonians whose ground states are equivalent to resource states for MBQC under stochastic protocols comprised solely of local operations and classical communication.

D'Souza, Adam G.; Feder, David L.

2008-03-01

321

Derivation of novel human ground state naive pluripotent stem cells.  

PubMed

Mouse embryonic stem (ES) cells are isolated from the inner cell mass of blastocysts, and can be preserved in vitro in a naive inner-cell-mass-like configuration by providing exogenous stimulation with leukaemia inhibitory factor (LIF) and small molecule inhibition of ERK1/ERK2 and GSK3? signalling (termed 2i/LIF conditions). Hallmarks of naive pluripotency include driving Oct4 (also known as Pou5f1) transcription by its distal enhancer, retaining a pre-inactivation X chromosome state, and global reduction in DNA methylation and in H3K27me3 repressive chromatin mark deposition on developmental regulatory gene promoters. Upon withdrawal of 2i/LIF, naive mouse ES cells can drift towards a primed pluripotent state resembling that of the post-implantation epiblast. Although human ES cells share several molecular features with naive mouse ES cells, they also share a variety of epigenetic properties with primed murine epiblast stem cells (EpiSCs). These include predominant use of the proximal enhancer element to maintain OCT4 expression, pronounced tendency for X chromosome inactivation in most female human ES cells, increase in DNA methylation and prominent deposition of H3K27me3 and bivalent domain acquisition on lineage regulatory genes. The feasibility of establishing human ground state naive pluripotency in vitro with equivalent molecular and functional features to those characterized in mouse ES cells remains to be defined. Here we establish defined conditions that facilitate the derivation of genetically unmodified human naive pluripotent stem cells from already established primed human ES cells, from somatic cells through induced pluripotent stem (iPS) cell reprogramming or directly from blastocysts. The novel naive pluripotent cells validated herein retain molecular characteristics and functional properties that are highly similar to mouse naive ES cells, and distinct from conventional primed human pluripotent cells. This includes competence in the generation of cross-species chimaeric mouse embryos that underwent organogenesis following microinjection of human naive iPS cells into mouse morulas. Collectively, our findings establish new avenues for regenerative medicine, patient-specific iPS cell disease modelling and the study of early human development in vitro and in vivo. PMID:24172903

Gafni, Ohad; Weinberger, Leehee; Mansour, Abed AlFatah; Manor, Yair S; Chomsky, Elad; Ben-Yosef, Dalit; Kalma, Yael; Viukov, Sergey; Maza, Itay; Zviran, Asaf; Rais, Yoach; Shipony, Zohar; Mukamel, Zohar; Krupalnik, Vladislav; Zerbib, Mirie; Geula, Shay; Caspi, Inbal; Schneir, Dan; Shwartz, Tamar; Gilad, Shlomit; Amann-Zalcenstein, Daniela; Benjamin, Sima; Amit, Ido; Tanay, Amos; Massarwa, Rada; Novershtern, Noa; Hanna, Jacob H

2013-12-12

322

Fine structure excitation transfer between the potassium 4 2 P states induced by collisions with caesium atoms  

Microsoft Academic Search

Applying diode-laser resonant fluorescence method, the cross sections for the excitation energy transfer of the collisional process K*(42P1\\/2)+Cs(62S1\\/2)?K*(42P3\\/2)+Cs(62S1\\/2) have been measured. The values we have obtained are s(1\\/2?3\\/2)=77 Å2 and s(3\\/2?1\\/2)=48 Å2. These results complete the sequence of data for the fine-structure mixing of the first-resonance states of alkali atoms colliding with the ground-state caesium atoms.

S. Knezovic; C. Vadla; M. Movre

1992-01-01

323

GSGPEs: A MATLAB code for computing the ground state of systems of Gross-Pitaevskii equations  

NASA Astrophysics Data System (ADS)

GSGPEs is a Matlab/GNU Octave suite of programs for the computation of the ground state of systems of Gross-Pitaevskii equations. It can compute the ground state in the defocusing case, for any number of equations with harmonic or quasi-harmonic trapping potentials, in spatial dimension one, two or three. The computation is based on a spectral decomposition of the solution into Hermite functions and direct minimization of the energy functional through a Newton-like method with an approximate line-search strategy. Program summaryProgram title: GSGPEs Catalogue identifier: AENT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AENT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1417 No. of bytes in distributed program, including test data, etc.: 13673 Distribution format: tar.gz Programming language: Matlab/GNU Octave. Computer: Any supporting Matlab/GNU Octave. Operating system: Any supporting Matlab/GNU Octave. RAM: About 100 MB for a single three-dimensional equation (test run output). Classification: 2.7, 4.9. Nature of problem: A system of Gross-Pitaevskii Equations (GPEs) is used to mathematically model a Bose-Einstein Condensate (BEC) for a mixture of different interacting atomic species. The equations can be used both to compute the ground state solution (i.e., the stationary order parameter that minimizes the energy functional) and to simulate the dynamics. For particular shapes of the traps, three-dimensional BECs can be also simulated by lower dimensional GPEs. Solution method: The ground state of a system of Gross-Pitaevskii equations is computed through a spectral decomposition into Hermite functions and the direct minimization of the energy functional. Running time: About 30 seconds for a single three-dimensional equation with d.o.f. 40 for each spatial direction (test run output).

Caliari, Marco; Rainer, Stefan

2013-03-01

324

Determination of Ground-Laboratory to In-Space Effective Atomic Oxygen Fluence for DC 93.500 Silicone.  

National Technical Information Service (NTIS)

The objective of this research was to calibrate the ground-to-space effective atomic oxygen fluence for DC 93-500 silicone in a thermal energy electron cyclotron resonance (ECR) oxygen plasma facility. Silicones, commonly used spacecraft materials, do not...

K. K. deGroh B. A. Banks D. Ma

2004-01-01

325

Atomic homodyne detection of continuous-variable entangled twin-atom states.  

PubMed

Historically, the completeness of quantum theory has been questioned using the concept of bipartite continuous-variable entanglement. The non-classical correlations (entanglement) between the two subsystems imply that the observables of one subsystem are determined by the measurement choice on the other, regardless of the distance between the subsystems. Nowadays, continuous-variable entanglement is regarded as an essential resource, allowing for quantum enhanced measurement resolution, the realization of quantum teleportation and quantum memories, or the demonstration of the Einstein-Podolsky-Rosen paradox. These applications rely on techniques to manipulate and detect coherences of quantum fields, the quadratures. Whereas in optics coherent homodyne detection of quadratures is a standard technique, for massive particles a corresponding method was missing. Here we report the realization of an atomic analogue to homodyne detection for the measurement of matter-wave quadratures. The application of this technique to a quantum state produced by spin-changing collisions in a Bose-Einstein condensate reveals continuous-variable entanglement, as well as the twin-atom character of the state. Our results provide a rare example of continuous-variable entanglement of massive particles. The direct detection of atomic quadratures has applications not only in experimental quantum atom optics, but also for the measurement of fields in many-body systems of massive particles. PMID:22139418

Gross, C; Strobel, H; Nicklas, E; Zibold, T; Bar-Gill, N; Kurizki, G; Oberthaler, M K

2011-12-01

326

Are the superstructures seen in the Cu-Pd phase-diagram ground states? First-principles predicted structures.  

NASA Astrophysics Data System (ADS)

Ordered phases appear in nature either as ordinary,small- unit cell-structures ( L10,L11,DO22,etc) or as ``Long Period Superstructures'' ( LPS) having huge cells. Examples of the latter are the 1D polytypes of SiC or the 1D and 2D LPS's seen in the phase diagram of Cu-Pd. Finding via first-principles calculations, if such structures correspond to thermodynamic ground states or represent kinetically frozen-in structures has been hindered by the large number of atoms O(10^3) in such LPS's. We use instead a set of directly-calculated first-principles total energies to construct a Cluster-Expansion Hamiltonian whose ground states can be rapidly surveyed.We predict for Cu- Pd (i) a yet undiscovered Cu7Pd( =S1) ground state at X(Pd)= 12.5% and the LPS3 structure ( =S2) at 25% . (ii) In the low- temperature regime a single L12 phase cannot be stable, even at the presence of antisites. Instead we find that an S2-phase with an S1-like ordering tendency will form. (iii) 2D-LPSs are probably kinetically-stabilized structures which transform into the 1D-LPS ground-state structures in thermal equilibrium.

Müller, Stefan; Bärthlein, Stefan; Winning, Elke; Hart, Gus; Zunger, Alex

2007-03-01

327

Majorana edge States in atomic wires coupled by pair hopping.  

PubMed

We present evidence for Majorana edge states in a number conserving theory describing a system of spinless fermions on two wires that are coupled by pair hopping. Our analysis is based on a combination of a qualitative low energy approach and numerical techniques using the density matrix renormalization group. In addition, we discuss an experimental realization of pair-hopping interactions in cold atom gases confined in optical lattices. PMID:24206486

Kraus, Christina V; Dalmonte, Marcello; Baranov, Mikhail A; Läuchli, Andreas M; Zoller, P

2013-10-25

328

Majorana Edge States in Atomic Wires Coupled by Pair Hopping  

NASA Astrophysics Data System (ADS)

We present evidence for Majorana edge states in a number conserving theory describing a system of spinless fermions on two wires that are coupled by pair hopping. Our analysis is based on a combination of a qualitative low energy approach and numerical techniques using the density matrix renormalization group. In addition, we discuss an experimental realization of pair-hopping interactions in cold atom gases confined in optical lattices.

Kraus, Christina V.; Dalmonte, Marcello; Baranov, Mikhail A.; Läuchli, Andreas M.; Zoller, P.

2013-10-01

329

Steady-state, high dose neutron generation and concentration apparatus and method for deuterium atoms  

NASA Astrophysics Data System (ADS)

A steady-state source of neutrons is produced within an electrically grounded and temperature controlled chamber confining tritium or deuterium plasma at a predetermined density to effect implantation of ions in the surface of a palladium target rod coated with diffusion barrier material and immersed in such plasma. The rod is enriched with a high concentration of deuterium atoms after a prolonged plasma ion implantation. Collision of the deuterium atoms in the target by impinging ions of the plasma initiates fusion reactions causing emission of neutrons during negative voltage pulses applied to the rod through a high power modulator. The neutrons are so generated at a relatively high dose rate under optimized process conditions.

Uhm, Han S.; Lee, Woong M.

1991-07-01

330

Shape of polygonal quantum dots and ground-state instability in the spin polarization  

NASA Astrophysics Data System (ADS)

We theoretically investigate the ground-state electronic structure and the spin polarization of four electrons confined in two-dimensional (2D) polygonal quantum dots. We employ standard mean-field theory approaches using unrestricted Hartree-Fock (UHF) and density functional theory (DFT) calculations. Resonant UHF configuration interaction (res-UHF CI) calculations were also performed to incorporate the electron correlation more intuitively. Odd polygons (trigons and pentagons) preferentially generate the ground-state triplet as predicted by Hund's rule, whereas even polygons (tetragons, hexagons, and octagons) promote ground-state instability in the spin multiplicity and tend to produce an anti-Hund state of the ground-state singlet with strengthening of the interelectron interaction. The circle, a limited polygon having an infinite number of apexes, divides these odd and even polygons, and the ground-state instability can be well classified by the area of the polygon apexes that protrudes from an equisized circle.

Ishizuki, Masamu; Takemiya, Hannyo; Okunishi, Takuma; Takeda, Kyozaburo; Kusakabe, Kouichi

2012-04-01

331

Binary mixture of pseudo-spin-(1/2) Bose gases with interspecies spin exchange: From classical fixed points and ground states to quantum ground states  

SciTech Connect

We consider the effective spin Hamiltonian describing a mixture of two species of pseudo-spin-(1/2) Bose gases with interspecies spin exchange. First we analyze the stability of the fixed points of the corresponding classical dynamics, of which the signature is found in quantum dynamics with a disentangled initial state. Focusing on the case without an external potential, we find all the ground states by taking into account quantum fluctuations around the classical ground state in each parameter regime. The nature of entanglement and its relation with classical bifurcation is investigated. When the total spins of the two species are unequal, the maximal entanglement at the parameter point of classical bifurcation is possessed by the excited state corresponding to the classical fixed point which bifurcates, rather than by the ground state.

Wu Rukuan [State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433 (China); Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Shi Yu [State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433 (China)

2011-12-15

332

Ground beef consumption patterns in the United States, FoodNet, 2006 through 2007.  

PubMed

Infection resulting from foodborne pathogens, including Escherichia coli O157:H7, is often associated with consumption of raw or undercooked ground beef. However, little is known about the frequency of ground beef consumption in the general population. The objective of this study was to describe patterns of self-reported ground beef and pink ground beef consumption using data from the 2006 through 2007 FoodNet Population Survey. From 1 July 2006 until 30 June 2007, residents of 10 FoodNet sites were contacted by telephone and asked about foods consumed within the previous week. The survey included questions regarding consumption of ground beef patties both inside and outside the home, the consumption of pink ground beef patties and other types of ground beef inside the home, and consumption of ground beef outside the home. Of 8,543 survey respondents, 75.3% reported consuming some type of ground beef in the home. Of respondents who ate ground beef patties in the home, 18.0% reported consuming pink ground beef. Consumption of ground beef was reported most frequently among men, persons with incomes from $40,000 to $75,000 per year, and persons with a high school or college education. Ground beef consumption was least often reported in adults ?65 years of age. Men and persons with a graduate level education most commonly reported eating pink ground beef in the home. Reported consumption of ground beef and pink ground beef did not differ by season. Ground beef is a frequently consumed food item in the United States, and rates of consumption of pink ground beef have changed little since previous studies. The high rate of consumption of beef that has not been cooked sufficiently to kill pathogens makes pasteurization of ground beef an important consideration, especially for those individuals at high risk of complications from foodborne illnesses such as hemolytic uremic syndrome. PMID:22289595

Taylor, Ethel V; Holt, Kristin G; Mahon, Barbara E; Ayers, Tracy; Norton, Dawn; Gould, L Hannah

2012-02-01

333

Pair supersolid with atom-pair hopping on the state-dependent triangular lattice  

NASA Astrophysics Data System (ADS)

We systematically study an extended Bose-Hubbard model with atom hopping and atom-pair hopping in the presence of a three-body constraint on the triangular lattice. By means of large-scale quantum Monte Carlo simulations, the ground-state phase diagram is studied. We find a first-order transition between the atomic superfluid phase and the pair superfluid phase when the ratio of the atomic hopping and the atom-pair hopping is adapted. The first-order transition remains unchanged under various conditions. We then focus on the interplay among the atom-pair hopping, the on-site repulsion, and the nearest-neighbor repulsion. With on-site repulsion present, we observe first-order transitions between the Mott insulators and pair superfluid driven by the pair hopping. With the nearest-neighbor repulsion turning on, three typical solid phases with 2/3, 1, and 4/3 filling emerge at small atom-pair hopping region. A stable pair supersolid phase is found at small on-site repulsion. This is due to the three-body constraint and the pair hopping, which essentially make the model a quasihardcore boson system. Thus the pair supersolid state emerges basing on the order-by-disorder mechanism, by which hardcore bosons avoid classical frustration on the triangular lattice. Without on-site repulsion, the transitions between the pair supersolid and the atom superfluid or pair superfluid are first order, except for the particle-hole symmetric point. With weak on-site repulsion and atom hopping turning on, the transition between the pair supersolid and pair superfluid phase becomes continuous. The transition between solid and pair supersolid is three-dimensional XY university, with dynamical exponent z=1 and correlation exponent ?=0.67155. The thermal melting of pair supersolid belongs to the two-dimensional Ising university. We check both energetic and mechanical balance of pair supersolid phase. Lowering the three-body constraint, no pair supersolid is found due to the absence of degeneracy of pair solids in classical limits. We describe the experimental realization of pair tunneling on state dependent lattice.

Zhang, Wanzhou; Yin, Ruoxi; Wang, Yancheng

2013-11-01

334

Theoretical Studies of Rydberg Atom Collisions.  

National Technical Information Service (NTIS)

Theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg atom collisions. A strong dc...

R. E. Olson

1984-01-01

335

First-principles calculation of the phase stability and elastic properties of ZrPt compounds at ground state  

NASA Astrophysics Data System (ADS)

The phase stability, elastic properties, electronic structure and thermodynamics properties of ZrPt compounds are investigated by first-principles approach. The calculated formation enthalpies show that the CrB-type phase at ground state is more stable than that of CsCl-type, which is in good agreement with the experimental phenomena. The bulk modulus of CrB-type is close to the CsCl-type phase. However, the shear constant C44 and shear modulus for the former are two times larger than the latter. Furthermore, we found that the Debye temperature of CrB-type (288.5 K) is higher than that of CsCl-type (186 K) phase, indicates that the atomic cohesion of the former is stronger than the latter at ground state.

Pan, Y.; Guan, W. M.; Zhang, K. H.

2013-10-01

336

Inelastic processes in atomic collisions involving ground state and laser-prepared atoms  

NASA Astrophysics Data System (ADS)

In dit proefschrift worden experimenten beschreven waarbij ionen of atomen met een bepaalde snelheid op een ensemble van doelwitatomen worden gericht. Wanneer twee deeltjes elkaar voldoende genaderd hebben, vindt er wissel- werking plaats waarbij allerlei processen kunnen optreden. Deze processen resulteren in specieke eindproducten. Kennis over de interactie tussen twee botsingspartners wordt verkregen door te bekijken welke eindproducten ontstaan, en in welke mate. Een belangrijke grootheid die van invloed is op mogelijke processen is de onderlinge snelheid van de twee kernen, oftewel de botsingssnelheid. Wanneer de botsingssnelheid voldoende klein is dan kunnen de verschillende reactiemechanismen zowel kwalitatief als kwanti- tatief vaak goed voorspeld worden door het systeem te beschouwen als een kort-stondig molecuul, opgebouwd uit de twee botsende deeltjes. De ver- schillende processen die kunnen optreden worden gekwaliceerd afhankelijk van de vorming van bepaalde eindproducten. Ruwweg de volgende indeling kan gemaakt worden: 1. de interne structuur van de eindproducten zijn identiek aan die van de beginproducten. We spreken dan van een elastische botsing. 2. e en van de deeltjes of beiden worden in een aangeslagen toestand ge- bracht (of ge¨oniseerd). Dit zijn processen waarbij de herschikte elek- tronen zich bij de oorspronkelijke kern bevinden. We spreken dan van excitatie of ionisatie. 3. e en of meerdere elektronen bevinden zich bij de andere kern na de botsing (eventueel in aangeslagen toestand). We spreken dan van elek- tronenoverdracht. In het eerste deel van deze dissertatie worden botsingsexperimenten tussen heliumionen en natriumatomen beschreven waarbij het proces van elek- tronenoverdracht wordt onderzocht. Bij dit mechanisme is het buitenste 117?Samenvatting natriumelektron betrokken. Deze kan relatief gemakkelijk `overspringen' naar het heliumion wanneer deze zich dicht in de buurt van het natrium- atoom bevindt. Het elektron kan hierbij een bepaalde (aangeslagen) toe- stand bezetten. Wij meten de bezetting van de heliumtoestanden die onder uitzending van XUV licht ( ? 58 nm) vervallen naar de heliumgrondtoe- stand. Door de lichtintensiteit te meten onderzoeken we de mate van elek- tronenoverdracht naar een selecte groep van singlet helium`eind'toestanden, namelijk He(1s2p), He(1s3s), He(1s3p) en He(1s3d). In een reactie- vergelijking ziet het mechanisme er als volgt uit: He + (1s) + ( Na(3s) Na(3p) e- -! He + Na + -! He(1s 2 ) +h(58 nm) + Na + Het experiment kent een extra dimensie door het feit dat het, in beginsel bol- symmetrische, natriumatoom een bepaalde ruimtelijk uitlijning kan worden meegegeven. Met behulp van laserlicht van een specieke frequentie en po- larisatie, wordt het buitenste natriumelektron in een aangeslagen p toestand gebracht. Het aanslaan naar deze toestand heeft als gevolg dat het valentie- elektron zich op grotere afstand van zijn kern bevindt dan voorheen. Daar- naast kan, afhankelijk van de gebruikte laserpolarisatie, het buitenste elek- tron zich nu rond de natriumkern bewegen volgens een bepaalde anisotrope verdeling, de bolsymmetrie is doorbroken. De eecten van de excitatie en ruimtelijk verdeling van dit natriumelektron op het proces van elektronen- overdracht zijn onderzocht voor botsingsenergie¨en vari¨erend van 0.5 keV tot 6.0 keV. De metingen laten zien dat het eect van laserexcitatie een bezettingstoe- name van de beschouwde singlet heliumtoestanden betekent, ongeacht de uitlijning van het natrium 3p elektron. Dit is simpelweg te begrijpen uit het feit dat het 3p natrium elektron minder sterk gebonden is en elektro- nenoverdracht makkelijker gaat. Daarnaast is de uitlijning van het aanges- lagen elektron van invloed op de elektronenoverdracht. De resultaten zijn vergeleken met berekeningen van S.E. Nielsen en T.H. Rod [13], die de elek- tronoverdracht beschrijven in een model waarbij het betrokken elektron zich beweegt in bepaalde eectieve potentiaalvelden. De goede overeenkomsten van onze metingen met de berekeningen rechtvaardigen de theoretische be- naderin

Planje, Willem Gilles

1999-11-01

337

State-dependent energy shifts of Rydberg atoms in a ponderomotive optical lattice.  

PubMed

We demonstrate the state dependence of the ponderomotive energy shift of Rydberg atoms in an optical lattice using microwave spectroscopy. Unique to Rydberg atoms, this dependence results from a state-dependent aspect ratio between Rydberg-atom size and lattice period. A semiclassical simulation reproduces all features observed in the microwave spectra and indicates the presence of trapped Rydberg atoms. PMID:20482104

Younge, K C; Knuffman, B; Anderson, S E; Raithel, G

2010-04-30

338

Non-magnetic Ground State of a Pr-based Caged Compound PrRu2Zn20  

NASA Astrophysics Data System (ADS)

Recently there has been considerable interest in rare-earth based compounds with caged structures, because they show a variety of ground states originating from the caged structures, for example, heavy-fermion superconductivity in PrOs4Sb12, a phase transition attributed to scalar-type multipolar degrees of freedom in PrFe4P12, etc. We have studied Pr-based caged compounds of PrRu2Zn20 crystallizing in the cubic CeCr2Al20-type structure, where a Pr-ion is encapsulated in a cage formed of sixteen zinc atoms. In analogy of the filled-skutterudite structure, the large coordination number of the Pr-ion, CN=16, suggests weak crystalline electric field (CEF) effect and strong hybridization of the cage and f electrons of the Pr-ion. In PrRu2Zn20, the magnetic susceptibility obeys the Curie-Weiss law above 25 K, suggesting the trivalent state of the Pr-ion suffering from weak CEF effect. A Schottky peak of the specific heat appearing at 2.5 K is the manifestation of a first excited state located around 7 K above the CEF ground state. No phase transition has been observed down to 0.4 K, indicating the non-mangnetic singlet ground state.

Onimaru, Takahiro; Matsumoto, Keisuke; Inoue, Yukihiro F.; Umeo, Kazunori; Saiga, Yuta; Takabatake, Toshiro; Matsushita, Yoshitaka; Nishimoto, Kazue; Tamura, Ryuji

2010-03-01

339

Generation of atom-photon entangled states in atomic Bose-Einstein condensate via electromagnetically induced transparency  

Microsoft Academic Search

In this paper, we present a method to generate continuous-variable-type entangled states between photons and atoms in atomic Bose-Einstein condensate (BEC). The proposed method involves an atomic BEC with three internal states, a weak quantized probe laser, and a strong classical coupling laser, which form a three-level Lambda-shaped BEC system. We consider a situation where the BEC is in electromagnetically

Le-Man Kuang; Lan Zhou

2003-01-01

340

A site-selective antiferromagnetic ground state in layered pnictide-oxide BaTi2As2O  

NASA Astrophysics Data System (ADS)

The electronic and magnetic properties of BaTi2As2O have been investigated using both the first-principles and analytical methods. The full-potential linearized augmented plane-wave calculations show that the most stable state is a site-selective antiferromagnetic (AFM) metal with a 2×1×1 magnetic unit cell containing two nonmagnetic Ti atoms and two other Ti atoms with antiparallel moments. Further analysis to Fermi surface and spin susceptibility shows that the site-selective AFM ground state is driven by the Fermi surface nesting and the Coulomb correlation. Meanwhile, the charge density distribution remains uniform, suggesting that the phase transition at 200 K in experiment is a spin-density-wave transition.

Yu, Xiang-Long; Liu, Da-Yong; Quan, Ya-Min; Jia, Ting; Lin, Hai-Qing; Zou, Liang-Jian

2014-05-01

341

Production and Trapping of Ultracold Potassium Molecules in the Electronic Ground State  

NASA Astrophysics Data System (ADS)

In the past two years, methods of producing and trapping molecules have emerged that promise to open new avenues in ultracold molecular physics. We have developed an efficient new method to produce ultracold (T <= 1 mK) potassium molecules( A. N. Nikolov et al. al) Phys. Rev. Lett., 84, 246 (2000).. We have also made progress in experiments to trap molecules in an optical dipole potential. Our production technique uses two-photon "R-transfer." Pairs of ultracold potassium atoms in a MOT are first photoassociated at large internuclear separations to a specific level of the 1g molecular state, which is then excited with a second laser to a specific level of the 5 or 6 ^1?u Rydberg states. The Rydberg states have favorable Franck-Condon factors for spontaneous decay into low vibrational levels of the ground X ^1?^+g electronic state. The molecules are detected via two-color resonant ionization with pulsed lasers. By scanning one of the detection lasers we observe transitions from several vibrational levels of the X state. The largest observed formation rate for a single vibrational level is about 10^5 molecules/s for ?=25. Molecules are also observed in the lowest vibrational states, including ?=0, with slightly smaller production rates. Analysis of the ballistic departure of molecules from the detection region shows that they have a translational temperature of approximately 500 ?K. Currently we are attempting to load the cold molecules into an optical dipole trap consisting of a CO2 laser focused to a 50 ?m beam waist. With modest loading efficiencies, we expect to trap >= 10^3 molecules for about 1 sec., which would allow studies of collisions and reactions of ultracold molecules.

Ensher, Jason R.

2000-06-01

342

Coherent control of entangled states of atomic ensembles  

NASA Astrophysics Data System (ADS)

The realization of quantum communication protocols over a scalable quantum network depends on precise control of entangled states. Recent experimental progress toward a scalable quantum network has included the demonstration of heralded entanglement creation and the distribution of entanglement amongst the nodes of a network. In our system quantum nodes are realized with a pair of atomic ensembles of laser cooled Cs atoms. We will discuss recent developments including the storage and retrieval of entanglement into and out of a quantum memory [1] and an investigation of the processes by which entanglement decays in our system [2]. [1] K. S. Choi, H. Deng, J. Laurat, and H. J. Kimble, arXiv:0712.3571v2 (2008). [2] J. Laurat, K. S. Choi, H. Deng, C.-W. Chou, and H. J. Kimble, Phys. Rev. Lett. 99, 180504 (2007).

Papp, Scott B.; Choi, Kyung S.; Deng, Hui; Kimble, H. Jeff

2008-05-01

343

Manipulating frequency-bin entangled states in cold atoms.  

PubMed

Optical manipulation of entanglement harnessing the frequency degree of freedom is important for encoding of quantum information. We here devise a phase-resonant excitation mechanism of an atomic interface where full control of a narrowband single-photon two-mode frequency entangled state can be efficiently achieved. We illustrate the working physical mechanism for an interface made of cold (87)Rb atoms where entanglement is well preserved from degradation over a typical 100??m length scale of the interface and with fractional delays of the order of unity. The scheme provides a basis for efficient multi-frequency and multi-photon entanglement, which is not easily accessible to polarization and spatial encoding. PMID:24487523

Zavatta, A; Artoni, M; Viscor, D; La Rocca, G

2014-01-01

344

Relaxation of an unstable state in parametrically excited cold atoms.  

PubMed

We investigate the scaling behavior of the relaxation process for an unstable state near a subcritical Hopf bifurcation point. When the parametric modulation is applied to a magneto-optical trap, the atomic cloud becomes unstable and decays to the dynamic bistable states. Near the subcritical Hopf bifurcation point, we experimentally show that the relaxation process exhibits the scaling behavior; the relaxation time shows a scaling exponent of -1.002 (±0.024). We also present the passage time distribution for the statistical interpretation of the escape process associated with the relaxation of the unstable state. We compare the experimental results to the numerical and analytic results, demonstrating the good agreement between them. PMID:22060485

Moon, Geol; Kim, Yonghee; Heo, Myoung-Sun; Park, Jina; Yum, Dahyun; Lee, Wanhee; Noh, Heung-Ryoul; Jhe, Wonho

2011-09-01

345

On continuum- and bound-state ell--decay rates of pionic and kaonic hydrogen in the ground state  

Microsoft Academic Search

We calculate the continuum- and bound-state ell--decay rates of pionic and kaonic hydrogen in the ground state, where ell- is either the electron e- or the muon mu-. We find that the bound-state ell--decay rates are of many orders of magnitude and smaller than the continuum-state ell--decay rates.

M. Faber; A. N. Ivanov; V. A. Ivanova; J. Marton; M. Pitschmann; N. I. Troitskaya; M. Wellenzohn

2009-01-01

346

Electronic energy transfer collisions between Cd(5 3P 0,1) and ground state CdH (CdD)  

NASA Astrophysics Data System (ADS)

Emission from excited CdH (CdD) molecules in the A 2? 3/2 and 2? 1/2 states could be observed when ground state Cd atoms were excited to the 5 3P 1 state by a pulsed dye laser in the presence of H 2 (D 2). From the analyses of the temporal profiles of the emission, it was revealed that these excited CdH (CdD) molecules are formed in electronic energy transfer collisions between Cd(5 3P 0,1) and ground state CdH (CdD) molecules. The ground state CdH (CdD) molecules are the products of reactions between Cd(5 3P 0,1) and H 2 (D 2).

Umemoto, Hironobu; Kikuma, Jun; Sato, Shin

1988-12-01

347

Remote preparation of atomic and field cluster states from a pair of tri-partite GHZ states  

Microsoft Academic Search

We propose two simple and resource-economical schemes for remote preparation of four-partite atomic as well as cavity field cluster states. In the case of atomic state generation, we utilize simultaneous resonant and dispersive interactions of the two two-level atoms at the preparation station. Atoms involved in these interactions are individually pair-wise entangled into two different tri-partite GHZ states. After interaction,

H. Khosa Ashfaq; Rameez-ul-Islam; Saif Farhan

2010-01-01

348

LASSP: The Laboratory of Atomic and Solid State Physics  

NSDL National Science Digital Library

The Laboratory of Atomic and Solid State Physics (LASSP) at Cornell University is a center for research in condensed matter physics. Scientists can read about the work of the thirty faculty members in topics such as theoretical condensed matter physics, low temperature physics, experimental liquid physics, and experimental soft-condensed matter and biological physics. With a number of images and animations at the website, students can learn about diffraction patterns of an icosahedral quasicrystal, Coarsening, and Spiral Defect Turbulence. Physicists can find employment opportunities at LASSP as well as information on upcoming seminars, conferences, and meetings.

349

Imaging of quantum Hall states in ultracold atomic gases  

SciTech Connect

We examine off-resonant light scattering from ultracold atoms in the quantum Hall regime. When the light scattering is spin dependent, we show that images formed in the far field can be used to distinguish states of the system. The spatial dependence of the far-field images is determined by the two-particle spin-correlation functions, which the images are related to by a transformation. Quasiholes in the system appear in images of the density formed by collecting the scattered light with a microscope, where the quasihole statistics are revealed by the reduction in density at the quasihole position.

Douglas, James S.; Burnett, Keith [University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

2011-11-15

350

Excitation of {sup 1}S and {sup 3}S Metastable Helium Atoms to Doubly Excited States  

SciTech Connect

We present spectra of triplet and singlet metastable helium atoms resonantly photoexcited to doubly excited states. The first members of three dipole-allowed {sup 1,3}P{sup o} series have been observed and their relative photoionization cross sections determined, both in the triplet (from 1s2s {sup 3}S{sup e}) and singlet (from 1s2s {sup 1}S{sup e}) manifolds. The intensity ratios are drastically different with respect to transitions from the ground state. When radiation damping is included the results for the singlets are in agreement with theory, while for triplets spin-orbit interaction must also be taken into account.

Alagia, M. [CNR-ISMN Sezione Roma, Piazzale A. Moro 5, I-00185 Roma (Italy); Laboratorio Nazionale TASC, CNR-INFM, I-34012 Trieste (Italy); Coreno, M. [CNR-IMIP, Montelibretti, I-00016 Roma (Italy); Farrokhpour, H.; Omidyan, R.; Tabrizchi, M. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Franceschi, P. [Dipartimento di Fisica, Universita di Trento, I-38050 Povo (Tunisia) (Italy); Mihelic, A.; Zitnik, M. [Jozef Stefan Institute, P.O. Box 3000, SI-1001 Ljubljana (Slovenia); Moise, A.; Prince, K. C.; Richter, R. [Sincrotrone Trieste, in Area Science Park, I-34012 Basovizza, Trieste (Italy); Soederstroem, J. [Department of Physics, Uppsala University, Box 530, S-75121 Uppsala (Sweden); Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Stranges, S. [Dipartimento di Chimica, Universita'La Sapienza', I-00185 Roma (Italy); Laboratorio Nazionale TASC, CNR-INFM, I-34012 Trieste (Italy)

2009-04-17

351

Block entanglement entropy of ground states with long-range magnetic order  

NASA Astrophysics Data System (ADS)

In this paper we calculate the block entanglement entropies of spin models whose ground states have perfect antiferromagnetic or ferromagnetic long-range order. In the latter case the definition of entanglement entropy is extended to properly take into account the ground state degeneracy. We find in both cases the entropy grows logarithmically with the block size. Implication of our results on states with general long-range order will be discussed.

Ding, Wenxin; Bonesteel, Nicholas E.; Yang, Kun

2008-05-01

352

Formation of the atom-vacated state of a zinc sulfide surface upon adsorption of hydrogen atoms  

NASA Astrophysics Data System (ADS)

Experimental results are cited according to which the adsorption of hydrogen atoms into ZnS produces an atom-vacated state of the surface of a solid body. The consequences of an AVS are: anomalously rapid vaporization of ZnS (T> 500°K), sputtering of ZnS on recombination of the H atoms (T=300 500°K), a high rate of diffusion of impurities and adsorbed H atoms, and the initiation of self-oscillations of a number of absorbed H atoms.

Kharlamov, V. F.

1986-07-01

353

Matrix elements for the ground-state to ground-state 2{nu}{beta}{sup -}{beta}{sup -} decay of Te isotopes in a hybrid model  

SciTech Connect

Theoretical matrix elements, for the ground-state to ground-state two-neutrino double-{beta}-decay mode (2{nu}{beta}{sup -}{beta}{sup -}gs->gs) of {sup 128,130}Te isotopes, are calculated within a formalism that describes interactions between neutrons in a superfluid phase and protons in a normal phase. The elementary degrees of freedom of the model are proton-pair modes and pairs of protons and quasineutrons. The calculation is basically a parameter-free one, because all relevant parameters are fixed from the phenomenology. A comparison with the available experimental data is presented.

Bes, D. R. [Department of Physics, Tandar Labratory, Centro Atomico Constituyentes-Comision Nacional de Energia Atomica Avda Gral Paz 1499, 1650 Gral San Martin, Argentina and (Argentina); Civitarese, O. [Department of Physics, University of La Plata, Casilla de Correo 67 1900, La Plata (Argentina)

2010-01-15

354

Bulk-edge correspondence of entanglement spectrum in two-dimensional spin ground states  

NASA Astrophysics Data System (ADS)

General local spin S ground states, described by a valence bond solid (VBS) on a two-dimensional lattice are studied. The norm of these ground states is mapped to a classical O(3) model on the same lattice. Using this quantum-to-classical mapping, we obtain the partial density matrix ?A associated with a subsystem A of the original ground state. We show that the entanglement spectrum of ?A in a translation invariant lattice is related with the spectrum of a quantum XXX Heisenberg model and all its conserved charges on the boundary of the region A.

Santos, Raul A.

2013-01-01

355

The Ground State Energy of the Multi-Polaron in the Strong Coupling Limit  

NASA Astrophysics Data System (ADS)

We consider the Fröhlich N-polaron Hamiltonian in the strong coupling limit and bound its ground state energy from below. In particular, our lower bound confirms that the ground state energy of the Fröhlich polaron and the ground state energy of the associated Pekar-Tomasevich variational problem are asymptotically equal in the strong coupling limit. We generalize the operator approach that was used to prove a similar result in the N = 1 case in Lieb and Thomas (Commun. Math. Phys. 183:511-519, 1997) and apply a Feynman-Kac formula to obtain the same result for an arbitrary particle number N ? 1.

Anapolitanos, Ioannis; Landon, Benjamin

2013-12-01

356

Ground state properties of superheavy nuclei with Z=117 and Z=119  

NASA Astrophysics Data System (ADS)

We review the current studies on the ground-state properties of superheavy nuclei. It is shown that there is shape coexistence for the ground state of many superheavy nuclei from different models and many superheavy nuclei are deformed. This can lead to the existence of isomers in superheavy region and it plays an important role for the stability of superheavy nuclei. Some new results on Z=117 and Z=119 isotopes are presented. The agreement between theoretical results and experimental data clearly demonstrates the validity of theoretical models for the ground-state properties of superheavy nuclei.

Ren, Zhongzhou; Chen, Dinghan; Xu, Chang

2006-11-01

357

Ground state and infrared response of triple concentric quantum ring structures  

NASA Astrophysics Data System (ADS)

Within local-spin density-functional theory, we study the ground state and infrared response of two-dimensional, triple concentric quantum ring nanostructures. Changes in their physical properties are presented as a function of the number of electrons or the intensity of a perpendicularly applied magnetic field. We discuss the addition spectrum of few-electron triple quantum rings at zero magnetic field, as well as the physical appearance of the ground state and dipole response of selected systems containing up to 50 electrons. We also investigate the ground state, persistent currents, and charge- and spin-density responses of a system made of 30 electrons.

Escartín, José María; Barranco, Manuel; Pi, Martí

2010-11-01

358

Use of an atom trap for measuring electron-impact excitation cross sections out of the excited states of rubidium  

NASA Astrophysics Data System (ADS)

A large fraction (fe ˜ 0.4) of the atoms in a MOT are in the excited Rb(5^2P) level. We previously used this source of excited atoms to measure ionization cross sections out of the 5^2P level of Rb.(M.L. Keeler, et al.), Phys. Rev. Lett. 85, 3353 (2000). In this work, we use trapped atoms as a target for measurement of electron-impact phexcitation cross sections. An electron beam is incident upon the cloud of trapped atoms and the fluorescence given off by the decay of the excited atoms is detected by a PMT. If the trapping lasers are turned off during the electron beam pulse, the trap contains only 5^2S atoms. By leaving the lasers on during the electron beam pulse, the trap contains both 5^2S and 5^2P atoms. From the ratio of signals for the two cases and the measured excited state fraction we find the ratio of the excitation cross sections from the 5^2S and 5^2P levels. Using previously measured ground state cross sections,(See for example, Z. Wei, et al.), Phys. Rev. A 47, 1918 (1978). we obtain cross sections out of the 5^2P_3/2 level. Results for excitation into the 5^2P_1/2, 5^2D, and 7^2S levels will be presented.

Larsen, M.; Zimmerman, Todd A.; Boffard, John B.; Anderson, L. W.; Lin, Chun C.

2002-05-01

359

Ionization of ytterbium atoms from an excited state  

SciTech Connect

The cross sections of the photoionization and the electron impact-induced ionization of Yb atoms from the excited 6s6p({sup 3}P{sub 1}) state are numerically calculated. Matrix elements are computed in multielectron relativistic and nonrelativistic approximations with allowance for the superposition of configurations and a relaxation effect. The radial part of the electron wavefunction in a continuous spectrum is calculated using the solutions to one-configuration Hartree-Fock and Dirac-Fock equations. The cross sections calculated by a relativistic method are compared to those for a nonrelativistic approximation. The ratios of the radiation reduced matrix elements and the phase shifts of the wavefunctions of a continuous spectrum calculated for the 6p {epsilon}s and 6p {sup {yields} {epsilon}}d transitions are compared to the values obtained by approximating the experimental dependences of the angular distribution of photoelectrons for the photoionization by ultraviolet radiation from an oriented excited state.

Elizarov, A. Yu., E-mail: a.elizarov@mail.ioffe.r [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Tupitsyn, I. I., E-mail: tup@tup.usr.pu.r [St. Petersburg State University (Russian Federation)

2010-06-15

360

Relativistic potential energy surfaces of initial oxidations of Si(100) by atomic oxygen: The importance of surface dimer triplet state  

NASA Astrophysics Data System (ADS)

The non-relativistic and relativistic potential energy surfaces (PESs) of the symmetric and asymmetric reaction paths of Si(100)-2×1 oxidations by atomic oxygen were theoretically explored. Although only the singlet PES turned out to exist as a major channel leading to ``on-dimer'' product, both the singlet and triplet PESs leading to ``on-top'' products are attractive. The singlet PESs leading to the two surface products were found to be the singlet combinations (open-shell singlet) of the low-lying triplet state of surface silicon dimer and the ground 3P state of atomic oxygen. The triplet state of the ``on-top'' product can also be formed by the ground singlet state of the surface silicon dimer and the same 3P oxygen. The attractive singlet PESs leading to the ``on-dimer'' and ``on-top'' products made neither the intersystem crossings from triplet to singlet PES nor high energy 1D of atomic oxygen necessary. Rather, the low-lying triplet state of surface silicon dimer plays an important role in the initial oxidations of silicon surface.

Kim, Tae-Rae; Shin, Seokmin; Choi, Cheol Ho

2012-06-01

361

Time-dependent localized Hartree-Fock density-functional linear response approach for photoionization of atomic excited states  

SciTech Connect

We present a time-dependent localized Hartree-Fock density-functional linear response approach for the treatment of photoionization of atomic systems. This approach employs a spin-dependent localized Hartree-Fock exchange potential to calculate electron orbitals and kernel functions, and thus can be used to study the photoionization from atomic excited states. We have applied the approach to the calculation of photoionization cross sections of Ne ground state. The results are in agreement with available experimental data and have comparable accuracies with other ab initio theoretical results. We have also extended the approach to explore the photoionization from Ne excited states and obtained some results for the photoionization from outer-shell and inner-shell excited states.

Zhou Zhongyuan; Chu, S.-I [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States)

2009-05-15

362

Remote preparation of atomic and field cluster states from a pair of tri-partite GHZ states  

NASA Astrophysics Data System (ADS)

We propose two simple and resource-economical schemes for remote preparation of four-partite atomic as well as cavity field cluster states. In the case of atomic state generation, we utilize simultaneous resonant and dispersive interactions of the two two-level atoms at the preparation station. Atoms involved in these interactions are individually pair-wise entangled into two different tri-partite GHZ states. After interaction, the passage of the atoms through a Ramsey zone and their subsequent detection completes the protocol. However, for field state generation we first copy the quantum information in the cavities to the atoms by resonant interactions and then adapt the same method as in the case of atomic state generation. The method can be generalised to remotely generate any arbitrary graph states in a straightforward manner.

Ashfaq, H. Khosa; Rameez-ul-Islam; Farhan, Saif

2010-04-01

363

Contribution to the Study of Order Effects in the Ising Model Framework: Ground States and Phase Diagrams.  

National Technical Information Service (NTIS)

Some aspects of order phenomena on a fixed underlying lattice are studied. The Ising model framework is considered. The ground states at zero temperature are determined. An algorithm is developed to determine exactly the ground states of the linear chain ...

A. Finel

1989-01-01

364

Ground State Lifetime of Strong-Coupling Magnetopolaron in AN Asymmetric Quantum Dot  

NASA Astrophysics Data System (ADS)

The ground state lifetime of a magnetopolaron was investigated with electron-LO-phonon strong coupling in an asymmetric quantum dot using the linear combination operator and unitary transformation methods. Quantum transition, which cause changes of the magnetopolaron lifetime, occurs in the quantum system due to electron-phonon interaction and the influence of external temperature, that is, the magnetopolaron leaps from the ground state to the first excited state after absorbing a LO-phonon. The expressions of the ground state lifetime of the magnetopolaron as a function of the ground state energy, the transverse and longitudinal confinement lengths of quantum dot, the electron-phonon coupling strength, the cyclotron vibration frequency and the external temperature were obtained. Numerical calculations have been performed and the results show that the ground state lifetime of the magnetopolaron increases with increasing the ground state energy and the cyclotron vibration frequency, and decreases with increasing the transverse and longitudinal confinement lengths of the quantum dot, the coupling strength and the external temperature.

Li, Zhixin; Xiao, Jinglin

365

How to measure nuclear ground-state properties in simple systems such as 11Li or U 91+?  

NASA Astrophysics Data System (ADS)

Atomic spectroscopy yields key information on properties of ground and isomeric states via a determination of the hyperfine structure and isotope shift. In order to deduce precise nuclear moments and charge radii, the electromagnetic fields produced by the electrons at the site of the nucleus must be known with high accuracy. This is presently possible only for simple systems with very few electrons. This contribution describes two scenarios for such experiments: the determination of the charge radius of the neutron-rich isotopes 8,9Li and of the halo nucleus 11Li at the on-line isotope separators at GSI and TRIUMF and the Highly charged Ion TRAP (HITRAP) facility which is under construction at GSI. HITRAP will enable the determination of atomic and nuclear properties of highly charged ions such as isotopes of hydrogen-like uranium with very high accuracy. For this purpose novel experimental set-ups are being built up by the international HITRAP collaboration.

Kluge, H.-Jürgen; Herfurth, Frank; Kester, Oliver; Nörtershäuser, Wilfried; Quint, Wolfgang

2008-10-01

366

A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit  

SciTech Connect

A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984)x10{sup 16} at./cm{sup 2} s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.

Huang Yongxian; Tian Xiubo; Yang Shiqin; Chu, Paul K. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China and Shenzhen Key Laboratory of Composite Materials, Shenzhen-Tech-Innovation International, Shenzhen 518057 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2007-10-15

367

A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit.  

PubMed

A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal. PMID:17979410

Huang, Yongxian; Tian, Xiubo; Yang, Shiqin; Chu, Paul K

2007-10-01

368

van der Waals interactions between excited-state atoms and dispersive dielectric surfaces  

Microsoft Academic Search

van der Waals interactions between atoms and dielectric surfaces are reinvestigated. To describe the nonretarded interaction potential between a dispersive dielectric surface and an atom in an arbitrary internal energy state, we derive a general expression in terms of an integral, over real frequency, of the combined atom and surface polarizabilities. It is shown that, for excited atoms, the expression

M. Fichet; F. Schuller; D. Bloch; M. Ducloy

1995-01-01

369

Federal and state efforts to protect ground water  

SciTech Connect

Federal and state efforts to protect the nation's groundwater supplies are discussed. The report provides information on the nature and scope of groundwater contamination, adequacy of federal and state authority and resources to deal with groundwater contamination, and the federal government's role in formulating, administering, and supporting a national groundwater protection policy.

Not Available

1984-02-21

370

Earthquake Ground Motion Simulations in the Central United States  

Microsoft Academic Search

The Central United States (CUS) includes two of the major seismic zones east of the Rockies: the New Madrid and Wabash Valley Seismic Zones. The winter 1811-1812 New Madrid Seismic Zone (NMSZ) events were the largest intraplate sequence ever recorded in the United States. Together with their aftershocks, these earthquakes produced large areas of liquefaction, new lakes, and landslides in

L. Ramirez Guzman; O. S. Boyd; S. Hartzell; R. A. Williams

2010-01-01

371

Evolution of dark state of an open atomic system in constant intensity laser field  

SciTech Connect

We studied experimentally and theoretically the evolution of open atomic systems in the constant intensity laser field. The study is performed by analyzing the line shapes of Hanle electromagnetically induced transparency (EIT) obtained in different segments of a laser beam cross section of constant intensity, i.e., a {Pi}-shaped laser beam. Such Hanle EIT resonances were measured using a small movable aperture placed just in front of the photodetector, i.e., after the entire laser beam had passed through the vacuum Rb cell. The laser was locked to the open transition F{sub g}=2{yields}F{sub e}=1 at the D{sub 1} line of {sup 87}Rb with laser intensities between 0.5 and 4 mW/cm{sup 2}. This study shows that the profile of the laser beam determines the processes governing the development of atomic states during the interaction. The resonances obtained near the beam center are narrower than those obtained near the beam edge, but the significant changes of the linewidths occur only near the beam edge, i.e., right after the atom enters the beam. The Hanle EIT resonances obtained near the beam center exhibit two pronounced minima next to the central maximum. The theoretical model reveals that the occurrence of these transmission minima is a joint effect of the preparation of atoms into the dark state and the optical pumping into the uncoupled ground level F{sub g}=1. The appearance of the transmission minima, although similar to that observed in the wings of a Gaussian beam [A. J. Krmpot et al., Opt. Express 17, 22491 (2009)], is of an entirely different nature for the {Pi}-shaped laser beam.

Krmpot, A. J.; Radonjic, M.; Cuk, S. M.; Nikolic, S. N.; Grujic, Z. D.; Jelenkovic, B. M. [Institute of Physics, University of Belgrade, Pregrevica 118, RS-11080 Belgrade (Serbia)

2011-10-15

372

Ground-state properties of gapped graphene using the random phase approximation  

NASA Astrophysics Data System (ADS)

We study the effect of band gap on the ground-state properties of Dirac electrons in a doped graphene within the random phase approximation at zero temperature. Band gap dependence of the exchange, correlation, and ground-state energies and the compressibility are calculated. In addition, we show that the conductance in the gapped graphene is smaller than gapless one. We also calculate the band-gap dependence of charge compressibility and it decreases with increasing the band-gap values.

Qaiumzadeh, Alireza; Asgari, Reza

2009-02-01

373

Variational calculation on ground-state energy of bound polarons in parabolic quantum wires  

Microsoft Academic Search

Within the framework of Feynman path-integral variational theory, we calculate the ground-state energy of a polaron in parabolic quantum wires in the presence of a Coulomb potential. It is shown that the polaronic correction to the ground-state energy is more sensitive to the electron-phonon coupling constant than the Coulomb binding parameter and it increases monotonically with decreasing effective wire radius.

Zhuang-bing Wang; Fu-li Wu; Qing-hu Chen; Zheng-kuan Jiao

2001-01-01

374

Exact ground state properties of the one-dimensional Coulomb gas  

Microsoft Academic Search

The ground state properties of a single-component one-dimensional Coulomb gas\\u000aare investigated. We use Bose-Fermi mapping for the ground state wave function\\u000awhich permits to solve the Fermi sign problem in the following respects (i) the\\u000anodal surface is known, permitting exact calculations (ii) evaluation of\\u000adeterminants is avoided, reducing the numerical complexity to that of a bosonic\\u000asystem, thus

G. E. Astrakharchik; M. D. Girardeau

2010-01-01

375

Exact ground-state properties of a one-dimensional Coulomb gas  

Microsoft Academic Search

The ground-state properties of a single-component one-dimensional Coulomb gas are investigated. We use Bose-Fermi mapping for the ground-state wave function which permits solution of the Fermi sign problem in the following respects: (i) the nodal surface is known, permitting exact calculations; and (ii) evaluation of determinants is avoided, reducing the numerical complexity to that of a bosonic system and, thus,

G. E. Astrakharchik; M. D. Girardeau

2011-01-01

376

Many electron variational ground state of the two dimensional Anderson lattice  

SciTech Connect

A variational upper bound of the ground state energy of two dimensional finite Anderson lattices is determined as a function of lattice size (up to 16 x 16). Two different sets of many-electron basis vectors are used to determine the ground state for all values of the coulomb integral U. This variational scheme has been successfully tested for one dimensional models and should give good estimates in two dimensions.

Zhou, Y.; Bowen, S.P. [Argonne National Lab., IL (United States). Materials Science Div.; Mancini, J.D. [Fordham Univ., Bronx, NY (United States). Dept. of Physics

1991-02-01

377

A CI study of the ground state potential energy surface of He 3  

Microsoft Academic Search

Large gaussian basis sets are employed in configuration interaction calculations for the ground state of the He+3 trimer. The resulting potential energy surfaces for collinear and C2v-configurations show a global minimum at a linear symmetrical ion geometry with an internuclear distance of Re = 2·33 Bohr. For the corresponding ground state 2Sigmag the three fundamental modes are studied and the

J. Ackermann; H. Hogreve

1989-01-01

378

Theoretical atomic and molecular physics  

Microsoft Academic Search

In this first year of the grant, emphasis has been placed on theoretical investigations of: differential elastic and charge-transfer scattering and alignment and orientation of the excited electron cloud in ion-atom, atom-atom and ion-molecule collisions, using a molecular-orbital representation; quenching of low-lying Rydberg states of a Na atom in a collision with a ground-state He atom, using a semiclassical representation;

1988-01-01

379

Three-beam atom interferometer  

Microsoft Academic Search

We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the

H. Hinderthür; A. Pautz; V. Rieger; F. Ruschewitz; J. L. Peng; K. Sengstock; W. Ertmer

1997-01-01

380

Quantum State Control in Electrical Circuits: Artificial Superconducting `Atoms'  

NASA Astrophysics Data System (ADS)

In recent years there has been a remarkable convergence and synergy of interests between condensed matter and AMO physics. The AMO community is studying larger and larger collections of atoms and beginning to study collective effects and quantum phase transitions in condensates and artificial `solids' made with optical lattices. At the same time the condensed matter community has been striving to make smaller and smaller objects that will behave like artifical atoms having a high degree of quantum coherence. Recent experimental breakthroughs have led to the construction of superconducting electrical circuits whose state variables are intrinsically quantum mechanical. Through proper engineering, decoherence rates are beginning to approach the theoretical limits set by spontaneous emission of microwave photons into the cold vacuum and as many as 10^4 Rabi oscillations have now been detected. [1] Rapid progress is also occurring towards the development of novel single-shot high quantum efficiency read out schemes for superconducting quantum bits. [2] This talk will give an introduction to these experimental developments and discuss some of the related theoretical issues which they open up. 1. D. Vion, A. Aassime, A. Cottet, P. Joyez, H. Pothier, C. Urbina, D. Esteve and M. H. Devoret (submited to Science, December, 2001). 2. A. Cottet, D. Vion, P. Joyez, A. Aassime, D. Esteve, and M. H. Devoret, Physica C (in press).

Girvin, Steven

2002-05-01

381

Perturbation of the excited states of the hydrogen atom and hydrogen-like ions by a neutral atom  

SciTech Connect

Owing to the degeneracy of the energy levels, the wavefunction of the electron in the excited states of the hydrogen atom and hydrogen-like ions perturbed by a neutral atom B is significantly different from the wavefunction of the unperturbed state. The perturbed function has a wide high maximum in the region of atom B, which is explained by multiple collisions of the electron with atom B, because the classical trajectories in the Coulomb field are closed and the size of atom B is much smaller than the size of the excited-state orbit. The radiative lifetimes of the excited states are much larger than those of unperturbed states. The orbital angular momentum L of the excited electron is strongly changed in collisions with atom B owing to the quantum interference or mixing of the temporal phases of adiabatic wavefunctions. The cross sections for such a change in the orbital angular momentum are several orders of magnitude larger than the cross sections found in early investigations in the approximation of the single collision of the electron with atom B.

Chibisov, M. I., E-mail: mchibisov@yahoo.co [Russian Research Centre Kurchatov Institute (Russian Federation)

2009-12-15

382

Beyond the molecular orbital conception of electronically excited states through the quantum theory of atoms in molecules.  

PubMed

We show that the use of the quantum theory of atoms in molecules (QTAIM) in electronically excited states allows expanding the knowledge that the molecular orbital (MO) framework provides about electronic rearrangements. Despite that historical prejudice seemed to preclude the use of QTAIM beyond the electronic ground state, this paper evidences that QTAIM is versatile enough to deal with excited states. As an example, the paradigmatic n ? ?* electronic transition of formaldehyde is analyzed. Using QTAIM, an energy partition of excited state energies into atomic and diatomic energies is carried out for the first time. This partition shows that upon electronic excitation the atoms of the CO bond experience a stabilization in their net energies, accompanied by a destabilization in their interaction, a fact which is in accordance with the idea of populating an antibonding ?* MO. The associated C-O bond elongation in the n?* state does not involve a change in the ? atomic populations - as one would expect from a ?* orbital - but in the ? ones. Moreover, it is also found that the n?* state is characterized by a weaker C-O interaction energy in comparison to that in the electronic ground state. In order to strengthen this interaction, the electron-electron repulsion between C and O is reduced via a symmetry-breaking of the electron density, causing the C pyramidalization. A topological analysis based on the Laplacian of the electron density and on the electron localization function (ELF) reveals that the n ? ?* transition can be visualized as a rotation of 90° of the oxygen lone pairs. PMID:24709865

Ferro-Costas, David; Pendás, Angel Martín; González, Leticia; Mosquera, Ricardo A

2014-04-23

383

Theoretical Studies of Rydberg Atom Collisions.  

National Technical Information Service (NTIS)

During the last two years, theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg a...

R. E. Olson

1981-01-01

384

Optics with an Atom Laser Beam  

Microsoft Academic Search

We report on the atom optical manipulation of an atom laser beam. Reflection, focusing, and its storage in a resonator are demonstrated. Precise and versatile mechanical control over an atom laser beam propagating in an inhomogeneous magnetic field is achieved by optically inducing spin flips between atomic ground states with different magnetic moment. The magnetic force acting on the atoms

Immanuel Bloch; Michael Koehl; Markus Greiner; Theodor W. Haensch; Tilman Esslinger

2001-01-01

385

Quantum Nature of Hydrogen on Metals: Ground-State Geometry of Vacancies  

NASA Astrophysics Data System (ADS)

When hydrogen is adsorbed on a Pd(111) surface, very simple vacancy defects -- which form quite commonly -- exhibit fundamentally quantum wavelike behavior. Conventional wisdom has it that the quantum nature of hydrogen and other light atoms is only rarely manifested, typically in specially designed experimental protocols. A great many studies have proceeded under the assumption that, for most purposes, as long as the electronic motion is handled quantum mechanically, the nuclear motion of hydrogen can be treated classically. We show that this approximation fails badly in a very simple system. Moreover, by treating the problem fully quantum mechanically, several recent experimental finding [Mitsui et al, Nature 422, 705 (2003)] can be plausibly interpreted as having a fundamentally quantum origin. In particular, we present new ground-state geometry of hydrogen vacancies on Pd(111) surface that are obtained from a full quantum treatment of the hydrogen nuclear motion. This new structures enable us to predict that all vacancy defects to have an unexpected triangular appearance in scanning tunneling microscopy; recent experiments have found precisely this behavior.

Kim, Sungho; Kim, Seong-Gon; Erwin, Steven C.

2006-03-01

386

Quantum Nature of Hydrogen on Metals: Ground-State Geometry of Vacancies  

NASA Astrophysics Data System (ADS)

When hydrogen is adsorbed on a Pd(111) surface, very simple vacancy defects -- which form quite commonly -- exhibit fundamentally quantum wavelike behavior. Conventional wisdom has it that the quantum nature of hydrogen and other light atoms is only rarely manifested, typically in specially designed experimental protocols. A great many studies have proceeded under the assumption that, for most purposes, as long as the electronic motion is handled quantum mechanically, the nuclear motion of hydrogen can be treated classically. We show that this approximation fails badly in a very simple system. Moreover, by treating the problem fully quantum mechanically, several recent experimental finding [Mitsui et al, Nature 422, 705 (2003)] can be plausibly interpreted as having a fundamentally quantum origin. In particular, we present new ground-state geometry of hydrogen vacancies on Pd(111) surface that are obtained from a full quantum treatment of the hydrogen nuclear motion. This new structures enable us to predict that all vacancy defects to have an unexpected triangular appearance in scanning tunneling microscopy; recent experiments have found precisely this behavior.

Kim, Sungho; Erwin, Steven C.

2005-11-01

387

Unified description of ground and excited states of finite systems: the self-consistent GW approach  

NASA Astrophysics Data System (ADS)

Fully self-consistent GW calculations -- based on the iterative solution of the Dyson equation -- provide an approach for consistently describing ground and excited states on the same quantum mechanical level. Based on our implementation in the all-electron localized basis code FHI-aims [1], we show that for finite systems self-consistent GW reaches the same final Green function regardless of the starting point. The results show that self-consistency systematically improves ionization energies and total energies of closed shell systems compared to perturbative GW calculations (G0W0) based on Hartree-Fock or (semi)local density-functional theory. These improvements also translate to the electron density as demonstrated by a better description of the dipole moments of hetero-atomic dimers and the similarity with the coupled cluster singles doubles (CCSD) density. The starting-point independence of the self-consistent Green function facilitates a systematic and unbiased assessment of the performance of the GW approximation for finite systems. It therefore constitutes an unambiguous reference for the future development of vertex corrections and beyond GW schemes. [1] V. Blum et al., Comp. Phys. Comm. 180, 2175 (2009).

Caruso, Fabio; Rinke, Patrick; Ren, Xinguo; Rubio, Angel; Scheffler, Matthias

2012-02-01

388

DFT calculations of 2,4,6-trinitrophenylbenzoate derivatives: Structure, ground state properties and spectral properties  

NASA Astrophysics Data System (ADS)

2,4,6-Trinitrophenylbenzoate derivatives 3( a- g) were synthesised and their optimum molecular geometries, ground state properties, IR, UV and NMR spectra were calculated using the B3LYP method with 6-31G ** Pople basis set. The predicted geometry showed that the aryl-oxygen bond is stronger than acyl-oxygen bond. Bond lengths are affected by the presence of electron donating or electron withdrawing groups in benzoyl moiety. The orientation of the two aryl rings with respect to each other is neither in the same plane nor perpendicular. Hammett plot showed good linearity between substituent constant and the HOMO as well as LUMO energies. Mulliken and NBO charges indicate that the carbonyl carbon (C7) is more positively charged than the ipso carbon (C10), while the inspection of the coefficient on the carbonyl carbon and the ipso carbon atom for LUMO showed that its value is greater for C10 compared to C7. The correlation between the experimental and the theoretical results indicates that density functional theory B3LYP method is able to provide satisfactory results for predicting IR, UV and NMR properties.

Ibrahim, Mahmoud F.; Senior, S. A.; El-atawy, Mohamed A.; El-Sadany, Samir K.; Hamed, Ezzat A.

2011-12-01

389

Analytical fittings for the global potential energy surface of the ground state of methylene  

NASA Astrophysics Data System (ADS)

The global potential energy surface (PES) corresponding to the dissociation reaction of the ground state of methylene (CH2) is studied with the coupled-cluster method with single, double and perturbative triplet excitations, CCSD(T), in conjunction with the correlation-consistent cc-pVTZ basis set, and fitted by three analytical potential functions in terms of the Simons-Parr-Finlan (SPF) polynomial, Jensen function and the Sorbie-Murrell (SM) function. Ab initio single-point calculations over a distributed range of grids are performed first, and totally 12 085 converged points are fed into these functions. The fitting of each analytical PES function is done with an unconstrained minimization of the difference between the evaluations of the analytical function and the ab initio results, solved by a modified Levenberg-Marquardt algorithm with a finite-difference Jacobian in the IMSL package. The SPF polynomial is found to have the best global description, while the SM function behaves superior in the dissociation region forming three atoms. The spline function is potentially feasible to interpolate the computationally divergent points in the ab initio calculations.

Yu, Jen-Shiang K.; Chen, Sue-Ying; Yu, Chin-Hui

2003-01-01

390

First observation of ultrafast intramolecular proton transfer rate between electronic ground states in solution.  

PubMed

Despite the importance of ultrafast (time scale exceeding 10(-11) s) intramolecular proton transfer (PT) events between electronic ground states in solution, experimental determination of the rates of such reactions has not yet been accomplished because of the limitations of the utilized methods. The objective of this study was to evaluate the PT rates of intramolecular O···H···O hydrogen-bonded systems in solution through the (1)H spin-lattice relaxation times of the hydroxyl protons, induced by the (1)H-(17)O dipolar interactions (T(1dd)(OH)), taking into account the contribution of the OH reorientational motion to T(1dd)(OH). Solutions of the benzoic acid dimer (BA dimer), 1-benzoyl-6-hydroxy-6-phenylfulvene (Fulvene), and dibenzoylmethane (DBM) were chosen as test systems. For Fulvene in CCl(4), the PT time, ?(PT), was deduced to be 7 × 10(-11) s. In the case of the BA dimer in CCl(4), the ?(PT) value was considerably greater than the OH reorientational correlation time, ?(R(OH)) = 4.3 × 10(-11) s. In contrast, the experimental results for DBM in CCl(4) indicated that the proton is located about midway between the two oxygen atoms, that is, the PT potential energy surface is a single well or a double well with a PT barrier near or below the zero-point energy. PMID:22510164

Masuda, Yuichi; Nakano, Tomoko; Sugiyama, Midori

2012-05-10

391

Fermionized photons in the ground state of one-dimensional coupled cavities  

NASA Astrophysics Data System (ADS)

The density matrix renormalization group algorithm is used to characterize the ground states of one-dimensional coupled cavities in the regime of low photon densities. Numerical results for photon and spin excitation densities, one- and two-body correlation functions, superfluid and condensate fractions, as well as the entanglement entropy and localizable entanglement are obtained for the Jaynes-Cummings-Hubbard (JCH) model and are compared with those for the Bose-Hubbard (BH) model where applicable. The results indicate that a Tonks-Girardeau phase, in which the photons are strongly fermionized, appears between the Mott-insulating and superfluid phases as a function of the intercavity coupling. In fact, the superfluid density is found to be zero in a wide region outside the Mott-insulator phase boundary. The presence of two different species of excitation (spin and photon) in the JCH model gives rise to properties with no analog in the BH model, such as the (quasi)condensation of spin excitations and the spontaneous generation of entanglement between the atoms confined to each cavity.

D'Souza, Adam G.; Sanders, Barry C.; Feder, David L.

2013-12-01

392

Wigner Functions for Nonclassical States of a Collection of Two-Level Atoms.  

National Technical Information Service (NTIS)

The general theory of atomic angular momentum states is used to derive the Wigner distribution function for atomic angular momentum number states, coherent states, and squeezed states. These Wigner functions W(theta,phi) are represented as a pseudo-probab...

G. S. Agarwal J. P. Dowling W. P. Schleich

1993-01-01

393

Collisional and thermal ionization of sodium Rydberg atoms: II. Theory for nS, nP and nD states with n = 5 25  

Microsoft Academic Search

A stochastic model of associative ionization in collisions of Rydberg atoms with ground-state atoms is presented. The conventional Duman-Shmatov-Mihajlov-Janev (DSMJ) model treats the ionization as excitation of Rydberg electron to the continuum by the electric-dipole field generated by exchange interaction within the quasi-molecular ion. The stochastic model essentially extends this treatment by taking into account redistribution of population over a

K. Miculis; I. I. Beterov; N. N. Bezuglov; I. I. Ryabtsev; D. B. Tretyakov; A. Ekers; A. N. Klucharev

2005-01-01

394

Average ground-state energy of finite Fermi systems  

SciTech Connect

Semiclassical theories such as the Thomas-Fermi and Wigner-Kirkwood methods give a good description of the smooth average part of the total energy of a Fermi gas in some external potential when the chemical potential is varied. However, in systems with a fixed number of particles N, these methods overbind the actual average of the quantum energy as N is varied. We describe a theory that accounts for this effect. Numerical illustrations are discussed for fermions trapped in a harmonic oscillator potential and in a hard-wall cavity, and for self-consistent calculations of atomic nuclei. In the latter case, the influence of deformations on the average behavior of the energy is also considered.

Centelles, M.; Vinas, X. [Departament d'Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain); Leboeuf, P.; Roccia, J. [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS, Universite de Paris-Sud, UMR 8626, F-91405 Orsay Cedex (France); Monastra, A. G. [TU Dresden Institut fuer Theoretische Physik, D-01062 Dresden (Germany); Schuck, P. [Institut de Physique Nucleaire, IN2P3-CNRS, Universite de Paris-Sud, F-91406 Orsay Cedex (France)

2006-09-15

395

Ground-state properties of boron-doped diamond  

SciTech Connect

Boron-doped diamond undergoes an insulator-metal or even a superconducting transition at some critical value of the dopant concentration. We study the equilibrium lattice parameter and bulk modulus of boron-doped diamond experimentally and in the framework of the density functional method for different levels of boron doping. We theoretically consider the possibility for the boron atoms to occupy both substitutional and interstitial positions and investigate their influence on the electronic structure of the material. The data suggest that boron softens the lattice, but softening due to substitutions of carbon with boron is much weaker than due to incorporation of boron into interstitial positions. Theoretical results obtained for substitution of carbon are in very good agreement with our experiment. We present a concentration dependence of the lattice parameter in boron-doped diamond, which can be used for to identify the levels of boron doping in future experiments.

Zarechnaya, E. Yu., E-mail: ezarechnaya@yahoo.com; Isaev, E. I. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation)], E-mail: eyvaz_isaev@yahoo.com; Simak, S. I. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden); Vekilov, Yu. Kh. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation); Dubrovinsky, L. S. [University of Bayreuth, Bayerisches Geoinstitut (Germany); Dubrovinskaia, N. A. [University of Heidelberg, Mineralogisches Institut (Germany); Abrikosov, I. A. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden)

2008-04-15

396

Ground-state fragmentation phase transition for attractive bosons in anisotropic traps  

NASA Astrophysics Data System (ADS)

We construct a two-state theoretical model describing attractively interacting bosons in a cylindrical harmonic potential of varied anisotropy. These systems exhibit true many-body ground-state energy minima stable against variations in single-particle state radial and axial widths and occupation number. The many-body ground state undergoes a phase transition from pure to fragmented as the aspect ratio increases above an anisotropy threshold dependent on the interaction energy per particle. This fragmentation is robust and does not require careful tuning of experimental parameters.

Cizek, N. C.; Kasevich, M. A.

2013-12-01

397

Predicting complex ground state structures from first principles: genetic algorithm for finding accurate coarse-grained Hamiltonians  

NASA Astrophysics Data System (ADS)

First-principles quantum-mechanical (QM) calculations allow to evaluate many interesting properties of a given nano-scale configuration of atoms with high accuracy. However, predicting stable structures or finite-T thermodynamic configurational averages with QM accuracy remains a challenge: even for a binary solid with N atoms per unit cell, 2^N distinct configurations must be evaluated. Such large numbers of calculations can be made affordable by mapping the QM Hamiltonian onto a computationally simpler ``coarse-grained'' Hamiltonian. The ability to predict ground state structures then depends on the shape of the coarse-grained Hamiltonian, but this shape is not a priori clear. For instance, a few simple assumed generic interactions will allow only a few simple ground states, but any more complex structures will be missed. For the generalized Ising model for binary alloys (cluster expansion), I show how a genetic algorithm^1,2 can identify the leading interactions which characterize a given system. I illustrate the method for the bcc binary alloys of Nb, Ta, Mo, W. A rich spectrum of ground state structures is found, including both well-known and unsuspected complex structures, far beyond what is envisioned from ``usual-suspect'' structure listings or from simple generic interactions. At the same time, order-disorder temperatures are significantly lower than those from simple intuition-based interactions, in agreement with experimental observations for these systems. This work was done at the National Renewable Energy Laboratory, supported by DOE-SC-BES, in collaboration with A. Zunger and G. Hart. ^1G. Hart, V. Blum, M. Walorski and A. Zunger, Nature Materials 4, 391 (2005); ^2V. Blum, G. Hart, M. Walorski and A. Zunger, Phys. Rev. B 72, 165113 (2005).

Blum, Volker

2006-03-01

398

Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification  

SciTech Connect

The effects of atomic oxygen on boron nitride, silicon nitride, solar cell interconnects used on the Intelsat 6 satellite, organic polymers, and MoS{sub 2} and WS{sub 2} dry lubricant have been studied in low Earth orbit (LEO) flight experiments and in our ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed in situ electrical resistance measurements to detect penetration of atomic oxygen through materials and ESCA analysis to measure chemical composition changes. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN overcoated on thin silver was observed. No permeation of atomic oxygen through Si{sub 3}N{sub 4} was observed. Test results on the Intelsat 6 satellite interconnects used on its photovoltaic array indicate that more than 60--80% of the original thickness of silver should remain after completion of the proposed Space Shuttle rescue/reboost mission. Gas phase reaction products produced by the interaction of high kinetic energy atomic oxygen (AO) with Kapton were found to be H{sub 2}, H{sub 2}O, CO, and CO{sub 2} with NO being a possible secondary product. Hydrogen abstraction at high AO kinetic energy is postulated to be the key reaction controlling the erosion rate of Kapton. An Arrhenius-like expression having an activation barrier of 0.4 eV can be fit to the data, which suggests that the rate limiting step in the AO/Kapton reaction mechanism can be overcome by translational energy. Oxidation of MoS{sub 2} and WS{sub 2} dry lubricants in both ground-based and orbital exposures indicated the formation of MoO{sub 3} and WO{sub 3} respectively. A protective oxide layer is formed {approx}30 monolayers thick which has a high initial friction coefficient until the layer is worn off.

Cross, J.B. (Los Alamos National Lab., NM (United States)); Koontz, S.L. (National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center); Lan, E.H. (McDonnell Douglas Space Systems Co., Huntington Beach, CA (United States))

1991-01-01

399

Equilibrium states and ground state of two-dimensional fluid foams  

NASA Astrophysics Data System (ADS)

We study the equilibrium energies of two-dimensional (2D) noncoarsening fluid foams, which consist of bubbles with fixed areas. The equilibrium states correspond to local minima of the total perimeter. We present a theoretical derivation of energy minima; experiments with ferrofluid foams, which can be either highly distorted, locally relaxed, or globally annealed; and Monte Carlo simulations using the extended large-Q Potts model. For a dry foam with small size variance we develop physical insight and an electrostatic analogy, which enables us to (i) find an approximate value of the global minimum perimeter, accounting for (small) area disorder, the topological distribution, and physical boundary conditions; (ii) conjecture the corresponding pattern and topology: small bubbles sort inward and large bubbles sort outward, topological charges of the same signs ``repel'' while charges of the opposite signs ``attract'' (iii) define local and global markers to determine directly from an image how far a foam is from its ground state; (iv) conjecture that, in a local perimeter minimum at prescribed topology, the pressure distribution and thus the edge curvature are unique. Some results also apply to 3D foams.

Graner, F.; Jiang, Y.; Janiaud, E.; Flament, C.

2001-01-01

400

Equilibrium states and ground state of two-dimensional fluid foams  

SciTech Connect

We study the equilibrium energies of two-dimensional (2D) noncoarsening fluid foams, which consist of bubbles with fixed areas. The equilibrium states correspond to local minima of the total perimeter. We present a theoretical derivation of energy minima; experiments with ferrofluid foams, which can be either highly distorted, locally relaxed, or globally annealed; and Monte Carlo simulations using the extended large-Q Potts model. For a dry foam with small size variance we develop physical insight and an electrostatic analogy, which enables us to (i) find an approximate value of the global minimum perimeter, accounting for (small) area disorder, the topological distribution, and physical boundary conditions; (ii) conjecture the corresponding pattern and topology: small bubbles sort inward and large bubbles sort outward, topological charges of the same signs ''repel'' while charges of the opposite signs ''attract;'' (iii) define local and global markers to determine directly from an image how far a foam is from its ground state; (iv) conjecture that, in a local perimeter minimum at prescribed topology, the pressure distribution and thus the edge curvature are unique. Some results also apply to 3D foams.

Graner, F.; Jiang, Y.; Janiaud, E.; Flament, C.

2001-01-01

401

Joint Accreditation and State Program Reviews: Breaking New Ground.  

ERIC Educational Resources Information Center

To meet increasing demand, the State University System (SUS) of Florida has initiated joint program evaluations with the major professional accrediting bodies. As accreditation and program reviews typically demand similar information and similar procedures the two activities can be synchronized. The purpose of assessing and enhancing quality, a…

LeMon, R. E.; Pitter, Gita Wijesinghe

402

Single-Axis Atom-Optic Accelerometer for Army Ground Vehicles.  

National Technical Information Service (NTIS)

The unparalleled accuracies of accelerometers, gyroscopes and gravity sensors based on light-pulse atom interferometry methods hold great promise for a broad range of demanding military and commercial applications in navigation and geophysical exploration...

A. Black F. Roller M. M. Boyd T. Gustavson T. Loftus

2012-01-01

403

Fluctuating parts of nuclear ground-state correlation energies  

NASA Astrophysics Data System (ADS)

Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions.Purpose: Investigate the influence of higher-order correlation effects on nuclear binding energies using Skyrme's effective interaction.Methods: A cutoff in relative momenta is introduced to remove ultraviolet divergencies caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation and second-order many-body perturbation theory.Result: Contributions to the correlation energies are evaluated for several isotopic chains and an attempt is made to disentangle which parts give rise to fluctuations that may be difficult to incorporate on the HFB level. The dependence of the results on the cutoff is also investigated.Conclusions: The improved interaction allows explicit summations of perturbation series, which is useful for the description of some nuclear observables. However, refits of the interaction parameters are needed to obtain more quantitative results.

Carlsson, B. G.; Toivanen, J.; von Barth, U.

2013-05-01

404

Theoretical study of the reaction of carbon monoxide with oxygen molecules in the ground triplet and singlet delta states.  

PubMed

Quantum chemical calculations were carried out to study the reaction of carbon monoxide with molecular oxygen in the ground triplet and singlet delta states. Transition states and intermediates that connect the reactants with products of the reaction on the triplet and singlet potential energy surfaces were identified on the base of coupled-cluster method. The values of energy barriers were refined by using compound techniques such as CBS-Q, CBS-QB3, and G3. The calculations showed that there exists an intersection of triplet and singlet potential energy surfaces. This fact leads to the appearance of two channels for the triplet CO+O(2)(X(3)?(g)(-)) reaction, which produces atomic oxygen in the ground O((3)P) and excited O((1)D) states. The appropriate rate constants of all reaction paths were estimated on the base of nonvariational transition-state theory. It was found that the singlet reaction rate constant is much greater than the triplet one and that the reaction channel CO+O(2)(a(1)?(g)) should be taken into consideration to interpret the experimental data on the oxidation of CO by molecular oxygen. PMID:21338155

Sharipov, Alexander; Starik, Alexander

2011-03-17

405

Directly measuring the concurrence of atomic two-qubit states through the detection of cavity decay  

NASA Astrophysics Data System (ADS)

We present a scheme for directly measuring the concurrence of atomic two-qubit states (including pure states and mixed states) by detecting the photons leaking from the cavities where the atoms are located. We found that it is possible to encode the concurrence of two-atom entangled states in the photon detection results on the cavities. Cavity decay usually plays a passive role in quantum information processing, but in our scheme the decay of cavity mode plays a constructive role, and the state detection for trapped atoms were replaced by the photon detection. Our scheme is more implementable and may be feasible within the current technology.

Zhang, Li-Hua; Yang, Ming; Cao, Zhuo-Liang

2014-05-01

406

The ground state of nuclear matter with virtual ?-isobar excitations  

NASA Astrophysics Data System (ADS)

The equation of state of nuclear matter is studied in the framework of the Bethe-Brueckner-Goldstone theory using the local Argonne v28 potential which explicitly includes ?-isobar degrees of freedom. The self-consistent two-body reaction matrix is obtained with all possible allowed couplings to the N? and ?? states. Saturation occurs around kF=1.2 fm -1 with a binding energy per particle {B}/{A}=-10.31 MeV, confirming the effect of the isobar in pushing the saturation point to the upper side of the Coester band. The present results are very close to the ones obtained in full coupled-channel relativistic calculations.

Baldo, M.; Ferreira, L. S.

1991-11-01

407

Towards the ground state of an electron-hole bilayer  

NASA Astrophysics Data System (ADS)

Transport measurements down to 50 mK have been performed on independently contacted electron-hole bilayers (EHBL) with a 10 nm barrier, close to the excitonic Bohr radius of the system ( ?12 nm). Coulomb drag measured reveals a departure from that expected for two Fermi liquids, exhibiting an upturn that may be followed by a downturn or even a sign-reversal at the lowest temperatures. Concurrently an insulating state in the single-layer resistivities has been found for low sheet resistances ( ??h/e2), well away from where the metal-insulator transition has been previously observed in two-dimensional systems. We can unambiguously show that this insulating state is caused by the interlayer interaction, as opposed to disorder. We consider the possibility of excitonic and collective mode driven phases that have been anticipated in EHBLs.

Croxall, A. F.; Das Gupta, K.; Nicoll, C. A.; Farrer, I.; Beere, H. E.; Ritchie, D. A.; Pepper, M.

2010-02-01

408

Cyclooctatetraenes tetrakis-annelated with alpha-dithio- or alpha-diselenocarbonyl groups: diradicals predicted to have ground states with 10 pi electrons in the eight-membered ring and two-center, three-electron, sigma bonds between two pairs of chalcogen atoms.  

PubMed

(U)B3LYP calculations with the 6-31+G(d) and 6-311+G(2df) basis sets have been carried out on cyclooctatetraenes 6 and 7, in which the COT ring is tetrakis-annelated with alpha-dithio- or alpha-diselenocarbonyl groups. Transferring two electrons from the high-lying b(1g) and e(u) sigma MOs in 6 and 7 into the unoccupied, nonbonding, COT pi orbital is computed to be energetically favorable. The lowest D(4h) electronic state is calculated to be (3)E(u), which formally contains 10 pi electrons in the eight-membered ring and has two unpaired electrons in sigma MOs. The (3)E(u) state undergoes a first-order Jahn-Teller distortion to form 6d and 7d, in which the pair of one-electron holes in the sigma MOs is stabilized by the formation of two, two-center, three-electron bonds between pairs of chalcogen atoms that are diagonally across the eight-membered ring from each other. The corresponding open-shell singlets are computed to be about 1 kcal/mol lower in energy than the Jahn-Teller distorted triplets. Molecules 6i and 7i, in which the C-C bond in one four-membered ring is cleaved, are computed to be lower in energy than 6d and 7d. However, a substantial barrier is predicted to separate each of the two pairs of isomers so that 6d and 7d should, at least in principle, be isolable. PMID:20151691

Zhou, Xin; Hrovat, David A; Borden, Weston Thatcher

2010-03-18

409

Performing measurement based quantum computation on ground states  

NASA Astrophysics Data System (ADS)

One of the most exciting developments in quantum computing in recent years has been the realisation that there exist states of quantum many-body systems that can serve as a universal resource for quantum computing, where computation proceeds solely through single-qubit measurements. Although currently only a few isolated examples of such universal resource states are known, we discuss the possibility that there exist models of interacting spin systems in which an ordered phase is characterized by the ability to perform measurement-based quantum computation (MBQC). To identify such phases, we propose to use nonlocal correlation functions that quantify the fidelity of quantum gates performed between well separated qubits. The quantum computing phase is then characterized by set of order parameters corresponding to a universal set of quantum gates. We investigate a simple spin-lattice system based on the cluster-state model for MBQC by using a series of dualities with better studied models. We demonstrate that the model possesses a zero temperature phase transition between a disordered phase and an ordered ``cluster phase'' in which it is possible to perform a large class of one and two qubit quantum gates.

Doherty, Andrew; Bartlett, Stephen

2009-03-01

410

Ground-state phase in the three-dimensional topological Dirac semimetal Na3Bi  

NASA Astrophysics Data System (ADS)

By means of the first-principles calculations, we found that the early characterized 3D topological Dirac semimetal P63/mmc-Na3Bi is dynamically unstable at the ground state due to the presence of the large imaginary phonon frequencies around the K point. Alternatively, our calculations suggested a new ground-state phase crystalizing in a P3¯c1 structure with buckled graphite-like Na/Bi sheets, which is both energetically and dynamically stable. Moreover, the calculations also uncovered that the P3¯c1 phase is a 3D topological Dirac semimetal, with exactly the same electronic states of the metastable P63/mmc phase.

Cheng, Xiyue; Li, Ronghan; Sun, Yan; Chen, Xing-Qiu; Li, Dianzhong; Li, Yiyi

2014-06-01

411

Controlling ground-state rotational dynamics of molecules by shaped femtosecond laser pulses  

SciTech Connect

We report controlled excitation of ground-state rotational wave packet by pulse-shaping technique. The experiment is conducted in nitrogen (N{sub 2}) at room temperature and atmospheric pressure. A femtosecond laser pulse produces rotational coherences in the vibronic ground state of N{sub 2} through an impulsive Raman process. The laser pulse is tailored using a spatial light modulator producing spectral phase modulation. Periodic phase steps are applied in order to control the excitation of specific rotational Raman transitions. The outcome is the modification of the relative excitation between odd and even rotational states which allows the control of the symmetry and rephasing period of the wave packet.

Renard, M.; Hertz, E.; Lavorel, B.; Faucher, O. [Laboratoire de Physique de l'Universite de Bourgogne, UMR CNRS 5027, Boite Postale 47 870, 21 078 Dijon cedex (France)

2004-04-01

412

Magnetic ground state of single and coupled permalloy rectangles.  

PubMed

We have studied the magnetic domain structure in Permalloy rectangles that reveal flux-closure domain configurations. Arrays with varying spacing between the rectangles are investigated by scanning electron microscopy with polarization analysis as well as by micromagnetic simulation. In contrast to general expectation, rectangles in the flux-closure Landau state show significant coupling and form a magnetic pattern of common chirality. The coupling is due to the stray field that originates from small changes of the magnetization alignment, which is sensitive to the exact shape and the separation of the rectangles. PMID:19905600

Hankemeier, S; Frömter, R; Mikuszeit, N; Stickler, D; Stillrich, H; Pütter, S; Vedmedenko, E Y; Oepen, H P

2009-10-01

413

The Transition Rate of the Ground State of Polaron in a Parabolic Quantum Dot  

NASA Astrophysics Data System (ADS)

The ground-state energy of polaron was obtained with strong electron-LO-phonon coupling by using a variational method of the Pekar type in a parabolic quantum dot (QD). Quantum transition occurred in the quantum system due to the electron-phonon interaction and the influence of temperature. That is, the polaron transits from the ground state to the first excited state after absorbing a LO-phonon. Numerical calculations are performed and the results illustrate the relations of the transition rate of the polaron on the ground-state energy of polaron, the cyclotron frequency parameter, the Coulomb binding parameter, the temperature, the electron-LO-phonon coupling strength and the confinement length of the quantum dot.

Li, Wei-Ping; Yin, Ji-Wen; Yu, Yi-Fu; Xiao, Jing-Lin; Wang, Zi-Wu

414

Bose-Einstein quantum statistics and the ground state of solid 4He  

Microsoft Academic Search

The ground state of solid 4He is studied using the diffusion Monte Carlo method and a new trial wave function able to describe the supersolid. This wave function is symmetric under the exchange of particles and used as a guiding function in the method allows for reproducing the experimental equation of state. The use of this zero-temperature technique overcomes the

C. Cazorla; G. E. Astrakharchik; J. Casulleras; J. Boronat

2009-01-01

415

On the Growth of the Ground-State Binding Energy with Increase in Potential Strength.  

National Technical Information Service (NTIS)

The paper presents a study of the asymptotic behavior of the ground-state binding energy G(lambda) of -delta + lambda V as lambda approaches infinity. Unlike the number of bound states, G(lambda) does not have a universal power growth as lambda approaches...

B. Simon

1969-01-01

416

Long-range interaction between metastable helium and ground state helium.  

NASA Technical Reports Server (NTRS)

Results of analysis for the long-range interaction between ground state helium and triplet metastable helium, which shows that the long-range coefficient is the same for both gerade and ungerade states. Those terms which lead to the second term on the right hand side of a developed equation vanish through spin selection rules.

Victor, G. A.; Sando, K.

1971-01-01

417

Ground-State Properties of 16O in Unitary-Model-Operator Approach with Bonn Potential  

NASA Astrophysics Data System (ADS)

The unitary-model-operator approach (UMOA) is applied to the calculation of the ground-state energy, the charge radius and the single-particle energies of occupied states in 16O with the Bonn potential. The calculation reproduces the experimental saturation property fairly well beyond the Coester band.

Suzuki, K.; Kumagai, H.; Okamoto, R.

1993-07-01

418

Ground State Lost but Degeneracy Found: The Effective Thermodynamics of Artificial Spin Ice  

Microsoft Academic Search

We analyze the rotational demagnetization of artificial spin ice, a recently realized array of nanoscale single-domain ferromagnetic islands. Demagnetization does not anneal this model system into its antiferromagnetic ground state: the moments have a static disordered configuration similar to the frozen state of the spin ice materials. We demonstrate that this athermal system has an effective extensive degeneracy and we

Cristiano Nisoli; Ruifang Wang; Jie Li; William F. McConville; Paul E. Lammert; Peter Schiffer; Vincent H. Crespi

2007-01-01

419

A high flux pulsed source of energetic atomic oxygen. [for spacecraft materials ground testing  

NASA Technical Reports Server (NTRS)

The design and demonstration of a pulsed high flux source of nearly monoenergetic atomic oxygen are reported. In the present test setup, molecular oxygen under several atmospheres of pressure is introduced into an evacuated supersonic expansion nozzle through a pulsed molecular beam valve. A 10J CO2 TEA laser is focused to intensities greater than 10 to the 9th W/sq cm in the nozzle throat, generating a laser-induced breakdown with a resulting 20,000-K plasma. Plasma expansion is confined by the nozzle geometry to promote rapid electron-ion recombination. Average O-atom beam velocities from 5-13 km/s at fluxes up to 10 to the 18th atoms/pulse are measured, and a similar surface oxygen enrichment in polyethylene samples to that obtained on the STS-8 mission is found.

Krech, Robert H.; Caledonia, George E.

1986-01-01

420

Tunable ground-state degeneracies in double quantum dots  

NASA Astrophysics Data System (ADS)

We have studied the effect of electron-electron interactions on planar double quantum dots subjected to an external magnetic field. Contrary to all other earlier works on similar systems, our accurate results for the energy levels and the dipole-allowed transition energies reveal the absence of singlet-triplet crossing (due to electron correlations only) in the case when the dots occupy only two electrons. For a larger number of electrons, we find the expected crossing of the energy levels. The corresponding far-infrared optical absorption spectra show the effect of electronic interactions as well as the underlying symmetries of these systems. The hyper-exponential increase of the exchange energy, as derived in our model, would facilitate the coherent control of the spin states in a double dot, as proposed in recent experiments.

Chen, Hong-Yi; Garcia, Jaime Zaratiegui; Chakraborty, Tapash; Pietilainen, Pekka

2008-06-01

421

Scheme for entanglement concentration of unknown partially entangled three-atom W states in cavity QED  

Microsoft Academic Search

We propose a practical scheme to concentrate entanglement in a pair of unknown partially entangled three-atom W states in cavity quantum electrodynamics (QED). In the scheme, Alice, Bob, and Charlie at three distant parties can obtain\\u000a one maximally entangled three-atom W state with the certain success probability from two identical partially entangled three-atom W states by local operations and classical

Hong-Fu Wang; Li-Li Sun; Shou Zhang; Kyu-Hwang Yeon

422

Improved quantum hard-sphere ground-state equations of state.  

PubMed

The London ground-state energy formula as a function of number density for a system of identical boson hard spheres, corrected for the reduced mass of a pair of particles in a "sphere-of-influence" picture, and generalized to fermion hard-sphere systems with two and four intrinsic degrees of freedom, has a double-pole at the ultimate regular (or periodic, e.g., face-centered-cubic) close-packing density usually associated with a crystalline branch. Improved fluid branches are constructed based upon exact, field-theoretic perturbation-theory low-density expansions for many-boson and many-fermion systems, extrapolated to intermediate densities via Padé and other approximants, but whose ultimate density is irregular or random closest close-packing as suggested in studies of a classical system of hard spheres. Results show substantially improved agreement with the best available Green-function Monte Carlo and diffusion Monte Carlo simulations for bosons, as well as with ladder, variational Fermi hypernetted chain, and so-called L -expansion data for two-component fermions. PMID:17930217

Solís, M A; de Llano, M; Clark, J W; Baker, George A

2007-09-01

423

Improved quantum hard-sphere ground-state equations of state  

SciTech Connect

The London ground-state energy formula as a function of number density for a system of identical boson hard spheres, corrected for the reduced mass of a pair of particles in a 'sphere-of-influence' picture, and generalized to fermion hard-sphere systems with two and four intrinsic degrees of freedom, has a double-pole at the ultimate regular (or periodic, e.g., face-centered-cubic) close-packing density usually associated with a crystalline branch. Improved fluid branches are constructed based upon exact, field-theoretic perturbation-theory low-density expansions for many-boson and many-fermion systems, extrapolated to intermediate densities via Pade and other approximants, but whose ultimate density is irregular or random closest close-packing as suggested in studies of a classical system of hard spheres. Results show substantially improved agreement with the best available Green-function Monte Carlo and diffusion Monte Carlo simulations for bosons, as well as with ladder, variational Fermi hypernetted chain, and so-called L-expansion data for two-component fermions.

Solis, M. A. [Department of Physics, Washington University, St. Louis, Missouri 63130 (United States); Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, 01000 Mexico, D.F. (Mexico); Llano, M. de [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, 04510 Mexico, D.F. (Mexico) and Consortium of the Americas for Interdisciplinary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Clark, J. W. [Department of Physics, Washington University, St. Louis, Missouri 63130 (United States); Baker, George A. Jr. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-09-15

424

Synergistic Mechanisms of DNA Demethylation during Transition to Ground-State Pluripotency  

PubMed Central

Summary Pluripotent stem cells (PSCs) occupy a spectrum of reversible molecular states ranging from a naive ground-state in 2i, to metastable embryonic stem cells (ESCs) in serum, to lineage-primed epiblast stem cells (EpiSCs). To investigate the role of DNA methylation (5mC) across distinct pluripotent states, we mapped genome-wide 5mC and 5-hydroxymethycytosine (5hmC) in multiple PSCs. Ground-state ESCs exhibit an altered distribution of 5mC and 5hmC at regulatory elements and dramatically lower absolute levels relative to ESCs in serum. By contrast, EpiSCs exhibit increased promoter 5mC coupled with reduced 5hmC, which contributes to their developmental restriction. Switch to 2i triggers rapid onset of both the ground-state gene expression program and global DNA demethylation. Mechanistically, repression of de novo methylases by PRDM14 drives DNA demethylation at slow kinetics, whereas TET1/TET2-mediated 5hmC conversion enhances both the rate and extent of hypomethylation. These processes thus act synergistically during transition to ground-state pluripotency to promote a robust hypomethylated state.

Hackett, Jamie A.; Dietmann, Sabine; Murakami, Kazuhiro; Down, Thomas A.; Leitch, Harry G.; Surani, M. Azim

2013-01-01

425

Preparation of genuine Yeo-Chua entangled state and teleportation of two-atom state via cavity QED  

NASA Astrophysics Data System (ADS)

We first propose a scheme for preparing the genuine Yeo-Chua 4-qubit entangled state via cavity QED. Using the genuine Yeo-Chua atomic state, we further propose a cavity QED scheme for teleporting an arbitrary two-atom state. In two schemes the large-detuning is chosen and the necessary time is designed to be much shorter than Rydberg-atom's lifespan. Both schemes share the distinct advantage that cavity decay and atom decay can be neglected. As for the interaction manipulation, our preparation scheme is more feasible than a recent similar one. Compared with the Yeo and Chua's scheme, our teleportation scheme has significantly reduced the measuring difficulty.

Zhang, Wen; Liu, Yimin; Zuo, Xueqin; Zhang, Zhanjun

2010-12-01

426

Anomalous magnetic ground state in PrSi evidenced by the magnetocaloric effect  

NASA Astrophysics Data System (ADS)

Previous investigations into the physical properties of PrSi have shown this compound to order ferromagnetically at 54 K. However, the magnetic ground state has not yet been determined unambiguously. PrSi crystallizes in the orthorhombic FeB-type structure. Typically, the crystalline electric field (CEF) would uplift the degeneracy of the J=4 Pr3+ free-ion ground state multiplet, yielding nine (normally non-magnetic) singlets. It is known that magnetic order in such systems may be established via the admixture of two singlets into a doublet state, analogous to TmNi, which crystallizes in the same structure. From symmetry considerations, collinear ferromagnetically ordered moments should lie parallel to the crystallographic b-axis. However, neutron diffraction experiments have shown that the easy magnetic axis lies in the ac-plane. This is the first suggestion that the ground state in PrSi is not determined by the CEF alone. Here, we investigate the ground state properties of PrSi by analyzing its specific heat. A Schottky contribution associated with the thermal population of CEF-split energy levels is absent from the 4f-electron contribution to the specific heat and the magnetic configurational entropy points to a full nine-fold degenerate J=4 multiplet magnetic ground state. The strongest evidence for such a ground state is found when the magnetocaloric effect (MCE) in this system is considered. Furthermore, the MCE indicates the presence of a significant higher order exchange term in the magnetic Hamiltonian.

Snyman, J. L.; Strydom, A. M.

2012-04-01

427

Historically grounded spatial population projections for the continental United States  

NASA Astrophysics Data System (ADS)

Large-scale spatial population projections are of growing importance to the global change community. Spatial settlement patterns are a key determinant of vulnerability to climate-related hazards as well as to land-use and its consequences for habitat, energy use, and emissions of greenhouse gases and air pollutants. Few projections exist of spatial distribution at national or larger scales, and while recent efforts improve on earlier approaches that simply scaled or extrapolated existing spatial patterns, important methodological shortcomings remain and models have not been calibrated to nor validated against historical trends. Here we present spatially explicit 100-year projections for the continental United States consistent with two different scenarios of possible socio-economic development. The projections are based on a new model that is calibrated to observed changes in regional population distribution since 1950, corrects for distorting effects at borders, and employs a spatial mask for designating protected or uninhabitable land. Using new metrics for comparing spatial outcomes, we find that our projections anticipate more moderate trends in urban expansion and coastal settlement than widely used existing projections. We also find that differences in outcomes across models are much larger than differences across alternative socio-economic scenarios for a given model, emphasizing the importance of better understanding of methods of spatial population projection for improved integrated assessments of social and environmental change.

Jones, Bryan; O'Neill, Brian C.

2013-12-01

428

Stability and related properties of vacua and ground states  

SciTech Connect

We consider the formal non-relativistic limit (nrl) of the :{phi}{sup 4}:{sub s+1} relativistic quantum field theory (rqft), where s is the space dimension. Following the work of R. Jackiw [R. Jackiw, in: A. Ali, P. Hoodbhoy (Eds.), Beg Memorial Volume, World Scientific, Singapore, 1991], we show that, for s = 2 and a given value of the ultraviolet cutoff {kappa}, there are two ways to perform the nrl: (i) fixing the renormalized mass m{sup 2} equal to the bare mass m{sub 0}{sup 2}; (ii) keeping the renormalized mass fixed and different from the bare mass m{sub 0}{sup 2}. In the (infinite-volume) two-particle sector the scattering amplitude tends to zero as {kappa} {yields} {infinity} in case (i) and, in case (ii), there is a bound state, indicating that the interaction potential is attractive. As a consequence, stability of matter fails for our boson system. We discuss why both alternatives do not reproduce the low-energy behaviour of the full rqft. The singular nature of the nrl is also nicely illustrated for s = 1 by a rigorous stability/instability result of a different nature.

Wreszinski, Walter F. [Departamento de Fisica Matematica, Universidade de Sao Paulo (Brazil)], E-mail: wreszins@fma.if.usp.br; Jaekel, Christian D. [Instituto de Matematica y Fisica, Universidad de Talca (Chile)], E-mail: christian.jaekel@mac.com

2008-02-15