Ground-state structures of Hafnium clusters
Energy Technology Data Exchange (ETDEWEB)
Ng, Wei Chun; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technoloty, Multimedia University, Melaca Campus, 75450 Melaka (Malaysia)
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.
Ground state correlations and structure of odd spherical nuclei
International Nuclear Information System (INIS)
Mishev, S.; Voronov, V. V.
2006-01-01
It is well known that the Pauli principle plays a substantial role at low energies because the phonon operators are not ideal boson operators. Calculating the exact commutators between the quasiparticle and phonon operators one can take into account the Pauli principle corrections. Besides the ground state correlations due to the quasiparticle interaction in the ground state influence the single particle fragmentation as well. In this paper, we generalize the basic QPM equations to account for both mentioned effects. As an illustration of our approach, calculations on the structure of the low-lying states in "1"3"1Ba have been performed.
Ground state correlations and structure of odd spherical nuclei
International Nuclear Information System (INIS)
Mishev, S.; Voronov, V.V.
2008-01-01
It is well known that the Pauli principle plays a substantial role at low energies because the phonon operators are not ideal boson operators. Calculating the exact commutators between the quasiparticle and phonon operators one can take into account the Pauli principle corrections. Besides, the ground state correlations due to the quasiparticle interaction in the ground state influence the single-particle fragmentation as well. In this paper, we generalize the basic equations of the quasiparticle-phonon nuclear model to account for both effects mentioned. As an illustration of our approach, calculations on the structure of the low-lying states in 133 Ba have been performed
Ground-state electronic structure of actinide monocarbides and mononitrides
DEFF Research Database (Denmark)
Petit, Leon; Svane, Axel; Szotek, Z.
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 increa...
Ground-State Structures of Ice at High-Pressures
McMahon, Jeffrey M.
2011-01-01
\\textit{Ab initio} random structure searching based on density functional theory is used to determine the ground-state structures of ice at high pressures. Including estimates of lattice zero-point energies, ice is found to adopt three novel crystal phases. The underlying sub-lattice of O atoms remains similar among them, and the transitions can be characterized by reorganizations of the hydrogen bonds. The symmetric hydrogen bonds of ice X and $Pbcm$ are initially lost as ice transforms to s...
On the ground state and infrared divergences of Goldstone bosons in two dimensions
International Nuclear Information System (INIS)
Jevicki, A.
1977-01-01
The O(N) invariant Goldstone field theory is studied in two dimensions where rigorous theorems forbid the occurrence of spontaneous symmetry breaking. It is agreed that for computation of the ground state energy at weak coupling it is still the standard Goldstone perturbation expansion that is applicable. This happens due to cancellation of infrared divergences and this fact is demonstrated explicitly at the two-loop level. (Auth.)
The ground state infrared spectrum of the MnH radical ( 7Σ) from diode laser spectroscopy
Urban, Rolf-Dieter; Jones, Harold
1989-11-01
The infrared spectrum of the manganese hydride radical ( 55MnH) in its ground electronic state ( 7Σ) has been observed using a diode laser spectrometer. The wavenumbers of twelve transitions of the v=1→0 band, five of the v=2→1 band and seven of the v=3→2 band have been measured with a nominal accuracy of ±0.001 cm -1. Coupling between the electronic spin ( S=3) and the overall molecular rotation causes each ro-vibrational transition with N>3 to be split (γ splitting) into seven components each separated by a few hundredths of a wavenumber. In most cases the complete structure was resolved. Correction terms arising from spin-spin coupling had to be included in the analysis. This work has produced the most accurate set of ground-state parameters available for MnH.
Ground state structures and properties of small hydrogenated silicon
Indian Academy of Sciences (India)
Unknown
To understand the structural evolutions and properties of silicon cluster due to hydrogenation ... partly due to the growing importance of these systems in applications like .... of the system. Using the Lagrangian (1), equations of motions for the.
Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner
2011-06-30
A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.
Ground state structures and properties of Si3Hn (n= 1–6) clusters
Indian Academy of Sciences (India)
The ground state structures and properties of Si3H (1 ≤ ≤ 6) clusters have been calculated using Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as a function of ...
van Wilderen, Luuk J G W; Clark, Ian P; Towrie, Michael; van Thor, Jasper J
2009-12-24
Multipulse picosecond mid-infrared spectroscopy has been used to study photochemical reactions of the cyanobacterial phytochrome photoreceptor Cph1. Different photophysical schemes have been discussed in the literature to describe the pathways after photoexcitation, particularly, to identify reaction phases that are linked to photoisomerisation and electronic decay in the 1566-1772 cm(-1) region that probes C=C and C=O stretching modes of the tetrapyrrole chromophore. Here, multipulse spectroscopy is employed, where, compared to conventional visible pump-mid-infrared probe spectroscopy, an additional visible pulse is incorporated that interacts with populations that are evolving on the excited- and ground-state potential energy surfaces. The time delays between the pump and the dump pulse are chosen such that the dump pulse interacts with different phases in the reaction process. The pump and dump pulses are at the same wavelength, 640 nm, and are resonant with the Pr ground state as well as with the excited state and intermediates. Because the dump pulse additionally pumps the remaining, partially recovered, and partially oriented ground-state population, theory is developed for estimating the fraction of excited-state molecules. The calculations take into account the model-dependent ground-state recovery fraction, the angular dependence of the population transfer resulting from the finite bleach that occurs with linearly polarized intense femtosecond optical excitation, and the partially oriented population for the dump field. Distinct differences between the results from the experiments that use a 1 or a 14 ps dump time favor a branching evolution from S1 to an excited state or reconfigured chromophore and to a newly identified ground-state intermediate (GSI). Optical dumping at 1 ps shows the instantaneous induced absorption of a delocalized C=C stretching mode at 1608 cm(-1), where the increased cross section is associated with the electronic ground-state
Ground state structure of U2Mo: static and lattice dynamics study
International Nuclear Information System (INIS)
Mukherjee, D.; Sahoo, B.D.; Joshi, K.D.; Kaushik, T.C.
2016-01-01
According to experimental reports, the ground state stable structure of U 2 Mo is tetragonal. However, various theoretical studies performed in past do not get tetragonal phase as the stable structure at ambient conditions. Therefore, the ground state structure of U 2 Mo is still unresolved. In an attempt to understand the ground state properties of this system, we have carried out first principle electronic band structure calculations. The structural stability analysis carried out using evolutionary structure search algorithm in conjunction with ab-inito method shows that a hexagonal structure (space group P6/mmm) is the lowest enthalpy structure at ambient condition and remains stable upto 200 GPa. The elastic and lattice dynamical stability further supports the stability of this phase at ambient condition. Further, using the 0 K calculations in conjunction with finite temperature corrections, we have derived the isotherm and shock adiabat (Hugoniot) of this material. Various equilibrium properties such as ambient pressure volume, bulk modulus, pressure derivative of bulk modulus etc. are derived from equation of state. (author)
Structural Distortion Stabilizing the Antiferromagnetic and Semiconducting Ground State of BaMn2As2
Directory of Open Access Journals (Sweden)
Ekkehard Krüger
2016-09-01
Full Text Available We report evidence that the experimentally found antiferromagnetic structure as well as the semiconducting ground state of BaMn 2 As 2 are caused by optimally-localized Wannier states of special symmetry existing at the Fermi level of BaMn 2 As 2 . In addition, we find that a (small tetragonal distortion of the crystal is required to stabilize the antiferromagnetic semiconducting state. To our knowledge, this distortion has not yet been established experimentally.
The resonating group method three cluster approach to the ground state 9 Li nucleus structure
International Nuclear Information System (INIS)
Filippov, G.F.; Pozdnyakov, Yu.A.; Terenetsky, K.O.; Verbitsky, V.P.
1994-01-01
The three-cluster approach for light atomic nuclei is formulated in frame of the algebraic version of resonating group method. Overlap integral and Hamiltonian matrix elements on generating functions are obtained for 9 Li nucleus. All permissible by Pauli principle 9 Li different cluster nucleon permutations were taken into account in the calculations. The results obtained can be easily generalised on any three-cluster system up to 12 C. Matrix elements obtained in the work were used in the variational calculations of the ground state energetic and geometric 9 Li characteristics. It is shown that 9 Li ground state is not adequate to the shell model limit and has pronounced three-cluster structure. (author). 16 refs., 4 tab., 2 figs
Structural instability and ground state of the U{sub 2}Mo compound
Energy Technology Data Exchange (ETDEWEB)
Losada, E.L., E-mail: losada@cab.cnea.gov.ar [SIM" 3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E. [Gerencia de Investigación y Aplicaciones Nucleares, Comisión Nacional de Energía Atómica (Argentina)
2015-11-15
This work reports on the structural instability at T = 0 °K of the U{sub 2}Mo compound in the C11{sub b} structure under the distortion related to the C{sub 66} elastic constant. The electronic properties of U{sub 2}Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11{sub b} structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D{sub 6} distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U{sub 2}Mo due to the D{sub 6} distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U{sub 2}Mo compound is not the assumed C11{sub b} structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U{sub 2}Mo compound.
Structural instability and ground state of the U_2Mo compound
International Nuclear Information System (INIS)
Losada, E.L.; Garcés, J.E.
2015-01-01
This work reports on the structural instability at T = 0 °K of the U_2Mo compound in the C11_b structure under the distortion related to the C_6_6 elastic constant. The electronic properties of U_2Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11_b structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D_6 distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U_2Mo due to the D_6 distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U_2Mo compound is not the assumed C11_b structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U_2Mo compound.
The magnetic structure on the ground state of the equilateral triangular spin tube
International Nuclear Information System (INIS)
Matsui, Kazuki; Goto, Takayuki; Manaka, Hirotaka; Miura, Yoko
2016-01-01
The ground state of the frustrated equilateral triangular spin tube CsCrF_4 is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by "1"9F-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120°-type structure in ab-plane does not accord with the NMR spectra of ordered state.
Lofrumento, C.; Arci, F.; Carlesi, S.; Ricci, M.; Castellucci, E.; Becucci, M.
2015-02-01
The analysis of ground state structural and vibrational properties of Safranin-O is presented. The experimental results, obtained by FTIR, Raman and SERS spectroscopy, are discussed in comparison to the results of DFT calculations carried out at the B3LYP/6-311 + G(d,p) level of theory. The calculated spectra reproduce quite satisfactorily the experimental data. The calculated Safranin-O equilibrium structure and the assignment of the vibrational spectra are reported as well. From the changes between Raman and SERS spectra a model is presented for the interaction of Safranin-O with silver nanoparticles.
Electronic and structural ground state of heavy alkali metals at high pressure
Fabbris, G.; Lim, J.; Veiga, L. S. I.; Haskel, D.; Schilling, J. S.
2015-02-01
Alkali metals display unexpected properties at high pressure, including emergence of low-symmetry crystal structures, which appear to occur due to enhanced electronic correlations among the otherwise nearly free conduction electrons. We investigate the high-pressure electronic and structural ground state of K, Rb, and Cs using x-ray absorption spectroscopy and x-ray diffraction measurements together with a b i n i t i o theoretical calculations. The sequence of phase transitions under pressure observed at low temperature is similar in all three heavy alkalis except for the absence of the o C 84 phase in Cs. Both the experimental and theoretical results point to pressure-enhanced localization of the valence electrons characterized by pseudogap formation near the Fermi level and strong s p d hybridization. Although the crystal structures predicted to host magnetic order in K are not observed, the localization process appears to drive these alkalis closer to a strongly correlated electron state.
The use of quadratic forms in the calculation of ground state electronic structures
International Nuclear Information System (INIS)
Keller, Jaime; Weinberger, Peter
2006-01-01
There are many examples in theoretical physics where a fundamental quantity can be considered a quadratic form ρ=Σ i ρ i =vertical bar Ψ vertical bar 2 and the corresponding linear form Ψ=Σ i ψ 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 Ψ is a function of the 3N configuration space coordinates and ρ 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
Prediction of new ground-state crystal structure of T a2O5
Yang, Yong; Kawazoe, Yoshiyuki
2018-03-01
Tantalum pentoxide (T a2O5 ) is a wide-gap semiconductor which has important technological applications. Despite the enormous efforts from both experimental and theoretical studies, the ground-state crystal structure of T a2O5 is not yet uniquely determined. Based on first-principles calculations in combination with evolutionary algorithm, we identify a triclinic phase of T a2O5 , which is energetically much more stable than any phases or structural models reported previously. Characterization of the static and dynamical properties of the phase reveals the common features shared with previous metastable phases of T a2O5 . In particular, we show that the d spacing of ˜3.8 Å found in the x-ray diffraction patterns of many previous experimental works is actually the radius of the second Ta-Ta coordination shell as defined by radial distribution functions.
Effects of ground state correlations on the structure of odd-mass spherical nuclei
International Nuclear Information System (INIS)
Mishev, S.; Voronov, V. V.
2008-01-01
It is well known that the Pauli principle plays a substantial role at low energies because the quasiparticle and phonon operators, used to describe them, are built of fermions and as a consequence they are not ideal bosons. The correct treatment of this problem requires calculation of the exact commutators between the quasiparticle and phonon operators and in this way to take into account the Pauli principle corrections. In addition to the correlations due to the quasiparticle interaction in the ground-state influence the single-particle fragmentation as well. In this article, we generalize the basic equations of the quasiparticle-phonon nuclear model to account for both effects mentioned above. As an illustration of our approach, calculations of the structure of the low-lying states in the odd-mass nuclei 131-137 Ba have been performed
Ground State Structure of a Coupled 2-Fermion System in Supersymmetric Quantum Mechanics
Finster, Felix
1997-05-01
We prove the uniqueness of the ground state for a supersymmetric quantum mechanical system of two fermions and two bosons, which is closely related to theN=1 WZ-model. The proof is constructive and gives detailed information on what the ground state looks like
Ground state structure of a coupled 2-fermion system in supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Finster, F.
1997-01-01
We prove the uniqueness of the ground state for a supersymmetric quantum mechanical system of two fermions and two bosons, which is closely related to the N=1 WZ-model. The proof is constructive and gives detailed information on what the ground state looks like. copyright 1997 Academic Press, Inc
First-principles determination of the ground-state structure of Mg(BH4)(2)
DEFF Research Database (Denmark)
Caputo, R.; Tekin, Adem; Sikora, W.
2009-01-01
The ground-state structure of magnesium tetrahydroborate, Mg(BH4)(2), is still under debate. The experimentally and theoretically proposed structures mismatch, and even among the computationally determined structures a disagreement still exists. The main debated question is related to the lattice...
Shell structure of the A = 6 ground states from three-body dynamics
International Nuclear Information System (INIS)
Lehman, D.R.; Parke, W.C.
1983-01-01
Three-body (αNN) models of the 6 He and 6 Li ground states are used to investigate their shell structure. Three models for each nucleus are considered: simple, full (nn), and full (np) for 6 He, and simple, full (0%), and full (4%) for 6 Li. The full models in both cases are obtained by including the S/sub 1/2/, P/sub 1/2/, and P/sub 3/2/ partial waves of the αN interaction, whereas the simple model truncates to only the strongly resonant P/sub 3/2/ wave. The 6 He full models distinguish between use of the nn or np parameters for the 1 S 0 NN interaction, while the 6 Li full models have either a pure 3 S 1 NN interaction (0%) or a 3 S 1 - 3 D 1 interaction that leads to a 4% d-wave component in the deuteron (4%). These models are used to calculate the probabilities of the orbital components of the wave functions, the configuration-space single-particle orbital densities, and the configuration-space two-particle wave function amplitudes in j-j coupling with the nucleon coordinates referred to the alpha particle as the ''core'' or ''center of force.'' The results are then compared with those from phenomenological and realistic-interaction shell models. Major findings of the comparison are the following: None of the shell models considered have a distribution of orbital probabilities across shells like that predicted by three-body models; the orbital rms radii from three-body models indicate an ordering of the orbits within shells, i.e., p/sub 1/2/ outside p/sub 3/2/, unlike oscillator shell models with a single oscillator parameter where the p-shell orbitals have the same shape; and, as expected, three-body orbital densities decay at large radial distances as exponentials rather than the too compact Gaussian falling off of oscillator shell models
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.
International Nuclear Information System (INIS)
Pelling, M.
1977-01-01
Transitions 2πsub(1/2), j = 5/2, F = 3 → 2πsub(3/2), j = 3/2, F = 2 and 2πsub(1/2), j = 5/2, F = 2 → 2πsub(3/2), J = 3/2, F = 1 have overlapping Doppler line wings at a kinetic temperature of 100 K. This alters the transport of radiation in each line from that which would occur in the absence of line overlap. As a result, the upper levels of the ground state Λ-doublet become overpopulated. (author)
Structure and magnetic ground states of spin-orbit coupled compound alpha-RuCl3
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.
International Nuclear Information System (INIS)
Wei, Jie; Li, Xiao-Ping; Sessler, A.M.
1993-01-01
In order to employ Molecular Dynamics method, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing
International Nuclear Information System (INIS)
Wei, Jie; Li, Xiao-Ping
1993-01-01
In order to employ molecular dynamics (MD) methods, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations using MD methods has been performed to obtain the equilibrium crystalline beam structure. The effect of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Schiffer et al. depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing
International Nuclear Information System (INIS)
Wei, J.; Li, X.P.
1993-01-01
In order to employ the Molecular Dynamics method, commonly used in condensed matter physics, the authors have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. They include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing
Qing-Hui, Wang; Xu-Ping, Shao; Xiao-Hua, Yang
2016-01-01
Hyperfine structures of ICl in its vibronic ground state due to the nuclear spin and electric quadruple interactions are determined by diagonalizing the effective Hamiltonian matrix. Furthermore, the Stark sub-levels are precisely determined as well. The results are helpful for electro-static manipulation (trapping or further cooling) of cold ICl molecules. For example, an electric field of 1000 V/cm can trap ICl molecules less than 637 μK in the lowest hyperfine level. Project supported by the National Natural Science Foundation of China (Grant No. 11034002), the National Basic Research Program of China (Grant No. 2011CB921602), and Qing Lan Project, China.
International Nuclear Information System (INIS)
Tawancy, H.M.; Aboelfotoh, M.O.
2014-01-01
We have studied the effect of atom arrangements in the ground state structures of substitutional ordered alloys on their mechanical properties using nickel–molybdenum-based alloys as model systems. Three alloys with nominal compositions of Ni–19.43 at% Mo, Ni–18.53 at% Mo–15.21 at% Cr and Ni–18.72 at% Mo–6.14 at% Nb are included in the study. In agreement with theoretical predictions, the closely related Pt 2 Mo-type, DO 22 and D1 a superlattices with similar energies are identified by electron diffraction of ground state structures, which can directly be derived from the parent disordered fcc structure by minor atom rearrangements on {420} fcc planes. The three superlattices are observed to coexist during the disorder–order transformation at 700 °C with the most stable superlattice being determined by the exact chemical composition. Although most of the slip systems in the parent disordered fcc structure are suppressed, many of the twinning systems remain operative in the superlattices favoring deformation by twinning, which leads to considerable strengthening while maintaining high ductility levels. Both the Pt 2 Mo-type and DO 22 superlattices are distinguished by high strength and high ductility due to their nanoscale microstructures, which have high thermal stability. However, the D1 a superlattice is found to exhibit poor thermal stability leading to considerable loss of ductility, which has been correlated with self-induced recrystallization by migration of grain boundaries
Study of structure and potential energy curve for ground state X1Σ+ of LaF
International Nuclear Information System (INIS)
Chen Linhong; Shang Rencheng
2002-01-01
The equilibrium geometry, harmonic frequency and dissociation energy of the molecule LaF have been calculated on several kinds of computation levels with energy-consistent relativistic effective core potentials and valence basis sets including polarization functions 4f2g and diffuse functions 1s1p1d. The possible electronic state and its reasonable dissociation limit for the ground state of LaF are determined based on Atomic and Molecular Reaction Statics (AMRS). The potential energy curve scan for the ground state X 1 Σ + has been carried out with B3LYP method of density functional theory. Murrell-Sorbie analytic potential energy function and its Dunham expansion around equilibrium position have been also derived with a nonlinear least-square fit. The calculated spectroscopic constants are in good agreement with the experimental results of vibrational spectra. The analytical function obtained here is of great realistic importance due to its use in calculating fine transitional structure of vibrational spectra and the reaction dynamic process between atoms and molecules
Energy Technology Data Exchange (ETDEWEB)
Tawancy, H.M., E-mail: tawancy@kfupm.edu.sa [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, KFUPM Box 1639, Dhahran 31261 (Saudi Arabia); Aboelfotoh, M.O., E-mail: oaboelfotoh@gmail.com [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606 (United States)
2014-05-01
We have studied the effect of atom arrangements in the ground state structures of substitutional ordered alloys on their mechanical properties using nickel–molybdenum-based alloys as model systems. Three alloys with nominal compositions of Ni–19.43 at% Mo, Ni–18.53 at% Mo–15.21 at% Cr and Ni–18.72 at% Mo–6.14 at% Nb are included in the study. In agreement with theoretical predictions, the closely related Pt{sub 2}Mo-type, DO{sub 22} and D1{sub a} superlattices with similar energies are identified by electron diffraction of ground state structures, which can directly be derived from the parent disordered fcc structure by minor atom rearrangements on {420}{sub fcc} planes. The three superlattices are observed to coexist during the disorder–order transformation at 700 °C with the most stable superlattice being determined by the exact chemical composition. Although most of the slip systems in the parent disordered fcc structure are suppressed, many of the twinning systems remain operative in the superlattices favoring deformation by twinning, which leads to considerable strengthening while maintaining high ductility levels. Both the Pt{sub 2}Mo-type and DO{sub 22} superlattices are distinguished by high strength and high ductility due to their nanoscale microstructures, which have high thermal stability. However, the D1{sub a} superlattice is found to exhibit poor thermal stability leading to considerable loss of ductility, which has been correlated with self-induced recrystallization by migration of grain boundaries.
Ground state structures and properties of Si3Hn (n = 1–6) clusters
Indian Academy of Sciences (India)
Unknown
Keywords. Car–Parrinello molecular dynamics; hydrogenated silicon clusters; electronic structure calcula- ... the molecular dynamics simulation, allows us to describe dynamics of ... work through charge density analysis (Balamurugan and.
The ground state infrared spectra of several isotopic forms of the CdH and ZnH radicals
International Nuclear Information System (INIS)
Urban, R.; Magg, U.; Birk, H.; Jones, H.
1990-01-01
The infrared spectra of six isotopic forms of cadmium monohydride, [ 116 CdH (7.6%), 114 CdH (28.9%), 113 CdH (12.3%), 112 CdH (24.1%), 111 CdH (12.7%), and 110 CdH (12.4%)] and four isotopic forms of zinc hydride [ 68 ZnH (18.6%), 67 ZnH (4.1%), 66 ZnH (27.8%), and 64 ZnH (48.9%)] have been observed in natural abundance in their ground electronic state ( 2 Σ + ) in the gas phase using a diode laser spectrometer. A number of transitions of 108 CdH (0.9%) and 106 CdH (1.2%) and 70 ZnH (0.6%) were also observed, but too little data was accumulated to allow a good analysis. The hydrides were produced by reaction of hydrogen with metal vapor at elevated temperature in an electric discharge. The analysis of the experimental data was carried out in two ways. (a) A complete set of Dunham parameters and spin--rotation parameters (γ parameters) was determined for each isotopic species of the two radicals and (b) a set of mass-independent parameters were calculated for both ZnH and CdH. Since only information over the isotopic species of the heavy atom was produced in each case, effects arising from a breakdown of the Born--Oppenheimer approximation were negligible. The effects of the strong anharmonicity present in these two molecules on the values of the parameters are discussed
International Nuclear Information System (INIS)
Molayem, M.; Tayebi-Rad, Gh.; Esmaeli, L.; Namiranian, A.; Fouladvand, M. E.; Neek-Amal, M.
2006-01-01
Using the diffusion quantum monte Carlo method, the ground state energy of an Hydrogen atom confined in a carbon nano tube and a C60 molecule is calculated. For Hydrogen atom confined in small diameter tubes, the ground state energy shows significant deviation from a free Hydrogen atom, while with increasing the diameter this deviation tends to zero.
Minenkov, Yury
2017-11-29
We tested a battery of density functional theory (DFT) methods ranging from generalized gradient approximation (GGA) via meta-GGA to hybrid meta-GGA schemes as well as Møller–Plesset perturbation theory of the second order and a single and double excitation coupled-cluster (CCSD) theory for their ability to reproduce accurate gas-phase structures of di- and triatomic molecules derived from microwave spectroscopy. We obtained the most accurate molecular structures using the hybrid and hybrid meta-GGA approximations with B3PW91, APF, TPSSh, mPW1PW91, PBE0, mPW1PBE, B972, and B98 functionals, resulting in lowest errors. We recommend using these methods to predict accurate three-dimensional structures of inorganic molecules when intramolecular dispersion interactions play an insignificant role. The structures that the CCSD method predicts are of similar quality although at considerably larger computational cost. The structures that GGA and meta-GGA schemes predict are less accurate with the largest absolute errors detected with BLYP and M11-L, suggesting that these methods should not be used if accurate three-dimensional molecular structures are required. Because of numerical problems related to the integration of the exchange–correlation part of the functional and large scattering of errors, most of the Minnesota models tested, particularly MN12-L, M11, M06-L, SOGGA11, and VSXC, are also not recommended for geometry optimization. When maintaining a low computational budget is essential, the nonseparable gradient functional N12 might work within an acceptable range of error. As expected, the DFT-D3 dispersion correction had a negligible effect on the internuclear distances when combined with the functionals tested on nonweakly bonded di- and triatomic inorganic molecules. By contrast, the dispersion correction for the APF-D functional has been found to shorten the bonds significantly, up to 0.064 Å (AgI), in Ag halides, BaO, BaS, BaF, BaCl, Cu halides, and Li and
Minenkov, Yury; Cavallo, Luigi
2017-01-01
-GGA approximations with B3PW91, APF, TPSSh, mPW1PW91, PBE0, mPW1PBE, B972, and B98 functionals, resulting in lowest errors. We recommend using these methods to predict accurate three-dimensional structures of inorganic molecules when intramolecular dispersion
Changing the Usual Interpretation of the Structure and Ground State of Cu2+-Layered Perovskites
DEFF Research Database (Denmark)
Aramburu, J. A.; García-Fernández, P.; Mathiesen, N. R.
2018-01-01
Intense research on hybrid organic-inorganic layered copper perovskites are currently being carried out. Many interesting properties of these materials rest on the strong correlation between electronic structure and local geometry. As up to now no reliable information on the pressure dependence...
A search for the ground state structure and the phase stability of tantalum pentoxide
International Nuclear Information System (INIS)
Pérez-Walton, S; Valencia-Balvín, C; Padilha, A C M; Dalpian, G M; Osorio-Guillén, J M
2016-01-01
Tantalum pentoxide (Ta 2 O 5 ) is a wide-gap semiconductor that presents good catalytic and dielectric properties, conferring to this compound promising prospective use in a variety of technological applications. However, there is a lack of understanding regarding the relations among its crystalline phases, as some of them are not even completely characterized and there is currently no agreement about which models better explain the crystallographic data. Additionally, its phase diagram is unknown. In this work we performed first-principles density functional theory calculations to study the structural properties of the different phases and models of Ta 2 O 5 , the equation of state and the zone-centered vibrational frequencies. From our results, we conclude that the phases that are built up from only distorted octahedra instead of combinations with pentagonal and/or hexagonal bipyramids are energetically more favorable and dynamically stable. More importantly, this study establishes that, given the pressure range considered, the B-phase is the most favorable structure and there is no a crystallographic phase transition to another phase at high-pressure. Additionally, for the equilibrium volume of the B-phase and the λ-model, the description of the electronic structure and optical properties were performed using semi-local and hybrid functionals. (paper)
Energy Technology Data Exchange (ETDEWEB)
Kunishige, Sachi; Katori, Toshiharu; Baba, Masaaki, E-mail: baba@kuchem.kyoto-u.ac.jp [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Nakajima, Masakazu; Endo, Yasuki [Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)
2015-12-28
We observed microwave absorption spectra of some deuterated benzenes and accurately determined the rotational constants of all H/D isotopomers in the ground vibrational state. Using synthetic analysis assuming that all bond angles are 120°, the mean bond lengths were obtained to be r{sub 0}(C–C) = 1.3971 Å and r{sub 0}(C–H) = r{sub 0}(C–D) = 1.0805 Å. It has been concluded that the effect of deuterium substitution on the molecular structure is negligibly small and that the mean bond lengths of C–H and C–D are identical unlike small aliphatic hydrocarbons, in which r{sub 0}(C–D) is about 5 mÅ shorter than r{sub 0}(C–H). It is considered that anharmonicity is very small in the C–H stretching vibration of aromatic hydrocarbons.
DEFF Research Database (Denmark)
Baldacci, A.; Stoppa, P.; Visinoni, R.
2012-01-01
.710 cm-1) and ν9 (930.295 cm-1) fundamental bands. The ground state constants up to sextic centrifugal distortion terms have been obtained for the first time by ground-state combination differences from the three bands and subsequently employed for the evaluation of the excited state parameters. Watson...... and a high-order coupling constant which takes into account the interaction between ν5 and ν9 have been determined....
Friedrich, Manuel; Stefanelli, Ulisse
2018-06-01
Graphene is locally two-dimensional but not flat. Nanoscale ripples appear in suspended samples and rolling up often occurs when boundaries are not fixed. We address this variety of graphene geometries by classifying all ground-state deformations of the hexagonal lattice with respect to configurational energies including two- and three-body terms. As a consequence, we prove that all ground-state deformations are either periodic in one direction, as in the case of ripples, or rolled up, as in the case of nanotubes.
International Nuclear Information System (INIS)
Negele, J.W.
1975-01-01
The nuclear ground state is surveyed theoretically, and specific suggestions are given on how to critically test the theory experimentally. Detailed results on 208 Pb are discussed, isolating several features of the charge density distributions. Analyses of 208 Pb electron scattering and muonic data are also considered. 14 figures
Singlet Ground State Magnetism:
DEFF Research Database (Denmark)
Loidl, A.; Knorr, K.; Kjems, Jørgen
1979-01-01
The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width...
Chen, Tao; Zhu, Shaobing; Li, Xiaolin; Qian, Jun; Wang, Yuzhu
2014-06-01
Using fitted model potential curves of the ground and lowest three excited states yielded by the relativistic Kramers-restricted multireference configuration interaction method with 19 electrons correlated, we theoretically investigate the rovibrational properties including the number of vibrational state and diagonally distributed Franck-Condon factors for a 87Rb84Sr molecule. Benefiting from a turning point at about v'=20 for the Franck-Condon factors between the ground state and spin-orbit 2(Ω=1/2) excited state, we choose |2(Ω=1/2),v'=21,J'=1> as the intermediate state in the three-level model to theoretically analyze the possibility of performing stimulated Raman adiabatic passage to transfer weakly bound RbSr molecules to the rovibrational ground state. With 1550 nm pump laser (2 W/cm2) and 1342 nm dump laser (10 mW/cm2) employed and appropriate settings of pulse time length (about 300 μs), we have formalistically achieved a round-trip transfer efficiency of 60%, namely 77% for one-way transfer. The results demonstrate the possibility of producing polar 87Rb84Sr molecules efficiently in a submicrokelvin regime, and further provide promising directions for future theoretical and experimental studies on alkali-alkaline(rare)-earth dimers.
International Nuclear Information System (INIS)
Abdel-Rahim, G P; Rodríguez M, J A; Moreno-Armenta, M G
2013-01-01
We study the structural and electronic properties of YC in volume using density functional theory (DFT) within the generalized gradient approximation (GGA), using the scheme of Wu-Cohen 2006 and Tran et al. 2007. Several crystal structures were considered: Nickel Arsenide (NiAs), Sodium Chloride (NaCl), Cesium Chloride (CsCl), and zincblende (ZB). A new fact that we present in this paper is the inclusion of the NiAs-like structure, which is the true ground state (GS) for YC. We calculated the density of states (DOS) and the band structure and found that YC is non-magnetic and its behavior is metallic-like. The lattice parameter alatt is 3.69 Å and the c/a = 1.47. Cohesion energy (Ecoh) is −12.90 eV, which is very close to Ecoh of the NaCl structure. Therefore, YC exists in these two structures. Our results with respect to alatt, bulk modulus (B), Ecoh, and the main features of the electronic properties are in good agreement with those found by other researchers. Other researchers found a transition from NaCl to CsCl, but we found a new transition from NiAs to CsCl, where the volume diminishes ∼10% and its transition pressure (PT ∼79 GPa) is very close to the 80 GPa of the former. The contraction can fracture the material if it is worked on near the transition. For pressures before and after the transition, YC maintains non-magnetic and metallic behaviors
International Nuclear Information System (INIS)
Wang Xiaolu; Lu Wenlai; Gao Xiang; Li Jiaming
2009-01-01
The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections on the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addition to spin-orbit interactions for precise calculations. (authors)
On the ground state of Yang-Mills theory
Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.
2011-01-01
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 ...
Cavity optomechanics -- beyond the ground state
Meystre, Pierre
2011-05-01
The coupling of coherent optical systems to micromechanical devices, combined with breakthroughs in nanofabrication and in ultracold science, has opened up the exciting new field of cavity optomechanics. Cooling of the vibrational motion of a broad range on oscillating cantilevers and mirrors near their ground state has been demonstrated, and the ground state of at least one such system has now been reached. Cavity optomechanics offers much promise in addressing fundamental physics questions and in applications such as the detection of feeble forces and fields, or the coherent control of AMO systems and of nanoscale electromechanical devices. However, these applications require taking cavity optomechanics ``beyond the ground state.'' This includes the generation and detection of squeezed and other non-classical states, the transfer of squeezing between electromagnetic fields and motional quadratures, and the development of measurement schemes for the characterization of nanomechanical structures. The talk will present recent ``beyond ground state'' developments in cavity optomechanics. We will show how the magnetic coupling between a mechanical membrane and a BEC - or between a mechanical tuning fork and a nanoscale cantilever - permits to control and monitor the center-of-mass position of the mechanical system, and will comment on the measurement back-action on the membrane motion. We will also discuss of state transfer between optical and microwave fields and micromechanical devices. Work done in collaboration with Dan Goldbaum, Greg Phelps, Keith Schwab, Swati Singh, Steve Steinke, Mehmet Tesgin, and Mukund Vengallatore and supported by ARO, DARPA, NSF, and ONR.
Atomic oxygen fine-structure splittings with tunable far-infrared spectroscopy
Zink, Lyndon R.; Evenson, Kenneth M.; Matsushima, Fusakazu; Nelis, Thomas; Robinson, Ruth L.
1991-01-01
Fine-structure splittings of atomic oxygen (O-16) in the ground state have been accurately measured using a tunable far-infrared spectrometer. The 3P0-3pl splitting is 2,060,069.09 (10) MHz, and the 3Pl-3P2 splitting is 4,744,777.49 (16) MHz. These frequencies are important for measuring atomic oxygen concentration in earth's atmosphere and the interstellar medium.
On the ground state of Yang-Mills theory
International Nuclear Information System (INIS)
Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.
2011-01-01
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.
Ground state searches in fcc intermetallics
International Nuclear Information System (INIS)
Wolverton, C.; de Fontaine, D.; Ceder, G.; Dreysse, H.
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
On the ground state of Yang-Mills theory
Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.
2011-08-01
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.
Ground states of quantum spin systems
International Nuclear Information System (INIS)
Bratteli, Ola; Kishimoto, Akitaka; Robinson, D.W.
1978-07-01
The authors prove that ground states of quantum spin systems are characterized by a principle of minimum local energy and that translationally invariant ground states are characterized by the principle of minimum energy per unit volume
Classical many-particle systems with unique disordered ground states
Zhang, G.; Stillinger, F. H.; Torquato, S.
2017-10-01
Classical ground states (global energy-minimizing configurations) of many-particle systems are typically unique crystalline structures, implying zero enumeration entropy of distinct patterns (aside from trivial symmetry operations). By contrast, the few previously known disordered classical ground states of many-particle systems are all high-entropy (highly degenerate) states. Here we show computationally that our recently proposed "perfect-glass" many-particle model [Sci. Rep. 6, 36963 (2016), 10.1038/srep36963] possesses disordered classical ground states with a zero entropy: a highly counterintuitive situation . For all of the system sizes, parameters, and space dimensions that we have numerically investigated, the disordered ground states are unique such that they can always be superposed onto each other or their mirror image. At low energies, the density of states obtained from simulations matches those calculated from the harmonic approximation near a single ground state, further confirming ground-state uniqueness. Our discovery provides singular examples in which entropy and disorder are at odds with one another. The zero-entropy ground states provide a unique perspective on the celebrated Kauzmann-entropy crisis in which the extrapolated entropy of a supercooled liquid drops below that of the crystal. We expect that our disordered unique patterns to be of value in fields beyond glass physics, including applications in cryptography as pseudorandom functions with tunable computational complexity.
A Model Ground State of Polyampholytes
International Nuclear Information System (INIS)
Wofling, S.; Kantor, Y.
1998-01-01
The ground state of randomly charged polyampholytes (polymers with positive and negatively charged groups along their backbone) is conjectured to have a structure similar to a necklace, made of weakly charged parts of the chain, compacting into globules, connected by highly charged stretched 'strings' attempted to quantify the qualitative necklace model, by suggesting a zero approximation model, in which the longest neutral segment of the polyampholyte forms a globule, while the remaining part will form a tail. Expanding this approximation, we suggest a specific necklace-type structure for the ground state of randomly charged polyampholyte's, where all the neutral parts of the chain compact into globules: The longest neutral segment compacts into a globule; in the remaining part of the chain, the longest neutral segment (the second longest neutral segment) compacts into a globule, then the third, and so on. A random sequence of charges is equivalent to a random walk, and a neutral segment is equivalent to a loop inside the random walk. We use analytical and Monte Carlo methods to investigate the size distribution of loops in a one-dimensional random walk. We show that the length of the nth longest neutral segment in a sequence of N monomers (or equivalently, the nth longest loop in a random walk of N steps) is proportional to N/n 2 , while the mean number of neutral segments increases as √N. The polyampholytes in the ground state within our model is found to have an average linear size proportional to dN, and an average surface area proportional to N 2/3
International Nuclear Information System (INIS)
Furukawa, Y.; Watanabe, K.; Kumagai, K.; Borsa, F.; Gatteschi, D.
2001-01-01
55 Mn nuclear magnetic resonance (NMR) measurements have been carried out in an oriented powder sample of Mn12 acetate at low temperature (1.4--3 K) in order to investigate locally the static and dynamic magnetic properties of the molecule in its high-spin S=10 ground state. We report the observation of three 55 MnNMR lines under zero external magnetic field. From the resonance frequency and the width of the lines we derive the internal hyperfine field and the quadrupole coupling constant at each of the three nonequivalent Mn ion sites. From the field dependence of the spectrum we obtain a direct confirmation of the standard picture, in which spin moments of Mn 4+ ions (S=3/2) of the inner tetrahedron are polarized antiparallel to that of Mn 3+ ions (S=2) of the outer ring with no measurable canting from the easy axis up to an applied field of 6 T. It is found that the splitting of the 55 Mn-NMR lines when a magnetic field is applied at low temperature allows one to monitor the off-equilibrium population of the molecules in the different low lying magnetic states. The measured nuclear spin-lattice relaxation time T 1 strongly depends on temperature and magnetic field. The behavior could be fitted well by considering the local-field fluctuations at the nuclear 55 Mn site due to the thermal reorientation of the total S=10 spin of the molecule. From the fit of the data one can derive the product of the spin-phonon coupling constant times the mean-square value of the fluctuating hyperfine field. The two constants could be estimated separately by making some assumptions. The comparison of the mean-square fluctuation from relaxation with the static hyperfine field from the spectrum suggests that nonuniform terms (q≠0) are important in describing the spin dynamics of the local Mn moments in the ground state
Pace, Vittorio; Holzer, Wolfgang; Meng, Guangrong; Shi, Shicheng; Lalancette, Roger; Szostak, Roman; Szostak, Michal
2016-10-04
Herein, we show that acyclic amides that have recently enabled a series of elusive transition-metal-catalyzed N-C activation/cross-coupling reactions are highly twisted around the N-C(O) axis by a new destabilization mechanism of the amide bond. A unique effect of the N-glutarimide substituent, leading to uniformly high twist (ca. 90°) irrespective of the steric effect at the carbon side of the amide bond has been found. This represents the first example of a twisted amide that does not bear significant steric hindrance at the α-carbon atom. The (15) N NMR data show linear correlations between electron density at nitrogen and amide bond twist. This study strongly supports the concept of amide bond ground-state twist as a blueprint for activation of amides toward N-C bond cleavage. The new mechanism offers considerable opportunities for organic synthesis and biological processes involving non-planar amide bonds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Rowe, Mary A.
1999-01-01
This thesis describes an experiment in which a neutral atom laser trap loaded with radioactive 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 21 Na to the experiment. Efficient manipulation of the 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 21 Na. She measured the 3S 1/2 (F=1,m=0)-3S 1/2 (F=2,m=0) atomic level splitting of 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
Energy Technology Data Exchange (ETDEWEB)
Rowe, Mary Anderson [Univ. of California, Berkeley, CA (United States)
1999-05-01
This thesis describes an experiment in which a neutral atom laser trap loaded with radioactive ^{21}Na was improved and then used for measurements. The sodium isotope (half-life=22 sec) is produced on line at the 88 in. cyclotron at Lawrence Berkeley National Laboratory. The author developed an effective magnesium oxide target system which is crucial to deliver a substantive beam of ^{21}Na to the experiment. Efficient manipulation of the ^{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 ^{21}Na. She measured the 3S_{1/2}(F=1,m=0)-3S_{1/2}(F=2,m=0) atomic level splitting of ^{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.
Hara, Akito; Awano, Teruyoshi
2017-06-01
Ultrashallow thermal donors (USTDs), which consist of light element impurities such as carbon, hydrogen, and oxygen, have been found in Czochralski silicon (CZ Si) crystals. To the best of our knowledge, these are the shallowest hydrogen-like donors with negative central-cell corrections in Si. We observed the ground-state splitting of USTDs by far-infrared optical absorption at different temperatures. The upper ground-state levels are approximately 4 meV higher than the ground-state levels. This energy level splitting is also consistent with that obtained by thermal excitation from the ground state to the upper ground state. This is direct evidence that the wave function of the USTD ground state is made up of a linear combination of conduction band minimums.
Bencini, Alessandro; Berti, Elisabetta; Caneschi, Andrea; Gatteschi, Dante; Giannasi, Elisa; Invernizzi, Ivana
2002-08-16
The ground state electronic structure of the mixed-valence systems [Ni(2)(napy)(4)X(2)](BPh(4)) (napy=1,8-naphthyridine; X=Cl, Br, I) was studied with combined experimental (X-ray diffraction, temperature dependence of the magnetic susceptibility, and high-field EPR spectroscopy) and theoretical (DFT) methods. The zero-field splitting (zfs) ground S=3/2 spin state is axial with /D/ approximately 3 cm(-1). The iodide derivative was found to be isostructural with the previously reported bromide complex, but not isomorphous. The compound crystallizes in the monoclinic system, space group P2(1)/n, with a=17.240(5), b=26.200(5), c=11.340(5) A, beta=101.320(5) degrees. DFT calculations were performed on the S=3/2 state to characterize the ground state potential energy surface as a function of the nuclear displacements. The molecules can thus be classified as Class III mixed-valence compounds with a computed delocalization parameter, B=3716, 3583, and 3261 cm(-1) for the Cl, Br, and I derivatives, respectively.
Rotational structure in molecular infrared spectra
di Lauro, Carlo
2013-01-01
Recent advances in infrared molecular spectroscopy have resulted in sophisticated theoretical and laboratory methods that are difficult to grasp without a solid understanding of the basic principles and underlying theory of vibration-rotation absorption spectroscopy. Rotational Structure in Molecular Infrared Spectra fills the gap between these recent, complex topics and the most elementary methods in the field of rotational structure in the infrared spectra of gaseous molecules. There is an increasing need for people with the skills and knowledge to interpret vibration-rotation spectra in many scientific disciplines, including applications in atmospheric and planetary research. Consequently, the basic principles of vibration-rotation absorption spectroscopy are addressed for contemporary applications. In addition to covering operational quantum mechanical methods, spherical tensor algebra, and group theoretical methods applied to molecular symmetry, attention is also given to phase conventions and their effe...
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.
International Nuclear Information System (INIS)
Ravindran, P.; Johansson, B.; Eriksson, O.
1998-01-01
In order to understand the role of Ni site substitution on the electronic structure and chemical bonding in YNi 2 B 2 C, we have made systematic electronic-structure studies on YNi 2 B 2 C as a function of Co and Cu substitution using the supercell approach within the local density approximation. The equilibrium volume, bulk modulus (B 0 ) and its pressure derivative (B 0 ' ), Grueneisen constant (γ G ), Debye temperature (Θ D ), cohesive energy (E c ), and heat of formation (ΔH) are calculated for YNi 2-x (Co/Cu) x B 2 C (x=0,0.5,1.0,1.5,2). From the total energy, electron-energy band structure, site decomposed density of states, and charge-density contour we have analyzed the structural stability and chemical bonding behavior of YNi 2 B 2 C as a function of Co/Cu substitution. We find that the simple rigid band model successfully explains the electronic structure and structural stability of Co/Cu substitution for Ni. In addition to studying the chemical bonding and electronic structure we present a somewhat speculative analysis of the general trends in the behavior of critical temperature for superconductivity as a function of alloying. copyright 1998 The American Physical Society
Search for C+ C clustering in Mg ground state
Indian Academy of Sciences (India)
2017-01-04
Jan 4, 2017 ... Finite-range knockout theory predictions were much larger for (12C,212C) reaction, indicating a very small 12C−12C clustering in 24Mg. (g.s.) . Our present results contradict most of the proposed heavy cluster (12C+12C) structure models for the ground state of 24Mg. Keywords. Direct nuclear reactions ...
International Nuclear Information System (INIS)
Amato, M.A.; March, N.H.
1988-09-01
Using the quantum Monte Carlo charge-charge structure factor S qq (k) it is argued that (i) in the metallic phase the small k expasion is non-analytic at order k 5 , reflecting plasmon dispersion, while in the insulating phase the non-analyticity occurs at O(k 3 ), due to van der Waals interaction between the protons. (author) [pt
Search for the QCD ground state
International Nuclear Information System (INIS)
Reuter, M.; Wetterich, C.
1994-05-01
Within the Euclidean effective action approach we propose criteria for the ground state of QCD. Despite a nonvanishing field strength the ground state should be invariant with respect to modified Poincare transformations consisting of a combination of translations and rotations with suitable gauge transformations. We have found candidate states for QCD with four or more colours. The formation of gluon condensates shows similarities with the Higgs phenomenon. (orig.)
International Nuclear Information System (INIS)
Childs, W.J.; Cok, D.R.; Goodman, L.S.
1982-01-01
The hyperfine structure of the X 2 Σ + state of Ca 35 Cl and Ca 37 Cl, unresolved in previous studies, has been investigated in detail by the molecular-beam, laser-rf, double-resonance technique. Results for the spin-rotation interaction and the dipole and quadrupole hfs constants are given in the form of Dunham coefficients so that the N'' and v'' dependence of each constant can be explicitly exhibited. The results, after dividing out the purely nuclear effects, fall between the corresponding values for CaF and CaBr, as expected
Shrestha, Kushal; Jakubikova, Elena
2015-08-20
Light-harvesting antennas are protein-pigment complexes that play a crucial role in natural photosynthesis. The antenna complexes absorb light and transfer energy to photosynthetic reaction centers where charge separation occurs. This work focuses on computational studies of the electronic structure of the pigment networks of light-harvesting complex I (LH1), LH1 with the reaction center (RC-LH1), and light-harvesting complex II (LH2) found in purple bacteria. As the pigment networks of LH1, RC-LH1, and LH2 contain thousands of atoms, conventional density functional theory (DFT) and ab initio calculations of these systems are not computationally feasible. Therefore, we utilize DFT in conjunction with the energy-based fragmentation with molecular orbitals method and a semiempirical approach employing the extended Hückel model Hamiltonian to determine the electronic properties of these pigment assemblies. Our calculations provide a deeper understanding of the electronic structure of natural light-harvesting complexes, especially their pigment networks, which could assist in rational design of artificial photosynthetic devices.
Calculations of the ground state of 16O
International Nuclear Information System (INIS)
Pieper, S.C.
1989-01-01
One of the central problems in nuclear physics is the description of nuclei as systems of nucleons interacting via realistic potentials. There are two main aspects of this problem: specification of the Hamiltonian, and calculation of the ground states of nuclei with the given interaction. Realistic interactions must contain both two- and three-nucleon potentials and these potentials have a complicated non-central operator structure consisting, for example, of spin, isospin and tensor dependences. This structure results in formidable many-body problems in the computation of the ground states of nuclei. At present, reliable solutions of the Faddeev equations for the A = 3 nuclei with such interactions are routine. Recently, Carlson has made an essentially exact GFMC calculation of the He ground state using just a two-nucleon interaction, and there are reliable variational calculations for more complete potential models. Nuclear matter calculations can also be made with reasonable reliability. However, there have been very few calculations of nuclei with A > 5 using realistic interactions, and none with a modern three-nucleon interaction. In the present paper I present a new technique for variational calculations for such nuclei and apply it to the ground state of 16 O. 15 refs., 2 figs., 3 tabs
Electronic and ground state properties of ThTe
Energy Technology Data Exchange (ETDEWEB)
Bhardwaj, Purvee, E-mail: purveebhardwaj@gmail.com; Singh, Sadhna, E-mail: drsadhna100@gmail.com [High Pressure Research Lab. Department of Physics Barkatullah University, Bhopal (MP) 462026 (India)
2016-05-06
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.
Antiferrodistortive phase transitions and ground state of PZT ceramics
International Nuclear Information System (INIS)
Pandey, Dhananjai
2013-01-01
The ground state of the technologically important Pb(Zr x Ti (1-x) )O 3 , commonly known as PZT, ceramics is currently under intense debate. The phase diagram of this material shows a morphotropic phase boundary (MPB) for x∼0.52 at 300K, across which a composition induced structural phase transition occurs leading to maximization of the piezoelectric properties. In search for the true ground state of the PZT in the MPB region, Beatrix Noheda and coworkers first discovered a phase transition from tetragonal (space group P4mm) to an M A type monoclinic phase (space group Cm) at low temperatures for x=0.52. Soon afterwards, we discovered yet another low temperature phase transition for the same composition in which the M A type (Cm) monoclinic phase transforms to another monoclinic phase with Cc space group. We have shown that the Cm to Cc phase transition is an antiferrodistortive (AFD) transition involving tilting of oxygen octahedra leading to unit cell doubling and causing appearance of superlattice reflections which are observable in the electron and neutron diffraction patterns only and not in the XRD patterns, as a result of which Noheda and coworkers missed the Cc phase in their synchrotron XRD studies at low temperatures. Our findings were confirmed by leading groups using neutron, TEM, Raman and high pressure diffraction studies. The first principles calculations also confirmed that the true ground state of PZT in the MPB region has Cc space group. However, in the last couple of years, the Cc space group of the ground state has become controversial with an alternative proposal of R3c as the space group of the ground state phase which is proposed to coexist with the metastable Cm phase. In order to resolve this controversy, we recently revisited the issue using pure PZT and 6% Sr 2+ substituted PZT, the latter samples show larger tilt angle on account of the reduction in the average cationic radius at the Pb 2+ site. Using high wavelength neutrons and high
Thermodynamic Ground States of Complex Oxide Heterointerfaces
DEFF Research Database (Denmark)
Gunkel, F.; Hoffmann-Eifert, S.; Heinen, R. A.
2017-01-01
The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature...
Infrared photonic bandgap materials and structures
Sundaram, S. K.; Keller, P. E.; Riley, B. J.; Martinez, J. E.; Johnson, B. R.; Allen, P. J.; Saraf, L. V.; Anheier, N. C., Jr.; Liau, F.
2006-02-01
Three-dimensional periodic dielectric structure can be described by band theory, analogous to electron waves in a crystal. Photonic band gap (PBG) structures were introduced in 1987. The PBG is an energy band in which optical modes, spontaneous emission, and zero-point fluctuations are all absent. It was first theoretically predicted that a three-dimensional photonic crystal could have a complete band gap. E. Yablonovitch built the first three-dimensional photonic crystal (Yablonovite) on microwave length scale, with a complete PBG. In nature, photonic crystals occur as semiprecious opal and the microscopic structures on the wings of some tropical butterflies, which are repeating structures (PBG structure/materials) that inhibit the propagation of some frequencies of light. Pacific Northwest National Laboratory (PNNL) has been developing tunable (between 3.5 and 16 μm) quantum cascade lasers (QCL), chalcogenides, and all other components for an integrated approach to chemical sensing. We have made significant progress in modeling and fabrication of infrared photonic band gap (PBG) materials and structures. We modeled several 2-D designs and defect configurations. Transmission spectra were computed by the Finite Difference Time Domain Method (with FullWAVE TM). The band gaps were computed by the Plane Wave Expansion Method (with BandSOLVE TM). The modeled designs and defects were compared and the best design was identified. On the experimental front, chalcogenide glasses were used as the starting materials. As IIS 3, a common chalcogenide, is an important infrared (IR) transparent material with a variety of potential applications such as IR sensors, waveguides, and photonic crystals. Wet-chemical lithography has been extended to PBG fabrication and challenges identified. An overview of results and challenges will be presented.
Luque-Ceballos, Jonathan C.; Posada-Borbón, Alvaro; Herrera-Urbina, Ronaldo; Aceves, R.; Juárez-Sánchez, J. Octavio; Posada-Amarillas, Alvaro
2018-03-01
Spectroscopic properties of gas-phase copper sulfide clusters (CuS)n (n = 2-6) are calculated using Density Functional Theory (DFT) and time-dependent (TD) DFT approaches. The energy landscape of the potential energy surface is explored through a basin-hopping DFT methodology. Ground-state and low-lying isomer structures are obtained. The global search was performed at the B3PW91/SDD level of theory. Normal modes are calculated to validate the existence of optimal cluster structures. Energetic properties are obtained for the ground-state and isomer clusters and their relative energies are evaluated for probing isomerization. This is a few tenths of an eV, except for (CuS)2 cluster, which presents energy differences of ∼1 eV. Notable differences in the infrared spectra exist between the ground-state and first isomer structures, even for the (CuS)5 cluster, which has in both configurations a core copper pyramid. TDDFT provides the simulated absorption spectrum, presenting a theoretical description of optical absorption bands in terms of electronic excitations in the UV and visible regions. Results exhibit a significant dependence of the calculated UV/vis spectra on clusters size and shape regarding the ground state structures. Optical absorption is strong in the UV region, and weak or forbidden in the visible region of the spectrum.
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 singlet ground state systems
International Nuclear Information System (INIS)
Diederix, K.M.
1979-01-01
Experiments are described determining the properties of a magnetic system consisting of a singlet ground state. Cu(NO 3 ) 2 .2 1/2H 2 O has been studied which is a system of S = 1/2 alternating antiferromagnetic Heisenberg chains. The static properties, spin lattice relaxation time and field-induced antiferromagnetically ordered state measurements are presented. Susceptibility and magnetic cooling measurements of other compounds are summarised. (Auth.)
DEFF Research Database (Denmark)
Severin, Gregory; Knutson, L. D.; Voytas, P. A.
2014-01-01
The ground state branch of the β decay of 66Ga is an allowed Fermi (0+ → 0+) transition with a relatively high f t value. The large f t and the isospin-forbidden nature of the transition indicates that the shape of the β spectrum of this branch may be sensitive to higher order contributions...... to the decay. Two previous measurements of the shape have revealed deviations from an allowed spectrum but disagree about whether the shape factor has a positive or negative slope. As a test of a new iron-free superconducting β spectrometer, we have measured the shape of the ground state branch of the 66Ga β...... spectrum above a positron energy of 1.9 MeV. The spectrum is consistent with an allowed shape, with the slope of the shape factor being zero to within ±3 × 10−3 per MeV. We have also determined the endpoint energy for the ground state branch to be 4.1535 ± 0.0003 (stat.) ±0.0007 (syst.) MeV, in good...
Ground states of a spin-boson model
International Nuclear Information System (INIS)
Amann, A.
1991-01-01
Phase transition with respect to ground states of a spin-boson Hamiltonian are investigated. The spin-boson model under discussion consists of one spin and infinitely many bosons with a dipole-type coupling. It is shown that the order parameter of the model vanishes with respect to arbitrary ground states if it vanishes with respect to ground states obtained as (biased) temperature to zero limits of thermic equilibrium states. The ground states of the latter special type have been investigated by H. Spohn. Spohn's respective phase diagrams are therefore valid for arbitrary ground states. Furthermore, disjointness of ground states in the broken symmetry regime is examined
RPA ground state correlations in nuclei
International Nuclear Information System (INIS)
Lenske, H.
1990-01-01
Overcounting in the RPA theory of ground state correlations is shown to be avoided if exact rather than quasiboson commutators are used. Single particle occupation probabilities are formulated in a compact way by the RPA Green function. Calculations with large configuration spaces and realistic interactions are performed with 1p1h RPA and second RPA (SRPA) including 2p2h mixing in excited states. In 41 Ca valence hole states are found to be quenched by about 10% in RPA and up to 18% in SRPA. Contributions from low and high lying excitations and their relation to long and short range correlations in finite nuclei are investigated. (orig.)
International Nuclear Information System (INIS)
Wu, J D; Lin, J W; Huang, Y S; Charles, W O; Shen, A; Zhang, Q; Tamargo, M C
2009-01-01
Contactless electroreflectance (CER) and Fourier transform infrared (FTIR) spectroscopy were used to study the intersubband transitions of a Zn x Cd 1-x Se/Zn x' Cd y' Mg 1-x'-y' Se multiple quantum well (MQW) structure grown by molecular beam epitaxy for mid-infrared device applications. The CER spectrum revealed a wide range of possible optical transitions in the MQW structure. The ground state transition was assigned by comparison with the photoluminescence emission signal taken from the same structure. A comprehensive analysis of the CER spectrum led to the identification of various interband transitions. The intersubband transitions were estimated and confirmed by FTIR measurements. The results demonstrate the potential of using CER as a complementary technique for the contactless and nondestructive characterization of the wide band gap II-VI MQW structures for mid-IR intersubband device applications.
Zethrenes, Extended p -Quinodimethanes, and Periacenes with a Singlet Biradical Ground State
Sun, Zhe
2014-08-19
ConspectusResearchers have studied polycyclic aromatic hydrocarbons (PAHs) for more than 100 years, and most PAHs in the neutral state reported so far have a closed-shell electronic configuration in the ground state. However, recent studies have revealed that specific types of polycyclic hydrocarbons (PHs) could have a singlet biradical ground state and exhibit unique electronic, optical, and magnetic activities. With the appropriate stabilization, these new compounds could prove useful as molecular materials for organic electronics, nonlinear optics, organic spintronics, organic photovoltaics, and energy storage devices. However, before researchers can use these materials to design new devices, they need better methods to synthesize these molecules and a better understanding of the fundamental relationship between the structure and biradical character of these compounds and their physical properties. Their biradical character makes these compounds difficult to synthesize. These compounds are also challenging to physically characterize and require the use of various experimental techniques and theoretic methods to comprehensively describe their unique properties.In this Account, we will discuss the chemistry and physics of three types of PHs with a significant singlet biradical character, primarily developed in our group. These structures are zethrenes, Z-shaped quinoidal hydrocarbons; hydrocarbons that include a proaromatic extended p-quinodimethane unit; and periacenes, acenes fused in a peri-Arrangement. We used a variety of synthetic methods to prepare these compounds and stabilized them using both thermodynamic and kinetic approaches. We probed their ground-state structures by electronic absorption, NMR, ESR, SQUID, Raman spectroscopy, and X-ray crystallography and also performed density functional theory calculations. We investigated the physical properties of these PHs using various experimental methods such as one-photon absorption, two-photon absorption
Ground state of high-density matter
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.
Structural characterization of ammonium uranate by infrared spectroscopy
International Nuclear Information System (INIS)
Rodriguez S, A.
1994-01-01
Infrared spectroscopy have been used to investigate the chemical composition of some ammonium uranates. In this study, I have attempted to establish the interrelationship between the structure of the products, the character of their infrared spectra and x-ray diffraction data capable of consistent interpretation in terms of defining the compounds. (Author)
Energy Technology Data Exchange (ETDEWEB)
Song, Xiaowei; Fagiani, Matias R. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstrasse 2, D-04103 Leipzig (Germany); Gewinner, Sandy; Schöllkopf, Wieland [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Asmis, Knut R., E-mail: knut.asmis@uni-leipzig.de, E-mail: js@chemie.hu-berlin.de [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstrasse 2, D-04103 Leipzig (Germany); Bischoff, Florian A.; Berger, Fabian; Sauer, Joachim, E-mail: knut.asmis@uni-leipzig.de, E-mail: js@chemie.hu-berlin.de [Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099 Berlin (Germany)
2016-06-28
We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D{sub 2}-tagged AlO{sub 1-4}{sup −} and Al{sub 2}O{sub 3-6}{sup −} are measured in the region from 400 to 1200 cm{sup −1}. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al{sub 2}O{sub 3-6}{sup −} anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO{sub 3}{sup −}. Terminal Al–O stretching modes are found between 1140 and 960 cm{sup −1}. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm{sup −1}) and lower energies (850-570 cm{sup −1}), respectively. Four modes in-between 910 and 530 cm{sup −1} represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al–(O){sub 2}–Al ring.
Study of ground state optical transfer for ultracold alkali dimers
Bouloufa-Maafa, Nadia; Londono, Beatriz; Borsalino, Dimitri; Vexiau, Romain; Mahecha, Jorge; Dulieu, Olivier; Luc-Koenig, Eliane
2013-05-01
Control of molecular states by laser pulses offer promising potential applications. The manipulation of molecules by external fields requires precise knowledge of the molecular structure. Our motivation is to perform a detailed analysis of the spectroscopic properties of alkali dimers, with the aim to determine efficient optical paths to form molecules in the absolute ground state and to determine the optimal parameters of the optical lattices where those molecules are manipulated to avoid losses by collisions. To this end, we use state of the art molecular potentials, R-dependent spin-orbit coupling and transition dipole moment to perform our calculations. R-dependent SO coupling are of crucial importance because the transitions occur at internuclear distances where they are affected by this R-dependence. Efficient schemes to transfer RbCs, KRb and KCs to the absolute ground state as well as the optimal parameters of the optical lattices will be presented. This work was supported in part by ``Triangle de la Physique'' under contract 2008-007T-QCCM (Quantum Control of Cold Molecules).
Neutrino ground state in a dense star
International Nuclear Information System (INIS)
Kiers, K.; Tytgat, M.H.
1998-01-01
It has recently been argued that long range forces due to the exchange of massless neutrinos give rise to a very large self-energy in a dense, finite-ranged, weakly charged medium. Such an effect, if real, would destabilize a neutron star. To address this issue we have studied the related problem of a massless neutrino field in the presence of an external, static electroweak potential of finite range. To be precise, we have computed to one loop the exact vacuum energy for the case of a spherical square well potential of depth α and radius R. For small wells, the vacuum energy is reliably determined by a perturbative expansion in the external potential. For large wells, however, the perturbative expansion breaks down. A manifestation of this breakdown is that the vacuum carries a non-zero neutrino charge. The energy and neutrino charge of the ground state are, to a good approximation for large wells, those of a neutrino condensate with chemical potential μ=α. Our results demonstrate explicitly that long-range forces due to the exchange of massless neutrinos do not threaten the stability of neutron stars. copyright 1998 The American Physical Society
Ground state configurations in antiferromagnetic ultrathin films with dipolar anisotropy
International Nuclear Information System (INIS)
León, H.
2013-01-01
The formalism developed in a previous work to calculate the dipolar energy in quasi-two-dimensional crystals with ferromagnetic order is now extended to collinear antiferromagnetic order. Numerical calculations of the dipolar energy are carried out for systems with tetragonally distorted fcc [001] structures, the case of NiO and MnO ultrathin film grown in non-magnetic substrates, where the magnetic phase is a consequence of superexchange and dipolar interactions. The employed approximation allows to demonstrate that dipolar coupling between atomic layers is responsible for the orientation of the magnetization when it differs from the one in a single layer. The ground state energy of a given NiO or MnO film is found to depend not only on the strain, but also on how much the interlayer separation and the 2D lattice constant are changed with respect to the ideal values corresponding to the non-distorted cubic structure. Nevertheless, it is shown that the orientation of the magnetization in the magnetic phase of any of these films is determined by the strain exclusively. A striped phase with the magnetization along the [112 ¯ ] direction appears as the ground state configuration of NiO and MnO ultrathin films. In films with equally oriented stripes along the layers this magnetic phase is twofold degenerate, while in films with multidomain layers it is eightfold degenerate. These results are not in contradiction with experimentally observed out-of-plane or in-plane magnetization of striped phases in NiO and MnO ultrathin films. - Highlights: ► Dipolar energy in collinear antiferromagnetic ultrathin films is calculated. ► Numerical results are presented for distorted fcc [001] structures. ► The lowest energy of a system depends on how the tetragonal distortion is achieved. ► A striped phase with magnetization in the [112 ¯ ] direction is the ground state. ► In multidomain NiO and MnO films it is eightfold degenerate.
Is the ground state of Yang-Mills theory Coulombic?
Heinzl, Thomas; Ilderton, Anton; Langfeld, Kurt; Lavelle, Martin; Lutz, Wolfgang; McMullan, David
2008-01-01
We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-abelian Coulomb fields is found to have a good overlap with the ground state for all ch...
International Nuclear Information System (INIS)
Walter, C W; Gibson, N D; Field, R L III; Snedden, A P; Shapiro, J Z; Janczak, C M; Hanstorp, D
2009-01-01
The negative ion As - has been investigated using infrared threshold photodetachment spectroscopy. The relative cross section for neutral atom production was measured with a crossed OPO-ion beam apparatus over selected photon energy ranges between 0.63 - 0.82 eV. s-wave thresholds were observed for detachment from As - (4p 4 3 P 0,1,2 ) to the As (4p 3 4 S 3/2 ) ground state. The measurements yield preliminary values for the electron affinity of As (0.8048(2)) eV) and the fine structure intervals of As - (0.1276(2) eV for 3 P 1 - 3 P 2 and 0.1643(10) eV for 3 P 0 - 3 P 2 ). The present results substantially reduce the uncertainties in these quantities.
Engineering an all-optical route to ultracold molecules in their vibronic ground state
Koch, Christiane P.; Moszynski, Robert
2008-01-01
We propose an improved photoassociation scheme to produce ultracold molecules in their vibronic ground state for the generic case where non-adiabatic effects facilitating transfer to deeply bound levels are absent. Formation of molecules is achieved by short laser pulses in a Raman-like pump-dump process where an additional near-infrared laser field couples the excited state to an auxiliary state. The coupling due to the additional field effectively changes the shape of the excited state pote...
Probing the 8He ground state via the 8He(p,t)6He reaction
International Nuclear Information System (INIS)
Keeley, N.; Skaza, F.; Lapoux, V.; Alamanos, N.; Auger, F.; Beaumel, D.; Becheva, E.; Blumenfeld, Y.; Delaunay, F.; Drouart, A.; Gillibert, A.; Giot, L.; Kemper, K.W.; Nalpas, L.; Pakou, A.; Pollacco, E.C.; Raabe, R.; Roussel-Chomaz, P.; Rusek, K.; Scarpaci, J.-A.; Sida, J.-L.; Stepantsov, S.; Wolski, R.
2007-01-01
The weakly-bound 8 He nucleus exhibits a neutron halo or thick neutron skin and is generally considered to have an α+4n structure in its ground state, with the four valence neutrons each occupying 1p 3/2 states outside the α core. The 8 He(p,t) 6 He reaction is a sensitive probe of the ground state structure of 8 He, and we present a consistent analysis of new and existing data for this reaction at incident energies of 15.7 and 61.3A MeV, respectively. Our results are incompatible with the usual assumption of a pure (1p 3/2 ) 4 structure and suggest that other configurations such as (1p 3/2 ) 2 (1p 1/2 ) 2 may be present with significant probability in the ground state wave function of 8 He
Centrifugal stretching along the ground state band of 168Hf
International Nuclear Information System (INIS)
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.
2009-01-01
The lifetimes of the J π =4 + , 6 + , 8 + , and 10 + levels along the ground state band in 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 168 Hf were populated using the 124 Sn( 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 168 Hf. The data agree with the predictions from the geometrical confined β-soft (CBS) rotor model that involves centrifugal stretching in a soft potential
Infrared spectroscopy of different phosphates structures.
Jastrzębski, W; Sitarz, M; Rokita, M; Bułat, K
2011-08-15
Infrared (IR) spectroscopic studies of mineral and synthetic phosphates have been presented. The interpretation of the spectra has been preceded by the isolated [PO(4)](3-) tetrahedron spectra analyse. The K(3)PO(4) saturated aqueous solution was measured in the special cell for liquids. The obtained IR results have been compared with the theoretical number of IR-active modes. The number and positions of the bands due to P-O vibrations have been established. The phase composition of the phosphates has been determined using XRD and IR spectroscopy methods. The influence of non-tetrahedral cations on the shape of the spectra and the positions of bands has been analysed and the crystalline field splitting effect has been discussed. Copyright © 2010 Elsevier B.V. All rights reserved.
Solving satisfiability problems by the ground-state quantum computer
International Nuclear Information System (INIS)
Mao Wenjin
2005-01-01
A quantum algorithm is proposed to solve the satisfiability (SAT) problems by the ground-state quantum computer. The scale of the energy gap of the ground-state quantum computer is analyzed for the 3-bit exact cover problem. The time cost of this algorithm on the general SAT problems is discussed
Ground state phase diagram of extended attractive Hubbard model
International Nuclear Information System (INIS)
Robaszkiewicz, S.; Chao, K.A.; Micnas, R.
1980-08-01
The ground state phase diagram of the extended Hubbard model with intraatomic attraction has been derived in the Hartree-Fock approximation formulated in terms of the Bogoliubov variational approach. For a given value of electron density, the nature of the ordered ground state depends essentially on the sign and the strength of the nearest neighbor coupling. (author)
Is the ground state of Yang-Mills theory Coulombic?
Heinzl, T.; Ilderton, A.; Langfeld, K.; Lavelle, M.; Lutz, W.; McMullan, D.
2008-08-01
We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-Abelian Coulomb fields is found to have a good overlap with the ground state for all charge separations. In fact, the overlap increases as the lattice regulator is removed. This opens up the possibility that the Coulomb state is the true ground state in the continuum limit.
Directory of Open Access Journals (Sweden)
Akrawy Dashty T.
2018-01-01
Full Text Available Theoretical α-decay half-lives of some nuclei from ground state to ground state are calculated using different nuclear potential model including Coulomb proximity potential (CPPM, Royer proximity potential and Broglia and Winther 1991. The calculated values comparing with experimental data, it is observed that the CPPM model is in good agreement with the experimental data.
Electron scattering from the ground state of mercury
International Nuclear Information System (INIS)
Fursa, D.; Bray, I.
2000-01-01
effect by adding a short ranged local potential with parameters chosen to reproduce ground state ionization energy. Singlet-triplet mixing in mercury has been accounted for in the framework of the fine-structure approximation. Theoretical calculation of the 6s6p 1 P state differential cross sections crucially depends on accurate 6s6p 1 P optical oscillator strength. For mercury it was found that core polarization effects are very large. In our calculations these effects are modeled by two-electron polarization potential which reduced optical oscillator strength from 2.12 a.u. to 1.18 a.u. in close agreement with experimental values. We will present comparison between our close-coupling calculations of e-Hg mercury scattering and available experimental data, showing very good agreement with experimental differential cross section data for elastic scattering and excitation of the 6s6p 1 P state
Construction of ground-state preserving sparse lattice models for predictive materials simulations
Huang, Wenxuan; Urban, Alexander; Rong, Ziqin; Ding, Zhiwei; Luo, Chuan; Ceder, Gerbrand
2017-08-01
First-principles based cluster expansion models are the dominant approach in ab initio thermodynamics of crystalline mixtures enabling the prediction of phase diagrams and novel ground states. However, despite recent advances, the construction of accurate models still requires a careful and time-consuming manual parameter tuning process for ground-state preservation, since this property is not guaranteed by default. In this paper, we present a systematic and mathematically sound method to obtain cluster expansion models that are guaranteed to preserve the ground states of their reference data. The method builds on the recently introduced compressive sensing paradigm for cluster expansion and employs quadratic programming to impose constraints on the model parameters. The robustness of our methodology is illustrated for two lithium transition metal oxides with relevance for Li-ion battery cathodes, i.e., Li2xFe2(1-x)O2 and Li2xTi2(1-x)O2, for which the construction of cluster expansion models with compressive sensing alone has proven to be challenging. We demonstrate that our method not only guarantees ground-state preservation on the set of reference structures used for the model construction, but also show that out-of-sample ground-state preservation up to relatively large supercell size is achievable through a rapidly converging iterative refinement. This method provides a general tool for building robust, compressed and constrained physical models with predictive power.
Stevens, Amy E.; Feigerle, C. S.; Lineberger, W. C.
1983-05-01
The laser photoelectron spectra of MnH- and MnD-, and FeH- and FeD- are reported. A qualitative description of the electronic structure of the low-spin and high-spin states of the metal hydrides is developed, and used to interpret the spectra. A diagonal transition in the photodetachment to the known high-spin, 7Σ+, ground state of MnH is observed. An intense off-diagonal transition to a state of MnH, at 1725±50 cm-1 excitation energy, is attributed to loss of an antibonding electron from MnH-, to yield a low-spin quintet state of MnH. For FeH- the photodetachment to the ground state is an off-diagonal transition, attributed to loss of the antibonding electron from FeH-, to yield a low-spin quartet ground state of FeH. A diagonal transition results in an FeH state at 1945±55 cm-1; this state of FeH is assigned as the lowest-lying high-spin sextet state of FeH. An additional excited state of MnH and two other excited states of FeH are observed. Excitation energies for all the states are reported; vibrational frequencies and bond lengths for the ions and several states of the neutrals are also determined from the spectra. The electron affinity of MnH is found to be 0.869±0.010 eV; and the electron affinity of FeH is determined to be 0.934±0.011 eV. Spectroscopic constants for the various deuterides are also reported.
Numerical study of ground state and low lying excitations of quantum antiferromagnets
International Nuclear Information System (INIS)
Trivedi, N.; Ceperley, D.M.
1989-01-01
The authors have studied, via Green function Monte Carlo (GFMC), the S = 1/2 Heisenberg quantum antiferromagnet in two dimensions on a square lattice. They obtain the ground state energy with only statistical errors E 0 /J = -0.6692(2), the staggered magnetization m † = 0.31(2), and from the long wave length behavior of the structure factor, the spin wave velocity c/c o = 1.14(5). They show that the ground state wave function has long range pair correlations arising from the zero point motion of spin waves
Infrared thermography for examination of paper structure
Kiiskinen, Harri T.; Pakarinen, Pekka I.
1998-03-01
The paper industry has used IR cameras primarily for troubleshooting, where the most common examples include the examination of the condition of dryer fabrics and dryer cylinders and the analysis of moisture variations in a paper web. Another application extensively using IR thermography is non-destructive testing of composite materials. This paper presents some recently developed laboratory methods using an IR camera to examine paper structure. Specific areas include cockling, moisture content, thermal uniformity, mechanism of failure, and an analysis of the copying process.
Infrared thermography examination of paper structure
International Nuclear Information System (INIS)
Kiiskinen, H.T.; Kukkonen, H.K.; Pakarinen, P.I.; Laine, A.J.
1997-01-01
The paper industry has used IR cameras primarily for troubleshooting, where the most common examples include the examination of the condition of dryer fabrics and dryer cylinders and the analysis of moisture variations in a paper web. Another application extensively using IR thermography is non-destructive testing of composite materials. This paper presents some recently developed laboratory methods using an IR camera to examine paper structure. Specific areas include cockling, moisture content, thermal uniformity, mechanism of failure, and an analysis of the copying process. (author)
Ground states and formal duality relations in the Gaussian core model
Cohn, H.; Kumar, A.; Schürmann, A.
2009-01-01
We study dimensional trends in ground states for soft-matter systems. Specifically, using a high-dimensional version of Parrinello-Rahman dynamics, we investigate the behavior of the Gaussian core model in up to eight dimensions. The results include unexpected geometric structures, with surprising
Search for 12 C+ 12 C clustering in 24 Mg ground state
Indian Academy of Sciences (India)
In the backdrop of many models, the heavy cluster structure of the ground state of 24 Mg has been probed experimentally for the first time using the heavy cluster knockout reaction 24 Mg( 12 C, 212 C) 12 C in thequasifree scattering kinematic domain. In the ( 12 C, 212 C) reaction, the direct 12 C-knockout cross-section was ...
Ground State Energy of the Modified Nambu-Goto String
Hadasz, Leszek
We calculate, using zeta function regularization method, semiclassical energy of the Nambu-Goto string supplemented with the boundary, Gauss-Bonnet term in the action and discuss the tachyonic ground state problem.
Ground state energy of the modified Nambu-Goto string
Hadasz, Leszek
1997-01-01
We calculate, using zeta function regularization method, semiclassical energy of the Nambu-Goto string supplemented with the boundary, Gauss-Bonnet term in the action and discuss the tachyonic ground state problem.
Approximating the ground state of gapped quantum spin systems
Energy Technology Data Exchange (ETDEWEB)
Michalakis, Spyridon [Los Alamos National Laboratory; Hamza, Eman [NON LANL; Nachtergaele, Bruno [NON LANL; Sims, Robert [NON LANL
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.
On the ground state for fractional quantum hall effect
International Nuclear Information System (INIS)
Jellal, A.
1998-09-01
In the present letter, we investigate the ground state wave function for an explicit model of electrons in an external magnetic field with specific inter-particle interactions. The excitation states of this model are also given. (author)
The ground state energy of a classical gas
International Nuclear Information System (INIS)
Conlon, J.G.
1983-01-01
The ground state energy of a classical gas is treated using a probability function for the position of the particles and a potential function. The lower boundary for the energy when the particle number is large is defined as ground state energy. The coulomb gas consisting of positive and negative particles is also treated (fixed and variable density case) the stability of the relativistic system is investigated as well. (H.B.)
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 energy fluctuations in the nuclear shell model
International Nuclear Information System (INIS)
Velazquez, Victor; Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Zuker, Andres P.
2005-01-01
Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well-defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states
On calculations of the ground state energy in quantum mechanics
International Nuclear Information System (INIS)
Efimov, G.V.
1991-02-01
In nonrelativistic quantum mechanics the Wick-ordering method called the oscillator representation suggested to calculate the ground-state energy for a wide class of potentials allowing the existence of a bound state. The following examples are considered: the orbital excitations of the ground-state in the Coulomb plus linear potential, the Schroedinger equation with a ''relativistic'' kinetic energy √p 2 +m 2 , the Coulomb three-body problem. (author). 22 refs, 2 tabs
Rich Ground State Chemical Ordering in Nanoparticles: Exact Solution of a Model for Ag-Au Clusters
DEFF Research Database (Denmark)
Larsen, Peter Mahler; Jacobsen, Karsten Wedel; Schiøtz, Jakob
2018-01-01
We show that nanoparticles can have very rich ground state chemical order. This is illustrated by determining the chemical ordering of Ag-Au 309-atom Mackay icosahedral nanoparticles. The energy of the nanoparticles is described using a cluster expansion model, and a Mixed Integer Programming (MIP......) approach is used to find the exact ground state configurations for all stoichiometries. The chemical ordering varies widely between the different stoichiometries, and display a rich zoo of structures with non-trivial ordering....
Highly twisted 1,2:8,9-dibenzozethrenes: Synthesis, ground state, and physical properties
Sun, Zhe; Zheng, Bin; Hu, Pan; Huang, Kuo-Wei; Wu, Jishan
2014-01-01
Two soluble and stable 1,2:8,9-dibenzozethrene derivatives (3a,b) are synthesized through a palladium-catalyzed cyclodimerization reaction. X-ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken-symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet-triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit farred/near-infrared absorption/emission and amphoteric redox behaviors.
Highly twisted 1,2:8,9-dibenzozethrenes: Synthesis, ground state, and physical properties
Sun, Zhe
2014-08-08
Two soluble and stable 1,2:8,9-dibenzozethrene derivatives (3a,b) are synthesized through a palladium-catalyzed cyclodimerization reaction. X-ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken-symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet-triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit farred/near-infrared absorption/emission and amphoteric redox behaviors.
Experimental Insights into Ground-State Selection of Quantum XY Pyrochlores
Hallas, Alannah M.; Gaudet, Jonathan; Gaulin, Bruce D.
2018-03-01
Extensive experimental investigations of the magnetic structures and excitations in the XY pyrochlores have been carried out over the past decade. Three families of XY pyrochlores have emerged: Yb2B2O7, Er2B2O7, and, most recently, [Formula: see text]Co2F7. In each case, the magnetic cation (either Yb, Er, or Co) exhibits XY anisotropy within the local pyrochlore coordinates, a consequence of crystal field effects. Materials in these families display rich phase behavior and are candidates for exotic ground states, such as quantum spin ice, and exotic ground-state selection via order-by-disorder mechanisms. In this review, we present an experimental summary of the ground-state properties of the XY pyrochlores, including evidence that they are strongly influenced by phase competition. We empirically demonstrate the signatures for phase competition in a frustrated magnet: multiple heat capacity anomalies, suppressed TN or TC, sample- and pressure-dependent ground states, and unconventional spin dynamics.
Magnetostriction-driven ground-state stabilization in 2H perovskites
International Nuclear Information System (INIS)
Porter, D. G.; Senn, M. S.; University of Oxford; Khalyavin, D. D.; Cortese, A.
2016-01-01
In this paper, the magnetic ground state of Sr_3ARuO_6, 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. Finally, the symmetry considerations used to rationalize the magnetic ground state are very general and will apply to many systems in this family, such as Ca_3ARuO_6, with A = (Li,Na), and Ca_3LiOsO_6 whose magnetic ground states are still not completely understood.
Global optimization of proteins using a dynamical lattice model: Ground states and energy landscapes
Dressel, F.; Kobe, S.
2004-01-01
A simple approach is proposed to investigate the protein structure. Using a low complexity model, a simple pairwise interaction and the concept of global optimization, we are able to calculate ground states of proteins, which are in agreement with experimental data. All possible model structures of small proteins are available below a certain energy threshold. The exact lowenergy landscapes for the trp cage protein (1L2Y) is presented showing the connectivity of all states and energy barriers.
Ground-state fidelity in the BCS-BEC crossover
International Nuclear Information System (INIS)
Khan, Ayan; Pieri, Pierbiagio
2009-01-01
The ground-state fidelity has been introduced recently as a tool to investigate quantum phase transitions. Here, we apply this concept in the context of a crossover problem. Specifically, we calculate the fidelity susceptibility for the BCS ground-state wave function, when the intensity of the fermionic attraction is varied from weak to strong in an interacting Fermi system, through the BCS-Bose-Einstein Condensation crossover. Results are presented for contact and finite-range attractive potentials and for both continuum and lattice models. We conclude that the fidelity susceptibility can be useful also in the context of crossover problems.
Measurement of the ground-state hyperfine splitting of antihydrogen
Juhász, B; Federmann, S
2011-01-01
The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, consisting of a cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of ~10−7. The first preliminary measurements of the hyperfine transitions will start in 2011.
A Ground State Tri-pí-Methane Rearrangement
Czech Academy of Sciences Publication Activity Database
Zimmerman, H. E.; Církva, Vladimír; Jiang, L.
2000-01-01
Roč. 41, č. 49 (2000), s. 9585-9587 ISSN 0040-4039 Institutional research plan: CEZ:AV0Z4072921 Keywords : tri-pi-methane * ground state Subject RIV: CC - Organic Chemistry Impact factor: 2.558, year: 2000
Ground state energy of a polaron in a superlattice
International Nuclear Information System (INIS)
Mensah, S.Y.; Allotey, F.K.A.; Nkrumah, G.; Mensah, N.G.
2000-10-01
The ground state energy of a polaron in a superlattice was calculated using the double-time Green functions. The effective mass of the polaron along the planes perpendicular to the superlattice axis was also calculated. The dependence of the ground state energy and the effective mass along the planes perpendicular to the superlattice axis on the electron-phonon coupling constant α and on the superlattice parameters (i.e. the superlattice period d and the bandwidth Δ) were studied. It was observed that if an infinite square well potential is assumed, the ground state energy of the polaron decreases (i.e. becomes more negative) with increasing α and d, but increases with increasing Δ. For small values of α, the polaron ground state energy varies slowly with Δ, becoming approximately constant for large Δ. The effective mass along the planes perpendicular to the superlattice axis was found to be approximately equal to the mass of an electron for all typical values of α, d and Δ. (author)
Observation of Hyperfine Transitions in Trapped Ground-State Antihydrogen
Olin, Arthur
2015-01-01
This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.
Fast Preparation of Critical Ground States Using Superluminal Fronts
Agarwal, Kartiek; Bhatt, R. N.; Sondhi, S. L.
2018-05-01
We propose a spatiotemporal quench protocol that allows for the fast preparation of ground states of gapless models with Lorentz invariance. Assuming the system initially resides in the ground state of a corresponding massive model, we show that a superluminally moving "front" that locally quenches the mass, leaves behind it (in space) a state arbitrarily close to the ground state of the gapless model. Importantly, our protocol takes time O (L ) to produce the ground state of a system of size ˜Ld (d spatial dimensions), while a fully adiabatic protocol requires time ˜O (L2) to produce a state with exponential accuracy in L . The physics of the dynamical problem can be understood in terms of relativistic rarefaction of excitations generated by the mass front. We provide proof of concept by solving the proposed quench exactly for a system of free bosons in arbitrary dimensions, and for free fermions in d =1 . We discuss the role of interactions and UV effects on the free-theory idealization, before numerically illustrating the usefulness of the approach via simulations on the quantum Heisenberg spin chain.
Entanglement of two ground state neutral atoms using Rydberg blockade
DEFF Research Database (Denmark)
Miroshnychenko, Yevhen; Browaeys, Antoine; Evellin, Charles
2011-01-01
We report on our recent progress in trapping and manipulation of internal states of single neutral rubidium atoms in optical tweezers. We demonstrate the creation of an entangled state between two ground state atoms trapped in separate tweezers using the effect of Rydberg blockade. The quality...... of the entanglement is measured using global rotations of the internal states of both atoms....
α-clustering in the ground state of 40Ca
International Nuclear Information System (INIS)
Michel, F.
1976-01-01
The anomalous large angle scattering observed in 40 Ca(α, α) is studied in the frame of a semi-microscopic model taking into account the presence of α-correlations in the ground state of 40 Ca. The calculations, performed between 18 and 29 MeV, assert the potential, non resonant nature of the phenomenon. (Auth.)
Ground states of the massless Derezinski-Gerard model
International Nuclear Information System (INIS)
Ohkubo, Atsushi
2009-01-01
We consider the massless Derezinski-Gerard model introduced by Derezinski and Gerard in 1999. We give a sufficient condition for the existence of a ground state of the massless Derezinski-Gerard model without the assumption that the Hamiltonian of particles has compact resolvent.
Magnetic excitons in singlet-ground-state ferromagnets
DEFF Research Database (Denmark)
Birgeneau, R.J.; Als-Nielsen, Jens Aage; Bucher, E.
1971-01-01
The authors report measurements of the dispersion of singlet-triplet magnetic excitons as a function of temperature in the singlet-ground-state ferromagnets fcc Pr and Pr3Tl. Well-defined excitons are observed in both the ferromagnetic and paramagnetic regions, but with energies which are nearly...
Correlation induced paramagnetic ground state in FeAl
Czech Academy of Sciences Publication Activity Database
Mohn, P.; Persson, C.; Blaha, P.; Schwarz, K.; Novák, Pavel; Eschrig, H.
2001-01-01
Roč. 87, č. 19 (2001), s. 196401-1-196401-4 ISSN 0031-9007 Institutional research plan: CEZ:AV0Z1010914 Keywords : FeAl * paramagnetic ground state Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.668, year: 2001
Observation of hyperfine transitions in trapped ground-state antihydrogen
Energy Technology Data Exchange (ETDEWEB)
Collaboration: A. Olin for the ALPHA Collaboration
2015-08-15
This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4 parts in 10{sup 3}. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.
International Nuclear Information System (INIS)
Farasat, M; Golzan, M M; Shojaei, S H R; Morini, F; Deleuze, M S
2016-01-01
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. (paper)
Induced quadrupolar singlet ground state of praseodymium in a modulated pyrochlore
van Duijn, J.; Kim, K. H.; Hur, N.; Ruiz-Bustos, R.; Adroja, D. T.; Bridges, F.; Daoud-Aladine, A.; Fernandez-Alonso, F.; Wen, J. J.; Kearney, V.; Huang, Q. Z.; Cheong, S.-W.; Perring, T. G.; Broholm, C.
2017-09-01
The complex structure and magnetism of Pr2 -xBixRu2O7 was investigated by neutron scattering and extended x-ray absorption fine structure. Pr has an approximate doublet ground state and the first excited state is a singlet. While the B -site (Ru) is well ordered throughout, this is not the case for the A -site (Pr/Bi). A broadened distribution for the Pr-O2 bond length at low temperature indicates the Pr environment varies from site to site even for x =0 . The environment about the Bi site is highly disordered ostensibly due to the 6 s lone pairs on Bi3 +. Correspondingly, we find that the non-Kramers doublet ground-state degeneracy, otherwise anticipated for Pr in the pyrochlore structure, is lifted so as to produce a quadrupolar singlet ground state with a spatially varying energy gap. For x =0 , below TN, the Ru sublattice orders antiferromagnetically, with propagation vector k =(0 ,0 ,0 ) as for Y2Ru2O7 . No ordering associated with the Pr sublattice is observed down to 100 mK. The low-energy magnetic response of Pr2 -xBixRu2O7 features a broad spectrum of magnetic excitations associated with inhomogeneous splitting of the Pr quasidoublet ground state. For x =0 (x =0.97 ), the spectrum is temperature dependent (independent). It appears disorder associated with Bi alloying enhances the inhomogeneous Pr crystal-field level splitting so that intersite interactions become irrelevant for x =0.97 . The structural complexity for the A -site may be reflected in the hysteretic uniform magnetization of B -site ruthenium in the Néel phase.
Ground-state kinetics of bistable redox-active donor-acceptor mechanically interlocked molecules.
Fahrenbach, Albert C; Bruns, Carson J; Li, Hao; Trabolsi, Ali; Coskun, Ali; Stoddart, J Fraser
2014-02-18
The ability to design and confer control over the kinetics of theprocesses involved in the mechanisms of artificial molecular machines is at the heart of the challenge to create ones that can carry out useful work on their environment, just as Nature is wont to do. As one of the more promising forerunners of prototypical artificial molecular machines, chemists have developed bistable redox-active donor-acceptor mechanically interlocked molecules (MIMs) over the past couple of decades. These bistable MIMs generally come in the form of [2]rotaxanes, molecular compounds that constitute a ring mechanically interlocked around a dumbbell-shaped component, or [2]catenanes, which are composed of two mechanically interlocked rings. As a result of their interlocked nature, bistable MIMs possess the inherent propensity to express controllable intramolecular, large-amplitude, and reversible motions in response to redox stimuli. In this Account, we rationalize the kinetic behavior in the ground state for a large assortment of these types of bistable MIMs, including both rotaxanes and catenanes. These structures have proven useful in a variety of applications ranging from drug delivery to molecular electronic devices. These bistable donor-acceptor MIMs can switch between two different isomeric states. The favored isomer, known as the ground-state co-conformation (GSCC) is in equilibrium with the less favored metastable state co-conformation (MSCC). The forward (kf) and backward (kb) rate constants associated with this ground-state equilibrium are intimately connected to each other through the ground-state distribution constant, KGS. Knowing the rate constants that govern the kinetics and bring about the equilibration between the MSCC and GSCC, allows researchers to understand the operation of these bistable MIMs in a device setting and apply them toward the construction of artificial molecular machines. The three biggest influences on the ground-state rate constants arise from
Radiant energy during infrared neural stimulation at the target structure
Richter, Claus-Peter; Rajguru, Suhrud; Stafford, Ryan; Stock, Stuart R.
2013-03-01
Infrared neural stimulation (INS) describes a method, by which an infrared laser is used to stimulate neurons. The major benefit of INS over stimulating neurons with electrical current is its spatial selectivity. To translate the technique into a clinical application it is important to know the energy required to stimulate the neural structure. With this study we provide measurements of the radiant exposure, at the target structure that is required to stimulate the auditory neurons. Flat polished fibers were inserted into scala tympani so that the spiral ganglion was in front of the optical fiber. Angle polished fibers were inserted along scala tympani, and rotating the beveled surface of the fiber allowed the radiation beam to be directed perpendicular to the spiral ganglion. The radiant exposure for stimulation at the modiolus for flat and angle polished fibers averaged 6.78+/-2.15 mJ/cm2. With the angle polished fibers, a 90º change in the orientation of the optical beam from an orientation that resulted in an INS-evoked maximum response, resulted in a 50% drop in the response amplitude. When the orientation of the beam was changed by 180º, such that it was directed opposite to the orientation with the maxima, minimum response amplitude was observed.
Structural properties of maize hybrids established by infrared spectra
Directory of Open Access Journals (Sweden)
Radenović Čedomir N.
2015-01-01
Full Text Available This paper discusses the application of the infrared (IR spectroscopy method for determination of structural properties of maize hybrid grains. The IR spectrum of maize grain has been registered in the following hybrids: ZP 341, ZP 434 and ZP 505. The existence of spectral bands varying in both number and intensity, as well as their shape, frequency and kinetics have been determined. They have been determined by valence oscillations and deformation oscillations of the following organic compounds: alkanes, alkenes, alkynes, amides, alcohols, ethers, carboxylic acids, esters and aldehydes and ketones, characteristic for biogenic compounds such as carbohydrates, proteins and lipids. In this way, possible changes in the grain structure of observed maize hybrids could be detected.
Infrared Fibers for Use in Space-Based Smart Structures
Tucker, Dennis S.; Nettles, Alan T.; Brantley, Lott W. (Technical Monitor)
2001-01-01
Infrared optical fibers are finding a number of applications including laser surgery, remote sensing, and nuclear radiation resistant links. Utilizing these fibers in space-based structures is another application, which can be exploited. Acoustic and thermal sensing are two areas in which these fibers could be utilized. In particular, fibers could be embedded in IM7/8552 toughened epoxy and incorporated into space structures both external and internal. ZBLAN optical fibers are a candidate, which have been studied extensively over the past 20 years for terrestrial applications. For the past seven years the effects of gravity on the crystallization behavior of ZBLAN optical fiber has been studied. It has been found that ZBLAN crystallization is suppressed in microgravity. This lack of crystallization leads to a fiber with better transmission characteristics than its terrestrial counterpart.
Hylleraas-Configuration Interaction study of the 1S ground state of the negative Li ion.
Sims, James S
2017-12-28
In a previous work Sims and Hagstrom [J. Chem. Phys. 140, 224312 (2014)] reported Hylleraas-Configuration Interaction (Hy-CI) method variational calculations for the neutral atom and positive ion 1 S ground states of the beryllium isoelectronic sequence. The Li - ion, nominally the first member of this series, has a decidedly different electronic structure. This paper reports the results of a large, comparable calculation for the Li - ground state to explore how well the Hy-CI method can represent the more diffuse L shell of Li - which is representative of the Be(2sns) excited states as well. The best non-relativistic energy obtained was -7.500 776 596 hartree, indicating that 10 - 20 nh accuracy is attainable in Hy-CI and that convergence of the r 12 r 34 double cusp is fast and that this correlation type can be accurately represented within the Hy-CI model.
Ground state of a hydrogen ion molecule immersed in an inhomogeneous electron gas
International Nuclear Information System (INIS)
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, H 2 + , 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 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 2.35a.u. from the first atomic layer of the solid
Study of polonium isotopes ground state properties by simultaneous atomic- and nuclear-spectroscopy
Koester, U H; Kalaninova, Z; Imai, N
2007-01-01
We propose to systematically study the ground state properties of neutron deficient $^{192-200}$Po isotopes by means of in-source laser spectroscopy using the ISOLDE laser ion source coupled with nuclear spectroscopy at the detection setup as successfully done before by this collaboration with neutron deficient lead isotopes. The study of the change in mean square charge radii along the polonium isotope chain will give an insight into shape coexistence above the mid-shell N = 104 and above the closed shell Z = 82. The hyperfine structure of the odd isotopes will also allow determination of the nuclear spin and the magnetic moment of the ground state and of any identifiable isomer state. For this study, a standard UC$_{x}$ target with the ISOLDE RILIS is required for 38 shifts.
Cluster expansion for ground states of local Hamiltonians
Directory of Open Access Journals (Sweden)
Alvise Bastianello
2016-08-01
Full Text Available 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.
Nuclear quadrupole moment of the 99Tc ground state
International Nuclear Information System (INIS)
Errico, Leonardo; Darriba, German; Renteria, Mario; Tang Zhengning; Emmerich, Heike; Cottenier, Stefaan
2008-01-01
By combining first-principles calculations and existing nuclear magnetic resonance (NMR) experiments, we determine the quadrupole moment of the 9/2 + ground state of 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 2 and ZrTc 2 . If this calculated information would be combined with yet to be performed Tc-NMR experiments in these compounds, the error bar on the 99 Tc ground state quadrupole moment could be further reduced
Coherent Control of Ground State NaK Molecules
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-state properties of a supersymmetric fermion chain
International Nuclear Information System (INIS)
Fendley, Paul; Hagendorf, Christian
2011-01-01
We analyze the ground state of a strongly interacting fermion chain with a supersymmetry. We conjecture a number of exact results, such as a hidden duality between weak and strong couplings. By exploiting a scale-free property of the perturbative expansions, we find exact expressions for the order parameters, yielding the critical exponents. We show that the ground state of this fermion chain and another model in the same universality class, the XYZ chain along a line of couplings, are both written in terms of the same polynomials. We demonstrate this explicitly for up to N = 24 sites and provide consistency checks for large N. These polynomials satisfy a recursion relation related to the Painlevé VI differential equation and, using a scale-free property of these polynomials, we derive a simple and exact formula for their N→∞ limit
Dissociation energy of the ground state of NaH
International Nuclear Information System (INIS)
Huang, Hsien-Yu; Lu, Tsai-Lien; Whang, Thou-Jen; Chang, Yung-Yung; Tsai, Chin-Chun
2010-01-01
The dissociation energy of the ground state of NaH was determined by analyzing the observed near dissociation rovibrational levels. These levels were reached by stimulated emission pumping and fluorescence depletion spectroscopy. A total of 114 rovibrational levels in the ranges 9≤v '' ≤21 and 1≤J '' ≤14 were assigned to the X 1 Σ + state of NaH. The highest vibrational level observed was only about 40 cm -1 from the dissociation limit in the ground state. One quasibound state, above the dissociation limit and confined by the centrifugal barrier, was observed. Determining the vibrational quantum number at dissociation v D from the highest four vibrational levels yielded the dissociation energy D e =15 815±5 cm -1 . Based on new observations and available data, a set of Dunham coefficients and the rotationless Rydberg-Klein-Rees curve were constructed. The effective potential curve and the quasibound states were discussed.
Three-body problem in the ground-state representation
International Nuclear Information System (INIS)
Gonzalez, A.
1993-01-01
The ground-state probability density of a three-body system is used to construct a classical potential U whose minimum coincides exactly with the ground-state energy. The spectrum of excited states may approximately be obtained by imposing quasiclassical quantization conditions over the classical motion in U. We show nontrivial one-dimensional models in which either this quantization condition is exact or considerably improves the usual semiclassical quantization. For three-dimensional problems, the small-oscillation frequencies in states with total angular momentum L = 0 are computed. These frequencies could represent an improvement over the frequencies of triatomic molecules computed with the use of ordinary quasiclassics for the motion of the nuclei in the molecular term. By providing a semiclassical description of the first excited quantum states, the sketched approach rises some interesting questions such as, for example, the relevance (once again) of classical chaos to quantum mechanics
Ground state of the parallel double quantum dot system.
Zitko, Rok; Mravlje, Jernej; Haule, Kristjan
2012-02-10
We resolve the controversy regarding the ground state of the parallel double quantum dot system near half filling. The numerical renormalization group predicts an underscreened Kondo state with residual spin-1/2 magnetic moment, ln2 residual impurity entropy, and unitary conductance, while the Bethe ansatz solution predicts a fully screened impurity, regular Fermi-liquid ground state, and zero conductance. We calculate the impurity entropy of the system as a function of the temperature using the hybridization-expansion continuous-time quantum Monte Carlo technique, which is a numerically exact stochastic method, and find excellent agreement with the numerical renormalization group results. We show that the origin of the unconventional behavior in this model is the odd-symmetry "dark state" on the dots.
Magnetic activity at infrared frequencies in structured metallic photonic crystals
International Nuclear Information System (INIS)
O'Brien, S.; Pendry, J.P.
2002-01-01
We derive the effective permeability and permittivity of a nanostructured metallic photonic crystal by analysing the complex reflection and transmission coefficients for slabs of various thicknesses. These quantities were calculated using the transfer matrix method. Our results indicate that these structures could be used to realize a negative effective permeability, at least up to infrared frequencies. The origin of the negative permeability is a resonance due to the internal inductance and capacitance of the structure. We also present an analytic model for the effective permeability of the crystal. The model reveals the importance of the inertial inductance due to the finite mass of the electrons in the metal. We find that this contribution to the inductance has implications for the design of metallic magnetic structures in the optical region of the spectrum. We show that the magnetic activity in the structure is accompanied by the concentration of the incident field energy into very small volumes within the structure. This property will allow us to considerably enhance non-linear effects with minute quantities of material. (author)
Variational calculation for the ground state of 12C
International Nuclear Information System (INIS)
Consoni, L.H.A.; Coelho, H.T.; Das, T.K.
1983-01-01
A variational calculation is done for the ground state of a 3α-particle system. Two simple trial wavefunctions are used and results are compared with an exact calculation done by the Hyperspherical Harmonic method. A modifed Ali-Bodmer potential for the α-α interaction is considered for all calculations. It is found that these simple wave functions can be very useful for phenomenological calculations. (Author) [pt
Bethe ansatz study for ground state of Fateev Zamolodchikov model
International Nuclear Information System (INIS)
Ray, S.
1997-01-01
A Bethe ansatz study of a self-dual Z N spin lattice model, originally proposed by V. A. Fateev and A. B. Zamolodchikov, is undertaken. The connection of this model to the Chiral Potts model is established. Transcendental equations connecting the zeros of Fateev endash Zamolodchikov transfer matrix are derived. The free energies for the ferromagnetic and the anti-ferromagnetic ground states are found for both even and odd spins. copyright 1997 American Institute of Physics
Ground-state correlations within a nonperturbative approach
Czech Academy of Sciences Publication Activity Database
De Gregorio, G.; Herko, J.; Knapp, F.; Lo Iudice, N.; Veselý, Petr
2017-01-01
Roč. 95, č. 2 (2017), č. článku 024306. ISSN 2469-9985 R&D Projects: GA ČR GA13-07117S Institutional support: RVO:61389005 Keywords : ground state * harmonic oscillator frequency * space dimensions Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 3.820, year: 2016
Ground state solutions for non-local fractional Schrodinger equations
Directory of Open Access Journals (Sweden)
Yang Pu
2015-08-01
Full Text Available In this article, we study a time-independent fractional Schrodinger equation with non-local (regional diffusion $$ (-\\Delta^{\\alpha}_{\\rho}u + V(xu = f(x,u \\quad \\text{in }\\mathbb{R}^{N}, $$ where $\\alpha \\in (0,1$, $N > 2\\alpha$. We establish the existence of a non-negative ground state solution by variational methods.
Ground state energy values and moments of the anharmonic oscillator
International Nuclear Information System (INIS)
Seetharaman, M.; Raghavan, Sekhar; Subba Rao, G.
1981-01-01
It is shown that a very satisfactory estimate of the energy values (for all values of the anharmonicity) and moments of the ground state of the quartic anharmonic oscillator can be obtained in the variational method, by considering trial wavefunctions which have the correct asymptotic properties. The results derived with a single variational parameter are a considerable improvement over the recent results of C.A. Ginsburg and E.W. Montroll (1978). (author)
Ground states for light and heavy quark hadrons
Energy Technology Data Exchange (ETDEWEB)
Anderson, J T [Physics Dept., Philippines Univ., Manila (Philippines)
1994-01-01
According to de Rujula et al. if the degenerate multiplet masses are known then it is not necessary to parametrize the interactions. With degenerate multiplet masses calculated from the spinorial decomposition of the SU(2)xSU(2) part of the SU(6)xSU(6) symmetry, the ground states for 3, 4 and 5 quark hadrons are calculated in terms of the Cartan matrix integers n[sub [alpha
Ground state solutions for diffusion system with superlinear nonlinearity
Directory of Open Access Journals (Sweden)
Zhiming Luo
2015-03-01
where $z=(u,v\\colon\\mathbb{R}\\times\\mathbb{R}^{N}\\rightarrow\\mathbb{R}^{2}$, $b\\in C^{1}(\\mathbb{R}\\times\\mathbb{R}^{N}, \\mathbb{R}^{N}$ and $V(x\\in C(\\mathbb{R}^{N},\\mathbb{R}$. Under suitable assumptions on the nonlinearity, we establish the existence of ground state solutions by the generalized Nehari manifold method developed recently by Szulkin and Weth.
Design of a far infrared interferometer diagnostic support structure
International Nuclear Information System (INIS)
Brooksby, C.A.; Rice, B.W.; Peebles, W.A.
1987-10-01
The Far Infrared Interferometer (FIR) diagnostic will operate in the 119 to 400 micron range to measure the plasma electron density on the Microwave Tokamak Experiment (MTX) being set up at LLNL. This diagnostic is a multi-channel system which incorporates a long elliptically shaped beam that passes through the plasma and is imaged onto an array of 14 detectors that are located on a table above the machine. The reference beam is brought around the machine and mixed with the plasma beam onto the detectors. The density is measured by a phase shift between these beams and is, therefore, very sensitive to path length changes between the two beam paths due to motion of the support structure. The design goal for allowable phase shifts caused by changes in the path length due to structure movement is 1/50th of a wavelength (2.4 to 8 microns). The structure needs to maintain this stability during the 0.5 second plasma shot. The structure is approximately 5 meters tall to support the optics table above the machine. In order to reduce the structure motion to the required level the forces acting on it were evaluated. The forces evaluated were eddy currents from the pulsed electromagnetic fields, the ambient ground motion, and the floor movement as the magnets are pulsed. The designs for similar diagnostic interferometers on other tokamaks were also reviewed to evaluate the forces and motions that might cause such small deflections in the support structure. Our structure is somewhat unique in that it is designed for operation in relatively large pulsed magnetic fields (100 to 7000 gauss) arising from the air core transformer of MTX. The design chosen incorporates a very rigid structure with high resistive and non-conductive materials. The choice of materials selected is discussed with reference to their response to expected forces. 14 refs., 10 figs
Normal ground state of dense relativistic matter in a magnetic field
International Nuclear Information System (INIS)
Gorbar, E. V.; Miransky, V. A.; Shovkovy, I. A.
2011-01-01
The properties of the ground state of relativistic matter in a magnetic field are examined within the framework of a Nambu-Jona-Lasinio model. The main emphasis of this study is the normal ground state, which is realized at sufficiently high temperatures and/or sufficiently large chemical potentials. In contrast to the vacuum state, which is characterized by the magnetic catalysis of chiral symmetry breaking, the normal state is accompanied by the dynamical generation of the chiral shift parameter Δ. In the chiral limit, the value of Δ determines a relative shift of the longitudinal momenta (along the direction of the magnetic field) in the dispersion relations of opposite chirality fermions. We argue that the chirality remains a good approximate quantum number even for massive fermions in the vicinity of the Fermi surface and, therefore, the chiral shift is expected to play an important role in many types of cold dense relativistic matter, relevant for applications in compact stars. The qualitative implications of the revealed structure of the normal ground state on the physics of protoneutron stars are discussed. A noticeable feature of the Δ parameter is that it is insensitive to temperature when T 0 , where μ 0 is the chemical potential, and increases with temperature for T>μ 0 . The latter implies that the chiral shift parameter is also generated in the regime relevant for heavy ion collisions.
High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb
International Nuclear Information System (INIS)
Sirohi, Anshu; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Sheet, Goutam; Singh, Chandan K.; Kabir, Mukul; Thakur, Gohil S.; Haque, Zeba; Gupta, L. C.; Ganguli, Ashok K.
2016-01-01
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.
High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb
Energy Technology Data Exchange (ETDEWEB)
Sirohi, Anshu; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Sheet, Goutam, E-mail: goutam@iisermohali.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli PO 140306 (India); Singh, Chandan K.; Kabir, Mukul [Department of Physics, Indian Institute of Science Education and Research, Pune 411008 (India); Thakur, Gohil S.; Haque, Zeba; Gupta, L. C. [Department of Chemistry, Indian Institute of Technology, New Delhi 110016 (India); Ganguli, Ashok K. [Department of Chemistry, Indian Institute of Technology, New Delhi 110016 (India); Institute of Nano Science & Technology, Mohali 160064 (India)
2016-06-13
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.
Vollmer, M.
2013-11-01
'Infrared' is a very wide field in physics and the natural sciences which has evolved enormously in recent decades. It all started in 1800 with Friedrich Wilhelm Herschel's discovery of infrared (IR) radiation within the spectrum of the Sun. Thereafter a few important milestones towards widespread use of IR were the quantitative description of the laws of blackbody radiation by Max Planck in 1900; the application of quantum mechanics to understand the rotational-vibrational spectra of molecules starting in the first half of the 20th century; and the revolution in source and detector technologies due to micro-technological breakthroughs towards the end of the 20th century. This has led to much high-quality and sophisticated equipment in terms of detectors, sources and instruments in the IR spectral range, with a multitude of different applications in science and technology. This special issue tries to focus on a few aspects of the astonishing variety of different disciplines, techniques and applications concerning the general topic of infrared radiation. Part of the content is based upon an interdisciplinary international conference on the topic held in 2012 in Bad Honnef, Germany. It is hoped that the information provided here may be useful for teaching the general topic of electromagnetic radiation in the IR spectral range in advanced university courses for postgraduate students. In the most general terms, the infrared spectral range is defined to extend from wavelengths of 780 nm (upper range of the VIS spectral range) up to wavelengths of 1 mm (lower end of the microwave range). Various definitions of near, middle and far infrared or thermal infrared, and lately terahertz frequencies, are used, which all fall in this range. These special definitions often depend on the scientific field of research. Unfortunately, many of these fields seem to have developed independently from neighbouring disciplines, although they deal with very similar topics in respect of the
Resonant Ion Pair Formation in Electron Collisions with Ground State Molecular Ions
International Nuclear Information System (INIS)
Zong, W.; Dunn, G.H.; Djuric, N.; Greene, C.H.; Neau, A.; Zong, W.; Larsson, M.; Al-Khalili, A.; Neau, A.; Derkatch, A.M.; Vikor, L.; Shi, W.; Rosen, S.; Le Padellec, A.; Danared, H.; Ugglas, M. af
1999-01-01
Resonant ion pair formation from collisions of electrons with ground state diatomic molecular ions has been observed and absolute cross sections measured. The cross section for HD + is characterized by an abrupt threshold at 1.9thinspthinspeV and 14 resolved peaks in the range of energies 0≤E≤14 eV . The dominant mechanism responsible for the structures appears to be resonant capture and stabilization, modified by two-channel quantum interference. Data on HF + show structure correlated with photoionization of HF and with dissociative recombination of electrons with this ion. copyright 1999 The American Physical Society
Jurčišinová, E.; Jurčišin, M.
2018-04-01
Anomalies of the specific heat capacity are investigated in the framework of the exactly solvable antiferromagnetic spin- 1 / 2 Ising model in the external magnetic field on the geometrically frustrated tetrahedron recursive lattice. It is shown that the Schottky-type anomaly in the behavior of the specific heat capacity is related to the existence of unique highly macroscopically degenerated single-point ground states which are formed on the borders between neighboring plateau-like ground states. It is also shown that the very existence of these single-point ground states with large residual entropies predicts the appearance of another anomaly in the behavior of the specific heat capacity for low temperatures, namely, the field-induced double-peak structure, which exists, and should be observed experimentally, along with the Schottky-type anomaly in various frustrated magnetic system.
Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state
Directory of Open Access Journals (Sweden)
M Majidiyan
2010-09-01
Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.
Sideband cooling of micromechanical motion to the quantum ground state.
Teufel, J D; Donner, T; Li, Dale; Harlow, J W; Allman, M S; Cicak, K; Sirois, A J; Whittaker, J D; Lehnert, K W; Simmonds, R W
2011-07-06
The advent of laser cooling techniques revolutionized the study of many atomic-scale systems, fuelling progress towards quantum computing with trapped ions and generating new states of matter with Bose-Einstein condensates. Analogous cooling techniques can provide a general and flexible method of preparing macroscopic objects in their motional ground state. Cavity optomechanical or electromechanical systems achieve sideband cooling through the strong interaction between light and motion. However, entering the quantum regime--in which a system has less than a single quantum of motion--has been difficult because sideband cooling has not sufficiently overwhelmed the coupling of low-frequency mechanical systems to their hot environments. Here we demonstrate sideband cooling of an approximately 10-MHz micromechanical oscillator to the quantum ground state. This achievement required a large electromechanical interaction, which was obtained by embedding a micromechanical membrane into a superconducting microwave resonant circuit. To verify the cooling of the membrane motion to a phonon occupation of 0.34 ± 0.05 phonons, we perform a near-Heisenberg-limited position measurement within (5.1 ± 0.4)h/2π, where h is Planck's constant. Furthermore, our device exhibits strong coupling, allowing coherent exchange of microwave photons and mechanical phonons. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion, possibly even testing quantum theory itself in the unexplored region of larger size and mass. Because mechanical oscillators can couple to light of any frequency, they could also serve as a unique intermediary for transferring quantum information between microwave and optical domains.
Spectroscopic factor of the 7He ground state
International Nuclear Information System (INIS)
Beck, F.; Frekers, D.; Neumann-Cosel, P. von; Richter, A.; Ryezayeva, N.; Thompson, I.J.
2007-01-01
The neutron spectroscopic factor S n of the 7 He ground state is extracted from an R-matrix analysis of a recent measurement of the 7 Li(d, 2 He) 7 He reaction with good energy resolution. The width extracted from a deconvolution of the spectrum is Γ=183(22) keV (full width at half maximum, FWHM). The result S n =0.64(9) is slightly larger than predictions of recent 'ab initio' Green's function Monte Carlo and fermionic molecular dynamics calculations
Kohn-Sham Theory for Ground-State Ensembles
International Nuclear Information System (INIS)
Ullrich, C. A.; Kohn, W.
2001-01-01
An electron density distribution n(r) which can be represented by that of a single-determinant ground state of noninteracting electrons in an external potential v(r) is called pure-state v -representable (P-VR). Most physical electronic systems are P-VR. Systems which require a weighted sum of several such determinants to represent their density are called ensemble v -representable (E-VR). This paper develops formal Kohn-Sham equations for E-VR physical systems, using the appropriate coupling constant integration. It also derives local density- and generalized gradient approximations, and conditions and corrections specific to ensembles
Ground state depletion – A step towards mid-IR lasing of doped silver halides
Energy Technology Data Exchange (ETDEWEB)
Tsur, Yuval, E-mail: yuvaltsu@post.tau.ac.il [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel); Goldring, Sharone [Applied Physics Division, Soreq NRC, Yavne 81800 (Israel); Galun, Ehud [DDR& D, Ministry of Defense (Israel); Katzir, Abraham [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel)
2016-07-15
We show for the first time ground state absorption saturation in a doped silver halide crystal (AgCl{sub x}Br{sub 1−x}), specifically with cobalt. Spectroscopic studies showed absorption bands in the 1.4–2.5 μm region and emission bands in the 3.8–5.0 μm region, with a 1.5 ms lifetime at low temperatures. Absorption saturation indicates a good low and room temperature lasing feasibility at 4.1 μm. In addition, a comparison of cobalt, nickel and iron as dopants is presented. These doped silver halide crystals can be extruded to form optical fibers, possibly introducing a new family of fiber lasers for the middle infrared.
Cluster decay of Ba isotopes from ground state and as an excited ...
Indian Academy of Sciences (India)
otherwise, inclusion of excitation energy decreases the T1/2 values. ... penetrates the nuclear barrier and reaches scission configuration after running .... between the ground-state energy levels of the parent nuclei and the ground-state energy.
Line list for the ground state of CaF
Hou, Shilin; Bernath, Peter F.
2018-05-01
The molecular potential energy function and electronic dipole moment function for the ground state of CaF were studied with MRCI, ACPF, and RCCSD(T) ab initio calculations. The RCCSD(T) potential function reproduces the experimental vibrational intervals to within ∼2 cm-1. The RCCSD(T) dipole moment at the equilibrium internuclear separation agrees well with the experimental value. Over a wide range of internuclear separations, far beyond the range associated with the observed spectra, the ab initio dipole moment functions are similar and highly linear. An extended Morse oscillator (EMO) potential function was also obtained by fitting the observed lines of the laboratory vibration-rotation and pure rotation spectra of the 40CaF X2Σ+ ground state. The fitted potential reproduces the observed transitions (v ≤ 8, N ≤ 121, Δv = 0, 1) within their experimental uncertainties. With this EMO potential and the RCCSD(T) dipole moment function, line lists for 40CaF, 42CaF, 43CaF, 44CaF, 46CaF, and 48CaF were computed for v ≤ 10, N ≤ 121, Δv = 0-10. The calculated emission spectra are in good agreement with an observed laboratory spectrum of CaF at a sample temperature of 1873 K.
A new representation for ground states and its Legendre transforms
International Nuclear Information System (INIS)
Cedillo, A.
1994-01-01
The ground-state energy of an electronic system is a functional of the number of electrons (N) and the external potential (v): E = E(N,V), this is the energy representation for ground states. In 1982, Nalewajski defined the Legendre transforms of this representation, taking advantage of the strict concavity of E with respect to their variables (concave respect v and convex respect N), and he also constructed a scheme for the reduction of derivatives of his representations. Unfortunately, N and the electronic density (p) were the independent variables of one of these representations, but p depends explicitly on N. In this work, this problem is avoided using the energy per particle (ε) as the basic variables, and the Legendre transformations can be defined. A procedure for the reduction of derivatives is generated for the new four representations and, in contrast to the Nalewajski's procedure, it only includes derivatives of the four representations. Finally, the reduction of derivatives is used to test some relationships between the hardness and softness kernels
Leading infrared logarithms and vacuum structure of QCD3
International Nuclear Information System (INIS)
Guendelman, E.I.
1990-01-01
QCD 3 is a superrenormalizable, massless theory; therefore off-mass-shell infrared divergences appear in the loop expansion. This paper shows how certain infrared divergences can be subtracted by changing the boundary conditions in the functional integral, letting the vector potentials approach non-zero constant values at infinity. Infrared divergences, in the Green's functions, come together with powers of logarithms of the external momenta, and among the infrared divergences we deal with, there are those that give rise to the leading and first subleading logarithms. The authors show how for two-point functions it is possible to sum the leading and first subleading logarithms to all orders. This procedure defines a nonperturbative approximation for QCD 3 . The authors find that in the ultraviolet region these summations are well defined, while in the infrared region, some additional prescription is needed to make sense out of them
Existence of a ground state for the confined hydrogen atom in non-relativistic QED
International Nuclear Information System (INIS)
Amour, Laurent; Faupin, Jeremy
2008-01-01
We consider a system of a hydrogen atom interacting with the quantized electromagnetic field. Instead of fixing the nucleus, we assume that the system is confined by its center of mass. This model is used in theoretical physics to explain the Lamb-Dicke effect. After a brief review of the literature, we explain how to verify some properly chosen binding conditions which lead to the existence of a ground state for our model, and for all values of the fine-structure constant
Ground-state properties of a dilute homogeneous Bose gas of hard disks in two dimensions
International Nuclear Information System (INIS)
Mazzanti, F.; Polls, A.; Fabrocini, A.
2005-01-01
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∼0.001. The condensate fraction in 2D is also computed and found generally lower than the 3D one at the same x
The relation between the (N) and (N-1) electrons atomic ground state
International Nuclear Information System (INIS)
Briet, P.
1984-05-01
The relation between the ground state of an N and (N-1) electrons atomic system are studied. We show that in some directions of the configuration space, the ratio of the N electrons atomic ground state to the one particle density is asymptotically equivalent to the (N-1) electrons atomic ground state
Langley, Stuart K; Chilton, Nicholas F; Moubaraki, Boujemaa; Murray, Keith S
2011-12-07
) metallic core, indicates large spin ground states, with likely values of S = 16 (±1) for each. Solid state AC susceptibility measurements confirm the large spin ground state values and is also suggestive of SMM behaviour for 2-5 as observed via the onset of frequency dependent out-of-phase peaks.
Energy of ground state of laminar electron-hole liquid
International Nuclear Information System (INIS)
Andryushin, E.A.
1976-01-01
The problem of a possible existence of metal electron-hole liquid in semiconductors is considered. The calculation has been carried out for the following model: two parallel planes are separated with the distance on one of the planes electrons moving, on the other holes doing. Transitions between the planes are forbidden. The density of particles for both planes is the same. The energy of the ground state and correlation functions for such electron-and hole system are calculated. It is shown that the state of a metal liquid is more advantageous against the exciton gas. For the mass ratio of electrons and holes, msub(e)/msub(h) → 0 a smooth rearrangement of the system into a state with ordered heavy particles is observed
Liquid 4He: Modified LOCV ground-state energy calculations
International Nuclear Information System (INIS)
Skjetne, B.; Ostgaard, E.
1996-01-01
The ground-state energetics of liquid 4 He is studied in a constrained variational approach, where the significance of neglecting terms beyond second order in the cluster expansion is estimated in a crude way. An adjustment to the conditions of healing on the two-body correlation function excludes from the global average field the effects of pairwise clustering to higher orders. To this end, open-quotes virtualclose quotes particles beyond nearest neighbors are included in the average correlation volume. Results within the scope of such modifications are consistent with GFMC and QDMC calculations, falling within the range -7.25 ± 0.05 K when recent interaction models are used
Symmetry Breakdown in Ground State Dissociation of HD+
International Nuclear Information System (INIS)
Ben-Itzhak, I.; Wells, E.; Carnes, K. D.; Krishnamurthi, Vidhya; Weaver, O. L.; Esry, B. D.
2000-01-01
Experimental studies of the dissociation of the electronic ground state of HD + following ionization of HD by fast proton impact indicate that the H + +D 1s dissociation channel is more likely than the H1s+D + dissociation channel by about 7% . This isotopic symmetry breakdown is due to the finite nuclear mass correction to the Born-Oppenheimer approximation which makes the 1sσ state 3.7 meV lower than the 2pσ state at the dissociation limit. The measured fractions of the two dissociation channels are in agreement with coupled-channels calculations of 1sσ to 2pσ transitions. (c) 2000 The American Physical Society
Ground-state properties of neutron magic nuclei
Energy Technology Data Exchange (ETDEWEB)
Saxena, G., E-mail: gauravphy@gmail.com [Govt. Women Engineering College, Department of Physics (India); Kaushik, M. [Shankara Institute of Technology, Department of Physics (India)
2017-03-15
A systematic study of the ground-state properties of the entire chains of even–even neutron magic nuclei represented by isotones of traditional neutron magic numbers N = 8, 20, 40, 50, 82, and 126 has been carried out using relativistic mean-field plus Bardeen–Cooper–Schrieffer approach. Our present investigation includes deformation, binding energy, two-proton separation energy, single-particle energy, rms radii along with proton and neutron density profiles, etc. Several of these results are compared with the results calculated using nonrelativistic approach (Skyrme–Hartree–Fock method) along with available experimental data and indeed they are found with excellent agreement. In addition, the possible locations of the proton and neutron drip-lines, the (Z, N) values for the new shell closures, disappearance of traditional shell closures as suggested by the detailed analyzes of results are also discussed in detail.
Mid-infrared studies of GaAs/AlGaAs quantum cascade structures
International Nuclear Information System (INIS)
Keightley, Peter Thomas
2001-01-01
This thesis describes an investigation of GaAs/AIGaAs Quantum Cascade (QC) structures. Mid-infrared spectroscopic techniques are employed to study several QC LED and laser structures, in order to investigate the fundamental principles underlying the operation of these state of the art devices. The results presented in this thesis include the demonstration of intersubband lasing in a GaAs/AIGaAs QC laser, which closely followed the first report of QC lasing using this materials system in 1998, and form a basis from which further research into QC lasers can be built upon. Initially, a spectroscopic investigation of several QC LEDs is presented, beginning with a comparison of the performance of two designs incorporating an active region based on a diagonal transition. These devices have single quantum well (SQW), or multi-quantum well (MQW) bridging regions and are investigated using intersubband electroluminescence (EL) spectroscopy. It is found that although growth and design are simplified by the use of a SQW bridging region, superior performance is obtained by the use of MQW bridging regions, intersubband EL and photocurrent (PC) spectroscopy are employed to study the operating characteristics of a QC LED incorporating a graded superlattice active region. EL is observed at 9 and 11μm arising from interminiband radiative transitions. Complementary intersubband and interband spectroscopic techniques have been employed to study the evolution of the electron distribution within a QC LED, with increasing bias. Below the device turn on, the transfer of electrons from the donors to the active region ground state is observed. As the bias is increased the redistribution of electrons through the bridging region is observed, in conjunction with an alignment of energy levels within the structure, close to the operating bias. Intersubband lasing has been demonstrated from a GaAs/AIGaAs QC laser at λ∼9μm. Reciprocal gain measurements have been performed to determine the
International Nuclear Information System (INIS)
Clouthier, D.J.; Huang, G.; Adam, A.G.; Merer, A.J.
1994-01-01
High-resolution intracavity dye laser spectroscopy has been used to obtain sub-Doppler spectra of transitions to 350 rotational levels in the 4 1 0 band of the A 1 A 2 --X 1 A 1 electronic transition of thioformaldehyde. Ground state combination differences from the sub-Doppler spectra, combined with microwave and infrared data, have been used to improve the ground state rotational and centrifugal distortion constants of H 2 CS. The upper state shows a remarkable number of perturbations. The largest of these are caused by nearby triplet levels, with matrix elements of 0.05--0.15 cm -1 . A particularly clear singlet--triplet avoided crossing in K a ' = 7 has been shown to be caused by interaction with the F 1 component of the 3 1 6 2 vibrational level of the a 3 A 2 state. At least 53% of the S 1 levels show evidence of very small perturbations by high rovibronic levels of the ground state. The number of such perturbations is small at low J, but increases rapidly beyond J=5 such that 40%--80% of the observed S 1 levels of any given J are perturbed by ground state levels. Model calculations show that the density and J dependence of the number of perturbed levels can be explained if there is extensive rotation-induced mixing of the vibrational levels in the ground state
Lim, Zhenglong
2015-11-12
Quinoidal π-conjugated polycyclic hydrocarbons have attracted intensive research interest due to their unique optical/electronic properties and possible magnetic activity, which arises from a thermally excited triplet state. However, there is still lack of fundamental understanding on the factors that determine the electronic ground states. Herein, by using quinoidal oligo(9,10-anthryl)s, it is demonstrated that both aromatic stabilisation and steric strain release play balanced roles in determining the ground states. Oligomers with up to four anthryl units were synthesised and their ground states were investigated by electronic absorption and electron spin resonance (ESR) spectroscopy, assisted by density functional theory (DFT) calculations. The quinoidal 9,10-anthryl dimer 1 has a closed-shell ground state, whereas the tri- (2) and tetramers (3) both have an open-shell diradical ground state with a small singlet-triplet gap. Such a difference results from competition between two driving forces: the large steric repulsion between the anthryl/phenyl units in the closed-shell quinoidal form that drives the molecule to a flexible open-shell diradical structure, and aromatic stabilisation due to the gain of more aromatic sextet rings in the closed-shell form, which drives the molecule towards a contorted quinoidal structure. The ground states of these oligomers thus depend on the overall balance between these two driving forces and show chain-length dependence. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ground-state hyperfine splitting for Rb, Cs, Fr, Ba+, and Ra+
Ginges, J. S. M.; Volotka, A. V.; Fritzsche, S.
2017-12-01
We have systematically investigated the ground-state hyperfine structure for alkali-metal atoms 87Rb,133Cs, and 211Fr and alkali-metal-like ions +135Ba and +225Ra, which are of particular interest for parity violation studies. The quantum electrodynamic one-loop radiative corrections have been rigorously evaluated within an extended Furry picture employing core-Hartree and Kohn-Sham atomic potentials. Moreover, the effect of the nuclear magnetization distribution on the hyperfine structure intervals has been studied in detail and its uncertainty has been estimated. Finally, the theoretical description of the hyperfine structure has been completed with full many-body calculations performed in the all-orders correlation potential method.
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.
Electromagnetic properties of the three-nucleon ground state
International Nuclear Information System (INIS)
Strueve, W.
1985-01-01
The electromagnetic form factors of the three-nucleon ground state are calculated on the base of an exact solution of the Faddeev equations. In a Hilbert space of nucleons and a possible Δ-isobar the effects of a non-perturbative description of the Δ-isobar on the magnetic form factors are studied. Pure nucleonic current operators with two- and three-particle character can be described in the extended Hilbert space by simpler one-body operators. Additionally nonrelativistic meson-exchange corrections due to π and ρ exchange are calculated consistently with the requirements of current conservation. Further relativistic corrections are estimated on selected examples. The calculations yield a total magnetic contribution of the Δ-isobar which is smaller than hitherto assumed, a static approximation of the Δ propagation is proved as inadmissible and must be rejected. Together with the meson-exchange corrections a well agreement with the experimental data at low momentum transfers results. Especially the magnetic moments and magnetization radii can be explained. For higher momentum transfers the results show the importance of further corrections. The regard of selected relativistic corrections leads to a good description of the experimental magnetic form factors. Also by this way the position of the minimum and the height of the second maximum in the 3 He charge form factor can be explained. The comparison with the latest experimental results reveals furthermore unresolved problems in the description of the 3 H charge form factor. (orig.) [de
Ground state analysis of magnetic nanographene molecules with modified edge
International Nuclear Information System (INIS)
Gorjizadeh, Narjes; Ota, Norio; Kawazoe, Yoshiyuki
2013-01-01
Highlights: ► Graphene molecules can become ferromagnetic by edge modifications. ► Dihydrogenation of one zigzag edge of rectangular flakes make them ferromagnetic. ► Triangular flakes become high-spin state by dehydrogenization of one zigzag edge. - Abstract: We study spin states of edge modified nanographene molecules with rectangular and triangular shapes by first principle calculations using density functional theory (DFT) and Hartree–Fock (HF) methods with Møller–Plesset (MP) correlation energy correction at different levels. Anthracene (C 14 H 10 ) and phenalenyl (C 13 H 9 ), which contain three benzene rings combined in two different ways, can be considered as fragments of a graphene sheet. Carbon-based ferromagnetic materials are of great interest both in fundamental science and technological potential in organic spintronics devices. We show that non-magnetic rectangular molecules such as C 14 H 10 can become ferromagnetic with high-spin state as the ground state by dihydrogenization of one of the zigzag edges, while triangular molecules such as C 13 H 9 become ferromagnetic with high-spin state by dehydrogenization of one of the zigzag edges
Anomalous Ground State of the Electrons in Nano-confined Water
2016-06-13
Anomalous ground state of the electrons in nano -confined water G. F. Reiter1*, Aniruddha Deb2*, Y. Sakurai3, M. Itou3, V. G. Krishnan4, S. J...electronic ground state of nano -confined water must be responsible for these anomalies but has so far not been investigated. We show here for the first time...using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nano
Ground state solutions for asymptotically periodic Schrodinger equations with critical growth
Directory of Open Access Journals (Sweden)
Hui Zhang
2013-10-01
Full Text Available Using the Nehari manifold and the concentration compactness principle, we study the existence of ground state solutions for asymptotically periodic Schrodinger equations with critical growth.
Correlated ground state and E2 giant resonance built on it
International Nuclear Information System (INIS)
Tohyama, Mitsuru
1995-01-01
Taking 16 O as an example of realistic nuclei, we demonstrate that a correlated ground state can be obtained as a long time solution of a time-dependent density-matrix formalism (TDDM) when the residual interaction is adiabatically treated. We also study in TDDM the E2 giant resonance of 16 O built on the correlated ground state and compare it with that built on the Hartree-Fock ground state. It is found that a spurious mixing of low frequency components seen in the latter is eliminated by using the correlated ground state. (author)
Scheidsteger, T.; Urbschat, H.; Griffiths, R. B.; Schellnhuber, H. J.
1997-01-01
A procedure is described for efficiently finding the ground state energy and configuration for a Frenkel-Kontorova model in a periodic potential, consisting of N parabolic segments of identical curvature in each period, through a numerical solution of the convex minimization problem described in the preceding paper. The key elements are the use of subdifferentials to describe the structure of the minimization problem; an intuitive picture of how to solve it, based on motion of quasiparticles;...
Magnetic ground states in nanocuboids of cubic magnetocrystalline anisotropy
Energy Technology Data Exchange (ETDEWEB)
Bonilla, F.J., E-mail: fbonilla@cicenergigune.com; Lacroix, L.-M.; Blon, T., E-mail: thomas.blon@insa-toulouse.fr
2017-04-15
Flower and easy-axis vortex states are well-known magnetic configurations that can be stabilized in small particles. However, <111> vortex (V<111>), i.e. a vortex state with its core axis along the hard-axis direction, has been recently evidenced as a stable configuration in Fe nanocubes of intermediate sizes in the flower/vortex transition. In this context, we present here extensive micromagnetic simulations to determine the different magnetic ground states in ferromagnetic nanocuboids exhibiting cubic magnetocrystalline anisotropy (MCA). Focusing our study in the single-domain/multidomain size range (10–50 nm), we showed that V<111> is only stable in nanocuboids exhibiting peculiar features, such as a specific size, shape and magnetic environment, contrarily to the classical flower and easy-axis vortex states. Thus, to track experimentally these V<111> states, one should focused on (i) nanocuboids exhibiting a nearly perfect cubic shape (size distorsion <12%) made of (ii) a material which combines a zero or positive MCA and a high saturation magnetization, such as Fe or FeCo; and (iii) a low magnetic field environment, V<111> being only observed in virgin or remanent states. - Highlights: • The <111> vortex is numerically determined in nanocubes of cubic anisotropy. • It constitutes an intermediate state in the single-domain limit. • Such a vortex can only be stabilized in perfect or slightly deformed nanocuboids. • It exists in nanocuboids made of materials with zero or positive cubic anisotropy. • The associated magnetization reversal is described by a rotation of the vortex axis.
Mathematical aspects of ground state tunneling models in luminescence materials
International Nuclear Information System (INIS)
Pagonis, Vasilis; Kitis, George
2015-01-01
Luminescence signals from a variety of natural materials have been known to decrease with storage time at room temperature due to quantum tunneling, a phenomenon known as anomalous fading. This paper is a study of several mathematical aspects of two previously published luminescence models which describe tunneling phenomena from the ground state of a donor–acceptor system. It is shown that both models are described by the same type of integral equation, and two new analytical equations are presented. The first new analytical equation describes the effect of anomalous fading on the dose response curves (DRCs) of naturally irradiated samples. The DRCs in the model were previously expressed in the form of integral equations requiring numerical integration, while the new analytical equation can be used immediately as a tool for analyzing experimental data. The second analytical equation presented in this paper describes the anomalous fading rate (g-Value per decade) as a function of the charge density in the model. This new analytical expression for the g-Value is tested using experimental anomalous fading data for several apatite crystals which exhibit high rate of anomalous fading. The two new analytical results can be useful tools for analyzing anomalous fading data from luminescence materials. In addition to the two new analytical equations, an explanation is provided for the numerical value of a constant previously introduced in the models. - Highlights: • Comparative study of two luminescence models for feldspars. • Two new analytical equations for dose response curves and anomalous fading rate. • The numerical value z=1.8 of previously introduced constant in models explained.
Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach
Energy Technology Data Exchange (ETDEWEB)
Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E., E-mail: stepanov@depni.sinp.msu.ru [Moscow State University, Faculty of Physics (Russian Federation); Tretyakova, T. Yu. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)
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.
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.; 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 124Xe has been investigated via measurements of the β+/EC decay of 124Cs with the 8 π 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 (E 2 ;23+→02+) =78 (13 ) W.u. and B (E 2 ;24+→03+) =53 (12 ) W.u. were determined. The 03+ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te (3He,n )124Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.
Dral, Pavlo O; Wu, Xin; Spörkel, Lasse; Koslowski, Axel; Thiel, Walter
2016-03-08
The semiempirical orthogonalization-corrected OMx methods (OM1, OM2, and OM3) go beyond the standard MNDO model by including additional interactions in the electronic structure calculation. When augmented with empirical dispersion corrections, the resulting OMx-Dn approaches offer a fast and robust treatment of noncovalent interactions. Here we evaluate the performance of the OMx and OMx-Dn methods for a variety of ground-state properties using a large and diverse collection of benchmark sets from the literature, with a total of 13035 original and derived reference data. Extensive comparisons are made with the results from established semiempirical methods (MNDO, AM1, PM3, PM6, and PM7) that also use the NDDO (neglect of diatomic differential overlap) integral approximation. Statistical evaluations show that the OMx and OMx-Dn methods outperform the other methods for most of the benchmark sets.
International Nuclear Information System (INIS)
Pucello, N.; D'Agostino, G.; Pisacane, F.
1997-01-01
A genetic algorithm for the optimization of the ground-state structure of a metallic cluster has been developed and ported on a SIMD-MIMD parallel platform. The SIMD part of the parallel platform is represented by a Quadrics/APE100 consisting of 512 floating point units, while the MIMD part is formed by a cluster of workstations. The proposed algorithm is composed by a part where the genetic operators are applied to the elements of the population and a part which performs a further local relaxation and the fitness calculation via Molecular Dynamics. These parts have been implemented on the MIMD and on the SIMD part, respectively. Results have been compared to those generated by using Simulated Annealing
Analytical model of ground-state lasing phenomenon in broadband semiconductor quantum dot lasers
Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.
2013-05-01
We introduce an analytical approach to the description of broadband lasing spectra of semiconductor quantum dot lasers emitting via ground-state optical transitions of quantum dots. The explicit analytical expressions describing the shape and the width of lasing spectra as well as their temperature and injection current dependences are obtained in the case of low homogeneous broadening. It is shown that in this case these dependences are determined by only two dimensionless parameters, which are the dispersion of the distribution of QDs over the energy normalized to the temperature and loss-to-maximum gain ratio. The possibility of optimization of laser's active region size and structure by using the intentionally introduced disorder is also carefully considered.
Energy Technology Data Exchange (ETDEWEB)
Woods, K.
2005-01-14
Using an intense source of far-infrared radiation, the absorption spectrum of liquid water is measured at a temperature ranging from 269 to 323 K. In the infrared spectrum we observe modes that are related to the local structure of liquid water. Here we present a FIR measured spectrum that is sensitive to the low frequency (< 100cm{sup -1}) microscopic details that exist in liquid water.
Competition of ground states in URu2Si2 and UCoGe
International Nuclear Information System (INIS)
Hassinger, E.
2010-10-01
In this thesis, two uranium based heavy fermion compounds are studied under pressure. URu2Si2 has a mysterious ground state below T0 = 17.5 K at ambient pressure. The order parameter has not been identified yet which led to the name 'hidden order' (HO). In addition, below 1.5 K the system becomes superconducting. With pressure, the ground state switches from the HO phase to an antiferromagnetic (AF) phase at a critical pressure and superconductivity is concomitantly suppressed. Shubnikov-de Haas measurements under pressure show that the Fermi surface doesn't change between the two phases. The folding of the Fermi surface which occurs in the high pressure AF phase therefore already happens in the HO phase, indicating a unit cell doubling. Our measurements of the complete angular dependence of the oscillation frequencies test the electronic structure and support new theoretical band structure calculations with rather itinerant 5f electrons. The second part of my research focuses on another uranium compound, UCoGe. It is one of the few known materials where superconductivity (Tsc = 0.6 K) coexists with ferromagnetism (T Curie = 2.8 K). Precise studies of the pressure phase diagram by resistivity, ac calorimetry and ac susceptibility show that the ferromagnetic phase is suppressed at a pressure of about 1 GPa and the superconducting phase extends into the paramagnetic phase induced by pressure. When ferromagnetism is suppressed to the superconducting transition no further distinct ferromagnetic anomalies are observed. Thus, the pressure phase diagram of UCoGe is unique in the class of ferromagnetic superconductors. (author)
Tricriticality for dimeric Coulomb molecular crystals in ground state
Travěnec, Igor; Šamaj, Ladislav
2017-12-01
We study the ground-state properties of a system of dimers. Each dimer consists in a pair of equivalent charges at a fixed distance, immersed in a neutralizing homogeneous background. All charges interact pairwisely by Coulomb potential. The dimer centers form a two-dimensional rectangular lattice with the aspect ratio α\\in [0, 1] and each dimer is allowed to rotate around its center. The previous numerical simulations, made for the more general Yukawa interaction, indicate that only two basic dimer configurations can appear: either all dimers are parallel or they have two different angle orientations within alternating (checkerboard) sublattices. As the dimer size increases, two second-order phase transitions, related to two kinds of the symmetry breaking in dimer’s orientations, were reported. In this paper, we use a recent analytic method based on an expansion of the interaction energy in Misra functions which converges quickly and provides an analytic derivation of the critical behaviour. Our main result is that there exists a specific aspect ratio of the rectangular lattice α^*=0.714 106 840 000 71\\ldots which divides the space of model’s phases onto two distinct regions. If the lattice aspect ratio α>α* , we recover both types of the second-order phase transitions and find that they are of mean-field type with the critical exponent β = 1/2 . If 0.711 535≤slantα<α* , the phase transition associated with the discontinuity of dimer’s angles on alternating sublattices becomes of first order. For α=α* , the first- and second-order phase transitions meet at the tricritical point, characterized by the different critical index β = 1/4 . Such phenomenon is known from literature about the Landau theory of one-component fields, but in our two-component version the scenario is more complicated: the component which is already in the symmetry-broken state at the tricritical point also interferes and exhibits unexpectedly the mean-field singular
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
Salient man-made structure detection in infrared images
Li, Dong-jie; Zhou, Fu-gen; Jin, Ting
2013-09-01
Target detection, segmentation and recognition is a hot research topic in the field of image processing and pattern recognition nowadays, among which salient area or object detection is one of core technologies of precision guided weapon. Many theories have been raised in this paper; we detect salient objects in a series of input infrared images by using the classical feature integration theory and Itti's visual attention system. In order to find the salient object in an image accurately, we present a new method to solve the edge blur problem by calculating and using the edge mask. We also greatly improve the computing speed by improving the center-surround differences method. Unlike the traditional algorithm, we calculate the center-surround differences through rows and columns separately. Experimental results show that our method is effective in detecting salient object accurately and rapidly.
Construction and study of exact ground states for a class of quantum antiferromagnets
International Nuclear Information System (INIS)
Fannes, M.
1989-01-01
Techniques of quantum probability are used to construct the exact ground states for a class of quantum spin systems in one dimension. This class in particular contains the antiferromagnetic models introduced by various authors under the name of VBS-models. The construction permits a detailed study of these ground states. (A.C.A.S.) [pt
Ground state of charged Base and Fermi fluids in strong coupling
International Nuclear Information System (INIS)
Mazighi, R.
1982-03-01
The ground state and excited states of the charged Bose gas were studied (wave function, equation of state, thermodynamics, application of Feynman theory). The ground state of the charged Fermi gas was also investigated together with the miscibility of charged Bose and Fermi gases at 0 deg K (bosons-bosons, fermions-bosons and fermions-fermions) [fr
Long range order in the ground state of two-dimensional antiferromagnets
International Nuclear Information System (INIS)
Neves, E.J.; Perez, J.F.
1985-01-01
The existence of long range order is shown in the ground state of the two-dimensional isotropic Heisenberg antiferromagnet for S >= 3/2. The method yields also long range order for the ground state of a larger class of anisotropic quantum antiferromagnetic spin systems with or without transverse magnetic fields. (Author) [pt
Ab initio calculation atomics ground state wave function for interactions Ion- Atom
International Nuclear Information System (INIS)
Shojaee, F.; Bolori zadeh, M. A.
2007-01-01
Ab initio calculation atomics ground state wave function for interactions Ion- Atom Atomic wave function expressed in a Slater - type basis obtained within Roothaan- Hartree - Fock for the ground state of the atoms He through B. The total energy is given for each atom.
Infrared investigation of the temperature structure of the solar atmosphere
International Nuclear Information System (INIS)
Allen, R.G.
1978-01-01
Narrow-band continuum limb darkening observations of the sun were taken with the Infrared Spectrometer and the West Auxiliary of the McMath Solar Telescope during the first half of 1974. The infrared limb darkening measures were used with a few absolute intensity and limb darkening measures of other investigators to develop a series of empirical solar models. The temperatures in most of the solar models were adjusted until the predictions of the model atmosphere program matched the observational measures as well as possible. Limb darkening residuals were calculated by subtracting the observational measures of the limb darkening from the limb darkening measures that were computed from the program. Experiments with several models indicated that a steep temperature gradient was needed to fit the observations at short wavelengths while a rather low temperature gradient was needed at long wavelengths. Non-LTE effects and errors in the H - opacity were ruled out as possible sources of this discrepancy. An excellent fit to the observations was ultimately achieved with a two-component LTE solar model. The hot component of this model represents the half of the solar surface that is above the median temperature at each depth; while the cool component represents the half of the solar surface that is below the median temperature. Most of the observations are fitted to within the expected errors by this model. Discrepancies below 4500 A are probably due to line blanketing. The splitting between the hot and cool components of the model is consistent with current estimates of the rms intensity fluctuations in the solar atmosphere. The model also resembles several theoretical two-component models that have recently appeared in the literature
Infrared spectroscopic and theoretical study of the HC2n+1O+ (n = 2-5) cations
Jin, Jiaye; Li, Wei; Liu, Yuhong; Wang, Guanjun; Zhou, Mingfei
2017-06-01
The carbon chain cations, HC2n+1O+ (n = 2-5), are produced via pulsed laser vaporization of a graphite target in supersonic expansions containing carbon monoxide and hydrogen. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO "tagged" [HC2n+1O.CO]+ cation complexes in the 1600-3500 cm-1 region. The geometries and electronic ground states of these cation complexes are determined by their infrared spectra compared to the predications of theoretical calculations. All of the HC2n+1O+ (n = 2-5) core cations are characterized to be linear carbon chain derivatives terminated by hydrogen and oxygen, which have the closed-shell singlet ground states with polyyne-like carbon chain structures.
International Nuclear Information System (INIS)
Schultz, T.P.; Glasser, W.G.
1986-01-01
Empirical quantitative relationships were established between infrared (IR) spectral information and several structural features in lignins as determined by conventional methods. The structural composition of average phenylpropane (C g ) units which significantly correlated (0.01 level) with IR peak intensities included methoxy content, aromatic hydrogen content, phenolic hydroxy content, guaiacyl/syringyl ratio, and ''hydrolysis'' and ''condensation'' ratios
Conductive Oxides Trench Structures as Hyperbolic Metamaterials in Mid-infrared Range
DEFF Research Database (Denmark)
Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee
,2]. Moreover plasmonics for mid-infrared offer unique applications such as bio-sensing, thermal imaging and quest for novel materials and structures has been continuing [3]. In this report we show that vertical trench structures made of, for example, aluminum-doped ZnO (AZO) or other transparent conductive...
Towards 6Li-40K ground state molecules
International Nuclear Information System (INIS)
Brachmann, Johannes Felix Simon
2013-01-01
The production of a quantum gas with strong long - range dipolar interactions is a major scientific goal in the research field of ultracold gases. In their ro - vibrational ground state Li-K dimers possess a large permanent dipole moment, which could possibly be exploited for the realization of such a quantum gas. A production of these molecules can be achieved by the association of Li and K at a Feshbach resonance, followed by a coherent state transfer. In this thesis, detailed theoretical an experimental preparations to achieve state transfer by means of Stimulated Raman Adiabatic Passage (STIRAP) are described. The theoretical preparations focus on the selection of an electronically excited molecular state that is suitable for STIRAP transfer. In this context, molecular transition dipole moments for both transitions involved in STIRAP transfer are predicted for the first time. This is achieved by the calculation of Franck-Condon factors and a determination of the state in which the 6 Li- 40 K Feshbach molecules are produced. The calculations show that state transfer by use of a single STIRAP sequence is experimentally very well feasible. Further, the optical wavelengths that are needed to address the selected states are calculated. The high accuracy of the data will allow to carry out the molecular spectroscopy in a fast and efficient manner. Further, only a comparatively narrow wavelength tuneability of the spectroscopy lasers is needed. The most suitable Feshbach resonance for the production of 6 Li- 40 K molecules at experimentally manageable magnetic field strengths is occurring at 155 G. Experimentally, this resonance is investigated by means of cross-dimensional relaxation. The application of the technique at various magnetic field strengths in the vicinity of the 155 G Feshbach resonance allows a determination of the resonance position and width with so far unreached precision. This reveals the production of molecules on the atomic side of the resonance
Cooper pairs versus Bose condensed molecules: The ground-state current in superfluid 3He-A
International Nuclear Information System (INIS)
Mermin, N.D.; Muzikar, P.
1980-01-01
We present a new calculation of the current g flowing in a ground state of the Bardeen-Cooper-Schrieffer (BCS) form for a weakly inhomogeneous superfluid with the symmetry of 3 He-A. When the structure of the order parameter not determined by symmetry is appropriate to 3 He-A and when the mass density rho of the helium is essentially uniform, our current reduces to that calculated by Cross. If the mass density is allowed to vary, we find a generalization of the Cross current which shows that when v/sub s/=0 and the anisotropy axis l is uniform, then the current is simply (h/4M) del-arrow-rightrho x l. We show that this property of the BCS ground state, which taken with the Cross definition leads to an ''intrinsic angular momentum density'' of rhoh/2M at zero temperature, also follows directly from the Gor'kov equations. If the range of the order parameter is taken to be small compared with the interatomic separation, then the ground state does not describe 3 He-A, but a Bose-Einstein condensate of tightly bound diatomic molecules. In this limit our current reduces to the form calculated by Ishikawa et al. We indicate why their analysis is only valid in this limit, and offer some rather more general remarks on the differences between Cooper pairing and the Bose-Einstein condensation of diatomic molecules
Li, Yuan
2012-09-12
Polycyclic aromatic hydrocarbons with an open-shell singlet biradical ground state are of fundamental interest and have potential applications in materials science. However, the inherent high reactivity makes their synthesis and characterization very challenging. In this work, a convenient synthetic route was developed to synthesize two kinetically blocked heptazethrene (HZ-TIPS) and octazethrene (OZ-TIPS) compounds with good stability. Their ground-state electronic structures were systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman, and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. All these demonstrated that the heptazethrene derivative HZ-TIPS has a closed-shell ground state while its octazethrene analogue OZ-TIPS with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (y = 0.56). Large two-photon absorption (TPA) cross sections (σ(2)) were determined for HZ-TIPS (σ(2)max = 920 GM at 1250 nm) and OZ-TIPS (σ(2)max = 1200 GM at 1250 nm). In addition, HZ-TIPS and OZ-TIPS show a closely stacked 1D polymer chain in single crystals. © 2012 American Chemical Society.
Nested structures approach in designing an isotropic negative-index material for infrared
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2009-01-01
We propose a new generic approach for designing isotropic metamaterial with nested cubic structures. As an example, a three-dimensional isotropic unit cell design "Split Cube in Cage" (SCiC) is shown to exhibit an effective negative refractive index on infrared wavelengths. We report on the refra......We propose a new generic approach for designing isotropic metamaterial with nested cubic structures. As an example, a three-dimensional isotropic unit cell design "Split Cube in Cage" (SCiC) is shown to exhibit an effective negative refractive index on infrared wavelengths. We report...
The significant role of covalency in determining the ground state of cobalt phthalocyanines molecule
Directory of Open Access Journals (Sweden)
Jing Zhou
2016-03-01
Full Text Available To shed some light on the metal 3d ground state configuration of cobalt phthalocyanines system, so far in debate, we present an investigation by X-ray absorption spectroscopy (XAS at Co L2,3 edge and theoretical calculation. The density functional theory calculations reveal highly anisotropic covalent bond between central cobalt ion and nitrogen ligands, with the dominant σ donor accompanied by weak π-back acceptor interaction. Our combined experimental and theoretical study on the Co-L2,3 XAS spectra demonstrate a robust ground state of 2A1g symmetry that is built from 73% 3d7 character and 27% 3 d 8 L ¯ ( L ¯ denotes a ligand hole components, as the first excited-state with 2Eg symmetry lies about 158 meV higher in energy. The effect of anisotropic and isotropic covalency on the ground state was also calculated and the results indicate that the ground state with 2A1g symmetry is robust in a large range of anisotropic covalent strength while a transition of ground state from 2A1g to 2Eg configuration when isotropic covalent strength increases to a certain extent. Here, we address a significant anisotropic covalent effect of short Co(II-N bond on the ground state and suggest that it should be taken into account in determining the ground state of analogous cobalt complexes.
Exact many-electron ground states on diamond and triangle Hubbard chains
International Nuclear Information System (INIS)
Gulacsi, Zsolt; Kampf, Arno; Vollhardt, Dieter
2009-01-01
We construct exact ground states of interacting electrons on triangle and diamond Hubbard chains. The construction requires (1) a rewriting of the Hamiltonian into positive semidefinite form, (2) the construction of a many-electron ground state of this Hamiltonian, and (3) the proof of the uniqueness of the ground state. This approach works in any dimension, requires no integrability of the model, and only demands sufficiently many microscopic parameters in the Hamiltonian which have to fulfill certain relations. The scheme is first employed to construct exact ground state for the diamond Hubbard chain in a magnetic field. These ground states are found to exhibit a wide range of properties such as flat-band ferromagnetism and correlation induced metallic, half-metallic or insulating behavior, which can be tuned by changing the magnetic flux, local potentials, or electron density. Detailed proofs of the uniqueness of the ground states are presented. By the same technique exact ground states are constructed for triangle Hubbard chains and a one-dimensional periodic Anderson model with nearest-neighbor hybridization. They permit direct comparison with results obtained by variational techniques for f-electron ferromagnetism due to a flat band in CeRh 3 B 2 . (author)
Gálisová, Lucia
2018-05-01
Ground-state properties of a hybrid double-tetrahedral chain, in which the localized Ising spins regularly alternate with triangular plaquettes occupied by a variable number of mobile electrons, are exactly investigated. We demonstrate that the zero-temperature phase diagram of the model involves several non-degenerate, two-fold degenerate and macroscopically degenerate chiral phases. Low-temperature dependencies of the entropy and specific heat are also examined in order to gain a deeper insight into the degeneracy of individual ground-state phases and phase transitions. It is shown that a diversity of the ground-state degeneracy manifests itself in multiple-peak structures of both thermodynamic quantities. A remarkable temperature dependencies of the specific heat with two and three Schottky-type maxima are discussed in detail.
Infrared Spectroscopic and Theoretical Study of the HC_nO^+(N=5-12) Cations
Li, Wei; Jin, Jiaye; Wang, Guanjun; Zhou, Mingfei
2017-06-01
Carbon chains and derivatives are highly active species, which are widely existed as reactive intermediates in many chemical processes including atmospheric chemistry, hydrocarbon combustion, as well as interstellar chemistry. The carbon chain cations, HC_nO^+ (n = 5-12) are produced via pulsed laser vaporization of a graphite target in supersonic expansions containing carbon monoxide and hydrogen. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO "tagged" [HC_nO.CO] cation complexes in the 1600-3500 \\wn region. The geometries and electronic ground states of these cation complexes are determined by their infrared spectra in conjunction with theoretical calculations. All the HC_nO^+ (n = 5-12) core cations are characterized to be linear carbon chain derivatives terminated by hydrogen and oxygen. The HC_nO^+ cations with odd n have closed-shell singlet ground states with polyyne-like structures, while those with even n have triplet ground states with allene-like structures.
International Nuclear Information System (INIS)
Helgesen, P.
1992-04-01
In this work the author investigate the subband nature of multiple quantum well structures by photoconductance spectroscopy, optical absorption measurements and tunneling experiments. Both interband and intraband transitions have been studied. The work is aimed at making an infrared detector using wide band gap semiconductors. 14 refs
Monolithic dual-band HgCdTe infrared detector structure
CSIR Research Space (South Africa)
Parish, G
1997-07-01
Full Text Available A monolithic HgCdTe photoconductive device structure is presented that is suitable for dual-band optically registered infrared photodetection in the two atmospheric transmission windows of 3-5 mu m and 8-12 mu m, which correspond to the mid...
Accurate Determination of Rotational Energy Levels in the Ground State of ^{12}CH_4
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).
On infrared spectroscopic analysis of transfer RNA secondary structure
Energy Technology Data Exchange (ETDEWEB)
Semenov, M A; Starikov, E B
1987-07-14
Various techniques of IR spectroscopy in the 1550-1750 cm/sup -1/ region employed to analyse the tRNA secondary structure are discussed and a novel improved method is proposed. The main novel features of this method are the approximation of tRNA helical region spectra by catalogue carbonyl absorption bands and approximation of tRNA nonhelical region spectra by those of homopolyribonucleotides. The IR spectra of tRNA/sub yeast//sup phe/ and tRNA/sub E.coli//sup fmet/ in the carbonyl vibration region are explained on the basis of calculated transition moment coupling.
Nodal ground states and orbital textures in semiconductor quantum dots
Czech Academy of Sciences Publication Activity Database
Lee, J.; Výborný, Karel; Han, J.E.; Žutič, I.
2014-01-01
Roč. 89, č. 4 (2014), "045315-1"-"045315-17" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : quantum dots * electronic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014
Ground state magnetic properties of Fe nanoislands on Cu(111)
International Nuclear Information System (INIS)
Kishi, Tomoya; David, Melanie; Nakanishi, Hiroshi; Kasai, Hideaki; Dino, Wilson Agerico; Komori, Fumio
2005-01-01
We investigate magnetic properties of Fe nanoislands on Cu(111) in the relaxed structure within the density functional theory. We observe that the nanoislands exhibit the ferromagnetic properties with large magnetic moment. We find that the change in the magnetic moment of each Fe atom is induced by deposition on Cu(111) and structure relaxation of Fe nanoislands. Moreover, we examine the stability of ferromagnetic states of Fe nanoislands by performing the total energy calculations. (author)
Nonspherical atomic ground-state densities and chemical deformation densities from x-ray scattering
International Nuclear Information System (INIS)
Ruedenberg, K.; Schwarz, W.H.E.
1990-01-01
Presuming that chemical insight can be gained from the difference between the molecular electron density and the superposition of the ground-state densities of the atoms in a molecule, it is pointed out that, for atoms with degenerate ground states, an unpromoted ''atom in a molecule'' is represented by a specific ensemble of the degenerate atomic ground-state wave functions and that this ensemble is determined by the anisotropic local surroundings. The resulting atomic density contributions are termed oriented ground state densities, and the corresponding density difference is called the chemical deformation density. The constraints implied by this conceptual approach for the atomic density contributions are formulated and a method is developed for determining them from x-ray scattering data. The electron density of the appropriate promolecule and its x-ray scattering are derived, the determination of the parameters of the promolecule is outlined, and the chemical deformation density is formulated
Dumoulin, Jean
2013-04-01
Infrared thermography for Non Destructive Testing (NDT) has encountered a wide spreading this last 2 decades, in particular thanks to emergence on the market of low cost uncooled infrared camera. So, infrared thermography is not anymore a measurement technique limited to laboratory application. It has been more and more involved in civil engineering and cultural heritage applications, but also in many other domains, as indicated by numerous papers in the literature. Nevertheless, laboratory, measurements are done as much as possible in quite ideal conditions (good atmosphere conditions, known properties of materials, etc.), while measurement on real site requires to consider the influence of not controlled environmental parameters and additional unknown thermal properties. So, dedicated protocol and additional sensors are required for measurement data correction. Furthermore, thermal excitation is required to enhance the signature of defects in materials. Post-processing of data requires to take into account the protocol used for the thermal excitation and sometimes its nature to avoid false detection. This analysis step is based on signal and image processing tool and allows to carry out the detection. Characterization of anomalies detected at the previous step can be done by additional signal processing in particular for manufactured objects. The use of thermal modelling and inverse method allows to determine properties of the defective area. The present paper will first address a review of some protocols currently in use for field measurement with passive and/or active infrared measurements. Illustrations in various experiments carried out on civil engineering structure will be shown and discussed. In a second part, different post-processing approaches will be presented and discussed. In particular, a review of the most standard processing methods like Fast Fourier Analysis, Principal Components Analysis, Polynomial Decomposition, defect characterization using
Use of infrared spectroscopy to study the γ-irradiated dextran structure
International Nuclear Information System (INIS)
Komar, V.P.; Bondarenko, N.T.; Zhbankov, R.G.; Markevich, S.V.
1977-01-01
Infrared spectra of the fractions of γ-irradiated dextran aqueous solutions have been investigated in the range 3800 -1 -400 cm -1 . Infrared spectra of the irradiated non-fractionated dextran do not differ from those of non-irradiated dextran whereas the spectra of the fractions beginning with the molecular weight 50x1O 3 dalton and lower differ considerably. With decreasing molecular weight of the fractions, more significant changes in the spectra are observed. A polymer obtained as a result of γ-irradiation of dextran differs in structure from the initial product. It is assumed that similar transformations can take place upon irradiation of other polysaccharides
Pade approximants for the ground-state energy of closed-shell quantum dots
International Nuclear Information System (INIS)
Gonzalez, A.; Partoens, B.; Peeters, F.M.
1997-08-01
Analytic approximations to the ground-state energy of closed-shell quantum dots (number of electrons from 2 to 210) are presented in the form of two-point Pade approximants. These Pade approximants are constructed from the small- and large-density limits of the energy. We estimated that the maximum error, reached for intermediate densities, is less than ≤ 3%. Within that present approximation the ground-state is found to be unpolarized. (author). 21 refs, 3 figs, 2 tabs
A simple parameter-free wavefunction for the ground state of two-electron atoms
International Nuclear Information System (INIS)
Ancarani, L U; Rodriguez, K V; Gasaneo, G
2007-01-01
We propose a simple and pedagogical wavefunction for the ground state of two-electron atoms which (i) is parameter free (ii) satisfies all two-particle cusp conditions (iii) yields reasonable ground-state energies, including the prediction of a bound state for H - . The mean energy, and other mean physical quantities, is evaluated analytically. The simplicity of the result can be useful as an easy-to-use wavefunction when testing collision models
Many electron variational ground state of the two dimensional Anderson lattice
International Nuclear Information System (INIS)
Zhou, Y.; Bowen, S.P.; Mancini, J.D.
1991-02-01
A variational upper bound of the ground state energy of two dimensional finite Anderson lattices is determined as a function of lattice size (up to 16 x 16). Two different sets of many-electron basis vectors are used to determine the ground state for all values of the coulomb integral U. This variational scheme has been successfully tested for one dimensional models and should give good estimates in two dimensions
Ground-state energy for 1D (t,U,X)-model at low densities
International Nuclear Information System (INIS)
Buzatu, F.D.
1992-09-01
In describing the properties of quasi-1D materials with a highly-screened interelectronic potential, an attractive hopping term has to be added to the Hubbard Hamiltonian. The effective interaction and the ground-state energy in ladder approximation are analyzed. At low electronic densities, the attractive part of the interaction, initially smaller than the repulsive term, can become more effective, the ground-state energy decreasing below the unperturbed value. (author). 12 refs, 4 figs
Mode structure in an optically pumped D2O far infrared ring laser
International Nuclear Information System (INIS)
Yuan, D.C.; Soumagne, G.; Siegrist, M.R.
1989-07-01
The mode structures in an optically pumped D 2 O far infrared ring laser and a corresponding linear resonator have been compared. While single mode operation can be obtained over the whole useful pressure range in the ring structure, this is only possible at pressures greater than 8 Torr in the linear resonator case. A numerical model predicts quite well the pulse shape, pressure dependence and influence of the resonator quality in the ring cavity. (author) 12 figs., 8 refs
Energy Technology Data Exchange (ETDEWEB)
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.
Energy Technology Data Exchange (ETDEWEB)
Bauer, Eric D [Los Alamos National Laboratory; Booth, C H [LBNL; Walter, M D [LBNL; Kazhdan, D [LBNL; Hu, Y - J [LBNL; Lukens, Wayne [LBNL; Maron, Laurent [INSA TOULOUSE; Eisentein, Odile [UNIV MONTPELLIER 2; Anderson, Richard [LBNL
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.
Characterization of photonic structures using visible and infrared polarimetry
Directory of Open Access Journals (Sweden)
Kral Z.
2010-06-01
Full Text Available Photonic Crystals are materials with a spatial periodic variation of the refractive index on the wavelength scale. This confers these materials interesting photonic properties such as the existence of photonic bands and forbidden photon frequency ranges, the photonic band gaps. Among their applications it is worth mentioning the achievement of low-threshold lasers and high-Q resonant cavities. A particular case of the Photonic Crystals is well-known and widely studied since a long time: the periodic thin film coatings. The characterization of thin film coatings is a classical field of study with a very well established knowledge. However, characterization of 2D and 3D photonic crystals needs to be studied in detail as it poses new problems that have to be solved. In this sense, Polarimetry is a specially suited tool given their inherent anisotropy: photonic bands depend strongly on the propagation direction and on polarization. In this work we show how photonic crystal structures can be characterized using polarimetry equipment. We compare the numerical modeling of the interaction of the light polarization with the photonic crystal with the polarimetry measurements. With the S-Matrix formalism, the Mueller matrix of a Photonic Crystal for a given wavelength, angle of incidence and propagation direction can be obtained. We will show that useful information from polarimetry (and also from spectrometry can be obtained when multivariate spectra are considered. We will also compare the simulation results with Polarimetry measurements on different kinds of samples: macroporous silicon photonic crystals in the near-IR range and Laser-Interference-Lithography nanostructured photoresist.
Splitting of ISGMR strength in the light-mass nucleus 24Mg due to ground-state deformation
Directory of Open Access Journals (Sweden)
Y.K. Gupta
2015-09-01
Full Text Available The isoscalar giant monopole resonance (ISGMR strength distribution in 24Mg has been determined from background-free inelastic scattering of 386-MeV α particles at extreme forward angles, including 0∘. The ISGMR strength distribution has been observed for the first time to have a two-peak structure in a light-mass nucleus. This splitting of ISGMR strength is explained well by microscopic theory in terms of the prolate deformation of the ground state of 24Mg.
Scanning near-field infrared microscopy on semiconductor structures
Energy Technology Data Exchange (ETDEWEB)
Jacob, Rainer
2011-01-15
literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots. (orig.)
Scanning near-field infrared microscopy on semiconductor structures
International Nuclear Information System (INIS)
Jacob, Rainer
2011-01-01
literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots. (orig.)
Magnetic ground state and Fermi surface of bcc Eu
Czech Academy of Sciences Publication Activity Database
Kuneš, Jan; Laskowski, R.
2004-01-01
Roč. 70, č. 17 (2004), 174415/1-174415/6 ISSN 1098-0121 R&D Projects: GA AV ČR(CZ) IAA1010214; GA MŠk(CZ) ME 547 Grant - others:DE-FG(XX) 03-01ER45876 Institutional research plan: CEZ:AV0Z1010914 Keywords : europium * spin structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.075, year: 2004
Three-body problem in d-dimensional space: Ground state, (quasi)-exact-solvability
Turbiner, Alexander V.; Miller, Willard; Escobar-Ruiz, M. A.
2018-02-01
As a straightforward generalization and extension of our previous paper [A. V. Turbiner et al., "Three-body problem in 3D space: Ground state, (quasi)-exact-solvability," J. Phys. A: Math. Theor. 50, 215201 (2017)], we study the aspects of the quantum and classical dynamics of a 3-body system with equal masses, each body with d degrees of freedom, with interaction depending only on mutual (relative) distances. The study is restricted to solutions in the space of relative motion which are functions of mutual (relative) distances only. It is shown that the ground state (and some other states) in the quantum case and the planar trajectories (which are in the interaction plane) in the classical case are of this type. The quantum (and classical) Hamiltonian for which these states are eigenfunctions is derived. It corresponds to a three-dimensional quantum particle moving in a curved space with special d-dimension-independent metric in a certain d-dependent singular potential, while at d = 1, it elegantly degenerates to a two-dimensional particle moving in flat space. It admits a description in terms of pure geometrical characteristics of the interaction triangle which is defined by the three relative distances. The kinetic energy of the system is d-independent; it has a hidden sl(4, R) Lie (Poisson) algebra structure, alternatively, the hidden algebra h(3) typical for the H3 Calogero model as in the d = 3 case. We find an exactly solvable three-body S3-permutationally invariant, generalized harmonic oscillator-type potential as well as a quasi-exactly solvable three-body sextic polynomial type potential with singular terms. For both models, an extra first order integral exists. For d = 1, the whole family of 3-body (two-dimensional) Calogero-Moser-Sutherland systems as well as the Tremblay-Turbiner-Winternitz model is reproduced. It is shown that a straightforward generalization of the 3-body (rational) Calogero model to d > 1 leads to two primitive quasi
Variational Monte Carlo calculations of nuclear ground states
International Nuclear Information System (INIS)
Wiringa, R.B.
1990-01-01
A major goal in nuclear physics is to understand how nuclear structure comes about from the underlying interactions between nucleons. This requires modelling nuclei as collections of strongly interacting nucleons. We start with realistic nucleon-nucleon potentials, supplemented with consistent three-nucleon potentials and two-body electroweak current operators, and try to predict nuclear ground properties, such as the binding energy, density and momentum distributions, and electromagnetic form factors. We also seek to predict other properties of nuclei such as excited states and low-energy reactions. 21 refs., 14 figs., 5 tabs
Excited-state properties from ground-state DFT descriptors: A QSPR approach for dyes.
Fayet, Guillaume; Jacquemin, Denis; Wathelet, Valérie; Perpète, Eric A; Rotureau, Patricia; Adamo, Carlo
2010-02-26
This work presents a quantitative structure-property relationship (QSPR)-based approach allowing an accurate prediction of the excited-state properties of organic dyes (anthraquinones and azobenzenes) from ground-state molecular descriptors, obtained within the (conceptual) density functional theory (DFT) framework. The ab initio computation of the descriptors was achieved at several levels of theory, so that the influence of the basis set size as well as of the modeling of environmental effects could be statistically quantified. It turns out that, for the entire data set, a statistically-robust four-variable multiple linear regression based on PCM-PBE0/6-31G calculations delivers a R(adj)(2) of 0.93 associated to predictive errors allowing for rapid and efficient dye design. All the selected descriptors are independent of the dye's family, an advantage over previously designed QSPR schemes. On top of that, the obtained accuracy is comparable to the one of the today's reference methods while exceeding the one of hardness-based fittings. QSPR relationships specific to both families of dyes have also been built up. This work paves the way towards reliable and computationally affordable color design for organic dyes. Copyright 2009 Elsevier Inc. All rights reserved.
3,4,5,6-Tetrafluorophenylnitren-2-yl: a ground-state quartet triradical.
Grote, Dirk; Finke, Christopher; Kossmann, Simone; Neese, Frank; Sander, Wolfram
2010-04-19
The photochemistry of 2-iodo-3,4,5,6-tetrafluorophenyl azide (7 d) has been investigated in argon and neon matrices at 4 K, and the products characterized by IR and EPR spectroscopy. The primary photochemical step is loss of a nitrogen molecule and formation of phenyl nitrene 1 d. Further irradiation with UV or visible light results in mixtures of 1 d with azirine 5 d', ketenimine 6 d', nitreno radical 2 d, and azirinyl radical 9. The relative amounts of these products strongly depend on the matrix and on the irradiation conditions. Nitreno radical 2 d with a quartet ground state was characterized by EPR spectroscopy. Electronic structure calculations in combination with the experimental results allow for a detailed understanding of the properties of this unusual new type of organic high-spin molecules. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hydrogen-like spectrum of spontaneously created brane universes with de-Sitter ground state
Davidson, Aharon
2018-05-01
Unification of Randall-Sundrum and Regge-Teitelboim brane cosmologies gives birth to a serendipitous Higgs-deSitter interplay. A localized Dvali-Gabadadze-Porrati scalar field, governed by a particular (analytically derived) double-well quartic potential, becomes a mandatory ingredient for supporting a deSitter brane universe. When upgraded to a general Higgs potential, the brane surface tension gets quantized, resembling a Hydrogen atom spectrum, with deSitter universe serving as the ground state. This reflects the local/global structure of the Euclidean manifold: From finite energy density no-boundary initial conditions, via a novel acceleration divide filter, to exact matching conditions at the exclusive nucleation point. Imaginary time periodicity comes as a bonus, with the associated Hawking temperature vanishing at the continuum limit. Upon spontaneous creation, while a finite number of levels describe universes dominated by a residual dark energy combined with damped matter oscillations, an infinite tower of excited levels undergo a Big Crunch.
Nuclear Ground State Properties in Strontium by Fast Beam Laser Spectroscopy
2002-01-01
Hyperfine structures and isotope shifts of strontium isotopes with A=78 to A=100 were measured by collinear fast beam laser spectroscopy. Nuclear spins, moments and changes in mean square charge radii are extracted from the data. The spins and moments of most of the odd isotopes are explained in the framework of the single particle model. The changes in mean square charge radii show a decrease with increasing neutron number below the N=50 shell closure. Above N=50 the charge radii increase regularly up to N=59 before revealing a strong discontinuity, indicating the onset of strong ground state deformation. A comparison of the droplet model shows that for the transitional isotopes below and above N=50, the zero point quadrupole motion describes part of the observed shell effect. Calculations carried out in the Hartree-Fock plus BCS model suggest an additional change in the surface region of the charge distribution at spherical shape. From these calculations it is furthermore proposed, that the isotopes $^7
Theories of the nuclear ground state beyond Hartree-Fock
International Nuclear Information System (INIS)
Gogny, D.
1979-01-01
Intensive efforts have been invested toward defining a microscopic approach, simple enough to render feasible systematic calculations of nuclear structure and of the some time sufficiently rich in information as to serve for updating traditional microscopic approaches to the collective excitations. Our starting point is the mean field approximation with density dependent effective forces. To describe the collective excitations we use the two well known extensions based on the H.F. theory namely the random phase approximation and the adiabatic approximation to the time dependent Hartree-Fock theory. The purpose of this paper is to show what sort of calculations can be effectively carried out in the frame of such fully self consistent approaches. (KBE) 891 KBE/KBE 892 ARA
International Nuclear Information System (INIS)
Yamanaka, Masanori; Honjo, Shinsuke; Kohmoto, Mahito
1996-01-01
We investigate one-dimensional strongly correlated electron models which have the resonating-valence-bond state as the exact ground state. The correlation functions are evaluated exactly using the transfer matrix method for the geometric representations of the valence-bond states. In this method, we only treat matrices with small dimensions. This enables us to give analytical results. It is shown that the correlation functions decay exponentially with distance. The result suggests that there is a finite excitation gap, and that the ground state is insulating. Since the corresponding noninteracting systems may be insulating or metallic, we can say that the gap originates from strong correlation. The persistent currents of the present models are also investigated and found to be exactly vanishing
Structure of cesium loaded iron phosphate glasses: An infrared and Raman spectroscopy study
International Nuclear Information System (INIS)
Joseph, Kitheri; Premila, M.; Amarendra, G.; Govindan Kutty, K.V.; Sundar, C.S.; Vasudeva Rao, P.R.
2012-01-01
The structure of cesium loaded iron phosphate glasses (IPG) was investigated using infrared and Raman spectroscopy. The spectra of the cesium doped samples revealed a structural modification of the parent glass owing to the incorporation of cesium. The structural changes could be correlated with the variation observed in the glass transition temperature of these glasses. Increased Cs-mediated cationic cross linking appears to be the reason for the initial rise in glass transition temperature up to 21 mol% Cs 2 O in IPG; while, breakdown of the phosphate network with increasing cesium content, brings down the glass transition temperature.
Ground state properties of MnB{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Winter, Jan Lennart; Steinki, Nico; Schulze Grachtrup, Dirk; Menzel, Dirk; Suellow, Stefan [Institut fuer Physik der Kondensierten Materie, TU Braunschweig (Germany); Knappschneider, Arno; Albert, Barbara [Eduard-Zintl-Institut fuer Anorganische und Physikalische Chemie, TU Darmstadt (Germany)
2016-07-01
Recently, single crystalline MnB{sub 4} was synthesized for the first time, yielding microscale crystals with dimensions of the order of 200 μm. Based on band structure calculations, it was argued that the material is semiconducting as result of a Peierls distortion. Conversely, in a study of polycrystalline material it was concluded that the material is a weakly ferromagnetic metal. To establish if MnB{sub 4} is a semiconductor we have carried out single crystal four point resistivity measurements. For this purpose a setup for measuring microscale samples was developed and characterized. Qualitatively, we find semiconducting behavior (increasing resistivity for decreasing temperature), although a band gap could not be derived because of a non-linear Arrhenius plot. Our data are consistent with MnB{sub 4} being a pseudogap/small gap material as proposed. A pronounced sample dependence of the transport properties points to the presence of impurity states. For the single crystals no ferromagnetic signatures could be obtained, suggesting an extrinsic cause of it in polycrystalline material.
Semiphenomenological studies of the ground state binding energies of hypernuclei
International Nuclear Information System (INIS)
Mian, M.
1987-01-01
We show that the binding energies of /sub Λ/ 5 He and p-shell hypernuclei can be satisfactorily explained in the folding model approach using a density dependent effective ΛN interaction. Our analysis predicts a very reasonable value of the range of the ΛN interaction. The calculated value of B/sub Λ/ of /sub Λ/ 7 Li using the cluster model density for 6 Li and the best fit parameters of this potential supports the view that 6 Li possesses an α-d cluster structure. Using this potential we also determine the average size parameter (a 0 ) of the oscillator shell model density of nucleons in Nnot =Z core nuclei from fitting the B/sub Λ/ values of the corresponding hypernuclei. The effect of different forms of density distribution of core nuclei on the values of potential parameters is investigated and is found to be very small. As regards the form of density dependence, a rho/sup 2/3/ form is found to be the most appropriate for this purpose and is used throughout this work. Other forms do not give a satisfactory account of the data
Mandrà, Salvatore; Zhu, Zheng; Katzgraber, Helmut G
2017-02-17
We study the performance of the D-Wave 2X quantum annealing machine on systems with well-controlled ground-state degeneracy. While obtaining the ground state of a spin-glass benchmark instance represents a difficult task, the gold standard for any optimization algorithm or machine is to sample all solutions that minimize the Hamiltonian with more or less equal probability. Our results show that while naive transverse-field quantum annealing on the D-Wave 2X device can find the ground-state energy of the problems, it is not well suited in identifying all degenerate ground-state configurations associated with a particular instance. Even worse, some states are exponentially suppressed, in agreement with previous studies on toy model problems [New J. Phys. 11, 073021 (2009)NJOPFM1367-263010.1088/1367-2630/11/7/073021]. These results suggest that more complex driving Hamiltonians are needed in future quantum annealing machines to ensure a fair sampling of the ground-state manifold.
Infrared spectroscopy for studying structure and aging effects in rhamnolipid biosurfactants
Kiefer, Johannes; Radzuan, Mohd Nazren; Winterburn, James
2017-01-01
Biosurfactants are produced by microorganisms and represent amphiphilic compounds with polar and non-polar moieties; hence they can be used to stabilize emulsions, e.g. in the cosmetic and food sectors. Their structure and its changes when exposed to light and elevated temperature are yet to be fully understood. In this study, we demonstrate that attenuated total reflection infrared (ATR-IR) spectroscopy is a useful tool for the analysis of biosurfactants, using rhamnolipids produced by ferme...
Das, Soumyajit
2014-07-23
Polycyclic hydrocarbon compounds with a singlet biradical ground state show unique physical properties and promising material applications; therefore, it is important to understand the fundamental structure/biradical character/physical properties relationships. In this study, para-quinodimethane (p-QDM)-bridged quinoidal perylene dimers 4 and 5 with different fusion modes and their corresponding aromatic counterparts, the pericondensed quaterrylenes 6 and 7, were synthesized. Their ground-state electronic structures and physical properties were studied by using various experiments assisted with DFT calculations. The proaromatic p-QDM-bridged perylene monoimide dimer 4 has a singlet biradical ground state with a small singlet/triplet energy gap (-2.97 kcalmol-1), whereas the antiaromatic s-indacene-bridged N-annulated perylene dimer 5 exists as a closed-shell quinoid with an obvious intramolecular charge-transfer character. Both of these dimers showed shorter singlet excited-state lifetimes, larger two-photon-absorption cross sections, and smaller energy gaps than the corresponding aromatic quaterrylene derivatives 6 and 7, respectively. Our studies revealed how the fusion mode and aromaticity affect the ground state and, consequently, the photophysical properties and electronic properties of a series of extended polycyclic hydrocarbon compounds. A matter of fusion mode! Fusion of a para-quinodimethane (p-QDM) subunit at the peri and β positions of perylene dimers leads to systems with different ground states, that is, open and closed shell (see picture). These systems showed large two-photon absorption cross sections and ultrafast excited-state dynamics relative to their corresponding pericondensed aromatic quaterrylene counterparts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Luo, Ding
2014-01-01
Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y0 = 0.269) and a small singlet-triplet energy gap (ΔES-T ≅ -1.78 kcal mol-1), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future. This journal
Gapless Spin-Liquid Ground State in the S =1 /2 Kagome Antiferromagnet
Liao, H. J.; Xie, Z. Y.; Chen, J.; Liu, Z. Y.; Xie, H. D.; Huang, R. Z.; Normand, B.; Xiang, T.
2017-03-01
The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S =1 /2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. By studying the ground-state energy, the finite magnetic order appearing at finite tensor bond dimensions, and the effects of a next-nearest-neighbor coupling, we demonstrate that the ground state is a gapless spin liquid. We discuss the comparison with other numerical studies and the physical interpretation of this result.
Extended random-phase approximation with three-body ground-state correlations
International Nuclear Information System (INIS)
Tohyama, M.; Schuck, P.
2008-01-01
An extended random-phase approximation (ERPA) which contains the effects of ground-state correlations up to a three-body level is applied to an extended Lipkin model which contains an additional particle-scattering term. Three-body correlations in the ground state are necessary to preserve the hermiticity of the Hamiltonian matrix of ERPA. Two approximate forms of ERPA which neglect the three-body correlations are also applied to investigate the importance of three-body correlations. It is found that the ground-state energy is little affected by the inclusion of the three-body correlations. On the contrary, three-body correlations for the excited states can become quite important. (orig.)
Quantum ground state and single-phonon control of a mechanical resonator.
O'Connell, A D; Hofheinz, M; Ansmann, M; Bialczak, Radoslaw C; Lenander, M; Lucero, Erik; Neeley, M; Sank, D; Wang, H; Weides, M; Wenner, J; Martinis, John M; Cleland, A N
2010-04-01
Quantum mechanics provides a highly accurate description of a wide variety of physical systems. However, a demonstration that quantum mechanics applies equally to macroscopic mechanical systems has been a long-standing challenge, hindered by the difficulty of cooling a mechanical mode to its quantum ground state. The temperatures required are typically far below those attainable with standard cryogenic methods, so significant effort has been devoted to developing alternative cooling techniques. Once in the ground state, quantum-limited measurements must then be demonstrated. Here, using conventional cryogenic refrigeration, we show that we can cool a mechanical mode to its quantum ground state by using a microwave-frequency mechanical oscillator-a 'quantum drum'-coupled to a quantum bit, which is used to measure the quantum state of the resonator. We further show that we can controllably create single quantum excitations (phonons) in the resonator, thus taking the first steps to complete quantum control of a mechanical system.
Learning Approach on the Ground State Energy Calculation of Helium Atom
International Nuclear Information System (INIS)
Shah, Syed Naseem Hussain
2010-01-01
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.
Van der Waals potential and vibrational energy levels of the ground state radon dimer
Sheng, Xiaowei; Qian, Shifeng; Hu, Fengfei
2017-08-01
In the present paper, the ground state van der Waals potential of the Radon dimer is described by the Tang-Toennies potential model, which requires five essential parameters. Among them, the two dispersion coefficients C6 and C8 are estimated from the well determined dispersion coefficients C6 and C8 of Xe2. C10 is estimated by using the approximation equation that C6C10/C82 has an average value of 1.221 for all the rare gas dimers. With these estimated dispersion coefficients and the well determined well depth De and Re the Born-Mayer parameters A and b are derived. Then the vibrational energy levels of the ground state radon dimer are calculated. 40 vibrational energy levels are observed in the ground state of Rn2 dimer. The last vibrational energy level is bound by only 0.0012 cm-1.
Antibonding hole ground state in InAs quantum dot molecules
Energy Technology Data Exchange (ETDEWEB)
Planelles, Josep [Departament de Química Física i Analítica, Universitat Jaume I, E-12080, Castelló (Spain)
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.
Exact ground-state correlation functions of an atomic-molecular Bose–Einstein condensate model
Links, Jon; Shen, Yibing
2018-05-01
We study the ground-state properties of an atomic-molecular Bose–Einstein condensate model through an exact Bethe Ansatz solution. For a certain range of parameter choices, we prove that the ground-state Bethe roots lie on the positive real-axis. We then use a continuum limit approach to obtain a singular integral equation characterising the distribution of these Bethe roots. Solving this equation leads to an analytic expression for the ground-state energy. The form of the expression is consistent with the existence of a line of quantum phase transitions, which has been identified in earlier studies. This line demarcates a molecular phase from a mixed phase. Certain correlation functions, which characterise these phases, are then obtained through the Hellmann–Feynman theorem.
The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.
Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria
2014-09-01
The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.
Nano-structured Cu(In,Al)Se{sub 2} near-infrared photodetectors
Energy Technology Data Exchange (ETDEWEB)
Chang, Ruo-Ping [Institute of Microelectronics and Department of Electrical Engineering, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Perng, Dung-Ching, E-mail: dcperng@ee.ncku.edu.tw [Institute of Microelectronics and Department of Electrical Engineering, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China)
2013-02-01
We have demonstrated nano-structured Cu(In,Al)Se{sub 2} (CIAS) near-infrared (NIR) photodetectors (PDs). The CIAS NIR PDs were fabricated on ZnO nanowires (NWs)/ZnO/Mo/ITO (indium tin oxide) glass substrate. CIAS film acted as a sensing layer and sparse ZnSe NWs, which were converted from ZnO NWs after selenization process, were embedded in the CIAS film to improve the amplification performance of the NIR PDs. X-ray diffraction patterns show that the CIAS film is a single phased polycrystalline film. Scanning electron microscopy was used to examine the morphology of the CIAS film and the growth of NWs. Two detection schemes, plain Al–CIAS–Al metal–semiconductor–metal structure and vertical structure with CIAS/ZnSe NWs annular p–n junctions, were studied. The nano-structured NIR PDs demonstrate two orders of magnitude for the annular p–n junction and one order of magnitude for the MSM structure in photocurrent amplification. The responsivities of the PDs using both sensing structures have the same cut-off frequency near 790 nm. - Highlights: ► We demonstrate nano-structured Cu(In,Al)Se{sub 2} near-infrared photodetectors. ► Photodetectors were fabricated on ZnO nanowires/ZnO/Mo/ITO glass substrate. ► Two detection schemes studied: a plain MSM structure and a vertical structure. ► Photocurrent amplification for the vertical structure is two orders of magnitude. ► Photocurrent amplification for the MSM structure is one order of magnitude.
International Nuclear Information System (INIS)
Setti, G.; Fazio, G.
1978-01-01
This volume contains lectures describing the important achievements in infrared astronomy. The topics included are galactic infrared sources and their role in star formation, the nature of the interstellar medium and galactic structure, the interpretation of infrared, optical and radio observations of extra-galactic sources and their role in the origin and structure of the universe, instrumental techniques and a review of future space observations. (C.F.)
International Nuclear Information System (INIS)
Plekhov, O.A.; Saintier, N.; Palin-Luc, T.; Uvarov, S.V.; Naimark, O.B.
2007-01-01
The infrared and structural investigations of energy dissipation processes in metals subjected to cyclic loading have given impetus to the development of a new thermodynamic model with the capability of describing the energy balance under plastic deformation. The model is based on the statistical description of the mesodefect ensemble evolution and its influence on the dissipation ability of the material. Constitutive equations have been formulated for plastic and structural strains, which allow us to describe the stored and dissipated parts of energy under plastic flow. Numerical results indicate that theoretical predictions are in good agreement with the experimentally observed temperature data
A treatment of hard processes sensitive to the infrared structure of QCD
International Nuclear Information System (INIS)
Amati, D.; Veneziano, G.; Bassetto, A.; Marchesini, F.
1980-01-01
We propose a modified jet evolution equation which resums large corrections to the usual leading logarithmic approximation when phase-space constraints expose the singular infrared structure of QCD. The modification, which consists simply of a rescaling of the argument of the running coupling constant, is based on perturbative arguments verified at the fourth-order level. Processes analyzed by this method include the quark (Sudakov) form factor, the large moments of structure and fragmentation functions, the asymptotic behaviour of multiplicities and the clustering of final quanta in colourless systems which occupy finite regions of (momentum and position) phase space. (orig.)
Stability of the electroweak ground state in the Standard Model and its extensions
International Nuclear Information System (INIS)
Di Luzio, Luca; Isidori, Gino; Ridolfi, Giovanni
2016-01-01
We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.
Stability of the electroweak ground state in the Standard Model and its extensions
Energy Technology Data Exchange (ETDEWEB)
Di Luzio, Luca, E-mail: diluzio@ge.infn.it [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy); Isidori, Gino [Department of Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy)
2016-02-10
We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.
Stability of the electroweak ground state in the Standard Model and its extensions
Directory of Open Access Journals (Sweden)
Luca Di Luzio
2016-02-01
Full Text Available We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.
Ground State of Bosons in Bose-Fermi Mixture with Spin-Orbit Coupling
Sakamoto, Ryohei; Ono, Yosuke; Hatsuda, Rei; Shiina, Kenta; Arahata, Emiko; Mori, Hiroyuki
2017-07-01
We study an effect of spin-1/2 fermions on the ground state of a Bose system with equal Rashba and Dresselhaus spin-orbit coupling. By using mean-field and tight-binding approximations, we show the ground state phase diagram of the Bose system in the spin-orbit coupled Bose-Fermi mixture and find that the characteristic phase domain, where a spin current of fermions may be induced, can exist even in the presence of a significantly large number of fermions.
Numerical study of the t-J model: Exact ground state and flux phases
International Nuclear Information System (INIS)
Hasegawa, Y.; Poilblanc, D.
1990-01-01
Strongly correlated 2D electrons described by the t-J model are investigated numerically. Exact ground state for one and two holes in a finite cluster with periodic boundary conditions are obtained by using the Lanczos algorithm. The effects of Coulomb repulsion of the holes on the nearest neighbor sites are taken into account. Commensurate flux phases are investigated for the same size of clusters. They are shown to be a good approximation for the ground state specially in the intermediate value of J/t. (author). 21 refs, 3 figs
Fission barriers and asymmetric ground states in the relativistic mean-field theory
International Nuclear Information System (INIS)
Rutz, K.; Reinhard, P.G.; Greiner, W.
1995-01-01
The symmetric and asymmetric fission path for 240 Pu, 232 Th and 226 Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations. (orig.)
Ground state energy and width of 7He from 8Li proton knockout
International Nuclear Information System (INIS)
Denby, D. H.; DeYoung, P. A.; Hall, C. C.; Baumann, T.; Bazin, D.; Spyrou, A.; Breitbach, E.; Howes, R.; Brown, J.; Frank, N.; Gade, A.; Mosby, S. M.; Peters, W. A.; Thoennessen, M.; Hinnefeld, J.; Hoffman, C. R.; Jenson, R. A.; Luther, B.; Olson, C. W.; Schiller, A.
2008-01-01
The ground state energy and width of 7 He has been measured with the Modular Neutron Array (MoNA) and superconducting dipole Sweeper magnet experimental setup at the National Superconducting Cyclotron Laboratory. 7 He was produced by proton knockout from a secondary 8 Li beam. The measured decay energy spectrum is compared to simulations based on Breit-Wigner line shape with an energy-dependent width for the resonant state. The energy of the ground state is found to be 400(10) keV with a full-width at half-maximum of 125( -15 +40 ) keV
The ground-state phase diagrams of the spin-3/2 Ising model
International Nuclear Information System (INIS)
Canko, Osman; Keskin, Mustafa
2003-01-01
The ground-state spin configurations are obtained for the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic exchange interactions and a single-ion crystal field. The interactions are assumed to be only between nearest-neighbors. The calculated ground-state phase diagrams are presented on diatomic lattices, such as the square, honeycomb and sc lattices, and triangular lattice in the (Δ/z vertical bar J vertical bar ,K/ vertical bar J vertical bar) and (H/z vertical bar J vertical bar, K/ vertical bar J vertical bar) planes
Singlet Ground State Magnetism: III Magnetic Excitons in Antiferromagnetic TbP
DEFF Research Database (Denmark)
Knorr, K.; Loidl, A.; Kjems, Jørgen
1981-01-01
The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined.......The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined....
Ground-state properties of third-row elements with nonlocal density functionals
International Nuclear Information System (INIS)
Bagno, P.; Jepsen, O.; Gunnarsson, O.
1989-01-01
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
Traces of Lorentz symmetry breaking in a hydrogen atom at ground state
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.
Traces of Lorentz symmetry breaking in a hydrogen atom at ground state
Energy Technology Data Exchange (ETDEWEB)
Borges, L.H.C. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil); Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil)
2016-02-15
Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger 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. (orig.)
Traces of Lorentz symmetry breaking in a hydrogen atom at ground state
International Nuclear Information System (INIS)
Borges, L.H.C.; Barone, F.A.
2016-01-01
Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger 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. (orig.)
International Nuclear Information System (INIS)
Fuchs, J; Duffy, G J; Rowlands, W J; Lezama, A; Hannaford, P; Akulshin, A M
2007-01-01
We present an experimental study of sub-natural width resonances in fluorescence from a collimated beam of 6 Li atoms excited on the D 1 and D 2 lines by a bichromatic laser field. We show that in addition to ground-state Zeeman coherence, coherent population oscillations between ground and excited states contribute to the sub-natural resonances. High-contrast resonances of electromagnetically induced transparency and electromagnetically induced absorption due to both effects, i.e., ground-state Zeeman coherence and coherent population oscillations, are observed
On the ground state of the two-dimensional non-ideal Bose gas
International Nuclear Information System (INIS)
Lozovik, Yu.E.; Yudson, V.I.
1978-01-01
The theory of the ground state of the two-dimensional non-ideal Bose gas is presented. The conditions for the validity of the ladder and the Bogolubov approximations are derived. These conditions ensure the existence of a Bose condensate in the ground state of two-dimensional systems. These conditions are different from the corresponding conditions for the three-dimensional case. The connection between the effective interaction and the two-dimensional scattering amplitude at some characteristic energy kappa 2 /2m (not equal to 0) is obtained (f(kappa = 0) = infinity in the two-dimensional case). (Auth.)
Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb Breakup
Directory of Open Access Journals (Sweden)
Chakraborty S.
2014-03-01
Full Text Available Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s⊗νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al.
Trapping cold ground state argon atoms for sympathetic cooling of molecules
Edmunds, P. D.; Barker, P. F.
2014-01-01
We trap cold, ground-state, argon atoms in a deep optical dipole trap produced by a build-up 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 co-trapped metastable argon atoms using a new type of parametric loss spectroscopy. Using this technique we als...
International Nuclear Information System (INIS)
Chakraborty, S.; Datta Pramanik, U.; Chatterjee, S.
2013-01-01
The region of the nuclear chart around neutron magic number, N∼20 and proton number (Z), 10≤ Z≤12 is known as the Island of Inversion. The valance neutron(s) of these nuclei, even in their ground state, are most likely occupying the upper pf orbitals which are normally lying above sd orbitals, N∼20 shell closure. Nuclei like 34,35 Al are lying at the boundary of this Island of Inversion. Little experimental information about their ground state configuration are available in literature
Unambiguous assignment of the ground state of a nearly degenerate cluster
International Nuclear Information System (INIS)
Gutsev, G. L.; Khanna, S. N.; Jena, P.
2000-01-01
A synergistic approach that combines first-principles theory and electron photodetachment experiment is shown to be able to uniquely identify the ground state of a nearly degenerate cluster in the gas phase. Additionally, this approach can complement the Stern-Gerlach technique in determining the magnetic moment of small clusters unambiguously. The method, applied to a Fe 3 cluster, reveals its ground state to have a magnetic moment of 10μ B --in contrast with earlier predictions. (c) 2000 The American Physical Society
The structural and optical constants of Ag2S semiconductor nanostructure in the Far-Infrared.
Zamiri, Reza; Abbastabar Ahangar, Hossein; Zakaria, Azmi; Zamiri, Golnoosh; Shabani, Mehdi; Singh, Budhendra; Ferreira, J M F
2015-01-01
In this paper a template-free precipitation method was used as an easy and low cost way to synthesize Ag2S semiconductor nanoparticles. The Kramers-Kronig method (K-K) and classical dispersion theory was applied to calculate the optical constants of the prepared samples, such as the reflective index n(ω) and dielectric constant ε(ω) in Far-infrared regime. Nanocrystalline Ag2S was synthesized by a wet chemical precipitation method. Ag2S nanoparticle was characterized by X-ray diffraction, Scanning Electron Microscopy, UV-visible, and FT-IR spectrometry. The refinement of the monoclinic β-Ag2S phase yielded a structure solution similar to the structure reported by Sadanaga and Sueno. The band gap of Ag2S nanoparticles is around 0.96 eV, which is in good agreement with previous reports for the band gap energy of Ag2S nanoparticles (0.9-1.1 eV). The crystallite size of the synthesized particles was obtained by Hall-Williamson plot for the synthesized Ag2S nanoparticles and it was found to be 217 nm. The Far-infrared optical constants of the prepared Ag2S semiconductor nanoparticles were evaluated by means of FTIR transmittance spectra data and K-K method. Graphical abstractThe Far-infrared optical constants of Ag2S semiconductor nanoparticles.
International Nuclear Information System (INIS)
Ghosh, Barnali; Raychaudhuri, A.K.; Siruguri, V.; Chatterji, Tapan; Thomas, Hansen; Mukovskii, Ya.M.
2013-01-01
Depending on the doping level x the hole-doped perovskite manganites, like La 1-x Ca x MnO 3 exhibit a wide variety of physical properties. These compounds lead their high sensitivity to thermodynamic variables like temperature, magnetic field and pressure. The structure can be modified by application of high pressure and it can be quantitative that changes the Mn-O bond length and increases the Mn-O-Mn bond angle. In some cases the pressure can bring about qualitative changes in the structure like change in the lattice structure or its symmetry. These structural factors can contribute to the effective electron transfer integral between Mn ions, which in turn can change the magnetic exchanges like the double-exchange as well as the super exchange. For low hole doping (0.15 ≤ x ≤ 0.2), the low temperature ground state is Ferromagnetic insulator (FMI). The ground state of the low doped manganite La 0.79 Ca 0.21 MnO 3 (LCMO) can be destabilized by external hydrostatic pressure. We have done electrical transport measurement under magnetic field and under high pressure for understanding the nature of the resulting phase(s) that arise from the applied hydrostatic pressure. We find that the metallic phase so created under pressure has no appreciable magnetoresistance (MR). The Neutron powder diffraction measurement done on D20 diffractometer (λ=1.3Å) at ILL, Grenoble, France under high hydrostatic pressure up to 10GPa shows that the pressure leads to a change in the crystal structure from orthorhombic to rhombohedral and leading to a change in magnetic structure also; and most importantly collapse of the magnetic moment to a low value that leads to absence of any MR under pressure induced metallization. (author)
The influence of melt purification and structure defects on mid-infrared light emitting diodes
Krier, A
2003-01-01
Mid-infrared light emitting diodes which exhibit more than 7 mW (pulsed) and 0.35 mW dc output power at 3.3 mu m and at room temperature have been fabricated by liquid phase epitaxy using Pb as a neutral solvent. Using Pb solution an increase in pulsed output power of between two and three times was obtained compared with InAs light emitting diodes (LEDs) made using rare-earth gettering. The performance improvements were attributed to a reduction in residual carrier concentration arising from the removal of un-intentional donors and structure defects in the InAs active region material. These LEDs are well matched to the CH sub 4 absorption spectrum and potentially could form the basis of a practical infrared CH sub 4 gas sensor.
Ross, Kate
In the search for novel quantum states of matter, such as highly entangled Quantum Spin Liquids, ``geometrically frustrated'' magnetic lattices are essential for suppressing conventional magnetic order. In three dimensions, the pyrochlore lattice is the canonical frustrated geometry. Magnetic materials with pyrochlore structures have the potential to realize unusual phases such as ``quantum spin ice'', which is predicted to host emergent magnetic monopoles, electrons, and photons as its fundamental excitations. Even in pyrochlores that form long range ordered phases, this often occurs through unusual routes such as ``order by disorder'', in which the fluctuation spectrum dictates the preferred ordered state. The rare earth-based pyrochlore series R2Ti2O7 provides a fascinating variety of magnetic ground states. I will introduce the general anisotropic interaction Hamiltonian that has been successfully used to describe several materials in this series. Using inelastic neutron scattering, the relevant anisotropic interaction strengths can be extracted quantitatively. I will discuss this approach, and its application to two rare earth pyrochlore materials, Er2Ti2O7 and Yb2Ti<2O7, whose ground state properties have long been enigmatic. From these studies, ErTi2O7 and Yb2Ti2O7 have been suggested to be realizations of "quantum order by disorder" and "quantum spin ice", respectively. This research was supported by NSERC of Canada and the National Science Foundation.
2018-01-01
We introduce a simple scheme to efficiently compute photon exchange-correlation contributions due to the coupling to transversal photons as formulated in the newly developed quantum-electrodynamical density-functional theory (QEDFT).1−5 Our construction employs the optimized-effective potential (OEP) approach by means of the Sternheimer equation to avoid the explicit calculation of unoccupied states. We demonstrate the efficiency of the scheme by applying it to an exactly solvable GaAs quantum ring model system, a single azulene molecule, and chains of sodium dimers, all located in optical cavities and described in full real space. While the first example is a two-dimensional system and allows to benchmark the employed approximations, the latter two examples demonstrate that the correlated electron-photon interaction appreciably distorts the ground-state electronic structure of a real molecule. By using this scheme, we not only construct typical electronic observables, such as the electronic ground-state density, but also illustrate how photon observables, such as the photon number, and mixed electron-photon observables, for example, electron–photon correlation functions, become accessible in a density-functional theory (DFT) framework. This work constitutes the first three-dimensional ab initio calculation within the new QEDFT formalism and thus opens up a new computational route for the ab initio study of correlated electron–photon systems in quantum cavities. PMID:29594185
Competing ground states in LuFe{sub 4}Ge{sub 2} tuned by external pressure
Energy Technology Data Exchange (ETDEWEB)
Ajeesh, Mukkattu Omanakuttan; Weber, Katharina; Reis, Ricardo dos; Geibel, Christoph; Nicklas, Michael [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)
2016-07-01
Tuning competing ground-state properties using external pressure has attracted much attention in current condensed matter research. This is due to the fact that exotic phenomena and unconventional phases occur in regions of competing energy scales. Here, we present an investigation on LuFe{sub 4}Ge{sub 2} by electrical resistivity experiments under external pressure in order to understand the interplay between competing ground states in a frustrated, itinerant magnetic system. At ambient pressure LuFe{sub 4}Ge{sub 2} orders antiferromagnetically below 32 K. The antiferromagnetic (AFM) transition is connected with a structural transition. We have established the temperature - pressure phase diagram: pressure suppresses the original antiferromagnetically ordered state to zero temperature at around 1.7 GPa. Upon further increasing pressure a new pressure-induced phase emerges. This phase exhibits a qualitatively different magnetoresistance compared with the AFM phase suggesting a different type of ordering than at lower pressures. Furthermore, above 1.5 GPa we find a metamagnetic transition at higher magnetic fields. The onset of this phase shifts to lower fields with increasing pressure. Further studies to understand the nature of the new phases are on the way.
Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping
Chen, K.; Strigari, F.; Sundermann, M.; Hu, Z.; Fisk, Z.; Bauer, E. D.; Rosa, P. F. S.; Sarrao, J. L.; Thompson, J. D.; Herrero-Martin, J.; Pellegrin, E.; Betto, D.; Kummer, K.; Tanaka, A.; Wirth, S.; Severing, A.
2018-01-01
We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4 ,5 edges of Cd- and Sn-doped CeCoIn5. The 4 f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In1-xCdx) 5 suggests that the 4 f -conduction-electron (c f ) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In1-ySny) 5 compresses the 4 f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4 f and conduction electrons, even conveying information about direction dependencies.
Dybalski, Wojciech; Pizzo, Alessandro
2018-02-01
Let $H_{P,\\sigma}$ be the single-electron fiber Hamiltonians of the massless Nelson model at total momentum $P$ and infrared cut-off $\\sigma>0$. We establish detailed regularity properties of the corresponding $n$-particle ground state wave functions $f^n_{P,\\sigma}$ as functions of $P$ and $\\sigma$. In particular, we show that \\[ |\\partial_{P^j}f^{n}_{P,\\sigma}(k_1,\\ldots, k_n)|, \\ \\ |\\partial_{P^j} \\partial_{P^{j'}} f^{n}_{P,\\sigma}(k_1,\\ldots, k_n)| \\leq \\frac{1}{\\sqrt{n!}} \\frac{(c\\lambda_0)^n}{\\sigma^{\\delta_{\\lambda_0}}} \\prod_{i=1}^n\\frac{ \\chi_{[\\sigma,\\kappa)}(k_i)}{|k_i|^{3/2}}, \\] where $c$ is a numerical constant, $\\lambda_0\\mapsto \\delta_{\\lambda_0}$ is a positive function of the maximal admissible coupling constant which satisfies $\\lim_{\\lambda_0\\to 0}\\delta_{\\lambda_0}=0$ and $\\chi_{[\\sigma,\\kappa)}$ is the (approximate) characteristic function of the energy region between the infrared cut-off $\\sigma$ and the ultraviolet cut-off $\\kappa$. While the analysis of the first derivative is relatively straightforward, the second derivative requires a new strategy. By solving a non-commutative recurrence relation we derive a novel formula for $f^n_{P,\\sigma}$ with improved infrared properties. In this representation $\\partial_{P^{j'}}\\partial_{P^{j}}f^n_{P,\\sigma}$ is amenable to sharp estimates obtained by iterative analytic perturbation theory in part II of this series of papers. The bounds stated above are instrumental for scattering theory of two electrons in the Nelson model, as explained in part I of this series.
Ziegler, Tom; Krykunov, Mykhaylo; Autschbach, Jochen
2014-09-09
The random phase approximation (RPA) equation of adiabatic time dependent density functional ground state response theory (ATDDFT) has been used extensively in studies of excited states. It extracts information about excited states from frequency dependent ground state response properties and avoids, thus, in an elegant way, direct Kohn-Sham calculations on excited states in accordance with the status of DFT as a ground state theory. Thus, excitation energies can be found as resonance poles of frequency dependent ground state polarizability from the eigenvalues of the RPA equation. ATDDFT is approximate in that it makes use of a frequency independent energy kernel derived from the ground state functional. It is shown in this study that one can derive the RPA equation of ATDDFT from a purely variational approach in which stationary states above the ground state are located using our constricted variational DFT (CV-DFT) method and the ground state functional. Thus, locating stationary states above the ground state due to one-electron excitations with a ground state functional is completely equivalent to solving the RPA equation of TDDFT employing the same functional. The present study is an extension of a previous work in which we demonstrated the equivalence between ATDDFT and CV-DFT within the Tamm-Dancoff approximation.
Ground state properties of exotic nuclei in deformed medium mass region
International Nuclear Information System (INIS)
Manju; Chatterjee, R.; Singh, Jagjit; Shubhchintak
2017-01-01
The dipole moment, size of the nucleus and other ground state properties of deformed nuclei 37 Mg and 31 Ne are presented. Furthermore with this deformed wave function the electric dipole strength distribution for deformed nuclei 37 Mg and 31 Ne is calculated. This will allow us to investigate the two dimensional scaling phenomenon with two parameters: quadrupole deformation and separation energy
Some fundamental properties of the ground state of atoms and molecules
International Nuclear Information System (INIS)
Lieb, E.H.
1986-01-01
This paper studies the ground states of atoms and molecules in quantum mechanics and reports on some mathematically rigourous results pertaining to the matter. The non-relativistic Hamiltonian for a molecule in the static nucleus approximation is presented along with notations
Search for 12 C+ 12 C clustering in 24 Mg ground state
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 88; Issue 2. Search for 12C+12C clustering in 24Mg ground state. B N JOSHI ARUN K JAIN D C BISWAS B V JOHN Y K GUPTA L S DANU R P VIND G K PRAJAPATI S MUKHOPADHYAY A SAXENA. Regular Volume 88 Issue 2 February 2017 Article ID 29 ...
A Rigorous Investigation on the Ground State of the Penson-Kolb Model
Yang, Kai-Hua; Tian, Guang-Shan; Han, Ru-Qi
2003-05-01
By using either numerical calculations or analytical methods, such as the bosonization technique, the ground state of the Penson-Kolb model has been previously studied by several groups. Some physicists argued that, as far as the existence of superconductivity in this model is concerned, it is canonically equivalent to the negative-U Hubbard model. However, others did not agree. In the present paper, we shall investigate this model by an independent and rigorous approach. We show that the ground state of the Penson-Kolb model is nondegenerate and has a nonvanishing overlap with the ground state of the negative-U Hubbard model. Furthermore, we also show that the ground states of both the models have the same good quantum numbers and may have superconducting long-range order at the same momentum q = 0. Our results support the equivalence between these models. The project partially supported by the Special Funds for Major State Basic Research Projects (G20000365) and National Natural Science Foundation of China under Grant No. 10174002
A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates
Energy Technology Data Exchange (ETDEWEB)
Wang, Hanquan, E-mail: hanquan.wang@gmail.com [School of Statistics and Mathematics, Yunnan University of Finance and Economics, Kunming, Yunnan Province, 650221 (China); Yunnan Tongchang Scientific Computing and Data Mining Research Center, Kunming, Yunnan Province, 650221 (China)
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.
Lower bounds for the ground states of He-isoelectronic series
International Nuclear Information System (INIS)
Fraga, Serafin
1981-01-01
A formulation, based on the concept of null local kinetic energy regions, has been developed for the determination of lower bounds for the ground state of a two-electron atom. Numerical results, obtained from Hartree-Fock functions, are presented for the elements He through Kr of the two-electron series
On the topological ground state of E-infinity spacetime and the super string connection
International Nuclear Information System (INIS)
El Naschie, M.S.
2007-01-01
There are at present a huge number of valid super string ground states, making the one corresponding to our own universe extremely hard to determine. Therefore it may come as quite a surprise that it is a rather simple undertaking to determine the exact topological ground state of E-infinity Cantorian spacetime theory. Similar to the ground state of the Higgs for E-infinity, the expectation value of the topological ground state is non-zero and negative. Its value is given exactly by -bar o -∼ n(1/φ) n =-(4+φ 3 ) where φ=(5-1)/2 and n represents an integer Menger-Uhryson dimension running from n=0 to n=-∼. Recalling that the average dimension of ε (∼) is given by ∼ =4+φ 3 , one could interpret this result as saying that our E-infinity spacetime may be viewed as an in itself closed manifold given by the remarkable equation: + =zeroThus in a manner of speaking, the universe could have spontaneously tunnelled into existence from virtual nothingness
Ground state properties of the bond alternating spin-1/2 anisotropic Heisenberg chain
Directory of Open Access Journals (Sweden)
S. Paul
2017-06-01
Full Text Available Ground state properties, dispersion relations and scaling behaviour of spin gap of a bond alternating spin-1/2 anisotropic Heisenberg chain have been studied where the exchange interactions on alternate bonds are ferromagnetic (FM and antiferromagnetic (AFM in two separate cases. The resulting models separately represent nearest neighbour (NN AFM-AFM and AFM-FM bond alternating chains. Ground state energy has been estimated analytically by using both bond operator and Jordan-Wigner representations and numerically by using exact diagonalization. Dispersion relations, spin gap and several ground state orders have been obtained. Dimer order and string orders are found to coexist in the ground state. Spin gap is found to develop as soon as the non-uniformity in alternating bond strength is introduced in the AFM-AFM chain which further remains non-zero for the AFM-FM chain. This spin gap along with the string orders attribute to the Haldane phase. The Haldane phase is found to exist in most of the anisotropic region similar to the isotropic point.
Relativistic analysis of nuclear ground state densities at 135 to 200 ...
Indian Academy of Sciences (India)
fitting of differential cross-section and analyzing power, and the appearance of wine-bottle- ... So, the effect of different nuclear density distributions is quite conspicuous in the relativistic ap- proach. Hence, we have analyzed five different nuclear ground state .... The NEG and FNEG densities have been used to see the effect.
Patterns of the ground states in the presence of random interactions : Nucleon systems
Zhao, YM; Arima, A; Shimizu, N; Ogawa, K; Yoshinaga, N; Scholten, O
We present our results on properties of ground states for nucleonic systems in the presence of random two-body interactions. In particular, we calculate probability distributions for parity, seniority, spectroscopic (i.e., in the laboratory frame) quadrupole moments, and discuss a clustering in the
Quantum double-well chain: Ground-state phases and applications to hydrogen-bonded materials
International Nuclear Information System (INIS)
Wang, X.; Campbell, D.K.; Gubernatis, J.E.
1994-01-01
Extrapolating the results of hybrid quantum Monte Carlo simulations to the zero temperature and infinite-chain-length limits, we calculate the ground-state phase diagram of a system of quantum particles on a chain of harmonically coupled, symmetric, quartic double-well potentials. We show that the ground state of this quantum chain depends on two parameters, formed from the ratios of the three natural energy scales in the problem. As a function of these two parameters, the quantum ground state can exhibit either broken symmetry, in which the expectation values of the particle's coordinate are all nonzero (as would be the case for a classical chain), or restored symmetry, in which the expectation values of the particle's coordinate are all zero (as would be the case for a single quantum particle). In addition to the phase diagram as a function of these two parameters, we calculate the ground-state energy, an order parameter related to the average position of the particle, and the susceptibility associated with this order parameter. Further, we present an approximate analytic estimate of the phase diagram and discuss possible physical applications of our results, emphasizing the behavior of hydrogen halides under pressure
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.
Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state
Sun, Zhe; Huang, Kuo-Wei; Wu, Jishan
2011-01-01
A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.
A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates
International Nuclear Information System (INIS)
Wang, Hanquan
2014-01-01
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
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.; Qian, Ying; Schwingenschlö gl, Udo; Yan, Z.-C.
2013-01-01
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition
A nonlinear programming approach to lower bounds for the ground-state energy of helium
International Nuclear Information System (INIS)
Porras, I.; Feldmann, D.M.; King, F.W.
1999-01-01
Lower-bound estimates for the ground-state energy of the helium atom are determined using nonlinear programming techniques. Optimized lower bounds are determined for single-particle, radially correlated, and general correlated wave functions. The local nature of the method employed makes it a very severe test of the accuracy of the wave function
Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state
Sun, Zhe
2011-08-10
A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.
Ground-state energy of an exciton-(LO) phonon system in a parabolic quantum well
Gerlach, B.; Wüsthoff, J.; Smondyrev, M. A.
1999-12-01
This paper presents a variational study of the ground-state energy of an exciton-(LO) phonon system, which is spatially confined to a quantum well. The exciton-phonon interaction is of Fröhlich type, the confinement potentials are assumed to be parabolic functions of the coordinates. Making use of functional integral techniques, the phonon part of the problem can be eliminated exactly, leading us to an effective two-particle system, which has the same spectral properties as the original one. Subsequently, Jensen's inequality is applied to obtain an upper bound on the ground-state energy. The main intention of this paper is to analyze the influence of the quantum-well-induced localization of the exciton on its ground-state energy (or its binding energy, respectively). To do so, we neglect any mismatch of the masses or the dielectric constants, but admit an arbitrary strength of the confinement potentials. Our approach allows for a smooth interpolation of the ultimate limits of vanishing and infinite confinement, corresponding to the cases of a free three-dimensional and a free two-dimensional exciton-phonon system. The interpolation formula for the ground-state energy bound corresponds to similar formulas for the free polaron or the free exciton-phonon system. These bounds in turn are known to compare favorably with all previous ones, which we are aware of.
Dumoulin, Jean; Crinière, Antoine; Averty, Rodolphe
2015-04-01
An infrared system has been developed to monitor transport infrastructures in a standalone configuration. Results obtained on bridges open to traffic allows to retrieve the inner structure of the decks. To complete this study, experiments were carried out over several months to monitor two reinforced concrete beams of 16 m long and 21 T each. Detection of a damaged area over one of the two beams was made by Pulse Phase Thermography approach. Measurements carried out over several months. Finally, conclusion on the robustness of the system is proposed and perspectives are presented.
Infrared structure and large Psub(T) behavior of quantum chromodynamics
International Nuclear Information System (INIS)
Rafael, Eduardo de.
1977-09-01
The study of the infrared structure of QCD in perturbation theory is an interesting problem per se regardless of its relationship to the confinement problem. The ultimate motivation for the study of the large transverse momentum behavior of QCD is to provide a field theoretic framework to the large Psub(T)-phenomena in hadronic interactions. As a first step towards that aim it is of interest to explore the possibility that the QCD Green's functions in 'some' regions of exceptional momenta, like the large-Psub(T) regime, may still obey some kind of renormalization group type equations
Orthous-Daunay, F.-R.; Quirico, E.; Beck, P.; Brissaud, O.; Dartois, E.; Pino, T.; Schmitt, B.
2013-03-01
Insoluble Organic Matter (IOM) found in primitive meteorites was formed in the Early Solar System and subsequently processed on the parent asteroids. The location, temporal sequence and processes of formation of this IOM are still a matter of debate. In particular, there is no consensus on the actual effect of post-accretional aqueous alteration processes on the chemical composition and structure of IOM. In the most primitive chondrites (types 1 and 2), these alterations have so far been either neglected or generically assigned to oxidation processes induced by fluid circulation. A series of IOM samples extracted from 14 chondrites with extensively documented post-accretional histories have been studied by infrared spectroscopy. Aqueous alteration shows no detectable effect on the chemical composition and structure of IOM within or across chondrite classes. Indeed, the most effective post-accretional process appears to be a high-temperature short-duration heating event and concerns essentially type 2 chondrites. In any case, post-accretional processes cannot account for all the chemical and structural variations of IOM. Chondrites from the CI, CR and CM classes accreted IOM precursors with moderately variable compositions, suggesting a chemical heterogeneity of the protosolar disk. The 3.4 μm band, and possibly its overtones and combinations in the near-infrared range, appear to be tracer(s) of the chemical class and possibly of surface heating processes triggered by impacts.
Design and Preparation of a Micro-Pyramid Structured Thin Film for Broadband Infrared Antireflection
Directory of Open Access Journals (Sweden)
Shaobo Ge
2018-05-01
Full Text Available A micro-pyramid structured thin film with a broad-band infrared antireflection property is designed and fabricated by using the single-point diamond turning (SPDT technique and combined with nano-imprint lithography (NIL. A structure with dimensions of 10 μm pitch and 5 μm height is transferred from the copper mold to the silicon nitride optical film by using NIL and proportional inductively-coupled plasma (ICP etching. Reflectance of the micro-optical surface is reduced below 1.0% over the infrared spectral range (800–2500 nm. A finite-difference-time-domain (FDTD analysis indicates that this micro-structure can localize photons and enhance the absorption inside the micro-pyramid at long wavelengths. As described above, the micro-pyramid array has been integrated in an optical film successfully. Distinguishing from the traditional micro-optical components, considering the effect of refraction and diffraction, it is a valuable and flexible method to take account of the interference effect of optical film.
Hyperfine structure of ScI by infrared Fourier transform spectroscopy
International Nuclear Information System (INIS)
Aboussaid, A.; Carleer, M.; Hurtmans, D.; Biemont, E.; Godefroid, M.R.
1996-01-01
The spectrum of scandium was recorded in the infrared region using a high resolution Fourier transform spectrometer and a hollow-cathode discharge. Hyperfine structures of the lines connecting the 3d 2 4s and 3d4s4p level systems of Sc 45 I were observed between 4000 and 5000 cm -1 . The structures were not completely resolved but the individual line contributions to the complex profiles were simulated using the 3d 2 4s 4 F J hyperfine structure constants previously measured with a high precision by laser techniques. We investigate the possibility of extracting the hyperfine constants of the 3d4s4p levels from a least-squares fit of the line profiles, assuming a Doppler lineshape and theoretical relative intensities. New results are presented for 12 levels. (orig.)
Structural dynamics of N-ethylpropionamide clusters examined by nonlinear infrared spectroscopy
International Nuclear Information System (INIS)
Wang, Jianping; Yang, Fan; Zhao, Juan; Shi, Jipei
2015-01-01
In this work, the structural dynamics of N-ethylpropionamide (NEPA), a model molecule of β-peptides, in four typical solvents (DMSO, CH 3 CN, CHCl 3 , and CCl 4 ), were examined using the N—H stretching vibration (or the amide-A mode) as a structural probe. Steady-state and transient infrared spectroscopic methods in combination with quantum chemical computations and molecular dynamics simulations were used. It was found that in these solvents, NEPA exists in different aggregation forms, including monomer, dimer, and oligomers. Hydrogen-bonding interaction and local-solvent environment both affect the amide-A absorption profile and its vibrational relaxation dynamics and also affect the structural dynamics of NEPA. In particular, a correlation between the red-shifted frequency for the NEPA monomer from nonpolar to polar solvent and the vibrational excitation relaxation rate of the N—H stretching mode was observed
Marin, F.; Rojas Lobos, P. A.; Hameury, J. M.; Goosmann, R. W.
2018-05-01
Context. From stars to active galactic nuclei, many astrophysical systems are surrounded by an equatorial distribution of dusty material that is, in a number of cases, spatially unresolved even with cutting edge facilities. Aims: In this paper, we investigate if and how one can determine the unresolved and heterogeneous morphology of dust distribution around a central bright source using time-resolved polarimetric observations. Methods: We used polarized radiative transfer simulations to study a sample of circumnuclear dusty morphologies. We explored a grid of geometrically variable models that are uniform, fragmented, and density stratified in the near-infrared, optical, and ultraviolet bands, and we present their distinctive time-dependent polarimetric signatures. Results: As expected, varying the structure of the obscuring equatorial disk has a deep impact on the inclination-dependent flux, polarization degree and angle, and time lags we observe. We find that stratified media are distinguishable by time-resolved polarimetric observations, and that the expected polarization is much higher in the infrared band than in the ultraviolet. However, because of the physical scales imposed by dust sublimation, the average time lags of months to years between the total and polarized fluxes are important; these time lags lengthens the observational campaigns necessary to break more sophisticated, and therefore also more degenerated, models. In the ultraviolet band, time lags are slightly shorter than in the infrared or optical bands, and, coupled to lower diluting starlight fluxes, time-resolved polarimetry in the UV appears more promising for future campaigns. Conclusions: Equatorial dusty disks differ in terms of inclination-dependent photometric, polarimetric, and timing observables, but only the coupling of these different markers can lead to inclination-independent constraints on the unresolved structures. Even though it is complex and time consuming, polarized
International Nuclear Information System (INIS)
Guerout, R.; Aymar, M.; Dulieu, O.
2010-01-01
In this study, we investigate the structure of the polar alkali-metal-atom-strontium diatomic molecules as possible candidates for the realization of samples of ultracold polar molecular species not yet investigated experimentally. Using a quantum chemistry approach based on effective core potentials and core polarization potentials, we model these systems as effective three-valence-electron systems, allowing for calculation of electronic properties with full configuration interaction. The potential curve and the permanent dipole moment of the 2 Σ + ground state are determined as functions of the internuclear distance for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-metal-atom-Rb molecules.
Kekulé-based Valence Bond Model.I. The Ground-state Properties of Conjugated π-Systems
Institute of Scientific and Technical Information of China (English)
LI,Shu-Hua(黎书华); MA,Jing(马晶); JIANG,Yuan-Sheng(江元生)
2002-01-01
The Kekulé-based valence bond ( VB ) method, in which the VB model is solved using covalent Kekulé structures as basis functions, is justified in the present work. This method is dimonstrated to provide satisfactory descriptions for resoance energies and bond ang lengths of benzenoid hydrocarbons, being in good agreement with SCF-MO and experimental results. In additicn, an alternative way of discyssing characters of localizedsubstructures within a polyclic benzenoid system is suggested based upon such sunokufied VB calculations. Finally,the symmetries of VB ground states for nonalternant conjugated systems are also illustrated to be obtainable through these calculations, presenting very useful information for understanding the chemical behaviors of some nonalternant conjugated molecules.
Spielberg, Eike T; Gilb, Aksana; Plaul, Daniel; Geibig, Daniel; Hornig, David; Schuch, Dirk; Buchholz, Axel; Ardavan, Arzhang; Plass, Winfried
2015-04-06
We present the synthesis and crystal structure of the trinuclear copper complex [Cu3(saltag)(bpy)3]ClO4·3DMF [H5saltag = tris(2-hydroxybenzylidene)triaminoguanidine; bpy = 2,2'-bipyridine]. The complex crystallizes in the trigonal space group R3̅, with all copper ions being crystallographically equivalent. Analysis of the temperature dependence of the magnetic susceptibility shows that the triaminoguanidine ligand mediates very strong antiferromagnetic interactions (JCuCu = -324 cm(-1)). Detailed analysis of the magnetic susceptibility and magnetization data as well as X-band electron spin resonance spectra, all recorded on both powdered samples and single crystals, show indications of neither antisymmetric exchange nor symmetry lowering, thus indicating only a very small splitting of the degenerate S = (1)/2 ground state. These findings are corroborated by density functional theory calculations, which explain both the strong isotropic and negligible antisymmetric exchange interactions.
Energy Technology Data Exchange (ETDEWEB)
Hudson, C. E.; Ramsbottom, C. A.; Scott, M. P., E-mail: c.hudson@qub.ac.uk, E-mail: c.ramsbottom@qub.ac.uk, E-mail: p.scott@qub.ac.uk [Department of Applied Maths and Theoretical Physics, The Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom)
2012-05-01
We have carried out a 29-state R-matrix calculation in order to calculate collision strengths and effective collision strengths for the electron impact excitation of S III. The recently developed parallel RMATRX II suite of codes have been used, which perform the calculation in intermediate coupling. Collision strengths have been generated over an electron energy range of 0-12 Ryd, and effective collision strength data have been calculated from these at electron temperatures in the range 1000-100,000 K. Results are here presented for the fine-structure transitions between the ground-state configurations of 3s {sup 2}3p {sup 23} P{sub 0,1,2}, {sup 1}D{sub 2}, and {sup 1} S{sub 0}, and the values given resolve a discrepancy between two previous R-matrix calculations.
Validity of single term energy expression for ground state rotational band of even-even nuclei
International Nuclear Information System (INIS)
Sharma, S.; Kumar, R.; Gupta, J.B.
2005-01-01
Full text: There are large numbers of empirical studies of gs band of even-even nuclei in various mass regions. The Bohr-Mottelson's energy expression is E(I) = AX + BX 2 +CX 3 +... where X = I(I+1). The anharmonic vibrator energy expression is: E(I) = al + bl 2 + cl 3 SF model with energy expression: E(I)= pX + qI + rXI... where the terms represents the rotational, vibrational and R-V interaction energy, respectively. The validity f the various energy expressions with two terms had been tested by Sharma for light, medium and heavy mass regions using R I s. R 4 plots (where, spin I=6, 8, 10, 12), which are parameter independent. It was also noted, that of the goodness of energy expression can be judged with the minimum input of energies (i.e. only 2 parameters) and predictability's of the model p to high spins. Recently, Gupta et. al proposed a single term energy expression (SSTE) which was applied for rare earth region. This proposed power law reflected the unity of rotation - vibration in a different way and was successful in explaining the structure of gs-band. It will be useful for test the single term energy expression for light and heavy mass region. The single term expression for energy of ground state band can be written as: E I =axI b , where the index b and the coefficient a are the constant for the band. The values of b+1 and a 1 are as follows: b 1 =log(R 1 )/log(I/2) and a 1 =E I /I b ... The following results were gained: 1) The sharp variation in the value of index b at given spin will be an indication of the change in the shape of the nucleus; 2) The value of E I /I b is fairly constant with spin below back-bending, which reflects the stability of shape with spin; 3) This proposed power law is successful in explaining the structure of gs-band of nuclei
ITO/Au/ITO sandwich structure for near-infrared plasmonics.
Fang, Xu; Mak, Chee Leung; Dai, Jiyan; Li, Kan; Ye, Hui; Leung, Chi Wah
2014-09-24
ITO/Au/ITO trilayers with varying gold spacer layer thicknesses were deposited on glass substrates by pulsed laser deposition. Transmission electron microscopy measurements demonstrated the continuous nature of the Au layer down to 2.4 nm. XRD patterns clearly showed an enhanced crystallinity of the ITO films promoted by the insertion of the gold layer. Compared with a single layer of ITO with a carrier concentration of 7.12 × 10(20) cm(-3), the ITO/Au/ITO structure achieved an effective carrier concentration as high as 3.26 × 10(22) cm(-3). Transmittance and ellipsometry measurements showed that the optical properties of ITO/Au/ITO films were greatly influenced by the thickness of the inserted gold layer. The cross-point wavelength of the trilayer samples was reduced with increasing gold layer thickness. Importantly, the trilayer structure exhibited a reduced loss (compared with plain Au) in the near-infrared region, suggesting its potential for plasmonic applications in the near-infrared range.
Near-Infrared Trigged Stimulus-Responsive Photonic Crystals with Hierarchical Structures.
Lu, Tao; Pan, Hui; Ma, Jun; Li, Yao; Zhu, Shenmin; Zhang, Di
2017-10-04
Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe 3 O 4 nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout. It is noteworthy that the whole process is durable and stable mainly owing to the chemical bonding formed between PNIPAM and the biotemplate. We envision that this biologically inspired approach could be utilized in a broad range of applications and would have a great impact on various monitoring processes and medical sensing.
Energy Technology Data Exchange (ETDEWEB)
Bazuev, G V; Shveikin, G P [AN SSSR, Sverdlovsk. Inst. Khimii
1975-12-01
In the range 400-800 cm/sup -1/ a study has been made of infrared absorption spectra of perowskites ABO/sub 3/, where A is a rare-earth element or yttrium, B is Ti or V. A common feature of the infrared absorption spectra of perowskites ABO/sub 3/ is the presence of two intensive wide bands in the range 400-700 cm/sup -1/ one of which (low-frequency) is splitted into two or three components. The spectrum of LaTiO/sub 3/ is distinguished from spectra of other compounds. In the range measured this compound is non-transparent for electromagnetic radiation. On the basis of determination of temperature dependences of the electric resistance it is found that LaTiO/sub 3/ has metallic conductivity unlike other perowskites studied which are semiconductors. The spectrum of EuTiO/sub 3/ also differs from other spectra. It is close in its structure and position of bands to the spectrum of cubic perowskite, SrTiO/sub 3/. The splitting of the low-frequency band into two and in the case of TbVO/sub 3/ into three components is caused by deformation of crystal structures of these compounds. A direct dependence between the value of splitting and the deformation degree is observed.
Lora Gonzalez, Federico
Controlling the reflection of visible and infrared (IR) light at interfaces is extremely important to increase the power efficiency and performance of optics, electro-optical and (thermo)photovoltaic systems. The eye of the moth has evolved subwavelength protuberances that increase light transmission into the eye tissue and prevent reflection. The subwavelength protuberances effectively grade the refractive index from that of air (n=1) to that of the tissue (n=1.4), making the interface gradual, suppressing reflection. In theory, the moth-eye (ME) structures can be implemented with any material platform to achieve an antireflectance effect by scaling the pitch and size of protuberances for the wavelength range of interest. In this work, a bio-inspired, scalable and substrate-independent surface modification protocol was developed to realize broadband antireflective structures based on the moth-eye principle. Quasi-ordered ME arrays were fabricated in IR relevant materials using a colloidal lithography method to achieve highly efficient, omni-directional transmission of mid and far infrared (IR) radiation. The effect of structure height and aspect ratio on transmittance and scattering is explored, with discussion on experimental techniques and effective medium theory (EMT). The highest aspect ratio structures (AR = 9.4) achieved peak single-side transmittance of 98%, with >85% transmission for lambda = 7--30 microns. A detailed photon balance constructed by transmission, forward scattering, specular reflection and diffuse reflection measurements to quantify optical losses due to near-field effects will be discussed. In addition, angle-dependent transmission measurements showed that moth-eye structures provide superior antireflective properties compared to unstructured interfaces over a wide angular range (0--60° incidence). Finally, subwavelength ME structures are incorporated on a Si substrate to enhance the absorption of near infrared (NIR) light in PtSi films to
Unveiling the chemistry of interstellar CH. Spectroscopy of the 2 THz N = 2 ← 1 ground state line
Wiesemeyer, H.; Güsten, R.; Menten, K. M.; Durán, C. A.; Csengeri, T.; Jacob, A. M.; Simon, R.; Stutzki, J.; Wyrowski, F.
2018-04-01
Context. The methylidyne radical CH is commonly used as a proxy for molecular hydrogen in the cold, neutral phase of the interstellar medium. The optical spectroscopy of CH is limited by interstellar extinction, whereas far-infrared observations provide an integral view through the Galaxy. While the HF ground state absorption, another H2 proxy in diffuse gas, frequently suffers from saturation, CH remains transparent both in spiral-arm crossings and high-mass star forming regions, turning this light hydride into a universal surrogate for H2. However, in slow shocks and in regions dissipating turbulence its abundance is expected to be enhanced by an endothermic production path, and the idea of a "canonical" CH abundance needs to be addressed. Aim. The N = 2 ← 1 ground state transition of CH at λ149 μm has become accessible to high-resolution spectroscopy thanks to the German Receiver for Astronomy at Terahertz Frequencies (GREAT) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Its unsaturated absorption and the absence of emission from the star forming regions makes it an ideal candidate for the determination of column densities with a minimum of assumptions. Here we present an analysis of four sightlines towards distant Galactic star forming regions, whose hot cores emit a strong far-infrared dust continuum serving as background signal. Moreover, if combined with the sub-millimeter line of CH at λ560 μm , environments forming massive stars can be analyzed. For this we present a case study on the "proto-Trapezium" cluster W3 IRS5. Methods: While we confirm the global correlation between the column densities of HF and those of CH, both in arm and interarm regions, clear signposts of an over-abundance of CH are observed towards lower densities. However, a significant correlation between the column densities of CH and HF remains. A characterization of the hot cores in the W3 IRS5 proto-cluster and its envelope demonstrates that the sub-millimeter/far-infrared
Meola, Carosena
2012-01-01
This e-book conveys information about basic IRT theory, infrared detectors, signal digitalization and applications of infrared thermography in many fields such as medicine, foodstuff conservation, fluid-dynamics, architecture, anthropology, condition monitoring, non destructive testing and evaluation of materials and structures.
Stepanenko, Olesya V.; Stepanenko, Olga V.; Bublikov, G. S.; Kuznetsova, I. M.; Verkhusha, V. V.; Turoverov, K. K.
2017-07-01
Near-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes and their mutants with different location of Cys residues, which able to bind a biliverdin chromophore, or without these Cys residues were studied using intrinsic tryptophan fluorescence, NIR fluorescence and circular dichroism. It was shown that a covalent binding of the biliverdin chromophore to a Cys residue via thioether group substantially stabilizes the spatial structure of NIR FPs. The stability of the protein structure and the chromophore association strength strongly depends on the location of Cys residues and decreases in the following order: a protein with Cys residues in both domains, a protein with Cys in PAS domains, and a protein with Cys in GAF domains. NIR FPs without Cys residues capable to covalently attach biliverdin have the lowest stability, comparable to NIR FP apoforms.
Zeng, Zebing
2012-09-05
Stable open-shell polycyclic aromatic hydrocarbons (PAHs) are of fundamental interest due to their unique electronic, optical, and magnetic properties and promising applications in materials sciences. Chichibabin\\'s hydrocarbon as a classical open-shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin\\'s hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure and geometry in the ground state were studied by various experiments (steady-state and transient absorption spectra, NMR, electron spin resonance (ESR), superconducting quantum interference device (SQUID), FT Raman, X-ray crystallographic etc.) and density function theory (DFT) calculations. 1-CS and 2-OS exhibited tunable ground states, with a closed-shell quinoidal structure for 1-CS and an open-shell biradical form for 2-OS. Their corresponding excited-state forms 1-OS and 2-CS were also chemically approached and showed different decay processes. The biradical 1-OS displayed an unusually slow decay to the ground state (1-CS) due to a large energy barrier (95 ± 2.5 kJ/mol) arising from severe steric hindrance during the transition from an orthogonal biradical form to a butterfly-like quinoidal form. The quick transition from the quinoidal 2-CS (excited state) to the orthogonal biradicaloid 2-OS (ground state) happened during the attempted synthesis of 2-CS. Compounds 1-CS and 2-OS can be oxidized into stable dications by FeCl 3 and/or concentrated H 2SO 4. The open-shell 2-OS also exhibited a large two-photon absorption (TPA) cross section (760 GM at 1200 nm). © 2012 American Chemical Society.
Luo, Ding; Lee, Sangsu; Zheng, Bin; Sun, Zhe; Zeng, Wangdong; Huang, Kuo-Wei; Furukawa, Ko; Kim, Dongho; Webster, Richard D.; Wu, Jishan
2014-01-01
and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate
Theory of Nonlinear Dispersive Waves and Selection of the Ground State
International Nuclear Information System (INIS)
Soffer, A.; Weinstein, M.I.
2005-01-01
A theory of time-dependent nonlinear dispersive equations of the Schroedinger or Gross-Pitaevskii and Hartree type is developed. The short, intermediate and large time behavior is found, by deriving nonlinear master equations (NLME), governing the evolution of the mode powers, and by a novel multitime scale analysis of these equations. The scattering theory is developed and coherent resonance phenomena and associated lifetimes are derived. Applications include Bose-Einstein condensate large time dynamics and nonlinear optical systems. The theory reveals a nonlinear transition phenomenon, 'selection of the ground state', and NLME predicts the decay of excited state, with half its energy transferred to the ground state and half to radiation modes. Our results predict the recent experimental observations of Mandelik et al. in nonlinear optical waveguides
The influence of nonlocal hybridization on ground-state properties of the Falicov-Kimball model
International Nuclear Information System (INIS)
Farkasovsky, Pavol
2005-01-01
The density matrix renormalization group is used to examine effects of nonlocal hybridization on ground-state properties of the Falicov-Kimball model (FKM) in one dimension. Special attention is devoted to the problem of hybridization-induced insulator-metal transition. It is shown that the picture of insulator-metal transitions found for the FKM with nonlocal hybridization strongly differs from one found for the FKM without hybridization (as well as with local hybridization). The effect of nonlocal hybridization is so strong that it can induce the insulator-metal transition, even in the half-filled band case where the ground states of the FKM without hybridization are insulating for all finite Coulomb interactions. Outside the half-filled band case the metal-insulator transition driven by pressure is found for finite values of nonlocal hybridization
Rayleigh approximation to ground state of the Bose and Coulomb glasses
Ryan, S. D.; Mityushev, V.; Vinokur, V. M.; Berlyand, L.
2015-01-01
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. PMID:25592417
The Ground State Energy of a Dilute Bose Gas in Dimension $n\\geq 3$
DEFF Research Database (Denmark)
Aaen, Anders Gottfred
We consider a Bose gas in spatial dimension n≥3 with a repulsive, radially symmetric two-body potential V. In the limit of low density ρ, the ground state energy per particle in the thermodynamic limit is shown to be (n−2)|Sn−1|an−2ρ, where |Sn−1| denotes the surface measure of the unit sphere...... in Rn, and a is the scattering length of V. Furthermore, for smooth and compactly supported two-body potentials, we derive an upper bound to the ground state energy with a correction term (1+γ)8π4a6ρ2|ln(a4ρ)| in 4 dimensions, where 0... dimensions. Finally, we use a grand canonical construction to give a simplified proof of the second order upper bound to the Lee-Huang-Yang formula, a result first obtained by Yau and Yin. We also test this method in 4 dimensions, but with a negative outcome....
Ground state properties of new element Z=113 and its alpha decay chain
International Nuclear Information System (INIS)
Tai Fei; Chen Dinghan; Xu Chang; Ren Zhongzhou
2005-01-01
The authors investigate the ground state properties of the new element 278 113 and of the α-decay chain with different models, where the new element Z=113 has been produced at RIKEN in Japan by cold-fusion reaction. The experimental decay energies are reproduced by the deformed relativistic mean-field model, by the Skyrme-Hartree-Fock (SHF) model, and by the macroscopic-microscopic model. Theoretical half-lives also reasonably agree with the data. Calculations further show that prolate deformation is important for the ground states of the nuclei in the α-decay chain of 278 113. The common points and differences among different models are compared and discussed. (author)
The ground state energy of 3He droplet in the LOCV framework
International Nuclear Information System (INIS)
Modarres, M.; Motahari, S.; Rajabi, A.
2012-01-01
The (extended) lowest order constrained variational method was used to calculate the ground state energy of liquid helium 3 ( 3 He) droplets at zero temperature. Different types of density distribution profiles, such as the Gaussian, the Quasi-Gaussian and the Woods-Saxon were used. It was shown that at least, on average, near 20 3 He atoms are needed to get the bound state for 3 He liquid droplet. Depending on the choice of the density profiles and the atomic radius of 3 He, the above estimate can increase to 300. Our calculated ground state energy and the number of atoms in liquid 3 He droplet were compared with those of Variational Monte Carlo method, Diffusion Monte Carlo method and Density Functional Theory, for which a reasonable agreement was found.
Non-Gaussian ground-state deformations near a black-hole singularity
Hofmann, Stefan; Schneider, Marc
2017-03-01
The singularity theorem by Hawking and Penrose qualifies Schwarzschild black holes as geodesic incomplete space-times. Albeit this is a mathematically rigorous statement, it requires an operational framework that allows us to probe the spacelike singularity via a measurement process. Any such framework necessarily has to be based on quantum theory. As a consequence, the notion of classical completeness needs to be adapted to situations where the only adequate description is in terms of quantum fields in dynamical space-times. It is shown that Schwarzschild black holes turn out to be complete when probed by self-interacting quantum fields in the ground state and in excited states. The measure for populating quantum fields on hypersurfaces in the vicinity of the black-hole singularity goes to zero towards the singularity. This statement is robust under non-Gaussian deformations of and excitations relative to the ground state. The physical relevance of different completeness concepts for black holes is discussed.
2D XXZ model ground state properties using an analytic Lanczos expansion
International Nuclear Information System (INIS)
Witte, N.S.; Hollenberg, L.C.L.; Weihong Zheng
1997-01-01
A formalism was developed for calculating arbitrary expectation values for any extensive lattice Hamiltonian system using a new analytic Lanczos expansion, or plaquette expansion, and a recently proved exact theorem for ground state energies. The ground state energy, staggered magnetisation and the excited state gap of the 2D anisotropic antiferromagnetic Heisenberg Model are then calculated using this expansion for a range of anisotropy parameters and compared to other moment based techniques, such as the t-expansion, and spin-wave theory and series expansion methods. It was found that far from the isotropic point all moment methods give essentially very similar results, but near the isotopic point the plaquette expansion is generally better than the others. 20 refs., 6 tabs
Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation
Energy Technology Data Exchange (ETDEWEB)
Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Schöps, O.; Kolarczik, M.; Woggon, U.; Owschimikow, N. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Röhm, A.; Lingnau, B.; Lüdge, K. [Institut für Theoretische Physik, Technische Universität Berlin, Berlin (Germany); Schmeckebier, H.; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Mikhelashvili, V.; Eisenstein, G. [Technion Institute of Technology, Faculty of Electrical Engineering, Haifa (Israel)
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.
Towards the measurement of the ground-state hyperfine splitting of antihydrogen
Energy Technology Data Exchange (ETDEWEB)
Juhasz, Bertalan, E-mail: bertalan.juhasz@oeaw.ac.at [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)
2012-12-15
The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, which will consist of a superconducting cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of better than {approx} 10{sup - 6}. The first preliminary measurements of the hyperfine transitions will start in 2011.
Influence of mass-asymmetry and ground state spin on fission fragment angular distributions
International Nuclear Information System (INIS)
Thomas, R.G.; Biswas, D.C.; Saxena, A.; Pant, L.M.; Nayak, B.K.; Vind, R.P.; Sahu, P.K.; Sinha, Shrabani; Choudhury, R.K.
2001-01-01
The strong influence of the target or/and projectile ground state spin on the anomalously large anisotropies of fission fragments produced in the heavy-ion induced fission of actinide targets were reported earlier. Interestingly, all those systems studied were having a mass asymmetry greater than the Businaro-Gallone critical asymmetry and hence the presence of pre-equilibrium fission was unambiguously ruled out. The observed anisotropies were successfully explained using the ECD-K-States model. It is of interest to know the influence of the target/projectile ground state spin on systems having an entrance channel mass asymmetry less than the critical value where pre-equilibrium fission cannot be ignored. With this motivation we performed measurements of fission fragment angular distributions of the 16 O+ 235 U (spin=7/2) system
Ground-state properties of K-isotopes from laser and $\\beta$-NMR spectroscopy
Lievens, P; Rajabali, M M; Krieger, A R
By combining high-resolution laser spectroscopy with $\\beta$-NMR spectroscopy on polarized K-beams we aim to establish the ground-state spins and magnetic moments of the neutron-rich $^{48,49,50,51}$K isotopes from N=29 to N=32. Spins and magnetic moments of the odd-K isotopes up to N=28 reveal an inversion of the ground-state, from the normal $\\,{I}$=3/2 ($\\pi{d}_{3/2}^{-1}$) in $^{41-45}$K$\\to\\,{I}$=1/2 ($\\pi{s}_{1/2}^{-1}$) in $^{47}$K. This inversion of the proton single particle levels is related to the strong proton $d_{3/2}$ - neutron $f_{7/2}$ interaction which lowers the energy of the $\\pi{d}_{3/2}$ single particle state when filling the $\
Green function iterative solution of ground state wave function for Yukawa potential
International Nuclear Information System (INIS)
Zhang Zhao
2003-01-01
The newly developed single trajectory quadrature method is applied to solve central potentials. First, based on the series expansion method an exact analytic solution of the ground state for Hulthen potential and an approximate solution for Yukawa potential are obtained respectively. Second, the newly developed iterative method based on Green function defined by quadratures along the single trajectory is applied to solve Yukawa potential using the Coulomb solution and Hulthen solution as the trial functions respectively. The results show that a more proper choice of the trial function will give a better convergence. To further improve the convergence the iterative method is combined with the variational method to solve the ground state wave function for Yukawa potential, using variational solutions of the Coulomb and Hulthen potentials as the trial functions. The results give much better convergence. Finally, the obtained critical screen coefficient is applied to discuss the dissociate temperature of J/ψ in high temperature QGP
Mandal, Sudhansu S.; Mukherjee, Sutirtha; Ray, Koushik
2018-03-01
A method for determining the ground state of a planar interacting many-electron system in a magnetic field perpendicular to the plane is described. The ground state wave-function is expressed as a linear combination of a set of basis functions. Given only the flux and the number of electrons describing an incompressible state, we use the combinatorics of partitioning the flux among the electrons to derive the basis wave-functions as linear combinations of Schur polynomials. The procedure ensures that the basis wave-functions form representations of the angular momentum algebra. We exemplify the method by deriving the basis functions for the 5/2 quantum Hall state with a few particles. We find that one of the basis functions is precisely the Moore-Read Pfaffian wave function.
Prospects for studies of ground-state proton decays with the Holifield Radioactive Ion Beam Facility
International Nuclear Information System (INIS)
Toth, K.S.
1994-01-01
By using radioactive ions from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory it should be possible to identify many new ground-state proton emitters in the mass region from Sn to Pb. During this production and search process the limits of stability on the proton-rich side of the nuclidic chart will be delineated for a significant fraction of medium-weight elements and our understanding of the proton-emission process will be expanded and improved
Ground-state triply and doubly heavy baryons in a relativistic three-quark model
International Nuclear Information System (INIS)
Martynenko, A.P.
2008-01-01
Mass spectra of the ground-state baryons consisting of three or two heavy (b or c) and one light (u,d,s) quarks are calculated in the framework of the relativistic quark model and the hyperspherical expansion. The predictions of masses of the triply and doubly heavy baryons are obtained by employing the perturbation theory for the spin-independent and spin-dependent parts of the three-quark Hamiltonian
Ground state representation of the infinite one-dimensional Heisenberg ferromagnet. Pt. 2
International Nuclear Information System (INIS)
Babbitt, D.; Thomas, L.
1977-01-01
In its ground state representation, the infinite, spin 1/2 Heisenberg chain provides a model for spin wave scattering, which entails many features of the quantum mechanical N-body problem. Here, we give a complete eigenfunction expansion for the Hamiltonian of the chain in this representation, for all numbers of spin waves. Our results resolve the questions of completeness and orthogonality of the eigenfunctions given by Bethe for finite chains, in the infinite volume limit. (orig.) [de
Czech Academy of Sciences Publication Activity Database
Vackář, Jiří; Šipr, Ondřej; Šimůnek, Antonín
2008-01-01
Roč. 77, č. 4 (2008), 045112/1-045112/6 ISSN 1098-0121 R&D Projects: GA AV ČR IAA100100514; GA AV ČR(CZ) IAA100100637 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : core levels * ab-initio calculations * electronic states * ground state properties Subject RIV: BE - Theoretical Physics Impact factor: 3.322, year: 2008
International Nuclear Information System (INIS)
Radozycki, T.
1990-01-01
The properties of the virtual cloud around the hydrogen atom in the ground state are studied with the use of quantum field theory methods. The relativistic expression for the electromagnetic energy density around the atom, with the electron spin taken into account, is obtained. The distribution of the angular momentum contained in the cloud and the self-interaction kernel for the electrons bound in atom are also investigated. (author)
Ground-state projection multigrid for propagators in 4-dimensional SU(2) gauge fields
International Nuclear Information System (INIS)
Kalkreuter, T.
1991-09-01
The ground-state projection multigrid method is studied for computations of slowly decaying bosonic propagators in 4-dimensional SU(2) lattice gauge theory. The defining eigenvalue equation for the restriction operator is solved exactly. Although the critical exponent z is not reduced in nontrivial gauge fields, multigrid still yields considerable speedup compared with conventional relaxation. Multigrid is also able to outperform the conjugate gradient algorithm. (orig.)
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.
Stable π-Extended p -Quinodimethanes: Synthesis and Tunable Ground States
Zeng, Zebing
2014-12-18
© 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. p-Quinodimethane (p-QDM) is a highly reactive hydrocarbon showing large biradical character in the ground state. It has been demonstrated that incorporation of the p-QDM moiety into an aromatic hydrocarbon framework could lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. On the other hand, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. Therefore, the synthesis of stable π-extended p-QDMs is very challenging. In this Personal Account we will briefly discuss different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties, including two types of polycyclic hydrocarbons: (1) tetrabenzo-Tschitschibabin\\'s hydrocarbons, and (2) tetracyano-rylenequinodimethanes. We will discuss how the aromaticity, substituents and steric hindrance play important roles in determining their ground states and properties. Incorporation of the p-quinodimethane moiety into aromatic hydrocarbon frameworks can lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. Furthermore, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. In this Personal Account, different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties are briefly discussed, including the roles of aromaticity, substituents and steric hindrance.
Effect of the ground state correlations in the density distribution and zero point fluctuations
International Nuclear Information System (INIS)
Barranco, F.; Broglia, R.A.
1985-01-01
The existence of collective vibrations in the spectrum implies that the description of the ground state in an independent particle model must be corrected. This is because of the zero point fluctuations induced by the collective vibrations, so that ground state correlations have to be included. These are taken into account via the diagrammatic expansion of the Nuclear Field Theory, giving place to a renormalization in the different properties of the ground state. As far as the density distribution is concerned, in a NFT consistent calculation, the largest contributions arise from diagrams that cannot be expressed in terms of backward going amplitudes of the phonon RPA wave function. For a given multipolarity the main correction comes from the low lying state. The giant resonance is of smaller relevance since it lies at larger energies in the response function. The octupole modes give the dominant contribution, and the effect in average becomes smaller as the multipolarity increases. These results agree quite well with those obtained taking into account the zero point fluctuations of the nuclear surface in the collective model with the Esbensen and Bertsch prescription, which the authors use to explain the anomalous behaviour of the mean square radii of the Calcium isotopes
Random interactions, isospin, and the ground states of odd-A and odd-odd nuclei
International Nuclear Information System (INIS)
Horoi, Mihai; Volya, Alexander; Zelevinsky, Vladimir
2002-01-01
It was recently shown that the ground state quantum numbers of even-even nuclei have a high probability to be reproduced by an ensemble of random but rotationally invariant two-body interactions. In the present work we extend these investigations to odd-A and odd-odd nuclei, considering in particular the isospin effects. Studying the realistic shell model as well as the single-j model, we show that random interactions have a tendency to assign the lowest possible total angular momentum and isospin to the ground state. In the sd shell model this reproduces correctly the isospin but not the spin quantum numbers of actual odd-odd nuclei. An odd-even staggering effect in probability of various ground state quantum numbers is present for even-even and odd-odd nuclei, while it is smeared out for odd-A nuclei. The observed regularities suggest the underlying mechanism of bosonlike pairing of fermionic pairs in T=0 and T=1 states generated by the off-diagonal matrix elements of random interactions. The relation to the models of random spin interactions is briefly discussed
Exact ground state of finite Bose-Einstein condensates on a ring
International Nuclear Information System (INIS)
Sakmann, Kaspar; Streltsov, Alexej I.; Alon, Ofir E.; Cederbaum, Lorenz S.
2005-01-01
The exact ground state of the many-body Schroedinger equation for N bosons on a one-dimensional ring interacting via a pairwise δ-function interaction is presented for up to 50 particles. The solutions are obtained by solving Lieb and Liniger's system of coupled transcendental equations numerically for finite N. The ground-state energies for repulsive and attractive interactions are shown to be smoothly connected at the point of zero interaction strength, implying that the Bethe ansatz can be used also for attractive interactions for all cases studied. For repulsive interactions the exact energies are compared to (i) Lieb and Liniger's thermodynamic limit solution and (ii) the Tonks-Girardeau gas limit. It is found that the energy of the thermodynamic limit solution can differ substantially from that of the exact solution for finite N when the interaction is weak or when N is small. A simple relation between the Tonks-Girardeau gas limit and the solution for finite interaction strength is revealed. For attractive interactions we find that the true ground-state energy is given to a good approximation by the energy of the system of N attractive bosons on an infinite line, provided the interaction is stronger than the critical interaction strength of mean-field theory
DEFF Research Database (Denmark)
Johnsen, Kristinn; Yngvason, Jakob
1996-01-01
We report on a numerical study of the density matrix functional introduced by Lieb, Solovej, and Yngvason for the investigation of heavy atoms in high magnetic fields. This functional describes exactly the quantum mechanical ground state of atoms and ions in the limit when the nuclear charge Z...... and the electron number N tend to infinity with N/Z fixed, and the magnetic field B tends to infinity in such a way that B/Z4/3→∞. We have calculated electronic density profiles and ground-state energies for values of the parameters that prevail on neutron star surfaces and compared them with results obtained...... by other methods. For iron at B=1012 G the ground-state energy differs by less than 2% from the Hartree-Fock value. We have also studied the maximal negative ionization of heavy atoms in this model at various field strengths. In contrast to Thomas-Fermi type theories atoms can bind excess negative charge...
Ground state properties of a spin chain within Heisenberg model with a single lacking spin site
International Nuclear Information System (INIS)
Mebrouki, M.
2011-01-01
The ground state and first excited state energies of an antiferromagnetic spin-1/2 chain with and without a single lacking spin site are computed using exact diagonalization method, within the Heisenberg model. In order to keep both parts of a spin chain with a lacking site connected, next nearest neighbors interactions are then introduced. Also, the Density Matrix Renormalization Group (DMRG) method is used, to investigate ground state energies of large system sizes; which permits us to inquire about the effect of large system sizes on energies. Other quantum quantities such as fidelity and correlation functions are also studied and compared in both cases. - Research highlights: → In this paper we compute ground state and first excited state energies of a spin chain with and without a lacking spin site. The next nearest neighbors are introduced with the antiferromagnetic Heisenberg spin-half. → Exact diagonalization is used for small systems, where DMRG method is used to compute energies for large systems. Other quantities like quantum fidelity and correlation are also computed. → Results are presented in figures with comments. → E 0 /N is computed in a function of N for several values of J 2 and for both systems. First excited energies are also investigated.
Emergent Ising degrees of freedom above a double-stripe magnetic ground state
Zhang, Guanghua; Flint, Rebecca
2017-12-01
Double-stripe magnetism [Q =(π /2 ,π /2 )] has been proposed as the magnetic ground state for both the iron-telluride and BaTi2Sb2O families of superconductors. Double-stripe order is captured within a J1-J2-J3 Heisenberg model in the regime J3≫J2≫J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π ,π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one.
Kvaal, Simen; Helgaker, Trygve
2015-11-14
The relationship between the densities of ground-state wave functions (i.e., the minimizers of the Rayleigh-Ritz variation principle) and the ground-state densities in density-functional theory (i.e., the minimizers of the Hohenberg-Kohn variation principle) is studied within the framework of convex conjugation, in a generic setting covering molecular systems, solid-state systems, and more. Having introduced admissible density functionals as functionals that produce the exact ground-state energy for a given external potential by minimizing over densities in the Hohenberg-Kohn variation principle, necessary and sufficient conditions on such functionals are established to ensure that the Rayleigh-Ritz ground-state densities and the Hohenberg-Kohn ground-state densities are identical. We apply the results to molecular systems in the Born-Oppenheimer approximation. For any given potential v ∈ L(3/2)(ℝ(3)) + L(∞)(ℝ(3)), we establish a one-to-one correspondence between the mixed ground-state densities of the Rayleigh-Ritz variation principle and the mixed ground-state densities of the Hohenberg-Kohn variation principle when the Lieb density-matrix constrained-search universal density functional is taken as the admissible functional. A similar one-to-one correspondence is established between the pure ground-state densities of the Rayleigh-Ritz variation principle and the pure ground-state densities obtained using the Hohenberg-Kohn variation principle with the Levy-Lieb pure-state constrained-search functional. In other words, all physical ground-state densities (pure or mixed) are recovered with these functionals and no false densities (i.e., minimizing densities that are not physical) exist. The importance of topology (i.e., choice of Banach space of densities and potentials) is emphasized and illustrated. The relevance of these results for current-density-functional theory is examined.
Kamnev, Alexander A.; Tugarova, Anna V.; Dyatlova, Yulia A.; Tarantilis, Petros A.; Grigoryeva, Olga P.; Fainleib, Alexander M.; De Luca, Stefania
2018-03-01
A set of experimental data obtained by Fourier transform infrared (FTIR) spectroscopy (involving the use of samples ground and pressed with KBr, i.e. in a polar halide matrix) and by matrix-free transmission FTIR or diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic methodologies (involving measurements of thin films or pure powdered samples, respectively) were compared for several different biomacromolecular substances. The samples under study included poly-3-hydroxybutyrate (PHB) isolated from cell biomass of the rhizobacterium Azospirillum brasilense; dry PHB-containing A. brasilense biomass; pectin (natural carboxylated heteropolysaccharide of plant origin; obtained from apple peel) as well as its chemically modified derivatives obtained by partial esterification of its galacturonide-chain hydroxyl moieties with palmitic, oleic and linoleic acids. Significant shifts of some FTIR vibrational bands related to polar functional groups of all the biomacromolecules under study, induced by the halide matrix used for preparing the samples for spectroscopic measurements, were shown and discussed. A polar halide matrix used for preparing samples for FTIR measurements was shown to be likely to affect band positions not only per se, by affecting band energies or via ion exchange (e.g., with carboxylate moieties), but also by inducing crystallisation of metastable amorphous biopolymers (e.g., PHB of microbial origin). The results obtained have important implications for correct structural analyses of polar, H-bonded and/or amphiphilic biomacromolecular systems using different methodologies of FTIR spectroscopy.
Infrared detectors and emitters on the basis of semiconductor quantum structures
International Nuclear Information System (INIS)
Kruck, P. R.
1997-08-01
Intersubband transitions in Si/SiGe and GaAs/AlGaAs semiconductor quantum structures have been investigated with respect to possible application as infrared detectors and emitters. Investigation of the polarization dependence of subband absorption in Si/SiGe quantum wells shows both transverse magnetic and transverse electric polarized excitations. Intersubband transitions to several excited states are identified by comparison with self-consistent Luttinger-Kohn type calculations. On the basis of these investigations a quantum well infrared photodetector operating between 3 and 8 μm with a detectivity as high as D*=2 x 10 10 cm Hz 1/2 W -1 under normal incidence illumination and at an operating temperature of T=77K is realized. The polarization dependence of the photoconductivity shows the importance of both the absorption and the vertical transport properties of the photoexcited carriers for the detection mechanism. On the basis of the GaAs/AlGaAs material system a unipolar quantum cascade light emitting diode (LED) has been realized. The LED operates at a wavelength of 6.9 μm. A detailed analysis of the electroluminescence spectra shows a linewidth as narrow as 14 meV at cryogenic temperatures, increasing to 20 meV at room temperature. For typical drive-current densities of 1 kA/cm 2 the optical output power lies in the ten nanowatt range. (author)
Energy Technology Data Exchange (ETDEWEB)
Chen, Guang-Ping [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Zhi-Yuan [The School of Physics and Mech-tronic Engineering, Sichuan University of Art and Science, DaZhou 635000 (China); Dong, Biao [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Lin-Xue [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Zhang, Xiao-Fei, E-mail: xfzhang@ntsc.ac.cn [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); Zhang, Shou-Gang, E-mail: szhang@ntsc.ac.cn [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China)
2015-10-02
We consider a two-component Bose–Einstein condensate under extreme elongation in a harmonic plus quartic trap. The ground-state and rotational properties of such a system are numerically studied as a function of intra- and inter-component contact interactions, and of the rotational frequency. For the nonrotational case, we obtain the exact phase diagram showing the ground-state density distributions as contact-interactions varied. For both slowly and ultrarapidly rotational cases, we demonstrate that the vortex configurations depend strongly on the relative strength of the contact interactions, as well as on the rotational frequency. The controllable system may be used to investigate the interplay of interaction and rotation, and to explore more exotic quantum phases. - Highlights: • Quartic trap extends the parameter space to a fast rotating region. • Different ground state density distributions and novel vortex structures are obtained within the full parameter space. • Effects of the contact interactions and rotation are discussed in detail.
International Nuclear Information System (INIS)
Chen, Guang-Ping; Zhang, Zhi-Yuan; Dong, Biao; Wang, Lin-Xue; Zhang, Xiao-Fei; Zhang, Shou-Gang
2015-01-01
We consider a two-component Bose–Einstein condensate under extreme elongation in a harmonic plus quartic trap. The ground-state and rotational properties of such a system are numerically studied as a function of intra- and inter-component contact interactions, and of the rotational frequency. For the nonrotational case, we obtain the exact phase diagram showing the ground-state density distributions as contact-interactions varied. For both slowly and ultrarapidly rotational cases, we demonstrate that the vortex configurations depend strongly on the relative strength of the contact interactions, as well as on the rotational frequency. The controllable system may be used to investigate the interplay of interaction and rotation, and to explore more exotic quantum phases. - Highlights: • Quartic trap extends the parameter space to a fast rotating region. • Different ground state density distributions and novel vortex structures are obtained within the full parameter space. • Effects of the contact interactions and rotation are discussed in detail
Ektarawong, A.
2018-05-01
The phase stability of icosahedral boron subselenide B12(B1-xSex) 2 , where 0.5 ≤x ≤1 , is explored using a first-principles cluster expansion. The results shows that, instead of a continuous solid solution, B12(B1-xSex) 2 is thermodynamically stable as an individual line compound at the composition of B9.5Se . The ground-state configuration of B9.5Se is represented by a mixture of B12(Se-Se), B12(B-Se), and B12(Se-B) with a ratio of 1:1:1, where they form a periodic A B C A B C ⋯ stacking sequence of B12(Se-Se), B12(B-Se), and B12(Se-B) layers along the c axis of the hexagonal conventional unit cell. The structural and electronic properties of the ground-state B9.5Se are also derived and discussed. By comparing the derived ground-state properties of B9.5Se to the existing experimental data of boron subselenide B˜13Se , I proposed that the as-synthesized boron subselenide B˜13Se , as reported in the literature, has the actual composition of B9.5Se .
Ogura, Hiroshi; Evans, John P.; Peng, Dungeng; Satterlee, James D.; de Montellano, Paul R. Ortiz; Mar, Gerd N. La
2009-01-01
The active site electronic structure of the azide complex of substrate-bound human heme oxygenase-1, (hHO) has been investigated by 1H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. 2D 1H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts, that places the lone iron π-spin in the dxz orbital, rather than the dyz orbital found in the cyanide complex. Comparison of iron spin relaxivity, magnetic anisotropy and magnetic susceptibilities argues for a low-spin, (dxy)2(dyz,dxz)3, ground state in both azide and cyanide complexes. The switch from singly-occupied dyz for the cyanide to dxz for the azide complex of hHO is shown to be consistent with the orbital hole determined by the azide π-plane in the latter complex, which is ∼90° in-plane rotated from that of the imidazole π-plane. The induction of the altered orbital ground state in the azide relative to the cyanide hHO complex, as well as the mean low-field bias of methyl hyperfine shifts and their paramagnetic relaxivity relative to those in globins, indicate that azide exerts a stronger ligand field in hHO than in the globins, or that the distal H-bonding to azide is weaker in hHO than in globins. The Asp140 → Ala hHO mutant that abolishes activity retains the unusual WT azide complex spin/orbital ground state. The relevance of our findings for other HO complexes and the HO mechanism is discussed. PMID:19243105
Ogura, Hiroshi; Evans, John P; Peng, Dungeng; Satterlee, James D; Ortiz de Montellano, Paul R; La Mar, Gerd N
2009-04-14
The active site electronic structure of the azide complex of substrate-bound human heme oxygenase 1 (hHO) has been investigated by (1)H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. Two-dimensional (1)H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts that places the lone iron pi-spin in the d(xz) orbital, rather than the d(yz) orbital found in the cyanide complex. Comparison of iron spin relaxivity, magnetic anisotropy, and magnetic susceptibilities argues for a low-spin, (d(xy))(2)(d(yz),d(xz))(3), ground state in both azide and cyanide complexes. The switch from singly occupied d(yz) for the cyanide to d(xz) for the azide complex of hHO is shown to be consistent with the orbital hole determined by the azide pi-plane in the latter complex, which is approximately 90 degrees in-plane rotated from that of the imidazole pi-plane. The induction of the altered orbital ground state in the azide relative to the cyanide hHO complex, as well as the mean low-field bias of methyl hyperfine shifts and their paramagnetic relaxivity relative to those in globins, indicates that azide exerts a stronger ligand field in hHO than in the globins, or that the distal H-bonding to azide is weaker in hHO than in globins. The Asp140 --> Ala hHO mutant that abolishes activity retains the unusual WT azide complex spin/orbital ground state. The relevance of our findings for other HO complexes and the HO mechanism is discussed.
Application of far-infrared spectroscopy to the structural identification of protein materials.
Han, Yanchen; Ling, Shengjie; Qi, Zeming; Shao, Zhengzhong; Chen, Xin
2018-05-03
Although far-infrared (IR) spectroscopy has been shown to be a powerful tool to determine peptide structure and to detect structural transitions in peptides, it has been overlooked in the characterization of proteins. Herein, we used far-IR spectroscopy to monitor the structure of four abundant non-bioactive proteins, namely, soybean protein isolate (SPI), pea protein isolate (PPI) and two types of silk fibroins (SFs), domestic Bombyx mori and wild Antheraea pernyi. The two globular proteins SPI and PPI result in broad and weak far-IR bands (between 50 and 700 cm-1), in agreement with those of some other bioactive globular proteins previously studied (lysozyme, myoglobin, hemoglobin, etc.) that generally only have random amino acid sequences. Interestingly, the two SFs, which are characterized by a structure composed of highly repetitive motifs, show several sharp far-IR characteristic absorption peaks. Moreover, some of these characteristic peaks (such as the peaks at 260 and 428 cm-1 in B. mori, and the peaks at 245 and 448 cm-1 in A. pernyi) are sensitive to conformational changes; hence, they can be directly used to monitor conformational transitions in SFs. Furthermore, since SF absorption bands clearly differ from those of globular proteins and different SFs even show distinct adsorption bands, far-IR spectroscopy can be applied to distinguish and determine the specific SF component within protein blends.
Infrared Spectroscopic Study For Structural Investigation Of Lithium Lead Silicate Glasses
International Nuclear Information System (INIS)
Ahlawat, Navneet; Aghamkar, Praveen; Ahlawat, Neetu; Agarwal, Ashish; Monica
2011-01-01
Lithium lead silicate glasses with composition 30Li 2 O·(70-x)PbO·xSiO 2 (where, x = 10, 20, 30, 40, 50 mol %)(LPS glasses) were prepared by normal melt quench technique at 1373 K for half an hour in air to understand their structure. Compositional dependence of density, molar volume and glass transition temperature of these glasses indicates more compactness of the glass structure with increasing SiO 2 content. Fourier transform infrared (FTIR) spectroscopic data obtained for these glasses was used to investigate the changes induced in the local structure of samples as the ratio between PbO and SiO 2 content changes from 6.0 to 0.4. The observed absorption band around 450-510 cm -1 in IR spectra of these glasses indicates the presence of network forming PbO 4 tetrahedral units in glass structure. The increase in intensity with increasing SiO 2 content (upto x = 30 mol %) suggests superposition of Pb-O and Si-O bond vibrations in absorption band around 450-510 cm -1 . The values of optical basicity in these glasses were found to be dependent directly on PbO/SiO 2 ratio.
Energy Technology Data Exchange (ETDEWEB)
Inami, H. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Armus, L.; Stierwalt, S.; Díaz-Santos, T.; Surace, J.; Howell, J.; Marshall, J. [Spitzer Science Center, California Institute of Technology, CA 91125 (United States); Charmandaris, V. [Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion (Greece); Groves, B. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Kewley, L. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Petric, A. [Department of Astronomy, California Institute of Technology, MS 320-47, Pasadena, CA 91125 (United States); Rich, J. [The Observatories, Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Haan, S. [CSIRO Astronomy and Space Science, Marsfield, NSW 2122 (Australia); Evans, A. S. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Mazzarella, J.; Lord, S. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Appleton, P. [NASA Herschel Science Center, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Spoon, H. [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Frayer, D. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Matsuhara, H., E-mail: inami@noao.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (Japan); and others
2013-11-10
We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [S IV], [Ne II], [Ne V], [Ne III], [S III]{sub 18.7{sub μm}}, [O IV], [Fe II], [S III]{sub 33.5{sub μm}}, and [Si II]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [Ne V]/[Ne II] line flux ratios and equivalent width of the 6.2 μm polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [S IV]/[Ne II] and [Ne III]/[Ne II] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2 Z{sub ☉}, and ionization parameters of 2-8 × 10{sup 7} cm s{sup –1}. Based on the [S III]{sub 33.5{sub μm}}/[S III]{sub 18.7{sub μm}} ratios, the electron density in LIRG nuclei is typically one to a few hundred cm{sup –3}, with a median electron density of ∼300 cm{sup –3}, for those sources above the low density limit for these lines. We also find that strong shocks are likely present in 10 starburst-dominated sources of our sample. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM ≥600 km s{sup –1}) and five show clear differences in the velocities of the [Ne III] or [Ne V] emission lines, relative to [Ne II], of more than 200 km s{sup –1}. Furthermore, six starburst and five active galactic nucleus dominated LIRGs show a clear trend of increasing line width with ionization potential
Ground state of the U{sub 2}Mo compound: Physical properties of the Ω-phase
Energy Technology Data Exchange (ETDEWEB)
Losada, E.L. [SIM3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E., E-mail: garces@cab.cnea.gov.ar [GIA, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina)
2016-10-15
Using ab initio calculations, unexpected structural instability was recently found in the ground state of the U{sub 2} Mo compound. Instead of the unstable I4/mmm and the Pmmn structures, in this work the P6/mmm (#191) space group, usually called Ω-phase, is proposed as the fundamental state. Total energy calculations using Wien2k code slightly favoured the last structure. Electronic and elastic properties are studied in this work in order to characterize the physical properties of this new phase. The stability of the Ω-phase is studied by means of its elastic constants calculation and phonon dispersion spectrum. Analysis of isotropic indices shows that the new phase is a ductile material with a minimal degree of anisotropy, suggesting that U{sub 2} Mo in the P6/mmm structure is an elastic isotropic material. Analysis of charge density, density of electronic states (DOS) and the character of the bands revealed a high level of hybridization between d-molybdenum electronic states and d- and f-uranium ones.
Directory of Open Access Journals (Sweden)
Khodakov A.
1999-07-01
Full Text Available The effect of wetting on the structure and localisation of cobalt species on various supports (Al2O3, SiO2, TiO2, HZSM-5 zeolite was studied using X-ray diffraction, Fourier transform infrared spectroscopy with CO as a molecular probe, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis. Aqueous impregnation to incipient wetness of reduced and passivated cobalt catalysts results, even in the absence of any promoter, in a considerable decrease in the concentration of Co crystalline phases and modifies the surface sites. The decrease in the concentration of Co3O4 crystallites was especially pronounced on silica supported catalysts prepared via impregnation of cobalt and on a mixture of Co3O4 and HZSM-5 zeolite. Saturation with water of the passivated Co/SiO2 sample results in an amorphous solid with a local structure close to that of Co2SiO4. For Co/Al2O3 and Co/TiO2 catalysts, the effect of wetting on the concentration of Co3O4 crystalline phase was considerably smaller.
The structure of betaxolol studied by infrared spectroscopy and natural bond orbital theory.
Canotilho, João; Castro, Ricardo A E
2010-08-01
Betaxolol is a selective beta(1) receptor blocker used in the treatment of hypertension and glaucoma. A study of the betaxolol structure based on infrared spectroscopy and natural bond orbital (NBO) theory is the main aim of the present research. FTIR spectra of the solid betaxolol were recorded in the region from 4000 to 400cm(-1), in the temperature range between 25 and -170 degrees C. For spectral interpretation, spectrum of the deuterated betaxolol and the theoretical vibrational spectra of the conformer present in the solid obtained at the B3LYP/6-31G* level of theory, were used. Further insight into the structure was provided by natural bond orbital theory. NBO analysis of the conformer, before and after optimization, was carried out at the same level of theory referred above. Vibrational modes involved in hydrogen bond in the stretching and bending region were used in the estimation of the enthalpy using empirical correlations between enthalpy and the frequency shift that occurs as a result of the establishment of intermolecular hydrogen bonds. A detailed study of the structure of betaxolol and of its intermolecular interactions was obtained from the combination spectroscopy and NBO theory. Copyright 2010 Elsevier B.V. All rights reserved.
Zhang, Changjiang; Dai, Lijie; Ma, Leiming; Qian, Jinfang; Yang, Bo
2017-10-01
An objective technique is presented for estimating tropical cyclone (TC) innercore two-dimensional (2-D) surface wind field structure using infrared satellite imagery and machine learning. For a TC with eye, the eye contour is first segmented by a geodesic active contour model, based on which the eye circumference is obtained as the TC eye size. A mathematical model is then established between the eye size and the radius of maximum wind obtained from the past official TC report to derive the 2-D surface wind field within the TC eye. Meanwhile, the composite information about the latitude of TC center, surface maximum wind speed, TC age, and critical wind radii of 34- and 50-kt winds can be combined to build another mathematical model for deriving the innercore wind structure. After that, least squares support vector machine (LSSVM), radial basis function neural network (RBFNN), and linear regression are introduced, respectively, in the two mathematical models, which are then tested with sensitivity experiments on real TC cases. Verification shows that the innercore 2-D surface wind field structure estimated by LSSVM is better than that of RBFNN and linear regression.
Sini, Gjergji; Sears, John S.; Brédas, Jean-Luc
2011-01-01
We have evaluated the performance of several density functional theory (DFT) functionals for the description of the ground-state electronic structure and charge transfer in donor/acceptor complexes. The tetrathiafulvalene- tetracyanoquinodimethane (TTF-TCNQ) complex has been considered as a model test case. Hybrid functionals have been chosen together with recently proposed long-range corrected functionals (ωB97X, ωB97X-D, LRC-ωPBEh, and LC-ωPBE) in order to assess the sensitivity of the results to the treatment and magnitude of exact exchange. The results show an approximately linear dependence of the ground-state charge transfer with the HOMO TTF-LUMOTCNQ energy gap, which in turn depends linearly on the percentage of exact exchange in the functional. The reliability of ground-state charge transfer values calculated in the framework of a monodeterminantal DFT approach was also examined. © 2011 American Chemical Society.
Sini, Gjergji
2011-03-08
We have evaluated the performance of several density functional theory (DFT) functionals for the description of the ground-state electronic structure and charge transfer in donor/acceptor complexes. The tetrathiafulvalene- tetracyanoquinodimethane (TTF-TCNQ) complex has been considered as a model test case. Hybrid functionals have been chosen together with recently proposed long-range corrected functionals (ωB97X, ωB97X-D, LRC-ωPBEh, and LC-ωPBE) in order to assess the sensitivity of the results to the treatment and magnitude of exact exchange. The results show an approximately linear dependence of the ground-state charge transfer with the HOMO TTF-LUMOTCNQ energy gap, which in turn depends linearly on the percentage of exact exchange in the functional. The reliability of ground-state charge transfer values calculated in the framework of a monodeterminantal DFT approach was also examined. © 2011 American Chemical Society.
Energy Technology Data Exchange (ETDEWEB)
Harrington, B J; Shepard, H K [New Hampshire Univ., Durham (USA). Dept. of Physics
1976-03-22
By fully exploiting the mathematical and physical analogy to the Ginzburg-Landau theory of superconductivity, a complete discussion of the ground state behavior of the four-dimensional Abelian Higgs model in the static tree level approximation is presented. It is shown that a sufficiently strong external magnetic field can alter the ground state of the theory by restoring a spontaneously broken symmetry, or by creating a qualitatively different 'vortex' state. The energetically favored ground state is explicitly determined as a function of the external field and the ratio between coupling constants of the theory.
International Nuclear Information System (INIS)
Yuan Qingxin; Ding Guohui
2005-01-01
We investigate the phenomena of symmetry breaking and phase transition in the ground state of Bose-Einstein condensates (BECs) trapped in a double square well and in an optical lattice well, respectively. By using standing-wave expansion method, we present symmetric and asymmetric ground state solutions of nonlinear Schroedinger equation (NLSE) with a symmetric double square well potential for attractive nonlinearity. In particular, we study the ground state wave function's properties by changing the depth of potential and atomic interactions (here we restrict ourselves to the attractive regime). By using the Fourier grid Hamiltonian method, we also reveal a phase transition of BECs trapped in one-dimensional optical lattice potential.
International Nuclear Information System (INIS)
Paraan, Francis N. C.; Korepin, Vladimir E.
2010-01-01
We calculate the first-order perturbation correction to the ground-state energy and chemical potential of a harmonically trapped boson gas with contact interactions about the infinite repulsion Tonks-Girardeau limit. With c denoting the interaction strength, we find that, for a large number of particles N, the 1/c correction to the ground-state energy increases as N 5/2 , in contrast to the unperturbed Tonks-Girardeau value that is proportional to N 2 . We describe a thermodynamic scaling limit for the trapping frequency that yields an extensive ground-state energy and reproduces the zero temperature thermodynamics obtained by a local-density approximation.
Gropengiesser, Uwe
1995-06-01
We compare various evlutionary strategies to determine the ground-state energy of the ± J spin glass. We show that the choice of different evolution laws is less important than a suitable treatment of the "free spins" of the system At least one combination of these strategies does not give the correct results, but the ground states of the other different strategies coincide. Therefore we are able to extrapolate the infinit-size ground-state energy for the square lattice to -1.401±0.0015 and for the simple cubic lattice to -1.786±0.004.
International Nuclear Information System (INIS)
Cirak, C.; Saglam, A.; Ucun, F.
2010-01-01
The ground state hydrogen conformations of 2-, 3-, 4- and 5-dihydroxybenzaldehyde have been investigated using density functional theory (B3LYP) methods with 6-31G (d,p) basis set. The calculations have indicated that the compounds in the ground state exist with the carbonyl group O atom linked intra molecularly by the two hydrogen bonds of the two hydroxyl groups. The vibrational analyses of the ground state conformers of all the compounds were done and their optimized geometry parameters were given.
Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model
International Nuclear Information System (INIS)
Canko, Osman; Keskin, Mustafa; Deviren, Bayram
2008-01-01
We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and J 0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found
Structure of the Large Magellanic Cloud from near infrared magnitudes of red clump stars
Subramanian, S.; Subramaniam, A.
2013-04-01
Context. The structural parameters of the disk of the Large Magellanic Cloud (LMC) are estimated. Aims: We used the JH photometric data of red clump (RC) stars from the Magellanic Cloud Point Source Catalog (MCPSC) obtained from the InfraRed Survey Facility (IRSF) to estimate the structural parameters of the LMC disk, such as the inclination, i, and the position angle of the line of nodes (PAlon), φ. Methods: The observed LMC region is divided into several sub-regions, and stars in each region are cross-identified with the optically identified RC stars to obtain the near infrared magnitudes. The peak values of H magnitude and (J - H) colour of the observed RC distribution are obtained by fitting a profile to the distributions and by taking the average value of magnitude and colour of the RC stars in the bin with largest number. Then the dereddened peak H0 magnitude of the RC stars in each sub-region is obtained from the peak values of H magnitude and (J - H) colour of the observed RC distribution. The right ascension (RA), declination (Dec), and relative distance from the centre of each sub-region are converted into x,y, and z Cartesian coordinates. A weighted least square plane fitting method is applied to this x,y,z data to estimate the structural parameters of the LMC disk. Results: An intrinsic (J - H)0 colour of 0.40 ± 0.03 mag in the Simultaneous three-colour InfraRed Imager for Unbiased Survey (SIRIUS) IRSF filter system is estimated for the RC stars in the LMC and a reddening map based on (J - H) colour of the RC stars is presented. When the peaks of the RC distribution were identified by averaging, an inclination of 25°.7 ± 1°.6 and a PAlon = 141°.5 ± 4°.5 were obtained. We estimate a distance modulus, μ = 18.47 ± 0.1 mag to the LMC. Extra-planar features which are both in front and behind the fitted plane are identified. They match with the optically identified extra-planar features. The bar of the LMC is found to be part of the disk within 500
Energy Technology Data Exchange (ETDEWEB)
Szalontai, G; Simon, Z; Csapo, Z; Farkas, M; Pfeifer, Gy [Nehezvegyipari Kutato Intezet, Veszprem (Hungary)
1980-01-01
The results obtained from the computer-aided interpretation of /sup 13/C NMR and IR spectra using the artificial intelligence approach are presented. In its present state the output of the system is a list of functional groups which are resonable candidates for the final structural isomers. The input requires empirical formula, /sup 13/C NMR data (off resonance data also) and IR spectral data. The confirmation of the presence of a functional group is based on comparison of the experimental data with the spectral properties of functional groups stored in a property matrix. If the molecular weight of the compounds studied is less or equal 500, the output contains usually 1.5-2.5 times more groups than really present, in most cases without the loss of the real ones.
Application of the random phase approximation to some atoms with ns2 ground state configurations
International Nuclear Information System (INIS)
Wright, L.A.
1975-01-01
Atomic bound state properties such as excitation energies and oscillator strengths were calculated by the Random Phase Approximation (RPA), also known as the Time Dependent Hartree-Fock Approximation (TDHFA). The RPA is equivalent to describing excited states as the creation of particle-hole pairs and the application to atoms is important for two reasons: the wide range of densities in an atom will cause the physical interpretation and mathematical approximations to be much different than with a uniform density system, such as an electron gas; this method could detect the existence of collective states in atoms similar to those responsible for the giant dipole resonances in nuclei. The method is shown to be superior to the H-F method in three basic ways: (1) The RPA contains explicit correlations between the excited and ground states. These are not included in the H-F theory. One can apply this method to large atoms since only these correlations are explicitly included. (2) The RPA calculates excitation energies directly without recourse to highly correlated ground state wavefunctions. This is in contrast to the method of configuration mixing which is known to have slow convergence properties. (3) Oscillator strengths and photoionization cross sections can be calculated by finding the eigenvectors corresponding excitation energy eigenvalues. The strength of the RPA is that the excitation energies and oscillator strengths, which are relative quantities, are calculated directly. The results for the oscillator strengths show an improvement of up to 45 percent over the H-F values and an improvement over the RPA done with Hartree wavefunctions by as much as 65 percent. The work was limited to atoms with an ns 2 ground state configuration. These atoms were He, Be, Mg and Ca
Spin-polarized ground state and exact quantization at ν=5/2
Pan, Wei
2002-03-01
The nature of the even-denominator fractional quantum Hall effect at ν=5/2 remains elusive, in particular, its ground state spin-polarization. An earlier, so-called "hollow core" model arrived at a spin-unpolarized wave function. The more recent calculations based on a model of BCS-like pairing of composite fermions, however, suggest that its ground state is spin-polarized. In this talk, I will first review the earlier experiments and then present our recent experimental results showing evidence for a spin-polarized state at ν=5/2. Our ultra-low temperature experiments on a high quality sample established the fully developed FQHE state at ν=5/2 as well as at ν=7/3 and 8/3, manifested by a vanishing R_xx and exact quantization of the Hall plateau. The tilted field experiments showed that the added in-plane magnetic fields not only destroyed the FQHE at ν=5/2, as seen before, but also induced an electrical anisotropy, which is now interpreted as a phase transition from a paired, spin-polarized ν=5/2 state to a stripe phase, not unlike the ones at ν=9/2, 11/2, etc in the N > 1 higher Landau levels. Furthermore, in the experiments on the heterojunction insulated-gate field-effect transistors (HIGFET) at dilution refrigerator temperatures, a strong R_xx minimum and a concomitant developing Hall plateau were observed at ν=5/2 in a magnetic field as high as 12.6 Tesla. This and the subsequent density dependent studies of its energy gap largely rule out a spin-singlet state and point quite convincingly towards a spin-polarized ground state at ν=5/2.
Isospin mixing in the ground state of sup 5 sup 2 Mn
Schuurmans, P; Phalet, T; Severijns, N; Vereecke, B; Versyck, S
2000-01-01
The presence of isospin mixing into the ground state of sup 5 sup 2 Mn was studied via anisotropic positron emission from nuclei. With this method the isospin forbidden Fermi-component in the Gamow-Teller dominated beta decay was determined. It is shown that sample purity and the control of positron scattering is of vital importance. Comparison between theory and experiment shows that shell model calculations of the isospin mixing probability deviate by a factor three to seven from experiment. For more recent Hartree-Fock-RPA based calculations the difference is over two orders of magnitude.
Ground state shape and crossing of near spherical and deformed bands in 182Hg
International Nuclear Information System (INIS)
Ma, W.C.; Ramayya, A.V.; Hamilton, J.H.; Robinson, S.J.; Barclay, M.E.; Zhao, K.; Cole, J.D.; Zganjar, E.F.; Spejewski, E.H.
1983-01-01
The energy levels of 182 Hg have been identified for the first time through comparison of in-beam studies of the reactions 156 154 Gd( 32 S,4n) 184 182 Hg. Levels up to 12 + in 182 Hg were established from γ-γ coincidence and singles measurement. The data establish that the ground state shape is near spherical, and that the ground band is crossed by a well deformed band at 4 + . In contrast to IBA model predictions that the deformed band will rise in energy in 182 Hg compared to 184 Hg, the energies of the deformed levels in 182 Hg continue to drop. 7 references
Directory of Open Access Journals (Sweden)
Zhigang Hu
2014-01-01
Full Text Available In this paper, we apply the method of the Nehari manifold to study the fractional differential equation (d/dt((1/2 0Dt-β(u′(t+(1/2 tDT-β(u′(t= f(t,u(t, a.e. t∈[0,T], and u0=uT=0, where 0Dt-β, tDT-β are the left and right Riemann-Liouville fractional integrals of order 0≤β<1, respectively. We prove the existence of a ground state solution of the boundary value problem.
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
Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation
International Nuclear Information System (INIS)
Albus, Alexander P.; Wilkens, Martin; Illuminati, Fabrizio
2003-01-01
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
Composite model approach to the 2He4 nucleus ground state
International Nuclear Information System (INIS)
Mehrotra, I.; Agarwal, B.K.
1986-12-01
Assuming that the nucleons are (πμ) composite systems the helium nucleus is compared to a molecule consisting of four hydrogen-like atoms where pions are like nuclei and muons are like electrons. Ground state energy of 2 He 4 nucleus has been estimated in the framework of valence-bond method. Good agreement with the experimental value can be obtained if it is assumed that μ + μ - coupling is 3% stronger than the μ ± μ ± coupling. (author). 11 refs, 1 tab
Relativistic Quadrupole Polarizability for the Ground State of Hydrogen-Like Ions
International Nuclear Information System (INIS)
Zhang Yong-Hu; Zhang Xian-Zhou; Tang Li-Yan; Shi Ting-Yun; Mitroy Jim
2012-01-01
The static quadrupole polarizabilities for hydrogen-like ions from Z = 1 to Z = 100 in the 1S 1/2 ground state are calculated to high precision by solving the Dirac equation using the B-spline Galerkin method. The results are consistent with the expression of Kaneko [J. Phys. B 10 (1977) 3347] at low Z. The quadrupole oscillator strength sum Σ n f (2) gn is computed to be zero to a very high degree of precision. (atomic and molecular physics)
Quantifying confidence in density functional theory predictions of magnetic ground states
Houchins, Gregory; Viswanathan, Venkatasubramanian
2017-10-01
Density functional theory (DFT) simulations, at the generalized gradient approximation (GGA) level, are being routinely used for material discovery based on high-throughput descriptor-based searches. The success of descriptor-based material design relies on eliminating bad candidates and keeping good candidates for further investigation. While DFT has been widely successfully for the former, oftentimes good candidates are lost due to the uncertainty associated with the DFT-predicted material properties. Uncertainty associated with DFT predictions has gained prominence and has led to the development of exchange correlation functionals that have built-in error estimation capability. In this work, we demonstrate the use of built-in error estimation capabilities within the BEEF-vdW exchange correlation functional for quantifying the uncertainty associated with the magnetic ground state of solids. We demonstrate this approach by calculating the uncertainty estimate for the energy difference between the different magnetic states of solids and compare them against a range of GGA exchange correlation functionals as is done in many first-principles calculations of materials. We show that this estimate reasonably bounds the range of values obtained with the different GGA functionals. The estimate is determined as a postprocessing step and thus provides a computationally robust and systematic approach to estimating uncertainty associated with predictions of magnetic ground states. We define a confidence value (c-value) that incorporates all calculated magnetic states in order to quantify the concurrence of the prediction at the GGA level and argue that predictions of magnetic ground states from GGA level DFT is incomplete without an accompanying c-value. We demonstrate the utility of this method using a case study of Li-ion and Na-ion cathode materials and the c-value metric correctly identifies that GGA-level DFT will have low predictability for NaFePO4F . Further, there
Topological Invariants and Ground-State Wave functions of Topological Insulators on a Torus
Directory of Open Access Journals (Sweden)
Zhong Wang
2014-01-01
Full Text Available We define topological invariants in terms of the ground-state wave functions on a torus. This approach leads to precisely defined formulas for the Hall conductance in four dimensions and the topological magnetoelectric θ term in three dimensions, and their generalizations in higher dimensions. They are valid in the presence of arbitrary many-body interactions and disorder. These topological invariants systematically generalize the two-dimensional Niu-Thouless-Wu formula and will be useful in numerical calculations of disordered topological insulators and strongly correlated topological insulators, especially fractional topological insulators.
Optimized RVB states of the 2-d antiferromagnet: ground state and excitation spectrum
Chen, Yong-Cong; Xiu, Kai
1993-10-01
The Gutzwiller projection of the Schwinger-boson mean-field solution of the 2-d spin- {1}/{2} antiferromagnet in a square lattice is shown to produce the optimized, parameter-free RVB ground state. We get -0.6688 J/site and 0.311 for the energy and the staggered magnetization. The spectrum of the excited states is found to be linear and gapless near k≅0. Our calculation suggests, upon breaking of the rotational symmetry, ɛ k≅2JZ r1-γ 2k with Zr≅1.23.
Light-cone distribution amplitudes of the ground state bottom baryons in HQET
Energy Technology Data Exchange (ETDEWEB)
Ali, A.; Wang, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hambrock, C. [Technische Univ. Dortmund (Germany); Parkhomenko, A.Ya. [P.G. Demidov Yaroslavl State Univ., Yaroslavl (Russian Federation)
2012-12-15
We provide the definition of the complete set of light-cone distribution amplitudes (LCDAs) for the ground state heavy bottom baryons with the spin-parities J{sup P}=1/2{sup +} and J{sup P}=3/2{sup +} in the heavy quark limit. We present the renormalization effects on the twist-2 light-cone distribution amplitudes and use the QCD sum rules to compute the moments of twist-2, twist-3, and twist-4 LCDAs. Simple models for the heavy baryon distribution amplitudes are analyzed with account of their scale dependence.
The ground state energy of a bound polaron in the presence of a magnetic field
Energy Technology Data Exchange (ETDEWEB)
Zorkani, I [International Centre for Theoretical Physics, Trieste (Italy); Belhissi, R [Faculte des Sciences Dhar Mahraz, Fes (Morocco). Dept. de Physique
1995-09-01
A theoretical calculation for the ground state energy of a bound polaron as a function of the magnetic field is presented. The theory is based on a variational approach using a trial wave function proposed by Devreese et al. in the absence of the magnetic field. It was shown that his function is adequate for all electron - phonon coupling {alpha} and all parameter {gamma}{sub 0} which is the ratio between the L.O. phonon energy and the Colombian one. Analytical results are obtained in the weak coupling limit. (author). 27 refs, 4 figs, 1 tab.
Positive ground state solutions to Schrodinger-Poisson systems with a negative non-local term
Directory of Open Access Journals (Sweden)
Yan-Ping Gao
2015-04-01
Full Text Available In this article, we study the Schrodinger-Poisson system $$\\displaylines{ -\\Delta u+u-\\lambda K(x\\phi(xu=a(x|u|^{p-1}u, \\quad x\\in\\mathbb{R}^3, \\cr -\\Delta\\phi=K(xu^{2},\\quad x\\in\\mathbb{R}^3, }$$ with $p\\in(1,5$. Assume that $a:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ and $K:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ are nonnegative functions and satisfy suitable assumptions, but not requiring any symmetry property on them, we prove the existence of a positive ground state solution resolved by the variational methods.
Fahrenbach, Albert C; Bruns, Carson J; Cao, Dennis; Stoddart, J Fraser
2012-09-18
Fashioned through billions of years of evolution, biological molecular machines, such as ATP synthase, myosin, and kinesin, use the intricate relative motions of their components to drive some of life's most essential processes. Having control over the motions in molecules is imperative for life to function, and many chemists have designed, synthesized, and investigated artificial molecular systems that also express controllable motions within molecules. Using bistable mechanically interlocked molecules (MIMs), based on donor-acceptor recognition motifs, we have sought to imitate the sophisticated nanoscale machines present in living systems. In this Account, we analyze the thermodynamic characteristics of a series of redox-switchable [2]rotaxanes and [2]catenanes. Control and understanding of the relative intramolecular movements of components in MIMs have been vital in the development of a variety of applications of these compounds ranging from molecular electronic devices to drug delivery systems. These bistable donor-acceptor MIMs undergo redox-activated switching between two isomeric states. Under ambient conditions, the dominant translational isomer, the ground-state coconformation (GSCC), is in equilibrium with the less favored translational isomer, the metastable-state coconformation (MSCC). By manipulating the redox state of the recognition site associated with the GSCC, we can stimulate the relative movements of the components in these bistable MIMs. The thermodynamic parameters of model host-guest complexes provide a good starting point to rationalize the ratio of GSCC to MSCC at equilibrium. The bistable [2]rotaxanes show a strong correlation between the relative free energies of model complexes and the ground-state distribution constants (K(GS)). This relationship does not always hold for bistable [2]catenanes, most likely because of the additional steric and electronic constraints present when the two rings are mechanically interlocked with each other
Frequency dependent polarizabilities for the ground state of H2, HD, and D2
International Nuclear Information System (INIS)
Rychlewski, J.
1983-01-01
A variation-perturbation method has been employed to calculate the dynamic dipole polarizability for the ground state of the hydrogen molecule. The explicit correlated electronic wave functions were used. The averaged values of α(#betta#) and #betta#(#betta#) for several vibration-rotation states of HD and D 2 are presented. Similar values for H 2 have also been calculated and were used to test the efficiency of the method and the validity of the assumption applied in the present calculation. The agreement of the present theoretical results with the existing experimental data is found to be satisfactory
Simulations of ground state fluctuations in mean-field Ising spin glasses
International Nuclear Information System (INIS)
Boettcher, Stefan
2010-01-01
The scaling of fluctuations in the distribution of ground state energies or costs with the system size N for Ising spin glasses is considered using an extensive set of simulations with the extremal optimization heuristic across a range of different models on sparse and dense graphs. These models exhibit very diverse behaviors, and an asymptotic extrapolation is often complicated by higher-order corrections in size. The clearest picture, in fact, emerges from the study of graph bipartitioning, a combinatorial optimization problem closely related to spin glasses. Asides from two-spin interactions with discrete bonds, we also consider problems with Gaussian bonds and three-spin interactions, which behave quite differently
Ground state solutions for Choquard type equations with a singular potential
Directory of Open Access Journals (Sweden)
Tao Wang
2017-02-01
Full Text Available This article concerns the Choquard type equation $$ -\\Delta u+V(xu=\\Big(\\int_{\\mathbb{R}^N}\\frac{|u(y|^p}{|x-y|^{N-\\alpha}}dy\\Big |u|^{p-2}u,\\quad x\\in \\mathbb{R}^N, $$ where $N\\geq3$, $\\alpha\\in ((N-4_+,N$, $2\\leq p <(N+\\alpha/(N-2$ and V(x is a possibly singular potential and may be unbounded below. Applying a variant of the Lions' concentration-compactness principle, we prove the existence of ground state solution of the above equations.
Ground-state candidate for the classical dipolar kagome Ising antiferromagnet
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.
Ground-State Band and Deformation of the Z = 102 Isotope N 254
International Nuclear Information System (INIS)
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.; Leino, M.; Vetter, K.; Siem, S.
1999-01-01
The ground-state band of the Z=102 isotope 254 No has been identified up to spin 14, indicating that the nucleus is deformed. The deduced quadrupole deformation, β=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 254 No up to spin 14 means that its fission barrier persists at least up to that spin. copyright 1999 The American Physical Society
Linear geologic structure and magic rock discrimination as determined from infrared data
Offield, T. W.; Rowan, L. C.; Watson, R. D.
1970-01-01
Color infrared photographs of the Beartooth Mountains, Montana show the distribution of mafic dikes and amphibolite bodies. Lineaments that cross grassy plateaus can be identified as dikes by the marked constrast between the dark rocks and the red vegetation. Some amphibolite bodies in granitic terrain can also be detected by infrared photography and their contacts can be accurately drawn due to enchanced contrast of the two types of rock in the near infrared. Reflectance measurements made in the field for amphibolite and granite show that the granite is 25% to 50% more reflective in the near infrared than in the visible region. Further enhancement is due to less atmospheric scattering than in the visible region. Thermal infrared images of the Mill Creek, Oklahoma test site provided information on geologic faults and fracture systems not obtainable from photographs. Subtle stripes that cross outcrop and intervening soil areas and which probably record water distribution are also shown on infrared photographs.
International Nuclear Information System (INIS)
Bonwell, E.; Fisher, T.; Fritz, A.; Wetzel, D.
2008-01-01
One molecular aspect of mature hard wheat protein quality for breadmaking is the relative amount of endosperm protein in the a-helix form compared with that in other secondary structure forms including β-sheet. Modeling of a-helix and β-sheet absorption bands that contribute to the amide I band at 1650 cm-1 was applied to more than 1500 spectra in this study. The microscopic view of wheat endosperm is dominated by many large starch granules with protein in between. The spectrum produced from in situ microspectroscopy of this mixture is dominated by carbohydrate bands from the large starch granules that fill up the field. The high spatial resolution achievable with synchrotron infrared microspectroscopy enables revealing good in situ spectra of the protein located interstitially. Synchrotron infrared microspectroscopic mapping of 4 μm thick frozen sections of endosperm in the subaleurone region provides spectra from a large number of pixels. Pixels with protein-dominated spectra are sorted out from among adjacent pixels to minimize the starch absorption and scattering contributions. Subsequent data treatment to extract information from the amide I band requires a high signal to noise ratio. Although spectral interference of the carbohydrate band on the amide band is not a problem, the scattering produced by the large starch granules diminishes the signal to noise ratio throughout the spectrum. High density mapping was done on beamlines U2B and U10B at the National Synchrotron Light Source at Brookhaven National Laboratory, Upton, NY. Mapping with a single masked spot size of 5.5 μm diameter or confocal 5 μm x 5 μm spot size, respectively, on the two beamlines used produced spectra for new breeding lines under current consideration. Appropriate data treatment allows calculation of a numerical estimate of the a-helix population relative to other secondary protein structures from the position and shape of the amide I absorption band. Current breeding lines show a
The ground state of long-range Schrödinger equations and static qq̄ potential
Energy Technology Data Exchange (ETDEWEB)
Beccaria, Matteo [Dipartimento di Matematica e Fisica Ennio De Giorgi,Università del Salento, Via Arnesano, 73100 Lecce (Italy); INFN, Via Arnesano, 73100 Lecce (Italy); Metafune, Giorgio [Dipartimento di Matematica e Fisica Ennio De Giorgi,Università del Salento, Via Arnesano, 73100 Lecce (Italy); Pallara, Diego [Dipartimento di Matematica e Fisica Ennio De Giorgi,Università del Salento, Via Arnesano, 73100 Lecce (Italy); INFN, Via Arnesano, 73100 Lecce (Italy)
2016-05-06
Motivated by the recent results in http://arxiv.org/abs/1601.05679 about the quark-antiquark potential in N=4 SYM, we reconsider the problem of computing the asymptotic weak-coupling expansion of the ground state energy of a certain class of 1d Schrödinger operators −((d{sup 2})/(dx{sup 2}))+λ V(x) with long-range potential V(x). In particular, we consider even potentials obeying ∫{sub ℝ}dx V(x)<0 with large x asymptotics V∼−a/x{sup 2}−b/x{sup 3}+⋯. The associated Schrödinger operator is known to admit a bound state for λ→0{sup +}, but the binding energy is rigorously non-analytic at λ=0. Its asymptotic expansion starts at order O(λ), but contains higher corrections λ{sup n} log{sup m} λ with all 0≤m≤n−1 and standard Rayleigh-Schrödinger perturbation theory fails order by order in λ. We discuss various analytical tools to tame this problem and provide the general expansion of the binding energy at O(λ{sup 3}) in terms of quadratures. The method is tested on a soluble potential that is fully under control, and on various non-soluble cases as well. A supersymmetric case, arising in the study of the quark-antiquark potential in N=6 ABJ(M) theory, is also exploited to provide a further non-trivial consistency check. Our analytical results confirm at third order a remarkable exponentiation of the leading infrared logarithms, first noticed in N=4 SYM where it may be proved by Renormalization Group arguments. We prove this interesting feature at all orders at the level of the Schrödinger equation for general potentials in the considered class.
International Nuclear Information System (INIS)
Potter, W.T.; Tucker, M.P.; Houtchens, R.A.; Caughey, W.S.
1987-01-01
The dioxygen stretch bands in infrared spectra for solutions of oxy species of human hemoglobin A and its separated subunits, human mutant hemoglobin Zurich (β63His to Arg), rabbit hemoglobin, lamprey, hemoglobin, sperm whale myoglobin, bovine myoglobin, and a sea worm chlorocruorin are examined. Each protein exhibits multiple isotope-sensitive bands between 1160 and 1060 cm -1 for the liganded 16 O 2 , 17 O 2 , and 18 O 2 . The O-O stretch bands for each of the mammalian myoglobins and hemoglobins are similar, with frequencies that differ between proteins by only 3-5 cm -1 . The spectra for the lamprey and sea worm hemoglobins exhibit greater diversity. For all proteins an O-O stretch band expected to occur near 1125 cm -1 for 16 O 2 and 17 O 2 , but not 18 O 2 , appears split by ∼25 cm -1 due to an unidentified perturbation. The spectrum for each dioxygen isotope, if unperturbed, would contain two strong bands for the mammalian myoglobins (1150 and 1120 cm -1 ) and hemoglobins (1155 and 1125 cm -1 ). Two strong bands separated by ∼30 cm -1 for each oxy heme protein subunit indicate that two major protein conformations (structure) that differ substantially in O 2 bonding are present. The two dioxygen structures can result from a combination of dynamic distal and proximal effects upon the O 2 ligand bound in a bent-end-on stereochemistry
Buurmans, I.L.C.; Soulimani, F.; Ruiz Martinez, J.; van der Bij, H.E.; Weckhuysen, B.M.
2013-01-01
A synchrotron-based infrared micro-spectroscopy study has been conducted to investigate the structure as well as the Brønsted and Lewis acidity of Fluid Catalytic Cracking (FCC) catalyst particles at the individual particle level. Both fresh and laboratory-deactivated catalyst particles have been
3D reconstruction of internal structure of animal body using near-infrared light
Tran, Trung Nghia; Yamamoto, Kohei; Namita, Takeshi; Kato, Yuji; Shimizu, Koichi
2014-03-01
To realize three-dimensional (3D) optical imaging of the internal structure of animal body, we have developed a new technique to reconstruct CT images from two-dimensional (2D) transillumination images. In transillumination imaging, the image is blurred due to the strong scattering in the tissue. We had developed a scattering suppression technique using the point spread function (PSF) for a fluorescent light source in the body. In this study, we have newly proposed a technique to apply this PSF for a light source to the image of unknown light-absorbing structure. The effectiveness of the proposed technique was examined in the experiments with a model phantom and a mouse. In the phantom experiment, the absorbers were placed in the tissue-equivalent medium to simulate the light-absorbing organs in mouse body. Near-infrared light was illuminated from one side of the phantom and the image was recorded with CMOS camera from another side. Using the proposed techniques, the scattering effect was efficiently suppressed and the absorbing structure can be visualized in the 2D transillumination image. Using the 2D images obtained in many different orientations, we could reconstruct the 3D image. In the mouse experiment, an anesthetized mouse was held in an acrylic cylindrical holder. We can visualize the internal organs such as kidneys through mouse's abdomen using the proposed technique. The 3D image of the kidneys and a part of the liver were reconstructed. Through these experimental studies, the feasibility of practical 3D imaging of the internal light-absorbing structure of a small animal was verified.
International Nuclear Information System (INIS)
Hirschfeld, Julian Arndt
2012-01-01
Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One candidate is doped zirconia. In the past, the electrical resistance of zirconia based SOFC electrolytes has mainly been decreased by reducing its thickness. But there are limits to reducing the thickness and one can say that nowadays the normal ways are basically exhausted to further enhance the conductivity of well-known electrolyte materials. Hence, new approaches need to be found to discover windows of enhanced ionic conductivity. This can be achieved by understanding the quantum-mechanical oxygen transport in unconventional configurations of doped zirconia. Therefore, such an understanding is of fundamental importance. In this thesis two approaches are pursued, the investigation of the strain dependent ionic migration in zirconia based electrolytes and the designing of an electrolyte material structure with enhanced and strongly anisotropic ionic conductivity. The first approach expands the elementary understanding of oxygen migration in oxide lattices. The migration barrier of the oxygen ion jumps in zirconia is determined by applying the Density Functional Theory (DFT) calculations in connection with the Nudged Elastic Band (NEB) method. These computations show an unexpected window of decreased migration barriers at high compressive strains. Similar to other publications a decrease in the migration barrier for expansive strain is observed. But, in addition, a migration barrier decrease under high compressive strains is found beyond a maximal height of the migration barrier. A simple analytic model offers an explanation. The drop of the migration barrier at high compressions originates from the elevation of the ground-state energy. This means: Increasing ground state energies becomes an interesting alternative to facilitate ionic mobility. The second approach is based on the idea, that actually, only in the direction of ion
Energy Technology Data Exchange (ETDEWEB)
Hirschfeld, Julian Arndt
2012-12-11
Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One candidate is doped zirconia. In the past, the electrical resistance of zirconia based SOFC electrolytes has mainly been decreased by reducing its thickness. But there are limits to reducing the thickness and one can say that nowadays the normal ways are basically exhausted to further enhance the conductivity of well-known electrolyte materials. Hence, new approaches need to be found to discover windows of enhanced ionic conductivity. This can be achieved by understanding the quantum-mechanical oxygen transport in unconventional configurations of doped zirconia. Therefore, such an understanding is of fundamental importance. In this thesis two approaches are pursued, the investigation of the strain dependent ionic migration in zirconia based electrolytes and the designing of an electrolyte material structure with enhanced and strongly anisotropic ionic conductivity. The first approach expands the elementary understanding of oxygen migration in oxide lattices. The migration barrier of the oxygen ion jumps in zirconia is determined by applying the Density Functional Theory (DFT) calculations in connection with the Nudged Elastic Band (NEB) method. These computations show an unexpected window of decreased migration barriers at high compressive strains. Similar to other publications a decrease in the migration barrier for expansive strain is observed. But, in addition, a migration barrier decrease under high compressive strains is found beyond a maximal height of the migration barrier. A simple analytic model offers an explanation. The drop of the migration barrier at high compressions originates from the elevation of the ground-state energy. This means: Increasing ground state energies becomes an interesting alternative to facilitate ionic mobility. The second approach is based on the idea, that actually, only in the direction of ion
Brandow, B. H.
1986-01-01
A variational study of ground states of the orbitally nondegenerate Anderson lattice model, using a wave function with one variational parameter per Bloch state k, has been extended to deal with essentially metallic systems having a nonintegral number of electrons per site. Quasiparticle excitations are obtained by direct appeal to Landau's original definition for interacting Fermi liquids, scrEqp(k,σ)=δEtotal/δn qp(k,σ). This approach provides a simple and explicit realization of the Luttinger picture of a periodic Fermi liquid. A close correspondence is maintained between the ``interacting'' (U=∞) system and the corresponding ``noninteracting'' (U=0) case, i.e., ordinary band theory; the result can be described as a renormalized band or renormalized hybridization theory. The occupation-number distribution for the conduction orbitals displays a finite discontinuity at the Fermi surface. If the d-f hybridization is nonzero throughout the Brillouin zone, the quasiparticle spectrum will always exhibit a gap, although this gap becomes exponentially small (i.e., of order TK) in the Kondo-lattice regime. In the ``ionic'' case with precisely two electrons per site, such a system may therefore exhibit an insulating (semiconducting) gap. The quasiparticle state density exhibits a prominent spike on each side of the spectral gap, just as in the elementary hybridization model (the U=0 case). For the metallic case, with a nonintegral number of electrons per site, the Fermi level falls within one of the two sharp density peaks. The effective mass at the Fermi surface tends to be very large; enhancements by a factor >~102 are quite feasible. The foregoing variational theory has also been refined by means of a trial wave function having two variational parameters per Bloch state k. The above qualitative features are all retained, with some quantitative differences, but there are also some qualitatively new features. The most interesting of these is the appearance, within
Ground State Structures of Boron-Rich Rhodium Boride: An Ab Initio Study
Chu, Bin-Hua; Zhao, Yuan; Yan, Jin-Liang; Li, Da
2018-01-01
Not Available Supported by the Natural Science Foundation of Shandong Province under Grant Nos ZR2016AP02, ZR2016FM38 and ZR2016EMP01, the Innovation Project of Ludong University under Grant No LB2016013, the Open Project of State Key Laboratory of Superhard Materials of Jilin University under Grant No 201605, and the National Natural Science Foundation of China under Grant Nos 11704170 and 61705097.
Ground state structure of some double-λ hypernuclei by a three ...
Indian Academy of Sciences (India)
In view of the new data we decided to undertake a re-study of the 6 He hypernucleus using the same three-body model (--) with a simple coordinate space variational approach which was employed earlier with the old data on 6 He. After ﬁtting different - potentials to the new data of 6 He we have ...
Study of ЃЃdynamics and ground state structure of low and medium ...
Indian Academy of Sciences (India)
The hyperspherical harmonics expansion method, which is an essentially exact method has been employed for the three body system. A convergence in binding energy up to 0.15% for max = 20 has been achieved. In our calculation we have made no approximation in restricting the allowed -values of the interacting ...
Measurement of the hyperfine structure of the ground state of muonic helium(3)
International Nuclear Information System (INIS)
Arnold, K.P.
1984-01-01
Polarization measurements by the muon spin rotation method yielded the detection that in the formation of 3 Heμ - e - the hfs states are occupied differently. In pure helium(3) a residual polarization of 2.6(4)% of the ( 3 Heμ - ) + ion was found. At an admixture of 2% xenon the neutral 3 Heμ - e - atom is formed with a polarization of 1.8(4)%. The hfs measurements were performed by means of the high-frequency spectroscopy. By inducing of Δmsub(F)=+-1 transitions the muon polarization is changed. This effects a change of the asymmetric electron distribution which arises by the parity-violating muon decay and can be detected by plastic scintillators. The measurements were performed at a highly pure gas target of 19.90 bar helium(3) to which 1.6% Xe were admixed, at 20 0 C and in a magnetic zero field. The pressure shift for the hfs measurements of 3 Heμ - e - , extrapolated to the buffer gas pressure zero, is: Δνsub(hfs)=4166.41(5) MHz. (orig./HSI) [de
Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model
Energy Technology Data Exchange (ETDEWEB)
Canko, Osman; Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr
2008-05-15
We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and J<0, respectively, on the diatomic lattice and have found the conditions for the existence of uniform and intermediate or non-uniform phases. We have also constructed the exact ground-state phase diagrams of the model on the triangular lattice and found 20 and 59 fundamental phase diagrams for J>0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found.
Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory
DEFF Research Database (Denmark)
Olsen, Thomas; Thygesen, Kristian Sommer
2014-01-01
We demonstrate that ground-state energies approaching chemical accuracy can be obtained by combining the adiabatic-connection fluctuation-dissipation theorem with time-dependent densityfunctional theory. The key ingredient is a renormalization scheme, which eliminates the divergence...
CSIR Research Space (South Africa)
de Clercq, L
2010-09-01
Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible...
International Nuclear Information System (INIS)
Liu Jia; Xiao Jingling
2006-01-01
We study theoretically the ground state energy of a polaron near the interface of a polar-polar semiconductor by considering the Rashba spin-orbit (SO) coupling with the Lee-Low-Pines intermediate coupling method. Our numerical results show that the Rashba SO interaction originating from the inversion asymmetry in the heterostructure splits the ground state energy of the polaron. The electron areal density and vector dependence of the ratio of the SO interaction to the total ground state energy or other energy composition are obvious. One can see that even without any external magnetic field, the ground state energy can be split by the Rashba SO interaction, and this split is not a single but a complex one. Since the presents of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the polaron are more stable than electron's.
Structure and composition of enamel and dentin after thermal treatment or infrared laser irradiation
International Nuclear Information System (INIS)
Bachmann, Luciano
2004-01-01
The main purpose of this work is to identify the crystallographic structure, optical properties, chemical composition and electron paramagnetic signals that laser irradiation or oven heating produces on the tissue. The thermal treatment was conducted in oven with temperature range below 1000 deg C and the laser irradiation with holmium (Ho:YLF - 2,065 μm) and erbium (Er:YAG - 2,94 μm) laser. The tissue characterization was carried out with X-ray diffraction, scanning electron microscopy, ultraviolet and visible transmission spectroscopy, light microscopy, infrared transmission/reflection spectroscopy and electron paramagnetic resonance. The holmium irradiated enamel (600-800 J/cm 2 ) shows the presence of tetracalcium phosphate that coexists with the natural phase (hydroxyapatite). The irradiated dentin shows only the sharper diffraction peaks of the natural phase. The narrows peaks, observed after irradiation, could be assigned to the dentin crystal growth and impurities elimination. Tissue discoloration is observed after thermal treatment with temperatures above 100 deg C. Heated enamel become white-opaque and the origin is assigned to the water elimination, which promotes higher light scattering by the prismatic structure. On the other hand, heated dentin, with similar temperatures becomes brown. The dentin browning changes with the temperature and shown two peaks, at 375 deg C and 700 deg C. The peak at 375 deg C is assigned to the collagen structure degradation and at 700 deg C to the cyanate formation. The dentin discoloration produced with temperatures below 200 deg C is reversible after the tissue hydration. Both enamel and dentin discoloration are also observed in erbium irradiated tissues. Thermal treatments, heating in oven or laser irradiation, change mainly the organic matrix composition and water present in the tissues. The inorganic matrix is more stable and its radicals are changed, with more predominance, only at temperatures higher than 500 deg
High Fidelity Preparation of a Single Atom in Its 2D Center of Mass Ground State
Sompet, Pimonpan; Fung, Yin Hsien; Schwartz, Eyal; Hunter, Matthew D. J.; Phrompao, Jindaratsamee; Andersen, Mikkel F.
2017-04-01
Complete control over quantum states of individual atoms is important for the study of the microscopic world. Here, we present a push button method for high fidelity preparation of a single 85Rb atom in the vibrational ground state of tightly focused optical tweezers. The method combines near-deterministic preparation of a single atom with magnetically-insensitive Raman sideband cooling. We achieve 2D cooling in the radial plane with a ground state population of 0.85, which provides a fidelity of 0.7 for the entire procedure (loading and cooling). The Raman beams couple two sublevels (| F = 3 , m = 0 〉 and | F = 2 , m = 0 〉) that are indifferent to magnetic noise to first order. This leads to long atomic coherence times, and allows us to implement the cooling in an environment where magnetic field fluctuations prohibit previously demonstrated variations. Additionally, we implement the trapping and manipulation of two atoms confined in separate dynamically reconfigurable optical tweezers, to study few-body dynamics.
Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids
International Nuclear Information System (INIS)
Abedinpour, Saeed H.; Asgari, Reza; Tanatar, B.; Polini, Marco
2014-01-01
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
Hartree–Fock many-body perturbation theory for nuclear ground-states
Directory of Open Access Journals (Sweden)
Alexander Tichai
2016-05-01
Full Text Available 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.
Hartree–Fock many-body perturbation theory for nuclear ground-states
Energy Technology Data Exchange (ETDEWEB)
Tichai, Alexander, E-mail: alexander.tichai@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Langhammer, Joachim [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Binder, Sven [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Roth, Robert, E-mail: robert.roth@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany)
2016-05-10
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.
Electron pumping of the ground state of 21Ne. Transfers and multiple diffusion processes
International Nuclear Information System (INIS)
Stoeckel, F.; Lombardi, M.
1978-01-01
The electron-pumping process of the ground state of 21 Ne has been studied. It is demonstrated how in a neon cell at a pressure of 10 -4 to 10 -2 torr, a high frequency discharge can create a nuclear spin alignment in the fundamental level (I=3/2) when the excited levels are themselves aligned. The nuclear alignment is observed by monitoring the change of the linear polarization of several optical transitions during the magnetic resonance of the fundamental level. Various transfers of the alignments are investigated and a detailed study of the influence of the multiple diffusion is carried out. The multiple diffusion produces a depolarization and a relaxation of the nuclear spin. A theoretical calculation has been made for a two-level system with a J=1 radiative level and a J=0 ground state. Experimentally a relaxation time of the nuclear alignment varying from 37 ms to 240 ms is observed when the neon pressure decreases from 10 -2 to 10 -4 torr [fr
Ground-state energy of the interacting Bose gas in two dimensions: An explicit construction
International Nuclear Information System (INIS)
Beane, Silas R.
2010-01-01
The isotropic scattering phase shift is calculated for nonrelativistic bosons interacting at low energies via an arbitrary finite-range potential in d space-time dimensions. Scattering on a (d-1)-dimensional torus is then considered, and the eigenvalue equation relating the energy levels on the torus to the scattering phase shift is derived. With this technology in hand, and focusing on the case of two spatial dimensions, a perturbative expansion is developed for the ground-state energy of N identical bosons which interact via an arbitrary finite-range potential in a finite area. The leading nonuniversal effects due to range corrections and three-body forces are included. It is then shown that the thermodynamic limit of the ground-state energy in a finite area can be taken in closed form to obtain the energy per particle in the low-density expansion by explicitly summing the parts of the finite-area energy that diverge with powers of N. The leading and subleading finite-size corrections to the thermodynamic limit equation of state are also computed. Closed-form results--some well known, others perhaps not--for two-dimensional lattice sums are included in an Appendix.
The magnetic ground state and relationship to Kitaev physics in α-RuCl3
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.
Energy Technology Data Exchange (ETDEWEB)
Gumberidze, A.; Stoehlker, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)]|[Frankfurt Univ. (Germany). Inst. fuer Kernphysik; Banas, D. [Pedagogical Univ., Kielce (PL). Inst. of Phys.] [and others
2005-05-01
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 observation geometry, allowed us to determine the ground-state Lamb shift in hydrogen-like 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. (orig.)
International Nuclear Information System (INIS)
Morini, Filippo; Deleuze, Michael Simon; Watanabe, Noboru; Kojima, Masataka; Takahashi, Masahiko
2015-01-01
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 2b 1 , 6a 1 , 4b 2 , and 1a 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 1 , B 1 , and B 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
Haertelt, M.; Lapoutre, V. J. F.; Bakker, J. M.; Redlich, B.; Harding, D. J.; Fielicke, A.; Meijer, G.
2011-01-01
We report vibrational spectra of anionic metal clusters, measured via electron detachment following resonant absorption of multiple infrared photons. To facilitate the sequential absorption of the required large number of photons, the cluster beam interacts with the infrared radiation inside the
Nielsen, L; Frokjaer, S; Carpenter, J F; Brange, J
2001-01-01
Fibril formation (aggregation) of insulin was investigated in acid media by visual inspection, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. Insulin fibrillated faster in hydrochloric acid than in acetic acid at elevated temperatures, whereas the fibrillation tendencies were reversed at ambient temperatures. Electron micrographs showed that bovine insulin fibrils consisted of long fibers with a diameter of 5 to 10 nm and lengths of several microns. The fibrils appeared either as helical filaments (in hydrochloric acid) or arranged laterally in bundles (in acetic acid, NaCl). Freeze-thawing cycles broke the fibrils into shorter segments. FTIR spectroscopy showed that the native secondary structure of insulin was identical in hydrochloric acid and acetic acid, whereas the secondary structure of fibrils formed in hydrochloric acid was different from that formed in acetic acid. Fibrils of bovine insulin prepared by heating or agitating an acid solution of insulin showed an increased content of beta-sheet (mostly intermolecular) and a decrease in the intensity of the alpha-helix band. In hydrochloric acid, the frequencies of the beta-sheet bands depended on whether the fibrillation was induced by heating or agitation. This difference was not seen in acetic acid. Freeze-thawing cycles of the fibrils in hydrochloric acid caused an increase in the intensity of the band at 1635 cm(-1) concomitant with reduction of the band at 1622 cm(-1). The results showed that the structure of insulin fibrils is highly dependent on the composition of the acid media and on the treatment. Copyright 2001 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 90: 29-37, 2001
International Nuclear Information System (INIS)
Nguyen Dinh Dang; Voronov, V.V.
1983-01-01
A system of basic equations of the quasiparticle-phonon model is obtained for energies and a structure of excited states described by the wave functions containing one- and two-phonon components. The effects due to the Pauli principle for two-phonon components and the phonon ground state correlations of a spherical nucleus are taken here into account. The quantitative estimations of these effects are given by a simplified scheme. The relation between these equations with the results from other theoretical approaches is discussed
Ogura, Hiroshi; Evans, John P.; Peng, Dungeng; Satterlee, James D.; de Montellano, Paul R. Ortiz; Mar, Gerd N. La
2009-01-01
The active site electronic structure of the azide complex of substrate-bound human heme oxygenase-1, (hHO) has been investigated by 1H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. 2D 1H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts, that places the lone iron π-spin in the dxz orbital, rather than the dyz orbital found in the cya...
Classification of structurally related commercial contrast media by near infrared spectroscopy.
Yip, Wai Lam; Soosainather, Tom Collin; Dyrstad, Knut; Sande, Sverre Arne
2014-03-01
Near infrared spectroscopy (NIRS) is a non-destructive measurement technique with broad application in pharmaceutical industry. Correct identification of pharmaceutical ingredients is an important task for quality control. Failure in this step can result in several adverse consequences, varied from economic loss to negative impact on patient safety. We have compared different methods in classification of a set of commercially available structurally related contrast media, Iodixanol (Visipaque(®)), Iohexol (Omnipaque(®)), Caldiamide Sodium and Gadodiamide (Omniscan(®)), by using NIR spectroscopy. The performance of classification models developed by soft independent modelling of class analogy (SIMCA), partial least squares discriminant analysis (PLS-DA) and Main and Interactions of Individual Principal Components Regression (MIPCR) were compared. Different variable selection methods were applied to optimize the classification models. Models developed by backward variable elimination partial least squares regression (BVE-PLS) and MIPCR were found to be most effective for classification of the set of contrast media. Below 1.5% of samples from the independent test set were not recognized by the BVE-PLS and MIPCR models, compared to up to 15% when models developed by other techniques were applied. Copyright © 2013 Elsevier B.V. All rights reserved.
Cloud top structure of Venus revealed by Subaru/COMICS mid-infrared images
Sato, T. M.; Sagawa, H.; Kouyama, T.; Mitsuyama, K.; Satoh, T.; Ohtsuki, S.; Ueno, M.; Kasaba, Y.; Nakamura, M.; Imamura, T.
2014-11-01
We have investigated the cloud top structure of Venus by analyzing ground-based images taken at the mid-infrared wavelengths of 8.66 μm and 11.34 μm. Venus at a solar phase angle of ∼90°, with the morning terminator in view, was observed by the Cooled Mid-Infrared Camera and Spectrometer (COMICS), mounted on the 8.2-m Subaru Telescope, during the period October 25-29, 2007. The disk-averaged brightness temperatures for the observation period are ∼230 K and ∼238 K at 8.66 μm and 11.34 μm, respectively. The obtained images with good signal-to-noise ratio and with high spatial resolution (∼200 km at the sub-observer point) provide several important findings. First, we present observational evidence, for the first time, of the possibility that the westward rotation of the polar features (the hot polar spots and the surrounding cold collars) is synchronized between the northern and southern hemispheres. Second, after high-pass filtering, the images reveal that streaks and mottled and patchy patterns are distributed over the entire disk, with typical amplitudes of ∼0.5 K, and vary from day to day. The detected features, some of which are similar to those seen in past UV images, result from inhomogeneities of both the temperature and the cloud top altitude. Third, the equatorial center-to-limb variations of brightness temperatures have a systematic day-night asymmetry, except those on October 25, that the dayside brightness temperatures are higher than the nightside brightness temperatures by 0-4 K under the same viewing geometry. Such asymmetry would be caused by the propagation of the migrating semidiurnal tide. Finally, by applying the lapse rates deduced from previous studies, we demonstrate that the equatorial center-to-limb curves in the two spectral channels give access to two parameters: the cloud scale height H and the cloud top altitude zc. The acceptable models for data on October 25 are obtained at H = 2.4-4.3 km and zc = 66-69 km; this supports
He, Chenchen; Bao, Xun; Zhu, Yanlong; Strobehn, Stephen; Kimutai, Bett; Nei, Y.-W.; Chow, C. S.; Rodgers, M. T.; Gao, Juehan; Oomens, J.
2015-06-01
To gain a better understanding of the binding mechanism and assist in the optimization of relevant drug and chemical probe design, both experimental and theoretical studies were performed on a series of amino acid-linked cisplatin derivatives, including glycine-, lysine-, and ornithine-linked cisplatin, Gplatin, Kplatin, and Oplatin, respectively. Cisplatin, the first FDA-approved platinum-based anticancer drug, has been widely used in cancer chemotherapy. Its pharmacological mechanism has been identified as its ability to coordinate to genomic DNA, and guanine is its major target. In previous reports, cisplatin was successfully utilized as a chemical probe to detect solvent accessible sites in ribosomal RNA (rRNA). Among the amino-acid-linked cisplatin derivatives, Oplatin exhibits preference for adenine over guanine. The mechanism behind its different selectivity compared to cisplatin may relate to its potential of forming a hydrogen bond between the carboxylate group in Pt (II) complex and the 6-amino moiety of adenosine stabilizes A-Oplatin products. Tandem mass spectrometry analysis also indicates that different coordination sites of Oplatin on adenosine affect glycosidic bond stability. Infrared multiple photon dissociation (IRMPD) action spectroscopy experiments were performed on all three amino acid-linked cisplatin to characterize their structures. An extensive theoretical study has been performed on Gplatin to guide the selection of the most effective theory and basis set based on its geometric information. The results for Gplatin provide the foundation for characterization of the more complex amino acid-linked cisplatin derivatives, Oplatin and Kplatin. Structural and energetic information elucidated for these compounds, particularly Oplatin reveal the reason for its alternative selectivity compared to cisplatin.
A STATISTICAL STUDY OF THE MASS AND DENSITY STRUCTURE OF INFRARED DARK CLOUDS
International Nuclear Information System (INIS)
Peretto, N.; Fuller, G. A.
2010-01-01
How and when the mass distribution of stars in the Galaxy is set is one of the main issues of modern astronomy. Here, we present a statistical study of mass and density distributions of infrared dark clouds (IRDCs) and fragments within them. These regions are pristine molecular gas structures and progenitors of stars and so provide insights into the initial conditions of star formation. This study makes use of an IRDC catalog, the largest sample of IRDC column density maps to date, containing a total of ∼11,000 IRDCs with column densities exceeding N H 2 = 1x10 22 cm -2 and over 50,000 single-peaked IRDC fragments. The large number of objects constitutes an important strength of this study, allowing a detailed analysis of the completeness of the sample and so statistically robust conclusions. Using a statistical approach to assigning distances to clouds, the mass and density distributions of the clouds and the fragments within them are constructed. The mass distributions show a steepening of the slope when switching from IRDCs to fragments, in agreement with previous results of similar structures. IRDCs and fragments are divided into unbound/bound objects by assuming Larson's relation and calculating their virial parameter. IRDCs are mostly gravitationally bound, while a significant fraction of the fragments are not. The density distribution of gravitationally unbound fragments shows a steep characteristic slope such as ΔN/Δlog(n) ∝ n -4.0±0.5 , rather independent of the range of fragment mass. However, the incompleteness limit at a number density of ∼10 3 cm -3 does not allow us to exclude a potential lognormal density distribution. In contrast, gravitationally bound fragments show a characteristic density peak at n ≅ 10 4 cm -3 but the shape of the density distributions changes with the range of fragment masses. An explanation for this could be the differential dynamical evolution of the fragment density with respect to their mass as more massive
Energy Technology Data Exchange (ETDEWEB)
Sauerzopf, Clemens, E-mail: clemens.sauerzopf@oeaw.ac.at [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Capon, Aaron A.; Diermaier, Martin; Fleck, Markus; Kolbinger, Bernadette [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Malbrunot, Chloé [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Organisation Européenne pour la Recherche Nucléaire (CERN), 1211 Geneva 23 (Switzerland); Massiczek, Oswald; Simon, Martin C.; Vamosi, Stefan; Zmeskal, Johann; Widmann, Eberhard [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria)
2017-02-11
The matter-antimatter asymmetry observed in the universe today still lacks a quantitative explanation. One possible mechanism that could contribute to the observed imbalance is a violation of the combined Charge-, Parity- and Time symmetries (CPT). A test of CPT symmetry using anti-atoms is being carried out by the ASACUSA-CUSP collaboration at the CERN Antiproton Decelerator using a low temperature beam of antihydrogen—the most simple atomic system built only of antiparticles. While hydrogen is the most abundant element in the universe, antihydrogen is produced in very small quantities in a laboratory framework. A detector for in-beam measurements of the ground state hyperfine structure of antihydrogen has to be able to detect very low signal rates within high background. To fulfil this challenging task, a two layer barrel hodoscope detector was developed. It is built of plastic scintillators with double sided readout via Silicon Photomultipliers (SiPMs). The SiPM readout is done using novel, compact and cost efficient electronics that incorporate power supply, amplifier and discriminator on a single board. This contribution will evaluate the performance of the new hodoscope detector. - Highlights: • A novel detector for Antihydrogen was successfully commissioned. • A time of flight resolution of better than 1 ns was achieved. • Rudimentary 3D tracking is possible without bar segmentation.
Classical ground states of Heisenberg and X Y antiferromagnets on the windmill lattice
Jeevanesan, Bhilahari; Orth, Peter P.
2014-10-01
We investigate the classical Heisenberg and planar (X Y ) spin models on the windmill lattice. The windmill lattice is formed out of two widely occurring lattice geometries: a triangular lattice is coupled to its dual honeycomb lattice. Using a combination of iterative minimization, heat-bath Monte Carlo simulations, and analytical calculations, we determine the complete ground-state phase diagram of both models and find the exact energies of the phases. The phase diagram shows a rich phenomenology due to competing interactions and hosts, in addition to collinear and various coplanar phases, also intricate noncoplanar phases. We briefly outline different paths to an experimental realization of these spin models. Our extensive study provides a starting point for the investigation of quantum and thermal fluctuation effects.
Lisewski, Andreas Martin; Lichtarge, Olivier
2010-08-15
Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.
Nuclear level densities with pairing and self-consistent ground-state shell effects
Arnould, M
1981-01-01
Nuclear level density calculations are performed using a model of fermions interacting via the pairing force, and a realistic single particle potential. The pairing interaction is treated within the BCS approximation with different pairing strength values. The single particle potentials are derived in the framework of an energy-density formalism which describes self-consistently the ground states of spherical nuclei. These calculations are extended to statistically deformed nuclei, whose estimated level densities include rotational band contributions. The theoretical results are compared with various experimental data. In addition, the level densities for several nuclei far from stability are compared with the predictions of a back-shifted Fermi gas model. Such a comparison emphasizes the possible danger of extrapolating to unknown nuclei classical level density formulae whose parameter values are tailored for known nuclei. (41 refs).
Ground state magnetization of conduction electrons in graphene with Zeeman effect
Energy Technology Data Exchange (ETDEWEB)
Escudero, F., E-mail: federico.escudero@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Ardenghi, J.S., E-mail: jsardenhi@gmail.com [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Sourrouille, L., E-mail: lsourrouille@yahoo.es [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Jasen, P., E-mail: pvjasen@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina)
2017-05-01
In this work we address the ground state magnetization in graphene, considering the Zeeman effect and taking into account the conduction electrons in the long wavelength approximation. We obtain analytical expressions for the magnetization at T=0 K, where the oscillations given by the de Haas van Alphen (dHvA) effect are present. We find that the Zeeman effect modifies the magnetization by introducing new peaks associated with the spin splitting of the Landau levels. These peaks are very small for typical carrier densities in graphene, but become more important for higher densities. The obtained results provide insight of the way in which the Zeeman effect modifies the magnetization, which can be useful to control and manipulate the spin degrees of freedom. - Highlights: • The magnetization has peaks whenever the last energy level changes discontinuously. • The peaks amplitude depends on the electron density. • The Zeeman effect introduces new peaks in the magnetization.
Ground states of linear rotor chains via the density matrix renormalization group
Iouchtchenko, Dmitri; Roy, Pierre-Nicholas
2018-04-01
In recent years, experimental techniques have enabled the creation of ultracold optical lattices of molecules and endofullerene peapod nanomolecular assemblies. It was previously suggested that the rotor model resulting from the placement of dipolar linear rotors in one-dimensional lattices at low temperature has a transition between ordered and disordered phases. We use the density matrix renormalization group (DMRG) to compute ground states of chains of up to 100 rotors and provide further evidence of the phase transition in the form of a diverging entanglement entropy. We also propose two methods and present some first steps toward rotational spectra of such molecular assemblies using DMRG. The present work showcases the power of DMRG in this new context of interacting molecular rotors and opens the door to the study of fundamental questions regarding criticality in systems with continuous degrees of freedom.
A Continuous Family of Equilibria in Ferromagnetic Media are Ground States
Su, Xifeng; de la Llave, Rafael
2017-09-01
We show that a foliation of equilibria (a continuous family of equilibria whose graph covers all the configuration space) in ferromagnetic transitive models are ground states. The result we prove is very general, and it applies to models with long range and many-body interactions. As an application, we consider several models of networks of interacting particles including models of Frenkel-Kontorova type on Z^d and one-dimensional quasi-periodic media. The result above is an analogue of several results in the calculus of variations (fields of extremals) and in PDE's. Since the models we consider are discrete and long range, new proofs need to be given. We also note that the main hypothesis of our result (the existence of foliations of equilibria) is the conclusion (using KAM theory) of several recent papers. Hence, we obtain that the KAM solutions recently established are minimizers when the interaction is ferromagnetic and transitive (these concepts are defined later).
Orbital physics in sulfur spinels: ordered, liquid and glassy ground states
International Nuclear Information System (INIS)
Buettgen, N; Hemberger, J; Fritsch, V; Krimmel, A; Muecksch, M; Nidda, H-A Krug von; Lunkenheimer, P; Fichtl, R; Tsurkan, V; Loidl, A
2004-01-01
Measurements of magnetization M(T, H), heat capacity C(T), NMR lineshift K(T) and linewidth Δ(T), neutron scattering S(Q, ω, T) and broadband dielectric spectroscopy ε(ω, T) provide experimental evidence of the different orbital ground states in the cubic sulfur spinels under investigation. In all compounds, the tetrahedrally coordinated Jahn-Teller ions Fe 2+ are characterized by a degeneracy of the orbital degrees of freedom. Particularly, we found a long-range orbital ordering in polycrystalline (PC) FeCr 2 S 4 , and a glassy freezing of the orbital degrees of freedom in FeCr 2 S 4 (single crystals) (SCs). In contrast, FeSc 2 S 4 belongs to the rare class of spin-orbital liquids, where quantum fluctuations accompanying the glassy freezing of the orbitals suppress long-range magnetic order
A comparative icMRCI study of some NO+, NO and NO- electronic ground state properties
International Nuclear Information System (INIS)
Polak, R.; Fiser, J.
2004-01-01
Potential energy, electric field gradient (EFG) at both nuclei, and electric dipole moment functions for the electronic ground states of NO + , NO and NO - were calculated at the internally contracted multireference configuration interaction (icMRCI) level using augmented correlation-consistent basis sets. The changes in the EFG's with internuclear separation R were used to interpret the character of bonding in the triad of NO species. The vibrational dependences of the electric properties were estimated and the EFG's were employed to determine the 14 N nuclear quadrupole coupling constants. The effects of the choice of the basis set and reference configuration space were investigated. While the results obtained for NO + and NO served primarily to assess the quality of calculations by comparison with available experimental and theoretical data, new information was obtained on NO - , including electric property functions and some notions about the existence of metastable states
DEFF Research Database (Denmark)
Reynisson, J.; Wilbrandt, R.; Brinck, V.
2002-01-01
. The physical and chemical properties of the excited singlet state of the trioxatriangulenium (TOTA(+)) carbenium ion are investigated by experimental and Computational means. The degeneracy of the lowest excited states is counteracted by Jahn-Teller-type distortion, which leads to vibronic broadening...... of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...... triphenylenes is studied separately. Phosphorescence spectra, triplet lifetimes, and triplet-triplet absorption spectra are provided. In the discussion, TOTA(+) is compared to the unsubstituted xanthenium ion and its 9-phenyl derivative with respect to the excited state properties....
Uniqueness of non-linear ground states for fractional Laplacians in R
DEFF Research Database (Denmark)
Frank, Rupert L.; Lenzmann, Enno
2013-01-01
We prove uniqueness of ground state solutions Q = Q(|x|) ≥ 0 of the non-linear equation (−Δ)sQ+Q−Qα+1=0inR,where 0 fractional Laplacian in one dimension. In particular, we answer affirmatively an open question...... recently raised by Kenig–Martel–Robbiano and we generalize (by completely different techniques) the specific uniqueness result obtained by Amick and Toland for s=12 and α = 1 in [5] for the Benjamin–Ono equation. As a technical key result in this paper, we show that the associated linearized operator L...... + = (−Δ) s +1−(α+1)Q α is non-degenerate; i.e., its kernel satisfies ker L + = span{Q′}. This result about L + proves a spectral assumption, which plays a central role for the stability of solitary waves and blowup analysis for non-linear dispersive PDEs with fractional Laplacians, such as the generalized...
Measurement of the ground state spectroscopic quadrupole moments of 191Os and 193Os
International Nuclear Information System (INIS)
Ernst, H.; Hagn, E.; Zech, E.
1979-01-01
Radioactive 191 Os and 193 Os nuclei have been aligned in an Os single crystal at temperatures down to 4 mK. From the temperature dependence of the γ-anisotropy the quadrupole frequencies vsub(Q) = e 2 qQ/h have been determined as vsub(Q)( 191 OsOs) = -278+-9 MHz and vsub(Q)( 193 OsOs) = -96+-15 MHz. With the known electric field gradient for OsOs of eq = (-4.54+-0.24) x 10 17 V/cm 2 the ground state spectroscopic quadrupole moments are deduced to be Q( 191 Os) = +2.53+-0.16 b and Q( 193 Os) = +0.87+-0.15 b. (orig.)
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.
2013-10-09
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.
Ground state and elementary excitations of a model valence-fluctuation system
International Nuclear Information System (INIS)
Brandow, B.H.
1979-01-01
The nature of the valence fluctuation problem is described, and motivations are given for an Anderson-lattice model Hamiltonian. A simple trial wave function is posed for the ground state, and the variational problem is solved. This demonstrates clearly that there is no Kondo-like divergence; the present concentrated Kondo problem is thus more simple mathematically than the sngle-impurity problem. Elementary excitations are studies by the Green's function techniques of Zubarev and Hubbard. Quenching of local moments and a large specific heat are found at low temperatures. The quasi-particle spectrum exhibits a gap, but epsilon/sub F/ does not lie in this gap. The insulation-like feature of SmB 6 , SmS, and TmSe at very low temperatures is explained in terms of a strongly reduced mobility for states near the gap, and reasons are given why this feature is not observed in other valence-fluctuation compounds. 73 references
The ground state magnetic moment and susceptibility of a two electron Gaussian quantum dot
Boda, Aalu; Chatterjee, Ashok
2018-04-01
The problem of two interacting electrons moving in a two-dimensional semiconductor quantum dot with Gaussian confinement under the influence of an external magnetic field is studied by using a method of numerical diagonalization of the Hamiltonian matrix with in the effective-mass approximation. The energy spectrum is calculated as a function of the magnetic field. We find the ground state magnetic moment and the magnetic susceptibility show zero temperature diamagnetic peaks due to exchange induced singlet-triplet oscillations. The position and the number of these peaks depend on the size of the quantum dot and also strength of the electro-electron interaction. The theory is applied to a GaAs quantum dot.
Degenerate Ground State in a Mesoscopic YBa2Cu3O
International Nuclear Information System (INIS)
Il'ichev, E.; Grajcar, M.; Hlubina, R.; IJsselsteijn, R. P. J.; Hoenig, H. E.; Meyer, H.-G.; Golubov, A.; Amin, M. H. S.; Zagoskin, A. M.; Omelyanchouk, A. N.
2001-01-01
We have measured the current-phase relationship I (var-phi) of symmetric 45 degree YBa 2 Cu 3 O 7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T , a local minimum at a temperature T * . (ii) At T∼T * , the first harmonic of I(var-phi) changes sign. (iii) For T * , the second harmonic of I(var-phi) is comparable to the first harmonic, and (iv) the ground state of the junction becomes degenerate. The results are in good agreement with a microscopic model of Josephson junctions between d -wave superconductors
Strongly correlated quasi-one-dimensional bands: Ground states, optical absorption, and phonons
International Nuclear Information System (INIS)
Campbell, D.K.; Gammel, J.T.; Loh, E.Y. Jr.
1989-01-01
Using the Lanczos method for exact diagonalization on systems up to 14 sites, combined with a novel ''phase randomization'' technique for extracting more information from these small systems, we investigate several aspects of the one-dimensional Peierls-Hubbard Hamiltonian, in the context of trans-polyacetylene: the dependence of the ground state dimerization on the strength of the electron-electron interactions, including the effects of ''off-diagonal'' Coulomb terms generally ignored in the Hubbard model; the phonon vibrational frequencies and dispersion relations, and the optical absorption properties, including the spectrum of absorptions as a function of photon energy. These three different observables provide considerable insight into the effects of electron-electron interactions on the properties of real materials and thus into the nature of strongly correlated electron systems. 29 refs., 11 figs
Does the ground-state resonance of 10Li overlap neutron threshold
International Nuclear Information System (INIS)
McVoy, K.W.; Van Isacker, P.
1994-01-01
Recent measurements suggest that the ground state of 10 Li is a resonance which may well be wide enough to overlap the (n + 9 Li) threshold. In this context we recall some of the curious properties of resonances located near threshold and entered from a non-decay channel, including their asymmetry and the fact that the peak observed in the cross section occurs at neither the R-matrix nor the S-matrix energy, but rather between the two. Because of these and other complications, it does not seem likely that either the l-value of the resonance or the energy of the corresponding state can accurately be determined form the shape of the resonance peak alone. (authors). 5 refs., 4 figs., 2 tabs
Atomic mass and characteristic constant of nuclear ground state (CENPL.MCC). Pt. 1
International Nuclear Information System (INIS)
Su Zongdi; Ma Lizhen; Zhou Chunmei; Ge Zhigang
1994-01-01
Atomic mass and characteristic constants for nuclear ground states are basic data for nuclear physics, and necessary ones for basic researches, theoretical calculations, as well as many applied researches. The atomic mass of exotic nuclei quite far from the valley stability are also very important for astrophysics researches. The above-requirement is paid attention to in our setting up this file. The recent and as many as possible data (such as the half-lives of the new nuclides 202 Pt, 208 Hg and 185 Hf and the mass excess of 199 Ir, which were produced and distinguished by Chinese scientists) have been collected, and put into the computer-based data file in brief table format. (1 fig.)
Energy Technology Data Exchange (ETDEWEB)
Ellis, J. Michael; Altman, Michael D.; Cash, Brandon; Haidle, Andrew M.; Kubiak, Rachel L.; Maddess, Matthew L.; Yan, Youwei; Northrup, Alan B. (Merck)
2016-12-08
Optimization of a series of highly potent and kinome selective carbon-linked carboxamide spleen tyrosine kinase (Syk) inhibitors with favorable drug-like properties is described. A pervasive Ames liability in an analogous nitrogen-linked carboxamide series was obviated by replacement with a carbon-linked moiety. Initial efforts lacked on-target potency, likely due to strain induced between the hinge binding amide and solvent front heterocycle. Consideration of ground state and bound state energetics allowed rapid realization of improved solvent front substituents affording subnanomolar Syk potency and high kinome selectivity. These molecules were also devoid of mutagenicity risk as assessed via the Ames test using the TA97a Salmonella strain.
Electron-impact excitation and ionization cross sections for ground state and excited helium atoms
International Nuclear Information System (INIS)
Ralchenko, Yu.; Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de
2008-01-01
Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n≤4 are treated individually, while the states with n≥5 are considered degenerate. For the processes involving transitions to and from n≥5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form
Lisewski, Andreas Martin; Lichtarge, Olivier
2010-08-01
Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.
Application of Stochastic variational method with correlated Ground States to coulombic systems
Energy Technology Data Exchange (ETDEWEB)
Usukura, Junko; Suzuki, Yasuyuki [Niigata Univ. (Japan); Varga, K.
1998-07-01
Positronium molecule, Ps{sub 2} has not been found experimentally yet, and it has been believed theoretically that Ps{sub 2} has only one bound state with L = 0. We predicted the existence of new bound state of Ps{sub 2}, which is the excited state with L = 1 and comes from Pauli principle, by Stochastic variational method. There are two decay mode with respect to Ps{sub 2}(P); one is pair annihilation and another is electric dipole (E1) transition to the ground state. While it is difficult to tell {gamma}-ray caused by annihilation of Ps{sub 2} from that of Ps since both of them have same energy, Energy (4.94 eV) of the photon emitted in E1 transition is specific enough to distinguish from other spectra. Then the excited state is one of clues to observe Ps{sub 2}. (author)
Role of entropy in the ground state formation of frustrated systems
Sereni, Julian G.
2018-05-01
The absence of magnetic order in Rare Earth-based frustrated compounds allows to recognize the action of the third law of thermodynamics in the low temperature behavior of those systems. One of the most relevant findings is the appearance of a coincident specific heat Cm / T|T→0 ≈ 7 J /molK2 'plateau' in six Yb systems. This characteristic feature occurs after a systematic modification of the thermal trajectory of their entropies Sm (T) in the range of a few hundred milikelvin degrees. Such behavior is explained by the formation of an entropy-bottleneck imposed by the third law constraint (Sm|T→0 ≥ 0), that drives the system into alternative ground states. Based in these finding, three possible approaches to the Sm|T→0 limit observed in real systems are analyzed in terms of the ∂2Sm / ∂T2 dependencies.
International Nuclear Information System (INIS)
Savolainen, Janne; Buckup, Tiago; Hauer, Juergen; Jafarpour, Aliakbar; Serrat, Carles; Motzkus, Marcus; Herek, Jennifer L.
2009-01-01
Ultrafast relaxation of a carotenoid in an artificial light-harvesting complex has been studied by transient absorption spectroscopy. The transient signal amplitudes at several wavelengths as well as the amplitudes of the underlying species associated spectra (SAS) are analysed for several excitation energies ranging over more than two orders of magnitude (10 nJ/pulse up to 3000 nJ/pulse). Our analysis shows that the contribution from the so-called S* signal on the long-wavelength side of the first allowed S 0 → S 2 transition has a markedly different excitation energy dependence and saturation behaviour than the electronic excited state S 1 . These observations are modelled and explained in terms of a two-photon excitation of a vibrationally hot ground state via an impulsive stimulated Raman scattering (ISRS). The experimental observations of the varying pulse energy dependencies of different excited state species are supported by an analysis based on a density-matrix formalism
Ground state oxygen holes and the metal-insulator transition in rare earth nickelates
Energy Technology Data Exchange (ETDEWEB)
Schmitt, Thorsten; Bisogni, Valentina; Huang, Yaobo; Strocov, Vladimir [Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Catalano, Sara; Gibert, Marta; Scherwitzl, Raoul; Zubko, Pavlo; Triscone, Jean-Marc [Departement de Physique de la Matiere Condensee, University of Geneva (Switzerland); Green, Robert J.; Balandeh, Shadi; Sawatzky, George [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)
2015-07-01
Perovskite rare-earth (Re) nickelates ReNiO{sub 3} continue to attract a lot of interest owing to their intriguing properties like a sharp metal to insulator transition (MIT), unusual magnetic order and expected superconductivity in specifically tuned super-lattices. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). From X-ray absorption (XAS) at the Ni 2p{sub 3/2} edge of thin films of NdNiO{sub 3} and corresponding RIXS maps vs. incident and transferred photon energies we reveal that the electronic GS configuration of NdNiO{sub 3} is composed of delocalized and localized components. Our study conveys that a Ni 3d{sup 8}-like configuration with holes at oxygen takes on the leading role in the GS and the MIT of ReNiO{sub 3} as proposed by recent model theories.
Far-infrared observations of Sagittarius B2 - reconsideration of source structure
International Nuclear Information System (INIS)
Thronson, H.A. Jr.; Harper, D.A.; Yerkes Observatory, Williams Bay, WI)
1986-01-01
New moderate-angular-resolution far-infrared observations of the Sagittarius B2 star-forming region are presented, discussed, and compared with recent radio molecular and continuum observations of this source. In contrast to previous analyses, its far-infrared spectrum is interpreted as the result of a massive frigid cloud overlying a more-or-less normal infrared source, a natural explanation for the object's previously-noted peculiarities. The characteristics derived for the obscuring cloud are similar to those found for the W51 MAIN object. Both sources have high sub-millimeter surface brightness, a high ratio of sub-millimeter to far-infrared flux, and numerous regions of molecular maser emission. 28 references
Xue, Gang; Song, Wen-qi; Li, Shu-chao
2015-01-01
In order to achieve the rapid identification of fire resistive coating for steel structure of different brands in circulating, a new method for the fast discrimination of varieties of fire resistive coating for steel structure by means of near infrared spectroscopy was proposed. The raster scanning near infrared spectroscopy instrument and near infrared diffuse reflectance spectroscopy were applied to collect the spectral curve of different brands of fire resistive coating for steel structure and the spectral data were preprocessed with standard normal variate transformation(standard normal variate transformation, SNV) and Norris second derivative. The principal component analysis (principal component analysis, PCA)was used to near infrared spectra for cluster analysis. The analysis results showed that the cumulate reliabilities of PC1 to PC5 were 99. 791%. The 3-dimentional plot was drawn with the scores of PC1, PC2 and PC3 X 10, which appeared to provide the best clustering of the varieties of fire resistive coating for steel structure. A total of 150 fire resistive coating samples were divided into calibration set and validation set randomly, the calibration set had 125 samples with 25 samples of each variety, and the validation set had 25 samples with 5 samples of each variety. According to the principal component scores of unknown samples, Mahalanobis distance values between each variety and unknown samples were calculated to realize the discrimination of different varieties. The qualitative analysis model for external verification of unknown samples is a 10% recognition ration. The results demonstrated that this identification method can be used as a rapid, accurate method to identify the classification of fire resistive coating for steel structure and provide technical reference for market regulation.
Xi, Teli; Dou, Jiazhen; Di, Jianglei; Li, Ying; Zhang, Jiwei; Ma, Chaojie; Zhao, Jianlin
2017-06-01
Short-coherence in-line phase-shifting digital holographic microscopy based on Michelson interferometer is proposed to measure internal structure in silicon. In the configuration, a short-coherence infrared laser is used as the light source in order to avoid the interference formed by the reference wave and the reflected wave from the front surface of specimen. At the same time, in-line phase-shifting configuration is introduced to overcome the problem of poor resolution and large pixel size of the infrared camera and improve the space bandwidth product of the system. A specimen with staircase structure is measured by using the proposed configuration and the 3D shape distribution are given to verify the effectiveness and accuracy of the method.
Energy Technology Data Exchange (ETDEWEB)
Seki, Hirofumi, E-mail: Hirofumi-Seki@trc.toray.co.jp; Hashimoto, Hideki [Toray Research Center, Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567 (Japan); Ozaki, Yukihiro [Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1, Gakuen, Sanda, Hyogo 669-1337 (Japan)
2016-09-07
Microscopic Fourier-transform infrared (FT-IR) spectra are measured for a Cu/low-k interconnect structure using polarized IR light for different widths of low-k spaces and Cu lines, and for different heights of Cu lines, on Si substrates. Although the widths of the Cu line and the low-k space are 70 nm each, considerably smaller than the wavelength of the IR light, the FT-IR spectra of the low-k film were obtained for the Cu/low-k interconnect structure. A suitable method was established for measuring the process-induced damage in a low-k film that was not detected by the TEM-EELS (Transmission Electron Microscope-Electron Energy-Loss Spectroscopy) using microscopic IR polarized light. Based on the IR results, it was presumed that the FT-IR spectra mainly reflect the structural changes in the sidewalls of the low-k films for Cu/low-k interconnect structures, and the mechanism of generating process-induced damage involves the generation of Si-OH groups in the low-k film when the Si-CH{sub 3} bonds break during the fabrication processes. The Si-OH groups attract moisture and the OH peak intensity increases. It was concluded that the increase in the OH groups in the low-k film is a sensitive indicator of low-k damage. We achieved the characterization of the process-induced damage that was not detected by the TEM-EELS and speculated that the proposed method is applicable to interconnects with line and space widths of 70 nm/70 nm and on shorter scales of leading edge devices. The location of process-induced damage and its mechanism for the Cu/low-k interconnect structure were revealed via the measurement method.
Optical properties of InAs/GaAs quantum dot superlattice structures
Imran, Ali; Jiang, Jianliang; Eric, Deborah; Zahid, M. Noaman; Yousaf, M.; Shah, Z. H.
2018-06-01
Quantum dot (QD) structure has potential applications in modern highly efficient optoelectronic devices due to their band-tuning. The device dimensions have been miniatured with increased efficiencies by virtue of this discovery. In this research, we have presented modified analytical and simulation results of InAs/GaAs QD superlattice (QDSL). We have applied tight binding model for the investigation of ground state energies using timeindependent Schrödinger equation (SE) with effective mass approximation. It has been investigated that the electron energies are confined due to wave function delocalization in closely coupled QD structures. The minimum ground state energy can be obtained by increasing the periodicity and decreasing the barrier layer thickness. We have calculated electronics and optical properties which includes ground state energies, transition energies, density of states (DOS), absorption coefficient and refractive index, which can be tuned by structure modification. In our results, the minimum ground state energy of QDSL is achieved to be 0.25 eV with a maximum period of 10 QDs. The minimum band to band and band to continuum transition energies are 63 meV and 130 meV with 2 nm barrier layer thickness respectively. The absorption coefficient of our proposed QDSL model is found to be maximum 1.2 × 104 cm-1 and can be used for highly sensitive infrared detector and high efficiency solar cells.
Energy Technology Data Exchange (ETDEWEB)
Stehr, D.
2007-12-28
This thesis deals with infrared studies of impurity states, ultrafast carrier dynamics as well as coherent intersubband polarizations in semiconductor quantum structures such as quantum wells and superlattices, based on the GaAs/AlGaAs material system. In the first part it is shown that the 2p{sub z} confined impurity state of a semiconductor quantum well develops into an excited impurity band in the case of a superlattice. This is studied by following theoretically the transition from a single to a multiple quantum well or superlattice by exactly diagonalizing the three-dimensional Hamiltonian for a quantum well system with random impurities. These results also require reinterpretation of previous experimental data. The relaxation dynamics of interminiband transitions in doped GaAs/AlGaAs superlattices in the mid-IR are studied. This involves single-color pump-probe measurements to explore the dynamics at different wavelengths, which is performed with the Rossendorf freeelectron laser (FEL), providing picosecond pulses in a range from 3-200 {mu}m and are used for the first time within this thesis. In these experiments, a fast bleaching of the interminiband transition is observed followed by thermalization and subsequent relaxation, whose time constants are determined to be 1-2 picoseconds. This is followed by an additional component due to carrier cooling in the lower miniband. In the second part, two-color pump-probe measurements are performed, involving the FEL as the pump source and a table-top broad-band tunable THz source for probing the transmission changes. In addition, the dynamics of excited electrons within the minibands is explored and their contribution quantitatively extracted from the measurements. Intersubband absorption experiments of photoexcited carriers in single quantum well structures, measured directly in the time-domain, i.e. probing coherently the polarization between the first and the second subband, are presented. By varying the carrier
Kwac, Kijeong; Geva, Eitan
2012-03-08
We present a mixed quantum-classical molecular dynamics study of the hydrogen-bonding structure and dynamics of a vibrationally excited hydroxyl stretch in methanol/carbon-tetrachloride mixtures. The adiabatic Hamiltonian of the quantum-mechanical hydroxyl is diagonalized on-the-fly to obtain the ground and first-excited adiabatic energy levels and wave functions which depend parametrically on the instantaneous configuration of the classical degrees of freedom. The dynamics of the classical degrees of freedom are determined by Hellmann-Feynman forces obtained by taking the expectation value of the force with respect to the ground or excited vibrational wave functions. Polarizable force fields are used which were previously shown to reproduce the experimental infrared absorption spectrum rather well, for different isotopomers and over a wide composition range [Kwac, K.; Geva, E. J. Phys. Chem. B 2011, 115, 9184]. We show that the agreement of the absorption spectra with experiment can be further improved by accounting for the dependence of the dipole moment derivatives on the configuration of the classical degrees of freedom. We find that the propensity of a methanol molecule to form hydrogen bonds increases upon photoexcitation of its hydroxyl stretch, thereby leading to a sizable red-shift of the corresponding emission spectrum relative to the absorption spectrum. Treating the relaxation from the first excited to the ground state as a nonadiabatic process, and calculating its rate within the framework of Fermi's golden rule and the harmonic-Schofield quantum correction factor, we were able to predict a lifetime which is of the same order of magnitude as the experimental value. The experimental dependence of the lifetime on the transition frequency is also reproduced. Nonlinear mapping relations between the hydroxyl transition frequency and bond length in the excited state and the electric field along the hydroxyl bond axis are established. These mapping relations
Tomaschitz, R
1989-01-01
We consider geodesic motion on three-dimensional Riemannian manifolds of constant negative curvature, topologically equivalent to S x ]0,1[, S a compact surface of genus two. To those trajectories which are bounded and recurrent in both directions of the time evolution a fractal limit set is associated whose Hausdorff dimension is intimately connected with the quantum mechanical energy ground state, determined by the Schrodinger operator on the manifold. We give a rather detailed and pictorial description of the hyperbolic spaces we have in mind, discuss various aspects of classical and quantum mechanical motion on them as far as they are needed to establish the connection between energy ground state and Hausdorff dimension and give finally some examples of ground state calculations in terms of Hausdorff dimensions of limit sets of classical trajectories.
International Nuclear Information System (INIS)
Zhang Guangming; Yu Lu
2000-04-01
The ground-state phase diagram of a half-filled anisotropic Kondo lattice model is calculated within a mean-field theory. For small transverse exchange coupling J perpendicular perpendicular c1 , the ground state shows an antiferromagnetic long-range order with finite staggered magnetizations of both localized spins and conduction electrons. When J perpendicular > J perpendicular c2 , the long-range order is destroyed and the system is in a disordered Kondo singlet state with a hybridization gap. Both ground states can describe the low-temperature phases of Kondo insulating compounds. Between these two distinct phases, there may be a coexistent regime as a result of the balance between local Kondo screening and magnetic interactions. (author)
International Nuclear Information System (INIS)
Tomaschitz, R.
1989-01-01
We consider geodesic motion on three-dimensional Riemannian manifolds of constant negative curvature, topologically equivalent to S x ]0,1[, S a compact surface of genus two. To those trajectories which are recurrent in both directions of the time evolution t → +∞, t → -∞ a fractal limit set is associated whose Hausdorff dimension is intimately connected with the quantum mechanical energy ground state, determined by the Schroedinger operator on the manifold. We give a rather detailed and pictorial description of the hyperbolic spaces we have in mind, discuss various aspects of classical and quantum mechanical motion on them as far as they are needed to establish the connection between energy ground state and Hausdorff dimension and give finally some examples of ground state calculations in terms of Hausdorff dimensions of limit sets of classical trajectories. (orig.)
Infrared spectroscopy and density functional calculations on titanium-dinitrogen complexes
Yoo, Hae-Wook; Choi, Changhyeok; Cho, Soo Gyeong; Jung, Yousung; Choi, Myong Yong
2018-04-01
Titanium-nitrogen complexes were generated by laser ablated titanium (Ti) atoms and N2 gas molecules in this study. These complexes were isolated on the pre-deposited solid Ar matrix on the pre-cooled KBr window (T ∼ 5.4 K), allowing infrared spectra to be measured. Laser ablation experiments with 15N2 isotope provided distinct isotopic shifts in the infrared spectra that strongly implicated the formation of titanium-nitrogen complexes, Ti(NN)x. Density functional theory (DFT) calculations were employed to investigate the molecular structures, electronic ground state, relative energies, and IR frequencies of the anticipated Ti(NN)x complexes. Based on laser ablation experiments and DFT calculations, we were able to assign multiple Ti(NN)x (x = 1-6) species. Particularly, Ti(NN)5 and Ti(NN)6, which have high nitrogen content, may serve as good precursors in preparing polynitrogens.
Combined effects of Sr substitution and pressure on the ground states in CaFe2As2
Knöner, S.; Gati, E.; Köhler, S.; Wolf, B.; Tutsch, U.; Ran, S.; Torikachvili, M. S.; Bud'ko, S. L.; Canfield, P. C.; Lang, M.
2016-10-01
We present a detailed study of the combined effects of Sr substitution and hydrostatic pressure on the ground-state properties of CaFe2As2 . Measurements of the electrical resistance and magnetic susceptibility, both at ambient and finite pressure P ≤2 GPa, were performed on Ca1 -xSrxFe2As2 single crystals grown out of Sn flux. We find that by Sr substitution the transition temperature to the magnetic/structural phase is enhanced and therefore a higher pressure is needed to suppress the transition to lowest temperature. In addition, the transition to the collapsed tetragonal phase is found at a pressure, which is distinctly higher than in the pure compound. This implies that the stability ranges of both phases shift on the pressure-axis upon doping, but the latter one with a higher rate. These observations suggest the possibility of separating the two phase lines, which intersect already at elevated temperatures for x =0 and low Sr concentration levels. For x =0.177 , we find strong evidence that both phases remain separated down to the lowest temperature and that a zero-resistance state emerges in this intermediate pressure window. This observation indicates that Sr substitution combined with hydrostatic pressure provides another route for stabilizing superconductivity in CaFe2As2 . Our results are consistent with the notion that (i) preserving the fluctuations associated with the structural-magnetic transition to low temperatures is vital for superconductivity to form in this material and that (ii) the nonmagnetic collapsed tetragonal phase is detrimental for superconductivity.
International Nuclear Information System (INIS)
Chen, Liang-Chia; Le, Manh-Trung; Phuc, Dao Cong; Lin, Shyh-Tsong
2014-01-01
The article presents the development of in-situ integrated circuit (IC) chip defect detection techniques for automated clipping detection by proposing infrared imaging and full-field volumetric topography. IC chip inspection, especially held during or post IC packaging, has become an extremely critical procedure in IC fabrication to assure manufacturing quality and reduce production costs. To address this, in the article, microscopic infrared imaging using an electromagnetic light spectrum that ranges from 0.9 to 1.7 µm is developed to perform volumetric inspection of IC chips, in order to identify important defects such as silicon clipping, cracking or peeling. The main difficulty of infrared (IR) volumetric imaging lies in its poor image contrast, which makes it incapable of achieving reliable inspection, as infrared imaging is sensitive to temperature difference but insensitive to geometric variance of materials, resulting in difficulty detecting and quantifying defects precisely. To overcome this, 3D volumetric topography based on 3D infrared confocal measurement with active structured light, as well as light refractive matching principles, is developed to detect defects the size, shape and position of defects in ICs. The experimental results show that the algorithm is effective and suitable for in-situ defect detection of IC semiconductor packaging. The quality of defect detection, such as measurement repeatability and accuracy, is addressed. Confirmed by the experimental results, the depth measurement resolution can reach up to 0.3 µm, and the depth measurement uncertainty with one standard deviation was verified to be less than 1.0% of the full-scale depth-measuring range. (paper)
International Nuclear Information System (INIS)
Su Zongdi; Ma Lizhen
1994-01-01
The management code of the sub-library of atomic mass and characteristic constants for nuclear ground state (MCC) is used for displaying the basic information on the MCC sub-library on the screen, and retrieving the required data. The MCC data file contains the data of 4800 nuclides ranging from Z 0, A = 1 to Z = 122, A = 318. The MCC sub-library has been set up at Chinese Nuclear Data Center (CNDC), and has been used to provide the atomic masses and characteristic constants of nuclear ground states for the nuclear model calculation, nuclear data evaluations and other fields
International Nuclear Information System (INIS)
Zheng Gong-Ping; Qin Shuai-Feng; Wang Shou-Yang; Jian Wen-Tian
2013-01-01
The ground states of the ultracold spin-1 atoms trapped in a deep one-dimensional double-well optical superlattice in a weak magnetic field are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic condensates. The transition between the singlet state and nematic state is observed for the antiferromagnetic interaction atoms, which can be realized by modulating the tunneling parameter or the quadratic Zeeman energy. An experiment to distinguish the different spin states is suggested. (general)
Experimental studies of the NaRb ground-state potential up to the v''=76 level
International Nuclear Information System (INIS)
Docenko, O.; Nikolayeva, O.; Tamanis, M.; Ferber, R.; Pazyuk, E.A.; Stolyarov, A.V.
2002-01-01
Laser induced fluorescence spectra of the C 1 Σ + -X 1 Σ + system of 23 Na 85 Rb and 23 Na 87 Rb have allowed vibrational levels of the electronic ground state up to v '' =76, spanning 99.85% of the potential well to be observed. The ground-state term values have been fitted to a Dunham polynomial expansion, and also to a direct modified Lennard-Jones (MLJ) potential. The analytical MLJ construction allowed us to match previous measured term values for v '' ≤30 with long-range behavior of the potential through the intermediate internuclear distance region covered by the present investigation
International Nuclear Information System (INIS)
Toenhardt, M.
1987-01-01
In this thesis only nuclei with even proton and even neutron number have been studied. This constraint allows to use a for the description of excitation spectra very successful model, the interacting boson model (IBM) and to combine this with the density functional method. From the obtained Hamiltonian via an energy-density functional an effective potential is constructed which can be applied in the framework of the density-functional method in order to calculate ground state energies and densities. From the density distributions radii and values for the static deformation are determined. As further ground state property the separation energy for two neutrons is studied. (orig./HSI) [de
Non-local ground-state functional for quantum spin chains with translational broken symmetry
Energy Technology Data Exchange (ETDEWEB)
Libero, Valter L.; Penteado, Poliana H.; Veiga, Rodrigo S. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica
2011-07-01
Full text. Thanks to the development and use of new materials with special doping, it becomes relevant the study of Heisenberg spin-chains with broken translational symmetry, induced for instance by finite-size effects, bond defects or by impurity spin in the chain. The exact numerical results demands huge computational efforts, due to the size of the Hilbert space involved and the lack of symmetry to exploit. Density Functional Theory (DFT) has been considered a simple alternative to obtain ground-state properties for such systems. Usually, DFT starts with a uniform system to build the correlation energy and after implement a local approximation to construct local functionals. Based on our prove of the Hohenberg-Kohn theorem for Heisenberg models, and in order to describe more realistic models, we have recently developed a non-local exchange functional for the ground-state energy of quantum-spin chains. A alternating-bond chain is used to obtain the correlation energy and a local unit-cell approximation - LUCA, is defined in the context of DFT. The alternating chain is a good starting point to construct functionals since it is intrinsically non-homogeneous, therefore instead of the usual local approximation (like LDA for electronic systems) we need to introduce an approximation based upon a unit cell concept, that renders a non-local functional in the bond exchange interaction. The agreement with exact numerical data (obtained only for small chains, although the functional can be applied for chains with arbitrary size) is significantly better than in our previous local formulation, even for chains with several ferromagnetic or antiferromagnetic bond defects. These results encourage us to extend the concept of LUCA for chains with alternating-spin magnitudes. We also have constructed a non-local functional based on an alternating-spin chain, instead of a local alternating-bond, using spin-wave-theory. Because of its non-local nature, this functional is expected to
High-field magnetoconductance in La-Sr manganites of FM and AFM ground states
Jirák, Zdeněk; Kaman, Ondřej; Knížek, Karel; Levinský, Petr; Míšek, Martin; Veverka, Pavel; Hejtmánek, Jiří
2018-06-01
Large-grain La1-xSrxMnO3 ceramic samples of compositions x = 0.45 and 0.55, representing the ferromagnetic (FM) and A-type antiferromagnetic (AFM) ground states, were produced via classical sintering at 1500 °C of cold-pressed sol-gel prepared single-phase nanoparticles. Using the same precursors, nanogranular forms of both manganite ceramics were prepared by fast spark plasma sintering at low temperature of 900 °C, which limits the growth of crystal grains. The magnetotransport of both the bulk and nanogranular forms was investigated in a broad range of magnetic fields up to 130 kOe and analyzed on the basis of detailed magnetic measurements. Both the large-grain and nanogranular systems with x = 0.45, possessing a pure FM state with similar Curie tempereature TC ≈ 345 K), show nearly the same conductivity enhancement in external fields when expressed relatively to the zero-field values. This positive magnetoconductance (MC) can be separated into two terms: (i) the hysteretic low-field MC that reflects the field-induced orientation of magnetic moments of individual grains, and (ii) the high-field MC that depends linearly on external field. In the case of large-grain ceramics with x = 0.55, a partially ordered FM state formed below TC = 264 K is replaced by pure A-type AFM ground state below 204 K. This A-type AFM state is characterized by positive magnetoconductance that is essentially of quadratic dependence on external field in the investigated range up to 130 kOe. On contrary, the nanogranular product with x = 0.55 exhibits a mixed FM/AFM state at low temperatures, and, as a consequence, its magnetotransport combines the features of FM and A-type AFM systems, in which the quadratic term is much enhanced and clearly dominates at high fields. For interpretation of observed behaviors, the theory of grain-boundary tunneling is revisited.
Non-local ground-state functional for quantum spin chains with translational broken symmetry
International Nuclear Information System (INIS)
Libero, Valter L.; Penteado, Poliana H.; Veiga, Rodrigo S.
2011-01-01
Full text. Thanks to the development and use of new materials with special doping, it becomes relevant the study of Heisenberg spin-chains with broken translational symmetry, induced for instance by finite-size effects, bond defects or by impurity spin in the chain. The exact numerical results demands huge computational efforts, due to the size of the Hilbert space involved and the lack of symmetry to exploit. Density Functional Theory (DFT) has been considered a simple alternative to obtain ground-state properties for such systems. Usually, DFT starts with a uniform system to build the correlation energy and after implement a local approximation to construct local functionals. Based on our prove of the Hohenberg-Kohn theorem for Heisenberg models, and in order to describe more realistic models, we have recently developed a non-local exchange functional for the ground-state energy of quantum-spin chains. A alternating-bond chain is used to obtain the correlation energy and a local unit-cell approximation - LUCA, is defined in the context of DFT. The alternating chain is a good starting point to construct functionals since it is intrinsically non-homogeneous, therefore instead of the usual local approximation (like LDA for electronic systems) we need to introduce an approximation based upon a unit cell concept, that renders a non-local functional in the bond exchange interaction. The agreement with exact numerical data (obtained only for small chains, although the functional can be applied for chains with arbitrary size) is significantly better than in our previous local formulation, even for chains with several ferromagnetic or antiferromagnetic bond defects. These results encourage us to extend the concept of LUCA for chains with alternating-spin magnitudes. We also have constructed a non-local functional based on an alternating-spin chain, instead of a local alternating-bond, using spin-wave-theory. Because of its non-local nature, this functional is expected to
Chen, Y.; Guan, J.; Hu, H.; Gao, H.; Zhang, L.
2016-07-01
A series of natural rubber/styrene butadiene rubber/polybutadiene rubber composites was prepared with nanometer silica and micron kaolin by a dry modification process, mechanical compounding, and mold vulcanization. Fourier transform infrared spectroscopy and a scanning electron microscope were used to investigate the structural changes and interfacial interactions in composites. The results showed that the "seesaw" structure was formed particularly with the incorporation of silica particles in the preparation process, which would be beneficial to the dispersibility of fillers in the rubber matrix. The kaolinite platelets were generally arranged in directional alignment. Kaolinite with smaller particle size and low-defect structure was more stable in preparation, but kaolinite with larger particle size and high defect structure tended to change the crystal structure. The composite prepared in this research exhibited excellent mechanical and thermal properties.
Characterisation of structure-dependent functional properties of lignin with infrared spectroscopy
Boeriu, C.G.; Bravo, D.; Gosselink, R.J.A.; Dam, van J.E.G.
2004-01-01
Fourier-transformed infrared spectroscopy (FT-IR) was evaluated as an analytical technique for the estimation of the chemical composition and functional properties of lignin. A sample set containing various non-wood, hardwood and softwood lignins isolated by different processing technologies was
Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure
Varga, J.; Gabányi, K. É.; Ábrahám, P.; Chen, L.; Kóspál, Á.; Menu, J.; Ratzka, Th.; van Boekel, R.; Dullemond, C. P.; Henning, Th.; Jaffe, W.; Juhász, A.; Moór, A.; Mosoni, L.; Sipos, N.
2017-08-01
Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 μm silicate feature from emission to absorption temporarily. Aims: We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods: Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results: The inner disk (r 1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions: For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk. Based on observations made with the ESO Very Large
Existence of ground state of an electron in the BDF approximation
Sok, Jérémy
2014-05-01
The Bogoliubov-Dirac-Fock (BDF) model allows us to describe relativistic electrons interacting with the Dirac sea. It can be seen as a mean-field approximation of Quantum Electrodynamics (QED) where photons are neglected. This paper treats the case of an electron together with the Dirac sea in the absence of any external field. Such a system is described by its one-body density matrix, an infinite rank, self-adjoint operator. The parameters of the model are the coupling constant α > 0 and the ultraviolet cut-off Λ > 0: we consider the subspace of squared integrable functions made of the functions whose Fourier transform vanishes outside the ball B(0, Λ). We prove the existence of minimizers of the BDF energy under the charge constraint of one electron and no external field provided that α, Λ-1 and α log(Λ) are sufficiently small. The interpretation is the following: in this regime the electron creates a polarization in the Dirac vacuum which allows it to bind. We then study the non-relativistic limit of such a system in which the speed of light tends to infinity (or equivalently α tends to zero) with αlog(Λ) fixed: after rescaling and translation the electronic solution tends to a Choquard-Pekar ground state.
Ioffe, Ilya; Dobryakov, Alexander L; Granovsky, Alexander A; Ernsting, Nikolaus P; Lustres, J Luis Pérez
2011-07-11
Photoisomerization around a central fulvene-type double bond is known to proceed through a conical intersection at the perpendicular geometry. The process is studied with an indenylidene-dihydropyridine model compound, allowing the use of visible excitation pulses. Transient absorption shows that 1) stimulated emission shifts to the red and loses oscillator strength on a 50 fs timescale, and 2) bleach recovery is highly nonexponential and not affected by solvent viscosity or methyl substitution at the dihydropyridine ring. Quantum-chemical calculations are used to explain point 1 as a result of initial elongation of the central C=C bond with mixing of S(2) and S(1) states. From point 2 it is concluded that internal conversion of S(1)→S(0) does not require torsional motion to the fully perpendicular state. The S(1) population appears to encounter a sink on the torsional coordinate before the conical intersection is reached. Rate equations cannot model the observed ground-state recovery adequately. Instead the dynamics are best described with a strongly damped oscillatory contribution, which could indicate coherent S(1)-S(0) population transfer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Equilibrium states and ground state of two-dimensional fluid foams
International Nuclear Information System (INIS)
Graner, F.; Jiang, Y.; Janiaud, E.; Flament, C.
2001-01-01
We study the equilibrium energies of two-dimensional (2D) noncoarsening fluid foams, which consist of bubbles with fixed areas. The equilibrium states correspond to local minima of the total perimeter. We present a theoretical derivation of energy minima; experiments with ferrofluid foams, which can be either highly distorted, locally relaxed, or globally annealed; and Monte Carlo simulations using the extended large-Q Potts model. For a dry foam with small size variance we develop physical insight and an electrostatic analogy, which enables us to (i) find an approximate value of the global minimum perimeter, accounting for (small) area disorder, the topological distribution, and physical boundary conditions; (ii) conjecture the corresponding pattern and topology: small bubbles sort inward and large bubbles sort outward, topological charges of the same signs ''repel'' while charges of the opposite signs ''attract;'' (iii) define local and global markers to determine directly from an image how far a foam is from its ground state; (iv) conjecture that, in a local perimeter minimum at prescribed topology, the pressure distribution and thus the edge curvature are unique. Some results also apply to 3D foams