Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3

International Nuclear Information System (INIS)

Qing-Li, Zhang; Kai-Jie, Ning; Jin, Xiao; Li-Hua, Ding; Wen-Long, Zhou; Wen-Peng, Liu; Shao-Tang, Yin; Hai-He, Jiang

2010-01-01

A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb 3+ in Sc 2 O 3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Generalized field-splitting algorithms for optimal IMRT delivery efficiency

Energy Technology Data Exchange (ETDEWEB)

Kamath, Srijit [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Sahni, Sartaj [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Li, Jonathan [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Ranka, Sanjay [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Palta, Jatinder [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States)

2007-09-21

Intensity-modulated radiation therapy (IMRT) uses radiation beams of varying intensities to deliver varying doses of radiation to different areas of the tissue. The use of IMRT has allowed the delivery of higher doses of radiation to the tumor and lower doses to the surrounding healthy tissue. It is not uncommon for head and neck tumors, for example, to have large treatment widths that are not deliverable using a single field. In such cases, the intensity matrix generated by the optimizer needs to be split into two or three matrices, each of which may be delivered using a single field. Existing field-splitting algorithms used the pre-specified arbitrary split line or region where the intensity matrix is split along a column, i.e., all rows of the matrix are split along the same column (with or without the overlapping of split fields, i.e., feathering). If three fields result, then the two splits are along the same two columns for all rows. In this paper we study the problem of splitting a large field into two or three subfields with the field width as the only constraint, allowing for an arbitrary overlap of the split fields, so that the total MU efficiency of delivering the split fields is maximized. Proof of optimality is provided for the proposed algorithm. An average decrease of 18.8% is found in the total MUs when compared to the split generated by a commercial treatment planning system and that of 10% is found in the total MUs when compared to the split generated by our previously published algorithm. For more information on this article, see medicalphysicsweb.org.

Effect of pressure on the crystal field splitting in rare earth pnictides and chalcogenides

International Nuclear Information System (INIS)

Schirber, J.E.; Weaver, H.T.

1978-01-01

The experimental situation for the pressure dependence of the crystal field of praseodymium pnictides and chalcogenides is reviewed and compared with the predictions of the point charge model. The problem of separating exchange and crystal field contributions from the measured NMR frequency shift or susceptibility measurements is discussed as well as problems explaining these effects with conduction electron related models

An energy-stable convex splitting for the phase-field crystal equation

KAUST Repository

Vignal, P.; Dalcin, L.; Brown, D. L.; Collier, N.; Calo, V. M.

2015-01-01

Abstract The phase-field crystal equation, a parabolic, sixth-order and nonlinear partial differential equation, has generated considerable interest as a possible solution to problems arising in molecular dynamics. Nonetheless, solving this equation is not a trivial task, as energy dissipation and mass conservation need to be verified for the numerical solution to be valid. This work addresses these issues, and proposes a novel algorithm that guarantees mass conservation, unconditional energy stability and second-order accuracy in time. Numerical results validating our proofs are presented, and two and three dimensional simulations involving crystal growth are shown, highlighting the robustness of the method. © 2015 Elsevier Ltd.

An energy-stable convex splitting for the phase-field crystal equation

KAUST Repository

Vignal, P.

2015-10-01

Abstract The phase-field crystal equation, a parabolic, sixth-order and nonlinear partial differential equation, has generated considerable interest as a possible solution to problems arising in molecular dynamics. Nonetheless, solving this equation is not a trivial task, as energy dissipation and mass conservation need to be verified for the numerical solution to be valid. This work addresses these issues, and proposes a novel algorithm that guarantees mass conservation, unconditional energy stability and second-order accuracy in time. Numerical results validating our proofs are presented, and two and three dimensional simulations involving crystal growth are shown, highlighting the robustness of the method. © 2015 Elsevier Ltd.

On standardization of low symmetry crystal fields

Science.gov (United States)

Gajek, Zbigniew

2015-07-01

Standardization methods of low symmetry - orthorhombic, monoclinic and triclinic - crystal fields are formulated and discussed. Two alternative approaches are presented, the conventional one, based on the second-rank parameters and the standardization based on the fourth-rank parameters. Mainly f-electron systems are considered but some guidelines for d-electron systems and the spin Hamiltonian describing the zero-field splitting are given. The discussion focuses on premises for choosing the most suitable method, in particular on inadequacy of the conventional one. Few examples from the literature illustrate this situation.

ISR split-field magnet

CERN Multimedia

CERN PhotoLab

1975-01-01

The experimental apparatus used at intersection 4 around the Split-Field Magnet by the CERN-Bologna Collaboration (experiment R406). The plastic scintillator telescopes are used for precise pulse-height and time-of-flight measurements.

Theoretical calculation of zero field splitting parameters of Cr{sup 3+} doped ammonium oxalate monohydrate

Energy Technology Data Exchange (ETDEWEB)

Kripal, Ram, E-mail: ram_kripal2001@rediffmail.com; Yadav, Awadhesh Kumar, E-mail: aky.physics@gmail.com

2015-06-15

Zero field splitting parameters (ZFSPs) D and E of Cr{sup 3+} ion doped ammonium oxalate monohydrate (AOM) are calculated with formula using the superposition model. The theoretically calculated ZFSPs for Cr{sup 3+} in AOM crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). Theoretical ZFSPs are in good agreement with the experimental ones. The energy band positions of optical absorption spectra of Cr{sup 3+} in AOM crystal calculated with CFA package are in good match with the experimental values.

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting.

Science.gov (United States)

Meng, Ming; Zhou, Sihua; Yang, Lun; Gan, Zhixing; Liu, Kuili; Tian, Fengshou; Zhu, Yu; Li, ChunYang; Liu, Weifeng; Yuan, Honglei; Zhang, Yan

2018-04-02

We report the design, fabrication and characterization of novel TiO 2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO 2 nanotube photonic crystals are fabricated by annealing of anodized TiO 2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO 2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm -2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO 2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Crystal electric field splitting of R{sup 3+}-ions in pure and Co- and Cu-doped RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm)

Energy Technology Data Exchange (ETDEWEB)

Gasser, U.; Allenspach, P.; Henggeler, W.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-09-01

From the crystal-electric-field (CEF) splitting of the R{sup 3+}-ions, the CEF parameters of RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm) were deduced. In order to get information about the influence of the variation of the density of states (DOS) at the Fermi level (E{sub F}), CEF spectroscopy measurements with Co- and Cu-doped ErNi{sub 2}B{sub 2}C-samples were performed. (author) 1 fig., 1 tab., 1 ref.

Split Octonion electrodynamics and unified fields of dyons

International Nuclear Information System (INIS)

Bisht, P.S.

2004-01-01

Split octonion electrodynamics has been developed in terms of Zorn's vector matrix realization by reformulating electromagnetic potential, current, field tensor and other dynamical quantities. Corresponding field equation (Unified Maxwell's equations) and equation of motion have been reformulated by means of split octonion and its Zorn vector realization in unique, simpler and consistent manner. It has been shown that this theory reproduces the dyon field equations in the absence of gravito-dyons and vice versa

Revealing the consequences and errors of substance arising from the inverse confusion between the crystal (ligand) field quantities and the zero-field splitting ones

Science.gov (United States)

Rudowicz, Czesław; Karbowiak, Mirosław

2015-01-01

Survey of recent literature has revealed a doubly-worrying tendency concerning the treatment of the two distinct types of Hamiltonians, namely, the physical crystal field (CF), or equivalently ligand field (LF), Hamiltonians and the zero-field splitting (ZFS) Hamiltonians, which appear in the effective spin Hamiltonians (SH). The nature and properties of the CF (LF) Hamiltonians have been mixed up in various ways with those of the ZFS Hamiltonians. Such cases have been identified in a rapidly growing number of studies of the transition-ion based systems using electron magnetic resonance (EMR), optical spectroscopy, and magnetic measurements. These findings have far ranging implications since these Hamiltonians are cornerstones for interpretation of magnetic and spectroscopic properties of the single transition ions in various crystals or molecules as well as the exchange coupled systems (ECS) of transition ions, e.g. single molecule magnets (SMM) or single ion magnets (SIM). The seriousness of the consequences of such conceptual problems and related terminological confusions has reached a level that goes far beyond simple semantic issues or misleading keyword classifications of papers in journals and scientific databases. The prevailing confusion, denoted as the CF=ZFS confusion, pertains to the cases of labeling the true ZFS quantities as purportedly the CF (LF) quantities. Here we consider the inverse confusion between the CF (LF) quantities and the SH (ZFS) ones, denoted the ZFS=CF confusion, which consists in referring to the parameters (or Hamiltonians), which are the true CF (LF) quantities, as purportedly the ZFS (or SH) quantities. Specific cases of the ZFS=CF confusion identified in recent textbooks, reviews and papers, especially SMM- and SIM-related ones, are surveyed and the pertinent misconceptions are clarified. The serious consequences of the terminological confusions include misinterpretation of data from a wide range of experimental techniques and

Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields

Science.gov (United States)

Bertaina, S.; Shim, J. H.; Gambarelli, S.; Malkin, B. Z.; Barbara, B.

2009-11-01

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several μs) and the Rabi frequency ΩR is anisotropic. Here, we present a study of the variations of ΩR(H→0) with the magnitude and direction of the static magnetic field H→0 for the odd Er167 isotope in a single crystal CaWO4:Er3+. The hyperfine interactions split the ΩR(H→0) curve into eight different curves which are fitted numerically and described analytically. These “spin-orbit qubits” should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

Computational split-field finite-difference time-domain evaluation of simplified tilt-angle models for parallel-aligned liquid-crystal devices

Science.gov (United States)

Márquez, Andrés; Francés, Jorge; Martínez, Francisco J.; Gallego, Sergi; Álvarez, Mariela L.; Calzado, Eva M.; Pascual, Inmaculada; Beléndez, Augusto

2018-03-01

Simplified analytical models with predictive capability enable simpler and faster optimization of the performance in applications of complex photonic devices. We recently demonstrated the most simplified analytical model still showing predictive capability for parallel-aligned liquid crystal on silicon (PA-LCoS) devices, which provides the voltage-dependent retardance for a very wide range of incidence angles and any wavelength in the visible. We further show that the proposed model is not only phenomenological but also physically meaningful, since two of its parameters provide the correct values for important internal properties of these devices related to the birefringence, cell gap, and director profile. Therefore, the proposed model can be used as a means to inspect internal physical properties of the cell. As an innovation, we also show the applicability of the split-field finite-difference time-domain (SF-FDTD) technique for phase-shift and retardance evaluation of PA-LCoS devices under oblique incidence. As a simplified model for PA-LCoS devices, we also consider the exact description of homogeneous birefringent slabs. However, we show that, despite its higher degree of simplification, the proposed model is more robust, providing unambiguous and physically meaningful solutions when fitting its parameters.

Automatic feathering of split fields for step-and-shoot intensity modulated radiation therapy

International Nuclear Information System (INIS)

Dogan, Nesrin; Leybovich, Leonid B; Sethi, Anil; Emami, Bahman

2003-01-01

Due to leaf travel range limitations of the Varian Dynamic Multileaf Collimator (DMLC) system, an IMRT field width exceeding 14.5 cm is split into two or more adjacent abutting sub-fields. The abutting sub-fields are then delivered as separate treatment fields. The accuracy of the delivery is very sensitive to multileaf positioning accuracy. The uncertainties in leaf and carriage positions cause errors in the delivered dose (e.g., hot or cold spots) along the match line of abutting sub-fields. The dose errors are proportional to the penumbra slope at the edge of each sub-field. To alleviate this problem, we developed techniques that feather the split line of IMRT fields. Feathering of the split line was achieved by dividing IMRT fields into several sub-groups with different split line positions. A Varian 21EX accelerator with an 80-leaf DLMC was used for IMRT delivery. Cylindrical targets with varying widths (>14.5 cm) were created to study the split line positions. Seven coplanar 6 MV fields were selected for planning using the NOMOS-CORVUS TM system. The isocentre of the fields was positioned at the centre of the target volume. Verification was done in a 30 x 30 x 30 cm 3 polystyrene phantom using film dosimetry. We investigated two techniques to move the split line from its original position or cause feathering of them: (1) varying the isocentre position along the target width and (2) introduction of a 'pseudo target' outside of the patient (phantom). The position of the 'pseudo target' was determined by analysing the divergence of IMRT fields. For target widths of 14-28 cm, IMRT fields were automatically split into two sub-fields, and the split line was positioned along the centre of the target by CORVUS. Measured dose distributions demonstrated that the dose to the critical structure was 10% higher than planned when the split line crossed through the centre of the target. Both methods of modifying the split line positions resulted in maximum shifts of ∼1 cm

Electric-Field Effects in ESR Spectrum of Low-Spin Center Ni3+ in KTaO3 Crystals (Preprint)

National Research Council Canada - National Science Library

Sochava, L. S; Basun, S. A; Bursian, V. E; Razdobarin, A. G; Evans, Dean R

2007-01-01

...+ was studied in KTaO3 single crystals. Orientation of the centers as well as splitting of the resonance lines was found resulting from the external E-field interaction with the electric dipole moment of the center...

Clarification of the confusion concerning the crystal-field quantities vs the zero-field splitting quantities in magnetism studies: Part II-Survey of literature dealing with model studies of spin systems

International Nuclear Information System (INIS)

Rudowicz, C.

2008-01-01

For respective quantities, i.e., Hamiltonians, parameters, and energy level splittings, related to two physically distinct notions X and Y, various cases of confused terminology have been identified in literature. Referring to a quantity related actually to the notion Y using incorrectly the name of another well-defined notion X constitutes, what may be defined for short as, the type X=Y confusion. An ongoing survey of magnetism literature indicates that quantities related to zero-field splitting (ZFS) or equivalently fine structure (FS) are most often confused with those related to crystal-field (CF) or equivalently ligand field (LF). In this review the CF=ZFS confusion cases, i.e., labelling actual ZFS/FS quantities as purportedly 'CF/LF' ones, appearing in magnetism studies are surveyed and clarified. Part I covers the cases occurring in literature dealing with specific compounds. In this part model studies of spin systems are surveyed. The cases of terminology mixing up actual ZFS/FS quantities with purported CF/LF ones are identified and presented comprehensively in tabular form. To facilitate discussion, problems pertinent for the CF=ZFS confusion are categorized into several groups, including origin of the two notions, physical consequences, usage of specific numerical values, invoking real magnetic spin systems, and properties of spin S=1/2 systems. Physical implications of this confusion for interpretation of model results are also considered. Overall implications of incorrect terminology go beyond simple semantic issues and concern possible misinterpretation of data describing various physical properties of models studied. Such terminology contributes also to misleading keyword classifications of papers in journals and scientific databases. Other types of confusion identified in survey of magnetism literature will be discussed in separate reviews

Gauge invariant frequency splitting of the continuum Yang-Mills field

International Nuclear Information System (INIS)

Mitter, P.K.; Valent, G.

1977-01-01

Frequency splitting plays an important role in Wilson's theory of critical phenomena. Here the authors give a theory of gauge invariant frequency splitting of the Yang-Mills field in 4 dimensions. (Auth.)

Gigantic spin splitting of exciton states in CdSe:Mn hexagonal crystal

International Nuclear Information System (INIS)

Komarov, A.V.; Ryabchenko, S.M.; Semenov, Yu.G.; Shanina, B.D.; Vitrikhovskij, N.I.; AN Ukrainskoj SSR, Kiev. Inst. Poluprovodnikov)

1980-01-01

Gigantic spin splitting of exciton states in magneto-doped semiconductors is observed for the first time in the CdSe: Mn hexagonal crystal. A theoretical interpretation of some features of the effect due to the anisotropy of the crystal is presented. The parameters of the band structure are determined by comparing with the experiments: Δ 1 =46+-3, Δ 2 =137+-1, Δ 3 =140.6+-0.3 meV. It is shown that in CdSe:Mn just as in cubic semiconductors, exchange interaction with magnetic impurities is ferromagnetic for electrons of the conductivity band and antiferromagnetic for electrons of the valence band. The exchange constants are of the same order of magnetude as those for the CdTe:Mn, ZnTe:Mn and ZnSe:Mn crystals

DETECTION OF FLUX EMERGENCE, SPLITTING, MERGING, AND CANCELLATION OF NETWORK FIELD. I. SPLITTING AND MERGING

Energy Technology Data Exchange (ETDEWEB)

Iida, Y.; Yokoyama, T. [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hagenaar, H. J. [Lockheed Martin Advanced Technology Center, Org. ADBS, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

2012-06-20

Frequencies of magnetic patch processes on the supergranule boundary, namely, flux emergence, splitting, merging, and cancellation, are investigated through automatic detection. We use a set of line-of-sight magnetograms taken by the Solar Optical Telescope (SOT) on board the Hinode satellite. We found 1636 positive patches and 1637 negative patches in the data set, whose time duration is 3.5 hr and field of view is 112'' Multiplication-Sign 112''. The total numbers of magnetic processes are as follows: 493 positive and 482 negative splittings, 536 positive and 535 negative mergings, 86 cancellations, and 3 emergences. The total numbers of emergence and cancellation are significantly smaller than those of splitting and merging. Further, the frequency dependence of the merging and splitting processes on the flux content are investigated. Merging has a weak dependence on the flux content with a power-law index of only 0.28. The timescale for splitting is found to be independent of the parent flux content before splitting, which corresponds to {approx}33 minutes. It is also found that patches split into any flux contents with the same probability. This splitting has a power-law distribution of the flux content with an index of -2 as a time-independent solution. These results support that the frequency distribution of the flux content in the analyzed flux range is rapidly maintained by merging and splitting, namely, surface processes. We suggest a model for frequency distributions of cancellation and emergence based on this idea.

Crystal-field and clustering effects in the specific heat of Dy in Pd

International Nuclear Information System (INIS)

Devine, R.A.B.; Jacques, P.; Poirier, M.

1975-01-01

Recent results of specific-heat measurements on dilute alloys of Dy in Pd are reanalyzed. Assuming the ionic ground state found from paramagnetic-resonance measurements, the Schottky-anomaly and cluster contributions are segregated and the crystal-field splitting of the ground and first-excited states is found to be in reasonable agreement with theoretical predictions. The nature of the cluster contribution is discussed and an upper limit to the range of the Ruderman-Kittel-Kasuya-Yosida interaction deduced

Split-Field Magnet facility upgraded

CERN Multimedia

CERN PhotoLab

1977-01-01

The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton. Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In 1976 an improved programme was started with tw...

Plasmonic enhancement in BiVO4 photonic crystals for efficient water splitting.

Science.gov (United States)

Zhang, Liwu; Lin, Chia-Yu; Valev, Ventsislav K; Reisner, Erwin; Steiner, Ullrich; Baumberg, Jeremy J

2014-10-15

Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm(-2) at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field.

Science.gov (United States)

Zhao, Chuan; Norden, Tenzin; Zhang, Peiyao; Zhao, Puqin; Cheng, Yingchun; Sun, Fan; Parry, James P; Taheri, Payam; Wang, Jieqiong; Yang, Yihang; Scrace, Thomas; Kang, Kaifei; Yang, Sen; Miao, Guo-Xing; Sabirianov, Renat; Kioseoglou, George; Huang, Wei; Petrou, Athos; Zeng, Hao

2017-08-01

Exploiting the valley degree of freedom to store and manipulate information provides a novel paradigm for future electronics. A monolayer transition-metal dichalcogenide (TMDC) with a broken inversion symmetry possesses two degenerate yet inequivalent valleys, which offers unique opportunities for valley control through the helicity of light. Lifting the valley degeneracy by Zeeman splitting has been demonstrated recently, which may enable valley control by a magnetic field. However, the realized valley splitting is modest (∼0.2 meV T -1 ). Here we show greatly enhanced valley spitting in monolayer WSe 2 , utilizing the interfacial magnetic exchange field (MEF) from a ferromagnetic EuS substrate. A valley splitting of 2.5 meV is demonstrated at 1 T by magnetoreflectance measurements and corresponds to an effective exchange field of ∼12 T. Moreover, the splitting follows the magnetization of EuS, a hallmark of the MEF. Utilizing the MEF of a magnetic insulator can induce magnetic order and valley and spin polarization in TMDCs, which may enable valleytronic and quantum-computing applications.

Symmetrical analysis of the defect level splitting in two-dimensional photonic crystals

International Nuclear Information System (INIS)

Malkova, N; Kim, S; Gopalan, V

2003-01-01

In this paper doubly degenerate defect states in the band gap of the two-dimensional photonic crystal are studied. These states can be split by a convenient distortion of the lattice. Through analogy with the Jahn-Teller effect in solids, we present a group theoretical analysis of the lifting of the degeneracy of doubly degenerate states in a square lattice by different vibronic modes. The effect is supported by the supercell plane-wave model and by the finite difference time domain technique. We suggest ways for using the effect in photonic switching devices and waveguides

Split-field vs extended-field intensity-modulated radiation therapy plans for oropharyngeal cancer: Which spares the larynx? Which spares the thyroid?

Energy Technology Data Exchange (ETDEWEB)

Yu, Yao; Chen, Josephine [Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA (United States); Leary, Celeste I. [Department of Radiation Medicine, Oregon Health Sciences University, Portland, OR (United States); Shugard, Erin [Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA (United States); Yom, Sue S., E-mail: yoms@radonc.ucsf.edu [Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA (United States); Department of Otolaryngology—Head and Neck Surgery, University of California, San Francisco, San Francisco, CA (United States)

2016-07-01

Radiation of the low neck can be accomplished using split-field intensity-modulated radiation therapy (sf-IMRT) or extended-field intensity-modulated radiation therapy (ef-IMRT). We evaluated the effect of these treatment choices on target coverage and thyroid and larynx doses. Using data from 14 patients with cancers of the oropharynx, we compared the following 3 strategies for radiating the low neck: (1) extended-field IMRT, (2) traditional split-field IMRT with an initial cord-junction block to 40 Gy, followed by a full-cord block to 50 Gy, and (3) split-field IMRT with a full-cord block to 50 Gy. Patients were planned using each of these 3 techniques. To facilitate comparison, extended-field plans were normalized to deliver 50 Gy to 95% of the neck volume. Target coverage was assessed using the dose to 95% of the neck volume (D{sub 95}). Mean thyroid and larynx doses were computed. Extended-field IMRT was used as the reference arm; the mean larynx dose was 25.7 ± 7.4 Gy, and the mean thyroid dose was 28.6 ± 2.4 Gy. Split-field IMRT with 2-step blocking reduced laryngeal dose (mean larynx dose 15.2 ± 5.1 Gy) at the cost of a moderate reduction in target coverage (D{sub 95} 41.4 ± 14 Gy) and much higher thyroid dose (mean thyroid dose 44.7 ± 3.7 Gy). Split-field IMRT with initial full-cord block resulted in greater laryngeal sparing (mean larynx dose 14.2 ± 5.1 Gy) and only a moderately higher thyroid dose (mean thyroid dose 31 ± 8 Gy) but resulted in a significant reduction in target coverage (D{sub 95} 34.4 ± 15 Gy). Extended-field IMRT comprehensively covers the low neck and achieves acceptable thyroid and laryngeal sparing. Split-field IMRT with a full-cord block reduces laryngeal doses to less than 20 Gy and spares the thyroid, at the cost of substantially reduced coverage of the low neck. Traditional 2-step split-field IMRT similarly reduces the laryngeal dose but also reduces low-neck coverage and delivers very high doses to the thyroid.

Crystal-field and Nd-Mn exchange interaction in Nd{sub 2/3}Ca{sub 1/3}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Beznosov, A; Fertman, E; Desnenko, V; Loginov, A [B Verkin Institute for Low Temperature Physics and Engineering, NASU, 47 Lenin Ave., 61103 Kharkov (Ukraine); Feher, A; Kajnakova, M, E-mail: fertman@ilt.kharkov.u [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kotice (Slovakia)

2010-01-01

A study of the low field magnetization and specific heat in magnetic fields up to 9 T of Nd{sub 2/3}Ca{sub 1/3}MnO{sub 3} perovskite in the 2-30 K temperature range has been done. All the specific heat data show broadened Schottky-like anomaly below 20 K. We suppose that such a behavior originates from the Nd magnetic ordering caused by the splitting of the Nd{sup 3+} ions ground-state doublet (GSD) in the effective molecular field H{sub ex} of Mn spin system supplemented by an applied external magnetic field. The zero field GSD splitting is an evidence of a strong exchange coupling between Nd and Mn magnetic subsystems. The Nd-ions magnetic ordering introduces an additional contribution to the ferromagnetic moment producing anomalies of the field-cooled and zero-field-cooled magnetizations of the system below 28 K. The broadened Schottky-like anomalies found are fitted for every field by a set of three Schottky functions. Applied magnetic field extends the anomaly region and shifts it to the higher temperatures. Splitting of the higher crystal field Kramers doublets gives an additional contribution to the heat capacity under magnetic fields. The GSD g-factors g{sub ||} and g{sub p}erpendicular was estimated as 3.4 and 2.2, respectively, and H{sub ex} as 9 T.

Light propagation in a magneto-optical hyperbolic biaxial crystal

Science.gov (United States)

Kuznetsov, Evgeniy V.; Merzlikin, Alexander M.

2017-12-01

The light propagation through a magneto-optical hyperbolic biaxial crystal is investigated. Magnetization of the structure results in splitting and reconnection of an isofrequency near the self-intersection point and thus it leads to the disappearance of conical refraction in a crystal. In its turn the isofrequency splitting leads to band gap opening and makes it possible to steer the beam. These effects allow to control the light propagation by means of an external magnetostatic field. The Poynting's vector distribution in the crystal is calculated by means of a Fourier transform in order to demonstrate the aforementioned effects.

Crystal field excitations of YbMn{sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Mole, R.A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia); School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Hofmann, M. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, 85747 Garching (Germany); Adroja, D.T. [ISIS Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, OX11 OQX (United Kingdom); Moze, O. [Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia, Modena (Italy); Campbell, S.J., E-mail: stewart.campbell@adfa.edu.au [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia)

2013-12-15

The crystal field excitations of the rare earth intermetallic compound YbMn{sub 2}Si{sub 2} have been measured by inelastic neutron scattering over the temperature range 2.5–50 K. The YbMn{sub 2}Si{sub 2} spectra exhibit three low energy excitations (∼3–7 meV) in the antiferromagnetic AFil region above the magnetic phase transition at T{sub N2} = 30(5) K. The crystal field parameters have been determined for YbMn{sub 2}Si{sub 2} in the antiferromagnetic AFil region. A further two inelastic excitations (∼9 meV, 17 meV) are observed below T{sub N2}=30(5) K, the temperature at which the high temperature antiferromagnetic structure is reported to exhibit doubling of the magnetic cell. Energy level diagrams have been determined for Yb{sup 3+} ions in the different sites above (single site) and below the magnetic transition temperature (two sites). The excitation energies for both sites are shown to be temperature independent with the temperature dependences of the transition intensities for the two sites described well by a simple Boltzmann model. The spectra below T{sub N2} cannot be described fully in terms of molecular field models based on either a single Yb{sup 3+} site or two Yb{sup 3+} sites. This indicates that the magnetic behaviour of YbMn{sub 2}Si{sub 2} is more complicated than previously considered. The inability to account fully for excitations below the magnetic phase transition may be due to an, as yet, unresolved structural transition associated with the magnetic transition. - Highlights: • The inelastic neutron scattering from YbMn{sub 2}Si{sub 2} has been investigated over the temperature range 2.5–50 K. • The crystal field splitting has been monitored through the magnetic transition at 30(5) K. • We have determined the crystal field parameters for the antiferromagnetic AFil region. • The transition intensities are described well by Boltzmann occupancy models. • The spectra below the magnetic transition have been analysed by

Numerical investigation on splitting of ferrofluid microdroplets in T-junctions using an asymmetric magnetic field with proposed correlation

Science.gov (United States)

Aboutalebi, Mohammad; Bijarchi, Mohamad Ali; Shafii, Mohammad Behshad; Kazemzadeh Hannani, Siamak

2018-02-01

The studies surrounding the concept of microdroplets have seen a dramatic increase in recent years. Microdroplets have applications in different fields such as chemical synthesis, biology, separation processes and micro-pumps. This study numerically investigates the effect of different parameters such as Capillary number, Length of droplets, and Magnetic Bond number on the splitting process of ferrofluid microdroplets in symmetric T-junctions using an asymmetric magnetic field. The use of said field that is applied asymmetrically to the T-junction center helps us control the splitting of ferrofluid microdroplets. During the process of numerical simulation, a magnetic field with various strengths from a dipole located at a constant distance from the center of the T-junction was applied. The main advantage of this design is its control over the splitting ratio of daughter droplets and reaching various microdroplet sizes in a T-junction by adjusting the magnetic field strength. The results showed that by increasing the strength of the magnetic field, the possibility of asymmetric splitting of microdroplets increases in a way that for high values of field strength, high splitting ratios can be reached. Also, by using the obtained results at various Magnetic Bond numbers and performing curve fitting, a correlation is derived that can be used to accurately predict the borderline between splitting and non-splitting zones of microdroplets flow in micro T-junctions.

Tunnel splitting for a high-spin molecule in an in-plane field

Science.gov (United States)

Zhu, Jia-Lin

2000-08-01

Direction and strength effects of a magnetic field on the ground-state tunnel splitting for a biaxial spin molecule with the model Hamiltonian H = k1Sz2 + k2Sy2- gµBHzSz- gµBHySy have been investigated within a continuous-spin approach including the Wess-Zumino-Berry term. The topological oscillation and the non-Kramers freezing indicated in the approach are in agreement with those observed in a recent experiment on Fe8 molecular nanomagnets. The behaviour of tunnel splitting with multiple orbits induced by strong fields has been revealed clearly.

Phenomenological crystal-field model of the magnetic and thermal properties of the Kondo-like system UCu2Si2

Science.gov (United States)

Troć, R.; Gajek, Z.; Pikul, A.; Misiorek, H.; Colineau, E.; Wastin, F.

2013-07-01

The transport properties described previously [Troć , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.224434 85, 224434 (2012)] as well as the magnetic and thermal properties presented in this paper, observed for single-crystalline UCu2Si2, are discussed by assuming a dual (localized-itinerant) scenario. The electronic states of the localized 5f electrons in UCu2Si2 are constructed using the effective Hamiltonian known for ionic systems, allowing us to treat the Coulomb, spin-orbital, and crystal-field interactions on equal footing. The space of parameters has been restricted in the initial steps with the aid of the angular overlap model approximation. The final crystal-field parameters, obtained from the refined steps of calculations, are relatively large (in absolute values), which we attribute to the hybridization characteristic of the metallic systems on the verge of localization. The proposed crystal-field model reproduces correctly with satisfactory accuracy the magnetic and thermal properties of UCu2Si2 in agreement also with the transport properties reported previously. Considerable crystal-field splitting of the ground multiplet of 2760 K is responsible for a large anisotropy in the magnetic behavior, observed in the whole temperature range explored.

Magnetic-field-induced martensitic transformation of off-stoichiometric single-crystal Ni2MnGa

International Nuclear Information System (INIS)

Inoue, Kazuko; Yamaguchi, Yasuo; Shishido, Toetsu; Ishii, Yoshinobu; Yamauchi, Hiroki

2009-01-01

The effect of a magnetic field on the martensitic transformation of an off-stoichiometric Heusler type Ni 2.16 Mn 0.78 Ga 1.06 single crystal has been revealed by neutron diffraction. The alloy undergoes a martensitic transformation at room temperature, which is nearly coincident with its Curie temperature. Splitting of the cubic (020) peak on the reciprocal lattice cubic c * -plane was traced at 293 K by a triple-axis neutron spectrometer under an increasing magnetic field of up to 10 T. It was found that the magnetic field causes the martensitic transformation from the cubic structure to the orthorhombic structure, which is the same as that caused by decreasing the temperature without a magnetic field. The increase in the magnetic field to 10 T appears to correspond to a decrease in temperature of nearly 12 K, i.e., from 293 to 281 K. The present experiment suggests the possibility of realizing a magnetic-field-induced shape memory alloy. (author)

Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

International Nuclear Information System (INIS)

Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

2015-01-01

We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics

Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

Science.gov (United States)

Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

2015-07-01

We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics.

Crystal-field effect in UO2

International Nuclear Information System (INIS)

Gajek, Z.; Lahalle, M.P.; Krupa, J.C.; Mulak, J.

1988-01-01

Simple ab initio model perturbation calculations of the crystal-field parameters for the U 4+ ion in UO 2 crystals are reported. The crystal-field parameters obtained, B 0 4 = -7130 cm -1 and B 0 6 = 2890 cm -1 , turn out to be much lower in value, particularly the first one, than those usually assumed for this compound. They are found, however, to agree with new spectroscopic data and recent inelastic neutron scattering measurements. (orig.)

Application of split field technique with 42 MeV betatron bremsstrahlung

Energy Technology Data Exchange (ETDEWEB)

Spurny, V; Caha, A; Krystof, V; Ott, O [Vyzkumny Ustav Klinicke a Experimentalni Onkologie, Brno (Czechoslovakia)

1977-03-01

The split field technique of external irradiation in oncology is described. A 120x28x79 mm lead shielding block was manufactured for a bremsstrahlung radiation with 42 MeV maximum energy. The block was secured to a holder whose design corresponded to tube holders. The block shielding capacity was tested by phantom measurements at a focal depth of 130 mm and at a distance of the block from the phantom surface of 990 mm. For the 42 MeV bremsstrahlung the reduction was found to be 15% of the focal dose in the 20x20 cm/sup 2/ field in the focal depth at a distance of 1200 mm from the bremsstrahlung focus. Dose distribution was established by using two opposite fields in combination as well as by the courses of the maximum and the relative doses in variation with the female patient's antero-posterior diameter. The results show that the split field technique permits a short adjustment time, is simple and reproducible. As against cobalt application, the beam characteristics permit reducing the integral dose.

Split Field magnet at the I4 ISR intersection

CERN Multimedia

1974-01-01

The Split-Field Magnet (SFM) at I4 had an unconventional topology, consisting of two dipole magnets of opposite polarity. It formed the heart of the first general facility at the ISR. It had a useful magnetic field volume of 28 m3 and a field in the median plane of 1.14 T. With a gap height of 1.1 m and length of 10.5 m, the magnet weighed about 1000 t. The SFM spectrometer featured the first large-scale application of MWPCs (about 70,000 wires), which filled the main magnet, visible here in 1974, and the two large compensator magnets.

Superposition model analysis of nickel(II) ions in trigonal bipyramidal complexes exhibiting huge zero field splitting (aka ‘giant magnetic anisotropy’)

Energy Technology Data Exchange (ETDEWEB)

Rudowicz, Czesław, E-mail: crudowicz@zut.edu.pl [Faculty of Chemistry, A. Mickiewicz University, 61-614 Poznań (Poland); Institute of Physics, West Pomeranian University of Technology, Szczecin (Poland); Açıkgöz, Muhammed [Department of Chemistry, Rutgers University, Newark, New Jersey 07102 (United States); Gnutek, Paweł [Institute of Physics, West Pomeranian University of Technology, Szczecin (Poland)

2017-07-15

Graphical abstract: Using crystal structure data for [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) as well as taking into account the Jahn-Teller distortions of five-fold coordinated Ni-complexes revealed by DFT geometry optimization, the ZFSPs are predicted for several structural models and wide ranges of model parameters. - Highlights: • Semiempirical study of potential SMM [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br). • Superposition model analysis of zero field splitting (ZFS) parameters carried out. • Jahn-Teller distortions revealed by DFT geometry optimization considered. • SPM predicts D(ZFS) of observed magnitudes with positive or negative signs. • Results corroborate giant ZFS, which shall not be equated with magnetic anisotropy. - Abstract: Potential single-ion magnet Ni{sup 2+} systems: [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) reveal unusually high zero field splitting (ZFS). The ZFS parameter (ZFSP) D{sub expt} = −120 to −180 cm{sup −1} was determined indirectly by high-magnetic field, high-frequency electron magnetic resonance (HMF-EMR). Modeling ZFSPs using the density functional theory (DFT) codes predicts D values: −100 to −200 cm{sup −1}. Such ZFSP values may seem controversial in view of the D values usually not exceeding several tens of cm{sup −1} for Ni{sup 2+} ions. To corroborate or otherwise these results and elucidate the origin of the huge ZFS (named inappropriately as ‘giant uniaxial magnetic anisotropy’) and respective wavefunctions, we have undertaken semiempirical modeling based on the crystal field (CF) and spin Hamiltonians (SH) theory. In this paper, a feasibility study is carried out to ascertain if superposition model (SPM) calculations may yield such huge D values for these Ni{sup 2+} systems. Using crystal structure data for [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) as well as taking into account the Jahn

Irradiation-induced amorphization in split-dislocation cores

International Nuclear Information System (INIS)

Ovid'ko, I.A.; Rejzis, A.B.

1999-01-01

The model describing special splitting of lattice and grain-boundary dislocations as one of the micromechanisms of solid-phase amorphization in irradiated crystals is proposed. Calculation of energy characteristics of the process of dislocations special splitting is carried out [ru

Crystal growth under external electric fields

International Nuclear Information System (INIS)

Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

2014-01-01

This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal

Crystal growth under external electric fields

Energy Technology Data Exchange (ETDEWEB)

Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)

2014-10-06

This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

The effective crystal field potential

CERN Document Server

Mulak, J

2000-01-01

As it results from the very nature of things, the spherical symmetry of the surrounding of a site in a crystal lattice or an atom in a molecule can never occur. Therefore, the eigenfunctions and eigenvalues of any bound ion or atom have to differ from those of spherically symmetric respective free ions. In this way, the most simplified concept of the crystal field effect or ligand field effect in the case of individual molecules can be introduced. The conventional notion of the crystal field potential is narrowed to its non-spherical part only through ignoring the dominating spherical part which produces only a uniform energy shift of gravity centres of the free ion terms. It is well understood that the non-spherical part of the effective potential "seen" by open-shell electrons localized on a metal ion plays an essential role in most observed properties. Light adsorption, electron paramagnetic resonance, inelastic neutron scattering and basic characteristics derived from magnetic and thermal measurements, ar...

Multipole induced splitting of metal-cage vibrations in crystalline endohedral D2d-M2@C84 dimetallofullerenes.

Science.gov (United States)

Krause, M; Popov, V N; Inakuma, M; Tagmatarchis, N; Shinohara, H; Georgi, P; Dunsch, L; Kuzmany, H

2004-01-22

Metal-carbon cage vibrations of crystalline endohedral D2d-M2@C84 (M=Sc,Y,Dy) dimetallofullerenes were analyzed by temperature dependent Raman scattering and a dynamical force field model. Three groups of metal-carbon cage modes were found at energies of 35-200 cm(-1) and assigned to metal-cage stretching and deformation vibrations. They exhibit a textbook example for the splitting of molecular vibrations in a crystal field. Induced dipole-dipole and quadrupole-quadrupole interactions account quantitatively for the observed mode splitting. Based on the metal-cage vibrational structure it is demonstrated that D2d-Y2@C84 dimetallofullerene retains a monoclinic crystal structure up to 550 K and undergoes a transition from a disordered to an ordered orientational state at a temperature of approximately 150 K.

High-field magnetization of rare-earth ions in scandium

DEFF Research Database (Denmark)

Roeland, L. W.; Touborg, P.

1978-01-01

The magnetic moments of Tb, Dy, or Er ions in dilute Sc single-crystal alloys have been measured in fields up to 280 × 105 A/m (350 kOe). The Zeeman energies in this high field are comparable to the total crystal-field splittings. This gives rise to characteristic features in the magnetization cu...... curves. The crystal-field parameters obtained previously from experiments in low fields and the Zeeman interaction give a satisfactory quantitative acount of the experimental results....

Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock

Directory of Open Access Journals (Sweden)

Weichao Wang

2016-01-01

Full Text Available The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals.

Influence of ligand spin-orbit coupling to the sign of the zero-field splitting and pressure-induced spectral shift for ZnS:Mn2+ (bulk/nanocrystal)

International Nuclear Information System (INIS)

Zhao, M.G.; Lei, Y.

2004-01-01

Serious difficulties exist in explaining the zero-field splitting (ZFS) of 3d 5 ions in crystal, with the current crystal-field theory. The calculated cubic ZFS a-value of 3d 5 ion is positive identically. However, K.A. Mueller and W. Low found experimentally that a is negative for some ZnS:Mn 2+ crystals. In this work, an unified explanation is developed for the ZFS, optical spectra and pressure-induced spectral shift for the ZnS:Mn 2+ (bulk/nanocrystal) by considering the influence of the spin-orbit coupling to the ZFS and spectral bands. The excellent agreement between calculation and experiments shows that the above-mentioned difficulties can be removed based on the calculation model proposed by authors. Calculation result shows that there are two kinds of stable electron states with (λ π , λ σ , λ s ) = (0.2713448, -0.1619936, -0.08) and (0.2713448, 0.346885, -0.220), respectively, where (λ π , λ σ , λ s ) denote the mixing coefficients of Mn 2+ - 4S 2- anti-bonding in ZnS:Mn 2+

Field-Split Preconditioned Inexact Newton Algorithms

KAUST Repository

Liu, Lulu

2015-06-02

The multiplicative Schwarz preconditioned inexact Newton (MSPIN) algorithm is presented as a complement to additive Schwarz preconditioned inexact Newton (ASPIN). At an algebraic level, ASPIN and MSPIN are variants of the same strategy to improve the convergence of systems with unbalanced nonlinearities; however, they have natural complementarity in practice. MSPIN is naturally based on partitioning of degrees of freedom in a nonlinear PDE system by field type rather than by subdomain, where a modest factor of concurrency can be sacrificed for physically motivated convergence robustness. ASPIN, originally introduced for decompositions into subdomains, is natural for high concurrency and reduction of global synchronization. We consider both types of inexact Newton algorithms in the field-split context, and we augment the classical convergence theory of ASPIN for the multiplicative case. Numerical experiments show that MSPIN can be significantly more robust than Newton methods based on global linearizations, and that MSPIN can be more robust than ASPIN and maintain fast convergence even for challenging problems, such as high Reynolds number Navier--Stokes equations.

Field-Split Preconditioned Inexact Newton Algorithms

KAUST Repository

Liu, Lulu; Keyes, David E.

2015-01-01

The multiplicative Schwarz preconditioned inexact Newton (MSPIN) algorithm is presented as a complement to additive Schwarz preconditioned inexact Newton (ASPIN). At an algebraic level, ASPIN and MSPIN are variants of the same strategy to improve the convergence of systems with unbalanced nonlinearities; however, they have natural complementarity in practice. MSPIN is naturally based on partitioning of degrees of freedom in a nonlinear PDE system by field type rather than by subdomain, where a modest factor of concurrency can be sacrificed for physically motivated convergence robustness. ASPIN, originally introduced for decompositions into subdomains, is natural for high concurrency and reduction of global synchronization. We consider both types of inexact Newton algorithms in the field-split context, and we augment the classical convergence theory of ASPIN for the multiplicative case. Numerical experiments show that MSPIN can be significantly more robust than Newton methods based on global linearizations, and that MSPIN can be more robust than ASPIN and maintain fast convergence even for challenging problems, such as high Reynolds number Navier--Stokes equations.

Thulium doped crystals for quantum information storage

Energy Technology Data Exchange (ETDEWEB)

Lauro, R., E-mail: romain.lauro@lac.u-psud.f [Laboratoire Aime Cotton, CNRS-UPR 3321, Univ Paris Sud, Batiment 505, 91405 Orsay cedex (France); Ruggiero, J.; Louchet, A.; Alexander, A.; Chaneliere, T.; Lorgere, I.; Bretenaker, F.; Goldfarb, F.; Le Gouet, J.-L. [Laboratoire Aime Cotton, CNRS-UPR 3321, Univ Paris Sud, Batiment 505, 91405 Orsay cedex (France)

2009-12-15

Optically driving nuclear spin waves in a Tm:YAG crystal, we experimentally demonstrate the feasibility of a three-level {Lambda} system in this material, which is a foundation step in the prospect of quantum memory investigations. Varying the spin state splitting with an external magnetic field, we show that the nuclear spin coherence lifetime remains close to 350mus over a wide range of variation of this splitting. Finally, we demonstrate fast coherent population transfer between the spin states.

Crystal field splitting and spin states of Co ions in cobalt ferrite with composition Co{sub 1.5}Fe{sub 1.5}O{sub 4} using magnetization and X-ray absorption spectroscopy measurements

Energy Technology Data Exchange (ETDEWEB)

Sinha, A.K., E-mail: anil@rrcat.gov.in [HXAL, Synchrotrons Utilization Section, RRCAT, Indore 452013 (India); Homi Bhabha National Institute, RRCAT, Indore 452013 (India); Singh, M.N. [HXAL, Synchrotrons Utilization Section, RRCAT, Indore 452013 (India); Achary, S.N. [Chemistry Division, BARC, Anushaktinagar, Mumbai 400085 (India); Sagdeo, A. [HXAL, Synchrotrons Utilization Section, RRCAT, Indore 452013 (India); Homi Bhabha National Institute, RRCAT, Indore 452013 (India); Shukla, D.K.; Phase, D.M. [UGC-DAE Consortium for Scientific Research, Indore 452010 (India)

2017-08-01

Highlights: • Co ions in Co{sub 1.5}Fe{sub 1.5}O{sub 4} are found to be in high spin states. • XAS measurements have been used to estimate TM crystal field and core hole contributions to 3d orbital splitting. • The polycrystalline Co{sub 1.5}Fe{sub 1.5}O{sub 4} sample show two pinning centers and large magneto crystalline anisotropy. - Abstract: Structural, magnetic and electronic properties of partially inverted Cobalt Ferrite with composition Co{sub 1.5}Fe{sub 1.5}O{sub 4} is discussed in the present work. Single phase (SG: Fd3m) sample is synthesized by co-precipitation technique and subsequent air annealing. The values of saturation magnetization obtained from careful analysis of approach to saturation in initial M(H) curves are used to determine spin states of Co ions in tetrahedral (T{sub H}) and octahedral (O{sub H}) sites. Spin states of Co{sup 3+} ions in T{sub H} sites, which has not been reported in literature, were found to be in high spin state. Temperature variation of magnetic parameters has been studied. The sample shows magneto-crystalline anisotropy with two clearly distinct pinning centers. Oxygen K-edge and Fe as well as Co L{sub 2,3}-edge X-ray absorption (XAS) spectra have been used as complementary measurements to study crystal field splitting and core hole effects on transition metal (TM) 3d orbitals. The ratio of intensities of t{sub 2g} and e{sub g} absorption bands in O-K edge XAS spectrum is used to estimate the spin states of Co ions at O{sub H} and T{sub H} sites. The results are in agreement with those obtained from magnetization data, and favors Co{sup 3+} ions in T{sub H} sites in high spin states. Normalized areas of the satellite peaks in TM L{sub 2},{sub 3}-edge XAS spectra have been used to estimate 3d{sub n+1}L contribution in ground state wave function and the contributions were found to be significant.

Energetic band structure of Zn3P2 crystals

Science.gov (United States)

Stamov, I. G.; Syrbu, N. N.; Dorogan, A. V.

2013-01-01

Optical functions n, k, ε1, ε2 and d2ε2/dE2 have been determined from experimental reflection spectra in the region of 1-10 eV. The revealed electronic transitions are localized in the Brillouin zone. The magnitude of valence band splitting caused by the spin-orbital interaction ΔSO is lower than the splitting caused by the crystal field ΔCR in the center of Brillouin zone and L and X points. The switching effects are investigated in Zn3P2 crystals. The characteristics of experimental samples with electric switching, adjustable resistors, and time relays based on Zn3P2 are presented.

Experimental study of broadband unidirectional splitting in photonic crystal gratings with broken structural symmetry

Science.gov (United States)

Colak, Evrim; Serebryannikov, Andriy E.; Ozgur Cakmak, A.; Ozbay, Ekmel

2013-04-01

It is experimentally demonstrated that the combination of diode and splitter functions can be realized in one broadband reciprocal device. The suggested performance is based on the dielectric photonic crystal grating whose structural symmetry is broken owing to non-deep corrugations placed at one of the two interfaces. The study has been performed at a normally incident beam-type illumination obtained from a microwave horn antenna. The two unidirectionally transmitted, deflected beams can show large magnitude and high contrast, while the angular distance between their maxima is 90° and larger. The dual-band unidirectional splitting is possible when using TM and TE polarizations.

Heteroplasmon hybridization in stacked complementary plasmo-photonic crystals.

Science.gov (United States)

Iwanaga, Masanobu; Choi, Bongseok

2015-03-11

We constructed plasmo-photonic crystals in which efficient light-trapping, plasmonic resonances couple with photonic guided resonances of large density of states and high-quality factor. We have numerically and experimentally shown that heteroplasmon hybrid modes emerge in stacked complementary (SC) plasmo-photonic crystals. The resonant electromagnetic-field distributions evidence that the two hybrid modes originate from two different heteroplasmons, exhibiting a large energy splitting of 300 meV. We further revealed a series of plasmo-photonic modes in the SC crystals.

Crystal Field Levels of Pr3+ in PrFeO3 and PrGaO3 Determined by Inelastic Neutron Scattering

DEFF Research Database (Denmark)

Feldmann, K.; Henning, K.; Kaun, L.

1975-01-01

The crystal field splitting of the 3H4 ground state of the Pr ion in PrFeO3 and PrGaO3 has been investigated by inelastic scattering of thermal neutrons. At several temperatures the transitions have been measured by TAS and TOF methods for polycrystalline PrFeO3 and by the TOF method...... for polycrystalline PrGaO3. Energy level schemes which are different for these materials are given....

Crystal-field study of magnetization and specific heat properties of frustrated pyrochlore Pr2Zr2O7

International Nuclear Information System (INIS)

Alam, J.; Jana, Y.M.; Biswas, A. Ali

2016-01-01

The experimental results of temperature dependent dc magnetic susceptibility, field dependent isothermal magnetization, magnetic specific heat and entropy of the pyrochlore Pr 2 Zr 2 O 7 are simulated and analyzed using appropriate D 3d crystal-field (CF) and anisotropic molecular field tensors at Pr-sites in the self-consistent mean-field approach involving four magnetically non-equivalent rare-earth spins on the tetrahedral unit of the pyrochlore structure. CF level pattern and wave-functions of the ground 3 H 4 multiplet of the Pr 3+ ions are obtained considering intermediate coupling between different Russell-Saunders terms of the 4f 2 electronic configurations of Pr-ion and J-mixing effects. CF analysis shows that the CF ground-state of the Pr 3+ ion in Pr 2 Zr 2 O 7 is a well-isolated doublet, with significant admixtures of terms coming from |M J =±4〉 and |M J =±1〉, and the Pr-spins are effectively Ising-like along the local <111> axes. Magnetic specific heat in zero-field is simulated by considering a temperature dependence of the exchange splitting of the ground doublet. - Highlights: • Full CF diagonalization using intermediate coupling and J-mixing. • Pr-spins are Ising-like along local [111] axis. • Magnetic specific heat is due to temperature dependence exchange splitting of ground CF doublet.

Experimental investigation and crystal-field modeling of Er{sup 3+} energy levels in GSGG crystal

Energy Technology Data Exchange (ETDEWEB)

Gao, J.Y., E-mail: jygao1985@sina.com [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Sun, D.L.; Zhang, Q.L. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, X.F. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Liu, W.P.; Luo, J.Q.; Sun, G.H.; Yin, S.T. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China)

2016-06-25

The Er{sup 3+}-doped Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12} (Er{sup 3+}:GSGG) single crystal, a excellent medium of the mid-infrared and anti-radiation solid state laser pumped by laser diode, was grown by Czochralski method successfully. The absorption spectra were measured and analyzed in a wider spectral wavelength range of 350–1700 nm at different temperatures of 7.6, 77, 200 and 300 K. The free-ions and crystal-field parameters were fitted to the experimental energy levels with the root mean square deviation of 9.86 cm{sup −1}. According to the crystal-field calculations, 124 degenerate energy levels of Er{sup 3+} in GSGG host crystals were assigned. The fitting results of free-ions and crystal-field parameters were compared with those already reported of Er{sup 3+}:YSGG. The results indicated that the free-ions parameters for Er{sup 3+} in GSGG host are similar to those in YSGG host crystals, and the crystal-field interaction of GSGG is weaker than that of YSGG, which may result in the better laser characterization of Er{sup 3+}:GSGG crystal. - Highlights: • The efficient diode-end-pumped laser crystal Er:GSGG has been grown successfully. • The absorption spectra of Er:GSGG have been measured in range of 350–1700 nm. • The fitting result is very well for the root mean square deviation is 9.86 cm{sup −1}. • The 124 levels of Er:GSGG have been assigned from the crystal-field calculations.

Scaling of magnetic relaxation in Mn-12: a distribution of tunnel splittings

Science.gov (United States)

Sarachik, Myriam P.

2002-03-01

In magnetic fields applied parallel to the anisotropy axis, the relaxation of the magnetization of Mn_12-acetate measured for different sweep rates collapses onto a single scaled curve.(K. M. Mertes, Y. Suzuki, M. P. Sarachik, Y. Paltiel, H. Shtrikman, E. Zeldov, E. M. Rumberger, and G. Christou, Phys. Rev. Lett. 87), 227205 (2001). The form of the scaling(E. M. Chudnovsky and D. A. Garanin, Phys. Rev. Lett. 87, 187203 (2001).) implies that the dominant symmetry-breaking process responsible for tunneling is a locally varying second-order transverse anisotropy, forbidden by tetragonal symmetry in the perfect crystal, which gives rise to a broad distribution of tunnel splittings in a real crystal of Mn_12-acetate. Different forms applied to even and odd-numbered steps provide a clear distinction between even resonances (associated with crystal anisotropy) and odd resonances (which require a transverse magnetic field).

Charge-transfer potentials for ionic crystals: Cauchy violation, LO-TO splitting, and the necessity of an ionic reference state.

Science.gov (United States)

Sukhomlinov, Sergey V; Müser, Martin H

2015-12-14

In this work, we study how including charge transfer into force fields affects the predicted elastic and vibrational Γ-point properties of ionic crystals, in particular those of rock salt. In both analytical and numerical calculations, we find that charge transfer generally leads to a negative contribution to the Cauchy pressure, P(C) ≡ C12 - C66, where C12 and C66 are elements of the elastic tensor. This contribution increases in magnitude with pressure for different charge-transfer approaches in agreement with results obtained with density functional theory (DFT). However, details of the charge-transfer models determine the pressure dependence of the longitudinal optical-transverse optical splitting and that for partial charges. These last two quantities increase with density as long as the chemical hardness depends at most weakly on the environment while experiments and DFT find a decrease. In order to reflect the correct trends, the charge-transfer expansion has to be made around ions and the chemical (bond) hardness has to increase roughly exponentially with inverse density or bond lengths. Finally, the adjustable force-field parameters only turn out meaningful, when the expansion is made around ions.

Method and split cavity oscillator/modulator to generate pulsed particle beams and electromagnetic fields

Science.gov (United States)

Clark, M. Collins; Coleman, P. Dale; Marder, Barry M.

1993-01-01

A compact device called the split cavity modulator whose self-generated oscillating electromagnetic field converts a steady particle beam into a modulated particle beam. The particle beam experiences both signs of the oscillating electric field during the transit through the split cavity modulator. The modulated particle beam can then be used to generate microwaves at that frequency and through the use of extractors, high efficiency extraction of microwave power is enabled. The modulated beam and the microwave frequency can be varied by the placement of resistive wires at nodes of oscillation within the cavity. The short beam travel length through the cavity permit higher currents because both space charge and pinching limitations are reduced. The need for an applied magnetic field to control the beam has been eliminated.

Zero field spin splitting in asymmetric quantum wells

International Nuclear Information System (INIS)

Hao Yafei

2012-01-01

Spin splitting of asymmetric quantum wells is theoretically investigated in the absence of any electric field, including the contribution of interface-related Rashba spin-orbit interaction as well as linear and cubic Dresselhaus spin-orbit interaction. The effect of interface asymmetry on three types of spin-orbit interaction is discussed. The results show that interface-related Rashba and linear Dresselhaus spin-orbit interaction can be increased and cubic Dresselhaus spin-orbit interaction can be decreased by well structure design. For wide quantum wells, the cubic Dresselhaus spin-orbit interaction dominates under certain conditions, resulting in decreased spin relaxation time.

Spin-polarized spin-orbit-split quantum-well states in a metal film

Energy Technology Data Exchange (ETDEWEB)

Varykhalov, Andrei; Sanchez-Barriga, Jaime; Gudat, Wolfgang; Eberhardt, Wolfgang; Rader, Oliver [BESSY Berlin (Germany); Shikin, Alexander M. [St. Petersburg State University (Russian Federation)

2008-07-01

Elements with high atomic number Z lead to a large spin-orbit coupling. Such materials can be used to create spin-polarized electronic states without the presence of a ferromagnet or an external magnetic field if the solid exhibits an inversion asymmetry. We create large spin-orbit splittings using a tungsten crystal as substrate and break the structural inversion symmetry through deposition of a gold quantum film. Using spin- and angle-resolved photoelectron spectroscopy, it is demonstrated that quantum-well states forming in the gold film are spin-orbit split and spin polarized up to a thickness of at least 10 atomic layers. This is a considerable progress as compared to the current literature which reports spin-orbit split states at metal surfaces which are either pure or covered by at most a monoatomic layer of adsorbates.

Nuclearity, split-property and duality for the Klein-Gordon field in curved spacetime

International Nuclear Information System (INIS)

Verch, R.

1993-05-01

Nuclearity, Split-Property and Duality are establihed for the nets of von Neumann algebras associated with the representations of distinguished states of the massive Klein-Gordon field propagating in particular classes of curved spacetimes. (orig.)

Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

International Nuclear Information System (INIS)

Yang Tao; Chen Zheng; Zhang Jing; Wang Yongxin; Lu Yanli

2016-01-01

By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. (paper)

Study of Events with Identified Forward Particles at the Split Field Magnet

CERN Multimedia

2002-01-01

This experiment will study two aspects of particle production in the forward region : \\item 1) In the recent discovery of charm production in hadronic interactions at the Split Field Magnet, the triggering on strange particles at medium p^t has proven to be a very effective tool for the study of heavy resonances, especially those carrying new flavours like charm and beauty. We want to carry out a more detailed investigation of the production-dynamics of charmed particles, together with a search for beauty mesons and baryons. \\item 2) A trigger on forward particles at high p^t ($>$ 5GeV/c) provides unique features to determine the properties of the parton-parton subprocesses. We want to study the relative contributions of quark, diquark and gluon scattering.\\\\ \\\\ This experimental programme will be carried out, using the improved Split Field Magnet spectrometer (SFM). The different detection systems provide : \\item a) Detection and momentum analysis of charged particles in 4@p solid angle. An improved programm...

Validation of SplitVectors Encoding for Quantitative Visualization of Large-Magnitude-Range Vector Fields.

Science.gov (United States)

Henan Zhao; Bryant, Garnett W; Griffin, Wesley; Terrill, Judith E; Jian Chen

2017-06-01

We designed and evaluated SplitVectors, a new vector field display approach to help scientists perform new discrimination tasks on large-magnitude-range scientific data shown in three-dimensional (3D) visualization environments. SplitVectors uses scientific notation to display vector magnitude, thus improving legibility. We present an empirical study comparing the SplitVectors approach with three other approaches - direct linear representation, logarithmic, and text display commonly used in scientific visualizations. Twenty participants performed three domain analysis tasks: reading numerical values (a discrimination task), finding the ratio between values (a discrimination task), and finding the larger of two vectors (a pattern detection task). Participants used both mono and stereo conditions. Our results suggest the following: (1) SplitVectors improve accuracy by about 10 times compared to linear mapping and by four times to logarithmic in discrimination tasks; (2) SplitVectors have no significant differences from the textual display approach, but reduce cluttering in the scene; (3) SplitVectors and textual display are less sensitive to data scale than linear and logarithmic approaches; (4) using logarithmic can be problematic as participants' confidence was as high as directly reading from the textual display, but their accuracy was poor; and (5) Stereoscopy improved performance, especially in more challenging discrimination tasks.

Organic field-effect transistors using single crystals

International Nuclear Information System (INIS)

Hasegawa, Tatsuo; Takeya, Jun

2009-01-01

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm 2 Vs -1 , achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps. (topical review)

Simultaneous near field imaging of electric and magnetic field in photonic crystal nanocavities

NARCIS (Netherlands)

Vignolini, S.; Intonti, F.; Riboli, F.; Wiersma, D.S.; Balet, L.P.; Li, L.H.; Francardi, M.; Gerardino, A.; Fiore, A.; Gurioli, M.

2012-01-01

The insertion of a metal-coated tip on the surface of a photonic crystal microcavity is used for simultaneous near field imaging of electric and magnetic fields in photonic crystal nanocavities, via the radiative emission of embedded semiconductor quantum dots (QD). The photoluminescence intensity

Infrared transmission study of crystal-field excitation in La.sub.2-x-y./sub.Nd.sub.x./sub.Sr.sub.y./sub.CuO.sub.4./sub..

Czech Academy of Sciences Publication Activity Database

Riou, G.; Jandl, S.; Poirier, M.; Nekvasil, Vladimír; Maryško, Miroslav; Fábry, Jan; Jurek, Karel; Diviš, M.; Hölsä, J.; Sutjahja, I. M.; Menovsky, A. A.; Barilo, S. N.; Shiryaev, S. V.; Kurnevich, L. N.

2002-01-01

Roč. 66, - (2002), s. 224508-1 - 221508-7 ISSN 0163-1829 R&D Projects: GA ČR GA202/00/1602; GA ČR GA203/02/0436 Institutional research plan: CEZ:AV0Z1010914 Keywords : cuprate superconductors * level splitting * interactions * crystal-field theory * rare-earth magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.327, year: 2002

Rotation of dust plasma crystals in an axial magnetic field

International Nuclear Information System (INIS)

Cheung, F.; Prior, N.; Mitchell, L.

2000-01-01

Full text: Micron-sized melamine formaldehyde particles were introduced into argon plasma. As a result, the particles were negatively charged due to collision with the electrons within the plasma. With the right conditions, these particles formed a stable macroscopic crystal lattice, known as dust plasma crystal. In our experiment we conduct at Flinders University, we apply an external axial magnetic field to various configurations of dust plasma crystal. These configurations include small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The magnetic field strength ranged from 0-32G and was uniform over the extent of the crystal. The crystals were observed to be rotating collectively in the left-handed direction under the influence of the axial magnetic field. In the case of the large crystals, the angular velocity was about 2 complete rotations per minute and was proportional to the applied magnetic field. The angular velocity changes only slightly depending on the plasma conditions. Neither radial variance in the angular velocity nor shear velocity in the vertical direction was observed in the crystal's rotational motion. In the case of the small crystals, we managed to rotate 2-6 particles (whether they are planar, 2 layers or tetrahedral). We discovered that the ease and the uniformity of the rotation of the different crystals increase as its rotational symmetry increases. Also an increase in the magnetic field strength will correspond to an increase in the angular velocity. Crystals in the shape of an annulus were also tested for theoretical reasons. The poster presentation will contain the experimental procedures, a detailed analysis and an explanation for such dust plasma crystal rotational motion

Full splitting of the first zero-field steps in the I-V curve of Josephson junctions of intermediate length

International Nuclear Information System (INIS)

Hansen, J.B.; Divin, Y.Y.; Mygind, J.

1986-01-01

We report on the observation of full splitting of the first zero-field steps in the I-V curves of Josephson transmission lines of intermediate length Lroughly-equal(3--5)lambda/sub J/, where lambda/sub J/ is the Josephson penetration length. We study in detail how this splitting of the step into two branches depends on the temperature of the junction and on a weak applied magnetic field. We relate the splitting to excitations in the junctions whose behavior is described by the perturbed Sine-Gordon equation

Valley Zeeman splitting of monolayer MoS2 probed by low-field magnetic circular dichroism spectroscopy at room temperature

Science.gov (United States)

Wu, Y. J.; Shen, C.; Tan, Q. H.; Shi, J.; Liu, X. F.; Wu, Z. H.; Zhang, J.; Tan, P. H.; Zheng, H. Z.

2018-04-01

The valley Zeeman splitting of monolayer two-dimensional (2D) materials in the magnetic field plays an important role in the valley and spin manipulations. In general, a high magnetic field (6-65 T) and low temperature (2-30 K) were two key measurement conditions to observe the resolvable valley Zeeman splitting of monolayer 2D materials in current reported experiments. In this study, we experimentally demonstrate an effective measurement scheme by employing magnetic circular dichroism (MCD) spectroscopy, which enables us to distinguish the valley Zeeman splitting under a relatively low magnetic field of 1 T at room temperature. MCD peaks related to both A and B excitonic transitions in monolayer MoS2 can be clearly observed. Based on the MCD spectra under different magnetic fields (-3 to 3 T), we obtained the valley Zeeman splitting energy and the g-factors of A and B excitons, respectively. Our results show that MCD spectroscopy is a high-sensitive magneto-optical technique to explore the valley and spin manipulation in 2D materials.

Crystal field and magnetocrystalline anisotropy in various crystalline systems

International Nuclear Information System (INIS)

Adam, S.A.

1983-01-01

Systematic derivation of the one-perticle crystal field Hamiltonians is given for all possible site symmetries in crystals. Distinct parametrizations are found to occur for the eleven Laue-symmetry groups. The functional dependence of the Hamiltonian on the choice of the coordinate axes is also investigated. A general method is developed for the derivation of the one-particle crYstal field potential characteristic of a given crystallographic symmetry, for arbitrary effective interatomic forces. Calculations performed for cubic and hexagonal structures lead to the standard representations in spherical harmonics with the coefficients given, however, by power series of rsup(n) rather than by simgle rsup(n) terms as obtained within the usual hypothesis of Coulombian interatomic forces. This result has implications on the interpretation of some theoretical and experimental data. Theoretical results are obtained for the crystal field coefficients which enable us to develop an approach to the use of the crystal field data for the derivation of information on the effective interatomic forces in crystals. The method is applied to the magnetic Sm 3+ ion in SmCo 5 , and it is shown to provide valuable results both for the effective interatomic potential and for the consistency of various sets of crystal field parameters previously proposed in the literature. Maqnetocrystalline anisotropy of the rare-earth intermetallic compounds are discussed. Single-ion anisotropy model is used for SmCo 5 and the theoreticalpr predictions are compared with the experimental data. (author)

Split of the superconducting transition and magnetism in UPt3

International Nuclear Information System (INIS)

Marikhin, V.G.

1992-01-01

A possible reason for splitting the superconducting phase transition in UPt 3 is discussed. The strong coupling of conduction electrons with uranium atom magnetic moments may be such a cause. The given assertion is based on the simple model described by the two-component order parameter φ Ginzburg -Landau functional. The Ginzburg - Landau functional without coupling has the whole symmetry D 6h of hexagonal crystal. Due to the presence of uranium atom magnetic moments M the symmetry is broken locally with the coupling term γ|Mφ| 2 in the Ginzburg - Landau functional. Averaging over the vector M configurations with the involment of the finite correlation radius a is performed. The inequality a 6h . This means that in a real crystal the hexagonal symmetry is not broken at the scales larger ξ. In the framework of the given theory the expressions for the specific heat jumps and equation combining the upper critical field H c2 and the phase transition split ΔT c with the pressure variation are obtained. The difficulties connencted with the small experimental magnitude of uranium atom magnetic moments are discussed

Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4

Science.gov (United States)

Yiu, Yuen; Le, Manh Duc; Toft-Peterson, Rasmus; Ehlers, Georg; McQueeney, Robert J.; Vaknin, David

2017-03-01

We report on the spin waves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN=50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2 + due to splitting of the S =2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other Li M PO4 (M =Mn , Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.

Energy relaxation between low lying tunnel split spin-states of the single molecule magnet Ni4

Science.gov (United States)

de Loubens, G.; Chaves-O'Flynn, G. D.; Kent, A. D.; Ramsey, C.; Del Barco, E.; Beedle, C.; Hendrickson, D. N.

2007-03-01

We have developed integrated magnetic sensors to study quantum tunneling of magnetization (QTM) in single molecule magnet (SMMs) single crystals. These sensors incorporate a microstrip resonator (30 GHz) and a micro-Hall effect magnetometer. They have been used to investigate the relaxation rates between the 2 lowest lying tunnel split spin-states of the SMM Ni4 (S=4). EPR spectroscopy at 30 GHz and 0.4 K and concurrent magnetization measurements of several Ni4 single crystals are presented. EPR enables measurement of the energy splitting between the 2 lowest lying superposition states as a function of the longitudinal and transverse fields. The energy relaxation rate is determined in two ways. First, in cw microwave experiments the change in spin-population together with the microwave absorption directly gives the relaxation time from energy conservation in steady-state. Second, direct time-resolved measurements of the magnetization with pulsed microwave radiation have been performed. The relaxation time is found to vary by several orders of magnitude in different crystals, from a few seconds down to smaller than 100 μs. We discuss this and the form of the relaxation found for different crystals and pulse conditions.

Temperature fields in a growing solar silicon crystal

Directory of Open Access Journals (Sweden)

Kondrik A. I.

2012-06-01

Full Text Available The optimal thermal terms for growing by Czochralski method Si single-crystals, suitable for making photoelectric energy converters, has been defined by the computer simulation method. Dependences of temperature fields character and crystallization front form on the diameter of the crystal, stage and speed of growing, and also on correlation between diameter and height of the crystal has been studied.

Quasiparticle excitations in valence-fluctuation materials: effects of band structure and crystal fields

International Nuclear Information System (INIS)

Brandow, B.H.

1985-01-01

Evidence is now quite strong that the elementary hybridization model is the correct way to understand the lattice-coherent Fermi liquid regime at very low temperatures. Many-body theory leads to significant renormalizations of the input parameters, and many of the band-theoretic channels for hybridization are suppressed by the combined effects of Hund's-rule coupling, crystal-field splitting, and the f-f Coulomb repulsion U. Some exploratory calculations based on this picture are described, and some inferences are drawn about the band structures of several heavy-fermion materials. These inferences can and should be tested by suitably modified band-theoretic calculations. We find evidence for a significant Baber-scattering contribution in the very-low-temperature resistivity. A new mechanism is proposed for crossover from the coherent Fermi-liquid regime to the incoherent dense-Kondo regime. 28 refs

Synthesis of single-crystal-like nanoporous carbon membranes and their application in overall water splitting

KAUST Repository

Wang, Hong

2017-01-04

Nanoporous graphitic carbon membranes with defined chemical composition and pore architecture are novel nanomaterials that are actively pursued. Compared with easy-to-make porous carbon powders that dominate the porous carbon research and applications in energy generation/conversion and environmental remediation, porous carbon membranes are synthetically more challenging though rather appealing from an application perspective due to their structural integrity, interconnectivity and purity. Here we report a simple bottom–up approach to fabricate large-size, freestanding and porous carbon membranes that feature an unusual single-crystal-like graphitic order and hierarchical pore architecture plus favourable nitrogen doping. When loaded with cobalt nanoparticles, such carbon membranes serve as high-performance carbon-based non-noble metal electrocatalyst for overall water splitting.

Synthesis of single-crystal-like nanoporous carbon membranes and their application in overall water splitting

KAUST Repository

Wang, Hong; Min, Shixiong; Ma, Chun; Liu, Zhixiong; Zhang, Weiyi; Wang, Qiang; Li, Debao; Li, Yangyang; Turner, Stuart; Han, Yu; Zhu, Haibo; Abou-Hamad, Edy; Hedhili, Mohamed N.; Pan, Jun; Yu, Weili; Huang, Kuo-Wei; Li, Lain-Jong; Yuan, Jiayin; Antonietti, Markus; Wu, Tao

2017-01-01

Nanoporous graphitic carbon membranes with defined chemical composition and pore architecture are novel nanomaterials that are actively pursued. Compared with easy-to-make porous carbon powders that dominate the porous carbon research and applications in energy generation/conversion and environmental remediation, porous carbon membranes are synthetically more challenging though rather appealing from an application perspective due to their structural integrity, interconnectivity and purity. Here we report a simple bottom–up approach to fabricate large-size, freestanding and porous carbon membranes that feature an unusual single-crystal-like graphitic order and hierarchical pore architecture plus favourable nitrogen doping. When loaded with cobalt nanoparticles, such carbon membranes serve as high-performance carbon-based non-noble metal electrocatalyst for overall water splitting.

Organic field-effect transistors using single crystals

Directory of Open Access Journals (Sweden)

Tatsuo Hasegawa and Jun Takeya

2009-01-01

Full Text Available Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs, the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

The use of single-crystal iron frames in transient field measurements

International Nuclear Information System (INIS)

Zalm, P.C.; Laan, J. van der; Middelkoop, G. van

1979-01-01

Single-crystal Fe frames have been investigated for use as a ferromagnetic backing in transient magnetic field experiments. For this purpose the surface magnetization as a function of applied magnetic field has been determined with the magneto-optical Kerr effect. The frames, which have two sides parallel to the crystal axis, can be fully magnetized at low external fields such that fringing fields are negligibly small. These single-crystal Fe backings have been used in several transient magnetic field experiments. Comparison of the measured precession angles with previous results, obtained in polycrystalline Fe foils at high external magnetic fields, shows that the single-crystal backings are satisfactory. After extended periods of heavy-ion bombardment the crystals exhibited no radiation damage effects. The absence of fringing fields leads to a reduction of a factor of four in the measuring time for transient field experiments. (Auth.)

Splitting of the luminescent excited state of the uranyl ion

International Nuclear Information System (INIS)

Flint, C.D.; Sharma, P.; Tanner, P.A.

1982-01-01

The luminescence spectra of some uranyl compounds has been studied. It has been proposed that the splitting of the luminescent excited state of the uranyl ion is due to a descent in symmetry experienced by the uranyl ion when it is placed in a crystal field. In recent years there has been developed a highly successful model of the electronic structure of the uranyl ion. In this paper the authors use this model to interpret the luminescence spectra of a variety of uranyl compounds

Phase-field crystal simulation facet and branch crystal growth

Science.gov (United States)

Chen, Zhi; Wang, Zhaoyang; Gu, Xinrui; Chen, Yufei; Hao, Limei; de Wit, Jos; Jin, Kexin

2018-05-01

Phase-field crystal model with one mode is introduced to describe morphological transition. The relationship between growth morphology and smooth density distribution was investigated. The results indicate that the pattern selection of dendrite growth is caused by the competition between interface energy anisotropy and interface kinetic anisotropy based on the 2D phase diagram. When the calculation time increases, the crystal grows to secondary dendrite at the dimensionless undercooling equal to - 0.4. Moreover, when noise is introduced in the growth progress, the symmetry is broken in the growth mode, and there becomes irregular fractal-like growth morphology. Furthermore, the single crystal shape develops into polycrystalline when the noise amplitude is large enough. When the dimensionless undercooling is less than - 0.3, the noise has a significant effect on the growth shape. In addition, the growth velocity of crystal near to liquid phase line is slow, while the shape far away from the liquid adapts to fast growth. Based on the simulation results, the method was proved to be effective, and it can easily obtain different crystal shapes by choosing the different points in 2D phase diagram.

An Overview of Hardware for Protein Crystallization in a Magnetic Field

Directory of Open Access Journals (Sweden)

Er-Kai Yan

2016-11-01

Full Text Available Protein crystallization under a magnetic field is an interesting research topic because a magnetic field may provide a special environment to acquire improved quality protein crystals. Because high-quality protein crystals are very useful in high-resolution structure determination using diffraction techniques (X-ray, neutron, and electron diffraction, research using magnetic fields in protein crystallization has attracted substantial interest; some studies have been performed in the past two decades. In this research field, the hardware is especially essential for successful studies because the environment is special and the design and utilization of the research apparatus in such an environment requires special considerations related to the magnetic field. This paper reviews the hardware for protein crystallization (including the magnet systems and the apparatus designed for use in a magnetic field and progress in this area. Future prospects in this field will also be discussed.

Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal FeK3+-OI2- defect center in KTaO3 crystal

International Nuclear Information System (INIS)

Gnutek, P; Rudowicz, C; Yang, Z Y

2009-01-01

The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g || and g perpendicular , are theoretically investigated for the Fe K 3+ -O I 2- center in KTaO 3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the Fe K 3+ -O I 2- defect center in KTaO 3 . This modeling reveals that the off-center displacement of the Fe 3+ ions, Δ 1 (Fe 3+ ), combined with an inward relaxation of the nearest oxygen ligands, Δ 2 (O 2- ), and the existence of the interstitial oxygen O I 2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the Fe K 3+ -O I 2- center in KTaO 3 . Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of Δ 1 (Fe 3+ ) and Δ 2 (O 2- ) as well as the possible location of O I 2- ligands around Fe 3+ ions in KTaO 3 . The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g || and g perpendicular and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing

Local fields in ionic crystals

International Nuclear Information System (INIS)

Claro, F.

1981-08-01

Local fields arising from the electronic distortion in perfect ionic crystals are described in terms of multipolar excitations. Field factors for the alkali halides and chalcogenide ions are found to differ significantly from the Lorentz value of 4π/3, the correction size following an exponential dependence on the difference in ionic radii. Local fields are only slightly modified by these corrections however, and together with the Clausius-Mossotti relation may be regarded as accurate to within 2% if the Lorentz value is adopted. (author)

Sub-wavelength imaging and field mapping via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms

Energy Technology Data Exchange (ETDEWEB)

Holloway, Christopher L., E-mail: holloway@boulder.nist.gov; Gordon, Joshua A. [National Institute of Standards and Technology (NIST), Electromagnetics Division, U.S. Department of Commerce, Boulder Laboratories, Boulder, Colorado 80305 (United States); Schwarzkopf, Andrew; Anderson, David A.; Miller, Stephanie A.; Thaicharoen, Nithiwadee; Raithel, Georg [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2014-06-16

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of ≈100 μm, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime.

Mapping the absolute electromagnetic field strength of individual field components inside a photonic crystal

NARCIS (Netherlands)

Denis, T.; Reijnders, B.; Lee, J.H.H.; Vos, Willem L.; Boller, Klaus J.; van der Slot, Petrus J.M.

2013-01-01

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We demonstrate our method by applying it to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to create a

Experimental determination of the relativistic fine structure splitting in a pionic atom

International Nuclear Information System (INIS)

Wang, K.-C.; Boehm, F.; Hahn, A.A.; Henrikson, H.E.; Miller, J.P.; Powers, R.J.; Vogel, P.; Vuilleumier, J.-L.; Kunselman, R.

1978-01-01

Using a high-resolution crystal spectrometer, the authors have measured the energy splitting of the pionic 5g-4f and 5f-4d transitions in Ti. The observed fine structure splitting agrees, within the experimental error of 3%, with the splitting arising from the calculated relativistic term and other small corrections for spinless particles. (Auth.)

Internal bias field in glycine phosphite crystal

International Nuclear Information System (INIS)

Nayeem, Jannatul; Wakabayashi, Hiroshi; Kikuta, Toshio; Yamazaki, Toshinari; Nakatani, Noriyuki

2003-01-01

The distributions of internal bias field E b have been investigated under the carbon-powder pattern and mercury electrode techniques in GPI ferroelectric crystals. Polarity and intensity of E b are distributed depending on crystal growth sectors. Crystal symmetry 2/m is observed obviously in the distribution of E b . The polarities of E b are head-to-head manner in those growth sectors where a surface is growing parallel to the crystallographic a-axis and tail-to-tail manner in the other growth sectors in the crystal. The maximum intensity of E b is found in the sectors (010) where the growing surfaces are perpendicular to the ferroelectric b-axis

Energetic band structure of Zn{sub 3}P{sub 2} crystals

Energy Technology Data Exchange (ETDEWEB)

Stamov, I.G. [Tiraspol State Corporative University, Lablocicin Street 5, 2069 Tiraspol (Moldova, Republic of); Syrbu, N.N., E-mail: sirbunn@yahoo.com [Technical University of Moldova, 168 Stefan cel Mare Avenue, 2004 Chisinau (Moldova, Republic of); Dorogan, A.V. [Technical University of Moldova, 168 Stefan cel Mare Avenue, 2004 Chisinau (Moldova, Republic of)

2013-01-01

Optical functions n, k, {epsilon}{sub 1}, {epsilon}{sub 2} and d{sup 2}{epsilon}{sub 2}/dE{sup 2} have been determined from experimental reflection spectra in the region of 1-10 eV. The revealed electronic transitions are localized in the Brillouin zone. The magnitude of valence band splitting caused by the spin-orbital interaction {Delta}{sub SO} is lower than the splitting caused by the crystal field {Delta}{sub CR} in the center of Brillouin zone and L and X points. The switching effects are investigated in Zn{sub 3}P{sub 2} crystals. The characteristics of experimental samples with electric switching, adjustable resistors, and time relays based on Zn{sub 3}P{sub 2} are presented.

Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

Energy Technology Data Exchange (ETDEWEB)

Koizumi, H.; Uda, S.; Fujiwara, K.; Nozawa, J. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 (Japan); Tachibana, M. [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027 (Japan); Kojima, K. [Department of Education, Yokohama Soei University, 1 Miho-tyou, Midori-ku, Yokohama, 226-0015 (Japan)

2014-10-06

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

EPR spectroscopy of MRI-related Gd(III) complexes: simultaneous analysis of multiple frequency and temperature spectra, including static and transient crystal field effects.

Science.gov (United States)

Rast, S; Borel, A; Helm, L; Belorizky, E; Fries, P H; Merbach, A E

2001-03-21

For the first time, a very general theoretical method is proposed to interpret the full electron paramagnetic resonance (EPR) spectra at multiple temperatures and frequencies in the important case of S-state metal ions complexed in liquid solution. This method is illustrated by a careful analysis of the measured spectra of two Gd3+ (S = 7/2) complexes. It is shown that the electronic relaxation mechanisms at the origin of the EPR line shape arise from the combined effects of the modulation of the static crystal field by the random Brownian rotation of the complex and of the transient zero-field splitting. A detailed study of the static crystal field mechanism shows that, contrarily to the usual global models involving only second-order terms, the fourth and sixth order terms can play a non-negligible role. The obtained parameters are well interpreted in the framework of the physics of the various underlying relaxation processes. A better understanding of these mechanisms is highly valuable since they partly control the efficiency of paramagnetic metal ions in contrast agents for medical magnetic resonance imaging (MRI).

Splitting of an electromagnetically induced transparency window of a cascade system with 133Cs Rydberg atoms in a static magnetic field

International Nuclear Information System (INIS)

Bao Shanxia; Yang Wenguang; Zhang Hao; Zhang Linjie; Zhao Jianming; Jia Suotang

2015-01-01

We investigate the electromagnetically induced transparency (EIT) of 133 Cs vapor at the room temperature in a magnetic field. In a cascade three-level system involved Rydberg state, two collinearly counter-propagating and orthogonally linear-polarized laser fields act on cascaded two transitions, 6S 1/2 → 6P 3/2 and 6P 3/2 ↔ 47D 5/2 , respectively. The EIT window become broadening and split into several sub-EIT windows when the magnetic field is applied. The dependences of splitting shape and intervals of sub-EIT windows on magnetic field are measured experimentally and compared with the theoretical calculation considering the different magnetic effects on ground state, low excited state and Rydberg state. The splitting intervals of sub-EIT windows are well consistent with theoretical calculation. (author)

Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

Science.gov (United States)

Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

2016-01-19

We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.

Zero-Magnetic-Field Spin Splitting of Polaron's Ground State Energy Induced by Rashba Spin-Orbit Interaction

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.

Far-field coupling in nanobeam photonic crystal cavities

Energy Technology Data Exchange (ETDEWEB)

Rousseau, Ian, E-mail: ian.rousseau@epfl.ch; Sánchez-Arribas, Irene; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas [Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2016-05-16

We optimized the far-field emission pattern of one-dimensional photonic crystal nanobeams by modulating the nanobeam width, forming a sidewall Bragg cross-grating far-field coupler. By setting the period of the cross-grating to twice the photonic crystal period, we showed using three-dimensional finite-difference time-domain simulations that the intensity extracted to the far-field could be improved by more than three orders of magnitude compared to the unmodified ideal cavity geometry. We then experimentally studied the evolution of the quality factor and far-field intensity as a function of cross-grating coupler amplitude. High quality factor (>4000) blue (λ = 455 nm) nanobeam photonic crystals were fabricated out of GaN thin films on silicon incorporating a single InGaN quantum well gain medium. Micro-photoluminescence spectroscopy of sets of twelve identical nanobeams revealed a nine-fold average increase in integrated far-field emission intensity and no change in average quality factor for the optimized structure compared to the unmodulated reference. These results are useful for research environments and future nanophotonic light-emitting applications where vertical in- and out-coupling of light to nanocavities is required.

Crystal growth and spectroscopic characterization of Yb3+:LiTaO3

International Nuclear Information System (INIS)

Gruber, John B.; Allik, Toomas H.; Sardar, Dhiraj K.; Yow, Raylon M.; Scripsick, Michael; Wechsler, Barry

2006-01-01

Spectroscopic properties are presented for Yb 3+ incorporated into single crystals of LiTaO 3 grown by the top-seeded solution growth method. From an analysis of the absorption and fluorescence spectra, we are able to determine the Stark-level components of the 2 F 7/2 (the ground-state multiplet manifold) and the 2 F 5/2 (the excited-state multiplet manifold of Yb 3+ (4f 13 )). The room-temperature fluorescence lifetime of 2 F 5/2 is 678μs as measured on a thin sample to reduce possibilities for reabsorption. Spectral comparisons of Yb 3+ -doped LiTaO 3 and LiNbO 3 are drawn. The crystal-field splitting of Yb 3+ (4f 13 ) in both crystal hosts is modeled using a set of crystal-field splitting parameters, B nm , determined from a recent spectroscopic analysis of Er 3+ (4f 11 ) in LiNbO 3 . Without adjustment of the B nm parameters, the model predicts the Stark-level energy and the symmetry label for each level in reasonable agreement with the experimental values. Less photorefractive than its niobate cousin, LiTaO 3 has potential for use in numerous integrated electro-optical circuits and devices

Giant optical anisotropy in M-plane GaN/AlGaN quantum wells due to crystal-field effect

International Nuclear Information System (INIS)

Chen, C.-N.; Su, W.-L.; Chang, K.-C.; Chang, S.-H.; Chiang, J.-C.; Lo Ikai; Wang, W.-T.; Kao, H.-F.; Lee, M.-E.

2008-01-01

The optical polarization of GaN/AlGaN wurtzite quantum wells in various orientations is studied using an arbitrarily-oriented [hkil] Hamiltonian potential matrix. The optical matrix elements in the wurtzite quantum wells are calculated using the k.p finite difference scheme. The results reveal the presence of giant in-plane optical anisotropy (polarized normal to [0001]) in the M-plane (i.e., the (101-bar0)-oriented layer plane) GaN/Al 0.2 Ga 0.8 N quantum well, due to the positive crystal-field split energy effect (Δ CR >0). The present theoretical results are consistent with the photoluminescence measurements presented in the literature [B. Rau, et al., Appl. Phys. Lett. 77 (2000) 3343

A field ion microscope study of the surface reaction of tungsten with n-octanol under an applied positive voltage: reaction conditions for the 'splitting' of (110) plane

International Nuclear Information System (INIS)

Terao, T.; Iwatsu, F.; Morikawa, H.

1993-01-01

Field ion microscopy is a powerful tool for the study of surface phenomena on an atomic scale, especially when they are crystal plane dependent, because the microscope shows many crystal planes of the sample tip simultaneously. Although a large number of FIM studies on vapor deposition, surface diffusion and surface reactions at a metal-gas interface have been reported, those on reactions at a metal-liquid interface are few. The authors have studied the corrosion or tungsten with aqueous solutions and found that water corroded the tungsten tips very severely to reduce the radius of curvature of the tip cap drastically. The reaction was so severe that it was not possible to trace it back to the very initial stages. They adopted, as a weaker reagent, one of the higher alcohols, n-octanol(C 8 H 17 OH), and found that it reacted with tungsten tips when an electrical pulse with a positive voltage between 5 and 10V was applied to the tip, giving very interesting field ion images in which the central (110) plane was divided into two parts located side by side across the [001] zone line. This means that some anisotropic surface reaction occurred which made a groove along the [001] zone line going through the (110) plane, usually the most stable plane chemically for bcc metals. They named this phenomenon 'splitting'. This reaction was less severe than that with water and some results on the morphology of the groove and on the reaction sequence have been reported. In the present paper more detailed reaction conditions which give rise to the splitting are described

Dependence of magnetization on crystal fields and exchange interactions in magnetite

Energy Technology Data Exchange (ETDEWEB)

Ouaissa, Mohamed, E-mail: m.ouaissa@yahoo.fr [Laboratoire de Génie Physique et Environnement, Faculté des Sciences, Université Ibn Tofail, Campus Universitaire BP 133, Kénitra 14000 (Morocco); Benyoussef, Abdelilah [Laboratory of Magnetism and Physics of High Energy, Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Abo, Gavin S. [Department of Electrical and Computer Engineering and MINT Center, The University of Alabama, Tuscaloosa, AL 35487 (United States); Ouaissa, Samia; Hafid, Mustapha [Laboratoire de Génie Physique et Environnement, Faculté des Sciences, Université Ibn Tofail, Campus Universitaire BP 133, Kénitra 14000 (Morocco); Belaiche, Mohammed [Laboratoire de Magnétisme, Matériaux Magnétiques, Microonde et Céramique, Ecole Normale Supérieure, Université Mohammed V-Agdal, B.P. 9235, Océan, Rabat (Morocco)

2015-11-15

In this work, we study the magnetization of magnetite (Fe{sub 3}O{sub 4}) with different exchange interactions and crystal fields using variational method based on the Bogoliubov inequality for the Gibbs free energy within the mean field theory. The magnetic behavior was investigated in the absence and presence of crystal fields. The investigations also revealed that the transition temperature depends on the crystal fields of the octahedral and tetrahedral sites. Magnetite exhibits ferrimagnetic phase with second order transition to paramagnetic phase at 850 K. This result is confirmed using the mean field theory within the Heisenberg model. Important factors that can affect the magnetic behavior of the system are exchange interactions and crystal field. Indeed, a new magnetic behavior was observed depending on these parameters. A first order phase transition from ferrimagnetic to ferromagnetic was found at low temperature, and a second order transition from ferromagnetic to paramagnetic was observed at high temperature. - Highlights: • Magnetization of magnetite versus temperature was studied by mean field theory. • The critical temperature of magnetite (Fe{sub 3}O{sub 4}) was approximately obtained. • Effect of sublattice crystal fields on the magnetization of Fe{sub 3}O{sub 4} was investigated.

Time-domain electric field enhancement on micrometer scale in coupled split ring resonator upon terahertz radiation

DEFF Research Database (Denmark)

Lange, Simon Lehnskov; Iwaszczuk, Krzysztof; Hoffmann, Matthias

2016-01-01

We present here a novel design for a coupled split ring resonator antenna optimized for time-domain electric field enhancement in the 0.1 to 1 terahertz (THz) range. The antenna is designed to be sensitive to the incident field polarization and seeks to avoid metal damage due to electron bombardm...

Field-induced spin splitting and anomalous photoluminescence circular polarization in C H3N H3Pb I3 films at high magnetic field

Science.gov (United States)

Zhang, Chuang; Sun, Dali; Yu, Zhi-Gang; Sheng, Chuan-Xiang; McGill, Stephen; Semenov, Dmitry; Vardeny, Zeev Valy

2018-04-01

The organic-inorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using high-field magneto-optical measurements up to 17.5 T at cryogenic temperatures, we have studied the spin-dependent optical transitions in the prototype C H3N H3Pb I3 , which are manifested in the field-induced circularly polarized photoluminescence emission. The energy splitting between left and right circularly polarized emission bands is measured to be ˜1.5 meV at 17.5 T, from which we obtained an exciton effective g factor of ˜1.32. Also from the photoluminescence diamagnetic shift we estimate the exciton binding energy to be ˜17 meV at low temperature. Surprisingly, the corresponding field-induced circular polarization is "anomalous" in that the photoluminescence emission of the higher split energy band is stronger than that of the lower split band. This "reversed" intensity ratio originates from the combination of long electron spin relaxation time and hole negative g factor in C H3N H3Pb I3 , which are in agreement with a model based on the k.p effective-mass approximation.

Spin Splitting in Different Semiconductor Quantum Wells

International Nuclear Information System (INIS)

Hao Yafei

2012-01-01

We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field. The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included. The results show that the structure of quantum well plays an important role in spin splitting. The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different. The origin of the distinction is discussed in this work. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals

Science.gov (United States)

2017-01-01

We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime. PMID:29541653

Optical spectroscopy and crystal-field analysis of U3+: Ba2YCl7

International Nuclear Information System (INIS)

Karbowiak, M.; Mech, A.; Drozdzyndki, J.; Gajek, Z.; Edelstein, N.M.

2002-01-01

High resolution absorption spectra of a U 3+ (0.3%): Ba 2 YCl 7 single crystal were recorded in the 4000-50 000 cm -1 range at 7 K. The observed crystal-field levels were assigned and fit to the parameters of the simplified angular overlap model (AOM) as well as a semi-empirical Hamiltonian representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab initio calculations. The analysis of the spectra allowed the assignment of 65 crystal-field levels with a relatively small rms deviation of 25 cm -1 and has shown that the AOM approach can predict quite well the B q k crystal-field parameters. The value determined for the crystal-field strength parameter, N v , corresponds well with those determined for U 3+ in other chloride single crystals. (authors)

Calculations of the electronic levels, spin-Hamiltonian parameters and vibrational spectra for the CrCl{sub 3} layered crystals

Energy Technology Data Exchange (ETDEWEB)

Avram, C.N. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Gruia, A.S., E-mail: adigruia@yahoo.com [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barb, A.M. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania)

2015-12-01

Calculations of the Cr{sup 3+} energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl{sub 3} crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr{sup 3+} ion in CrCl{sub 3} crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.

Synthesis and crystal structure of the solid solution Co3(SeO3)3-x(PO3OH)x(H2O) involving crystallographic split positions of Se4+ and P5+.

Science.gov (United States)

Zimmermann, Iwan; Johnsson, Mats

2013-10-21

Three new cobalt selenite hydroxo-phosphates laying in the solid solution Co3(SeO3)3-x(PO3OH)x(H2O), with x = 0.8, x = 1.0, and x = 1.2 are reported. Single crystals were obtained by hydrothermal synthesis and the crystal structure was determined by single crystal X-ray diffraction. The structure can be described as a 3D framework having selenite and hydroxo-phosphate groups protruding into channels in the crystal structure. Se(4+) and P(5+) share a split position in the structure so that either SeO3 groups having a stereochemically active lone pair or tetrahedrally coordinated PO3OH groups are present. The OH-group is thus only present when the split position is occupied by P(5+). The crystal water is coordinated to a cobalt atom and TG and IR measurements show that the water and hydroxyl groups leave the structure at unusually high temperatures (>450 °C). Magnetic susceptibility measurements show antiferromagnetic coupling below 16 K and a magnetic moment of 4.02(3) μB per Co atom was observed.

Splitting Fermi Surfaces and Heavy Electronic States in Non-Centrosymmetric U3Ni3Sn4

Science.gov (United States)

Maurya, Arvind; Harima, Hisatomo; Nakamura, Ai; Shimizu, Yusei; Homma, Yoshiya; Li, DeXin; Honda, Fuminori; Sato, Yoshiki J.; Aoki, Dai

2018-04-01

We report the single-crystal growth of the non-centrosymmetric paramagnet U3Ni3Sn4 by the Bridgman method and the Fermi surface properties detected by de Haas-van Alphen (dHvA) experiments. We have also investigated single-crystal U3Ni3Sn4 by single-crystal X-ray diffraction, magnetization, electrical resistivity, and heat capacity measurements. The angular dependence of the dHvA frequencies reveals many closed Fermi surfaces, which are nearly spherical in topology. The experimental results are in good agreement with local density approximation (LDA) band structure calculations based on the 5f-itinerant model. The band structure calculation predicts many Fermi surfaces, mostly with spherical shape, derived from 12 bands crossing the Fermi energy. To our knowledge, the splitting of Fermi surfaces due to the non-centrosymmetric crystal in 5f-electron systems is experimentally detected for the first time. The temperature dependence of the dHvA amplitude reveals a large cyclotron effective mass of up to 35 m0, indicating the heavy electronic state of U3Ni3Sn4 due to the proximity of the quantum critical point. From the field dependence of the dHvA amplitude, a mean free path of conduction electrons of up to 1950 Å is detected, reflecting the good quality of the grown crystal. The small splitting energy related to the antisymmetric spin-orbit interaction is most likely due to the large cyclotron effective mass.

Mounting an ISR intersection chamber in the Split Field Magnet(SFM)

CERN Multimedia

1977-01-01

The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton.Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In the course of the years different types of vacu...

Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer.

Science.gov (United States)

Sun, Baozhou; Yang, Deshan; Esthappan, Jackie; Garcia-Ramirez, Jose; Price, Samantha; Mutic, Sasa; Schwarz, Julie K; Grigsby, Perry W; Tanderup, Kari

2015-01-01

Dose accumulation of split-field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. We developed a method to determine biologically effective dose parameters for combined split-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were computed on the 3D combined EQD2 dose based on rigid image registration. The dose accumulation uncertainty introduced by organ deformations between IMRT and BT was evaluated. According to International Commission on Radiation Unit and Measurement and GEC European Society for Therapeutic Radiology and Oncology recommendations, D98, D90, D50, and D2cm3 EQD2 dose-volume histogram parameters were computed. GTV D98 was 84.0 ± 26.5 Gy and D2cc was 99.6 ± 13.9 Gy, 67.4 ± 12.2 Gy, 75.0 ± 10.1 Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1 ± 4 Gy, -3 ± 5 Gy, 2 ± 3 Gy, and -3 ± 5 Gy for bladder, rectum, sigmoid, and GTV, respectively. It is feasible to perform 3D EQD2 dose accumulation to assess high and intermediate dose regions for combined split-field IMRT and BT. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Reliability of conventional crystal field models in f-electron systems

Energy Technology Data Exchange (ETDEWEB)

Gajek, Z. [Polska Akademia Nauk, Wroclaw (Poland). Inst. Niskich Temperatur i Badan Strukturalnych

1995-03-15

Crystal field models commonly applied to explain the electronic properties of solid f-electron compounds are discussed from the point of view of their inherent limitations and the false conclusions they may lead to. Both phenomenological and ab initio approximate models are considered. The discussion is based on generalized perturbation model calculations of the crystal field parameters for europium, uranium, plutonium and neptunium ions in various crystals. The results reveal the inadequacy of various electrostatic approaches and the correctness of models based on renormalization terms. ((orig.))

Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model

DEFF Research Database (Denmark)

Tarp, Jens M.; Angheluta, Luiza; Mathiesen, Joachim

2014-01-01

Plastic deformation mediated by collective dislocation dynamics is investigated in the two-dimensional phase-field crystal model of sheared single crystals. We find that intermittent fluctuations in the dislocation population number accompany bursts in the plastic strain-rate fluctuations...... propose a simple stochastic model of dislocation reaction kinetics that is able to capture these statistical properties of the dislocation density fluctuations as a function of shear rate....

Conduction band-edge d-states in high-k dielectrics due to Jahn-Teller term splittings

International Nuclear Information System (INIS)

Lucovsky, G.; Fulton, C.C.; Zhang, Y.; Luning, J.; Edge, L.; Whitten, J.L.; Nemanich, R.J.; Schlom, D.G.; Afanase'v, V.V.

2005-01-01

X-ray absorption spectroscopy (XAS) is used to study conduction band edge electronic structure of high-k transition metal (TM) and trivalent lanthanide series rare earth (RE) oxide dielectrics. Empty TM/RE d-states are studied by intra-atomic transitions originating in core level spin-orbit split p-states, and conduction band states are studied in inter-atomic transitions which originate in the oxygen atom 1s core level state. In non-crystalline Zr and Hf silicate alloys, the local bonding symmetry, or crystal field splits these d-states into doubly and triply degenerate features. In nano-crystalline oxides, there are additional d-state splittings due to contributions of more distant neighbors that completely remove d-state degeneracies via the Jahn-Teller effect mechanism. This gives rise to highly localized band edge states that are electronically active in photoconductivity, internal photoemission, and act as bulk traps in metal oxide semiconductor (MOS) devices

Simple nonempirical calculations of the zero-field splitting in transition metal systems: I. The Ni(II)-water complexes

International Nuclear Information System (INIS)

Ribbing, C.; Odelius, M.; Laaksonen, A.; Kowalewski, J.; Roos, B.

1990-01-01

A simple nonempirical scheme is presented for calculating the splittings of ground state multiplets (the zero-field splitting) is transition metal complexes. The method employs single reference, single excitation CI calculations based on open-shell RHF. The spin-orbit coupling is described using an effective one-electron, one-center operators. The method is applied to the triplet state Ni(II) complexes with one to six water molecules. the validity of the second-order perturbation theory approach and of the spin-Hamiltonian formalism is found to be limited to slightly distorted octahedral systems. Generally, small changes in the geometries of the complexes are found to cause substantial variations of the splitting pattern

Crystal-fields at rare-earth sites in R2Fe14B compounds

International Nuclear Information System (INIS)

Adam, S.; Adam, G.; Burzo, E.

1985-12-01

Crystal-field effects are expected to be important in R 2 Fe 14 B compounds. Within a model-independent approach, it is proved that four distinct rare-earth sites exist with respect to the crystalline electric fields, namely, R(4f; z=0), R(4f; z=0.5 c), R(4g; z=0), and R(4g; z=0.5 c), and relationships are established between the corresponding crystal-fields coefficients. Further, generalized Stevens parametrizations of the crystal field coefficients are derived at three levels of approximation for the interatomic forces inside the crystal. A crystal lattice dressing effect upon the radial electronic integrals is found to occur, the magnitude of which depends on the deviation of the interatomic forces from Coulombian. Finally, computation of crystal-field coefficients in Nd 2 Fe 14 B leads to results which raise questions about the validity of the simple Coulomb point-charge model. (author)

Global mean-field phase diagram of the spin-1 Ising ferromagnet in a random crystal field

Science.gov (United States)

Borelli, M. E. S.; Carneiro, C. E. I.

1996-02-01

We study the phase diagram of the mean-field spin-1 Ising ferromagnet in a uniform magnetic field H and a random crystal field Δi, with probability distribution P( Δi) = pδ( Δi - Δ) + (1 - p) δ( Δi). We analyse the effects of randomness on the first-order surfaces of the Δ- T- H phase diagram for different values of the concentration p and show how these surfaces are affected by the dilution of the crystal field.

Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

Directory of Open Access Journals (Sweden)

Ilya eLisenker

2016-03-01

Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

Electric field gradient at nuclei on orthorhombic sites in CaF2 and SrCl2 : comparison with electronic zero-field splitting

NARCIS (Netherlands)

Ormondt, van D.; Andriessen, J.; Dam, J.A.M.; Ast, van M.A.; Hartog, den H.W.; Bijvank, E.J.

1979-01-01

The electric field gradients (EFG) Vzz and Vxx-Vyy at the nucleus of 157Gd3+ have been determined, using ENDOR, for CaF2:Gd3+M+(M+=Li,K+) and SrCl2:Gd3+Na+. The results are compared with the electronic zero-field splitting parameters of Gd3+, B20 and B22 for the same sites. A simple relation between

Dislocation motion in InSb crystals under a magnetic field

CERN Document Server

Darinskaya, E V; Erofeeva, S A

2002-01-01

Dislocation displacements under the action of a permanent magnetic field without mechanical loading in differently doped InSb crystals are investigated. The dependences of the mean dislocation path length and the relative number of divergence and tightening half-loops on the magnetic induction and preliminary load are obtained. Experiments on n-InSb crystals with Te impurities and on p-InSb crystals with Ge impurities have shown a sensitivity of the magnetoplasticity to the conductivity type and the dopant content. Study of the magnetoplastic effect in the initial deformed InSb crystals shows that internal stresses decrease the lengths of divergence dislocation paths and simultaneously increase the threshold magnetic field above which the magnetoplastic effect exists. Possible reasons for the observed phenomena are discussed.

Plasmonic gold nanocrystals coupled with photonic crystal seamlessly on TiO2 nanotube photoelectrodes for efficient visible light photoelectrochemical water splitting

KAUST Repository

Zhang, Zhonghai

2013-01-09

A visible light responsive plasmonic photocatalytic composite material is designed by rationally selecting Au nanocrystals and assembling them with the TiO2-based photonic crystal substrate. The selection of the Au nanocrystals is so that their surface plasmonic resonance (SPR) wavelength matches the photonic band gap of the photonic crystal and thus that the SPR of the Au receives remarkable assistance from the photonic crystal substrate. The design of the composite material is expected to significantly increase the Au SPR intensity and consequently boost the hot electron injection from the Au nanocrystals into the conduction band of TiO2, leading to a considerably enhanced water splitting performance of the material under visible light. A proof-of-concept example is provided by assembling 20 nm Au nanocrystals, with a SPR peak at 556 nm, onto the photonic crystal which is seamlessly connected on TiO2 nanotube array. Under visible light illumination (>420 nm), the designed material produced a photocurrent density of ∼150 μA cm-2, which is the highest value ever reported in any plasmonic Au/TiO2 system under visible light irradiation due to the photonic crystal-assisted SPR. This work contributes to the rational design of the visible light responsive plasmonic photocatalytic composite material based on wide band gap metal oxides for photoelectrochemical applications. © 2012 American Chemical Society.

Method to map individual electromagnetic field components inside a photonic crystal

NARCIS (Netherlands)

Denis, T.; Reijnders, B.; Lee, J.H.H.; van der Slot, Petrus J.M.; Vos, Willem L.; Boller, Klaus J.

2012-01-01

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the dominant electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing

Crystal field in rare-earth metals and intermetallic compounds

International Nuclear Information System (INIS)

Ray, D.K.

1978-01-01

Reasons for the success of the crystal-field model for the rare-earth metals and intermetallic compounds are discussed. A review of some of the available experimental results is made with emphasis on cubic intermetallic compounds. Various sources of the origin of the crystal field in these metals are discussed in the background of the recent APW picture of the conduction electrons. The importance of the non-spherical part of the muffin-tin potential on the single-ion anisotropy is stressed. (author)

A Navier-Stokes phase-field crystal model for colloidal suspensions.

Science.gov (United States)

Praetorius, Simon; Voigt, Axel

2015-04-21

We develop a fully continuous model for colloidal suspensions with hydrodynamic interactions. The Navier-Stokes Phase-Field Crystal model combines ideas of dynamic density functional theory with particulate flow approaches and is derived in detail and related to other dynamic density functional theory approaches with hydrodynamic interactions. The derived system is numerically solved using adaptive finite elements and is used to analyze colloidal crystallization in flowing environments demonstrating a strong coupling in both directions between the crystal shape and the flow field. We further validate the model against other computational approaches for particulate flow systems for various colloidal sedimentation problems.

Single crystal EPR determination of the quantum energy level structure for Fe8 molecular clusters

Science.gov (United States)

Maccagnano, S.; Hill, S.; Negusse, E.; Lussier, A.; Mola, M. M.; Achey, R.; Dalal, N. S.

2001-05-01

Using a high sensitivity resonance cavity technique,^1 we are able to obtain high field/frequency (up to 9 tesla/210 GHz) EPR spectra for oriented single crystals of [Fe_8O_2(OH)_12(tacn)_6]Br_8.9H_2O (or Fe8 for short). Extrapolating the frequency dependence of transitions to zero-field (for any orientation of the field) allows us to directly, and accurately (to within 0.5 percent), determine the first five zero-field splittings, which are in reasonable agreement with recent inelastic neutron studies.^2 The dependence of these splittings on the applied field strength, and its orientation with respect to the crystal, enables us to identify (to within 1^o) the easy, intermediate and hard magnetic axes. Subsequent analysis of EPR spectra for field parallel to the easy axis yields a value of for gz which is appreciably different from the value assumed in a recent high field EPR study by Barra et al.^3 ^1 M.M. Mola, S. Hill, P. Goy, and M. Gross, Rev. Sci. Inst. 71, 186 (2000). ^2 R. Caciuffo, G. Amoretti, R. Sessoli, A. Caneschi, and D. Gatteschi, Phys. Rev. Lett. 81, 4744 (1998). ^3 A. L. Barra, D. Gatteschi, and R. Sessoli, cond?mat/0002386 (Feb, 2000).

A Novel X-ray Diffractometer for the Florida Split Coil 25 Tesla Magnet

Science.gov (United States)

Wang, Shengyu; Kovalev, Alexey; Suslov, Alexey; Siegrist, Theo

2014-03-01

At National High Magnetic Field Laboratory (NHMFL), we are developing a unique X-ray diffractometer for the 25 Tesla Florida Split Coil Magnet for scattering experiments under extremely high static magnetic fields. The X-ray source is a sealed tube (copper or molybdenum anode), connected to the magnet by an evacuated beam tunnel. The detectors are either an image plate or a silicon drift detector, with the data acquisition system based on LabVIEW. Our preliminary experimental results showed that the performance of the detector electronics and the X-ray generator is reliable in the fringe magnetic fields produced at the highest field of 25 T. Using this diffractometer, we will make measurements on standard samples, such as LaB6, Al2O3 and Si, to calibrate the diffraction system. Magnetic samples, such as single crystal HoMnO3 and stainless steel 301 alloys will be measured subsequently. The addition of X-ray diffraction to the unique split coil magnet will significantly expand the NHMFL experimental capabilities. Therefore, external users will be able to probe spin - lattice interactions at static magnetic fields up to 25T. This project is supported by NSF-DMR Award No.1257649. NHMFL is supported by NSF Cooperative Agreement No. DMR-1157490, the State of Florida, and the U.S. DoE.

Correlation theory of crystal field and anisotropic exchange effects

DEFF Research Database (Denmark)

Lindgård, Per-Anker

1985-01-01

A general theory for including correlation effects in static and dynamic properties is presented in terms of Raccah or Stevens operators. It is explicitly developed for general crystal fields and anisotropic interactions and systems with several sublattices, like the rare earth compounds....... The theory gives explicitly a temperature dependent renormalization of both the crystal field and the interactions, and a damping of the excitations and in addition a central park component. The general theory is illustrated by a discussion of the singlet-doublet system. The correlation effects...

Crystal fields at light rare-earth ions in Y and Lu

DEFF Research Database (Denmark)

Touborg, P.; Nevald, Rolf; Johansson, Torben

1978-01-01

Crystal-field parameters have been deduced for the light rare-earth solutes Ce, Pr, and Nd in Y or Lu hosts from measurements of the paramagnetic susceptibilities. In the analysis all multiplets in the lowest LS term were included. For a given host, crystal-field parameters divided by Stevens fac...

Link between optical spectra, crystal-field parameters, and local environments of Eu3+ ions in Eu2O3-doped sodium disilicate glass

International Nuclear Information System (INIS)

Qin, T.; Mountjoy, G.; Afify, N. D.; Reid, M. F.; Yeung, Y. Y.; Speghini, A.; Bettinelli, M.

2011-01-01

Rare-earth-doped glasses are key materials for optical technology due to the luminescent properties of 4f n ions. The crystal-field model describes the effect of local environment on transitions between 4f electrons. We present a detailed modeling study of the optical spectra of sodium disilicate glass, 33Na 2 O·67SiO 2 , doped with 0.2% and 1.0 mol%Eu 2 O 3 . This study uses very large molecular dynamics models with up to 100 Eu 3+ ions, the superposition model for covalent and overlap effects on crystal-field parameters, and realistic values for homogeneous linewidth broadening. The simulated spectra are in reasonable agreement with experiment. The trends in 7 F J energy levels across different Eu 3+ ion sites have been examined and a very detailed analysis is presented that looks at how features of the spectra are related to features of the local environment of Eu 3+ ions. Increasing the crystal-field strength S total causes the 7 F 0 energy level to decrease and causes the splitting of 7 F J manifolds to increase, and this is due to increasing mixing of 4f wave functions. To a reasonable approximation the crystal-field strength components S k depend on angular positions of ligands independently of distances to ligands. The former are seen to be more significant in determining S k , which are closely related to the rotationally invariant bond-orientational order parameters Q k . The values of S 2 are approximately linear in Q 2 , and the values of Q 2 are higher for fivefold than sixfold coordinated rare-earth ions. These results can be of importance for efforts to enhance the local environment of rare-earth ions in oxide glasses for optical applications.

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Energy Technology Data Exchange (ETDEWEB)

Lisenker, Ilya; Stoldt, Conrad R., E-mail: stoldt@colorado.edu [Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO (United States)

2016-03-31

The effect of high-frequency (HF) electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP) ion conducting ceramic was investigated. LAGP with the nominal composition Li{sub 1.5}Al{sub 0.5}Ge{sub 1.5}(PO{sub 4}){sub 3} was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy to compare conventionally and field-sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 h of sintering were minor with measured sintering strains of 31 vs. 26% with and without field, respectively. Ionic conductivity of the sintered pellets was evaluated, and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

Integral parameters of crystal field for RE spectra

International Nuclear Information System (INIS)

Kustov, E.F.; Maketov, T.K.; Prgevudsky, A.K.; Steczko, G.

1980-01-01

The integral parameters of the crystal field are introduced for the interpretation of the spectra of RE ions in various crystals. The main formula of the method, the expression of the parameters for various states of Ce, Pr, Nd, Eu, Tb, Er, Tu, and Yb are determined. Integral parameters of A 2 , A 4 , A 6 and parameter of the spin-orbit interaction xi are calculated for 40 laser crystals with Nd, Er. An interpretation of the symmetry of the Eu 3+ centres of the NaBaZn silicate glass is given using integral parameters A 2 , A 4 . (author)

2-Photon tandem device for water splitting

DEFF Research Database (Denmark)

Seger, Brian; Castelli, Ivano Eligio; Vesborg, Peter Christian Kjærgaard

2014-01-01

Within the field Of photocatalytic water splitting there are several strategies to achieve the goal of efficient and cheap photocatalytic water splitting. This work examines one particular strategy by focusing on monolithically stacked, two-photon photoelectrochemical cells. The overall aim...... for photocatalytic water splitting by using a large bandgap photocathode and a low bandgap photoanode with attached protection layers....

Urban pattern: Layout design by hierarchical domain splitting

KAUST Repository

Yang, Yongliang; Wang, Jun; Vouga, Etienne; Wonka, Peter

2013-01-01

We present a framework for generating street networks and parcel layouts. Our goal is the generation of high-quality layouts that can be used for urban planning and virtual environments. We propose a solution based on hierarchical domain splitting using two splitting types: streamline-based splitting, which splits a region along one or multiple streamlines of a cross field, and template-based splitting, which warps pre-designed templates to a region and uses the interior geometry of the template as the splitting lines. We combine these two splitting approaches into a hierarchical framework, providing automatic and interactive tools to explore the design space.

Urban pattern: Layout design by hierarchical domain splitting

KAUST Repository

Yang, Yongliang

2013-11-06

We present a framework for generating street networks and parcel layouts. Our goal is the generation of high-quality layouts that can be used for urban planning and virtual environments. We propose a solution based on hierarchical domain splitting using two splitting types: streamline-based splitting, which splits a region along one or multiple streamlines of a cross field, and template-based splitting, which warps pre-designed templates to a region and uses the interior geometry of the template as the splitting lines. We combine these two splitting approaches into a hierarchical framework, providing automatic and interactive tools to explore the design space.

Photon Splitting in a Strong Magnetic Field: Recalculation and Comparison with Previous Calculations

International Nuclear Information System (INIS)

Adler, S.L.; Schubert, C.

1996-01-01

We recalculate the amplitude for photon splitting in a strong magnetic field below the pair production threshold, using the world line path integral variant of the Bern-Kosower formalism. Numerical comparison (using programs that we have made available for public access on the Internet) shows that the results of the recalculation are identical to the earlier calculations of Adler and later of Stoneham, and to the recent recalculation by Baier, Milstein, and Shaisultanov. copyright 1996 The American Physical Society

On the laws of disordering of the Ln3+ -ion crystal field in insulating crystals

International Nuclear Information System (INIS)

Kaminskij, A.A.

1988-01-01

Results of the study of fundamental regularities, which cause crystal field (CF) disordering on Ln 3+ ions in dielectric crystals are summed up. Analysis and systematization of the investigation results of atomic structure of disordered laser crystals and conducted investigations on spectroscopic properties and induced radiation (IR) permitted to come to the conclusion that the nature of disordering on CF is related to two fundamental regularities. The first regularity- the structural-dynamic one- is pronounced in numerous nonstoichiometric phases; the second one - determines spectroscopic properties and IR character

Mixed spin Ising model with four-spin interaction and random crystal field

International Nuclear Information System (INIS)

Benayad, N.; Ghliyem, M.

2012-01-01

The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.

Polarization-dependent optics using gauge-field metamaterials

International Nuclear Information System (INIS)

Liu, Fu; Xiao, Shiyi; Li, Jensen; Wang, Saisai; Hang, Zhi Hong

2015-01-01

We show that effective gauge field for photons with polarization-split dispersion surfaces, being realized using uniaxial metamaterials, can be used for polarization control with unique opportunities. The metamaterials with the proposed gauge field correspond to a special choice of eigenpolarizations on the Poincaré sphere as pseudo-spins, in contrary to those from either conventional birefringent crystals or optical active media. It gives rise to all-angle polarization control and a generic route to manipulate photon trajectories or polarizations in the pseudo-spin domain. As demonstrations, we show beam splitting (birefringent polarizer), all-angle polarization control, unidirectional polarization filter, and interferometer as various polarization control devices in the pseudo-spin domain. We expect that more polarization-dependent devices can be designed under the same framework

Crystal Fields in Dilute Rare-Earth Metals Obtained from Magnetization Measurements on Dilute Rare-Earth Alloys

DEFF Research Database (Denmark)

Touborg, P.; Høg, J.

1974-01-01

Crystal field parameters of Tb, Dy, and Er in Sc, Y, and Lu are summarized. These parameters are obtained from magnetization measurements on dilute single crystals, and successfully checked by a number of different methods. The crystal field parameters vary unpredictably with the rare-earth solute....... B40, B60, and B66 are similar in Y and Lu. Crystal field parameters for the pure metals Tb, Dy, and Er are estimated from the crystal fields in Y and Lu....

Influence of magnetic field on the morphology of the andrographolide crystal from supercritical carbon dioxide extraction crystallization

Science.gov (United States)

Chen, Kexun; Zhang, Xingyuan; Pan, Jian; Zhang, Wencheng; Yong, Ji; Yin, Wenhong

2003-10-01

In this paper, a supercritical fluid extraction-crystallization of andrographolide, a kind of Chinese traditional medicine, was investigated. We have studied the extraction-crystallization process with or without magnet in the extractor, respectively. It was found that the presence of magnetic field is an important factor influencing the quality of the products. SEM images showed that the crystal was slice-like in shape, and many slices reunited together in the absence of magnet. Further research showed that pressure had a certain effect on the morphology of the crystal.

A special correcting winding for the l = 2 torsatron with split-type helical coils

International Nuclear Information System (INIS)

Kotenko, V.G.

2012-01-01

A split-type special correcting winding (split-type SCW) for the l = 2 torsatron toroidal magnetic system with split-type helical coils is considered. The split-type SCW gives the possibility of controlling the position of the magnetic surface configuration in the direction perpendicular to the torus equatorial plane. Numerical simulations were carried out to investigate the influence of the split-type SCW magnetic field on centered and distant relative to the torus surface magnetic surface configuration with a plane magnetic axis, being promising for the fusion reactor. The configuration is realized in the l = 2 torsatron with split-type helical coils and with the coils of an additional toroidal magnetic field. The calculations show that the split-type SCW magnetic field influence on the initial magnetic surface configuration leads mainly to the magnetic surface configuration displacement along the straight z axis of torus rotation. The displacement of ∼0.1a, a is the minor radius of the torus, has no critical effect on the magnetic surface parameters. An idea on the split-type SCW magnetic field structure is obtained by numerical simulations of the effect of this field as a minority magnetic field imposed on the magnetic field of a well-known configuration. The split-type SCW magnetic field is directed, predominantly along the major radius of the torus within its volume. The displacement range of the closed magnetic surface configuration depends on the split-type SCW magnetic field value.

Strangeness, charm and beauty production at the split field magnet detector

International Nuclear Information System (INIS)

Geist, W.M.

1982-01-01

The Split Field Magnet detector is used to investigate heavy flavour production at the ISR by various techniques: (a) Decays of neutral strange particles are reconstructed in full phase space yielding detailed information on K 0 sub(s) and Λ production. (b) A trigger telescope with electron identification was added to the standard set-up at a polar angle of 90 0 to measure the prompt electron flux due to semileptonic decays of charmed and beauty hadrons. (c) Events with a triggering electron were also fully reconstructed to search for associated production of open charm and-open beauty. (d) A different study of charmed particle production is based on data taken with a K - trigger at forward angles

Thermal conductivity of niobium single crystals in a magnetic field

International Nuclear Information System (INIS)

Gladun, C.; Vinzelberg, H.

1980-01-01

The thermal conductivity in longitudinal magnetic fields up to 5 T and in the temperature range 3.5 to 15 K is measured in two high purity niobium single crystals having residual resistivity ratios of 22700 and 19200 and orientations of the rod axis [110] and [100]. The investigations show that by means of the longitudinal magnetic field the thermal conductivity may decrease only to a limiting value. In the crystal directions [110] and [100] for the ratio of the thermal conductivity in zero field and the thermal conductivity in the saturation field the temperature-independent factors 1.92 and 1.27, respectively, are determined. With the aid of these factors the thermal conductivity in the normal state is evaluated from the measured values of thermal conductivity below Tsub(c) in the magnetic field. The different conduction and scattering mechanisms are discussed. (author)

Crystal field splitting and spin states of Co ions in cobalt ferrite with composition Co1.5Fe1.5O4 using magnetization and X-ray absorption spectroscopy measurements

Science.gov (United States)

Sinha, A. K.; Singh, M. N.; Achary, S. N.; Sagdeo, A.; Shukla, D. K.; Phase, D. M.

2017-08-01

Structural, magnetic and electronic properties of partially inverted Cobalt Ferrite with composition Co1.5Fe1.5O4 is discussed in the present work. Single phase (SG: Fd3m) sample is synthesized by co-precipitation technique and subsequent air annealing. The values of saturation magnetization obtained from careful analysis of approach to saturation in initial M(H) curves are used to determine spin states of Co ions in tetrahedral (TH) and octahedral (OH) sites. Spin states of Co3+ ions in TH sites, which has not been reported in literature, were found to be in high spin state. Temperature variation of magnetic parameters has been studied. The sample shows magneto-crystalline anisotropy with two clearly distinct pinning centers. Oxygen K-edge and Fe as well as Co L2,3-edge X-ray absorption (XAS) spectra have been used as complementary measurements to study crystal field splitting and core hole effects on transition metal (TM) 3d orbitals. The ratio of intensities of t2g and eg absorption bands in O-K edge XAS spectrum is used to estimate the spin states of Co ions at OH and TH sites. The results are in agreement with those obtained from magnetization data, and favors Co3+ ions in TH sites in high spin states. Normalized areas of the satellite peaks in TM L2,3-edge XAS spectra have been used to estimate 3dn+1L contribution in ground state wave function and the contributions were found to be significant.

CONSTRAINING THE SOLAR CORONAL MAGNETIC FIELD STRENGTH USING SPLIT-BAND TYPE II RADIO BURST OBSERVATIONS

Energy Technology Data Exchange (ETDEWEB)

Kishore, P.; Ramesh, R.; Hariharan, K.; Kathiravan, C. [Indian Institute of Astrophysics, 2nd Block, Koramangala, Bangalore—560034 (India); Gopalswamy, N., E-mail: kishore@iiap.res.in [Code 671, Solar Physics Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States)

2016-11-20

We report on low-frequency radio (85–35 MHz) spectral observations of four different type II radio bursts, which exhibited fundamental-harmonic emission and split-band structure. Each of the bursts was found to be closely associated with a whitelight coronal mass ejection (CME) close to the Sun. We estimated the coronal magnetic field strength from the split-band characteristics of the bursts, by assuming a model for the coronal electron density distribution. The choice of the model was constrained, based on the following criteria: (1) when the radio burst is observed simultaneously in the upper and lower bands of the fundamental component, the location of the plasma level corresponding to the frequency of the burst in the lower band should be consistent with the deprojected location of the leading edge (LE) of the associated CME; (2) the drift speed of the type II bursts derived from such a model should agree closely with the deprojected speed of the LE of the corresponding CMEs. With the above conditions, we find that: (1) the estimated field strengths are unique to each type II burst, and (2) the radial variation of the field strength in the different events indicate a pattern. It is steepest for the case where the heliocentric distance range over which the associated burst is observed is closest to the Sun, and vice versa.

On the additive splitting procedures and their computer realization

DEFF Research Database (Denmark)

Farago, I.; Thomsen, Per Grove; Zlatev, Z.

2008-01-01

Two additive splitting procedures are defined and studied in this paper. It is shown that these splitting procedures have good stability properties. Some other splitting procedures, which are traditionally used in mathematical models used in many scientific and engineering fields, are sketched. All...

Split brain: divided perception but undivided consciousness.

Science.gov (United States)

Pinto, Yair; Neville, David A; Otten, Marte; Corballis, Paul M; Lamme, Victor A F; de Haan, Edward H F; Foschi, Nicoletta; Fabri, Mara

2017-05-01

In extensive studies with two split-brain patients we replicate the standard finding that stimuli cannot be compared across visual half-fields, indicating that each hemisphere processes information independently of the other. Yet, crucially, we show that the canonical textbook findings that a split-brain patient can only respond to stimuli in the left visual half-field with the left hand, and to stimuli in the right visual half-field with the right hand and verbally, are not universally true. Across a wide variety of tasks, split-brain patients with a complete and radiologically confirmed transection of the corpus callosum showed full awareness of presence, and well above chance-level recognition of location, orientation and identity of stimuli throughout the entire visual field, irrespective of response type (left hand, right hand, or verbally). Crucially, we used confidence ratings to assess conscious awareness. This revealed that also on high confidence trials, indicative of conscious perception, response type did not affect performance. These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Sub-threshold investigation of two coupled photonic crystal cavities

DEFF Research Database (Denmark)

Schubert, Martin; Frandsen, Lars Hagedorn; Skovgård, Troels Suhr

2009-01-01

The behavior of two coupled photonic crystal membrane cavities with quantum dots separated by different number of holes is investigated. The measured spectral splitting with increased coupling is verified by 3D calculations and discussed.......The behavior of two coupled photonic crystal membrane cavities with quantum dots separated by different number of holes is investigated. The measured spectral splitting with increased coupling is verified by 3D calculations and discussed....

Stroboscopic topographies on iron borate crystal in 9.6 MHz rf magnetic field

International Nuclear Information System (INIS)

Mitsui, Takaya; Imai, Yasuhiko; Kikuta, Seishi

2003-01-01

The influence of magnetoacoustic wave on the crystal deformation was studied by stroboscopic double crystal X-ray topography. The acoustic wave was excited by the rf magnetic field, which was synchronized with synchrotron radiation X-ray pulse. In measured rocking curves of FeBO 3 (4 4 4) reflection, we observed, for the first time, that the application of rf magnetic field (|H rf | max >8.4 Oe) brought about the extreme narrowing of full width at half maximum (FWHM). Recorded topographs showed that the narrowing of FWHM was due to the magnetoacoustic standing wave which is excited in FeBO 3 crystal. In our experiments, the influence of additional static magnetic field on the magnetoacoustic standing wave of FeBO 3 crystal was investigated too

Temporal self-splitting of optical pulses

Science.gov (United States)

Ding, Chaoliang; Koivurova, Matias; Turunen, Jari; Pan, Liuzhan

2018-05-01

We present mathematical models for temporally and spectrally partially coherent pulse trains with Laguerre-Gaussian and Hermite-Gaussian Schell-model statistics as extensions of the standard Gaussian Schell model for pulse trains. We derive propagation formulas of both classes of pulsed fields in linearly dispersive media and in temporal optical systems. It is found that, in general, both types of fields exhibit time-domain self-splitting upon propagation. The Laguerre-Gaussian model leads to multiply peaked pulses, while the Hermite-Gaussian model leads to doubly peaked pulses, in the temporal far field (in dispersive media) or at the Fourier plane of a temporal system. In both model fields the character of the self-splitting phenomenon depends both on the degree of temporal and spectral coherence and on the power spectrum of the field.

Resonant Photonic States in Coupled Heterostructure Photonic Crystal Waveguides

Directory of Open Access Journals (Sweden)

Sabarinathan J

2010-01-01

Full Text Available Abstract In this paper, we study the photonic resonance states and transmission spectra of coupled waveguides made from heterostructure photonic crystals. We consider photonic crystal waveguides made from three photonic crystals A, B and C, where the waveguide heterostructure is denoted as B/A/C/A/B. Due to the band structure engineering, light is confined within crystal A, which thus act as waveguides. Here, photonic crystal C is taken as a nonlinear photonic crystal, which has a band gap that may be modified by applying a pump laser. We have found that the number of bound states within the waveguides depends on the width and well depth of photonic crystal A. It has also been found that when both waveguides are far away from each other, the energies of bound photons in each of the waveguides are degenerate. However, when they are brought close to each other, the degeneracy of the bound states is removed due to the coupling between them, which causes these states to split into pairs. We have also investigated the effect of the pump field on photonic crystal C. We have shown that by applying a pump field, the system may be switched between a double waveguide to a single waveguide, which effectively turns on or off the coupling between degenerate states. This reveals interesting results that can be applied to develop new types of nanophotonic devices such as nano-switches and nano-transistors.

Crystal orientation effects on wurtzite quantum well electromechanical fields

DEFF Research Database (Denmark)

Duggen, Lars; Willatzen, Morten

2010-01-01

in the literature for semiconductors, is inaccurate for ZnO/MgZnO heterostructures where shear-strain components play an important role. An interesting observation is that a growth direction apart from [1̅ 21̅ 0] exists for which the electric field in the quantum well region becomes zero. This is important for, e......A one-dimensional continuum model for calculating strain and electric field in wurtzite semiconductor heterostructures with arbitrary crystal orientation is presented and applied to GaN/AlGaN and ZnO/MgZnO heterostructure combinations. The model is self-consistent involving feedback couplings...... of spontaneous polarization, strain, and electric field. Significant differences between fully coupled and semicoupled models are found for the longitudinal and shear-strain components as a function of the crystal-growth direction. In particular, we find that the semicoupled model, typically used...

Crystal fields of dilute Tb, Dy, Ho, or Er in Lu obtained by magnetization measurements

International Nuclear Information System (INIS)

Touborg, P.; Hog, J.

1975-01-01

Magnetization measurements are reported on single crystals of dilute Tb, Dy, Ho, or Er in Lu. These measurements were performed in the temperature range 1.5--100 K and field range 0--6 T and include measurements of initial susceptibility, isothermal and isofield magnetization, and basal-plane anisotropy. The results show features similar to the corresponding Y-R alloys, where R is a rare earth. Crystal-field and molecular-field parameters could be unabiguously deduced from the experimental data. The effects of crystal-field level broadening were investigated and demonstrated for Ho. Comparison of the Y-R and Lu-R results makes possible an estimate of the crystal-field parameters in the pure-rare-earth metals

Dosimetric Comparison of Split Field and Fixed Jaw Techniques for Large IMRT Target Volumes in the Head and Neck

International Nuclear Information System (INIS)

Srivastava, Shiv P.; Das, Indra J.; Kumar, Arvind; Johnstone, Peter A.S.

2011-01-01

Some treatment planning systems (TPSs), when used for large-field (>14 cm) intensity-modulated radiation therapy (IMRT), create split fields that produce excessive multiple-leaf collimator segments, match-line dose inhomogeneity, and higher treatment times than nonsplit fields. A new method using a fixed-jaw technique (FJT) forces the jaw to stay at a fixed position during optimization and is proposed to reduce problems associated with split fields. Dosimetric comparisons between split-field technique (SFT) and FJT used for IMRT treatment is presented. Five patients with head and neck malignancies and regional target volumes were studied and compared with both techniques. Treatment planning was performed on an Eclipse TPS using beam data generated for Varian 2100C linear accelerator. A standard beam arrangement consisting of nine coplanar fields, equally spaced, was used in both techniques. Institutional dose-volume constraints used in head and neck cancer were kept the same for both techniques. The dosimetric coverage for the target volumes between SFT and FJT for head and neck IMRT plan is identical within ±1% up to 90% dose. Similarly, the organs at risk (OARs) have dose-volume coverage nearly identical for all patients. When the total monitor unit (MU) and segments were analyzed, SFT produces statistically significant higher segments (17.3 ± 6.3%) and higher MU (13.7 ± 4.4%) than the FJT. There is no match line in FJT and hence dose uniformity in the target volume is superior to the SFT. Dosimetrically, SFT and FJT are similar for dose-volume coverage; however, the FJT method provides better logistics, lower MU, shorter treatment time, and better dose uniformity. The number of segments and MU also has been correlated with the whole body radiation dose with long-term complications. Thus, FJT should be the preferred option over SFT for large target volumes.

EPR of some low-spin dsup(5) tris-chelate complexes of Fe(3), Ru(3), Os(3) in liquid-crystal matrix

International Nuclear Information System (INIS)

Domracheva, N.E.; Konstantinov, V.N.; Luchkona, S.A.; Ovchinnikov, I.V.

1985-01-01

Using the EPR method low-spin trischelate complexes of Fe, Ru, Os with 8-mercaptoquinoline and 8-oxyquinoline in oriented vitrified liquid-crystal matrix have been studied. Analtysis of angular dependences of EPR spectra of the complexes permitted to correlate the main axes of g-tensor with molecular axes and, consequently, to determine unambiguously the main electron states of the systems, as well as the value of crystal splittings. It is shown that in the complexes studied the splitting of energy levels is mainly determined by spin-orbital interaction, and not by axial or rhombic components of crystal field. However, rhombic distortion is responsible for anisotropy of g-tensor in xy plane and anisotropy of x- and y-axes orientation. The way to orient complexes in liquid-crystal matrix is substantiated; symmetry axis of the third order C 3 (Z) is mainly oriented along the director. Parameters of the function of orientational distribution of the complex axes are obtained

Optical spectroscopy and crystal-field analysis of U{sup 3+}: Ba{sub 2}YCl{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Karbowiak, M.; Mech, A.; Drozdzyndki, J. [Wroclaw Univ., Faculty of Chemistry (Poland); Gajek, Z. [Polish Academy of Sciences, W. Trzebiatowski Institute of Low Temperature and Structure Research, Wroclaw (Poland); Edelstein, N.M. [Lawrence Berkeley National Lab., Chemical Sciences Div., CA (United States)

2002-11-01

High resolution absorption spectra of a U{sup 3+}(0.3%): Ba{sub 2}YCl{sub 7} single crystal were recorded in the 4000-50 000 cm{sup -1} range at 7 K. The observed crystal-field levels were assigned and fit to the parameters of the simplified angular overlap model (AOM) as well as a semi-empirical Hamiltonian representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab initio calculations. The analysis of the spectra allowed the assignment of 65 crystal-field levels with a relatively small rms deviation of 25 cm{sup -1} and has shown that the AOM approach can predict quite well the B{sub q}{sup k} crystal-field parameters. The value determined for the crystal-field strength parameter, N{sub v}, corresponds well with those determined for U{sup 3+} in other chloride single crystals. (authors)

Splitting of turbulent spot in transitional pipe flow

Science.gov (United States)

Wu, Xiaohua; Moin, Parviz; Adrian, Ronald J.

2017-11-01

Recent study (Wu et al., PNAS, 1509451112, 2015) demonstrated the feasibility and accuracy of direct computation of the Osborne Reynolds' pipe transition problem without the unphysical, axially periodic boundary condition. Here we use this approach to study the splitting of turbulent spot in transitional pipe flow, a feature first discovered by E.R. Lindgren (Arkiv Fysik 15, 1959). It has been widely believed that spot splitting is a mysterious stochastic process that has general implications on the lifetime and sustainability of wall turbulence. We address the following two questions: (1) What is the dynamics of turbulent spot splitting in pipe transition? Specifically, we look into any possible connection between the instantaneous strain rate field and the spot splitting. (2) How does the passive scalar field behave during the process of pipe spot splitting. In this study, the turbulent spot is introduced at the inlet plane through a sixty degree wide numerical wedge within which fully-developed turbulent profiles are assigned over a short time interval; and the simulation Reynolds numbers are 2400 for a 500 radii long pipe, and 2300 for a 1000 radii long pipe, respectively. Numerical dye is tagged on the imposed turbulent spot at the inlet. Splitting of the imposed turbulent spot is detected very easily. Preliminary analysis of the DNS results seems to suggest that turbulent spot slitting can be easily understood based on instantaneous strain rate field, and such spot splitting may not be relevant in external flows such as the flat-plate boundary layer.

Far-Field Focus and Dispersionless Anticrossing Bands in Two-Dimensional Photonic Crystals

Directory of Open Access Journals (Sweden)

Xiaoshuang Chen

2007-01-01

Full Text Available We review the simulation work for the far-field focus and dispersionless anticrossing bands in two-dimensional (2D photonic crystals. In a two-dimensional photonic-crystal-based concave lens, the far-field focus of a plane wave is given by the distance between the focusing point and the lens. Strong and good-quality far-field focusing of a transmitted wave, explicitly following the well-known wave-beam negative refraction law, can be achieved. The spatial frequency information of the Bloch mode in multiple Brillouin zones (BZs is investigated in order to indicate the wave propagation in two different regions. When considering the photonic transmission in a 2D photonic crystal composed of a negative phase-velocity medium (NPVM, it is shown that the dispersionless anticrossing bands are generated by the couplings among the localized surface polaritons of the NPVM rods. The photonic band structures of the NPVM photonic crystals are characterized by a topographical continuous dispersion relationship accompanied by many anticrossing bands.

Splitting Ward identity

Energy Technology Data Exchange (ETDEWEB)

Safari, Mahmoud [Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2016-04-15

Within the background-field framework we present a path integral derivation of the splitting Ward identity for the one-particle irreducible effective action in the presence of an infrared regulator, and make connection with earlier works on the subject. The approach is general in the sense that it does not rely on how the splitting is performed. This identity is then used to address the problem of background dependence of the effective action at an arbitrary energy scale. We next introduce the modified master equation and emphasize its role in constraining the effective action. Finally, application to general gauge theories within the geometric approach is discussed. (orig.)

Splitting Ward identity

International Nuclear Information System (INIS)

Safari, Mahmoud

2016-01-01

Within the background-field framework we present a path integral derivation of the splitting Ward identity for the one-particle irreducible effective action in the presence of an infrared regulator, and make connection with earlier works on the subject. The approach is general in the sense that it does not rely on how the splitting is performed. This identity is then used to address the problem of background dependence of the effective action at an arbitrary energy scale. We next introduce the modified master equation and emphasize its role in constraining the effective action. Finally, application to general gauge theories within the geometric approach is discussed. (orig.)

Tune splitting in the presence of linear coupling

International Nuclear Information System (INIS)

Parzen, G.

1991-01-01

The presence of random skew quadrupole field errors will couple the x and y motions. The x and y motions are then each given by the sum of 2 normal modes with the tunes v 1 and v 2 , which may differ appreciably from v x and v y , the unperturbed tunes. This is often called tune splitting since |v 1 - v 2 | is usually larger than |v x - v y |. This tune splitting may be large in proton accelerators using superconducting magnets, because of the relatively large random skew quadrupole field errors that are expected in these magnets. This effect is also increased by the required insertions in proton colliders which generate large β-functions in the insertion region. This tune splitting has been studied in the RHIC accelerator. For RHIC, a tune splitting as large as 0.2 was found in one worse case. A correction system has been developed for correcting this large tune splitting which uses two families of skew quadrupole correctors. It has been found that this correction system corrects most of the large tune splitting, but a residual tune splitting remains that is still appreciable. This paper discusses the corrections to this residual time

YbNi{sub 4}P{sub 2}. Single crystal growth by the Czochralski method and high-field magnetization measurements

Energy Technology Data Exchange (ETDEWEB)

Kliemt, Kristin; Krellner, Cornelius [Goethe-University, Frankfurt (Germany); Foerster, Tobias [HLD, Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Brando, Manuel [MPI for Chemical Physics of Solids, Dresden (Germany)

2016-07-01

We have investigated a new generation of YbNi{sub 4}P{sub 2} single crystals that were grown from a levitating melt by the Czochralski method. With T{sub C}= 0.17 K, this ferromagnetic material has the lowest Curie temperature ever observed among stoichiometric compounds. A quantum critical point occurs in the substitution series YbNi{sub 4}(P{sub 1-x}As{sub x}){sub 2} at x ∼ 0.1. The hybridization between localized f-electrons and the conduction electrons leads to a Fermi-liquid ground state with narrow bands and strongly enhanced effective electronic masses (heavy fermion system, Kondo temperature 8 K). An external magnetic field can split the bands, deform the Fermi surface and simultaneously suppress the Kondo interaction. If such a deformation changes the topology, it is called a Lifshitz transition. Previous thermodynamic and electrical transport studies have found indications for Lifshitz transitions in this Kondo lattice system. We report on results of high-field magnetization measurements at low temperature to further investigate the putative Lifshitz transitions in YbNi{sub 4}P{sub 2}.

Electrokinetic control of sample splitting at a channel bifurcation using isotachophoresis

International Nuclear Information System (INIS)

Persat, Alexandre; Santiago, Juan G

2009-01-01

We present a novel method for accurately splitting ionic samples at microchannel bifurcations. We leverage isotachophoresis (ITP) to focus and transport sample through a one-inlet, two-outlet microchannel bifurcation. We actively control the proportion of splitting by controlling potentials at end-channel reservoirs (and thereby controlling the current ratio). We explore the effect of buffer chemistry and local electric field on splitting dynamics and propose and validate a simple Kirchoff-type rule controlling the split ratio. We explore the effects of large applied electric fields on sample splitting and attribute a loss of splitting accuracy to electrohydrodynamic instabilities. We propose a scaling analysis to characterize the onset of this instability. This scaling is potentially useful for other electrokinetic flow problems with self-sharpening interfaces.

Direct observation of electronic and nuclear ground state splitting in external magnetic field by inelastic neutron scattering on oxidized ferrocene and ferrocene containing polymers

Science.gov (United States)

Appel, Markus; Frick, Bernhard; Elbert, Johannes; Gallei, Markus; Stühn, Bernd

2015-01-01

The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene). They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.

A simple model for localized-itinerant magnetic systems: crystal field effects

International Nuclear Information System (INIS)

Iannarella, L.; Silva, X.A. da; Guimarares, A.P.

1989-01-01

The magnetic behavior of a system consisting of localized electrons coupled to conduction electrons and submitted to an axial crystral field at T=0 K is ivestigated within the framework of the molecular field approximation. An analytical ionic magnetic state equation is deduced; it shows how the magnetization depends on the model parameters (exchange, crystal field, band occupation) and external magnetic field. A condition for the onset of spontaneous magnetic order is obtained and the ferro - and paramagnetic phases are studied. This study displays several features of real magnetic systems, including quenching or total suppression of the magnetic moments (depending on the relative value of the crystal field parameter) and exchange enhacement. The relevance of such model for the description of rare-earth intermetallic compounds is discussed. (author) [pt

Moessbauer radiation dynamical diffraction in crystals being subjected to the action of external variable fields

International Nuclear Information System (INIS)

Baryshevskii, V.G.; Skadorov, V.V.

1986-01-01

A dynamical theory is developed of the Moessbauer radiation diffraction by crystals being subjected to an variable external field action. Equations describing the dynamical diffraction by nonstationary crystals are obtained. It is shown that the resonant interaction between Moessbauer radiation and shift field induced in the crystal by a variable external field giving rise to an effective conversion of the incident wave into a wave with changed frequency. (author)

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores.

Science.gov (United States)

Malkin, B Z; Lummen, T T A; van Loosdrecht, P H M; Dhalenne, G; Zakirov, A R

2010-07-14

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R(2)Ti(2)O(7) (R = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed.

Standard Model Particles from Split Octonions

Directory of Open Access Journals (Sweden)

Gogberashvili M.

2016-01-01

Full Text Available We model physical signals using elements of the algebra of split octonions over the field of real numbers. Elementary particles are corresponded to the special elements of the algebra that nullify octonionic norms (zero divisors. It is shown that the standard model particle spectrum naturally follows from the classification of the independent primitive zero divisors of split octonions.

Valley photonic crystals for control of spin and topology.

Science.gov (United States)

Dong, Jian-Wen; Chen, Xiao-Dong; Zhu, Hanyu; Wang, Yuan; Zhang, Xiang

2017-03-01

Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley-spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.

Electromagnetic-field amplification in finite one-dimensional photonic crystals

International Nuclear Information System (INIS)

Gorelik, V. S.; Kapaev, V. V.

2016-01-01

The electromagnetic-field distribution in a finite one-dimensional photonic crystal is studied using the numerical solution of Maxwell’s equations by the transfer-matrix method. The dependence of the transmission coefficient T on the period d (or the wavelength λ) has the characteristic form with M–1 (M is the number of periods in the structure) maxima with T = 1 in the allowed band of an infinite crystal and zero values in the forbidden band. The field-modulus distribution E(x) in the structure for parameters that correspond to the transmission maxima closest to the boundaries of forbidden bands has maxima at the center of the structure; the value at the maximum considerably exceeds the incident-field strength. For the number of periods M ~ 50, more than an order of magnitude increase in the field amplification is observed. The numerical results are interpreted with an analytic theory constructed by representing the solution in the form of a linear combination of counterpropagating Floquet modes in a periodic structure.

Measuring 20-100 T B-fields using Zeeman splitting of sodium emission lines on a 500 kA pulsed power machine

Energy Technology Data Exchange (ETDEWEB)

Banasek, J. T., E-mail: jtb254@cornell.edu; Engelbrecht, J. T.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A. [Cornell University, Ithaca, New York 14850 (United States)

2016-11-15

We have shown that Zeeman splitting of the sodium (Na) D-lines at 5890 and 5896 Å can be used to measure the magnetic field (B-field) produced in high current pulsed power experiments. We have measured the B-field next to a return current conductor in a hybrid X-pinch experiment near a peak current of about 500 kA. Na is deposited on the conductor and then is desorbed and excited by radiation from the hybrid X-pinch. The D-line emission spectrum implies B-fields of about 20 T with a return current post of 4 mm diameter or up to 120 T with a return current wire of 0.455 mm diameter. These measurements were consistent or lower than the expected B-field, thereby showing that basic Zeeman splitting can be used to measure the B-field in a pulsed-power-driven high-energy-density (HED) plasma experiment. We hope to extend these measurement techniques using suitable ionized species to measurements within HED plasmas.

Particulate photocatalysts for overall water splitting

Science.gov (United States)

Chen, Shanshan; Takata, Tsuyoshi; Domen, Kazunari

2017-10-01

The conversion of solar energy to chemical energy is a promising way of generating renewable energy. Hydrogen production by means of water splitting over semiconductor photocatalysts is a simple, cost-effective approach to large-scale solar hydrogen synthesis. Since the discovery of the Honda-Fujishima effect, considerable progress has been made in this field, and numerous photocatalytic materials and water-splitting systems have been developed. In this Review, we summarize existing water-splitting systems based on particulate photocatalysts, focusing on the main components: light-harvesting semiconductors and co-catalysts. The essential design principles of the materials employed for overall water-splitting systems based on one-step and two-step photoexcitation are also discussed, concentrating on three elementary processes: photoabsorption, charge transfer and surface catalytic reactions. Finally, we outline challenges and potential advances associated with solar water splitting by particulate photocatalysts for future commercial applications.

Near-field probing of photonic crystal directional couplers

DEFF Research Database (Denmark)

Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

2006-01-01

We report the design, fabrication and characterization of a photonic crystal directional with a size of ~20 x 20 mm2 fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths....... By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample....

Multiplet mass splitting in a gravitational field

International Nuclear Information System (INIS)

Maia, M.D.

An expression for the mass splitting of particles belonging to the same spin multiplet defined in a space-time of general relativity is derived. The geometrical symmetry is a subgroup of SO(r,s), 9 >=r > 3, 5 >=s >=1, the mass operator being proportional to the second order Casimir operator of that subgroup. A brief analysis of the calculated values as compared to the experimental data is included. (Author) [pt

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Gao, Zhen; Gao, Fei [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Zhang, Baile, E-mail: blzhang@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore, Singapore 637371 (Singapore)

2016-01-25

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated surface-wave devices with suppressed crosstalk.

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

International Nuclear Information System (INIS)

Gao, Zhen; Gao, Fei; Zhang, Baile

2016-01-01

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated surface-wave devices with suppressed crosstalk

The effect of magnetic field on the shape of etch pits of paracetamol crystals

Energy Technology Data Exchange (ETDEWEB)

Ivashchenko, V.E. [Kemerovo State University, Novosibirsk (Russian Federation); Research and Educational Center, Novosibirsk State University (Russian Federation); Boldyrev, V.V.; Shakhtshneider, T.P. [Institute of Solid State Chemistry and Mechanochemistry, RAS, Novosibirsk (Russian Federation); Zakharov, Yu.A.; Krasheninin, V.I. [Kemerovo State University, Novosibirsk (Russian Federation); Ermakov, A.E. [Institute of Physics of Metals, Ural Branch of RAS, Ekaterinburg (Russian Federation)

2002-04-01

In the present study we investigate the effect of magnetic field on the shape of etch pits of the crystals of p-hydroxyacetanilide (paracetamol), which is widely used in pharmacy as antipyretic, antiphlogistic medicine. It was discovered that the magnetic field (H=0.5 T, {tau}=15 min) changes the morphology of etch pits and shifts dislocations in paracetamol crystal. Activation energy of the changes induced by the action of the magnetic field was determined to be 63 kJ/mol, which is comparable with the energy of hydrogen bonds in crystal lattice. (orig.)

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

NARCIS (Netherlands)

Malkin, B. Z.; Lummen, T. T. A.; van Loosdrecht, P. H. M.; Dhalenne, G.; Zakirov, A. R.

2010-01-01

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R2Ti2O7 (R = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the

Calculations of spin Hamiltonian parameters and analysis of trigonal distortions in LiSr(Al,Ga)F6:Cr3+ crystals

International Nuclear Information System (INIS)

Brik, M.G.; Avram, C.N.; Avram, N.M.

2006-01-01

The effective spin-Hamiltonian (SH) parameters (zero-field splitting D and g factors g - parallel and g - perpendicular ) for Cr 3+ ions in LiSr(Al,Ga)F 6 crystals are calculated from the complete high-order perturbation formulae for a d 3 ion. Parameters of trigonal crystal field acting on the Cr 3+ ion are calculated. The magnitude of trigonal distortion of the [CrF 6 ] 3- clusters is related to the experimental measurements of the spin-Hamiltonian parameters in the considered systems. Since in both crystals g parallel perpendicular , [CrF 6 ] 3- clusters undergo an axial compression along the C 3 axis. Experimental values of the hyperfine structure constants A parallel and A perpendicular are used to evaluate the core polarization constant κ for Cr 3+ ion in both crystals

Experimental determination of the relativistic fine-structure splitting in pionic Ti and Fe atoms

International Nuclear Information System (INIS)

Wang, K.; Boehm, F.; Bovet, E.; Hahn, A.A.; Henrikson, H.E.; Miller, J.P.; Powers, R.J.; Vogel, P.; Vuilleumier, J.; Kunselman, A.R.

1980-01-01

Using a high-resolution crystal spectrometer we have measured the relativistic angular-momentum splittings of the 5g-4f and 5f-4d transitions in pionic Ti and Fe atoms. The observed fine-structure splittings of 85.3 +- 3.0 eV in π - Ti and 158.5 +- 7.8 eV in π - Fe agree with the calculated splittings of 88.5 and 167.6 eV, respectively, arising from the Klein-Gordon equation and from small corrections due to vacuum polarization, strong interaction, and electron screening

Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

Science.gov (United States)

Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

2002-01-01

The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

The diluted tri-dimensional spin-one Ising model with crystal field interactions

International Nuclear Information System (INIS)

Saber, M.

1988-09-01

3D spin-one Ising models with nearest-neighbour ferromagnetic interactions with crystal-field exhibit tricritical behaviour. A new method that applies to a wide class of random systems is used to study the influence of site and bond dilution on this behaviour. We have calculated temperature-crystal-field-concentration phase diagrams and determined, in particular, the influence of dilution on the zero temperature tricritical temperature. (author). 10 refs, 8 figs

Zero Field Splitting of the chalcogen diatomics using relativistic correlated wave-function methods

DEFF Research Database (Denmark)

Rota, Jean-Baptiste; Knecht, Stefan; Fleig, Timo

2011-01-01

The spectrum arising from the (π*)2 configuration of the chalcogen dimers, namely the X21, a2 and b0+ states, is calculated using Wave-Function Theory (WFT) based methods. Two-component (2c) and four-component (4c) MultiReference Configuration Interaction (MRCI) and Fock-Space Coupled Cluster (FSCC......) methods are used as well as two-step methods Spin-Orbit Complete Active Space Perturbation Theory at 2nd order (SO-CASPT2) and Spin-Orbit Difference Dedicated Configuration Interaction (SODDCI). The energy of the X21 state corresponds to the Zero-Field Splitting (ZFS) of the ground state spin triplet...

Black Phosphorus: Critical Review and Potential for Water Splitting Photocatalyst

Directory of Open Access Journals (Sweden)

Tae Hyung Lee

2016-10-01

Full Text Available A century after its first synthesis in 1914, black phosphorus has been attracting significant attention as a promising two-dimensional material in recent years due to its unique properties. Nowadays, with the development of its exfoliation method, there are extensive applications of black phosphorus in transistors, batteries and optoelectronics. Though, because of its hardship in mass production and stability problems, the potential of the black phosphorus in various fields is left unexplored. Here, we provide a comprehensive review of crystal structure, electronic, optical properties and synthesis of black phosphorus. Recent research works about the applications of black phosphorus is summarized. Among them, the possibility of black phosphorous as a solar water splitting photocatalyst is mainly discussed and the feasible novel structure of photocatalysts based on black phosphorous is proposed.

Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

International Nuclear Information System (INIS)

Shu, Deming; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je

2016-01-01

A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

Energy Technology Data Exchange (ETDEWEB)

Shu, Deming, E-mail: shu@aps.anl.gov; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, U.S.A (United States)

2016-07-27

A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

A thermal model for czochralski silicon crystal growth with an axial magnetic field

Science.gov (United States)

Hjellming, L. N.

1990-07-01

This paper presents a thermal model for molten silicon in a Czochralski crystal puller system with an applied uniform axial magnetic field. The melt depth is treated as continually decreasing, which affects the thermal environment of the melt and crystal. The radiative heat loss and the input heat flux are treated as functions of time, with a constraint placed on the heat lost to the crystal from the melt. As the melt motion reaches a steady state rapidly, the temperature and flow fields are treated as instantaneously steady at each melt depth. The heat transport is a mixture of conduction and convection, and by considering the crystal and crucible to be rotating with the same angular velocity, the flows driven by buoyancy and thermocapillarity are isolated and provide the convective heat transport in the melt for the range of magnetic field strengths 0.2 ≤ B ≤ 1.0T.

Source splitting via the point source method

International Nuclear Information System (INIS)

Potthast, Roland; Fazi, Filippo M; Nelson, Philip A

2010-01-01

We introduce a new algorithm for source identification and field splitting based on the point source method (Potthast 1998 A point-source method for inverse acoustic and electromagnetic obstacle scattering problems IMA J. Appl. Math. 61 119–40, Potthast R 1996 A fast new method to solve inverse scattering problems Inverse Problems 12 731–42). The task is to separate the sound fields u j , j = 1, ..., n of n element of N sound sources supported in different bounded domains G 1 , ..., G n in R 3 from measurements of the field on some microphone array—mathematically speaking from the knowledge of the sum of the fields u = u 1 + ... + u n on some open subset Λ of a plane. The main idea of the scheme is to calculate filter functions g 1 ,…, g n , n element of N, to construct u l for l = 1, ..., n from u| Λ in the form u l (x) = ∫ Λ g l,x (y)u(y)ds(y), l=1,... n. (1) We will provide the complete mathematical theory for the field splitting via the point source method. In particular, we describe uniqueness, solvability of the problem and convergence and stability of the algorithm. In the second part we describe the practical realization of the splitting for real data measurements carried out at the Institute for Sound and Vibration Research at Southampton, UK. A practical demonstration of the original recording and the splitting results for real data is available online

Crystal Growth of High-Quality Protein Crystals under the Presence of an Alternant Electric Field in Pulse-Wave Mode, and a Strong Magnetic Field with Radio Frequency Pulses Characterized by X-ray Diffraction

Directory of Open Access Journals (Sweden)

Adela Rodríguez-Romero

2017-06-01

Full Text Available The first part of this research was devoted to investigating the effect of alternate current (AC using four different types of wave modes (pulse-wave at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and crystal quality, were obtained when protein crystals were grown under the influence of electric fields in a very specific wave mode (“breathing” wave, giving the highest resolution up to 1.34 Å in X-ray diffraction analysis compared with controls and with those crystals grown in gel. In the second part, we evaluated the effect of a strong magnetic field of 16.5 Tesla combined with radiofrequency pulses of 0.43 μs on the crystal growth in gels of tetragonal hen egg white (HEW lysozyme. The lysozyme crystals grown, both in solution applying breathing-wave and in gel under the influence of this strong magnetic field with pulses of radio frequencies, produced the larger-in-size crystals and the highest resolution structures. Data processing and refinement statistics are very good in terms of the resolution, mosaicity and Wilson B factor obtained for each crystal. Besides, electron density maps show well-defined and distinctly separated atoms at several selected tryptophan residues for the crystal grown using the “breathing wave pulses”.

Quantitative analysis on electric dipole energy in Rashba band splitting.

Science.gov (United States)

Hong, Jisook; Rhim, Jun-Won; Kim, Changyoung; Ryong Park, Seung; Hoon Shim, Ji

2015-09-01

We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime.

Embryo splitting

Directory of Open Access Journals (Sweden)

Karl Illmensee

2010-04-01

Full Text Available Mammalian embryo splitting has successfully been established in farm animals. Embryo splitting is safely and efficiently used for assisted reproduction in several livestock species. In the mouse, efficient embryo splitting as well as single blastomere cloning have been developed in this animal system. In nonhuman primates embryo splitting has resulted in several pregnancies. Human embryo splitting has been reported recently. Microsurgical embryo splitting under Institutional Review Board approval has been carried out to determine its efficiency for blastocyst development. Embryo splitting at the 6–8 cell stage provided a much higher developmental efficiency compared to splitting at the 2–5 cell stage. Embryo splitting may be advantageous for providing additional embryos to be cryopreserved and for patients with low response to hormonal stimulation in assisted reproduction programs. Social and ethical issues concerning embryo splitting are included regarding ethics committee guidelines. Prognostic perspectives are presented for human embryo splitting in reproductive medicine.

Crystal growth and magnetic properties of equiatomic CeAl

Science.gov (United States)

Das, Pranab Kumar; Thamizhavel, A.

2015-03-01

Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 μB/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

Conformal scalar fields and chiral splitting on super Riemann surfaces

International Nuclear Information System (INIS)

D'Hoker, E.; Phong, D.H.

1989-01-01

We provide a complete description of correlation functions of scalar superfields on a super Riemann surface, taking into account zero modes and non-trivial topology. They are built out of chirally split correlation functions, or conformal blocks at fixed internal momenta. We formulate effective rules which determine these completely in terms of geometric invariants of the super Riemann surface. The chirally split correlation functions have non-trivial monodromy and produce single-valued amplitudes only upon integration over loop momenta. Our discussion covers the even spin structure as well as the odd spin structure case which had been the source of many difficulties in the past. Super analogues of Green's functions, holomorphic spinors, and prime forms emerge which should pave the way to function theory on super Riemann surfaces. In superstring theories, chirally split amplitudes for scalar superfields are crucial in enforcing the GSO projection required for consistency. However one really knew how to carry this out only in the operator formalism to one-loop order. Our results provide a way of enforcing the GSO projection to any loop. (orig.)

An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics

International Nuclear Information System (INIS)

Pyzer-Knapp, Edward O.; Thompson, Hugh P. G.; Day, Graeme M.

2016-01-01

An empirically parameterized intermolecular force field is developed for crystal structure modelling and prediction. The model is optimized for use with an atomic multipole description of electrostatic interactions. We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%

Near-field characterization of photonic crystal Y-splitters

DEFF Research Database (Denmark)

Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

2005-01-01

A scanning near-field optical microscope (SNOM) is used to directly map the propagation of light in a specially designed 50/50 photonic crystal (PC) Y-splitter fabricated on silicon-on-insulator (SOI) wafers. SNOM images are obtained for TE- and TM-polarized light in the wavelength range 1425...

Crystal-field-modulated magnon squeezing states in a ferromagnet

International Nuclear Information System (INIS)

Peng Feng

2003-01-01

The magnon squeezing states in some magnetic crystals allow a reduction in the quantum fluctuations of the spin component to below the zero-point quantum noise level of the coherent magnon states. It is known that there are the magnon squeezing states in an antiferromagnet. However, their generating mechanism is not suitable for the ferromagnet. In this paper, we discuss the possibility of generating the magnon squeezing states in a ferromagnet, and discuss the effect of the crystal field on the magnon squeezing states

Analyses of crystal field and exchange interaction of Dy3Ga5O12 under extreme conditions

International Nuclear Information System (INIS)

Wang Wei; Qi Xin; Yue Yuan

2011-01-01

This paper theoretically investigates the effects of crystal field and exchange interaction field on magnetic properties in dysprosium gallium garnet under extreme conditions (low temperatures and high magnetic fields) based on quantum theory. Here, five sets of crystal field parameters are discussed and compared. It demonstrates that, only considering the crystal field effect, the experiments can not be successfully explained. Thus, referring to the molecular field theory, an effective exchange field associated with the Dy—Dy exchange interaction is further taken into account. Under special consideration of crystal field and the exchange interaction field, it obtains an excellent agreement between the theoretical results and experiments, and further confirms that the exchange interaction field between rare-earth ions has great importance to magnetic properties in paramagnetic rare-earth gallium garnets. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Absorption measurement s in InSe single crystal under an applied electric field

International Nuclear Information System (INIS)

Ates, A.; Guerbulak, B.; Guer, E.; Yildirim, T.; Yildirim, M.

2002-01-01

InSe single crystal was grown by Bridgman-Stockberger method. Electric field effect on the absorption measurements have been investigated as a function of temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and decreased of intensity in absorption spectra under an electric field. Using absorption measurements, Urbach energy was calculated under an electric field. Applied electric field caused a increasing in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively

Field-induced optically isotropic state in bent core nematic liquid crystals: unambiguous proof of field-induced optical biaxiality

International Nuclear Information System (INIS)

Elamain, Omaima; Komitov, Lachezar; Hegde, Gurumurthy; Fodor-Csorba, Katalin

2013-01-01

The behaviour of bent core (BC) nematic liquid crystals was investigated under dc applied electric field. The optically isotropic state of a sample containing BC nematic was observed under application of low dc electric fields. The quality of the dark state when the sample was inserted between two crossed polarizers was found to be superb and it did not change when rotating the sample between the polarizers. The coupling between the net molecular dipole moment and the applied dc electric field was considered as the origin of the out-of-plane switching of the BC molecules resulting in switching from the field-off bright state to the field-on dark state. The field-induced optically isotropic state is an unambiguous proof of the field-induced biaxiality in the BC nematic liquid crystal. A simple model explaining the appearance of the isotropic optical state in BC nematics and the switching of the sample slow axis between three mutually orthogonal directions under dc applied electric field is proposed. (paper)

Crystal-field magnetic anisotropy of dilute dysprosium or erbium in yttrium single crystals

DEFF Research Database (Denmark)

Høg, J.; Touborg, P.

1974-01-01

Magnetization measurements have been performed between 1.3 and 300 K in fields up to 50 × 105 A/m in the a, b, and c directions of hcp crystals of pure Y and Y doped with 0.14-at.% Dy or 0.14-at.% Er, using the Faraday method and a vibrating-sample method. The characteristic behavior of both...

Crystallization of inorganic salts from aqueous solutions in a microwave field

International Nuclear Information System (INIS)

Kochetkov, S. E.; Kuznetsov, V. A.; Lyashenko, A. V.; Bakshutov, V. S.

2006-01-01

The crystallization of some inorganic salts (KH 2 PO 4 , NaCl, Sr(NO 3 ) 2 , KNO 2 , Ca(OH) 2 ) by the thermal-gradient (with decreasing temperature) and solvent-evaporation methods using microwave heating of solutions is investigated. It is established that the growth rates of single crystals in a microwave field are an order of magnitude higher than obtained in other known techniques at comparable crystallization temperatures and supersaturations. For example, the growth rate of prismatic faces {100} of KH 2 PO 4 crystals is as high as 11 mm/day at supersaturations of ∼1.2%. The results obtained are discussed in the context of the effect of microwave radiation on the adsorption surface layers of crystals. Fine-grained phases of the salts under study are obtained by evaporation of the solvent

Study of Rare Events at the Split Field Magnet

CERN Multimedia

2002-01-01

The aim of the experiment is the study of full events associated with special, rare triggers using the almost 4 @p geometry of the improved Split Field Magnet (SFM) detector. Two triggers are used: a) a trigger on an electron produced around 90|0 with a transverse momentum p^t @$>$ 0.5 GeV/c; b) a trigger on very high p^t hadrons (p^t $>$ 5 GeV/c) at @Q @C 45|0, using the SFM chambers to define roads pointing to the interaction region. In the first case, the associated event will be studied to determine the origin of direct electron production in charmed particle production. In the second case, the production of jets or jet-like objects when a high p^t particle is produced in pp collisions will be investigated. To carry out this program, the detection system consists of : \\item a) An improved SFM detector chamber system and layout to detect more of the produced particles and to simplify the pattern recognition problem in multiparticle events. \\item b) An improved program chain for the analysis of SFM events, ...

Valley photonic crystals for control of spin and topology

Energy Technology Data Exchange (ETDEWEB)

Dong, Jian-Wen; Chen, Xiao-Dong; Zhu, Hanyu; Wang, Yuan; Zhang, Xiang

2016-11-28

Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing1,2,3,4. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points5,6,7,8,9,10. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials11,12,13,14,15. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley–spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.

Effect of grain boundary on the field-effect mobility of microrod single crystal organic transistors.

Science.gov (United States)

Kim, Jaekyun; Kang, Jingu; Cho, Sangho; Yoo, Byungwook; Kim, Yong-Hoon; Park, Sung Kyu

2014-11-01

High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.

Variable valence ion spectra in a crystal field

International Nuclear Information System (INIS)

Ghiordanescu, V.

1979-01-01

Using the Cadmium chloride as a host lattice, the optical spectra and RES of Mnsup(2+) were studied and the following results were obtained: a) By controlled dopings, the absorbtion and excitation spectra of ion Mnsup(2+) in CdCl 2 within the concentration range between 0.01 M and 25 M were plotted. Thus, the band structure for small concentrations was pointed out to differ from the structure observed for high concentrations. In the literature, this effect has not been observed on similar compounds, due to the small intensity values of the absorbtion spectra. b) Considering that for CdCl 2 :Mnsup(2+) 0.1 M, the optical spectra correspond to the isolated ion in the lattice, the energy levels were evaluated using electrostatic and spin-orbit terms in a perturbation calculation of the crystal field approximation. c) The calculation of parameter a which represents the effect of the cubic field in the spjn Hamiltonian of Mnsup(2+), is closer to the experjmental value -0.5.10 -4 cm -1 of the crystal field Dq and zeta parameters are used, respectively, parameters of the spin-orbit interaction obtained under b). d) The coupling effects of spins into more concentrated crystals with Mn 2+ are a function of temperature. The emjssion yield was given a quasi-cantitative evaluation in thjs paper as a function of temperature and concentratjon on the basis of which the isolated centers of Mn 2+ were found to display ectra whose intensity vary with temperature according to the Laporte forbidden transitions and spin rule theory, and the clusters including Mn 2+ - Mn 2+ pairs provide spectra whose intensity vary with the strength of the spin-spin coupling. (author)

Capsize of polarization in dilute photonic crystals.

Science.gov (United States)

Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

2017-11-29

We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

Luminescence of Cr{sup 3+} ions in ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} spinels: correlation between experimental spectroscopic studies and crystal field calculations

Energy Technology Data Exchange (ETDEWEB)

Brik, M.G., E-mail: mikhail.brik@ut.ee [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa PL-42200 (Poland); Papan, J.; Jovanović, D.J. [University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, Belgrade 11001 (Serbia); Dramićanin, M.D., E-mail: dramican@vinca.rs [University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, Belgrade 11001 (Serbia)

2016-09-15

Details of preparation, spectroscopic and structural studies along with crystal field calculations for two Cr{sup 3+} doped spinels MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} are given in the present paper. Both compounds show efficient red emission at about 685 nm, which is due to the {sup 2}E{sub g} → {sup 4}A{sub 2g} spin-forbidden transition of Cr{sup 3+} ions located at the sites with D{sub 3d} local symmetry. Analysis of structure of the CrO{sub 6} clusters was performed; comparison of the crystal field effects in both compounds revealed that the low-symmetry splitting of the orbital triplet states is more pronounced in ZnAl{sub 2}O{sub 4}. Both compounds show potential for applications as red-emitting phosphors. - Highlights: • Cr{sup 3+}-doped MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} spinels were synthesized. • Excitation/emission spectra were recorded and analyzed. • Symmetry properties of the Cr-sites were analyzed. • Cr{sup 3+} energy levels in trigonal crystal field were calculated. • Cr{sup 3+}-doped MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} spinels can be used as red phosphors.

LO-TO splittings, effective charges and interactions in electro-optic meta-nitroaniline crystal as studied by polarized IR reflection and transmission spectra

Science.gov (United States)

Szostak, M. M.; Le Calvé, N.; Romain, F.; Pasquier, B.

1994-10-01

The polarized IR reflection spectra of the meta-nitroaniline ( m-NA) single crystal along the a, b and c crystallographic axes as well as the b and c polarized transmission spectra have been measured in the 100-400 cm -1 region. The LO-TO splitting values have been calculated from the reflection spectra by fitting them with the four parameter dielectric function. The dipole moment derivatives, relevant to dynamic effective charges, of the vibrations have also been calculated and used to check the applicability of the oriented gas model (OGM) to reflection spectra. The discrepancies from the OGM have been discussed in terms of vibronic couplings, weak hydrogen bondings (HB) and intramolecular charge transfer.

Computer experiments on the imaging of the (111) split crowdion interstitial in tungsten by transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Krakow, W [Xerox Corp., Rochester, N.Y. (USA)

1978-06-01

Computer simulated dark-field electron micrographs at atomic resolutions have been generated by calculating the diffuse elastic scattering distribution of short range order objects with the important point being that images are formed from regions of reciprocal space that do not contain Bragg reflections of the perfect crystal. Interpretation of these images in terms of atom positions and atom correlations becomes straightforward and it is a simple matter to distinguish between real structural information and image artifacts produced by the phase contrast mechanism in the electron optical imaging process. In this paper images were calculated under a variety of microscope conditions for a (111) split crowdion interstitial in tungsten which included up to 182 atoms of the surrounding strain field. The effect of specimen orientation, microscope objective lens defocus and the contribution of atoms lying in different shells around the defect have been considered. To aid in image interpretation accompanying diffraction patterns have been computed for different specimen orientations which show either the perfect crystal Bragg diffraction pattern or the diffuse scattering distribution produced by the crowdion defect.

Magnetic property and pressure effect of a single crystal CeRhGe

International Nuclear Information System (INIS)

Ueda, Taiki; Honda, Daisuke; Shiromoto, Tomoyuki; Thamizhavel, Arumugam; Sugiyama, Kiyohiro; Settai, Rikio; Onuki, Yoshichika; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Haga, Yoshinori; Matsuda, Tatsuma D.; Kindo, Kouichi

2005-01-01

We measured the electrical resistivity, specific heat, magnetic susceptibility, high-field magnetization, neutron scattering and electrical resistivity under pressure for CeRhGe. The anisotropy of the magnetic susceptibility and magnetization are very large, reflecting the orthorhombic crystal structure. The magnetic easy-axis is found to be oriented along the a-axis. From the neutron scattering experiment, the magnetic structure is, however, not simple, indicating an incommensurate antiferromagnetic structure. The magnetic susceptibility and magnetization were analyzed on the basis of the crystalline electric field scheme of localized-4f energy levels, indicating a very large splitting energy of the 4f levels. (author)

Calculated Pourbaix Diagrams of Cubic Perovskites for Water Splitting: Stability Against Corrosion

DEFF Research Database (Denmark)

Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

2014-01-01

We use density functional theory calculations to investigate the stability of cubic perovskites for photo-electrochemical water splitting taking both materials in their bulk crystal structure and dissolved phases into account. The method is validated through a detailed comparison of the calculated...

Crystal structure prediction of flexible molecules using parallel genetic algorithms with a standard force field.

Science.gov (United States)

Kim, Seonah; Orendt, Anita M; Ferraro, Marta B; Facelli, Julio C

2009-10-01

This article describes the application of our distributed computing framework for crystal structure prediction (CSP) the modified genetic algorithms for crystal and cluster prediction (MGAC), to predict the crystal structure of flexible molecules using the general Amber force field (GAFF) and the CHARMM program. The MGAC distributed computing framework includes a series of tightly integrated computer programs for generating the molecule's force field, sampling crystal structures using a distributed parallel genetic algorithm and local energy minimization of the structures followed by the classifying, sorting, and archiving of the most relevant structures. Our results indicate that the method can consistently find the experimentally known crystal structures of flexible molecules, but the number of missing structures and poor ranking observed in some crystals show the need for further improvement of the potential. Copyright 2009 Wiley Periodicals, Inc.

Origin of gigantic magnetostriction and crystal field effects in terbium dititanate

International Nuclear Information System (INIS)

Aleksandrov, I.V.; Lidskij, B.V.; Mamsurova, L.G.

1985-01-01

The temperature and magnetic field dependences of the magnetostriction and magnetization and the temperature dependences of the magnetic susceptibility, specific heat and lattice parameter are investigated experimentally in a broad range of temperature and field strength for polycrystalline and single crystal Tb 2 Ti 2 O 7 . A conclusion is drawn regarding the structure of the energy levels of Tb 3+ in Tb 2 Ti 2 O 7 . A qualitative and quantitative explanation of all observed magnetic effects, and in particular of gigantic magnetostriction in Tb 2 Ti 2 O 7 , is presented which is based on the crystal field theory. It is shown that the huge magnitude of the magnetostriction in terbium dititanate is due to the specificity of the energy spectrum of Tb 3+ in Tb 2 Ti 2 O 7

Spectroscopic properties of Fe2+ ions at tetragonal sites-Crystal field effects and microscopic modeling of spin Hamiltonian parameters for Fe2+ (S=2) ions in K2FeF4 and K2ZnF4

International Nuclear Information System (INIS)

Rudowicz, C.; Piwowarska, D.

2011-01-01

Magnetic and spectroscopic properties of the planar antiferromagnet K 2 FeF 4 are determined by the Fe 2+ ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K 2 FeF 4 is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe 2+ ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K 2 FeF 4 , the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe 2+ ions in K 2 FeF 4 and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground 5 D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe 2+ ions in K 2 FeF 4 and Fe 2+ :K 2 ZnF 4 . Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe 2+ ions at axial symmetry sites in related systems, i.e. Fe:K 2 MnF 4 , Rb 2 Co 1-x Fe x F 4 , Fe 2+ :Rb 2 CrCl 4 , and Fe 2+ :Rb 2 ZnCl 4 . - Highlights: → Truncated zero field splitting (ZFS) terms for Fe 2+ in K

Split and delay photon correlation spectroscopy with a visible light

International Nuclear Information System (INIS)

Rasch, Marten

2016-04-01

The development and performance of a setup constructed with the aim for the split pulse photon correlation spectroscopy is presented in this thesis. The double pulse time structure is accomplished with help of an Acusto-Optic Modulator (AOM) crystal, which mimics the splitting and delaying of photon pulses. The setup provides double pulses and allows to control the pulse width and delay and to synchronize them into one camera exposure window. The performance of the setup was successfully verified in a proof of principle experiment with a model system of polystyrene particles following Brownian motion. The measured radius of particles obtained with from the split pulse experiment (R h =(2.567±0.097) μm) is in agreement with the particle size provided by the manufacturer (R=(2.26±0.08) μm). The achieved results show higher statistics compared to a standard Dynamic Light Scattering (DLS) measurement.

Dual gauge field theory of quantum liquid crystals in three dimensions

International Nuclear Information System (INIS)

Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; Zaanen, Jan

2017-01-01

The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. Lastly, we also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.

Dual gauge field theory of quantum liquid crystals in three dimensions

Science.gov (United States)

Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; Zaanen, Jan

2017-10-01

The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. We also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.

Magnetic response of localized spins coupled to itinerant electrons in an inhomogeneous crystal field

International Nuclear Information System (INIS)

Iannarella, L.; Guimaraes, A.P.; Silva, X.A. da.

1990-01-01

The magnetic behavior at T = O K of a system consisting of conduction electrons coupled to localized electrons, the latter submitted to an inhomogeneous crystal field distribution, is studied. The study implies that the inhomogeneity of the crystal field attenuates the quenching effects. The model is interesting to the study of disordered rare-earth intermetallic compounds. (A.C.A.S.) [pt

Neutron Crystal-Field Spectroscopy and Susceptibility in ErcY1-cA1

DEFF Research Database (Denmark)

Heer, H.; Furrer, A.; Walker, E.

1974-01-01

Inelastic neutron scattering experiments and susceptibility measurements have been carried out on polycrystalline ErcY1-cAl2. A least-squares fitting procedure has been applied to the neutron data which favours four sets of crystal-field parameters. The results are compared with the measured...... susceptibility and other bulk magnetic properties. From this it is concluded that the crystal-field parameters x=-0.54 and W=-0.018 meV are the most probable ones....

Field-controllable Spin-Hall Effect of Light in Optical Crystals: A Conoscopic Mueller Matrix Analysis.

Science.gov (United States)

Samlan, C T; Viswanathan, Nirmal K

2018-01-31

Electric-field applied perpendicular to the direction of propagation of paraxial beam through an optical crystal dynamically modifies the spin-orbit interaction (SOI), leading to the demonstration of controllable spin-Hall effect of light (SHEL). The electro- and piezo-optic effects of the crystal modifies the radially symmetric spatial variation in the fast-axis orientation of the crystal, resulting in a complex pattern with different topologies due to the symmetry-breaking effect of the applied field. This introduces spatially-varying Pancharatnam-Berry type geometric phase on to the paraxial beam of light, leading to the observation of SHEL in addition to the spin-to-vortex conversion. A wave-vector resolved conoscopic Mueller matrix measurement and analysis provides a first glimpse of the SHEL in the biaxial crystal, identified via the appearance of weak circular birefringence. The emergence of field-controllable fast-axis orientation of the crystal and the resulting SHEL provides a new degree of freedom for affecting and controlling the spin and orbital angular momentum of photons to unravel the rich underlying physics of optical crystals and aid in the development of active photonic spin-Hall devices.

Scanning near-field optical microscopy of quantum dots in photonic crystal cavities

Energy Technology Data Exchange (ETDEWEB)

Skacel, Matthias; Fiore, Andrea [COBRA Research Institute, Technical University Eindhoven, Den Dolech 2, 5600 MB Eindhoven (Netherlands); Prancardi, Marco; Gerardino, Annamaria [Institute of Photonics and Nanotechnology, CNR, via del Cineto Romano 42, 00156 Roma (Italy); Alloing, Blandine; Li Lianhe, E-mail: m.s.skacel@tue.n [Institute of Photonics and Quantum Electronics, EPFL, CH-1015 Lausanne (Switzerland)

2010-09-01

Nanophotonic devices are of major interest for research and future quantum communication applications. Due to their nanometer feature size the resolution limit of far-field microscopy poses a limitation on the characterization of their optical properties. A method to overcome the resolution limit is the Scanning Near-Field Optical Microscope (SNOM). By approaching a fiber tip into the close vicinity of the sample the optical emission in the near-field regime is collected. This way of collecting the light is not affected by the diffraction limit. We employ a low temperature SNOM to investigate the photoluminescence of InAs QDs emitting at 1300nm wavelength embedded in photonic crystal cavities. At each location of an image scan the tip is stopped and a spectrum is acquired. We then plot maps of the photoluminescence for each wavelength. With this instrument it is now possible to directly observe the coupling of QDs to photonic crystal cavities both spectrally and spatially. We show first results of photoluminescence mapping of InAs QDs in photonic crystal cavities.

Grand unification in higher dimensions with split supersymmetry

International Nuclear Information System (INIS)

Schuster, Philip C.

2006-01-01

We investigate gauge coupling unification in higher dimensional GUT models with split supersymmetry. We focus on 5d and 6d orbifold GUTs, which permit a simple solution to several problems of 4D GUTs as well as control over GUT scale threshold corrections. In orbifold GUTs, calculable threshold corrections can raise or lower the prediction for α s (M Z ) in a way that depends on the location of Higgs fields. On the other hand, split supersymmetry lowers the prediction for α s (M Z ). Consequently, split supersymmetry changes the preferred location of the Higgs fields in orbifold GUTs. In the simplest models, we find that gauge coupling unification favors higgs doublets that live on the orbifold fixed points instead of in the bulk. In addition, relatively high scales of supersymmetry breaking of 10 10±2 GeV are generically favored

Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer

DEFF Research Database (Denmark)

Sun, Baozhou; Yang, Deshan; Esthappan, Jackie

2015-01-01

-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. METHODS AND MATERIALS: Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were...... included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were...

Spin splitting in band structures of BiTeX (X=Cl, Br, I) monolayers

Science.gov (United States)

Hvazdouski, D. C.; Baranava, M. S.; Stempitsky, V. R.

2018-04-01

In systems with breaking of inversion symmetry a perpendicular electric field arises that interacts with the conduction electrons. It may give rise to electron state splitting even without influence of external magnetic field due to the spin-orbital interaction (SOI). Such a removal of the spin degeneracy is called the Rashba effect. Nanostructure with the Rashba effect can be part of a spin transistor. Spin degeneracy can be realized in a channel from a material of this type without additive of magnetic ions. Lack of additive increases the charge carrier mobility and reliability of the device. Ab initio simulations of BiTeX (X=Cl, Br, I) monolayers have been carried out using VASP wherein implemented DFT method. The study of this structures is of interest because such sort of structures can be used their as spin-orbitronics materials. The crystal parameters of BiTeCl, BiTeBr, BiTeI have been determined by the ionic relaxation and static calculations. It is necessary to note that splitting of energy bands occurs in case of SOI included. The values of the Rashba coefficient aR (in the range from 6.25 to 10.00 eV·Å) have high magnitudes for spintronics materials. Band structure of monolayers structures have ideal Rashba electron gas, i.e. there no other energy states near to Fermi level except Rashba states.

Tricritical behavior in the diluted transverse spin-1 Ising model with a longitudinal crystal field

International Nuclear Information System (INIS)

Htoutou, K.; Oubelkacem, A.; Ainane, A.; Saber, M.

2005-01-01

The transverse spin-1 Ising model with a longitudinal crystal field exhibits a tricritical behavior. Within the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the influence of site dilution on this behavior and have calculated the temperature-transverse field-longitudinal crystal field-concentration phase diagrams and determined, in particular, the influence of the concentration of magnetic atoms c on the tricritical behavior. We have found that the tricritical point appears for large values of the concentration c of magnetic atoms and disappears with the increase in dilution (small values of c). Results for square lattice are calculated numerically and some interesting results are obtained. In certain ranges of values of the strength of the longitudinal crystal field D/J when it becomes sufficiently negative, we found re-entrant phenomenon, which disappears with increase in the value of the strength of the transverse field

Split supersymmetry in brane models

Indian Academy of Sciences (India)

Type-I string theory in the presence of internal magnetic fields provides a concrete realization of split ... quantum picture of the Universe. It was then ... where the integers m, n correspond to the respective magnetic and electric charges; m is the ...

Theory of electrolyte crystallization in magnetic field

DEFF Research Database (Denmark)

Madsen, Hans Erik Lundager

2007-01-01

phenomena. The basis of the theory is a crystal model of a sparingly soluble salt with NaCl structure, where the ions are divalent, and the anion is a base. It is assumed that almost all the anions in the surface layer are protonized, and that an approaching metal ion pushes the proton away...... enter an excited state due to its momentum. Spin relaxation in magnetic field may remove hindrances to proton transfer. The theory is supported by numerical results from model calculations....

Low-frequency electromagnetic field in a Wigner crystal

OpenAIRE

Stupka, Anton

2016-01-01

Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.

Strong crystal field effect in ? - optical absorption study

Science.gov (United States)

Gajek, Z.; Krupa, J. C.

1998-12-01

=-1 Results of optical absorption measurements in polarized light on tetravalent neptunium diluted in a 0953-8984/10/50/021/img6 single crystal are reported. The recorded spectra are complex, pointing to the presence of an 0953-8984/10/50/021/img7 impurity. The electronic transitions assigned to the 0953-8984/10/50/021/img8 ion are interpreted in terms of the usual model, following the actual understanding of the neptunium electronic structure and independent theoretical predictions. R.m.s. deviations of the order of 0953-8984/10/50/021/img9 have been obtained for 42 levels fitted with 11 free parameters. The crystal field effect resulting from the fitting is considerably larger than that observed for the uranium ion in the same host.

AOM reconciling of crystal field parameters for UCl 3, UBr 3, UI 3 series

Science.gov (United States)

Gajek, Z.; Mulak, J.

1990-07-01

Available inelastic neutron scattering interpretations of crystal field effect in the uranium trihalides have been verified in terms of Angular Overlap Model. For UCl 3 a good reconciling of both INS and optical interpretations of crystal field effect has been obtained. On the contrary, the parameterizations for UBr 3 and UI 3 were found to be highly artificial and suggestion is given to experimentalists to reinterpret their INS spectra.

AOM reconciling of crystal field parameters for UCl3, UBr3, Ul3 series

International Nuclear Information System (INIS)

Gajek, Z.; Mulak, J.

1990-01-01

Available inelastic neutron scattering interpretations of crystal field effect in the uranium trihalides have been verified in terms of Angular Overlap Model. For UCl 3 a good reconciling of both INS and optical interpretations of crystal field effect has been obtained. On the contrary, the parameterizations for UBr 3 and UI 3 were found to be highly artificial and suggestion is given to experimentalists to reinterpret their INS spectra

Two-Photon Rabi Splitting in a Coupled System of a Nanocavity and Exciton Complexes

Science.gov (United States)

Qian, Chenjiang; Wu, Shiyao; Song, Feilong; Peng, Kai; Xie, Xin; Yang, Jingnan; Xiao, Shan; Steer, Matthew J.; Thayne, Iain G.; Tang, Chengchun; Zuo, Zhanchun; Jin, Kuijuan; Gu, Changzhi; Xu, Xiulai

2018-05-01

Two-photon Rabi splitting in a cavity-dot system provides a basis for multiqubit coherent control in a quantum photonic network. Here we report on two-photon Rabi splitting in a strongly coupled cavity-dot system. The quantum dot was grown intentionally large in size for a large oscillation strength and small biexciton binding energy. Both exciton and biexciton transitions couple to a high-quality-factor photonic crystal cavity with large coupling strengths over 130 μ eV . Furthermore, the small binding energy enables the cavity to simultaneously couple with two exciton states. Thereby, two-photon Rabi splitting between the biexciton and cavity is achieved, which can be well reproduced by theoretical calculations with quantum master equations.

Energy-level splitting of multicharged ions due to interaction with own radiation field

International Nuclear Information System (INIS)

Gajnutdinov, R.Kh.; Kalashnikov, K.K.

1991-01-01

The overlapping of the energy levels of He-like uranium states with identical principal quantum numbers is investigated. Results are presented of a numerical calculation of the states produced as a result of mixing of the 2s 1/2 8p 1/2 and 2p 1/2 8p 1/2 states and of the respective spectral lines. It is shown that the interaction between the ion and its own radiation field splits each of the overlapping energy levels into several sublevels. The sublevels are isolated from each to other such an extent that interference effects become insignificant. The shapes of the spectral lines differ pronouncedly from the Lorentz shape and many of the line are anomaously narrow

Moessbauer investigation of static-disorder crystalline media. V. Hyperfine fields' dispersion in static-disordered crystalline media of tetragonal and trigonal iron germanates

International Nuclear Information System (INIS)

Constantinescu, S.

2007-01-01

The refined 57 Fe Moessbauer spectra of some static-disordered crystalline media (with melilite and Ca-gallate structure) evidenced observable electric and magnetic crystal field dispersions. It is the fifth in a series of papers published previously in the same journal on this subject. The data of crystalline hyperfine fields and their dispersion parameters have calculated using the modeling procedure given in a paper by Kaminskii, et al. published in 1986. The obtained values of the magnetic and quadrupole splitting parameters compared with to experimental data showed the possibility to predict the crystal fields' dispersion. (author)

Fine structure of fields in 2D photonic crystal waveguides

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Volkov, V. S.; Bozhevolnyi, S. I.

2006-01-01

We resolve fine structure of fields in a single-row missing photonic crystal waveguide by finite-difference time-domain modelling and SNOM measurements. Both linear dispersion and slow-light regimes in proximity of the cutoff are addressed in the analysis....

The use of single-crystal iron frames in transient field measurements, ch. 3

International Nuclear Information System (INIS)

Zalm, P.C.

1977-01-01

An experimental technique for measuring g-factors of short-lived states (tausub(m)=0.1-10 ps) is discussed. In this method, one uses the strong hyperfine interaction caused by the transient magnetic field. The transient field method dates from 1967. A gain in measuring time of at least a factor of four is shown to be obtained by the use of a single crystal iron frame as a ferromagnetic target backing in which the excited nuclei, formed in a nuclear reaction, recoil. Such frames can be fully magnetized with low external fields as shown by magneto-optical Kerr-effect measurements. The important improvement is that the associated magnetic fringing field near the target is negligible. This is in contrast to the conventional set-up in which strong external fields, with corresponding large disturbing fringing fields, were necessary. The single-crystal set-up is compared to the conventional set-up in several transient field experiments and proves to be successful

radiation and electric field induced effects on the order-disorder phase in lithium sodium sulphate crystals

Science.gov (United States)

Hamed, A. E.; Kassem, M. E.; El-Wahidy, E. F.; El-Abshehy, M. A.

1995-03-01

The temperature dependence of specific heat at constant pressure, Cp(T), has been measured for lithium sodium sulphate, LiNaSo4 crystals, at different ?-radiation doses and external bias electric field (Eb), in the temperature range 300-900 K. A nonlinear dependence of transition temperature, T1 and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ?-radiation. The effect of ?-radiation doses on the phase transition in LiNaSO4 crystals was explained as due to an internal bias field, Eb, originating from the interaction of polar defects with the order parameter of the host lattice. The internal bias field effect on the behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the external electric field (E).

Crystal field parameters in UCl4: Experiment versus theory

International Nuclear Information System (INIS)

Zolnierek, Z.; Gajek, Z.; Khan Malek, C.

1984-01-01

Crystal field effect on U 4+ ion with the 3 H 4 ground term in tetragonal ligand field of UCl 4 has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CEP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A 4 4 4 > and lowering the A 2 0 2 > values in comparison to those found in the experiments. The discrepancies are, however, within an accuracy of calculations. A large reduction of expectation values of the magnetic moment operator for the eigenvectors of lowest CF levels (17.8%), determined from magnetic susceptibility, cannot be attributed to the overlap and covalency effects only. The detailed calculations have shown that the latter effects provide about 4.6% reduction of respective matrix elements, and the applied J-J mixing procedure increases this factor up to 6.5%. Since similar, as in UCl 4 , reduction factor (proportional15%) has already been observed in a number of different uranium compounds, it seems to be likely that this feature is involved in the intrinsic properties of the U 4+ ion. We endeavor to explain this effect in terms of configuration interaction mechanisms. (orig.)

Crystal field parameters in UCI 4: Experiment versus theory

Science.gov (United States)

Zolnierek, Z.; Gajek, Z.; Malek, Ch. Khan

1984-08-01

Crystal field effect on U 4+ ion with the 3H 4 ground term in tetragonal ligand field of UCl 4 has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CFP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A44 and lowering the A02 values in comparison to those found in the experiments. The discrepancies are, however, within an accuracy of calculations. A large reduction of expectation values of the magnetic moment operator for the eigenvectors of lowest CF levels (17.8%), determined from magnetic susceptibility, cannot be attributed to the overlap and covalency effects only. The detailed calculations have shown that the latter effects provide about 4.6% reduction of respective matrix elements, and the applied J-J mixing procedure increases this factor up to 6.5%. Since similar, as in UCl 4, reduction factor(≈15%) has already been observed in a number of different uranium compounds, it seems likely that this feature is involved in the intrinsic properties of the U 4+ ion. We endeavor to explain this effect in terms of configuration interaction mechanisms.

A Cosserat crystal plasticity and phase field theory for grain boundary migration

Science.gov (United States)

Ask, Anna; Forest, Samuel; Appolaire, Benoit; Ammar, Kais; Salman, Oguz Umut

2018-06-01

The microstructure evolution due to thermomechanical treatment of metals can largely be described by viscoplastic deformation, nucleation and grain growth. These processes take place over different length and time scales which present significant challenges when formulating simulation models. In particular, no overall unified field framework exists to model concurrent viscoplastic deformation and recrystallization and grain growth in metal polycrystals. In this work a thermodynamically consistent diffuse interface framework incorporating crystal viscoplasticity and grain boundary migration is elaborated. The Kobayashi-Warren-Carter (KWC) phase field model is extended to incorporate the full mechanical coupling with material and lattice rotations and evolution of dislocation densities. The Cosserat crystal plasticity theory is shown to be the appropriate framework to formulate the coupling between phase field and mechanics with proper distinction between bulk and grain boundary behaviour.

SplitDist—Calculating Split-Distances for Sets of Trees

DEFF Research Database (Denmark)

Mailund, T

2004-01-01

We present a tool for comparing a set of input trees, calculating for each pair of trees the split-distances, i.e., the number of splits in one tree not present in the other.......We present a tool for comparing a set of input trees, calculating for each pair of trees the split-distances, i.e., the number of splits in one tree not present in the other....

A simple localized-itinerant model for PrAl3: crystal field and exchange effects

International Nuclear Information System (INIS)

Ranke, P.J. von; Palermo, L.

1990-01-01

We present a simple magnetic model for PrAl sub(3). The effects of crystal field are treated using a reduced set of levels and the corresponding wave functions are extracted from the actual crystal field levels of Pr sup(+3) in a hexagonal symmetry. The exchange between 4f- and conduction electrons are dealt within a molecular field approximation. An analytical magnetic state equation is derived and the magnetic behaviour discussed. The parameters of the model are estimated from a fitting of the inverse susceptibility of PrAl sub(3) given in the literature. (author)

Waveguide modes of 1D photonic crystals in a transverse magnetic field

Energy Technology Data Exchange (ETDEWEB)

Sylgacheva, D. A., E-mail: sylgacheva.darjja@physics.msu.ru; Khokhlov, N. E.; Kalish, A. N.; Belotelov, V. I. [Moscow State University, Physics Department (Russian Federation)

2016-11-15

We analyze waveguide modes in 1D photonic crystals containing layers magnetized in the plane. It is shown that the magnetooptical nonreciprocity effect emerges in such structures during the propagation of waveguide modes along the layers and perpendicularly to the magnetization. This effect involves a change in the phase velocity of the mode upon reversal of the direction of magnetization. Comparison of the effects in a nonmagnetic photonic crystal with an additional magnetic layer and in a photonic crystal with magnetic layers shows that the magnitude of this effect is several times larger in the former case in spite of the fact that the electromagnetic field of the modes in the latter case is localized in magnetic regions more strongly. This is associated with asymmetry of the dielectric layers contacting with the magnetic layer in the former case. This effect is important for controlling waveguide structure modes with the help of an external magnetic field.

Kondo peak splitting and Kondo dip in single molecular magnet junctions

Energy Technology Data Exchange (ETDEWEB)

Niu, Pengbin, E-mail: 120233951@qq.com [Institute of Solid State Physics, Shanxi Datong University, Datong 037009 (China); Shi, Yunlong; Sun, Zhu [Institute of Solid State Physics, Shanxi Datong University, Datong 037009 (China); Nie, Yi-Hang [Institute of Theoretical Physics, Shanxi University, Taiyuan 030006 (China); Luo, Hong-Gang [Center for Interdisciplinary Studies & Key Laboratory for Magnetism and Magnetic Materials of the MoE, Lanzhou University, Lanzhou 730000 (China); Beijing Computational Science Research Center, Beijing 100084 (China)

2016-01-15

Many factors containing bias, spin–orbit coupling, magnetic fields applied, and so on can strongly influence the Kondo effect, and one of the consequences is Kondo peak splitting (KPS). It is natural that KPS should also appear when another spin degree of freedom is involved. In this work we study the KPS effects of single molecular magnets (SMM) coupled with two metallic leads in low-temperature regime. It is found that the Kondo transport properties are strongly influenced by the exchange coupling and anisotropy of the magnetic core. By employing Green's function method in Hubbard operator representation, we give an analytical expression for local retarded Green's function of SMM and discussed its low-temperature transport properties. We find that the anisotropy term behaves as a magnetic field and the splitting behavior of exchange coupling is quite similar to the spin–orbit coupling. These splitting behaviors are explained by introducing inter-level or intra-level transitions, which account for the seven-peak splitting structure. Moreover, we find a Kondo dip at Fermi level under proper parameters. These Kondo peak splitting behaviors in SMM deepen our understanding to Kondo physics and should be observed in the future experiments. - Highlights: • We study Kondo peak splitting in single molecular magnets. • We study Kondo effect by Hubbard operator Green's function method. • We find Kondo peak splitting structures and a Kondo dip at Fermi level. • The exchange coupling and magnetic anisotropy induce fine splitting structure. • The splitting structures are explained by inter-level or intra-level transitions.

Oxidation and crystal field effects in uranium

Energy Technology Data Exchange (ETDEWEB)

Tobin, J. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Booth, C. H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shuh, D. K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); van der Laan, G. [Diamond Light Source, Didcot (United Kingdom); Sokaras, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Weng, T. -C. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Yu, S. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bagus, P. S. [Univ. of North Texas, Denton, TX (United States); Tyliszczak, T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nordlund, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States)

2015-07-06

An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (UO₂), uranium trioxide (UO₃), and uranium tetrafluoride (UF₄). As a result, a discussion of the role of non-spherical perturbations, i.e., crystal or ligand field effects, will be presented.

Splitting of photoluminescent emission from nitrogen–vacancy centers in diamond induced by ion-damage-induced stress

International Nuclear Information System (INIS)

Olivero, P; Bosia, F; Fairchild, B A; Gibson, B C; Greentree, A D; Spizzirri, P; Prawer, S

2013-01-01

We report a systematic investigation on the spectral splitting of negatively charged, nitrogen–vacancy (NV − ) photoluminescent emission in single-crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a high-pressure–high-temperature diamond, clearly distinguishable spectral components in the NV − emission develop over a range of ∼4.8 THz corresponding to distinct alignment of sub-ensembles which were mapped with micron spatial resolution. This method provides opportunities for the creation and selection of aligned NV − centers for ensemble quantum information protocols. (paper)

Drift of nonequilibrium charge carriers in GaAs-crystals with traps in ultrasonic fields

International Nuclear Information System (INIS)

Zaveryukhina, N.N.; Zaveryukhin, B.N.; Zaveryukhina, E.B.

2007-01-01

Full text: The drift of nonequilibrium charge carriers in a semiconductor is one of the basic processes determining the efficiency of semiconductor photodetectors. Gallium arsenide possesses certain advantages to other semiconductors in this respect, which allow GaAs-photodetectors to be obtained which possess the maximum efficiency in comparison with all other systems. The purpose of this study was to deepen and expand our knowledge about the acoustic-drift processes in GaAs- crystals. As is known, the drift of nonequilibrium charge carriers in a semiconductor is determined either by external electric fields and/or by internal (built-in) electrostatic fields related to an impurity concentration gradient in the semiconductor. Gallium arsenide is a piezoelectric semiconductor with a structure possessing no center of symmetry. An electric field applied to such a crystal produces deformation of the crystal, and vice versa, any deformation of the crystal leads to the appearance of an induced electric field. Therefore, investigation of the effect of deformation on the drift of nonequilibrium charge carriers is a very important task. One of the possible straining factors is ultrasonic wave. Interaction of the charge carriers with ultrasonic waves in piezo-semiconductors is mediated by piezo exertion. Straining a semiconductor by an ultrasonic wave field gives rise to a force acting upon the charge carriers, which is proportional to the wave vector and the piezoelectric constant of the crystal. The physics of interaction between an ultrasonic wave and nonequilibrium charge carriers in GaAs, as well as in non-polar semiconductors (Si, Ge), consists in the energy and momentum exchange between the wave and the carriers. Besides the ultrasonic waves interact with the traps of carriers and devastate them. These both acoustic effects lead to rise of amplitude of signal of GaAs-photodetectors. (authors)

Dipolar local field in homogeneously magnetized quasi-two-dimensional crystals

International Nuclear Information System (INIS)

Leon, H; Estevez-Rams, E

2009-01-01

A formalism to calculate the dipolar local field in homogeneously magnetized quasi-two-dimensional (Q2D) crystals is comprehensively presented. Two fundamental tests for this formalism are accomplished: the transition from the Q2D quantities to the corresponding 3D ones; and the recovering of the macroscopic quantities of the 3D continuum theory. The additive separation between lattice and shape contributions to the local field allows an unambiguous interpretation of the respective effects. Calculated demagnetization tensors for square and circular lateral geometries of dipole layers show that for a single crystal layer an extremely thin film, but still with a finite thickness, is a better physical representation than a strictly 2D plane. Distinct close-packed structures are simulated and calculations of the local field at the nodes of the stacked 2D lattices allow one to establish the number of significantly coupled dipole layers, depending on the ratio between the interlayer distance and the 2D lattice constant. The conclusions drawn are of interest for the study of the dipolar interaction in magnetic ultrathin films and other nanostructured materials, where magnetic nanoparticles are embedded in non-magnetic matrices.

Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors

NARCIS (Netherlands)

De Boer, R.W.I.; Stassen, A.F.; Craciun, M.F.; Mulder, C.L.; Molinari, A.; Rogge, S.; Morpurgo, A.F.

2005-01-01

We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches

Cortical splitting of the mandible after irradiation. Special reference to osteoradionecrosis

International Nuclear Information System (INIS)

Katsura, Kouji; Ito, Jusuke; Hayashi, Takafumi; Taira, Shuhzou; Nakajima, Syunichi

2001-01-01

The purpose of this study was to discuss the relationship between radiation bone injuries and a splitting of the cortical bone in the radiation field. Between January 1993 and September 1998, 53 patients with head and neck cancer received radiotherapy. The study cohort consisted of 23 patients who were followed with computed tomographic scans more than one year after radiotherapy. We evaluated clinical and computed tomographic features. Computed tomographic scanning was performed with a section thickness of 3 or 4 mm. Bone images were obtained with identical window width (4000 Haunsfield units) and window level (1000 Haunsfield units). Splitting of the cortical bone was defined as disappearance of bone density in the cortical bone, showing a linear shape running parallel to the surface of the cortex. Splitting appeared in 9 sites in 8 patients. All patients fulfilled UICC criteria for classifying oral cancer. Most of the patients received external irradiation with a total radiation dose of 50 or 60 Gy. In all cases, splitting was found in the mandibular cortex at the site of muscle attachment, that was included in the radiation field. Appearance of bone changes in chronological order were periosteal reaction, splitting and bone necrosis. We speculate that splitting results from injuries to bone structure cells caused by blood flow disturbance after surgery and radiotherapy. It is suggested that such splitting can be a predictor of osteoradionecrosis. (author)

Numerical investigation of magnetic field effect on pressure in cylindrical and hemispherical silicon CZ crystal growth

International Nuclear Information System (INIS)

Mokhtari, F.; Bouabdallah, A.; Merah, A.; Oualli, H.

2012-01-01

The effect of axial magnetic field of different intensities on pressure in silicon Czochralski crystal growth is investigated in cylindrical and hemispherical geometries with rotating crystal and crucible and thermocapillary convection. As one important thermodynamic variable, the pressure is found to be more sensitive than temperature to magnetic field with strong dependence upon the vorticity field. The pressure at the triple point is proposed as a convenient parameter to control the homogeneity of the grown crystal. With a gradual increase of the magnetic field intensity the convection effect can be reduced without thermal fluctuations in the silicon melt. An evaluation of the magnetic interaction parameter critical value corresponding to flow, pressure and temperature homogenization leads to the important result that a relatively low axial magnetic field is required for the spherical system comparatively to the cylindrical one. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Numerical investigation of magnetic field effect on pressure in cylindrical and hemispherical silicon CZ crystal growth

Energy Technology Data Exchange (ETDEWEB)

Mokhtari, F. [Universite Mouloud Mammeri de Tizi Ouzou (Algeria); LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); Bouabdallah, A. [LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); Merah, A. [LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); M' hamed Bougara University, Boumerdes (Algeria); Oualli, H. [EMP, Bordj ElBahri, Algiers (Algeria)

2012-12-15

The effect of axial magnetic field of different intensities on pressure in silicon Czochralski crystal growth is investigated in cylindrical and hemispherical geometries with rotating crystal and crucible and thermocapillary convection. As one important thermodynamic variable, the pressure is found to be more sensitive than temperature to magnetic field with strong dependence upon the vorticity field. The pressure at the triple point is proposed as a convenient parameter to control the homogeneity of the grown crystal. With a gradual increase of the magnetic field intensity the convection effect can be reduced without thermal fluctuations in the silicon melt. An evaluation of the magnetic interaction parameter critical value corresponding to flow, pressure and temperature homogenization leads to the important result that a relatively low axial magnetic field is required for the spherical system comparatively to the cylindrical one. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

Energy Technology Data Exchange (ETDEWEB)

Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: kerouad@fs-umi.ac.ma

2017-02-15

In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction J{sub s} on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined. - Highlights: • Phase diagrams of a ferromagnetic nanowire are examined by the Monte Carlo simulation. • Different types of the phase diagrams are obtained. • The effect of the random crystal field on the hysteresis loops is studied. • Single, double and para hysteresis regions are explicitly determined.

Superconducting transition and low-field magnetoresistance of a niobium single crystal at 4.2 deg. K

International Nuclear Information System (INIS)

Perriot, G.

1967-01-01

We report the study of the electrical resistance of a niobium single crystal, at 4.2 deg. K, from the beginning of the superconductive transition to 80 kilo oersteds. Critical fieldsH c2 and H c3 have been determined. Influences on superconductive transition of current density, field-current angle, crystal orientation and magnetoresistance have been studied. Variation laws of low-field transverse and longitudinal magneto-resistances have been determined. (author) [fr

Phase field modeling of rapid crystallization in the phase-change material AIST

Science.gov (United States)

Tabatabaei, Fatemeh; Boussinot, Guillaume; Spatschek, Robert; Brener, Efim A.; Apel, Markus

2017-07-01

We carry out phase field modeling as a continuum simulation technique in order to study rapid crystallization processes in the phase-change material AIST (Ag4In3Sb67Te26). In particular, we simulate the spatio-temporal evolution of the crystallization of a molten area of the phase-change material embedded in a layer stack. The simulation model is adapted to the experimental conditions used for recent measurements of crystallization rates by a laser pulse technique. Simulations are performed for substrate temperatures close to the melting temperature of AIST down to low temperatures when an amorphous state is involved. The design of the phase field model using the thin interface limit allows us to retrieve the two limiting regimes of interface controlled (low temperatures) and thermal transport controlled (high temperatures) dynamics. Our simulations show that, generically, the crystallization velocity presents a maximum in the intermediate regime where both the interface mobility and the thermal transport, through the molten area as well as through the layer stack, are important. Simulations reveal the complex interplay of all different contributions. This suggests that the maximum switching velocity depends not only on material properties but also on the precise design of the thin film structure into which the phase-change material is embedded.

High-field Transport in Low Symmetry β-Ga2O3 Crystal

Science.gov (United States)

Ghosh, Krishnendu; Singisetti, Uttam

High-field carrier transport plays an important role in many disciplines of electronics. Conventional transport theories work well on high-symmetry materials but lacks insight as the crystal symmetry goes down. Newly emerging materials, many of which possess low symmetry, demand more rigorous treatment of charge transport. We will present a comprehensive study of high-field transport using ab initio electron-phonon interaction (EPI) elements in a full-band Monte Carlo (FBMC) algorithm. We use monoclinic β-Ga2O3 as a benchmark low-symmetry material which is also an emerging wide-bandgap semiconductor. β-Ga2O3 has a C2m space group and a 10 atom primitive cell. In this work the EPIs are calculated under density-functional perturbation theory framework. We will focus on the computational challenges arising from many phonon modes and low crystal symmetry. Significant insights will be presented on the details of energy relaxation by the hot electrons mediated by different phonon modes. We will also show the velocity-field curves of electrons in different crystal directions. The authors acknowledge the support from the National Science Foundation Grant (ECCS 1607833). The authors also acknowledge the computing support provided by the Center for Computational Research at the University at Buffalo.

Crystal field effect in YbMnO.sub.3./sub..

Czech Academy of Sciences Publication Activity Database

Diviš, M.; Hölsä, J.; Lastusaari, M.; Litvinchuk, A. P.; Nekvasil, Vladimír

2008-01-01

Roč. 451, 1-2 (2008), s. 662-665 ISSN 0925-8388 R&D Projects: GA AV ČR IAA100100627 Institutional research plan: CEZ:AV0Z10100521 Keywords : ytterbium * manganites * IR spectroscopy * crystal field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.510, year: 2008

Phase field simulations of ice crystal growth in sugar solutions

NARCIS (Netherlands)

Sman, Van Der R.G.M.

2016-01-01

We present the first model ever, that describes explicitly ice crystal growth in a sugar solution during freezing. This 2-D model uses the phase field method, supplemented with realistic, and predictive theories on the thermodynamics and (diffusion) kinetics of this food system. We have to make

The influence of magnetic fields on protein crystal growth and quality; Zum Einfluss magnetischer Felder auf das Wachstum und die Qualitaet von Proteinkristallen

Energy Technology Data Exchange (ETDEWEB)

Meents, Alke

2005-08-01

Magnetic fields can affect protein crystal growth in several ways. In homogeneous magnetic fields molecules and crystallites line up themselves along the magnetic field direction due to their magnetic anisotropy. Inhomogeneous magnetic fields exert a force on diamagnetic and paramagnetic compounds towards regions of lower or higher field strength. This effect can be used to create a microgravity-like environment for diamagnetic proteins and an environment comparable to hypergravity for paramagnetic proteins. Crystallization in homogeneous magnetic fields and a microgravity-like environment are reported to have a positive effect on crystal quality. The aim of this work was to systematically investigate the effect of protein crystallization in magnetic fields on the crystal quality by comparing a large number of crystals grown under identical conditions with- and without magnetic fields. Crystal quality was determined by means of high resolution rocking-curve measurements. Furthermore in certain cases complete diffraction datasets were collected. Any possible influence of magnetic fields on the mosaicity and the quality of the diffraction data was evaluated statistically by applying Wilcoxon-Ranksum tests. To investigate the effect of protein crystallization in homogeneous magnetic fields the diamagnetic proteins Thaumatin, Trypsin, and Lysozyme and paramagnetic Myoglobin were crystallized in magnetic fields of 5 T, 8.8 T, and 15.8 T. The analysis of crystal mosaicity and quality of the diffraction data of the diamagnetic proteins did not reveal a significant influence on the crystal quality. In contrast the crystals of paramagnetic Myoglobin grew up to 14 times larger than the ones in the control experiment. In addition they had a significant lower mosaicity, and diffracted to a higher resolution than ever reported before. Special pole pieces for an existing magnet were designed and build to grow protein crystals in an inhomogeneous magnetic field The experimental

Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

Science.gov (United States)

Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

2016-06-01

Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings.

Splitting method for the combined formulation of fluid-particle problem

International Nuclear Information System (INIS)

Choi, Hyung Gwon; Yoo, Jung Yul; Joseph, D. D.

2000-01-01

A splitting method for the direct numerical simulation of solid-liquid mixtures is presented, where a symmetric pressure equation is newly proposed. Through numerical experiment, it is found that the newly proposed splitting method works well with a matrix-free formulation for some bench mark problems avoiding an erroneous pressure field which appears when using the conventional pressure equation of a splitting method. When deriving a typical pressure equation of a splitting method, the motion of a solid particle has to be approximated by the 'intermediate velocity' instead of treating it as unknowns since it is necessary as a boundary condition. Therefore, the motion of a solid particle is treated in such an explicit way that a particle moves by the known form drag(pressure drag) that is calculated from the pressure equation in the previous step. From the numerical experiment, it was shown that this method gives an erroneous pressure field even for the very small time step size as a particle velocity increases. In this paper, coupling the unknowns of particle velocities in the pressure equation is proposed, where the resulting matrix is reduced to the symmetric one by applying the projector of the combined formulation. It has been tested over some bench mark problems and gives reasonable pressure fields

The crystal structure of the Split End protein SHARP adds a new layer of complexity to proteins containing RNA recognition motifs.

Science.gov (United States)

Arieti, Fabiana; Gabus, Caroline; Tambalo, Margherita; Huet, Tiphaine; Round, Adam; Thore, Stéphane

2014-06-01

The Split Ends (SPEN) protein was originally discovered in Drosophila in the late 1990s. Since then, homologous proteins have been identified in eukaryotic species ranging from plants to humans. Every family member contains three predicted RNA recognition motifs (RRMs) in the N-terminal region of the protein. We have determined the crystal structure of the region of the human SPEN homolog that contains these RRMs-the SMRT/HDAC1 Associated Repressor Protein (SHARP), at 2.0 Å resolution. SHARP is a co-regulator of the nuclear receptors. We demonstrate that two of the three RRMs, namely RRM3 and RRM4, interact via a highly conserved interface. Furthermore, we show that the RRM3-RRM4 block is the main platform mediating the stable association with the H12-H13 substructure found in the steroid receptor RNA activator (SRA), a long, non-coding RNA previously shown to play a crucial role in nuclear receptor transcriptional regulation. We determine that SHARP association with SRA relies on both single- and double-stranded RNA sequences. The crystal structure of the SHARP-RRM fragment, together with the associated RNA-binding studies, extend the repertoire of nucleic acid binding properties of RRM domains suggesting a new hypothesis for a better understanding of SPEN protein functions. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Effect of an external magnetic field on polytypism of CdI2 crystals grown from solutions

International Nuclear Information System (INIS)

Palosz, B.; Przedmojski, J.

1982-01-01

The effect of growth conditions on the polytypic structure of crystals of CdI 2 was analyzed for crystallization from solutions. Three solvents were used: H 2 O, 3 H 2 O + 1 C 2 H 5 OH and 1 H 2 O + 1 C 2 H 5 OH. Crystals were grown at two temperatures: 5 and 25 0 C with low and high growth rates; an external magnetic field of about 0.25 tesla was used. The effect of the above three parameters on the formation of the basic polytypes 2H and 4H and on the ordering of faults in disordered structures and in polytype cells was studied by X-ray analysis of crystal surfaces. Some distinct relations between the polytypic structure of crystals of CdI 2 and the magnetic field were found. (author)

Nanoscale strontium titanate photocatalysts for overall water splitting.

Science.gov (United States)

Townsend, Troy K; Browning, Nigel D; Osterloh, Frank E

2012-08-28

SrTiO(3) (STO) is a large band gap (3.2 eV) semiconductor that catalyzes the overall water splitting reaction under UV light irradiation in the presence of a NiO cocatalyst. As we show here, the reactivity persists in nanoscale particles of the material, although the process is less effective at the nanoscale. To reach these conclusions, Bulk STO, 30 ± 5 nm STO, and 6.5 ± 1 nm STO were synthesized by three different methods, their crystal structures verified with XRD and their morphology observed with HRTEM before and after NiO deposition. In connection with NiO, all samples split water into stoichiometric mixtures of H(2) and O(2), but the activity is decreasing from 28 μmol H(2) g(-1) h(-1) (bulk STO), to 19.4 μmol H(2) g(-1) h(-1) (30 nm STO), and 3.0 μmol H(2) g(-1) h(-1) (6.5 nm STO). The reasons for this decrease are an increase of the water oxidation overpotential for the smaller particles and reduced light absorption due to a quantum size effect. Overall, these findings establish the first nanoscale titanate photocatalyst for overall water splitting.

On the neutron diffraction in a crystal in the field of a standing laser wave

International Nuclear Information System (INIS)

Grigoryan, K.K.; Hayrapetyan, A.G.; Petrosyan, R.G.

2010-01-01

The possibility of high-energy neutron diffraction in a crystal is shown by applying the solution of time-dependent Schroedinger equation for a neutron in the field of a standing laser wave. The scattering picture is examined within the framework of non-stationary S-matrix theory, where the neutron-laser field interaction is considered exactly and the neutron-crystal interaction is considered as a perturbation described by Fermi pseudopotential (Farri representation). The neutron-crystal interaction is elastic, and the neutron-laser field interaction has both inelastic and elastic behaviors which results in the observation of an analogous to the Kapitza-Dirac effect for neutrons. The neutron scattering probability is calculated and the analysis of the results are adduced. Both inelastic and elastic diffraction conditions are obtained and the formation of a 'sublattice' is illustrated in the process of neutron-photon-phonon elastic interaction.

Magnetic field drift shell splitting: Cause of unusual dayside particle pitch angle distributions during storms and substorms

International Nuclear Information System (INIS)

Sibeck, D.G.; McEntire, R.W.; Lui, A.T.Y.; Lopez, R.E.; Krimigis, S.M.

1987-01-01

We present a magnetic field drift shell--splitting model for the unusual butterfly and head-and-shoulder energetic (E>25 keV) particle pitch angle distributions (PADs) which appear deep within the dayside magnetosphere during the course of storms and substorms. Drift shell splitting separates the high and low pitch angle particles in nightside injections as they move to the dayside magnetosphere, so that the higher pitch angle particles move radially away from Earth. Consequently, butterfly PADs with a surplus of low pitch angle particles form on the inner edge of the injection, but head-and-shoulder PADs with a surplus of high pitch angle particles from on the outer edge. A similar process removes high pitch angle particles from the inner dayside magnetosphere during storms, leaving the remaining lower pitch angle particles to form butterfly PADs on the inner edge of the ring current. A detailed case and statistical study of CCE/MEPA observations, as well as a review of previous work, shows most examples of unusual PADs to be consistent with the model. copyright American Geophysical Union 1987

Superradiance from an ultrathin film of three-level V-type atoms: interplay between splitting, quantum coherence and local-field effects

International Nuclear Information System (INIS)

Malyshev, V A; Carreno, F; Anton, M A; Calderon, Oscar G; Dominguez-Adame, F

2003-01-01

We carry out a theoretical study of the collective spontaneous emission (superradiance) from an ultrathin film comprised of three-level atoms with V configuration of the operating transitions. As the thickness of the system is small compared to the emission wavelength inside the film, the local-field correction to the averaged Maxwell field is relevant. We show that the interplay between the low-frequency quantum coherence within the subspace of the upper doublet states and the local-field correction may drastically affect the branching ratio of the operating transitions. This effect may be used for controlling the emission process by varying the doublet splitting and the amount of low-frequency coherence

Creating physically-based three-dimensional microstructures: Bridging phase-field and crystal plasticity models.

Energy Technology Data Exchange (ETDEWEB)

Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Owen, Steven J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Abdeljawad, Fadi F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hanks, Byron [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

In order to better incorporate microstructures in continuum scale models, we use a novel finite element (FE) meshing technique to generate three-dimensional polycrystalline aggregates from a phase field grain growth model of grain microstructures. The proposed meshing technique creates hexahedral FE meshes that capture smooth interfaces between adjacent grains. Three dimensional realizations of grain microstructures from the phase field model are used in crystal plasticity-finite element (CP-FE) simulations of polycrystalline a -iron. We show that the interface conformal meshes significantly reduce artificial stress localizations in voxelated meshes that exhibit the so-called "wedding cake" interfaces. This framework provides a direct link between two mesoscale models - phase field and crystal plasticity - and for the first time allows mechanics simulations of polycrystalline materials using three-dimensional hexahedral finite element meshes with realistic topological features.

Electrical resistance of flaky crystals in the longitudinal quantizing magnetic field

International Nuclear Information System (INIS)

Askerov, B.M.; Figarova, S.R.; Makhmudov, M.M.

2005-01-01

Specific resistance of the quasi-two-dimensional electrical gas in the longitudinal quantizing magnetic field is investigated in this work. Common expression for resistivity in the flaky crystals was received. In quantum limit was analyzed dependence of the resistivity from the size of magnetic field and parameters energetic spectra in case of strong degenerate gas. It was tagged that, the conduct of specific resistance is formed by the dependence of chemical potential from the size of magnetic field. At the defined value of the chemical potential and size of magnetic field obtains inflation of the specific resistance. (author)

Fast fringe-field switching of a liquid crystal cell by two-dimensional confinement with virtual walls

OpenAIRE

Choi, Tae-Hoon; Oh, Seung-Won; Park, Young-Jin; Choi, Yeongyu; Yoon, Tae-Hoon

2016-01-01

We report a simple method for reducing the response time of a fringe-field switching liquid crystal cell by using two-dimensional confinement of the liquid crystals. Through both numerical calculations and experiments, we show that the switching speed can be increased by several fold in a fringe-field switching cell by simply using a rubbing angle of zero, which causes virtual walls to be built when an electric field is applied between the interdigitated electrodes and the common electrode, w...

Study on the influence of optical electronegativity of fluoride host structures on the crystal field components' position of the [Xe]4f15d1-configuration of trivalent praseodymium

International Nuclear Information System (INIS)

Herden, Benjamin

2014-03-01

As alternative radiation sources for mercury containing lamps LEDs cover the normal range, but efficient alternatives for UV radiations are still not available. Xenon excimer discharge lamps could be candidate as alternatives to mercury low-pressure discharge lamps. The discharge wavelength of these lamps is 172 nm that has to be converted in other spectral ranges. The theses deals with trivalent praseodymium as activator ion in binary and ternary fluoride host structures. The host structure and the crystallographic position of the praseodymium ion influence the development of emissions line and bands and the energetic position of the emission. The results are explained by the interaction of the nephelauxetic effect and the crystal field splitting of 5d orbitals, called optical electronegativity.

Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2

Science.gov (United States)

Pikul, A. P.; Kaczorowski, D.; Gajek, Z.; Stȩpień-Damm, J.; Ślebarski, A.; Werwiński, M.; Szajek, A.

2010-05-01

Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific-heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab initio band-structure calculations performed within the density-functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma No.74, Pearson symbol: oI24 ) with the lattice parameters a=7.1330(14)Å , b=9.7340(19)Å , and c=5.6040(11)Å . Analysis of the magnetic and XPS data revealed the presence of well-localized magnetic moments of trivalent cerium ions. All the physical properties were found to be highly anisotropic over the whole temperature range studied and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN=4.70(1)K and their subsequent spin rearrangement at Tt=4.48(1)K manifest themselves as distinct anomalies in the temperature characteristic of all the physical properties investigated and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2 , similar to that recently reported for an isostructural compound CeIr3Si2 . The electronic band-structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well-reproduced the experimental XPS valence-band spectrum.

Salt splitting with ceramic membranes

International Nuclear Information System (INIS)

Kurath, D.

1996-01-01

The purpose of this task is to develop ceramic membrane technologies for salt splitting of radioactively contaminated sodium salt solutions. This technology has the potential to reduce the low-level waste (LLW) disposal volume, the pH and sodium hydroxide content for subsequent processing steps, the sodium content of interstitial liquid in high-level waste (HLW) sludges, and provide sodium hydroxide free of aluminum for recycle within processing plants at the DOE complex. Potential deployment sites include Hanford, Savannah River, and Idaho National Engineering Laboratory (INEL). The technical approach consists of electrochemical separation of sodium ions from the salt solution using sodium (Na) Super Ion Conductors (NaSICON). As the name implies, sodium ions are transported rapidly through these ceramic crystals even at room temperatures

Photoelectrochemical solar water splitting: From basic principles to advanced devices

Directory of Open Access Journals (Sweden)

Bandar Y.Alfaifi

2018-02-01

Full Text Available Photoelectrochemical water splitting (PEC offers a promising path for sustainable generation of hydrogen fuel. However, improving solar fuel water splitting efficiency facing tremendous challenges, due to the energy loss related to fast recombination of the photogenerated charge carriers, electrode degradation, as well as limited light harvesting. This review focuses on the brief introduction of basic fundamental of PEC water splitting and the concept of various types of water splitting approaches. Numerous engineering strategies for the investgating of the higher efficiency of the PEC, including charge separation, light harvesting, and co-catalysts doping, have been discussed. Moreover, recent remarkable progress and developments for PEC water splitting with some promising materials are discussed. Recent advanced applications of PEC are also reviewed. Finally, the review concludes with a summary and future outlook of this hot field.

Electron paramagnetic resonance investigations of Fe3+ doped layered TiInS2 and TiGaSe2 single crystals

International Nuclear Information System (INIS)

Faik, Mikailov; Bulat, Rameev; Sinan, Kazan; Bekir, Aktash; Faik, Mikailov; Bulat, Rameev

2005-01-01

Full text : TiInS 2 and TiGaSe 2 single crystals doped by paramagnetic Fe ions have been studied at room temperature by Electron Paramagnetic Resonance (EPR) technique. A fine structure of EPR spectra of paramagnetic Fe 3 + ions was observed. The spectra were interpreted to correspond to the transitions among spin multiplet which are splitted by the local ligand crystal field (CF) of orthorhombic symmetry. Four equivalent Fe 3 + centers have been observed in the EPR spectra and the local symmetry of crystal field at the Fe 3 + site and CF parameters were determined. It was established that symmetry axis of the axial component in the CF is making an angle of about 48 and 43 degree with the plane of layers of TiInS 2 and TiGaSe 2 crystals respectively. Experimental results indicate that the Fe ions substitute In (GA) at the center of InS 4 (GaSe 4 ) tetrahedrons, and the rhombic distortion of the CF is caused by the TI ions located in the trigonal cavities between the tethedral complexes

Crystal field and magnetism with Wannier functions: Orthorhombic rare-earth manganites

Czech Academy of Sciences Publication Activity Database

Novák, Pavel; Nekvasil, Vladimír; Knížek, Karel

358-359, MAY (2014), s. 228-232 ISSN 0304-8853 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : crystal field * rare- earth magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.970, year: 2014

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas.

Science.gov (United States)

Wallace, M S; Haque, S; Neill, P; Pereira, N R; Presura, R

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Photonic crystal fiber injected with Fe{sub 3}O{sub 4} nanofluid for magnetic field detection

Energy Technology Data Exchange (ETDEWEB)

Thakur, Harneet V.; Nalawade, Sandipan M.; Gupta, Swati [Photonics Group, Department of Applied Physics, Defence Institute of Advanced Technology, Girinagar, Pune 411 025 (India); Kitture, Rohini [Department of Electronic-Science, Fergusson College, Pune 411 004 (India); Kale, S. N. [Nanotechnology Group, Department of Applied Physics, Defence Institute of Advanced Technology, Girinagar, Pune 411 025 (India)

2011-10-17

We report a magnetic field sensor having advantages of both photonic crystal fiber and optofluidics, combining them on a single platform by infiltrating small amount of Fe{sub 3}O{sub 4} magnetic optofluid/nanofluid in cladding holes of polarization-maintaining photonic crystal fiber. We demonstrated that magnetic field of few mT can be easily and very well detected with higher sensitivity of 242 pm/mT. The change in the birefringence values has been correlated to the response of nanofluid to applied field.

Noncrucial role of the defects in the splitting for hydrogen implanted silicon with high boron concentration

International Nuclear Information System (INIS)

Popov, V.P.; Stas, V.F.; Antonova, I.V.

1999-01-01

The present work deals with the investigation of the electrical and structural properties of heavily boron-doped silicon irradiated by hydrogen. Blistering and splitting processes are enhanced with an increase in boron concentration in the crystal. The measured values of perpendicular strain are over 0.7% which corresponds to a gas overpressure of 0.5 GPa. Processes which lead to blistering and splitting is better described in the frame of a gas pressure model than a model of local stress caused by the defects

Evaluation of the exchange interaction and crystal fields in a prototype Dy2 SMM

Science.gov (United States)

Zhang, Qing; Sarachik, Myriam; Baker, Michael; Chen, Yizhang; Kent, Andrew; Pineda, Eufemio; McInnes, Eric

In order to gain an understanding of the INS and magnetization data obtained for Dy2, the simplest member of a newly synthesized family of dysprosium-based molecular magnets, we report on calculations of the magnetic behavior of a Dy2 cluster with the formula [hqH2][Dy2(hq)4(NO3)3].MeOH. The molecular complex contains one high symmetry Dy(III) ion and one low symmetry Dy(III) ion. Our calculations suggest that exchange coupling between the two ions controls the behavior of the magnetization at low temperature, while the crystal field of the low symmetry Dy(III) ion controls the behavior at higher temperature. A point charge electrostatic model, based on crystallographic coordinates, provides a starting point for the determination of the crystal field. Parameters in these calculations are adjusted to provide best fits to inelastic neutron scattering data (INS) and low temperature magnetometry: the INS measurements access crystal field energies and low temperature magnetization probes the Dy-Dy exchange interaction. Work supported by ARO W911NF-13-1-1025 (CCNY) and NSF-DMR-1309202 (NYU).

Study of ln s Physics in $\\bar{p}p$ Interactions at the Split Field Magnet

CERN Multimedia

2002-01-01

This experiment uses the Split Field Magnet detector to investigate the low p^t, ``ln~s'', type of interactions that dominate the @*p cross-section. Systematic comparisons will be made to pp interactions. \\\\ \\\\ Specific areas to be studied include elastic scattering in the regions 0.05 $<$ !t! $<$ 0.8 GeV|2 and 0.8 $<$ !t! $<$ 4.0 GeV|2, and the use of a minimum bias trigger to study topological cross-sections, inclusive spectra, and two-body correlations. Some specialized triggers, run simultaneously with the high t elastic scattering trigger, are being studied. Examples are a trigger requiring Cerenkov identification in a limited region of phase space, and a trigger to select diffractively produced events.

Beam-splitter switches based on zenithal bistable liquid-crystal gratings.

Science.gov (United States)

Zografopoulos, Dimitrios C; Beccherelli, Romeo; Kriezis, Emmanouil E

2014-10-01

The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.

Absorption spectra of CsNd(MoO4)2 and CsGd(MoO4)2-Nd3+ crystals in strong magnetic fields

International Nuclear Information System (INIS)

Gorban', I.S.; Kozeeva, L.P.; Slobodyanyuk, A.V.; Shevchenko, V.A.

1987-01-01

The comparison of the electronic structure of Nd 3+ in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 - Nd 3+ crystals is made. It is established that in these crystals the activator centers, mainly, of the certain type with the symmetry of the local environment C 2 are formed. The absorption spectra of self-activated CsNd(MoO 4 ) 2 crystal differ from spectra of CsGd(MoO 4 ) 2 - Nd 3+ by the presence of the vibrating structure. The Stark splittings of energy levels of Nd 3+ in the investigated crystalline matrices are more sensitive to the environment effect than the Zeeman ones. The ground state of Nd 3+ ion in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 molybdates is characterized by the similar values of g-factors

Circularly polarized zero-phonon transitions of vacancies in diamond at high magnetic fields

Science.gov (United States)

Braukmann, D.; Glaser, E. R.; Kennedy, T. A.; Bayer, M.; Debus, J.

2018-05-01

We study the circularly polarized photoluminescence of negatively charged (NV-) and neutral (NV0) nitrogen-vacancy ensembles and neutral vacancies (V0) in diamond crystals exposed to magnetic fields of up to 10 T. We determine the orbital and spin Zeeman splitting as well as the energetic ordering of their ground and first-excited states. The spin-triplet and -singlet states of the NV- are described by an orbital Zeeman splitting of about 9 μ eV /T , which corresponds to a positive orbital g -factor of gL=0.164 under application of the magnetic field along the (001) and (111) crystallographic directions, respectively. The zero-phonon line (ZPL) of the NV- singlet is defined as a transition from the 1E' states, which are split by gLμBB , to the 1A1 state. The energies of the zero-phonon triplet transitions show a quadratic dependence on intermediate magnetic field strengths, which we attribute to a mixing of excited states with nonzero orbital angular momentum. Moreover, we identify slightly different spin Zeeman splittings in the ground (gs) and excited (es) triplet states, which can be expressed by a deviation between their spin g -factors: gS ,es=gS ,gs+Δ g with values of Δ g =0.014 and 0.029 in the (001) and (111) geometries, respectively. The degree of circular polarization of the NV- ZPLs depends significantly on the temperature, which is explained by an efficient spin-orbit coupling of the excited states mediated through acoustic phonons. We further demonstrate that the sign of the circular polarization degree is switched under rotation of the diamond crystal. A weak Zeeman splitting similar to Δ g μBB measured for the NV- ZPLs is also obtained for the NV0 zero-phonon lines, from which we conclude that the ground state is composed of two optically active states with compensated orbital contributions and opposite spin-1/2 momentum projections. The zero-phonon lines of the V0 show Zeeman splittings and degrees of the circular polarization with opposite

Random crystal field effects on the integer and half-integer mixed-spin system

Science.gov (United States)

Yigit, Ali; Albayrak, Erhan

2018-05-01

In this work, we have focused on the random crystal field effects on the phase diagrams of the mixed spin-1 and spin-5/2 Ising system obtained by utilizing the exact recursion relations (ERR) on the Bethe lattice (BL). The distribution function P(Di) = pδ [Di - D(1 + α) ] +(1 - p) δ [Di - D(1 - α) ] is used to randomize the crystal field.The phase diagrams are found to exhibit second- and first-order phase transitions depending on the values of α, D and p. It is also observed that the model displays tricritical point, isolated point, critical end point and three compensation temperatures for suitable values of the system parameters.

Coupled Photonic Crystal Cavity Array Laser

DEFF Research Database (Denmark)

Schubert, Martin

in the quadratic lattice. Processing techniques are developed and optimized in order fabricate photonic crystals membranes in gallium arsenide with quantum dots as gain medium and in indium gallium arsenide phosphide with quantum wells as gain medium. Several key issues in process to ensure good quality....... The results are in good agreement with standard coupled mode theory. Also a novel type of photonic crystal structure is proposed called lambda shifted cavity which is a twodimensional photonic crystal laser analog of a VCSEL laser. Detailed measurements of the coupled modes in the photonic crystals...... with quantum dots are carried out. In agreement with a simple gain model the structures do not show stimulated emission. The spectral splitting due to the coupling between single cavities as well as arrays of cavities is studied theoretically and experimentally. Lasing is observed for photonic crystal cavity...

Far-field and Fresnel Liquid Crystal Geometric Phase Holograms via Direct-Write Photo-Alignment

Directory of Open Access Journals (Sweden)

Xiao Xiang

2017-12-01

Full Text Available We study computer-generated geometric-phase holograms (GPHs realized by photo-aligned liquid crystals, in both simulation and experiment. We demonstrate both far-field and Fresnel holograms capable of producing far-field and near-field images with preserved fidelity for all wavelengths. The GPHs are fabricated by patterning a photo-alignment layer (PAL using a direct-write laser scanner and coating the surface with a polymerizable liquid crystal (i.e., a reactive mesogen. We study various recording pixel sizes, down to 3 μm, that are easily recorded in the PAL. We characterize the fabricated elements and find good agreement with theory and numerical simulation. Because of the wavelength independent geometric phase, the (phase fidelity of the replay images is preserved for all wavelengths, unlike conventional dynamic phase holograms. However, governed by the diffraction equation, the size and location of a reconstructed image depends on the replay wavelength for far-field and near-field GPHs, respectively. These offer interesting opportunities for white-light holography.

Crystal field and magnetism with Wannier functions: rare-earth dopedaluminum garnets

Czech Academy of Sciences Publication Activity Database

Mihóková, Eva; Novák, Pavel; Laguta, Valentyn

2015-01-01

Roč. 33, č. 12 (2015), 1316-1323 ISSN 1002-0721 R&D Projects: GA ČR GA13-09876S Institutional support: RVO:68378271 Keywords : crystal field * ab initio calculations * garnets * rare earths Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.188, year: 2015

Crystal-field investigations of rare-earth-doped wide band gap semiconductors

CERN Multimedia

Muller, S; Wahl, U

Crystal field investigations play a central role in the studies of rare earth doped semiconductors. Optical stark level spectroscopy and lattice location studies of radioactive rare earth isotopes implanted at ISOLDE have provided important insight into these systems during the last years. It has been shown that despite a major site preference of the probe atoms in the lattice, several defect configurations do exist. These sites are visible in the optical spectra but their origin and nature aren't deducible from these spectra alone. Hyperfine measurements on the other hand should reveal these defect configurations and yield the parameters necessary for a description of the optical properties at the atomic scale. In order to study the crystal field with this alternative approach, we propose a new concept for perturbed $\\gamma\\gamma$-angular correlation (PAC) experiments at ISOLDE based on digital signal processing in contrast to earlier analog setups. The general functionality of the spectrometer is explained ...

40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction

Science.gov (United States)

Duc, F.; Tonon, X.; Billette, J.; Rollet, B.; Knafo, W.; Bourdarot, F.; Béard, J.; Mantegazza, F.; Longuet, B.; Lorenzo, J. E.; Lelièvre-Berna, E.; Frings, P.; Regnault, L.-P.

2018-05-01

We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.

Exchange and crystal field effects in the ESR spectra of Eu2+ in LaB6

Science.gov (United States)

Duque, J. G. S.; Urbano, R. R.; Venegas, P. A.; Pagliuso, P. G.; Rettori, C.; Fisk, Z.; Oseroff, S. B.

2007-09-01

Electron spin resonance of Eu2+ ( 4f7 , S=7/2 ) in a La hexaboride (LaB6) single crystal shows a single anisotropic Dysonian resonance. From the observed negative g shift of the resonance, it is inferred that the Eu2+ ions are covalent exchange coupled to the B2p -like host conduction electrons. From the anisotropy of the spectra (linewidth and field for resonance), we found that the S ground state of Eu2+ ions experience a cubic crystal field of a negative fourth order crystal field parameter (CFP), b4=-11.5(2.0)Oe , in agreement with the negative fourth order CFP, A4 , found for the non- S ground state R hexaborides. These results support covalency as the dominant contribution to the fourth order CFP for the whole R hexaboride family.

Nuclear reorientation in static and radio-frequency electro-magnetic fields

International Nuclear Information System (INIS)

Dubbers, D.

1976-01-01

Nuclear reorientation by external electromagnetic fields is treated using Fano's irreducible tensor formulation of the problem. Although the main purpose of this paper is the description of the effects of nuclear magnetic resonance (NMR) on an ensemble of oriented nuclei in the presence of a crystal electric field gradient (efg), the results are applicable to all types of nuclear or atomic orientation or angular correlation work. The theory is applied to a number of exemplary cases: magnetic field dependence of nuclear orientation in the presence of quadrupole interactions; sign determination in electric quadrupole coupling; line shapes of nuclear acoustic resonance (NAR) signals; quadrupole splitting and multiquantum transitions in NMR with oriented nuclei. (orig./WBU) [de

Crystal field parameters in UCl/sub 4/: Experiment versus theory

Energy Technology Data Exchange (ETDEWEB)

Zolnierek, Z.; Gajek, Z. (Polska Akademia Nauk, Wroclaw. Inst. Niskich Temperatur i Badan Strukturalnych); Khan Malek, C. (Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire)

1984-08-01

Crystal field effect on U/sup 4 +/ ion with the /sup 3/H/sub 4/ ground term in tetragonal ligand field of UCl/sub 4/ has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CEP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A/sub 4//sup 4/ and lowering the A/sub 2//sup 0/ values in comparison to those found in the experiments. The discrepancies are, however, within an accuracy of calculations. A large similar reduction of expectation values of the magnetic moment operator for the eigenvectors of lowest CF levels (17.8%), determined from magnetic susceptibility, cannot be attributed to the overlap and covalency effects only. The detailed calculations have shown that the latter effects provide about 4.6% reduction of respective matrix elements, and the applied J-J mixing procedure increases this factor up to 6.5%. Since similar reduction factor has already been observed in a number of different uranium compounds, as in UCl/sub 4/ it seems to be likely that this feature is involved in the intrinsic properties of the U/sup 4 +/ ion. The authors endeavor to explain this effect in terms of configuration interaction mechanisms.

Algebraic techniques for diagonalization of a split quaternion matrix in split quaternionic mechanics

International Nuclear Information System (INIS)

Jiang, Tongsong; Jiang, Ziwu; Zhang, Zhaozhong

2015-01-01

In the study of the relation between complexified classical and non-Hermitian quantum mechanics, physicists found that there are links to quaternionic and split quaternionic mechanics, and this leads to the possibility of employing algebraic techniques of split quaternions to tackle some problems in complexified classical and quantum mechanics. This paper, by means of real representation of a split quaternion matrix, studies the problem of diagonalization of a split quaternion matrix and gives algebraic techniques for diagonalization of split quaternion matrices in split quaternionic mechanics

Relative work function of clean molybdenum single-crystal planes determined by field emission microscopy

International Nuclear Information System (INIS)

Bergeret, G.; Abon, M.; Tardy, B.; Teichner, S.J.

1974-01-01

A probe-hole field emission microscope was used to determine the work function of clean molybdenum single crystal planes relative to the average work function of the field emitter, assumed to be 4.20 eV. Results are compared with other available data

Local Electric Field Strength in a Hollow Cathode Determined by Stark Splitting of the 2S Level of Hydrogen Isotopes by Optogalvanic Spectroscopy

International Nuclear Information System (INIS)

Perez, C.; Rosa, M. I. de la; Gruetzmacher, K.; Fuentes, L. M.; Gonzalo, A. B.

2008-01-01

In this work we present Doppler-free two-photon optogalvanic spectroscopy as a tool to measure the electric field strength in the cathode fall region of a hollow cathode discharge via the Stark splitting of the 2S level of atomic deuterium. The strong electric field strength present in the hollow cathode is determined for various discharge conditions which allows studying the corresponding variations of the cathode fall, and its changes with discharge operation time.

Split brain : Divided perception but undivided consciousness

NARCIS (Netherlands)

Pinto, Y.; Neville, D.A.; Otten, M.; Corballis, P.M.; Lamme, V.A.F.; de Haan, E.H.F.; Foschi, N.; Fabri, M.

In extensive studies with two split-brain patients we replicate the standard finding that stimuli cannot be compared across visual half-fields, indicating that each hemisphere processes information independently of the other. Yet, crucially, we show that the canonical textbook findings that a

Liquid crystal boojum-colloids

International Nuclear Information System (INIS)

Tasinkevych, M; Silvestre, N M; Telo da Gama, M M

2012-01-01

Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

Wave dispersion relation of two-dimensional plasma crystals in a magnetic field

International Nuclear Information System (INIS)

Uchida, G.; Konopka, U.; Morfill, G.

2004-01-01

The wave dispersion relation in a two-dimensional strongly coupled plasma crystal is studied by theoretical analysis and molecular dynamics simulation taking into account a constant magnetic field parallel to the crystal normal. The expression for the wave dispersion relation clearly shows that high-frequency and low-frequency branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz force acting on the dust particles. The high-frequency and the low-frequency branches are found to belong to right-hand and left-hand polarized waves, respectively

Determination and significance of the Mn(II) Zero-Field Splitting (ZFS) interaction in the geochemistry of travertines

Energy Technology Data Exchange (ETDEWEB)

Montegrossi, G. [Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche (CNR), via G. La Pira 4, I-50121, Florence (Italy)]. E-mail: giordano@geo.unifi.it; Di Benedetto, F. [Museo di Storia Naturale, Universita di Firenze, via G. La Pira 4, I-50121, Florence (Italy); Minissale, A. [Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche (CNR), via G. La Pira 4, I-50121, Florence (Italy); Paladini, M. [Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche (CNR), via G. La Pira 4, I-50121, Florence (Italy); Pardi, L.A. [Istituto per i Processi Chimico-Fisici, CNR, via G. Moruzzi 1, I-56124 Pisa (Italy); Romanelli, M. [Dipartimento di Chimica, Universita di Firenze, via della Lastruccia 3, I-50019 Sesto Fiorentino (Italy); Romei, F. [Dipartimento di Biologia Animale e Genetica, Universita di Firenze, Via Romana 17, I-50100 Florence (Italy)

2006-05-15

An analytical approach, based on the electron paramagnetic resonance (EPR) spectroscopy of Mn(II) in travertines, has been developed in order to obtain relevant information about the local inhomogeneity of calcite and about the thermodynamic conditions which control the formation of travertine deposits. This information is crucial to constrain the precipitation of travertine under different geochemical contexts. An empirical correlation between the spectral features and the zero-field splitting (ZFS) interaction has been established through numerical simulations of EPR spectra. The variability of the investigated parameters and the applicability of the method have been tested on several travertines from Central Italy.

Determination and significance of the Mn(II) Zero-Field Splitting (ZFS) interaction in the geochemistry of travertines

International Nuclear Information System (INIS)

Montegrossi, G.; Di Benedetto, F.; Minissale, A.; Paladini, M.; Pardi, L.A.; Romanelli, M.; Romei, F.

2006-01-01

An analytical approach, based on the electron paramagnetic resonance (EPR) spectroscopy of Mn(II) in travertines, has been developed in order to obtain relevant information about the local inhomogeneity of calcite and about the thermodynamic conditions which control the formation of travertine deposits. This information is crucial to constrain the precipitation of travertine under different geochemical contexts. An empirical correlation between the spectral features and the zero-field splitting (ZFS) interaction has been established through numerical simulations of EPR spectra. The variability of the investigated parameters and the applicability of the method have been tested on several travertines from Central Italy

Multiplexing 32,000 spectra onto 8 detectors: the HARMONI field splitting, image slicing, and wavelength selecting optics

Science.gov (United States)

Tecza, Matthias; Thatte, Niranjan; Clarke, Fraser; Freeman, David; Kosmalski, Johan

2012-09-01

HARMONI, the High Angular Resolution Monolithic Optical & Near-infrared Integral field spectrograph is one of two first-light instruments for the European Extremely Large Telescope. Over a 256x128 pixel field-of-view HARMONI will simultaneously measure approximately 32,000 spectra. Each spectrum is about 4000 spectral pixels long, and covers a selectable part of the 0.47-2.45 μm wavelength range at resolving powers of either R≍4000, 10000, or 20000. All 32,000 spectra are imaged onto eight HAWAII4RG detectors using a multiplexing scheme that divides the input field into four sub-fields, each imaged onto one image slicer that in turn re-arranges a single sub-field into two long exit slits feeding one spectrograph each. In total we require eight spectrographs, each with one HAWAII4RG detector. A system of articulated and exchangeable fold-mirrors and VPH gratings allows one to select different spectral resolving powers and wavelength ranges of interest while keeping a fixed geometry between the spectrograph collimator and camera avoiding the need for an articulated grating and camera. In this paper we describe both the field splitting and image slicing optics as well as the optics that will be used to select both spectral resolving power and wavelength range.

Splitting of quantum information in travelling wave fields using only linear optical elements

Energy Technology Data Exchange (ETDEWEB)

Cardoso, W B; De Almeida, N G; Avelar, A T; Baseia, B [Instituto de Fisica, Universidade Federal de Goias, 74.001-970, Goiania-GO (Brazil)

2011-02-28

In this paper we present a feasible post-selection scheme to split quantum information in the realm of travelling waves with success probability of 50%. Taking advantage of this scheme we have also proposed the generation of a class of W states useful for perfect teleportation and superdense coding. The scheme employs only linear optical elements as beam splitters (BS) and phase shifters, plus two photon counters and a source of two spontaneous parametric down-conversion photons. It is shown that splitting of quantum information with high fidelity is possible, even when using inefficient detectors and photoabsorption BS.

Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals

International Nuclear Information System (INIS)

Yang Xuefeng; Wang Zhengxiong

2012-01-01

Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.

Realization of a free-space 2 × 4 90° optical hybrid based on the birefringence and electro-optic effects of crystals

International Nuclear Information System (INIS)

Wan, Lingyu; Zhou, Yu; Liu, Liren; Sun, Jianfeng

2013-01-01

A free-space 2 × 4 90° optical hybrid with electro-optic modulation is presented. The hybrid principally consists of two pairs of electro-optic crystal plates coated with gold electrodes and a polarization analyzer. The optical hybrid uses the birefringence effect of a crystal to split and combine a signal beam and a local oscillator beam, uses the electro-optic effect to introduce a phase modulation and produce a phase shift, and outputs four-channel signal/local oscillator mixed beams whose phase difference can be adjusted continuously. A LiNbO 3 crystal is used to design and manufacture the space optical hybrid, and an experimental system is used to verify its performance. The results show that the output phase of the hybrid is continuously adjustable, enabling the hybrid to function perfectly as a 2 × 4 90° space optical hybrid under an appropriate electric field, and that the phase error can be compensated for by an electric field adjustment. (paper)

Observation of Rashba zero-field spin splitting in a strained germanium 2D hole gas

International Nuclear Information System (INIS)

Morrison, C.; Rhead, S. D.; Foronda, J.; Leadley, D. R.; Myronov, M.; Wiśniewski, P.

2014-01-01

We report the observation, through Shubnikov-de Haas oscillations in the magnetoresistance, of spin splitting caused by the Rashba spin-orbit interaction in a strained Ge quantum well epitaxially grown on a standard Si(001) substrate. The Shubnikov-de Haas oscillations display a beating pattern due to the spin split Landau levels. The spin-orbit parameter and Rashba spin-splitting energy are found to be 1.0 × 10 −28   eVm 3 and 1.4 meV, respectively. This energy is comparable to 2D electron gases in III-V semiconductors, but substantially larger than in Si, and illustrates the suitability of Ge for modulated hole spin transport devices.

Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

Directory of Open Access Journals (Sweden)

Amanda García-García

2016-06-01

Full Text Available Single-wall carbon nanotubes (SWCNT are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules.

Polarization Insensitivity in Double-Split Ring and Triple-Split Ring Terahertz Resonators

International Nuclear Information System (INIS)

Wu Qian-Nan; Lan Feng; Tang Xiao-Pin; Yang Zi-Qiang

2015-01-01

A modified double-split ring resonator and a modified triple-split ring resonator, which offer polarization-insensitive performance, are investigated, designed and fabricated. By displacing the two gaps of the conventional double-split ring resonator away from the center, the second resonant frequency for the 0° polarized wave and the resonant frequency for the 90° polarized wave become increasingly close to each other until they are finally identical. Theoretical and experimental results show that the modified double-split ring resonator and the modified triple-split ring resonator are insensitive to different polarized waves and show strong resonant frequency dips near 433 and 444 GHz, respectively. The results of this work suggest new opportunities for the investigation and design of polarization-dependent terahertz devices based on split ring resonators. (paper)

Flood field uniformity testing - effects of crystal hydration

International Nuclear Information System (INIS)

Dimcheva, M.; Sergieva, S.; Doldurova, M.; Jovanovska, A.

2012-01-01

The most basic and sensitive routine quality control (QC) of gamma camera is that of intrinsic flood-field uniformity. The routine QC test must be assessed daily and any nonuniformity must be eliminated before patient testing to eliminate artifacts and false positive or false-negative patient results. The purpose of this study was to compare uniformity analysis results for scintillation crystal hydration with symmetric and asymmetric energy window on the Siemens Symbia T2 SPECTCT camera. Integral and differential uniformity analysis was performed by placing a point source 99m Tc in front of the detector with removed collimator to measure the effect of correction matrix, a count rate and activity volume on intrinsic uniformity. A 15% energy window set symmetrically over the 99m Tc photo peak is equivalent to 140±10% keV or a window spanning 126-154 keV. The results, received from Detector 2 gave the following uniformity parameter values: Both asymmetric energy window images show clearly multiple focal spots due to crystal hydration: discrete hot spots in the asymmetric low window image and discrete cold spots in the asymmetric high window image. The above results are not seen yet on the symmetric window image. We had replaced Detector 2 in order to avoid spots become visible in flood images obtained with the clinical energy window. The uniformity of a gamma camera is maybe the most important parameter that expresses the quality of the camera's performance. Non uniform areas in the field of view can result in misdiagnosed patients and low quality of clinical services. (authors)

Zeeman splitting of surface-scattered neutrons

International Nuclear Information System (INIS)

Felcher, G.P.; Adenwalla, S.; De Haan, V.O.; Van Well, A.A.

1995-01-01

If a beam of slow neutrons impinges on a solid at grazing incidence, the neutrons reflected can be used to probe the composition and magnetization of the solid near its surface. In this process, the incident and reflected neutrons generally have identical kinetic energies. Here we report the results of an experiment in which subtle inelastic scattering processes are revealed as relatively large deviations in scattering angle. The neutrons are scattered from a ferromagnetic surface in the presence of a strong ambient magnetic field, and exhibit a small but significant variation in kinetic energy as a function of the reflection angle. This effect is attributable to the Zeeman splitting of the energies of the neutron spin states due to the ambient magnetic field: some neutrons flip their spins upon reflection from the magnetized surface, thereby exchanging kinetic energy for magnetic potential energy. The subtle effects of Zeeman splitting are amplified by the extreme sensitivity of grazing-angle neutron scattering, and might also provide a useful spectroscopic tool if significant practical obstacles (such as low interaction cross-sections) can be overcome. (author)

Pressure-induced effects on the spectroscopic properties of Nd{sup 3+} in MgO:LiNbO{sub 3} single crystal. A crystal field approach

Energy Technology Data Exchange (ETDEWEB)

Muñoz Santiuste, J.E., E-mail: jems@fis.uc3m.es [Departamento de Física, Escuela Politécnica Superior, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28913 Leganés, Madrid (Spain); MALTA Consolider Team (Spain); Lavín, V.; Rodríguez-Mendoza, U.R. [MALTA Consolider Team (Spain); Departamento de Física, INM and IUdEA, Universidad de La Laguna, Apdo. 456. E-38200 San Cristóbal de La Laguna, Santa Cruz de Tenerife (Spain); Tardio, M.M.; Ramírez-Jiménez, R. [Departamento de Física, Escuela Politécnica Superior, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28913 Leganés, Madrid (Spain)

2017-04-15

The effects of pressure on the Nd{sup 3+}-doped MgO:LiNbO{sub 3} single crystal have been studied by luminescence spectroscopy at low temperature and high pressures from ambient conditions up to 33 GPa. Specifically, the pressure-induced evolution of the emission spectra, corresponding to the {sup 4}F{sub 3/2}→{sup 4}I{sub 9/2},{sup 4}I{sub 11/2} transitions, and the excitation spectra, corresponding to the {sup 4}I{sub 9/2}→{sup 4}F{sub 5/2}+{sup 2}H{sub 9/2}, and {sup 4}I{sub 9/2}→{sup 4}F{sub 7/2}+{sup 4}S{sub 3/2} transitions, show a gradual red-shift that follows a linear pressure dependence and a decrease in the intensity of the spectra with increasing pressure. The initial effect of increasing pressure on the MgO:LiNbO{sub 3} crystal is the modification of the relative amount of the several centers in the sample. At pressures around 20 GPa the characteristic multicenter Nd{sup 3+} structure eventually disappears indicating that all the centers have very similar environments near this pressure. At higher pressures, observed changes seem to have a different origin. The evolution of Nd{sup 3+} luminescence is studied in the frame of crystal-field theory in order to evaluate its capability of monitoring the pressure-induced structural changes. Crystal-field analysis, under approximated C{sub 3v} symmetry, shows a smooth increase of the overall crystal-field strength on the luminescent ion, which can be related to the volume reduction as pressure increases. Crystal-field parameters also show a general monotonic behavior with pressure that indicates a structural modification of the local structure that, maintaining the trigonal symmetry around the impurity ion, evolves towards a lower axial character. No evidences of a phase transition have been observed in the studied pressure range.

Magnetic ordering in single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta

CERN Document Server

Uma, S; Gmelin, E; Rangarajan, G; Skanthakumar, S; Lynn, J W; Walter, R; Lorenz, T; Büchner, B; Walker, E; Erb, A

1998-01-01

Heat capacity measurements on pure but twinned single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta reveal a sharp peak at T sub N sup P sup sub T =16.6 K, which according to thermal expansion, neutron diffraction, and magnetic susceptibility measurements originates from an antiferromagnetic ordering of the Pr-ion moments. A modest coupling to the Cu(2) spin system is observed. Below T sub N sup P sup sub T a first-order transition in the magnetic structure of the Pr spin system (at 13.4 K in warming; approx. 11 K in cooling) is found. Field-dependent heat capacity data show anisotropic temperature dependences of the c sub p -peaks and recover a Schottky-like anomaly due to the crystal-field-split ground state of the Pr sup 3 sup +. (author). Letter-to-the-editor

Bad splits in bilateral sagittal split osteotomy: systematic review of fracture patterns.

Science.gov (United States)

Steenen, S A; Becking, A G

2016-07-01

An unfavourable and unanticipated pattern of the mandibular sagittal split osteotomy is generally referred to as a 'bad split'. Few restorative techniques to manage the situation have been described. In this article, a classification of reported bad split pattern types is proposed and appropriate salvage procedures to manage the different types of undesired fracture are presented. A systematic review was undertaken, yielding a total of 33 studies published between 1971 and 2015. These reported a total of 458 cases of bad splits among 19,527 sagittal ramus osteotomies in 10,271 patients. The total reported incidence of bad split was 2.3% of sagittal splits. The most frequently encountered were buccal plate fractures of the proximal segment (types 1A-F) and lingual fractures of the distal segment (types 2A and 2B). Coronoid fractures (type 3) and condylar neck fractures (type 4) have seldom been reported. The various types of bad split may require different salvage approaches. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Behaviour of Er/sup 3 +/ ion in tetragonal crystalline field

Energy Technology Data Exchange (ETDEWEB)

Kumar, V; Dass, N; Chandra, K [Roorkee Univ. (India). Dept. of Physics

1976-12-01

Crystal field parameters for ErGaG and Er/sup 3 +/ YAlG are used to compute the temperature dependence of Schottky specific heat, paramagnetic susceptibility, magnetic anisotropy, sup(..mu..)eff and quadrupole splitting in the range 10-400 K. The hyperfine interaction parameters A and B for /sup 16/ /sup 166/Er and /sup 167/Er in both the systems are also obtained and in turn used to estimate the nuclear specific heat contribution. The studied parameters compare well with the available experimental results.

Lattice distortion under an electric field in BaTiO3 piezoelectric single crystal

International Nuclear Information System (INIS)

Tazaki, Ryoko; Fu Desheng; Daimon, Masahiro; Koshihara, Shin-ya; Itoh, Mitsuru

2009-01-01

Lattice distortions under an electric field in a mono-domain of BaTiO 3 ferroelectric crystal have been detected with synchrotron x-ray radiation. The variation of the lattice constant with an electric field observed with high angle diffraction shows a linear response nature of the piezoelectric effect. When an electric field is applied along the spontaneous polarization direction, the c-axis of the lattice elongates and the a-axis of the lattice shrinks at a rate of d 33 = 149 ± 54 pm V -1 and d 31 = -82 ± 61 pm V -1 ; these represent the longitudinal and transverse piezoelectric coefficients of BaTiO 3 crystal, respectively. These results give an insight into the intrinsic piezoelectric response on the lattice scale in BaTiO 3 that has been widely used to explore high performance lead-free piezoelectric alloys.

Electron refrigeration in hybrid structures with spin-split superconductors

Science.gov (United States)

Rouco, M.; Heikkilä, T. T.; Bergeret, F. S.

2018-01-01

Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a nonlinear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel coupling spin-split superconductors with regular ones allows for a highly efficient refrigeration of the latter.

Pulsed zero field NMR of solids and liquid crystals

International Nuclear Information System (INIS)

Thayer, A.M.

1987-02-01

This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs

Magnetic properties and crystal field effects in TlLnX2 compounds (X=S, Se, Te)

International Nuclear Information System (INIS)

Duczmal, M.; Pawlak, L.

1997-01-01

Ternary thallium lanthanide chalcogenides TlLnX 2 (X=S, Se or Te) crystallize in the α-NaFeO 2 type of structure (R anti 3m). Each kind of the metal ions, surrounded by the distorted chalcogenide octahedra, forms separate layers. The TlX 6 octahedra are strongly elongated and the LnX 6 octahedra slightly shrunk along the threefold axis. The deformations of the coordination polyhedra and the cell volumes change regularly with the lanthanide ionic radii. The difference between the experimental and the calculated M-X distances increases on going from sulphides to tellurides, as a result of the growing covalent character of the bonds. The crystal field parameters were estimated from the high field magnetization (0-14 T) assuming trigonal distortion of the octahedral symmetry of LnX 6 polyhedra. The second-order crystal field parameters were found to correlate with the deformation of the lanthanide ions' environments. No magnetic transition was observed down to 4.2 K. (orig.)

Performance of a beam-multiplexing diamond crystal monochromator at the Linac Coherent Light Source

DEFF Research Database (Denmark)

Zhu, Diling; Feng, Yiping; Stoupin, Stanislav

2014-01-01

A double-crystal diamond monochromator was recently implemented at the Linac Coherent Light Source. It enables splitting pulses generated by the free electron laser in the hard x-ray regime and thus allows the simultaneous operations of two instruments. Both monochromator crystals are High-Pressu...

Photonic Crystal Polarizing and Non-Polarizing Beam Splitters

International Nuclear Information System (INIS)

Chun-Ying, Guan; Jin-Hui, Shi; Li-Boo, Yuan

2008-01-01

A polarizing beam splitter (PBS) and a non-polarizing beam splitter (NPBS) based on a photonic crystal (PC) directional coupler are demonstrated. The photonic crystal directional coupler consists of a hexagonal lattice of dielectric pillars in air and has a complete photonic band gap. The photonic band structure and the band gap map are calculated using the plane wave expansion (PWE) method. The splitting properties of the splitter are investigated numerically using the finite difference time domain (FDTD) method

Simulations of singularity dynamics in liquid crystal flows: A C finite element approach

International Nuclear Information System (INIS)

Lin Ping; Liu Chun

2006-01-01

In this paper, we present a C finite element method for a 2a hydrodynamic liquid crystal model which is simpler than existing C 1 element methods and mixed element formulation. The energy law is formally justified and the energy decay is used as a validation tool for our numerical computation. A splitting method combined with only a few fixed point iteration for the penalty term of the director field is applied to reduce the size of the stiffness matrix and to keep the stiffness matrix time-independent. The latter avoids solving a linear system at every time step and largely reduces the computational time, especially when direct linear system solvers are used. Our approach is verified by comparing its computational results with those obtained by C 1 elements and by mixed formulation. Through numerical experiments of a few other splittings and explicit-implicit strategies, we recommend a fast and reliable algorithm for this model. A number of examples are computed to demonstrate the algorithm

Systematic theoretical investigation of the zero-field splitting in Gd(III) complexes: Wave function and density functional approaches

Energy Technology Data Exchange (ETDEWEB)

Khan, Shehryar, E-mail: sherkhan@fysik.su.se; Odelius, Michael, E-mail: odelius@fysik.su.se [Department of Physics, Stockholm University, AlbaNova University Center, S-106 91 Stockholm (Sweden); Kubica-Misztal, Aleksandra [Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL-30-059 Krakow (Poland); Kruk, Danuta [Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, Sloneczna 54, Olsztyn PL-10710 (Poland); Kowalewski, Jozef [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden)

2015-01-21

The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H{sub 2}O){sup −}, Gd(III)DTPA(H{sub 2}O){sup 2−}, and Gd(III)(H{sub 2}O){sub 8}{sup 3+} in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude.

Symmetry-adaptation and selection rules for effective crystal field Hamiltonians

International Nuclear Information System (INIS)

Tuszynski, J.A.

1986-01-01

The intention of this paper is to systematically derive an effective Hamiltonian in the presence of crystal fields in such a way as to incorporate relativistic effects and higher order perturbation corrections including configuration mixing. This Hamiltonian will then be conveniently represented as a symmetry-adapted series of one- and two-body double tensor operators whose matrix elements will be analyzed for selection rules. 16 references, 4 tables

Study of photon–magnon coupling in a YIG-film split-ring resonant system

Energy Technology Data Exchange (ETDEWEB)

Bhoi, B.; Aiyar, R. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); CRNTS, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Cliff, T.; Maksymov, I. S.; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au [School of Physics M013, University of Western Australia, Crawley 6009 (Australia); Venkataramani, N. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Prasad, S. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Stamps, R. L. [School of Physics M013, University of Western Australia, Crawley 6009 (Australia); SUPA, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2014-12-28

By using the stripline Microwave Vector–Network Analyser Ferromagnetic Resonance and Time Domain spectroscopy techniques, we study a strong coupling regime of magnons to microwave photons in the planar geometry of a lithographically formed split-ring resonator (SRR) loaded by a single-crystal epitaxial yttrium–iron–garnet (YIG) film. Strong anti-crossing of the photon modes of SRR and of the magnon modes of the YIG film is observed in the applied-magnetic-field resolved measurements. The coupling strength extracted from the experimental data reaches 9% at 3 GHz. Theoretically, we propose an equivalent circuit model of the SRR loaded by a magnetic film. This model follows from the results of our numerical simulations of the microwave field structure of the SRR and of the magnetisation dynamics in the YIG film driven by the microwave currents in the SRR. The results obtained with the equivalent-circuit model are in good agreement with the experiment. This model provides a simple physical explanation of the process of mode anti-crossing. Our findings are important for future applications in microwave quantum photonic devices as well as in nonlinear and magnetically tuneable metamaterials exploiting the strong coupling of magnons to microwave photons.

Modelling of uranium/plutonium splitting in purex process

International Nuclear Information System (INIS)

Boullis, B.; Baron, P.

1987-06-01

A mathematical model simulating the highly complex uranium/plutonium splitting operation in PUREX process has been achieved by the french ''Commissariat a l'Energie Atomique''. The development of such a model, which includes transfer and redox reactions kinetics for all the species involved, required an important experimental work in the field of basis chemical data acquisition. The model has been successfully validated by comparison of its results with those of specific trials achieved (at laboratory scale), and with the available results of the french reprocessing units operation. It has then been used for the design of french new plants splitting operations

An Examination Of Fracture Splitting Parameters Of Crackable Connecting Rods

Directory of Open Access Journals (Sweden)

Zafer Özdemir

2000-06-01

Full Text Available Fracture splitting method is an innovative processing technique in the field of automobile engine connecting rod (con/rod manufacturing. Compared with traditional method, this technique has remarkable advantages. Manufacturing procedures, equipment and tools investment can be decreased and energy consumption reduced remarkably. Furthermore, product quality and bearing capability can also be improved. It provides a high quality, high accuracy and low cost route for producing connecting rods (con/rods. With the many advantages mentioned above, this method has attracted manufacturers attention and has been utilized in many types of con/rod manufacturing. In this article, the method and the advantages it provides, such as materials, notches for fracture splitting, fracture splitting conditions and fracture splitting equipment are discussed in detail. The paper describes an analysis of examination of fracture splitting parameters and optik-SEM fractography of C70S6 crackable connectıng rod. Force and velocity parameters are investigated. That uniform impact force distrubition starting from the starting notch causes brittle and cleavage failure mode is obtained as a result. This induces to decrease the toughness.

Millimeter wave detection via Autler-Townes splitting in rubidium Rydberg atoms

Energy Technology Data Exchange (ETDEWEB)

Gordon, Joshua A., E-mail: josh.gordon@nist.gov; Holloway, Christopher L. [National Institute of Standards and Technology (NIST), Electromagnetics Division, U.S. Department of Commerce, Boulder Laboratories, Boulder, Colorado 80305 (United States); Schwarzkopf, Andrew; Anderson, Dave A.; Miller, Stephanie; Thaicharoen, Nithiwadee; Raithel, Georg [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2014-07-14

In this paper, we demonstrate the detection of millimeter waves via Autler-Townes splitting in {sup 85}Rb Rydberg atoms. This method may provide an independent, atom-based, SI-traceable method for measuring mm-wave electric fields, which addresses a gap in current calibration techniques in the mm-wave regime. The electric-field amplitude within a rubidium vapor cell in the WR-10 wave guide band is measured for frequencies of 93.71 GHz and 104.77 GHz. Relevant aspects of Autler-Townes splitting originating from a four-level electromagnetically induced transparency scheme are discussed. We measured the E-field generated by an open-ended waveguide using this technique. Experimental results are compared to a full-wave finite element simulation.

Single crystal growth and anisotropic magnetic properties of HoAl2Ge2

Science.gov (United States)

Matin, Md.; Mondal, Rajib; Thamizhavel, A.; Provino, A.; Manfrinetti, P.; Dhar, S. K.

2018-05-01

We have grown a single crystal of HoAl2Ge2, which crystallizes in the hexagonal CaAl2Si2 type structure with Ho ions in the trigonal coordination in the ab plane. The data obtained from the bulk measurement techniques of magnetization, heat capacity and transport reveal that HoAl2Ge2 orders antiferromagnetically at TN ˜6.5 K. The susceptibility below TN and isothermal magnetization at 2 K indicate the ab plane as the easy plane of magnetization. Heat capacity data reveal a prominent Schottky anomaly with a broad peak centered around 25 K, suggesting a relatively low crystal electric field (CEF) splitting. The electrical resistivity reveals the occurrence of a superzone gap below TN. The point charge model of the CEF is applied to the magnetization and the heat capacity data. While a good fit to the paramagnetic susceptibility is obtained, the CEF parameters do not provide a satisfactory fit to the isothermal magnetization at 2 K and the Schottky anomaly.

Market Structure and Stock Splits

OpenAIRE

David Michayluk; Paul Kofman

2001-01-01

Enhanced liquidity is one possible motivation for stock splits but empirical research frequently documents declines in liquidity following stock splits. Despite almost thirty years of inquiry, little is known about all the changes in a stock's trading activity following a stock split. We examine how liquidity measures change around more than 2,500 stock splits and find a pervasive decline in most measures. Large stock splits exhibit a more severe liquidity decline than small stock splits, esp...

Fast Geodesic Active Fields for Image Registration Based on Splitting and Augmented Lagrangian Approaches.

Science.gov (United States)

Zosso, Dominique; Bresson, Xavier; Thiran, Jean-Philippe

2014-02-01

In this paper, we present an efficient numerical scheme for the recently introduced geodesic active fields (GAF) framework for geometric image registration. This framework considers the registration task as a weighted minimal surface problem. Hence, the data-term and the regularization-term are combined through multiplication in a single, parametrization invariant and geometric cost functional. The multiplicative coupling provides an intrinsic, spatially varying and data-dependent tuning of the regularization strength, and the parametrization invariance allows working with images of nonflat geometry, generally defined on any smoothly parametrizable manifold. The resulting energy-minimizing flow, however, has poor numerical properties. Here, we provide an efficient numerical scheme that uses a splitting approach; data and regularity terms are optimized over two distinct deformation fields that are constrained to be equal via an augmented Lagrangian approach. Our approach is more flexible than standard Gaussian regularization, since one can interpolate freely between isotropic Gaussian and anisotropic TV-like smoothing. In this paper, we compare the geodesic active fields method with the popular Demons method and three more recent state-of-the-art algorithms: NL-optical flow, MRF image registration, and landmark-enhanced large displacement optical flow. Thus, we can show the advantages of the proposed FastGAF method. It compares favorably against Demons, both in terms of registration speed and quality. Over the range of example applications, it also consistently produces results not far from more dedicated state-of-the-art methods, illustrating the flexibility of the proposed framework.

Electroweak splitting functions and high energy showering

Science.gov (United States)

Chen, Junmou; Han, Tao; Tweedie, Brock

2017-11-01

We derive the electroweak (EW) collinear splitting functions for the Standard Model, including the massive fermions, gauge bosons and the Higgs boson. We first present the splitting functions in the limit of unbroken SU(2) L × U(1) Y and discuss their general features in the collinear and soft-collinear regimes. These are the leading contributions at a splitting scale ( k T ) far above the EW scale ( v). We then systematically incorporate EW symmetry breaking (EWSB), which leads to the emergence of additional "ultra-collinear" splitting phenomena and naive violations of the Goldstone-boson Equivalence Theorem. We suggest a particularly convenient choice of non-covariant gauge (dubbed "Goldstone Equivalence Gauge") that disentangles the effects of Goldstone bosons and gauge fields in the presence of EWSB, and allows trivial book-keeping of leading power corrections in v/ k T . We implement a comprehensive, practical EW showering scheme based on these splitting functions using a Sudakov evolution formalism. Novel features in the implementation include a complete accounting of ultra-collinear effects, matching between shower and decay, kinematic back-reaction corrections in multi-stage showers, and mixed-state evolution of neutral bosons ( γ/ Z/ h) using density-matrices. We employ the EW showering formalism to study a number of important physical processes at O (1-10 TeV) energies. They include (a) electroweak partons in the initial state as the basis for vector-boson-fusion; (b) the emergence of "weak jets" such as those initiated by transverse gauge bosons, with individual splitting probabilities as large as O (35%); (c) EW showers initiated by top quarks, including Higgs bosons in the final state; (d) the occurrence of O (1) interference effects within EW showers involving the neutral bosons; and (e) EW corrections to new physics processes, as illustrated by production of a heavy vector boson ( W ') and the subsequent showering of its decay products.

Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

Energy Technology Data Exchange (ETDEWEB)

Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

2017-03-31

The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

Formation of temperature fields in doped anisotropic crystals under spatially inhomogeneous light beams passing through them

Energy Technology Data Exchange (ETDEWEB)

Zaitseva, E. V.; Markelov, A. S.; Trushin, V. N., E-mail: trushin@phys.unn.ru; Chuprunov, E. V. [Nizhni Novgorod State University (Russian Federation)

2013-12-15

The features of formation of thermal fields in potassium dihydrophosphate crystal doped with potassium permanganate under a 532-nm laser beam passing through it have been investigated. Data on the influence of birefringence on the temperature distribution in an anisotropic crystal whose surface is illuminated by a spatially modulated light beam are presented.

Raphide crystal structure in agave tequilana determined by x-ray originating from synchrotron radiation

International Nuclear Information System (INIS)

Tadokoro, Makoto; Ozawa, Yoshiki; Mitsumi, Minoru; Toriumi, Kohshiro; Ogura, Tetsuya

2005-01-01

The first single crystal structure of small natural raphides in an agave plant is completely determined using an intense X-ray originating from a synchrotron radiation. The SEM image shows that the tip of the crystal is approximately hundreds of nanometer in width sharply grow to stick to the tissue of herbivorous vermin. Furthermore, the crystal develops cracks that propagate at an inclination of approximately 45deg towards the direction of crystal growth such that the crystal easily splits into small pieces in the tissue. (author)

A study on Sorghum bicolor (L. Moench response to split application of herbicides

Directory of Open Access Journals (Sweden)

Kaczmarek Sylwia

2017-06-01

Full Text Available Field experiments to evaluate the split application of mesotrione + s-metolachlor, mesotrione + terbuthylazine, dicamba + prosulfuron, terbuthylazine + mesotrione + s-metolachlor, and sulcotrione in the cultivation of sorghum var. Rona 1 were carried out in 2012 and 2013. The field tests were conducted at the field experimental station in Winna Góra, Poznań, Poland. Treatments with the herbicides were performed directly after sowing (PE and at leaf stage 1–2 (AE1 or at leaf stage 3–4 (AE2 of sorghum. The treatments were carried out in a laid randomized block design with 4 replications. The results showed that the tested herbicides applied at split doses were effective in weed control. After the herbicide application weed density and weed biomass were significantly reduced compared to the infested control. The best results were achieved after the application of mesotrione tank mixture with s-metolachlor and terbuthylazine. Application of split doses of herbicides was also correlated with the density, biomass, and height of sorghum.

Photoelectrochemical water splitting standards, experimental methods, and protocols

CERN Document Server

Chen, Zhebo; Miller, Eric

2014-01-01

This book outlines many of the techniques involved in materials development and characterization for photoelectrochemical (PEC) - for example, proper metrics for describing material performance, how to assemble testing cells and prepare materials for assessment of their properties, and how to perform the experimental measurements needed to achieve reliable results towards better scientific understanding. For each technique, proper procedure, benefits, limitations, and data interpretation are discussed. Consolidating this information in a short, accessible, and easy to read reference guide will allow researchers to more rapidly immerse themselves into PEC research and also better compare their results against those of other researchers to better advance materials development. This book serves as a "how-to" guide for researchers engaged in or interested in engaging in the field of photoelectrochemical (PEC) water splitting. PEC water splitting is a rapidly growing field of research in which the goal is to deve...

Normal-Mode Splitting in a Weakly Coupled Optomechanical System

Science.gov (United States)

Rossi, Massimiliano; Kralj, Nenad; Zippilli, Stefano; Natali, Riccardo; Borrielli, Antonio; Pandraud, Gregory; Serra, Enrico; Di Giuseppe, Giovanni; Vitali, David

2018-02-01

Normal-mode splitting is the most evident signature of strong coupling between two interacting subsystems. It occurs when two subsystems exchange energy between themselves faster than they dissipate it to the environment. Here we experimentally show that a weakly coupled optomechanical system at room temperature can manifest normal-mode splitting when the pump field fluctuations are antisquashed by a phase-sensitive feedback loop operating close to its instability threshold. Under these conditions the optical cavity exhibits an effectively reduced decay rate, so that the system is effectively promoted to the strong coupling regime.

Crystal field parameters with Wannier functions: application to rare-earth aluminates

Czech Academy of Sciences Publication Activity Database

Novák, Pavel; Knížek, Karel; Kuneš, Jan

2013-01-01

Roč. 87, č. 20 (2013), "205139-1"-"205139-7" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/0713 Institutional support: RVO:68378271 Keywords : crystal-field * rare earths * Wannier functions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013 http://link.aps.org/doi/10.1103/PhysRevB.87.205139

Regularization of a λφ4 type tensor model, using point-splitting

International Nuclear Information System (INIS)

Moura Melo, W.A.; Helayel-Neto, J.A.

1997-01-01

The idea of using point-splitting to avoid field products in the same point was first introduced by Dirac. This splitting would be applied for example, redefining the fields present in a small vertex, at different points. More recently, Osland and Wu, in a series of papers presented used the idea as a regularization method. An generalized Lagrangian was obtained for the Qed, with interaction terms not presenting field products at the same point, exhibiting however non-locality problems. Nevertheless this fact, the authors obtained satisfactory results with this formulation, such as the Higgs mass (190 GeV) and the divergence free top quark (120 GeV). This work intends to obtain a generalized Lagrangian, modifying the original theory to avoid that the interaction terms present field products at the same point

Near-field-optical-microscopy studies of micro-modifications caused by femtosecond laser irradiation in lithium niobate crystals

International Nuclear Information System (INIS)

Lamela, J.; Jaque, D.; Rodenas, A.; Jaque, F.; Torchia, G.A.; Vazquez, J.R.; Mendez, C.; Roso, L.

2008-01-01

Near-field-optical-microscopy has been used to study the micro-modifications caused by femtosecond laser pulses focused at the surface and in the volume of lithium niobate crystals. We have found experimental evidence of the existence, close to femtosecond ablation craters, of periodic modifications in the surface reflectivity. In addition, the potential application of near-field-optical microscopy for the spatial location of permanent modifications caused by femtosecond pulses focused inside lithium niobate crystals has been also demonstrated. (orig.)

Observation of field-induced long-range order in disordered Sr14Cu24O41

International Nuclear Information System (INIS)

Ohsugi, S.; Matsumoto, S.; Kitaoka, Y.; Matsuda, M.; Uehara, M.; Nagata, T.; Akimitsu, J.

2004-01-01

Field-induced magnetic order in a structural disordered single-crystal Sr 14 Cu 24 O 41 (Sr 14 -B) has been observed in the Cu-nuclear magnetic resonance (NMR) measurements for the ladder sites below 20 K under the magnetic field H∼11 T. For the Zhang Rice (ZR) sites in the chains, the spectrum splits below 20 K due to an appearance of the internal field, whereas that of less disordered Sr 14 -A does not. This gives an evidence of three-dimensional (3D) long-range (LR) ordering in Sr 14 -B below T N ∼20 K under H∼11 T

Bending and splitting of spoof surface acoustic waves through structured rigid surface

Directory of Open Access Journals (Sweden)

Sujun Xie

2018-03-01

Full Text Available In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC, which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect, the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

Crystal field levels of tetravalent actinide ions in actinide dioxides UO2, NpO2 and PuO2

International Nuclear Information System (INIS)

Krupa, J.C.; Gajek, Z.

1991-01-01

Crystal-field parameters resulting from analysis of optical spectroscopy and neutron diffraction data recorded on UO 2 and NpO 2 as well as ab-initio calculated parameters were used to calculate the crystal-field eigenfunctions and eigenvalues for the J ground-state manifold of U 4+ , Np 4+ and Pu 4+ in UO 2 , NpO 2 and PuO 2

Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

Science.gov (United States)

Zhang, Duo; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

2012-05-01

The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission.

Design of single-polarization wavelength splitter based on photonic crystal fiber.

Science.gov (United States)

Zhang, Shanshan; Zhang, Weigang; Geng, Pengcheng; Li, Xiaolan; Ruan, Juan

2011-12-20

A new single-polarization wavelength splitter based on the photonic crystal fiber (PCF) has been proposed. The full-vector finite-element method (FEM) is applied to analyze the single-polarization single-mode guiding properties. Splitting of two different wavelengths is realized by adjusting the structural parameters. The semi-vector three-dimensional beam propagation method is employed to confirm the wavelength splitting characteristics of the PCF. Numerical simulations show that the wavelengths of 1.3 μm and 1.55 μm are split for a fiber length of 10.7 mm with single-polarization guiding in each core. The crosstalk between the two cores is low over appreciable optical bandwidths.

Unit-cell design for two-dimensional phase-field simulation of microstructure evolution in single-crystal Ni-based superalloys during solidification

Directory of Open Access Journals (Sweden)

Dongjia Cao

2017-12-01

Full Text Available Phase-field simulation serves as an effective tool for quantitative characterization of microstructure evolution in single-crystal Ni-based superalloys during solidification nowadays. The classic unit cell is either limited to γ dendrites along crystal orientation or too ideal to cover complex morphologies for γ dendrites. An attempt to design the unit cell for two-dimensional (2-D phase-field simulations of microstructure evolution in single-crystal Ni-based superalloys during solidification was thus performed by using the MICRESS (MICRostructure Evolution Simulation Software in the framework of the multi-phase-field (MPF model, and demonstrated in a commercial TMS-113 superalloy. The coupling to CALPHAD (CALculation of PHAse Diagram thermodynamic database was realized via the TQ interface and the experimental diffusion coefficients were utilized in the simulation. Firstly, the classic unit cell with a single γ dendrite along crystal orientation was employed for the phase-field simulation in order to reproduce the microstructure features. Then, such simple unit cell was extended into the cases with two other different crystal orientations, i.e., and . Thirdly, for crystal orientations, the effect of γ dendritic orientations and unit cell sizes on microstructure and microsegregation was comprehensively studied, from which a new unit cell with multiple γ dendrites was proposed. The phase-field simulation with the newly proposed unit cell was further performed in the TMS-113 superalloy, and the microstructure features including the competitive growth of γ dendrites, microsegregation of different solutes and distribution of γ′ grains, can be nicely reproduced.

Auroral-arc splitting by intrusion of a new convection channel

Directory of Open Access Journals (Sweden)

H. U. Frey

Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

Auroral-arc splitting by intrusion of a new convection channel

Directory of Open Access Journals (Sweden)

H. U. Frey

1996-12-01

Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

Spin-splitting in p-type Ge devices

Energy Technology Data Exchange (ETDEWEB)

Holmes, S. N., E-mail: s.holmes@crl.toshiba.co.uk; Newton, P. J.; Llandro, J.; Mansell, R.; Barnes, C. H. W. [Cavendish Laboratory, Department of Physics, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Morrison, C.; Myronov, M. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2016-08-28

Compressively strained Ge quantum well devices have a spin-splitting in applied magnetic field that is entirely consistent with a Zeeman effect in the heavy hole valence band. The spin orientation is determined by the biaxial strain in the quantum well with the relaxed SiGe buffer layers and is quantized in the growth direction perpendicular to the conducting channel. The measured spin-splitting in the resistivity ρ{sub xx} agrees with the predictions of the Zeeman Hamiltonian where the Shubnikov-deHaas effect exhibits a loss of even filling factor minima in the resistivity ρ{sub xx} with hole depletion from a gate field, increasing disorder or increasing temperature. There is no measurable Rashba spin-orbit coupling irrespective of the structural inversion asymmetry of the confining potential in low p-doped or undoped Ge quantum wells from a density of 6 × 10{sup 10} cm{sup −2} in depletion mode to 1.7 × 10{sup 11} cm{sup −2} in enhancement.

Ultrasonic splitting of oil-in-water emulsions

DEFF Research Database (Denmark)

Hald, Jens; König, Ralf; Benes, Ewald

1999-01-01

Standing resonant ultrasonic wave fields can be utilized for liquid–liquid separation of the dispersed particles and the fluid caused by the acoustic radiation pressure and the induced particle agglomeration or coagulation/coalescence process. For the splitting of oil-in-water emulsions, the avai......Standing resonant ultrasonic wave fields can be utilized for liquid–liquid separation of the dispersed particles and the fluid caused by the acoustic radiation pressure and the induced particle agglomeration or coagulation/coalescence process. For the splitting of oil-in-water emulsions......, the available piezoelectric composite transducer technology was improved and a dedicated resonator with crossed plane wave sonication geometry has been developed. The resonator chamber is entirely made of aluminium or tempax glass and the PZT piezoceramic transducer delivers an acoustic energy flow density...... of up to 24 W/cm2 into the sonication volume. The chosen resonance frequency is kept stable by automatic frequency control utilizing the maximum true power criterion. Physically and chemically well-defined low and high density pure laboratory and also industrially used cooling-lubricating oil...

Crystal and solution spectroscopy of einsteinium

International Nuclear Information System (INIS)

Carnall, W.T.

1978-01-01

Work on spectra and electronic structure of Es 3+ is reviewed. Laser-excited fluorescence spectroscopy was used to study Es 3+ -doped LaCl 3 crystals; fluorescence transitions and lifetimes were determined. A complete ground-state splitting diagram was also constructed for Es 3+ : LaCl 3 . Some data on excited states of Fm 3+ are also included. 12 figures

Magnetic islands modelled by a phase-field-crystal approach

Science.gov (United States)

Faghihi, Niloufar; Mkhonta, Simiso; Elder, Ken R.; Grant, Martin

2018-03-01

Using a minimal model based on the phase-field-crystal formalism, we study the coupling between the density and magnetization in ferromagnetic solids. Analytical calculations for the square phase in two dimensions are presented and the small deformation properties of the system are examined. Furthermore, numerical simulations are conducted to study the influence of an external magnetic field on various phase transitions, the anisotropic properties of the free energy functional, and the scaling behaviour of the growth of the magnetic domains in a crystalline solid. It is shown that the energy of the system can depend on the direction of the magnetic moments, with respect to the crystalline direction. Furthermore, the growth of the magnetic domains in a crystalline solid is studied and is shown that the growth of domains is in agreement with expected behaviour.

Ground-state splitting of ultrashallow thermal donors with negative central-cell corrections in silicon

Science.gov (United States)

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.

Splitting methods for split feasibility problems with application to Dantzig selectors

International Nuclear Information System (INIS)

He, Hongjin; Xu, Hong-Kun

2017-01-01

The split feasibility problem (SFP), which refers to the task of finding a point that belongs to a given nonempty, closed and convex set, and whose image under a bounded linear operator belongs to another given nonempty, closed and convex set, has promising applicability in modeling a wide range of inverse problems. Motivated by the increasingly data-driven regularization in the areas of signal/image processing and statistical learning, in this paper, we study the regularized split feasibility problem (RSFP), which provides a unified model for treating many real-world problems. By exploiting the split nature of the RSFP, we shall gainfully employ several efficient splitting methods to solve the model under consideration. A remarkable advantage of our methods lies in their easier subproblems in the sense that the resulting subproblems have closed-form representations or can be efficiently solved up to a high precision. As an interesting application, we apply the proposed algorithms for finding Dantzig selectors, in addition to demonstrating the effectiveness of the splitting methods through some computational results on synthetic and real medical data sets. (paper)

Mechano-chemical pathways to H2O and CO2 splitting

Science.gov (United States)

Vedadi, Mohammad H.; Haas, Stephan

2011-10-01

The shock-induced collapse of CO2-filled nanobubbles is investigated using molecular dynamics simulations based on a reactive force field. The energetic nanojet and high-pressure water hammer shock formed during and after collapse of the nanobubble trigger mechano-chemical H2O-CO2 reactions, some of which lead to splitting of water and formation of O2 molecules. The dominant pathways through which splitting of water molecules occur are identified.

A portable high-field pulsed-magnet system for single-crystal x-ray scattering studies

International Nuclear Information System (INIS)

Islam, Zahirul; Lang, Jonathan C.; Ruff, Jacob P. C.; Ross, Kathryn A.; Gaulin, Bruce D.; Nojiri, Hiroyuki; Matsuda, Yasuhiro H.; Qu Zhe

2009-01-01

We present a portable pulsed-magnet system for x-ray studies of materials in high magnetic fields (up to 30 T). The apparatus consists of a split-pair of minicoils cooled on a closed-cycle cryostat, which is used for x-ray diffraction studies with applied field normal to the scattering plane. A second independent closed-cycle cryostat is used for cooling the sample to near liquid helium temperatures. Pulsed magnetic fields (∼1 ms in total duration) are generated by discharging a configurable capacitor bank into the magnet coils. Time-resolved scattering data are collected using a combination of a fast single-photon counting detector, a multichannel scaler, and a high-resolution digital storage oscilloscope. The capabilities of this instrument are used to study a geometrically frustrated system revealing strong magnetostrictive effects in the spin-liquid state.

Split coil made of (RE)BCO pancake coils for IC(B) anisotropy measurements of superconductors

International Nuclear Information System (INIS)

Frolek, L; Pardo, E; Gömöry, F; Šouc, J; Pitel, J

2014-01-01

Measurement of the I c (B) anisotropy is standard characterization of superconducting tapes, wires or cables. This contribution presents a split coil consisting on two superconducting pancake coils in order to generate the magnetic field necessary for this kind of measurement. Both coils were made using (RE)BCO – based second generation (2G) coated conductor tape with cross section 0.1 mm × 12 mm. The individual turns of the tape were insulated by a fiberglass tape without impregnation. These coils have identical inner and outer diameter and number of turns. Their inner and outer diameters are 50 mm and 80 mm, respectively, and they have 62 turns. The length of conductor in each coil is approximately 13 m. The distance between both pancake coils is 22 mm. Individual coils and the complete split coil were characterized in liquid nitrogen bath. Their parameters, like the critical currents, E(I) characteristics and magnetic field of complete split coil, were measured and interpreted. The split coil can be used up to magnetic fields of 210 mT. The length between the potential taps on the sample can be up to 20 mm, while the magnetic field decrease is lower than 1% on this length.

X-ray diffraction from ideal mosaic crystals in external fields of certain types. I. Atomic displacements and the corresponding diffraction patterns

International Nuclear Information System (INIS)

Treushnikov, E.N.

2000-01-01

The problem of the theoretical description of X-ray diffraction from ideal mosaic crystals under the effect of various external fields has been formulated. Electric, magnetic, electromagnetic, and acoustic perturbations are considered. The atomic displacements in crystals under the effect of external fields and the types of the corresponding diffraction patterns are analyzed for various types of perturbations. The crystal classes are determined in which atomic displacements can be recorded experimentally. Diffraction patterns formed under the effect of various external factors are considered on the basis of the derived dependence of the structure factor on the characteristics of an applied force field

Crystal field influence on vibration spectra: anhydrous uranyl chloride and dihydroxodiuranyl chloride tetrahydrate

International Nuclear Information System (INIS)

Perrin, Andre; Caillet, Paul

1976-01-01

Vibrational spectra of anhydrous uranyl chloride UO 2 Cl 2 and so called basic uranyl chloride: dihydroxodiuranyl chloride tetrahydrate /UO 2 (OH) 2 UO 2 /Cl 2 (H 2 O) 4 are reported. Factor group method analysis leads for the first time to complete and comprehensive interpretation of their spectra. Two extreme examples of crystal field influence on vibrational spectra are pointed out: for UO 2 Cl 2 , one is unable to explain spectra without taking into account all the elements of primitive crystalline cell, whilst for dihydroxodiuranyl dichloride tetrahydrate the crystal packing has very little effect on vibrational spectra [fr

Coded Splitting Tree Protocols

DEFF Research Database (Denmark)

Sørensen, Jesper Hemming; Stefanovic, Cedomir; Popovski, Petar

2013-01-01

This paper presents a novel approach to multiple access control called coded splitting tree protocol. The approach builds on the known tree splitting protocols, code structure and successive interference cancellation (SIC). Several instances of the tree splitting protocol are initiated, each...... instance is terminated prematurely and subsequently iterated. The combined set of leaves from all the tree instances can then be viewed as a graph code, which is decodable using belief propagation. The main design problem is determining the order of splitting, which enables successful decoding as early...

Near-field imaging of out-of-plane light scattering in photonic crystal slabs

DEFF Research Database (Denmark)

Volkov, Valentyn; Bozhevolnyi, Sergey; Taillaert, Dirk

2003-01-01

A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PC) slabs, which combine slab waveguides with in-plane PCs consisting of one- and two-dimensional gratings. The efficient out...

Effect of the Cu and Ni content on the crystallization temperature and crystallization mechanism of La–Al–Cu(Ni metallic glasses

Directory of Open Access Journals (Sweden)

Peiyou Li

2016-02-01

Full Text Available The effect of the Cu and Ni content on the crystallization mechanism and the crystallization temperatures of La–Al–Cu(Ni metallic glasses (MGs was studied by differential scanning calorimetry (DSC. The experimental results have shown that the DSC curves obtained for the La–Al–Cu and La–Al–Ni MGs exhibit two and three crystallization temperatures, respectively. The crystallization temperatures of the La–Al–Cu and La–Al–Ni MGs result from the merging and splitting of thermal events related to the corresponding eutectic atomic pairs in the La72Cu28 and La81.6Al18.4 MGs, and La72Ni28 and La81.6Al18.4 MGs, respectively. In addition, Al- and Ni-containing clusters with weak or strong atomic interaction in the Al–Ni atomic pairs strongly affect the crystallization mechanism and thus the crystallization temperature of La–Al–Ni MGs. This study provides a novel understanding of the relation between the crystallization temperature and the underlying crystallization mechanisms in La–Al–Cu(Ni MGs.

Crystal field effect in the uranium compounds - model calculations for CsUF6, Cs2UCl6 and UCl4

International Nuclear Information System (INIS)

Gajek, Z.; Mulak, J.

1987-01-01

A practical crystal field model allowing one to estimate the crystal field parameters from first principles is presented and applied to the actinide compounds. The model results directly from the renormalization (and reduction) procedure of the true Schroedinger equation for an effective Hamiltonian acting on the 5f spin-orbitals only. In practice this approach becomes convergent with the ab initio model of Newman. Three ionic uranium compounds: CsUF 6 , Cs 2 UCl 6 and UCl 4 have served as examples of the application. The results obtained, particularly for the first two compounds, are in good agreement with the experimental data. The contributions of different mechanisms responsible for the crystal field effect are discussed. (author)

Angular and magnetic field dependences of critical current in irradiated YBaCuO single crystals

International Nuclear Information System (INIS)

Petrusenko, Yu.

2010-01-01

The investigation of mechanisms responsible for the current-carrying capability of irradiated high-temperature superconductors (HTSC) was realized. For the purpose, experiments were made to investigate the effect of point defects generated by high-energy electron irradiation on the critical temperature and the critical current in high-Tc superconducting single crystals YBa 2 Cu 3 O 7-x . The transport current density measured in HTSC single crystals YBa 2 Cu 3 O 7-x by the dc-method was found to exceed 80000 A/cm 2 . The experiments have demonstrated a more than 30-fold increase in the critical current density in single crystals irradiated with 2.5 MeV electrons to a dose of 3·10 18 el/cm 2 . Detailed studies were made into the anisotropy of critical current and the dependence of critical current on the external magnetic field strength in irradiated single crystals. A high efficiency of point defects as centers of magnetic vortex pinning in HTSC single crystals was first demonstrated.

Thermal field emission observation of single-crystal LaB6

International Nuclear Information System (INIS)

Nagata, H.; Harada, K.; Shimizu, R.

1990-01-01

TFE (thermal field emission) properties of LaB 6 left-angle 100 right-angle and left-angle 310 right-angle single crystals were investigated by emission pattern observation. It was found that field evaporation with the tip temperature held at ∼1500 degree C is very useful to get a clean pattern of fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to left-angle 310 right-angle emission. It is proposed, as the most appropriate operating condition, to use the left-angle 310 right-angle LaB 6 tip at a temperature ∼1000 degree C in vacuum of 10 -9 Torr region, promising a new TF emitter of high brightness and stability for practical use

All-electron ab initio calculations of YBa2Cu3O7 with self-consistence crystal field

Institute of Scientific and Technical Information of China (English)

刘洪霖; 陈念贻

1995-01-01

The quantum chemical calculations of cluster YBa2Cu3O7 considering all electrons have been per-formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtaina relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.Thesuggestions that there exists a covalent bonding complex,[CuO2-O-CuO-O-Cu2]6,8-,in the cell unit ofthe crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results.The importantcontribution of the apical oxygen to superconductivities is emphasized as well.

Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal

International Nuclear Information System (INIS)

Bandiera, L.; Mazzolari, A.; Bagli, E.; Germogli, G.; Guidi, V.; Sytov, A.; Kirillin, I.V.; Shul'ga, N.F.; Berra, A.; Lietti, D.; Prest, M.; De Salvador, D.; Vallazza, E.

2016-01-01

An investigation on the mechanism of relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal was carried out at the extracted line H8 from CERN Super Proton Synchrotron. The experimental results were critically compared to computer simulations, showing a good agreement. We identified a necessary condition for the exploitation of axial confinement or its relaxation for particle beam manipulation in high-energy accelerators. We introduce the idea of using a short bent crystal, aligned with one of its main axis to the beam direction, as a beam steerer or a beam splitter with adjustable intensity in the field of particle accelerators. In particular, in the latter case, a complete relaxation from axial confinement to planar channeling takes place, resulting in beam splitting into the two strongest skew planar channels. (orig.)

Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal

Energy Technology Data Exchange (ETDEWEB)

Bandiera, L.; Mazzolari, A.; Bagli, E.; Germogli, G.; Guidi, V. [Universita di Ferrara, Dipartimento di Fisica, Ferrara (Italy); INFN, Ferrara (Italy); Sytov, A. [Universita di Ferrara, Dipartimento di Fisica, Ferrara (Italy); Belarusian State University, Research Institute for Nuclear Problems, Minsk (Belarus); INFN, Ferrara (Italy); Kirillin, I.V. [National Science Center ' ' Kharkov Institute of Physics and Technology' ' , Akhiezer Institute for Theoretical Physics, Kharkov (Ukraine); Shul' ga, N.F. [National Science Center ' ' Kharkov Institute of Physics and Technology' ' , Akhiezer Institute for Theoretical Physics, Kharkov (Ukraine); V.N. Karazin Kharkov National University, Kharkov (Ukraine); Berra, A.; Lietti, D.; Prest, M. [Universita dell' Insubria, Como (Italy); INFN Sezione di Milano Bicocca, Milan (Italy); De Salvador, D. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Universita di Padova, Dipartimento di Fisica, Padua (Italy); Vallazza, E. [INFN Sezione di Trieste, Trieste (Italy)

2016-02-15

An investigation on the mechanism of relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal was carried out at the extracted line H8 from CERN Super Proton Synchrotron. The experimental results were critically compared to computer simulations, showing a good agreement. We identified a necessary condition for the exploitation of axial confinement or its relaxation for particle beam manipulation in high-energy accelerators. We introduce the idea of using a short bent crystal, aligned with one of its main axis to the beam direction, as a beam steerer or a beam splitter with adjustable intensity in the field of particle accelerators. In particular, in the latter case, a complete relaxation from axial confinement to planar channeling takes place, resulting in beam splitting into the two strongest skew planar channels. (orig.)

A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography

Directory of Open Access Journals (Sweden)

Jasper J. van Thor

2015-01-01

Full Text Available In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe” which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF, in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse.

Electric-field-induced flow-aligning state in a nematic liquid crystal.

Science.gov (United States)

Fatriansyah, Jaka Fajar; Orihara, Hiroshi

2015-04-01

The response of shear stress to a weak ac electric field as a probe is measured in a nematic liquid crystal under shear flow and dc electric fields. Two states with different responses are clearly observed when the dc electric field is changed at a constant shear rate: the flow aligning and non-flow aligning states. The director lies in the shear plane in the flow aligning state and out of the plane in the non-flow aligning state. Through application of dc electric field, the non-flow aligning state can be changed to the flow aligning state. In the transition from the flow aligning state to the non-flow aligning state, it is found that the response increases and the relaxation time becomes longer. Here, the experimental results in the flow aligning state are discussed on the basis of the Ericksen-Leslie theory.

Effect of elastic deformation and the magnetic field on the electrical conductivity of p-Si crystals

Science.gov (United States)

Lys, R.; Pavlyk, B.; Didyk, R.; Shykorjak, J.; Karbovnyk, I.

2018-03-01

It is shown that at a deformation rate of 0.41 kg/min, the characteristic feature of the dependence of the surface resistance of the p-Si sample on the magnitude of its elastic deformation (R(σ)) is the reduction of the resistance during compression and unclamping. With the increase in the number of "compression-unclamping" cycles, the difference between the positions of the compression and unclamping curves decreases. The transformation of two types of magnetically sensitive defects occurs under the impact of a magnetic field on p-Si crystals. The defects are interrelated with two factors that cause the mutually opposite influence on the conductivity of the crystal. The first factor is that the action of the magnetic field decreases the activation energy of the dislocation holders, which leads to an increase in the electrical conductivity of the sample. The second factor is that due to the decay of molecules of oxygen-containing impurities in the magnetic field, the stable chemisorption bonds appear in the crystal that leads to a decrease in its conductivity. If the sample stays in the magnetic field for a long time, the one or the other mechanism predominates, causing a slow growth or decrease in resistance around a certain (averaged) value. Moreover, the frequency of such changes is greater in the deformed sample. The value of the surface resistance of p-Si samples does not change for a long time without the influence of the magnetic field.

Evaluation of Mandibular Anatomy Associated With Bad Splits in Sagittal Split Ramus Osteotomy of Mandible.

Science.gov (United States)

Wang, Tongyue; Han, Jeong Joon; Oh, Hee-Kyun; Park, Hong-Ju; Jung, Seunggon; Park, Yeong-Joon; Kook, Min-Suk

2016-07-01

This study aimed to identify risk factors associated with bad splits during sagittal split ramus osteotomy by using three-dimensional computed tomography. This study included 8 bad splits and 47 normal patients without bad splits. Mandibular anatomic parameters related to osteotomy line were measured. These included anteroposterior width of the ramus at level of lingula, distance between external oblique ridge and lingula, distance between sigmoid notch and inferior border of mandible, mandibular angle, distance between inferior outer surface of mandibular canal and inferior border of mandible under distal root of second molar (MCEM), buccolingual thickness of the ramus at level of lingula, and buccolingual thickness of the area just distal to first molar (BTM1) and second molar (BTM2). The incidence of bad splits in 625 sagittal split osteotomies was 1.28%. Compared with normal group, bad split group exhibited significantly thinner BTM2 and shorter sigmoid notch and inferior border of mandible (P bad splits. These anatomic data may help surgeons to choose the safest surgical techniques and best osteotomy sites.

Large piezoelectricity in electric-field modified single crystals of SrTiO3

Science.gov (United States)

Khanbabaee, B.; Mehner, E.; Richter, C.; Hanzig, J.; Zschornak, M.; Pietsch, U.; Stöcker, H.; Leisegang, T.; Meyer, D. C.; Gorfman, S.

2016-11-01

Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO3 forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO3, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d33 ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.

Condensed matter optical spectroscopy an illustrated introduction

CERN Document Server

Ionita, Iulian

2014-01-01

Molecular Symmetry and the Symmetry GroupsSymmetry Elements and Symmetry OperationsPoint Groups and Molecular SymmetrySymmetry Classification of MoleculesMatrix Representation of Symmetry TransformationGroup RepresentationsProperties of Irreducible RepresentationsTables of CharactersSymmetry of Crystals and Space GroupsRotation Groups and OperatorsExamples of SymmetryStudy QuestionsReferencesCrystal Field TheoryStates and Energies of Free Atoms and IonsOptical Spectra of Ionic CrystalsImpurities in Crystal Lattice: Splitting of Levels and Terms in Lattice SymmetryWeak Crystalline Field of Octahedral SymmetryEffect of a Weak Crystalline Field of Lower SymmetriesSplitting of Multielectron dn Configurations in the Crystalline FieldJahn-Teller EffectConstruction of Energy-Level DiagramsTanabe-Sugano DiagramsExample of the Co IonLimitations of the Crystal Field TheoryStudy QuestionsReferencesSymmetry and Molecular Orbitals TheoryMolecular OrbitalsHybridization Scheme for σ OrbitalsHybridization Scheme for π Orbi...

Influence of Superconductivity on Crystal Electric Field Transitions in La1-xTbxAl2

DEFF Research Database (Denmark)

Feile, R.; Loewenhaupt, M.; Kjems, Jørgen

1981-01-01

Inelastic neutron scattering from the crystal electric field transitions in La1-xTbxAl2 single crystals has revealed an abrupt increase in the lifetimes of these transitions when the system becomes superconducting. An increase in the integrated intensities is also observed. The lifetime effects...... are quantitatively reproduced by existing theories, which take into account the reduced scattering of the conduction electrons by the magnetic ions due to the creation of the superconducting energy gap 2Δ(T)....

Orientation selection process during the early stage of cubic dendrite growth: A phase-field crystal study

International Nuclear Information System (INIS)

Tang Sai; Wang Zhijun; Guo Yaolin; Wang Jincheng; Yu Yanmei; Zhou Yaohe

2012-01-01

Using the phase-field crystal model, we investigate the orientation selection of the cubic dendrite growth at the atomic scale. Our simulation results reproduce how a face-centered cubic (fcc) octahedral nucleus and a body-centered cubic (bcc) truncated-rhombic dodecahedral nucleus choose the preferred growth direction and then evolve into the dendrite pattern. The interface energy anisotropy inherent in the fcc crystal structure leads to the fastest growth velocity in the 〈1 0 0〉 directions. New { 1 1 1} atomic layers prefer to nucleate at positions near the tips of the fcc octahedron, which leads to the directed growth of the fcc dendrite tips in the 〈1 0 0〉 directions. A similar orientation selection process is also found during the early stage of bcc dendrite growth. The orientation selection regime obtained by phase-field crystal simulation is helpful for understanding the orientation selection processes of real dendrite growth.

Electric field influence on exciton absorption of Er doped and undoped InSe single crystals

International Nuclear Information System (INIS)

Guerbulak, B; Kundakci, M; Ates, A; Yildirim, M

2007-01-01

Undoped InSe and Er doped InSe (InSe:Er) single crystals were grown by using the Stockbarger method. Ingots had no cracks and voids on the surface. The absorption measurements were carried out in InSe and InSe:Er samples for U=0 and U=30 V in the temperature range 10-320 K with a step of 10 K. Electric field effects on excitons are observed in InSe and InSe:Er single crystals. The absorption edge shifted towards longer wavelengths and decreased intensity in absorption spectra under an electric field E≅5.9 kV cm -1 . The applied electric field caused a shifting and a decreasing of intensity in the absorption spectra. The shifting of the absorption edge can be explained on the basis of the Franz-Keldysh effect (FKE) or thermal heating of the sample under the electric field. At 10 and 320 K, the first exciton energies for InSe were calculated as 1.336 and 1.291 eV for zero voltage and 1.331 and 1.280 eV for electric field and InSe:Er as 1.329 and 1.251 eV for zero voltage and 1.318 and 1.248 eV for electric field, respectively

Modelling of thermal field and point defect dynamics during silicon single crystal growth using CZ technique

Science.gov (United States)

Sabanskis, A.; Virbulis, J.

2018-05-01

Mathematical modelling is employed to numerically analyse the dynamics of the Czochralski (CZ) silicon single crystal growth. The model is axisymmetric, its thermal part describes heat transfer by conduction and thermal radiation, and allows to predict the time-dependent shape of the crystal-melt interface. Besides the thermal field, the point defect dynamics is modelled using the finite element method. The considered process consists of cone growth and cylindrical phases, including a short period of a reduced crystal pull rate, and a power jump to avoid large diameter changes. The influence of the thermal stresses on the point defects is also investigated.

AN ARECIBO SURVEY FOR ZEEMAN SPLITTING IN OH MEGAMASER GALAXIES

International Nuclear Information System (INIS)

McBride, James; Heiles, Carl

2013-01-01

We present the results of a comprehensive survey using the Arecibo Observatory for Zeeman splitting of OH lines in OH megamasers (OHMs). A total of 77 sources were observed with the Arecibo telescope. Of these, maser emission could not be detected for eight sources, and two sources were only ambiguously detected. Another 27 sources were detected at low signal-to-noise ratios or with interference that prevented placing any useful limits on the presence of magnetic fields. In 26 sources, it was possible to place upper limits on the magnitude of magnetic fields, typically between 10 and 30 mG. For 14 sources, the Stokes V spectra exhibit features consistent with Zeeman splitting. Eleven of these 14 are new detections, and the remaining three are re-detections of Stokes V detections in Robishaw et al. Among confident new detections, we derive magnetic fields associated with maser regions with magnitudes ranging from 6.1 to 27.6 mG. The distribution of magnetic field strengths suggests the magnetic fields in OH masing clouds in OHMs are larger than those in Galactic OH masers. The results are consistent with magnetic fields playing a dynamically important role in OH masing clouds in OHMs.

Fundamental optical absorption edge in MnGa2Te4 single crystals

International Nuclear Information System (INIS)

Medvedkin, G.A.; Rud, Yu.V.; Tairov, M.A.

1988-01-01

A study is made of the optical properties of oriented MnGa 2 Te 4 crystals in the region of the fundamental absorption edge. The energy gap width for the temperatures 77, 300, and 370 K is determined to be E G = 1.635, 1.52, and 1.50 eV. The spectral response α(ℎω/2π) is found to follow Urbach's rule thoughout the temperature range studied, the slope of the absorption edge remaining constant (α = 10 2 cm -1 ). Crystal annealing with subsequent rapid cooling results in a shift of the absorption edge longward by 25 meV with the exponential form of α(ℎω/2π) prevailing over the range T = 77 to 370 K. An analysis shows the optical absorption in the region of the fundamental edge to be a sum of the effects coming from the density-of-states tails, local scattering centers associated with a high vacancy concentration, and electron-phonon interaction. Optical linear dichroism of the absorption edge of MnGa 2 Te 4 single crystals with pseudotetragonal structure is revealed and studied. The single crystals are established to be optically uniaxial, their optical transmission dichroism being negative. It is shown that the minimal direct optical transitions in MnGa 2 Te 4 are allowed in the E parallel c polarization in the temperature range 77 to 370 K, the crystal-field splitting of the valence band increasing with temperature. (author)

Light Modulation and Water Splitting Enhancement Using a Composite Porous GaN Structure.

Science.gov (United States)

Yang, Chao; Xi, Xin; Yu, Zhiguo; Cao, Haicheng; Li, Jing; Lin, Shan; Ma, Zhanhong; Zhao, Lixia

2018-02-14

On the basis of the laterally porous GaN, we designed and fabricated a composite porous GaN structure with both well-ordered lateral and vertical holes. Compared to the plane GaN, the composite porous GaN structure with the combination of the vertical holes can help to reduce UV reflectance and increase the saturation photocurrent during water splitting by a factor of ∼4.5. Furthermore, we investigated the underlying mechanism for the enhancement of the water splitting performance using a finite-difference time-domain method. The results show that the well-ordered vertical holes can not only help to open the embedded pore channels to the electrolyte at both sides and reduce the migration distance of the gas bubbles during the water splitting reactions but also help to modulate the light field. Using this composite porous GaN structure, most of the incident light can be modulated and trapped into the nanoholes, and thus the electric fields localized in the lateral pores can increase dramatically as a result of the strong optical coupling. Our findings pave a new way to develop GaN photoelectrodes for highly efficient solar water splitting.

Multiparty hierarchical quantum-information splitting

International Nuclear Information System (INIS)

Wang Xinwen; Zhang Dengyu; Tang Shiqing; Xie Lijun

2011-01-01

We propose a scheme for multiparty hierarchical quantum-information splitting (QIS) with a multipartite entangled state, where a boss distributes a secret quantum state to two grades of agents asymmetrically. The agents who belong to different grades have different authorities for recovering the boss's secret. Except for the boss's Bell-state measurement, no nonlocal operation is involved. The presented scheme is also shown to be secure against eavesdropping. Such a hierarchical QIS is expected to find useful applications in the field of modern multipartite quantum cryptography.

Tellurium adsorption on single crystal faces of molybdenum and tungsten field emitters

International Nuclear Information System (INIS)

Collins, R.A.; Kiwanga, C.A.

1978-01-01

The purpose of this letter is to report the extension of previous studies of Te adsorption on Mo and W field emitters to measurements on single crystal planes. The adsorption of semiconductors on metallic emitters has been found to be characterized by simultaneous decreases in emission current and the Fowler-Nordheim work function for adsorbate coverages of less than a monolayer. (Auth.)

Entropy Analysis of Solar Two-Step Thermochemical Cycles for Water and Carbon Dioxide Splitting

Directory of Open Access Journals (Sweden)

Matthias Lange

2016-01-01

Full Text Available The present study provides a thermodynamic analysis of solar thermochemical cycles for splitting of H2O or CO2. Such cycles, powered by concentrated solar energy, have the potential to produce fuels in a sustainable way. We extend a previous study on the thermodynamics of water splitting by also taking into account CO2 splitting and the influence of the solar absorption efficiency. Based on this purely thermodynamic approach, efficiency trends are discussed. The comprehensive and vivid representation in T-S diagrams provides researchers in this field with the required theoretical background to improve process development. Furthermore, results about the required entropy change in the used redox materials can be used as a guideline for material developers. The results show that CO2 splitting is advantageous at higher temperature levels, while water splitting is more feasible at lower temperature levels, as it benefits from a great entropy change during the splitting step.

Broken symmetry phase transition in solid p-H 2, o-D 2 and HD: crystal field effects

Science.gov (United States)

Freiman, Yu. A.; Hemley, R. J.; Jezowski, A.; Tretyak, S. M.

1999-04-01

We report the effect of the crystal field (CF) on the broken symmetry phase transition (BSP) in solid parahydrogen, orthodeuterium, and hydrogen deuteride. The CF was calculated taking into account a distortion from the ideal HCP structure. We find that, in addition to the molecular field generated by the coupling terms in the intermolecular potential, the Hamiltonian of the system contains a crystal-field term, originating from single-molecular terms in the intermolecular potential. Ignoring the CF is the main cause of the systematic underestimation of the transition pressure, characteristic of published theories of the BSP transition. The distortion of the lattice that gives rise to the negative CF in response to the applied pressure is in accord with the general Le Chatelier-Braun principle.

Magnetic Order and Crystal Field Excitations in Er2Ru2O7: A Neutron Scattering Study

International Nuclear Information System (INIS)

Ehlers, Georg; Gardner, Jason

2009-01-01

The magnetic pyrochlore Er 2 Ru 2 O 7 has been studied with neutron scattering and susceptibility measurements down to a base temperature of 270 mK. For the low temperature phase in which the Er sublattice orders, new magnetic Bragg peaks are reported which can be indexed with integer (hkl) for a face centered cubic cell. Inelastic measurements reveal a wealth of crystal field levels of the Er ion and a copious amount of magnetic scattering below 15 meV. The three lowest groups of crystal field levels are at 6.7, 9.1 and 18.5 meV.

Trapped field properties of a Y–Ba–Cu–O bulk by pulsed field magnetization using a split coil inserted by iron yokes with various geometries and electromagnetic properties

Energy Technology Data Exchange (ETDEWEB)

Takahashi, K., E-mail: t2216017@iwate-u.ac.jp [Department of Physical Science and Materials Engineering, Faculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Ainslie, M.D. [Bulk Superconductivity Group, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Fujishiro, H.; Naito, T. [Department of Physical Science and Materials Engineering, Faculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Shi, Y-H.; Cardwell, D.A. [Bulk Superconductivity Group, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

2017-05-15

Highlights: • The trapped field characteristics of a standard Y–Ba–Cu–O bulk magnetized by PFM was investigated using a split coil with three kinds of iron yokes inserted in the bores of coil,both experimentally and numerically. • Numerical results encourage better understanding of the role of yoke, including the typical behavior of the magnetic flux, such as a flux jump during PFM. • A higher saturation magnetic flux density of the yoke material was effective to reduce flux flow in the descending stage of the pulsed field. • A conductivity of the yoke material also acts to reduce the velocity of the flux intruding the bulk because of eddy currents that flow in the yoke that oppose the magnetization, which reduces the temperature rise in the bulk. - Abstract: We have investigated, both experimentally and numerically, the trapped field characteristics of a standard Y–Ba–Cu–O bulk of 30 mm in diameter and 14 mm in thickness magnetized by pulsed field magnetization (PFM) using a split coil, in which three kinds of iron yoke are inserted in the bore of the coil: soft iron with a flat surface, soft iron with a taper, and permendur (50Fe + 50Co alloy) with a flat surface. The highest trapped field, B{sub Tmax}, of 2.93 T was achieved at 40 K in the case of the permendur yoke, which was slightly higher than that obtained for the flat soft iron or the tapered soft iron yokes, and was much higher than 2.20 T in the case without the yoke. The insertion effect of the yoke on the trapped field characteristics was also investigated using numerical simulations. The results suggest that the saturation magnetic flux density, B{sub sat}, of the yoke acts to reduce the flux flow due to its hysteretic magnetization curve and the higher electrical conductivity, σ, of the yoke material also acts to suppress the flux increase rate. A flux jump (or flux leap) can be reproduced in the ascending stage of PFM using numerical simulation, using an assumption of relatively

MyCrystals - a simple visual data management program for laboratory-scale crystallization experiments

DEFF Research Database (Denmark)

Løvgreen, Monika Nøhr; Løvgreen, Mikkel; Christensen, Hans Erik Mølager

2009-01-01

MyCrystals is designed as a user-friendly program to display crystal images and list crystallization conditions. The crystallization conditions entry fields can be customized to suit the experiments. MyCrystals is also able to sort the images by the entered crystallization conditions, which...

Photonic time crystals.

Science.gov (United States)

Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia

2017-12-07

When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.

Magnetic field effect on microplastic strain rate in C690 single crystals

International Nuclear Information System (INIS)

Smirnov, B.I.; Shpejzman, V.V.; Peschanskaya, N.N.; Nikolaev, R.K.

2002-01-01

Microplastic strain in magnetic field and beyond it, as well as, subsequent to preliminary exposure of C 60 crystals to magnetic field was investigated by means of laser interferometer enabling to measure rate of strain on the basis of 0.15 μm linear shifting. It is shown that introduction and removal of specimen from 0.2 T induction field immediately during deformation of specimen result in variation of its rate, and at reduction of rate one observes discontinuous interruption of deformation. Sign of effect depends on temperature: at room temperature magnetic field promotes deformation, at 100 K - shows it down. Effect of preliminary exposure within 0.2 and 2T induction field turned to be analogous one. One analyzed possible reasons of the observed manifestation of magnetoplastic effect in C 60 and relation of its sign with phase transition under 260 K temperature [ru

Anisotropic p-f mixing mechanism explaining anomalous magnetic properties in Ce monopnictides

International Nuclear Information System (INIS)

Takahashi, H.; Kasuya, T.

1985-01-01

The crystal-field splittings in CeP, PrP and NdP are calculated by considering the point-charge Coulomb interaction, the intra-atomic d-f Coulomb interaction, and the p-f and d-f mixings. The p-f mixing mechanisms, not only between the occupied 4f states and the conduction bands, but also between the unoccupied 4f states and the valence bands make an important contribution to the crystal-field splitting. The fact that the crystal-field potential in CeP is smaller than those in PrP and NdP is due to the occupied 4f level in CeP being shallower. The values of the Slater-Koster integrals, (pfσ) and (pfπ), are determined uniquely from the crystal-field fitting for PrP and NdP. (author)

The Split-Brain Phenomenon Revisited: A Single Conscious Agent with Split Perception.

Science.gov (United States)

Pinto, Yair; de Haan, Edward H F; Lamme, Victor A F

2017-11-01

The split-brain phenomenon is caused by the surgical severing of the corpus callosum, the main route of communication between the cerebral hemispheres. The classical view of this syndrome asserts that conscious unity is abolished. The left hemisphere consciously experiences and functions independently of the right hemisphere. This view is a cornerstone of current consciousness research. In this review, we first discuss the evidence for the classical view. We then propose an alternative, the 'conscious unity, split perception' model. This model asserts that a split brain produces one conscious agent who experiences two parallel, unintegrated streams of information. In addition to changing our view of the split-brain phenomenon, this new model also poses a serious challenge for current dominant theories of consciousness. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calculation of spin-spin zero-field splitting within periodic boundary conditions: Towards all-electron accuracy

Science.gov (United States)

Biktagirov, Timur; Schmidt, Wolf Gero; Gerstmann, Uwe

2018-03-01

For high-spin centers, one of the key spectroscopic fingerprints is the zero-field splitting (ZFS) addressable by electron paramagnetic resonance. In this paper, an implementation of the spin-spin contribution to the ZFS tensor within the projector augmented-wave (PAW) formalism is reported. We use a single-determinant approach proposed by M. J. Rayson and P. R. Briddon [Phys. Rev. B 77, 035119 (2008), 10.1103/PhysRevB.77.035119], and complete it by adding a PAW reconstruction term which has not been taken into account before. We benchmark the PAW approach against a well-established all-electron method for a series of diatomic radicals and defects in diamond and cubic silicon carbide. While for some of the defect centers the PAW reconstruction is found to be almost negligible, in agreement with the common assumption, we show that in general it significantly improves the calculated ZFS towards the all-electron results.

Fractional-topological-charge-induced vortex birth and splitting of light fields on the submicron scale

Science.gov (United States)

Fang, Yiqi; Lu, Qinghong; Wang, Xiaolei; Zhang, Wuhong; Chen, Lixiang

2017-02-01

The study of vortex dynamics is of fundamental importance in understanding the structured light's propagation behavior in the realm of singular optics. Here, combining with the large-angle holographic lithography in photoresist, a simple experiment to trace and visualize the vortex birth and splitting of light fields induced by various fractional topological charges is reported. For a topological charge M =1.76 , the recorded microstructures reveal that although it finally leads to the formation of a pair of fork gratings, these two vortices evolve asynchronously. More interestingly, it is observed on the submicron scale that high-order topological charges M =3.48 and 3.52, respectively, give rise to three and four characteristic forks embedded in the samples with one-wavelength resolution of about 450 nm. Numerical simulations based on orbital angular momentum eigenmode decomposition support well the experimental observations. Our method could be applied effectively to study other structured matter waves, such as the electron and neutron beams.

Extensional flow of nematic liquid crystal with an applied electric field

KAUST Repository

CUMMINGS, L. J.; LOW, J.; MYERS, T. G.

2013-01-01

Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fibres), albeit with a modified 'Trouton ratio'. However, with a symmetry-breaking electric field gradient applied, behaviour deviates from the Newtonian case, and the sheet can undergo finite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations. Copyright © Cambridge University Press 2013.

Extensional flow of nematic liquid crystal with an applied electric field

KAUST Repository

CUMMINGS, L. J.

2013-10-17

Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fibres), albeit with a modified \\'Trouton ratio\\'. However, with a symmetry-breaking electric field gradient applied, behaviour deviates from the Newtonian case, and the sheet can undergo finite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations. Copyright © Cambridge University Press 2013.

Plasmonic photonic crystals realized through DNA-programmable assembly.

Science.gov (United States)

Park, Daniel J; Zhang, Chuan; Ku, Jessie C; Zhou, Yu; Schatz, George C; Mirkin, Chad A

2015-01-27

Three-dimensional dielectric photonic crystals have well-established enhanced light-matter interactions via high Q factors. Their plasmonic counterparts based on arrays of nanoparticles, however, have not been experimentally well explored owing to a lack of available synthetic routes for preparing them. However, such structures should facilitate these interactions based on the small mode volumes associated with plasmonic polarization. Herein we report strong light-plasmon interactions within 3D plasmonic photonic crystals that have lattice constants and nanoparticle diameters that can be independently controlled in the deep subwavelength size regime by using a DNA-programmable assembly technique. The strong coupling within such crystals is probed with backscattering spectra, and the mode splitting (0.10 and 0.24 eV) is defined based on dispersion diagrams. Numerical simulations predict that the crystal photonic modes (Fabry-Perot modes) can be enhanced by coating the crystals with a silver layer, achieving moderate Q factors (∼10(2)) over the visible and near-infrared spectrum.

Triadic split-merge sampler

Science.gov (United States)

van Rossum, Anne C.; Lin, Hai Xiang; Dubbeldam, Johan; van der Herik, H. Jaap

2018-04-01

In machine vision typical heuristic methods to extract parameterized objects out of raw data points are the Hough transform and RANSAC. Bayesian models carry the promise to optimally extract such parameterized objects given a correct definition of the model and the type of noise at hand. A category of solvers for Bayesian models are Markov chain Monte Carlo methods. Naive implementations of MCMC methods suffer from slow convergence in machine vision due to the complexity of the parameter space. Towards this blocked Gibbs and split-merge samplers have been developed that assign multiple data points to clusters at once. In this paper we introduce a new split-merge sampler, the triadic split-merge sampler, that perform steps between two and three randomly chosen clusters. This has two advantages. First, it reduces the asymmetry between the split and merge steps. Second, it is able to propose a new cluster that is composed out of data points from two different clusters. Both advantages speed up convergence which we demonstrate on a line extraction problem. We show that the triadic split-merge sampler outperforms the conventional split-merge sampler. Although this new MCMC sampler is demonstrated in this machine vision context, its application extend to the very general domain of statistical inference.

Crystallization In Multicomponent Glasses

International Nuclear Information System (INIS)

Kruger, A.A.; Hrma, P.R.

2009-01-01

In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

CRYSTALLIZATION IN MULTICOMPONENT GLASSES

Energy Technology Data Exchange (ETDEWEB)

KRUGER AA; HRMA PR

2009-10-08

In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

Coherent Dynamics of Quantum Dots in Photonic-Crystal Cavities

DEFF Research Database (Denmark)

Madsen, Kristian Høeg

deviations. Similar measurements on a quantum dot in a photonic-crystal cavity sow a Rabi splitting on resonance, while time-resolved measurements prove that the system is in the weak coupling regime. Whle tuning the quantum dot through resonance of the high-Q mode we observe a strong and surprisingly...

Sensitized charge carrier injection into organic crystals studied by isotope effects in weak magnetic fields

International Nuclear Information System (INIS)

Bube, W.; Michel-Beyerle, M.E.; Haberkorn, R.; Steffens, E.

1977-01-01

The magnetic field (H approximately 50 Oe) dependence of the rhodamine sensitized triplet exciton density in anthracene crystals is influenced by isotopic substitution. This confirms the hyperfine interaction as mechanism explaining the change of the spin multiplicity in the initially formed singlet state of the radical pair. The isotope effect occurs in the sensitizing dye ( 14 N/ 15 N) rather than at the molecular site of the injected charge within the crystal. This can be understood in terms of the high hopping frequency of the charge carriers as compared to the time constant of the hyperfine induced singlet-triplet transition. Since the dye molecules adsorb in an oriented fashion, the angular dependence of the magnetic field modulation of the triplet exciton density can be interpreted without assuming any additional interactions. (Auth.)

Particles at fluid-fluid interfaces: A new Navier-Stokes-Cahn-Hilliard surface- phase-field-crystal model.

Science.gov (United States)

Aland, Sebastian; Lowengrub, John; Voigt, Axel

2012-10-01

Colloid particles that are partially wetted by two immiscible fluids can become confined to fluid-fluid interfaces. At sufficiently high volume fractions, the colloids may jam and the interface may crystallize. The fluids together with the interfacial colloids form an emulsion with interesting material properties and offer an important route to new soft materials. A promising approach to simulate these emulsions was presented in Aland et al. [Phys. Fluids 23, 062103 (2011)], where a Navier-Stokes-Cahn-Hilliard model for the macroscopic two-phase fluid system was combined with a surface phase-field-crystal model for the microscopic colloidal particles along the interface. Unfortunately this model leads to spurious velocities which require very fine spatial and temporal resolutions to accurately and stably simulate. In this paper we develop an improved Navier-Stokes-Cahn-Hilliard-surface phase-field-crystal model based on the principles of mass conservation and thermodynamic consistency. To validate our approach, we derive a sharp interface model and show agreement with the improved diffuse interface model. Using simple flow configurations, we show that the new model has much better properties and does not lead to spurious velocities. Finally, we demonstrate the solid-like behavior of the crystallized interface by simulating the fall of a solid ball through a colloid-laden multiphase fluid.

A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm.

Science.gov (United States)

Kobayashi, Ryoya; Takashima, Toshihiro; Tanigawa, Satoshi; Takeuchi, Shugo; Ohtani, Bunsho; Irie, Hiroshi

2016-10-12

We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRh 2 O 4 ) and bismuth vanadium oxide (Bi 4 V 2 O 11 ), which functioned as hydrogen (H 2 ) and oxygen (O 2 ) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline Bi 4 V 2 O 11 (p-Bi 4 V 2 O 11 ) powders were utilized to form ZnRh 2 O 4 /Ag/p-Bi 4 V 2 O 11 , which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-Bi 4 V 2 O 11 with a powder obtained by pulverizing single crystals of Bi 4 V 2 O 11 (s-Bi 4 V 2 O 11 ) to form ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 , and demonstrated that this heterojunction photocatalyst had enhanced water-splitting activity. In addition, ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 was able to utilize nearly the entire range of visible light up to a wavelength of 740 nm. These properties were attributable to the higher O 2 evolution activity of s-Bi 4 V 2 O 11 .

Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields

Energy Technology Data Exchange (ETDEWEB)

Armas-Pérez, Julio C.; Londono-Hurtado, Alejandro [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Guzmán, Orlando [Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, DF 09340, México (Mexico); Hernández-Ortiz, Juan P. [Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Sede Medellín, Medellín (Colombia); Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Pablo, Juan J. de, E-mail: depablo@uchicago.edu [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2015-07-28

A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields.

Energy Technology Data Exchange (ETDEWEB)

Armas-Perez, Julio C.; Londono-Hurtado, Alejandro; Guzman, Orlando; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.

2015-07-27

A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

Elimination of image flicker in a fringe-field switching liquid crystal display by applying a bipolar voltage wave.

Science.gov (United States)

Oh, Seung-Won; Park, Jun-Hee; Lee, Ji-Hoon; Yoon, Tae-Hoon

2015-09-07

Recently, low-frequency driving of liquid crystal display (LCD) panels to minimize power consumption has drawn much attention. In the case in which an LCD panel is driven by a fringe-field at a low frequency, the image flickering phenomenon occurs when the sign of the applied electric field is reversed. We investigated image flickering induced by the flexoelectric effect in a fringe-field switching (FFS) liquid crystal cell in terms of the transmittance difference between frames and the ripple phenomenon. Experimental results show that image flicker due to transmittance difference can be eliminated completely and that the ripple phenomena can be reduced significantly by applying a bipolar voltage wave to the FFS cell.

Transport properties of PrxOs4Sb12 single crystals with high Pr-site filling fraction grown under high pressure

International Nuclear Information System (INIS)

Tanaka, Kenya; Namiki, Takahiro; Saito, Takashi; Tatsuoka, Sho; Imamura, Atsushi; Kuwahara, Keitaro; Aoki, Yuji; Sato, Hideyuki

2009-01-01

We have succeeded in growing Pr x Os 4 Sb 12 single crystals under ∼4GPa with high Pr-site filling fraction x. The electrical resistance measurements clearly show that the superconducting (SC) transition is sharper and the onset temperatures is lower in the single crystal samples grown under high pressure compared to that of the sample grown under ambient pressure. These results suggest that the double SC transition ascribed to sample inhomogeneity is suppressed in the sample grown under high pressure. The change of 4f-electron crystalline electric field energy splitting between the Γ 1 ground state and the Γ 4 (2) first excited state in the sample made under high pressure is proposed as one of the possible origins of the suppression of the double SC transition.

Analysis of quadrupole splitting of multiple Fe sites intermixed in Si(111) with Mössbauer spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kawauchi, Taizo, E-mail: kawauchi@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Zhang, Xiaowei [Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Fukutani, Katsuyuki [Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

2016-12-01

The iron silicide has various interesting phases both fundamentally and technologically, which have acquired much attention to date. Iron silicides are often fabricated on a Si substrate by a solid phase epitaxy method, and the initial stage of intermixing of iron atoms with substrate Si is of crucial importance for silicide fabrication, which remains to be clarified. Here, we have investigated the initial stage of the iron-silicide formation before crystallization with Mössbauer spectroscopy suited to characterization of magnetic and chemical properties of {sup 57}Fe atoms in materials. The sample was prepared by deposition of {sup 57}Fe of 1 nm on a Si(111) surface at 450 K. Conventional Mössbauer spectroscopy in the energy domain revealed presence of two iron sites with similar quadrupole splits and isomer shifts, which hampered complete analysis of this system. By combining the time-domain spectroscopy using polarized synchrotron radiation, we have separately analyzed the quadrupole splits and isomer shifts for the two iron sites. By using the theoretical simulation, furthermore, we successfully reproduced the experimentally observed time spectrum of the nuclear resonant scattering on the assumption that iron atoms randomly occupy the substitutional sites for Si at the initial stage of intermixing before crystallization of an iron silicide. - Highlights: • Quadrupole split of Fe in an iron silicide is measured by Mossbauer spectroscopy. • Two components are separately analyzed with time- and energy-domain spectra. • The time spectrum is well reproduced by numerical simulation. • Results indicate that Fe atoms randomly occupy two possible sites in Fe silicide.

Splitting: The Development of a Measure.

Science.gov (United States)

Gerson, Mary-Joan

1984-01-01

Described the development of a scale that measures splitting as a psychological structure. The construct validity of the splitting scale is suggested by the positive relationship between splitting scores and a diagnostic measure of the narcissistic personality disorder, as well as a negative relationship between splitting scores and levels of…

Bad splits in bilateral sagittal split osteotomy: systematic review and meta-analysis of reported risk factors.

Science.gov (United States)

Steenen, S A; van Wijk, A J; Becking, A G

2016-08-01

An unfavourable and unanticipated pattern of the bilateral sagittal split osteotomy (BSSO) is generally referred to as a 'bad split'. Patient factors predictive of a bad split reported in the literature are controversial. Suggested risk factors are reviewed in this article. A systematic review was undertaken, yielding a total of 30 studies published between 1971 and 2015 reporting the incidence of bad split and patient age, and/or surgical technique employed, and/or the presence of third molars. These included 22 retrospective cohort studies, six prospective cohort studies, one matched-pair analysis, and one case series. Spearman's rank correlation showed a statistically significant but weak correlation between increasing average age and increasing occurrence of bad splits in 18 studies (ρ=0.229; Pbad split among the different splitting techniques. A meta-analysis pooling the effect sizes of seven cohort studies showed no significant difference in the incidence of bad split between cohorts of patients with third molars present and concomitantly removed during surgery, and patients in whom third molars were removed at least 6 months preoperatively (odds ratio 1.16, 95% confidence interval 0.73-1.85, Z=0.64, P=0.52). In summary, there is no robust evidence to date to show that any risk factor influences the incidence of bad split. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Effects of electric fields on the photonic crystal formation from block copolymers

Science.gov (United States)

Lee, Taekun; Ju, Jin-wook; Ryoo, Won

2012-03-01

Effects of electric fields on the self-assembly of block copolymers have been investigated for thin films of polystyrene-bpoly( 2-vinyl pyridine); PS-b-P2VP, 52 kg/mol-b-57 kg/mol and 133 kg/mol-b-132 kg/mol. Block copolymers of polystyrene and poly(2-vinyl pyridine) have been demonstrated to form photonic crystals of 1D lamellar structure with optical band gaps that correspond to UV-to-visible light. The formation of lamellar structure toward minimum freeenergy state needs increasing polymer chain mobility, and the self-assembly process is accelerated usually by annealing, that is exposing the thin film to solvent vapor such as chloroform and dichloromethane. In this study, thin films of block copolymers were spin-coated on substrates and placed between electrode arrays of various patterns including pin-points, crossing and parallel lines. As direct or alternating currents were applied to electrode arrays during annealing process, the final structure of thin films was altered from the typical 1D lamellae in the absence of electric fields. The formation of lamellar structure was spatially controlled depending on the shape of electrode arrays, and the photonic band gap also could be modulated by electric field strength. The spatial formation of lamellar structure was examined with simulated distribution of electrical potentials by finite difference method (FDM). P2VP layers in self-assembled film were quaternized with methyl iodide vapor, and the remaining lamellar structure was investigated by field emission scanning electron microscope (FESEM). The result of this work is expected to provide ways of fabricating functional structures for display devices utilizing photonic crystal array.

The relationship between elastic constants and structure of shock waves in a zinc single crystal

Science.gov (United States)

Krivosheina, M. N.; Kobenko, S. V.; Tuch, E. V.

2017-12-01

The paper provides a 3D finite element simulation of shock-loaded anisotropic single crystals on the example of a Zn plate under impact using a mathematical model, which allows for anisotropy in hydrostatic stress and wave velocities in elastic and plastic ranges. The simulation results agree with experimental data, showing the absence of shock wave splitting into an elastic precursor and a plastic wave in Zn single crystals impacted in the [0001] direction. It is assumed that the absence of an elastic precursor under impact loading of a zinc single crystal along the [0001] direction is determined by the anomalously large ratio of the c/a-axes and close values of the propagation velocities of longitudinal and bulk elastic waves. It is shown that an increase in only one elastic constant along the [0001] direction results in shock wave splitting into an elastic precursor and a shock wave of "plastic" compression.

Random tree growth by vertex splitting

International Nuclear Information System (INIS)

David, F; Dukes, W M B; Jonsson, T; Stefánsson, S Ö

2009-01-01

We study a model of growing planar tree graphs where in each time step we separate the tree into two components by splitting a vertex and then connect the two pieces by inserting a new link between the daughter vertices. This model generalizes the preferential attachment model and Ford's α-model for phylogenetic trees. We develop a mean field theory for the vertex degree distribution, prove that the mean field theory is exact in some special cases and check that it agrees with numerical simulations in general. We calculate various correlation functions and show that the intrinsic Hausdorff dimension can vary from 1 to ∞, depending on the parameters of the model

Uniform angular overlap model interpretation of the crystal field effect in U(5+) fluoride compounds

Energy Technology Data Exchange (ETDEWEB)

Gajek, Z.; Mulak, J. (W. Trzebiatowski Inst. of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland))

1990-11-01

The uniform interpretation of the crystal field effect in three different U(5+) fluoride compounds: CsUF{sub 6}, {alpha}-UF{sub 5} and {beta}-UF{sub 5} within the angular overlap model (AOM) is given. Some characteristic relations between the AOM parameters and their distance dependencies resulting from ab initio calculations are introduced and examined from a phenomenological point of view. The traditional simplest approach with only one independent parameter, i.e. e{sub {sigma}} with e{sub {pi}}:e{sub {sigma}} = 0.32 and e{sub {delta}} = 0, is shown to provide a consistent interpretation of the crystal field effect of the whole class of the compounds. The parameters obtained for one compound are easily and successfully extrapolated to others. The specificity and importance of the e{sub {delta}} parameter for 5f{sup 1} systems is discussed. (orig.).

Split Malcev algebras

Indian Academy of Sciences (India)

project of the Spanish Ministerio de Educación y Ciencia MTM2007-60333. References. [1] Calderón A J, On split Lie algebras with symmetric root systems, Proc. Indian. Acad. Sci (Math. Sci.) 118(2008) 351–356. [2] Calderón A J, On split Lie triple systems, Proc. Indian. Acad. Sci (Math. Sci.) 119(2009). 165–177.

Two-Loop Splitting Amplitudes

International Nuclear Information System (INIS)

Bern, Z.

2004-01-01

Splitting amplitudes govern the behavior of scattering amplitudes at the momenta of external legs become collinear. In this talk we outline the calculation of two-loop splitting amplitudes via the unitarity sewing method. This method retains the simple factorization properties of light-cone gauge, but avoids the need for prescriptions such as the principal value or Mandelstam-Leibbrandt ones. The encountered loop momentum integrals are then evaluated using integration-by-parts and Lorentz invariance identities. We outline a variety of applications for these splitting amplitudes

Two-loop splitting amplitudes

International Nuclear Information System (INIS)

Bern, Z.; Dixon, L.J.; Kosower, D.A.

2004-01-01

Splitting amplitudes govern the behavior of scattering amplitudes at the momenta of external legs become collinear. In this talk we outline the calculation of two-loop splitting amplitudes via the unitarity sewing method. This method retains the simple factorization properties of light-cone gauge, but avoids the need for prescriptions such as the principal value or Mandelstam-Leibbrandt ones. The encountered loop momentum integrals are then evaluated using integration-by-parts and Lorentz invariance identities. We outline a variety of applications for these splitting amplitudes

Effects of Drift-Shell Splitting by Chorus Waves on Radiation Belt Electrons