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Sample records for high-resolution electron collision

  1. ELECTRONICS UPGRADE OF HIGH RESOLUTION MASS SPECTROMETERS

    SciTech Connect

    Mcintosh, J; Joe Cordaro, J

    2008-03-10

    High resolution mass spectrometers are specialized systems that allow researchers to determine the exact mass of samples to four significant digits by using magnetic and electronic sector mass analyzers. Many of the systems in use today at research laboratories and universities were designed and built more than two decades ago. The manufacturers of these systems have abandoned the support for some of the mass spectrometers and parts to power and control them have become scarce or obsolete. The Savannah River National Laboratory has been involved in the upgrade of the electronics and software for these legacy machines. The Electronics Upgrade of High Resolution Mass Spectrometers consists of assembling high-end commercial instrumentation from reputable manufacturers with a minimal amount of customization to replace the electronics for the older systems. By taking advantage of advances in instrumentation, precise magnet control can be achieved using high resolution current sources and continuous feedback from a high resolution hall-effect probe. The custom equipment include a precision voltage divider/summing amplifier chassis, high voltage power supply chassis and a chassis for controlling the voltage emission for the mass spectrometer source tube. The upgrade package is versatile enough to interface with valve control, vacuum and other instrumentation. Instrument communication is via a combination of Ethernet and traditional IEEE-488 GPIB protocols. The system software upgrades include precision control, feedback and spectral waveform analysis tools.

  2. Computer synthesis of high resolution electron micrographs

    NASA Technical Reports Server (NTRS)

    Nathan, R.

    1976-01-01

    Specimen damage, spherical aberration, low contrast and noisy sensors combine to prevent direct atomic viewing in a conventional electron microscope. The paper describes two methods for obtaining ultra-high resolution in biological specimens under the electron microscope. The first method assumes the physical limits of the electron objective lens and uses a series of dark field images of biological crystals to obtain direct information on the phases of the Fourier diffraction maxima; this information is used in an appropriate computer to synthesize a large aperture lens for a 1-A resolution. The second method assumes there is sufficient amplitude scatter from images recorded in focus which can be utilized with a sensitive densitometer and computer contrast stretching to yield fine structure image details. Cancer virus characterization is discussed as an illustrative example. Numerous photographs supplement the text.

  3. High resolution electron crystallography of protein molecules

    SciTech Connect

    Glaeser, R.M. |; Downing, K.H.

    1993-06-01

    Electron diffraction data and high resolution images can now be used to obtain accurate, three-dimensional density maps of biological macromolecules. These density maps can be interpreted by building an atomic-resolution model of the structure into the experimental density. The Cowley-Moodie formalism of dynamical diffraction theory has been used to validate the use of kinematic diffraction theory, strictly the weak phase object approximation, in producing such 3-D density maps. Further improvements in the preparation of very flat specimens and in the retention of diffraction to a resolution of 0.2 nm or better could result in electron crystallography becoming as important a technique as x-ray crystallography currently is for the field of structural molecular biology.

  4. Improved methods for high resolution electron microscopy

    SciTech Connect

    Taylor, J.R.

    1987-04-01

    Existing methods of making support films for high resolution transmission electron microscopy are investigated and novel methods are developed. Existing methods of fabricating fenestrated, metal reinforced specimen supports (microgrids) are evaluated for their potential to reduce beam induced movement of monolamellar crystals of C/sub 44/H/sub 90/ paraffin supported on thin carbon films. Improved methods of producing hydrophobic carbon films by vacuum evaporation, and improved methods of depositing well ordered monolamellar paraffin crystals on carbon films are developed. A novel technique for vacuum evaporation of metals is described which is used to reinforce microgrids. A technique is also developed to bond thin carbon films to microgrids with a polymer bonding agent. Unique biochemical methods are described to accomplish site specific covalent modification of membrane proteins. Protocols are given which covalently convert the carboxy terminus of papain cleaved bacteriorhodopsin to a free thiol. 53 refs., 19 figs., 1 tab.

  5. Improved methods for high resolution electron microscopy

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    1987-04-01

    Existing methods of making support films for high resolution transmission electron microscopy are investigated and novel methods are developed. Existing methods of fabricating fenestrated, metal reinforced specimen supports (microgrids) are evaluated for their potential to reduce beam induced movement of monolamellar crystals of C44H90 paraffin supported on thin carbon films. Improved methods of producing hydrophobic carbon films by vacuum evaporation, and improved methods of depositing well ordered monolamellar paraffin crystals on carbon films are developed. A novel technique for vacuum evaporation of metals is described which is used to reinforce microgrids. A technique is also developed to bond thin carbon films to microgrids with a polymer bonding agent. Unique biochemical methods are described to accomplish site specific covalent modification of membrane proteins. Protocols are given which covalently convert the carboxy terminus of papain cleaved bacteriorhodopsin to a free thiol.

  6. A compact, light weight, high resolution electron monochromator

    NASA Astrophysics Data System (ADS)

    Goembel, L.; Doering, J. P.

    1995-06-01

    A high resolution electron monochromator that incorporates Vespel polyimide plastic in its construction is described. A great saving in bulk can be realized by mounting the electron optical elements in Vespel tubes rather than mounting them by traditional means.

  7. Phase contrast in high resolution electron microscopy

    DOEpatents

    Rose, H.H.

    1975-09-23

    This patent relates to a device for developing a phase contrast signal for a scanning transmission electron microscope. The lens system of the microscope is operated in a condition of defocus so that predictable alternate concentric regions of high and low electron density exist in the cone of illumination. Two phase detectors are placed beneath the object inside the cone of illumination, with the first detector having the form of a zone plate, each of its rings covering alternate regions of either higher or lower electron density. The second detector is so configured that it covers the regions of electron density not covered by the first detector. Each detector measures the number of electrons incident thereon and the signal developed by the first detector is subtracted from the signal developed by the record detector to provide a phase contrast signal. (auth)

  8. Electron Gun Technologies for High Resolution Electron Microscopes

    NASA Astrophysics Data System (ADS)

    Fujita, Shin

    High-brightness electron gun technologies for high resolution electron microscopes are reviewed. High performance electron beam apparatuses today are equipped with either Schottky emission or field emission type cathodes, both of which have sharply etched tips for electric field enhancement that promotes electron emission. One of the key elements in these pointed cathodes is a proper control of the tip geometry. It substantially affects the emitter optics and performance. It is shown that the geometry is dictated by the faceting of the tip, which is in turn determined by the Equilibrium Crystal Shape (ECS). The ECS is the tip geometry that minimizes the surface free energy and dependent on the emitter operation environment. By proper choice of the tip field and temperature, one can control the degree of faceting and achieve optically desirable tip geometries.

  9. High resolution electron attachment to CO₂ clusters.

    PubMed

    Denifl, Stephan; Vizcaino, Violaine; Märk, Tilmann D; Illenberger, Eugen; Scheier, Paul

    2010-01-01

    Electron attachment to CO₂ clusters performed at high energy resolution (0.1 eV) is studied for the first time in the extended electron energy range from threshold (0 eV) to about 10 eV. Dissociative electron attachment (DEA) to single molecules yields O(-) as the only fragment ion arising from the well known (2)Π(u) shape resonance (ion yield centered at 4.4 eV) and a core excited resonance (at 8.2 eV). On proceeding to CO₂ clusters, non-dissociated complexes of the form (CO₂)(n)(-) including the monomer CO₂(-) are generated as well as solvated fragment ions of the form (CO₂)(n)O(-). The non-decomposed complexes appear already within a resonant feature near threshold (0 eV) and also within a broad contribution between 1 and 4 eV which is composed of two resonances observed for example for (CO₂)(4)(-) at 2.2 eV and 3.1 eV (peak maxima). While the complexes observed around 3.1 eV are generated via the (2)Π(u) resonance as precursor with subsequent intracluster relaxation, the contribution around 2.2 eV can be associated with a resonant scattering feature, recently discovered in single CO₂ in the selective excitation of the higher energy member of the well known Fermi dyad [M. Allan, Phys. Rev. Lett., 2001, 87, 0332012]. Formation of (CO₂)(n)(-) in the threshold region involves vibrational Feshbach resonances (VFRs) as previously discovered via an ultrahigh resolution (1 meV) laser photoelectron attachment method [E. Leber, S. Barsotti, I. I. Fabrikant, J. M. Weber, M.-W. Ruf and H. Hotop, Eur. Phys. J. D, 2000, 12, 125]. The complexes (CO₂)(n)O(-) clearly arise from DEA at an individual molecule within the cluster involving both the (2)Π(u) and the core excited resonance. PMID:21491691

  10. High-resolution spectroscopic probes of collisions and half-collisions

    SciTech Connect

    Hall, G.E.

    1993-12-01

    Research in this program explores the dynamics of gas phase collisions and photodissociation by high-resolution laser spectroscopy. Simultaneous state and velocity detection frequently permits a determination of scalar or vector correlations among products. The correlated product distributions are always more informative, and often easier to interpret than the uncorrelated product state distributions. The authors have recently built an apparatus to record transient absorption spectra with 50 nS time resolution and 20 MHz frequency resolution using a single frequency Ti:sapphire laser. The photodissociation of NCCN and C{sub 2}H{sub 5}SCN at 193 nm is discussed.

  11. Collision cross section measurements for biomolecules within a high-resolution FT-ICR cell: theory.

    PubMed

    Guo, Dan; Xin, Yi; Li, Dayu; Xu, Wei

    2015-04-14

    In this study, an energetic hard-sphere ion-neutral collision model was proposed to bridge-link ion collision cross section (CCS) with the image current collected from a high-resolution Fourier transform ion cyclotron resonance (FT-ICR) cell. By investigating the nonlinear effects induced by high-order electric fields and image charge forces, the energetic hard-sphere collision model was validated through experiments. Suitable application regions for the energetic hard-sphere collision model, as well as for the conventional Langevin and hard-sphere collision models, were also discussed. The energetic hard-sphere collision model was applied in the extraction of ion CCSs from high-resolution FT-ICR mass spectra. Discussions in the present study also apply to FT-Orbitraps and FT-quadrupole ion traps. PMID:25754983

  12. The theory and practice of high resolution scanning electron microscopy

    SciTech Connect

    Joy, D.C. Oak Ridge National Lab., TN )

    1990-01-01

    Recent advances in instrumentation have produced the first commercial examples of what can justifiably be called High Resolution Scanning Electron Microscopes. The key components of such instruments are a cold field emission gun, a small-gap immersion probe-forming lens, and a clean dry-pumped vacuum. The performance of these microscopes is characterized by several major features including a spatial resolution, in secondary electron mode on solid specimens, which can exceed 1nm on a routine basis; an incident probe current density of the order of 10{sup 6} amps/cm{sup 2}; and the ability to maintain these levels of performance over an accelerating voltage range of from 1 to 30keV. This combination of high resolution, high probe current, low contamination and flexible electron-optical conditions provides many new opportunitites for the application of the SEM to materials science, physics, and the life sciences. 27 refs., 14 figs.

  13. Robust High-Resolution Cloth Using Parallelism, History-Based Collisions and Accurate Friction

    PubMed Central

    Selle, Andrew; Su, Jonathan; Irving, Geoffrey; Fedkiw, Ronald

    2015-01-01

    In this paper we simulate high resolution cloth consisting of up to 2 million triangles which allows us to achieve highly detailed folds and wrinkles. Since the level of detail is also influenced by object collision and self collision, we propose a more accurate model for cloth-object friction. We also propose a robust history-based repulsion/collision framework where repulsions are treated accurately and efficiently on a per time step basis. Distributed memory parallelism is used for both time evolution and collisions and we specifically address Gauss-Seidel ordering of repulsion/collision response. This algorithm is demonstrated by several high-resolution and high-fidelity simulations. PMID:19147895

  14. High Resolution Scanning Electron Microscopy of Cells Using Dielectrophoresis

    PubMed Central

    Tang, Shi-Yang; Zhang, Wei; Soffe, Rebecca; Nahavandi, Sofia; Shukla, Ravi; Khoshmanesh, Khashayar

    2014-01-01

    Ultrastructural analysis of cells can reveal valuable information about their morphological, physiological, and biochemical characteristics. Scanning electron microscopy (SEM) has been widely used to provide high-resolution images from the surface of biological samples. However, samples need to be dehydrated and coated with conductive materials for SEM imaging. Besides, immobilizing non-adherent cells during processing and analysis is challenging and requires complex fixation protocols. In this work, we developed a novel dielectrophoresis based microfluidic platform for interfacing non-adherent cells with high-resolution SEM at low vacuum mode. The system enables rapid immobilization and dehydration of samples without deposition of chemical residues over the cell surface. Moreover, it enables the on-chip chemical stimulation and fixation of immobilized cells with minimum dislodgement. These advantages were demonstrated for comparing the morphological changes of non-budding and budding yeast cells following Lyticase treatment. PMID:25089528

  15. High-resolution electron microscopy of advanced materials

    SciTech Connect

    Mitchell, T.E.; Kung, H.H.; Sickafus, K.E.; Gray, G.T. III; Field, R.D.; Smith, J.F.

    1997-11-01

    This final report chronicles a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The High-Resolution Electron Microscopy Facility has doubled in size and tripled in quality since the beginning of the three-year period. The facility now includes a field-emission scanning electron microscope, a 100 kV field-emission scanning transmission electron microscope (FE-STEM), a 300 kV field-emission high-resolution transmission electron microscope (FE-HRTEM), and a 300 kV analytical transmission electron microscope. A new orientation imaging microscope is being installed. X-ray energy dispersive spectrometers for chemical analysis are available on all four microscopes; parallel electron energy loss spectrometers are operational on the FE-STEM and FE-HRTEM. These systems enable evaluation of local atomic bonding, as well as chemical composition in nanometer-scale regions. The FE-HRTEM has a point-to-point resolution of 1.6 {angstrom}, but the resolution can be pushed to its information limit of 1 {angstrom} by computer reconstruction of a focal series of images. HRTEM has been used to image the atomic structure of defects such as dislocations, grain boundaries, and interfaces in a variety of materials from superconductors and ferroelectrics to structural ceramics and intermetallics.

  16. Multilayer Patterning of High Resolution Intrinsically Stretchable Electronics

    NASA Astrophysics Data System (ADS)

    Tybrandt, Klas; Stauffer, Flurin; Vörös, Janos

    2016-05-01

    Stretchable electronics can bridge the gap between hard planar electronic circuits and the curved, soft and elastic objects of nature. This has led to applications like conformal displays, electronic skin and soft neuroprosthetics. A remaining challenge, however, is to match the dimensions of the interfaced systems, as all require feature sizes well below 100 μm. Intrinsically stretchable nanocomposites are attractive in this context as the mechanical deformations occur on the nanoscale, although methods for patterning high performance materials have been lacking. Here we address these issues by reporting on a multilayer additive patterning approach for high resolution fabrication of stretchable electronic devices. The method yields highly conductive 30 μm tracks with similar performance to their macroscopic counterparts. Further, we demonstrate a three layer micropatterned stretchable electroluminescent display with pixel sizes down to 70 μm. These presented findings pave the way towards future developments of high definition displays, electronic skins and dense multielectrode arrays.

  17. A miniature high-resolution accelerometer utilizing electron tunneling

    NASA Technical Reports Server (NTRS)

    Rockstad, Howard K.; Kenny, T. W.; Reynolds, J. K.; Kaiser, W. J.; Vanzandt, T. R.; Gabrielson, Thomas B.

    1992-01-01

    New methods have been developed to implement high-resolution position sensors based on electron tunneling. These methods allow miniaturization while utilizing the position sensitivity of electron tunneling to give high resolution. A single-element tunneling accelerometer giving a displacement resolution of 0.002 A/sq rt Hz at 10 Hz, corresponding to an acceleration resolution of 5 x 10 exp -8 g/sq rt Hz, is described. A new dual-element tunneling structure which overcomes the narrow bandwidth limitations of a single-element structure is described. A sensor with an operating range of 5 Hz to 10 kHz, which can have applications as an acoustic sensor, is discussed. Noise is analyzed for fundamental thermal vibration of the suspended masses and is compared to electronic noise. It is shown that miniature tunnel accelerometers can achieve resolution such that thermal noise in the suspended masses is the dominant cause of the resolution limit. With a proof mass of order 100 mg, noise analysis predicts limiting resolutions approaching 10 exp -9 g/sq rt Hz in a 300 Hz band and 10 exp -8 g/sq rt Hz at 1 kHz.

  18. High-Resolution Electronics: Spontaneous Patterning of High-Resolution Electronics via Parallel Vacuum Ultraviolet (Adv. Mater. 31/2016).

    PubMed

    Liu, Xuying; Kanehara, Masayuki; Liu, Chuan; Sakamoto, Kenji; Yasuda, Takeshi; Takeya, Jun; Minari, Takeo

    2016-08-01

    On page 6568, T. Minari and co-workers describe spontaneous patterning based on the parallel vacuum ultraviolet (PVUV) technique, enabling the homogeneous integration of complex, high-resolution electronic circuits, even on large-scale, flexible, transparent substrates. Irradiation of PVUV to the hydrophobic polymer surface precisely renders the selected surface into highly wettable regions with sharply defined boundaries, which spontaneously guides a metal nanoparticle ink into a series of circuit lines and gaps with the widths down to a resolution of 1 μm. PMID:27511534

  19. Multilayer Patterning of High Resolution Intrinsically Stretchable Electronics.

    PubMed

    Tybrandt, Klas; Stauffer, Flurin; Vörös, Janos

    2016-01-01

    Stretchable electronics can bridge the gap between hard planar electronic circuits and the curved, soft and elastic objects of nature. This has led to applications like conformal displays, electronic skin and soft neuroprosthetics. A remaining challenge, however, is to match the dimensions of the interfaced systems, as all require feature sizes well below 100 μm. Intrinsically stretchable nanocomposites are attractive in this context as the mechanical deformations occur on the nanoscale, although methods for patterning high performance materials have been lacking. Here we address these issues by reporting on a multilayer additive patterning approach for high resolution fabrication of stretchable electronic devices. The method yields highly conductive 30 μm tracks with similar performance to their macroscopic counterparts. Further, we demonstrate a three layer micropatterned stretchable electroluminescent display with pixel sizes down to 70 μm. These presented findings pave the way towards future developments of high definition displays, electronic skins and dense multielectrode arrays. PMID:27157804

  20. Multilayer Patterning of High Resolution Intrinsically Stretchable Electronics

    PubMed Central

    Tybrandt, Klas; Stauffer, Flurin; Vörös, Janos

    2016-01-01

    Stretchable electronics can bridge the gap between hard planar electronic circuits and the curved, soft and elastic objects of nature. This has led to applications like conformal displays, electronic skin and soft neuroprosthetics. A remaining challenge, however, is to match the dimensions of the interfaced systems, as all require feature sizes well below 100 μm. Intrinsically stretchable nanocomposites are attractive in this context as the mechanical deformations occur on the nanoscale, although methods for patterning high performance materials have been lacking. Here we address these issues by reporting on a multilayer additive patterning approach for high resolution fabrication of stretchable electronic devices. The method yields highly conductive 30 μm tracks with similar performance to their macroscopic counterparts. Further, we demonstrate a three layer micropatterned stretchable electroluminescent display with pixel sizes down to 70 μm. These presented findings pave the way towards future developments of high definition displays, electronic skins and dense multielectrode arrays. PMID:27157804

  1. High-resolution electron microscopy and its applications.

    PubMed

    Li, F H

    1987-12-01

    A review of research on high-resolution electron microscopy (HREM) carried out at the Institute of Physics, the Chinese Academy of Sciences, is presented. Apart from the direct observation of crystal and quasicrystal defects for some alloys, oxides, minerals, etc., and the structure determination for some minute crystals, an approximate image-contrast theory named pseudo-weak-phase object approximation (PWPOA), which shows the image contrast change with crystal thickness, is described. Within the framework of PWPOA, the image contrast of lithium ions in the crystal of R-Li2Ti3O7 has been observed. The usefulness of diffraction analysis techniques such as the direct method and Patterson method in HREM is discussed. Image deconvolution and resolution enhancement for weak-phase objects by use of the direct method are illustrated. In addition, preliminary results of image restoration for thick crystals are given. PMID:3505590

  2. [High resolution scanning electron microscopy of isolated outer hair cells].

    PubMed

    Koitschev, A; Müller, H

    1996-11-01

    Isolated hair cell preparations have gained wide acceptance as a model for studying physiological and molecular properties of the sensory cells involved in the hearing process. Ultrastructural details, such as stereocilia links, lateral membrane substructure or synaptic links are of crucial importance for normal sensory transduction. For this reason, we developed a high-resolution scanning electron microscopy (SEM) procedure to study the surface of isolated hair cells. Cells were mechanically and/or enzymatically separated, isolated and immobilized on cover slips by alcian blue and fixed by 2% glutardialdehyde or 1% OsO4. After dehydration, preparations were critical point-dried and sputter-coated with gold-palladium (2-4 nm). Up to 5 nm resolution was achieved. Optimal fixation kept the cells in their typical cylindrical forms. Preservation of the stereocilia and the apical plates of the outer hair cells depended strongly on the fixation process. Tip- and side-links were observed only sporadically because of the aggressive preparation procedure. The lateral plasma membranes of the cell bodies showed regular granular structures of 5-7 nm diameter at maximal magnification. The granular structure of the cell membrane seemed to correspond to putative transmembrane proteins believed to generate membrane-based motility. The remnants of the nerve endings and/or supporting cells usually covered the cell base. The preservation of the cells was better when enzymatic isolation was omitted. The technique used allowed for high resolution ultrastructural examination of isolated hair cells and, when combined with immunological labeling, may permit the identification of proteins at a molecular level. PMID:9064297

  3. High Resolution Transmission Electron Microscopy (HRTEM) of nanophase ferric oxides

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Morris, R. V.; Ming, D. W.; Lauer, H. V., Jr.

    1994-01-01

    Iron oxide minerals are the prime candidates for Fe(III) signatures in remotely sensed Martian surface spectra. Magnetic, Mossbauer, and reflectance spectroscopy have been carried out in the laboratory in order to understand the mineralogical nature of Martian analog ferric oxide minerals of submicron or nanometer size range. Out of the iron oxide minerals studied, nanometer sized ferric oxides are promising candidates for possible Martian spectral analogs. 'Nanophase ferric oxide (np-Ox)' is a generic term for ferric oxide/oxihydroxide particles having nanoscale (less than 10 nm) particle dimensions. Ferrihydrite, superparamagnetic particles of hematite, maghemite and goethite, and nanometer sized particles of inherently paramagnetic lepidocrocite are all examples of nanophase ferric oxides. np-Ox particles in general do not give X-ray diffraction (XRD) patterns with well defined peaks and would often be classified as X-ray amorphous. Therefore, different np-Oxs preparations should be characterized using a more sensitive technique e.g., high resolution transmission electron microscopy (HRTEM). The purpose of this study is to report the particle size, morphology and crystalline order, of five np-Ox samples by HRTEM imaging and electron diffraction (ED).

  4. High Resolution Measurements and Electronic Structure Calculations of a Diazanaphthalene

    NASA Astrophysics Data System (ADS)

    Gruet, Sébastien; Goubet, Manuel; Pirali, Olivier

    2014-06-01

    Polycyclic Aromatic Hydrocarbons (PAHs) have long been suspected to be the carriers of so called Unidentified Infrared Bands (UIBs). Most of the results published in the literature report rotationally unresolved spectra of pure carbon as well as heteroatom-containing PAHs species. To date for this class of molecules, the principal source of rotational informations is ruled by microwave (MW) spectroscopy while high resolution measurements reporting rotational structure of the infrared (IR) vibrational bands are very scarce. Recently, some high resolution techniques provided interesting new results to rotationally resolve the IR and far-IR bands of these large carbonated molecules of astrophysical interest. One of them is to use the bright synchrotron radiation as IR continuum source of a high resolution Fourier transform (FTIR) spectrometer. We report the very complementary analysis of the [1,6] naphthyridine (a N-bearing PAH) for which we recorded the microwave spectrum at the PhLAM laboratory (Lille) and the high resolution far-infrared spectrum on the AILES beamline at synchrotron facility SOLEIL. MW spectroscopy provided highly accurate rotational constants in the ground state to perform Ground State Combinations Differences (GSCD) allowing the analysis of the two most intense FT-FIR bands in the 50-900 wn range. Moreover, during this presentation the negative value of the inertial defect in the GS of the molecule will be discussed. A. Leger, J. L. Puget, Astron. Astrophys. 137, L5-L8 (1984) L. J. Allamandola et al. Astrophys. J. 290, L25-L28 (1985). Z. Kisiel et al. J. Mol. Spectrosc. 217, 115 (2003) S. Thorwirth et al. Astrophys. J. 662, 1309 (2007) D. McNaughton et al. J. Chem. Phys. 124, 154305 (2011). S. Albert et al. Faraday Discuss. 150, 71-99 (2011) B. E. Brumfield et al. Phys. Chem. Lett. 3, 1985-1988 (2012) O. Pirali et al. Phys. Chem. Chem. Phys. 15, 10141 (2013).

  5. High-resolution simulations of the head-on collision of white dwarfs

    NASA Astrophysics Data System (ADS)

    García-Senz, D.; Cabezón, R. M.; Arcones, A.; Relaño, A.; Thielemann, F. K.

    2013-12-01

    The direct impact of white dwarfs has been suggested as a plausible channel for Type Ia supernovae. In spite of their (a priori) rareness, in highly populated globular clusters and in galactic centres, where the amount of white dwarfs is considerable, the rate of violent collisions between two of them might be non-negligible. Even more, there are indications that binary white dwarf systems orbited by a third stellar-mass body have an important chance to induce a clean head-on collision. Therefore, this scenario represents a source of contamination for the supernova light-curve sample that it is used as standard candles in cosmology, and it deserves further investigation. Some groups have conducted numerical simulations of this scenario, but their results show several differences. In this paper, we address some of the possible sources of these differences, presenting the results of high-resolution hydrodynamical simulations jointly with a detailed nuclear post-processing of the nuclear abundances, to check the viability of white dwarf collisions to produce significant amounts of 56Ni. To that purpose, we use a 2D axisymmetric smoothed particle hydrodynamic code to obtain a resolution considerably higher than in previous studies. In this work, we also study how the initial mass and nuclear composition affect the results. The gravitational wave emission is also calculated, as this is a unique signature of this kind of events. All calculated models produce a significant amount of 56Ni, ranging from 0.1 to 1.1 M⊙, compatible not only with normal-branch Type Ia supernova but also with the subluminous and super-Chandrasekhar subset. Nevertheless, the distribution mass function of white dwarfs favours collisions among 0.6-0.7 M⊙ objects, leading to subluminous events.

  6. Dose-dependent high-resolution electron ptychography

    NASA Astrophysics Data System (ADS)

    D'Alfonso, A. J.; Allen, L. J.; Sawada, H.; Kirkland, A. I.

    2016-02-01

    Recent reports of electron ptychography at atomic resolution have ushered in a new era of coherent diffractive imaging in the context of electron microscopy. We report and discuss electron ptychography under variable electron dose conditions, exploring the prospects of an approach which has considerable potential for imaging where low dose is needed.

  7. Extracting biomolecule collision cross sections from the high-resolution FT-ICR mass spectral linewidths.

    PubMed

    Jiang, Ting; Chen, Yu; Mao, Lu; Marshall, Alan G; Xu, Wei

    2016-01-14

    It is known that the ion collision cross section (CCS) may be calculated from the linewidth of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectral peak at elevated pressure (e.g., ∼10(-6) Torr). However, the high mass resolution of FT-ICR is sacrificed in those experiments due to high buffer gas pressure. In this study, we describe a linewidth correction method to eliminate the windowing-induced peak broadening effect. Together with the energetic ion-neutral collision model previously developed by our group, this method enables the extraction of CCSs of biomolecules from high-resolution FT-ICR mass spectral linewidths, obtained at a typical operating buffer gas pressure of modern FT-ICR instruments (∼10(-10) Torr). CCS values of peptides including MRFA, angiotensin I, and bradykinin measured by the proposed method agree well with ion mobility measurements, and the unfolding of protein ions (ubiquitin) at higher charge states is also observed. PMID:26314765

  8. COMPARATIVE ANALYSIS OF DIOXINS AND FURANS BY HIGH RESOLUTION AND ELECTRON CAPTURE MASS SPECTROMETRY

    EPA Science Inventory

    Known mixtures and unknown atmospheric sample extracts containing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/P) were analyzed by both electron impact, high resolution, mass spectrometry (HRMS) and by electron capture, negative ion, low resolution ma...

  9. High resolution threshold photoelectron spectroscopy by electron attachment

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Ajello, J. M. (Inventor)

    1979-01-01

    A system is provided for determining the stable energy levels of a species ion, of an atomic, molecular, or radical type, by application of ionizing energy of a predetermined level, such as through photoionization. The system adds a trapping gas to the gaseous species to provide a technique for detection of the energy levels. The electrons emitted from ionized species are captured by the trapping gas, only if the electrons have substantially zero kinetic energy. If the electrons have nearly zero energy, they are absorbed by the trapping gas to produce negative ions of the trapping gas that can be detected by a mass spectrometer. The applied energies (i.e. light frequencies) at which large quantities of trapping gas ions are detected, are the stable energy levels of the positive ion of the species. SF6 and CFCl3 have the narrowest acceptance bands, so that when they are used as the trapping gas, they bind electrons only when the electrons have very close to zero kinetic energy.

  10. Copper Decoration of Carbon Nanotubes and High Resolution Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Probst, Camille

    A new process of decorating carbon nanotubes with copper was developed for the fabrication of nanocomposite aluminum-nanotubes. The process consists of three stages: oxidation, activation and electroless copper plating on the nanotubes. The oxidation step was required to create chemical function on the nanotubes, essential for the activation step. Then, catalytic nanoparticles of tin-palladium were deposited on the tubes. Finally, during the electroless copper plating, copper particles with a size between 20 and 60 nm were uniformly deposited on the nanotubes surface. The reproducibility of the process was shown by using another type of carbon nanotube. The fabrication of nanocomposites aluminum-nanotubes was tested by aluminum vacuum infiltration. Although the infiltration of carbon nanotubes did not produce the expected results, an interesting electron microscopy sample was discovered during the process development: the activated carbon nanotubes. Secondly, scanning transmitted electron microscopy (STEM) imaging in SEM was analysed. The images were obtained with a new detector on the field emission scanning electron microscope (Hitachi S-4700). Various parameters were analysed with the use of two different samples: the activated carbon nanotubes (previously obtained) and gold-palladium nanodeposits. Influences of working distance, accelerating voltage or sample used on the spatial resolution of images obtained with SMART (Scanning Microscope Assessment and Resolution Testing) were analysed. An optimum working distance for the best spatial resolution related to the sample analysed was found for the imaging in STEM mode. Finally, relation between probe size and spatial resolution of backscattered electrons (BSE) images was studied. An image synthesis method was developed to generate the BSE images from backscattered electrons coefficients obtained with CASINO software. Spatial resolution of images was determined using SMART. The analysis shown that using a probe

  11. High resolution fluorescent bio-imaging with electron beam excitation.

    PubMed

    Kawata, Yoshimasa; Nawa, Yasunori; Inami, Wataru

    2014-11-01

    We have developed electron beam excitation assisted (EXA) optical microscope[1-3], and demonstrated its resolution higher than 50 nm. In the microscope, a light source in a few nanometers size is excited by focused electron beam in a luminescent film. The microscope makes it possible to observe dynamic behavior of living biological specimens in various surroundings, such as air or liquids. Scan speed of the nanometric light source is faster than that in conventional near-field scanning optical microscopes. The microscope enables to observe optical constants such as absorption, refractive index, polarization, and their dynamic behavior on a nanometric scale. The microscope opens new microscopy applications in nano-technology and nano-science.Figure 1(a) shows schematic diagram of the proposed EXA microscope. An electron beam is focused on a luminescent film. A specimen is put on the luminescent film directly. The inset in Fig. 1(a) shows magnified image of the luminescent film and the specimen. Nanometric light source is excited in the luminescent film by the focused electron beam. The nanometric light source illuminates the specimen, and the scattered or transmitted radiation is detected with a photomultiplier tube (PMT). The light source is scanned by scanning of the focused electron beam in order to construct on image. Figure 1(b) shows a luminescence image of the cells acquired with the EXA microscope, and Fig. 1(c) shows a phase contrast microscope image. Cells were observed in culture solution without any treatments, such as fixation and drying. The shape of each cell was clearly recognized and some bright spots were observed in cells. We believe that the bright spots indicated with arrows were auto-fluorescence of intracellular granules and light- grey regions were auto-fluorescence of cell membranes. It is clearly demonstrated that the EXA microscope is useful tool for observation of living biological cells in physiological conditions.jmicro;63/suppl_1/i

  12. High-resolution α and electron spectroscopy of Cf24998

    NASA Astrophysics Data System (ADS)

    Ahmad, I.; Greene, J. P.; Kondev, F. G.; Zhu, S.

    2015-04-01

    α -particle spectra of 249Cf have been measured with a double-focusing magnetic spectrometer and with passivated implanted planar silicon (PIPS) detectors. The conversion-electron spectra of 249Cf have been measured with a cooled Si(Li) detector and with a room-temperature PIPS detector. Precise energies of α groups in the decay of 249Cf have been measured with respect to the known energy of 250Cf. In addition, α -electron, α -γ , and γ -γ coincidence measurements were also performed to determine the spin-parity of the previously known 643.64-keV level. From electron intensities, conversion coefficients of transitions in the daughter 245Cm have been determined. The measured L3 conversion coefficients of the 333.4- and 388.2-keV transitions are found to be in agreement with the theoretical conversion coefficients for pure E 1 multipolarity. On the other hand, the K ,L1+L2 ,M , and N conversion coefficients are approximately twice the theoretical values for pure E 1 transitions. These measurements indicate anomalous E 1 conversion coefficients for the 333.4- and 388.2-keV transitions, as has been pointed out in earlier measurements. The measured conversion coefficient of the 255.5-keV transition gives an M 1 multipolarity for this transition which establishes a spin-parity of 7/2- and the 7/2-[743 ] single-particle assignment to the 643.64-keV level.

  13. Computer simulation of high resolution transmission electron micrographs: theory and analysis

    SciTech Connect

    Kilaas, R.

    1985-03-01

    Computer simulation of electron micrographs is an invaluable aid in their proper interpretation and in defining optimum conditions for obtaining images experimentally. Since modern instruments are capable of atomic resolution, simulation techniques employing high precision are required. This thesis makes contributions to four specific areas of this field. First, the validity of a new method for simulating high resolution electron microscope images has been critically examined. Second, three different methods for computing scattering amplitudes in High Resolution Transmission Electron Microscopy (HRTEM) have been investigated as to their ability to include upper Laue layer (ULL) interaction. Third, a new method for computing scattering amplitudes in high resolution transmission electron microscopy has been examined. Fourth, the effect of a surface layer of amorphous silicon dioxide on images of crystalline silicon has been investigated for a range of crystal thicknesses varying from zero to 2 1/2 times that of the surface layer.

  14. High-Resolution Transmission Electron Microscopy Observation of Colloidal Nanocrystal Growth Mechanisms using Graphene Liquid Cells

    SciTech Connect

    Yuk, Jong Min; Park, Jungwon; Ercius, Peter; Kim, Kwanpyo; Hellebusch, Danny J.; Crommie, Michael F.; Lee, Jeong Yong; Zettl, A.; Alivisatos, A. Paul

    2011-12-12

    We introduce a new type of liquid cell for in-situ electron microscopy based upon entrapment of a liquid film between layers of graphene. We employ this cell to achieve high-resolution imaging of colloidal platinum nanocrystal growth. The ability to directly image and resolve critical steps at atomic resolution provides new insights into nanocrystal coalescence and reshaping during growth.

  15. High resolution simulation of beam dynamics in electron linacs for x-ray free electron lasers

    NASA Astrophysics Data System (ADS)

    Qiang, J.; Ryne, R. D.; Venturini, M.; Zholents, A. A.; Pogorelov, I. V.

    2009-10-01

    In this paper we report on large-scale high resolution simulations of beam dynamics in electron linacs for the next-generation x-ray free electron lasers (FELs). We describe key features of a parallel macroparticle simulation code including three-dimensional (3D) space-charge effects, short-range structure wakefields, coherent synchrotron radiation (CSR) wakefields, and treatment of radio-frequency (rf) accelerating cavities using maps obtained from axial field profiles. We present a study of the microbunching instability causing severe electron beam fragmentation in the longitudinal phase space which is a critical issue for future FELs. Using parameters for a proposed FEL linac at Lawrence Berkeley National Laboratory (LBNL), we show that a large number of macroparticles (beyond 100 million) is generally needed to control the numerical macroparticle shot noise and avoid overestimating the microbunching instability. We explore the effect of the longitudinal grid on simulation results. We also study the effect of initial uncorrelated energy spread on the final uncorrelated energy spread of the beam for the FEL linac.

  16. Gas-Phase Molecular Dynamics: High Resolution Spectroscopy and Collision Dynamics of Transient Species

    SciTech Connect

    Hall G. E.; Goncharov, V.

    2012-05-29

    This research is carried out as part of the Gas-Phase Molecular Dynamics program in the Chemistry Department at Brookhaven National Laboratory. Chemical intermediates in the elementary gas-phase reactions involved in combustion chemistry are investigated by high resolution spectroscopic tools. Production, reaction, and energy transfer processes are investigated by transient, double resonance, polarization and saturation spectroscopies, with an emphasis on technique development and connection with theory, as well as specific molecular properties.

  17. Gas-Phase Molecular Dynamics: High Resolution Spectroscopy and Collision Dynamics of Transient Species

    SciTech Connect

    Hall, G.E.

    2011-05-31

    This research is carried out as part of the Gas-Phase Molecular Dynamics program in the Chemistry Department at Brookhaven National Laboratory. Chemical intermediates in the elementary gas-phase reactions involved in combustion chemistry are investigated by high resolution spectroscopic tools. Production, reaction, and energy transfer processes are investigated by transient, double resonance, polarization and saturation spectroscopies, with an emphasis on technique development and connection with theory, as well as specific molecular properties.

  18. Electron-electron collisions at TESLA

    NASA Astrophysics Data System (ADS)

    Schreiber, Siegfried; Reyzl, Ingrid

    2001-07-01

    Electron-electron collisions at the future TESLA linear collider is a promising complement to e+e- collisions. A critical issue for the physics potential of this option is the achievable luminosity. For e+e- collisions, the pinch effect enhances the luminosity, while due to the repelling forces for e-e- collisions, the luminosity is significantly reduced and is more sensitive to beam separations. This report discusses the e-e- option for TESLA and the expected luminosity.

  19. High-Resolution Analytical Electron Microscopy Characterization of Corrosion and Cracking at Buried Interfaces

    SciTech Connect

    Bruemmer, Stephen M.; Thomas, Larry E.

    2001-07-01

    Recent results are presented demonstrating the application of cross-sectional analytical transmission electron microscopy (ATEM) to corrosion and cracking in high-temperature water environments. Microstructural, chemical and crystallographic characterization of buried interfaces at near-atomic resolutions is shown to reveal evidence for unexpected local environments, corrosion reactions and material transformations. Information obtained by a wide variety of high-resolution imaging and analysis methods indicates the processes occurring during crack advance and provides insights into the mechanisms controlling environmental degradation.

  20. The Potential for Bayesian Compressive Sensing to Significantly Reduce Electron Dose in High Resolution STEM Images

    SciTech Connect

    Stevens, Andrew J.; Yang, Hao; Carin, Lawrence; Arslan, Ilke; Browning, Nigel D.

    2014-02-11

    The use of high resolution imaging methods in the scanning transmission electron microscope (STEM) is limited in many cases by the sensitivity of the sample to the beam and the onset of electron beam damage (for example in the study of organic systems, in tomography and during in-situ experiments). To demonstrate that alternative strategies for image acquisition can help alleviate this beam damage issue, here we apply compressive sensing via Bayesian dictionary learning to high resolution STEM images. These experiments successively reduce the number of pixels in the image (thereby reducing the overall dose while maintaining the high resolution information) and show promising results for reconstructing images from this reduced set of randomly collected measurements. We show that this approach is valid for both atomic resolution images and nanometer resolution studies, such as those that might be used in tomography datasets, by applying the method to images of strontium titanate and zeolites. As STEM images are acquired pixel by pixel while the beam is scanned over the surface of the sample, these post acquisition manipulations of the images can, in principle, be directly implemented as a low-dose acquisition method with no change in the electron optics or alignment of the microscope itself.

  1. Refinement procedure for the image alignment in high-resolution electron tomography.

    PubMed

    Houben, L; Bar Sadan, M

    2011-01-01

    High-resolution electron tomography from a tilt series of transmission electron microscopy images requires an accurate image alignment procedure in order to maximise the resolution of the tomogram. This is the case in particular for ultra-high resolution where even very small misalignments between individual images can dramatically reduce the fidelity of the resultant reconstruction. A tomographic-reconstruction based and marker-free method is proposed, which uses an iterative optimisation of the tomogram resolution. The method utilises a search algorithm that maximises the contrast in tomogram sub-volumes. Unlike conventional cross-correlation analysis it provides the required correlation over a large tilt angle separation and guarantees a consistent alignment of images for the full range of object tilt angles. An assessment based on experimental reconstructions shows that the marker-free procedure is competitive to the reference of marker-based procedures at lower resolution and yields sub-pixel accuracy even for simulated high-resolution data. PMID:21930024

  2. Toward an image compression algorithm for the high-resolution electronic still camera

    NASA Technical Reports Server (NTRS)

    Nerheim, Rosalee

    1989-01-01

    Taking pictures with a camera that uses a digital recording medium instead of film has the advantage of recording and transmitting images without the use of a darkroom or a courier. However, high-resolution images contain an enormous amount of information and strain data-storage systems. Image compression will allow multiple images to be stored in the High-Resolution Electronic Still Camera. The camera is under development at Johnson Space Center. Fidelity of the reproduced image and compression speed are of tantamount importance. Lossless compression algorithms are fast and faithfully reproduce the image, but their compression ratios will be unacceptably low due to noise in the front end of the camera. Future efforts will include exploring methods that will reduce the noise in the image and increase the compression ratio.

  3. Exploring semiconductor quantum dots and wires by high resolution electron microscopy

    SciTech Connect

    Molina Rubio, Sergio I; Galindo, Pedro; Gonzalez, Luisa; Ripalda, JM; Varela del Arco, Maria; Pennycook, Stephen J

    2010-01-01

    We review in this communication our contribution to the structural characterisation of semiconductor quantum dots and wires by high resolution electron microscopy, both in phase-contrast and Z-contrast modes. We show how these techniques contribute to predict the preferential sites of nucleation of these nanostructures, and also determine the compositional distribution in 1D and 0D nanostructures. The results presented here were produced in the framework of the European Network of Excellence entitled 'Self-Assembled semiconductor Nanostructures for new Devices in photonics and Electronics (SANDiE)'.

  4. High-Resolution Infrared and Electron-Diffraction Studies of Trimethylenecyclopropane ([3]-Radialene)

    SciTech Connect

    Wright, Corey; Holmes, Joshua; Nibler, Joseph W.; Hedberg, Kenneth; White, James D.; Hedberg, Lise; Weber, Alfons; Blake, Thomas A.

    2013-05-16

    Combined high-resolution spectroscopic, electron-diffraction, and quantum theoretical methods are particularly advantageous for small molecules of high symmetry and can yield accurate structures that reveal subtle effects of electron delocalization on molecular bonds. The smallest of the radialene compounds, trimethylenecyclopropane, [3]-radialene, has been synthesized and examined in the gas phase by these methods. The first high-resolution infrared spectra have been obtained for this molecule of D3h symmetry, leading to an accurate B0 rotational constant value of 0.1378629(8) cm-1, within 0.5% of the value obtained from electronic structure calculations (density functional theory (DFT) B3LYP/cc-pVTZ). This result is employed in an analysis of electron-diffraction data to obtain the rz bond lengths (in Å): C-H = 1.072 (17), C-C = 1.437 (4), and C=C = 1.330 (4). The analysis does not lead to an accurate value of the HCH angle; however, from comparisons of theoretical and experimental angles for similar compounds, the theoretical prediction of 117.5° is believed to be reliable to within 2°. The effect of electron delocalization in radialene is to reduce the single C-C bond length by 0.07 Å compared to that in cyclopropane.

  5. Comet Shoemaker-Levy 9/Jupiter collision observed with a high resolution speckle imaging system

    SciTech Connect

    Gravel, D.

    1994-11-15

    During the week of July 16, 1994, comet Shoemaker-Levy 9, broken into 20 plus pieces by tidal forces on its last orbit, smashed into the planet Jupiter, releasing the explosive energy of 500 thousand megatons. A team of observers from LLNL used the LLNL Speckle Imaging Camera mounted on the University of California`s Lick Observatory 3 Meter Telescope to capture continuous sequences of planet images during the comet encounter. Post processing with the bispectral phase reconstruction algorithm improves the resolution by removing much of the blurring due to atmospheric turbulence. High resolution images of the planet surface showing the aftermath of the impact are probably the best that were obtained from any ground-based telescope. We have been looking at the regions of the fragment impacts to try to discern any dynamic behavior of the spots left on Jupiter`s cloud tops. Such information can lead to conclusions about the nature of the comet and of Jupiter`s atmosphere. So far, the Hubble Space Telescope has observed expanding waves from the G impact whose mechanism is enigmatic since they appear to be too slow to be sound waves and too fast to be gravity waves, given the present knowledge of Jupiter`s atmosphere. Some of our data on the G and L impact region complements the Hubble observations but, so far, is inconclusive about spot dynamics.

  6. High-Resolution Electron Energy-Loss Spectroscopy (HREELS) Using a Monochromated TEM/STEM

    NASA Technical Reports Server (NTRS)

    Sai, Z. R.; Bradley, J. P.; Erni, R.; Browning, N.

    2005-01-01

    A 200 keV FEI TF20 XT monochromated (scanning) transmission electron microscope funded by NASA's SRLIDAP program is undergoing installation at Lawrence Livermore National Laboratory. Instrument specifications in STEM mode are Cs =1.0 mm, Cc =1.2 mm, image resolution =0.18 nm, and in TEM mode Cs =1.3 mm, Cc =1.3 mm, information limit =0.14 nm. Key features of the instrument are a voltage-stabilized high tension (HT) supply, a monochromator, a high-resolution electron energy-loss spectrometer/energy filter, a high-resolution annular darkfield detector, and a solid-state x-ray energy-dispersive spectrometer. The high-tension tank contains additional sections for 60Hz and high frequency filtering, resulting in an operating voltage of 200 kV plus or minus 0.005V, a greater than 10-fold improvement over earlier systems. The monochromator is a single Wien filter design. The energy filter is a Gatan model 866 Tridiem-ERS high resolution GIF spec d for less than or equal to 0.15 eV energy resolution with 29 pA of current in a 2 nm diameter probe. 0.13 eV has already been achieved during early installation. The x-ray detector (EDAX/Genesis 4000) has a take-off angle of 20 degrees, an active area of 30 square millimeters, and a solid angle of 0.3 steradians. The higher solid angle is possible because the objective pole-piece allows the detector to be positioned as close as 9.47 mm from the specimen. The voltage-stabilized HT supply, monochromator and GIF enable high-resolution electron energy-loss spectroscopy (HREELS) with energy resolution comparable to synchrotron XANES, but with approximately 100X better spatial resolution. The region between 0 and 100 eV is called the low-loss or valence electron energy-loss spectroscopy (VEELS) region where features due to collective plasma oscillations and single electron transitions of valence electrons are observed. Most of the low-loss VEELS features we are detecting are being observed for the first time in IDPs. A major focus of

  7. Live correlative light-electron microscopy to observe molecular dynamics in high resolution.

    PubMed

    Kobayashi, Shouhei; Iwamoto, Masaaki; Haraguchi, Tokuko

    2016-08-01

    Fluorescence microscopy (FM) is a powerful tool for observing specific molecular components in living cells, but its spatial resolution is relatively low. In contrast, electron microscopy (EM) provides high-resolution information about cellular structures, but it cannot provide temporal information in living cells. To achieve molecular selectivity in imaging at high resolution, a method combining EM imaging with live-cell fluorescence imaging, known as live correlative light-EM (CLEM), has been developed. In this method, living cells are first observed by FM, fixed in situ during the live observation and then subjected to EM observation. Various fluorescence techniques and tools can be applied for FM, resulting in the generation of various modified methods that are useful for understanding cellular structure in high resolution. Here, we review the methods of CLEM and live-cell imaging associated with CLEM (live CLEM). Such methods can greatly advance the understanding of the function of cellular structures on a molecular level, and thus are useful for medical fields as well as for basic biology. PMID:27385786

  8. Soot Nanostructure: Using Fringe Analysis Software on High Resolution Transmission Electron Microscopy of Carbon Soot

    NASA Technical Reports Server (NTRS)

    King, James D.

    2004-01-01

    Using high resolution transmission electron images of carbon nanotubes and carbon particles, we are able to use image analysis program to determine several carbon fringe properties, including length, separation, curvature and orientation. Results are shown in the form of histograms for each of those quantities. The combination of those measurements can give a better indication of the graphic structure within nanotubes and particles of carbon and can distinguish carbons based upon fringe properties. Carbon with longer, straighter and closer spaced fringes are considered graphite, while amorphous carbon contain shorter, less structured fringes.

  9. Magnetic lens apparatus for a low-voltage high-resolution electron microscope

    DOEpatents

    Crewe, Albert V.

    1996-01-01

    A lens apparatus in which a beam of charged particles of low accelerating voltage is brought to a focus by a magnetic field, the lens being situated behind the target position. The lens comprises an electrically-conducting coil arranged around the axis of the beam and a magnetic pole piece extending along the axis of the beam at least within the space surrounded by the coil. The lens apparatus comprises the sole focusing lens for high-resolution imaging in a low-voltage scanning electron microscope.

  10. Crack tip shielding observed with high-resolution transmission electron microscopy

    PubMed Central

    Adhika, Damar Rastri; Tanaka, Masaki; Daio, Takeshi; Higashida, Kenji

    2015-01-01

    The dislocation shielding field at a crack tip was experimentally proven at the atomic scale by measuring the local strain in front of the crack tip using high-resolution transmission electron microscopy (HRTEM) and geometric phase analysis (GPA). Single crystalline (110) silicon wafers were employed. Cracks were introduced using a Vickers indenter at room temperature. The crack tip region was observed using HRTEM followed by strain measurements using GPA. The measured strain field at the crack tip was compressive owing to dislocation shielding, which is in good agreement with the strain field calculated from elastic theory. PMID:26115957

  11. High Resolution UV Emission Spectroscopy of Molecules Excited by Electron Impact

    NASA Technical Reports Server (NTRS)

    James, G. K.; Ajello, J. M.; Beegle, L.; Ciocca, M.; Dziczek, D.; Kanik, I.; Noren, C.; Jonin, C.; Hansen, D.

    1999-01-01

    Photodissociation via discrete line absorption into predissociating Rydberg and valence states is the dominant destruction mechanism of CO and other molecules in the interstellar medium and molecular clouds. Accurate values for the rovibronic oscillator strengths of these transitions and predissociation yields of the excited states are required for input into the photochemical models that attempt to reproduce observed abundances. We report here on our latest experimental results of the electron collisional properties of CO and N2 obtained using the 3-meter high resolution single-scattering spectroscopic facility at JPL.

  12. Quantitative high resolution electron microscopy of III-V compounds: A fuzzy logic approach

    NASA Astrophysics Data System (ADS)

    Hillebrand, R.; Hofmeister, H.; Werner, P.; Gösele, U.

    1995-09-01

    In the study of interdiffusion phenomena in layered structures of III-V compounds by high resolution electron microscopy, contrast features in the micrographs can be correlated with the variation of the chemical composition of the crystals. For quantitative interpretation of the micrographs a fuzzy logic approach is adapted to extract chemical information. The linguistic variable ``similarity of images'' is derived from the standard deviation (SD) of their difference patterns, which proved to be an appropriate measure. The approach developed is used to analyze simulated contrast tableaus of GaAs/P (As/P variation) and experimental micrographs of Al/GaAs (Al/Ga variation).

  13. High resolution electron microscopy of GaAs capped GaSb nanostructures

    SciTech Connect

    Molina Rubio, Sergio I; Beltran, AM; Ben, Teresa; Galindo, P.L.; Taboada, Alfonso G; Chisholm, Matthew F

    2012-01-01

    We show in this work that GaAs capping of 2 ML of GaSb grown by molecular beam epitaxy results in the formation of very small (with heights of about 1 nm) GaAsxSb1 x nanostructures surrounded by a GaAs rich layer. This conclusion is obtained by analyzing the morphology of the GaAsxSb1 x nanostructures by high resolution scanning transmission electron microscopy in Z-contrast mode. This result shows that a significant fraction of the Sb atoms must segregate along the growth direction during the GaAs capping process.

  14. High-resolution infrared detector and its electronic unit for space application

    NASA Astrophysics Data System (ADS)

    Meftah, M.; Montmessin, F.; Korablev, O.; Trokhimovsky, A.; Poiet, G.; Bel, J.-B.

    2015-05-01

    High-resolution infrared detector is used extensively for military and civilian purposes. Military applications include target acquisition, surveillance, night vision, and tracking. Civilian applications include, among others, scientific observations. For our space systems, we want to use the products developed by SOFRADIR Company. Thus, we have developed a space electronic unit that is used to control the high-resolution SCORPIO-MW infrared detector, which has a format of 640×512 pixels with 15μm×15μm pixel pitch. The detector within microelectronics based on infrared mid-wave (MW) complementary metal oxide semiconductors (CMOS) uses a micro-cooler in order to keep its temperature around 100 K. The standard wavelength range (3 to 5μm) is adapted to the 2.2 to 4.3μm wavelength range thanks to adaptation of the optical interface of the detector and with an antireflection coating. With our electronic system, we can acquire 3 images per second. To increase the signal to noise ratio, we have the opportunity to make a summation of 15 frames per image. Through this article, we will describe the space electronic system that we have developed in order to achieve space observations (e.g. Atmospheric Chemistry Suite package for ExoMars Trace Gas Orbiter).

  15. Computer Simulation of High Resolution Transmission Electron Micrographs: Theory and Analysis.

    NASA Astrophysics Data System (ADS)

    Kilaas, Roar

    Computer simulation of electron micrographs is an invaluable aid in their proper interpretation and in defining optimum conditions for obtaining images experimentally. Since modern instruments are capable of atomic resolution, simulation techniques employing high precision are required. This thesis makes contributions to four specific areas of this field. First, the validity of a new method for simulating high resolution electron microscope images has been critically examined. This method, which has been termed the real space method (RSP) since the entire calculation is performed without any Fourier transforms, offers a considerable reduction in computing time over the conventional multislice approach when identical sampling conditions are employed. However, for the same level of accuracy the real space method requires more sampling points and more computing time than the conventional multislice method. These characteristics are illustrated with calculated results using both methods to identify practical limitations. Second, three different methods for computing scattering amplitudes in High Resolution Transmission Electron Microscopy (HRTEM) have been investigated as to their ability to include upper Laue layer (ULL) interaction. The conventional first order multislice method using fast Fourier transform (FFT) and the second order multislice (SOM) method are shown to yield calculated intensities of first order Laue reflections with the use of slice thicknesses smaller than the crystal periodicity along the incident electron beam direction. It is argued that the calculated intensities of ULL reflections approach the correct values in the limiting case of vanishing slice thickness and electron wavelength. The third method, the improved phasegrating method (IPG) does also in principle include ULL effects, but is severely limited as to choice of slice thickness and sampling interval. A practical way to use slice thicknesses less than the crystal periodicity along the

  16. High-resolution spin-polarized scanning electron microscopy (spin SEM).

    PubMed

    Kohashi, Teruo; Konoto, Makoto; Koike, Kazuyuki

    2010-01-01

    We have developed spin-polarized scanning electron microscopy (spin SEM) with a 5-nm resolution. The secondary electron optics is very important, as it needs to transfer a sufficient number of secondary electrons to the spin polarimeter, due to the low efficiency of the polarimeter. The optics was designed using a three-dimensional (3D) simulation program of the secondary electron trajectories, and it achieves highly efficient collection and transport of the secondary electrons even though the distance between the sample and the objective lens exit of the electron gun remains short. Moreover, the designed optics enables us to obtain clear SEM images in the spin SEM measurement and to precisely adjust the probe beam shape. These functions lead to images with high spatial resolution and sufficient signal-to-noise (S/N) ratios. This optics has been installed in an ultra-high vacuum (UHV) spin SEM chamber with a Schottky-type electron gun for the probe electron beam. We observed recorded bits on a perpendicular magnetic recording medium and visualized small irregularities in the bit shapes around the track edges and bit boundaries. The high resolution of 5 nm was demonstrated by observing the smallest domain composed by a single grain in the recording medium. PMID:19840986

  17. Random vs realistic amorphous carbon models for high resolution microscopy and electron diffraction

    SciTech Connect

    Ricolleau, C. Alloyeau, D.; Le Bouar, Y.; Amara, H.; Landon-Cardinal, O.

    2013-12-07

    Amorphous carbon and amorphous materials in general are of particular importance for high resolution electron microscopy, either for bulk materials, generally covered with an amorphous layer when prepared by ion milling techniques, or for nanoscale objects deposited on amorphous substrates. In order to quantify the information of the high resolution images at the atomic scale, a structural modeling of the sample is necessary prior to the calculation of the electron wave function propagation. It is thus essential to be able to reproduce the carbon structure as close as possible to the real one. The approach we propose here is to simulate a realistic carbon from an energetic model based on the tight-binding approximation in order to reproduce the important structural properties of amorphous carbon. At first, we compare this carbon with the carbon obtained by randomly generating the carbon atom positions. In both cases, we discuss the limit thickness of the phase object approximation. In a second step, we show the influence of both carbons models on (i) the contrast of Cu, Ag, and Au single atoms deposited on carbon and (ii) the determination of the long-range order parameter in CoPt bimetallic nanoalloys.

  18. Application of high-resolution transmission electron microscopy to the study of aragonite crystallography and diagenesis

    SciTech Connect

    Haywick, D.W. . Geology Dept.); Ness, S.E. . Instrumentation Centre)

    1993-03-01

    High-resolution transmission electron microscopy (HRTEM) is a valuable technique by which to study the ultrastructure of various organic and inorganic compounds. Some biogeological minerals, including skeletal aragonite, have proven to be relatively unstable under an electron beam. Nevertheless, these compounds can be examined by HRTEM provided that minimal exposure techniques are employed. The authors have successfully applied HRTEM to examine diagenetically altered Plio-Pleistocene aragonitic faunas from New Zealand. To date, they have obtained high-resolution images of lattice-fringes with a spacing of 3.7 [angstrom] using a defocused, low-intensity electron beam. At least two of the samples imaged revealed clusters of lattice planes which together, form an interlocking mosaic of variably oriented micro-domains between 5 and 100 nm across. These micro-domains suggest that at least some of the aragonite is heterogeneous at a nm-scale; however, the individual micro-domains, when averaged together, generate single crystal electron diffraction patterns typical of well-ordered aragonite. The origin of the micro-domains is presently unclear. They may be an artifact of diagenetic alteration of an ultrastructurally homogeneous crystal. It is more likely, however, that the micro-domains were produced during aragonite precipitation. If this scenario is correct, it could have major implications for carbonate diagenesis, particularly if micro-domains prove to be ubiquitous within biogenic carbonate minerals. Inter-domains boundaries would be zones of comparative weakness and may provide nucleation points for diagenetic alteration. The intent now is to apply HRTEM in conjunction with other analytical techniques (e.g. x-ray diffraction, electron microprobe, stable isotope geochemistry) to characterize crystallographic changes during progressive diagenesis of aragonite, especially the aragonite-calcite transformation.

  19. Nanoscale deformation analysis with high-resolution transmission electron microscopy and digital image correlation

    DOE PAGESBeta

    Wang, Xueju; Pan, Zhipeng; Fan, Feifei; Wang, Jiangwei; Liu, Yang; Mao, Scott X.; Zhu, Ting; Xia, Shuman

    2015-09-10

    We present an application of the digital image correlation (DIC) method to high-resolution transmission electron microscopy (HRTEM) images for nanoscale deformation analysis. The combination of DIC and HRTEM offers both the ultrahigh spatial resolution and high displacement detection sensitivity that are not possible with other microscope-based DIC techniques. We demonstrate the accuracy and utility of the HRTEM-DIC technique through displacement and strain analysis on amorphous silicon. Two types of error sources resulting from the transmission electron microscopy (TEM) image noise and electromagnetic-lens distortions are quantitatively investigated via rigid-body translation experiments. The local and global DIC approaches are applied for themore » analysis of diffusion- and reaction-induced deformation fields in electrochemically lithiated amorphous silicon. As a result, the DIC technique coupled with HRTEM provides a new avenue for the deformation analysis of materials at the nanometer length scales.« less

  20. Nanoscale deformation analysis with high-resolution transmission electron microscopy and digital image correlation

    SciTech Connect

    Wang, Xueju; Pan, Zhipeng; Fan, Feifei; Wang, Jiangwei; Liu, Yang; Mao, Scott X.; Zhu, Ting; Xia, Shuman

    2015-09-10

    We present an application of the digital image correlation (DIC) method to high-resolution transmission electron microscopy (HRTEM) images for nanoscale deformation analysis. The combination of DIC and HRTEM offers both the ultrahigh spatial resolution and high displacement detection sensitivity that are not possible with other microscope-based DIC techniques. We demonstrate the accuracy and utility of the HRTEM-DIC technique through displacement and strain analysis on amorphous silicon. Two types of error sources resulting from the transmission electron microscopy (TEM) image noise and electromagnetic-lens distortions are quantitatively investigated via rigid-body translation experiments. The local and global DIC approaches are applied for the analysis of diffusion- and reaction-induced deformation fields in electrochemically lithiated amorphous silicon. As a result, the DIC technique coupled with HRTEM provides a new avenue for the deformation analysis of materials at the nanometer length scales.

  1. Ultrastable gold substrates: Properties of a support for high-resolution electron cryomicroscopy of biological specimens

    PubMed Central

    Russo, Christopher J.; Passmore, Lori A.

    2016-01-01

    Electron cryomicroscopy (cryo-EM) allows structure determination of a wide range of biological molecules and specimens. All-gold supports improve cryo-EM images by reducing radiation-induced motion and image blurring. Here we compare the mechanical and electrical properties of all-gold supports to amorphous carbon foils. Gold supports are more conductive, and have suspended foils that are not compressed by differential contraction when cooled to liquid nitrogen temperatures. These measurements show how the choice of support material and geometry can reduce specimen movement by more than an order of magnitude during low-dose imaging. We provide methods for fabrication of all-gold supports and preparation of vitrified specimens. We also analyse illumination geometry for optimal collection of high resolution, low-dose data. Together, the support structures and methods herein can improve the resolution and quality of images from any electron cryomicroscope. PMID:26592474

  2. A digitally configurable measurement platform using audio cards for high-resolution electronic transport studies.

    PubMed

    Gopman, D B; Bedau, D; Kent, A D

    2012-05-01

    We report on a software-defined digitally configurable measurement platform for determining electronic transport properties in nanostructures with small readout signals. By using a high-resolution audio analog-to-digital/digital-to-analog converter in a digitally compensated bridge configuration we significantly increase the measurement speed compared to established techniques and simultaneously acquire large and small signal characteristics. We characterize the performance (16 bit resolution, 100 dB dynamic range at 192 kS/s) and demonstrate the application of this measurement platform for studying the transport properties of spin-valve nanopillars, a two-terminal device that exhibits giant magnetoresistance and whose resistance can be switched between two levels by applied magnetic fields and by currents applied by the audio card. The high resolution and fast sampling capability permits rapid acquisition of deep statistics on the switching of a spin-valve nanopillar and reduces the time to acquire the basic properties of the device - a state-diagram showing the magnetic configurations as function of applied current and magnetic field - by orders of magnitude. PMID:22667635

  3. A digitally configurable measurement platform using audio cards for high-resolution electronic transport studies

    NASA Astrophysics Data System (ADS)

    Gopman, D. B.; Bedau, D.; Kent, A. D.

    2012-05-01

    We report on a software-defined digitally configurable measurement platform for determining electronic transport properties in nanostructures with small readout signals. By using a high-resolution audio analog-to-digital/digital-to-analog converter in a digitally compensated bridge configuration we significantly increase the measurement speed compared to established techniques and simultaneously acquire large and small signal characteristics. We characterize the performance (16 bit resolution, 100 dB dynamic range at 192 kS/s) and demonstrate the application of this measurement platform for studying the transport properties of spin-valve nanopillars, a two-terminal device that exhibits giant magnetoresistance and whose resistance can be switched between two levels by applied magnetic fields and by currents applied by the audio card. The high resolution and fast sampling capability permits rapid acquisition of deep statistics on the switching of a spin-valve nanopillar and reduces the time to acquire the basic properties of the device - a state-diagram showing the magnetic configurations as function of applied current and magnetic field - by orders of magnitude.

  4. High Resolution Electron Microscopy Of Dislocation Ribbons In A CMSX-4 Superalloy single crystal

    SciTech Connect

    Vorontsov, V. A.; Kovarik, Libor; Mills, M. J.; Rae, Catherine

    2012-07-01

    High-resolution scanning transmission electron microscopy (HR STEM) has been used to study the structure of dislocations in single crystal superalloy samples that have been subjected to conditions that favour the primary creep regime. The study has revealed the detailed structure of extended a 2 h112i dislocations as they shear the 0 precipitates during creep. These dislocations dissociate in a manner that is consistent with the PFMD predictions made and also suggests the importance of the reordering process during their movement. The shearing done by the ah112i dislocationswas also found to distort the/ 0 interface, changing its appearance from linear to a 'saw tooth' pattern. Another important observation was the segregation of alloying element with high atomic mass to the stacking faults to reduce their energies during shear. Numerous a 2 h110i dissociated dislocations were also observed in the channels of the superalloy. The high resolution provided by the STEM imaging enables one to study the high energy faults that are usually di*cult to observe in conventional weak-beam TEM, such as CISF and CESF-1 in the 0 andthe ISF in the, and to make estimates of their energies. Key

  5. High resolution electron microscopy and spectroscopy of ferritin in thin window liquid cells

    NASA Astrophysics Data System (ADS)

    Wang, Canhui; Qiao, Qiao; Shokuhfar, Tolou; Klie, Robert

    2014-03-01

    In-situ transmission electron microscopy (TEM) has seen a dramatic increase in interest in recent years with the commercial development of liquid and gas stages. High-resolution TEM characterization of samples in a liquid environment remains limited by radiation damage and loss of resolution due to the thick window-layers required by the in-situ stages. We introduce thin-window static-liquid cells that enable sample imaging with atomic resolution and electron energy-loss (EEL) spectroscopy with 1.3 nm resolution. Using this approach, atomic and electronic structures of biological samples such as ferritin is studied via in-situ transmission electron microscopy experiments. Ferritin in solution is encapsulated using the static liquid cells with reduced window thickness. The integrity of the thin window liquid cell is maintained by controlling the electron dose rate. Radiation damage of samples, such as liquid water and protein, is quantitatively studied to allow precision control of radiation damage level within the liquid cells. Biochemical reactions, such as valence change of the iron in a functioning ferritin, is observed and will be quantified. Relevant biochemical activity: the release and uptake of Fe atoms through the channels of ferritin protein shell is also imaged at atomic resolution. This work is funded by Michigan Technological University. The UIC JEOL JEM-ARM200CF is supported by an MRI-R2 grant from the National Science Foundation (Grant No. DMR-0959470).

  6. Detecting non-maxwellian electron velocity distributions at JET by high resolution Thomson scattering.

    PubMed

    Beausang, K V; Prunty, S L; Scannell, R; Beurskens, M N; Walsh, M J; de la Luna, E

    2011-03-01

    The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV. PMID:21585113

  7. Detecting non-Maxwellian electron velocity distributions at JET by high resolution Thomson scattering

    SciTech Connect

    Beausang, K. V.; Prunty, S. L.; Scannell, R.; Beurskens, M. N.; Walsh, M. J.; Collaboration: JET EFDA Contributors

    2011-03-15

    The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6-7 keV, where in some cases the ECE electron temperature measurements can be 15%-20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV.

  8. A High-resolution 3D Geodynamical Model of the Present-day India-Asia Collision System

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Baumann, T.

    2015-12-01

    We present a high-resolution, 3D geodynamic model of the present-day India-Asia collision system. The model is separated into multiple tectonic blocks, for which we estimate the first order rheological properties and the impact on the dynamics of the collision system. This is done by performing systematic simulations with different rheologies to minimize the misfit to observational constraints such as the GPS-velocity field. The simulations are performed with the parallel staggered grid FD code LaMEM using a numerical resolution of at least 512x512x256 cells to resolve dynamically important shear zones reasonably well. A fundamental part of this study is the reconstruction of the 3D present-day geometry of Tibet and the adjacent regions. Our interpretations of crust and mantle lithosphere geometry are jointly based on a globally available shear wave tomography (Schaeffer and Lebedev, 2013) and the Crust 1.0 model (Laske et al. http://igppweb.ucsd.edu/~gabi/crust1.html). We regionally refined and modified our interpretations based on seismicity distributions and focal mechanisms and incorporated regional receiver function studies to improve the accuracy of the Moho in particular. Results suggest that we can identify at least one "best-fit" solution in terms of rheological model properties that reproduces the observed velocity field reasonably well, including the strong rotation of the GPS velocity around the eastern syntax of the Himalaya. We also present model co-variances to illustrate the trade-offs between the rheological model parameters, their respective uncertainties, and the model fit. Schaeffer, A.J., Lebedev, S., 2013. Global shear speed structure of the upper mantle and transition zone. Geophysical Journal International 194, 417-449. doi:10.1093/gji/ggt095

  9. Very high resolution soft x-ray spectrometer for an electron beam ion trap

    SciTech Connect

    Beiersdorfer, P.; Crespo Lopez-Urrutia, J.R.; Foerster, E.; Mahiri, J. |; Widmann, K.

    1997-01-01

    A very high resolution vacuum flat-crystal spectrometer was constructed for analyzing soft x rays emitted by an electron beam ion trap. The spectrometer was designed to operate at large Bragg angles ({theta}{le}85{degree}) in order to maximize the spectral dispersion and thus the resolving power. Using a quartz (100) crystal at a Bragg angle of 82{degree}, a measurement of the 2p{sub 1/2}, 2p{sub 3/2}{r_arrow}1s{sub 1/2} transitions in hydrogenic Mg{sup 11+} situated near 8.42 {Angstrom} was made. The nominal resolving power of the instrument was better than 30000 allowing us to infer the ion temperature (246{plus_minus}20 eV) from the observed line widths. A comparison with an existing flat-crystal spectrometer demonstrates the great improvement in resolving power achieved. {copyright} {ital 1997 American Institute of Physics.}

  10. High-resolution electron microscopy in spin pumping NiFe/Pt interfaces

    SciTech Connect

    Ley Domínguez, D. Sáenz-Hernández, R. J.; Faudoa Arzate, A.; Arteaga Duran, A. I.; Ornelas Gutiérrez, C. E.; Solís Canto, O.; Botello-Zubiate, M. E.; Rivera-Gómez, F. J.; Matutes-Aquino, J. A.; Azevedo, A.; Silva, G. L. da; Rezende, S. M.

    2015-05-07

    In order to understand the effect of the interface on the spin pumping and magnetic proximity effects, high resolution transmission electron microscopy and ferromagnetic resonance (FMR) were used to analyze Py/Pt bilayer and Pt/Py/Pt trilayer systems. The samples were deposited by dc magnetron sputtering at room temperature on Si (001) substrates. The Py layer thickness was fixed at 12 nm in all the samples and the Pt thickness was varied in a range of 0–23 nm. A diffusion zone of approximately 8 nm was found in the Py/Pt interfaces and confirmed by energy dispersive X-ray microanalysis. The FMR measurements show an increase in the linewidth and a shift in the ferromagnetic resonance field, which reach saturation.

  11. Nano features of Al/Au ultrasonic bond interface observed by high resolution transmission electron microscopy

    SciTech Connect

    Ji Hongjun; Li Mingyu Kim, Jong-Myung; Kim, Dae-Won; Wang Chunqing

    2008-10-15

    Nano-scale interfacial details of ultrasonic AlSi1 wire wedge bonding to a Au/Ni/Cu pad were investigated using high resolution transmission electron microscopy (HRTEM). The intermetallic phase Au{sub 8}Al{sub 3} formed locally due to diffusion and reaction activated by ultrasound at the Al/Au bond interface. Multilayer sub-interfaces roughly parallel to the wire/pad interface were observed among this phase, and interdiffusional features near the Au pad resembled interference patterns, alternately dark and bright bars. Solid-state diffusion theory cannot be used to explain why such a thick compound formed within milliseconds at room temperature. The major formation of metallurgical bonds was attributed to ultrasonic cyclic vibration.

  12. High-resolution transmission electron microscopy with an electrostatic Zach phase plate

    NASA Astrophysics Data System (ADS)

    Hettler, S.; Dries, M.; Zeelen, J.; Oster, M.; Schröder, R. R.; Gerthsen, D.

    2016-05-01

    A new method to control lattice-fringe contrast in high-resolution transmission electron microscopy (HRTEM) images by the implementation of a physical phase plate (PP) is proposed. PPs are commonly used in analogy to Zernike PPs in light microscopy to enhance the phase contrast of weak-phase objects with nm-sized features, which often occur in life science applications. Such objects otherwise require strong defocusing, which leads to a degradation of the instrumental resolution and impedes intuitive image interpretation. The successful application of an electrostatic Zach PP in HRTEM is demonstrated by the investigation of single crystalline Si and Ge samples. The influence of the Zach PP on the image formation process is assessed by analyzing the amplitudes of (111) reflections in power spectra which show a cosine-type dependence on the induced phase shift under certain conditions as predicted by theory.

  13. Time-resolved high-resolution electron microscopy of structural stability in MgO clusters

    SciTech Connect

    Kizuka, T.; Tanaka, N.

    1996-12-31

    Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science. In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.

  14. High resolution transmission electron microscopic in-situ observations of plastic deformation of compressed nanocrystalline gold

    SciTech Connect

    Wang, Guoyong; Lian, Jianshe; Jiang, Qing; Sun, Sheng; Zhang, Tong-Yi

    2014-09-14

    Nanocrystalline (nc) metals possess extremely high strength, while their capability to deform plastically has been debated for decades. Low ductility has hitherto been considered an intrinsic behavior for most nc metals, due to the lack of five independent slip systems actively operating during deformation in each nanograin. Here we report in situ high resolution transmission electron microscopic (HRTEM) observations of deformation process of nc gold under compression, showing the excellent ductility of individual and aggregate nanograins. Compression causes permanent change in the profile of individual nanograins, which is mediated by dislocation slip and grain rotation. The high rate of grain boundary sliding and large extent of widely exited grain rotation may meet the boundary compatibility requirements during plastic deformation. The in situ HRTEM observations suggest that nc gold is not intrinsically brittle under compressive loading.

  15. Oxidation of diamond films by atomic oxygen: High resolution electron energy loss spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Shpilman, Z.; Gouzman, I.; Grossman, E.; Akhvlediani, R.; Hoffman, A.

    2007-12-01

    Diamond surface oxidation by atomic oxygen, annealing up to ˜700°C, and in situ exposure to thermally activated hydrogen were studied by high resolution electron energy loss spectroscopy (HREELS). After atomic oxygen (AO) exposure, HREELS revealed peaks associated with CHx groups, carbonyl, ether, and peroxide-type species and strong quenching of the diamond optical phonon and its overtones. Upon annealing of the oxidized surfaces, the diamond optical phonon overtones at 300 and 450meV emerge and carbonyl and peroxide species gradually desorb. The diamond surface was not completely regenerated after annealing to ˜700°C and in situ exposure to thermally activated hydrogen, probably due to the irreversible deterioration of the surface by AO.

  16. High resolution transmission electron microscopy of two stony meteorites - Murchison and Kenna

    NASA Technical Reports Server (NTRS)

    Mackinnon, I. D. R.; Buseck, P. R.

    1979-01-01

    Matrix material from the Murchison C2(M) carbonaceous chondrite and less than micrometer-size pyroxene inclusions in an olivine from the Kenna ureilite have been characterized using high resolution transmission electron microscopy. A diversity of textures and mineral associations, including serpentine-type and brucite-type mixed-layering, occur in the Murchison matrix. Such mixed layer structures are new types of layer silicate. Their presence in the matrix may prove to be genetically significant. The Kenna inclusions, formed at the olivine grain margins, are of two types: (1) a disordered orthopyroxene-clinopyroxene which may have inverted from protopyroxene and (2) a pigeonite with narrow anti-phase domains (80 A to 250 A) and boundaries parallel to (100).

  17. High-resolution electron microscopy in spin pumping NiFe/Pt interfaces

    NASA Astrophysics Data System (ADS)

    Ley Domínguez, D.; Sáenz-Hernández, R. J.; Faudoa Arzate, A.; Arteaga Duran, A. I.; Ornelas Gutiérrez, C. E.; Solís Canto, O.; Botello-Zubiate, M. E.; Rivera-Gómez, F. J.; Azevedo, A.; da Silva, G. L.; Rezende, S. M.; Matutes-Aquino, J. A.

    2015-05-01

    In order to understand the effect of the interface on the spin pumping and magnetic proximity effects, high resolution transmission electron microscopy and ferromagnetic resonance (FMR) were used to analyze Py/Pt bilayer and Pt/Py/Pt trilayer systems. The samples were deposited by dc magnetron sputtering at room temperature on Si (001) substrates. The Py layer thickness was fixed at 12 nm in all the samples and the Pt thickness was varied in a range of 0-23 nm. A diffusion zone of approximately 8 nm was found in the Py/Pt interfaces and confirmed by energy dispersive X-ray microanalysis. The FMR measurements show an increase in the linewidth and a shift in the ferromagnetic resonance field, which reach saturation.

  18. Installation of electric field electron beam blanker in high-resolution transmission electron microscopy

    SciTech Connect

    Hayashida, Misa; Kimura, Yoshihide; Taniguchi, Yoshifumi; Otsuka, Masayuki; Takai, Yoshizo

    2006-11-15

    We have newly installed an electric field electron beam blanker in a transmission electron microscopy, which chops an electron beam very quickly without the effect of hysteresis. The electric field, which is generated by the electron beam blanker, deflects the electron beam, and the electron beam is intercepted by an aperture. The response time of the beam blanker is 50 {mu}s. Therefore, a very short pulsed electron beam enables a charge-coupled device camera to directly expose an electron beam spot or diffraction pattern. Moreover, we measured the response of a deflector coil, which is usually used as an electron beam blanker, using our electron beam blanker. Our beam blanker will become a key component in a computer-assisted minimal dose system, which enables us to reduce the electron dose of the sample.

  19. Analysis of high quality monatomic chromium films used in biological high resolution scanning electron microscopy.

    PubMed

    Apkarian, R P

    1994-01-01

    During the recent employment of field emission (FE) in-lens scanning electron microscopes (SEMs), refractory metal deposition technology has co-evolved to provide enhanced contrast of 1-10 nm hydrocarbon based biological structures imaged at high magnifications (> 200,000 times). Pioneer development employing the Penning sputter system in a high vacuum chamber proved that imaging of chromium (Cr) coated biological specimens contained enriched secondary electron (SE)-(I) contrasts. Single nanometer size fibrillar and particulate ectodomains within the context of complex biological membranes were accurately imaged without significant enlargement using the high resolution SE-I mode (HRSEM). This paper reports the transmission electron microscopy (TEM) testing of ultrathin (0.5-2.0 nm) Cr films deposited by planar magnetron sputter coating (PMSC). Essential parameters necessary to reproduce quality sputtered films of refractory metals used in HRSEM studies were described for the vacuum system and target operation conditions (current, voltage, and target distance). HRSEM imaging of biological specimens is presented to assess contrast attained from ultrathin fine grain Cr films deposited by PMSC. High magnification images were recorded to illustrate high quality contrasts attainable by HRSEM at low (1-5 kV) and high (10-30 kV) voltages. Dispersed molecules on formvar coated grids were sputter coated with a 1 nm thick Cr film before employing scanning transmission (STEM)/SEM modes of the FESEM to establish non-decorative image accuracy in the transmitted electron mode. PMID:7701300

  20. High resolution electron energy loss spectroscopy with two-dimensional energy and momentum mapping.

    PubMed

    Zhu, Xuetao; Cao, Yanwei; Zhang, Shuyuan; Jia, Xun; Guo, Qinlin; Yang, Fang; Zhu, Linfan; Zhang, Jiandi; Plummer, E W; Guo, Jiandong

    2015-08-01

    High resolution electron energy loss spectroscopy (HREELS) is a powerful technique to probe vibrational and electronic excitations at surfaces. The dispersion relation of surface excitations, i.e., energy as a function of momentum, has in the past, been obtained by measuring the energy loss at a fixed angle (momentum) and then rotating sample, monochromator, or analyzer. Here, we introduce a new strategy for HREELS, utilizing a specially designed lens system with a double-cylindrical Ibach-type monochromator combined with a commercial VG Scienta hemispherical electron energy analyzer, which can simultaneously measure the energy and momentum of the scattered electrons. The new system possesses high angular resolution (<0.1°), detecting efficiency and sampling density. The capabilities of this system are demonstrated using Bi2Sr2CaCu2O(8+δ). The time required to obtain a complete dispersion spectrum is at least one order of magnitude shorter than conventional spectrometers, with improved momentum resolution and no loss in energy resolution. PMID:26329206

  1. High resolution electron energy loss spectroscopy with two-dimensional energy and momentum mapping

    SciTech Connect

    Zhu, Xuetao; Cao, Yanwei; Zhang, Shuyuan; Jia, Xun; Guo, Qinlin; Yang, Fang; Zhu, Linfan; Zhang, Jiandi; Plummer, E. W.; Guo, Jiandong

    2015-08-15

    High resolution electron energy loss spectroscopy (HREELS) is a powerful technique to probe vibrational and electronic excitations at surfaces. The dispersion relation of surface excitations, i.e., energy as a function of momentum, has in the past, been obtained by measuring the energy loss at a fixed angle (momentum) and then rotating sample, monochromator, or analyzer. Here, we introduce a new strategy for HREELS, utilizing a specially designed lens system with a double-cylindrical Ibach-type monochromator combined with a commercial VG Scienta hemispherical electron energy analyzer, which can simultaneously measure the energy and momentum of the scattered electrons. The new system possesses high angular resolution (<0.1°), detecting efficiency and sampling density. The capabilities of this system are demonstrated using Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ}. The time required to obtain a complete dispersion spectrum is at least one order of magnitude shorter than conventional spectrometers, with improved momentum resolution and no loss in energy resolution.

  2. High-resolution scanning electron microscopy of frozen-hydrated cells.

    PubMed

    Walther, P; Chen, Y; Pech, L L; Pawley, J B

    1992-11-01

    Cryo-fixed yeast Paramecia and sea urchin embryos were investigated with an in-lens type field-emission SEM using a cold stage. The goal was to further develop and investigate the processing of frozen samples for the low-temperature scanning electron microscope (LTSEM). Uncoated frozen-hydrated samples were imaged with the low-voltage backscattered electron signal (BSE). Resolution and contrast were sufficient to visualize cross-fractured membranes, nuclear pores and small vesicles in the cytoplasm. It is assumed that the resolution of this approach is limited by the extraction depth of the BSE which depends upon the accelerating voltage of the primary beam (V0). In this study, the lowest possible V0 was 2.6 kV because below this value the sensitivity of the BSE detector is insufficient. It is concluded that the resolution of the uncoated specimen could be improved if equipment were available for high-resolution BSE imaging at 0.5-2 kV. Higher resolution was obtained with platinum cryo-coated samples, on which intramembranous particles were easily imaged. These images even show the ring-like appearance of the hexagonally arranged intramembranous particles known from high-resolution replica studies. On fully hydrated samples at high magnification, the observation time for a particular area is limited by mass loss caused by electron irradiation. Other potential sources of artefacts are the deposition of water vapour contamination and shrinkage caused by the sublimation of ice. Imaging of partially dehydrated (partially freeze-dried) samples, e.g. high-pressure frozen Paramecium and sea urchin embryos, will probably become the main application in cell biology. In spite of possible shrinkage problems, this approach has a number of advantages compared with any other electron microscopy preparation method: no chemical fixation is necessary, eliminating this source of artefacts; due to partial removal of the water additional structures in the cytoplasm can be investigated

  3. Electron-beam-enhanced oxidation processes in II-VI compound semiconductors observed by high-resolution electron microscopy

    SciTech Connect

    Thangaraj, N.; Wessels, B.W.

    1990-02-01

    Enhanced oxidation of ZnS and ZnSe semiconductor surfaces has been observed in situ during electron irradiation in a high-resolution electron microscope. The phase present at the surface region has been identified as ZnO by optical diffractogram and selected area electron diffraction techniques. For ZnS oxidation, both hexagonal ZnO having a random orientation and cubic ZnO in perfect epitaxial relationship with the bulk ZnS were observed. Enhanced oxidation of ZnSe to ZnO has also been observed under electron beam irradiation. However, only the hexagonal form was observed. The oxidation rates for both ZnS and ZnSe depended on electron flux but was independent of orientation. A model in which the oxidation process is limited by diffusion through the oxide film is proposed. By electron irradiation the diffusion rate is enhanced presumably by a nonthermal process.

  4. Transient Thermometry and High-Resolution Transmission Electron Microscopy Analysis of Filamentary Resistive Switches.

    PubMed

    Kwon, Jonghan; Sharma, Abhishek A; Chen, Chao-Yang; Fantini, Andrea; Jurczak, Malgorzata; Herzing, Andrew A; Bain, James A; Picard, Yoosuf N; Skowronski, Marek

    2016-08-10

    We present data on the filament size and temperature distribution in Hf0.82Al0.18Ox-based Resistive Random Access Memory (RRAM) devices obtained by transient thermometry and high-resolution transmission electron microscopy (HRTEM). The thermometry shows that the temperature of the nonvolatile conducting filament can reach temperatures as high as 1600 K at the onset of RESET at voltage of 0.8 V and power of 40 μW. The size of the filament was estimated at about 1 nm in diameter. Hot filament increases the temperature of the surrounding high resistivity oxide, causing it to conduct and carry a significant fraction of the total current. The current spreading results in slowing down the filament temperature increase at higher power. The results of thermometry have been corroborated by HRTEM analysis of the as-fabricated and switched RRAM devices. The functional HfAlOx layer in as-fabricated devices is amorphous. In devices that were switched, we detected a small crystalline region of 10-15 nm in size. The crystallization temperature of the HfAlOx was determined to be 850 K in an independent annealing experiment. The size of the crystalline region agrees with thermal modeling based on the thermometry data. Scanning transmission electron microscopy (TEM) coordinated with electron energy loss spectroscopy could not detect changes in the chemical makeup of the filament. PMID:27351065

  5. Magnetic lens apparatus for use in high-resolution scanning electron microscopes and lithographic processes

    DOEpatents

    Crewe, Albert V.

    2000-01-01

    Disclosed are lens apparatus in which a beam of charged particlesis brought to a focus by means of a magnetic field, the lens being situated behind the target position. In illustrative embodiments, a lens apparatus is employed in a scanning electron microscopeas the sole lens for high-resolution focusing of an electron beam, and in particular, an electron beam having an accelerating voltage of from about 10 to about 30,000 V. In one embodiment, the lens apparatus comprises an electrically-conducting coil arranged around the axis of the beam and a magnetic pole piece extending along the axis of the beam at least within the space surrounded by the coil. In other embodiments, the lens apparatus comprises a magnetic dipole or virtual magnetic monopole fabricated from a variety of materials, including permanent magnets, superconducting coils, and magnetizable spheres and needles contained within an energy-conducting coil. Multiple-array lens apparatus are also disclosed for simultaneous and/or consecutive imaging of multiple images on single or multiple specimens. The invention further provides apparatus, methods, and devices useful in focusing charged particle beams for lithographic processes.

  6. Earle K. Plyler Prize Talk: Using High Resolution Electronic Spectroscopy to Probe Reactive Chemical Intermediates

    NASA Astrophysics Data System (ADS)

    Miller, Terry

    2009-03-01

    Gas phase chemical reactions, such as occur in atmospheric chemistry, combustion, plasma processing, etc. are of great importance to our economy and society. These reactions are typically very complex involving up to 1000's of elementary steps with a corresponding number of reactive chemical intermediates. Spectrospic diagnostics, based upon well analyzed and well understood spectra of the intermediates, are crucial for monitoring such reactions and unraveling their mechanisms. These spectral analyses often benefit from the guidance provided by quantum chemical calculations and conversely the molecular parameters, experimentally determined from the spectra, serve as ``gold standards'' for benchmarking such calculations. Such standards are especially valuable for reactive intermediates whose electronic or geometric structure is particularly complex because of electron-spin interactions, Jahn-Teller effects or other vibronic interactions, hindered internal motions, large molecular size and weight, etc. The organic alkoxy, RO., and peroxy, RO2., (R=alkyl group) free radicals are excellent examples of such species. The talk will focus on our recent characterization of these radicals via their ``high-resolution,'' mostly rotationally resolved, electronic spectra utilizing the techniques of laser induced fluorescence, stimulated emission pumping, and cavity ringdown spectroscopy. Selected spectra, their analysis, and the molecular information resulting therefrom will be discussed.

  7. Elemental analysis of organic species with electron ionization high-resolution mass spectrometry.

    PubMed

    Aiken, Allison C; DeCarlo, Peter F; Jimenez, Jose L

    2007-11-01

    We present a new elemental analysis (EA) technique for organic species (CHNO) that allows fast on-line analysis (10 s) and reduces the required sample size to approximately 1 ng, approximately 6 orders of magnitude less than standard techniques. The composition of the analyzed samples is approximated by the average elemental composition of the ions from high-resolution electron ionization (EI) mass spectra. EA of organic species can be performed on organic/inorganic mixtures. Elemental ratios for the total organic mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addition to the organic mass to organic carbon ratio (OM/OC), can be determined. As deviations between the molecular and the ionic composition can appear due to chemical influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compounds from the NIST database and from 35 laboratory standards sampled with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The analysis of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (average absolute value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at +/-5% in the absence of air for AMS data. AMS OM/OC has an average error of 5%. Additional calibration is recommended for types of species very different from those analyzed here. EA was applied to organic mixtures and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS. PMID:17914892

  8. The first observation of titanate nanotubes by spherical aberration corrected high-resolution transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Miao, L.; Tanemura, S.; Jiang, T.; Tanemura, M.; Yoshida, K.; Tanaka, N.; Xu, G.

    2009-07-01

    Multi-wall titanate nanotubes (MW-TNNTs) with high aspect ratio, large surface area and good uniformity were produced by alkaline hydrothermal treatment of grounded TiO 2 aerogels and further by applying freeze-drying. Not only the crystal phase and diameter, but also morphology of the starting materials impact on the aspect ratio and transformation efficiency of the obtained nanotubes. Other parameters, such as pH value during neutralization process and drying method for the final products, are important to control length and dispersion of MW-TNNTs. By spherical aberration corrected high-resolution transmission-electron-microscopy (Cs-corrected HRTEM) with lateral space resolution of 0.14 nm at 200 kV accelerating voltage and electron energy loss spectrum (EELS), the detailed structural analysis of MW-TNNTs reveals that (1) diameters of inner and outer tubes are about 4-7 nm and 10 nm, respectively, (2) numbers of layers are different from part to part along the longitudinal tube axis, (3) the walls of the tubes have interlayer spacing of 0.70-0.80 nm and the lateral fringes which are vertical to the walls have spacing of 0.32 nm, (4) each layer of MW-TNNT is the nanosheet composed by the arrayed TiO 6 octahedrons, and respective octahedron being slightly strained, and (5) no chirality of MW-TNNT tubular structure is observed.

  9. High-resolution far ultraviolet spectrum of electron-excited SO(sub 2)

    NASA Technical Reports Server (NTRS)

    Palle, P. V.; Ajello, J.; Bhardwaj, A.

    2004-01-01

    The high resolution UV capabilities (lamda/delta lambda = 10(sup 5)) of the Hubble Space Telscope (HST) equipped with the Space Telescope Imaging Spectrograph (STIS) reflects a need for high resolution laboratory UV spectral data base for comparison with observation.

  10. Transfer-printing of single DNA molecule arrays on graphene for high resolution electron imaging and analysis

    PubMed Central

    Cerf, Aline; Alava, Thomas; Barton, Robert A.; Craighead, Harold G.

    2011-01-01

    Graphene represents the ultimate substrate for high-resolution transmission electron microscopy, but the deposition of biological samples on this highly hydrophobic material has until now been a challenge. We present a reliable method for depositing ordered arrays of individual elongated DNA molecules on single-layer graphene substrates for high resolution electron beam imaging and electron energy loss spectroscopy analysis. This method is a necessary step towards the observation of single elongated DNA molecules with single base spatial resolution to directly read genetic and epigenetic information. PMID:21919532

  11. [High resolution electron microscopy of the crystalline structure in remineralized enamel].

    PubMed

    Tanaka, N

    1989-09-01

    The present work was designed to elucidate crystallographic changes in enamel that had been demineralized in a 0.01 M acetate buffer (pH 4.0) for 2 days at 50 degrees C and then remineralized in a solution containing 1 mM Ca, 0.6 mM P, and 0.05 mM F for 1 or 2 weeks at 37 degrees C. The demineralized and remineralized enamel samples were observed by means of high-resolution electron microscopy, electron-probe analysis, and small area X-ray or electron diffraction. Before remineralization, demineralized enamel had been composed of sparsely arranged apatite crystals with either a central perforation or lateral surface defects or both. Measurements of crystalline (001) planes indicated that crystals in demineralized enamel were significantly larger than those in intact enamel, thus suggesting that crystal growth had taken place during demineralization. Small, newly formed, hexagonal crystals occurred in remineralized enamel. In some cases, precipitation of such small crystals together with localized enamel-crystal regrowth restored central perforations and lateral defects. A number of the small, newly formed crystals and preexisting enamel crystals aggregated to form a group with a roughly hexagonal outline. After the growth and fusion of these grouping crystals, a large, regular-hexagonal crystal formed. Such various kinds of lattice defects as edge dislocation, small-angle grain boundary, and lattice displacement were frequently detected in fusing crystal boundaries. Prolonging remineralization duration seemed to reinforce these lattice defects. Electron-probe and X-ray diffraction studies led to the assumption that the large hexagonal crystals were fluoroapatite. These results indicate that remineralization of demineralized enamel proceeds through several stages, including formation and growth of new crystals and regrowth of preexisting enamel crystals. PMID:2641199

  12. Electron Collisions with Large Molecules

    NASA Astrophysics Data System (ADS)

    McKoy, Vincent

    2006-10-01

    In recent years, interest in electron-molecule collisions has increasingly shifted to large molecules. Applications within the semiconductor industry, for example, require electron collision data for molecules such as perfluorocyclobutane, while almost all biological applications involve macromolecules such as DNA. A significant development in recent years has been the realization that slow electrons can directly damage DNA. This discovery has spurred studies of low-energy collisions with the constituents of DNA, including the bases, deoxyribose, the phosphate, and larger moieties assembled from them. In semiconductor applications, a key goal is development of electron cross section sets for plasma chemistry modeling, while biological studies are largely focused on understanding the role of localized resonances in inducing DNA strand breaks. Accurate calculations of low-energy electron collisions with polyatomic molecules are computationally demanding because of the low symmetry and inherent many-electron nature of the problem; moreover, the computational requirements scale rapidly with the size of the molecule. To pursue such studies, we have adapted our computational procedure, known as the Schwinger multichannel method, to run efficiently on highly parallel computers. In this talk, we will present some of our recent results for fluorocarbon etchants used in the semiconductor industry and for constituents of DNA and RNA. In collaboration with Carl Winstead, California Institute of Technology.

  13. High resolution transmission electron microscopy study of diamond films grown from fullerene precursors

    SciTech Connect

    Luo, J.S.; Gruen, D.M.; Krauss, A.R.

    1995-07-01

    High-resolution transmission electron microscopy (HRTEM) has been used to investigate the microstructure of diamond films grown by plasma-assisted chemical vapor deposition using fullerene precursors. HRTEM observations of as-grown films revealed an array of larger crystals (>200 nm) within a polycrystalline matrix of much smaller crystallites (<20 nm). The randomly oriented small crystallites were nearly free of structural imperfections such as stacking faults or twins, while the larger ones had preferred <110> orientations with respect to the Si (100) substrate and showed evidence of structural defects on the periphery of the crystals. The most common defects were V-shaped {Sigma}9 twin boundaries, which are generally believed to serve as re-entrant sites for diamond nucleation and growth. The observation of growth steps on both (111) and (110) surfaces seems to support a reaction model in which fragments of C{sub 60}, including C{sub 2}, are considered the growth species. In particular, the nanocrystallinity of the films is most likely due to a high carbon cluster density from C{sub 60} fragmentation at or near the diamond surface, which can serve as nucleation sites for the growth of new crystallites.

  14. High-resolution electron microscopy study of synthetic carbonate and aluminum containing apatites.

    PubMed

    Layani, J D; Cuisinier, F J; Steuer, P; Cohen, H; Voegel, J C; Mayer, I

    2000-05-01

    Aluminum (Al)-containing calcium-deficient carbonated hydroxyapatites were produced by a precipitation method from aqueous solution with carbonate (0-6.1%) and aluminum (0.1-0.5%) concentrations close to those found in biological materials. Two series of apatites were prepared: one at pH 7.0 and another at pH 9. 0. High-resolution electron microscopy has shown that many of them possess structural defects such as screw dislocations, grain boundaries, and central defects. Samples with high carbonate content and high water and high Al(3+) content had a high amount of structural defects. Accordingly, a sample (7Al1) with a relatively high carbonate content (6.1%) and a sample (7Al6) without carbonate but with a relatively high water (2.0 mol) and Al(3+) content (0. 39%) presented the highest amount of structural defects, 54% and 47%, respectively. A sample (7Al13) with a low level of crystalline water (1 mol) and low carbonate (2.5%) showed a small amount of defects. The presence of water associated with Al(3+) induced a high number of crystals having a central defect with a great similarity to the so-called water layer of octacalcium phosphate (OCP). Observed images of all these crystals have shown good correspondence with the computer-simulated image based on the crystal structure of hydroxyapatite, indicating that the addition of Al(3+) and carbonate does not perturb the apatitic structure. PMID:10679685

  15. Direct imaging of CdTe(001) surface reconstructions by high-resolution electron microscopy

    NASA Astrophysics Data System (ADS)

    Lu, Ping; Smith, David J.

    1991-08-01

    Novel reconstructions of the CdTe(001) surface have been directly observed using high-resolution electron microscopy in the profile-imaging geometry. The CdTe(001) surface, obtained by in situ annealing under ultrahigh vacuum conditions, is found to have a (2 × 1) structure at temperatures of less than about 200° C, but it transforms reversibly into a (3 × 1) structure at temperatures above 200 °C. Structural models for the reconstructions have been proposed and confirmed by extensive computer simulations. The (2 × 1) reconstruction, stabilized by Cd atoms, consists of a {1}/{2} monolayer of Cd vacancies and a large inward relaxation of the remaining surface Cd atoms, similar to the (2 × 1) reconstruction previously proposed for the GaAs(001) surface. The (3 × 1) reconstruction, stabilized by Te atoms, involves formation of surface dimers and the presence of vacancies. In both reconstructions, atomic displacements are observed that extend a few layers into the bulk and serve to reduce the strain energy.

  16. In-Situ High-Resolution Transmission Electron Microscopy Investigation of Overheating of Cu Nanoparticles

    PubMed Central

    Chen, Chunlin; Hu, Ziyu; Li, Yanfen; Liu, Limin; Mori, Hirotaro; Wang, Zhangchang

    2016-01-01

    Synthesizing and functionalizing metal nanoparticles supported on substrates is currently the subject of intensive study owing to their outstanding catalytic performances for heterogeneous catalysis. Revealing the fundamental effect of the substrates on metal nanoparticles represents a key step in clarifying mechanisms of stability and catalytic properties of these heterogeneous systems. However, direct identification of these effects still poses a significant challenge due to the complicacy of interactions between substrates and nanoparticles and also for the technical difficulty, restraining our understanding of these heterogeneous systems. Here, we combine in situ high-resolution transmission electron microscopy with molecular dynamics simulations to investigate Cu nanoparticles supported on graphite and Cu2O substrates, and demonstrate that melting behavior and thermal stability of Cu nanoparticles can be markedly influenced by substrates. The graphite-supported Cu nanoparticles do not melt during annealing at 1073 K until they vanish completely, i.e. only the sublimation occurs, while the Cu2O-supported Cu nanoparticles suffer melting during annealing at 973 K. Such selective superheating of the Cu nanoparticles can be attributed to the adsorption of a thin carbon layer on the surface of the Cu nanoparticles, which helps guide further stability enhancement of functional nanoparticles for realistic applications. PMID:26785839

  17. High-resolution electron microscopy study of mesoporous dichalcogenides and their hydrogen storage properties

    NASA Astrophysics Data System (ADS)

    She, Lan; Li, Jing; Gu, Dong; Shi, Yifeng; Che, Renchao; Zhao, Dongyuan

    2011-02-01

    In this work, we report a detailed investigation on the surface topology of ordered mesoporous WS2 nanoarrays nanocast from the silica SBA-15 template. Using a high-resolution scanning electron microscopy (HRSEM) technique, we acquire distinguishably clear images of the WS2 surface. A large number of small nanorods are found to be evenly distributed among the nanowire arrays, supporting their ordered mesostructures. Based on these observations, tunnel-like connecting pores are proposed to have a similar distribution in the mother mesoporous silica SBA-15 template. Interestingly, we observe the atomic crystal lattices of the layered WS2 on the HRSEM image. To the best of our knowledge, this is the first time that atomic crystal lattices have been directly observed using a SEM technique. In addition, both materials show good adsorption-desorption capabilities with hydrogen, and the maximum amount of hydrogen that can be taken up is 0.34 wt% for mesoporous WS2 and 0.52 wt% for mesoporous MoS2 at a pressure of 10 bar, indicating that both are potential hydrogen storage materials.

  18. 5f-electron states in uranium dioxide investigated using high-resolution neutron spectroscopy

    NASA Astrophysics Data System (ADS)

    Amoretti, G.; Blaise, A.; Caciuffo, R.; Fournier, J. M.; Hutchings, M. T.; Osborn, R.; Taylor, A. D.

    1989-07-01

    High-resolution, high-energy-transfer, inelastic neutron scattering has been used to explore the crystal-field (CF) excitations in UO2. As all the dipole-allowed transitions within the free-ion ground manifold have been identified, the observations provide a complete determination of the crystal-field potential and 5f-electron eigenstates. The fourth- and sixth-degree CF parameters are V4=-123 meV and V6=26.5 meV. In spite of the strength of the CF, the ground state is accurately given by the intermediate-coupling approximation with little modification by J-mixing effects. In the antiferromagnetic phase below TN=30.8 K, a splitting of the cubic CF levels, due to the combined effects of the molecular field and the distortion of the oxygen-ligand cage surrounding the U4+ ions, has been observed. Detailed CF calculations are presented both for the case of a double-k magnetic structure with a monoclinic distortion of the oxygen sublattice, and for a combined triple-k distortion and magnetic order. The observed splittings are shown to be more consistent with the triple-k model.

  19. High resolution transmission electron microscopy of melamine-formaldehyde aerogels and silica aerogels

    SciTech Connect

    Ruben, G.C. . Dept. of Biological Sciences)

    1991-09-01

    The goal of the high resolution transmission electron microscopy (HRTEM) was to image the structure of two tetramethyl orthosilicate (TMOS) and two melamine-formaldehyde (MF) aerogels at the single polymer chain level{sup 1,2}. With this level of structural resolution we hoped to interrelate each aerogel's structure with its physical properties and its method of synthesis. Conventional single-step base catalysed TMOS aerogels show strings of spheroidal particles linked together with minimal necking. The spheroidal particles range from 86--132 {Angstrom} and average 113{plus minus}10 {Angstrom} in diameter{sup 2}. In contrast the TMOS aerogels reported on here were made by a two step method. After extended silica chains are grown in solution under acidic conditions with a substoichiometric amount of water, the reaction is stopped and the methanol hydrolysed from TMOS is removed. Then base catalysis and additional water are added to cause gel formation is a nonalcoholic solvent. The MF aerogels were prepared for HRTEM by fracturing them on a stereo microscope stage with razor knife so that fractured pieces with smooth flat surfaces could be selected for platinum-carbon replication. The two silica (TMOS) aerogels were both transparent and difficult to see. These aerogels were fractured on a stereo microscope stage with tweezers. 6 refs., 4 figs.

  20. High-resolution electron momentum spectroscopy of valence satellites of carbon disulfide

    NASA Astrophysics Data System (ADS)

    Huang, Chengwu; Shan, Xu; Zhang, Zhe; Wang, Enliang; Li, Zhongjun; Chen, XiangJun

    2010-09-01

    The binding energy spectrum of carbon disulphide (CS2) in the energy range of 9-23 eV has been measured by a high-resolution (e,2e) spectrometer employing asymmetric noncoplanar kinematics at an impact energy of 2500 eV plus the binding energy. Taking the advantage of the high energy resolution of 0.54 eV, four main peaks and five satellites in the outer-valence region are resolved. The assignments and pole strengths for these satellite states are achieved by comparing the experimental electron momentum profiles with the corresponding theoretical ones calculated using Hartree-Fock and density functional theory methods. The results are also compared in detail with the recent SAC-CI general-R calculations. General agreement is satisfactory, while the present experiment suggests cooperative contributions from Π2u, Σg+2 states to satellite 2 and Σg+2, Π2g states to satellite 3. Besides, relatively low pole strength for X Π2g state is obtained which contradicts all the theoretical calculations [2ph-TDA, ADC(3), SAC-CI general-R, ADC(4)] so far.

  1. A high-resolution coherent transition radiation diagnostic for laser-produced electron transport studies (invited)

    SciTech Connect

    Storm, M.; Begishev, I. A.; Brown, R. J.; Mileham, C.; Myatt, J. F.; Nilson, P. M.; Sangster, T. C.; Stoeckl, C.; Theobald, W.; Zuegel, J. D.; Guo, C.; Meyerhofer, D. D.

    2008-10-15

    High-resolution images of the rear-surface optical emission from high-intensity (I{approx}10{sup 19} W/cm{sup 2}) laser illuminated metal foils have been recorded using coherent transition radiation (CTR). CTR is generated as relativistic electrons, generated in high-intensity laser-plasma interactions, exit the target's rear surface and move into vacuum. A transition radiation diagnostic (TRD) records time-integrated images in a 24 nm bandwidth window around {lambda}=529 nm. The optical transmission at {lambda}=1053 nm, the laser wavelength, is 15 orders of magnitude lower than the transmission at the wavelength of interest, {lambda}=527 nm. The detector is a scientific grade charge-coupled device (CCD) camera that operates with a signal-to-noise ratio of 10{sup 3} and has a dynamic range of 10{sup 4}. The TRD has demonstrated a spatial resolution of 1.4 {mu}m over a 1 mm field of view, limited only by the CCD pixel size.

  2. Microstructure of massively transformed {gamma}-TiAl phase studied by high-resolution electron microscopy

    SciTech Connect

    Abe, E.; Kumagai, T.; Kajiwara, S.; Nakamura, M.

    1997-12-31

    A microstructure of the massively transformed {gamma}-TiAl ({gamma}{sub m}) phase in a Ti-48at.%Al alloy, which was heat treated in the high-temperature {alpha}-Ti (disordered hcp) single phase field (1,683 K), followed by ice water quenching, has been examined using high-resolution electron microscopy. The characteristic features of the microstructure originated from the {alpha}{yields}{gamma} massive transformation have been clarified in detail, which are as follows. (1) Extremely thin hcp plates (about 0.8--2nm in thickness), which are considered to be a retained {alpha} phase, are found to exist in the {gamma}{sub m} phase. (2) Twin boundaries are found to be not flat interfaces, that is, twin interfaces are not on the exact (111) mirror plane. This situation is attributed to the existence of a number of partial dislocations at the twin boundaries. (3) Antiphase relationship between the regions either side of the thin rotated domain wall is confirmed. The validity of this situation is explained by assuming that the thin rotated domain wall has been grown from a simple antiphase domain boundary. On the basis of these facts, mechanism of the {alpha}{yields}{gamma} massive transformation has been discussed.

  3. In-Situ High-Resolution Transmission Electron Microscopy Investigation of Overheating of Cu Nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Chunlin; Hu, Ziyu; Li, Yanfen; Liu, Limin; Mori, Hirotaro; Wang, Zhangchang

    2016-01-01

    Synthesizing and functionalizing metal nanoparticles supported on substrates is currently the subject of intensive study owing to their outstanding catalytic performances for heterogeneous catalysis. Revealing the fundamental effect of the substrates on metal nanoparticles represents a key step in clarifying mechanisms of stability and catalytic properties of these heterogeneous systems. However, direct identification of these effects still poses a significant challenge due to the complicacy of interactions between substrates and nanoparticles and also for the technical difficulty, restraining our understanding of these heterogeneous systems. Here, we combine in situ high-resolution transmission electron microscopy with molecular dynamics simulations to investigate Cu nanoparticles supported on graphite and Cu2O substrates, and demonstrate that melting behavior and thermal stability of Cu nanoparticles can be markedly influenced by substrates. The graphite-supported Cu nanoparticles do not melt during annealing at 1073 K until they vanish completely, i.e. only the sublimation occurs, while the Cu2O-supported Cu nanoparticles suffer melting during annealing at 973 K. Such selective superheating of the Cu nanoparticles can be attributed to the adsorption of a thin carbon layer on the surface of the Cu nanoparticles, which helps guide further stability enhancement of functional nanoparticles for realistic applications.

  4. High-Resolution Transmission Electron Microscopy Calibration of Critical Dimension (CD) Reference Materials

    SciTech Connect

    ALLEN, RICHARD A.; CRESSWELL, MICHAEL W.; EVERIST, SARAH C.; GHOSHTAGORE, RATHINDRA N.; HEADLEY, THOMAS J.; LINHOLM, LOREN W.

    1999-09-21

    NIST and Sandia have developed a procedure for producing and calibrating critical dimension (CD), or linewidth, reference materials. These reference materials will be used to calibrate metrology instruments used in semiconductor manufacturing. The artifacts, with widths down to 100 nm, are produced in monocrystalline silicon with all feature edges aligned to specific crystal planes. A two-part calibration of these linewidths is used: the primary calibration, with accuracy to within a few lattice plane thicknesses, is accomplished by counting the lattice planes across the sample as-imaged through use of high-resolution transmission electron microscopy (HRTEM). The secondary calibration is the high-precision electrical CD technique. NIST and Sandia are developing critical dimension (CD), or linewidth, reference materials for use by the semiconductor industry. To meet the current requirements of this rapidly changing industry, the widths of the reference features must be at or below the widths of the finest features in production and/or development. Further, these features must produce consistent results no matter which metrology tool (e.g., scanning electron microscope, scanned probe microscope, electrical metrology) is used to make the measurement. This leads to a requirement for the samples to have planar surfaces, known sidewall angles, and uniform material composition. None of the production techniques in use in semiconductor manufacturing can produce features with all these characteristics. In addition, requirements specified in the National Technology Roadmap for Semiconductors indicate that the width of the feature must be accurately calibrated to approximately 1-2 nm, a value well beyond the current capabilities of the instruments used for semiconductor metrology.

  5. Photonic, Electronic and Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    Plenary. Electron collisions - past, present and future / J. W. McConkey. Collisions of slow highly charged ions with surfaces / J. Burgdörfer ... [et al.]. Atomic collisions studied with "reaction-microscopes" / R. Moshammer ... [et al.]. Rydberg atoms: a microscale laboratory for studying electron-molecule tnteractions / F. B. Dunning -- Collisions involvintg photons. Quantum control of photochemical reaction dynamics and molecular functions / M. Yamaki ... [et al.]. Manipulating and viewing Rydberg wavepackets / R. R. Jones. Angle-resolved photoelectrons as a probe of strong-field interactions / M. Vrakking. Ultracold Rydberg atoms in a structured environment / I. C. H. Liu and J. M. Rost. Synchrotron-radiation-based recoil ion momentum spectroscopy of laser cooled and trapped cesium atoms / L. H. Coutinho. Reconstruction of attosecond pulse trains / Y. Mairesse ... [et al.]. Selective excitation of metastable atomic states by Femto- and attosecond laser pulses / A. D. Kondorskiy. Accurate calculations of triple differential cross sections for double photoionization of the hygrogen molecule / W. Vanroose ... [et al.]. Double and triple photoionization of Li and Be / J. Colgan, M. S. Pindzola and F. Robicheaux. Few/many body dynamics in strong laser fields / J. Zanghellini and T. Brabec. Rescattering-induced effects in electron-atom scattering in the presence of a circularly polarized laser field / A. V. Flegel ... [et al.]. Multidimensional photoelectron spectroscopy / P. Lablanquie ... [et al.]. Few photon and strongly driven transitions in the XUV and beyond / P. Lambropoulos, L. A. A. Nikolopoulos and S. I. Themelis. Ionization dynamics of atomic clusters in intense laser pulses / U. Saalmann and J. M. Rost. On the second order autocorrelation of an XUV attosecond pulse train / E. P. Benis ... [et al.]. Evidence for rescattering in molecular dissociation / I. D. Williams ... [et al.]. Photoionizing ions using synchrotron radiation / R. Phaneuf. Photo double

  6. High resolution infrared ``vision'' of dynamic electron processes in semiconductor devices (abstract)

    NASA Astrophysics Data System (ADS)

    Malyutenko, V. K.

    2003-01-01

    Infrared cameras have been traditionally used in semiconductor industry for noncontact measurements of printed circuit boards (PCBs) local overheating. While an effective way to prevent defective PCB application in a "find-problems-before-your-customer-do" manner, this conventional static (25-50 frames/s) and small spatial resolution (>100 μm) approach is incapable, in principle, of explaining the physical reason for the PCB failure. What follows in this report is the demonstration of an IR camera based new approach in high-resolution dynamic study of electron processes responsible for single device performance. More specifically, time resolved two-dimensional visualization of current carrier drift and diffusion processes across the device base that happen in microsecond scale is of prime concern in the work. Thus, contrary to the conventional visualization-through-heating measurements, objective is mapping of electron processes in a device base through negative and positive luminescence (provoked by band-to-band electron transitions) and nonequilibrium thermal emission (provoked by intraband electron transitions) studies inside the region in which current flows. Therefore, the parameters of interest are not only a device thermal mass and thermal conductance, but also free carrier lifetime, surface recombination velocity, diffusion length, and contact properties. The micro-mapping system developed consists of reflective type IR microscope coaxially attached to calibrated scanning IR thermal imaging cameras (3-5 and 8-12 μm spectral ranges, HgCdTe cooled photodetectors, scene spatial resolution of some 20 μm, minimum time resolved interval of 10 μs, and temperature resolution of about 0.5 °C at 30 °C). Data acquisition and image processing (emissivity equalization, noise reduction by image averaging, and external triggering) are computer controlled. Parallel video channel equipped with a CCD camera permits easy positioning and focusing of <1×1 mm2 object

  7. Magnetic dynamics studied by high-resolution electron spectroscopy and time-resolved electron microscopy

    NASA Astrophysics Data System (ADS)

    Jayaraman, Rajeswari

    Future information technology requires an increased magnetically encoded data density and novel electromagnetic modes of data transfer. While to date magnetic properties are observed and characterized mostly statically, the need emerges to monitor and capture their fast dynamics. In this talk, I will focus on the spin dynamics i.e. spin wave excitations and the dynamics of a new topological distribution of spins termed ``skyrmions''. Wave packets of spin waves offer the unique capability to transport a quantum bit, the spin, without the transport of charge or mass. Here, large wave-vector spin waves are of particular interest as they admit spin localization within a few nanometers. By using our recently developed electron energy loss spectrometer, we could study such spin waves in ultrathin films with an unprecedented energy resolution of 4 meV. By virtue of the finite penetration depth of low energy electrons, spin waves localized at interfaces between a substrate and a thin capping layer can be been studied yielding information about the exchange coupling between atoms at the interface. The quantization of spin waves with wave vectors perpendicular to the film gives rise to standing modes to which EELS has likewise access. Such studies when carried out as function of the film thickness again yield information on the layer dependence of the exchange coupling. Magnetic skyrmions are promising candidates as information carriers in logic or storage devices. Currently, little is known about the influence of disorder, defects, or external stimuli on the spatial distribution and temporal evolution of the skyrmion lattice. In this talk, I will describe the dynamical role of disorder in a large and flat thin film of Cu2OSeO3, exhibiting a skyrmion phase in an insulating material. We image up to 70,000 skyrmions by means of cryo-Lorentz Transmission Electron Microscopy as a function of the applied magnetic field. In the skyrmion phase, dislocations are shown to cause the

  8. Microstructure development in latex coatings: High-resolution cryo-scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Ge, Haiyan

    2005-07-01

    High-resolution cryogenic scanning electron microscopy (Cryo-SEM) was used to investigate microstructure development in drying latex coatings: from a colloidal stable suspension into a coherent strong film by drying. Useful sample preparation artifacts during the freeze-fracture, i.e., pullouts were documented and analyzed. Pullouts indicate both physical properties of latex particles and the drying stages in latex coatings. The mechanism of pullout formation was studied both theoretically and experimentally. Latex coatings must possess satisfactory freeze-thaw stability to avoid problems during transportation and storage in cold winter. The behavior of latex particles during freeze-thaw cycles was visualized by Cryo-SEM. The images indicated that high concentration of polymerizable surfactant in a latex suspension improved its freeze-thaw stability. In film formation, skinning was captured from edge in and top down in coatings of 80nm diameter styrene-butadiene latex particles with exceptional low Tg (-65°C). Effects on skinning of drying conditions and the way the latex was initially stabilized against flocculation were investigated. A skinned pocket was unexpectedly found in the coating. The cause of such a skin around the air bubble was explained by both simple models calculating the dissolution time and force analysis on the particles. The film formation processes in conventional and low volatile organic compound (VOC) latex coatings were compared by time-sectioning Cryo-SEM. Some low-VOC latex coatings were found to dry as fast as conventional ones without deteriorating final good film properties.

  9. High-resolution cryo-electron microscopy on macromolecular complexes and cell organelles.

    PubMed

    Hoenger, Andreas

    2014-03-01

    Cryo-electron microscopy techniques and computational 3-D reconstruction of macromolecular assemblies are tightly linked tools in modern structural biology. This symbiosis has produced vast amounts of detailed information on the structure and function of biological macromolecules. Typically, one of two fundamentally different strategies is used depending on the specimens and their environment. A: 3-D reconstruction based on repetitive and structurally identical unit cells that allow for averaging, and B: tomographic 3-D reconstructions where tilt-series between approximately ± 60 and ± 70° at small angular increments are collected from highly complex and flexible structures that are beyond averaging procedures, at least during the first round of 3-D reconstruction. Strategies of group A are averaging-based procedures and collect large number of 2-D projections at different angles that are computationally aligned, averaged together, and back-projected in 3-D space to reach a most complete 3-D dataset with high resolution, today often down to atomic detail. Evidently, success relies on structurally repetitive particles and an aligning procedure that unambiguously determines the angular relationship of all 2-D projections with respect to each other. The alignment procedure of small particles may rely on their packing into a regular array such as a 2-D crystal, an icosahedral (viral) particle, or a helical assembly. Critically important for cryo-methods, each particle will only be exposed once to the electron beam, making these procedures optimal for highest-resolution studies where beam-induced damage is a significant concern. In contrast, tomographic 3-D reconstruction procedures (group B) do not rely on averaging, but collect an entire dataset from the very same structure of interest. Data acquisition requires collecting a large series of tilted projections at angular increments of 1-2° or less and a tilt range of ± 60° or more. Accordingly, tomographic data

  10. Photonic, Electronic and Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    Plenary. Electron collisions - past, present and future / J. W. McConkey. Collisions of slow highly charged ions with surfaces / J. Burgdörfer ... [et al.]. Atomic collisions studied with "reaction-microscopes" / R. Moshammer ... [et al.]. Rydberg atoms: a microscale laboratory for studying electron-molecule tnteractions / F. B. Dunning -- Collisions involvintg photons. Quantum control of photochemical reaction dynamics and molecular functions / M. Yamaki ... [et al.]. Manipulating and viewing Rydberg wavepackets / R. R. Jones. Angle-resolved photoelectrons as a probe of strong-field interactions / M. Vrakking. Ultracold Rydberg atoms in a structured environment / I. C. H. Liu and J. M. Rost. Synchrotron-radiation-based recoil ion momentum spectroscopy of laser cooled and trapped cesium atoms / L. H. Coutinho. Reconstruction of attosecond pulse trains / Y. Mairesse ... [et al.]. Selective excitation of metastable atomic states by Femto- and attosecond laser pulses / A. D. Kondorskiy. Accurate calculations of triple differential cross sections for double photoionization of the hygrogen molecule / W. Vanroose ... [et al.]. Double and triple photoionization of Li and Be / J. Colgan, M. S. Pindzola and F. Robicheaux. Few/many body dynamics in strong laser fields / J. Zanghellini and T. Brabec. Rescattering-induced effects in electron-atom scattering in the presence of a circularly polarized laser field / A. V. Flegel ... [et al.]. Multidimensional photoelectron spectroscopy / P. Lablanquie ... [et al.]. Few photon and strongly driven transitions in the XUV and beyond / P. Lambropoulos, L. A. A. Nikolopoulos and S. I. Themelis. Ionization dynamics of atomic clusters in intense laser pulses / U. Saalmann and J. M. Rost. On the second order autocorrelation of an XUV attosecond pulse train / E. P. Benis ... [et al.]. Evidence for rescattering in molecular dissociation / I. D. Williams ... [et al.]. Photoionizing ions using synchrotron radiation / R. Phaneuf. Photo double

  11. High-resolution patterning of graphene by screen printing with a silicon stencil for highly flexible printed electronics.

    PubMed

    Hyun, Woo Jin; Secor, Ethan B; Hersam, Mark C; Frisbie, C Daniel; Francis, Lorraine F

    2015-01-01

    High-resolution screen printing of pristine graphene is introduced for the rapid fabrication of conductive lines on flexible substrates. Well-defined silicon stencils and viscosity-controlled inks facilitate the preparation of high-quality graphene patterns as narrow as 40 μm. This strategy provides an efficient method to produce highly flexible graphene electrodes for printed electronics. PMID:25377870

  12. The Application of High-Resolution Electron Microscopy to Problems in Solid State Chemistry: The Exploits of a Peeping TEM.

    ERIC Educational Resources Information Center

    Eyring, LeRoy

    1980-01-01

    Describes methods for using the high-resolution electron microscope in conjunction with other tools to reveal the identity and environment of atoms. Problems discussed include the ultimate structure of real crystalline solids including defect structure and the mechanisms of chemical reactions. (CS)

  13. Experimentally characterizing the electronic structures of f-electron systems using advanced high resolution Fourier transform microwave spectroscopies

    SciTech Connect

    Cooke, Stephen, A

    2013-02-03

    We aim to (i) provide data that directly addresses the fundamental roles of actinide valence electrons in chemical bonding, and (ii) serve to provide prototypical data for the heavy element computational chemistry community. These goals will be achieved through the first pure rotational spectroscopic measurements on prototypical systems at ultra-high resolution. These systems encompass low oxidation state uranium and thorium compounds including, but not limited to, UX and ThX, X = F, Cl, Br, I, and UY and ThY, Y = O, S, and other simple U and Th-containing compounds. Our primary experimental tools involve time-domain rotational spectroscopy achieving line widths and resolutions of a few kHz.

  14. Extended-range grazing-incidence spectrometer for high-resolution extreme ultraviolet measurements on an electron beam ion trap

    SciTech Connect

    Beiersdorfer, P.; Magee, E. W.; Brown, G. V.; Träbert, E.; Widmann, K.; Hell, N.

    2014-11-15

    A high-resolution grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for performing very high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Å to above 300 Å. The instrument operates without an entrance slit and focuses the light emitted by highly charged ions located in the roughly 50 μm wide electron beam onto a cryogenically cooled back-illuminated charge-coupled device detector. The measured line widths are below 0.025 Å above 100 Å, and the resolving power appears to be limited by the source size and Doppler broadening of the trapped ions. Comparisons with spectra obtained with existing grating spectrometers show an order of magnitude improvement in spectral resolution.

  15. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    SciTech Connect

    Hawryluk, A.M.; Ceglio, N.M.

    1991-04-10

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  16. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    DOEpatents

    Hawryluk, A.M.; Ceglio, N.M.

    1993-01-12

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  17. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    DOEpatents

    Hawryluk, Andrew M.; Ceglio, Natale M.

    1993-01-01

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  18. Contrast transfer and resolution limits for sub-angstrom high-resolution transmission electron microscopy.

    PubMed

    Lentzen, Markus

    2008-02-01

    The optimum imaging of an object structure at the sub-angstrom length scale requires precise adjustment of the lens aberrations of a high-resolution instrument up to the fifth order. A least-squares optimization of defocus aberration C1, third-order spherical aberration C3, and fifth-order spherical aberration C5 yields two sets of aberration coefficients for strong phase contrast up to the information limit: one for variable C1 and C3, at fixed C5, another for variable C1, C3, and C5. An additional correction to the defocus aberration, dependent on object thickness, is described, which becomes important for the use of image simulation programs in predicting optimum high-resolution contrast from thin objects at the sub-angstrom scale. For instruments with a sub-angstrom information limit the ultimate structure resolution, the power to resolve adjacent atom columns in a crystalline object, depends on both the instrumental pointspread and an object pointspread due to finite width of the atomic column potentials. A simulation study on a simple double-column model yields a range for structure resolutions, dependent on the atomic scattering power, from 0.070 nm down to 0.059 nm, for a hypothetical 300-kV instrument with an information limit of 0.050 nm. PMID:18096097

  19. Sample preparation of biological macromolecular assemblies for the determination of high-resolution structures by cryo-electron microscopy.

    PubMed

    Stark, Holger; Chari, Ashwin

    2016-02-01

    Single particle cryo-EM has recently developed into a powerful tool to determine the 3D structure of macromolecular complexes at near-atomic resolution, which allows structural biologists to build atomic models of proteins. All technical aspects of cryo-EM technology have been considerably improved over the last two decades, including electron microscopic hardware, image processing software and the ever growing speed of computers. This leads to a more widespread use of the technique, and it can be anticipated that further automation of electron microscopes and image processing tools will soon fully shift the focus away from the technological aspects, onto biological questions that can be answered. In single particle cryo-EM, no crystals of a macromolecule are required. In contrast to X-ray crystallography, this significantly facilitates structure determination by cryo-EM. Nevertheless, a relatively high level of biochemical control is still essential to obtain high-resolution structures by cryo-EM, and it can be anticipated that the success of the cryo-EM technology goes hand in hand with further developments of sample purification and preparation techniques. This will allow routine high-resolution structure determination of the many macromolecular complexes of the cell that until now represent evasive targets for X-ray crystallographers. Here we discuss the various biochemical tools that are currently available and the existing sample purification and preparation techniques for cryo-EM grid preparation that are needed to obtain high-resolution images for structure determination. PMID:26671943

  20. Comparative analysis of dioxins and furans in ambient air by high-resolution and electron-capture mass spectrometry

    SciTech Connect

    Koester, C.J.; Harless, R.L.; Hites, R.A.

    1992-01-01

    Known mixtures and unknown atmospheric sample extracts containing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) were analyzed by both electron impact, high resolution, mass spectrometry (HRMS) and by electron capture, negative ion, low resolution mass spectrometry (ECNI). PCDD/F concentrations measured by the two methods were comparable, typically agreeing with + or - 33%. The major difference between the two techniques is that HRMS easily detects 2,3,7,8- tetrachlorodibenzo-p-dioxin but ECNI does not. Results suggest that ECNI can be a sensitive low cost alternative to HRMS for the determination of PCDD/F concentrations.

  1. Strain measurement at the nanoscale: Comparison between convergent beam electron diffraction, nano-beam electron diffraction, high resolution imaging and dark field electron holography.

    PubMed

    Béché, A; Rouvière, J L; Barnes, J P; Cooper, D

    2013-08-01

    Convergent beam electron diffraction (CBED), nano-beam electron diffraction (NBED or NBD), high resolution imaging (HRTEM and HRSTEM) and dark field electron holography (DFEH or HoloDark) are five TEM based techniques able to quantitatively measure strain at the nanometer scale. In order to demonstrate the advantages and disadvantages of each technique, two samples composed of epitaxial silicon-germanium layers embedded in a silicon matrix have been investigated. The five techniques are then compared in terms of strain precision and accuracy, spatial resolution, field of view, mapping abilities and ease of performance and analysis. PMID:23673283

  2. THE APPLICATION OF HIGH RESOLUTION ELECTRON ENERGY LOSS SPECTROSCOPY TO THE CHARACTERIZATION OF ADSORBED MOLECULES ON RHODIUM SINGLE CRYSTAL SURFACES

    SciTech Connect

    Dubois, L.H.; Somorjai, G.A.

    1980-01-01

    The scattering of low energy electrons by metal surfaces has been studied for many years now. The electron's ease of generation and detection and high surface sensitivity (low penetration depth) make it an ideal probe for surface scientists. The impinging electron can interact with the surface in basically two ways: it can either elastically reflect (or diffract) from the surface without losing energy or lose a portion of it's incident energy and inelastically scatter. In this paper we will be concerned with only one of many possible inelastic scattering processes: the loss of the electron's energy to the vibrational modes of atoms and molecules chemisorbed on the surface. This technique is known as high resolution electron energy loss spectroscopy (or ELS, EELS, HRELS, HREELS, etc.).

  3. Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques†

    PubMed Central

    Plascencia-Villa, Germán; Starr, Clarise R.; Armstrong, Linda S.; Ponce, Arturo

    2016-01-01

    Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO2, TiO2 and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO2 and TiO2, whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution. PMID:23023106

  4. Metal-carbonyl organometallic polymers, PFpP, as resists for high-resolution positive and negative electron beam lithography.

    PubMed

    Zhang, J; Cao, K; Wang, X S; Cui, B

    2015-12-25

    Metal-containing resists for electron beam lithography (EBL) are attracting attention owing to their high dry etching resistance and possibility for directly patterning metal-containing nanostructures. The newly developed organometallic metal carbonyl polymers, PFpP, can function as EBL resists with strong etching resistance. One significant feature of the PFpP resist is its high resolution. Line arrays with line-widths as narrow as 17 nm have been created. The resist can also be used in positive tone. PMID:26481609

  5. Method and apparatus for a high-resolution three dimensional confocal scanning transmission electron microscope

    DOEpatents

    de Jonge, Niels [Oak Ridge, TN

    2010-08-17

    A confocal scanning transmission electron microscope which includes an electron illumination device providing an incident electron beam propagating in a direction defining a propagation axis, and a precision specimen scanning stage positioned along the propagation axis and movable in at least one direction transverse to the propagation axis. The precision specimen scanning stage is configured for positioning a specimen relative to the incident electron beam. A projector lens receives a transmitted electron beam transmitted through at least part of the specimen and focuses this transmitted beam onto an image plane, where the transmitted beam results from the specimen being illuminated by the incident electron beam. A detection system is placed approximately in the image plane.

  6. Principles and prospects of direct high resolution electron image acquisition with CMOS detectors at low energies

    NASA Astrophysics Data System (ADS)

    Faruqi, A. R.

    2009-08-01

    Two types of direct electron detectors, potentially useful in low energy electron microscopy and photoemission electron microscopy (LEEM/PEEM) experiments, are reviewed in this paper. Hybrid pixel detectors, using a silicon sensor and based on Medipix2 offer a high detective quantum efficiency, due to an essentially noiseless readout, but are technically challenging. Backthinned monolithic active pixel sensors (MAPS) are not noise-free but have other advantages as discussed in this review.

  7. High-resolution error detection in the capture process of a single-electron pump

    NASA Astrophysics Data System (ADS)

    Giblin, S. P.; See, P.; Petrie, A.; Janssen, T. J. B. M.; Farrer, I.; Griffiths, J. P.; Jones, G. A. C.; Ritchie, D. A.; Kataoka, M.

    2016-01-01

    The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential barrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum point contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in a GaAs heterostructure. Using a two-step measurement protocol to compensate for 1/f noise in the QPC current, and repeating the protocol more than 106 times, we are able to resolve errors with probabilities of order 10 - 6 . For the studied sample, one-electron capture is affected by errors in ˜ 30 out of every million cycles, while two-electron capture was performed more than 106 times with only one error. For errors in one-electron capture, we detect both failure to capture an electron and capture of two electrons. Electron counting measurements are a valuable tool for investigating non-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy of semiconductor electron pumps.

  8. The potential for Bayesian compressive sensing to significantly reduce electron dose in high-resolution STEM images.

    PubMed

    Stevens, Andrew; Yang, Hao; Carin, Lawrence; Arslan, Ilke; Browning, Nigel D

    2014-02-01

    The use of high-resolution imaging methods in scanning transmission electron microscopy (STEM) is limited in many cases by the sensitivity of the sample to the beam and the onset of electron beam damage (for example, in the study of organic systems, in tomography and during in situ experiments). To demonstrate that alternative strategies for image acquisition can help alleviate this beam damage issue, here we apply compressive sensing via Bayesian dictionary learning to high-resolution STEM images. These computational algorithms have been applied to a set of images with a reduced number of sampled pixels in the image. For a reduction in the number of pixels down to 5% of the original image, the algorithms can recover the original image from the reduced data set. We show that this approach is valid for both atomic-resolution images and nanometer-resolution studies, such as those that might be used in tomography datasets, by applying the method to images of strontium titanate and zeolites. As STEM images are acquired pixel by pixel while the beam is scanned over the surface of the sample, these postacquisition manipulations of the images can, in principle, be directly implemented as a low-dose acquisition method with no change in the electron optics or the alignment of the microscope itself. PMID:24151325

  9. High-resolution imaging by scanning electron microscopy of semithin sections in correlation with light microscopy.

    PubMed

    Koga, Daisuke; Kusumi, Satoshi; Shodo, Ryusuke; Dan, Yukari; Ushiki, Tatsuo

    2015-12-01

    In this study, we introduce scanning electron microscopy (SEM) of semithin resin sections. In this technique, semithin sections were adhered on glass slides, stained with both uranyl acetate and lead citrate, and observed with a backscattered electron detector at a low accelerating voltage. As the specimens are stained in the same manner as conventional transmission electron microscopy (TEM), the contrast of SEM images of semithin sections was similar to TEM images of ultrathin sections. Using this technique, wide areas of semithin sections were also observed by SEM, without the obstruction of grids, which was inevitable for traditional TEM. This study also applied semithin section SEM to correlative light and electron microscopy. Correlative immunofluorescence microscopy and immune-SEM were performed in semithin sections of LR white resin-embedded specimens using a FluoroNanogold-labeled secondary antibody. Because LR white resin is hydrophilic and electron stable, this resin is suitable for immunostaining and SEM observation. Using correlative microscopy, the precise localization of the primary antibody was demonstrated by fluorescence microscopy and SEM. This method has great potential for studies examining the precise localization of molecules, including Golgi- and ER-associated proteins, in correlation with LM and SEM. PMID:26206941

  10. Sixteenth International Conference on the physics of electronic and atomic collisions

    SciTech Connect

    Dalgarno, A.; Freund, R.S.; Lubell, M.S.; Lucatorto, T.B.

    1989-01-01

    This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter.

  11. High resolution low-energy electron attachment to CF3I

    NASA Astrophysics Data System (ADS)

    Marienfeld, S.; Fabrikant, I. I.; Braun, M.; Ruf, M.-W.; Hotop, H.

    2006-01-01

    Using several variants of the laser photoelectron attachment method, we have measured the energy-dependent yield for I- formation resulting from dissociative electron attachment (DEA) to CF3I molecules over the energy range 0.5-500 meV. One approach involved a static target gas (TG = 300 K) and pulsed electron production/anion extraction. In another approach, a collimated target was provided by a differentially pumped, seeded supersonic beam (10% CF3I in helium carrier gas, stagnation pressure 1 bar, nozzle temperature 300 K and 600 K). At the onsets for excitation of one and two quanta for the C-I stretching mode ν3, clear downward cusps are detected. With reference to the recommended thermal DEA rate coefficient kA(Te = TG = 300 K) = 1.9 × 10-7 cm3 s-1, a new highly resolved absolute cross section for I- formation has been determined. Our experimental results are well reproduced by a cross section calculated in the framework of the resonance R-matrix theory. The input for the theory includes the known energetic and structural parameters of the neutral molecule and its anion and adopts a revised vertical attachment energy and a surface amplitude chosen to reproduce the thermal DEA rate coefficient. The theory is also applied to predict absolute cross sections for vibrational excitation of the C-I stretching mode ν3. Using our experimental and theoretical DEA cross sections we derive rate coefficients for Rydberg electron transfer (RET) and the dependence of the rate coefficients for free electron attachment of a Maxwellian electron ensemble on the mean electron energy from 0.002 to 2 eV at the constant gas temperature TG = 300 K; in both cases good agreement is observed with direct RET and swarm measurements.

  12. Inner-shell excitations of krypton 3d investigated by electron impact with high resolution

    SciTech Connect

    Yuan Zhensheng; Zhu Linfan; Liu Xiaojing; Li Wenbin; Cheng Huadong; Sun Jianmin; Xu Kezun

    2005-06-15

    The inner-shell excitation spectra of krypton 3d electrons were measured at scattering angles of 0 deg. and 4 deg. by a fast-electron energy-loss spectrometer at an incident energy of 2.5 keV with an energy resolution better than 80 meV. Some interesting optically forbidden transitions were observed and the natural widths of the optically allowed and optically forbidden transitions were analyzed. It shows that the natural widths for the resonances having the same core hole are nearly equal, no matter whether they are optically allowed, optically forbidden, or different members of a Rydberg series.

  13. Electron Paramagnetic Resonance: A High-Resolution Tool for Muscle Physiology

    PubMed Central

    Thompson, LaDora V.; Lowe, Dawn A.; Ferrington, Deborah A.; Thomas, David D.

    2015-01-01

    Skeletal muscle function can be altered by changes in protein structure and motion. Electron paramagnetic resonance (EPR) paired with site-directed spin labeling has been used to study the relationships between (a) muscle force and myosin structure and (b) muscle relaxation and Ca-ATPase motion and structure. PMID:11210444

  14. Virtual nanoscopy: Generation of ultra-large high resolution electron microscopy maps

    PubMed Central

    Avramut, M. Cristina; M. van den Berg, Bernard; Mommaas, A. Mieke; Koster, Abraham J.

    2012-01-01

    A key obstacle in uncovering the orchestration between molecular and cellular events is the vastly different length scales on which they occur. We describe here a methodology for ultrastructurally mapping regions of cells and tissue as large as 1 mm2 at nanometer resolution. Our approach employs standard transmission electron microscopy, rapid automated data collection, and stitching to create large virtual slides. It greatly facilitates correlative light-electron microscopy studies to relate structure and function and provides a genuine representation of ultrastructural events. The method is scalable as illustrated by slides up to 281 gigapixels in size. Here, we applied virtual nanoscopy in a correlative light-electron microscopy study to address the role of the endothelial glycocalyx in protein leakage over the glomerular filtration barrier, in an immunogold labeling study of internalization of oncolytic reovirus in human dendritic cells, in a cryo-electron microscopy study of intact vitrified mouse embryonic cells, and in an ultrastructural mapping of a complete zebrafish embryo slice. PMID:22869601

  15. Understanding the structure of nanocatalysts with high resolution scanning/transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Francis, L. D.; Rivas, J.; José-Yacamán, M.

    2014-03-01

    Nanomaterials including nanoparticles, nanowires and nanotubes play an important role in heterogeneous catalysis. Thanks to the rapid improvement of the electron microscopic techniques and with the advent of aberration corrected electron microscopy as well as theoretical methodologies, the potential effects induced by nanocatalysts are better understood than before by unravelling their atomic structure. A brief introduction to advanced electron microscopic techniques namely aberration corrected scanning transmission electron microscopy (Cs-STEM) is presented and subsequently two examples of nanocatalysts are considered in the present review. The first example will focus on the study of bimetallic/core-shell nanoalloys. In heterogeneous catalysis, catalysts containing two or more metals might show significantly different catalytic properties compared to the parent metals and thus are widely utilized in several catalytic reactions. Atom-by-atom insights of the nanoalloy based catalysts ex: Au-Pd will be described in the present review using a combination of advanced electron microscopic and spectroscopic techniques. A related example on the understanding of bimetallic clusters by HAADF-STEM will also be presented in addition to nanoparticles. In the second case understanding the structure of transition metal chalcogenide based nanocatalysts by HRTEM and aberration corrected STEM, for the case of MoS2 will be discussed. MoS2-based catalysts serve as model catalysts and are employed in the hydrodesulphurisations (HDS) reactions in the removal of sulphur from gasoline and related petrochemical products. They have been studied in various forms including nanowires, nanotubes and nanoplates. Their structure, atomic insights and as a consequence elucidation of their corresponding catalytic activity are thus important.

  16. Spontaneous Patterning of High-Resolution Electronics via Parallel Vacuum Ultraviolet.

    PubMed

    Liu, Xuying; Kanehara, Masayuki; Liu, Chuan; Sakamoto, Kenji; Yasuda, Takeshi; Takeya, Jun; Minari, Takeo

    2016-08-01

    A spontaneous patterning technique via parallel vacuum ultraviolet is developed for fabricating large-scale, complex electronic circuits with 1 μm resolution. The prepared organic thin-film transistors exhibit a low contact resistance of 1.5 kΩ cm, and high mobilities of 0.3 and 1.5 cm(2) V(-1) s(-1) in the devices with channel lengths of 1 and 5 μm, respectively. PMID:27184834

  17. High-resolution in situ observations of electron precipitation-causing EMIC waves

    SciTech Connect

    Rodger, Craig J.; Hendry, Aaron T.; Clilverd, Mark A.; Kletzing, Craig A.; Brundell, James B.; Reeves, Geoffrey D.

    2015-11-21

    Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced electron precipitation inferred from coincident precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. As a result, these observations will better constrain modeling into the importance of EMIC wave-particle interactions.

  18. High-resolution in situ observations of electron precipitation-causing EMIC waves

    DOE PAGESBeta

    Rodger, Craig J.; Hendry, Aaron T.; Clilverd, Mark A.; Kletzing, Craig A.; Brundell, James B.; Reeves, Geoffrey D.

    2015-11-21

    Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size,more » and energy range of EMIC-induced electron precipitation inferred from coincident precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. As a result, these observations will better constrain modeling into the importance of EMIC wave-particle interactions.« less

  19. Acquisition of a High Resolution Field Emission Scanning Electron Microscope for the Analysis of Returned Samples

    NASA Technical Reports Server (NTRS)

    Nittler, Larry R.

    2003-01-01

    This grant furnished funds to purchase a state-of-the-art scanning electron microscope (SEM) to support our analytical facilities for extraterrestrial samples. After evaluating several instruments, we purchased a JEOL 6500F thermal field emission SEM with the following analytical accessories: EDAX energy-dispersive x-ray analysis system with fully automated control of instrument and sample stage; EDAX LEXS wavelength-dispersive x-ray spectrometer for high sensitivity light-element analysis; EDAX/TSL electron backscatter diffraction (EBSD) system with software for phase identification and crystal orientation mapping; Robinson backscatter electron detector; and an in situ micro-manipulator (Kleindiek). The total price was $550,000 (with $150,000 of the purchase supported by Carnegie institution matching funds). The microscope was delivered in October 2002, and most of the analytical accessories were installed by January 2003. With the exception of the wavelength spectrometer (which has been undergoing design changes) everything is working well and the SEM is in routine use in our laboratory.

  20. Development of an Apparatus for High-Resolution Auger Photoelectron Coincidence Spectroscopy (APECS) and Electron Ion Coincidence (EICO) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kakiuchi, Takuhiro; Hashimoto, Shogo; Fujita, Narihiko; Mase, Kazuhiko; Tanaka, Masatoshi; Okusawa, Makoto

    We have developed an electron electron ion coincidence (EEICO) apparatus for high-resolution Auger photoelectron coincidence spectroscopy (APECS) and electron ion coincidence (EICO) spectroscopy. It consists of a coaxially symmetric mirror electron energy analyzer (ASMA), a miniature double-pass cylindrical mirror electron energy analyzer (DP-CMA), a miniature time-of-flight ion mass spectrometer (TOF-MS), a magnetic shield, an xyz stage, a tilt-adjustment mechanism, and a conflat flange with an outer diameter of 203 mm. A sample surface was irradiated by synchrotron radiation, and emitted electrons were energy-analyzed and detected by the ASMA and the DP-CMA, while desorbed ions were mass-analyzed and detected by the TOF-MS. The performance of the new EEICO analyzer was evaluated by measuring Si 2p photoelectron spectra of clean Si(001)-2×1 and Si(111)-7×7, and by measuring Si-L23VV-Si-2p Auger photoelectron coincidence spectra (Si-L23VV-Si-2p APECS) of clean Si(001)-2×1.

  1. Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

    SciTech Connect

    Swadling, G. F.; Lebedev, S. V.; Burdiak, G.; Suttle, L.; Patankar, S.; Smith, R. A.; Bennett, M.; Hall, G. N.; Suzuki-Vidal, F.; Bland, S.; Harvey-Thompson, A. J.; Rozmus, W.; Yuan, J.

    2015-07-15

    An optical Thomson scattering diagnostic has been used to investigate collisions between supersonic, magnetized plasma flows, in particular the transition from collisionless to collisional interaction dynamics. These flows were produced using tungsten wire array z-pinches, driven by the 1.4 MA 240 ns Magpie generator at Imperial College London. Measurements of the collective-mode Thomson scattering ion-feature clearly indicate that the ablation flows are interpenetrating at 100 ns (after current start), and this interpenetration continues until at least 140 ns. The Thomson spectrum at 150 ns shows a clear change in the dynamics of the stream interactions, transitioning towards a collisional, shock-like interaction of the streams near the axis. The Thomson scattering data also provide indirect evidence of the presence of a significant toroidal magnetic field embedded in the “precursor” plasma near the axis of the array over the period 100–140 ns; these observations are in agreement with previous measurements [Swadling et al., Phys. Rev. Lett. 113, 035003 (2014)]. The Thomson scattering measurements at 150 ns suggest that this magnetic field must collapse at around the time the dense precursor column begins to form.

  2. Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

    NASA Astrophysics Data System (ADS)

    Swadling, G. F.; Lebedev, S. V.; Harvey-Thompson, A. J.; Rozmus, W.; Burdiak, G.; Suttle, L.; Patankar, S.; Smith, R. A.; Bennett, M.; Hall, G. N.; Suzuki-Vidal, F.; Bland, S.; Yuan, J.

    2015-07-01

    An optical Thomson scattering diagnostic has been used to investigate collisions between supersonic, magnetized plasma flows, in particular the transition from collisionless to collisional interaction dynamics. These flows were produced using tungsten wire array z-pinches, driven by the 1.4 MA 240 ns Magpie generator at Imperial College London. Measurements of the collective-mode Thomson scattering ion-feature clearly indicate that the ablation flows are interpenetrating at 100 ns (after current start), and this interpenetration continues until at least 140 ns. The Thomson spectrum at 150 ns shows a clear change in the dynamics of the stream interactions, transitioning towards a collisional, shock-like interaction of the streams near the axis. The Thomson scattering data also provide indirect evidence of the presence of a significant toroidal magnetic field embedded in the "precursor" plasma near the axis of the array over the period 100-140 ns; these observations are in agreement with previous measurements [Swadling et al., Phys. Rev. Lett. 113, 035003 (2014)]. The Thomson scattering measurements at 150 ns suggest that this magnetic field must collapse at around the time the dense precursor column begins to form.

  3. Observation of Shock-Induced Phases of Nb2O5 Single Crystal under High-Resolution Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Kikuchi, Masae; Kusaba, Keiji; Bannai, Eisuke; Fukuoka, Kiyoto; Syono, Yasuhiko; Hiraga, Kenji

    1985-12-01

    Shock-loading experiments on Nb2O5 single crystals were carried out up to 54 GPa by the gun method. The shock-loaded materials are recovered by using both closed and open recovery fixtures and were examined by powder X-ray diffraction analysis and high-resolution electron microscopy. Complete conversion to T-Nb2O5 of μm size, denser by 12% than H-Nb2O5, was found in the pressure range from 20-40 GPa. When single-crystal H-Nb2O5 was shocked perpendicular to the b-axis using the open-system recovery fixture, an unidentified phase referred to as the X-phase, besides T-Nb2O5 and shock-reduced NbxO2 with the rutile structure, was observed. The high-resolution image of the X-phase is interpreted as two-dimensionally disordered H-Nb2O5. The X-phase is probably formed in the rapid decompression process from the shock-induced high-pressure phase.

  4. High-Resolution {alpha} and Electron Spectroscopy of {sup 249}{sub 98}Cf

    SciTech Connect

    Ahmad, I.; Greene, J. P.; Kondev, F. G.; Zhu, S.

    2015-04-13

    alpha-particle spectra of Cf-249 have been measured with a double-focusing magnetic spectrometer and with passivated implanted planar silicon (PIPS) detectors. The conversion-electron spectra of Cf-249 have been measured with a cooled Si(Li) detector and with a room-temperature PIPS detector. Precise energies of a groups in the decay of Cf-249 have been measured with respect to the known energy of Cf-250. In addition, alpha-electron, alpha-gamma, and gamma-gamma coincidence measurements were also performed to determine the spin-parity of the previously known 643.64-keV level. From electron intensities, conversion coefficients of transitions in the daughter Cm-245 have been determined. The measured L-3 conversion coefficients of the 333.4- and 388.2-keV transitions are found to be in agreement with the theoretical conversion coefficients for pure E1 multipolarity. On the other hand, the K, L-1 + L-2, M, and N conversion coefficients are approximately twice the theoretical values for pure E1 transitions. These measurements indicate anomalous E1 conversion coefficients for the 333.4- and 388.2-keV transitions, as has been pointed out in earlier measurements. The measured conversion coefficient of the 255.5-keV transition gives an M1 multipolarity for this transition which establishes a spin-parity of 7/2(-) and the 7/2(-)[743] single-particle assignment to the 643.64-keV level.

  5. Carbon Nanostructure Examined by Lattice Fringe Analysis of High Resolution Transmission Electron Microscopy Images

    NASA Technical Reports Server (NTRS)

    VanderWal, Randy L.; Tomasek, Aaron J.; Street, Kenneth; Thompson, William K.; Hull, David R.

    2003-01-01

    The dimensions of graphitic layer planes directly affect the reactivity of soot towards oxidation and growth. Quantification of graphitic structure could be used to develop and test correlations between the soot nanostructure and its reactivity. Based upon transmission electron microscopy images, this paper provides a demonstration of the robustness of a fringe image analysis code for determining the level of graphitic structure within nanoscale carbon, i.e., soot. Results, in the form of histograms of graphitic layer plane lengths, are compared to their determination through Raman analysis.

  6. Carbon Nanostructure Examined by Lattice Fringe Analysis of High Resolution Transmission Electron Microscopy Images

    NASA Technical Reports Server (NTRS)

    VanderWal, Randy L.; Tomasek, Aaron J.; Street, Kenneth; Thompson, William K.

    2002-01-01

    The dimensions of graphitic layer planes directly affect the reactivity of soot towards oxidation and growth. Quantification of graphitic structure could be used to develop and test correlations between the soot nanostructure and its reactivity. Based upon transmission electron microscopy images, this paper provides a demonstration of the robustness of a fringe image analysis code for determining the level of graphitic structure within nanoscale carbon, i.e. soot. Results, in the form of histograms of graphitic layer plane lengths, are compared to their determination through Raman analysis.

  7. Recent Developments of an Opto-Electronic THz Spectrometer for High-Resolution Spectroscopy

    PubMed Central

    Hindle, Francis; Yang, Chun; Mouret, Gael; Cuisset, Arnaud; Bocquet, Robin; Lampin, Jean-François; Blary, Karine; Peytavit, Emilien; Akalin, Tahsin; Ducournau, Guillaume

    2009-01-01

    A review is provided of sources and detectors that can be employed in the THz range before the description of an opto-electronic source of monochromatic THz radiation. The realized spectrometer has been applied to gas phase spectroscopy. Air-broadening coefficients of HCN are determined and the insensitivity of this technique to aerosols is demonstrated by the analysis of cigarette smoke. A multiple pass sample cell has been used to obtain a sensitivity improvement allowing transitions of the volatile organic compounds to be observed. A solution to the frequency metrology is presented and promises to yield accurate molecular line center measurements. PMID:22291552

  8. High-resolution width-modulated pulse rebalance electronics for strapdown gyroscopes and accelerometers

    NASA Technical Reports Server (NTRS)

    Kennedy, E. J.; Blalock, T. V.; Bryan, W. L.; Rush, K.

    1974-01-01

    Three different rebalance electronic loops were designed, implemented, and evaluated. The loops were width-modulated binary types using a 614.4 kHz keying signal; they were developed to accommodate the following three inertial sensors with the indicated resolution values: (1) Kearfott 2412 accelerometer - resolution = 260 micro-g/data pulse, (2) Honeywell GG334 gyroscope - resolution = 3.9 milli-arc-sec/data pulse, (3) Kearfott 2401-009 accelerometer - resolution = 144 milli-g/data pulse. Design theory, details of the design implementation, and experimental results for each loop are presented.

  9. In-situ measurement of objective lens data of a high-resolution electron microscope.

    NASA Technical Reports Server (NTRS)

    Heinemann, K.

    1971-01-01

    Bragg-reflex images of small individual crystallites in the size range of 20-100 A diameter with known crystallographic orientation were used in a transmission electron microscope to determine in-situ: (a) the relationship between objective lens current (or accelerating voltage) changes in discrete steps and corresponding defocus, (b) the spherical aberration coefficient, and (c) the axial chromatic aberration coefficient of the objective lens. The accuracy of the described method is better than 5%. The same specimen can advantageously be used to properly aline the illuminating beam with respect to the optical axis.

  10. High-resolution patterning electronic polymers using dopant induced solubility control (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Moule, Adam J.; Jacobs, Ian E.; Li, Jun; Burg, Stephanie L.; Bilsky, David J.; Rotondo, Brandon T.; Stroeve, Pieter

    2015-08-01

    Organic electronics promise to provide flexible, large-area circuitry such as photovoltaics, displays, and light emitting diodes that can be fabricated inexpensively from solutions. A major obstacle to this vision is that most conjugated organic materials are miscible, making solution-based fabrication of multilayer or micro- to nanoscale patterned films problematic. Here we demonstrate that the solubility of prototypical conductive polymer poly(3-hexylthiophene) (P3HT) can be reversibly "switched off" using high electron affinity molecular dopants, then later recovered with light or a suitable dedoping solution. Using this technique, we are able to stack mutually soluble materials and laterally pattern polymer films using evaporation of dopants through a shadow mask or with light, achieving sub-micrometer, optically limited feature sizes. After forming these structures, the films can be dedoped without disrupting the patterned features; dedoped films have identical optical characteristics, charge carrier mobilities, and NMR spectra as as-cast P3HT films. This method greatly simplifies solution-based device fabrication, is easily adaptable to current manufacturing workflows, and is potentially generalizable to other classes of materials.

  11. High resolution patterning for flexible electronics via roll-to-roll nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Sabik, Sami; de Riet, Joris; Yakimets, Iryna; Smits, Edsger

    2014-03-01

    Flexible electronics is a growing field and is currently maturing in applications such as displays, smart packaging, organic light-emitting diodes and organic photovoltaic cells. In order to process on flexible substrates at high throughput and large areas, novel patterning techniques will be essential. Conventional optical lithography is limited in throughput as well as resolution, and requires several alignment steps to generate multi-layered patterns, required for applications such as thin-film transistors. It therefore remains a complex and expensive process. Nanoimprint lithography is an emerging alternative to optical lithography, demonstrating patterning capabilities over a wide range of resolutions, from several microns down to a few nanometres. For display applications, nanoimprint lithography can be used to pattern various layers. Micron sized thin-film transistors for backplane can be fabricated where a self-aligned geometry is used to decrease the number of alignment steps, and increase the overlay accuracy. In addition, nano-structures can be used for optical applications such as anti-reflective surfaces and nano patterned transparent electrodes. Imprint lithography is a fully roll-to-roll compatible process and enables large area and high throughput fabrication for flexible electronics. In this paper we discuss the possibilities and the challenges of large area patterning by roll-to-roll nanoimprint lithography, reviewing micron and nano sized structures realized on our roll-to-roll equipment. Nano patterned transparent electrodes, moth-eye antireflective coatings, and multilevel structures will be covered.

  12. Electron-atom /molecule/ collision processes

    NASA Technical Reports Server (NTRS)

    Trajmar, S.

    1980-01-01

    Electron-atom (molecule) collision processes at low and intermediate energies, from near threshold to a few hundred electron volts, are discussed. Attention is given to experimental techniques and procedures, electron impact cross sections, impact excitation and electron-atom scattering in laser fields. Specific examples are presented that illustrate various experimental techniques and interpretations of observations.

  13. Observation of New Hollow States of Li^+ in High-Resolution Electron-Spectroscopy Experiments

    NASA Astrophysics Data System (ADS)

    Diehl, S.; Cubaynes, D.; Bizau, J.-M.; Wuilleumier, F. J.; Mosnier, J.-P.; Kennedy, E. T.

    1998-05-01

    Using the synchrotron radiation emitted by the Super-ACO storage ring in Orsay and an electron spectrometer with decelerating optics, we have observed new highly-excited (2l,3l') and (2l, 4l'') hollow states of the singly-charged lithium ion. They were observed in the second step of the autoionization decay of atomic hollow states created by photoexcitation of lithium atoms at excitation energies below the triple-ionization potential (203 eV), and after direct ionization into the continuum at photon energies above 203 eV . We have measured the energies and widths of the new states, and found that they are in excellent agreement with theoretical calculations by K. T. Chung using the saddle point approximation.

  14. Preparation of the planarian Schmidtea mediterranea for high-resolution histology and transmission electron microscopy

    PubMed Central

    Brubacher, John L.; Vieira, Ana P.; Newmark, Phillip A.

    2014-01-01

    The flatworm Schmidtea mediterranea is an emerging model species in such fields as stem-cell biology, regeneration, and evolutionary biology. Excellent molecular tools have been developed for S. mediterranea, but ultrastructural techniques have received far less attention. Processing specimens for histology and transmission electron microscopy is notoriously idiosyncratic for particular species or specimen types. Unfortunately however, most methods for S. mediterranea described in the literature lack numerous essential details, and those few that do provide them rely on specialized equipment that may not be readily available. Here we present an optimized protocol for ultrastructural preparation of S. mediterranea. The protocol can be completed in six days, much of which is “hands-off” time. To aid with troubleshooting, we also illustrate the significant effects of seemingly minor variations in fixative, buffer concentration, and dehydration steps. This procedure will be useful for all planarian researchers, particularly those with relatively little experience in tissue processing. PMID:24556788

  15. Simulation of High Resolution Vibrational and Electronic Spectra with a Multifrequency Virtual Spectrometer

    NASA Astrophysics Data System (ADS)

    Biczysko, Malgorzata; Bloino, Julien; Barone, Vincenzo

    2013-06-01

    Moving from the common practice of extracting numerical data from experiment to be compared with quantum mechanical (QM) results toward a direct vis-à-vis} comparison of experimental and simulated spectra would strongly reduce any arbitrariness in analysis of complex experimental outcomes and allow a proper account of the information connected to both position and shape of spectral bands. The development of such ``virtual ab initio spectrometers'' for a wide range of wavelengths has been one of our major research goals in the last years [1,2]. Recent methodological advances from our group allow simulation of optical (IR, Raman, UV-vis, etc.) spectra line-shapes for medium-to-large closed- and open-shell molecular systems. Vibrational spectra are computed including anharmonicities through perturbative corrections while electronic spectra line-shapes are simulated accounting for the vibrational structure. Well resolved and accurate theoretical spectra provide data as close as possible to the results directly available from experiment allowing to avoid ambiguities in analysis of the latter. Several examples illustrating interpretation, assignment or revision of experimental spectra for prototypes of bio-molecular systems (phenyl radical, glycine, thymine, pyrimidine, anisole dimer) will be presented. 1. V. Barone, A. Baiardi, M. Biczysko, J. Bloino, C. Cappelli, F. Lipparini Phys. Chem. Chem. Phys, 14, 12404, 2012 2. M. Biczysko, J. Bloino, G. Brancato, et al. Theor. Chem. Acc. 113, 1201, 2012

  16. Extended depth of field for high-resolution scanning transmission electron microscopy.

    PubMed

    Hovden, Robert; Xin, Huolin L; Muller, David A

    2011-02-01

    Aberration-corrected scanning transmission electron microscopes (STEMs) provide sub-Angstrom lateral resolution; however, the large convergence angle greatly reduces the depth of field. For microscopes with a small depth of field, information outside of the focal plane quickly becomes blurred and less defined. It may not be possible to image some samples entirely in focus. Extended depth-of-field techniques, however, allow a single image, with all areas in focus, to be extracted from a series of images focused at a range of depths. In recent years, a variety of algorithmic approaches have been employed for bright-field optical microscopy. Here, we demonstrate that some established optical microscopy methods can also be applied to extend the ∼ 6 nm depth of focus of a 100 kV 5th-order aberration-corrected STEM (α max = 33 mrad) to image Pt-Co nanoparticles on a thick vulcanized carbon support. These techniques allow us to automatically obtain a single image with all the particles in focus as well as a complimentary topography map. PMID:21122192

  17. Extended Depth of Field for High-Resolution Scanning Transmission Electron Microscopy

    SciTech Connect

    Hovden, Robert; Xin, Huolin L.; Muller, David A.

    2010-12-02

    Aberration-corrected scanning transmission electron microscopes (STEMs) provide sub-Angstrom lateral resolution; however, the large convergence angle greatly reduces the depth of field. For microscopes with a small depth of field, information outside of the focal plane quickly becomes blurred and less defined. It may not be possible to image some samples entirely in focus. Extended depth-of-field techniques, however, allow a single image, with all areas in focus, to be extracted from a series of images focused at a range of depths. In recent years, a variety of algorithmic approaches have been employed for bright-field optical microscopy. Here, we demonstrate that some established optical microscopy methods can also be applied to extend the ~6 nm depth of focus of a 100 kV 5th-order aberration-corrected STEM (α{sub max} = 33 mrad) to image Pt-Co nanoparticles on a thick vulcanized carbon support. These techniques allow us to automatically obtain a single image with all the particles in focus as well as a complimentary topography map.

  18. High-Resolution Hypernuclear Spectroscopy Electron Scattering at Jlab, Hall A

    SciTech Connect

    Franco Garibaldi

    2010-12-01

    Hypernuclear spectroscopy via electromagnetic induced reactions is a valuable and powerful way to study hypernuclei, hadronic systems with non-zero strangeness content, providing an alternative to the hadron induced reactions mainly studied so far. Electron-induced hypernuclear spectroscopy has been studied in Hall A at Jefferson Lab on three nuclei, 12C, 16O, and 9Be with unprecedented resolution and with an improved particle identification system, using a RICH detector, in order to unambiguously identify kaons, thus allowing the measurement of high-quality, almost background-free, hypernuclear spectra. Two superconducting septum magnets were added to the existing apparatus in order to permit particle detection at very forward angle providing a reasonable counting rate. These studies have provided the first quantitative information on, for instance, core-excited states in hypernuclei. In the case of oxygen, a waterfall target has been employed allowing for the simultaneous measurement of hypernuclear production on oxygen and of elementary kaon-Lambda electro-production on protons: a crucial measurement to disentangle the contribution of the elementary reaction from the measured hypernuclear production cross section, yielding direct access to the nucleus-hypernucleus transition structure. Final results for 12C and 16O as well as preliminary results on 9Be will be presented.

  19. High-resolution transmission electron microscopy study of carbon deposited on the NiO/MgO solid solution catalysts

    SciTech Connect

    Hu, Y.H.; Ruckenstein, E.

    1999-05-15

    The carbon deposition due to the CH{sub 4} decomposition at 790 C over NiO/MgO catalysts was investigated by high-resolution transmission electron microscopy. While no deposits could be detected over the catalysts with a NiO content smaller than 9.1 wt%, they were detected over the catalysts with NiO contents of 23 and 50 wt%. The carbon deposits are composed of platelets located at distances of about 0.34 nm, corresponding to the graphitic carbon. Various structures of the deposited carbon were observed: (a) carbon consisting of platelets parallel to the surface of the particle, which covers a catalyst particle, (b) nanotubes composed of platelets parallel to their axis, and (c) carbon vortexes consisting of platelets parallel to their axis.

  20. High-resolution electron microscopy of glycoproteins: the crystalline cell wall of Lobomonas.

    PubMed

    Roberts, K; Shaw, P J; Hills, G J

    1981-10-01

    Lobomonas piriformis is a member of an order of green algae (Volvocales) that have crystalline glycoprotein cell walls. As part of a program of investigation of these glycoproteins and their architecture we have studied the cell wall of Lobomonas by a variety of chemical, electron-microscopical and image-analysis techniques. Lobomonas and Vitreochlamys incisa show a very similar structure in their cell walls and represent I of the 4 classes into which all the structures of the wall of these algae that we have so far examined fall. The 2 classes that we have previously studied in detail, represented by Chlamydomonas reinhardii and chlorogonium elongatum, have a crystalline component of the wall that is a more or less smooth continuous surface overlying an amorphous inner wall layer. Although Lobomonas also has this 2-layer structure, the crystalline layer consists of distinct plates, each of which is built around a single, very coherent crystal lattice. The polar nature of the architecture of the cell wall is shown by sectioning and by examination of the cell-wall surface by metal-shadowing of carbon replicas, both of intact cells and of isolated cell-wall plates. There are great similarities in chemical composition between the glycoproteins of the cell wall of C. reinhardii and those of Lobomonas. Both has a large content of hydroxyproline in their amino acid composition and a sugar/hydroxyproline ratio of about 6.0, and both contain sugar sulphates. Lobomonas however has a large glucose content, whereas Chlamydamonas has almost none. Electron micrographs of walls stained with methylamine tungstate and shadowed specimens show that the Lobomonas crystal structure is entirely different from that of C. Reinhardii, and that there is a distinctly different structure in the centre of the plates from that at their edges, although the transition between the 2 areas occurs with no distortion of the crystal lattice. Computer image analysis has been used to calculate

  1. High resolution electron diffraction analysis of structural changes associated with the photocycle of bacteriorhodopsin

    SciTech Connect

    Han, B. -G.

    1994-04-01

    Changes in protein structure that occur during the formation of the M photointermediate of bacteriorhodopsin can be directly visualized by electron diffraction techniques. Samples containing a high percentage of the M intermediate were trapped by rapidly cooling the crystals with liquid nitrogen following illumination with filtered green light at 240K and 260K respectively. Difference Fourier projection maps for M minus bR at two temperatures and for M{sub 260K} minus M{sub 240K} are presented. While it is likely that a unique M-substate is trapped when illuminated at 260K produces a mixture of the M{sub 240K} substate and a second M-substate which may have a protein structure similar to the N-intermediate. The diffraction data clearly show that statistically significant structural changes occur upon formation of the M{sub 240K} specimen and then further upon formation of the second substate which is present in the mixture that is produced at 260K. A preliminary 3-D difference map, based on data collected with samples tilted up to 30{degree}, has been constructed at a resolution of 3.5{angstrom} parallel to the membrane plane and a resolution of 8.5{angstrom} perpendicular to the membrane. The data have been analyzed by a number of different criteria to ensure that the differences seen reflect real conformation changes at a level which is significantly above the noise in the map. Furthermore, a comparison of the positions of specific backbone and side-chain groups relative to significant difference peaks suggests that it will be necessary to further refine the atomic resolution model before it will be possible to interpret the changes in chemical structure that occur in the protein at this stage of the photocycle.

  2. High-resolution total electron content observations of severe ionospheric disturbances using dense GPS receiver networks

    NASA Astrophysics Data System (ADS)

    Tsugawa, Takuya; Kato, Hisao; Kubota, Minoru; Hidekatsu, Jin; Maruyama, Takashi; Nagatsuma, Tsutomu; Saito, Akinori; Nishioka, Michi; Otsuka, Yuichi; Miyake, Wataru; Supnithi, Pornchai; Kenpankho, Prasert

    Two-dimensional total electron content (TEC) maps have been derived from ground-based GPS receiver networks and applied to studies of various ionospheric disturbances since mid-1990s. For the purpose of monitoring and researching ionospheric disturbances which can degrade GNSS navigations and cause loss-of-lock on GNSS signals, National Institute of Information and Communications Technology (NICT), Japan has developed TEC maps over Japan using the dense GPS network, GEONET, which consists of more than 1,200 GPS receivers and is operated by Geophysical Survey Institute, Japan. Currently, we are providing two-dimensional maps of absolute TEC, detrended TEC with 60, 30, 15-minute window, rate of TEC change index (ROTI), and loss-of-lock on GPS signal over Japan. These data and quick-look maps since 1997 are archived and available in the website of NICT (http://wdc.nict.go.jp/IONO/). Recently developed GPS receiver networks in North America and Europe make it possible to obtain regional TEC maps with higher spatial and temporal resolution than the global weighted mean TEC maps in the IONEX format provided by several institutes such as International GNSS Service (IGS) and another global TEC map provided by MIT Haystack observatory. Recently, we have also developed the regional TEC maps over North America and Europe. These data and quick-look maps are also available in the NICT website. In this presentation, we will show some severe ionospheric events such as high latitude storm-time plasma bubbles and storm enhanced density events observed over Japan using the GPS-TEC database. These events cause loss-of-lock of GPS signals and large GPS positioning errors. We will also introduce some interesting ionospheric events over Europe and North America, and discuss about a future direction of our GPS-TEC data service.

  3. High-resolution electronic spectroscopy of the doorway states to intramolecular charge transfer.

    PubMed

    Fleisher, Adam J; Bird, Ryan G; Zaleski, Daniel P; Pate, Brooks H; Pratt, David W

    2013-04-25

    Reported here are several of the ground, first, and second excited state structures and dipole moments of three benchmark intramolecular charge transfer (ICT) systems; 4-(1H-pyrrol-1-yl)benzonitrile (PBN), 4,4'-dimethylaminobenzonitrile (DMABN), and 4-(1-pyrrolidinyl)benzonitrile (PYRBN), isolated in the gas phase and probed by rotationally resolved spectroscopy in a molecular beam. The related molecules 1-phenylpyrrole (PP) and 4-aminobenzonitrile (ABN) also are discussed. We find that the S1 electronic state is of B symmetry in all five molecules. In PBN, a second excited state (S2) of A symmetry is found only ~400 cm(-1) above the presumed origin of the S1 state. The change in dipole moment upon excitation to the A state is measured to be Δμ ≈ 3.0 D, significantly smaller than the value predicted by theory and also smaller than that observed for the "anomalous" ICT band of PBN in solution. The B state dipole moments of DMABN and PYRBN are large, ~10.6 D, slightly larger than those attributed to "normal" LE fluorescence in solution. In addition, we find the unsaturated donor molecules (PP, PBN) to be twisted in their ground states and to become more planar upon excitation, even in the A state, whereas the saturated donor molecules (ABN, DMABN, PYRBN), initially planar, either remain planar or become more twisted in their excited states. It thus appears that the model that is appropriate for describing ICT in these systems depends on the geometry of the ground state. PMID:22913563

  4. mr-PosEBR: a novel positive tone resist for high resolution electron beam lithography and 3D surface patterning

    NASA Astrophysics Data System (ADS)

    Pfirrmann, Stefan; Kirchner, Robert; Lohse, Olga; Guzenko, Vitaliy A.; Voigt, Anja; Harder, Irina; Kolander, Anett; Schift, Helmut; Grützner, Gabi

    2016-03-01

    In this contribution, we present the results of a systematic material variation for the development of a resist material for high resolution positive tone electron beam lithography (EBL). Several acrylic copolymer materials with different compositions, that is varying mass fractions of the comonomers and different molecular weights, were synthesized and - as resist solutions - evaluated in terms of EBL performance at acceleration voltages of 30 kV and 100 kV. The resist material exhibiting the best combination of the desired properties, named mr-PosEBR, is two times more sensitive than PMMA 495k and performs comparably to the known high resolution resist ZEP520A at 30 kV. For example, a grating pattern with 29 nm wide lines with a period of 100 nm could be lithographically generated in films of mr-PosEBR with an area dose of 100 μC/cm2. In terms of resolution, single lines of only 35 nm width could be fabricated via metal liftoff. Furthermore, the dry etch stability of mr-PosEBR in a CF4/SF6 process is similar to the one of ZEP520A. Consequently, via dry etching nano patterns in mr-PosEBR could be smoothly transferred into the underlying Si substrate with high fidelity. Moreover, mr-PosEBR was evaluated as electron beam grayscale patterning and reflow resist. It was shown that the resist exhibits a good grayscale and reflow performance very similar to PMMA 120k and ZEP520A. Via these well controllable processes the generation of a wide variety of features and applications is possible.

  5. Efficient cross-section preparation method for high-resolution imaging of hard polymer composites with a scanning electron microscope.

    PubMed

    Brodusch, N; Yourdkhani, M; Hubert, P; Gauvin, R

    2015-11-01

    Characterization of distribution and arrangement of filler particles in polymer composites is of primary importance to understand and maximize their mechanical, electrical and thermal properties. An innovative procedure that allows reliable and straightforward preparation of cross-sections of polymer composites with the use of mechanical polishing, ion beam etching and soft gaseous etching is presented in this paper. Because of the inherent difference between the organic amorphous matrix and the inorganic crystalline nature of composite fillers, the removal of matrix layers at the surface of the cross-section at the expense of the inorganic materials allowed characterizing the composite filler particles structure and distribution over the surface. Since beam broadening did not occur before the beam hit the nanoparticles, high-resolution imaging in the scanning electron microscope was possible and true dimensions and orientation of the particles were observed. This provided more flexibility in selecting the primary beam voltage; especially, the use of low beam energy greatly improved the image contrast and reduced charging effects resulting from the primary electron beam bombardment. It was shown that only polymers with a carbonated main chain could be etched selectively by the gaseous etching process. PMID:26098996

  6. Soot Structure and Reactivity Analysis by Raman Microspectroscopy, Temperature-Programmed Oxidation, and High-Resolution Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Knauer, Markus; Schuster, Manfred E.; Su, Dangsheng; Schlögl, Robert; Niessner, Reinhard; Ivleva, Natalia P.

    2009-11-01

    Raman microspectroscopy (RM), temperature-programmed oxidation (TPO), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) were combined to get comprehensive information on the relationship between structure and reactivity of soot in samples of spark discharge (GfG), heavy duty engine diesel (EURO VI and IV) soot, and graphite powder upon oxidation by oxygen at increasing temperatures. GfG soot and graphite powder represent the higher and lower reactivity limits. Raman microspectroscopic analysis was conducted by determination of spectral parameters using a five band fitting procedure (G, D1-D4) as well as by evaluation of the dispersive character of the D mode. The analysis of spectral parameters shows a higher degree of disorder and a higher amount of molecular carbon for untreated GfG soot samples than for samples of untreated EURO VI and EURO IV soot. The structural analysis based on the dispersive character of the D mode revealed substantial differences in ordering descending from graphite powder, EURO IV, VI to GfG soot. HRTEM images and EELS analysis of EURO IV and VI samples indicated a different morphology and a higher structural order as compared to GfG soot in full agreement with the Raman analysis. These findings are also confirmed by the reactivity of soot during oxidation (TPO), where GfG soot was found to be the most reactive and EURO IV and VI soot samples exhibited a moderate reactivity.

  7. High-resolution electron microscopic evidence for the filamentous structure of the cyst wall in Giardia muris and Giardia duodenalis.

    PubMed

    Erlandsen, S L; Bemrick, W J; Pawley, J

    1989-10-01

    High-resolution morphological studies of the cyst wall of Giardia spp. were performed using low-voltage scanning electron microscopy (LVSEM) and transmission electron microscopy (TEM). The cyst wall was composed of membranous and filamentous layers. The membranous layer consisted of an inner and an outer cyst membrane separated by a thin layer of cytoplasm. The filamentous layer contained individual filaments that ranged from 7 to 20 nm in diameter when measured by LVSEM, formed a dense meshwork with branches or interconnections, and were occasionally arranged on the surface in whorled patterns. Cysts of Giardia muris from mice, Giardia duodenalis from dogs, pigs, voles, beavers, muskrats, and humans, and Giardia psittaci from a bird (parakeet), possessed an essentially identical wall composed of filaments. Inducement of excystation in viable Giardia cysts produced a dramatic increase in the interfilament spacing over an entire cyst, but none was observed in heat-killed or chemically fixed control cysts. These results demonstrated that the cyst wall of Giardia spp. was composed of a complex arrangement of filaments, presumably formed during the process of encystment. PMID:2795382

  8. Conformational ordering of biomolecules in the gas phase: nitrogen collision cross sections measured on a prototype high resolution drift tube ion mobility-mass spectrometer.

    PubMed

    May, Jody C; Goodwin, Cody R; Lareau, Nichole M; Leaptrot, Katrina L; Morris, Caleb B; Kurulugama, Ruwan T; Mordehai, Alex; Klein, Christian; Barry, William; Darland, Ed; Overney, Gregor; Imatani, Kenneth; Stafford, George C; Fjeldsted, John C; McLean, John A

    2014-02-18

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid "omni-omic" characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  9. Conformational Ordering of Biomolecules in the Gas Phase: Nitrogen Collision Cross Sections Measured on a Prototype High Resolution Drift Tube Ion Mobility-Mass Spectrometer

    PubMed Central

    2014-01-01

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid “omni-omic” characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  10. Electron-Atom Collisions in Gases

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2013-01-01

    Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.

  11. Secondary Electron Focusing to Retain High-Resolution Measurements in Linear-Electric- Field Time-of-Flight Telescopes

    NASA Astrophysics Data System (ADS)

    Gilbert, J. A.; Lundgren, R. A.; Panning, M. H.; Rogacki, S. A.; Zurbuchen, T. H.

    2008-12-01

    Linear-electric-field time-of-flight (LEF TOF) analyzers are useful for space applications of mass spectrometry. Particles pass through a thin Carbon foil and enter the analyzer with one of several charge states, typically different than that of the incident ion. High mass resolution (m/Δ m~ 100) is obtained for positive charge states whose isochronous flight times are not dependent on the particle's energy, while low mass resolution (m/Δ m~ 10) is recorded for charge states that travel straight through the analyzer and are affected by collisional scattering when passing through the Carbon foil. When the flight times of different masses and charge states are recorded by the same anode, it is sometimes difficult to extract the lower-count-rate isochronous measurements. We present a technique for overcoming this issue using a modified instrument geometry combined with a novel position-sensitive detector. This modified geometry of a cylindrically symmetric LEF TOF analyzer has inner electrostatic rings, which focus secondary electrons created by isochronous ion impact. Electrons are guided toward the central area of a position-sensitive serpentine delay line anode, and position and flight time information are processed by a time-to-digital converter in a field-programmable-gate-array chip. Neutrals and negative ions will impact the anode in regions other than the center, and can be separated out by their position. Using these advanced electronics with the modified design, the high-resolution measurement can be extracted from the data as a focused peak at the center of the anode, providing improved measurements without an increase in the instrument size. We report the results from simulations and laboratory measurements used to experimentally confirm the expected performance of this design.

  12. Wide-band, high-resolution soft x-ray spectrometer for the Electron Beam Ion Trap

    SciTech Connect

    Brown, G.V.; Beiersdorfer, P.; Widmann, K.

    1999-01-01

    We have constructed two wide-band, high-resolution vacuum flat crystal spectrometers and implemented them on the Electron Beam Ion Trap located at the Lawrence Livermore National Laboratory. Working in unison, these spectrometers can measure an x-ray bandwidth {le}9 {Angstrom} in the soft x-ray region below 21 {Angstrom}. In order to achieve this large bandwidth each spectrometer houses either two 125 mm {times} 13 mm {times} 2 mm RAP (rubidium acid phthalate, 2d=26.121 {Angstrom}), two 114 mm {times} 13 mm {times} 2 mm TlAP (thallium acid phthalate, 2d=25.75 {Angstrom}) crystals, or some combination thereof, for dispersion and two position sensitive proportional counters for detection of x rays. The spectrometers are used to measure wavelengths and relative intensities of the L-shell line emission from FethinspXVII{endash}XXIV for comparison with spectra obtained from astrophysical and laboratory plasmas. The wide wavelength coverage attainable by these spectrometers makes it possible to measure all the L-shell emission from a given iron ion species simultaneously. {copyright} {ital 1999 American Institute of Physics.}

  13. XRD (x-ray diffraction) and HREM (high resolution electron microscopy) studies of nanocrystalline Cu and Pd

    SciTech Connect

    Nieman, G.W.; Weertman, J.R. . Dept. of Materials Science and Engineering); Siegel, R.W. )

    1990-12-01

    Consolidated powders of nanocrystalline Cu and Pd have been studied by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) as part of an investigation of the mechanical behavior of nanocrystalline pure metals. XRD line broadening measurements were made to estimate grain size, qualitative grain size distribution and average long range strains in a number of samples. Mean grain sizes range from 4--60 nm and have qualitatively narrow grain size distributions. Long range lattice strains are of the order of 0.2--3% in consolidated samples. These strains apparently persist and even increase in Cu samples after annealing at 0.35 Tm (498K) for 2h, accompanied by an apparent increase in grain size of {ge}2x. Grain size, grain size distribution width and internal strains vary somewhat among samples produced under apparently identical processing conditions. HREM studies show that twins, stacking faults and low-index facets are abundant in as-consolidated nanocrystalline Cu samples. Methodology, results, and analysis of XRD and HREM experiments are presented. 17 refs., 2 figs., 2 tabs.

  14. Genesis of presolar diamonds: Comparative high-resolution transmission electron microscopy study of meteoritic and terrestrial nano-diamonds

    SciTech Connect

    Daulton, T.L. |; Eisenhour, D.D.; Buseck, P.R.

    1996-12-01

    Nano-diamonds isolated from acid dissolution residues of primitive carbonaceous meteorites (Allende and Murchison) were studied using high-resolution transmission electron microscopy. To discriminate among their most likely formation mechanisms, high-pressure shock-induced metamorphism or low-pressure vapor condensation. the microstructures of presolar diamond crystallites were compared to those of (terrestrial) synthesized nano-diamonds. The synthesized diamonds used for comparison in this study were produced by high-pressure shock waves generated in controlled detonations and by direct nucleation and homoepitaxial growth from the vapor phase in low-pressure chemical vapor deposition (CVD)-type processes. Microstructural features were identified that appear unique to shock metamorphism and to nucleation from the vapor phase, respectively. A comparison of these features to the microstructures found in presolar diamonds indicates that the predominant mechanism for presolar diamond formation is a vapor deposition process, suggesting a circumstellar condensation origin. A new presolar grain component has also been identified in the meteoritic residues, the (2H) hexagonal polytype of diamond (lonsdaleite). 93 refs., 17 figs., 1 tab.

  15. Separating strain from composition in unit cell parameter maps obtained from aberration corrected high resolution transmission electron microscopy imaging

    SciTech Connect

    Schulz, T.; Remmele, T.; Korytov, M.; Markurt, T.; Albrecht, M.; Duff, A.; Lymperakis, L.; Neugebauer, J.; Chèze, C.

    2014-01-21

    Based on the evaluation of lattice parameter maps in aberration corrected high resolution transmission electron microscopy images, we propose a simple method that allows quantifying the composition and disorder of a semiconductor alloy at the unit cell scale with high accuracy. This is realized by considering, next to the out-of-plane, also the in-plane lattice parameter component allowing to separate the chemical composition from the strain field. Considering only the out-of-plane lattice parameter component not only yields large deviations from the true local alloy content but also carries the risk of identifying false ordering phenomena like formations of chains or platelets. Our method is demonstrated on image simulations of relaxed supercells, as well as on experimental images of an In{sub 0.20}Ga{sub 0.80}N quantum well. Principally, our approach is applicable to all epitaxially strained compounds in the form of quantum wells, free standing islands, quantum dots, or wires.

  16. Study of Explosive Electron Emission from a Pin Cathode Using High Resolution Point-Projection X-Ray Radiography

    NASA Astrophysics Data System (ADS)

    Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Parkevich, E. V.; Tilikin, I. N.; Mingaleev, A. R.; Agafonov, A. V.

    2015-11-01

    Most studies of Explosive Electron Emission (EEE) are based on the idea of cathode flares developing after explosion of metal whiskers (micron scale pins) on the cathode surface. The physical state of the pin material, the spatial structure of the explosion and its origin are still a matter of conjecture. In this work we used high-resolution point projection x-ray radiography to observe micron scale pin explosion in a high-current diode. Pin cathodes made from 10-25 micron Cu or Mo wires were placed in gaps in return current circuits of hybrid X-pinches on the XP and BIN pulsers. Pin lengths were varied over a range 1-4 mm and pin-anode gaps within 0.05-3 mm. The diode current and voltage were measured. In experiments with small pin-anode gap (0.1 - 1 mm) development of an expanded dense core of the pin was observed except the pin tip with length 100-200 microns indicating significant energy deposition in the wire material. In experiments with bigger gaps there was no visible wire core expansion within the spatial resolution of the experimental technique. Work at Cornell was supported by the National Nuclear Security Administration Stewardship Sciences Academic Programs under Department of Energy Cooperative Agreement No. DE-NA0001836 and at the Lebedev Institute by the RSF grant 142200273.

  17. High-resolution transmission electron microscopy observations on textured rapidly quenched NdFeB permanent magnets

    NASA Astrophysics Data System (ADS)

    Li, Lin; Luzzi, D. E.; Graham, C. D., Jr.

    1991-11-01

    High-resolution transmission electron microscopy (HRTEM) has been used to examine the microstructures of NdFeB magnets made by rapid solidification. The samples were General Motors MQ-3 magnets, and also MQ-3 magnets that had been recompressed perpendicular to the original compression axis. A major finding is that the Nd-rich grain-boundary phase is not uniformly distributed on all grain boundaries of the Nd2Fe14B phase. Some boundaries are completely clean, and where the Nd-rich phase does appear, its thickness varies widely. The grain-boundary phase (whose structure has been variously identified) is partially ordered at room temperature after slow cooling. Ordered domains and antiphase boundaries have been observed in this phase by HRTEM. Using the Nd2Fe14B fringe spacing as calibration, the lattice parameter of the grain-boundary phase is found to be 5.58 Å. In the completely ordered state, this phase is neither bcc nor fcc; it is simple cubic with a lower-symmetry space group Pm3m.

  18. Hydrogenated graphene on Ir(111): A high-resolution electron energy loss spectroscopy study of the vibrational spectrum

    NASA Astrophysics Data System (ADS)

    Kyhl, Line; Balog, Richard; Angot, Thierry; Hornekær, Liv; Bisson, Régis

    2016-03-01

    Hydrogen atom adsorption on high-quality graphene on Ir(111) [gr/Ir(111)] is investigated using high-resolution electron energy loss spectroscopy. The evolution of the vibrational spectrum, up to 400 meV, of gr/Ir(111) upon increasing hydrogen atom exposures is measured. The two dominant binding configurations of atomic hydrogen are identified as (1) graphanelike hydrogen clusters on the parts of the graphene more strongly interacting with the Ir(111) surface and (2) dimers bound more weakly to the freestanding parts of the graphene. The graphanelike surface structures lead to increased corrugation of the graphene sheet, yielding graphane-related phonon components. Additionally, a recent theoretical prediction of the existence of a bending character for a LO/TO graphane chair phonon mode is experimentally verified. No clear evidence was found for hydrogen bound on both sides of a high-quality graphene sheet and phonon features strongly suggest interactions between graphanelike hydrogen clusters and Ir atoms in the substrate.

  19. Characterization of Al2O3 in High-Strength Mo Alloy Sheets by High-Resolution Transmission Electron Microscopy.

    PubMed

    Zhou, Yucheng; Gao, Yimin; Wei, Shizhong; Hu, Yajie

    2016-02-01

    A novel type of alumina (Al2O3)-doped molybdenum (Mo) alloy sheet was prepared by a hydrothermal method and a subsequent powder metallurgy process. Then the characterization of α-Al2O3 was investigated using high-resolution transmission electron microscopy as the research focus. The tensile strength of the Al2O3-doped Mo sheet is 43-85% higher than that of the pure Mo sheet, a very obvious reinforcement effect. The sub-micron and nanometer-scale Al2O3 particles can increase the recrystallization temperature by hindering grain boundary migration and improve the tensile strength by effectively blocking the motion of the dislocations. The Al2O3 particles have a good bond with the Mo matrix and there exists an amorphous transition layer at the interface between Al2O3 particles and the Mo matrix in the as-rolled sheet. The sub-structure of α-Al2O3 is characterized by a number of nanograins in the $\\left[ {2\\bar{2}1} \\right]$ direction. Lastly, a new computer-based method for indexing diffraction patterns of the hexagonal system is introduced, with 16 types of diffraction patterns of α-Al2O3 indexed. PMID:26914997

  20. High resolution transmission electron microscope Imaging and first-principles simulations of atomic-scale features in graphene membrane

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Bhandari, Sagar; Yi, Wei; Bell, David; Westervelt, Robert; Kaxiras, Efthimios

    2012-02-01

    Ultra-thin membranes such as graphene[1] are of great importance for basic science and technology applications. Graphene sets the ultimate limit of thinness, demonstrating that a free-standing single atomic layer not only exists but can be extremely stable and strong [2--4]. However, both theory [5, 6] and experiments [3, 7] suggest that the existence of graphene relies on intrinsic ripples that suppress the long-wavelength thermal fluctuations which otherwise spontaneously destroy long range order in a two dimensional system. Here we show direct imaging of the atomic features in graphene including the ripples resolved using monochromatic aberration-corrected transmission electron microscopy (TEM). We compare the images observed in TEM with simulated images based on an accurate first-principles total potential. We show that these atomic scale features can be mapped through accurate first-principles simulations into high resolution TEM contrast. [1] Geim, A. K. & Novoselov, K. S. Nat. Mater. 6, 183-191, (2007). [2] Novoselov, K. S.et al. Science 306, 666-669, (2004). [3] Meyer, J. C. et al. Nature 446, 60-63, (2007). [4] Lee, C., Wei, X. D., Kysar, J. W. & Hone, J. Science 321, 385-388, (2008). [5] Nelson, D. R. & Peliti, L. J Phys-Paris 48, 1085-1092, (1987). [6] Fasolino, A., Los, J. H. & Katsnelson, M. I. Nat. Mater. 6, 858-861, (2007). [7] Meyer, J. C. et al. Solid State Commun. 143, 101-109, (2007).

  1. High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets

    SciTech Connect

    Volk, Alexander; Thaler, Philipp; Koch, Markus; Ernst, Wolfgang E.; Fisslthaler, Evelin; Grogger, Werner

    2013-06-07

    We present a first investigation of structural properties of Ag clusters with a diameter of up to 5.5 nm grown inside superfluid helium nanodroplets (He{sub N}) and deposited on an amorphous C surface. With high resolution transmission electron microscope images we are able to show that in addition to the crystalline face centered cubic (fcc) structure, noncrystalline icosahedral (Ih), and decahedral (Dh) morphologies are grown. Relative abundances (56% fcc, 31% Dh, and 13% Ih) as well as the size distribution of each morphology (mean diameters d{sub fcc}=2.62(5) nm, d{sub Dh}=3.34(7) nm, and d{sub Ih}=3.93(2) nm) do not reflect the situation expected from pure energetic considerations, where small Ihs should be followed by medium sized Dhs and large fccs. Instead, kinetic factors seem to play an important role in the formation of these structures, as it appears to be the case for clusters formed by inert gas aggregation. Considering the low temperatures (0.37 K) and extremely high cooling rates, we discuss basic ideas that might lead to a qualitative picture of the cluster formation process inside He{sub N}.

  2. High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets.

    PubMed

    Volk, Alexander; Thaler, Philipp; Koch, Markus; Fisslthaler, Evelin; Grogger, Werner; Ernst, Wolfgang E

    2013-06-01

    We present a first investigation of structural properties of Ag clusters with a diameter of up to 5.5 nm grown inside superfluid helium nanodroplets (He(N)) and deposited on an amorphous C surface. With high resolution transmission electron microscope images we are able to show that in addition to the crystalline face centered cubic (fcc) structure, noncrystalline icosahedral (Ih), and decahedral (Dh) morphologies are grown. Relative abundances (56% fcc, 31% Dh, and 13% Ih) as well as the size distribution of each morphology (mean diameters d(fcc)=2.62(5) nm, d(Dh)=3.34(7) nm, and d(Ih)=3.93(2) nm) do not reflect the situation expected from pure energetic considerations, where small Ihs should be followed by medium sized Dhs and large fccs. Instead, kinetic factors seem to play an important role in the formation of these structures, as it appears to be the case for clusters formed by inert gas aggregation. Considering the low temperatures (0.37 K) and extremely high cooling rates, we discuss basic ideas that might lead to a qualitative picture of the cluster formation process inside He(N). PMID:23758376

  3. Wide-band, high-resolution soft x-ray spectrometer for the Electron Beam Ion Trap

    NASA Astrophysics Data System (ADS)

    Brown, G. V.; Beiersdorfer, P.; Widmann, K.

    1999-01-01

    We have constructed two wide-band, high-resolution vacuum flat crystal spectrometers and implemented them on the Electron Beam Ion Trap located at the Lawrence Livermore National Laboratory. Working in unison, these spectrometers can measure an x-ray bandwidth ⩽9 Å in the soft x-ray region below 21 Å. In order to achieve this large bandwidth each spectrometer houses either two 125 mm × 13 mm × 2 mm RAP (rubidium acid phthalate, 2d=26.121 Å), two 114 mm × 13 mm × 2 mm TlAP (thallium acid phthalate, 2d=25.75 Å) crystals, or some combination thereof, for dispersion and two position sensitive proportional counters for detection of x rays. The spectrometers are used to measure wavelengths and relative intensities of the L-shell line emission from Fe XVII-XXIV for comparison with spectra obtained from astrophysical and laboratory plasmas. The wide wavelength coverage attainable by these spectrometers makes it possible to measure all the L-shell emission from a given iron ion species simultaneously.

  4. Comparative analysis of dioxins and furans by electron impact, high-resolution mass spectrometry and by electron capture, negative ionization, low-resolution mass spectrometry

    SciTech Connect

    Koester, C.J.; Harless, R.L.; Hites, R.A.

    1990-01-01

    Electron impact, high resolution mass spectrometry (HRMS) is currently the method of choice for the analysis of polychlorinated dibenso-p-dioxins and dibenzofurans (PCDD/F) because of its ability to detect PCDD/F in the presence of interfering compounds, such as polychlorinated biphenyls (PCB), which cannot be resolved by low resolution methods. The PDCC/F analyses may also be performed using electron capture, negative ionization (ECNI) low resolution mass spectrometry, providing extensive sample preparation is done to remove interferences. Before ECNI low resolution mass spectrometry (MS) can be accepted as a routine method for PCDD/F analysis, it is necessary to show that results generated by this method are comparable to those obtained by HRMS. Known mixtures and unknown air samples were analyzed by electron impact HRMS (Finnigan MAT 90 system) and by ECNI low resolution MS (Hewlett Packard 5985B). Both instruments were fitted with a gas chromatographic inlet. The PCDD/F concentrations determined by the two techniques compare favorably, typically within 20%. The major difference between these two methods is that the ECNI low resolution method shows poor sensitivity in detecting 2,3,7,8-tetrachlorodioxin. However, ECNI MS offers the advantage of lower detection limits (50-100 fg) than electron impact HRMS (0.1 to 0.5 pg). These results suggest that ECNI low resolution MS can be a simple, low cost alternative to the common high resolution methods used for PCDD/F analysis.

  5. A High Resolution Look at Black Sand Particles from Sand Dunes of Saudi Arabia Using Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Hussain, M. M.; Aburizaiza, O. S.; Siddique, A.; Hershey, D. L.; Guerrieri, D. A.; Qurashi, J.; Abbass, M.; Blake, D. R.; Khwaja, H. A.

    2013-12-01

    Particulate air pollution is a problem of health concern. The microscopic make-up of different varieties of sand particles found and collected at a sand dune site in Badr, Saudi Arabia has been determined. Primary emphasis is given to the use of multiple high resolution electron microscopy (viz., Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM/EDS) and Laser Scanning Microscopy (LSM)) to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of ';coatings or contaminants' adsorbed or carried on by the black sand particles. White sand contains natural coarse particles associated with wind-blown releases from crustal surfaces, weathering of an igneous/metamorphic rock source, and volcanic activities. Silicates (alumino-silicates) and quartz (clear, milky, rose) dominate white sand and rest appears to contain calcite, olivine, feldspar, and magnetite. Black sand particles exhibit very different morphologies and microstructures (surface roughness) compared with white sand and volcanic ash. Morphological analyses have shown that the black sand contain ultrafine particles. Black sand is strongly magnetic, which indicates the mineral magnetite (strongly magnetic) or elemental iron. Iron, C, O, Ti, Si, V, and S particles dominate the black sand. Natural and anthropogenic sources have been implicated for the observed particles. Analysis revealed that the surface of white sand particles is mainly covered with the fine particles. It is known that emissions from combustion contain carbon soot and other contaminants that are easily absorbed by soil particles during a long-range transport.

  6. High-resolution electron spectroscopy of lanthanide (Ce, Pr, and Nd) complexes of cyclooctatetraene: The role of 4f electrons

    SciTech Connect

    Kumari, Sudesh; Roudjane, Mourad; Hewage, Dilrukshi; Yang Dongsheng; Liu Yang

    2013-04-28

    Cerium, praseodymium, and neodymium complexes of 1,3,5,7-cyclooctatetraene (COT) complexes were produced in a laser-vaporization metal cluster source and studied by pulsed-field ionization zero electron kinetic energy spectroscopy and quantum chemical calculations. The computations included the second-order Moller-Plesset perturbation theory, the coupled cluster method with single, double, and perturbative triple excitations, and the state-average complete active space self-consistent field method. The spectrum of each complex exhibits multiple band systems and is assigned to ionization of several low-energy electronic states of the neutral complex. This observation is different from previous studies of M(COT) (M = Sc, Y, La, and Gd), for which a single band system was observed. The presence of the multiple low-energy electronic states is caused by the splitting of the partially filled lanthanide 4f orbitals in the ligand field, and the number of the low-energy states increases rapidly with increasing number of the metal 4f electrons. On the other hand, the 4f electrons have a small effect on the geometries and vibrational frequencies of these lanthanide complexes.

  7. Electron-electron interactions in fast neutral-neutral collisions

    SciTech Connect

    DuBois, R.D. ); Manson, S.T. . Dept. of Physics and Astronomy)

    1992-11-01

    Differential electron emission is studied for 50--500 keV H[sup +] and H atom impact on helium. Using the first Born formulation, it is shown that projectile electron-target electron interactions are expected to dominate the differential cross sections for low energy target electron emission induced by fast neutral projectile impact on any target. Measurements of the 15[degrees] electron emission were made in order to investigate this prediction. For low impact energies, a constant ratio between the hydrogen atom and proton impact cross sections was found for emitted electron velocities less than half the projectile velocity, V[sub p] But as the collision energy increased, for electron velocities less than 0.25 V[sub p], the cross section ratio increased as the emitted electron velocity decreased. This is interpreted as a signature of projectile electron-target electron interactions becoming dominant for distant collisions between neutral particles.

  8. Electron-electron interactions in fast neutral-neutral collisions

    SciTech Connect

    DuBois, R.D.; Manson, S.T.

    1992-11-01

    Differential electron emission is studied for 50--500 keV H{sup +} and H atom impact on helium. Using the first Born formulation, it is shown that projectile electron-target electron interactions are expected to dominate the differential cross sections for low energy target electron emission induced by fast neutral projectile impact on any target. Measurements of the 15{degrees} electron emission were made in order to investigate this prediction. For low impact energies, a constant ratio between the hydrogen atom and proton impact cross sections was found for emitted electron velocities less than half the projectile velocity, V{sub p} But as the collision energy increased, for electron velocities less than 0.25 V{sub p}, the cross section ratio increased as the emitted electron velocity decreased. This is interpreted as a signature of projectile electron-target electron interactions becoming dominant for distant collisions between neutral particles.

  9. High-resolution study of electron capture by 72- and 52-MeV 3He projectiles from targets of high atomic number

    NASA Astrophysics Data System (ADS)

    Katayama, I.; Ikegami, H.; Ogawa, H.; Haruyama, Y.; Tozaki, M.; Aoki, A.; Fukuzawa, F.; Yoshida, K.; Sugai, I.

    1996-01-01

    An electron capture at the cyclotron energy has been explored by using a high-resolution magnetic spectrograph. The K-shell electron capture from heavy elements (V, Cr, Cu, Ge, Nb, Ag, and Sn) by 3He2+ projectiles at 52 and 72 MeV was measured. The dependence of the cross sections on the atomic number of the target obtained at these two energies are compared with current electron-capture theories.

  10. Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Ferreira da Silva, F.; Lange, E.; Limão-Vieira, P.; Jones, N. C.; Hoffmann, S. V.; Hubin-Franskin, M.-J.; Delwiche, J.; Brunger, M. J.; Neves, R. F. C.; Lopes, M. C. A.; de Oliveira, E. M.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Blanco, F.; García, G.; Lima, M. A. P.; Jones, D. B.

    2015-10-01

    The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

  11. Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations.

    PubMed

    Ferreira da Silva, F; Lange, E; Limão-Vieira, P; Jones, N C; Hoffmann, S V; Hubin-Franskin, M-J; Delwiche, J; Brunger, M J; Neves, R F C; Lopes, M C A; de Oliveira, E M; da Costa, R F; Varella, M T do N; Bettega, M H F; Blanco, F; García, G; Lima, M A P; Jones, D B

    2015-10-14

    The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range. PMID:26472380

  12. Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

    SciTech Connect

    Ferreira da Silva, F.; Lange, E.; Limão-Vieira, P. E-mail: michael.brunger@flinders.edu.au; Jones, N. C.; Hoffmann, S. V.; Hubin-Franskin, M.-J.; Delwiche, J.; Brunger, M. J. E-mail: michael.brunger@flinders.edu.au; and others

    2015-10-14

    The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5–10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

  13. Neutron irradiation damage of nuclear graphite studied by high-resolution transmission electron microscopy and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Krishna, R.; Jones, A. N.; McDermott, L.; Marsden, B. J.

    2015-12-01

    Nuclear graphite components are produced from polycrystalline artificial graphite manufacture from a binder and filler coke with approximately 20% porosity. During the operational lifetime, nuclear graphite moderator components are subjected to fast neutron irradiation which contributes to the change of material and physical properties such as thermal expansion co-efficient, young's modulus and dimensional change. These changes are directly driven by irradiation-induced changes to the crystal structure as reflected through the bulk microstructure. It is therefore of critical importance that these irradiation changes and there implication on component property changes are fully understood. This work examines a range of irradiated graphite samples removed from the British Experimental Pile Zero (BEPO) reactor; a low temperature, low fluence, air-cooled Materials Test Reactor which operated in the UK. Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) have been employed to characterise the effect of increased irradiation fluence on graphite microstructure and understand low temperature irradiation damage processes. HRTEM confirms the structural damage of the crystal lattice caused by irradiation attributed to a high number of defects generation with the accumulation of dislocation interactions at nano-scale range. Irradiation-induced crystal defects, lattice parameters and crystallite size compared to virgin nuclear graphite are characterised using selected area diffraction (SAD) patterns in TEM and Raman Spectroscopy. The consolidated 'D'peak in the Raman spectra confirms the formation of in-plane point defects and reflected as disordered regions in the lattice. The reduced intensity and broadened peaks of 'G' and 'D' in the Raman and HRTEM results confirm the appearance of turbulence and disordering of the basal planes whilst maintaining their coherent layered graphite structure.

  14. High resolution analytical electron microscopy reveals cell culture media induced changes to the chemistry of silver nanowires

    PubMed Central

    Chen, Shu; Theodorou, Ioannis G.; Goode, Angela E.; Gow, Andrew; Schwander, Stephan; Zhang, Junfeng (Jim); Chung, Kian Fan; Tetley, Teresa D.; Shaffer, Milo S.; Ryan, Mary P.; Porter, Alexandra E.

    2014-01-01

    There is a growing concern about the potential adverse effects on human health upon exposure to engineered silver nanomaterials (particles, wires and plates). However, the majority of studies testing the toxicity of silver nanomaterials have examined nominally ‘as-synthesized’ materials without considering the fate of the materials in biologically relevant fluids. Here, in-house silver nanowires (AgNWs) were prepared by a modified polyol process and were incubated in three cell culture media (DMEM, RPMI-1640 and DCCM-1) to examine the impact of AgNW-medium interactions on the physicochemical properties of the AgNWs. High-resolution analytical transmission electron microscopy revealed that Ag2S crystals form on the surface of AgNWs within 1 hour of incubation in DCCM-1. In contrast, the incubation of AgNWs in RPMI-1640 or DMEM did not lead to sulfidation. When the DCCM-1 cell culture medium was separated into its small molecule solutes and salts and protein components, the AgNWs were found to sulfidize in the fraction containing small molecule solutes and salts, but not in the fraction containing the protein component of the media. Further investigation showed the AgNWs did not readily sulfidize in the presence of isolated sulfur containing amino acids or proteins, such as cysteine or bovine serum albumin (BSA). The results demonstrate that the AgNWs can be transformed by the media before and during the incubation with cells and therefore the effects of cell culture media must be considered in the analysis of toxicity assays. Appropriate media and material controls must be in place to allow accurate predictions about the toxicity, and ultimately, the health risk of this commercially relevant class of nanomaterial. PMID:24160871

  15. Identifying the crystallinity, phase, and arsenic uptake of the nanomineral schwertmannite using analytical high resolution transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    French, R. A.; Kim, B.; Murayama, M.; Hochella, M. F.

    2010-12-01

    Schwertmannite, an iron oxyhydroxide sulfate nanomineral, plays a significant role in the geochemistry of acid mine drainage (AMD) as a metastable phase with respect to goethite and by retaining toxic metals, e.g. arsenic [1]. Schwertmannite’s characteristic morphology is needles 100-300 nm long and only 5-10 nm in diameter extending from a dense aggregate. The poorly-and nano-crystalline nature of this mineral requires using high resolution electron microscopy (HRTEM) to be fully characterized. We used HRTEM to identify the polyphasic nature of natural samples of schwertmannite collected from the Iberian Pyrite Belt in Spain. In order to analyze the dense core, samples were prepared in thin section using an ultramicrotome. Data on a sample identified as pure schwertmannite through powder XRD shows the presence of 5-10 nm goethite nanocrystals making up a significant portion of one of the nanoneedle tips (Figure 1). These nanocrystals exhibit lattice fringes and faceted surfaces, both of which match that expected for goethite. The great majority of the nanoneedles are poorly-crystalline (no lattice fringes) with atomically rough surfaces which may be highly active in the uptake of As. The presence of a range of phases and crystallinities in this sample demonstrate incipient stages of the mechanism that results in transformation of schwertmannite to goethite. Further analytical TEM analyses will help us track sorption/desorption, as well as the specific locations of As within these materials upon initial formation, as well as during transformation. [1] Acero et al. (2006) GCA 70, 4130-4139. Figure 1. HRTEM image of 'schwertmannite' nanoneedle with FFT data (inset).

  16. Prominent conjugate processes in the PCI recapture of photoelectrons revealed by high resolution Auger electron measurements of Xe

    NASA Astrophysics Data System (ADS)

    Azuma, Yoshiro; Kosugi, Satoshi; Suzuki, Norihiro; Shigemasa, Eiji; Iwayama, Hiroshi; Koike, Fumihiro

    2016-05-01

    The Xe (N5O2 , 3O2 , 3) Auger electron spectrum originating from 4d5/ 2 - 1 photoionization was measured with the photon energy tuned very close above the ionization threshold. As the photon energy approached the 4d5/ 2 - 1 photoionization threshold, Rydberg series structures including several angular momentum components were formed within the Auger profile by the recapture of the photoelectrons into high-lying final ion orbitals. Our spectrum with resolution much narrower than the lifetime width of the corresponding core excited state allowed us to resolve detailed structures due to the orbital angular momenta very clearly. Unexpectedly, conjugate peaks originating from the exchange of angular momentum between the photoelectron and the Auger electron through Post-Collision-Interaction were found to dominate the spectrum. The new assignments were in accord with the quantum defect values obtained for the high Rydberg series for singly charged ionic Xe + 5 p(1S0) ml. This work was supported by Japan Society for the Promotion of Science through Grants-in-Aid for Scientific Research No. 23600009.

  17. Tryptamine in the gas phase. A high resolution laser study of the structural and dynamic properties of its ground and electronically excited states

    NASA Astrophysics Data System (ADS)

    Nguyen, T. V.; Korter, T. M.; Pratt, D. W.

    High resolution S1←S0 fluorescence excitation spectra of tryptamine have been observed in the collision-free environment of a supersonic molecular beam. Each origin band has been assigned to a unique conformer of the isolated molecule based on its observed rotational constants. For the first time, subbands have been detected in the rotationally resolved spectra of bands Cblue and D. A possible hindered motion is proposed to account for the appearance of these subbands. This motion connects the minima associated with the Antipy and Antiph conformers, and thus explores new regions of the energy landscape of this important biomolecule.

  18. Molecular Dissociation Induced by Electron Collisions

    NASA Astrophysics Data System (ADS)

    Wolf, Andreas

    2009-05-01

    Free electrons can efficiently break molecules or molecular ions in low-energy collisions by the processes of dissociative recombination or attachment. These processes make slow electrons efficient chemical agents in many environments. For dissociative recombination, in particular, studies of the underlying reaction paths and mechanisms have become possible on a uniquely elementary level in recent years both for theory and experiment. On the experimental side, collisions can be prepared at resolved collision energies down to the meV (10 Kelvin) level, increasingly gaining control also over the initial molecular quantum level, and individual events are detected and kinematically analyzed by fast-beam coincidence fragment imaging. Experiments are reported from the ion cooler ring TSR in Heidelberg. Stored beams of molecular ions cooled in their external and internal degrees of freedom are collinearly merged with intense and cold electron beams from cryogenic GaAs photocathodes, recently shown to yield fast cooling of the center-of-mass motion also for heavy and correspondingly slow molecular ion beams. To reconstruct the molecular fragmentation events multiparticle imaging can now be used systematically with collision energies set a wide range, especially aiming at specific electron capture resonances. Thus, for CF^+ it is found that the electronic state of the C fragment (^3P or ^1D) switches resonantly when the collision energy is changed by only a small fraction. As a new powerful tool, an energy-sensitive multi-strip surface-barrier detector (EMU) has been set up to measure with near-unity efficiency the masses of all fragments together with their hit positions in high-multiplicity events. Among many uses, this device allows internal molecular excitations to be derived for individual chemical channels in polyatomic fragmentation. New results will be presented in particular on the breakup of the hydronium ion (D3O^+).

  19. Direct Observation of Iron-Induced Conformational Changes of Mitochondrial DNA by High-Resolution Field-Emission in-Lens Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Yaffee, Marcus; Walter, Patrick; Richter, Christoph; Muller, Martin

    1996-05-01

    When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolution field-emission in-lens scanning electron microscopy with backscattered electron detection imaging permits simultaneous detailed visual analysis of DNA topology, iron dose-dependent mtDNA unwinding, and assessment of iron colloid formation on mtDNA strands.

  20. Electron Impact Collision Strength in Si IX

    NASA Astrophysics Data System (ADS)

    Noman, Hala; Gokce, Y.; Nahar, Sultana; Pradhan, Anil

    2016-05-01

    Results from work in progress under Iron Project on the electron impact excitation collision strengths and rate coefficients for transitions between the fine-structure levels of the 2s2 2p2 , 2 s 2p3 , 2p4 , 2s2 2 p 3 s , 2s2 2 p 3 p , and 2s2 2 p 3 d configurations in Si IX will be presented. The fine structure collision strength has been calculated at very fine energy mesh using relativistic effects in Breit-Pauli R-matrix method. Maxwellian averaged collision strengths have been tabulated for all possible transitions among all 46 enrgy levels. We made comparisions of our results with the previously reported results in the literature and found significant differences in low the temperature range (Te < 106 K) for few of the transitions. The correction to the previous reported values results due to more extensive expansion for Si IX target states.

  1. Very high resolution radiometer

    NASA Technical Reports Server (NTRS)

    Aronson, A. I.

    1974-01-01

    A primary sensor used in environmental and earth-resource observation, the Very High Resolution Radiometer (VHRR) was designed for use on the ITOS D series spacecraft. The VHRR provides a 0.47 mile resolution made possible with a mercury-cadmium-telluride detector cooled to approximately 105 K by a passive radiator cooler. The components of this system are described. The optical subsystem of the VHRR consists of a scanning mirror, a Dall-Kirkham telescope, a dichroic beam splitter, relay lenses, spectral filters, and an IR detector. Signal electronics amplify and condition the signals from the infrared and visible light detector. Sync generator electronics provides the necessary time signals. Scan-drive electronics is used for commutation of the motor winding, velocity, and phase control. A table lists the performance parameters of the VHRR.

  2. IRAS high resolution studies and modeling of closely interacting galaxies. Galaxy collisions: Infrared observations and analysis of numerical models. UV spectroscopy of massive young stellar populations in interacting galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, Susan A.

    1993-01-01

    The Final Technical Report covering the period from 15 Aug. 1989 to 14 Aug. 1991 is presented. Areas of research included Infrared Astronomy Satellite (IRAS) high resolution studies and modeling of closely interacting galaxies; galaxy collisions: infrared observations and analysis of numerical models; and UV spectroscopy of massive young stellar populations in interacting galaxies. Both observational studies and theoretical modelling of interacting galaxies are covered. As a consequence the report is divided into two parts, one on each aspect of the overall project.

  3. High-resolution spectroscopy using synchrotron radiation for surface structure determination and the study of correlated electron systems

    SciTech Connect

    Moler, E.J. Jr.

    1996-05-01

    The surface structure of three molecular adsorbate systems on transition metal surfaces, ({radical}3 x {radical}3)R30{degrees} and (1.5 x 1.5)R18{degrees} CO adsorbed on Cu(111), and c(2x2) N2/Ni(100), have been determined using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS). The adsorption site and bond lengths are reported for the adsorbate-metal bond and the first two substrate layers. The ARPEFS diffraction pattern of the shake-up peak for c(2x2) N2/Ni(100) is also discussed. A unique method of experimentally determining the angular momentum and intrinsic/extrinsic origin of core-level satellites is presented. We show for the first time that satellite peaks not associated with chemically differentiated atomic species display an ARPEFS intensity oscillation. Specifically, we present data for the C 1s from ({radical}3x{radical}3)R30 CO/Cu(111) and p2mg(2x1)CO/Ni(110), N is from c(2x2) N2/Ni(100), and Ni 3p from clean nickel(111). The satellite peaks in all cases exhibit ARPEFS curves which indicate an angular momentum identical to the main peak and are of an intrinsic nature. A Fourier Transform Soft X-ray spectrometer (FF-SX) has been designed and is under construction for the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. The spectrometer is designed for ultra-high resolution theoretical resolving power E/{Delta}E{approx}-10{sup 6} in the photon energy region of 60-120 eV. This instrument is expected to provide experimental results which sensitively test models of correlated electron processes in atomic and molecular physics. The design criteria and consequent technical challenges posed by the short wavelengths of x-rays and desired resolving power are discussed. The fundamental and practical aspects of soft x-ray interferometry are also explored.

  4. Evaluation of gas chromatography - electron ionization - full scan high resolution Orbitrap mass spectrometry for pesticide residue analysis.

    PubMed

    Mol, Hans G J; Tienstra, Marc; Zomer, Paul

    2016-09-01

    Gas chromatography with electron ionization and full scan high resolution mass spectrometry with an Orbitrap mass analyzer (GC-EI-full scan Orbitrap HRMS) was evaluated for residue analysis. Pesticides in fruit and vegetables were taken as an example application. The relevant aspects for GC-MS based residue analysis, including the resolving power (15,000 to 120,000 FWHM at m/z 200), scan rate, dynamic range, selectivity, sensitivity, analyte identification, and utility of existing EI-libraries, are assessed and discussed in detail. The optimum acquisition conditions in full scan mode (m/z 50-500) were a resolving power of 60,000 and an automatic-gain-control target value of 3E6. These conditions provided (i) an optimum mass accuracy: within 2 ppm over a wide concentration range, with/without matrix, enabling the use of ±5 ppm mass extraction windows (ii) adequate scan speed: minimum 12 scans/peak, (iii) an intra-scan dynamic range sufficient to achieve LOD/LOQs ≤0.5 pg in fruit/vegetable matrices (corresponding to ≤0.5 μg kg(-1)) for most pesticides. EI-Orbitrap spectra were consistent over a very wide concentration range (5 orders) with good match values against NIST (EI-quadrupole) spectra. The applicability for quantitative residue analysis was verified by validation of 54 pesticides in three matrices (tomato, leek, orange) at 10 and 50 μg/kg. The method involved a QuEChERS-based extraction with a solvent switch into iso-octane, and 1 μL hot splitless injection into the GC-HRMS system. A recovery between 70 and 120% and a repeatability RSD <10% was obtained in most cases. Linearity was demonstrated for the range ≤5-250 μg kg(-1). The pesticides could be identified according to the applicable EU criteria for GC-HRMS (SANTE/11945/2015). GC-EI-full scan Orbitrap HRMS was found to be highly suited for quantitative pesticide residue analysis. The potential of qualitative screening to extend the scope makes it an attractive alternative to GC

  5. Large-Volume Reconstruction of Brain Tissue from High-Resolution Serial Section Images Acquired by SEM-Based Scanning Transmission Electron Microscopy

    PubMed Central

    Kuwajima, Masaaki; Mendenhall, John M.; Harris, Kristen M.

    2013-01-01

    With recent improvements in instrumentation and computational tools, serial section electron microscopy has become increasingly straightforward. A new method for imaging ultrathin serial sections is developed based on a field emission scanning electron microscope fitted with a transmitted electron detector. This method is capable of automatically acquiring high-resolution serial images with a large field size and very little optical and physical distortions. In this chapter, we describe the procedures leading to the generation and analyses of a large-volume stack of high-resolution images (64 μm × 64 μm × 10 μm, or larger, at 2 nm pixel size), including how to obtain large-area serial sections of uniform thickness from well-preserved brain tissue that is rapidly perfusion-fixed with mixed aldehydes, processed with a microwave-enhanced method, and embedded into epoxy resin. PMID:23086880

  6. Progress in Computational Electron-Molecule Collisions

    NASA Astrophysics Data System (ADS)

    Rescigno, Tn

    1997-10-01

    The past few years have witnessed tremendous progress in the development of sophisticated ab initio methods for treating collisions of slow electrons with isolated small molecules. Researchers in this area have benefited greatly from advances in computer technology; indeed, the advent of parallel computers has made it possible to carry out calculations at a level of sophistication inconceivable a decade ago. But bigger and faster computers are only part of the picture. Even with today's computers, the practical need to study electron collisions with the kinds of complex molecules and fragments encountered in real-world plasma processing environments is taxing present methods beyond their current capabilities. Since extrapolation of existing methods to handle increasingly larger targets will ultimately fail as it would require computational resources beyond any imagined, continued progress must also be linked to new theoretical developments. Some of the techniques recently introduced to address these problems will be discussed and illustrated with examples of electron-molecule collision calculations we have carried out on some fairly complex target gases encountered in processing plasmas. Electron-molecule scattering continues to pose many formidable theoretical and computational challenges. I will touch on some of the outstanding open questions.

  7. The contribution of electron collisions to rotational excitations of cometary water

    NASA Technical Reports Server (NTRS)

    Xie, Xingfa; Mumma, Michael J.

    1992-01-01

    The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in comet Halley during the Giotto spacecraft encounter. In the case of the O(sub 00) yields 1(sub 11) rotational transition, the e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus. Thus, the rotational temperature of the water molecule in the intermediate coma may be controlled by collisions with electrons rather than with neutral collisions, and the rotational temperature retrieved from high resolution infrared spectra of water in comet Halley may reflect electron temperatures rather than neutral gas temperature in the intermediate coma.

  8. Electron collisions with coherently prepared atomic targets

    SciTech Connect

    Trajmar, S.; Kanik, I.; LeClair, L.R.; Khakoo, M.S.; Bray, I.; Fursa, D.; Csanak, G.

    1998-02-01

    The subject of electron scattering by laser-excited atoms is briefly reviewed. To demonstrate some aspects of these electron collision processes, the authors describe the procedures and the results of a joint experimental and theoretical study concerning elastic scattering by coherently excited {sup 138}Ba (...6s6p {sup 1}P{sub 1}) atoms. Examples of experimental and theoretical collision parameters and magnetic sublevel differential cross sections for elastic scattering are given and compared. The convergent close coupling calculations (with the neglect of spin-orbit interaction) are in good agreement with experiment at 20 eV impact energy and 10, 15 and 20{degree} scattering angles and can be expected to yield reliable integral magnetic sublevel and alignment creation cross sections. The role of these quantities in plasma polarization spectroscopy is pointed out.

  9. Theory of Electron-Ion Collisions

    SciTech Connect

    Griffin, Donald C

    2009-10-02

    Collisions of electrons with atoms and ions play a crucial role in the modeling and diagnostics of fusion plasmas. In the edge and divertor regions of magnetically confined plasmas, data for the collisions of electrons with neutral atoms and low charge-state ions are of particular importance, while in the inner region, data on highly ionized species are needed. Since experimental measurements for these collisional processes remain very limited, data for such processes depend primarily on the results of theoretical calculations. Over the period of the present grant (January 2006 - August 2009), we have made additional improvements in our parallel scattering programs, generated data of direct fusion interest and made these data available on The Controlled Fusion Atomic Data Center Web site at Oak Ridge National Laboratory. In addition, we have employed these data to do collsional-radiative modeling studies in support of a variety of experiments with magnetically confined fusion plasmas.

  10. Cross Sections for Electron Collisions with Methane

    SciTech Connect

    Song, Mi-Young Yoon, Jung-Sik; Cho, Hyuck; Itikawa, Yukikazu; Karwasz, Grzegorz P.; Kokoouline, Viatcheslav; Nakamura, Yoshiharu; Tennyson, Jonathan

    2015-06-15

    Cross section data are compiled from the literature for electron collisions with methane (CH{sub 4}) molecules. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment. The data derived from swarm experiments are also considered. For each of these processes, the recommended values of the cross sections are presented. The literature has been surveyed through early 2014.

  11. High-Resolution Electron Energy Loss Studies of Oxygen, Hydrogen, Nitrogen, Nitric Oxide, and Nitrous Oxide Adsorption on Germanium Surfaces.

    NASA Astrophysics Data System (ADS)

    Entringer, Anthony G.

    The first high resolution electron energy loss spectroscopy (HREELS) studies of the oxidation and nitridation of germanium surfaces are reported. Both single crystal Ge(111) and disordered surfaces were studied. Surfaces were exposed to H, O_2, NO, N _2O, and N, after cleaning in ultra-high vacuum. The Ge surfaces were found to be non-reactive to molecular hydrogen (H_2) at room temperature. Exposure to atomic hydrogen (H) resulted hydrogen adsorption as demonstrated by the presence of Ge-H vibrational modes. The HREEL spectrum of the native oxide of Ge characteristic of nu -GeO_2 was obtained by heating the oxide to 200^circC. Three peaks were observed at 33, 62, and 106 meV for molecular oxygen (O_2) adsorbed on clean Ge(111) at room temperature. These peaks are indicative of dissociative bonding and a dominant Ge-O-Ge bridge structure. Subsequent hydrogen exposure resulted in a shift of the Ge-H stretch from its isolated value of 247 meV to 267 meV, indicative of a dominant +3 oxidation state. A high density of dangling bonds and defects and deeper oxygen penetration at the amorphous Ge surface result in a dilute bridge structure with a predominant +1 oxidation state for similar exposures. Molecules of N_2O decompose at the surfaces to desorbed N_2 molecules and chemisorbed oxygen atoms. In contrast, both oxygen and nitrogen are detected at the surfaces following exposure to NO molecules. Both NO and N_2O appear to dissociate and bond at the top surface layer. Molecular nitrogen (N_2) does not react with the Ge surfaces, however, a precursor Ge nitride is observed at room temperature following exposure to nitrogen atoms and ions. Removal of oxygen by heating of the NO-exposed surface to 550^circC enabled the identification of the Ge-N vibrational modes. These modes show a structure similar to that of germanium nitride. This spectrum is also identical to that of the N-exposed surface heated to 550^circC. Surface phonon modes of the narrow-gap semiconducting

  12. Direct observation of the intergrown {alpha}-phase in {beta}-TmAlB{sub 4} via high-resolution electron microscopy

    SciTech Connect

    Yubuta, Kunio; Mori, Takao; Leithe-Jasper, Andreas; Grin, Yuri; Okada, Shigeru; Shishido, Toetsu

    2009-08-05

    A TmAlB{sub 4} crystal with a ThMoB{sub 4}-type ({beta}-type) structure phase related to a hexagonal AlB{sub 2}-type structure was studied by electron diffraction and high-resolution electron microscopy. A high-resolution image clearly exhibits an intergrown lamellar structure of a YCrB{sub 4}-type ({alpha}-type) phase in the matrix of the {beta}-type phase in TmAlB{sub 4} crystal. The lamellar structure can be characterized by a tiling of deformed hexagons, which are a common structure unit in the {alpha}-type and {beta}-type structures. The intergrown nanostructure is considered to be attributed to the origin of low temperature anomalies in physical properties.

  13. In Situ Real-time Environmental High Resolution Electron Microscopy of Nanometer Size Novel Xerogel Catalysts for Hydrogenation Reactions in Nylon 6,6.

    PubMed

    Gai; Kourtakis; Ziemecki

    2000-07-01

    In situ real-time environmental high resolution electron microscopy (EHREM) under controlled reaction environments permits direct atomic resolution imaging of dynamic surface and sub-surface microstructures of reacting catalysts. Using the EHREM and complementary microscopy methods, we have investigated selective hydrogenation reaction mechanisms over novel xerogel catalysts of ruthenium and Ru with Co and Au promoters on titania supports, and report an alternative heterogeneous catalytic process for the hydrogenation of adiponitrile (ADN) in the manufacture of Nylon 6,6. The direct EHREM observations are supported by ultra-high resolution low voltage scanning electron microscope (SEM) of spatial distributions of the highly dispersed nanometer-size catalyst particles and parallel chemical studies. The results demonstrate the important role of in situ EHREM in the design of heterogeneous catalytic hydrogenation processes on the nanoscale. PMID:10898817

  14. Nature of One- and Two-Phonon Mixed Symmetry States in 92Zr and 94Mo from High-Resolution Electron and Proton Scattering

    SciTech Connect

    Neumann-Cosel, P. von; Burda, O.; Kuhar, M.; Lenhardt, A.; Ponomarev, V. Yu.; Richter, A.; Wambach, J.; Botha, N. T.; Fearick, R. W.; Carter, J.; Sideras-Haddad, E.; Foertsch, S. V.; Neveling, R.; Smit, F. D.; Fransen, C.; Fujita, H.; Pietralla, N.

    2006-03-13

    High-resolution inelastic electron (performed at the S-DALINAC) and proton (performed at iThemba LABS) scattering experiments on 92Zr and 94Mo with emphasis on E2 transitions are presented The measured form factors and angular distributions provide a measure for the F-spin purity, respectively the isovector nature, of the proposed one-phonon mixed symmetry states and furthermore provide a sensitive test of a possible two-phonon character of excited 2+ states.

  15. Investigations of atomic configurations of 60° basal dislocations in wurtzite GaN film by high-resolution transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Chang, Yunjie; Wang, Yumei; Deng, Zhen; Chen, Hong; Ge, Binghui

    2016-04-01

    GaN epitaxial films grown on Si (111) substrates were observed using a 200 kV high-resolution (HR) transmission electron microscope. Both perfect and dissociated 60° basal dislocations were found in ? HR images. By utilizing the image deconvolution method, the HR images were transformed into structure maps with an improved resolution, and then the atomic configurations of perfect and partial dislocations were determined. Afterwards, the possible dissociation schemes for the dissociated dislocations were derived.

  16. Studies of electron correlation effects in multicharged ion atom collisions involving double capture

    SciTech Connect

    Stolterfoht, N.; Sommer, K.; Griffin, D.C.; Havener, C.C.; Huq, M.S.; Phaneuf, R.A.; Swenson, J.K.; Meyer, F.W.

    1988-01-01

    We review measurements of L-Coster Kronig and Auger electron production in slow, multicharged collision systems to study electron correlation effects in the process of double electron capture. The n/sup /minus/3/ law was confirmed for the production of the Coster-Kronig configurations 1s/sup 2/2pn/ell/ (n greater than or equal to 6) in O/sup 6 +/ + He collisions. Enhancement of high angular momentum /ell/ in specific 1s/sup 2/2pn/ell/ configurations was observed by means of high-resolution measurements of the Coster-Kronig lines. The importance of electron correlation effects in couplings of potential energy curves leading to the 1s/sup 2/2pn/ell/ configurations is verified by means of Landau-Zener model calculations. 32 refs., 4 figs.

  17. High Resolution Emission Spectroscopy of the Alpha Pi-1 - Chi Sigma-1(+) Fourth Positive Band System of CO from Electron Impact

    NASA Technical Reports Server (NTRS)

    Beegle, Luther W.; Ajello, Joseph M.; James, Geoffrey K.; Alvarez, Marcos; Dziczek, Dariusz

    2000-01-01

    We report electron-impact induced fluorescence spectra [300 mA full width at half maximum (FWHM)] of CO for 20 and 100 eV impact energies of the spectral region of 1300 to 2050 A and high resolution spectra (FWHM) of the v'=5 to v"=l and the v'=3 to v"=O bands showing that the rotational structure of the band system are modeled accurately. The excitation function of the (0,1) band (1597 A) was measured from electron impact in the energy range from threshold to 750 eV and placed on an absolute scale from modem calibration standards.

  18. Electron-ion collision operator in strong electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Fraiman, Gennadiy; Balakin, Alexey

    2012-10-01

    The pair electron-ion collision operator is found for the kinetic equation describing the one-particle drift distribution in strong electromagnetic fields [1]. The pair collisions are studied under the conditions when the oscillation velocity of an electron driven by an external electromagnetic wave is much larger than the electron drift velocity. The operator is presented in the Boltzmann form and describes collisions with both small and large changes of the particle momentum. In contrast with the Landau collision operator, which describes diffusion in the momentum space, the collision operator that we propose describes a new and very important effect, namely, Coulomb attraction of a wave-driven oscillating electron to an ion due to multiple returns of the electron to the same ion. This effect leads to a large increase of the collision cross-section of electron-ion collisions in strong laser fields, to increased efficiency of the Joule heating in plasma, to the generation of fast electrons through e-i collisions, etc. [4pt] [1] A. A. Balakin and G. M. Fraiman, Electron-ion collision operator in strong electromagnetic fields, EPL 93, 35001 (2011).

  19. Flat-field grating spectrometer for high-resolution soft x-ray and EUV measurements on an electron beam ion trap

    SciTech Connect

    Beiersdorfer, P; Magee, E; Trabert, E; Chen, H; Lepson, J K; Gu, M F; Schmidt, M

    2004-03-27

    A R = 44.3 m grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Angstrom up to 50 Angstrom. The instrument uses a grating with variable line spacing (about 2400 l/mm) for a flat field of view. Spectra are recorded with a back-illuminated charge-coupled device detector. The new instrument greatly improves upon the resolution achieved with existing grating spectrometers and complements crystal spectrometers at the shorter wavelengths both in terms of wavelength coverage and polarization independent reflectivity response.

  20. High-resolution transmission electron microscopy study of electrically-driven reversible phase change in ge2sb2te5 nanowires.

    PubMed

    Jung, Yeonwoong; Nam, Sung-Wook; Agarwal, Ritesh

    2011-03-01

    By combining high-resolution transmission electron microscopy (HRTEM) characterization and electrical measurements on a unique device platform, we study the reversible electrically-driven phase-change characteristics of self-assembled Ge(2)Sb(2)Te(5) nanowires. Detailed HRTEM analyses are used to correlate and understand the effect of full and intermediate structural transformations on the measured electrical properties of the nanowire devices. The study demonstrates that our unique approach has the potential to provide new information regarding the dynamic structural and electrical states of phase-change materials at the nanoscale, which will aid the design of future phase-change memory devices. PMID:21271735

  1. High resolution multiple electron impact ionisation of He, Ne, Ar, Kr and Xe atoms close to threshold: Appearance energies and Wannier exponents

    NASA Astrophysics Data System (ADS)

    Gstir, B.; Denifl, S.; Hanel, G.; Rümmele, M.; Fiegele, T.; Stano, M.; Feketeova, L.; Matejcik, S.; Becker, K.; Scheier, P.; Märk, T. D.

    2003-05-01

    We have determined appearance energies AE(X n+ /X) for the formation of multiply charged He, Ne, Ar, Kr and Xe ions up to charge state n=2 (He), n=4 (Ne), n=6 (Ar), n=6 (Kr) and n=8 (Xe) using a recently commissioned high-resolution electron impact ionization mass spectrometer. The data analysis is based on the Marquart-Levenberg algorithm, involving an iterative, non-linear least-squares fitting of the threshold data assuming a 2-function or a 3-function fit based on a Wannier-type power law. This allows us to extract the relevant AEs and corresponding Wannier exponents.

  2. Probing the electronic and vibrational structure of Au2Al2(-) and Au2Al2 using photoelectron spectroscopy and high resolution photoelectron imaging.

    PubMed

    Lopez, Gary V; Czekner, Joseph; Jian, Tian; Li, Wei-Li; Yang, Zheng; Wang, Lai-Sheng

    2014-12-14

    The electronic and vibrational structures of Au2Al2(-) and Au2Al2 have been investigated using photoelectron spectroscopy (PES), high-resolution photoelectron imaging, and theoretical calculations. Photoelectron spectra taken at high photon energies with a magnetic-bottle apparatus reveal numerous detachment transitions and a large energy gap for the neutral Au2Al2. Vibrationally resolved PE spectra are obtained using high-resolution photoelectron imaging for the ground state detachment transition of Au2Al2(-) at various photon energies (670.55-843.03 nm). An accurate electron affinity of 1.4438(8) eV is obtained for the Au2Al2 neutral cluster, as well as two vibrational frequencies at 57 ± 8 and 305 ± 13 cm(-1). Hot bands transitions yield two vibrational frequencies for Au2Al2(-) at 57 ± 10 and 144 ± 12 cm(-1). The obtained vibrational and electronic structure information is compared with density functional calculations, unequivocally confirming that both Au2Al2(-) and Au2Al2 possess C2v tetrahedral structures. PMID:25494751

  3. Probing the electronic and vibrational structure of Au2Al2- and Au2Al2 using photoelectron spectroscopy and high resolution photoelectron imaging

    NASA Astrophysics Data System (ADS)

    Lopez, Gary V.; Czekner, Joseph; Jian, Tian; Li, Wei-Li; Yang, Zheng; Wang, Lai-Sheng

    2014-12-01

    The electronic and vibrational structures of Au2Al2- and Au2Al2 have been investigated using photoelectron spectroscopy (PES), high-resolution photoelectron imaging, and theoretical calculations. Photoelectron spectra taken at high photon energies with a magnetic-bottle apparatus reveal numerous detachment transitions and a large energy gap for the neutral Au2Al2. Vibrationally resolved PE spectra are obtained using high-resolution photoelectron imaging for the ground state detachment transition of Au2Al2- at various photon energies (670.55-843.03 nm). An accurate electron affinity of 1.4438(8) eV is obtained for the Au2Al2 neutral cluster, as well as two vibrational frequencies at 57 ± 8 and 305 ± 13 cm-1. Hot bands transitions yield two vibrational frequencies for Au2Al2- at 57 ± 10 and 144 ± 12 cm-1. The obtained vibrational and electronic structure information is compared with density functional calculations, unequivocally confirming that both Au2Al2- and Au2Al2 possess C2v tetrahedral structures.

  4. Newly appreciated roles for electrons in ion-atom collisions

    SciTech Connect

    Sellin, I.A. . Dept. of Physics and Astronomy Oak Ridge National Lab., TN )

    1990-01-01

    Since the previous Debrecen workshop on High-Energy Ion-Atom Collisions there have been numerous experiments and substantial theoretical developments in the fields of fast ion-atom and ion- solid collisions concerned with explicating the previously largely underappreciated role of electrons as ionizing and exciting agents in such collisions. Examples to be discussed include the double electron ionization problem in He; transfer ionization by protons in He; double excitation in He; backward scattering of electrons in He; the role of electron-electron interaction in determining beta parameters for ELC; projectile K ionization by target electrons; electron spin exchange in transfer excitation; electron impact ionization in crystal channels; resonant coherent excitation in crystal channels; excitation and dielectronic recombination in crystal channels; resonant transfer and excitation; the similarity of recoil ion spectra observed in coincidence with electron capture vs. electron loss; and new research on ion-atom collisions at relativistic energies.

  5. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

    PubMed Central

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-01-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

  6. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer's disease.

    PubMed

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F; Arellano-Jiménez, M Josefina; Zhu, Xiongwei; Rogers, Jack T; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-01-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer's disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

  7. A high-resolution time-of-flight energy analyzer for femtosecond electron pulses at 30 keV

    NASA Astrophysics Data System (ADS)

    Gliserin, Alexander; Walbran, Matthew; Baum, Peter

    2016-03-01

    We report a time-of-flight spectrometer for electron pulses at up to 30 keV, which is a suitable energy for atomic-resolution femtosecond investigations via time-resolved electron diffraction, microscopy, and energy loss spectroscopy. For realistic femtosecond beams without apertures, the instrument's energy resolution is ˜0.5 eV (full width at half maximum) or 2 × 10-5 at a throughput of 50%-90%. We demonstrate the analyzer's versatility by three first applications, namely, femtosecond electron pulse metrology via optical streaking, in situ drift correction in laser-microwave synchronization for electron pulse compression, and time-resolved electron energy loss spectroscopy of aluminum, showing the instrument's capability of tracking plasmonic loss peak positions with few-meV accuracy.

  8. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

    NASA Astrophysics Data System (ADS)

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-04-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

  9. A high-resolution time-of-flight energy analyzer for femtosecond electron pulses at 30 keV.

    PubMed

    Gliserin, Alexander; Walbran, Matthew; Baum, Peter

    2016-03-01

    We report a time-of-flight spectrometer for electron pulses at up to 30 keV, which is a suitable energy for atomic-resolution femtosecond investigations via time-resolved electron diffraction, microscopy, and energy loss spectroscopy. For realistic femtosecond beams without apertures, the instrument's energy resolution is ∼0.5 eV (full width at half maximum) or 2 × 10(-5) at a throughput of 50%-90%. We demonstrate the analyzer's versatility by three first applications, namely, femtosecond electron pulse metrology via optical streaking, in situ drift correction in laser-microwave synchronization for electron pulse compression, and time-resolved electron energy loss spectroscopy of aluminum, showing the instrument's capability of tracking plasmonic loss peak positions with few-meV accuracy. PMID:27036767

  10. Real-time high-resolution transmission electron microscopy observation of the growth process of ( 0 0 1 ) surfaces on a nanometer-sized Si multiply twinned particle

    NASA Astrophysics Data System (ADS)

    Takeguchi, Masaki; Tanaka, Miyoko; Yasuda, Hidehiro; Furuya, Kazuo

    2001-11-01

    A nanometer-sized Si multiply twinned particle (MTP) was fabricated by electron-induced SiO 2-decomposition technique inside an ultrahigh vacuum electron microscope. Structure and growth kinetics of the (0 0 1) surface on the MTP were observed by profile imaging high-resolution transmission electron microscopy (HRTEM). Real-time HRTEM observation indicated that the (0 0 1) surfaces were covered with single domain of 1×2 reconstruction and that a new top-layer formation was accompanied by the break of dimer structure of its subsurface. It was also found that the layer growth on the (0 0 1) surfaces showed an unusual behavior, due to a strain field caused by elastic deformation of the MTP.

  11. The determination of potential energy curve and dipole moment of the (5)0(+) electronic state of (85)Rb(133)Cs molecule by high resolution photoassociation spectroscopy.

    PubMed

    Yuan, Jinpeng; Zhao, Yanting; Ji, Zhonghua; Li, Zhonghao; Kim, Jin-Tae; Xiao, Liantuan; Jia, Suotang

    2015-12-14

    We present the formation of ultracold (85)Rb(133)Cs molecules in the (5)0(+) electronic state by photoassociation and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 vibrational and lowest J = 0 levels are identified with rotationally resolved high resolution photoassociation spectra. Precise Dunham coefficients are determined for the (5)0(+) state with high accuracy, then the Rydberg-Klein-Rees potential energy curve is derived. The electric dipole moments with respect to the vibrational numbers of the (5)0(+) electronic state of (85)Rb(133)Cs molecule are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0(+) state are helpful to understand the molecular structure and discover suitable transition pathways for transferring ultracold atoms to deeply bound rovibrational levels of the electronic ground state. PMID:26671380

  12. The determination of potential energy curve and dipole moment of the (5)0+ electronic state of 85Rb133Cs molecule by high resolution photoassociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuan, Jinpeng; Zhao, Yanting; Ji, Zhonghua; Li, Zhonghao; Kim, Jin-Tae; Xiao, Liantuan; Jia, Suotang

    2015-12-01

    We present the formation of ultracold 85Rb133Cs molecules in the (5)0+ electronic state by photoassociation and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 vibrational and lowest J = 0 levels are identified with rotationally resolved high resolution photoassociation spectra. Precise Dunham coefficients are determined for the (5)0+ state with high accuracy, then the Rydberg-Klein-Rees potential energy curve is derived. The electric dipole moments with respect to the vibrational numbers of the (5)0+ electronic state of 85Rb133Cs molecule are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0+ state are helpful to understand the molecular structure and discover suitable transition pathways for transferring ultracold atoms to deeply bound rovibrational levels of the electronic ground state.

  13. Electron diffraction and high-resolution electron microscopy studies on layered Li2-δ(Mn1-xCox)1+δO3

    NASA Astrophysics Data System (ADS)

    Fujii, Hiroki; Ozawa, Kiyoshi; Mochiku, Takashi

    2013-07-01

    The structure of Li2MnO3-LiCoO2 solid solutions or Li2-δ(Mn1-xCox)1+δO3 (LMCO) which are promising lithium-battery cathodes was studied by high-resolution electron microscopy (HREM). X-ray diffraction (XRD) analyses indicate that Li1.6Mn0.2Co1.2O3 and Li1.7Mn0.4Co0.9O3 take a rhombohedral (R3¯m space group) structure, whereas Li1.85Mn0.7Co0.45O3 and Li1.95Mn0.9Co0.15O3 take a monoclinic (C2/m) superstructure. HREM studies on those samples reveal that all of the observed crystallites in sample Li1.95Mn0.9Co0.15O3 contain sharp stripe structures due to the planar defects along the ch-axis (stacking direction of the hexagonal close-packed planes) of parent rhombohedral R3¯m cell. Such stripe structures become faint with increasing x, Co content. The origin of the planar defects is mainly attributed not to the different structures but to the different local orientations of the monoclinic LMCO. Local disordering of Li and (Mn,Co) in (Li,Mn,Co) planes is developed with increasing x and the structures are transformed from C2/m to R3¯m. The alternative (Li,Mn,Co)-plane stacking structure, trigonal P3112 LMCO, was occasionally observed. However, only P3112 LMCO platelets with a thickness of a single unit cell were detected.

  14. Electronic Structure of AC-Clusters and High-Resolution X-ray Spectra of Actinides in Solids

    SciTech Connect

    Kulagin, Nicolay Alex

    2007-07-01

    Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RAn+:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray lines are presented for AC ions with unoccupied 5f-shell in the clusters in oxides, chlorides and fluorides environment. Possibility of collapse of nf-shell for the separate clusters and identification of electronic state of ions with unstable nuclei, are discussed, too. (author)

  15. Intense energetic electron flux enhancements in Mercury's magnetosphere: An integrated view with high-resolution observations from MESSENGER

    NASA Astrophysics Data System (ADS)

    Baker, Daniel N.; Dewey, Ryan M.; Lawrence, David J.; Goldsten, John O.; Peplowski, Patrick N.; Korth, Haje; Slavin, James A.; Krimigis, Stamatios M.; Anderson, Brian J.; Ho, George C.; McNutt, Ralph L.; Raines, Jim M.; Schriver, David; Solomon, Sean C.

    2016-03-01

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from MESSENGER's Energetic Particle Spectrometer, as well as data arising from energetic electrons recorded by the X-Ray Spectrometer and Gamma-Ray and Neutron Spectrometer (GRNS) instruments, recent work greatly extends our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near-tail region of Mercury's magnetosphere and are subsequently "injected" onto closed magnetic field lines on the planetary nightside. The electrons populate the plasma sheet and drift rapidly eastward toward the dawn and prenoon sectors, at times executing multiple complete drifts around the planet to form "quasi-trapped" populations.

  16. Energetic-electron flux enhancements in Mercury's magnetosphere: An integrated view with high-resolution observations from MESSENGER

    NASA Astrophysics Data System (ADS)

    Baker, Daniel N.

    2016-04-01

    The MESSENGER mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from MESSENGER's Energetic Particle Spectrometer (EPS), as well as data arising from energetic electrons recorded by the X-Ray Spectrometer (XRS) and Gamma-Ray and Neutron Spectrometer (GRNS) instruments, recent work greatly extends our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near-tail region of Mercury's magnetosphere and are subsequently "injected" onto closed magnetic field lines on the planetary night side. The electrons populate the plasma sheet and drift rapidly eastward toward the dawn and pre-noon sectors, at time executing multiple complete drifts around the planet to form "quasi-trapped" populations.

  17. Variation of mesospheric ozone during the highly relativistic electron event in May 1992 as measured by the High Resolution Doppler Imager instrument on UARS

    NASA Astrophysics Data System (ADS)

    Pesnell, W. Dean; Goldberg, Richard A.; Jackman, Charles H.; Chenette, D. L.; Gaines, E. E.

    2000-10-01

    Highly relativistic electron precipitation events (HREs) include long-lived enhancements of the flux of electrons with E>1MeV into the Earth's atmosphere. HREs also contain increased fluxes of electrons with energies above 100 keV that have been predicted to cause large depletions of mesospheric ozone. For some of the measured instantaneous values of the electron fluxes during the HRE of May 1992, relative depletions greater than 22% were predicted to occur between altitudes of 55 and 80 km, where HOx reactions cause local minima in both the ozone number density and mixing ratio altitude profiles. These ozone depletions should follow the horizontal distribution of the electron precipitation, having a distinct boundary equatorward of the L=3 magnetic shell. To search for these effects, we have analyzed ozone data from the High Resolution Doppler Imager (HRDI) instrument on UARS. Owing to the multiple, off-track viewing angles of HRDI, observations in the region affected by the electrons are taken at similar local solar times before, during, and after the electron flux increase. Our analysis limits the relative ozone depletion to values <10% during the very intense May 1992 HRE. We do observe decreases in the ozone mixing ratio at several points in the diurnal cycle that may be associated with the transport of water vapor into the mesosphere during May 1992. This masking of the precipitating electron effects by the seasonal variations in water vapor can complicate the detection of those effects.

  18. A high-resolution field-emission-gun, scanning electron microscope investigation of anisotropic hydrogen decrepitation in Nd-Fe-B-based sintered magnets

    SciTech Connect

    Soderznik, Marko; McGuiness, Paul; Zuzek-Rozman, Kristina; Kobe, Spomenka; Skulj, Irena; Yan Gaolin

    2010-05-15

    In this investigation commercial magnets based on (Nd,Dy){sub 14}(Fe,Co){sub 79}B{sub 7} were prepared by a conventional powder-metallurgy route with a degree of alignment equal to {approx}90% and then exposed to hydrogen at a pressure of 1 bar. The magnets, in the form of cylinders, were observed to decrepitate exclusively from the ends. High-resolution electron microscopy was able to identify the presence of crack formation within the Nd{sub 2}Fe{sub 14}B grains, with the cracks running parallel to the c axis of these grains. Based on the concentration profile for hydrogen in a rare-earth transition-metal material, it is clear that the presence of hydrogen-induced cracks running perpendicular to the ends of the magnet provides for a much more rapidly progressing hydrogen front in this direction than from the sides of the magnet. This results in the magnet exhibiting a macroscopic tendency to decrepitate from the poles of the magnet toward the center. This combination of microstructural modification via particle alignment as part of the sintering process and direct observation via high-resolution electron microscopy has led to a satisfying explanation for the anisotropic hydrogen-decrepitation effect.

  19. Helium ion microscopy and ultra-high-resolution scanning electron microscopy analysis of membrane-extracted cells reveals novel characteristics of the cytoskeleton of Giardia intestinalis.

    PubMed

    Gadelha, Ana Paula Rocha; Benchimol, Marlene; de Souza, Wanderley

    2015-06-01

    Giardia intestinalis presents a complex microtubular cytoskeleton formed by specialized structures, such as the adhesive disk, four pairs of flagella, the funis and the median body. The ultrastructural organization of the Giardia cytoskeleton has been analyzed using different microscopic techniques, including high-resolution scanning electron microscopy. Recent advances in scanning microscopy technology have opened a new venue for the characterization of cellular structures and include scanning probe microscopy techniques such as ultra-high-resolution scanning electron microscopy (UHRSEM) and helium ion microscopy (HIM). Here, we studied the organization of the cytoskeleton of G. intestinalis trophozoites using UHRSEM and HIM in membrane-extracted cells. The results revealed a number of new cytoskeletal elements associated with the lateral crest and the dorsal surface of the parasite. The fine structure of the banded collar was also observed. The marginal plates were seen linked to a network of filaments, which were continuous with filaments parallel to the main cell axis. Cytoplasmic filaments that supported the internal structures were seen by the first time. Using anti-actin antibody, we observed a labeling in these filamentous structures. Taken together, these data revealed new surface characteristics of the cytoskeleton of G. intestinalis and may contribute to an improved understanding of the structural organization of trophozoites. PMID:25956335

  20. Entanglement creation in electron-electron collisions at solid surfaces

    NASA Astrophysics Data System (ADS)

    Feder, R.; Giebels, F.; Gollisch, H.

    2015-08-01

    For spin-polarized low-energy electrons impinging on a crystalline surface, an important reaction channel is the collision with a bound valence electron of opposite spin, followed by the emission of a correlated electron pair with antiparallel spins. While primary and valence electrons are not entangled, the screened Coulomb interaction generates spin entanglement between the two outgoing electrons. As a quantitative measure of this entanglement, we calculated a modified von Neumann entropy in terms of direct and exchange transition matrix elements. For coplanar symmetric setups with equal energies of antiparallel-spin electrons, maximal entanglement is analytically shown to occur quite universally, irrespective of the choice of the primary electron energy, the outgoing electron energy, and polar emission angle, and even of the choice of the surface system. Numerical results for Fe(110) and Cu(111) demonstrate first that strong entanglement can persist for unequal energies and second that an overall entanglement reduction due to nonentangled parallel-spin electrons can be avoided for ferromagnetic and even for nonmagnetic surfaces.

  1. Cross Sections for Electron Collisions with Carbon Monoxide

    SciTech Connect

    Itikawa, Yukikazu

    2015-03-15

    Cross section data are collected and reviewed for electron collisions with carbon monoxide. Collision processes included are total scattering, elastic scattering, momentum transfer, excitations of rotational, vibrational and electronic states, ionization, and dissociation. For each process, recommended values of the cross sections are presented, when possible. The literature has been surveyed through to the end of 2013.

  2. High resolution study of structural and electronic properties of epitaxial graphene grown on off-axis 4H-SiC (0001)

    NASA Astrophysics Data System (ADS)

    Giannazzo, F.; Deretzis, I.; Nicotra, G.; Fisichella, G.; Ramasse, Q. M.; Spinella, C.; Roccaforte, F.; La Magna, A.

    2014-05-01

    In this paper, the structural and electronic properties of epitaxial graphene (EG) grown on 8°-off 4H-SiC (0001) by high temperature thermal processes have been extensively investigated by a combination of several high resolution characterization techniques. The increase in the number of graphene layers with the growth temperature (from 1600 to 1700 °C) was studied by microRaman spectroscopy and high resolution transmission electron microscopy (HRTEM) on cross-sectioned samples. The few layers of graphene reside on a stepped SiC surface with alternating (0001) terraces and (11-2n) facets. Peculiar corrugations (wrinkles) in the graphene membrane preferentially oriented perpendicularly to the substrate steps were also observed. Motivated by recent atomic resolution studies of the EG/SiC interface revealing a local delamination of the interfacial C buffer from the (11-2n) facets, we searched for a correlation of these interfacial structural properties with the macroscopic electronic transport in EG field effect transistors (FETs). In particular, electrical characterization of EG top gated FETs fabricated with the channel length parallel or perpendicular to the substrate steps revealed a peculiar anisotropy of the channel conductance with respect to the steps' orientation. This effect was explained in terms of a local enhancement of EG resistance on the (11-2n) facets with respect to the (0001) basal plane, which is consistent with a reduced doping due to the local buffer layer delamination from those facets. Furthermore, scanning probe microscopy-based local electron mean free path measurements on EG showed a ~3× enhancement of mean free path on the buffer-layer-free (11-2n) facets with respect to (0001) terraces, probably associated to a strong reduction of Coulomb scattering effects on graphene's electrons.

  3. High-resolution spot-scan electron microscopy of microcrystals of an alpha-helical coiled-coil protein.

    PubMed

    Bullough, P A; Tulloch, P A

    1990-09-01

    We describe the electron microscopy of a crystalline assembly of an alpha-helical coiled-coil protein extracted from the ootheca of the praying mantis. Electron diffraction patterns of unstained crystals show crystal lattice sampling of the coiled-coil molecular transform to a resolution beyond 1.5 A. Using a "spot-scan" method of electron imaging, micrographs of unstained crystals have been obtained that visibly diffract laser light from crystal spacings as small as 4.3 A. A projection map was calculated to 4 A using electron diffraction amplitudes and phases from computer-processed images. The projection map clearly shows modulations in density arising from the 5.1 A alpha-helical repeat, the first time this type of modulation has been revealed by electron microscopy. The crystals have p2 plane group symmetry with a = 92.4 A, b = 150.7 A, y = 92.4 degrees. Examination of tilted specimens shows that c is approximately 18 A, indicating that the unit cell is only one molecule thick. A preliminary interpretation shows tightly packed molecules some 400 A long lying with their long axes in the plane of the projection. The molecules have a coiled-coil configuration for most of their length. The possible modes of packing of the molecules in three dimensions are discussed. PMID:2398496

  4. Low-energy electron collisions with biomolecules

    NASA Astrophysics Data System (ADS)

    Winstead, Carl; McKoy, Vincent

    2012-11-01

    We report recent progress in applying the Schwinger multichannel computational method to the interactions of slow electrons with biomolecules. Calculations on constituents of DNA, including nucleobases, phosphate esters, and models of the backbone sugar, have provided insight into the nature of the low-energy shape resonances, and thereby into possible sites and mechanisms for electron attachment that may lead to strand-breaking. At the same time, more approximate calculations on larger assemblies such as nucleosides and deoxyadenosine monophosphate indicate how the resonance properties of the subunits will or will not persist in DNA itself. We are pursuing a similar strategy for another major class of biomolecules, the proteins, by beginning with fixed-nuclei studies of the constituent amino acids; here we present preliminary results for the simplest amino acid, glycine. We also describe efforts directed at an improved understanding electron collisions with alcohols, which, in addition to basic scientific interest, may prove useful in the modeling of ignition and combustion within biofuel-powered engines.

  5. Intense energetic-electron flux enhancements in Mercury's magnetosphere: An integrated view with high-resolution observations from MESSENGER

    NASA Astrophysics Data System (ADS)

    Dewey, R. M.; Baker, D. N.; Slavin, J. A.; Raines, J. M.; Lawrence, D. J.; Goldsten, J. O.; Peplowski, P. N.; Korth, H.; Krimigis, S. M.; Anderson, B. J.; Ho, G. C.; McNutt, R. L., Jr.; Schriver, D.; Solomon, S. C.

    2015-12-01

    One of the surprising observations by Mariner 10 during its March 1974 flyby of Mercury was the detection of intense bursts of energetic particles in Mercury's magnetosphere in association with substorm-like magnetic field reconfigurations. A full understanding of where, when, and how such particle bursts occur was not possible from the limited Mariner 10 data. The MESSENGER mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from MESSENGER's Energetic Particle Spectrometer (EPS), as well as data arising from energetic electrons recorded by the X-Ray Spectrometer (XRS) and Gamma-Ray and Neutron Spectrometer (GRNS) instruments, recent work has greatly extended our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near-tail region of Mercury's magnetosphere and are subsequently "injected" onto closed magnetic field lines on the planetary night side. The electrons evidently fill the plasma sheet volume and drift rapidly eastward toward the dawn and pre-noon sectors, at time executing multiple complete drifts around the planet to form "quasi-trapped" populations.

  6. Identification of biological molecules in situ at high resolution via the fluorescence excited by a scanning electron beam.

    PubMed Central

    Hough, P V; McKinney, W R; Ledbeter, M C; Pollack, R E; Moos, H W

    1976-01-01

    Proteins, nucleic acids, and fluorescein-conjugated antibody are shown to be identifidable in situ via the fluorescence excited by the focused electron beam of a canning electron microscope. A molecular species is identified by its characteristic fluorescence spectrum and by a characteristic alteration of the spectrum with time under the electron beam. Primary protein fluorescence is relatively rapidly destroyed by the beam, but protein photoproduct fluorescence is more rugged and will in some cases permit detection of small numbers of protein molecules. Nucleic acid fluorescence is extremely long-lived and will permit detection of small numbers of nucleic acid residues. The theoretical resolution limit for localization of a particular molecular species -- about 20 A--is determined by the known maximum distance for molecular excitation by fast electrons. Drect extapolation from an observed resolution of 900 A in the localization of nucleic acid using a low-efficiency detector leads to an experimental resolution limit of less than 60 A. Fluorescence is strongly quenched by residual water in the specimen. Similar quenching is produced by some macromolecular associations and so may serve to localize such associations. Images PMID:768980

  7. High resolution scanning electron microscopy of rabbit corneal endothelium to show effects of UV-visible irradiation in the presence of chlorpromazine

    SciTech Connect

    Lea, P.J.; Hollenberg, M.J.; Menon, I.A.; Temkin, R.J.; Persad, S.D.; Basu, P.K. )

    1989-01-01

    The ultrastructure of rabbit cornea endothelial cells was examined by scanning electron microscopy (SEM) in freeze-cleaved corneas using a Hitachi S-570 scanning electron microscope in the high resolution mode (HRSEM). In order to study phototoxic effects in vitro, rabbit corneas (experimental) were cultured as organ culture in the presence of 5 micrograms/ml chlorpromazine (CPZ) and irradiated. For comparison, control 1 corneas were not irradiated but incubated in the dark without CPZ in the medium; control 2 corneas were also kept in the dark but in the presence of CPZ; control 3 corneas were irradiated with no CPZ in the medium. Cellular damage was not seen in the three types of control corneas, but in the experimental corneas the endothelial cells showed extensive disruption of the cell membrane and some deterioration of the intracellular components. Our study confirmed that HRSEM is a satisfactory new technique for visualizing damage of the intracellular organelles of corneal endothelium.

  8. High-resolution electron-energy-loss spectroscopy and photoelectron-diffraction studies of the geometric structure of adsorbates on single-crystal metal surfaces

    SciTech Connect

    Rosenblatt, D.H.

    1982-11-01

    Two techniques which have made important contributions to the understanding of surface phenomena are high resolution electron energy loss spectroscopy (EELS) and photoelectron diffraction (PD). EELS is capable of directly measuring the vibrational modes of clean and adsorbate covered metal surfaces. In this work, the design, construction, and performance of a new EELS spectrometer are described. These results are discussed in terms of possible structures of the O-Cu(001) system. Recommendations for improvements in this EELS spectrometer and guidelines for future spectrometers are given. PD experiments provide accurate quantitative information about the geometry of atoms and molecules adsorbed on metal surfaces. The technique has advantages when used to study disordered overlayers, molecular overlayers, multiple site systems, and adsorbates which are weak electron scatterers. Four experiments were carried out which exploit these advantages.

  9. Phase-modulated electronic wave packet interferometry reveals high resolution spectra of free Rb atoms and Rb*He molecules.

    PubMed

    Bruder, Lukas; Mudrich, Marcel; Stienkemeier, Frank

    2015-10-01

    Phase-modulated wave packet interferometry is combined with mass-resolved photoion detection to investigate rubidium atoms attached to helium nanodroplets in a molecular beam experiment. The spectra of atomic Rb electronic states show a vastly enhanced sensitivity and spectral resolution when compared to conventional pump-probe wave packet interferometry. Furthermore, the formation of Rb*He exciplex molecules is probed and for the first time a fully resolved vibrational spectrum for transitions between the lowest excited 5Π3/2 and the high-lying electronic states 2(2)Π, 4(2)Δ, 6(2)Σ is obtained and compared to theory. The feasibility of applying coherent multidimensional spectroscopy to dilute cold gas phase samples is demonstrated in these experiments. PMID:26309123

  10. A High Resolution On-Chip Delay Sensor with Low Supply-Voltage Sensitivity for High-Performance Electronic Systems

    PubMed Central

    Sheng, Duo; Lai, Hsiu-Fan; Chan, Sheng-Min; Hong, Min-Rong

    2015-01-01

    An all-digital on-chip delay sensor (OCDS) circuit with high delay-measurement resolution and low supply-voltage sensitivity for efficient detection and diagnosis in high-performance electronic system applications is presented. Based on the proposed delay measurement scheme, the quantization resolution of the proposed OCDS can be reduced to several picoseconds. Additionally, the proposed cascade-stage delay measurement circuit can enhance immunity to supply-voltage variations of the delay measurement resolution without extra self-biasing or calibration circuits. Simulation results show that the delay measurement resolution can be improved to 1.2 ps; the average delay resolution variation is 0.55% with supply-voltage variations of ±10%. Moreover, the proposed delay sensor can be implemented in an all-digital manner, making it very suitable for high-performance electronic system applications as well as system-level integration. PMID:25688590