bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal trend of stratospheric NO2 over Calgary
Authors: Syed M. Q. , Harrison A. W.
Published: April 2011

Evening twilight sky spectra in the region 437–451 nm obtained from the Aeronomy Observatory, University of Calgary (50.08, 114.13°W) in the period May 1978–April 1979 have been analyzed to determine the vertical column abundance of stratospheric NO2. The analysis shows approximately a three-fold seasonal change in the NO2 column abundance with a maximum value in summer of 5.6 × 1015 cm−2.
Collision-induced absorption in ethane in the microwave and far-infrared regions
Authors: Dagg I. R. , Smith W. , Read L. A. A.
Published: April 2011

The collision-induced absorption spectrum of gaseous ethane has been measured at 295 K over a density range from 12 to 45 amagat in the 50–360 cm−1 region and at densities up to 59 amagat at 4.6, 17.4, and 29.6 cm−1. The measurements were made using a Fourier transform spectrometer, an HCN laser, a FIR laser, and microwave techniques. A collision-induced torsional absorption is observed which is centred at 280 cm−1 and is superimposed on the collision-induced rotation–translation absorption. Theoretically, the latter absorption can be ascribed to quadrupolar interaction. This theory has been used to extract estimates for the quadrupole moment of ethane. The results provide an upper limit for the value of Q = −1.28 × 10−26 esu. Lower estimates are also given which reflect a larger contribution to the absorption from the torsional band by using the known absorption profiles for N2 and C2H4. These estimates are compared with other theoretical and experimental values.
The cloudy bag model. IV. Pionic corrections to the nucleon properties
Authors: Théberge Serge , Miller Gerald A. , Thomas A. W.
Published: April 2011

A detailed formulation of the Hamiltonian formalism, together with a consistent renormalization procedure, is described for the cloudy bag model. The electromagnetic properties of the nucleon are calculated with center-of-mass corrections included. Good agreement with the experimental results is obtained for bag radii ranging from 0.8 to 1.0 fm.
Laser induced fluorescence of the 0–6, 1–6, and 0–5 bands of the transition of Bi2
Authors: Fabre G. , Bacci J. P. , Athenour C. , Stringat R. , Bernath P.
Published: April 2011

Analysis of the 0–6, 1–6, and 0–5 bands of the A–X transition of Bi2 with a single-mode, tunable cw dye laser gave the following rotational constant values: A state: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]; X state: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text].The electronic symmetries of the A and X states are confirmed to be [Formula: see text] and [Formula: see text], respectively, supporting the assignment of the X state as the ground state.
Interaction induced light scattering spectra of amorphous solid and liquid NaOD heavy water solutions
Authors: Briganti G. , Fornarini L. , Mazzacurati V. , Ricci M. A. , Signorelli G. , Nardone M.
Published: April 2011

Low frequency translational spectra of 15 M NaOD heavy water solutions are analyzed in both liquid and amorphous phases. Confirming the results of previous findings in KOH water solutions, the analysis suggests that the spectra reflect in both phases the translational density of the states of the system. In agreement with inelastic neutron scattering experiments, these can be thought of as propagating quasi-phonon excitations. A polarization analysis of the spectra based on the results of a model recently developed for orientationally disordered crystals, allows a separation between acoustic-like and optic-like modes and clearly shows the presence of a low frequency relaxation process. The presence of this feature is also related to radiation coupling coefficients of the acoustic-like modes.
A study of the quantum oscillations in the thermopower of molybdenum
Authors: Fletcher R.
Published: April 2011

This paper is concerned with quantum oscillations in the thermoelectric coefficients of metals which do not undergo magnetic breakdown, and in particular focuses on the compensated metal Mo. An expression for the amplitude of the oscillations in the thermopower has been developed and is tested using a detailed set of experimental results on Mo taken with [Formula: see text] over the range 1.5–8 T at liquid helium temperatures. Good agreement is obtained for the temperature and field dependence, and absolute amplitudes are predicted to within a factor near unity. Oscillations of appreciable amplitude arc neither expected nor observed in the Nernst–Ettingshausen (N.E.) coefficient of Mo. Available thermopower data on In have also been analysed; it is concluded that, contrary to a previous speculation. In does not undergo magnetic breakdown at fields of the order of 2 T. It is suggested that, contrary to the thermopower. the N.E. coefficient will provide an unambiguous test for the occurrence of breakdown in metals since it is expected to exhibit large amplitude quantum oscillations only under breakdown conditions.
Mark IV "Grasshopper" grazing incidence monochromator for the Canadian Synchrotron Radiation Facility (CSRF)
Authors: Tan K. H. , Bancroft G. M. , Coatsworth L. L. , Yates B. W.
Published: April 2011

The vacuum, mechanical, and optical characteristics of a "Grasshopper" grazing incidence monochromator, for use with a synchrotron radiation source in the 30–300 eV range, is described. The monochromator is compatible with ultrahigh vacuum (≤ 5 × 10−10 Torr throughout), and the motor driven scan mechanism is linear and reliable. The monochromator has been calibrated using several known absorption edges between 36 and 102 eV and a nonlinear least squares fit to the scan equation. These same absorption edges, plus a scan over zero order, show that the present resolution of the monochromator (with 10 and 16 μm exit and entrance slits respectively) is 0.16 Å (0.06 eV at the Al L2.3 edge). With 10 μm entrance and exit slits, the resolution will be very close to the theoretical Δλ = 0.083 Å.
Deuteron photoabsorption sum rule: Two-body effects
Authors: Goulard Gisèle , Lorazo Bernard
Published: April 2011

In deuteron photoabsorption, the effect of mesonic exchange currents is considered in detail. Related to the electric dipole operator D1 (Siegert form) and to the nuclear interactions, a factor k appears in the integrated cross-section σ0, previously obtained by the Thomas–Reiche–Kuhn dipole sum rule. The introduction of the two-body density [Formula: see text] modifies the form of D1 and increases κ which becomes κ + Δκ. The influence of several NN potentials is clearly shown on the factor Δκ, some 25% difference occurring between a super soft core potential and the Paris potential. In this last case the value of Δκ is about 50% of the initial κ value.
L'explosion isotherme
Authors: Brun L. , Roguet R.
Published: April 2011

The isothermal explosion model of Korobeinikov has been generalized to include the specific heat varying as temperature to the power k. Unlike Korobeinikov the different phases of the motion arc considered. The eventual self-similar solutions only exist for k > −1/2 and resemble that for k = 0 (the Korobeinikov value). For all k ≥ 0 the limiting expansion velocity is given by the von Neumann–Taylor–Sedov result (independent of k) and for k > 0 the internal energy decreases steadily. For k > 1/2 there is first an intermediate detonation phase. For −1/2 < k < 0 the kinetic energy first increases, then decreases, and the expansion law depends on k.
Positron annihilation in fatigued copper
Authors: Kupca S. , Kerr D. P. , Hogg B. G. , Basinski Z. S.
Published: April 2011

Positron lifetimes have been measured in an isochronal annealing study of dynamically fatigued, high purity Cu single crystals. Decomposition of the lifetime spectra into two components results in a description of the annealing process in terms of the lifetime and fraction of trapped positrons. Positron lifetimes were also determined at a series of low temperatures (10–300 K) at different stages of annealing. The lifetime of positrons trapped at point defects is found to vary with temperature indicating that a description of the trapping process according to a simple diffusion limited model is not applicable.
Elastic and photo-elastic constants of CH4 and CD4 obtained by Brillouin scattering
Authors: Rand S. C. , Stoicheff B. P.
Published: April 2011

The elastic constants and Pockels coefficients of CH4 and CD4 single crystals near their triple points have been determined using high-resolution Brillouin spectroscopy. For CH4 at 90.4 K, the elastic constants are C11 = 19.57 ± 0.30, C12 = 14.46 ± 0.20, C44 = 9.20 ± 0.15 kbar, and the ratios of the Pockels coefficients are p12/p11 = 1.031 ± 0.035 and p44/p11 = 0.069 ± 0.010. For CD4 at 89.2 K, C12 = 20.04 ± 0.30, C12 = 15.00 ± 0.25, C44 = 9.15 ± 0.15 kbar, and p12/p11 = 1.027 ± 0.020, P44/p11 = 0.138 ± 0.010. The velocities of the low-frequency transverse modes in CH4 and CD4 are anomalously slow in the [Formula: see text] direction, indicative of rotational–translational coupling of molecules. Isotopic differences are also evident: the Pockels coefficient p44 in CD4 is double that in CH4; and the velocities of both transverse modes in the principle directions [Formula: see text], [Formula: see text], and [Formula: see text] are in the ratio V(CH4)/V(CD4) = 1.130 instead of 1.118 as expected from the isotopic mass ratio.
On the critical behaviour of the two dimensional spin XY model
Authors: Rogiers Jos
Published: April 2011

Transformation methods are used to analyse the series for the second order fluctuation of the transverse magnetization for the triangular and square lattices. For the triangular lattice some evidence is found for an exponential behaviour of this quantity near the critical point with a tentative estimate for the exponent [Formula: see text].
Higher order contributions to ion acoustic solitary waves in a plasma consisting of warm ions and nonisothermal electrons
Authors: Kalita M. K. , Bujarbarua S.
Published: April 2011

Considering the electron velocity distribution far from Maxwellian, we have investigated the nonlinear propagation of ion acoustic waves in a plasma consisting of warm ions. The solitary wave solution has been obtained for this case retaining terms up to the third order in the usual reductive perturbation method.
Fluids in electric and magnetic fields: Pressure variation and stability
Authors: Brevik I.
Published: April 2011

The variation of the hydrostatic pressure with position in a dielectric or magnetic fluid acted upon by electric or magnetic forces may be somewhat delicate. For instance, the dominant role played by the striction forces in fluids having positive susceptibility is a physical phenomenon whose importance does not seem to be sufficiently well-known. Closely related to the pressure balance is the thermodynamic stability problem. In this paper two examples are analysed in detail in order to elucidate the pressure variation and thermodynamic stability for dielectric, paramagnetic, and diamagnetic liquids.
Positronium and quantum electrodynamics
Authors: Gidley D. W.
Published: April 2011

Experimental tests of quantum electrodynamics using positronium are reviewed. These tests include measurements of the ground state hyperfine structure, excited state fine structure, and the annihilation decay rates of positronium. Emphasis is given to describing the present experimental techniques, comparing the most recent results with theory, and summarizing possible future improvements in the measurements.
Some comments on positron–atom scattering at intermediate energy
Authors: Byron Jr. F. W.
Published: April 2011

A brief survey of available theoretical techniques is given for positron–atom scattering. The distinction between methods involving a finite number of target states and those with an infinite number of target states is emphasized. The situation regarding total cross sections is summarized, and a new, non-perturbative, eikonal-type approximation, based on the work of Wallace, is introduced.
An experimentalist's view of the galvanomagnetic and thermomagnetic properties of potassium
Authors: Fletcher R.
Published: April 2011

This paper provides a brief survey of the experimental and theoretical situation regarding the galvano- and thermomagnetic properties of potassium viewed within the context of the behaviour of other metals. Most of the data are consistent with various sample imperfections as being the major source of the anomalies that are found. However, the precise nature of the imperfections and the mechanism by which the imperfections produce the anomalies are not yet known. It is argued that the recently discovered detailed structure in the high field induced torque of K should be subjected to intensive experimental investigation before drawing any conclusions with regards to the possible presence of a charge density wave; the other magnetotransport properties offer little evidence either for or against such a possibility.
High precision electrical resistivity measurements on potassium below 1 K
Authors: Pratt Jr. William P.
Published: April 2011

New ultra-high precision (0.1 ppm) measurements of the resistivity of potassium down to 70 mK are discussed. Between 0.35 and 1.2 K. the resistivity has a T2 temperature dependence which is independent of the sample parameters and the room temperature treatment of the samples. This behavior is consistent with the predictions for simple electron–electron scattering, but such a simple model cannot adequately explain previous data. Below 0.35 K the data are anomalous in that the temperature variation is slower than T2.
Size effects and low-temperature conductivity anomalies in metallic conductors
Authors: Maldague Pierre F.
Published: April 2011

It is shown in this paper that the weak localization theory of logarithmic transport anomalies in two-dimensional metals can be understood in terms of a spatially varying diffusion constant. The calculation uses perturbation theory to calculate the eigenstates of a finite, random system. The results demonstrate that perturbation theory provides a powerful tool for studying transport anomalies in finite systems.
The quark–gluon phase in strong interacting matter
Authors: Gagnon R.
Published: April 2011

A system of free quarks and gluons in thermal and in chemical equilibrium has been investigated in the context of hadronic phase transitions. The dependence on temperature of various quantities (i.e., chemical potentials and number and energy densities) was obtained. Calculations of number and energy densities at a given critical temperature have been performed for different valence number densities. A brief discussion of a phase transition occurring in the laboratory is also given.
Comparative study of momentum and rapidity spectra of pions produced in hadron–nucleon and hadron–nucleus collisions
Authors: Kaur M. , Kohli J. M.
Published: April 2011

A study of momentum and rapidity spectra of fast pions produced in π− – nucleon and π− – nucleus collisions at 50 GeV/c indicates no significant difference between the two reactions, which reflects that the mechanism whereby the particles are generated is the same in both cases. No intranuclear cascading is thereby indicated in hadron–nucleus interactions.
Single-particle currents in the cranked harmonic oscillator model
Authors: Habeeb M. A. Z. , Aziz A. R. K.
Published: April 2011

Using exact wave functions of the cranked triaxial harmonic oscillator model in coordinate space, an expression for the single-particle probability current density is derived. This expression, valid to all orders in the angular velocity is then used to calculate current distributions for some typical harmonic oscillator single-particle states. Comparisons with perturbative first-order calculations indicate differences at high angular velocities where new features of the current distributions become apparent. This suggests the extension of the present calculations to real nuclei.
On gaseous sodium halide dimers
Authors: Islam A. K. M. A.
Published: April 2011

Equilibrium configurations and dimerization energies of the rhombohedral form of the sodium halide dimer molecules have been re-evaluated using more reliable, recently published data. The results are compared with experiment as well as with other calculations and the need for further works on dimers is stressed.
A calculation of the neon pair polarizability including correlation effects. II. Inclusion of the configuration interaction basis extension corrections
Authors: Dacre Peter D.
Published: April 2011

Basis extension corrections associated with the configuration interaction (CI) calculation of the neon pair polarizability are reported. The incremental polarizabilities, anisotropy, and trace are thereby obtained to greater accuracy. The corrections have a particularly marked effect on the CI contributions to the trace. The anisotropy and trace are compared with spectral models. The second dielectric virial coefficient is computed to be −0.15 cm6/mol2, which is, however, outside the error bounds of the experimental values. CI contributions to the pair polarizabilities calculated using only valence excitations are found to be almost equivalent to the results from the full calculations.
Excitation spectra of a three-level atom in the "lambda" configuration at high photon densities. II. Numerical results
Authors: Woloschuk K. J. , Hontzeas S. , Mavroyannis Constantine
Published: April 2011

We have performed a numerical calculation for the excitation spectra arising from the interaction of a three-level atom in the lambda configuration with a strong electromagnetic field whose frequency mode is initially populated. The excitation spectra are considered for equal detunings, which refer to the cooperative two-photon resonance process, as well as for different detunings. The computed cooperative two-photon resonance spectra are compared with those derived by analytical methods. In the presence of different detunings, conditions are established under which the laser field induces sidebands at the frequency equal to that for the forbidden transition. Numerical calculations for a wide range of Rabi frequencies and detunings are presented graphically. Detailed discussion of the computed spectral intensities is given and a comparison is made between the spectra of three-level atoms in the lambda and cascade configurations.
Charge transfer from rare gas atoms to Kr+
Authors: Hird B. , Ali S. P.
Published: April 2011

The cross section for electron capture by Kr+ ions from rare gas atoms between 30 and 120 keV is found to be in good agreement with previous measurements where these exist, except for neon. The Rapp–Francis model gives an acceptable fit to the energy dependence of these and higher energy data but is too large by a factor of about five. In contrast the Landau–Zener model predictions are too large for helium and neon and too small for the heavier targets unless metastable states of krypton with large polarizabilities dominate the cross section.
Thickness contours of highly aberrant phase objects. II. Double-exposure grating interferometer for direct phase measurement at reduced sensitivity
Authors: Grover C. P. , Tremblay R.
Published: April 2011

An analysis of a double-exposure grating interferometer for the study of transparent phase samples is presented. This shows that, if the test sample is placed behind the grating in contact with it, the resulting interferogram gives directly its absolute thickness contours as they would be obtained by a desensitized two beam interferometer. The presence of a finite distance between the grating and the test sample introduces an additional path difference that corresponds to shearing the object wave in the direction perpendicular to grating lines. The conditions under which the two effects could be separated have been examined. The low sensitivity inherent in the double-exposure grating interferometer makes it useful for measuring the absolute phase variations of highly aberrant samples. However, restoration of high sensitivity in order to visualize low phase variations is also possible. The limitations imposed on the nature of the test samples have been pointed out.
Determination of atmospheric aerosol particle size distribution and visibility using a mobile laboratory
Authors: Mathai C. V. , Harrison A. W.
Published: April 2011

As part of an ongoing general research program on the effects of atmospheric aerosols on visibility and its dependence on aerosol size distributions in Calgary, this paper presents the results of a comparative study of particle size distribution and visibility in residential (NW) and industrial (SE) sections of the city using a mobile laboratory. The study was conducted in the period October–December, 1979. An active scattering aerosol spectrometer measured the size distributions and the corresponding visibilities were deduced from scattering coefficients measured with an integrating nephelometer.The results of this transit study show significantly higher suspended particle concentrations and reduced visibilities in the SE than in the NW. The mean values of the visibilities are 44 and 97 km for the SE and the NW respectively. The exponent of R (particle radius) in the power law aerosol size distribution has a mean value of −3.36 ± 0.24 in the SE compared with the corresponding value of −3.89 ± 0.39 for the NW. These results arc in good agreement with the observations of Alberta Environment; however, they are in contradiction with a recent report published by the City of Calgary.
Collision-induced absorption in the far infrared region in ethylene – rare gas mixtures
Authors: Dagg I. R. , Read L. A. A. , Smith W.
Published: April 2011

The collision-induced spectra of mixtures of ethylene and each of the rare gases He, Ne, Ar, Kr, and Xe in the 40–360 cm−1 region has been obtained using a Michelson Fourier transform spectrometer. In addition, improved results for the collision-induced spectrum of pure ethylene gas are reported using this spectrometer as well as a far infrared laser source. All the results from the pure gas and gas mixtures have been analyzed according to the theory for quadrupolar-induced translation–rotational absorption. From this analysis the following values for the components of the quadrupolar tensor are: Qxx = −3.12, Qvy = 1.55, and Qzz = 1.57 B, which are somewhat lower estimates (in absolute value) than previously reported by us. Evidence for induction by other mechanisms (other than quadrupolar) has been obtained for the He–C2H4 and Ne–C2H4 mixtures.
Les moments du flux parallèle non-collisionnel
Authors: Fridman M.
Published: April 2011

The partially integrated equations of the one particle, non-collisional Liouville equation are not normally used in order to have information from the experimental data. We give the moment and semi-moment equations which must be satisfied by the plasma flux, parallel to the magnetic field (as in the solar or polar wind, auroral precipitation, etc.).
Electrical conduction in granular Cu–SiO2 films
Authors: Savvides N. , McAlister S. P. , Hurd C. M.
Published: April 2011

We have measured the temperature dependence of the electrical resistivity ρ of Cu – SiO2 co-sputtered films in the range 4–300 K for metal volume fractions between 0.5 – 0.8. The films range between the metallic (ρ ~ T) and "strongly-localized" (log ρ ~ T−1/2) regimes. In the intermediate regime we find a complex behaviour for ρ(T) with a concentration dependent local minimum that separates the low temperature ρ ~ log T and the high temperature ρ ~ T behaviour. We attribute this to temperature dependent localization of electrons.
Hologram and image storage in photo-ferroelectrics
Authors: Guibaly F. el
Published: April 2011

The electrooptic effect in ferroelectric materials allows volume phase holograms and two-dimensional images to be stored as a spatial distribution of electric charge density. The kinetics of the build up of the photo-induced space charge field is analyzed for the general case of nonuniform illumination. The nonuniformity of light gives rise to the fatigue phenomenon observed during multiple hologram storage or when several hologram write–read/erase cycles are performed. This phenomenon is analyzed and discussed in the model we present. In image storage applications, the nonuniformity of light is shown to introduce nonlinearities in the recorded image at large exposures. The nonlinearity however, can be reduced by flooding the electrooptic material with strong uniform illumination during the storage process.
A study of particle–nucleus collisions at 24, 50, and 400 GeV/c
Authors: Khushnood H. , Irfan M. , Zafar M. , Ahmad A. , Khan A. R. , Ahmad S. , Ali U. , Shafi M.
Published: April 2011

An attempt has been made to investigate multiplicity, dispersion, and pseudorapidity distributions of shower particles produced in 24, 50, and 400 GeV/c hadron–nucleus collisions. The study of pseudorapidity reveals that with the increase in the mass number of the target nucleus, the excess of particles appears in the target fragmentation region, shifting the maxima of the distributions towards smaller values of rapidity. Further, with the increase in the incident energy, the excess of particles appears in the projectile fragmentation region. Finally, on using the additive quark model, the mean normalized multiplicity has been observed to be independent of the energy and nature of the projectile, suggesting a new kind of scaling in hadron–nucleus collisions.
Levels in 145Nd studied with the (d, t) reaction
Authors: Årdal J. , Lien J. R. , Løvhøiden G. , Burke D. G. , Waddington J. C.
Published: April 2011

The 146Nd(d, t)145Nd 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 13 angles from 5 to 45° using a magnetic spectrograph equipped with photographic emulsions in the focal plane. The measured analyzing powers for strongly populated levels are well described with standard distorted wave Born approximation calculations and made it possible to confirm previous spin assignments as well as give unambiguous assignments for some states for which the spin information was previously conflicting, incomplete, or lacking.
Equivalence principle for massive bodies in a generalized theory of gravitation. II
Authors: McDow J. C. , Moffat J. W.
Published: April 2011

The three-body equations of motion are examined for periodic perturbations in an earth centered coordinate frame. The lunar-laser-ranging data is then used to place upper bounds on the new l parameters associated with the earth and sun.
A study of the host lattice effect in the lanthanide hydroxides. 34 GHz Gd3+ impurity ion EPR spectra at 77 and 294 K
Authors: Malhotra V. M. , Buckmaster H. A.
Published: April 2011

The 34 GHz EPR spectra of 5-state (4f7, 8S) Gd3+ impurity ions (~1%) in the isostructural [Formula: see text] symmetry Ln(OH)3 host lattice (Ln ≡ La, Sm, Eu, Tb, Ho, Y) have been studied at 77 and 294 K. The expected seven line ΔM = ± 1 spectrum is observed for Ln = La, Eu, Ho, and Y whereas only a single broad transition is observed for Ln ≡ Sm and Tb. The observed values of the zero field splitting (ZFS) parameter B20 as well as the TZFS are found to be related linearly to (i) the ionic radius, (ii) the Ln–O1 distance, and (iii) the Ln–O2 distance where O1 and O2 are the nearest neighbour equatorial and apical oxygens. However, the slopes are opposite to that predicted by a point charge lattice model. This paper discusses (i) the SH parameters, (ii) the host lattice effect, (iii) the ZFS processes, and (iv) the linewidths observed in the Ln(OH)3 host lattice and attempts to explain the observations using the existing theory. It is found that this apparently simple host lattice exhibits complex effects which do not change systematically with the host lanthanide ion, unlike that observed in most other isostructural lanthanide hosts that have been studied using Gd3+ impurity ions.
Spin–orbit effects in optical model analyses of 3He elastic scattering on oxygen isotopes
Authors: Abdel-Wahab M. S. , Potvin L. , Roy R. , Bricault P. , Larue R. , Pouliot D. , Rioux C. , Slobodrian R. J.
Published: April 2011

Angular distributions of elastically scattered 3He on 16,17,18O at 14 MeV were measured. Optical model analysis of the data has been performed. In the case 16O case, a spin–orbit term is needed to provide better fits of the data at backward angles and this term allows a satisfactory calculation of the 16O(3He, α)15O reaction.
The N–P final state interaction in the 2H(d,np)2H reaction at 12 MeV
Authors: Jeremie H. , Lessard L. , Gujrathi S. , Zeitnitz B.
Published: April 2011

The energy spectrum of protons in coincidence with deuterons from the reaction d + d → n + p + d at 12 MeV was measured at the following three pairs of angles: θP = 45°, θd = 26.5°; θP = 45°, θd = 28.0°; θP = 45°, θd = 29.5°. The observed spectra can be explained by a superposition of triplet n–p final state interaction and quasifree scattering.
The temperature dependence of the electrical conductivity and switching phenomena in Cu2O single crystals
Authors: Wang G. J. , Weichman F. L.
Published: April 2011

Optical transmission work had shown that three distinct types of Cu2O single crystals could be created by means of different annealing processes. We have now made mobility measurements and a series of current–voltage measurements over the ambient to 200 °C range. All types of crystals were subject to breakdown at sufficiently high electric fields and temperatures in accordance with a previously known mechanism. Two new switching effeets, one of which is optically induced, are shown to exist in the highest resistivity material.
Absorption at 10 μm in CO2–He and CO2–N2 mixtures at elevated temperatures
Authors: Robinson A. M. , Weiss J. S.
Published: April 2011

Absorption by CO2–He and CO2–N2 mixtures has been measured as a function of temperature on the J = 16–22 lines of the P and R branch of the 10.4 μm CO2 laser transitions. The relative optical broadening coefficients were determined from 300 to 650 K.
Preferred orientation of rapidly frozen metals
Authors: Blake N. W. , Smith R. W.
Published: April 2011

When metals are rapidly frozen, a preferred orientation may be observed in the grains of the chilled surface. The extent and stability of this preferred orientation has been examined, using X-ray diffraction, for a variety of metals produced by melt-spinning i.e., by directing a fine stream of liquid against a rapidly rotating copper drum to produce a thin tape. It is shown that metals with a hcp crystal structure tend to display the greatest degree of preferred orientation. In particular, the degree of preferred orientation displayed by as-spun zinc ribbon is such that it could be used as an inexpensive crystal analyser for X-ray diffraction, comparing favourably with quartz.
The effect of a magnetic field on the impurity band density of states in the atomic limit
Authors: Liu K. L. , Modrak P. , Bergersen B.
Published: April 2011

A marked magnetic field dependence is found for the impurity band density of states in an idealized model of a doped semiconductor. The calculations are based on the Hubbard model in the atomic limit. We have obtained exactly the first eight moments of the distribution using a Gaussian model for the hopping integral, and the first seven moments with a hydrogenic model. A simple Zeeman type response of the spin system to the magnetic field is assumed. The predicted density of states is then obtained using a modified moment method with a trial density of states function obtained from the expected asymptotic behaviour of the distribution. Finally, we adjust the parameters of our models to correspond to phosphorous doped silicon below the metal insulator transition.
Combined effect of exciton–exciton and exciton–phonon interaction on crystal's dielectric properties
Authors: Mirjanić D. , Luburić-Kozmidis U. , Marinković M. M. , Tošić B. S.
Published: April 2011

The two-time temperature Green functions method is used to investigate the combined effect of the exciton–exciton and the exciton–phonon interactions on the dielectric properties of the molecular crystals. It is shown that those effects are of the same order of magnitude. The most interesting result is nevertheless the appearance of a double peak in the region ω < ωexciton whereby the narrow peak is due to the exciton–phonon interaction whereas the other, located in the longer wavelength region, is due to the exciton–exciton interaction. The possible further generalization of the results obtained is also discussed.
Near field and far field induced mismatch on O + e → e second harmonic waves
Authors: Sharma K. K. , Goyal M. L. , Srivastava G. P.
Published: April 2011

The inhomogeneities induced in the process of second harmonic generation (SHG) in collimated light beams (Rw > 1) of Gaussian nature is studied for O + e → e type interactions. The coherence length lc and phase matching conditions Δk change considerably and degrade harmonic conversion efficiency. The results are obtained in terms of τD (dimensionless temperature), Rw (collimation), and ξF (field variable) in the near field (NF) and far fields (FF) respectively. This work extends previous work on inhomogeneity mismatch on plane-wave approximations for O + O → e interactions.
Derivation of the external field in the Dirac equation based on quantum electrodynamics
Authors: Neghabian A. R. , Glöckle W.
Published: April 2011

The multiphoton exchange between two charged spin [Formula: see text] particles of light (m) and heavy (M) mass is considered and it is shown how, in the limit M → ∞, the Dirac equation with an external potential including radiative corrections emerges. This result can only be achieved if diagrams with photons attached to the heavy particle line cancel among themselves for M → ∞. We have shown this in the lowest order where the individual diagrams have nonvanishing limits.
Mass hierarchies and scalar field self-couplings
Authors: Elias V. , Sherry T. N.
Published: April 2011

One (internal gauge boson) loop corrections to the scalar field self-couplings of a spontaneously broken Abelian gauge theory are shown to be independent of one loop shifts in mass (and vacuum expectation value) from tree approximation values, suggesting that stability of arbitrarily large mass ratios under perturbation theory may be possible under an appropriately chosen set of renormalization conditions. However, imposition of a large mass ratio is shown to lead to overly large first order corrections to scalar field self-couplings, independent of the choice of renormalization conditions.
Systematics of the (t, p) reaction in Yb and Hf isotopes near the N = 108 "subshell closure"
Authors: Burke D. G. , Nowikow I. , Peng Y. K. , Yanch J. C.
Published: April 2011

Angular distributions of protons from the 170, 174, 176Yb(t, p)172, 176, 178Yb and 178,180Hf(t, p)180, 182Hf reactions have been studied using beams of 15 MeV tritons from the McMaster University tandem Van de Graaff accelerator. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Levels up to ~2.5 MeV excitation were studied in each nuclide, with a typical overall resolution of ~15 keV (full-width half-maximum). Measurements were also made with targets of natural Yb and natural Hf, to improve the accuracy of relative strengths in each chain of isotopes, and with a target of 172Yb to facilitate the normalization of previously published data to the present results. One of the most notable features of the data is the large amount of L = 0 strength to excited Iπ = 0+ states for all cases where the residual nucleus has a neutron number N ≤ 108. The populations of these states are not explained by either the pairing rotational or vibrational models. The SU(3) limit of the interacting boson model yields qualitative but not quantitative agreement. For two of the residual nuclides studied, 178Yb and 182Hf, there was little or no nuclear structure information previously available. The (t, p) experiments have located a number of excited states in each of these cases, and also give the first measurements of two-neutron separation energies; S(n) = 12 333 ± 6 keV for 178Yb and 12 413 ± 6 keV for 182Hf.
The sticking probability for hydrogen atoms on the surface of liquid 4He
Authors: Zimmerman D. S. , Berlinsky A. J.
Published: April 2011

A calculation is presented of the sticking probability for hydrogen atoms colliding with a liquid 4He surface. The calculation is based on a model potential for the H–liquid 4He interaction which is used to derive both bound and free atom wave functions and the linear H atom–ripplon coupling. Results are presented in terms of the energy and angle dependent sticking probability s(E, θ) and the thermally averaged probability s(T), and comparison is made to the experimental result s(T) = 0.035 ± 0.005 for 0.18 < T < 0.27 K.
Les intensités dans la pentade ν11, ν2 + ν12, 2ν10 + νl2, ν9 et ν3 + ν8 + ν10 de 12C2H4
Authors: Dang-Nhu M. , Pine A. S. , Fayt A. , Vleeschouwer M. De , Lambeau C.
Published: April 2011

Analysis of the intensities of an interacting polyad of bands is complicated by basis function mixing. Fortunately it is usually possible to find lines belonging principally to one band or to subsets of the polyad to begin an iterative procedure to derive intensity parameters. Five bands of ethylene in the 3 μm region have been investigated for line intensities by this method, using 148 selected measurements of about 6800 Doppler-limited transitions recorded with a difference-frequency laser spectrometer. Finally two band strengths and two Herman–Wallis parameters have been determined with statistical significance, permitting the observed intensities of the pentad to be calculated with 1%.
Classical field descriptions of one-dimensional systems
Authors: Bourbonnais C. , Caron L. G.
Published: April 2011

In this paper we discuss the limitations of classical field treatments of one-dimensional systems in the static approximation. Two exactly solvable Hamiltonians, the ferromagnetic Ising model, and its extension to a zero-width half-filled band, are studied after their transformation to a classical field form via the Hubbard–Stratonovich identity. The more usual two-field transformation consists of using one field to describe the divergent order parameter and another to represent the nondivergent modes. The fluctuations in this latter one are usually neglected and this is shown to lead to incorrect thermodynamic behavior throughout the critical region, which is unusually large in one-dimensional systems, and even beyond to the high temperature limit. Any limited expansion of the free energy is further seen to lead to incorrect treatment of the amplitude fluctuations. A rigorous treatment of both fields is required. Alternately, a one-field transformation can assure a simpler approach although all terms in the free energy expansion must be retained. The findings are extrapolated to other known Hamiltonians: Hubbard, Peierls and spin-Peierls, and Bardeen–Cooper–Schrieffer (BCS) superconductivity. The Peierls case is examined in some detail because the usual one-field free energy functional is not obtained by a straightforward use of the Hubbard–Stratonovich transformations. As for the BCS Hamiltonian, it is seen to be in a special class because both symmetry fields are equally divergent and are automatically treated on an equal footing.
Compositional characterization of microwave plasma a-Si: H films
Authors: Currie J. F. , Depelsenaire P. , Huot J. P. , Paquin L. , Wertheimer M. R. , Yelon A. , Brassard C. , L'Ecuyer J. , Groleau R. , Martin J. P.
Published: April 2011

The concentration of hydrogen in amorphous hydrogenated silicon films prepared by microwave glow discharge decomposition of silane has been measured as a function of several fabrication parameters: substrate temperature, deposition rate, and partial pressures of silane and of argon. Hydrogen concentration profiles have been obtained by two techniques: elastic recoil detection (ERD) with a 30 MeV 35Cl beam, and by the resonant nuclear reaction 15N + 1H → 12C + 4He + γ. Both offer very high depth resolution (in the order of 100 Å) and have revealed important inhomogencities in chemical composition, both at the free surface and the substrate – film interface. Using standard infrared absorption measurements between 1950 and 2150 cm−1, the intensities of the lines normally associated with SiH, SiH2, and SiH3 bonds were measured. As has been previously reported for reactively sputtered films for some fabrication conditions the sum of the three intensities is not consistent with the total hydrogen concentration obtained from the nuclear measurements. The average hydrogen concentration decreases with increasing substrate temperature, changes little with deposition rate, and increases as the silane to argon ratio is increased. These observations are related to the chemical reactions which take place in the plasma, and at the plasma–film interface during film growth.
Resonant and nonresonant electron scattering in an inhomogeneous laser field
Authors: Gayet R. , Taylor H. S.
Published: April 2011

Potential electron scattering by atoms immersed in a laser field is investigated in the case where the laser beam presents a strong transverse macroscopic inhomogeneity, due, for instance, to the need of focusing the laser beam. A reasonable model of inhomogeneity is introduced to study the important case where an isolated Feshbach resonance exists. The nonresonant scattering process with a net number N of photons absorbed or emitted is also studied. In a weak field, the inhomogeneity results in the enhancement of the N = 0 process to the detriment of the others; in addition the probability of the N ≠ 0 process decreases when [Formula: see text] increases. The decline is more pronounced in a weak inhomogeneous field than in an homogeneous field whose strength is the central strength of the inhomogeneous field. In intense laser fields the situation depends on the value of the field.Similar conclusions are drawn when only the Feshbach resonance is observed. In that case it is shown that a strong inhomogeneity could be an advantage if intense enough central laser fields may be achieved. It could be of help in the search of Feshbach resonances in electron–atom collisions at energies below the first excitation threshold.It is worthwhile to note that our treatment may be used without change in the case of a macroscopic laser field inhomogeneity in time.
X-ray Raman scattering on polycrystalline graphite in the scattering angle range 0–120°
Authors: Kavogli Z. I. , Leventouri D. K. , Koumelis C. N.
Published: April 2011

X-ray Raman scattering was studied on polycrystalline graphite for various scattering angles in the range 0–120°. A mosaic graphite spectrometer without collimators and Crkβ radiation were used.The shape of the Raman spectrum depended slightly on the scattering angle. The peak intensity of the Raman line increases with scattering angle but in a different way to that resulting from the calculation of Mizuno and Ohmura. Additional components were observed in the spectrum on both sides of the Raman line.
Collision-induced absorption in ethane–rare gas mixtures
Authors: Dagg I. R. , Read L. A. A. , Anderson A.
Published: April 2011

The collision-induced spectra of mixtures of ethane and each of the rare gases He, Ar, Kr, and Xe in the 40–360 cm−1 region have been obtained using a Michelson Fourier transform spectrometer. In addition, the temperature dependence of the absorption in ethane and ethane–xenon mixtures is reported. All results have been analyzed according to the theory for quadrupole induced rotation–translation absorption. The absolute value of the quadrupole moment of ethane is estimated to be less than 1.0 B and most likely less than 0.5 B. Various speculations are made concerning the induction mechanisms (other than quadrupolar) for each of the mixtures.
Input admittance of a thin dielectric-sleeved finite antenna excited by a uniform field
Authors: Rao T. C. K. , Hamid M. A. K.
Published: April 2011

The input admittance of a long hollow conducting cylindrical antenna with an infinitely long dielectric sleeve surrounding it, and excited by a uniform field applied across a gap of a given width at the center, is determined by a variational method. A suitable trial field is chosen and the resulting integrals are evaluated asymptotically with the assumptions that the electrical radius of the antenna is small and its length is large. The final expression is easy to evaluate and some numerical results are presented.
The density of states in dc glow discharge deposited a-Si: H from Schottky barrier diode admittance measurements
Authors: Jain P. K. , Kruzélecky R. V. , Zukotynski S.
Published: April 2011

An experimental and theoretical study of the admittance of a-Si:H Schottky barrier diodes versus frequency, temperature, and voltage is presented. A full numerical analysis of the admittance of the Schottky diode with an arbitrary density of states (DOS) distribution is given. It is based on a general model using an equivalent circuit of the devices. The analysis takes into account the thermal response time of gap states as well as the transport of carriers. The DOS distribution near the Fermi level is determined for diodes prepared using direct current glow discharge deposited a-Si:H. It is shown from the admittance study that the thermionic theory is appropriate to describe the transport of electrons across the junction. It is demonstrated that the occupancy of bulk states is controlled mainly by the interaction kinetics of these states with the electrons in the conduction band and not by transport of these electrons.
On the photoconductivity of hot electrons in semiconductors at low temperatures
Authors: El-Wahidy E. F.
Published: April 2011

A theoretical study is made of the photoconductivity of hot photoelectrons interacting with acoustic phonons in n-type germanium at low temperature, T = 4 K, when the equipartition of the energy of phonons is not obeyed. Assuming that the energy relaxation of photoelectrons takes place by the spontaneous emission of acoustic phonons, the energy distribution of photoelectrons is obtained using the deformation potential scattering by acoustic phonons for the zero point lattice. The distribution function is then used in calculating the photoconductivity and average lifetime of photoelectrons. New temperature dependences of the photoconductivity and average lifetime arc obtained. It is shown that the new results differ from those reported when equipartition is obeyed.
Thermodynamics of weak coupling anisotropic superconductors with energy dependent electronic density of states
Authors: Zarate H. G. , Carbotte J. P.
Published: April 2011

We derive analytical expressions for the gap edge and thermodynamic functions of anisotropic weak coupling superconductors with a model energy dependent electronic density of states N (ε). We choose N (ε) to be a Lorentzian superimposed on a constant background with the Fermi energy at an arbitrary distance from the maximum. Significant modification to the Bardeen–Cooper–Schrieffer (BCS) expressions are found for sharp peaks and for valleys in the density of states when the peak width is on the scale of the Debye energy. In this last case corrections can be very important.
The property of type II adsorption isotherms which allows determination of specific surface area of the adsorbent
Authors: Rodriguez J. M. , Rodriguez C.
Published: April 2011

A new method is proposed, based on a certain property of the spreading pressure, for determining the specific surface area of those solids which, when adsorbing gases isothermically, do so according to the type II isotherm of the Brunauer classification.