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The charge distributions and elastic electron form factors for [sup.18]O, [sup.42,44]Ca, [sup.58]Ni, and [sup.118]Sn nuclei were considered using the cluster expansion of the 1- and 2-body terms. Inelastic electron form factors to [2.sup.+] states with core-polarization effects were studied, where the nuclear collective modes were considered alongside the shell model transition density. The influence of short-range correlations (SRCs) was calculated by the parameter [beta], which was introduced into the ground-state charge distribution and concluded the Jastrow-type function. It is found that the inclusion of 2-body correlations is necessary to describe the observed data of elastic and inelastic form factors at high momentum transfer q > 3 f[m.sup.-1]. Key words: elastic electron scattering, Jastrow type function, charge density distributions, core-polarization, inelastic electron scattering, short-range correlation. Nous etudions les distributions de charge et les facteurs de forme electroniques elastiques pour les noyaux [sup.18]O, 42, 44Ca, [sup.58]Ni et [sup.118]Sn, en utilisant l'expansion en grappes (clusters) de termes a 1 et 2 corps. Nous examinons aussi les facteurs de forme electroniques inelastiques des etats [2.sup.+], avec effets de polarisation du creur, ou sont considerees les densites de transition des modes collectifs aussi bien que du modele en couches. L'influence des correlations a courte portee (CCP/SRC) est evaluee par le parametre [beta] qui est introduit dans la distribution de charge du fondamental dans une fonction de type Jastrow. Nous trouvons que l'inclusion des correlations a deux corps est necessaire pour decrire les donnees observees des facteurs de forme, elastique et inelastique, dans le domaine eleve de transfert d'impulsion q > 3 f[m.sup.-1]. [Traduit par la Redaction] Mots-cles : diffusion electronique elastique, fonction de type Jastrow, distributions de densite de charge, polarisation du creur, diffusion electronique inelastique, correlation a courte portee., 1. Introduction The great challenge for studying nuclear properties (statical and dynamical properties) comes from the complicated structure of the nucleus and the wave function, which describes the interaction among [...]

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network.sup.1, including unusually efficient vibrational energy redistribution and relaxation.sup.2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments.sup.2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch. Liquid ultrafast electron scattering measures structural responses in liquid water with femtosecond temporal and atomic spatial resolution to reveal a transient hydrogen bond contraction then thermalization preceding relaxation of the OH stretch., Author(s): Jie Yang [sup.1] [sup.2] [sup.11] , Riccardo Dettori [sup.3] , J. Pedro F. Nunes [sup.4] , Nanna H. List [sup.1] [sup.2] [sup.5] , Elisa Biasin [sup.1] [sup.2] , Martin [...]

Elastic electron-proton scattering (e-p) and the spectroscopy of hydrogen atoms are the two methods traditionally used to determine the proton charge radius, r.sub.p. In 2010, a new method using muonic hydrogen atoms.sup.1 found a substantial discrepancy compared with previous results.sup.2, which became known as the 'proton radius puzzle'. Despite experimental and theoretical efforts, the puzzle remains unresolved. In fact, there is a discrepancy between the two most recent spectroscopic measurements conducted on ordinary hydrogen.sup.3,4. Here we report on the proton charge radius experiment at Jefferson Laboratory (PRad), a high-precision e-p experiment that was established after the discrepancy was identified. We used a magnetic-spectrometer-free method along with a windowless hydrogen gas target, which overcame several limitations of previous e-p experiments and enabled measurements at very small forward-scattering angles. Our result, r.sub.p = 0.831 [plus or minus] 0.007.sub.stat [plus or minus] 0.012.sub.syst femtometres, is smaller than the most recent high-precision e-p measurement.sup.5 and 2.7 standard deviations smaller than the average of all e-p experimental results.sup.6. The smaller r.sub.p we have now measured supports the value found by two previous muonic hydrogen experiments.sup.1,7. In addition, our finding agrees with the revised value (announced in 2019) for the Rydberg constant.sup.8--one of the most accurately evaluated fundamental constants in physics. A magnetic-spectrometer-free method for electron-proton scattering data reveals a proton charge radius 2.7 standard deviations smaller than the currently accepted value from electron-proton scattering, yet consistent with other recent experiments., Author(s): W. Xiong [sup.1] , A. Gasparian [sup.2] , H. Gao [sup.1] , D. Dutta [sup.3] , M. Khandaker [sup.4] , N. Liyanage [sup.5] , E. Pasyuk [sup.6] , C. [...]

We present results of the energy distribution function of trapped electrons through a measurement of their axial oscillation in a quadrupole Penning trap. Electrons emitted from a thoriated tungsten filament with a range of energies (3-5 eV) are trapped in a low magnetic field quadrupole Penning trap. Subsequent to storage the trapped electrons are detected through monitoring their axial oscillations by an electronic tank circuit that is weakly coupled to the trap, by resonant energy transfer to the electrons. The technique, developed using LabVIEW, enables a direct measurement of the energy distribution function of the electrons in the trap. We obtain a normal distribution of energy, with a maximum that coincides with the potential applied on the electron filament, indicating that the energy distribution of electrons in the trap reflects the energy distribution of the thermionically emitted electrons from the filament. Key words: ion trap, Penning trap, quadrupole trap, non-neutral plasma, electron energy distribution. Nous presentons nos resultats pour la fonction de distribution en energie d'electrons pieges via la mesure de leur oscillation axiale dans un piege Penning quadripolaire. Les electrons, emis par un filament de tungstene thorie, dans un domaine d'energie 3-5 eV sont stockes dans un piege Penning quadripolaire a faible champ magnetique. Suite au stockage, les electrons pieges sont detectes en suivant leurs oscillations axiales a l'aide d'un circuit LC faiblement couple au piege, via l'energie de resonance transferee a l'electron. La technique developpee en utilisant LabVIEW permet une mesure directe de la fonction de distribution d'energie des electrons dans le piege. Nous obtenons une distribution normale en energie, avec un maximum qui correspond au potentiel applique au filament generant les electrons, indiquant que la distribution en energie des electrons pieges reflete la distribution en energie des electrons emis du filament de facon thermoionique. [Traduit par la Redaction] Mots-cles: piege a ions, piege Penning, piege quadripolaire, plasma non neutre, distribution en energie des electrons., 1. Introduction A quadrupole Penning trap [1-4] confines charged particles through combining a static electric quadrupole potential $ with a uniform magnetic field B along the symmetry axis of the [...]

The processes of electron scattering on a short-range potential caused by interaction with polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain, and neutral and ionized impurities in wurtzite n-ZnO with impurity concentration ~1 x [10.sup.17] [cm.sup.-3] are considered. The temperature dependences of electron mobility and Hall factor in the range 15/550 K are calculated. PACS Nos.: 72.10.-d, 72.10.Di, 72.10.Fk. Nous etudions ici la diffusion des electrons dans la wurtzite n-ZnO, par un potentiel a courte portee cause par l'interaction avec des phonons optiques polaires et non polaires, des phonons piezoelectriques et acoustiques, une deformation statique ou des impuretes neutres ou ionisees de concentration ~1 x [10.sup.17] [cm.sup.-3]. Nous calculons la dependance de la mobilite des electrons et du facteur de Hall sur la temperature dans le domaine 15/550 K. [Traduit par la Redaction], 1. Introduction Zinc oxide is a semiconducting material that finds a wide application in device structures; ZnO is very resistive to high-energy radiation making it a very suitable candidate for [...]

The dense soup of matter in the core of neutron stars is hard to model, but particle-accelerator experiments in which energetic electrons scatter off atomic nuclei could help to explore this high-density regime. A test of effective nucleon-nucleon interactions at short separations., Author(s): Alexandra Gade Author Affiliations: High-energy-electron scattering probes the strong nuclear interaction at close range Modelling the fundamental strong force between protons and neutrons -- collectively called nucleons -- is [...]

Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not (1,2). Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings [C.sub.2q], sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly (3,4) only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2[C.sub.2u] - [C.sub.2d] (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the [C.sub.2q] couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future., In parity-violating electron scattering (PVES) experiments, an asymmetry is measured that can be expressed as [A.sub.PV] = [σ.sub.R] - [σ.sub.L]/[σ.sub.R] + [σ.sub.L] (1) where [σ.sub.R]([σ.sub.L]) are the cross-sections for scattering [...]

We have obtained expressions for the creation, destruction, and transfer of atomic multipole moments by electron scattering under relativistic conditions. More specifically, we have obtained separate expressions for different-level processes (inelastic scattering) and for same-level processes (elastic and inelastic scattering). The cross sections for different-level processes are expressed in terms of inelastic magnetic sublevel cross sections, except for the coherence transfer cross section, which is expressed in terms of an angular integral of a product of inelastic magnetic sublevel amplitudes. The same-level cross sections are expressed in terms of the imaginary part of the elastic forward scattering amplitude and in terms of elastic scattering magnetic sublevel cross sections, except for the coherence transfer cross section, which is expressed in terms of the (complex) forward elastic scattering amplitudes and an angular integral of a product of elastic scattering magnetic sublevel amplitudes. If the collisional model supports the optical theorem, then the same-level cross sections can be rewritten in such a form that they are broken up into two parts: an elastic scattering part and an inelastic scattering part. In carrying out this work, we have used the density matrix formalism of Fano and Blum in combination with the electron scattering formalism of Gell-Mann and Goldberger. PACS Nos: 34.80Pa, 34.80 Bm, 34.80 Dp, 52.20 Hv Nous avons obtenu des expressions pour la creation, la destruction et le transfert de moments multipolaires atomiques par diffusion d'electrons relativistes. Plus precisement, nous avons obtenu des expressions differentes pour des mecanismes entre des niveaux differents (diffusion inelastique) et pour des mecanismes impliquant le meme niveau (diffusion elastique et inelastique). Les sections efficaces pour les mecanismes entre niveaux differents sont exprimees en fonction de sections efficaces inelastiques de sous-niveaux magnetiques, sauf pour la section efficace de transfert de coherence, qui est exprimee en fonction d' une integrale angulaire d' un produit d' amplitudes inelastiques de sous-niveaux magnetiques. Les sections efficaces impliquant le meme niveau sont donnees en fonction de la partie imaginaire d'une amplitude de diffusion avant elastique et en fonction de sections efficaces elastiques de sous-niveaux magnetiques, sauf pour la section efficace de transfert de coherence, qui est exprimee en fonction d'amplitudes (complexes) elastiques de diffusion avant et une integrale angulaire d'un produit d'amplitudes elastiques de sous-niveaux magnetiques. Si le modele de collisions supporte le theoreme optique, alors les sections efficaces impliquant le meme niveau peuvent etre reecrites sous une forme ou elles sont brisees en deux parties : une partie elastique et une partie inelastique. Dans le cours de ce travail, nous avons utilise le formalisme de matrices de densite de Fano et Blum avec le formalisme de diffusion d'electrons de Gell-Mann et Goldberger. [Traduit par la Redaction], 1. Introduction In [1] and [2], cross sections for the creation, destruction, and transfer of atomic multipole moments by electron scattering have been defined using the wave-packet propagation scheme along [...]

In nanoscale metal wires, electrical current can cause structural changes through electromigration, in which the momentum of electrons biases atomic motion, but the microscopic details are complex. Using in situ scanning tunneling microscopy, we examined the effects of thermally excited defects on the current-biased displacement of monatomic islands of radius 2 to 50 nanometers on single-crystal Ag(111). The islands move opposite to the current direction, with velocity varying inversely with radius. The force is thus in the same direction as electron flow and acts on atomic defect sites at the island edge. The unexpectedly large force on the boundary atoms can be decreased by over a factor of 10 by adding a mildly electron-withdrawing adsorbate, [C.sub.60], which also modifies the step geometry. The tow coordination of the identified scattering sites is the likely origin of the large force. 10.1126/science.1186648

Nonadiabatic coupling of nuclear motion to electronic excitations at metal surfaces is believed to influence a host of important chemical processes and has generated a great deal of experimental and theoretical interest. We applied a recently developed theoretical framework to examine the nature and importance of nonadiabatic behavior in a system that has been extensively studied experimentally: the scattering of vibrationally excited nitric oxide molecules from a Au(111) surface. We conclude that the nonadiabatic transition rate depends strongly on both the N-O internuclear separation and the molecular orientation and, furthermore, that molecule-surface forces can steer the molecule into strong-coupling configurations. This mechanism elucidates key features of the experiments and provides several testable predictions regarding the dependence of vibrational energy transfer on the initial vibrational energy, molecular orientation, and incident angle. 10.1126/science.1179240

When electrons pair in a superconductor, quasi-particles develop an acute sensitivity to different types of scattering potential that is described by the appearance of coherence factors in the scattering amplitudes. Although the effects of coherence factors are well established in isotropic superconductors, they are much harder to detect in their anisotropic counterparts, such as high-superconducting-transition-temperature cuprates. We demonstrate an approach that highlights the momentum-dependent coherence factors in [Ca.sub.2-x][Na.sub.x]Cu[O.sub.2][Cl.sub.2]. We used Fourier-transform scanning tunneling spectroscopy to reveal a magnetic-field dependence in quasi-particle scattering interference patterns that is sensitive to the sign of the anisotropic gap. This result is associated with the d-wave coherence factors and quasi-particle scattering off vortices. Our technique thus provides insights into the nature of electron pairing as well as quasi-particle scattering processes in unconventional superconductors.

We present new experimental results about channel hot carrier degradation of enclosed layout transistors as a function of previous accumulated total ionizing dose, stress temperature, and transistor geometry. We show that the parametric degradation follows a power law, whose exponent is higher than in conventional open layout transistors, possibly due to a different diffusion geometry of hydrogen. Through physical simulation we attribute this effect to the electric field at the device corners, which leads to a non-uniform impact ionization. Previous irradiation reduces the channel hot carrier degradation in MOSFETs with 5.2-nm gate oxide, while having a minor influence with 2.2-nm gate dielectric. Index Terms--CHC, enclosed layout transistor, hot-electrons, TID, X-ray.

Dynamics of the real and imaginary parts of the dielectric permittivity of a photoexcited silver layer has been investigated by means of femtosecond pump-probe spectroscopy in a surface plasmon resonance Kretschmann configuration. Both real and imaginary permittivity parts experience changes in the visible-near--IR regions under silver excitation at 400 nm. The changes are stronger, particularly those of the imaginary part, at longer wavelengths. Three excited states are formed during the relaxation process, which are attributed to the nonequilibrium and equilibrium heated electron distributions and lattice heating. Different time evolutions of the real and imaginary dielectric permittivity parts are explained by different contributions from interband and intraband transitions caused by plasma frequency and electron scattering frequency variations. OCIS codes: 300.6530, 310.6860, 240.6680.

Quantitative microstructural analysis of zircon using electron backscatter diffraction (EBSD) requires a comparison of empirically collected electron backscatter patterns with theoretical patterns or 'match units' derived from known crystallographic parameters. There are 23 possible crystallographic data sets for zircon, and associated match units, derived from natural and synthetic zircon and from theoretical calculations over a range of pressures and different rare earth element (REE) compositions. A systematic assessment of these match units has been undertaken by EBSD analysis of each of four zircons from a range of geological environments combined with principal components analysis and self-organizing map networks. Comparison of the different match units shows a systematic relationship across all samples that are related to changes in unit-cell dimensions associated with pressure and compositional variations. Systematic variations in the data generated from 96 EBSD maps, each comprising 10 000 electron backscatter patterns, indicate that match units associated with increasing pressure or REE dopants yield poorer quality EBSD data. The match units from low-pressure, undoped, natural zircon consistently yield the best EBSD results and are recommended for natural zircon EBSD studies irrespective of the zircon source or U content. The results provide a clear strategy for optimizing the acquisition and analysis of EBSD data from zircon from both crustal and mantle sources. In addition, the developed approach to match unit analysis may be applied to all other crystalline materials, potentially optimizing EBSD analyses from a range of materials. Keywords: EBSD, microstructure, zircon, reflector file, match unit, REE, pressure, rare earth element

An algorithm for the self-consistent solution of the Boltzmann transport equation (BTE) and Poisson-Schroinger (PS) equation in two dimensions is studied. Findings reveal that the proposed algorithm allows the full exploration of the entire range from drift-diffusion to ballistic regime in nanoscale field-effect transistors.

The main scattering mechanisms limiting mobility in SiC MOSFETs were examined with the help of Hall-effect mechanisms of n-channel MOS devices. Findings reveal that surface-roughness scattering and Coulomb scattering were the main scattering mechanisms limiting electron mobility found in SiC MOSFETs at room temperature.

Radiation damage in a (initially crystalline) silicon wafer was generated by microbeam ion implantation with 600 keV [Si.sup.+] ions (fluence 5 x [10.sup.14] ions/[cm.sup.2]). To produce micro-areas with different degrees of damage, 14 implantations at different temperatures (between 23 and 225 [degrees]C) were done. The structural state of irradiated areas was characterized using Raman spectroscopy and electron back-scatter diffraction. All irradiated areas showed strong structural damage in surficial regions (estimated depth Keywords: Back-scattered electron images, Raman spectroscopy, electron back-scatter diffraction, radiation damage, silicon

Abstract: We summarize various analyses of the world data on elastic electron scattering for the determination of the most precise charge rms-radius of the proton. We also present the Zemach [...]

A two-color (ultraviolet and near-infrared), femtosecond, pump-probe spectroscopic technique were used to observe time-resolved intervalley transitions of electrons between the conduction band [Gamma] and L valley in GaN single crystals. It was found that the threshold for the [Gamma] L transition appears at the energy of 4.51 [plusminus] 0.05 eV and the electron scattering time from the [Gamma] to L valley is comparable to the 170 fs width of our pump pulses, while the return process f electrons from L to [Gamma] is measurably slower.

In 2003, a model for the geostationary electron environment: POLE (Particle ONERA-LANL Environment) has been developed at ONERA/DESP. This model is based on the full complement of Los Alamos National Laboratory geostationary satellites, covers the period 1976-2001 and is valid from 30 keV up to 2.5 MeV and takes into account the solar cycle variation. Over the period 1976 to present, three different detectors were flown: CPA (Charged Particle Analyzer), SOPA (Synchronous Orbit Particle Analyzer) and ESP (Energetic Spectra for Particles). The first two were studied to develop the first version of POLE (up to 2.5 MeV). Here, in order to extend the energy coverage of the model, we analyze the data of the third detector: ESP, where the electron detection covers the range 0.7 MeV-25.8 MeV. The new version thus obtained cover energies from 30 keV up to 5.2 MeV. Index Terms--Electrons, electron data, electron radiation effects, modeling, space radiation effects, space vehicle reliability.

A review of the research on electron and ion transport in dense rare gases is presented. The investigation of the transport properties of electrons in dense rare gases aims at understanding the dynamics and energetics of electron states in a dense medium and at elucidating how changes of the environment influence their nature and scattering properties. The quantum nature of electrons couples them to the environment is such a way to produce a density-dependent shift of their energy that is the key to rationalize the observed phenomena. Index Terms--Charge carrier mobility, electron-atom scattering, multiple scattering effects, electron localization, resonant electron attachment, excimer fluorescence.

We propose a pair of discrete geometric formulations to model two-dimensional (2-D) photonic crystals. Photonic crystals are periodic materials able to guide light by Bragg's reflection. We compared the results with an independent approach based on the multiple-scattering technique (MST). Index Terms--Discrete approaches, photonic crystals, wave propagation.

We have theoretically analyzed the influence of temperature on the performance of a fiber-optic sensor based on surface-plasmon resonance (SPR). The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for temperature dependence includes the thermo-optic effect in the fiber core and sensing layer, and phonon-electron scattering along with electron-electron scattering in the metal layer. The effect of temperature on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the sensing layers with positive and negative thermo-optic coefficients. The theoretical model has been analyzed for both the nonremote and remote sensing cases. This detailed analysis of temperature-dependent SNR and sensitivity leads to achieving the best possible performance from a fiber-optic SPR sensor against the temperature variation. OCIS codes: 060.0060, 060.2370, 120.6810.

A new method of measuring the electron-antineutrino angular correlation coefficient, little 'a', from neutron decay--to be performed at the National Institute of Standards and Technology--will require an electron spectrometer that […]

We have performed two-dimensional, relativistic, electromagnetic, particle-in-cell simulations for an axially extracted vircator. With a copper foil anode, the output frequency of the vircator is found to be strongly dependent upon the variation of foil transparency with electron energy. Using an average transparency for all electron energies yields results that are markedly different from those obtained using the actual variation. However, the output power shows only mild sensitivity. Using the full energy-dependent form of the transparency, we get fairly good agreement with published experimental results. Increasing the energy resolution for the calculation of foil transparency increases the accuracy of calculation of the dominant frequency, although the frequency tends to saturate beyond a certain resolution. However, an increase in the resolution must necessarily be accompanied by an increase in the number of simulation particles, in order to limit statistical fluctuations to an acceptable level. A physical explanation has also been provided for these trends. Index Terms--Electron scattering, microwave, PIC, vircator.

The report proposed a novel technique for the weight redistribution after the electron-electron scattering between weighted electrons in the weighted ensemble Monte Carlo simulation. The proposed technique has been successfully applied to an ideal gas simulation. The study showed that the relaxation time of silicon has a different value when electron-electron scattering is taken into consideration.

Low uncertainty measurements on pure element stable isotope pairs demonstrate that mass has no influence on the backscattering of electrons at typical electron microprobe energies. The traditional prediction of average […]

Experiment E158 at the Stanford Linear Accelerator Center (SLAC) will make the first measurement of parity violation in Moller scattering. The left-right cross-section asymmetry in the elastic scattering of a 45-GEV polarized electron beam with unpolarized electrons in a liquid hydrogen target will be measured to an accuracy of better than [10.sup.-8], with the expected Standard Model asymmetry being approximately [10.sup.-7]. Because helicity-correlated (left-right) charge and position asymmetries in the electron beam can give rise to systematic errors in the measurement, great care must be given to beam monitoring and control. We have developed beam current monitors that measure the charge per pulse at the 3 x [10.sup.-5] level and RF cavity beam position monitors that measure the position per pulse to 1 [micro]m, which should allow precisions of 1 ppb and 1 nm for the final integrated charge and position asymmetries, respectively. In addition, since most helicity-correlated systematics in the electron beam can be traced back to the laser that drives the photoemission from the GaAs source cathode, we first use careful control of laser beam polarization, point-to-point imaging, and other techniques to minimize systematics. We also provide the capability of modulating in a helicity-correlated way the laser beam's intensity and position as it strikes the photocathode, allowing the implementation of active feedbacks to ensure that the average charge and position asymmetries integrate close to zero over the course of the experiment. We present this system of precision beam monitoring and control and report on its performance during a recent commissioning run, T-437 at SLAC, which demonstrated charge and position asymmetry precisions of 12 ppb and 2 nm, respectively. Index Terms--Beam control, beam monitoring, parity violation, polarized electron beam.

Electrical conductivity of quantum wires was investigated with regard to correlated roughness effects.

Byline: John Avery (1) Keywords: generalized Sturmians; inelastic scattering; excitation; quantum theory; atomic structure Abstract: The generalized Sturmian method for solving the many-electron Schrodinger equation is reviewed. This method yields rapidly convergent solutions directly, without the use of the SCF approximation. As a simple illustrative example, differential cross sections are calculated for inelastic scattering of fast electrons by atoms and ions in the 2-electron isoelectronic series. Author Affiliation: (1) H.C. Arsted Institute, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark, 2100 Article History: Registration Date: 08/10/2004

The results of an experimental investigation of the two-dimensional electron gas formation in AlGaN/GaN heterostructures with different polarities grown by plasma-induced molecular beam epitaxy and metalorganic chemical vapor deposition on sapphire substrates are presented.

A description of high accuracy field integral measurement for TJNAF beam energy determination is provided.

High-level ab initio calculations have been used to investigate the torsional potentials of methoxy and hydroxyl groups of omichron-hydroxyanisole. It was established that the intramolecular bond significantly stabilizes the energy minimum structure.

Issues concerning the formation of a heterobridging bond, Ca-O-Si, when a Si-O pendant bond of SiO2 comes close to the Ca atom on the surface of calcium oxide or hydroxide are considered. Precursor formation toward calcium silicate during milling of a mixture of Ca(OH)2 and SiO2 is discussed.

In a scanning electron microscope (SEM) an electron beam sets up an omni-directional source of scattered electrons within a specimen. Diffraction of these electrons will occur simultaneously on all lattice planes in the sample and the backscattered electrons (BSE), which escape from the specimen, will form a diffraction pattern that can be imaged on a phosphor screen. This is the basis of electron backscatter diffraction (EBSD). Similar diffraction effects cause individual grains of different orientations to give different total BSE. SEM images that exploit this effect will show orientation contrast (OC). EBSD and OC imaging are SEM-based crystallographic tools. EBSD enables measurement of the crystallographic orientation of individual rock-forming minerals as small as 1 (mu)m, and the calculation of misorientation axes and angles between any two data points. OC images enable mapping of all misorientation boundaries in a specimen and thus provide a location map for EBSD analyses. EBSD coupled to OC imaging in the SEM enables complete specimen microtextures and mesotextures to be determined. EBSD and OC imaging can be applied to any mineral at a range of scales and enable us to expand the microstructural approach, so successful in studies of quartz rocks, for example, to the full range of rock-forming minerals. Automated EBSD analysis of rocks remains problematic, although continuing technical developments are enabling progress in this area. EBSD and OC are important new tools for petrologists and petrographers. Present and future applications of EBSD and OC imaging include phase identification, studying deformation mechanisms, constraining dislocation slip systems, empirical quantification of microstructures, studying metamorphic processes, studying magmatic processes, and constraining geochemical microsampling. In all these cases, quantitative crystallographic orientation data enable more rigorous testing of models to explain observed microstructures.

The electron densities of tissues for medical applications and those of materials for industrial applications can be determined through Compton scattering tomography. There were many attempts in solving the reconstruction problem, and one is the analytic transform method proposed by S.J. Norton. However, the response function he presented is difficult to associate with the measurement quantity.

In our previous paper [V. Lazurik, V. Moskvin and T. Tabata, IEEE Trans. Nucl. Sci. 45, pp. 626-631 (1998)] the average depth of electron penetration, [R.sub.av], has been introduced as the average of the maximum depths on the trajectories of electrons passing through a target. In the present work the dependence of [R.sub.av] on the angle of incidence of an electron beam has been studied. A semi-empirical equation is derived to calculate [R.sub.av] as a function of angle of incidence. We extend the study of [R.sub.av] from using it to characterize the average behavior of electron beams in a target to describing the generation of secondary electrons by photon beams. It is shown that [R.sub.av] can be used in a wide variety of applications in which the characteristic size of the spatial region of electron production is important.

A study relating to spin-dependent scattering in heterogeneous magnetic structures describes thickness-dependent resistance measurements used to examine the contributions of diffuse and specular scattering to the overall conductance in polycrystalline sputtered metal/metal bilayers. The experiment aimed to understand how these interfaces contribute to the transport in spin-valve structures. Interface systems investigated included Co/Cu, Co/Ta, and Ni80Fe20/Ta.

Research was conducted to examine the anisotropy of the effective mass and scattering mechanisms of electrons by the Shubnikov-de Haas effect. Samples were investigated at temperatures ranging from 4.2 to 30 K in magnetic fields of up to 15 T. Results indicate that the anisotropic behavior both of negative magnetoresistance and of SdH oscillations due to mechanical strain caused by the difference in the thermal expansion coefficient with InP and Si.

Research was conducted to examine the scattering rates for the intra- and intersubband transitions of electrons in a GaAs/AlAs quantum well with a central AlAs thin layer assisted by the emission and absorption of optical phonon modes. The electron behavior demonstrates that electrons of different subbands can be separated in real space by the applied transversal electric field.

Low-temperature scanning tunneling microscopy was used in studying the anisotropic scattering from point defects on the surface of graphite. The experiments were done using an ultrahigh-vacuum STM at 77 K. The experimental results obtained were in close agreement with theoretical calculations made by Mizes and Foster. The images are similar with those of three-fold scattering using a C60-functionalized probe tip at room temperature.

Electron transport parallel to dislocation lines is not affected by the scattering at charged dislocation lines, according to research based on a model developed to analyze the low transverse mobility of GaN by scattering of electrons at charged dislocation lines. The repulsive band bending around dislocations and the directional dependence of the dislocation scattering prevent vertical devices being affected by the scattering of electrons at threading dislocation lines.

Dielectric continuum and hybrid models were utilized to determine whether a reduction in the total electron-phonon scattering rate in a quantum well can be achieved through the inclusion of a monolayer of a different material. The distinctions of the two models were taken into account. Results revealed that a significant reduction in the scattering rates of electron and photon, which utilized these models, was not produced although a zero thickness monolayer inclusion in the center of the quantum well was performed.

The formalism of pair population analysis can be applied to the level of ab initio SCF theory. This allows the visualization of the structure of a number of electron deficient boranes for which the presence of multicenter bonding is widely accepted. Statistical nonlinear population analysis can be regarded as offering new potential for the detection and localization of multicenter bonding patterns. This will in turn boost understanding of the nature of bonding in electron deficient systems.

A study was conducted on nonlinear photon-electron scattering processes. Nonlinear scattering was found to occur during the rest mass of the oscillatory energy of the powerful laser's electron. Multiphoton Compton scattering is observed when the electron rest mass and the electron rest frame's photon energy become comparable. Harmonics are emitted when the electron rest mass is higher than the photon energy.