bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of Noise Temperature and Conversion Loss of SIS Junction Mixers
Authors: Macfarlane JC , Whitbourn LB , Batchelor RA
Published: June 2013

Experiments on the performance of superconductor-insulator-superconductor (SIS) tunnel junctions as heterodyne mixers at 40 GHz are reported. The techniques developed for the fabrication of multi-junction SIS series arrays differ from, and are considerably simpler than, other methods described in the literature. Results are reported on mixer noise temperature, conversion loss, saturation, local oscillator power levels and mixer dynamic range. Factors affecting the mixer's conversion performance are identified and comparisons are made with other reported results. It is concluded that mixer performance in the present experiments is limited by imperfect impedance matching at the signal frequency, due to relatively large values of parasitic capacitance in the junctions. Future work is aimed at both reducing the junction capacitance and redesigning the mixer mount to give improved r.f. matching.
Intensity Correlation Functions for 'Thermalised' TEMn0 Laser Beams
Authors: Hoare R , Mardling R , Troup GJ
Published: June 2013

A well-stabilised, single mode laser beam will give zero intensity correlation. However, a laser beam may be 'thermalised' by shining it on a rotating ground glass disc, and then intensity correlation experiments will give nonzero results. We present here calculations of the intensity correlation functions of the TEMlO, TEM20, TEM30 and TEM40 Gaussian-Hermite beams. We were led to perform these calculations by the results of intensity correlation measurements on a laser with 'butted-on' mirrors nearing the end of its useful life.
The Influence of the Spatial Harmonics on the Rotating Magnetic Field Current Drive
Authors: Hugrass WN
Published: June 2013

In rotating magnetic field (RMF) current drive experiments, the RMF is usually generated by means of a two-phase radio frequency (r.f.) system which feeds a pair of orthogonal coils. The magnetic field generated in this manner consists of the desired RMF as well as the (undesired) odd spatial harmonics. The (2j-l)th spatial harmonic field rotates about the axis at an angular speed (-1)-i-lwl(2j-1), where w is the angular frequency of the r.f. current. In order to evaluate the effect of these spatial harmonics on the performance of the RMF current drive experiments, we have developed a simplified theoretical model for the plasma. In this model, the ions are assumed immobile and the motion of the electron fluid in the azimuthal direction is assumed to be a rigid rotation. It has been found using this model that the presence of the spatial harmonics makes the RMF current drive less efficient. It has also been found that the effect of the spatial harmonics can be made negligible by (a) making the width of the coils sufficiently larger than the diameter of the plasma, (b) carefully designing the coil configuration to eliminate the fifth harmonic or (c) using a three-phase system to generate the RMF.
Satellite Intensities in Photoelectron Spectroscopy and Electron Momentum Spectroscopy-Synchrotron Radiation Studies of Argon 3s and Xenon 5s Photoionisation (hv - 60?130 eV)
Authors: Brion CE , Tan KH
Published: June 2013

Binding energy spectra for the main line, satellite lines and associated double ionization continuum for argon 3s and xenon 5s photoionisation have been measured in the photon energy range 60-130 eV using monochromatised synchrotron radiation and magic angle photoelectron spectroscopy. In particular the ratio of satellite to main line intensities has been investigated and compared with the results of earlier experiments using X-ray and ultraviolet photoelectron spectroscopy as well as with recent measurements by electron momentum [i.e. binary (e,2e)] spectroscopy. The results of the presently reported photoelectron measurements show that the satellite intensity relative to that of the main ns -1 line increases with increasing photon energy and approaches the value given by electron momentum spectroscopy. These findings are contrary to predictions based on recent calculations of photoelectron intensities. The present work lends support to the direct interpretation of satellite intensities (pole strengths or spectroscopic factors) in binary� (e, 2e) spectroscopy using the plane wave impulse approximation. The need for improved calculations of photoionisation intensities as well as further photoelectron measurements in the X-ray region is stressed.
A Numerical Variational Method for Calculating Accurate Vibrational Energy Separations of Small Molecules and Their Ions
Authors: Doherty G , Hamilton MJ , Burton PG , von Nagy-Felsobuki EI
Published: June 2013

A combination of known methods have been spliced together in order to calculate accurate vibrational energies and wavefunctions. The algorithm is based on the Rayleigh-Ritz variational procedure in which the trial wavefunction is a linear combination of configuration products of one-dimensional basis functions. The Hamiltonian is that due to Carney and Porter (1976). The kernel of the algorithm consists o( the one-dimensional basis functions, which are the finite element solutions of the associated one-dimensional problems.
Multivacancy Effects in Atomic and Molecular Spectra
Authors: D Deslattes Richard
Published: June 2013

Chemical applications of X-ray spectra are inhibited by the general occurrence of multivacancy processes. These manifest themselves in emission �spectra as extra lines (or satellites) while opening of channels to these initial configurations leads to extra detail in absorption spectra. While there are a few simple cases where this situation has been more or less fully discussed, the more interesting areas are those which are both not simple and not understood. There is, however, a fairly general experimental procedure by which this .complex situation could, in principle, be clarified. This involves carrying out high resolution emission spectroscopy as a function of exciting photon energy in regions containing both single and multiple vacancy thresholds. In earlier work summarised here, it was possible to demonstrate the procedure for a monatomic gas, argon. Subsequently, we have built and now operate a beamline designed specifically for such studies at the National Synchrotron Light Source (NSLS) in Brookhaven. Very recent results from this line and from a few experiments using conventional sources are summarised.
Kirkwood Theory of Shear Viscosity in a Simple Dense Fluid
Authors: Collings AF , J Evans Denis
Published: June 2013

The molecular theory of momentum transport in dense fluids developed by Kirkwood is examined for the case of the Lennard-lones (12,6) fluid. The radial distribution functions and one-particle friction constants used are based on molecular dynamics studies. Shear viscosity coefficients calculated with elk = 120 K and 0' = 3.405x10- 10 m vary from one-third to two-thirds of comparable experimental data for argon. The significance of an approximate relationship between the pair friction tensor and the one-particle friction constant is discussed.
Nonlinear Bifurcations to Time-dependent Rayleigh?Benard Convection
Authors: Lopez JM , Murphy JO
Published: June 2013

The single-mode equations of Boussinesq thermal convection have been extended to include a toroidal component of velocity and hence the associated vertical component of vorticity. This formulation allows, under certain determined conditions, the purely poloidal solutions to become unstable to toroidal perturbations via symmetry breaking bifurcations. The bifurcation sequences are governed by a three parameter family: the aspect ratio of the convection cell, the Prandtl number of the fluid and the Rayleigh number of the flow. The initial growth of the vertical vorticity has been found always to be steady. However, in certain parameter ranges there are transitions leading to time-dependent behaviour via a Hopf bifurcation which may be in the form of symmetrical oscillations, asymmetrical oscillations, doubly-periodic behaviour or, possibly, chaos, depending on the form of the transient poloidal phase of the evolution.
A Search for Tachyons in Cosmic Ray Showers
Authors: Clay RW
Published: June 2013

A search has been made for tachyons associated with cosmic ray showers of energies about 1015 eV by searching for any precursor effects observed in plastic scintillator detectors. Detection thresholds well below most other similar experiments have been reached but no statistically significant effects have been found.
Precision Peak Determination in X-ray Powder Diffraction
Authors: Huang TC
Published: June 2013

A systematic study of the derivative methods for peak search analysis of X-ray powder diffraction data was made to evaluate the relative merits of the methods. Results of analysing computer simulated diffraction peaks show that the peak positions can be precisely determined by the first derivative of a least-squares fitted cubic polynomial. The technique has an accuracy of 0 . 00 1" and precisions ranging from �0�003" to 0�02" depending on the levels of counting statistical noise. The study also shows that reliable resolution of overlaps has been obtained using the second derivative of a quadratic/cubic polynomial. A method of combining the first derivative of a cubic polynomial and the second derivative quadratic/cubic polynomial has thus been used for precision peak search analysis. The combined first/second derivative method has been tested with experimental diffraction patterns recorded with various step sizes, levels of counting statistical noise and degrees of overlaps. Analysis results agree with those obtained from the computer simulated data. A comparison between the peak search and the profile fitting results showed good matches in the peak positions but relatively poor agreements in the peak intensities especially for the heavily overlapping peaks
Accurate Structure Factor Measurements by Powder Methods
Authors: Sabine TM
Published: June 2013

Powder diffraction data are normally analysed by Rietveld refinement. In this technique the observed diffraction. pattern is fitted to a calculated pattern by least-squares methods. The accuracy with which structure factors can be determined is dependent on the parameters in the model being an accurate representation of the physical situation. The Rietveld model is derived in the kinematic approximation. Deviations from kinematic behaviour because of extinction, absorption, thermal diffuse scattering, and multiple scattering are then included in the model. As a test of the method the Debye-Waller factor (which is the only unknown component of the structure factor) is determined for magnesium oxide from time-of-Bight neutron data on four specimens of very different grain size.
Simple Method for Estimating the Contribution of Neighbouring n-beam Interactions to Two-beam Structure Factors
Authors: Juretschke HJ , Wagenfeld HK
Published: June 2013

Unless special precautions are taken, the experimental determination of two-beam structure factors to better than 1 % may include contributions from neighbouring n-beam interactions. In any particular experimental configuration, corrections for such contributions are easily carried out using the modified two-beam structure factor formalism developed recently (Juretschke 1984), once the full indexing of the pertinent n-beam interactions is known. The method is illustrated for both weak and strong primary reflections and its applicability in special cases, as well as for less than perfect crystals, is discussed.
Recent Advances in the Calculation and Measurement of the X-ray Dispersion Corrections
Authors: Creagh DC
Published: June 2013

This paper discusses some modem techniques for the calculation of the X-ray dispersion corrections and compares the calculated data with experimental data taken near to, and remote from, the absorption edges of atoms.
Thermal Expansion of Fe2MnSi
Authors: Miles JR , Smith TF , Finlayson TR
Published: June 2013

Measurements of the thermal expansion of FezMnSi in the temperature range 200-300 K are reported. A large, relatively narrow peak is found at the magnetic re-ordering temperature in contrast to a broad, weak anomaly at the Curie temperature. Values for the magnetic Gruneisen parameter 'Y m are derived from the thermal expansion data and previously reported specific heat data following the subtraction of a non-magnetic background.
A CEPA2 Study of the H2?H2 Isotropic Potential Function
Authors: Senff UE , Burton PC
Published: June 2013

A CEPA2 study of the DDl (Koide and Kihara 1974) conformation of two hydrogen molecules has been carried out using a basis set consisting of 102 independent gaussian functions to describe the interacting system. Calculations using a smal\er basis set indicate that this conformation provides a close approximation to the isotropic Vooo potential function. The study was carried out for intermolecular separations ranging from R = 2�0 to 15�0 a.u. keeping the H2 bond lengths fixed at r = 1 �449 a.u. The wel\ depth was determined to be 104� 73/ih at Rm = 6�597 a.u. and the zero point crossing at Ro = 5�825 a.u.
Experimental Studies of Plasma Confined in a Toroidal Heliac
Authors: Blackwell BD , Hamberger SM , Sharp LE , Shi X-H
Published: June 2013

The design, construction and operation of the prototype heliac SHEILA are described. Gas breakdown conditions are compared with high frequency discharges. Plasma isobars obtained from local measurements are shown to agree closely with computed magnetic flux surfaces for a range of magnetic configurations. The effect of changing the configuration on fluctuation mode numbers is demonstrated and shown to be consistent with the calculated rotational transforms.
An Improved Scheme Using the Shooting Method to Solve Degenerate Four-wave Mixing Equations
Authors: Ja YH
Published: June 2013

A modified scheme using the shooting method to solve the nonlinear coupled�wave equations for degenerate four-wave mixing is proposed. This simple scheme significantly improves the efficiency of this numerical method and the accuracy of computed results.
Lunisolar Atmospheric Tides. II
Authors: Brahde R
Published: June 2013

In an earlier paper (Brahde 1988) it was shown that series of measurements of the atmospheric pressure in Oslo contained information about a one�day oscillation with mean amplitude 0�17 mb. The data consisted of measurements every second hour during the years 1957-67, 1969 and 1977. In the present paper the intervening years plus 1978 and 1979 have been included, increasing the basis from 13 to 23 years. In addition the phase shift occurring when the Moon crosses the celestial equator has been defined precisely, thus making it possible to include all the data.
Structure of Four Families of Layered Copper-oxide High Tc Superconductors
Authors: Norman Peter
Published: June 2013

Four major families of copper�oxide based high Tc superconductors have been identified by the following research groups: Bednorz and Muller (1986), Cava et al. (1988), Hor et al. (1987), Maeda et al. (1988), Sheng and Herman (1988) and Wu et al. (1987). It is now well established that the superconductivity is associated with the layers of copper�oxide and that some of the remaining structural building blocks in each primitive cell act as electron acceptors which induce the holes in the copper�oxide layers necessary for superconductivity.
Slowing of Sound Waves in Powdered Media
Authors: Brettell JM
Published: June 2013

The velocities of longitudinal sound waves in powdered media are considerably less than the corresponding value in bulk material. To understand this further, an examination has been made of how the sound velocity varies with pressure for the particular case of ultrasonic wave propagation in fine-grain sand. An analysis of the data has been made by treating the particles as linear chains of coupled oscillators.
Large Scale Structure of the Universe: Theoretical Problems
Authors: Saar E
Published: June 2013

Implications of the observed large scale structure on the physics of the early universe are described. A short review of Soviet work on the subject is given, and the present status of the fractal model of the large scale structure is discussed.
Analysis of the Astrophysical Significance of Radio Source Counts Obtained in Different Frequency Ranges
Authors: Sokolov KP
Published: June 2013

A qualitative analysis of the possible existence in principle of the 'flux density-distance' correlation, which constitutes the basis for a source count test, is presented for samples of radio sources observed at high (v ~ 1000 MHz) and very low (v < 100 MHz) frequencies. It has been shown that conditions for the existence of the correlation are best fulfilled at very low frequencies where the source flux densities are conditioned by isotropic radiation from their extended components with steep spectra.
Evolutionary Studies of Galaxies at Intermediate Redshifts
Authors: Couch WJ
Published: June 2013

Photometric and spectroscopic studies of cluster and field galaxies out to redshifts of -0�5 have provided clear evidence for strong evolution over recent epochs. The development of this picture is reviewed by contrasting and comparing the investigations of distant galaxies in rich clusters and the low density field. A common link is found in that the evolution of galaxies in both environments is related to short-lived bursts of star formation. The triggering mechanism for these bursts is discussed with special attention being paid to the role of galaxy merging
Nonlinear Instability of Circularly Polarised Waves in a Magnetised Relativistic Plasma
Authors: Paul SN
Published: June 2013

An intensity dependent nonlinear dispersion relation of a circularly polarised wave in a magnetised relativistic plasma is derived using a special Lorentz transformation and then the stability criteria of the wave are investigated. From numerical estimations it is observed that electromagnetic waves, having powers much below that for the occurrence of nonlinear phenomena due to self-action effects, are unstable in a magnetised relativistic dense plasma. The effects of a strong magnetic field on the group velocity and cut-off frequency in a dense plasma are also discussed.
Guest Comment
Authors: Stelbovics AT
Published: June 2013

In February 1990 an international workshop on Interfaces in Molecular, Electron and Surface Physics was held in Perth. The idea for the theme was due in large part to Jim Williams, professor of physics at the University of Western Australia. It grew from a series of informal working seminars involving contributions from groups in the physics and electrical engineering departments of the University of Western Australia and from the physics program at Murdoch University. The contributions fell broadly into the two categories, atomic and surface physics. In the two years the seminar series has run there has been such a fruitful exchange of ideas and techniques between the two research areas that it was decided to focus the workshop in this direction.
Imaging Semiconductors, Metals and Molecules with Scanning Tunneling Microscopy
Authors: Wilson RJ , Chiang S , Chambliss DD
Published: June 2013

A brief review of applications of scanning tunneling microscopy (STM) to studies of clean and adsorbate covered surfaces is given. For metal-semiconductor systems, high resolution images provide insight into nucleation phenomena and atomic scale structure. For the metal on metal systems of Ag and Ni on Au(l11) we report surprising new nucleation phenomena. Finally, we show that images of flat lying aromatic molecules can be obtained.
Auger Lineshape Analysis of Disorder and Rehydrogenation Induced Changes in the Electronic Structure of Silicon Surfaces
Authors: Lund CP , Clare BW , Cornish JCL , Hefter GT , Jennings PJ , Klauber C
Published: June 2013

X-ray excited Si LZ3 VV spectra have been measured for both disordered crystalline silicon and chemical vapour deposited amorphous silicon. A method, based on the Simplex algorithm, has been applied to enable the Si LZ3VV peak to be decomposed into its L23MJM23, L23Mz3M23 and localised two-hole components. Changes in the relative amounts of the LZ3 VV components have been compared with changes upon hydrogenation by direct hydrogen ion bombardment for both the disordered c-Si and a,Si samples. Recent published results related to monitoring the effects of disorder and then hydrogenation on silicon surfaces using the Si LZ3 VV Auger line shape are reviewed and show good agreement with the results obtained. In agreement with others it is concluded that the hydrogen decreases the localised defect states in the bandgap and creates new states in the valence band. It is shown that the effect is more pronounced in disordered a-Si than in disordered coSio Hydrogenation of this sort is effective in improving the electrical properties of the films, especially for chemical vapour deposition films.
Linear and Nonlinear Light Scattering from the Surfaces of Liquids
Authors: Buckingham AD
Published: June 2013

The linear optical properties of matter, e.g. the refractive index, the absorption coefficient and the reflectivity, can be interpreted in terms of the oscillating charge and current densities induced by the optical field. For most purposes, it is sufficient to consider the oscillating dipole moment 11= OI.E = OI.E(O) exp(-ioot+ik. r), where 01. is the mean polarisability of a molecule, or of a unit cell, in a plane wave propagating with wave vector k, angular frequency 00 and amplitude E(O). A static electric field F polarises the material and may affect the reflected light linearly in F. If F is in the plane of incidence there is a change of phase of the reflected light, and if F is perpendicular to the plane of incidence there is a change in polarisation and intensity. If the intensity of the optical field is high, nonlinear scattering is observed from the surface of a liquid. The surface breaks the symmetry of the fluid, leading to partial molecular orientation and hence to a non�vanishing first hyperpolarisability P that gives the induced dipole at the frequency 200 proportional to the square of E. With intense laser sources a molecular monolayer or sub-monolayer can be detected. Surface selectivity can be achieved by tuning an infrared laser of frequency oolR to a vibrational frequency of the monolayer and detecting a coherent beam at the sum frequency oo+ooIR, when the surface is simultaneously subjected to pulses at 00 and oolR.
An Experimental Investigation of Electron Transport in E x B Discharges
Authors: Brennan MJ , Garvie AM
Published: June 2013

The 'photon flux' technique has been used to study electron transport in molecular nitrogen for steady stream discharges under the influence of Ex B fields. The results, the first for the range of conditions 350 < E/N < 550 Td, 0 < B/N < 1009xl0-17 Gcm3, are reported and comparisons between the experimentally determined transport parameters and those obtained under similar conditions by Monte Carlo simulation are made.
Relativistic Bound States
Authors: McKellar BHJ
Published: June 2013

The standard resul ts of the quark model rely on nonrelativistic descriptions of the wavefunctions of the quarks in the hadron. However, simple uncertainty principle considerations show that the momenta of the quarks are comparable to their (constituent) masses, so that relativistic dynamics must be used in the description of the hadronic structure. In this paper I describe a number of new and old results which illustrate relativistic effects on the quark structure of hardons, and which employ the method of light cone quantisation to handle relativity.
The 12C(a,g)16O Cross Section at Low Energies
Authors: Barker FC , Kajino T
Published: June 2013

An R-matrix formula for the cross section for radiative capture reactions is developed and applied to fit recently measured 12C(oc,y)160 data, for both ground-state transitions and cascade transitions through the 6�92 and 7 �12 MeV levels. The correct treatment of the channel contributions is significant for the E2 cascade transitions. Consistent fits of the cascade and ground-state data suggest a value of the channel radius larger than those previously used, and consequently a value of the low-energy astrophysical S-factor appreciably larger than that adopted recently.
VLBI in Australia ? A Review
Authors: Jauncey DL
Published: June 2013

After two decades of Australian VLBI (very long baseline interferometry), high-resolution radio astronomy continues to be an active and fruitful research field. The status of Australian VLBI programs in astrophysics, astrometry and geodesy is reviewed and likely future developments are outlined. In addition to research programs with the Australian VLBI network, a number of successful collaborative projects are underway with overseas VLBI observatories. The inception of the Asia-Pacific Telescope will provide an important formal basis for fostering and extending international VLBI experiments in the Australian hemisphere. The APT will also serve a vital function in coordinating ground-based observations when the Soviet and Japanese VLBI space missions, Radioastron and VSOP, are launched in the middle of this decade. However, continued viable Australian participation in VLBI into the nineties will require new wide-bandwidth recording systems and an Australian VLBI correlator.
Studies of Electron-Molecule Collisions on Distributed-memory Parallel Computers
Authors: Winstead Carl , Sun Qiyan , G Hipes Paul , AP Lima Marco , McKoy Vincent
Published: June 2013

We review recent progress in the study of low-energy collisions between electrons and polyatomic molecules which has resulted from the application of distributed-memory parallel computing to this challenging problem. Recent studies of electronically elastic and inelastic scattering from several molecular systems, including ethene, propene, cyclopropane, and disilane, are presented. We also discuss the potential of ab initio methods combined with cost-effective parallel computation to provide critical data for the modeling of materials-processing plasmas.
The Rate of Star Formation in Galactic Disks
Authors: Silk Joseph
Published: June 2013

A simple prescription is -presented for the rate of star formation in normal galactic disks, motivated by semi-phenomenological dynamical arguments. When energy input into the interstellar medium is included as a feedback mechanism to couple the star formation driven by disk instabilities with gaseous dissipation, one can obtain expressions for both disk surface density and the Tully-Fisher relation in good accord with observation. One plausibly expects variations at a level of order ~10% in the Tully-Fisher zero-point due to age and/or star formation history that may be correlated over supercluster scales. I also show that there is a limiting rate of star formation, maintained by the porosity of the hot component of the multiphase interstellar medium, that can be interpreted as arising in starbursts that are triggered by galaxy mergers. The predicted star formation rate is found to be sensitive to the ambient pressure and results in enhanced star formation in galaxies that are undergoing first infall at cluster peripheries (out to ~10h-l Mpc from an Abell cluster).
The Gas-phase Chemical Evolution of Dark Clouds
Authors: Bettens RPA
Published: June 2013

A rich chemistry exists within dark clouds. In the most chemically studied dark cloud, Taurus molecular cloud one (TMC-l), more than 40 molecules have been detected. In this paper I look at the current isochoric, i.e. constant density, isothermal time-dependent gas-phase chemical models of dark clouds such as TMC-l and very briefly outline the present understanding of the chemistry of these objects. The above chemical models agree very well with the observed abundances of almost all chemical species at times earlier than steady state, i.e. earlier than thirty million years. However, the models are fraught with uncertainty and are not physically realistic representations of the full dynamical evolution of dark clouds from a more diffuse state. Nevertheless the agreement with observation is striking.
Fermi-Dirac Equations
Authors: Delbourgo R , M Jones Lorella
Published: June 2013

Assuming that space-time is accompanied by hidden anticommuting coordinates, we have constructed 'fermionic' eneralisations of the Dirac equation; these equations involve matrices (which can be construed as operating in an internal space) multiplying the Grassmann derivatives. We discuss several models, of varying degrees of complexity, with 'internal symmetries' including Sp(2) and S (N). By appending the space-time Dirac operator, one is led to mass spectra with quantised alues, suggesting that this approach may provide a model relating generations to internal symmetries.
pp Coulomb Phase Shift for Different Proton Charge Distributions
Authors: A Hassan Mohamed , SA Hassan Samia
Published: June 2013

The dependence of the pp Coulomb phase shift on the form of the proton charge distribution function is studied and discussed. The uniform, exponential and Gaussian distributions are used. The dependence- on the form of the charge distribution for impact parameter values less than the radius of the proton is clear. The charge distribution effect leads to a decrease in the absolute value of the Coulomb phase shift.
Ab Initio Ro-Vibrational Structure of the C2? Isotopes of H2O+
Authors: Wang F , von Nagy-Felsobuki EI
Published: June 2013

The ro-vibrational structures of the C2" isotopes ofH20+ have been calculated from variational solution of the normal coordinate Eckart-Watson Hamiltonian. The calculations use the discrete ab initio potential energy surface of Weis et al. (1989). Where comparisons can be made, the assignment of the vibrational states is in excellent agreement with experiment and with the ab initio variational calculation of Weis et al., who utilised a different force field and an internal coordinate nuclear Hamiltonian (instead of the Eckart-Watson amiltonian). Furthermore, the calculated rotational levels of the ground and the first excited vibrational states of H20+ and D20+ are in excellent agreement with experiment.
Group Travel Time of EM Waves with Frequencies near the Ion Cyclotron Frequency in the Two-ion Magnetosphere
Authors: Hu YD , Fraser BJ
Published: June 2013

The oblique propagation of electromagnetic (EM) waves with frequencies below the equatorial proton cyclotron frequency is investigated for a two-ion magnetospheric plasma. Attention is focused on the wave group travel time along a geomagnetic field line rom the equatorial wave source region to the ionosphere or the location where the wave is reflected. It is found that the coupling between eft- and right-hand polarised waves occurring at a crossover frequency significantly modifies features of the frequency-time spectrum. ecause of this modification, the spectral tone change of Pc 1 waves observed on the ground (e.g. Dowden 1966; Gendrin and Laurent 1979) is not caused solely by dispersion effects in a multi-component plasma.
Quantum Mechanics and Superconductivity in a Magnetic Field
Authors: MacDonald AH , Akera Hiroshi , Norman MR
Published: June 2013

The influence of a magnetic field on superconductivity is usually described either phenomenologically, using Ginzburg-Landau theory, or semiclassically, using Gor'kov theory. In this article we discuss the influence of magnetic fields on the mean-field theory of the superconducting instability from a completely quantum-mechanical point of view. The suppression of superconductivity by an external magnetic field is seen in this more physically accurate picture to be due to the impossibility, in quantum mechanics, of precisely specifying both the centre-of-mass state of a pair and the individual electron kinetic energies. We also discuss the possibility of novel aspects of superconductivity at extremely strong magnetic fields, where recent work has shown that the transition temperature may be enhanced rather than suppressed by a magnetic field and where a quantum treatment is essential.
Electronic Properties of Quasi-One-Dimensional Semiconductor Nanostructures: Plasmons and Exchange-Correlation Effects in Quantum Wires
Authors: Das Sarma S , Yu-Kuang Hu Ben
Published: June 2013

We review the many-body exchange-correlation properties of electrons confined to the lowest sub-band of a quantum wire, including effects of impurity scattering. Without impurity scattering, the virtual excitations of arbitrarily low energy one-dimensional plasmons destroy the Fermi surface of the electrons, whereas the presence of impurity scattering damps out the low energy plasmons and restores the Fermi surface. The electron inelastic scattering rate r in the absence of scattering is zero below a critical wavevector kc corresponding to the plasmon emission threshold, above which r diverges as (k - kc )-1/2 for k -t kc. For typical wire widths and electron densities currently available, the calculated bandgap renormalisation is found to be on the order of 10-20 meV. We also calculate the finite-temperature inelastic scattering rates and mean free paths of electrons injected into a quantum wire containing a quasi-one-dimensional electron gas. We show that there is a very sharp increase in the electron scattering rate at the one-dimensional plasmon emission threshold. Based on these results, we suggest the possibility of a one-dimensional hot-electron device which possesses an I - V curve with a sharp onset of a large negative differential resistance. We also present a general method for obtaining expressions for the analytic continuation of finite-temperature self-energies which are suitable for use in numerical computations. In the case of the GW approximation for the self-energy, this method gives the finite-temperature generalisation of the zero-temperature 'line and pole' decomposition. This formalism is used to calculate the finite-temperature self-energy and bandgap renormalisation of electrons in the extreme quantum limit of a quantum wire. A brief review of the experimental and theoretical status of plasmons in quantum wire structures is given.
Magnetic Properties of Layered Heisenberg Ferromagnets
Authors: Du A , Wei GZ
Published: June 2013

The double-time-temperature spin Green's function method is used to study the magnetic properties of layered ferromagnets with arbitrary spin S, within Tyablikov's decoupling approximation. According to the extent to which interlayer coupling suppresses twodimensional spin fluctuations, we divide the low-temperature region into two new ones, and give the asymptotic expressions for magnetisation and susceptibility over different temperature regions, including the low-temperature region, the vicinity of the Curie temperature and the high-temperature region. We also give the Curie temperature in an asymptotic form when inter layer coupling is weak.
Band Structure Calculations for the Heavy Transition Metals: Parametrisation Methods, Band Structures and Problems with Iteration Techniques
Authors: Osborne CF
Published: June 2013

This paper discusses a parametrisation method developed by the author as a technique for the determination of band structures for the 4d transition metals and their compounds. It is suggested that some of the earlier work that has been published may not have found all the roots. Re-examination of the earlier work of the author reveals systematic discrepancies from benchmark band structure calculations. It is suggested that these results are an example of the unreliability of the earlier parametric band structure calculations, in which iteration techniques were used to determine the roots. Examples presented exhibit well known repeller behaviour, and so provide an early example where variation of initial conditions could have led to the discovery of bifurcation behaviour associated with the onset of chaos. The paper concludes with an application of the method to the calculation of electron-phonon interaction elements in the nonrelativistic limit.
Electrons in Transition Metals at High Temperatures
Authors: White CK
Published: June 2013

At high temperatures kT may be large compared with the scale on which major changes in the electronic density of states occur near to the Fermi energy E F , particularly for the transition elements. Mott first discussed the qualitative effects of this 'smearing' of the Fermi edge on the electrical resistance and thermopower of Pt, Pd, W, etc. Later Shimizu and colleagues examined the correlations in high-temperature behaviour of different transport properties, electronic heat capacity and susceptibility. Since then improved data have become available, largely through the use of sub-second measuring techniques. Is it now possible to provide a quantitative theoretical framework?
A VLA Survey of Rich Clusters of Galaxies II. The Stronger Sources: Maps, Polarisations and Identifications
Authors: Slee OB , Roy AL , Savage Ann
Published: June 2013

We present detailed radio and optical parameters for the stronger radio sources in 58 Abell cluster fields observed with the Very Large Array (VLA) using scaled arrays at 1�5 and 4�9 GHz. These sources comprise a complete sample with 1� 5 GHz flux density :;::20 mJy and cover a combined sky area of 3�5 X 10-5 sr. The cluster fields were distributed over 24 h of RA and between declinations +350 and -300 Contour maps at two frequencies are presented and source parameters such as position, angular size, spectral index, linear polarisation and core flux density are tabulated. We also derive the emitted power and linear size for those sources close to the cluster centres and therefore highly likely to be cluster members. We attempt to identify all these radio sources with optical images on the Palomar and SERC survey plates and give their accurate optical coordinates, morphologies and apparent magnitudes.
Mott-Schwinger Effect in the Elastic Scattering of Neutrons from 209Bi
Authors: Alexander N , Amos K , Berge L
Published: June 2013

The Mott-Schwinger potential arising from the interaction of the magnetic moment of a neutron incident upon an electric field (of 209Bi) is found to have a profound effect upon the elastic scattering cross sections and polarisations at 0�5, 14�5 and 24 MeV. These effects are evaluated by specific solution of the relevant Schrodinger equations (for 100 partial waves) and with the Born approximation used to define the influence upon all higher ones. These 'exact' results agree with the estimations made under approximation in the past, but not Schr6dinger 100 with 'exact' results calculated by a different method.
The Ratio DT/µ for Electrons in Water Vapour at 294 K
Authors: Elford MT
Published: June 2013

The ratio DT /� for electrons in water vapour (294 K) has been measured by the TownsendHuxley method as a function of E/N (where E is the electric field strength and N the gas number density) at vapour pressures ranging from 0 �103 to 0�413 kPa. For E/N 30 Td were found to be strongly pressure dependent, the strength and sign of the dependence depending on E/N and the current ratio relation used. Since extrapolation to infinite pressure at each E/N value did not give the same value of DT/ u, it has not been possible to derive reliable DT/ J.l values for this higher E/N range. Possible causes of the observed pressure dependences are discussed. The present data are in good agreement with the values predicted by Ness and Robson for values of E/N ~ 24 Td.
Angular and Polarisation Correlations between Cascade Photons
Authors: Wang JB , Williams JF
Published: June 2013

The density matrix theory is applied to establish a connection between the configuration of the excited atomic states and the intensity and polarisation of the cascade photons emitted during the decay process. Explicit expressions are obtained for the P, D and F states of hydrogen and helium atoms. These formulae can be used to assist experimental design for the most efficient and revealing measurements. In addition, formulae for the integrated polarisation of the emitted photons from the P, D, F and G states of hydrogen and helium are presented in terms of partial excitation cross sections.
Electron - Auger Electron Coincidence Experiments: Current Status and Future Prospects
Authors: Lohmann Birgit
Published: June 2013

Approximately ten years ago the first experiments were performed in which the Auger electrons produced after inner-shell ionisation of atoms by electron impact were detected in coincidence with the scattered electrons. Only a limited number of such experiments have been performed since that time, mainly due to the very low count rates characteristic of these measurements. Recent developments in the field are discussed and the future prospects for such measurements are considered.
Spin Effects in the (e, 2e) Cross Section of Xenon
Authors: Granitza B , Guo X , Hum JM , Lower J , Mazevet S , McCarthy IE , Shen Y , Weigold E
Published: June 2013

In a series of experiments investigating the spin-dependent aspects of electron impact induced ionisation of atoms with a spin-resolved incident electron beam we have measured spin-resolved (e, 2e) cross sections for xenon. By experimentally resolving the fine structure levels of the ground state residual ion the existence of an effect analogous to the fine structure effect in excitation has been established, whereby strong and opposite polarisation effects are observed in the ionisation of a spinless closed shell target leading to a fine structure doublet.
Dissociative Attachment Studies of Halogen-containing Molecules: Problems, Applications and Challenges
Authors: Burrow PD , Gallup GA , Fabrikant II , Jordan KD
Published: June 2013

The dissociative attachment (DA) process appears in a surprisingly diverse number of research disciplines. Although gas phase studies have been carried out for approximately 30 years, there are no calculations of the cross sections for this process in molecules larger than diatomics. In this presentation, we review briefly the role of DA in several contexts generally unfamiliar to workers in atomic and molecular physics, and touch on some of the theoretical difficulties. We continue with a discussion of our work, both experimental and theoretical, on compounds containing a single halogen atom and conclude with results showing how the DA process can be used to study intramolecular electron transfer.
Spatially Resolved Inter-electron Interaction of Autoionising States
Authors: Story JG , Duncan DI , Gallagher TF
Published: June 2013

We have observed transitions to autoionising states in Mg using two short optical pulses. Mg atoms are initially prepared in a high lying Rydberg wave packet with the first picosecond (ps) laser. A second ps laser is then used to excite the inner electron, producing an autoionising state. The dependence of the transition probability on the delay between the two lasers shows that when the second laser is tuned away from the ionic resonance, the inner electron can make a transition only when the Rydberg wave packet is near the core.
New Data from Laser Interrogation of Electron-Atom Collisions Experiments
Authors: Masters AT , Sang RT , MacGillivray WR , Standage MC
Published: June 2013

Recent data from two methods in which high resolution laser radiation is used to assist in determining electron-atom collision parameters are presented. The electron superelastic method has yielded the first measurement of Stokes parameters for electron de-excitation of the 32D5/2–32P3/2,1/2 transition of atomic Na, the upper level having been optically prepared by resonant, stepwise excitation from the 32S1/2 ground level via the 32P3/2 level using two single mode lasers. As well, we report on the development of a model to determine the optical pumping parameters for superelastic scattering from the 32P3/2 level when it is prepared by two lasers exciting from the F = 1 and F = 2 states respectively of the 32S1/ 2 ground level. Data are also presented for collision parameters for the excitation of the 61So–61 PI transition of the I = 0 isotope of Hg by electrons of 50 eV incident energy. The technique employed for these measurements is the stepwise electron–laser excitation coincidence method, in which the electron excited atom is further excited by resonant laser radiation, and fluorescence photons emitted by relaxation from the laser excited state are detected in coincidence with the scattered electron.
Inelastic Proton Scattering Analyses and Ambiguities in SpinParity Assignments of States in 12C
Authors: Karataglidis S , Dortmans PJ , Amos K , de Swiniarski R
Published: June 2013

Data from the excitation of the 13�35, 18�35, 19�20 and 19�40 MeV states in 12C by the inelastic scattering of protons have been analysed using a fully microscopic distorted wave approximation to determine optimal assignments from amongst the current and ambiguous J π; T values of each state involved. While not conclusive, the present analysis suggests the assignments of 4-1; 0, 2-2; 0, 4-2; 0 and 22-2; 1 respectively.
Mobility of Hg+ and Br+ Implanted in Quartz
Authors: Wang Ke-Ming , Shi Bo-Rong , Zhai Hong-Ying , Ma Shi-Jie , Liu Xiang-Dong , Liu Ji-Tian , Liu Xi-Ju
Published: June 2013

Both Hg+ and Br+ were implanted in quartz (Si02) 7 years ago. The mobilities of the implanted Hg+ and Br+ at room and higher temperatures are investigated by Rutherford backscattering of 2�1 MeV He2+ ions. The results show that both Hg+ and Br+ are still immobile at room temperature after 7 years. The depth distributions of Hg+ agree well with those calculated by the transport of ions in matter program (TRIM'90). However, for the case of Br+ the mean projected range is shallower than the TRIM'90 prediction with increasing implantation energy. It is found that 300 keV Hg+ and 250 keV Br+ are mobile after 6000°C and 5000°C annealing respectively. Both diffusion and evaporation during annealing are observed.
Vector Quantum Field Theory of Atoms: Nonlinear Atom Optics and Bose - Einstein Condensate
Authors: Zhang Weiping
Published: June 2013

The recent experimental progress in laser cooling and trapping of neutral atoms brings the atomic samples into the ultracold regime where the bosonic atoms and fermionic atoms are expected to have different dynamic behaviours in the laser fields. In this paper we systematically introduce the theoretical study of interaction of an ultracold atomic ensemble with a light wave in the frame of a vector quantum field theory. The many-body quantum correlation in the ultracold regime of atom optics is studied in terms of vector quantum field theory. A general formalism of nonlinear atom optics for a coherent atomic beam is developed.
A VLA Survey of Rich Clusters of Galaxies III. The Weaker Sources: Maps and Identifications
Authors: Slee OB , Roy AL , Andernach H
Published: June 2013

We present radio and optical parameters for 737 weak sources in 60 Abell cluster fields observed with the Very Large Array (VLA) using scaled arrays at 1.5 and 4.9 GHz. The measurements extend to a lower 1.5 GHz limit of 1.0 mJy and comprise a complete sample with 1.5 GHz flux density 2.5 ≤ S1.5 −3 sr, and the cluster fields are distributed over 24 h of right ascension and between declinations +35° and −30°. Contour maps of the extended sources at 1.5 GHz are presented and source parameters such as position, angular size and spectral index are tabulated. We also derive the emitted power and linear size for those sources with published redshifts. We try to identify the radio sources with optical images on the Palomar and SERC survey plates and give their accurate optical positions, morphologies and apparent magnitudes.
Correlations in Electron - Atom Collisions involving Polarised Electrons and Photons
Authors: Hanne G. F.
Published: June 2013

More sophisticated experimental methods to study inelastic electron–atom
collisions include polarisation-correlation measurements such as
electron–photon (e, eγ) and electron–electron (e, 2e)
coincidence studies or stepwise electron–photon (eγ, γ)
correlations. Electron correlations and spin effects can be explored on the
most fundamental level in such experiments. In this paper recent (e, eγ)
studies with Hg and Xe, (eγ, γ) studies with Ne and (e, 2e) studies
with Xe using polarised electrons and/or polarised photons are reviewed.