bluuebunny/crossref_metadata_2025 huggingface dataset:
On the reflection of internal gravity waves
Authors: Whitehead J. D.
Published: April 2011

Recently Einaudi and Hines discussed the fact that different wave parameters of acoustic–gravity waves may have different reflection heights. This raises the problem that there will be a range of heights over which one parameter is evanescent, whereas another parameter is in its normal propagation region. It is not obvious that for this second parameter the range of heights does not encompass many wavelengths and thus there would be a large relative phase change between the two parameters.However, it is shown that the extent of the relative phase change will often be less than 2π, and the conditions under which it may exceed 2π are derived.
Weak interaction of photons and neutrino bremsstrahlung
Authors: Chaudhuri Probhas Ray
Published: April 2011

Assuming that photons can interact weakly with neutrinos, the cross section for the neutrino bremsstrahlung [Formula: see text] has been calculated. From this, the rate of stellar energy loss due to neutrino pair emission has been derived and is compared with the result obtained on the basis of the current–current coupling theory. Also, for a comparative study, the neutrino luminosity has been calculated according to both the theories.
Absorption spectrum of CS2 in the region from 600 to 1015 Å
Authors: Ogawa M. , Chang H. C.
Published: April 2011

The absorption spectrum of CS2 in the wavelength region from 600 to 1015 Å has been reinvestigated. In addition to the Rydberg series, III to VIII, found by Tanaka et al., many new Rydberg series were observed, especially in the region from 940 to 1015 Å. Two new series consisting of seven vibrational series with doublet bands have been identified. The convergence limits of these series (12.59 to 13.02 eV) correspond probably to the first excited 2Πu state of CS2+. Series III, IV, and III′ (new series) converging to 14.47 eV are accompanied by weak bands at the longer wavelength side with a separation of about 40 cm−1. It was found that series V also is accompanied by a weak band 40 cm−1 on the longer wavelength side of its own individual bands. A new series, V′, converging to the same limit as series V (16.19 eV) was also identified. There are two series converging to the limit at 19.38 eV, one of which is a new one, IX, and this value of the limit is smaller by 0.12 eV (1070 cm−1) than the previous value reported by Tanaka et al.
Screening numbers and the scaled hydrogen-like wave functions for some systems with large atomic numbers
Authors: Saxena K. M. S.
Published: April 2011

Values of the screening numbers σnl for obtaining the analytic scaled hydrogen-like wave functions are calculated for a large number of atoms and ions from Z = 87 to Z = 103.
Magnetoresistance of gallium
Authors: Cook J. R. , Datars W. R.
Published: April 2011

The magnetoresistance of gallium has been studied for b-axis current direction in fields up to 20 k0e. "Rotation curves" of magnetoresistance versus magnetic field direction exhibited both principal and subsidiary minima. These minima are discussed using the pseudopotential model of the Fermi surface and major topological dimensions of the sixth-band hole surface are measured using observed angular ranges of subsidiary minima. The principal minima result from the ka and kc open trajectories. The subsidiary minima are shown to occur by means of nonsaturating ka open trajectories, extended orbits, and [Formula: see text] effects involving local variations in both effective mass and relaxation time parameters. The temperature dependence of the magnetoresistance was measured for field directions in the ac plane. Relaxation time ratios derived through Kohler's rule are anisotropically scaled with temperature, indicating deviations from Kohler's rule.
Elastic Scattering of Positrons by Hydrogen Molecules
Authors: Lodge J. G. , Darewych J. W. , McEachran R. P.
Published: April 2011

Elastic positron–hydrogen molecule collisions are considered below the first electronic excitation threshold. The interaction of the incoming positron with the hydrogen molecule is represented by a superposition of single center static and nonspherical polarization potentials. The static potential is expanded to second degree in Legendre polynomials. The Chebyshev polynomials are used to improve the truncated Legendre series approximation and the effect of including the fourth degree contribution is shown to be slight. Positronium formation effects are neglected. Two semiphenomenological polarization potentials are used, and it is shown that the parameters can be suitably adjusted to reproduce the results obtained if the Henry and Lane polarization potential is used. It is shown that the partial Ramsauer–Townsend effect is useful in determining the values of polarization potential parameters. Total elastic scattering cross sections are given for incoming positron energies between about 0.4 and 14 eV while the positron annihilation coefficient is given to about 60 eV.
Structure of the Pressure-Induced Infrared Spectrum of Hydrogen in the First Overtone Region
Authors: Watanabe A. , Hunt J. L. , Welsh H. L.
Published: April 2011

The pressure-induced infrared spectrum of hydrogen in the first overtone region (1.1–1.25 μ) has been recorded at various temperatures and pressures. The spectrum observed at 24 K with a path length of 13.6 m and a gas density of 31 amagat is analyzed on the basis of the Van Kranendonk theory of quadrupole-induced absorption. The relative intensities of the 15 single and double transitions composing the band and the integrated intensity of the band are in satisfactory agreement with the theory.
Temperature Dependence of the Crystal-Field Splittings in Gd3+:CaWO4
Authors: Harvey J. S. M. , Kiefte H.
Published: April 2011

The spin-Hamiltonian parameters for Gd3+ in CaWO4 have been measured by the method of electron spin resonance at a number of temperatures between 4.2 °K and 300 °K. The results at 78 °K are in agreement with previous measurements by Hempstead and Bowers.The variations in the crystal-field parameters are interpreted in terms of a limiting low temperature value and a normalized slope at the Debye temperature for each parameter. These quantities are compared with the corresponding quantities for Eu2+ in CaWO4 and, in the case of the fourth-order parameters, for Eu2+ and Gd3+ in cubic CaF2, SrF2, and BaF2. We conclude that the second- and fourth-order splittings each arise from at least three competing mechanisms and that these include a dependence on the amplitude of lattice vibrations. In the case of the trivalent ion, Coulomb forces are also considered to be important.
Nuclear Spin Relaxation in Dilute Gas Mixtures
Authors: Lalita Krovvidi , Bloom Myer
Published: April 2011

Measurements of the proton spin relaxation time T1 have been carried out in hydrogen–helium dilute gas mixtures between room temperature and 730 K and in hydrogen–carbon dioxide mixtures between room temperature and 500 K as a function of density and concentration. When the measurements on H2–He are combined with those previously made at lower temperatures, a pronounced minimum in the dependence of T1 on temperature is obtained in the vicinity of 70 K for the limit of 100% helium. The data are analyzed on the assumption that collisions between hydrogen molecules and helium atoms which change the rotational quantum number J of the H2 are much less frequent than those which cause molecular reorientation with no change in J. Under this assumption, the data over the entire temperature range are fitted remarkably well by the theory of Kinsey, Riehl, and Waugh for the velocity dependence of the cross section for molecular reorientation in H2–He collisions using an exponential–6,H2–He potential based on "a priori considerations". The high temperature data are consistent with a reorientation cross section behaving approximately as σ α ν2.4 in the limit of high velocities. The H2–CO2 data below 400 K are consistent with a CO2 quadrupole moment of 4.1 × 10−26 e.s.u. but the behavior of the proton spin relaxation above 400 K is not yet understood.
Comments on Nonlinear Resonant Ion Heating in a Magnetoplasma
Authors: Tulle Pierre A.
Published: April 2011

In these comments, we point out that the coupled power calculated in the case of a plasma slab is too optimistic because a density profile makes the region of interaction inaccessible.
Theory of Spin Waves in the Heavy Rare Earth Metals
Authors: Goodings D. A. , Southern B. W.
Published: April 2011

A theory of spin waves for the spin structures found in the rare earth metals of h.c.p. crystal structure is described. The theory is developed for the conical spiral spin structure which contains the planar spiral, the nonplanar ferromagnet, and the planar ferromagnet as special cases. Included in the Hamiltonian are isotropic and anisotropic exchange interactions, single-ion crystal field terms, and magnetoelastic terms, both of the single-ion type (linear in the strains and up to fourth order in the spin operators) and of the two-ion type (linear in the strains and second order in the spin operators). The magnetoelastic effects are discussed in considerable detail, both in the "frozen lattice approximation" and in the opposite limit in which the strains closely follow the motion of the (uniformly) processing spins. Equations of motion for the spin operators are linearized with the help of the random phase approximation which makes it possible to express some spin-wave interaction effects in terms of powers of the reduced magnetization. Expressions for the spin-wave energies are given for the planar spiral, the nonplanar ferromagnet, and the planar ferromagnet, taking advantage of the simplifying features in each case.
Note on Resonant Raman Scattering in Polar Materials
Authors: Malm H. , Haering R. R.
Published: April 2011

The multiplicity and relative intensity of LO phonon lines observed in resonant Raman scattering experiments on Group II–VI semiconductors are analyzed in terms of a configuration coordinate model for excitons and exciton complexes.
A Propos de la Création de Photoporteurs à Partir d'Excitons dans CdS
Authors: Coret A. , Malm H. L.
Published: April 2011

According to the variation of the photoconductivity spectrum of CdS with light intensity it appears that excitons do not play a role in the recombination processes of photocarriers. Excitons first dissociate and give free carriers. The existence of maxima of photocurrent is related to the creation of photocarriers near the surface.
Kinetics of Photolytic Formation of F-Aggregate Centers in KBr
Authors: McCarty Jr. M. , Maycock J. N.
Published: April 2011

The rate of formation of M, R, and N centers in KBr arising from radiation in the F band has been investigated. By a detailed kinetic analysis, it has been shown that the slow step in the reaction does not involve the migration and reaction of an α center with an F or F-aggregate center. The data are consistent with the slow step resulting from the process α + Fn′. By assuming that in KCl all F centers are equally likely to be converted to F-aggregate centers, it was shown that neither of the mechanisms considered for KBr is consistent with the existent data on KCl.
Transitional Nuclei. II. Properties of the Levels in 152Sm and 152Gd from the Decay of the 152Eum,g Isomeric Pair
Authors: Barrette J. , Barrette M. , Boutard A. , Lamoureux G. , Monaro S. , Markiza S.
Published: April 2011

The γ rays emitted in the decay of the 152Eum,g isomeric pair have been studied with the use of high-efficiency, high-resolution, solid-state detectors. These measurements together with Ge(Li)–Ge(Li) coincidence experiments revealed the existence of several new gamma transitions never previously reported. In all, 93 and 30 γ rays were observed in the decay of 152Eug and 152Eum, respectively. Calculations of the β- and γ-band mixing into the ground-state rotational band and into each other were carried out. These calculations showed that this mixing is insufficient in explaining the B(E2) ratios from the members of both the β and γ band. In addition, the very likely existence of a Kπ = 2− band in 152Sm, with levels at 1649.90 (2−) and 1757.0 keV (3−), has been unveiled in these measurements. Furthermore, the existence of a new Kπ = 0− octupole rotational band (levels at 1680.58 (1−) and 1730.3 (3−)) built on the β-vibrational band and the presence of a collective Kπ = 2+ vibrational state at 1769.1 keV, which most probably can be described as a coupled (βγ) two phonon state, are also proposed. Moreover, a new level at 1292.75 keV has been established through coincidence experiments in 152Sm. This level may be considered either as the 2+ member of a second β-vibrational band or, more likely, can be described as a truly spherical state in light of recent experiments involving (t,p) and (p,t) transfer reactions to levels of 152Sm. Finally, a qualitative analysis of the level structure of 152Gd, as well as 150Sm, seems to show that these two nuclei display a more rotational nature than a spherical (or vibrational) one as previously suggested.
Imaging Properties of a Novel Electrostatic Lens
Authors: Youssef E. A. , Vermeulen F. E. , Chute F. S.
Published: April 2011

A study is made of the imaging properties of an electrostatic quadrupole that has been uniformly twisted about its axis. It is shown that the structure is capable of identically reproducing the injection coordinates and momenta of a system of particles in a coordinate plane which is located some distance along the quadrupole. The imaging takes place with a small amount of aberration. This aberration can be greatly reduced by constructing the lens of two sections which follow each other and which have equal and opposite twists.
Lifetimes of States in 29Si, 27Al, and 26Mg
Authors: McDonald A. B. , Alexander T. K. , Häusser O. , Ewan G. T.
Published: April 2011

The recoil-distance method was used to measure the lifetimes of the 29Si, 3626 keV (7/2−) level (4.2 ± 0.5 ps) from the 12C(19F,npγ)29Si reaction, the 26Mg, 1809 keV (2+) level (0.7 ± 0.3 ps) from the 12C-(19F,αpγ)26Mg reaction, and the 27Al, 843 keV (1/2+) level (45 ± 6 ps) from the 27Al(35Cl,35Cl)27Al Coulomb excitation reaction. The Doppler shift attenuation method was employed to determine the lifetime of the 27Al, 1013 keV (5/2+) level [Formula: see text] from the line shape for thick target Coulomb excitation by 67 MeV 35Cl. The results are compared with model predictions.
On the Uniqueness of MHD Aligned Flows with given Streamlines
Authors: Chandna O. P. , Nath V. I.
Published: April 2011

Physical conditions and geometric implications are determined if two stationary, MHD aligned flows have the same streamline patterns. This study is carried out for incompressible and irrotational compressible plane flows; incompressible axially symmetric flow and incompressible spatial doubly laminar flow.
Levels of 33Cl Via the 32S(d,n)33Cl Reaction
Authors: Elbakr S. A. , Glavina C. , Dawson W. K. , Gupta V. K. , McDonald W. J. , Neilson G. C.
Published: April 2011

The 32S(d,n)33Cl reaction has been studied at two bombarding energies of 4.70 and 5.50 MeV. The Q value of this reaction has been measured to be 62 ± 9 keV. The excitation energies of the levels observed are 812 ± 4, 1993 ± 6, 2351 ± 5, 2688 ± 4, and 2851 ± 4 keV. Neutron angular distributions for transitions to these states have been analyzed with DWBA and Hauser–Feshbach theories to yield lp values and spectroscopic factors. The lp values for transitions to the ground, 0.812 and 2.851 MeV states are 2, 0, and 1 respectively, in agreement with previous results. The analysis also favors lp values of 2 and 3 for transitions to the 2.351 and 2.688 MeV states respectively. The results have been compared with several other experimental and theoretical investigations.
Détermination de la Surface de Cohérence à Partir d'une Expérience de Photocomptage
Authors: Bures Jacques , Delisle Claude , Zardecki Andrzej
Published: April 2011

The theoretical distribution, with exact second moment, of the number of photoelectrons emitted by an extended photodetector illuminated with partially coherent light is first derived. Then the parameter N, the number of degrees of freedom, is obtained from the second moment of the distribution, for [Formula: see text] (T is the detection time and Tc the coherence time). N is then plotted as a function of the surface of the detector expressed in three different ways for both circular source and detector and square source and detector. In both cases the source is considered to be of uniform brightness. An elementary surface called the surface of coherence is determined by extrapolating towards small values the asymptotical behavior of N for large values of the detection surface. For both sources, this surface of coherence is equal to [Formula: see text]. λ0 is the mean wavelength, D the distance between the source and the detector, and Ss the surface of the source.
Alternating Current Photoconductivity of Vacuum-Deposited Films of CdSe, CdS, and CdTe, Excited with Intensity-Modulated Light
Authors: Tokarsky R. W. , Brodie D. E.
Published: April 2011

An experimental investigation of the use of sinusoidally intensity-modulated light (IML) to investigate vacuum-deposited CdSe, CdS, and CdTe films has been carried out. A definite plateau has been observed in the amplitude–frequency response for the first time reflecting the direct observation of a discrete trapping level by this technique. The trap energy is 0.09 eV with a trapping cross section of 10−17 cm2 and a trap density of 1016 cm−3 for the level observed in specially prepared films of CdSe. These results were confirmed by thermally stimulated current studies on the same samples. The effects of temperature, light intensity, and certain fabrication parameters on the amplitude–frequency response of the films are presented.Applying the theory for extrinsic IML, studies of CdS films show that excitation occurs from localized levels to the conduction band. CdTe films also show trapping due to localized levels, but a complete analysis of this material was not possible because its response time is too fast.
Remarks on the OH Rotational Temperature in the Night Glow
Authors: Shefov N. N.
Published: April 2011

Attention is drawn to a discrepancy between the population distributions of the OH rotational levels (K′ are 1 to 5) obtainable from the night-glow spectra recorded with the spectral resolutions of 2–5 Å and 27 Å.
Rotational Dependence of Franck–Condon Factors in the System of 24Mg2
Authors: Balfour W. J. , Whitlock R. F.
Published: April 2011

The rotational dependence of the Franck–Condon factors in the A–X system of Mg2 has been calculated using RKR potential curves. Excellent agreement is found between theoretical and experimental intensity distributions.
Alternating Current Photoconductivity in a Negative Photoconductivity Region
Authors: Tokarsky R. W. , Brodie D. E.
Published: April 2011

A.C. photoconductance measurements on Cu-doped CdSe films are carried out for the first time in a negative photoconductive region, using intensity modulated light (intrinsic). A unique feature of the frequency response is an increase in photoconductance, with increasing frequency, for frequencies between 1.5 and 10 Hz. This anomaly in the photoconductance is explained by including the effect of a mobility dependence on impurity level occupancy (i.e. charged impurity scattering).
Spin-Up-Spin-Down Pair Distribution Function at Metallic Densities
Authors: Hede B. B. J. , Carbotte J. P.
Published: April 2011

Correlations in an electron gas are particularly important at metallic densities because the potential energy cannot be ignored in comparison with the kinetic energy; in particular, interactions are not weak as r → 0, so that a simple Born approximation does not hold in this limit. Short-range correlations between oppositely-spinned electrons can be accounted for by an infinite series of particle–particle ladder diagrams. It leads to a Bethe–Goldstone type of equation which can be solved by an angle-averaged approximation. The resultant spin-up-down p.d.f. is positive over a wide range of metallic densities. A further correction by including particle–hole scattering effects changes the previous results only slightly.
Quantitative Spectroscopy of the Aurora. I. The Spectrum of Bright Aurora between 7000 and 9000 Å at 7.5 Å Resolution
Authors: Jones A. Vallance , Gattinger R. L.
Published: April 2011

Averaged spectra of bright aurora [Formula: see text] in the wavelength range 7000–9000 Å with a resolution of 7.5 Å are presented. These spectra, divided into four 500 Å intervals, were obtained by averaging about 20 separate 12 s scans in each region. Intensity fluctuations during the scans were corrected by normalizing the spectrometer output by means of the signal from a λ5577 photometer covering the same field of view. The spectra, corrected for atmospheric scattering and spectrometer sensitivity, were matched with synthetic spectra of the N2 first positive, [Formula: see text] Meinel, [Formula: see text] first negative, O2 atmospheric, and OH vibration–rotation bands so as to give values of the relative intensities of the bands and atomic lines within each 500 Å region. The resulting intensities have been tabulated after having been normalized approximately to IBC3 aurora. The synthetic spectrum (together with known atomic lines) provides a very good match to the observed spectrum except at several wavelengths where weak unidentified features seem to be present.
The Temperature Dependence of the Resistivity of Liquid Gallium to 1000 °C
Authors: Yahia J. , Thobe J. P.
Published: April 2011

The electrical resistivity of liquid gallium has been measured to 1000 °C and found to be linear over the entire range measured, the temperature coefficient of resistivity being 0.0194 ± 0.0005 μΩ cm °C−1. A discussion of our results in terms of the theory is given.
Total Pair Production Cross Sections from 1.120 to 2.754 MeV
Authors: Henry L. C. , Kennett T. J.
Published: April 2011

Relative pair cross sections σp(EγZ) have been measured for energies 1.120, 1.172, 1.333, 1.560, 2.225, and 2.754 MeV and Z = 22, 29, 42, 48, 74, and 82. Results obtained through intensity analysis of annihilation spectra have been normalized to σ(2.754, 82) = 3.30 b/atom.
Electron Impact Double Ionization of Noble Gas Atoms
Authors: Roy B. N. , Tripathi D. N. , Rai D. K.
Published: April 2011

Cross sections for double ionization by electron impact for noble gas atoms have been calculated using Gryzinski's classical expression. The effect of including ionization from the inner shell has been discussed in connection with possible Auger emission. Calculated cross sections have been compared with the available experimental results and also with calculated values of proton impact double ionization cross sections.
Lowest-Order Mode Selection in a Laser Interferometer
Authors: Hill K. O. , Campbell C. K.
Published: April 2011

An analysis is given of the effect of introducing an angle-selecting aperture into a Fabry–Perot laser interferometer. In the model exemplified, the Fox and Li integral equation relating transverse-mode propagation in an infinite-strip mirror resonator is modified to include such an aperture, defined in terms of an Angular number A. Results are given for the effect of this aperture on the power loss and phase shift per transit of the lowest-order even mode. The number of transits to convergence of an initially launched plane wave is also evaluated as a function of A, to yield a measure of the selective attenuation of higher-order modes of the laser resonator.
Electromagnetic Scattering by a Transversely Moving Conducting Cylinder of Arbitrary Cross Section
Authors: Hunter J. D.
Published: April 2011

A method of calculating the electromagnetic scattering from a transversely moving conducting cylinder of arbitrary cross section is derived in terms of the surface current density on the cylinder, with a particular view to computational efficiency. It is shown that the required numerical calculations are only slightly more complicated than those for a stationary cylinder. Results are presented for a transversely moving conducting triangular cylinder for both TM and TE polarizations of the incident field.
Amplification of Light in an Optical Wave-Guiding Structure with Evanescent-Wave Pumping
Authors: Watanabe A. , Hill K. O. , MacDonald R. I.
Published: April 2011

A symmetric dielectric-slab wave guide with a passive core and an active cladding is considered. A bound mode of the structure is assumed to propagate in the guide with the objective of optically pumping the cladding region adjacent to the core to induce an optical gain condition there. A signal beam whose frequency differs from that of the pump mode is simultaneously allowed to propagate as a bound mode of the structure. It is shown theoretically that the signal mode is amplified through the interaction of its evanescent field with the active region of the cladding. The advantages of evanescent-wave active devices are illustrated and discussed. A noteworthy effect is that of gain enhancement obtained by means of evanescent-wave pumping over that gain obtainable by conventional means.
Comparison of the Critical Properties of the S = 1/2 XY Model and Liquid Helium Near the Lambda Transition
Authors: Betts D. D. , Lothian J. R.
Published: April 2011

Experimental properties of the lambda line of liquid helium are used together with properties of the zero-field spin 1/2 XY model to determine, on the one hand, the point on the lambda line to which the zero-field model applies, and on the other hand, to determine the lattice spacing of the model. On the f.c.c. lattice the specific heat of the model, C/NkB ~ −0.255 ln (1 − Tc/T) − 0.190 near Tc. This result is shown to be in good agreement with recent experimental results of Ahlers on liquid helium. Other properties of the S = 1/2 XY model are also calculated and, where comparison can be made, agree well with experiment.
Free Surface of a Rotating HeII Film
Authors: Vittoratos E. , Cole M. W. , Meincke P. P. M.
Published: April 2011

Stimulated by recent conflicting experimental results, we have investigated the properties of quantized vortex lines in thin films of superfluid helium. The shape of the liquid–vapor interface in the presence of a single line is calculated. The depression of the interface ("dimple") that results is considerably smaller for the film than for the bulk liquid. The critical rotational frequency for the appearance of the first vortex line is only slightly reduced below the bulk value.
Modulation spectrale à de très grandes différences de marche
Authors: Cielo Paolo , Brochu Michel , Delisle Claude
Published: April 2011

A 300 m path difference has been attained in a white light interference experiment aimed to show the spectral modulation as a function of the path difference. This has been made possible by placing the optical components of the interferometer on two independent tables. The inconveniences related to such an interferometer are analyzed as well as the results expected with such a system.
Comparison of Spherical Cell, OPW, and APW Methods for Hyperfine Contact Densities
Authors: Perdew J. P. , Nickerson S. B. , Vosko S. H. , Moore R. A.
Published: April 2011

The spherical cell, OPW, and APW methods for the determination of the direct hyperfine contact density PFd are compared by means of explicit calculations for lithium metal. Serious deficiencies of the first two methods are discussed. In particular the OPW method is found to converge very slowly for the absolute value of PFd, although it predicts relative changes in PFd due to changes in atomic volume reasonably well. The Fermi level density of states, another quantity which affects the Knight shift, is also considered.
Surface Ejection in Single Crystal Sputtering
Authors: Jackson D. P.
Published: April 2011

Surface atom ejection, an essential component of single crystal sputtering phenomena, is investigated for a realistic surface model using computer simulation. The dynamics of ejection are analyzed in terms of the collective attractive field of the surface and binary repulsive collisions of the ejected atom with its neighbors in the surface. In-surface correlated collision sequences initiated by ejection are also discussed in detail. It is found that ejection from the surface layer is a fundamentally anisotropic process exhibiting a complex range of interaction types.
Nuclear g Factor of the g9/2 Level in 65Zn
Authors: Wender S. A. , Cameron J. A.
Published: April 2011

The integral rotation of the 1066 keV 9/2 + level of 65Zn has been measured using the (α,n) reaction in a target of the alloy Ni10Fe90. The average rotation angle measured was ωτ = 150 ± 20 mrad. Using the known lifetime of 829 ± 37 ps and the internal field of −110 ± 25 kOe found for a similar alloy with the 184 keV level of 67Zn, the g factor is g = −0.35 ± 0.10.
Phase diagrams for impurity-doped VO2
Authors: Reyes J. M. , Segel S. L. , Sayer M.
Published: April 2011

The general form of the phase diagrams for impurity-doped VO2 is considered and shown to include mixed phase boundary regions. Phase diagrams for Cr and Al-doped VO2 are established on the basis of the temperature dependence of the 51V nuclear magnetic resonance (NMR) signal. In Cr-doped VO2, the (M2) phase is shown to exist over a smaller temperature–concentration range than reported previously and in Al-doped VO2, two intermediate single phases (M2) and (M3) are found. The (T) phase which has been previously suggested to be a definite phase having triclinic symmetry is shown to be a mixed phase region in which the contributions from the components change with temperature. Changes in NMR signal intensity at the phase boundaries show that half the V sites have paired spins in both the(M2) and (M3) phases.
A continued fraction representation of the mass operator
Authors: Saraswati Dipak K.
Published: April 2011

We explore some further possibilities of application of the projection operator method of Zwanzig to the theory of Green's functions of quantum statistical mechanics, initiated by lchiyanagi, and present a continued fraction representation of the mass operator involving a hierarchy of the random forces. As an application of the theory, we calculate the polarization operator of the phonon Green's function of the Frohlich Hamiltonian in the first approximation which corresponds to the assumption that the electron momenta are orthogonal to the phonon momentum.
Anharmonic potential constants and the large amplitude bending vibration in nitrogen dioxide
Authors: Hardwick J. L. , Brand J. C. D.
Published: April 2011

The anharmonic potential function of the ground electronic state of nitrogen dioxide has been determined within the framework of three different vibrational Hamiltonians. The first of these, which involves a perturbation expansion of the vibrational wave functions in terms of normal coordinate harmonic oscillator wave functions, is the most widely used and generally applicable of the three. It suffers, however, from demonstrably large systematic errors. The other two are vibration–rotation Hamiltonians which allow explicitly for a large amplitude vibration in the bending vibration of a triatomic molecule; they set up the Hamiltonian operator as an explicit function of the bond angle and solve the Schrödinger equation numerically. The more sophisticated of these, the so-called nonrigid bender Hamiltonian, reproduces the spin-free virtual term values to the (0, ν2, 0) manifold of 14NO2 to a standard deviation of 0.026 cm−1 for states with N ≤ 10 and ν2 ≤ 3. It is, moreover, observed to be a more useful tool for extrapolation than is the ordinary parametrized Hamiltonian.The potential function for the bending coordinate is defined by αe = 133.888 ± 0.002°, fαα = 1.61022 ± 0.00005 mdyn Å/rad2, fααα = −2.1172 ± 0.0003 mdyn Å/rad3, and fαααα = 6.0228 ± 0.0020 mdyn Å/rad4. The equilibrium bond length, re, is found to be 1.19464 ± 0.00015 Å.
Studies of gamma-ray transitions in 146Eu
Authors: Sen P. , Kingman M. , Bakhru H. , Cue N.
Published: April 2011

The decay of 146Gd to levels of 146Eu has been studied using high resolution X-ray and γ-ray detectors. γ–γ directional correlation studies, using X and γ-ray Ge(Li) detectors, were made to assign the spins of the low lying states in 146Eu. γ–γ coincidence experiments with two Ge(Li) detectors and between Eu X rays and γ rays were performed to pin down the levels of 146Eu. On the basis of these measurements, Jπ of 4−, 3−, 2−, and 1− have been assigned respectively to the ground, 115.66, 230.51, and 385.11 keV states in 146Eu. More accurate evaluation of the E2 admixtures in the M1 transitions, 114.85, 115.66, and 154.60 keV, have been obtained. Based on the above results a tentative level scheme for 146Eu has been proposed.
Low temperature nuclear magnetic resonance studies of NH4ClO4
Authors: Code R. F. , Higinbotham J. , Sharp A. R.
Published: April 2011

The properties of ammonium perchlorate were investigated in the temperature range between 1.3 and 50 K by nuclear magnetic resonance and relaxation experiments. The observed increase in the proton second moment from its high temperature value of ~ 1.18 G2 to the value of 4.30 G2 below 4.2 K was associated with a characteristic activation energy of ~ 4 × 10−21 J molecule−1 (~ 0.6 kcal mole−1). No evidence could be found for nuclear spin conversion between the symmetry species of the ammonium ion from measurements of the static proton magnetic susceptibility above 1.3 K. An asymptotic analysis of the low temperature proton lineshapes identified the broad wings of the lines with ammonium ions of T type symmetry. Measurements of the proton relaxation times T1 and T1ρ agreed with previous work by others on NH4ClO4, and were similar to observations on other ammonium compounds having low reorientational barriers.
The effect of rotation on electrohydrodynamic instability
Authors: Takashima M.
Published: April 2011

The effect of uniform rotation on the onset of convective instability in a dielectric fluid confined between two horizontal planes under the simultaneous action of a vertical ac electric field and a vertical temperature gradient is considered. Applying linear perturbation theory and approximations analogous to the usual Boussinesq approximations, an equation of tenth order is derived. Under somewhat artificial boundary conditions, this equation is solved exactly and the eigenvalue equation is obtained. It is shown that (1) the principle of the exchange of stabilities is valid for most dielectric fluids; (2) the Coriolis force has an inhibiting effect on the onset of instability even if the electrical effect is taken into account; (3) as the speed of rotation increases the coupling between the two agencies causing instability (electrical force and buoyancy) becomes tighter.
Transport properties of impurity-doped VO2
Authors: Reyes J. M. , Sayer M. , Mansingh A. , Chen R.
Published: April 2011

The temperature dependence of the DC conductivity in the semiconducting phase of undoped and Al, Cr, and Ti-doped VO2 has been interpreted with the aid of AC conductivity and thermopower measurements down to 77 K. A hopping conductivity is shown to be dominant for T < 180 K and to make up about 10% of the total conductivity at the metal–semiconductor transition temperature. The frequency dependence of the AC conductivity, σ~fs, is shown to be sensitive to crystalline disorder through the parameter s; s ~0.5 for 'good' crystals and 0.7–0.9 for highly doped or nonstoichiometric material. For the best crystals, a phonon drag contribution is found to exist in the thermopower. The hopping component of the DC conductivity is analyzed in terms of variable range hopping within a nonuniform density of states. For a total density of states between 1018–1020 this leads to a localization radius of 3–11 Å and the conclusion that the position of the Fermi level within the gap strongly influences the relative contributions of hopping and band conduction. A model for the density of states within the energy gap for both pure and doped VO2 is presented on the basis of localized correlations between electrons on pairs of vanadium or vanadium–impurity sites.
Diffraction order asymmetries in the scattering of light by surface waves
Authors: Goruk W. S. , Stegeman G. I.
Published: April 2011

The diffraction of light by surface waves on transmission through the propagation surface was investigated and a suitable Raman Nath parameter defined. Asymmetries in the intensities of the ± 1 diffraction orders were predicted, shown to be much larger than for the equivalent bulk wave case, and were verified experimentally for light incident on 96 and 480 MHz surface waves on y–z lithium niobate. Also analyzed theoretically are the diffraction of light by Blaustein–Gulyaev waves and the intensities of the ± 2 orders for transmission diffraction of light by surface waves.
Preparation and properties of amorphous CdTe
Authors: Ng P. , Webb J. B. , Brodie D. E.
Published: April 2011

The preparation of amorphous alloys of CdTe by vacuum deposition and the effects on the resulting films of using different sources are described. When using a flash evaporation source, it is shown that the source material must contain ~10% excess cadmium by weight to produce a purely amorphous film with a near-stoichiometric ratio of Cd to Te. Optical measurements on Cd and Te alloys are presented together with some Seebeck and conductivity data, with special emphasis on near-stoichiometric amorphous CdTe and a partial band diagram is given for this latter material.
Pressure-induced absorption in nonpolar gases containing tetrahedral molecules
Authors: Buckingham A. D. , Ladd A. J. C.
Published: April 2011

The theory of pressure-induced absorption of far infrared radiation by gases is extended to include the contribution of the dipole moment induced in a molecule by the field gradient due to its neighbours. This dipole is nonzero when the molecule lacks a centre of inversion, as in a tetrahedron. In the collision of two tetrahedra, the dipole induced in molecule 2 by the electric field of the octopole moment Ω1 of the partner leads to transitions in which ΔJ(1) = 0, ± 1, ±2, ±3, and ΔJ(2) = 0. The dipole induced by the field gradient of Ω1 leads to ΔJ(1) = 0, ±1, ±2, ±3, and ΔJ(2) = 0, ±1, ±2, ±3, and therefore gives a required increase in absorption at higher frequencies. The field-gradient contribution vanishes in a collision involving a tetrahedral and a spherical molecule. General expressions are given for the field-gradient contributions to the integrated intensity and to the −2 spectral moment.
Dynamic susceptibility of Fermi liquids at finite temperature
Authors: Khanna F. C. , Glyde H. R.
Published: April 2011

A closed expression for the dynamic susceptibility of a noninteracting Fermi liquid at finite temperature is presented. The expression for the imaginary part is particularly simple while the real part appears as a sum. The calculation of the sum is discussed and numerical examples displaying the temperature dependence of the susceptibility are given.
Hybrid modes of the passive-core corrugated-waveguide laser
Authors: MacDonald R. I. , Hill K. O. , Makios V.
Published: April 2011

Coupled-mode theory is employed to obtain the threshold gains for oscillation on hybrid modes of a passive-core corrugated-waveguide laser pumped in a central portion of its length. Methods are developed for calculating intermode coupling coefficients and loss coefficients resulting from diffraction into any order of waveguide corrugations of arbitrary shape. Experimental observations that have been reported in the literature are compared with the hybrid-mode threshold gains computed from coupled-mode theory. It is shown that the oscillation frequencies for such a laser are determined by the length of the corrugated structure, the proportion that is pumped, and the effects of coupling into leaky modes.
The (p,d) reaction at intermediate beam energies. I. Plane-wave Born approximation (semi-analytical) calculations
Authors: Grabowski Janusz W. , Fleming Donald G. , Vogt Erich W.
Published: April 2011

Plane-wave Born approximation calculations have been carried out for the (p,d) reaction at intermediate beam energies with the purpose of elucidating the manner in which the various physical parameters of the problem determine the behaviour of the cross-sections. Analytical formulae for the differential cross section are derived for three choices of the bound state wave function: square well, Woods–Saxon, and truncated harmonic oscillator. The formulae can essentially be factored into two parts, one which oscillates rapidly with momentum transfer q(and is not physically important) and the other which varies smoothly with q and describes the 'envelope' of the calculated angular distribution. For the square well and truncated harmonic oscillator form factors, this envelope function varies as q−8 and q−10 respectively, but in the Woods–Saxon case it is given predominantly by an exponential q-dependence. To illustrate our main points, calculations are presented for the 208Pb(p,d) reaction, primarily at 200 MeV, as well as normalized fits to presently available data at 185 MeV on light and intermediate mass nuclei and at 700 MeV on 12C. The envelope dependence of the square well and Woods–Saxon form factors gives a reasonably good account of these data.
The electrical resistivity and thermopower of pure and of hydrogen-charged barium
Authors: Cook J. G. , Laubitz M. J.
Published: April 2011

Data for the electrical resistivity (ρ) and thermopower (S) are presented for pure and H-charged Ba from 300 to 750 K. The ρ data for pure Ba differ from previous values in that they show no evidence of a phase transition at any temperature. Charging Ba with H causes ρ to increase by an amount which is sharply temperature dependent and related to the solubility of H in Ba and the total amount of H present. Both ρ and S data for pure and H-charged Ba are explained semi-quantitatively using a simple model.
Vélocimétrie Doppler par modulation spectrale
Authors: Cielo P. , Delisle C.
Published: April 2011

A new approach to Doppler velocimetry applicable to speeds greater than 1 m/s is described. The method is based on the phenomenon of spectral modulation of a large bandwidth source, such as a white light source. Spectral modulation is obtained from an interferometer with a path difference larger than the coherence length of the illuminating source. The linear speed of a corner cube prism attached to the rim of a rotating disc has been measured experimentally.[Journal translation]
Superoperator methods of calculating cross sections: II. Distorted wave Born approximation
Authors: Snider R. F. , Turner R. E.
Published: April 2011

The superoperator form of the collision cross section is evaluated within the distorted wave Born approximation. It is first verified that the obvious expansion methods give a result identical to that obtained by standard methods. Formalistically, the algebraic expansions of the transition operator and superoperator are shown to have parallel structures. The distorted wave Born approximation for the cross section also has a structure parallel to the structure of the Born approximation cross section. This is especially brought out by formulating the results in terms of time correlation functions. Certain simplifying features are found for cross sections averaged over initial and final velocity directions. These cross sections for internal state transitions are further simplified by averaging over a Maxwellian distribution of initial velocities in such a way as to obtain 'kinetic cross sections' appropriate for gas kinetic phenomena. Connection is also made with the 'constant acceleration approximation' used to estimate correlation functions in gas phase NMR.
Propagation d'un mode (EH) pair dans un guide elliptique supraconducteur
Authors: Alaux A. , Wybouw M.
Published: April 2011

The propagation of a progressive wave for the even (EH)Mn mode in an undefined elliptical superconducting wave guide has been studied. We suppose that the coherence length, Ω0, of the superconducting material is large and establish an expression for the attenuation constant.
The renormalization group method for quantum mechanical systems. I. The s = 1/2 XY model on the square lattice
Authors: Betts D. D. , Plischke M.
Published: April 2011

The renormalization group method is reformulated for application to quantum mechanical many-particle systems situated on regular lattices in two or three-dimensional configuration space. The method is applied to the spin 1/2 XY model on the square lattice. The free energy curve is in excellent agreement with that obtained from high temperature series expansion. No critical temperature is found.
Estimates of the critical exponent β for the Potts model using a variational approximation
Authors: Kelland S. B.
Published: April 2011

The q-state Potts model on a square lattice is transformed into a staggered ice model. A variational principle for the largest eigenvalue of the transfer matrix of this model is used to develop a set of matrix equations. In the limit of these matrices becoming infinite, the equations determine the partition function and order parameter of the Potts model exactly. We have solved the equations numerically for finite matrices, obtaining estimates of these quantities and, as a result, the critical exponent β.
Generation of low tehmperature series for Ising models with nearest and next nearest neighbor interactions
Authors: Plischke M. , Chan C. F. S.
Published: April 2011

We have generalized the code method of Sykes et al. and applied it to the Ising model with nearest and next nearest neighbor interactions. On the bcc lattice, we have obtained the first seven low temperature polynomials for arbitrary sign of the interactions. Special cases of this model are the Ising ferromagnet and the Ising antiferromagnet with next nearest neighbor ferromagnetic interactions. The latter system exhibits a tricritical point which we plan to study using our low temperature data and high temperature series to be obtained in the future.
Sodium NMR in the trigonal phase of sodium hydrosulfide
Authors: Jeffrey Kenneth R. , Segel Stanley L.
Published: April 2011

Measurements of the sodium nuclear quadrupole coupling constant and spin–lattice relaxation time, while confined mainly to the trigonal phase, show the existence of the two known phase transitions at 358 and 113 K. The quadrupole coupling constant is 206 kHz at 358 K and decreases roughly linearly with decreasing temperature at a rate of about 0.66 kHz/K. The satellite peaks in the quadrupolar split powder pattern disappear above 358 K in the cubic phase. Below 130 K. where there is no known phase transition, the satellites broaden and again disappear but in this case it is because the fluctuation rate of the electric field gradient at the sodium site due to reorientation of the SH− ion is about equal to the quadrupolar splitting of the spectrum at this temperature. Only the resonance from the −1/2 ↔ 1/2 transition is observed down to 77 K.The spin–lattice relaxation of the sodium spins shows a very strong temperature dependence and a well-defined minimum similar to the previously observed results for the protons. The relaxation is caused by the nuclear quadrupole interaction made time dependent by the reorientation of the neighbouring SH− ions. A simple model calculation gives reasonable agreement between the calculated and experimental values of T1 at the minimum if the SH− ion is considered to move between two positions parallel and antiparallel to the trigonal axis. An extension of this model suggests that the lack of an enhanced relaxation rate at the 113 K phase transition may be a result of a parallel ordering of neighbouring SH− ions along the trigonal axis in the lowest temperature phase.