bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of multiparticle rapidity clustering in hadronic interaction at 70 GeV/c
Authors: Ghosh Dipak , Roy Jaya , Naha Sadhan , Basu Madhumita , Sengupta Kaushik
Published: April 2011

This paper presents a study of multiparticle rapidity clustering in proton–nucleon interaction at 70 GeV/c using the generalized rapidity-gap method. The observed rapidity-gap distribution has been compared with those from a model of uncorrelated particle production. A clear indication of cluster production was observed.
Gamma decay of d5/2 isobaric analogue resonances in the 64Zn(p,γ) reaction
Authors: Rangacharyulu C. , Chatterjee M. B. , Pruneau C. , St-Pierre C.
Published: April 2011

The resonances at Ep = 3.249 and 3.253 MeV in 64Zn(p,γ) are identified as fragments of the d5/2 isobaric analogue resonance from (p,p′γ) angular distributions. Gamma decay schemes and angular distributions are measured. In 65Ga, the level at 2.21 MeV is assigned a spin of Jπ = 5/2−. From angular distributions and symmetry potential considerations, the level at 2.82 MeV is considered to be the antianalogue state. The analogue–antianalogue transition strength is found to be compatible with single nucleon transfer data, thus showing that the interference effects from core polarized components arc negligible in this case.
Broadband photon yield of Kr excited by monoenergetic electron impact above the ionization threshold. Part I: 22–26 eV
Authors: Boulay M. , Marchand P.
Published: April 2011

The broadband photon yield of Kr excited by monoenergetic electron impact above the ionization threshold has been measured by means of an improved apparatus. Results are given for the energy region 22–26 eV. The observed structures are interpreted as being due to highly excited neutral states and to highly excited negative-ion states.
Localisation de l'énergie transportée par une onde électromagnétique à la surface d'un conducteur de section circulaire
Authors: Wick Alain , Zepp Gérard , Ritoux Georges , Fabre Georges
Published: April 2011

We have been interested in the localization of the energy carried by an electromagnetic wave of the TM type propagated at the surface of a cylindrical conductor coated with two dielectrics. The present study takes into account both the finite conductivity of the metal and dielectric losses. It is shown that it is possible to reconcile an excellent energy concentration with a very low attenuation of the wave.
Transient conditions in inductively heated plasmas: thermodynamic equilibrium and temperature measurements
Authors: Meubus Paul
Published: April 2011

A study has been made on transient extinction conditions in an inductively heated argon plasma. It was observed that local thermodynamic equilibrium (LTE) conditions do exist between the metastable 3P2 level and upper energy levels, so that during the decay time it is possible to determine a meaningful temperature, using the 3P2 level as a fundamental level and the partition functions being calculated accordingly. Together with the temperature determination, a concentration distribution of argon metastables was obtained.Studies of this type are useful for the investigation of quenching processes in plasmas, affecting favorably chemical reactions or solid–gas interactions, thus leading to enhanced catalytic effects or modifications of solid particle structures which are liable to generate new electrical, thermal, etc. properties of interest.
Thin-film Cu2O/Cu photovoltaic cells
Authors: Fortin E. , Sears W. M.
Published: April 2011

Thin-film Cu2O/Cu Schottky barrier photovoltaic back cells are studied in view of their possible application as solar cells. Graphs are constructed showing the dependence of the oxide layer thickness (in the 3 – 50 μm range) on the oxidation parameters such as the temperature, oxygen pressure, and time of oxidation. The solar-cell parameters such as Voc, Vsc and the spectral response are in turn investigated as functions of the oxide layer thickness. The results indicate that cells of possible practical interest will have an oxide layer thickness of the order of 1 μm, grown at high temperature, high oxygen pressure for oxidation times of less than 1 s.
Magnetic and chemical ordering in the Heusler system Co2Mn1−xTixSn
Authors: Dunlap R. A. , Stroink G.
Published: April 2011

119Sn Mössbauer effect, magnetization, and X-ray diffraction measurements have been made on the series of Heusler alloys CO2Mn1−xTixSn (0 ≤ x ≤ 1). The Mössbauer measurements are used to obtain the distribution of hyperfine fields by the Fourier expansion method of Window, This distribution is discussed in terms of the state of chemical ordering of the alloys, as indicated by the X-ray measurements. The magnetization measurements are compared with previous results by Webster and Sobezak, and are used to estimate the magnetic hyperfine fields as predicted by the Jena–Geldart theory.
Thermoreflectance measurements on SnS2 and SnSe2
Authors: Brebner J. L. , Perluzzo G.
Published: April 2011

We present thermoreflectance data on single crystals of SnS2 and SnSe2 at 100 K. The results are compared with previously published reflectivity and wavelength modulation spectra and with the predictions of band theoretical calculations. For SnS2 gross features as predicted by theory are in fair agreement with experiment but more fine structure is apparent in the experimental data. For SnSe2 much more structure is found than for SnS2 and the agreement with theory is poor.
Electron loss cross sections from rare gas atoms to Ar+
Authors: Hird B. , Ali S. P.
Published: April 2011

Measurements of the σ10 cross section for a beam of Ar+ ions of energies between 30 and 120 keV passing through a thin target of the rare gases show good agreement with the few previous measurements in this energy region.
Thickness contours of highly aberrant phase objects. I. Reduced sensitivity holographic interferometry for direct phase measurement
Authors: Grover C. P. , Tremblay R.
Published: April 2011

A double-exposure holographic method is described that permits one to visualize thickness contours of highly aberrant thin phase samples. The hologram is recorded using a reference wave that bears a simple phase relationship with the subject wave while the reconstruction is made with a plane wave. The phase shaping of the reference wave is accomplished by making it traverse the test sample. If the test sample is thin and the hologram is recorded in the plane in contact with its rear surface, the phases of the hologram producing waves are correlated to each other at all points through a constant. Consequently, the reconstructed object wave contains direct phase variations of the object at reduced sensitivity, which can be varied by changing the hologram recording geometry. A double-exposure technique has been used for the vizualization of the phase variations of the object wave. Furthermore, a finite distance between the sample and the plane of the hologram produces a lateral shearing interferogram receiving variations of the phase gradients of the object. The method is applicable to thin samples that do not have high, rapidly varying surface deformations.
A comparison of approximations for the elastic electron–electron scattering amplitude in jellium
Authors: MacDonald A. H. , Geldart D. J. W.
Published: April 2011

An approximation for the electron–electron scattering amplitude, Γ, in jellium, motivated by comparing formal many-body theory and density-functional theory expressions for the jellium response function, is suggested. The approximation is compared with previously suggested approximations for Γ, using an exact result for the forward scattering limit to assess the reliability of each approximation. It is pointed out that the magnetic interaction contribution to Γ becomes dominant at low density in jellium and that this contribution is absent in most commonly adopted approximations. Mean free paths for low energy electrons in jellium-like metals have been calculated for various approximations to Γ and the magnetic-interaction effect is identified as being responsible for a previously noted discrepancy between Thomas–Fermi-like and more sophisticated approximations to Γ. A systematic method, using the parquet expansion technique, has been proposed for antisymmetrizing the density-functional based approximation to Γ when necessary.
Weak coupling superconductor with varying electronic density of states
Authors: Carbotte J. P. , El-Rahman A. Abd
Published: April 2011

Analytic expressions are derived and evaluated for the critical temperature (Tc) and the zero temperature gap edge (Δ0) of a weak coupling superconductor with a model electronic density of states: a Lorentzian superimposed on a constant background with Fermi energy falling at some arbitrary position within the peak. The shift in chemical potential, the gap edge near Tc, and the specific heat jump at Tc are also evaluated in closed form.
Phonon echo technique applied to adsorption isotherm measurement
Authors: Poirier M. , Cheeke J. D. N.
Published: April 2011

We have measured by the phonon echo technique the ultrasonic attenuation in an adsorbed 4He film on silica powder as a function of pressure at 35 MHz and low temperatures. The attenuation curves present the typical shape of a multilayer adsorption isotherm of type II according to the Brunauer, Emmett, Teller (BET) classification and the Frenkel–Halsey–Hill (FHH) slab theory may be used to describe the attenuation in the adsorbed film. This is important because the adsorption isotherm cannot be obtained by the traditional technique on a powder with small specific surface.
Spatial discrimination in SQUID gradiometers and 3rd order gradiometer performance
Authors: Vrba J. , Fife A. A. , Burbank M. B. , Weinberg H. , Brickett P. A.
Published: April 2011

A detailed description of SQUID gradiometers is presented with the aim of improving their near field detection response while operating in unshielded, magnetically harsh urban environments. Spatial gradiometers of various orders are compared (0th, 1st, 2nd. and 3rd) and the effects on performance of constructional errors, near and far noise sources, and gradiometer baseline are examined. It is shown theoretically that the noise characteristics of a 3rd order spatial gradiometer are expected to be superior to that of lower order designs, particularly for noise sources located within intermediate distances (1.5–50 m) from the gradiometer. Following this analysis, a 3rd order SQUID gradiometer has been designed, constructed, and evaluated. Data are presented on the instrument noise characteristics for operation within an unshielded urban laboratory and examples of the 3rd order gradiometer response to various biomagnetic signals are shown. The results support the theoretical expectations and confirm that the 3rd order gradiometer exhibits better noise characteristics than a 2nd order gradiometer operating in similar environments.
A note on bounds to central potential scattering parameters
Authors: Darewych J. W.
Published: April 2011

We derive a bound to the absolute value of the difference between the exact and approximate values of central potential scattering phase shifts. This bound, which is first order in the difference between the exact and approximate radial wave functions, is applicable to a wide class of potentials and/or partial waves, namely those for which dU/dr < 2l(l + 1)/r3 It is illustrated by using it to obtain simple, analytic bounds to the scattering length and total cross section for a screened Coulomb potential.
Energy gap values by optical absorption in I III IV Se4 compounds
Authors: Goodchild R. G. , Hughes O. H. , Lopez-Rivera S. A. , Woolley J. C.
Published: April 2011

Polycrystalline samples have been prepared of 12 defect chalcopyrite quaternary compounds of the form I III IV Se4, where I is Cu or Ag, III Al, Ga or In, and IV Ge or Sn. In all cases room temperature optical absorption measurements have been made to determine values of the fundamental energy gap (Eg) and all gaps shown to be direct. For the cases of AgGaSnSe4 and AgGaGeSe4, values of Eg have been determined as a function of temperature from helium to room and the data fitted to a Manoogian–Leclerc equation. The energy gap values of the quaternary compounds (EgT) have been compared with those of the corresponding ternary chalcopyrite compounds (EgT) and a relation between the values of EgQ−EgT and EgT shown.
Beam-foil spectroscopy of Se IV, V, and VI
Authors: Bahr J. L. , Pinnington E. H. , Kernahan J. A. , O'Neill J. A.
Published: April 2011

Six new transitions are assigned in Se V, resulting in the classification of three new levels: 4s4d1D, 4s5s1S, and 4s5p1P0. Lifetimes and multiplet f-values are presented for the 4s24d2D, 4s4p22P, 4s4p22S, and 4s4p22D terms of Se IV, the 4s5s3S, 4s4d3D, 4s4d and 4p21D, 4s4p1P0, and 4p23P terms of Se V and the 5s2S, 4d2D, and 4p2P0 terms of Se VI. The cascade repopulation problems were analyzed by using the ANDC method on the terms 4s4p1P0 of Se V and 4p2P0 of Se VI.
Positron annihilation studies of quenching and recovery of single crystals of Al and Al – 1.5 × 10−2 at.% Mn
Authors: Hood G. M. , Schultz R. J.
Published: April 2011

Single crystals of Al and Al – 1.5 × 10−2 at.% Mn have been quenched from 753 K. The quenched state and its recovery have been studied by positron annihilation. The Doppler-broadening technique was used and the results analyzed in terms of characteristic peak (S) and wing (W) parameters, chosen to emphasize annihilation with valence and core electrons, respectively. The prime effects of the Mn are to enhance both the quenched-in defect signal for S and the rise in S observed during the initial stages of vacancy recovery (180–250 K). In surprising contrast, the W data are remarkably similar for the two materials and show little sign of vacancy recovery below 240 K. At higher temperatures, the recovery data for S and W do appear to complement one another. The main recovery stage is centred at 300 K and a second, broad stage extends from ~370–480 K. The main vacancy recovery stages found here show a good correspondence with earlier resistivity and quenching data. Measurements of the temperature dependence of S and W in Al for both the well-annealed and quenched states are in reasonable accord with results from a previous investigation.
Diffraction by an infinite set of soft/hard parallel half-planes: the Riemann approach
Authors: Lüneburg E.
Published: April 2011

We consider the diffraction of a plane wave by an infinite set of parallel equidistant half-planes. On each plate the total field vanishes on one side and the normal derivative vanishes on the other side. A closed-form solution for Bragg angle incidence is obtained by reducing the boundary value problem to a solvable Riemann problem.
Filtering properties of volume holograms
Authors: Guibaly F. El
Published: April 2011

The filtering of optical information by volume holograms is studied analytically. It is shown that the volume hologram, in general, has limited filtering capabilities because of the restrictive Bragg conditions necessary for diffraction.
Non-leading mass effects in the effective weak Hamiltonian for Δc = 1 decays
Authors: McKeon Gerry
Published: April 2011

Recently Altarelli, Curci, Martinelli, and Petrarca have calculated the second order corrections induced by quantum chromodynamics to the effective weak Hamiltonian in Δc = 1 processes. We extend their analysis by including the effects of the heavy t and b quarks. The technique used is that first introduced by Witten to study the effects of heavy quarks in deep inelastic scattering and used by Gilman and Wise and Guberina and Peccei to discuss how quark masses alter the effective weak Hamiltonian to leading order in [Formula: see text] processes.
A study of postnoon bite-out in foF2 at Karachi
Authors: Majeed Tariq
Published: April 2011

The characteristic variations of postnoon bite-out in foF2 were studied by using f-plots obtained at Karachi (gcog. coord. 24.95°N, 67.14°E; mag. dip 36°N) from March 1976 to February 1978. It has been found that the % occurrence of bite-out was minimum in June and maximum in February. The development of bite-out during magnetically quiet and disturbed days was also studied. The % occurrence of bite-out was found to be greater during magnetically quiet days but the depression of foF2 was larger during magnetically disturbed days.
Higher order molecular spectroscopic constants and dipole moment derivatives for diatomic alkali halides
Authors: Shanker J. , Agrawal H. B.
Published: April 2011

Higher order molecular spectroscopic constants γe and βe are calculated for diatomic alkali halide molecules using new polarizabilities derived recently from the Seitz–Ruffa (SR) energy level analysis. The results for 20 alkali halide diatomic molecules are obtained using the Rittner potential and three forms of repulsion, viz. the Born–Mayer repulsion, the Hellmann repulsion, and the Born–Lande repulsion form. The dependence of the dipole moment on the vibrational quantum number is studied by evaluating the first and higher order derivatives of dipole moment using the SR energy level analysis. The results obtained are discussed and compared with the available experimental data as well as with quantum-mechanical results obtained by Matcha.
Projected evolution superoperators and the density operator: theory and applications to inelastic scattering
Authors: Turner R. E. , Dahler J. S. , Snider R. F.
Published: April 2011

The projection operator method of Zwanzig and Feshbach is used to construct the time dependent density operator associated with a binary scattering event. The formula developed to describe this time dependence involves time-ordered cosine and sine projected evolution (memory) superoperators. Both Sehrödinger and interaction picture results are presented. The former is used to demonstrate the equivalence of the time dependent solution of the von Neumann equation and the more familiar, frequency dependent Laplaee transform solution. For two particular classes of projection superoperators projected density operators arc shown to be equivalent to projected wave functions. Except for these two special eases, no projected wave function analogs of projected density operators exist. Along with the decoupled-motions approximation, projected interaction picture density operators arc applied to inelastic scattering events. Simple illustrations arc provided of how this formalism is related to previously established results for two-state processes, namely, the theory of resonant transfer events, the first order Magnus approximation, and the Landau–Zener theory.
The preparation and some properties of transparent conducting ZnO for use in solar cells
Authors: Morgan J. H. , Brodie D. E.
Published: April 2011

The fabrication of transparent conducting films of ZnO is described. These films are deposited on room temperature glass substrates using an enhanced reactive evaporation technique in which the power in a dc glow discharge, the oxygen pressure, and the zinc evaporation rate are controlled separately. Each of these parameters is adjusted to optimize the required film property.Films with ρ = 0.0014 Ω cm and an absorption of ~ 1% at 550 nm and 40 Ω/⁯ have been prepared with no annealing. The electron carrier densities are ~ 1.3 × 1020 cm−3 and the mobilities are ~ 34 cm2/(Vs) with a variation of less than ~ 15% between −120 and +150 °C.
The instability of streaming fluids in a porous medium
Authors: Sharma R. C. , Spanos T. J. T.
Published: April 2011

The instability of the plane interface between two uniform, superposed, and streaming fluids through porous media is considered. The configuration is taken to be bottom-heavy. In the absence of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbation in the direction of streaming are ignored, whereas for perturbations in all other directions there exists instability for a certain wavenumber range. The surface tension is able to suppress this Kelvin–Helmholtz instability for small wavelength perturbations and the medium porosity reduces the stability range given in terms of a difference in streaming velocities. For the top-heavy configurations, the surface tension stabilizes a certain wavenumber range.
On the light shift in optical pumping of rubidium 87: the techniques of "separated" and "integrated" hyperfine filtering
Authors: Vanier J. , Kunski R. , Paulin P. , Têtu M. , Cyr N.
Published: April 2011

Results of measurements of light shifts observed in the optical pumping of rubidium 87 by means of electrodeless rubidium lamps are reported. The techniques of separated and integrated hyperfine filtering by means of the rubidium 85 isotope are compared. A phenomenological theory which explains qualitatively the results obtained is presented. Conclusions are drawn in relation to the use of either technique in passive rubidium frequency standards.
Theoretical diffraction efficiency of nearly unslanted volume multiplexed amplitude holograms
Authors: Couture Jean J. A. , Lessard R. A.
Published: April 2011

Kogelnik's coupled wave differential equations are solved for many incoherent amplitude transmission holograms superimposed in a photosensitive medium and recorded with small equiangular transverse displacements [Formula: see text] between them. Firstly, the case of two transmission amplitude volume overlaid holograms is analysed and a generalization for the case of N incoherently superimposed holograms is presented. Diffraction efficiency and wave amplitude formulas arc given for incidence "near" and "at the Bragg angle."
Dimensional reduction and background field quantization
Authors: McKeon Gerry
Published: April 2011

It is pointed out that if one uses dimensional reduction to regularize integrals that arise when one evaluates S-matrix elements defined by background field quantization, a considerable simplification occurs.
Dynamics of linear and wrap-around flux shuttles
Authors: Blackburn James A.
Published: April 2011

Flux dynamics have been studied, by means of computer simulations, in two systems: (1) a flux shuttle field biased at one end and (2) a wrap-around flux shuttle (SQUID wheel).
Mean life predictions in respect of Kπ = 2+ collective excitations in deformed even nuclei
Authors: Varshney V. P. , Gupta K. K. , Chaubey A. K. , Gupta D. K.
Published: April 2011

The figures of Gupta et al. (Nuovo Cimento B, 58, 101 (1980)) regarding the E2 transitions in heavy mass nuclei have been modified. Medium mass nuclei of range 20° < γ < 30°, which reflect the asymmetry of the nuclei, have been included. We have employed the asymmetric rotor model dependent Q0 for the sake of consistency in theoretical predictions instead of its experimental values. It is observed that theoretical values of B(E2) branching ratios viz. 2+′ → 2+/0+, 2+′ → 2+/2+ → 0+, and 2+′ → 0+/2+ → 0+ coincide excellently with experimental ones for the nuclei, which consistently show a low-lying second 2+ state at about the same energy as the first 4+ state. In general, the agreement with experimental values is found to be within a factor of two. On using absolute B(E2: 2+ → 0+) and γ data, the values of B(E2: 2+′ → 0+), B(E2: 2+′ → 2+), and the mean life of 2+′ states have been predicted.
Saturation effects in resonant coherent anti-Stokes Raman spectroscopy of inhomogeneously broadened media
Authors: Ouellette F. , Denariez-Roberge M. -M.
Published: April 2011

The effects of pump field intensity are investigated for resonant coherent anti-Stokes Raman spectroscopy (CARS) in inhomogeneously broadened media. It is shown that the CARS line, although Doppler broadened for low intensity, is narrowed to its natural linewidth as intensity is increased and that higher order selectively saturating processes become dominant. Splitting effects are also discussed. Analog results are found for "double electronic resonances."
Determination of the dilation and vibrational contributions to the temperature shift of excitons in CdS: melting of semiconductors
Authors: Manoogian A.
Published: April 2011

An empirical method was used to separate the temperature shift curves of the A- and B-exciton energies in CdS. It was found that the lattice dilation contributed an amount −2.3 × 10−5 eV/K to the temperature shift, and the frequencies of the terms representing the electron–phonon interaction were found to correspond to the average frequencies of the phonons in CdS. The data on the semiconductors analyzed up to now by the empirical method (C, Si, Ge, CdS) were examined at the melting point temperatures of the materials and it was found that the combined results could be described by simple equations. It was found that the r.m.s. vibrational amplitude of the atoms in the above four materials was nearly identical at their melting temperatures.
Optical measurements of vapor pressures of Rb and a Rb–K mixture
Authors: Thompson David C. , Xu Gen-Xing
Published: April 2011

Vapor pressure measurements of Rb and of a Rb–K solution have been made by the equivalent width method in the 400–520 K temperature range. The pure Rb results agree well with existing data and the analytic approximation of Nesmyanov. For the Rb–K solution, the Rb partial pressure data agree well with expectations based on theoretical and experimental heats of mixing, but the data for K do not.
Nuclear level densities
Authors: Haq R. U. , Wong S. S. M.
Published: April 2011

Nuclear level densities are obtained by first calculating the density for non-interacting particles using the Darwin–Fowler method and then folding in approximately the effects of the residual two-body interaction. For the former, the equations resulting from the method of steepest descent are solved numerically with a realistic set of single particle energies and the latter is then incorporated using statistical spectroscopy considerations. Good agreement with experimental data is found.
On the geometric nature of high energy nucleus–nucleus reaction cross sections
Authors: Townsend L. W. , Wilson J. W. , Bidasaria H. B.
Published: April 2011

Within the context of a high energy double-folding optical potential approximation to the exact nucleus–nucleus multiple-scattering series, eikonal scattering theory is used to investigate the validity of geometric reaction cross sections in relativistic heavy ion collisions. The potential used includes a finite range interaction and nuclear single-particle densities extracted from nuclear charge distributions by unfolding the finite proton charge distribution. Pauli correlation effects are also included in an approximate way. The sensitivity of the predictions to the assumed interaction, Pauli correlation approximation, and nuclear density distributions is investigated. These results are in agreement with early predictions concerning the geometric nature of relativistic heavy ion collisions and in disagreement with a recent analysis, utilizing the zero range approximation, which suggested otherwise. Reasons for the lack of agreement between the analyses are also presented. Finally, approximate applicability limits for geometric reaction cross sections are determined.
De Haas–van Alphen effect in metals containing screw dislocations
Authors: Coman V. , Crişan M.
Published: April 2011

The influence of the electron–dislocation interaction on the Landau diamagnetism and de Haas–van Alphen oscillations of the susceptibility is studied for screw dislocations. The effect of the dislocations is of second order in the lattice constant in the Landau diamagnetism and de Haas–van Alphen effect.
Equivalence principle for massive bodies in a generalized theory of gravitation. I
Authors: McDow J. C. , Moffat J. W.
Published: April 2011

The equations of motion are examined for the behaviour of massive bodies in the nonsymmetric theory of gravitation. There are two parameters η and ζ which determine the ratio of gravitational and inertial mass mg/mi = 1 + Δ. In the parameterized post-Newtonian order of the nonsymmetric theory it is shown that η = ζ = 0, where η is the Nordtvedt parameter. The magnitudes of the dominant terms in the equations of motion are given for various planet–sun systems.
The optical activity of intergalactic space
Authors: Clarke J. N. , Karl G. , Watson P. J. S.
Published: April 2011

We obtain an experimental bound on the optical activity of intergalactic space for radio waves, and discuss the expected magnitude in some simple models.
The crystal dynamics of cuprous halides
Authors: Kushwaha Manvir S.
Published: April 2011

The lattice dynamics of cuprous halides have been thoroughly investigated by means of an 8-parameter bond-bending force model (BBFM), recently developed and applied successfully to study phonons in various II–VI and III–V compound semiconductors having zinc-blende (ZB) structure. The application of BBFM is made to calculate the phonon dispersion relations, phonon density of states, and temperature variation of the Debye characteristic temperature [Formula: see text] of CuCl, CuBr, and CuI. The room-temperature neutron scattering measurements for phonon dispersion curves along three principal symmetry directions and calorimetric experimental data for the Debye characteristic temperature have been used to check the validity of BBFM for the three crystals. The overall good agreement between theoretical and experimental results supports its use as an appropriate model for the dynamical description of ZB crystals.
Zakharov–Manakov solution of the stimulated Brillouin backscattering generator problem for "spliced" potentials
Authors: Enns R. H.
Published: April 2011

Making use of the inverse scattering transform method (ISTM), one would like to solve the Zakharov–Manakov (Z–M) problem relevant to nonlinear light scattering for "realistic" nonrectangular input shapes, i.e., shapes which might simulate actual experimental conditions. One approach, which is illustrated in this paper with a specific simple example, is to "splice" potentials together, using potentials for which the Z–M eigenvalue problem is exactly solvable in terms of known functions. A table of such potentials discovered to date is presented. An alternate approach, which avoids splicing, but involves seeking a series solution to the Z–M eigenvalue problem is also briefly discussed.
Horizon line scanning telephotometry
Authors: Harrison A. W. , Lant J.
Published: April 2011

The horizon line softening method of determining the atmospheric spectral extinction coefficient σ(λ) is analyzed in detail indicating an inherent lower limit σ0(λ) on the range of σ(λ) which can be measured by this technique. As the observation height h above the earth surface increases, σ0(λ) decreases. A comparative experimental study of horizon line scanning telephotometry and contrast telephotometry is described, the results of which show the former technique to be useful under certain observing conditions.
Study of the and ν2 + 2ν3 infrared bands of methyl chloride
Authors: Bensari-Zizi Najate , Alamichel Claude
Published: April 2011

The [Formula: see text] and ν2 + 2ν3 combination bands have been identified, their band centres lying around 2751 and 2796 cm−1 respectively. Their lines are mixed with those of the strong ν2 + ν5 band. For the [Formula: see text] unperturbed band, in the case of the CH335Cl isotopic species, a standard deviation of 0.007 cm−1 has been obtained over 355 lines. For the ν2 + 2ν3 band, coupled to 2ν3 + ν5 by a Coriolis resonance, a standard deviation of 0.008 cm−1 has been obtained over 237 lines of the CH335Cl isotopic species.
Cross section of the reaction 9Be(γ, n) near threshold
Authors: Fujishiro M. , Tabata T. , Okamoto K. , Tsujimoto T.
Published: April 2011

Six kinds of radioisotopes were used to measure cross sections of the 9Be(γ, n) reaction near its threshold. The results obtained were 0.88 ± 0.16, 1.33 ± 0.24, 1.10 ± 0.20, 0.73 ± 0.13, 0.47 ± 0.09, and 0.18 ± 0.04 mb at 1674.7, 1705.2, 1724.9, 1778.9, 1836.0, and 2167.6 keV, respectively. The cross sections measured show a sharp peak near the threshold, and its width is narrower than that observed by Jakobson with Bremsstrahlung X-rays. Comparison of the present results with theories based on the valence neutron model indicates that the agreement is only qualitative.
e+e− → e + heavy lepton by one photon exchange
Authors: Resnick L.
Published: April 2011

The reaction e+e− → e + heavy lepton is studied in the forward quadrant, where one photon exchange is expected to dominate. The electron–heavy lepton–photon vertex is given by the standard SU(2) × U(1) model with an extended Higgs sector (containing a second weak isodoublet). A numerical estimate is made for the reaction rate.
Photoluminescence studies of isoelectronic bound excitons associated with the deep acceptors In and Tl in Si
Authors: Thewalt M. L. W. , Ziemelis U. O. , Watkins S. P. , Parsons R. R.
Published: April 2011

We present a detailed account of photoluminescence measurements, including thermal activation energy and transient luminescence decay time results, on isoelectronic bound excitons associated with complex binding centers containing either of the deep acceptors In or Tl. The number of these centers can be greatly increased by a simple thermal quenching procedure, resulting in very intense photoluminescence due to the high radiative efficiencies of these new centers. The In and Tl spectra show both striking similarities and differences, which lead to some tentative conclusions as to the nature of the binding centers. In particular, the Tl-related center displays a number of unique features which lead us to suggest that it can exist in two forms, having quite different luminescence properties. These two forms exist in thermal equilibrium with each other, and we propose that they differ in that the low temperature center binds a lattice defect, either a Si interstitial or a vacancy, whereas the high temperature center results from the thermal 'evaporation' of this defect.
Magnetohydrodynamic free convective flow and mass transfer through a porous medium bounded by an infinite vertical porous plate with constant heat flux
Authors: Raptis A. , Kafousias N.
Published: April 2011

A theoretical analysis of steady free convective and mass transfer flow is presented when a viscous, incompressible, and electrically conducting fluid flows through a porous medium occupying a semi-infinite region of the space bounded by an infinite vertical porous plate. A magnetic field of uniform strength is applied perpendicular to the plate and the fluid is subjected to a normal suction velocity while the heat flux at the plate is constant. An analytic solution of the problem is obtained and the effects of a porous medium, a magnetic parameter, as well as the other parameter entering into the problem, are discussed and shown graphically.
The cw NMR of 13CH4 adsorbed in zeolites 13X and 5A
Authors: Higinbotham John , Code R. Fraser
Published: April 2011

The results of a cw NMR investigation of 13C labelled methane molecules adsorbed in Linde (TM) type 13X and 5A zeolites are reported. The observed proton second moments of the adsorbed molecules at liquid helium temperatures are 9 × 10−8 T2. Absolute determinations of the proton susceptibility at temperatures near 2 K indicate that proton spin conversion occurs.
NMR study of magnetic doped semiconducting (SnTe)100−x (MnTe)x compounds
Authors: Perrin B. , Hedgcock F. T.
Published: April 2011

NMR shift and line width between T = 4.2 and 300 K at the Sn and Te sites have been measured in a series of Mn doped p-type semiconductors (SnTe)100−x (MnTe)x, with x = 0, 0.2, 0.5, 1, 2, and 5. An analysis of Sn Knight shift based on a molecular field model yields a value for the s–d exchange between Mn localized moments and conduction holes of Jsd = −0.07 ± 0.02 eV. The same model applied to the Sn and Te line widths yields fair agreement with the measurements. The Te Knight shift is much less sensitive to the Mn magnetization than Pb.
Brillouin scattering in thin film optical waveguides. I. Theory of the phonon modes
Authors: Rowell N. L. , Stegeman G. I.
Published: April 2011

The phonon modes of a thick plate and a thick plate coated with a thin film are discussed in the light of recent experiments on Brillouin scattering in thin film optical waveguides. Using the reflection coefficients for bulk waves, we have obtained the field structures, the mode normalization for excitation by thermal fluctuations, and the density of states for these modes. Both bulk and surface (Rayleigh, Sezawa, and Love) phonons are discussed.
Brillouin scattering in thin film optical waveguides. II. Scattering theory
Authors: Rowell N. L. , Stegeman G. I.
Published: April 2011

The general theory of Brillouin scattering out of the guided optical modes by the acoustic modes of a thin film optical waveguide is formulated in terms of a total field analysis which includes the effects of both the elastooptic and corrugation scattering mechanisms. The general analytical forms for the field discontinuities at the film boundaries are given and the spectral densities are evaluated for two particular radiative geometries. The results of numerical calculations for the geometries are presented.
Excitation of lithium atoms by electron impact
Authors: Ganas P. S.
Published: April 2011

A realistic analytic central potential is used to generate wave functions for the ground and excited states of lithium. Generalized oscillator strengths and integrated cross sections from threshold up to 5 keV are calculated in the Born approximation for 2s–ns, 2s–np and 2s–nd excitations. Comparison of the results with experimental data is discussed.
The magnetic rotation spectrum of formaldehyde: singlet–triplet perturbations in the 2141, 2143, 2243, and 2341 levels of the Ã lA2 state of H2CO
Authors: Kerr C. M. L. , Moule D. C. , Ramsay D. A.
Published: April 2011

The absorption spectra and magnetic rotation spectra of the [Formula: see text],[Formula: see text],[Formula: see text], and [Formula: see text] bands of the [Formula: see text] system of formaldehyde have been studied at high resolution. The earlier analyses of the absorption bands have been refined and improved molecular constants obtained. Several singlet–singlet perturbations have been noted and possible mechanisms discussed.The magnetic activity falls into two classes. Three of the bands show limited singlet–singlet activity with characteristics similar to those found earlier for the [Formula: see text] and [Formula: see text] bands. All the bands show singlet–triplet activity which is characterized by the appearance of rR, rP, pR, and PP transitions associated with a common upper level. Tables of perturbed excited-state singlet levels are given. No appreciable shifts of the perturbed levels have been found indicating that the matrix elements are small. For the [Formula: see text] band two perturbation mechanisms are proposed and the vibrational symmetries and energies of the perturbing triplet states are determined. The energies are too high to permit unambiguous vibrational assignments.
Mesure experimental du diametre de la zone non-adiabatique dans un systeme cuspide
Authors: Couture Pierre , Stansfield Barry L.
Published: April 2011

From a study of the trajectories of individual particles in a cusp magnetic field, we have developed an experimental technique to measure the diameter of the nonadiabatic region. We have shown that the adiabatic parameter is useful for distinguishing between adiabatic and nonadiabatic particles, and we have measured the critical adiabatic parameter for the first time. We observe that the experimentally determined value of this parameter is slightly different from that estimated by Van Norton and calculated by Namba et al.
4d75s–4d75p Transitions in Ag IV
Authors: vanKleef Th. A. M. , Joshi Y. N.
Published: April 2011

The spectrum of silver was photographed in the wavelength region 400–2300 Å on a variety of spectrographs including a 10.7 m normal incidence vacuum spectrograph. The sources used were a sliding spark and a triggered spark. On the basis of these observations, 12 missing levels of the 4d75p configuration and all levels of the 4d75s configuration have been established. The least squares fit and Hartree–Fock calculations support the analysis. Seven hundred and twelve additional lines have been classified in this spectrum, 40 of which are doubly classified and four are trebly classified.
Multiple reflection effects in the theory of the Faraday effect and ellipticity for propagation through three distinct media
Authors: O'Connell R. F. , Wallace G.
Published: April 2011

Donovan and Medcalf formulated the theory of the free-carrier Faraday effect in semiconductors for a vacuum–medium–vacuum, taking into account multiple internal reflections of the electromagnetic radiation in the medium. Here, we generalize Donovan and Medcalf's results to the case of three distinct media and also extend their analysis in the sense of obtaining a unique decomposition of the multiple pass rotation [Formula: see text] which gives added physical insight into the various contributions to [Formula: see text]. The multiple pass ellipticity Δ is similarly treated. We also present an alternate and simpler method of carrying out the calculations.
Widths of excited impurity levels in phosphorus-doped silicon
Authors: Barrie Robert , Parent L. G. , Parsons R. R.
Published: April 2011

A model is presented to explain the breadths of the excited impurity levels of phosphorus-doped silicon at zero temperature. The model assumes that the widths of optical transitions involving absorption by the neutral donor and so-called two-electron luminescence from an exciton bound to the neutral donor are the sums of level widths of the initial and final states. The excited s states' level widths are accounted for by assuming that they are governed by the lifetime of the levels for two-phonon decay to the ground state. This decay is brought about by the interaction of the bound electron with the phosphorus ion.
Differential thermal analysis of linear chain mercury compounds
Authors: Chartier D. , Datars W. R. , Gillespie R. J.
Published: April 2011

Differential thermal analysis of powders and single crystals of Hg3-δAsF6 is reported for the temperature interval 100 to 500 K. There is an endotherm at 234 K, corresponding to the melting of mercury during warming, but no exotherm at this temperature during cooling. The amount of mercury detected during warming is 1.3 ± 0.4% of the mercury in a sample. This is greater than the amount of mercury expected from simple contraction of the lattice from room temperature. These results are explained by the presence of a phase of dispersed, solid mercury in the sample. Mercury is formed at the order–disorder transition of the mercury chains and melts at 235 K. Mercury in samples with some decomposition showed a freezing exotherm after supercooling at 18 K. There is irreversible thermal decomposition of Hg3-δAsF6 above 400 K.
Abrasion cross sections for 20Ne projectiles at 2.1 GeV/nucleon
Authors: Townsend L. W.
Published: April 2011

Utilizing eikonal scattering theory, an optical model potential approximation to the exact nucleus–nucleus multiple scattering series is used in an abrasion–ablation collision formalism to predict abrasion cross sections for relativistic 20Ne projectile nuclei. Excellent agreement with recent experimental abrasion results is obtained. The sensitivity of the abrasion predictions to Pauli exclusion principle correlation effects and to the assumed shape of the nuclear single-particle density distribution is also demonstrated.
Master hierarchy of kinetic equations for binary interactions in the adiabatic approximation
Authors: Vasilopoulos P. , Vliet C. M. Van
Published: April 2011

The inhomogeneous master equation obtained in a previous paper is employed to derive a hierarchy of moment equations (quantum mechanical) analogous to the BBGKY hierarchy; the method used is the generating function according to Laplace. In this master equation, and in all these moment equations as well, the effect of the interaction between the particles of the system is represented by relaxation terms; further, there are streaming terms due to the external field. The interactions considered are of a binary nature, fermion–boson or boson–boson. The resulting equations have a simple form (especially for fermion–boson interaction) since the terms representing the interaction can be cast in a form in which only the Boltzmann operator (appropriate to the one-body description) and the second order Fokker–Planck moment appear. The Boltzmann equations obtained by the new method are the same as before (K. M. van Vliet. J/Math. Phys.).
Intercalate order–disorder transition in stage-2 AgxTiS2
Authors: Plischke M. , Bardhan K. K. , Leonelli R. , Irwin J. C.
Published: April 2011

Stage 2 samples of AgxTiS2 have been prepared by the electrointercalation of Ag into TiS2. The intercalated silver atoms are observed to undergo an order–disorder transition with Tc = 265 K. Raman spectra from the ordered phase of the samples contain both the modes expected from the pure crystal and two additional modes. The new modes are attributed to a zone-folding mechanism and a theoretical model is presented to describe this process. The model predicts that the intensity of the zone-folding modes should vary as the order parameter squared (η2). Values η2 as a function of temperature were calculated using a two-dimensional lattice gas model and Monte Carlo techniques. Good agreement is obtained between the calculations and the experimentally observed temperature dependence of the zone-folded mode intensities. The results are discussed and compared with recent theoretical and experimental developments.
Theory of intercollisional interference effects VI: an exactly solvable model exhibiting a shallow interference dip
Authors: Lewis John Courtenay
Published: April 2011

The theory of intercollisional interference effects developed in earlier publications in this series is applied to a model comprising a Lorentz gas with disks or spheres as the fixed seatterers, and a central induced dipole moment 1/R2ν varying as an inverse power of the intermolecular separation. It is shown that the integrated induced dipole moment [Formula: see text] and the relative dip height 1 – γ can be evaluated analytically and in closed form for this model. The interference dip is relatively shallow owing to a cusp in [Formula: see text] with a maximum where the impact parameter b equals the collision diameter. An asymptotic analysis indicates that the dip actually fills in as ν increases, contrary to earlier expectations. The same analysis is applied with minor modifications to an exponential induced dipole moment, and shows that the interference dip also fills in as the range goes to zero for that system. The applicability of the model to a system with more realistic interactions is discussed.
Phenomenological quantum electrodynamics when εμ = 1: theory and some applications including the Casimir effect
Authors: Brevik I.
Published: April 2011

The canonical quantum theory for an electromagnetic field within an isotropic nondispersive medium, whose permittivity ε and permeability μ satisfy the condition εμ = 1, is developed. This condition is found to simplify the electromagnetic formalism considerably and is of interest not only to quantum electrodynamics (QED) but also to quantum chromodynamics (QCD) in view of the formal analogy existing between these two theories to the zero-order in the gauge coupling constant. After giving a survey of the general formalism, this paper discusses appropriate modifications of known experiments in optics: the Ashkin–Dziedzic pressure experiment (1973), the Barlow torque experiment (1912), and the levitation experiment of Ashkin (1970) and others. Finally, a calculation is given of Casimir (i.e., zero-point) surface force acting on one of two spherical interfaces separating three media from each other, under certain simplifying conditions.
Dependence of the positronium hyperfine interaction on the environment: a simple model
Authors: McMullen T. , Stott M. J.
Published: April 2011

A model that displays the essential environmental effects that influence the self-annihilation rate and hyperfine coupling constant of positronium in condensed matter is described. The model, which is exactly solvable, is based on harmonic forces. Ways in which the model can be extended are discussed.