bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of crystal-field interactions in solid hydrogen. I. Single ortho impurities in solid parahydrogen
Authors: Luryi S. , Kranendonk J. Van
Published: April 2011

The theory of the crystal-field splitting, Ve, of the J = 1 level of an ortho impurity in a parahydrogen matrix, due to the coupling of the rotational motion of the ortho molecule to the lattice vibrations, is developed taking due account of the quantum-crystal nature of the solid. Two contributions to Ve are identified, both arising from the anisotropy in the lattice vibrations. One contribution is due to the difference in the relative zero-point motion of the molecules in in-plane and out-of-plane pairs in the hcp lattice, and is parametrized in terms of the second moments of the pair distribution function. The other contribution is due to the local, quasi-state distortion of the lattice around the impurity induced by the terms in the coupling linear in the phonon variables. This self-energy effect is calculated using a generalized Debye model for the self-consistent harmonic phonons, in which the anisotropy of the velocity and of the polarization of the sound waves is parametrized in terms of the elastic constants of the crystal. The theory is compared with that of Raich and Kanney, which is shown to be based on unrealistic assumptions. The remaining uncertainties in the anisotropic pair potential and the phonon renormalization factors are discussed in connection with the available experimental data.
Angular correlation of two-photon positron annihilation in hydrogen gas
Authors: Darewych J. W.
Published: April 2011

The expression for the angular correlation of two-photon annihilation radiation for positrons colliding with molecular hydrogen is derived. The one-state approximation is used, and a one-centre expansion of the hydrogen wave function is assumed. Results obtained using a simple H2 wave function yield a half-width of the angular distribution which is in agreement with the observed results for positrons annihilating in liquid hydrogen. Comparison is made with corresponding results for the annihilation rate.
4d95s–4d95p transitions in Sb VI and Te VII
Authors: Kleef Th. A. M. Van , Joshi Y. N.
Published: April 2011

The sixth spectrum of antimony (Sb VI) and the seventh spectrum of tellurium (Te VII) have been photographed in the region 600–2100 Å on a 10.7 m normal incidence spectrograph using a triggered spark source. All levels of the 4d95s and 4d95p configurations of Sb VI and Te VII given in Atomic Energy Levels Volume III have been found to be completely wrong. New level values of the levels of both configurations for these spectra have been established. Thirty-four lines have been classified in the Sb VI spectrum and thirty-three in the Te VII spectrum. The new analyses have been confirmed by parametric level fitting calculations and by intensity calculations of the transitions. A comparison between the least-squares fitted (LSF) parameter values and the Hartree–Fock (HF) parameter values in the Ag II–Te VII sequence is given.
Cross focusing of mixed mode operation in an extra dense plasma
Authors: Soni V. S. , Nayyar V. P.
Published: April 2011

This paper presents a study of the nonlinear propagation of a mixture of two degenerate modes (TEM00 and TEM10) of a high power laser beam in an extradense plasma. The high irradiance inhomogeneous laser beam creates an electron density gradient region in the overdense plasma (n > nc) through which the beam can propagate. The focusing effects have been studied for different power ratios of the two modes (TEM00 mode is considered to be stronger than theTEM10 mode). Self-focusing of the beam in x and y directions for critical power has been extensively studied.
The Muskhelishvili–Omnés equation and final state interactions
Authors: Kamal A. N.
Published: April 2011

The Muskhelishvili–Omnés equation is discussed for single- and multi-channel problems. Particular attention is paid to the discussion of boundary conditions and ambiguities in the solution. Numerical illustrations are provided both in the single- and the multi-channel case with different parametrizations of the two-body scattering amplitude.
Piezospectroscopic studies of phosphorus-, boron-, and lithium-doped silicon
Authors: Thewalt M. L. W. , Rostworowski J. A. , Kirczenow G.
Published: April 2011

We report the results of piezospectroscopic studies of bound multiexciton complexes in silicon doped with phosphorus, lithium, and boron; and of biexcitons in pure silicon. The bound exciton and bound multiexciton complex spectra are interpreted with the aid of a simple extension of the shell model to the case of non-zero stress. Many new results were obtained and almost all have been explained by our model. The lithium spectra are very different from those of phosphorus, as expected in the shell model since the valley-orbit states of the two donors are ordered differently. Large differences between the relative intensities of the lines in the boron phonon-assisted and no-phonon spectra are explained by a new treatment of the no-phonon process for boron complexes which relies on the fact that in an indirect gap semiconductor no-phonon recombination must proceed via the k-space tail of the electron or hole wavefunction.
Possible structure dependence in the Al reaction
Authors: Shahabuddin M. A. M. , Waddington J. C.
Published: April 2011

In the [Formula: see text] Al reaction at Ep = 17.0 MeV, the cross section and analyzing power angular distributions for several Jπ = 5/2+ states are found to be quite different. Except for the ground state, neither the back angle cross sections nor the analyzing powers for these states can be reproduced by cluster DWBA or CCBA calculations. It is thus inferred that this might be due to the dependence of the reaction on the structure of these states.
The 4d95d and 4d96s configurations in Sb VI and the 4d95d configuration in Te VII
Authors: Joshi Y. N. , Kleef Th. A. M. van
Published: April 2011

The spectra of antimony and tellurium have been photographed in the region 550–2100 Å on a 10.7 m normal incidence spectrograph. The source used was a triggered vacuum spark. On the basis of these observations all levels of the 4d95d configuration in Sb VI and Te VII, except the 1S0 level, and the levels of the 4d96s configuration in Sb VI have been established. Parametric level fitting configuration calculations of the levels and intensity calculations of the observed transitions confirm the analyses. Additional 108 lines in Sb VI and 60 lines in Te VII have been classified.
Multiphonon relaxations in crystalline uranyl salts
Authors: Chan W. K. , Chun K. H. , Lai T. W. , Leung A. F.
Published: April 2011

The fluorescence decay rate observed is associated mainly with the intramolecular relaxation of the excited uranyl ion despite the presence of impurities, defects, and self-absorption of fluorescence light in the crystal. Multiphonon transitions dominate the relaxation at temperatures higher than room temperature. The parameters of the multiphonon relaxation are extracted from the temperature dependence of fluorescence decay rate. The parameters show that at low temperatures the quantum efficiency of the fluorescent level is greater than 0.80 and that of the electronic level above the fluorescent level is less than 0.13. The absence of fluorescence from the electronic level above the fluorescent level is due to fast depopulation by non-radiative processes and low quantum efficiency.
Thermionic work function of low index planes of rhenium
Authors: Robichaud J. , Girouard F. E.
Published: April 2011

The thermionic emission constants of a rhenium spherical single crystal have been determined for the [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] orientations. Examination of the crystal surface revealed plateau-like structure in the [0001], [Formula: see text], [Formula: see text], and [Formula: see text] directions.
Ultrasonic attenuation and bulk viscosity in liquid krypton
Authors: Cowan J. A. , Ball R. N.
Published: April 2011

Ultrasonic attenuation measurements were recorded in liquid krypton for temperatures between 120 and 208 K and pressures between saturated vapor and 6.5 MPa. Values of bulk viscosity were calculated and compared to theoretical results as well as to previous argon results through the law of corresponding states.
New Kα satellites of 30Zn following electron bombardment
Authors: Nigam Anand N. , Kothari Sushma
Published: April 2011

The α-region of the electron excited K-X-ray emission spectrum of 30Zn, registered with the help of 20 and 40 cm curved muscovite mica crystal spectrographs of the transmission (Cauchois) type, has been microphotographically investigated.Four new high frequency satellites at 1415.2, 1411.4, 1401.7, and 1408.5 xu have been observed. On the basis of Relativistic Dirac–Fock (RDF) energy calculations for different initial and final configurations, the first three have been assigned to specific transitions (1s)−1(2p)−n → (2p)−n−1, with n = 3, 4, 5, respectively. However, the fourth one has been only tentatively assigned to the transition (1s)−1(2s)−1(2p)−4 → (2s)−1(2p)−5, since RDF calculations for these configurations were not available.The presence of two other satellites, reported earlier by Edamoto, has been confirmed. These have been observed at 1428.7 and 1424.4 xu and assigned for the first time to the transitions (1s)−1(2p)−n → (2p)−n−1 with n = 1 and 2, respectively.
CO2 laser induced gas breakdown in preionized argon
Authors: Santiago J. , Robinson A. M.
Published: April 2011

CO2 laser induced breakdown of argon is investigated as a function of pressure and preionization. The gas is preionized by uv photons from an electric discharge. By varying the time between the discharge and laser pulses, initial densities in the focal region vary from 109 cm−3 to 1012 cm−3. Numerical calculations of the breakdown process based on a cascade model yield thresholds which are in good agreement with measurements.
Generalized hydrodynamic analysis of neutron scattering data in liquid neon
Authors: Lonngi P. A. , García-Colín L. S.
Published: April 2011

The generalized hydrodynamic expression for the dynamic structure factor S (Q, v) obtained within Mori's approach has been compared with neutron scattering data from liquid neon. Models postulating either instantaneous, exponential, or Gaussian memory functions and an "extreme thermal coupling" assumption involving the Q→0 limit γ = Cp/Cv have been tested up to Q = 38 nm−1. This study shows that: (a) the neutron spectra for the different models are very similar in the quasielastic region; (b) conventional hydrodynamics with non-local transport coefficients gives very good overall agreement with the data far from the hydrodynamic regime; (c) insertion of memory effects in the stress tensor predicts strong sound-like modes in the exponential case, while a Gaussian decay shows no such propagating modes; and (d) memory effects associated to the heat flux do not seem to be important.
ΣN strong interactions
Authors: Johnstone J. A. , Law J.
Published: April 2011

The recent data of Batty et al. and those of Koch on Σ− atoms level shifts and widths have been analyzed together with the two sets of ΣN scattering lengths extracted by Alexander, Gell, and Stumer to determine if all the data are consistent and also to extract effective ΣN complex potentials. Our results indicate that the Σ− atoms data do not yet distinguish between the two sets of scattering lengths owing to the large uncertainties in level shift and width measurements. However, our best fit set of ΣN potentials preclude the Σ−n or Σ−nn system being bound.
Change of the de Haas – van Alphen frequency of potassium with pressure
Authors: Altounian Z. , Datars W. R.
Published: April 2011

The pressure dependence of the de Haas – van Alphen frequency in oriented potassium samples has been investigated with pressures up to 4.6 kbar. The change of frequency with pressure is less than that expected from free-electron scaling and the Fermi surface anisotropy increases from 0.13% at zero pressure to 0.47% at 4 kbar. These results are discussed in terms of band structure calculations and the charge density wave (CDW) model of potassium. The CDW energy gap changes with pressure for the CDW model to be applicable.
Temperature dependence of the linewidth of the CO2 laser transitions
Authors: Robinson A. M. , Weiss J. S.
Published: April 2011

Comparison of calculated and experimental values of the line-center absorption coefficients of the R(10)–R(24) 10.4 μm CO2 laser transitions has been performed to determine how the pressure-broadened linewidth varies with temperature. Assuming the linewidth varies as T−x, calculation and experiment agree most closely for [Formula: see text] over the temperature range 300–650 K.
Cross sections and thermonuclear reaction rates for the 24Mg(α,n)27Si, 25Mg(p,n)25Al, 27Al(p,n)27Si, and 28Si(α,n)31S reactions
Authors: Cheng C. W. , King J. D.
Published: April 2011

Cross sections for the 24Mg(α,n)27Si, 25Mg(p,n)25Al, 27Al(p,n)27Si, and 28Si(α,n)31S reactions have been measured at energies from near threshold to 3 to 4 MeV above threshold by detection of 0.511 MeV γ-rays in coincidence following positron decay of the product nuclei. Comparison with the theoretical calculations of Woosley, Fowler, Holmes, and Zimmerman shows good agreement between experiment and theory except at low energies where the statistical model calculations tend to overestimate the cross section. Reaction rates have been calculated for temperatures of interest in explosive nucleosynthesis and found to be in good agreement with the statistical model predictions for temperatures above 2 × 109 K.
Interference effects in the resonance fluorescence of a three-level atom at high proton densities
Authors: Mavroyannis Constantine
Published: April 2011

A theory on interference effects at high photon densities has been developed for two types of a single three-level atom for which transitions occur: (i) from two different upper levels to a common lower one and (ii) from a common upper level to two different lower levels. The excitation spectrum for the interference effects for the two types of atoms results from the symmetric and antisymmetric interference between the two electronic transitions of the system, respectively. The spectral function for the symmetric modes consists of three Lorentzian lines peaked at the frequencies ω = Δ and ω = Δ ± Ω and having spectral widths of the order of γ0 and 3γ0/4, respectively, where Δ is the beat frequency, Ω is the Rabi frequency, and γ0/2 is equal to the natural linewidth for a photon spontaneously emitted from an isolated atom. The antisy mmetric spectrum consists of the peak of ω = Δ, which has a delta-function distribution indicating the stability of the mode in question, and two Lorentzian lines peaked at ω = Δ ± Ω with radiative widths of the order of γ0/2. The excitation spectrum of each type of atom contains also a Lorentzian line describing the very low frequency mode of the system, respectively.
Superselection rules, quantum measurement, and the Schrödinger's cat
Authors: Wan Kay-Kong
Published: April 2011

A precise formulation of superselection rules in quantum mechanics is presented. An explicit measurement model is then constructed using the idea of superselection rules so formulated. The model is free from the usual difficulties associated with the projection postulate and it also allows a measurement to be completed within finite time interval.
Quasi-spherical compression of a spark-channel plasma
Authors: Panarella E.
Published: April 2011

An axial spark channel in deuterium has been used as a target for implosive shock waves created with a conventional cylindrical theta-pinch device. The compression of the channel by the implosive waves raised the plasma electron temperature to ~ 120 eV for ~ 6 kJ of condenser bank energy and 1 Torr initial gas pressure.In order to improve the efficiency of compression, of the channel plasma and to reduce the end losses inherent in the cylindrical configuration, the theta-pinch geometry was then converted from cylindrical into spherical. Under identical conditions of gas pressure and condenser bank energy, the electron temperature now peaked at ~ 400 eV. When the bank energy was increased to ~ 10 kJ, neutron production was observed. The total neutron output per shot ranged from 105 to 106 and increased inversely with the pinch discharge volume.
52P1/2 ↔ 52P3/2 excitation transfer in rubidium induced in collisions with CH4, CH2D2, and CD4 molecules
Authors: Phaneuf R. A. , Krause L.
Published: April 2011

The temperature dependence of cross sections for 52P1/2 ↔ 52P3/2 excitation transfer in rubidium, induced in collisions with CH4, CH2D2, and CD4 molecules, has been investigated using methods of sensitized fluorescence over a temperature range 300–650 K. The cross sections, which are of the order of 30 Å2 and which exceed similar cross sections for collisions with noble gas atoms by at least two orders of magnitude, exhibit an isotope effect which is ascribed to the phenomenon of electronic-to-rotational energy transfer.
Addendum: A comparison of the chlorine nuclear relaxation in the dense paramagnetic insulators K2IrCl6 and K2ReCl6
Authors: D'Iorio Marie , Armstrong Robin L.
Published: April 2011

New room temperature measurements of the chlorine spin–lattice and spin–spin relaxation times in the dense paramagnetic insulator K2ReCl6 yield hyperfine parameters parallel and perpendicular to the Re—Cl bond which are in acceptable agreement with the more accurate spectroscopic values extracted from nuclear magnetic resonance measurements.
Radio-auroral scattering at two closely spaced frequencies
Authors: Sinclair I. P. W. , Forsyth P. A.
Published: April 2011

Two radio frequencies near 40 MHz and separated by 500 Hz were used to investigate the type of radio-auroral scattering which arises in ion-acoustic waves. The results confirm those of Haldoupis and Sofko who found that individual ion-acoustic wave trains have lifetimes of only tenths of seconds. In addition it was found that instantaneous signal amplitudes on these two frequencies were sometimes poorly correlated indicating the coexistence of widely separated ion-acoustic wave trains. It appears that the radio-auroral scattering region is typically large but within it individual ion-acoustic wave trains grow and decay rapidly. Significant periodicities were found in the signals and these are attributed to magnetospheric modulation of the auroral process.
Line positions and intensities for the 2ν2, ν1, and ν3 bands of H218O
Authors: Flaud J.-M. , Camy-Peyret C. , Toth R. A.
Published: April 2011

A very good fit of 434 line intensities of the 2ν2, ν1 and ν3 bands of H218O has been performed leading to the determination of the constants involved in the expansion of the transformed transition moment operators relative to these three bands. It has been possible to derive the values of the coefficients of the expansion of the dipole moment with respect to normal coordinates: 22μx = 0.013 ± 0.003 D, 1μx = −0.020908 ± 0.00023 D, 3μx = 0.096867 ± 0.00099 D.Moreover, using the constants determined from the fit, the complete spectrum of the 2ν2, ν1 and ν3 bands of H218O has been computed including line positions, intensities, and assignments.
High temperature multigraph expansions for general Ising systems
Authors: Oitmaa J.
Published: April 2011

A high temperature expansion, in terms of connected graphs with single and multiple edges, is developed for general Ising systems with interactions of more than one type. The graphical information obtained is sufficient to derive 11 terms in the expansion of the high temperature zero-field susceptibility and 12 terms in the zero-field free energy for any Ising system. Series to this order are presented for the square lattice with nearest and next nearest neighbour interactions.
Angular speed, angular momentum, and nonconnected shapes of free rotating fluid masses held by surface tension
Authors: Fortes M. A.
Published: April 2011

The classical problem of determining the axisymmetric equilibrium configurations of the interface between two fluids in rigid body rotation in the absence of gravity is re-examined. A clear distinction is made between the situations where either the angular speed ω or the total angular momentum Lt is fixed.Bifurcation of the sequence of equilibrium shapes of a given type may occur in some cases as ω or Lt is varied; the possibility of bifurcation as Lt changes depends on the total mass of the system. The stability of the shapes, in situations of bifurcation, is examined using a simple but conclusive argument. Finally the possibility of nonconnected interfaces, in the case where the surrounding fluid has lower density, is analysed leading to the conclusion that the imposed angular speed can reach slightly higher values than those allowed for simply connected shapes.
On the image representation of the fields of a line current source above finitely conducting earth
Authors: Mohsen A. , Shafai L.
Published: April 2011

The problem of an electric line source above a conducting earth is investigated. Approximations to the integrals appearing in the solution of the problem are considered. An estimate of the neglected terms is given and interpretation of their physical resemblance is presented. The analysis does not restrict the relative magnitudes of earth and air propagation constants as in previous work. It is shown that the approximation presented is legitimate for far field computation and the results are comparable to those known for the quasi-static limit.
Spectroscopie résonance électrique des jets moléculaires : formes des raies de résonance en présence d'effet Doppler
Authors: Chardon Jean-Claude , Miller Jean-Jacques
Published: April 2011

We describe effects related to the overlapping of Doppler lines (50 MHz to 1.5 GHz frequency band) in molecular beam electron resonance spectroscopy. We study the line shape when the width of one single resonance line is greater or smaller than the Doppler shift. Several results in low irradiation fields can be explained as interference of transition probability amplitude. In strong fields, the oscillations of the transition probability can increase and we observe also multiphoton transitions (incident and reflected photons). We show how important the effect of the phase of the reflection coefficient is.
Modèle de transitions de phase pour les monocouches de molécules amphiphiles à deux têtes polaires
Authors: Albinet G. , Legré J. P. , Firpo J. L. , Caillé A.
Published: April 2011

We propose a mean field model with two states to describe the monolayers of bipolar amphiphilous molecules (acido-basic, acid-ester, diacid, molecules, etc.) at the air–water interface. We show that the asymmetry and the width of the coexistence curve are related to intermolecular parameters (proportion of molecules in each state, interaction energy) and also to intramolecular parameters such as the curving of the aliphatic chains with increasing density that can even bring one of the polar heads to leave the surface, and with the variation of entropy in passing from one molecular state to the other. This last factor is also solely responsible for the coexistence curve asymmetry near the critical point.[Journal translation]
Quantum theory of hydrogen recombination
Authors: Greben J. M. , Thomas A. W. , Berlinsky A. J.
Published: April 2011

A fully quantum mechanical treatment is presented of the three-body recombination process H + H + 4He → H2 + 4He for T = 1 K where measurements have recently been performed. The calculation employs accurate interatomic potentials and thermal averaging. An impulse approximation is used to obtain the most important contributions to the rate constant. Off-shell effects are found to be important and are included in the final results which are in reasonable agreement with experiment. We find that the rate of formation of ortho-H2 is substantially larger than that of para-H2. The magnetic field dependence of the recombination rate is also discussed.
Analysis of a generalized N-particle interaction with application to the elastic constants of BCC crystals
Authors: Moore R. A.
Published: April 2011

In an earlier work a self-consistency condition for lattice dynamic models was proposed and applied for the purpose of comparing a number of existing models for BCC and FCC crystals. The unphysical result that the Cauchy relation is always satisfied, even in the general tensor force constant model, was obtained. In order to resolve this unsatisfactory situation the previous analysis is re-examined in some detail. The possibility that deficiencies exist in the form assumed previously for the internal potential energy function is checked by starting with a generalized form. That is, the potential energy is written as the sum of arbitrary two-particle and arbitrary three-particle angular contributions. It is then shown that general translational and rotational invariance requires the former to be central whereas the latter satisfy these invariances by definition. It thus follows and is demonstrated that the self-consistency condition was implemented improperly previously and that, in fact, the resultant interparticle forces give rise to pure deformation modes without restriction. This reverses the above unphysical conclusion. As an illustration all of the elastic constants for monatomic BCC systems are determined and those obtained from static deformations are shown to be identical to those obtained from lattice dynamics. The present analysis yields the detailed structure of the standard force constants and demonstrates that it is essential to interpret them as composite quantities. Further, the present analysis is sufficiently complete and general that it gives a basis for the discussion of any particular model.
Le spectre électronique de BS. Partie I : Analyse des perturbations du système A2Π–X2Σ+
Authors: Jenouvrier A. , Pascat B.
Published: April 2011

The deperturbed vibration–rotation constants of the A2Π and X2Σ+ states of BS are obtained. The perturbations in the levels of the A2Π state observed in the A2Π–X2Σ+ system are treated and are the result of interactions with high levels of the X2Σ+ state. The electronic factors of the spin–orbit and rotation–electronic perturbation matrix elements for the A ~ X interaction are evaluated. The deperturbed spin–orbit coupling constant of the A state is determined.
Rayonnement panoramique d'un train d'impulsions brèves par un laser à Rhodamine 6G dont le résonateur est fermé en géométrie cylindrique
Authors: Galarneau P. , Bedard G. , Chin S. L.
Published: April 2011

A "halo" type laser system is presented whose radiation is characterized by a propagation planar beam rather than a unidirectional beam. A doubled Nd:glass laser mode-locked picosecond pulse train is used to pump a Rhodamine 6G dye solution filling a cylindrical closed resonator. The laser short pulse train propagates in a plane across 360°, with mrad divergence transversely to the propagation plane.
On charmonium decays
Authors: Parashar D.
Published: April 2011

The decay rates of charmonium ([Formula: see text]bound states) are studied in the context of a simple quark confining potential model proposed earlier. In particular, we calculate the leptonic and hadronic decay rates of the S-states and a comparison is made with the available experimental data. The model prescriptions are then applied to predict the decay rates of the P-states of charmonium which are found to be consistent with other theoretical expectations.
The ν3 vibration–rotation band of DCP and the equilibrium structure of methinophosphide
Authors: Lavigne Jacques , Cabana Aldée
Published: April 2011

The ν3 band of D12CP(C—P stretching) has been recorded at a resolution of about 0.03 cm−1. The band centre, ν0, is found to be at 1231.4025(6) cm−1, whereas a force constant calculation had previously given a value of 1216 cm−1. The rotational constant B3 is determined and this allows the calculation of Be since the constants B1 and B2 are already known. Finally, the equilibrium moment of inertia, Ie, of the D12CP molecule is calculated. Since Ie for the H12CP molecule is also known, the equilibrium internuclear distances of methinophosphide may be calculated. One obtains: re (C—H) 1.0666(2) Å, and re(C≡P) 1.54020(3) Å.
The Fermi energy and screening length in n-type GaAs
Authors: Sritrakool W. , Glyde H. R. , Sa-Yakanit V.
Published: April 2011

The Fermi energy, EF, and the screening length, Q−1, in heavily doped n-type GaAs are calculated using the impurity band tail density of states derived recently by Sa-yakanit and Glyde. This density of states agrees with Halperin and Lax's result at low energies and can be extended to higher energies. The resulting EF and Q−1 agree well with values computed by Hwang using the Halperin and Lax density plus a somewhat arbitrary extrapolation. Compensation with attractive impurities is also introduced to lower EF and increase its sensitivity to the band tail density of states. However, EF can be lowered only a little without violating the Thomas–Fermi approximation upon which the concept of a screening length is based.
Scattered wave functions and electronic states of dislocations
Authors: De Hosson J. Th. M.
Published: April 2011

This article outlines a model for calculating the localized electronic states of a [Formula: see text] edge dislocation in α-Fe and in Mo. A method is presented using a Wannier function approach for calculating the scattered wave function of a dislocated lattice. The model used for the calculations of the electronic structure is based on the multiple scattering model. In addition the computer simulation procedure for calculating the atomic configuration of dislocations is combined with classical linear elasticity theory and the self-consistent scattered wave model.
The occurrence of the dynamic Stark effect in resonant CARS spectroscopy of a homogeneous medium
Authors: Ouellette F. , Denariez-Roberge M. M.
Published: April 2011

We discuss the occurrence of the dynamic Stark effect in resonant CARS spectroscopy for a homogeneously broadened medium. We use a four-level system interaction with three monochromatic fields of different frequencies. The equations of the density matrix are obtained in a rotating frame and solved numerically for the steady-state solutions. Analytical expressions are derived for five cases and show a splitting or a broadening of the CARS line. Stark shifts due to intense off-resonance fields are discussed.
Racah algebra for the double trigonal group
Authors: Lulek B. , Lulek T. , Chatterjee R.
Published: April 2011

A complete set of the 3jΓγ symbols for the double trigonal group [Formula: see text] is presented together with appropriate tables allowing evaluation of the numerical value of any Clebsch–Gordan coefficient for this group. The corresponding permutation matrices are derived. The complete set of 6Γ-symbols for both tensor and spinor representations is tabulated. The symmetry reduction problem for the chain [Formula: see text] involving a change of the axis of quantization is discussed in detail, and a full list of appropriate decomposition and reduction coefficients is given.
Inclusive cross sections, in the central region, in terms of a Pomeron which saturates the Froissart bound
Authors: Georgalas C. G. , Papargyropoulos P. H.
Published: April 2011

This paper explores further the implications of an approach previously suggested, in which the Pomeron contribution σp(S) to the hadronic cross sections is obtained as an approximate solution of an integral equation. The inclusive cross sections f(pc) for pp → cX, where c = π±, k±, [Formula: see text], are calculated, in the central region, in terms of σp(S), and found in good agreement with experiment. If σp(S) saturates the Froissart bound the main high-energy features of f(pc) are obtainable without free parameters.
The plasma resonance of electron-hole drops in uniaxially stressed germanium
Authors: Zarate H. G. , Timusk T.
Published: April 2011

The far infrared absorption spectrum of electron-hole drops in Ge under uniaxial stress S ≤ 20 kg/mm2 is studied. Large variations in positions and lineshape are observed for different stress values and direction of polarization of the infrared electric field with respect to the stress direction. A sharp decrease in the plasma frequency occurs at S ~ 3 kg/mm2, reflecting the change in occupancy of the conduction band valleys. The density of the fluid, n, as a function of [111] stress is obtained from the fit of the experimental results to a theory with the band structure modified by stress.
Raman studies of the and bombarded silicon surface
Authors: Mathur M. S. , Derenchuk V. P. , McKee J. S. C.
Published: April 2011

The surface of a P-type Si wafer was bombarded with [Formula: see text] and then [Formula: see text], and the Raman spectrum of the implanted surface was obtained. The recorded Raman spectrum not only confirms the formation of various silicon–oxygen, silicon–nitrogen, and silicon–oxygen–nitrogen complexes, but enables the identification of other ones.
On the entropy production in dissipative radiative plasmas
Authors: Schweizer Martin Andreas
Published: April 2011

An entropy production formula for dissipative radiative plasmas is derived. This result is consistent with Israel's theory of relativistic transient thermodynamics and it generalizes a formula obtained earlier by Weinberg from conventional relativistic hydrodynamics. It is shown that our formula follows independently from a phenomenological as well as from a kinetic approach. The emphasis in this paper is on the kinetic derivation. A special section is devoted to the role of bulk-viseous entropy production.
Photon interaction measurements of certain compounds in the energy range 30–660 keV
Authors: Perumallu A. , Rao A. S. Nageswara , Rao G. Krishna
Published: April 2011

The total photon interaction cross sections at six energies in the energy range 30–660 keV are determined in ten compounds, (NaNO3, KNO3, Sr(NO3)2, NaCl, SrCl2∙6H2O, BaCl2∙2H2O, NaClO3, (NH4)2SO4, MgSO4∙7H2O, and K2SO4) using a NaI(Tl) scintillation spectrometer in a good geometry setup. Analysis of the experimental data in terms of cross sections and effective atomic numbers is presented.
Fuzzy bag model: nucleon self-energy due to pion interaction
Authors: Nogami Y. , Suzuki Akira , Yamanishi Naoko
Published: April 2011

As pointed out earlier, the pion–quark interaction based on a bag model with a sharp, fixed surface gives rise to the divergence of various quantities such as the nucleon self-energy. This is due to quark excitation in the intermediate states. We examine how this difficulty can be moderated in a "fuzzy bag model" in which the surface is smeared. The nucleon self-energy due to pion interaction converges in the fuzzy bag model. We find, however, that the convergence is quite slow, and the contribution of processes such as [Formula: see text] pair creation, which have not been considered in earlier calculations, is very important.
Crystal-field theory for the Rydberg states of polyatomic molecules
Authors: Chiu Ying-Nan
Published: April 2011

The potential on a Rydberg electron due to the cluster of atoms near the center of a polyatomic molecule is expanded in powers of spherical harmonics. Nonvanishing potentials in totally symmetric irreducible representations are obtained using the crystal field of the cluster of atoms in D3h, C3v, D4v, C4v, Td, and D2d symmetries. Odd as well as the usual even powers of spherical harmonics are included up to [Formula: see text]. Spectroscopically observable differences in potentials between a planar versus a nonplanar XY3 molecule and among a square planar, pyramidal, tetrahedral, and dihedral XY4 molecule are exhibited. First-order energies are given for a Rydberg [Formula: see text] state showing λ dependence. Second-order energies due to mixing of Rydberg states by odd and even power potentials and splitting of ±λ degeneracies are shown analytically for an nd as well as an nf Rydberg electron. The formalism is applicable to nonpenetrating Rydberg orbitals. Approximate radial integrals are obtained. Exact angular integrals for the first- and second-order energies are given. Symmetry-adapted combinations of the separated Y3 and Y4 ligand atomic orbitals are derived up to d orbitals. The correlations between these linear combinations of atomic orbitals as molecular configurations change are shown, e.g., as an XY4 molecule distorts from (D4h, C4v) to (D2d, Td) and vice versa.
First experimental observation of far-infrared translational absorption in He–Ne mixtures
Authors: Marteau Ph. , Obriot J. , Fondere F.
Published: April 2011

Collision-induced absorption in He–Ne mixtures has been observed for the first time, in a path of 1.25 m at a total pressure of 1500 bar and a temperature of 77 K. The measured zeroth and second spectral moments are in good agreement with the calculated ones. Some details of the absorption profile are also discussed.
Collision-induced absorption in gaseous mixtures of nitrogen and methane
Authors: Dagg I. R. , Anderson A. , Yan S. , Smith W. , Joslin C. G. , Read L. A. A.
Published: April 2011

The collision-induced absorption spectra of nitrogen–methane gas mixtures have been measured in the spectral region below 400 cm−1 at four temperatures, namely, 212, 179, 149, and 126 K. The measurements have involved the use of Fourier-transform infrared and microwave techniques as well as a far-infrared laser operating at 84.2 and at 15.1 cm−1. These are compared with a theoretical line shape obtained from a convolution of free rotational spectra and a translational component as determined from information theory. The calculated spectra show good agreement with the experimental results only in the lower frequency region. An important feature of the theoretical development is that no adjustable parameters need be introduced.
Rigorous solution of a dipole antenna with lumped impedance loading
Authors: Saoudy S. , Hamid M.
Published: April 2011

Hurd's Wiener–Hopf solution for the input impedance of long dipoles is extended to yield analytic expressions for the input admittance, current distribution, and far-field radiation pattern of a linear cylindrical dipole antenna symmetrically loaded with lumped impedances along its length. Results from this model provide a more accurate expression for the current distribution on an infinitely long dipole antenna than previously reported by Shen et al. and are in good agreement with reported experimental and theoretical data. The new expressions give a better insight into the concept of standing- and travelling-wave antennas as well as the difference between loading with passive and active loads.
Magnetoresistance of intermediate concentration n-Ge at helium temperatures
Authors: El-Rafey E. , El-Atawy S. A.
Published: April 2011

Transverse magnetoresistance (TMR) measurements have been carried out at 4.2 and 1.7 K for magnetic fields up to 25 kG. The sample used is Sb-doped Ge with an intermediate level of concentration, ~6 × 1016 cm−1. At this doping level, two conduction regimes compete in the temperature range below 4.2 K. The temperature at which one regime gives way to another is 2.6 K. The TMR at 1.7 K has been found to be greater than that at 4.2 K. Moreover, at both temperatures, TMR is larger than that predicted by TMR theory for conduction-band electrons. In our case, TMR is mainly caused by carrier reduction with partial compensation by mobility increase. It has also been found that a magnetic field of 5.6 kG has no effect on the activation energies that exist at temperatures higher than 2.6 K, while it increases the lower temperature ones.
The magneto-optical properties of Cd3As2 exposed to circularly polarized radiation: interband transitions
Authors: Lamrani H. El Alaoui , Aubin M. J.
Published: April 2011

The first measurements of the interband magnetotransmission of Cd3As2 using circularly polarized radiation are reported. The single crystals were mounted in the Faraday configuration at 10 K. An analysis of the experimental results on the basis of the Bodnar model shows that spin splitting of the conduction electrons has been observed. A further analysis of the model shows, however, that it predicts an unrealistic behavior of the valence-band Landau levels (this constitutes the first reported results concerning this band). Thus, it is not possible to fit the data to the model, but by assuming a flat heavy-hole band, a reasonable fit is obtained. A calculation of the transition probabilities also leads to consistent results. It is concluded that changes in the Bodnar model are necessary to describe the valence band correctly.
Short-range order and concentration fluctuations in binary molten alloys
Authors: Singh R. N.
Published: April 2011

The quasi-chemical theory and the quasi-lattice theory are discussed with a view to obtaining information about concentration fluctuations, SCC(0), and the short-range order parameter, α1, for regular and compound-forming molten alloys. The influence of the coordination number z and the interchange energy ω on the mixing properties of the alloy is critically examined. SCC(0) and α1 have been found to be very useful in extracting microscopic information, like local ordering and segregation in molten systems. The problem of glass formation in compound-forming binary molten alloys is also briefly discussed.
A variational perturbation theory of inhomogeneous liquid metals: applications to the calculation of surface properties
Authors: Hasegawa M. , Watabe M.
Published: April 2011

Assuming that the electron–ion interaction can be treated by a weak pseudopotential, we develop a theory for calculating the thermodynamic properties of inhomogeneous liquid metals. We first derive an effective Hamiltonian for the classical ion system using an improved perturbation expansion in the pseudopotential, in which an averaged ionic potential is effectively included in the unperturbed electron system. The Helmholtz free energy is then calculated using the variational method based on the Gibbs – Bogoliubov inequality. The results of this formulation are compared with the previous theories, and the approximations involved in these theories are critically analyzed. Finally, the formulation is applied to liquid-metal surfaces and the surface tension is calculated. In these applications, we use the classical one-component plasma as the reference system of the variational method.
Electron capture and loss by fast fluorine atoms in collisions with rare gas targets
Authors: Hird B. , Rahman F. , Orakzai M. W.
Published: April 2011

Cross sections are reported for the production of fast negative fluorine ions in collisions between a neutral fluorine beam and single atoms of each of the rare gases, at collision energies between 20 and 110 keV. The energies at which the cross sections pass through a maximum fit very well with the Massey criterion, assuming a simple electron-transfer theory. The cross sections for the production of fast fluorine positive ions are also reported. These are found to be smallest for the heavy targets and reach a maximum in helium and neon, which have higher ionization potentials than fluorine.
Geodetic study of some homogeneous space–times
Authors: Krori K. D. , Goswami D.
Published: April 2011

We present here a geodetic study of three homogeneous space–times, viz., (a) Hoenselaers–Vishveshwara space–time, (b) Som–Raychaudhuri space–time, and (c) Reboucas space–time. Each of them exhibits the property of gravitational confinement. There are, however, some basic differences between the three space–times that we point out at the end of the paper.
Nondestructive analysis of thick-target specimens by γ-ray backscatter
Authors: MacKenzie I. K.
Published: April 2011

A multipurpose X- and γ-ray spectrometer for nondestructive analysis is described. It achieves high throughput through its axially symmetric geometry. Its evolution from a research program in positron annihilation is outlined as is its historical background in the determination of electron-momentum spectra. Several applications are discussed but special attention is paid to the nondestructive analysis of the new Canadian dollar coin.
Primary energy estimation in proton–nucleon and proton-nucleus interactions at 800 GeV
Authors: Shivpuri R. K. , Prasad A. , Joseph R. R.
Published: April 2011

The validity of various available methods for the estimation of the primary energy in proton–nucleon and proton–nucleus interactions has been examined by using the data of the highest available machine energy for fixed targets, i.e., 800 GeV. To test the different methods for primary-energy determination for various subsamples, the data was divided into different secondary-particle multiplicity groups. It was found that Castagnoli's method (C. Castagnoli, G. Cortini, C. Franzinetti, A. Mannfredini, and A. Moreno. Nuovo Cimento, 10, 1539 (1953)). yields the best results for energy estimation for proton–nucleon collisions while the method of Gibbs et al. (R. E. Gibbs, J. R. Florian, L. D. Kirkpatrick, J. J. Lord, and J. W. Martin. Phys. Rev. D, (10, 783 (1974)). yields the best results for proton–nucleus collisions.
Global asymptotic analysis of the Kelvin–Helmholtz instability of supersonic shear layers
Authors: Choudhury S. Roy
Published: April 2011

A global asymptotic analysis of the traveling wave Kelvin–Helmholtz instability of a supersonic finite-width velocity shear layer, having a linear velocity profile, is carried out. The structure of the resulting traveling wave solutions, comprising a composite Wilhelm–Kramers–Brillouin–Jeffreys and boundary-layer solution that satisfies outgoing spatially damping radiative wave boundary conditions, agrees closely with previously computed numerical results. The condition for the occurrence of the traveling wave instability is derived and the absence of this mode in compressible vortex sheets is explained. The energy density and energy flux density of both the unstable standing and traveling wave modes is considered in the context of the radiative boundary conditions.
The Schrödinger equation in a generalized noncovariant gauge
Authors: Islam Jamal Nazrul
Published: April 2011

The Schrödinger functional equation for the pure Yang–Mills theory with SU(2) as the gauge group is considered in a generalized noncovariant gauge, and related to the Schrödinger equation in the temporal gauge.
Molecular constants of 128Te2
Authors: Babaky O. , Hussein K.
Published: April 2011

Laser-excited fluorescence spectra of 128Te2 were studied by high-resolution Fourier transform spectroscopy, the sources of excitation used were Ar+ and Kr+ laser lines at 5145, 4880, 4579, and 4131 Å. (1 Å = 10−10 m). Transitions involving three upper states, [Formula: see text] and [Formula: see text] and three lower states [Formula: see text] and [Formula: see text] have been identified. The molecular constants of the lower states were determined with high precision. These constants were used to obtain the Rydberg–Klein–Rees potential curves of the states for vibrational levels ν up to 42. Limited results were also obtained for the upper states [Formula: see text] and [Formula: see text]
An integral approach to the calculation of skin friction and heat transfer in the laminar flow of a high-Prandtl-number power-law non-Newtonian fluid past a wedge
Authors: Ramamurty G. , Rao K. Narasimha , Seetharamu K. N.
Published: April 2011

An integral approach to the theoretical analysis for the skin friction of a non-Newtonian, power-law-fluid flow over a wedge is presented, when the inertia terms in the boundary-layer equations are small but need consideration. The method adopted for the solution of the equations considers an integrated average value of the inertia terms in the momentum equation. The values of the velocities and the boundary-layer thickness obtained from the hydrodynamic analysis are used for the calculation of the thermal-boundary-layer thickness. A linear velocity profile is assumed for the flow field within the thermal boundary layer as the fluids chosen for the analysis are high-Prandtl-number fluids. The results of the skin friction and the rates of the heat transfer are tabulated for a number of values of the flow behaviour index, n, varying from 0.05 to 5.0. This analysis is applicable to viscous polymer solutions having high Prandtl numbers.