bluuebunny/crossref_metadata_2025 huggingface dataset:
The paramagnetic germanium–sodium impurity centres and in α-quartz
Authors: Dickson R. S. , Weil J. A , Davis P. H.
Published: April 2011

Centres [Formula: see text] formed in α-quartz by 77 K x irradiation and warming above ca. 165 K, both exhibit a reversible change in symmetry of the centres from C1 at 75 K to C2 at 295 K, as observed by X-band electronic paramagnetic resonance spectroscopy. Each centre contains a Ge3+ ion (S = 1/2) substituted for a Si4+ ion, with a nearby Na+ interstitial ion. Spin-Hamiltonian electronic Zeeman, 73Ge and 23Na nuclear hyperfine and quadrupole parameter matrices for these centres were measured at temperatures 75, 190, and 295 K. They show that the change is associated with the defect reorienting between sites related by a two-fold crystallographic axis a, with energy barrier 0.223(6) eV for A and 0.178(14) eV for C. In both centres, ca. 50% of the spin density is located in a Ge sp orbital; in A, the sp orbital is oriented close to a, while in C it is nearly parallel to an O–Si–O bond-angle bisector that is nearly normal to a. Theoretical hyperfine matrices indicate that the Na ions are located near a, in a c-axis channel near the Ge site. Above ca. 270 K, A and C are observably in equilibrium, and are thus deemed to be isomeric species.
Higher order nonlinear and dispersive effects on ion-acoustic solitary waves
Authors: Das K. P. , Majumdar S. R.
Published: April 2011

Starting from an integrated form of the system of governing equations in terms of pseudopotential, higher order nonlinear and dispersive effects are obtained for an ion-acoustic solitary wave. The advantage of the method developed here is that instead of solving a second-order inhomogeneous differential equation at each order in the reductive perturbation method, we are to solve a first-order inhomogeneous equation at each order. Expressions are obtained for both the Mach number and the width of the solitary wave as functions of amplitude, including higher order corrections.
Branching ratios for the decay of the 8.78 and 8.91 MeV states of 14N
Authors: King J. D.
Published: April 2011

Branching ratios for the decays of the 8.78 MeV [Formula: see text]; T = 1 and 8.91 MeV [Formula: see text]; T = 1 states in 14N were determined following their population by proton capture on an enriched 13C target. This is the first detailed study of the decay of the 0− state; five transitions were observed. Branching ratios for the 3− decay are in good agreement with previous results.
Ballooning and drift-Alfven modes in tokamaks
Authors: Hirose A. , Choudhury S. Roy , Ishihara O.
Published: April 2011

The magnetohydrodynamic (MHD) ballooning mode in tokamaks was analyzed in the compressible limit. The stability boundary becomes strongly dependent on the toroidicity parameter, εn. This was confirmed by a semilocal kinetic dispersion relation that incorporates kinetic resonances of both ions and electrons. The stability boundary found from the kinetic dispersion relation is insensitive to the degree of plasma compressibility. A nonideal MHD analysis revealed a marginally stable drift-Alfven mode described by [Formula: see text] when βθ (poloidal beta) is of order unity.
Numerical investigation of high-temperature effects in the UTIAS–RPI hypersonic impulse tunnel
Authors: Groth C. P. T. , Gottlieb J. J. , Sullivan P. A.
Published: April 2011

The hypersonic impulse tunnel of the University of Toronto Institute for Aerospace Studies (UTIAS) and Ryerson Polytechnical Institute (RPI) is a short-duration blow-down experimental wind tunnel capable of producing high-Mach-number flows (Ma ≈ 8). A generalized quasi-one-dimensional nonstationary flow analysis and associated total-variation-diminishing (TVD) finite-difference solution schemes, including aproximate Riemann solvers, are presented for predicting the high-temperature flows in such facilities. The analysis is used to investigate the operation of the UTIAS–RPI facility and produce performance data that are not always easily determined or available from experimental measurements. The thermodynamic state of the nozzle-exit flow and high-temperature or real-gas effects are assessed for this facility under various operating conditions. Numerical results, coupled with additional comparisons with available experimental data, demonstrate the range of test-section flows that may be achieved. They also illustrate that for typical operating conditions, the air (working gas used in UTIAS–RPI facility) freezes in the nozzle very close to the throat and results in test-section flows with considerable energy bound in the vibrational modes of the nitrogen (N2) and oxygen (O2) molecules. In particular, the test-section temperatures associated with the vibrational modes of N2 are only marginally less than barrel-end stagnation temperatures, whereas the vibrational temperatures of O2, although lower than stagnation temperatures, are still much higher than the predicted translational–rotational temperatures.
On using the Freedman–Townsend model to generate massive vectors
Authors: McKeon D. G. C.
Published: April 2011

The Freedman–Townsend model involves a gauge invariant coupling of an antisymmetric tensor field [Formula: see text] to a non-Abelian vector gauge field [Formula: see text] and an auxiliary gauge field [Formula: see text]. We analyze the dynamical degrees of freedom in this model and investigate unitarity by considering several four-point functions at the tree level. The model is found to describe a massive vector meson with the transverse degrees of freedom residing in [Formula: see text] and the longitudinal degree of freedom in [Formula: see text]. If an extra gauge-invariant term involving the square of the divergence of [Formula: see text] is added to the Lagrangian, then a scalar polarization appears in this field and [Formula: see text] is no longer simply auxiliary. This scalar mode serves to cancel the bad ultraviolet behaviour of the longitudinal mode, but only at the expense of having no lower bound to the energy spectrum of the theory. Furthermore, an examination of four-point tree level graphs indicates that if we consider elastic scattering of longitudinal modes, the amplitudes grows with the energy scale of the process, whether or not the scalar mode is present.
On the application of supersymmetric WKB (Wentzel–Kramers–Brillouin) method to quasi-exactly solvable problems
Authors: Roy P. , Roychoudhury R. , Varshni Y. P.
Published: April 2011

The WKB (Wentzel–Kramers–Brillouin) as well as the SWKB quantization rules are applied to a number of quasi-exactly solvable problems (which apart from being SU(2) symmetric are also supersymmetric). The results obtained by these methods are compared with the exact numerical results.
Systematic trends along the potassium sequence: Study of ns2S–mp2P0 transitions
Authors: Martin Inmaculada , Lavín Carmen , Barrientos Carmen
Published: April 2011

The quantum defect orbital (QDO) method, with the use of a core polarization-corrected dipole transition operator, was employed to determine oscillator strengths for potassium and some of its isoelectronic ions (CaII–CrVI). The inclusion of core-valence polarization effects leads to a general improvement of the QDO f values. Systematic trends of individual oscillator strengths along the isoelectronic sequence are also shown in a graphical form.
Distribution of quantum states in enclosures of finite size: II
Authors: Souto J. Hugo , Chaba A. N.
Published: April 2011

By making use of the modified form of Poisson's summation formula, we calculate the expression for the number of eigenstates, N(K), with eigenvalues [Formula: see text] of a particle in spherical and cylindrical enclosures of finite size, and with its wave-function subject to Dirichlet boundary conditions and Neumann boundary conditions at the walls of the container. We also obtain the oscillatory terms in addition to the important nonoscillatory terms already known and compare our results with the actual number of such states computed from the tables of the zeros of the relevant special mathematical functions. The inclusion of these oscillatory terms improves the accuracy of the expressions in all cases, especially in the case of the cylinder, where these are quite significant. Some possible applications of the results obtained here are also indicated.
Thermal effect in the resonance fluorescence of a two-level system
Authors: Fonseca C. H. A. , Ribeiro L. A. Amarante
Published: April 2011

The damped two-level system, driven by a strong incident classical field near resonance frequency is subjected to the effect of thermal fluctuations. To simulate the thermal bath we introduce a large system of harmonic oscillators that represents the normal modes of the thermal radiation field. From the Heisenberg equations of motion we calculate the power spectrum of the scattered field and the intensity correlation function. The results show that the presence of the bath dramatically modifies the light scattered by the two-level system when compared with the case without a thermal bath.
New transmission-line matrix node for two-dimensional electromagnetic field problems
Authors: Simons N. R. S. , Sebak A. A.
Published: April 2011

In this paper a new transmission-line matrix (TLM) node for solving two-dimensional electromagnetic field problems is presented. The node is based on a hexagonal rather than rectangular lattice. The scattering matrix and dispersion relation of the new node are provided. The hexagonal TLM method is equivalent to an explicitly time-stepped finite difference algorithm that uses second-order accurate central difference approximations to spatial and temporal derivatives. Comparisons of the propagation characteristics are made with the original rectangular two-dimensional node. The propagation characteristics of the new node are a weak function of the direction of propagation. Therefore in general problems, the amount of velocity error at a given frequency can be obtained from the dispersion relation. A simple method for correcting the velocity error can be utilized to achieve accurate frequency-domain results for coarse discretizations.
Transitions induites entre deux niveaux d'énergie par une impulsion; effets de la durée
Authors: Chardon Jean-Claude , Genty Claude , Labrune Jean-Claude
Published: April 2011

From direct measurement of probabilities of molecule transitions induced, between two energy levels, by an electrical pulse field, the influence of different perturbations is here studied according to their time width D, at constant amplitude. When the sudden passage condition is attained, the transition probability oscillates with a period depending on the integral of action. We principally develop here the case in which this condition is not respected, with a weak electrical field, for some typical impulsion shapes: rectangular, triangular, trapezoidal, and sinusoidal. It is shown that rise time and fall time of the impulsion play an important role and that some effects can be explained when taking into account the evolution of the rect(t/D) function spectrum, characteristic of the finite impulsion duration. These results can be connected with resonance effects in physics of collisions: the D parameter is then equivalent to the interaction time. When the impulsion is a complete sinusoid, it is shown that the resonance frequency is lower than the transition frequency.
The estimation of doping profiles in gallium arsenide using capacitance measurements
Authors: Hui D. , Leong H. , Young L.
Published: April 2011

Measurement of the capacitance (C) of Schottky diodes as a function of voltage (V) is widely used to probe doping profiles in GaAs but the theory that is used is oversimplified and does not work well when the doping changes rapidly with distance. The region beyond the maximum of an implanted Gaussian profile for GaAs is of particular interest in connection with ingot qualification tests and it is just there that the problem is the most serious. We investigated some technically important aspects of the C(V) method by numerical simulation. The doping profile is input into a program, which then predicts the profile that will be obtained if the C(V) method is applied to a specimen with this assumed doping profile. It is found that the estimated maximum doping is not excessively in error and that although the predicted profile is indeed too high in the tail region, differences in constant background doping or in simulated tails due to channelling give differences in the predicted profile that are fairly close to the actual differences in doping. This is important for some practical applications. The estimation of the "percentage activation" of the implanted dopant is analyzed. Fitting a truncated Gaussian to the C(V)-derived profile is shown to give a useful estimate of the input dose.
Born–Oppenheimer breakdown in the ground state of carbon monoxide: A direct reduction of spectroscopic line positions to analytical radial Hamiltonian operators
Authors: Coxon John A. , Hajigeorgiou Photos G.
Published: April 2011

A collection of 10 866 of the most precise ground-state (X1Σ+) vibration–rotational and pure rotational line positions of four carbon monoxide isptopomers (12C16O, 12C18O, 13C16O, and 13C18O) is employed simultaneously in a direct determination of the radial Hamiltonian operator in compact analytical form. The 22-parameter isotopically self-consistent operator takes full account of the Born–Oppenheimer breakdown and its quantum-mechanical eigenvalues represent all the available spectroscopic line positions of CO isotopomers to within the experimental uncertainties. Rayleigh–Schrödinger perturbation theory is employed to calculate quantum-mechanical molecular constants of rotation (Bν – Mν) for nine common isotopomeric forms of CO. Together with the quantum-mechanical vibrational eigenvalues these are fully consistent with the exact eigenvalues obtained by direct solution of the radial wave equation. The set of constants is expected to provide an accurate prediction of line positions of CO isotopomers that have not yet been experimentally observed.
Scattering by a perfectly conducting multislotted cylinder
Authors: Hussein Mousa I. , Hamid M.
Published: April 2011

The problem of scattering by a perfectly conducting multislotted circular cylinder excited by a z-polarized incident plane wave is presented. The solution is carried out using two methods of analysis. In the first method, the fields in and around the cylinder are found in terms of the aperture fields, using the boundary value technique. Then Galerkin's method is introduced to solve for the unknown aperture fields. In the second method, the aperture-field integral equation method is employed and the fields in and around the cylinder are found in terms of the aperture fields, while the resulting equations are solved using the method of moments. Results are obtained and presented using the two methods.
Laser-induced Compton scattering from a bound electron
Authors: Ehlotzky F.
Published: April 2011

We investigate nonrelativistically Compton scattering by an electron bound in hydrogen in a powerful laser field. The corresponding nonlinear rates and cross sections are evaluated in a Keldysh-type of approximation and compared with the rates and cross sections of multiphoton ionization and harmonic generation. We find that multiphoton ionization overshadows Compton scattering by many orders of magnitude, however, Compton scattering may well compete with harmonic generation above the ionization threshold, since, in particular, both processes have the same angular distribution and only odd harmonics can be created by bound electrons, while in bound-free Compton scattering all harmonics will be generated.
An indirect method of measuring gas- and particulate-phase velocities of shock-induced dusty-gas flows
Authors: Gottlieb James J.
Published: April 2011

A method of indirectly measuring the temporally varying velocities of both the particulate and gas phases in the nonequilibrium region of a shock wave moving at constant speed in a dusty-gas mixture is described. This method is implemented by using experimental data from shock-induced air flows containing glass beads 40 μm in diameter in a dusty-gas shock-tube facility featuring a large horizontal channel 197 mm high by 76 mm wide with a special dust-injection device. Simultaneous measurements of the shock-front speed with time-of-arrival gauges, particulate concentration by light extinctiometry, and combined particulate concentration and gas density by beta-ray absorption are used in conjunction with two mass conservation laws to provide these indirect two-phase velocity measurements. Direct measurements of the particulate-phase velocity by laser-Doppler velocimetry are also presented for comparison, and the capability of the indirect velocity-measurement method is assessed.
Étude des résidus numériques en ajustement de données spectroscopiques
Authors: Féménias Jean-Louis , Cheval Gérard
Published: April 2011

We show that a detailed study of the residuals of a fitting to data may bring some statistical information about the numerical pertinence of the theoretical model and about the quality of its optimization. It also provides an interesting way to obtain the pure experimental error with a slightly wrong model. The theory of the method is presented in the framework of least-squares fittings of linear (or almost linear) models. Next, the analysis of results from fittings to a set of spectroscopic measurements on niobium nitride, NbN, gives rise to a discussion about the interest of the method and about its limits.
Far-field patterns of line sources mounted between four-dielectric substrates
Authors: Diamandi Ioanna , Mertzianidis Costas , Sahalos John N.
Published: April 2011

The far-field pattern characteristics of line sources lying between the slabs of a four-dielectric substrate configuration are presented. The patterns are calculated for several cases of the substrate thickness as well as for several line-source locations. The considerations that are made give useful applications in remote sensing and microstrip antennas.
Level structure studies of 182W from the decay of 182Ta
Authors: Chand Bakhshish , Goswamy J. , Mehta Devinder , Singh Nirmal , Trehan P. N.
Published: April 2011

The relative intensities of X rays and γ rays from the decay of 182Ta were measured precisely using Si(Li) and HPGe detectors. The intensities of the different components of K and L X rays were measured for the first time. The conversion electron intensities for the transitions with energy above 800 keV from the 182Ta decay were measured using a mini-orange electron spectrometer and the internal conversion coefficients for various transitions in 182W deduced. The (M + N)-conversion coefficients for the 1001.7, 1189.1, 1231.0, 1257.2, 1289.2, and 1342.7 keV transitions in 182W were measured for the first time. Also, γ–γ coincidence and correlation measurements were carried out using a HPGe–HPGe coincidence setup (2τ = 7 ns). The directional correlation coefficients for the 928–229, 960–229, 1002–229, 1044–229, 1158–229, 1223–229, and 1002–222 keV cascades in 182W are determined for the first time. The multipole mixing ratio for the 152, 156, 179, 222, 928, 1002, 1113, 1158, 1223, and 1231 keV transitions are deduced from the present directional correlation and conversion coefficient measurements. Experimental ratios of reduced transition probabilities for the transitions in 182W from positive and negative parity states are deduced and compared with the values predicted by the symmetric rotor model. From this comparison a unique K assignment of Kπ = 1+ and Kπ = 1− is made to the bands built on the 1257 and 1553 keV levels, respectively.
P-matrix description of the two-particle interaction
Authors: Babenko V. A. , Petrov N. M. , Sitenko A. G.
Published: April 2011

This paper deals with the formalism of the P-matrix description of the two-particle interaction within the framework of which the inverse scattering problem is considered. Separating, explicitly the P-matrix background part, associated with the free motion, yields a simple expression for the off-energy-shell scattering amplitude that immediately provides its separable expansion. Such separation corresponds to the partial summation of the initial P-matrix series and improves the description of physical quantities as functions of energy, provided the residual P matrix is approximated by a finite number of pole terms.
Differential angular correlation of the 1408–122 keV cascade and the g factor of the 122 keV 2+ level of 152Sm
Authors: Dey C. C. , Das N. R. , Sinha B. K. , Bhattacharya R.
Published: April 2011

Time-differential angular-correlation measurements on the 1408–122 keV cascade of 152Sm were performed in liquid EuCl3 and Eu(NO3)3 sources at a time resolution of 450 ps. The results obtained are λ2 = (8.3 ± 2.0) × 107 s−1, A2(0) = 0.218 ± 0.008 in SmCl3 and λ2 = (2.5 ± 2.1) × 107 s−1, A2(0) = 0.206 ± 0.018 in Sm(NO3)3. Integral angular-correlation measurements on the 244–122, 964–122, and 1112–122 keV cascades were also performed in the same chloride and nitrate sources using a NaI(Tl)–HPGe system. Using the values of λ2, the unperturbed angular-correlation coefficients for these cascades are determined and therefrom the mixing ratio of the λ transitions are found to be δ(1408) = 0.05 ± 0.01, [Formula: see text] and [Formula: see text]. The magnetic moment of the 122 keV 2+ level was remeasured and a value of μ = 0.80 ± 0.06 nm was obtained.
Pseudopotential calculations of elastic scattering of low-energy electrons (< 20 eV) from neon atoms
Authors: Frongillo Y. , Plenkiewicz B. , Plenkiewicz P. , Jay-Gerin J.-P.
Published: April 2011

Pseudopotential calculations of phase shifts, differential, total, and momentum-transfer cross sections for electrons elastically scattered from neon atoms are reported in the impact energy range 0–20 eV. The results are found to be in very good agreement with existing experimental and other theoretical data.
Multiharmonic nuclear Hamiltonian
Authors: Anagnostatos G. S.
Published: April 2011

The present study successfully extends the independent-particle shell model by employing a multiharmonic oscillator potential for nuclei from 16O to 208Pb. Specifically, this study assumes a separate and different central potential for the nucleons of each shell, instead of a common central potential for all nucleons in a nucleus as is usually assumed by the conventional shell model. The present extension of the shell model leads to a simultaneous direct treatment of ground-state radii and binding energies for a sample of nuclei, i.e., 16O,28Si, 36Ar, 40Ar, 40Ca, 56Fe, 58Ni, 90Ni, 90Zr, 104Pd, 110Pd, 120Sn, 126Te,136Ba, 138Ba, 142Nd, 202Hg, and 208Pb.
Mid-latitude ionospheric disturbances produced by major magnetic storms
Authors: Blanc Elisabeth , Mercandalli-Rascalou Brigitte
Published: April 2011

Large-scale ionospheric disturbances were observed in France by HF ionospheric sounding measurements during major magnetic storms, specially during the March 13–14, 1989 storm. The experiment used a network of four stations (one continuous wave transmitting station and three receiving stations) to determine the horizontal component of the phase velocity of the travelling disturbances by triangulation. The vertical component was determined by using several frequencies on one of the links and ionograms indicated overall ionospheric changes every 30 min. During the first diurnal phase of the March 13, 1989 magnetic storm, four large oscillations of the F2-layer critical frequency f0F2 were observed. During the first and second f0F2 decreases, a dense F1 region, revealing strong compositional changes in the lower thermosphere, modulated the oscillations and contributed to a F2-region virtual height increase to above 800 km. The Doppler measurements at 150–180 km detected only magnetic pulsations and southward travelling acoustic waves. The large-scale disturbances reached the altitude of the Doppler measurements 30 min after the fourth f0F2 peak, with a rapid upward and downward plasma drift of 250 m s−1. This disturbance moved to the southwest at 860 m s−1. During the March 13–14 nocturnal phase an auroral type Es appeared, formed by irregularities extending over 800 km. The ionosphere almost disappeared at 0330 UT and a low-density spread F was observed until the sunrise; the Doppler links were interrupted all the night. During the March 14 morning phase, southward travelling acoustic waves were observed and the F region seemed to be limited to the F1 region. This is probably an effect of the extreme G condition, arising from a decrease of the F2-layer maximum below the F1-layer maximum. The principal features of this storm are compared with those of two other storms on April 12, 1990 and August 14–15, 1989.
Bound state QED effects from the Schrödinger equation
Authors: Zhang Tao , Xiao Lixin , Koniuk Roman
Published: April 2011

We present a new relativistic bound-state formalism for two interacting Fermi–Dirac particles. The kernel of the integral equation for the bound-state system is generated by summing Feynman scattering amplitudes and multiplying by a bound-state amplitude. The method is illustrated through calculations of the hyperfine and fine splittings of positronium up to order α5. Our calculations of the one-loop contributions are carried out in the explicitly covariant Feynman gauge. We also present new results for the hyperfine and fine splittings in positronium to order α5 for arbitrary principal quantum number n, which are easily obtained owing to the virtue of conceptual and calculational simplicity of our formalism. In addition, we present the one-loop renormalization scheme in our formalism.
Muonium hyperfine and fine splittings in a new bound-state formalism
Authors: Zhang Tao , Koniuk Roman
Published: April 2011

We apply our new formalism to the hyperfine and fine splittings in muonium (μ+, e−) and present our calculations to order α5, which include new results for both hyperfine and fine splittings in muonium for arbitrary principal quantum number n. We show that it is quite simple and straight forward to obtain these results in our formalism. Our calculations are carried out in an explicitly covariant gauge.
A low-frequency theorem on laser-assisted X-ray scattering
Authors: Ehlotzky F.
Published: April 2011

As we shall show, for laser-assisted X-ray scattering by free electrons, a similar low-frequency theorem can be derived, as was found many years ago by Kroll and Watson, for potential scattering of electrons in a laser field. If quantum mechanical recoil effects are neglected, our renormalized cross-section formula becomes independent of Planck's constant and therefore must have a classical counterpart.
The D–X system of the CuI molecule
Authors: Mishra G. P. , Singh V. B. , Rai S. B.
Published: April 2011

The fine structure of the D–X system of the CuI molecule has been reinvestigated following a doubtful and incomplete analysis of this system by Nair and Upadhya. The rotational structure was photographed in emission in the second order of a 10.6 m grating spectrograph with 0.33 Å/mm dispersion. Though the transition of the system was found to be the same as suggested by Nair and Upadhya, the molecular constants are considerably modified. The various molecular constants (cm−1) determined for the D1π state by using a weighted least-squares-fit computer program are as follows: Bc, 0.067 040(4); αc, 0.000 420(4); Dc, 0.250 × 10−7(3); q, −0.000 272(1); rc, 2.445 02(6) Å (1 Å = 10−10 m). The potential energy curve for the D1π state and Franck–Condon factors and r-centroids for the D–X system have also been reported.
Excitonic optical bistability in n-type-doped semiconductors
Authors: An Nguyen Ba , Tuong Le Thi Cat
Published: April 2011

A resonant monochromatic pump laser generates coherent excitons in an n-type-doped semiconductor. Both exciton–exciton and exciton–donor interactions come into play. The former interaction can give rise to the appearance of optical bistability, which is heavily influenced by the latter one. When optical bistability occurs at a fixed laser frequency both its holding intensity and hysteresis-loop size are shown to decrease with increasing donor concentration. Two possibilities are suggested for experimentally determinng one of the two parameters of the system, the exciton–donor coupling constant or the donor concentration if the other is known.
Angular distribution of Pu-239 photofission fragments near threshold, using neutron capture gamma rays
Authors: De Moraes Marco Antonio Proenca Vieira , Cesar Marilia T.
Published: April 2011

The angular distribution of Pu-239 photofission fragments produced by thermal neutron capture gamma rays in two targets placed in the IEA-R1 (Instituto de Energia Atomica-Reator 1) research reactor were measured. Angular distributions of the form W(θ) = A + B sin2θ were observed for discrete excitation energies of 5.43 MeV (sulphur target) and 7.35 MeV (lead target). An anisotropy that corresponds to (B/A = −0.122 ± 0.036) was recorded for E = 5.43 MeV. The angular distribution for E = 7.35 MeV was practically isotropic: (B/A = −0.01 ± 0.02).
Free-convection effects in the boundary layer along a vertically stretching flat surface
Authors: Daskalakis John E.
Published: April 2011

We assess the effects of free convection on the boundary layer formed along a flat surface stretching vertically in a quiescent fluid. The flow is laminar and incompressible, the buoyancy forces conform to the Boussinesq approximation and the surface temperature is variable. The two-point boundary value problem of the coupled momentum and energy equations is solved using a simple and accurate relaxation method that provides the general nonsimilar solution to the flow. The effect of free-convection currents on velocity and temperature profiles, skin friction, and heat transfer is studied by varying the flow Grashof and Prandtl numbers. Zero shear stress and heat-transfer rate are predicted at some axial coordinate on a surface with decreasing wall temperature. Also the skin friction is markedly modified by the buoyancy while the heat transfer at the surface is correspondingly only moderately influenced.
Frequency stabilization of laser resonators using a new temperature-compensated piezo-mirror translator
Authors: El-Kashef H.
Published: April 2011

For frequency stabilization and tuning of active and passive laser resonators, a new temperature-compensated piezo-mirror translator has been developed. It has compact size, high mechanical stability, high-voltage tensile strength, high adjustable speed, and low cost. It allows one to suppress, efficiently, frequency changes of laser resonators if a suitably high voltage is applied to it.
1/f Noise from levels in a linear or planar array: Dislocations in metals
Authors: Morrison S. Roy
Published: April 2011

This report compares the double-layer noise expected for metal dislocations with the earlier analysis of semiconductor dislocations. In both cases we describe the asymmetric trapping of charge over an electrical double layer at the dislocation. The earlier reports describe how a 1/f spectrum should be observed, in the form of a truncated Lorentzian, if the double-layer voltage shows fluctuations greater than kT/q. This report describes the origin of a double layer at metal dislocations that fulfills the requirements. It shows why, despite the substantial difference in parameters, the noise predicted for metals is of the same magnitude (in terms of the Hooge parameter) as that predicted for semiconductors.
An issue in evaluating the damping rate of an energetic fermion in a hot plasma
Authors: Baier R. , Nakkagawa H. , Niégawa A.
Published: April 2011

We point out the difficulties and ambiguities in evaluating the damping rate of a moving fermion in a hot plasma, within an improved one-loop order, in which the hard-thermal loop corrections are taken into account.
One-loop calculation of the background field quantum-chromodynamic β function
Authors: Eijck M. A. van
Published: April 2011

We present a one-loop calculation of a gauge invariant quantum-chromodynamic β function at finite temperature with rules coming from the background field method in the Landau gauge and from the retarded and advanced formulation of finite-temperature field theory.
Transition rates of reactions in the microcanonical ensemble and the finite-size effect
Authors: Niégawa A. , Takashiba K.
Published: April 2011

The calculational rules of a transition rate of a generic reaction taking place in a closed system are found. The rules are formulated in terms of the free energy of the system and the transition rate of the reaction in a finite temperature system. It is found that, in some kinematical regions, the finite-size effect is much larger than naively expected.
Self-consistent approximations for field theories at finite temperature
Authors: Thoma M. H.
Published: April 2011

Various mean field approximations at finite temperature are used for calculating ground state energies and propagators of the [Formula: see text] theory in two dimensions and quantum chromodynamics (QCD). In the case of the [Formula: see text] theory a symmetry restoration is observed above a critical coupling constant if a temperature independent renormalization is used. In the case of QCD the mean field approximation is insufficient but can be regarded as a starting point for more complicated approximations, which are discussed qualitatively.
The pressure dependence of the structure of liquid bromine
Authors: Szornel K. , Egelstaff P. A. , Whalley E. , McLaurin G.
Published: April 2011

The anisotropic intermolecular interaction has been known for many years to cause an anomalous feature at about 20 nm−1 in the static structure factor of liquid halogens. This feature increases sequentially for liquids fluorine to chlorine to bromine to iodine near their triple points, and we determined its shape as a function of pressure in liquid bromine at room temperature. While it apparently broadens with increasing pressure, after the underlying structure is removed a slight sharpening is found and discussed. Also at high pressure, we observe that the orientationally averaged structure of liquid bromine tends toward that of liquid chlorine at the same density.
Generalized hydrodynamics and linear stability analysis of cylindrical Couette flow of a dilute Lennard–Jones fluid
Authors: Khayat Roger E. , Eu Byung Chan
Published: April 2011

Linear stability analysis is carried out for cylindrical Couette flow of a Lennard–Jones fluid in the density range from the dense liquid to the dilute gas regime. Generalized hydrodynamic equations are used to calculate marginal stability curves and compare them with those obtained by using the Navier–Stokes–Fourier equations for compressible fluids and also for incompressible fluids. In the low Reynolds or Mach number regime, if the Knudsen number is sufficiently low, the marginal stability curves calculated by the generalized hydrodynamic theory coincide, within numerical errors, with those based on the Navier–Stokes theory. But there are considerable deviations between them in the regimes beyond those mentioned earlier, since nonlinear effects manifest themselves in the laminar mean flow through the nonlinear dissipation term and normal stresses. There are three marginal stability curves obtained in contrast to the Navier–Stokes theory, which yields only two. The previously observed phase-transition-like behavior in fluid variables and the slip phenomenon are found to occur beyond the hydrodynamic stability point. The disturbance entropy production associated with the Taylor–Couette vortices is calculated to first order in disturbances in flow variables and is found to decrease as the number of vortices increases and thereby the dynamic structure is progressively more organized.
Studies on carrier lifetime in heavily doped InGaAsP
Authors: De S. S. , Ghosh A. K. , Bera M. , Hazra A. K. , Haldar J. C.
Published: April 2011

A model is developed to study the carrier lifetime and quantum efficiency in heavily doped InGaAsP. In the analysis, bandgap narrowing, carrier degeneracy, and nonparabolicity of the band structure are considered as heavy doping effects. The variations of carrier lifetime and quantum efficiency with nominal current density at a given temperature are studied through numerical analysis.
Nonlocal exchange contribution to the free energy of inhomogeneous many–fermion systems. I: Formulation of the gradient expansion
Authors: Dunlap E. , Geldart D. J. W.
Published: April 2011

Nonlocal exchange contributions to the free energy of a weakly inhomogeneous many-fermion system at finite temperature are obtained to first order in the interparticle interaction. Explicit representations are given for the second-order gradient coefficient Bx (n(r); T). These results apply for arbitrary velocity-independent interparticle interaction and arbitrary temperature.
Infrared spectra of liquid hydrogen and deuterium
Authors: McKellar A. R. W. , Clouter M. J.
Published: April 2011

Precise high-resolution spectra of liquid H2 and D2 in the regions of their fundamental vibrational bands (4000–5000 and 2900–3600 cm−1, respectively) are reported for various temperatures in the range 18–30 K. In hydrogen, concentrations for the.J = 0 para-H2 species of 25% (normal H2), 95%, and 99% were studied. In deuterium, normal D2, with 67% in the, J = 0 ortho state, was studied. These are the first published spectra of liquid D2. A detailed analysis of these results is not possible within present theories of collision-induced absorption, but it is hoped that their publication will stimulate theoretical interest.
Revised analysis of the Zn VI spectrum
Authors: van het Hof G. J. , Joshi Y. N. , Raassen A. J. J.
Published: April 2011

The spectrum of zinc was photographed in the 100–300 Å (1 Å = 10−10 m) wavelength region on a 10.7 m grazing-incidence spectrograph. On the basis of these precise and extensive data the 3d7–3d64p transition array of Zn VI was reanalysed. All 19 levels of the ground configuration 3d7 were confirmed but the level values were revised. Out of the 161 levels of the 3d64p configuration reported earlier, 10 levels were rejected and 16 new levels were established thus totalling the known levels to 167. The number of the classified lines is 538, almost doubling the previous number. The least-squares-fitting parametric calculations adequately interpret the observed spectrum. The 3d7 configuration was also described by an orthogonal operator technique.
Mapping of the statistical auroral distribution into the magnetosphere
Authors: Feldstein Y. I. , Elphinstone R. D. , Hearn D. J. , Murphree J. S. , Cogger L. L.
Published: April 2011

Statistical auroral distributions are used in combination with an empirical model of the Earth's magnetic field in an attempt to determine the large-scale magnetospheric source regions for various types of auroral luminosity. The narrow ring of structured auroral emissions during magnetically quiet intervals appears to be associated with the inner region of the nightside central plasma sheet and the dayside entry layer. Under active conditions these discrete structures expand to fill the entire central plasma sheet. The high-altitude boundary plasma sheet on the other hand is more likely to be related to diffuse auroral emissions poleward of this "oval" and to high-latitude polar auroral arcs. Under this scenario, the region of the magnetosphere bounded by the inner edge of the tail current sheet, the plasmasphere, and the dayside entry layer is the source region for the most equatorward diffuse auroral precipitation.
Focus wave modes in conducting media
Authors: Borisov Victor V. , Utkin Andrei B.
Published: April 2011

A family of localized solutions of the homogeneous equation for waves in lossy media is derived. These solutions are analogues to the set of Brittingham's focus wave modes (J. Appl. Phys. 54, 1179 (1988)).
State space approach to unsteady two-dimensional free convection flow through a porous medium
Authors: Ezzat Magdy A.
Published: April 2011

The equations of magnetohydrodynamic unsteady two-dimensional free convection flow through a porous medium bounded by an infinite vertical porous plate are cast into matrix form using the state space and Laplace-transform techniques. The results obtained can be used to generate solutions in the Laplace-transform domain to a broad class of problems in magnetohydrodynamic free convection flow. The technique is applied to a heated vertical plate problem and to a problem pertaining to a plate under uniform heating. The inversion of the Laplace-transforms is carried out using a numerical approach. Numerical results for the temperature, velocity, and skin friction distributions are given and illustrated graphically for both problems.
q-Canonical transformations for many q-bosons and new q–k symmetry
Authors: Birman Joseph L.
Published: April 2011

A new symmetry is identified for the many particle q-Bose system, which permits carrying out a linear q-canonical transformation, i.e., one which preserves the q-deformed commutation rules. The symmetry is exhibited when the set of q-modes is partitioned into "positive" and "negative," each subset having its own type of deformation. For plane-wave modes, labelled by wave vector k, this means separate positive and negative wave vectors. Then, identifying the new symmetry: (q → q−1, k → −k) the transformation can be implemented. The new aspect is the simultaneous transformation of wave vector k and parameter q.
Braided GLq(2, C) and its dual space
Authors: Couture M.
Published: April 2011

We define Hopf algebras that are characterized by Pμ statistics where Pμ is a generalized permutation operator [Formula: see text]. These structures may be viewed as the end result of a deformation of the statistics of GLq(2, C) and Uq(sl(2, C)).
Generalized q-Bessel functions
Authors: Floreanini Roberto , Vinet Luc
Published: April 2011

An algebraic setting for a natural generalization of q-Bessel functions is provided. Many properties and formulas involving these functions are obtained and discussed.
Point group invariants in the Uqp(u(2)) quantum algebra picture
Authors: Kibler M.
Published: April 2011

Some consequences of a qp quantization of a point group invariant developed in the enveloping algebra of SU(2) are examined in the present note. A set of open problems concerning such invariants in the Uqp(u(2)) quantum algebra picture is briefly discussed.
The Mosseri–Sadoc tilings derived from the root lattice D6
Authors: Kramer P. , Papadopolos Z.
Published: April 2011

We derive the class of quasiperiodic tilings due to Mosseri and Sadoc, denoted by [Formula: see text], from the quasiperiodic tilings [Formula: see text] of Kramer et al., obtained by icosahedral projection from the 6-dimensional root lattice D6. Moreover, we determine all "windows" such that the tilings [Formula: see text] can be obtained by projection from the root lattice D6.
Spinor helicity technique and string reorganization for multiloop diagrams
Authors: Lam C. S.
Published: April 2011

Methods to apply the spinor helicity technique and string reorganization to multiloop amplitudes using the Feynman- and Schwinger-parameter representations are reviewed and expanded.
On the structure of the holomorphic representations of the noncompact symplectic and metaplectic groups
Authors: Rowe D. J.
Published: April 2011

We review the properties of the holomorphic representations with lowest weights for the noncompact real symplectic and metaplectic groups. The unitarizable sub representations of these representations are identified with the harmonic series. We define unitary characters for the holomorphic representations and show how they can be used to identify the unitarizable sub quotient representations. Explicit results are given for Sp(1, R), Sp(2, R), and Sp(3, R).
Quantum algebra embeddings: deforming functionals and algebraic approach
Authors: Jeugt J. Van der
Published: April 2011

The study of subalgebras of Lie algebras arising in physical models has been important for many applications. In the present paper we examine the q-deformation of such embeddings; the Lie algebras are then replaced by quantum algebras. Two methods are presented: one based upon deforming functionals, and a direct algebraic approach. A number of examples are given, e.g., [Formula: see text] and [Formula: see text]. For the last example, we give the q-boson construction, and the relevant overlap coefficients are related to a generalized basic hypergeometric function [Formula: see text].
Modified Dunham potential for rovibrational diatomic systems
Authors: Molski Marcin , Konarski Jerzy
Published: April 2011

A modified Dunham potential with parameters depending on the rotational quantum number is employed to describe the rovibrational states of diatomic molecules. This approach, applied to H81Br, 115InD, 7LiH, and 40Ar2, gives satisfactory reproduction of the observed transitions using fewer Dunham parameters than in the standard method. The results obtained indicate the possibility of introducing the local internal potentials, which, in contradiction to the global ones usually used, depend on the rotational states of a rotating–vibrating molecule. Such a J dependence may be a result of rovibronic interactions, in particular, Coriolis-type nonadiabatic interactions coupling other electronic states through the rotational angular momentum.
Analysing powers and differential cross sections of (3He,p) reactions on 6Li and 7Li at low energy
Authors: Baddou D. , Rioux C. , Slobodrian R. J. , Nelson J. M.
Published: April 2011

Angular distributions of the differential cross sections and analysing powers were measured at an energy of 4.6 MeV. The results are compared with the distorted wave Born approximation predictions for two-nucleon transfer and for a deuteron-cluster transfer. The agreement is qualitative at best, and a discussion of alternatives to improve it is presented.
Creation of a pn heterojunction in Hg1−xCdxTe (x ≈ 0.2) by laser annealing
Authors: Sheregii E. , Kuźma M. , Abeynayake C. , Pociask M.
Published: April 2011

A highly photosensitive diode area was created in solid solutions of Hg1−xCdxTe (x ≈ m 0.2) (MCT) without melting its surface. The idea of the possible formation of pn heterojunctions, which was indicated by computer modelling of the mass transportation processes under laser treatment of the MCT, was experimentally realized. MCT samples were irradiated with an Nd:YAG laser having an energy density of 0.7 J cm−2. The presence of a heterojunction on a surface not far below the upper surface has been verified by photovoltaic measurements and X-ray microanalysis as well as by current–voltage characteristics.
Studies of irradiated cadmium sulfide in a diamond anvil pressure cell
Authors: Carlone Cosmo , Buteau Monia
Published: April 2011

Cadmium sulfide (CdS) was irradiated with 7 MeV electrons in the fluence range 1013–1017 cm−2. The samples were subsequently studied in a diamond anvil cell up to a pressure of 100 kbar (1 bar = 105 Pa). Samples irradiated up to 1015 cm−2 underwent the wurtzite (yellow) to rock-salt (black) change of phase at 27 ± 2 kbar. Samples irradiated at 1016, 3 × 1016, and 1017 cm−2 also underwent the wurtzite to rock-salt transformation at 27 ± 2 kbar, but at the critical pressure they changed to an orange form which colour persisted as the pressure was increased. As the pressure was decreased, the orange samples reverted to the rock-salt structure at 30 ± 2 kbar, and then to the orange form, which persisted to atmospheric pressure. Heating the recovered orange CdS to 500 ± 50 °C returned it to its wurtzite form. X-ray diffraction studies of the irradiated but not pressurized samples revealed two peaks that correspond to the distance between planes (d) of 1.40 and 1.26 Å (1 Å = 10−10 m). In the irradiated and pressurized samples, we observed peaks having d = 1.47, 1.40, 1.32, 1.27, 1.19, 1.16, 1.09, and 0.96 Å. We attribute the orange form of CdS to defects. Irradiation of CdS with 7 MeV electrons to a fluence of 1016 cm−2 tends to suppress the wurtzite to rock-salt change of phase.