bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Biquadratic Exchange Upon Ferromagnetic Two-Magnon Bound States. II. Anisotropic Exchange
Authors: Pink D. A. , Ballard R.
Published: April 2011

We have investigated the two-magnon bound state spectrum of a ferromagnetically ordered system for which the Hamiltonian contains an anisotropic bilinear exchange term, an anisotropic biquadratic exchange term, and a single-ion anisotropy term. The bound states, labelled by a wave vector q which we have taken to be in the [111] direction, were calculated by using zero-temperature Green functions. The principal results are: (i) the existence of single-ion bound states in the absence of single-ion anisotropy and conversely, their absence in the presence of such anisotropy, in contrast to the case in which the exchange interactions are isotropic; (ii) the appearance of an S mode for values of q, [Formula: see text]; (iii) the ordering of bound states for isotropic exchange interactions wherein the S0 mode lies below the S1-mode, D-mode pair and where the S1 mode lies below (above) the D mode if they lie below (above) the band, no longer holds.
Boundary Conditions Describing Surface Relaxation in Conduction Electron Spin Resonance
Authors: Menard M. R. , Walker M. B.
Published: April 2011

Boundary conditions on the magnetization density describing surface spin relaxation at an interface between two metals are derived. Applications to the determination of the resonance line shape for simple geometries are described; the results are suitable for interpreting experiments such as those performed by Janossy and Monod on aluminum foils coated with zinc.
Voltage Gradients in Turbulent Arcs
Authors: Shkarofsky I. P.
Published: April 2011

A plausible formulation is offered relating the changes in resistivity or average voltage gradient at high flow rates to the fluctuations in gas temperature and velocity. A four-fold increase with flow rate in voltage gradient as observed by Frind and Damsky in an argon arc can be accounted for by a 10 to 20% r.m.s. fluctuation in gas temperature. The increase also depends on the ratio of electron neutral collision frequency to the total collision frequency, and thus tends to become smaller as the gas becomes singly ionized. In transitions to higher order Z ionizations, the theory predicts that the average resistivity may be slightly increased, and then with a rise in temperature, it is decreased below its nonturbulence values.
Monte Carlo and Perturbation Calculations for a Triangular Well Fluid
Authors: Card Damon N. , Walkley John
Published: April 2011

Monte Carlo data have been generated for a simple model fluid consisting of hard spheres with an attractive triangular well potential. The ranges spanned by the temperature and density are as follows. [Formula: see text] and [Formula: see text]. The machine data have been compared to the modern perturbation theories of (i) Barker, Henderson, and Smith and (ii) Weeks, Chandler, and Andersen. Comparison with the machine data shows that the latter theory is successful in the high density region only, but over a wide range of temperature. The Barker–Henderson approach is best in the low density region but the use of the superposition approximation limits the utility of this theory at high densities.
Isoscalar Transition Densities of Isovector Excitations
Authors: Goulard B. , Deal T. J. , Fallieros S.
Published: April 2011

An energy-weighted sum rule is written down containing both isoscalar and isovector transition densities. As an application, a previously obtained expression for the isoscalar transition density of a dipole state is rederived.
Temperature Dependence of the Zero-Field Splitting of Cr3+ Ions in CsAl(SO4)2∙12H2O
Authors: MacKinnon John A. , Stevenson G.
Published: April 2011

The zero-field splitting of Cr3+ ions in CsAl(SO4)2∙12H2O was studied in the temperature range 4.2 to 300 K. The experimental spectrum is described with a spin Hamiltonian with S = 3/2 and g = 1.975 ± 0.005; the zero-field splitting parameter D changes with temperature having a value of −0.074 ± 0.0003 cm−1 at room temperature and a value of −0.070 ± 0.0003 cm−1 at liquid helium temperature.
Further Evidence of Isospin Splitting in the Giant Resonance of 11B
Authors: Bianco W. Del , Boucher P. , Kundu S. , Rouben B.
Published: April 2011

The 90° differential cross section of the 9Be(d, γ0)11B reaction has been measured at deuteron energies from 3 to 12 MeV. The results of this experiment are consistent with a recent calculation of the dipole states of mass 11 nuclei, and with measurements of the 11B(γ, nγ′) and 11B(γ, pγ′) processes, and confirm the isospin splitting of the giant resonance in 11B.
The Mass Excesses of 91Tc and 90Tc
Authors: Iafigliola R. , Gujrathi S. C. , Tracy B. L. , Lee J. K. P.
Published: April 2011

The isotopes 91Tc and 90Tc have been identified by β- and γ-ray spectroscopy. The 91Tc ground state decays with a half-life of 3.12 ± 0.05 min, and has been assigned a Jπ of 9/2+. Two isomers in 90Tc with half-lives of 7.9 ± 0.2 s and 50 ± 2 s have been identified for the first time. The Jπ for the 7.9 s isomer has been deduced as 1+. The mass excess for 91Tc has been determined to be −76.0 ± 0.2 MeV, and the mass excess corresponding to the 7.9 s isomer in 90Tc has been determined to be −71.2 ±.2 eV.
Determination of Positronium – Atom Collision Cross Section
Authors: Spektor D. M. , Paul D. A. L.
Published: April 2011

We have determined the collision cross section of positronium in He, Ne, Ar, Kr, Xe, N2, and isobutane gases at thermal energies by studying the diffusion of positronium to the walls of a specially designed chamber. The time distribution of annihilations is measured as a function of pressure for each gas. The presence of an admixture of 20 Torr of isobutane in the chamber quenches the free positron component so that the orthopositronium component is the only exponential decay in the time spectrum of annihilations. Diffusion theory is used to obtain theoretical values of the orthopositronium decay constant λ2. These values are a function of three parameters, two of which are common to all results; the third one is σc, the collision cross section. Monte Carlo simulations of the isobutane experiments verify the theoretical results and determine the wall annihilation parameter which is common to all experiments. The Monte Carlo calculations also enable the determination of the second parameter common to all the experiments, which occurs in a correction term in the diffusion theory. The entire analysis has been carried out twice, one in each of the following extreme cases: (1) assuming that no triplet to singlet conversion takes place at the walls of the cells, and (2) assuming that the maximum conversion takes place at the walls.The cross sections in case (1) are, in units of πa02: He, 0.0166 ± 0.0017; Ne, 0.042 ± 0.003; Ar, 0.086 ± 0.005; Kr, 0.099 ± 0.006; Xe, 0.128 ± 0.008; N2, 0.238 ± 0.014; and isobutane, 0.534 ± 0.016. The implications for other types of experiment and theory are briefly discussed, in particular the bubble model for positronium in liquids.
Microwave Absorption and Relaxation Behavior of Some Simple Ketones in Dilute Solutions
Authors: Madan M. P.
Published: April 2011

The dielectric absorption of solutions of 2-hexanone, 4- and 5-nonanone, and 2-decanone has been examined in the microwave region over a range of temperatures in n-heptane, cyclohexane, and benzene. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The values of relaxation time are in reasonable agreement at the temperature at which there are available known data. Both the relaxation behavior and the thermodynamic processes are discussed and, where possible, compared with corresponding results of the other workers.
On Nonlinear Equations Amenable to the Inverse Scattering Method
Authors: Kingston J. G. , Rogers C.
Published: April 2011

The inverse scattering method can be used to solve the initial value problem for various nonlinear evolution equations of physical importance. Here an extensive class of equations for which the technique is available is delimited.
Complete Line Shape for the Impact, Static, and the Intermediate Regions
Authors: Srivastava R. P. , Zaidi H. R.
Published: April 2011

Line shapes are calculated for the resonance broadening of an excited level through the dipole–dipole interaction. The calculations are based on two main approximations: (1) two body collisions and (2) straight classical path for the translational motion. The results are valid over the complete region extending from the impact to the static regimes. It is shown that, under suitable conditions, the incomplete collisions can give rise to (a) a splitting of the line at the center and (b) nonlinear density dependence of the line width.
True Nuclear Magnetic Shielding Constants for Members of Isoelectronic Series with 3 to 10 Electrons
Authors: Mehrotra I. , Saxena K. M. S.
Published: April 2011

True values of the nuclear magnetic shielding constants are evaluated from approximate Hartree–Fock values for members of isoelectronic series with 3 to 10 electrons after making estimates of corrections due to the correlation effect. It is found that the correlation corrections are quite small and in certain cases their values turn out to be negative.
The Decay of 95Rh to Levels of 95Ru
Authors: Weiffenbach C. , Gujrathi S. C. , Lee J. K. P.
Published: April 2011

The decay of 95Rhg (T1/2 = 5.02 ± 0.10 min) and 95Rhm (T1/2 = 1.96 ± 0.04 min) have been studied using Ge(Li) detectors and a plastic β detector. A 543.3 ± 0.3 keV isomeric transition has been identified. Gamma–gamma and gamma–beta coincidence experiments were performed. From the β endpoint energy measurement, the mass excess of 95Rh was determined to be −78.34 ± 0.15 MeV. Decay schemes for the 95Rhg,m are proposed.
The Decay of 8.0 Min 74Ga
Authors: Taylor H. W. , Schulte R. L. , Tivin P. J. , Ing H.
Published: April 2011

74Ga was produced through the 74Ge(n,p)74Ga reaction using 94.48% enriched 74Ge. The cross section for the reaction and the half-life of 74Ga were measured. The energies and intensities of the γ rays emitted by 74Ga were measured using Ge(Li) spectrometers. A revised level scheme for 74Ge was deduced.
The (3He,d) Reaction on 69Ga
Authors: Labrie J. P. , Habib E. E. , Preibisz Z.
Published: April 2011

Excited levels of 70Ge and proton holes in 69Ga have been investigated by means of the 69Ga (3He, d)70Ge reaction at an incident beam energy of 22.5 MeV. Angular distributions were measured and are compared with the prediction of the distorted-wave-Born-approximation (DWBA) theory in order to obtain the spectroscopic strengths of each level.The number of proton holes in 69Ga was obtained from the sum rule of the spectroscopic strengths. The vacancy probability UJ2 and the center of gravity energy EJ for the 2p3/2, 1f5/2, and 2p1/2 subshells are[Formula: see text]These are compared with the pairing model calculations.
On Hanle Effects in the B(3Σu−)–X(3Σg−) Band System of the Se2 Molecule
Authors: Dalby F. W. , Vigué J. , Lehmann J. C.
Published: April 2011

Magnetic field level crossing has been studied for the excited states of 80Se2 produced by absorption of the 4880, 4765, and 4727 Å lines of an argon laser. The product of the radiative lifetime and the Lande g factor, gτ, together with the sign of the g factor, has been determined for each of the levels. An identification of the previously unobserved transition produced by 4727 Å excitation is presented.
Field Dependent Susceptibility and Localized Spin Fluctuations in PdRhNi Alloys
Authors: Cochrane R. W. , Hedgcock F. T. , Tidman J. P. , Zuckermann M. J.
Published: April 2011

Low temperature magnetization measurements in magnetic fields up to 55 kOe are reported for a series of PdRhNi alloys containing 1 to 7 at.% Rh and up to 1 at.% Ni. These data indicate a critical Ni concentration for ferromagnetism close to 2 at.%. Comparison of the field and concentration dependence of the susceptibility to the magnetoresistance data of Purwins et al. reveals that the coefficient of the T2 local spin fluctuation resistivity scales directly with the nickel susceptibility. Experimentally, the scaling parameter varies only slightly with Rh concentration, a result which extends to the binary PdNi alloys.
Diffraction of Electrons by Two and Three Mutually Orthogonal Standing Light Waves
Authors: Ehlotzky F.
Published: April 2011

The one-dimensional problem of electron scattering by a standing light wave, known as the Kapitza–Dirac effect, is shown to be easily extendable to two and three dimensions, thus showing all characteristics of diffraction of electrons by simple two- and three-dimensional rectangular lattices.
g Tensors and Tensor Interactions: Their Effect on Conduction Electron Spin Resonance. II
Authors: Walker M. B.
Published: April 2011

The spin–orbit coupling contribution to the electron–phonon matrix element is shown to give rise to a tensor interaction between electron quasi-particles. These tensor interactions and a conduction electron g tensor are incorporated into the framework of the Landau theory of Fermi liquids, and detailed calculations of the conduction electron spin resonance frequency and the transverse and longitudinal relaxation times are carried out, thereby extending previous work by the author. Tensor interactions are shown to be capable of qualitatively explaining results such as those obtained by Lubzens, Shanabarger, and Schultz. A possible qualitative explanation is given of the anisotropy observed by Shanabarger in the line width of silver. Finally, experiments to measure T1 are suggested, since they can distinguish between models making use of a scalar momentum dependent g and the models of the present paper in which a g tensor and tensor interactions are assumed.
Theoretical Oscillator Strengths for nP → nD Transitions in Mg
Authors: Fischer Charlotte Froese
Published: April 2011

Theoretical oscillator strengths for the transitions 3s np1,3P → 3s md1,3D of Mg are reported for n = 3,4, … and m = 3,4,…The results are based on an MCHF approximation to the total wave function which includes the correlation of the outer two electrons.
Coulomb Effect on the Proton–Proton Low Energy Scattering Parameters
Authors: Kermode M. W. , Nogami Y. , Dijk W. van
Published: April 2011

The effect of the Coulomb force on low energy proton–proton scattering is examined when the nuclear interaction is represented by a rank one separable potential of Tabakin's type. The scattering length which is obtained by switching off the Coulomb force is found to be −20.0 F. This value is appreciably different from those for local realistic potentials. This anomaly is similar to the one which was recently found by Sauer.
Ionic and Gamma-ray Induced Photoconductivity of MgO
Authors: Lynch G. F.
Published: April 2011

The d.c. electrical conductivity of MgO has been measured, both in the presence and in the absence of an intense γ-ray field, in the temperature range 300 to 600 K. Outside the radiation environment, the conductivity is attributed to the migration of positive ion vacancies, with an activation energy of 1.50 eV. The magnitude of the conductivity is much larger than would be expected from the normal vacancy concentration and this is explained by extra magnesium vacancies acting as charge compensators for trivalent transition metal ion impurities. In the γ-ray radiation field of a 60Co source the observed photoconductivity is described by a trapping model, with levels at 0.04,0.55, and 1.35 eV below the conduction band. The γ-ray induced conductivity is consistent with a linear dependence on the radiation dose rate up to 4.0 × 105 rad/h(H2O).
Low Lying Multiplets in the Spectra of Cu V and Cu VI
Authors: VanKleef Th. A. M. , Joshi Y. N. , Benschop H.
Published: April 2011

The spectrum of copper has been observed on 10.7 m normal incidence and 10.7 m grazing incidence spectrographs at the National Bureau of Standards, Washington, D.C., using a sliding spark source. In Cu V the ground state multiplet 3d74F and the low lying multiplets 3d6(5D)4p6P0, 4F0, and 4D0 have been determined. In Cu VI the ground state multiplet 3d65D and the low lying multiplets 3d5(6S)4p5P0, 3d5(4P)4p5P0, and 3d5(4D)4p5D0 have been determined. Twenty-three lines have been classified in Cu V and 29 lines have been classified in Cu VI. Predictions for the intervals in the ground state multiplets 3d74F in the spectra of Zn VI and Ga VII and 3d65D in the spectra of Zn VII and Ga VIII are given.
The Ultraviolet Emission Spectra of OH+ and OD+. Rotational Structure and Perturbations in the A3Πi–X3Σ− Transition
Authors: Merer A. J. , Malm D. N. , Martin R. W. , Horani M. , Rostas J.
Published: April 2011

The A3Πi–X3Σ− emission systems of OH+ and OD+ have been reinvestigated in detail. Fourteen bands have been analyzed (of which seven are new), and accurate rotational constants have been obtained for the levels ν = 0–2 in the two states of OH+ and ν = 0–3 in the two states of OD+. Corrected assignments are given for the low J lines in the bands of OH+ (which are important in astrophysical spectra, such as those of H2O containing comets).The perturbations in the A3Π states of both isotopes have been studied quantitatively, and the erratic Λ doubling explained in detail. The position of the perturbing b1Σ+ state has been determined to within a few cm−1, and minor perturbations by the A1Δ state have been characterized. Values of the spin–orbit coupling constant, A, and the spin–spin interaction parameter, α, have been extracted from the data for OD+A3Π ν = 0.
Electron–Phonon Interactions in an Insulator
Authors: Dunn Dennis
Published: April 2011

A new technique is presented for evaluating the electron Green function Gk(t) in an insulating electron–phonon system. The technique is particularly suitable for those electron–phonon interactions in which the long wavelength phonons are of prime importance such as the polaron and piezoelectric interactions.An exact formal expression is obtained for the time and temperature dependent Green function in the form[Formula: see text]where S is a functional of the differential operator d/dk. The Green function is then expressed as [Formula: see text], and from the exact result a series expansion is derived for the action function Ak(t).This series expansion has a very special property: to whatever order Ak(t) is evaluated the resulting expression for Gk(t) includes, in some way, every perturbation theory diagram. By this we mean that as in conventional techniques (the Hartree–Fock approximation, for example) an infinite subset of diagrams are summed exactly and in contrast to these techniques the remaining infinity of diagrams are not discarded but are evaluated approximately.The technique is applied to the polaron interaction.
Triplet and Higher Correlations in the Long Wavelength Limit
Authors: Ballentine L. E. , Lakshmi A.
Published: April 2011

The nth order structure function of a liquid, defined as the ensemble average of a product of n Fourier components of the atomic density, is studied in the limit of long wavelength for one or more Fourier components. It is shown by means of fluctuation theory that these limits are simply related to lower order structure functions and their derivatives with respect to pressure, and that they will be small in magnitude for normal liquids. This conclusion is important for the study of electronic properties of liquid metals because the screened ionic potential is always large in the long wavelength limit. Thus large spurious contributions may be obtained from the use of approximate structure functions that do not satisfy the correct long wavelength limits. In this respect the Kirkwood superposition approximation is very unsatisfactory.
Transition A2Σ+–X2 Π des molécules P16O et P18O. Perturbations de l'état A2Σ+
Authors: Coquart B. , Paz M. Da , Prudhomme J. C.
Published: April 2011

New emission bands of the A2Σ+–X2 Π system of the P16O molecule have been analyzed and this transition for P18O has been studied for the first time, with a mean dispersion of 0.30 Å/mm. The levels 0, 1, 2, 3, 4, 5, and 6 of the A2Σ+ state for P16O and the levels 0, 1, 2, 3, and 4 of this state for P18O show perturbations from various species, some of which, studied previously for P16O, are attributable to a 4Σ− state and to the C2Σ− state. A vibrational quantification of the 4Σ− state is tried.
New Results on the B2Σ+, b4Σ−, and X2Π States of PO
Authors: Verma R. D. , Singhal S. R.
Published: April 2011

An extensive study of the β system of the PO molecule has been carried out. The rotational analysis of 23 bands has yielded the constants of the ν = 0–9 levels of the B2Σ+ state and of the ν = 0–11 levels of the X2Π state with a precision higher than previous measurements. The spin coupling constant, Aν, evaluated for the 12 levels of X2Π is found to follow the equation Aν = 224.03 + 0.18ν–0.013ν2. The perturbations observed in the B2Σ (ν = 6 and 7) levels have been interpreted as being caused by a 4Σ− state and the B′2Π state. A deperturbation calculation has been carried out to evaluate the molecular constants of the PO molecule in the 4Σ− state. Several new bands were also observed; some of these belong to the β and B′–X systems and others are left unassigned.
Quantum Number Dependence of the Spin–Orbit Coupling in the X2Π State of PO
Authors: Zaidi H. R. , Verma R. D.
Published: April 2011

Expressions are derived for the spin–orbit coupling constant, AvJ, for an isolated 2Π state of a diatomic molecule. These results are applied to the X2Π states of PO. Comparison with the available experimental results allows a determination of the first three derivatives of the coupling parameter at the equilibrium position. It is found that the second derivative gives the largest contribution, thus invalidating a common assumption of the existing theories.
Study of the Intermolecular Potentials for Hydrogen–Noble Gas Pairs via Molecular Beam Differential Scattering Measurements
Authors: Bickes Jr. R. W. , Scoles G. , Smith K. M.
Published: April 2011

Differential collision cross sections for H2–noble gas pairs have been measured and analyzed via a best fit procedure. The data are well described by Lennard–Jones (12,6) (LJ) and Buckingham–Corner (BC) potentials and yield model independent values for σ, the location of the zero of the potential. For H2–Ne, H2–Ar, and H2–Kr, σ values are respectively 2.85, 3.07, and 3.21 Å, with uncertainties [Formula: see text].
Pressure Dependence of Positron Annihilation in Alkali Metals
Authors: Kubica P. , Stott M. J.
Published: April 2011

The observed pressure dependence of the total positron annihilation rates in alkali metals has been studied. The observation that the rates increase more rapidly with pressure than the estimated valence annihilation rates alone has been explained in terms of increased positron penetration into the ion cores. This picture is shown to be consistent with observed changes with pressure in angular correlation data for Na.
Experimental Determination of Absolute A Coefficients for 'Forbidden' Atomic Oxygen Lines
Authors: Kernahan J. A. , Pang P. H-L.
Published: April 2011

We have obtained the transition probabilities of the 5577 Å, and 6300 Å lines of [OI] by simultaneously measuring the absolute intensity and the population of the upper state of each line in an inert gas–oxygen discharge. Further, we have obtained A values for the 2972 Å and 6364 Å lines by measuring relative intensities of lines from the 1S0 and 1D2 levels.
de Haas–van Alphen Effect in Antimony–Tellurium Alloys
Authors: Altounian Z. , Datars W. R.
Published: April 2011

The de Haas–van Alphen frequencies, cyclotron masses, and Dingle temperatures of antimony–tellurium alloys with up to 0.11 at. % Te were measured using the low frequency field modulation technique. The hole and electron frequencies decreased and increased respectively, as predicted by the rigid band model. At the highest concentration, the increase is about 25% that of pure Sb and the decrease is about 20%. The cyclotron masses of electrons and holes changed with concentration. This dependence resulted from the nonparabolicity of the Sb bands. Estimates of the Fermi surface volume of the alloys indicated that each Te atom contributes one electron to the alloy. The present results are compared with previous de Haas–van Alphen results on antimony–tin alloys.
The Visible Absorption Spectrum of Diatomic Calcium
Authors: Balfour Walter J. , Whitlock Rodger F.
Published: April 2011

The electronic spectrum of calcium vapor has been photographed in absorption from 460 to 600 nm. A many line spectrum due to Ca2 has been identified from vibrational and rotational analyses and a total of 3800 lines involving 47 bands in the A1Σu+ ← X1Σg+ system of 40Ca2 have been assigned. Analysis shows that the X1Σg+ state is weakly bound with a dissociation energy De″ = 1075 ± 150 cm−1. The A1Σu+ state is considerably more stable. Term values, Dunham coefficients, and RKR potential energy curves have been determined for both electronic states, and Franck–Condon factors, with their dependence on rotation, have been evaluated. The more important constants for the ground state are ωe″ = 64.93 cm−1, ωexe″ = 1.07 cm−1, re″ = 0.4277 nm and those of the upper state are, [Formula: see text], [Formula: see text].Le spectre électronique de la vapeur de calcium a été photographié en absorption, de 460 à 600 nm. Un spectre de plusieurs raies provenant de Ca2 a été identifié à partir des analyses vibrationnelle et rotationnelle; on a déterminé les transitions correspondant à un total de 3800 raies appartenant à 47 bandes du système A1Σu+ ← X1Σg+ de 40Ca2. L'analyse montre que l'état X1Σg+ est faiblement lié, avec une énergie de dissociation
The Spectrum of Doubly Ionized Silver: Ag III
Authors: Benschop H. , Joshi Y. N. , VanKleef Th. A. M.
Published: April 2011

The spectrum of silver has been observed in the range 400–2300 Å using a variety of spectrographs including the 10.7 m normal incidence vacuum spectrograph at the NBS Laboratory in Washington, D.C. Two levels, 4d85s4P1/2 and 4d85s4P1/2, established earlier have been rejected. All the eight missing levels in the 4d85s and 4d85p configurations have been established. The agreement between the observed and the calculated values of the energy levels is very good. Seventy-nine additional lines have been classified in the Ag III spectrum.
Spatial Characteristics of Auroral Brightness Fluctuation Spectra
Authors: Pemberton E. V. , Shepherd G. G.
Published: April 2011

Observed fluctuations in auroral brightness are reported for the frequency band 0.05 < ƒ < 15 Hz from a site at 60.7° invariant latitude. Four clearly distinct frequency bands were found to exist: at 7 and 2.4 s period, and at 3 and 10 Hz. The spatial distribution of the fluctuations was studied; it is several hundred km in longitudinal extent, narrow in the evening in latitudinal extent but broadening to perhaps 200 km in the early morning, homogeneous and stationary in the sky, equatorward of discrete quiet auroral forms, and strongly responsive to the level of geomagnetic disturbance. The relationship of this fluctuating region to the recently discovered diffuse auroral belt, and the region of hard drizzle precipitation observed by a number of workers is described and discussed. The pulsation mechanism described by Coroniti and Kennel seems very plausible for the 7 and 2.4 s period pulsations.
Méthode du moment angulaire inversé. Partie I : La théorie MI
Authors: Féménias J-L. , Athénour C.
Published: April 2011

In order to present a general method of calculating wave functions, matrix elements, and intensity factors in molecular rotational problems, we deal here with a theory of reversed angular momentum (MI theory), i.e. momentum whose components obey commutation relations with an anomalous minus sign. This theory is built following the principal corresponding steps of the normal theory and a simple correspondence is established between both of them allowing us to perform calculations in the former and to give the results using the formalism of the latter.In particular we dwell here on the consistency of conventions and notations and on a rigorous presentation of spherical tensor operators in MI theory together with the choice of the optimal set of them leading to simplest calculations.
The Radius of the Coulomb Hole
Authors: Boyd Russell J.
Published: April 2011

The radius of the Coulomb hole in an atom or molecule is discussed in general terms and illustrated in detail for the ground state of the helium isoelectronic sequence. The calculations demonstrate a general tendency for the radius of the Coulomb hole to increase as a function of the distance of the reference electron from the nucleus and the existence of a nonzero lower limit (0.800 a.u. in He and 0.111 a.u. in Mg10+) for the radius of the Coulomb hole. This limit is slightly larger than the radial distance at which the radial density distribution reaches its maximum. By expressing the correlation energy of an atom in terms of certain one and two electron expectation values, the relationship between the correlation energy and the size and shape of the Coulomb hole is discussed. Detailed comparisons for the ground and 23S states of He are used to demonstrate the relationship.
Decay Instability of the Ion Acoustic Wave
Authors: Seshadri S. R.
Published: April 2011

The parametric excitation of the longitudinal, plasma mode and the transverse, electromagnetic mode in a warm, uniform plasma is investigated for the case in which the pump wave is another electromagnetic mode. The three interacting waves are assumed to propagate in the same direction. The longitudinal mode has two branches, namely, the electron plasma mode and the ion plasma mode. The parametric coupling of the longitudinal and the transverse waves in the presence of the pump wave leads to instabilities of the interacting waves. Illustrative numerical results are presented for the parametric instabilities of the electron plasma oscillation which is a part of the electron plasma mode and those of the ion acoustic waves and the ion plasma oscillations which are parts of the ion plasma mode. The ion acoustic wave is efficiently excited when the pump and the idler wave frequencies are approximately equal to one and a half times the electron plasma frequency.
Monte Carlo Calculations of the Diffusion of Ultra Cold Neutrons
Authors: Winfield D. , Robson J. M.
Published: April 2011

The intensity of ultra cold neutrons transmitted along a copper tube has been calculated by Monte Carlo techniques and compared with experimental intensities and with pure diffusion theory calculations. The possibility of focussing ultra cold neutrons by using a conical tube is also illustrated by this technique.
Quantum Mechanical Calculations for the Electron Impact Broadening and Shift of the Line 43s → 23p of Helium in a Hot Plasma
Authors: Bassalo J. M. , Yamamoto Y. , Cattani M.
Published: April 2011

In this paper we apply the quantum mechanical formalism developed by Bassalo and Cattani to calculate the broadening and shift produced by electronic collisions of the43s → 23p line of helium in a plasma. The effect of the ions is also taken into account. Our theoretical predictions are compared with the experimental results of Bötticher et al. and with the semiclassical estimates of Griem et al.
Second Spectrum of Silver: Ag II
Authors: Benschop H. , Joshi Y. N. , Vankleef Th. A. M.
Published: April 2011

The spectrum of silver has been observed in the range 400 Å – 2300 Å using the spectrographs at the Zeeman Laboratory in Amsterdam, at the N.B.S. Laboratory in Washington, and at the St. Francis Xavier University Physics Laboratory in Antigonish. On the basis of the improved measurements Ag II analysis has been confirmed. 4d8 5s21S0 and 4d9 9s3,1D levels have been established. 4d9 6p3p20 has been revised.In the Ag II spectrum 64 additional lines have been classified. Configuration calculations have been made. The parameter values are given. The agreement between the observed and the calculated values of the energy levels is good.
Gas Phase Spin Relaxation of ZX3Y Molecules in the Dipolar Approximation
Authors: Sanctuary B. C. , Snider R. F.
Published: April 2011

The gas kinetic theory of nuclear magnetic relaxation of a polyatomic gas, as formulated in the previous paper, is evaluated for ZX3Y molecules relaxing via a dipolar coupling Hamiltonian. Stress is given to a proper treatment of point group symmetry, here C3v, and the possibility of molecular inversion is included. The detailed formula for the spin traces is however restricted to X nuclei with spin 1/2. A subsequent paper uses these results to elucidate the structure of the high density dependence of T1 forCF3H.
Theoretical Analysis of Transient Stimulated Concentration Scattering in a Binary Mixture of Nonabsorbing Gases
Authors: Rangnekar S. S. , Enns R. H.
Published: April 2011

A small signal, small amplification calculation of the transient gain relevant to the stimulated concentration scattering of a laser beam in a binary mixture of nonabsorbing gases is presented. The results are applied to the He–Xe mixture with Xe at a partial pressure of 40 atm and varying He concentrations, and experimentally observable features of the transient gain are predicted.
Ionisation dissociative de N2
Authors: Wankenne H. , Bolduc E. , Marmet P.
Published: April 2011

Clearly resolved structures are observed in the appearance efficiency curve of N+ ions produced by the impact of monoenergetic electrons on N2. The observed structures between 24.3 and 25 eV are attributed to N+ ions arising from predissociation of the N2+ C2Σu+ state. Between 25 and 29.5 eV some new structures are reported. N+ ions resulting from collision induced dissociation of N2+ also appear in an energy region lower than the first N2+ limit. The structures observed in this energy range are attributed to autoionizing Rydberg states of N2.
The Vacuum Ultraviolet Spectrum of ICI
Authors: Venkateswarlu Putcha
Published: April 2011

The absorption spectrum of iodine chloride has been photographed in the high orders of a 10.7 m concave grating spectrograph in the region 1900–1220 Å. A number of band systems which correspond to Rydberg transitions have been obtained. In addition an extensive band system with closely spaced bands degraded to longer wavelengths has been observed in the region 1660–1580 Å. Among the Rydberg systems, 12 series have been found to converge to 81 362 ± 80 cm−1 which very likely represents the ionization potential of the molecule leading to the 2Π3/2 state of the molecular ion. They are due to transitions from the ground state to states arising from the configurations (σ2π4π32Π3/2)ns σ, (2Π3/2)np σ, (2Π3/2)np π, (2Π3/2)nd σ, (2Π3/2)nd π, (2Π3/2)nd δ, (2Π3/2)nf σ, (2Π3/2)nf π, and (2Π3/2)nf δ where n takes the running values 6, 7, 8, … for the first three configurations, 5, 6, 7, … for the next three configurations, and 4, 5, 6, … for the last three configurations. The first few numbers of 11 similar series corresponding to the transitions to the states involving the (σ2π4π32Π1/2) core have been identified and the ionization of these series is estimated to be at 85 996 ± 80 cm−1.
Electron Paramagnetic Resonance of Ti3+ Ions in KAl(SO4)2∙12H2O
Authors: MacKinnon John A. , Shannon M.
Published: April 2011

The paramagnetic resonance spectrum of Ti3+ ions in potassium alum (KAl(SO4)2∙12H2O) single crystals has been studied in the {100} planes at 4.2 K with an X band microwave spectrometer. The spectrum is an analogue of that reported by Dionne for Ti3+ ions in rubidium alum (RbAl(SO4)2∙12H2O) and by MacKinnon and Dionne for Ti3+ ions in the thallium alum (TlAl(SO4)2∙12H2O). The spectrum was explained with a model of 12 magnetic complexes, the complexes being related to each other through the symmetry elements of the [Formula: see text] point group of the alum lattice. The three g factors for the spin Hamiltonian with S = 1/2 were found to be 1.979, 1.898, and 1.828, with an accuracy of ±0.005.
Effective Oscillator Strengths of Neon from Electron Impact Excitation
Authors: Roy D. , Carette J.-D.
Published: April 2011

From experimental data about relative excitation cross sections of many electronic states of neon, the effective oscillator strengths of these transitions have been computed. There is a good agreement between these results and the single available value of optical oscillator strength.
Magnetic Properties of the Random Mixture of the Classical Heisenberg Spins
Authors: Katsura Shigetoshi
Published: April 2011

The specific heat, the susceptibility, and the correlation function at zero field above the critical temperature of the random mixture (quenched site and bond problems) of the classical Heisenberg spins with nearest neighbor interaction were obtained exactly for the linear chain and for an infinite Bethe lattice (Bethe approximation of the two and three dimensional lattices) above the critical temperature. The results are simply expressed by the replacements of 2 cosh K → 4π (sinh K)/K and tanh K → L(K) (L(K) = Langevin function) for K = KAA, KAB, KBA, and KBB in the corresponding expressions of the random mixture of the Ising spins, and qualitative properties of both models are similar.
Study of 18O States by the 17O(d,p)18O Reaction
Authors: Drain D. , Chambon B. , Vidal J. L. , Dauchy A. , Beaumevieille H.
Published: April 2011

The 17O(d,p)18O reaction was studied at Ed = 3.6 and 4.0 MeV. Absolute differential cross sections were measured for the ground state and the 1.98, 3.55, 3.63, 3.91, 4.45, 5.09, 5.25, and 5.37 MeV states in 18O. The experimental data are analyzed using the DWBA and Hauser–Feshbach theoreies and spectroscopic factors are deduced. These results are compared to previous data and shell model calculations. The correspondence between the above states and their analogue states in 18F is discussed.
Mixed Positive Parity States in 165Er
Authors: Stott W. R. , Waddington J. C. , Burke D. G. , Løvhøiden G.
Published: April 2011

Positive parity states in 165Er have been studied using the 167Er(p,t)165Er reaction. Two 7/2+ states at excitation energies of 63 and 465 keV were populated via l = 0 transitions. Because of the lack of a pronounced minimum in the l = 0 angular distributions, some l ≠ 0 strength may contribute to the population processes. Eight l ≠ 0 transitions were seen below 1 MeV excitation energy. A description of the observed positive parity levels has been attempted in the context of a Coriolis coupled Nilsson model calculation.
Swirling Flows of a Gas with Tangent Equation of State
Authors: Smith A. C. , Chandna O. P.
Published: April 2011

An example is given of plane steady swirling flow of a gas with tangent equation of state and streamlines which are the involutes of an arbitrary closed convex sectionally smooth curve.
Ondes de surface dans les cristaux liquides smectiques et cholestériques
Authors: Rapini Albert
Published: April 2011

Theoretical predictions are given concerning the spectrum of the free surface fluctuation modes in liquid crystals such as smectics and cholesterics. We find drastic differences with simple liquids and nematic liquid crystals. These differences came from two new properties: the elastic energy associated with the layered structure and the permeation, that is the diffusion process of the fluid through the layers.
A Simple Iteration for Shock Wave Calculations with the Enthalpy Coefficient
Authors: Ahlborn Boye
Published: April 2011

The enthalpy coefficient g = h/u can be used to separate the thermodynamical and the hydrodynamical aspects of shock and other step waves in partially ionized gases, providing a simple recursion formalism for the exact calculation of the equilibrium end parameters of such waves.
Crossfield Magnetosonic Two Stream Instability
Authors: Cipolla Jr. J. W. , Golden K. I.
Published: April 2011

In this article, a detailed analysis was made on the plasma magnetosonic instabilites whose propagation is perpendicular to the magnetic field and whose two streams cross the magnetic field during the time of development of the instability.We have also studied the role of the magnetosonic instabilities in the structure of perpendicular shock waves. Since these instabilities are not stationary in the shock interior, one can ultimately deduce that they do not play a principal role in the structure.
Some Aspects of the Theory of Passive Rubidium Frequency Standards
Authors: Missout Gilles , Vanier Jacques
Published: April 2011

This paper gives a theory of the signal strength in rubidium vapor frequency standards for various situations encountered in practice. The density matrix formalism is used and the signal strength is given as a function of light intensity, rubidium density, absorption cell length, and applied microwave power. The results obtained are found to be in good agreement with published data.A theory is also developed giving the strength and the phase of the signal as a function of the modulation frequency and of the frequency excursion amplitude. This theory uses a model of a simple harmonic oscillator. The results are similar to those obtained by previous authors using a more complex model.
Electron Impact Ionization Cross Sections of N2 and O2
Authors: Chandra Suresh , Narain Udit
Published: April 2011

The ionization cross sections of N2 and O2 have been calculated in the energy range from threshold to 20 keV using a modified approach. The results are in good agreement with the available experimental data.
Effect of Magnetic Breakdown on the Magnetoconductivity of Cadmium
Authors: Douglas R. J. , Datars W. R.
Published: April 2011

The magnetoconductivity and magnetoresistivity tensors of cadmium have been calculated by the path integral method for magnetic fields in the [Formula: see text] and [Formula: see text] directions. A uniform relaxation time and a modified nearly free electron Fermi surface were used. Magnetic breakdown across the HAL spin–orbit energy gap vitiated Kohler's rule and necessitated separate calculations for different relaxation times. Even with open orbits, cadmium was found to be a 'compensated' metal in that the Hall terms never dominated the conductivity tensor determinant. A single breakdown field was found to be inadequate to describe magnetic breakdown on the sheaf of orbits which touch the HAL plane. A range of breakdown fields was calculated across the sheaf of open orbits. From an explanation of induced torque data, it was found that the ratio of the spin–orbit energy gap in the HAL plane to the Fermi velocity is 1.4 × 10−8 eV s cm−1. The resulting field dependences of the magnetoconductivity and magnetoresistivity tensor components are presented and discussed. The use of the path integral technique when there is magnetic breakdown is also presented.
Field Transforms for Multilayered Cylindrical and Spherical Structures of Finite Conductivity
Authors: Bahar E.
Published: April 2011

Problems of propagation around multilayered cylindrical or spherical structures possessing highly conducting cores have been analyzed in terms of discrete sets of modes. However, when propagation through the core of the structure is significant and of particular interest, the discrete set of modes is not suitable for the complete expansion of the electromagnetic fields.To provide a suitable basis for the expansion of the electromagnetic field in nonuniform multilayered, cylindrical or spheroidal, dielectric structures we derive expressions for the electric and magnetic field transforms consisting of both a discrete and a continuous spectrum of waves. The relationship between these transforms, the Kontorowich–Lebedev transform, and the discrete Watson transform is discussed. When the radius of curvature of the structure is infinite these transforms merge with generalized Fourier type transforms.The transforms can be used to investigate electromagnetic propagation through irregularly shaped dielectric wave guides, and through irregularly shaped spheroids. It can also be used to solve the problem of propagation in the interior (concave side) of irregularly shaped conducting cylinders or spheroids.
Interband Effects in the Coherent Potential Approximation: Simple Two Band Model
Authors: Glasser M. L. , Sievert P. R.
Published: April 2011

The CPA is applied to a two band separable pseudopotential model for a hot binary liquid alloy. The variation of the band gap with concentration is strictly linear, but the band broadening is found to be asymmetric about C = 50% and to depend in a complicated way on interband interaction.
Quadrupolar Relaxation of X Type Nuclei in R2MX6 and RMX3 Compounds
Authors: Driel Henry M. van , Armstrong Robin L.
Published: April 2011

Calculations of nuclear quadrupolar spin–lattice relaxation times are presented. The expressions obtained for the first order Raman and anharmonic Raman processes are applicable to a pure nuclear quadrupole resonance investigation of the X nuclei in R2MX6 and RMX3 solids. On the basis of realistic assumptions it is shown that the anharmonic Raman process will provide the dominant relaxation mechanism for these nuclei in these compounds. The relation between the spin–lattice relaxation time and the lattice dynamics is obtained explicitly without recourse to an assumed form of lattice vibrational normal mode spectrum. In favorable cases it is shown that the spin–lattice relaxation times can be related to Brillouin zone averaged rotary mode frequencies which are useful for the analysis of experimental data.
Combinatorial Solution of the Free Fermion Model
Authors: Wiegel F. W.
Published: April 2011

It is shown that the free fermion model can be solved by means of a combinatorial method which is tantamount to counting free random walks.
A Simple Analytic Method for Interpreting the Selfoc® Rod Interferograms of Rawson and Murray
Authors: Bélanger P. A.
Published: April 2011

The mathematical analysis in analytic form has been achieved for the Selfoc® rod interferograms of Rawson and Murray by supposing a radial distribution of the dielectric constant in the form ε(r) = ε 0[1 − β2 tanh2 (αr/β)]. For small incidence angles (γ0 < 10°), a simple equation is obtained for the value of the coefficients α and C4 of the dielectric constant from the position of the first zeros in the interferogram. It is also shown that when an exactly focusing length of optical rod or fiber is used, the position of the zeros varies as the fourth root of the odd numbers.
Dispersion Characteristics of the Dipolar Modes in a Wave Guide Partially Filled with a Magnetoplasma Column
Authors: Yip G. L. , Le-Ngoc S.
Published: April 2011

The electromagnetic wave propagation in a partially filled plasma wave guide is studied by using both the quasistatic and the exact analyses. The cutoff and resonant frequencies are examined analytically to predict all possible modes, and numerical methods are then used to study the complete dispersion characteristics. Because of the geometrical generality of the problem, the fully filled plasma wave guide and the plasma column in free space can be considered as special cases. The classifications of the modes existing in various regions are clarified. The effect of the ratio of the plasma and wave guide radii and the d.c. axial magnetic field on the modes is observed and discussed. With a close study of cutoffs, it is shown that the 'special unpaired mode,' named by Bevc, can now be paired with another mode in the gyroresonance region. For large values of the propagation constant, asymptotic dispersion equations can be derived and turn out to be the same in both analyses. Comparisons between the two sets of results are also made to examine the validity of the quasistatic analysis.
On the Computation of Dipole Transitions in the HD Molecule
Authors: Wolniewicz L.
Published: April 2011

A method is presented allowing accurate computations of the weak dipole transition moments in HD. As an illustration the method is applied to the calculation of the Σu components of the wave functions. The Σu contributions to the transition moments are computed and upper bounds for the energy corrections due to Σg–Σu coupling are given. It is argued that the j dependence of the total transition moment is of the order of 10−6 D.