Showing papers in "Canadian Journal of Physics in 1991"
TL;DR: In this article, night and early morning data from the Johns Hopkins University, Applied Physics Laboratory HF radar at Goose Bay and from the magnetometers in the Canadian CANOPUS array often show structured spectra.
Abstract: Night and early morning data from the Johns Hopkins University, Applied Physics Laboratory HF radar at Goose Bay and from the magnetometers in the Canadian CANOPUS array often show structured spect...
125 citations
TL;DR: In this paper, the operation and performance of an atomic-oxygen (AO) beam facility developed at the University of Toronto Institute for Aerospace Studies (UTIAS), capable of providing ground-state neutral oxygen atoms at 2.2
Abstract: This paper describes the operation and performance of an atomic-oxygen (AO) beam facility developed at the University of Toronto Institute for Aerospace Studies (UTIAS), capable of providing ground-state neutral oxygen atoms at ~ 2.2 eV for flux levels as high as ~ 1016 atoms (cm2 s)−1. Results are presented on the AO erosion of polymer thin films and composite materials containing graphite and aramid fibres in epoxy matrices. Comparisons with space flight tests are also given, including studies of samples recently retrieved from the UTIAS composite-materials experiment on the NASA Long Duration Exposure Facility after 70 months exposure in low Earth orbit. Parameters that have been investigated include synergistic effects of UV radiation, surface-morphology changes, and accelerated testing.
99 citations
TL;DR: A real-time wind system from Saskatoon has operated with the Tromso medium frequency (MF) (partial reflection) radar (70°N, 20°E) since mid-1987.
Abstract: A real-time winds system from Saskatoon has operated with the Tromso medium frequency (MF) (partial reflection) radar (70°N, 20°E) since mid-1987. Although the system has a poorer data yield than u...
47 citations
TL;DR: In this article, a new optical temperature measurement technique for use in molecular beam epitaxy is demonstrated with GaAs substrates, where the temperature of the semiconductor is inferred from its band gap.
Abstract: A new optical temperature measurement technique for use in molecular beam epitaxy is demonstrated with GaAs substrates. The temperature of the semiconductor is inferred from its band gap, which is ...
43 citations
TL;DR: Ferroelectric thin films have recently proven viable for nonvolatile memory applications in semiconductor technology as discussed by the authors, and current research is focused on the development of processing technologies and d...
Abstract: Ferroelectric thin films have recently proven viable for nonvolatile memory applications in semiconductor technology. Current research is focused on the development of processing technologies and d...
35 citations
TL;DR: In this article, the effect of phosphine and trimethylindium molar fluxes on the epitax of a low pressure, horizontal MOCVD (metal-organic chemical vapour deposition) reactor was studied.
Abstract: The development of a low pressure, horizontal MOCVD (metal-organic chemical vapour deposition) reactor has allowed us to study the effect of phosphine and trimethylindium molar fluxes on the epitax...
33 citations
TL;DR: In this paper, the spatial distribution of optical emission rates within an auroral arc may be recovered from rocket photometer measurements made in a tomographic spin scan mode using two inversion algorithms that are particularly well suited for dealing with the problem of noise in the observational data.
Abstract: This paper demonstrates how the spatial distribution of optical emission rates within an auroral arc may be recovered from rocket photometer measurements made in a tomographic spin scan mode. The tomographic inversion procedures required to recover this information and the implementation of two inversion algorithms that are particularly well suited for dealing with the problem of noise in the observational data are described. The performance of the inversion algorithms and the limitations of the rocket tomography technique are assessed using various sets of simulated rocket measurements that were generated from 'known' auroral emission-rate distributions. The simulations are used to investigate how the quality of the tomographic recovery may be influenced by various factors such as noise in the data, rocket penetration of the auroral form, background sources of emission, smearing due to the photometer field of view, and temporal variations in the auroral form.
30 citations
TL;DR: In this article, a new lidar facility has been established for atmospheric measurements from the ground up to ~90 km altitude, where measurements of stratospheric aerosols and ozone are presented, and density and temperature profiles into the mesosphere are analyzed to derive information about atmospheric gravity waves.
Abstract: This paper describes a new lidar facility that has been established for atmospheric measurements from the ground up to ~90 km altitude. Measurements of stratospheric aerosols and ozone are presented, and density and temperature profiles into the mesosphere are analyzed to derive information about atmospheric gravity waves.
29 citations
TL;DR: In this paper, a set of two-dimensional nonlinear calculations has been done to simulate the auroral region electrojet and to examine the effect of the electric field on the dynamics and thermodynamics of the thermosphere.
Abstract: A set of two-dimensional nonlinear calculations has been done to simulate the auroral region electrojet and to examine the effect of the electric field on the dynamics and thermodynamics of the thermosphere. A large number of physical and dynamical processes in the ionosphere have been considered, including the ion-drag force, the Coriolis force, gravitation, Joule heating, viscous heating and viscous work, solar extreme ultraviolet heating, thermal conduction, and cooling to space owing to infrared radiation of different species. Navier–Stokes equations for a compressible, viscous and thermal conducting fluid flow with source terms have been solved by a MacCormack explicit, alternative forward-backward finite differencing scheme in spherical coordinates. Results have been recorded at various time intervals for three hours simulation time, for altitudes between 80 and 450 km, and from the north pole to the equator. In addition to a strong zonal drift motion and to the basic upward and meridional motion aw...
27 citations
TL;DR: In this article, the energy and mass-number dependence of the pre-equilibrium fraction of the reaction fraction were analyzed using the Hauser-Feshbach formalism with and without the inclusion of a first chance neutron emission.
Abstract: Excitation functions for the 121Sb (α, n)+ 123Sb(α, 3n),,21Sb(α, 2n)+ 123Sb(α, 4n), 121Sb(α, 4n), 121Sb(α, 3np), and 123Sb(α, n) reactions are measured in the energy range 30–60 MeV using the stacked foil technique. In the cases of the 121Sb(α, n)+ 123Sb(α, 3n) and 121Sb(α, 2n)+ 123Sb(α, 4n) reaction pairs, the excitation functions for individual reactions were deduced using theoretical calculations. Excitation functions are also calculated theoretically using the compound-nucleus model with and without the inclusion of a pre-equilibrium emission. As expected, inclusion of a pre-equilibrium contribution based on the exciton model along with compound-nucleus calculations using the Hauser–Feshbach formalism reproduces well the measured excitation functions. Analysis of the data indicates a preference for a first chance neutron emission over charged-particle emission, and interesting trends in the energy and mass-number dependence of the pre-equilibrium fraction are observed.
25 citations
TL;DR: In this article, a generalized quasi-one-dimensional nonstationary flow analysis and associated total-variation-diminishing (TVD) finite-difference solution schemes, including aproximate Riemann solvers, are presented for predicting the high-temperature flows in such facilities.
Abstract: The hypersonic impulse tunnel of the University of Toronto Institute for Aerospace Studies (UTIAS) and Ryerson Polytechnical Institute (RPI) is a short-duration blow-down experimental wind tunnel capable of producing high-Mach-number flows (Ma ≈ 8). A generalized quasi-one-dimensional nonstationary flow analysis and associated total-variation-diminishing (TVD) finite-difference solution schemes, including aproximate Riemann solvers, are presented for predicting the high-temperature flows in such facilities. The analysis is used to investigate the operation of the UTIAS–RPI facility and produce performance data that are not always easily determined or available from experimental measurements. The thermodynamic state of the nozzle-exit flow and high-temperature or real-gas effects are assessed for this facility under various operating conditions. Numerical results, coupled with additional comparisons with available experimental data, demonstrate the range of test-section flows that may be achieved. They als...
TL;DR: More than 180 nitrogen-shifting coefficients have been measured at 300 K, for vibro-rotational lines of the water molecule absorbing between 5000 and 10, 700 cm−1 as mentioned in this paper.
Abstract: More than 180 nitrogen-shifting coefficients have been measured at 300 K, for vibro-rotational lines of the water molecule absorbing between 5000 and 10 700 cm−1. The average uncertainty is 0.4 × 10−3 cm−1 atm−1 (1 atm = 1013 hPa); most of the measured N2-shifting coefficients are negative, they vary between +5 and −27 × 10−3 cm−1 atm−1. A review of the existing measurements and calculations concerning the pressure-shifts of H2O lines is presented, and the measurement methodology is discussed.
TL;DR: In this article, the authors report on observations of broadband ULF signals before and during the Upland quake of April 17, 1990 (Ms'='4.6), centered 200'km N of San Diego.
Abstract: Although questioned for a long time, there is accumulating growing evidence for the existence of detectable seismo-electromagnetic phenomena worldwide. California is geologically as well as seismically a unique region for studying these phenomena in depth; and, in particular, the southern California geologic province with a multitude of offshore and inland fault zones with San Diego in its center. At the Naval Ocean Systems Center Low Frequency Noise Laboratory, San Diego CA., we monitor 0.1–10 Hz ultra-low frequency (ULF) and 10–40 Hz extremely low-frequency (ELF) signals using mu-metal loaded multitum search coil sensors, as well as 10–100 kHz very low-frequency signals using large 1 m diameter loop antennas. We have observed precursor seismo-electromagnetic emissions of several earthquake events. In this paper, we report on observations of broadband ULF signals before and during the Upland quake of April 17, 1990 (Ms = 4.6), centered 200 km N of San Diego. The signals were detected with the vertically ...
TL;DR: In this article, the authors make predictions notablement plus precises du spectre diade moins diade des deux isotopes, dans le domaine de frequence 0−300 GHz avec des intensites superieures a 10 −11 cm −2 atm −1 a 296 K, ont ete ainsi realisees.
Abstract: Des observations recentes de transitions diade-diade ont ete introduites, en plus de transitions «purement rotationnelles» et de transitions infrarouges, dans un ajustement simultane des parametres des niveaux de base et superieur de la diade v 2 /v 4 des deux isotopes 12 CH 4 et 13 CH 4 . A l'aide d'un Hamiltonien reduit du sixieme ordre, ces donnees ont permis d'observer des ameliorations significatives des parametres du niveau superieur de la diade, precedemment obtenus a partir des seules transitions infrarouges. Des predictions notablement plus precises du spectre diade moins diade des deux isotopes, dans le domaine de frequence 0−300 GHz avec des intensites superieures a 10 −11 cm −2 atm −1 a 296 K, ont ete ainsi realisees
TL;DR: In this article, a boundary value solution to the problem of transverse magnetic multiple scattering by M parallel perfectly conducting elliptic cylinders is presented, which is an exact one and based on the...
Abstract: A boundary value solution to the problem of transverse magnetic multiple scattering by M parallel perfectly conducting elliptic cylinders is presented. The solution is an exact one and based on the...
TL;DR: In this paper, the defect reorienting between sites related by a two-fold crystallographic axis a, with energy barrier 0.223(6)eV for A and 0.178(14)
Abstract: Centres formed in α-quartz by 77 K x irradiation and warming above ca. 165 K, both exhibit a reversible change in symmetry of the centres from C1 at 75 K to C2 at 295 K, as observed by X-band electronic paramagnetic resonance spectroscopy. Each centre contains a Ge3+ ion (S = 1/2) substituted for a Si4+ ion, with a nearby Na+ interstitial ion. Spin-Hamiltonian electronic Zeeman, 73Ge and 23Na nuclear hyperfine and quadrupole parameter matrices for these centres were measured at temperatures 75, 190, and 295 K. They show that the change is associated with the defect reorienting between sites related by a two-fold crystallographic axis a, with energy barrier 0.223(6) eV for A and 0.178(14) eV for C. In both centres, ca. 50% of the spin density is located in a Ge sp orbital; in A, the sp orbital is oriented close to a, while in C it is nearly parallel to an O–Si–O bond-angle bisector that is nearly normal to a. Theoretical hyperfine matrices indicate that the Na ions are located near a, in a c-axis channel n...
TL;DR: In this article, the authors studied O2-CF4 plasma etching of commercial polymers, particularly KaptonR polyimide, using a reactor in which the plasma can be excited by radio-frequency (rf, 13.56 MHz), microwave power (MWP) and other power sources.
Abstract: We have studied O2–CF4 plasma etching of commercial polymers, particularly KaptonR polyimide, using a reactor in which the plasma can be excited by radio-frequency (rf, 13.56 MHz), microwave power ...
TL;DR: A significant negative correlation exists between June-August sea surface temperatures (SSTs) in the eastern equatorial Pacific and 15-31 October total ozone values at South Pole, Antarctica as mentioned in this paper.
Abstract: A significant negative correlation exists between June–August sea surface temperatures (SSTs) in the eastern equatorial Pacific and 15–31 October total ozone values at South Pole, Antarctica. SSTs ...
TL;DR: In this article, the authors have grown thin buried Gen (monolayers) films on (100) Si by molecular beam epitaxy and studied their structural properties by a variety of techniques including Raman scattering spectroscopy, glancing incidence X-ray reflection, Rutherford backscattering, transmission electron microscopy, and extended Xray absorption fine structure analysis.
Abstract: The understanding of the epitaxy of pure Ge layers on Si is an important step towards the synthesis of SimGen (m, n < 10 monolayers) short-period superlattices. The possibility of a direct band-gap character makes these structures extremely attractive. We have grown thin buried Gen ( monolayers) films on (100) Si by molecular beam epitaxy and studied their structural properties by a variety of techniques including Raman scattering spectroscopy, glancing incidence X-ray reflection, Rutherford backscattering, transmission electron microscopy, and extended X-ray absorption fine structure analysis. All these techniques allowed detection of the thin Ge layers and provided information about the thickness, morphology, strain distribution, and interface sharpness of these heterostructures. The Ge„ films with had a two-dimensional nature and showed no sign of strain relaxation. Intermixing at the Si–Ge interfaces was present in all these films and estimated to be not more than two monolayers. This smearing at the ...
TL;DR: In this paper, the passivation of the InP surface by sulfur treatment was studied in the temperature range between 150-300 °C by angle resolved X-ray photoelectron spectroscopy and photoluminescence measurements.
Abstract: The passivation of the InP surface by sulfur treatment is studied in the temperature range between 150–300 °C by angle resolved X-ray photoelectron spectroscopy and photoluminescence measurements. ...
TL;DR: In this article, an elegant but simple formalism is used to construct the three-dimensional harmonic oscillator in Cartesian, cylindrical, and spherical coordinates, and transformation coefficients between these representations are derived using straightforward angular-momentum and combinatorial algebra.
Abstract: An elegant but simple formalism is used to construct the three-dimensional harmonic oscillator in Cartesian, cylindrical, and spherical coordinates. Then, transformation coefficients between these representations are derived using straightforward angular-momentum and combinatorial algebra. Such coefficients, which should be applicable to many fields of physics, have been particularly useful in studies of nuclear shapes.
TL;DR: In this paper, two experimental techniques for charge-carrier drift-mobility lifetime (μτ) measurements and their application to a-Se and Cl-doped Se:0.35% as electro-radiographic films are described.
Abstract: Charge-carrier drift-mobility-lifetime (μτ) product, the range of the carrier, is one of the most important electronic properties of a semiconductor material for device applications. The determination of μτ is, therefore, of fundamental importance in the characterization of amorphous semiconductors and has been the key issue in a number of recent papers. This paper describes two experimental techniques for μτ product measurements and their application to a-Se and Cl-doped Se:0.35%As electro-radiographic films. Xerographic measurements involve corona charging the surface of an amorphous semiconductor film to a voltage Vo. The film is then exposed to a highly absorbed step illumination at the end of which the residual potential, VR1, on the surface is measured. VR1/Vo is then related to μτ. In the interrupted field time-of-flight (IFTOF) measurement technique, during the flight of the photoinjected holes through the specimen, the applied field is removed at time T1 for an interruption duration of ti and the...
TL;DR: In this article, a model for the inversion of twilight O2(1Δg) and O2 (1Σg) emission-rate measurements to obtain O3 height profiles was described.
Abstract: Improvements in the sensitivity and automation of high-resolution, ground-based spectrometers and interferometers allow the routine acquisition of measurements not only in the nightglow, but in the twilight. Measurements of the emission rate of the O2(1Δg) and O2(1Σg) bands have been used, primarily in the dayglow, to infer mesospheric O3 profiles. This paper describes a model for the inversion of twilight O2(1Δg) and O2(1Σg) emission-rate measurements to obtain O3 height profiles, concentrating on the sensitivity of the results to temperature profile, solar flux, photodissociations rates, uncertainties in the reaction rates, and constants, and the importance of transfer chemistry as a contribution to the O2(1Δg) emission rate, using a fixed O3 profile. The sensitivity of the calculations to inputs other than the desired O3 density shows this method may not be suitable for the absolute value of the O3 density (to better than about 25%), but can successfully determine the shape of the O3-density profile in...
TL;DR: In this article, the details and performance of a shot-noise-limited high-resolution Raman gain spectrometer are discussed and compared to a "standard" continuous wave (cw) spectrometers.
Abstract: The details and performance of a shot-noise-limited high-resolution (≤ 2 MHz) Raman gain spectrometer are discussed and compared to a "standard" continuous wave (cw) spectrometer. For a single pass cell and 1 s integration time, a signal-to-noise ratio greater than 1000 is obtained for the Q(2) line of D2 at pressures above a few atmospheres. The quality of the spectrometer for the determination of spectral profiles is demonstrated by examining the Dicke narrowing of the line.
TL;DR: In this paper, the quantum defect orbital (QDO) method with the use of a core polarization-corrected dipole transition operator was employed to determine oscillator strengths for potassium and some of its isoelectronic ions (CaII-CrVI).
Abstract: The quantum defect orbital (QDO) method, with the use of a core polarization-corrected dipole transition operator, was employed to determine oscillator strengths for potassium and some of its isoelectronic ions (CaII–CrVI). The inclusion of core-valence polarization effects leads to a general improvement of the QDO f values. Systematic trends of individual oscillator strengths along the isoelectronic sequence are also shown in a graphical form.
TL;DR: In this article, a comparison between the space-based CO data and concurrent, direct CO measurements taken aboard aircraft is presented, and a strategy for comparing the tropospheric CO measurements over the remote oceans is presented.
Abstract: The measurements of air pollution from satellites (MAPS) experiment measured the distribution of middle tropospheric carbon monoxide (CO) from the Space Shuttle during October 1984. A critical area of the experiment is the assessment of experimental error of the MAPS data. This error is determined by the comparison between the space-based CO data and concurrent, direct CO measurements taken aboard aircraft. Because of the variability in the CO measurements near land sources, a strategy for comparing the tropospheric CO measurements over the remote oceans is presented.
TL;DR: In this article, the topological structure of non-Abelian dyons is investigated in connection with the issue of quark confinement in quantum chromodynamics (QCD), and extended gauge theory is formulated in SU(2) and SU(3) gauge groups from the corresponding restricted chromodynamics.
Abstract: To investigate the possible physical implications of the topological structure of non-Abelian dyons in connection with the issue of quark confinement in quantum chromodynamics (QCD), extended gauge theory is formulated in SU(2) and SU(3) gauge groups from the corresponding restricted chromodynamics (RCD) by reactivating the suppressed dynamical degrees of freedom and constructing the gauge potential in terms of the binding gluons (the RCD piece) and the valence gluons (the reactivated piece). It is shown that in this extended QCD, the confinement mechanism of the corresponding RCD remains intact. The physical spectrum contains color-singlet generalized electric glueballs made of valence gluon pairs as well as the generalized magnetic glueballs as massive collective modes of the condensed vacuum.
TL;DR: The thermal neutron capture γ rays from natural molybdenum and ruthenium have been studied using a pair spectrometer and the tangential facility at the McMaster University Nuclear Reactor as mentioned in this paper.
Abstract: The thermal neutron capture γ rays from natural molybdenum and ruthenium have been studied using a pair spectrometer and the tangential facility at the McMaster University Nuclear Reactor. Precise transition, level, and neutron separation energies of different isotopes are inferred. The separation energies are: Sn(93Mo) = 8069.76 ± 0.09, Sn(95Mo) = 7369.10 ± 0.10, Sn(96Mo) = 9154.31 ± 0.05, Sn(97Mo) = 6821.15 ± 0.25, Sn(98Mo) = 8642.55 ± 0.07, Sn(99Mo) = 5925.42 ± 0.15, Sn(100Ru) = 9673.48 ± 0.05, and Sn(102Ru) = 9219.64 ± 0.05 keV. The M1 strength functions of 100Ru,102Ru, 96Mo, and 98Mo are (34 ± 15) × 10−9, (82 ± 41) × 10−9, (22 ± 7) × 10−9, and (25 ± 8) × 10−9 MeV−3, respectively. All values but that for 102Ru agree with the global average of (20 ± 6) × 10−9 MeV−3. The average of 96Mo observed is 247 ± 175 e2 fm4 MeV−1.
TL;DR: In this article, a photopyroelectric spectrometer with real-time and self-normalization capability was used for both conventional transmission and thermal-wave spectroscopic measurements of amorphous Si thin films, deposited on crystalline Si substrates.
Abstract: A photopyroelectric spectrometer with real-time and(or) self-normalization capability was used for both conventional transmission and thermal-wave spectroscopic measurements of amorphous Si thin films, deposited on crystalline Si substrates. Optical-absorption-coefficient spectra were obtained from these measurements and the superior dynamic range of the out-of-phase (quadrature) photopyroelectric signal was established as the preferred measurement method, owing to its zero-background compensation capability. An extension of a photopyroelectric theoretical model was established and successfully tested in the determination of the optical absorption coefficient and the thermal diffusivity of the sample under investigation. Instrumental sensitivity limits of βt ≈ 5 × 10−3 were demonstrated.
TL;DR: In this article, it was found that the dark decay rate of charge on the selenium surface can be reduced by the presence of a thin aluminum oxide film between the material and the substrate metal, and different methods were explored for forming this film, including direct thermal oxidation and various glow discharges.
Abstract: Amorphous selenium is often used as the basic photoreceptor material in xerography in the form of a layer on an aluminum substrate. It is found that the dark decay rate of charge on the selenium surface can be reduced by the presence of a thin aluminum oxide film between the selenium and the substrate metal. In this study, different methods were explored for forming this film, including direct thermal oxidation and various glow-discharge methods. It was found that with thermal oxidation and low voltage glow discharge, the film thicknesses were limited to about 200 A (1 A = 10−10 m). However, with dc reactive sputtering, aluminum oxide films with thicknesses of more than 2000 A could be prepared. Evaluation of the films, with the selenium layer present, indicated that the low voltage glow-discharge and direct thermal oxidation methods gave the best results xerographically.