bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave equation for dissipative systems derived from a quantized many-body problem
Authors: Razavy M.
Published: April 2011

A classical many-body problem composed of an infinite number of mass points coupled together by springs is quantized. The masses and the spring constants in this system are chosen in such a way that the motion of each particle is exponentially damped. Because of the quadratic form of the Hamiltonian, the many-body wave function of the system can be written as a product of two terms: a time-dependent phase factor which contains correlations between the classical motions of the particles, and a stationary state solution of the Schrödinger equation. By assuming a Hartree type wave function for the many-particle Schrödinger equation, the contribution of the time-dependent part to the single particle wave function is determined, and it is shown that the time-dependent wave function of each mass point satisfies the nonlinear Schrödinger–Langevin equation. The characteristic decay time of any part of the subsystem, in this model, is related to the stiffness of the springs, and is the same for all particles.
Spatial modes and spectral narrowing of the amplified spontaneous emission in dye amplifiers
Authors: Efthymiopoulos T. , Garside B. K.
Published: April 2011

The propagation of amplified spontaneous emission (ASE) in a planar cell having a width large with respect to the absorption length of the optical pump wavelength in material is investigated. Both the spectral narrowing and the spatial behaviour of the ASE are considered. A model for the spatial inhomogeneity of the index of refraction and the gain across the cell is developed and the results are compared with experiment. It is shown that refraction-index step changes of the order of 5.0 × 10−5 can be produced by thermalization processes within the dye molecules. This, in turn, provides a guiding structure such that low loss field modes can propagate in the cell.
Some characteristics and observations of long diffuse discharges produced by the focussing of a TEA-CO2 pulse with an axicon
Authors: Roy G. , d'Astous Y. , Blanchard M. , Tremblay R.
Published: April 2011

A theoretical and an experimental study of long diffuse laser produced plasmas with axicon lenses is presented. It is shown that the heating of a helium plasma is strongly dependent on the nitrogen tail of the TEA-CO2 laser pulse when the initial electronic density (produced by photopreionization) is sufficiently high, but still below the breakdown threshold. Furthermore, a theoretical model is used to evaluate the radial expansion of the plasma in order to determine the effective volume of the plasma when dealing with rapidly evolving processes.
Disorientation and disalignment of 42P3/2 potassium atoms, induced in resonant collisions
Authors: Skalinski P. , Krause L.
Published: April 2011

The total cross sections for disorientation (σ1) and disalignment (σ2) of 42P3/2 potassium atoms, induced in collisions with the ground-state atoms, have been determined using a modified Zeeman scanning method. Potassium vapor at densities of the order of 1011 cm−3, contained in a fluorescence cell located in a kilogauss variable magnetic field, was irradiated with circularly polarized 7665 Å resonance radiation emitted from a discharge lamp located in a constant field of 5.4 kG. Scans of the variable field permitted selective excitation of single Zeeman components in the absorbing vapor. The σ+ and σ− components of the resulting resonance fluorescence emitted parallel to the scanning field were monitored in relation to the vapor density, as were the π and σ components emitted in the perpendicular direction. As the vapor density increased so did the frequency of the collisions which caused transfers among the Zeeman states in the vapor and thus disorientation and disalignment. The observed dependence of circular and linear depolarization of the fluorescence on the potassium density yielded the cross sections σ1 = 17 × 10−12 cm2 and σ2 = 21 × 10−2 cm2, corrected for imprisonment of radiation.
X-ray Raman scattering in colloidal and polycrystalline graphite
Authors: Koumelis C. N. , Londos C. A.
Published: April 2011

Raman scattering was measured in colloidal and polycrystalline graphite for a scattering angle 45°, using X-ray CrKβ radiation and a mosaic graphite analysing crystal spectrometer without collimators. The use of such a spectrometer was necessary because of the weakness of the Raman effect.For the colloidal graphite, an energy shift of ΔE = 288.3 ± 0.6 eV from the primary line was observed. For the polycrystalline graphite, the above shift was ΔE = 284.9 ± 0.5 eV. These shifts can be ascribed to the transition of the 1s electrons onto and above the Fermi level, constituting the so-called Raman band.In the polycrystalline graphite, an additional anomaly was observed in the spectrum, beyond the Raman band towards the low energies, i.e., in 311 eV. This fine structure is a verification of the Weaire–Thorp concept about the difference in the spectra, due to the short-range and long-range order.
Some aspects on the generation and transmission of light in phosphor screens excited by an electron beam
Authors: Giakoumakis G. E. , Nomicos C. D. , Euthymiou P. C.
Published: April 2011

The relation between the electrons' penetration depth, photogeneration, and phototransmission in fluorescent screens excited by an electron beam is theoretically studied. All the above phenomena are discussed in terms of appropriately modulated Hammaker's equations and expressions for the intensity of the outgoing light are given. On the basis of these expressions the scattering and absorption constants have been determined from absolute efficiency measurements on ZnCdS:Ag screens.
Basis states for equivalent electrons. III. States for the Lie group SO(2l + 1) × SU(2) using Sp(4l + 2) states
Authors: Ross William R.
Published: April 2011

The Lie group SO(2l + 1) × EU(2) is a subgroup of the symplectic group Sp(4l + 2), which in turn is a subgroup of the unitary group U(4l + 2). The Slater basis states for N equivalent electrons form the basis for the irreducible representation (1N) of U(4l + 2). The basis states for the irreducible representations of SO(2l + 1) × SU(2) are expressed in terms of the states for irreducible representations of Sp(4l + 2). The basis states for SO(2l + 1) × SU(2) are also expressed in terms of the Slater basis states.
The rotation and precession of relativistic reference frames
Authors: Hamilton J. Dwayne
Published: April 2011

The Clifford algebra of three- and four-vectors is reviewed and used to examine the nature of the rotation and precession of accelerating reference frames in Minkowskian space-time, and freely falling reference frames in general relativity. It is shown that the usual interpretation of Thomas precession must be modified because in space-time three-vectors in one frame of reference cannot be related to three-vectors in another.
Hydrogen burning of 39K in explosive oxygen burning
Authors: Cheng C.-W. , Saha S. K. , Keinonen J. , Mak H.-B. , McLatchie W.
Published: April 2011

The absolute strengths of the 39K(p,γ)40Ca resonances at Ep = 1130, 1344, and 2043 keV have been determined to be Scm = 1.6 ± 0.2, 4.1 ± 0.5, and 14.3 ± 1.3 eV, respectively. Relative strengths were measured for resonances in the range 0.7 < Ep < 2.9 MeV. The astrophysical reaction rates of hydrogen burning of 39K in explosive oxygen burning in the stellar temperature region of T = (1.0–7.0) × 109 K are compared with Hauser–Feshbach calculations. The effect of the revised reaction rates on the 39K abundance is discussed.
Evaluation of dielectric parameters for dilute solutions at microwave frequencies using a numerical curve fitting technique
Authors: Krishna J. Gowri , Jeyaraj M. , Sobhanadri J.
Published: April 2011

A new method involving an elegant computer curve fitting technique is discussed for evaluating ε′ and ε″, for dilute solutions at X- and Q-bands, with a greater accuracy. Four compounds with rigid (chlorobenzene) and nonrigid (anisole, phenol, and guaiacol) molecules have been tested with this method. The important advantage of the present method is that it involves no mathematical assumptions. The error involved in evaluating ε′ and ε″ is estimated to be 1% and 1–2% respectively.
The A–X system of the CuCl molecule
Authors: Mishra G. P. , Rai S. B. , Upadhya K. N.
Published: April 2011

The A–X band system of CuCl has been photographed in emission under high resolution in the 2nd order of a 10.6 m concave grating spectrograph. Rotational structure in four bands, viz. (1,0), (0,0), (0,1), and (1,2) has been analysed. The present analysis confirms that in the A–X system the electronic transition involved is 1Π–1Σ where 1Σ is the ground state of the molecule. The Λ-type doubling in the 1Π state is found to be appreciable. The molecular constants for the excited A state of 63Cu35Cl are (with standard deviations in parentheses): Be = 0.168432(7) cm−1; αe = 0.001067(7); De = 0.1134(11) × 10−6; q = 0.000871(9); qD = 0.85(18) × 10−8; ν10 = 19 500.271(8); ν00 = 18 999.104(7); ν01 = 18 579.735(10); and ν12 = 18 574.745(11).
General solution of the spin Hamiltonian for complex electron nuclear double resonance spectra
Authors: Ziaei M. E.
Published: April 2011

An electron nuclear double resonance investigation of CsCdF3:M (M = Mn2+, Ni2+, Cr3+, and Co2+) has been carried out to measure the transferred hyperfine interaction (thfi) between M and nearest neighbour fluorine ions. A general spin Hamiltonian which takes account of the multiplicity of the interacting nuclei, is solved for a general orientation of the magnetic field. An example is given to show that theory agrees well with experiment. Spin transfer parameters obtained are of similar order of magnitude for the same ions in similar host lattices.
Near field index inhomogeneities in third harmonic generation
Authors: Goyal M. L. , Sharma K. K. , Srivastava G. P.
Published: April 2011

Near field index inhomogeneity effects on harmonic generations ξ ≤ 1 (ξ = focusing parameter) become appreciable when a high power narrow collimated beam passes through a nonlinear medium under phase matching condition (PMC). The effect has been described in terms of two parameters Rw (collimation) and τD (birefringence) of the beam in the near field of the crystal. Large values of the parameters τD for Rw > 1 refer to intense absorption-induced index inhomogeneity effects when high power (repetitively Q-switched) collimated laser beams are used. Due to this effect the third harmonic (TH) conversion efficiency degrades considerably and causes appreciable thermal mismatch (ΔK3w ≠ 0) within the crystal. The coherence length lcoh under such conditions also decreases rapidly with the increase of inhomogeneity and with the temperature dependent birefringence of the medium. The TH peak corresponding toΔk3w = 0 under such circumstances shifts towards the higher temperature region of the crystal. Thermal retuning (depending primarily on absorption Wab) is desirable under such conditions to restore normal phase matching and enhance TH generation efficiency within the crystal.
Charmonium: the mass spectrum
Authors: Mahmood Sajjad , Ilyas M. M.
Published: April 2011

The charmonium mass spectrum is evaluated using the oscillator potential as responsible for long range confinement. Hyperfine splittings for the color singlet [Formula: see text] system are discussed using various approaches. The mass of [Formula: see text] and [Formula: see text] are also briefly touched upon.
A singularity-free solution for a static charged fluid sphere in Einstein–Cartan theory
Authors: Krori K. D. , Sheikh A. R. , Mahanta Lakshmi
Published: April 2011

A singularity-free solution for a static charged fluid sphere in the presence of spin density is obtained in Einstein–Cartan theory. It is shown that the solution satisfies physical conditions throughout the sphere.
Quantitative spectroscopy of the aurora. V. The spectrum of strong aurora between 10 000 and 16 000 Å
Authors: Gattinger R. L. , Jones A. Vallance
Published: April 2011

The auroral spectrum between 10 000 and 16 000 Å has been examined with a resolution of 12 Å by means of a Michelson interferometer. As a result of the high accuracy of the spectral data obtained by this technique, it has been possible to derive a pure auroral spectrum by subtracting the nightglow spectrum obtained under identical conditions in the absence of aurora. The spectrum was then matched by a synthetic spectrum composing N2 and N2+ bands and atomic lines so as to measure the intensities of the components of the auroral spectrum. The first positive N2 band intensities agree well with the values predicted from analysis of the spectrum below 11 000 Å. On the other hand the intensities of the Δν = −1 bands of the N2+ Meinel system make possible an improved electronic transition moment function, [Formula: see text], for the system. The vibrational population rates derived from the spectrum by means of the new function are closer than before to values predicted by the Franck–Condon principle.
Magnetic properties of a random anisotropy model with both ferromagnetic and antiferromagnetic exchange coupling
Authors: Pozo J. , Ferrer R. , Zuckermann M. J.
Published: April 2011

The model of Harris et al. for random magnetic anisotropy is examined for the case of nearest neighbour antiferromagnetic and next-nearest neighbour ferromagnetic exchange coupling. Initial magnetization curves, critical fields for the metamagnetic transition, and hysteresis loops were obtained for a variety of parameters using the molecular field approximation and were compared with previous work. It is shown that the metamagnetic transition becomes a discontinuous transition and that the hysteresis loops change their shape considerably in the presence of ferromagnetic exchange. The results are discussed in the light of experimental work.
Surface plasmon dispersion on a single-sheeted hyperboloid
Authors: Becker R. S. , Anderson V. E. , Birkhoff R. D. , Ferrell T. L. , Ritchie R. H.
Published: April 2011

The surface-plasmon dispersion relation is obtained for a single-sheeted hyperboloid of revolution. The effects of retardation are neglected, and the electric potential is obtained from Laplace's equation in oblate spheroidal coordinates. Our results are applicable to the description of eigenmodes for a submicron hole in a material which may be supposed to have a local dielectric function.
Single-mode laser fluorescence of NO2 excited at 488 nm
Authors: Armstrong M. J. , Brand J. C. D. , Lauro C. di
Published: April 2011

The 488 nm line of the Ar+ laser operated in a single cavity mode excites absorption–fluorescence cycles in which an unusually high proportion exhibit anomalies in the selection rules, including transitions to a1 vibrational levels with values of ΔK = Kinitial – Kfinal of 4,2,0, and −2. Many transitions in the fluorescence, especially the weaker bands, show an intensity distribution different from that expected for type A bands of a 2B2–2A1 transition; this is attributed to interference between the dominant μa moment and a secondary, perpendicular transition moment considered to result from a perturbation of the intermediate state of the cycle by the 2B1 state.Data from about 20 fluorescence bands are used to determine the coefficient of a sextic anharmonic resonance, ν1ν2ν3, ν1, − 3, ν2 + 1, ν3 + 2 in the ground state of NO2.
The Fermi contact contribution to the Knight shift in Be from self-consistent spin-polarized calculations
Authors: Wilk L. , Nusair M. , Vosko S. H.
Published: April 2011

The linear augmented plane wave method in the muffin-tin approximation was used to perform self-consistent spin-polarized calculations of the electron number density n(r) and spin (magnetic moment) density m(r) in metallic Be, within the framework of the spin density functional formalism. For the exchange-correlation functional we used the recent accurate results of Vosko et al. in the local spin density approximation. The Fermi contact contribution to the Knight shift is proportional to the sum of three spin densities (evaluated at the nucleus) arising from (i) the valence electrons at the Fermi surface, (ii) the core electrons, and (iii) the valence electrons below the Fermi surface. We find a 90% cancellation between (i) and (ii) which greatly magnifies the significance of the relatively small effect (iii). Although our contact term is still positive in sign, its magnitude is nearly one-fourth of the previous smallest first principles result and thus requires a smaller orbital diamagnetic contribution than previously invoked to explain the negative experimental value of the Knight shift.
Padé approximants applied to perturbation theory for the linear confining potential
Authors: Lai C. S. , Lin W. C.
Published: April 2011

By forming the [6,6] and [6,7] Padé approximants to the energy perturbation series for the linear confining potential, we calculate energy eigenvalues of the 1s, 2s–2p, 3s–3d, and 4s–4f states. The bound-state energies calculated are found to follow the order of levels: Enl < Enl′ for l > l′.
Application of a diagram technique to the problem of resonance fluorescence from strongly driven two level atoms
Authors: Zaidi H. R.
Published: April 2011

A Green's function formulation, valid for thermal as well as nonthermal equilibrium, is developed for the resonance fluorescence from strongly driven two level atoms. Translational motion and the Doppler broadening are also taken into account (collisions are considered in a second paper). The Feynman diagram technique is used to calculate the contribution of the physically important processes. The formulation is not based on the Markovian approximation or the quantum regression theorem. It takes full account of the dynamic Stark splitting and the saturation, and leads to a generalization of the "dressed atom" approach. Our "generalized dressed atom" (GDA) approach is valid for arbitrary values of the detuning and the pump field strength. The lowest order diagrams in the GDA picture give results equivalent to the existing theories. Some higher order diagrams are also considered. Although the resulting corrections are small, the physical processes involved are of some interest. These corrections include nonMarkovian effects.
The 11B(d,γ0)13C reaction in the region of the giant dipole resonance
Authors: Kajrys G. , Bianco W. Del , Kim J. , Landsberger S. , Lecomte R. , Monaro S. , Paradis P.
Published: April 2011

The 90° differential cross section of the 11B(d,γ0)13C reaction has been measured at deuteron energies from 1.95 to 12.0 MeV in steps varying from 100 to 200 keV. The γ-rays have been detected by a 23 cm long × 23 cm diameter NaI(Tl) crystal spectrometer enclosed in a plastic scintillator anticoincidence shield. The yield curve shows a resonant structure at the energies Eexe = 20.4 ± 0.1 and 22.0 ± 0.2 MeV.
Two-dimensional liquid model for graphite intercalation compounds
Authors: Plischke Michael
Published: April 2011

A simple classical liquid theory (the Ornstein–Zernike equation treated in the hypernetted chain and Percus–Yevick approximations) is applied to the graphite intercalation compounds C24CS and C24K. The interparticle potential is taken to be infinite for distances less than a particle diameter and a screened coulomb potential for longer distance. A layered free electron model is used in the screening calculation. The calculated pair correlation function agrees extremely well with X-ray diffraction measurements of this function at room temperature.
Levels in 149Nd studied with the reaction
Authors: Haugen L. , Lien J. R. , Løvhøiden G. , Straume O. , Burke D. G. , Waddington J. C.
Published: April 2011

The 150Nd(d,t)149Nd reaction has been studied with 16 MeV deuterons with a vector polarization of ~0.75 from the McMaster University tandem Van de Graaff accelerator. Measurements were made at 11 angles from 5.5 to 37.5° using a magnetic spectrograph equipped with photographic emulsions in the focal plane. The measured analyzing powers which are well described with standard distorted wave Born approximation calculations, made it possible to give unambiguous assignments for 14 states for which spin information was previously conflicting, incomplete, or lacking.
Electron transport and conduction band structure of GaSb
Authors: Lee Hyung Jae , Woolley John C.
Published: April 2011

Calculations have been made using the Fletcher and Butcher method in a three conduction band model to fit a wide range of experimental transport data for n-type samples of GaSb: viz. Hall coefficient and electrical conductivity as a function of temperature and as a function of pressure at room temperature, magnetoresistance as a function of magnetic field at different temperatures, and Nernst–Ettingshausen coefficients as a function of magnetic field. Various energy gap parameters and scattering coefficients have been taken as adjustable and values determined for these which give good fits to all of the experimental data. Values of mobility for each of the Γ, L, and X bands have then been calculated as a function of temperature.
Le spectre électronique de BS. Partie II : Structure des états dans le domaine d'énergie 36 000–46 000 cm−1
Authors: Jenouvrier A. , Pascat B.
Published: April 2011

The study of the structure of the B2Σ+ and C2Π states has been carried out on the B2Σ+–A2Πi and C2Π–X2Σ+ transitions. In the 36 000–46 000 cm−1 energy range, the perturbations observed particularly in the C2Π state levels are discussed. The location of the different perturbing states allows a discussion on all the states of the first four excited electronic configurations.
Scattering by hard and soft parallel half-planes
Authors: Hurd R. A. , Lüneburg E.
Published: April 2011

We consider the diffraction of a scalar plane wave by two parallel half-planes. On one half-plane the total field vanishes whilst on the other its normal derivative is zero. This is a new canonical diffraction problem and we give an exact closed-form solution to it. The problem has applications to the design of acoustic barriers.
Analysis of 4d8–4d75p transitions in trebly ionized silver: Ag IV
Authors: VanKleef Th. A. M. , Joshi Y. N.
Published: April 2011

The spectrum of silver was photographed in the region 625–300 Å on a 10.7 m grazing incidence spectrograph. The sources used were a sliding spark and a triggered spark. The earlier analysis of the resonance lines has been revised. All levels of the 4d8 configuration and 98 out of 110 levels of the 4d75p configuration have been established. Parametric level fitting calculations confirm the analysis. Two hundred and ninety-four (294) lines have been classified in this spectrum.
Measurements and calculations of self-broadening coefficients of lines belonging to the 2ν2, ν1, and ν3 bands of H216O
Authors: Mandin J.-Y. , Camy-Peyret C. , Flaud J.-M. , Guelachvili G.
Published: April 2011

Using Fourier transform spectra (resolution ≈ 0.005 cm−1), the self-broadening coefficients of 340 lines belonging to the 2ν2, ν1 and ν3 bands, and to the ν2 + ν3 − ν2 hot band of H216O, have been measured. The average uncertainty is about 19% and varies from 15 to 28% depending on the line involved. The broadening coefficients, by natural water vapor, of 40 other lines belonging to the ν3 and ν1 bands of H217O and H218O have also been measured. Theoretical calculations of self-broadening coefficients are performed, using the Anderson–Tsao–Curnutte method, and taking into account the four intermolecular interactions: dipole–dipole, dipole–quadrupole, quadrupole–dipole, and quadrupole–quadrupole. In these calculations, accurate spectroscopic data have been used: precise energy levels, realistic wavefunctions, and a complete dipole moment operator expansion in order to compute the transition probabilities. Particularly, all resonances between the three interacting vibrational states (020), (100), and (001) have been fully taken into account. For B-type bands, comparisons are made with the self-broadening coefficients previously calculated by Benedict and Kaplan for the pure rotational lines. The Anderson–Tsao–Curnutte method has proved to be very efficient for calculating self-broadening coefficients: the relative differences between observed and calculated values are less than 20% respectively for 68, 79, and 79% of the lines in the 2ν2, ν1, and ν3 bands. These self-broadening coefficients will be useful for the study of the absorption coefficient in line wings.
Quadrupole polarizabilities and Sternheimer antishielding factors in the density functional theory
Authors: Stott M. J. , Zaremba E. , Zobin D.
Published: April 2011

The quadrupole polarizability and Sternheimer antishielding factor have been calculated for selected closed-shell atoms and ions using the density functional theory. In most cases, the results agree favourably with coupled Hartree–Fock calculations. However, for atoms with valence (d-shells the local density approximation used in the calculations is found to be inadequate. Our results suggest that refinements to the exchange-correlation energy functional are required in order to obtain accurate values for the polarizability and shielding factor of (d-shell atoms within a density functional approach.
Temperature dependent Zeeman study of bound exciton and bound multiexciton complex photoluminescence in Si(P) and Si(Li)
Authors: Ziemelis U. O. , Parsons R. R. , Thewalt M. L. W.
Published: April 2011

The Zeeman spectra of the α1 to α4 photoluminescence lines of Si(P) and the Li1 to Li4 photoluminescence lines of Si(Li) have been measured as a function of temperature in the range 1.5–4.2 K. As expected on the basis of the Kirczenow BMEC shell model (SM), the thermalization behaviour indicated by the Si(P) spectra differs substantially from that indicated by the Si(Li) spectra. This is related to the different valley–orbit state ordering of the two systems. The observed Zeeman substructure and thermalization behaviour in both the Si(P) and Si(Li) systems is shown to be in very good agreement with the predictions of the SM. Specifically the SM predicts two unique effects: no low temperature thermalization for the Zeeman sub-components of α4 and the disappearance of all the Zeeman sub-components of Li1 at the lowest temperatures; these effects have both been observed.
Temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer and for quenching in cesium, induced in collisions with H2, N2, CH4, and CD4
Authors: Siara I. N. , Dubois R. U. , Krause L.
Published: April 2011

The temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer in cesium, as well as the effective quenching of these states, induced in collisions with H2, N2, CH4, and CD4 molecules have been investigated in a series of sensitized fluorescence experiments over a temperature range 390–640 K. The 72P mixing cross sections are of the order of 10−15 cm2 and exceed by at least one order of magnitude similar cross sections for mixing by collisions with Ne, Ar, Kr, and Xe. The large sizes of the mixing cross sections and their variation with temperature are ascribed to a phenomenon of electronic-to-rotational energy transfer.
Second order infrared absorption spectrum of carbon dioxide in the condensed phase
Authors: Umapathy S. , Krishnamurthy N.
Published: April 2011

Solid carbon dioxide crystallizes in the space group [Formula: see text] with four molecules in the primitive unit cell. In the infrared absorption spectra of solid CO2 Mannik and Allin have observed extensive second order features involving combinations of the intermolecular vibrations with the components of the Fermi doublet (ν1, 2ν2) at 88 and 150 K. In the present investigation an interpretation of these second order infrared absorption spectra is carried out employing the rigid ion model of Powell et al. in the framework of external mode formalism and Stephen's theory of the two phonon infrared absorption. Reasonable agreement is observed in the phonon branches along the symmetry directions in our rigid molecule approximation and also in the observed infrared absorption spectra.
Magnetic field dependence of plate wave velocity and attenuation in metallic-glass ribbon
Authors: Poirier M. , Cheeke J. D. N. , Germain L.
Published: April 2011

Piezoelectric transducers were used to study the propagation of two elastic plate waves in the amorphous material Metglas 2605 SC in its as-quenched state during magnetization. For both modes domain boundary losses are responsible for the large attenuation with the expected field orientation dependence relative to strain. The velocity changes are related to an elastic modulus effect which arises mainly during domain rotation processes in a magnetostrictive material. It has been possible to differentiate between the different contributions to these effects by magnetization and frequency dependence studies.
Interatomic potential from density functional theory with application to metallic hydrogen
Authors: Magaña F. , Whitmore M. D. , Carbotte J. P.
Published: April 2011

We propose an extension of the usual perturbative approach for calculating interatomic potentials in simple metals which is based on the density functional formalism. The procedure uses nonlinear self-consistent calculations of the displaced electron charge density distribution Δnλ(r) about an external charge λZ immersed in an electron gas, with λ ranging from 0 to 1. The interatomic potential is then obtained by an integration over λ of a function involving Δnλ(r). Results are obtained for the case of two protons (Z = 1) and applied to metallic hydrogen. The resulting phonons and superconducting transition temperatures are found not to differ much from those obtained in a recent calculation using a different approach.
Positron–gas cross-section measurements
Authors: Kauppila W. E. , Stein T. S.
Published: April 2011

The purpose of this paper is to review the progress in positron–gas cross-section measurements. Total cross-section measurements for 0.3–1000 eV e+–He, Ne, Ar, Kr, Xe, H2, N2, CO2, O2, CH4, and CO are summarized. Interesting shape features in the total cross-section curves, such as Ramsauer–Townsend effects and the onsets of positronium formation are discussed. An effort is made to compare total cross-section measurements from different laboratories to see if there are any consistencies which could provide information on the reliability of the various measurements. Comparisons of total cross-section measurements for positrons and electrons colliding with several of the above gases are presented in an attempt to illustrate the similarities and differences between positron and electron scattering. Some recent positron cross-section investigations pertaining to differential scattering, positronium formation, inelastic scattering, atomic excitation, and resonance searches are also discussed.
Positron lifetime spectra for gases
Authors: Heyland G. R. , Charlton M. , Griffith T. C. , Wright G. L.
Published: April 2011

Recent observations on the lifetime spectra for gases are presented and discussed. There is little to report on the inert gases helium, neon, and argon and the spectra for these gases are thought to be understood. New lifetime data for krypton and xenon have revealed two fast components which, although probably connected with the low positronium fractions for these gases, have yet to receive a satisfactory interpretation.The polarized orbital calculations for Zeff's and momentum transfer cross sections for all the inert gases by the York group are now complete and are generally in good agreement with experiment.For the molecular gases some information on rotational excitation cross sections has been obtained from thermalization times for nitrogen, hydrogen, and deuterium. In general, the [Formula: see text] parameter is dependant on gas density and temperature with some gases showing a pronounced maximum in the density dependance. The gases C3H8, C4H10, and CH3Cl have very large values of [Formula: see text] which indicate localization or capture of the positron by one or more molecules. These three gases exhibit a maximum in the instantaneous decay rate of the "free" positron component at low densities from which a "capture" cross section can be estimated.The positronium fraction, F, generally increases with the gas density, usually approaching a limiting value asymptotically, but for nitrogen this density dependance has a maximum at ~ 140 amagat. No satisfactory explanation has been offered for this behaviour.Positronium formation cross sections for several gases have been deduced from measurements of the variation of F with the concentration of the gas in helium. These cross sections are similar in magnitude to those deduced from the total cross section beam measurements.
The interaction of positrons with large atoms and molecules: theory
Authors: Schrader D. M. , Svetic R. E.
Published: April 2011

Calculations of positron–atom and positron–molecule scattering are reviewed. The polarized orbital results of the York group are found to be of the same reliability as recent experimental determinations in the elastic region for the noble gases. The temperature dependence of the annihilation rate is suggested as a sensitive point of contact between theory and experiment. Using a new, direct experimental determination of the positronium formation cross section below the ionization threshold for argon and helium, we have made an improved Ore-type estimate of the positronium fraction of the noble gases. The new estimates agree perfectly with experiment for the three lighter gases. However, for krypton and xenon, the new estimates are much too high, which suggests the existence of an unknown process which suppresses or depletes positronium. Recent calculations on other atoms and on simple diatomic molecules are also reviewed.
The theoretical KLL Auger spectrum of atomic Na+ and Ne
Authors: Petrini D.
Published: April 2011

KLL Auger transition rates for Ne and Na+ are obtained from the resonant behaviour of the S matrix for electron scattering by Ne2+ and Na3+ respectively. Both the close coupling and distorted wave methods are used to compute the S scattering matrix. Our results arc in good agreement with experimental data and also with Kelly's theoretical Ne results.
The anomalous mass dimension to two loops in quantum chromodynamics
Authors: Phillips Stephen
Published: April 2011

A calculation of the anomalous mass dimension, δ, to second order in quantum chromodynamies, done in the zero-mass renormalization scheme of Weinberg, is presented. By different limiting procedures we obtain two different results for δ giving an explicit example of renormalization scheme dependence.
Déplacements des raies d'émission de l'ion ArII dans un plasma dense
Authors: Simard P. A.
Published: April 2011

A spectroscopic study of the emission from an argon plasma produced by a small theta-pinch is described. The electron density in the plasma is very high and the temperature relatively cool. Values obtained for these quantities are [Formula: see text] and [Formula: see text]. Wavelengths of many ArII lines have been measured between 2700 and 5000 Å. Many of these lines exhibit small shifts to the blue or to the red but others show large red shifts. Particularly significant are the multiplets 4p4P−4d4P, 4p4P−5s4P and 4p4S−4d4P where the measured shifts are about 6.0 ± 0.8 cm−1. These shifts have been interpreted as plasma polarization shifts. A plasma effect on the spin–orbit coupling in ArII has also been observed for the first time. A qualitative analysis of these phenomena is given.
Étude des bandes infrarouges en résonance 2ν2, ν2 + ν5, , , 2ν3 + ν5 et 4ν3 du chlorure de méthyle
Authors: Binsari-Zizi Najath , Alamichel Claude , Guelachvili Guy
Published: April 2011

The spectrum of methyl chloride has been analyzed between 2650 and 2950 cm−1 from Fourier transform recordings obtained with a very high resolution. More than 3000 lines of CH335Cl and more than 1500 lines of CH337Cl, most of them belonging to ν2 + ν5 and [Formula: see text], have been assigned: the 2ν2, [Formula: see text], 4ν3 and 2ν3 + ν5 bands are very weak and only appear when there are level crossings. The main interaction is the Coriolis resonance between the ν2 and ν5 modes, which links the rovibrational levels six by six. The Fermi resonance between [Formula: see text] and ν1, whose existence has just been shown, does not seem to have important consequences. Numerous other resonances, particularly making the 4ν3 and 2ν3 + ν5 bands visible, must be added to the basic coupling model; they make the general interaction scheme extremely complex. A least squares calculation, according to a simplified model, has given a standard deviation of 0.029 cm−1 over 784 lines of CH337Cl, from which crossings and locally perturbed subbands were excluded.
Models for the phase transition in a monolayer of amphiphilic bipolar molecules on an aqueous substrate
Authors: Legré J. P. , Albinet G. , Caillé A.
Published: April 2011

Models are proposed to explain the mechanism of the phase transition observed in a monolayer of amphiphilic dipolar molecules of which one of the two polar groups may, under lateral compression, leave the interface between the monolayer and the aqueous substrate. Good agreement with the experimental results are obtained when the binding energy of the polar group leaving the substrate, the molecular size effects, and the intramolecular free energies are taken into consideration. In this framework we propose the following interpretation for the first-order phase transition. The monolayer goes from a low surface density phase, where both polar groups of the molecule are anchored to the substrate, to a condensed phase where a large fraction of the molecules have only one polar group attached to the aqueous substrate.
Millimetre wave spectrum of silyl acetylene in the ground vibrational state
Authors: Carlier J. , Bauer A.
Published: April 2011

The millimetre wave spectrum of silyl acetylene in the ground vibrational state has been observed from 125 to 231 GHz. A new signal processing system using Stark effect has been carried out for the detection of the weakest lines. Refined rotational and centrifugal distortion constants have been derived.
Structure fine de l'intensité du faisceau électronique réfléchi par le W(110) et l'influence de la chimisorption de l'hydrogène
Authors: Baribeau J. M. , Carette J. D.
Published: April 2011

Measurements with high resolution in energy and angle of the intensity of the electron beam reflected from W(110) in the [10] azimuth are presented. For high values of the reflected angles (θi ≥ 65°) intensity profiles present narrow fluctuations related to the emergence of the [Formula: see text] diffracted beam. This LEED fine structure is caused by the interference of the wave directly reflected from the crystal with a wave temporarily trapped between the substrate and its surface potential barrier. The shape of these singularities is studied in detail for a clean target and for the same target submitted to various hydrogen exposures. In the latter case, a gradual modification of the lineshape as a function of the hydrogen coverage is observed. This phenomenon is explained by the modification of the substrate scattering properties rather than by a transformation of its surface barrier. The LEED fine structure accentuation induced by hydrogen adsorption could be the indication of the ordered chemisorption of this gas in interstitial sites on W(110).
Excitation and polarization analysis of the OD fragment radiation produced by dissociative electron impact on D2O
Authors: Becker Kurt , Schulz Günther
Published: April 2011

The formation of electronically excited OD(A2Σ+) radicals following dissociative electron impact on D2O has been studied and a comparison with the H2O/OH (A2Σ+) dissociation system is made. Measurements of excitation functions reveal that the dissociation paths are largely unaffected by the deuteration of the parent molecule and even the weighting of the different dissociation channels leading to respectively slowly and rapidly rotating OD radicals is similar to the H2O dissociation process. On the other hand, the level of polarization of OD as compared with OH fragment radiation is found to be reduced by roughly a factor of 3. This may be explained in terms of an enhanced ratio of lifetime to rotational period for the parent D2O states. Thus the dissociation dynamics, i.e., the time scale between excitation and fragmentation, is demonstrated to react very sensitively when normal water is replaced by its deuterated specimen.
Zakharov–Manakov solution of the stimulated Brillouin backscattering generator problem for non-rectangular envelopes
Authors: Enns R. H.
Published: April 2011

Making use of the inverse scattering transform method (ISTM), we have solved the Zakharov–Manakov problem for the stimulated Brillouin backscattering of a laser pulse by an acoustic fluctuation for a situation where the envelopes are non-rectangular. We have chosen input potentials which simulate rapidly rising pulses with exponentially decaying tails. The extension of the analysis to other input shapes is discussed.
Bäcklund transformation according to Gerdzikov and Kullish for the Korteweg–de Vries equation
Authors: Gautrin Henri-François
Published: April 2011

A study of solutions of the Gel'fand–Levitan equation permits one to establish new Bäcklund transformations for the Korteweg–de Vries equation. To a specific change in the scattering parameters, there corresponds a family of Bäcklund transformations. A means to construct these transformations is presented.
On the diffraction of an arbitrary wave by a wedge
Authors: Mohsen A.
Published: April 2011

Some of the basic contributions to the problem of diffraction of an arbitrary wave by a wedge are reviewed. Generalizations to some of the previous approaches are presented. The resulting solutions are in integral form. These solutions reduce to the well-known special cases for simple excitations.
A new electronic transition C2πr–A2πi, of AlO
Authors: Singh M. , Saksena M. D.
Published: April 2011

Several weak bands of AlO, degraded to the violet and occurring as wide doublets 200 cm−1 apart, have been observed in the region 3300–4000 Å, in emission from a high frequency discharge through a flowing mixture of AlCl3 vapour, oxygen, and argon. These bands have been identified as due to a new electronic transition C2πr–A2πi of AlO. This has been confirmed from a detailed rotational analysis of the 1–0 and 0–1 bands (heads, respectively, at 3481.92, 3506.09 Å and 3683.30, 3710.98 Å) from high resolution spectra. Numerous rotational perturbations have been found in both the C2π3/2 and C2π1/2 substates. Effective rotational constants have been determined for these substates. Λ-doubling has been observed even in the substate C2π3/2.
Direct evidence for mixing of two-quasiproton and two-quasineutron configurations in 172Yb
Authors: Burke D. G. , Blezius J. W.
Published: April 2011

The 175Lu(p,α)172Yb reaction has been studied using beams of 17 MeV protons from the McMaster University tandem Van de Graaff accelerator. The alpha particle reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Levels up to an excitation energy of 2.8 MeV were studied with a resolution of 20 keV FWHM. The spin 3, 4, 5, and 6 members of the Kπ = 3+ band at 1172 keV were populated appreciably, indicating the existence of a significant two-quasiproton admixture in this band. The measured angular distributions and relative intensities within the band are consistent only with a Kπ = 3+, {7/2+ [404] − 1/2+ [411]} configuration for this admixture, and the absolute intensities indicate that it makes up (27 ± 10)% of the state. This observation provides a quantitative explanation for the observed magnetic moment of the 1172 keV level and also for the observed E2–M1 mixing ratios within the band. It may also be important in the explanation of other anomalous properties of this band. The present measurements also show large Kπ = 3+, {7/2+ [404] − 1/2+ [411]} admixtures in the previously assigned Kπ = 2+ band at 1609 keV and the Kπ = 3+ band at 1663 keV. In addition, the assignment of the 2073 and 2192 keV levels as Iπ = 4+ and 5+ members of a Kπ = 4+, {7/2+ [404] + 1/2+[411]} band has been confirmed.
Transport properties of solid and liquid Cs
Authors: Cook J. G.
Published: April 2011

The thermal conductivity, electrical resistivity, and thermoelectric power of Cs have been measured from 40 K, through the melting point which is near 300 K, up to 600 K. The thermal resistivity of both solid and liquid Cs contains a contribution from electron–electron scattering, which agrees well with theory. The electrical resistivity shows an appreciable "premelting" effect, which is tentatively attributed to impurities.
Broadband photon yield of Kr excited by monoenergetic electron impact. Part II: 12–15 eV
Authors: Marchand P.
Published: April 2011

The broadband photon yield in the spectral range 165–650 nm of Kr excited by monoenergetic electrons with energies from 12 to 15 eV has been measured. Several negative-ion states are observed both below and above the 2P3/2 ionization threshold. No structures are detected above the 2P1/2 limit, even with a total accumulation of 200 million counts per observation point.
Brillouin scattering in thin film optical waveguides. III. Experiments
Authors: Rowell N. L. , So V. C-Y. , Normandin R. , Stegeman G. I.
Published: April 2011

A series of experimental results on Brillouin scattering in thin film optical waveguides is discussed for two scattering geometries and for three types of planar waveguides. The results of these experiments are compared with the theory presented in the previous two papers.
Resonance fluorescence spectra from a three level atom interacting with a strong bichromatic field: induced two photon transitions
Authors: Hutchinson Douglas A. , Downie Christine , Mavroyannis Constantine
Published: April 2011

This investigation describes the interaction of a three level atom with two laser fields. One of the transitions from the ground state is in resonance with twice the frequency of the first laser and the other transition from the ground state is in resonance with the second laser. The Green's function formalism is used to derive expressions from which the induced two photon and one photon excitation spectra are computed. Also, approximate expressions are derived for the excitation spectra in the appropriate frequency regions. These results agree well with the numerical computations based upon the precise expressions. The interference between the two transitions produce some splittings; these splittings depend upon the Rabi frequency of the one photon transition. The intensities of the weak peaks depend upon the ratio of the Rabi frequency of the two photon transition to the frequency of the first laser. Some features of the excitation spectra are interpreted in terms of previous knowledge about the behavior of two level atoms in strong laser fields.
Lattice dynamical study of face centred tetragonal indium
Authors: Ramamurthy V. , Rajendraprasad S. B.
Published: April 2011

The phonon dispersion relations and the phonon frequency distribution function of fct indium have been deduced, for the first time, using a lattice dynamical model which expresses the atomic interactions in terms of central, angular, and volume forces. Six elastic constants, four zone boundary frequencies, and an equilibrium condition were used in the evaluation of the force constants. It is shown that this model is elastically consistent and conforms with the translational symmetry of the lattice; the phonon frequencies of indium deduced from it are in very good agreement with the experimental values of Reichardt and Smith and the theoretical values of Garrett and Swihart, but disagree with the theoretical values of Chulkov et al. as well as those of Gunton and Saunders at several wave vectors and polarizations. In addition the phonon frequency distribution curve obtained from this model is in overall agreement with those obtained from the electron tunnelling data, the inelastic scattering of neutrons as well as a pseudopotential model. The apparent characteristic features of these curves, the implications of the crystallographic equivalence between fct and bet lattices, and their relevance in the lattice dynamical study of indium are discussed.