bluuebunny/crossref_metadata_2025 huggingface dataset:
The infrared spectrum of the ν2 fundamental band of the molecular ion
Authors: Watson J. K. G. , Foster S. C. , McKellar A. R. W.
Published: April 2011

Measurements of 60 infrared lines of the molecular ion [Formula: see text] in the region 1810–2180 cm−1 are reported. These lines are observed in a hollow-cathode discharge through deuterium gas as absorptions of tunable diode-laser radiation. The present data are combined with 45 lines (five in common) from laser ion-beam experiments of Wing and colleagues in a detailed analysis of the ν2(e′) band of [Formula: see text]. Altogether, 84 lines are fitted with a standard deviation of 0.0024 cm−1, employing a 25-parameter effective Hamiltonian that uses a Padé representation of the centrifugal distortion effects. Five other lines assigned to specific transitions have larger residuals, while 11 lines that may be rotationally or vibrationally hotter remain unassigned. The value obtained for ν2 is 1834.669 cm−1, and both it and the observed ground-state combination differences and principal molecular parameters agree well with ab initio calculations. The values of the higher order parameters in the effective Hamiltonian do not agree well with theoretical perturbation formulas because of the slow convergence of perturbation series for this light molecule.
The soliton capture of conversion electrons from an atom attached to a molecular chain
Authors: Ajazaj H. , Shemsidini Z. , Stepančić B. , Žakula R. B.
Published: April 2011

In this paper we have calculated an expression for the probability of capture of atomic, low-energy conversion electrons by Davydov's solitons, the atom being attached to a one-dimensional molecular crystal.
On the diagnosis of X-ray satellites and hypersatellites for low-Z atoms
Authors: Mukherjee Tapan Kumar , Sengupta Sankar
Published: April 2011

In this paper, the idea of the Moseley plot is extended to X-ray satellites and hypersatellites with great advantage for atoms having low atomic number. It gives a fair understanding of the assignments of the X-ray satellite and hypersatellite lines.
Rotational analysis of the B2Σ+ – A2Πi system of the 12C16O+ molecule
Authors: Jakubek Z. , Kepa R. , Para A. , Rytel M.
Published: April 2011

The three bands (0–0, 1–0, 0–1) of the B2Σ+ – A2Πi system of the 12C16O+ molecule have been photographed at high resolution. In total, 824 lines were measured, from which 608 were fitted by a nonlinear least squares method to determine 33 molecular constants. The band-by-band results were merged to obtain 23 molecular constants for the B2Σ+, ν = 0 and 1, and A2Πi, ν = 0 and 1, states. The Λ-doubling constants and spin-orbit constants in the A2Πi, ν = 1 state and spin-rotation constants in the B2Σ+, ν = 0 and 1 states were obtained for the first time, and other constants were defined more precisely.
Intermolecular and intramolecular contributions to the proton spin-lattice relaxation of the liquid crystal 4-cyano-4′-n-pentyl-d11-biphenyl: nematic and supercooled nematic regions
Authors: Lewis John S. , Tomchuk E. , Bock E.
Published: April 2011

The intermolecular and intramolecular contributions to proton spin-lattice relaxation in 4-cyano-4′-n-pentyl-d11-biphenyl (5CB-d11) have been measured as a function of temperature and frequency. The theories of relaxation in nematic liquid crystals are presented in a form suitable for nonlinear least squares fitting to the data, and the experimental results compared with appropriate theories. It is found experimentally that it is not possible to distinguish between the Freed and the Ukleja et al. theories on intramolecular spin-lattice relaxation or between the Zumer–Vilfan and the Ukleja et al. theories on intermolecular spin-lattice relaxation. All three theories are in more or less equal qualitative agreement with experimental results and yield fitting parameters of comparable physical plausibility.
Beam-energy conditions for efficient ion-beam mixing
Authors: Cherian Sunny , Reid Ian , Gecim Huseyin S.
Published: April 2011

To investigate the energy dependence of ion-beam mixing, Ni films approximately 80 nm thick were deposited on (100) Si wafers and bombarded with energies from 100 to 400 keV by Ar ions, at doses up to 1017 ions∙cm−2. The thickness and composition of the mixed layer were determined by Rutherford backscattering spectroscopy (RBS). Some samples were also investigated using Auger depth-profile analysis. At 100 keV, no mixing was detected, but by 200 keV, and up to 400 keV, the mixed layer grew initially at 15 ± 2 nm per 1016 ions∙cm−2. The rising efficiency in the energy range of 100–200 keV corresponded with the expected increase in energy deposited at the Ni–Si interface. However, the constant efficiency observed between 200 and 400 keV could not be explained in terms of deposited energy. The composition of the mixed layer was graded, but had approximately the overall composition of Ni2Si, and became approximately NiSi at high doses. For bombardment doses that were too low to produce detectable mixing by themselves, they were shown to enhance the formation of thermally grown silicides. During the thermal growth of this silicide, oxygen was found to accumulate at the Ni–silicide interface. This oxygen accumulation might have impeded the diffusion of Ni to such an extenet that another silicide phase formed before all the Ni film was consumed.
Externally stimulated excitonic system
Authors: Djajić-Jovanović R. P. , Ćirić D. M. , Marinković M. M. , Tošić B. S.
Published: April 2011

The behaviour of the excitonic system stimulated by an external microscopic electric field is analyzed. The mathematical analysis is applied using the Green function of the type [Formula: see text]. This opens the possibility of strictly applying Wick's theorem for the decoupling. The pairing of operators is performed for the same, as well as for different, moments of time. Using the Green function calculated in this way, we derive the dielectric constant and the refraction and absorption indices. It is shown that the presense of external stimulation shifts the principal absorption and refraction peaks towards higher frequencies, making them, at the same time, less prominent. Thus, the conclusion is that external stimulation cannot be used to construct better absorbers of the light energy although external stimulation is able to increase absorption as well as the refraction at frequencies higher than the resonant one.
Electroionization study of ethylene: ionization and appearance energies, ion-pair formations, and negative ions
Authors: Plessis Pierre , Marmet Paul
Published: April 2011

Monoenergetic electron-impact threshold ionization and appearance curves of very high sensitivity of ethylene and all fragments containing at least one carbon atom are analyzed in detail. Ionization or appearance energies are measured for all ions, including the [Formula: see text] fragment. Structures are observed in the immediate [Formula: see text] threshold region, which are attributed to hot bands and to Rydberg autoionizing states. [Formula: see text],[Formula: see text] and [Formula: see text] ion-pair formations are reported for the first time. Simultaneous production of positive and negative ions is seen to be a common mechanism by electron impact. Appearance energies of some fragments are several electron volts lower than those of previous works.
Expansion of symmetric group products and states
Authors: Mirman R.
Published: April 2011

The expansions of the product of states of subgroups of a symmetric group in terms of states from the full group, and of a state of the full group in terms of products of subgroup states, are studied, with a particular emphasis on understanding them using the properties of the labeling tableaux. The question of the appearance of the completely symmetric representation of one subgroup in the expansion of a state is emphasized.
Structure and forces in liquid metals and alloys
Authors: March N. H.
Published: April 2011

The so-called force equation relating the pair function g(r), the three-body correlation function, and the assumed pair potential [Formula: see text] is first discussed from the standpoint of extracting force fields from diffraction measurements of the structure factor of liquid metals. Recent progress has been possible in this area by making use of the modified hypernetted-chain approximation, including the bridge function.A discussion is then given that relates the bridge function to vacancy-formation energy in hot close-packed metals, and also to the structure factor of the liquid. The possible role of cooperative effects in liquid metals on the inversion procedure is considered, as is the relation between three-body direct and total correlation functions.Pressing further the relation between liquid structure just above the melting point and the hot solid, advances in the theory of freezing are considered. The so-called Verlet rule on the height of the principal peak of the structure factor at melting is considered in relation to Lindemann's Law.After a brief discussion of the relation between structure and forces in liquid-metal alloys, the theory of inhomogeneous systems used to discuss freezing is applied to liquid surfaces, and in particular to surface segregation. The final topic treated is that of the critical constants of the fluid alkali metals, where it is argued that Coulomb forces are of decisive importance.
Liquid metals and semiconductors under pressure
Authors: Endo Hirohisa , Tamura Kozaburo , Yao Makoto
Published: April 2011

Studies on the electronic and thermodynamic properties of liquid metals and semiconductors at high temperatures and high pressures are reviewed. A substantial decrease of volume for liquid alkali metals is brought about by the application of pressure. The interference function of liquid alkali metals with high pressure can be described by the hard-sphere model with a fixed packing fraction when one proceeds along the melting curve. For liquid Cs, the s–d resonance scattering plays an important role in the electron-transport properties at high pressures. In expanded liquid Hg, a metal–nonmetal transition occurs at a density near 9 g∙cm−3, and anomalous behaviour is found in the thermodynamic properties such as equation-of-state and density fluctuations. At low densities, substantial volume contraction and a large increase in conductivity are brought about by the addition of a small amount of Bi. At high temperatures and high pressures, liquid Se is transformed from a semiconducting state to a metallic state, accompanied by modification of chain structure. The measurements of sound velocity and optical properties reveal that the temperature and pressure at which the semiconductor–metal transition occurs are lowered by the addition of Te. It is suggested that the semiconductor–metal transition observed in liquid Se is induced by increasing fluctuations in the interchain distance and increasing interchain coupling. The electronic properties of liquid Se are substantially changed by the addition of impurity elements such as alkalis and halogens. Modification of chain structure is associated with the charge transfer between Se chains and impurity elements. To understand how the interchain coupling affects the electronic properties of liquid Se, the properties of the isolated Se chains confined in the pores of mordenite are studied. The pressure effects on the two-phase separation of liquid binary mixtures, such as metal–metal, metal–semiconductor, and metal – ionic salt mixtures, are also discussed.
Studies on surfaces of Zr(0001) that contain oxygen and show (2 × 2)-type low-energy electron diffraction patterns
Authors: Wong P. C. , Mitchell K. A. R.
Published: April 2011

Oxygen chemisorption on the Zr(0001) surface has been studied in the low-exposure regime with Auger electron spectroscopy and measurements of the width of a half-order low-energy electron diffraction (LEED) beam. The new observations and conclusions are as follows. (i) The diffusion of O atoms to the bulk effectively starts at around 236 °C. (ii) Oxygen adsorbs in a disordered state at room temperature and orders sufficiently to show a (2 × 2)-type LEED pattern on heating to 220 °C. (iii) With increasing O exposure, 1/4, 1/2, and 3/4 of the available adsorption sites can be systematically filled, while showing the apparent (2 × 2)-LEED pattern, prior to the establishment of an ordered (1 × 1)-O surface. (iv) The process in (iii) can be reversed by starting with the (1 × 1)-O surface and heating above 236 °C.
Further observations with low-energy electron diffraction for the Cu(100)-(2 × 2)-S surface structure: spot-profile and multiple-scattering analyses
Authors: Zeng H. C. , Mitchell K. A. R.
Published: April 2011

This study involves analyses by low-energy electron diffraction (LEED) for surface structures formed by S adsorbed on the (100) surface of copper. A LEED spot-profile investigation for a surface that shows a (2 × 2) diffraction pattern, supplemented by the effects of antiphase scattering, indicates that the domain boundaries do not correspond to microregions with local c(2 × 2) structure but rather that the beam elongations observed are consistent with local regions of the c(4 × 2) type in the approach to ¼ monolayer coverage. Diffracted-beam intensity-versus-energy curves calculated for the (2 × 2), c(2 × 2), and (2 × 1) translational symmetries, for fixed adsorption sites and S–Cu interlayer spacings, show that the intensity curves of corresponding beams can remain closely independent of actual symmetry and coverage even as the polar angle of incidence θ departs from the normal (although differences between the curves do tend to increase with θ). This observation can help simplify calculations of LEED intensities from adsorption systems with large unit meshes when the adsorbed species are in a constant environment; also, it provides an economical route for checking values of θ estimated from positions of diffraction spots on conventional LEED screens. When the latter is tested on the off-normal intensity data used in our previous analysis of the Cu(100)-(2 × 2)-S surface structure (Surf. Sci. 177, 329 (1986)), θ is indicated to be modified by 1° from the previously estimated value, but this does not significantly affect the determined S–Cu nearest neighbour bond length.
Ultraviolet and visible fluorescence produced by controlled electron impact on SO2
Authors: Miller Jr. K. , Becker K.
Published: April 2011

The emission spectrum in the ultraviolet and visible region of the optical spectrum (2000–8000 Å) produced by electron impact on SO2 has been studied under single-collision conditions. Two major features have been observed: the A3Π → X3Σ− system of the SO fragment (2400–2650 Å) and a broad, unstructured emission extending from 2500 to 4600 Å, which has been identified as arising from the excitation–de-excitation of the SO2 molecule. Absolute emission cross sections for the SO system have been measured for incident electron energies from threshold to 500 eV, and a value of 5.2 × 10−18 cm2 has been found at 100 eV with an uncertainty of approximately ± 18%. The maximum in the emission cross section is at 30 eV (6.5 × 10−18 cm2). The measured threshold of 11.5 eV is about 1 eV above the minimum energy required for partial fragmentation of SO2 into SO (A3Π) and a ground-state oxygen atom, indicating that very little translational kinetic energy is carried away by the dissociation fragments in the near-threshold region. A complex excitation–de-excitation scheme involving three different excited states of the SO2 molecule, e.g., the 8a1 → 3b1, 1.3B1 states and the 5b2 → 3b11A2 state, produces the broad 2500–4600 Å emission feature. At 100 eV, an emission cross section of 12.2 × 10−18 cm2 has been measured for the SO2 system. Several O1 and S1 emission lines have also been identified, yet they are found to be extremely weak with estimated emission cross sections smaller than 10−21 cm2 at 100 eV impact energy.
Polarization transfer in (p, n) reactions
Authors: Taddeucci T. N.
Published: April 2011

Polarization-transfer studies for (p, n) reactions with normally polarized (N-type) beams have been pursued at the Indiana University Cyclotron Facility, Bloomington, IN, since 1983. A variety of targets having values of A ranging from 2 to 90 have been studied at 0° for bombarding energies between 80 and 200 MeV. Transitions to well-resolved final states in the lighter nuclei have yielded data that lend plausibility to distorted-wave impulse approximation interpretations of intermediate-energy nucleon–nucleus reactions. Measurements on heavier nuclei have revealed interesting nuclear-structure effects at high excitation energies.
(n, p) studies at the University of California at Davis
Authors: Brady F. Paul
Published: April 2011

In recent years, we have been developing facilities for studying neutron-induced reactions at energies near 60 MeV. An important aspect of this program has been the development of capabilities for (n, p) reaction studies. Early data on a range of nuclei taken first with simple telescopes and later with large-area multiwire chamber telescopes are presented. Recently, a magnet and dual target system have been installed, which allow (n, p) measurements down to 0°. Spectra have been measured for 12C, 13C, 14C, and 90Zr(n,p) for 0°–40° at 65 MeV. The 90Zr data confirm the recently discovered isovector monopole resonance and provide evidence for two new isovector giant resonances: the spin monopole and the isospin T + 1 component of the quadrupole.
Isovector excitations in nuclei with composite projectiles: (3He, t), (d, 2He), and heavy ions
Authors: Ellegaard Clive
Published: April 2011

A variety of charge-exchange reactions involving complex particles has been used to study the response of a nucleus to a spin–isospin probe. The reactions have been the (3He, t) reaction, the (d, 2He) reaction, and reactions with the heavy ions 12C, 14N, 16O, and 20Ne as beam and charge exchange both ways. With all reactions, transitions are observed to the low-lying giant-resonance region, the quasi-elastic region, and the Δ region. With the (d, 2He) reaction, the spin structure of the response is studied.
New facilities for nucleon charge exchange at the Los Alamos Meson Physics Facility
Authors: McClelland J. B.
Published: April 2011

A progress report is given on the upgraded facilities at the Los Alamos Meson Physics Facility to support (p, n) and (n, p) charge-exchange studies at intermediate energies. These include a beam-swinger system, a 600 m flight path and neutron polarimeter for (p, n) reactions, and a medium-resolution spectrometer with a focal-plane polarimeter for (n, p). A general overview of the physics program being planned is also presented.
Abstract: Enhancement of the nuclear spin response in 300 MeV inelastic proton scattering
Authors: Fergerson R. W. , Glashausser C.
Published: April 2011

The spin transfer ΔS = 1 response function of 48Ca and 54Fe has been determined by measuring the spin-flip probability Snn for 300 MeV proton inelastic scattering at the Los Alamos Meson Physics Facility, Los Alamos, NM, and TRIUMF. Data have been recorded between 3° and 15° for excitation energies up to about 40 MeV. Except at the largest angles, Snn in the 35–40 MeV range is more than 50% above the isospin-averaged values from free NN scattering, and 25 to 50% above a calculation using Glauber theory and a slab-response function. This enhancement observed with the supposed weakly spin-dependent (p,p′) probe should be contrasted with the apparent quenching observed with the strongly spin-dependent (p,n) probe. There, at 0° and 40 MeV, Snn is only slightly above the (p,p′) values and well below the free values.
Effect of ion temperature on ion-acoustic solitary waves: a pseudopotential approach
Authors: Roychoudhury R. K. , Bhattacharyya Sikha
Published: April 2011

Using the pseudopotential approach of Sagdeev, we have found analytically exact conditions for the existence of solitary waves for a system of collisionless plasmas with a mixture of warm ion-fluid and hot isothermal electrons. The analytical soliton solution for small amplitudes has also been obtained and has been compared with the published result. It is found that the finite ion temperature considerably modifies the restriction on the Mach number obtained for cold ions.
Ambiguïtés de l'hamiltonien d'ordre 3 de la triade (0200, 0101, 0002) des molécules XY4
Authors: Pierre C. , Loete M. , Pierre G.
Published: April 2011

Ambiguities among parameters of the effective Hamiltonian for the three interacting states 0200, 0101, 0002 of tetrahedral XY4 molecules are studied. Using the contact transformation technique in tensorial form, we calculate relations between parameters of type q4 and q4J. We show how these relations allow a reduction of the Hamiltonian to the third order of the approximation.
Statistical mechanics of quantum one-dimensional damped harmonic oscillators: II
Authors: Borges O. N. , Ribeiro L. A. Amarante
Published: April 2011

We show that the Caldirola–Kanai Hamiltonian of the one-dimensional damped oscillator describes in a specified basis a Gaussian, Markoffian process, in the weak coupling limit. We also discuss which assumption makes the process stationary and clarify the relationship with the master-equation approach.
Search for the shape-isomeric gamma decay in muonic uranium
Authors: Ahmad S. , Beer G. A. , Olaniyi B. H. , Olin A. , Kaplan S. N. , Mireshghi A. , Macdonald J. A. , Häusser O.
Published: April 2011

A search for the gamma decay of nuclear shape isomers excited by the atomic cascade of a negative muon has been undertaken in 236U and 238U. No candidate gammas have been found with yields greater than 0.2% per stopping muon. Muon capture lifetimes in 235U, 236U, and 238U are also reported.
Photoionization of magnesium
Authors: Fischer Charlotte Froese , Saha Hari P.
Published: April 2011

Photoionization from the 3s subshell of magnesium is investigated in the energy region near threshold where several resonances have been observed. Theoretical cross sections are reported. The latter have been computed using the multi-configuration Hartree–Fock approximation extended to include a continuum function. Results are compared with other theories and experiment.
H218O: line positions and intensities between 9500 and 11 500 cm−1. The (041), (220), (121), (300), (201), (102), and (003) interacting states
Authors: Chevillard J. -P. , Mandin J. -Y. , Flaud J.-M. , Camy-Peyret C.
Published: April 2011

The spectrum of 18O-enriched water vapor has been recorded between 9500 and 11 500 cm−1, with the aid of a Fourier-transform spectrometer. Its analysis has allowed the determination of 419 accurate rotational energy levels belonging to seven interacting vibrational states of H218O: (041), (220), (121), (300), (201), (102), and (003). Moreover, 622 line intensities belonging to the 4ν2 + ν3, 2ν1 + 2ν2, ν1 + 2ν2 + ν3, 3ν1, 2ν1 + ν3, ν1 + 2ν3, and 3ν3 bands have been measured with an average uncertainty of 6%.
A study of the rapidity-gap distribution of showers by eliminating phase-space effects
Authors: Tufail A. , Ahrar H. , Ahmad S. , Zafar M. , Shafi M.
Published: April 2011

The rapidity-gap method has been used to check the formation of clusters in multiparticle production at 50, 340, and 400 GeV∙c−1. Pseudoevents have been generated to eliminate the phase-space effects from the rapidity-gap distributions.
Band-shape analysis of an infrared double transition in CO2 + N2 gas mixtures
Authors: Brodbeck C. , Bouanich J. P. , Penner A. R. , Meinander N. , Tabisz G. C.
Published: April 2011

Band shapes of the double vibrational transition in the infrared absorption spectrum of N2 (fundamental) + CO2 (ν3) are presented for a series of total pressures of the gas mixtures. Normalized profiles calculated from the convolution product of the infrared ν3, band of CO2 perturbed by N2, the isotropic and anisotropic Raman bands of N2 in a mixture with CO2, and a translational broadening function are in satisfactory agreement with the experimental profiles.
Operator regularization in the Weinberg–Salam model
Authors: Chowdhury A. M. , McKeon D. G. C.
Published: April 2011

The technique of operator regularization is applied to the Weinberg–Salam model. By directly regulating operators that arise in the course of evaluating path integrals in the background-field formalism, we preserve all symmetries of the theory. An expansion due to Schwinger is employed to compute amplitudes perturbatively, thereby avoiding Feynman diagrams. No explicitly divergent quantities arise in this approach. The general features of the method are outlined with particular attention paid to the problem of simultaneously regulating functions of an operator A and inverse functions upon which A itself depends. Specific application is made to computation of the one-loop contribution to the muon–photon vertex in the Weinberg–Salam model in the limit of zero momentum transfer to the photon.
Nonlinear transport coefficients and plane Couette flow of a viscous, heat-conducting gas between two plates at different temperatures
Authors: Eu Byung Chan , Khayat Roger E. , Billing Gert D. , Nyeland Carl
Published: April 2011

By using the example of plane Couette flow between two plates maintained at different temperatures, we present a method of calculating flow profiles for rarefied gases. In the method, generalized hydrodynamic equations are derived from the Boltzmann equation. They are then solved with boundary conditions calculated by taking into consideration the interfacial interaction between the surface and the gas molecule. The nonlinear transport coefficients employed in the generalized hydrodynamic equations are obtained from the Boltzmann equation by means of the modified-moment method. The profiles calculated are in agreement with the Liu–Lees theory as long as the boundary values are in agreement. It is found that the viscous-heating effect has a significant influence on the temperature and velocity profiles. The nonlinearity of transport coefficients also has significant effects on the profiles as the Knudsen and Mach numbers increase.
A re-examination of the 19F(n,γ)20F reaction
Authors: Kennett T. J. , Prestwich W. V. , Tsai J. S.
Published: April 2011

A re-examination of the 19F(n,γ)20F reaction has been conducted in which several factors were selected for optimization. These included sample purity, high statistical precision and hence sensitivity, sufficient energy precision and resolution to permit confident application of the Ritz combinational method, and efficiency calibration to test intensity balance in a meaningful way. The results obtained, besides increasing level-energy precision, revealed the likely existence of a new level and failed to agree with some aspects of earlier studies. The degree with which direct capture plays a role in this reaction was also explored and found to account for 35–50% of the 9 mb capture cross section. The neutron separation energy was found to be 6601.36 ± 0.05 keV, based upon the mass scale. A new level, forming a doublet with that at 3587 keV, was inferred to be at 3590 keV.
Transmission d'électrons de 0–15 eV à travers des films minces de solides bio-organiques à 300 K : application au tryptophane
Authors: Leclerc Grégoire , Goulet Thomas , Cloutier Pierre , Jay-Gerin Jean-Paul , Sanche Léon
Published: April 2011

We present an experimental method for measuring low-energy (0–15 eV) electron transmission through bio-organic, solid, thin films at 300 K. This method is used to determine the energy of the first electronic transitions and the energy of the lowest conduction level of an electron in those solids. By measuring the density and thickness of the films precisely and analyzing the experimental data with a theoretical simulation model, it is possible, for the first time, to estimate values of the interaction cross sections for low-energy electrons in a biological solid. As an illustration of the method, results obtained for tryptophan are presented. [Translated by the journal]
Multiphoton ionization of the hydrogen atom
Authors: Haque S. N. , Mustafa M. G.
Published: April 2011

In this paper, we have presented the analytical and numerical calculations of the ionization rate (σ/I in units of cm4∙W−1) for the hydrogen atom in the ground state. The summation over infinite intermediate states, discrete plus continuous, has been carried out using our modified technique based on Bebb and Gold's concept of average frequency. Our method improves the results of Bebb and Gold at all frequencies, and the results obtained are in good agreement with the results of Gontier and Trahin, Chan and Tang, and Klarsfeld.
Noncollinear spin structures
Authors: Coey J. M. D.
Published: April 2011

A survey of experimental results on noncollinear spin structures in crystalline and amorphous ionic materials is given. The occurrence of coherent helical, triangular, and canted structures in pure crystals is related to the presence of competing interactions: topologically frustrated antiferromagnetic superexchange, positive and negative exchange coupling with different shells of neighbours, symmetric and antisymmetric exchange, or exchange and single-ion anisotropy. These ideas are extended to crystal surfaces, disordered crystals, mixed crystals, amorphous compounds, and complex multicomponent glasses. Random noncollinear structures found in all these materials are due to randomly competing interactions. A distinction is made between isotropic random structures, where spin correlations are very short-ranged in all directions, and those structures where comparatively long-range longitudinal ferro-, antiferro-, or ferrimagnetic correlations coexist with transverse spin freezing having correlations only on the scale of nearest neighbour distances. A generalized magnetic phase diagram for diluted random magnets is presented. It is emphasized that important aspects of those systems now known as "reentrant spin glasses" had already been described in diamagnetically substituted ferrites many years previously.
Recent advances in the magnetism of fine particles
Authors: Haneda K.
Published: April 2011

Recent advances in fine-particle magnetism are reviewed from an experimental point of view, especially with reference to surface magnetism and also to magnetism in low dimensions. Emphasis is placed on intrinsic properties as compared with the behavior of bulk ferromagnets. The spontaneous magnetization is discussed in connection with magnetic-surface reconstruction. Other intrinsic parameters such as magnetic hyperfine fields and magnetic anisotropy of fine particles are also discussed. Emphasis is placed on information provided by Mössbauer spectroscopy.Recent development in applications based on fine-particle magnetism are presented, including the following topics: magnetic fluids, particulate magnetic-recording media, permanent magnets, and catalysts. Finally, some future research prospects are reviewed.
Applications of 61Ni Mössbauer spectroscopy
Authors: McCammon C. A.
Published: April 2011

The number of 61Ni Mössbauer studies, although small, indicates that definitive measurements are possible once experimental obstacles have been overcome. The experimental method and hyperfine interactions in 61Ni are discussed briefly, followed by a review of results obtained from 61Ni Mössbauer experiments during the last 10 years. The results are discussed in relation to the determination of spin structures, the study of electronic transitions, and the study of hyperfine interactions.
A study of quasi-crystalline Al–Fe alloys by Mössbauer-effect spectroscopy and diffraction techniques
Authors: Woude F. van der , Schurer P. J.
Published: April 2011

After an introduction to quasi crystals, special attention is paid to icosahedral Al6(Cr0.7Fe0.3) and decagonal Al7(Mn1−xFex)2. These alloys have been studied with Mössbauer-effect spectroscopy and diffraction techniques. Isomer-shift and quadrupole-splitting data on the icosahedral alloys are successfully described with a Mackay cluster. The X-ray diffractogram of pure decagonal Al7(Mn1−xFex)2, x = 0 and 0.3, has been indexed with a basis-vector set that is closely related to the icosahedral set.
Dielectric relaxation of nitromethane, some nitriles, and their mixtures in dilute solutions
Authors: Madan M. P.
Published: April 2011

The dielectric absorption of nitromethane, benzonitrile, and acetonitrile and their binary mixtures has been studied in the microwave region over a range of temperatures in dilute benzene solutions. The data on static and optical permittivities at 20 °C have also been obtained, from measurements at 100 kHz and from measuring the refractive index for sodium-D lines, for a few cases. These data have been used to determine the relaxation times and the thermodynamic parameters for the activated state. The results obtained have been discussed in terms of the molecular motion of the systems. A new empirical relation has been proposed to represent the relaxation behaviour of a system of two Debye-type polar components in a nonpolar solvent. The relation has been tested, along with a previously suggested relation, by comparing the calculated values with those determined experimentally.
A theoretical study of the fundamental absorption band of solid HD
Authors: Bose S. K. , Poll J. D.
Published: April 2011

A theoretical study of absorption into the fundamental band of solid HD in the neighbourhood of the R1(0) transition is presented. The spectrum, calculated by using a one-phonon approximation, shows qualitative agreement with the experimental absorption curve in the region lying between the Q1(0) and R1(0) transition energies. In particular, we are able to show that the absorption at an energy immediately below that of the R1(0) peak should almost vanish, as observed in the experiment. The role of various dipoles as well as their interference effects is discussed. Such effects are found to be significant near the R1(0) transition peak. The influence of the double-excitation states, in which the rotational and the vibrational excitations reside on two different molecules, is considered. There is no direct absorption into such states, implying the lack of a Q1(0) + R0(0) peak in the spectrum. However, because these states are close in energy to those in which the vibrational and the rotational excitations reside on the same molecule, they somewhat modify the absorption spectrum in the region of the R1(0) peak. Away from this peak, the effect of the double-excitation states on the absorption profile is negligible.
Study of collisional broadening in oxygen lines by high-resolution coherent anti-Stokes Raman spectroscopy
Authors: Ouazzany Y. , Boquillon J. P. , Lavorel B.
Published: April 2011

The Q-branch line widths of oxygen were measured by using high resolution coherent anti-Stokes Raman spectroscopy. The first nine transitions (N = 1–17) were recorded at pressures from 0.094 to 1 atm (1 atm = 101 kPa) at room temperature. The transitions were excited by injection-locked flashlamp-pumped dye lasers of very high spectral quality. A least squares program was employed to fit calculated spectra to experimental spectra by adjusting different parameters. The collisional broadening coefficients obtained were consistent with available Raman data.
Unitary group approach for equivalent electrons. I. Relations between nonorthogonal and orthogonal basis states
Authors: Ross William R.
Published: April 2011

In an earlier paper we obtained orthogonal and nonorthogonal basis states for equivalent electrons using the Lie group U(2l + 1) × SU(2). In this paper we find expressions for the nonorthogonal basis states in terms of the orthogonal basis states.
96Tc levels populated in the (α,n) reaction
Authors: Mach H. A. , Johns M. W.
Published: April 2011

The levels of odd–odd 96Tc have been investigated using the 93Nb(α,nγ)96Tc reaction at an alpha-beam energy of 14 MeV. The experiments involved singles, gamma–gamma coincidences, detailed excitation functions, gamma-ray angular distributions, measurements of the gamma-ray linear polarization coefficients, and electron internal-conversion coefficients. Spin and parity assignments are given with a high degree of confidence to most of the 105 energy levels, which are interconnected by 251 gamma-ray transitions. In particular, a new energy level at 36.24 keV completes a sextet of lowest lying levels ranging in spin from 2+ to 7+ formed by a coupling of an odd g9/2 proton to an odd d5/2 neutron. The structure of 96Tc shows some vibrational features coexisting with a significant configuration mixing. Thus, a quartet of nuclei at the onset of a deformation region at A ~ 100, 94,95Mo and 95,96Tc, provides a challenging ground for testing of the microscopic models and may give further insight into the nature of the neutron–proton interaction in complex nuclei.
Triple differential cross sections for the ionization of helium by intermediate-energy electrons
Authors: Baliyan K. S. , Srivastava M. K.
Published: April 2011

The recent triple differential cross-section data of Jung for the ionization of helium in the coplanar asymmetric geometry at 250 eV incident electron energy is analyzed within the framework of the second Born (B2) and modified Glauber (MG) approximations. At this energy B2 and MG results, although better than those obtained by using the first Born and Glauber approximations, do not lead to a satisfactory description of the experimental data in all the kinematic situations considered here.
A model for a relativistic, many-particle Lagrangian with electromagnetic interactions
Authors: Moore R. A. , Scott T. C. , Monagan M. B.
Published: April 2011

It is shown that the Fokker–Wheeler–Feynman theory for the relativistic modelling of a system of massive, charged, point particles interacting via action-at-a-distance forces, electromagnetic in origin, can be reformulated and reinterpreted so that it retains all of its required physical attributes but is devoid of the absurdities originally ascribed to it. That is, Lorentz covariance, time-reversal symmetry, and particle-interchange symmetry are maintained, whereas lack of causality and the paradox of "discontinuous" forces are removed. The reformulated theory yields a physically acceptable relativistic, many-particle Lagrangian. The Euler–Lagrange equations of motion can be written down for either closed or open systems. For closed systems, a generalized Hamiltonian, linear momentum, and angular momentum are constants of the motion. The concept of an open system is used to show that radiation reaction follows straightforwardly from the Euler–Lagrange equations of motion and their past and present time solutions. It is concluded that the basis for this type of modelling of such systems is now established.
Coulomb wave functions in the theory of the circular paraboloidal waveguide
Authors: LoVetri J. , Hamid M.
Published: April 2011

In this paper it is shown how the Coulomb wave functions, commonly used in the description of a Coulomb field surrounding a nucleus, can be used in the description of electromagnetic fields that are symmetric with respect of [Formula: see text] inside a paraboloidal waveguide. The Abraham potentials Q and U, which are useful in describing fields with rational symmetry, are used to simplify the problem. It is shown that these potentials must satisfy a partial differential equation that when separated yields the Coulomb wave equation of order L = 0. Electromagnetic fields due to simple source distributions inside the paraboloid are expanded in terms of these functions. Specifically, solutions for current-loop sources located in the focal plane of the paraboloid are obtained. The case where the wall of the paraboloidal waveguide is assumed to be perfectly conducting is treated as well as the case where the wall has finite impedance. The finite paraboloid is also considered, and the far field is formulated using Huygen's principle. It is found that for the finite surface-impedance case, the far-field pattern due to a current loop operating at 100 MHz in the focal plane of a paraboloidal reflector of 1 m focal length is different from the perfectly conducting case. Specifically, the pattern seems to be more omnidirectional for the impedance case than for the perfectly conducting case. Numerical results are presented for relevant aspects of the problem.
Nonperturbative quantum chromodynamic vacuum and hadron–hadron scattering
Authors: Nicolaidis A.
Published: April 2011

We investigate the influence of the gluon condensate upon hadron–hadron scattering at intermediate transverse momenta (pT). We treat the gluon condensate as an external field, and we calculate the gluon propagator in such an external field using the heat-kernel expansion. We insert the nonperturbative gluon propagator into the hard-scattering subprocesses, and we derive a formula for hadron–hadron scattering at intermediate pT that contains the usual perturbative component [Formula: see text] and a non-perturbative component that varies as [Formula: see text]. The transition from the [Formula: see text] to the [Formula: see text] regime occurs at [Formula: see text], a value smaller than the actual pT transition value.
A nonrelativistic operator for pion electroproduction
Authors: Dressler Edward T.
Published: April 2011

In this paper, a nonrelativistic operator for pion electroproduction from nuclei is presented. It approximates a combination of pseudovector Born plus Δ-resonance diagrams using a method that does not break up the nucleon propagators into their positive and negative energy parts as was done in previous efforts. This result gives an operator that maintains its gauge-invariance cancellations exactly. Comparisons are made with a sample of photoproduction and electroproduction data.
3d-Shell excitation in photoabsorption of atomic selenium
Authors: Joshi Y. N. , Mazzoni M.
Published: April 2011

The photoabsorption spectrum of the inner 3d-shell excitation of atomic selenium was observed in the 500–170 Å region using the flash-pyrolysis technique. The observations, aided by the Hartree–Fock ab initio calculations and least squares fitted parametric calculations, have lead to the classification of 15 lines in the 4p4–3d94s24p5 transition array and 26 lines in the 4p4–3d94s24p4np transitions. Two series ionization limits have been calculated as 517 500 cm−1 (64.15 eV) and 530 000 cm−1 (67.70 eV).
On the combined Doppler and pressure broadening of nonresonant spectral lines
Authors: Diaz M. A. , Palomares F. , Veguillas J.
Published: April 2011

An explicit spectral function for nonresonant transitions has been derived that includes pressure broadening, Doppler broadening, and diffusional narrowing. This has been accomplished through a kinetic-equation approach. The kinetic equation has been resolved by using an extension of the Bhatnagar–Gross–Krook collision model to inelastic collisions, characterized by two collision frequencies: one associated with elastic collisions and the other associated with inelastic ones. The high- and low-density limits have been discussed, and the standard formula for Debye relaxation has been reproduced. Finally, a discussion concerning the above aspects and their possible extensions has been included as well.
Beam-foil lifetime measurements in Pb III and Pb IV
Authors: Ansbacher W. , Pinnington E. H. , Kernahan J. A.
Published: April 2011

Beam-foil intensity decay curves for transitions in the wavelength range from 900 to 2200 Å are used to derive the lifetimes of the 6s6p1P1 and 3P1 6s6d1D2, 6s7s1S0, and 6p21D2 levels of Pb III, and the 6p2P1/2 and 2P3/2, 6d2D3/2 and 2D5/2, 7s2S1/2, and 5d96s22D3/2 levels of Pb IV, arbitrarily normalized decay curve (ANDC) analyses being used for the 6s6p and 6p levels. In the case of the two 6s6p levels studied in Pb III, good agreement is found with a recent calculation in which a polarization model accounts for valence–core correlation. However, the agreement between the lifetimes observed for the 6p levels in Pb IV and a similar, earlier calculation is only fair.
Effect of ion temperature on ion-acoustic solitary waves in a two-ion plasma
Authors: Bhattacharyya Sikha , Roychoudhury R. K.
Published: April 2011

The effect of ion temperature on ion-acoustic solitary waves in the case of a two-ion plasma has been investigated using the pseudopotential approach of Sagdeev. An analytical solution for relatively small amplitudes has also been obtained. Our result has been compared, whenever possible, with the experimental result obtained by Nakamura. It is found that a finite ion temperature considerably modifies the restrictions on the Mach number obtained for cold ions.
Hydrogen diffusion in amorphous Cu50Ti50 studied by positron-annihilation spectroscopy
Authors: Dunlap R. A. , Putnam A. M. , Vardy D. S.
Published: April 2011

Positron-annihilation spectroscopy has been used to study the density of trapping sites in amorphous and crystalline Cu50Ti50. The effects of hydrogenation on the positron-annihilation spectrum in the amorphous alloy are also investigated. It is shown that the amorphous alloy has a higher concentration of trapping sites than the crystalline alloy and that in the hydrogenated amorphous alloy, the positrons are annihilated by electrons having a momentum distribution that is very nearly the same as in the crystalline alloy.
Weak nucleon–nucleon–meson couplings and nuclear parity violation
Authors: Holstein Barry R.
Published: April 2011

After many years of careful theoretical and experimental study of nuclear parity violation, rough empirical values for weak parity violating nucleon–nucleon–meson vertices have been deduced. We address some of the physics which has been learned from this effort and show that it has implications for work going on outside this field.
Bates parity-violation experiment
Authors: Kowalski S.
Published: April 2011

An experiment designed to measure precisely the parity-violating interference in the elastic scattering of longitudinally polarized electrons from 12C is under way at the Bates Accelerator Center. The experiment has required the construction of a high-intensity polarized injector whose successful operation has recently been demonstrated. Present efforts are aimed towards the understanding and control of sources of systematic errors.
Noise factors for parallel plate ionization chambers
Authors: Page S. A.
Published: April 2011

Sources of intrinsic detector noise for ionization chambers operated in dc mode, suitable for parity violation measurements in proton–proton scattering at intermediate and high energy are discussed. Measurements of the intrinsic noise factor for axial and transverse-field parallel plate ionization chambers used in high-precision proton beam current measurements at TRIUMF are reported.
On the analysis of parity violation in proton scattering experiments
Authors: Simonius Markus
Published: April 2011

Methods of analysis of parity violation in scattering experiments are presented. The main emphasis is on p–p scattering below pion threshold. It is shown how effects depend on strong interaction physics, in particular, the well-determined p–p scattering phase shifts. The different physical content of the two lowest parity-violating partial wave scattering amplitudes is discussed, as is the optimal choice of energy for their determination. The crucial role of the different anomalous magnetic-moment couplings for the analysis of parity-violating ρ and ω exchange is emphasized. The unexpectedly large parity violation found at 6 GeV/c proton momentum is then discussed with the conclusion that no satisfactory explanation yet exists. At the end, p–α and p–d scattering are discussed briefly.