bluuebunny/crossref_metadata_2025 huggingface dataset:
Systematics in the testing of theories through polarization
Authors: Goldstein Gary R. , Moravcsik Michael J.
Published: April 2011

The weakest test of a theory for particle reactions is comparison with an unpolarized differential cross section only. The strongest test is through a complete set of complex reaction amplitudes, the attainment of which is a considerable experimental task. It is shown how intermediate stages of testing of intermediate stringency can be established. The process is illustrated on the spinwise fairly complex reaction of n + p → d + γ.
Utilisation d'un asservissement de fréquence pour la détermination précise des paramètres décalage et d'élargissement de la raie J: 2 → 3 d'OCS en fonction de la pression
Authors: Lamalle B. , Suzeau P. , Truchetet F. , Chanussot J.
Published: April 2011

An original microwave-frequency monitoring to be used in microwave spectrometry, in the Ka band, has been achieved. By means of this device, the monitoring of a source frequency at three particular points in a resonance line; i.e., center frequency and both symmetrical bending points, may be allowed without any static error.This experimental device enabled us to study the half-width parameters ΔνL/p and shift parameter δν0/p of line J = 2 → 3 of OCS versus pressure. As regards ΔνL/p, our values of the half-width parameter, ΔνL/p = 6.25 ± 0.15 KHz∙m Torr−1, have been checked by the conventional direct method (1 Torr = 133.3 Pa). Although more accurate, they agree with the other published values. However, δν0/p = 0.66 ± 0.05 KHz∙m Torr−1 is in disagreement with the two values published to date (these values being contradictory).An accurate study about the eventual causes of error ensures the reliability of this value.
Combination of the successive perturbation method with other common methods
Authors: Popescu V. A. , Popescu I. M.
Published: April 2011

For the hydrogen atom in the fundamental state perturbed by βr−1, it is shown how the successive perturbation method can be combined with the method in which some fraction of a nonperturbed term (in the Hamiltonian) is included in the perturbation. Thus, the radius of convergence of the perturbation series is increased.
Étude des surstructures de la magnétorésistance de InSb
Authors: Galibert J. , Perrier P. , Askenazy S. , Stradling R. A. , Wallace P. R.
Published: April 2011

We have carried out experiments of magnetophonon resonance on n-InSb doped at 4.6 × 1013 cm−3 at a temperature of 135 K. The second derivative of longitudinal and transverse magnetoresistance exhibits obviously spin-resolved peaks of magnetophonon resonances involving one or two longitudinal optical phonons. Among these "over-structures" appear spin-flip resonances, particularly the 0−0+ resonance.The structures of the magnetoresistance are explained from the calculation of resonance fields, based on our method of determination of the Landau levels.
Low-loss liquid-crystal-clad waveguide switch with a large angular separation of the optical beams
Authors: Verly Pierre G.
Published: April 2011

We propose a new nematic liquid-crystal-clad electrooptic waveguide beamsplitter simultaneously capable of very high beam deflections and relatively low losses. A trade-off between the deflection and the cross talk due to unswitched spatial frequencies of a realistic diverging beam is discussed with respect to waveguide materials and geometries.
The role of a Lorentz-Iike transformation in nonrelativistic field theory
Authors: Takahashi Yasushi , Ropchan Carmen
Published: April 2011

The energy-density flows are calculated for the phonon and elastic fields, and it is shown that they are proportional to the respective momentum densities. These proportionality relations are used, together with the energy-conservation law, to show that the time change of the centre of energy divided by the square of the speed of sound is equal to the total momentum. This relation corresponds to the well-known Einstein relation E = mc2 in relativistic theory. A partially Galilei and partially Lorentz transformation is introduced, which may be useful for collective modes of massive particles.
Numerical simulation of a cubic Fermi-Pasta-Ulam ring
Authors: Leech J. W. , Janzen A. R.
Published: April 2011

A 16-particle ring with cubic Fermi–Pasta–Ulam potentials between nearest neighbours is studied by computer simulation. Emphasis is placed on the frequency content rather than the time development of the "modes" (the spatial, discrete Fourier transforms of the particle displacements). The simulations are found to be highly reversible.It is also pointed out that some commonly used numerical methods cause a systematic upward shift in the frequencies of a simulation.
Time-dependent invariant for the quadratic Hamiltonian and the stable squeezed states
Authors: Hong-Yi Fan , Zaidi H. R.
Published: April 2011

The conditions for the existence of a time-dependent invariant for the general quadratic Hamiltonian are investigated. A general expression for such an invariant is obtained, and it is shown that the stable squeezed states are eigenstates of this invariant.
Energy distribution of pions in the nucleon–nucleus interaction at 70 GeV
Authors: Saha A. C. , Samanta M. M. , Pal D. K. , Nandy R. N. , Bandopadhyay B. K.
Published: April 2011

Production of pions through the intermediate state called fireballs has been considered to study the energy distribution of pions in the fireball-rest system. Nikfi-R-type photoemulsion plates exposed to the 70-GeV proton beam of the Surpukhov Accelerator, Dubna, USSR, are used for this purpose. A graphical representation of the distribution of energies among the pions is shown. It is observed that this distribution closely resembles Planck's distribution of photons. Furthermore, this study reveals that the Maxwell–Boltzmann distribution deviates greatly from experimental observations. The average energy of the pions is found to be (0.770 ± 0.03) GeV.
Studies of the (p,n) reaction at medium energies
Authors: Watson J. W. , Anderson B. D. , Madey R.
Published: April 2011

We measured differential cross sections, analyzing powers, and the polarization-transfer coefficient [Formula: see text] for 135 MeV (p,n) reactions on 40Ca and 48Ca. The observed shapes for the analyzing-power angular distributions are in good overall agreement with distorted-wave-impulse-approximation calculations, and are more sensitive to nuclear structure than to whether or not spin transfer is involved. Measured spin-flip probabilities for [Formula: see text] combined with a multipole analysis of differential cross sections reveal that at 0°, the apparent continuum under and adjacent to the Gamow–Teller giant resonance is also primarily 1+ strength. A comparison of [Formula: see text] and [Formula: see text] shows no discernable signature of Gamow–Teller strength in the region –30 < Q(MeV) < –45. Utilizing information from high-resolution cross-section measurements and spin-flip probabilities, we decompose the spin-dipole resonance of 40Sc into its 0−, 1−, and 2− components.
The TRIUMF charge-exchange facility
Authors: Helmer R.
Published: April 2011

A facility for studying charge–exchange reactions at TRIUMF is described. Essentially, the same facility can be used for either (p, n) or (n, p) reactions. The design considerations on which the facility is based are discussed, and the results of some early experiments are presented.
(n,p) studies at TRIUMF
Authors: Yen Stanley
Published: April 2011

This paper discusses some preliminary results from the (n,p) experiments performed with the new TRIUMF nucleon charge-exchange facility. Data are presented for the 26Mg(n,p), 54Fe(n,p), 90Zr(n,p), and 208Pb(n,p) reactions. For 26Mg and 54Fe, the Gamow–Teller (GT) strength is apparently quenched to the same extent in (n,p) as in (p,n) reactions. For 90Zr and 208Pb, little GT strength is observed in the (n,p) reaction, but 208Pb(n,p) exhibits a strong spin-dipole peak. Some future (n,p) experiments at TRIUMF are briefly mentioned.
Heavy-ion reactions as spin probes
Authors: Austin Sam M. , Anantaraman N. , Winfield J. S.
Published: April 2011

Heavy-ion reactions can be powerful probes for spin-transfer strength in nuclei, provided their reaction mechanism is simple so that a correlation can be established between cross sections and the relevant matrix elements. We discuss the desirable features of heavy-ion reactions in general and a series of tests of reaction mechanisms that have been carried out for two of the most favorable reactions; (6Li, 6He) and (12C, 12N). We establish that the (6Li, 6He) reaction is one-step in nature above 25 MeV∙nucleon−1 and establish a calibration function relating cross sections and Gamow–Teller matrix elements. We also find that the (12C, 12N) reaction is likely to be dominated by the one-step process above about 50 MeV∙nucleon−1.
Multipole decomposition of Gamow–Teller strength
Authors: Moinester Murray A.
Published: April 2011

Doubly differential continuum cross sections from the 90Zr(p, n)90Nb reaction have been analyzed via a multipoledecomposition technique. No quasi-free charge-exchange background has been subtracted, following the assumption that the observed cross sections are primarily due to one-step charge-exchange leading to 1p–1h states of all multipolarities to all excitations. The theoretical shapes of the differential cross sections for each Jπ multipole have been taken from random-phase approximation (RPA)–distorted-wave impulse approximation (DWIA) calculations. The experimental dσ/dΩ, for each 1 MeV excitation-energy bin have been decomposed into different multipole components by a least squares fit. This RPA-based analysis should determine the Jπ = 1+ cross sections with different, and also fewer, assumptions than usual for describing the underlying background. It can be of general importance in determining the extent of possible quenching of Gamow–Teller (GT) strength. The present decomposition accounts for all the theoretically predicted GT strength. The purpose of the present report is to illustrate an analysis based on RPA–DWIA shapes rather than to present final-decomposition results.
Isovector excitation of stretched states in nuclei: effects of meson exchange currents, unbound wave functions, and knockout exchange amplitudes on the extraction of particle–hole strengths
Authors: Lindgren R. A. , Leuschner M. , Clausen B. L. , Peterson R. J. , Plum M. A. , Petrovich F.
Published: April 2011

It is well known that the strength for excitations of [Formula: see text] high spin, stretched states observed via inelastic scattering, is generally much smaller than that predicted by spherical shell-model calculations. In addition, results obtained from electromagnetic and hadronic studies have discrepancies at the 20% level. For us to gain a better understanding of reduced magnetic strength in electron scattering and hopefully close the gap between experiment and theory, calculations of the electron-scattering form factors have been performed including the effects due to meson exchange currents in the transition amplitude and the effects due to unbound wave functions for the valence nucleon. The effect of the meson exchange-current contributions is to uniformly enhance the form factors near the first maximum, resulting in a 16 to 20% further reduction of the stretched particle–hole strength. The effect due to the radial wave functions deduced from Woods–Saxon potentials in which the nucleon is not bound is to reduce the form factors, thereby resulting in an increase in the spectroscopic strength. As regards the comparison of results obtained with electromagnetic and hadronic probes, the implied sensitivity to higher order current and spin–current transition densities associated with the nonlocality due to the tensor knockout exchange amplitudes in nucleon–nucleus scattering is considered explicitly. It is found that the simplest correspondence between electron and nucleon–nucleus scattering is preserved for isovector excitations but not for isoscalar excitations under the usual assumptions for the tensor interaction. It is clear that precise comparisons between experiment and theory (or between probes) cannot be made unless these and related effects are consistently included.
(γ, n) studies of the giant isovector E2 resonance in lead, cadmium, and calcium
Authors: Storm D. W. , Halpern I. , Gossett C. A. , Murakami T. , Rosenzweig D. P. , Tieger D. R. , Debevec P. T. , Freytag A. , Morford L. J. , Wender S. A. , Dowell D. H.
Published: April 2011

We have measured the angular asymmetry in the (γ, n) reaction on natural lead, cadmium, and calcium in the energy region of the isovector quadrupole resonance (20–40 MeV). The asymmetry increases from low values, about 0.2, to high values, 0.6–0.8, where this resonance is expected. This increasing asymmetry is interpreted as resulting from the interference between the E1 and E2 isovector amplitudes. We have fitted direct−semidirect calculations for lead and cadmium and have obtained resonance energies of 23.5 ± 1.5 and 26.5 ± 1.5 MeV for these elements, respectively. For calcium, preliminary results indicate a resonance energy of 34 ± 2 MeV. The widths are found to be considerably larger than those of the E1 resonance.
First (n, p) measurements with the Indiana University Cyclotron Facility
Authors: Počanić D. , Wang K. , Martoff C. J. , Hanna S. S. , Byrd R. C. , Foster C. C. , Friesel D. L. , Rapaport J.
Published: April 2011

A new monochromatic neutron-beam facility has been set up at the Indiana University Cyclotron Facility, primarily for (n, p) reaction measurements at intermediate energies (100–200 MeV). Reported are the experimental layout of the facility and preliminary results of the first measurements: 6Li(n,p)6He cross sections at six angles ranging from Θcm = 0–22°, with En = 118 MeV (laboratory). Good agreement is found between the measured σ(0°) and the cross sections measured for the mirror reaction 6Li(p, n) at 120 and 144 MeV. Results of a distorted wave calculation, while slightly lower, are consistent with the preliminary experimental 0° cross section.
Possible experimental signature of a quark–gluon plasma in a 12C–AgBr interaction at 4.5 GeV∙c−1∙n−1
Authors: Ghosh Dipak , Roy Jaya , Sengupta Ranjan
Published: April 2011

This paper reports possible evidence of a quark–gluon plasma (QGP) state formed in relativistic heavy-ion collisions using 12C–AgBr interaction data at 4.5 GeV∙c−1∙nucleon−1(n). The experimental data on the three-particle angular correlation function for the target protons have been subject to a Monte Carlo analysis, and a statistically significant deviation has been observed that shows a dynamical correlation among the target protons. This may be due to possible formation of a QGP state.
Detachment cross sections for sulphur negative ion – rare gas collisions
Authors: Hird B. , Bruyère M. , Fafard S.
Published: April 2011

The atomic cross sections for single and double electron detachment from sulphur negative ions in single collisions with He, Ne, Ar, Kr, and Xe are determined at collision energies between 12.5 and 110 keV.
Electronic spectrum of D2O+
Authors: Lew H. , Groleau R.
Published: April 2011

An analysis of 15 bands of the [Formula: see text] system of D2O+ is given. All assigned lines are tabulated. The rotational structures of the [Formula: see text], 1, and 3 levels of the ground state are fitted to the Watson asymmetric rotor Hamiltonian with added spin-rotation terms. For the upper state, the rotational structures of various substates are expressed: for [Formula: see text], in terms of a simple formula for linear molecules; and for [Formula: see text], 2, and 3, in terms of a modified Hill – Van Vleck formula given by Jungen, Hallin, and Merer. From the rotational constants of the ground state, term values are calculated and a small portion of a Type-B infrared band is derived. Some predicted microwave lines are also given. The bond length and bond angle of the molecule in the ground state (ν = 0) are r0 = 0.9987 ± 0.0002 Å and θ0 = 110.17 ± 0.02 deg.
Tunnelling resistance of a one-dimensional random lattice
Authors: Barrie Robert , Carvalho I. C. D. S.
Published: April 2011

The resistivity of a one-dimensional lattice consisting of randomly distributed conducting and insulating sites is considered. Tunnelling resistance of the form R0iebi is assumed for a cluster of i adjacent insulating sites. Three different ensembles are considered and compared. In the first ensemble, the number of insulating "atoms" is fixed and distributed in a linear chain; in the second one, there exists a fixed probability p of having an insulator "atom" occupying a site in a linear chain; and finally in the third one, a line is bent into a circle and the probability p is considered. It is observed that in the thermodynamic limit, the average ensemble resistance per site diverges at the critical filling fraction pc = e−b, while the variance of the resistance diverges at the lower filling fraction [Formula: see text]. Computer simulations of large but finite systems, however, exhibit a much weaker divergence of the resistance per site at pc and no divergence of the variance at pc1.
Elasticity of a percolation system: silica smoke
Authors: Forsman J. , Harrison J. P. , Rutenberg A.
Published: April 2011

Cab-O-Sil powder is a cluster aggregate of silica spheres formed from silica smoke. The fractal dimension of clusters of 14 nm diameter spheres is determined to be [Formula: see text], in good agreement with that calculated for the cluster-aggregate model, [Formula: see text]. Measurements of Young's modulus (Y) of packed 7 nm Cab-O-Sil powder, with an occupied volume fraction in the range 0.035 < f < 0.3, are well described by the percolation threshold fc = 0.017 ± 0.002 and an elasticity exponent τ = 2.9 ± 0.2. The measured exponent is larger than the calculated scalar Born (balls and springs) result, τ = 2.0, but smaller than the more realistic bond-bending result, τ > 3.55. The measured result is attributed to bond bending within a complex percolation structure.
Oxygen on an approximately W(110) single crystal: electron reflection, electron energy-loss spectroscopy, and work-function measurements
Authors: Baribeau J.-M. , Roy D.
Published: April 2011

Adsorption of oxygen on W(110) at room temperature has been studied by means of electron reflection, high-resolution electron energy-loss spectroscopy, and work-function measurements. Data collected with these different techniques show that a change in the structure of the adlayer takes place at a coverage of about a 0.2 monolayer. In the low-coverage state, sharp low-energy electron diffraction fine structures in the reflected current, a slow variation in the work-function variation, and a single vibration loss at 68 meV are observed. At higher coverage, a damping of the fine-structure features, a normal work-function increase, and a shift of the 68 meV loss peak to 73 meV together with the growth of a 48 meV loss are observed. These observations seem to support models involving initial dissociation near surface defects and subsequent p(2 × 1) island growth).
One-loop finiteness of the string theory on the T22/G manifold
Authors: Li Da-Xi
Published: April 2011

We explicitly evaluate the one-loop amplitude of the string theory on the T22/G manifold and show that the theory is finite at the one-loop level. The twisted sectors play a crucial role in the proof of the modular-group invariance.
The millimetre-wave spectrum of dimethylsulfide: internal-rotation and centrifugal-distortion analysis
Authors: Vacherand J. M. , Wlodarczak G. , Dubrulle A. , Demaison J.
Published: April 2011

The rotational spectrum of dimethylsulfide has been measured in the millimetre-wave range between 140 and 300 GHz. A new computer program based on the internal-axis method has been used to analyze the rotational spectrum in its torsional ground state. It has allowed us to fit the spectrum satisfactorily and to determine the rotational, internal-rotation, and centrifugal-distortion constants accurately. The influence of the approximations made during the internal-rotation analysis on the moment of inertia (Ia, Ib, Ic, and Iα) is pointed out. It shows the difficulty in determining accurate geometrical structures of two-top molecules from microwave data. For the AA substate, effective rotational parameters are given that allow the calculation of transition frequencies of possible astrophysical interest.
Electromagnetic direction finding from an antenna array configured near an elliptic cylinder
Authors: Siakavara K. , Sahalos J. N.
Published: April 2011

In this paper, an effort is made to attack the problem of electromagnetic direction finding (DF) by an antenna array configured near a perfectly conducting elliptic cylinder. Over the range of interest, the cylinder has an axial ratio that varies from 1:1 to 1:30. Results for the array with three wire dipoles show the practicality of such an array.
Magnetism and liquid crystals
Authors: Dekker A. J.
Published: April 2011

Superficial similarities and essential differences between nematic liquid crystals and magnetically ordered systems as well as some magnetic-field effects in nematics are recalled. Magnetic anisotropy, field alignment, and the determination of elastic constants of nematics are discussed briefly. Landau theory is used to discuss the effect of a magnetic field on the nematic-isotropic phase transition; the predictions are compared with experiment.
Spin glasses: recent advances in mean-field theory
Authors: Southern B. W.
Published: April 2011

A survey of recent advances in the mean-field theory of Ising spin glasses is presented. The physical picture of the spin-glass phase predicted by this theory is described, and its relationship to real three-dimensional systems is discussed.
The experimental status on the question of a phase transition in spin glasses
Authors: Williams Gwyn
Published: April 2011

Following a brief introduction to spin-glass systems, the current status of experimental evidence on the occurrence of a phase transition is reviewed. Recent analyses of dynamical properties of spin glasses are discussed in terms of several model predictions, including the conclusion of a divergent relaxation time τ at a finite temperature, although with large, non-mean-field indices z and v. The role of regular terms (leading to corrections to scaling) in the nonlinear response are reviewed, stressing their influence on the evaluation of the susceptibility and order-parameter exponents γ′ and β′.
The electronic structure and superexchange interactions in transition-metal compounds
Authors: Zaanen J. , Sawatzky G. A.
Published: April 2011

In this paper, we discuss the electronic structure of transition-metal compounds in light of a new theoretical approach using an Anderson impurity Hamiltonian. We arrive at conclusions concerning the magnitude of parameters such as the d–d Coulomb interaction (U) and the charge-transfer energy (Δ) for the transition-metal monoxides, based on theoretical calculations of the band gaps, the optical spectra, photoelectron and inverse-photoelectron spectral shapes, and comparison with experiment. We find that both Δ and U are large but comparable in magnitude.We discuss the implications for superexchange interactions and show that the observed trends in the Néel temperatures are now well described, whereas the traditional Anderson approach gave a qualitatively different trend.
Refinement of the critical V–V separation for spontaneous magnetism in oxides
Authors: Manthiram A. , Goodenough J. B.
Published: April 2011

Cubic Liy[V2]O4 (0.7 ≤ y ≤ 2.0) samples with the [V2] O4 spinel framework have been prepared by room-temperature chemical delithiation–lithiation of Li[V2]O4. The Li+-ion distribution in the interstitial sites is distinguishable in different compositional regions: all-tetrahedral lithium in Li1−x[V2]O4 and in Li1+x[V2]O4 tetrahedral–octahedral pairs in association with tetrahedral lithium for 0 < x ≤ 0.4 transforming to all-octahedral lithium as x → 1.0. Identification of localized V3+:d2 configurations in Li2[V2]O4 narrows the range for a critical V–V separation to 2.89 Å < Rc < 2.93 Å for spontaneous magnetism in oxides containing a periodic network of energetically equivalent V3+ ions. The cubic spinel Li[V2]O4 has been prepared from stoichiometric LiVO2 by room-temperature lithium extraction with bromine to Li0.5VO2 followed by heating to T > 570 K. The extraction product Li1−xVO2 (0 ≤ x ≤ 0.3) has the low-temperature LiVO2 phase; Li0.3VO2 is nearly cubic with V displaced to the Li-deficient layers, and the compositional range 0.3 < x < 0.7 is two-phase. LiVO2 is air sensitive; surface-adsorbed oxidants extract lithium from the bulk up to the phase limit Li0.7VO2. Heating Li1−xVO2 to above T1, which increases with x, causes it to disproportionate into LiVO2 and Li[V2]O4, which explains the anomalies reported by Hewston and Chamberland on thermal cycling acid-leached LiVO2.
Collision-induced absorption in the fundamental band of nitrogen gas
Authors: Joslin C. G.
Published: April 2011

Compressed nitrogen gas absorbs weakly in the vicinity of its vibrational fundamental frequency (ωvib = 2330 cm−1), with an intensity proportional to the square of the density. This absorption arises through vibrational modulation of the quadrupole-induced collisional dipole moment of a pair of N2 molecules. By neglecting the small anisotropy in the N2 intermolecular potential, we represent the spectral profile as the convolution of a single-molecule vibration–rotation band with a two-molecule translational component. Information theory is used to estimate the "least biased" form for the latter, based on our knowledge of its first four nonvanishing spectral moments. Our theory contains no adjustable parameters, yet yields results in good agreement with experiment. Our analysis shows that the anisotropic component of the molecular polarizability makes a fairly substantial contribution, about 12%, to the spectral intensity.
High-resolution Fourier-transform study of the ν10 fundamental band and the (ν10 + ν7) − ν7 hot band of trans-glyoxal
Authors: Auwera J. Vander , Godefroid M. , Herman M. , Huet T. R. , Johns J. W. C.
Published: April 2011

The spectrum of trans-glyoxal has been recorded at a resolution of about 0.005 cm−1 in the region from 1650 to 1800 cm−1. More than 1500 lines have been assigned to the bu fundamental ν10 (asymmetric C=O stretching) and about 300 to the (ν10 + ν7) − ν7 "hot" band. Improved ground-state constants have been obtained as well as constants for ν10 and (ν10 + ν7).
Paramètres effectifs du moment dipolaire des molecules tétraédriques XY4. Application au methane 12CH4
Authors: Loete M.
Published: April 2011

The first order transformed dipole moment of tetrahedral XY4 molecules is studied using a tetrahedral formalism. Corresponding expressions of involved parameters are given and discussed, for both isolated bands and polyadic studies. A set of calculated and adjusted parameters is given for the 12CH4 molecule.
Line shapes in resonance fluorescence for external sources near unit optical depth
Authors: Brooks W. S. C. , Kendall D. J. W. , Llewellyn E. J. , McDade I. C.
Published: April 2011

The angle-dependent resonant scattering line shape is calculated for a two-state atomic gas with a kinetic temperature similar to that of an external beam source for optical depths of less than or equal to unity. It is demonstrated that narrowing of the backscattered line shape occurs for all source temperature to absorber temperature ratios. It is also shown that there is no appreciable broadening when the source and absorption temperatures are different. The small amount of broadening that does occur is due to an enhancement of scattered radiation at frequencies away from the resonance-line centre frequency.Rocket-based resonance lamp measurements of atomic oxygen concentrations are complicated by the height-dependent optical depth for the 130.2, 130.4, and 130.6 nm oxygen emissions as well as by the nodification of the local environment and relative positions of the emission and absorption line shapes due to the motion of the rocket vehicle through the atmosphere.
Comment on: Flicker-noise fluctuations in α-radioactive decay
Authors: Prestwich W. V. , Kennett T. J. , Pepper G. T.
Published: April 2011

A discrepancy between experiments to establish the existence of 1/f fluctuations in α decay is discussed. It is argued that the flicker floor reported for direct α counting cannot be due to fluctuations intrinsic to the decay process.
Surface-recombination and doping effects on the minority carriers in polycrystalline silicon
Authors: Damaskinos S. , Dixon A. E.
Published: April 2011

A scanning laser microscope was used in a spatially resolved photoconductivity experiment to determine the minority-carrier diffusion length (L) and surface-recombination velocity at grain boundaries (SGB) in (i) n- and p-type Wacker polysilicon and (ii) neutron-transmutation-doped Metron polysilicon as a function of beam intensity. Different values of L were measured on opposite sides of the grain boundaries. For the Metron samples, L was measured at the same grain boundary using a series of samples doped to different levels. These samples had dopant concentrations between 1013 and 1017 atoms/cm3. L was found to decrease from 50 to 5 μm, with decreasing beam intensity, reaching a constant value at low beam intensities. L was also found to remain relatively unchanged for low dopant concentrations. The SGB values were found to increase with increasing beam intensity in both Wacker and Metron samples, ranging between 104 and 105 cm/s. L was also measured with a light-beam-induced-current technique (perpendicular geometry) and found to be in close agreement with values obtained using the photoconductivity technique.
Optical properties of monolayer NbS2 suspensions
Authors: Li Z. M. , Bergersen B. , Palffy-Muhoray P. , Beigie D.
Published: April 2011

We present a theory for the anisotropic optical and magnetic properties of monolayer NbS2 platelets suspended in water and oriented in a magnetic field. We compare experimental data obtained by Liu and Frindt and calculated properties using a dielectric function obtained from a Drude–Lorentz fit to reflectivity data for the bulk material. The anisotropic magnetic susceptibility of the material allows a separate study of the extinction coefficients of light with polarizations perpendicular and parallel to the flake plane. We estimate the contributions from scattering and absorption using the fitted dielectric constant; and we find that for monolayer flakes, absorption should be the dominant mechanism. We also estimate the effects of local-field corrections on absorption and scattering to be small. A puzzling feature is that the experimental ratio of the optical anisotropy for the extinction coefficients fails to satisfy a predicted 2:1 ratio suggested by symmetry considerations.
Ondes électromagnétiques de surface de type HE11
Authors: Zepp G. , Wick A. , Boubakra A. , Fabre G. , Ritoux G.
Published: April 2011

We have studied the electromagnetic microwave propagation of the HE11 mode on the surface of a cylindrical conductor coated with a dielectric and embedded in a second dielectric. The present study takes into account the finite conductivity of the metal and dielectric losses for the determination of precise analytical expressions of the attenuation factor and phase shift.
Current conservation as a geometric property of space–time
Authors: Ali S. Twareque , Brooke J. A. , Busch P. , Gagnon R. , Schroeck Jr. F. E.
Published: April 2011

Working within the framework of stochastic quantum mechanics, we prove that a mild reality constraint on the radial part of the resolution generator renders the (probability) current, for a single particle with only positive (or only negative) energies and having arbitrary integer spin, conserved. The result is proven both nonrelativistically and relativistically. This extends some earlier results that had been obtained for spinless systems. We argue that the origin of such a conservation law is a consequence of the particular geometry of space–time predicated by the formalism of stochastic quantum mechanics.
Comparative modal dispersion in multilayered fibres
Authors: Subramanyam K. V. S. , Dey K. K. , Ojha S. P. , Khastgir P.
Published: April 2011

Pulse broadening in multilayer, multimode fibres has been studied for different distributions of layer widths and refractive indices. A layer-width distribution, which simulates the parabolic graded-index profile, is obtained by the method of Gaussian best fit. The ratio of the root-mean-square pulse width for a multilayer fibre and a single core layer fibre (σN/σ1) has been determined, for N = 3 and 4, for various distributions of layer widths and refractive indices. It has been found that the pulse broadening is dependent on the layer-width distribution; and for some distributions, the pulse broadening is significantly less than that for the equal-width layer fibre for certain ranges of the profile parameter α.
Operator regularization beyond lowest order
Authors: McKeon D. G. C. , Samant S. S. , Sherry T. N.
Published: April 2011

We pursue operator regularization beyond lowest order. In lowest order, it is the determinants of operators that are regulated; beyond lowest order it is the inverses of operators. As in lowest order, operator regularization to two-loop order and beyond avoids explicit infinities both in the integrals that are evaluated and in the regulating parameter s as it approaches its limiting value of zero. Operator regularization also replaces the Feynman diagrammatic expansion with an expansion due to Schwinger. No explicit symmetry-breaking regulating parameter is inserted into the original Lagrangian. We illustrate our technique by examining the two-point function in [Formula: see text] scalar theory, the effective potential in [Formula: see text] scalar theory, the vacuum polarization in massless quantum electrodynamics, and the two-point function in the Wess–Zumino model using both the superfield and component-field formalism. In all cases we find expressions that are divergence free and remain finite as the regulating parameter approaches its limiting value. In the final model we explicitly show that the supersymmetry Ward identity for the two-point functions is satisfied to two-loop order.
Singularity of electromagnetic field near the trajectory of point particles: the general case
Authors: Dormale Bernard M. de
Published: April 2011

The singularity of the electromagnetic field created by a point particle has been investigated by Dirac in the special case where the trajectory is approached in the rest frame of the particle. His result, fundamental in the study of radiation reaction, is generalized here to the case of an arbitrary inertial frame.
The generation of rotational bands by deep, diffuse potentials
Authors: Merchant A. C.
Published: April 2011

Numerical integration of the single-particle Schrödinger equation containing a deep, diffuse, spherically symmetric, attractive, local potential often gives rise to bound-state energy eigenvalues, which lie on almost perfect rotational bands. Each band is characterized by a constant value of (2n + l), where n is the number of interior nodes in the radial wave function and l is the orbital angular-momentum quantum number of a member state. The constants of near-proportionality between the state energies and l(l + 1) for the various bands are considered. An expression for them derived from the Bohr–Sommerfeld quantization rule is found to give numerical results in excellent agreement with those obtained by direct numerical integration of the Schrödinger equation. However, no analytic expressions could be obtained from it, except in the most trivial cases. Also, an approximate expression for these rotational parameters is derived using the Rayleigh–Schrödinger perturbation theory up to fourth order for the case of any potential that may be expanded in ascending even powers of the radial coordinate, r, for which the perturbation expansion converges. This approximation is excellent if (2n + l + 3/2)[Formula: see text], where m is the mass appearing in the Schrödinger equation, V0 is the depth of the attractive potential, and a is a length parameter characterizing its diffuseness. The general results are illustrated with applications to some deep attractive Gaussian potentials of various widths.
Estimation of the electromagnetic field in a sea with rough upper and lower surfaces
Authors: Bishay Samira T.
Published: April 2011

We present initial results of calculated electric and magnetic fields at an arbitrary distance, r, from a transmitter antenna by investigating the effect of roughness of both upper and lower sea surfaces on electromagnetic wave propagation in seas. The part of the sea under investigation is considered in terms of a three-layer medium (air – sea water – ground). Sea waves lead to the variations that occur in both upper and lower sea surfaces. These variations are studied using the perturbation technique. The solution holds for low frequencies and is only limited by the fact that the variations of the upper and lower boundaries of the sea about a mean height must be small with respect to the mean depth of the sea. The problem is evaluated mathematically using the residue and saddle point methods.
Electron–lithium elastic scattering in a strong laser field
Authors: Youssef M. K. , Lal M. , Srivastava M. K.
Published: April 2011

The elastic scattering of electrons by lithium in the presence of a laser field, which is strong by laboratory standards but weak compared with 1 au of electric-field strength, is studied near the forward direction to investigate the effect of the target "dressing." The scattering cross section is found to increase to more than 50 times the undressed value at scattering angles of [Formula: see text].
Radiative capture of fast neutrons in 160Gd
Authors: Singh R. K. Y. , Ansari M. Afzal , Gautam R. P. , Rizvi I. A. , Kailas S.
Published: April 2011

Radiative neutron capture cross sections for 160Gd have been measured at eight different neutron energies: 0.46 ± 0.04, 0.57 ± 0.04, 0.75 ± 0.04, 0.97 ± 0.20, 1.22 ± 0.19, 1.52 ± 0.17, 2.22 ± 0.17, and 3.05 ± 0.18 MeV. The activation technique has been employed in the present measurement. Our experimental values are compared with the theoretical values calculated using the FISPRO II code, using the most recent set of parameters available in the published literatures.
Torsional dipoles
Authors: Roberts M. D.
Published: April 2011

An attempt is made to introduce dipole structure into gravitational theory. We do this by trying to produce torsion tensors with the same form as the electric-field tensor for an electric dipole. First, we construct Ricci tensors for space-times with vanishing Christoffel connections. Then we discuss the conditions to put on the tensors. Each condition gives differential equations; however, none of the solutions provides an entirely satisfactory dipole structure. Finally, we briefly discuss how to "force" axially symmetric space-times having dipole structure.
A class of physically acceptable, classical, relativistic, many-particle Lagrangians
Authors: Moore R. A. , Scott T. C.
Published: April 2011

It is shown that the Fokker–Wheeler–Feynman theory for relativistic, massive, charged point particles interacting via action-at-a-distance forces of electromagnetic origin can be generalized to define a class of model systems all with the same physically acceptable properties. These properties include the satisfaction of the correct Lorentz covariance, time-reversal symmetry, particle-interchange symmetry, and causality. For closed systems there exists a generalized Hamiltonian function, linear momentum, and angular momentum that are constants of the motion. This generalization thus yields a relativistic, dynamic description of this class, analogous to nonrelativistic classical mechanics. Included in this class, within the appropriate limits, are the so-called linear relativistic scalar and vector interactions. It is anticipated that this work will be useful for the examination and understanding of physical systems, both classically and quantum mechanically, insofar as they can be modelled from a classical approach.
The variational approach to the extended Glashow–Weinberg–Salam model
Authors: Mańka R. , Sladkowski J.
Published: April 2011

A generalization of the variational approach to the SU(2) × U(1) × U(1) gauge theory of electroweak interactions based on canonical quantization is presented.
Scattering by two conducting strips with parallel edges
Authors: Ragheb H. A. , Hamid M.
Published: April 2011

An exact treatment using the boundary-value method for solving the problem of plane-wave scattering by two strips is presented. An infinite number of multiply scattered fields between the two strips is included in the solution. The solution is given for the general case of any orientation of the two strips and an arbitrary separation between them.In addition to the exact solution, a new asymptotic technique is employed for an approximate solution of the problem. The technique is based on the idea used by Karp and Russek for solving scattering by a wide slit. Results for the echo width pattern of two strips with different orientations using both exact and approximate techniques are compared with data based on a numerical technique for solving the same problem. An excellent agreement is found between the results based on the analytical and numerical solutions for a wide separation between the strips. The only restriction on the approximate technique is that the ratio between either strip width and the separation between the centers of the strips must be much greater than unity.
Electronic polarizability of ions in the alkali-halide crystals
Authors: Sharma S. K. , Misra R. M. , Sharma M. N. , Madan M. P.
Published: April 2011

A theoretical estimate of the high-frequency dielectric constants is made using the molar polarizabilities for a number of alkali halides. These are shown to be in good agreement with the new and more reliable experimental data. Analysis by means of the additivity rule within the family of salts is used to compute the total free ion polarizability of ionic constituents and the change in polarizability when the ions are placed in a crystalline environment. Furthermore, the anion electronic polarizability in ionic crystals has been determined. It is found to vary from crystal to crystal, as opposed to the generally accepted assumption that each ion has the same polarizability in all compounds. The dependence of polarizability upon ionic radii has been discussed. The results from this simple analysis compare well with other determinations.
Modèle quantitatif pour l'étude des couches minces diffusantes
Authors: Thériault Jean-Marc , Boivin Germain
Published: April 2011

The phenomenon of light scattering by dielectric thin films is studied by a photometric analysis method. This method is based on an empirical model of the diffusing film and has been validated using lead iodide. The model is presented here together with the analysis results that made it possible (i) to establish a precise microstructure for the films and (ii) to study the evolution of the microstructure via the thickness of the films. [Translated by the journal]
Higher dimensional Einstein–Cartan cosmology
Authors: Krori K. D. , Goswami D.
Published: April 2011

We derive in this paper exact solutions in (9 + 1)-dimensional Einstein–Cartan cosmology.
Total cross section for electron-impact ionization from the ground state of atomic hydrogen using the distorted-wave polarized orbital method
Authors: Mukherjee K. K. , Mazumdar P. S. , Brajamani S.
Published: April 2011

The total cross-section for electron-impact ionization from the ground state of atomic hydrogen is studied by using the distorted-wave polarized orbital method. In the present calculation we have taken into account the matrix elements arising from the distorted part of the target wave function. The present results are in good agreement with experimental findings.
Radiation from a vertical electric dipole in the presence of a lossy ground
Authors: Helaly A. , Shafai L.
Published: April 2011

Expressions for the radiation fields of a vertical electric dipole located over a homogeneous lossy ground are derived using the dyadic Green's functions. The resulting field vectors are then split into the primary and secondary components. The primary components represent those that would exist in the absence of the ground, leaving the secondary components to represent the contribution of the Earth. For different operating frequencies and various ground conductivities, the secondary components are computed and compared with the primary ones. The results indicate that the secondary fields have the same magnitude as the primary ones in the ground and in the vicinity of the air–Earth interface. However, in the air region between the source location and the interface, their magnitude decreases progressively as the field point moves away from the interface. The case of an electric dipole located inside the ground is also considered, and a few representative results are presented.
The quadrupole moment of acetylene from collision-induced absorption in a gaseous mixture with argon
Authors: Dagg I. R. , Anderson A. , Smith W. , Missio M. , Joslin C. G. , Read L. A. A.
Published: April 2011

The collision-induced spectrum of a mixture of argon and acetylene (100:1) is reported in the frequency range below 240 cm−1. The spectrum is obtained from the total absorption in the mixture at pressures up to 1400 psi (1 psi = 6.89 kPa) and subtraction of the contribution from an allowed difference band of pure acetylene centred near 113 cm−1. The measurements are made with a Michelson Fourier-transform interferometer and with a laser source at 84.1 cm−1. The quadrupole moment of acetylene determined from the experimental spectrum and existing theory for the integrated absorption coefficient is 5.42 (± 0.41) B if a theoretical estimate of the hexadecapole moment is used. Alternatively, a value of 6.14 (± 0.46) B is obtained if the contribution from the hexadecapole moment is assumed to be zero. An extension of the line-shape theory, 1T6, that includes the contribution from hexadecapolar induction is also reported. The resulting theoretical line shape is compared with the experimental spectrum.
Positronium-formation cross sections in the eikonal approximation
Authors: Tripathi S. , Sinha C. , Sil N. C.
Published: April 2011

Positronium-formation cross sections have been studied in the framework of the eikonal approximation, where the boundary condition has been properly satisfied, taking consistent account of the internuclear potential term both in the eikonal phase and in the interaction potential. The six-dimensional integral of the Glauber eikonal amplitude has been reduced to a single-dimensional one. The differential as well as the total cross sections have been studied and compared with other existing theoretical results, as the experimental data are not yet available in the literature. The eikonal results are found to give reasonable estimates at intermediate, high, and extremely high energies.
Parity nonconservation in proton scattering at higher energies
Authors: Mischke R. E.
Published: April 2011

Parity-nonconservation experiments in the scattering of longitudinally polarized protons at incident proton momenta of 1.5 and 6 GeV/c are examined. These experiments indicate a change with energy of the total cross section correlated with proton helicity that was unexpected. This energy dependence is due to the strong part of the interaction and may indicate the role of a diquark component in the nucleon. New experiments at higher energies are needed to confirm such a model. Future experiments can benefit from an analysis of sources of systematic error that have been encountered in the experiments discussed here.