bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Ethylene Molecule Clusters in a Gas Jet Radioactivity Transport System
Authors: Wiesehahn W. J. , D'Auria J. M. , Dautet H. , Pate B. D.
Published: April 2011

An ethylene gas jet radioactivity transport system has been studied in detail to elucidate the mechanism of the transport process. The role of impurities and formation of polymers were shown to play a minor role. The results obtained indicate that clusters, in the ethylene gas supply cylinder at pressures and temperatures above the critical values for ethylene, are necessary for the successful transport of the radioactive products of fast neutron-induced reactions. Other gases which also were used successfully to transport radioactivity were ethane and CO2. A possible mechanism is discussed.
A Study of Levels in 153Gd Using the (d,t) and (3He,α) Reactions
Authors: Løvhøiden G. , Burke D. G.
Published: April 2011

Triton spectra from the 154Gd(d,t)153Gd reaction have been measured at 15 angles using a beam of 15 MeV deuterons. The 154Gd(3He,α)153Gd reaction was studied at 4 angles with a 24 MeV 3He beam. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected with photographic emulsions. The (d,t) angular distributions and ratios of the (3He,α) and (d,t) cross sections were used to determine l values for a number of transitions. Members of the strongly perturbed band consisting of a mixture of Nilsson states from the i13/2 shell have been populated. An attempt has been made to describe some of the positive parity states in terms of the Nilsson model with Coriolis and ΔN = 2 mixings included. As spin assignments are now available for a large number of positive parity levels, it is possible to see a better developed pattern for this mixing than was presented previously. Although the observed intensity pattern for the 3/2−[521] ground-state band agrees with expectations, the remaining negative parity states cannot be easily explained in terms of the basic Nilsson model.
Muonuclear Absorption and the Factorization Method
Authors: Joseph J. , Goulard B.
Published: April 2011

Muon absorption by a nucleus [μ− + [Z,A] → [Z – 1,A]* + vμ] is treated in the framework of a factorization method already tested in photonuclear physics. The transition rates to various states 0−,1−,2− of the final nucleus [Z – 1,A]* and the energy spectra of the subsequent outgoing neutrons are analyzed in the case of 16O and 40Ca.
Electromagnetic Scattering by a Moving Conducting Cylinder of Arbitrary Cross Section
Authors: Hunter J. D.
Published: April 2011

A method is derived for calculating the electromagnetic scattering from a conducting cylinder of arbitrary cross section moving with arbitrary velocity relative to the field source and the observer. Results are presented for a moving square cylinder for both TM and TE polarizations of the incident field.
Diameter Measurement of Dow Latexes EP-1358-38 by Three Optical Methods
Authors: Robillard F. , Patitsas A. J.
Published: April 2011

Dow latexes EP-1358-38 were measured by three optical methods: hexagonal array diffraction, optical microscopy, and Mie scattering. All measurements were made on two-dimensional dry preparations. Particular attention was given to the study of the relation between the position, the shift of the diffraction peaks, and the size of the hexagonal arrays. Comparison was made with results obtained by other methods.
Shell Model and Collective Excitations in 72Ge
Authors: Castel B. , Micklinghoff M. , Johnstone I. P.
Published: April 2011

The importance of core excitations in the shell model structure of 72Ge is investigated in a model which couples two neutrons in the p1/2 and g9/2 subshells to the low-lying excitations of 70Ge. Particle excitations from the p3/2 and f5/2 subshells are taken into account through second-order perturbation diagrams. Satisfactory agreement is obtained for energy levels and E2 and E0 rates in 72Ge in a calculation involving essentially two parameters.
Ultrasonic Modulation of Microwaves in Piezoelectric Semiconductors
Authors: Mathur S. S. , Sagoo M. S.
Published: April 2011

The propagation of microwaves in piezoelectric semiconductors irradiated with an acoustic field has been discussed. It has been shown that the acoustic wave produces appreciably large variation in the carrier concentration in a piezoelectric semiconductor as opposed to a nonpiezoelectric semiconductor. Consequently, the microwaves propagating through such piezoelectric semiconductors get modulated. The resulting sum and difference microwave frequencies do not have the same magnitude. This modulation of the difference frequency under optimum conditions is found to be of the order of 3% in cadmium sulfide, and is measurable. This measurement can be used to determine the piezoelectric constant of a semiconductor.
Quantum Mechanics of the Two Mass-Point Model for the Rotational Spectra of Deformed Even–Even Nuclei
Authors: Prakash V. R. , Bahal B. M. , Deshpande V. K.
Published: April 2011

The representation of a deformed nucleus by a two mass-point system is treated quantum mechanically to obtain absolute values of energies of the ground state rotational band and the first excited 0+ vibrational state of even–even nuclei in the rare-earth region. Calculations are made using both harmonic and anharmonic restoring potentials. Although the model is not applicable to spherical nuclei, it is found that for the deformed nuclei in the rare-earth region it correlates the quadrupole moment and the moment inertia data more satisfactorily than the rigid-body and hydrodynamic models. The values of energies, quadrupole moments, and the ratio B(E2; 4+ → 2+)/B(E2; 2+ → 0+), predicted on the basis of the model, are in agreement with the corresponding experimental values for the nuclei around the middle of the region [Formula: see text]. The variation of the stiffness of the potential with neutron and proton numbers is studied.
Superconductive Tunneling Parameters of Strain-Free Pb Films
Authors: Banks Donald E. , Blackford B. L.
Published: April 2011

Lead film tunnel junctions have been fabricated on Pb crystal substrates to reduce the thermal strain that arises upon cooling to liquid helium temperatures. The energy gap has been measured, 1.360 ± 0.007 meV, and compared to that obtained from similar films deposited on glass slide substrates, 1.390 ± 0.005 meV. The expected energy gap shift, due to the thermal strain, has been estimated and compared to the experimental result. The effect of this shift on previous measurements of energy gap anisotropy in Pb crystals is discussed. Changes in the phonon structure appearing in d2I/dV2 have also been measured.
Infrared Behavior in a Model for Quantum Electrodynamics
Authors: Manoukian Edward B.
Published: April 2011

In another paper, a particular solution of the Ward–Takahashi identity was set up as a model for quantum electrodynamics. The high energy behavior of the electron and photon propagators was investigated. The purpose of the present work is to investigate the asymptotic infrared behavior of the electron propagator near the mass shell in our model–theory. It is shown that, in general, it has a branch point, rather than just a pole at p2 = −m2, with the "singularity" being different from the known result of Abrikosov and Solov'ev, and coincides with theirs only in the gauge G = −1. The electron propagator, however, has rigorously a pole in the Yennie gauge.
Méthode d'orientation optimale d'un polygone optique par rapport à l'axe d'une table tournante
Authors: Bouillon Gratien , Tremblay Gilles , Delisle Claude
Published: April 2011

A procedure for the optimum orientation of an optical polygon is given. Such a procedure is recommended when an optical polygon is used for the calibration of instruments such as optical dividing heads and rotary tables. Theoretical formulas as well as numerical examples are given.
Far-Infrared Measurements of the Optical Properties of CsI between 12 and 300 °K, Compared with Calculations Based on Cubic Anharmonicity Only
Authors: Beairsto J. A. B. , Eldridge J. E.
Published: April 2011

Measurements of the absorption coefficient of bulk CsI from 15 to 60 and from 90 to 200 cm−1 at 12, 77, and 300 °K, together with the normal reflectivity at 300 °K, are reported. These have been compared with calculations based on cubic anharmonicity, which involved the derivation of the cubic coupling coefficient for the CsI lattice. From inspection of this coefficient, certain selection rules have been obtained for the two-phonon relaxation of the transverse-optic resonance. These rules and other criteria, when applied to CsI, predict just two main features, due to the summation processes from R25′R15 and X5X5′. The agreement in intensity at low temperatures is very good, and confirms the need to include next-nearest neighbors in the lattice repulsive potential. Wavenumber discrepancies of the features appear to be a result of inaccuracies in the deformation-dipole input data. By 300 °K the need for quartic anharmonicity is evident both in the resonance region and at high wavenumbers. Portions of the damping spectra from these terms have been obtained and are discussed.
A Comment on "Ambipolar Drift, Deformation, and Diffusion of a Plasma in a Magnetic Field" by Richard L. Monroe
Authors: Byrne J. C.
Published: April 2011

When the displacement current is negligible in Maxwell's equations an additional assumption of charge neutrality is not a redundant assumption, as was recently claimed by Monroe, for a plasma in a magnetic field when there are no externally maintained electric fields.
Longitudinal Relaxation Time Measurements in Hydrogen Gas Mixtures at Low Densities
Authors: Armstrong Robin L. , Kisman Kenneth E. , Kalechstein Wallace
Published: April 2011

Measurements of the longitudinal nuclear spin relaxation time through the region of the characteristic minimum at 49 MHz in mixtures of molecular hydrogen with the noble gases helium and argon and with molecular nitrogen are reported at 298 K. The data obtained serve as a further test of the basic approximations in the Bloom–Oppenheim theory and provide preliminary information concerning the role of inelastic collisions in the nuclear spin relaxation process.
The Pressure–Temperature Description in Nonlinear Light Scattering
Authors: Enns R. H. , Jones B. L. , Rangnekar S. S.
Published: April 2011

In this paper, we show that two different pressure descriptions may be introduced into the standard treatment of stimulated light scattering by one- and two-component fluids. By deriving the basic equations in these two descriptions, we are able to ascertain that an erroneous mixing of nonlinear source terms from the two descriptions has taken place in the literature. The relevant literature is thoroughly discussed.
Line Shape of the A Band of s2 Configuration Ions in Alkali Halide Crystals
Authors: Tsuboi Taiju , Oyama K. , Jacobs P. W. M.
Published: April 2011

A systematic investigation of the line shape of the A band of several ions with the s2 configuration dissolved in alkali halides has been made on KCl:In+, KBr:In+, KCl:Sn2+, KBr:Sn2+, KI:Sn2+, RbCl:Sn2+, KCl:Tl+, KBr:Tl+, KI:Tl+, and KBr:Pb2+ crystals. A temperature sensitive doublet structure was observed for In+ and Sn2+ doped crystals and for KCl:Tl+, while a single band, which is asymmetric at high temperatures, was observed for KBr:Tl+ and KBr:Pb2+. The temperature dependence of the line shape supports Toyozawa and Inoue's theory in which the fine structure is ascribed to the dynamical Jahn–Teller effect. A discussion is given of the importance of quadratic electron–lattice interaction and its effect on the asymmetry of the line shape.
Low Energy n–16O Elastic Scattering Phase Shifts Derived from the Sussex Interaction
Authors: Betz M. , Jeukenne J. P. , Lejeune A.
Published: April 2011

The properties of the Sussex interaction are tested in the study of the n–16O elastic scattering described by the potential scattering in the Hartree–Fock field. This force leads to an easy determination of the self-consistent field, but gives s1/2 and d3/2 phase shifts which are not very satisfactory. This results from the important gap separating bound and unbound states. Further, some uncertainty in the calculation arises from approximations necessary in order to obtain some nondiagonal matrix elements of the two body force which are necessary in the determination of the phase shifts.
An Investigation of the Reaction 55Mn(n,γ)56Mn
Authors: Colenbrander A. H. , Kennett T. J.
Published: April 2011

A pair spectrometer has been used to make a detailed study of the 55Mn(n,γ)56Mn reaction. A total of 268 transitions has been observed and most of the intense components have been included within a proposed decay scheme. The agreement between level energies deduced from (d,p) measurements and the present (n,γ) data is excellent. A recently reported technique for analyzing complex spectra has been used to obtain an estimate of the nuclear temperature and to permit the establishment of an absolute intensity scale.
Calculation of the Franck–Condon Factors: Single-α Approximation Method
Authors: Lin C. S.
Published: April 2011

It is shown that when the vibrational wave function is expanded in a set of harmonic oscillator eigenfunctions [Formula: see text], where α is the conventional nonlinear parameter, the energy eigenvalue remains very stationary over a wide range of α. The reason for this weak functional dependence is analyzed in some detail.The single-α approximation method is introduced, which gives the Franck–Condon factor in the closed form. Using three band systems of contrasting nature as test cases, these factors are also shown to change only weakly as a function of α. Comparison with the numerical integration method and the experiment clearly establishes the validity of this approximation. Various other advantages of the method are also briefly mentioned.
Capture Gamma-Ray Spectra for the 59Co(n, γ)60Co Reaction Using Resonance Energy Neutrons
Authors: Prestwich W. V. , Lopez A. M.
Published: April 2011

Capture gamma-ray spectra for the reaction 59Co(n, γ)60Co were obtained for different neutron energy distributions. Significant contributions from the high energy resonances were observed. Analysis of the data for the ground state transition indicates that the contribution to the process from potential direct capture is substantially smaller than previous estimates. No retardation of transitions to final states exhibiting an ln = 3 (d,p) stripping pattern, such as that observed for 132 eV capture, is evident for the higher energy resonances.
Levels in 146Sm Populated by the Decay of 146Eu and the (α,2n), (d,t), and (3He,α) Reactions
Authors: Singh B. , Johns M. W.
Published: April 2011

The levels in 146Sm have been investigated through the electron capture of 146Eu, and by means of the (α,2n), (d,t), and (3He,α) particle reactions. Spins and parities of a large number of levels have been determined by combining the results of γγ(θ) and γ(θ) distributions in the electron capture and (α,2n) reactions respectively and electron spectra associated with the (α,2n) reaction. The low lying states of 146Sm can be interpreted in terms of the vibrational model. The high spin states populated at higher excitation seem to be associated with particle excitations.
Applicability of Born Criteria to Charge Transfer Collisions
Authors: Band Yehuda B.
Published: April 2011

Born transition matrix elements for rearrangement collisions are discussed. Experimental and theoretical evidence is provided which shows the threshold of validity of the Born criteria in charge transfer reactions being considerably lower than in inelastic and ionization reactions. An explanation for the disparity in the threshold of applicability of the Born criteria is provided.
The Electrical Resistivity, Thermal Conductivity, and Thermoelectric Power of Calcium from 30 K to 300 K
Authors: Cook J. G. , Laubitz M. J. , Meer M. P. Van der
Published: April 2011

Data are presented for the thermal and electrical resistivity and thermoelectric power of two samples of Ca (having residual resistance ratios of 10 and 70) between 30 and 300 K. Large deviations from both Matthiessen's rule and the Wiedemann–Franz relationship are observed. The former are tentatively attributed to the presence of two distinct groups of carriers in Ca, and analyzed using the two band model. The latter deviations are interpreted as the effects of band structure. The thermoelectric power of Ca is large. In many respects the transport properties of Ca appear to be similar to those of the transition metals.
Temperature Dependence of the Elastic Constants of Gallium
Authors: Langill T. J. , Trivisonno J.
Published: April 2011

A modified ultrasonic pulse overlap technique was employed to measure the single crystal elastic constants of high purity gallium from 4.2 K to 190 K. The results are compared with data obtained by a technique which employed direct electromagnetic generation of acoustic waves as well as with earlier pulse echo measurements.
Determination of Surface Potentials of Thin Semiconducting Films
Authors: Stinson M. R.
Published: April 2011

Localized surface electronic states produce surface space charge regions in semiconductors. When the thickness of a thin film compares in magnitude with the width of the space charge layer, marked changes in the effective conductivity of the film may occur. Relations are derived expressing the conductance of thin film semiconducting slabs as a function of film thickness and surface potential. Using these relations, the surface potential — the amount by which the band structure is displaced between surface and bulk material — is determined experimentally by a technique involving the simultaneous evaporation of several thin film slabs of varying thickness, on the same substrate.
NMR Theory of Gaseous CX3Y Molecules: High Frequency Effects of CF3H
Authors: Sanctuary B. C. , Snider R. F.
Published: April 2011

A general theory of nuclear spin relaxation is applied to gaseous CX3Y molecules and the effects of high frequency terms studied theoretically. Although there is experimental disagreement as to what the correct high density dependence is for CF3H, it is demonstrated that rotational high frequency contributions can have a dramatic effect on the density dependence of T1. Moreover, for 'reasonable' values of the linewidth, shift, and collisional overlap parameters, the density dependence is limited in variation when the parameters are changed, making it impossible to fit Courtney's initial large 'step'. A reasonable fit to Waugh's data and the higher density dependence of Courtney can be obtained with a low density T1/n value of 0.8 s/amagat. Only a dipolar intramolecular mechanism is considered for the high frequency contributions.
Photoneutron Reactions in 18O
Authors: Allan J. D. , Jury J. W. , Johnson R. G. , McNeill K. G. , Woodworth J. G. , Horowitz Y. S.
Published: April 2011

Photoneutron energy spectra from 18O have been measured by time-of-flight spectroscopy at bremsstrahlung endpoint energies from 11 to 18 MeV in 1 MeV steps to obtain the (γ, n0) and (γ, n1) differential cross sections. The ground state photoneutron cross section contains at least 8 major resonances in the region from 10 to 17 MeV and has an average value of 100 μb/sr. The cross section to the first excited state of 17O contains only two major resonances, at 11.4 and 14.4 MeV, and the average cross section in the region from 11 to 16 MeV is about 40 μb/sr. Of particular interest is a resonance at 14.4 MeV which appears to reflect a simple excitation of one of the valence neutrons to the 2p3/2 state. Analysis of the (γ, n0) and (γ, n1) cross sections for this continuum state leads to estimates of the configuration amplitudes of the 2s1/2 and 1d5/2 components of this state to be 0.62 ± 0.06 and 0.78 ± 0.08 respectively and the ratio of the (2s1/2)2 to (1d5/2)2 amplitudes in the ground state of 18O to be 0.39 ± 0.02.
Photoneutrons from 20Ne
Authors: Woodworth J. G. , Jury J. W. , Lokan K. H. , Sherman N. K.
Published: April 2011

Photoneutron energy distributions from a target of liquid neon have been measured at 90° by time of flight for bremsstrahlung endpoint energies increasing in 1 MeV steps from 19 to 32 MeV. The differential ground state cross section for the major (91%) isotope 20Ne has been obtained, together with an estimate of the strength of transitions to excited states of 19Ne. Six photoneutron groups are observed, reflecting photon absorption which correlates excellently with existing photoproton data, although the absolute cross section is about 10% smaller.It is noted that the giant dipole resonance, estimated by combining the photoneutron and photoproton data, is centered at approximately 20 MeV, which is anomalously low, and that the integrated cross section up to 28 MeV exhausts only half of the dipole sum.
The Discrete Eigenvalue of the Angular Neutron Density with Anisotropic Scattering
Authors: Attia E. A. , Harms A. A. , Kushneriuk S. A.
Published: April 2011

The discrete eigenvalue appearing in the one speed description of neutron transport is studied for the case of anisotropic scattering. A more complete and corrected tabulation of this parameter is provided and its effect on the neutron density is assessed.
Escape of Photons from Cylindrically Symmetric Distribution of Matter in Longitudinal Electric and Magnetic Fields
Authors: Krori K. D. , Barua Jayantimala
Published: April 2011

The escape of photons in a plane perpendicular to the axis of a cylindrical matter distribution surrounded by a longitudinal electric or magnetic field has been investigated in this paper. It has been found that only those photons which issue radially may escape to infinity.
Velocity Distribution of Secondary π Mesons Produced in Interactions of 70 GeV/c Protons with the Nuclei (CNO) and (Ag, Br)
Authors: Bandyopadhyay B. K. , Daftari I. K.
Published: April 2011

One hundred nuclear interactions produced by 70 GeV/c protons with photoemulsion nuclei have been analyzed. The velocity distribution of the secondary π mesons produced in these interactions was studied. A Gaussian type function is observed to simulate the experimental data which confirms the usual criterion of isotropy in the center of mass frame.
Intercollisional Interference in the S Lines of H2–He Mixtures
Authors: Poll J. D. , Hunt J. L. , Mactaggart J. W.
Published: April 2011

Further experimental results on the pressure induced spectrum of normal H2–He in the region of the S(1) branch of the fundamental band are presented. These results show a well-defined minimum at the transition frequency of the free molecule. The S line is found to be the sum of two components. One of these is of essentially the same nature as the Q branch and should therefore show a pronounced intercollisional interference minimum. The second component shows the usual quadrupolar line shape without a minimum. Finally, a value for the strength parameter characterizing the short range component of the induced dipole moment is determined.
Photoconductivity Analysis in High Resistivity p Type Zinc Compensated Silicon
Authors: Rabie S. , Rumin N.
Published: April 2011

The decay of photoconductivity following band gap radiation has been measured in the temperature range 180–300 K on p type zinc compensated silicon samples containing approximately 1016 cm−3 of As and having room temperature resistivities between 0.7 and 50 K Ω cm. A strong correlation was found between the concentration of the neutral zinc atoms Nz0, deduced from resistivity vs. temperature measurements, and the measured decay time, suggesting that the recombination traffic was predominantly via the lower zinc level E1 and without the interference of any other traps. This enabled us to estimate the capture cross section for electrons on neutral zinc atoms, Szn0, to be approximately 1.2 × 10−16 cm2 and to be temperature independent in the measurement range. The resistivity measurements confirmed that E1 is located 0.31 eV above the top of the valence band and indicated that the concentration of any 'unwanted' traps that may be present in our samples was appreciably less than 2 × 1013 cm−3 in the range 0.07–0.15 eV below the center of the band gap. Correlation of the above results with our previously published data on n type zinc doped samples indicates that the electron trap influencing the photodecay times in n samples is a single acceptor center having a capture cross section of approximately 10−16 cm2. The results of measurements on more than seven zinc compensated samples with room temperature resistivities covering the range of 70 Ω cm n type, through near intrinsic, to 500 Ω cm p type results in a unified model capable of consistently explaining all our observations.
Diffraction by Multiple Slits at the Interface between Two Different Media
Authors: Sachdeva B. K. , Hurd R. A.
Published: April 2011

A general solution is obtained for the diffraction of a plane electromagnetic wave incident upon n parallel, unequal slits in a perfectly conducting plane. The media on either side of the plane may have different permittivities and permeabilities. The cases of both E and H polarization are considered. The solution is obtained in the form of a power series in (wave number × maximum dimension of the slit region) and is therefore valid only when this dimension is small. Expressions are found for the transmission coefficient and some numerical results are given for some particular values of the parameters involved.
Les propriétés optiques du hafnium dans l'ultraviolet à vide
Authors: Leblanc L. J. , Truong Vo-Van
Published: April 2011

The reflectance of hafnium was measured at five different angles of incidence in the spectral region from 500 to 1900 Å. By iterative calculations the centroid of the points of intersection of the isoreflectance curves was determined, thus yielding the complex index of refraction. Analysis of the optical constants indicates that interband transitions could be found near 7.3, 8.4, and 13.5 eV. A plasma peak is observed near 18.7 eV.
Application de la modulation spectrale à la transmission de l'information
Authors: Delisle Claude , Cielo Paolo
Published: April 2011

It is shown, theoretically as well as experimentally, that a system of communication based on the modulation of the spectrum of a light source is feasible. A white light source has been used for the experimental investigations; however, the method is applicable to other thermal sources and even to laser sources under certain conditions. [Translated by the Journal]
On the Order Dependence of The Thermoelectric Power of Binary Alloys
Authors: Wang K. P.
Published: April 2011

We present a simple model for calculating the order dependent part of the thermoelectric power of binary alloys.
Promising Results in Nuclear Matter with Recent Nonlocal Separable Interactions
Authors: Meunier J. P. , Pigeon J. , Meyer J. , Elbaz E.
Published: April 2011

New parametrizations of nonlocal separable interactions have been proposed recently by different authors. All of these potentials reproduce the two nucleon data fairly well without increasing the rank of the interaction. In this paper the nuclear matter properties have been calculated in the Brückner pair approximation. Two of these parametrizations give results comparable with the Reid soft core local interaction. Thus, such nonlocal interactions may be promising candidates for further nuclear structure calculations.
Electron Detachment Cross Sections of Negative Alkali Ions
Authors: Narain Udit , Jain N. K.
Published: April 2011

The electron detachment cross sections of negative alkali ions have been calculated semi-empirically in the energy range of 0.147 to 100 Ry with and without Coulomb effect. The inclusion of Coulomb repulsion leads to satisfactory agreement with the available data.
Direct Relativistic Formulation of Constant Magnetic and Electric Field Effects in Simple Atoms. II
Authors: Moore R. A.
Published: April 2011

A previously developed method of obtaining approximate solutions to the Dirac equation for the electron is applied to the problem of constant electric and magnetic effects in simple atoms. This method makes the relativistic formulation of these problems straightforward. In all cases the standard expressions are reproduced, as one would expect, and hence illustrates the simplicity and utility of the method. The Zeeman effect is calculated to order α2, α being the usual fine structure constant, and it is seen that only the lowest order solutions are required. That is, one needs only the nonrelativistic solutions. The Stark effect and dipole transition matrix elements are calculated only to zero order in α as it is felt that that is all that is required for comparison with experiment. One concludes that the discrepancies between the theoretical values and experimental values of the oscillator strengths must be explained on the basis of nonrelativistic effects.
Direct Relativistic Formulation of the Hyperfine Interaction in Simple Atoms. III
Authors: Moore R. A.
Published: April 2011

We apply a previously developed procedure for obtaining approximate solutions for the Dirac equation for the electron to the formulation of the hyperfine interaction in spherically symmetric atoms. Expressions are obtained to order α2, α being the usual fine structure constant. The hydrogen 1S state is solved and seen to be correct to order α2. This result is taken to be a positive test of the procedure. Further, one sees that the first order equations are solvable, the form of the solutions, and that all the required contributions are finite. Also, in terms of numerical work the time required will not be appreciably greater than needed for a nonrelativistic calculation. This leads to the conclusion that one has a practical and valid method of solving relativistic problems to order α2.
Kinetic Theory of Molecular Gases II: Calculation of Time Dependent Correlation Functions
Authors: Tenti G. , Desai Rashmi C.
Published: April 2011

Kinetic model equations, based on the Waldmann–Snider equation and valid over a wide range of wavelength and frequency, are applied to the study of time dependent correlation functions in a dilute molecular gas. In particular, the density autocorrelation function is calculated and its double Fourier transform compared with the polarized Rayleigh–Brillouin light scattering. Similarly, the tensor polarization autocorrelation function is studied and its spectrum compared to the depolarized Rayleigh light scattering. Thus, both scalar and tensorial phenomena are studied from a unified viewpoint. Furthermore, the asymptotic form of the theory is used to study in detail the behavior of the tensor polarization correlation function in the pressure broadening region.
Effect of Short Range Correlations in Charged Pion Photoproduction from 16O
Authors: Rao K. Srinivasa , Devanathan V.
Published: April 2011

Short range correlations in nuclei are introduced into the nuclear wave function using a unitary operator whose form was originally suggested by Villars. Their effect on positive pion photoproduction from 16O is found to be small for the correlation function we have assumed.
The Conductivity of Crystalline NaI
Authors: Kostopoulos D. , Varotsos P. , Mourikis S.
Published: April 2011

The d.c. conductivity of NaI has been measured in the intrinsic and extrinsic temperature regions. The formation energy Es for the Schottky defects and the energy Em+ for the cation vacancy migration have been determined. The Em+ value has been found to be slightly higher than that required for the motion of the 'bound' vacancy in the system NaI + Ca++. The formation energy Es obtained is smaller than that of NaF, NaCl, and NaBr as was expected.
Vectorial Impedance Identity for the Natural Dependence of Harmonic Fields on Closed Boundaries
Authors: Aboul-Atta O. A. , Boerner W. M.
Published: April 2011

The exact description of the harmonic electromagnetic field solution at scattering surfaces is shown to require, in general, two impedances to relate the tangential electric field to the tangential magnetic field. The consequences lead to the generation of two independent surface vectors that are orthogonal, of equal norm, and have a realizable direction. They are used to describe the surface by two scalar equations. For the first time, the details of this vectorial impedance identity, the derivation of those two vectors, and the two scalar inverse scattering surface equations are shown.
Investigation of Fine Structure in the Photoneutron Cross Sections of 16O and 208Pb
Authors: Johnson R. G. , Irish J. D. , McNeill K. G.
Published: April 2011

The structure in the photoneutron cross sections of 16O and 208Pb has been studied by the measurement of high resolution photoneutron energy spectra using the neutron time-of-flight technique and bremsstrahlung irradiations. For 16O, the ground state differential cross section at 98° has been deduced between 17.3 and 28.5 MeV and is in good agreement with most previous studies. Fine structure is seen throughout the cross section. Eight neutron energy spectra for 208Pb from bremsstrahlung endpoint energies in the range 11.0 to 15.5 MeV were obtained. Strong peaks are seen at center of mass neutron energies of 1.67, 1.85, 2.06, 2.19, 2.68, 3.15, 3.27, 3.50, 3.77, and 4.03 MeV with weaker peaks elsewhere. The energies of these peaks are in good agreement with previous measurements in this laboratory. The energies of peaks in the spectra are compared with recent cross section measurements.
Photoionization of Li and its Isoelectronic Sequence from an Independent Particle Model
Authors: Tiwari P. , Hashim M. A. , Ojha S. P.
Published: April 2011

Photoionization cross sections for Li and its isoelectronic sequence have been calculated. Continuous wave functions are obtained by solving the radial Schrödinger equation employing a GSZ independent particle model potential and the Yunta et al. single parameter self-consistent analytic potential. The best wave function of Roothaan et al. for the ground state has been adopted in the present calculations. Results so obtained are compared with experimental and recent theoretical investigations.
Intermolecular Potentials from NMR Data: I. CH4–N2 and CH4–CO2
Authors: Rajan S. , Lalita K. , Babu S. V.
Published: April 2011

Proton spin–lattice relaxation times have been measured in the gaseous mixtures CH4–N2 and CH4–CO2 as a function of density and composition in the temperature region 300–600 K. The values of T1/ρ extrapolated to 100% N2 and CO2 respectively were found to be proportional to T−n where n = 0.87 ± 0.14 for CH4–N2 and n = 0.91 ± 0.10 for CH4–CO2. It is not possible to fit these data using a hard sphere potential for the isotropic part. Using the Bloom–Oppenheim theory and assuming that the correlation time of the spin–rotation interaction can be approximated by the average lifetime of a molecule in the given J state, it is shown that the above temperature dependence can be fitted by a 12–6 Lennard–Jones potential combined with an appropriate anisotropic potential. We have obtained the strengths of the repulsive and attractive terms in the anisotropic potential by a least squares fit of the data. Using the known values of the quadrupole moments of N2 and CO2, the octopole moment of CH4 has been obtained.
Excitation of the N = 28 Core in 53Mn
Authors: Benson H. G. , Johnstone I. P.
Published: April 2011

The structure of 53Mn is examined using a shell model basis of f7/2−2 and all f7/2−4j states, with an effective interaction derived from previous studies of fp shell nuclei. With few exceptions, the lowest one particle, four hole states are found to be predominantly neutron excitations, which make up over 99% of the lowest J = 13/2 level. The calculation successfully accounts for the observed high spin states, but comparison with experiment strongly suggests that two particle excitations from the f7/2 shell are the dominant configuration of several states lying below 3.5 MeV.
A Microscopic Self-consistent Calculation with Saturation Diagrams in 16O
Authors: Rouben B. , Padjen R. , Gogny D. , Pirès P.
Published: April 2011

Self-consistent calculations are performed in 16O with effective G matrices obtained from two different soft core interactions. The calculations possess the 'triple' self-consistency: (a) on the single particle basis, (b) on the single particle eigenvalues (Brueckner self-consistency), and (c) on the occupation probabilities. Two different procedures of calculating the latter are carried out, one involving a truncation of the unoccupied state space, one involving no truncation. The truncation effects are studied and shown to increase with the hardness of the interaction. A comparison is also made to calculations where the Brueckner self-consistency is satisfied only on the average. The total and single particle removal energies for both forces are quite satisfactory, the Pirès – Gogny – de Tourreil interaction performing slightly better than that of de Tourreil – Sprung. The charge radius is approximately 10% too small.
Electron Excitation of 21S, 23S, 21P, and 23P States of Helium
Authors: Barros H. G. P. Lins de , Brandi H. S.
Published: April 2011

Calculations for the total excitation cross sections of the 21S, 23S, 21P, and 23P states of He by electron impact have been carried out assuming the Born–Ochkur approximation for the scattering amplitude and a parametrization previously proposed by the authors for the total cross section. For the atomic wave functions we used LS coupling and obtained the one electron orbitals using the Xα method for three characteristic values of the parameter α. The results are compared with other experimental and theoretical calculations.
Photoproduction of Gravitational Radiation in Static Electromagnetic Fields. Radiative Corrections
Authors: Papini G. , Valluri S. -R.
Published: April 2011

The radiative corrections of second and third order for the process of photoproduction of gravitons in Coulomb and magnetic dipole fields have been calculated.All divergences have been removed either by charge renormalization or regularization. No approximations have been made in the calculation of the second order cross section. In the third order calculation only the extreme relativistic approximation is given. The forms of the effective Lagrangian, corresponding to the low energy approximations have been determined.
Tenseurs d'impulsion–énergie asymétriques et moment angulaire à six composantes dans le problème des deux impulsions du photon et celui de l'effet magnétodynamique
Authors: Beauregard O. Costa de
Published: April 2011

When an asymmetrical momentum–energy tensor Tij is used in the relativistic covariant formulation of the six component angular momentum conservation, and when this formulation is particularized in Newtonian style (initial and final integrals at constant times t and t + dt, origin of point instants simultaneous with t), there is a compensation of terms which substitutes the energy flux T4α for the momentum density Tα4.Three applications of this general result are given.If Tij is the Maxwell–Minkowski tensor, the integrated momentum density D × B is fully replaced by the energy flux E × H, or in other terms, the Minkowski momentum of the photon nhv/c is replaced by the Abraham momentum hv/nrc (n and nr = n cos θ are the refractive indices of the diopter for the directions normal to the equiphase planes and parallel to the extraordinary ray). This is a general solution of the photon two momenta paradox for refringent media.An analogous problem exists for the Fresnel evanescent wave associated with total reflection, in relation to the Goos–Hänchen and Imbert shifts. The solution is identical, but uses the de Broglie and Géhéniau canonical tensor (the Maxwell–Minkowski tensor, being symmetrical in vacuum, cannot be used). A third similar problem is that of the momentum [Formula: see text] 'hidden' in an electric field E = ∂V (Penfield–Haus effect). In terms of densities, the energy flux Vj is seen to appear instead of momentum density qA expected a priori (A, iV: 4 potential, j, iq: current density). In this case, the paradox is solved by using the momentum–energy tensor Akjl or Akjl – (1/2)Aijiδkl. [Translated by the Journal]
Excitation de l'argon par impact électronique entre 43 et 60 eV
Authors: Marmet P. , Bolduc E. , Quémener J. J.
Published: April 2011

This work reports numerous atomic levels of Ar observed between 43.38 and 60 eV above the ground state of Ar I. These levels, until now undetected, produce weak perturbations on the double ionization curve obtained by electron impact. The cross section near this Ar++ threshold varies very nearly as a quadratic function. Most of the reported levels of argon have the configuration 3s3p54l 4l′. Ionic states are also responsible for some of these structures.
Theory of Self-Broadening of Spectral Lines
Authors: Royer Antoine
Published: April 2011

Low density expressions are derived for the spectrum radiated by a gas of identical atoms, in a way exhibiting clearly the physical meaning of the approximations made. We make use of the Liouville space formalism and, contrary to other treatments, retain the effect of the initial correlations between atoms. The expressions obtained are very similar to those of foreign gas broadening theory, the main difference being that, instead of having a collision or 'memory' operator acting in the Liouville space of the radiator, we have it acting on a single atom space representing the atom carrying the excitation at any instant. Also, the one atom reduced density matrix as well as the collision operator contain a part corresponding to transfer of the excitation between atoms.
The Crystallization of a-ZnTe
Authors: Webb J. B. , Brodie D. E.
Published: April 2011

The crystallization of amorphous zinc telluride (a-ZnTe) has been studied as a function of temperature in the range 350 K < T < 390 K. The crystallization process is thermally activated with an activation energy of 1.6 eV. The time for the onset of significant crystallization at room temperature for films of air-annealed a-ZnTe is found to be ~100 years. The study of the crystallization process is essential in order to determine the maximum time allowed for a measurement to be performed at a given temperature on a sample of amorphous material without significantly altering its amorphous state.
Shapes of Optical Emission Lines from Atoms Excited by Fast Ion Impact: I. Calculated Profiles
Authors: Morgan F. J. , Marcuzzi A. , Dugan C. H.
Published: April 2011

After an inelastic collision between a neutral gas atom and a fast ion incident in a beam the excited gas atom emits radiation. The emitting gas atom has a variety of line-of-sight velocities relative to some fixed observer. This is a consequence of the kinematics of the collision and the angular dependence of the collision cross section. An expression for the intensity as a function of the frequency of the radiation is derived and then synthetic profiles for several viewing angles are obtained through numerical integration of this expression. Then the utility of the line profile as a means of determining the angular dependence of the inelastic collision cross section is examined.
A Model Dielectric Function for Semiconductors
Authors: Grimes R. D. , Cowley E. R.
Published: April 2011

The microscopic dielectric function is calculated for a simple model of a semiconductor, originally proposed by Penn, in which the energy bands and wave functions are those of a one-dimensional, nearly free electron system, isotropically extended to three dimensions. The dielectric function is evaluated numerically so that all unnecessary approximations are avoided. The relationship between the static dielectric constant and the energy gap is found to be[Formula: see text]where S0 is about 0.6. The results for finite wave vectors, for a range of energy gaps, have been fitted to an interpolation formula to facilitate their use.
Rotational Structure in the Absorption Spectrum of SO2 between 3000 Å and 3300 Å
Authors: Hamada Y. , Merer A. J.
Published: April 2011

Rotational analyses have been carried out, with varying degrees of completeness, for nine bands of S16O2 and two bands of S18O2 in the region 3000–3300 Å. The bands are all highly perturbed type C bands, which go to b2 vibrational levels of the ππ* Ã1A2 electronic state. The [Formula: see text] electronic transition shows an anomalous vibrational intensity distribution, which indicates that the Ã1A2 state undergoes strong Born–Oppenheimer (nuclear momentum) vibronic coupling with the [Formula: see text] electronic state. All the obvious banded structure in this wavelength region can be assigned to the [Formula: see text] transition. Although no analyses of bands belonging to the [Formula: see text] transition have been carried out (since the [Formula: see text] state is so massively perturbed by the ground state), reasons are presented for placing its (0,0) band between 3100 and 3160 Å.
On the Analysis of Steady State Microwave Double Resonance Experiments: Level Degeneracies and M Dependence
Authors: Lees R. M.
Published: April 2011

The analysis of data on collisional transfer of rotational energy obtained by the technique of steady state four-level microwave double resonance is reviewed, with emphasis on the roles of the spatial degeneracies of the levels and the M dependence of their populations. Exact expressions are given for the collisional transfer signal in a general four-level system, with the level degeneracies included rigorously, and with M dependent and M independent contributions formally separated. The possible effects of the M dependence are illustrated for several test systems of CH3OH, with the use of a simplified first-order dipolar model for the collisional rate constants. Collisional transfer signals calculated with this model for a number of CH3OH systems are in reasonable relative agreement with observed values, but in poor absolute agreement. It is suggested that the latter feature may be due to neglect of higher-order transitions in the simple dipolar model.
Neutron Spectra from the 3H(7Li, 2n)2α Reaction
Authors: Jérémie H. , Baltar J.
Published: April 2011

A time-of-flight spectrometer with two scintillation counters was used to look for n–n coincidences in the reaction 3H(7Li,8Begs)2n at 0° and at 117°. The mean incident energies of the Li ions were 14.6 and 22.7 MeV. No evidence for a n–n final state interaction peak was found, with the upper limit on the cross section being of the order of 10−26 cm2/sr2.The observed time difference spectra were compared with the following reaction models: (1) direct break-up; (2) sequential decay via the channel, 4He + 6He* → 2α + 2n; and (3) independent successive emission of the two neutrons from a compound nucleus. This latter reaction mechanism is favored by the data.
The Large Polaron as an Infinite Number of Degrees of Freedom System
Authors: Matz D.
Published: April 2011

We study the solutions of the Fröhlich Hamiltonian eigenvalue problem that depend specifically on the properties of systems with infinite number of degrees of freedom. Our major concern is then to sort out those solutions which can be given on a separable Hilbert space and those that cannot, as apparently both types exist. The former solutions are then the only ones applicable to solid state problems, whereas the latter are not. An example of the latter is the usual translational invariant Fock approximation and of the former the translationally noninvariant Fock approximation. Although our major vehicle for studying these problems is the Fock approximation itself, most of our results can readily be extended beyond it. We also bring out some properties of the system which are due to the nonapplicability of the quasiparticle concept when one studies low lying excited states of the large polaron using certain dynamical approximations.
The Structure of RbHSO4 in its Paraelectric Phase
Authors: Ashmore J. P. , Petch H. E.
Published: April 2011

The structure of the paraelectric phase of RbHSO4 has been determined by X-ray and neutron diffraction at T = 23 °C. The structure consists of two crystallographically independent molecules in the asymmetric unit. Each of the independent sulphate tetrahedra is linked to a translationally equivalent sulphate by acentrically ordered hydrogen bonds. Some evidence is found for the disordering of one of the sulphate groups in the asymmetric unit. The bond lengths and angles are similar to those found in isomorphous NH4HSO4.