NASA Astrophysics Data System (ADS)
Böhm, Ch.; Borgmann, Ch.; Audi, G.; Beck, D.; Blaum, K.; Breitenfeldt, M.; Cakirli, R. B.; Cocolios, T. E.; Eliseev, S.; George, S.; Herfurth, F.; Herlert, A.; Kowalska, M.; Kreim, S.; Lunney, D.; Manea, V.; Minaya Ramirez, E.; Naimi, S.; Neidherr, D.; Rosenbusch, M.; Schweikhard, L.; Stanja, J.; Wang, M.; Wolf, R. N.; Zuber, K.
2014-10-01
High-precision mass measurements of neutron-deficient Tl (A =184, 186, 190, 193-195, 198) isotopes as well as Pb (A =202,208), Fr (A =207,208), and Ra (A =224) are performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The improved precision of the mass data now allows the study of subtle odd-even effects. The gradual development of collectivity with the removal of protons from the magic Z =82 core is analyzed by combining the new mass results with nuclear charge-radii data and mean-field model predictions.
Nuclear ground-state masses and deformations: FRDM(2012)
Moller, P.; Sierk, A. J.; Ichikawa, T.; Sagawa, H.
2016-03-25
Here, we tabulate the atomic mass excesses and binding energies, ground-state shell-plus-pairing corrections, ground-state microscopic corrections, and nuclear ground-state deformations of 9318 nuclei ranging from 16O to A=339. The calculations are based on the finite-range droplet macroscopic and the folded-Yukawa single-particle microscopic nuclear-structure models, which are completely specified. Relative to our FRDM(1992) mass table in Möller et al. (1995), the results are obtained in the same model, but with considerably improved treatment of deformation and fewer of the approximations that were necessary earlier, due to limitations in computer power. The more accurate execution of the model and the more extensivemore » and more accurate experimental mass data base now available allow us to determine one additional macroscopic-model parameter, the density-symmetry coefficient LL, which was not varied in the previous calculation, but set to zero. Because we now realize that the FRDM is inaccurate for some highly deformed shapes occurring in fission, because some effects are derived in terms of perturbations around a sphere, we only adjust its macroscopic parameters to ground-state masses.« less
Nuclear ground-state masses and deformations: FRDM(2012)
NASA Astrophysics Data System (ADS)
Möller, P.; Sierk, A. J.; Ichikawa, T.; Sagawa, H.
2016-05-01
We tabulate the atomic mass excesses and binding energies, ground-state shell-plus-pairing corrections, ground-state microscopic corrections, and nuclear ground-state deformations of 9318 nuclei ranging from 16O to A = 339. The calculations are based on the finite-range droplet macroscopic and the folded-Yukawa single-particle microscopic nuclear-structure models, which are completely specified. Relative to our FRDM(1992) mass table in Möller et al. (1995), the results are obtained in the same model, but with considerably improved treatment of deformation and fewer of the approximations that were necessary earlier, due to limitations in computer power. The more accurate execution of the model and the more extensive and more accurate experimental mass data base now available allow us to determine one additional macroscopic-model parameter, the density-symmetry coefficient L, which was not varied in the previous calculation, but set to zero. Because we now realize that the FRDM is inaccurate for some highly deformed shapes occurring in fission, because some effects are derived in terms of perturbations around a sphere, we only adjust its macroscopic parameters to ground-state masses.
Magnetic Field Measurement with Ground State Alignment
NASA Astrophysics Data System (ADS)
Yan, Huirong; Lazarian, A.
Observational studies of magnetic fields are crucial. We introduce a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields (1 G ≳ B ≳ 10^{-15} G). In fact, the effects of atomic/ionic alignment were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this chapter, we shall review the basic physical processes involved in atomic realignment. We shall also discuss its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields in the Epoch of Reionization.
Nuclear quadrupole moment of the {sup 99}Tc ground state
Errico, Leonardo; Darriba, German; Renteria, Mario; Tang Zhengning; Emmerich, Heike; Cottenier, Stefaan
2008-05-15
By combining first-principles calculations and existing nuclear magnetic resonance (NMR) experiments, we determine the quadrupole moment of the 9/2{sup +} ground state of {sup 99}Tc to be (-)0.14(3)b. This confirms the value of -0.129(20)b, which is currently believed to be the most reliable experimental determination, and disagrees with two earlier experimental values. We supply ab initio calculated electric-field gradients for Tc in YTc{sub 2} and ZrTc{sub 2}. If this calculated information would be combined with yet to be performed Tc-NMR experiments in these compounds, the error bar on the {sup 99}Tc ground state quadrupole moment could be further reduced.
Nuclear ground state charge radii from electromagnetic interactions
Frickle, G.; Bernhardt, C.; Heilig, K.
1995-07-01
The Tables summarize experimental results from muonic atom transition energies, nuclear charge parameters from elastic electron scattering, and K x-ray isotope shifts in so far as they provide information on nuclear ground-state charge radii. Numerous experimental results for optical isotope shifts have been published elsewhere; for eight elements the relevant information is condensed ({open_quotes}project{close_quotes}) here to one optical line per element. A model-independent analysis which combines data from all three experimental methods is applied to these elements and is presented as an illustration of the improved accuracy for the rms radii and Barrett radii which result from this analysis. 51 refs., 11 figs, 1 tab.
Measured atomic ground-state polarizabilities of 35 metallic elements
NASA Astrophysics Data System (ADS)
Ma, Lei; Indergaard, John; Zhang, Baiqian; Larkin, Ilia; Moro, Ramiro; de Heer, Walt A.
2015-01-01
Advanced pulsed cryogenic molecular-beam electric deflection methods involving position-sensitive mass spectrometry and 7.87-eV ionizing radiation were used to measure the polarizabilities of more than half of the metallic elements in the Periodic Table. Concurrent Stern-Gerlach deflection measurements verified the ground-state condition of the measured atoms. Comparison with state-of-the-art calculations exposes significant systematic and isolated discrepancies throughout the Periodic Table.
New Measurement of the 5H Ground State
NASA Astrophysics Data System (ADS)
McNeel, Daniel G.; Wuosmaa, A. H.; Bedoor, S.; Newton, A. S.; Brown, K. W.; Charity, R. J.; Sobotka, L. G.; Buhro, W. W.; Chajecki, Z.; Lynch, W. G.; Manfredi, J.; Showalter, R. H.; Tsang, M. B.; Winklebauer, J. R.; Marley, S. T.; Shetty, D. V.
2015-10-01
We have studied the ground state of 5H using the 6He(d,3He)5H reaction in inverse kinematics. Existing data for 5H are in conflict with each other and with many theoretical predictions. This measurement provides a clear evidence for the 5H ground state, and the previously unreported 6He(d,t)5Heg.s. reaction is also observed. A 6He beam at 55 MeV/A produced at the National Superconducting Cyclotron Laboratory at Michigan State University bombarded a 1.9 mg/cm2 (CD2)n target. The reaction products were detected with HiRA (the High Resolution Array). The 3He and 3H particles from the 6He(d,3He/3H)5H/5He reactions were detected in coincidence with the decay products of the unstable 5H and 5He nuclei, providing signatures for the transitions of interest. The properties of the 5He ground state provide information about the calibration and response of the apparatus. Details of the measurement, and a comparison of the data with earlier results and theoretical calculations, will be presented. Work supported by the U.S. Department of Energy under Contracts DE-FG02-04ER41320 and DE-FG02-87ER40316, and the U. S. National Science Foundation under Grant Numbers PHY-1068217 and PHY-1068192.
Measured Atomic Ground State Polarizabilities of 35 Metallic Elements
NASA Astrophysics Data System (ADS)
Indergaard, John; Ma, Lei; Zhang, Baiqian; Larkin, Ilia; Moro, Ramiro; de Heer, Walter
2015-03-01
Advanced pulsed cryogenic molecular beam electric deflection methods utilizing a position-sensitive mass spectrometer and 7.87 eV ionizing radiation were used to measure the polarizabilities of more than half of the metallic elements in the periodic table for the first time. These measurements increase the total number of experimentally obtained atomic polarizabilities from 23 to 57. Concurrent Stern-Gerlach deflection measurements verified the ground state condition of the measured atoms. Generating higher temperature beams allowed for the comparison of relative populations of the ground and excited states in order to extract the true temperature of the atomic beam, which followed the nominal temperature closely over a wide temperature range. Comparison of newly measured polarizabilities with state-of-the-art calculations exposes significant systematic and isolated discrepancies throughout the periodic table. Cluster Lab at Georgia Tech.
NEW GROUND-STATE MEASUREMENTS OF ETHYL CYANIDE
Brauer, Carolyn S.; Pearson, John C.; Drouin, Brian J.; Yu, Shanshan
2009-09-01
The spectrum of ethyl cyanide, or propionitrile (CH{sub 3}CH{sub 2}CN), has been repeatedly observed in the interstellar medium with large column densities and surprisingly high temperatures in hot core sources. The construction of new, more sensitive, observatories accessing higher frequencies such as Herschel, ALMA, and SOFIA have made it important to extend the laboratory data for ethyl cyanide to coincide with the capabilities of the new instruments. We report extensions of the laboratory measurements of the rotational spectrum of ethyl cyanide in its ground vibrational state to 1.6 THz. A global analysis of the ground state, which includes all of the previous data and 3356 newly assigned transitions, has been fitted to within experimental error to J = 132, K = 36, using both Watson A-reduced and Watson S-reduced Hamiltonians.
Probes of shape transitions from mass and charge radii of nuclear ground states
NASA Astrophysics Data System (ADS)
Sun, B. H.; Liu, C. Y.
2016-09-01
The masses and sizes of nuclear ground states constitute two of the most precise and extensive arrays of experimental information. These data make a model-independent view of microscopic nuclear structure possible. Relevant differential observables of nuclear mass and charge radius can be highly sensitive to nuclear shape transitions. In this contribution, we examine the correlation of these two bulk properties to nuclear shape transitions. By combining different observables, it is even possible to isolate shape transitions from nuclear shell closures.
NASA Astrophysics Data System (ADS)
Farasat, M.; Shojaei, S. H. R.; Morini, F.; Golzan, M. M.; Deleuze, M. S.
2016-04-01
The electronic structure, electron binding energy spectrum and (e, 2e) momentum distributions of aniline have been theoretically predicted at an electron impact energy of 1.500 keV on the basis of Born-Oppenheimer molecular dynamical simulations, in order to account for thermally induced nuclear motions in the initial electronic ground state. Most computed momentum profiles are rather insensitive to thermally induced alterations of the molecular structure, with the exception of the profiles corresponding to two ionization bands at electron binding energies comprised between ˜10.0 and ˜12.0 eV (band C) and between ˜16.5 and ˜20.0 eV (band G). These profiles are found to be strongly influenced by nuclear dynamics in the electronic ground state, especially in the low momentum region. The obtained results show that thermal averaging smears out most generally the spectral fingerprints that are induced by nitrogen inversion.
Ground state hyperfine splitting in 6,7Li atoms and the nuclear structure.
Puchalski, Mariusz; Pachucki, Krzysztof
2013-12-13
Relativistic and QED corrections are calculated for a hyperfine splitting of the 2S1/2 ground state in 6,7Li atoms with a numerically exact account for electronic correlations. The resulting theoretical predictions achieve such a precision level that, by comparison with experimental values, they enable determination of the nuclear properties. In particular, the obtained results show that the 7Li nucleus, having a charge radius smaller than 6Li, has about a 40% larger Zemach radius. Together with known differences in the electric quadrupole and magnetic dipole moments, this calls for a deeper understanding of the Li nuclear structure.
NASA Astrophysics Data System (ADS)
Ishida, A.; Namba, T.; Asai, S.
2016-03-01
The thermalization parameter of positronium in pure isobutane gas was measured in order to take into account the thermalization effect on precision measurements of the ground-state hyperfine splitting (HFS) of positronium. The momentum-transfer cross section was measured to be {σ }{{m}}=47.2+/- 6.7 {\\mathringA }2 for positroniums with kinetic energy below 0.17 eV. Using this value, our new HFS experiment revealed that the positronium thermalization effect on HFS was as large as 10+/- 2 {ppm}. In this article, we show the details of Ps thermalization measurement, which have not been published before, and also its effect on HFS.
Morini, Filippo; Deleuze, Michael Simon; Watanabe, Noboru; Kojima, Masataka; Takahashi, Masahiko
2015-10-07
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b{sub 1}, 6a{sub 1}, 4b{sub 2}, and 1a{sub 2} orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A{sub 1}, B{sub 1}, and B{sub 2} symmetries, which correspond to C–H stretching and H–C–H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
NASA Astrophysics Data System (ADS)
Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko
2015-10-01
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko
2015-10-01
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
An upper limit to ground state energy fluctuations in nuclear masses
Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Velazquez, Victor; Isacker, Piet van; Zuker, Andres P.
2007-02-12
Shell model calculations are employed to estimate un upper limit of statistical fluctuations in the nuclear ground state energies. In order to mimic the presence of quantum chaos associated with neutron resonances at energies between 6 to 10 MeV, calculations include random interactions in the upper shells. The upper bound for the energy fluctuations at mid-shell is shown to have the form {sigma}(A) {approx_equal} 20A-1.34 MeV. This estimate is consistent with the mass errors found in large shell model calculations along the N=126 line, and with local mass error estimated using the Garvey-Kelson relations, all being smaller than 100 keV.
Covariant energy density functionals: Nuclear matter constraints and global ground state properties
NASA Astrophysics Data System (ADS)
Afanasjev, A. V.; Agbemava, S. E.
2016-05-01
The correlations between global description of the ground state properties (binding energies, charge radii) and nuclear matter properties of the state-of-the-art covariant energy density functionals have been studied. It was concluded that the strict enforcement of the constraints on the nuclear matter properties (NMP) defined in Dutra et al. [Phys. Rev. C 90, 055203 (2014), 10.1103/PhysRevC.90.055203] will not necessarily lead to the functionals with good description of the binding energies and other ground and excited state properties. In addition, it will not substantially reduce the uncertainties in the predictions of the binding energies in neutron-rich systems. It turns out that the functionals, which come close to satisfying these NMP constraints, have some problems in the description of existing data. On the other hand, these problems are either absent or much smaller in the functionals which are carefully fitted to finite nuclei but which violate some NMP constraints. This is a consequence of the fact that the properties of finite nuclei are defined not only by nuclear matter properties but also by underlying shell effects. The mismatch of phenomenological content, existing in all modern functionals, related to nuclear matter physics and the physics of finite nuclei could also be responsible.
Measurements of the Ground-State Polarizabilities of Cs, Rb, and K using Atom Interferometry
NASA Astrophysics Data System (ADS)
Gregoire, Maxwell; Hromada, Ivan; Holmgren, William; Trubko, Raisa; Cronin, Alex
2016-05-01
We measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms with 0.2% uncertainty using a three-nanograting Mach-Zehnder atom beam interferometer. Since thermal Cs atoms have short de Broglie wavelengths, we developed measurement methods that do not require resolved atom diffraction: we used phase choppers to measure atomic beam velocity distributions, and electric field gradients to induce polarizability-dependent phase shifts. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to interpret atomic parity non-conservation experiments.
Wave-function frozen-density embedding: Approximate analytical nuclear ground-state gradients.
Heuser, Johannes; Höfener, Sebastian
2016-05-01
We report the derivation of approximate analytical nuclear ground-state uncoupled frozen density embedding (FDEu) gradients for the resolution of identity (RI) variant of the second-order approximate coupled cluster singles and doubles (RICC2) as well as density functional theory (DFT), and an efficient implementation thereof in the KOALA program. In order to guarantee a computationally efficient treatment, those gradient terms are neglected which would require the exchange of orbital information. This approach allows for geometry optimizations of single molecules surrounded by numerous molecules with fixed nuclei at RICC2-in-RICC2, RICC2-in-DFT, and DFT-in-DFT FDE level of theory using a dispersion correction, required due to the DFT-based treatment of the interaction in FDE theory. Accuracy and applicability are assessed by the example of two case studies: (a) the Watson-Crick pair adenine-thymine, for which the optimized structures exhibit a maximum error of about 0.08 Å for our best scheme compared to supermolecular reference calculations, (b) carbon monoxide on a magnesium oxide surface model, for which the error amount up to 0.1 Å for our best scheme. Efficiency is demonstrated by successively including environment molecules and comparing to an optimized conventional supermolecular implementation, showing that the method is able to outperform conventional RICC2 schemes already with a rather small number of environment molecules, gaining significant speed up in computation time. PMID:26804310
Robinson, A P; Woods, P J; Seweryniak, D; Davids, C N; Carpenter, M P; Hecht, A A; Peterson, D; Sinha, S; Walters, W B; Zhu, S
2005-07-15
Ground-state proton radioactivity has been identified from 121Pr. A transition with a proton energy of E(p)=882(10) keV [Q(p)=900(10) keV] and half-life t(1/2)=10(+6)(-3) ms has been observed and is assigned to the decay of a highly prolate deformed 3/2(+) or 3/2(-) Nilsson state. The present result is found to be incompatible with a previously reported observation of ground-state proton radioactivity from 121Pr, which would have represented the discovery of this phenomenon.
Isomeric and ground state energy level measurements of natural tellurium isotopes via (γ,n) reaction
NASA Astrophysics Data System (ADS)
Tamkas, M.; Akcali, O.; Durusoy, A.
2015-04-01
We have planned to measure isomeric and ground state energy levels in 120Te(γ,n)119m,gTe, 122Te(γ,n)121m,gTe, 128Te(γ,n)127m,gTe, 130Te(γ,n)129m,gTe photonuclear reactions of natural tellurium induced by bremsstrahlung photons with end-point energy at 18 MeV. The sample was irradiated in the clinical linear electron accelerator (Philips SLi-25) at Akdeniz University Hospital. The gamma spectrum of the tellurium sample was measured using HP(Ge) semiconductor detector (ORTEC) and multi channel analyzer. We used both MAESTRO (ORTEC) and home made root based gui program (Theia) for data analyzing. The obtained experimental data values are compared with NUDAT energy values.
Time and frequency-domain measurement of ground-state recovery times in red fluorescent proteins.
Manna, Premashis; Jimenez, Ralph
2015-04-16
The field of bioimaging and biosensors has been revolutionized by the discovery of fluorescent proteins (FPs) and their use in live cells. FPs are characterized with rich photodynamics due to the presence of nonfluorescent or dark states which are responsible for fluorescence intermittency or "blinking", which has been exploited in several localization-based super-resolution techniques that surpass the diffraction-limited resolution of conventional microscopy. Molecules that convert to these dark states recover to the ground states either spontaneously or upon absorption of another photon, depending on the particular FP and the structural transition that is involved. In this work, we demonstrate time- and frequency-domain methods for the measurement of the ground-state recovery (GSR) times of FPs both in live cells and in solutions. In the time-domain method, we excited the sample with millisecond pulses at varying dark times to obtain percent-recovery. In the frequency-domain method, dark-state hysteresis was employed to obtain the positive phase shift or "phase advance". We extracted the GSR time constants from our measurements using calculations and simulations based on a three-state model system. The GSR time constants of the red FPs studied in these experiments fall in the range from μs to msec time-scales. We find that the time- and frequency-domain techniques are complementary to each other. While accurate GSR times can be extracted from the time-domain technique, frequency-domain measurements are primarily sensitive to the rates of dark-state conversion (DSC) processes. A correlation between GSR times, DSC, and photobleaching rates for the red FPs mCherry, TagRFP-T, and Kriek were observed. These time- and frequency-domain methods can be used in high-throughput screening and sorting of FPs clones based on GSR time constant and photostability and will therefore be valuable for the development of new photoswitchable or photoactivatable FPs.
Measurements of the ground-state polarizabilities of Cs, Rb, and K using atom interferometry
NASA Astrophysics Data System (ADS)
Gregoire, Maxwell D.; Hromada, Ivan; Holmgren, William F.; Trubko, Raisa; Cronin, Alexander D.
2015-11-01
We measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms using a three-nanograting Mach-Zehnder atom beam interferometer. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to interpret atomic parity-nonconservation experiments. We measured αCs=4 π ɛ0×59.39 (9 ) Å3,αRb=4 π ɛ0×47.39 (8 ) Å3 , and αK=4 π ɛ0×42.93 (7 ) Å3 . In atomic units, these measurements are αCs=401.2 (7 ) ,αRb=320.1 (6 ) , and αK=290.0 (5 ) . We report ratios of polarizabilities αCs/αRb=1.2532 (10 ) ,αCs/αK=1.3834 (9 ) , and αRb/αK=1.1040 (9 ) with smaller fractional uncertainty because the systematic errors for individual measurements are largely correlated. Since Cs atom beams have short de Broglie wavelengths, we developed measurement methods that do not require resolved atom diffraction. Specifically, we used phase choppers to measure atomic beam velocity distributions, and we used electric field gradients to give the atom interference pattern a phase shift that depends on atomic polarizability.
Hartree-Fock many-body perturbation theory for nuclear ground-states
NASA Astrophysics Data System (ADS)
Tichai, Alexander; Langhammer, Joachim; Binder, Sven; Roth, Robert
2016-05-01
We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT) as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree-Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.
NASA Astrophysics Data System (ADS)
Bradley, T. D.; Ilinova, E.; McFerran, J. J.; Jouin, J.; Debord, B.; Alharbi, M.; Thomas, P.; Gérôme, F.; Benabid, F.
2016-09-01
We report on the measurement of ground-state atomic polarization relaxation time of Rb vapor confined in five different hypocycloidal core-shape Kagome hollow-core photonic crystal fibers made with uncoated silica glass. We are able to distinguish between wall-collision and transit-time effects in an optical waveguide and deduce the contribution of the atom’s dwell time at the core wall surface. In contrast with conventional macroscopic atomic cell configuration, and in agreement with Monte Carlo simulations, the measured relaxation times were found to be at least one order of magnitude longer than the limit set by atom-wall collisional from thermal atoms. This extended relaxation time is explained by the combination of a stronger contribution of the slow atoms in the atomic polarization build-up, and of the relatively significant contribution of dwell time to the relaxation process of the ground state polarization.
Precision measurements of proton emission from the ground states of {sup 156}Ta and {sup 160}Re
Darby, I. G.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Judson, D. S.; Simpson, J.; Eeckhaudt, S.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppaenen, A.-P.; Nyman, M.; Rahkila, P.; Saren, J.; Scholey, C.; Steer, A. N.
2011-06-15
The decays of the {pi}d{sub 3/2} ground states of {sup 156}Ta and {sup 160}Re have been studied in detail using the GREAT spectrometer. More than 7000 {sup 160}Re nuclei were produced in reactions of 290- and 300-MeV {sup 58}Ni ions with an isotopically enriched {sup 106}Cd target and separated in flight using the RITU separator. The proton and {alpha} decays of the {pi}d{sub 3/2} level were confirmed and the half-life and branching ratios of this state were determined with improved precision to be t{sub 1/2}=611{+-}7 {mu}s and b{sub p}=89{+-}1% and b{sub {alpha}=}11{+-}1%, respectively. The {alpha}-decay branch populated the ground state of {sup 156}Ta, allowing improved values for the proton-decay energy and half-life to be obtained (E{sub p}=1011{+-}5 keV; t{sub 1/2}=106{+-}4 ms). The {beta} decay of this level was identified for the first time and a branching ratio of b{sub {beta}=}29{+-}3% was deduced. The spectroscopic factors deduced from these measurements are compared with predictions.
Hutson, William O; Spencer, Austin P; Harel, Elad
2016-09-15
Vibrations play a critical role in many photochemical and photophysical processes in which excitations reside on the electronically excited state. However, difficulty in assigning signals from spectroscopic measurements uniquely to a specific electronic state, ground or otherwise, has exposed limitations to their physical interpretation. Here, we demonstrate the selective excitation of vibrational coherences on the ground electronic state through impulsive Raman scattering, whose weak fifth-order signal is resonantly enhanced by coupling to strong electronic transitions. The six-wave mixing signals measured using this technique are free of lower-order cascades and represent correlations between zero-quantum vibrational coherences in the ground state and single-quantum coherences between the ground and electronic states. We believe that this technique has the potential to shed much-needed insight onto some of the mysteries regarding the origin of long-lived coherences observed in photosynthetic and other coupled chromophore systems. PMID:27574915
NASA Technical Reports Server (NTRS)
Nerheim, N. M.
1977-01-01
The population densities of both the ground and the 2D(5/2) metastable states of copper atoms in a double-pulsed copper-chloride laser are correlated with laser energy as a function of time after the dissociation current pulse. Time-resolved density variations of the ground and excited copper atoms were derived from measurements of optical absorption at 324.7 and 510.6 nm, respectively, over a wide range of operating conditions in laser tubes with diameters of 4 to 40 mm. The minimum delay between the two current pulses at which lasing was observed is shown to be a function of the initial density and subsequent decay of the metastable state. Similarly, the maximum delay is shown to be a function of the initial density and decay of the ground state.
NASA Astrophysics Data System (ADS)
Adamczak, A.; Baccolo, G.; Bakalov, D.; Baldazzi, G.; Bertoni, R.; Bonesini, M.; Bonvicini, V.; Campana, R.; Carbone, R.; Cervi, T.; Chignoli, F.; Clemenza, M.; Colace, L.; Curioni, A.; Danailov, M.; Danev, P.; D'Antone, I.; De Bari, A.; De Vecchi, C.; De Vincenzi, M.; Furini, M.; Fuschino, F.; Gadedjisso-Tossou, K. S.; Guffanti, D.; Iaciofano, A.; Ishida, K.; Iugovaz, D.; Labanti, C.; Maggi, V.; Margotti, A.; Marisaldi, M.; Mazza, R.; Meneghini, S.; Menegolli, A.; Mocchiutti, E.; Moretti, M.; Morgante, G.; Nardò, R.; Nastasi, M.; Niemela, J.; Previtali, E.; Ramponi, R.; Rachevski, A.; Rignanese, L. P.; Rossella, M.; Rossi, P. L.; Somma, F.; Stoilov, M.; Stoychev, L.; Tomaselli, A.; Tortora, L.; Vacchi, A.; Vallazza, E.; Zampa, G.; Zuffa, M.
2016-05-01
The high precision measurement of the hyperfine splitting of the muonic-hydrogen atom ground state with pulsed and intense muon beam requires careful technological choices both in the construction of a gas target and of the detectors. In June 2014, the pressurized gas target of the FAMU experiment was exposed to the low energy pulsed muon beam at the RIKEN RAL muon facility. The objectives of the test were the characterization of the target, the hodoscope and the X-ray detectors. The apparatus consisted of a beam hodoscope and X-rays detectors made with high purity Germanium and Lanthanum Bromide crystals. In this paper the experimental setup is described and the results of the detector characterization are presented.
NASA Astrophysics Data System (ADS)
Yulianto, Yacobus; Su'ud, Zaki
2016-08-01
It has been performed the nuclear ground state properties investigation of 232Th and 238U using Skyrme interaction. The local density, the kinetic energy density, and the spin-orbit density for proton and neutron have been calculated using Extended-Thomas-Fermi approach method. Then the calculation results have been compared with Skyrme-Hartree-Fock results (using HAFOMN and HFBRAD codes). Total energy calculations obtained from this research are -1792.973947 MeV (for 232Th) deviated 0.29244% from experiment energy and -1761.519459 MeV (for 238U) deviated 0.48369% from experiment energy. The distribution profiles of local density and local potential for 232Th and 238U are quite similar with Skyrme- Hartree-Fock results. It is indicated that Skyrme-Extended-Thomas-Fermi method can be used to study the nuclear ground state properties, especially even nuclei.
Towards measuring the ground state hyperfine splitting of antihydrogen - a progress report
NASA Astrophysics Data System (ADS)
Sauerzopf, C.; Capon, A. A.; Diermaier, M.; Dupré, P.; Higashi, Y.; Kaga, C.; Kolbinger, B.; Leali, M.; Lehner, S.; Rizzini, E. Lodi; Malbrunot, C.; Mascagna, V.; Massiczek, O.; Murtagh, D. J.; Nagata, Y.; Radics, B.; Simon, M. C.; Suzuki, K.; Tajima, M.; Ulmer, S.; Vamosi, S.; Gorp, S. van; Zmeskal, J.; Breuker, H.; Higaki, H.; Kanai, Y.; Kuroda, N.; Matsuda, Y.; Venturelli, L.; Widmann, E.; Yamazaki, Y.
2016-12-01
We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.
Lifetime measurements of the first 2+ states in 104,106Zr: Evolution of ground-state deformations
NASA Astrophysics Data System (ADS)
Browne, F.; Bruce, A. M.; Sumikama, T.; Nishizuka, I.; Nishimura, S.; Doornenbal, P.; Lorusso, G.; Söderström, P.-A.; Watanabe, H.; Daido, R.; Patel, Z.; Rice, S.; Sinclair, L.; Wu, J.; Xu, Z. Y.; Yagi, A.; Baba, H.; Chiga, N.; Carroll, R.; Didierjean, F.; Fang, Y.; Fukuda, N.; Gey, G.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kameda, D.; Kojouharov, I.; Kurz, N.; Kubo, T.; Lalkovski, S.; Li, Z.; Lozeva, R.; Nishibata, H.; Odahara, A.; Podolyák, Zs.; Regan, P. H.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Simpson, G. S.; Suzuki, H.; Takeda, H.; Tanaka, M.; Taprogge, J.; Werner, V.; Wieland, O.
2015-11-01
The first fast-timing measurements from nuclides produced via the in-flight fission mechanism are reported. The lifetimes of the first 2+ states in 104,106Zr nuclei have been measured via β-delayed γ-ray timing of stopped radioactive isotope beams. An improved precision for the lifetime of the 21+ state in 104Zr was obtained, τ (21+) =2.90-20+25 ns, as well as a first measurement of the 21+ state in 106Zr, τ (21+) =2.60-15+20 ns, with corresponding reduced transition probabilities of B (E2 ; 21+ → 0g.s.+) = 0.39 (2) e2b2 and 0.31 (1) e2b2, respectively. Comparisons of the extracted ground-state deformations, β2 = 0.39 (1) (104Zr) and β2 = 0.36 (1) (106Zr) with model calculations indicate a persistence of prolate deformation. The data show that 104Zr is the most deformed of the neutron-rich Zr isotopes measured so far.
Susceptibility measurements in PrxLa1-xInAg2 with Γ3 doublet ground state
NASA Astrophysics Data System (ADS)
Sato, Y.; Nakamura, Y.; Morodomi, H.; Hasuo, T.; Inagaki, Y.; Kawae, T.; Suzuki, Hs; Mito, M.; Kitai, T.
2012-12-01
We have measured the susceptibility and magnetization of PrxLa1-xInAg2 at Pr concentrations x=1 and 0.1 down to T ~ 0.5 K by SQUID magnetometer with a home-made 3He insert. The susceptibility above T = 15 K is well reproduced by the crystal-electric-field level scheme with a non-Kramers Γ3 doublet in the ground state for each concentration, while that below T = 15 K shows a non-Fermi-liquid (NFL) behavior with — ln T-dependence at low magnetic field. With increasing magnetic field, — ln T-dependence is suppressed and —T1-2-dependence appears at H = 7 T The magnetization at T = 0.5 K increases with increasing magnetic fields up to H = 7 T, indicating that the increase of the susceptibility does not come from impurity ions. These results suggest that the quadrupolar Kondo effect is responsible for NFL behavior of the susceptibility.
NASA Astrophysics Data System (ADS)
Mohammed, H. E. Abu-Sei'leek
2011-01-01
A non-relativistic microscopic mean field theory of finite nuclei is investigated where the nucleus is described as a collection of nucleons and delta resonances. The ground state properties of 90Zr nucleus have been investigated at equilibrium and large amplitude compression using a realistic effective baryon-baryon Hamiltonian based on Reid Soft Core (RSC) potential. The sensitivity of the ground state properties is studied, such as binding energy, nuclear radius, radial density distribution, and single particle energies to the degree of compression. It is found that the most of increasing in the nuclear energy generated under compression is used to create the massive Δ particles. For 90Zr nucleus under compression at 2.5 times density of the normal nuclear density, the excited nucleons to Δ's are increased sharply up to 14% of the total number of constituents. This result is consistent with the values extracted from relativistic heavy-ion collisions. The single particle energy levels are calculated and their behaviors under compression are examined too. A good agreement between results with effective Hamiltonian and the phenomenological shell model for the low lying single-particle spectra is obtained. A considerable reduction in compressibility for the nucleus, and softening of the equation of state with the inclusion of the Δ's in the nuclear dynamics are suggested by the results.
Nuclear magnetic moments of the ground states of sup 124 I, sup 126 I, and sup 130 I
Ohya, S.; Yamazaki, T.; Harasawa, T.; Katsurayama, M.; Mutsuro, N. ); Muto, S.; Heiguchi, K. )
1992-01-01
The nuclear magnetic moments of {sup 124}I, {sup 126}I, and {sup 130}I have been measured by the techniques of low-temperature nuclear orientation and nuclear magnetic resonance on oriented nuclei. The magnetic hyperfine splitting frequency {vert bar}{ital g}{mu}{sub {ital N}BHF}/{ital h}{vert bar} for {sup 124}I{ital Fe} was determined to be 630.2(2) MHz from a field-shift analysis of the measured resonances at the external field of 0.1, 0.2, 0.4, 0.6, and 0.8 T. The resonances for {sup 126}I{ital Fe} and {sup 130}I{ital Fe} were observed in an external magnetic field of 0.2 T at {nu}({sup 126}I{ital Fe})=627.7(2) MHz and {nu}({sup 130}I{ital Fe})=585.7(2) MHz, respectively. Using the recalculated hyperfine field of {ital B}{sub HF}({sup 131}I{ital Fe})=114.50(5) T, the magnetic moments were deduced: {vert bar}{mu}({sup 124}I,2{sup {minus}}){vert bar}=1.444(4){mu}{sub {ital N}}, {vert bar}{mu}({sup 126}I,2{sup {minus}}){vert bar}=1.436(5){mu}{sub {ital N}}, and {vert bar}{mu}({sup 130}I,5{sup +}){vert bar}=3.349(7){mu}{sub {ital N}}. The present value of the magnetic moment of {sup 124}I is very different from the value of 1.14(8){mu}{sub {ital N}} reported previously. The measured values of the magnetic moments are discussed using Lande formula.
Fahrenbach, Albert C.; Barnes, Jonathan C.; Li, Hao; Benítez, Diego; Basuray, Ashish N.; Fang, Lei; Sue, Chi-Hau; Barin, Gokhan; Dey, Sanjeev K.; Goddard, William A.; Stoddart, J. Fraser
2011-01-01
In donor–acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers—present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor–acceptor vintage—can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes—one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites—the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor–acceptor interactions brought about by both π-electron-rich recognition sites being part of a macrocyclic polyether. PMID:22135467
NASA Astrophysics Data System (ADS)
Appel, Markus; Frick, Bernhard; Elbert, Johannes; Gallei, Markus; Stühn, Bernd
2015-01-01
The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene). They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.
NASA Astrophysics Data System (ADS)
Abu-Sei'leek, Mohammed H. E.; Hasan, Mahmoud A.
2010-08-01
The ground state properties of the spherical nucleus 40Ca have been investigated by using constrained spherical Hartree-Fock (CSHF) approximation at equilibrium and under high radial compression in a six major shells. The effective baryon-baryon interaction that includes the Δ(1236) resonance freedom degrees to calculate nuclear properties is used. The nucleon-nucleon (N-N) interaction is based on Reid soft core (RSC) potential. The results of calculations show that much of increase in the nuclear energy generated under compression is used to create the massive Δ particles. The number of Δ's can be increased to about 2.1% of constituents of nucleus when nuclear density reaches about 1.34 times of normal density. The single particle energy levels are calculated and their behavior under compression is also examined. A good agreement has been found between current calculations and phenomenological shell model for low lying single-particle spectra. The gap between shells is very clear and L-S coupling become stronger as increasing the static load on the nucleus. The results show a considerable reduction in compressibility when freedom degrees of Δ's are taken into account. It has been found that the total nuclear radial density becomes denser in the interior and less dense in the exterior region of nucleus. The surface of nucleus becomes more and more responsive to compression than outer region.
Klemm, R.B.; Nesbitt, F.L.; Skolnik, E.G.; Lee, J.H.; Smalley, J.F.
1987-03-12
The rate constant for the reaction of ground-state atomic oxygen with ethylene was determined by using two techniques: flash photolysis-resonance fluorescence (FP-RF, 244-1052 K) and discharge flow-resonance fluorescence (DF-RF, 298-1017 K). Kinetic complications due to the presence of molecular oxygen in the FP-RF experiments at high temperatures (T > 800 K) were overcome by using NO as the photolytic source of the O atoms. The rate constant, k/sub 1/ (T), derived in this study exhibits extreme non-Arrhenius behavior, but it can be successfully fit to the sum of exponentials expression, 244-1052 K, k/sub 1/(T) = (1.02 +/- 0.06) x 10/sup -11/ exp(-753 +/- 17 K/T) + (2.75 +/- 0.26) x 10/sup -10/ exp(-4220 +/- 550 K/T), in units of cm/sup 3/ molecule/sup -1/ s/sup -1/. Additionally, a fit of the results of this work to a simple transition-state theory expression and the comparison of these results with those of other workers are discussed.
NASA Astrophysics Data System (ADS)
Choi, Jungu; Elliott, Dan; Elliott's Lab Team
2016-05-01
We present a detailed analysis of an experimental setup for parity non-conserving (PNC) measurements in a cesium atomic beam. We employ a parallel-plate transmission line (PPTL) structure and highly reflective cylindrical mirrors to form a microwave cavity resonator to excite the PNC transitions in the cesium hyperfine ground states. In addition, a variable external dc field is applied to observe the Stark-induced transition, which would interfere with the PNC transition as the dc field amplitude changes. Finally, strong Raman lasers are used to excite the ground hyperfine transition. The Raman fields interfere with the weak transitions, and by varying the phase difference between the Raman fields and the microwave fields, we would infer the weak transition amplitudes from the signal modulation. The experimental setup requires maintaining coherent phase relations between all fields, well-characterized dc and rf field patterns, the two co-propagating Raman lasers, and suppression of the magnetic dipole contribution. Our analysis of the field modes supported by the PPTL structure indicates that with a moderate rf power and a few tens of seconds of data collection time, the PNC measurement of less than 3% uncertainty would be feasible.
NASA Technical Reports Server (NTRS)
Fang, Z.; Kwong, Victor H. S.
1997-01-01
The charge transfer rate coefficient for the reaction N(2+)(2p(sup 2)P(sup 0)) + He yields products is measured by recording the time dependence of the N(2+) ions stored in an ion trap. A cylindrical radio-frequency ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The decay of the ion signals was analyzed by single exponential least-squares fits to the data. The measured rate coefficient is 8.67(0.76) x 10(exp -11)sq cm/s. The N(2+) ions were at a mean energy of 2.7 eV while He gas was at room temperature, corresponding to an equivalent temperature of 3.9 x 10(exp 3) K. The measured value is in good agreement with a recent calculation.
Kawasaki, Shinji; Lin, Chengtian; Kuhns, Philip L; Reyes, Arneil P; Zheng, Guo-qing
2010-09-24
We report the results of the Knight shift by ⁶³,⁶⁵Cu-NMR measurements on single-layered copper-oxide Bi₂Sr(₂-x)La(x)CuO(₆+δ) conducted under very high magnetic fields up to 44 T. The magnetic field suppresses superconductivity completely, and the pseudogap ground state is revealed. The ⁶³Cu-NMR Knight shift shows that there remains a finite density of states at the Fermi level in the zero-temperature limit, which indicates that the pseudogap ground state is a metallic state with a finite volume of Fermi surface. The residual density of states in the pseudogap ground state decreases with decreasing doping (increasing x) but remains quite large even at the vicinity of the magnetically ordered phase of x ≥ 0.8, which suggests that the density of states plunges to zero upon approaching the Mott insulating phase.
Rowe, Mary A.
1999-05-24
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.
Pieper, S.C.; Usmani, A.; Usmani, Q.N.
1995-08-01
The cluster variational Monte Carlo calculation of nuclei was adapted for hypernuclei such as {sub {Lambda}}{sup 17}O, {sub {Lambda}}{sup 16}, {sub {Lambda}}{sup 12}C. In this calculation we use the same realistic nuclear Hamiltonians that we use for normal nuclei with the addition of phenomenological N{Lambda} and NN{Lambda} potentials such as those studied previously by Bodmer and Usmani. The wave function is also of the same form as in normal nuclei with additional N{Lambda} and NN{Lambda} non-central correlations. The development work for these calculations was done principally by A. Usmani and Q.N. Usmani at Jamia Millia. Final production calculations were done on the NERSC computers. During the summer of 1994, an article describing this work was written while S.C. Pieper was a visitor at Trieste, Italy, where A. Usmani is a postdoctoral research fellow.
Ground states of holographic superconductors
Gubser, Steven S.; Nellore, Abhinav
2009-11-15
We investigate the ground states of the Abelian Higgs model in AdS{sub 4} with various choices of parameters, and with no deformations in the ultraviolet other than a chemical potential for the electric charge under the Abelian gauge field. For W-shaped potentials with symmetry-breaking minima, an analysis of infrared asymptotics suggests that the ground state has emergent conformal symmetry in the infrared when the charge of the complex scalar is large enough. But when this charge is too small, the likeliest ground state has Lifshitz-like scaling in the infrared. For positive mass quadratic potentials, Lifshitz-like scaling is the only possible infrared behavior for constant nonzero values of the scalar. The approach to Lifshitz-like scaling is shown in many cases to be oscillatory.
Ground state mass of 81Kr and the solar neutrino problem
NASA Astrophysics Data System (ADS)
Kouzes, R. T.; Lowry, M. M.; Bennett, C. L.
1982-02-01
The 81Br(3He,t)81Kr, reaction has been used to determine an improved value for the ground state mass of 81Kr. A comparison is made with 51V(3He,t)51Cr and the implications for calibration of the proposed bromine solar neutrino detector are presented. NUCLEAR REACTIONS 81Br(3He,t)81Kr, 51V(3He,t)51Cr, 87Rb(3He,t)87Sr, 85Rb(3He,t)85Sr, E(3He)=24.7 MeV; Q values measured, ground state 81Kr mass inferred.
Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet
Fu, Mingxuan; Imai, Takahashi; Han, Tian -Heng; Lee, Young S.
2015-11-06
Here, the kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu3(OH)6Cl2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction. Combined with themore » magnetic field dependence of χkagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.« less
Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet.
Fu, Mingxuan; Imai, Takashi; Han, Tian-Heng; Lee, Young S
2015-11-01
The kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu3(OH)6Cl2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χ(kagome), deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction. Combined with the magnetic field dependence of χ(kagome) that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap. PMID:26542565
Moving Toward the Ground State.
Kumar, Ishan; Ivanova, Natalia
2015-10-01
Transferring mouse ESCs to a media supplemented with Mek and Gsk3β inhibitors (2i) provokes marked transcriptional and epigenetic changes, embodying a shift toward ground-state pluripotency. In this issue of Cell Stem Cell, Kolodziejczyk et al. (2015) examine population structures of ESCs while Galonska et al. (2015) unravel the mechanisms underlying regulatory network rewiring during 2i-mediated reprogramming. PMID:26431178
On the ground state of Yang-Mills theory
Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.
2011-08-15
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.
Precision Penning Trap Mass Measurements for Nuclear Structure at Triumf
NASA Astrophysics Data System (ADS)
Kwiatkowski, A. A.; Dilling, J.; Andreoiu, C.; Brunner, T.; Chaudhuri, A.; Chowdhury, U.; Delheij, P.; Ettenauer, S.; Frekers, D.; Gallant, A. T.; Grossheim, A.; Gwinner, G.; Lennarz, A.; Mané, E.; Pearson, M. R.; Schultz, B. E.; Simon, M. C.; Simon, V. V.
2013-03-01
Precision determinations of ground state or even isomeric state masses reveal fingerprints of nuclear structure. In particular at the limits at existence for very neutron-rich or deficient isotopes, this allows one to find detailed information about nuclear structure from separation energies or binding energies. This is important to test theoretical predictions or to refine model approaches, for example for new "magic numbers," as predicted around N = 34, where strong indications exist that the inclusion of NNN forces in theoretical calculations for Ca isotopes leads to significantly better predictions for ground state binding energies. Similarly, halo nuclei present an excellent application for ab-initio theory, where ground state properties, like masses and radii, present prime parameters for testing our understanding of nuclear structure. Precision mass determinations at TRIUMF are carried out with the TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) system. It is an ion trap setup coupled to the on-line facility ISAC. TITAN has measured masses of isotopes as short-lived as 9 ms (almost an order of magnitude shorter-lived than any other Penning trap system) and the only one with charge breeding capabilities, a feature that allows us to boost the precision by almost 2 orders of magnitude. We recently were able to make use of this feature by measuring short-lived Rb-isotopes, up to 74Rb, and reaching the 12+ charge state, which together with other improvements lead to an increase in precision by a factor 36.
Ground state magnetic dipole moment of {sup 35}K
Mertzimekis, T.J.; Mantica, P.F.; Liddick, S.N.; Tomlin, B.E.; Davies, A.D.
2006-02-15
The ground state magnetic moment of {sup 35}K has been measured using the technique of nuclear magnetic resonance on {beta}-emitting nuclei. The short-lived {sup 35}K nuclei were produced following the reaction of a {sup 36}Ar primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the {sup 35}K nuclei produced at 2 deg. relative to the normal primary beam axis was confirmed. Together with the mirror nucleus {sup 35}S, the measurement represents the heaviest T=3/2 mirror pair for which the spin expectation value has been obtained. A linear behavior of g{sub p} vs g{sub n} has been demonstrated for the T=3/2 known mirror moments and the slope and intercept are consistent with the previous analysis of T=1/2 mirror pairs.
Proteome Analysis of Ground State Pluripotency
Taleahmad, Sara; Mirzaei, Mehdi; Parker, Lindsay M.; Hassani, Seyedeh-Nafiseh; Mollamohammadi, Sepideh; Sharifi-Zarchi, Ali; Haynes, Paul A.; Baharvand, Hossein; Salekdeh, Ghasem Hosseini
2015-01-01
The differentiation potential of pluripotent embryonic stem cells (ESCs) can be manipulated via serum and medium conditions for direct cellular development or to maintain a naïve ground state. The self-renewal state of ESCs can thus be induced by adding inhibitors of mitogen activated protein kinase (MAPK) and glycogen synthase kinase-3 (Gsk3), known as 2 inhibitors (2i) treatment. We have used a shotgun proteomics approach to investigate differences in protein expressions between 2i- and serum-grown mESCs. The results indicated that 164 proteins were significantly upregulated and 107 proteins downregulated in 2i-grown cells compared to serum. Protein pathways in 2i-grown cells with the highest enrichment were associated with glycolysis and gluconeogenesis. Protein pathways related to organ development were downregulated in 2i-grown cells. In serum-grown ESCs, protein pathways involved in integrin and focal adhesion, and signaling proteins involved in the actin cytoskeleton regulation were enriched. We observed a number of nuclear proteins which were mostly involved in self-renewal maintenance and were expressed at higher levels in 2i compared to serum - Dnmt1, Map2k1, Parp1, Xpo4, Eif3g, Smarca4/Brg1 and Smarcc1/Baf155. Collectively, the results provided an insight into the key protein pathways used by ESCs in the ground state or metastable conditions through 2i or serum culture medium, respectively. PMID:26671762
Ground state of high-density matter
NASA Technical Reports Server (NTRS)
Copeland, ED; Kolb, Edward W.; Lee, Kimyeong
1988-01-01
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.
Ensemble Theory for Stealthy Hyperuniform Disordered Ground States
NASA Astrophysics Data System (ADS)
Torquato, Salvatore
Disordered hyperuniform many-particle systems have been receiving recent attention because they are distinguishable exotic states of matter poised between a crystal and liquid that are endowed with novel thermodynamic and physical properties. It has been shown numerically that systems of particles interacting with ``stealthy'' bounded, long-ranged pair potentials (similar to Friedel oscillations) have classical ground states that are, counterintuitively, disordered, hyperuniform and highly degenerate. The task of formulating an ensemble theory that yields analytical predictions for the structural characteristics and other properties of stealthy degenerate ground states in d-dimensional Euclidean space is highly nontrivial because the dimensionality of the configuration space depends on the number density and there is a multitude of ways of sampling the ground-state manifold, each with its own probability measure for finding a particular ground-state configuration. A new type of statistical-mechanical theory had to be invented to characterize these exotic states of matter. I report on some initial progress that we have made in this direction. We show that stealthy disordered ground states behave like ''pseudo''-equilibrium hard-sphere systems in Fourier space. Our theoretical predictions for the structure and thermodynamic properties of the stealthy disordered ground states and associated excited states are in excellent agreement with computer simulations across dimensions.
Probing quantum frustrated systems via factorization of the ground state.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2010-05-21
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.
Probing quantum frustrated systems via factorization of the ground state.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2010-05-21
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
Triplet (S = 1) Ground State Aminyl Diradical
Rajca, Andrzej; Shiraishi, Kouichi; Pink, Maren; Rajca, Suchada
2008-04-02
Aminyl diradical, which is stable in solution at low temperatures, is prepared. EPR spectra and SQUID magnetometry indicate that the diradical is planar and it possesses triplet ground state, with strong ferromagnetic coupling.
NASA Astrophysics Data System (ADS)
Mürtz, P.; Zink, L. R.; Evenson, K. M.; Brown, J. M.
1998-12-01
Thirteen new rotational transitions of H2O+ in the (0,0,0) level of the X˜ 2B1 state have been measured in the wavenumber region between 80 and 200 cm-1 (50 and 120 μm) by far-infrared laser magnetic resonance (LMR) spectroscopy. LMR data measured previously between 25 and 90 cm-1 (110 and 400 μm), as well as optical and infrared combination differences, have been combined with the new LMR data in a weighted least-squares analysis using an A-reduced expression of the rotational-fine structure Hamiltonian. Thirty-two molecular constants were simultaneously determined, some sextic centrifugal distortion parameters and some quartic and sextic spin-rotation parameters for the first time. From this improved set of molecular parameters, very accurate calculations of rotational term values and zero-field predictions of the 111-000 transition, including hyperfine structure, have been performed. Moreover, the electronic g-tensors and the hyperfine coupling constants are consistent with ab initio calculations which had been carried out for these constants.
Bowers, C.R.; Reno, J.L.; Simmons, J.A.; Vitkalov, S.A.
1998-12-01
A new method for measuring the spin of the electrically charged ground state excitations m the Q$j~j quantum Hall effect ia proposed and demonstmted for the tirst time in GaAs/AIGaAs nndtiquantum wells. The method is &sed on the nuclear spin orientation dependence of" the 2D dc conductivity y in the quantum Hall regime due to the nuclear hyperfine interaction. As a demonstration of this method the spin of the electrically charged excitations of the ground state is determined at filling factor v = 1.
Ensemble Theory for Stealthy Hyperuniform Disordered Ground States
NASA Astrophysics Data System (ADS)
Torquato, S.; Zhang, G.; Stillinger, F. H.
2015-04-01
It has been shown numerically that systems of particles interacting with isotropic "stealthy" bounded long-ranged pair potentials (similar to Friedel oscillations) have classical ground states that are (counterintuitively) disordered, hyperuniform, and highly degenerate. Disordered hyperuniform systems have received attention recently because they are distinguishable exotic states of matter poised between a crystal and liquid that are endowed with novel thermodynamic and physical properties. The task of formulating an ensemble theory that yields analytical predictions for the structural characteristics and other properties of stealthy degenerate ground states in d -dimensional Euclidean space Rd is highly nontrivial because the dimensionality of the configuration space depends on the number density ρ and there is a multitude of ways of sampling the ground-state manifold, each with its own probability measure for finding a particular ground-state configuration. The purpose of this paper is to take some initial steps in this direction. Specifically, we derive general exact relations for thermodynamic properties (energy, pressure, and isothermal compressibility) that apply to any ground-state ensemble as a function of ρ in any d , and we show how disordered degenerate ground states arise as part of the ground-state manifold. We also derive exact integral conditions that both the pair correlation function g2(r ) and structure factor S (k ) must obey for any d . We then specialize our results to the canonical ensemble (in the zero-temperature limit) by exploiting an ansatz that stealthy states behave remarkably like "pseudo"-equilibrium hard-sphere systems in Fourier space. Our theoretical predictions for g2(r ) and S (k ) are in excellent agreement with computer simulations across the first three space dimensions. These results are used to obtain order metrics, local number variance, and nearest-neighbor functions across dimensions. We also derive accurate analytical
Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet
Fu, Mingxuan; Imai, Takahashi; Han, Tian -Heng; Lee, Young S.
2015-11-06
Here, the kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu_{3}(OH)_{6}Cl_{2}], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction. Combined with the magnetic field dependence of χ_{kagome} that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.
Trapped antihydrogen in its ground state.
Gabrielse, G; Kalra, R; Kolthammer, W S; McConnell, R; Richerme, P; Grzonka, D; Oelert, W; Sefzick, T; Zielinski, M; Fitzakerley, D W; George, M C; Hessels, E A; Storry, C H; Weel, M; Müllers, A; Walz, J
2012-03-16
Antihydrogen atoms (H¯) are confined in an Ioffe trap for 15-1000 s-long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons (p¯) and positrons (e(+)) interact, 5±1 simultaneously confined ground-state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped H¯ are critical if laser cooling of trapped H¯ is to be demonstrated and spectroscopic studies at interesting levels of precision are to be carried out.
Transport properties of ground state oxygen atoms
NASA Technical Reports Server (NTRS)
Holland, Paul M.; Biolsi, Louis
1988-01-01
The transport properties of dilute monatomic gases depend on the two-body interactions between like atoms. When two ground-state oxygen atoms interact, they can follow any of 18 potential energy curves corresponding to O2, all of which contribute to the transport properties of the ground-state atoms. Transport collision integrals have been calculated for those interactions with an attractive minimum in the potential, and repulsive ab initio potential-energy curves have been accurately represented. Results are given for viscosity, thermal conductivity, and diffusion and they are compared with previous theoretical calculations.
Ground-state properties of strontium isotopes
Baran, A.; Hoehenberger, W.
1995-10-01
We present systematic constrained Hartree-Fock calculations of ground-state properties of even strontium isotopes ({ital A}=76--100) with the Skyrme interaction. Approximate projection of angular momentum is done after variation by explicit inclusion of the rotational energy {minus}{l_angle}{ital {cflx j}}{sup 2}{sub {ital x}}{r_angle}/J. This procedure allows for the determination of the ground-state deformations as well as the low rotational states. The binding energies, rms radii, quadrupole moments, and rotational states are discussed.
Mizel, Ari
2004-07-01
Ground-state quantum computers mimic quantum-mechanical time evolution within the amplitudes of a time-independent quantum state. We explore the principles that constrain this mimicking. A no-cloning argument is found to impose strong restrictions. It is shown, however, that there is flexibility that can be exploited using quantum teleportation methods to improve ground-state quantum computer design.
Application of nuclear resonance scattering for in vivo measurements
Wielopolski, L.; Vartsky, D.; Cohn, S.H.
1983-01-01
Nuclear resonance scattering is applied in our laboratory to measure hepatic and cardiac iron overload. For iron analysis, a gaseous source of 4 mg MnCl/sub 2/ is introduced into an evacuated quartz vial. Following irradiation in a nuclear reactor, /sup 56/Mn decays by beta emission to the 847-keV level of /sup 56/Fe, which subsequently decays to the ground state of /sup 56/Fe with a 7 ps half-life. The principal aim of this work is to evaluate the efficacy of the iron chelation therapy. Serial measurements over a time period of 6 to 12 months of a given patient will enable us to see how the iron is removed from the critical organs.
The ground state g factor of {sup 44}Cl : a probe for the reduced gaps at Z 16 and N = 28
Mertzimekis, Theo J.
2011-10-28
The g factor of the {sup 44}Cl ground state is measured at the LISE fragment separator at the Grand Accelerateur National d'Ions Lourds (GANIL) using the {beta} nuclear magnetic resonance technique, resulting in g({sup 44}Cl) (-)0.2749(2). An analysis of the g factor value and of the theoretical level scheme in the shell-model framework reveals the presence of odd-proton s{sub 1/2} configurations and neutron excitation across the N = 28 shell gap in the {sup 44}Cl ground state. In addition, the measured g factor strongly supports a 2{sup -} spin assignment for the {sup 44}Cl ground state.
Global Calculations of Ground-State Axial Shape Asymmetry of Nuclei
Moeller, Peter; Bengtsson, Ragnar; Carlsson, B. Gillis; Olivius, Peter; Ichikawa, Takatoshi
2006-10-20
Important insight into the symmetry properties of the nuclear ground-state (gs) shape is obtained from the characteristics of low-lying collective energy-level spectra. In the 1950s, experimental and theoretical studies showed that in the gs many nuclei are spheroidal in shape rather than spherical. Later, a hexadecapole component of the gs shape was identified. In the 1970-1995 time frame, a consensus that reflection symmetry of the gs shape was broken for some nuclei emerged. Here we present the first calculation across the nuclear chart of axial symmetry breaking in the nuclear gs. We show that we fulfill a necessary condition: Where we calculate axial symmetry breaking, characteristic gamma bands are observed experimentally. Moreover, we find that, for those nuclei where axial asymmetry is found, a systematic deviation between calculated and measured masses is removed.
On the possibility to measure 0{nu}{beta}{beta}-decay nuclear matrix element for {sup 48}Ca
Rodin, Vadim
2011-12-16
As shown in Ref. [2], the Fermi part M{sub F}{sup 0{nu}} of the total 0{nu}{beta}{beta}-decay nuclear matrix element M{sup 0{nu}} can be related to the single Fermi transition matrix element between the isobaric analog state (IAS) of the ground state of the initial nucleus and the ground state of the final nucleus. The latter matrix element could be measured in charge-exchange reactions. Here we discuss a possibility of such a measurement for {sup 48}Ca and estimate the cross-section of the reaction {sup 48}Ti(n,p){sup 48}Sc(IAS).
Terahertz spectroscopy of ground state HD18O
NASA Astrophysics Data System (ADS)
Yu, Shanshan; Pearson, John C.; Drouin, Brian J.; Miller, Charles E.; Kobayashi, Kaori; Matsushima, Fusakazu
2016-10-01
Terahertz absorption spectroscopy was employed to measure the ground state pure rotational transitions of the water isotopologue HD18O . A total of 105 pure rotational transitions were observed in the 0.5-5.0 THz region with ∼ 100 kHz accuracy for the first time. The observed positions were fit to experimental accuracy using the Euler series expansion of the asymmetric-top Hamiltonian together with the literature Microwave, Far-IR and IR data in the ground state and ν2 . The new measurements and predictions reported here support the analysis of astronomical observations by high-resolution spectroscopic telescopes such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or less are required for proper analysis of velocity resolved astrophysical data.
Trapping cold ground state argon atoms.
Edmunds, P D; Barker, P F
2014-10-31
We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39) C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10) cm(3) s(-1).
Magnetic properties of ground-state mesons
NASA Astrophysics Data System (ADS)
Šimonis, V.
2016-04-01
Starting with the bag model a method for the study of the magnetic properties (magnetic moments, magnetic dipole transition widths) of ground-state mesons is developed. We calculate the M1 transition moments and use them subsequently to estimate the corresponding decay widths. These are compared with experimental data, where available, and with the results obtained in other approaches. Finally, we give the predictions for the static magnetic moments of all ground-state vector mesons including those containing heavy quarks. We have a good agreement with experimental data for the M1 decay rates of light as well as heavy mesons. Therefore, we expect our predictions for the static magnetic properties ( i.e., usual magnetic moments) to be of sufficiently high quality, too.
Room temperature skyrmion ground state stabilized through interlayer exchange coupling
Chen, Gong Schmid, Andreas K.; Mascaraque, Arantzazu; N'Diaye, Alpha T.
2015-06-15
Possible magnetic skyrmion device applications motivate the search for structures that extend the stability of skyrmion spin textures to ambient temperature. Here, we demonstrate an experimental approach to stabilize a room temperature skyrmion ground state in chiral magnetic films via exchange coupling across non-magnetic spacer layers. Using spin polarized low-energy electron microscopy to measure all three Cartesian components of the magnetization vector, we image the spin textures in Fe/Ni films. We show how tuning the thickness of a copper spacer layer between chiral Fe/Ni films and perpendicularly magnetized Ni layers permits stabilization of a chiral stripe phase, a skyrmion phase, and a single domain phase. This strategy to stabilize skyrmion ground states can be extended to other magnetic thin film systems and may be useful for designing skyrmion based spintronics devices.
First evidence for a virtual 18B ground state
NASA Astrophysics Data System (ADS)
Spyrou, A.; Baumann, T.; Bazin, D.; Blanchon, G.; Bonaccorso, A.; Breitbach, E.; Brown, J.; Christian, G.; DeLine, A.; DeYoung, P. A.; Finck, J. E.; Frank, N.; Mosby, S.; Peters, W. A.; Russel, A.; Schiller, A.; Strongman, M. J.; Thoennessen, M.
2010-01-01
The decay of the neutron unbound ground state of 18B was studied for the first time through a single-proton knockout reaction from a 62 MeV/u 19C beam. The decay energy spectrum was reconstructed from coincidence measurements between the emitted neutron and the 17B fragment using the MoNA/Sweeper setup. An s-wave line shape was used to describe the experimental spectrum resulting in an upper limit for the scattering length of - 50 fm which corresponds to a decay energy <10 keV. Observing an s-wave decay of 18B provides an experimental verification that the ground state of 19C includes a large s-wave component. The presence of this s-wave component shows that s-d mixing is still present in 18B and that the s1 / 2 orbital has not moved significantly below the d5 / 2 orbital.
Ground state energy of large polaron systems
Benguria, Rafael D.; Frank, Rupert L.; Lieb, Elliott H.
2015-02-15
The last unsolved problem about the many-polaron system, in the Pekar–Tomasevich approximation, is the case of bosons with the electron-electron Coulomb repulsion of strength exactly 1 (the “neutral case”). We prove that the ground state energy, for large N, goes exactly as −N{sup 7/5}, and we give upper and lower bounds on the asymptotic coefficient that agree to within a factor of 2{sup 2/5}.
Ground State Studies of Spin Glass Models.
NASA Astrophysics Data System (ADS)
Kolan, Amy Joanne
The ground state energy and degeneracy for a set of spin glass models, PQR models, has been studied in detail. For the pure frustration case, a subset of the general PQR case, we have studied the spacial distribution of frustrated plaquettes at T = 0. We investigated the "frustration -frustration" correlation function, which involved a series expansion analysis and a computer analysis, to examine a phase transition mechanism proposed by Schuster (1981). Schuster suggested that a pair of plaquettes is bound together above, and dissociated below a critical concentration of antiferromagnetic bonds. Our analysis, however, led us to conclude that there is no sharp "unbinding" of frustration pairs. We have developed an efficient algorithm to compute the ground state energy and degeneracy of sample PQR lattices and have studied the general PQR model numerically. Our algorithm is similar in essence to Morgenstern and Binder's (1980) transfer matrix approach used to calculate the partition function of a sample of spins in the pure frustration case. The algorithm involves computing times of order ALM 2('L), where L is the width of the lattice, M is the length, and A is a constant of proportionality. We have used the results of our analysis to investigate the possibility of a paramagnetic (<--->) spin glass phase transition in the PQR model at T = 0. Although scatter in our results for the ground state degeneracy/spin obscures evidence of a possible non-analyticity in this function, we do see evidence of a "break" in the curves for the ground state energy/spin. We have used this "break" to plot the phase transition line between the spin glass and paramagnetic regimes.
Ground state searches in fcc intermetallics
Wolverton, C.; de Fontaine, D. ); Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)
1991-12-01
A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.
Interface Representations of Critical Ground States
NASA Astrophysics Data System (ADS)
Kondev, Jane
1995-01-01
We study the critical properties of the F model, the three-coloring model on the honeycomb lattice, and the four-coloring model on the square lattice, by mapping these models to models of rough interfaces. In particular, we construct operators in a systematic way, which is provided by the interface representation, and we show that their scaling dimensions can be related to the stiffness of the interface. Two types of operators are found, and they correspond to electric and magnetic charges in the Coulomb gas which is related to the interface model by the usual duality transformation. Furthermore, we find that the stiffness of the interface models, and therefore all the critical exponents, can be calculated exactly by considering the contour correlation function which measures the probability that two points on the interface belong to the same contour loop. The exact information about the stiffness also allows us to analyze in detail the conformal field theories (CFT) that represent the scaling limits of the interface models. We find that CFT's associated with the F model, the three -coloring model, and the four-coloring model, have chiral symmetry algebras given by the su(2)_{k=1 }, su(3)_{k=1}, and su(4) _{k=1} Kac-Moody algebras, respectively. The three-coloring and the four coloring-model are ground states of certain antiferromagnetic Potts models, and the behavior of these Potts models at small but finite temperatures is determined by topological defects that can be defined in the associated interface models. In this way we calculate the correlation length and the specific heat of the Potts models, and they are in good agreement with numerical simulations. We also present our Monte-Carlo results for the scaling dimensions of operators in the four-coloring model, and they are in excellent agreement with our analytical results. Finally, we define geometrical exponents for contour loops on self -affine interfaces and calculate their values as a function of the
Mixed configuration ground state in iron(II) phthalocyanine
NASA Astrophysics Data System (ADS)
Fernández-Rodríguez, Javier; Toby, Brian; van Veenendaal, Michel
2015-06-01
We calculate the angular dependence of the x-ray linear and circular dichroism at the L2 ,3 edges of α -Fe(II) Phthalocyanine (FePc) thin films using a ligand-field model with full configuration interaction. We find the best agreement with the experimental spectra for a mixed ground state of 3Eg(a1g 2eg3b2g 1) and 3B2 g(a1g 1eg4b2g 1) with the two configurations coupled by the spin-orbit interaction. The 3Eg(b ) and 3B2 g states have easy-axis and easy-plane anisotropies, respectively. Our model accounts for an easy-plane magnetic anisotropy and the measured magnitudes of the in-plane orbital and spin moments. The proximity in energy of the two configurations allows a switching of the magnetic anisotropy from easy plane to easy axis with a small change in the crystal field, as recently observed for FePc adsorbed on an oxidized Cu surface. We also discuss the possibility of a quintet ground state (5A1 g is 250 meV above the ground state) with planar anisotropy by manipulation of the Fe-C bond length by depositing the complex on a substrate that is subjected to a mechanical strain.
Graph states as ground states of two-body frustration-free Hamiltonians
NASA Astrophysics Data System (ADS)
Darmawan, Andrew S.; Bartlett, Stephen D.
2014-07-01
The framework of measurement-based quantum computation (MBQC) allows us to view the ground states of local Hamiltonians as potential resources for universal quantum computation. A central goal in this field is to find models with ground states that are universal for MBQC and that are also natural in the sense that they involve only two-body interactions and have a small local Hilbert space dimension. Graph states are the original resource states for MBQC, and while it is not possible to obtain graph states as exact ground states of two-body Hamiltonians, here we construct two-body frustration-free Hamiltonians that have arbitrarily good approximations of graph states as unique ground states. The construction involves taking a two-body frustration-free model that has a ground state convertible to a graph state with stochastic local operations, then deforming the model such that its ground state is close to a graph state. Each graph state qubit resides in a subspace of a higher dimensional particle. This deformation can be applied to two-body frustration-free Affleck-Kennedy-Lieb-Tasaki (AKLT) models, yielding Hamiltonians that are exactly solvable with exact tensor network expressions for ground states. For the star-lattice AKLT model, the ground state of which is not expected to be a universal resource for MBQC, applying such a deformation appears to enhance the computational power of the ground state, promoting it to a universal resource for MBQC. Transitions in computational power, similar to percolation phase transitions, can be observed when Hamiltonians are deformed in this way. Improving the fidelity of the ground state comes at the cost of a shrinking gap. While analytically proving gap properties for these types of models is difficult in general, we provide a detailed analysis of the deformation of a spin-1 AKLT state to a linear graph state.
Molecular spectroscopy for producing ultracold ground-state NaRb molecules
NASA Astrophysics Data System (ADS)
Wang, Dajun; Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier
2016-05-01
Recently, we have successfully created an ultracold sample of absolute ground-state NaRb molecules by two-photon Raman transfer of weakly bound Feshbach molecules. Here we will present the detailed spectroscopic investigations on both the excited and the rovibrational ground states for finding the two-photon path. For the excited state, we focus on the A1Σ+ /b3 Π singlet and triplet admixture. We discovered an anomalously strong coupling between the Ω =0+ and 0- components which renders efficient population transfer possible. In the ground state, the pure nuclear hyperfine levels have been clearly resolved, which allows us to create molecules in the absolute ground state directly with Raman transfer. This work is jointly supported by Agence Nationale de la Recherche (#ANR-13- IS04-0004-01) and Hong Kong Research Grant Council (#A-CUHK403/13) through the COPOMOL project.
Half-life determination of the ground state decay of ¹¹¹Ag.
Collins, S M; Harms, A V; Regan, P H
2016-02-01
The radioactive decay half-life of the β(-)-emitter (111)Ag has been measured using decay transitions identified using a high purity germanium γ-ray spectrometer. The time series of measurements of the net peak areas of the 96.8 keV, 245.4 keV and 342.1 keV γ-ray emissions following the β(-) decay of (111)Ag were made over approximately 23 days, i.e. ~3 half-life periods. The measured half-life of the ground state decay of (111)Ag was determined as 7.423 (13) days which is consistent with the Evaluated Nuclear Structure Data File (ENSDF) recommended half-life of 7.45 (1) days at k=2. Utilising all available experimental half-life values, a revised recommended half-life of 7.452 (12) days has been determined. PMID:26720263
Half-life determination of the ground state decay of ¹¹¹Ag.
Collins, S M; Harms, A V; Regan, P H
2016-02-01
The radioactive decay half-life of the β(-)-emitter (111)Ag has been measured using decay transitions identified using a high purity germanium γ-ray spectrometer. The time series of measurements of the net peak areas of the 96.8 keV, 245.4 keV and 342.1 keV γ-ray emissions following the β(-) decay of (111)Ag were made over approximately 23 days, i.e. ~3 half-life periods. The measured half-life of the ground state decay of (111)Ag was determined as 7.423 (13) days which is consistent with the Evaluated Nuclear Structure Data File (ENSDF) recommended half-life of 7.45 (1) days at k=2. Utilising all available experimental half-life values, a revised recommended half-life of 7.452 (12) days has been determined.
Ground state fidelity from tensor network representations.
Zhou, Huan-Qiang; Orús, Roman; Vidal, Guifre
2008-02-29
For any D-dimensional quantum lattice system, the fidelity between two ground state many-body wave functions is mapped onto the partition function of a D-dimensional classical statistical vertex lattice model with the same lattice geometry. The fidelity per lattice site, analogous to the free energy per site, is well defined in the thermodynamic limit and can be used to characterize the phase diagram of the model. We explain how to compute the fidelity per site in the context of tensor network algorithms, and demonstrate the approach by analyzing the two-dimensional quantum Ising model with transverse and parallel magnetic fields. PMID:18352611
Best Possible Strategy for Finding Ground States
NASA Astrophysics Data System (ADS)
Franz, Astrid; Hoffmann, Karl Heinz; Salamon, Peter
2001-06-01
Finding the ground state of a system with a complex energy landscape is important for many physical problems including protein folding, spin glasses, chemical clusters, and neural networks. Such problems are usually solved by heuristic search methods whose efficacy is judged by empirical performance on selected examples. We present a proof that, within the large class of algorithms that simulate a random walk on the landscape, threshold accepting is the best possible strategy. In particular, it can perform better than simulated annealing and Tsallis statistics. Our proof is the first example of a provably optimal strategy in this area.
Exact ground states of disordered systems
NASA Astrophysics Data System (ADS)
Mienke, Jan Hermann
Finding the ground state of disordered systems is in general a hard problem. Mappings of disordered systems to problems from computer science for which efficient, i.e., polynomial algorithms are known allow the numerical study of large systems. I study the ground state of the random-field Ising model both analytically using mean field approximations and numerically in 3D. I find that the behavior for the infinite-range model is nonuniversal in the sense that the critical exponent beta can vary continuously. On the Cayley tree, however, the behavior is universal. I develop a theory for the roughening of the minimum energy fracture surface in polycrystalline materials as a function of the relevant energy parameter epsilon = epsiloni/epsilon g. epsilong is the internal binding energy of the grain and epsiloni is the adhesion energy. Both local and global effects contribute to the roughening and have to be taken into account. This leads to an epsilon-dependent critical length Lc. For systems with L > L c and epsilon < 1 the interface is always rough.
Ground-state structures of Hafnium clusters
Ng, Wei Chun; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
Hafnium (Hf) is a very large tetra-valence d-block element which is able to form relatively long covalent bond. Researchers are interested to search for substitution to silicon in the semi-conductor industry. We attempt to obtain the ground-state structures of small Hf clusters at both empirical and density-functional theory (DFT) levels. For calculations at the empirical level, charge-optimized many-body functional potential (COMB) is used. The lowest-energy structures are obtained via a novel global-minimum search algorithm known as parallel tempering Monte-Carlo Basin-Hopping and Genetic Algorithm (PTMBHGA). The virtue of using COMB potential for Hf cluster calculation lies in the fact that by including the charge optimization at the valence shells, we can encourage the formation of proper bond hybridization, and thus getting the correct bond order. The obtained structures are further optimized using DFT to ensure a close proximity to the ground-state.
Spatial competition of the ground states in 1111 iron pnictides
NASA Astrophysics Data System (ADS)
Lang, G.; Veyrat, L.; Gräfe, U.; Hammerath, F.; Paar, D.; Behr, G.; Wurmehl, S.; Grafe, H.-J.
2016-07-01
Using nuclear quadrupole resonance, the phase diagram of 1111 R FeAsO1 -xFx (R =La , Ce, Sm) iron pnictides is constructed as a function of the local charge distribution in the paramagnetic state, which features low-doping-like (LD-like) and high-doping-like (HD-like) regions. Compounds based on magnetic rare earths (Ce, Sm) display a unified behavior, and comparison with La-based compounds reveals the detrimental role of static iron 3 d magnetism on superconductivity, as well as a qualitatively different evolution of the latter at high doping. It is found that the LD-like regions fully account for the orthorhombicity of the system, and are thus the origin of any static iron magnetism. Orthorhombicity and static magnetism are not hindered by superconductivity but limited by dilution effects, in agreement with two-dimensional (2D) (respectively three-dimensional) nearest-neighbor square lattice site percolation when the rare earth is nonmagnetic (respectively magnetic). The LD-like regions are not intrinsically supportive of superconductivity, contrary to the HD-like regions, as evidenced by the well-defined Uemura relation between the superconducting transition temperature and the superfluid density when accounting for the proximity effect. This leads us to propose a complete description of the interplay of ground states in 1111 pnictides, where nanoscopic regions compete to establish the ground state through suppression of superconductivity by static magnetism, and extension of superconductivity by proximity effect.
All-optical reconstruction of atomic ground-state population
NASA Astrophysics Data System (ADS)
London, P.; Firstenberg, O.; Shuker, M.; Ron, A.
2010-04-01
The population distribution within the ground state of an atomic ensemble is of great significance in a variety of quantum-optics processes. We present a method to reconstruct the detailed population distribution from a set of absorption measurements with various frequencies and polarizations, by utilizing the differences between the dipole matrix elements of the probed transitions. The technique is experimentally implemented on a thermal rubidium vapor, demonstrating a population-based analysis in two optical-pumping examples. The results are used to verify and calibrate an elaborated numerical model, and the limitations of the reconstruction scheme, which result from the symmetry properties of the dipole matrix elements, are discussed.
First Observation of Ground State Dineutron Decay: Be16
NASA Astrophysics Data System (ADS)
Spyrou, A.; Kohley, Z.; Baumann, T.; Bazin, D.; Brown, B. A.; Christian, G.; Deyoung, P. A.; Finck, J. E.; Frank, N.; Lunderberg, E.; Mosby, S.; Peters, W. A.; Schiller, A.; Smith, J. K.; Snyder, J.; Strongman, M. J.; Thoennessen, M.; Volya, A.
2012-03-01
We report on the first observation of dineutron emission in the decay of Be16. A single-proton knockout reaction from a 53MeV/u B17 beam was used to populate the ground state of Be16. Be16 is bound with respect to the emission of one neutron and unbound to two-neutron emission. The dineutron character of the decay is evidenced by a small emission angle between the two neutrons. The two-neutron separation energy of Be16 was measured to be 1.35(10) MeV, in good agreement with shell model calculations, using standard interactions for this mass region.
Evidence for the Ground-State Resonance of O26
NASA Astrophysics Data System (ADS)
Lunderberg, E.; DeYoung, P. A.; Kohley, Z.; Attanayake, H.; Baumann, T.; Bazin, D.; Christian, G.; Divaratne, D.; Grimes, S. M.; Haagsma, A.; Finck, J. E.; Frank, N.; Luther, B.; Mosby, S.; Nagi, T.; Peaslee, G. F.; Schiller, A.; Snyder, J.; Spyrou, A.; Strongman, M. J.; Thoennessen, M.
2012-04-01
Evidence for the ground state of the neutron-unbound nucleus O26 was observed for the first time in the single proton-knockout reaction from a 82MeV/u F27 beam. Neutrons were measured in coincidence with O24 fragments. O26 was determined to be unbound by 150-150+50keV from the observation of low-energy neutrons. This result agrees with recent shell-model calculations based on microscopic two- and three-nucleon forces.
Thermodynamic ground states of platinum metal nitrides
Aberg, D; Sadigh, B; Crowhurst, J; Goncharov, A
2007-10-09
We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.
Centrifugal stretching along the ground state band of {sup 168}Hf
Costin, A.; Pietralla, N.; Reese, M.; Moeller, O.; Ai, H.; Casten, R. F.; Heinz, A.; McCutchan, E. A.; Meyer, D. A.; Qian, J.; Werner, V.; Dusling, K.; Fitzpatrick, C. R.; Guerdal, G.; Petkov, P.; Rainovski, G.
2009-02-15
The lifetimes of the J{sup {pi}}=4{sup +}, 6{sup +}, 8{sup +}, and 10{sup +} levels along the ground state band in {sup 168}Hf were measured by means of the recoil distance Doppler shift (RDDS) method using the New Yale Plunger Device (NYPD) and the SPEEDY detection array at Wright Nuclear Structure Laboratory of Yale University. Excited states in {sup 168}Hf were populated using the {sup 124}Sn({sup 48}Ti,4n) fusion evaporation reaction. The new lifetime values are sufficiently precise to clearly prove the increase of quadrupole deformation as a function of angular momentum in the deformed nucleus {sup 168}Hf. The data agree with the predictions from the geometrical confined {beta}-soft (CBS) rotor model that involves centrifugal stretching in a soft potential.
Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun
2016-01-01
Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986
On the Stable Ground State of Mackinawite
NASA Astrophysics Data System (ADS)
Kwon, K.; Refson, K.; Sposito, G.
2009-12-01
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.
Magnetic ground state of FeSe.
Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K; Iida, K; Christianson, A D; Walker, H C; Adroja, D T; Abdel-Hafiez, M; Chen, Xiaojia; Chareev, D A; Vasiliev, A N; Zhao, Jun
2016-01-01
Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986
The ground state construction of bilayer graphene
NASA Astrophysics Data System (ADS)
Giuliani, Alessandro; Jauslin, Ian
2016-09-01
We consider a model of half-filled bilayer graphene, in which the three dominant Slonczewski-Weiss-McClure hopping parameters are retained, in the presence of short-range interactions. Under a smallness assumption on the interaction strength U as well as on the inter-layer hopping ɛ, we construct the ground state in the thermodynamic limit, and prove that the pressure and two-point Schwinger function, away from its singularities, are analytic in U, uniformly in ɛ. The interacting Fermi surface is degenerate, and consists of eight Fermi points, two of which are protected by symmetries, while the locations of the other six are renormalized by the interaction, and the effective dispersion relation at the Fermi points is conical. The construction reveals the presence of different energy regimes, where the effective behavior of correlation functions changes qualitatively. The analysis of the crossover between regimes plays an important role in the proof of analyticity and in the uniform control of the radius of convergence. The proof is based on a rigorous implementation of fermionic renormalization group methods, including determinant estimates for the renormalized expansion.
Strangeness in the baryon ground states
NASA Astrophysics Data System (ADS)
Semke, A.; Lutz, M. F. M.
2012-10-01
We compute the strangeness content of the baryon octet and decuplet states based on an analysis of recent lattice simulations of the BMW, PACS, LHPC and HSC groups for the pion-mass dependence of the baryon masses. Our results rely on the relativistic chiral Lagrangian and large-Nc sum rule estimates of the counter terms relevant for the baryon masses at N3LO. A partial summation is implied by the use of physical baryon and meson masses in the one-loop contributions to the baryon self energies. A simultaneous description of the lattice results of the BMW, LHPC, PACS and HSC groups is achieved. From a global fit we determine the axial coupling constants F ≃ 0.45 and D ≃ 0.80 in agreement with their values extracted from semi-leptonic decays of the baryons. Moreover, various flavor symmetric limits of baron octet and decuplet masses as obtained by the QCDSF-UKQCD group are recovered. We predict the pion- and strangeness sigma terms and the pion-mass dependence of the octet and decuplet ground states at different strange quark masses.
Tuning the Ground State Symmetry of Acetylenyl Radicals
2015-01-01
The lowest excited state of the acetylenyl radical, HCC, is a 2Π state, only 0.46 eV above the ground state, 2Σ+. The promotion of an electron from a π bond pair to a singly occupied σ hybrid orbital is all that is involved, and so we set out to tune those orbital energies, and with them the relative energetics of 2Π and 2Σ+ states. A strategy of varying ligand electronegativity, employed in a previous study on substituted carbynes, RC, was useful, but proved more difficult to apply for substituted acetylenyl radicals, RCC. However, π-donor/acceptor substitution is effective in modifying the state energies. We are able to design molecules with 2Π ground states (NaOCC, H2NCC (2A″), HCSi, FCSi, etc.) and vary the 2Σ+–2Π energy gap over a 4 eV range. We find an inconsistency between bond order and bond dissociation energy measures of the bond strength in the Si-containing molecules; we provide an explanation through an analysis of the relevant potential energy curves. PMID:27162981
Tuning the Ground State Symmetry of Acetylenyl Radicals.
Zeng, Tao; Danovich, David; Shaik, Sason; Ananth, Nandini; Hoffmann, Roald
2015-08-26
The lowest excited state of the acetylenyl radical, HCC, is a (2)Π state, only 0.46 eV above the ground state, (2)Σ(+). The promotion of an electron from a π bond pair to a singly occupied σ hybrid orbital is all that is involved, and so we set out to tune those orbital energies, and with them the relative energetics of (2)Π and (2)Σ(+) states. A strategy of varying ligand electronegativity, employed in a previous study on substituted carbynes, RC, was useful, but proved more difficult to apply for substituted acetylenyl radicals, RCC. However, π-donor/acceptor substitution is effective in modifying the state energies. We are able to design molecules with (2)Π ground states (NaOCC, H2NCC ((2)A″), HCSi, FCSi, etc.) and vary the (2)Σ(+)-(2)Π energy gap over a 4 eV range. We find an inconsistency between bond order and bond dissociation energy measures of the bond strength in the Si-containing molecules; we provide an explanation through an analysis of the relevant potential energy curves. PMID:27162981
Two different ground states in K-intercalated polyacenes
NASA Astrophysics Data System (ADS)
Phan, Quynh T. N.; Heguri, Satoshi; Tamura, Hiroyuki; Nakano, Takehito; Nozue, Yasuo; Tanigaki, Katsumi
2016-02-01
The electronic states of potassium- (K-) intercalated zigzag-type polycyclic aromatic (PLA) hydrocarbon [polyacene PLAs] Kx(PLAs ) are studied for a series of the four smallest molecules: naphthalene (NN), anthracene (AN), tetracene (TN), and pentacene (PN), focusing on their 1:1 stoichiometric phases. Clear experimental differences are identified between the first group [K1(NN ) and K1(AN ) ] and the second group [K1(TN ) and K1(PN ) ] by magnetic, vibrational, and optical measurements. The first group is categorized as a Mott insulator with an antiferromagnetic ground state with energy of ˜10 meV, whereas the second group is classified as a band insulator via dimer formation due to the spin Peierls instability. In the latter system, the first thermally accessible triplet states are located far apart from the singlet ground states and are not detected by electron spin-resonance spectroscopy until 300 K being very different from what is observed for the hole-doped PN reported earlier. The results give a new systematic understanding on the electronic states of electron-doped PLAs sensitive to the energetic balance among on-site Coulomb repulsion, bandwidth, and the Peierls instability.
Tuning the Ground State Symmetry of Acetylenyl Radicals.
Zeng, Tao; Danovich, David; Shaik, Sason; Ananth, Nandini; Hoffmann, Roald
2015-08-26
The lowest excited state of the acetylenyl radical, HCC, is a (2)Π state, only 0.46 eV above the ground state, (2)Σ(+). The promotion of an electron from a π bond pair to a singly occupied σ hybrid orbital is all that is involved, and so we set out to tune those orbital energies, and with them the relative energetics of (2)Π and (2)Σ(+) states. A strategy of varying ligand electronegativity, employed in a previous study on substituted carbynes, RC, was useful, but proved more difficult to apply for substituted acetylenyl radicals, RCC. However, π-donor/acceptor substitution is effective in modifying the state energies. We are able to design molecules with (2)Π ground states (NaOCC, H2NCC ((2)A″), HCSi, FCSi, etc.) and vary the (2)Σ(+)-(2)Π energy gap over a 4 eV range. We find an inconsistency between bond order and bond dissociation energy measures of the bond strength in the Si-containing molecules; we provide an explanation through an analysis of the relevant potential energy curves.
Unresolved Question of the He10 Ground State Resonance
NASA Astrophysics Data System (ADS)
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
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).
Fresh nuclear fuel measurements at Ukrainian nuclear power plants
Kuzminski, Jozef; Ewing, Tom; Dickman, Debbie; Gavrilyuk, Victor; Drapey, Sergey; Kirischuk, Vladimir; Strilchuk, Nikolay
2009-01-01
In 2005, the Provisions on Nuclear Material Measurement System was enacted in Ukraine as an important regulatory driver to support international obligations in nuclear safeguards and nonproliferation. It defines key provisions and requirements for material measurement and measurement control programs to ensure the quality and reliability of measurement data within the framework of the State MC&A System. Implementing the Provisions requires establishing a number of measurement techniques for both fresh and spent nuclear fuel for various types of Ukrainian reactors. Our first efforts focused on measurements of fresh nuclear fuel from a WWR-1000 power reactor.
Nuclear Magnetic Resonance Measurements and Electronic Structure of Pu(IV) in [(Me)4N]2PuCl6.
Mounce, Andrew M; Yasuoka, Hiroshi; Koutroulakis, Georgios; Lee, Jeongseop A; Cho, Herman; Gendron, Frédéric; Zurek, Eva; Scott, Brian L; Trujillo, Julie A; Slemmons, Alice K; Cross, Justin N; Thompson, Joe D; Kozimor, Stosh A; Bauer, Eric D; Autschbach, Jochen; Clark, David L
2016-09-01
The synthesis, electronic structure, and characterization via single-crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, and magnetic susceptibility of (Me4N)2PuCl6 are reported. NMR measurements were performed to both search for the direct (239)Pu resonance and to obtain local magnetic and electronic information at the Cl site through (35)Cl and (37)Cl spectra. No signature of (239)Pu NMR was observed. The temperature dependence of the Cl spectra was simulated by diagonalizing the Zeeman and quadrupolar Hamiltonians for (35)Cl, (37)Cl, and (14)N isotopes. Electronic structure calculations predict a magnetic Γ5 triplet ground state of Pu(IV) in the crystalline electric field of the undistorted PuCl6 octahedron. A tetragonal distortion would result in a very small splitting (∼20 cm(-1)) of the triplet ground state into a nonmagnetic singlet and a doublet state. The Cl shifts have an inflection point at T ≈ 15 K, differing from the bulk susceptibility, indicating a nonmagnetic crystal field ground state. The Cl spin-lattice relaxation time is constant to T = 15 K, below which it rapidly increases, also supporting the nonmagnetic crystal field ground state.
Ground-state rotational constants of 12CH 3D
NASA Astrophysics Data System (ADS)
Chackerian, C.; Guelachvili, G.
1980-12-01
An analysis of ground-state combination differences in the ν2( A1) fundamental band of 12CH 3D ( ν0 = 2200.03896 cm -1) has been made to yield values for the rotational constants B0, D0J, D0JK, H0JJJ, H0JJK, H0JKK, LJJJJ, L0JJJK, and order of magnitude values for L0JJKK and L0JKKK. These constants should be useful in assisting radio searches for this molecule in astrophysical sources. In addition, splittings of A1A2 levels ( J ≥ 17, K = 3) have been measured in both the ground and excited vibrational states of this band.
Experimental Proposal to Detect Topological Ground State Degeneracy
NASA Astrophysics Data System (ADS)
Barkeshli, Maissam; Oreg, Yuval; Qi, Xiao-Liang
2014-03-01
One of the most profound features of topologically ordered states of matter, such as the fractional quantum Hall (FQH) states, is that they possess topology-dependent ground state degeneracies that are robust to all local perturbations. Here we present the first proposal to directly detect these topological degeneracies in an experimentally accessible setup. The detection scheme uses nonlinear electrical conductance measurements in a double layer FQH system, with appropriately patterned top and bottom gates. We propose two experimental platforms; in the first, the detection of topo- logically degenerate states coincides with the detection of ZN parafermion zero modes. We map the relevant physics to a single-channel ZN quantum impurity model, providing a novel generalization of the Kondo model. Our proposal can also be adapted to detect the ZN parafermion zero modes recently discovered in FQH line junctions proximitized with superconductivity.
Triaxiality of the ground states in the 174W
NASA Astrophysics Data System (ADS)
Ya, Tu; Chen, Y. S.; Liu, L.; Gao, Z. C.
2016-05-01
We have performed calculations for the ground states in 174W by using the projected total energy surface (PTES) calculations. Both the ground state (g.s.) band and its γ band reproduce the experimental data. Further discussion about the triaxiality in 174W has been made by transition quardrupole moment (Qt) and comparing between the PTES and TRS methods.
Creation of an Ultracold Gas of Ground-State Dipolar 23Na 87 Molecules
NASA Astrophysics Data System (ADS)
Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier; Wang, Dajun
2016-05-01
We report the successful production of an ultracold sample of absolute ground-state 23Na 87Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 1011 cm-3 . By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state 23Na 87Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state 23Na 87Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.
Creation of an Ultracold Gas of Ground-State Dipolar ^{23}Na^{87}Rb Molecules.
Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier; Wang, Dajun
2016-05-20
We report the successful production of an ultracold sample of absolute ground-state ^{23}Na^{87}Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 10^{11} cm^{-3}. By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state ^{23}Na^{87}Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state ^{23}Na^{87}Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions. PMID:27258875
Ground states of stealthy hyperuniform potentials: I. Entropically favored configurations
NASA Astrophysics Data System (ADS)
Zhang, G.; Stillinger, F. H.; Torquato, S.
2015-08-01
Systems of particles interacting with "stealthy" pair potentials have been shown to possess infinitely degenerate disordered hyperuniform classical ground states with novel physical properties. Previous attempts to sample the infinitely degenerate ground states used energy minimization techniques, introducing algorithmic dependence that is artificial in nature. Recently, an ensemble theory of stealthy hyperuniform ground states was formulated to predict the structure and thermodynamics that was shown to be in excellent agreement with corresponding computer simulation results in the canonical ensemble (in the zero-temperature limit). In this paper, we provide details and justifications of the simulation procedure, which involves performing molecular dynamics simulations at sufficiently low temperatures and minimizing the energy of the snapshots for both the high-density disordered regime, where the theory applies, as well as lower densities. We also use numerical simulations to extend our study to the lower-density regime. We report results for the pair correlation functions, structure factors, and Voronoi cell statistics. In the high-density regime, we verify the theoretical ansatz that stealthy disordered ground states behave like "pseudo" disordered equilibrium hard-sphere systems in Fourier space. The pair statistics obey certain exact integral conditions with very high accuracy. These results show that as the density decreases from the high-density limit, the disordered ground states in the canonical ensemble are characterized by an increasing degree of short-range order and eventually the system undergoes a phase transition to crystalline ground states. In the crystalline regime (low densities), there exist aperiodic structures that are part of the ground-state manifold but yet are not entropically favored. We also provide numerical evidence suggesting that different forms of stealthy pair potentials produce the same ground-state ensemble in the zero
Dissociative recombination of the ground state of N2(+)
NASA Technical Reports Server (NTRS)
Guberman, Steven L.
1991-01-01
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.
Phase diagram of the ground states of DNA condensates
NASA Astrophysics Data System (ADS)
Hoang, Trinh X.; Trinh, Hoa Lan; Giacometti, Achille; Podgornik, Rudolf; Banavar, Jayanth R.; Maritan, Amos
2015-12-01
The phase diagram of the ground states of DNA in a bad solvent is studied for a semiflexible polymer model with a generalized local elastic bending potential characterized by a nonlinearity parameter x and effective self-attraction promoting compaction. x =1 corresponds to the wormlike chain model. Surprisingly, the phase diagram as well as the transition lines between the ground states are found to be a function of x . The model provides a simple explanation for the results of prior experimental and computational studies and makes predictions for the specific geometries of the ground states. The results underscore the impact of the form of the microscopic bending energy at macroscopic observable scales.
Anomalous magnetic hyperfine structure of the 229Th ground-state doublet in muonic atoms
NASA Astrophysics Data System (ADS)
Tkalya, E. V.
2016-07-01
The magnetic hyperfine (MHF) splitting of the ground and low-energy 3 /2+(7.8 ±0.5 eV) levels in the 229Th nucleus in the muonic atom (μ1S1 /2 -229Th) * is calculated considering the distribution of the nuclear magnetization in the framework of the collective nuclear model with wave functions of the Nilsson model for the unpaired neutron. It is shown that (a) deviation of the MHF structure of the isomeric state exceeds 100% from its value for a pointlike nuclear magnetic dipole (the order of sublevels is reversed); (b) partial inversion of levels of the 229Th ground-state doublet and spontaneous decay of the ground state to the isomeric state occur; (c) the E 0 transition, which is sensitive to differences in the mean-square charge radii of the doublet states, is possible between mixed sublevels with F =2 ; and (d) MHF splitting of the 3 /2+ isomeric state may be in the optical range for certain values of the intrinsic gK factor and a reduced probability of a nuclear transition between the isomeric and the ground states.
NASA Astrophysics Data System (ADS)
Obukhov, A. E.
2012-06-01
The help of the measurements (the methods are the NMR 1H and 13C, infrared (IR) and the UV-absorption, Raman scattering of light, the fluorescence and the phosphorescence, the pumping of the lasers and lamps, the low-temperature of the spectroscopy in the solutions (77 K) and the Jet-spectroscopy of vapor (2,6 K) and others) and the calculations with application of the developed new complex of the computer of the programs realizing of the quantum-chemical LCAO-MO SCF extended-CI INDO / S of methods are investigated of the photophysical properties of some news and also some known the organic compounds for variations of the electronic and the spatial structures in the series is the mono-, bi-, three, penta- and quincli-cyclic and the bi- and the bis- phenyl, furyl- and tienyl- oxazoles and - oxadiazoles have been studied of the spectroscopy properties in the wavelength range max λ max abs,osc = 208 ÷ 760 nm.
Exploring chaos in the Dicke model using ground-state fidelity and Loschmidt echo.
Bhattacharya, Utso; Dasgupta, Sayak; Dutta, Amit
2014-08-01
We study the quantum critical behavior of the Dicke Hamiltonian with finite number of atoms and explore the signature of quantum chaos using measures like the ground-state fidelity and the Loschmidt echo and the time-averaged Loschmidt echo. We show that these quantities clearly point to the classically chaotic nature of the system in the superradiant (SR) phase. While the ground-state fidelity shows aperiodic oscillations as a function of the coupling strength, the echo shows aperiodic oscillations in time and decays rapidly when the system is in the SR phase. We clearly demonstrate how the time-averaged value of the echo already incorporates the information about the ground-state fidelity and stays much less than unity, indicating the classically chaotic nature of the model in the SR phase.
NASA Astrophysics Data System (ADS)
Sebastian, Suchitra
2015-03-01
Over the last few years, evidence has gradually built for a charge ordered normal ground state in the underdoped region of the cuprate high temperature superconductors. I will address the electronic structure of the normal ground state of the underdoped cuprates as accessed by quantum oscillations, and relate it to complementary measurements by other experimental techniques. The interplay of the charge ordered ground state with the antinodal gapped pseudogap state, and overarching magnetic and superconducting correlations will be further explored. This work was performed in collaboration with N. Harrison, G. G. Lonzarich, B. J. Ramshaw, B. S. Tan, P. A. Goddard, F. F. Balakirev, C. H. Mielke, R. Liang, D. A. Bonn, and W. N. Hardy
Resonant two-photon ionization spectroscopy of jet-cooled UN: Determination of the ground state
NASA Astrophysics Data System (ADS)
Matthew, Daniel J.; Morse, Michael D.
2013-05-01
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 Ω = 3.5, with a bond length of 1.7650(12) Å. 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.
Magnetic ground state of an individual Fe2+ ion in strained semiconductor nanostructure
Smoleński, T.; Kazimierczuk, T.; Kobak, J.; Goryca, M.; Golnik, A.; Kossacki, P.; Pacuski, W.
2016-01-01
Single impurities with nonzero spin and multiple ground states offer a degree of freedom that can be utilized to store the quantum information. However, Fe2+ dopant is known for having a single nondegenerate ground state in the bulk host semiconductors and thus is of little use for spintronic applications. Here we show that the well-established picture of Fe2+ spin configuration can be modified by subjecting the Fe2+ ion to high strain, for example, produced by lattice mismatched epitaxial nanostructures. Our analysis reveals that high strain induces qualitative change in the ion energy spectrum and results in nearly doubly degenerate ground state with spin projection Sz=±2. We provide an experimental proof of this concept using a new system: a strained epitaxial quantum dot containing individual Fe2+ ion. Magnetic character of the Fe2+ ground state in a CdSe/ZnSe dot is revealed in photoluminescence experiments by exploiting a coupling between a confined exciton and the single-iron impurity. We also demonstrate that the Fe2+ spin can be oriented by spin-polarized excitons, which opens a possibility of using it as an optically controllable two-level system free of nuclear spin fluctuations. PMID:26818580
Approximating the ground state of gapped quantum spin systems
Michalakis, Spyridon; Hamza, Eman; Nachtergaele, Bruno; Sims, Robert
2009-01-01
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.
The factorization method and ground state energy bounds
NASA Astrophysics Data System (ADS)
Schmutz, M.
1985-04-01
We discuss the relationship between the factorization method and the Barnsley bound to the ground state energy. The latter method is extended in such a way that both lower and upper analytic bounds can be obtained.
Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124Xe
Radich, A. J.; Garrett, P. E.; Allmond, J. M.; Andreoiu, C.; Ball, G. C.; Bianco, L.; Bildstein, V.; Chagnon-Lessard, S.; Cross, D. S.; Demand, G. A.; et al
2015-04-01
The nuclear structure of 124Xe has been investigated via measurements of the β+/EC decay of 124Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2+ → 0+ in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, $B(E2; 2^+_3 → 0^+_2)$ = 78(13) W.u. and $B(E2; 2^+_4 → 0^+_3)$ = 53(12) W.u. were determined. The $0^+_3$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te(3He,n)124Xemore » measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.« less
Theory of ground state factorization in quantum cooperative systems.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2008-05-16
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.
Ground-state properties of the periodic Anderson model
NASA Technical Reports Server (NTRS)
Blankenbecler, R.; Fulco, J. R.; Gill, W.; Scalapino, D. J.
1987-01-01
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.
Theory of ground state factorization in quantum cooperative systems.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2008-05-16
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
Three-body correlations in the ground-state decay of 26O
NASA Astrophysics Data System (ADS)
Kohley, Z.; Baumann, T.; Christian, G.; DeYoung, P. A.; Finck, J. E.; Frank, N.; Luther, B.; Lunderberg, E.; Jones, M.; Mosby, S.; Smith, J. K.; Spyrou, A.; Thoennessen, M.
2015-03-01
Background: Theoretical calculations have shown that the energy and angular correlations in the three-body decay of the two-neutron unbound 26O can provide information on the ground-state wave function, which has been predicted to have a dineutron configuration and 2 n halo structure. Purpose: To use the experimentally measured three-body correlations to gain insight into the properties of 26O , including the decay mechanism and ground-state resonance energy. Method: 26O was produced in a one-proton knockout reaction from 27F and the 24O+n +n decay products were measured using the MoNA-Sweeper setup. The three-body correlations from the 26O ground-state resonance decay were extracted. The experimental results were compared to Monte Carlo simulations in which the resonance energy and decay mechanism were varied. Results: The measured three-body correlations were well reproduced by the Monte Carlo simulations but were not sensitive to the decay mechanism due to the experimental resolutions. However, the three-body correlations were found to be sensitive to the resonance energy of 26O . A 1 σ upper limit of 53 keV was extracted for the ground-state resonance energy of 26O . Conclusions: Future attempts to measure the three-body correlations from the ground-state decay of 26O will be very challenging due to the need for a precise measurement of the 24O momentum at the reaction point in the target.
Ground states of a prescribed mean curvature equation
NASA Astrophysics Data System (ADS)
del Pino, Manuel; Guerra, Ignacio
We study the existence of radial ground state solutions for the problem -div({∇u√{1+|})=u, u>0 in R, u(x)→0 as |x|→∞, N⩾3, q>1. It is known that this problem has infinitely many ground states when q⩾N+2}/{N-2}, while no solutions exist if q⩽N/N-2. A question raised by Ni and Serrin in [W.-M. Ni, J. Serrin, Existence and non-existence theorems for ground states for quasilinear partial differential equations, Atti Convegni Lincei 77 (1985) 231-257] is whether or not ground state solutions exist for N/N-2ground states with fast decay O(|) as |x|→+∞ provided that q lies below but close enough to the critical exponent {N+2}/{N-2}. These solutions develop a bubble-tower profile as q approaches the critical exponent.
Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters
Souza, T. X. R.; Macedo, C. A.
2016-01-01
In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh’s conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653
Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters.
Souza, T X R; Macedo, C A
2016-01-01
In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh's conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653
Estimation of beryllium ground state energy by Monte Carlo simulation
Kabir, K. M. Ariful; Halder, Amal
2015-05-15
Quantum Monte Carlo method represent a powerful and broadly applicable computational tool for finding very accurate solution of the stationary Schrödinger equation for atoms, molecules, solids and a variety of model systems. Using variational Monte Carlo method we have calculated the ground state energy of the Beryllium atom. Our calculation are based on using a modified four parameters trial wave function which leads to good result comparing with the few parameters trial wave functions presented before. Based on random Numbers we can generate a large sample of electron locations to estimate the ground state energy of Beryllium. Our calculation gives good estimation for the ground state energy of the Beryllium atom comparing with the corresponding exact data.
Magnetization ground state and reversal modes of magnetic nanotori
NASA Astrophysics Data System (ADS)
Vojkovic, Smiljan; Nunez, Alvaro S.; Altbir, Dora; Carvalho-Santos, Vagson L.
2016-07-01
In this work, and by means of micromagnetic simulations, we study the magnetic properties of toroidal nanomagnets. The magnetization ground state for different values of the aspect ratio between the toroidal and polar radii of the nanotorus has been obtained. Besides, we have shown that the vortex and the in-plane single domain states can appear as ground states for different ranges of the aspect ratio, while a single domain state with an out-of-plane magnetization is not observed. The hysteresis curves are also obtained, evidencing the existence of two reversal modes depending on the geometry: a vortex mode and a coherent rotation. A comparison between toroidal and cylindrical nanoparticles has been performed evidencing that nanotori can accommodate a vortex as the ground state for smaller volume than cylindrical nanorings.
Ground state and constrained domain walls in Gd /Fe multilayers
NASA Astrophysics Data System (ADS)
Van Aken, Bas B.; Prieto, José L.; Mathur, Neil D.
2005-03-01
The magnetic ground state of antiferromagnetically coupled Gd /Fe multilayers and the evolution of in-plane domain walls is modeled with micromagnetics. The twisted state is characterized by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios MFe:MGd, the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio MFe:MGd but also by the thicknesses of the layers; that is by the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe-aligned and the Gd-aligned state in favor of the twisted state. On the other hand, ultrathin layers exclude the twisted state, since wider domain walls cannot form in these ultrathin layers.
Ground-state geometric quantum computing in superconducting systems
Solinas, P.; Moettoenen, M.
2010-11-15
We present a theoretical proposal for the implementation of geometric quantum computing based on a Hamiltonian which has a doubly degenerate ground state. Thus the system which is steered adiabatically, remains in the ground-state. The proposed physical implementation relies on a superconducting circuit composed of three SQUIDs and two superconducting islands with the charge states encoding the logical states. We obtain a universal set of single-qubit gates and implement a nontrivial two-qubit gate exploiting the mutual inductance between two neighboring circuits, allowing us to realize a fully geometric ground-state quantum computing. The introduced paradigm for the implementation of geometric quantum computing is expected to be robust against environmental effects.
Efficient algorithm for approximating one-dimensional ground states
Aharonov, Dorit; Arad, Itai; Irani, Sandy
2010-07-15
The density-matrix renormalization-group method is very effective at finding ground states of one-dimensional (1D) quantum systems in practice, but it is a heuristic method, and there is no known proof for when it works. In this article we describe an efficient classical algorithm which provably finds a good approximation of the ground state of 1D systems under well-defined conditions. More precisely, our algorithm finds a matrix product state of bond dimension D whose energy approximates the minimal energy such states can achieve. The running time is exponential in D, and so the algorithm can be considered tractable even for D, which is logarithmic in the size of the chain. The result also implies trivially that the ground state of any local commuting Hamiltonian in 1D can be approximated efficiently; we improve this to an exact algorithm.
Polarization memory in the nonpolar magnetic ground state of multiferroic CuFeO2
NASA Astrophysics Data System (ADS)
Beilsten-Edmands, J.; Magorrian, S. J.; Foronda, F. R.; Prabhakaran, D.; Radaelli, P. G.; Johnson, R. D.
2016-10-01
We investigate polarization memory effects in single-crystal CuFeO2, which has a magnetically induced ferroelectric phase at low temperatures and applied B fields between 7.5 and 13 T. Following electrical poling of the ferroelectric phase, we find that the nonpolar collinear antiferromagnetic ground state at B =0 T retains a strong memory of the polarization magnitude and direction, such that upon reentering the ferroelectric phase a net polarization of comparable magnitude to the initial polarization is recovered in the absence of external bias. This memory effect is very robust: in pulsed-magnetic-field measurements, several pulses into the ferroelectric phase with reverse bias are required to switch the polarization direction, with significant switching only seen after the system is driven out of the ferroelectric phase and ground state either magnetically (by application of B >13 T) or thermally. The memory effect is also largely insensitive to the magnetoelastic domain composition, since no change in the memory effect is observed for a sample driven into a single-domain state by application of stress in the [1 1 ¯0 ] direction. On the basis of Monte Carlo simulations of the ground-state spin configurations, we propose that the memory effect is due to the existence of helical domain walls within the nonpolar collinear antiferromagnetic ground state, which would retain the helicity of the polar phase for certain magnetothermal histories.
Magnetostriction-driven ground-state stabilization in 2H perovskites
NASA Astrophysics Data System (ADS)
Porter, D. G.; Senn, M. S.; Khalyavin, D. D.; Cortese, A.; Waterfield-Price, N.; Radaelli, P. G.; Manuel, P.; zur-Loye, H.-C.; Mazzoli, C.; Bombardi, A.
2016-10-01
The magnetic ground state of Sr3A RuO6 , with A =(Li ,Na ) , is studied using neutron diffraction, resonant x-ray scattering, and laboratory characterization measurements of high-quality crystals. Combining these results allows us to observe the onset of long-range magnetic order and distinguish the symmetrically allowed magnetic models, identifying in-plane antiferromagnetic moments and a small ferromagnetic component along the c axis. While the existence of magnetic domains masks the particular in-plane direction of the moments, it has been possible to elucidate the ground state using symmetry considerations. We find that due to the lack of local anisotropy, antisymmetric exchange interactions control the magnetic order, first through structural distortions that couple to in-plane antiferromagnetic moments and second through a high-order magnetoelastic coupling that lifts the degeneracy of the in-plane moments. The symmetry considerations used to rationalize the magnetic ground state are very general and will apply to many systems in this family, such as Ca3A RuO6 , with A =(Li ,Na ) , and Ca3LiOsO6 whose magnetic ground states are still not completely understood.
A Remark on the Ground State Energy of Bosonic Atoms
NASA Astrophysics Data System (ADS)
Hogreve, H.
2011-08-01
Monotonicity properties of the ground state energy of bosonic atoms as established in a recent paper by M.K.H. Kiessling [J. Stat. Phys. 139:1063 (2009)] are studied. Symmetry and scaling arguments lead to a more direct proof of a slightly stronger result of this monotonicity and the behavior of the ground state energy as a function of the number of bosonic electrons. Furthermore, invoking appropriate lower and upper bounds on two-electron systems, the stability of the bosonics He- ion is rigorously demonstrated.
Ground state microstructure of a ferrofluid thin layer
Prokopieva, T. A.; Danilov, V. A.; Kantorovich, S. S.
2011-09-15
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.
Spin of the sup 219 Ra ground state
Hackett, E.D.; Kuehner, J.A.; Waddington, J.C. ); Jones, G.D.
1989-09-01
The {sup 208}Pb({sup 18}O,3{ital n}){sup 223}Th reaction at 83 MeV bombarding energy was used to populate the alpha-radioactive nucleus {sup 223}Th. Out-of-beam alpha-gamma coincidences were recorded at correlation angles of 90{degree} and 180{degree}. The {ital a}{sub 2} angular correlation coefficient was extracted for an alpha-gamma cascade to the {sup 215}Rn ground state via the 0.316 MeV excited state. This limited the assignment of the ground-state spin of {sup 219}Ra to ((7/2, 11) / 2 ){sup +}. .AE
Toward Triplet Ground State NaLi Molecules
NASA Astrophysics Data System (ADS)
Ebadi, Sepehr; Jamison, Alan; Rvachov, Timur; Jing, Li; Son, Hyungmok; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang
2016-05-01
The NaLi molecule is expected to have a long lifetime in the triplet ground-state due to its fermionic nature, large rotational constant, and weak spin-orbit coupling. The triplet state has both electric and magnetic dipole moments, affording unique opportunities in quantum simulation and ultracold chemistry. We have mapped the excited state NaLi triplet potential by means of photoassociation spectroscopy. We report on this and our further progress toward the creation of the triplet ground-state molecules using STIRAP. NSF, ARO-MURI, Samsung, NSERC.
Nuclear lifetime measurements from data with independently varying observation times
NASA Astrophysics Data System (ADS)
Gray, T. J.; Reed, M. W.; Lane, G. J.; Akber, A.; Litvinov, Yu. A.; Walker, P. M.
2016-09-01
A method is presented for obtaining ground-state and isomeric lifetimes from storage-ring data. The method published by Schmidt et al. is extended to the problems and solutions associated with applying their method to storage-ring data. These developed procedures are applied to real experimental data for 193Re, and a mean-lifetime value of 37-7+9 s is obtained. This is consistent with a previous measurement.
Ruben, Eliza A; Schwans, Jason P; Sonnett, Matthew; Natarajan, Aditya; Gonzalez, Ana; Tsai, Yingssu; Herschlag, Daniel
2013-02-12
We compared the binding affinities of ground state analogues for bacterial ketosteroid isomerase (KSI) with a wild-type anionic Asp general base and with uncharged Asn and Ala in the general base position to provide a measure of potential ground state destabilization that could arise from the close juxtaposition of the anionic Asp and hydrophobic steroid in the reaction's Michaelis complex. The analogue binding affinity increased ~1 order of magnitude for the Asp38Asn mutation and ~2 orders of magnitude for the Asp38Ala mutation, relative to the affinity with Asp38, for KSI from two sources. The increased level of binding suggests that the abutment of a charged general base and a hydrophobic steroid is modestly destabilizing, relative to a standard state in water, and that this destabilization is relieved in the transition state and intermediate in which the charge on the general base has been neutralized because of proton abstraction. Stronger binding also arose from mutation of Pro39, the residue adjacent to the Asp general base, consistent with an ability of the Asp general base to now reorient to avoid the destabilizing interaction. Consistent with this model, the Pro mutants reduced or eliminated the increased level of binding upon replacement of Asp38 with Asn or Ala. These results, supported by additional structural observations, suggest that ground state destabilization from the negatively charged Asp38 general base provides a modest contribution to KSI catalysis. They also provide a clear illustration of the well-recognized concept that enzymes evolve for catalytic function and not, in general, to maximize ground state binding. This ground state destabilization mechanism may be common to the many enzymes with anionic side chains that deprotonate carbon acids.
Tuning ground states and excitations in complex electronic materials
Bishop, A.R.
1996-09-01
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.
The Ground State Energy of Heavy Atoms: The Leading Correction
NASA Astrophysics Data System (ADS)
Handrek, Michael; Siedentop, Heinz
2015-10-01
For heavy atoms (large atomic number Z) described by no-pair operators in the Furry picture, we find the ground state's leading energy correction. We compare the result with (semi-)empirical values and Schwinger's prediction showing more than qualitative agreement.
Electronic ground state properties of Coulomb blockaded quantum dots
NASA Astrophysics Data System (ADS)
Patel, Satyadev Rajesh
Conductance through quantum dots at low temperature exhibits random but repeatable fluctuations arising from quantum interference of electrons. The observed fluctuations follow universal statistics arising from the underlying universality of quantum chaos. Random matrix theory (RMT) has provided an accurate description of the observed universal conductance fluctuations (UCF) in "open" quantum dots (device conductance ≥e 2/h). The focus of this thesis is to search for and decipher the underlying origin of similar universal properties in "closed" quantum dots (device conductance ≤e2/ h). A series of experiments is presented on electronic ground state properties measured via conductance measurements in Coulomb blockaded quantum dots. The statistics of Coulomb blockade (CB) peak heights with zero and non-zero magnetic field measured in various devices agree qualitatively with predictions from Random Matrix Theory (RMT). The standard deviation of the peak height fluctuations for non-zero magnetic field is lower than predicted by RMT; the temperature dependence of the standard deviation of the peak height for non-zero magnetic field is also measured. The second experiment summarizes the statistics of CB peak spacings. The peak spacing distribution width is observed to be on the order of the single particle level spacing, Delta, for both zero and non-zero magnetic field. The ratio of the zero field peak spacing distribution width to the non-zero field peak spacing distribution width is ˜1.2; this is good agreement with predictions from spin-resolved RMT predictions. The standard deviation of the non-zero magnetic field peak spacing distribution width shows a T-1/2 dependence in agreement with a thermal averaging model. The final experiment summarizes the measurement of the peak height correlation length versus temperature for various quantum dots. The peak height correlation length versus temperature saturates in small quantum dots, suggesting spectral scrambling
Realization of ground-state artificial skyrmion lattices at room temperature
Gilbert, Dustin A.; Maranville, Brian B.; Balk, Andrew L.; Kirby, Brian J.; Fischer, Peter; Pierce, Daniel T.; Unguris, John; Borchers, Julie A.; Liu, Kai
2015-10-08
We report that the topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. We demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from the dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. In conclusion, the imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices.
Realization of ground-state artificial skyrmion lattices at room temperature
Gilbert, Dustin A.; Maranville, Brian B.; Balk, Andrew L.; Kirby, Brian J.; Fischer, Peter; Pierce, Daniel T.; Unguris, John; Borchers, Julie A.; Liu, Kai
2015-10-08
We report that the topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. We demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from themore » dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. In conclusion, the imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices.« less
Realization of ground-state artificial skyrmion lattices at room temperature
Gilbert, Dustin A.; Maranville, Brian B.; Balk, Andrew L.; Kirby, Brian J.; Fischer, Peter; Pierce, Daniel T.; Unguris, John; Borchers, Julie A.; Liu, Kai
2015-01-01
The topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. Here, we demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from the dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. The imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices. PMID:26446515
Ground state spontaneous fission half-lives from thorium to fermium
Holden, N.E.
1988-01-01
Measurements of the half-lives for spontaneous fission of the nuclidic ground states of elements from thorium to fermium have been compiled and evaluated. Recommended values are presented. An attempt has been made to distinguish between spontaneous fission and heavy ion emission. Spontaneously fissioning isomers have not been considered here. The difference between even-even nuclides and odd-even, even-odd and odd-odd nuclides are discussed. 3 tabs.
Measuring the Fr Weak Nuclear Charge by Observing a Linear Stark Shift with Small Atomic Samples
Bouchiat, Marie-Anne
2008-03-28
We study the chirality of ground-state alkali atoms in E and B fields, dressed with a circularly-polarized beam near-detuned (< or approx. )1 GHz) from an E-field-assisted forbidden transition such as 7S-8S in Fr. We predict parity violating energy shifts of their sublevels, linear in E and the weak nuclear charge Q{sub W}. A dressing beam of 10 kW/cm{sup 2} at 506 nm produces a shift of {approx}100 {mu}Hz at E=100 V/cm, B > or approx. 50 mG which should be observable with {approx}10{sup 4} Fr atoms confined in an optical dipole trap. We discuss optimal conditions, parameter reversals, and a calibration procedure to measure Q{sub W}.
Andrews, Logan D; Fenn, Tim D; Herschlag, Daniel
2013-07-01
Enzymes stabilize transition states of reactions while limiting binding to ground states, as is generally required for any catalyst. Alkaline Phosphatase (AP) and other nonspecific phosphatases are some of Nature's most impressive catalysts, achieving preferential transition state over ground state stabilization of more than 10²²-fold while utilizing interactions with only the five atoms attached to the transferred phosphorus. We tested a model that AP achieves a portion of this preference by destabilizing ground state binding via charge repulsion between the anionic active site nucleophile, Ser102, and the negatively charged phosphate monoester substrate. Removal of the Ser102 alkoxide by mutation to glycine or alanine increases the observed Pi affinity by orders of magnitude at pH 8.0. To allow precise and quantitative comparisons, the ionic form of bound P(i) was determined from pH dependencies of the binding of Pi and tungstate, a P(i) analog lacking titratable protons over the pH range of 5-11, and from the ³¹P chemical shift of bound P(i). The results show that the Pi trianion binds with an exceptionally strong femtomolar affinity in the absence of Ser102, show that its binding is destabilized by ≥10⁸-fold by the Ser102 alkoxide, and provide direct evidence for ground state destabilization. Comparisons of X-ray crystal structures of AP with and without Ser102 reveal the same active site and P(i) binding geometry upon removal of Ser102, suggesting that the destabilization does not result from a major structural rearrangement upon mutation of Ser102. Analogous Pi binding measurements with a protein tyrosine phosphatase suggest the generality of this ground state destabilization mechanism. Our results have uncovered an important contribution of anionic nucleophiles to phosphoryl transfer catalysis via ground state electrostatic destabilization and an enormous capacity of the AP active site for specific and strong recognition of the phosphoryl group in
Coherent Control of Ground State NaK Molecules
NASA Astrophysics Data System (ADS)
Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin
2016-05-01
Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE
Ground states of trapped spin-1 condensates in magnetic field
Matuszewski, Michal
2010-11-15
We consider a spin-1 Bose-Einstein condensate trapped in a harmonic potential under the influence of a homogeneous magnetic field. We investigate spatial and spin structure of the mean-field ground states under constraints on the number of atoms and the total magnetization. We show that the trapping potential can make the antiferromagnetic condensate separate into three distinct phases and ferromagnetic condensate into two distinct phases. In the ferromagnetic case, the magnetization is located in the center of the harmonic trap, while in the antiferromagnetic case magnetized phases appear in the outer regions. We describe how the transition from the Thomas-Fermi regime to the single-mode approximation regime with decreasing number of atoms results in the disappearance of the domains. We suggest that the ground states can be created in experiment by adiabatically changing the magnetic-field strength.
Simulation of the hydrogen ground state in stochastic electrodynamics
NASA Astrophysics Data System (ADS)
Nieuwenhuizen, Theo M.; Liska, Matthew T. P.
2015-10-01
Stochastic electrodynamics is a classical theory which assumes that the physical vacuum consists of classical stochastic fields with average energy \\frac{1}{2}{{\\hslash }}ω in each mode, i.e., the zero-point Planck spectrum. While this classical theory explains many quantum phenomena related to harmonic oscillator problems, hard results on nonlinear systems are still lacking. In this work the hydrogen ground state is studied by numerically solving the Abraham-Lorentz equation in the dipole approximation. First the stochastic Gaussian field is represented by a sum over Gaussian frequency components, next the dynamics is solved numerically using OpenCL. The approach improves on work by Cole and Zou 2003 by treating the full 3d problem and reaching longer simulation times. The results are compared with a conjecture for the ground state phase space density. Though short time results suggest a trend towards confirmation, in all attempted modellings the atom ionises at longer times.
Kac-Moody symmetries of critical ground states
NASA Astrophysics Data System (ADS)
Kondev, Jané; Henley, Christopher L.
1996-02-01
The symmetries of critical ground states of two-dimensional lattice models are investigated. We show how mapping a critical ground state to a model of a rough interface can be used to identify the chiral symmetry algebra of the conformal field theory that describes its scaling limit. This is demonstrated in the case of the six-vertex model, the three-coloring model on the honeycomb lattice, and the four-coloring model on the square lattice. These models are critical and they are described in the continuum by conformal field theories whose symmetry algebras are the su(2) k=1 , su(3) k=1 , and the su(4) k=1 Kac-Moody algebra, respectively. Our approach is based on the Frenkel-Kac-Segal vertex operator construction of level-one Kac-Moody algebras.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; Ramos, Mike; Trouw, Frans; Zhu, Jian-Xin; Haule, Kristjan; Kotliar, Gabriel; Bauer, Eric D.
2015-01-01
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. Our study reveals that the ground state of plutonium is governed by valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials. PMID:26601219
Cluster expansion for ground states of local Hamiltonians
NASA Astrophysics Data System (ADS)
Bastianello, Alvise; Sotiriadis, Spyros
2016-08-01
A central problem in many-body quantum physics is the determination of the ground state of a thermodynamically large physical system. We construct a cluster expansion for ground states of local Hamiltonians, which naturally incorporates physical requirements inherited by locality as conditions on its cluster amplitudes. Applying a diagrammatic technique we derive the relation of these amplitudes to thermodynamic quantities and local observables. Moreover we derive a set of functional equations that determine the cluster amplitudes for a general Hamiltonian, verify the consistency with perturbation theory and discuss non-perturbative approaches. Lastly we verify the persistence of locality features of the cluster expansion under unitary evolution with a local Hamiltonian and provide applications to out-of-equilibrium problems: a simplified proof of equilibration to the GGE and a cumulant expansion for the statistics of work, for an interacting-to-free quantum quench.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; Ramos, Mike; Trouw, Frans; Zhu, Jian -Xin; Haule, Kristjan; Kotliar, Gabriel; Bauer, Eric D.
2015-07-10
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. In addition, our study reveals that the ground state of plutonium is governed by valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.
Role of the helium ground state in (e,3e) processes
Ancarani, L.U.; Montagnese, T.; Dal Cappello, C.
2004-07-01
Absolute (e,3e) measurements on helium, at high incident energy, have been recently reproduced by a calculation in the first Born approximation [Phys. Rev. Lett. 91, 73201 (2003)]. The theoretical model is based on the product of three Coulomb waves for the final state and the use of Pluvinage wave function for the initial helium ground state. The authors suggest that the good agreement obtained is strongly related to the quality of the initial state, in particular to the fact that it is diagonal in all Coulomb interactions. In this paper, we show that this conclusion is not correct. We construct three other helium ground states to demonstrate that diagonalizing the Hamiltonian is not the deciding factor in obtaining agreement with the absolute experimental data.
NASA Astrophysics Data System (ADS)
Nagasawa, Yutaka; Ando, Yoshito; Okada, Tadashi
1999-10-01
We have studied femtosecond ground state recovery dynamics of the triphenylmethane dyes brilliant green (BG) and malachite green (MG) by pump-probe spectroscopy at the center wavelength of 635 nm with a time resolution of 33 fs. The ultrafast recovery of the ground state bleach was highly nonexponential and depended on the solvent viscosity, although all time constants were shorter than the solvation times obtained from other measurements. We observed a plateau or a rise component in the signal, which indicates an intermediate state. The rise time showed a viscosity dependence, even in the ultrafast time domain. It should be noted that the decay times were always longer for BG than MG, while the rise time did not show a solute dependence. The torsional motion of the amino-substituted phenyl group may be involved in the ultrafast process to the intermediate state, but lack of a solute dependence indicates that only a small conformational change is involved.
Ultracold triplet molecules in the rovibrational ground state.
Lang, F; Winkler, K; Strauss, C; Grimm, R; Denschlag, J Hecker
2008-09-26
We report here on the production of an ultracold gas of tightly bound Rb2 triplet molecules in the rovibrational ground state, close to quantum degeneracy. This is achieved by optically transferring weakly bound Rb2 molecules to the absolute lowest level of the ground triplet potential with a transfer efficiency of about 90%. The transfer takes place in a 3D optical lattice which traps a sizeable fraction of the tightly bound molecules with a lifetime exceeding 200 ms. PMID:18851446
Electronic and ground state properties of ThTe
NASA Astrophysics Data System (ADS)
Bhardwaj, Purvee; Singh, Sadhna
2016-05-01
The electronic properties of ThTe in cesium chloride (CsCl, B2) structure are investigated in the present paper. To study the ground state properties of thorium chalcogenide, the first principle calculations have been calculated. The bulk properties, including lattice constant, bulk modulus and its pressure derivative are obtained. The calculated equilibrium structural parameters are in good agreement with the available experimental and theoretical results.
Improvement in a phenomenological formula for ground state binding energies
NASA Astrophysics Data System (ADS)
Gangopadhyay, G.
2016-07-01
The phenomenological formula for ground state binding energy derived earlier [G. Gangopadhyay, Int. J. Mod. Phys. E 20 (2011) 179] has been modified. The parameters have been obtained by fitting the latest available tabulation of experimental values. The major modifications include a new term for pairing and introduction of a new neutron magic number at N = 160. The new formula reduced the root mean square deviation to 363keV, a substantial improvement over the previous version of the formula.
Attractive Correlated Electron-Pair Ground State of Resonant Bosons
NASA Astrophysics Data System (ADS)
Chakraverty, B. K.
We consider a strictly one-band Hamiltonian of electrons with attractive interaction between them. We show that in the interesting intermediate density regime, where V ≤ ɛF, the system admits a mixed state of free fermions and dynamic correlated pairs or resonant bosons. The inevitable coupling between the two sub-system produces a superconducting ground state. This should be called Schafroth Condensation.
Ground-state energy and relativistic corrections for positronium hydride
Bubin, Sergiy; Varga, Kalman
2011-07-15
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.
Correlation between ground state and orbital anisotropy in heavy fermion materials
Willers, Thomas; Strigari, Fabio; Hu, Zhiwei; Sessi, Violetta; Brookes, Nicholas B.; Bauer, Eric D.; Sarrao, John L.; Thompson, J. D.; Tanaka, Arata; Wirth, Steffen; et al
2015-02-09
The interplay of structural, orbital, charge, and spin degrees of freedom is at the heart of many emergent phenomena, including superconductivity. We find that unraveling the underlying forces of such novel phases is a great challenge because it not only requires understanding each of these degrees of freedom, it also involves accounting for the interplay between them. Cerium-based heavy fermion compounds are an ideal playground for investigating these interdependencies, and we present evidence for a correlation between orbital anisotropy and the ground states in a representative family of materials. We have measured the 4f crystal-electric field ground-state wave functions ofmore » the strongly correlated materials CeRh1₋xIrxIn5 with great accuracy using linear polarization-dependent soft X-ray absorption spectroscopy. These measurements show that these wave functions correlate with the ground-state properties of the substitution series, which covers long-range antiferromagnetic order, unconventional superconductivity, and coexistence of these two states.« less
Structural Studies of Metastable and Ground State Vortex Lattice Domains in MgB2
NASA Astrophysics Data System (ADS)
de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.
2015-03-01
Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. Application of an AC magnetic field to drive the VL to the ground state revealed a two-step power law behavior, indicating a slow nucleation of ground state domains followed by a faster growth. The dependence on the number of applied AC cycles is reminiscent of jamming of soft, frictionless spheres. Here, we report on detailed structural studies of both metastable and ground state VL domains. These include measurements of VL correlation lengths as well as spatially resolved SANS measurements showing the VL domain distribution within the MgB2 single crystal. We discuss these results and how they may help to resolve the mechanism responsible for stabilizing the metastable VL phases. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.
High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb
NASA Astrophysics Data System (ADS)
Sirohi, Anshu; Singh, Chandan K.; Thakur, Gohil S.; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Haque, Zeba; Gupta, L. C.; Kabir, Mukul; Ganguli, Ashok K.; Sheet, Goutam
2016-06-01
CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number of measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high (˜47%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane are strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.
Correlation between ground state and orbital anisotropy in heavy fermion materials
Willers, Thomas; Strigari, Fabio; Hu, Zhiwei; Sessi, Violetta; Brookes, Nicholas B.; Bauer, Eric D.; Sarrao, John L.; Thompson, J. D.; Tanaka, Arata; Wirth, Steffen; Tjeng, Liu Hao; Severing, Andrea
2015-02-09
The interplay of structural, orbital, charge, and spin degrees of freedom is at the heart of many emergent phenomena, including superconductivity. We find that unraveling the underlying forces of such novel phases is a great challenge because it not only requires understanding each of these degrees of freedom, it also involves accounting for the interplay between them. Cerium-based heavy fermion compounds are an ideal playground for investigating these interdependencies, and we present evidence for a correlation between orbital anisotropy and the ground states in a representative family of materials. We have measured the 4f crystal-electric field ground-state wave functions of the strongly correlated materials CeRh_{1₋x}Ir_{x}In_{5} with great accuracy using linear polarization-dependent soft X-ray absorption spectroscopy. These measurements show that these wave functions correlate with the ground-state properties of the substitution series, which covers long-range antiferromagnetic order, unconventional superconductivity, and coexistence of these two states.
Variable energy, high flux, ground-state atomic oxygen source
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Orient, Otto J. (Inventor)
1987-01-01
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.
Alternative ground states enable pathway switching in biological electron transfer
Abriata, Luciano A.; Alvarez-Paggi, Damian; Ledesma, Gabirela N.; Blackburn, Ninian J.; Vila, Alejandro J.; Murgida, Daniel H.
2012-10-10
Electron transfer is the simplest chemical reaction and constitutes the basis of a large variety of biological processes, such as photosynthesis and cellular respiration. Nature has evolved specific proteins and cofactors for these functions. The mechanisms optimizing biological electron transfer have been matter of intense debate, such as the role of the protein milieu between donor and acceptor sites. Here we propose a mechanism regulating long-range electron transfer in proteins. Specifically, we report a spectroscopic, electrochemical, and theoretical study on WT and single-mutant CuA redox centers from Thermus thermophilus, which shows that thermal fluctuations may populate two alternative ground-state electronicmore » wave functions optimized for electron entry and exit, respectively, through two different and nearly perpendicular pathways. In conclusion, these findings suggest a unique role for alternative or “invisible” electronic ground states in directional electron transfer. Moreover, it is shown that this energy gap and, therefore, the equilibrium between ground states can be fine-tuned by minor perturbations, suggesting alternative ways through which protein–protein interactions and membrane potential may optimize and regulate electron–proton energy transduction.« less
Periodic Striped Ground States in Ising Models with Competing Interactions
NASA Astrophysics Data System (ADS)
Giuliani, Alessandro; Seiringer, Robert
2016-11-01
We consider Ising models in two and three dimensions, with short range ferromagnetic and long range, power-law decaying, antiferromagnetic interactions. We let J be the ratio between the strength of the ferromagnetic to antiferromagnetic interactions. The competition between these two kinds of interactions induces the system to form domains of minus spins in a background of plus spins, or vice versa. If the decay exponent p of the long range interaction is larger than d + 1, with d the space dimension, this happens for all values of J smaller than a critical value J c ( p), beyond which the ground state is homogeneous. In this paper, we give a characterization of the infinite volume ground states of the system, for p > 2 d and J in a left neighborhood of J c ( p). In particular, we prove that the quasi-one-dimensional states consisting of infinite stripes ( d = 2) or slabs ( d = 3), all of the same optimal width and orientation, and alternating magnetization, are infinite volume ground states. Our proof is based on localization bounds combined with reflection positivity.
Alternative ground states enable pathway switching in biological electron transfer
Abriata, Luciano A.; Álvarez-Paggi, Damián; Ledesma, Gabriela N.; Blackburn, Ninian J.; Vila, Alejandro J.; Murgida, Daniel H.
2012-01-01
Electron transfer is the simplest chemical reaction and constitutes the basis of a large variety of biological processes, such as photosynthesis and cellular respiration. Nature has evolved specific proteins and cofactors for these functions. The mechanisms optimizing biological electron transfer have been matter of intense debate, such as the role of the protein milieu between donor and acceptor sites. Here we propose a mechanism regulating long-range electron transfer in proteins. Specifically, we report a spectroscopic, electrochemical, and theoretical study on WT and single-mutant CuA redox centers from Thermus thermophilus, which shows that thermal fluctuations may populate two alternative ground-state electronic wave functions optimized for electron entry and exit, respectively, through two different and nearly perpendicular pathways. These findings suggest a unique role for alternative or “invisible” electronic ground states in directional electron transfer. Moreover, it is shown that this energy gap and, therefore, the equilibrium between ground states can be fine-tuned by minor perturbations, suggesting alternative ways through which protein–protein interactions and membrane potential may optimize and regulate electron–proton energy transduction. PMID:23054836
Coherent Transfer of Photoassociated Molecules into the Rovibrational Ground State
NASA Astrophysics Data System (ADS)
Inouye, Shin
2011-05-01
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 41 K and 87 Rb atoms were first photo-associated into loosely-bound molecules in the X 1 Σ potential. Using v = 41, J = 1 level in the (3) 1 Σ potential as an intermediate level, we succeeded in transferring molecules in the v = 91, J = 0 level into the absolute ground state (X 1 Σ , 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.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.
Periodic Striped Ground States in Ising Models with Competing Interactions
NASA Astrophysics Data System (ADS)
Giuliani, Alessandro; Seiringer, Robert
2016-06-01
We consider Ising models in two and three dimensions, with short range ferromagnetic and long range, power-law decaying, antiferromagnetic interactions. We let J be the ratio between the strength of the ferromagnetic to antiferromagnetic interactions. The competition between these two kinds of interactions induces the system to form domains of minus spins in a background of plus spins, or vice versa. If the decay exponent p of the long range interaction is larger than d + 1, with d the space dimension, this happens for all values of J smaller than a critical value J c (p), beyond which the ground state is homogeneous. In this paper, we give a characterization of the infinite volume ground states of the system, for p > 2d and J in a left neighborhood of J c (p). In particular, we prove that the quasi-one-dimensional states consisting of infinite stripes (d = 2) or slabs (d = 3), all of the same optimal width and orientation, and alternating magnetization, are infinite volume ground states. Our proof is based on localization bounds combined with reflection positivity.
QED calculation of the ground-state energy of berylliumlike ions
NASA Astrophysics Data System (ADS)
Malyshev, A. V.; Volotka, A. V.; Glazov, D. A.; Tupitsyn, I. I.; Shabaev, V. M.; Plunien, G.
2014-12-01
Ab initio QED calculations of the ground-state binding energies of berylliumlike ions are performed for the wide range of the nuclear charge number: Z =18 -96 . The calculations are carried out in the framework of the extended Furry picture starting with three different types of the screening potential. The rigorous QED calculations up to the second order of the perturbation theory are combined with the third- and higher-order electron-correlation contributions obtained within the Breit approximation by the use of the large-scale configuration-interaction Dirac-Fock-Sturm method. The effects of nuclear recoil and nuclear polarization are taken into account. The ionization potentials are obtained by subtracting the binding energies of the corresponding lithiumlike ions. In comparison with the previous calculations the accuracy of the binding energies and the ionization potentials is significantly improved.
NASA Astrophysics Data System (ADS)
Wu, Ling-Na; You, L.
2016-03-01
We show that the ground state of a spin-1 atomic condensate with antiferromagnetic interactions constitutes a useful resource for quantum metrology upon approaching the Heisenberg limit. Unlike a ferromagnetic condensate state where individual atomic spins are aligned in the same direction, the antiferromagnetic ground-state condensate is a condensate of spin-singlet atom pairs. The inherent correlation between paired atoms allows for parameter estimation at precisions beyond the standard quantum limit (SQL) for uncorrelated atoms. The degree of improvement over the SQL is measured by the scaled quantum Fisher information (QFI), whose dependence on the ratio of linear Zeeman shift p to spin-dependent atomic interaction c is studied. At a typical value of p =0.4 c , which corresponds to a magnetic field of 28.6 μ G for c =50 h Hz (for 23Na atom condensate in the F =1 state at a typical density of ˜1014cm-3 ), the scaled QFI can reach ˜0.48 N , which approaches the limit of 0.5 N for the twin-Fock state |N/2 > +|N/2 > - . Our work encourages experimental efforts to reach the ground state of an antiferromagnetic condensate at a extremely low magnetic field.
The ground state of a spin-1 anti-ferromagnetic atomic condensate for Heisenberg limited metrology
NASA Astrophysics Data System (ADS)
Wu, Ling-Na; You, Li
2016-05-01
The ground state of a spin-1 atomic condensate with anti-ferromagnetic interaction can be applied to quantum metrology approaching the Heisenberg limit. Unlike a ferromagnetic condensate state where individual atomic spins are aligned in the same direction, atoms in an anti-ferromagnetic ground state condensate exist as spin singlet pairs, whose inherent correlation promises metrological precisions beyond the standard quantum limit (SQL) for uncorrelated atoms. The degree of improvement over the SQL is measured by quantum Fisher information (QFI), whose dependence on the ratio of linear Zeeman shift p to spin-dependent atomic interaction c is studied. At a typical value of p = 0 . 4 c corresponding to a magnetic field of 28 . 6 μ G with c = h × 50 Hz (for 23 Na atom condensate in the F = 1 state at a typical density of ~1014cm-3), the scaled QFI can reach ~ 0 . 48 N , which is close to the limits of N for NooN state, or 0 . 5 N for twin-Fock state. We hope our work will stimulate experimental efforts towards reaching the anti-ferromagnetic condensate ground state at extremely low magnetic fields.
Ground state of a resonantly interacting Bose gas
Diederix, J. M.; Heijst, T. C. F. van; Stoof, H. T. C.
2011-09-15
We show that a two-channel mean-field theory for a Bose gas near a Feshbach resonance allows for an analytic computation of the chemical potential, and therefore the universal constant {beta}, at unitarity. To improve on this mean-field theory, which physically neglects condensate depletion, we study a variational Jastrow ansatz for the ground-state wave function and use the hypernetted-chain approximation to minimize the energy for all positive values of the scattering length. We also show that other important physical quantities such as Tan's contact and the condensate fraction can be directly obtained from this approach.
The ground state of the Frenkel-Kontorova model
NASA Astrophysics Data System (ADS)
Babushkin, A. Yu.; Abkaryan, A. K.; Dobronets, B. S.; Krasikov, V. S.; Filonov, A. N.
2016-09-01
The continual approximation of the ground state of the discrete Frenkel-Kontorova model is tested using a symmetric algorithm of numerical simulation. A "kaleidoscope effect" is found, which means that the curves representing the dependences of the relative extension of an N-atom chain vary periodically with increasing N. Stairs of structural transitions for N ≫ 1 are analyzed by the channel selection method with the approximation N = ∞. Images of commensurable and incommensurable structures are constructed. The commensurable-incommensurable phase transitions are stepwise.
Unparticle contribution to the hydrogen atom ground state energy
NASA Astrophysics Data System (ADS)
Wondrak, Michael F.; Nicolini, Piero; Bleicher, Marcus
2016-08-01
In the present work we study the effect of unparticle modified static potentials on the energy levels of the hydrogen atom. By using Rayleigh-Schrödinger perturbation theory, we obtain the energy shift of the ground state and compare it with experimental data. Bounds on the unparticle energy scale ΛU as a function of the scaling dimension dU and the coupling constant λ are derived. We show that there exists a parameter region where bounds on ΛU are stringent, signaling that unparticles could be tested in atomic physics experiments.
Ground state solutions for non-autonomous fractional Choquard equations
NASA Astrophysics Data System (ADS)
Chen, Yan-Hong; Liu, Chungen
2016-06-01
We consider the following nonlinear fractional Choquard equation, {(‑Δ)su+u=(1+a(x))(Iα ∗ (|u| p))|u| p‑2uin RN,u(x)→0as |x|→∞, here s\\in (0,1) , α \\in (0,N) , p\\in ≤ft[2,∞ \\right) and \\frac{N-2s}{N+α}<\\frac{1}{p}<\\frac{N}{N+α} . Assume {{\\lim}|x|\\to ∞}a(x)=0 and satisfying suitable assumptions but not requiring any symmetry property on a(x), we prove the existence of ground state solutions for (0.1).
Two-electron photoionization of ground-state lithium
Kheifets, A. S.; Fursa, D. V.; Bray, I.
2009-12-15
We apply the convergent close-coupling (CCC) formalism to single-photon two-electron ionization of the lithium atom in its ground state. We treat this reaction as single-electron photon absorption followed by inelastic scattering of the photoelectron on a heliumlike Li{sup +} ion. The latter scattering process can be described accurately within the CCC formalism. We obtain integrated cross sections of single photoionization leading to the ground and various excited states of the Li{sup +} ion as well as double photoionization extending continuously from the threshold to the asymptotic limit of infinite photon energy. Comparison with available experimental and theoretical data validates the CCC model.
Ground state solutions for non-autonomous fractional Choquard equations
NASA Astrophysics Data System (ADS)
Chen, Yan-Hong; Liu, Chungen
2016-06-01
We consider the following nonlinear fractional Choquard equation, {(-Δ)su+u=(1+a(x))(Iα ∗ (|u| p))|u| p-2uin RN,u(x)→0as |x|→∞, here s\\in (0,1) , α \\in (0,N) , p\\in ≤ft[2,∞ \\right) and \\frac{N-2s}{N+α}<\\frac{1}{p}<\\frac{N}{N+α} . Assume {{\\lim}|x|\\to ∞}a(x)=0 and satisfying suitable assumptions but not requiring any symmetry property on a(x), we prove the existence of ground state solutions for (0.1).
Structure of best possible strategies for finding ground states
NASA Astrophysics Data System (ADS)
Hoffmann, Karl Heinz; Franz, Astrid; Salamon, Peter
2002-10-01
Finding the ground state of a system with a complex energy landscape is important for many physical problems including protein folding, spin glasses, chemical clusters, and neural networks. Such problems are usually solved by heuristic search methods whose efficacy is judged by empirical performance on selected examples. We present a proof that for a wide range of objective functions threshold accepting is the best possible strategy within a large class of algorithms that simulate random walks on the landscape. In particular, it can perform better than simulated annealing, Tsallis and Glauber statistics.
Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach
Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E.; Tretyakova, T. Yu.
2015-12-15
Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.
Singlet Ground State of the Quantum Antiferromagnet Ba3CuSb2O9
NASA Astrophysics Data System (ADS)
Quilliam, J. A.; Bert, F.; Kermarrec, E.; Payen, C.; Guillot-Deudon, C.; Bonville, P.; Baines, C.; Luetkens, H.; Mendels, P.
2012-09-01
We present local probe results on the honeycomb lattice antiferromagnet Ba3CuSb2O9. Muon spin relaxation measurements in a zero field down to 20 mK show unequivocally that there is a total absence of spin freezing in the ground state. Sb NMR measurements allow us to track the intrinsic susceptibility of the lattice, which shows a maximum at around 55 K and drops to zero in the low-temperature limit. The spin-lattice relaxation rate shows two characteristic energy scales, including a field-dependent crossover to exponential low-temperature behavior, implying gapped magnetic excitations.
Ground-state and pairing-vibrational bands with equal quadrupole collectivity in ^{124}Xe
Radich, A. J.; Garrett, P. E.; Allmond, J. M.; Andreoiu, C.; Ball, G. C.; Bianco, L.; Bildstein, V.; Chagnon-Lessard, S.; Cross, D. S.; Demand, G. A.; Diaz Varela, A.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Hackman, G.; Hadinia, B.; Jigmeddorj, B.; Laffoley, A. T.; Leach, K. G.; Michetti-Wilson, J.; Orce, J. N.; Rajabali, M. M.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wang, Z. M.; Wood, J. L.; Wong, J.; Williams, S. J.; Yates, S. W.
2015-04-01
The nuclear structure of ^{124}Xe has been investigated via measurements of the β^{+}/EC decay of ^{124}Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2^{+} → 0^{+} in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, $B(E2; 2^+_3 → 0^+_2)$ = 78(13) W.u. and $B(E2; 2^+_4 → 0^+_3)$ = 53(12) W.u. were determined. The $0^+_3$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous ^{122}Te(^{3}He,n)^{124}Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; et al
2015-07-10
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. In addition, our study reveals that the ground state of plutonium is governed bymore » valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.« less
Ground state energies from converging and diverging power series expansions
NASA Astrophysics Data System (ADS)
Lisowski, C.; Norris, S.; Pelphrey, R.; Stefanovich, E.; Su, Q.; Grobe, R.
2016-10-01
It is often assumed that bound states of quantum mechanical systems are intrinsically non-perturbative in nature and therefore any power series expansion methods should be inapplicable to predict the energies for attractive potentials. However, if the spatial domain of the Schrödinger Hamiltonian for attractive one-dimensional potentials is confined to a finite length L, the usual Rayleigh-Schrödinger perturbation theory can converge rapidly and is perfectly accurate in the weak-binding region where the ground state's spatial extension is comparable to L. Once the binding strength is so strong that the ground state's extension is less than L, the power expansion becomes divergent, consistent with the expectation that bound states are non-perturbative. However, we propose a new truncated Borel-like summation technique that can recover the bound state energy from the diverging sum. We also show that perturbation theory becomes divergent in the vicinity of an avoided-level crossing. Here the same numerical summation technique can be applied to reproduce the energies from the diverging perturbative sums.
Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers
Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; Okamoto, Satoshi; Xiao, Di
2015-06-16
Layered transition-metal trichalcogenides with the chemical formula ABX_{3} have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J_{2} and J_{3}) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe_{3} is an antiferromagnet with a zigzag spin texture due to significant contribution from J_{3}, whereas CrGeTe_{3} is a ferromagnet with a Curie temperature of 106 K. Monolayers of Mn compounds (MnPS_{3} and MnPSe_{3}) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX_{3} can be a promising platform to explore two-dimensional magnetic phenomena.
Quantum gas of deeply bound ground state molecules.
Danzl, Johann G; Haller, Elmar; Gustavsson, Mattias; Mark, Manfred J; Hart, Russell; Bouloufa, Nadia; Dulieu, Olivier; Ritsch, Helmut; Nägerl, Hanns-Christoph
2008-08-22
Molecular cooling techniques face the hurdle of dissipating translational as well as internal energy in the presence of a rich electronic, vibrational, and rotational energy spectrum. In our experiment, we create a translationally ultracold, dense quantum gas of molecules bound by more than 1000 wave numbers in the electronic ground state. Specifically, we stimulate with 80% efficiency, a two-photon transfer of molecules associated on a Feshbach resonance from a Bose-Einstein condensate of cesium atoms. In the process, the initial loose, long-range electrostatic bond of the Feshbach molecule is coherently transformed into a tight chemical bond. We demonstrate coherence of the transfer in a Ramsey-type experiment and show that the molecular sample is not heated during the transfer. Our results show that the preparation of a quantum gas of molecules in specific rovibrational states is possible and that the creation of a Bose-Einstein condensate of molecules in their rovibronic ground state is within reach. PMID:18719277
Ground-state Electronic Structure of Actinide Monocarbides and Mononitrides
Petit, Leon; Svane, Axel; Szotek, Zdzislawa; Temmerman, Walter M; Stocks, George Malcolm
2009-01-01
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 (f{sup 7}), CmN (f{sup 7}), and AmN (f{sup 6}). 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.
Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers
Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; Okamoto, Satoshi; Xiao, Di
2015-06-16
Layered transition-metal trichalcogenides with the chemical formula ABX3 have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J2 and J3) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe3 is an antiferromagnet with a zigzag spin texture due to significant contribution from J3, whereas CrGeTe3 is a ferromagnet with a Curie temperaturemore » of 106 K. Monolayers of Mn compounds (MnPS3 and MnPSe3) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX3 can be a promising platform to explore two-dimensional magnetic phenomena.« less
Au42: a possible ground-state noble metallic nanotube.
Wang, Jing; Ning, Hua; Ma, Qing-Min; Liu, Ying; Li, You-Cheng
2008-10-01
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
Au42: A possible ground-state noble metallic nanotube
NASA Astrophysics Data System (ADS)
Wang, Jing; Ning, Hua; Ma, Qing-Min; Liu, Ying; Li, You-Cheng
2008-10-01
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,…, Δn =5) tubelike structures has been constructed. The highest occupied molecular orbital-lowest unoccupied molecular orbital gaps suggested a significant semiconductor-conductor alternation in n ɛ[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.
Holdup measurement for nuclear fuel manufacturing plants
Zucker, M.S.; Degen, M.; Cohen, I.; Gody, A.; Summers, R.; Bisset, P.; Shaub, E.; Holody, D.
1981-07-13
The assay of nuclear material holdup in fuel manufacturing plants is a laborious but often necessary part of completing the material balance. A range of instruments, standards, and a methodology for assaying holdup has been developed. The objectives of holdup measurement are ascertaining the amount, distribution, and how firmly fixed the SNM is. The purposes are reconciliation of material unbalance during or after a manufacturing campaign or plant decommissioning, to decide security requirements, or whether further recovery efforts are justified.
Rationalization of the solvation effects on the AtO+ ground-state change.
Ayed, Tahra; Réal, Florent; Montavon, Gilles; Galland, Nicolas
2013-09-12
(211)At radionuclide is of considerable interest as a radiotherapeutic agent for targeted alpha therapy in nuclear medicine, but major obstacles remain because the basic chemistry of astatine (At) is not well understood. The AtO(+) cationic form might be currently used for (211)At-labeling protocols in aqueous solution and has proved to readily react with inorganic/organic ligands. But AtO(+) reactivity must be hindered at first glance by spin restriction quantum rules: the ground state of the free cation has a dominant triplet character. Investigating AtO(+) clustered with an increasing number of water molecules and using various flavors of relativistic quantum methods, we found that AtO(+) adopts in solution a Kramers restricted closed-shell configuration resembling a scalar-relativistic singlet. The ground-state change was traced back to strong interactions, namely, attractive electrostatic interactions and charge transfer, with water molecules of the first solvation shell that lift up the degeneracy of the frontier π* molecular orbitals (MOs). This peculiarity brings an alternative explanation to the highly variable reproducibility reported for some astatine reactions: depending on the production protocols (with distillation in gas-phase or "wet chemistry" extraction), (211)At may or may not readily react. PMID:23944251
Static Properties and Stark Effect of the Ground State of the HD Molecular Ion
NASA Technical Reports Server (NTRS)
Bhatia, A. K.; Drachman, Richard J.
1999-01-01
We have calculated static properties of the ground state of the HD(+) ion and its lowest-lying P-state without making use of the Born-Oppenheimer approximation, as was done in the case of H2(+) and D2(+) [Phys. Rev. A 58, 2787 (1998)]. The ion is treated as a three-body system whose ground state is spherically symmetric. The wavefunction is of generalized Hylleraas type, but it is necessary to include high powers of the internuclear distance to localize the nuclear motion. We obtain good values of the energies of the ground S-state and lowest P-state and compare them with earlier calculations. Expectation values are obtained for various operators, the Fermi contact parameters, and the permanent quadrupole moment. The cusp conditions are also calculated. The polarizability was then calculated using second-order perturbation theory with intermediate P pseudostates. Since the nuclei in HD(+) are not of equal mass there is dipole coupling between the lowest two rotational states, which are almost degenerate. This situation is carefully analyzed, and the Stark shift is calculated variationally as a function of the applied electric field.
Towards photonic quantum simulation of ground states of frustrated Heisenberg spin systems.
Ma, Xiao-song; Dakić, Borivoje; Kropatschek, Sebastian; Naylor, William; Chan, Yang-hao; Gong, Zhe-xuan; Duan, Lu-ming; Zeilinger, Anton; Walther, Philip
2014-01-01
Photonic quantum simulators are promising candidates for providing insight into other small- to medium-sized quantum systems. Recent experiments have shown that photonic quantum systems have the advantage to exploit quantum interference for the quantum simulation of the ground state of Heisenberg spin systems. Here we experimentally characterize this quantum interference at a tuneable beam splitter and further investigate the measurement-induced interactions of a simulated four-spin system by comparing the entanglement dynamics using pairwise concurrence. We also study theoretically a four-site square lattice with next-nearest neighbor interactions and a six-site checkerboard lattice, which might be in reach of current technology.
Excitations of {sup 1}P levels of zinc by electron impact on the ground state
Fursa, Dmitry V.; Bray, Igor; Panajotovic, R.; Sevic, D.; Pejcev, V.; Marinkovic, B.P.; Filipovic, D.M.
2005-07-15
We present results of a joint theoretical and experimental investigation of electron scattering from the 4s{sup 2} {sup 1}S ground state of zinc. The 4s4p {sup 1}P{sup o} and 4s5p {sup 1}P{sup o} differential cross sections were measured at scattering angles between 10 degree sign and 150 degree sign and electron-energies of 15, 20, 25, 40, and 60 eV. Corresponding convergent close-coupling calculations have been performed and are compared with experiment.
Antiferromagnetic Spin-S Chains with Exactly Dimerized Ground States
NASA Astrophysics Data System (ADS)
Michaud, Frédéric; Vernay, François; Manmana, Salvatore R.; Mila, Frédéric
2012-03-01
We show that spin S Heisenberg spin chains with an additional three-body interaction of the form (Si-1·Si)(Si·Si+1)+H.c. possess fully dimerized ground states if the ratio of the three-body interaction to the bilinear one is equal to 1/[4S(S+1)-2]. This result generalizes the Majumdar-Ghosh point of the J1-J2 chain, to which the present model reduces for S=1/2. For S=1, we use the density matrix renormalization group method to show that the transition between the Haldane and the dimerized phases is continuous with a central charge c=3/2. Finally, we show that such a three-body interaction appears naturally in a strong-coupling expansion of the Hubbard model, and we discuss the consequences for the dimerization of actual antiferromagnetic chains.
Ground state of naphthyl cation: Singlet or triplet?
Dutta, Achintya Kumar; Vaval, Nayana Pal, Sourav; Manohar, Prashant U.
2014-03-21
We present a benchmark theoretical investigation on the electronic structure and singlet-triplet(S-T) gap of 1- and 2-naphthyl cations using the CCSD(T) method. Our calculations reveal that the ground states of both the naphthyl cations are singlet, contrary to the results obtained by DFT/B3LYP calculations reported in previous theoretical studies. However, the triplet states obtained in the two structural isomers of naphthyl cation are completely different. The triplet state in 1-naphthyl cation is (π,σ) type, whereas in 2-naphthyl cation it is (σ,σ{sup ′}) type. The S-T gaps in naphthyl cations and the relative stability ordering of the singlet and the triplet states are highly sensitive to the basis-set quality as well as level of correlation, and demand for inclusion of perturbative triples in the coupled-cluster ansatz.
Ground states of partially connected binary neural networks
NASA Technical Reports Server (NTRS)
Baram, Yoram
1990-01-01
Neural networks defined by outer products of vectors over (-1, 0, 1) are considered. Patterns over (-1, 0, 1) define by their outer products partially connected neural networks consisting of internally strongly connected, externally weakly connected subnetworks. Subpatterns over (-1, 1) define subnetworks, and their combinations that agree in the common bits define permissible words. It is shown that the permissible words are locally stable states of the network, provided that each of the subnetworks stores mutually orthogonal subwords, or, at most, two subwords. It is also shown that when each of the subnetworks stores two mutually orthogonal binary subwords at most, the permissible words, defined as the combinations of the subwords (one corresponding to each subnetwork), that agree in their common bits are the unique ground states of the associated energy function.
Calculation of electron scattering from the ground state of ytterbium
Bostock, Christopher J.; Fursa, Dmitry V.; Bray, Igor
2011-05-15
We report on the application of the convergent close-coupling method, in both relativistic and nonrelativistic formulations, to electron scattering from ytterbium. Angle-differential and integrated cross sections are presented for elastic scattering and excitation of the states (6s6p){sup 3}P{sub 0,1,2}, (6s6p){sup 1}P{sub 1}{sup o}, (6s7p){sup 1}P{sub 1}{sup o}, and (6s5d){sup 1}D{sub 2}{sup e} for a range of incident electron energies. We also present calculations of the total cross section, and angle-differential Stokes parameters for excitation of the (6s6p){sup 3}P{sub 1}{sup o} state from the ground state. A comparison is made with the relativistic distorted-wave method and experiments.
Absence of Quantum Time Crystals in Ground States
NASA Astrophysics Data System (ADS)
Watanabe, Haruki; Oshikawa, Masaki
2015-03-01
In analogy with crystalline solids around us, Wilczek recently proposed the idea of ``time crystals'' as phases that spontaneously break the continuous time translation into a discrete subgroup. The proposal stimulated further studies and vigorous debates whether it can be realized in a physical system. However, a precise definition of the time crystal is needed to resolve the issue. Here we first present a definition of time crystals based on the time-dependent correlation functions of the order parameter. We then prove a no-go theorem that rules out the possibility of time crystals defined as such, in the ground state of a general Hamiltonian which consists of only short-range interactions.
a New Phenomenological Formula for Ground-State Binding Energies
NASA Astrophysics Data System (ADS)
Gangopadhyay, G.
A phenomenological formula based on liquid drop model has been proposed for ground-state binding energies of nuclei. The effect due to bunching of single particle levels has been incorporated through a term resembling the one-body Hamiltonian. The effect of n-p interaction has been included through a function of valence nucleons. A total of 50 parameters has been used in the present calculation. The root mean square (r.m.s.) deviation for the binding energy values for 2140 nuclei comes out to be 0.376 MeV, and that for 1091 alpha decay energies is 0.284 MeV. The correspondence with the conventional liquid drop model is discussed.
Diagrammatic perturbation theory - The ground state of the carbon monosulfide molecule
NASA Technical Reports Server (NTRS)
Wilson, S.
1977-01-01
Diagrammatic many-body perturbation theory is employed in a study of the ground state of the carbon monosulfide molecule for bond lengths close to the equilibrium value. The calculations are complete through third order in the energy within the algebraic approximation. Two different zero-order Hamiltonians are considered, and all two-, three-, and four-body terms are determined for the corresponding perturbation expansions. Many-body effects are found to be very important. Pade approximants to the energy expansion are constructed, and upper bounds evaluated. Almost 53 percent of the estimated correlation energy is recovered. The variation of components of the correlation energy with nuclear separation is investigated. Spectroscopic constants are also calculated.
Fragile singlet ground-state magnetism in the pyrochlore osmates R2Os2O7 (R =Y and Ho)
NASA Astrophysics Data System (ADS)
Zhao, Z. Y.; Calder, S.; Aczel, A. A.; McGuire, M. A.; Sales, B. C.; Mandrus, D. G.; Chen, G.; Trivedi, N.; Zhou, H. D.; Yan, J.-Q.
2016-04-01
The singlet ground-state magnetism in pyrochlore osmates Y2Os2O7 and Ho2Os2O7 is studied by dc and ac susceptibility, specific heat, and neutron powder diffraction measurements. Despite the expected nonmagnetic singlet in the strong spin-orbit coupling (SOC) limit for Os4 + (5 d4 ), Y2Os2O7 exhibits a spin-glass ground state below 4 K with weak magnetism, suggesting possible proximity to a quantum phase transition between the nonmagnetic state in the strong SOC limit and a magnetic state in the strong superexchange limit. Ho2Os2O7 has the same structural distortion as in Y2Os2O7 ; however, the Os sublattice in Ho2Os2O7 shows long-range magnetic ordering below 36 K. The sharp difference of the magnetic ground state between Y2Os2O7 and Ho2Os2O7 signals that the singlet ground-state magnetism in R2Os2O7 is fragile and can be disturbed by the weak 4 f -5 d interactions.
Laboratory rotational ground state transitions of NH3D+ and CF+
NASA Astrophysics Data System (ADS)
Stoffels, A.; Kluge, L.; Schlemmer, S.; Brünken, S.
2016-09-01
Aims: This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods: Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10-00), and the two hyperfine components of the ground state transition of CF+ (J = 1-0) were measured with a relative precision better than 10-7. Results: For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1-0 transition towards the Horsehead photon-dominated region (PDR).
Neutron capture measurements for nuclear astrophysics
NASA Astrophysics Data System (ADS)
Reifarth, Rene
2005-04-01
Almost all of the heavy elements are produced via neutron capture reactions in a multitude of stellar production sites. The predictive power of the underlying stellar models is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. Neutron captures measurements on heavy radioactive isotopes provide a unique opportunity to largely improve these physics components, and thereby address important questions of nuclear astrophysics. Such species are branch-points in the otherwise uniquely defined path of subsequent n-captures along the s-process path in the valley of stability. These branch points reveal themselves through unmistakable signatures recovered from pre-solar meteoritic grains that originate in individual element producing stars. Measurements on radioactive isotopes for neutron energies in the keV region represent a stringent challenge for further improvements of experimental techniques. This holds true for the neutron sources, the detection systems and the technology to handle radioactive material. Though the activation method or accelerator mass spectroscopy of the reaction products could be applied in a limited number of cases, Experimental facilities like DANCE at LANL, USA and n-TOF at CERN, Switzerland are addressing the need for such measurements on the basis of the more universal method of detecting the prompt capture gamma-rays, which is required for the application of neutron time-of-flight (TOF) techniques. With a strongly optimized neutron facility at the Rare Isotope Accelerator (RIA) isotopes with half-lives down to tens of days could be investigated, while present facilities require half-lives of a few hundred days. Recent neutron capture experiments on radioactive isotopes with relevance for nuclear astrophysics and possibilities for future experimental setups will be discussed during the talk.
Feasibility study of measuring the 229Th nuclear isomer transition with 233U-doped crystals
NASA Astrophysics Data System (ADS)
Stellmer, Simon; Schreitl, Matthias; Kazakov, Georgy A.; Sterba, Johannes H.; Schumm, Thorsten
2016-07-01
We propose a simple approach to measure the energy of the few-eV isomeric state in 229Th. To this end, 233U nuclei are doped into VUV-transparent crystals, where they undergo α decay into 229Th, and, with a probability of 2%, populate the isomeric state. These Thm229 nuclei may decay into the nuclear ground state under emission of the sought-after VUV γ ray, whose wavelength can be determined with a spectrometer. Based on measurements of the optical transmission of 238U:CaF2 crystals in the VUV range, we expect a signal at least two orders of magnitude larger compared to current schemes using surface implantation of recoil nuclei. The signal background is dominated by Cherenkov radiation induced by β decays of the thorium decay chain. We estimate that, even if the isomer undergoes radiative de-excitation with a probability of only 0.1%, the VUV γ ray can be detected within a reasonable measurement time.
New Ground-State Crystal Structure of Elemental Boron.
An, Qi; Reddy, K Madhav; Xie, Kelvin Y; Hemker, Kevin J; Goddard, William A
2016-08-19
Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β-B). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β-B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ-B, is based on the Cmcm orthorhombic space group. Quantum mechanics predicts that the newly identified τ-B structure is 13.8 meV/B more stable than β-B. The τ-B structure allows 6% more charge transfer from B_{57} units to nearby B_{12} units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ-B structure to be the ground state structure for elemental boron at atmospheric pressure. PMID:27588864
Tunable ground states in helical p-wave Josephson junctions
NASA Astrophysics Data System (ADS)
Cheng, Qiang; Zhang, Kunhua; Yu, Dongyang; Chen, Chongju; Zhang, Yinhan; Jin, Biao
2016-07-01
We study new types of Josephson junctions composed of helical p-wave superconductors with {k}x\\hat{x}+/- {k}y\\hat{y} and {k}y\\hat{x}+/- {k}x\\hat{y}-pairing symmetries using quasi-classical Green’s functions with generalized Riccati parametrization. The junctions can host rich ground states: π phase, 0 + π phase, φ 0 phase and φ phase. The phase transition can be tuned by rotating the magnetization in the ferromagnetic interface. We present the phase diagrams in the parameter space formed by the orientation of the magnetization or by the magnitude of the interfacial potentials. The selection rules for the lowest order current which are responsible for the formation of the rich phases are summarized from the current-phase relations based on the numerical calculation. We construct a Ginzburg–Landau type of free energy for the junctions with d-vectors and the magnetization, which not only reveals the interaction forms of spin-triplet superconductivity and ferromagnetism, but can also directly lead to the selection rules. In addition, the energies of the Andreev bound states and the novel symmetries in the current-phase relations are also investigated. Our results are helpful both in the prediction of novel Josephson phases and in the design of quantum circuits.
New Ground-State Crystal Structure of Elemental Boron
NASA Astrophysics Data System (ADS)
An, Qi; Reddy, K. Madhav; Xie, Kelvin Y.; Hemker, Kevin J.; Goddard, William A.
2016-08-01
Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β -B ). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β -B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ -B , is based on the C m c m orthorhombic space group. Quantum mechanics predicts that the newly identified τ -B structure is 13.8 meV /B more stable than β -B . The τ -B structure allows 6% more charge transfer from B57 units to nearby B12 units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ -B structure to be the ground state structure for elemental boron at atmospheric pressure.
Antiferromagnetic ground state in NpCoGe
NASA Astrophysics Data System (ADS)
Colineau, E.; Griveau, J.-C.; Eloirdi, R.; Gaczyński, P.; Khmelevskyi, S.; Shick, A. B.; Caciuffo, R.
2014-03-01
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 <μNp>=0.80μB. 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.
Realization of Ground State Artificial Skyrmion Lattices at Room Temperature
NASA Astrophysics Data System (ADS)
Gilbert, Dustin A.; Maranville, Brian B.; Balk, Andrew J.; Kirby, Brian J.; Pierce, Daniel T.; Unguris, John; Borchers, Julie A.; Fischer, Peter; Liu, Kai
Artificial skyrmion lattices stable at ambient conditions offer a convenient and powerful platform to explore skyrmion physics and topological phenomena and motivates their inclusion in next-generation data and logic devices. In this work we present direct experimental evidence of artificial skyrmion lattices with a stable ground state at room temperature. Our approach is to pattern vortex-state Co nanodots (560 nm diameter) in hexagonal arrays on top of a Co/Pd multilayer with perpendicular magnetic anisotropy; the skyrmion state is prepared using a specific magnetic field sequence. Ion irradiation has been employed to suppress PMA in the underlayer and allow imprinting of the vortex structure from the nanodots to form skyrmion lattices, as revealed by polarized neutron reflectometry. Circularity control is realized through Co dot shape asymmetry, and confirmed by microscopy and FORC magnetometry. The vortex polarity is set during the field sequence and confirmed by magnetometry. Spin-transport studies further demonstrate a sensitivity to the skyrmion spin texture.Work supported by NSF (DMR-1008791, ECCS-1232275 and DMR-1543582)
Tunable ground states in helical p-wave Josephson junctions
NASA Astrophysics Data System (ADS)
Cheng, Qiang; Zhang, Kunhua; Yu, Dongyang; Chen, Chongju; Zhang, Yinhan; Jin, Biao
2016-07-01
We study new types of Josephson junctions composed of helical p-wave superconductors with {k}x\\hat{x}+/- {k}y\\hat{y} and {k}y\\hat{x}+/- {k}x\\hat{y}-pairing symmetries using quasi-classical Green’s functions with generalized Riccati parametrization. The junctions can host rich ground states: π phase, 0 + π phase, φ 0 phase and φ phase. The phase transition can be tuned by rotating the magnetization in the ferromagnetic interface. We present the phase diagrams in the parameter space formed by the orientation of the magnetization or by the magnitude of the interfacial potentials. The selection rules for the lowest order current which are responsible for the formation of the rich phases are summarized from the current-phase relations based on the numerical calculation. We construct a Ginzburg-Landau type of free energy for the junctions with d-vectors and the magnetization, which not only reveals the interaction forms of spin-triplet superconductivity and ferromagnetism, but can also directly lead to the selection rules. In addition, the energies of the Andreev bound states and the novel symmetries in the current-phase relations are also investigated. Our results are helpful both in the prediction of novel Josephson phases and in the design of quantum circuits.
Bao, Xiaoguang; Hrovat, David; Borden, Weston; Wang, Xue B.
2013-03-20
Cyclobutane-1,2,3,4-tetraone has been both predicted and found to have a triplet ground state, in which a b2g MO and an a2u MO is each singly occupied. In contrast, (CO)5 and (CO)6 have each been predicted to have a singlet ground state. This prediction has been tested by generating the (CO)5 - and (CO)6 - anions in the gas-phase by electrospray vaporization of solutions of, respectively, the croconate (CO)52- and rhodizonate (CO)62- dianions. The negative ion photoelectron (NIPE) spectra of the (CO)5•- radical anion give electron affinity (EA) = 3.830 eV and a singlet ground state for (CO)5, with the triplet higher in energy by 0.850 eV (19.6 kcal/mol). The NIPE spectra of the (CO)6•- radical anion give EA = 3.785 eV and a singlet ground state for (CO)6, with the triplet higher in energy by 0.915 eV (21.1 kcal/mol). (RO)CCSD(T)/aug-cc-pVTZ//(U)B3LYP/6-311+G(2df) calculations give EA values that are only ca. 1 kcal/mol lower than those measured and EST values that are only 2 - 3 kcal/mol higher than those obtained from the NIPE spectra. Thus, the calculations support the interpretations of the NIPE spectra and the finding, based on the spectra, that (CO)5 and (CO)6 both have a singlet ground state.
Gumberidze, A.; Stoehlker, Th.; Tashenov, S.; Banas, D.; Beckert, K.; Beller, P.; Beyer, H.F.; Bosch, F.; Hagmann, S.; Kozhuharov, C.; Liesen, D.; Nolden, F.; Mokler, P.H.; Steck, M.; Ma, X.; Sierpowski, D.
2005-06-10
X-ray spectra following radiative recombination of free electrons with bare uranium ions (U{sup 92+}) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 deg. observation geometry, allowed us to determine the ground-state Lamb shift in hydrogenlike uranium (U{sup 91+}) from the observed x-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime.
Direct experimental evidence for a multiparticle-hole ground state configuration of deformed 33Mg
NASA Astrophysics Data System (ADS)
Datta, Ushasi; Rahaman, A.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Jonson, B.; Johansson, H.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Scheit, H.; Scheidenberger, C.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.
2016-09-01
The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich 33Mg isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part ˜(70 ±13 )% of the cross section is observed to populate the excited states of 32Mg after the Coulomb breakup of 33Mg. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s1 /2 and p3 /2 orbitals. These experimental findings suggest a significant reduction and merging of s d -p f shell gaps at N ˜20 and 28. The ground state configuration of 33Mg is predominantly a combination of 32Mg(3.0 ,3.5 MeV ;2-,1-) ⨂νs1/2 , 32Mg(2.5 MeV ;2+) ⨂νp3/2 , and 32Mg(0 ;0+) ⨂νp3/2 . The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N =20 .
Majdi, Youssef; Hochlaf, Majdi; Pan, Yi; Lau, Kai-Chung; Poisson, Lionel; Garcia, Gustavo A; Nahon, Laurent; Al-Mogren, Muneerah Mogren; Schwell, Martin
2015-06-11
We report on the vibronic structure of the ground state X̃(2)A″ of the thymine cation, which has been measured using a threshold photoelectron photoion coincidence technique and vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum, recorded over ∼0.7 eV above the ionization potential (i.e., covering the whole ground state of the cation) shows rich vibrational structure that has been assigned with the help of calculated anharmonic modes of the ground electronic cation state at the PBE0/aug-cc-pVDZ level of theory. The adiabatic ionization energy has been experimentally determined as AIE = 8.913 ± 0.005 eV, in very good agreement with previous high resolution results. The corresponding theoretical value of AIE = 8.917 eV has been calculated in this work with the explicitly correlated method/basis set (R)CCSD(T)-F12/cc-pVTZ-F12, which validates the theoretical approach and benchmarks its accuracy for future studies of medium-sized biological molecules.
Quantum ground state effect on fluctuation rates in nano-patterned superconducting structures
Eftekharian, Amin; Jafari Salim, Amir; Atikian, Haig; Akhlaghi, Mohsen K.; Hamed Majedi, A.
2013-12-09
In this Letter, we present a theoretical model with experimental verifications to describe the abnormal behaviors of the measured fluctuation rates occurring in nano-patterned superconducting structures below the critical temperature. In the majority of previous works, it is common to describe the fluctuation rate by defining a fixed ground state or initial state level for the singularities (vortex or vortex-antivortex pairs), and then employing the well-known rate equations to calculate the liberation rates. Although this approach gives an acceptable qualitative picture, without utilizing free parameters, all the models have been inadequate in describing the temperature dependence of the rate for a fixed width or the width dependence of the rate for a fixed temperature. Here, we will show that by defining a current-controlled ground state level for both the vortex and vortex-antivortex liberation mechanisms, the dynamics of these singularities are described for a wide range of temperatures and widths. According to this study, for a typical strip width, not only is the vortex-antivortex liberation higher than the predicted rate, but also quantum tunneling is significant in certain conditions and can not be neglected.
The magnetic ground state and relationship to Kitaev physics in α-RuCl3
NASA Astrophysics Data System (ADS)
Banerjee, Arnab
The 2D Kitaev candidate alpha-RuCl3 consists of stacked honeycomb layers weakly coupled by Van der Waals interactions. Here we report the measurements of bulk properties and neutron diffraction in both powder and single crystal samples. Our results show that the full three dimensional magnetic ground state is highly pliable with at least two dominant phases corresponding to two different out-of-plane magnetic orders. They have different Neel temperatures dependent on the stacking of the 2D layers, such as a broad magnetic transition at TN = 14 K as observed in phase-pure powder samples, or a sharp magnetic transition at a lower TN = 7 K as observed in homogeneous single crystals with no evidence for stacking faults. The magnetic refinements of the neutron scattering data will be discussed, which in all cases shows the in-plane magnetic ground state is the zigzag phase common in Kitaev related materials including the honeycomb lattice Iridates. Inelastic neutron scattering in all cases shows that this material consistently exhibit strong two-dimensional magnetic fluctuations leading to a break-down of the classical spin-wave picture. Work performed at ORNL is supported by U.S. Dept. of Energy, Office of Basic Energy Sciences and Office of User Facilities Division.
Structural anomalies and the orbital ground state in FeCr2S4
NASA Astrophysics Data System (ADS)
Tsurkan, V.; Zaharko, O.; Schrettle, F.; Kant, Ch.; Deisenhofer, J.; Krug von Nidda, H.-A.; Felea, V.; Lemmens, P.; Groza, J. R.; Quach, D. V.; Gozzo, F.; Loidl, A.
2010-05-01
We report on high-resolution x-ray synchrotron powder-diffraction, magnetic-susceptibility, sound-velocity, thermal-expansion, and heat-capacity studies of the stoichiometric spinel FeCr2S4 . We provide clear experimental evidence of a structural anomaly which accompanies an orbital-order transition at low temperatures due to a static cooperative Jahn-Teller effect. At 9 K, magnetic susceptibility, ultrasound velocity, and specific heat reveal pronounced anomalies that correlate with a volume contraction as evidenced by thermal-expansion data. The analysis of the low-temperature heat capacity using a mean-field model with a temperature-dependent gap yields a gap value of about 18 K and is interpreted as the splitting of the electronic ground state of Fe2+ by a cooperative Jahn-Teller effect. This value is close to the splitting of the ground state due to spin-orbit coupling for isolated Fe2+ ions in an insulating matrix, indicating that Jahn-Teller and spin-orbit coupling are competing energy scales in this system. We argue that due to this competition, the spin-reorientation transition at around 60 K marks the onset of short-range orbital ordering accompanied by a clear broadening of Bragg reflections, an enhanced volume contraction compared to usual anharmonic behavior, and a softening of the lattice observed in the ultrasound measurements.
Ground State and Excited State H-Atom Temperatures in a Microwave Plasma Diamond Deposition Reactor
NASA Astrophysics Data System (ADS)
Gicquel, A.; Chenevier, M.; Breton, Y.; Petiau, M.; Booth, J. P.; Hassouni, K.
1996-09-01
Ground electronic state and excited state H-atom temperatures are measured in a microwave plasma diamond deposition reactor as a function of a low percentage of methane introduced in the feed gas and the averaged input microwave power density. Ground state H-atom temperatures (T_H) and temperature of the H-atom in the n=3 excited state (T_{Hα}) are obtained from the measurements respectively of the excitation profile by Two-photon Allowed transition Laser Induced Fluorescence (TALIF) and the Hα line broadening by Optical Emission Spectroscopy (OES). They are compared to gas temperatures calculated with a 1D diffusive non equilibrium H{2} plasma flow model and to ground electronic state rotational temperatures of molecular hydrogen measured previously by Coherent Anti-Stokes Raman Spectroscopy.
Geochemical Controls on Nuclear Magnetic Resonance Measurements
Knight, Rosemary; Prasad, Manika; Keating, Kristina
2003-11-11
OAK-B135 Our research objectives are to determine, through an extensive set of laboratory experiments, the effect of the specific mineralogic form of iron and the effect of the distribution of iron on proton nuclear magnetic resonance (NMR) relaxation mechanisms. In the first nine months of this project, we have refined the experimental procedures to be used in the acquisition of the laboratory NMR data; have ordered, and conducted preliminary measurements on, the sand samples to be used in the experimental work; and have revised and completed the theoretical model to use in this project. Over the next year, our focus will be on completing the first phase of the experimental work where the form and distribution of the iron in the sands in varied.
The 75As(n,2n) Cross Sections into the 74As Isomer and Ground State
Younes, W; Garrett, P E; Becker, J A; Bernstein, L A; Ormand, W E; Dietrich, F S; Nelson, R O; Devlin, M; Fotiades, N
2003-06-30
The {sup 75}As(n, 2n) cross section for the population of the T{sub 1/2} = 26.8-ns isomer at E{sub x} = 259.3 keV in {sup 74}As has been measured as a function of incident neutron energy, from threshold to E{sub n} = 20 MeV. The cross section was measured using the GEANIE spectrometer at LANSCE/WNR. For convenience, the {sup 75}As(n, 2n) population cross section for the {sup 74}As ground state has been deduced as the difference between the previously-known (n, 2n) reaction cross section and the newly measured {sup 75}As(n, 2n){sup 74}As{sup m} cross section. The (n, 2n) reaction, ground-state, and isomer population cross sections are tabulated in this paper.
{alpha} decay of nuclei in the range 67{<=}Z{<=}91 from the ground state and isomeric state
Santhosh, K. P.; Joseph, Jayesh George; Sahadevan, Sabina
2010-12-15
The Coulomb and proximity potential model for deformed nuclei (CPPMDN) is used to study the favored and unfavored {alpha} decay of nuclei in the range 67{<=}Z{<=}91 from both the ground state (g.s.) and isomeric state (i.s.). The computed half-lives are in good agreement with experimental data. The standard deviation of half-life is found to be 0.44. Geiger-Nuttall (GN) plots for various parent isotopes are studied. It is found that all four types of transitions (g.s.{yields}g.s., g.s.{yields}i.s., i.s.{yields}g.s., i.s.{yields}i.s.) lie on a straight line. The isomeric state {alpha} decay shows a behavior similar to that of the ground state and the nuclear structure of the isomeric states imitates that of the ground states. Some predictions are done for {alpha} transition from both ground and isomeric states, which will be useful for future experiments.
Kolomeisky, Eugene B.; Kalas, Ryan M.; Straley, Joseph P.
2004-06-01
We analyze the ground-state properties of an artificial atom made out of repulsive bosons attracted to a center for the case that all the interactions are short ranged. Such bosonic atoms could be created by optically trapping ultracold particles of alkali-metal vapors; we present the theory describing how their properties depend on experimentally adjustable strength of 'nuclear' attraction and interparticle repulsion. The binding ability of the short-range potential increases with space dimensionality, only a limited number of particles can be bound in one dimension, while in two and three dimensions the number of bound bosons can be chosen at will. Particularly in three dimensions we find an unusual effect of enhanced resonant binding: for not very strong interparticle repulsion the equilibrium number of bosons bound to a nuclear potential having a sufficiently shallow single-particle state increases without bound as the nuclear potential becomes less attractive. As a consequence of the competing nuclear attraction enhanced by the Bose statistics and interparticle repulsions, the dependence of the ground-state energy of the atom on the number of particles has a minimum whose position is experimentally tunable. This implies a staircase dependence of the equilibrium number of bound bosons on external parameters which may be used to create a single-atom pipette--an arrangement which allows the transport of atoms into and out of a reservoir, one at a time.
Electromagnetic structure of few-nucleon ground states
Marcucci, Laura E.; Istituto Nazionale di Fisica Nucleare; Gross, Franz L.; Thomas Jefferson National Accelerator Facility; Peña, M. T.; Piarulli, M.; Old Dominion Univ., Norfolk, VA; Schiavilla, Rocco; Old Dominion Univ., Norfolk, VA; Sick, Ingo; et al
2016-01-08
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled ChiEFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). Furthermore, for momentum transfers belowmore » Q < 5 fm-1 there is satisfactory agreement between experimental data and theoretical results in all three approaches. Conversely, at Q > 5 fm-1, particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron A structure function extend to Q ~ 12 fm-1, and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, there is no evidence for new effects coming from quark and gluon degrees of freedom at short distances.« less
Electromagnetic structure of few-nucleon ground states
NASA Astrophysics Data System (ADS)
Marcucci, L. E.; Gross, F.; Peña, M. T.; Piarulli, M.; Schiavilla, R.; Sick, I.; Stadler, A.; Van Orden, J. W.; Viviani, M.
2016-02-01
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled χEFT) the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). For momentum transfers below Q≲ 5 fm-1 there is satisfactory agreement between experimental data and theoretical results in all three approaches. However, at Q≳ 5 fm-1, particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron A structure function extend to Q≃ 12 fm-1, and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, the study of few-body form factors provides no evidence for new effects coming from quark and gluon degrees of freedom at short distances.
Energy splitting of the ground-state doublet in the nucleus 229Th.
Beck, B R; Becker, J A; Beiersdorfer, P; Brown, G V; Moody, K J; Wilhelmy, J B; Porter, F S; Kilbourne, C A; Kelley, R L
2007-04-01
The energy splitting of the 229Th ground-state doublet is measured to be 7.6+/-0.5 eV, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of 233U (105 muCi) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state (29.19-->0 keV).
Energy Splitting of the Ground-State Doublet in the Nucleus Th229
NASA Astrophysics Data System (ADS)
Beck, B. R.; Becker, J. A.; Beiersdorfer, P.; Brown, G. V.; Moody, K. J.; Wilhelmy, J. B.; Porter, F. S.; Kilbourne, C. A.; Kelley, R. L.
2007-04-01
The energy splitting of the Th229 ground-state doublet is measured to be 7.6±0.5eV, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of U233 (105μCi) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state (29.19→0keV).
Nonlinear Ultrasonic Measurements in Nuclear Reactor Environments
NASA Astrophysics Data System (ADS)
Reinhardt, Brian T.
Several Department of Energy Office of Nuclear Energy (DOE-NE) programs, such as the Fuel Cycle Research and Development (FCRD), Advanced Reactor Concepts (ARC), Light Water Reactor Sustainability, and Next Generation Nuclear Power Plants (NGNP), are investigating new fuels, materials, and inspection paradigms for advanced and existing reactors. A key objective of such programs is to understand the performance of these fuels and materials during irradiation. In DOE-NE's FCRD program, ultrasonic based technology was identified as a key approach that should be pursued to obtain the high-fidelity, high-accuracy data required to characterize the behavior and performance of new candidate fuels and structural materials during irradiation testing. The radiation, high temperatures, and pressure can limit the available tools and characterization methods. In this thesis, two ultrasonic characterization techniques will be explored. The first, finite amplitude wave propagation has been demonstrated to be sensitive to microstructural material property changes. It is a strong candidate to determine fuel evolution; however, it has not been demonstrated for in-situ reactor applications. In this thesis, finite amplitude wave propagation will be used to measure the microstructural evolution in Al-6061. This is the first demonstration of finite amplitude wave propagation at temperatures in excess of 200 °C and during an irradiation test. Second, a method based on contact nonlinear acoustic theory will be developed to identify compressed cracks. Compressed cracks are typically transparent to ultrasonic wave propagation; however, by measuring harmonic content developed during finite amplitude wave propagation, it is shown that even compressed cracks can be characterized. Lastly, piezoelectric transducers capable of making these measurements are developed. Specifically, three piezoelectric sensors (Bismuth Titanate, Aluminum Nitride, and Zinc Oxide) are tested in the Massachusetts
Aygor, H. Ali; Maras, Ismail; Cakmak, Necla; Selam, Cevad
2008-11-11
Within quasiparticle random phase approximation (QRPA), Pyatov-Salamov method for the self-consistent determination of the isovector effective interaction strength parameter, restoring a broken isotopic symmetry for the nuclear part of the Hamiltonian, is used. The isospin admixtures in the ground state of the parent nucleus, and the isospin structure of the isobar analog resonance (IAR) state are investigated by including the pairing correlations between nucleons for {sup 72-80}Kr isotopes. Our results are compared with the spherical case and with other theoretical results.
Observation of γ vibrations and alignments built on non-ground-state configurations in 156Dy
NASA Astrophysics Data System (ADS)
Majola, S. N. T.; Hartley, D. J.; Riedinger, L. L.; Sharpey-Schafer, J. F.; Allmond, J. M.; Beausang, C.; Carpenter, M. P.; Chiara, C. J.; Cooper, N.; Curien, D.; Gall, B. J. P.; Garrett, P. E.; Janssens, R. V. F.; Kondev, F. G.; Kulp, W. D.; Lauritsen, T.; McCutchan, E. A.; Miller, D.; Piot, J.; Redon, N.; Riley, M. A.; Simpson, J.; Stefanescu, I.; Werner, V.; Wang, X.; Wood, J. L.; Yu, C.-H.; Zhu, S.
2015-03-01
The exact nature of the lowest Kπ=2+ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ bands have been traced past the usual backbending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N =90 nucleus 156Dy , using the 148Nd(12C,4 n ) 156Dy reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the Kπ=2+ γ band are observed up to 32+ and 31+, respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ vibration built on the aligned yrast S band are observed up to spins 28+ and 27+. An even-spin positive-parity band, observed up to spin 24+, is a candidate for an aligned S band built on the seniority-zero configuration of the 02+ state at 676 keV. The crossing of this band with the 02+ band is at ℏ ωc=0.28 (1 ) MeV and is consistent with the configuration of the 02+ band not producing any blocking of the monopole pairing.
A ground state depleted laser in neodymium doped yttrium orthosilicate
Beach, R.; Albrecht, G.; Solarz, R.; Krupke, W.; Comaskey, B.; Mitchell, S.; Brandle, C.; Berkstresser, G.
1990-01-16
A ground state depleted (GSD){sup 1,2} laser has been demonstrated in the form of a Q-switched oscillator operating at 912 nm. Using Nd{sup 3+} as the active ion and Y{sub 2}SiO{sub 5} as the host material, the laser transition is from the lowest lying stark level of the Nd{sup 3t}F{sub 3/2} level to a stark level 355 cm{sup {minus}1} above the lowest lying one in the {sup 4}I{sub 9/2} manifold. The necessity of depleting the ground {sup 4}I{sub 9/2} manifold is evident for this level scheme as transparency requires a 10% inversion. To achieve the high excitation levels required for the efficient operation of this laser, bleach wave pumping using an alexandrite laser at 745 nm has been employed. The existence of a large absorption feature at 810 nm also allows for the possibility of AlGaAs laser diode pumping. Using KNbO{sub 3}, noncritical phase matching is possible at 140{degree}C using d{sub 32} and has been demonstrated. The results of Q-switched laser performance and harmonic generation in KNbO{sub 3} will be presented. Orthosilicate can be grown in large boules of excellent optical quality using a Czochralski technique. Because of the relatively small 912 nm emission cross section of 2-3 {times} 10{sup {minus}20} cm{sup 2} (orientation dependent) fluences of 10-20 J/cm{sup 2} must be circulated in the laser cavity for the efficient extraction of stored energy. This necessitates very aggressive laser damage thresholds. Results from the Reptile laser damage facility at Lawrence Livermore National Laboratory (LLNL) will be presented showing Y{sub 2}SiO{sub 5} bulk and AR sol-gel coated surface damage thresholds of greater than 40 J/cm{sup 2} for 10 nsec, 10 Hz, 1.06 {mu} pulses. 16 refs., 18 figs., 6 tabs.
Derivation of novel human ground state naive pluripotent stem cells.
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
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 GSK3β 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
Exploring the spin-orbital ground state of Ba3CuSb2O9
NASA Astrophysics Data System (ADS)
Smerald, Andrew; Mila, Frédéric
2014-09-01
Motivated by the absence of both spin freezing and a cooperative Jahn-Teller effect at the lowest measured temperatures, we study the ground state of Ba3CuSb2O9. We solve a general spin-orbital model on both the honeycomb and the decorated honeycomb lattice, revealing rich phase diagrams. The spin-orbital model on the honeycomb lattice contains an SU(4) point, where previous studies have shown the existence of a spin-orbital liquid with algebraically decaying correlations. For realistic parameters on the decorated honeycomb lattice, we find a phase that consists of clusters of nearest-neighbor spin singlets, which can be understood in terms of dimer coverings of an emergent square lattice. While the experimental situation is complicated by structural disorder, we show qualitative agreement between our theory and a range of experiments.
Ground-state and transition charge densities in /sup 192/Os
Reuter, W.; Shera, E.B.; Hoehn, M.V.; Hersman, F.W.; Milliman, T.; Finn, J.M.; Hyde-Wright, C.; Lourie, R.; Pugh, B.; Bertozzi, W.
1984-11-01
Elastic and inelastic electron-scattering cross sections of an Os-Pt transition region nucleus, /sup 192/Os, have been measured in a momentum transfer range from 0.6 to 2.9 fm/sup -1/. The data for the ground and the J/sup ..pi../ = 2/sup +/, 2/sup +/', 4/sup +/, and 3/sup -/ states were analyzed model independently with a Fourier-Bessel parametrization of the ground state and transition charge densities. The normalization of the (e,e') cross sections was obtained from a combined analysis with muonic-atom data for the ground and first 2/sup +/ states. The densities and their radial moments are compared with theoretical predictions of the Davydov model and with axially symmetric deformed density-matrix-expansion Hartree-Fock calculations (including the Legendre expansion and the small-amplitude vibration model extensions).
Spatial entanglement entropy in the ground state of the Lieb-Liniger model
NASA Astrophysics Data System (ADS)
Herdman, C. M.; Roy, P.-N.; Melko, R. G.; Del Maestro, A.
2016-08-01
We consider the entanglement between two spatial subregions in the Lieb-Liniger model of bosons in one spatial dimension interacting via a contact interaction. Using ground-state path integral quantum Monte Carlo we numerically compute the Rényi entropy of the reduced density matrix of the subsystem as a measure of entanglement. Our numerical algorithm is based on a replica method previously introduced by the authors, which we extend to efficiently study the entanglement of spatial subsystems of itinerant bosons. We confirm a logarithmic scaling of the Rényi entropy with subsystem size that is expected from conformal field theory, and compute the nonuniversal subleading constant for interaction strengths ranging over two orders of magnitude. In the strongly interacting limit, we find agreement with the known free fermion result.
Exotic Ground State and Elastic Softening under Pulsed Magnetic Fields in PrTr2Zn20 (Tr = Rh, Ir)
NASA Astrophysics Data System (ADS)
Ishii, Isao; Goto, Hiroki; Kamikawa, Shuhei; Yasin, Shadi; Zherlitsyn, Sergei; Wosnitza, Joachim; Onimaru, Takahiro; Matsumoto, Keisuke T.; Takabatake, Toshiro; Suzuki, Takashi
2016-04-01
To investigate a field-induced level crossing of the ground-state doublet in PrTr2Zn20 (Tr = Rh, Ir), we performed ultrasonic measurements in pulsed magnetic fields applied along the [110] and [001] directions and analyzed the results in the framework of the strain-susceptibility approach. Above 40 T for H || [110], we observed an elastic softening of the transverse modulus (C11 - C12)/2 corresponding to the ground-state doublet. In both compounds the softening is followed by a minimum at about 47 T at low temperatures. We predict the presence of a new field-induced phase boundary in PrTr2Zn20 at this field with two possible cases. The magnetic field of the minimum cannot be explained by only the quadrupole interaction.
Molecular spectroscopy for ground-state transfer of ultracold RbCs molecules.
Debatin, Markus; Takekoshi, Tetsu; Rameshan, Raffael; Reichsöllner, Lukas; Ferlaino, Francesca; Grimm, Rudolf; Vexiau, Romain; Bouloufa, Nadia; Dulieu, Olivier; Nägerl, Hanns-Christoph
2011-11-14
We perform one- and two-photon high resolution spectroscopy on ultracold samples of RbCs Feshbach molecules with the aim to identify a suitable route for efficient ground-state transfer in the quantum-gas regime to produce quantum gases of dipolar RbCs ground-state molecules. One-photon loss spectroscopy allows us to probe deeply bound rovibrational levels of the mixed excited (A(1)Σ(+)-b(3)Π)0(+) molecular states. Two-photon dark state spectroscopy connects the initial Feshbach state to the rovibronic ground state. We determine the binding energy of the lowest rovibrational level |v'' = 0, J'' = 0> of the X(1)Σ(+) ground state to be D = 3811.5755(16) cm(-1), a 300-fold improvement in accuracy with respect to previous data. We are now in the position to perform stimulated two-photon Raman transfer to the rovibronic ground state. PMID:21853182
Fitzpatrick, Ann E; Lincoln, Craig N; van Wilderen, Luuk J G W; van Thor, Jasper J
2012-01-26
The primary photoreactions of the red absorbing ground state (Pr) of the cyanobacterial phytochrome Cph1 from Synechocystis PCC 6803 involve C15═C16 Z-E photoisomerization of its phycocyanobilin chromophore. The first observable product intermediate in pump-probe measurements of the photocycle, "Lumi-R", is formed with picosecond kinetics and involves excited state decay reactions that have 3 and 14 ps time constants. Here, we have studied the photochemical formation of the Lumi-R intermediate using multipulse picosecond visible spectroscopy. Pump-dump-probe (PDP) and pump-repump-probe (PRP) experiments were carried out by employing two femtosecond visible pulses with 1, 14, and 160 ps delays, together with a broadband dispersive visible probe. The time delays between the two excitation pulses have been selected to allow interaction with the dominant (3 and 14 ps) kinetic phases of Lumi-R formation. The frequency dependence of the PDP and PRP amplitudes was investigated at 620, 640, 660, and 680 nm, covering excited state absorption (λ(max) = 620 nm), ground state absorption (λ(max) = 660 nm), and stimulated emission (λ(max) = 680 nm) cross sections. Experimental double difference transient absorbance signals (ΔΔOD), from the PDP and PRP measurements, required corrections to remove contributions from ground state repumping. The sensitivity of the resulting ΔΔOD signals was systematically investigated for possible connectivity schemes and photochemical parameters. When applying a homogeneous (sequentially decaying) connectivity scheme in both the 3 and 14 ps kinetic phases, evidence for repumping of an intermediate that has an electronic ground state configuration (GSI) is taken from the dump-induced S1 formation with 620, 640, and 660 nm wavelengths and 1 and 14 ps repump delays. Evidence for repumping a GSI is also seen, for the same excitation wavelengths, when imposing a target connectivity scheme proposed in the literature for the 1 ps repump delay. In
NASA Astrophysics Data System (ADS)
Shi, De-Heng; Zhang, Jin-Ping; Sun, Jin-Feng; Ma, Heng; Liu, Yu-Fang; Zhu, Zun-Lue
2010-02-01
The PD(X3Σ-) interaction potential is constructed using the CCSD(T) theory and the basis set, aug-cc-pV5Z. Using this potential, the spectroscopic parameters are accurately determined. The present Do, De, Re, ωe, ωeχe, αe, and Be are of 3.056 99 eV, 3.161 75 eV, 0.142 39 nm, 1701.558 cm-1, 23.6583 cm-1, 0.085 99 cm-1, and 4.3963 cm-1, respectively, which almost perfectly conform with the measurements. A total of 26 vibrational states is predicted when J = 0 by solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which favorably agree with the experiments. The total and various partial-wave cross sections are calculated for the elastic impact between two ground-state P and D atoms at 1.0 × 10-12 - 1.0 × 10-4 a.u. when they approach each other along the PD(X3Σ-) potential. No shape resonances exist in the total elastic cross sections, though the peaks can be found for each partial wave until l = 6. The shape of the total elastic cross sections is dominated by the s partial wave at very low temperatures. Due to the weakness of the shape resonances of each partial wave, they are all passed into oblivion by the strong total elastic cross sections.
The Measurement of Nuclear War Attitudes: Methods and Concerns.
ERIC Educational Resources Information Center
Mayton, Daniel M., II
Measures of adults' attitudes toward nuclear war are briefly discussed, and Mayton's Modified World Affairs Questionnaire (MWAQ) is described. The 23-item MWAQ was developed from Novak and Lerner's World Affairs Questionnaire, a nuclear war attitude measure by Mayton and Delamater, and related interview items by Jeffries. When the MWAQ was…
Microwave Spectroscopy of Trans-Ethyl Methyl Ether in the Ground State
NASA Astrophysics Data System (ADS)
Kobayashi, Kaori; Sakai, Yusuke; Tsunekawa, Shozo; Miyamoto, Taihei; Fujitake, Masaharu; Ohashi, Nobukimi
2013-06-01
The trans-ethyl methyl ether molecule (CH_3CH_2OCH_3) has two inequivalent methyl group internal rotors which corresponds to the two vibrational motions, ν_{28} and ν_{29}. Due to these internal rotations, a rotational transition could be split into maximum five components. The skeletal torsion (ν_{30}) is another low-lying state (ν_{30}) that interacts with the ν_{28} and ν_{29} modes. The microwave spectra of the trans-ethyl methyl ether molecule in the ν_{28} = 1, ν_{29} = 1, and ν_{30} = 1, 2 and 3 have been extensively studied by using Hougen's tunneling matrix formalism. The microwave spectroscopy in the ground state was studied by several groups. The splitting due to the ν_{28} mode (C-CH_3 internal rotation) is small in the ground state and was not fully resolved in most of the previous studied rotational transitions. In this paper, we report the results of the pulsed nozzle-jet Fourier transform microwave spectroscopy so as to measure the fully resolved spectra. The submillmeter wave spectroscopy was also carried out. Our analysis including the previously reported transitions would be useful for astronomical observations. K. Kobayashi, T. Matsui, N. Mori, S. Tsunekawa, and N. Ohashi J. Mol. Spectrosc. {269}, 242 2011. K. Kobayashi, T. Matsui, S. Tsunekawa, and N. Ohashi J. Mol. Spectrosc. {255}, 164 2009. K. Kobayashi, T. Matsui, N. Mori, S. Tsunekawa, and N. Ohashi J. Mol. Spectrosc.{251}, 301 2008. K. Kobayashi, K. Murata, S. Tsunekawa, and N. Ohashi Int. Symposium on Mol. Spectrosc., 65th Meeting TH15 2010.} M. Hayashi, and K. Kuwada J. Mol. Structure {28}, 147 1975. M. Hayashi, and M. Adachi J. Mol. Structure {78}, 53 1982. S. Tsunekawa, Y. Kinai, Y. Kondo, H. Odashima, and K. Takagi Molecules {8}, 103 2003. U. Fuchs, G. Winnewisser, P. Groner, F. C. De Lucia, and E. Herbst Astrophys. J. Suppl. {144}, 277 2003.
Development of Nuclear Emulsion for Fast Neutron Measurement
NASA Astrophysics Data System (ADS)
Machii, Shogo; Kuwabara, Kenichi; Morishima, Kunihiro
Nuclear emulsion is high sensitive photographic film used for detection of three-dimensional trajectory of charged particles. Energy resolution of nuclear emulsion is 21% (12%) FWHM against neutron energy of 2.8 MeV (4.9 MeV). Nuclear emulsion has high gamma ray rejection power. For now, at least 2×104 gamma rays/cm2, no increase of as a background for neutron measurement when scan using automatic nuclear emulsion read out system HTS. This value suggests that it is applicable even under high gamma ray environment, such as nuclear fusion reactor.
Ward, W. Luke; DeRose, Victoria J.
2012-01-01
Although the Hammerhead ribozyme (HHRz) has long been used as a model system in the field of ribozyme enzymology, several details of its mechanism are still not well understood. In particular, significant questions remain concerning the disposition and role of catalytic metals in the HHRz. Previous metal-rescue experiments using a “minimal” HHRz resulted in prediction of a catalytic metal that is bound in the A9/G10.1 site in the ground state of the reaction and that bridges to the scissile phosphate further along the reaction pathway. “Native” or extended HHRz constructs contain tertiary contacts that stabilize a more compact structure at moderate ionic strength. We performed Cd2+ rescue experiments on an extended HHRz from Schistosoma mansoni using stereo-pure scissile phosphorothioate-substituted substrates in order to determine whether a metal ion makes contact with the scissile phosphate in the ground state or further along the reaction coordinate. Inhibition in Ca2+/Mg2+ and rescue by thiophilic Cd2+ was specific for the Rp–S stereoisomer of the scissile phosphate. The affinity of the rescuing Cd2+, measured in two different ionic strength backgrounds, increased fourfold to 17-fold when the pro-Rp oxygen is replaced by sulfur. These data support a model in which the rescuing metal ion makes a ground-state interaction with the scissile phosphate in the native HHRz. The resulting model for Mg2+ activation in the HHRz places a metal ion in contact with the scissile phosphate, where it may provide ground-state electrostatic activation of the substrate. PMID:22124015
Ward, W Luke; Derose, Victoria J
2012-01-01
Although the Hammerhead ribozyme (HHRz) has long been used as a model system in the field of ribozyme enzymology, several details of its mechanism are still not well understood. In particular, significant questions remain concerning the disposition and role of catalytic metals in the HHRz. Previous metal-rescue experiments using a "minimal" HHRz resulted in prediction of a catalytic metal that is bound in the A9/G10.1 site in the ground state of the reaction and that bridges to the scissile phosphate further along the reaction pathway. "Native" or extended HHRz constructs contain tertiary contacts that stabilize a more compact structure at moderate ionic strength. We performed Cd(2+) rescue experiments on an extended HHRz from Schistosoma mansoni using stereo-pure scissile phosphorothioate-substituted substrates in order to determine whether a metal ion makes contact with the scissile phosphate in the ground state or further along the reaction coordinate. Inhibition in Ca(2+)/Mg(2+) and rescue by thiophilic Cd(2+) was specific for the R(p)-S stereoisomer of the scissile phosphate. The affinity of the rescuing Cd(2+), measured in two different ionic strength backgrounds, increased fourfold to 17-fold when the pro-R(p) oxygen is replaced by sulfur. These data support a model in which the rescuing metal ion makes a ground-state interaction with the scissile phosphate in the native HHRz. The resulting model for Mg(2+) activation in the HHRz places a metal ion in contact with the scissile phosphate, where it may provide ground-state electrostatic activation of the substrate.
The ground-state rotational spectrum and molecular geometry of ethynylstannane.
Guillemin, Jean-Claude; Legoupy, Stéphanie; Batten, Susan; Legon, Anthony
2006-05-14
The ground-state rotational spectra of 24 isotopomers of ethynylstannane have been observed by pulsed-jet, Fourier-transform microwave spectroscopy. The spectroscopic constants, B(0,)D(J) and D(JK) are reported for symmetric-top isotopomers H(3)(n)Sn(12)C(12)CH, where n = 116, 117, 118, 119, 120, 122 and 124, D(3)(n)Sn(12)C(12)CH, where n = 116, 118, 120, 122 and 124, H(3)(n)Sn(13)C(12) CH and H(3)(n)Sn(12)C(13)CH , where n = 116,118 and 120, and H(3)(n)Sn(12)C(12)CD, where n = 116, 118 and 120. In addition, the values of A(0), B(0), C(0), Delta(J) and Delta(JK) were obtained for the three asymmetric-top isotopomers DH(2)(n)Sn(12)C(12)CH, where n = 116, 118 and 120. Hyperfine structure was resolved and assigned in the transitions of the isotopomers H(3)(n)SnCCD, where n = 116, 118 and 120, and in the isotopomers H(3)(117)SnCCH and H(3)(119)SnCCH. In the former group, the hyperfine structure arises from D nuclear quadrupole coupling while in the latter group its origin lies in the spin-rotation coupling of the I = 1/2 Sn nuclear spin to the rotational motion. For these isotopomers, D nuclear quadrupole and spin-rotation coupling constants are determined where appropriate. The rotational constants obtained for the 24 isotopomers of H(3)SnCCH were used to obtain the following types of molecular geometry for ethynylstannane: r(0), r(s), and r(m).
A Laboratory Experiment on the Statistical Theory of Nuclear Reactions
ERIC Educational Resources Information Center
Loveland, Walter
1971-01-01
Describes an undergraduate laboratory experiment on the statistical theory of nuclear reactions. The experiment involves measuring the relative cross sections for formation of a nucleus in its meta stable excited state and its ground state by applying gamma-ray spectroscopy to an irradiated sample. Involves 3-4 hours of laboratory time plus…
Exact ground states of large two-dimensional planar Ising spin glasses
NASA Astrophysics Data System (ADS)
Pardella, G.; Liers, F.
2008-11-01
Studying spin-glass physics through analyzing their ground-state properties has a long history. Although there exist polynomial-time algorithms for the two-dimensional planar case, where the problem of finding ground states is transformed to a minimum-weight perfect matching problem, the reachable system sizes have been limited both by the needed CPU time and by memory requirements. In this work, we present an algorithm for the calculation of exact ground states for two-dimensional Ising spin glasses with free boundary conditions in at least one direction. The algorithmic foundations of the method date back to the work of Kasteleyn from the 1960s for computing the complete partition function of the Ising model. Using Kasteleyn cities, we calculate exact ground states for huge two-dimensional planar Ising spin-glass lattices (up to 30002 spins) within reasonable time. According to our knowledge, these are the largest sizes currently available. Kasteleyn cities were recently also used by Thomas and Middleton in the context of extended ground states on the torus. Moreover, they show that the method can also be used for computing ground states of planar graphs. Furthermore, we point out that the correctness of heuristically computed ground states can easily be verified. Finally, we evaluate the solution quality of heuristic variants of the L. Bieche approach.
Fifty years of nuclear fission: Nuclear data and measurements series
Lynn, J.E.
1989-06-01
This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.
Bes, D. R.; Civitarese, O.
2010-01-15
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.
NASA Technical Reports Server (NTRS)
Danilowicz, R.
1973-01-01
Ground-state properties of quantum crystals have received considerable attention from both theorists and experimentalists. The theoretical results have varied widely with the Monte Carlo calculations being the most successful. The molecular field approximation yields ground-state properties which agree closely with the Monte Carlo results. This approach evaluates the dynamical behavior of each pair of molecules in the molecular field of the other N-2 molecules. In addition to predicting ground-state properties that agree well with experiment, this approach yields data on the relative importance of interactions of different nearest neighbor pairs.
Ground state energy from the single trajectory propagation of the Schrödinger-Langevin equation
NASA Astrophysics Data System (ADS)
Chou, Chia-Chun
2015-07-01
The Schrödinger-Langevin equation is approximately solved for the ground state energy of quantum systems by propagating one single trajectory at a fixed point. Equations of motion for the amplitude of the wave function and the spatial derivatives of the complex action are derived through use of the derivative propagation method. The ground state energy is calculated from the amplitude of the wave function propagated along the single trajectory. Excellent ground state energies are obtained for the Morse potential, the strongly anharmonic potential, the coupled Morse oscillator-harmonic oscillator system, and the ground vibrational state of methyl iodide.
Ground state properties of superheavy nuclei with Z=117 and Z=119
Ren Zhongzhou; Chen Dinghan; Xu Chang
2006-11-02
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.
Configuration space Faddeev calculations. I. Triton ground state properties
NASA Astrophysics Data System (ADS)
Payne, G. L.; Friar, J. L.; Gibson, B. F.; Afnan, I. R.
1980-08-01
The formulation of Faddeev-type equations in configuration space is discussed. Numerical solutions are obtained using splines and the method of orthogonal collocation. Triton observables and wave-function probabilities are calculated for s-wave NN interaction models of Malfliet and Tjon and the tensor force model of Reid. Comparison with previously published triton results is made; our full five-channel results for the Reid soft-core potential are in excellent agreement with those obtained by Afnan and Birrell using separable expansion methods. NUCLEAR STRUCTURE 3H, Faddeev calculations configuration space.
Observation of Ground-state Two-neutron Decay
NASA Astrophysics Data System (ADS)
Thoennessen, M.; Kohley, Z.; Spyrou, A.; Lunderberg, E.; DeYoung, P. A.; Attanayake, H.; Baumann, T.; Bazin, D.; Brown, B. A.; Christian, G.; Divaratne, D.; Grimes, S. M.; Haagsma, A.; Finck, J. E.; Frank, N.; Luther, B.; Mosby, S.; Nagi, T.; Peaslee, G. F.; Peters, W. A.; Schiller, A.; Smith, J. K.; Snyder, J.; Strongman, M.; Volya, A.
Neutron decay spectroscopy has become a successful tool to explore nuclear properties of nuclei with the largest neutron-to-proton ratios. Resonances in nuclei located beyond the neutron dripline are accessible by kinematic reconstruction of the decay products. The development of two-neutron detection capabilities of the Modular Neutron Array (MoNA) at NSCL has opened up the possibility to search for unbound nuclei which decay by the emission of two neutrons. Specifically this exotic decay mode was observed in 16Be and 26O.
NASA Astrophysics Data System (ADS)
Kohley, Z.; Spyrou, A.; Lunderberg, E.; DeYoung, P. A.; Attanayake, H.; Baumann, T.; Bazin, D.; Brown, B. A.; Christian, G.; Divaratne, D.; Grimes, S. M.; Haagsma, A.; Finck, J. E.; Frank, N.; Luther, B.; Mosby, S.; Nagi, T.; Peaslee, G. F.; Peters, W. A.; Schiller, A.; Smith, J. K.; Snyder, J.; Strongman, M. J.; Thoennessen, M.; Volya, A.
2013-03-01
The two-neutron unbound ground state resonances of 26O and 16Be were populated using one-proton knockout reactions from 27F and 17B beams. A coincidence measurement of 3-body system (fragment + n + n) allowed for the decay energy of the unbound nuclei to be reconstructed. A low energy resonance, < 200 keV, was observed for the first time in the 240 + n + n system and assigned to the ground state of 26O. The 16Be ground state resonance was observed at 1.35 MeV. The 3-body correlations of the 14Be + n + n system were compared to simulations of a phase-space, sequential, and dineutron decay. The strong correlations in the n-n system from the experimental data could only be reproduced by the dineutron decay simulation providing the first evidence for a dineutron-like decay.
Fishman, Randy Scott; Campo, Javier; Vos, Thomas E.; Miller, Joel S.
2012-01-01
The diruthenium compound [Ru2(O2CMe)4]3[Cr(CN)6] contains two weakly coupled, ferrimag- netically ordered sublattices occupying the same volume. The magnetic field Hc 800 Oe required to align the two sublattice moments is proportional to the antiferromagnetic dipolar interaction Kc B Hc 5 10 3 meV between sublattices. Powder neutron-diffraction measurements on a deuterated sample reveal that the sublattice moments are restricted by the anisotropy of the diruthenium paddle-wheel complexes to the cubic diagonals. Those measurements also suggest that the quantum corrections to the ground state are significant.
Ground-state energies of the nonlinear sigma model and the Heisenberg spin chains
NASA Technical Reports Server (NTRS)
Zhang, Shoucheng; Schulz, H. J.; Ziman, Timothy
1989-01-01
A theorem on the O(3) nonlinear sigma model with the topological theta term is proved, which states that the ground-state energy at theta = pi is always higher than the ground-state energy at theta = 0, for the same value of the coupling constant g. Provided that the nonlinear sigma model gives the correct description for the Heisenberg spin chains in the large-s limit, this theorem makes a definite prediction relating the ground-state energies of the half-integer and the integer spin chains. The ground-state energies obtained from the exact Bethe ansatz solution for the spin-1/2 chain and the numerical diagonalization on the spin-1, spin-3/2, and spin-2 chains support this prediction.
One-dimensional extended Hubbard model with spin-triplet pairing ground states
NASA Astrophysics Data System (ADS)
Tanaka, Akinori
2016-10-01
We show that the one-dimensional extended Hubbard model has saturated ferromagnetic ground states with the spin-triplet electron pair condensation in a certain range of parameters. The ground state wave functions with fixed electron numbers are explicitly obtained. We also construct two ground states in which both the spin-rotation and the gauge symmetries are broken, and show that these states are transferred from one to the other by applying the edge operators. The edge operators are reduced to the Majorana fermions in a special case. These symmetry breaking ground states are shown to be stabilized by a superconducting mean field Hamiltonian which is related to the Kitaev chain with the charge-charge interaction.
Bott Periodicity for Z_2 Symmetric Ground States of Gapped Free-Fermion Systems
NASA Astrophysics Data System (ADS)
Kennedy, R.; Zirnbauer, M. R.
2016-03-01
Building on the symmetry classification of disordered fermions, we give a proof of the proposal by Kitaev, and others, for a "Bott clock" topological classification of free-fermion ground states of gapped systems with symmetries. Our approach differs from previous ones in that (i) we work in the standard framework of Hermitian quantum mechanics over the complex numbers, (ii) we directly formulate a mathematical model for ground states rather than spectrally flattened Hamiltonians, and (iii) we use homotopy-theoretic tools rather than K-theory. Key to our proof is a natural transformation that squares to the standard Bott map and relates the ground state of a d-dimensional system in symmetry class s to the ground state of a ( d + 1)-dimensional system in symmetry class s + 1. This relation gives a new vantage point on topological insulators and superconductors.
No-go theorem for ground state cooling given initial system-thermal bath factorization
NASA Astrophysics Data System (ADS)
Wu, Lian-Ao; Segal, Dvira; Brumer, Paul
2013-05-01
Ground-state cooling and pure state preparation of a small object that is embedded in a thermal environment is an important challenge and a highly desirable quantum technology. This paper proves, with two different methods, that a fundamental constraint on the cooling dynamic implies that it is impossible to cool, via a unitary system-bath quantum evolution, a system that is embedded in a thermal environment down to its ground state, if the initial state is a factorized product of system and bath states. The latter is a crucial but artificial assumption included in numerous tools that treat system-bath dynamics, such as master equation approaches and Kraus operator based methods. Adopting these approaches to address ground state and even approximate ground state cooling dynamics should therefore be done with caution, considering the fundamental theorem exposed in this work.
Lower bounds to energies for cusped-gaussian wavefunctions. [hydrogen atom ground state
NASA Technical Reports Server (NTRS)
Eaves, J. O.; Walsh, B. C.; Steiner, E.
1974-01-01
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.
Ground state properties of solid and liquid spin-aligned atomic hydrogen
NASA Technical Reports Server (NTRS)
Danilowicz, R. L.; Dugan, J. V., Jr.; Etters, R. D.
1976-01-01
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.
Booth, Corwin H.; Walter, Marc D.; Kazhdan, Daniel; Hu, Yung-Jin; Lukens, Wayne W.; Bauer, Eric D.; Maron, Laurent; Eisenstein, Odile; Andersen, Richard A.
2009-04-22
Partial ytterbium f-orbital occupancy (i.e., intermediate valence) and open-shell singlet formation are established for a variety of bipyridine and diazabutadiene adducts with decamethylytterbocene, (C5Me5)2Yb, abbreviated as Cp*2Yb. Data used to support this claim include ytterbium valence measurements using Yb LIII-edge X-ray absorption near-edge structure spectroscopy, magnetic susceptibility, and complete active space self-consistent field (CASSCF) multiconfigurational calculations, as well as structural measurements compared to density functional theory calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground-state wave function that has both an open-shell singlet f13(?*)1, where pi* is the lowest unoccupied molecular orbital of the bipyridine or dpiazabutadiene ligands, and a closed-shell singlet f14 component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the lack of temperature dependence of the measured intermediate valence. These results have implications for understanding chemical bonding not only in organolanthanide complexes but also for f-element chemistry in general, as well as understanding magnetic interactions in nanoparticles and devices.
Ground states of stealthy hyperuniform potentials. II. Stacked-slider phases
NASA Astrophysics Data System (ADS)
Zhang, G.; Stillinger, F. H.; Torquato, S.
2015-08-01
Stealthy potentials, a family of long-range isotropic pair potentials, produce infinitely degenerate disordered ground states at high densities and crystalline ground states at low densities in d -dimensional Euclidean space Rd. In the previous paper in this series, we numerically studied the entropically favored ground states in the canonical ensemble in the zero-temperature limit across the first three Euclidean space dimensions. In this paper, we investigate using both numerical and theoretical techniques metastable stacked-slider phases, which are part of the ground-state manifold of stealthy potentials at densities in which crystal ground states are favored entropically. Our numerical results enable us to devise analytical models of this phase in two, three, and higher dimensions. Utilizing this model, we estimated the size of the feasible region in configuration space of the stacked-slider phase, finding it to be smaller than that of crystal structures in the infinite-system-size limit, which is consistent with our recent previous work. In two dimensions, we also determine exact expressions for the pair correlation function and structure factor of the analytical model of stacked-slider phases and analyze the connectedness of the ground-state manifold of stealthy potentials in this density regime. We demonstrate that stacked-slider phases are distinguishable states of matter; they are nonperiodic, statistically anisotropic structures that possess long-range orientational order but have zero shear modulus. We outline some possible future avenues of research to elucidate our understanding of this unusual phase of matter.
Assays to measure nuclear mechanics in interphase cells.
Isermann, Philipp; Davidson, Patricia M; Sliz, Josiah D; Lammerding, Jan
2012-09-01
The nucleus is the characteristic hallmark of all eukaryotic cells. The physical properties of the nucleus reflect important biological characteristics, such as chromatin organization or nuclear envelope composition; they can also directly affect cellular function, e.g., when cells pass through narrow constrictions, where the stiff nucleus may present a limiting factor. We present two complementary techniques to probe the mechanical properties of the nucleus. In the first, nuclear stiffness relative to the surrounding cytoskeleton is inferred from induced nuclear deformations during strain application to cells on an elastic substrate. In the second approach, nuclear deformability is deduced from the transit time through a perfusion-based microfabricated device with constrictions smaller than the size of the nucleus. These complementary methods, which can be applied to measure nuclear stiffness in large numbers of living adherent or suspended cells, can help identify important changes in nuclear mechanics associated with disease or development.
Assays to measure nuclear mechanics in interphase cells
Isermann, Philipp; Davidson, Patricia M.; Sliz, Josiah D.
2012-01-01
The nucleus is the characteristic hallmark of all eukaryotic cells. The physical properties of the nucleus reflect important biological characteristics, such as chromatin organization or nuclear envelope composition; they can also directly affect cellular function, for example, when cells pass through narrow constrictions, where the stiff nucleus may present a limiting factor. We present two complementary techniques to probe the mechanical properties of the nucleus. In the first, nuclear stiffness relative to the surrounding cytoskeleton is inferred from induced nuclear deformations during strain application to cells on an elastic substrate. In the second approach, nuclear deformability is deduced from the transit time through a perfusion-based microfabricated device with constrictions smaller than the size of the nucleus. These complementary methods, which can be applied to measure nuclear stiffness in large numbers of living adherent or suspended cells, can help identify important changes in nuclear mechanics associated with disease or development. PMID:22968843
Hadronization measurements in cold nuclear matter
Dupre, Raphael
2015-05-01
Hadronization is the non-perturbative process of QCD by which partons become hadrons. It has been studied at high energies through various processes, we focus here on the experiments of lepto-production of hadrons in cold nuclear matter. By studying the dependence of observables to the atomic number of the target, these experimentscan give information on the dynamic of the hadronization at the femtometer scale. In particular, we will present preliminary results from JLab Hall B (CLAS collaboration), which give unprecedented statistical precision. Then, we will present results of a phenomenological study showing how HERMES data can be described with pure energyloss models.
Measuring Neutrino Oscillations with Nuclear Reactors
McKeown, R. D.
2007-10-26
Since the first direct observations of antineutrino events by Reines and Cowan in the 1950's, nuclear reactors have been an important tool in the study of neutrino properties. More recently, the study of neutrino oscillations has been a very active area of research. The pioneering observation of oscillations by the KamLAND experiment has provided crucial information on the neutrino mixing matrix. New experiments to study the remaining unknown mixing angle are currently under development. These recent studies and potential future developments will be discussed.
Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions
Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.
2009-03-10
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: ΔSºHAT = -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 ΔSºHAT 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 ΔSºHAT. Calorimetry on TEMPOH + tBu3PhO• gives ΔHºHAT = 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 |ΔSºHAT| for the metal complexes is vibrational entropy, ΔSºvib. The common assumption that ΔSºHAT ≈ 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 |ΔSºHAT| 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, ΔSºET, in aprotic solvents. ΔSºET and
NASA Astrophysics Data System (ADS)
Delahaye, Thibault; Nikitin, Andrei; Rey, Michaël; Szalay, Péter G.; Tyuterev, Vladimir G.
2014-09-01
In this paper we report a new ground state potential energy surface for ethylene (ethene) C2H4 obtained from extended ab initio calculations. The coupled-cluster approach with the perturbative inclusion of the connected triple excitations CCSD(T) and correlation consistent polarized valence basis set cc-pVQZ was employed for computations of electronic ground state energies. The fit of the surface included 82 542 nuclear configurations using sixth order expansion in curvilinear symmetry-adapted coordinates involving 2236 parameters. A good convergence for variationally computed vibrational levels of the C2H4 molecule was obtained with a RMS(Obs.-Calc.) deviation of 2.7 cm-1 for fundamental bands centers and 5.9 cm-1 for vibrational bands up to 7800 cm-1. Large scale vibrational and rotational calculations for 12C2H4, 13C2H4, and 12C2D4 isotopologues were performed using this new surface. Energy levels for J = 20 up to 6000 cm-1 are in a good agreement with observations. This represents a considerable improvement with respect to available global predictions of vibrational levels of 13C2H4 and 12C2D4 and rovibrational levels of 12C2H4.
NASA Astrophysics Data System (ADS)
Cieplicka-Oryńczak, N.; Szpak, B.; Leoni, S.; Fornal, B.; Bazzacco, D.; Blanc, A.; Bocchi, G.; Bottoni, S.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Ur, C.; Urban, W.
2016-07-01
The multipolarity of the main transition leading to the ground state in 210Bi was investigated using the angular correlations of γ rays. The analyzed γ -coincidence data were obtained from the 209Bi(n ,γ )210Bi experiment performed at Institut Laue-Langevin Grenoble at the PF1B cold-neutron facility. The EXILL (EXOGAM at the ILL) multidetector array, consisting of 16 high-purity germanium detectors, was used to detect γ transitions. The mixing ratio of the 320-keV γ ray was defined by minimizing a multivariable χΣ2 function constructed from the coefficients of angular correlation functions for seven pairs of strong transitions in 210Bi. As a result, the almost pure M 1 multipolarity of the 320-keV γ ray was obtained, with an E 2 admixture of less than 0.6% only (95% confidence limit). Based on this multipolarity the neutron-capture cross section leading to the ground state in 210Bi, that decays in turn to radiotoxic 210Po, was determined to be within the limits 21.3(9) and 21.5(9) mb. This result is important for nuclear reactor applications.
Bauer, Eric D; Booth, C H; Walter, M D; Kazhdan, D; Hu, Y - J; Lukens, Wayne; Maron, Laurent; Eisentein, Odile; Anderson, Richard
2009-01-01
Partial ytterbium f-orbital occupancy (i.e. intermediate valence) and open-shell singlet Draft 12/formation are established for a variety of bipyridine and diazabutadiene adducts to decamethylytterbocene, (C{sub 5}Me{sub 5}){sub 2}Yb or Cp*{sub 2}Yb. Data used to support this claim includes ytterbium valence measurements using Yb Lm-edge x-ray absorption near-edge structure (XANES) spectroscopy, magnetic susceptibility and Complete Active Space Self-Consistent Field (CASSCF) multi configurational calculations, as well as structural measurements compared to density-functional theory (DFT) calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground state wave function that has both an open-shell singlet f{sup 13} and a closed-shell singlet f{sup 14} component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the presence of intermediate valence and its lack of any significant temperature dependence. These results have implications for understanding chemical bonding not only in organolanthanide complexes, but also for organometallic chemistry in general, as well as understanding magnetic interactions in nanopartic1es and devices.
Extreme ground-state deformation of the N = Z nucleus 76Sr
NASA Astrophysics Data System (ADS)
Lemasson, A.; Iwasaki, H.; Morse, C.; Baugher, T.; Bazin, D.; Berryman, J.; Gade, A.; McDaniel, S.; Ratkiewicz, A.; Stroberg, S.; Weisshaar, D.; Wimmer, K.; Winkler, R.; Dewald, A.; Fransen, C.; Nichols, A.; Wadsworth, R.
2011-10-01
The shape of the atomic nucleus is determined by the interplay of macroscopic and microscopic effects within this quantum mechanical many-body system. Self-conjugate nuclei give an opportunity to study the role of np correlations in deformation and have attracted a great interest due to drastic shape evolution along the N = Z line. Strong ground-state deformation is expected to occur for N = Z nuclei above Z = 36 from the 2+ energy systematic as well as from theoretical predictions. Reduced transition strengths B(E2) can guide our understanding of the onset of collectivity along N = Z line. Here, we report on the first determination of B(E2; 2+ -->0+) for the N = Z = 38 nucleus 76Sr obtained from the measurement of the 2+ state lifetime using a line shape technique. 76Sr nuclei were produced at the NSCL in charge exchange reaction from fast secondary 76Rb beam. γ-rays emitted at the reaction target position were measured with the SeGA HPGe array in coincidence with reaction residues detected in the S800 spectrometer. Results will be discussed in the light of available data and theoretical predictions to provide insight into the evolution of shell structure and deformation in this region.
NASA Astrophysics Data System (ADS)
Chen, Zhan-Bin; Dong, Chen-Zhong; Xie, Lu-You; Jiang, Jun
2014-03-01
Electron impact excitation cross sections from the ground state and the lowest metastable state 5p56s J = 2 to the excited states of the 5p57p configuration of xenon are calculated systematically using the fully relativistic distorted wave method. Special attention is paid to the configuration interaction effects in the wave-function expansion of target states. The results are in good agreement with the recent experimental data by Jung et al. [Phys. Rev. A 80 (2009) 062708] over the measured energy range. These accurate theoretical results can be used in the modeling and diagnosis of plasmas containing xenon.
Rauscher, T.; Mohr, P.; Dillmann, I.; Plag, R.
2011-09-10
Modern models of s-process nucleosynthesis in stars require stellar reaction rates of high precision. Most neutron-capture cross-sections in the s-process have been measured, and for an increasing number of reactions the required precision is achieved. This does not necessarily mean, however, that the stellar rates are constrained equally well, because only the capture of the ground state of a target is measured in the laboratory. Captures of excited states can contribute considerably to stellar rates that are already at typical s-process temperatures. We show that the ground-state contribution X to a stellar rate is the relevant measure to identify reactions that are or could be well constrained by experiments and apply it to (n,{gamma}) reactions in the s-process. We further show that the maximum possible reduction in uncertainty of a rate via determination of the ground-state cross-section is given directly by X. An error analysis of X is presented, and it is found that X is a robust measure with mostly small uncertainties. Several specific examples (neutron capture of {sup 79}Se, {sup 95}Zr, {sup 121}Sn, {sup 187}Os, and {sup 193}Pt) are discussed in detail. The ground-state contributions for a set of 412 neutron-capture reactions around the s-process path are presented in a table. This allows identification of reactions that may be better constrained by experiments and that cannot be constrained solely by measuring ground-state cross-sections (and thus require supplementary studies). General trends and implications are discussed.
DNA and Chromatin Modification Networks Distinguish Stem Cell Pluripotent Ground States*
Song, Jing; Saha, Sudipto; Gokulrangan, Giridharan; Tesar, Paul J.; Ewing, Rob M.
2012-01-01
Pluripotent stem cells are capable of differentiating into all cell types of the body and therefore hold tremendous promise for regenerative medicine. Despite their widespread use in laboratories across the world, a detailed understanding of the molecular mechanisms that regulate the pluripotent state is currently lacking. Mouse embryonic (mESC) and epiblast (mEpiSC) stem cells are two closely related classes of pluripotent stem cells, derived from distinct embryonic tissues. Although both mESC and mEpiSC are pluripotent, these cell types show important differences in their properties suggesting distinct pluripotent ground states. To understand the molecular basis of pluripotency, we analyzed the nuclear proteomes of mESCs and mEpiSCs to identify protein networks that regulate their respective pluripotent states. Our study used label-free LC-MS/MS to identify and quantify 1597 proteins in embryonic and epiblast stem cell nuclei. Immunoblotting of a selected protein subset was used to confirm that key components of chromatin regulatory networks are differentially expressed in mESCs and mEpiSCs. Specifically, we identify differential expression of DNA methylation, ATP-dependent chromatin remodeling and nucleosome remodeling networks in mESC and mEpiSC nuclei. This study is the first comparative study of protein networks in cells representing the two distinct, pluripotent states, and points to the importance of DNA and chromatin modification processes in regulating pluripotency. In addition, by integrating our data with existing pluripotency networks, we provide detailed maps of protein networks that regulate pluripotency that will further both the fundamental understanding of pluripotency as well as efforts to reliably control the differentiation of these cells into functional cell fates. PMID:22822199
Probing commensurate ground states of Josephson vortex in layered superconductors.
Takahashi, Y; Luo, M-B; Nishizaki, T; Kobayashi, N; Hu, X
2014-04-01
Because of the commensurability condition between the vortex lattice constant determined by external magnetic field and the nano-scale layered structure, interlayer Josephson vortices (JVs) in high-Tc cuprate superconductors can take various configurations. We have simulated with Langevin scheme the in-plane flux-flow dynamics of JVs subject to point-like pinning centers. Oscillation in resistivity is found with the applied magnetic field, where the resistivity peaks occur around commensurate JV configurations. We have also measured the resistivity experimentally using single crystals of underdoped YBa2Cu3Oy with the anisotropy parameter gamma approximately equal to 50. A unique JV lattice has been detected for the first time.
Search for collisional exchange of ground-state atomic alignment between rubidium isotopes
NASA Astrophysics Data System (ADS)
Bahr, E. J.; Kimball, D. F. Jackson; Coste, B.; Rangwala, S. A.; Higbie, J. M.; Ledbetter, M. P.; Rochester, S. M.; Yashchuk, V. V.; Budker, D.
2009-05-01
The collisional transfer of pure atomic alignment (related to coherences between Zeeman sublevels with δM=2) between isotopes of rubidium is searched for using time-dependent magneto-optical rotation. Alignment-exchange collisions are fundamentally different than the commonly studied orientation-exchange collisions: for example, spin-exchange collisions preserve the net orientation in an atomic vapor (because of angular momentum conservation) but do not conserve alignment. Collisional transfer of alignment in alkali atoms has seldom been studied because the cross-sections are expected to be three to four orders of magnitude smaller than the nominal spin-exchange cross-sections. This is due to the fact that ground-state alkali atoms have electronic angular momentum J=1/2 and so the electronic state cannot support a δM=2 coherence. Thus collisional transfer of alignment is only possible because of hyperfine re-coupling during the collision. Implications of the measurement for searches for anomalous spin-dependent forces will be discussed.
Ground state of underdoped cuprates in vicinity of superconductor-to-insulator transition
Wu, Jie; Bollinger, Anthony T.; Sun, Yujie; Božović, Ivan
2016-08-15
When an insulating underdoped cuprate is doped beyond a critical concentration (xc), high-temperature superconductivity emerges. We have synthesized a series of La2–xSrxCuO4 (LSCO) samples using the combinatorial spread technique that allows us to traverse the superconductor-to-insulator transition (SIT) in extremely fine doping steps, Δx≈0.00008. We have measured the Hall resistivity (ρH) as a function of temperature down to 300 mK in magnetic fields up to 9 T. At very low temperatures, ρH shows an erratic behavior, jumps and fluctuations exceeding 100%, hysteresis, and memory effects, indicating that the insulating ground state is a charge-cluster glass (CCG). Furthermore, based on themore » phase diagram depicted in our experiment, we propose a unified picture to account for the anomalous electric transport in the vicinity of the SIT, suggesting that the CCG is in fact a disordered and glassy version of the charge density wave.« less
Chen, Dong; Porada, Jan H.; Hooper, Justin B.; Klittnick, Arthur; Shen, Yongqiang; Tuchband, Michael R.; Korblova, Eva; Bedrov, Dmitry; Walba, David M.; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.
2013-01-01
Freeze-fracture transmission electron microscopy study of the nanoscale structure of the so-called “twist–bend” nematic phase of the cyanobiphenyl (CB) dimer molecule CB(CH2)7CB reveals stripe-textured fracture planes that indicate fluid layers periodically arrayed in the bulk with a spacing of d ∼ 8.3 nm. Fluidity and a rigorously maintained spacing result in long-range-ordered 3D focal conic domains. Absence of a lamellar X-ray reflection at wavevector q ∼ 2π/d or its harmonics in synchrotron-based scattering experiments indicates that this periodic structure is achieved with no detectable associated modulation of the electron density, and thus has nematic rather than smectic molecular ordering. A search for periodic ordering with d ∼ in CB(CH2)7CB using atomistic molecular dynamic computer simulation yields an equilibrium heliconical ground state, exhibiting nematic twist and bend, of the sort first proposed by Meyer, and envisioned in systems of bent molecules by Dozov and Memmer. We measure the director cone angle to be θTB ∼ 25° and the full pitch of the director helix to be pTB ∼ 8.3 nm, a very small value indicating the strong coupling of molecular bend to director bend. PMID:24006362
Ground-state properties of linear-exchange quantum spin models
NASA Astrophysics Data System (ADS)
Danu, Bimla; Kumar, Brijesh; Pai, Ramesh V.
2012-10-01
We study a class of one-dimensional antiferromagnetic quantum spin-1/2 models using DMRG. The exchange interaction in these models decreases linearly with the separation between the spins, Jij = R - |i - j| for |i - j| < R, where R is a positive integer ⩾2. For |i - j| ⩾ R, the interaction is zero. It is known that all the odd-R models have the same exact dimer ground state as the Majumdar-Ghosh (MG) model. In fact, R = 3 is the MG model. However, for an even R, the exact ground state is not known in general, except for R = 2 (the integrable nearest-neighbor Heisenberg chain) and the asymptotic limit of R in which the MG dimer state emerges as the exact ground state. Therefore, we numerically study the ground-state properties of the finite even-R ≠ 2 models, particularly for R = 4, 6 and 8. We find that, unlike R = 2, the higher even-R models are spin-gapped, and exhibit robust dimer order of the MG type in the ground state. The spin-spin correlations decay rapidly to zero, albeit showing weak periodic revivals.
Exact ground states and topological order in interacting Kitaev/Majorana chains
NASA Astrophysics Data System (ADS)
Katsura, Hosho; Schuricht, Dirk; Takahashi, Masahiro
2015-09-01
We study a system of interacting spinless fermions in one dimension that, in the absence of interactions, reduces to the Kitaev chain [Kitaev, Phys. Usp. 44, 131 (2001), 10.1070/1063-7869/44/10S/S29]. In the noninteracting case, a signal of topological order appears as zero-energy modes localized near the edges. We show that the exact ground states can be obtained analytically even in the presence of nearest-neighbor repulsive interactions when the on-site (chemical) potential is tuned to a particular function of the other parameters. As with the noninteracting case, the obtained ground states are twofold degenerate and differ in fermionic parity. We prove the uniqueness of the obtained ground states and show that they can be continuously deformed to the ground states of the noninteracting Kitaev chain without gap closing. We also demonstrate explicitly that there exists a set of operators each of which maps one of the ground states to the other with opposite fermionic parity. These operators can be thought of as an interacting generalization of Majorana edge zero modes.
Precision molecular spectroscopy for ground state transfer of molecular quantum gases.
Danzl, Johann G; Mark, Manfred J; Haller, Elmar; Gustavsson, Mattias; Bouloufa, Nadia; Dulieu, Olivier; Ritsch, Helmut; Hart, Russell; Nägerl, Hanns-Christoph
2009-01-01
One possibility for the creation of ultracold, high phase space density quantum gases of molecules in the rovibronic ground state relies on first associating weakly-bound molecules from quantum-degenerate atomic gases on a Feshbach resonance and then transferring the molecules via several steps of coherent two-photon stimulated Raman adiabatic passage (STIRAP) into the rovibronic ground state. Here, in ultracold samples of Cs2 Feshbach molecules produced out of ultracold samples of Cs atoms, we observe several optical transitions to deeply-bound rovibrational levels of the excited 0(u)+ molecular potentials with high resolution. At least one of these transitions, although rather weak, allows efficient STIRAP transfer into the deeply-bound vibrational level (see text for symbols)v = 73 > of the singlet X1 sigma(g)+ ground state potential, as recently demonstrated (J. G. Danzl, E. Haller, M. Gustavsson, M. J. Mark, R. Hart, N. Bouloufa, O. Dulieu, H. Ritsch, and H.-C. Nägerl, Science, 2008, 321, 1062). From this level, the rovibrational ground state (see text for symbols)v = 0, J = 0 > can be reached with one more transfer step. In total, our results show that coherent ground state transfer for Cs2 is possible using a maximum of two successive two-photon STIRAP processes or one single four-photon STIRAP process. PMID:20151549
Interactions leading to disordered ground states and unusual low-temperature behavior.
Batten, Robert D; Stillinger, Frank H; Torquato, Salvatore
2009-09-01
We have shown that any pair potential function v(r) possessing a Fourier transform V(k) that is positive and has compact support at some finite wave number K yields classical disordered ground states for a broad density range [R. D. Batten, F. H. Stillinger, and S. Torquato, J. Appl. Phys. 104, 033504 (2008)]. By tuning a constraint parameter chi (defined in the text), the ground states can traverse varying degrees of local order from fully disordered to crystalline ground states. Here, we show that in two dimensions, the " k -space overlap potential," where V(k) is proportional to the intersection area between two disks of diameter K whose centers are separated by k , yields anomalous low-temperature behavior, which we attribute to the topography of the underlying energy landscape. At T=0 , for the range of densities considered, we show that there is continuous energy degeneracy among Bravais-lattice configurations. The shear elastic constant of ground-state Bravais-lattice configurations vanishes. In the harmonic regime, a significant fraction of the normal modes for both amorphous and Bravais-lattice ground states have vanishing frequencies, indicating the lack of an internal restoring force. Using molecular-dynamics simulations, we observe negative thermal-expansion behavior at low temperatures, where upon heating at constant pressure, the system goes through a density maximum. For all temperatures, isothermal compression reduces the local structure of the system unlike typical single-component systems. PMID:19905060
Lifetime Measurements of Tagged Exotic- and Unbound Nuclear States
Cullen, D. M.
2011-11-30
A new Differential Plunger device for measuring pico-second lifetimes of Unbound Nuclear States (DPUNS) is being built at The University of Manchester. DPUNS has been designed to work with alpha-, beta- and isomer-tagging methods using the existing JUROGAM II--RITU--GREAT infrastructure at the University of Jyvaskyla, Finland. The importance of proton emission from nuclei is that it provides valuable nuclear-structure information as direct input to nuclear models beyond the drip line. New experimental data beyond the drip line can provide new extensions to these models especially with the possible coupling of weakly bound and unbound states to the continuum. The results of the first experiments to measure lifetimes of unbound nuclear states with this method was discussed along with possible future experiments which can be addressed with DPUNS using proton-, isomer- and alpha-tagging.
Measurements of nuclear spin dynamics by spin-noise spectroscopy
Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S.; Kavokin, K. V.; Glazov, M. M.; Vladimirova, M.; Scalbert, D.; Cronenberger, S.; Lemaître, A.; Bloch, J.
2015-06-15
We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.
Phase Space Diagnostics of Trapped Atoms By Magnetic Ground-State Manipulation
NASA Astrophysics Data System (ADS)
Cahn, S. B.; Kumarakrishnan, A.; Shim, U.; Sleator, T.
1997-04-01
The in-situ measurement of the phase space distribution of atoms in a trap is important in the study of both ordinary and Bose-condensed matter. The current techniques for measuring the density distribution involve imaging the light emitted by atoms in the trap, time-of-flight measurement of the atoms as they fall through a sheet of light(C.D. Wallace, et al, JOSA B,11),703 (1994), resonant absorption imaging of the cloud(J.R. Ensher, et al, PRL 77), 4984 (1996), or off-resonant dispersive imaging. The first two techniques are in general use for imaging magneto-optical traps (MOTs) and the second two for Bose condensates. Velocity information is obtained indirectly by recording the expansion of the trap at different times following shut-off. By exploiting the magnetic field dependence of ground-state magnetic sublevel coherences, we have employed two techniques, MGE and MGFID(B. Dubetsky and P.R. Berman, Appl. Phys. B, 59), 147 (1994), to obtain atomic spatial information. This variant of atomic beam magnetic imaging(J.E. Thomas and L.J. Wang, Physics Reports 262), 311-366 (1995) also yields correlated position-velocity information by appropriate orientation of the applied magnetic field, as the detuning of the atom depends on both its position and velocity. Initial studies have given the velocity distribution and size of the MOT, and future experiments to measure correlations are proposed.
Determination of parameters of a nuclear reactor through noise measurements
Cohn, C.E.
1975-07-15
A method of measuring parameters of a nuclear reactor by noise measurements is described. Noise signals are developed by the detectors placed in the reactor core. The polarity coincidence between the noise signals is used to develop quantities from which various parameters of the reactor can be calculated. (auth)
A dc amplifier for nuclear particle measurement
NASA Technical Reports Server (NTRS)
Macnee, A. B.; Masnari, N. A.
1978-01-01
A monolithic preamplifier-postamplifier combination has been developed for use with solid state particle detectors. The direct coupled amplifiers employ interdigitated n-channel JFET's, diodes, and diffused resistors. The circuits developed demonstrate the feasibility of matching the performance of existing discrete component designs. The fabrication procedures for the monolithic amplifier fabrication are presented and the results of measurements on a limited number of sample amplifiers are given.
High resolution image measurements of nuclear tracks
NASA Technical Reports Server (NTRS)
Shirk, E. K.; Price, P. B.
1980-01-01
The striking clarity and high contrast of the mouths of tracks etched in CR-39 plastic detectors allow automatic measurement of track parameters to be made with simple image-recognition equipment. Using a commercially available Vidicon camera system with a microprocessor-controlled digitizer, resolution for normally incident C-12 and N-14 ions at 32 MeV/amu equivalent to a 14sigma separation of adjacent charges was demonstrated.
Learning Approach on the Ground State Energy Calculation of Helium Atom
Shah, Syed Naseem Hussain
2010-07-28
This research investigated the role of learning approach on the ground state energy calculation of Helium atom in improving the concepts of science teachers at university level. As the exact solution of several particles is not possible here we used approximation methods. Using this method one can understand easily the calculation of ground state energy of any given function. Variation Method is one of the most useful approximation methods in estimating the energy eigen values of the ground state and the first few excited states of a system, which we only have a qualitative idea about the wave function.The objective of this approach is to introduce and involve university teacher in new research, to improve their class room practices and to enable teachers to foster critical thinking in students.
Ordering and Magnetism in Fe-Co: Dense Sequence of Ground-State Structures
NASA Astrophysics Data System (ADS)
Drautz, Ralf; Díaz-Ortiz, Alejandro; Fähnle, Manfred; Dosch, Helmut
2004-08-01
We discover that Fe-Co alloys develop a series of ordered ground-state structures in addition to the known CsCl-type structure. This new set of structures is found from a combinatorial ground-state search of 1.5×1010 bcc-based structures. The energies of the searched bcc structures are constructed with the cluster expansion method from few first-principles calculations of ordered Fe-Co structures. The set of new ground-state structures is explained from the decay behavior of the cluster expansion coefficients which allows us to identify a simple geometric motif common to all structures. The appearance of these FeCo superstructures offers a broader view of the ordering reactions in bipartite-lattice based binary alloys.
The Network Source Location Problem: Ground State Energy, Entropy and Effects of Freezing
NASA Astrophysics Data System (ADS)
Huang, Haiping; Raymond, Jack; Wong, K. Y. Michael
2014-07-01
Ground state entropy of the network source location problem is evaluated at both the replica symmetric level and one-step replica symmetry breaking level using the entropic cavity method. The regime that is a focus of this study, is closely related to the vertex cover problem with randomly quenched covered nodes. The resulting entropic message passing inspired decimation and reinforcement algorithms are used to identify the optimal location of sources in single instances of transportation networks. The conventional belief propagation without taking the entropic effect into account is also compared. We find that in the glassy phase the entropic message passing inspired decimation yields a lower ground state energy compared to the belief propagation without taking the entropic effect. Using the extremal optimization algorithm, we study the ground state energy and the fraction of frozen hubs, and extend the algorithm to collect statistics of the entropy. The theoretical results are compared with the extremal optimization results.
Ground State Properties of the 1/2 Flux Harper Hamiltonian
NASA Astrophysics Data System (ADS)
Kennedy, Colin; Burton, William Cody; Chung, Woo Chang; Ketterle, Wolfgang
2015-05-01
The Harper Hamiltonian describes the motion of charged particles in an applied magnetic field - the spectrum of which exhibits the famed Hofstadter's butterfly. Recent advances in driven optical lattices have made great strides in simulating nontrivial Hamiltonians, such as the Harper model, in the time-averaged sense. We report on the realization of the ground state of bosons in the Harper Hamiltonian for 1/2 flux per plaquette utilizing a tilted two-dimensional lattice with laser assisted tunneling. We detail progress in studying various ground state properties of the 1/2 flux Harper Hamiltonian including ground state degeneracies, gauge-dependent observables, effects of micromotion, adiabatic loading schemes, and emergence and decay of coherence. Additionally, we describe prospects for flux rectification using a period-tripled superlattice and generalizations to three dimensions. MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, Department of Physics, Massachusetts Institute of Technology.
Learning Approach on the Ground State Energy Calculation of Helium Atom
NASA Astrophysics Data System (ADS)
Shah, Syed Naseem Hussain
2010-07-01
This research investigated the role of learning approach on the ground state energy calculation of Helium atom in improving the concepts of science teachers at university level. As the exact solution of several particles is not possible here we used approximation methods. Using this method one can understand easily the calculation of ground state energy of any given function. Variation Method is one of the most useful approximation methods in estimating the energy eigen values of the ground state and the first few excited states of a system, which we only have a qualitative idea about the wave function. The objective of this approach is to introduce and involve university teacher in new research, to improve their class room practices and to enable teachers to foster critical thinking in students.
Formation of antihydrogen in the ground state and {ital n}=2 level
Tripathi, S.; Biswas, R.; Sinha, C.
1995-05-01
The cross sections of antihydrogen formation in the ground state and {ital n}=2 level by the impact of antiprotons on the ground state of positronium have been calculated under the framework of the eikonal approximation for incident energy of 30--1000 keV. The excited-state capture cross sections are quite appreciable and are even larger than the ground-state cross sections for impact energies {le}75 keV. The total eikonal cross sections ({sigma}={sigma}{sub 1{ital s}}+{sigma}{sub 2{ital s}}+{sigma}{sub 2{ital p}}) are always higher than the corresponding first-order Born approximation cross section throughout the present energy span.
Tree based machine learning framework for predicting ground state energies of molecules
NASA Astrophysics Data System (ADS)
Himmetoglu, Burak
2016-10-01
We present an application of the boosted regression tree algorithm for predicting ground state energies of molecules made up of C, H, N, O, P, and S (CHNOPS). The PubChem chemical compound database has been incorporated to construct a dataset of 16 242 molecules, whose electronic ground state energies have been computed using density functional theory. This dataset is used to train the boosted regression tree algorithm, which allows a computationally efficient and accurate prediction of molecular ground state energies. Predictions from boosted regression trees are compared with neural network regression, a widely used method in the literature, and shown to be more accurate with significantly reduced computational cost. The performance of the regression model trained using the CHNOPS set is also tested on a set of distinct molecules that contain additional Cl and Si atoms. It is shown that the learning algorithms lead to a rich and diverse possibility of applications in molecular discovery and materials informatics.
2013-01-01
We investigate the nature of the S* excited state in carotenoids by performing a series of pump–probe experiments with sub-20 fs time resolution on spirilloxanthin in a polymethyl-methacrylate matrix varying the sample temperature. Following photoexcitation, we observe sub-200 fs internal conversion of the bright S2 state into the lower-lying S1 and S* states, which in turn relax to the ground state on a picosecond time scale. Upon cooling down the sample to 77 K, we observe a systematic decrease of the S*/S1 ratio. This result can be explained by assuming two thermally populated ground state isomers. The higher lying one generates the S* state, which can then be effectively frozen out by cooling. These findings are supported by quantum chemical modeling and provide strong evidence for the existence and importance of ground state isomers in the photophysics of carotenoids. PMID:23577754
Trajectory approach to the Schrödinger-Langevin equation with linear dissipation for ground states
NASA Astrophysics Data System (ADS)
Chou, Chia-Chun
2015-11-01
The Schrödinger-Langevin equation with linear dissipation is integrated by propagating an ensemble of Bohmian trajectories for the ground state of quantum systems. Substituting the wave function expressed in terms of the complex action into the Schrödinger-Langevin equation yields the complex quantum Hamilton-Jacobi equation with linear dissipation. We transform this equation into the arbitrary Lagrangian-Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation is simultaneously integrated with the trajectory guidance equation. Then, the computational method is applied to the harmonic oscillator, the double well potential, and the ground vibrational state of methyl iodide. The excellent agreement between the computational and the exact results for the ground state energies and wave functions shows that this study provides a synthetic trajectory approach to the ground state of quantum systems.
Ground state and magnetic susceptibility of intermediate-valence Tm impurities
NASA Astrophysics Data System (ADS)
Allub, R.; Aligia, A. A.
1995-09-01
We consider the appropriate generalization of the Anderson model for a Tm impurity in a cubic crystal field. In the 4f12 configuration we include only the two multiplets of lowest energy: a single Γ1 and a triplet Γ4. Similarly we include only the doublet ground state of the 4f13 configuration, and (to make our numerical method feasible) we assume that the conduction-electron partial waves with symmetry Γ8 can be neglected. We study the model using Wilson's renormalization group. The resulting ground state is a singlet or a doublet depending mainly of the relative strength of the hybridization of the 4f13 doublet with both 4f12 states. A doublet ground state is consistent with the experimental evidence.
Antibonding hole ground state in InAs quantum dot molecules
Planelles, Josep
2015-01-22
Using four-band k⋅p Hamiltonians, we study how strain and position-dependent effective masses influence hole tunneling in vertically coupled InAs/GaAs quantum dots. Strain reduces the tunneling and hence the critical interdot distance required for the ground state to change from bonding to antibonding. Variable mass has the opposite effect and a rough compensation leaves little affected the critical bonding-to-antibonding ground state crossover. An alternative implementation of the magnetic field in the envelope function Hamiltonian is given which retrieves the experimental denial of possible after growth reversible magnetically induced bonding-to-antibonding ground state transition, predicted by the widely used Luttinger-Kohn Hamiltonian.
Ground-state features in the THz spectra of molecular clusters of β-HMX.
Huang, Lulu; Shabaev, Andrew; Lambrakos, Samuel G; Massa, Lou
2012-10-01
We present calculations of absorption spectra arising from molecular vibrations at THz frequencies for molecular clusters of the explosive HMX using density functional theory (DFT). The features of these spectra can be shown to follow from the coupling of vibrational modes. In particular, the coupling among ground-state vibrational modes provides a reasonable molecular-level interpretation of spectral features associated with the vibrational modes of molecular clusters. THz excitation from the ground state is associated with frequencies that characteristically perturb molecular electronic states, in contrast to frequencies, which are usually substantially above the mid-infrared (mid-IR) range, that can induce appreciable electronic-state transition. Owing to this characteristic of THz excitation, one is able to make a direct association between local oscillations about ground-state minima of molecules, either isolated or comprising a cluster, and THz absorption spectra. The DFT software program GAUSSIAN was used for the calculations of the absorption spectra presented here.
Fragile singlet ground-state magnetism in the pyrochlore osmates R2Os2O7 ( R=Y and Ho)
Zhao, Z. Y.; Calder, S.; Aczel, A. A.; McGuire, M. A.; Sales, B. C.; Mandrus, D. G.; Chen, G.; Trivedi, N.; Zhou, H. D.; Yan, J. -Q.
2016-04-25
The singlet ground state magnetism in pyrochlore osmates Y2Os2O7 and Ho2Os2O7 is studied by DC and AC susceptibility, specific heat, and neutron powder di raction measurements. Despite the expected non-magnetic singlet in the strong spin-orbit coupling (SOC) limit for Os4+ (5d4), Y2Os2O7 exhibits a spin-glass (SG) ground state below 4 K with weak magnetism, suggesting possible proximity to a quantum phase transition between the non-magnetic state in the strong SOC limit and the magnetic state in the strong superexchange limit. Ho2Os2O7 has the same structural distortion as occurs in Y2Os2O7. However, the Os sublattice in Ho2Os2O7 shows long- range magneticmore » ordering below 36 K. We find that the sharp difference of the magnetic ground state between Y2Os2O7 and Ho2Os2O7 signals the singlet ground state magnetism in R2 Os2 O7 is fragile and can be disturbed by the weak 4f—5d interactions.« less
From ground state to fission fragments: A complex, multi-dimensional multi-path problem
Moeller, P.; Nix, J.R.; Swiatecki, W.J.
1992-03-01
Experimental results on the fission properties of nuclei close to {sup 264}Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus {sup 258}Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic-energy distribution peaked at about 235 MeV whereas {sup 256}Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic-energy distribution peaked at about 200 MeV. Qualitatively, these sudden changes have been postulated to be due to the emergence of fragment shells in symmetric-fission products close to {sup 132}Sn. Here we present a quantitative calculation that shows where high-kinetic-energy symmetric fusion occurs and why it is associated with a sudden and large decrease in fission half-lives. We base our study on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. We use the three-quadratic-surface parameterization to generate the shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. Since these shapes are thought to correspond to the scission shapes for the high-kinetic-energy events it is of crucial importance that a continuous sequence of shapes leading from the nuclear ground state to these configurations can be studied within the framework of the model. We present the results of the calculations in terms of potential-energy surfaces and fission half-lives for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. They clearly show the appearance of a second fission valley, which leads to scission configurations close to tow touching spheres, for fissioning systems in the vicinity of {sup 264}Fm.
From ground state to fission fragments: A complex, multi-dimensional multi-path problem
Moeller, P. ); Nix, J.R. ); Swiatecki, W.J. )
1992-01-01
Experimental results on the fission properties of nuclei close to {sup 264}Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus {sup 258}Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic-energy distribution peaked at about 235 MeV whereas {sup 256}Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic-energy distribution peaked at about 200 MeV. Qualitatively, these sudden changes have been postulated to be due to the emergence of fragment shells in symmetric-fission products close to {sup 132}Sn. Here we present a quantitative calculation that shows where high-kinetic-energy symmetric fusion occurs and why it is associated with a sudden and large decrease in fission half-lives. We base our study on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. We use the three-quadratic-surface parameterization to generate the shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. Since these shapes are thought to correspond to the scission shapes for the high-kinetic-energy events it is of crucial importance that a continuous sequence of shapes leading from the nuclear ground state to these configurations can be studied within the framework of the model. We present the results of the calculations in terms of potential-energy surfaces and fission half-lives for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. They clearly show the appearance of a second fission valley, which leads to scission configurations close to tow touching spheres, for fissioning systems in the vicinity of {sup 264}Fm.
Ground state of Ho atoms on Pt(111) metal surfaces: Implications for magnetism
NASA Astrophysics Data System (ADS)
Karbowiak, M.; Rudowicz, C.
2016-05-01
We investigated the ground state of Ho atoms adsorbed on the Pt(111) surface, for which conflicting results exist. The density functional theory (DFT) calculations yielded the Ho ground state as | Jz=±8 > . Interpretation of x-ray absorption spectroscopy and x-ray magnetic circular dichroism spectra and the magnetization curves indicated the ground state as | Jz=±6 > . Superposition model is employed to predict the crystal-field (CF) parameters based on the structural data for the system Ho/Pt(111) obtained from the DFT modeling. Simultaneous diagonalization of the free-ion (HFI) and the trigonal CF Hamiltonian (HCF) within the whole configuration 4 f10 of H o3 + ion was performed. The role of the trigonal CF terms, neglected in the pure uniaxial CF model used previously for interpretation of experimental spectra, is found significant, whereas the sixth-rank CF terms may be neglected in agreement with the DFT predictions. The results provide substantial support for the experimental designation of the | Jz=±6 > ground state, albeit with subtle difference due to admixture of other | Jz> states, but run against the DFT-based designation of the | Jz=±8 > ground state. A subtle splitting of the ground energy level with the state (predominantly), | Jz=±6 > is predicted. This paper provides better insight into the single-ion magnetic behavior of the Ho/Pt(111) system by helping to resolve the controversy concerning the Ho ground state. Experimental techniques with greater resolution powers are suggested for direct confirmation of this splitting and C3 v symmetry experienced by the Ho atom.
Electronic ground state conformers of β-carotene and their role in ultrafast spectroscopy
NASA Astrophysics Data System (ADS)
Lukeš, Vladimír; Christensson, Niklas; Milota, Franz; Kauffmann, Harald F.; Hauer, Jürgen
2011-04-01
We present a study of ground state conformations of all-trans β-carotene using Density Functional Theory (DFT). To reproduce the carotenoid spectrum, the DFT approach was combined with the Multi-Reference Configuration Interaction. Our results show that the global minimum corresponds to an asymmetric structure where the β-ionone rings are twisted with respect to the polyene chain. The next higher-lying conformer is more s-cis symmetric and is populated at room temperature (30%). We discuss the relation of these conformers to S∗ and show that our model readily explains the temperature dependence and the narrowing of the ground state bleach at long population times.
Meron ground state of Rashba spin-orbit-coupled dipolar bosons.
Wilson, Ryan M; Anderson, Brandon M; Clark, Charles W
2013-11-01
We study the effects of dipolar interactions on a Bose-Einstein condensate with synthetically generated Rashba spin-orbit coupling. The dipolar interaction we consider includes terms that couple spin and orbital angular momentum in a way perfectly congruent with the single-particle Rashba coupling. We show that this internal spin-orbit coupling plays a crucial role in the rich ground-state phase diagram of the trapped condensate. In particular, we predict the emergence of a thermodynamically stable ground state with a meron spin configuration.
Investigation of the ground state of the anisotropic extended Hubbard chain at weak coupling
NASA Astrophysics Data System (ADS)
Ding, Hanqin; Zhang, Jun
2016-09-01
We study a one-dimensional anisotropic extended Hubbard model, where the inter-site density (V) and exchange (J) interactions are spin-dependent. Use of bosonization and renormalization helps investigate phase diagram. At half filling, the ground state characterizes insulating phases. The spin-dependent repulsion leads to a bond-spin-density-wave (BSDW) phase. The antiferromagnetic exchange enhances the bond-order-wave (BOW) phase while weakens the charge-density-wave (CDW) phase. When J > 4 V, the BSDW and CDW phases disappear. Away from half filling, the ground state exhibits superconducting behavior. The anisotropic interactions have an important effect on the phase structures.
Traces of Lorentz symmetry breaking in a hydrogen atom at ground state
NASA Astrophysics Data System (ADS)
Borges, L. H. C.; Barone, F. A.
2016-02-01
Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schrödinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector.
On Asymptotic Stability in Energy Space of Ground States for Nonlinear Schrödinger Equations
NASA Astrophysics Data System (ADS)
Cuccagna, Scipio; Mizumachi, Tetsu
2008-11-01
We consider nonlinear Schrödinger equations iu_t +Δ u +β (|u|^2)u=0 , text{for} (t,x)in mathbb{R}× mathbb{R}^d, where d ≥ 3 and β is smooth. We prove that symmetric finite energy solutions close to orbitally stable ground states converge to a sum of a ground state and a dispersive wave as t → ∞ assuming the so called the Fermi Golden Rule (FGR) hypothesis. We improve the “sign condition” required in a recent paper by Gang Zhou and I.M.Sigal.
Ground-state and finite-temperature energetics and topologies of germanium microclusters
Antonio, G.A.; Feuston, B.P.; Kalia, R.K.; Vashishta, P.
1988-06-15
We have investigated the ground-state and finite-temperature properties of Ge microclusters (N = 2 to 14) using molecular dynamics (MD) simulation along with the method of steepest-descent quench (SDQ). The interaction potential adopted is the three-body Stillinger--Weber potential as modified by Ding and Andersen for amorphous Ge. Our results indicate that the experimentally observed greater stability of certain cluster sizes can be explained by the topology and energetics of the clusters at finite temperature rather than by the binding energies of the ground-state structures.
Optical pumping of metastable NH radicals into the paramagnetic ground state
Meerakker, Sebastiaan Y.T. van de; Mosk, Allard P.; Jongma, Rienk T.; Sartakov, Boris G.; Meijer, Gerard
2003-09-01
We here report on the optical pumping of both {sup 14}NH and {sup 15}NH radicals from the metastable a {sup 1}{delta} state into the X {sup 3}{sigma}{sup -} ground state in a molecular beam experiment. By inducing the hitherto unobserved spin-forbidden A {sup 3}{pi} <- a {sup 1}{delta} transition, followed by spontaneous emission to the X {sup 3}{sigma}{sup -} state, a unidirectional pathway for population transfer from the metastable state into the electronic ground state is obtained. The optical pumping scheme demonstrated here opens up the possibility to accumulate NH radicals in a magnetic or optical trap.
Ground State of Magnetic Dipoles on a Two-Dimensional Lattice: Structural Phases in Complex Plasmas
Feldmann, J. D.; Kalman, G. J.; Hartmann, P.; Rosenberg, M.
2008-02-29
We study analytically and by molecular dynamics simulations the ground state configuration of a system of magnetic dipoles fixed on a two-dimensional lattice. We find different phases, in close agreement with previous results. Building on this result and on the minimum energy requirement we determine the equilibrium lattice configuration, the magnetic order (ferromagnetic versus antiferromagnetic), and the magnetic polarization direction of a system of charged mesoscopic particles with magnetic dipole moments, in the domain where the strong electrostatic coupling leads to a crystalline ground state. Orders of magnitudes of the parameters of the system relevant to possible future dusty plasma experiments are discussed.
Ground states of spin-2 condensates in an external magnetic field
Zheng, G.-P.; Tong, Y.-G.; Wang, F.-L.
2010-06-15
The possible ground states of spin-2 Bose-Einstein condensates in an external magnetic field are obtained analytically and classified systematically according to the population of the condensed atoms at the hyperfine sublevels. It is shown that the atoms can populate simultaneously at four hyperfine sublevels in a weak magnetic field with only the linear Zeeman energy, in contrast to that in a stronger magnetic field with the quadratic Zeeman energy, where condensed atoms can at most populate at three hyperfine sublevels in the ground states. Any spin configuration we obtained will give a closed subspace in the order parameter space of the condensates.
Ground-state properties of third-row elements with nonlocal density functionals
Bagno, P.; Jepsen, O.; Gunnarsson, O.
1989-07-15
The cohesive energy, the lattice parameter, and the bulk modulus of third-row elements are calculated using the Langreth-Mehl-Hu (LMH), the Perdew-Wang (PW), and the gradient expansion functionals. The PW functional is found to give somewhat better results than the LMH functional and both are found to typically remove half the errors in the local-spin-density (LSD) approximation, while the gradient expansion gives worse results than the local-density approximation. For Fe both the LMH and PW functionals correctly predict a ferromagnetic bcc ground state, while the LSD approximation and the gradient expansion predict a nonmagnetic fcc ground state.
Dimerized ground state in the one-dimensional spin-1 boson Hubbard model
Apaja, Vesa; Syljuaasen, Olav F.
2006-09-15
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.
Preparing Ground States of Quantum Many-Body Systems on a Quantum Computer
Poulin, David; Wocjan, Pawel
2009-04-03
Preparing the ground state of a system of interacting classical particles is an NP-hard problem. Thus, there is in general no better algorithm to solve this problem than exhaustively going through all N configurations of the system to determine the one with lowest energy, requiring a running time proportional to N. A quantum computer, if it could be built, could solve this problem in time {radical}(N). Here, we present a powerful extension of this result to the case of interacting quantum particles, demonstrating that a quantum computer can prepare the ground state of a quantum system as efficiently as it does for classical systems.
Measurements of nitric oxide after a nuclear burst
NASA Technical Reports Server (NTRS)
Mcghan, M.; Shaw, A.; Megill, L. R.; Sedlacek, W.; Guthals, P. R.; Fowler, M. M.
1981-01-01
Measurements of ozone and nitric oxide in a nuclear cloud 7 days after the explosion are reported. No measurable increase above ambient density of either ozone or nitric oxide was found. Results from a chemistry model of the cloud do not agree with the measurement unless 'nonstandard' assumptions are made with regard to the operating chemical processes. A number of possible explanations of the results are discussed.
Recent measurements for hadrontherapy and space radiation: nuclear physics.
Miller, J
2001-01-01
The particles and energies commonly used for hadron therapy overlap the low end of the charge and energy range of greatest interest for space radiation applications, Z=1-26 and approximately 100-1000 MeV/nucleon. It has been known for some time that the nuclear interactions of the incident ions must be taken into account both in treatment planning and in understanding and addressing the effects of galactic cosmic ray ions on humans in space. Until relatively recently, most of the studies of nuclear fragmentation and transport in matter were driven by the interests of the nuclear physics and later, the hadron therapy communities. However, the experimental and theoretical methods and the accelerator facilities developed for use in heavy ion nuclear physics are directly applicable to radiotherapy and space radiation studies. I will briefly review relevant data taken recently at various accelerators, and discuss the implications of the measurements for radiotherapy, radiobiology and space radiation research.
Recent measurements for hadrontherapy and space radiation: nuclear physics
NASA Technical Reports Server (NTRS)
Miller, J.
2001-01-01
The particles and energies commonly used for hadron therapy overlap the low end of the charge and energy range of greatest interest for space radiation applications, Z=1-26 and approximately 100-1000 MeV/nucleon. It has been known for some time that the nuclear interactions of the incident ions must be taken into account both in treatment planning and in understanding and addressing the effects of galactic cosmic ray ions on humans in space. Until relatively recently, most of the studies of nuclear fragmentation and transport in matter were driven by the interests of the nuclear physics and later, the hadron therapy communities. However, the experimental and theoretical methods and the accelerator facilities developed for use in heavy ion nuclear physics are directly applicable to radiotherapy and space radiation studies. I will briefly review relevant data taken recently at various accelerators, and discuss the implications of the measurements for radiotherapy, radiobiology and space radiation research.
Federal Register 2010, 2011, 2012, 2013, 2014
2013-07-29
... COMMISSION Compensatory and Alternative Regulatory Measures for Nuclear Power Plant Fire Protection (CARMEN-FIRE) AGENCY: Nuclear Regulatory Commission. ACTION: Notice of availability; request for public comment.../CR-7135, ``Compensatory and Alternative Regulatory Measures for Nuclear Power Plant Fire...
Evolution of superconducting gap and metallic ground state in cuprates from transport
NASA Astrophysics Data System (ADS)
Taillefer, Louis
2006-03-01
We report on fundamental characteristics of the ground state of cuprates in the limit of T=0, for both normal and superconducting states, obtained from transport measurements on high-quality single crystals of YBCO and Tl-2201, as a function of hole concentration. The superconducting gap is extracted from thermal conductivity; it is found to scale with the superconducting transition temperature throughout the overdoped regime, with a gap-to-Tc ratio of 5 [1]. The normal state is accessed by suppressing superconductivity with magnetic fields up to 60 T and is characterized by the limiting behavior of its electrical resistivity; while carrier localization is observed in YBCO at low temperature for carrier concentrations p below 0.1 hole/planar Cu, at p=0.1 and above the material remains highly metallic down to T=0 [2]. This shows that the non-superconducting state of underdoped cuprates, deep in the pseudogap phase, is remarkably similar to that of strongly overdoped cuprates, e.g. at p=0.3. We compare these results with similar measurements on other cuprates and discuss their implication for our understanding of the cuprate phase diagram. [1] In collaboration with: D.G. Hawthorn, S.Y. Li, M. Sutherland, E. Boaknin, R.W. Hill, C. Proust, F. Ronning, M. Tanatar, J. Paglione, D. Peets, R. Liang, D.A. Bonn, W.N. Hardy, and N.N. Kolesnikov. [2] In collaboration with: C. Proust, M. Sutherland, N. Doiron- Leyraud, S.Y. Li, R. Liang, D.A. Bonn, W.N. Hardy, N.E. Hussey, S. Adachi, S. Tajima, J. Levallois, and M. Narbone.
Electronic excitation of ground state atoms by collision with heavy gas particles
NASA Technical Reports Server (NTRS)
Hansen, C. Frederick
1993-01-01
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.
Competing magnetic ground states and their coupling to the crystal lattice in CuFe2Ge2
NASA Astrophysics Data System (ADS)
May, Andrew F.; Calder, Stuart; Parker, David S.; Sales, Brian C.; McGuire, Michael A.
2016-10-01
Identifying and characterizing systems with coupled and competing interactions is central to the development of physical models that can accurately describe and predict emergent behavior in condensed matter systems. This work demonstrates that the metallic compound CuFe2Ge2 has competing magnetic ground states, which are shown to be strongly coupled to the lattice and easily manipulated using temperature and applied magnetic fields. Temperature-dependent magnetization M measurements reveal a ferromagnetic-like onset at 228 (1) K and a broad maximum in M near 180 K. Powder neutron diffraction confirms antiferromagnetic ordering below TN ≈ 175 K, and an incommensurate spin density wave is observed below ≈125 K. Coupled with the small refined moments (0.5–1 μB/Fe), this provides a picture of itinerant magnetism in CuFe2Ge2. The neutron diffraction data also reveal a coexistence of two magnetic phases that further highlights the near-degeneracy of various magnetic states. These results demonstrate that the ground state in CuFe2Ge2 can be easily manipulated by external forces, making it of particular interest for doping, pressure, and further theoretical studies.
NASA Astrophysics Data System (ADS)
Paul, Susobhan; Ghosh, Asim Kumar
2014-08-01
The ground state energy and the spin gap of a spin-12 Heisenberg antiferromagnetic XXZ chain in the presence of longitudinal staggered field (hz) have been estimated by using Jordan-Wigner representation, exact diagonalization and perturbative analysis. All those quantities have been obtained for a region of anisotropic parameter (Δ) defined by 0≤Δ≤1. For Δ=0, the exact value of ground state energy is found for finite values of hz. The spin gap is found to develop as soon as the staggered field is switched on. The magnitude of spin gap is compared with the field induced gap measured in magnetic compounds CuBenzoate and Yb4As3 when Δ=1. The dependence of spin gap on both Δ and hz has been found which gives rise to scaling laws associated with hz. Scaling exponents obtained in two different cases show excellent agreements with the previously determined values. The variation of scaling exponents with Δ can be fitted with a regular function.
Competing magnetic ground states and their coupling to the crystal lattice in CuFe2Ge2
May, Andrew F.; Calder, Stuart; Parker, David S.; Sales, Brian C.; McGuire, Michael A.
2016-01-01
Identifying and characterizing systems with coupled and competing interactions is central to the development of physical models that can accurately describe and predict emergent behavior in condensed matter systems. This work demonstrates that the metallic compound CuFe2Ge2 has competing magnetic ground states, which are shown to be strongly coupled to the lattice and easily manipulated using temperature and applied magnetic fields. Temperature-dependent magnetization M measurements reveal a ferromagnetic-like onset at 228 (1) K and a broad maximum in M near 180 K. Powder neutron diffraction confirms antiferromagnetic ordering below TN ≈ 175 K, and an incommensurate spin density wave is observed below ≈125 K. Coupled with the small refined moments (0.5–1 μB/Fe), this provides a picture of itinerant magnetism in CuFe2Ge2. The neutron diffraction data also reveal a coexistence of two magnetic phases that further highlights the near-degeneracy of various magnetic states. These results demonstrate that the ground state in CuFe2Ge2 can be easily manipulated by external forces, making it of particular interest for doping, pressure, and further theoretical studies. PMID:27739477
Competing magnetic ground states and their coupling to the crystal lattice in CuFe2Ge2
May, Andrew F.; Calder, Stuart; Parker, David S.; Sales, Brian C.; McGuire, Michael A.
2016-10-14
Identifying and characterizing systems with coupled and competing interactions is central to the development of physical models that can accurately describe and predict emergent behavior in condensed matter systems. This work demonstrates that the metallic compound CuFe2Ge2 has competing magnetic ground states, which are shown to be strongly coupled to the lattice and easily manipulated using temperature and applied magnetic fields. The temperature-dependent magnetization M measurements reveal a ferromagnetic-like onset at 228 (1) K and a broad maximum in M near 180 K. Powder neutron diffraction confirms antiferromagnetic ordering below TN ≈ 175 K, and an incommensurate spin density wavemore » is observed below ≈125 K. Coupled with the small refined moments (0.5–1 μB/Fe), this provides a picture of itinerant magnetism in CuFe2Ge2. Furthermore, the neutron diffraction data reveal a coexistence of two magnetic phases that further highlights the near-degeneracy of various magnetic states. Our results demonstrate that the ground state in CuFe2Ge2 can be easily manipulated by external forces, making it of particular interest for doping, pressure, and further theoretical studies.« less
Nuclear resonance scattering measurement of human iron stores
Wielopolski, L.; Ancona, R.C.; Mossey, R.T.; Vaswani, A.N.; Cohn, S.H.
1985-07-01
Hepatic iron stores were measured noninvasively in 31 patients (thalassemia, hemodialysis, hemosiderosis, refractory anemia) with suspected iron overload, employing a nuclear resonance scattering (NRS) technique. The thalassemia patients were undergoing desferrioxamine chelation therapy during the NRS measurements. The hemodialysis patients were measured before chelation therapy. Iron levels measured by NRS were in general agreement with those determined in liver biopsies by atomic absorption spectroscopy. In addition, NRS measurements from the thorax of some of these patients suggest that this method may also prove useful for clinical assessment of cardiac iron.
van Wilderen, Luuk J G W; Clark, Ian P; Towrie, Michael; van Thor, Jasper J
2009-12-24
structure of the ZZZ configuration of the linear tetrapyrrole chromophore. The dump-induced absorption decays with time constants of 5 and 19 ps to the Pr ground state. Employing a dump pulse at 14 ps results in an instantaneous decrease of the absorption of the 1608 cm(-1) band, indicating repumping of the GSI. The dump-induced absorption recovers back to the GSI with a 6 ps lifetime. A spectral similarity is observed between the 6 ps phase in the dump experiment and the 3 ps component found in the two-pulse pump-probe measurement. Combined with the dominance of ground-state absorption bands in the dump-induced spectrum, this indicates the presence of a GSI, which is additionally characterized by previously unidentified induced absorption at 1710 and 1570-80 cm(-1). The metastable photoproduct Lumi-R, which is in the electronic ground state and populated at 500 ps after excitation of Pr, is highly efficiently repumped into the Pr ground state with the power density used. After repumping, Lumi-R is not recovered on the 500 ps time scale of the experiment and is distinct from the GSI of Pr since it is not associated with its characteristic induced absorption at 1710 and 1570-80 cm(-1). PMID:19950906
Bao, Weizhu; Chern, I-Liang; Zhang, Yanzhi
2013-11-15
In this paper, we propose efficient numerical methods for computing ground states of spin-1 Bose–Einstein condensates (BECs) with/without the Ioffe–Pritchard magnetic field B(x). When B(x)≠0, a numerical method is introduced to compute the ground states and it is also applied to study properties of ground states. Numerical results suggest that the densities of m{sub F}=±1 components in ground states are identical for any nonzero B(x). In particular, if B(x)≡B≠0 is a constant, the ground states satisfy the single-mode approximation. When B(x)≡0, efficient and simpler numerical methods are presented to solve the ground states of spin-1 BECs based on their ferromagnetic/antiferromagnetic characterizations. Numerical simulations show that our methods are more efficient than those in the literature. In addition, some conjectures are made from our numerical observations.
Mass coefficient and Grodzins relation for the ground-state band and {gamma} band
Jolos, R. V.; Brentano, P. von
2006-12-15
It is shown that the available experimental data on the energies of the first and the {gamma}-vibrational 2{sup +} states and the reduced E2 transition probabilities from these states to the ground state require for the explanation significantly different values of the mass coefficients for the rotational motion and {gamma}-vibrations.
Reactive ground-state pathways are not ubiquitous in red/green cyanobacteriochromes.
Chang, Che-Wei; Gottlieb, Sean M; Kim, Peter W; Rockwell, Nathan C; Lagarias, J Clark; Larsen, Delmar S
2013-09-26
Recent characterization of the red/green cyanobacteriochrome (CBCR) NpR6012g4 revealed a high quantum yield for its forward photoreaction [J. Am. Chem. Soc. 2012, 134, 130-133] that was ascribed to the activity of hidden, productive ground-state intermediates. The dynamics of the pathways involving these ground-state intermediates was resolved with femtosecond dispersed pump-dump-probe spectroscopy, the first such study reported for any CBCR. To address the ubiquity of such second-chance initiation dynamics (SCID) in CBCRs, we examined the closely related red/green CBCR NpF2164g6 from Nostoc punctiforme. Both NpF2164g6 and NpR6012g4 use phycocyanobilin as the chromophore precursor and exhibit similar excited-state dynamics. However, NpF2164g6 exhibits a lower quantum yield of 32% for the generation of the isomerized Lumi-R primary photoproduct, compared to 40% for NpR6012g4. This difference arises from significantly different ground-state dynamics between the two proteins, with the SCID mechanism deactivated in NpF2164g6. We present an integrated inhomogeneous target model that self-consistently fits the pump-probe and pump-dump-probe signals for both forward and reverse photoreactions in both proteins. This work demonstrates that reactive ground-state intermediates are not ubiquitous phenomena in CBCRs. PMID:23725062
Green's function Monte Carlo calculation for the ground state of helium trimers
Cabral, F.; Kalos, M.H.
1981-02-01
The ground state energy of weakly bound boson trimers interacting via Lennard-Jones (12,6) pair potentials is calculated using a Monte Carlo Green's Function Method. Threshold coupling constants for self binding are obtained by extrapolation to zero binding.
Creation of a strongly dipolar gas of ultracold ground-state 23 Na87 Rb molecules
NASA Astrophysics Data System (ADS)
Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Wang, Dajun; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier
2016-05-01
We report on successful creation of an ultracold sample of ground-state 23 Na87 Rb molecules with a large effective electric dipole moment. Through a carefully designed two-photon Raman process, we have successfully transferred the magneto-associated Feshbach molecules to the singlet ground state with high efficiency, obtaining up to 8000 23 Na87 Rb molecules with peak number density over 1011 cm-3 in their absolute ground-state level. With an external electric field, we have induced an effective dipole moment over 1 Debye, making 23 Na87 Rb the most dipolar ultracold particle ever achieved. Contrary to the expectation, we observed a rather fast population loss even for 23 Na87 Rb in the absolute ground state with the bi-molecular exchange reaction energetically forbidden. The origin for the short lifetime and possible ways of mitigating it are currently under investigation. Our achievements pave the way toward investigation of ultracold bosonic molecules with strong dipolar interactions. This work is supported by the Hong Kong RGC CUHK404712 and the ANR/RGC Joint Research Scheme ACUHK403/13.
Effect of spin-orbit coupling on the ground state structure of mercury
NASA Astrophysics Data System (ADS)
Mishra, Vinayak; Gyanchandani, Jyoti; Chaturvedi, Shashank; Sikka, S. K.
2014-05-01
Near zero kelvin ground state structure of mercury is the body centered tetragonal (BCT) structure (β Hg). However, in all previously reported density functional theory (DFT) calculations, either the rhombohedral or the HCP structure has been found to be the ground state structure. Based on the previous calculations it was predicted that the correct treatment of the SO effects would improve the result. We have performed FPLAPW calculations, with and without inclusion of the SO coupling, for determining the ground state structure. These calculations determine rhombohedral structure as the ground state structure instead of BCT structure. The calculations, without inclusion of SO effect, predict that the energies of rhombohedral and BCT structures are very close to each other but the energy of rhombohedral structure is lower than that of BCT structure at ambient as well as high pressure. On the contrary, the SO calculations predict that though at ambient conditions the rhombohedral structure is the stable structure but on applying a pressure of 3.2 GPa, the BCT structure becomes stable. Hence, instead of predicting the stability of BCT structure at zero pressure, the SO calculations predict its stability at 3.2 GPa. This small disagreement is expected when the energy differences between the structures are small.
Massless ground state for a compact SU (2) matrix model in 4D
NASA Astrophysics Data System (ADS)
Boulton, Lyonell; Garcia del Moral, Maria Pilar; Restuccia, Alvaro
2015-09-01
We show the existence and uniqueness of a massless supersymmetric ground state wavefunction of a SU (2) matrix model in a bounded smooth domain with Dirichlet boundary conditions. This is a gauge system and we provide a new framework to analyze the quantum spectral properties of this class of supersymmetric matrix models subject to constraints which can be generalized for arbitrary number of colors.
Weatherall, James Owen; Search, Christopher P.
2010-02-15
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.
A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates
Wang, Hanquan
2014-10-01
In this paper, a projection gradient method is presented for computing ground state of spin-2 Bose–Einstein condensates (BEC). We first propose the general projection gradient method for solving energy functional minimization problem under multiple constraints, in which the energy functional takes real functions as independent variables. We next extend the method to solve a similar problem, where the energy functional now takes complex functions as independent variables. We finally employ the method into finding the ground state of spin-2 BEC. The key of our method is: by constructing continuous gradient flows (CGFs), the ground state of spin-2 BEC can be computed as the steady state solution of such CGFs. We discretized the CGFs by a conservative finite difference method along with a proper way to deal with the nonlinear terms. We show that the numerical discretization is normalization and magnetization conservative and energy diminishing. Numerical results of the ground state and their energy of spin-2 BEC are reported to demonstrate the effectiveness of the numerical method.
Ground-state properties of small-size nonlinear dynamical lattices
NASA Astrophysics Data System (ADS)
Buonsante, P.; Kevrekidis, P. G.; Penna, V.; Vezzani, A.
2007-01-01
We investigate the ground state of a system of interacting particles in small nonlinear lattices with M⩾3 sites, using as a prototypical example the discrete nonlinear Schrödinger equation that has been recently used extensively in the contexts of nonlinear optics of waveguide arrays and Bose-Einstein condensates in optical lattices. We find that, in the presence of attractive interactions, the dynamical scenario relevant to the ground-state and the lowest-energy modes of such few-site nonlinear lattices reveals a variety of nontrivial features that are absent in the large/infinite lattice limits: the single-pulse solution and the uniform solution are found to coexist in a finite range of the lattice intersite coupling where, depending on the latter, one of them represents the ground state; in addition, the single-pulse mode does not even exist beyond a critical parametric threshold. Finally, the onset of the ground-state (modulational) instability appears to be intimately connected with a nonstandard (“double transcritical”) type of bifurcation that, to the best of our knowledge, has not been reported previously in other physical systems.
Lattice modes in molecular crystals measured with nuclear inelastic scattering
Kohn, V. G.; Chumakov, A. I.; Rueffer, R.
2006-03-01
We reveal an important property of nuclear inelastic scattering in a molecular crystal with well-separated lattice and molecular modes: The presence of the molecular modes does not change the shape but merely rescales the lattice part of the energy dependence of nuclear inelastic scattering. Therefore, the density of states (DOS) of the lattice vibrations can be properly derived even from the lattice part of nuclear inelastic scattering alone. In this case, one has to substitute the mean recoil energy of a nucleus by the effective recoil energy of the molecule. In first approximation, the ratio of the recoil energies is close to the ratio of the nuclear and molecular masses. More precisely, it is given by the relative area of the lattice part in the entire DOS. The theoretical analysis is verified with numerical calculations for a model DOS and with the experimental data for the decamethyl ferrocene molecular crystal. More generally, the analysis is valid for any region of nuclear inelastic scattering around the central elastic peak with sufficiently narrow lines beyond it. Therefore, the demonstrated property of nuclear inelastic scattering allows for a much shorter measuring time in studies of lattice modes in molecular crystals, low-energy molecular modes in proteins, and in investigations of glass dynamics with molecular probes.
Using Nuclear Magnetic Resonance Spectroscopy for Measuring Ternary Phase Diagrams
ERIC Educational Resources Information Center
Woodworth, Jennifer K.; Terrance, Jacob C.; Hoffmann, Markus M.
2006-01-01
A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate…
Accurate Determination of Rotational Energy Levels in the Ground State of ^{12}CH_4
NASA Astrophysics Data System (ADS)
Abe, M.; Iwakuni, K.; Okubo, S.; Sasada, H.
2013-06-01
We have measured absolute frequencies of saturated absorption of 183 allowed and 21 forbidden transitions in the νb{3} band of ^{12}CH_4 using an optical comb-referenced difference-frequency-generation spectrometer from 86.8 to 93.1 THz (from 2890 to 3100 wn). The pump and signal sources are a 1.06-μ m Nd:YAG laser and a 1.5-μ m extended-cavity laser diode. An enhanced-cavity absorption cell increases the optical electric field and enhances the sensitivity. The typical uncertainty is 3 kHz for the allowed transitions and 12 kHz for the forbidden transitions. Twenty combination differences are precisely determined, and the scalar rotational and centrifugal distortion constants of the ground state are thereby yielded as r@ = l@ r@ = l B_{{s}} (157 122 614.2 ± 1.5) kHz, D_{{s}} (3 328.545 ± 0.031) kHz, H_{{s}} (190.90 ± 0.26) Hz, and L_{{s}} (-13.16 ± 0.76) mHz. Here, B_{{s}} is the rotational constant and D_{{s}}, H_{{s}} and L_{{s}} are the scalar quartic, sextic, octic distortion constants. The relative uncertainties are considerably smaller than those obtained from global analysis of Fourier-transform infrared spectroscopy. S. Okubo, H. Nakayama, K. Iwakuni, H. Inaba and H. Sasada, Opt. Express 19, 23878 (2011). M. Abe, K. Iwakuni, S. Okubo, and H. Sasada, J. Opt. Soc. Am. B (to be published). S. Albert, S. Bauerecker, V. Boudon, L. R. Brown, J. -P. Champion, M. Loëte, A. Nikitin, and M. Quack, Chem. Phys. 356, 131 (2009).
Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transtion.
Jaramillo, R.; Feng, Y.; Lang, J. C.; Islam, Z.; Srajer, G.; Littlewood, P. B.; Mc Whan, D. B.; Rosenbaum, T. F.; Univ. of Chicago; Univ. of Cambridge; Massachusetts Innst. of Tech.
2009-05-21
Advances in solid-state and atomic physics are exposing the hidden relationships between conventional and exotic states of quantum matter. Prominent examples include the discovery of exotic superconductivity proximate to conventional spin and charge order, and the crossover from long-range phase order to preformed pairs achieved in gases of cold fermions and inferred for copper oxide superconductors. The unifying theme is that incompatible ground states can be connected by quantum phase transitions. Quantum fluctuations about the transition are manifestations of the competition between qualitatively distinct organizing principles, such as a long-wavelength density wave and a short-coherence-length condensate. They may even give rise to 'protected' phases, like fluctuation-mediated superconductivity that survives only in the vicinity of an antiferromagnetic quantum critical point. However, few model systems that demonstrate continuous quantum phase transitions have been identified, and the complex nature of many systems of interest hinders efforts to more fully understand correlations and fluctuations near a zero-temperature instability. Here we report the suppression of magnetism by hydrostatic pressure in elemental chromium, a simple cubic metal that demonstrates a subtle form of itinerant antiferromagnetism formally equivalent to the Bardeen-Cooper-Schrieffer (BCS) state in conventional superconductors. By directly measuring the associated charge order in a diamond anvil cell at low temperatures, we find a phase transition at pressures of 10 GPa driven by fluctuations that destroy the BCS-like state but preserve the strong magnetic interaction between itinerant electrons and holes. Chromium is unique among stoichiometric magnetic metals studied so far in that the quantum phase transition is continuous, allowing experimental access to the quantum singularity and a direct probe of the competition between conventional and exotic order in a theoretically tractable
Activation of C-Cl by ground-state aluminum atoms: an EPR and DFT investigation.
Joly, Helen A; Newton, Trevor; Myre, Maxine
2012-01-01
The reaction of ground-state Al atoms with dichloromethane (CH(2)Cl(2)) in an adamantane matrix at 77 K yielded two mononuclear Al species. The magnetic parameters, extracted from the axial EPR spectrum of Species A/A' (g(1) = 2.0037, g(2) = g(3) = 2.0030, a(Al,1) = 1307 MHz, a(Al,2) = a(Al,3) = 1273 MHz, a(35Cl) = 34 MHz and a(37Cl) = 28 MHz) were assigned to the Al-atom insertion product, ClCH(2)AlCl. Density functional theory (DFT) calculations of the values of the Al and Cl hyperfine interaction (hfi) of the Cl(1)-Cl(2)gauche conformer were in close agreement with the experimental values of ClCH(2)AlCl. The second species, B/B', had identical magnetic parameters to those of ClCH(2)AlCl with the exception that the Al hfi was 15% smaller. Coordination of a ligand, possessing a lone pair of electrons, to the Al atom of the insertion product, [ClCH(2)AlCl]:X, could cause the a(Al) to decrease by 15%. Alternatively, it is possible that the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl is also isolated in the matrix. Support for the spectral assignments is given by calculation of the nuclear hfi of [ClCH(2)AlCl]:H(2)O and the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl using a DFT method. The potential energy hypersurface for an Al atom approaching CH(2)Cl(2), calculated at the B3LYP level, suggests that Al atom abstraction of Cl forming AlCl and CH(2)Cl is favoured in the gas phase. When produced in a matrix, the close proximity of AlCl and CH(2)Cl could account for the formation of ClCH(2)AlCl. EPR evidence was also found for the formation of the CHCl(2) radical. PMID:22086441
Delahaye, Thibault Rey, Michaël Tyuterev, Vladimir G.; Nikitin, Andrei; Szalay, Péter G.
2014-09-14
In this paper we report a new ground state potential energy surface for ethylene (ethene) C{sub 2}H{sub 4} obtained from extended ab initio calculations. The coupled-cluster approach with the perturbative inclusion of the connected triple excitations CCSD(T) and correlation consistent polarized valence basis set cc-pVQZ was employed for computations of electronic ground state energies. The fit of the surface included 82 542 nuclear configurations using sixth order expansion in curvilinear symmetry-adapted coordinates involving 2236 parameters. A good convergence for variationally computed vibrational levels of the C{sub 2}H{sub 4} molecule was obtained with a RMS(Obs.–Calc.) deviation of 2.7 cm{sup −1} for fundamental bands centers and 5.9 cm{sup −1} for vibrational bands up to 7800 cm{sup −1}. Large scale vibrational and rotational calculations for {sup 12}C{sub 2}H{sub 4}, {sup 13}C{sub 2}H{sub 4}, and {sup 12}C{sub 2}D{sub 4} isotopologues were performed using this new surface. Energy levels for J = 20 up to 6000 cm{sup −1} are in a good agreement with observations. This represents a considerable improvement with respect to available global predictions of vibrational levels of {sup 13}C{sub 2}H{sub 4} and {sup 12}C{sub 2}D{sub 4} and rovibrational levels of {sup 12}C{sub 2}H{sub 4}.
TAS measurements for reactor physics and nuclear structure
NASA Astrophysics Data System (ADS)
Algora, A.; Jordan, D.; Taín, J. L.; Rubio, B.; Agramunt, J.; Caballero, L.; Nácher, E.; Perez-Cerdan, A. B.; Molina, F.; Estevez, E.; Krasznahorkay, A.; Hunyadi, M. D.; Gulyás, J.; Vitéz, A.; Csatlós, M.; Csige, L.; ńysto, J.; Penttilä, H.; Rinta-Antila, S.; Moore, I.; Eronen, T.; Jokinen, A.; Nieminen, A.; Hakala, J.; Karvonen, P.; Kankainen, A.; Hager, U.; Sonoda, T.; Saastamoinen, A.; Rissanen, J.; Kessler, T.; Weber, C.; Ronkainen, J.; Rahaman, S.; Elomaa, V.; Burkard, K.; Hüller, W.; Batist, L.; Gelletly, W.; Nichols, A. L.; Yoshida, T.; Sonzogni, A. A.; Peräjärvi, K.
2011-10-01
In this contribution we will present recent total absorption measurements of the beta decay of neutron-rich nuclei performed at the IGISOL facility of the Univ. of Jyväskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
Generalized isotropic Lipkin-Meshkov-Glick models: ground state entanglement and quantum entropies
NASA Astrophysics Data System (ADS)
Carrasco, José A.; Finkel, Federico; González-López, Artemio; Rodríguez, Miguel A.; Tempesta, Piergiulio
2016-03-01
We introduce a new class of generalized isotropic Lipkin-Meshkov-Glick models with \\text{su}(m+1) spin and long-range non-constant interactions, whose non-degenerate ground state is a Dicke state of \\text{su}(m+1) type. We evaluate in closed form the reduced density matrix of a block of L spins when the whole system is in its ground state, and study the corresponding von Neumann and Rényi entanglement entropies in the thermodynamic limit. We show that both of these entropies scale as alog L when L tends to infinity, where the coefficient a is equal to (m - k)/2 in the ground state phase with k vanishing \\text{su}(m+1) magnon densities. In particular, our results show that none of these generalized Lipkin-Meshkov-Glick models are critical, since when L\\to ∞ their Rényi entropy R q becomes independent of the parameter q. We have also computed the Tsallis entanglement entropy of the ground state of these generalized \\text{su}(m+1) Lipkin-Meshkov-Glick models, finding that it can be made extensive by an appropriate choice of its parameter only when m-k≥slant 3 . Finally, in the \\text{su}(3) case we construct in detail the phase diagram of the ground state in parameter space, showing that it is determined in a simple way by the weights of the fundamental representation of \\text{su}(3) . This is also true in the \\text{su}(m+1) case; for instance, we prove that the region for which all the magnon densities are non-vanishing is an (m + 1)-simplex in {{{R}}m} whose vertices are the weights of the fundamental representation of \\text{su}(m+1) .
Preparing ground states of quantum many-body systems on a quantum computer
NASA Astrophysics Data System (ADS)
Poulin, David
2009-03-01
The simulation of quantum many-body systems is a notoriously hard problem in condensed matter physics, but it could easily be handled by a quantum computer [4,1]. There is however one catch: while a quantum computer can naturally implement the dynamics of a quantum system --- i.e. solve Schr"odinger's equation --- there was until now no general method to initialize the computer in a low-energy state of the simulated system. We present a quantum algorithm [5] that can prepare the ground state and thermal states of a quantum many-body system in a time proportional to the square-root of its Hilbert space dimension. This is the same scaling as required by the best known algorithm to prepare the ground state of a classical many-body system on a quantum computer [3,2]. This provides strong evidence that for a quantum computer, preparing the ground state of a quantum system is in the worst case no more difficult than preparing the ground state of a classical system. 1 D. Aharonov and A. Ta-Shma, Adiabatic quantum state generation and statistical zero knowledge, Proc. 35th Annual ACM Symp. on Theo. Comp., (2003), p. 20. F. Barahona, On the computational complexity of ising spin glass models, J. Phys. A. Math. Gen., 15 (1982), p. 3241. C. H. Bennett, E. Bernstein, G. Brassard, and U. Vazirani, Strengths and weaknessess of quantum computing, SIAM J. Comput., 26 (1997), pp. 1510--1523, quant-ph/9701001. S. Lloyd, Universal quantum simulators, Science, 273 (1996), pp. 1073--1078. D. Poulin and P. Wocjan, Preparing ground states of quantum many-body systems on a quantum computer, 2008, arXiv:0809.2705.
Evolution of ground state nuclear shapes in tungsten nuclei in terms of interacting boson model
NASA Astrophysics Data System (ADS)
Khalaf, A. M.; El-Shal, A. O.; Taha, M. M.; El-Sayed, M. A.
2016-03-01
The tungsten nuclei 180-190W are investigated within the framework of the interacting boson model using an intrinsic coherent state formalism. The Hamiltonian operator contains only multipole operators of the subalgebra associated with the dynamical symmetries SU(3) and O(6). The study includes the behavior of potential energy surfaces (BES's) and critical points in the space of the model parameters to declare the geometric character of the tungsten isotopic chain. Some selected energy levels and reduced E2 transition probabilities B(E2) for each nucleus are calculated to adjust the model parameters by using a computer code PH INT and simulated computer fitting programme to fit the experimental data with the IBM calculation by minimizing the root mean square deviations. The 180-190W isotopes lies in shape transition SU(3)-O(6) region of the IBM such that the lighter isotopes comes very clare to the SU(3) limit, while the behavior ones tend to be near the γ-unstable O(6) limit.
B2N2O4: Prediction of a Magnetic Ground State for a Light Main-Group Molecule
Varga, Zoltan; Truhlar, Donald G.
2015-09-08
Cyclobutanetetrone, (CO)4, has a triplet ground state. Here we predict, based on electronic structure calculations, that the B2N2O4 molecule also has a triplet ground state and is therefore paramagnetic; the structure is an analogue of (CO)4 in which the carbon ring is replaced by a (BN)2 ring. Similar to (CO)4, the triplet ground-state structure of B2N2O4 is also thermodynamically unstable. Besides analysis of the molecular orbitals, we found that the partial atomic charges are good indicators for predicting magnetic ground states.
Ground states at the filling factors ν = 7 / 3 and 8 / 3 in the second Landau level
NASA Astrophysics Data System (ADS)
Ito, Toru; Shibata, Naokazu; Nomura, Kentaro; Department of Physics, Tohoku University Team
2013-03-01
The Laughlin state successfully describe the fractional quantum Hall state at ν = 1 / 3 in the lowest Landau level. However, it is known that the Laughlin wavefunction has little overlap with the ground state wavefunction at ν = 7 / 3 in the second Landau level. The ground states at ν = 7 / 3 and 8 / 3 are still unknown.To determine the ground states at these fillings, we use the exact diagonalization method and density-matrix renormalization group (DMRG) method. We calculate overlaps between the ground state and the trial wavefunctions, the ground state energies, and the ground-state pair-correlation functions. We find that the ground state wavefunction at ν = 8 / 3 have very high overlap between the parafermion state, and the ground state energy of the parafermion state is lower than that of the Laughlin state. Further, the short-range structures of pair-correlation functions are significantly different from that of the Lauglin state.From these results, we consider that the parafermion state is a strong candidate of the ground state at ν = 7 / 3 and ν = 8 / 3 .
Spin waves in the ferromagnetic ground state of the kagome staircase system Co3V2O8
NASA Astrophysics Data System (ADS)
Ramazanoglu, M.; Adams, C. P.; Clancy, J. P.; Berlinsky, A. J.; Yamani, Z.; Szymczak, R.; Szymczak, H.; Fink-Finowicki, J.; Gaulin, B. D.
2009-01-01
Inelastic neutron-scattering measurements were performed on single-crystal Co3V2O8 wherein magnetic cobalt ions reside on distinct spine and cross-tie sites within kagome staircase planes. This system displays a rich magnetic phase diagram which culminates in a ferromagnetic ground state below TC˜6K . We have studied the low-lying magnetic excitations in this phase within the kagome plane. Despite the complexity of the system at higher temperatures, linear spin-wave theory describes most of the quantitative detail of the inelastic neutron measurements. Our results show two spin-wave branches, the higher energy of which displays finite spin-wave lifetimes well below TC , and that, surprisingly, the magnetic exchange coupling between Co moments on the spine sites is negligible.
Nuclear fragmentation measurements for hadrontherapy and space radiation protection
De Napoli, M.; Agodi, C.; Blancato, A. A.; Cavallaro, M.; Cirrone, G. A. P.; Cuttone, G.; Sardina, D.; Scuderi, V.; Battistoni, G.; Bondi, M.; Cappuzzello, F.; Carbone, D.; Nicolosi, D.; Raciti, G.; Tropea, S.; Giacoppo, F.; Morone, M. C.; Pandola, L.; Rapisarda, E.; Romano, F.; and others
2013-04-19
Nuclear fragmentation measurements are necessary in hadrontherapy and space radiation protection, to predict the effects of the ion nuclear interactions within the human body. Nowadays, a very limited set of carbon fragmentation cross sections has been measured and in particular, to our knowledge, no double differential fragmentation cross sections at intermediate energies are available in literature. We have measured the double differential cross sections and the angular distributions of the secondary fragments produced in the {sup 12}C fragmentation at 62 AMeV on a thin carbon target. The experimental data have been also used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before.
Fourier transform far infrared spectrum of CD 3OD: detailed analysis in the torsional ground state
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Indranath; Duan, Yun-Bo; Klee, Stefan
2004-06-01
High resolution Fourier transform (FT) far infrared (FIR) spectra of CD 3OD isotopomer of methanol have been measured in the range 20-350 cm -1 at a resolution of 0.0017 cm -1 using a Bruker spectrometer. The spectra were recorded in various runs at pressure in the range of 0.2-0.8 mbar both at room temperature and at -60 °C. The spectra show complicated splitting due to strong torsional-rotational interactions in the molecule. Detailed assignments have been achieved mainly for the torsional ground state levels. The assigned transition wavenumbers along with the previously known microwave (MW) [J. Chem. Phys. 23 (1955) 1195; J. Chem. Phys. 56 (1972) 5887; Spectrochim. Acta A 54 (1998) 1375], and recently measured millimeter-wave (MMW) lines [I. Mukhopadhyay, R.A.H. Butler, F.C. DeLucia, E. Herbst, in preparation], were fit to an eighth order Hamiltonian [J. Chem. Phys. 104 (1996) 3914; J. Chem. Phys. 110 (1999) 927; J. Mol. Spectrosc. 193 (1999) 418; Chem. Phys. 263 (2001) 263; Chem. Phys. 257 (2000) 91; Chem. Phys. 280 (2002) 119; Chem. Phys. (2003) in press] with 62 varied parameters. The data set consisted of a total of 3211 transitions with 2959 FIR transitions from the ground torsional state with rotational angular momentum K ranging from 0 to 19 and J ranging from 0 to 45, and 237 MW and MMW transitions. The fit converged with a standard deviation of 0.0007 cm -1 for the FIR component of the data and the standard deviation for the MW and MMW transitions was 560 kHz. The standard deviation for the FIR lines is well compared with the estimated experimental accuracy of 0.0002 cm -1 for clean unblended lines. Here we report the actual measured wavenumbers with their assignments, some of these were not included in the fit. The complete data set fitted is not included here for the sake of economy of space but can be obtained from IM.
Fine tuning the heavy fermion ground state: A new handle on cerium cobalt indium
NASA Astrophysics Data System (ADS)
Pham, Long D.
A Two Fluid Description of the Kondo Lattice CeCoIn5 has been extended to include additional entropy terms that were not considered in the original work by S. Nakatsuji et al. [1]. The use of a Matlab computer code was successful at iteratively solving for f, the fraction of itinerant interacting heavy quasiparticles, and showed that it converges to a temperature dependent function invariant under successive iterations. The linear specific heat coefficient, gamma, was extracted from transport consideration in conjunction with f(T) and the Kadowacki-Woods ratio to be 204mJ/mole-K2, in good agreement from heat capacity measurements of 290mJ/mole-K2 for CeCoIn 5 [32]. Antiferromagnetism has been induced in CeCoIn5 as well as its two isostructural, isovalent sister compounds CeRhIn5 and CeIrIn 5. Cadmium-doping the heavy-fermion superconductor CeCoIn5 at the percent level acts as an electronic tuning agent, sensitively shifting the balance between superconductivity and antiferromagnetism and opening new ambient-pressure phase space in the study of heavy-fermion ground states. At nominal concentrations of x>0.070, CeCo(In1-xCd x)5 displays a two phase region of antiferromagnetism coexisting with superconductivity up to x<0.15, above which no trace of superconductivity persists in specific heat. Similar results was seen in CeIr(In1-xCd x)5 where a quantum critical point (QCP) was observed, separating superconductivity from antiferromagnetism at a nominal critical concentration of x≈0.0475, while CeRh(In1-xCdx)5 goes through an incommensurate to commensurate antiferromagnetic transition nominally at x≈0.10. Amazingly, pressure completely recovers Tc in CeCo(In1-x Cdx)5 measured at nominal concentrations of x=0.10, and 0.15. Phase diagrams were constructed from specific heat and confirmed with resistivity and magnetization. An introduction to strongly correlated physics, relevant to the 115 family, will be worked out followed by a description of general techniques of
Thermal measurements in the nuclear winter fire test
Schneider, M.E.; Keltner, N.R.; Kent, L.A.
1989-01-01
In March, 1987, a large open pool fire test was performed to provide test measurements to help define the thermal characteristics of large open pool fires and estimates of the smoke source term for the nuclear winter (global effects) scenario. This report will present the results of the thermal measurements as well as comparisons with previous test results. These measurements included flame temperatures, heat fluxes to a variety of calorimeters, and gas velocities in the lower flame regions. 13 refs., 76 figs., 7 tabs.
Light nuclear charge measurement with Alpha Magnetic Spectrometer Electromagnetic Calorimeter
NASA Astrophysics Data System (ADS)
Basara, Laurent; Choutko, Vitaly; Li, Qiang
2016-06-01
The Alpha Magnetic Spectrometer (AMS) is a high energy particle detector installed and operating on board of the International Space Station (ISS) since May 2011. So far more than 70 billion cosmic ray events have been recorded by AMS. In the present paper the Electromagnetic Calorimeter (ECAL) detector of AMS is used to measure cosmic ray nuclear charge magnitudes up to Z=10. The obtained charge magnitude resolution is about 0.1 and 0.3 charge unit for Helium and Carbon, respectively. These measurements are important for an accurate determination of the interaction probabilities of various nuclei with the AMS materials. The ECAL charge calibration and measurement procedures are presented.
Cold collisions of ground-state calcium atoms in a laser field: A theoretical study
Bussery-Honvault, Beatrice; Launay, Jean-Michel; Moszynski, Robert
2003-09-01
State-of-the-art ab initio techniques have been applied to compute the potential-energy curves for the ground X {sup 1}{sigma}{sub g}{sup +} and excited {sup 1}{pi}{sub g}(4s3d) states of the calcium dimer in the Born-Oppenheimer approximation. The weakly bound ground state was calculated by symmetry-adapted perturbation theory, while the strongly bound excited state was computed using a combination of the linear-response theory within the coupled-cluster singles and doubles framework for the core-valence electronic correlation and of the full configuration interaction for the valence-valence correlation. The ground-state potential has been corrected by considering the relativistic terms resulting from the first-order many-electron Breit theory, and the retardation corrections. The magnetic electronic transition dipole moment governing the {sup 1}{pi}{sub g}(leftarrow){sup 1}{sigma}{sub g}{sup +} transitions has been obtained as the first residue of the polarization propagator computed with the coupled-cluster method restricted to single and double excitations. The computed energies and transition moments have been analytically fitted and used in the dynamical calculations of the rovibrational energy levels, ground-state scattering length, photoassociation intensities at ultralow temperatures, and spontaneous emission coefficients from the {sup 1}{pi}{sub g}(4s3d) to the X {sup 1}{sigma}{sub g}{sup +} state. The spectroscopic constants of the theoretical ground-state potential are in a good agreement with the experimental values derived from the Fourier-transform spectra [O. Allard et al., Eur. Phys. J. D (to be published)]. The theoretical s-wave scattering length for the ground state is a=44 bohrs, suggesting that it should be possible to obtain a stable Bose-Einstein condensate of calcium atoms. Finally, the computed photoassociation intensities and spontaneous emission coefficients suggest that it should be possible to obtain cold calcium molecules by
NASA Astrophysics Data System (ADS)
Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar
2016-07-01
The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.
Neutron polarization analysis study of the frustrated magnetic ground state of β-Mn1-xAlx
NASA Astrophysics Data System (ADS)
Stewart, J. R.; Andersen, K. H.; Cywinski, R.
2008-07-01
We have performed a neutron polarization analysis study of the short-range nuclear and magnetic correlations present in the dilute alloy, β-Mn1-xAlx with 0.03≤x≤0.16 , in order to study the evolution of the magnetic ground state of this system as it achieves static spin-glass order at concentrations x>0.09 . To this end we have developed a reverse-Monte Carlo algorithm which has enabled us to extract Warren-Cowley nuclear short-range order parameters and magnetic spin correlations. Using conventional neutron powder diffraction, we show that the nonmagnetic Al substituents preferentially occupy the magnetic site II Wyckoff positions in the β-Mn structure—resulting in a reduction of the magnetic topological frustration of the Mn atoms. These Al impurities are found to display strong anticlustering behavior. The magnetic spin correlations are predominantly antiferromagnetic, persisting over a short range which is similar for all the samples studied—above and below the spin-liquid-spin-glass boundary—while the observed static (disordered) moment is shown to increase with increasing Al concentration.
Atomic mass measurements and nuclear spectroscopy at TRISTAN
NASA Astrophysics Data System (ADS)
Brenner, D. S.
1981-02-01
This research program is concerned with measuring atomic masses and decay schemes of short-lived, neutron-rich fission products with the TRISTAN on-line mass separator located at the High Flux Beam Reactor (HFBR), Brookhaven National Laboratory. The determination of accurate masses for neutron rich nuclei is useful in refining mass equations which, in turn, are important for calculations related to astrophysical processes and to control and to safety of nuclear reactors. During the period covered by this report, efforts were made to aid Brookhaven personnel in the installation and testing of TRISTAN and the associated computer systems, and to begin a program of measurements of beta-ray end-point energies and nuclear decay schemes following successful demonstration of the facility.
Avoiding nuclear war, Confidence-building measures for crisis stability
Borawski, J.; Goodby, J.E.
1986-01-01
Confidence-building measures (CBMs) may offer one way out of the contemporary arms control morass. Instead of focusing on limiting the number and types of weaponry, CBMs are designed to control how, when, where, and why military activities are employed. By clarifying military intentions and regulating the operations of military forces in times of both crisis and calm, CBMs can help diminish the opportunities for war arising from surprise attack or from miscalculation, accident, or failure of communication. This volume assembles CBM experts from government and academia to assess the utility of CBMs in a wide variety of areas. CONTENTS: Foreword; Prologue; Introduction; The World of CBMs; The Accidents Measures Agreement; Avoiding Incidents at Sea; The Stockholm CDE Conference; CBMs in the UN Setting; Soviet Views of CBMs; Beyond the Hotline: Controlling a Nuclear Crisis; CBMs for Stabilizing the Strategic Nuclear Competition; Risk Reduction and Crisis Prevention; An East-West Center for Military Cooperation; The Limits of Confidence.
A nuclear data approach for the Hubble constant measurements
Pritychenko, B.
2015-06-09
An extraordinary number of Hubble constant measurements challenges physicists with selection of the best numerical value. The standard U.S. Nuclear Data Program (USNDP) codes and procedures have been applied to resolve this issue. The nuclear data approach has produced the most probable or recommended Hubble constant value of 67.00(770) (km/sec)/Mpc. This recommended value is based on the last 25 years of experimental research and includes contributions from different types of measurements. The present result implies (14.6±1.7) x 10^{9} years as a rough estimate for the age of the Universe. The complete list of recommended results is given and possible implications are discussed.
Li, Li; Nishihara, Sadafumi; Inoue, Katsuya; Kurmoo, Mohamedally
2016-03-21
We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, T(B) = 7 K) and ferrimagnet (FI, T(C) = 18 K), for one crystal structure of [{Mn(II)(D/L-NH2ala)}3{Mn(III)(CN)6}]·3H2O obtained from [Mn(CN)6](3-) and D/L-aminoalanine, in contrast to one MGS for [{Mn(II)(L-NH2ala)}3{Cr(III)(CN)6}]·3H2O. They consist of three Mn(NH2ala) helical chains bridged by M(III)(CN)6 to give the framework with disordered water molecules in channels and between the M(III)(CN)6. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the ac susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both T(crit) and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn(III)-CN-Mn(II) antiferromagnetic (J1 and J2), the weak Mn(II)-OCO-Mn(II) (J3), and Dzyaloshinkii-Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn(III)(CN)6 and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn(III)(CN)6 in good accordance with the Mn-Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique c axis of the hexagonal space group. PMID:26893217
Tuning the ground state of the Kondo lattice in UT Bi2 (T = Ag, Au) single crystals
NASA Astrophysics Data System (ADS)
Rosa, Priscila; Luo, Yongkang; Pagliuso, Pascoal; Bauer, Eric; Thompson, Joe; Fisk, Zachary
2015-03-01
Motivated by the interesting magnetic anisotropy found in the Ce-based heavy fermion family Ce TX2 (T = transition metal, X = pnictogen), here we study the novel U-based parent compounds U TBi2 (T = Ag, Au) by combining magnetization, electrical resistivity, and heat-capacity measurements. The single crystals, synthesized by the self-flux method, also crystallize in the tetragonal HfCuSi2-type structure (space group P4/nmm). Interestingly, although UAgBi2 is a low- γ antiferromagnet below TN = 181 K, UAuBi2 is a moderately heavy uniaxial ferromagnet below Tc = 22 K. Nevertheless, both compounds display the easy-magnetization direction along the c-axis and a large magnetocrystalline anisotropy. Our results point out to an incoherent Kondo behaviour in the paramagnetic state and an intricate competition between crystal field effects and two anisotropic exchange interactions, which lead to the remarkable difference in the observed ground states.
NASA Astrophysics Data System (ADS)
Hou, Qing; Goldenfeld, Nigel; Sasa, Shin-Ichi
1996-03-01
We study the kinetics of a phase transition in a 2D system quenched from a uniform state to one whose ground state is spatially periodic; examples include Rayleigh-Benard convection, isotropic-smectic and nematic-smectic transitions in liquid crystals and the Swift-Hohenberg model. Computer simulation(K.R. Elder, J. Vinals and M. Grant, Phys. Rev. A), 46, 7618 (1992). shows that dynamical scaling occurs; by exploring different models, we show that power law depends upon the presence of grain-boundaries (Q. Hou, N. Goldenfeld and S. Sasa, unpublished.) We measure the scaling exponents and give a scaling theory for their dependence on defect dynamics and bulk relaxation. Crossover phenomena corresponding to different physical mechanisms for pattern relaxation are also discussed.
Lowering of ground state induced by core-shell structure in strontium titanate
NASA Astrophysics Data System (ADS)
Kiat, J. M.; Hehlen, B.; Anoufa, M.; Bogicevic, C.; Curfs, C.; Boyer, B.; Al-Sabbagh, M.; Porcher, F.; Al-Zein, A.
2016-04-01
A new ground state of textbook compound strontium titanate (SrTi O3) is obtained by inducing a specific core-shell structure of the particles. Using a combination of high energy synchrotron and neutron diffraction, we demonstrate a lowering of the ferroelastic ground state towards a new antiferrodistortive phase, accompanied with strong shifts of the critical temperature. This new phase is discussed within the Landau theory and compared with the situation in thin films and during pressure experiments. The crucial competition between particle shape anisotropy, surface tension, and shear strain is analyzed. Inducing a specific core-shell structure is therefore an easy way to tailor structural properties and to stabilize new phases that cannot exist in bulk material, just like film deposition on a substrate.
Phase diagram of quantum critical system via local convertibility of ground state
Liu, Si-Yuan; Quan, Quan; Chen, Jin-Jun; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2016-01-01
We investigate the relationship between two kinds of ground-state local convertibility and quantum phase transitions in XY model. The local operations and classical communications (LOCC) convertibility is examined by the majorization relations and the entanglement-assisted local operations and classical communications (ELOCC) via Rényi entropy interception. In the phase diagram of XY model, LOCC convertibility and ELOCC convertibility of ground-states are presented and compared. It is shown that different phases in the phase diagram of XY model can have different LOCC or ELOCC convertibility, which can be used to detect the quantum phase transition. This study will enlighten extensive studies of quantum phase transitions from the perspective of local convertibility, e.g., finite-temperature phase transitions and other quantum many-body models. PMID:27381284
Ground state cooling of a nanomechanical resonator using electron transport in hybrid systems
NASA Astrophysics Data System (ADS)
Rastelli, Gianluca; Stadler, Pascal; Belzig, Wolfgang
A still open challenge in nanoelectromechanical systems is the achievement of the quantum regime via active cooling and using electron transport. I will discuss active ground state cooling in a bottom-up device, viz. a carbon nanotube quantum dot suspended between two electric nano-contacts, and for two different coherent transport regimes: (i) spin-polarized current between two ferromagnets and (ii) sub-gap Andreev current between a superconductor and a normal metal. I will show that efficient ground state cooling of the resonator can be achieved for realistic parameters of the system and varying the transport parameters, e.g. gate voltage, magnetic field, etc. Finally I will discuss the signatures in the current-voltage characteristics of the non-equilibrium state of the nanoresonator. Zukunftskolleg of the University of Konstanz; DFG through SFB 767 and BE 3803/5.
Universal Wave-Function Overlap and Universal Topological Data from Generic Gapped Ground States.
Moradi, Heidar; Wen, Xiao-Gang
2015-07-17
We propose a way-universal wave-function overlap-to extract universal topological data from generic ground states of gapped systems in any dimensions. Those extracted topological data might fully characterize the topological orders with a gapped or gapless boundary. For nonchiral topological orders in (2+1)D, these universal topological data consist of two matrices S and T, which generate a projective representation of SL(2,Z) on the degenerate ground state Hilbert space on a torus. For topological orders with a gapped boundary in higher dimensions, these data constitute a projective representation of the mapping class group MCG(M^{d}) of closed spatial manifold M^{d}. For a set of simple models and perturbations in two dimensions, we show that these quantities are protected to all orders in perturbation theory. These overlaps provide a much more powerful alternative to the topological entanglement entropy and allow for more efficient numerical implementations.
The theoretical study of the ground-state polar chromium-alkali-metal-atom molecules
NASA Astrophysics Data System (ADS)
Deng, Lijuan; Gou, Dezhi; Chai, Junshuai
2016-04-01
Potential energy curves and permanent dipole moments of the 6Σ+ and 8Σ+ ground state of CrX (X = Li, Na, K, Rb and Cs) are calculated by employing the complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods. The spectroscopic constants for the 6Σ+ and 8Σ+ ground state of these molecules are calculated. Moreover, CrK, CrRb and CrCs molecules with large values of permanent dipole moment (CrK: 5.553 D, CrRb: 6.341 D and CrCs: 6.731 D) at the equilibrium bond distance are potentially interesting candidates for ultracold anisotropic long-range dipole-dipole interactions and many-body physics studies.
Extremal Optimization for Ground States of the Sherrington-Kirkpatrick Spin Glass with Levy Bonds
NASA Astrophysics Data System (ADS)
Boettcher, Stefan
Ground states of Ising spin glasses on fully connected graphs are studied for a broadly distributed bond family. In particular, bonds J distributed according to a Levy distribution P(J) / 1/|J|1+α; |J| > 1; are investigated for a range of powers α. We determine ground state energy density variation with α and their finite-size corrections. We find that the energies attain universally the Parisi-energy of the SK as long as the second moment of P (J) exists (α > 2). They compare favorably with recent one-step replica symmetry breaking predictions well below α = 2. At and just below α = 2, the simulations deviate significantly from theoretical expectations. The finite-size investigation reveals that the corrections exponent ω decays from the putative SK value ωSK = = 2/3 already well above α = 2, at which point it reaches a minimum.
Cavity cooling to the ground state of an ensemble quantum system
NASA Astrophysics Data System (ADS)
Wood, Christopher J.; Cory, David G.
2016-02-01
We describe a method for initializing an ensemble of qubits in a pure ground state by applying collective cavity cooling techniques in the presence of local dephasing noise on each qubit. To solve the dynamics of the ensemble system we introduce a method for dissipative perturbation theory that applies average Hamiltonian theory in an imaginary-time dissipative interaction frame to find an average effective dissipator for the system dynamics. We use SU(4) algebra generators to analytically solve the first-order perturbation for an arbitrary number of qubits in the ensemble. We find that to first order the effective dissipator describes local T1 thermal relaxation to the ground state of each qubit in the ensemble at a rate equal to the collective cavity cooling dissipation rate. The proposed technique should permit the parallel initialization of high purity states in large ensemble quantum systems based on solid-state spins.
Rayleigh approximation to ground state of the Bose and Coulomb glasses
Ryan, S. D.; Mityushev, V.; Vinokur, V. M.; Berlyand, L.
2015-01-16
Glasses are rigid systems in which competing interactions prevent simultaneous minimization of local energies. This leads to frustration and highly degenerate ground states the nature and properties of which are still far from being thoroughly understood. We report an analytical approach based on the method of functional equations that allows us to construct the Rayleigh approximation to the ground state of a two-dimensional (2D) random Coulomb system with logarithmic interactions. We realize a model for 2D Coulomb glass as a cylindrical type II superconductor containing randomly located columnar defects (CD) which trap superconducting vortices induced by applied magnetic field. Ourmore » findings break ground for analytical studies of glassy systems, marking an important step towards understanding their properties.« less
Ground state phase transition in the Nilsson mean-field plus standard pairing model
NASA Astrophysics Data System (ADS)
Guan, Xin; Xu, Haocheng; Zhang, Yu; Pan, Feng; Draayer, Jerry P.
2016-08-01
The ground state phase transition in Nd, Sm, and Gd isotopes is investigated by using the Nilsson mean-field plus standard pairing model based on the exact solutions obtained from the extended Heine-Stieltjes correspondence. The results of the model calculations successfully reproduce the critical phenomena observed experimentally in the odd-even mass differences, odd-even differences of two-neutron separation energy, and the α -decay and double β--decay energies of these isotopes. Since the odd-even effects are the most important signatures of pairing interactions in nuclei, the model calculations yield microscopic insight into the nature of the ground state phase transition manifested by the standard pairing interaction.
Phase diagram of quantum critical system via local convertibility of ground state.
Liu, Si-Yuan; Quan, Quan; Chen, Jin-Jun; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2016-01-01
We investigate the relationship between two kinds of ground-state local convertibility and quantum phase transitions in XY model. The local operations and classical communications (LOCC) convertibility is examined by the majorization relations and the entanglement-assisted local operations and classical communications (ELOCC) via Rényi entropy interception. In the phase diagram of XY model, LOCC convertibility and ELOCC convertibility of ground-states are presented and compared. It is shown that different phases in the phase diagram of XY model can have different LOCC or ELOCC convertibility, which can be used to detect the quantum phase transition. This study will enlighten extensive studies of quantum phase transitions from the perspective of local convertibility, e.g., finite-temperature phase transitions and other quantum many-body models.
Understanding degenerate ground states of a protected quantum circuit in the presence of disorder
NASA Astrophysics Data System (ADS)
Dempster, Joshua M.; Fu, Bo; Ferguson, David G.; Schuster, D. I.; Koch, Jens
2014-09-01
A recent theoretical proposal suggests that a simple circuit utilizing two superinductors may produce a qubit with ground-state degeneracy [Brooks, Phys. Rev. A 87, 052306 (2013), 10.1103/PhysRevA.87.052306]. We perform a full circuit analysis along with exact diagonalization of the circuit Hamiltonian to elucidate the nature of the spectrum and low-lying wave functions of this 0-π device. We show that the ground-state degeneracy is robust to disorder in charge, flux, and critical current as well as insensitive to modest variations in the circuit parameters. Our treatment is nonperturbative, provides access to excited states and matrix elements, and is immediately applicable also to intermediate parameter regimes of experimental interest.
Rayleigh approximation to ground state of the Bose and Coulomb glasses
Ryan, S. D.; Mityushev, V.; Vinokur, V. M.; Berlyand, L.
2015-01-16
Glasses are rigid systems in which competing interactions prevent simultaneous minimization of local energies. This leads to frustration and highly degenerate ground states the nature and properties of which are still far from being thoroughly understood. We report an analytical approach based on the method of functional equations that allows us to construct the Rayleigh approximation to the ground state of a two-dimensional (2D) random Coulomb system with logarithmic interactions. We realize a model for 2D Coulomb glass as a cylindrical type II superconductor containing randomly located columnar defects (CD) which trap superconducting vortices induced by applied magnetic field. Our findings break ground for analytical studies of glassy systems, marking an important step towards understanding their properties.
Ground states for irregular and indefinite superlinear Schrödinger equations
NASA Astrophysics Data System (ADS)
Ackermann, Nils; Chagoya, Julián
2016-11-01
We consider the existence of a ground state for the subcritical stationary semilinear Schrödinger equation - Δu + u = a (x) | u| p - 2 u in H1, where a ∈L∞ (RN) may change sign. Our focus is on the case where loss of compactness occurs at the ground state energy. By providing a new variant of the Splitting Lemma we do not need to assume the existence of a limit problem at infinity, be it in the form of a pointwise limit for a as | x | → ∞ or of asymptotic periodicity. That is, our problem may be irregular at infinity. In addition, we allow a to change sign near infinity, a case that has never been treated before.
Ground state of a hydrogen ion molecule immersed in an inhomogeneous electron gas
NASA Astrophysics Data System (ADS)
Diaz-Valdes, J.; Gutierrez, F. A.; Matamala, A. R.; Denton, C. D.; Vargas, P.; Valdes, J. E.
2007-01-01
In this work we have calculated the ground state energy of the hydrogen molecule, H2+, immersed in the highly inhomogeneous electron gas around a metallic surface within the local density approximation. The molecule is perturbed by the electron density of a crystalline surface of Au <1 0 0> with the internuclear axis parallel to the surface. The surface spatial electron density is calculated through a linearized band structure method (LMTO-DFT). The ground state of the molecule-ion was calculated using the Born-Oppenheimer approximation for a fixed-ion while the screening effects of the inhomogeneous electron gas are depicted by a Thomas-Fermi like electrostatic potential. We found that within our model the molecular ion dissociates at the critical distance of 2.35 a.u. from the first atomic layer of the solid.
Creation of Ultracold Sr2 Molecules in the Electronic Ground State
NASA Astrophysics Data System (ADS)
Stellmer, Simon; Pasquiou, Benjamin; Grimm, Rudolf; Schreck, Florian
2012-09-01
We report on the creation of ultracold Sr284 molecules in the electronic ground state. The molecules are formed from atom pairs on sites of an optical lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a transfer efficiency of 30% and obtain 4×104 molecules with full control over the external and internal quantum state. STIRAP is performed near the narrow S01-P13 intercombination transition, using a vibrational level of the 1(0u+) potential as an intermediate state. In preparation of our molecule association scheme, we have determined the binding energies of the last vibrational levels of the 1(0u+), 1(1u) excited-state and the XΣg+1 ground-state potentials. Our work overcomes the previous limitation of STIRAP schemes to systems with magnetic Feshbach resonances, thereby establishing a route that is applicable to many systems beyond alkali-metal dimers.
Karolewski, Andreas; Kronik, Leeor; Kümmel, Stephan
2013-05-28
Optimally tuned range separated hybrid functionals are a new class of implicitly defined functionals. Their important new aspect is that the range separation parameter in these functionals is determined individually for each system by iteratively tuning it until a fundamental, non-empirical condition is fulfilled. Such functionals have been demonstrated to be extremely successful in predicting electronic excitations. In this paper, we explore the use of the tuning approach for predicting ground state properties. This sheds light on one of its downsides - the violation of size consistency. By analyzing diatomic molecules, we reveal size consistency errors up to several electron volts and find that binding energies cannot be predicted reliably. Further consequences of the consistent ground-state use of the tuning approach are potential energy surfaces that are qualitatively in error and an incorrect prediction of spin states. We discuss these failures, their origins, and possibilities for overcoming them.
RKKY Interaction and the Nature of the Ground State of Double Dots in Parallel
Kulkarni, M.; Konik, R.
2011-06-23
We argue through a combination of slave-boson mean-field theory and the Bethe ansatz that the ground state of closely spaced double quantum dots in parallel coupled to a single effective channel are Fermi liquids. We do so by studying the dots conductance, impurity entropy, and spin correlation. In particular, we find that the zero-temperature conductance is characterized by the Friedel sum rule, a hallmark of Fermi-liquid physics, and that the impurity entropy vanishes in the limit of zero temperature, indicating that the ground state is a singlet. This conclusion is in opposition to a number of numerical renormalization-group studies. We suggest a possible reason for the discrepancy.
Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation
Kaptan, Y. Herzog, B.; Schöps, O.; Kolarczik, M.; Woggon, U.; Owschimikow, N.; Röhm, A.; Lingnau, B.; Lüdge, K.; Schmeckebier, H.; Arsenijević, D.; Bimberg, D.; Mikhelashvili, V.; Eisenstein, G.
2014-11-10
The impact of ground state amplification on the laser emission of In(Ga)As quantum dot excited state lasers is studied in time-resolved experiments. We find that a depopulation of the quantum dot ground state is followed by a drop in excited state lasing intensity. The magnitude of the drop is strongly dependent on the wavelength of the depletion pulse and the applied injection current. Numerical simulations based on laser rate equations reproduce the experimental results and explain the wavelength dependence by the different dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously broadened quantum dots. At high injection levels, the observed response even upon perturbation of the lasing sub-ensemble is small and followed by a fast recovery, thus supporting the capacity of fast modulation in dual-state devices.
Gas flow dependence of ground state atomic oxygen in plasma needle discharge at atmospheric pressure
Sakiyama, Yukinori; Graves, David B.; Knake, Nikolas; Schroeder, Daniel; Winter, Joerg; Schulz-von der Gathen, Volker
2010-10-11
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 high flow rate, a ring-shaped density distribution appears. The peak density is on the order of 10{sup 21} m{sup -3} in both cases. The results are consistent with a previous report of the flow-dependent bacterial killing pattern observed under similar conditions.
Understanding the Yang-Mills ground state: The origin of colour confinement
NASA Astrophysics Data System (ADS)
Preparata, Giuliano
1988-01-01
The essential magnetic instability of the perturbative ground state of a non-abelian Yang-Mills theory recently discovered, is shown to lead to a family of degenerate states, the Savvidy states, where the Yang-Mills fields undergo an infinite (when the ultraviolet cut-off Λ-->∞M) condensation process. These states build up the real Yang-Mills ground state, in which colour is confined and governed by the effective lagrangian of anisotropic chromodynamics (ACD), proposed by the present author a few years ago. This appears to solve the problem of confinement in QCD. On leave of absence from Dipartimento di Fisica, Università di Bari, I-70126 Bari, Italy.
Method and apparatus for measuring nuclear magnetic properties
Weitekamp, D.P.; Bielecki, A.; Zax, D.B.; Zilm, K.W.; Pines, A.
1987-12-01
A method for studying the chemical and structural characteristics of materials is disclosed. The method includes placement of a sample material in a high strength polarizing magnetic field to order the sample nuclei. The condition used to order the sample is then removed abruptly and the ordering of the sample allowed to evolve for a time interval. At the end of the time interval, the ordering of the sample is measured by conventional nuclear magnetic resonance techniques. 5 figs.
NASA Astrophysics Data System (ADS)
Cruse, H. A.; Jungen, Ch.; Merkt, F.
2008-04-01
The hyperfine structure of transitions between n=51-53d and n=54-57f Rydberg states belonging to series converging on the XΣ2g+ (v+=0,N+=1) , ground state of para- D2+ has been measured at an experimental resolution of about 1 MHz by millimeter-wave spectroscopy and assigned on the basis of combination differences. A map of the hyperfine structure of these Rydberg states has been determined. The analysis of the hyperfine structure of the nf series by multichannel quantum defect theory has confirmed the experimental assignments and enabled the derivation of the hyperfine structure of the ground state of para- D2+ with a precision of better than 1 MHz.
Quasipotential equation for hydrogen isotopes. Muonic atoms. Ground state energy levels
NASA Astrophysics Data System (ADS)
Bakalov, D.
1980-06-01
The quasipotential for the electromagnetic interaction of two particles of spin {1}/{2} or 1 with arbitrary electromagnetic interaction of two particles of spin {1}/{2} or 1 with arbitrary electromagnetic structure is constructed in the one-photon approximation. Todorov's quasipotential equation is applied to calculate the ground state energy levels of the muonic atoms pμ, dμ and tμ with accuracy 10 -3 eV.
Generalized Klein-Gordon models: behavior around the ground state condensate.
Kuetche, Victor K
2014-07-01
In this work, we investigate the balance between the nonlinear and linear interaction energy of an interparticle anharmonic system in the vicinity of the ground state condensate. As a result, we find that the nonlinear interaction energy is very significant in the vicinity of each degree of freedom. We address some potential applications of the findings to miscellaneous areas of interests such as soliton theory, hydrodynamics, solid state physics, ferromagnetic and ferroelectric domain walls, condensed matter physics, and particle physics, among others.
Diagrammatic perturbation theory applied to the ground state of the water molecule
NASA Technical Reports Server (NTRS)
Silver, D. M.; Wilson, S.
1977-01-01
The diagrammatic many-body perturbation theory is applied to the ground state of the water molecule within the algebraic approximation. Using four different basis sets, the total energy, the equilibrium OH bond length, and the equilibrium HOH bond angle are examined. The latter is found to be a particularly sensitive test of the convergence of perturbation expansions. Certain third-order results, which incorporate all two-, three-, and four-body effects, show evidence of good convergence properties.
Ground State of the Universe and the Cosmological Constant. A Nonperturbative Analysis.
Husain, Viqar; Qureshi, Babar
2016-02-12
The physical Hamiltonian of a gravity-matter system depends on the choice of time, with the vacuum naturally identified as its ground state. We study the expanding Universe with scalar field in the volume time gauge. We show that the vacuum energy density computed from the resulting Hamiltonian is a nonlinear function of the cosmological constant and time. This result provides a new perspective on the relation between time, the cosmological constant, and vacuum energy.
Creating Ground State Molecules with Optical Feshbach Resonances in Tight Traps
Koch, Christiane P.; Masnou-Seeuws, Francoise; Kosloff, Ronnie
2005-05-20
We propose to create ultracold ground state molecules in an atomic Bose-Einstein condensate by adiabatic crossing of an optical Feshbach resonance. We envision a scheme where the laser intensity and possibly also frequency are linearly ramped over the resonance. Our calculations for {sup 87}Rb show that for sufficiently tight traps it is possible to avoid spontaneous emission while retaining adiabaticity, and conversion efficiencies of up to 50% can be expected.
Generalized Klein-Gordon models: Behavior around the ground state condensate
NASA Astrophysics Data System (ADS)
Kuetche, Victor K.
2014-07-01
In this work, we investigate the balance between the nonlinear and linear interaction energy of an interparticle anharmonic system in the vicinity of the ground state condensate. As a result, we find that the nonlinear interaction energy is very significant in the vicinity of each degree of freedom. We address some potential applications of the findings to miscellaneous areas of interests such as soliton theory, hydrodynamics, solid state physics, ferromagnetic and ferroelectric domain walls, condensed matter physics, and particle physics, among others.
Halogenated benzene radical cations and ground state degeneracy splitting by asymmetric substitution
Bondybey, V.E.; Vaughn, C.R.; Miller, T.A.; English, J.H.; Shiley, R.H.
1981-01-01
The absorption and laser induced fluorescence of several halogenated benzene radical cations were studied in solid Ne matrices. The spectra of 1,2,4-trifluorobenzene, l,3-dichloro-5-fluorobenzene, and l-chloro-3,5- difluorobenzene radical cations are observed and analyzed. Studies of fluorescence polarization and a photoselection technique were used to examine the splitting of the degeneracy of the benzene cation ground state by asymmetric subsitution. ?? 1981 American Institute of Physics.
Relativistic corrections to the ground-state energy of the positronium molecule
Bubin, Sergiy; Stanke, Monika; Kedziera, Dariusz; Adamowicz, Ludwik
2007-06-15
The leading-order relativistic corrections to the ground-state energy of the positronium molecule (Ps{sub 2}) have been computed within the framework of perturbation theory. As the zero-order wave function we used a highly accurate nonrelativistic variational expansion in terms of 6000 explicitly correlated Gaussians that yielded the lowest variational upper bound for this system to date. We also report some expectation values representing the properties of Ps{sub 2}.
Ground state energy and mass gap of a generalized quantum spin ladder
NASA Astrophysics Data System (ADS)
Batchelor, M. T.; Maslen, M.
2000-01-01
We show that a two-leg ladder Hamiltonian introduced recently by Albeverio and Fei can be made to satisfy the Hecke algebra. As a result we have found an equivalent representation of the eigenspectrum in terms of the spin- 1/2 antiferromagnetic XXZ chain at icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> = -(5/3). The values of thermodynamic quantities such as the ground state energy and mass gap follow from the known XXZ results.
A simple, radially correlated ground state wavefunction for two electron atoms.
NASA Technical Reports Server (NTRS)
Altick, P. L.
1972-01-01
A one parameter function is presented as an approximation to the ground state wavefunction of the two electron radial hamiltonian. The parameter may be fixed by a nonvariational criterion. The resulting expectation value of the radial hamiltonian differs from its exact eigenvalue by about 2 parts in 3000 for helium while the 'local energy' never differs by more than 10% from the exact value over the entire r1-r2 plane. The cases Z = 1 and Z = 3 are also investigated.
The role of correlation in the ground state energy of confined helium atom
Aquino, N.
2014-01-14
We analyze the ground state energy of helium atom confined by spherical impenetrable walls, and the role of the correlation energy in the total energy. The confinement of an atom in a cavity is one way in which we can model the effect of the external pressure on an atom. The calculations of energy of the system are carried out by the variational method. We find that the correlation energy remains almost constant for a range values of size of the boxes analyzed.
Problems in detection and measurement in nuclear medicine
NASA Astrophysics Data System (ADS)
Aysun Ugur, Fatma
2015-07-01
Nuclear Medicine studies are performed with a variety of types of radiation measurement instruments, depending on the kind of radiation source that is being measured and the type of information sought. For example, some instruments are designed for in vitro measurements on blood samples, urine specimens, and so forth. Others are designed for in vivo measurements of radioactivity in patients. All these instruments have special design characteristics to optimize them for their specific tasks, as described in this study; however, some considerations of design characteristics and performance limitations are common to all of them. An important consideration for any radiation measurement instrument is its detection efficiency. Maximum detection efficiency is desirable because one thus obtains maximum information with a minimum amount of radioactivity. Also important are instrument's counting rate limitations. There are finite counting rate limits for all counting and imaging instruments used in nuclear medicine, above which accurate results are obtained because of data losses and other data distortions. Non penetrating radiations, such as ß particles, have special detection and measurement problems. In this study, some of these general considerations have been discussed.
Nuclear abundance measurements inside MIR and ISS with Sileye experiments
NASA Astrophysics Data System (ADS)
Casolino, M.
In this work we present measurements of cosmic ray nuclear abundances above 150 MeV/n performed inside Mir space station between 1998 and 2000. Data have been obtained with SilEye-2 detector, a 6 plane silicon strip detector telescope designed to measure environmental radiation and investigate on the Light Flash phenomenon. In standalone mode, SilEye-2 is capable to measure LET distribution spectra and identify nuclear species with energy above 100 MeV/n: a total of 100 sessions comprising more than 1000 hours of observation were perfomed in the years 1998-2000, recording also several Solar Energetic Particle (SEP) events. Cosmic ray abundances inside a spacecraft can differ from the primary component due to interaction with the interposed material of the hull and the instruments. We report on LET measurements and relative abundances from Boron to Iron measured in different regions and at different geomagnetic cutoffs, in solar quiet conditions and during SEP events, showing how the composition varies in these different situations. We also report on preliminary results on cosmic ray measurements inside ISS (27/4/2002 - 4/5/2002) obtained with Sileye-3/Alteino experiment.
NASA Astrophysics Data System (ADS)
Ng, L. L.; Tan, T. L.
2016-06-01
The Fourier transform infrared (FTIR) spectrum of the c-type ν8 band of 13C2HD3 was recorded for the first time at a unapodized resolution of 0.0063 cm-1 in the wavenumber region of 830-1000 cm-1. Through the fitting of a total of 1057 assigned infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation, rovibrational constants for the upper state (v8 = 1) up to five quartic centrifugal distortion terms were derived for the first time with a root-mean-square (rms) deviation of 0.00073 cm-1. The band center of ν8 of 13C2HD3 was found to be 913.011021(55) cm-1. Ground state rovibrational constants up to five quartic terms of 13C2HD3 were also determined from a fit of 453 ground state combination-differences from the present infrared measurements with an rms deviation of 0.00072 cm-1 for the first time. The uncertainty of the measured infrared lines was estimated to be ±0.0012 cm-1. From the ground state rotational constants, the inertial defect of 13C2HD3 was calculated to be 0.06973(16) uÅ2, showing the high planarity of the molecule.
Gamiz-Hernandez, Ana P; Magomedov, Artiom; Hummer, Gerhard; Kaila, Ville R I
2015-02-12
Proton-coupled electron transfer (PCET) processes are elementary chemical reactions involved in a broad range of radical and redox reactions. Elucidating fundamental PCET reaction mechanisms are thus of central importance for chemical and biochemical research. Here we use quantum chemical density functional theory (DFT), time-dependent density functional theory (TDDFT), and the algebraic diagrammatic-construction through second-order (ADC(2)) to study the mechanism, thermodynamic driving force effects, and reaction barriers of both ground state proton transfer (pT) and photoinduced proton-coupled electron transfer (PCET) between nitrosylated phenyl-phenol compounds and hydrogen-bonded t-butylamine as an external base. We show that the obtained reaction barriers for the ground state pT reactions depend linearly on the thermodynamic driving force, with a Brønsted slope of 1 or 0. Photoexcitation leads to a PCET reaction, for which we find that the excited state reaction barrier depends on the thermodynamic driving force with a Brønsted slope of 1/2. To support the mechanistic picture arising from the static potential energy surfaces, we perform additional molecular dynamics simulations on the excited state energy surface, in which we observe a spontaneous PCET between the donor and the acceptor groups. Our findings suggest that a Brønsted analysis may distinguish the ground state pT and excited state PCET processes.
Antiferromagnetic ground state with pair-checkerboard order in FeSe
NASA Astrophysics Data System (ADS)
Cao, Hai-Yuan; Chen, Shiyou; Xiang, Hongjun; Gong, Xin-Gao
2015-01-01
A monolayer FeSe thin film grown on SrTiO3(001) (STO) shows the sign of Tc>77 K , which is higher than the Tc record of 56 K for bulk FeAs-based superconductors. However, little is known about the magnetic ground state of FeSe, which should be closely related to its unusual superconductivity. Previous studies presume the collinear stripe antiferromagnetic (AFM) state as the ground state of FeSe, the same as that in FeAs superconductors. Here we find a magnetic order named the "pair-checkerboard AFM" as the magnetic ground state of tetragonal FeSe. The pair-checkerboard order results from the interplay between the nearest-, next-nearest, and unnegligible next-next-nearest neighbor magnetic exchange couplings of Fe atoms. The monolayer FeSe in pair-checkerboard order shows an unexpected insulating behavior with a Dirac-cone-like band structure related to the specific orbital order of the dx z and dy z characters of Fe atoms, which could explain the recently observed insulator-superconductor transition. The present results cast insights on the magnetic ordering in FeSe monolayer and its derived superconductors.
Ground state of the Frenkel-Kontorova model with a transverse degree of freedom
NASA Astrophysics Data System (ADS)
Braun, O. M.; Peyrard, M.
1995-05-01
We study the ground state of a generalized Frenkel-Kontorova model with a transverse degree of freedom. The model describes a lattice of atoms with a fixed concentration, interacting by long-range repulsive forces, which is submitted to a two-dimensional substrate potential periodic (sinusoidal) in one direction and symmetric (parabolic) or asymmetric (Toda-like) in the transverse direction. When the magnitude of the interatomic repulsion increases, the ground state of the model undergoes a series of bifurcations. In particular, the first bifurcation leads to a zigzag ground state and results in drastic change of system properties, including a cusp in the average elastic constant. For incommensurate cases, the bifurcation can interplay with the Aubry transition from a pinned to a sliding state. A reentrant pinned state has, for instance, been found. The nature (continuous or discontinuous) of the next bifurcations depends on the symmetry of the substrate potential in the transverse direction. Finally, we discuss briefly the applicability of the model to describe conductivity of superionic conductors, surface diffusion, and crystal growth.
NASA Astrophysics Data System (ADS)
Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander
2016-01-01
Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.
Resetting transcription factor control circuitry toward ground-state pluripotency in human.
Takashima, Yasuhiro; Guo, Ge; Loos, Remco; Nichols, Jennifer; Ficz, Gabriella; Krueger, Felix; Oxley, David; Santos, Fatima; Clarke, James; Mansfield, William; Reik, Wolf; Bertone, Paul; Smith, Austin
2014-09-11
Current human pluripotent stem cells lack the transcription factor circuitry that governs the ground state of mouse embryonic stem cells (ESC). Here, we report that short-term expression of two components, NANOG and KLF2, is sufficient to ignite other elements of the network and reset the human pluripotent state. Inhibition of ERK and protein kinase C sustains a transgene-independent rewired state. Reset cells self-renew continuously without ERK signaling, are phenotypically stable, and are karyotypically intact. They differentiate in vitro and form teratomas in vivo. Metabolism is reprogrammed with activation of mitochondrial respiration as in ESC. DNA methylation is dramatically reduced and transcriptome state is globally realigned across multiple cell lines. Depletion of ground-state transcription factors, TFCP2L1 or KLF4, has marginal impact on conventional human pluripotent stem cells but collapses the reset state. These findings demonstrate feasibility of installing and propagating functional control circuitry for ground-state pluripotency in human cells. PMID:25215486
Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander
2016-01-01
Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751
Ground state spin and excitation energies in half-filled Lieb lattices
NASA Astrophysics Data System (ADS)
Ţolea, M.; Niţǎ, M.
2016-10-01
We present detailed spectral calculations for small Lieb lattices having up to N =4 number of cells, in the regime of half-filling, an instance of particular relevance for the nanomagnetism of discrete systems such as quantum dot arrays, due to the degenerate levels at midspectrum. While for the Hubbard interaction model—and even number of sites—the ground state spin is given by the Lieb theorem, the inclusion of long-range interaction—or odd number of sites—makes the spin state not known a priori, which justifies our approach. We calculate also the excitation energies, which are of experimental importance, and find significant variation induced by the interaction potential. One obtains insights on the mechanisms involved that impose as ground state the Lieb state with lower spin rather than the Hund one with maximum spin for the degenerate levels, showing this in the first and second orders of the interaction potential for the smaller lattices. The analytical results agree with the numerical ones, which are performed by exact diagonalization calculations or by a combined mean-field and configuration interaction method. While the Lieb state is always lower in energy than the Hund state, for strong long-range interaction, when possible, another minimal spin state is imposed as ground state.
Resetting Transcription Factor Control Circuitry toward Ground-State Pluripotency in Human
Takashima, Yasuhiro; Guo, Ge; Loos, Remco; Nichols, Jennifer; Ficz, Gabriella; Krueger, Felix; Oxley, David; Santos, Fatima; Clarke, James; Mansfield, William; Reik, Wolf; Bertone, Paul; Smith, Austin
2014-01-01
Summary Current human pluripotent stem cells lack the transcription factor circuitry that governs the ground state of mouse embryonic stem cells (ESC). Here, we report that short-term expression of two components, NANOG and KLF2, is sufficient to ignite other elements of the network and reset the human pluripotent state. Inhibition of ERK and protein kinase C sustains a transgene-independent rewired state. Reset cells self-renew continuously without ERK signaling, are phenotypically stable, and are karyotypically intact. They differentiate in vitro and form teratomas in vivo. Metabolism is reprogrammed with activation of mitochondrial respiration as in ESC. DNA methylation is dramatically reduced and transcriptome state is globally realigned across multiple cell lines. Depletion of ground-state transcription factors, TFCP2L1 or KLF4, has marginal impact on conventional human pluripotent stem cells but collapses the reset state. These findings demonstrate feasibility of installing and propagating functional control circuitry for ground-state pluripotency in human cells. PMID:25215486
Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander
2016-01-01
Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.
NASA Astrophysics Data System (ADS)
Mukherjee, Sutirtha; Mandal, Sudhansu
The internal structure and topology of the ground states for fractional quantum Hall effect (FQHE) are determined by the relative angular momenta between all the possible pairs of electrons. Laughlin wave function is the only known microscopic wave function for which these relative angular momenta are homogeneous (same) for any pair of electrons and depend solely on the filling factor. Without invoking any microscopic theory, considering only the relationship between number of flux quanta and particles in spherical geometry, and allowing the possibility of inhomogeneous (different) relative angular momenta between any two electrons, we develop a general method for determining a closed-form ground state wave function for any incompressible FQHE state. Our procedure provides variationally obtained very accurate wave functions, yet having simpler structure compared to any other known complex microscopic wave functions for the FQHE states. This method, thus, has potential in predicting a very accurate ground state wave function for the puzzling states such as the state at filling fraction 5/2. We acknowledge support from Department of Science and Technology, India.
Tunable Splitting of the Ground-State Degeneracy in Quasi-One-Dimensional Parafermion Systems.
Chen, Chun; Burnell, F J
2016-03-11
Systems with topologically protected ground-state degeneracies are currently of great interest due to their potential applications in quantum computing. In practice, this degeneracy is never exact, and the magnitude of the ground-state degeneracy splitting imposes constraints on the time scales over which information is topologically protected. In this Letter, we use an instanton approach to evaluate the splitting of topological ground-state degeneracy in quasi-1D systems with parafermion zero modes, in the specific case where parafermions are realized by inducing a superconducting gap in pairs of fractional quantum Hall edges. We show that, like 1D topological superconducting wires, this splitting has an oscillatory dependence on the chemical potential, which arises from an intrinsic Berry phase that produces interference between distinct instanton tunneling events. These Berry phases can be mapped to chiral phases in a (dual) quantum clock model using a Fradkin-Kadanoff transformation. Comparing our low-energy spectrum to that of phenomenological parafermion models allows us to evaluate the real and imaginary parts of the hopping integral between adjacent parafermionic zero modes as functions of the chemical potential. PMID:27015499
Tunable Splitting of the Ground-State Degeneracy in 1D Parafermionic Wires
NASA Astrophysics Data System (ADS)
Chen, Chun; Burnell, Fiona
Systems with topologically protected ground-state degeneracies are currently of great interest due to their potential applications in quantum computing. In practise this degeneracy is never exact, and the magnitude of the ground-state degeneracy splitting imposes constraints on the timescales over which information is topologically protected. In this Letter we use an instanton approach to evaluate the splitting of topological ground-state degeneracy in quasi-1D systems with parafermion zero modes, in the specific case where parafermions are realized by inducing a superconducting gap in pairs of fractional quantum Hall (FQH) edges. We show that, like 1D topological superconducting wires, this splitting has an oscillatory dependence on the chemical potential, which arises from an intrinsic Berry phase that produces interference between distinct instanton tunneling events. These Berry phases can be mapped to chiral phases in a (dual) quantum clock model using a Fradkin-Kadanoff transformation. Comparing our low-energy spectrum to that of phenomenological parafermion models allows us to evaluate the real and imaginary parts of the hopping integral between adjacent parafermionic zero modes as functions of the chemical potential.
Tunable Splitting of the Ground-State Degeneracy in Quasi-One-Dimensional Parafermion Systems
NASA Astrophysics Data System (ADS)
Chen, Chun; Burnell, F. J.
2016-03-01
Systems with topologically protected ground-state degeneracies are currently of great interest due to their potential applications in quantum computing. In practice, this degeneracy is never exact, and the magnitude of the ground-state degeneracy splitting imposes constraints on the time scales over which information is topologically protected. In this Letter, we use an instanton approach to evaluate the splitting of topological ground-state degeneracy in quasi-1D systems with parafermion zero modes, in the specific case where parafermions are realized by inducing a superconducting gap in pairs of fractional quantum Hall edges. We show that, like 1D topological superconducting wires, this splitting has an oscillatory dependence on the chemical potential, which arises from an intrinsic Berry phase that produces interference between distinct instanton tunneling events. These Berry phases can be mapped to chiral phases in a (dual) quantum clock model using a Fradkin-Kadanoff transformation. Comparing our low-energy spectrum to that of phenomenological parafermion models allows us to evaluate the real and imaginary parts of the hopping integral between adjacent parafermionic zero modes as functions of the chemical potential.
Classification of ground states and normal modes for phase-frustrated multicomponent superconductors
NASA Astrophysics Data System (ADS)
Weston, Daniel; Babaev, Egor
2013-12-01
We classify ground states and normal modes for n-component superconductors with frustrated intercomponent Josephson couplings, focusing on n=4. The results should be relevant not only to multiband superconductors, but also to Josephson-coupled multilayers and Josephson-junction arrays. It was recently discussed that three-component superconductors can break time-reversal symmetry as a consequence of phase frustration. We discuss how to classify frustrated superconductors with an arbitrary number of components. Although already for the four-component case there are a large number of different combinations of phase-locking and phase-antilocking Josephson couplings, we establish that there are a much smaller number of equivalence classes where properties of frustrated multicomponent superconductors can be mapped to each other. This classification is related to the graph-theoretical concept of Seidel switching. Numerically, we calculate ground states, normal modes, and characteristic length scales for the four-component case. We report conditions of appearance of new accidental continuous ground-state degeneracies.
Calculated ground state potential surface and excitation energies for the copper trimer
NASA Technical Reports Server (NTRS)
Walch, S. P.; Laskowski, B. C.
1986-01-01
In the context of their relevance to catalysis and to materials science problems, transition metals and transition metal (TM) compounds are currently of considerable interest, and studies have been conducted of the copper trimer, Cu3. The present investigation is concerned with a study of the ground state surface and several groups of excited states in order to improve the understanding of the spectroscopy of Cu3. Differences of the current study from previous investigations are related to an employment of larger basis sets and a more extensive electron correlation. This was done with the objective to obtain a more accurate definition of the ground state surface. Features of the bonding in the copper dimer are considered to obtain a basis for an understanding of the copper trimer. Attention is given to calculational details, the ground state surface, and calculated vertical excitation energies. The results of SCF/SDCI calculations are reported for portions of the ground surface, for two groups of excited states, and for the ionization potential of Cu3.
Sign structure and ground-state properties for a spin-S t-J chain
NASA Astrophysics Data System (ADS)
Wang, Qing-Rui; Ye, Peng
2014-07-01
The antiferromagnetic Heisenberg spin chain of odd spin S is in the Haldane phase with several defining physical properties, such as thermodynamical ground-state degeneracy, symmetry-protected edge states, and nonzero string order parameter. If nonzero hole concentration δ and hole hopping energy t are considered, the spin chain is replaced by a spin-S t-J chain. The motivation of this paper is to generalize the discussions of the Haldane phase to the doped spin chain. The first result of this paper is that, for the model considered here, the Z2 sign structure in the usual Ising basis can be totally removed by two consecutive unitary transformations consisting of a spatially local one and a nonlocal one. Direct from the sign structure, the second result of this paper is that the Marshall theorem and the Lieb-Mattis theorem for pure spin systems are generalized to the t-J chain for arbitrary S and δ. A corollary of the theorem provides us with the ground-state degeneracy in the thermodynamic limit. The third result of this paper is about the phase diagram. We show that the defining properties of the Haldane phase survive in the small t /J limit. The large t /J phase supports a gapped spin sector with similar properties (ground-state degeneracy, edge state, and string order parameter) of the Haldane chain, although the charge sector is gapless.
Indirect measurement of nuclear reactions of astrophysical interest
Liu, W. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.; Guo, B.; Lian, G.; Su, J.; Zeng, S.; Wang, B. X.; Yan, S. Q.; Li, Y. J.; Li, E. T.; Jin, S. J.
2010-05-12
Systematic indirect measurements of nuclear astrophysical reactions using the unstable ion beam facility GIRAFFE in CIAE were performed. We have measured the angular distributions of transfer reactions, such as {sup 8}Li(d,p){sup 9}Li, {sup 8}Li(d,n){sup 9}Be and {sup 8}Li(p,d){sup 7}Li in inverse kinematics, and derived the astrophysical S-factors or reaction rates for {sup 8}Li(n,gamma){sup 9}Li and {sup 8}Li(p,gamma){sup 9}Be by using asymptotic normalization coefficient (ANC) or spectroscopic factor methods.
Ground-state depleted laser in neodymium-doped yttrium orthosilicate
NASA Astrophysics Data System (ADS)
Beach, Raymond J.; Albrecht, George F.; Solarz, Richard W.; Krupke, William F.; Comaskey, Brian J.; Mitchell, Scott C.; Brandle, Charles D.; Berkstresser, George W.
1990-04-01
A ground state depleted (GSD)1,2 laser has been demonstrated in the form of a Q-switched oscillator operating at 912 nm. Using Nd3+ as the active ion and Y2SiO5 as the host material, the laser transition is from the lowest lying stark level of the Nd3+4F3/2 level to a stark level 355 cm-1 above the lowest lying one in the 4I9/2 manifold. The necessity of depleting the ground 4I9/2 manifold is evident for this level scheme as transparency requires a 10% inversion. To achieve the high excitation levels required for the efficient operation of this laser, bleach wave pumping using an alexandrite laser at 745 nm has been employed. The existence of a large absorption feature at 810 nm also allows for the possibility of A1GaAs laser diode pumping. Using KNbO3, noncritical phase matching is possible at 140°C using d32 and has been demonstrated. The results of Q-switched laser performance and harmonic generation in KNbO3 will be presented. Orthosilicate is a monoclinic biaxial crystal. An oriented spectroscopic evaluation consisting of a Judd-Ofelt analysis of oriented absorption spectra and the measurements of oriented emission spectra has been completed and will be presented. Results of modeling using these spectroscopically determined parameters will be compared with the actual laser performance. The performance of this laser at 911 nm which allows accessing Cs atomic resonance filters through harmonic doubling will also be discussed. Orthosilicate can be grown in large boules of excellent optical quality using a Czochralski technique. Because of the relatively small 912 nm emission cross section of 2-3 x 10-20cm2 (orientation dependent) fluences of 10-20 J/cm2 must be circulated in the laser cavity for the efficient extraction of stored energy. This necessitates very aggressive laser damage thresholds. Results from the Reptile laser damage facility at Lawrence Livermore National Laboratory (LLNL) will be presented showing Y2SiO5 bulk and AR sol-gel coated surface
Charged fusion product loss measurements using nuclear activation
Bonheure, G.; Hult, M.; Gonzalez de Orduna, R.; Wieslander, E.; Arnold, D.; Dombrowski, H.; Laubenstein, M.; Murari, A.; Collaboration: JET-EFDA Contributors
2010-10-15
In ITER, {alpha} particle loss measurements will be required in order to understand the alpha particle physics. Techniques capable of operating in a fusion reactor environment need further development. Recent experimental studies on JET demonstrated the potential of nuclear activation to measure the flux of escaping MeV ions. New results from MeV ion induced activation of metallic, ceramic, and crystal samples placed near the plasma edge are reported. Activation products were measured as function of orientation with respect to the magnetic field as well as function of the distance to the plasma. Sample activity was measured using ultralow-level gamma-ray spectrometry. Distribution of 14.68 MeV fusion proton induced activation products is strongly anisotropic in agreement with simulations and falls off sharply with increasing distance to the plasma. Prospects for using the technique in ITER are discussed.
Gamma Ray Mirrors for Direct Measurement of Spent Nuclear Fuel
Pivovaroff, Dr. Michael J.; Ziock, Klaus-Peter; Harrison, Mark J; Soufli, Regina
2014-01-01
Direct measurement of the amount of Pu and U in spent nuclear fuel represents a challenge for the safeguards community. Ideally, the characteristic gamma-ray emission lines from different isotopes provide an observable suitable for this task. However, these lines are generally lost in the fierce flux of radiation emitted by the fuel. The rates are so high that detector dead times limit measurements to only very small solid angles of the fuel. Only through the use of carefully designed view ports and long dwell times are such measurements possible. Recent advances in multilayer grazing-incidence gamma-ray optics provide one possible means of overcoming this difficulty. With a proper optical and coating design, such optics can serve as a notch filter, passing only narrow regions of the overall spectrum to a fully shielded detector that does not view the spent fuel directly. We report on the design of a mirror system and a number of experimental measurements.
Huang, Rui; Phan, Hoa; Herng, Tun Seng; Hu, Pan; Zeng, Wangdong; Dong, Shao-Qiang; Das, Soumyajit; Shen, Yongjia; Ding, Jun; Casanova, David; Wu, Jishan
2016-08-17
Higher order acenes (i.e., acenes longer than pentacene) and extended zethrenes (i.e., zethrenes longer than zethrene) are theoretically predicted to have an open-shell singlet ground state, and the radical character is supposed to increase with extension of molecular size. The increasing radical character makes the synthesis of long zethrenes and acenes very challenging, and so far, the longest reported zethrene and acene derivatives are octazethrene and nonacene, respectively. In addition, there is a lack of fundamental understanding of the differences between these two closely related open-shell singlet systems. In this work, we report the first synthesis of a challenging nonazethrene derivative, HR-NZ, and its full structural and physical characterizations including variable temperature NMR, ESR, SQUID, UV-vis-NIR absorption and electrochemical measurements. Compound HR-NZ has an open-shell singlet ground state with a moderate diradical character (y0 = 0.48 based on UCAM-B3LYP calculation) and a small singlet-triplet gap (ΔES-T = -5.2 kcal/mol based on SQUID data), thus showing magnetic activity at room temperature. It also shows amphoteric redox behavior, with a small electrochemical energy gap (1.33 eV). Its electronic structure and physical properties are compared with those of Anthony's nonacene derivative JA-NA and other zethrene derivatives. A more general comparison between higher order acenes and extended zethrenes was also conducted on the basis of ab initio electronic structure calculations, and it was found that zethrenes and acenes have very different spatial localization of the unpaired electrons. As a result, a faster decrease of singlet-triplet energy gap and a faster increase of radical character with increase of the number of benzenoid rings were observed in zethrene series. Our studies reveal that spatial localization of the frontier molecular orbitals play a very important role on the nature of radical character as well as the excitation
Effective S =1/2 Hamiltonians and the Quantum Spin Ice Ground State of Yb2Ti2O7
NASA Astrophysics Data System (ADS)
Gaulin, Bruce D.
2013-03-01
New neutron scattering instrumentation offers unprecedented opportunities for mapping out the full dispersion and dynamic susceptibility of magnetic materials. In turn, these measurements can be exploited to determine their microscopic spin Hamiltonians in great detail. We've used these techniques to examine the exotic quantum spin ice ground state of Yb2Ti2O7, a pyrochlore magnet, which can be thought of in terms of spins decorating a network of corner-sharing tetrahedra. In this environment, Yb3+displays a ground state crystal field doublet which is very well separated from its excited states, resulting in an effective S =1/2 description for the Yb moments. It's positive Curie-Weiss constant of ~ 0.5 K indicates net ferromagnetic interactions and it displays a g-tensor with XY anisotropy. However strong spin orbit effects give rise to an anisotropic exchange Hamiltonian, which can be understood in quantitative detail by modeling time-of-flight neutron scattering in a high field polarized state with spin wave theory using anisotropic exchange. The resulting Hamiltonian shows strong coupling between local z-components of spin, as in spin ice, but also substantial terms that encourage quantum fluctuations. Armed with the microscopic spin Hamiltonian, the mean field phase diagram and a range of physical properties can be calculated and compared with experiment. We see that any possible ordering is strongly suppressed relative to mean field theory by the presence of geometrical frustration, quantum fluctuations, or both; and the low temperature bulk properties are well accounted for by the effective S =1/2 Hamiltonian we determine.
Temperature measuring analysis of the nuclear reactor fuel assembly
NASA Astrophysics Data System (ADS)
F., Urban; Ä½., Kučák; Bereznai, J.; Závodný, Z.; Muškát, P.
2014-08-01
Study was based on rapid changes of measured temperature values from the thermocouple in the VVER 440 nuclear reactor fuel assembly. Task was to determine origin of fluctuations of the temperature values by experiments on physical model of the fuel assembly. During an experiment, heated water was circulating in the system and cold water inlet through central tube to record sensitivity of the temperature sensor. Two positions of the sensor was used. First, just above the central tube in the physical model fuel assembly axis and second at the position of the thermocouple in the VVER 440 nuclear reactor fuel assembly. Dependency of the temperature values on time are presented in the diagram form in the paper.
Spin-liquid ground state in the frustrated J1-J2 zigzag chain system BaTb2O4
Aczel, A. A.; Li, L.; Garlea, V. O.; Yan, J. -Q.; Weickert, F.; Zapf, V. S.; Movshovich, R.; Jaime, M.; Baker, P. J.; Keppens, V.; et al
2015-07-13
We have investigated polycrystalline samples of the zigzag chain system BaTb2O4 with magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation measurements. No magnetic transitions are observed in the bulk measurements, while neutron diffraction reveals low-temperature, short-range, intrachain magnetic correlations between Tb3+ ions. Muon spin relaxation measurements indicate that these correlations are dynamic, as the technique detects no signatures of static magnetism down to 0.095 K. Altogether these findings provide strong evidence for a spin liquid ground state in BaTb2O4.
NASA Technical Reports Server (NTRS)
Cooksy, A. L.; Saykally, R. J.; Brown, J. M.; Evenson, K. M.
1986-01-01
Accurate values are presented for the fine-structure intervals in the 3P ground state of neutral atomic C-12 and C-13 as obtained from laser magnetic resonance spectroscopy. The rigorous analysis of C-13 hyperfine structure, the measurement of resonant fields for C-12 transitions at several additional far-infrared laser frequencies, and the increased precision of the C-12 measurements, permit significant improvement in the evaluation of these energies relative to earlier work. These results will expedite the direct and precise measurement of these transitions in interstellar sources and should assist in the determination of the interstellar C-12/C-13 abundance ratio.
Vibrational Relaxation of Ground-State Oxygen Molecules With Atomic Oxygen and Carbon Dioxide
NASA Astrophysics Data System (ADS)
Saran, D. V.; Pejakovic, D. A.; Copeland, R. A.
2008-12-01
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(ν2) emission in the 6.8 μm region. Collisional deactivation of vibrationally excited O2, O2(X3Σ-g, υ = 1) + H2O ↔ O2(X3Σ-g, υ = 0) + H2O(ν2), is an important source of H2O(ν2). A recent study has identified two other processes involving excited O2 that control H2O(ν2) population in the MLT: (1) the vibrational-translational (V-T) relaxation of O2(X3Σ-g, υ = 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(ν2) emission [1]. Here we report laboratory studies of the collisional removal of O2(X3Σ-g, υ = 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(X3Σ-g, υ = 1) population, a technically simpler approach is used in which the υ = 1 level of the O2(a1Δg) 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(a1Δg, υ = 1), and the pulsed output of the second laser detects O2(a1Δg, υ = 1) via resonance-enhanced multiphoton ionization. With ground-state O2 present, owing to the rapid equilibration of the O2(X3Σ-g, υ = 1) and O2(a1Δg, υ = 1) populations via the processes O2(a1Δg, υ = 1) + O2(X3Σ-g, υ = 0) ↔ O2(a1Δg, υ = 0) + O2(X3Σ-g, υ = 1), the information on the O2(X3Σ-g, υ = 1) kinetics is extracted from the O2(a1Δg, υ = 1) temporal evolution. In addition, measurements of the removal of O2(X3Σ-g, υ = 1) by CO2 at room temperature will also
NASA Astrophysics Data System (ADS)
Yakut, H.; Guliyev, E.; Guner, M.; Tabar, E.; Zenginerler, Z.
2012-08-01
A new microscopic method has been developed in the framework of the Quasiparticle-Phonon Nuclear Model (QPNM) in order to investigate spin polarization effects on the magnetic properties such as magnetic moment, intrinsic magnetic moment and effective gs factor of the ground state of odd-mass 157-167Er isotopes. The calculations were performed using both Tamm-Dancoff Approximation (TDA) and Quasiparticle Random-Phase Approximation (QRPA). Reasonably good agreement has been obtained between the QRPA results and the relevant experimental data. Furthermore the variation of the intrinsic magnetic moment gK values with the mass number A exhibits similar behavior for both theoretical and experimental results. From the compression of the calculated intrinsic magnetic moment values with the experimental data the spin-spin interaction parameter has been found as χ=(30/A) MeV for odd-mass 157-167Er isotopes. Our results clarify the possibility of using this new method to describe the magnetic properties of odd-mass deformed nuclei.
NASA Technical Reports Server (NTRS)
Brown, J. M.; Evenson, K. M.; Sears, T. J.
1985-01-01
The GeH radical has been detected in its ground 2 Pi state in the gas phase reaction of fluorine atoms with GeH4 by laser magnetic resonance techniques. Rotational transitions within both 2 Pi 1/2 and 2 Pi 3/2 manifolds have been observed at far-infrared wavelengths and rotational transitions between the two fine structure components have been detected at infrared wavelengths (10 microns). Signals have been observed for all five naturally occurring isotopes of germanium. Nuclear hyperfine structure for H-1 and Ge-73 has also been observed. The data for the dominant isotope (/Ge-74/H) have been fitted to within experimental error by an effective Hamiltonian to give a set of molecular parameters for the X 2 Pi state which is very nearly complete. In addition, the dipole moment of GeH in its ground state has been estimated from the relative intensities of electric and magnetic dipole transitions in the 10 micron spectrum to be 1.24(+ or - 0.10) D.
Levy, Mel E-mail: mlevy@tulane.edu; Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W. E-mail: mlevy@tulane.edu
2014-05-14
Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.
Egorova, Dassia
2015-06-07
Several recent experiments report on possibility of dark-state detection by means of so called beating maps of two-dimensional photon-echo spectroscopy [Ostroumov et al., Science 340, 52 (2013); Bakulin et al., Ultrafast Phenomena XIX (Springer International Publishing, 2015)]. The main idea of this detection scheme is to use coherence induced upon the laser excitation as a very sensitive probe. In this study, we investigate the performance of ground-state coherence in the detection of dark electronic states. For this purpose, we simulate beating maps of several models where the excited-state coherence can be hardly detected and is assumed not to contribute to the beating maps. The models represent strongly coupled electron-nuclear dynamics involving avoided crossings and conical intersections. In all the models, the initially populated optically accessible excited state decays to a lower-lying dark state within few hundreds femtoseconds. We address the role of Raman modes and of interstate-coupling nature. Our findings suggest that the presence of low-frequency Raman active modes significantly increases the chances for detection of dark states populated via avoided crossings, whereas conical intersections represent a more challenging task.
Heat transfer in nuclear fuels: Measurements of gap conductance
NASA Astrophysics Data System (ADS)
Cho, Chun Hyung
Heat transfer in the fuel-clad gap in a nuclear reactor impacts the overall temperature distribution, stored energy and the mechanical properties of a nuclear fuel rod. Therefore, an accurate estimation of the gap conductance between the fuel and the clad is critically important for reactor design and operations. To obtain the requisite accuracy in the gap conductance estimation, it is important to understand the effects of the convective heat transfer coefficient, the gas composition, pressure and temperature, and so forth. The objectives of this study are to build a bench-scale experimental apparatus for the measurement of thermal gap conductances and to develop a better understanding of the differences that have been previously observed between such measured values and those predicted theoretically. This is accomplished by employing improved analyses of the experiments and improved theoretical models. Using laser heating of slightly separated stainless-steel plates, the gap conductance was measured using a technique that compares the theoretical and experimental time dependent temperatures at the back surface of the second plate. To consider the effects of surface temperature and gas pressure, the theoretical temperatures were calculated using a convective heat transfer coefficient that was dependent upon both the temperature and the gas pressure.
NASA Astrophysics Data System (ADS)
Budrikis, Zoe; Morgan, J. P.; Akerman, J.; Stein, A.; Politi, Paolo; Langridge, S.; Marrows, C. H.; Stamps, R. L.
2012-07-01
Quenched disorder affects how nonequilibrium systems respond to driving. In the context of artificial spin ice, an athermal system comprised of geometrically frustrated classical Ising spins with a twofold degenerate ground state, we give experimental and numerical evidence of how such disorder washes out edge effects and provide an estimate of disorder strength in the experimental system. We prove analytically that a sequence of applied fields with fixed amplitude is unable to drive the system to its ground state from a saturated state. These results should be relevant for other systems where disorder does not change the nature of the ground state.
Competing ground states of strongly correlated bosons in the Harper-Hofstadter-Mott model
NASA Astrophysics Data System (ADS)
Natu, Stefan S.; Mueller, Erich J.; Das Sarma, S.
2016-06-01
Using an efficient cluster approach, we study the physics of two-dimensional lattice bosons in a strong magnetic field in the regime where the tunneling is much weaker than the on-site interaction strength. We study both the dilute, hard-core bosons at filling factors much smaller than unity occupation per site and the physics in the vicinity of the superfluid-Mott lobes as the density is tuned away from unity. For hard-core bosons, we carry out extensive numerics for a fixed flux per plaquette ϕ =1 /5 and ϕ =1 /3 . At large flux, the lowest-energy state is a strongly correlated superfluid, analogous to He-4, in which the order parameter is dramatically suppressed, but nonzero. At filling factors ν =1 /2 ,1 , we find competing incompressible states which are metastable. These appear to be commensurate density wave states. For small flux, the situation is reversed and the ground state at ν =1 /2 is an incompressible density wave solid. Here, we find a metastable lattice supersolid phase, where superfluidity and density wave order coexist. We then perform careful numerical studies of the physics near the vicinity of the Mott lobes for ϕ =1 /2 and ϕ =1 /4 . At ϕ =1 /2 , the superfluid ground state has commensurate density wave order. At ϕ =1 /4 , incompressible phases appear outside the Mott lobes at densities n =1.125 and n =1.25 , corresponding to filling fractions ν =1 /2 and 1, respectively. These phases, which are absent in single-site mean-field theory, are metastable and have slightly higher energy than the superfluid, but the energy difference between them shrinks rapidly with increasing cluster size, suggestive of an incompressible ground state. We thus explore the interplay between Mott physics, magnetic Landau levels, and superfluidity, finding a rich phase diagram of competing compressible and incompressible states.
Theoretical study of the ground-state structures and properties of niobium hydrides under pressure
NASA Astrophysics Data System (ADS)
Gao, Guoying; Hoffmann, Roald; Ashcroft, N. W.; Liu, Hanyu; Bergara, Aitor; Ma, Yanming
2013-11-01
As part of a search for enhanced superconductivity, we explore theoretically the ground-state structures and properties of some hydrides of niobium over a range of pressures and particularly those with significant hydrogen content. A primary motivation originates with the observation that under normal conditions niobium is the element with the highest superconducting transition temperature (Tc), and moreover some of its compounds are metals again with very high Tc's. Accordingly, combinations of niobium with hydrogen, with its high dynamic energy scale, are also of considerable interest. This is reinforced further by the suggestion that close to its insulator-metal transition, hydrogen may be induced to enter the metallic state somewhat prematurely by the addition of a relatively small concentration of a suitable transition metal. Here, the methods used correctly reproduce some ground-state structures of niobium hydrides at even higher concentrations of niobium. Interestingly, the particular stoichiometries represented by NbH4 and NbH6 are stabilized at fairly low pressures when proton zero-point energies are included. While no paired H2 units are found in any of the hydrides we have studied up to 400 GPa, we do find complex and interesting networks of hydrogens around the niobiums in high-pressure NbH6. The Nb-Nb separations in NbHn are consistently larger than those found in Nb metal at the respective pressures. The structures found in the ground states of the high hydrides, many of them metallic, suggest that the coordination number of hydrogens around each niobium atom grows approximately as 4n in NbHn (n = 1-4), and is as high as 20 in NbH6. NbH4 is found to be a plausible candidate to become a superconductor at high pressure, with an estimated Tc ˜ 38 K at 300 GPa.
Umetsu, R Y; Fujita, A; Ito, W; Kanomata, T; Kainuma, R
2011-08-17
DC and AC magnetic measurements were carried out to clarify the difference in the magnetic ground state depending on the kinds of Z element used in the martensite phase in Ni-Mn-Z (Z = In, Sn and Sb) off-stoichiometric Heusler alloys. Magnetic field cooling effects were observed in the DC thermomagnetization curves in the low temperature regions, and a frequency dependence on AC susceptibility was also observed in both real and imaginary parts of the susceptibility. Negative divergence was clearly observed in nonlinear AC susceptibility only for the Ni(50)Mn(40)Sb(10) alloy, suggesting that the magnetic feature of its ground state is the spin-glass state. The magnetic ground state of the martensite phase in these alloys would relate to the magnetic configuration of the Mn atoms in the ferromagnetic austenite phase.
NASA Astrophysics Data System (ADS)
Marinero, E. E.; Rettner, C. T.; Zare, R. N.
1982-09-01
Using tunable anti-Stokes orders of a frequency-doubled dye laser, rotationally-selective excited-state populations in H2 are prepared by two-photon excitation. The ensuing photoionization allows direct determination of (v'', J'') populations.
Superconducting calorimetric alpha particle sensors for nuclear nonproliferation applications
Horansky, Robert D.; Ullom, Joel N.; Beall, James A.; Hilton, Gene C.; Irwin, Kent D.; Dry, Donald E.; Hastings, Elizabeth P.; Lamont, Stephen P.; Rudy, Clifford R.; Rabin, Michael W.
2008-09-22
Identification of trace nuclear materials is usually accomplished by alpha spectrometry. Current detectors cannot distinguish critical elements and isotopes. We have developed a detector called a microcalorimeter, which achieves a resolution of 1.06 keV for 5.3 MeV alphas, the highest resolving power of any energy dispersive measurement. With this exquisite resolution, we can unambiguously identify the {sup 240}Pu/{sup 239}Pu ratio in Pu, a critical measurement for ascertaining the intended use of nuclear material. Furthermore, we have made a direct measurement of the {sup 209}Po ground state decay.
NASA Astrophysics Data System (ADS)
Ran, Shi-Ju
2016-05-01
In this work, a simple and fundamental numeric scheme dubbed as ab initio optimization principle (AOP) is proposed for the ground states of translational invariant strongly correlated quantum lattice models. The idea is to transform a nondeterministic-polynomial-hard ground-state simulation with infinite degrees of freedom into a single optimization problem of a local function with finite number of physical and ancillary degrees of freedom. This work contributes mainly in the following aspects: (1) AOP provides a simple and efficient scheme to simulate the ground state by solving a local optimization problem. Its solution contains two kinds of boundary states, one of which play the role of the entanglement bath that mimics the interactions between a supercell and the infinite environment, and the other gives the ground state in a tensor network (TN) form. (2) In the sense of TN, a novel decomposition named as tensor ring decomposition (TRD) is proposed to implement AOP. Instead of following the contraction-truncation scheme used by many existing TN-based algorithms, TRD solves the contraction of a uniform TN in an opposite way by encoding the contraction in a set of self-consistent equations that automatically reconstruct the whole TN, making the simulation simple and unified; (3) AOP inherits and develops the ideas of different well-established methods, including the density matrix renormalization group (DMRG), infinite time-evolving block decimation (iTEBD), network contractor dynamics, density matrix embedding theory, etc., providing a unified perspective that is previously missing in this fields. (4) AOP as well as TRD give novel implications to existing TN-based algorithms: A modified iTEBD is suggested and the two-dimensional (2D) AOP is argued to be an intrinsic 2D extension of DMRG that is based on infinite projected entangled pair state. This paper is focused on one-dimensional quantum models to present AOP. The benchmark is given on a transverse Ising
Electronic Structure and Ground State Properties of Non-Magnetic NiPt Systems
NASA Astrophysics Data System (ADS)
PAUDYAL, DURGA; MOOKERJEE, ABHIJIT
We have studied the electronic properties like density of states and band structures and also the ground state properties like formation energy, cohesive energy, bulk modulus and structural energy of NiPt system using the linearized muffin-tin orbital method introduced by Andersen.1,2 In an earlier communication we had argued that both charge neutrality and scalar relativistic corrections are very important for the high concentration of Pt alloys. The calculations here, were, therefore, carried out with charge neutrality as well as with and without scalar relativistic correction for comparison.
Quantum Cohesion Oscillation of Electron Ground State in Low Temperature Laser Plasma
NASA Technical Reports Server (NTRS)
Zhao, Qingxun; Zhang, Ping; Dong, Lifang; Zhang, Kaixi
1996-01-01
The development of radically new technological and economically efficient methods for obtaining chemical products and for producing new materials with specific properties requires the study of physical and chemical processes proceeding at temperature of 10(exp 3) to 10(exp 4) K, temperature range of low temperature plasma. In our paper, by means of Wigner matrix of quantum statistical theory, a formula is derived for the energy of quantum coherent oscillation of electron ground state in laser plasma at low temperature. The collective behavior would be important in ion and ion-molecule reactions.
NASA Technical Reports Server (NTRS)
Chong, D. P.; Langhoff, S. R.
1986-01-01
A modified coupled pair functional (CPF) method is presented for the configuration interaction problem that dramatically improves properties for cases where the Hartree-Fock reference configuration is not a good zeroth-order wave function description. It is shown that the tendency for CPF to overestimate the effect of higher excitations arises from the choice of the geometric mean for the partial normalization denominator. The modified method is demonstrated for ground state dipole moment calculations of the NiH, CuH, and ZnH transition metal hydrides, and compared to singles-plus-doubles configuration interaction and the Ahlrichs et al. (1984) CPF method.
Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation
Albus, Alexander P.; Wilkens, Martin; Illuminati, Fabrizio
2003-06-01
We introduce density-functional theory for inhomogeneous Bose-Fermi mixtures, derive the associated Kohn-Sham equations, and determine the exchange-correlation energy in local-density approximation. We solve numerically the Kohn-Sham system, and determine the boson and fermion density distributions and the ground-state energy of a trapped, dilute mixture beyond mean-field approximation. The importance of the corrections due to exchange correlation is discussed by a comparison with current experiments; in particular, we investigate the effect of the repulsive potential-energy contribution due to exchange correlation on the stability of the mixture against collapse.
Ground-State Band and Deformation of the Z = 102 Isotope N {sup 254}
Reiter, P.; Khoo, T.L.; Lister, C.J.; Seweryniak, D.; Ahmad, I.; Alcorta, M.; Carpenter, M.P.; Cizewski, J.A.; Davids, C.N.; Gervais, G.; Greene, J.P.; Henning, W.F.; Janssens, R.V.; Lauritsen, T.; Siem, S.; Sonzogni, A.A.; Sullivan, D.; Uusitalo, J.; Wiedenhoever, I.; Amzal, N.; Butler, P.A.; Chewter, A.J.; Greenlees, P.T.; Herzberg, R.; Jones, G.D.; Cizewski, J.A.; Ding, K.Y.; Fotiades, N.; Fox, J.D.; Korten, W.; Vetter, K.; Siem, S.
1999-01-01
The ground-state band of the Z=102 isotope {sup 254}No has been identified up to spin 14, indicating that the nucleus is deformed. The deduced quadrupole deformation, {beta}=0.27 , is in agreement with theoretical predictions. These observations confirm that the shell-correction energy responsible for the stability of transfermium nuclei is partly derived from deformation. The survival of {sup 254}No up to spin 14 means that its fission barrier persists at least up to that spin. {copyright} {ital 1999} {ital The American Physical Society }
The ground state of the D = 11 supermembrane and matrix models on compact regions
NASA Astrophysics Data System (ADS)
Boulton, Lyonell; Garcia del Moral, Maria Pilar; Restuccia, Alvaro
2016-09-01
We establish a general framework for the analysis of boundary value problems of matrix models at zero energy on compact regions. We derive existence and uniqueness of ground state wavefunctions for the mass operator of the D = 11 regularized supermembrane theory, that is the N = 16 supersymmetric SU (N) matrix model, on balls of finite radius. Our results rely on the structure of the associated Dirichlet form and a factorization in terms of the supersymmetric charges. They also rely on the polynomial structure of the potential and various other supersymmetric properties of the system.
Magnetic Polarization of the Americium J =0 Ground State in AmFe2
NASA Astrophysics Data System (ADS)
Magnani, N.; Caciuffo, R.; Wilhelm, F.; Colineau, E.; Eloirdi, R.; Griveau, J.-C.; Rusz, J.; Oppeneer, P. M.; Rogalev, A.; Lander, G. H.
2015-03-01
Trivalent americium has a nonmagnetic (J =0 ) ground state arising from the cancellation of the orbital and spin moments. However, magnetism can be induced by a large molecular field if Am3 + is embedded in a ferromagnetic matrix. Using the technique of x-ray magnetic circular dichroism, we show that this is the case in AmFe2 . Since ⟨Jz⟩=0 , the spin component is exactly twice as large as the orbital one, the total Am moment is opposite to that of Fe, and the magnetic dipole operator ⟨Tz⟩ can be determined directly; we discuss the progression of the latter across the actinide series.
NASA Astrophysics Data System (ADS)
Liu, Zhisu; Guo, Shangjiang
2015-06-01
In this paper, we consider the following semilinear Kirchhoff type equation where is a small parameter, , a, b are positive constants, μ > 0 is a parameter, and the nonlinear growth of | u|4 u reaches the Sobolev critical exponent since 2* = 6 for three spatial dimensions. We prove the existence of a positive ground state solution with exponential decay at infinity for μ > 0 and sufficiently small under some suitable conditions on the nonnegative functions V, K and Q. Moreover, concentrates around a global minimum point of V as . The methods used here are based on the concentration-compactness principle of Lions.
Competing Magnetic Ground States in A-Site Layer Ordered Manganites
NASA Astrophysics Data System (ADS)
Dabrowski, B.; Chmaissem, O.; Ren, Y.; Brown, D. E.; Kolesnik, S.; Mais, J.
2010-03-01
We report the discovery of competing ground states near a multicritical point in A-site layer ordered La1-xBa1+xMn2O6 materials. We demonstrate the dual effects of deliberately introduced disorder on the system's stability, the freezing of the competing states, and the drastic reduction in magnetic fields required for the suppression of charge and orbital ordered phases. Our work suggests that quenched disorder is not the primary reason for phase separation and magnetoresistance, and that increased doping leads to electronic phase separation.
Ground states of bilayered and extended t-J-U models
NASA Astrophysics Data System (ADS)
Voo, Khee-Kyun
2015-09-01
The ground states of bilayered and extended t-J-U models are investigated with renormalized mean field theory. The trial wave functions are Gutzwiller projected Hartree-Fock states, and the site double occupancies are variational parameters. It is found that a spontaneous interlayer phase separation (PS) may arise in bilayers. In electron-hole doping asymmetric systems, the propensity for PS is stronger in electron doped bands. Via a PS, superconductivity can survive to lower doping densities, and antiferromagnetism in electron doped systems may survive to higher doping densities. The result is related to the superconducting cuprates.
Auditory Power-Law Activation Avalanches Exhibit a Fundamental Computational Ground State
NASA Astrophysics Data System (ADS)
Stoop, Ruedi; Gomez, Florian
2016-07-01
The cochlea provides a biological information-processing paradigm that we are only beginning to understand in its full complexity. Our work reveals an interacting network of strongly nonlinear dynamical nodes, on which even a simple sound input triggers subnetworks of activated elements that follow power-law size statistics ("avalanches"). From dynamical systems theory, power-law size distributions relate to a fundamental ground state of biological information processing. Learning destroys these power laws. These results strongly modify the models of mammalian sound processing and provide a novel methodological perspective for understanding how the brain processes information.
Ground-state candidate for the classical dipolar kagome Ising antiferromagnet
NASA Astrophysics Data System (ADS)
Chioar, I. A.; Rougemaille, N.; Canals, B.
2016-06-01
We have investigated the low-temperature thermodynamic properties of the classical dipolar kagome Ising antiferromagnet using Monte Carlo simulations, in the quest for the ground-state manifold. In spite of the limitations of a single-spin-flip approach, we managed to identify certain ordering patterns in the low-temperature regime and we propose a candidate for this unknown state. This configuration presents some intriguing features and is fully compatible with the extrapolations of the at-equilibrium thermodynamic behavior sampled so far, making it a very likely choice for the dipolar long-range ordered state of the classical kagome Ising antiferromagnet.
Auditory Power-Law Activation Avalanches Exhibit a Fundamental Computational Ground State.
Stoop, Ruedi; Gomez, Florian
2016-07-15
The cochlea provides a biological information-processing paradigm that we are only beginning to understand in its full complexity. Our work reveals an interacting network of strongly nonlinear dynamical nodes, on which even a simple sound input triggers subnetworks of activated elements that follow power-law size statistics ("avalanches"). From dynamical systems theory, power-law size distributions relate to a fundamental ground state of biological information processing. Learning destroys these power laws. These results strongly modify the models of mammalian sound processing and provide a novel methodological perspective for understanding how the brain processes information.
Fast ground-state cooling of mechanical resonators with time-dependent optical cavities
NASA Astrophysics Data System (ADS)
Li, Yong; Wu, Lian-Ao; Wang, Z. D.
2011-04-01
We propose a feasible scheme to cool down a mechanical resonator (MR) in a three-mirror cavity optomechanical system with controllable external optical driving fields. Under the Born-Oppenheimer approximation, the whole dynamics of the mechanical resonator and cavities is reduced to that of a time-dependent harmonic oscillator, whose effective frequency can be controlled through the optical driving fields. The fast cooling of the MR can be realized by controlling the amplitude of the optical driving fields. Significantly, we further show that the ground-state cooling may be achieved via the three-mirror cavity optomechanical system without the resolved sideband condition.
Ground-state properties of a dilute homogeneous Bose gas of hard disks in two dimensions
Mazzanti, F.; Polls, A.; Fabrocini, A.
2005-03-01
The energy and structure of a dilute hard-disks Bose gas are studied in the framework of a variational many-body approach based on a Jastrow correlated ground-state wave function. The asymptotic behaviors of the radial distribution function and the one-body density matrix are analyzed after solving the Euler equation obtained by a free minimization of the hypernetted chain energy functional. Our results show important deviations from those of the available low density expansions, already at gas parameter values x{approx}0.001. The condensate fraction in 2D is also computed and found generally lower than the 3D one at the same x.
Theoretical investigation of boundary contours of ground-state atoms in uniform electric fields
NASA Astrophysics Data System (ADS)
Shi, Hua; Zhao, Dong-Xia; Yang, Zhong-Zhi
2015-12-01
The boundary contours were investigated for first 54 ground-state atoms of the periodic table when they are in uniform electric fields of strengths 106, 107 and 108 V/m. The atomic characteristic boundary model in combination with an ab-initio method was employed. Some regularities of the deformation of atoms, ΔR, in above electric fields are revealed. Furthermore, atomic polarisabilities of the first 54 elements of the periodic table are shown to correlate strongly with the mean variation rate of atomic radial size divided by the strength of the electric field F, ?, which provides a predictive method of calculating atomic polarisabilities of 54 atoms.
Ground State Properties of Ising Chain with Random Monomer-Dimer Couplings
NASA Astrophysics Data System (ADS)
Ardebili, S. Bahareh Seyedein; Sepehrinia, Reza
2016-05-01
We study analytically the one-dimensional Ising model with a random binary distribution of ferromagnetic and antiferromagnetic exchange couplings at zero temperature. We introduce correlations in the disorder by assigning a dimer of one type of coupling with probability x, and a monomer of the other type with probability 1-x. We find that the magnetization behaves differently from the original binary model. In particular, depending on which type of coupling comes in dimers, magnetization jumps vanish at a certain set of critical fields. We explain the results based on the structure of ground state spin configuration.
Auditory Power-Law Activation Avalanches Exhibit a Fundamental Computational Ground State.
Stoop, Ruedi; Gomez, Florian
2016-07-15
The cochlea provides a biological information-processing paradigm that we are only beginning to understand in its full complexity. Our work reveals an interacting network of strongly nonlinear dynamical nodes, on which even a simple sound input triggers subnetworks of activated elements that follow power-law size statistics ("avalanches"). From dynamical systems theory, power-law size distributions relate to a fundamental ground state of biological information processing. Learning destroys these power laws. These results strongly modify the models of mammalian sound processing and provide a novel methodological perspective for understanding how the brain processes information. PMID:27472144
Asymptotic Behaviour of the Ground State of Singularly Perturbed Elliptic Equations
NASA Astrophysics Data System (ADS)
Piatnitski, Andrey L.
The ground state of a singularly perturbed nonselfadjoint elliptic operator
GSGPEs: A MATLAB code for computing the ground state of systems of Gross-Pitaevskii equations
NASA Astrophysics Data System (ADS)
Caliari, Marco; Rainer, Stefan
2013-03-01
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. 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).
Indirect measurements of nuclear astrophysics reactions at CIAE
Liu Weiping; Li Zhihong; Bai Xixiang; Wang Youbao; Lian Gang; Guo Bing; Zeng Sheng; Yan Shengquan; Wang Baoxiang; Su Jun; Shu Nengchuan; Chen Yongshou
2006-11-02
This paper described the nuclear astrophysical studies using the unstable ion beam facility GIRAFFE, by indirect measurements. We measured the angular distributions for some single proton or neutron transfer reactions, such as 7Be(d,n)8B, 11C(d,n)12N, 8Li(d,n)9Be, 8Li(d,p)9Li and 13N(d,n)14O in inverse kinematics, and derived the astrophysical S-factors or reaction rates of 7Be(p,{gamma})8B, 11C(p,{gamma})12N, 8Li(n,{gamma})9Li, 13N(p,{gamma})14O by asymptotic normalization coefficient, spectroscopic factor, and R-matrix approach at astrophysically relevant energies.
Nuclear Technology Series. Course 11: Radiation Detection and Measurement.
ERIC Educational Resources Information Center
Technical Education Research Center, Waco, TX.
This technical specialty course is one of thirty-five courses designed for use by two-year postsecondary institutions in five nuclear technician curriculum areas: (1) radiation protection technician, (2) nuclear instrumentation and control technician, (3) nuclear materials processing technician, (4) nuclear quality-assurance/quality-control…
Mobilities of ground-state and metastable O/+/, O2/+/, O/2+/, and O2/2+/ ions in helium and neon
NASA Astrophysics Data System (ADS)
Johnsen, R.; Biondi, M. A.; Hayashi, M.
1982-09-01
The ionic mobilities of O(+), O2(+), O(2+), and O2(2+) in helium and neon have been measured using a selected-ion drift apparatus (SIDA). It is found that the mobilities of both O(+) and O2(+) ions in the metastable states (2D or 4Pi u) are measurably smaller than those of the same ions carried out by using known, state-selective ion-molecule reactions. A similar mobility differentiation of ground-state and metastable ions was not observed for the O(2+) and O2(2+) ions.
Observation of γ-vibrations and alignments built on non-ground-state configurations in ¹⁵⁶Dy
Zhu, C. -H.; Hartley, D. J.; Riedinger, L. L.; Sharpey-Schafer, J. F.; Almond, J. M.; Beausang, C.; Carpenter, M. P.; Chiara, C. J.; Cooper, N.; Curien, D.; Gall, B. J. P.; Garrett, P. E.; Janssens, R. V. F.; Kondev, F. G.; Kulp, W. D.; Lauritsen, T.; McCutchan, E. A.; Miller, D.; Piot, J.; Redon, N.; Riley, M. A.; Simpson, J.; Stefanescu, I.; Werner, V.; Wang, X.; Wood, J. L.; Majola, S. N. T.; Zhu, S.
2015-03-26
The exact nature of the lowest K^{π}=2⁺ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus ¹⁵⁶Dy, using the ¹⁴⁸Nd(¹²C,4n)¹⁵⁶Dy reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the ^{π}=2⁺ γ-band are observed to 32⁺ and 31⁺ respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ-vibration built on the aligned yrast S-band are observed to spins 28⁺ and 27⁺. An even-spin positive-parity band, observed to spin 24⁺, is a candidate for an aligned S-band built on the seniority-zero configuration of the 0₂⁺ state at 676 keV. As a result, the crossing of this band with the 0₂⁺ band is at hw_{c} = 0.28(1) MeV and is consistent with the configuration of the 0₂⁺ band not producing any blocking of the monopole pairing.
Observation of γ-vibrations and alignments built on non-ground-state configurations in ¹⁵⁶Dy
Zhu, C. -H.; Hartley, D. J.; Riedinger, L. L.; Sharpey-Schafer, J. F.; Almond, J. M.; Beausang, C.; Carpenter, M. P.; Chiara, C. J.; Cooper, N.; Curien, D.; et al
2015-03-26
The exact nature of the lowest Kπ=2⁺ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus ¹⁵⁶Dy, using the ¹⁴⁸Nd(¹²C,4n)¹⁵⁶Dy reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the π=2⁺ γ-band are observed to 32⁺ and 31⁺ respectively.more » This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ-vibration built on the aligned yrast S-band are observed to spins 28⁺ and 27⁺. An even-spin positive-parity band, observed to spin 24⁺, is a candidate for an aligned S-band built on the seniority-zero configuration of the 0₂⁺ state at 676 keV. As a result, the crossing of this band with the 0₂⁺ band is at hwc = 0.28(1) MeV and is consistent with the configuration of the 0₂⁺ band not producing any blocking of the monopole pairing.« less
NASA Astrophysics Data System (ADS)
Blanchard, J. W.; Sjolander, T. F.; King, J. P.; Ledbetter, M. P.; Levine, E. H.; Bajaj, V. S.; Budker, D.; Pines, A.
2015-12-01
Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from the effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultralow-field NMR measurements of residual dipolar couplings in acetonitrile-2-13C aligned in stretched polyvinyl acetate gels. This permits the investigation of dipolar couplings as a perturbation on the indirect spin-spin J coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultralow-field NMR and has potential applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.
NASA Astrophysics Data System (ADS)
Tkalya, E. V.; Nikolaev, A. V.
2016-07-01
Background: The search for new opportunities to investigate the low-energy level in the 229Th nucleus, which is nowadays intensively studied experimentally, has motivated us to theoretical studies of the magnetic hyperfine (MHF) structure of the 5 /2+ (0.0 eV) ground state and the low-lying 3 /2+ (7.8 eV) isomeric state in highly charged 89+229Th and 87+229Th ions. Purpose: The aim is to calculate, with the maximal precision presently achievable, the energy of levels of the hyperfine structure of the 229Th ground-state doublet in highly charged ions and the probability of radiative transitions between these levels. Methods: The distribution of the nuclear magnetization (the Bohr-Weisskopf effect) is accounted for in the framework of the collective nuclear model with Nilsson model wave functions for the unpaired neutron. Numerical calculations using precise atomic density functional theory methods, with full account of the electron self-consistent field, have been performed for the electron structure inside and outside the nuclear region. Results: The deviations of the MHF structure for the ground and isomeric states from their values in a model of a pointlike nuclear magnetic dipole are calculated. The influence of the mixing of the states with the same quantum number F on the energy of sublevels is studied. Taking into account the mixing of states, the probabilities of the transitions between the components of the MHF structure are calculated. Conclusions: Our findings are relevant for experiments with highly ionized 229Th ions in a storage ring at an accelerator facility.
Ratio of forbidden transition rates in the ground-state configuration of O ii
NASA Astrophysics Data System (ADS)
Han, Xiao-Ying; Gao, Xiang; Zeng, De-Ling; Yan, Jun; Li, Jia-Ming
2012-06-01
Based on a set of “quasicomplete bases,” using the large-scale multiconfiguration Dirac-Fock (MCDF) method, we calculate the forbidden electric quadrupole (E2) and magnetic dipole (M1) transition rates of the transitions 2D5/2,3/2o→4S3/2o of the O ii ground state considering the quantum electrodynamics (QED) corrections. Our calculations demonstrate that the Breit interactions are most important among all the QED corrections. The calculated E2 and M1 transition rates converge in a systematical and uniform manner with the extending orbital basis and the calculation uncertainty of 2.5% is achieved by considering the valence- and core-excitation correlations totally. With the converged transition rates, a value of the intensity ratio between the two transitions in high-electron-density limit in planetary nebulas is given, that is, r(∞)=0.363±0.009, which is within the overlap of the different observations and with the least uncertainty up to now. In addition, the E2 and M1 transition rates of two transitions 2P3/2,1/2o→4S3/2o of O ii ground state and the ratio between the two transition rates in high-electron-density limit are calculated and compared with the previous results.
Ground State Geometries of Polyacetylene Chains from Many-Particle Quantum Mechanics.
Barborini, Matteo; Guidoni, Leonardo
2015-09-01
Due to the crucial role played by electron correlation, the accurate determination of ground state geometries of π-conjugated molecules is still a challenge for many quantum chemistry methods. Because of the high parallelism of the algorithms and their explicit treatment of electron correlation effects, Quantum Monte Carlo calculations can offer an accurate and reliable description of the electronic states and of the geometries of such systems, competing with traditional quantum chemistry approaches. Here, we report the structural properties of polyacetylene chains H-(C₂H₂)(N)-H up to N = 12 acetylene units, by means of Variational Monte Carlo (VMC) calculations based on the multi-determinant Jastrow Antisymmetrized Geminal Power (JAGP) wave function. This compact ansatz can provide for such systems an accurate description of the dynamical electronic correlation as recently detailed for the 1,3-butadiene molecule [J. Chem. Theory Comput. 2015 11 (2), 508-517]. The calculated Bond Length Alternation (BLA), namely the difference between the single and double carbon bonds, extrapolates, for N → ∞, to a value of 0.0910(7) Å, compatible with the experimental data. An accurate analysis was able to distinguish between the influence of the multi-determinantal AGP expansion and of the Jastrow factor on the geometrical properties of the fragments. Our size-extensive and self-interaction-free results provide new and accurate ab initio references for the structures of the ground state of polyenes.
Adiabatic corrections to holographic entanglement in thermofield doubles and confining ground states
NASA Astrophysics Data System (ADS)
Marolf, Donald; Wien, Jason
2016-09-01
We study entanglement in states of holographic CFTs defined by Euclidean path integrals over geometries with slowly varying metrics. In particular, our CFT space-times have S 1 fibers whose size b varies along one direction ( x) of an {{R}}^{{{}^d}^{-1}} base. Such examples respect an {{R}}^{{{}^d}^{-2}} Euclidean symmetry. Treating the S 1 direction as time leads to a thermofield double state on a spacetime with adiabatically varying redshift, while treating another direction as time leads to a confining ground state with slowly varying confinement scale. In both contexts the entropy of slab-shaped regions defined by | x - x 0| ≤ L exhibits well-known phase transitions at length scales L = L crit characterizing the CFT entanglements. For the thermofield double, the numerical coefficients governing the effect of variations in b( x) on the transition are surprisingly small and exhibit an interesting change of sign: gradients reduce L crit for d ≤ 3 but increase L crit for d ≥ 4. This means that, while for general L > L crit they significantly increase the mutual information of opposing slabs as one would expect, for d ≥ 4 gradients cause a small decrease near the phase transition. In contrast, for the confining ground states gradients always decrease L crit, with the effect becoming more pronounced in higher dimensions.
Rotational Spectroscopy on Ultracold 23 Na40 K Ground State Molecules
NASA Astrophysics Data System (ADS)
Will, Sebastian; Park, Jee Woo; Yan, Zoe; Loh, Huanqian; Zwierlein, Martin
2016-05-01
Ultracold molecules with controllable dipolar long-range interactions will open up new routes for quantum simulation and the creation of novel states of matter. In particular, the molecules' rich internal degrees of freedom allow for versatile control of intermolecular interactions by applying static electric and microwave fields. Starting from an ultracold, spin-polarized ensemble of trapped fermionic 23 Na40 K molecules in the absolute ground state, we perform microwave spectroscopy on the first rotationally excited state for a range of magnetic and electric fields. Extracting the rotational and hyperfine coupling constants, we comprehensively understand the observed spectra. Following the coherent transfer of the entire ensemble of chemically stable 23 Na40 K molecules to the first rotationally excited state, we observe a lifetime of more than 3 sec, comparable to the lifetime in the rovibrational ground state. The collisional stability of excited rotational states opens up intriguing prospects for the control of intermolecular van-der-Waals interactions via electric fields.
Accurate nonrelativistic ground-state energies of 3d transition metal atoms
Scemama, A.; Applencourt, T.; Giner, E.; Caffarel, M.
2014-12-28
We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |E{sub c}|.
Vexiau, R.; Lepers, M. Aymar, M.; Bouloufa-Maafa, N.; Dulieu, O.
2015-06-07
We have calculated the isotropic C{sub 6} coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X{sup 1}Σ{sup +}. We consider the ten species made up of {sup 7}Li, {sup 23}Na, {sup 39}K, {sup 87}Rb, and {sup 133}Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.
The Icosahedral Ti-Zr-Ni Quasicrystal - A Ground State Quasicrystal?
NASA Astrophysics Data System (ADS)
Hennig, R. G.; Carlsson, A. E.; Kelton, K. F.; Henley, C. L.
2001-03-01
The icosahedral Ti-Zr-Ni quasicrystal is known to be thermodynamically stable [1]. Most stable quasicrystals form at high temperatures from the liquid phase. In contrast to those quasicrystals, however, the Ti-Zr-Ni quasicrystal forms at lower temperatures, near 570^circC, by a solid state transformation of crystal phases that are stable at higher temperatures. A decorated canonical cell tiling for the structure of this quasicrystal was determined by a refinement to x-ray and neutron diffraction data and results from ab initio calculations. The energetic stability of the icosahedral Ti-Zr-Ni quasicrystal was investigated by total energy calculations using the density-functional code VASP [2]. The ternary ground state phase diagram for Ti-Zr-Ni was determined. The energy of the structural model of the quasicrystal is found to be lower than the energy of any known competing phase. This result, coupled with the continued stability with long anneals at lower temperatures, strongly suggest that the icosahedral Ti-Zr-Ni quasicrystal is a ground state quasicrystal. [1] K. F. Kelton, W. J. Kim, and R. M. Stroud. Appl. Phys. Let. 70, 3230 (1997). [2] G. Kresse and J. Hafner, Phys. Rev. B47, RC 558 (1993); G. Kresse and J. Furthmüller, Phys. Rev. B54, 11169 (1996).
Optical cooling of AlH+ to the rotational ground state
NASA Astrophysics Data System (ADS)
Lien, Chien-Yu; Seck, Christopher; Odom, Brian
2014-05-01
We demonstrate cooling of the rotational degree of freedom of trapped diatomic molecular ions to the rotational ground state. The molecule of interested, AlH+, is co-trapped and sympathetically cooled with Ba+ to milliKelvin temperatures in its translational degree of freedom. The nearly diagonal Franck-Condon-Factors between the electronic X and A states of AlH+ create semi-closed cycling transitions between the vibrational ground states of X and A states. A spectrally filtered femtosecond laser is used to optically pump the population to the two lowest rotational levels, with opposite parities, in as fast as 100 μs via driving the A-X transition. In addition, a cooling scheme relying on vibrational relaxation brings the population to the N = 0 positive-parity level in as fast as 100 ms. The population distribution among the rotational levels is detected by resonance-enhanced multiphoton dissociation (REMPD) and time-of-flight mass-spectrometry (TOFMS). Although the current two-photon state readout scheme is destructive, a scheme of single-molecule fluorescence detection is also considered.
Ground state study of the thin ferromagnetic nano-islands for artificial spin ice arrays
Vieira Júnior, D. S.; Leonel, S. A. Dias, R. A. Toscano, D. Coura, P. Z. Sato, F.
2014-09-07
In this work, we used numerical simulations to study the magnetic ground state of the thin elongated (elliptical) ferromagnetic nano-islands made of Permalloy. In these systems, the effects of demagnetization of dipolar source generate a strong magnetic anisotropy due to particle shape, defining two fundamental magnetic ground state configurations—vortex or type C. To describe the system, we considered a model Hamiltonian in which the magnetic moments interact through exchange and dipolar potentials. We studied the competition between the vortex states and aligned states—type C—as a function of the shape of each elliptical nano-islands and constructed a phase diagram vortex—type C state. Our results show that it is possible to obtain the elongated nano-islands in the C-state with aspect ratios less than 2, which is interesting from the technological point of view because it will be possible to use smaller islands in spin ice arrays. Generally, the experimental spin ice arrangements are made with quite elongated particles with aspect ratio approximately 3 to ensure the C-state.
Ground State Geometries of Polyacetylene Chains from Many-Particle Quantum Mechanics
2015-01-01
Due to the crucial role played by electron correlation, the accurate determination of ground state geometries of π-conjugated molecules is still a challenge for many quantum chemistry methods. Because of the high parallelism of the algorithms and their explicit treatment of electron correlation effects, Quantum Monte Carlo calculations can offer an accurate and reliable description of the electronic states and of the geometries of such systems, competing with traditional quantum chemistry approaches. Here, we report the structural properties of polyacetylene chains H–(C2H2)N–H up to N = 12 acetylene units, by means of Variational Monte Carlo (VMC) calculations based on the multi-determinant Jastrow Antisymmetrized Geminal Power (JAGP) wave function. This compact ansatz can provide for such systems an accurate description of the dynamical electronic correlation as recently detailed for the 1,3-butadiene molecule [J. Chem. Theory Comput. 2015 11 (2), 508–517]. The calculated Bond Length Alternation (BLA), namely the difference between the single and double carbon bonds, extrapolates, for N → ∞, to a value of 0.0910(7) Å, compatible with the experimental data. An accurate analysis was able to distinguish between the influence of the multi-determinantal AGP expansion and of the Jastrow factor on the geometrical properties of the fragments. Our size-extensive and self-interaction-free results provide new and accurate ab initio references for the structures of the ground state of polyenes. PMID:26405437
Modified Magnetic Ground State in Nimn (2) O (4) Thin Films
Nelson-Cheeseman, B.B.; Chopdekar, R.V.; Iwata, J.M.; Toney, M.F.; Arenholz, E.; Suzuki, Y.; /SLAC
2012-08-23
The authors demonstrate the stabilization of a magnetic ground state in epitaxial NiMn{sub 2}O{sub 4} (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low T. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+}, while the canted moment ferrimagnetic ordering is preserved below 60 K.
Modified magnetic ground state in NiMn2O4 thin films
Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Toney, M. F.; Arenholz, E.; Suzuki, Y.; Iwata, J.M.
2010-08-03
We demonstrate the stabilization of a magnetic ground state in epitaxial NiMn2O4 (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low temperature. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+} while the canted moment ferrimagnetic ordering is preserved below 60 K.
Gozem, Samer; Huntress, Mark; Schapiro, Igor; Lindh, Roland; Granovsky, Alexander A; Angeli, Celestino; Olivucci, Massimo
2012-11-13
The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed. PMID:26605574
Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids
Abedinpour, Saeed H.; Asgari, Reza; Tanatar, B.; Polini, Marco
2014-01-15
We study the ground-state properties of a two-dimensional spin-polarized fluid of dipolar fermions within the Euler–Lagrange Fermi-hypernetted-chain approximation. Our method is based on the solution of a scattering Schrödinger equation for the “pair amplitude” √(g(r)), where g(r) is the pair distribution function. A key ingredient in our theory is the effective pair potential, which includes a bosonic term from Jastrow–Feenberg correlations and a fermionic contribution from kinetic energy and exchange, which is tailored to reproduce the Hartree–Fock limit at weak coupling. Very good agreement with recent results based on quantum Monte Carlo simulations is achieved over a wide range of coupling constants up to the liquid-to-crystal quantum phase transition. Using the fluctuation–dissipation theorem and a static approximation for the effective inter-particle interactions, we calculate the dynamical density–density response function, and furthermore demonstrate that an undamped zero-sound mode exists for any value of the interaction strength, down to infinitesimally weak couplings. -- Highlights: •We have studied the ground state properties of a strongly correlated two-dimensional fluid of dipolar fermions. •We have calculated the effective inter-particle interaction and the dynamical density–density response function. •We have shown that an undamped zero sound mode exists at any value of the interaction strength.
The use of quadratic forms in the calculation of ground state electronic structures
Keller, Jaime; Weinberger, Peter
2006-08-15
There are many examples in theoretical physics where a fundamental quantity can be considered a quadratic form {rho}={sigma}{sub i}{rho}{sub i}=vertical bar {psi} vertical bar{sup 2} and the corresponding linear form {psi}={sigma}{sub i}{psi}{sub i} is highly relevant for the physical problem under study. This, in particular, is the case of the density and the wave function in quantum mechanics. In the study of N-identical-fermion systems we have the additional feature that {psi} is a function of the 3N configuration space coordinates and {rho} is defined in three-dimensional real space. For many-electron systems in the ground state the wave function and the Hamiltonian are to be expressed in terms of the configuration space (CS), a replica of real space for each electron. Here we present a geometric formulation of the CS, of the wave function, of the density, and of the Hamiltonian to compute the electronic structure of the system. Then, using the new geometric notation and the indistinguishability and equivalence of the electrons, we obtain an alternative computational method for the ground state of the system. We present the method and discuss its usefulness and relation to other approaches.
Ground state structures of tantalum tetraboride and triboride: an ab initio study.
Wei, Shuli; Li, Da; Lv, Yunzhou; Liu, Zhao; Xu, Chunhong; Tian, Fubo; Duan, Defang; Liu, Bingbing; Cui, Tian
2016-07-21
Tantalum-boron compounds, which are potential candidates for superhard multifunctional materials, may possess multiple stoichiometries and structures under pressure. Using first-principle methods, ground-state TaB3 with the monoclinic C2/m space group and high-pressure TaB4 with the orthorhombic Amm2 space group have been found. They are more stable than the previously proposed structures. High-pressure boron-rich Amm2-TaB4 can be quenched to ambient pressure. The ground-state C2/m-TaB3 and high-pressure Amm2-TaB4 are two potential ultra-incompressible and hard materials with a calculated hardness of 17.02 GPa and 30.02 GPa at ambient pressure, respectively. Detailed electronic structure and chemical bonding analysis proved that the high hardness value of Amm2-TaB4 mainly stems from the strong covalent boron-boron bonds in graphene-like B layers as well as B-B bonds between layers. PMID:27327210
Structure and magnetic ground states of spin-orbit coupled compound alpha-RuCl3
NASA Astrophysics Data System (ADS)
Banerjee, Arnab; Bridges, Craig; Yan, Jiaqiang; Mandrus, David; Stone, Matthew; Aczel, Adam; Li, Ling; Yiu, Yuen; Lumsden, Mark; Chakoumakos, Bryan; Tennant, Alan; Nagler, Stephen
2015-03-01
The layered material alpha-RuCl3 is composed of stacks of weakly coupled honeycomb lattices of octahedrally coordinated Ru3 + ions. The Ru ion ground state has 5 d electrons in the low spin state, with spin-orbit coupling very strong compared to other terms in the single ion Hamiltonian. The material is therefore an excellent candidate for investigating possible Heisenberg-Kitaev physics. In addition, this compound is very amenable to investigation by neutron scattering to explore the magnetic ground state and excitations in detail. In this talk, we discuss the synthesis of phase-pure alpha-RuCl3 and the characterization of the magnetization, susceptibility, and heat-capacity. We also report neutron diffraction on both powder and single crystal alpha-RuCl3, identifying the low temperature magnetic order observed in the material. The results, when compared to theoretical calculations, shed light on the relative importance of Kitaev and Heisenberg terms in the Hamiltonian. The research is supported by the DOE BES Scientific User Facility Division.
Loading Bose-Einstein-condensed atoms into the ground state of an optical lattice
Julienne, P. S.; Williams, C. J.; Band, Y. B.; Trippenbach, Marek
2005-11-15
We optimize the turning on of a one-dimensional optical potential, V{sub L}(x,t)=S(t)V{sub 0} cos{sup 2}(kx) to obtain the optimal turn-on function S(t) so as to load a Bose-Einstein condensate into the ground state of the optical lattice of depth V{sub 0}. Specifically, we minimize interband excitations at the end of the turn-on of the optical potential at the final ramp time t{sub r}, where S(t{sub r})=1, given that S(0)=0. Detailed numerical calculations confirm that a simple unit cell model is an excellent approximation when the turn-on time t{sub r} is long compared with the inverse of the band excitation frequency and short in comparison with nonlinear time ({Dirac_h}/2{pi})/{mu} where {mu} is the chemical potential of the condensate. We demonstrate using the Gross-Pitaevskii equation with an optimal turn-on function S(t) that the ground state of the optical lattice can be loaded with no significant excitation even for times t{sub r} on the order of the inverse band excitation frequency.
NASA Astrophysics Data System (ADS)
Margules, L.; Motiyenko, R. A.; Groner, P.; De Chirico, F.; Turk, A.; Cooke, S. A.
2013-06-01
Measurements on the rotational spectrum of 1,1-difluoroacetone have been extended from the cm-wave region into the mm-wave region. Measurements between 150 GHz and 600 GHz were performed a t Lille at room temperature. About 2000 transitions have been added to the known line listing for the ground state. The range of J and K_{-1} values, for both the A and E torsional substates, now span 1 - 60 and 0 - 30, respectively. Analysis of the cm-wave spectrum was only possible using the Watson S-reduced Hamiltonian, with the A-reduction producing a poor spectral fit. For that analysis only quartic centrifugal distortion terms were required. With the newly recorded higher J and K_{-1} measurements it is necessary to expand the Hamiltonian to now include sextic and octic centrifugal distortion terms. This should allow us to extend the assignment to even higher J and K_{-1} and perhaps to shed more light into failure of the A-reduction Hamiltonian to achieve a satisfactory fit for the cm-wave transitions. The effective barrier to methyl group internal rotation has been determined more accurately. G. S. Grubbs II, P. Groner, S. E. Novick and S. A. Cooke J. Mol. Spectrosc. {280} 21-26, 2012.
Measurement of nuclear fuel pin hydriding utilizing epithermal neutron scattering
Miller, W.H.; Farkas, D.M.; Lutz, D.R.
1996-12-31
The measurement of hydrogen or zirconium hydriding in fuel cladding has long been of interest to the nuclear power industry. The detection of this hydrogen currently requires either destructive analysis (with sensitivities down to 1 {mu}g/g) or nondestructive thermal neutron radiography (with sensitivities on the order of a few weight percent). The detection of hydrogen in metals can also be determined by measuring the slowing down of neutrons as they collide and rapidly lose energy via scattering with hydrogen. This phenomenon is the basis for the {open_quotes}notched neutron spectrum{close_quotes} technique, also referred to as the Hysen method. This technique has been improved with the {open_quotes}modified{close_quotes} notched neutron spectrum technique that has demonstrated detection of hydrogen below 1 {mu}g/g in steel. The technique is nondestructive and can be used on radioactive materials. It is proposed that this technique be applied to the measurement of hydriding in zirconium fuel pins. This paper summarizes a method for such measurements.
Brünken, Sandra; Müller, Holger S P; Lewen, Frank; Giesen, Thomas F
2005-10-22
We present an analysis of a global, field-free data set of the methylene radical CH2 in its X 3B1 vibronic ground state by means of a novel Euler expansion of the Hamiltonian. The data set comprises pure rotational transitions up to 2 THz obtained with microwave accuracies of 30-500 kHz as well as nu2 ground-state combination differences and pure rotational data obtained with infrared accuracies of 0.001-0.010 cm(-1). Highly accurate spectroscopic parameters have been determined. These include rotational, spin-spin, spin-rotation, and electron-spin-nuclear-spin coupling terms along with several centrifugal distortion corrections. The spectroscopic model has been tested and improved by recording newly three weak DeltaN not equalDeltaJ fine-structure components of the N(KaKc)=2(12)-3(03) and 5(05)-4(14) transitions near 434, 454, and 581 GHz. These lines were rather close to the predictions. Overall weighted root mean squares of 1.28 and 0.83 were achieved for fits in which the Euler expansion was used only for the rotational part of the Hamiltonian or for the rotational and spin-spin terms of the Hamiltonian, respectively. The resulting spectroscopic parameters allow for precise frequency predictions of astrophysically important rotational transitions of methylene.
Nuclear radiation-warning detector that measures impedance
Savignac, Noel Felix; Gomez, Leo S; Yelton, William Graham; Robinson, Alex; Limmer, Steven
2013-06-04
This invention is a nuclear radiation-warning detector that measures impedance of silver-silver halide on an interdigitated electrode to detect light or radiation comprised of alpha particles, beta particles, gamma rays, X rays, and/or neutrons. The detector is comprised of an interdigitated electrode covered by a layer of silver halide. After exposure to alpha particles, beta particles, X rays, gamma rays, neutron radiation, or light, the silver halide is reduced to silver in the presence of a reducing solution. The change from the high electrical resistance (impedance) of silver halide to the low resistance of silver provides the radiation warning that detected radiation levels exceed a predetermined radiation dose threshold.