Showing papers in "Canadian Journal of Physics in 1972"
Abstract: The dispersion relations in platinum have been measured at 90 °K by the inelastic scattering of thermal neutrons. Born–von Karman models of the force system have been calculated by fitting to the dispersion curves. Fourth-neighbor forces, with weaker interactions probably extending to at least sixth neighbors, are required to fit the data. A frequency distribution has been calculated from the force constants of the most realistic model.Some measurements are also reported of frequencies at a temperature of 473 °K. The mean frequency shift from 90 to 473 °K was found to be −2.0%.In the [0ζζ]T1 branch, anomalous behavior, similar to that observed in palladium, has been studied at temperatures of 90, 296, and 473 °K. As in Pd, the anomaly in Pt is markedly broadened and weakened with increasing temperature. The phonon wave vectors corresponding to possible Kohn transitions in the (001) plane have been determined by machine calculation, using Fermi surfaces given in the literature. These results strongly sugge...
143 citations
TL;DR: In this article, an integral equation approach for the analysis of a horizontal wire antenna(s) located in free space near a lossy half-space is described, based on the Sommerfeld form.
Abstract: An integral equation approach for the analysis of a horizontal wire antenna(s) located in free space near a lossy half-space is described. Two methods, a rigorous one based upon the Sommerfeld form...
121 citations
TL;DR: Within the framework of the Wang Chang-Uhlenbeck kinetic equation, the authors proposed a model description of molecular gases, which is related to the models earlier discussed by Hanson and Morse.
Abstract: Within the framework of the Wang Chang–Uhlenbeck kinetic equation, we propose a model description of molecular gases. The model is related to the models earlier discussed by Hanson and Morse. In ou...
112 citations
TL;DR: In this article, the magnetic properties of synthetic Fe3S4 have been studied using both static magnetization measurements and Mossbauer effect spectrometry and two alternative band schemes are proposed to account for this feature and explain the magnetic moment.
Abstract: The magnetic properties of a number of samples of synthetic Fe3S4 have been studied using both static magnetization measurements and Mossbauer effect spectrometry. The distinction is made between the intrinsic properties of bulk Fe3S4 and observations resulting from superparamagnetic behavior and nonstoichiometry. Mossbauer spectra in applied fields show that the bulk material has a simple Neel ferrimagnetic spin arrangement. The magnetic moment at 4.2 °K is 2.2 ± 0.3 μB per formula unit and the ordering temperature is 606 ± 2 °K. Conductivity measurements indicate semimetallic behavior and two alternative band schemes are proposed to account for this feature and explain the magnetic moment.
104 citations
TL;DR: Propagation along a thin dielectric coated wire parallel to the interface between two homogeneous half-spaces is considered in this article, where the solution accounts for the presence of the interface provided the coa...
Abstract: Propagation along a thin dielectric coated wire parallel to the interface between two homogeneous half-spaces is considered. The solution accounts for the presence of the interface provided the coa...
74 citations
TL;DR: In this paper, data from the IMP-1 satellite were used to determine the lag time between the response of the index of geomagnetic activity AE to fluctuations in the azimuthal component of the interplanetary electric field as measured in the solar ecliptic coordinate system.
Abstract: Data from the IMP-1 satellite are used to determine the lag time between the response of the index of geomagnetic activity AE to fluctuations in the azimuthal component of the interplanetary electric field as measured in the solar ecliptic coordinate system. The lag time is found to lie in the range 30–50 min. The magnitude of the lag time is related to the average energy content of the magnetosphere.
69 citations
TL;DR: The infrared fundamental band and the five strongest near-infrared and visible electronic bands of gaseous oxygen were studied from 90 to 115 k with path lengths up to 140 km in two low-temperature multiple-traversal absorption cells as discussed by the authors.
Abstract: The infrared fundamental band and the five strongest near-infrared and visible electronic bands of gaseous oxygen were studied from 90 to 115 K with path lengths up to 140 m in two low-temperature multiple-traversal absorption cells. The profile of the fundamental band is in good agreement with the theory of quadrupole-induced absorption except for a low-intensity residual in the Q-branch region. Although the electronic bands are less amenable to complete analysis, the general validity of a Boltzmann relation in their intensity distributions confirms their collision-induced nature. The temperature variation of the integrated band intensities is indicative of quadrupole induction for the fundamental and of overlap induction for the electronic bands; a somewhat too sharp rise at low temperatures may be due to the neglect of the quadrupole–quadrupole coupling in evaluating the pair distribution function.
64 citations
TL;DR: The dynamical processes responsible for laser emission in the pulsed pumping of a transversely excited atmospheric (TEA) CO2 laser are investigated in this article, where an explanation for the formation of the giant pulse is proposed on the basis of a gain-switching mechanism in which it is assumed that with short strong-current pulses a high population inversion can be achieved prior to the onset of laser action.
Abstract: The dynamical processes responsible for laser emission in the pulsed pumping of a transversely excited atmospheric (TEA) CO2 laser are investigated An explanation for the formation of the giant pulse is proposed on the basis of a gain-switching mechanism in which it is assumed that with short strong-current pulses a high population inversion can be achieved prior to the onset of laser action The kinetics of the mechanism are described by means of a set of nonlinear rate equations idealized to a four-energy-state system With suitable initial conditions on the populations, the transient solution of these equations for the mixtures CO2–He and CO–N2–He appears to be consistent with the major features of experimental observation
62 citations
TL;DR: In this paper, stopping powers for 4He, 16O, and 35Cl ions at energies of 1 to 3 MeV per nucleon in Ni, Ge, Y, Ag, and Au foils were measured.
Abstract: Stopping powers have been measured for 4He, 16O, and 35Cl ions at energies of ~1 to ~3 MeV per nucleon in Ni, Ge, Y, Ag, and Au foils. The absolute accuracy is of the order of ± 4%. The results are compared with the semiempirical values tabulated by Northcliffe and Schilling and with previous experimental values.
58 citations
TL;DR: In this paper, the magnetic resonance spectra of the ground 2P multiplets of 11B and 27Al have been remeasured by the method of atomic beams and the coupling constants A3/2, B3 2, and gJ(2P3 2 ) for 11B, and A1/2 for 27Al, have been redetermined to higher precision.
Abstract: The magnetic resonance spectra of the ground 2P multiplets of 11B and 27Al have been remeasured by the method of atomic beams and the coupling constants A3/2, B3/2, and gJ(2P3/2) and gJ(2P1/2) for 11B, and A1/2 for 27Al, have been redetermined to higher precision. Measurements have also been made, by the triple resonance method, of two ΔMJ = 0, ΔMI = ± 1 transitions in both 11B and27 Al and from these the off-diagonal magnetic dipole coupling constants A3/2,1/2 have been determined.These measurements have enabled us to evaluate the magnetic dipole radial parameters , , and for both boron and aluminum. The departures of and the ratio from their restricted Hartree–Fock values are plotted as functions of the occupation number N for all elements with (2p)N and (3p)N ground configuration for which data are available. The trends are briefly discussed.
58 citations
TL;DR: In this paper, rotational analysis for the 0−20−000 bands of the electronic transition of PH2 with ν−2−1−8 lines has been carried out, and approximately 1000 lines have been assigned.
Abstract: Rotational analyses have been carried out for the 0ν′20–000 bands of the electronic transition of PH2 with ν′2 = 1–8. Approximately 1000 lines have been assigned. The earlier analysis of the 000–00...
TL;DR: In this paper, a spectroscopic method using a monochromatic, single mode stabilized laser source has been used to study the 0001-1000-0200 (I) band of CO2.
Abstract: The 0001–(1000-0200)I band of CO2 has been studied by a spectroscopic method using a monochromatic, single mode stabilized laser source. Half-width and integrated intensity values have been deduced for every line.
TL;DR: Spectra of H2-Ne and D2−Ne Van der Waals complexes with collision-induced fundamental bands of hydrogen and deuterium have been obtained with an absorption path of 110'm at temperatures around 27'K in a specially designed multiple-traversal cell.
Abstract: Spectra of H2–Ne and D2–Ne Van der Waals complexes accompanying transitions in the collision-induced fundamental bands of hydrogen and deuterium have been obtained with an absorption path of 110 m at temperatures around 27 K in a specially designed multiple-traversal cell. The observed structure is similar to that of H2– and D2–Ar, Kr, and Xe complexes studied earlier, but the number of lines observed for the Ne complexes is fewer because of the shallower intermolecular potential. Well-resolved R and P branches (Δl= ±1, where l is the rotational quantum number of the complex) accompanying the overlap-induced Q1 (0) transitions are analyzed directly to give rotational (B) and centrifugal stretching (D) constants for the complexes. Unlike the other H2– rare gas complexes the spectra accompanying quadrupole-induced transitions show no direct evidence of anisotropy of the intermolecular forces.
TL;DR: In this paper, second-order Raman spectra have been obtained from oriented single crystals of ZnSe and the results have been used to determine the zone boundary frequencies at the critical points X, L, and W. The resulting set of frequencies are consistent with known polarization selection rules and with a theoretical model.
Abstract: Second-order Raman spectra have been obtained from oriented single crystals of ZnSe. The spectra have been interpreted and the results have been used to determine the zone boundary frequencies at the critical points X, L, and W. The resulting set of frequencies are consistent with known polarization selection rules and with a theoretical model. The frequencies in turn serve to determine the parameters in the theoretical model and the resulting model has been used to calculate the phonon dispersion throughout the Brillouin zone, the density of states, and the specific heat. The results are compared to the small amount of experimental data that is available.
TL;DR: In this paper, the authors presented precision measurements of positron lifetimes in aluminum at 42 temperatures and analyzed the data in a manner consistent with both trapping and nontrapping models of POS-vacancy.
Abstract: Precision measurements of positron lifetimes in aluminum at 42 temperatures are presented. The data are analyzed in a manner consistent with both trapping and nontrapping models of positron–vacancy...
TL;DR: In this paper, a model for the magnetic pinning interaction at a phase boundary is proposed and the problem of the summation procedure for individual pinning interactions is discussed and it is concluded that the distortion of the flux line lattice caused by large normal particles is large enough for a simple direct summation to apply.
Abstract: The pinning of flux lines by large normal particles has been investigated as a function of field and temperature. The results are compared with a model for the magnetic pinning interaction at a phase boundary. The problem of the summation procedure for individual pinning interactions is discussed and it is concluded that the distortion of the flux line lattice caused by large normal particles is large enough for a simple direct summation to apply. This conclusion is supported by the experimental results. The experimental results also indicate that Anderson flux creep is not significant in this type of pinning system.
TL;DR: In this paper, the total scattering cross section for e+ in He has been measured through two energy intervals, 1 to 4'eV and 17 to 26 'eV, and the results are consistent with the calculations of Drachman.
Abstract: The total scattering cross section for e+ in He has been measured through two energy intervals, 1 to 4 eV and 17 to 26 eV. Through the lower elastic-scattering interval our results are consistent with the calculations of Drachman. From below the positronium formation threshold, at 17.8 eV to above the He ionization threshold, our results agree qualitatively with the calculations of Kraidy, who includes in his model virtual positronium and positronium polarization. Just below 17.8 eV the cross section is 0.35 ± 0.04 πa02. In these experiments a high-current linac has been used as a source of positrons and total beam attenuation has been used to determine the cross section.
TL;DR: In this article, the spin-lattice relaxation time T1 of the 19F nuclei was measured in gaseous samples of CF4, SiF4, GeF4 and SF6 at room temperature for densities from 0.015 to 20 amagat.
Abstract: The spin–lattice relaxation time T1 of the 19F nuclei was measured in gaseous samples of CF4, SiF4, GeF4, and SF6 at room temperature for densities from 0.015 to 20 amagat. In each case T1 was observed to pass through a minimum for some density less than 0.50 amagat. In addition, T1 was measured in the extreme narrowing region for SF6 at 238, 265, 293, 313, and 349.5 K.. The spin–rotation interaction provides the dominant relaxation mechanism in all cases. The data are analyzed on the basis of the assumption that the collision modulated spin–rotation interaction may be described by a single correlation function which is a simple exponential function of time. Values of an effective spin–rotation constant and a cross section for molecular reorientation are obtained for each gas. Assuming the validity of the model used to analyze the relaxation data, the combination of nuclear magnetic relaxation results with molecular beam measurements yields more accurate values of the anisotropic spin–rotation constant Cd...
TL;DR: In this paper, the limits of the determination method of the quadrupole moment have been shown by measuring the linewidths of CO2 lines and the influence of dispersion forces has been pointed out, if a semi-empirical potential is used.
Abstract: The theory of Anderson, Tsao, and Curnutte has been applied to the calculation of self-broadened linewidths of CO2 The setting up of an experimental method using a laser source allowed us to measure systematically the broadening ability of nitrogen upon CO2 lines The application of Anderson's theory has been extended to this type of interactions In this study the limits of the determination method of the quadrupole moment have been shown by measuring the linewidths In an other way, the influence of dispersion forces has been pointed out, if a semi-empirical potential is used
TL;DR: In this article, the rotational constant Bν for vibrational levels near the dissociation limit D of a diatomic molecule is explicitly related to the nature of the long-range inter-cell communication.
Abstract: A simple expression is derived which explicitly relates the rotational constant Bν for vibrational levels near the dissociation limit D of a diatomic molecule, to the nature of the long-range inter...
TL;DR: In this paper, the orange system of ScO has been reanalyzed as a 2Π → 2Σ transition and all the branches which are compatible with the selection rules ΔJ = 0, ± 1.
Abstract: The orange system of ScO has been reanalyzed as a 2Π → 2Σ transition. We have observed all the branches which are compatible with the selection rules ΔJ = 0, ± 1. We have not detected the hyperfine structure in the excited state, the coupling case being therefore aβ. The magnetic hyperfine interaction inducing the ground state doubling is the only one which appears; it has been analyzed by other authors who have shown that the coupling case for this state is of the type bβS.The use of an alloy hollow-cathode lamp, cooled with liquid nitrogen, has enabled us to improve the frequency measurements. The values of the constants have been obtained by a method by which, working directly with the Hamiltonian, the introduction of each parameter can be justified. The study of the Λ doubling in 2Π3/2 and 2Π1/2 levels leads us to values of ξ and η very close to those predicted for a pure precession case.
TL;DR: In this article, a simple theoretical model based on the necessity of treating the positronium electron and the remaining electrons in the crystal as indistinguishable was proposed, which yields results compatible with both momentum and lifetime data.
Abstract: Previous experiments with positron annihilation in single crystals of quartz have revealed an interesting series of narrow peaks on the momentum distribution of the annihilation photons. Our experiments repeat these observations and also confirm that no very long lifetime exists. We outline a simple theoretical model based upon the necessity of treating the positronium electron and the remaining electrons in the crystal as indistinguishable. The model yields results compatible with both momentum and lifetime data.
TL;DR: In this article, the authors derived full wave solutions to the problem of radio wave propagation in stratified media with non-uniform boundaries and varying electromagnetic parameters, and exact boundary conditions are imposed and the solutions are shown to be consistent with the reciprocity relationships.
Abstract: Full wave solutions are derived to the problem of radio wave propagation in stratified media with non-uniform boundaries and varying electromagnetic parameters. The analysis employs a complete set of forward and backward travelling waves. The continuous parts of the wavenumber spectrum constitute the radiation field and the lateral waves, and the discrete part of the spectrum is identified as the surface wave term. The solutions are not restricted by the approximate surface impedance concept and the source and receiver can be situated on opposite sides of the interface. Exact boundary conditions are imposed and the solutions are shown to be consistent with the reciprocity relationships.
TL;DR: In this article, an expression for the electrostatic potential in a system in which similar charges are distributed over all the points of a s.c. lattice, contained within an ellipsoidal surface, was obtained.
Abstract: An expression is obtained for the electrostatic potential in a system in which similar charges are distributed over all the points of a s.c. lattice, contained within an ellipsoidal surface. The potential consists of two components: one, the intrinsic potential, is (a) a periodic function of position, with the period of the lattice, (b) a function of the geometry of the lattice, and (c) independent of the size and shape of the ellipsoid; the other, the extrinsic potential, is, (a) independent of the geometry of the lattice, (b) a quadratic function of position, and (c) a function of the shape and size of the ellipsoid. The intrinsic potential is shown to be equal to the Ewald transformed potential at high symmetry points (cube corner, face centers, body center).The finite crystal potential results are applied to the case of an electrically neutral point charge model of a cubic ionic crystal. Both the electrostatic potential within the crystal and the electrostatic energy per charge repetition unit prove, ...
TL;DR: The profile of the depolarized Rayleigh line has been measured in H2, D2, HD, and in H 2 -He and H 2-Ne mixtures as mentioned in this paper.
Abstract: The profile of the depolarized Rayleigh line has been measured in H2, D2, HD, and in H2–He and H2–Ne mixtures. In addition the profile of the S0(1) rotational Raman line was determined in H2 and H2...
TL;DR: In this article, the normal spinel Fe[Cr2]S4 has been studied using the Mossbauer effect over the temperature range 7-170 °K, and it has been shown that the magnetically split spectra can be fitted using a zero value of the asymmetry parameter over a temperature range of 2-500 °K.
Abstract: The normal spinel Fe[Cr2]S4 has been studied using the Mossbauer effect. Spectra have been collected over the temperature range 2–500 °K. Results are presented for the quantity , the hyperfine field, and the isomer shift. We find that the magnetically split spectra can be fitted using a zero value of the asymmetry parameter over the temperature range 7–170 °K. But for an asymmetry parameter is required to fit the spectrum. Experiments in applied fields at 7 and 81 °K show that the quadrupole interaction is not produced by a crystallographic distortion. Attention is drawn to features of the spectra which suggest the presence of relaxation effects in the compound. The isomer shift shows deviations from the Debye model behavior. A model, which allows explanations of the observations, is proposed.
TL;DR: In this article, a slotted-cylinder antenna coated with a homogeneous material was investigated and it was found that for some values of the coating thickness certain modes may resonate, which greatly enhance the radiated power and affect the shape of the radiation patterns.
Abstract: Radiation from a slotted-cylinder antenna coated with a homogeneous material is investigated. It is found that for some values of the coating thickness certain modes may resonate, which greatly enhance the radiated power and affect the shape of the radiation patterns.
TL;DR: In this paper, the beam-foil technique was used to study the OI-OV spectra between 1050 and 1800 A. Mean lives were obtained for 22 levels in OI OOV.
Abstract: Oxygen spectra between 1050 and 1800 A were studied by the beam–foil technique. Mean lives were obtained for 22 levels in OI–OV. Some amended mean lives from studies below 650 A are also given.
TL;DR: In this paper, the de Haas van Alphen effect was studied in very dilute copper-based alloys of Cr, Mn, Fe, and Co. The results indicated an antiferromagnetic interaction between conduction electrons and polarized impurity spins with very little Kondo screening.
Abstract: Modification of the Zeeman splitting of conduction-electron spins by an s–d exchange interaction has been studied in the de Haas – van Alphen effect at fields up to 50 kG and temperatures of order 1 K in very dilute copper-based alloys of Cr, Mn, Fe, and Co. In Cu(Cr) there is a linear relationship between an effective exchange energy and solute concentration, and the results indicate an antiferromagnetic interaction between conduction electrons and polarized impurity spins with very little Kondo screening. The effects of increasing field or decreasing temperature are consistent with a simple polarization of the impurity spins. The variation of the exchange energy from orbit to orbit is explained by the variation over the copper Fermi surface of the d-like part of the wave function. The occurrence of clean spin-splitting zeros in the Cu(Cr) system is believed to be a fortuitous result of a symmetrical positioning of the Friedel virtual bound states relative to the Fermi energy. In Cu(Mn) the exchange ener...
TL;DR: The magnitude and sign of the hyperfine field at the tin site in the Heusler alloys were measured by means of the Mossbauer effect and found to be + 200 ǫ as mentioned in this paper.
Abstract: The magnitude and sign of the hyperfine field at the tin site in the Heusler alloys Cu2MnSn, Ni2MnSn, and Pd2MnSn have been measured at 77 °K by means of the Mossbauer effect and found to be + 200 ...