bluuebunny/crossref_metadata_2025 huggingface dataset:
The Resonant Faraday Effect
Authors: Camm D. M. , Curzon F. L.
Published: April 2011

The resonant Faraday effect occurs for radiation at frequencies close to the absorption lines of a magneto-active material. In the paper we present a theory for isolated absorption lines with Voigt profiles. The background source is also assumed to have a Voigt profile. The theory shows how the resonant Faraday effect can be used to determine relative transition probabilities, as well as the magnitude of the Lorentzian component of the line profiles.Experimental results for an argon plasma are presented and show that the relative transition probabilities of atomic transitions with a common lower level can be measured to an accuracy of ± 1%. For strong absorption lines, the Voigt "a" parameter can also be determined to an accuracy of 10%, even when the Doppler width is 14 times larger than the Lorentzian width.
Theory of Intercollisional Interference Effects. II. Induced Absorption in a Real Gas
Authors: Lewis J. Courtenay
Published: April 2011

The kinetic theory of intercollisional interference effects in induced infrared spectra developed in the first publication of this series for a Lorentz gas is extended to a real gas.A principal conclusion is that intercollisional interference in absorption is always destructive in the systems considered. Though the theory is mathematically less tractable for the real gas than for the Lorentz gas, a useful upper bound to the intercollisional interference dip minimum is obtained. This upper bound is evaluated for the exponential model developed previously, for all values of the mass ratio m1/m2. The intercollisional interference minimum itself is calculated for this model with m1 = m2. Finally, a simplification of the expression for the line-shape function is discussed.
Spectre d'Emission de la Molécule PO : la Transition E2 Δ–X2Πr; Etude de l'Etat Rydberg E2Δ
Authors: Coquart B. , Larzillière M. , Ngo T. A.
Published: April 2011

The rotational analysis for the E–X system of the PO molecule, between 1810 and 1930 Å, is carried out with a dispersion of 0.24 Å/mm. The levels 0, 1, and 2 of the E2Δ(b) state are studied. Rotational and vibrational constants are determined. Local predissociations, particularly at levels 1 and 2, are discussed. The E2Δ (3dδ) Rydberg state is certainly predissociatcd above its level 2.
On a Set of Continuous Wave Electromagnetic Inverse Scattering Boundary Conditions
Authors: Boerner W. M. , Ahluwalia H. P. S.
Published: April 2011

The inverse problem of continuous wave electromagnetic scattering is considered. The shape and the material constituents of an unknown scatterer need to be determined from bistatic measurement data for a given transmitted field. Although methods have been outlined on how to determine the material constituents of a semi-transparent scatterer, no suitable method has been found which may be employed to simultaneously specify the shape and the material constituents of an unknown smooth, convex-shaped, close, and imperfectly conducting scatterer. Namely, such boundary conditions are sought which do not depend on either the shape or the material constituents of the scattering body and its enclosing surface, but allow one to specify the relevant characteristic parameters uniquely from the recovered near field.The main incentive of this study is to show that the unknown geometrical and material surface parameters can be determined from a set of equations which is derived from the Leontovich impedance boundary condition. The resulting inverse scattering boundary conditions are analyzed in detail and it is shown that in the perfectly conducting case these boundary conditions degenerate to those conditions investigated by Weston and Boerner.The theoretical analysis is verified by computation proving the importance of the result to the inverse theory of electromagnetic scattering.
Comment on Paper by T. Tietz: Potential-Energy Function for Diatomic Molecules
Authors: Dickinson A. S.
Published: April 2011

The claim by Tietz to have obtained a new example of a spherically symmetric potential for which the energy levels may be obtained analytically is shown to be unfounded.
X-Ray Diffraction by Compressed Solid Argon
Authors: Bronsveld P. M. , Kumra S. K. , Stryland J. C.
Published: April 2011

A technique is described to perform precision measurements of the lattice parameter of solid argon under pressure. Details are given of the apparatus which consists of a beryllium pressure vessel, a liquid nitrogen cryostat, a two-circle goniometer, and a cylindrical camera. Small argon crystals are grown in the pressure vessel and one suitable crystal is selected and correctly oriented with a precision of 1 min of arc, using the oscillation method. The single-crystal rotation method is used to measure the lattice parameter with an estimated precision of 0.01%. Measurements were carried out along the melting line in the range from the triple point (83.8 K and 0.7 bar) to 95 K and 450 bar. The result obtained for the lattice parameter of solid argon near the triple point, a0 = 5.4676 ± 0.0005 Å, is in close agreement with the low pressure result of Peterson et al. Some values are calculated for the molar volume, density, coefficient of thermal expansion, and bulk modulus of solid argon, and these results are compared with those obtained by other workers using different methods.
Motional Narrowing and Other Effects in the Q Branch of HD
Authors: Dion P. , May A. D.
Published: April 2011

Observations of the Q(J) lines in the Raman spectrum of HD are reported for a range of densities at room temperature. The broadening of the individual components at low densities and the eventual overlap and collapse of the band at high densities is shown to be in agreement with the theory of motional narrowing of Alekseev and Sobel'man. A brief comparison of the broadening and shifting of the Q branch of HD with that for H2 is made.
The 1333.1 and 1559.4 keV Isomers in 176Hf
Authors: Khoo T. L. , Waddington J. C. , Johns M. W.
Published: April 2011

The half-lives of the 1333.1 and 1559.4 keV isomers in 176Hf have been determined to be 9.5 ± 0.2 and 9.8 ± 0.2 μs respectively. The upper isomer feeds the lower by means of a 226.25 ± 0.06 keV (M2) transition and a 53.49 ± 0.07–172.75 ± 0.04 keV cascade. The multipolarities of the members of the cascade are E1 and {M1(76 ± 13%) + E2(24 ± 13%)} respectively. Because it is fed from the upper state, the 1333.1 keV state appears to decay with a half-life significantly longer than its true value. The half-life of this state was therefore determined by using a TAC to measure the elapsed time between the detection of a gamma ray feeding the state and one deexciting it.
Magnetoviscosity of Colloidal Suspensions
Authors: Levi A. C. , Hobson R. F. , McCourt F. R.
Published: April 2011

A theoretical description of the effect of an applied magnetic field on the viscosity of a colloidal suspension of single-domain ferromagnetic particles is given from the point of view of linearized hydrodynamics, starting from a microscopic Fokker–Planck equation. Reasonable agreement is found between theoretical results and previous experimental measurements of the effect. A comparison with an earlier theoretical explanation of the effect is given. It is found, in particular, that a consideration of the role of Brownian motion is not only desirable but crucial to a proper explanation of the magnetoviscosity effect.
Levels of 186W from the Decay of 186Ta
Authors: Gujrathi S. C. , Mark S. K.
Published: April 2011

Gamma rays from the decay of 10.5 min 186Ta have been studied using high resolution Ge(Li) detectors. More than 90 gamma rays have been observed. Several photo-peaks previously reported as single lines were found to be close doublets. The results of this study have been correlated with the published γ–γ coincidence data and the recent (d,d′) reaction work and a decay scheme for 186Ta has been constructed. The scheme incorporates more than 85 transitions among 23 excited states in 186W. The level at 1661 keV has been discussed in terms of a two-proton quasi-particle state arising from the Nilsson orbitals Ωπ[NnzΛ] = 7/2+[404] and 1/2+[411]. Several transition probabilities have been extracted and compared with other recent experimental data and with the calculations of Kumar and Baranger as well as with the predictions of various phenomenological models.
Inelastic Collisions between Excited Alkali Atoms and Molecules. VIII. 62P1/2–62P3/2 Mixing and Quenching in Mixtures of Rubidium with H2, HD, D2, N2, CH4, and CD4
Authors: Siara I. N. , Krause L.
Published: April 2011

Excitation transfer between the 62P fine-structure substates in rubidium, induced in inelastic collisions with ground-state molecules, has been studied using techniques of sensitized fluorescence. Rubidium vapor in mixtures with various molecular gases was irradiated with each component of the 2P rubidium doublet in turn, and measurements of sensitized-to-resonance fluorescent intensity ratios yielded the following mixing cross sections Q12(2P1/2 → 2P3/2) and Q21(2P1/2 ← 2P3/2), as well as effective quenching cross sections Q1X(2P1/2 → 2XJ″) and Q2X(2P3/2 → 2XJ″). For collisions with H2: Q12(2P1/2 → 2P3/2) = (41 ± 5) Å2; Q21(2P1/2 ← 2P3/2) = (26 ± 3) Å2; Q1X(2P1/2 → 2XJ″) = (36 ± 9) Å2; Q2X(2P3/2 → 2XJ″) = (31 ± 8) Å2. For HD: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (47 ± 13) Å2; Q2X = (38 ± 10) Å2. For D2: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (28 ± 8) Å2; Q2X = (21 ± 7) Å2. For N2: Q12 = (107 ± 15) Å2; Q21 = (70 ± 10) Å2; Q1X = (128 ± 44) Å2; Q2X = (126 ± 33) Å2. For CH4: Q12 = (38 ± 6) Å2; Q21 = (24 ± 3) Å2; Q1X = (129 ± 41) Å2; Q2X = (114 ± 37) Å2. For CD4: Q12 = (52 ± 7) Å2; Q21 = (34 ± 5) Å2; Q1X = (82 ± 30) Å2; Q2X = (76 ± 22) Å2. An analysis of these results suggests the possibility of resonances with various molecular rotational and vibrational transitions.
Population Distribution of Triplet Vibrational Levels of CO Produced by Photodissociation of CO2
Authors: Lee L. C. , Judge D. L.
Published: April 2011

The CO fluorescence of the a′ 3Σ+, d3Δi, and e3Σ− → a3Π systems, produced by photodissociation of CO2 is identified and analyzed and the population distributions of the vibrational levels of the a′ 3Σ+ and d3Δi states are obtained. The data are found to be reasonably represented by a Poisson distribution.
Rotating Incoherent Matter in General Relativity
Authors: Pachner J.
Published: April 2011

Under the assumption of rotational symmetry a method is developed for the numerical integration of exact Einstein equations describing the time evolution of a rotating incoherent matter. The complete system of equations deduced earlier for the case of an ideal fluid reduces here to six Einstein field equations and to the equation of continuity. The choice of the system of comoving cylindrical coordinates (z, r, [Formula: see text], t) is restricted by further conditions so that the only allowed coordinate transformations are the translations of the origin of the coordinates z, [Formula: see text], and t, and the reflections in these three axes. To any set of the permissible initial values of the field corresponds then only one physical situation. The exact field equations are deduced. With the exception of a few terms they are invariant with respect to certain permutations. The requirements upon the field to be regular at the initial moment and its infinitesimal past and future imposes restrictions on the functions appearing in the components of the metric field. Even then the field equations contain terms that have an indeterminate form 0/0, but are finite, at the z axis. Therefore two sets of field equations must be used : one set for the z axis in which the indeterminacy is analytically evaluated, and the other set for the space with r > 0. The junction conditions for the external field are formulated and proved that the corresponding external field does exist. The problem of the Lichnerowicz initial conditions is solved. An analytical proof is given that the rotation can stop the contraction of incoherent matter and revert it to a new expansion even along the axis of rotation. In terrestrial physics the axial acceleration is negligibly small, but it may play an essential role in cosmology.
Fluctuations Near the λ Transition in 4He
Authors: Revzen M. , Trainor L. E. H.
Published: April 2011

The Guyon–Maki model of the λ transition in liquid 4He is reconsidered with the inclusion of quantum fluctuations. The quantum fluctuations remove spurious divergences whilst retaining such successful features of the model as the logarithmic divergence of the specific heat. In addition, an explicit formula is obtained for the thermodynamic potential due to fluctuations near Tλ.
Optical Pumping of Spin-Polarized Conduction Electrons and Inelastic Scattering by Neutral Acceptors
Authors: Parsons R. R.
Published: April 2011

The energy relaxation mechanisms of conduction electrons in p-type GaSb at 1.9 °K are investigated by an optical pumping technique. Spin-polarized electrons are excited across the forbidden band gap with circularly polarized light. The number of photocreated electrons is obtained from the intensity of the photoluminescence; and the spin polarization from the degree of polarization of the photoluminescence. The experiment shows that the number of electrons and the spin polarization at the conduction band edge depend on the initial energy of the electrons and on the number of neutral acceptors. An explanation of the results is given in terms of two processes of energy relaxation for conduction electrons: (i) the emission of longitudinal optical phonons, and (ii) inelastic scattering by neutral acceptors.
Correlation of Orthopositronium Annihilation and the Surface Properties of Silica Gels as a Function of Temperature
Authors: Chuang S. Y. , Tao S. J.
Published: April 2011

The lifetime spectra of positrons annihilating in silica gels of various pore sizes as a function of temperature are investigated. There are two long lifetime components which are attributed to the annihilation of o-Ps under various processes. The intensities of the two long lifetime components change with temperature. These changes cannot be attributed solely to the diffusion process. Other processes, such as the formation, quenching, and thermalization of o-Ps in silica gels, must also be taken into consideration.The mean life of the longest lifetime component also changes with temperature. The pattern of this change varies with the pore size and grain size of the silica gel. It seems that positronium atoms are adsorbed on the pore surface of silica gels. A potential model including the effect of adsorption is proposed to explain this phenomenon. The change of annihilation rate of o-Ps is not found to be solely due to the vibration of surface atoms. The quenching due to the presence of the "strained" surface silica groups and its change with the temperature is offered as an explanation.
A Simple Bond Charge Model for the Phonon Dispersion Relations in Tellurium
Authors: Cowley E. R.
Published: April 2011

The phonon dispersion relations in tellurium are calculated on the basis of a bond charge model. In this model the effects of covalent bonding are simulated by the action of point charges positioned midway between nearest neighboring atoms. The electrostatic forces are supplemented by two-body interactions between the atoms. A model with 5 adjustable parameters provides a fair overall representation of the dispersion curves.
Effect of Core Excitations on 29Si and on the Giant Dipole Resonance in 28Si
Authors: Johnstone I. P. , Castel B.
Published: April 2011

The structure of 29Si is studied in a model which couples a neutron onto low-lying core states of 28Si. Very satisfactory agreement is obtained for energy levels, E2 transition rates, and spectroscopic factors. The splitting of the 28Si dipole strength is then investigated using a particle–core and hole–core interaction derived from this 29Si study, and the effect of various approximations is examined.
The 40Ca(p,2p)39K Reaction at 45.0 MeV
Authors: Bray K. H. , Bunker S. N. , Jain Mahavir , Jayaraman K. S. , Miller C. A. , Nelson J. M. , Oers W. T. H. van , Wells D. O.
Published: April 2011

A study of the 40Ca(p,2p)39K reaction has been made for two states of 39K, the 1d3/2−1(g.s.) and 2s1/2−1(2.53 MeV). Angular correlations at symmetric, coplanar angles between 30 and 105° have been measured. The data are compared with a distorted wave t-matrix calculation which utilizes a nonlocal bound state wave function. A further comparison is made with the angular correlation for unequal energies of the final state protons.
A New Method for Band Contour Analysis with Application to the Spectrum of Pyridine-4-d1
Authors: Birss F. W. , Colson S. D. , Ramsay D. A.
Published: April 2011

A new method for generating band contours is described which is both rapid and accurate. One contour is generated from another using the differentials of the energy levels with respect to the rotational constants, thus avoiding the need for repeated diagonalization of the asymmetric rotor matrices.The method is applied to two C-type bands in the near ultraviolet π*–n transition of pyridine-4-d1. For the 0–0 band the following constants are obtained: A′ = 0.19843 ± 0.00008 cm−1, B′ = 0.17957 ± 0.00008 cm−1, C′ = 0.09426 ± 0.00020 cm−1, ν0 = 34 800.31 cm−1. These constants are slightly smaller than the ground state constants, indicating a very small increase in the molecular dimensions in the excited state.
Electromagnetic Induction in a Stratified Conducting Half-Space by an Arbitrary Periodic Source
Authors: Summers D. M. , Weaver J. T.
Published: April 2011

A general theory of induction in a horizontally stratified plane conductor by an external, time-periodic, magnetic source is presented. The analysis is a generalization to the case of an N-layered conductor of a previously published theory for induction in a uniform conducting half-space, in which the electromagnetic field was expressed in terms of electric and magnetic Hertz vectors oriented normally to the surface of the conductor. With the aid of this representation the entire theory is developed in terms of the one scalar component of the magnetic Hertz vector. Solutions for the electric and magnetic fields above and within the conductor are obtained in the form of double integrals whose integrands are related through a recursion formula to the Fourier transform of the magnetic Hertz potential of the source evaluated at the surface of the conductor. Special formulas applicable to 1- and 2-layer conductors are derived and the form of solution for some elementary sources is also discussed. As an illustration of the theory, numerical calculations are given for an infinite line current above a 10-layer conductor whose conductivity increases (i) linearly and (ii) exponentially with depth.
New Dynamical Theory of the Large Polaron. I. Mathematical Formulation
Authors: Matz D.
Published: April 2011

We have developed a new equation of motion Green's function theory for the large polaron, that is completely nonperturbative in origin, and therefore gives a unified treatment of the polaron ground state energy for all interaction strengths. The theory also incorporates translational invariance rigorously, a priori. We find the following new results. (a) Previous theories that are valid for all coupling strengths are based on a nonperturbative summation of infinite subsets of entire diagrams (equations of motion), rather than on recoil parts of all diagrams. We can thus recover lowest order results of Feynman for example, via a translationally noninvariant form of the Fock approximation, which resembles that reported in a previous work. (b) The total ground state energy we obtain in the strong coupling limit is E0 = −0.426α2 to lowest order in the coupling constant α, a result substantially below that of previous calculations, E0 = −0.106α2 (using gaussian trial functions in both cases). Our result is also below the lower bound of Lieb and Yamazaki, although we show in a following paper that our result is an upper bound. (c) The origin of the difference of our results compared to that of other strong coupling theories is several fold, and will be presented in detail in subsequent papers. However, the essence of the difference is that the phonons in the field, via their interaction with the electron, assume the role of independent degrees of freedom, in the limit of an infinite number of phonons. We then have a field theoretic problem with an infinite number of degrees of freedom which can exhibit a totally different physical behavior compared to one with a finite number of degrees of freedom. This aspect of the problem has not been given explicit recognition in all other theories, including that of Lieb and Yamazaki.
Suboptical Dielectric Losses by Condensed Nonpolar Media
Authors: Frood D. G. , Morita A.
Published: April 2011

Debye theory applied to the observed microwave and far-infrared losses by nonpolar liquids based on the assumption either of (a)temporary, multipole-induced dipoles or (b) a number of equivalent equilibrium positions for the molecular charges separated by potential barriers is shown to be inadequate. In dense non-polar media absorption at suboptical frequencies, i.e. frequencies below visible and near-infrared will arise from nonharmonic properties of the relative motions of electrons and nuclei. To develop a phenomenological theory of the effect in condensed fluids, we introduce the cell model and assume densities sufficiently high that a nonpolar particle is bound harmonically to the cell center through short-range interaction with its immediate neighbors for times long compared to its period of oscillation. It also interacts with all others through long-range dipolar forces provided by the Lorentz field. Assuming the fluctuating forces lead to velocity damping of the cell, the dielectric constant is shown to have the same form as found in ionic crystals in the harmonic approximation with the residual ray frequency replaced by the infrared normal mode frequency—prescribed by the present model. The medium thus shows a maximum in its absorption coefficient at the infrared mode frequency and all nonpolar media at sufficiently high densities will exhibit infrared losses. As the density of an insulating nonpolar liquid is raised, the infrared mode frequency shifts to lower values and ultimately to zero (the "dielectric catastrophe") at which point the liquid becomes metallic.
Nondissipative Conducting Flows with Hj Lines in the Osculating Plane of the Streamlines
Authors: Rogers C.
Published: April 2011

A class of stratified magnetogasdynamic flows is analyzed by employing an anholonomic characterization of three-dimensional vector fields. Specific reference is made to helical flows of a conducting polytropic gas.
Quantum Corrections to the Thomas–Fermi Approximation—The Kirzhnits Method
Authors: Hodges C. H.
Published: April 2011

The method of Kirzhnits for the calculation of quantum corrections to the Thomas–Fermi approximation is reviewed. An equation is derived whose iteration gives quantum corrections to the density matrix directly in terms of gradients of the potential. This is then used to calculate the correct form of the quantum correction to power 4 in the gradient operator. The validity of the quantum correction or gradient expansion method is examined by comparing the results of linear response theory using truncated gradient expansions with the exact Lindhardt result.
Quadrupole Interaction in Hafnium Metal
Authors: Zmora H. , Lowe L. M. , Prestwich W. V.
Published: April 2011

The electric quadrupole interaction of 181Ta in Hf metal has been measured as a function of the annealing temperatures of the irradiated samples. The asymmetry parameter obtained was η = 0.3, independent of the thermal history of the samples.
A Possible Role of Universal Length in the Theory of Weak Interactions
Authors: Kim D. Y.
Published: April 2011

The discovery and role of already existing universal constants h and c in modern physics have been reviewed from a particular point of view. This viewpoint is characterized by a pattern of logic in terms of which one may possibly find a new universal constant, i.e. the elementary length. One of the main objectives of this paper is to find out whether the elementary length introduced this way would resolve inherent difficulties in relativistic quantum field theory. This has been explicitly studied in terms of the nonlocal field theory in connection with the CP violating kaon decay. This produced a relation [Formula: see text] which leads, on the one hand, to a consistent explanation of the possible mechanism of CP violation and, on the other hand, gives a result which is most probably the first direct link between the elementary length (nonlocality) and an experiment without having the inherent disorder in the small distance behavior in quantum field theory.
Excitation Cross Sections of Alkali-Metal Atoms Colliding with Slow Electrons
Authors: Felden Madeleine M. , Felden Marceau A.
Published: April 2011

A previously developed model is extended to the case of excitation of the alkali metals (Li, Na, K, Rb, Cs) by electron impact. The results of the cross-section calculations to transitions n0s → n0p (n0s being the ground state) are compared with experimental values. Numerical results concerning some other transitions are given in tabular form.
Rotational Bands in 171Lu
Authors: Gregory P. R. , Preibisz Z. , Waddington J. C. , Johns M. W.
Published: April 2011

A variety of experiments has been performed in order to establish and identify the states in the rare earth deformed nucleus 171Lu. Proton particle states have been studied using (3He,d) and (α,t) stripping reactions. The reaction products were analyzed with an "Enge" split-pole magnetic spectrograph. The expected components of the following intrinsic proton states have been identified: 7/2+[404] (ground state), 1/2−[541], 1/2+[411], 5/2+[402], and 9/2−[514]. In addition, tentative assignments are made for rotational states based on the 3/2−[532], 1/2−[530], and 1/2+[660] orbitals, and for states which are mixtures of β and γ vibrations and particle states. The cross-section ratios of the two stripping reactions were used as an indication of l value and spectroscopic factors were extracted using DWBA calculations. Gamma radiation and conversion electrons following the reaction 169Tm(α,2n)171Lu have been studied, using high resolution Ge(Li) detectors in singles and coincidence mode, and an on-line, double-focussing, electron spectrometer. Coincidence probabilities have been calculated and have been used to determine the intensities of unresolved gamma transitions. Excitation functions of gamma rays following the 168Er(7Li,.xn) reaction were used to check isotopic assignments. The ratio of the relative intensities of gamma transitions following the 7Li and 4He induced reactions was found to be a good indicator of the spin of the deexciting level. A level scheme is proposed which includes a number of K-forbidden inter-band transitions.
Theory of Impurity-Induced Infrared Absorption in Noncubic Crystals
Authors: Benson H. J.
Published: April 2011

We present the theory of impurity-induced infrared absorption in crystals with a single substitutional impurity. The expressions derived are not restricted to crystals with cubic symmetry. A T-matrix formalism is employed to obtain the perturbed Green's functions needed in calculating the induced absorption. The theory is applied to MnF2:X with a nearest neighbor force constant change model for the impurity and a rigid ion model for the pure MnF2. Semiquantitative agreement is obtained with the experimental results of Alexander and Sievers with Tm and Eu impurities.
Flow Stress of Pb–4 at.% In Alloy in the Normal and Superconducting States
Authors: Hutchison T. S. , McBride S. L.
Published: April 2011

In the alloy Pb–4 at.% In, the normal flow stress is found to increase with temperature up to about 15 K, thus removing a foreseen difficulty in our thermal conductivity model describing the flow stress difference in the normal and superconducting states for this alloy.
Lattice Dynamical Properties of Nickel
Authors: Pal Satya
Published: April 2011

The frequency spectrum of nickel has been calculated on the basis of the lattice dynamical model of Sharma and Joshi. The frequency spectrum has been computed with the help of Blackman's root sampling technique for a discrete subdivision in the reciprocal space. The computed frequency distribution has been employed for the calculation of the specific heat and the temperature variation of the Debye–Waller factor of nickel. The theoretically computed values of specific heat are compared with the experimental data in terms of the Debye characteristic temperatures. The theoretical results are in reasonable agreement with the experimental data.
Schottky Energy Calculations for the Alkali Halides; Details and Results of Successive Approximations
Authors: Boswarva I. M. , Simpson J. H.
Published: April 2011

Results of theoretical determinations of the energy to form a Schottky defect, using a point-dipole model, are presented for alkali halides of the NaCl structure. The calculations were made under the following conditions: (1) Region I (in which the electrostatic and short-range interactions for each ion are treated in detail) contained 6, 18, 26, and 32 ions respectively. (2) Short-range parameters were determined from both the elastic and dielectric properties and the results compared. The "dielectric" parameters produced a better match between the dielectric properties of regions I and II (the dielectric continuum region) and showed better agreement with experimental values for the Schottky energy. (3) Derivations of detailed expressions and calculations were performed independently in two laboratories and cross-checked to eliminate errors.Region I displacements which are presented for the four cases indicate that an instability occurs in the 32-ion case for crystals in which the ions differ considerably in size. An analysis of this problem suggests that a modification of the Born repulsive energy expression is desirable when interaction between negative ions is appreciable.
Radiative Mean-Life Measurements in Neon below 1000 Å
Authors: Irwin D. J. G. , Livingston A. E. , Kernahan J. A.
Published: April 2011

Neon spectra between 379 and 914 Å were studied by the beam-foil technique. Mean lives have been obtained for 21 levels in Ne I – Ne VII. In addition, mean lives are reported for upper levels of 12 unassigned lines.
The Decay of 151Pm to Levels in 151Sm
Authors: Cook W. B. , Waddington J. C. , Burke D. G. , Nelson D. E.
Published: April 2011

The energy levels of 151Sm have been investigated through a study of the decay of 28.4 h 151Pm. Singles gamma-ray spectra were obtained with high resolution Ge(Li) detectors having volumes of 0.9 and 12 cm3. Two Ge(Li) coincidence spectrometers (37 cm3 – 50 cm3 and 0.9 cm3 – 50 cm3) operated in a two-parameter configuration (4096 × 4096) were employed in collecting coincidence data. Two hundred and seventeen transitions have been incorporated into a level scheme involving 39 levels in 151Sm. On the basis of beta and gamma selection rules, spin–parity assignments have been suggested for most of the levels.
Nuclear Spectra in the 1f7/2 Shell
Authors: Brut François
Published: April 2011

Energy spectra of nuclei of masses 43 through 53 have been studied. Within the framework of the spherical shell model, we have assumed an “inert" core of 40Ca plus Z − 20 protons and N − 20 neutrons in the lf7/2 shell. With the assumption of pure configurations, two residual interactions have been investigated by treating them exactly for all states. We have first used the “realistic" effective interaction of Kuo and Brown. We have also taken the effective interaction of Dieperink and Brussaard which has been determined in a least-squares fitting procedure. Calculated low-lying states of these nuclei are in good agreement with experimental levels. Among all results, only those for 46Sc, 47V, 48Ti, and 48Cr nuclei are reported here. Some discrepancies, which arise in particular from the restriction we have made for the configuration space, remain.
Inelastic Electron Scattering from 20,22Ne
Authors: Singhal R. P. , Caplan H. S. , Moreira J. R. , Drake T. E.
Published: April 2011

The scattering of electrons from the low lying excited states of 20Ne and 22Ne has been studied in the momentum transfer range from 0.41 fm−1 to 1.04 fm−1. Over a limited range of momentum transfer the study of 20Ne has been extended to excited states up to 8 MeV. A phase shift code has been used to extract the ground state transition probabilities of the states observed. The model dependence of the results is investigated. The experimental results have been compared with the predictions of the Nilsson and the alpha-particle model.
A New Experimental Method Allowing a Quantitative Measure of Orthopositronium Magnetic Quenching
Authors: Falciglia F. , Iaci G. , Savio M. Lo , Turrisi E.
Published: April 2011

A new method for determining the amount of magnetic quenching of the orthopositronium atom is described. This method, still using angular correlation techniques, allows a direct measure of the quantities which the orthopositronium magnetic quenching deals with. By this way, an experimental measurement has been performed, as a check, in water at temperature T = 20 °C and with a magnetic field H = 10 kG. The obtained value ΔIs = (1.73 ± 0.22)% is in very good agreement with the theoretical one.
Molecular Reorientation in Solid Chlorine
Authors: Obermyer R. T. , Jones E. P.
Published: April 2011

Nuclear quadrupole resonance frequencies and relaxation times of 35Cl and 37Cl in solid chlorine have been measured from 4.2 °K to near the melting point. An analysis of the temperature dependence of the nuclear quadrupole resonance frequencies was made using values for three librational mode frequencies determined previously from Raman spectra. The frequency of a fourth mode was predicted from this analysis. The spin–lattice relaxation times were analyzed using the Bayer model extended by Woessner and Gutowsky and using the librational mode frequencies determined from Raman spectra and the temperature dependence of the nuclear quadrupole resonance frequencies.
Magnetic Aftereffect Due to Hydrogen in NdCo5
Authors: Maartense I.
Published: April 2011

In single crystals of NdCo5 containing small amounts of hydrogen, a.c. susceptibility measurements reveal disaccommodation effects and low frequency loss peaks between 130 and 220 °K. Relaxation times, measured over ~5 decades, fit an Arrhenius relation of the form τ = τ0 exp (E/kT), with E = 0.40 ± 0.02 eV and τ0 = 10−12.3 ± 0.4 s. Hydrogen can be introduced by exposing the sample to the gas, or by etching it in acids; it can be removed by heating in a vacuum at ~750 °K. In the degassed material, additional relaxations, of unknown origin, are found near 375 and 720 °K, with E = 0.7 ± 0.1 and 1.6 ± 0.3 eV respectively. The possible importance of these effects to the coercivity of RCo5 compounds is pointed out.
Intercomponent Momentum Transport and Electrical Conductivity of Collisionless Plasma
Authors: Wilhelm H. E.
Published: April 2011

Based on the Lenard–Balescu equation, the interaction integral for the intercomponent momentum transfer in a two-component, collisionless plasma is evaluated in closed form. The distribution functions of the electrons and ions are represented in the form of nonisothermal, displaced Max wellians corresponding to the 5-moment approximation. As an application, the transport of electrical current in an electric field is discussed for infrasonic up to sonic electron–ion drift velocities.
Ground State Energy of Polaron Bound in a Coulomb Potential
Authors: Matsuura Mitsuru
Published: April 2011

The path integral method is used to obtain an expression, involving a sum over the complete set of solutions for the effective trial Hamiltonian, for the ground state energy of the bound polaron. The numerical calculations of this expression are performed for the hydrogenic and harmonic oscillator effective potentials. The present method together with several previous theories and their numerical results are discussed over a wide range of the electron–phonon coupling constant α and the electron–massive hole coupling β. It is shown that, for the experimentally important region, the present method with the hydrogenic potential yields the lowest energy—slightly lower than obtained by the Larsen's variational calculation.
Electric Field and Temperature Dependence of Positron Annihilation in Argon Gas
Authors: Lee Gregory F. , Jones Garth
Published: April 2011

The annihilation rate of positrons in argon gas has been measured over the temperature range of 135 to 573 K with applied d.c. electric fields per unit gas density up to 35 V cm−1 amagat−1. An analysis of these data was carried out assuming that the annihilation rate and the momentum-transfer rate can both be approximated by functions of the form AνB over this velocity range. Results of the analysis indicate a strong velocity dependence for both the annihilation rate and the momentum-transfer rate. For velocities in atomic units [Formula: see text], the annihilation rate could be represented by va(ν)/D = (1.195 × 106) ν−0.480 s−1 amagat−1 over the velocity range: 0.03 to [Formula: see text]. The momentum-transfer rate was similarly determined as ν(ν)/D = (2.11 × 1011) ν−0.49 s−1 amagat−1. The statistical errors in these results are velocity dependent, with the largest being 16%. A modified effective range parameterization of the momentum-transfer cross section gives a zeroth-order scattering length of A0 = (−4.4 ± 0.5)a0 for positron–argon collisions.No evidence of a velocity dependence in the orthopositronium quenching rate at room temperature was detected.
Dielectric Loss Measurements on Nonpolar Liquids in the Microwave Region 8 to 12 GHz
Authors: Dagg I. R. , Reesor G. E.
Published: April 2011

The results of dielectric-constant measurements on a number of low-loss liquids in the microwave frequency region from 8 to 12 GHz are reported. An improved wave-guide technique is described which gives precise values of the real part of the dielectric constant and improved accuracy in determining the dielectric loss. Liquids measured include the alkane series : n-pentane, n-hexane, n-heptane, n-nonane, n-decane, and n-dodecane. Results for cyclohexane and carbon tetrachloride are also given for comparison with those results of other workers. The data for the loss tangent for the alkane series of liquids are compared with previous results in the 18 to 37 GHz region.
Electron Paramagnetic Resonance and X-ray Studies of the Phase Transformation in Pb3P2O8
Authors: Ng H. N. , Calvo C.
Published: April 2011

The compound Pb3P2O8 has a low temperature monoclinic phase with space group C2/c and a high temperature phase with space group [Formula: see text], both with two crystallographically inequivalent cationic sites. X-ray data taken at five temperatures have indicated that an F-centered monoclinic cell is developed prior to its transition to the rhombohedral phase. The EPR spectra at room temperature show that Mn2+ substitutes only at the cationic site on the twofold axis. A phase transition occurs at 185 °C and approaching this temperature from below the magnetic axes in the ac plane rotate continuously, by about 40°. At 185 °C the Z axis coincides with the c axis of the hexagonal cell (a* axis of the monoclinic cell). The crystal field splitting parameter b20 increases from −423 G to −222 G while b22 goes from 280 G to zero. A model based on the theory of Blume and Orbach for the zero-field splitting and with point charges as the source of the electric field is used to relate the EPR parameters to the atomic displacements.
A High Resolution Neutron Camera for Diffraction Experiments
Authors: Stinson R. H. , Egelstaff P. A. , Holden T. M.
Published: April 2011

An area detector for thermal neutrons which uses track etch techniques has been designed and tested. In the method neutrons are captured in a 6Li foil and emergent α particles and tritons are recorded in a cellulose nitrate film. High spatial resolution is achieved, although the detection efficiency for 1 Å neutrons is small.
Numerical Solution of the Coupled Steady State Gain Equations for Stimulated Backward Scattering in Absorbing Fluids
Authors: Enns R. H. , Rangnekar S. S.
Published: April 2011

A numerical solution to the problem of steady state stimulated backward scattering of light in absorbing fluids is presented. The solution is compared with Tang's solution to the corresponding problem in transparent media.
High Field Magnetoresistance and Quantum Oscillations in Iron Whiskers
Authors: Angadi M. A. , Fawcett E. , Rasolt Mark
Published: April 2011

[100] and [111] iron whiskers were measured to determine the origin of open orbits responsible for anisotropy of the high field magnetoresistance. The marked strain dependence of the minima resulting from [Formula: see text] open orbits permits their unambiguous identification as resulting from magnetic breakdown at a symmetry degeneracy, de Haas–Shubnikov oscillations were observed, and complementary de Haas–van Alphen measurements showed the lower frequencies (in the range 1.2–1.5 MG) to correspond to a hole pocket of the minority spin Fermi surface.
Nitrogen Implanted Germanium: Damage, Lattice Location, and Electrical Properties
Authors: Campbell A. B. , Mitchell J. B. , Shewchun J. , Thompson D. A. , Davies J. A.
Published: April 2011

The radiation damage, implanted atom location, and electrical properties of nitrogen implanted germanium have been studied following anneals in the temperature range of 300–700 °C. Helium ion backscattering was used to measure the damage while two nuclear reactions, the 14N(d, α)12C and the 15N(p, α)12C, were used together with channeling techniques for the atom site location study. The results indicate that ~85% of the implanted nitrogen was located on nonsubstitutional sites, and also that the nitrogen did not outdiffuse from the germanium for anneals as high as 700 °C. The I–V characteristics of mesa structures formed in the implanted germanium indicate that, nitrogen had not become a donor in germanium.
The Rayleigh – Brillouin Spectrum of Normal and Parahydrogen: A Test of Model Solutions of the Wang–Chang Uhlenbeck Equation
Authors: Hubert M. , May A. D.
Published: April 2011

This paper reports the observation at high resolution of the Rayleigh–Brillouin spectrum of normal and parahydrogen at room temperature. The spectra are compared with a number of kinetic model calculations based on the Wang–Chang Uhlenbeck equation. It is concluded that n-H2 behaves effectively as a system characterized by a single relaxation time for the internal degrees of freedom and that the S6 model of Tenti et al. gives a very good description of the Rayleigh–Brillouin spectrum of a molecular gas at low and medium densities. At higher densities the models fail because the Wang–Chang Uhlenbeck equation is no longer valid.
Etude de la transition A6Σ+–X6Σ+ de l'oxyde de manganèse MnO
Authors: Pinchemel B. , Schamps J.
Published: April 2011

In order to obtain information relating to the electronic structure of MnO, the visible system of this molecule has been photographed from an arc at a low pressure of oxygen. New bands have been observed. The rotational analysis of the 1–0 band has shown that this system comes from a A6Σ+–X6Σ+ transition, the lower state of which is the ground state of MnO. The rotational and spin–spin constants of the two states involved in the transition have been determined.
Méthode du moment angulaire inversé. Partie II : Application aux problèmes hyperfins diatomiques
Authors: Féménias J-L. , Athénour C.
Published: April 2011

We present a straightforward method of calculation in rotational molecular problems based on the theory of reversed angular momentum (MI theory) previously discussed. After some general remarks and calculations, we test this method by calculating some well known hyperfine matrix elements in diatomic problems, showing thus its easy handling. The first experimental verification relative to intensity factors in hyperfine diatomic transitions that the method enabled us to calculate, is presented with a brief survey of the recent experimental results obtained from the analysis of the [Formula: see text] system of NbN.
Effect of a Conducting Overburden on the Fields of a Buried Dipole Source
Authors: Ramaswamy V. , Dosso H. W.
Published: April 2011

Analytical solutions for the low frequency electromagnetic fields of a dipole source situated in the lower layer of a two layer conductor are derived. The sources considered are a vertical electric dipole, a horizontal electric dipole, and a horizontal magnetic dipole. The numerical results discussed in this paper describe the general behavior of the electric and magnetic fields for various upper layer conductivities, upper layer thickness, and source depths. The results are of interest in the application of electromagnetic techniques to locate miners trapped underground following a mine disaster.
N2O and H2O Atmospheric Thermal Emissions
Authors: Harrison A. W.
Published: April 2011

Atmospheric thermal emission spectra 4.1–6.3 μm have been measured at a spectral resolution of 140 Å under clear skies for low ground temperatures (~273 K) and low absolute humidities (~1.6 g m−3). Specific emission features attributed to atmospheric H2O and N2O have been interpreted in terms of a simple layer model of the atmosphere. Spectra obtained from a brown smog and an ice fog urban atmosphere are compared with spectra from a clear atmosphere.
Electron Excitation in Noble Gases
Authors: Barros H. G. P. Lins De , Brandi H. S.
Published: April 2011

Calculations for cross sections for some states of Ne excited by electron impact have been carried out. A parametrization of total and differential cross section in the Born–Ochkur approximation has been proposed. Using this parametrization and appropriate wave functions for the states involved in the collision processes, differential and total cross sections have been calculated. The results have shown that this parametrization is very convenient to study this type of problem.
Kinetic Theory of Nuclear Magnetic Relaxation of Polyatomic Molecules
Authors: Sanctuary B. C. , Snider R. F.
Published: April 2011

Nuclear magnetic relaxation of polyatomic gases is discussed in terms of a Boltzmann equation. Weak intramolecular coupling is used to obtain formal expressions for the spin relaxation times and the chemical shift. In particular, restrictions arising from spin symmetry and from molecular point group symmetry are included.In carrying out the weak coupling calculation, it is necessary to approximate the time dependence of the rotational degrees of freedom. Here this is done with the aid of the 'rotating frame approximation', that is, all polarizations in the gas rotate in phase with the spins. This approximation is discussed from several points of view, including a mathematical discussion for a particular example. Finally the rotating frame approximation is related to the memory effects of general relaxation theory.