Electronic structure of transition metal monoantimonides: Analogy to the transition metals

A simple metallic band model is proposed for the transition metal monoantimonides, by analogy to the transition metals. It is assumed that the metal 3d electrons are itinerant in narrow bands which energetically overlap broader antimony 5p-derived bands, and the Fermi level lies in the overlap region. Consistency of the model with available data is assessed and found to be quite good.     

Coupling of one and three quasiparticles to a collective core projected from quadrupole coherent states

The excitation energies and the electromagnetic properties of some odd-mass isotopes of Pt are treated in the framework of a particle-core coupling model. The collective motion of the core is treated by the coherent state model (CSM). A system of interacting shell model nucleons is coupled to the core through aλ-pole-λ-pole term withλ=0, 2, 4. The coupled system is treated alternatively in the strong and weak coupling limit. Numerical applications to the isotopes^189,191,193Pt show a good agreement with the available data. The backbending of the yrast band is interpreted as being caused by the intersection of the one and three quasiparticle bands.     

A self-consistent mean-field study of Z = 120 nuclei and α-decay chains of 292,298,299,300,304120 isotopes

A self-consistent mean-field investigation is done to test the model accuracy, model dependence, and the dependence on different model parameters in the study of superheavy nuclei. This is done within the self-consistent mean-field models-the Skyrme-Hartree-Fock-Bogoliubov (HFB), and the Relativistic-Hartree-Bogoliubov (RHB) with density-dependent couplings. A systematic comparison is made with experimental data, as well as with the macro-microscopic Finite Range Droplet Model(FRDM). The bulk ground state properties and the microscopic structure of Z=120 superheavy nuclei are investigated. Further investigation is made of α-decay series for the five isotopes ^{292,298,299,300,304}120 of Z=120 nuclei. A spontaneous fission investigation is done to account the number of α-decay before spontaneous fission starts. The experimental data available for α-decay energies and half-lives are produced reasonably. The RHB model with NL3* parameter set, and with ImSahu and UNIV2 formula to calculate the α-decay half-lives is found to be the best suited for accurately predicting the ground state properties and the α-decay half-lives of the superheavy nuclei.     

Diffractive resonance production and f-dominance of the pomeron

A model for predicting diffractive production of meson resonances is presented. From a study of the s and t dependence of the available cross section and density matrix data, we deduce that the assumption of f, f′ dominance of the pomeron is violated. Relative to elastic scattering, where f, f′ dominance works well, the pomeron component in these inelastic processes appears to be about one half as strong in amplitude.     

Dynamique de reseau et frequences des modes de vibration pour des impuretes substitutionnelles dans InP,GaP et ZnS

The model used is a rigid-ion model with an effective ionic charge including general interactions for nearest and next nearest neighbours and long range Coulomb interactions. It provides a good fit with available neutron data and with IR absorption results for InP. In this model, no hypothesis is made apriori on the interatomic forces and the eleven parameters given by the model are used. A mathematical model which employs a Green's function technique in the mass defect and the nearest neighbour force constant defect approximation is used to calculate the lattice dynamics of the imperfect crystal. The frequencies of the local modes, the gap modes and the band modes, are given for isolated substitutional impurities. The same calculation is achieved for GaP and ZnS and the results are compared with IR data.     

On the scissors type mode in 46Ti and lighter nuclei

A microscopic formulation of the scissors mode, based on the angular-momentum projected Hartree-Fock Bogoljubov approximation, is applied to the Ti and Ne isotopes. Results for M1 transition strengths and form factors are presented and compared to available experimental data and shell model calculations. For ⁴⁶Ti the B(M1)↑ value obtained is in excellent agreement with the experimental data for the 1⁺ state at 4.3 MeV.     

Analysis of a six-quark model with right-handed currents

A model for the weak interactions using the six-quark model of Harari, right-handed currents, and heavy leptons which was proposed previously by some of us is analyzed in considerable detail. The model is one of a class of “vector-like” theories that are free of gauge theory anomalies. The neutral current is pure vector, which leads to predictions for diffractive production of vector mesons by neutrinos that are different from the predictions of the standard Weinberg-Salam model; the A₁ uncouples and the fractions of ? and ω are enhanced. It is also predicted that relative production of $\text{I =}\text{1}\text{2}$ final states is larger than $\text{I =}\text{3}\text{2}$ final states in vN → vNπ in contrast to the Weinberg-Salam model. The non-leptonic decays of hyperons and mesons and the restrictions imposed by chiral symmetry are discussed. The decays of the charmed mesons are shown to be very rich due to the presence of both V ? A and V + A interactions. The y-anomalies in neutrino interactions are discussed and calculations of $\text{d}\text{σ}\text{d}\text{x}\text{and}\text{d}\text{σ}\text{d}\text{y}$ for both neutrinos and antineutrinos using modified Kuti-Weisskopf distributions are presented. Cross sections and ratios of neutrino and a neutrino cross sections are shown along with available experimental data. The v-distribution of dimuon events is also presented and compared with experiment. It is concluded that the model is not inconsistent with the currently available data.     

Calculation of the thermoelectric characteristics of n-and p-type PbTe using a three-band electron spectrum

In this paper we study the thermoelectric properties of n-and p-type PbTe theoretically in a wide temperature interval of 300 to 900 K. A three-band model of the PbTe electron-energy spectrum was used in these calculations for the first time. The full set of the relevant kinetic characteristics is calculated, including the electrical and thermal conductivities, as well as the Seebeck coefficient and the thermoelectric figure-of-merit. The calculated thermoelectric quantities are in good agreement with the available experimental data.     

Continuum reconstruction of the pore scale microstructure for Fontainebleau sandstone

A stochastic geometrical modeling technique is used to reconstruct a laboratory scale Fontainebleau sandstone with a sidelength of 1.5 cm. The model reconstruction is based on crystallite properties and diagenetic parameters determined from two-dimensional images. The three-dimensional pore scale microstructure of the sandstone is represented by a list of quartz crystallites defined geometrically and placed in the continuum. This allows generation of synthetic μ-CT images of the rock model at arbitrary resolutions. Quantitative microstructure comparison based on Minkowski functionals, two-point correlation function and local porosity theory indicates that this modeling technique can provide more realistic and accurate models of sandstones than many existing techniques used currently. Synthetic μ-CT images at different resolutions from a laboratory scale model of Fontainebleau sandstone are made available to the scientific community for resolution dependent petrophysical analysis.     

IBM-2 description of M1 properties in deformed nuclei

Results of schematic calculations are presented in which various terms breaking F-spin symmetry are considered in the hamiltonian of the neutron-proton interacting boson model (IBM-2). Specific attention is paid to the effect of F-spin symmetry breaking on γ → ground and γ → γ M1 transitions in deformed nuclei. A comparison with available M1 data in the rare-earth nuclei is presented. The constraints implied by these data on the form of the IBM-2 hamiltonian in well-deformed nuclei are discussed.     

Calculated line broadening coefficients in the ν2 band of CH3D perturbed by helium

Line broadening coefficients have been calculated, at room temperature, for lines in the P and R branches of the ν₂ band of monodeuterated methane. A properly symmetrized semiclassical model with parabolic relative trajectories has been used. Two interaction potential models have been considered. The first is a Lennard-Jones type atom-atom potential, while the second one was derived from ab initio calculations. The calculated line widths were compared to the available experimental data and a satisfactory agreement was found, although the model contains no other adjustable parameters than the four atomic Lennard-Jones ones. Nonetheless, failures of calculations have also been evidenced for the highest rotational quantum numbers.     

Lattice dynamics of II-VI mixed semiconductor ZnS1−xSex

Lattice dynamical properties of II-VI compounds having zinc-blende structure have been calculated by three-body shell model. This model incorporates the effect of the short-range repulsive interactions up to and including the second nearest neighbours, in addition to the long-range Coulombic interactions in the frame work of the rigid-shell model with both the ions are polarizable. The model involves in total eleven disposable parameters. Using the above proposed model the phonon dispersion relations for mixed II-VI semiconductor ZnS_1−xSe_x are plotted. We find an overall good agreement with the experimental results. The application of the present model has been made to calculate the phonon dispersion relations of ZnS, ZnSe and mixed semiconductor ZnS_1−xSe_x. The comparison of the theoretical results with the available experimental has been made along high symmetry directions. A reasonably good agreement is observed between theory and experiments.     

Dynamics of Ξ-hyperon production on nucleon

A phenomenological model of Ξ-hyperon production from nucleons by antikaons is developed. The model successfully reproduces available experimental data on integral and differential cross sections of the reaction in the different charge channels at the center-of-mass energies from the threshold up to 3.2 GeV. It is shown that the baryonic (u-channel) exchange is the dominant reaction mechanism.     

Hadron-nucleus interactions and the leading particle effect in a dual-parton model

We describe hadron-nucleus interactions at smallP _T in the framework of a dual-parton model which is a generalization of the two-chain dual-partonmodel of hadron-hadron interactions introduced recently in the literature. The model (of a multiple scattering type) is formulated in the framework of the 1/N expansion in dual theories. Regge singularities are used to determine the (joint) momentum distribution functions of the various sets of constituents (valence and sea quarks) which yield hadron jets in successive orders of the 1/N expansion. These jets result from a standard color separation mechanism, inspired by QCD. We study the inclusive spectra of various types of secondaries for various projectiles and targets. Particular emphasis is laid on theA-dependence in the projectile fragmentation region. A comparison with available experimental data is presented.     

Multifragmentation versus evaporation of target residues in high-energy proton-nucleus collisions

The cascade-fragmentation-evaporation model is developed for proton-nucleus collisions at high energies. Comparison of the calculated fragment mass and energy distributions with the available experimental data shows the important role played by the explosive multifragmentation break-up of target residues. A systematic study of correlated emission of several heavy fragments (Z⩾3) is necessary to obtain decisive conclusions concerning the mechanism of deexcitation of highly excited residual nuclei.     

Antikaon production in nucleon- nucleon reactions near threshold

The antikaon production cross section from nucleon-nucleon reactions near threshold is studied in a meson exchange model. We include both pion and kaon exchange, but neglect the interference between the amplitudes. In case of pion exchange the antikaon production cross section can be expressed in terms of the antikaon production cross section from a pion-nucleon interaction, which we take from the experimental data if available. Otherwise, a K* -resonance exchange model is introduced to relate the different reaction cross sections. In case of kaon exchange the antikaon production cross section is related to the elastic KN and K?N cross sections, which are again taken from experimental measurements. We find that the one-meson exchange model gives a satisfactory fit to the available data for the NN → NN KK? cross section at high energies. We compare our predictions for the cross section near threshold with an earlier empirical parameterization and that from phase space models.     

Large quadratic interaction for the coexistence of two kinds of Jahn-Teller distortions in KI:T1-type phosphors

A modified Fukuda model, which is based on the coexistence of T¹ tetragonal and X rhombic minima on the ³T¹_1u energy levels due to Jahn-Teller effect, is tested by means of the available experimental data concerning absorption and emission bands positions and the electron-lattice coupling constant for E_g modes. The model is satisfactory only if a strong difference in curvature between the ground and excited levels $\text{(β ? 0.75)}$ is assumed; this suggests that second order Jahn-Teller effect terms may be important.     

Change of force constant around a point defect in a solid

The local or gap mode frequencies of a host lattice-point defect system. XY:Z may be predicted from the properties of the end member pure crystals XY and XZ alone whenever pertinent data on pure crystals are available, without invoking any arbitrary force constant softening. In this instance the molecular model has been used, and relevant examples from alkali halides are presented. A modification of the Green's function technique is also discussed.