Showing papers in "Canadian Journal of Physics in 1982"
TL;DR: In this article, the first reliable constants for the vibration-rotation emission bands of the hydroxyl radical with 6"≤"ν′"µ≤10 have been obtained in the range λ6250 −8500 A.
Abstract: Seven vibration–rotation emission bands of the hydroxyl radical with 6 ≤ ν′ ≤10 have been recorded photoelectrically in the range λ6250–8500 A. The first reliable constants for levels 6 ≤ ν ≤10 of ...
118 citations
TL;DR: In this article, the relationship between polar cap and oval aurora during periods when the interplanetary magnetic field is strongly northward, i.e., B2 < 3.5 nT, was investigated.
Abstract: Optical images of the polar cap region at both 5577 and 3914 A obtained from 1400 km above the earth have been used to study the relationship between polar cap and oval aurora during periods when the interplanetary magnetic field is strongly northward, i.e., B2 > 3.5 nT. When this rather rare condition occurs, the distinction between the two types of aurora is no longer as clear as depicted on the basis of statistical definitions of the auroral oval. Diffuse, weak emission can fill in the region between the auroral oval and discrete auroral features in the polar cap. The polar cap discrete features can appear very similar to auroral oval arcs in intensity, intensity ratio, and structure. Even more striking are the situations where discrete polar cap features merge with oval auroras. From this study it is concluded that under conditions of large positive B2 the region of closed magnetic field lines can expand poleward to occupy much of the high latitude region.
102 citations
TL;DR: In this article, a detailed formulation of the Hamiltonian formalism, together with a consistent renormalization procedure, is described for the cloudy bag model, and the electromagnetic properties of the nucleon are calculated with center-of-mass corrections included.
Abstract: 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.
97 citations
TL;DR: In this paper, powder X-ray diffraction experiments on lithium intercalation compounds are described using a unique electrochemical cell which incorporates a unique beryllium Xray window.
Abstract: We describe powder X-ray diffraction experiments on lithium intercalation compounds. Using a unique electrochemical cell which incorporates a beryllium X-ray window we are able to monitor changes i...
84 citations
TL;DR: In this article, a theoretical analysis of steady free convective and mass transfer flow is presented when a viscous, incompressible, and electrically conducting fluid flows through a porous medium occupying a semi-horizon.
Abstract: A theoretical analysis of steady free convective and mass transfer flow is presented when a viscous, incompressible, and electrically conducting fluid flows through a porous medium occupying a semi...
81 citations
TL;DR: The fabrication of transparent conducting films of ZnO is described in this paper, where the power in dc glow discharge, the oxygen pressure, and the zinc evaporation rate are adjusted to optimize the required film property.
Abstract: The fabrication of transparent conducting films of ZnO is described. These films are deposited on room temperature glass substrates using an enhanced reactive evaporation technique in which the power in a dc glow discharge, the oxygen pressure, and the zinc evaporation rate are controlled separately. Each of these parameters is adjusted to optimize the required film property.Films with ρ = 0.0014 Ω cm and an absorption of ~ 1% at 550 nm and 40 Ω/ have been prepared with no annealing. The electron carrier densities are ~ 1.3 × 1020 cm−3 and the mobilities are ~ 34 cm2/(Vs) with a variation of less than ~ 15% between −120 and +150 °C.
80 citations
TL;DR: In this paper, an analysis of both the infrared and visible spectrum was carried out by means of an appropriate Hamiltonian written in terms of the rotational angular momentum R and the electronic orbital angular momentum L.
Abstract: In addition to the H3 and D3 bands previously analysed a strong and extensive band was observed near 5800 A consisting of a large number of irregularly spaced sharp lines. This band can only be accounted for by transitions from the states derived from a 3d electron (2A1, 2E″, 2E′) to the 2p state which is also the lower state of the band at 6025 A (paper I). The complexity of the spectrum arises from the interaction among the three component states brought about by uncoupling of the 3d electron from the symmetry axis, together with the perturbation of these states by the 3p state (the upper state of the diffuse band at 5600 A). The 3d group of states emits also to the 3p2E′ state, giving rise to an infrared band at 3950 cm−1. The analysis of both the infrared and the visible band was carried out by means of an appropriate Hamiltonian written in terms of the rotational angular momentum R and the electronic orbital angular momentum L. On this basis the great majority of the lines have been assigned and sets...
62 citations
TL;DR: The half-life of 176Lu has been measured to be T 1/2/2 = 3.59/0.05/1.05 as discussed by the authors, which is the longest known half life for a Ge detector.
Abstract: The half-life of 176Lu has been measured to be T1/2 = 3.59 ± 0.05 × 1010 years. Coincidences between pairs of Ge detectors were used to eliminate the uncertainties associated with detector efficiency, solid angle, and gamma ray absorption.
61 citations
TL;DR: In this article, a two channel version of the Kohn variational method is used with trial functions containing up to 120 linear variational parameters to calculate the R-matrix elements and the positronium formation cross section for the scattering of s-wave positrons by atomic hydrogen.
Abstract: A two channel version of the Kohn variational method is used with trial functions containing up to 120 linear variational parameters to calculate the R-matrix elements and the positronium formation cross section for the scattering of s-wave positrons by atomic hydrogen. Results are obtained in the energy range between the positronium formation threshold and the lowest excitation threshold of the atom. The positronium formation cross section rises very steeply to a value of just above the positronium formation threshold and then rises approximately linearly with positron energy to a value of just below the excitation threshold. Owing to the weakness of the coupling between the positron and positronium channels, the elastic scattering cross section for the positron continues smoothly across the positronium formation threshold.
60 citations
TL;DR: In this paper, a detailed description of SQUID gradiometers is presented with the aim of improving their near field detection response while operating in unshielded, magnetically harsh urban environments.
Abstract: A detailed description of SQUID gradiometers is presented with the aim of improving their near field detection response while operating in unshielded, magnetically harsh urban environments. Spatial gradiometers of various orders are compared (0th, 1st, 2nd. and 3rd) and the effects on performance of constructional errors, near and far noise sources, and gradiometer baseline are examined. It is shown theoretically that the noise characteristics of a 3rd order spatial gradiometer are expected to be superior to that of lower order designs, particularly for noise sources located within intermediate distances (1.5–50 m) from the gradiometer. Following this analysis, a 3rd order SQUID gradiometer has been designed, constructed, and evaluated. Data are presented on the instrument noise characteristics for operation within an unshielded urban laboratory and examples of the 3rd order gradiometer response to various biomagnetic signals are shown. The results support the theoretical expectations and confirm that the...
58 citations
TL;DR: In this paper, the Grasshopper grazing incidence monochromator has been used with a synchrotron radiation source in the 30 −300 ǫ eV range.
Abstract: 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 A (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 A.
TL;DR: In this article, the authors introduced the normalized brightness-per-volt (NBV) for beam design, which takes into account the transverse energy spread as well as the conversion efficiency.
Abstract: Recent methods of producing high flux. (105–106) s−1 slow positron beams are briefly reviewed. Currently, slow positron beams are produced most efficiently using a single crystal Cu(111) + S backscatter geometry moderator for ultra-high vacuum (UHV) conditions and an annealed W-vane converter for non-UHV conditions. The respective fast positron to slow positron conversion efficiencies for the Cu(111) + S and W-vane converters are (9 ± 3) × 10−4 and (1.2 ± 0.2) × 10−4. A new figure of merit, the "normalized brightness-per-volt", for converters is introduced which takes into account the transverse energy spread as well as the conversion efficiency. The importance of the normalized-brightness-per-volt in beam design and future methods to improve this figure of merit are discussed.
TL;DR: In this article, the defect chalcopyrite quaternary compounds of the form I III IV Se4, where I is Cu or Ag, III Al, Ga or In, and IV Ge or Sn.
Abstract: Polycrystalline samples have been prepared of 12 defect chalcopyrite quaternary compounds of the form I III IV Se4, where I is Cu or Ag, III Al, Ga or In, and IV Ge or Sn. In all cases room tempera...
TL;DR: In this article, the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, using time-of-flight energy loss spectrometry, are reported.
Abstract: Measurements of the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, utilising time-of-flight energy loss spectrometry, are reported. Scattering into forward angles up to 60° is observed and the measurements suggest that sharp forward lobes exist in the angular distributions of positrons scattered following atomic excitation. Multiple scattering corrections to the measurements are described. Comparison is made with the inelastic scattering of electrons by the same atoms, and connections drawn between the present results and those of the recent complementary studies of Griffith et al. and Charlton et al.
TL;DR: In this article, the progress in positron-gas cross-section measurements is reviewed and the shape features in the total crosssection curves, such as Ramsauer-Townsend effects and the onsets of positronium formation are discussed.
Abstract: 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.
TL;DR: In this article, a new, direct experimental determination of the positronium formation cross section below the ionization threshold for argon and helium has been made, which suggests the existence of an unknown process which suppresses or depletes positronium.
Abstract: 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.
TL;DR: The anomalous transport properties of the charge-density-wave system niobium triselenide are surveyed in this article, where the effect of impurities, the non-ohmic Hall effect, conduction noise, and ac conduction are described.
Abstract: The anomalous transport properties of the charge-density-wave system niobium triselenide are surveyed. Early experiments on the frequency dependence and non-ohmicity of the electrical conductivity are described together with interpretations using the sliding mode mechanism. The effect of impurities, the non-ohmic Hall effect, conduction noise, and ac conduction are described. Theoretical models which have been proposed arc discussed, together with difficulties from the experimental viewpoint. Lastly, mention is made of recent experiments on NbSe3 as well as other similar systems.
TL;DR: In this article, about 1500 N2O absolute wavenumbers measured in vacuum were provided, covering a range of 225 to 125 cm−1, with accuracies from 50 to 125cm−1.
Abstract: About 1500 N2O absolute wavenumbers measured in vacuum are provided. They cover a range of 225 cm−1, centered around 1250 cm−1. Their absolute accuracy extends from 50 to 125 × 10−6 cm−1 (1.5 to 4 ...
TL;DR: In this paper, a report on recent progress in the theory of small atomic systems including a positron is presented, focusing on four main topics that seem interesting, instead of trying to cover the entire extensi...
Abstract: This is a report on recent progress in the theory of small atomic systems including a positron. I have selected four main topics that seem interesting, instead of trying to cover the entire extensi...
TL;DR: In this paper, the contributions of dislocations and grain boundaries to the residual electrical resistivity in metals are reviewed and a summary of experimental data on dislocatio... is provided.
Abstract: Progress in understanding the contributions of dislocations and grain boundaries to the residual electrical resistivity in metals is reviewed. Following a summary of experimental data on dislocatio...
TL;DR: In this article, it is shown that "near-dissociation expansions", empirical functions constrained to have the correct theoretically-predicted limiting behaviour at dissociation, provide representations of rotational and centrifugal distortion constants of diatomic molecules which are often much more compact, and which always provide much more reliable extrapolations beyond the range of available experimental data than comparable Dunham (ν +1/2) expansions.
Abstract: It is shown that "near-dissociation expansions", empirical functions constrained to have the correct theoretically-predicted limiting behaviour at dissociation, provide representations of rotational and centrifugal distortion constants of diatomic molecules which are often much more compact, and which always provide much more reliable extrapolations beyond the range of available experimental data than comparable Dunham (ν + 1/2) expansions. The capabilities of these expansions are illustrated by applications to the extensive data for the state of I2.
TL;DR: In this paper, six new transitions are assigned in Se V, resulting in the classification of three new levels: 4s4d1D, 4s5s1S, and 4s 5p1P0.
Abstract: Six new transitions are assigned in Se V, resulting in the classification of three new levels: 4s4d1D, 4s5s1S, and 4s5p1P0. Lifetimes and multiplet f-values are presented for the 4s24d2D, 4s4p22P, ...
TL;DR: In this paper, the instability of the plane interface between uniform, superposed, and streaming fluids through porous media is considered, and the configuration is taken to be bottom-heavy.
Abstract: The instability of the plane interface between two uniform, superposed, and streaming fluids through porous media is considered. The configuration is taken to be bottom-heavy. In the absence of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbation in the direction of streaming are ignored, whereas for perturbations in all other directions there exists instability for a certain wavenumber range. The surface tension is able to suppress this Kelvin–Helmholtz instability for small wavelength perturbations and the medium porosity reduces the stability range given in terms of a difference in streaming velocities. For the top-heavy configurations, the surface tension stabilizes a certain wavenumber range.
TL;DR: In this paper, the authors measured the self-broadening coefficients of 340 lines belonging to the 2ν2, ν1 and ν3 bands of H216O and H218O.
Abstract: 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) ...
TL;DR: The elastic constants and Pockels coefficients of CH4 and CD4 single crystals near their triple points have been determined using high-resolution Brillouin spectroscopy.
Abstract: 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 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 , , and are in the ratio V(CH4)/V(CD4) = 1.130 instead of 1.118 as expected from the isotopic mass ratio.
TL;DR: In this article, the radial variations of radiative and metastable atom densities in an argon plasma column produced by a microwave surface wave are obtained, and a large variety of radial profiles are observed as a function of wave frequency (300-1000 MHz), gas pressure (50-200mTorr), tube diameter (17.5-34mm), and axial magnetic field.
Abstract: The radial variations of radiative and metastable atom densities in an argon plasma column produced by a microwave surface wave are obtained. A large variety of radial profiles is observed as a function of wave frequency (300–1000 MHz), gas pressure (50–200 mTorr), tube diameter (17.5–34 mm) and axial magnetic field. The results differ significantly from those reported for the dc positive column, where the radial distributions keep approximately the same J0 Bessel-like profile.
TL;DR: In this paper, a phenomenological theory which explains qualitatively the results obtained is presented and conclusions are drawn in relation to the use of either technique in passive rubidium frequency standards.
Abstract: Results of measurements of light shifts observed in the optical pumping of rubidium 87 by means of electrodeless rubidium lamps are reported. The techniques of separated and integrated hyperfine filtering by means of the rubidium 85 isotope are compared. A phenomenological theory which explains qualitatively the results obtained is presented. Conclusions are drawn in relation to the use of either technique in passive rubidium frequency standards.
TL;DR: In this paper, Singlet-triplet perturbations in the and bands of the, system of H2CS have been studied by high resolution absorption and magnetic rotation spectroscopy.
Abstract: Singlet–triplet perturbations in the and bands of the , system of H2CS have been studied by high resolution absorption and magnetic rotation spectroscopy. Extensive perturbations in the band are associated with corresponding activity in the magnetic rotation spectrum. The shifts of the levels are consistent with interaction matrix elements up to ~ 1 cm−1. The selection rules indicate that the zeroth vibrational level of the 1A2 state is perturbed by the 4361 level of the 3A2 state. A number of perturbations are also observed in the band.
Abstract: Transitions combining the state of diatomic iodine with a new ion-pair state designated have been observed using Doppler-limited polarization-labelling spectroscopy. A number of vibration – rotation states of have been measured and the following vibration and vib-rotational constants determined: Te = 47 027.63(18), ωe = 103.904(18), ωexe = 0.1988(5), Be = 0.020780(14), αe = 5.48(6) × 10−5 and D = 3.5(4) × 10−9cm−1. These constants were derived for f state levels with v = 13 – 25.
TL;DR: The vertical distribution of stratospheric nitrogen dioxide was measured during the Atmospheric Environment Service STRATOPROBE projects in August of 1975 and 1976 as mentioned in this paper, which measured the NO2 absorption of sunlight from a balloon platform during sunrise and sunset and inverting the absorption curves.
Abstract: The vertical distribution of stratospheric nitrogen dioxide was measured during the Atmospheric Environment Service STRATOPROBE projects in August of 1975 and 1976. Vertical profiles of NO2 are determined by measuring the NO2 absorption of sunlight from a balloon platform during sunrise and sunset and inverting the absorption curves. A total of four sunrise/sunset pairs of observations were obtained from balloon flights of August 10 and 17, 1975 and August 19 and 28, 1976. The measurements show significant stability of the NO2 profile from flight to flight with variations of less than 15% between individual profiles. The average NO2 concentration at sunset was found to increase from about 0.3 ppbv at 10 km to 10 ppbv at 35 km. At sunrise the concentrations increase from 0.2 ppbv at 10 km to 5 ppbv at 35 km.