bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of Strong-Field Modulated Electromagnetic Waves in Plasmas
Authors: Bachynski M. P. , Gibbs B. W.
Published: April 2011

The distortion of the wave form of a modulated plane electromagnetic wave propagating in an anisotropic plasma has been experimentally investigated over a range of field strengths of the wave and plasma properties. By using right-hand circularly polarized waves, the effective frequency is [Formula: see text] (where ω is the r.f. radian frequency and ωb the cyclotron frequency) and hence the results are also applicable to the propagation of low-frequency waves in an isotropic plasma. Severe "overmodulation" of the wave form transmitted through the plasma is found in the regime [Formula: see text] where ν is the effective collision frequency for momentum transfer. The distortion of the wave form is found to increase with depth of modulation of the incident wave and decrease with increasing modulation frequency.The "demodulation" is in qualitative agreement with theory for an unmodulated wave with a non-Maxwellian (Druyvesteyn) velocity distribution for the electrons. Many of the effects of the modulation frequencies can also be qualitatively predicted by considering the variation of electron temperature in the presence of the strong-field modulated wave. A theory is developed for large changes in electron temperature induced by the incident field which shows that marked distortion of the modulation is possible.
Radiation Patterns of Antennas near Conducting Triangular and Square Towers
Authors: Shafai L.
Published: April 2011

Horizontal patterns of antennas near conducting towers of square and triangular cross sections are found by numerical evaluation of the integral equations for the induced currents. The computed patterns for moderate cross-sectional dimensions of the prisms and their distance from the antenna are presented and some similarities with the patterns of circular cylindrical towers are established.
Gain Method for the Measurement of Isotope Shift
Authors: Ballik E. A.
Published: April 2011

Gain measurements are used as a basis of a technique for the evaluation of isotope shifts. The technique is applied to the 0.63 μ and 1.15 μ transitions in 20Ne and 22Ne. Isotope shifts of 1052 ± 100 and 257 ± 25 mHz were observed for the 0.63 μ and 1.15 μ transitions respectively. These values are compared with results obtained by other methods.
Structure of the 23P–23S1 Optical Transition of 3He: A Study by Emission and Absorption Spectroscopy
Authors: Timsit R. S. , May A. D.
Published: April 2011

The intensity and frequency of the hyperfine components of the 1.083 μ transition in 3He is studied. A discrepancy between the calculated relative intensities and the intensities observed in both emission and absorption is noted. The measured frequencies are in excellent agreement with the calculated values.
Matrix Elements of the Spin–Orbit Coupling for an ln Configuration in a Crystalline Electric Field
Authors: Buckmaster H. A. , Chatterjee R. , Shing Y. H.
Published: April 2011

A general expression for the matrix elements of the spin–orbit coupling for an ln configuration in a crystalline electric field of arbitrary symmetry is derived using Racah formalism. This calculation is an extension of Lulek's treatment of this problem for an l1 configuration. This general expression is used to calculate the contribution to the ground-state splitting for the S-state lanthanide ion Gd3+ (4f7; 8S7/2)in an axial crystalline electric field of a second-order perturbation mechanism involving the matrix element of the spin–orbit coupling. It is shown that this mechanism, which was proposed by Lulek is incapable of explaining the observed ground-state splitting.
Resonance Widths and Unitarity
Authors: Tindle C. T.
Published: April 2011

The low energy neutron cross section of 135Xe is analyzed using both the R-matrix theory of Wigner and Eisenbud and the S-matrix theory of Humblet and Rosenfeld. Particular attention is given to the role played by the total resonance level width for it is well known that the R-matrix widths are energy dependent but the S-matrix widths are not. This different energy dependence leads to different analytic forms for the cross section and the n + 135Xe reaction offers what may be the simplest and best physical example for comparing these two forms. To the accuracy of the present data the difference is not detectable. The different energy dependence of the resonance widths is shown to be related to unitarity. A general proof that the R-matrix formalism is always unitary is given. The difficulty of satisfying unitarity in the S-matrix formalism is discussed and it is shown for the n + 135Xe reactions that this can lead to physically unacceptable solutions. This "lack of unitarity" does not, however, lead to any difficulties in fitting the present experimental data.
Umklapp Annihilation of Positronium in Crystals
Authors: Hodges C. H. , McKee B. T. A. , Triftshäuser W. , Stewart A. T.
Published: April 2011

Previous experiments with positron annihilation in single crystals of quartz have revealed an interesting series of narrow peaks on the momentum distribution of the annihilation photons. Our experiments repeat these observations and also confirm that no very long lifetime exists. We outline a simple theoretical model based upon the necessity of treating the positronium electron and the remaining electrons in the crystal as indistinguishable. The model yields results compatible with both momentum and lifetime data.
Zero-Field Level Crossing in the Helium Atom
Authors: Chien C. W. T. , Bardsley R. E. , Dalby F. W.
Published: April 2011

Zero-field level-crossing techniques have been used to measure some upper-state lifetimes of the helium atom. The half-widths of curves obtained by plotting the polarization against the magnetic field strength for the n1D–21D transitions yielded lifetimes of 2.03 × 10−8 s for the 31D state, 3.36 × 10−8 s for the 41D state, and 7.44 × 10−8 s for the 51D state. Collision cross sections for these 1D levels were also determined.
Dynamical Properties of the Three-Dimensional XY Model
Authors: Ditzian R. V. , Betts D. D.
Published: April 2011

The spin-1/2 XY model in three dimensions is a particularly suitable model for the study of dynamical critical properties, both for comparison with experimental systems such as liquid He near Tλ and certain magnetic systems, and for testing of the predictions of dynamic-scaling theory.Sixteen coefficients have been obtained in the high-frequency high-temperature expansion of the perpendicular (order-parameter) susceptibility, [Formula: see text]. Analysis of [Formula: see text] yields estimates of dynamic critical indices not in conflict with experiment or dynamic scaling, but longer series are needed for a definitive comparison.
Negative Magnetoresistance in Semiconductors with Overlapping Impurity and Conduction Bands
Authors: Lass J. S.
Published: April 2011

Negative magnetoresistance observed in many heavily doped semiconductors is considered as due to a change in the population of states for which the product Δ(E) of the mobility and the density of states varies rapidly with energy. A logarithmic form of Δ(E) is found to give an excellent fit to experimental data which can thereby be described as a simple function of H/(T + θ). The form of Δ(E) suggests that the Fermi level lies in a conduction-band tail with a width of 2kθ, typically 0.2 meV for Ge and CdS. Possible repopulation mechanisms are considered.
High-Temperature Transport Properties of Palladium
Authors: Laubitz M. J. , Matsumura T.
Published: April 2011

The thermal conductivity, electrical resistivity, and absolute thermoelectric power of pure palladium have been determined from 90 to 1300 K in two experimental systems of proven reliability. These properties are compared with the sparse available literature data, and show large deviations from them, particularly for the thermal conductivity at high temperatures. The results are also analyzed in terms of a simple two-band model, where one band contains the carriers, and the other acts as a trap into which phonons scatter the carriers. When the recent density of states values of Mueller et al. are used, the model predicts correctly the temperature variation of the electrical resistivity, and reasonably well its observed magnitude and the observed Wiedemann–Franz ratio. However, the model fails badly in respect to the absolute thermoelectric power, predicting values twice as large as the observed ones. Modifications to the model are suggested which may improve the fit between the predicted and observed values.
Interaction of CO2 Laser Radiation with Solids. II. Drilling of Fused Quartz
Authors: Duley W. W. , Gonsalves J. N.
Published: April 2011

A CW CO2 laser has been used to drill fused quartz sheets. The time dependence of hole depth and radius as a function of incident power in the range 20–150 W has been examined. Absorption of laser radiation at power levels above a critical value results in the propagation of a vaporization front into the solid. The velocity of this front is directly proportional to incident power for constant focussing. Resulting holes are funnel-shaped, tapering to [Formula: see text] in diameter from the initial focal diameter of [Formula: see text]. It is shown how these results can be generalized to provide a prediction of hole depth vs. absorbed laser intensity for other refractory oxide materials.
The Stokes' Shift in Impurity Spectral Lines. I. Mathematical Technique
Authors: Barrie Robert , Sharpe I. W.
Published: April 2011

A new method of deriving the Stokes' shift in impurity spectral lines is presented. The adiabatic approximation is not used. The method makes use of the fact that at most one electron can be bound at the impurity site and reduces the problem in a systematic fashion to the evaluation of traces over only phonon states. A new method is given of evaluating these traces for a particular electron–phonon system which has the chief features required to discuss the Stokes' shift.
Electromagnetic Scattering of a Small Spherical Obstacle Near the Ground
Authors: Hill David A. , Wait James R.
Published: April 2011

The field scattered by an ungrounded conducting sphere above a ground plane is considered. The quasi-static solution is facilitated by the use of bispherical coordinates. The approximate solution obtained by considering only the interaction of dipole modes with the interface is presented for comparison. The general results are used to calculate the backscatter of a low frequency ground wave by a small obstacle.
Field of a Truncated Gaussian Beam as Given by the Boundary-Diffraction-Wave Theory
Authors: Boulay Russell , Lit John W. Y.
Published: April 2011

The field of an incident wave with a Gaussian irradiance distribution diffracted by a circular aperture has been evaluated by using the boundary-diffraction-wave theory. Numerical results of the irradiance distributions, both along the axis and in transverse planes, are compared with those given by the Kirchhoff integral. Good agreement is obtained in all cases over wide regions of the diffracted field.
Mesures de Rapports d'Embranchement et de Vies Moyennes dans 30Si
Authors: Gallmann A. , Haas F. , Toulemonde M.
Published: April 2011

Gamma rays from the decay of 30Si levels with excitation energies less than 6.0 MeV have been studied by the 27Al(α, pγ)30Si reaction. The γ rays were detected in a Ge(Li) detector in coincidence with protons observed in an annular detector placed at 180°. Branching ratios and lifetimes have been extracted. The lifetimes have been measured by the Doppler-shift attenuation method.The electromagnetic matrix elements for some of the observed levels were compared with recent many-particle shell model and core-coupling calculations.
Microtron Supraconducteur: Limitations, Pertes
Authors: Alaux André , Audet Jean-Claude
Published: April 2011

The use of superconductivity allows us to consider the operation at continuous rate of a microtron type accelerator. The authors show here some of the theoretical results they have obtained. These results deal with the losses by Joules effect on one hand, and on the other hand, with the energy limitations caused by the critical value of the magnetic field. The superconductive material considered is niobium and the operating temperatures are 4.2 and 1.85 °K.
Theory of Intercollisional Interference Effects. I. Induced Absorption in a Lorentz Gas
Authors: Lewis J. Courtenay , Kranendonk J. Van
Published: April 2011

A general kinetic theory of intercollisional interference effects in induced infrared spectra is developed, in which the correlations between all the collisions in the collision sequence of a molecule are taken into account, but the effect of the ternary and higher-order collisions is neglected. The resulting series expression for the line-shape function is explicitly summed for a Lorentz gas. From this general theory expressions are derived for the depth of the intercollisional dip and the shape of the intercollisional spectrum assuming that the pair dipole moment and the intermolecular force are exponential functions with slightly different ranges. The extension of the theory to take into account the frequency dependence of the intracollisional spectrum, and the resulting inadequacy of the neglect of ternary collisions, are discussed.
Excitation and Relaxation of the Upper Laser State in a CO2 Discharge
Authors: Christophe B. M. , Offenberger A. A.
Published: April 2011

An experiment designed to measure excitation and relaxation of the upper laser level of CO2 under discharge conditions is described. Observation of the transient 4.3 μ fluorescence arising from this level following application of a Q-spoiled 10.6 μ pulse to a CO2 cell was the method employed. The experimental set-up was tested by measuring known relaxation times in CO2 and CO2–N2 mixtures. Using this technique a measured value for the CO2–CO energy transfer rate is given. The discharge effect on the level of 4.3 μ fluorescence and deexcitation rate of the (00°1) level was investigated and found to be significant. In particular, the electron role is comparable to molecular collisions in (00°1) relaxation. A quantum-mechanical calculation of electron excitation and deexcitation is included in an appendix.
Ultraviolet Absorption Spectrum of Thionylimide (HNSO)
Authors: Allegretti J. M. , Merer A. J.
Published: April 2011

Two regions of absorption have been discovered in the near ultraviolet spectrum of thionylimide (HNSO). These are a long series of diffuse bands between 2690 and 2387 Å, merging into a continuum with maximum extinction coefficient near 2170 Å, and a weak structureless absorption between 3250 and 3500 Å. The vibrational pattern of the 2690–2387 Å system is almost unchanged on deuteration, indicating that the electronic excitation is centered at the sulfur atom.
Reorientation Measurement in 56Fe
Authors: Cameron J. A. , Gibb A. W. , Taylor T. , Zámori Z.
Published: April 2011

The reorientation effect in Coulomb excitation has been used to measure the static quadrupole moment of the first 2+ level of 56Fe. Using beams of 4He and 16O on thin highly enriched targets and observing the spectrum of scattered particles in semiconductor detectors, we have obtained directly the ratios of inelastic to elastic cross sections. The measurements give[Formula: see text]The ambiguity arises from uncertainty in the relative signs of interfering matrix elements.For the case of He scattering, DWBA calculations were carried out to check the energy region where nuclear interaction begins to appear.
Spectrophotometry of the Aurora
Authors: Harrison A. W.
Published: April 2011

Systematic spectrophotometric measurements of the auroral spectrum in the (S-1) region and of the O I (5577) line involving digital recording and computer averaging techniques, and coupled with reliable background-airglow subtraction, have led to brightness determinations of the O I (8446) line and O2 At (0–1), N2 1PG, and [Formula: see text] M bands in agreement with current predictions.
Level Structure of 171Tm
Authors: Graham R. L. , Geiger J. S. , Johns M. W.
Published: April 2011

The properties of the γ-ray transitions in 171Tm, following beta decay of 7.5 h 171Er, have been studied using an iron-free π√2 beta spectrometer and Ge(Li) detectors, singly and in coincidence. The multipolarities of 8 lower-energy γ transitions have been established from a study of L- or M-subshell-internal-conversion lines. The measured K-line intensities of 20 higher-energy transitions yield K conversion coefficients and hence additional multipolarity assignments. Gamma-ray energy measurements, together with an extensive series of gamma–gamma coincidence experiments, have been used to establish the role of 59 (out of 65) γ transitions in the 171Tm level scheme. Sixteen excited states are identified at energies of 5.025 (3/2+), 116.6 (5/2+), 129.0 (7/2+), 326.7* (9/2+), 424.8 (7/2−), 635.4 (7/2+), 675.7 (3/2+), 737.2 (5/2+), 822.3* (7/2+), 912.8 (5/2+), 998.6 (7/2+), 1225.5* (3/2, 5/2, or 7/2+), 1284.7* (5/2+), 1296.3*, 1391.2*, and 1400.5* (5/2+) keV. The asterisks indicate levels which are new or at variance with those proposed by some other workers. The coincidence data does not support a level at 861 keV proposed by two other groups of workers on the basis of energy sums. Nilsson orbital assignments are proposed and discussed for 12 levels.
Possible Difficulties with u-Channel Exchange Degeneracy
Authors: Logan R. K.
Published: April 2011

We have explored the consequences of u-channel exchange degeneracy arising from a FESR bootstrap scheme for the case of [Formula: see text] and πΞ backward scattering and have discovered a possible difficulty with the scheme.
Glow-Discharge Oxidation of Freshly Evaporated Aluminum Films
Authors: Vrba J. , Woods S. B.
Published: April 2011

Glow-discharge-assisted oxide growth on the surface of freshly evaporated aluminum films at 14 °C is discussed with special attention to the preparation of tunnel junctions. It is shown that the rate of mass gain during the oxidation cannot be described by a single oxidation law covering the whole period of oxidation. The oxidation rate is found to depend only on the total current through the glow discharge; the applied voltage and oxygen pressure are not important.
L'effet de la dynamique d'une impulsion-laser sur le chauffage de plasmas confinés
Authors: Beaudry G. , Martineau J.
Published: April 2011

We evaluate theoretically the influence of the form of a laser pulse on the heating of a spherically confined (deuterium) plasma taking into account the mechanisms of inverse electron–ion bremsstrahlung and stimulated Compton scattering. We compare the case of a normal pulse (symmetric in time with respect to the maximum) with that of a modified pulse. Numerical calculations have also been made for a more realistic model of an elliptically confined plasma. In both cases the results show a temperature doubling effect under certain conditions.
Horizontal Magnetic Dipole Embedded in a Two-Layer Conducting Medium
Authors: Ramaswamy V. , Dosso H. W. , Weaver J. T.
Published: April 2011

The solutions for low-frequency fields of a horizontal magnetic dipole embedded within a two-layer conductor are derived. For convenience, the solutions are expressed in dimensionless form. The amplitudes and phases of the electric and magnetic fields along the surface of the bottom layer are calculated numerically and their dependence on the ratio of the conductivities of the two layers is investigated. Results indicate that, in general, the electric field induced by a subsurface horizontal magnetic dipole is more sensitive to the bottom-layer conductivity than is the magnetic field. Some of the results discussed in this paper are of interest in studying the seabed conductivity.
Surface Distributions of Alpha Particles from Odd-A Nuclei
Authors: Ahooja R. , Sharma R. C.
Published: April 2011

The alpha distributions on the nuclear surface are calculated for a number of odd-A alpha-emitting nuclei by an approximate method based on Nosov's work. The calculations are limited to alpha partial waves of l ≤ 4. An inspection of distributions shows little variation with A, unlike the distributions in the case of even–even alpha emitters. The lack of variation is interpreted as due to the screening influence of the unpaired odd nucleon. It is also concluded that there exists a possibility of significantly large relative phases between alpha waves before penetration of the barrier in odd-A nuclei.
Number-Conserving Algebraic Method for Pairing Theory
Authors: Pang Sing Chin , Klein Abraham
Published: April 2011

Several powerful approaches to the study of pairing interactions are based on the relation of seniority conservation to the number-nonconserving algebra of quasi spins. In this note, we develop an algebraic number-conserving treatment utilizing the simplest number-conserving algebra, nonlinear under commutation, which follows from the quasi-spin algebra. The development is carried out in detail for a two-level model and yields encouraging numerical results in the simplest viable approximation consistent with the limit of strong pairing interaction.
Measurements of Stratospheric Methane over North America
Authors: Lowe R. P. , McKinnon D.
Published: April 2011

The absorption due to the ν3 band of methane in solar spectra has been used to deduce the methane content of the lower stratosphere. The spectra were taken from an aircraft flying at altitudes between 10 and 18 km and at latitudes from 18 °N to 66 °N. It is concluded that methane is uniformly mixed up to 25 km with an average mixing ratio of 0.94 ± 0.16 p.p.m.v. No large latitudinal variation of the mixing ratio was observed.
Interference Effects in Two-Step Reaction Processes
Authors: Burke D. G. , Waddington J. C.
Published: April 2011

In reaction studies on even–even target nuclei, one is frequently interested in a state for which (a) the population by single-step processes is forbidden, (b) the dominant excitation mechanism is by two-step processes, and (c) two competing reaction paths are involved. A simple expression is given for such cases which offers some insight into the effects of interference between these two paths. A comparison of the predictions of this expression with several types of experiment is presented. In particular, an interpretation is presented for some recent (3He, α) reaction results which could not previously be explained.
Delves Principle Applied to Helium Using a Numerical Excited Hartree Basis
Authors: Sokoloff J.
Published: April 2011

Expectation values for [Formula: see text], n = 2, 1, −1, −2, and 1/r12 for the 1S state of helium have been calculated using numerical Hartree orbitals. These were then modified by use of the Delves principle, approximating the auxiliary vector of the Delves formalism with a nine-term basis formed from the numerical excited orbitals of the ground state Hartree operator. The modified expectations were then compared with the essentially exact calculations of Pekeris. Results are mixed: excellent for n = 1,2, modest for 1/r12, and poor for n = −1, −2. It is conjectured that the latter results are due to a deficiency of s orbitals in the basis used engendering a poor approximation to the auxiliary vector for these operators.
On the Inverse Problem of Scattering from a Perfectly Conducting Prolate Spheroid
Authors: Vandenberghe F. H. , Boerner W. M.
Published: April 2011

The inverse problem of electromagnetic scattering from a prolate spheroidal scatterer is considered. The approach is based on the model technique presented in Boerner and Vandenberghe, conjecturing that the salient features of the scatterer can be determined from the far scattered field via matrix inversion. An expansion in spherical wave functions for the scattered field based on the formulation of Senior is employed instead of an expansion in prolate spheroidal wave functions. It is then shown that the characteristic parameters of the ellipse generating the prolate spheroid (the interfocal distance d and the eccentricity ε) can be directly recovered from Senior's expansion coefficients.
Electron Spin Resonance in Neutron-Irradiated Diamond
Authors: Whippey P. W.
Published: April 2011

A comprehensive study has been made of electron spin resonance in neutron-irradiated diamond. The main feature is the A spectrum, a broad intense line centered at g = 2.00. The concentration of A centers is proportional to dose for doses up to 5 × 1019 n0 cm−2, when the concentration is 1021 centers cm−3. At least three centers contribute to the A spectrum. The anisotropic B and C spectra are observed in specimens irradiated to doses less than 1019 n0 cm−2. The anisotropic spectrum D is shown to be an annealing product. The spin Hamiltonian is [Formula: see text] either with D = (1.04 ± 0.01) × 10−2 cm−1, E = (2.7 ± 0.2) × 10−4 cm−1, S = 1, g = 2.00 or D = 0.52 × 10−2 cm−1, E = 1.3 × 10−4 cm−1, S = 3/2, g = 2.00. The A, B, and C spectra have been observed in electron-irradiated diamond by Owen. The models proposed here are in broad agreement with his proposals.
Strong-Field Electromagnetic Wave Interaction with Anisotropic Plasmas
Authors: Bachynski M. P. , Gibbs B. W.
Published: April 2011

Investigations of strong-field electromagnetic wave interactions with plasmas have been conducted. In the nonresonant frequency regions, the electron velocity distribution function is Maxwellian and considerations based on Maxwellian theory agree with experiment. At resonant and near-resonant frequencies considerations based on an electron velocity distribution which is non-Maxwellian explain the observations if enhanced electron diffusion is absent. However, at near-resonant frequencies, enhanced electron diffusion due to strong fields can be of great significance in reducing the electron density.
Violet Electronic Emission of SiN
Authors: Dunn E. M. , Dunn T. M.
Published: April 2011

The emission system in the violet attributed to the species SiN has been confirmed using 15N.
Gantmakher–Kaner Effect in Gallium Single Crystals
Authors: Gabel D. E. , Cochran J. F.
Published: April 2011

The periods of Gantmakher–Kaner oscillations for magnetic fields less than 1000 G and directed along the principle axes of gallium is reported. These oscillations were measured using a transmission technique at 1.74 MHz. The dependence of amplitude upon polarization of the RF magnetic field has enabled two of the observed periods to be identified with two small pieces of Fermi surface predicted by a recent theoretical model due to Reed. These pieces are Reed's sixth-band hole surface along T(6h), and the seventh-band electron surface along U(7e). The period which we observe for fields along the B direction in gallium, and which has its origin in Reed's 6h hole ellipsoid, is in excellent agreement with the period reported recently by Milligan and Castner using 9.2 GHz radiation.
The Z−1 Expansion of the Nuclear Magnetic Shielding Constant and X-Ray Form Factor for 2-, 3-, and 4-Electron Ions
Authors: Benesch Robert , Singh S. R. , Smith Jr. Vedene H.
Published: April 2011

The convergence of the Z−1 expansion of the nuclear magnetic shielding constant σ and the X-ray form factor F(μ) is studied within the Hartree–Fock (HF) approximation for the ground states of 2-, 3-, and 4-electron atoms and ions. The agreement of σ through first order with the total HF σ is excellent, whereas the agreement between first-order and total HF F(μ)'s is unsatisfactory.
Tone-Bursting of Quadrupolar Nuclei. Determination of the Spin–Lattice Relaxation Times in Ferroelectric Lithium Tantalate and Lithium Niobate
Authors: Stroud J. D. , Creel R. B. , Segel S. L. , Schoenberger R. J.
Published: April 2011

The technique of "tone-bursting" for the determination of spin–lattice relaxation times has been extended to quadrupolar nuclei and applied to two ferroelectric crystals: lithium tantalate and lithium niobate. The approach has been to analytically follow the populations of the Zeeman quadrupole levels through each passage through resonance and determine the effective T1 from the decrease in magnetization. The analytic results agree with the computer results obtained by Creel and Barnes. The results also agree with the conclusion of Walstedt that the relaxation rate is enhanced by a factor of [Formula: see text] when only the central resonance is being irradiated in a quadrupolar split pattern.Application of the technique to 7LiTaO3 yields a value of 3.0 ± 1.0 s for the effective T1, dominated by magnetic dipole relaxation. For 7LiNbO3, the effective T1 is 33 ± 5.0 s for the central transition and the relaxation mechanism is predominantly electric quadrupole relaxation.
Ethylsulfate Host Lattice Effects in the EPR Spectra of Gd3+ Ions
Authors: Buckmaster H. A. , Chatterjee R. , Shing Y. H.
Published: April 2011

Precision measurements and analysis have been made of the 290 °K, 10 GHz EPR spectra of the Gd3+ [4f7, 8S7/2] ion dilutely substituted (~5:103) into the C3h-site symmetry of the lanthanide host lattices Ln(C2H5SO4)3∙9H2O, where Ln ≡ La, Ce, Pr, Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb, and Lu as well as Y which is chemically lanthanide-like. It is found that empirical, linear relationships exist between the magnitude of the Gd3+ spin-Hamiltonian parameter B20 and (i) the ionic radius of the lanthanide host; (ii) the unit cell dimensions of the host lattice; (iii) the molar volume of the host lattice; and (iv) the estimated crystalline potential parameter [Formula: see text]. A similar linear relationship is found between the ionic radius of the lanthanide host and B60 but not B40. These spin-Hamiltonian parameters are related theoretically to the crystalline electric field parameters through the perturbation interactions of the ground state with the excited states. It is concluded from a review of these interactions that the empirical relations reported in this paper cannot be explained using the values of the crystalline electric field parameters calculated from either excited state optical data or lattice summations. The EPR spin-Hamiltonian parameters for Gd3+ in the Y lattice confirm the latter's lanthanide behavior and assign it an effective ionic radius of (0.0896 ± 0.0001) nm which locates it very close to Ho, (0.0894 ± 0.0001) nm, confirming the results of Von Hevesy, Zachariasen et al., and Ketelaar.
Lifetime Effects in Metal Soft X-Ray Spectra
Authors: McMullen T. , Bergersen B.
Published: April 2011

Methods of nonequilibrium quantum statistical mechanics are applied to the problem of estimating effects arising from the finite lifetime of the core hole in soft X-ray emission spectra. A comparison is made with the formalism for absorption spectra where equilibrium methods are appropriate. A diagrammatic method for estimating lifetime effects is described. It is shown how the validity of the Weisskopf and Wigner approximation is related to two basic assumptions on the decay of the core hole, namely the absence of memory effects and exponential decay of the core hole. Possible memory effects are discussed in detail using a solvable model, and their effect on the spectrum when present is indicated. In particular it is shown that in the model the recoil energy associated with an initial electron bombardment exciting the core, even if appreciable in magnitude, cannot be expected to give rise to a width of the core level, thus broadening the spectrum.
Dually Charged Particles and Dual Invariance
Authors: Schiff H.
Published: April 2011

Dual charges are introduced which differ essentially from the conventional (Dirac) magnetic monopoles. A natural vehicle is shown to be a dual invariant Lagrangian to represent observable charges; the dual invariance can be broken in a simple way by a class of dually charged objects which exhibit no electromagnetic interaction with observable dually charged particles. A triplet formulation can also be obtained and may be of interest in providing a basic description of bosons and fermions.
Mass Radius of the Nucleon
Authors: Hare M. G. , Papini G.
Published: April 2011

The mean radius of the mass distribution of the nucleon is determined to be [Formula: see text]. The calculation makes use of sidewise, unsubtracted, threshold dominated dispersion relations for the form factors appearing in the matrix elements of the contracted energy–momentum tensor. It uses a π meson–nucleon intermediate state expansion.
Note on the Characteristic Temperatures of Sphalerite-Structure Semiconductors
Authors: Aggarwal M. D. , Raju V. , Verma J. K. D.
Published: April 2011

The characteristic temperatures of III–V sphalerite semiconductors have been calculated by using the Reeber–McLachlan relation. These values do not follow the same trend as obtained for II–VI solids. However, the agreement with the Debye characteristic temperature is fair.
Coherent Radiation Damping
Authors: Zaidi H. R.
Published: April 2011

The frequency spectrum of the resonant scattering cross section is calculated from a boundary value solution of Maxwell's equation. The spectral width of the cross section gives the coherent radiation damping rate for the resonant medium. For a large sphere, the coherent width is found to be proportional to the radius, and is much larger than the collision and the Doppler widths in a gas. It is proposed that this effect may also be observable in some absorption experiments.
Dielectric Relaxation of Alkyl Acetates in Aromatic and Aliphatic Solvents at Microwave Frequencies
Authors: Srivastava G. P. , Mathur P. C. , Krishna Mrs.
Published: April 2011

The dielectric relaxation times and the dipole moments of methyl, ethyl, and amyl acetates are measured in six nonpolar solvents having different viscosities. The dielectric relaxation time is found to increase with the chain length in each nonpolar solvent. The relaxation times in aromatic solvents (benzene and p-xylene) are found to be higher than in carbon tetrachloride, even though the viscosity of the latter is more than that of the aromatic solvents This shows that the dielectric relaxation is not only due to the viscous resistance of the solvent but is also influenced by strong interactions between aromatic solvents and solute molecules.
Microwave Spectrum, Structure, and Dipole Moment of Cyanogen Azide, NCN3
Authors: Costain C. C. , Kroto H. W.
Published: April 2011

The microwave spectra of cyanogen azide, NCN3, and two isotopic species have been investigated between 11 and 37 GHz. From the observed rotational constants, the following structural parameters have been obtained:[Formula: see text]The observed data are consistent with a planar molecule. The values of the rotational constants of the normal species are:[Formula: see text]The inertial defect for the normal species is 0.347 uÅ2.The dipole moment components have been determined from the Stark effect of several μa lines as μa = 2.93 ± 0.06 D and μb = 0.44 ± 0.015 D. The relatively low value of μb was responsible for the difficulty encountered in observing and assigning μb type transitions.
Experimental Analysis of the Vibrational–Rotational Line Content of a Q-Switched CO2 Laser
Authors: Sizgoric S. , Waksberg A.
Published: April 2011

Both the "signature" and Q-switched output of a CO2 laser 1.5 m long were examined in detail. Relation between the line profile width in the signature and pulse stability was noted. The Q-switched pulses were found to be made up of more than one line oscillating simultaneously.
Fundamental and Overtone Vibrational Transitions in the Raman Spectrum of h.c.p. Solid Hydrogen
Authors: Prior William R. C. , Allin Elizabeth J.
Published: April 2011

The use of an argon laser of high intensity has made it possible to observe the vibrational overtone of solid hydrogen and to study the fundamental over a wider concentration range than previously. At ortho concentrations below ~ 15% the Q1(1) line has two components. The dependence on concentration and temperature of the frequency separation and relative intensity of these components is accounted for by the quadrupolar interaction between ortho molecules. Differences in the frequency shifts of the Q1(0) and the Q1(1) and of the Q2(0) and the Q1(1) lines in mixtures of all concentrations are also related to the quadrupolar interactions. The overtone lines show almost no frequency change with concentration. This is explained by a much smaller vibrational coupling due to the isotropic interactions in the ν = 2 than in the ν = 1 state. Confirmation of this is found in the small enhancement of the intensity of Q2(1) relative to Q2(0). The measurement of the frequency of Q2(0) makes it possible to determine the parameters μ1, and μ2, specifying the change in the intramolecular potential by the isotropic interactions, from transitions involving J = 0 states alone.
Half-Life of the 194Ir Decay
Authors: Geiger J. S.
Published: April 2011

The half-life of the 194Ir decay has been measured by following the decay of several of the prominent 194Pt γ rays as observed in a series of 254 successive 1 h Ge(Li) γ-ray spectra. The half-life is found to be 19.15 ± 0.03 h, a result in marked disagreement with the most accurately quoted value appearing in the literature. The γ spectra exhibit 45 γ rays which can be identified with transitions in 194Pt.
Radiative Recombination in Cadmium Sulfide
Authors: Colbow K. , Yuen K.
Published: April 2011

Luminescent centers involving Ag impurities were introduced into CdS single crystals through doping with 109Cd radioisotopes. Thus, the Ag concentration increases with time as more 109Cd decays. This enables a study of photoluminescence versus Ag concentration in a given crystal without changing the concentrations of other impurities.A new emission band at 5600 Å results in addition to the 6100 Å band present in Ag-doped crystals using conventional techniques. This new emission is quenched with increasing Ag concentration at high concentrations. Also concentration quenching by the Ag impurities occurs for the green edge, and the bound-exciton emissions I1, and I2. The quenching is explained by assuming a donor–acceptor recombination process.The new emission probably arises from the recombination of a bound electron with a bound hole at a distant donor–acceptor pair, with Ag as the acceptor. The acceptor role of Ag is supported by electrical conductivity measurements on 109Cd-doped crystals. Estimates are obtained for the acceptor binding energy, the donor concentrations, and the separations of pairs responsible for the new 5600 Å emission and the green-edge emission. The 6100 Å emission is attributed to Ag closely associated with other impurities. These conclusions are verified by our temperature annealing and quenching experiments.
A Study of Levels in 25Mg via the 22Ne(α, nγ)25Mg Reaction
Authors: Kean D. C. , Ollerhead R. W.
Published: April 2011

Levels in the nucleus 25Mg have been studied by measurement of the angular distributions and polarization of gamma rays from the 22Ne(α, nγ)25Mg reaction. Information regarding spins, parities, mixing ratios, and branching ratios has been obtained for the levels between 2.7 and 4.7 MeV excitation. Spin and parity assignments of 5/2+ and 7/2− have been made to the levels at 3.90 and 3.97 MeV. Mixing ratios have been determined or restricted for most of the observed transitions. The decay branch of the 3.40 MeV level to the ground state is found to be considerably stronger than previously reported, bringing the decay properties of this level into good agreement with the predictions of the simple rotational model. The significance of the results within the framework of the rotational model is discussed. There is evidence for considerable band mixing in levels belonging to the second Kπ = 1/2+ and the Kπ = 1/2− bands.
Quantum-Mechanical Theory of Orientational Ordering in Solid Methanes
Authors: Alexander S. , Lerner-Naor M.
Published: April 2011

The quantum-mechanical theory of the low temperature phase transitions of the solid methanes is discussed. It is shown how the standard techniques for treating the molecular field approximation can be applied to these problems. It is shown how internal and external symmetries should be combined so as to utilize the full symmetry of the problem. This analysis is quite general and applicable to all problems of orientational ordering. Results of detailed calculations for the James–Keenan model of CH4 and CD4 are presented and compared with experimental results. The calculations assume octupole interactions, include no crystal fields, and include all states up to J = 6. It is suggested that the inclusion of crystal field and possibly states of higher J is essential for describing the low temperature behavior.
Onset of Localized Correlation in a Narrow s Band
Authors: Cheung C. Y.
Published: April 2011

The correlation of electrons in a narrow s band is studied by examining the vertex part for the multiple scattering of two electrons of opposite spin. When bare electrons are used in the calculation, there exists a high-lying pole only for a band not approaching half filled. When the electrons are clothed by the simplest self-energy correction, a high energy pole exists even for the half-filled band, in which case, an insulating state is implied.
Particle–Nucleus Scattering at Intermediate Energies
Authors: Best Melvyn E.
Published: April 2011

For incident neutron energies between 20 MeV and 10 GeV the total neutron–nucleus [Formula: see text] cross sections were calculated using Glauber theory. Remarkably good agreement between experiment and theory was found at energies above 250 MeV. Using the same formalism with identical nuclear parameters, the π−–C cross sections were calculated for incident pion energies near the (3, 3) resonance. In this case, however, good agreement between theory and experiment was found for pion energies above 150 MeV.
The Concentration Dependences of the Binary Diffusion Coefficients of the Systems H2–Ne, D2–Ne, H2–N2, D2–N2, H2–Ar, and D2–Ar at 1 Atm Pressure and 300 K
Authors: Harris K. R. , Bell T. N. , Dunlop Peter J.
Published: April 2011

Binary diffusion coefficients have been measured as a function of concentration for the systems H2–Ne, D2–Ne, D2–N2, H2–Ar, and D2–Ar at 1 atm pressure and 300 K. Similar data have already been presented for the system H2–N2. As predicted by the Chapman–Enskog theory, the concentration dependences of the diffusion coefficients for the systems containing deuterium are somewhat less than for the corresponding systems containing hydrogen. The data for the systems containing Ne and N2 indicate that there may be differences between the parameters required to describe the assumed spherical intermolecular potentials for the systems H2–Ne and D2–Ne, and also for the systems H2–N2 and D2–N2. The concentration dependences of the diffusion coefficients of all six systems are, within the estimated experimental error of ±0.2%, linear in the mole fraction of the heavier component in each system, x2.
Effects of Thermal Lensing in Glass Lasers
Authors: Ninnis R. M. , Rieckhoff K. E.
Published: April 2011

Investigations into the influence of thermal lensing on the output energy, beam divergence, emission characteristics, and mode-locking behavior of Nd: glass lasers are reported. The astigmatic effects associated with Brewster-cut rod geometry are considered.
Pseudopotential Calculations of the Band Structure and Fermi Surface of Mercury
Authors: Jones J. C. , Datars W. R.
Published: April 2011

Semi-empirical local and nonlocal pseudopotentials have been used to calculate the energy bands and Fermi surface of crystalline mercury. The nonlocal pseudopotentials were an approximation in which the repulsive potentials of the outer core states were explicitly represented by nonlocal projection operators. A search in parameter space revealed three separate regions in which the Fermi surface generated by the pseudopotential was a good fit to experimental magneto-acoustic calipers and extremal sectional areas. One of the regions investigated was equivalent to the Animalu–Heine pseudopotential for mercury and a second was very similar to the Evans pseudopotential which has been used for liquid mercury. Although there were strong resemblances in the band structures generated by the different classes of pseudopotential, the symmetry characteristics of the bands were different. The nonlocal operators had a strong influence on the Fermi energy with p-like and d-like operators causing an increase in the Fermi energy. The influence of spin–orbit coupling and more general questions of pseudopotential theory and band symmetry were also considered.
Excitation Energy of the Fourth Excited State in 18F
Authors: Berka I. , Rolfs C. , Azuma R. E.
Published: April 2011

The excitation energy of the Jπ = 5+, fourth excited state in 18F has been determined to be Ex = 1119.0 ± 0.6 keV from a measurement of the energy of the γ-ray transition to the 937 keV, first excited state. This new excitation energy removes the discrepancies in the excitation energy of resonant states based on γ-ray decay schemes involving this state. The mean lifetime has been determined to be τ(1119) = 218 ± 8 ns by a delayed coincidence measurement between the γ rays populating and deexciting this state.
Zeeman Effect in the 2782 Å Band of HCP
Authors: Moehlmann Jon G. , Hartford Jr. A. , Lombardi John R.
Published: April 2011

The Zeeman effect in the 2782.22 Å band of HCP has been observed and indicates the excited state is 3Δ1. A formula is derived for a 3Δ1 state, intermediate between case (a) and case (b), which expresses the Zeeman splitting as a function of J and the spin–orbit coupling constant. By applying this formula the spin–orbit coupling constant is found to be +22.3 or −16.0 cm−1, depending on whether the 3Δ state is normal or inverted. The rotational constant and band origin for these two cases are also computed.
A Kinetic Interpretation of Sound Absorption in Mixtures of Argon and Nitrogen
Authors: Law A. K. , Bezanson D. S.
Published: April 2011

The ultrasonic absorption coefficient has been measured in mixtures of argon and nitrogen over the full range of the components at room temperature (23 °C) and at a frequency of 668 kHz. An attempt has been made to understand kinetically the relaxational absorption as a function of the concentration of either component. The relaxational absorption is found to be related to the collision frequencies as well as the probabilities of excitation of the nitrogen molecule by argon and by nitrogen.
Positron Annihilation and the Band Structure in Molybdenum
Authors: Kim S. M. , Buyers W. J. L.
Published: April 2011

Measurements have been made of the two-photon angular correlation from positrons annihilating in single-crystal molybdenum at room temperature. By means of a combination of conventional slits and Soller slits the number of annihilations for which the momentum lies along a line in the momentum distribution is obtained, and results are presented for the [ζ,ζ,0], [0,0,ζ, and [ζ,ζ,0.71] directions. Theoretical calculations of the angular correlation have been made based on the interpolation or pseudopotential scheme with s–d interaction included. The parameters of the interpolation scheme have been chosen so that an accurate representation is obtained of the APW band structure of Mattheiss. The positron wave function has been obtained in terms of 141 plane waves. The width of the calculated two-photon angular correlation is found to be much broader than the experimental width unless the relative s and d enhancement is considered.
Identification of Transverse Kelvin–Helmholtz Turbulence in a Magnetoplasma Column
Authors: Robinson J. E. , Lidsky L. M.
Published: April 2011

Transverse Kelvin–Helmholtz turbulence has been observed in a region of strong rotation and shear in a magnetoplasma column produced using a Lisitano structure. The turbulence is identified on the basis of radial density–potential fluctuation phase, wave localization, and steady-state characteristics of the column. A modified wave equation is used to check experimental observations with theory. This is a second type of magnetoplasma column where transverse Kelvin–Helmholtz turbulence has been identified and it supports previous investigations in Q machines.