bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental tests of a new theory of gravitation
Authors: Moffat J. W.
Published: April 2011

The predictions for the perihelion shift, the deflection of light, and the delay time of a light ray are calculated in the nonsymmetric theory of gravitation. An upper bound for the parameter l (that occurs as a constant of integration in the static, spherically symmetric solution of the field equations) is obtained for the sun for the experimental value of the perihelion shift of Mercury, yielding [Formula: see text]. The upper bound on [Formula: see text] obtained from the Viking spacecraft time-delay experiment is [Formula: see text]. For [Formula: see text], we find that the theory is consistent with the standard relativistic experiments for the solar system. The theory predicts that the perihelion of a satellite could reverse its direction of precession if it orbits close enough to the sun. The results for a highly eccentric satellite orbit are calculated in terms of the value [Formula: see text].
Analysis procedures for annihilation energy spectra with enhanced sensitivity to positron localization
Authors: Schultz P. J. , Ollerhead R. W. , Lichtenberger P. C. , Nickel B. G. , MacDonald Jack R. , MacKenzie I. K.
Published: April 2011

Annihilation energy spectra in a variety of defected and defect-free metal samples have been measured repeatedly in order to test the relative sensitivity of several lineshape parameters to changes induced by positron localization. Commonly used measures of the lineshape, such as the variance, are shown to be decidedly inferior to parameters which weight the data from each channel in accord with its sensitivity to positron trapping. The counting time required for a given precision can be approximately halved by using an appropriately weighted shape parameter.
High-resolution polarized far-infrared vibrational spectra of semiconducting TTF-TCNQ and TSeF-TCNQ
Authors: Bates Frances E. , Eldridge J. E. , Bryce M. R.
Published: April 2011

High-resolution polarized far-infrared spectra of TTF-h4-TCNQ-h4, TTF-h4-TCNQ-d4, TTF-d4-TCNQ-h4, TTF-d4-TCNQ-d4, and TSeF-TCNQ are presented. These have been obtained mainly by a bolometric technique, which is possible only at low temperatures, but some measurements of transmission through aligned mosaics of single crystals at various temperatures are also reported. The bolometric technique is described and its limitations and advantages demonstrated. The measured wavenumber shifts enabled us to assign most of the many TTF-TCNQ features. For [Formula: see text], a strong group is believed to be due to Rz librations, which should be optically inactive, and a quartet has been assigned to the TTFν10(au) mode (a torsion of the two fulvalene rings about the central bond), which should be very weak. The anomalous infrared activity of both of these modes indicates that they are probably large components of the Peierls distortion. Normally inactive gerade intramolecular modes of both molecules are also observed at low temperatures. In TSeF-TCNQ, all of the "activated" modes involve only the TSeF molecule, indicating that the Peierls distortion produces little displacement or rotation of the TCNQ molecule. Estimates of the TSeF-TCNQ intrinsic and impurity energy gaps are also given.
Magnetic structure of bornite, Cu5FeS4
Authors: Collins M. F. , Longworth G. , Townsend M. G.
Published: April 2011

Neutron powder diffraction techniques have been used to investigate the magnetic structure of bornite, Cu5FeS4. Below the antiferromagnetic ordering temperature of 76 ± 2 K extra peaks appear in the diffraction pattern corresponding to magnetic ordering. The data are consistent with an antiferromagnetic alignment of iron atoms with moments of 4.4 ± 0.3 μB on the iron sites proposed by Koto and Morimoto on the basis of X-ray measurements of the crystal structure. Mössbauer and neutron diffraction data suggest that the second magnetic phase transition at 8 K arises from a spin rotation. Since the magnetic structure gives only superexchange paths between iron atoms through two or more anions, it is difficult to understand why the Néel temperature is so high without invoking small moments on copper atoms
Systematic inclusion of the effect of an arbitrary surface profile on the dispersion of surface plasmons
Authors: Summerside P. , Paranjape B. V.
Published: April 2011

The classical Boltzmann equation approach is developed to systematically include the effect of surface diffuseness in the random phase approximation (RPA) surface plasmon dispersion relation. This is achieved by the introduction of an arbitrary surface potential energy barrier into the distribution function. The resulting Fourier-transformed, linearized equation is solved by a perturbative-iterative scheme based on an expansion of the response function beyond the usual step-function form. The surface plasmon dispersion curves obtained lend support to the more recent experimental results which indicate an almost flat to slightly increasing small wavenumber behaviour. Noticeable dipping of the curves only occurs for broad surface regions, suggestive of surface contamination.
On the validity of the approximations used in asymmetric charge transfer collision calculations
Authors: Hird B. , Ali S. P.
Published: April 2011

Some formalisms which have frequently been used in general noncrossing electron transfer theories are examined and shown to be analytically equivalent. The accuracy of the numerical approximations is found to be surprisingly good, partly because different approximations tend to have opposite effects. The hydrogenic wave function assumption of the Rapp and Francis theory is found to be seriously inadequate and the theory is generalized to Coulomb wavefunctions of higher n value. When these wavefunctions are suitably normalized the magnitude and overall energy dependence of the cross section is in good agreement with experiment in alkali metal collisions where this type of collision is expected to be the dominant transfer process.
Effect of temperature on organic Schottky barrier cells
Authors: Loutfy Rafik O. , Hsiao Cheng-Kuo
Published: April 2011

The effect of temperature on the photovoltaic properties of indium/metal-free phthalocyanine Schottky barrier solar cells was investigated in the range 260–350 K. In general, the short circuit photocurrent, Jsc, and fill factor, ff, increased with increasing temperature (in contrast to inorganic photocells). The device series resistance and open circuit photovoltage, Voc, decreased (similar to inorganic photocells) as temperature was raised. An increase in the overall power conversion efficiency, η, has been observed with increase of temperature. In the case of x-H2Pc, the power conversion efficiency increased by 2.5 times due to a temperature rise of 60 °C above ambient. Thus, for operation at temperatures above ambient, organic solar cells may offer a significant advantage over inorganic cells.Analysis of the variation of the photovoltage with temperature showed that the decrease in Voc is mainly due to variation injunction impedance, which is controlled by thermionic current at high temperature and ionized impurity at low temperature.
Leading particle and nuclear-mass effects on multiparticle production in 50 GeV/c π− interactions in nuclear emulsion
Authors: Varma S. C. , Kumar V. , Sharma A. P.
Published: April 2011

An experimental study is carried out on the effects of nuclear mass on leading particle multiplicity and multiparticle production with the help of an emulsion stack exposed to 50 GeV/c π− beam under a strong pulsed magnetic field. The study of the effect of nuclear mass on the forward–backward asymmetry in a π−–A collision is also carried out using the grey particle multiplicity data. The results support the concept of "formation length" of radiation. An attempt is made to explain the space–time structure of hadronic matter in terms of the additive quark model of multiparticle production.
Etalonnage de cales étalons angulaires par la méthode de zéro
Authors: Bouillon Gratien , Tremblay Gilles , Delisle Claude
Published: April 2011

A method used to calibrate a set of reference angle gage blocks is described. Only the equipment usually found in a dimensional metrology laboratory is used, such as autocollimators and a surface plate. Contrary to some other well-known methods, supplementary sets of angle gage blocks, a high precision dividing head or a rotary table are not needed. To benefit from the sensitivity and repeatability of the autocollimators, while eliminating their errors of accuracy, a null-balance method has been used.[Journal translation]
Reproducibility of vacuum deposited films of amorphous ZnTe
Authors: Moore C. J. , Bharaj B. S. , Brodie D. E.
Published: April 2011

The temperature dependence of the electrical conductivity of high purity amorphous ZnTe films has been measured and compared for films produced in the same way, and some films produced with different deposition parameters. We have demonstrated (probably for the first time) that pure vacuum deposited amorphous films can be fabricated with sample conductivities reproduced to better than a factor of two (14 samples over a two year period) between ~100 and ~400 K. This work was made possible with the help of a microprocessor monitored vacuum deposition system with a base pressure of 10−9 Torr. In addition, it is shown that samples fabricated in a system at a pressure of 10−6 Torr have conductivities which depend on the nature of the residual gas in the system because the sample conductivity varies significantly when different ambient gases are introduced.
On the K-dependence of the electrical field in a crystalline slab of oscillating charges
Authors: Grindlay J.
Published: April 2011

The short range part of the electric field of a crystalline slab array of oscillating charges (a) is related to the Ewald sum and (b) can be represented by a rapidly convergent trigonometric series involving the wave vector K. Values for the coefficients of the first few terms of this series are reported for lattice sites in the sc, fcc, bcc, NaCl, CsCl structures and the symmetry directions (1,0,0), (1,1,0), (1,1,1).
Coexistence curve of the binary fluid nitrobenzene–heptane
Authors: Shelton J. , Balzarini D.
Published: April 2011

The liquid–liquid coexistence curve of the binary fluid nitrobenzene–heptane has been measured by interferometric means. The mole fraction concentration difference, ΔX, between the two liquid phases is equal to (0.205 ± 0.010)[(Tc − T)/Tc]β with β = 0.3328 ± 0.0020. The critical concentration is 0.470 ± 0.003 mole fraction nitrobenzene.
Cross sections for the 16O(16O,8Beg.s.)24Mg reaction and mechanisms of α-rearrangement reactions
Authors: Čujec Bibiana , Ferguson A. J. , Häusser O. , Horn D. , Warner R. E.
Published: April 2011

The 16O(16O,8Beg.s.)24Mg reaction was studied at laboratory beam energy of 53 MeV detecting 24Mg nuclei in coincidence with α particles originating from the 8Beg.s. → 2α decay. Differential cross sections at θc.m. ≈ 90° were found to be approximately 40 μb/sr for the 24Mg ground and 1.37 MeV (unresolved) states as well as for the 24Mg 4.12, 4.24, and 5.23 MeV (unresolved) states. A comparison with other α-rearrangement reactions, leading to the ground and first excited states of final nuclei, shows that the cross sections for the,16O(16O,8Be)24Mg reaction are only ~ 1/25 as large as for the 16O(16O,12C)20Ne reaction and that they are of about equal magnitude as for the 16O(16O,α)28Si reaction. This suggests that the,16O(16O,8Be)24Mg and 16O(16O,α)28Si reactions occur in statistical competition and, consequently, via formation of a more or less equilibrated compound system, while the 16O(16O,12C)20Ne reaction is mainly a fast, one-α-exchange process.
Hybrid bistable optical device using an acoustooptic waveguide modulator
Authors: Albert J. , Vincent D. , Tremblay R.
Published: April 2011

In this paper, we present a hybrid bistable optical device based on acoustooptic TE–TM mode conversion in an optical waveguide made of sputtered Ta2O5 on a glass substrate. The essential nonlinear transmission is provided by acoustic resonances. Bistability and optical limiting have been observed with less than 5 mW of acoustic power. A minimum value of 50 for the acoustooptic figure of merit (M2, relative to fused silica) of Ta2O5 is estimated from the results.
Intermolecular potentials from proton spin–lattice relaxation time in H2–Ar and H2–N2 gas mixtures
Authors: Pandey Lakshman , Sarkar K. Lalita
Published: April 2011

Proton spin-lattice relaxation times, T1, have been measured in H2–Ar and H2–N2 gas mixtures as a function of density (10 < ρ < 70 amagat), composition (~ 18–65%), and temperature (300–600 K) with a 30 MHz spin-echo spectrometer using phase sensitive detection. These data together with the T1 data obtained by Foster and Rugheimer and by Williams in these mixtures below 300 K have been analysed using the Bloom–Oppenheim theory. Models for intermolecular potentials to explain the T1 data have been proposed. It is found that the relative anisotropy in the attractive part of the intermolecular potential which fits the T1 data best compares well with that evaluated using polarizability data.
Application of the inverse scattering transform method to stimulated Brillouin backscattering in a generator setup: The Zakharov–Manakov solution
Authors: Rangnekar S. S. , Enns R. H.
Published: April 2011

Making use of the inverse scattering transform method (ISTM), we have solved the Zakharov–Manakov problem for the stimulated Brillouin backscattering (SBBS) of a laser pulse by a fluctuation, the envelopes of both being rectangular. The results are consistent with those obtained by Kaup and co-workers using a combination of direct numerical integration and Zakharov–Shabat analysis.
The magnetic properties of the oxygen–hole aluminum centers in crystalline SiO2. III. [AlO4]+
Authors: Nuttall R. H. D. , Weil J. A.
Published: April 2011

The EPR spectra of [AlO4]+ have been measured in α-quartz at ca. 35 K after X-irradiation at 77 K. This center is believed to contain two electron holes, one at each of two symmetry-related oxygen ions bonded to an aluminum ion substituted for silicon, forming a triplet spin system. Measurements of the two primary 27Al hyperfine multiplets (Ms = 0 ↔ Ms = ± 1) as well as the quasi-forbidden multiplet (Ms = + 1 ↔ Ms = −1) at half field have been made, and have led to a spin-Hamiltonian (matrices [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]). A crystal two-fold axis contains the aluminum ion and relates the two-hole-bearing oxygen ions, as well as the two outer silicon ions bonded respectively to the latter. The electronic quadrupole matrix [Formula: see text] is attributed primarily to the magnetic dipole–dipole interaction between the two unpaired electrons. The results of a comparison among the matrices [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and the corresponding matrices for the related single-hole centers [AlO4]0 and [AlO4/M+]+ (where M = H, Li) are consistent with the model for [AlO4]+.
Vacuum ultraviolet excitation of N2 by low energy electrons: Polarization and excitation-function measurements
Authors: Huschilt J. C. , Dassen H. W. , McConkey J. W.
Published: April 2011

Polarization data are presented for both atomic and molecular emissions excited following electron impact on N2. Significant polarization fractions near threshold are observed for the molecular emissions but only qualitative agreement with theoretical predictions is obtained. Atomic emissions are unpolarized with the exception of the 124.3 nm transition. Relative excitation functions are derived from the polarization data and are compared with previous optical and electron scattering data.
The A2Πi–X2Πi absorption spectrum of BrO
Authors: Barnett M. , Cohen E. A. , Ramsay D. A.
Published: April 2011

Absorption spectra of isotopically enriched 81Br16O and of normal BrO have been obtained by the flash photolysis of mixtures of bromine and ozonized oxygen. Rotational analyses are given for the 7–0, 12–0, 18–0, 19–0, 20–0, 21–0, 7–1, and 20–1 A2Π3/2–X2Π3/2 sub-bands of 81Br16O. The value for [Formula: see text] is found to be 722.1 ± 1.1 cm−1 in good agreement with the value calculated from microwave constants. Several additional bands have been found at the long wavelength end of the spectrum, necessitating a revision of the vibrational numbering scheme for both the emission and absorption bands. "Hot" bands up to ν″ = 6 have been observed in the absorption spectrum for the 2Π3/2 component of the ground state but no bands have yet been identified from the 2Π1/2 component.
Optical mixing of frequencies of a strong bichromatic field interacting with a three-level atom
Authors: Mavroyannis Constantine
Published: April 2011

We have studied the excitation spectrum arising from the optical mixing of the frequencies of a strong bichromatic field interacting with a three-level atom, where the two initially populated modes ωa and ωb are equal to the two atomic transition frequencies, respectively. In the limit of high photon densities, the excitation spectrum near the frequency ω = ωa – 2ωb has been calculated as a function of the parameter η = Ωa2/Ωb2, where Ωa and Ωb are the Rabi frequencies of the two laser fields, respectively. For [Formula: see text] and for weak fields for which [Formula: see text], the spectral function describes a Lorentzian line peaked at the frequency ω = ωa – 2ωb and has a width of the order of γ0, where γ0/2 is the natural width for a two-level atom. When Ωb2 > γ02 and [Formula: see text], the band at ω = ωa – 2ωb splits into two bands described by two Lorentzian lines peaked at ω = ωa – 2ωb ± Ωb/√2 and have spectral widths of the order of 3γ0/4. The ratio of the height of the band ω = ωa – 2ωb to the height ω = ωa – 2ωb ± Ωb/2 is 3:2. The probability amplitudes for both bands take large negative values indicating that optical amplification of the signal field may be expected to occur at these frequencies. When Ωa = Ωb = Ω, η = 1, and for Ω2 < γ02, the spectral function describes a single band at ω = ωa – 2ωb while for Ω2 > γ02, the single band splits into five pairs of bands which are separated from the frequency ω = ωa – 2ωb by frequency shifts which are equal to: ± Ω/√2, [Formula: see text], ± Ω, ± Ω√2, and ± Ω√3, respectively, and have spectral widths of the order of 3γ0/4. For [Formula: see text] and for laser fields for which Ωa2 > γ02 and Ωb2 > γ02, the spectral function consists of three pairs of bands. The probability amplitudes for these bands vary linearly with η and may take large values for [Formula: see text]. A complete discussion of the excitation spectrum as well as a graphical representation of the derived results has been given.
Compensation by deep levels in semi-insulating GaAs
Authors: Lombos B. A. , Yemenidjian N. , Averous M.
Published: April 2011

A multilevel model was developed to calculate the position of the Fermi level in GaAs. All the electrically-active impurity concentrations, indicated by spark source mass spectrographic analysis, were taken into account in the computation. The deduced semiconducting or semi-insulating properties are in agreement with the measured characteristics of the investigated crystals. It is shown that, in the case of the large gap semiconductors, only deep-lying impurity compensation results in high resistivity, semi-insulating materials.
Constantes moléculaires de de NH2 : observation et estimation de la vibration ν3
Authors: Vervloet M. , Merienne-Lafore M. F.
Published: April 2011

From the high resolution photographic emission spectrum, a rotational analysis of the [Formula: see text] state of NH2 has been carried out. This analysis was aided by laser excited fluorescence spectra which exhibit some extra lines attributed to a Coriolis perturbation between the rotational levels of (100) and (001), [Formula: see text]. A Fermi resonance has also been observed between (100) and (020), [Formula: see text]. By deleting the perturbed rotational levels from the least squares fit, it has been possible to calculate some effective constants for the [Formula: see text] level with the origin at 3219.36 cm−1. In addition an estimated value of 3280 cm−1 is proposed for the frequency of ν3.
Dressed soliton in a plasma with two warm ion species
Authors: Tiwari R. S. , Sharma S. R.
Published: April 2011

Propagation of an ion acoustic soliton in a plasma consisting of two warm ion species and hot isothermal electrons is considered, using multiple space time variables in the reductive perturbation method. Expressions have been derived for first and second order potentials. Behaviour of the amplitude of the core part of the soliton shows that initially it decreases rapidly as the light ion concentration increases, assumes a minimum value, and then gradually attains maximum value at α = 1. It has been observed that the soliton may not exist in a certain range of light ion concentration determined by the mass ratio and temperature of ions. The velocity and the width of the soliton are also studied as function of its amplitude.
A variational–Green's function approach to theoretical treatment and applications of the capacitance of three-dimensional geometries
Authors: Mandelis Andreas
Published: April 2011

A combined variational–Green's function approach to the determination of the capacitance of various useful three-dimensional geometries is developed. This formalism leads to general, exact expressions for the capacitance, which can be used with all geometries provided the spatial distribution of the charge can be determined. In particular, the theory takes into account the finite thickness and unequal areas of the capacitor plates. Specific applications of the theory include circular capacitors with disc and ring-shaped charged plate geometries. Such geometries are commonly encountered in experimental set-ups for capacitive measurements of thin film thicknesses in the field of microelectronics. Numerical results indicate that the values of thin film thicknesses calculated via simplified one-dimensional formulae for the capacitance may be incorrect by more than 10%
Mid-latitude summertime measurements of stratospheric NO2
Authors: Kerr J. B. , McElroy C. T. , Evans W. F. J.
Published: April 2011

The vertical distribution of stratospheric nitrogen dioxide was measured during the Atmospheric Environment Service STRATOPROBE projects in August of 1975 and 1976. Vertical profiles of NO2 are determined by measuring the NO2 absorption of sunlight from a balloon platform during sunrise and sunset and inverting the absorption curves. A total of four sunrise/sunset pairs of observations were obtained from balloon flights of August 10 and 17, 1975 and August 19 and 28, 1976. The measurements show significant stability of the NO2 profile from flight to flight with variations of less than 15% between individual profiles. The average NO2 concentration at sunset was found to increase from about 0.3 ppbv at 10 km to 10 ppbv at 35 km. At sunrise the concentrations increase from 0.2 ppbv at 10 km to 5 ppbv at 35 km.
Scattering length and effective range for the Coulomb plus separable potential
Authors: Nogami Y. , Dijk W. van
Published: April 2011

A simple prescription is given for evaluating the scattering length and effective range, to first order in the fine structure constant, for the Coulomb plus separable potential. It can handle a separable potential of an arbitrary form, in contrast to earlier calculations for separable potentials with form factors that are rational functions in the momentum space. The method can easily be extended to higher partial waves.
The Curie temperature of a Heisenberg-Ising ferromagnet with uniaxial anisotropy
Authors: Tiwari M. , Srivastava R. N.
Published: April 2011

Effects of Ising anisotropy on Curie temperature have been studied in the presence of single ion anisotropy for a spin S = 1 system. The Green function technique with random phase approximation has been used taking into account all possible intersite correlations.
The effects of ground state correlations in 16O on the muonuclear sum rule
Authors: Duplain D. , Goulard B.
Published: April 2011

The total rate of muon capture by 16O is calculated using the linked cluster expansion to introduce ground state correlations. All diagrams up to the second order in the number of hole-lines are included. [Formula: see text] is reduced by some 15% and is shown to behave like σ−1,. [Formula: see text] and [Formula: see text] are strongly increased by about 30%. This enhancement is related to that part of the defect wave function which arises directly from the tensor component of the N–N potential. It is suggested that, for those transitions that are induced by spin operators, the mean neutrino energy may be smaller than usually thought.
Laser magnetic resonance of metastable krypton and xenon atoms
Authors: Sears Trevor J. , McKellar A. R. W.
Published: April 2011

Magnetic dipole transitions from the metastable ls5 (3P2) state to the ls4 (3P1) state in atomic krypton and xenon have been detected and measured using the technique of intracavity laser magnetic resonance spectroscopy with CO2 laser lines in the 10 μm region. The excited atoms were produced by a low voltage dc discharge in a flow of helium carrier gas. Precise values for the Kr and Xe ls4– ls5 interval and for the magnetic gj-factor of ls4 in Kr were determined in an analysis of the observed spectra.
On the logarithmic perturbation theory for screened Coulomb potentials
Authors: Lai C. S.
Published: April 2011

The ground-state logarithmic perturbation theory for screened Coulomb potentials is extended to the case of excited states. For states with I = n – 1, the recurrence relations obtained provide a convenient scheme for calculating the energy coefficients E(k). This logarithmic scheme is compared with an exponential scheme developed earlier.
Radial variation of excited atom densities in an argon plasma column produced by a microwave surface wave
Authors: Moisan M. , Pantel R. , Ricard A.
Published: April 2011

The radial variations of radiative and metastable atom densities in an argon plasma column produced by a microwave surface wave are obtained. A large variety of radial profiles is observed as a function of wave frequency (300–1000 MHz), gas pressure (50–200 mTorr), tube diameter (17.5–34 mm) and axial magnetic field. The results differ significantly from those reported for the dc positive column, where the radial distributions keep approximately the same J0 Bessel-like profile.
Evidence for precursor clusters associated with structural phase transitions in antifluorite crystals
Authors: Armstrong Robin L. , D'Iorio Marie , Ramia Maximo E.
Published: April 2011

Measurements of the temperature dependence of the intensities of the halogen nuclear quadrupole resonances in K2PtBr6 and K2ReCl6, in the cubic phase are reported. These results provide indirect evidence for the formation of dynamic clusters of the low symmetry phase as a precursor to the occurrence of rotative type phase transitions to tetragonal structures in these crystals.
A 20 MeV (p, d) study of nuclear structure in the even and odd tin isotopes
Authors: Fleming Donald G.
Published: April 2011

The nuclear structure of the even and odd tin isotopes has been studied by 20 MeV (p,d) reactions. States strongly populated in the odd isotopes are due to the valence neutron shells and extend up to only 2 MeV of excitation energy; "deep hole" states were not identified. The occupation probabilities extracted from finite-range distorted-wavc-Born-approximation calculations generally agree well with the predictions of the BCS theory of superconducting nuclei, particularly with the calculations of Clement and Baranger. In the even tin isotopes, strongly populated states are characterized predominantly by L = 2 transfers extending up to 4 MeV excitation energy. The experimental spectroscopic factors for transitions populating even final states are compared with the BCS calculated values of Clement and Baranger, Alzetta and Sawicki, and Van Gunsteren; relatively good agreement is obtained for L = 2 transitions, but not for L = 0 transitions. A considerable fraction of the expected sum rule L = 2 strength in 118Sn is missing in the 119Sn(p,d)118Sn experimental spectrum; in like manner, no 4+ strength could be identified in either 114Sn or 118Sn.
Inelastic scattering of slow positrons by helium, neon, and argon atoms
Authors: Coleman P. G. , Hutton J. T. , Cook D. R. , Chandler C. A.
Published: April 2011

Measurements of the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, utilising time-of-flight energy loss spectrometry, are reported. Scattering into forward angles up to 60° is observed and the measurements suggest that sharp forward lobes exist in the angular distributions of positrons scattered following atomic excitation. Multiple scattering corrections to the measurements are described. Comparison is made with the inelastic scattering of electrons by the same atoms, and connections drawn between the present results and those of the recent complementary studies of Griffith et al. and Charlton et al.
Low-energy positron–hydrogen molecule scattering
Authors: Sur Sukanya , Ghosh A. S.
Published: April 2011

The method of Hara using two centre formalism has been employed to investigate positron–hydrogen molecule scattering at low incident energies. Two model potentials have been used to see the importance of the choice of effective potential. It has been found that the total cross sections are sensitive to the details of the effective potential. The present results are in qualitative agreement with measured values and other existing theoretical predictions.
Positron diffusion in krypton and xenon
Authors: Câmpeanu R. I.
Published: April 2011

The equations describing diffusion of positrons in krypton and xenon are solved with the best theoretical scattering and annihilation data available to date to obtain the time variation of the positron annihilation rate. The theoretical shoulder lengths obtained with the data of McEachran et al. agree well with the experimental values given by the University College London group, while the shoulder lengths obtained with the data of Schrader are much larger. The present results allow for an assessment of the accuracy of the existent low energy e+Kr and e+Xe elastic cross sections.
The effect of core electrons on the spin transfer parameters
Authors: Ziaei M. E.
Published: April 2011

ENDOR measurements and covalency arguments have been used to investigate the electron distribution in CsCdF3 crystals containing Mn2+ and Ni2+. The bond structure is of the form M—F−—Cd2+ (M = Mn2+ or Ni2+) and the measured isotropic supertransferred hyperfine interaction (sthfi) at the Cd site is related to the unpaired spin fraction fσ in the 2pσ orbital of F− by three different theoretical approximations. In these three methods it is assumed that [Formula: see text] orbital of the 3d ion, and the 2pz orbital of the F− ion make eovalent bonds with the (4s), (3s,4s,5s), and (1s,2s,3s,4s,5s) sets of orbitals of the Cd2+ ion respectively. The results show that cadmium core s electrons make important contributions to the isotropic sthfi. However, it seems that fσ values obtained are fairly insensitive to the approximations used.
A stability theorem for dissipative magnetohydrodynamic equilibria
Authors: Teichmann J.
Published: April 2011

The global stability of stationary equilibria of dissipative magnetohydrodynamics is studied using the direct Liapunov method. Sufficient conditions for stability of the linearized Euler–Lagrangian system with the full dissipative operators are given for the first time. The case of the two-fluid isentropic flow is discussed.
A note on the diffraction of a dipole field by a perfectly conducting wedge
Authors: Mohsen A.
Published: April 2011

The paper considers the diffraction of the electromagnetic fields of a dipole in the presence of a perfectly conducting wedge. Starting from a general integral representation of the solution, a suitable form for the axial fields is derived. The solution to these fields is then given in terms of the known solution due to point source excitation. The resulting fields are shown to satisfy the required edge condition.
The 240 nm band system of methylamine: a preliminary analysis of the rotational structure of the 0–0 band of CH3ND2
Authors: Tsuboi Masamichi , Hirakawa Akiko Y.
Published: April 2011

The ultraviolet absorption spectrum of CH3ND2 has been observed in the 231–242 nm (43 300–41 300 cm−1) region with 10 m Eagle and 7.3 m Ebert vacuum spectrographs. An analysis has been made of the rotational structure in the 238.1–236.7 nm (42 000–42 240 cm−1) region. It has been shown that, in the excited electronic state, the methyl group is rotating freely with respect to the amino group around the C—N bond as axis. Here the moment of inertia of the methyl group was found to be 3.4054 Å2 amu around the molecular axis, and that of the deuterated amino group ND2 3.4081 Å2 amu. The sum 6.8135 Å2 amu is appreciably greater than IA = 6.6280 Å2 amu, the moment of inertia for the overall rotation of the molecule.
An automatic all sky scanning radiometer
Authors: Coombes Charles A. , Harrison A. W.
Published: April 2011

A microcomputer controlled all sky scanning radiometer covering the short wave (0.3–3.0 μm) and long wave (3.0–80.0 μm) regions and using a pyroelectric detector has been constructed for continuous automatic measurement of sky radiance. Angular distributions of short, long, and total wave sky radiance are recorded and plotted at each solar hour angle from which irradiances of tilted surfaces are computer calculated. Measurement of the local earth surface radiance facilitates estimation of short wave earth surface albedo and net income of radiation to variously oriented black surfaces. Total scanning, computation, and plotting time for each hour angle observation is 8 min.
Single particle inclusive leptoproduction in quantum chromodynamics
Authors: Campbell Bruce A.
Published: April 2011

The effects of scaling violations in current induced single particle inclusive lepto-production reactions is examined in the framework of asymptotic freedom. A set of quark fragmention functions is introduced which approximately satisfies the leading order asymptotic freedom constraints of quantum chromodynamics. These are then used to give a consistent leading order treatment of current induced single particle production processes, in particular: e+e− annihilation, charged current neutrino (antineutrino) reactions, electro (muo) production, and neutral current neutrino reactions. We emphasize the consistency of the different reactions with an asymptotically free parton picture.
Isospin impurity and core polarization of g9/2 IAR fragments in 59Cu
Authors: Szöghy I. M. , Rangacharyulu C.
Published: April 2011

The spin and parity of the 6.2 MeV level in 59Cu, populated by (p,γ) reaction, are found to be Jπ = 9/2+. The previously known two g9/2 fragments are situated 0.7 MeV higher in excitation energy. A description, consistent with (3He,d), (p,p′γ), and (p,γ) data, indicates the presence of isospin mixing and core polarization in these three states.
The rise of a cylindrical bubble in an inviscid liquid
Authors: Baumel R. T. , Burley S. K. , Freeman D. F. , Gammel J. L. , Nuttall J.
Published: April 2011

An expansion in powers of t2 is obtained which gives the shape of an initially horizontal cylindrical bubble filled with a massless gas as it rises through an incompressible inviscid infinite fluid in a uniform vertical gravitational field. For larger times the series does not converge but we have found that a variation of the Padé approximant method gives good results for the locations of the top and bottom of the bubble, although not for times quite as large as might be desired. The results compare favourably with experiment.
Energies of light atoms in uniform electronic host systems
Authors: Stott M. J. , Zaremba E.
Published: April 2011

The electronic structure of first row atoms immersed in a uniform electron gas has been calculated self-consistently as a function of gas density using the Kohn–Sham scheme with the LDA for electron exchange and correlation. The total energy as a function of density is the necessary ingredient in a recently devised approximate method for estimating the energy of an atom in an inhomogeneous host system. The results are interpreted with a view to further applications of this approximation.
Event horizon area in a slowly changing Weyl geometry
Authors: Brumbaugh B. E. , Price Richard H.
Published: April 2011

We consider a class of models of dynamically distorted black hole event horizons, based on a slow evolution of black hole Weyl geometries. With the time scale for the evolution taken arbitrarily large, a fairly simple mathematical description of the "quasistatic" geometry results. With this description it is shown how the constraint on event horizon area is related to the absence of singularities at the horizon. The evolution of intrinsic event horizon geometry is plotted for a specific example.
Far infrared absorption spectra in liquid and solid H2
Authors: Buontempo U. , Cunsolo S. , Dore P. , Nencini L.
Published: April 2011

The far infrared absorption spectra of hydrogen have been measured in solid and liquid phases in the frequency range 300–800 cm−1. We have found a remarkable similarity between the liquid and solid spectra. In the solid phase, we have performed measurements at different ortho-H2 concentrations, in order to investigate the influence of ortho-H2 molecules. In particular, we have studied the behaviour of the S(0) line at low ortho-H2 concentrations. We found that the rotational exciton picture describes our results well.
Phonon dispersions in calcium tungstate
Authors: Kesavasamy K. , Krishnamurthy N.
Published: April 2011

In their studies on phonons in CaWO4, Kanamori et al. investigated the phonon dispersion of translational modes alone, ignoring the finite moment of inertia of tungstate ions and Coulomb interactions. In our present investigations, based on external mode formalism (Venkataraman and Sahni), we consider the coupling of the translational and librational modes and include the long range interactions. The effective ionic charges of the Coulomb interactions and the effective ionic radii of Born–Mayer short range potential arc determined so that the dynamical equilibrium conditions are satisfied and lattice energy is of the right order in comparison with other complex ionic crystals (Rao et al.). The phonon dispersion relations in CaWO4 along [001] and [110] directions arc calculated and found to be in reasonable agreement with available neutron data (Steinman et al.). The generalized LST relations (Venkataraman et al.) computed with our model agree with the IR data of Barker. In the long wavelength limit, the acoustic branches fit well with experimental data, indicating that this model can explain the acoustic properties as well. Zone centre phonons in CaMoO4, SrWO4, SrMoO4, BaWO4, BaMoO4, PbWO4, and PbMoO4 are also investigated and compared with experimental data to study the influence of polarizability and a possible breakdown of external mode formalism.
Octupole resonance states in the nucleus oxygen 16
Authors: Nash G. F.
Published: April 2011

Three quanta excitations from a spherical core of oxygen 16 were studied. In particular the octupole vibrations, being a 14 dimensional manifold of vectors, transforming as the representation of the special unitary group SU3 with parameters (λμ) = (30) and permutation symmetry of the configuration's radial coordinates [f1f2 …] = [4444], were treated in detail.3− excited states of the nucleus oxygen 16 may be formed from a single excitation of a nucleon from the p shell to the sd shell, or from the triple excitations. The three quanta excitations may be states in which one, two, or three nucleons are excited from its spherical core. The resonance energy levels are calculated using the Sussex matrix elements, and the octupole strength to each of the seven physical (30) states are tabulated, together with their excitation energy for each of eight internucleon interactions. Most of the E3 strength was found to be lodged in the lowest two states at about 17 to 25 MeV, although an appreciable amount is shown to come from the highest state at about 50 MeV.
Dynamical derivation of the Yang–Mills S-matrix
Authors: Pugh Robert E.
Published: April 2011

The Feynman rules for self-interacting Yang–Mills fields are derived within the framework of conventional covariant quantum field theory by explicitly calculating the contributions of the nonphysical field components to the violations of the S-matrix equation of continuity.
A new theory of the liquid condensed–liquid expanded phase transition in lipid monolayers
Authors: Georgallas Alexandros , Pink David A.
Published: April 2011

A new model of the liquid condensed (LC) – liquid expanded (LE) phase transition in lipid monolayers is presented which accounts for the observed nonzero slopes of the pressure area isotherms across the transition. This model proposes that small cooperative units or "domains" of lipids with extended hydrocarbon chains in the LC phase gradually melt into large regions of lipids with disordered chains as the lateral pressure is decreased. Thus, the domain melting is coupled to the lipid chain order–disorder transition and hence, to the lipid chain order parameter [Formula: see text] where N signifies a domain of N molecules. In order to obtain [Formula: see text], an established Ising-like model of lipid monolayers is solved in the Bethe–Peierls approximation. By fitting two free parameters to one isotherm, we are able to calculate isotherms for other temperatures and find good agreement with experiment.
Etude par Fabry–Perot des spectres dépolarisés et polarisés du pentachlorobiphenyl liquide entre −54 et +150 °C
Authors: Bezot P. , Hesse-Bezot C.
Published: April 2011

A low frequency study (Fabry–Perot) of the polarized and depolarized light scattering spectra of liquid pentachlorobiphenyl is presented from −54 to +150 °C.The relaxation time deduced from the depolarized spectra is measured as a function of temperature and compared with the time obtained by means of other techniques.The weak propagative depolarized doublet is studied at high viscosity, from −54 to +42 °C. The value of the shear rigidity modulus Gx is obtained almost up to the relaxation domain.The Brillouin polarized doublet is also analyzed in the full temperature range and the values of the compressional moduli are calculated.
Annihilation of positrons in noble gases in the presence of an electric field
Authors: Arifov P. U. , Zhuravleva G. I.
Published: April 2011

The present article combines our earlier separate calculations of elastic scattering cross sections, annihilation parameters, and speed distribution functions of positrons slowing down in noble gases for the simultaneous interpretation of experimental data of both beam and drift experiments. Here we present the results on the calculations of phase shifts, annihilation parameter Z(k), speed distribution functions, and Zeff(F).
Formation and dissociation of by ruby laser radiation
Authors: Wagner G. , Isenor N. R.
Published: April 2011

The formation and dissociation of [Formula: see text] in an atomic beam by ruby laser radiation have been observed. Values of the dissociation energy of [Formula: see text] have been determined by the time of flight of the resulting Na+ ions and the potential needed to stop them. These results, with a mean of 1.02 ± 0.09 eV, have been compared with the calculated and observed values of others. The effects of laser polarization vs. dimer axis orientation have been clearly demonstrated.
Proton and deuteron magnetic resonance in single crystals of Fe(NH4)2(SO4)2∙6H2O
Authors: Raj T. F. S. , Murthy C. R. K.
Published: April 2011

Single crystal proton and deuteron magnetic resonance in Fe(NH4)2(SO4)2∙6H2O and Fe(ND4)2(SO4)2∙6D2O, respectively, are studied at room temperature. From the proton magnetic resonance study are found the orientations of the proton–proton vectors of the water molecules with respect to the crystallographic axes. Proton resonance data are used to determine the positions of the hydrogen atoms belonging to the water molecules in the crystal. A deuteron resonance study shows that the D2O molecules are flipping fast at room temperature. The quadrupole coupling tensor at the deuteron sites of D2O in the crystal are determined. The positions of the hydrogen atoms are also determined from the directions of the principal components of the quadrupole coupling tensor.
Propagation of vertically and horizontally polarized waves excited by distributions of electric and magnetic sources in irregular stratified spheroidal structures of finite conductivity – generalized field transforms
Authors: Bahar E. , Fitzwater M.
Published: April 2011

Transform pairs for the electromagnetic fields in radially stratified spherical structures are derived. These field transforms are used to convert Maxwell's equations into generalized telegraphists' equations for the scalar wave amplitudes. Arbitrary distributions of electric and magnetic sources are considered and the full-wave expansions account for both vertically and horizontally polarized waves. The analysis in this paper also provides the basis for the complete expansion of the electromagnetic fields in irregular spheroidal structures (bodies of revolution) in which the medium is varying as a function of the radial distance and the latitude. This work can be applied to propagation in irregular ionospheric and tropospheric ducts.
Scattering and depolarization of electromagnetic waves in irregular stratified spheroidal structures of finite conductivity – full wave analysis
Authors: Bahar E. , Fitzwater M.
Published: April 2011

Scattering and depolarization of electromagnetic waves in irregular stratified, spheroidal structures (bodies of revolution) are investigated. Using complete expansions for the electromagnetic fields, Maxwell's equations are converted into sets of first order coupled differential equations for the forward and backward wave amplitudes. To obtain these generalized telegraphists' equations, exact boundary conditions are imposed at each of the interfaces between the irregular layers of the structure and Green's theorems are used to avoid term-by-term differentiation of the complete expansions. The electromagnetic parameters of the medium are assumed to vary as functions of the radial distance and the latitude. Excitations by arbitrary distributions of electric and magnetic sources are considered. Thus, this work can be applied to propagation in irregular ionospheric and tropospheric ducts. The solutions are shown to satisfy duality and reciprocity relationships in electromagnetic theory.
Chemical order in the Heusler alloy system Ni2MnxV1−xSn
Authors: Martin Luc , Stager C. V.
Published: April 2011

The chemical order in single crystal samples of Ni2MnxV1−xSn has been estimated for x = 1.0, 0.8, and 0.6 by elastic neutron diffraction. The samples were long thin crystals with transverse dimensions less than 1 mm. Extinction was a problem even for these small cross-section samples. The data were fitted to a model that allowed for chemical disorder. All samples were highly ordered. Slight amounts of disorder, 4% or less, were sufficient to explain the data.