Contribution of the π<Superscript>0</Superscript>γ and ηγ intermediate states to vacuum polarization and the muon anomalous magnetic moment

Using new experimental data, we calculated, with a high precision, a contribution to the muon anomalous magnetic moment from the vacuum-polarization intermediate states π⁰γ and ηγ taking into account a correction for the trapezoidal rule: aμ(π⁰γ+aμ(ηγ)=(53.1± 1.5)×10^?11. We also determined a small contribution from the e⁺e^?π⁰, e⁺e^?η, and μ⁺μ^?π⁰ intermediate states, which was found to be equal to 0.5×10^?11.     

Characteristics of the discrete and continuous spectra of the <Superscript>4</Superscript>He + Λ system

In view of projected experiments on the production of relativistic hypernuclei and the investigation of reactions induced by them, the characteristics of the hypernucleus and low-energy parameters of the _Λ ⁵ He hyperon scattering from ⁴He were calculated. The interaction of the Λ hyperon and the α particle is described by the effective Λα potential in two different forms. The root-mean-square radius of the Λ hyperon in the _Λ ⁵ He hypernucleus, the vertex constant for the _Λ ⁵ He ? ⁴He + Λ process, and the corresponding asymptotic normalization coefficient of the _Λ ⁵ He wave function were calculated by solving the radial Schrödinger equation. The scattering length and the effective radius for the scattering of Λ from ⁴He were calculated by two methods. The calculated characteristics turn out to be sensitive to the form of the Λα potential.     

Raman scattering and electrical studies of the phase stability in the Hg<Subscript>1−x</Subscript>Cd<Subscript>x</Subscript>Te

Raman scattering is performed to access phase stability in the boron-implanted Hg_0.7Cd_0.3Te with fluences ranging from 1 × 10¹² to 1 × 10¹⁵ cm^?2. Threshold fluence for the formation of an amorphous phase is invoked here using Thomas–Fermi statistical model. Asymmetric broadening and red shift of the Raman active HgTe-like LO phonon mode are observed with varying fluencies. Electrical properties such as sheet carrier concentration and mobility are also changed with the fluence and reach their saturated values beyond threshold fluence of 5 × 10¹³ cm^?2. Threshold fluence for the formation of amorphous phase is also validated by the Raman measurements and electrical transport properties in the implanted layers. The excess free energy of 6.8 kJ/mole is found corresponding to the threshold fluence for phase transition.     

On the nature of the lowest 1/2<Superscript>-</Superscript> baryon nonet and decuplet<Superscript>⋆</Superscript>

From our recent study of properties of the lowest spin-parity 1/2^- baryons, N ^*(1535) and Δ^*(1620) , new pictures for the internal structure of the lowest 1/2^- baryon nonet and decuplet are proposed. While the lowest 1/2^- baryon nonet may have large diquark-diquark-antiquark component, the lowest 1/2^- baryon decuplet is proposed to have large vector-meson-baryon components. Evidence for “missing" members of the new pictures is pointed out and suggestions are made for detecting these predicted states from forthcoming experiments.     

Spin-reorientation phase transition on the surface and in the bulk of α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> single crystals

Direct comparison of the properties of a thin surface layer and the bulk of macroscopic hematite (α-Fe₂O₃) crystals was used to study the magnetic structure of the surface layer and the bulk and the processes attendant on spin-reorientation phase transition (SRT). The investigation tool was simultaneous γ-ray, X-ray, and electronic Mössbauer spectroscopy, which enabled us to study the bulk and surface properties of macroscopic samples simultaneously and to compare them directly. Direct evidence of the existence of a surface “transition layer” on hematite crystals is obtained. The existence of this layer was suggested and described by Krinchik and Zubov [JETP 69, 707 (1975)]. The study in the SRT region showed that (1) the Morin SRT in the crystal bulk occurs in a jump (as a first-order phase transition), whereas in the surface layer of about 200 nm thick, some smoothness appears in the mechanism of magnetic-moment reorientation; (2) SRT in the surface layer, as in the bulk, involves an intermediate state in which low-and high-temperature phases coexist; and (3) SRT in the surface layer occurs at a temperature several degrees higher than in the bulk. Our experimental evidence on the SRT mechanism in the surface layer correlates with the inferences from phenomenological theory developed by Kaganov [JETP 79, 1544 (1980)].     

Angular Distributions and Anisotropy of the Fragments from Neutron-Induced Fission of <Superscript>239</Superscript>Pu and <Superscript>nat</Superscript>Pb in the Energy Range of 1–200 MeV

The angular distributions of fragments from the neutron-induced fission of ^natPb and ²³⁹Pu nuclei have been measured in the energy of range 1–200 MeV using the neutron time-of-flight spectrometer GNEIS. Fission fragments have been detected by position sensitive multiwire proportional counters. The results for the anisotropy of fission fragments deduced from the measured angular distributions have been presented. The results have been compared with the experimental data of other authors.     

Features of the structure and properties of β-FeSi<Subscript>2</Subscript> nanofilms and a β-FeSi<Subscript>2</Subscript>/Si interface

The electronic, geometric, and magnetic structure of nanofilms of the β phase of iron disilicide FeSi₂ with the (001), (100), and (010) surfaces have been simulated through density functional calculations. A substantial reconstruction of the (001) surface terminated with silicon atoms has been observed, which was accompanied by an increase in the surface symmetry and appearance of “squares” of silicon atoms. Analysis of the electron density of states (DOS) and spin DOS projected on the contributions of layers of atoms (LSDOS) indicates that all plates have metallic properties. The main contribution near the Fermi level comes from the surface iron layers and it decreases rapidly with an increase in the distance from the surface of the plate. Analysis of the calculated effective magnetic moments of atoms shows that the surface layers in the plates have a significant magnetic moment, in particular, iron layers on the (001) surface (1.89 μ_B/atom). The moments of atoms decrease rapidly with an increase in their distance from the surface. The electron and geometric regions of a (001)Si/FeSi₂ interface have been studied. Analysis of the LSDOS shows that the surface conducting state mainly determined by the contribution from the near-surface silicide layers is implemented in this region. The possibility of the formation of the perfect and sharp Si/FeSi₂ interface has been demonstrated.     

Investigations on the local structure and the spin-Hamiltonian parameters for the tetragonal Cu<Superscript>2+</Superscript> centre in ZnGeF<Subscript>6</Subscript>⋅6H<Subscript>2</Subscript>O crystal

The spin-Hamiltonian parameters (g factors g_∥, g_⊥ and hyperfine structure constants A_∥, A_⊥) and the local structure for the tetragonal Cu²⁺ centre in trigonal ZnGeF₆?6H₂O crystal are theoretically studied using the perturbation formulae of these parameters for a 3 d⁹ ion in tetragonally elongated octahedra. In the calculations, the contributions to the spin-Hamiltonian parameters from ligand orbital and spin-orbit coupling are included on the basis of the cluster approach in view of moderate covalency of the studied systems, and the required crystal-field parameters are obtained using the superposition model and the local structures of the studied [Cu(H₂O)₆] ²⁺ cluster. According to the calculations, the ligand octahedra around Cu²⁺ suffer relative elongation τ (≈ 0.085 Å) along the [0 0 1] (or C₄) axis for the tetragonal Cu²⁺ centres in ZnGeF₆?6H₂O crystal, due to the Jahn–Teller effect. The calculated results show good agreement with the experimental data.     

Relationship between the microstructure and the microscopic piezoelectric response of the <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-phases of poly(vinylidene fluoride)

The piezoelectric and pyroelectric properties of PVDF mainly depend on its β-phase. This work reports the study by scanning force microscopy in a piezoresponse mode of the variations in the topological morphology and piezoelectric surface response of β-PVDF prepared by the main preparation methods of this phase. Clear differences in the poled region distribution and size, as well as in the local piezoactivity, have been identified. The piezoelectric activity at a mesoscale reflects the semicrystalline phase of the polymer.     

Effect of the Composition and the Crystal Structure on the Electrophysical Properties of the Ni<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>W<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> System at Low Temperatures

The problem of establishing the correlation between, on the one hand, the chemical and phase compositions of Ni_1–xW_x alloys (0 ≤ x ≤ 0.5) and, on the other hand, the character of the temperature dependences of the electrical resistivity, is considered. Based on the experimental ρ(T) curves, the concentration dependences of are reconstructed in the wide temperature range (50 K ≤ T ≤ 273 K). The ρ(x) curves have features related to a change in the crystal structures of the alloys (concentration fcc–bcc phase transition), their magnetic structures and percolation processes occurring in the two-phase fcc + bcc medium.     

New parameterization of the trinucleon wave function and its application to the π <Superscript>3</Superscript>He scattering length

We present a new parameterization of the trinucleon wave function. As a novel feature a separable parameterization for the complete wave function is given. In this way any calculation that considers two-body currents only is largely simplified. To demonstrate this we calculate the π³He scattering length in chiral-perturbation theory. We find reasonable agreement with experimental values inferred from data on level shifts in pionic ³He bound states. The relevance of the π-triton system for an alternative determination of the πN scattering lengths is discussed. Received: 12 August 2002 / Accepted: 25 November 2002 / Published online: 25 February 2003 RID="a" ID="a"e-mail: c.hanhart@fz.juelich.de Communicated by V. Vento     

Self-Consistent Calculations of the Quadrupole Moments of the Lowest 3<Superscript>–</Superscript> States in Sn and Pb Isotopes

self-consistent approach to anharmonic effects based on the quantum many-body theory is for the first time used to calculate the quadrupole moments of the lowest 3^– states in Sn and Pb isotopes, including the ¹⁰⁰Sn, ¹³²Sn, and ²⁰⁸Pb doubly magic ones. The consistency between the mean nuclear field and the effective interaction is maintained using the energy-density-functional method with known parameters of the Fayans functional. Thereby, the quadrupole moments of the lowest 3^– states of isotopes with nucleon pairing are reliably predicted, and the existing data for the ²⁰⁸Pb isotope are reproduced. It has been shown that the new three-quasiparticle correlations are responsible for slightly more than half of the observed effect and the remaining part is due to the quadrupole polarizability of the nucleus.     

Angular distributions and anisotropy of the fragments from neutron-induced fission of <Superscript>233</Superscript>U and <Superscript>209</Superscript>Bi in the intermediate energy range of 1–200 MeV

New results of the neutron-induced fission experiments carried out at the neutron time-of-flight spectrometer GNEIS of the PNPI are given. Angular distributions of fission fragments from the neutron-induced fission of ²³³U and ²⁰⁹Bi nuclei have been measured in the energy range 1–200 MeV using position sensitive multiwire proportional counters as fission fragment detector. The recent improvements of the measurement and data processing procedures are described. The data on anisotropy of fission fragments deduced from the measured angular distributions are presented in comparison with the experimental data of other authors.     

Mössbauer Studies and the Microwave Properties of Al<Superscript>3+</Superscript>- and In<Superscript>3+</Superscript>-Substituted Barium Hexaferrites

The correlation of the chemical composition, the structure, and the microwave characteristic of solid solutions of the BaFe_{12 – x}D_xO₁₉ (0.1 ≤ x ≤ 1.2) barium hexaferrite substituted with diamagnetic Al³⁺ and In³⁺ ions has been studied. The precise data on the crystal structure have been obtained by powder neutron diffraction using a high-resolution Fourier diffractometer (Dubna, JINR). The data on the distribution of the diamagnetic substituting ions in the hexaferrite structure have been obtained by Mössbauer spectroscopy. The microwave properties (the transmittance and the reflectance) have been studied in the frequency range 20–65 GHz and in external magnetic fields to 8 kOe. It is found that the transmission spectra are characterized by a peak that corresponds to the resonant frequency of the electromagnetic energy absorption, which is due to the ferromagnetic resonance phenomenon. The correlation of the chemical composition, the features of the ion distribution in the structure, and the electromagnetic properties has been revealed. It is shown that external magnetic fields shift the absorption peak of electromagnetic radiation to higher frequencies due to an increase in the magnetocrystal anisotropy. The results enable the conclusion that the features of the intrasublattice interactions and the electromagnetic properties should be explained using the phenomenological Goodenough–Kanamori model.     

Adhesion at the interfaces between BCC metals and α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Ab initio calculations of the atomic and electronic structures of Me(111)/α-Al₂O₃(0001) interfaces (Me = V, Cr, Nb, Mo, Ta, W) in the framework of density functional theory are reported. The energies of separation of metal films from oxide surfaces have been calculated. The structural and electronic factors responsible for the strong adhesion of bcc metal films on the oxygen termination of the surface of aluminum oxide have been analyzed.     

Investigation of the tunnel effect and dielectric parameters of α-LiIO<Subscript>3</Subscript> crystals

Temperature and frequency spectra of tanδ, ε′, and ε″ of laser lithium iodate single crystals are investigated at temperatures in the interval 77–450 K and frequencies in the range 5–10⁸ Hz. An analysis of these spectra and the Cole–Cole diagrams demonstrates tunneling of charge carriers and existence of relaxation oscillators of several types. The temperature interval for the tunnel effect is determined. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 39–42, February, 2009.     

Comparison of the Effects of Different <Superscript>19</Superscript>F <Emphasis Type="Italic">π</Emphasis> Pulses on the Sensitivity and Phaseability of the <Superscript>19</Superscript>F-<Superscript>13</Superscript>C HSQC

The ¹⁹F-¹³C heteronuclear single quantum coherence (HSQC) experiment is vital for the structural elucidation of polyfluorinated organic species, yet its sensitivity and phaseability are limited by difficulties in uniform excitation of the widely disperse ¹⁹F spectral window. Adiabatic pulses of different types have previously been employed to generate effective π pulses for inversion and refocussing, but a systematic comparison of various adiabatic and other inversion pulses has not been published. In this work, it was observed that the use of a broadband inversion pulse (BIP) during the t ₁ evolution period resulted in properly phaseable spectra for experiments optimized to detect ¹ J _CF, in contrast to CHIRP or WURST adiabatic pulses. For the INEPT and reverse-INEPT transfer segments of the HSQC, optimal sensitivity for resonances distant from the transmitter frequency was afforded by optimized universal rotation (BURBOP) or CHIRP pulses. In HSQC experiments with delays optimized for two-bond correlations, only the use of BURBOP pulses in INEPT and reverse-INEPT sequences afforded spectra cleanly phaseable across the F ₂ and F ₁ spectral windows. This observation is supported by off-resonance pulsed field gradient spin-echo experiments.     

Effect of spin structures and nesting on the shape of the fermi surface and pseudogap anisotropy in the <Emphasis Type="Italic">t</Emphasis>-<Emphasis Type="Italic">t</Emphasis>′-<Emphasis Type="Italic">U</Emphasis> Hubbard models

The effect of two types of spin structures on the shape of the Fermi surface and on the map of photoemission intensities for the t-t′-U Hubbard model is investigated. The stripe phase with a period of 8α and the spiral spin structure are calculated in the mean field approximation. It is shown that, in contrast to electron-type doping, hole-doped models are unstable to the formation of such structures. Pseudogap anisotropy is different for h-and e-doping and is determined by the spin structure. In accordance with ARPES data for La_2?xSr_xCuO₄, the stripe phase is characterized by quasi-one-dimensional FS segments in the vicinity of points M(±π, 0) and by suppression of the spectral density for k _x =k _y . It is shown that spiral structures exhibit polarization anisotropy: different segments of the FS correspond to electrons with different spin polarizations.     

Braided algebras and the <Emphasis Type="Italic">κ</Emphasis>-deformed oscillators

Recently there were presented several proposals how to formulate the binary relations describing κ-deformed oscillator algebras. In this paper we shall consider multilinear products of κ-deformed oscillators consistent with the axioms of braided algebras. In general case the braided triple products are quasi-associative and satisfy the hexagon condition depending on the coassociator \({\Phi \in A\otimes A\otimes A}\) . We shall consider only the products of κ-oscillators consistent with co-associative braided algebra, with \({\Phi =1}\) . We shall consider three explicit examples of binary κ-deformed oscillator algebra relations and describe briefly their multilinear coassociative extensions satisfying the postulates of braided algebras. The third example, describing κ-deformed oscillators in group manifold approach to κ-deformed fourmomenta, is a new result.