bluuebunny/crossref_metadata_2025 huggingface dataset:
Second-class constraints and quantization on the light cone
Authors: McKeon Gerry
Published: April 2011

Quantization on a surface orthogonal to a fixed lightlike vector leads to a set of second-class constraints in addition to the usual first-class constraints encountered in the conventional quantization procedure. This leads to an additional ghost field in the effective Lagrangian, but it is argued that this ghost field decouples in any computation of radiative corrections and does not enter the Becchi–Rouet–Stora identities.
Cutkosky rules and decay rates at finite temperature
Authors: Kobes R. L.
Published: April 2011

In this paper we outline some recent results concerning the generalization of the Cutkosky or cutting rules to include temperature effects. Differences between these rules and those at zero temperature are illustrated by the correspondence between decay rates and imaginary parts of self-energy graphs.
Regularization and noncovariant gauges
Authors: Leibbrandt George
Published: April 2011

We examine the advantages and disadvantages of noncovariant gauges, with special emphasis on the light-cone gauge. We describe the correct iε prescription in this gauge and discuss a number of other technical aspects. The role of the light-cone gauge in connection with Nicolai maps and stochastic quantization is also examined.
The importance of quantum effects in Kaluza–Klein theory
Authors: Toms D. J.
Published: April 2011

This paper presents a discussion of the role of quantum effects in Kaluza–Klein theories. It is demonstrated why it is not possible to examine the existence of self-consistent solutions induced by quantum corrections to the classical theory if only the vacuum energy is used. The importance of the induced gravity and induced Yang–Mills terms in the effective action are emphasized. General criteria are given for the existence of self-consistent solutions in certain cases, and an expression is given for the gauge-coupling constant. Quantization of five-dimensional gravity with a cosmological constant is considered. Expressions are given for the constants that multiply the induced gravity and Yang–Mills terms in the one-loop effective action for this theory. Although the theory is one-loop finite, the necessity for performing finite renormalizations—a fact that has hitherto been overlooked—is discussed. Results of an analysis of the stability of self-consistent solutions are given, where it is shown why many of the solutions are unstable to small perturbations. A number of prospects for future work are given.
The visible band systems of SnH+ and SnD+
Authors: Yamaguchi Sumio , Obase Hiroshi , Tsuji Masaharu , Nishimura Yukio
Published: April 2011

Visible emission spectra of SnH+ and SnD+ produced from the helium afterglow reactions of SnH4 and SnD4, respectively, have been recorded under higher resolution than the previous measurement. In addition to the three bands reported previously, three new bands of [Formula: see text] have been identified, while eleven bands of [Formula: see text] have been observed for the first time. Spectroscopic constants of the [Formula: see text] and X1Σ+ states have been improved for SnH+ and determined for SnD+.
Nuclear-spin relaxation in the presence of Mansfield–Ware-4 multipulse sequence
Authors: Blicharski J. S.
Published: April 2011

The effective relaxation time T2e is calculated in the weak-collision case, for identical nuclear spins in the presence of a Mansfield–Ware-4 multipulse sequence. The dipole–dipole, quadrupole, and spin-rotational interactions are taken into account.
The effect of nonlocal conductivity on the transmission of microwave radiation through ferromagnetic metals in the field-normal configuration
Authors: Urquhart K. B. , Cochran J. F.
Published: April 2011

Procedures are described for the numerical calculation of the electric-field distributions generated in a model ferromagnetic metal slab of thickness d by incident microwave radiation when a static magnetic field is directed along the slab normal and the mean free path ℓ of the charge carriers becomes comparable to, or greater than, the skin depth δ. The model metal is characterized by a local, frequency-dependent permeability; a spherical Fermi surface; and a nonlocal relationship between the current density and the electric-field distribution. The two limiting cases of specular and diffuse scattering of the charge carriers at the slab faces are considered. Electric-field distributions, transmission amplitudes, and surface impedances have been calculated for a wide range of ℓ and d using parameters that simulate nickel. For diffuse surface scattering, the transmission of the magnetically active mode increases at both ferromagnetic resonance (FMR) and cyclotron resonance (CR). A most striking result is the total absence of structure in the magnetic-field dependence of the transmission amplitude near fields corresponding to FMR or to CR for the case of specular scattering. It is demonstrated that very simple formulae provide a good estimate of the free-space transmission amplitudes for both specular and diffuse surface scattering when [Formula: see text] and d/ℓ ≥ 1.
Désign d'une source d'ions alcalins pour utilisation dans un spectromètre de masse à bombardement ionique (SIMS)
Authors: Noël Mario , Baril Marcel
Published: April 2011

A source of alkaline ions that is flexible, of simple design, and based on the use of a doped alumino-silicate, is presented in this paper. After giving a description of this source, a method to determine the configurations of the two-lens system giving a reduced image of the emissive deposit is described. A phase-space study leads then to an evaluation of which allowed configuration is the optimal one for transport of particles to the target. The diameter of the beam of that source is then determined experimentally to be 0.07 mm at the target. The final version, with an acceleration voltage of 8 kV, can deliver a current of 1 × 10−6 A, the density being of the order of 10 mA/cm2. [Translated by the journal]
Simulation of ultrafast switching of infrared radiation by laser-produced semiconductor plasma
Authors: Petrus O. , Kuhn S. , Dinescu Gh.
Published: April 2011

A comprehensive mathematical model of the physics involved in laser switching, its analytical solution for the linear case, and a computer code capable of simulating the process are presented. The transient optical properties for switches using pulses of 1.06 μm Nd laser radiation to control 10.6 μm CO2 laser radiation incident obliquely on a Ge sample are calculated. The results are found to be in qualitative and quantitative agreement with published experimental data.
The use of laser harmonic spectroscopy as a target diagnostic
Authors: Goldman L. M. , Seka W. , Tanaka K. , Short R. , Simon A.
Published: April 2011

Visible spectroscopy in the spectral region from ω0/2 to 2ω0 has been shown to be a powerful method of explaining the existence and the consequence of three-wave parametric instabilities in laser-produced plasmas. Experiments at 1054 and 351 nm have shown evidence for Brillouin, Raman, 2ωp, and ion parametric-decay instabilities. The details of the spectra can be used to deduce temperatures at quarter critical from ω/2 spectra and the Mach number and temperature from Brillouin scattering.
Wave–particle interactions and energetic tail formation in the electron distribution
Authors: Meyer J.
Published: April 2011

Both the stimulated Raman scattering and the two-plasmon decay instabilities are shown to generate energetic electrons by wave–particle interactions. The results of computer particle stimulations and a variety of experiments are discussed and compared. Many predictions derived from simulations are verified by experimental observations.
Ionization–radiation physics of laser fusion: the modeler's view
Authors: Duston Dwight
Published: April 2011

Of the many physics issues involved in laser fusion, one of the least understood is the role of ionization and radiation in laser-heated plasmas. Ionization and excitation processes are important since they serve as an energy sink, as well as affecting the various transport coefficients. In addition, the radiative processes occurring in the plasma can not only act as a depletion mechanism for the energy but can also redistribute internal plasma energy from the deposition region to other plasma regions inaccessible via other phenomena. This presentation will be from the point of view of the modeler, whose job it is to make sense of the passive-radiative data obtained by the experimentalist as well as to explain the unobservable phenomena taking place via sophisticated computer models of atomic and radiation physics. Three areas will be discussed: (i) an introduction to the numerical modeling of ionization–radiation in laser plasmas, (ii) radiation diagnostics for laser fusion, and (iii) radiation energetics in laser plasmas.
Magnetic properties of Gd-doped PbTe
Authors: Hedgcock F. T. , Sullivan P. C. , Grembowicz J. T. , Bartkowski M.
Published: April 2011

Electron paramagnetic resonance (EPR) and low-field ac susceptibility measurements were done on the rare-earth-doped semimagnetic semiconductor PbGdTe for the Gd composition range 100 ppm–10 at.%. For the lower concentrations, the EPR results indicate a fully resolved fine structure appropriate to the Gd3+ ion and g values close to the free-electron value. Susceptibility results show Curie–Weiss behaviour in all samples for temperatures above 10 K, small negative Curie temperatures, and Peff values corresponding to a Gd spin of 7/2. Deviations from this simple behaviour are observed for Gd concentrations greater than 5 at.% and for temperatures below 10 K. Evidence is observed for an antiferromagnetic clustering of impurity spins.
Electron–nuclear cusp check for self-consistent field wave functions for the neutral atoms from helium to uranium
Authors: Westgate William M. , Byrne Albert D. , Smith Jr. Vedene H. , Simas Alfredo M.
Published: April 2011

The values of the electron density ρ(0), its derivative at the nucleus ρ′(0), and the electron (e)–nuclear (n) cusp ratio Cen = –ρ′(0)/2Zρ(0) are evaluated for the popular self-consistent field functions of Clementi and Roetti (helium to xenon) and McLean and McLean (cesium to uranium). The Cen's for these functions exhibit deviations from the exact value of one.
Cascade-corrected lifetime measurements for singly and doubly ionized indium
Authors: Ansbacher W. , Pinnington E. H. , Kernahan J. A. , Gosselin R. N.
Published: April 2011

Lifetime measurements obtained by the beam-foil method are given for 13 levels in In II and 12 levels in In III. Particular attention has been paid to cascade correction with the application of a new arbitrarily normalized decay curves (ANDC) program. The results are compared with theory, and good agreement is found with recent multiconfiguration relativistic Hartree–Fock (MCRHF) calculations for the In II resonance transition. The results for 2P and 2D levels in In III and 1D levels in In II indicate a need for further calculations.
Structure of vacuum-deposited Zn3P2 films
Authors: Sacken U. von , Brodie D. E.
Published: April 2011

The structure of polycrystalline Zn3P2 films has been studied for 1- to 2-μm-thick vacuum-deposited films on glass substrates. Transmission electron microscopy and X-ray diffraction techniques have been used to obtain a detailed, quantitative analysis of the film structure. The initial growth consists of small (≤ 10 nm), randomly oriented grains. As the film thickness increases, the growth of crystallites with the {220} planes oriented approximately parallel to the substrate is favoured, and a columnar structure develops along with a highly preferred orientation. This structure has been observed directly by transmission electron microscopy of thin cross sections of the films. The size of the grains at the free surface increases with the film thickness, reaching approximately 200–300 nm when the film is 1 μm thick. The effects of substrate temperature and low-energy (0.5–2 keV) electron bombardment of the film during growth have also been studied. Neither substrate temperature nor electron bombardment appear to have a major effect on the film structure. The primary effect of electron bombardment appears to be the creation of preferred nucleation sites on the substrate.
The visible band systems of GeH+ and GeD+ in the helium afterglow
Authors: Yamaguchi Sumio , Tsuji Masaharu , Nishimura Yukio
Published: April 2011

The [Formula: see text] intercombination bands of GeH+ and GeD+ have been observed from the helium afterglow reactions of GeH4 and GeD4, respectively. Only the (0,0) band of [Formula: see text] had been rotationally analyzed before; the higher sensitivity of the new measurements made possible the rotational analyses of four weaker bands. Eleven bands of [Formula: see text] were observed for the first time, and rotational analyses were made of five dominant bands. By using isotope relationships, we obtained detailed spectroscopic constants for the [Formula: see text] and X1Σ+ states of GeH+ and GeD+. Franck–Condon factors and r centroids of the [Formula: see text] transitions of GeH+ and GeD+ have been calculated on the basis of Morse potentials. The dependence of the electronic transition moment on the r centroid and the relative vibrational populations of [Formula: see text] and [Formula: see text] have been estimated.
Rocket observations of ultraviolet and optical emissions in the dayside aurora
Authors: Christensen A. B. , Eastes R. W. , Feldman P. D. , Gentieu E. P.
Published: April 2011

Observations of emissions extending from the extreme ultraviolet to the near-infrared region of the spectrum were obtained from a rocket payload flown from Cape Parry, N.W.T., Canada, during the CENTAUR campaign December 7, 1981. The flight, NASA 29.017CE (Terrier-Malemute), was launched near local magnetic noon during an electron-precipitation event in the dayside cleft region. Emission rates versus altitude and zenith angle were obtained for the principal atomic-oxygen emission features OI (989 Å), OI (1304 Å), OI (1356 Å), OI (6300 Å), OI (7774 Å), and OI (8446 Å), as well as HI (1216 Å) and OII (834 Å). Some data were also obtained for the [Formula: see text] (first negative) bands. The results suggest an emission layer peaked in the vicinity of 250 to 300 km. Temporal and spatial fluctuations were most pronounced at apogee and on the downleg portion of the flight. Emissions strongly affected by multiple scattering fluctuated less than optically thin emissions.In this paper, estimates of the input energy flux and characteristic energy are made based on the intensity of the OI (6300 Å) and OI (1356 Å) emissions and the altitude of the emission layer. A value of 0.3 to 0.4 erg/cm2∙s for the energy flux and a characteristic energy of approximately 200 eV are consistent with the observations (1 erg = 0.1 μJ).
Rocket and satellite observations of electric fields and ion convection in the dayside auroral ionosphere
Authors: Marklund G. T. , Heelis R. A. , Winningham J. D.
Published: April 2011

Electric-field observations from two high-altitude rocket flights in the polar cusp have been combined with satellite observations of ion drifts and energetic particles to infer details of the electric field and convection pattern of the dayside auroral ionosphere. A region of shear flow reversal could be inferred from the electric-field observations on one flight near 1530 magnetic local time 20 min after the Dynamics Explorer 2 (DE-2) satellite crossed through the same region. The drift patterns observed by the two spacecrafts were very similar, although shifted by 0.5°, a shift that is expected from the observed change in the interplanetary magnetic-field (IMF) BZ component during this time. A region of rotational flow reversal was covered by the other flight shortly after magnetic noon, at the same time the DE-2 satellite travelled along roughly the dawn–dusk meridian. By joining points of equal potential, integrated from the two data sets, and assuming the reversal boundary to be an equipotential, we could draw the instantaneous convection pattern showing crescent-shaped convection contours in the dusk cell and more circular-shaped contours in the dawn cell. This pattern has been shown to be in qualitative agreement with the predictions of a geometrical model proposed by Crooker in 1979, when the IMF is oriented towards dawn. The same characteristic patterns but with the dusk and dawn cells reversed, as presented in a recent radar-satellite study for the IMF oriented towards dusk, may serve as additional evidence in favour of this model.
Rocket measurements of electron influx across the midday auroral oval
Authors: McEwen D. J. , Steele D. P.
Published: April 2011

A Black Brant IV rocket was flown through the dayside cusp from Cape Parry, N.W.T., (λ = 75°) on December 6, 1981. It flew to an apogee of 603 km and emerged into the polar cap at λ = 77°. The flight was through a fairly stable midday cusp at approximately 1230 magnetic local time. A very soft electron spectrum was observed, which was comparable with a Maxwellian distribution of E0 ≤ 10 eV. At energies above 100 eV, it was better fitted by a power law of form E−2. The energy flux was 0.2 erg∙cm−2∙s−1∙sr−1 (1 erg = 0.1 μJ), with most of this energy being deposited at heights below 400 km. The λ6300 emission intensity measured from the ground was about 1 kR, somewhat below average midday-cusp λ6300 intensity values. Three short intervals of electron energization were observed during the 11 min the rocket was within the cusp.
Killing vectors and Maxwell collineations in general relativity
Authors: Carigi L. , Herrera L.
Published: April 2011

The relationship between the symmetries of the gravitational field (Killing vectors) and the symmetries of the electromagnetic field (Maxwell collineations) for electrovac space–times is studied in the context of the Newman–Penrose formalism. Several theorems concerning different kinds of Killing vectors are derived for both null and non-null electromagnetic fields.
Electromagnetic-wave propagation over a rotating dielectric cylinder
Authors: Rao T. C. K.
Published: April 2011

The problem of guided electromagnetic-wave propagation over a rotating dielectric cylinder is solved by a boundary-value method assuming that the speed of rotation is much smaller than the velocity of light. From a numerical solution of the complex characteristic equation, the variation of the attenuation and the phase constants and their dependence on the speed of rotation are studied. The rotational process appears to divide the radial propagation constant inside a stationary cylinder into two waves with different propagation constants. The modes with positive and negative indices in the circumferential direction cease to be degenerate in the case of a rotating dielectric cylinder, and there appears to be a decrease in the attenuation with an increased speed of rotation for the dominant mode.
Periodic structures of clean, normal, and superconducting material II: order parameter and free-energy functions
Authors: Cleary Robert
Published: April 2011

The critical temperature of a clean, normal (n) and superconducting (s) material is calculated and found to differ very slightly from its bulk value. The order parameter at 0°, Δ(0), is found to be modified much more than its bulk value for periodic structures of various cell widths, superconducting-to-normal metal length ratios, and Fermi-velocity differences in the normal and superconducting regions. At intermediate temperatures, an expression for Δ(T)/Δ(0) as a function of T/Tc and Δ(0)/Tc is given. The free-energy functional Fs − Fn is calculated. As in the case of Δ(T)/Δ(0), numerical calculations are necessary. These integrands are carried out to the point where numerical quadrature is simple and straightforward. Because of the great number of parameters describing our system, we do not perform any numerical calculation. These are left to the interested experimentalist for his particular structure.
Models for aurora and airglow emissions from other planetary atmospheres
Authors: Fox J. L.
Published: April 2011

Models for aurora and airglow emissions from planetary atmospheres other than the Earth are surveyed, with emphasis on accomplishments of the last seven years. The goals of modeling the terrestrial planets and modeling the outer planets are very different. Because less is known about the atmospheres of the outer planets, models of their luminosity seek to provide information about the basic structure of the atmospheres and to identify the major production mechanisms. Models of the terrestrial planets have recently begun to address more complex questions about the abundances of trace and minor constituents, about transport phenomena, and about spatial and temporal variations in the atmosphere and in the processes that produce the emissions. In addition, there are a few instances in which models have been used to elucidate atomic and molecular processes that are difficult to study either in the terrestrial atmosphere or in the laboratory.
Theory of the atmospheric sodium layer: a review
Authors: Kirchhoff Volker W. J. H.
Published: April 2011

The advent of the laser-radar technique allowed sodium densities and sodium emissions to be monitored simultaneously, and great scientific progress has been achieved since. We describe these results in a broad sense, keeping a balance between theory and experiment, addressing the following subjects: evolution of the photochemical theory, the model for diurnal variations, the sodium source, tidal effects, and problems at the top of the layer.
Beam-foil measurements of lifetimes of energy levels belonging to Sn III and Sn IV
Authors: Pinnington E. H. , Kernahan J. A. , Ansbacher W.
Published: April 2011

Beam-foil intensity decay curves for transitions in the wavelength range 750–5250 Å are used to derive the lifetimes of the 6s1S, 5p1P, 6p1P, 5d1D, 6d1D, 5p21D, 4f1F, 6s3S, 6p3p, 5p23p, 5d3D, 6d3D, and 4f3F levels of Sn III, and of the 6s2S, 5p2P, 6p2P, 5d2D, 6d2D, 4d95 s22D, and 4f2F levels of Sn IV. The arbitrarily normalized decay-curve analyses are used for most levels. Good agreement is found between experiment and a recent (relativistic Hartree–Fock + core-polarization) calculation for the resonance transition in low-Z members of the Cd 1 isoelectronic sequence, but the experimental f values are found to lie systematically about 20% above the theoretical trend obtained from a similar calculation for the Ag I sequence. Configuration interaction is found to produce very different lifetimes for the two 4d95s22D levels of Sn IV, and the energy of the J = 3/2 level is determined to be 177 060 ± 50 cm−1.
Diffraction properties of a class of double wedges
Authors: Elsherbeni A. Z. , Hamid M.
Published: April 2011

The diffracted field due to an E-polarized plane wave incident on two cylindrical wedges forming a slit-type aperture is formulated using an integral equation for the surface current. The use of the ordinary method of moments to solve for the unknown surface currents does not yield a convergent solution, owing to the semi-infinite dimensions of the wedges and the fact that the total current does not vanish on the illuminated surface for this type of excitation. Therefore, the surface current is divided into two components, namely, a known noninteraction term and an unknown term due to the infinite number of interactions between the wedges. The noninteraction term is considered to be the physical optics current for those geometries that have wedges with nonsharp edges, whereas the exact surface current for a single wedge is used for double wedges with sharp edges. The interaction term may be evaluated using the ordinary method of moments, because it decays with increasing distance from the edge along the surface of either wedge. It is found that this technique leads to an efficient solution and makes it possible to use the method of moments for the multiple scattering by bodies of semi-infinite or large dimensions. Numerical results for the diffracted fields and transmission coefficients for a variety of related structures, such as the thin slit, the thick slit, the double truncated wedge, and the double capped wedge, are presented and compared with available solutions.
Interference effects in the infrared absorption of solid hydrogen due to localized electrons
Authors: Bose S. K. , Poll J. D.
Published: April 2011

Recent experiments on proton-irradiated solid hydrogen show a broad absorption in the spectral region 4000–8000 cm−1. This broad absorption has been interpreted as being due to the lowest bound-state transition of electrons localized in cavitylike states in the lattice. Superposed on this broad spectrum is an asymmetric line, which is centered around the Stark-shifted fundamental vibrational transition (ν = 0 → ν = 1) of the molecules in the nearest neighbour positions with respect to the localized center of the electron. We present a detailed calculation of this line shape and show that the asymmetry can be attributed to the interference between the dipole of the localized electron and the charge-induced molecular dipole, as a result of a coincidence in the energies of the molecular and the electronic transitions.
On the nitrogen-induced far-infrared absorption spectra
Authors: Dore P. , Filabozzi A.
Published: April 2011

The rototranslational absorption spectrum of gaseous N2 is analyzed, considering quadrupolar and hexadecapolar induction mechanisms. The available experimental data are accounted for by using a line-shape analysis in which empirical profiles describe the single-line translational profiles. We thus derive the simple procedure that allows one to predict the N2 spectrum at any temperature. On the basis of the results obtained for the pure gas, we also propose a procedure to compute the far-infrared spectrum of the N2–Ar gaseous mixture. The good agreement between computed and experimental N2–Ar data indicates that it is possible to predict the far-infrared absorption induced by N2 on the isotropic polarizability of any interacting partner.
Tensors of symmetric and unitary groups
Authors: Mirman R.
Published: April 2011

A realization of unitary-group basis states by multinomials (tensors) that realize symmetric-group representation basis states requires that there be the proper set of numbers of these tensors and that unitary-group transformation properties be obtainable from their labels. That these requirements are met is shown here, allowing the actual construction of the unitary states and matrix elements.
Electron transport in liquid metals and alloys
Authors: Lugt W. van der , Geertsma W.
Published: April 2011

This paper deals with a number of selected topics from the field of electric transport properties in liquid metals and alloys. First, some nearly free electron systems are considered; it appears that some problems associated with the properties of liquid Na–Cs alloys and of amalgams are still unsolved. Then, systems exhibiting strong compound formation, particularly alkali–nonalkali alloys with a large electronegativity difference between the components, are reviewed. A qualitative interpretation in terms of chemical-valence rules, based upon our knowledge of the solid state, is given. Next, recently developed theories dealing with transport properties in disordered media are critically discussed. Some models for the interpretation of the alkali – group IV alloys are presented. The basic ideas derived from these models are used also as guidelines for a more qualitative discussion of the alkali – group III and alkali – group V alloy systems.
Resonant mode conversion of a shear Alfvén wave
Authors: Shivamoggi Bhimsen K.
Published: April 2011

A new mechanism for the resonant absorption of a shear Alfvén wave is proposed that involves a direct mode conversion of the latter to an ion-acoustic wave without bringing in the intermediary — the kinetic Alfvén wave. The fraction of the incident Alfvén-wave energy that is mode-converted to an ion-acoustic wave is calculated. This mechanism likely operates in the solar wind, where it might lead to heating of the plasma.
Flicker-noise fluctuations in α-radioactive decay
Authors: Kousik G. S. , Gong J. , Vliet C. M. Van , Bosman G. , Ellis W. H. , Carroll E. E. , Handel P. H.
Published: April 2011

Counting statistics of α particles from three sources, one containing 241Am; one containing 239Pu, 241Am, and 244Cu; and a source containing 148Gd, were determined over periods of 1–4000 min. In particular, the two-sample variance or Allan variance was determined for many sample runs. According to a recent theorem, there is a unique relation between the particle-flux spectral noise density and the Allan variance. It was found that for small counting periods, the statistics were Poissonian, corresponding to shot noise of the particle flux. For long periods[Formula: see text], the counting statistics were found to be non-Poissonian, indicating the presence of 1/f noise and (or) Lorentzian noise.The 1/f noise gave flicker floors of (0.5–0.7) × 10−7 for 239Pu, (1.0–1.3) × 10−7 for 241Am, and 3.0 × 10−7 for 244Cm. The Lorentzians were not reproducible in different runs and are probably associated with chemical oxidation-reduction rate processes in the source. The 1/f noise is likely inherent in the process of α-particle decay, indicating that the classical picture of alpha decay as a Poisson process is incomplete. Some forms of quantum 1/f noise associated with the tunnel-emission process are briefly discussed.
Temperature dependence of the structure of the antifluorite K2OsCl6: evidence for precursor tetragonal clusters near TC
Authors: Armstrong Robin L. , Morra Rose M. , Svare Ivar , Powell Brian M.
Published: April 2011

Neutron-diffraction profiles were obtained from a powder sample of K2OsCl6. Measurements were taken at six temperatures above TC, the temperature of the cubic-to-tetragonal structural phase transition, and at one temperature below TC. Profile-refinement analysis yielded temperature-dependent Debye–Waller factors that behaved as expected from the elastic properties of a harmonic cubic crystal. Of intrinsic interest is the conclusion that the data contain the first neutron-diffraction evidence for the occurrence of precursor clusters. These long-lived fluctuations, which possess the symmetry of the tetragonal phase but which occur in the cubic phase, were first identified from chlorine nuclear quadrupole relaxation data in K2OsCl6.
Weizsäcker–Williams method for a massive boson
Authors: Nigam B. P. , Sundaresan M. K.
Published: April 2011

The Weizsäcker–Williams approximation for the bremsstrahlung cross section in which a fermion emits a photon in the Coulomb field of a nculeus is generalized to the case when the emitted particle is a massive boson.
New high-temperature superconductor, Y–Ba–Cu–O
Authors: Luo Y. L. , Morrish A. H. , Pankhurst Q. A. , Pelletier G. H. , Roy G. J. , Zhang D. Y. , Zhou X. Z.
Published: April 2011

A new material with the nominal composition (Y0.4Ba0.6)CuO3 becomes superconducting at a temperature above 77 K.
Triple differential cross sections for the positron-impact ionization of hydrogen and helium
Authors: Saxena Sushma , Srivastava M. K.
Published: April 2011

Triple differential cross sections for the positron-impact ionization of hydrogen and helium in a coplanar, asymmetric geometry are calculated by using the second Born and the modified Glauber approximations. The present results are compared with those for the corresponding electron-impact case. The positron gives a larger binary- to recoil-peak maxima ratio than the electron.
High-resolution photon yield of xenon by monoenergetic electron impact
Authors: Le René , Marchand Pierre
Published: April 2011

The broad-band (165–650 nm) photon yield of xenon by monoenergetic electron excitation has been measured in the range from 10.9 eV to above 13.436 eV (2P1/2 limit). Neutral excited states and several new negative-ion states are detected. Interpretation and classification are discussed.
Nucleon charge-exchange reactions at intermediate energies
Authors: Love W. G. , Klein Amir , Franey M. A. , Nakayama K.
Published: April 2011

The nucleon charge–exchange reaction is investigated as a probe of isovector modes of nuclear excitation at both small and large momentum transfer. The calculated and extracted properties of the isovector nucleon–nucleon interaction are discussed and illustrated with an emphasis on incident energies in excess of 100 MeV. Particular emphasis is placed on spin observables and the roles played by different parts of the nucleon–nucleon coupling in their determination. Recent measurements of transverse polarization transfer at 0° in the charge-exchange continuum are compared with distorted wave impulse approximation calculations using random–phase approximation transition densities.
Overview of some time-of-flight (p, n) studies
Authors: Goodman Charles D.
Published: April 2011

An overview of some experimental work with the (p, n) reaction at Indiana University is given. The scientific motivation for the studies is discussed. A description of the apparatus at the Indiana University cyclotron is given. Some results of the experiments are displayed. It is shown that the cross section per unit Gamow–Teller strength does not vary smoothly with target mass. This is noted as an open problem in the field. A discussion of another open problem, the missing Gamow–Teller strength, is given.
Recent theoretical developments in nuclear charge-exchange reactions
Authors: Wambach J.
Published: April 2011

The (p, n) and (n, p) charge-exchange reactions are a suitable tool in nuclear-structure studies. At intermediate energies, the interaction with the target resembles that between free nucleons, which makes the probes mostly susceptible to the spin dynamics of the nucleus. We review the current theoretical picture of nucleon–nucleus charge-exchange reactions. A brief introduction to the theory of direct reactions in the impulse approximation is given. We then discuss the random-phase approximation (RPA) linear response theory, which is widely used in the calculation of cross sections and related observables. To understand correctly the shape of the continuum cross sections, one needs a more sophisticated theory. We discuss suitable extensions of the RPA that incorporate spreading effects as well as escape effects. Charge-exchange reactions of the (n, p) type have important implications for the evolution of massive stars. The relevance for Type-II supernovae is discussed.
Charge-exchange studies at the Los Alamos Meson Physics Facility – Weapon Neutron Research Facility
Authors: Lind D. A.
Published: April 2011

The Los Alamos Meson Physics Facility – Weapon Neutron Research Facility has been used for (p,n) charge-exchange studies leading to a paper on the energy dependence of the nucleon–nucleon spin–isospin interaction at up to 800 MeV. Because of program changes connected with the use of the proton storage ring and the need for a "white" neutron source, a new facility for neutron time-of-flight studies of the (p,n) reaction up to 800 MeV has been designed. In addition, a proposed facility using the white source for (n,p) studies up to 200 MeV is being built. A brief discussion of the results achieved thus far from the (p,n) work is given. Specific plans for the (p,n) facility with a flight path of 250 m, as well as the design for the proposed (n,p) white source, are discussed. Initial results with the (p,n) line at 256, 600, and 880 MeV show that the time spread due to proton-drift distance results in roughly constant neutron resolution.
The Uppsala (n,p) facility
Authors: Condé H. , Crona S. , Håkansson A. , Jonsson O. , Lindholm A. , Nilsson L. , Renberg P.-U. , Tibell G. , Bergqvist I. , Ekström P.
Published: April 2011

A facility for (n,p)-reaction studies being built at the upgraded Gustaf Werner cyclotron of the The Svedberg Laboratory, Uppsala, Sweden, is presented. Well-collimated, monoenergetic neutron beams will be used with a fairly long distance between the neutron source and the (n,p) sample to reduce background radiation. The (n,p) magnetic spectrometer has large angular and momentum acceptance. Initially, studies of isovector monopole and Gamow–Teller giant resonances are planned.
Why study on nuclei?
Authors: Yavin Avivi I.
Published: April 2011

A brief summary of the first elastic and inelastic scattering results obtained at the European low-energy antiproton ring facility is presented. The constraints thereby put on the antiproton–nucleus interaction are discussed, and the unique features of the antiproton as a probe of the nucleus are pointed out. In particular, it is stressed that the near blackness of the nucleus to antiprotons could be exploited in the [Formula: see text] reaction to specific states excited mainly by the long-range part of the nucleon–antinucleon interaction. The spin–isospin parts of the interaction as well as some isovector nuclear excitations could thus be studied.
Isovector resonances in pion single-charge-exchange reactions
Authors: Bowman J. David
Published: April 2011

I report on the experimental study of L = 0, 1, and 2 isovector resonances in pion charge-exchange reactions.
Electromagnetic scattering by a perfectly conducting elliptic disk
Authors: Björkberg Jonas , Kristensson Gerhard
Published: April 2011

Electromagnetic scattering from a perfectly conducting elliptic disk is treated by means of the null-field approach. The disk is obtained as the zero-thickness limit of an ellipsoid. It is shown that in this limit all relevant matrix elements have a well-defined limit. Owing to the lack of axial symmetry, an integral that can not be solved analytically remains in the azimuthal angle. In an appendix, an efficient algorithm to solve these integrals by means of recurrence relations is presented. The formalism is attractive for numerical computations, and stable results for very eccentric disks have been obtained. The first few terms in the low-frequency expansion of the total cross section are derived. Numerical computations of the scattering amplitude and the total cross section illustrate the theoretical results. In a final appendix, the thin wire limit of the elliptic disk is discussed, and a comparison with corresponding results of a prolate spheroid is presented.
Electroionization study of ethylene: structures in the ionization and appearance curves
Authors: Plessis Pierre , Marmet Paul
Published: April 2011

Ionization-efficiency curves with very high signal-to-noise ratios for ethylene and all fragments consisting of at least one carbon atom are presented and analyzed. The curves are produced by monoenergetic electron impact and extend up to 10 eV above threshold. Most of the structures observed thus far by this method for these regions are reported here for the first time. Competition between [Formula: see text] production and [Formula: see text] and [Formula: see text] fragment production is clearly seen in the respective curves. Features occurring at the same energy in several of the curves indicate that these are due to a common progenitor, particularly the [Formula: see text] complex. The appearance of different fragmentation processes accounts for the onset-type structure found in some of the fragment-ion curves.
The shape of ionospheric irregularities in the auroral zone
Authors: Lyon G. F. , Davies J. , Forsyth P. A.
Published: April 2011

The evidence that ionospheric irregularities are elongated along the magnetic field is overwhelming. The actual extent of the elongation may, at least for mid-latitude locations, be considerably more than is usually quoted. Several years ago it was suggested that ionospheric irregularities, particularly at night in the auroral zone, are also elongated in the horizontal direction along the L shells. Since that time, there have been a number of investigations of this phenomenon, but there still seems to be some doubt about the actual degree of the anisotropy. This paper uses a limited number of navy navigation satellite system data from a high-latitude station (Sach's Harbour, N.W.T.) and a much more extensive HILAT satellite data set collected at Churchill, Man., to explore the question in a somewhat more direct, though statistically less definitive, way. The results give no clear support for the postulated L-shell extension.
Poisson brackets of the super-Hamiltonian and the supermomenta
Authors: Skinner Ray , Steinke Kim , Wood W. Robert
Published: April 2011

The Poisson brackets of the super-Hamiltonian and the supermomenta are related to the commutators of the normal basis vectors on the space of embeddings (K. Kuchar, J. Math. Phys. 17, 777 (1976)). The Poisson brackets are calculated without requiring the super-Hamiltonian and the supermomenta to be weakly zero, contrary to the claim of Teitelboim (Ann. Phys. (NY), 79, 542 (1973)).
Diamagnetic and structural characterization of orthorhombic high-temperature superconductors in the system Y–Ba–Cu–O
Authors: Raudsepp M. , Hawthorne F. C. , Zhou X. Z. , Maartense I. , Morrish A. H. , Luo Y. L.
Published: April 2011

Ceramic samples of the 90 K superconductor with nominal composition YBa2Cu3O7−x were made under varying preparation conditions. Some samples have a narrow transition-temperature range of about 1.5 K and a 100% "ac Meissner effect" near 77 K. The magnetic losses below 85 K were much reduced in these samples. Rietveld structure refinement in space group Pmmm using powder X-ray diffraction data showed significant oxygen vacancies in the square-planar CuO2 chains parallel to the y axis in the y–z plane, and Cu disorder about the origin along the x axis. The sample with the superior superconducting properties has the formula YBa2Cu3O6.92.
Static and dynamic crystal-field effects in ferrous fluosilicate
Authors: Price D. C.
Published: April 2011

This paper examines the crystal fields acting on Fe2+ ions in ferrous fluosilicate, and the way that they influence the magnetic and spectroscopic properties of the compound. The crystal structures of ferrous fluosilicate and of the structurally similar magnesium, manganese, cobalt, nickel, and zinc compounds are described to establish the point symmetries of the metal-ion sites. In the low-temperature monoclinic (P21/c) phase of the Fe2+, Mg2+, Co2+, and Mn2+ compounds, although the metal-ion site is required crystallographically to have only inversion symmetry, all of the available low-temperature data are consistent with a crystal field of C2h symmetry. In the high-temperature phases of these salts, and for nickel and zinc fluosilicates at all temperatures, the site symmetries are either exactly or approximately C3i. The dominant effect of the phase transition on the Fe2+ crystal field in FeSiF6∙6H2O is to remove the nonaxial terms [Formula: see text] and [Formula: see text] that are present in the low-temperature phase. The other terms appear to be relatively unaffected.Both the time-dependent (spin-lattice relaxation) and time-independent (vibronic coupling) manifestations of the dynamic crystal field at the Fe2+ ions are qualitatively examined. A new interpretation of the 57Fe Mössbauer spectra of FeSiF6∙6H2O in the low-temperature phase is described, from which relaxation rates comparable to those deduced from other measurements are obtained. Evidence that the measured 57Fe Mössbauer quadrupole splittings of Fe2+ ions in FeSiF6∙6H2O and in ZnSiF6∙6H2O show significant effects of vibronic coupling is examined.
Thermodynamic properties of the quasi-one-dimensional Heisenberg system CsMnBr3
Authors: Franco B. J. O. , Pires A. S. T.
Published: April 2011

Correlation functions and correlation lengths are calculated by transfer-matrix formalism for the magnetic compound CsMnBr3 and compared with Monte Carlo calculations.
Spin temperature experiments in β-phase palladium hydride
Authors: Avram Hector E. , Armstrong Robin L.
Published: April 2011

Spin temperature experiments are reported in β-phase palladium hydride (β-Pd HX) where X = 0.80, 0.75, and 0.71 at a temperature of 40 K. These nuclear magnetic resonance experiments serve to verify the existence of a proton spin temperature in this nonstoichiometric alloy. Further, the experiments provide values of the local field [Formula: see text] at the proton sites; the parameter δ, which is a measure of the correlation of the fluctuating magnetic fields throughout the sample; and the Knight shift. The measured local field increases as the concentration decreases, in contrast to the behaviour predicted for a rigid lattice and dipolar interactions. The correlation parameter increases linearly with concentration. The Knight shift measurements are supplemented by measurements of T1zT and are compared with the prediction of the Korringa relation.
Far-infrared collision-induced absorption in compressed gaseous polar linear molecules: application to N2O
Authors: Van-Thanh Nguyen- , Rossi I.
Published: April 2011

This paper deals with computations of the far-infrared collision-induced absorptions for polar linear molecules. We have considered Frost's theory for dipole- and quadrupole-induced dipole absorptions in bimolecular collisions, taking the anisotropy of the molecular polarizability into account. In addition to the induced rotational interaction, a translational effect may not be negligible. Detailed expressions for different contributions to the integrated intensities are reported for N2O. Using these calculated expressions and the moderately low pressure data, we have deduced a value for the quadrupole moment of N2O, [Formula: see text].
Susceptibilité radiofréquence d'une jonction vis-à-vis d'un champ électrique parallèle au plan métallurgique
Authors: Blanc François , Fanguin René , Raoult Gaston , Labrune Jean-Claude , Lomaglio Germaine , Theobald Jean-Gérard
Published: April 2011

When an alternating electric field is applied parallel to a junction, the radiofrequency susceptibility gives an absorption having a maximum versus the direct current polarization of the junction; the real part of the susceptibility is negative. The explanation of both features involves an internal field parallel to the alternating field. The experiment allows the measurement of the concentration of minority carriers.
Nonlinear ion-acoustic waves in multicomponent plasmas
Authors: Das G. C. , Karmakar B.
Published: April 2011

By applying the reductive perturbation technique to the basic system of equations governing plasma dynamics, a modified Korteweg–de Vries (KdV) equation is derived. The inclusion of nonisothermality, together with its reduction to a small magnitude, yields various interesting characteristics relating to the existence of solitons in multicomponent plasmas that include several ionic species and multiple nonisothermal electrons. The mathematical development shows that a closed relation among the solitons existing in the various plasmas arises due to the different magnitude of nonisothermalities.
Low-lying activated states of chloroiridium phthalocyanine aggregates in glassy solution at low temperatures
Authors: Chen W.-H. , Rieckhoff K. E. , Voigt E.-M.
Published: April 2011

Studies of phosphorescence intensities and lifetimes of two chloroiridium phthalocyanine aggregates in α-chloronaphthalene between 5 and 80 K have revealed the existence of low-lying activated states only a few tens of cm−1 above the zero-point vibration in both lowest singlet and triplet states. From the data, activation energies of intersystem crossings between the two multiplicities associated with these states have been obtained as follows: for crossing from the first excited singlet to the lowest triplet state, Ea = 42 ± 10 and 29 ± 10 cm−1, respectively, for the two aggregates; for crossing from the lowest triplet to the ground singlet state, [Formula: see text] and 23 ± 5 cm−1, respectively. These activated states are tentatively attributed to certain intermolecular modes of vibration in aggregates. Specifically, they fit the model of molecular torsional oscillation of two and three parallel-sheet arrangements. On the basis of these findings, we propose that the first Ea (or [Formula: see text]) is the fundamental librational frequency of the dimer and the second Ea (or [Formula: see text]) is that for the trimer.