bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference effects in the spectrum of HD: IV: the pure rotational band at room temperature
Authors: McKellar A. R. W.
Published: April 2011

The rotational spectrum of HD has been studied in absorption at room temperature for a density range of 6–57 amagat. Spectra were obtained in the 170- to 360-cm−1 region, including the R0(1), R0(2), and R0(3) transitions, with a 1-m path length and a spectral resolution varying from 0.05 to 0.20 cm−1. The observed line strengths were used to determine values for the dipole transition moments of HD in the range of 7.4 to 7.8 × 10−4 D, which is somewhat lower than currently accepted theoretical values of about 8.3–8.4 × 10−4 D. Only very small effects (≈0.2% per amagat) were found due to collisional interference on the line strengths; this result contrasts with much larger interference effects observed in the fundamental band, and it also casts some doubt on other recent studies of the rotational spectrum where larger interference effects were reported.
Further results relating to the electronic spectrum of 175Lu16O
Authors: Bernard A. , Effantin C.
Published: April 2011

Further results are presented concerning the three known systems of the molecule LuO; i.e., A2Π, B2Π, C2Σ+ → X2Σ+. The observed wavenumbers in each of the 12 analyzed bands are reduced using an iterative, least squares fitting procedure. Rotational constants are given for vibrational levels ν = 0 and 1 in the C state and up to ν = 7 in the X and B states. The 1–1 band of the A → X system is partly analyzed. These new calculations confirm level B to be the 3/2 component of a 2Π state; but they give no such confirmation for the identification of the A level, whose 2Π nature is well established, as the 1/2 component of the same state.Moreover, a unique band at 5120 Å that cannot be classified into any of the three known systems is described and attributed to a new system of LuO. A partial rotational analysis is made showing that the band corresponds to a transition involving the level ν = 0 in the ground state. The nature of the upper state is discussed.
Superexchange interaction and spin transfer to a ligand in K2CuCl4∙2H2O-type crystals
Authors: Han Tae Jong , Kim In-Mook , Choh Sung Ho
Published: April 2011

The superexchange interaction between magnetic copper ions in the paramagnetic state of K2CuCl4∙2H2O-type crystals has been investigated in terms of the molecular-orbital method. A formalism for the exchange constant, proportional to the square of the spin transfer to the nonmagnetic ligand that is involved in the superexchange path, is obtained. The temperature-dependent exchange constant resulting from the temperature-dependent spin transfer to H is compared with that determined by Cu2+ electron spin resonance and with the thermal average of the exchange interaction. A reasonable agreement is observed.
Dissociative excitation of SF6 by controlled electron impact
Authors: Forand J. L. , Becker K. , McConkey J. W.
Published: April 2011

Dissociative excitation of SF6 by electron impact has been studied under single-collision conditions for incident energies up to 600 eV. The emission spectrum in the spectral range 450–1850 Å shows many features arising from neutral and singly ionized fluorine and sulphur fragments. Absolute cross sections for many of the emissions were measured, and excitation functions and appearance potentials were determined for selected features from each of the four systems. The largest cross sections were found for the FI transitions at 955 Å (2.3 × 10−18 cm2) and 975 Å (1.7 × 10−18 cm2).
Intensités des raies d'absorption dans la bande chaude ν8 + ν11 − ν11 de l'aliène 12C3H4
Authors: Dang-Nhu M. , Pine A. S.
Published: April 2011

Strengths of individual lines of the hot band ν8 + ν11 − ν11 of 12C3H4 at 3 μm have been measured with a high-resolution difference-frequency laser spectrometer. Finally, two intensity parameters have been determined using a general formulation written for hot bands E′ × E ← E of group D2d.
Revised and extended analysis of the 3d10nl configurations in As V, Se VI, and Br VII
Authors: Joshi Y. N. , Kleef Th. A. M. Van
Published: April 2011

The spectra of arsenic, selenium, and bromine were photographed in the wavelength region 450–2000 Å on 6.65- and 3-m normal-incidence spectrographs using a triggered spark source. The new observations have led us to revise and extend the As V, Se VI, and Br VII spectra.
Maximum pseudorapidity gap and diffractive dissociation in hadron–nucleus interactions at 22.6–400 GeV
Authors: Ghosh Dipak
Published: April 2011

This paper presents the first detailed investigation of the maximum gap (Δmax) in the pseudorapidity distribution of charged particles in individual events and hence the diffractive dissociation for proton–emulsion interactions over the entire, machine energy range (22.6–400) GeV/c. The location of the Δmax in an event has been studied, and the experimental Δmax distribution at all energies has been compared with the theoretical prediction of Jones and Snider.
Test of a model of hadron–nucleus interactions at high energies
Authors: Kaur M.
Published: April 2011

A model that establishes the multiplicity generating functions of hadron–nucleus interactions at high energies, proposed by Munõz–Cobo and co-workers, has been tested for calculating the absorption cross sections and multiplicity ratios for various hadron-induced processes. The agreement between experimental and predicted values is found to be excellent.
Étude par transformée de Fourier, du spectre, du silane dans la région de 1000 cm−1. Analyse de la diade ν2 et ν4
Authors: Pierre G. , Valentin A. , Henry L.
Published: April 2011

A Fourier-transform absorption spectrum of the three silicium isotopes of silane in natural abundance have been recorded from 840 to 1040 cm−1. The line width is 3 × 10−3 cm−1 and the absolute accuracy is estimated to be about 2 × 10−4 cm−1 for non-saturated and non-overlapped lines. The analysis of this spectrum is achieved, using a Hamiltonian, formulated with an irreducible tensorial set in the Td group.For the dyad ν2 and ν4 and for each isotopic species, 30 reduced effective Hamiltonian parameters are determined, giving the line wave numbers with 2.5 × 10−4 cm−1 for 28SiH4, 3.4 × 10−4 cm−1 for 29SiH4, and 5.5 × 10−4 cm−1 for 30SiH4 as the standard deviation for J = 0–20.
An approach to the effective potential
Authors: Grigjanis R. , Kobes R. , Fujimoto Y.
Published: April 2011

We present a relatively efficient method for calculating perturbatively the first two terms in the expansion of the effective action. The method can also be used to find the renormalization group coefficients in a fairly simple manner.
Perturbative, nonperturbative, and topological aspects of anomalies
Authors: Mann R. B.
Published: April 2011

A review of recent research concerning the perturbative, nonperturbative, and topological aspects of anomalies is presented.
Finite-dimensional approximation of the scattering matrix
Authors: Kröger Helmut , Smailagic Anais , Girard Ralph
Published: April 2011

A finite-dimensional nonperturbative approximation scheme of the time-evolution operator and the S matrix for relativistic field theories is discussed. It is amenable to computer calculations. Parallels with lattice-field theory are drawn. The method is outlined for the ϕ4 theory. Equivalence to standard perturbation theory in the weak-coupling regime is obtained in the limit of the approximation parameters. The method is tested numerically for nonrelativistic proton–proton s-wave scattering and the the ϕ4 model in the weak-coupling regime in 1 + 1 dimensions. In both examples, convergence to the reference solution is found.
Kaluza–Klein cosmology with an external scalar field
Authors: Gegenberg J. D.
Published: April 2011

Simple cosmologies are constructed from solutions of the five-dimensional Einstein equations with a real, massless, non-self-interacting scalar-field source. It is demonstrated that nontrivial cosmological models occur only if the metric of the homogeneous and isotropic 3-space of the universe has nonpositive constant curvature. For the case of flat 3-space, it is further demonstrated that two classes of solutions result, one of which has a power-law type of expansion for 3-space and contraction of the one-dimensional internal space, while the other class has an exponential expansion for 3-space and exponential contraction of the internal space. The exponentially expanding solutions are the limiting case of the power-law expanding solutions. Hence, our model is consistent with a simple inflationary scenario.
The light-cone gauge
Authors: Lee H. C.
Published: April 2011

Some aspects of recent development in the light-cone gauge and its special role in quantum-field theories are reviewed. Topics discussed include the two- and four-component formulations of the light-cone gauge, Slavnov–Taylor and Becchi– Rouet–Stora identities, quantum electrodynamics, quantum chromodynamics, renormalization of Yang–Mills theory and supersymmetric theory, gravity, and the quantum-induced compactification of Kaluza–Klein theories in the light-cone gauge.
Confining the scalar field of the Kaluza–Klein monopole
Authors: Kunstatter G. , Vincent D.
Published: April 2011

A discussion is given of the Kaluza–Klein monopole and the inherent problem associated with its scalar field. A model that achieves a confinement of this scalar field is presented, whereby a thin boundary layer is imposed on the monopole geometry allowing an exterior geometry with a constant scalar field to be attached. The Gauss–Codazzi formalism then puts strong constraints on the effective stress energy of the boundary.
On the consistency of self-consistent dimensional reduction
Authors: Kunstatter G. , Toms D. J.
Published: April 2011

Several aspects of self-consistent dimensional reduction in Kaluza–Klein theory are addressed. First, the validity of the one-loop approximation in quantum gravity with a cosmological constant is discussed. Second, a distinction is made between mathematical self-consistency and physical self-consistency. Finally, the possible gauge dependence of the physical predictions for the radius and gauge coupling constant is analyzed within the context of recent theorems concerning the gauge invariance of the one-loop gravitational effective action.
Optical-model potentials from potential inversion at fixed energy
Authors: Hodgson R. J. W.
Published: April 2011

A fixed-energy potential-inversion method is employed to generate an optical-model potential to fit the elastic-scattering data for 16O + 28Si at 21.1 and 34.8 MeV. The fit yields a potential that is based on a standard Woods–Saxon potential and yields minor modifications to it.
A comparison of structural relaxation in Ni64B36 and Fe83B17 metallic glasses
Authors: Dini K. , Cowlam N. , Gregan G. P. , Davies H. A.
Published: April 2011

An investigation has been made of the structural changes that accompany low-temperature annealing (structural relaxations) in two different metallic glasses using X-ray and neutron diffraction, calorimetry, and density measurements. The structure of Fe83B17 having the archetypal composition of transition-metal – metalloid glasses appears to be more susceptible to structural relaxation than Ni64B36 glass with a higher metalloid content. This behaviour is reflected in the smaller enthalpy of relaxation of the Ni64B36 glass. The structural changes observed are discussed in terms of current structural models.
Acoustic radiation from thin rods in water
Authors: Jarosz B. J. , Clarke R. L.
Published: April 2011

The ultrasound pressure distribution produced by end-excited stainless-steel rods immersed in water has been investigated. Rod diameters of 0.238 and 0.319 cm were tested at frequencies between 1.0 and 3.5 MHz. Immersion depths up to 10 cm were studied. Semiperiodic patterns were observed along the rods, with repetition lengths of 0.6 and 1.1 cm. Fast Fourier-transform analysis of the patterns showed the presence of three spatial frequencies interpreted to be the lowest mode longitudinal wave, Rayleigh-type surface waves, and the Stoneley wave propagating in the liquid.
A study of proton total reaction cross sections for several medium-mass nuclei between 20 and 48 MeV
Authors: McCamis R. H. , Davison N. E. , van Oers W. T. H. , Carlson R. F. , Cox A. J.
Published: April 2011

Proton total reaction cross sections (σR) have been measured for 51V, 54Fe, 56Fe, 57Fe, and 59Co at seven incident proton energies between 20.8 and 47.8 MeV at the University of Manitoba's Cyclotron Laboratory. Our results are compared with an optical-model analysis using global parameters. In general, the predicted total reaction cross sections agree quite well with the measured values. Nuclear transparency calculations have been made for these nuclei using all existing data between 8 and 100 MeV, and nuclei are found to be most reactive between 10 and 25 MeV, with nuclei becoming increasingly transparent as the incident proton energy increases above about 25 MeV. Using previously measured data from Si to 68Zn, along with the current measurements, we observe that when nuclear size effects are removed, the reaction cross section shows departures from average behavior near shell closings corresponding to N or Z values of 20 and 28.
High-resolution studies of the near-ultraviolet bands of oxygen: III: the system
Authors: Coquart B. , Ramsay D. A.
Published: April 2011

Ten bands of the [Formula: see text] system of oxygen have been observed in absorption using longer path lengths than in the earlier work of Herzberg (1953). Rotational analysis of the bands confirms that the A′ 3Δu state is an inverted state as expected from electron-configuration arguments. Rotational assignments are given for the [Formula: see text] and [Formula: see text] sub-bands with ν′ = 2–11; weaker [Formula: see text] sub-bands are identified for ν′ = 5–11. Sub-band origins and rotational constants are given for all the bands. The following derived molecular constants are obtained:[Formula: see text]A comparison of the frequencies of the diffuse bands of oxygen with the sub-band origins of the [Formula: see text] bands shows convincingly that the diffuse bands can be assigned to a weak (O2)2 complex in which one of the O2 molecules is excited to the A′ 3Δu state.
Calculated energy levels and intensities for the ν1 + ν2 and 3ν2 bands of HDO
Authors: Perrin A. , Camy-Peyret C. , Flaud J. -M.
Published: April 2011

A Hamiltonian taking into account both Fermi- and Coriolis-type interactions has been used to reproduce very satisfactorily the available rotational energy levels of the (1 1 0) and (0 3 0) interacting vibrational states of HDO. Then, a least squares fit of the line intensities of the ν1 + ν2 and 3ν2 bands of HDO has provided us with the transformed transition-moment operators of these two bands expanded in a form adapted to the Cs symmetry type of the molecule. The strong influence of the resonances on both line positions and intensities has been exemplified. Finally, the synthetic spectrum of the ν1 + ν2 and 3ν2 hybrid bands of HDO has been computed.
Quenching of the forward Stokes by phase matching
Authors: Marchand R. , Fedosejevs R. , Tomov I. V.
Published: April 2011

Quenching of the forward Stokes by phase matching in a Raman-active medium is revisited. A parameter range is identified where the small signal gain of the forward Stokes is a decreasing function of the pump intensity. The relevance of this effect to the reduction of the troublesome second Stokes in a Raman laser-pulse compressor is also discussed.
The first hexad {(040), (120), (021), (200), (101), (002)} of H218O: experimental energy levels and line intensities
Authors: Chevillard J.-P. , Mandin J.-Y. , Camy-Peyret C. , Flaud J.-M.
Published: April 2011

The spectrum of 18O-enriched water vapor has been recorded between 5900 and 8000 cm−1, with the aid of a Fourier-transform spectrometer. Its analysis allowed the determination of 437 accurate rotational levels belonging to the hexad of interacting states {(040), (120), (021), (200), (101), (002)}of H218O. Among these vibrational states, the (040), (120), and (002) ones had never been observed before. Moreover, 726 line intensities belonging to the 4ν2, ν1 + 2ν2, 2ν2 + ν3, 2ν1, ν1 + ν3, and 2ν3 bands have been measured with an uncertainty of 6%.
Collision–induced absorption in gaseous methane at low temperatures
Authors: Dagg I. R. , Anderson A. , Yan S. , Smith W. , Joslin C. G. , Read L. A. A.
Published: April 2011

A recently developed theory for collision-induced absorption in methane is compared with experimental results over a wider spectral range and at lower temperatures than previously reported. The present experimental results covering the frequency range below 400 cm−1 exhibit good agreement with other recently published data. The theory shows excellent agreement with experiment in the low-frequency region below approximately 200 cm−1 but underestimates the experimental data somewhat at higher frequencies. Possible theoretical reasons for this discrepancy are given. The theory represents a simple method of obtaining a good estimate of the collision-induced absorption spectra of methane in this frequency region and for extrapolating to lower temperatures for which experimentation is not feasible. In addition, the moments α1 and γ1are compared with earlier determinations and indicate good agreement with the previously obtained values for the octupole and hexadecapole moments of methane.
Excitation of hydrogen and hydrogenlike ions by impact of hydrogen
Authors: Khurana Indira , Srivastava Rajesh , Tripathi A. N.
Published: April 2011

A 1s–2s excitation of H atoms and H-like ions by impact of a hydrogen atom is reported for the second Born approximation as well as in the distorted-wave Born approximation. Differential and total cross sections are presented and compared with previous calculations and experimental measurements.
Chiral anomalies and dimensional regularization
Authors: Treml T. F.
Published: April 2011

The chiral anomaly associated with a massless Dirac fermion interacting with vector, axial-vector, scalar, and pseudoscalar background fields is derived in a nonperturbative manner in any even dimension using a coordinate-space form of dimensional regularization. Scalar and pseudoscalar external fields are shown not to contribute to the minimal chiral anomaly, for which explicit formulae are presented. The minimal chiral anomaly is argued to be independent of the specific form of the higher dimensional non-fully-anticommuting generalization of γ5 that is used in dimensional regularization, although the validity of this argument is possibly restricted by the fact that only the vector-current-conserving anomaly has been obtained.
On the finite-rank approximation of wave operators and the S matrix using Hermite expansion functions
Authors: Kröger Helmut
Published: April 2011

For the quantum mechanical, nonrelativistic two-body system, wave operators can be approximated by exponentials of finite-rank operators obtained by finite-dimensional projections of the full and the asymptotic Hamiltonian onto a set of Hermite functions. This yields a weak approximation of the S matrix.
Fluctuations in laser-produced plasmas
Authors: Rozmus W.
Published: April 2011

The theory of stable fluctuations, sustained owing to particle discreteness, is discussed in the context of laser-fusion plasmas. After a short review of basic results from fluctuation theory, the kinetic description of homogeneous underdense plasmas in the field of a strong electromagnetic wave is presented. The enhancement of the fluctuation level in the subthreshold regime of parametric instabilities and its effect on collisionality are discussed. The theory of hydrodynamical fluctuations in highly compressed cold plasmas is then derived. The kinetic model for this strongly coupled, two-component plasma is renormalized, taking proper account of static correlations. The results for electron conductivities are presented, extending Braginskii's theory into the strongly coupled regime.
Laser–plasma interaction physics in underdense coronal plasmas
Authors: Boyd T. J. M.
Published: April 2011

After a brief review of stimulated Raman scattering and two-plasmon decay, which dominate the physics of laser–plasma interactions at and below the quarter-critical density, we summarize some of the principal characteristics of emission from targets at half-harmonics of the laser frequency. Two mechanisms in particular are thought to contribute to the emission; Raman conversion and the direct linear conversion of plasmons generated by two-plasmon decay. Both processes are reviewed and the implications of each for the emission spectra examined.The effect of strong self-generated magnetic fields on harmonic generation is considered briefly and attention is drawn to ways in which the coincidence of interactions in the underdense plasma may influence their basic characteristics. A finite-amplitude ion wave, for example, modifies the spectrum of Raman scattered light, including significant frequency splitting.
Computer simulations of absorption and scattering
Authors: Langdon A. Bruce
Published: April 2011

This paper discusses computer simulation of absorption and scattering of laser light, under conditions relevant to laboratory achievement of thermonuclear fusion by laser-driven inertial-confinement methods. We enumerate the principal absorption and scattering processes and their requirements for accurate mathematical modelling. The principal tool, so-called particle-in-cell simulation, tracks particles through electromagnetic fields calculated self-consistently from the charge and current densities of the particles themselves, external sources, and boundaries. Many references are given. Special attention is given to two-plasmon decay.
Plasma effects in laser fusion: past and future
Authors: Johnston Tudor Wyatt
Published: April 2011

Plasma effects in laser fusion are given a quick overview (past and present) and major trends are indicated. No prior familiarity with laser fusion or with plasma physics is assumed.
Comments on the present state of laser fusion
Authors: Thompson W. B.
Published: April 2011

A brief survey is presented of the present state of laser fusion. After a short introduction and a comparison with magnetic confinement, a discussion of current research is presented, largely reviewing papers collected in this issue of the Canadian Journal of Physics.
Fractons and the fractal dimension of proteins
Authors: MacDonald Mairi , Jan Naeem
Published: April 2011

We present numerical results and theoretical arguments to support the model introduced by Stapleton–Helman to describe the fractal and fracton dimensionalities of a protein. We postulate that the model, which is a self-avoiding walk with massless bonds, may have limited applicability in satisfying the known bonding requirement of proteins but a folding model may have the desired characteristics.
Difference-frequency laser spectroscopy of the ν4 fundamental band of NH3D+
Authors: Nakanaga T. , Amano T.
Published: April 2011

The high-resolution spectrum of the ν4 fundamental band of NH3D+ has been observed in absorption in a hollow-cathode discharge with a difference-frequency laser system. The molecular constants have been determined through a least squares fit of the observed transition wave numbers to an effective Hamiltonian. The equilibrium rotational constant is estimated to be 4.438 ± 0.027 cm−1, from which the equilibrium N—H bond length is calculated to be 1.021 ± 0.003 Å. Some low-lying rotational transition frequencies in the ground state are calculated to assist in the search for pure rotational transitions in the laboratory and in interstellar space.
Exchange collisions between positronium and lanthanide ions
Authors: Bisi A. , Consolati G. , Zappa L.
Published: April 2011

Collisions of the Ps atom with unpaired electrons were studied in aqueous solutions of lanthanide ions through measurements of lifetimes and through a magnetic-quenching experiment. It was found that the ortho–para conversion rate per ion is proportional to the number of unpaired electrons. To each of these there corresponded a spin-conversion cross section σ of 1.5 × 10−20 cm2.
A flux-tube model of hadrons in nuclear matter
Authors: Mathieu P. , Watson P. J. S.
Published: April 2011

A flux-tube model of hadrons is used to study the modification of hadronic properties in nuclear matter. It is shown that nuclear binding and the EMC effect are consequences of partial deconfinement, and that complete deconfinement occurs at about six times normal nuclear density. It is predicted that nucleon resonances are much more strongly bound than the nucleon, and that there is a maximum l beyond which nucleon resonances do not exist in nuclear matter.
Birkeland currents correlated with direct-current electric fields observed during the CENTAUR Black Brant X rocket experiment
Authors: Primdahl F. , Marklund G.
Published: April 2011

Vector magnetic-field observations from two rocket flights in the winter polar cusp during the CENTAUR project show several groups of upward and downward flowing small-scale Birkeland current sheets in the afternoon region of the cusp, whereas none are detected at noon. High correlation with electric-field observations allow calculation of the height-integrated Pedersen conductivity, and an estimate is made of the ionospheric input power density associated with the Birkeland currents. This input power density is comparable to that of a similar summertime experiment at nearly the same magnetic local time and under almost the same interplanetary magnetic-field conditions, despite an order-of-magnitude difference in ionospheric conductivity. Indications are that the magnetospheric energy source for these two events more closely resembles a constant-power generator rather than a constant-voltage or a constant-current generator.
Dynamics of the postnoon auroral oval
Authors: McEwen D. J. , Creutzberg F.
Published: April 2011

The morphology of the postnoon auroral oval (1300–1500 magnetic local time) as determined by ground-based optical observations with all-sky TV's and meridian scanners at Sachs Harbour, N.W.T., and Cape Parry, N.W.T., is described. Arcs associated with the "inverted-V" type of precipitation events, frequently observed with rocket and spacecraft particle detectors during this time period, are found to be short-lived, narrow, and sometimes of very restricted east–west extent. These arcs form the main feature of the auroral oval, which appears to be delineated almost ex0clusively by 6300-Å emission. The mechanism for their generation is consistent with local injections of magnetosheath plasma into the dayside boundary layer.
Diffraction by a half plane in a gyrotropic medium (normal incidence)
Authors: Przeździecki S. , Hurd R. A.
Published: April 2011

An exact, closed-form solution is found for the following problem of half-plane diffraction in a gyrotropic medium. (i) A perfectly conducting half-plane is parallel to the distinguished axis of the medium with the edge perpendicular to the axis. (ii) The incident-wave direction is normal to the edge of the half-plane.The problem is phrased as a boundary-value problem for a system of two coupled second-order partial differential equations. Two basic properties characterize the problem. (i) It is two-moded; that is, superpositions of both ordinary and extraordinary waves are necessary for the spectral representation of the solution. (ii) It involves reflection coupling of the modes; that is, modes couple on reflection from an entire plane.The formulation of the problem leads to two uncoupled Wiener–Hopf equations that are solved in the classical manner. This is in contrast to previous two-mode half-plane gyrotropic problems where Wiener–Hopf equations were coupled, requiring advanced techniques for their solution. Basic properties of the solution (for example, excitation of surface waves) are briefly discussed.
The quadrupole moment of cyanogen: a comparative study of collision-induced absorption in gaseous C2N2, CO2, and mixtures with argon
Authors: Dagg I. R. , Anderson A. , Yan S. , Smith W. , Joslin C. G. , Read L. A. A.
Published: April 2011

The collision-induced spectra of C2N2 gas and a gaseous mixture of C2N2 and Ar at 298 K have been obtained in the spectral region below 120 cm−1 using far-infrared laser and microwave techniques as well as a Fourier-transform spectrometer. In addition, the collision-induced spectra of a gaseous mixture of CO2 and Ar are reported at temperatures of 233 and 298 K in the spectral region below 230 cm−1. The theoretical values for the spectral moments α1 and γ1 for CO2 are much smaller than the experimental values, as expected for a molecule with a relatively large quadrupole moment. However, for CO2–Ar mixtures, the agreement between the theoretically and experimentally determined spectral moments is relatively good, resulting in a value of 4.6 B for the quadrupole moment of CO2 instead of the generally accepted value of 4.3 B. The quadrupole moment of C2N2 is estimated to be 6.2 ± 0.4 B from our data and the theory for the spectral moments, if a correction is made for an overestimate of the quadrupole moment similar to that obtained for the CO2–Ar mixture. This value is considerably smaller than a previously reported calculated result of 9.0 B. Line-shape expressions based on information theory (IT6) do not yield good agreement with experiment, a result that is attributed to the large anisotropy of the molecules.
Scaling of the multiplicity distribution of target protons emitted in relativistic heavy-ion collisions and antiproton annihilation in nuclei
Authors: Ghosh Dipak , Roy Jaya , Sengupta Ranjan
Published: April 2011

This paper reports the observation of Koba–Neilsen–Olesen-type scaling in the multiplicity distribution of medium-energy protons emitted in relativistic heavy-ion interactions and antiproton [Formula: see text] annihilations in nuclei. The data have been taken from 12C–AgBr (emulsion) interactions at 4.5 GeV∙c−1∙nucleon−1 and [Formula: see text] annihilation in emulsions at 1.4 GeV∙c−1
Direct detection of two-quantum coherence
Authors: Bloom Myer , LeGros Mark A.
Published: April 2011

A theoretical analysis of the oscillating voltage at twice the Larmor frequency (2ω0), due to quadrupolar polarization of 14N nuclei, predicts a signal at least ten orders of magnitude smaller than the magnetic-induction signal produced by the same sample. However, nonsecular parts of the quadrupolar interaction are predicted to give rise to observable magnetic-induction signals at 2ω0 that provide a monitor of "two-quantum coherence." The theoretical prediction is verified using a single crystal of NaNO2 at room temperature. The corresponding signal from a crystalline powder is zero. Some limitations and possible extensions of the experiment are proposed.
The time evolution of quantum systems with discrete energy spectra
Authors: Lupaşcu A. I. , Popescu I. M.
Published: April 2011

Using the method of matrix functions, we describe the time evolution of quantum systems with discrete energy spectra. The time evolution of the state vectors and expressions for the perturbed eigenfunctions and their associated projectors are obtained for an atom with n discrete levels. The particular cases n = 2 and n = 3 are presented; level crossing and nonexponential decay of coupled states are emphasized.
Confinement of disordered radiation by a false vacuum
Authors: Wolf C.
Published: April 2011

The common belief that ultrarelativistic particles and disordered radiation obeying the equation of state P = ε/3 cannot be contained by the gravitational field is shown to be incorrect if a thin film of Higgs vacuum (away from the minimum of the potential) is allowed to provide a transition region between the interior and the true vacuum outside the astrophysical object.
Electromagnetic field and losses from a vibrating wire carrying current parallel to a conducting slab
Authors: Ciric I. R. , Mathur R. M.
Published: April 2011

Exact expressions of the electromagnetic-field quantities and the power loss for an infinite conducting slab in the proximity of a straight wire carrying direct current and vibrating in a plane parallel to the slab surface have been obtained by means of the magnetic vector potential, assuming a two-dimensional field. The solutions are valid for both nonmagnetic and magnetic slabs, within the linear material characteristics, and for any values of the parameters characterizing the system geometry and the vibration. Simple formulas for the losses have been derived for a range of parameters that may have a practical application. The results presented can be used for evaluating the electromagnetic effects due to vibrating-current distributions, and also for measuring the amplitude of their vibration.
O2-triplet emissions in the nightglow
Authors: Murtagh D. P. , Witt G. , Stegman J.
Published: April 2011

Measurements of the volume-emission profiles of O2-triplet emissions have been obtained in conjunction with determinations of atomic-oxygen density under different geophysical conditions. Recent results pertaining to the altitude distribution of the different vibrational levels of [Formula: see text] are discussed, and the excitation mechanism of this state is considered. A critical analysis of some laboratory measurements relevant to O2-triplet emissions is undertaken, and suggestions for further work are made. Also discussed is the relative intensity of the Herzberg-I and Chamberlain bands.
The formation of O2(a1Δg) in homogeneous and heterogeneous atom recombination
Authors: Ali A. A. , Ogryzlo E. A. , Shen Y. Q. , Wassell P. T.
Published: April 2011

The recombination of oxygen atoms has been studied in a discharge flow system at room temperature. The yield of O2(a1Δg) in the recombination on Pyrex has been found to be 0.08 (±0.02). In the gas phase, O2(a) was found to be formed in a process that is second order in [O] and first order in [N2]. The rate constant for this third-order reaction was found to be 3.4 (±0.4) × 10−34 cm6∙molecule−2∙s−1, representing a yield of 0.07 (±0.02). In the presence of molecular oxygen, the rate of production of O2(a) was found to increase. A kinetic study of this effect led to the conclusion that collisions of molecular oxygen with an unidentified precursor can produce O2(a) with high efficiency.
Windows in direct dissociative recombination cross sections
Authors: Guberman Steven L.
Published: April 2011

Model potential curves are used to show that large windows are present in direct dissociative-recombination cross sections from excited molecular-ion vibrational levels. The windows are due to the overlap of vibrational wave functions of the repulsive neutral states with the nodes of the ion vibrational wave functions.
Uniaxial stress and strain derivatives of the Fermi-surface necks in gold
Authors: Klimker H. , Perz J. M. , Lee M. J. G.
Published: April 2011

Simultaneous measurements of quantum oscillations in magnetostriction and torque in a single crystal of gold have been used to determine precise values for the derivatives of the cross-sectional area of the [111] neck of the Fermi surface with respect to uniaxial tensile stress along the [110] and [Formula: see text] directions. Independent estimates of the derivative with respect to uniaxial tensile stress along [111] of the neck area have been deduced from appropriate combinations of the [110] and [Formula: see text] stress derivatives with the established hydrostatic-pressure derivative. These estimates are in excellent agreement, giving ∂ lnA111/∂σ111 = (11.5 ± 0.3) × 10−12cm2∙dyn−1 (1 dyn = 10 μN). This result is significantly larger than the result of early direct-tension measurements in gold, suggesting that the latter suffered from systematic error. The present result is consistent with, and more precise than, earlier magnetostriction and direct uniaxial compression data. The angular shear derivative ∂ ln A/∂γ = 5.56 ± 0.17, deduced from the present data, is slightly larger than the theoretical value of 4.80 ± 0.20 obtained from a relativistic Korringa–Kohn–Rostoker phase-shift calculation based a rigid spherical muffin-tin pseudopotential.
Boundary-layer growth on a rotating and accelerating sphere
Authors: Karahalios G. T. , Theofilis V.
Published: April 2011

Boundary-layer growth on a sphere is studied when it is set into motion with constant acceleration and constant angular velocity, the latter being normal to the former. Analytic expressions are derived for the velocity components of the incompressible fluid in terms of a power series of the time of motion as well as for the skin friction.
Zero-temperature properties of quantum spin models on the triangular lattice II: the antiferromagnet
Authors: Fujiki S. , Betts D. D.
Published: April 2011

The calculation of two- and four-spin correlations of the [Formula: see text] antiferromagnet has been extended to an N = 21 site triangular lattice. By fitting a quadratic in 1/N to the nearest neighbour transverse spin correlations, we have estimated the ground-state energy per bond on the infinite lattice to be E0/3NJ = −0.2716 ± 0.005. The nearest neighbour longitudinal correlation is estimated to be [Formula: see text]. A short-range order parameter, the chirality, is defined and estimated for the infinite lattice. From the N dependence of the three sublattice or helical magnetization, the spin correlation is conjectured to decay algebraically as [Formula: see text].
The driven quantum-mechanical two-level system: small fields and long relaxation times
Authors: Grindlay J.
Published: April 2011

A formal theory of the long-term response of a dissipative two-level quantum-mechanical system to a monochromatic applied electric field is used to describe the fundamental and third-harmonic resonances in the small-field and long relaxation-times regime. Resonance frequencies, including Bloch–Siegert shifts, and resonance amplitudes for the dipole-moment components and the upper level probability function are obtained. A comparison with the rotating-wave approximation is made.
Decay of 96Tc as a test of statistical methods of spin assignment
Authors: Mach H. , Johns M. W.
Published: April 2011

Statistical methods of spin assignment have been tested on the 96Tc nucleus populated in the (α, n) reaction. Simple model calculations reproduce two intensity-spin correlations and confirm that the energy corresponding to the maximum in the excitation function and the ratio of gamma-ray intensities obtained at two beam energies both show smooth and strong spin dependence. These correlations are found to be marginally influenced by the yrast and non-yrast character of the levels and are not influenced by level-excitation energy. Contribution from pre-equilibrium reactions and competition between neutron and gamma decay channels may be responsible for minor discrepancies between the calculated and experimental excitation functions.
Angle-of-arrival measurements of ionospheric irregularities
Authors: Griffioen E. , Lyon G. F.
Published: April 2011

Recent improvements in instrumentation permit sufficient resolution in angular-deviation measurements to yield information on the shape of irregularities. The expected deviation imposed upon very high frequency signals from an orbiting satellite by an irregularity with a Gaussian electron-density distribution is modelled. The model predictions are fitted to experimental observations made at Churchill, Man. (59°N, 94°W geodetic). The data used are differential phase measurements of the coherent 150- and 400-MHz transmissions from satellites of the Navy Navigation Satellite System. Irregularities with both electron-density enhancements and depletions are found, with elongations in the direction of the magnetic field somewhat less than had been previously reported.
Effect of hydrostatic pressure on the structural phase transition in K2OsCl6:a35Cl nuclear quadrupole resonance
Authors: Krupski Marcin , Armstrong Robin L. , Maćkowiak Mariusz , Zdanowska-Fraczek Maria
Published: April 2011

The 35Cl nuclear quadrupole resonance frequency is reported in K2OsCl6 at temperatures in the vicinity of the structural phase transition for three externally applied hydrostatic pressures. The phase-transition temperature, Tc, decreases linearly with pressure, and the pressure coefficient, (dTc/dP), is measured to be −(2.2 ± 0.3) × 10−2 K∙MPa−1. This value is compared with that measured for K2ReCl6 and is consistent with the prediction of a calculation based on a modified rigid-sphere model. Measurements of (∂v/∂P)T show precursor behaviour as Tc is approached from the high-temperature cubic phase.
Time-resolved photoluminescence in CdIn2S4
Authors: Charbonneau S. , Fortin E. , Beauvais J.
Published: April 2011

Photoluminescence spectra of CdIn2S4 single crystals at 1.8 K under both continuous-wave (CW) and pulsed excitation were obtained. In the latter case, a variable time-window technique was used to observe the time evolution of the spectra between 0 and 100 μs. In contrast to previous studies, four spectral bands were observed under both CW and pulsed, intrinsic or extrinsic excitation. In particular, two bands previously unobserved under extrinsic excitation were detected at 1.35 and 1.68 eV, and have been attributed to donor–acceptor pairs and free-electron to acceptor transitions respectively.
Decimation transformations in high-temperature renormalization-group methods
Authors: Fujiki N. M. , De'Bell K.
Published: April 2011

The high-temperature series renormalization group developed by Betts et al. is modified by using the decimation transformation. A conventional fixed-point analysis of the recursion relations is discussed and, in addition, an analysis based on scaling relations for correlation functions is considered. As test cases, we apply these methods to two-dimensional Ising systems with nearest neighbour interactions. The results for a triangular and a square lattice are presented.
Thermodynamic theory of simple liquid metals and alloys
Authors: Young W. H.
Published: April 2011

The ab initio theory of the thermodynamic properties of simple s–p bonded liquid metals and alloys is reviewed. The first part deals with pure metals, where the ideas of pseudopotential theory (governing the electronic motion) and thermodynamic perturbation theory (governing the atomic motion) are combined. The result is a credible description, which is mostly semiquantitative. The second part deals with alloys for which a similar formal approach is possible; a variety of alloy properties are thus explainable. The extent, however, to which the conventional formulation of pseudopotential theory can be straightforwardly applied to alloys has yet to be delineated.
Charge distribution in liquid metals and alloys
Authors: Tamaki S.
Published: April 2011

Electron distribution in liquid metals and charge transfer in liquid alloys are qualitatively and quantitatively discussed in terms of the structure factors and the thermodynamic quantities obtained experimentally. The electron distribution around an ion in liquid metals has been derived from the difference in structure factors determined by X-ray and neutron-diffraction methods with the help of a theoretical calculation of the electron–electron correlation function. Charge transfer in liquid alloys is also estimated by using the partial structure factors in the long-wavelength limit and the Thomas–Fermi screening theory. The charge-transfer effect in liquid alloys is also verified by the measurements of partial structure factors and magnetic susceptibilities.
The transient behaviour of the electric field strength above an atmospheric surface duct
Authors: Bishay Samira T.
Published: April 2011

The duct model used here is that of Kahan and Eckart. It has a discontinuous drop of the otherwise constant relative permittivity at the upper duct boundary. The earth is assumed to be a perfect conductor and an ideal plane. The source of the electromagnetic field is taken to be a vertical magnetic dipole, in the upper surface layer, with an arbitrary time-varying moment. The method used for solution is essentially based on the application of two functional transforms. Starting with the wave equation of the electric field strength and applying a Laplace transform in time, one then finds a two-dimensional Fourier transform in the horizontal coordinates in space leading to an integral representation of the solution of the wave equation in transform space, considering initial, boundary, and transition conditions. Having chosen a horizontal polarization of the primary source, one can determine the transient behaviour of the electric field strength at any distance above the duct.
Radiative lifetimes of 4snflF3 states of calcium
Authors: Bhatia K. S.
Published: April 2011

By using stepwise excitation and the pulse-modulated laser spectroscopy technique, lifetimes of 4snf1F3 states have been measured for n = 4, 5, and 6. These states were reached by photon absorption from the intermediate 4s 3d1D2 metastable state populated by a dc discharge. Values obtained for the lifetimes were τ(4f1F3) = 24.6(1.4)ns, τ(5f1F3) = 62.1(2)ns, and τ(6f1F3) = 99(4)ns. Results have been compared with the t values obtained for some of these levels by other authors using the Hanley method and single-pulse excitation techniques.
e±–He scattering using model polarization potentials
Authors: Mandal Sunil K. , Basu Madhumita
Published: April 2011

Different variants of model polarization potentials have been employed for electron (e)±–He scattering. Present model polarization potentials contain only one adjustable parameter. The s-, p-, and d-wave phase shifts have been computed for the system. Results are found to be in good agreement with those of variational calculations.
Generalized moments for low-frequency modes in tokamaks and their application to drift and ballooning instabilities
Authors: Hirose Akira
Published: April 2011

It is shown that the recently proposed electrostatic ballooning formulation in tokamak geometry absolutely destabilizes electrostatic drift waves (universal instability), and also further destabilizes the magnetohydrodynamic ballooning instability (finite ion Larmor-radius destabilization). The ion-density perturbation responsible for electrostatic ballooning effects have been derived by three independent methods: fluid approximation, the gyro-kinetic equation in a toroidal geometry, and the full kinetic equation in a plane-slab geometry with effective g (gravitational acceleration). All have yielded a consistent result. Toroidicity-induced frequency downshift is responsible for the universal mode, which smoothly reduces to the (stable) drift mode in slab geometry. For finite ion Larmor-radius destabilization of ballooning modes, toroidicity (due to magnetic drifts)-induced coupling with drift waves is also responsible.
Oscillator-strength distribution in the discrete and continuous spectra of the alkali elements
Authors: Barrientos Carmen , Martin Inmaculada
Published: April 2011

The oscillator-strength distribution between the discrete and continuous regions of the spectrum of the alkali elements Li, Na, K, Rb, and Cs has been obtained by following the quantum defect orbital (QDO) procedure. Continuity across the spectral-series limit has been found, and ionization-threshold cross sections are also reported.
Flow and pressure transients in a pulsed plasma jet
Authors: Haley R. , Simeoni D. , Smy P. R.
Published: April 2011

Simultaneous streak photographs of plasma luminosity within and without a pulsed plasma–jet cavity provide strong evidence that arc instabilities inside the cavity arc responsible for the well-known inhomogeneities in the luminous pattern of the jet. Pressure measurements obtained with a high-speed optical technique reveal that most of the gas is expelled from the cavity within about 30 μs and that the luminosity inhomogeneities do indeed correspond to substantial fluctuations in mass flow rather than just variations in temperature. It is concluded that such variations in How constitute a likely source of intense turbulence, and as such, form an important part of the igniter's known ability to enhance the rate of combustion in its vicinity.