bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophotographic and charge transport measurements on amorphous semiconductor films of (Se1−xTex)1−yPy
Authors: Kasap S. O. , Polischuk B. , Aiyah Viswanath , Bekirov A. , Jain J. , Baillie A. , Wagner T. , Tichy L.
Published: April 2011

Amorphous Se–Te–P photoreceptor films of various compositions were deposited on to Al substrates by conventional vacuum evaporation techniques. Both xerographic and charge transport measurements have been carried out on the films to evaluate their possible suitability for photoreceptor applications. In xerographic measurements, the photoreceptor films were corona charged to a voltage (V0) and then photodischarged by illumination under light of preselected wavelength (λ) and constant intensity (I). Xerographic photosensitivity (S) was obtained from the photoinduced discharge characteristic via the empirical definition S = (V0 – V1/2)/V0t1/2I where V1/2 = V0/2 is half the initial voltage and t1/2 is the time taken to photo-discharge the surface potential to V1/2. The photosensitivity was studied as a function of illumination wavelength and material composition. Charge transport measurements were carried out using a time-of-flight transient photoconductivity technique to determine the electron and hole mobility – lifetime (μτ) products in the films. The results indicate that Se–Te–P alloys have poor xerographic photosensitivity in the short wavelength region (e.g., λ ~ 500 nm) owing to poor electron and hole transport, but in the long wavelength region (e.g., λ ~ 800 nm) the photosensitivity is considerably higher than the Se–Te system.
Photoresponse of high Tc superconductor thin films
Authors: Hegmann F. A. , Preston J. S.
Published: April 2011

A fast photoresponse is observed in a current-biased epitaxial YBa2Cu3O7 thin-film bridge structure exposed to 100 ps laser pulses. A bolometric response, with a pulse width of the order of 10 ns, dominates at temperatures close to Tc and at high laser fluences. At lower temperatures and fluences, the observed transient response contains distinct fast and slow components. Preliminary results indicate a pulse width for the fast component less than 500 ps. Application of a small magnetic field perpendicular to the sample increases the amplitude of the slow component while leaving the fast component relatively unaffected. Comparison of these results with resistance versus temperature measurements in the same magnetic field suggests that the fast component is nonthermal in origin.
Electrical characteristics and photolytic tuning of poly(3-hexylthiophene) thin film metal–insulator–semiconductor field-effect transistors (MISFETs)
Authors: Xie Z. , Abdou M. S. A. , Lu X. , Deen M. J. , Holdcroft S.
Published: April 2011

In this paper, we present results on the electrical characteristics of both thick and thin film polymer metal–insulator–semiconductor field-effect transistors (MISFETs) based on poly(3-hexylthiophene) semiconducting substrate. These MISFETs were fabricated in eight steps using conventional semiconductor processing technology. The MISFETs had excellent current–voltage characteristics and showed little degradation with time. Electrical parameters of threshold voltage, mobility, and transconductance were − 1 V, 10−4–10−5 cm2 V−1 s−1, and 10−9 S, respectively. These values are typical of π-conjugated polymer-based MISFETs. Electrical transport in MISFETs were by both bulk (or resistive) and FET-like mechanisms in the thick film transistors. The resistive current component and the electrical characteristics were found to be tunable by photolytic degradation of the semiconducting polymer. In this process, the semiconducting π-conjugated regions were spatially converted to insulating regions by novel photo-oxidative chemistry. We were also successful in modelling the MISFETs as an intrinsic FET with parasitic source and drain resistances in series with it and a varistor (for the bulk current component) in parallel with the intrinsic FET. Using this circuit model, we obtained very good agreements between SPICE simulations and the experimental results.
N-quantum approach to the BCS theory of superconductivity
Authors: Greenberg O. W.
Published: April 2011

A method of general applicability to the solution of second-quantized field theories at finite temperature is illustrated using the BCS (Bardeen–Cooper–Schrieffer) model of superconductivity. Finite-temperature field theory is treated using the thermo field-theory formalism of Umezawa and collaborators. The solution of the field theory uses an expansion in thermal modes analogous to the Haag expansion in asymptotic fields used in the N-quantum approximation at zero temperature. The lowest approximation gives the usual gap equation.
Effect of a deformation potential coupling on the ground-state energy of a tight-binding Fröhlich polaron
Authors: Lépine Y. , Frongillo Y.
Published: April 2011

An upper bound to the ground-state energy of a tight-binding polaron (a polaron in a narrow band material) in a polar crystal is obtained, in the nonadiabatic limit, from a Hamiltonian that includes two contributions to the electron–phonon coupling: a short-range deformation potential interaction and a long-range dipolar interaction. A Debye cutoff on the phonon wave vectors is also assumed. A variational ground-state energy is deduced, using a modification of a tight-binding type Ansatz used in small-polaron theory, in the nonadiabatic limit. In the weak-coupling limit the ground state corresponds to that of a large polaron, while the strong-coupling limit gives a small-polaron state. The bandwidth greatly influences the state of the system and phase diagrams are presented that show the regions where the small and the large polarons are energetically favored. We find, in this variational context, that for a narrow band, the transition between the self-trapped state and the band state is continuous and that an intermediate-polaron state is involved. For a larger but moderate bandwidth, the system is found to switch abruptly from one state to the other, with a coexistence of both states around the transition region. Each of the two types of coupling is found to have an equivalent role in increasing the trapping energy of the electron and in reducing the bandwidth exponentially. Furthermore, their effect is cumulative.
Force de répulsion entre un courant sinusoïdal linéique et une bande conductrice mince : application aux problèmes de lévitation
Authors: Attaf M. T. , Allab D.
Published: April 2011

In a previous work, the authors presented a semianalytical treatment of the electromagnetic field distribution in the case of a straight conductor carrying a sinusoidal current parallel to a thin conducting plate. The result of this investigation is extended here to the evaluation of the repulsive forces accompanying this type of electromagnetic interaction. The variation of such forces with geometric parameters is studied in the presence of a single conductor, and in the case of several conductors laying in a plane parallel to the surface of the material submitted to the induction phenomenon. The problem of lévitation in steady-state conditions is examined, in the light of this arrangement, for various conducting materials. Graphs illustrate the results obtained and make evident their practical interest particularly in the stationary case of magnetically levitated vehicles.
Erratum: The renormalization group functions and the effective potential
Authors: McKeon D. G. C. , Kotikov A.
Published: April 2011

It is first demonstrated how the effective potential Veff in a self-interacting scalar theory can be computed using operator regularization. We examine [Formula: see text] and [Formula: see text] theories, recovering the usual results in the former case and showing how Veff is a power series in the square root of the coupling λ in the latter. Scheme dependence of Veff is considered. Since no explicit divergences occur when one uses operator regularization, the renormalization group functions (β and γ) associated with the dependence of λ and [Formula: see text] on the radiatively induced scale parameter μ must be determined by considering the finite effective potential. It is shown that one must in fact compute Veff to a higher power in the perturbative expansion than if β and γ were to be computed using Green's functions. The usual results to lowest order are recovered in the [Formula: see text] model. Finally, a nonperturbative β function is determined by requiring that the mass generated by radiative effects be independent of μ2; it is found that both [Formula: see text] and [Formula: see text] are asymptoticly free with this β function. In the appendix we explicitly compute a two-loop integral encountered in the evaluation of Veff.
Vacuum polarization in a background magnetic field in (2 + 1)-dimensional QED
Authors: McKeon D. G. C.
Published: April 2011

The one-loop vacuum polarization in the presence of a background magnetic field is computed in (2 + 1)-dimensional electrodynamics in which the spinor mass is parity violating. The quantum-mechanical path-integral technique is used to compute matrix elements arising in the context operator regularization.
The de Haas van Alphen effect of MoF6− intercalated graphite
Authors: Wang G. , Ummat P. K. , Datars W. R. , Hu Zhibing
Published: April 2011

The de Haas van Alphen (dHvA) effect of the stage-1 MoF6− graphite intercalation compound was investigated in magnetic fields up to 5.5 T. The dHvA-frequency spectrum of the stage-1 compound consists of a high frequency, a midfrequency, and a set of low frequencies. The dominant oscillation is the high frequency at 1530 T. It is associated with the single graphite energy band of the stage-1 compound. The cyclotron mass of the carrier with the dominant frequency is 0.31 m0 where m0 is the free-electron mass. The electron charge transfer per intercalated MoF6− molecule is 0.3 for the C8.4MoF6 compound. The low frequencies and midfrequencies are compared with those in other stage-1 chloride graphite intercalation compounds.
Measurements of proton total reaction cross sections for 112,114,116,118,120,122,124Sn from 22 to 48 MeV
Authors: Carlson R. F. , Cox A. J. , Eliyakut-Roshko T. , Oers W. T. H. van
Published: April 2011

Using a standard beam attenuation technique, proton total-reaction cross sections (σR) were measured for seven even isotopes of tin (112,114,116,118,120,122,124Sn) from 22 to 48 MeV with a typical accuracy of 2–3%. Two parameterizations of the data are presented, one based on an expression for the nuclear transparency, and the other on a semiempirical relation that has recently been developed.
Caractérisation structurale de couches minces de silicium polycristallin fabriquées par dépôt chimique en phase vapeur sous basse pression du SiH4 et dopées en phosphore in situ
Authors: Béïque Geneviève , Caron Mario , Currie John F. , Meunier Michel
Published: April 2011

not available
Perturbation model for the X1 Σ+ and a3 Σ+ states of NaK at intermediate internuclear distances beyond 6 Å
Authors: Hussein K. , Aubert-Frecon M.
Published: April 2011

The energy of the X1Σ+ and a3Σ+ states of NaK was estimated from a perturbative model for intermediate- and long-range internuclear distances. Both the charge overlap effects calculated from a model previously published and the exchange contribution estimated from the asymptotic formula were taken into account. Fitted analytical expressions are proposed for electrostatic and induction energy terms as well as for various dispersion damping functions. From comparison with accurate experimental results, the present model is seen to be valid for values of R greater than 6 Å (1 Å = 10−10 m) for the X1Σ+ state and R greater than 8 Å for the a3Z+ state.
Positronium spin exchange with spin 1/2 paramagnetic species
Authors: Senba Masayoshi
Published: April 2011

Electron spin exchange of positronium (Ps = e+e−) with spin 1/2 paramagnetic species was investigated. First, the concept of spin flip (nonflip) collisions is examined in the light of the difference in phase shifts between electron spin singlet and triplet encounters. Then, the effects of spin exchange on positron spin dynamics and on Ps lifetimes are discussed and results are compared to muon (electron) spin dynamics in the muon spin rotation (electron spin resonance) techniques.
Solid neon moderator for positron-trapping experiments
Authors: Greaves R. G. , Surko C. M.
Published: April 2011

A solid neon moderator using a two-stage, closed-cycle refrigerator was installed in an experiment to accumulate positrons in a Penning trap. This moderator replaced a single-crystal tungsten film moderator and yielded an approximate 20-fold improvement in the positron-trapping rate. Experience with the new moderator in a relatively poor vacuum environment of p ~ 1 × 10−7 Torr is discussed.
Differential elastic electron scattering
Authors: Crowe Albert , Cvejanović Danica
Published: April 2011

We present the energy dependence of electron–argon and electron–krypton differential cross sections for elastic scattering, discuss their general characteristics, and compare them with existing equivalent data on positron scattering. The present measurements were stimulated by corresponding positron–heavy rare-gas-atom results. Our first aim is to provide a set of data that can be directly compared with the data on positron scattering and hence possibly contribute to the understanding of structures in that data.
Positron–inert-gas-atom elastic DCS measurements
Authors: Kauppila W. E. , Kwan C. K. , Przybyla D. , Smith S. J. , Stein T. S.
Published: April 2011

In this paper we review prior measurements and report new measurements of elastic differential cross sections (DCSs) obtained in our laboratory for positron scattering by the inert gas atoms He, Ne, Ar, Kr, and Xe. The gases (Ne, Ar, Kr, and Xe) for which low-energy measurements have been made below and above the positronium (Ps)-formation thresholds show evidence that the Ps-formation channel is having an observable "absorption" effect on the elastic scattering channel when compared with calculations that only consider the elastic channel. At low energies where only the elastic channel is open, good agreement is found with available calculations. DCS measurements made at high energies (≥200 eV) for He, Ne, and Ar are also found to be consistent with theoretical calculations. At intermediate energies (above the Ps-formation thresholds and below a few hundred eV) theory has not yet been able to match the relative DCSs obtained experimentally owing to the difficulty of including the effects of the most important inelastic channels (i.e., Ps formation and direct ionization). Some initial attempts by our group to obtain absolute elastic DCSs at fixed scattering angles versus positron energy revealed unexpected structure between 55–60 eV for Ar and at 25 and 200 eV for Kr. Our most recent measurements reported here do not confirm the prior observations of these structural features.
Possibilities for antihydrogen formation by antiproton-positronium collisions
Authors: Charlton Michael
Published: April 2011

Progress made towards the production of antihydrogen by antiproton–positronium collisions is surveyed. This includes an outline of how antiprotons ejected in short bursts from the low energy antiproton ring (LEAR) at CERN are captured, cooled, and stored in a Penning trap. Details are given of how a source of low-energy positrons can be interfaced to this trap to promote antihydrogen formation. Production rates and a possible scenario are outlined. We conclude with some comments on what might happen after the closure of LEAR, currently scheduled to take place at the end of 1996.
Positronium-beam production and positronium scattering from molecular hydrogen
Authors: Garner A. J. , Laricchia G.
Published: April 2011

The efficiency with which a positron beam is converted into an positronium beam, via charge exchange in molecular hydrogen and argon gases was investigated. At certain incident positron energies, molecular hydrogen was found to be over three times as efficient as argon for this purpose. The beam conversion efficiency was investigated with respect to both gas pressure and energy. Preliminary measurements for the total cross section of Ps scattering from molecular hydrogen are also presented.
Quadronium and quantum electrodynamics
Authors: Griffin James J.
Published: April 2011

The composite-particle scenario is a phenomenology that can organize the data of the "sharp lepton problem" posed by heavy-ion and (β+ + atom) studies. It hypothesizes a new composite particle (of mass ~3mc2) as the source of the observed sharp energy (e+e−) decay pairs. Available data rule out the possibilities that the source is a new elementary particle or that it is a quasi-bound state of (e+e−). Occam's razor therefore currently favors the quadronium structure, Q0 = (e+e+e−e−). Implications of quadronium for high-precision quantum electrodynamics (QED) are considered, and calculated and (or) measured deviations in QED that are sensitive to the existence of Q0 are identified. In particular, for the electron magnetic-moment anomaly, a(e) = (ge − 2)/2, a Q0–pole effects a small correction to the contributions of O(α4), which is therefore small compared to the largest current (theoretical) uncertainty. For photon–photon scattering, Q0 corrects the leading order matrix element, and allows resonant Q0 creation in photon–nucleus scattering. Finally, a Q0 bound state corrects the O(α) correction to the leading 3γ annihilation rate of triplet positronium. Therefore Q0 may contribute significantly to this decay rate, which is currently in a 10σ discrepancy with experiment. A current experimental gap is the lack of corroborative data on the sharp (Γ ≤ 2.1 keV) 330.1 keV electrons reported by Sakai from irradiations of U and Th with β+-decay positrons. A study of these (and (or) their expected partner positrons of the same energy) in collisions of (~3 MeV) beam positrons (or electrons) upon high-Z neutral atoms could fill this gap. Similar studies with positrons of 660–795 keV would test the expectation that recoilless resonance creation of the Q0 source of these pairs is also possible.
(e,2e) studies of processes involving inner-shell ionization
Authors: Lohmann Birgit , Cavanagh Steven
Published: April 2011

The (e,2e) technique has been applied to the problem of direct outer shell ionization for many years, with considerable success. In recent years an increasing number of groups have explored the process of inner shell ionization, with a view to obtaining information on the dynamics of the process. In this paper, the existing theoretical and experimental studies of this process are discussed. Our recent measurements of the triple differential cross section for 2p ionization in argon, performed at lower energies than have been used previously, are presented.
Calculation of electron momentum distributions using density functional theory
Authors: Duffy Patrick
Published: April 2011

The theoretical momentum profiles (TMPs) for all the valence orbitals of the hydrides CH4, NH3, H2O, HF, SiH4, PH3, H2S, and HCl are calculated using density functional theory (DFT) methods and compared with both configuration interaction (CI) calculations of the ion-neutral overlap and available experimental data. In all cases, it is found that DFT provides, within either the local or nonlocal approximation for the exchange and correlation potential, a close match to the experimental data and the CI calculations for shape. In cases where correlation and relaxation have been observed to have little effect on the shape of the TMP, DFT provides a close match in normalized intensity to the calculated momentum distribution as well. In cases where correlation and relaxation have a pronounced effect on the magnitude of the TMP, density functional theory is shown to consistently significantly overestimate the normalized intensity as predicted by the CI calculations. Use of a nonlocal functional is an improvement in this regard.
EMS studies of larger molecules of chemical and biochemical interest
Authors: Neville J. J. , Zheng Y. , Hollebone B. P. , Cann N. M. , Brion C. E. , Kim C-K. , Wolfe S.
Published: April 2011

The challenges involved in extending electron momentum spectroscopy (EMS) studies beyond small polyatomic molecules to more complicated systems are discussed. EMS results for the highest occupied (frontier) molecular orbitals of glycine (NH2CH2COOH) and dimethoxymethane ((CH3O)2CH2) demonstrate possible approaches to overcoming such challenges as closely spaced valence orbitals, low volatility, and the conformational mobility of the target compound. The increased sensitivity available from recently developed multichannel electron momentum spectrometers is a key factor in overcoming these challenges and making such EMS studies feasible. The utility of Kohn–Sham density functional theory (DFT) for EMS calculations on larger molecules such as glycine and dimethoxymethane using the recently formulated target Kohn–Sham approximation is also investigated as experimental momentum profiles are compared with theoretical momentum profiles generated via Kohn–Sham DFT and a range of Hartree–Fock calculations. The Kohn–Sham DFT calculations provide better agreement with experiment for the frontier orbitals of glycine and dimethoxymethane than even the near Hartree–Fock limit results.
Photodouble ionization of atoms and molecules near threshold
Authors: Dawber G. , McConkey A. G. , Rojas H. , Gulley N. , King G. C. , Avaldi L. , Zubek M. , MacDonald M. A. , Hall R. I.
Published: April 2011

New experimental techniques have been applied to the study of single-photon double ionization of atoms and molecules. A coincidence technique is described in which the spectra of nearly zero energy photoelectrons are recorded in two identical photoelectron energy analysers. The results are discussed in terms of the available theoretical calculations. New techniques for the measurement of double differential cross sections (DDCS) and triple differential cross sections (TDCS) are discussed. New results using these techniques are presented, in which DDCS and TDCS are measured as continuous functions of photon energy.
Reflection (e,2e) experiments from surfaces
Authors: Stefani G.
Published: April 2011

The application of electron–electron coincidence experiments (e,2e) to solid samples, although begun in the earliest stages of the development of such a spectroscopy, has been extensively exploited only during the past few years and the applicability to surfaces has just started to be pursued. The feasibility of (e,2e) experiments in grazing angle reflection geometry has been recently established for the first time. In spite of the success, the possibility of using the grazing angle (e,2e) technique as a binding energy and (or) momentum spectroscopy of surface states rests on the accurate knowledge of the ionization mechanism. To understand which is the dominant process responsible for the reflection (e,2e) events, under various energies and kinematical conditions, is still an open problem. Two possible mechanisms are envisaged that can generate pairs of correlated electrons in the reflection geometry: a single inelastic collision at large momentum transfer or a double collision (elastic and inelastic) at high and low momentum transfer, respectively. In the present paper are reviewed the results of recent (e,2e) experiments performed at energies from threshold up to 300 eV and with kinematics from normal to grazing incidence. They allow elucidation of the (e,2e) ionization mechanism on surfaces at both grazing and normal impact.
Data reduction in multiple-parameter (e,2e) experiments
Authors: Vos M. , Caprari R. S. , Storer P. , McCarthy I. E. , Weigold E.
Published: April 2011

The data reduction of multiple-parameter (e,2e) experiments is described. The origin of the response functions for correcting for the variations in data collection efficiency is discussed. The determination and meaning of the energy-scale and momentum-scale zeros is explained. Finally we report the count rate versus beam current characteristics.
Recent advances in (e,3e) and e,(3-1)e experiments
Authors: Lahmam-Bennani A. , Duguet A.
Published: April 2011

The experimental advances in the study of electron impact double ionization using double coincidence e,(3-1)e or triple coincidence (e,3e) techniques are reviewed. The recent advent and extension of multianalysis and multidetection systems have allowed a second generation of (e,3e) spectrometers to be born. Their most pertinent characteristics are described. Illustrative results from both e,(3-1)e and (e,3e) experiments are discussed, showing all the promising potential of these highly differential studies for the detailed investigation of the fundamentals of the double ionization process.
Polarization and orientation in electron impact excitation to Ne*(2p53p) states
Authors: Baerveldt A. W. , Westerveld W. B. , Eck J. van , Heideman H. G. M.
Published: April 2011

The electron impact excitation of ground-state neon atoms to several, generally not LS-coupled, Ne*(2p53p) states is studied by electron-polarized photon coincidence experiments on the Ne*(2p53p) → Ne*(2p53s) decay radiation. For four transitions the Stokes' parameters P1 to P4 are published at fixed incident electron energies of 50 and 80 eV and in the electron scattering range of 22°–70°. A theoretical discussion is presented to show how information about the collision process can be extracted from the experimental results. For excitation to the three excited states with total angular momentum J = 2 the behaviour of the total angular momentum transfer [Formula: see text] as a function of the electron-scattering angle at 50 eV strongly suggests a common excitation mechanism.
Peculiarities of spontaneous-grating formation in light-sensitive films under elliptically polarized laser radiation
Authors: Miloslavsky V K , Ageev L A , Nahal A
Published: April 2011

The formation of spontaneous gratings in thin waveguide AgClAg photosensitive films was studied under elliptically polarized laser radiation. New peculiarities of the gratings growth were found (i) a deviation in angular position of the wave vectors of the most probable microgratings from π / 2 about the major axis of the polarization ellipse; and (ii) an asymmetry, which depends on the ellipticity sign, in the diffraction and small-angle scattering patterns. The experimental results are explained within the framework of a model that shows the scattering of incident light by small prolate absorptive Ag spheroids oriented across the major axis of the ellipse and arising from the stage of photoinduced dichroism that precedes grating formation. We show that the dependence of the diffraction patterns' asymmetry on the ellipticity sign is related to an instability due to the angular position of the wave vectors of the most probable microgratings.

PACS No. 78.65
The spherically symmetric model of eH scattering
Authors: Temkin A , Wang Y D , Bhatia A K , Sullivan E C
Published: April 2011

The spherically symmetric model (SSM) for electron--hydrogen scattering is one in which the Coulomb repulsion between the electrons, 2/r12, is replaced by 2/r>, where r> is the greater of r1 or r2. The partial wave decomposition of the wave function for this model is carried out with emphasis on L > 0 partial waves, in which case it is shown that singlet and triplet results are identical. The model, nevertheless, retains all inelastic and ionization channels, and therefore provides a nontrivial testing ground for methods of calculation. The decomposition results in two-dimensional partial differential equations (PDEs). Here numerical calculations are carried out in two ways using (i) a propagation method, and (ii) a noniterative PDE method. The latter is augmented by an integral formula, which greatly enhances the practicality of the method. Elastic phase shifts for L = 1,2,3 partial waves in the elastic region are presented.

PACS No. 34.80
B2Σ+ state lifetime in CO+
Authors: Scholl T J , Rosner S D , Holt R A
Published: April 2011

We measured the lifetime of the B2Σ+, v = 0 level of the astrophysically important CO+ molecule by applying the collinear beam-laser method. Ions in the long-lived A2Π level were excited to the B2Σ+ state by a single-frequency laser beam in resonance with a transition in the B2Σ+  A2Π BaldetJohnson band, and the laser-induced fluorescence from the B2Σ+  X2Σ+ First Negative band was monitored as a function of distance from the excitation region. We claim that our result of 54.9 ± 0.7 ns is less likely to have suffered from systematic error than previous measurements, which were mutually discordant.

PACS No. 33.70Ca
MAF solution for bounded potential problems
Authors: Ghatak A K , Goyal I C , Jindal R , Varshni Y P
Published: April 2011

We present here the solutions of a bounded linear harmonic potential and abounded quartic potential using the modified Airy function (MAF) method. Resultsobtained by the MAF method have been compared with the analytical (numerical)results and with those obtained by the JWKB method. The comparison showsthat the MAF method gives very accurate results and is, in general, the moreaccurate of the two methods. The MAF method also gives an accurate descriptionof the eigenfunction. A perturbation correction when applied to MAF helps usto get very accurate eigenvalues. The method should be useful in determiningthe eigenvalues and the eigenfunctions of any smoothly varying arbitrarypotential confined by infinite walls.PACS No. 03.65
Article
Authors: Kurunczi P , Becker K , Martus K
Published: April 2011

The vacuum ultraviolet (VUV) emissions of the hydrogen Lyman series following the dissociative excitation of the Si-organic compounds tetraethoxysilane (TEOS), tetramethylsilane (TMS), and hexamethyldisiloxane (HMDSO) by controlled electron impact were analyzed. Absolute photoemission cross sections from threshold to 200 eV and appearance potentials were determined for the Lyman-α and Lyman-β emissions for each of the three targets. The measured apparent emission cross sections at 100 eV impact energy for the Lyman-α lines are 6.0 x 10-19 cm2 for TMS, 6.5 x 10-19 cm2 for HMDSO and 1.1 x 10-18 cm2 for TEOS. The apparent Lyman-α cross sections for all three targets contained significant cascade contributions from the H Balmer series. Detailed studies of the near threshold regions indicated that several break-up mechanisms of the parent molecules contribute to the emissions. The lowest onsets for HMDSO, and TEOS were attributed to the removal of a single excited atomic hydrogen atom in the n=2 state. Additional onsets at higher energies could not be uniquely correlated in all cases with a particular break-up channel and (or) cascading, since the other fragments in these processes were not identified. The Lyman-β apparent emission cross sections were also measured and we found values of 1.3 x 10-19 cm2 for TMS, 1.6 x 10-19 cm2 for HMDSO, and 2.0 x 10-19 cm2 for TEOS at an impact energy of 100 eV.

PACS Nos. 52.20Fs and 34.80Gs
Sur les opérateurs différentiels symétrisants relatifs aux systèmes non-conservatifs
Authors: Abdi R El , Gambart G
Published: April 2011

For nonconservative systems, which we call systems with follower loads, a study is proposed concerning the differential operators which lead to a self-adjoint problem for a generalization of the Rayleigh quotient.In the case of punctual loads, we give the general expression for the identification of these operators. For some systems under follower loads, a new method is developed for the identification of the eigenvalues (critical load and critical frequency) when these operators do not exist. A numerical comparison is presented when the exact solutions do exist.

PACS Nos. : 02.00 et 03.00
Article
Authors: Smolyakov A I
Published: April 2011

The structure of gyroviscous forces due to the collisionless magneticviscosity is considered for a plasma with finite temperature gradients andanisotropic perturbed pressure. The standard gyroviscous cancellation isgeneralized for a plasma with ∇ T ≠ to 0 by including effects of thethird-order moments in the Braginskii's gyroviscosity tensor. New reducedplasma-density and parallel momentum-balance equations are derived takinginto account particle and heat flows along the equilibrium magnetic field. PACS Nos.: 52.25Dg, 52.25j, 52.30-q, and 52.35Ra
Article
Authors: Bunge C F , J'auregui R , Ley-Koo E
Published: April 2011

When the one-body part of the relativistic Hamiltonian H is asum of one-electron Dirac Hamiltonians, relativistic configurationinteraction (CI) calculations are carried out on an ad hocbasis of positive-energy orbitals, {u+j; j=1,2,...,m}, andmore recently, with the full bases of positive-energy andnegative-energy orbitals, {u+j ,u-j ;j=1,2,...,m}. Therespective eigenproblems,H+C+k=E+kC+k, k=1,2,..., N(m),andHCk=EkCk ; k=1,2,...,N(2m)are related throughE+k <= Ek+N(2m)-N(m)establishing a new variational principle for relativistic calculationsof electronic structures.In this paper, on the basis of Brillouin's theorem and a relativisticmulticonfiguration Hartree-Fock (RMCHF) expansion in the{u+j, u-j; j=1,2,...,m} basis, we develop equations to annihilatethe coefficients of all single excitations to obtain very accurateRMCHF solutions.Moreover, after nullifying the coefficients of single excitations,the above inequality among energies becomes an equality,leading to a particular instance of an exact decoupling ofpositive-energy and negative-energy orbitals, irrespective of anyad hoc choice of potentials, hence rigorously justifying, forthe first time, the absence of explicit projection operators in allcurrent relativistic work where one-electron Dirac Hamiltoniansare involved.We present, also for the first time, relativistic Hartree-Fockapproximations for the ground states of He through Ar, which areaccurate to six decimals in a.u., and which converge to thenonrelativistic results when the speed of light c -> infinity.This accuracy was obtained by means of compact Slater-type orbitalexpansions through a direct translation of nonrelativistic Hartree-Fockwithout need to reoptimize nonlinear parameters. Our SCFequations are also valid for any open shells and for anyexcited states within a given symmetry, as exemplified withapplications to odd-parity, J = 1/2, 1s22s22p2np statesof neutral nitrogen.

PACS Nos.: 31.10+z, 11.80Fv, 31.20Tz, 31.30Jv
Ultrashort-pulse generation by self-mode-locked Ti:sapphire lasers without apertures and with low pumping powers
Authors: Hajiesmaeilbaigi Fereshteh , Azima Ahmad
Published: April 2011

We demonstrate the low-pump-power operation of a self-mode-locked Ti:sapphirelaser without hard apertures.The pump power was reduced owing to the tight focusing geometryin our design. Stable sub-25-fs duration pulses for pump powers in the range 2.83.0 W for the10 mm long Ti:sapphire crystal, and sub-15-fs duration pulses for pump powers in the range0.50.6 W for the 2 mm crystal were obtained.

PACS No.: 42.60
High-algebraic, high-phase lag methods for accurate computations for the elastic- scattering phase shift problem
Authors: Simos T E
Published: April 2011

A family of three new hybrid eighth-algebraic-order two-step methods with phase lag of order 16, 18, and 20 are developed for computing elastic-scattering phase shifts of the one-dimensional Schrödinger equation. Based on these new methods, we obtain some new embedded variable-step procedures for the numerical integration of the Schrödinger equation. Numerical results obtained for both the integration of the phase-shift problem for the well known case of the LennardJones potential and the integration of coupled differential equation arising from the Schrödinger equation show that these new methods are better than other finite-difference methods.

PACS Nos.: 02.00, 02.70, 03.00, 03.65
Article
Authors: Karshenboim S G , Ivanov V G , Shabaev V M
Published: April 2011

We analyze the Uehling correction to the hyperfine structure of the ground state in hydrogenlike electronic and muonic atoms with a pointlike nucleus. The results are obtained analytically without any expansion over Zalpha.

PACS No.: 31.20D
Article
Authors: Bracken P
Published: April 2011

A method for calculating complete secular polynomials is discussedthat is based on the evaluation of matrix elementsof a specific Hamiltonian.Several Hamiltonians are presented and described in detail as well astheir physical significance. It is shown that theycan be transformed into an equivalent form in termsof raising and lowering operators, and the third componentof the spin operator. A basis set is definedand the action of a specific Hamiltonian on thebasis set is described in detail. Several Hamiltoniansare given explicitly and in matrix form. Results in terms of secularpolynomials for an anisotropic Hamiltonian with one anisotropyparameter and a Hamiltonian with two anisotropy parameters forseveral values of N are reported. These polynomialsthat have not appeared before are given in terms of both theenergy and anisotropy variables.PACS Nos.: 05.50+q, 75.10Dg, and 75.10 Jm
Radial structure of electron drift waves and anomalous transport in the edge plasma
Authors: Lewandowski J LV
Published: April 2011

The radial structure of electron drift waves in a low-pressure tokamak plasma is presented. The ions are cold and an electrostatic approximation for the fluctuating potential is used. It is shown that the problem of the radial structure of drift waves in toroidal geometry is amenable to a two-step solution; in first approximation, the radial structure of the mode is neglected and the problem to be solved is the usual eigenmode equation along the (extended) poloidal angle; in second approximation, the mode amplitude is expanded in ascending powers of the parameter (k⊥Ln)-1/2 , where k⊥ is the magnitude of the lowest-order wavevector and Ln is the radial density scale length. It is shown that the radial structure of drift-type modes can depend strongly on the magnetic shear and the scalar magnetic curvature. Numerical calculations for plasma parameters relevant to the edge region of medium-size tokamaks are presented. PACS Nos.: 52.35Kt, 52.30Jb, and 52.35Ra
Pseudorapidity distribution of relativistic singly charged particles in heavy-ion collisions at high energy
Authors: Liu F -H , Panebratsev Y A
Published: April 2011

The pseudorapidity distribution of relativistic singly charged particles produced in high-energy heavy-ion collisions is described by the thermalized cylinder picture. The calculated results are in agreement with the experimental data of lead-induced interactions at 158A GeV/c. PACS Nos.:25.75.-q and 25.75.Dw
Are the Dirac particles of the Standard Model dynamically confined states in a higher dimensional flat space?
Authors: Bryan R
Published: April 2011

Some time ago Rubakov and Shaposhnikov suggested that elementary particles might be excitations trapped on a soliton in a flat higher dimensional space. They gave, as an example, ϕ4 theory in five dimensions with a bosonic excitation on a domain wall ϕcl in the fifth dimension. They also trapped a chiral Dirac particle on the domain wall with the interaction Lagrangian g [Formula: see text] ϕψ. The field equation for the Dirac field was -i[Formula: see text]. We show that a Dirac equation in eight flat dimensions with -gϕ replaced by a harmonic-oscillator "potential" in the four higher dimensions (plus a large constant M0) generates bound states in approximate SU (4) × SU (2) representations. These representations have corresponding "orbital" times "spin" quantum numbers and bear some resemblance to the quarks and leptons of the Standard Model. Soliton theory suggests that the harmonic-oscillator potential should rise only a finite amount. This will then limit the number of generations in a natural way. It will also mean that particles with sufficient energy might escape the well altogether and propagate freely in the higher dimensions. It may be worthwhile to search for a soliton (instanton?) that can confine Dirac particles in the manner of the harmonic-oscillator potential.PACS No.: 12.10.Dm
A self-consistent lumped radio frequency linear network model for MOSFETs taking into account the gate resistance
Authors: Abou-Allam E , Manku T , Chen C -H , Deen M J
Published: April 2011

This paper describes a self-consistent lumped linear network model for MOSFETs that takes into account the distributed nature of the gate resistance. The model is verified with experimental results. The self-consistent model consists of placing a lumped resistance in series with the gate. The lumped resistance takes the value of the total gate resistance divided by a factor of three. To second order in jω, this is shown to be almost an exact approximation in determining all y-parameters and the equivalent noise resistance. The third-order terms, however, give rise to a 17% error. The value of ft for a MOS transistor shows no dependence with the gate resistance to all orders in jω. Furthermore, we also show that the thermal noise arising from the distributed gate resistance does not contribute to any additional equivalent input current noise. PACS No.: 73.40
Comparative studies of the influence of hydrogen incorporation on the electronic properties of a-Ge:H films prepared by two different techniques
Authors: Bouizem Y , Sib J D , Chahed L , Thèye M L
Published: April 2011

We present the results of a detailed investigation of hydrogen incorporation and optical absorption in the 0.6-1.3 eV range for two series of hydrogenated amorphous germanium films (a-Ge:H) deposited by reactive sputtering (series A) and by plasma-enhanced chemical vapor deposition from germane (series B). Our results clearly show that the series A samples are characterized by a larger bonded hydrogen concentration (CH), a more rapid gap variation with increasing CH, a smaller refractive index, and a lower density than the series B samples. We also compare in detail the energy distribution of the localized states in the pseudo-gap and the deep-defect states density as deduced from a decomposition of the optical absorption spectra based on a theoretical model for the gap states density in amorphous tetracoordinated semiconductors.PACS No.: 71.90
The significance of the Mathieu-Hill differential equation for Newton's apsidal precession theorem
Authors: Valluri S R , Biggs R , Harper W , Wilson C
Published: April 2011

Newton's precession theorem in Proposition 45 of Book I of Principia relates a centripetal force of magnitude μrn-3 as a power of the distance from the center to the apsidal angle θ, where θ is the angle between the point of greatest distance and the point of least distance. The formula θ = π/[Formula: see text] is essentially restricted to orbits of small eccentricity. A study of the apsidal angle for appreciable orbital eccentricity leads to an analysis of the differential equation of the orbit. We show that a detailed perturbative approach leads to a Mathieu-Hill-type of inhomogeneous differential equation. The homogeneous and inhomogeneous differential equations of this type occur in many interesting problems across several disciplines. We find that the approximate solution of this equation is the same as an earlier one obtained by a bootstrap perturbative approach. A more thorough analysis of this inhomogeneous differential equation leads to a modified Hill determinant. We show that the roots of this determinant equation can be solved to obtain an accurate solution for the orbit. This approach may be useful even for cases where n deviates noticeably from 1. The derived analytic results were applied to the Moon, Mercury, the asteroid Icarus, and a hypothetical object. We show that the differential equation that occurs in a perturbative relativistic treatment of the perihelion precession of Mercury also leads to a simplified form of the Mathieu-Hill differential equation.PACS Nos.: 95.100.C, 95.10.E, 95.90, and 02.30.H
Improved finite-lattice estimates of the properties of two quantum spin models on the infinite square lattice
Authors: Betts D D , Lin H Q , Flynn J S
Published: April 2011

This paper describes an improvement in the method of exact diagonalization of Hamiltonians of quantum spin models on finite square lattices and the statistical analysis of the data so obtained to estimate the physical properties of the models on the infinite square lattices at zero temperature. The geometry and topology of finite square lattices are described. The models studied are the spin one-half XY and Heisenberg antiferromagnets using 28 finite square lattices with up to 32 vertices. Our estimates of the energy and magnetization on each model on the infinite lattice at zero temperature compare very well with recent estimates using quantum Monte Carlo, series expansion, and spin wave estimates. Estimates of spin wave velocity and transverse susceptibilities are more scattered.PACS No.: 75.10J
Effect of magnetic field structure on collisional drift waves
Authors: Lewandowski J LV , Persson M
Published: April 2011

A 3-field model for collisional drift waves, in the ballooning representation, for a low-pressure stellarator plasma is presented. The 3-field model, which includes the effects of a finite radial mode number (θk) , is solved as an initial-value problem along the magnetic field line. It is shown that for a stellarator with low global magnetic shear, θk= 0 corresponds to the fastest linear growth rate. The effects of the magnetic field structure for the tokamak and stellarator configurations are discussed in a comparative way. PACS Nos.: 52.35Kt, 52.30Jb, 52.35Ra
Optical conductivity in model with anisotropic inelastic scattering
Authors: Branch D , Carbotte J P
Published: April 2011

Inelastic scattering is very strong in the oxides and large momentum space anisotropies exist in models in which the effective interactionis strongly peaked at (π, π) in the 2-dimensional Brillouin zone.This situation is favourable to d-wave superconductivity and may apply to the oxides. We calculate the normal state optical conductivity and describe the relationship of the derived optical-scattering rates and effective masses to the underlying self energies with emphasis on frequency dependence and on anisotropy. Comparison with experimentsis made. It is found that anisotropy leads to an energy dependence in the optical rate even when the scattering is elastic.PACS Nos.: 74.25Gz, 74.20Mn
The powder Zeeman study of CH3NH3Hg2Cl5 by the nuclear quadrupole resonance
Authors: Saygin Neslihan
Published: April 2011

The temperature dependence of the Cl nuclear quadrupole resonance (NQR) frequency in CH3NH3Hg2Cl5 was investigated for temperatures between 77 and 340 K where three frequencies were found. The Zeeman effect on the NQR of 35Cl in a crystalline powder of CH3NH3Hg2Cl5 was studied. The asymmetry parameter (η) of the electric field gradient for the second frequency was obtained.

PACS No.: 33.25
VUV lasing on puff metal vapor of neon-like aluminum ions produced by Z-pinch plasma
Authors: Rahmani B , Liu S Y , Yasuoka K , Belbachir H A , Ishii S
Published: April 2011

A collisional-radiative equilibrium model was developed to investigate the population inversion on metal vaporaluminum plasma. The population inversion has been establishedbetween lower3s(3P1 °, 1P1°) and upper 3p(3P0, 1S°) levels. The vacuumultra-violet lasing on neon-like aluminum ions provideswavelengths of 111.9, 143.2, and 157.3 nm. The rate of relativedensity population, between lower 3s1P1° and upper 3p3P0 levels, reaches its highest valueof 7.16 at the electron density of 1019 cm-3. Themodified expression of the optical escape factor, in the case of the Doppler profile, was introduced in the calculation of the opacityeffect on the gain magnitudes. The Holstein expressionunderestimates the optical escape factor in the region ofrelatively small thickness. The resonance radiation trapping by the 3dconfiguration drastically alters the gain values. A gain greater than 1 cm-1 was found between lasing levels 3s 3P1 ° and3p3P0. The enhancement of gain was due to the pumping of heupper level by a dielectronic recombination process from the groundstate of fluorine-like and by the inner-shell ionization processfrom excited levels of sodium-like ions.PACS No.: 52.00