bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaky and surface wave diffraction by an asymmetric impedance half plane
Authors: Nasalski W.
Published: April 2011

An exact solution is obtained for the problem of a leaky or surface wave incident on an impedance half plane in a homogeneous, isotropic medium. The impedance half plane is asymmetric, i.e., with different constant surface impedances at the upper and lower faces, respectively. The incident leaky wave propagates in a direction normal to the edge of the half plane.The diffraction problem leads to a set of two coupled Wiener–Hopf equations, from which two Hilbert problems on a new contour are obtained and solved. The Wiener–Hopf–Hilbert method is used. Expressions for the geometrical optical field are also derived and results arc discussed from the point of view of the uniqueness of the solution.
The 10B(d, α) 8Be(2α) reaction mechanism at Ed = 1.85 MeV
Authors: D'Amico V. , Fazio G. , Giardina G. , Mezzanares F.
Published: April 2011

The 10B(d, α)8Be(2α) reaction at Ed = 1.85 MeV has been studied by using the bidimensional spectra technique. The results obtained from the α−α angular correlation analysis are consistent with the presence of a heavy particle stripping mechanism.
Self-pulsing and chaos in acoustooptic bistability
Authors: Chrostowski J. , Vallee R. , Delisle C.
Published: April 2011

The output of a hybrid acoustooptic bistable device with delayed feedback is investigated. Depending on the input intensity, such a system exhibits periodic and chaotic behaviour. Period doubling up to period-8 with the reverse Lorentz sequence is presented. The sequence of bifurcations is truncated by the additive electrical shot noise and the multiplicative noise due to the laser intensity fluctuations. Frequency locked oscillations are also presented.
Particles, antiparticles, and generalized anomalies in grand unified theories
Authors: Singer Mark
Published: April 2011

Grand unified theories of strong–weak electromagnetic interactions require both chiral states of all charged fermions to be present so that the theories will have no massless charged particles. For a large class of theories this condition requires not only the absence of all triangle anomalies, but the absence of "odd-number generalized anomalies" as well. Conversely, the requirement that these theories be odd-number generalized anomaly free guarantees that both chiral states of all charged fermions arc present, and thus all charged fermions can acquire mass.
Laser annealed ohmic contact to n+-GaAs
Authors: Sircar P.
Published: April 2011

Ohmic contacts were made on n+-GaAs substrates by evaporating a gold–germanium eutectic film with or without a thin nickel overlayer and then alloying these samples either in a furnace or by means of an excimer laser. It is found that laser annealing gives a better surface morphology and a lower contact resistance than furnace annealing.
Pion electroproduction from and near threshold
Authors: Dressler Edward T.
Published: April 2011

The differential cross sections for [Formula: see text], n and [Formula: see text], 2n are calculated and compared with some recent data (Caplan and Sealock, manuscript in preparation). The theoretical model in this calculation uses essentially the same approximations as were used by Dressier et al. (1979) for the [Formula: see text] total threshold cross section. The results of this new calculation are in good agreement with the [Formula: see text], n data. However, comparing our results to the [Formula: see text] data at an incident electron energy of 200 MeV and a pion energy of 15 MeV seems to indicate that the [Formula: see text], 2n calculation somewhat overestimates this cross section.
Slowly rotating fluid spheres in the Einstein–Yukawa theory
Authors: Krori K. D. , Sheikh A. R.
Published: April 2011

We introduce slow rotation to a solution given by Krori et al. which represents fluid spheres in the Einstein–Yukawa theory, and present two new analytic solutions which are nonsingular and satisfy physical conditions throughout the spheres. One of the interior solutions represents uniformly rotating spheres and the other represents differentially rotating spheres. We also match the interior and exterior solutions on the boundary.
Simple derivation of the exp(S) equations
Authors: Dabrowski Janusz
Published: April 2011

It is shown that equations for the n-particle, n-hole amplitudes of the exp (S) theory of the interacting many-body system may be easily obtained by analyzing the structure of the Goldstone diagrams for the wave function of the system.
Far infrared reflectivity of liquid Ga–Te alloys
Authors: Johnston S. F. , Crozier E. D. , Clayman B. P.
Published: April 2011

The far infrared (FIR) reflectivities of liquid Ga–Te alloys as a function of composition, temperature, and frequency have been measured using both a far infrared laser and Fourier-transform spectroscopy. The reflectivity R is anomalously enhanced between the compositions GaTe and Ga2Te3, suggesting molecular clustering in this alloy range. The temperature dependence of R appears to correspond to an activated conductivity, and is strongest near Ga2Te3. The variation of R with frequency for the stoichiometric alloys is Drude-like at higher frequencies, but is nearly constant below 175 cm−1 for GaTe. The FIR conductivities extrapolated to zero frequency are significantly larger than the direct current (dc) values. The data are similar to liquid Mg–Bi measurements and to the spectra of several amorphous glasses. The composition dependence of R is consistent with a superposed band model for ionic constituents with some covalent bonding. Agreement of the frequency dependence of R with experimental values requires a small constant density of states at the Fermi energy.
Anomalies in the temperature dependence of the yield stress of metals at low temperatures
Authors: Raza S. M.
Published: April 2011

Yield stress "anomalies" have been studied in polycrystalline nickel at low temperatures. Both quantum effects and structural changes below 0.1–0.2 of the Debye temperature contribute to low-temperature anomalies in the temperature dependence of the yield stress. The anomalies appear to be basically a consequence of the effect of zero-point vibrations on the rates of transition in the localized process of activation. An attempt is made to explain the anomalies by introducing a "strain-enhancement" effect, i.e., f(T), semiempirically in the logrithmic creep equation [Formula: see text] where Teff = T0 + AT2 (T0 and A are constants), which allows for quantum effects below a certain temperature.
Motional narrowing in CO2: a hydrodynamic description?
Authors: Tam R. C. H. , May A. D.
Published: April 2011

The motionally narrowed depolarized Raman spectrum of compressed CO2 is reexamined in terms of classical rotational diffusion. The analysis shows that a hydrodynamic interpretation of the width of the spectrum in terms of rotational Brownian motion and viscous damping is not warranted for CO2 and probably not for any single component fluid. The analysis also gives a physical reason for the τ0 arbitrarily introduced by several authors while inflicting a hydrodynamic interpretation on motionally narrowed rotational spectra.
Periodic Lamé functions and applications to the diffraction by a plane angular sector
Authors: Sahalos John N. , Thiele Gary A.
Published: April 2011

In this paper we improve the exact eigenfunction solution of diffraction by a plane angular sector. Previous work on the problem has used the continued fraction method and results have only been presented for the quarter plane. The continued fraction method is useless because it requires computation times that become unreasonably long for larger eigenvalues due to instability in the method. In this work we will describe a method which overcomes all these difficulties. Results will be shown for eigenfunctions and eigenvalues on angular sectors of various shapes. Results for the current distribution and the far field will also be shown.
Relativistic dynamics and quark confinement ?
Authors: Moore R. A. , Edwards G. W. R. , Filipkowski J. D.
Published: April 2011

First, starting from a relativistic d'Alembert's principle for a one-particle system, it is shown that whenever a classical Lagrangian formulation exists for one observer in terms of his space-time variables, a corresponding formulation exists for any Lorentz-related observer. The relationship is unique and guarantees the correct description of any physical one-particle problem for all such observers. One is then able to identify unambiguously the relativistic scalar, vector, etc. interactions classically. Second, some simple one-dimensional exactly solvable problems are discussed in order to illustrate the differences in the motions caused by relativistic scalar and vector interactions. One of the scalar interactions suggests the possibility of quark confinement classically. Finally, some generalizing comments are presented.
Broken chiral symmetry and the classification of B mesons
Authors: Hatzis M.
Published: April 2011

We consider broken SU(5) × SU(5) chiral symmetry and we assume that the vacuum is SU(5)-symmetric. Using the observed mass spectrum of pseudoscalar mesons, and setting the [Formula: see text] mass in the range 5.2 ± 0.06 GeV, we predict the masses of [Formula: see text], [Formula: see text], and ηb states as well as axial current couplings fi/fπ. SU(5) × SU(5) is found to be consistent with SU(4) × SU(4) breaking. The problem of η − η′ − ηe − ηb mixing is also discussed.
Consequences of nonuniqueness in spin-relaxation theory
Authors: Hagston W. E. , Holmes B. J.
Published: April 2011

Various aspects of a general theorem, which asserts the lack of uniqueness of the density operator ρA for a composite system having subsystems B and C, are exploited in a systematic manner to obtain the maximum simplification in the equation of motion for the density operator ρB describing the subsystem. In particular, these ideas are applied to relaxation in spin systems in which only the second order terms in the interaction between subsystems B and C are retained in the master equation.
Experimental evidence for as the predissociating state in the B3Πg and a1Πg states of N2
Authors: Verma R. D.
Published: April 2011

Predissociation in the B3Πg, ν = 12 level of N2 is reexamined from a study of the 12–8 band of the [Formula: see text] transition in absorption as well as in emission under different conditions. New intensity perturbations are discovered at N′ = 27 and 28 for the R22 and R33 branches respectively and at about N′ = 29 for the Q11, Q22, and Q33 branches. These intensity perturbations, as well as the one already known at about N = 33, are suppressed in emission by increasing the pressure of N2. A new break-off point at N′ ≥ 42 is observed at high pressure. The analysis of these results confirms the existence of a [Formula: see text] state with a shallow potential well. The experimental molecular parameters of the [Formula: see text]state are in good agreement with the theoretical values.
De la combinatoire du modèle de l'échiquier de Feynman et des fonctions spéciales
Authors: Williams J. G.
Published: April 2011

The exact solution of the Feynman checkerboard model is given both in terms of the hypergeometric series and in terms of Jacobi polynomials. It is shown how this leads, in the continuous limit, to the Dirac equation in two-dimensional space-time.
An inverse scattering study of the radiation solution of the sine–Gordon equation
Authors: Enns R. H. , Rangnekar S. S.
Published: April 2011

Making use of the diagrammatic approach to the inverse scattering transform method that we pioneered on the 3-wave interaction problem, we have studied the complete temporal and spatial evolution of the radiation solution of the sine–Gordon equation. The analytic results are consistent with numerical simulations as well as qualitative ideas prevalent in the literature. The extension of the diagrammatic approach to the sinh–Gordon and other nonlinear evolution equations of physical significance is also briefly discussed.
Magnetic properties of amorphous Fe–Mo–B alloys
Authors: Dunlap R. A. , Stroink G.
Published: April 2011

The magnetization and Fe hyperfine fields of the series of amorphous alloys Fe80−xMoxB20 for x = 0, 2, 4, 7, 10, and 14 have been investigated. The magnetization at 4.2 K decreases from a value of 180 ± 2 emu/g for Fe80B20 to 79 ± 2 emu/g for Fe66Mo14B20 (1 emu = 10 A). The Fe hyperfine field is 2.91 × 105 Oe in Fe80B20 and shows a decrease of approximately 8 × 103 Oe/at. % of Mo (1 Oe = 79.6 A/m). The hyperfine field distributions show a growing low-field component with increasing x. Results are discussed in terms of previous measurements on similar alloys and the local environment of Fe atoms in transition metal glasses.
Long-wavelength phonons in 2H–NbS2, 2H–TaS2, and AgxTaS2
Authors: McMullan W. G. , Irwin J. C.
Published: April 2011

The Raman spectra of 2H–NbS2 and 2H–TaS2 have been analyzed in terms of a valence-force-field (VFF) model that incorporates four parameters. Analytic expressions for the Brillouin-zone-centre phonon frequencies have been obtained from the model and used in conjunction with the Raman frequencies to evaluate the four force constants for the two compounds. The results are compared with the known phonon spectra of similar compounds. The Raman spectrum of AgxTaS2 has also been investigated as a function of silver concentration x. Three new phonon modes appear in the Raman spectrum of AgxTaS2 with x < 1/3 and these new modes are attributed to a zone-folding mechanism. The plausibility of this interpretation has been investigated using phonon dispersion curves calculated from the VFF model.
Thickness and doping effects observed in impure vacuum deposited a-Si films
Authors: Talukder G. , Cowan J. A. , Brodie D. E. , Leslie J. D.
Published: April 2011

Films of a-Si have been prepared by vacuum deposition from crucibles of BeO and BN in a hydrogen ambient. The electrical conductivity of these impure films was modified by the addition of aluminum that was coevaporated during the film deposition. The changes observed are consistent with the assumption that the aluminum doping results in a p-type film for low conconcentrations (<2.3 at.%) whereas high concentrations introduce band structure changes as well. Thickness dependent sample resistivities are observed. This result is interpreted using a layer model to approximate two surface layers with resistivities ρs = 108 Ω∙cm and a bulk layer with ρB = 8 × 103 Ω∙cm. Each high-resistance layer, which is approximately 0.12 μm thick, seems to be caused by the increased hydrogen concentration at both surfaces, which is observed in the hydrogen profiling study. It is suggested that these high-resistance surface layers are due to a wider band gap material with the Fermi level near midgap. The bulk material has a smaller band gap with the Fermi level closer to one of the band edges.
134Cs level structure deduced from the (n, γ) reaction
Authors: Kennett T. J. , Prestwich W. V. , Tsai J. S.
Published: April 2011

A detailed study of the radiation following thermal neutron capture by 133Cs is reported. The statistical precision attained and the signal processing used to enhance resolution to the equivalent of 1.5 keV are combined to provide insight into the complex level structure of 134Cs. A statistical model is used to establish that the observed transitions consist mainly of primary transitions, and hence directly reflect the presence of bound levels. Comparisons are made with high resolution crystal spectrometer results to demonstrate the reliability and effectiveness of the data processing techniques employed. A neutron separation energy of 6891.584(17) keV was obtained through use of the 15N neutron binding energy and 40 low-lying levels reported from the crystal measurements. The properties of this nucleus, within the context of a statistical model, are examined and the energy dependences of level density and radiative widths are explored. Parameters such as nuclear temperature and reduced radiation widths are also given.
Classical electrodynamics of spinning particles
Authors: Hoeneisen Bruce
Published: April 2011

We consider particles with mass, charge, intrinsic magnetic and electric dipole moments, and intrinsic angular momentum in interaction with a classical electromagnetic field. From this action we derive the equations of motion of the position and intrinsic angular momentum of the particle including the radiation reaction, the wave equations of the fields, the current density, and the energy-momentum and angular momentum of the system. The theory is covariant with respect to the general Lorentz group, is gauge invariant, and contains no divergent integrals.
Cross relaxation at the lysozyme–water interface: an NMR line-shape-relaxation correlation study
Authors: Peemoeller H. , Kydon D. W. , Sharp A. R. , Schreiner L. J.
Published: April 2011

In wet hen egg white lysozyme (HEWL), the molecular dynamics at the lysozyme–water interface was studied using a proton NMR line-shape-relaxation correlation approach that employed selective inversion of the proton magnetization. The intrinsic lysozyme proton spin-lattice relaxation rate, the intrinsic water proton spin-lattice relaxation rate, and the lysozyme proton – water proton cross-relaxation rate were determined. The lysozyme proton – water proton intermolecular interaction couples these protons and contributes to spin-lattice relaxation as well. The results suggest that a minimum of three different correlation times are needed to characterize the water molecule dynamics in wet HEWL.
Electromagnetic breakup of the deuteron in the Δ resonance region
Authors: Leidemann W. , Arenhövel H.
Published: April 2011

The processes d(γ, p)n and d(e, e′p)n have been studied in the Δ resonance region with explicit Δ degrees of freedom in a coupled channel treatment that includes all final state interactions. In particular, the dependence on the model for the potential and the Δ parametrization has been investigated. The main emphasis has been put on the photodisintegration. The total cross section for this process is considerably reduced by inclusion of the Δ interactions, resulting in better agreement with a recent experiment. The angular distribution up to the resonance region shows a stronger forward and backward peaking than experimental results do, while above the resonance the agreement is better. Whereas the γ asymmetry is affected very little by the coupled channel calculation compared with the impulse approximation, the proton polarization is quite sensitive to the proper treatment of the Δ degrees of freedom.
Experiments at TRIUMF on radiative processes
Authors: Hutcheon D. A.
Published: April 2011

The current program of nucleon and pion radiative capture and proton–proton bremsstrahlung measurements at TRIUMF is described. Neutron radiative capture with polarized beam and target is suggested as a possible future experiment.
Intermolecular forces and the properties of interacting molecules
Authors: Buckingham A. D.
Published: April 2011

Intermolecular forces, and their effects on the properties of gases, liquids, and solids, are related, by long-range theory, to the properties of the isolated molecules. The usefulness of this approach is expounded, and its limitations investigated by means of ab initio computations. It is suggested that the structures of many Van der Waals molecules, and particularly those with a hydrogen bond, are attributable to electrostatic forces.
General relativity: progress, problems, and prospects
Authors: Israel Werner
Published: April 2011

This is an informal review of progress in gravitational physics and cosmological theory during the past decade and a half, and of challenges currently facing the theory.
Local driving field and the existence of a coherent mode in a system of driven two-level atoms
Authors: Zaidi H. R.
Published: April 2011

Using a diagram technique, the equations of motion for the density matrix and the field inside the medium are derived for a system of driven two-level atoms. It is pointed out that these equations do not necessarily imply that the local driving field is perfectly coherent even if the external field is. In fact, by calculating the emission spectrum, it is shown that the coherent-scattering component acquires a small nonzero width in the strong-field region. It is concluded that the local driving field is only quasi-coherent. The physical origin of this effect lies in the peculiar nature of resonant interaction between two atoms. The results are compared with the previously obtained results for the foreign gas broadening type of collisions. It is found that there are qualitative as well as quantitative differences between the two results.
The general product average decomposition equation and the Ising ferromagnet
Authors: Frank B. , Nath K.
Published: April 2011

A method is found whereby the product average decomposition (PAD) approximation of Frank and Mitran may be directly applied to the thermal average of any well-behaved function of Oi = ΣjJijSj, for the spin-1/2 Ising model with nearest-neighbour interactions. A general formula is derived by considering a fictitious spin system wherein the PAD is exact. It is applied to the calculation of transition temperatures in d dimensions, for d = 3 to d = 20.
Observations of magnetic aspect effects in auroral radar backscatter
Authors: Koehler J. A. , Sofko G. J. , Mehta V. , McNamara A. G. , McDiarmid D. R.
Published: April 2011

A series of experiments have been performed to investigate VHF auroral backscatter. The equipment is basically a bistatic CW radar using narrow beam antennas. One objective has been to investigate the dependence of backscatter power and spectral characteristics on aspect angle: the angle between the line of sight and the local magnetic field in the scattering region. The results indicate that the effects of aspect angle are much more complex than earlier measurements have indicated.
Calcul des forces d'oscillateur des premières transitions permises des donneurs dans le silicium et comparaison avec l'expérience
Authors: Bara M. , Astier M. , Pajot B.
Published: April 2011

The calculation of the oscillator strength of the optical transitions between two electronic states necessitates the knowledge of the wave functions of these states. In the case of hydrogenic donor impurities in semiconductors, these wave functions are eigenvectors of a matrix whose elements couple hydrogenic basis wave functions of appropriate parity, angular momenta, and projection of angular momentum through a one-electron effective mass Hamiltonian, provided the set of eigenvalues of interest has been minimized with respect to the variational parameters included in the basis wave functions. In his well-known paper, Faulkner has given the eigenvalues of the first donor states for Si and Ge, but neither the eigenvectors nor the variational parameters. We have reproduced the calculations of Faulkner for Si, finding quite similar results for the eigenvalues. The coefficients of the linear combinations of the basis functions show that except for the very first levels, the labeling of the eigenvectors does not correspond to the basis function with the greatest weight, and that the labeling is somewhat arbitrary from that point of view. The eigenvectors are used to calculate the electric-dipole matrix elements. The values so obtained for the oscillator strengths are in qualitative agreement with the relative intensities of the observed lines for substitutional donors in Si. This seems to demonstrate that the eigenvectors obtained through the Rayleigh–Ritz procedure are reliable enough for the evaluation of spectroscopical quantities where they are needed.
Response of the equatorial ionosphere to solar magnetic sector crossing
Authors: Sastri J. Hanumath
Published: April 2011

A superposed epoch analysis has been carried out of h′F values at Kodaikanal (10°14′N, 77°28′E, dip 3.0°N) pertaining to years of high sunspot activity using solar wind sector boundary passages past the earth as key days. It is found that there is a reduction in h′F values at 2000 LT 1 or 2 days after the sector boundary crossing. The amplitude of this effect which is noticed with both (+, −) and (−, +) sector boundary crossings is higher in equinoxes than in solstices. The response of the equatorial F region to sector boundary crossing seems to originate from perturbations of the equatorial east–west electric field in the post-sunset period associated with the enhancement in geomagnetic activity in the wake of sector boundary crossing.
Far-infrared collision-induced absorption in some compressed gaseous halogenated methanes
Authors: Van-Thanh Nguyen- , Rossi I.
Published: April 2011

Calculations of the collision-induced rotational and translational absorptions have been performed for seven pure halogenated methanes CH3F, CH3Cl, CF3H, CF3Cl, CF3Br, CCl3H, and CCl3F. We have considered the theory of Frost for multipole-induced dipolar absorption in bimolecular collisions taking the anisotropy of the molecular polarizability into account. The comparison with experimental literature data of CF3H and CF3Cl was reported; a reasonable agreement was obtained only for CF3Cl.
Estimation of spin transfer parameters through the anisotropic supertransferred hyperfine interaction
Authors: Ziaei M. E.
Published: April 2011

Using the experimental transferred and anisotropic supertransferred hyperfine interactions, with the configuration interaction model of covalent bonding for the linear bonds of M2+(3dσ)–F−(2pσ)–Cd2+(4pσ) and M2+(3dπ)–F−(2pπ)–Cd2+(4pπ) existing in crystals of CsCdF3: M2+ (where M = Mn or Ni), suggests that fσ, the σ-type spin transfer parameter for the Mn2+–F− bond, is about 3.1%. This value is much larger than estimates from neutron scattering data, although it is in reasonable agreement with the works of Ziaei and Owen, and Rinneberg and Shirley.
Multiplicity distribution at high energies
Authors: Ling S. H. , Young K.
Published: April 2011

The break in the multiplicity distribution at [Formula: see text] in the [Formula: see text] collider is explained in a broad class of geometric models. The break is predicted to move slowly to higher z as energy increases.
About explanations for X-ray bursts with double peaks and precursors
Authors: Schweizer Martin Andreas
Published: April 2011

Current explanations for X-ray bursts with double peaks and precursors are discussed. Order of magnitude considerations reveal problems with the basic assumptions of proposed models with expanding photospheres. It is found that the low temperature in the outer layers has only a limited influence on the spectrum of the emergent X radiation. The formation of double peaks and precursors from originally single-peaked profiles caused by hyperbolic photon diffusion through marginally optically thick layers is reviewed. It is pointed out that the physics connected with expanding photospheres requires the application of fully relativistic and causal diffusion equations introduced earlier.
A rocket measurement of O(1S) and emissions in a pulsating aurora
Authors: McDade I. C. , Llewellyn E. J. , Solheim B. H.
Published: April 2011

Rocket measurements of the O(1S–1D) 557.7-nm and [Formula: see text] (0–0) 391.4-nm emission profiles for the steady component of an international brightness coefficient 1+ aurora, which exhibited irregular pulsations, are presented. The [Formula: see text] volume emission profile is found to be in good agreement with theoretical profiles calculated from the primary-electron energy spectra recorded near apogee on the same flight. The O(1S) emission is found to increase with altitude relative to the [Formula: see text] emission between 100 and 130 km, and possible mechanisms for the excitation of O(1S) are examined. It is found that either energy transfer from [Formula: see text] or the reaction of N+ with O2 can explain most of the observed O(1S) emission, but the possibility of a different excitation mechanism cannot be ruled out.
Neutron-diffraction study of the structural phase transitions in the antifluorite K2PtBr6
Authors: Armstrong Robin L. , Morra Rose M. , Powell Brian M.
Published: April 2011

Neutron-powder-diffraction profiles are reported for the antifluorite K2PtBr6 at temperatures of 296, 160, 141, and 120 K. Bromine nuclear-quadrupole-resonance measurements have shown that each of these temperatures corresponds to a different crystal structure and have provided information on the most probable structures. A variety of structural models with symmetries obtained from a group theoretical classification of structural phase transitions are fitted to the diffraction data. A comparison of goodness-of-fit parameters for the models considered at each temperature allows the space group of each phase to be identified. The results provide (i) a definitive test of the validity of a classification scheme proposed for nuclear-quadrupole-resonance spectral characteristics, and (ii) support for the proposition that the allowable, continuous distortions of a crystal are given by the nondisruptive criterion rather than the more restrictive group–subgroup criterion.
High-resolution laser-excitation spectrum of the A2Π ← X2Σ system of TiN: rotational analysis of the 0–0, 1–1, and 2–2 bands
Authors: Brabaharan K. , Coxon J. A. , Yamashita A. Brian
Published: April 2011

The 0–0, 1–1, and 2–2 bands of the A2Π ← X2Σ system of TiN have been recorded using the technique of laser-excitation spectroscopy. Molecular constants have been obtained from direct least squares fits of the measured line positions of individual bands. The fitted constants confirm and extend previous determinations; for the A2Π state, some of the constants show unusually large variations with ν, in accord with the already known perturbation of this state in the ν = 0 level.
Cosmological models with both radiation and matter
Authors: Coley A.
Published: April 2011

A class of flat, homogeneous and isotropic, relativistic cosmological models containing both radiation and pressure-free matter is investigated.
Total and differential cross sections for pion production via coherent isobar and giant resonance formation in heavy-ion collisions
Authors: Deutchman P. A. , Norbury J. W. , Townsend L. W.
Published: April 2011

A quantal many-body formalism is presented that investigates pion production through the coherent formation of a nucleonic isobar in the projectile and its subsequent decay to various pion charge states along with concomitant excitation of the target to a coherent spin–isospin giant resonance via a peripheral collision of relativistic heavy ions. Total cross sections as a function of the incident energy per nucleon and Lorentz-invariant differential cross sections as a function of pion energy and angle are calculated. It is shown that the pion angular distributions, in coincidence with the target giant resonance excitations, might provide a well-defined signature for these coherent processes.
Time-dependent coupled Hartree–Fock calculations of triplet excited states of closed-shell atoms
Authors: Kundu B. , Mukherjee P. K.
Published: April 2011

The nonrelativistic, time-dependent coupled Hartree–Fock theory has been applied to generate the excitation spectrum of two-electron atoms for the forbidden transitions 11S → n3S(n = 2, …, 8), and transition properties are estimated. A simple but effective form of the time-dependent perturbation operator is chosen to get such an excitation spectrum. Reasonable agreement is observed with the available experimental and theoretical estimates.
Remarks on broken chiral SU(5) × SU(5) symmetry and B mesons
Authors: Kim D. Y. , Sinha S. N.
Published: April 2011

In a recent paper, Hatzis has estimated the masses and weak decay constants of b-flavored pseudoscalar mesons in a broken chiral SU(5) × SU(5) symmetry method. The estimated weak decay constant of B meson, [Formula: see text], however, does not agree with the value [Formula: see text] evaluated by Mathur et al. with the quantum chromodynamics (QCD) sum-rule model. We re-examined the problem applying the broken chiral SU(5) × SU(5) symmetry approach using a set of mass formulae. With this method we estimate the symmetry-breaking parameters and decay constants of pseudoscalar mesons. We found a consistent result for the decay constant: [Formula: see text]. The explicit numerical value of these constants, however, are lower than that of the QCD sum rule. This may be due to the limited validity of the broken chiral symmetry approach for heavy mesons.
Experimental transition probabilities of the infrared lines 3p–4s of Ne I and 4p–5s of Ar I
Authors: Tanarro I. , Campos J.
Published: April 2011

Relative transition probabilities for the infrared lines 3p–4s of Ne I and 4p–5s of Ar I have been determined from emission line-intensity measurements of optically thin light sources. In this experiment a photoconductive cell and a digital phase-sensitive amplifier have been used for light detection. Transition probabilities have been put on an absolute scale by using the Coulomb approximation. The present experimental data are compared with the existing theoretical data for neon and with experimental and theoretical data for argon.
Refined molecular constants for the states of H2
Authors: Larzillière Michel , Launay Françoise , Roncin Jean-Yves
Published: April 2011

Refined molecular constants for the states C, D, D′, and D″ [Formula: see text] of H2 have been obtained using the best values of the ground-state constants derived recently by Dabrowski. A few high J values of C and D states are reassigned.
Absolute differential cross section for the 7Li(3He, ααd) reaction at
Authors: D'Amico V. , Fazio G. , Femino S. , Giardina G. , Italiano A. , Mezzanares F.
Published: April 2011

The analysis of the dα bidimensional spectra of the 7Li(3He, ααd) reaction at [Formula: see text] is a suitable way of calculating the absolute differential cross section and estimating the competition among the various (d, 8Be) and (α, 6Li) channels when the ground state, the 3.04-MeV 8Be states, and the 5.65-MeV 6Li state are involved.
Quantum defect orbital calculations on the alkaline-earth elements: oscillator strengths and photoionization cross sections
Authors: Barrientos Carmen , Martin Inmaculada
Published: April 2011

The quantum defect orbital (QDO) formalism is applied to the computation of oscillator strengths of Mg, Ca, Sr, and Ba and photoionization cross sections of Mg and Ca. For [Formula: see text] transitions, QDO oscillator strengths reproduce fairly well the experimental values both in magnitude and trend. Photoionization cross sections for ns2 → nsεp transitions agree well with experimental results where no autoionization resonances are present. The results of both sets of calculations are at least comparable in quality to those of other more complex procedures.
Multiparticle production in proton–proton collisions at high energies
Authors: Hussein M. T. , Hassan N. M. , Hegab M. K.
Published: April 2011

The multiplicity distribution and the inelasticity coefficient are studied for proton–proton collisions at incident energies of 6, 19, 25, and 69 GeV. A theoretical model is proposed, based on a sequential decay system formed by the two interacting protons. The Monte Carlo technique is used to calculate the phase-space integral and for simulation of events for the different reactions.
Critical field H for thin type-II superconducting films coated with normal metal
Authors: Cleary Robert
Published: April 2011

We calculate the critical magnetic field of thin films of superconducting material coated with normal metal. The proximity effect is taken into account in a brief discussion in the body of this paper. In particular, we consider the normal-metal coating to range from very thin to very thick and to have a critical temperature ranging from [Formula: see text] to [Formula: see text], where Tc is the critical temperature of the superconductor. For material with sufficient dosing in paramagnetic impurities, [Formula: see text]. We obtain eigenvalue equations involving confluent hypergeometric functions for the critical field of a given film thickness for all possible normal-metal coatings.
Pumping light intensity transmitted through an inhomogeneously broadened line system: application to passive rubidium frequency standards
Authors: Tremblay Pierre , Cyr Normand , Têtu Michel
Published: April 2011

This paper presents a theoretical evaluation of the pumping light intensity transmitted through an inhomogeneously broadened line system submitted to a coherent microwave excitation. A model is developed for the case of rubidium 87 atoms interacting with a buffer gas and optically pumped by all components of the D1 and D2 lines. The light generated by an electrodeless lamp is considered incoherent and the coherent signal is produced in a microwave cavity. The spatial distribution of the light intensity transmitted through the absorption cell is shown to be related to the microwave magnetic-field axial-component distribution. Then the resonance curve obtained with a photodetector is a function of its shape and location. When applied to the case of a passive rubidium frequency standard, this model allows the calculation of the ultimate short-term frequency stability of the device.
A variational theory for the wave-vector-dependent transverse spin susceptibility and spin-wave velocity of a two-sublattice antiferromagnet
Authors: Liu K. L. , Vosko S. H.
Published: April 2011

Based on the Hohenberg and Kohn theorems, we derive a variational lower bound expression for the static wave-vector-dependent transverse spin susceptibility χ+−(q) of a two sublattice commensurate antiferromagnet that has a characteristic magnetic reciprocal lattice vector Q. The variational result is valid for a general exchange-correlation energy functional. When appropriate trial functions are adopted, the variational expressions for χ+−(q) and χ+−(Q + q) have the correct small-q behavior, the latter being divergent as q−2 in accord with Wagner's 1/q2 theorem for broken symmetry. For systems in which spin waves are the only low-lying excitations, these approximate susceptibilities can be used to yield an upper bound for the antiferromagnetic spin-wave velocity [Formula: see text].
Rotational line strengths in 3Δ–3Σ electronic transitions. The Herzberg III system of molecular oxygen
Authors: Kerr C. M. L. , Watson J. K. G.
Published: April 2011

Electronic transitions of the type 3Δ–3Σ are forbidden in the absence of spin–orbit or orbit–rotation coupling, but spin–orbit perturbations produce three transition moments, two perpendicular (Y1 and Y2) and one parallel (Z1) while low-order orbit–rotation couplings introduce three further perpendicular transition moments (X1, X2, and X3). Formulas are presented for the rotational line strengths in a 3Δ(a)–3Σ(int) transition in terms of these parameters and are applied to recent data of Coquart and Ramsay for the Herzberg III system [Formula: see text] of molecular oxygen. It is shown that all six parameters are significant, and that there are noticeable departures from the first-order relations Y1 = Y2, Z1 = 0, X1 = X2 = X3. The observation of orbit–rotation intensity effects led to the first identification of lines of the Ω′ = 3 subbands of the 4–0 to 7–0 bands of the Herzberg III system, which are forbidden for the spin–orbit mechanism. The wave numbers of these lines are in satisfactory agreement with the analysis of the A′3Δu → a1Δg emission by Slanger and Huestis.
On the behaviour of a weak discontinuity in a radiation-induced flow field
Authors: Sharma Rishi R. , Mosa Mahdi F.
Published: April 2011

The growth and decay behavior of weak gas-dynamic discontinuities has been studied by taking into account the influence of coupling between the time-dependent gas-dynamic field and the radiation field. The thermal radiation effects have been investigated using a quasi-equilibrium and quasi-isotropic hypothesis of the differential approximation to the radiative-heat-transfer equation. It is proved that the time-dependent radiation field, gives rise to a radiation-induced weak wave, which has a negligible influence on the nonrelativistic flow properties of the gas-dynamic field. It is also shown that there is an interesting competition between radiation stresses to resist the steepening tendency of a compressive, weak wave to stabilize itself and the thermal conduction effects to destabilize the wave. It is found that under thermal radiation effects, shock wave formation is either disallowed or delayed. Three cases, diverging waves, converging waves, and plane waves, have been studied separately with reference to the growth and decay behavior of their amplitudes. For converging waves, it is found that either they form a caustic under curvature effects or if it happens to be a compressive wave with the magnitude of its initial amplitude greater than a certain critical value, then it grows into a shock wave within a finite critical time before a caustic can be formed.
Magnetohydrodynamic unsteady free convective flow through a porous medium bounded by an infinite vertical porous plate
Authors: El Dabe Nabile T.
Published: April 2011

Unsteady, free convection flow of an incompressible electrically conducting viscous liquid through a porous medium past a hot, vertical, porous plate in the presence of a transverse magnetic field has been studied in this paper. The flow phenomena have been characterized by the nondimensional numbers P (Prandtl number), G (Grashoff number), M (magnetic number), W (frequency parameter), and K (permeability parameter). The effect of these parameters on the velocity and temperature distribution, the skin friction, and the heat flux have been tabulated and represented graphically.
Effects of Coriolis force and nonuniform temperature gradient on the Rayleigh–Benard convection
Authors: Rudraiah N. , Chandna O. P.
Published: April 2011

The effects of the Coriolis force and a nonuniform temperature gradient on the onset of the Rayleigh–Benard convection in a thin, horizontal, rotating fluid layer is studied using linear-stability analysis. It is shown analytically that the method and rate of heating, the Coriolis force, and the nature of the bounding surfaces of the fluid layer significantly influence the value of the Rayleigh number at the onset of marginal convection. The mechanism for suppressing or augmenting convection is discussed in detail. The Galerkin technique employed here is much easier to use than that the method of Chandrasekhar (5). The analytical results obtained from using this procedure are compared with the published experimental data and the results obtained from numerical procedures; good agreement is found.
Some practical applications of the isotropic time in rotating coordinates
Authors: Henriksen R. N.
Published: April 2011

This paper uses the isotropic time in a noninertial frame to discuss the principle of the ring-laser gyro and related phase-coherent systems. The gravitational effects of a slowly rotating massive body, such as the Earth, are also allowed for. The use of time-synchronization networks and very long baseline radio interferometry as probes of both the stationary and low-frequency gravitational fields near the Earth is suggested.
Experimental consequences of the nonsymmetric gravitational theory including the apsidal motion of binaries
Authors: Moffat J. W.
Published: April 2011

The experimental consequences of the nonsymmetric gravitational theory (NGT) are reviewed. The observed periastron motion of the binary system DI Her is compared with the predictions of general relativity and NGT. The systems NY Cep, DH Cep, and ι Ori are proposed as potentially significant candidates to test the gravitational theories.
Energy levels, decay scheme, gamma-ray branching ratios, and lifetimes in 49V with (p, nγ) reaction
Authors: Khaliquzzaman M. , Dawson W. K. , Fielding H. W. , Green P. W. , Helmer R. L. , McDonald W. J. , Neilson G. C. , Robertson B. C. , Sheppard D. M.
Published: April 2011

The reaction 49Ti(p, nγ)49V has been studied at an incident energy of Ep = 5.74 MeV using a pulsed beam. Energy levels, a decay scheme, and gamma-ray branching ratios have been obtained from the observed gamm-ray spectra. Lifetimes are obtained by a direct timing technique. Energy levels up to 3667 keV excitation have been observed including some that were seen previously only through other reactions. New gamma-ray transitions have also been observed. The results obtained are compared with those from previous works.
Correlation among target fragments produced in a heavy-ion interactions: search for shock-wave phenomenon
Authors: Ghosh Dipak , Roy Jaya , Sengupta Kaushik , Dutta Anuradha , Basu Madhumita , Naha Sadhan
Published: April 2011

This paper presents a study of two-particle inclusive angular correlations among "black" and "grey" particles produced in the interaction O16 nuclei with photoemulsions at 2.1 GeV/nucleon. The experimental data have been compared with the Monte Carlo simulated values assuming an independent emission. It has been observed that there is some short-range correlation among the target fragments, which may indicate shock-wave formation.
Photoluminescence spectrum of tetracyanoquinodimethane crystals at 25 K: temperature and pressure dependence
Authors: Desgreniers S. , Roubi L. , Carlone C. , Hochheimer H. D.
Published: April 2011

Using 488.0 and 514.5 nm laser radiation, we have obtained the luminescence spectrum of excited tetracyanoquinodimethane (TCNQ) crystals from 10 to 36 K at a pressure of 0 GPa. At 10 K, the luminescent peaks occur at 14 100, 15 000, 15 700 (±100), 16 300, 16 600, 16 800, and 17 200 (±50) cm−1. The temperature shift of the spectrum is −16 ± 7 cm−1∙K−1. At a constant temperature of 25 K, we followed the luminescent peaks as a function of pressure up to 8.5 GPa. The pressure shift of the luminescence, at low pressures, is −100 ± 50 cm−1∙GPa−1. We estimate that the volume-dilation contribution to the total temperature dependence is at most +2 cm−1∙K−1, in which case the electron–phonon-interaction contribution is −18 cm−1∙K−1. We have also examined the Raman spectrum at 25 K and have found the 1389 cm−1 ν4 (C=C) wing-stretching vibration of TCNQ−; its pressure behaviour is similar to that observed in TCNQ salts. The measurements were made on crystals grown very differently in two separate laboratories, and the effects induced by temperature or pressure were reversible. We attribute the luminescence to the 2B2g → 2B1μ transition of the TCNQ− anion radical, whose presence is due to impurities having a concentration of less than 0.01%.
Approximate solutions to the one-particle Dirac equation: numerical results
Authors: Moore R. A. , Scott T. C.
Published: April 2011

The zero-, first-, and second-order differential equations in a previously defined hierarchy of equations giving approximate solutions to the one-particle Dirac equation and the corresponding eigenvalue contributions are each written as power series in α, the fine structure constant, for an arbitrary, spherically symmetric potential. These equations are solved numerically for the hydrogen-atom potential to obtain wave functions to order α2 and eigenvalues to order α4 for all states with n = 1–4, inclusive. The numerical solutions are then used to evaluate a number of matrix elements to order α2. A comparison with the exact expressions shows that the numerical values for the coefficients of the different powers of α have at least six significant figures in the eigenfunctions and eigenvalues and five in the matrix elements. Thus, the procedure is validated and can be applied with confidence to other atomic systems.
Quasi-soliton and other behaviour of the nonlinear cubic-quintic Schrödinger equation
Authors: Cowan Stuart , Enns R. H. , Rangnekar S. S. , Sanghera Sukhpal S.
Published: April 2011

The stability of the solitary-wave solutions of the nonlinear cubic–quintic Schrödinger equation (NLCQSE) is examined numerically. The solutions are found not to be solitons, but quasi-soliton behaviour is found to persist over wide regions of parameter space. Outside these regions dispersive and explosive behaviour is observed in solitary-wave interactions.