bluuebunny/crossref_metadata_2025 huggingface dataset:
Plane gasdynamic flows in an orthogonal magnetic field
Authors: Kingston J. G.
Published: April 2011

The title flows are classified for when the pressure is proportional to a power (>1) of the fluid density and a conjecture is made as to the nature of the flows for more general equations of state.
Photoproduction of gravitational radiation by some astrophysical objects
Authors: Papini G. , Valluri S.-R.
Published: April 2011

Estimates are given for the amounts of gravitational radiation produced in the interaction of photons with the static electromagnetic fields of some astrophysical objects. These are the Sun, Quasar 3C273, Seyfert galaxies NGC 1068 and NGC 4151, the Galactic Center, and neutron stars.
Experimental transition probabilities of 'forbidden' selenium lines
Authors: Kernahan J. A. , Pang P. H.-L.
Published: April 2011

Absolute transition probabilities for the 'forbidden' lines at 4887 Å and 7768 Å in [SeI] have been obtained experimentally.
High voltage static breakdown in vacuum
Authors: Watson Alan
Published: April 2011

A static voltage breakdown mechanism in uniform fields is proposed for widely encountered, although physically limited, situations in which prebreakdown current arises from a semiconducting layer on a cathode protrusion. Conditions are given for the simultaneous establishment of an electron reservoir and virtual cathode with an opposing ionic space charge bubble at the anode. Electron impact ionization of evaporated anode material supports a parabolic current beam through which the two electrode space charge regions interact. Ions interact electrostatically with electrons in the reservoir, the density of which determines the Debye length and, hence, the dimensions. Emission from feasibly sized protrusions is possible only from semiconducting surfaces, limiting the applicability of the model. Instability in the form of rapid beam contraction is shown to begin before reaching the anode melting point, after which the voltage collapse starts. Criteria for this runaway indicate that it is initiated for applied voltages which increase as the square root of gap separation, the proportionality being determined by various thermo-physical parameters of the anode material and its vapor. Calculation shows that the breakdown voltage for copper electrodes agrees well with the measured value obtained after high energy conditioning.
Radiative pion decay in a simple quark loop model
Authors: Resnick L. , Kim J. H.
Published: April 2011

The weak decay of pions into leptons and into leptons plus photon is examined in a simple model at the one loop level. A basic assumption made is that there is more than one pair of quarks to which the pion couples and the masses and coupling constants are such that all amplitudes are finite. The amplitudes are defined by means of dimensional regularization and gauge invariance is rigorously maintained throughout. The experimental lifetimes for charged and neutral pion decay give one constraint among the quark masses and the parameter γ, the ratio of structure dependent axial to vector form factor, gives a second. Quark masses can be found to satisfy either condition, but no solution exists for both constraints simultaneously.
A comparison of correlation function and kinetic theory methods in the calculation of NMR relaxation times in dilute monatomic gases
Authors: Shizgal B.
Published: April 2011

The values of T1 in monatomic spin ½ Systems calculated with the constant acceleration approximation (CAA) are compared with the values of T1 calculated with an exact kinetic theory. The hard sphere potential as well as realistic potential functions for the spherical interaction between atoms are employed in the comparisons. T1 is calculated for both the dipolar and spin–rotation spin dependent interactions. The results indicate that the constant acceleration approximation will be useful for Systems having a slowly varying repulsive spherical potential and a long-range radial dependence for the spin dependent interation. Also, if the symmetry properties of the anisotropic potential are such that large impact parameters make the major contribution, then the CAA will be a valid approximation.
Investigation of the superconducting proximity effect by Josephson tunneling
Authors: Rowell N. L. , Smith H. J. T.
Published: April 2011

Josephson junctions have been made with a superconductor on one side of the oxide and with a normal–superconducting (N–S) sandwich on the other side. Measurements of the temperature dependence of the maximum DC Josephson current have been taken.A simple model is proposed for the order parameters within the N–S system. Within the superconducting layer of this system the linear Ginzburg–Landau equation is used to describe the behavior of the order parameter. Within the normal metal, Werthamer's solution is used. Application of de Gennes' boundary conditions completes the determination of the order parameter. Josephson currents are calculated by using the de Gennes formulation. Agreement between experiment and theory has been obtained.
Rotational analysis of selected bands from the electronic spectrum of the LuF molecule
Authors: Effantin C. , Wannous G. , d'Incan J. , Athenour C.
Published: April 2011

Rotational analysis of 20 selected bands from the electronic spectrum of the LuF molecule has been carried out. No perturbation was detected; the molecular constants deduced from a 'direct approach' including all the bands are given for the fundamental state X1Σ (ωe = 611.79, Be = 0.26764) and the excited states A1Σ (ωe = 587.95, Be = 0.26356), B1Π (ωe = 581.3, Be = 0.2632), E1Π (ωe = 543.42, Be = 0.25647), and F1Σ (ωe = 560.8, Be = 0.25815).
The nucleon–nucleon interaction. I. Scalar mesons
Authors: Capri A. Z. , Menon D. , Teshima R.
Published: April 2011

The two-nucleon interaction, via the exchange of scalar mesons, is examined in a nonperturbative manner. 'Schrödinger' equations are derived, and nonlocal potentials arise naturally. Both scattering and bound states are examined. A half-off-shell T matrix is obtained, and corresponding phase shifts are evaluated. In the bound state, a variational calculation is employed to determine the coupling constant.
The nucleon–nucleon interaction. II. Pseudoscalar mesons
Authors: Capri A. Z. , Menon D. , Teshima R.
Published: April 2011

An earlier paper examined the role of scalar mesons in the nucleon–nucleon interaction. A more realistic model, with pseudoscalar mesons, is studied here. Unlike previous treatments of this problem, this approach seems to yield more repulsion than would be required to reproduce experimental data. Calculations are performed on the spin singlet, isospin triplet state; a brief discussion of the deuteron channel and the resulting potentials is also included.
Amplitude analyses from incomplete data using fixed-t dispersion relations
Authors: Contogouris A. P.
Published: April 2011

A general method combining fixed-t dispersion relations with an incomplete set of experimental data and leading to amplitude analyses is presented. Applications to several two-body nondiffractive reactions are considered and certain regularities in the t structure of the resulting amplitudes are pointed out. Finite-energy sum rules (FESR) are also considered and discussed. Confrontation of the high energy solutions with FESR leads to an understanding of the t structure of the real parts of the amplitudes.
On the multipole expansion in the theory of optical activity
Authors: Kranendonk J. Van , Sipe J. E.
Published: April 2011

The different Hamiltonians for a molecule interacting with the electromagnetic field, which have been used in the literature on the optical activity of isotropic media, are shown to be related by a canonical transformation and hence to be equivalent. Because of its greater simplicity, the use of the multipole Hamiltonian in the theory of optical activity is advocated.
Spherical tensor approach to multipole expansions. II. Magnetostatic interactions
Authors: Gray C. G. , Stiles P. J.
Published: April 2011

The magnetic field due to a given current distribution, the interaction energy of a current distribution with an arbitrary external magnetic field, and the magnetostatic interaction energy between two current distributions are decomposed into multipolar components using spherical harmonic expansions. Diamagnetic interactions and the spin contributions to the multipole expansions are also discussed.
The absorption and emission spectra of HD in the vacuum ultraviolet
Authors: Dabrowski I. , Herzberg G.
Published: April 2011

The absorption spectrum of HD has been studied under high resolution in the vacuum ultraviolet to 840 Å, the emission spectrum to 1000 Å. The analysis of the latter gives accurate rotational constants and vibrational intervals of the ground state right up to the dissociation limit. Comparing these experimental data with calculations from ab initio theory, agreement to the same extent as was previously found for H2 and D2 is obtained. Extrapolation of the obs. – calc. values from H2 and D2 to infinite mass yields agreement with the recently revised theoretical values to within less than 0.1 for v < 7 and less than 0.5 cm−1 for the whole range of observed v values. The deviations for finite mass (H2 and D2) are clearly due to the non-adiabatic corrections neglected in the ab initio calculations. The results for HD are not halfway between H2 and D2 but are closer to H2. This apparent anomaly can be quantitatively accounted for, on the basis of recent calculations of Wolniewicz, by the effect of additional nonadiabatic corrections caused by the excited Σu states which in HD, unlike H2 and D2, can interact with the ground state.The rotational and vibrational constants of the excited states B1Σu+, C1Πu, and B′1Σu+ show somewhat larger deviations from ab initio values ranging for v0v from 5 to 120 cm−1, just as for H2 and D2. The electronic isotope shift of HD lies approximately half-way between the values of H2 and D2 as expected. In addition to the B–X, C–X, and B′–X systems the absorption spectrum of HD, unlike that of H2 and D2, shows an extensive progression of weak transitions to the double minimum state EF1Σg+ and a few very weak transitions to the G1Σg+ and I1Πg states. For the EF state both levels in the outer minimum (F) and levels above the maximum are observed. The correlation of the six excited states B, C, B′, EF, G, and I to the two close-lying dissociation limits corresponding to H + D* and H* + D is briefly discussed.
Coherent parity violation
Authors: Karl Gabriel
Published: April 2011

Recent theoretical speculations about parity violating effects in the forward scattering of massless and massive particles are reviewed at an elementary level. These phenomena are analogous to optical activity, whose history is also briefly reviewed. Order of magnitude estimates for the rotatory power are presented, and the feasibility of experiments with neutron beams is discussed.
Measurement of the broadening of the sodium resonance lines by helium
Authors: Copley G. H.
Published: April 2011

A nitrogen-pumped, tunable dye laser has been used to excite Na D-line fluorescence in a re-entrant scattering cell (maintained at 500 K) filled with He at pressures up to 300 Torr. The laser was scanned across the D lines, broadened in collisions with He atoms. The intensity of the resonantly scattered light was recorded at right angles to the laser beam since, in this direction, the absorption coefficient was independent of the laser intensity. D-line profiles obtained in this fashion were then analyzed to obtain collision-broadening coefficients. These coefficients of values 2.4 ± 0.3 and 2.8 ± 0.4 (in units of 10−9 rad s−1 cm3), for the D1 and D2 lines respectively, are compared with recent measurements at high and low temperatures and with several quantum mechanical calculations.
Ratio of in zirconium isotopes
Authors: Ghosh M. K. , Majumdar S. R. , Samanta B.C.
Published: April 2011

The modified random phase approximation is applied for studying pairing vibrations in Zr isotopes. The ratio of [Formula: see text], which is related to the ratio of the square of the two-nucleon transition amplitude, is calculated for different zirconium isotopes and compared with the experimental result.
On bounds for the rho–omega mixing parameter
Authors: Gien T. T.
Published: April 2011

By considering only the order of the coupling strength responsible for the G parity violation mixing in the ρ–ω system, we can find a new bound for the mixing parameters in the 2π decay channel which is stricter than the one obtained previously (Gien). It is also shown that if the sign of the ratio of the transition amplitudes for the decays of 'bare' rho and omega in the 2π channel is known, a part of the bound may even be shown independent of the magnitude of the coupling strength. A new graphical representation is given for comparison.
4f → 5d Transition studies of Tb+3 and Dy+3 in calcium fluoride
Authors: Schlesinger M. , Szczurek T. , Wiltshire M. C. K.
Published: April 2011

4f → 5d transitions of the Tb+3 and Dy+3 ions in CaF2 are investigated. The phonon structure associated with some electronic transition, no-phonon, lines is interpreted in terms of localized and delocalized CaF2 frequencies. The present results are in good agreement with previous work on Ce+3 and Ho+3 in the same host lattice.
Beam–foil spectroscopy of sulfur in the vacuum ultraviolet
Authors: Irwin D. J. G. , Livingston A. E.
Published: April 2011

We report mean-life results for 16 terms in S III–S VI, obtained from vacuum ultraviolet transitions in sulfur excited by beam–foil interaction. Ten of the mean lives have been measured for the first time. Many of the mean lives reported here are in the neighborhood of 0.1 ns, beyond the time resolution capability of a previous experiment, as indicated by comparison of results for five of the remaining six terms. For those transitions that are unbranched. we have computed the absorption oscillator strength and we discuss the values in the context of isoelectronic-sequence trends. In an appendix, we discuss the determination of short mean lives and describe the apparatus we have developed to measure them, and its limitations.
Subgroups of the similitude group of three-dimensional Minkowski space
Authors: Patera J. , Winternitz P. , Sharp R. T. , Zassenhaus H.
Published: April 2011

All continuous subgroups of E(2,1) and of the similitude group of three-dimensional Minkowski space are found and classified into conjugacy classes under inner automorphisms and under the corresponding conformal group O(3,2). All the subalgebras are also classified up to isomorphisms and their invariants (Casimir operators and their generalizations) are found. The results are summarized in tables.
Etude d'une transition possible à trois multipoles dans la désintégration gamma du niveau à 1612 keV de l'37Ar
Authors: Vaillancourt R. , Taras P.
Published: April 2011

The γ-ray decay of the 1612 keV level (τ = 6.38 ± 0.15 ns) in 37Ar has been analyzed in terms of a mixture of three multipoles. The data was obtained from the simultaneous measurement of the linear polarization and angular distribution of the decay γ rays, in coincidence with the neutrons emitted along the beam axis, the level being populated via the 34S(α, n)37Ar reaction at Eα = 10.5 MeV. The results definitively eliminate the possibility of the γ rays consisting of a mixture of three multipoles, thereby confirming the Jπ = 7/2− assignment to the level.
Diurnal variation of the Ring effect
Authors: Harrison A. W.
Published: April 2011

The filling-in or Ring effect for the three Fraunhofer lines 4227 Å CaI, 4326 Å FeI, and 4340 Å HI has been observed in the day sky under clear and cloudy conditions. A pronounced diurnal variation for all three lines shows a midday minimum with a three-fold increase as the solar zenith angle increases from 30° to 90°.
The A2Πi–X2Πi band system of ClO: Reinvestigation of the absorption spectrum
Authors: Coxon J. A. , Ramsay D. A.
Published: April 2011

The A2Πi–X2Πi band system of 35ClO has been reinvestigated in absorption in the flash photolysis of ClO2 and Cl2/O2 mixtures, using higher resolving power than in earlier work. The rotational assignments for the ν′–0 progression have been revised and extended and new molecular constants have been obtained. In addition, four new bands with ν″ = 1 and 2 have been observed for the first time. The value for the ground state vibrational interval is found to be [Formula: see text]. Widths are given for levels with 2 ≤ ν′ ≤ 25 and show that all these levels are predissociated. With the help of the theory of long-range interactions, an improved value for the ground state dissociation energy is obtained, viz. D0″ = 22 184 ± 3 cm−1 (≡ 63.427 ± 0.008 kcal/mole ≡ 2.7504 ± 0.0004 eV).
Properties of the levels in 22Na deduced from the 19F(α,nγ)22Na reaction
Authors: MacArthur J. D. , Brown A. J. , Butler P. A. , Green L. L. , Lister C. J. , James A. N. , Nolan P.J. , Sharpey-Schafer J. F.
Published: April 2011

For gamma rays following the 19F(α,nγ)22Na reaction, angular distribution, linear polarization, and DSA measurements have been analysed to extend the experimental information on the rotational bands in 22Na. In particular the spins, parities, and mean lifetimes of the following states belonging to the indicated bands have been determined; (Ex, Jπ, τm, K); 3.707 MeV, 6+, 110 ± 10 fs, K = 3+; 1.984 MeV, 3+, —, K = 0+; 4.710 MeV, 5+, 50 ± 20 fs, K = 0+; 4.071 MeV, 4+, —, K = 0+. In addition, the spins, parities and lifetimes of the 4.360, 5.063, and 5.100 MeV states were determined to be 2+, <10 fs; 2+, <20 fs; and 4+, 55 ± 15 fs respectively. Besides the known branches from the 4.710 MeV state, a 5 ± 1% branch to the 2.969 MeV state was observed; while for the 5.100 MeV state, branches of 18 ± 2, 15 ± 5, 12 ± 2, 18 ± 2, and 37 ± 3% were observed to the ground, 0.891, 1.528, 3.060, and 4.071 MeV states. All the positive parity states below 5.1 MeV have been interpreted in terms of spherical shell model configurations for six particles in the s–d shell predicted by the Manchester–Glasgow shell model program, using the Preedom and Wildenthal interaction.
Short term proton spin conversion in solid CH4
Authors: Code R. F. , Higinbotham J.
Published: April 2011

Short term measurements were made of the static proton magnetic susceptibility of solid CH4 containing O2 impurities in the temperature range between 1.6 and 80 K. The samples were slowly crystallized and annealed above 80 K. A low level NMR Q-meter detector was used to measure the temperature dependence of the polarization of the hydrogen nuclei in methane relative to the polarization of fluorine nuclei in a thick teflon coil form surrounding the sample after thermal equilibration times of up to 2 h. The results can be consistently interpreted according to the James–Keenan model for Phase II of solid methane by assuming that, during a 2 h period, proton spin symmetry conversion essentially comes to equilibrium on the two disordered sublattices whose molecules are in states of nearly free rotation, but that conversion does not significantly occur within this time for molecules on the six remaining ordered sublattices.
Etats de valence de NSe : Mise en évidence d'un état a(4Πi)
Authors: Daumont Dominique , Jenouvrier Alain , Pascat Bernard
Published: April 2011

The complexity of the spectral region 3500–5500 Å has been noted in an earlier study and is due to the presence of many vibrational and rotational perturbations. New data which have been obtained, in particular from a complete study of the spectrum of 15N80Se, have led us to re-examine thoroughly our interpretation of the 3300–5800 Å region. We have thus arrived at a new vibrational assignment and have found evidence for two perturbing states: the b(4Σ−) state for which a transition to one level has been observed weakly and analyzed; the a (4Πi) state which has been identified and for which we have been able to determine vibrational and rotational constants. The relative position of the six observed states may be accounted for in terms of energy level and potential energy curve diagrams.
A study of 187Re, 189Re, and 191Re using the (t,α) reaction
Authors: Hirning C. R. , Burke D. G.
Published: April 2011

The proton states in 187Re, 189Re, and 191Re have been studied using the (t,α) reaction. The beam of 15 MeV tritons was obtained from the Los Alamos Scientific Laboratory model FN tandem Van de Graaff accelerator. The reaction products were analyzed with a Q3D magnetic spectrometer and detected with a helical-cathode position sensitive proportional counter. Previous assignments for 187Re are adopted, and assignments in 189Re are based on characteristic intensity patterns and a previous γ-decay study. The Nilsson orbitais 5/2+[402], 9/2−[514], and 1/2+[411] are identified in 189Re, and possible assignments of these orbitals are suggested for 191Re. It is found that the spectroscopic strengths of low-lying 11/2− states are much smaller than would be expected for pure h11/2 shell model states but are consistent with values expected for a deformed model. However, the basic Nilsson model does not describe all the features well. The results are compared with the predictions of the Nilsson model with a hexadecapole deformation included.
Nonlinear wave equation with intrinsic wave particle dualism
Authors: Klein J. J.
Published: April 2011

A nonlinear wave equation[Formula: see text]derived from the sine–Gordon equation is shown to possess a variety of solutions, the most interesting of which is a solution that describes a wave packet travelling with velocity uc modulating a carrier wave travelling with velocity uc. The envelop and carrier wave speeds agree precisely with the group and phase velocities found by de Broglie for matter waves. No spreading is exhibited by the soliton, so that it behaves exactly like a particle in classical mechanics. Moreover, the classically computed energy E of the disturbance turns out to be exactly equal to the frequency ω of the carrier wave, so that the Planck relation [Formula: see text] is automatically satisfied without postulating a particle–wave dualism.
Relative yield of low energy positrons from various solid moderators
Authors: Pendyala S. , Bartell D. , Girouard F. E. , McGowan J. Wm.
Published: April 2011

Relative yields and half widths of low energy positron spectra from a variety of solid moderators, obtained using a high resolution (~1.5%) electrostatic spectrometer, are summarized. Variations in yields due to moderate heat treatment of the moderators are reported.
Multiple-plane wave calculation of the electron–phonon interaction in Al
Authors: Leung H. K. , Carbotte J. P. , Taylor D. W. , Leavens C. R.
Published: April 2011

We have computed from first principles the electron–phonon spectral weight αk2(ω)Fk(ω) for many points k on the aluminum Fermi surface (FS). According to Migdal's theorem this spectral weight completely determines the self-energy of the electrons. The calculations involve an integral over final states on the Fermi surface which we calculate from Ashcroft's 4-plane wave pseudopotential model fit to the de Haas–van Alphen data. For the electron–phonon matrix element 15 plane waves are included. The phonons are taken from a Born–von Karman model fit to the measured dispersion curves. From the spectral weights we compute the Fermi surface variation of the electron–phonon effective mass and the quasiparticle lifetimes at various temperatures.
Microwave absorption in compressed CF4, CH4, and CF4–Ar, CH4–Ar mixtures in the 2.3 cm−1 region
Authors: Urbaniak J. L. , Reesor G. E. , Dagg I. R.
Published: April 2011

Microwave absorption is reported in gaseous CF4 and CH4 in the region of 2.3 cm−1. For CF4, loss factor measurements are given at temperatures ranging from 248 K to 318 K and densities in the range 30 to 100 amagat. The parts in the loss factor which are proportional linearly to the density and to the square of the density are found to depend on temperature as T−0.40 ± 1.05 and T−1.98 ± 0.15 respectively. For CH4, loss factor measurements are given at temperatures ranging from 208 K to 295 K and at densities in the range 60 to 200 amagat. The part in the loss factor which is proportional to the square of the density is found to depend on temperature as T−1.55 ± 0.23. The present results are compared with the extrapolated infrared results and both have been used to calculate the octopole and hexadecapole moments. Loss factor measurements are also reported in CF4–Ar and CH4–Ar gas mixtures at 295 K at various density ratios and total densities up to 200 amagat.
On the vibronic spectrum of rare earths in calcium fluoride
Authors: Schlesinger M. , Drake G. W. F.
Published: April 2011

The phonon side-band peak near 490 cm−1 accompanying 4f → 5d transitions of ten triply-ionized rare earth elements in the CaF2 matrix and some of the corresponding peaks in SrF2 and BaF2 are investigated. All the data taken together confirm an earlier identification of the peaks as a local mode associated with the rare earth ion and its nearest-neighbour fluorine ions.
Helium gas jet spectral calibration of acoustic emission transducers and systems
Authors: McBride S. L. , Hutchison T. S.
Published: April 2011

The excitation and spectral calibration of acoustic emission systems using a helium gas jet is shown to produce system independent acoustic emission spectral information. The calibration source makes no mechanical contact with the specimen or structure under investigation and can be conveniently used for specimen or structural response mapping.
Transmission of creeping-wave modes around a periodically modulated impedance cylinder
Authors: Cho S. H. , Wait J. R.
Published: April 2011

Motivated by recent advances in radio oceanography, an idealized two-dimensional model of diffraction by a non-uniform cylinder is analyzed. The cylinder is characterized by a surface impedance that varies in a periodic fashion in the azimuthal direction. For excitation by a magnetic line source, a solution for the resulting field is obtained that satisfies the specified periodic boundary condition. This representation for the fields is converted, via a Watson transform procedure, to a form that is more convergent and useful for short wavelengths. It is shown that, for each creeping-wave mode, an infinite number of spatial harmonics is excited. These harmonics are a consequence of the periodic non-uniformity of the surface and they include the backward scattered waves. The latter becomes very strong in the region where the spatial period is half the radio wavelength in accordance with the well-known Bragg phenomenon. In this case, contrary to what is sometimes assumed, the attenuation of the forward creeping waves is much increased. This suggests that perturbation methods, such as used to interpret radio-oceanographic data, may be invalid just in the region when they appear to have the most diagnostic value.
Some remarks on a recent Mössbauer effect study of the β-phase iron germanide
Authors: Fatséas G. A.
Published: April 2011

A Mössbauer study of iron germanide was published recently in this journal (Daniels, Moore, and Panda). The authors reported that they reproduced, by computer analysis, their Mössbauer spectra in terms of three six-line iron sites, rejecting our earlier results of several FeI and FeII sites identified from a model of statistical (binomial) distribution of vacancies on the iron-site positions (Fatséas, Dormann, and Brossard). We would like, in this paper, to make some remarks and also to present some of our unpublished results for eventual future discussions.
Solution of the Bohr Hamiltonian for J ≤ 20
Authors: Smith B. C. , Ko C. -M.
Published: April 2011

The Bohr collective Hamiltonian, with arbitrary inertial functions and collective potential, is solved numerically for angular momentum as high as J = 20. Applying the technique in the case of a two-minima potential, it is shown that a shape change in the Yrast band can cause backbending.
Lattice relaxation around impurity pairs in alkali halides
Authors: Templeton T. L. , Clayman B. P.
Published: April 2011

The rigid ion model is applied to the calculation of the relaxation of the lattice around single impurities and pairs of impurities in alkali halide host-defect systems. The calculated relaxation of nearest neighbors is typically a few percent of the host crystal lattice constant. Relaxation falls off with increasing distance from the defects. Nearest neighbor force constants derived from this calculation are, in some cases, in good agreement with those obtained by fitting the resonant absorption frequencies of the vibrational modes of these impurity centres to a molecular model. In other cases the extreme anisotropy of the relaxed force constants is seen to prevent the application of a simple molecular model. The calculated force constants, when used in a linear chain model, give good qualitative agreement with experiment.
Is the nuclear strength function Lorentzian? Suggestions from a solvable model
Authors: Lukac E. G.
Published: April 2011

The study of the shape of the nuclear strength function is a line spreading problem in which one examines how a residual interaction spreads a model state into the actual states of a system. In previous studies of the strength function the matrix elements of the residual interaction have been treated as the elements of a random matrix whose connection with the underlying physics was rather tenuous. Here a model consisting of one-dimensional harmonic oscillators, which has a more visualizable correspondence than random matrixes to a microscopic picture of nuclear reactions, is employed. In this model it is shown that the strength function is not Lorentzian and how it differs from a Lorentzian. The calculations suggest that preferential population of certain types of states can be expected in nuclear reactions. Attention is also drawn to the importance for heavy ion reactions of cluster states in the compound nucleus.
Photoelectric cross sections derived from the measured total absorption cross sections at 52.2 and 84.3 keV in Al, Cu, Zr, Ag, Sn, Ta, Au, and Pb
Authors: Gowda Ramakrishna , Puttaswamy K. S. , Sanjeevaiah B.
Published: April 2011

Photoelectric cross sections for 52.2 and 84.3 keV photons in Al, Cu, Zr, Ag, Sn, Ta, Au, and Pb are obtained by subtracting the total scattering cross sections from the measured total absorption cross sections. The scattering cross sections are taken from the recent tabulated values of Veigele, for subtracting purpose. The results are compared with the values interpolated from the theoretical results of (1) Schmickley and Pratt and (2) Scofield.
Magnetization studies of the Heusler alloys, Ni2MnxTi1−xSn, Ni2MnxV1−xSn, and Ni2MnxCr1−xSn
Authors: Campbell C. C. M. , Stager C. V.
Published: April 2011

Magnetization measurements are reported for the alloy series, Ni2MnxTi1−xSn, where T is Ti, V, or Cr. Alloys containing Ti or V were studied at compositions corresponding to x = 1, 0.8, 0.6, 0.4, 0.2, and 0.0. The Cr series was studied for x = 1, 0.8, 0.6, and 0.4; beyond this composition, the samples are polyphase. For the Ti series, all of the alloys containing Mn are ferromagnetic with Currie temperatures in the range 345 K to 261 K, and saturation moments in the range 4.04 μB to 0.47 μB per molecule. All of the V alloys containing Mn are ferromagnetic with Curie points between 345 K and 45 K, and saturation moments between 4.04 μB and 0.60 μB per molecule. Curie points for the Cr series range between 345 K and 220 K and the saturation moments vary from 4.04 μB to 2.11 μB per molecule. Susceptibility studies on the Ti, V, and Cr series show Curie–Weiss behaviour and indicate an effective moment of ~5 μB per Mn atom. The interpretation of the results is consistent with a contribution of ~ −1 μB by a Ti atom to the magnetic moment, zero contribution by a V atom, and ~ +1 μB by a Cr atom.
Null-plane quantum electrodynamics in an external radiation field
Authors: Neville R. A.
Published: April 2011

The formalism developed in this paper is designed to treat the interaction of an electron with a laser pulse. Precisely, it is a formulation on null hyperplanes of quantum electrodynamics in an external radiation field.The result is a quantum electrodynamic formulation in which one works in the Furry picture. The electron field operator in this picture is a solution to the Dirac equation with external field, and is appropriately represented by an expansion in terms of wave packets of Volkov solutions, the latter being exact, explicitly known solutions to the above named equation. The null-plane formulation is required for the consistent construction and implementation of the Volkov wave packets.This formalism permits one to do calculations which take the external field (laser field) into account exactly while treating the quantized photon field (self-field) via the usual perturbation method as adapted to null planes.
Quasimolecular treatment of Stark broadening in hydrogen
Authors: Szudy J. , Baylis W. E.
Published: April 2011

The recently developed unified Franck–Condon (UFC) treatment of pressure broadening of spectral lines is applied to Stark-broadened hydrogen lines to determine the profile at intermediate frequencies where both impact and quasistatic treatments are expected to fail. In the JWKB approximation the UFC lineshape is given by an analytic expression, the classical limit of which is a generalization of results obtained by the Green-function and phase-shift methods.
Observation and vibrational study of the A2Π–X2Σ and B2Σ–X2Σ transitions of ScS
Authors: Stringat R. , Fenot B.
Published: April 2011

The A2Π–X2Σ, and B2Σ–X2Σ, transitions of ScS were observed in the near infrared. The vibrational quantum numbers of the A2Π state could not be determined absolutely because of the lack of sensitivity of the film at the longer wavelengths. The vibrational constants for the X (ωe = 565.2 cm−1) and B (ωe = 488.2 cm−1) states were deduced from the band heads.
An analytical investigation of the optical mixing of two laser beams of identical frequencies in a spatially homogeneous collisionless plasma
Authors: Spyrou Orestes , Meyer Jochen
Published: April 2011

Two laser beams of the same frequency and intensity propagating in opposite directions are mixed in a uniform collisionless plasma.A standing longitudinal wave of wave number k0 = 2kL (kL being the wave number of one of the lasers) is excited and traps charged particles. Including trapped particle dynamics and making use of the properties of the Jacobi elliptic functions, an expression for the power P(t) and the energy. ΔU0 absorbed by the plasma electrons is derived. It is found that the power varies sinusoidally with time. Then the energy density ΔU0 is plotted as a function of the variable E10/kL, E10 being the electric field intensity of the lasers, and the validity of the results is discussed.
High resolution spectrum of GdO
Authors: Yadav B. R. , Rai S. B. , Rai D. K.
Published: April 2011

The visible emission spectrum of the GdO molecule has been produced in a DC arc source and has been photographed in the first order of a 10.6 m grating spectrograph. Bands are shown to have a six-headed structure and improved vibrational constants have been obtained in this study. Isotopic shifts have been calculated for the various isotopic molecules. Tentative suggestions regarding the nature of the transition have been made.
Reinvestigation of the A2Π–X2Σ+band system of the BeI molecule
Authors: Carleer M. , Colin R.
Published: April 2011

The 0–0 band of the A2Π–X2Σ+ transition of the BeI molecule has been reinvestigated at high resolution. The rotational assignments of the 2Π1/2–2Σ+ subband have been revised and the analysis has been extended to the 2Π3/2–2Σ+ subband. The principal molecular constants determined are:[Formula: see text]The anomaly between the B values of the A2Π1/2 and A2Π3/2 substates and in the intensity ratio of both subbands is tentatively explained.
Pion production spectrum from primary cosmic ray spectrum and scaling constants
Authors: Bhattacharyya D. P. , Choudhury R. K. Roy , Basu D.
Published: April 2011

The scaling hypothesis of Dao et at. in p + p → π− + X reactions has been used to derive the sea level spectrum of cosmic muons from the satellite data of primary cosmic ray nucleons. It is found that the derived pion production spectrum depends on [Formula: see text], the average value of the Feynman variable x. Taking as input the energy spectrum of primary cosmic ray nucleons determined by Grigorov et al., as well as the sea level muon spectrum determined by Allkofer, Carstensen, and Dau, the value of [Formula: see text] at different pion energies has been estimated. A fit to the calculated results gives the following energy dependence of [Formula: see text]:[Formula: see text]
Time evolution and thermalization of an ideal gas in a box
Authors: Kreuzer H. J. , Teshima R.
Published: April 2011

We study the time evolution of a gas of particles enclosed in a one-dimensional box the walls of which are in random thermal motion.
Nucleations of pressure induced phase transitions in mercury selenide
Authors: Lombos B. A. , Mahdaly H. M. , Pant B. C.
Published: April 2011

The resistance discontinuity technique combined with a three-dimensional heterogeneous nucleation theory permitted the direct determination of the rate of pressure induced phase transitions in mercury selenide. A direct relationship between the activation volumes and kinetic transition pressures was found which facilitated the determination of the thermodynamical transition pressure by extrapolating to zero activation volume. At low nucleation concentration, a faster rate of transition is observed.
Stark broadening of the lines 4121 Å and 4437 Å of helium in a plasma: Quantum-mechanical calculations for the electron impact effects
Authors: Bassalo J. M. , Cattani M.
Published: April 2011

We calculate the broadening and shift of two lines (4121 Å and 4437 Å) for neutral helium in a plasma. To obtain the effect of the electron collisions the quantum-mechanical formalism developed by Bassalo and Cattani is used. Our theoretical predictions are compared with the experimental results of Wulff and of Bötticher, Roder, and Wobig and with the semi-classical estimates of Griem, Baranger, Kolb, and Oertel.
A study of breakdown delay in electrically pumped laser gases
Authors: Savic P. , Kekez M. M.
Published: April 2011

When a steep-fronted voltage step is applied to the electrodes in a preionized gas, the high electric field in the cathode sheath, together with current continuity across the sheath causes preferential heating and pressure increase of the gas in the sheath region. The situation is somewhat analogous to that in a shock tube at the instant of diaphragm rupture. However, owing to the current, the cathode sheath goes unstable, forming filaments of hot gas from the sheath. Expressions are derived for the breakdown delay in the two extreme cases of high and low power deposited in the gas, in terms of four time constants, i.e. the relaxation time, the 'power time', being the time required for the electric power to raise the pressure level of the gas to ambient, the 'asperity time', i.e. the time taken by a sound wave to traverse a roughness element or asperity of the electrode surface, and the 'sheath time', being the time of the wave's traverse of the sheath thickness. It is shown that the theory is in substantial agreement with existing experimental findings, including those of the authors. It is further indicated to what extent the new theory goes beyond older concepts, namely in that not only thermoacoustic but also surface phenomena are taken into account.The history of gas laser development is illustrated graphically in the theoretical and experimental curves of breakdown delay vs. surface asperity and deposited energy.
The ultraviolet band systems of arsenic monofluoride: Rotational analysis of the e0−–X21 and f0+–X21 transitions
Authors: Vasudev R. , Jones W. E.
Published: April 2011

The band system of AsF tentatively designated as B–X21 by Liu and Jones has been shown to actually consist of two transitions, designated here as e0−–X21 and f0+–X21. The Ω doubling in the c1 state, which is due to the proximity of the e0− and f0+ states, is interpreted in terms of a model describing the interactions.
Anisotropy in the Kondo effect of single crystal Zn–Mn alloys
Authors: Muir W. B. , Stroink G. , Wassermann E. F.
Published: April 2011

The anisotropy in the Kondo effect of single crystal ZnMn alloys (10–500 at. ppm Mn) has been studied between 0.3 and 8 K. The impurity resistivity with current flowing perpendicular to the c-axis of the hexagonal crystal is 1.6 times greater than the impurity resistivity with the current flowing parallel to the c-axis for all the ZnMn alloys. The resistivity of a Zn 500 at. ppm Al alloy was found to be isotropic and, in agreement with previous results, the resistivity of pure zinc was found to be nearly isotropic. On the basis of a two band model for zinc we show that the ratio the relaxation time on the monster and lens portions of the Fermi surface τL/τM is 1.3 ± 0.1 for pure Zn, 1.1 ± 0.3 for the ZnAl alloy, and 0.43 ± 0.05 for the ZnMn alloys. We attribute the threefold variation of τM/τL between magnetic Mn (d-type) impurities and the nonmagnetic (s,p-type) impurities in pure Zn and the ZnAl alloys to the nature of the conduction electron wave functions on the monster and lens portions of the Fermi surface of Zn. We require the partial density of s,p-like wave functions to 1.2 times greater on the lens surface than on the monster surface while the partial density of d-like wave functions on the lens surface must be 0.4 times their density on the monster surface.
Axial heating of magnetically confined plasma with CO2 lasers
Authors: Offenberger A. A.
Published: April 2011

The coupled electron–ion heating equations, neglecting losses, in a CO2 laser heated solenoid are solved for a laser intensity varying with time as I = I0t2/3. An analytical solution, without restriction on the ratio of electron-to-ion temperatures Te/Ti is found, showing Te,i ~ t2/3.The heating wave which propagates along the solenoid is found to be supersonic having a velocity independent of time and varying as I03/5. Low intensity heating is found to maximize Ti/Te and minimize plasma length and laser energy requirements. The heating wave propagation is found to be consistent with an optical thickness of order unity in the heated plasma column. Considerations of electron–ion energy transfer, supersonic heating wave propagation, and laser beam trapping lead to an optimum laser intensity parameter [Formula: see text].
Nuclear orientation of 206Bi in nickel
Authors: McConnell P. R. H. , Martin P. W. , Turrell B. G.
Published: April 2011

A study of the 206Pb decay was performed by nuclear orientation of 206Bi nuclei in a nickel host at low temperatures. The hyperfine field of 206Bi/Ni was determined to be 400 ± 34 kG, with 65% of the bismuth nuclei occupying lattice sites. Mixing ratios were determined for several transitions in the 206Pb decay. Attenuation coefficients due to reorientation effects in the isomeric state at 2200 keV excitation in 206Pb were measured.A discussion of the reasons for fractional occupation of lattice sites by the bismuth nuclei is given.
Precise atomic masses and mass differences for W and Re
Authors: Sharma K. S. , Kozier K. S. , Barnard J. W. , Barber R. C. , Haque S. S. , Duckworth H. E.
Published: April 2011

The 1 m radius, second order double focusing mass spectrometer at the University of Manitoba has been used to obtain atomic mass differences for eleven mass doublets. These data are combined with well known values for the atomic masses of 13C, l6O, 35Cl, and 37Cl to derive both atomic masses and mass differences for all of the naturally-occurring isotopes of W and Re.
Two OPW calculations of electronic transport properties of copper below 20 K
Authors: Brett M. E. , Black J. E.
Published: April 2011

The results of numerical calculations of the electrical and thermal lattice resistivity of copper at temperatures (T) below 20 K are presented. We have calculated the matrix element for electron–phonon scattering using two OPW electronic states and the Born – von Karman method of determining the phonon frequencies and eigenvectors. We have used the eight-cone model of the Fermi surface in which necks intersecting the Brillouin zone and the spherical belly regions are both present.The lattice electrical resistivity is calculated for two limiting cases. In the first case the resistivity is that expected when no impurities are present in the metal. In the second case the impurity resistivity is taken to dominate the lattice resistivity. We show that the T3 behaviour of lattice resistivity recently observed experimentally below 10 K can be understood as occurring when the temperature is lowered and the total resistivity moves from the lattice dominated to impurity dominated case.The results of a preliminary calculation, in which a more exact Fermi surface and 27 APW electronic states were used, are also described.
Sphericity in the interacting boson model
Authors: Ogata H.
Published: April 2011

The interacting boson model (IBM) of Arima and Iachello is examined. The transition between the rotational and vibrational modes of even–even nuclei is presented as a function of a sphericity parameter, which is determined primarily from yrast band spectra. The backbending feature is reasonably reproduced.
Ferromagnetic antiresonance transmission of 24 GHz radiation through nickel (20 to 364 °C)
Authors: Dewar G. , Heinrich B. , Cochran J. F.
Published: April 2011

Ferromagnetic antiresonance (FMAR) transmission measurements at 24 GHz, and at temperatures between 20 °C and 364 °C, are reported for polycrystalline nickel foil 20 µm thick. The results can be described by the usual equation of motion for the magnetization and using a Landau–Lifshitz damping parameter of 2.45 ± 0.1 × 108 s−1 and a g factor of 2.187 ± 0.005, both temperature independent. The temperature independence of the damping was confirmed by measurements of the maximum transmission amplitude at FMAR as a function of temperature. The data were corrected for magnetostrictive effects in order to obtain the g factor and magnetization.
Ground configuration splitting in UCl5
Authors: Leung A. F. , Poon Ying-Ming
Published: April 2011

The absorption spectra of UCl5 single crystal were observed in the region between 0.6 and 2.4 μm at room, 77, and 4.2 K temperatures. Five pure electronic transitions were assigned at 11 665, 9772, 8950, 6643, and 4300 cm−1. The energy levels associated with these transitions were identified as the splittings of the 5f1 ground configuration under the influence of the spin–orbit coupling and a crystal field of C2v symmetry. The number of crystal field parameters was reduced by assuming the point-charge model where the positions of the ions were determined by X-ray crystallography. Then, the crystal field parameters and the spin–orbit coupling constant were calculated to be [Formula: see text],[Formula: see text], [Formula: see text], and ξ = 1760 cm−1. The vibronic analysis showed that the 90, 200, and 320 cm−1 modes were similar to the T2u(v6), T1u(v4), and T1u(v3) of an UCl6− octahedron, respectively.
Electric multipole interactions in the solid phases of the hydrogen halides
Authors: Vesel J. E. , Torrie B. H.
Published: April 2011

The ferroelectric and proposed paraelectric phases of the hydrogen halides have been studied using a lattice of molecules which are represented by a set of electric multipoles. This model shows the dominance of quadrupole–quadrupole interactions and the importance of other multipole interactions which affect the librational motions of these molecular crystals. A dynamic ferroelectric phase model was used to calculate the frequencies of the four librational modes.
Etude comparée des constantes moléculaires de HBr et de DBr : Application à la détermination des constantes moléculaires de TBr
Authors: Bernage P. , Niay P.
Published: April 2011

In this paper, the adiabatic and non-adiabatic corrections to the Born–Oppenheimer approximation are numerically determined for Dunham's equilibrium constants Y10 and Y01 of H Br and DBr molecules.In the case of the Y20, Y11, and Y02 constants, only the adiabatic corrections are significant.The correct isotopic relations using these corrections allow the TBr equilibrium constants calculation from the HBr and DBr ones.