bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffraction images of extended circular targets in presence of coma
Authors: Gupta A. K. , Singh R. N. , Singh K.
Published: April 2011

The intensity distribution in the diffraction images of extended circular targets in the paraxial receiving plane has been evaluated in presence of third order coma using the transfer function approach. Results presented graphically are studied to bring out the degrading effects of coma on the image quality using various sizes of the circular targets. The loss of rotational symmetry in the resulting images and the shift of the position of the principal maximum with respect to the centre of the aberration free image of target in various azimuths are investigated for various amounts of coma.
Rotational structure of triplet–singlet transitions in orthorhombic molecules in intermediate and high magnetic fields
Authors: Lauro C. di , Perri E.
Published: April 2011

The Zeeman band profiles are calculated for near-case (b) triplet–singlet transitions in asymmetric rotors, making allowance for the intensity perturbations induced by an external magnetic field. It is shown that new bands correlating with zero-field forbidden lines can be observed under the effect of sufficiently high fields. Band profiles and the patterns of the magnetic sublevels of the triplet state split by the external field are discussed in detail for the Paschen–Back limit.
States in 152Sm populated by the (t,α) reaction
Authors: Hirning C. R. , Burke D. G.
Published: April 2011

Levels in the deformed even–even nucleus 152Sm have been populated by the (t,α) reaction using beams of 15 MeV tritons from the model FN tandem Van de Graaff accelerator at the Los Alamos Scientific Laboratory. For the initial experiments in the series the reaction products were analyzed in an Elbek magnetic spectrograph and detected with nuclear emulsions. Those done later made use of the Q3D magnetic spectrometer and helical-cathode focal plane detector. On the basis of levels observed in adjacent odd-Z nuclei and some previous (α,2nγ) results, a rotational band built on the Kπ = 5−, 5/2+[413] + 5/2−[532] two-quasiparticle state has been identified. A Coriolis coupling calculation has been done, which gives good agreement with experimental energies and cross sections when an attenuation factor of 0.31 is used for the Coriolis matrix elements.
Microwave absorption by ortho-H2 pairs in solid hydrogen
Authors: Hardy W. N. , Berlinsky A. J. , Harris A. B.
Published: April 2011

Measurements of the microwave absorption spectrum of pairs of (J = 1) H2 molecules at low concentration in (J = 0) solid hydrogen in the frequency ranges 10–26 and 60–90 GHz are reported. Observation of absorptions with coefficients 10−5 cm−1 is accomplished by a novel calorimetric method. These absorptions result from transitions between energy levels of near neighboring pairs of (J = 1) molecules and assignments are made on the basis of selection rules, relative intensities, temperature dependences, and time evolution due to migration of (J = 1) molecules. Clustering of in-plane and of out-of-plane nearest neighbor pairs are observed to have time constants of 100 and 10 h, at 1.2 K and with 0.2% concentration of (J = 1) species. Peak frequencies, widths, and line shapes are determined with a resolution typically of order 5 to 50 MHz. Comparison is made to theoretical expressions for the transition frequencies, developed in the following paper, and several anisotropic potential parameters are determined, namely: the effective quadrupole coupling constant [Formula: see text], non-quadrupolar coupling constants ε0 = −1.55 × 10−2 cm−1 and ε2 = 1.1 × 10−2 cm−1, the crystal field Vc = 9.8 × 10−3 cm−1, and the difference in the quadrupole coupling for in- and out-of-plane nearest neighbor pairs ΔΓ/Γ = −1.4 × 10−3. The intensities of the observed transitions agree reasonably well with those calculated assuming a quadrupole-induced-dipole absorption process and using known values of the polarizability tensor of the H2 molecule. At low (J = 1) concentrations, the line widths are generally caused by inhomogeneous variations in Γ. At higher concentrations, the line widths agree qualitatively with the theory of Fujio, Hama, and Nakamura for spectral width due to longer range quadrupole interactions, although the line shapes do not correspond very well. Tentative assignments of transitions from further than nearest neighbor pairs are proposed.
An electrical resistivity determination of the density of states variation in Pd–Ag alloys
Authors: Chiu J.C. H. , Devine R. A. B.
Published: April 2011

It is shown that electrical resistivity measurement may be used to determine the concentration dependence of the density of states in Pd–Ag alloys. The Debye temperatures for the alloys are also determined and there is some difference found between these results and those from other measurements.
Collective excitation transfer effect in dielectric susceptibility
Authors: Zaidi H. R.
Published: April 2011

The combined effect of two collective processes in the resonant dielectric susceptibility is investigated. The first is the coherent excitation transfer process, which gives rise to the Lorentz–Lorenz shift. The second is the many body shielding of the resonant interaction between the atoms. The combined treatment of these effects leads to a qualitatively different behaviour of the susceptibility of a high density gas. The frequency dependence of the susceptibility is obtained from the detailed numerical solution of the self-consistent equations. In the quasi-static limit, an analytical solution is also obtained. In this limit, the result depends upon two parameters: one proportional to the gas density, and the other proportional to the square root of it.
Étude de l'effet lentille convergent dans les lasers CO2-TEA à configuration hélicoïdale des électrodes
Authors: Verreault M. , Tremblay R.
Published: April 2011

This article presents the results of a theoretical and experimental study of the convergent lensing effect in TEA-CO2 laser tubes with helical electrodes. The new characteristic is that all the excitation discharges are eccentric with respect to the axis of the tube. A model of the lensing effect, based on the theory of a gas lens, has been used to study the influence of the energy of excitation, the composition of the gas mixture, and the distance separating each discharge from the tube axis. An experimental study reveals the importance of these factors. [Journal translation
Theory and phenomenology of radiative meson decays
Authors: O'Donnell P. J.
Published: April 2011

The experimental data on the radiative decays of mesons (not involving charm) are reviewed. The consistency of these data with SU(3) symmetry, vector dominance, and the quark model is discussed.
Heat treatment-induced effects in metallic Si(P): photoluminescence and electron paramagnetic resonance
Authors: Parsons R. R. , Rostworowski J. A. , Halliwell R. E. , Barrie R.
Published: April 2011

Heat treatment of silicon doped with phosphorus is found to produce marked changes in the photoluminescence and the electron paramagnetic resonance for samples containing impurity concentrations above the critical concentration [Formula: see text] for the semiconductor–metal transition. A possible explanation is suggested in terms of a heat-induced defect which is populated only when the phosphorus-doped electrons are delocalized. Clusters of Si-interstitials are considered. At concentrations greater than about 2.0 × 1019 P/cm3 the heat-induced changes are exceedingly small.
The behaviour of the meteoric O I 5577 Å emission
Authors: Baggaley W. J. , Cummack C. H.
Published: April 2011

A better understanding of the mechanisms important in the production of the forbidden O I green line feature in meteor wakes may result from a theoretical approach to the relevant dynamic and reaction processes in a plasma column. A model is developed in which the rates of excitation and removal of metastable atoms permit a description of the resulting 5577 Å emission.
The two photon absorption spectrum of NO C2Π(ν = 0) ← X2Π(ν = 0)
Authors: Freedman Philip A.
Published: April 2011

The C, 2Π, ν = 0 state of NO has been investigated using two photon spectroscopy (a) as a quantitative test of the technique and (b) to study the predissociation of this state.The agreement between the computed and experimental spectra is reasonable, though small but definite discrepancies remain.
The valence bandstructure and the hole mobility in silicon
Authors: Nakagawa H. , Zukotynski S.
Published: April 2011

The hole mobility in silicon is calculated as a function of temperature. The calculation takes into account both the non-parabolicity and the warping of the valence band. The effect of both light and heavy holes on the total mobility is considered. The contribution of light holes varies from 30% at low temperature to 15% at room temperature. The values of the band parameters are correlated to the temperature dependence of the mobility and the results agree very well with experimental data in the entire range from 10 to 450 K. For best fit the value of the acoustic deformation potential constant Eeff is found to be 5.2 eV and the optical phonon coupling constant DtK is found to be 7 × 108 eV/cm.
Stimulated electromagnetic shock radiation (SESR) in frequency-dispersive media
Authors: Schneider S. , Spitzer R.
Published: April 2011

The interaction in a frequency-dispersive medium of a coherent electromagnetic wave with an electron moving faster than a critical (Mach) speed produces electromagnetic radiation with novel characteristics. Theory predicts emission of intense radiation in the form of shock fronts at specific angles from the electron trajectory. The shock fronts are correlated with specific frequencies shifted significantly from that of the incident wave. We have named this effect stimulated electromagnetic shock radiation (SESR). The shock frequencies depend dynamically on the populations of the energy levels that give rise to the medium resonances. A given shock frequency changes from below to above the resonance frequency of the medium with which it is associated as the populations of the two energy levels corresponding to this resonance frequency change from an equilibrium distribution to an inverted one. This dynamic resonance crossing points to the possibility of new synergisms between SESR emission and stimulated emission between discrete levels.
Influence de la courbure dans les guides d'ondes supraconducteurs à section circulaire
Authors: Zepp G. , Wick A. , Fabre G.
Published: April 2011

The propagation of electromagnetic waves in superconducting curved waveguides of circular cross section has been studied. The different models of superconducting materials are taken into account.
Neutron scattering and proton spin conversion in solid CH4
Authors: Lushington K. J. , Morrison J. A.
Published: April 2011

The total neutron cross section of pure and O2-doped condensed CH4 has been measured in the temperature range 0.75 < T < 100 K. The neutron wave length was sufficiently long (4.7 Å) so that changes in cross section could be directly related to changes in [Formula: see text], the mean squared proton nuclear angular momentum per molecule, to a sensitivity of about 1%. The temperature dependences of [Formula: see text] for the pure and doped specimens differ considerably in solid phase II (T < 20.4 K). For the former specimen, the change in cross section is consistent with conversion occurring between the nuclear spin symmetry species on the orientationally disordered sublattices only. The addition of oxygen enhances the rate of conversion such that the value of [Formula: see text] corresponds to conversion on both the disordered and ordered sublattices. The characteristic lifetimes of the catalyzed and uncatalyzed conversion processes have been estimated.
Phase transformation in AlPO4 and quartz studied by electron paramagnetic resonance of Fe3+
Authors: Lang R. , Calvo C. , Datars W. R.
Published: April 2011

Electron paramagnetic resonance (EPR) of Fe3+ in AlPO4 and quartz were studied as a function of temperature using a microwave spectrometer operated at 35 GHz. Electron paramagnetic resonance of Fe3+ in AlPO4 changed with temperature and gave direct evidence of the α–β phase transition. The EPR signal from Fe3+ in quartz was greatly reduced above 670 K. The change of the EPR parameters below 670 K was similar in both materials. There is a continuous rotation of 86° of the magnetic axes between room temperature and the phase transition in AlPO4. This is compared with the rotation of the PO4 and AlO4 tetrahedra measured by X-ray diffraction. The temperature dependence, but not the magnitude, of EPR parameters calculated using a point-charge model and the Blume–Orbach mechanism with the temperature dependence of quartz crystal parameters is similar to what is observed. Increased EPR line width near the phase transition was observed and was attributed to fluctuations at the phase transition.
Temperature dependence of the Hall effect in monocrystalline magnesium
Authors: McAlister S. P. , Alderson J. E. A. , Hurd C. M.
Published: April 2011

The Hall resistivity ρ21(B,T) observed when [Formula: see text] and [Formula: see text] has been measured in monocrystals of Mg in the temperature range 1.7–300 K and in an applied flux up to 2 T. A quantitative interpretation when [Formula: see text] is made using a path integral calculation of the magnetoresistive tensor produced by representative orbits on a model Fermi surface. The results explain the origins of the principal features in the behaviour of ρ21(B,T), and show the importance of magnetic breakdown in cyclotron motion in the basal plane.
Spherical diffuse Yukawa sources in relativity
Authors: Souza J. A. , Teixeira A. F. da F.
Published: April 2011

A system containing only two diffuse massless sources (bearing a uniform ratio) of two different short range scalar fields is studied, according to Einstein's gravitational theory. One field is attractive, the other is repulsive. The distribution is in static equilibrium with spherical symmetry. A class of solutions of the field equations is obtained, where the solutions are nonsingular and have simple physical interpretation. A Schwarzschild-type gravitation is found at infinity, with the mass parameter solely arising from the scalar fields; these rapidly disappear with a Yukawa-type behaviour. The stability of the system is briefly stated, and the applicability of the model to large or small physical systems is pointed out.
An electronic structure for a-ZnSe
Authors: Lim P. K. , Brodie D. E.
Published: April 2011

Some electrical and optical properties for a-ZnSe have been studied and the results have been analysed in a consistent manner with the help of a Mott-type model for an amorphous semiconductor. Mature samples are reproducible and for these an energy level scheme is obtained. Many experiments are required to characterize an amorphous material and hence we have presented the results for dc conductivity, photoconductivity, optical absorption, thermoelectric power, ac conductivity, and drift mobility experiments for this material. a-ZnSe is n-type, with the Fermi level near the middle of the mobility gap. Drift mobilities are dispersive and have values of the order of 10−6 cm2 V−1 s−1 at room temperature.
New bands attributed to scandium hydride
Authors: Bernard A. , Effantin C. , Bacis R.
Published: April 2011

New bands assigned to scandium hydride have been observed in emission in the green (5580 Å) and near infrared (8603 Å) regions. The identity of the carrier as ScH is established on the basis of the observed deuteride spectrum.
The 98° differential cross sections for the reactions 13C(γ,n0)12C and 13C(γ,n1)12C
Authors: Woodworth J. G. , McNeill K. G. , Jury J. W. , Georgopulos P. D. , Johnson R. G.
Published: April 2011

The differential cross sections at 98° for the reactions 13C(γ,n0)12C and 13C(γ,n1)12C were measured over the range of 6.0 to 37.0 MeV and 10.5 to 35.5 MeV, respectively. The cross sections are compared with previous results on the same nucleus or results from the similar reaction 12C(p,γ0)13N. In the region of the so-called pygmy resonance (about 13.5 MeV) there are many sharp resonances which correspond very well with the level structure of 13C as deduced from several other studies using various reactions. For the full energy region studied, further evidence for the isospin splitting of the 13C photoneutron cross section is obtained. In comparison of the cross sections with recent theoretical results, general agreement is obtained. However, several details of this comparison are in disagreement; the implications of this disagreement are discussed.
Polaronic conduction in lanthanum strontium chromite
Authors: Webb J. B. , Sayer M. , Mansingh A.
Published: April 2011

In many polycrystalline ceramic materials the transport properties are strongly affected by internal barrier effects or by the presence of contact barriers. The transport properties of La1−xSrxCrO3, 0 ≤ x ≤ 0.2 have been investigated and the degree to which these barriers affect the measured transport properties has been established. Measurements of the dc and ac conductivity in the range 77 K ≤ T ≤ 1300 K are consistent with the hopping of polarons in a defect band of localized states at the Fermi energy with the thermopower essentially independent of temperature. A polaron radius of 3.5 Å has been determined with room temperature mobility of 5 × 10−4 cm2 V−1 s−1.
High pressure SF6 pulse transmission near 10.4 μm
Authors: Ballik E. A. , Garside B. K. , Taylor R. S. , Znotins T. A.
Published: April 2011

Measurements were performed to determine the dynamical characteristics of high pressure SF6 absorption at the 10.4 μm band of CO2 as a function of laser pulse intensity. Both long (~ 200 ns FWHM) and short (~ 5 ns FWHM) CO2 laser pulses were employed. The observed pulse transmission characteristics can be accounted for using a vibrational bath model, which allows for the very large number of levels in the absorption spectrum of SF6.
On Meixner's edge condition for dielectric wedges
Authors: Hurd R. A.
Published: April 2011

It is pointed out that there is a difference between the electromagnetic field behaviour at the edge of a highly conducting wedge of angle greater than π (as predicted by Meixner) and the known field behaviour for a perfectly conducting wedge of the same angle. In particular, the perpendicular electric fields are infinite in the first case and finite in the latter. A careful examination of the theory suggests that Meixner's effect is real, but is only detectable in practical conductors if the wedge angle is very accurately machined.
On the nuclear mass parameter in asymmetric fission
Authors: Trinh C. T. , Sharma R. C.
Published: April 2011

The nuclear fission mass parameter is derived by solving Schrödinger's equation under adiabatic assumption for a pear-shaped asymmetric potential. It is also concluded that asymmetric fission proceeds faster than symmetric fission.
Far-infrared absorption in CdTe
Authors: Batalla E. , Koteles E. S. , Datars W. R.
Published: April 2011

Far-infrared absorption in the II–VI compound semiconductor Cd Te has been measured using a Fourier transform spectrometer. Two-phonon density-of-states curves were calculated from shell model parameters determined by Rowe, Nicklow, Price, and Zanio and were compared to the high-accuracy absorption spectrum. Two-phonon combinations and the location of the corresponding critical points in the Brillouin zone were identified with features in the absorption spectrum. From these assignments, accurate values of some normal mode frequencies at certain points in the Brillouin zone were determined.
Dipole oscillator strength distributions, sums, and some related properties for Li, N, O, H2, N2, O2, NH3, H2O, NO, and N2O
Authors: Zeiss G. D. , Meath William J. , MacDonald J. C. F. , Dawson D. J.
Published: April 2011

Dipole oscillator strength distributions (DOSDs) have been constructed for ground state Li, N, O, H2, N2, O2, NH3, H2O, NO, and N2O by using experimental and theoretical photoabsoiption and high energy electron inelastic scattering cross sections. Each DOSD is required to satisfy the Thomas–Reiche–Kuhn sum rule and additional constraints derived from available accurate experimental refractivity and dispersion measurements. The DOSDs, the data and procedure used to construct the DOSDs, and the values of the dipole oscillator strength sums Sk and Lk (for a variety of k values) and related atomic and molecular properties obtained from the DOSDs are reported. The discussion includes comments regarding the importance of the constraints imposed on the DOSD with respect to the evaluation of various dipole sums and properties and the accuracy of the results.
Non-relativistic Hartree–Fock scattering factors for the actinides and their positive ions
Authors: Benesch Robert , Saxena K. M. S.
Published: April 2011

Coherent X-ray scattering factors F(μ) for the neutral actinides (Z = 89 through Z = 102) and for various configurations of their positive ions have been computed from non-relativistic Hartree–Fock wave functions. The expectation values [Formula: see text] are also reported for the 119 systems considered in the present study.
Rotation of an isolated triaxial ellipsoid suspended in slow viscous flow
Authors: Gierszewski Paul J. , Chaffey Charles E.
Published: April 2011

A freely suspended triaxial ellipsoid, or particle with two perpendicular symmetry planes, orients in a creeping flow at a rate given by differential equations in the three Euler angles, derived here for simple shear flow. The parameters for a given particle are three components of Bretherton's tensor; observations along two directions in space suffice to determine these. Any ellipsoid's two axis ratios can be chosen with the second deviating from unity less than the square root of the first. Numerical integration shows that, in contrast to the orbits of Jeffery, the particle has no fixed period of rotation about the fluid's vorticity axis. The longest axis of a rod-like triaxial particle crosses the plane perpendicular to the fluid vorticity, a motion impossible for an axisymmetric particle. In typical graphs for a quarter rotation, times required and changes in orientation are shown. Lack of axial symmetry implies that a suspension of such particles can be more disoriented.
Thermal broadening of infrared energy levels of UCl5 single crystal
Authors: Leung A. F.
Published: April 2011

The thermal behavior of the linewidths of the infrared energy levels of UCl5 single crystal is explained by multiphonon processes. Processes involving more than five phonons are associated with the highest-energy phonons of the lattice. For lower order processes, lower-energy phonons can be important. In the calculations, the vibronic sidebands of the electronic levels provide a guide in choosing which phonons are to be involved in the relaxation processes. The measurements also show large spin–spin interactions between the uranium ions.
Formation du néon métastable entre 42 et 46 eV
Authors: Huard D. , Marmet P. , Bolduc E.
Published: April 2011

Some fine structure, having an amplitude of 1.5% of the total cross section for production of metastable neon, are observed for the first time above the ionization threshold. These perturbations are interpreted as highly excited neutral and negatively charged neon states around 44 eV.[Journal translation]
The harmonic lattice vibrations of a one-dimensional incommensurate lattice
Authors: Walker M. B.
Published: April 2011

The properties of the dynamical matrix for a one-dimensional incommensurate lattice are found, as are the normal mode vibrational frequencies and eigenvectors. A theory of the equilibrium state of the incommensurate structure is developed before the dynamical matrix is obtained, and a first harmonic lattice distortion of wave vector 2Q is found, in addition to the fundamental distortion of wave vector Q. New first harmonic phase and amplitude modes are also found, in addition to the previously discovered fundamental phase and amplitude modes; also, the previously discovered (Overhauser) phase mode is found to be mixed with the long-wavelength phonon mode. Several of the parameters of interest (e.g. the amplitude of the first harmonic distortion, the phason velocity, the frequency of the amplitude mode, and the effective mass) are evaluated using the microscopic Frohlich electron–phonon model, and are found to depend strongly on the magnitude of the dimensionless Frohlich coupling constant. The implications for various experiments, including inelastic neutron scattering, are discussed.
The transport properties of the cubic alkaline earths Ca, Sr, and Ba
Authors: Cook J. G. , Laubitz M. J.
Published: April 2011

The electrical resistivity (ρ), thermoelectric power(S), and thermal conductivity (κ) of two Sr samples and two Ba samples have been determined from 30 to 300 K. Large deviations from Matthiessen's rule (DMR) were observed. The estimated transport properties for ideally pure Sr and Ba indicate that these elements, like Ca, show large deviations from the Bloch–Gruneisen form for ρ(T) at all temperatures, large and positive diffusion thermopowers with a negative phonon-drag contribution, and large deviations from the Wiedemann–Franz relationship (DWFR). In these respects, they are much more like the transition metals than the monovalent metals.In the second, analytical, portion of the paper we study the DWFR in some detail. First, the effect of lattice conduction is estimated, and found to be large. Then, a function X(E) of the electron energy, closely related to the conventional conductivity function σ(E), is estimated from the ρ and S data now available for Ca, Sr, and Ba above 300 K, and used to compute S and the Lorenz function for elastic electron–phonon scattering below 300 K. Comparison with the experimental data indicates that the energy dependence of the electron parameters is responsible for the electronic DWFR, and effects the diffusion thermoelectric power. Such 'band effects' may also be seen in the thermal resistivity due to inelastic scattering in at least Sr. Regrettably, we are not able to explain the observed DMR.
Phase shift calculation for the inverse power singular potential with complex coupling constant
Authors: Das J. N. , Datta Madhabi
Published: April 2011

The WKB expression for the phase shift for inverse power potentials with complex coupling constants has been rigorously derived, which agrees formally with the expression for real potentials. The case n = 4 has been re-examined.
Spinor gauge field in the spinor space–time formalism
Authors: Hong Nguyen Thi
Published: April 2011

In our previous work a method of realizing the bilinear spinor representation of space–time has been suggested, in the language of the spinor coordinates the field equations of motion have been considered. In this work, proceeding from these equations of motion, we consider the spinor gauge fields appearing in the local gauge transformations in the spinor space–time.
Quantum mechanics in rotating frames. II. The lattice structure of current circulations for a rotating single-particle fluid
Authors: Gulshani P. , Rowe D. J.
Published: April 2011

It is shown that, in general, the current flow for a single particle in quantum mechanics exhibits circulations. These circulations are studied in detail for the anisotropic oscillator system in a slowly rotating frame.
Photoluminescence in heavily-doped Si(P)
Authors: Parsons R. R.
Published: April 2011

The photoluminescence spectrum of heavily doped Si(P) has been studied as a function of temperature, excitation level, and impurity concentration. Several new results are observed for the first time, which include: (i) a narrowing of the impurity band luminescence peak when the temperature is increased to about T = 15 K, (ii) a sudden disappearance of the impurity band emission at a certain temperature determined by the dopant concentration, and (iii) an excitation threshold behaviour for the luminescence observed at high excitation level.A new model is introduced to explain the data. In this model, the impurity band undergoes a localized-to-delocalized transition due to a sufficiently large concentration of photocreated carriers.
Stimulated emission from a He–Cd hollow-cathode discharge in a magnetic field
Authors: Cristescu C. P. , Lupaşcu A. I. , Popescu I. M. , Preda A. M.
Published: April 2011

The simultaneous oscillation on the 533.7 and 537.8 nm lines of Cd II of a hollow cathode laser with internal mirrors is studied as a function of an applied transverse magnetic field. The oscillations parallel to the field and perpendicular to it show different behaviour, but both of them are suppressed by magnetic fields in excess of certain values, which are different for the two oscillations. It is shown that the observed change of the power output with the increase of the magnetic field can be understood only if the effects of the field both on the plasma and on the atomic transition are taken into account.
The composition dependence of the effective vacancy formation enthalpy in copper-rich brass as deduced from the threshold temperature for positron trapping in vacancies
Authors: Schultz P. J. , Jackman T. E. , Fabian J. , Williams E. A. , MacDonald J. R. , MacKenzie I. K.
Published: April 2011

The temperature dependence of the Doppler-broadened positron annihilation lineshape has been measured for 13 brass specimens with compositions varying from 0 to 48% by weight of Zn. The vacancy formation enthalpy deduced from these measurements shows a linear decrease of 22% with increasing Zn concentration through the α phase and a further 31% decrease on changing from fcc to bcc structure.
Le spectre électronique de PS. Première partie : le systeme B2Π–X2Π
Authors: Jenouvrier A. , Pascat B.
Published: April 2011

The electronic transition B2Π–X2Π of PS has been studied in the region 3450–5700 Å. One hundred fourteen sub-bands have been put in the vibrational classification. They arise from 13 levels (ν = 0 to 12) of the B2Π state and from 10 levels (ν = 0 to 9) of the X2Π state.The rotational analysis of 50 sub-bands allows the determination of the equilibrium constants of the two states and presents the perturbations in the levels ν > 9 of the B2Π state.
Non-linear scattering of light in the limit of ultra-strong fields
Authors: Bhartia Prakash , Valluri Sreeram
Published: April 2011

The non-linear interaction of two electromagnetic waves in a vacuum is treated by the introduction of the Lagrangian for a strong electromagnetic field. The quantum mechanical effect of the scattering phenomenon between plane electromagnetic waves can be simulated within the framework of classical theory under the assumption of an effective non-linear interaction between the electromagnetic waves. The promise of continuous, intense, and monochromatic polarized radiation from electron synchrotrons and storage rings motivates the study. The scattered fields are obtained and a ratio of the power in the scattered fields to that of the incident fields is estimated for a simple case.
Crystallography and temperature dependance of the resistivity of SnS2−xSex solid solutions
Authors: Harbec J. Y. , Paquet Y. , Jandl S.
Published: April 2011

The iodine transport process was used to grow single crystals of SnS2−xSex with 0 ≤ x ≤ 2 Platelike crystals with dimensions of the order of 10 mm × 10 mm × 10−2 mm were obtained and their compositions were chemically analyzed. Measurements of lattice parameter and resistivity variation as a function of composition x were carried out.
Rotational ordering and nuclear spin-lattice relaxation in solid methane
Authors: Briganti G. , Calvani P. , Luca F. De , Maraviglia B.
Published: April 2011

The proton spin-lattice relaxation time has been measured in solid CH4 down to 0.4 K. In the ordered phase at 9 < T < 20 K the relaxation process is induced by librons. The energy of the librons (~75 K) is in excellent agreement with the theoretical prediction by Yamamoto, Kataoka, and Okada. T1 has been found constant within experimental error between 0.4 and 9 K. The mechanism responsible for relaxation in this lower temperature region is attributed to the adiabatic molecular reorientation of the ordered T molecules. The cooling procedure has been found in special cases to affect the experimental results.
Cross section for the excitation of helium by He+
Authors: Ojha S. P. , Tiwari P. , Srivastava K. P.
Published: April 2011

Cross sections for the singlet excitation of helium by He+ impact have been calculated under the Vainshtein, Presnyakov, and Sobelman (VPS) method with peaking approximation. Transitions from the ground state to the n1P(n = 2 and 3) states have been considered. The results are compared with other theoretical and experimental results.
Ground state spectroscopic constants and electric dipole moment of D14N12C32S from its microwave and millimetre wave spectra
Authors: Szalanski L. B. , Gerry M. C. L. , Winnewisser G. , Yamada K. , Winnewisser M.
Published: April 2011

The microwave and millimetre wave spectra of D14N12C32S in its ground vibrational state have been investigated in the frequency region 8–210 GHz. A large number of a-type Q branch and b-type P and R branch transitions up to J = 62 have been assigned and measured for the first time. Their frequencies have been combined with those of the a-type R branches up to K = 5 in an analysis for rotational, centrifugal distortion, and 14N quadrupole coupling constants. Constants obtained, in Watson's S reduction formalism, are: rotational constants in megahertz: A0 = 705 511(370); B0 = 5500.4391(15); C0 = 5445.2252(15); quartic centrifugal distortion constants in kilohertz: Dj = 1.0926(25); Djk = 1333.4(12); d1 = 3.455(5) × 10−2d2 = −7.8(14) × 10−3; 14N quadrupole coupling constants in megahertz: χaa = 1.19(6), χbb−χcc <0.05. The b-component of the dipole moment, μb, has been measured using the Stark effect as 1.08(15) D; this, when combined with μa = 1.67(3) D gives a total dipole moment of 1.99(15) D, essentially parallel to the HN bond.
The isotopic composition and atomic weight of palladium
Authors: Shima Masako , Rees C. E. , Thode H. G.
Published: April 2011

The isotopic composition of palladium was measured by solid source mass spectrometry. Artificial mixtures of separated palladium isotopes were prepared with accurately known isotopic composition and were used to determine the mass discrimination of the spectrometer. The corrected isotopic abundances give a revised value for the atomic weight of palladium of 106.415 ± 0.005 which is to be preferred to the currently accepted value of 106.4.
Estimating the error in variational scattering calculations
Authors: Darewych J. W. , Pooran R.
Published: April 2011

We derive bounds to the absolute value of the error that is made in variational estimates of scattering phase shifts. These bounds, like the variational estimates, are second order in 'small' quantities and are, in this respect, an improvement on similar but first-order error bounds derived previously by Bardsley, Gerjuoy, and Sukumar. The s-wave scattering by a square well potential, in the Born approximation, and by an exponential potential, using a many parameter trial function, are used to illustrate the results.
Classical theory of Klein–Gordon equations with logarithmic nonlinearities
Authors: Morris T. F.
Published: April 2011

The relativistic soliton theory of Bialynicki-Birula and Mycielski is reviewed, and extended by the addition of a term in [Formula: see text] to the nonlinear interaction. For suitable values of the coupling, the energy becomes a positive functional which can be treated by a variational method.Evidence is presented which suggests that all solutions with finite energy and nonzero charge are localized.
On Kolmogoroff's theory of turbulence and intermittency
Authors: Rollefson J. P.
Published: April 2011

Firstly, a simple model of high Reynolds number turbulence is proposed to give a clear understanding of the theory of Kolmogoroff. Three different types of intermittency are then defined, and their possible influence on the original theory of Kolmogoroff is considered in the light of this physical model. Secondly, an optical propagation experiment is described which has been used to study the characteristics of intermittency in the atmosphere.
Photonuclear sum rule for 3He and 3H
Authors: Boutin G. , Goulard B. , Torre J.
Published: April 2011

The augmentation κ of the classical Thomas–Reiche–Kuhn dipole sum rule for A = 3 nuclei is calculated using the Laverne–Gignoux bound state wave functions previously obtained by solving the Faddeev equations in the coordinate representation. Values of κ are in overall agreement with the published results of Drechsel and Kim, which, however, display a distribution at variance from our results.
Positron annihilation in the alkali halides
Authors: Kerr D. P. , Dannefaer S. , Dean G. W. , Hogg B. G.
Published: April 2011

Position lifetime spectra and Doppler broadening spectra have been measured for 17 alkali halides. Three significant lifetime components are found in almost all cases. The results are interpreted in terms of a model in which a fraction of the positrons form positronium and the remainder are initially in a state from which either annihilation or transitions may occur. The annihilation rate from the initial state is shown to depend on the distance separating negative ions, which suggests that the positron is in a bound state.Deconvoluted Doppler broadening data indicate that at least two momentum components are present.
Interband magneto-optical study of the In1−xGaxSb alloy system
Authors: Roth A. P. , Fortin E.
Published: April 2011

The In1−xGaxSb alloy system has been studied by interband magneto-optics at 6 K and in fields of up to 7 T. The magneto-optical spectra were detected directly by using the photovoltaic effect at metal–alloy semiconductor Schottky barriers. A complete set of low temperature band parameters throughout the alloy range is thus obtained in a single set of experiments. All the band parameters exhibit a non-linear composition dependence, which is compared to the predictions of existing models of alloy semiconductors.
Third-order WKBJ eigenvalues for Lennard-Jones and Varshni V potentials
Authors: Kesarwani R. N. , Varshni Y. P.
Published: April 2011

The WKBJ method is applied to the third order for obtaining the eigenvalues for the fifth potential of Varshni, and the relevant integrals are analytically evaluated. Numerical results are obtained for the Lennard-Jones potential, which is a special case of the Varshni V potential, and are compared to the results of Harrison and Bernstein obtained by a numerical integration of the wave equation. Error estimates are made. It is shown that for diatomic potentials, the Langer correction is not needed if the WKBJ approximation is carried to second and higher orders.
Rotational structure in the NO2 absorption spectrum between 8170 and 8280 Å
Authors: Merer A. J. , Hallin K-E. J.
Published: April 2011

Three parallel-polarized sub-bands, lying in the region 8170–8280 Å in the absorption spectrum of NO2, have been analysed rotationally from high dispersion grating spectra. These sub-bands are assigned as perturbed K = 0, 1, and 4 sub-bands of the [Formula: see text], which appear in absorption because of vibrational momentum coupling with the [Formula: see text], 030–000 band, which lies 137 cm−1 lower in energy. It is shown that in the photographic infrared region of the NO2 spectrum the level densities in the interacting [Formula: see text] and F[Formula: see text] states are sufficiently low that it is possible to identify progressions of vibronically-induced transitions that in zero order would be within the ground state manifold. The implications for a more detailed understanding of the NO2 spectrum are discussed.
Spectronephelometer studies of aerosols
Authors: Harrison A. W.
Published: April 2011

A spectronephelometer has been used to study scattering, settling, and diffusion effects of laboratory generated spherical aerosol particles. A polydisperse dioctyl phthalate (DOP) aerosol having a power law size distribution is shown to produce a scattering spectrum in agreement with the predictions of Mie theory. Under conditions of intense convective settling and diffusion DOP and latex spherical aerosols are found to obey an exponential type decay in concentration which can be explained in terms of a simple model based on convective transport and diffusion to the vertical walls and gravitational settling to the floor of the spectronephelometer.
Quenching of the Cabibbo angle and total muon capture rates
Authors: Parthasarathy R. , Sridhar V. N.
Published: April 2011

The results of the calculations of the total muon capture rates in heavy nuclei taking into account the hyperfine effects and nucleon-velocity terms in the muon capture Hamiltonian are presented along with the experimental data to test the Salam–Strathdee idea of vanishing of the Cabibbo angle at large electromagnetic fields. It is shown that for heavy nuclei, both the above corrections are negligible and hence the anomalous capture rates on 93Nb, 235U, and 239Pu could be largely due to the vanishing of the Cabibbo angle.
Optique bidimensionnelle en couche mince
Authors: Vincent Denis , Lit John W. Y.
Published: April 2011

We present in this paper a model for studying the propagation of an optical mode guided by a multilayer structure with variable thicknesses. Starting from the exact expression of electromagnetic field components for the TE and TM modes, and from the effective index seen by a mode, we define a two-dimensional field and an artificial dielectric with a refractive index equal to the effective index of the mode. It is then possible to reduce the problem of a plane guide with slowly varying thickness to the solution of a scalar wave equation for the field component perpendicular to the guide.[Traduit par le journal]
Rotational analysis of four bands of the γ′(B3Π–X3Δ) system of TiO
Authors: Hocking William H. , Gerry M. C. L. , Merer A. J.
Published: April 2011

The (0,0), (1,0), (0,1), and (1,1) bands of the γ′(B3Π–X3Δ) system of TiO have been rotationally analysed up to J = 55. Accurate molecular constants have been determined for the ν = 0and ν = 1 levels of the B3Π and X3Δ states. The three substates of the B3Π state all show significant Λ-type doubling, which has been analysed using a full matrix treatment. Our new results give corrected values for the ground state spin–orbit splittings; they also illustrate very clearly the problem of the correlation of the various centrifugal distortion parameters appearing in the Hamiltonian for a triplet electronic state.
Study of molecular collisions using a new interpolation scheme
Authors: Johri G. K. , Mehrotra Suresh C.
Published: April 2011

An interpolation scheme as suggested, by Mehrotra and Boggs in their time-dependent perturbation theory is applied for the first time to the study of strong collisions and to evaluate the collision induced transition probabilities when their absolute values are more than one. This approximation is used to compute the line width parameter of the rotational transition J = 1 → 2 of the OCS–OCS system.
Physical interpretation of and light propagation in the nonsymmetric unified field theory
Authors: Boal David H. , Noakes David R.
Published: April 2011

The geometric problems of unified theories of gravitation and electromagnetism which contain a nonsymmetric metric tensor are investigated. Although many of the familiar geometric properties of the Einstein–Maxwell theory are no longer valid, there do exist autoparallel 'geodesics' or paths, whose tangent vectors have constant length. It is shown in the weak field approximation that the theory allows for two oscillatory solutions, corresponding to electromagnetic and gravitational waves. The propagation of these waves is investigated in the geometric optics approximation. To the approximations used, light travels on null geodesics of the gravitational background in this theory, although not all relevant cases are solved.
On the observed gauge pressure due to the action of a tension pulse on a bubble in a viscous incompressible liquid
Authors: Lastman G. J. , Wentzell R. A.
Published: April 2011

A model of a bubble, consisting of an adiabatic gas surrounded by a viscous incompressible liquid with surface-tension at the liquid–gas interface, is studied in order to explain certain experimental results obtained for bubbles acted upon by a tension pulse. The theory developed explains the following experimental results: reproduction of the tension pulse in noncavitating conditions, and estimation of the magnitude of the observed initial pressure spike in the case of cavitation.
An improved value for the electron affinity of the negative hydrogen ion
Authors: Scherk Leonard R.
Published: April 2011

An expression is derived for the lifetime of a negative ion in a weak and static electric field. Using this expression, existing experimental data are analyzed to improve the empirical value of the electron affinity of the negative hydrogen ion by an order of magnitude.
Détermination des éléments de matrice d'un oscillateur anharmonique : utilisation des relations de commutation dans le cas particulier d'un potentiel de Dunham développé jusqu'au sixième ordre
Authors: Niay P. , Coquant C. , Bernage P.
Published: April 2011

not available
Energy spectra of secondary gamma rays at different atmospheric depths
Authors: Bhattacharyya D. P. , Roychoudhury R. K.
Published: April 2011

The CERN Intersecting Storage Ring (ISR) data for p + p → π0 + X inclusive reaction have been used to derive the spectrum of secondary gamma rays at the top of the atmosphere. The measured primary nucleon spectrum of the Goddard Space Flight Group has been taken as a nucleon source spectrum. Using the cascade theory, the gamma ray spectra at the atmospheric depths 540, 650, and 735 g cm−2 have been calculated. The results are approximately in accord with the emulsion chamber data at Mt. Chacaltaya, Mt. Norikura, and Mt. Fuji in the spectral range 0.2–4 TeV.
The microwave spectrum of the OH X2Π radical in the ground and vibrationally-excited (ν ≤ 6) levels
Authors: Coxon J. A. , Sastry K. V. L. N. , Austin J. A. , Levy D. H.
Published: April 2011

The microwave absorption spectrum of the OH X2Π radical has been observed in all vibrational levels up to ν = 6. Experimental details are described of the tunable cavity and parallel plate Stark-modulated spectrometers employed for transitions below and above 23 GHz, respectively. The observed line frequencies, together with those reported by other workers, have been fitted using a non-linear least-squares routine with numerical diagonalization of the Hamiltonian matrix. Pseudo high-order corrections for centrifugal distortion of the Λ-doubling are required for the ν = 0 data, which now extend to J = 19/2 in the 2Π1/2 component. The various adjustable parameters of the Hamiltonian are compared with those of other similar models. The Λ-doubling and magnetic hyperfine constants for the different vibrational levels are reported, and several line frequencies of potential astrophysical significance are predicted.
Modulational instability of ion acoustic waves in the presence of density gradients
Authors: Durrani I. R. , Murtaza G. , Rahman H. U.
Published: April 2011

Using the Krylov–Bogoliubov–Mitropolsky method of perturbation for weak non-linearities, we study the modulational instability of ion-acoustic waves in a collisionless plasma in the presence of a density gradient. We find that the density gradient of second or higher order of perturbation does not effect the dispersion and the non-linearity coefficients in the non-linear Schrödinger equation.
pp scattering in lD2 state
Authors: Edwards B. J. , Kamal A. N.
Published: April 2011

pp scattering in the 1D2 state is investigated in a multichannel N/D formalism with pp → pp, pp → NΔ, and NΔ → NΔ as the coupled channels. The driving force is calculated in the OPE and OBE approximations. The resulting 1D2 amplitude has the standard resonance-like features but has no complex pole corresponding to a diproton resonance.