bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural destabilization induced by lithium intercalation in MoS2 and related compounds
Authors: Py M. A. , Haering R. R.
Published: April 2011

2H-MoS2 is a semiconductor with a hexagonal layered structure. Each Mo atom is prismatically coordinated by six S atoms. Our in situ X-ray diffraction results indicate that, upon intercalation, the MoS2 host lattice undergoes a first order phase transition in which the Mo coordination changes from trigonal prismatic to octahedral (1T structure). The driving mechanism for this structural change is discussed in terms of a charge transfer from the lithium to the host and in terms of the respective energy-band diagrams for 2H and 1T polytypes. Intercalation-induced reversals in the relative stability of trigonal–prismatic and octahedral phases may also be expected in other semiconducting hosts.
The principle of minimum sensitivity and moments of nonsinglet structure functions
Authors: McKeon Gerry
Published: April 2011

The corrections implied by quantum chromodynamics to parton model predictions are not unique to finite order in perturbation theory on account of the possibility of choosing different renormalization schemes. Stevenson has provided a criterion for selecting the "best" renormalization procedure; the so-called "principle of minimum sensitivity" (PMS). This criterion is applied here to the Q2-dependent part of the moments of the nonsinglet structure functions in lepton–hadron scattering.
Vacancy formation energies in bcc and fcc stainless steels by positron annihilation
Authors: Kim S. M. , Buyers W. J. L.
Published: April 2011

The temperature dependence of the positron annihilation peak coincidence rate has been measured in bcc and fcc stainless steels. Trapping model analysis of the data shows that the vacancy formation energies in the bcc stainless steels are about 20% lower than those in the fcc stainless steels. The vacancy formation energies calculated from current theoretical models are about 10–15% larger than those determined experimentally.
Fermi surface pressure dependence in potassium
Authors: Coleridge P. T. , MacDonald A. H.
Published: April 2011

The pressure dependence of the Fermi surface of K has been calculated using the Korringa–Kohn–Rostoker (KKR) method and local exchange potentials adjusted to simulate the effect of a nonlocal operator. Agreement with the experimental data is obtained. Some effective masses have also been calculated.
Time evolution, relaxation function, and random force for a single-spin model via the method of Mori
Authors: Lee M. Howard
Published: April 2011

We introduce a single-spin model defined by the Hamiltonian H = aSz + bSx, where a and b are constants and Sx and Sz are the x- and z-components of the spin [Formula: see text] operator. We obtain for this model the time-dependent behavior exactly and completely via the method of Mori. To gain an insight into the quantum mechanical mechanisms of time evolution, we make a comparison with Brownian motion by deducing a number of Brownian analogs. Brownian analogs include the spin memory function as well as the random force and its power spectrum.
Energy spectrum of cosmic ray primaries at super high energies estimated from the recent balloon-borne calorimeter measurements
Authors: Bhattacharyya D. P.
Published: April 2011

The energy spectrum of primary cosmic ray particles has been estimated from the analysis of the chemical composition data of high energy cosmic rays, data obtained by the Japanese American cooperative emulsion experiments for proton and helium intensities and the Goddard Space Flight Centre measurements for cosmic ray nuclei. The results indicate no drastic change in abundance ratios at high energies. The elemental fluxes have been calculated by assuming that the primary cosmic ray nuclei break up into their constituent nucleons near the top of the atmosphere. The calculated total primary spectrum in the range 2–300 TeV follows the form N(E) dE = 2.24 × 104 E−2.7 dE where E is the energy expressed in GeV/nucleon and N(E) is the intensity expressed in (m2∙s∙sr∙GeV/nucleon) −1.Using this primary spectrum as the source of nucleons near the top of the atmosphere, the sea level proton and neutron spectra have been estimated by using the Feynman scaling hypothesis and the conventional nucleon-atmospheric diffusion equation. The derived spectra are in accord with the measured proton and neutron spectra of Brooke and Wolfendale, Ashton and Coates, and Ashton et al.
Coefficients du viriel de la réfractivité de l'azote a 25 °C
Authors: Montixi G. , Coulon R. , Occelli R.
Published: April 2011

We measured accurately the refractive index of nitrogen at 25 °C between 40 and 400 bar, and calculated the refractivity R = (n2 − 1)/(n2 + 2)1/ρ. Particular attention is given to the determination of the density ρ, which is the limitation of accuracy on R. We calculate the refractivity virial coefficients AR, BR, and CR, the last one being given for the first time.The results are compared with the published data, the dielectric virial coefficients, and the induced absorption. The Buckingham expression of BR is calculated for N2 and compared with our values.
A one-dimensional study of tokamak current reversal
Authors: Storey L. R. O.
Published: April 2011

The possibility of being able to reverse the toroidal current in a tokamak, without undue loss of plasma, is studied using diffusive magnetohydrodynamics (MHD), together with a one-dimensional model in which the torus is represented by a long cylindrical slab. For a plasma with free surfaces, it predicts that the entire plasma will expand outwards and be lost before the current even changes sign. However, interaction of the outer surface with conducting limiters can impede the expansion, and other ways of preserving the plasma may exist in two dimensions, so current reversal may be feasible after all.
A theoretical simulation of bulk water
Authors: Fraga Serafin
Published: April 2011

A new formulation developed at this laboratory has been used in the study of a water cluster with 65 molecules. The fact that the calculated average potential energy per molecule agrees with the Monte Carlo result at 300 K suggests that this method, which is fast and inexpensive, might be used to obtain estimates of such energies for other systems as well as in generating starting configurations for Monte Carlo calculations.
Thermal behavior of a solid particle in an arc discharge during transient cooling conditions
Authors: Meubus Paul , Elayoubi Mustapha
Published: April 2011

The thermal behavior of a tungsten particle has been studied in an argon arc discharge during transient extinction conditions. At the beginning of the transient process, the particle is electrically neutral and is at the cathode voltage. During this period of time, it is observed that the thermionic cooling effect plays a major role in the heat transfer mechanisms. Within the limits of the solid surface and surrounding gas temperatures investigated, which varied between 3600 and 3300 K for the surface and between 8000 and 6000 K for the argon gas, the heat transfer rates by convection and radiation are of the same magnitude but opposite in sign. Each of them amounts to less than 10% of the heat loss rate induced by thermionic emission. Besides the theoretical aspect of the study, the cooling effect observed (about 6 × 104 K s−1) may be of interest for improving solid surface properties, provided that the solid particle possesses characteristic thermionic emission properties.
Effects of energy dependence in the electronic density of states on some superconducting properties
Authors: Mitrović B. , Carbotte J. P.
Published: April 2011

We study the influence of energy dependence in the electronic density of states (EDOS) on the single particle tunneling characteristics into a superconductor. The Migdal–Eliashberg equations generalized to the case of a nonconstant EDOS are derived. Three equations are involved, one for the gap, another for the renormalization function, and a new one for the chemical potential shift which does not appear in the conventional formulation. Numerical solutions of these equations are obtained, from which current voltage characteristics are calculated for a model EDOS. The "inversion" of the calculated tunneling conductance shows that the effects of the peaks in the EDOS, on the scale of several Debye energies are important and cannot necessarily be reproduced within the usual Eliashberg theory by working with some effective value of electron–phonon spectral density α2(ω)F(ω) and/or Coulomb parameter μ* without introducing unphysical features to these parameters.
Free energy formula for a strong coupling superconductor with energy dependent electronic density of states
Authors: Mitrovic B. , Carbotte J. P.
Published: April 2011

Generalized expressions for the free energy difference between normal and superconducting states are derived for the case of an energy dependent (ED) electronic density of states (EDOS) with normal and paramagnetic impurity scattering included. The derivation starts from the Eliashberg expression for the grand thermodynamic potential and ends in explicit formulas for the case of a symmetric Lorentzian model EDOS. Some numerical results are given for the critical magnetic field deviation function and the ratio 2Δ0/kBTc of the Δ0 to the critical temperature Tc. For a peak at the Fermi energy of half width less than the Debye energy (ωD), the modified Eliashberg theory is needed to describe its effect on the thermodynamic properties, whereas for a half width greater than ωD, the corrections to a flat approximation are small.
Lineshifts in the first overtone band of CO self-perturbed and perturbed by N2 at 298, 193, and 133 K
Authors: Bouanich J.-P.
Published: April 2011

The very small frequency shifts of CO vibration–rotation lines self-broadened and broadened by N2 have been estimated in the 2–0 band at 25, −80, and −140 °C. At constant density, these lineshifts appear to decrease slightly with decreasing absolute temperature. Calculations of lineshifts have been carried out for the molecular pairs CO–CO and CO–N2 at 25 °C.
Binary collisions in fluids: I: single particle density correlation function
Authors: Fletcher T. J. , Ranganathan S.
Published: April 2011

Binary collision expansion is applied to the space–time memory function associated with the single particle density correlation function. The use of the potential of mean force as the interaction potential in the determination of two particle dynamics, thus taking into account the structural correlations of the fluid, is found to yield significantly improved results for the correlation function. Comparison of our results with molecular dynamics and experimental values shows very good agreement over a wide range of densities and wave vectors.
Doppler-free two-photon absorption spectrum of potassium
Authors: Thompson D. C. , O'Sullivan M. S. , Stoicheff B. P. , Xu Gen-Xing
Published: April 2011

Doppler-free two-photon spectroscopy has been used to investigate the transitions n2S ← 42S (n = 6 to 55) and n2D3/2.5/2 ← 42S (n = 5 to 50) of 39K. Wavelengths of these transitions have been measured to an accuracy of 1 part in 107, and term values, quantum defects, fine structure splittings, and isotope shifts have been evaluated. The value of the ionization limit determined from these measurements is 35 009.8232 ± 0.0010 cm−1.
The slowdownatron: A suggestion for increasing stopping rates by using shaped magnetic field and absorbers
Authors: Sundaresan M. K. , Watson P. J. S.
Published: April 2011

We suggest the possibility of combining a momentum separator, consisting of a uniform magnetic field at right angles to a beam of particles, with a shaped absorber to obtain enhanced stopping rates. It is shown that by suitably shaping the magnetic field, one can obtain a form of linear focussing and derive the relevant equations for the magnetic field and absorber. Straggling is taken into account. We show that with certain (optimistic) assumptions the device could give three orders of magnitude improvement in stopping rates. Other problems are outlined, and finally we discuss what such a device could be used for.
Attenuation of low frequency fields by conducting ellipsoidal shells
Authors: Curzon F. L. , Parfeniuk D. A.
Published: April 2011

The diffusion rate (λ, s−1) of a spatially uniform, switched-on, field through a prolate spheroidal shell, has been related to the geometry of the shell, and orientation of the field with respect to it. The shell is assumed to be an isotropic ohmic conductor; the fields are described by Poisson's equation.For a spatially uniform alternating field (frequency ω), the attenuated field inside the shell is shown to be a function of λ/ω; the smaller this ratio, the lower the attenuation. The computed results have been verified experimentally and by checking them against exact solutions which are available for limiting cases of the general problem. The results are relevant to the properties of an electric field meter whose sensor is a gas-filled glass bulb. The breakdown frequency of the gas depends on the field within it.
Far-infrared powder spectrum of (N(CH3)3D)(I)(TCNQ)
Authors: Eldridge J. E. , Fortier Normand , Bates Frances E. , Miller J. S.
Published: April 2011

We present the powder absorption spectrum of (TMA)(I)(TCNQ) in the far-infrared as a function of temperature. Below 160 K new absorption features appear and others increase in intensity. This behaviour supports the electron- and neutron-diffraction evidence of a distortion on the TCNQ chains below the first phase-transition temperature. Effects due to the second phase transition at 89 K are also observed. The results of a group-theoretical analysis are presented. These show that totally-symmetric internal modes ag are to be expected in the infrared spectra of this compound even in the undistorted phase.
Electrodeless breakdown in elliptically polarized fields at 60 Hz
Authors: Friedmann D. E. , Curzon F. L. , Feeley M.
Published: April 2011

Theoretical and experimental results are presented on the frequency of electrodeless breakdown (fB) of a gas in a spherical glass bulb immersed in an elliptically polarized field of maximum field strength [Formula: see text] and frequency fA (~60 Hz). It is found that the breakdown threshold is independent of the ellipticity and that graphs fB versus [Formula: see text] are stepped at low fields and linear at high ones. At high fields, fB = fAl/e0 where l is the circumference of the phasor and e0 is the breakdown strength of the gas ([Formula: see text] and [Formula: see text] respectively for circular and linear polarization). The implications of the results for measuring environmental fields are given.
The 1s–2s and 1s–2p excitation of helium ions by electron impact
Authors: Basu Madhumita , Mazumder P. S. , Ghosh A. S.
Published: April 2011

The electron impact excitation of He+ to the n = 2 level is studied using two variants of the polarized orbital method, one due to Daskhan et al. and the other due to Temkin and Lamkin. The present results for 1s–2p total excitation cross sections are in fair agreement with the measured values. For the 1s–2s excitation, our values fail to reproduce the more elaborate theoretical prediction by Morgan near the threshold energies.
C2Πr – X2Σ+ transition of AlO
Authors: Singh M. , Saksena M. D.
Published: April 2011

Several bands of the C2Πr – X2Σ+transition of AlO in the region 2800–3400 Å have been photographed at high resolution. A unique and unambiguous analysis of the rotational structure has been done for the first time for the 2–0, 1–0, 2–1, 0–0, 1–1, 0–1, 1–2, and 0–2 bands of this system. Fairly accurate rotational constants Beff and Deff have been determined for the ν = 2, 1, and 0 levels of the C2Πr state. Severe rotational perturbations have been observed in the C2Π, state.Equilibrium rotational constants (in cm−1) of the C2Π, state are Be ≈ 0.6049 and αe ≈ 0.0046.
Spin quenching and EPR of Mn2+ in K2Ni(SeO4)2∙6H2O single crystals
Authors: Malhotra R. K. , Seth V. P. , Jain V. K.
Published: April 2011

An electron paramagnetic resonance study of Mn2+ in K2Ni(SeO4)2∙6H2O single crystals has been made at 294 K and 9.45 GHz. The Mn2+ substitutes at Ni2+ sites in the lattice. The spin-Hamiltonian parameters are evaluated. The observations regarding the anisotropic and field dependent line widths of Mn2+ in the lattice are discussed using the spin-quenching concept.
Zakharov–Manakov solution of the 3-wave explosive interaction problem
Authors: Enns R. H. , Rangnekar S. S.
Published: April 2011

The inverse scattering transform method has been applied to the on-resonance 3-wave explosive interaction problem. In particular, the Zakharov–Manakov problem has been solved to yield the complete spatial and temporal evolution of the envelopes of the three waves involved. A comparison with numerically derived envelope shapes is made and the results are discussed.
Spectres microondes et structure du bromopentafluorure de soufre
Authors: Jurek R. , Goulet P. , Verry C. , Poinsot A.
Published: April 2011

Using microwave spectroscopy we obtain the rotational constants of SF5Br for various isotopic species. The geometry derived from these constants, compared with the SF5Cl geometry, shows important differences relative to the different bond lengths.
Hydrostatic pressure and uniaxial stress derivatives of the Fermi surface of rhenium
Authors: Anderson J. R. , Holroyd F. W. , Perz J. M. , Schirber J. E. , Templeton I. M.
Published: April 2011

Derivatives with respect to hydrostatic pressure of extremal cross-sectional areas normal to [Formula: see text] of all closed sheets of the Fermi surface of rhenium have been determined by both fluid–helium and solid–helium phase shift techniques. Precise values of de Haas–van Alphen frequencies and effective masses have also been measured for these cross sections. In addition, uniaxial stress derivatives of the zone seven cross sections have been deduced from quantum oseillations in magnetostriction and torque. Previously observed anomalies in the pressure dependence of the superconducting transition temperature are interpreted in terms of the present results.
The far-infrared spectrum of hydrogen sulfide. The (000) rotational constants of , , and
Authors: Flaud J.-M. , Camy-Peyret C. , Johns J. W. C.
Published: April 2011

The pure rotation spectrum of hydrogen sulfide has been recorded between 50 and 320 cm−1 with a Fourier transform spectrometer at an apodized resolution of 0.005 cm−1. This high resolution and a good signal-to-noise ratio lead to a significant improvement in the accuracy of the wavenumbers of the rotational transitions of the three isotopic species [Formula: see text], [Formula: see text], and [Formula: see text] that were observed in natural abundance. These rotational transitions, together with the available microwave data, have been included in a least squares fit leading to the determination of precise rotational constants for each isotopic species. Finally, these constants have been used to calculate precisely the absorption of natural hydrogen sulfide in the far-infrared region of the spectrum.
Infrared absorption in doped rare gas crystals
Authors: Vermesse J. , Levesque Dominique , Weis Jean-Jacques , Klein Michael L.
Published: April 2011

Molecular dynamics calculations based upon realistic pair potentials plus three body forces are used to investigate the properties of solid argon doped wth 2% krypton. The infrared absorption, which is computed using an expression for the interaction dipole moment derived from gas phase data, agrees well with experimental data.
The collision induced contribution to the depolarized Raman spectrum of compressed HCl, CO, N2 and CO2
Authors: Tam R. C. H. , May A. D.
Published: April 2011

The depolarized Raman spectrum of compressed HCl at 60 and 55 °C was measured at a number of densities. Several theoretical calculations and an analysis of the spectra support the view that the spectrum at densities above 80 amagat is dominated by a collision induced component. The calculations also show that the neglect of a collision induced contribution to the depolarized Raman spectrum of CO, N2, and CO2 is justified.
Binary collisions in fluids: II: velocity auto correlation function
Authors: Ranganathan S.
Published: April 2011

A calculation based on the Zwanzig–Mori formalism and the binary collision expansion is presented for the velocity auto correlation function (VCF) of simple classical fluids. The binary collision expansion is truncated after the second term, thus incorporating exactly all the effects of a single collision between two particles, and this expansion is applied to the memory function associated with the VCF. The only inputs required are the pair distribution function g(r) and a central potential U(r). The potential chosen is the Lennard–Jones potential. It is seen that the approximation of the memory function by the binary force auto correlation function yields results for VCF that are in very good agreement with molecular dynamics results over a wide range of densities from dilute gases to liquids.
Thermoelastic parameters of crystals
Authors: Mehrotra V. B. L. , Misra R. M. , Singh Ram , Shukla D. D. , Sharma M. N. , Madan M. P.
Published: April 2011

The parameters C1 = [∂(1/KT)/∂P]T, which describes the pressure variation of the compressibility, δT, the isothermal Anderson–Grüneisen parameter, and mT = (∂ ln KT/∂T)P, which describes the temperature variation of the compressibility, have been investigated for some face-centred cubic (f.c.c.) and body-centred cubic (b.c.c.) types of ionic crystals using a central force, rigid-ion interaction approach employing fewer approximations than has been usual heretofore. A theoretical estimate of these parameters is made by using thermodynamic relationships, including the expression for the parameter q that describes the volume variation of the Grüneisen parameter, and choosing a few modified and realistic potential functions. The results compare well with the available experimental data and exhibit an essential improvement over other theoretical determinations.
Sn hyperfine field systematics in Rh2MnZ Heusler alloys
Authors: Dunlap R. A. , Jha S. , Julian G. M.
Published: April 2011

Sn hyperfine fields were measured using Mössbauer spectroscopy in the Heusler alloys Rh2MnZ (Z = Ge, Sn). The measurements yielded values of −48 and +31 kOe at 77 K for Sn in Rh2MnGe and Rh2MnSn, respectively. These values showed that in these alloys the Sn hyperfine field decreases with increasing conduction electron density. These results are compared with those obtained for Sn hyperfine fields in X2MnZ and Co2YZ Heusler alloys and are discussed in terms of theoretical predictions.
Short-range and long-range correlations in cosmic ray interactions
Authors: Hasan R. , Khan M. Q. R. , Ahmad M. S. , Swami M. S.
Published: April 2011

Forward–backward correlations in the centre of mass system have been studied in nucleon–nucleon interactions at cosmic ray energies [Formula: see text]. The study indicates the presence of short-range as well as long-range correlations. The study also indicates the production of heavy clusters, predicted by Adamovich et al. in their multiperipheral model, in cosmic ray interactions.
Ultrasonic attenuation and electrical resistivity in p-InSb at low temperatures and high magnetic fields
Authors: Madore G. , Cheeke J. D. N.
Published: April 2011

A complete account is presented of electrical conduction and ultrasonic attenuation processes in p-InSb from 300 K down to 4 K. Four specimens were studied in the concentration range of 1014–1017 for net acceptor impurities. The ultrasonic measurements were made in the frequency range 30–700 MHz in magnetic fields up to 7 T. Supporting direct current (DC) conductivity and Hall effect data showed that carrier thermal freeze-out occurs near 5–6 K. At slightly higher temperatures we observe a relaxation peak in the attenuation for piezoelectric modes. This can be explained in detail by the theory of Hutson and White, which is used to make a qualitative determination of the piezoelectric coupling constant and the dc conductivity.
Empirical interionic potentials for alkali halide molecules
Authors: Szymanski J. E. , Matthew J. A. D.
Published: April 2011

A systematic study of families of empirical internuclear potential energy functions based on the Rittner potential is presented for alkali halide molecules, and comparison is made with recent binding energy and anharmonic constant data. It is concluded that the Rittner formalism, however parameterized, is incapable of consistent prediction of several molecular properties simultaneously, and that the potential seems to be failing to model some aspect of the detailed bonding of the molecule. Inclusion of a Gaussian form of repulsion potential in the model gives excellent agreement for the dissociation energies, but in general extreme care must be taken when applying empirical potentials of the Rittner form to more complex systems such as ionized molecules or clusters.
Search for dynamical correlation among relativistic particles produced in 300 GeV proton–nucleus interactions
Authors: Ghosh Dipak , Roy Jaya , Basu Madhumita , Sengupta Kaushik , Naha Sadhan , Bhattacharyya Anuradha
Published: April 2011

This paper presents a detailed study of the two-particle rapidity correlations among the relativistic particles produced in proton–nucleus interactions in emulsions at 300 GeV/c. A Monte Carlo simulation has been performed to search for dynamical effects. The target nucleus excitation dependence of the correlation has been studied. This dependence agrees with a prediction of the additive quark model.
Computation of electrical conductivity and thermoelectric power in strong-scattering disordered metals
Authors: Ballentine L. E. , Hammerberg J. E.
Published: April 2011

We describe a method of computing electronic transport coefficients in liquid and amorphous metals by numerical evaluation of the Kubo formula for a cluster of a few hundred atoms. s and d states are treated equally, and no assumptions need be made about the number of carriers per atom. Finite size and shape effects, and other computational aspects, are examined. The method is applied to liquid La. The calculated (measured) values are 151 μΩ∙cm (135 μΩ∙cm) for the resistivity, and −7 ± 1 μV/K (−7.5 μV/K) for the thermoelectric power. The relative contributions of s and d states to electronic transport are computed, and we find the d states to be dominant.
The diffusion cross section for atomic hydrogen in helium gas at low temperature and the H–He potential
Authors: Jochemsen R. , Berlinsky A. J. , Hardy W. N.
Published: April 2011

A calculation of the diffusion cross section QD of hydrogen atoms in helium gas at low temperature is performed and compared with recent experimental results. The comparison allows an improved determination of the H–He potential. Calculations were done for three different potentials: our own empirical potential based on experimental high-energy scattering results and calculated long-range dispersion terms, which gives good results for QD and total collision cross sections; a recently determined semi-empirical potential, and an ab initio calculated potential. All three potentials imply a strong temperature dependence of QD for T < 1.5 K.
Superconducting energy gap of NbS2
Authors: Kennedy R. J. , Clayman B. P.
Published: April 2011

The superconducting energy gaps of small particles (1–10 μm) of 2H–NbS2 and 2H–NbSe2 have been measured by far-infrared (FIR) transmission spectroscopy. Comparison of these results with previous FIR measurements made on millimetre-size single crystals of 2H–NbSe2 validates the use of the novel method of sample preparation used here. Comparison of the gap frequencies (νg) with the superconducting transition temperature (Tc) determined by magnetic susceptibility measurements indicates that 2H–NbS2, unlike 2H–NbSe2, exhibits non-Bardeen–Cooper–Schrieffer (BCS)-like behaviour, with hνg/kTc = 2.3.
Casimir stress in spherical media when εμ = 1
Authors: Brevik I. , Kolbenstvedt H.
Published: April 2011

The radial and azimuthal stress components of the electromagnetic zero-point field are calculated inside and outside a spherical surface dividing two media of permeabilities μ1 and μ2. The corresponding permittivities ε1 and ε2 are such that εμ = 1 everywhere. Schwinger's source theory is used. In the inside region all stress components are negative, corresponding to a negative pressure. In the outside region the signs of the angular stress components are reversed, similar to the case for the energy density.
A group theoretical method for the construction of the nonequivalent configurations of finite clusters with cellular disorder
Authors: Bonadeo H.
Published: April 2011

The nonequivalent configurations of finite clusters with cellular disorder may be constructed by combining subconfigurations of atoms located at lattice sites that are equivalent by symmetry. The combination laws depend only on the symmetry of the cluster and are obtained from point group theoretical arguments. The method may be applied to clusters of arbitrary symmetry and composition, and is illustrated with a simple example.
Gamma rays produced in the 209Bi(n, n′γ) reaction
Authors: Prestwich W. V. , Kennett T. J. , Tsai J. S.
Published: April 2011

A high-resolution study of the γ-ray spectrum induced by the inelastic scattering of reactor produced neutrons has been conducted. The γ rays observed have been assigned in a decay scheme involving 134 levels extending in excitation energy to 6 MeV. The results are discussed within the context of previously identified weak coupling configurations, and possible discrepancies are indicated. Levels in the high-energy region are also compared with recently reported photoexcitation studies.
Remarks on the microscopic derivation of the collective model
Authors: Toyoda Tadashi , Wildermuth Karl
Published: April 2011

The rotational part of the phenomenological collective model of Bohr and Mottelson and others is derived microscopically, starting with the Schrödinger equation written in projection form and introducing a new set of "relative Euler angles." In order to derive the local Schrödinger equation of the collective model, it is assumed that the intrinsic wave functions give strong peaking properties to the overlapping kernels.
Comment: On the nonsymmetric Jordan–Thiry theory
Authors: McKellar R. J.
Published: April 2011

This comment points out the fact that Kalinowski's "nonsymmetric metrization of fibre bundles" cannot be applied, owing to the vanishing of all bi-invariant 2-forms on a semisimple Lie group.
Recent studies of radiative capture and photodisintegration in few-nucleon systems
Authors: Meyer H. O.
Published: April 2011

A recent measurement of the neutron–proton radiative capture cross section at Tn = 185 MeV is discussed in the context of previous data and current theories. The method used to obtain an absolute normalization of the data is outlined. Recent data on proton–deuteron capture are also presented and discussed. Future plans are indicated.
The branching ratio in the decay of 7Be
Authors: Evans H. C. , Johnstone I. P. , Leslie J. R. , McLatchie W. , Mak H.-B. , Skensved P. , Alexander T. K.
Published: April 2011

A measurement of the branching ratio for electron capture (EC) decay of 7Be to the 478-keV level in 7Li is reported. The reaction 10B(p, α)7Be was used and the 7Be recoils were detected and stopped in a particle detector thin enough to transmit the protons. The absolute γ-ray emission rate of 478-keV γ rays from the implanted detector was determined with a well-shielded intrinsic Ge detector. The absolute efficiency of the Ge detector was established with 22Na, 137Cs, and 88Y standard sources. A value of 11.4 ± 0.7% was obtained for the EC branch to the 478-keV state. Calculations suggest that the axial vector coupling constant GA must be reduced by a factor of 0.94 ± 0.02 to obtain agreement with the experimental result.
Dynamics of quark–bag vibrations: alternative methods
Authors: Azam S. , Nogami Y. , Volkov A. B.
Published: April 2011

Two alternative methods are examined for solving the Schrödinger equation for the coupled quark–bag system in Nogami and Tomio's dynamical bag model.
Green's function equations of motion for driven two-level atoms
Authors: Zaidi H. R.
Published: April 2011

Using a diagram technique, equations of motion for N coherently driven two-level atoms are obtained from Green's functions. The longitudinal (Coulomb) dipole–dipole interaction is neglected. Three approximations (Born approximation, extended Born approximation, and screened interaction approximation) are considered. The existing theories are shown to be equivalent to the extended Born approximation. For a small sample, the equations of motion exhibit S conservation in this case. The screened interaction model predicts a different behaviour; in particular, S-breaking terms appear in the equations of motion for a small sample.
Efficiency of energy conversion using shock waves
Authors: Dewey J. M. , McMillin D. J.
Published: April 2011

The flux-corrected transport algorithm has been used to simulate shock-wave flows in linear and spherically converging and diverging tubes in order to determine the energy distributions in the flows and the conversion efficiencies of energy to mechanical work. This was done to evaluate the possibility of using the positive phase of a shock wave, rather than combustion products, as the driving mechanism in an internal-combustion engine, and to suggest the optimum configuration of a supercharging device that uses shock waves to extract energy from the exhaust gases of internal-combustion engines. It is concluded that the positive phase of a shock wave would not be especially useful as the primary driving mechanism of an internal-combustion engine. In the case of the supercharging energy exchangers, the simulations indicate that for charging pressure ratios lower than about 5:1, a linear tube with a compression-chamber length of about 40% would be most efficient, while at higher pressure ratios a converging conical tube with a compression-chamber length of about 10% would be preferred.
Finite-size scaling for the Bose condensate
Authors: Singh Surjit , Pathria R. K.
Published: April 2011

Following the approach of Barber and Fisher, we formulate a finite-size scaling theory for the Bose condensate. Using bulk results as input, we make a number of predictions for the behaviour of the condensate fraction f0(L, T) in an ideal Bose system confined to a hypercube, of side L, in d dimensions. A comparison is made with analytical results for a system in three dimensions under a variety of boundary conditions. While the standard temperature variable t[= (T – Tc)/Tc] is appropriate in the case of periodic and antiperiodic boundary conditions, the use of a shifted variable t[= t – ε(L), where ε(L) = O(L−1 In L)] is essential in the case of Neumann and Dirichlet boundary conditions. Nonetheless, in each case, the predictions of the scaling formulation are fully borne out. Finally, the formulation is extended (i) to include the so-called surface condensate, and (ii) to cover all temperature down to 0 K.
Electron–hole drops in -stressed germanium
Authors: Timusk T. , Scholes R. W. , Zarate H. G.
Published: April 2011

We show, using the Mie theory, that the phase separation of electron–hole drops in [Formula: see text]-stressed Ge, predicted by Kirzcenow and Singwi, can be observed by the splitting of the plasma resonance into two components, a high frequency line arising from the dense, hot-electron component and a low frequency line from the low density shell. We also present extinction measurements on electron–hole drops that show that in samples with small drop radii the phase separation does indeed take place as predicted. Samples that contain large drops show the presence of hot electrons but the phase separation is difficult to observe by our technique.
Percolation calculations and a Mössbauer study of iron–platinum alloys with the FePt3 structure
Authors: Daniels J. M. , Julian S. R. , Lam H.-Y. , Li P. L.
Published: April 2011

The magnetic properties of annealed iron–platinum alloys with 21–40 at.% Fe are different above and below a concentration of 30.5 at.% Fe. We show that this concentration corresponds to the percolation limit where Fe atoms on the face centres link the four corner atoms on that face into a cluster. Mössbauer spectra of 26.5 at.% Fe and 33.5 at.% Fe alloys confirm this model. The change in magnetic properties as alloys with less than 30.5 at.% Fe are cooled below the lower transition temperature is shown to correspond to a change from a fast relaxing regime to a static regime in which there is an incommensurate spin density wave.
Positron-impact ionization of hydrogen atoms
Authors: Ghosh A. S. , Majumdar P. S. , Basu Madhumita
Published: April 2011

The ionization cross section of hydrogen atoms by positron impact has been calculated by using a distorted-wave polarized-orbital method. We have employed two models depending on the choice of the final-channel wave function, and the two sets of results differ dramatically. We have also found that below 100 eV the total positron-impact ionization cross section including positronium formation is appreciably larger than the corresponding results for electron-impact ionization.
Laser nonenhancement of 3H-beta decay
Authors: Beder Douglas S. , Blevis Ira M.
Published: April 2011

The possibility of influencing nuclear beta decay with high intensity optical lasers is examined numerically with the appropriate exact wave functions of a Dirac electron in a plane-wave field, as in previous literature. The total β-decay rate for 3H is found to be unaffected by the laser field for a 2-eV laser with intensities in the range 1018–1020 W/cm2.
Feynman scaling and hadron–muon density in air showers
Authors: Sidhanta Jiben , Roychoudhury Rajkumar
Published: April 2011

Assuming Feynman scaling, we analytically solve the coupled diffusion equation for hadrons in air showers. We have also calculated the muon density using our analytical solutions. Our results are in agreement with numerical solutions and also with experimental results.
Convertisseur d'image infrarouge à visible 42,70
Authors: Leclerc Louise , Beaulieu René
Published: April 2011

Infrared (10.6 μm) images have been recorded on wax films and photographed in the visible after filtering using a Schlieren technique. The linearity of the recording medium has been verified and the dynamic range is ~ 5.
Lamb-dip laser Stark spectroscopy of propyne: Analysis of the ν5 band
Authors: Meyer F. , Dupre J. , Meyer C. , Lahaye J. G. , Fayt A.
Published: April 2011

Laser Stark spectra for the ν5 parallel band of CH3C2H were measured by using a 13CO2 laser. Sixty resonances were assigned to transitions with a lower state, K ≤ 5. These transitions were combined with previous 12CO2-laser Stark data and zero-field lines. Effective vibration–rotation parameters and the dipole moments of the lower and upper levels were determined with high accuracy.
The coherent anti-Stokes Raman spectroscopy spectrum of the Q-branch of the ν1 band of hydrogen sulfide
Authors: Frunder H. , Angstl R. , Illig D. , Schrötter H. W. , Lechuga-Fossat L. , Flaud J.-M. , Camy-Peyret C. , Murphy W. F.
Published: April 2011

The coherent anti-Stokes Raman spectroscopy (CARS) spectrum of the Q-branch of the ν1 band of natural H2S has been measured at a pressure of 1.3 kPa with continuous-wave excitation in the cavity of an argon-ion ring laser. For comparison with the experimental spectrum, Raman line positions and intensities were calculated from energy levels and wave functions that were previously obtained from the study of the pure rotation spectrum and the 2ν2, ν1, and ν3 bands by Fourier transform infrared spectroscopy. These Raman line positions and intensities formed the basis for the simulation of the theoretical CARS spectrum, which is in excellent agreement with the experimental one.
The effect of electrostatic interactions and water polarization on the properties of charged lipid membranes: a theoretical approach
Authors: Zuckermann M. J. , Georgallas A. , Pink D. A.
Published: April 2011

We describe the physical properties of a planar interface between an electrolyte and a charged lipid membrane. The model differs from the usual Gouy–Chapman–Debye–Huckel theory for electrolytes in that the dipolar nature of the water molecules is explicitly included. The polarization, dielectric constant, and electric potential of the electrolyte are calculated as functions of distance from the interface. The change in gel – liquid-crystal transition temperature is obtained as a function of pH and salt concentration from the free energy of the system. The results are compared to previous calculations using the Gouy–Chapman–Debye–Huckel theory and to experimental data for dimyristoyl-methylphosphoric acid.
Improvement of the Bethe–Peierls approximation to lattice gases
Authors: Asada Hiromu
Published: April 2011

The Bethe–Peierls approximation to lattice gases is improved by introducing new self-consistent parameters relating to positional correlation between atoms. The improved method is applied to the triangular lattice with first nearest neighbour attractive interactions. Calculated critical temperature and critical thermodynamic properties show better agreement with the exact ones than those in the normal Bethe–Peierls approximation.
Formation, structure, and crystallization of metastable quasi-crystalline Al–transition metal alloys prepared by rapid solidification
Authors: Dunlap R. A. , Dini K.
Published: April 2011

Metastable Al86Cr14, Al86Mn14, and Al86Fe14 were prepared by rapid quenching from the melt at a rate of approximately 2 × 106 K/s. The X-ray measurements of all three alloys show similar non-Bravais structures. Broadened diffraction peaks for the Al–Fe alloy suggest a crystallite size of about 60 Å. Thermal-analysis measurements show that all of the alloys transform into conventional crystal structures at approximately 670. The crystalline phases for the three alloys are Al11Cr2 + Al, Al6Mn + Al, and Al6Fe + Al. At approximately 800 K, Al–Fe undergoes the further transition Al6Fe → Al3Fe + Al.
Coherent analysis of 16O + 28Si excitation functions
Authors: Hodgson R. J. W.
Published: April 2011

A prescription for separating the elastic cross section into its coherent and incoherent parts is used to gain more information about the excitation function at 90° and at 180°. Approximations become useless over most of the energy range owing to the extreme sensitivity of the cross section. Despite the apparent smooth energy dependence of the coherent and incoherent parts, interpolation does not generate the observed structure in the excitation functions.
The nuclear structure of 168Er studied with the 170Er(p,t)168Er and 166Er(t,p)168Er reactions
Authors: Burke D. G. , Davidson W. F. , Cizewski J. A. , Brown Ronald E. , Flynn E. R. , Sunier J. W.
Published: April 2011

The 170Er(p,t)168Er and 166Er(t,p)168Er reactions have been studied using 18-MeV protons and 17-MeV tritons, respectively. The reaction products were analyzed with magnetic spectrographs providing overall resolutions ranging from 10 to 15 keV full width at half maximum. The chief aim of these studies was to search for previously unknown 0+ states in 168Er, and one new 0+ level, at 1833.5 keV, has been identified. All the known excited 0+ states were populated much more strongly in the (t,p) reaction than in the (p,t) reaction. Numerous natural parity states in known bands were also observed in both reactions. The significance of these results for some recently proposed interpretations of 168Er is discussed. The states with I,Kπ = 0,0+ at 1422 keV and 2,2+ at 1848 keV are both populated much more strongly in the (t,p) reaction than the single-phonon γ vibration. Thus the interpretation given these levels in the interacting boson description, as predominantly multiple-phonon excitations involving at least one γ phonon, does not satisfactorily describe these data. The quasiparticle-phonon model of Soloviev and co-workers is the only model that does not conflict in some way with the presently available experimental data.
Variations in the Fraunhofer filling-in for the visible region of day-sky spectra
Authors: Jadhav D. B. , Tillu A. D.
Published: April 2011

Observations of Fraunhofer filling-in (FFI) reported by various observers are critically reviewed in light of sky spectra obtained by us using grating monochromators of different resolutions under different sky conditions. A new parameter, colour gradient, was defined and measured simultaneously with Fraunhofer depths. A negative correlation for the red region and a positive correlation for the violet region were usually noticed between FFI and colour gradients. A maximum value of 30% was noticed for FFI. The above analysis and interpretation in light of existing theories indicate that about 90% of FFI is due to aerosol fluorescence and only about 10% is possibly due to rotational Raman scattering.
Pion form-factor behaviour in a modified quark-loop model
Authors: Dubnička S. , Georgios G. , Meshcheryakov V. A.
Published: April 2011

In the framework of a modified quark-loop model, which provides a pion charge-radius value that is consistent with the world-average value, the pion form-factor behaviour is calculated and compared with the data.
Theoretical diffraction efficiency for slanted uncoupled absorption multiplex holograms
Authors: Couture Jean J. A. , Lessard R. A.
Published: April 2011

Analytical solutions describing the reconstruction obtained from a multiplex hologram that has been made with two incoherent holographic exposures are presented. Angular separation between the two object waves is greater than the angular selectivity bandwidth of each of the two elementary uncoupled gratings. The analysis gives results characterizing the diffraction efficiency of these gratings. Incoherent superposition of N uncoupled and slanted gratings is easily described by a simple generalization.
Clock synchronization by accelerated observers: metric construction for arbitrary congruences of world lines
Authors: Henriksen R. N. , Nelson L. A.
Published: April 2011

This paper reviews the problem of synchronizing the clocks (locally orthogonalizing the three-space) of an arbitrarily accelerated observer congruence. A general solution is given that maintains the isotropy and coordinate independence of the one-way velocity of light, but various particular cases, such as the "rotating disc or ring" congruence, are also discussed in detail. The congruence-based space-time metric that is constructed by the Einstein synchronization procedure is given explicitly, and the Hamilton–Jacobi method is used to write a useful equation for the geodesics of this space-time.The formal theory is related to experimental efforts to establish synchronization to an accuracy of a few nanoseconds over the rotating earth (Costain et al. and Ashby and Allan). In particular, a formally correct derivation of the "Sagnac corrected time" is given, and the expected experimental consequences are reviewed and compared to current experimental results.The measurable "global Sagnac effect" is distinguished from the "local Sagnac effect", which is, in fact, indistinguishable from Einstein synchronization. This clarifies earlier discussion concerning an orbital experiment proposed by Cohen and Moses.A suggestion regarding the application of absolute phase, very long baseline, radio interferometry to the measurement of the Sagnac effect (and possibly higher order effects) is given briefly.