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Sample records for energy loss spectroscopy

  1. Image simulation for electron energy loss spectroscopy

    SciTech Connect

    Oxley, Mark P.; Pennycook, Stephen J.

    2007-10-22

    In this paper, aberration correction of the probe forming optics of the scanning transmission electron microscope has allowed the probe-forming aperture to be increased in size, resulting in probes of the order of 1 Å in diameter. The next generation of correctors promise even smaller probes. Improved spectrometer optics also offers the possibility of larger electron energy loss spectrometry detectors. The localization of images based on core-loss electron energy loss spectroscopy is examined as function of both probe-forming aperture and detector size. The effective ionization is nonlocal in nature, and two common local approximations are compared to full nonlocal calculations. Finally, the affect of the channelling of the electron probe within the sample is also discussed.

  2. Image simulation for electron energy loss spectroscopy

    DOE PAGES

    Oxley, Mark P.; Pennycook, Stephen J.

    2007-10-22

    In this paper, aberration correction of the probe forming optics of the scanning transmission electron microscope has allowed the probe-forming aperture to be increased in size, resulting in probes of the order of 1 Å in diameter. The next generation of correctors promise even smaller probes. Improved spectrometer optics also offers the possibility of larger electron energy loss spectrometry detectors. The localization of images based on core-loss electron energy loss spectroscopy is examined as function of both probe-forming aperture and detector size. The effective ionization is nonlocal in nature, and two common local approximations are compared to full nonlocal calculations.more » Finally, the affect of the channelling of the electron probe within the sample is also discussed.« less

  3. Probing battery chemistry with liquid cell electron energy loss spectroscopy

    DOE PAGES

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; ...

    2015-01-01

    Electron energy loss spectroscopy (EELS) was used to determine the chemistry and oxidation state of LiMn2O4 and Li4Ti5O12 thin film battery electrodes in liquid cells for in situ scanning/transmission electron microscopy (S/TEM). Using the L2,3 white line intensity ratio method we determine the oxidation state of Mn and Ti in a liquid electrolyte solvent and discuss experimental parameters that influence measurement sensitivity.

  4. Simulating electron energy loss spectroscopy with the MNPBEM toolbox

    NASA Astrophysics Data System (ADS)

    Hohenester, Ulrich

    2014-03-01

    Within the MNPBEM toolbox, we show how to simulate electron energy loss spectroscopy (EELS) of plasmonic nanoparticles using a boundary element method approach. The methodology underlying our approach closely follows the concepts developed by García de Abajo and coworkers (Garcia de Abajo, 2010). We introduce two classes eelsret and eelsstat that allow in combination with our recently developed MNPBEM toolbox for a simple, robust, and efficient computation of EEL spectra and maps. The classes are accompanied by a number of demo programs for EELS simulation of metallic nanospheres, nanodisks, and nanotriangles, and for electron trajectories passing by or penetrating through the metallic nanoparticles. We also discuss how to compute electric fields induced by the electron beam and cathodoluminescence. Catalogue identifier: AEKJ_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKJ_v2_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 38886 No. of bytes in distributed program, including test data, etc.: 1222650 Distribution format: tar.gz Programming language: Matlab 7.11.0 (R2010b). Computer: Any which supports Matlab 7.11.0 (R2010b). Operating system: Any which supports Matlab 7.11.0 (R2010b). RAM:≥1 GB Classification: 18. Catalogue identifier of previous version: AEKJ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 183 (2012) 370 External routines: MESH2D available at www.mathworks.com Does the new version supersede the previous version?: Yes Nature of problem: Simulation of electron energy loss spectroscopy (EELS) for plasmonic nanoparticles. Solution method: Boundary element method using electromagnetic potentials. Reasons for new version: The new version of the toolbox includes two additional classes for the simulation of electron energy

  5. Probing battery chemistry with liquid cell electron energy loss spectroscopy

    SciTech Connect

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; Unocic, Kinga A.; Sacci, Robert L.; Dudney, Nancy J.; More, Karren Leslie; Aguiar, Jeffery A.

    2015-01-01

    Electron energy loss spectroscopy (EELS) was used to determine the chemistry and oxidation state of LiMn2O4 and Li4Ti5O12 thin film battery electrodes in liquid cells for in situ scanning/transmission electron microscopy (S/TEM). Using the L2,3 white line intensity ratio method we determine the oxidation state of Mn and Ti in a liquid electrolyte solvent and discuss experimental parameters that influence measurement sensitivity.

  6. Probing Battery Chemistry with Liquid Cell Electron Energy Loss Spectroscopy

    SciTech Connect

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; Aguiar, Jeffery A.; Unocic, Kinga A.; Sacci, Robert L.; Dudney, Nancy J.; More, Karren L.

    2015-11-25

    We demonstrate the ability to apply electron energy loss spectroscopy (EELS) to follow the chemistry and oxidation states of LiMn2O4 and Li4Ti5O12 battery electrodes within a battery solvent. The use and importance of in situ electrochemical cells coupled with a scanning/transmission electron microscope (S/TEM) has expanded and been applied to follow changes in battery chemistry during electrochemical cycling. Furthermore, we discuss experimental parameters that influence measurement sensitivity and provide a framework to apply this important analytical method to future in situ electrochemical studies.

  7. Tomography of particle plasmon fields from electron energy loss spectroscopy.

    PubMed

    Hörl, Anton; Trügler, Andreas; Hohenester, Ulrich

    2013-08-16

    We theoretically investigate electron energy loss spectroscopy (EELS) of metallic nanoparticles in the optical frequency domain. Using a quasistatic approximation scheme together with a plasmon eigenmode expansion, we show that EELS can be rephrased in terms of a tomography problem. For selected single and coupled nanoparticles we extract the three-dimensional plasmon fields from a collection of rotated EELS maps. Our results pave the way for a fully three-dimensional plasmon-field tomography and establish EELS as a quantitative measurement device for plasmonics.

  8. Electron energy loss spectroscopy of gold nanoparticles on graphene

    SciTech Connect

    DeJarnette, Drew; Roper, D. Keith

    2014-08-07

    Plasmon excitation decay by absorption, scattering, and hot electron transfer has been distinguished from effects induced by incident photons for gold nanoparticles on graphene monolayer using electron energy loss spectroscopy (EELS). Gold nano-ellipses were evaporated onto lithographed graphene, which was transferred onto a silicon nitride transmission electron microscopy grid. Plasmon decay from lithographed nanoparticles measured with EELS was compared in the absence and presence of the graphene monolayer. Measured decay values compared favorably with estimated radiative and non-radiative contributions to decay in the absence of graphene. Graphene significantly enhanced low-energy plasmon decay, increasing mode width 38%, but did not affect higher energy plasmon or dark mode decay. This decay beyond expected radiative and non-radiative mechanisms was attributed to hot electron transfer, and had quantum efficiency of 20%, consistent with previous reports.

  9. Development of Electron Energy Loss Spectroscopy in the Biological Sciences

    PubMed Central

    Aronova, M.A.; Leapman, R.D.

    2012-01-01

    The high sensitivity of electron energy loss spectroscopy (EELS) for detecting light elements at the nanoscale makes it a valuable technique for application to biological systems. In particular, EELS provides quantitative information about elemental distributions within subcellular compartments, specific atoms bound to individual macromolecular assemblies, and the composition of bionanoparticles. The EELS data can be acquired either in the fixed beam energy-filtered transmission electron microscope (EFTEM) or in the scanning transmission electron microscope (STEM), and recent progress in the development of both approaches has greatly expanded the range of applications for EELS analysis. Near single atom sensitivity is now achievable for certain elements bound to isolated macromolecules, and it becomes possible to obtain three-dimensional compositional distributions from sectioned cells through EFTEM tomography. PMID:23049161

  10. Single-atom electron energy loss spectroscopy of light elements

    PubMed Central

    Senga, Ryosuke; Suenaga, Kazu

    2015-01-01

    Light elements such as alkali metal (lithium, sodium) or halogen (fluorine, chlorine) are present in various substances and indeed play significant roles in our life. Although atomic behaviours of these elements are often a key to resolve chemical or biological activities, they are hardly visible in transmission electron microscope because of their smaller scattering power and higher knock-on probability. Here we propose a concept for detecting light atoms encaged in a nanospace by means of electron energy loss spectroscopy using inelastically scattered electrons. In this method, we demonstrate the single-atom detection of lithium, fluorine, sodium and chlorine with near-atomic precision, which is limited by the incident probe size, signal delocalization and atomic movement in nanospace. Moreover, chemical shifts of lithium K-edge have been successfully identified with various atomic configurations in one-dimensional lithium compounds. PMID:26228378

  11. Electron energy-loss spectroscopy of branched gap plasmon resonators

    PubMed Central

    Raza, Søren; Esfandyarpour, Majid; Koh, Ai Leen; Mortensen, N. Asger; Brongersma, Mark L.; Bozhevolnyi, Sergey I.

    2016-01-01

    The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons. PMID:27982030

  12. Electron energy-loss spectroscopy of branched gap plasmon resonators

    NASA Astrophysics Data System (ADS)

    Raza, Søren; Esfandyarpour, Majid; Koh, Ai Leen; Mortensen, N. Asger; Brongersma, Mark L.; Bozhevolnyi, Sergey I.

    2016-12-01

    The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons.

  13. Data processing for atomic resolution electron energy loss spectroscopy.

    PubMed

    Cueva, Paul; Hovden, Robert; Mundy, Julia A; Xin, Huolin L; Muller, David A

    2012-08-01

    The high beam current and subangstrom resolution of aberration-corrected scanning transmission electron microscopes has enabled electron energy loss spectroscopy (EELS) mapping with atomic resolution. These spectral maps are often dose limited and spatially oversampled, leading to low counts/channel and are thus highly sensitive to errors in background estimation. However, by taking advantage of redundancy in the dataset map, one can improve background estimation and increase chemical sensitivity. We consider two such approaches--linear combination of power laws and local background averaging--that reduce background error and improve signal extraction. Principal component analysis (PCA) can also be used to analyze spectrum images, but the poor peak-to-background ratio in EELS can lead to serious artifacts if raw EELS data are PCA filtered. We identify common artifacts and discuss alternative approaches. These algorithms are implemented within the Cornell Spectrum Imager, an open source software package for spectroscopic analysis.

  14. Uranium trioxide behavior during electron energy loss spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Degueldre, Claude; Alekseev, Evgeny V.

    2015-03-01

    A sample of uranium trioxide (UO3) was produced by focused ion beam (~10 μm×~10 μm×<0.5 μm) for transmission electron and electron energy loss (EEL) spectroscopy examinations in a transmission electron microscope (TEM). The EEL spectra were recorded as a function of the thickness for the P and O edges in the low energy range 0-350 eV and were compared to spectra of UO3 small grains attached to a TEM grid. The EEL spectrum was studied through a range of thicknesses going from ~60 to ~260 nm. The EEL spectra recorded for UO3 are compared with those recorded for UO2. The reduction of UO3 into U4O9 and/or UO2 is readily observed apparently during the TEM investigations and as confirmed by electron diffraction (eD). This redox effect is similar to that known for other redox sensitive oxides. Recommendations are suggested to avoid sample decomposition.

  15. Reflection Electron Energy Loss Spectroscopy of Iron Monosilicide

    NASA Astrophysics Data System (ADS)

    Parshin, A. S.; Igumenov, A. Yu.; Mikhlin, Yu. L.; Pchelyakov, O. P.; Zhigalov, V. S.

    2017-02-01

    X-ray photoelectron spectra, reflection electron energy loss spectra, and inelastic electron scattering cross section spectra of iron monosilicide FeSi are investigated. It is shown that the spectra of inelastic electron scattering cross section have advantages over the reflection electron energy loss spectra in studying the processes of electron energy losses. An analysis of the fine structure of the inelastic electron scattering cross section spectra allows previously unresolved peaks to be identified and their energy, intensity, and nature to be determined. The difference between energies of fitting loss peaks in the spectra of inelastic electron scattering cross section of FeSi and pure Fe are more substantial than the chemical shifts in X-ray photoelectron spectra, which indicates the possibility of application of the fine structure of the spectra of inelastic electron scattering cross section for elemental analysis.

  16. Low-loss electron energy loss spectroscopy: An atomic-resolution complement to optical spectroscopies and application to graphene

    DOE PAGES

    Kapetanakis, Myron; Zhou, Wu; Oxley, Mark P.; ...

    2015-09-25

    Photon-based spectroscopies have played a central role in exploring the electronic properties of crystalline solids and thin films. They are a powerful tool for probing the electronic properties of nanostructures, but they are limited by lack of spatial resolution. On the other hand, electron-based spectroscopies, e.g., electron energy loss spectroscopy (EELS), are now capable of subangstrom spatial resolution. Core-loss EELS, a spatially resolved analog of x-ray absorption, has been used extensively in the study of inhomogeneous complex systems. In this paper, we demonstrate that low-loss EELS in an aberration-corrected scanning transmission electron microscope, which probes low-energy excitations, combined with amore » theoretical framework for simulating and analyzing the spectra, is a powerful tool to probe low-energy electron excitations with atomic-scale resolution. The theoretical component of the method combines density functional theory–based calculations of the excitations with dynamical scattering theory for the electron beam. We apply the method to monolayer graphene in order to demonstrate that atomic-scale contrast is inherent in low-loss EELS even in a perfectly periodic structure. The method is a complement to optical spectroscopy as it probes transitions entailing momentum transfer. The theoretical analysis identifies the spatial and orbital origins of excitations, holding the promise of ultimately becoming a powerful probe of the structure and electronic properties of individual point and extended defects in both crystals and inhomogeneous complex nanostructures. The method can be extended to probe magnetic and vibrational properties with atomic resolution.« less

  17. Low-loss electron energy loss spectroscopy: An atomic-resolution complement to optical spectroscopies and application to graphene

    SciTech Connect

    Kapetanakis, Myron; Zhou, Wu; Oxley, Mark P.; Lee, Jaekwang; Prange, Micah P.; Pennycook, Stephen J.; Idrobo Tapia, Juan Carlos; Pantelides, Sokrates T.

    2015-09-25

    Photon-based spectroscopies have played a central role in exploring the electronic properties of crystalline solids and thin films. They are a powerful tool for probing the electronic properties of nanostructures, but they are limited by lack of spatial resolution. On the other hand, electron-based spectroscopies, e.g., electron energy loss spectroscopy (EELS), are now capable of subangstrom spatial resolution. Core-loss EELS, a spatially resolved analog of x-ray absorption, has been used extensively in the study of inhomogeneous complex systems. In this paper, we demonstrate that low-loss EELS in an aberration-corrected scanning transmission electron microscope, which probes low-energy excitations, combined with a theoretical framework for simulating and analyzing the spectra, is a powerful tool to probe low-energy electron excitations with atomic-scale resolution. The theoretical component of the method combines density functional theory–based calculations of the excitations with dynamical scattering theory for the electron beam. We apply the method to monolayer graphene in order to demonstrate that atomic-scale contrast is inherent in low-loss EELS even in a perfectly periodic structure. The method is a complement to optical spectroscopy as it probes transitions entailing momentum transfer. The theoretical analysis identifies the spatial and orbital origins of excitations, holding the promise of ultimately becoming a powerful probe of the structure and electronic properties of individual point and extended defects in both crystals and inhomogeneous complex nanostructures. The method can be extended to probe magnetic and vibrational properties with atomic resolution.

  18. Anisotropic plasmons, excitons, and electron energy loss spectroscopy of phosphorene

    NASA Astrophysics Data System (ADS)

    Ghosh, Barun; Kumar, Piyush; Thakur, Anmol; Chauhan, Yogesh Singh; Bhowmick, Somnath; Agarwal, Amit

    2017-07-01

    In this article, we explore the anisotropic electron energy loss spectrum (EELS) in monolayer phosphorene based on ab initio time-dependent density-functional-theory calculations. Similarly to black phosphorus, the EELS of undoped monolayer phosphorene is characterized by anisotropic excitonic peaks for energies in the vicinity of the band gap and by interband plasmon peaks for higher energies. On doping, an additional intraband plasmon peak also appears for energies within the band gap. Similarly to other two-dimensional systems, the intraband plasmon peak disperses as ωpl∝√{q } in both the zigzag and armchair directions in the long-wavelength limit and deviates for larger wave vectors. The anisotropy of the long-wavelength plasmon intraband dispersion is found to be inversely proportional to the square root of the ratio of the effective masses: ωpl(q y ̂) /ωpl(q x ̂) =√{mx/my } .

  19. 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.

  20. 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.

  1. Optimization of monochromated TEM for ultimate resolution imaging and ultrahigh resolution electron energy loss spectroscopy.

    PubMed

    Lopatin, Sergei; Cheng, Bin; Liu, Wei-Ting; Tsai, Meng-Lin; He, Jr-Hau; Chuvilin, Andrey

    2017-09-01

    The performance of a monochromated transmission electron microscope with Wien type monochromator is optimized to achieve an extremely narrow energy spread of electron beam and an ultrahigh energy resolution with spectroscopy. The energy spread in the beam is improved by almost an order of magnitude as compared to specified values. The optimization involves both the monochromator and the electron energy loss detection system. We demonstrate boosted capability of optimized systems with respect to ultra-low loss EELS and sub-angstrom resolution imaging (in a combination with spherical aberration correction). Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Nanoscale mapping of optical band gaps using monochromated electron energy loss spectroscopy.

    PubMed

    Zhan, W; Granerød, C S; Venkatachalapathy, V; Johansen, K M H; Jensen, I J T; Kuznetsov, A Yu; Prytz, Ø

    2017-03-10

    Using monochromated electron energy loss spectroscopy in a probe-corrected scanning transmission electron microscope we demonstrate band gap mapping in ZnO/ZnCdO thin films with a spatial resolution below 10 nm and spectral precision of 20 meV.

  3. Nanoscale mapping of optical band gaps using monochromated electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhan, W.; Granerød, C. S.; Venkatachalapathy, V.; Johansen, K. M. H.; Jensen, I. J. T.; Kuznetsov, A. Yu; Prytz, Ø.

    2017-03-01

    Using monochromated electron energy loss spectroscopy in a probe-corrected scanning transmission electron microscope we demonstrate band gap mapping in ZnO/ZnCdO thin films with a spatial resolution below 10 nm and spectral precision of 20 meV.

  4. Angular-resolved electron energy loss spectroscopy on a split-ring resonator

    NASA Astrophysics Data System (ADS)

    von Cube, F.; Niegemann, J.; Irsen, S.; Bell, D. C.; Linden, S.

    2014-03-01

    We investigate the plasmonic near field of a lithographically defined split-ring resonator with angular-resolved electron energy loss spectroscopy in a scanning transmission electron microscope. By tilting the sample, different electric field components of the plasmonic modes can be probed with the electron beam. The electron energy loss spectra recorded under oblique incidence can feature plasmonic resonances that are not observable under normal incidence. Our experimental findings are supported by full numerical calculations based on the discontinuous Galerkin time-domain method.

  5. First-Principles Vibrational Electron Energy Loss Spectroscopy of β -Guanine

    NASA Astrophysics Data System (ADS)

    Radtke, G.; Taverna, D.; Lazzeri, M.; Balan, E.

    2017-07-01

    A general approach to model vibrational electron energy loss spectra obtained using an electron beam positioned away from the specimen is presented. The energy-loss probability of the fast electron is evaluated using first-principles quantum mechanical calculations (density functional theory) of the dielectric response of the specimen. The validity of the method is assessed using recently measured anhydrous β -guanine, an important molecular solid used by animals to produce structural colors. The good agreement between theory and experiments lays the basis for a quantitative interpretation of this spectroscopy in complex systems.

  6. Toward 10 meV electron energy-loss spectroscopy resolution for plasmonics.

    PubMed

    Bellido, Edson P; Rossouw, David; Botton, Gianluigi A

    2014-06-01

    Energy resolution is one of the most important parameters in electron energy-loss spectroscopy. This is especially true for measurement of surface plasmon resonances, where high-energy resolution is crucial for resolving individual resonance peaks, in particular close to the zero-loss peak. In this work, we improve the energy resolution of electron energy-loss spectra of surface plasmon resonances, acquired with a monochromated beam in a scanning transmission electron microscope, by the use of the Richardson-Lucy deconvolution algorithm. We test the performance of the algorithm in a simulated spectrum and then apply it to experimental energy-loss spectra of a lithographically patterned silver nanorod. By reduction of the point spread function of the spectrum, we are able to identify low-energy surface plasmon peaks in spectra, more localized features, and higher contrast in surface plasmon energy-filtered maps. Thanks to the combination of a monochromated beam and the Richardson-Lucy algorithm, we improve the effective resolution down to 30 meV, and evidence of success up to 10 meV resolution for losses below 1 eV. We also propose, implement, and test two methods to limit the number of iterations in the algorithm. The first method is based on noise measurement and analysis, while in the second we monitor the change of slope in the deconvolved spectrum.

  7. High-resolution monochromated electron energy-loss spectroscopy of organic photovoltaic materials.

    PubMed

    Alexander, Jessica A; Scheltens, Frank J; Drummy, Lawrence F; Durstock, Michael F; Hage, Fredrik S; Ramasse, Quentin M; McComb, David W

    2017-09-01

    Advances in electron monochromator technology are providing opportunities for high energy resolution (10 - 200meV) electron energy-loss spectroscopy (EELS) to be performed in the scanning transmission electron microscope (STEM). The energy-loss near-edge structure in core-loss spectroscopy is often limited by core-hole lifetimes rather than the energy spread of the incident illumination. However, in the valence-loss region, the reduced width of the zero loss peak makes it possible to resolve clearly and unambiguously spectral features at very low energy-losses (<3eV). In this contribution, high-resolution EELS was used to investigate four materials commonly used in organic photovoltaics (OPVs): poly(3-hexlythiophene) (P3HT), [6,6] phenyl-C61 butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and fullerene (C60). Data was collected on two different monochromated instruments - a Nion UltraSTEM 100 MC 'HERMES' and a FEI Titan(3) 60-300 Image-Corrected S/TEM - using energy resolutions (as defined by the zero loss peak full-width at half-maximum) of 35meV and 175meV, respectively. The data was acquired to allow deconvolution of plural scattering, and Kramers-Kronig analysis was utilized to extract the complex dielectric functions. The real and imaginary parts of the complex dielectric functions obtained from the two instruments were compared to evaluate if the enhanced resolution in the Nion provides new opto-electronic information for these organic materials. The differences between the spectra are discussed, and the implications for STEM-EELS studies of advanced materials are considered. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. A proximal retarding field analyzer for scanning probe energy loss spectroscopy.

    PubMed

    Bauer, Karl; Murphy, Shane; Palmer, Richard E

    2017-03-10

    A compact proximal retarding field analyzer for scanning probe energy loss spectroscopy measurements is described. Using the scanning tunneling microscope (STM) tip as a field emission (FE) electron source in conjunction with this analyzer, which is placed at a glancing angle to the surface plane, FE sample current and electron reflectivity imaging may be performed simultaneously. This is demonstrated in measurements of Ag nanostructures prepared on graphite by electron-beam lithography, where a material contrast of 13% is observed, with a lateral resolution of 25 nm, between the silver and graphite in electron reflectivity images. Topological contrast mechanisms such as edge enhancement and shadowing are also observed, giving rise to additional features in the electron reflectivity images. The same instrument configuration has been used to measure electron energy loss spectra on bare graphite, where the zero loss peak, π band plasmon loss peak and secondary electron peaks are observed. Using this simple and compact analyzer an STM, with sufficient open access to the tip-sample junction, may easily be augmented to provide simultaneous elemental and topographic mapping, supplementing STM image measurements with FE sample current and electron reflectivity images, as well as electron energy loss spectroscopy measurements, in the same instrument.

  9. A proximal retarding field analyzer for scanning probe energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Bauer, Karl; Murphy, Shane; Palmer, Richard E.

    2017-03-01

    A compact proximal retarding field analyzer for scanning probe energy loss spectroscopy measurements is described. Using the scanning tunneling microscope (STM) tip as a field emission (FE) electron source in conjunction with this analyzer, which is placed at a glancing angle to the surface plane, FE sample current and electron reflectivity imaging may be performed simultaneously. This is demonstrated in measurements of Ag nanostructures prepared on graphite by electron-beam lithography, where a material contrast of 13% is observed, with a lateral resolution of 25 nm, between the silver and graphite in electron reflectivity images. Topological contrast mechanisms such as edge enhancement and shadowing are also observed, giving rise to additional features in the electron reflectivity images. The same instrument configuration has been used to measure electron energy loss spectra on bare graphite, where the zero loss peak, π band plasmon loss peak and secondary electron peaks are observed. Using this simple and compact analyzer an STM, with sufficient open access to the tip-sample junction, may easily be augmented to provide simultaneous elemental and topographic mapping, supplementing STM image measurements with FE sample current and electron reflectivity images, as well as electron energy loss spectroscopy measurements, in the same instrument.

  10. Real-space imaging of nanotip plasmons using electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Schröder, Benjamin; Weber, Thorsten; Yalunin, Sergey V.; Kiel, Thomas; Matyssek, Christian; Sivis, Murat; Schäfer, Sascha; von Cube, Felix; Irsen, Stephan; Busch, Kurt; Ropers, Claus; Linden, Stefan

    2015-08-01

    We report the spatial mapping of surface plasmons on conical gold nanotips by electron energy loss spectroscopy. We observe standing-wave patterns resulting from reflections of the fundamental surface-plasmon mode at the nanotip apex. The experimental results are in very good agreement with numerical calculations using the discontinuous Galerkin time-domain method and analytical computations based on a cylindrical mode expansion.

  11. The electronic properties of potassium doped copper-phthalocyanine studied by electron energy-loss spectroscopy.

    PubMed

    Flatz, K; Grobosch, M; Knupfer, M

    2007-06-07

    The authors have studied the electronic structure of potassium doped copper-phthalocyanine using electron energy-loss spectroscopy. The evolution of the loss function indicates the formation of distinct KxCuPc phases. Taking into account the C1s and K2p core level excitations and recent results by Giovanelli et al. [J. Chem. Phys. 126, 044709 (2007)], they conclude that these are K2CuPc and K4CuPc. They discuss the changes in the electronic excitations upon doping on the basis of the molecular electronic levels and the presence of electronic correlations.

  12. Precessed electron beam electron energy loss spectroscopy of graphene: Beyond channelling effects

    SciTech Connect

    Yedra, Ll.; Estradé, S.; Torruella, P.; Eljarrat, A.; Peiró, F.; Darbal, A. D.; Weiss, J. K.

    2014-08-04

    The effects of beam precession on the Electron Energy Loss Spectroscopy (EELS) signal of the carbon K edge in a 2 monolayer graphene sheet are studied. In a previous work, we demonstrated the use of precession to compensate for the channeling-induced reduction of EELS signal when in zone axis. In the case of graphene, no enhancement of EELS signal is found in the usual experimental conditions, as graphene is not thick enough to present channeling effects. Interestingly, though it is found that precession makes it possible to increase the collection angle, and, thus, the overall signal, without a loss of signal-to-background ratio.

  13. Electron Energy-Loss Spectroscopy: Fundamentals and applications in the characterization of minerals

    SciTech Connect

    Krishnan, K.M.

    1989-04-01

    The combined use of an energy-loss spectrometer and an analytical electron microscope with fine probe forming capabilities provides a wealth of information about the sample at high spatial resolution. Fundamental principles governing the physics of the interaction between the fast electron and a thin foil sample, to account for the fine structure in the inelastically scattered fast electron distribution (Electron-Energy Loss Spectroscopy, EELS), will be reviewed. General application of EELS is in the area of low atomic number elements (Z < 11) microanalysis, where it significantly complements the more widely used Energy Dispersive X-ray Spectroscopy (EDXS). However, a careful analysis of the low loss plasmon oscillations and the fine structure in the core-loss edges, can provide additional information related to the bonding and electronic structure of the sample. An illustration of this is presented from our study of Cdelta diamond residue from the Allende carbonaceous chondrite. Combination of EELS with channeling effects can provide specific site occupation/valence information in crystalline materials. Details of this novel crystallographic method will be outlined and illustrated with an example of the study of chromite spinels. Finally, some pertinent experimental details will be discussed. 7 figs.

  14. Energy-loss- and thickness-dependent contrast in atomic-scale electron energy-loss spectroscopy

    SciTech Connect

    Tan, Haiyan; Zhu, Ye; Dwyer, Christian; Xin, Huolin L.

    2014-12-31

    Atomic-scale elemental maps of materials acquired by core-loss inelastic electron scattering often exhibit an undesirable sensitivity to the unavoidable elastic scattering, making the maps counter-intuitive to interpret. Here, we present a systematic study that scrutinizes the energy-loss and sample-thickness dependence of atomic-scale elemental maps acquired using 100 keV incident electrons in a scanning transmission electron microscope. For single-crystal silicon, the balance between elastic and inelastic scattering means that maps generated from the near-threshold Si-L signal (energy loss of 99 eV) show no discernible contrast for a thickness of 0.5λ (λ is the electron mean-free path, here approximately 110 nm). At greater thicknesses we observe a counter-intuitive “negative” contrast. Only at much higher energy losses is an intuitive “positive” contrast gradually restored. Our quantitative analysis shows that the energy-loss at which a positive contrast is restored depends linearly on the sample thickness. This behavior is in very good agreement with our double-channeling inelastic scattering calculations. We test a recently-proposed experimental method to correct the core-loss inelastic scattering and restore an intuitive “positive” chemical contrast. The method is demonstrated to be reliable over a large range of energy losses and sample thicknesses. The corrected contrast for near-threshold maps is demonstrated to be (desirably) inversely proportional to sample thickness. As a result, implications for the interpretation of atomic-scale elemental maps are discussed.

  15. Energy-loss- and thickness-dependent contrast in atomic-scale electron energy-loss spectroscopy

    DOE PAGES

    Tan, Haiyan; Zhu, Ye; Dwyer, Christian; ...

    2014-12-31

    Atomic-scale elemental maps of materials acquired by core-loss inelastic electron scattering often exhibit an undesirable sensitivity to the unavoidable elastic scattering, making the maps counter-intuitive to interpret. Here, we present a systematic study that scrutinizes the energy-loss and sample-thickness dependence of atomic-scale elemental maps acquired using 100 keV incident electrons in a scanning transmission electron microscope. For single-crystal silicon, the balance between elastic and inelastic scattering means that maps generated from the near-threshold Si-L signal (energy loss of 99 eV) show no discernible contrast for a thickness of 0.5λ (λ is the electron mean-free path, here approximately 110 nm). Atmore » greater thicknesses we observe a counter-intuitive “negative” contrast. Only at much higher energy losses is an intuitive “positive” contrast gradually restored. Our quantitative analysis shows that the energy-loss at which a positive contrast is restored depends linearly on the sample thickness. This behavior is in very good agreement with our double-channeling inelastic scattering calculations. We test a recently-proposed experimental method to correct the core-loss inelastic scattering and restore an intuitive “positive” chemical contrast. The method is demonstrated to be reliable over a large range of energy losses and sample thicknesses. The corrected contrast for near-threshold maps is demonstrated to be (desirably) inversely proportional to sample thickness. As a result, implications for the interpretation of atomic-scale elemental maps are discussed.« less

  16. Communication: Investigation of the electron momentum density distribution of nanodiamonds by electron energy-loss spectroscopy

    SciTech Connect

    Feng, Zhenbao; Yang, Bing; Lin, Yangming; Su, Dangsheng

    2015-12-07

    The electron momentum distribution of detonation nanodiamonds (DND) was investigated by recording electron energy-loss spectra at large momentum transfer in the transmission electron microscope (TEM), which is known as electron Compton scattering from solid (ECOSS). Compton profile of diamond film obtained by ECOSS was found in good agreement with prior photon experimental measurement and theoretical calculation that for bulk diamond. Compared to the diamond film, the valence Compton profile of DND was found to be narrower, which indicates a more delocalization of the ground-state charge density for the latter. Combining with other TEM characterizations such as high-resolution transmission electron spectroscopy, diffraction, and energy dispersive X-ray spectroscopy measurements, ECOSS was shown to be a great potential technique to study ground-state electronic properties of nanomaterials.

  17. Role of the kinematics of probing electrons in electron energy-loss spectroscopy of solid surfaces

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Silkin, V. M.; Krasovskii, E. E.

    2016-01-01

    Inelastic scattering of electrons incident on a solid surface is determined by two properties: (i) electronic response of the target system and (ii) the detailed quantum-mechanical motion of the projectile electron inside and in the vicinity of the target. We emphasize the equal importance of the second ingredient, pointing out the fundamental limitations of the conventionally used theoretical description of the electron energy-loss spectroscopy (EELS) in terms of the "energy-loss functions." Our approach encompasses the dipole and impact scattering as specific cases, with the emphasis on the quantum-mechanical treatment of the probe electron. Applied to the high-resolution EELS of Ag surface, our theory largely agrees with recent experiments, while some instructive exceptions are rationalized.

  18. High-resolution electron microscopy and electron energy-loss spectroscopy of giant palladium clusters

    NASA Astrophysics Data System (ADS)

    Oleshko, V.; Volkov, V.; Gijbels, R.; Jacob, W.; Vargaftik, M.; Moiseev, I.; van Tendeloo, G.

    1995-12-01

    Combined structural and chemical characterization of cationic polynuclear palladium coordination compounds Pd561L60(OAc)180, where L=1,10-phenantroline or 2,2'-bipyridine has been carried out by high-resolution electron microscopy (HREM) and analytical electron microscopy methods including electron energy-loss spectroscopy (EELS), zero-loss electron spectroscopic imaging, and energy-dispersive X-ray spectroscopy (EDX). The cell structure of the cluster matter with almost completely uniform metal core size distributions centered around 2.3 ±0.5 nm was observed. Zero-loss energy filtering allowed to improve the image contrast and resolution. HREM images showed that most of the palladium clusters had a cubo-octahedral shape. Some of them had a distorted icosahedron structure exhibiting multiple twinning. The selected-area electron diffraction patterns confirmed the face centered cubic structure with lattice parameter close to that of metallic palladium. The energy-loss spectra of the populations of clusters contained several bands, which could be assigned to the delayed Pd M4, 5-edge at 362 eV, the Pd M3-edge at 533 eV and the Pd M2-edge at 561 eV, the NK-edge at about 400 eV, the O K-edge at 532 eV overlapping with the Pd M3-edge and the carbon C K-edge at 284 eV. Background subtraction was applied to reveal the exact positions and fine structure of low intensity elemental peaks. EELS evaluations have been confirmed by EDX. The recorded series of the Pd M-edges and the N K-edge in the spectra of the giant palladium clusters obviously were related to Pd-Pd- and Pd-ligand bonding.

  19. Sensitivity of photoelectron energy loss spectroscopy to surface reconstruction of microcrystalline diamond films

    NASA Astrophysics Data System (ADS)

    David, Denis G. F.; Pinault-Thaury, Marie-Amandine; Ballutaud, Dominique; Godet, Christian

    2013-05-01

    In X-ray Photoelectron Spectroscopy (XPS), binding energies and intensities of core level peaks are commonly used for chemical analysis of solid surfaces, after subtraction of a background signal. This background due to photoelectron energy losses to electronic excitations in the solid (surface and bulk plasmon excitation, inter band transitions) contains valuable information related to the near surface dielectric function ɛ(ħω). In this work, the sensitivity of Photoelectron Energy Loss Spectroscopy (PEELS) is investigated using a model system, namely the well-controlled surface reconstruction of diamond. Boron-doped microcrystalline thin films with a mixture of (1 1 1) and (1 0 0) preferential orientations were characterized in the as-grown state, with a partially hydrogenated surface, and after annealing at 1150 °C in ultra high vacuum. After annealing, the bulk (σ + π) plasmon of diamond at 34.5 eV is weakly attenuated but no evidence for surface graphitization is observed near 6 eV, as confirmed by electronic properties. Unexpected features which appear at 10 ± 1 eV and 19 ± 1 eV in the energy loss distribution are well described by simulation of surface plasmon excitations in graphite-like materials; alternatively, they also coincide with experimental inter band transition losses in some graphene layers. This comparative study shows that the PEELS technique gives a clear signature of weak effects in the diamond surface reconstruction, even in the absence of graphitization. It confirms the sensitivity of PEELS acquisition with standard XPS equipment as a complementary tool for surface analysis.

  20. 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

  1. Application of Electron Energy Loss Spectroscopy for Single Wall Carbon Nanotubes (Review)

    NASA Astrophysics Data System (ADS)

    Mittal, N.; Jain, S.; Mittal, J.

    2015-03-01

    Electron energy loss spectroscopy (EELS) is among the few techniques that are available for the characterization of modified single wall carbon nanotubes (SWCNTs) having nanometer dimensions (~1-3 nm). CNTs can be modified either by surface functionalization or coating, between bundles of nanotubes by doping, intercalation and fully or partially filling the central core. EELS is an exclusive technique for the identification, composition analysis, and crystallization studies of the chemicals and materials used for the modification of SWCNTs. The present paper serves as a compendium of research work on the application of EELS for the characterization of modified SWCNTs.

  2. Visualizing and identifying single atoms using electron energy-loss spectroscopy with low accelerating voltage.

    PubMed

    Suenaga, Kazu; Sato, Yuta; Liu, Zheng; Kataura, Hiromichi; Okazaki, Toshiya; Kimoto, Koji; Sawada, Hidetaka; Sasaki, Takeo; Omoto, Kazuya; Tomita, Takeshi; Kaneyama, Toshikatsu; Kondo, Yukihito

    2009-08-01

    Visualizing atoms and discriminating between those of different elements is a goal in many analytical techniques. The use of electron energy-loss spectroscopy (EELS) in such single-atom analyses is hampered by an inherent difficulty related to the damage caused to specimens by incident electrons. Here, we demonstrate the successful EELS single-atom spectroscopy of various metallofullerene-doped single-wall nanotubes (known as peapods) without massive structural destruction. This is achieved by using an incident electron probe with a low accelerating voltage (60 kV). Single calcium atoms inside the peapods were unambiguously identified for the first time using EELS. Elemental analyses of lanthanum, cerium and erbium atoms were also demonstrated, which shows that single atoms with adjacent atomic numbers can be successfully discriminated with this technique.

  3. Valence electron energy-loss spectroscopy in monochromated scanning transmission electron microscopy.

    PubMed

    Erni, Rolf; Browning, Nigel D

    2005-10-01

    With the development of monochromators for (scanning) transmission electron microscopes, valence electron energy-loss spectroscopy (VEELS) is developing into a unique technique to study the band structure and optical properties of nanoscale materials. This article discusses practical aspects of spatially resolved VEELS performed in scanning transmission mode and the alignments necessary to achieve the current optimum performance of approximately 0.15 eV energy resolution with an electron probe size of approximately 1 nm. In particular, a collection of basic concepts concerning the acquisition process, the optimization of the energy resolution, the spatial resolution and the data processing are provided. A brief study of planar defects in a Y(1)Ba(2)Cu(3)O(7-)(delta) high-temperature superconductor illustrates these concepts and shows what kind of information can be accessed by VEELS.

  4. Mapping bright and dark modes in gold nanoparticle chains using electron energy loss spectroscopy.

    PubMed

    Barrow, Steven J; Rossouw, David; Funston, Alison M; Botton, Gianluigi A; Mulvaney, Paul

    2014-07-09

    We present a scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) investigation of gold nanosphere chains with lengths varying from 1 to 5 particles. We show localized EELS signals from the chains and identify energy-loss peaks arising due to l = 1, 2, 3, 4, and 5 plasmon modes through the use of EELS mapping. We also show the evolution of the energy of these modes as the length of a given chain increases, and we find that a chain containing N particles can accommodate at least N experimentally observable modes, in addition to the transverse mode. As the chain length is increased by the addition of one more gold particle to the chain, the new N + 1 mode becomes the highest energy mode, while the existing modes lower their energy and eventually asymptote as they delocalize along the chain. We also show that modes become increasingly difficult to detect with the EELS technique as l approaches N. The data are compared to numerical simulations.

  5. High-energy-resolution monochromator for aberration-corrected scanning transmission electron microscopy/electron energy-loss spectroscopy.

    PubMed

    Krivanek, Ondrej L; Ursin, Jonathan P; Bacon, Neil J; Corbin, George J; Dellby, Niklas; Hrncirik, Petr; Murfitt, Matthew F; Own, Christopher S; Szilagyi, Zoltan S

    2009-09-28

    An all-magnetic monochromator/spectrometer system for sub-30 meV energy-resolution electron energy-loss spectroscopy in the scanning transmission electron microscope is described. It will link the energy being selected by the monochromator to the energy being analysed by the spectrometer, without resorting to decelerating the electron beam. This will allow it to attain spectral energy stability comparable to systems using monochromators and spectrometers that are raised to near the high voltage of the instrument. It will also be able to correct the chromatic aberration of the probe-forming column. It should be able to provide variable energy resolution down to approximately 10 meV and spatial resolution less than 1 A.

  6. From electron energy-loss spectroscopy to multi-dimensional and multi-signal electron microscopy.

    PubMed

    Colliex, Christian

    2011-01-01

    This review intends to illustrate how electron energy-loss spectroscopy (EELS) techniques in the electron microscope column have evolved over the past 60 years. Beginning as a physicist tool to measure basic excitations in solid thin foils, EELS techniques have gradually become essential for analytical purposes, nowadays pushed to the identification of individual atoms and their bonding states. The intimate combination of highly performing techniques with quite efficient computational tools for data processing and ab initio modeling has opened the way to a broad range of novel imaging modes with potential impact on many different fields. The combination of Angström-level spatial resolution with an energy resolution down to a few tenths of an electron volt in the core-loss spectral domain has paved the way to atomic-resolved elemental and bonding maps across interfaces and nanostructures. In the low-energy range, improved energy resolution has been quite efficient in recording surface plasmon maps and from them electromagnetic maps across the visible electron microscopy (EM) domain, thus bringing a new view to nanophotonics studies. Recently, spectrum imaging of the emitted photons under the primary electron beam and the spectacular introduction of time-resolved techniques down to the femtosecond time domain, have become innovative keys for the development and use of a brand new multi-dimensional and multi-signal electron microscopy.

  7. Plasmons in layered nanospheres and nanotubes investigated by spatially resolved electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Kociak, M.; Henrard, L.; Stéphan, O.; Suenaga, K.; Colliex, C.

    2000-05-01

    We present an extensive electron energy loss spectroscopy study of the low-loss energy region, recorded on multishell carbon and boron-nitride nanotubes and carbon hyperfullerenes. Collections of spectra were recorded in a scanning transmission electron microscope by scanning a subnanometer probe from vacuum into the center of the nano-objects. This experimental technique provides the unique ability of disentangling and identifying the different excitation modes of a nanoparticle. We concentrate on the study of surface modes excited in a near-field geometry where the coupling distance between the electron beam and the surface of the nano-objects is accurately monitored. Similarities between surface collective excitations in the different layered nanostructures (cylindrical or spherical, boron nitride, or carbon constituted) are pointed out. Two surface modes at 12-13 eV and 17-18 eV are experimentally clearly evidenced. We show that these modes are accurately described by a classical continuum dielectric model taking fully into account the anisotropic character and the hollow geometry of the nanoparticles. These two modes are shown to be directly related to the in-plane and out-of-plane components of the dielectric tensor. The higher-energy mode (in-plane mode) is shown to shift to higher energy with decreasing impact parameter, as a result of an increase in the weights of the high-order multipolar modes while reaching the surface of the nano-objects.

  8. Band gap widening at random CIGS grain boundary detected by valence electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Keller, Debora; Buecheler, Stephan; Reinhard, Patrick; Pianezzi, Fabian; Bissig, Benjamin; Carron, Romain; Hage, Fredrik; Ramasse, Quentin; Erni, Rolf; Tiwari, Ayodhya N.

    2016-10-01

    Cu(In,Ga) Se2 (CIGS) thin film solar cells have demonstrated very high efficiencies, but still the role of nanoscale inhomogeneities in CIGS and their impact on the solar cell performance are not yet clearly understood. Due to the polycrystalline structure of CIGS, grain boundaries are very common structural defects that are also accompanied by compositional variations. In this work, we apply valence electron energy loss spectroscopy in scanning transmission electron microscopy to study the local band gap energy at a grain boundary in the CIGS absorber layer. Based on this example, we demonstrate the capabilities of a 2nd generation monochromator that provides a very high energy resolution and allows for directly relating the chemical composition and the band gap energy across the grain boundary. A band gap widening of about 20 meV is observed at the grain boundary. Furthermore, the compositional analysis by core-loss EELS reveals an enrichment of In together with a Cu, Ga and Se depletion at the same area. The experimentally obtained results can therefore be well explained by the presence of a valence band barrier at the grain boundary.

  9. Electron energy loss spectroscopy of excitons in two-dimensional-semiconductors as a function of temperature

    SciTech Connect

    Tizei, Luiz H. G.; Lin, Yung-Chang; Suenaga, Kazu; Lu, Ang-Yu; Li, Lain-Jong

    2016-04-18

    We have explored the benefits of performing monochromated Electron Energy Loss Spectroscopy (EELS) in samples at cryogenic temperatures. As an example, we have observed the excitonic absorption peaks in single layer Transition Metal Dichalcogenides. These peaks appear separated by small energies due to spin orbit coupling. We have been able to distinguish the split for MoS{sub 2} below 300 K and for MoSe{sub 2} below 220 K. However, the distinction between peaks is only clear at 150 K. We have measured the change in absorption threshold between 150 K and 770 K for MoS{sub 2} and MoSe{sub 2}. We discuss the effect of carbon and ice contamination in EELS spectra. The increased spectral resolution available made possible with modern monochromators in electron microscopes will require the development of stable sample holders which reaches temperatures far below that of liquid nitrogen.

  10. The applications of in situ electron energy loss spectroscopy to the study of electron beam nanofabrication.

    PubMed

    Chen, Shiahn J; Howitt, David G; Gierhart, Brian C; Smith, Rosemary L; Collins, Scott D

    2009-06-01

    An in situ electron energy loss spectroscopy (EELS) technique has been developed to investigate the dynamic processes associated with electron-beam nanofabrication on thin membranes. In this article, practical applications germane to e-beam nanofabrication are illustrated with a case study of the drilling of nanometer-sized pores in silicon nitride membranes. This technique involves successive acquisitions of the plasmon-loss and the core-level ionization-loss spectra in real time, both of which provide the information regarding the hole-drilling kinetics, including two respective rates for total mass loss, individual nitrogen and silicon element depletion, and the change of the atomic bonding environment. In addition, the in situ EELS also provides an alternative method for endpoint detection with a potentially higher time resolution than by imaging. On the basis of the time evolution of in situ EELS spectra, a qualitative working model combining knock-on sputtering, irradiation-induced mass transport, and phase separation can be proposed.

  11. Electron Energy Loss Spectroscopy imaging of surface plasmons at the nanometer scale.

    PubMed

    Colliex, Christian; Kociak, Mathieu; Stéphan, Odile

    2016-03-01

    Since their first realization, electron microscopes have demonstrated their unique ability to map with highest spatial resolution (sub-atomic in most recent instruments) the position of atoms as a consequence of the strong scattering of the incident high energy electrons by the nuclei of the material under investigation. When interacting with the electron clouds either on atomic orbitals or delocalized over the specimen, the associated energy transfer, measured and analyzed as an energy loss (Electron Energy Loss Spectroscopy) gives access to analytical properties (atom identification, electron states symmetry and localization). In the moderate energy-loss domain (corresponding to an optical spectral domain from the infrared (IR) to the rather far ultra violet (UV), EELS spectra exhibit characteristic collective excitations of the rather-free electron gas, known as plasmons. Boundary conditions, such as surfaces and/or interfaces between metallic and dielectric media, generate localized surface charge oscillations, surface plasmons (SP), which are associated with confined electric fields. This domain of research has been extraordinarily revived over the past few years as a consequence of the burst of interest for structures and devices guiding, enhancing and controlling light at the sub-wavelength scale. The present review focuses on the study of these surface plasmons with an electron microscopy-based approach which associates spectroscopy and mapping at the level of a single and well-defined nano-object, typically at the nanometer scale i.e. much improved with respect to standard, and even near-field, optical techniques. After calling to mind some early studies, we will briefly mention a few basic aspects of the required instrumentation and associated theoretical tools to interpret the very rich data sets recorded with the latest generation of (Scanning)TEM microscopes. The following paragraphs will review in more detail the results obtained on simple planar and

  12. Density Functional Theory Modeling of Low-Loss Electron Energy-Loss Spectroscopy in Wurtzite III-Nitride Ternary Alloys.

    PubMed

    Eljarrat, Alberto; Sastre, Xavier; Peiró, Francesca; Estradé, Sónia

    2016-06-01

    In the present work, the dielectric response of III-nitride semiconductors is studied using density functional theory (DFT) band structure calculations. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. In addition, the dependence of the most remarkable features with composition is tested, i.e. applying Vegard's law to band gap and plasmon energy. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through a wide compositional range (i.e., Al x Ga1-x N, In x Al1-x N, and In x Ga1-x N, with x=[0,1]). For this DFT calculations, the standard tools found in Wien2k software were used. In order to improve the band structure description of these semiconductor compounds, the modified Becke-Johnson exchange-correlation potential was also used. Results from these calculations are presented, including band structure, density of states, and complex dielectric function for the whole compositional range. Larger, closer to experimental values, band gap energies are predicted using the novel potential, when compared with standard generalized gradient approximation. Moreover, a detailed analysis of the collective excitation features in the dielectric response reveals their compositional dependence, which sometimes departs from a linear behavior (bowing). Finally, an advantageous method for measuring the plasmon energy dependence from these calculations is explained.

  13. Electron energy-loss spectroscopy of coupled plasmonic systems: beyond the standard electron perspective

    NASA Astrophysics Data System (ADS)

    Bernasconi, G. D.; Flauraud, V.; Alexander, D. T. L.; Brugger, J.; Martin, O. J. F.; Butet, J.

    2016-09-01

    Electron energy-loss spectroscopy (EELS) has become an experimental method of choice for the investigation of localized surface plasmon resonances, allowing the simultaneous mapping of the associated field distributions and their resonant energies with a nanoscale spatial resolution. The experimental observations have been well-supported by numerical models based on the computation of the Lorentz force acting on the impinging electrons by the scattered field. However, in this framework, the influence of the intrinsic properties of the plasmonic nanostructures studied with the electron energy-loss (EEL) measurements is somehow hidden in the global response. To overcome this limitation, we propose to go beyond this standard, and well-established, electron perspective and instead to interpret the EELS data using directly the intrinsic properties of the nanostructures, without regard to the force acting on the electron. The proposed method is particularly well-suited for the description of coupled plasmonic systems, because the role played by each individual nanoparticle in the observed EEL spectrum can be clearly disentangled, enabling a more subtle understanding of the underlying physical processes. As examples, we consider different plasmonic geometries in order to emphasize the benefits of this new conceptual approach for interpreting experimental EELS data. In particular, we use it to describe results from samples made by traditional thin film patterning and by arranging colloidal nanostructures.

  14. Numerical simulations of interference effects in photon-assisted electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Talebi, Nahid; Sigle, Wilfried; Vogelgesang, Ralf; van Aken, Peter

    2013-05-01

    Although the electromagnetic resonances of individual nanostructures can be studied by electron or photon interactions alone, exciting new possibilities open up through the simultaneous use of both. In photon-induced near-field electron microscopy (PINEM), for example, single nanostructures are optically excited by short, intense pulses and concurrently imaged with high spatial resolution by fast electrons, which act as negligible probes of electric fields. Controlling their relative arrival time provides access to the dynamics of the electromagnetic response in the near field by recording images of the electron energy loss (or gain) spectra. In this paper, we investigate the transition from optically dominated PINEM to conventional, electron-dominated electron energy-loss spectroscopy (EELS). During the systematic reduction of optical excitation intensity to zero, a novel electro-optical interference effect emerges. It reveals itself at those optical field strengths that lead to prominently visible constructive and destructive interference patterns of the optical and electron radiation fields which are scattered by a nanostructure. The interference patterns reported here allow one to achieve higher temporal, energy and spatial resolutions of the modal dynamics in electron microscopy.

  15. Reflection electron energy-loss spectroscopy and imaging for surface studies in transmission electron microscopes.

    PubMed

    Wang, Z L; Bentley, J

    1992-02-15

    A review is given on the techniques and applications of high-energy reflection electron energy-loss spectroscopy (REELS) and reflection electron microscopy (REM) for surface studies in scanning transmission electron microscopes (STEM) and conventional transmission electron microscopes (TEM). A diffraction method is introduced to identify a surface orientation in the geometry of REM. The surface dielectric response theory is presented and applied for studying alpha-alumina surfaces. Domains of the alpha-alumina (012) surface initially terminated with oxygen can be reduced by an intense electron beam to produce Al metal; the resistance to beam damage of surface domains initially terminated with Al+3 ions is attributed to the screening effect of adsorbed oxygen. Surface energy-loss near-edge structure (ELNES), extended energy-loss fine structure (EXELFS), and microanalysis using REELS are illustrated based on the studies of TiO2 and MgO. Effects of surface resonances (or channeling) on the REELS signal-to-background ratio are described. The REELS detection of a monolayer of oxygen adsorption on diamond (111) surfaces is reported. It is shown that phase contrast REM image content can be significantly increased with the use of a field emission gun (FEG). Phase contrast effects close to the core of a screw dislocation are discussed and the associated Fresnel fringes around a surface step are observed. Finally, an in situ REM experiment is described for studying atomic desorption and diffusion processes on alpha-alumina surfaces at temperatures of 1,300-1,400 degrees C.

  16. Electron Energy-Loss Spectroscopy Theory and Simulation Applied to Nanoparticle Plasmonics

    NASA Astrophysics Data System (ADS)

    Bigelow, Nicholas Walker

    In this dissertation, the capacity of electron energy-loss spectroscopy (EELS) to probe plasmons is examined in detail. EELS is shown to be able to detect both electric hot spots and Fano resonances in contrast to the prevailing knowledge prior to this work. The most detailed examination of magnetoplasmonic resonances in multi-ring structures to date and the utility of electron tomography to computational plasmonics is explored, and a new tomographic method for the reconstruction of a target is introduced. Since the observation of single-molecule surface-enhanced Raman scattering (SMSERS) in 1997, questions regarding the nature of the electromagnetic hot spots responsible for such observations still persist. A computational analysis of the electron- and photon-driven surface-plasmon resonances of monomer and dimer metal nanorods is presented to elucidate the differences and similarities between the two excitation mechanisms in a system with well understood optical properties. By correlating the nanostructure's simulated electron energy loss spectrum and loss-probability maps with its induced polarization and scattered electric field we discern how certain plasmon modes are selectively excited and how they funnel energy from the excitation source into the near- and far-field. Using a fully retarded electron-scattering theory capable of describing arbitrary three-dimensional nanoparticle geometries, aggregation schemes, and material compositions, we find that electron energy-loss spectroscopy (EELS) is able to indirectly probe the same electromagnetic hot spots that are generated by an optical excitation source. EELS is then employed in a scanning transmission electron microscope (STEM) to obtain maps of the localized surface plasmon modes of SMSERS-active nanostructures, which are resolved in both space and energy. Single-molecule character is confirmed by the bianalyte approach using two isotopologues of Rhodamine 6G. The origins of this observation are explored

  17. Electron energy loss spectroscopy of plasmon resonances in titanium nitride thin films

    SciTech Connect

    Herzing, Andrew A.; Guler, Urcan; Zhou, Xiuli; Norris, Theodore B.; Boltasseva, Alexandra; Shalaev, Vladimir

    2016-04-25

    The plasmon resonance characteristics of refractory TiN thin films were analyzed using electron energy-loss spectroscopy (EELS). A bulk plasmon resonance was observed at 2.81 eV and a weaker surface plasmon resonance peak was detected at 2.05 eV. These findings are compared to finite-difference time-domain simulations based on measured optical data. The calculated values for both the bulk and surface resonances (2.74 eV and 2.15 eV, respectively) show reasonable agreement with those measured via EELS. The amplitude of the experimentally observed surface resonance was weaker than that typically encountered in noble metal nanostructures, and this is discussed in the context of electron density and reduced spatial confinement of the resonance mode in the thin-film geometry.

  18. Quantification of ordering at a solid-liquid interface using plasmon electron energy loss spectroscopy

    SciTech Connect

    Gandman, Maria; Kauffmann, Yaron; Kaplan, Wayne D.

    2015-02-02

    We present an in situ electron energy loss spectroscopy (EELS) study of ordering of liquid Al at various Al-Al{sub 2}O{sub 3} interfaces. This technique utilizes precise measurements of the shifts in bulk plasmon resonance and their sensitivity to the valence electron density. Plasmon EELS combined with high resolution transmission electron microscopy provides information regarding the chemical composition in liquid Al at Al-Al{sub 2}O{sub 3} interfaces. Preferential oxygen segregation to the (0006) Al{sub 2}O{sub 3} plane was verified, and the (101{sup ¯}2) Al{sub 2}O{sub 3} plane was found to contain the lowest amount of segregated species.

  19. Fabrication of co-axial field emitter tips for scanning probe energy loss spectroscopy.

    PubMed

    Song, Mi Yeon; Robinson, Alex P G; Palmer, Richard E

    2010-04-16

    We report on the fabrication of a co-axial tip for application to scanning probe energy loss spectroscopy (SPELS). The device consists of a 23.3 microm tall tip on a 76 microm tall mesa with a multilayer Si/Au/HfO(2)/Au structure; the outer Au and HfO(2) layers are stripped from the apex of the tip. The inner Au layer is used as a field emitting layer and the outer Au layer is grounded to screen the electric field between the tip and the substrate. The co-axial tip shows comparable field emission characteristics to electrochemically etched tungsten tips. The SPELS spectra of graphite obtained with the new tips show pi and sigma plasmon peaks and intense secondary electron emission peaks. It is anticipated that such co-axial tips will present a significant advantage for future angular resolved SPELS measurements.

  20. Electron energy loss spectroscopy techniques for the study of microbial chromium(VI) reduction

    NASA Technical Reports Server (NTRS)

    Daulton, Tyrone L.; Little, Brenda J.; Lowe, Kristine; Jones-Meehan, Joanne

    2002-01-01

    Electron energy loss spectroscopy (EELS) techniques were used to determine oxidation state, at high spatial resolution, of chromium associated with the metal-reducing bacteria, Shewanella oneidensis, in anaerobic cultures containing Cr(VI)O4(2-). These techniques were applied to fixed cells examined in thin section by conventional transmission electron microscopy (TEM) as well as unfixed, hydrated bacteria examined by environmental cell (EC)-TEM. Two distinct populations of bacteria were observed by TEM: bacteria exhibiting low image contrast and bacteria exhibiting high contrast in their cell membrane (or boundary) structure which was often encrusted with high-contrast precipitates. Measurements by EELS demonstrated that cell boundaries became saturated with low concentrations of Cr and the precipitates encrusting bacterial cells contained a reduced form of Cr in oxidation state + 3 or lower.

  1. Detection of water and its derivatives on individual nanoparticles using vibrational electron energy-loss spectroscopy.

    PubMed

    Crozier, Peter A; Aoki, Toshihiro; Liu, Qianlang

    2016-10-01

    Understanding the role of water, hydrate and hydroxyl species on nanoparticle surfaces and interfaces is very important in both physical and life sciences. Detecting the presence of oxygen-hydrogen species with nanometer resolution is extremely challenging at present. Here we show that the recently developed vibrational electron energy-loss spectroscopy using subnanometer focused electron beams can be employed to spectroscopically identify the local presence and variation of OH species on nanoscale surfaces. The hydrogen-oxygen fingerprint can be correlated with highly localized structural and morphological information obtained from electron imaging. Moreover, the current approach exploits the aloof beam mode of spectral acquisition which does not require direct electron irradiation of the sample thus greatly reducing beam damage to the OH bond. These findings open the door for using electron microscopy to probe local hydroxyl and hydrate species on nanoscale organic and inorganic structures. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Electron energy loss spectroscopy techniques for the study of microbial chromium(VI) reduction

    NASA Technical Reports Server (NTRS)

    Daulton, Tyrone L.; Little, Brenda J.; Lowe, Kristine; Jones-Meehan, Joanne

    2002-01-01

    Electron energy loss spectroscopy (EELS) techniques were used to determine oxidation state, at high spatial resolution, of chromium associated with the metal-reducing bacteria, Shewanella oneidensis, in anaerobic cultures containing Cr(VI)O4(2-). These techniques were applied to fixed cells examined in thin section by conventional transmission electron microscopy (TEM) as well as unfixed, hydrated bacteria examined by environmental cell (EC)-TEM. Two distinct populations of bacteria were observed by TEM: bacteria exhibiting low image contrast and bacteria exhibiting high contrast in their cell membrane (or boundary) structure which was often encrusted with high-contrast precipitates. Measurements by EELS demonstrated that cell boundaries became saturated with low concentrations of Cr and the precipitates encrusting bacterial cells contained a reduced form of Cr in oxidation state + 3 or lower.

  3. Electron energy-loss spectroscopy of anomalous plutonium behavior in nuclear waste materials.

    PubMed

    Buck, Edgar C; Finn, Patricia A; Bates, John K

    2004-01-01

    Plutonium-enriched layer has been observed in corroded spent uranium oxide fuel (CSNF). These Pu-enriched regions were examined with analytical transmission electron microscopy combined with electron energy-loss spectroscopy (EELS). The enriched region also contained U, Am, Ru, Zr, but only minor enrichment of rare earth elements. The Pu, possibly as Pu(V) according to EELS measurements, was dispersed within re-precipitated uranium oxide (identified as U3O8) nano-crystals between U(VI) secondary phases and the CSNF surface. The U, Pu, and Am enrichment was observed in the corrosion products with tests on different nuclear fuels. This may have implications for the long-term behavior of CSNF under storage in a geologic waste repository. Furthermore, there may be an increased potential for the generation of Pu-bearing colloids from this type of weathered CSNF.

  4. Electron energy loss spectroscopy techniques for the study of microbial chromium(VI) reduction.

    PubMed

    Daulton, Tyrone L; Little, Brenda J; Lowe, Kristine; Jones-Meehan, Joanne

    2002-06-01

    Electron energy loss spectroscopy (EELS) techniques were used to determine oxidation state, at high spatial resolution, of chromium associated with the metal-reducing bacteria, Shewanella oneidensis, in anaerobic cultures containing Cr(VI)O4(2-). These techniques were applied to fixed cells examined in thin section by conventional transmission electron microscopy (TEM) as well as unfixed, hydrated bacteria examined by environmental cell (EC)-TEM. Two distinct populations of bacteria were observed by TEM: bacteria exhibiting low image contrast and bacteria exhibiting high contrast in their cell membrane (or boundary) structure which was often encrusted with high-contrast precipitates. Measurements by EELS demonstrated that cell boundaries became saturated with low concentrations of Cr and the precipitates encrusting bacterial cells contained a reduced form of Cr in oxidation state + 3 or lower.

  5. Electron energy loss spectroscopy study of Sr2-xGdxTiMnO6

    NASA Astrophysics Data System (ADS)

    Biskup, Nevenko; Alvarez-Serrano, Inmaculada; Veiga, Maria Luisa; Garcia-Hernandez, Mar; Lopez, Maria Luisa; Varela, Maria

    2012-02-01

    The newly synthesized double perovskite family Sr2-xGdxTiMnO6 (0energy loss spectroscopy. We find that, is spite of some precipitations of Mn and Ti rich regions that exist in 0.25<=x<=0.75, the manganese and titanium ions are generally well intermixed in both interior of the grains and on the grain boundaries. We discuss these results in the frame of highly non-linear electrical conductivity found in these materials.

  6. Transition metal d -band occupancy in skutterudites studied by electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Prytz, Ø.; Taftø, J.; Ahn, C. C.; Fultz, B.

    2007-03-01

    The transition-metal 3d occupancy of a series of thermoelectric skutterudites is investigated using electron energy-loss spectroscopy. We find that bonding causes an emptying of the 3d states in the binary skutterudites CoP3 , CoAs3 , CoSb3 , and NiP3 , while compared to the pure Fe the 3d occupancy in LaFe4P12 is significantly increased, consistent with the idea that each interstitial La atom (rattler) donates three electrons to compensate for missing valence electron of Fe as compared to Co. These experimental results are in agreement with previous models suggesting a predominantly covalent bonding between transition metal and pnictogen atoms in skutterudites, and provide evidence of charge transfer from La to the Fe-P complex in LaFe4P12 .

  7. Oswald-Kasper-Gaukler model for reflection electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Salvat-Pujol, F.; Werner, W. S. M.

    2011-05-01

    The Oswald-Kasper-Gaukler (OKG) model for elastic electron backscattering [J. Electr. Spectrosc. Rel. Phen.JESRAW0368-204810.1016/0368-2048(93)80019-I 61(1993)251] has been extended within the partial-intensity approach to take inelastic collisions into account. Analytical expressions have been derived for the path-length distribution and the partial intensities, achieving good agreement with results of Monte Carlo (MC) calculations of these quantities. A criterion is given to predict the validity of the model for a given material, geometry, and kinetic energy. Experimental reflection electron energy loss spectroscopy (REELS) spectra have been compared with REELS spectra calculated using the modified OKG model, obtaining good agreement between them. The proposed model is also applied in a quantitative analysis of experimental REELS. In all investigated cases, the single-scattering loss distributions retrieved from this analysis agree with results from previous analyses—based on MC calculations—within 5%. The presented model can therefore be employed in quantitative analyses of REELS of semi-infinite solids, while it is both numerically simpler and conceptually clearer than related approaches.

  8. Practical spatial resolution of electron energy loss spectroscopy in aberration corrected scanning transmission electron microscopy.

    PubMed

    Shah, A B; Ramasse, Q M; Wen, J G; Bhattacharya, A; Zuo, J M

    2011-08-01

    The resolution of electron energy loss spectroscopy (EELS) is limited by delocalization of inelastic electron scattering rather than probe size in an aberration corrected scanning transmission electron microscope (STEM). In this study, we present an experimental quantification of EELS spatial resolution using chemically modulated 2×(LaMnO(3))/2×(SrTiO(3)) and 2×(SrVO(3))/2×(SrTiO(3)) superlattices by measuring the full width at half maxima (FWHM) of integrated Ti M(2,3), Ti L(2,3), V L(2,3), Mn L(2,3), La N(4,5), La N(2,3) La M(4,5) and Sr L(3) edges over the superlattices. The EELS signals recorded using large collection angles are peaked at atomic columns. The FWHM of the EELS profile, obtained by curve-fitting, reveals a systematic trend with the energy loss for the Ti, V, and Mn edges. However, the experimental FWHM of the Sr and La edges deviates significantly from the observed experimental tendency. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. A Complete Overhaul of the Electron Energy-Loss Spectroscopy and X-Ray Absorption Spectroscopy Database: eelsdb.eu.

    PubMed

    Ewels, Philip; Sikora, Thierry; Serin, Virginie; Ewels, Chris P; Lajaunie, Luc

    2016-06-01

    The electron energy-loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS) database has been completely rewritten, with an improved design, user interface, and a number of new tools. The database is accessible at https://eelsdb.eu/ and can now be used without registration. The submission process has been streamlined to encourage spectrum submissions and the new design gives greater emphasis on contributors' original work by highlighting their papers. With numerous new filters and a powerful search function, it is now simple to explore the database of several hundred EELS and XAS spectra. Interactive plots allow spectra to be overlaid, facilitating online comparison. An application-programming interface has been created, allowing external tools and software to easily access the information held within the database. In addition to the database itself, users can post and manage job adverts and read the latest news and events regarding the EELS and XAS communities. In accordance with the ongoing drive toward open access data increasingly demanded by funding bodies, the database will facilitate open access data sharing of EELS and XAS spectra.

  10. Time-of-flight electron energy loss spectroscopy using TM110 deflection cavities.

    PubMed

    Verhoeven, W; van Rens, J F M; van Ninhuijs, M A W; Toonen, W F; Kieft, E R; Mutsaers, P H A; Luiten, O J

    2016-09-01

    We demonstrate the use of two TM110 resonant cavities to generate ultrashort electron pulses and subsequently measure electron energy losses in a time-of-flight type of setup. The method utilizes two synchronized microwave cavities separated by a drift space of 1.45 m. The setup has an energy resolution of 12 ± 2 eV FWHM at 30 keV, with an upper limit for the temporal resolution of 2.7 ± 0.4 ps. Both the time and energy resolution are currently limited by the brightness of the tungsten filament electron gun used. Through simulations, it is shown that an energy resolution of 0.95 eV and a temporal resolution of 110 fs can be achieved using an electron gun with a higher brightness. With this, a new method is provided for time-resolved electron spectroscopy without the need for elaborate laser setups or expensive magnetic spectrometers.

  11. Time-of-flight electron energy loss spectroscopy using TM110 deflection cavities

    PubMed Central

    Verhoeven, W.; van Rens, J. F. M.; van Ninhuijs, M. A. W.; Toonen, W. F.; Kieft, E. R.; Mutsaers, P. H. A.; Luiten, O. J.

    2016-01-01

    We demonstrate the use of two TM110 resonant cavities to generate ultrashort electron pulses and subsequently measure electron energy losses in a time-of-flight type of setup. The method utilizes two synchronized microwave cavities separated by a drift space of 1.45 m. The setup has an energy resolution of 12 ± 2 eV FWHM at 30 keV, with an upper limit for the temporal resolution of 2.7 ± 0.4 ps. Both the time and energy resolution are currently limited by the brightness of the tungsten filament electron gun used. Through simulations, it is shown that an energy resolution of 0.95 eV and a temporal resolution of 110 fs can be achieved using an electron gun with a higher brightness. With this, a new method is provided for time-resolved electron spectroscopy without the need for elaborate laser setups or expensive magnetic spectrometers. PMID:27704035

  12. Direct characterization of the energy level alignments and molecular components in an organic hetero-junction by integrated photoemission spectroscopy and reflection electron energy loss spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Yun, Dong-Jin; Shin, Weon-Ho; Bulliard, Xavier; Park, Jong Hwan; Kim, Seyun; Chung, Jae Gwan; Kim, Yongsu; Heo, Sung; Kim, Seong Heon

    2016-08-01

    A novel, direct method for the characterization of the energy level alignments at bulk-heterojunction (BHJ)/electrode interfaces on the basis of electronic spectroscopy measurements is proposed. The home-made in situ photoemission system is used to perform x-ray/ultraviolet photoemission spectroscopy (XPS/UPS), reflection electron energy loss spectroscopy (REELS) and inverse photoemission spectroscopy of organic-semiconductors (OSCs) deposited onto a Au substrate. Through this analysis system, we are able to obtain the electronic structures of a boron subphthalocyanine chloride:fullerene (SubPC:C60) BHJ and those of the separate OSC/electrode structures (SubPC/Au and C60/Au). Morphology and chemical composition analyses confirm that the original SubPC and C60 electronic structures remain unchanged in the electrodes prepared. Using this technique, we ascertain that the position and area of the nearest peak to the Fermi energy (EF = 0 eV) in the UPS (REELS) spectra of SubPC:C60 BHJ provide information on the highest occupied molecular orbital level (optical band gap) and combination ratio of the materials, respectively. Thus, extracting the adjusted spectrum from the corresponding SubPC:C60 BHJ UPS (REELS) spectrum reveals its electronic structure, equivalent to that of the C60 materials. This novel analytical approach allows complete energy-level determination for each combination ratio by separating its electronic structure information from the BHJ spectrum.

  13. Excitonic, vibrational, and van der Waals interactions in electron energy loss spectroscopy.

    PubMed

    Mizoguchi, T; Miyata, T; Olovsson, W

    2017-09-01

    The pioneer, Ondrej L. Krivanek, and his collaborators have opened up many frontiers for the electron energy loss spectroscopy (EELS), and they have demonstrated new potentials of the EELS method for investigating materials. Here, inspired by those achievements, we show further potentials of EELS based on the results of theoretical calculations, that is excitonic and van der Waals (vdW) interactions, as well as vibrational information of materials. Concerning the excitonic interactions, we highlight the importance of the two-particle calculation to reproduce the low energy-loss near-edge structure (ELNES), the Na-L2,3 edge of NaI and the Li-K edge of LiCl and LiFePO4. Furthermore, an unusually strong excitonic interaction at the O-K edge of perovskite oxides, SrTiO3 and LaAlO3, is shown. The effect of the vdW interaction in the ELNES is also investigated, and we observe that the magnitude of the vdW effect is approximately 0.1eV in the case of the ELNES from a solid and liquid, whereas its effect is almost negligible in the case of the ELNES from the gaseous phase owing to the long inter-molecular distance. In addition to the "static" information, the influence of the "dynamic" behavior of atoms in materials to EELS is also investigated. We show that measurements of the infrared spectrum are possible by using a modern monochromator system. Furthermore, an estimation of the atomic vibration in core-loss ELNES is also presented. We show the acquisition of vibrational information using the ELNES of liquid methanol and acetic acid, solid Al2O3, and oxygen gas. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Electron energy loss spectroscopy of carbon in dissociated dislocations in tantalum carbide

    NASA Astrophysics Data System (ADS)

    Allison, Craig; Hoffman, Mark; Williams, Wendell S.

    1982-10-01

    The carbon concentration in individual stacking faults in dissociated dislocations in tantalum carbide (TaCx) was analyzed using electron energy loss spectroscopy. Although the faulted region is less than 10 nm wide, the small diameter electron beam (0.5 nm) of a dedicated scanning transmission electron microscope allowed the carbon K x-ray excitation edge from the faulted region to be distinguished from the corresponding signal from the unfaulted region. The 50-nm thick foil was prepared by grinding, polishing, and ion milling a specimen sawed from a single crystal of TaC0.78. The analysis showed a significantly lower value for the carbon concentration in the fault, in accordance with crystallographic and energy considerations. The stacking fault in NaCl-structure TaCx must exhibit hcp symmetry, but the appropriate hcp phase, Ta2C, contains less carbon. Hence diffusion of carbon away from the moving dislocation must accompany plastic deformation. However, in view of the high melting point and high activation energy for carbon migration, diffusion is slow below approximately 1600 °C. This temperature corresponds approximately with the brittle-ductile transition for TaC. The isomorphic compound TiC does not exhibit dissociated dislocations, and hence this form of Suzuki hardening should not occur. Indeed, gross plastic deformation in TiC can occur at temperatures as low as 800 °C.

  15. The electronic states of pyrimidine studied by VUV photoabsorption and electron energy-loss spectroscopy.

    PubMed

    da Silva, F Ferreira; Almeida, D; Martins, G; Milosavljević, A R; Marinković, B P; Hoffmann, S V; Mason, N J; Nunes, Y; Garcia, G; Limão-Vieira, P

    2010-07-07

    The electronic state spectroscopy of pyrimidine C(4)H(4)N(2) has been investigated using both high resolution VUV photoabsorption in the energy range 3.7 to 10.8 eV (335 to 115 nm) and lower resolution electron energy loss in the range 2 to 15 eV. The low energy absorption band, assigned to the (pi*) <-- 7b(2)(n(N)) (1(1)B(1)<-- 1(1)A(1)) transition, at 3.85(4) eV and the vibrational progressions superimposed upon it have been observed for the first time, due to the availability of a high-resolution photon beam (0.075 nm), corresponding to 3 meV at the midpoint of the energy range studied. Vibronic coupling has been shown to play an important role dictating the nature of the observed excited states, especially for the lowest (1)B(1) state. The 2(1)B(1) state is proposed to have its origin at 7.026 eV according to the vibrational excitation reported in this energy region (7.8-8.4 eV). New experimental evidence of 4(1)A(1) state with a maximum cross section at 8.800 eV is supported by previous ab initio quantum chemical calculations. Rydberg series have been assigned converging to the three lowest ionisation energy limits, 9.32 eV ((2)B(2)), 10.41 eV ((2)B(1)) and 11.1 eV ((2)A(1) + (2)A(2)) with new members reported for the first time and classified according to the magnitude of the quantum defects (delta). Additionally, the absolute differential cross section for inelastic electron scattering has been measured for the most intense band from 6.9 to 7.8 eV assigned to (1)pipi* (3(1)A(1) + 2(1)B(2)).

  16. Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

    SciTech Connect

    Tahir, Dahlang; Kraaer, Jens; Tougaard, Sven

    2014-06-28

    We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300 eV to 10 keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(−1/ε) by using the QUEELS-ε(k,ω)-REELS software package. The complex dielectric functions ε(k,ω), in the 0–100 eV energy range, for Fe, Pd, and Ti were determined from the derived Im(−1/ε) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies between 300 and 1000 eV taken at widely different experimental geometries. In the present paper, we provide, for the first time, a further test on its validity and find that the model also gives consistent results when applied to REELS spectra in the full range of primary electron energies from 300 eV to 10000 eV. This gives confidence in the validity of the applied method.

  17. Study of the Dielectric Function of Graphene from Spectroscopic Ellipsometry and Electron Energy Loss Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nelson, Florence

    For more than 60 years, semiconductor research has been advancing up the periodic table. The first transistor was made from germanium. This later gave way to silicon-based devices due to the latter's ability to form an excellent interface with thermally-grown oxide. Now for the last ˜8 years, the focus has moved up one more row to carbon for post-CMOS devices in order to comply with the scaling limitations of Moore's law. However, for each of these, the measurements of film properties and dimensions have always been required for technological applications. These measurement methods often incorporate the use of light or electrons in order to take advantage of a wavelength that is on the order of, or smaller than, the feature sizes of interest. This thesis compares the dielectric function of graphene measured by an optical method to that obtained from an electron energy loss method in order to observe the effect of contamination and substrate on the optical properties of graphene exposed to the environment. Whether viewed in terms of how light affects a material (dielectric function) or how a material affects light (refractive index), the optical response is a quantity that may be used to obtain information about a film's thickness, energy structure, and the types of excitations that are responsible for energy loss. The three main experimental methods used in this thesis work are spectroscopic ellipsometry (SE), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). SE is commonly used in clean-room environments for optical measurement over the energy range of ˜0-5 eV. This method is used to study graphene's dielectric function from the ultraviolet (UV) through infrared (IR) regions through use of an oscillator dispersion model. A nearly constant absorbance over the IR and into the visible region is observed due to vertical transitions between graphene's linearly dispersed pi-bands at the Dirac points. An exciton

  18. Valence electron energy-loss spectroscopy study of ZrSiO₄ and ZrO₂.

    PubMed

    Jiang, Nan; Spence, John C H

    2013-11-01

    ZrSiO4 (zircon) and m-ZrO2 (zirconia) are fundamental and industrially important materials. This work reports the detailed valence electron energy-loss spectroscopy (VEELS) studies of these compounds. The dielectric response functions, as well as single-electron interband transition spectra, are derived from VEELS data for both ZrSiO4 and m-ZrO2, in the range 5-50 eV using the Kramers-Kronig analysis method. Our interpretation of the interband transitions is given with the aid of ab initio calculations of density of states. The bandgap energies for both materials are also measured using VEELS. The surface and bulk plasmons are identified: the surface plasmon peaks locate at around 12 eV, and two bulk plasmon peaks are ∼15-16 eV and ∼25-27 eV, respectively. Although similarities in the VEELS exist between ZrSiO4 and m-ZrO2, two major differences are also noticed and explained in terms of composition and structure differences. © 2013 Elsevier B.V. All rights reserved.

  19. Mode Coupling in Plasmonic Heterodimers Probed with Electron Energy Loss Spectroscopy.

    PubMed

    Flauraud, Valentin; Bernasconi, Gabriel D; Butet, Jérémy; Alexander, Duncan T L; Martin, Olivier J F; Brugger, Juergen

    2017-03-14

    While plasmonic antennas composed of building blocks made of the same material have been thoroughly studied, recent investigations have highlighted the unique opportunities enabled by making compositionally asymmetric plasmonic systems. So far, mainly heterostructures composed of nanospheres and nanodiscs have been investigated, revealing opportunities for the design of Fano resonant nanostructures, directional scattering, sensing and catalytic applications. In this article, an improved fabrication method is reported that enables precise tuning of the heterodimer geometry, with interparticle distances made down to a few nanometers between Au-Ag and Au-Al nanoparticles. A wide range of mode energy detuning and coupling conditions are observed by near field hyperspectral imaging performed with electron energy loss spectroscopy, supported by full wave analysis numerical simulations. These results provide direct insights into the mode hybridization of plasmonic heterodimers, pointing out the influence of each dimer constituent in the overall electromagnetic response. By relating the coupling of non-dipolar modes and plasmon-interband interaction with the dimer geometry, this work facilitates the development of plasmonic heterostructures with tailored responses, beyond the possibilities offered by homodimers.

  20. Challenging the nature of low-energy plasmon excitations in CaC6 using electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Roth, Friedrich; König, Andreas; Kramberger, Christian; Pichler, Thomas; Büchner, Bernd; Knupfer, Martin

    2013-04-01

    The nature of low-energy plasmon excitations plays an important role in understanding the low-energy electronic properties and coupling mechanism of different superconducting compounds such as CaC6. Recent ab initio studies predict a charge carrier intraband plasmon in keeping with a low-energy acoustic plasmon. Here, we have studied the low-energy electronic excitations of CaC6 using high-resolution electron energy-loss spectroscopy in transmission at low temperatures. The analysis of the core level excitations leads to the conclusion that hybridization between graphite and calcium states plays an essential role in this graphite-intercalated compound. Regarding the low-energy plasmon excitation, we observe the formation of an intraband (charge carrier) plasmon with a negative dispersion at about 3.5 eV in sound agreement with the theory. Finally, a weak excitation around 1.2 eV with an almost linear dispersion relation can be observed as predicted for an acoustic plasmon that may mediate the superconducting coupling in CaC6. However its optical limit at ~1 eV challenges the theoretical predictions and safely rules out an electronic superconducting coupling mechanism in CaC6

  1. Electronic and optical properties of selected polymers studied by reflection electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Tahir, Dahlang; Tougaard, Sven

    2012-03-01

    We have determined the electronic and optical properties of six polymers: Polymethyl-methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), polyester (PET), polypyrrole (PPY), and polyamide (PA6) for energy losses from 0 to 70 eV by analysis of reflection electron energy-loss spectroscopy (REELS) spectra. We found that the surface was easily damaged by the incident electron beam, in particular for energies above 500 eV. The damage results in new peaks in the bandgap region and the polymers become metallic. Great care was exerted to determine experimental conditions under which these effects are minimized. The REELS spectra were corrected for multiple inelastically scattered electrons with the QUASES-XS-REELS software to determine the effective inelastic-scattering cross sections. From these cross sections, we found that the band gaps for PMMA, PE, PVC, PET, PPY, and PA6 are 5.0 eV, 7.5 eV, 7.0 eV, 3.0 eV, 3.5 eV, and 5.1 eV, respectively. Quantitative analysis of the experimental cross sections was carried out by using the QUEELS-ɛ(k,ω)-REELS software to determine the dielectric function and optical properties. This is done by comparing the experimental REELS inelastic electron-scattering cross-section with a simulated cross section in which the only input is Im(-1/ɛ). The dielectric function is expressed as a sum of oscillators and the oscillator parameters are determined. Good agreement between the experimental and theoretical cross section is achieved for all polymers. From Im(-1/ɛ), the real and imaginary parts of ɛ (ω), the refractive index, and the extinction coefficient were determined for all polymers in the energy range ћω = 0 to 70 eV. An oscillator is clearly observed for PPY, PET, and PA6 at ˜ 6.7 eV, which corresponds to the π plasmon. This oscillator is not found for PMMA, PE, and PVC. A set of oscillators in the 20-30 eV energy range corresponding to the σ+π plasmon is found for all polymers.

  2. 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.

  3. 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.

  4. 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.

  5. Chemical Distribution and Bonding of Lithium in Intercalated Graphite: Identification with Optimized Electron Energy Loss Spectroscopy

    SciTech Connect

    Wang, Feng; Graetz, Jason; Moreno, M. Sergio; Ma, Chao; Wu, Lijun; Volkov, Vyacheslav; Zhu, Yimei

    2011-01-10

    Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer.

  6. Chemical Distribution and Bonding of Lithium in Intercalated Graphite: Identification with Optimized Electron Energy Loss Spectroscopy

    SciTech Connect

    Zhu, Y.; Wang, F.; Graetz, J.; Moreno, M.S.; Ma, C.; Wu, L.; Volkov, V.

    2011-02-01

    Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer.

  7. Electron energy-loss spectroscopy of carbon in interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Bradley, John P.; Thomas, Kathie L.; Mckay, David S.

    1994-01-01

    The nature of the carbon-bearing phases in IDP's provides information regarding the chemical and physical processes involved in the formation and evolution of the early solar system. Several carbon-bearing materials have been observed in IDP's, but details of their nature, abundance, and distribution are still poorly known. A knowledge of the abundance and nature of carbon in IDP's is useful in constraining the sources of IDP's and for comparisons with other chondritic materials. Estimates of carbon abundance in anhydrous and hydrated IDP's indicate that most of these particles have significantly higher carbon than the carbonaceous chondrites. Mineralogical analyses show that carbonates are only a minor component of most hydrated IDP's, and so the high carbon abundances in this group of IDP's indicates that other carbon-bearing phases are present in significant concentrations. Using the technique of electron energy-loss spectroscopy (EELS), we have identified two forms of carbon in a hydrated IDP, oxidized carbon (carbonates), and amorphous elemental carbon.

  8. Quantification of the boron speciation in alkali borosilicate glasses by electron energy loss spectroscopy

    PubMed Central

    Cheng, Shaodong; Yang, Guang; Zhao, Yanqi; Peng, MingYing; Skibsted, Jørgen; Yue, Yuanzheng

    2015-01-01

    Transmission electron microscopy and related analytical techniques have been widely used to study the microstructure of different materials. However, few research works have been performed in the field of glasses, possibly due to the electron-beam irradiation damage. In this paper, we have developed a method based on electron energy loss spectroscopy (EELS) data acquisition and analyses, which enables determination of the boron speciation in a series of ternary alkali borosilicate glasses with constant molar ratios. A script for the fast acquisition of EELS has been designed, from which the fraction of BO4 tetrahedra can be obtained by fitting the experimental data with linear combinations of the reference spectra. The BO4 fractions (N4) obtained by EELS are consistent with those from 11B MAS NMR spectra, suggesting that EELS can be an alternative and convenient way to determine the N4 fraction in glasses. In addition, the boron speciation of a CeO2 doped potassium borosilicate glass has been analyzed by using the time-resolved EELS spectra. The results clearly demonstrate that the BO4 to BO3 transformation induced by the electron beam irradiation can be efficiently suppressed by doping CeO2 to the borosilicate glasses. PMID:26643370

  9. Quasinormal mode theory and modelling of electron energy loss spectroscopy for plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Ge, Rong-Chun; Hughes, Stephen

    2016-05-01

    Understanding light-matter interactions using localized surface plasmons (LSPs) is of fundamental interest in classical and quantum plasmonics and has a wide range of applications. In order to understand the spatial properties of LSPs, electron energy loss spectroscopy (EELS) is a common and powerful method of spatially resolving the extreme localized fields that can be obtained with metal resonators. However, modelling EELS for general shaped resonators presents a major challenge in computational electrodynamics, requiring the full photon Green function as a function of two space points and frequency. Here we present an intuitive and computationally simple method for computing EELS maps of plasmonic resonators using a quasinormal mode (QNM) expansion technique. By separating the contribution of the QNM and the bulk material, we give closed-form analytical formulas for the plasmonic QNM contribution to the EELS maps. We exemplify our technique for a split ring resonator, a gold nanorod, and a nanorod dimer structure. The method is accurate, intuitive, and gives orders of magnitude improvements over direct dipole simulations that numerically solve the full 3D Maxwell equations. We also show how the same QNM Green function can be used to obtain the Purcell factor (and projected local density of optical states) from quantum dipole emitters or two level atoms, and we demonstrate how the spectral features differ in general to the EELS spectrum.

  10. Chemical Analysis of Individual Aerosols Particles by Electron Energy-Loss Spectroscopy (EELS)

    NASA Astrophysics Data System (ADS)

    Buseck, P. R.; Buseck, P. R.; Garvie, L. A.; Li, J.; Posfai, M.

    2001-12-01

    We use electron energy-loss spectroscopy (EELS) with a transmission electron microscope (TEM) to obtain chemical and bonding information on individual aerosol particles. EELS is ideally suited to this task because of its high spatial resolution and sensitivity to light elements such as C, N, and O. In addition, the spectral shapes provide information regarding bonding, atomic coordination and, for polyvalent elements, oxidation states. Our current focus is on carbonaceous aerosols both in the ambient air and emissions from biomass burning, with emphasis on the heterogeneous chemistry, particle structure, and chemical composition of soot particles. From the EELS spectra we were able to record for the first time, differences in composition between individual spherules within the same soot aggregate. We also found evidence of chemical variations even within individual soot spheres as small as 50 nm across. In the case of biomass burning, the most striking chemical differences are in the quantity of K, minor O and, in places, N. The quantity of elements associated with C decreases with the degree of graphitization of the soot spheres, as shown by the shapes of the C spectra and was corroborated by high-resolution TEM images of the analyzed particles. Knowledge of the degree of graphitization and quantity of associated elements is important for understanding and modeling their optical properties and in some case in source attributions.

  11. Electron energy-loss and soft X-ray emission spectroscopy of electronic structure of MgB4

    NASA Astrophysics Data System (ADS)

    Sato, Yohei; Saito, Taiki; Tsuchiya, Kohei; Terauchi, Masami; Saito, Hiroki; Takeda, Masatoshi

    2017-09-01

    The electronic structure of MgB4, with the characteristic crystal structure comprising one-dimensional pentagonal B6 cluster chain, was investigated using electron energy-loss spectroscopy and soft X-ray emission spectroscopy based on transmission electron microscopy. The dielectric function and density of state of unoccupied and occupied states were clarified experimentally for the first time. Although theoretical calculations has predicted MgB4 to be a semiconductor, the electron energy-loss spectrum in this study show a plasmon peak at 0.4 eV, which might be due to carrier electrons. Theoretical calculations suggested that the electronic states near the Fermi energy are localized along the one dimensional B6 cluster chain. Therefore, one-dimensional electric conductivity is expected.

  12. Angle-resolved electron energy loss spectroscopy in hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Fossard, Frédéric; Sponza, Lorenzo; Schué, Léonard; Attaccalite, Claudio; Ducastelle, François; Barjon, Julien; Loiseau, Annick

    2017-09-01

    Electron energy loss spectra were measured on hexagonal boron nitride single crystals employing an electron energy loss spectroscopic setup composed of an electron microscope equipped with a monochromator and an in-column filter. This setup provides high-quality energy-loss spectra and allows also for the imaging of energy-filtered diffraction patterns. These two acquisition modes provide complementary pieces of information, offering a global view of excitations in reciprocal space. As an example of the capabilities of the method we show how easily the core loss spectra at the K edges of boron and nitrogen can be measured and imaged. Low losses associated with interband and/or plasmon excitations are also measured. This energy range allows us to illustrate that our method provides results whose quality is comparable to that obtained from nonresonant x-ray inelastic scattering but with advantageous specificities such as an enhanced sensitivity at low q and a much greater simplicity and versatility that make it well adapted to the study of two-dimensional materials and related heterostructures. Finally, by comparing theoretical calculations to our measures, we are able to relate the range of applicability of ab initio calculations to the anisotropy of the sample and assess the level of approximation required for a proper simulation of our acquisition method.

  13. Signatures of distinct impurity configurations in atomic-resolution valence electron-energy-loss spectroscopy: Application to graphene

    DOE PAGES

    Kapetanakis, Myron D.; Oxley, Mark P.; Zhou, Wu; ...

    2016-10-31

    The detection and identification of impurities and other point defects in materials is a challenging task. Signatures for point defects are typically obtained using spectroscopies without spatial resolution. Here in this paper, we demonstrate the power of valence electron-energy-loss spectroscopy (VEELS) in an aberration-corrected scanning transmission-electron microscope (STEM) to provide energy-resolved and atomically resolved maps of electronic excitations of individual impurities which, combined with theoretical simulations, yield unique signatures of distinct bonding configurations of impurities. We report VEELS maps for isolated Si impurities in graphene, which are known to exist in two distinct configurations. We also report simulations of themore » maps, based on density functional theory and dynamical scattering theory, which agree with and provide direct interpretation of observed features. We show that theoretical VEELS maps exhibit distinct and unambiguous signatures for the threefold- and fourfold-coordinated configurations of Si impurities in different energy-loss windows, corresponding to impurity-induced bound states, resonances, and antiresonances. With the advent of new monochromators and detectors with high energy resolution and low signal-to-noise ratio, the present work ushers an atomically resolved STEM-based spectroscopy of individual impurities as an alternative to conventional spectroscopies for probing impurities and defects.« less

  14. Signatures of distinct impurity configurations in atomic-resolution valence electron-energy-loss spectroscopy: Application to graphene

    SciTech Connect

    Kapetanakis, Myron D.; Oxley, Mark P.; Zhou, Wu; Pennycook, Stephen J.; Idrobo, Juan-Carlos; Pantelides, Sokrates T.

    2016-10-31

    The detection and identification of impurities and other point defects in materials is a challenging task. Signatures for point defects are typically obtained using spectroscopies without spatial resolution. Here in this paper, we demonstrate the power of valence electron-energy-loss spectroscopy (VEELS) in an aberration-corrected scanning transmission-electron microscope (STEM) to provide energy-resolved and atomically resolved maps of electronic excitations of individual impurities which, combined with theoretical simulations, yield unique signatures of distinct bonding configurations of impurities. We report VEELS maps for isolated Si impurities in graphene, which are known to exist in two distinct configurations. We also report simulations of the maps, based on density functional theory and dynamical scattering theory, which agree with and provide direct interpretation of observed features. We show that theoretical VEELS maps exhibit distinct and unambiguous signatures for the threefold- and fourfold-coordinated configurations of Si impurities in different energy-loss windows, corresponding to impurity-induced bound states, resonances, and antiresonances. With the advent of new monochromators and detectors with high energy resolution and low signal-to-noise ratio, the present work ushers an atomically resolved STEM-based spectroscopy of individual impurities as an alternative to conventional spectroscopies for probing impurities and defects.

  15. Signatures of distinct impurity configurations in atomic-resolution valence electron-energy-loss spectroscopy: Application to graphene

    NASA Astrophysics Data System (ADS)

    Kapetanakis, Myron D.; Oxley, Mark P.; Zhou, Wu; Pennycook, Stephen J.; Idrobo, Juan-Carlos; Pantelides, Sokrates T.

    2016-10-01

    The detection and identification of impurities and other point defects in materials is a challenging task. Signatures for point defects are typically obtained using spectroscopies without spatial resolution. Here we demonstrate the power of valence electron-energy-loss spectroscopy (VEELS) in an aberration-corrected scanning transmission-electron microscope (STEM) to provide energy-resolved and atomically resolved maps of electronic excitations of individual impurities which, combined with theoretical simulations, yield unique signatures of distinct bonding configurations of impurities. We report VEELS maps for isolated Si impurities in graphene, which are known to exist in two distinct configurations. We also report simulations of the maps, based on density functional theory and dynamical scattering theory, which agree with and provide direct interpretation of observed features. We show that theoretical VEELS maps exhibit distinct and unambiguous signatures for the threefold- and fourfold-coordinated configurations of Si impurities in different energy-loss windows, corresponding to impurity-induced bound states, resonances, and antiresonances. With the advent of new monochromators and detectors with high energy resolution and low signal-to-noise ratio, the present work ushers an atomically resolved STEM-based spectroscopy of individual impurities as an alternative to conventional spectroscopies for probing impurities and defects.

  16. Effect of multipole excitations in electron energy-loss spectroscopy of surface plasmon modes in silver nanowires

    SciTech Connect

    Zhou, Xiuli; Norris, Theodore B.; Hörl, Anton; Trügler, Andreas; Hohenester, Ulrich; Herzing, Andrew A.

    2014-12-14

    We have characterized the surface plasmon resonance (SPR) in silver nanowires using spatially resolved electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope. Non-symmetric EELS spectra due to high-k SPR propagation along the nanowire and spectral shifts due to higher-order mode excitation are observed when the beam is positioned near the tip of the nanowire. When the beam is far from the tip region and on the side of nanowire, no spectral shifts are observed as the beam is scanned in the radial direction of the nanowire. The experimental spectra are compared with three different theoretical approaches: direct numerical calculation of the energy loss, analytical models for energy loss, and numerical simulations using an optical model. All three models reproduce the spectral shifts as the electron beam approaches the cap of the nanowire. The analytical model reveals the origin of the shifts in high-order plasmon mode excitation.

  17. Electronic properties of Mn-phthalocyanine-C60 bulk heterojunctions: Combining photoemission and electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Roth, Friedrich; Herzig, Melanie; Lupulescu, Cosmin; Darlatt, Erik; Gottwald, Alexander; Knupfer, Martin; Eberhardt, Wolfgang

    2015-11-01

    The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C60 (MnPc:C60) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) and electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C60. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C60 bulk heterojunction. Moreover, the results from our EELS investigations show that, despite the rather small interface interaction, the MnPc related electronic excitation spectrum changes significantly by admixing C60 to MnPc thin films.

  18. Electronic properties of Mn-phthalocyanine–C{sub 60} bulk heterojunctions: Combining photoemission and electron energy-loss spectroscopy

    SciTech Connect

    Roth, Friedrich; Lupulescu, Cosmin; Darlatt, Erik; Gottwald, Alexander; Eberhardt, Wolfgang

    2015-11-14

    The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C{sub 60} (MnPc:C{sub 60}) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) and electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C{sub 60}. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C{sub 60} bulk heterojunction. Moreover, the results from our EELS investigations show that, despite the rather small interface interaction, the MnPc related electronic excitation spectrum changes significantly by admixing C{sub 60} to MnPc thin films.

  19. Probing the bonding and electronic structure of single atom dopants in graphene with electron energy loss spectroscopy.

    PubMed

    Ramasse, Quentin M; Seabourne, Che R; Kepaptsoglou, Despoina-Maria; Zan, Recep; Bangert, Ursel; Scott, Andrew J

    2013-10-09

    A combination of scanning transmission electron microscopy, electron energy loss spectroscopy, and ab initio calculations reveal striking electronic structure differences between two distinct single substitutional Si defect geometries in graphene. Optimised acquisition conditions allow for exceptional signal-to-noise levels in the spectroscopic data. The near-edge fine structure can be compared with great accuracy to simulations and reveal either an sp(3)-like configuration for a trivalent Si or a more complicated hybridized structure for a tetravalent Si impurity.

  20. Comparison of theoretical and experimental dielectric functions: Electron energy-loss spectroscopy and density-functional calculations on skutterudites

    NASA Astrophysics Data System (ADS)

    Prytz, Ø.; Løvvik, O. M.; Taftø, J.

    2006-12-01

    We explore the possibility of combining density functional theory (DFT) and electron energy loss spectroscopy (EELS) to determine the dielectric function of materials. As model systems we use the skutterudites CoP3 , CoAs3 , and CoSb3 which are prototypes for thermoelectric materials. We achieve qualitative agreement between the theoretically and experimentally obtained low energy-loss spectra and dielectric function. Some of the remaining discrepancies may be caused by the challenge of refining the experimental spectra before Kramers-Kronig analysis. However, contrary to what is the case for some crystals with less complicated electronic structure, the DFT calculated plasmon energies deviate significantly from the experimental values. The great accuracy with which the plasmon energy can be determined by EELS, suggests that this technique may provide valuable inputs in further efforts to improve DFT calculations. The use of EELS as the experimental technique may become particularly powerful in studies of small volumes of materials.

  1. Electron energy-loss spectroscopy of excited states of the pyridine molecules

    NASA Astrophysics Data System (ADS)

    Linert, Ireneusz; Zubek, Mariusz

    2016-04-01

    Electron energy-loss spectra of the pyridine, C5H5N, molecules in the gas phase have been measured to investigate electronic excitation in the energy range 3.5-10 eV. The applied wide range of residual electron energy and the scattering angle range from 10° to 180° enabled to differentiate between optically-allowed and -forbidden transitions. These measurements have allowed vertical excitation energies of the triplet excited states of pyridine to be determined and tentative assignments of these states to be proposed. Some of these states have not been identified in the previous works. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  2. Dehydriding process of α-AlH3 observed by transmission electron microscopy and electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Muto, S.; Tatsumi, K.; Ikeda, K.; Orimo, S.

    2009-06-01

    The dehydriding reaction of α-AlH3 induced by high-energy electron irradiation was observed in situ by transmission electron microscopy and associated electron energy-loss spectroscopy (EELS). An α-AlH3 crystal decomposed into fine aluminum particles while retaining its initial external shape because of a thin rigid surface layer that covered the entire particle. EELS revealed that the thin surface layer was amorphous aluminum oxide, which stabilizes α-AlH3 particles at ambient temperature.

  3. Combination of electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy to determine indium concentration in InGaN thin film structures

    NASA Astrophysics Data System (ADS)

    Wang, X.; Chauvat, M. P.; Ruterana, P.; Walther, T.

    2015-11-01

    We demonstrate a method to determine the indium concentration, x, of In x Ga1-x N thin films by combining plasmon excitation studies in electron energy-loss spectroscopy (EELS) with a novel way of quantification of the intensity of x-ray lines in energy-dispersive x-ray spectroscopy (EDXS). The plasmon peak in EELS of InGaN is relatively broad. We fitted a Lorentz function to the main plasmon peak to suppress noise and the influence from the neighboring Ga 3d transition in the spectrum, which improves the precision in the evaluation of the plasmon peak position. As the indium concentration of InGaN is difficult to control during high temperature growth due to partial In desorption, the nominal indium concentrations provided by the growers were not considered reliable. The indium concentration obtained from EDXS quantification using Oxford Instrument ISIS 300 x-ray standard quantification software often did not agree with the nominal indium concentration, and quantification using K and L lines was inconsistent. We therefore developed a self-consistent iterative procedure to determine the In content from thickness-dependent k-factors, as described in recent work submitted to Journal of Microscopy. When the plasmon peak position is plotted versus the indium concentration from EDXS we obtain a linear relationship over the whole compositional range, and the standard error from linear least-squares fitting shows that the indium concentration can be determined from the plasmon peak position to within Δx = ± 0.037 standard deviation.

  4. Implementation of subcellular water mapping by electron energy loss spectroscopy in a medium-voltage scanning transmission electron microscope.

    PubMed

    Terryn, C; Michel, J; Thomas, X; Laurent-Maquin, D; Balossier, G

    2004-07-01

    The water concentration in biological cells plays a predominant role in cellular life. Using electron energy loss spectroscopy, the feasibility to measure the water content in cells has already been demonstrated. In this paper, we present an upgrade of water measurement in hydrated cryosections by spectrum imaging mode in a medium-voltage scanning transmission electron microscope. The electron energy loss spectra are recorded in spectrum imaging mode in a 2(n)x2(n) pixels array. Each spectrum is processed in order to determine the water mass content in the corresponding pixel. Then a parametric image is obtained in which grey levels are related to water concentration. In this image, it is possible to recognize the different subcellular compartments. By averaging the water concentration over the relevant pixels, we can determine the water mass content in the concerned subcellular compartment. As an example, we present water mass content measurement at subcellular level in rat hepatocytes.

  5. Blue and red shifts of interband transition energy in supported Au nanoclusters on SiO2 and HOPG investigated by reflection electron energy-loss spectroscopy.

    PubMed

    Borisyuk, P V; Troyan, V I; Pushkin, M A; Borman, V D; Tronin, V N

    2012-11-01

    Gold nanoclusters supported on SiO2 and HOPG are experimentally investigated by the reflection electron energy-loss spectroscopy. Two different trends in the size-dependence of the position of the energy-loss peak corresponding to the interband Au 5d --> 6s6p transition is observed: a blue shift for Au clusters on SiO2 and a red shift for Au clusters on HOPG. The different behaviors are qualitatively explained by the influence of the substrate on the spectrum of electronic states in Au nanoclusters.

  6. Combined study of the ground and unoccupied electronic states of graphite by electron energy-loss spectroscopy

    SciTech Connect

    Feng, Zhenbao; Löffler, Stefan; Eder, Franz; Meyer, Jannik C.; Su, Dangsheng; Schattschneider, Peter

    2013-11-14

    Both the unoccupied and ground electronic states of graphite have been studied by electron energy-loss spectroscopy in a transmission electron microscope. Electron energy-loss near-edge structures of the K-edge of carbon have been investigated in detail for scattering angles from 0 to 2.8 mrad. The π{sup *} and σ{sup *} components were separated. The angular and energy dependences of the π{sup *} and σ{sup *} structures were in fair agreement with theory. Electron energy loss Compton spectra of graphite were recorded at scattering angles from 45 to 68 mrad. One Compton scattering spectrum was obtained in 1 min compared with several hours or days using photons. The contributions of core electrons were calculated by the exact Hartree-Slater method in the Compton scattering region. The electron Compton profile for graphite is in good agreement with other conventional Compton profile measurements, as well as with theory, thus establishing the validity of the technique.

  7. A reverse Monte Carlo method for deriving optical constants of solids from reflection electron energy-loss spectroscopy spectra

    SciTech Connect

    Da, B.; Sun, Y.; Ding, Z. J.; Mao, S. F.; Zhang, Z. M.; Jin, H.; Yoshikawa, H.; Tanuma, S.

    2013-06-07

    A reverse Monte Carlo (RMC) method is developed to obtain the energy loss function (ELF) and optical constants from a measured reflection electron energy-loss spectroscopy (REELS) spectrum by an iterative Monte Carlo (MC) simulation procedure. The method combines the simulated annealing method, i.e., a Markov chain Monte Carlo (MCMC) sampling of oscillator parameters, surface and bulk excitation weighting factors, and band gap energy, with a conventional MC simulation of electron interaction with solids, which acts as a single step of MCMC sampling in this RMC method. To examine the reliability of this method, we have verified that the output data of the dielectric function are essentially independent of the initial values of the trial parameters, which is a basic property of a MCMC method. The optical constants derived for SiO{sub 2} in the energy loss range of 8-90 eV are in good agreement with other available data, and relevant bulk ELFs are checked by oscillator strength-sum and perfect-screening-sum rules. Our results show that the dielectric function can be obtained by the RMC method even with a wide range of initial trial parameters. The RMC method is thus a general and effective method for determining the optical properties of solids from REELS measurements.

  8. A reverse Monte Carlo method for deriving optical constants of solids from reflection electron energy-loss spectroscopy spectra

    NASA Astrophysics Data System (ADS)

    Da, B.; Sun, Y.; Mao, S. F.; Zhang, Z. M.; Jin, H.; Yoshikawa, H.; Tanuma, S.; Ding, Z. J.

    2013-06-01

    A reverse Monte Carlo (RMC) method is developed to obtain the energy loss function (ELF) and optical constants from a measured reflection electron energy-loss spectroscopy (REELS) spectrum by an iterative Monte Carlo (MC) simulation procedure. The method combines the simulated annealing method, i.e., a Markov chain Monte Carlo (MCMC) sampling of oscillator parameters, surface and bulk excitation weighting factors, and band gap energy, with a conventional MC simulation of electron interaction with solids, which acts as a single step of MCMC sampling in this RMC method. To examine the reliability of this method, we have verified that the output data of the dielectric function are essentially independent of the initial values of the trial parameters, which is a basic property of a MCMC method. The optical constants derived for SiO2 in the energy loss range of 8-90 eV are in good agreement with other available data, and relevant bulk ELFs are checked by oscillator strength-sum and perfect-screening-sum rules. Our results show that the dielectric function can be obtained by the RMC method even with a wide range of initial trial parameters. The RMC method is thus a general and effective method for determining the optical properties of solids from REELS measurements.

  9. Electronic transitions in α-oligothiophene thin films. Comparison of ultraviolet/visible absorption spectroscopy and high resolution electron energy loss spectroscopy investigations

    NASA Astrophysics Data System (ADS)

    Oeter, D.; Egelhaaf, H.-J.; Ziegler, Ch.; Oelkrug, D.; Göpel, W.

    1994-10-01

    Vapor deposited thin films of a series of α-oligothiophenes are investigated comparatively with polarized ultraviolet/visible absorption spectroscopy (UV/VIS) and by high resolution electron energy loss spectroscopy (HREELS) in specular reflection geometry. The complementary selection rules of these methods allow an assignment of the observed absorption and loss bands according to a Hückel molecular orbital model. By plotting the transition energies of corresponding bands of different members of the homologous series vs the reciprocal of the number of rings, the development of the one-dimensional ``π-band-structure'' with an increasing number of rings could be followed. The extrapolation to infinite chain length leads to the electronic properties of an ideal (defect free) polythiophene. Furthermore, characteristic differences were observed in the results obtained from the two methods. The orientation of the molecules in thin films is only detectable with UV/VIS spectroscopy. It is most pronounced for α-quinquethiophene. On the other hand, HREELS gives information about the position of optical parity forbidden electronic transitions.

  10. Si(111)(\\sqrt{3}× \\sqrt{3})-Al Surface Studied by Angle-Resolved Electron-Energy-Loss Spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Sung-Te; Hasegawa, Shigehiko; Nakamura, Shogo; Nakashima, Hisao

    1991-09-01

    The surface electronic structures of Si(111)(\\sqrt{3}× \\sqrt{3})-Al are investigated with the use of angle-resolved electron-energy-loss spectroscopy. Three new surface one-electron transitions (in specular reflection) are found at 1.8, 7.2, and 13.1 eV. Compared with the surface state band structures calculated by Northrup and STM results by Hamers and Demuth, the loss peak at 1.8 eV is ascribed to the one-electron transition between the occupied and unoccupied surface state bands which originate from the Al adatoms. The other two peaks are considered to be due to the Si-Si strained back bonds.

  11. Signatures of Fano interferences in the electron energy loss spectroscopy and cathodoluminescence of symmetry-broken nanorod dimers.

    PubMed

    Bigelow, Nicholas W; Vaschillo, Alex; Camden, Jon P; Masiello, David J

    2013-05-28

    Through numerical simulation, we predict the existence of the Fano interference effect in the electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) of symmetry-broken nanorod dimers that are heterogeneous in material composition and asymmetric in length. The differing selection rules of the electron probe in comparison to the photon of a plane wave allow for the simultaneous excitation of both optically bright and dark plasmons of each monomer unit, suggesting that Fano resonances will not arise in EELS and CL. Yet, interferences are manifested in the dimer's scattered near- and far-fields and are evident in EELS and CL due to the rapid π-phase offset in the polarizations between super-radiant and subradiant hybridized plasmon modes of the dimer as a function of the energy loss suffered by the impinging electron. Depending upon the location of the electron beam, we demonstrate the conditions under which Fano interferences will be present in both optical and electron spectroscopies (EELS and CL) as well as a new class of Fano interferences that are uniquely electron-driven and are absent in the optical response. Among other things, the knowledge gained from this work bears impact upon the design of some of the world's most sensitive sensors, which are currently based upon Fano resonances.

  12. Isolated energy level in the band gap of Yb2Si2O7 identified by electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Ogawa, Takafumi; Kobayashi, Shunsuke; Wada, Masashi; Fisher, Craig A. J.; Kuwabara, Akihide; Kato, Takeharu; Yoshiya, Masato; Kitaoka, Satoshi; Moriwake, Hiroki

    2016-05-01

    We report the detection of an isolated energy level in the band gap of crystalline Yb2Si2O7 in the low-energy-loss region of its electron energy-loss (EEL) spectrum, obtained using a monochromated scanning transmission electron microscope. The experimental results are corroborated by first-principles calculations of the theoretical EEL spectrum. The calculations reveal that unoccupied Yb 4 f orbitals constitute an isolated energy level about 1 eV below the conduction band minimum (CBM), resulting in a terrace about 1 eV wide at the band edge of the EEL spectrum. In the case of Yb2O3 , no band edge terrace is present because the unoccupied f level lies just below the CBM. We also examined optical absorption properties of Yb2Si2O7 using UV-vis diffuse reflectance spectroscopy, which shows that the isolated energy level could not be detected in the band edge of the obtained absorbance spectrum. These findings demonstrate the utility of low-loss EEL spectroscopy with high energy resolution for probing semilocalized electronic features.

  13. Band gap and defect states of MgO thin films investigated using reflection electron energy loss spectroscopy

    SciTech Connect

    Heo, Sung; Cho, Eunseog; Lee, Hyung-Ik; Park, Gyeong Su; Kang, Hee Jae; Nagatomi, T.; Choi, Pyungho; Choi, Byoung-Deog

    2015-07-15

    The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS) and high-energy resolution REELS (HR-REELS). HR-REELS with a primary electron energy of 0.3 keV revealed that the surface F center (FS) energy was located at approximately 4.2 eV above the valence band maximum (VBM) and the surface band gap width (E{sub g}{sup S}) was approximately 6.3 eV. The bulk F center (F{sub B}) energy was located approximately 4.9 eV above the VBM and the bulk band gap width was about 7.8 eV, when measured by REELS with 3 keV primary electrons. From a first-principles calculation, we confirmed that the 4.2 eV and 4.9 eV peaks were F{sub S} and F{sub B}, induced by oxygen vacancies. We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies. Finally, we calculated the secondary electron emission yields (γ) for various noble gases. He and Ne were not influenced by the defect states owing to their higher ionization energies, but Ar, Kr, and Xe exhibited a stronger dependence on the defect states owing to their small ionization energies.

  14. Determination of atomic hydrogen in hydrocarbons by means of the reflected electron energy loss spectroscopy and the X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Afanas'ev, V. P.; Gryazev, A. S.; Efremenko, D. S.; Kaplya, P. S.; Ridzel, O. Y.

    2016-09-01

    Elastic peaks electron spectroscopy (EPES) is a perspective tool for measuring the hydrogen atomic density in hydrocarbons. It is known that hydrogen elastic peaks overlap inelastic energy loss spectra. This fact complicates the quantitative interpretation of EPES spectra. In this paper, a novel technique based on the joint use of EPES and X-ray photoelectron spectroscopy (PES) is proposed. A key part of the method is the inelastic scattering background subtraction which is performed in two steps. At the first step, differential inelastic scattering cross-sections are retrieved from PES spectra, while at the second step, the retrieved cross-sections are used to remove the inelastic scattering signal from EPES spectra. Both REELS and PES spectra are described on the base of the invariant imbedding method forming a consistent framework for the surface state analysis. A good agreement is obtained between calculated spectra and experimental data.

  15. Surface plasmon excitations in metal spheres: Direct comparison of light scattering and electron energy-loss spectroscopy by modal decomposition

    NASA Astrophysics Data System (ADS)

    Collins, Sean M.; Midgley, Paul A.

    2013-06-01

    In previous publications, qualitative agreement between studies of surface plasmon excitations in nanoparticles by near-field light scattering and electron energy-loss spectroscopy (EELS) has been found for experiments and simulations. Here, we present a quantitative method for the comparison of light scattering and EELS for surface plasmons in metal spheres. Defining the Fourier transform of the modal component of the scattered electric field along the equivalent electron trajectory enables a direct evaluation of the relative weighting factor for light- and electron-excited surface plasmon modes. This common quantity for light scattering and EELS is examined for size, composition, and trajectory dependencies, facilitating the analysis of key differences between light and electron excitation. A single functional dependence on Drude model plasmon energies is identified to explain the relative modal weighting factors for light scattering and EELS. This method represents an important step toward the complete spectral and spatial reconstruction of EELS maps from near-field light scattering calculations.

  16. Specular and off-specular high resolution electron energy loss spectroscopy of acetylene and ethylene on tungsten (100)

    NASA Astrophysics Data System (ADS)

    Hamilton, J. C.; Swanson, N.; Waclawski, B. J.; Celotta, R. J.

    1981-04-01

    High resolution electron energy loss spectroscopy (EELS) in both specular and off-specular directions has been used to identify the vibrational modes of acetylene and ethylene on tungsten (100). The off-specular data were essential to this study since, at low coverages, some of the vibrational modes were detectable only for off-specular scattering. In addition, analysis of the relative intensities of the specular and off-specular loss peaks allows us to infer orientations of molecular dipole derivatives and bond directions for the adsorbed species. We find at 135 K that ethylene on tungsten (100) dissociates to acetylene and hydrogen for exposures less than 1 L. At saturation coverage molecular ethylene is also adsorbed. Warming of this adsorbed ethylene to 300 K causes dissociation to acetylene. Analysis of specular and off-specular loss intensities suggests a geometry with the C-H bonds lying parallel to the surface. Previous UPS data for this adsorption system can be reinterpreted giving a C-C bond length of 1.35 Å and a C-C-H bond angle of 180 °: This reinterpretation is consistent with the geometry suggested by our EELS measurements. We also present data for acetylene adsorption at room temperature and for ethylene physisorption at 82 K. Physisorbed ethylene shows vibrational losses identical to those seen in gas phase IR.

  17. Verifying the presence of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy.

    PubMed

    Buck, Edgar C; Douglas, Matt; Wittman, Rick S

    2010-01-01

    This paper examines the problems associated with analysis of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy (EELS) on the transmission electron microscope (TEM). The detection of neptunium in a matrix of uranium can be impeded by the occurrence of a plural scattering event from uranium (U-M(5)+U-O(4,5)) that results in severe overlap on the Np-M(5) edge at 3665 eV. Low levels of Np (1600-6300 ppm) can be detected in a uranium solid, uranophane [Ca(UO(2))(2)(SiO(3)OH)(2)(H(2)O)(5)], by confirming that the energy gap between the Np-M(5) and Np-M(4) edges is at 184 eV and showing that the M(4)/M(5) ratio for the neptunium is smaller than that for uranium. The Richardson-Lucy deconvolution method was applied to energy-loss spectral images and was shown to increase the signal to noise ratio.

  18. Verifying the Presence of Low Levels of Neptunium in a Uranium Matrix with Electron Energy-Loss Spectroscopy

    SciTech Connect

    Buck, Edgar C.; Douglas, Matthew; Wittman, Richard S.

    2010-01-01

    This paper examines the problems associated with the analysis of low levels of neptunium (Np) in a uranium (U) matrix with electron energy-loss spectroscopy (EELS) on the transmission electron microscope (TEM). The detection of Np in a matrix of uranium (U) can be impeded by the occurrence of a plural scattering event from U (U-M5 + U-O4,5) that results in severe overlap on the Np-M5 edge at 3665 eV. Low levels (1600 - 6300 ppm) of Np can be detected in U solids by confirming the energy gap between the Np-M5 and Np-M4 edges is at 184 eV and showing that the M4/M5 ratio for the Np is smaller than that for U. The Richardson-Lucy deconvolution method was applied to energy-loss spectral images and was shown to increase the signal to noise. This method also improves the limits of detection for Np in a U matrix.

  19. The beta-SiC(100) surface studied by low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectra

    NASA Technical Reports Server (NTRS)

    Dayan, M.

    1986-01-01

    The beta-SiC(100) surface has been studied by low energy electron diffraction, Auger electron spectroscopy, high resolution electron energy loss spectra (HREELS), and core level excitation EELS. Two new Si-terminated phases have been discovered, one with (3 x 2) symmetry, and the other with (2 x 1) symmetry. Models are presented to describe these phases. New results, for the C-rich surface, are presented and discussed. In addition, core level excitation EELS results are given and compared with theory.

  20. The beta-SiC(100) surface studied by low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectra

    NASA Technical Reports Server (NTRS)

    Dayan, M.

    1986-01-01

    The beta-SiC(100) surface has been studied by low energy electron diffraction, Auger electron spectroscopy, high resolution electron energy loss spectra (HREELS), and core level excitation EELS. Two new Si-terminated phases have been discovered, one with (3 x 2) symmetry, and the other with (2 x 1) symmetry. Models are presented to describe these phases. New results, for the C-rich surface, are presented and discussed. In addition, core level excitation EELS results are given and compared with theory.

  1. π-plasmon dispersion in free-standing graphene by momentum-resolved electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Liou, S. C.; Shie, C.-S.; Chen, C. H.; Breitwieser, R.; Pai, W. W.; Guo, G. Y.; Chu, M.-W.

    2015-01-01

    The π-plasmon dispersion in graphene was scrutinized by momentum-resolved electron energy-loss spectroscopy with an improved momentum q resolution and was found to display the square root of the q dispersion characteristic of the collective excitation of two-dimensional electron systems, in contrast to previous experimental and theoretical studies which reported a linear q dispersion. Our theoretical elaborations on the q -dependent spectra affirm this square root of q relation and further unveil an in-plane electronic anisotropy. The physical property of the π plasmon is thoroughly compared to that of the two-dimensional plasmon due to carriers of the Dirac fermions. A clear distinction between the π plasmon and the two-dimensional Dirac plasmon is demonstrated, clarifying the common notion about correlating the linearly dispersed Dirac cones with the linear dispersion of the π plasmon previously reported.

  2. π-Plasmon Dispersion in Free-Standing Monolayer Graphene Investigated by Momentum-Resolved Electron Energy-Loss Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liou, S. C.; Breitwieser, R.; Chen, C. H.; Pai, W. W.; Guo, G. Y.; Chu, M. W.

    2014-08-01

    The {\\pi}-plasmon dispersion in graphene was scrutinized by momentum(q)-resolved electron energy-loss spectroscopy with an improved q resolution and found to display the square root of q dispersion characteristic of the collective excitation of two-dimensional electron systems, in contrast with previous experimental and theoretical studies which reported a linear q dispersion. Our theoretical elaborations on the q-dependent spectra affirm this square root of q relation and further unveil an in-plane electronic anisotropy. The physical property of the {\\pi} plasmon is thoroughly compared to that of the two-dimensional plasmon due to carriers of the Dirac fermions. A clear distinction between the {\\pi} plasmon and the two-dimensional Dirac plasmon was demonstrated, clarifying the common notion on correlating the linearly-dispersed Dirac cones to the linear dispersion of the {\\pi} plasmon previously reported.

  3. Investigation of the oxidation states of Cu additive in colored borosilicate glasses by electron energy loss spectroscopy

    SciTech Connect

    Yang, Guang Cheng, Shaodong; Li, Chao; Ma, Chuansheng; Zhong, Jiasong; Xiang, Weidong; Wang, Zhao

    2014-12-14

    Three optically transparent colorful (red, green, and blue) glasses were synthesized by the sol-gel method. Nano-sized precipitates were found in scanning electron microscopy images. The precipitates were analyzed by transmission electron microscopy (TEM) and high resolution TEM. The measured lattice parameters of these precipitates were found to fit the metallic copper in red glass but deviate from single valenced Cu oxides in green and blue glasses. The chemistry of these nano-sized particles was confirmed by electron energy loss spectroscopy (EELS). By fitting the EELS spectra obtained from the precipitates with the linear combination of reference spectra from Cu reference compounds, the oxidation states of Cu in the precipitates have been derived. First principle calculations suggested that the Cu nano-particles, which are in the similar oxidation states as our measurement, would show green color in the visible light range.

  4. Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy

    SciTech Connect

    Palisaitis, J. Birch, J.; Hultman, L.; Persson, P. O. Å.; Lundskog, A.; Forsberg, U.; Janzén, E.

    2014-01-21

    The early stages of InGaN/GaN quantum well growth for In-reduced conditions have been investigated for varying thickness and composition of the wells. The structures were studied by monochromated scanning transmission electron microscopy–valence electron energy loss spectroscopy spectrum imaging at high spatial resolution. It is found that beyond a critical well thickness and composition, quantum dots (width >20 nm) are formed inside the well. These are buried by compositionally graded InGaN, which is formed as GaN is grown while residual In is incorporated into the growing structure. It is proposed that these dots act as carrier localization centers inside the quantum wells.

  5. Valence excitations and dopant distribution of Al doped ZnO nanowires analyzed by electron energy loss spectroscopy.

    PubMed

    Wang, Cheng-Yu; Kuo, Chien-Lin; Liu, Chuan-Pu; Wang, Ting-Yu; Zheng, Rong-Kun; Ringer, Simon P

    2011-11-01

    Valence electron energy loss spectroscopy (VEELS) with scanning transmission electron microscopy (STEM) has been employed to probe the valence excitations and dopant distribution of Al doped ZnO nanowires. The results reveal that while the typical Al concentration is on the order of 1020 1/cm3, Al tends to segregate at the surface leading to an Al-rich sheath. In VEEL spectra, O-2p, Zn-3d, Al-3p, O-2s, interband transitions as well as bulk plasmon have been identified. The bulk plasmon peak is blue-shifted, and the projected interband transition decreases from 2.14 to 1.88 eV as the doping concentration increases from 0.83 x 10(20) to 2.18 x 10(20) 1/cm3.

  6. Robust theoretical modelling of core ionisation edges for quantitative electron energy loss spectroscopy of B- and N-doped graphene

    NASA Astrophysics Data System (ADS)

    Hardcastle, T. P.; Seabourne, C. R.; Kepaptsoglou, D. M.; Susi, T.; Nicholls, R. J.; Brydson, R. M. D.; Scott, A. J.; Ramasse, Q. M.

    2017-06-01

    Electron energy loss spectroscopy (EELS) is a powerful tool for understanding the chemical structure of materials down to the atomic level, but challenges remain in accurately and quantitatively modelling the response. We compare comprehensive theoretical density functional theory (DFT) calculations of 1s core-level EEL K-edge spectra of pure, B-doped and N-doped graphene with and without a core-hole to previously published atomic-resolution experimental electron microscopy data. The ground state approximation is found in this specific system to perform consistently better than the frozen core-hole approximation. The impact of including or excluding a core-hole on the resultant theoretical band structures, densities of states, electron densities and EEL spectra were all thoroughly examined and compared. It is concluded that the frozen core-hole approximation exaggerates the effects of the core-hole in graphene and should be discarded in favour of the ground state approximation. These results are interpreted as an indicator of the overriding need for theorists to embrace many-body effects in the pursuit of accuracy in theoretical spectroscopy instead of a system-tailored approach whose approximations are selected empirically.

  7. Using Plasmon Peaks in Electron Energy-Loss Spectroscopy to Determine the Physical and Mechanical Properties of Nanoscale Materials

    SciTech Connect

    Howe, James M.

    2013-05-09

    In this program, we developed new theoretical and experimental insights into understanding the relationships among fundamental universality and scaling phenomena, the solid-state physical and mechanical properties of materials, and the volume plasmon energy as measured by electron energy-loss spectroscopy (EELS). Particular achievements in these areas are summarized as follows: (i) Using a previously proposed physical model based on the universal binding-energy relation (UBER), we established close phenomenological connections regarding the influence of the valence electrons in materials on the longitudinal plasma oscillations (plasmons) and various solid-state properties such as the optical constants (including absorption and dispersion), elastic constants, cohesive energy, etc. (ii) We found that carbon materials, e.g., diamond, graphite, diamond-like carbons, hydrogenated and amorphous carbon films, exhibit strong correlations in density vs. Ep (or maximum of the volume plasmon peak) and density vs. hardness, both from available experimental data and ab initio DFT calculations. This allowed us to derive a three-dimensional relationship between hardness and the plasmon energy, that can be used to determine experimentally both hardness and density of carbon materials based on measurements of the plasmon peak position. (iii) As major experimental accomplishments, we demonstrated the possibility of in-situ monitoring of changes in the physical properties of materials with conditions, e.g., temperature, and we also applied a new plasmon ratio-imaging technique to map multiple physical properties of materials, such as the elastic moduli, cohesive energy and bonding electron density, with a sub-nanometer lateral resolution. This presents new capability for understanding material behavior. (iv) Lastly, we demonstrated a new physical phenomenon - electron-beam trapping, or electron tweezers - of a solid metal nanoparticle inside a liquid metal. This phenomenon is

  8. Electron Energy Loss Spectroscopy study of surface plasmon resonances in noble metal nanostructures.

    NASA Astrophysics Data System (ADS)

    Aloni, Shaul

    2007-03-01

    Nobel metal nanostructures are of great interest because of their unique optical properties. Their optical properties are determined by the surface plasmon resonance of conduction electrons, the frequency of which is determined not only by the nature of the metal or alloy of which the particle is made but also by the particle's size and shape. Moreover, the properties can be further tailored by forming nanoparticle assemblies and by controlling the surrounding dielectric medium We focus on study of the shape effects of the plasmonic excitation in silver and gold nanostructures.The silver and gold nanostructures were synthesized by solution phase synthesis yielding highly faceted nanocrystals including cubes triangular plates bi-pyramids and rods of aspect rations up to 1:20. The results show that the optical properties of individual metallic nanoparticles, as extracted from the low-loss spectrum, can be correlated with the properties predicted based on the particle size, shape and composition. .

  9. Band gap opening in strongly compressed diamond observed by x-ray energy loss spectroscopy

    SciTech Connect

    Gamboa, E. J.; Fletcher, L. B.; Lee, H. J.; MacDonald, M. J.; Zastrau, U.; Gauthier, M.; Gericke, D. O.; Vorberger, J.; Granados, E.; Hastings, J. B.; Glenzer, S. H.

    2016-01-25

    The extraordinary mechanical and optical properties of diamond are the basis of numerous technical applications and make diamond anvil cells a premier device to explore the high-pressure behavior of materials. However, at applied pressures above a few hundred GPa, optical probing through the anvils becomes difficult because of the pressure-induced changes of the transmission and the excitation of a strong optical emission. Such features have been interpreted as the onset of a closure of the optical gap in diamond, and can significantly impair spectroscopy of the material inside the cell. In contrast, a comparable widening has been predicted for purely hydrostatic compressions, forming a basis for the presumed pressure stiffening of diamond and resilience to the eventual phase change to BC8. We here present the first experimental evidence of this effect at geo-planetary pressures, exceeding the highest ever reported hydrostatic compression of diamond by more than 200 GPa and any other measurement of the band gap by more than 350 GPa. We here apply laser driven-ablation to create a dynamic, high pressure state in a thin, synthetic diamond foil together with frequency-resolved x-ray scattering as a probe. The frequency shift of the inelastically scattered x-rays encodes the optical properties and, thus, the behavior of the band gap in the sample. Using the ultra-bright x-ray beam from the Linac Coherent Light Source (LCLS), we observe an increasing direct band gap in diamond up to a pressure of 370 GPa. This finding points to the enormous strains in the anvils and the impurities in natural Type Ia diamonds as the source of the observed closure of the optical window. Our results demonstrate that diamond remains an insulating solid to pressures approaching its limit strength.

  10. Comprehensive studies of the electronic structure of pristine and potassium doped chrysene investigated by electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Roth, Friedrich; Mahns, Benjamin; Schönfelder, Ronny; Hampel, Silke; Nohr, Markus; Büchner, Bernd; Knupfer, Martin

    2012-09-01

    We have performed electron energy-loss spectroscopy studies in order to investigate the electronic properties of chrysene molecular solids. The valence band electronic excitation spectra and the C 1s core level excitations have been measured for pristine and potassium doped chrysene. The core level studies show a fine structure which signals the presence of four close lying conduction bands close to the Fermi level. Upon potassium doping, these bands are filled with electrons, and we have reached a doping level of about K2.7chrysene. Furthermore, undoped chrysene is characterized by an optical gap of about 3.3 eV and five, relatively weak, excitonic features following the excitation onset. Doping induces major changes in the electronic excitation spectra, with a new, prominent low energy excitation at about 1.3 eV. The results of a Kramers-Kronig analysis indicate that this new feature can be assigned to a charge carrier plasmon in the doped material, and momentum dependent studies reveal a negative plasmon dispersion.

  11. Identification of local phase of nanoscale BaTiO₃ powders by high-resolution electron energy loss spectroscopy.

    PubMed

    Moon, Sun-Min; Wang, Xiaohui; Cho, Nam-Hee

    2013-08-01

    The electron energy loss spectroscopy (EELS) technique was applied to investigate the local variation in the phase of barium titanate (BaTiO₃) ceramics. It was found that the fine structure of the titanium L₂,₃ edge and their satellite peaks were sensitively varied with the tetragonal-cubic phase transition. The peak splitting of Ti-L₃ edge of tetragonal-phased BaTiO₃ ceramics was widened because of the increased crystal field effect compared with that of cubic-phased BaTiO₃. In case of nanoscale BaTiO₃ powders, the L₃ edge splitting of the core region was found to be smaller than that of the shell region. The energy gap between peaks t₂g and eg varied from 2.36 to 1.94 eV with changing the probe position from 1 to 20 nm from the surface. These results suggest that the EELS technique can be used to identify the local phase of sintered BaTiO₃ ceramics.

  12. Optical Dark-Field and Electron Energy Loss Imaging and Spectroscopy of Symmetry-Forbidden Modes in Loaded Nanogap Antennas.

    PubMed

    Brintlinger, Todd; Herzing, Andrew A; Long, James P; Vurgaftman, Igor; Stroud, Rhonda; Simpkins, B S

    2015-06-23

    We have produced large numbers of hybrid metal-semiconductor nanogap antennas using a scalable electrochemical approach and systematically characterized the spectral and spatial character of their plasmonic modes with optical dark-field scattering, electron energy loss spectroscopy with principal component analysis, and full wave simulations. The coordination of these techniques reveal that these nanostructures support degenerate transverse modes which split due to substrate interactions, a longitudinal mode which scales with antenna length, and a symmetry-forbidden gap-localized transverse mode. This gap-localized transverse mode arises from mode splitting of transverse resonances supported on both antenna arms and is confined to the gap load enabling (i) delivery of substantial energy to the gap material and (ii) the possibility of tuning the antenna resonance via active modulation of the gap material's optical properties. The resonant position of this symmetry-forbidden mode is sensitive to gap size, dielectric strength of the gap material, and is highly suppressed in air-gapped structures which may explain its absence from the literature to date. Understanding the complex modal structure supported on hybrid nanosystems is necessary to enable the multifunctional components many seek.

  13. Reflection electron energy loss spectroscopy as efficient technique for the determination of optical properties of polystyrene intermixed with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Deris, Jamileh; Hajati, Shaaker

    2017-01-01

    The electronic properties (electron inelastic cross section, energy loss function) of a nano-metalized polystyrene obtained by reflection electron energy loss spectroscopy (REELS) in a previous study [J. Deris, S. Hajati, S. Tougaard, V. Zaporojtchenko, Appl. Surf. Sci. 377 (2016) 44-47], which relies on the Yubero-Tougaard method, were used in the complementary application of Kramers-Kronig transformation to determine its optical properties such as the real part (ε1) and imaginary part (ε2) of the dielectric function (ε), refractive index (n), coefficients of extinction (k), reflection (R) and absorption (μ). The degree of intermixing of polystyrene thin film and gold nanoparticles of sizes 5.5 nm was controlled by annealing the sample to achieve a morphology in which the nanoparticles were homogeneously distributed within polystyrene. It is worth noting that no data are available on the optical properties of metalized polymers such as gold nanoparticles intermixed with polystyrene. Therefore, this work is of high importance in terms of both the sample studied here and the method applied. The advantage of the method applied here is that no information on the lateral distribution of the nanocomposite sample is required. This means that the REELS technique has been presented here to suitably, efficiently and easily obtain the optical properties of such nano-metalized polymer in which the metal nanoparticles have been vertically well distributed (homogeneous in depth). Therefore, for vertically homogeneous and laterally inhomogeneous samples, it is possible to make REELS imaging by scanning the sample and thus to make an image of their optical properties.

  14. High resolution electron energy loss spectroscopy of clean and hydrogen covered Si(001) surfaces: first principles calculations.

    PubMed

    Patterson, C H

    2012-09-07

    Surface phonons, conductivities, and loss functions are calculated for reconstructed (2×1), p(2×2) and c(4×2) clean Si(001) surfaces, and (2×1) H and D covered Si(001) surfaces. Surface conductivities perpendicular to the surface are significantly smaller than conductivities parallel to the surface. The surface loss function is compared to high resolution electron energy loss measurements. There is good agreement between calculated loss functions and experiment for H and D covered surfaces. However, agreement between experimental data from different groups and between theory and experiment is poor for clean Si(001) surfaces. Formalisms for calculating electron energy loss spectra are reviewed and the mechanism of electron energy losses to surface vibrations is discussed.

  15. High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of bulk and nanoparticle LaB6 in the near-infrared region.

    PubMed

    Sato, Yohei; Terauchi, Masami; Mukai, Masaki; Kaneyama, Toshikatsu; Adachi, Kenji

    2011-07-01

    The dielectric properties of LaB(6) crystals and the plasmonic behavior of LaB(6) nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB(6) crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB(6) nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB(6) nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB(6) crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB(6) area.

  16. 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.

  17. Electron Energy-Loss Spectroscopy (EELS)Calculation in Finite-Difference Time-Domain (FDTD) Package: EELS-FDTD

    NASA Astrophysics Data System (ADS)

    Large, Nicolas; Cao, Yang; Manjavacas, Alejandro; Nordlander, Peter

    2015-03-01

    Electron energy-loss spectroscopy (EELS) is a unique tool that is extensively used to investigate the plasmonic response of metallic nanostructures since the early works in the '50s. To be able to interpret and theoretically investigate EELS results, a myriad of different numerical techniques have been developed for EELS simulations (BEM, DDA, FEM, GDTD, Green dyadic functions). Although these techniques are able to predict and reproduce experimental results, they possess significant drawbacks and are often limited to highly symmetrical geometries, non-penetrating trajectories, small nanostructures, and free standing nanostructures. We present here a novel approach for EELS calculations using the Finite-difference time-domain (FDTD) method: EELS-FDTD. We benchmark our approach by direct comparison with results from the well-established boundary element method (BEM) and published experimental results. In particular, we compute EELS spectra for spherical nanoparticles, nanoparticle dimers, nanodisks supported by various substrates, and gold bowtie antennas on a silicon nitride substrate. Our EELS-FDTD implementation can be easily extended to more complex geometries and configurations and can be directly implemented within other numerical methods. Work funded by the Welch Foundation (C-1222, L-C-004), and the NSF (CNS-0821727, OCI-0959097).

  18. Measurement of vibrational spectrum of liquid using monochromated scanning transmission electron microscopy-electron energy loss spectroscopy.

    PubMed

    Miyata, Tomohiro; Fukuyama, Mao; Hibara, Akihide; Okunishi, Eiji; Mukai, Masaki; Mizoguchi, Teruyasu

    2014-10-01

    Investigations on the dynamic behavior of molecules in liquids at high spatial resolution are greatly desired because localized regions, such as solid-liquid interfaces or sites of reacting molecules, have assumed increasing importance with respect to improving material performance. In application to liquids, electron energy loss spectroscopy (EELS) observed with transmission electron microscopy (TEM) is a promising analytical technique with the appropriate resolutions. In this study, we obtained EELS spectra from an ionic liquid, 1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl) imide (C2mim-TFSI), chosen as the sampled liquid, using monochromated scanning TEM (STEM). The molecular vibrational spectrum and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap of the liquid were investigated. The HOMO-LUMO gap measurement coincided with that obtained from the ultraviolet-visible spectrum. A shoulder in the spectrum observed ∼0.4 eV is believed to originate from the molecular vibration. From a separately performed infrared observation and first-principles calculations, we found that this shoulder coincided with the vibrational peak attributed to the C-H stretching vibration of the [C2mim(+)] cation. This study demonstrates that a vibrational peak for a liquid can be observed using monochromated STEM-EELS, and leads one to expect observations of chemical reactions or aids in the analysis of the dynamic behavior of molecules in liquid.

  19. Electron energy loss spectroscopy of the L2,3 edge of phosphorus skutterudites and electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Sæterli, Ragnhild; Flage-Larsen, Espen; Prytz, Øystein; Taftø, Johan; Marthinsen, Knut; Holmestad, Randi

    2009-08-01

    In this study we report the results of experiments and theoretical calculations on the phosphorus L2,3 edges of the skutterudites CoP3 , LaFe4P12 , NiP3 , RhP3 , and IrP3 . Phosphorus s and d density of states above the Fermi level was studied by transmission electron energy loss spectroscopy while theoretical calculations were performed using both a real-space multiple-scattering procedure and density-functional theory. Generally, there are good agreements between both types of calculations and the experimental results. The near-edge structure of all the examined compounds shows the same overall features, including the metallic NiP3 and the metallic filled skutterudite LaFeP12 , and is well explained by comparison to phosphorus density of states. We also discuss the similarities to previously reported results on SiL2,3 edges and interpret the differences of the various skutterudites in terms of the electronegativities of the involved atom species.

  20. High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn{sub 3}O{sub 4} nanoparticles

    SciTech Connect

    Laffont, L.; Gibot, P.

    2010-11-15

    Manganese oxides particularly Mn{sub 3}O{sub 4} Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn{sub 3}O{sub 4}, a bivalent oxide, for which a precise characterization is necessary and for which the determination of the valency proves to be essential. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and particularly High Resolution Electron Energy Loss Spectroscopy (HREELS) allow us to perform these measurements on the nanometer scale. Well crystallized 10-20 nm sized Mn{sub 3}O{sub 4} particles with sphere-shaped morphology were thus successfully synthesized. Meticulous EELS investigations allowed the determination of a Mn{sup 3+}/Mn{sup 2+} ratio of 1.5, i.e. slightly lower than the theoretical value of 2 for the bulk Hausmannite manganese oxide. This result emphasizes the presence of vacancies on the tetrahedral sites in the structure of the as-synthesized nanomaterial. - Research Highlights: {yields}Mn{sub 3}O{sub 4} bulk and nano were studied by XRD, TEM and EELS. {yields}XRD and TEM determine the degree of crystallinity and the narrow grain size. {yields}HREELS gave access to the Mn{sup 3+}/Mn{sup 2+} ratio. {yields}Mn{sub 3}O{sub 4} nano have vacancies on the tetrahedral sites.

  1. The use of high resolution electron-energy-loss spectroscopy for refining the infrared optical constants of GaS, GaSe, and InSe

    NASA Astrophysics Data System (ADS)

    Yu, Li-Ming; Thiry, P. A.; Degiovanni, A.; Conard, Th.; Leclerc, G.; Caudano, R.; Lambin, Ph.; Debever, J.-M.

    1994-06-01

    Cleaved surfaces of III-VI lamellar semiconducting compounds GaS, GaSe, and InSe have been studied by high resolution electron-energy-loss spectroscopy (HREELS). The infrared optical constants of the materials were retrieved by using the dielectric theory taking account of the resonance frequencies published from infrared reflectivity (IRS) data. The limitations of the HREELS and IRS measurements in the case of these materials are discussed in detail. However, it is shown that, by combining the informations from both spectroscopies, it is possible to refine some of the oscillator strengths of these materials.

  2. Study of semiconductor valence plasmon line shapes via electron energy-loss spectroscopy in the transmission electron microscope

    SciTech Connect

    Kundmann, M.K.

    1988-11-01

    Electron energy-loss spectra of the semiconductors Si, AlAs, GaAs, InAs, InP, and Ge are examined in detail in the regime of outer-shell and plasmon energy losses (0--100eV). Particular emphasis is placed on modeling and analyzing the shapes of the bulk valence plasmon lines. A line shape model based on early work by Froehlich is derived and compared to single-scattering probability distributions extracted from the measured spectra. Model and data are found to be in excellent agreement, thus pointing the way to systematic characterization of the plasmon component of EELS spectra. The model is applied to three separate investigations. 82 refs.

  3. Study of the electronic structures of high T c cuprate superconductors by electron energy loss and secondary electron emission spectroscopies

    NASA Astrophysics Data System (ADS)

    Jayaram, V.; Kulkarni, G. U.; Rao, C. N. R.

    1989-10-01

    Energy loss spectra of superconducting YBa 2Cu 3O 6.9' Bi 1.5Pb 0.5Ca 2.5Sr 1.5Cu 3O 10+δ and Tl 2CaBa 2Cu 3O 8 obtained at primary electron energies in the 170-310 eV range show features reflecting the commonalities in their electronic structures. The relative intensity of the plasmon peak shows a marked drop across the transition temperature. Secondary electron emission spectra of the cuprates also reveal some features of the electronic structure.

  4. 2D atomic mapping of oxidation states in transition metal oxides by scanning transmission electron microscopy and electron energy-loss spectroscopy.

    PubMed

    Tan, Haiyan; Turner, Stuart; Yücelen, Emrah; Verbeeck, Jo; Van Tendeloo, Gustaaf

    2011-09-02

    Using a combination of high-angle annular dark-field scanning transmission electron microscopy and atomically resolved electron energy-loss spectroscopy in an aberration-corrected transmission electron microscope we demonstrate the possibility of 2D atom by atom valence mapping in the mixed valence compound Mn3O4. The Mn L(2,3) energy-loss near-edge structures from Mn2+ and Mn3+ cation sites are similar to those of MnO and Mn2O3 references. Comparison with simulations shows that even though a local interpretation is valid here, intermixing of the inelastic signal plays a significant role. This type of experiment should be applicable to challenging topics in materials science, such as the investigation of charge ordering or single atom column oxidation states in, e.g., dislocations.

  5. Doubly excited states of water as studied by electron energy loss spectroscopy in coincidence with detecting Lyman-α photons

    NASA Astrophysics Data System (ADS)

    Tsuchida, Toshinori; Odagiri, Takeshi; Ishikawa, Lisa; Yachi, Kazufumi; Shigemura, Keisuke; Ohno, Naruhito; Hosaka, Kouichi; Kitajima, Masashi; Kouchi, Noriyuki

    2011-09-01

    The electron energy loss spectrum of H2O in coincidence with detecting Lyman-α photons (CoEELS) has been measured at the incident electron energy of 100 eV and electron scattering angle of 8° in the inner valence range in order to investigate the formation and decay of the doubly excited states. The present CoEELS has been compared with that at the infinite incident electron energy and 0° electron scattering angle, which was derived from the density of the dipole oscillator strength of H2O for the emission of the Lyman-α photons against the incident photon energy (Nakano et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 215206). It is remarkable that there exists a large difference in shape between these CoEELSs. This difference has turned out to be attributed to the noticeable contribution of the forbidden doubly excited states at 100 eV incident electron energy and 8° scattering angle. They lie at 25.0 and 27.4 eV and have been found out in this study. The differential cross sections for the excitation to the superexcited states resulting in H(2p) formation have been obtained at 100 eV and 8° and compared with those at the infinite energy and 0°. The electron collisions at 100 eV and 8° enhance the dissociative double excitation against the dissociative single excitation as compared with the electron collision at the infinite energy and 0°.

  6. Study of the evolution of the atomic composition of thin NbN films under irradiation with mixed ion beams by methods of electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Dement'eva, M. M.; Prikhod'ko, K. E.; Gurovich, B. A.; Kutuzov, L. V.; Komarov, D. A.

    2016-11-01

    The variation in the atomic composition of ultrathin NbN films under irradiation by mixed ion beams to a doze of 4 dpa (for nitrogen) is experimentally studied by methods of electron energy loss spectroscopy with a transmission electron microscope in the transmission scan mode on cross-cut samples. The behavior of the substitution of nitrogen atoms by oxygen atoms has been established; it is characterized by changing the composition of the conducting part of the film from NbN to NbNO.

  7. Microwave fixation and localization of calcium in synaptic terminals using x-ray microanalysis and electron energy loss spectroscopy imaging.

    PubMed

    Mizuhira, V; Hasegawa, H

    1997-01-01

    The distribution of calcium ions is demonstrated in synaptic terminals by means of a two-step chemical precipitation of calcium ions in the rat brain. K-oxalate/K-antimonate chemical replacement with simultaneous computerized microwave irradiation was used. This precipitate in nerve cell structures was investigated by computerized electron probe x-ray microanalysis (EDX) and electron energy loss spectroscopic (EELS) imaging. The values obtained by EDX agreed with those of the standard sample and theoretical values of Ca-antimonate. Typical EELS spectra of Ca:L, O:K, and Sb:M were obtained from nerve terminals in the same tissue block as that used for EDX analysis. Excellent net Ca:L and Sb:M EELS digital images were obtained after their background images were subtracted. Calcium ions were distributed in the nerve terminals, synaptic vesicles, mitochondria, and synaptic membranes.

  8. Determination of electronic properties of nanostructures using reflection electron energy loss spectroscopy: Nano-metalized polymer as case study

    NASA Astrophysics Data System (ADS)

    Deris, Jamileh; Hajati, Shaaker; Tougaard, Sven; Zaporojtchenko, Vladimir

    2016-07-01

    In this work, Au was deposited with nominal effective thickness of 0.8 nm on polystyrene (PS) at room temperature. According to previous study, using XPS peak shape analysis [S. Hajati, V. Zaporojtchenko, F. Faupel, S. Tougaard, Surf. Sci. 601 (2007) 3261-3267], Au nanoparticles (Au-NPs) of sizes 5.5 nm were formed corresponding to such effective thickness (0.8 nm). Then the sample was annealed to 200 °C, which is far above the glass transition of PS. At this temperature, the Au-NPs were diffused within the depth 0.5 nm-6.5 nm as found using nondestructive XPS peak shape analysis. Electrons with primary energy 500 eV were used because the electronic properties will then be probed in utmost surface (∼1 IMFP range of depths that is 1.8 nm for PS). By using QUEELS software, theoretical and experimental electron inelastic cross section, energy loss function, electron inelastic mean free path and surface excitation parameters were obtained for the sample. The information obtained here, does not rely on any previously known information on the sample. This means that the method, applied here, is suitable for the determination of the electronic properties of new and unknown composite nanostructures.

  9. Trichroism in energy-loss near-edge structure spectroscopy: Polarization dependence of near-edge fine structures

    SciTech Connect

    Le Bosse, Jean-Claude; Epicier, Thierry; Chermette, Henry

    2007-08-15

    The goal of this paper is to relate the current of inelastically scattered electrons collected in a transmission electron microscope (TEM) to the double differential electron energy-loss cross section. Up to now, this relationship, which depends on the point symmetry around the probed atom site, has been essentially studied in a situation called dichroism. This situation can be encountered when a principal threefold, fourfold, or sixfold rotation axis through the probed atom site exists. The electron energy-loss cross section is then a linear combination of longitudinal and transversal cross sections, and the weights of these components are cos{sup 2} {theta}{sub q} and sin{sup 2} {theta}{sub q}, where {theta}{sub q} is the angle between the scattering wave vector q and the principal rotation axis. The first aim of this paper is to find the dependence on q of the cross section in all other cases, that is to say, when the symmetry around the probed atom site is described with one of the eight low symmetry point groups C{sub 1}, S{sub 2}, C{sub 1h}, C{sub 2}, C{sub 2h}, C{sub 2v}, D{sub 2}, and D{sub 2h}. In these eight cases of low symmetry, three distinct situations called trichroism can be distinguished. In these situations, the cross section is expressed in terms of the cross sections obtained for six, four, or three particular orientations of the scattering wave vector. The second aim of this paper is to provide an expression of the inelastically scattered electron current collected in a TEM for these three situations of trichroism. This current is expressed in terms of experimental parameters, such as the incident beam convergence, the collector acceptance, the electron beam kinetic energy, and the sample orientation. As in the case of dichroism, magic conditions can be found, for which the collected current becomes independent of the single-crystal sample orientation. The case of the C K edge in the nonstoichiometric V{sub 6}C{sub 5} metallic carbide with a

  10. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method.

    PubMed

    Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

    2015-06-28

    The technique of low energy (0-30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0-2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electronic bands. The vibrational energy-loss spectra correspond well to IR spectra except for a broadening (∼0.04 eV) caused by the liquid surroundings, and enhanced overtone activity indicating a contribution from resonant excitation mechanism. The spectra of four representative ILs were recorded in the energy range of electronic excitations and compared to density functional theory multireference configuration interaction (DFT/MRCI) calculations, with good agreement. The spectra up to about 8 eV are dominated by π-π* transitions of the aromatic cations. The lowest bands were identified as triplet states. The spectral region 2-8 eV was empty in the case of a cation without π orbitals. The EEL spectrum of a saturated solution of methylene green in an IL band showed the methylene green EEL band at 2 eV, indicating that ILs may be used as a host to study nonvolatile compounds by this technique in the future.

  11. Martensitic transformation of Ni2FeGa ferromagnetic shape-memory alloy studied via transmission electron microscopy and electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, H. R.; Ma, C.; Tian, H. F.; Wu, G. H.; Li, J. Q.

    2008-06-01

    The structural properties of Ni2FeGa Heusler alloy synthesized by melt-spinning technique have been systematically studied by means of in situ heating and cooling transmission electron microscopy. It was found that the Ni2FeGa alloy was annealed into a well-defined L21 structure at around 980 K, and complex microstructural domains appeared along with lowering temperature. At room temperature (293 K), a rich variety of micromodulated domains were observed. The domain structures were aligned along the ⟨110⟩ or ⟨100⟩ directions resulting to complex tweed structures. Below martensitic transformation (MT) temperature (Ms,˜142K) , the cubic parent phase transformed into unmodulated martensitic variants and modulated martensitic variants. The variants were alternated along the ⟨100⟩ direction with various arrangements and steplike incommensurate boundaries. The modulated martensitic variants were composed of lamellar structures that have predominately a 5M modulation structure along the ⟨110⟩ directions. The electron energy-loss spectroscopy analysis of the low-loss region and the electron energy-loss near-edge fine structure revealed a visible change of the electronic structure along with MT, which can be well interpreted by means of intra-atomic or intraband charge redistribution due to spd orbital hybridization among the Ni-Fe-Ga atoms.

  12. Observability of localized magnetoplasmons in quantum dots: Scrutinizing the eligibility of far-infrared, Raman, and electron-energy-loss spectroscopies

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2016-03-01

    We investigate a one-component, quasi-zero dimensional, quantum plasma exposed to a parabolic potential and an applied magnetic field in the symmetric gauge. If the size of such a system as can be realized in the semiconducting quantum dots is on the order of the de-Broglie wavelength, the electronic and optical properties become highly tunable. Then the quantum size effects challenge the observation of many-particle phenomena such as the magneto-optical absorption, Raman intensity, and electron energy-loss spectrum. An exact analytical solution of the problem leads us to infer that these many-particle phenomena are, in fact, dictated by the generalized Kohn's theorem (GKT) in the long-wavelength limit. Maneuvering the confinement and/or the magnetic field furnishes the resonance energies capable of being explored with the FIR, Raman, and/or electron-energy-loss spectroscopy. This implies that either of these probes is competent in observing the localized magnetoplasmons in the system. As an application of the rigorous analytical diagnosis of the system, we have presented various pertinent single-particle, such as Fock-Darwin spectrum, Fermi energy, zigzag excitation spectrum, and magneto-optical transitions, and the many-particle phenomena, such as magneto-optical absorption, Raman intensity, and electron energy-loss probability. In the latter, the energy position of the resonance peaks is observed to be independent of the electron-electron interactions and hence of the number of electrons in the quantum dot in compliance with the GKT. It is found that both confinement potential and magnetic field play a decisive role in influencing the aforementioned many-particle phenomena. Specifically, increasing (decreasing) the strength of the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots and results into a blue (red) shift in the respective spectra. Intensifying the magnetic field has two-fold effects in the resonance

  13. Observability of localized magnetoplasmons in quantum dots: Scrutinizing the eligibility of far-infrared, Raman, and electron-energy-loss spectroscopies

    SciTech Connect

    Kushwaha, Manvir S.

    2016-03-15

    We investigate a one-component, quasi-zero dimensional, quantum plasma exposed to a parabolic potential and an applied magnetic field in the symmetric gauge. If the size of such a system as can be realized in the semiconducting quantum dots is on the order of the de-Broglie wavelength, the electronic and optical properties become highly tunable. Then the quantum size effects challenge the observation of many-particle phenomena such as the magneto-optical absorption, Raman intensity, and electron energy-loss spectrum. An exact analytical solution of the problem leads us to infer that these many-particle phenomena are, in fact, dictated by the generalized Kohn’s theorem (GKT) in the long-wavelength limit. Maneuvering the confinement and/or the magnetic field furnishes the resonance energies capable of being explored with the FIR, Raman, and/or electron-energy-loss spectroscopy. This implies that either of these probes is competent in observing the localized magnetoplasmons in the system. As an application of the rigorous analytical diagnosis of the system, we have presented various pertinent single-particle, such as Fock-Darwin spectrum, Fermi energy, zigzag excitation spectrum, and magneto-optical transitions, and the many-particle phenomena, such as magneto-optical absorption, Raman intensity, and electron energy-loss probability. In the latter, the energy position of the resonance peaks is observed to be independent of the electron-electron interactions and hence of the number of electrons in the quantum dot in compliance with the GKT. It is found that both confinement potential and magnetic field play a decisive role in influencing the aforementioned many-particle phenomena. Specifically, increasing (decreasing) the strength of the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots and results into a blue (red) shift in the respective spectra. Intensifying the magnetic field has two-fold effects in the resonance

  14. Synthesis and investigation by means of electron energy loss spectroscopy of metal replicas fabricated from nuclear microfilters

    NASA Astrophysics Data System (ADS)

    Yarygin, V. I.; Mironov, V. S.; Solovyev, N. P.; Kolninov, O. V.; Kolesnikova, V. V.; Chernyavsky, A. I.; Smolyansky, A. S.

    2001-12-01

    This paper deals with the investigation of the possibility of using metal replicas, which were synthesized on the basis of chemically treated and heavy ion irradiated polyethylene terephtalate (PET) films, as collector rough surfaces in thermionic energy converters (TEC) with the low factor of the slow electron reflection from the collector surface. These collector surfaces decrease the voltage loss and, correspondingly, increase the efficiency. The procedures of the nickel- and copper-based replicas' fabrication were developed. The presence of the surface microrelief in the form of bulges with the height of 5-6 μm and diameter of 0.1 μm (the surface density is ˜2×10 9 cm-2) changes substantially the reflective properties of metal surfaces on exposure to light over the visible and infra-red range: in the case of copper the reflected light intensity decreases by more than an order of magnitude; for the nickel rough surfaces, which have acquired the black color, we determined the practically full absence of the light reflection in the range of wavelengths from 0.4 to 50 μm. The same was noted when studying the interaction of slow electrons with the synthesized microrough surfaces: 20% decrease of the electron reflection factor was detected. In this way, the nature of a metal has a determining effect on the nature of the light interaction with the metal replicas. The conclusion is made that the obtained rough surface hold much promise for the use as the collector surfaces in the new generation of TEC.

  15. Microstructure of highly strained BiFeO3 thin films: Transmission electron microscopy and electron-energy loss spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Heon Kim, Young; Bhatnagar, Akash; Pippel, Eckhard; Alexe, Marin; Hesse, Dietrich

    2014-01-01

    Microstructure and electronic structure of highly strained bismuth ferrite (BiFeO3) thin films grown on lanthanum aluminate substrates are studied using high-resolution transmission and scanning transmission electron microscopies and electron energy loss spectroscopy (EELS). Monoclinic and tetragonal phases were observed in films grown at different temperatures, and a mix of both phases was detected in a film grown at intermediate temperature. In this film, a smooth transition of the microstructure was found between the monoclinic and the tetragonal phases. A considerable increase in the c-axis parameters was observed in both phases compared with the rhombohedral bulk phase. The off-center displacement of iron (Fe) ions was increased in the monoclinic phase as compared with the tetragonal phase. EEL spectra show different electronic structures in the monoclinic and the tetragonal phases. These experimental observations are well consistent with the results of theoretical first-principle calculations performed.

  16. 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.

  17. Distributions of hafnia and titania cores in EUV metal resists evaluated by scanning transmission electron microscopy and electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Toriumi, Minoru; Sato, Yuta; Koshino, Masanori; Suenaga, Kazu; Itani, Toshiro

    2016-11-01

    The morphologies of hafnia (HfO x ) and titania (TiO x ) cores and their distributions in metal resists for EUV lithography were characterized at the atomic level by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The HfO x cores show a higher affinity to organic components, such as methacrylic acid and benzoic acid, than the TiO x cores, and the same core-shell state as in a solution is almost completely maintained in the HfO x resist film. Furthermore, it was found that the surface modification of the TiO x cores by silylation is effective for preventing their aggregation and improves the postcoating delay (PCD) of the resist.

  18. Measurement of the dielectric function of α-Al2O3 by transmission electron microscopy - Electron energy-loss spectroscopy without Cerenkov radiation effects.

    PubMed

    Sakaguchi, Norihito; Tanda, Luka; Kunisada, Yuji

    2016-10-01

    The dielectric function of α-Al2O3 was measured by electron energy-loss spectroscopy (EELS) coupled with the difference method. The influence of Cerenkov radiation was significant in measurements using a 200kV transmission electron microscope (TEM) and the correct dielectric function could not be obtained using the conventional EELS procedure. However, a good agreement between the optical data and EELS for the dielectric functions was obtained via a 60kV TEM. Combining EELS and the difference method, however, provided an accurate measurement of the dielectric function for α-Al2O3 even at an accelerating voltage of 200kV. The combination of EELS and the difference method in the nano-beam diffraction mode could derive an accurate dielectric function with superior spatial resolution regardless of the occurrence of Cerenkov radiation. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Iron sources used by the nonpathogenic lactic acid bacterium Lactobacillus sakei as revealed by electron energy loss spectroscopy and secondary-ion mass spectrometry.

    PubMed

    Duhutrel, Philippe; Bordat, Christian; Wu, Ting-Di; Zagorec, Monique; Guerquin-Kern, Jean-Luc; Champomier-Vergès, Marie-Christine

    2010-01-01

    Lactobacillus sakei is a lactic acid bacterium naturally found on meat. Although it is generally acknowledged that lactic acid bacteria are rare species in the microbial world which do not have iron requirements, the genome sequence of L. sakei 23K has revealed quite complete genetic equipment dedicated to transport and use of this metal. Here, we aimed to investigate which iron sources could be used by this species as well as their role in the bacterium's physiology. Therefore, we developed a microscopy approach based on electron energy loss spectroscopy (EELS) analysis and nano-scale secondary-ion mass spectrometry (SIMS) in order to analyze the iron content of L. sakei cells. This revealed that L. sakei can use iron sources found in its natural ecosystem, myoglobin, hemoglobin, hematin, and transferrin, to ensure long-term survival during stationary phase. This study reveals that analytical image methods (EELS and SIMS) are powerful complementary tools for investigation of metal utilization by bacteria.

  20. In Situ Environmental Cell-Transmission Electron Microscopy Study of Microbial Reduction of Chromium(VI) Using Electron Energy Loss Spectroscopy.

    PubMed

    Daulton, Tyrone L.; Little, Brenda J.; Lowe, Kristine; Jones-Meehan, Joanne

    2001-11-01

    Reduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in situ, environmental cell-transmission electron microscopy (EC-TEM) coupled with electron energy loss spectroscopy (EELS). Bacteria from rinsed cultures were placed directly in the environmental cell of the transmission electron microscope and examined under 100 Torr pressure. Bright field EC-TEM images show two distinct populations of S. oneidensis in incubated cultures containing Cr(VI)O2- 4: those that exhibit low image contrast and heavily precipitate-encrusted cells exhibiting high image contrast. Several EELS techniques were applied to determine the oxidation state of Cr associated with encrusted cells. The encrusted cells are shown to contain a reduced form of Cr in oxidation state +3 or lower. These results demonstrate the capability to determine the chemistry and valence state of reduction products associated with unfixed, hydrated bacteria in an environmental cell transmission electron microscope.

  1. Microstructure of highly strained BiFeO{sub 3} thin films: Transmission electron microscopy and electron-energy loss spectroscopy studies

    SciTech Connect

    Heon Kim, Young; Bhatnagar, Akash; Pippel, Eckhard; Hesse, Dietrich; Alexe, Marin

    2014-01-28

    Microstructure and electronic structure of highly strained bismuth ferrite (BiFeO{sub 3}) thin films grown on lanthanum aluminate substrates are studied using high-resolution transmission and scanning transmission electron microscopies and electron energy loss spectroscopy (EELS). Monoclinic and tetragonal phases were observed in films grown at different temperatures, and a mix of both phases was detected in a film grown at intermediate temperature. In this film, a smooth transition of the microstructure was found between the monoclinic and the tetragonal phases. A considerable increase in the c-axis parameters was observed in both phases compared with the rhombohedral bulk phase. The off-center displacement of iron (Fe) ions was increased in the monoclinic phase as compared with the tetragonal phase. EEL spectra show different electronic structures in the monoclinic and the tetragonal phases. These experimental observations are well consistent with the results of theoretical first-principle calculations performed.

  2. Beam damage suppression of low-kappa porous Si-O-C films by cryo-electron-energy loss spectroscopy (EELS).

    PubMed

    Otsuka, Yuji; Shimizu, Yumiko; Tanaka, Isao

    2009-04-01

    Porous Si-O-C films with lower dielectric constant (kappa) relative to silicon dioxide have been widely studied as inter-layer dielectrics in new-generation microelectronic devices. On the analysis of the film by transmission electron microscopy (TEM), it is susceptible of beam damage during both sample preparation by a focused ion beam (FIB) technique and TEM observation. We use electron energy loss spectroscopy (EELS) to quantify the magnitude of the beam damage during these processes. The intensity of the 285-eV peak in C-K electron energy loss near edge structures (ELNES) is enhanced by the damage, which can be ascribed to the formation of the C=C double bonds as a result of the decomposition of the methyl groups by the beam. The use of cryo-holder for TEM at 100 K is found to be essential to reduce the damage of the low-kappa layers. The lowering of the acceleration voltage of FIB down to 5 keV does not change the spectra. Since the FIB damage is localized at the surface, the use of thick regions in the TEM foil such as 130 nm is preferred to reduce the superposition of EELS of the damaged region on those from the sample of interest.

  3. Electronic structure of metastable bcc Cu-Cr alloy thin films: Comparison of electron energy-loss spectroscopy and first-principles calculations.

    PubMed

    Liebscher, C H; Freysoldt, C; Dennenwaldt, T; Harzer, T P; Dehm, G

    2016-07-12

    Metastable Cu-Cr alloy thin films with nominal thickness of 300nm and composition of Cu67Cr33 (at%) are obtained by co-evaporation using molecular beam epitaxy. The microstructure, chemical phase separation and electronic structure are investigated by transmission electron microscopy (TEM). The thin film adopts the body-centered cubic crystal structure and consists of columnar grains with ~50nm diameter. Aberration-corrected scanning TEM in combination with energy dispersive X-ray spectroscopy confirms compositional fluctuations within the grains. Cu- and Cr-rich domains with composition of Cu85Cr15 (at%) and Cu42Cr58 (at%) and domain size of 1-5nm are observed. The alignment of the interface between the Cu- and Cr-rich domains shows a preference for {110}-type habit plane. The electronic structure of the Cu-Cr thin films is investigated by electron energy loss spectroscopy (EELS) and is contrasted to an fcc-Cu reference sample. The experimental EEL spectra are compared to spectra computed by density functional theory. The main differences between bcc-and fcc-Cu are related to differences in van Hove singularities in the electron density of states. In Cu-Cr solid solutions with bcc crystal structure a single peak after the L3-edge, corresponding to a van Hove singularity at the N-point of the first Brillouin zone is observed. Spectra computed for pure bcc-Cu and random Cu-Cr solid solutions with 10at% Cr confirm the experimental observations. The calculated spectrum for a perfect Cu50Cr50 (at%) random structure shows a shift in the van Hove singularity towards higher energy by developing a Cu-Cr d-band that lies between the delocalized d-bands of Cu and Cr.

  4. Acetylene adsorption on the Si(111)-(7×7) surface: Ultraviolet photoemission and high-resolution electron-energy-loss spectroscopies

    NASA Astrophysics Data System (ADS)

    de Renzi, V.; Biagi, R.; del Pennino, U.

    2001-10-01

    The room temperature adsorption and the thermal reaction of acetylene on the Si(111)-(7×7) surface has been investigated by means of ultraviolet-photoemission spectroscopy and high-resolution electron-energy-loss spectroscopy (HREELS). In the first stage of the adsorption process, the evolution of the restatom- and adatom-related electronic states as a function of acetylene exposure is well described by a modified di-σ-bonding model, in which the metallic character of the (7×7) surface plays a fundamental role. For higher exposure, all the restatom dangling bonds are saturated and the adsorption process continues through saturation of the remaining adatoms. In this phase, a molecular tilting is observed, possibly accompanied by a surface atom rearrangement. Upon annealing to 600 °C, acetylene dehydrogenation and partial desorption occur, as demonstrated by the disappearance of the C-H modes in HREELS and the reappearance of the adatom and restatom dangling-bond states in valence-band spectra. At 700 °C the formation of a Si-C compound is observed. Atomic-force-microscopy topographic images taken ex situ after annealing to 800 °C show that the Si-C interface is constituted by islands with lateral dimension of ~300 Å, while the overall surface roughness is 10-20 Å.

  5. Assessing electron beam sensitivity for SrTiO3 and La0.7Sr0.3MnO3 using electron energy loss spectroscopy.

    PubMed

    Nord, Magnus; Vullum, Per Erik; Hallsteinsen, Ingrid; Tybell, Thomas; Holmestad, Randi

    2016-10-01

    Thresholds for beam damage have been assessed for La0.7Sr0.3MnO3 and SrTiO3 as a function of electron probe current and exposure time at 80 and 200kV acceleration voltage. The materials were exposed to an intense electron probe by aberration corrected scanning transmission electron microscopy (STEM) with simultaneous acquisition of electron energy loss spectroscopy (EELS) data. Electron beam damage was identified by changes of the core loss fine structure after quantification by a refined and improved model based approach. At 200kV acceleration voltage, damage in SrTiO3 was identified by changes both in the EEL fine structure and by contrast changes in the STEM images. However, the changes in the STEM image contrast as introduced by minor damage can be difficult to detect under several common experimental conditions. No damage was observed in SrTiO3 at 80kV acceleration voltage, independent of probe current and exposure time. In La0.7Sr0.3MnO3, beam damage was observed at both 80 and 200kV acceleration voltages. This damage was observed by large changes in the EEL fine structure, but not by any detectable changes in the STEM images. The typical method to validate if damage has been introduced during acquisitions is to compare STEM images prior to and after spectroscopy. Quantifications in this work show that this method possibly can result in misinterpretation of beam damage as changes of material properties.

  6. Electron-energy-loss spectroscopy of YBa sub 2 Cu sub 3 minus x Fe sub x O sub 7 minus y superconductors

    SciTech Connect

    Vaishnava, P.P.; Taylor, C.A. II ); Foiles, C.L. )

    1990-03-01

    YBa{sub 2}Cu{sub 3{minus}{ital x}}Fe{sub {ital x}}O{sub 7{minus}{ital y}} ({ital x}=0.0, 0.05, 0.1) compounds have been studied using energy-dispersive x-ray (EDX) and electron-energy-loss spectroscopy (EELS). X-ray diffraction data indicated the formation of structurally known superconducting compounds. Transition temperatures, as measured by a Faraday balance, showed a decrease as the iron concentration was increased. Using the spot mode in an analytical electron microscope, the EDX and EELS data were obtained for identifiable, well-defined small regions of the superconducting particles. EDX spectra have been used to analyze different components and phases present in the samples. Detailed EELS data for the O 1{ital s} excitation have been obtained, and a peak in the pre-edge continuum has been observed in all the samples. The intensity and the nature of this peak are found to depend upon the iron concentration. The results of this investigation suggest structural disorder and orthorhombic-to-tetragonal transition as major reasons for the decrease in transition temperature for the iron-doped superconductors.

  7. Detection of local chemical states of lithium and their spatial mapping by scanning transmission electron microscopy, electron energy-loss spectroscopy and hyperspectral image analysis.

    PubMed

    Muto, Shunsuke; Tatsumi, Kazuyoshi

    2017-02-08

    Advancements in the field of renewable energy resources have led to a growing demand for the analysis of light elements at the nanometer scale. Detection of lithium is one of the key issues to be resolved for providing guiding principles for the synthesis of cathode active materials, and degradation analysis after repeated use of those materials. We have reviewed the different techniques currently used for the characterization of light elements such as high-resolution transmission electron microscopy, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). In the present study, we have introduced a methodology to detect lithium in solid materials, particularly for cathode active materials used in lithium-ion battery. The chemical states of lithium were isolated and analyzed from the overlapping multiple spectral profiles, using a suite of STEM, EELS and hyperspectral image analysis. The method was successfully applied in the chemical state analyses of hetero-phases near the surface and grain boundary regions of the active material particles formed by chemical reactions between the electrolyte and the active materials. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  8. Hydrogen bonding configuration and thermal stability of ambient exposed and in situ hydrogenated polycrystalline diamond surfaces studied by high resolution electron energy loss spectroscopy.

    PubMed

    Michaelson, Sh; Akhvlediani, R; Hoffman, A

    2011-06-28

    In this work we report on an investigation of hydrogen bonding and thermal stability on the surface of poly-crystalline diamond by high resolution electron energy loss spectroscopy (HR-EELS). Diamond films were grown on silicon substrates from CH(4)/H(2) as well as from CD(4)/D(2) gas mixtures by hot filament chemical vapor deposition (HF-CVD). The impact of ex situ ambient exposure on hydrogen bonding and its thermal stability was examined for: (i) as deposited films from a CH(4)/H(2) gas mixture; (ii) the same sample treated ex situ in micro-wave activated hydrogen plasma; and (iii) as deposited films from a CD(4)/D(2) gas mixture. In order to clarify the changes in the hydrogen bonding configuration detected on the different surfaces as a function of thermal annealing in situ hydrogenation by thermally activated atomic hydrogen was performed and examined. This study provides direct evidence that the exposure to ambient conditions and low temperature vacuum annealing have a pronounced effect on the hydrogen-carbon bonding configuration onto the poly-crystalline diamond surfaces.

  9. Two bonding configurations of acetylene on Si(001)-(2 x 1): a combined high-resolution electron energy loss spectroscopy and density functional theory study.

    PubMed

    Mineva, T; Nathaniel, R; Kostov, K L; Widdra, W

    2006-11-21

    Two coexisting adsorption states of molecularly adsorbed acetylene on the Si(001)-(2 x 1) surface have been identified by a combined study based on the high-resolution electron energy loss spectroscopy and density functional computations. Seven possible adsorbate-substrate structures are considered theoretically including their full vibrational analysis. Based on a significantly enhanced experimental resolution, the assignment of 15 C2H2- and C2D2-derived vibrational modes identifies a dominant di-sigma bonded molecule adsorbed on top of a single Si-Si dimer. Additionally there is clear evidence for a second minority species which is di-sigma bonded between two Si-Si dimers within the same dimer row (end-bridge geometry). The possible symmetries of the adsorbate complexes are discussed based on the specular and off-specular vibrational measurements. They suggest lower than ideal C(2v) and C(s) symmetries for on-top and end-bridge species, respectively. At low coverages the symmetry reductions might be lifted.

  10. Probing optical band gaps at the nanoscale in NiFe₂O₄ and CoFe₂O₄ epitaxial films by high resolution electron energy loss spectroscopy

    SciTech Connect

    Dileep, K.; Loukya, B.; Datta, R.; Pachauri, N.; Gupta, A.

    2014-09-14

    Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct from the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.

  11. Direct band gap measurement of Cu(In,Ga)(Se,S){sub 2} thin films using high-resolution reflection electron energy loss spectroscopy

    SciTech Connect

    Heo, Sung; Lee, Hyung-Ik; Park, Jong-Bong; Ko, Dong-Su; Chung, JaeGwan; Kim, KiHong; Kim, Seong Heon; Yun, Dong-Jin; Ham, YongNam; Park, Gyeong Su; Song, Taewon; Lee, Dongho Nam, Junggyu; Kang, Hee Jae; Choi, Pyung-Ho; Choi, Byoung-Deog

    2015-06-29

    To investigate the band gap profile of Cu(In{sub 1−x},Ga{sub x})(Se{sub 1−y}S{sub y}){sub 2} of various compositions, we measured the band gap profile directly as a function of in-depth using high-resolution reflection energy loss spectroscopy (HR-REELS), which was compared with the band gap profile calculated based on the auger depth profile. The band gap profile is a double-graded band gap as a function of in-depth. The calculated band gap obtained from the auger depth profile seems to be larger than that by HR-REELS. Calculated band gaps are to measure the average band gap of the spatially different varying compositions with respect to considering its void fraction. But, the results obtained using HR-REELS are to be affected by the low band gap (i.e., out of void) rather than large one (i.e., near void). Our findings suggest an analytical method to directly determine the band gap profile as function of in-depth.

  12. Successful application of spatial difference technique to electron energy-loss spectroscopy studies of Mo/SrTiO3 interfaces.

    PubMed

    Gao, M; Scheu, C; Tchernychova, E; Rühle, M

    2003-04-01

    The electron energy-loss near-edge structure (ELNES) of Mo/SrTiO3 interfaces has been studied using high spatial resolution electron energy-loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope. Thin films of Mo with a thickness of 50 nm were grown on (001)-orientated SrTiO3 surfaces by molecular beam epitaxy at 600 degrees C. High-resolution transmission electron microscopy revealed that the interfaces were atomically abrupt with the (110)Mo plane parallel to the substrate surface. Ti-L2,3 ( approximately 460 eV), O-K ( approximately 530 eV), Sr-L2,3 ( approximately 1950 eV) and Mo-L2,3 ( approximately 2500 eV) absorption edges were acquired by using the Gatan Enfina parallel EELS system with a CCD detector. The interface-specific components of the ELNES were extracted by employing the spatial difference method. The interfacial Ti-L2,3 edge shifted to lower energy values and the splitting due to crystal field became less pronounced compared to bulk SrTiO3, which indicated that the Ti atoms at the interface were in a reduced oxidation state and that the symmetry of the TiO6 octahedra was disturbed. No interfacial Sr-L2,3 edge was observed, which may demonstrate that Sr atoms do not participate in the interfacial bonding. An evident interface-specific O-K edge was found, which differs from that of the bulk in both position (0.8 +/- 0.2 eV positive shift) and shape. In addition, a positive shift (0.9 +/- 0.3 eV) occurred for the interfacial Mo-L2,3, revealing an oxidized state of Mo at the interface. Our results indicated that at the interface SrTiO3 was terminated with TiO2. The validity of the spatial difference technique is discussed and examined by introducing subchannel drift intentionally.

  13. Energy losses in photovoltaic systems

    NASA Astrophysics Data System (ADS)

    Anis, Wagdy R.; Nour, M. Abdulsadek

    1994-10-01

    The maximum power generated by photovoltaic (PV) arrays is not fully used. During summer, the main cause for the energy loss is the system design that necessitates an oversizing of the PV array to supply the load during the winter season when the solar energy is limited. Other reasons that cause energy loss are: the mismatch between the array and the load or battery, the loss in the batteries, and the loss due to the PV array disconnect. The array disconnect loss takes place during summer season when the battery is fully charged. To avoid the disconnect loss, a novel battery voltage regulator (BVR) is used. This supplies the load directly from the array when the battery is fully charged. Energy losses have been analyzed and divided into fundamental (unavoidable) and non-fundamental losses. Both conventional (using a conventional BVR) and new (using a novel BVR) PV systems are studied. A load that consumes constant power for 24 h a day through the year is considered. The climatic condition of Cairo city is taken as the test case.

  14. Surface spin canting in F e3O4 and CoF e2O4 nanoparticles probed by high-resolution electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Negi, D. S.; Sharona, H.; Bhat, U.; Palchoudhury, S.; Gupta, A.; Datta, R.

    2017-05-01

    High-resolution electron energy loss spectroscopy (HR-EELS) is utilized to probe the surface spin canting in nanoparticles of two technologically important magnetic materials, i.e. F e3O4 and CoF e2O4 (CFO). A soft experimental technique has been developed that is capable of extracting EELS spectra with single atomic plane resolution recorded in a single frame. The technique yields information at different depths of the nanoparticle from the surface to the core regions with high signal-to-noise ratio and without beam damage. This enables comparing the fine structures between the surface and core regions of the nanoparticles. The results confirm earlier observations of uniformly oriented spin canting structure for CFO and provide additional information regarding atom site-selective spin canting information. In the case of F e3O4 , preferred canting orientation forming core and shell structure is deduced. Unlike earlier reports based on polarized spin-flip neutron scattering measurement, it is possible from the experimental spectra combined with the first principle-based calculations considering noncollinear magnetism to narrow down the canting angles for F e3O4 (Td,Oh tilts 40°, 40°) and CFO (Td,Oh tilts 17°, 17°). In addition, the role of Dzyaloshinskii-Moriya interaction in stabilizing the spin canting at the nanoparticle surface is discussed. The results demonstrate that HR-EELS can be a powerful technique to probe the magnetic structure in nanodimensional systems and has advantages over neutron-based techniques in terms of superior spatial resolution, site-specific information, and ease of sample preparation.

  15. Dynamical observation of lithium insertion/extraction reaction during charge-discharge processes in Li-ion batteries by in situ spatially resolved electron energy-loss spectroscopy.

    PubMed

    Shimoyamada, Atsushi; Yamamoto, Kazuo; Yoshida, Ryuji; Kato, Takehisa; Iriyama, Yasutoshi; Hirayama, Tsukasa

    2015-12-01

    All-solid-state Li-ion batteries (LIBs) with solid electrolytes are expected to be the next generation devices to overcome serious issues facing conventional LIBs with liquid electrolytes. However, the large Li-ion transfer resistance at the electrode/solid-electrolyte interfaces causes low power density and prevents practical use. In-situ-formed negative electrodes prepared by decomposing the solid electrolyte Li(1+x+3z)Alx(Ti,Ge)(2-x)Si(3z)P(3-z)O12 (LASGTP) with an excess Li-ion insertion reaction are effective electrodes providing low Li-ion transfer resistance at the interfaces. Prior to our work, however, it had still been unclear how the negative electrodes were formed in the parent solid electrolytes. Here, we succeeded in dynamically visualizing the formation by in situ spatially resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS). The Li-ions were gradually inserted into the solid electrolyte region around 400 nm from the negative current-collector/solid-electrolyte interface in the charge process. Some of the ions were then extracted in the discharge process, and the rest were diffused such that the distribution was almost flat, resulting in the negative electrodes. The redox reaction of Ti(4+)/Ti(3+) in the solid electrolyte was also observed in situ during the Li insertion/extraction processes. The in situ SR-TEM-EELS revealed the mechanism of the electrochemical reaction in solid-state batteries. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. INTRACELLULAR METAL COMPARTMENTALIZATION IN THE GREEN ALGAL MODEL SYSTEM MICRASTERIAS DENTICULATA (STREPTOPHYTA) MEASURED BY TRANSMISSION ELECTRON MICROSCOPY-COUPLED ELECTRON ENERGY LOSS SPECTROSCOPY(1).

    PubMed

    Volland, Stefanie; Andosch, Ancuela; Milla, Manuela; Stöger, Barbara; Lütz, Cornelius; Lütz-Meindl, Ursula

    2011-06-01

    Entry of metals in form of aerosols into areas of high air humidity such as peat bogs represents a serious danger for inhabiting organisms such as the unicellular desmid Micrasterias denticulata Bréb. ex Ralfs (Desmidiaceae, Zynematophyceae, Streptophyta). To understand cellular detoxification and tolerance mechanisms, detailed intracellular localization of metal pollutants is required. This study localizes the metals aluminum (Al), zinc (Zn), copper (Cu), and cadmium (Cd) in the green algal model system Micrasterias after experimental exposure to sulfate solutions by highly sensitive TEM-coupled electron energy loss spectroscopy (EELS). Concentrations of the metals shown to induce inhibiting effects on cell development and cytomorphogenesis were chosen for these experiments. Long-term exposure to these metal concentrations led to a pronounced impact on cell physiology expressed by a general decrease in apparent photosynthesis. After long-term treatment, Zn, Al, and Cu were detected in the cell walls by EELS. Zn was additionally found in vacuoles and mucilage vesicles, and Cu in starch grains and also in mucilage vesicles. Elevated amounts of oxygen in areas where Zn, Al, and Cu were localized suggest sequestration of these metals as oxides. The study demonstrated that Micrasterias can cope differently with metal pollutants. In low doses and during a limited time period, the cells were able to compartmentalize Cu the best, followed by Zn and Al. Cu and Zn were taken up into intracellular compartments, whereas Al was only bound to the cell wall. Cd was not compartmentalized at all, which explains its strongest impact on growth, cell division rate, and photosynthesis in Micrasterias. © 2011 Phycological Society of America.

  17. An in ovo investigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy.

    PubMed

    Venter, Chantelle; Oberholzer, Hester M; Taute, Helena; Cummings, Franscious R; Bester, Megan J

    2015-01-01

    Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 μM physiological dosage (PD) and 430 μM (×1000 PD) CdCl2, as well as 0.476 μM (PD) and 746 μM (×1000 PD) K2Cr2O7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light- and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscopy, the PD of both Cd and Cr had no effect on liver tissue or cellular morphology. At ×1000 PD both Cd and Cr caused sinusoid dilation and tissue necrosis. With TEM analysis, Cd exposed hepatocytes presented with irregular chromatin condensation, ruptured cellular membranes and damaged or absent organelles. In contrast Cr caused only slight mitochondrial damage. EELS revealed the bio-accumulation of Cd and Cr along the cristae of the mitochondria and chromatin of the nuclei.

  18. Spatially resolved chemical mapping of dry and hydrated polymer morphology by electron energy-loss spectroscopy in the scanning transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Sousa, Alioscka A. C. A.

    Electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a technique that allows compositional analysis to be performed at high spatial resolution in thin TEM specimens, and here we implement and apply this technique to quantitatively study the morphology of unstained dry and frozen-hydrated polymer films. While water can play a controlling role that determines many of the important properties of polymers, there has not yet been much experimental work performed to correlate water spatial distribution with variations in underlying polymer morphology. We show how a quantitative map of the nanoscale spatial distribution of water can be generated from frozen-hydrated polymer thin films using EELS in the STEM. We find that hydrated polymers are very sensitive to the incident electron irradiation, and there is a trade off between the spatial resolution that a compositional map can display and its signal-to-noise ratio. The identification of minor fluctuations in composition within small regions across a given water map is therefore challenging because one must distinguish the fluctuations that are significant from those within noise. We implement a methodology using scatter diagrams in combination with noise simulations to threshold water maps and separate real pixel-by-pixel compositional fluctuations from noise. We study a model system comprised of hydrophilic poly(vinyl pyrrolidone) and hydrophobic poly(styrene), and we show that the thresholding approach enables us to quantitatively identify statistically significant single-pixel fluctuations in water content. We also apply EELS in the STEM to characterize the morphology of a dry, solvent-cast thin-film biopolymer blend comprised of poly(caprolactone) and poly(DTE carbonate). We quantitatively show the effect that solvent evaporation rate has on the morphology development of this blend and how the underlying morphology can dramatically influence the spatial distribution of

  19. Temperature dependence of the plasmon energy in liquid and solid phases of pure Al and of an Al-Si alloy using electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Eswara Moorthy, Santhana K.; Howe, James M.

    2011-08-01

    The plasmon energy of the solid and liquid phases of pure Al, and an Al-Si alloy, was recorded as a function of temperature. For the case of pure Al, the trend in the solid and liquid phases followed the expected behavior based on a free (specific) volume change. Quantitatively, the slope of Ep versus T was -0.5 meV/K in the solid state and -2.2 meV/K in the liquid state. For the case of the Al-Si alloy, the trend in the solid phase was similar to that of pure Al, however, the trend in the liquid Al-Si phase was exactly opposite to what was observed for the pure Al liquid (i.e., +1.9 meV/K). This unexpected result is explained based on the variation, i.e., partitioning, of Si with temperature in the Al-Si alloy.

  20. Energy losses during cooking processes

    SciTech Connect

    Thapar, A.; Engira, R.M.; Sohal, J.S.

    1983-12-01

    A major chunk of the thermal energy of the cooking fuel is wasted due to incomplete consumption, unfunctional design of cooking stoves and utensils. Several studies and their findings which are reported in the present paper pertain to: determination of minimum fuel consumption required for cooking of selected dishes under controlled and normal conditions; analysis of relative amounts of heat loss through different techniques during cooking under normal conditions; evaluation of effectiveness of different energy saving techniques with regard to cooking vessel.

  1. Crystal and Electronic Structure of Lithiated Nanosized RutileTiO2 by Electron Diffraction and Electron Energy-loss Spectroscopy

    SciTech Connect

    Wang, Chong M.; Yang, Zhenguo; Thevuthasan, Suntharampillai; Liu, Jun; Baer, Donald R.; Choi, Daiwon; Wang, Donghai; Zhang, Jiguang; Saraf, Laxmikant V.; Nie, Zimin

    2009-06-11

    The electronic structure of the nanosized rutile TiO2 before and after mechanical lithiation were studied using TEM and EELS. EELS reveals the Li K-edge at the energy-loss position of ~ 61 eV. After lithiation, the separation of the t2g-eg crystal-field splitting on both Ti L2,3-edge and O K-edge decreases, the O K-edge shifts towards a higher energy-loss position and the separation between the pre-edge peak and main peak on the O K-edge decreases. These results suggest that the lithiation of rutile TiO2 was accompanied by the reduction of Ti ion and a charge transfer from Li to Ti.

  2. Mass loss from red giants - Infrared spectroscopy

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.

    1985-01-01

    A discussion is presented of IR spectroscopy, particularly high-resolution spectroscopy in the approximately 1-20 micron band, as it impacts the study of circumstellar envelopes. The molecular bands within this region contain an enormous amount of information, especially when observed with sufficient resolution to obtain kinematic information. In a single spectrum, it is possible to resolve lines from up to 50 different rotational/vibrational levels of a given molecule and to detect several different isotopic variants. When high resolution techniques are combined with mapping techniques and/or time sequence observations of variable stars, the resulting information can paint a very detailed picture of the mass-loss phenomenon. To date, near-IR observations have been made of 20 molecular species. CO is the most widely observed molecule and useful information has been gleaned from the observed rotational excitation, kinematics, time variability and spatial structure of its lines. Examples of different observing techniques are discussed in the following sections.

  3. Spectral restoration in high resolution electron energy loss spectroscopy based on iterative semi-blind Lucy-Richardson algorithm applied to rutile surfaces

    SciTech Connect

    Lazzari, Rémi Li, Jingfeng Jupille, Jacques

    2015-01-15

    A new spectral restoration algorithm of reflection electron energy loss spectra is proposed. It is based on the maximum likelihood principle as implemented in the iterative Lucy-Richardson approach. Resolution is enhanced and point spread function recovered in a semi-blind way by forcing cyclically the zero loss to converge towards a Dirac peak. Synthetic phonon spectra of TiO{sub 2} are used as a test bed to discuss resolution enhancement, convergence benefit, stability towards noise, and apparatus function recovery. Attention is focused on the interplay between spectral restoration and quasi-elastic broadening due to free carriers. A resolution enhancement by a factor up to 6 on the elastic peak width can be obtained on experimental spectra of TiO{sub 2}(110) and helps revealing mixed phonon/plasmon excitations.

  4. Spectral restoration in high resolution electron energy loss spectroscopy based on iterative semi-blind Lucy-Richardson algorithm applied to rutile surfaces.

    PubMed

    Lazzari, Rémi; Li, Jingfeng; Jupille, Jacques

    2015-01-01

    A new spectral restoration algorithm of reflection electron energy loss spectra is proposed. It is based on the maximum likelihood principle as implemented in the iterative Lucy-Richardson approach. Resolution is enhanced and point spread function recovered in a semi-blind way by forcing cyclically the zero loss to converge towards a Dirac peak. Synthetic phonon spectra of TiO2 are used as a test bed to discuss resolution enhancement, convergence benefit, stability towards noise, and apparatus function recovery. Attention is focused on the interplay between spectral restoration and quasi-elastic broadening due to free carriers. A resolution enhancement by a factor up to 6 on the elastic peak width can be obtained on experimental spectra of TiO2(110) and helps revealing mixed phonon/plasmon excitations.

  5. Spectral restoration in high resolution electron energy loss spectroscopy based on iterative semi-blind Lucy-Richardson algorithm applied to rutile surfaces

    NASA Astrophysics Data System (ADS)

    Lazzari, Rémi; Li, Jingfeng; Jupille, Jacques

    2015-01-01

    A new spectral restoration algorithm of reflection electron energy loss spectra is proposed. It is based on the maximum likelihood principle as implemented in the iterative Lucy-Richardson approach. Resolution is enhanced and point spread function recovered in a semi-blind way by forcing cyclically the zero loss to converge towards a Dirac peak. Synthetic phonon spectra of TiO2 are used as a test bed to discuss resolution enhancement, convergence benefit, stability towards noise, and apparatus function recovery. Attention is focused on the interplay between spectral restoration and quasi-elastic broadening due to free carriers. A resolution enhancement by a factor up to 6 on the elastic peak width can be obtained on experimental spectra of TiO2(110) and helps revealing mixed phonon/plasmon excitations.

  6. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    NASA Astrophysics Data System (ADS)

    Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  7. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    SciTech Connect

    Guedj, C.; Hung, L.; Sottile, F.; Zobelli, A.; Blaise, P.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO{sub 2}) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO{sub 2}, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO{sub 2} may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  8. The electronic states of oxazole studied by VUV absorption and electron energy-loss (EEL) spectroscopies, and ab initio configuration interaction methods

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.; Ganzenmüller, Georg; Walker, Isobel C.

    2007-04-01

    The oxazole VUV absorption spectrum over the range 5-12 eV shows intense bands centred near 6.3, 7.5, 8.3, 9.6 and 10.8 eV. The electron energy-loss (EEL) spectrum shows additional structure with a strong peak (˜1.4 eV) arising from resonant vibrational excitation of the molecule via a shape resonance, and a spin-forbidden 3ππ ∗ state at 4.6 eV. Electronic excitation energies for valence and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods. The CI studies used a triple zeta + polarisation basis set, augmented by diffuse (Rydberg) orbitals, to generate the theoretical singlet and triplet energy manifolds. The correlation of theory and experiment shows the nature of the more intense Rydberg state types, and identification of the main valence and Rydberg bands. Calculated energies for low-lying Rydberg states are relatively close (SD 0.38) to those expected, and there is generally a good correlation between the theoretical and experimental envelopes. Two of the three lowest electronic states arise from ππ ∗ excitation of the outer (3a″ and 2a″) π-orbitals, with one state (LP Nπ ∗) originating from the lone pair on nitrogen (15a') between them.

  9. The electronic states of buta-1,3-diene studied by ab initio configuration interaction and DFT methods, and electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    H., Michael; | Isobel C., Palmer; Walker

    2010-08-01

    The electronic vertical excitation energies for singlet and triplet valence, and Rydberg states of trans-buta-1,3-diene have been computed using ab initio multi-reference multi-root CI procedures with a [4s3p3d3f] set of Rydberg functions. Close numerical agreement between theory and experiment was found for a number of low-lying electronic states. The present CI and CASSCF [8MO,8e] calculations suggest that both the vertical and adiabatic order of the valence (ππ∗) states is: A˜1Aenergy-loss spectrum, reported here, in which the incident electrons have near-threshold energies, supports this order. Adiabatic excitation energies and structures were obtained for several singlet and triplet states using CASSCF and B3LYP procedures; the results from these methods are generally in good agreement with each other. The C 1C 2 to C 2C 3 bond length ratio in the excited states varies widely, and is discussed.

  10. Electron energy-loss spectra in molecular fluorine

    NASA Technical Reports Server (NTRS)

    Nishimura, H.; Cartwright, D. C.; Trajmar, S.

    1979-01-01

    Electron energy-loss spectra in molecular fluorine, for energy losses from 0 to 17.0 eV, have been taken at incident electron energies of 30, 50, and 90 eV and scattering angles from 5 to 140 deg. Features in the spectra above 11.5 eV energy loss agree well with the assignments recently made from optical spectroscopy. Excitations of many of the eleven repulsive valence excited electronic states are observed and their location correlates reasonably well with recent theoretical results. Several of these excitations have been observed for the first time and four features, for which there are no identifications, appear in the spectra.

  11. Examination of the electronic structure of crystalline and liquid Al versus temperature by in situ electron energy-loss spectroscopy (EELS).

    PubMed

    Palanisamy, Prakash; Jong, Maarten de; Asta, Mark; Howe, James M

    2015-09-01

    Electron energy-loss near-edge structure (ELNES) analysis using in situ heating in a transmission electron microscope (TEM) was performed to compare the electronic structure of crystalline and liquid Al versus temperature. It was found that the ELNES features in the L2,3 edges of crystalline and liquid Al are qualitatively similar, but that the edge threshold is modified and certain features in the energy range between 102 and 115eV vanish in the liquid, indicating that partial DOS is quantitatively different. Broadening of the L2,3 edge maximum for Al with temperature indicates a decay in the centrifugal barrier for the 2p electrons with increasing temperature. Comparison between the ELNES edge in supercooled liquid and crystalline Al at the same temperature of 600°C shows that the degree of order, i.e., crystallinity, plays an important role in determining the DOS. The ELNES edge of supercooled liquid Al closely resembles that of superheated liquid Al. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy

    SciTech Connect

    Dileep, K. E-mail: ranjan@jncasr.ac.in; Sahu, R.; Datta, R. E-mail: ranjan@jncasr.ac.in; Sarkar, Sumanta; Peter, Sebastian C.

    2016-03-21

    Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 and 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.

  13. A combined scanning tunneling microscopy and electron energy loss spectroscopy study on the formation of thin, well-ordered β-Ga2O3 films on CoGa(001)

    NASA Astrophysics Data System (ADS)

    Schmitz, G.; Gassmann, P.; Franchy, R.

    1998-03-01

    The formation of thin, well-ordered β-Ga2O3 films on CoGa(001) was studied by means of high resolution electron energy loss spectroscopy (EELS), scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and Auger electron spectroscopy. The crystalline β-Ga2O3 films on CoGa(001) are prepared upon adsorption of O2 at 300 K and subsequent annealing at 700 K or by oxidation of the sample directly at 700 K, respectively. EEL spectra of these films exhibit Fuchs-Kliewer modes at 305, 455, 645, and 785 cm-1 in good agreement with calculated spectra using the IR parameters of Ga2O3. The band gap was determined to be 4.5±0.2 eV. In addition, a gap state at 3.3 eV was found. The observed LEED pattern of β-Ga2O3/CoGa(001) can be explained by a (2×1) structure in two perpendicularly oriented domains. STM images exhibit atomically flat and large oxide terraces (up to 2500×700 Å2) mainly of rectangular shape. STM pictures with atomic resolution confirm the (2×1) structure. In addition, a square substructure can be observed which is related to the closed-packed oxygen lattice of β-Ga2O3.

  14. Far-UV Spectroscopy of the Planet-hosting Star WASP-13: High-energy Irradiance, Distance, Age, Planetary Mass-loss Rate, and Circumstellar Environment

    NASA Astrophysics Data System (ADS)

    Fossati, L.; France, K.; Koskinen, T.; Juvan, I. G.; Haswell, C. A.; Lendl, M.

    2015-12-01

    Several transiting hot Jupiters orbit relatively inactive main-sequence stars. For some of those, the {log}{R}{HK}\\prime activity parameter lies below the basal level (-5.1). Two explanations have been proposed so far: (i) the planet affects the stellar dynamo, (ii) the {log}{R}{HK}\\prime measurements are biased by extrinsic absorption, either by the interstellar medium (ISM) or by material local to the system. We present here Hubble Space Telescope/COS far-UV spectra of WASP-13, which hosts an inflated hot Jupiter and has a measured {log}{R}{HK}\\prime value (-5.26), well below the basal level. From the star’s spectral energy distribution we obtain an extinction E(B - V) = 0.045 ± 0.025 mag and a distance d = 232 ± 8 pc. We detect at ≳4σ lines belonging to three different ionization states of carbon (C i, C ii, and C iv) and the Si iv doublet at ˜3σ. Using far-UV spectra of nearby early G-type stars of known age, we derive a C iv/C i flux ratio-age relation, from which we estimate WASP-13's age to be 5.1 ± 2.0 Gyr. We rescale the solar irradiance reference spectrum to match the flux of the C iv 1548 doublet. By integrating the rescaled solar spectrum, we obtain an XUV flux at 1 AU of 5.4 erg s-1 cm-2. We use a detailed model of the planet’s upper atmosphere, deriving a mass-loss rate of 1.5 × 1011 g s-1. Despite the low {log}{R}{HK}\\prime value, the star shows a far-UV spectrum typical of middle-aged solar-type stars, pointing toward the presence of significant extrinsic absorption. The analysis of a high-resolution spectrum of the Ca ii H&K lines indicates that the ISM absorption could be the origin of the low {log}{R}{HK}\\prime value. Nevertheless, the large uncertainty in the Ca ii ISM abundance does not allow us to firmly exclude the presence of circumstellar gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities

  15. Nano-scale simultaneous observation of Li-concentration profile and Ti-, O electronic structure changes in an all-solid-state Li-ion battery by spatially-resolved electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kazuo; Yoshida, Ryuji; Sato, Takeshi; Matsumoto, Hiroaki; Kurobe, Hisanori; Hamanaka, Tadashi; Kato, Takehisa; Iriyama, Yasutoshi; Hirayama, Tsukasa

    2014-11-01

    All-solid-state Li-ion batteries having incombustible solid electrolytes are expected to be promising candidates for safe next-generation energy storage devices that have a long lifetime and high energy density. However, it is essential to address the large resistance of Li-ion transfer at the electrode/solid-electrolyte interfaces. A new concept electrode that is formed in situ from the Li2O-Al2O3-TiO2-P2O5-based glass-ceramic solid electrolytes with Si and Ge doping (LASGTP) produces atomic scale connection at the interfaces, which provides extremely low interfacial resistance. However, the formation mechanism and the reason for the low resistance are still unclear. Here we applied spatially-resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS) to visualize the nanometer-scale Li distribution and its effects on the electronic structures of other important elements (Ti and O). Local electron diffraction showed that the in situ formed electrode was an amorphous phase caused by the Li insertion. Picometer-scale expansion of O-O distance due to the Li insertion was also visualized in the electrode. These electronic and crystal changes and gradual Li distribution contribute to the low resistance and stable battery cycles.

  16. Distribution network reconfiguration for energy loss reduction

    SciTech Connect

    Taleski, R.; Rajicic, D.

    1997-02-01

    A new method for energy loss reduction for distribution networks is presented. It is based on known techniques and algorithms for radial network analysis--oriented element ordering, power summation method for power flow, statistical representation of load variations, and a recently developed energy summation method for computation of energy losses. These methods, combined with the heuristic rules developed to lead the iterative process, make the energy loss minimization method effective, robust and fast. It presents an alternative to the power minimization methods for operation and planning purposes.

  17. Energy loss of helium ions in zinc

    SciTech Connect

    Lantschner, G.H.; Eckardt, J.C.; Lifschitz, A.F.; Arista, N.R.; Araujo, L.L.; Duarte, P.F.; Santos, J.H.R. dos; Behar, M.; Dias, J.F.; Grande, P.L.; Montanari, C.C.; Miraglia, J.E.

    2004-06-01

    The energy loss of helium ions in zinc has been measured in the energy range from 37.5 to 1750 keV/amu using the transmission technique and the Rutherford backscattering method. In addition, calculations using the extended Friedel sum rule, the unitary convolution approximation, and the local plasma approximation have been performed. The contributions of the inner-shell and valence electrons to the total energy loss are separately evaluated. The measurements and calculations are in good agreement over an extended range of energies, and both of them yield stopping values higher than those provided by SRIM 2003.

  18. Microscopic mechanism of path-dependence on charge-discharge history in lithium iron phosphate cathode analysis using scanning transmission electron microscopy and electron energy-loss spectroscopy spectral imaging

    NASA Astrophysics Data System (ADS)

    Honda, Yoshitake; Muto, Shunsuke; Tatsumi, Kazuyoshi; Kondo, Hiroki; Horibuchi, Kayo; Kobayashi, Tetsuro; Sasaki, Tsuyoshi

    2015-09-01

    We revisited the "path-dependence" problem, i.e., the differing polarization observed in LiFePO4 cathode charge/discharge curves depending on the electrochemical treatment history of the material. The phase distributions of the active material particles with different charge/discharge histories in the LiFePO4 cathode were investigated through spectral imaging (SI) using scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). The STEM-EELS-SI experiments revealed that LiFePO4 (LFP) and FePO4 (FP) almost always coexist in the individual primary particles of Li0.5FePO4 (50% state of charge (SOC)) electrodes, forming core/shell structures. This is unlike the conventional domino-cascade model, in that LFP-inside/FP-outside is observed in the lithium-extracted Li0.5FePO4 particles, whereas FP-inside/LFP-outside is seen in the lithium-inserted Li0.5FePO4 particles. We examined the particle-size dependence of the core/total volume ratio of each Li0.5FePO4 particle, and the essential features of the path-dependent charge/discharge curves were semi-quantitatively reproduced by a simple static model that considered the ionic conductivity of the shell phase.

  19. Surgical weight loss: impact on energy expenditure.

    PubMed

    Thivel, David; Brakonieki, Katrina; Duche, Pascale; Morio, Béatrice; Béatrice, Morio; Boirie, Yves; Yves, Boirie; Laferrère, Blandine

    2013-02-01

    Diet-induced weight loss is often limited in its magnitude and often of short duration, followed by weight regain. On the contrary, bariatric surgery now commonly used in the treatment of severe obesity favors large and sustained weight loss, with resolution or improvement of most obesity-associated comorbidities. The mechanisms of sustained weight loss are not well understood. Whether changes in the various components of energy expenditure favor weight maintenance after bariatric surgery is unclear. While the impact of diet-induced weight loss on energy expenditure has been widely studied and reviewed, the impact of bariatric surgery on total energy expenditure, resting energy expenditure, and diet-induced thermogenesis remains unclear. Here, we review data on energy expenditure after bariatric surgery from animal and human studies. Bariatric surgery results in decreased total energy expenditure, mainly due to reduced resting energy expenditure and explained by a decreased in both fat-free mass and fat mass. Limited data suggest increased diet-induced thermogenesis after gastric bypass, a surgery that results in gut anatomical changes and modified the digestion processes. Physical activity and sustained intakes of dietary protein may be the best strategies available to increase non-resting and then total energy expenditure, as well as to prevent the decline in lean mass and resting energy expenditure.

  20. Surgical Weight Loss: Impact on Energy Expenditure

    PubMed Central

    Brakonieki, Katrina; Duche, Pascale; Béatrice, Morio; Yves, Boirie; Laferrère, Blandine

    2016-01-01

    Diet-induced weight loss is often limited in its magnitude and often of short duration, followed by weight regain. On the contrary, bariatric surgery now commonly used in the treatment of severe obesity favors large and sustained weight loss, with resolution or improvement of most obesity-associated comorbidities. The mechanisms of sustained weight loss are not well understood. Whether changes in the various components of energy expenditure favor weight maintenance after bariatric surgery is unclear. While the impact of diet-induced weight loss on energy expenditure has been widely studied and reviewed, the impact of bariatric surgery on total energy expenditure, resting energy expenditure, and diet-induced thermogenesis remains unclear. Here, we review data on energy expenditure after bariatric surgery from animal and human studies. Bariatric surgery results in decreased total energy expenditure, mainly due to reduced resting energy expenditure and explained by a decreased in both fat-free mass and fat mass. Limited data suggest increased diet-induced thermogenesis after gastric bypass, a surgery that results in gut anatomical changes and modified the digestion processes. Physical activity and sustained intakes of dietary protein may be the best strategies available to increase non-resting and then total energy expenditure, as well as to prevent the decline in lean mass and resting energy expenditure. PMID:23224568

  1. Ultrafast core-loss spectroscopy in four-dimensional electron microscopy

    PubMed Central

    van der Veen, Renske M.; Penfold, Thomas J.; Zewail, Ahmed H.

    2015-01-01

    We demonstrate ultrafast core-electron energy-loss spectroscopy in four-dimensional electron microscopy as an element-specific probe of nanoscale dynamics. We apply it to the study of photoexcited graphite with femtosecond and nanosecond resolutions. The transient core-loss spectra, in combination with ab initio molecular dynamics simulations, reveal the elongation of the carbon-carbon bonds, even though the overall behavior is a contraction of the crystal lattice. A prompt energy-gap shrinkage is observed on the picosecond time scale, which is caused by local bond length elongation and the direct renormalization of band energies due to temperature-dependent electron–phonon interactions. PMID:26798793

  2. Interferometric background reduction for femtosecond stimulated Raman scattering loss spectroscopy.

    PubMed

    Dobner, Sven; Cleff, Carsten; Fallnich, Carsten; Groß, Petra

    2012-11-07

    We present a purely optical method for background suppression in nonlinear spectroscopy based on linear interferometry. Employing an unbalanced Sagnac interferometer, an unprecedented background reduction of 17  dB over a broad bandwidth of 60  THz (2000  cm(-1)) is achieved and its application to femtosecond stimulated Raman scattering loss spectroscopy is demonstrated. Apart from raising the signal-to-background ratio in the measurement of the Raman intensity spectrum, this interferometric method grants access to the spectral phase of the resonant χ(3) contribution. The spectral phase becomes apparent as a dispersive lineshape and is reproduced numerically with a simple oscillator model.

  3. Energy loss of fast quarks in nuclei.

    PubMed

    Johnson, M B; Kopeliovich, B Z; Potashnikova, I K; McGaughey, P L; Moss, J M; Peng, J C; Garvey, G T; Leitch, M J; Adams, M R; Alde, D M; Baer, H W; Barlett, M L; Brown, C N; Cooper, W E; Carey, T A; Danner, G; Hoffmann, G W; Hsiung, Y B; Kaplan, D M; Klein, A; Lee, C; Lillberg, J W; McCarthy, R L; Mishra, C S; Wang, M J

    2001-05-14

    We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of 2H, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is -dE/dz = 2.32+/-0.52+/-0.5 GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in a nuclear environment.

  4. Electron energy loss spectrometry of interstellar diamonds

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.; Gibbons, Patrick C.; Lewis, Roy S.

    1990-01-01

    The results are reported of electron energy loss spectra (EELS) measurements on diamond residues from carbonaceous meteorites designed to elucidate the structure and composition of interstellar diamonds. Dynamic effective medium theory is used to model the dielectric properties of the diamonds and in particular to synthesize the observed spectra as mixtures of diamond and various pi-bonded carbons. The results are shown to be quantitatively consistent with the idea that diamonds and their surfaces are the only contributors to the electron energy loss spectra of the diamond residues and that these peculiar spectra are the result of the exceptionally small grain size and large specific surface area of the interstellar diamonds.

  5. Electron energy loss spectrometry of interstellar diamonds

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.; Gibbons, Patrick C.; Lewis, Roy S.

    1990-01-01

    The results are reported of electron energy loss spectra (EELS) measurements on diamond residues from carbonaceous meteorites designed to elucidate the structure and composition of interstellar diamonds. Dynamic effective medium theory is used to model the dielectric properties of the diamonds and in particular to synthesize the observed spectra as mixtures of diamond and various pi-bonded carbons. The results are shown to be quantitatively consistent with the idea that diamonds and their surfaces are the only contributors to the electron energy loss spectra of the diamond residues and that these peculiar spectra are the result of the exceptionally small grain size and large specific surface area of the interstellar diamonds.

  6. Interfacial phases in epitaxial growth of Y{sub 2}O{sub 3} on MgO studied via combining electron energy-loss spectroscopy and real-space self-consistent full multiple scattering calculations

    SciTech Connect

    Pailloux, F.; Jublot, M.; Gaboriaud, R.J.; Jaouen, M.; Paumier, F.; Imhoff, D.

    2005-09-15

    Electron energy loss spectroscopy (EELS), high resolution transmission electron microscopy (HRTEM), and electron diffraction were used to investigate Y{sub 2}O{sub 3} thin films epitaxially grown on (001) MgO substrate. In the vicinity of the film/substrate interface, HRTEM experiments evidenced the presence of grains with various crystallographic structures most of them crystallizing in the well-known Ia3 cubic phase. Some other grains, nanometric in size, and only observed in the vicinity of the film/substrate interface, have a different and unknown crystallographic structure. EELS spectra have been acquired close to the Y{sub 2}O{sub 3}/MgO interface, to get a better knowledge of the phases nucleated close to the substrate surface. Spectra exhibiting different fine structures have been recorded and compared to multiple scattering calculations. The Ia3 phase has been detected as constituting the main component of the Y{sub 2}O{sub 3} thin film in agreement with previous observations. It is found that calculations performed in a real space self-consistent full multiple scattering scheme (SC-FMS) and experiments are in pretty good agreement even for small cluster sizes. The second family of spectra has also been compared to calculations performed for monoclinic C2/m yttrium oxide, with a little success. Another approach considering a local oxygen neighboring close to a distorted rock-salt-like structure led to a good match between experimental and calculated spectra. Our results emphasize how powerful is the combination of spectroscopic measurements at nanometer scale, as feasible with EELS and modern microscopes, with ab initio calculations for structure determination at such small scale lengths.

  7. New insights into the chemical structure of Y2Ti2O7-δ nanoparticles in oxide dispersion-strengthened steels designed for sodium fast reactors by electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Badjeck, V.; Walls, M. G.; Chaffron, L.; Malaplate, J.; March, K.

    2015-01-01

    In this paper we study by high resolution scanning transmission electron microscopy coupled with electron energy-loss spectroscopy (STEM-EELS) an oxide dispersion-strengthened (ODS) steel with the nominal composition Fe-14Cr-1W-0.3TiH2-0.3Y2O3 (wt.%) designed to withstand the extreme conditions met in Gen. IV nuclear reactors. After denoising via principal component analysis (PCA) the data are analyzed using independent component analysis (ICA) which is useful in the investigation of the physical properties and chemical structure of the material by separating the individual spectral responses. The Y-Ti-O nanoparticles are found to be homogeneously distributed in the ferritic matrix, sized from 1 to 20 nm and match a non-stoichiometric pyrochlore-Y2Ti2O7-δ structure for sizes greater than 5 nm. We show that they adopt a (Y-Ti-O)-Cr core-shell structure and that Cr also segregates at the matrix grain boundaries, which may slightly modify the corrosion properties of the steel. Using Ti-L2,3 and O-K fine structure (ELNES) the Ti oxidation state is shown to vary from the center of the nanoparticles to their periphery, from Ti4+ in distorted Oh symmetry to a valency often lower than 3+. The sensitivity of the Ti "white lines" ELNES to local symmetry distortions is also shown to be useful when investigating the strain induced in the nanoparticles by the surrounding matrix. The Cr-shell and the variation of the Ti valence state highlight a complex nanoparticle-matrix interface.

  8. Energy expenditure, energy intake, and weight loss in Alzheimer disease.

    PubMed

    Poehlman, E T; Dvorak, R V

    2000-02-01

    Alzheimer disease is one of the leading causes of death among older individuals. Unexplained weight loss and cachexia are frequent clinical findings in patients with Alzheimer disease. Thus, it has been postulated that Alzheimer disease may be associated with dysfunction in body weight regulation. This brief review examines the interrelations among energy intake, energy expenditure, and body composition in Alzheimer disease. We explored whether abnormally high daily energy expenditures, low energy intakes, or both contribute to unexplained weight loss and a decline in nutritional status. Specifically, we considered studies that examined energy intake, body composition, and daily energy expenditure and its components. The application of doubly labeled water and indirect calorimetry to understand the etiology of wasting has increased our knowledge regarding the relation among energy expenditure, physical activity levels, and body composition in Alzheimer disease patients. Although the number of studies are limited, results do not support the notion that a hypermetabolic state contributes to unexplained weight loss in Alzheimer disease, even in cachectic patients. Recent findings are presented suggesting an association between abnormally elevated levels of physical activity energy expenditure and elevated appendicular skeletal muscle mass and energy intake in Alzheimer disease patients. Clinical strategies aimed at developing lifestyle and dietary interventions to maintain adequate energy intake, restore energy balance, and maintain skeletal muscle mass should be a future area of investigation in Alzheimer disease research.

  9. RHIC low energy beam loss projections

    SciTech Connect

    Satogata,T.

    2009-08-01

    For RHIC low-energy operations, we plan to collide Au beams with energies of E = 2:5-10 GeV/u in RHIC. Beams are injected into collision optics, and RHIC runs as a storage ring with no acceleration. At these low energies, observed beam lifetimes are minutes, with measured beam lifetimes of 3.5 min (fast) and 50 min (slow) at E=4.6 GeV/u in the March 2008 test run. With these lifetimes we can operate RHIC as a storage ring to produce reasonable integrated luminosity. This note estimates beam losses and collimator/dump energy deposition in normal injection modes of low energy operation. The main question is whether a normal injection run is feasible for an FY10 10-15 week operations run from a radiation safety perspective. A peripheral question is whether continuous injection operations is feasible from a radiation safety perspective. In continuous injection mode, we fill both rings, then continuously extract and reinject the oldest bunches that have suffered the most beam loss to increase the overall integrated luminosity. We expect to gain a factor of 2-3 in integrated luminosity from continuous injection at lowest energies if implemented[1]. Continuous injection is feasible by FY11 from an engineering perspective given enough effort, but the required extra safety controls and hardware dose risk make it unappealing for the projected luminosity improvement. Low-energy electron cooling will reduce beam losses by at least an order of magnitude vs normal low-energy operations, but low energy cooling is only feasible in the FY13 timescale and therefore beyond the scope of this note. For normal injection low energy estimates we assume the following: (1) RHIC beam total energies are E=2.5-10 GeV/u. (Continuous injection mode is probably unnecessary above total energies of E=7-8 GeV/u.); (2) RHIC operates only as a storage ring, with no acceleration; (3) 110 bunches of about 0.5-1.0 x 10{sup 9} initial bunch intensities (50-100% injection efficiency, likely conservative

  10. Photoneutrino energy losses in strong magnetic fields.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Fassio-Canuto, L.

    1973-01-01

    Previously computed rates of energy losses (Petrosian et al., 1967) ignored the presence of strong magnetic fields, hence the change brought in when such a field (about 10 to the 12th to 10 to the 13th power G) is included is studied. The results indicate that for T about 10 to the 8th power K and densities rho of about 10,000 g/cu cm, the presence of a strong H field decreases the energy losses by at the most a factor between 10 and 100 in the region up to rho = 1,000,000 g/cu cm. At higher densities the neutrino emissivities are almost identical.

  11. Photoneutrino energy losses in strong magnetic fields.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Fassio-Canuto, L.

    1973-01-01

    Previously computed rates of energy losses (Petrosian et al., 1967) ignored the presence of strong magnetic fields, hence the change brought in when such a field (about 10 to the 12th to 10 to the 13th power G) is included is studied. The results indicate that for T about 10 to the 8th power K and densities rho of about 10,000 g/cu cm, the presence of a strong H field decreases the energy losses by at the most a factor between 10 and 100 in the region up to rho = 1,000,000 g/cu cm. At higher densities the neutrino emissivities are almost identical.

  12. Collective Energy Loss of Attosecond Electron Bunches

    NASA Astrophysics Data System (ADS)

    Ogata, Atsushi; Kondoh, Takafumi; Norizawa, Kimihiro; Yang, Jinfeng; Yoshida, Yoichi

    2009-05-01

    The formalism of the stopping power for cluster beams was adapted to the stopping power for short electron bunches using the wake field of a medium characterized by plasma frequency. It was shown that, if the bunch length is in the 100 as range, the energy loss of the bunch is proportional to the square of the number of electrons in the bunch. If the number of electrons is large, the collective loss is able to excite a high-energy density state in the target. The target medium and beam parameters were examined to demonstrate the collective effect, and an accelerator system consisting of an accumulation ring and an inverse free-electron laser (IFEL) was considered to produce attosecond bunches.

  13. All-dielectric nanostructures for low-loss field enhanced spectroscopy and imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yano, Taka-aki; Tsuchimoto, Yuta; Hayashi, Tomohiro; Hara, Masahiko

    2016-09-01

    Dielectric nanostructures with high refractive index and low optical loss have attracted considerable attention as an alternative to plasmonic nanostructures. We experimentally demonstrated to control the visible electromagnetic resonances of Si-based core-shell nanostructures by thermally varying the core-shell ratio. We also found a Fano resonance which was generated by the interference between the electric and magnetic dipole moments excited in the core-shell nanostructures. The all-dielectric nanostructures realized low energy loss and high electromagnetic field enhancement comparable with that exhibited by plasmonic nanostructures. These unique optical properties would enable us to demonstrate effective field-enhanced spectroscopy and imaging with low heat generation.

  14. Van Vleck from Spectroscopy to Susceptibilities: Kuhn Losses Regained

    NASA Astrophysics Data System (ADS)

    Janssen, Michel

    2011-03-01

    As a young assistant professor in Minneapolis, John H. Van Vleck spent much of his time between 1923 and 1926 writing a book-length Bulletin for the National Research Council. As its title, Quantum Principles and Line Spectra, suggests, the book focuses almost exclusively on spectroscopy, the core pursuit of the old quantum theory. By the time it finally appeared in 1926, the old quantum theory had given way to the new quantum mechanics. Van Vleck soon realized that matrix mechanics reinstated some well-confirmed results of the classical theory of susceptibilities that had been lost in the old quantum theory. In the history and philosophy of science literature, such losses are called 'Kuhn losses'. Using mathematical techniques similar to those presented in his NRC Bulletin, Van Vleck started to work on the theory of susceptibilities. In 1929, now a full professor in Madison, he began writing another book, which appeared in 1932 and has become a classic: The Theory of Electric and Magnetic Susceptibilities. In this talk I follow Van Vleck's trajectory from spectroscopy to susceptibilities and examine how his two books reflect and helped shape research traditions.The talk is based on joint work with Charles Midwinter.

  15. DYNAMICS AND ENERGY LOSS IN SUPERBUBBLES

    SciTech Connect

    Krause, Martin G. H.; Diehl, Roland

    2014-10-20

    Interstellar bubbles appear to be smaller in observations than expected from calculations. Instabilities at the shell boundaries create three-dimensional (3D) effects and are probably responsible for part of this discrepancy. We investigate instabilities and dynamics in superbubbles using 3D hydrodynamics simulations with time-resolved energy input from massive stars, including supernova explosions. We find that the superbubble shells are accelerated by supernova explosions, coincident with substantial brightening in soft X-ray emission. In between the explosions, the superbubbles lose energy efficiently, approaching the momentum-conserving snowplow limit. This and enhanced radiative losses due to instabilities reduce the expansion compared to the corresponding radiative bubbles in pressure-driven snowplow models with constant energy input. We note generally good agreement with observations of superbubbles and some open issues. In particular, there are hints that the shell velocities in the X-ray-bright phases are underpredicted.

  16. Radiative Energy Loss by Galactic Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Ahern, Sean C.; Norbury, John W.; Tripathi, R. K.

    2002-01-01

    Interactions between galactic cosmic rays and matter are a primary focus of the NASA radiation problem. The electromagnetic forces involved are for the most part well documented. Building on previous research, this study investigated the relative importance of the weak forces that occur when a cosmic ray impinges on different types of materials. For the familiar electromagnetic case, it is known that energy lost in the form of radiation is more significant than that lost via contact collisions the rate at which the energy is lost is also well understood. Similar results were derived for the weak force case. It was found that radiation is also the dominant mode of energy loss in weak force interactions and that weak force effects are indeed relatively weak compared to electromagnetic effects.

  17. Energy loss of hydrogen projectiles in gases

    SciTech Connect

    Schiefermueller, A.; Golser, R.; Stohl, R.; Semrad, D. )

    1993-12-01

    The stopping cross sections of H[sub 2], D[sub 2], He, and Ne for hydrogen projectiles in the energy range 3--20 keV per nucleon have been measured by time of flight. We compare our experimental result to the sum of the individual contributions due to excitation and ionization of the target and of the projectile, respectively, and due to charge exchange, using published cross-section data. Satisfactory agreement is found only for the He target and only at moderate projectile velocities, whereas for H[sub 2] and D[sub 2] the calculated values are about 30% too low. A Monte Carlo program allows us to simulate the measured time-of-flight spectra and to explain minor trends in the experimental data: for increased Ne gas pressure, an increased specific energy loss has been found that can be traced to different regions of impact parameters selected in our transmission geometry. This also explains, in part, the increased specific energy loss for deuterons compared to protons of equal velocity that is most evident for Ne. In contrast, a decrease of the specific energy loss with increasing pressure for He may be explained by impurities in the target gas. If we correct for the effect of impurities, the stopping cross section of He at 4 keV per nucleon is slightly smaller (0.60[times]10[sup [minus]15] eV cm[sup 2]) than published earlier (0.72[times]10[sup [minus]15] eV cm[sup 2]) and depends on the 3.8th power of projectile velocity.

  18. Instrumental correction of counting losses in nuclear pulse spectroscopy

    NASA Astrophysics Data System (ADS)

    Westphal, G. P.

    1985-05-01

    The virtual pulse generator (VPG) method of counting loss correction [1-3] is the first truly quantitative instrumental correction procedure taking into account both dead-time and pileup losses of a spectroscopy system over its full operative range of counting rates without the need for fast signal detection channels [4-6] or ambiguous post-processing of data [7,8], or the necessity to process artificial test pulses in addition to the detector signals [9]. Consequently, the VPG method is not limited in test frequency thus enabling the on-line generation of loss correction factors of sufficient statistical accuracy within extremely short periods of time. By adding weighting factors to the channels addressed by the analog-to-digital converter during the course of the measurement (instead of one as in conventional pulse height analysis) real-time correction of counting losses is made possible with millisecond time of response. Increased statistical accuracy may be achieved when using the VPG principle for loss-dependent prolonging of the measuring time similar to the live-time clock method. Both real-time and live-time modes of operation are provided for in a commercially available VPG correction module [10]. After a description of the set-up procedure of the module in connection with a likewise commercial semi-Gaussian shaping amplifier the performance of the VPG correction is exemplified to a level of 0.2% with the aid of repetitive two-source measurements in both the real-time and the live-time mode of operation.

  19. Jet Quenching Beyond the Energy Loss Approach

    NASA Astrophysics Data System (ADS)

    Ovanesyan, Grigory

    2015-02-01

    We study the jet quenching effect in heavy ion collisions, based on medium-induced splitting functions calculated from Soft Collinear Effective Theory with Glauber Gluons. Our method is formulated in the language of DGLAP evolution equations with medium-induced splitting functions. In the small-x soft gluon approximation we analytically solve the evolution equations and find an intuitive connection to the energy loss approach. For central Pb+Pb collisions at the LHC we quantify the effect of finite-x corrections for the nuclear modification factor and compare to data.

  20. Energy losses in mechanically modified bacterial magnetosomes

    NASA Astrophysics Data System (ADS)

    Molcan, Matus; Gojzewski, Hubert; Skumiel, Andrzej; Dutz, Silvio; Kovac, Jozef; Kubovcikova, Martina; Kopcansky, Peter; Vekas, Ladislau; Timko, Milan

    2016-09-01

    Magnetosomes are isolated from the Magnetospirillum magneticum strain AMB-1 bacteria. Two samples are compared: magnetosomes normally prepared of a ‘standard’ length and magnetosomes of a short length. Chains of magnetosomes are shortened by mechanical modification (cleavage) by means of sonication treatment. They represent a new geometry of magnetosomes that have not been investigated before. The effect of the sonication is analysed using transmission and electron microscopy, atomic force microscopy, and dynamic light scattering. Scanning imaging reveals three types of shortening effect in a sample of shortened magnetosomes, namely, membrane collapse, membrane destruction, and magnetosome cleavage. Dynamic light scattering shows a reduction of hydrodynamic diameter in a sample of shortened magnetosomes. The magnetic properties of magnetosomes are analysed and compared in DC and AC magnetic fields based on the evaluation of quasi-static hysteresis loops (energy losses) and calorimetric hyperthermia measurements (specific absorption rate), respectively. A sample of shortened magnetosomes behaves magnetically in a different manner, showing that both the energy loss and the specific absorption rate are reduced, and thereby indicates a variation in the heating process. The magnetic properties of magnetosomes, together with the new and stable geometry, are balanced, which opens the way for a better adaptation of the magnetic field parameters for particular applications.

  1. Tau energy loss and ultrahigh energy skimming tau neutrinos

    NASA Astrophysics Data System (ADS)

    Jeong, Yu Seon; Luu, Minh Vu; Reno, Mary Hall; Sarcevic, Ina

    2017-08-01

    We consider propagation of high-energy earth-skimming taus produced in interactions of astrophysical tau neutrinos. For astrophysical tau neutrinos, we take generic power-law flux, E-2 and the cosmogenic flux initiated by the protons. We calculate tau energy loss in several approaches, such as dipole models and the phenomenological approach in which parametrization of the F2 is used. We evaluate the tau neutrino charged-current cross section using the same approaches for consistency. We find that uncertainty in the neutrino cross section and in the tau energy loss partially compensate giving very small theoretical uncertainty in the emerging tau flux for distances ranging from 2 to 100 km and for the energy range between 1 06 and 1 011 GeV , focusing on energies above 1 08 GeV . When we consider uncertainties in the neutrino cross section, inelasticity in neutrino interactions and the tau energy loss, which are not correlated, i.e. they are not all calculated in the same approach, theoretical uncertainty ranges from about 30% and 60% at 1 08 GeV to about factors of 3.3 and 3.8 at 1 011 GeV for the E-2 flux and the cosmogenic flux, respectively, for the distance of 10 km rock. The spread in predictions significantly increases for much larger distances, e.g., ˜1 ,000 km . Most of the uncertainty comes from the treatment of photonuclear interactions of the tau in transit through large distances. We also consider Monte Carlo calculation of the tau propagation and we find that the result for the emerging tau flux is in agreement with the result obtained using analytic approach. Our results are relevant to several experiments that are looking for skimming astrophysical taus, such as the Pierre Auger Observatory, HAWC and Ashra. We evaluate the aperture for the Auger and discuss briefly application to the other two experiments.

  2. Energy loss of coasting gold ions and deuterons in RHIC.

    SciTech Connect

    Abreu,N.; Blaskiewicz, M.; Brown, K.A.; Butler, J.J.; FischW; Harvey, M.; Tepikian, S.

    2008-06-23

    The total energy loss of coasting gold ion beams was measured at RHIC at two energies, corresponding to a gamma of 75.2 and 107.4. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.

  3. Zero kinetic energy photoelectron spectroscopy of pyrene.

    PubMed

    Zhang, Jie; Han, Fangyuan; Kong, Wei

    2010-10-28

    We report zero kinetic energy photoelectron (ZEKE) spectroscopy of pyrene via resonantly enhanced multiphoton ionization. Our analysis centers on the symmetry of the first electronically excited state (S(1)), its vibrational modes, and the vibration of the ground cationic state (D(0)). From comparisons between the observed vibrational frequencies and those from ab initio calculations at the configuration interaction singles level using the 6-311G (d,p) basis set, and based on other previous experimental and theoretical reports, we confirm the (1)B(2u) symmetry for the S(1) state. This assignment represents a reversal in the energy order of the two closely spaced electronically excited states from our theoretical calculation, and extensive configuration interactions are attributed to this result. Among the observed vibrational levels of the S(1) state, three are results of vibronic coupling due to the nearby second electronically excited state. The ZEKE spectroscopy obtained via the vibronic levels of the S(1) state reveals similar modes for the cation as those of the intermediate state. Although we believe that the ground ionic state can be considered a single electron configuration, the agreement between theoretical and experimental frequencies for the cation is limited. This result is somewhat surprising based on our previous work on cata-condensed polycyclic aromatic hydrocarbons and small substituted aromatic compounds. Although a relatively small molecule, pyrene demonstrates its nonrigidity via several out-of-plane bending modes corresponding to corrugation of the molecular plane. The adiabatic ionization potential of neutral pyrene is determined to be 59 888 ± 7 cm(-1).

  4. The molecular and electronic states of 1,2,4,5-tetrazine studied by VUV absorption, near-threshold electron energy-loss spectroscopy and ab initio multi-reference configuration interaction studies

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.; McNab, Hamish; Reed, David; Pollacchi, Anne; Walker, Isobel C.; Guest, Martyn F.; Siggel, Michele R. F.

    1997-01-01

    The VUV electronic absorption spectrum of 1,2,4,5-tetrazine has been re-investigated, and together with electron energy-loss spectra has led to identification of a number of new excited states. The valence and Rydberg excited states have been studied by multi-reference multi-root configuration interaction studies using MRDCI techniques. Initial studies with the RPA and TDA methods gave almost identical results for the excitation energies, but there is a substantial energy-lowering in the MRDCI calculations, which improves agreement with experiment substantially; these differences are a result of the double, triple and quadruple excited reference configurations included in the reference set of the latter method. The 1ππ ∗ excitations are calculated rather higher than experiment, except for the lowest-lying (weak) 1B 2u state at 5.0 eV. The calculated order for the next three ππ ∗ states is 1B 1u (weak) followed by 1B 2u (strong) and 1B 1u (strong), the last two bands being responsible for the dominant absorption near 7.5 and 8.5 eV. All of this group of four bands involve excitations from the pair of MOs 1b 2g and 1b 1g into the 1a u∗ and 4b 3u∗ VMOs. The sequence of nπ ∗ stakes are in a similar order to the ππ ∗ excitations, with respect to the upper state, and the two lowest singlet states, 1B 3u and 1A u are reasonably well determined. The triplet states follow a similar order to the singlets, and again the dominance of the effect of the two lowest VMOs is demonstrated, but considerable differences between the weighting of leading configurations occurs between singlet and triplet manifolds. The non-diagonal TDA method has been used to reconsider the UV-photoelectron spectrum. The ionisation potentials for tetrazine are reinterpreted with the first three bands being regrouped into 1, 2, 2 ionisations respectively. The ground state properties of tetrazine suggest that the NQR spectrum will show a principal axis 14N quadrupole coupling constant

  5. Low-loss energy storage flywheel

    NASA Technical Reports Server (NTRS)

    Evans, H. E.; Studer, P. A.

    1977-01-01

    Magnetically-levitated, ironless-armature spokeless rotor is used. Ironless armature construction eliminates core losses due to hysteresis and eddy currents. Device combines features of homopolar salient poles and stationary ironless electronically commutated armature.

  6. Study on energy loss compensation of back scattering conical cavity high-energy laser energy meter

    NASA Astrophysics Data System (ADS)

    Yu, Xun; Wang, Hui; Shang, Xiao-yan; Nie, Liang; Liu, Bao-yuan

    2009-05-01

    Because absolute quantity thermal laser energy meter based on conical cavity has some features, for example, wide wavelength adaptation range, high laser damage threshold value, extensive measuring energy range and so on, it is often used as the standard of high-energy laser energy meter, and is used extensively in the domain of high energy laser measurement. But, laser energy will lose because of back scattering of conical absorption cavity. So, only after the loss is compensated and amended, exact measurement of laser energy can be achieved. Aiming at energy loss compensation problem of conical cavity high-energy laser energy meter, we firstly, according to speckle statistics optical theory, analyze the back scattering of the conical absorption cavity in condition of uniform distribution laser incident on diffuse reflection surface, and secondly, we aim at high power laser's output facula shape: round, based on optical principles of interaction of the conical cavity inner face and the incident laser and utilize complexfication Simpson numerical method, the mathematical models of optical power density distribution at open-end of conical cavity and back scattering gross power are established. On this basis, the measured result is compensated and amended. The back scattering energy loss is about 0.5% to 2.5%.High-energy laser energy measuring accuracy is improved effectively.

  7. Research of the conical cavity high-energy laser energy meter energy loss compensation technique

    NASA Astrophysics Data System (ADS)

    Yu, Xun; Li, Qian; Nie, Liang; Shang, Xiaoyan; Liu, Baoyuan

    2008-09-01

    Because absolute quantity thermal laser energy meter based on conical cavity has some features, for example, wavelength adaptation range is wide and laser damage threshold value is high. It is used for the standard of the high-energy laser energy meter and extensively in the domain of the high energy laser measurement. However, laser energy will lose because of the heat exchange and the back scattering of the conical absorption cavity. Therefore, only after compensating and amending the loss, the exact measurement of the laser energy can be achieved. Aimed to the energy loss compensation problem of the conical cavity high-energy laser energy meter, firstly, according to the heat transfer theory, this paper analyzes the heat energy loss of the conical cavity due to the heat emission, the heat convection and the heat exchange, and construct the mathematical model of the heat energy loss, based on which measuring result is curved fit using the least squares technique, and is compensated and amended utilizing the fitting curve, whose measurement repetitiveness is 0.7%, from which we can know that measuring repetitiveness is increased consumedly. Secondly, according to the optics principles of reciprocity of the conical cavity inner face and the incident laser and utilizing complexification Simpson numerical method, the mathematical model of conical cavity jaw opening optical power density distribution and back scattering gross power is established, based on which measuring result is compensated and amended, the back scattering energy loss is about 0.5% to 2.5%, high-energy laser energy measuring accuracy is improved availably.

  8. Energy loss of relativistic electrons and positrons traversing cosmic matter

    NASA Technical Reports Server (NTRS)

    Gould, R. J.

    1975-01-01

    Questions of adiabatic expansion are considered along with aspects of Compton scattering, bremsstrahlung, electronic excitation, synchrotron radiation, and electron-positron pair production. It is found that, unless the intergalactic magnetic field is very small, synchrotron radiation will dominate all other energy loss processes at ultrahigh electron and positron energies. The dependence of the loss rates on the cosmic epoch is also discussed.

  9. Zero kinetic energy photoelectron spectroscopy of triphenylene

    SciTech Connect

    Harthcock, Colin; Zhang, Jie; Kong, Wei

    2014-06-28

    We report vibrational information of both the first electronically excited state and the ground cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited electronic state S{sub 1} of the neutral molecule is of A{sub 1}′ symmetry and is therefore electric dipole forbidden in the D{sub 3h} group. Consequently, there are no observable Franck-Condon allowed totally symmetric a{sub 1}′ vibrational bands in the REMPI spectrum. All observed vibrational transitions are due to Herzberg-Teller vibronic coupling to the E′ third electronically excited state S{sub 3}. The assignment of all vibrational bands as e′ symmetry is based on comparisons with calculations using the time dependent density functional theory and spectroscopic simulations. When an electron is eliminated, the molecular frame undergoes Jahn-Teller distortion, lowering the point group to C{sub 2v} and resulting in two nearly degenerate electronic states of A{sub 2} and B{sub 1} symmetry. Here we follow a crude treatment by assuming that all e′ vibrational modes resolve into b{sub 2} and a{sub 1} modes in the C{sub 2v} molecular frame. Some observed ZEKE transitions are tentatively assigned, and the adiabatic ionization threshold is determined to be 63 365 ± 7 cm{sup −1}. The observed ZEKE spectra contain a consistent pattern, with a cluster of transitions centered near the same vibrational level of the cation as that of the intermediate state, roughly consistent with the propensity rule. However, complete assignment of the detailed vibrational structure due to Jahn-Teller coupling requires much more extensive calculations, which will be performed in the future.

  10. Zero kinetic energy photoelectron spectroscopy of triphenylene

    NASA Astrophysics Data System (ADS)

    Harthcock, Colin; Zhang, Jie; Kong, Wei

    2014-06-01

    We report vibrational information of both the first electronically excited state and the ground cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited electronic state S1 of the neutral molecule is of A1' symmetry and is therefore electric dipole forbidden in the D3h group. Consequently, there are no observable Franck-Condon allowed totally symmetric a1' vibrational bands in the REMPI spectrum. All observed vibrational transitions are due to Herzberg-Teller vibronic coupling to the E' third electronically excited state S3. The assignment of all vibrational bands as e' symmetry is based on comparisons with calculations using the time dependent density functional theory and spectroscopic simulations. When an electron is eliminated, the molecular frame undergoes Jahn-Teller distortion, lowering the point group to C2v and resulting in two nearly degenerate electronic states of A2 and B1 symmetry. Here we follow a crude treatment by assuming that all e' vibrational modes resolve into b2 and a1 modes in the C2v molecular frame. Some observed ZEKE transitions are tentatively assigned, and the adiabatic ionization threshold is determined to be 63 365 ± 7 cm-1. The observed ZEKE spectra contain a consistent pattern, with a cluster of transitions centered near the same vibrational level of the cation as that of the intermediate state, roughly consistent with the propensity rule. However, complete assignment of the detailed vibrational structure due to Jahn-Teller coupling requires much more extensive calculations, which will be performed in the future.

  11. Zero kinetic energy photoelectron spectroscopy of triphenylene.

    PubMed

    Harthcock, Colin; Zhang, Jie; Kong, Wei

    2014-06-28

    We report vibrational information of both the first electronically excited state and the ground cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited electronic state S1 of the neutral molecule is of A1' symmetry and is therefore electric dipole forbidden in the D3h group. Consequently, there are no observable Franck-Condon allowed totally symmetric a1' vibrational bands in the REMPI spectrum. All observed vibrational transitions are due to Herzberg-Teller vibronic coupling to the E' third electronically excited state S3. The assignment of all vibrational bands as e' symmetry is based on comparisons with calculations using the time dependent density functional theory and spectroscopic simulations. When an electron is eliminated, the molecular frame undergoes Jahn-Teller distortion, lowering the point group to C2v and resulting in two nearly degenerate electronic states of A2 and B1 symmetry. Here we follow a crude treatment by assuming that all e' vibrational modes resolve into b2 and a1 modes in the C2v molecular frame. Some observed ZEKE transitions are tentatively assigned, and the adiabatic ionization threshold is determined to be 63 365 ± 7 cm(-1). The observed ZEKE spectra contain a consistent pattern, with a cluster of transitions centered near the same vibrational level of the cation as that of the intermediate state, roughly consistent with the propensity rule. However, complete assignment of the detailed vibrational structure due to Jahn-Teller coupling requires much more extensive calculations, which will be performed in the future.

  12. The electron energy loss rate due to radiative recombination

    NASA Astrophysics Data System (ADS)

    Mao, Junjie; Kaastra, Jelle; Badnell, N. R.

    2017-02-01

    Context. For photoionized plasmas, electron energy loss rates due to radiative recombination (RR) are required for thermal equilibrium calculations, which assume a local balance between the energy gain and loss. While many calculations of total and/or partial RR rates are available from the literature, specific calculations of associated RR electron energy loss rates are lacking. Aims: Here we focus on electron energy loss rates due to radiative recombination of H-like to Ne-like ions for all the elements up to and including zinc (Z = 30), over a wide temperature range. Methods: We used the AUTOSTRUCTURE code to calculate the level-resolved photoionization cross section and modify the ADASRR code so that we can simultaneously obtain level-resolved RR rate coefficients and associated RR electron energy loss rate coefficients. We compared the total RR rates and electron energy loss rates of H i and He i with those found in the literature. Furthermore, we utilized and parameterized the weighted electron energy loss factors (dimensionless) to characterize total electron energy loss rates due to RR. Results: The RR electron energy loss data are archived according to the Atomic Data and Analysis Structure (ADAS) data class adf48. The RR electron energy loss data are also incorporated into the SPEX code for detailed modeling of photoionized plamsas. Full Tables 1 and 2 are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A10

  13. Ethanol production: energy, economic, and environmental losses.

    PubMed

    Pimentel, David; Patzek, Tad; Cecil, Gerald

    2007-01-01

    The prime focus of ethanol production from corn is to replace the imported oil used in American vehicles, without expending more fossil energy in ethanol production than is produced as ethanol energy. In a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from corn, every step in the production and conversion process must be included. In this study, 14 energy inputs in average U.S. corn production are included. Then, in the fermentation/distillation operation, 9 more identified fossil fuel inputs are included. Some energy and economic credits are given for the by-products, including dried distillers grains (DDG). Based on all the fossil energy inputs, a total of 1.43 kcal fossil energy is expended to produced 1 kcal ethanol. When the energy value of the DDG, based on the feed value of the DDG as compared to that of soybean meal, is considered, the energy cost of ethanol production is reduced slightly, to 1.28 kcal fossil energy input per 1 kcal ethanol produced. Several proethanol investigators have overlooked various energy inputs in U.S. corn production, including farm machinery, processing machinery, and the use of hybrid corn. In other studies, unrealistic, low energy costs were attributed to such inputs as nitrogen fertilizer, insecticides, and herbicides. Controversy continues concerning the energy and economic credits that should be assigned to the by-products. The U.S. Department of Energy reports that 17.0 billion L ethanol was produced in 2005. This represents only less than 1% of total oil use in the U.S. These yields are based on using about 18% of total U.S. corn production and 18% of cornland. Because the production of ethanol requires large inputs of both oil and natural gas in production, the U.S. is importing both oil and natural gas to produce ethanol. Furthermore, the U.S. Government is spending about dollar 3 billion annually to subsidize ethanol production, a subsidy of dollar 0.79/L ethanol produced. With

  14. High energy resolution off-resonant X-ray spectroscopy

    SciTech Connect

    Wojciech, Blachucki

    2015-10-16

    This work treats of the high energy resolution off-resonant X-ray spectroscopy (HEROS) method of determining the density of unoccupied electronic states in the vicinity of the absorption edge. HEROS is an alternative to the existing X-ray absorption spectroscopy (XAS) methods and opens the way for new studies not achievable before.

  15. Nonionizing energy loss (NIEL) for protons

    NASA Technical Reports Server (NTRS)

    Jun, I.; Xapsos, M. A.; Messenger, S. R.; Burke, E. A.; Walters, R. J.; Jordan, T.

    2003-01-01

    The proton induced NIELs for representative spacecraft materials are presented for the energy range between the displacement thresholds of the material to 1000 MeV. All interaction mechanisms (Coulomb and nuclear elastic/inelastic) are fully accounted in the present NIEL calculations.

  16. Interference effect in elastic parton energy loss in a finitemedium

    SciTech Connect

    Wang, Xin-Nian

    2005-04-18

    Similar to the radiative parton energy loss due to gluonbremsstrahlung, elastic energy loss of a parton undergoing multiplescattering in a finite medium is demonstrated to be sensitive tointerference effect. The interference between amplitudes of elasticscattering via a gluon exchange and that of gluon radiation reduces theeffective elastic energy loss in a finite medium and gives rise to anon-trivial length dependence. The reduction is most significant for apropagation length L<4/\\pi T in a medium with a temperature T. Thoughthe finite size effect is not significant for the average partonpropagation in the most central heavy-ion collisions, it will affect thecentrality dependence of its effect on jet quenching.

  17. Analytic saddlepoint approximation for ionization energy loss distributions

    NASA Astrophysics Data System (ADS)

    Sjue, S. K. L.; George, R. N.; Mathews, D. G.

    2017-09-01

    We present a saddlepoint approximation for ionization energy loss distributions, valid for arbitrary relativistic velocities of the incident particle 0 < v / c < 1 , provided that ionizing collisions are still the dominant energy loss mechanism. We derive a closed form solution closely related to Moyal's distribution. This distribution is intended for use in simulations with relatively low computational overhead. The approximation generally reproduces the Vavilov most probable energy loss and full width at half maximum to better than 1% and 10%, respectively, with significantly better agreement as Vavilov's κ approaches 1.

  18. Holographic energy loss in non-relativistic backgrounds

    NASA Astrophysics Data System (ADS)

    Atashi, Mahdi; Fadafan, Kazem Bitaghsir; Farahbodnia, Mitra

    2017-03-01

    In this paper, we study some aspects of energy loss in non-relativistic theories from holography. We analyze the energy lost by a rotating heavy point particle along a circle of radius l with angular velocity ω in theories with general dynamical exponent z and hyperscaling violation exponent θ . It is shown that this problem provides a novel perspective on the energy loss in such theories. A general computation at zero and finite temperature is done and it is shown how the total energy loss rate depends non-trivially on two characteristic exponents (z,θ ). We find that at zero temperature there is a special radius l_c where the energy loss is independent of different values of (θ ,z). Also at zero temperature, there is a crossover between a regime in which the energy loss is dominated by the linear drag force and by the radiation because of the acceleration of the rotating particle. We find that the energy loss of the particle decreases by increasing θ and z. We note that, unlike in the zero temperature, there is no special radius l_c at finite temperature case.

  19. Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy.

    PubMed

    Gu, Lin; Sigle, Wilfried; Koch, Christoph T; Nelayah, Jaysen; Srot, Vesna; van Aken, Peter A

    2009-08-01

    The advent of electron monochromators has opened new perspectives on electron energy-loss spectroscopy at low energy losses, including phenomena such as surface plasmon resonances or electron transitions from the valence to the conduction band. In this paper, we report first results making use of the combination of an energy filter and a post-filter annular dark-field detector. This instrumental design allows us to obtain energy-filtered (i.e. inelastic) annular dark-field images in scanning transmission electron microscopy of the 2-dimensional semiconductor band-gap distribution of a GaN/Al(45)Ga(55)N structure and of surface plasmon resonances of silver nanoprisms. In comparison to other approaches, the technique is less prone to inelastic delocalization and relativistic artefacts. The mixed contribution of elastic and inelastic contrast is discussed.

  20. Defect engineering in GaAs using high energy light ion irradiation: Role of electronic energy loss

    SciTech Connect

    Kabiraj, D.; Ghosh, Subhasis

    2011-02-01

    We report on the application of high energy light ions (Li and O) irradiation for modification of defects, in particular, for annihilation of point defects using electronic energy loss in GaAs to minimize the defects produced by nuclear collisions. The high resolution x-ray diffraction and micro-Raman spectroscopy have been used to monitor that no lattice damage or amorphization take place due to irradiating ions. The effects of irradiation on defects and their energy levels have been studied using thermally stimulated current spectroscopy. It has been observed that till an optimum irradiation fluence of 10{sup 13} ions/cm{sup 2} there is annihilation of native defects but further increase in irradiation fluence results in accumulation of defects, which scales with the nuclear energy loss process, indicating that the rate of defects produced by the binary collision process exceeds rate of defect annihilation. Defect annihilation due to electronic energy loss has been discussed on the basis of breaking of bonds and enhanced diffusivity of ionized native defects.

  1. Low voltage TEM: influences on electron energy loss spectrometry experiments.

    PubMed

    Stöger-Pollach, M

    2010-08-01

    We discuss the advantages and disadvantages of electron energy loss spectrometry (EELS) a transmission electron microscope (TEM) at different high tensions. Instrumental effects such as energy resolution, spatial resolution, and point spread function of the detecting system, as well as physical effects like inelastic (Coloumb) delocalization and Cerenkov losses are dealt with. It is found that the actually available equipment is suitable for performing low voltage experiments. The energy resolution of a thermo-ionic emitter can be tremendously improved at lower energies, and the detector also has advantageous behaviour. (c) 2010 Elsevier Ltd. All rights reserved.

  2. The maintenance of energy balance is compromised after weight loss.

    PubMed

    Reed, Jennifer L; Chaput, Jean-Philippe; Tremblay, Angelo; Doucet, Éric

    2013-04-01

    Available literature reveals that of the majority of individuals who are able to lose weight, only a small number are able to maintain their weight loss over time. Effective weight maintenance strategies after weight loss are illusive, which is most likely the result of a number of yet poorly understood factors. In fact, both appetite and energy expenditure are profoundly altered in response to reductions in body energy reserves. Weight reduction leads to decreased energy needs, but to an augmented drive to eat, thus compromising the maintenance of energy balance in the weight-reduced state by widening the theoretical gap between the 2 components of energy balance. This review first provides a summary of the factors related to the control of feeding and energy expenditure during weight stability. More specifically related to the topic of this review, the bulk of the literature presented depicts the post weight-loss control of appetite and energy expenditure. The integration of the literature presented in this paper reveals that body weight loss seems to orchestrate a coordinated response to resist further energy depletion, that would seem to create a state of increased vulnerability of weight regain. It is argued that these changes are largely responsible for the more than apparent difficulty in maintaining weight maintenance after weight loss. Copyright © 2013 Canadian Diabetes Association. Published by Elsevier Inc. All rights reserved.

  3. Theory of photoelectron production, transport and energy loss

    NASA Technical Reports Server (NTRS)

    Nagy, A. F.

    1974-01-01

    Current understanding of the theory of ionospheric photoelectron production, transport and energy loss is summarized. The various approaches used in the theoretical calculations of photoelectron fluxes appear to be self consistent and sound; improved values for a number of input parameters are needed now in order to achieve significant improvements and more confidence in the results. The major remaining problem in the present day theory of photoelectron transport and energy loss is centered around the calculations of photoelectron transit through the protonosphere.

  4. Energy loss by resonance line photons in an absorbing medium

    NASA Technical Reports Server (NTRS)

    Hummer, D. G.; Kunasz, P. B.

    1980-01-01

    The mean path length of photons undergoing repeated scatterings in media of large optical thickness is calculated from accurate numerical solutions of the transfer equation including the effect of frequency redistribution characteristic of combined Doppler and natural broadening. Energy loss by continuous absorption processes, such as ionization or dust absorption, is discussed, and asymptotic scaling laws for the energy loss, the mean path length, and the mean number of scatterings are inferred from the numerical data.

  5. Mass loss from red giants - Results from ultraviolet spectroscopy

    NASA Technical Reports Server (NTRS)

    Linsky, J. L.

    1985-01-01

    New instrumentation in space, primarily the IUE spacecraft, has enabled the application of ultraviolet spectroscopic techniques to the determination of physical properties and reliable mass loss rates for red giant winds. One important result is the determination of where in the H-R diagram are found stars with hot outer atmospheres and with cool winds. So far it appears that single cool stars, except perhaps the so-called hybrid stars, have either hot outer atmospheres or cool winds but not both. The C II resonance (1335 A) and intersystem (2325 A) multiplets have been used to derive temperatures, densities, and geometrical extents for the chromospheric portions of red giant winds, with the result that the red giants and the earlier giants with hot coronae have qualitatively different chromospheres. Mass loss rates can now be derived accurately from the analysis of asymmetric emission lines, such as the Mg II resonance lines, and from P Cygni profile lines of atoms in the dominant ionization stage when a hot star is available to probe the wind of a red giant. The Zeta Aur systems, consisting of a K-M supergiant and a main sequence B star are important systems for reliable mass loss rates for the red supergiant components are becoming available.

  6. Tailoring the energy distribution and loss of 2D plasmons

    NASA Astrophysics Data System (ADS)

    Lin, Xiao; Rivera, Nicholas; López, Josué J.; Kaminer, Ido; Chen, Hongsheng; Soljačić, Marin

    2016-10-01

    The ability to tailor the energy distribution of plasmons at the nanoscale has many applications in nanophotonics, such as designing plasmon lasers, spasers, and quantum emitters. To this end, we analytically study the energy distribution and the proper field quantization of 2D plasmons with specific examples for graphene plasmons. We find that the portion of the plasmon energy contained inside graphene (energy confinement factor) can exceed 50%, despite graphene being infinitely thin. In fact, this very high energy confinement can make it challenging to tailor the energy distribution of graphene plasmons just by modifying the surrounding dielectric environment or the geometry, such as changing the separation distance between two coupled graphene layers. However, by adopting concepts of parity-time symmetry breaking, we show that tuning the loss in one of the two coupled graphene layers can simultaneously tailor the energy confinement factor and propagation characteristics, causing the phenomenon of loss-induced plasmonic transparency.

  7. Heat Loss Experiments: Teach Energy Savings with Cardboard "House"

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2011-01-01

    Using two cardboard boxes, a light bulb socket, light bulbs of varying wattage, a thermometer, and some insulation, students can learn some interesting lessons about how heat loss occurs in homes. This article describes practical experiments that work well on units related to energy, sustainable energy, renewables, engineering, and construction.…

  8. Heat Loss Experiments: Teach Energy Savings with Cardboard "House"

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2011-01-01

    Using two cardboard boxes, a light bulb socket, light bulbs of varying wattage, a thermometer, and some insulation, students can learn some interesting lessons about how heat loss occurs in homes. This article describes practical experiments that work well on units related to energy, sustainable energy, renewables, engineering, and construction.…

  9. Comments on GUT monopole energy loss and ionization

    SciTech Connect

    Hagstrom, R.

    1982-01-01

    A few comments about the likely behavior of the electromagnetic energy loss and ionization rates of super-slowly moving magnetic monopoles are presented. The questions of energy loss rates and ionization rates for super-low monopoles passing through matter are considered, concentrating on aspects of these issues which affect practical detection techniques. It is worthwhile here to emphasize that there is a potentially great distinction between energy loss rates and ionization rates and that the magnitude of this distinction is really the great issue which must be settled in order to understand the significance of experimental results from present and proposed investigations of the slow monopole question. Energy loss here means the total dE/dX of the projectile due to interactions with the electrons of the slowing medium. To the extent that nuclear collisions can be neglected, this so-called electronic energy loss is the relevant quantity in questions about whether monopoles stop within the earth's crust, whether they are slowed by interstellar plasmas, or the signal in a truly calorimetric measurement (measuring temperature rises along the trajectory), etc. Most of our successful detection techniques depend upon the promotion of ground state electrons into states which lie above some energy gap in the material of the detector: electrons must be knocked completely free from the gas atoms in a proportional chamber gas, electrons must be promoted to a higher band in solid scintillator plastics. These processes are generically identified as ionization. (WHK)

  10. Classical strongly coupled quark-gluon plasma. VII. Energy loss

    SciTech Connect

    Cho, Sungtae; Zahed, Ismail

    2010-12-15

    We use linear response analysis and the fluctuation-dissipation theorem to derive the energy loss of a heavy quark in the SU(2) classical Coulomb plasma in terms of the l=1 monopole and nonstatic structure factor. The result is valid for all Coulomb couplings {Gamma}=V/K, the ratio of the mean potential to kinetic energy. We use the Liouville equation in the collisionless limit to assess the SU(2) nonstatic structure factor. We find the energy loss to be strongly dependent on {Gamma}. In the liquid phase with {Gamma}{approx_equal}4, the energy loss is mostly metallic and soundless with neither a Cerenkov nor a Mach cone. Our analytical results compare favorably with the SU(2) molecular dynamics simulations at large momentum and for heavy quark masses.

  11. Exercise Training and Energy Expenditure following Weight Loss.

    PubMed

    Hunter, Gary R; Fisher, Gordon; Neumeier, William H; Carter, Stephen J; Plaisance, Eric P

    2015-09-01

    This study aims to determine the effects of aerobic or resistance training on activity-related energy expenditure (AEE; kcal·d(-1)) and physical activity index (activity-related time equivalent (ARTE)) following weight loss. It was hypothesized that weight loss without exercise training would be accompanied by decreases in AEE, ARTE, and nontraining physical activity energy expenditure (nonexercise activity thermogenesis (NEAT)) and that exercise training would prevent decreases in free-living energy expenditure. One hundred forty premenopausal women had an average weight loss of 25 lb during a diet (800 kcal·d(-1)) of furnished food. One group aerobically trained 3 times per week (40 min·d(-1)), another group resistance-trained 3 times per week (10 exercises/2 sets × 10 repetitions), and the third group did not exercise. Dual-energy x-ray absorptiometry was used to measure body composition, indirect calorimetry was used to measure resting energy expenditure (REE) and walking energy expenditure, and doubly labeled water was used to measure total energy expenditure (TEE). AEE, ARTE, and nontraining physical activity energy expenditure (NEAT) were calculated. TEE, REE, and NEAT all decreased following weight loss for the no-exercise group, but not for aerobic and resistance trainers. Only REE decreased in the two exercise groups. Resistance trainers increased ARTE. HR and oxygen uptake while walking on the flat and up a grade were consistently related to TEE, AEE, NEAT, and ARTE. Exercise training prevents a decrease in energy expenditure, including free-living energy expenditure separate from exercise training, following weight loss. Resistance training increases physical activity, whereas economy/ease of walking is associated with increased TEE, AEE, NEAT, and ARTE.

  12. Energy-Efficiency Options for Insurance Loss Prevention

    SciTech Connect

    Mills, E.; Knoepfel, I.

    1997-06-09

    Energy-efficiency improvements offer the insurance industry two areas of opportunity: reducing ordinary claims and avoiding greenhouse gas emissions that could precipitate natural disaster losses resulting from global climate change. We present three vehicles for taking advantage of this opportunity, including research and development, in- house energy management, and provision of key information to insurance customers and risk managers. The complementary role for renewable energy systems is also introduced.

  13. Estimating convective energy losses from solar central receivers

    SciTech Connect

    Siebers, D L; Kraabel, J S

    1984-04-01

    This report outlines a method for estimating the total convective energy loss from a receiver of a solar central receiver power plant. Two types of receivers are considered in detail: a cylindrical, external-type receiver and a cavity-type receiver. The method is intended to provide the designer with a tool for estimating the total convective energy loss that is based on current knowledge of convective heat transfer from receivers to the environment and that is adaptable to new information as it becomes available. The current knowledge consists of information from two recent large-scale experiments, as well as information already in the literature. Also outlined is a method for estimating the uncertainty in the convective loss estimates. Sample estimations of the total convective energy loss and the uncertainties in those convective energy loss estimates for the external receiver of the 10 MWe Solar Thermal Central Receiver Plant (Barstow, California) and the cavity receiver of the International Energy Agency Small Solar Power Systems Project (Almeria, Spain) are included in the appendices.

  14. Dependence of bunch energy loss in cavities on beam velocity

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergey S.

    1999-03-01

    Beam energy loss in a cavity can be easily computed for a relativistic bunch using time-domain codes like MAFIA or ABCI. However, for nonrelativistic beams the problem is more complicated because of difficulties with its numerical formulation in the time domain. We calculate the cavity loss factors for a bunch in frequency domain as a function of its velocity and compare results with the relativistic case.

  15. Exercise Training and Energy Expenditure following Weight Loss

    PubMed Central

    Hunter, Gary R.; Fisher, Gordon; Neumeier, William H.; Carter, Stephen J.; Plaisance, Eric P.

    2015-01-01

    Purpose Determine the effects of aerobic or resistance training on activity related energy expenditure (AEE, kcal/d) and physical activity index (ARTE) following weight loss. It was hypothesized that weight loss without exercise training would be accompanied by a decrease in AEE, ARTE, and non-training physical activity energy expenditure (NEAT) and that exercise training would prevent decreases in free living energy expenditure. Methods 140 pre-menopausal women underwent an average of 25 pound weight loss during an 800 kcal/day diet of furnished food. One group aerobically trained 3 times/wk (40 min/d), another resistance trained 3 times/wk (10 exercises/2 sets x10 repetitions) and the third group did not exercise. DXA was used to measure body composition, indirect calorimetry to measure resting (REE) and walking energy expenditure, and doubly labeled water to measure total energy expenditure (TEE). AEE, ARTE, and non-training physical activity energy expenditure (NEAT) were calculated. Results TEE, REE, and NEAT all decreased following weight loss for the no exercise group, but not for the aerobic and resistance trainers. Only REE decreased in the two exercise groups. The resistance trainers increased ARTE. Heart rate and oxygen uptake while walking on the flat and up a grade were consistently related to TEE, AEE, NEAT, and ARTE. Conclusion Exercise training prevents a decrease in energy expenditure, including free living energy expenditure separate from the exercise training, following weight loss. Resistance training increased physical activity, while ease and economy in walking associates with increased TEE, AEE, NEAT, and ARTE. PMID:25606816

  16. Data Acquisition System for Electron Energy Loss Coincident Spectrometers

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Yu, Xiaoqi; Yang, Tao

    2005-12-01

    A Data Acquisition System (DAQ) for electron energy loss coincident spectrometers (EELCS) has been developed. The system is composed of a Multiplex Time-Digital Converter (TDC) that measures the flying time of positive and negative ions and a one-dimension position-sensitive detector that records the energy loss of scattering electrons. The experimental data are buffered in a first-in-first-out (FIFO) memory module, then transferred from the FIFO memory to PC by the USB interface. The DAQ system can record the flying time of several ions in one collision, and allows of different data collection modes. The system has been demonstrated at the Electron Energy Loss Coincident Spectrometers at the Laboratory of Atomic and Molecular Physics, USTC. A detail description of the whole system is given and experimental results shown.

  17. An electron energy-loss study of picene and chrysene based charge transfer salts

    SciTech Connect

    Müller, Eric; Mahns, Benjamin; Büchner, Bernd; Knupfer, Martin

    2015-05-14

    The electronic excitation spectra of charge transfer compounds built from the hydrocarbons picene and chrysene, and the strong electron acceptors F{sub 4}TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and TCNQ (7,7,8,8-tetracyanoquinodimethan) have been investigated using electron energy-loss spectroscopy. The corresponding charge transfer compounds have been prepared by co-evaporation of the pristine constituents. We demonstrate that all investigated combinations support charge transfer, which results in new electronic excitation features at low energy. This might represent a way to synthesize low band gap organic semiconductors.

  18. Energy-gap spectroscopy of superconductors using a tunneling microscope

    NASA Technical Reports Server (NTRS)

    Le Duc, H. G.; Kaiser, W. J.; Stern, J. A.

    1987-01-01

    A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.

  19. Study of optical and electronic properties of nickel from reflection electron energy loss spectra

    NASA Astrophysics Data System (ADS)

    Xu, H.; Yang, L. H.; Da, B.; Tóth, J.; Tőkési, K.; Ding, Z. J.

    2017-09-01

    We use the classical Monte Carlo transport model of electrons moving near the surface and inside solids to reproduce the measured reflection electron energy-loss spectroscopy (REELS) spectra. With the combination of the classical transport model and the Markov chain Monte Carlo (MCMC) sampling of oscillator parameters the so-called reverse Monte Carlo (RMC) method was developed, and used to obtain optical constants of Ni in this work. A systematic study of the electronic and optical properties of Ni has been performed in an energy loss range of 0-200 eV from the measured REELS spectra at primary energies of 1000 eV, 2000 eV and 3000 eV. The reliability of our method was tested by comparing our results with the previous data. Moreover, the accuracy of our optical data has been confirmed by applying oscillator strength-sum rule and perfect-screening-sum rule.

  20. Energy loss of correlated ions in dense plasma

    NASA Astrophysics Data System (ADS)

    Ahmed, Baida Muhsen; Ahmed, Khalid A.; Ahmed, Riayhd Khalil

    2016-05-01

    The interaction between proton clusters and plasma gas is studied using the dielectric function by fried-conte formalism. The theoretical formula of the potential basis equation derived and the energy loss of incident proton (point-like, correlate and dicluster) with different parameters (velocity, distance, densities and temperatures) is calculated numerically. Two different equations were used to enhance the correlation stopping (ECS), it is clear that the present results are consistent with the dielectric calculation of energy loss at parameters ne = 1017cm-3 and T = (2 - 10) eV. The result showed a good correlation with the previous work.

  1. Low energy nuclear spin excitations in Ho metal investigated by high resolution neutron spectroscopy.

    PubMed

    Chatterji, Tapan; Jalarvo, Niina

    2013-04-17

    We have investigated the low energy excitations in metallic Ho by high resolution neutron spectroscopy. We found at T = 3 K clear inelastic peaks in the energy loss and energy gain sides, along with the central elastic peak. The energy of this low energy excitation, which is 26.59 ± 0.02 μeV at T = 3 K, decreased continuously and became zero at TN ≈ 130 K. By fitting the data in the temperature range 100-127.5 K with a power law we obtained the power-law exponent β = 0.37 ± 0.02, which agrees with the expected value β = 0.367 for a three-dimensional Heisenberg model. Thus the energy of the low energy excitations can be associated with the order parameter.

  2. Simulation of electron energy loss spectra of nanomaterials with linear-scaling density functional theory

    DOE PAGES

    Tait, E. W.; Ratcliff, L. E.; Payne, M. C.; ...

    2016-04-20

    Experimental techniques for electron energy loss spectroscopy (EELS) combine high energy resolution with high spatial resolution. They are therefore powerful tools for investigating the local electronic structure of complex systems such as nanostructures, interfaces and even individual defects. Interpretation of experimental electron energy loss spectra is often challenging and can require theoretical modelling of candidate structures, which themselves may be large and complex, beyond the capabilities of traditional cubic-scaling density functional theory. In this work, we present functionality to compute electron energy loss spectra within the onetep linear-scaling density functional theory code. We first demonstrate that simulated spectra agree withmore » those computed using conventional plane wave pseudopotential methods to a high degree of precision. The ability of onetep to tackle large problems is then exploited to investigate convergence of spectra with respect to supercell size. As a result, we apply the novel functionality to a study of the electron energy loss spectra of defects on the (1 0 1) surface of an anatase slab and determine concentrations of defects which might be experimentally detectable.« less

  3. Simulation of electron energy loss spectra of nanomaterials with linear-scaling density functional theory

    NASA Astrophysics Data System (ADS)

    Tait, E. W.; Ratcliff, L. E.; Payne, M. C.; Haynes, P. D.; Hine, N. D. M.

    2016-05-01

    Experimental techniques for electron energy loss spectroscopy (EELS) combine high energy resolution with high spatial resolution. They are therefore powerful tools for investigating the local electronic structure of complex systems such as nanostructures, interfaces and even individual defects. Interpretation of experimental electron energy loss spectra is often challenging and can require theoretical modelling of candidate structures, which themselves may be large and complex, beyond the capabilities of traditional cubic-scaling density functional theory. In this work, we present functionality to compute electron energy loss spectra within the onetep linear-scaling density functional theory code. We first demonstrate that simulated spectra agree with those computed using conventional plane wave pseudopotential methods to a high degree of precision. The ability of onetep to tackle large problems is then exploited to investigate convergence of spectra with respect to supercell size. Finally, we apply the novel functionality to a study of the electron energy loss spectra of defects on the (1 0 1) surface of an anatase slab and determine concentrations of defects which might be experimentally detectable.

  4. Uncertainty, loss aversion, and markets for energy efficiency

    SciTech Connect

    Greene, David L

    2010-01-01

    Increasing energy efficiency is critical to mitigating greenhouse gas emissions from fossil-fuel combustion, reducing oil dependence, and achieving a sustainable global energy system. The tendency of markets to neglect apparently cost-effective energy efficiency options has been called the efficiency gap or energy paradox. The market for energy efficiency in new, energy-using durable goods, however, appears to have a bias that leads to undervaluation of future energy savings relative to their expected value. This paper argues that the bias is chiefly produced by the combination of substantial uncertainty about the net value of future fuel savings and the loss aversion of typical consumers. This framework relies on the theory of contextdependent preferences. The uncertainty-loss aversion bias against energy efficiency is quantifiable, making it potentially correctible by policy measures. The welfare economics of such policies remains unresolved. Data on the costs of increased fuel economy of new passenger cars, taken from a National Research Council study, illustrate how an apparently cost-effective increase in energy efficiency would be uninteresting to lossaverse consumers.

  5. Energy loss of heavy ions in a dense hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Dietrich, K.-G.; Hoffmann, D. H. H.; Wahl, H.; Haas, C. R.; Kunze, H.; Brandenburg, W.; Noll, R.

    1990-12-01

    The energy loss of heavy ions with an energy of 1.4 MeV/u in a hydrogen plasma has been measured. A 20 cm long z-pinch has been used as plasma target. Our data show a strong enhancement of the stopping power of the plasma compared to that of a cold gas with equal density. The results completely confirm the predictions of the standard stopping power model.

  6. Viscous energy loss in the presence of abnormal aortic flow.

    PubMed

    Barker, Alex J; van Ooij, Pim; Bandi, Krishna; Garcia, Julio; Albaghdadi, Mazen; McCarthy, Patrick; Bonow, Robert O; Carr, James; Collins, Jeremy; Malaisrie, S Chris; Markl, Michael

    2014-09-01

    To present a theoretical basis for noninvasively characterizing in vivo fluid-mechanical energy losses and to apply it in a pilot study of patients known to express abnormal aortic flow patterns. Four-dimensional flow MRI was used to characterize laminar viscous energy losses in the aorta of normal controls (n = 12, age = 37 ± 10 yr), patients with aortic dilation (n = 16, age = 52 ± 8 yr), and patients with aortic valve stenosis matched for age and aortic size (n = 14, age = 46 ± 15 yr), using a relationship between the three-dimensional velocity field and viscous energy dissipation. Viscous energy loss was elevated significantly in the thoracic aorta in patients with dilated aorta (3.6 ± 1.3 mW, P = 0.024) and patients with aortic stenosis (14.3 ± 8.2 mW, P < 0.001) compared with healthy volunteers (2.3 ± 0.9 mW). The same pattern of significant differences was seen in the ascending aorta, where viscous energy losses in patients with dilated aortas (2.2 ± 1.1 mW, P = 0.021) and patients with aortic stenosis (10.9 ± 6.8 mW, P < 0.001) were elevated compared with healthy volunteers (1.2 ± 0.6 mW). This technique provides a capability to quantify the contribution of abnormal laminar blood flow to increased ventricular afterload. In this pilot study, viscous energy loss in patient cohorts was significantly elevated and indicates that cardiac afterload is increased due to abnormal flow. Copyright © 2013 Wiley Periodicals, Inc.

  7. Energy Drinks, Weight Loss, and Disordered Eating Behaviors

    ERIC Educational Resources Information Center

    Jeffers, Amy J.; Vatalaro Hill, Katherine E.; Benotsch, Eric G.

    2014-01-01

    Objective: The present study examined energy drink consumption and relations with weight loss attempts and behaviors, body image, and eating disorders. Participants/Methods: This is a secondary analysis using data from 856 undergraduate students who completed the American College Health Association-National College Health Assessment II…

  8. Energy Drinks, Weight Loss, and Disordered Eating Behaviors

    ERIC Educational Resources Information Center

    Jeffers, Amy J.; Vatalaro Hill, Katherine E.; Benotsch, Eric G.

    2014-01-01

    Objective: The present study examined energy drink consumption and relations with weight loss attempts and behaviors, body image, and eating disorders. Participants/Methods: This is a secondary analysis using data from 856 undergraduate students who completed the American College Health Association-National College Health Assessment II…

  9. Rotating gravity currents. Part 1. Energy loss theory

    NASA Astrophysics Data System (ADS)

    Martin, J. R.; Lane-Serff, G. F.

    2005-01-01

    A comprehensive energy loss theory for gravity currents in rotating rectangular channels is presented. The model is an extension of the non-rotating energy loss theory of Benjamin (J. Fluid Mech. vol. 31, 1968, p. 209) and the steady-state dissipationless theory of rotating gravity currents of Hacker (PhD thesis, 1996). The theory assumes the fluid is inviscid, there is no shear within the current, and the Boussinesq approximation is made. Dissipation is introduced using a simple method. A head loss term is introduced into the Bernoulli equation and it is assumed that the energy loss is uniform across the stream. Conservation of momentum, volume flux and potential vorticity between upstream and downstream locations is then considered. By allowing for energy dissipation, results are obtained for channels of arbitrary depth and width (relative to the current). The results match those from earlier workers in the two limits of (i) zero rotation (but including dissipation) and (ii) zero dissipation (but including rotation). Three types of flow are identified as the effect of rotation increases, characterized in terms of the location of the outcropping interface between the gravity current and the ambient fluid on the channel boundaries. The parameters for transitions between these cases are quantified, as is the detailed behaviour of the flow in all cases. In particular, the speed of the current can be predicted for any given channel depth and width. As the channel depth increases, the predicted Froude number tends to surd 2, as for non-rotating flows.

  10. Acceleration and energy loss in N = 4 SYM

    SciTech Connect

    Chernicoff, Mariano; Gueijosa, Alberto

    2009-04-20

    This contribution is based on two talks given at the XIII Mexican School of Particles and Fields. We revisit some of the results presented in [19], concerning the rate of energy loss of an accelerating quark in strongly-coupled N = 4 super-Yang-Mills.

  11. Energy losses through entrance condensation in small vapour engines

    SciTech Connect

    Bom, G.J. )

    1993-03-01

    The effects of entrance condensation were studied in a small piston type vapour engine as could be used for low power thermodynamic solar waterpumping (50-1000 W output). Indicative relations have been established between the magnitude of energy losses caused by this phenomenon and engine design features. 2 refs., 5 figs.

  12. Two Theorems on Dissipative Energy Losses in Capacitor Systems

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2005-01-01

    This article examines energy losses in charge motion in two capacitor systems. In the first charge is transferred from a charged capacitor to an uncharged one through a resistor. In the second a battery charges an originally uncharged capacitor through a resistance. Analysis leads to two surprising general theorems. In the first case the fraction…

  13. Two Theorems on Dissipative Energy Losses in Capacitor Systems

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2005-01-01

    This article examines energy losses in charge motion in two capacitor systems. In the first charge is transferred from a charged capacitor to an uncharged one through a resistor. In the second a battery charges an originally uncharged capacitor through a resistance. Analysis leads to two surprising general theorems. In the first case the fraction…

  14. Rupture dynamics with energy loss outside the slip zone

    USGS Publications Warehouse

    Andrews, D.J.

    2005-01-01

    Energy loss in a fault damage zone, outside the slip zone, contributes to the fracture energy that determines rupture velocity of an earthquake. A nonelastic two-dimensional dynamic calculation is done in which the slip zone is modeled as a fault plane and material off the fault is subject to a Coulomb yield condition. In a mode 2 crack-like solution in which an abrupt uniform drop of shear traction on the fault spreads from a point, Coulomb yielding occurs on the extensional side of the fault. Plastic strain is distributed with uniform magnitude along the fault, and it has a thickness normal to the fault proportional to propagation distance. Energy loss off the fault is also proportional to propagation distance, and it can become much larger than energy loss on the fault specified by the fault constitutive relation. The slip velocity function could be produced in an equivalent elastic problem by a slip-weakening friction law with breakdown slip Dc increasing with distance. Fracture energy G and equivalent Dc will be different in ruptures with different initiation points and stress drops, so they are not constitutive properties; they are determined by the dynamic solution that arrives at a particular point. Peak slip velocity is, however, a property of a fault location. Nonelastic response can be mimicked by imposing a limit on slip velocity on a fault in an elastic medium.

  15. Flow effects on jet energy loss with detailed balance

    NASA Astrophysics Data System (ADS)

    Cheng, Luan; Liu, Jia; Wang, EnKe

    2014-11-01

    In the presence of collective flow a new model potential describing the interaction of the hard jet with scattering centers is derived based on the static color-screened Yukawa potential. The flow effect on jet quenching with detailed balance is investigated in pQCD. It turns out, considering the collective flow with velocity v z along the jet direction, the collective flow decreases the LPM destructive interference comparing to that in the static medium. The gluon absorption plays a more important role in the moving medium. The collective flow increases the energy gain from gluon absorption, however, decreases the energy loss from gluon radiation, which is (1 - v z ) times as that in the static medium to the first order of opacity. In the presence of collective flow, the second order in opacity correction is relatively small compared to the first order. So that the total effective energy loss is decreased. The flow dependence of the energy loss will affect the suppression of high p T hadron spectrum and anisotropy parameter v 2 in high-energy heavy-ion collisions.

  16. Dynamic Energy Loss Characteristics in the Native Aortic Valve

    NASA Astrophysics Data System (ADS)

    Hwai Yap, Choon; Dasi, Laksmi P.; Yoganathan, Ajit P.

    2009-11-01

    Aortic Valve (AV) stenosis if untreated leads to heart failure. From a mechanics standpoint, heart failure implies failure to generate sufficient mechanical power to overcome energy losses in the circulation. Thus energy efficiency-based measures are direct measures of AV disease severity, which unfortunately is not used in current clinical measures of stenosis severity. We present an analysis of the dynamic rate of energy dissipation through the AV from direct high temporal resolution measurements of flow and pressure drop across the AV in a pulsatile left heart setup. Porcine AV was used and measurements at various conditions were acquired: varying stroke volumes; heart rates; and stenosis levels. Energy dissipation waveform has a distinctive pattern of being skewed towards late systole, attributed to the explosive growth of flow instabilities from adverse pressure gradient. Increasing heart rate and stroke volume increases energy dissipation, but does not alter the normalized shape of the dissipation temporal profile. Stenosis increases energy dissipation and also alters the normalized shape of dissipation waveform with significantly more losses during late acceleration phase. Since stenosis produces a departure from the signature dissipation waveform shape, dynamic energy dissipation analysis can be extended into a clinical tool for AV evaluation.

  17. High resolution energy loss research: Si compound ceramics and composites. [1990 annual progress report

    SciTech Connect

    Carpenter, R W; Lin, S H

    1990-12-31

    This report discusses proposed work on silicon compound ceramics and composites. High resolution composition and structure analysis of interfaces in ceramic and metal matrix composites and certain grain boundaries in silicon and its interfaces with oxides and nitrides is proposed. Composition and bonding analysis will be done with high spatial resolution (20 Angstroms or better) parallel electron energy loss spectroscopy using a field emission analytical electron microscope. Structural analysis will be done at the 1.8 Angstrom resolution level at 200kV by HREM. Theoretical electron energy loss cross section computations will be used to interpret electronic structure of these materials. Both self-consistent field MO and multiple scattering computational methods are being done and evaluated.

  18. Effect of physical activity on weight loss, energy expenditure, and energy intake during diet induced weight loss.

    PubMed

    DeLany, James P; Kelley, David E; Hames, Kazanna C; Jakicic, John M; Goodpaster, Bret H

    2014-02-01

    Objective measurements of physical activity (PA), energy expenditure (EE) and energy intake can provide valuable information regarding appropriate strategies for successful sustained weight loss. The total EE was examined by doubly labeled water, resting metabolic rate by indirect calorimetry, PA with activity monitors, and energy intake by the intake/balance technique in 116 severely obese undergoing intervention with diet alone (DO) or diet plus PA (D-PA). Weight loss of 9.6 ± 6.8 kg resulted in decreased EE which was not minimized in the D-PA group. Comparing the highest and lowest quartiles of increase in PA revealed a lower decrease in TDEE (-122 ± 319 vs. -376 ± 305 kcal day⁻¹), elimination of the drop in AEE (83 ± 279 vs. -211 ± 284 kcal day⁻¹) and greater weight loss (13.0 ± 7.0 vs. 8.1 ± 6.3 kg). Increased PA was associated with greater adherence to energy restriction and maintenance of greater weight loss during months 7-12. Noncompliance to prescribed PA in the DO and D-PA groups partially masked the effects of PA to increase weight loss and to minimize the reduced EE. Increased PA was also associated with improved adherence to prescribed caloric restriction. A strong recommendation needs to be made to improve interventions that promote PA within the context of behavioral weight loss interventions. Copyright © 2013 The Obesity Society.

  19. High-energy neutron spectroscopy with thick silicon detectors

    NASA Technical Reports Server (NTRS)

    Kinnison, James D.; Maurer, Richard H.; Roth, David R.; Haight, Robert C.

    2003-01-01

    The high-energy neutron component of the space radiation environment in thick structures such as the International Space Station contributes to the total radiation dose received by an astronaut. Detector design constraints such as size and mass have limited the energy range of neutron spectrum measurements in orbit to about 12 MeV in Space Shuttle studies. We present a new method for high-energy neutron spectroscopy using small silicon detectors that can extend these measurements to more than 500 MeV. The methodology is based on measurement of the detector response function for high-energy neutrons and inversion of this response function with measured deposition data to deduce neutron energy spectra. We also present the results of an initial shielding study performed with the thick silicon detector system for high-energy neutrons incident on polyethylene.

  20. Photon Detector For Inverse Photoemission Spectroscopy With Improved Energy Resolution

    SciTech Connect

    Maniraj, M.; D'Souza, S. W.; Barman, S. R.

    2011-07-15

    We present the results from newly designed and fabricated double window photon detector to improve the overall energy resolution for inverse photoemission spectroscopy (IPES). This simple design allows us to introduce an absorption gas (Krypton) to decrease the band-width of the energy selective photon detector and thus improve the resolution. Resonance absorption line of Kr of wavelength of 123.6 nm was used. By fitting the Fermi edge of the IPES spectrum of silver, we find an overall energy resolution improved by 73 meV. The design is modular and ensures ease and safety of handling.

  1. Measuring Conformational Energy Differences Using Pulsed-Jet Microwave Spectroscopy

    NASA Astrophysics Data System (ADS)

    Funderburk, Cameron M.; Gaster, Sydney A.; Taylor, Tiffany R.; Brown, Gordon G.

    2017-06-01

    The conformational energy differences of various chemicals have been measured using chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The hypothesis is that the relative intensities measured in a pulsed-jet instrument are proportional to the conformer populations present before the expansion occurs. Therefore, by measuring the relative intensities in a CP-FTMW spectrum, we aim to determine the relative energy difference between conformers. Experimentally, pulsed-jet CP-FTMW data will be compared to energy differences reported in the literature and to room-temperature CP-FTMW data acquired at Coker College. Results from ab initio calculations will also be used for comparison.

  2. Energy Spectroscopy of Andreev Levels between Two Superconductors

    SciTech Connect

    Morpurgo, A.F.; van Wees, B.J.; Klapwijk, T.M.; Borghs, G.

    1997-11-01

    We perform energy spectroscopy of Andreev reflection processes occurring at two superconducting electrodes connected in series via a ballistic two dimensional channel, by measuring the voltage dependence of that part of the conductance modulated by the macroscopic phase difference. The amplitude of the modulation oscillates as a function of energy and the phase exhibits an abrupt shift close to {pi} at the energy for which the amplitude is minimum. A microscopic theoretical description ascribes the phenomenon to the precursor of a bound state formed between the two superconductors. {copyright} {ital 1997} {ital The American Physical Society}

  3. Derivation of Hamaker Dispersion Energy of Amorphous Carbon Surfaces in Contact with Liquids Using Photoelectron Energy-Loss Spectra

    NASA Astrophysics Data System (ADS)

    Godet, Christian; David, Denis

    2017-08-01

    Hamaker interaction energies and cutoff distances have been calculated for disordered carbon films, in contact with purely dispersive (diiodomethane) or polar (water) liquids, using their experimental dielectric functions ɛ (q, ω) obtained over a broad energy range. In contrast with previous works, a q-averaged <ɛ (q, ω) > q is derived from photoelectron energy-loss spectroscopy (XPS-PEELS) where the energy loss function (ELF) < Im[-1/ɛ (q, ω)] > q is a weighted average over allowed transferred wave vector values, q, given by the physics of bulk plasmon excitation. For microcrystalline diamond and amorphous carbon films with a wide range of (sp3/sp2 + sp3) hybridization, non-retarded Hamaker energies, A 132 (L < 1 nm), were calculated in several configurations, and distance and wavenumber cutoff values were then calculated based on A 132 and the dispersive work of adhesion obtained from contact angles. A geometric average approximation, H 0 CVL = (H 0 CVC H 0 LVL )1/2, holds for the cutoff separation distances obtained for carbon-vacuum-liquid (CVL), carbon-vacuum-carbon (CVC) and liquid-vacuum-liquid (LVL) equilibrium configurations. The linear dependence found for A CVL, A CLC and A CLV values as a function of A CVC, for each liquid, allows predictive relationships for Hamaker energies (in any configuration) using experimental determination of the dispersive component of the surface tension, {γ}_{CV}^d , and a guess value of the cutoff distance H 0 CVC of the solid. [Figure not available: see fulltext.

  4. Deconvolution of the energy loss function of the KATRIN experiment

    NASA Astrophysics Data System (ADS)

    Hannen, V.; Heese, I.; Weinheimer, C.; Sejersen Riis, A.; Valerius, K.

    2017-03-01

    The KATRIN experiment aims at a direct and model independent determination of the neutrino mass with 0.2 eV/c2 sensitivity (at 90% C.L.) via a measurement of the endpoint region of the tritium beta-decay spectrum. The main components of the experiment are a windowless gaseous tritium source (WGTS), differential and cryogenic pumping sections and a tandem of a pre- and a main-spectrometer, applying the concept of magnetic adiabatic collimation with an electrostatic retardation potential to analyze the energy of beta decay electrons and to guide electrons passing the filter onto a segmented silicon PIN detector. One of the important systematic uncertainties of such an experiment are due to energy losses of β-decay electrons by elastic and inelastic scattering off tritium molecules within the source volume which alter the shape of the measured spectrum. To correct for these effects an independent measurement of the corresponding energy loss function is required. In this work we describe a deconvolution method to extract the energy loss function from measurements of the response function of the experiment at different column densities of the WGTS using a monoenergetic electron source.

  5. Aromatic Polyurea Possessing High Electrical Energy Density and Low Loss

    NASA Astrophysics Data System (ADS)

    Thakur, Yash; Lin, Minren; Wu, Shan; Zhang, Q. M.

    2016-10-01

    We report the development of a dielectric polymer, poly (ether methyl ether urea) (PEMEU), which possesses a dielectric constant of 4 and is thermally stable up to 150°C. The experimental results show that the ether units are effective in softening the rigid polymer and making it thermally processable, while the high dipole moment of urea units and glass structure of the polymer leads to a low dielectric loss and low conduction loss. As a result, PEMEU high quality thin films can be fabricated which exhibit exceptionally high breakdown field of >1.5 GV/m, and a low conduction loss at fields up to the breakdown. Consequently, the PEMEU films exhibit a high charge-discharge efficiency of 90% and a high discharged energy density of 36 J/cm3.

  6. Energy loss analysis of an integrated space power distribution system

    NASA Technical Reports Server (NTRS)

    Kankam, M. D.; Ribeiro, P. F.

    1992-01-01

    The results of studies related to conceptual topologies of an integrated utility-like space power system are described. The system topologies are comparatively analyzed by considering their transmission energy losses as functions of mainly distribution voltage level and load composition. The analysis is expedited by use of a Distribution System Analysis and Simulation (DSAS) software. This recently developed computer program by the Electric Power Research Institute (EPRI) uses improved load models to solve the power flow within the system. However, present shortcomings of the software with regard to space applications, and incompletely defined characteristics of a space power system make the results applicable to only the fundamental trends of energy losses of the topologies studied. Accountability, such as included, for the effects of the various parameters on the system performance can constitute part of a planning tool for a space power distribution system.

  7. Energy loss analysis of an integrated space power distribution system

    NASA Technical Reports Server (NTRS)

    Kankam, M. D.; Ribeiro, P. F.

    1992-01-01

    The results of studies related to conceptual topologies of an integrated utility-like space power system are described. The system topologies are comparatively analyzed by considering their transmission energy losses as functions of mainly distribution voltage level and load composition. The analysis is expedited by use of a Distribution System Analysis and Simulation (DSAS) software. This recently developed computer program by the Electric Power Research Institute (EPRI) uses improved load models to solve the power flow within the system. However, present shortcomings of the software with regard to space applications, and incompletely defined characteristics of a space power system make the results applicable to only the fundamental trends of energy losses of the topologies studied. Accountability, such as included, for the effects of the various parameters on the system performance can constitute part of a planning tool for a space power distribution system.

  8. Numerical simulation of electron energy loss near inhomogeneous dielectrics

    SciTech Connect

    Garcia de Abajo, F.J.

    1997-12-01

    The nonrelativistic energy loss suffered by fast electrons passing near dielectric interfaces of arbitrary shape is calculated by solving Poisson{close_quote}s equation using the boundary-charge method. The potential induced by a moving electron is expressed in terms of surface-charge distributions placed at the interfaces. These surface charges, obtained by self-consistently solving the resulting integral equation, act back on the electron producing a retarding force and hence energy loss. The dielectrics are described by frequency-dependent dielectric functions. Two particular cases are discussed in further detail: interfaces invariant under translation along one particular direction and axially symmetric interfaces. Previous results for simple geometries, such as planes, spheres, and cylinders, based upon analytical solutions, are fully reproduced within this approach. Calculations are presented for electrons moving near wedges, coupled parallel cylinders, coupled spheres, and toroidal surfaces. {copyright} {ital 1997} {ital The American Physical Society}

  9. Multiple parton scattering in nuclei: Parton energy loss

    SciTech Connect

    Wang, Xin-Nian; Guo, Xiao-feng

    2001-02-17

    Multiple parton scattering and induced parton energy loss are studied in deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering of a highly off-shell quark and the induced parton energy loss is expressed in terms of the modification to the quark fragmentation functions. The authors derive such modified quark fragmentation functions and their QCD evolution equations in DIS using the generalized factorization of higher twist parton distributions. They consider double-hard and hard-soft parton scattering as well as their interferences in the same framework. The final result, which depends on both the diagonal and off-diagonal twist-four parton distributions in nuclei, demonstrates clearly the Landau-Pomeranchuk-Migdal interference features and predicts a unique nuclear modification of the quark fragmentation functions.

  10. Charged-Particle Acceleration and Energy Loss Measurements on OMEGA

    NASA Astrophysics Data System (ADS)

    Hicks, D. G.; Li, C. K.; Séguin, F. H.; Ram, A. K.; Frenje, J. A.; Petrasso, R. D.; Soures, J. M.; Glebov, V. Yu.; Meyerhofer, D. D.; Roberts, S.; Sorce, C.; Stoeckl, C.; Sangster, T. C.; Phillips, T. W.

    2000-10-01

    Measurements have been made of charged fusion products produced in D ^3He-filled targets irradiated on OMEGA. Comparing the energy shifts of four particle types has probed two distinct physical processes: electrostatic acceleration in the low-density corona and energy loss in the high-density target. When the burn occurred during the laser pulse, particle energy shifts were dominated by acceleration effects. Using a simple mode, the time history of the target's electrostatic potential was found and shown to decay to zero soon after laser irradiation was complete. When the burn occurred after the pulse, particle energy shifts were dominated by energy losses in the target, allowing charged-particle stopping-power predictions to be tested. The results provide the first verification of the general form of stopping power theories over a wide velocity range. This work was supported by the U.S. DOE Office of ICF under Coop. Agreem. No. DE-FC03-92SF19460.

  11. Proton Nonionizing Energy Loss (NIEL) for Device Applications

    NASA Technical Reports Server (NTRS)

    Jun, Insoo; Xapsos, Michael A.; Messenger, Scott R.; Burke, Edward A.; Walters, Robert J.; Summers, Geoff; Jordan, Thomas

    2003-01-01

    Nonionizing energy loss (NIEL) is a quantity that describes the rate of energy loss due to atomic displacements as a particle traverses a material. The product of the NIEL and the particle fluence (time integrated flux) gives the displacement damage energy deposition per unit mass of material. NIEL plays the same role to the displacement damage energy deposition as the stopping power to the total ionizing dose (TID). The concept of NIEL has been very useful for correlating particle induced displacement damage effects in semiconductor and optical devices. Many studies have successfully demonstrated that the degradation of semiconductor devices or optical sensors in a radiation field can be linearly correlated to the displacement damage energy, and subsequently to the NIEL deposited in the semiconductor devices or optical sensors. In addition, the NIEL concept was also useful in the study of both Si and GaAs solar cells and of high temperature superconductors, and at predicting the survivability of detectors used at the LHC at CERN. On the other hand, there are some instances where discrepancies are observed in the application of NIEL, most notably in GaAs semiconductor devices. However, NIEL is still a valuable tool, and can be used to scale damages produced by different particles and in different environments, even though this is not understood at the microscopic level.

  12. Proton Nonionizing Energy Loss (NIEL) for Device Applications

    NASA Technical Reports Server (NTRS)

    Jun, Insoo; Xapsos, Michael A.; Messenger, Scott R.; Burke, Edward A.; Walters, Robert J.; Summers, Geoff; Jordan, Thomas

    2003-01-01

    Nonionizing energy loss (NIEL) is a quantity that describes the rate of energy loss due to atomic displacements as a particle traverses a material. The product of the NIEL and the particle fluence (time integrated flux) gives the displacement damage energy deposition per unit mass of material. NIEL plays the same role to the displacement damage energy deposition as the stopping power to the total ionizing dose (TID). The concept of NIEL has been very useful for correlating particle induced displacement damage effects in semiconductor and optical devices. Many studies have successfully demonstrated that the degradation of semiconductor devices or optical sensors in a radiation field can be linearly correlated to the displacement damage energy, and subsequently to the NIEL deposited in the semiconductor devices or optical sensors. In addition, the NIEL concept was also useful in the study of both Si and GaAs solar cells and of high temperature superconductors, and at predicting the survivability of detectors used at the LHC at CERN. On the other hand, there are some instances where discrepancies are observed in the application of NIEL, most notably in GaAs semiconductor devices. However, NIEL is still a valuable tool, and can be used to scale damages produced by different particles and in different environments, even though this is not understood at the microscopic level.

  13. Theoretical interpretation of electron energy-loss spectroscopic images

    DOE PAGES

    Allen, L. J.; D'Alfonso, Adrian J.; Findlay, Scott D.; ...

    2008-04-10

    In this paper, we discuss the theory of electron energy-loss spectroscopic images in scanning transmission electron microscopy. Three case studies are presented which have as common themes issues of inelastic scattering, coherence and image interpretation. The first is a state-by-state inelastic transitions analysis of a spectroscopic image which does not admit direct visual interpretation. The second compares theory and experiment for two-dimensional mapping. Finally, the third considers imaging in three dimensions via depth sectioning.

  14. Energy loss of ions implanted in MOS dielectric films

    NASA Astrophysics Data System (ADS)

    Shyam, Radhey

    Energy loss measurements of ions in the low kinetic energy regime have been made on as-grown SiO2(170-190nm) targets. Singly charged Na + ions with kinetic energies of 2-5 keV and highly charged ions Ar +Q (Q=4, 8 and 11) with a kinetic energy of 1 keV were used. Excitations produced by the ion energy loss in the oxides were captured by encapsulating the irradiated oxide under a top metallic contact. The resulting Metal-Oxide-Semiconductor (MOS) devices were probed with Capacitance-Voltage (C V) measurements and extracted the flatband voltages from the C-V curves. The C-V results for singly charged ion experiments reveal that the changes in the flatband voltage and slope for implanted devices relative to the pristine devices can be used to delineate effects due to implanted ions only and ion induced damage. The data shows that the flatband voltage shifts and C-V slope changes are energy dependent. The observed changes in flatband voltage which are greater than those predicted by calculations scaled for the ion dose and implantation range (SRIM). These results, however, are consistent with a columnar recombination model, where electron-hole pairs are created due to the energy deposited by the implanted ions within the oxide. The remaining holes left after recombination losses are diffused through the oxide at the room temperature and remain present as trapped charges. Comparison of the data with the total number of the holes generated gives a fractional yield of 0.0124 which is of the same order as prior published high energy irradiation experiments. Additionally, the interface trap density, extracted from high and low frequency C-V measurements is observed to increase by one order of magnitude over our incident beam energy. These results confirm that dose- and kinetic energy -dependent effects can be recorded for singly charged ion irradiation on oxides using this method. Highly charged ion results also confirm that dose as well as and charge-dependent effects can

  15. Dielectric spectroscopy measurements on very low loss cross-linked polyethylene power cables

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Fothergill, John; Dodd, Steve; Nilsson, Ulf

    2009-08-01

    The principles of dielectric spectroscopy are reviewed and the techniques in both time and frequency domains are explored in search of appropriate methods for measurement on low loss XLPE cables. By combining the techniques of frequency response analyzer, transformer ratio bridge and discharging current measurements, some preliminary tests results on homopolymer XLPE model cables have been presented and analyzed, in a wide frequency range of 10-4Hz~2×104Hz. Dielectric loss mechanisms of XLPE cables are discussed based on the measurement results.

  16. Power Loss Analysis and Comparison of Segmented and Unsegmented Energy Coupling Coils for Wireless Energy Transfer

    PubMed Central

    Tang, Sai Chun; McDannold, Nathan J.

    2015-01-01

    This paper investigated the power losses of unsegmented and segmented energy coupling coils for wireless energy transfer. Four 30-cm energy coupling coils with different winding separations, conductor cross-sectional areas, and number of turns were developed. The four coils were tested in both unsegmented and segmented configurations. The winding conduction and intrawinding dielectric losses of the coils were evaluated individually based on a well-established lumped circuit model. We found that the intrawinding dielectric loss can be as much as seven times higher than the winding conduction loss at 6.78 MHz when the unsegmented coil is tightly wound. The dielectric loss of an unsegmented coil can be reduced by increasing the winding separation or reducing the number of turns, but the power transfer capability is reduced because of the reduced magnetomotive force. Coil segmentation using resonant capacitors has recently been proposed to significantly reduce the operating voltage of a coil to a safe level in wireless energy transfer for medical implants. Here, we found that it can naturally eliminate the dielectric loss. The coil segmentation method and the power loss analysis used in this paper could be applied to the transmitting, receiving, and resonant coils in two- and four-coil energy transfer systems. PMID:26640745

  17. Power Loss Analysis and Comparison of Segmented and Unsegmented Energy Coupling Coils for Wireless Energy Transfer.

    PubMed

    Tang, Sai Chun; McDannold, Nathan J

    2015-03-01

    This paper investigated the power losses of unsegmented and segmented energy coupling coils for wireless energy transfer. Four 30-cm energy coupling coils with different winding separations, conductor cross-sectional areas, and number of turns were developed. The four coils were tested in both unsegmented and segmented configurations. The winding conduction and intrawinding dielectric losses of the coils were evaluated individually based on a well-established lumped circuit model. We found that the intrawinding dielectric loss can be as much as seven times higher than the winding conduction loss at 6.78 MHz when the unsegmented coil is tightly wound. The dielectric loss of an unsegmented coil can be reduced by increasing the winding separation or reducing the number of turns, but the power transfer capability is reduced because of the reduced magnetomotive force. Coil segmentation using resonant capacitors has recently been proposed to significantly reduce the operating voltage of a coil to a safe level in wireless energy transfer for medical implants. Here, we found that it can naturally eliminate the dielectric loss. The coil segmentation method and the power loss analysis used in this paper could be applied to the transmitting, receiving, and resonant coils in two- and four-coil energy transfer systems.

  18. Optimized free energies from bidirectional single-molecule force spectroscopy.

    PubMed

    Minh, David D L; Adib, Artur B

    2008-05-09

    An optimized method for estimating path-ensemble averages using data from processes driven in opposite directions is presented. Based on this estimator, bidirectional expressions for reconstructing free energies and potentials of mean force from single-molecule force spectroscopy-valid for biasing potentials of arbitrary stiffness-are developed. Numerical simulations on a model potential indicate that these methods perform better than unidirectional strategies.

  19. Research of the temperature measurement of high-energy laser energy meter and energy loss compensation technique

    NASA Astrophysics Data System (ADS)

    Yu, Xun; Wang, Hui; Wu, Ji'an; Wang, Fang; Li, Qian

    2009-11-01

    The energy measurement of high energy laser is converts incident laser energy into heat energy, calculates energy utilizing absorber temperature rise, thus the energy value can be gained. Temperature measurement of high-energy laser energy meter and energy loss compensation during the course of the measurement were studied here. Firstly, temperature-resistance characteristics of resistance wire was analyzed, which was winded on exterior surface of the absorbing cavity of high-energy laser energy meter and used in temperature measurement. Least square method was used to process experiment data and a compensation model was established to calibrate the relationship of temperature vs. resistance. Experiment proved that, error between resistance wire and Pt100 is less than 0.01Ω and temperature error is less than 0.02°C. This greatly improves accuracy of the high energy meter measurement result. Secondly, aimed to the compensation of laser energy loss caused by absorbing cavity's heat exchange, the heat energy loss of absorbing cavity, resulted from thermal radiation, heat convection and heat conduction was analyzed based on heat transfer theory. Its mathematics model was established. Least square method was used to fit a curve of experiment data in order to compensate energy loss. Repetitiveness of measurement is 0.7%, which is highly improved.

  20. Technology Roadmap. Energy Loss Reduction and Recovery in Industrial Energy Systems

    SciTech Connect

    none,

    2004-11-01

    To help guide R&D decision-making and gain industry insights on the top opportunities for improved energy systems, ITP sponsored the Energy Loss Reduction and Recoveryin Energy Systems Roadmapping Workshopin April 2004 in Baltimore, Maryland. This Technology Roadmapis based largely on the results of the workshop and additional industrial energy studies supported by ITP and EERE. It summarizes industry feedback on the top opportunities for R&D investments in energy systems, and the potential for national impacts on energy use and the environment.

  1. Assessing energy relaxation in 2d with ballistic electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Hohls, F.; Pepper, M.; Griffiths, J. P.; Jones, G. A. C.; Ritchie, D. A.

    2007-04-01

    We demonstrate the use of ballistic electron spectroscopy in a two-dimensional electron system to assess energy relaxation of non-equilibrium electrons. The spectrometer consists of a quantum dot tuned to the transition between none and one electron on the dot. The readout of the spectrometer is provided by a nearby one-dimensional wire used as charge detector. We prepare a well defined distribution of non-equilibrium ballistic electrons using a quantum point contact on the first conductance plateau. The energy distribution evolves due to scattering during the 2.5 μm long path towards the spectrometer were it is detected. We use varying injection energy to map out the energy relaxation.

  2. Spectroscopy of Light Nuclei with Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Lombardo, I.; Dell'Aquila, D.; Vigilante, M.

    2016-07-01

    We discuss new results concerning the investigation of the 19F(p,α 0)16O and 10B(p,α 0)7Be reactions at low energies. Both reactions are important for the nuclear spectroscopy of the formed compound nucleus, i.e. 20Ne and 11C respectively, and play a role in nuclear astrophysics. For the 10B(p,α 0)7Be case, a comprehensive analysis of our reaction data and other scattering data points out the possible presence of an unreported state in 11C at Ex ≈ 9.36 MeV. For the 19F(p,α 0)16O case, the study of the low energy angular distributions testifies the role played by low energy resonances in the S-factor, leading to an enhanced reaction rate at stellar energies.

  3. Dietary energy density and successful weight loss maintenance

    PubMed Central

    Raynor, Hollie A.; Van Walleghen, Emily L.; Bachman, Jessica L.; Looney, Shannon M.; Phelan, Suzanne; Wing, Rena R.

    2011-01-01

    Research shows a positive relationship between dietary energy density (ED) and body mass index (BMI), but dietary ED of weight loss maintainers is unknown. This preliminary investigation was a secondary data analysis that compared self-reported dietary ED and food group servings consumed in overweight adults (OW: BMI = 27 – 45 kg/m2), normal weight adults (NW: BMI = 19 – 24.9 kg/m2), and weight loss maintainers (WLM: current BMI = 19 – 24.9 kg/m2 [lost ≥ 10% of maximum body weight and maintained loss for ≥ 5 years]) participating in 2 studies, with data collected from July 2006 and March 2007. Three 24-hr phone dietary recalls from 287 participants (OW = 97, NW = 85, WLM = 105) assessed self-reported dietary intake. ED (kcal/g) was calculated by three methods (food + all beverages except water [F + AB], food + caloric beverages [F + CB], and food only [FO]). Differences in self-reported consumption of dietary ED, food group servings, energy, grams of food/beverages, fat, and fiber were assessed using one-way MANCOVA, adjusting for age, sex, and weekly energy expenditure from self-reported physical activity. ED, calculated by all three methods, was significantly lower in WLM than in NW or OW (FO: WLM = 1.39 ± 0.45 kcal/g; NW = 1.60 ± 0.43 kcal/g; OW = 1.83 ± 0.42 kcal/g). Self-reported daily servings of vegetables and whole grains consumed were significantly higher in WLM compared to NW and OW (vegetables: WLM = 4.9 ± 3.1 servings/day; NW = 3.9 ± 2.0 servings/day; OW = 3.4 ± 1.7 servings/day; whole grains: WLM = 2.2 ± 1.8 servings/day; NW = 1.4 ± 1.2 servings/day; OW = 1.3 ± 1.3 servings/day). WLM self-reported consuming significantly less energy from fat and more fiber than the other two groups. Self-reported energy intake per day was significantly lower in WLM than OW, and WLM self-reported consuming significantly more grams of food/beverages per day than OW. These preliminary findings suggest that consuming a diet lower in ED, characterized by

  4. Jet energy loss in heavy ion collisions from RHIC to LHC energies

    NASA Astrophysics Data System (ADS)

    Levai, Peter

    2011-07-01

    The suppression of hadron production originated from the induced jet energy loss is one of the most accepted and well understood phenomena in heavy ion collisions, which indicates the formation of color deconfined matter consists of quarks, antiquarks and gluons. This phenomena has been seen at RHIC energies and now the first LHC results display a very similar effect. In fact, the suppression is so close to each other at 200 AGeV and 2.76 ATeV, that it is interesting to investigate if such a suppression pattern can exist at all. We use the Gyulassy-Levai-Vitev description of induced jet energy loss combined with different nuclear shadowing functions and describe the experimental data. We claim that a consistent picture can be obtained for the produced hot matter with a weak nuclear shadowing. The interplay between nuclear shadowing and jet energy loss playes a crucial role in the understanding of the experimental data.

  5. Very low energy supernovae from neutrino mass loss

    SciTech Connect

    Lovegrove, Elizabeth; Woosley, S. E.

    2013-06-01

    It now seems likely that some percentage of more massive supernova progenitors do not explode by any of the currently discussed explosion mechanisms. This has led to speculation concerning the observable transients that might be produced if such a supernova fails. Even if a prompt outgoing shock fails to form in a collapsing presupernova star, one must still consider the hydrodynamic response of the star to the abrupt loss of mass via neutrinos as the core forms a protoneutron star. Following a suggestion by Nadezhin, we calculate the hydrodynamical responses of typical supernova progenitor stars to the rapid loss of approximately 0.2-0.5 M {sub ☉} of gravitational mass from their centers. In a red supergiant star, a very weak supernova with total kinetic energy ∼10{sup 47} erg results. The binding energy of a large fraction of the hydrogen envelope before the explosion is of the same order and, depending upon assumptions regarding the maximum mass of a neutron star, most of it is ejected. Ejection speeds are ∼100 km s{sup –1} and luminosities ∼10{sup 39} erg s{sup –1} are maintained for about a year. A significant part of the energy comes from the recombination of hydrogen. The color of the explosion is extremely red and the events bear some similarity to 'luminous red novae', but have much lower speeds.

  6. Very Low Energy Supernovae from Neutrino Mass Loss

    NASA Astrophysics Data System (ADS)

    Lovegrove, Elizabeth; Woosley, S. E.

    2013-06-01

    It now seems likely that some percentage of more massive supernova progenitors do not explode by any of the currently discussed explosion mechanisms. This has led to speculation concerning the observable transients that might be produced if such a supernova fails. Even if a prompt outgoing shock fails to form in a collapsing presupernova star, one must still consider the hydrodynamic response of the star to the abrupt loss of mass via neutrinos as the core forms a protoneutron star. Following a suggestion by Nadezhin, we calculate the hydrodynamical responses of typical supernova progenitor stars to the rapid loss of approximately 0.2-0.5 M ⊙ of gravitational mass from their centers. In a red supergiant star, a very weak supernova with total kinetic energy ~1047 erg results. The binding energy of a large fraction of the hydrogen envelope before the explosion is of the same order and, depending upon assumptions regarding the maximum mass of a neutron star, most of it is ejected. Ejection speeds are ~100 km s-1 and luminosities ~1039 erg s-1 are maintained for about a year. A significant part of the energy comes from the recombination of hydrogen. The color of the explosion is extremely red and the events bear some similarity to "luminous red novae," but have much lower speeds.

  7. Pig Organ Energy Loss Comparison Experiments Using BBs.

    PubMed

    Maiden, Nicholas R; Musgrave, Ian; Fisk, Wesley; Byard, Roger W

    2016-05-01

    Torso models for ballistics research require that the mechanical properties of simulant materials must match the heterogeneous nature of tissues/organs within the human thorax/abdomen. A series of energy loss experiments were conducted on fresh porcine organs/tissues at room temperature and 37°C, using steel 4.5 mm BBs fired from a Daisy(®) brand air rifle. They were compared to FBI and NATO specification ordnance gelatin and a candidate surrogate material called Simulant "A". Two CED M2 chronographs measured BB velocity. The resulting energy loss was established using KE = 1/2 mv² before and after target perforation. The combined results at room temperature and 37°C were as follows: FBI specification gelatin was similar (p > 0.05) to heart and lung, spleen was similar to NATO specification gelatin, Simulant "A" was similar to hindquarter muscle, and hindquarter muscle, kidney, and spleen were similar to each other regarding energy retardation. These results can be used as a basis for the development of simulant materials to create an anatomically correct heterogeneous model. © 2016 American Academy of Forensic Sciences.

  8. Effect of the electron energy distribution on total energy loss with argon in inductively coupled plasmas

    SciTech Connect

    Kim, June Young; Kim, Young-Cheol; Kim, Yu-Sin; Chung, Chin-Wook

    2015-01-15

    The total energy lost per electron-ion pair lost ε{sub T} is investigated with the electron energy distribution function (EEDF). The EEDFs are measured at various argon powers in RF inductively coupled plasma, and the EEDFs show a depleted distribution (a discontinuity occurring at the minimum argon excitation threshold energy level) with the bulk temperature and the tail temperature. The total energy loss per electron-ion pair lost ε{sub T} is calculated from a power balance model with the Maxwellian EEDFs and the depleted EEDFs and then compared with the measured ε{sub T} from the floating probe. It is concluded that the small population of the depleted high energy electrons dramatically increases the collisional energy loss, and the calculated ε{sub T} from the depleted EEDFs has a value that is similar to the measured ε{sub T}.

  9. The role of energy losses in photosynthetic light harvesting

    NASA Astrophysics Data System (ADS)

    Krüger, T. P. J.; van Grondelle, R.

    2017-07-01

    Photosynthesis operates at the bottom of the food chain to convert the energy of light into carbohydrates at a remarkable global rate of about 130 TW. Nonetheless, the overall photosynthetic process has a conversion efficiency of a few percent at best, significantly less than bottom-up photovoltaic cells. The primary photosynthetic steps, consisting of light harvesting and charge separation, are often presented as having near-unity quantum efficiency but this holds only true under ideal conditions. In this review, we discuss the importance of energy loss mechanisms to establish robustness in photosynthetic light harvesting. Thermal energy dissipation of light-harvesting complexes (LHCs) in different environments is investigated and the relationships and contrasts between concentration quenching of high pigment concentrations, photoprotection (non-photochemical quenching), quenching due to protein aggregation, and fluorescence blinking are discussed. The role of charge-transfer states in light harvesting and energy dissipation is highlighted and the importance of controlled protein structural disorder to switch the light-harvesting antennae between effective light harvesters and efficient energy quenchers is underscored. The main LHC of plants, LHCII, is used as a prime example.

  10. Development of decay energy spectroscopy using low temperature detectors.

    PubMed

    Jang, Y S; Kim, G B; Kim, K J; Kim, M S; Lee, H J; Lee, J S; Lee, K B; Lee, M K; Lee, S J; Ri, H C; Yoon, W S; Yuryev, Y N; Kim, Y H

    2012-09-01

    We have developed a high-resolution detection technique for measuring the energy and activity of alpha decay events using low-temperature detectors. A small amount of source material containing alpha-emitting radionuclides was enclosed in a 4π metal absorber. The energy of the alpha particles as well as that of the recoiled nuclides, low-energy electrons, and low-energy x-rays and γ-rays was converted into thermal energy of the gold absorber. A metallic magnetic calorimeter serving as a fast and sensitive thermometer was thermally attached to the metal absorber. In the present report, experimental demonstrations of Q spectroscopy were made with a new meander-type magnetic calorimeter. The thermal connection between the temperature sensor and the absorber was established with annealed gold wires. Each alpha decay event in the absorber resulted in a temperature increase of the absorber and the temperature sensor. Using the spectrum measured for a drop of (226)Ra solution in a 4π gold absorber, all of the alpha emitters in the sample were identified with a demonstration of good detector linearity. The resolution of the (226)Ra spectrum showed a 3.3 keV FWHM at its Q value together with an expected gamma escape peak at the energy shifted by its γ-ray energy. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Method for reducing energy losses in laser crystals

    DOEpatents

    Atherton, L. Jeffrey; DeYoreo, James J.; Roberts, David H.

    1992-01-01

    A process for reducing energy losses in crystals is disclosed which comprises: a. heating a crystal to a temperature sufficiently high as to cause dissolution of microscopic inclusions into the crystal, thereby converting said inclusions into point-defects, and b. maintaining said crystal at a given temperature for a period of time sufficient to cause said point-defects to diffuse out of said crystal. Also disclosed are crystals treated by the process, and lasers utilizing the crystals as a source of light.

  12. Method for reducing energy losses in laser crystals

    DOEpatents

    Atherton, L.J.; DeYoreo, J.J.; Roberts, D.H.

    1992-03-24

    A process for reducing energy losses in crystals is disclosed which comprises: a. heating a crystal to a temperature sufficiently high as to cause dissolution of microscopic inclusions into the crystal, thereby converting said inclusions into point-defects, and b. maintaining said crystal at a given temperature for a period of time sufficient to cause said point-defects to diffuse out of said crystal. Also disclosed are crystals treated by the process, and lasers utilizing the crystals as a source of light. 12 figs.

  13. Multiple scattering calculations of relativistic electron energy loss spectra

    NASA Astrophysics Data System (ADS)

    Jorissen, K.; Rehr, J. J.; Verbeeck, J.

    2010-04-01

    A generalization of the real-space Green’s-function approach is presented for ab initio calculations of relativistic electron energy loss spectra (EELS) which are particularly important in anisotropic materials. The approach incorporates relativistic effects in terms of the transition tensor within the dipole-selection rule. In particular, the method accounts for relativistic corrections to the magic angle in orientation resolved EELS experiments. The approach is validated by a study of the graphite CK edge, for which we present an accurate magic angle measurement consistent with the predicted value.

  14. Loss of Energy Concentration in Nonlinear Evolution Beam Equations

    NASA Astrophysics Data System (ADS)

    Garrione, Maurizio; Gazzola, Filippo

    2017-05-01

    Motivated by the oscillations that were seen at the Tacoma Narrows Bridge, we introduce the notion of solutions with a prevailing mode for the nonlinear evolution beam equation u_{tt} + u_{xxxx} + f(u)= g(x, t) in bounded space-time intervals. We give a new definition of instability for these particular solutions, based on the loss of energy concentration on their prevailing mode. We distinguish between two different forms of energy transfer, one physiological (unavoidable and depending on the nonlinearity) and one due to the insurgence of instability. We then prove a theoretical result allowing to reduce the study of this kind of infinite-dimensional stability to that of a finite-dimensional approximation. With this background, we study the occurrence of instability for three different kinds of nonlinearities f and for some forcing terms g, highlighting some of their structural properties and performing some numerical simulations.

  15. Nonequilibrium thermodynamics and energy efficiency in weight loss diets.

    PubMed

    Feinman, Richard D; Fine, Eugene J

    2007-07-30

    Carbohydrate restriction as a strategy for control of obesity is based on two effects: a behavioral effect, spontaneous reduction in caloric intake and a metabolic effect, an apparent reduction in energy efficiency, greater weight loss per calorie consumed. Variable energy efficiency is established in many contexts (hormonal imbalance, weight regain and knock-out experiments in animal models), but in the area of the effect of macronutrient composition on weight loss, controversy remains. Resistance to the idea comes from a perception that variable weight loss on isocaloric diets would somehow violate the laws of thermodynamics, that is, only caloric intake is important ("a calorie is a calorie"). Previous explanations of how the phenomenon occurs, based on equilibrium thermodynamics, emphasized the inefficiencies introduced by substrate cycling and requirements for increased gluconeogenesis. Living systems, however, are maintained far from equilibrium, and metabolism is controlled by the regulation of the rates of enzymatic reactions. The principles of nonequilibrium thermodynamics which emphasize kinetic fluxes as well as thermodynamic forces should therefore also be considered. Here we review the principles of nonequilibrium thermodynamics and provide an approach to the problem of maintenance and change in body mass by recasting the problem of TAG accumulation and breakdown in the adipocyte in the language of nonequilibrium thermodynamics. We describe adipocyte physiology in terms of cycling between an efficient storage mode and a dissipative mode. Experimentally, this is measured in the rate of fatty acid flux and fatty acid oxidation. Hormonal levels controlled by changes in dietary carbohydrate regulate the relative contributions of the efficient and dissipative parts of the cycle. While no experiment exists that measures all relevant variables, the model is supported by evidence in the literature that 1) dietary carbohydrate, via its effect on hormone levels

  16. Nonequilibrium thermodynamics and energy efficiency in weight loss diets

    PubMed Central

    Feinman, Richard D; Fine, Eugene J

    2007-01-01

    Carbohydrate restriction as a strategy for control of obesity is based on two effects: a behavioral effect, spontaneous reduction in caloric intake and a metabolic effect, an apparent reduction in energy efficiency, greater weight loss per calorie consumed. Variable energy efficiency is established in many contexts (hormonal imbalance, weight regain and knock-out experiments in animal models), but in the area of the effect of macronutrient composition on weight loss, controversy remains. Resistance to the idea comes from a perception that variable weight loss on isocaloric diets would somehow violate the laws of thermodynamics, that is, only caloric intake is important ("a calorie is a calorie"). Previous explanations of how the phenomenon occurs, based on equilibrium thermodynamics, emphasized the inefficiencies introduced by substrate cycling and requirements for increased gluconeogenesis. Living systems, however, are maintained far from equilibrium, and metabolism is controlled by the regulation of the rates of enzymatic reactions. The principles of nonequilibrium thermodynamics which emphasize kinetic fluxes as well as thermodynamic forces should therefore also be considered. Here we review the principles of nonequilibrium thermodynamics and provide an approach to the problem of maintenance and change in body mass by recasting the problem of TAG accumulation and breakdown in the adipocyte in the language of nonequilibrium thermodynamics. We describe adipocyte physiology in terms of cycling between an efficient storage mode and a dissipative mode. Experimentally, this is measured in the rate of fatty acid flux and fatty acid oxidation. Hormonal levels controlled by changes in dietary carbohydrate regulate the relative contributions of the efficient and dissipative parts of the cycle. While no experiment exists that measures all relevant variables, the model is supported by evidence in the literature that 1) dietary carbohydrate, via its effect on hormone levels

  17. Elastic deformation and energy loss of flapping fly wings.

    PubMed

    Lehmann, Fritz-Olaf; Gorb, Stanislav; Nasir, Nazri; Schützner, Peter

    2011-09-01

    During flight, the wings of many insects undergo considerable shape changes in spanwise and chordwise directions. We determined the origin of spanwise wing deformation by combining measurements on segmental wing stiffness of the blowfly Calliphora vicina in the ventral and dorsal directions with numerical modelling of instantaneous aerodynamic and inertial forces within the stroke cycle using a two-dimensional unsteady blade elementary approach. We completed this approach by an experimental study on the wing's rotational axis during stroke reversal. The wing's local flexural stiffness ranges from 30 to 40 nN m(2) near the root, whereas the distal wing parts are highly compliant (0.6 to 2.2 nN m(2)). Local bending moments during wing flapping peak near the wing root at the beginning of each half stroke due to both aerodynamic and inertial forces, producing a maximum wing tip deflection of up to 46 deg. Blowfly wings store up to 2.30 μJ elastic potential energy that converts into a mean wing deformation power of 27.3 μW. This value equates to approximately 5.9 and 2.3% of the inertial and aerodynamic power requirements for flight in this animal, respectively. Wing elasticity measurements suggest that approximately 20% or 0.46 μJ of elastic potential energy cannot be recovered within each half stroke. Local strain energy increases from tip to root, matching the distribution of the wing's elastic protein resilin, whereas local strain energy density varies little in the spanwise direction. This study demonstrates a source of mechanical energy loss in fly flight owing to spanwise wing bending at the stroke reversals, even in cases in which aerodynamic power exceeds inertial power. Despite lower stiffness estimates, our findings are widely consistent with previous stiffness measurements on insect wings but highlight the relationship between local flexural stiffness, wing deformation power and energy expenditure in flapping insect wings.

  18. Energy loss for heavy quarks in relation to light partons: is radiative energy loss for heavy quarks anomalous?

    PubMed

    Lacey, Roy A; Wei, R; Ajitanand, N N; Alexander, J M; Gong, X; Jia, J; Mawi, A; Mohapatra, S; Reynolds, D; Salnikov, S; Taranenko, A

    2009-10-02

    The scaling properties of jet-suppression measurements are compared for nonphotonic electrons (e+/-) and neutral pions (pi(0)) in Au+Au collisions at sqrt[S(NN)]=200 GeV. For a broad range of transverse momenta and collision centralities, the comparison is consistent with jet quenching dominated by radiative energy loss for both heavy and light partons. Less quenching is indicated for heavy quarks via e+/-; this gives an independent estimate of the transport coefficient q that agrees with its magnitude obtained from quenching of light partons via pi(0)'s.

  19. Advanced theory of driven birdcage resonator with losses for biomedical magnetic resonance imaging and spectroscopy.

    PubMed

    Novikov, Alexander

    2011-02-01

    A complete time-dependent physics theory of symmetric unperturbed driven hybrid birdcage resonator was developed for general application. In particular, the theory can be applied for radiofrequency (RF) coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green's functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the birdcage resonator. Values of generated resistances in legs and end-rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B(1) field polarization dependence is measured for eight-sections birdcage coil. It was shown that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy current loss is the major effect of coil shielding.

  20. Advanced Theory of Driven Birdcage Resonator with Losses for Biomedical Magnetic Resonance Imaging and Spectroscopy

    PubMed Central

    Novikov, Alexander

    2010-01-01

    A complete time-dependent physics theory of symmetric unperturbed driven Hybrid Birdcage resonator was developed for general application. In particular, the theory can be applied for RF coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green’s functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the Birdcage resonator. Values of generated resistances in Legs and End-Rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B1 field polarization dependence is measured for eight-sections Birdcage coil. It was shown, that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy currents losses is the major effect of coil shielding. PMID:20869184

  1. Mode-dependent dispersion in Raman line shapes: Observation and implications from ultrafast Raman loss spectroscopy

    SciTech Connect

    Umapathy, S.; Mallick, B.; Lakshmanna, A.

    2010-07-14

    Ultrafast Raman loss spectroscopy (URLS) enables one to obtain the vibrational structural information of molecular systems including fluorescent materials. URLS, a nonlinear process analog to stimulated Raman gain, involves a narrow bandwidth picosecond Raman pump pulse and a femtosecond broadband white light continuum. Under nonresonant condition, the Raman response appears as a negative (loss) signal, whereas, on resonance with the electronic transition the line shape changes from a negative to a positive through a dispersive form. The intensities observed and thus, the Franck-Condon activity (coordinate dependent), are sensitive to the wavelength of the white light corresponding to a particular Raman frequency with respect to the Raman pump pulse wavelength, i.e., there is a mode-dependent response in URLS.

  2. Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

    PubMed

    Jenke, T; Cronenberg, G; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H

    2014-04-18

    We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14  eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20  μm (95% C.L.).

  3. Visible/Infrared Imaging Spectroscopy and Energy-Resolving Detectors

    NASA Astrophysics Data System (ADS)

    Eisenhauer, Frank; Raab, Walfried

    2015-08-01

    Imaging spectroscopy has seen rapid progress over the past 25 years, leading to breakthroughs in many fields of astronomy that would not have been otherwise possible. This review overviews the visible/infrared imaging spectroscopy techniques as well as energy-resolving detectors. We introduce the working principle of scanning Fabry-Perot and Fourier transform spectrometers and explain the most common integral field concepts based on mirror slicers, lenslet arrays, and fibers. The main advantage of integral field spectrographs is the simultaneous measurement of spatial and spectral information. Although Fabry-Perot and Fourier transform spectrometers can provide a larger field of view, it is ultimately the higher sensitivity of integral field units that make them the technique of choice. This is arguably the case for image slicers, which make the most efficient use of the available detector pixels and have equal or higher transmission than lenslet arrays and fiber integral field units, respectively. We also address the more specific issues of large étendue operation, focal ratio degradation, anamorphic magnification, and diffraction-limited operation. This review also covers the emerging technology of energy-resolving detectors, which promise very simple and efficient instrument designs. These energy-resolving detectors are based on superconducting thin film technology and exploit either the very small superconducting energy to count the number of quasi-particles excited in the absorption of the photon or the extremely steep phase transition between the normal- and superconducting phase to measure a temperature increase. We have put special emphasis on an overview of the underlying physical phenomena as well as on the recent technological progress and astronomical path finder experiments.

  4. Nicotinamide prevents ultraviolet radiation-induced cellular energy loss.

    PubMed

    Park, Joohong; Halliday, Gary M; Surjana, Devita; Damian, Diona L

    2010-01-01

    UV radiation is carcinogenic by causing mutations in the skin and also by suppressing cutaneous antitumor immunity. We previously found nicotinamide (vitamin B3) to be highly effective at reducing UV-induced immunosuppression in human volunteers, with microarray studies on in vivo irradiated human skin suggesting that nicotinamide normalizes subsets of apoptosis, immune function and energy metabolism-related genes that are downregulated by UV exposure. Using human adult low calcium temperature keratinocytes, we further investigated nicotinamide's effects on cellular energy metabolism. We found that nicotinamide prevented UV-induced cellular ATP loss and protected against UV-induced glycolytic blockade. To determine whether nicotinamide alters the effects of UV-induced oxidative stress posttranslationally, we also measured UV-induced reactive oxygen species (ROS). Nicotinamide had no effect on ROS formation, and at the low UV doses used in these studies, equivalent to ambient daily sun exposure, there was no evidence of apoptosis. Hence, nicotinamide appears to exert its UV protective effects on the skin via its role in cellular energy pathways.

  5. Improving Diamagnetic Flux Temporal Resolution to Measure ELM Energy Loss

    NASA Astrophysics Data System (ADS)

    Sieck, P. E.; Baylor, L. R.; Evans, T. E.; Leonard, A. W.; Osborne, T. H.; Strait, E. J.

    2010-11-01

    When an ELM occurs in a tokamak, a substantial loss of stored thermal energy can occur in a very short time, resulting in a change in the plasma diamagnetism. A diamagnetic loop is therefore an attractive diagnostic for characterizing the change in energy during ELMs. A loop external to the vessel can be used but it is bandwidth-limited by the vessel wall, therefore the signal is severely attenuated above 40 Hz in DIII-D. The temporal resolution can be improved by combining the (slow) diamagnetic signal with a properly scaled internal (fast) toroidal BT signal. The results agree with finely-spaced EFIT equilibrium reconstructions to within 10% before each ELM, but the diamagnetic calculation often shows up to twice the drop in energy at the ELM. The BT signal reveals the magnetic change completes in 0.5 ms or less with occasional dynamics above 10 kHz. This improved temporal resolution allows comparison of phenomenology in natural vs. pellet-triggered ELMs, and also effects of partial ELM suppression under resonant magnetic perturbation.

  6. Energy loss and (de)coherence effects beyond eikonal approximation

    NASA Astrophysics Data System (ADS)

    Apolinário, Liliana; Armesto, Néstor; Milhano, Guilherme; Salgado, Carlos A.

    2014-11-01

    The parton branching process is known to be modified in the presence of a medium. Colour decoherence processes are known to determine the process of energy loss when the density of the medium is large enough to break the correlations between partons emitted from the same parent. In order to improve existing calculations that consider eikonal trajectories for both the emitter and the hardest emitted parton, we provide in this work the calculation of all finite energy corrections for the gluon radiation off a quark in a QCD medium that exist in the small angle approximation and for static scattering centres. Using the path integral formalism, all particles are allowed to undergo Brownian motion in the transverse plane and the offspring is allowed to carry an arbitrary fraction of the initial energy. The result is a general expression that contains both coherence and decoherence regimes that are controlled by the density of the medium and by the amount of broadening that each parton acquires independently.

  7. Collisional energy losses in relativistic nuclear collisions within an effective quasiparticle model

    SciTech Connect

    Tarasov, Yu. A.

    2009-10-15

    We investigate the collisional energy losses of the fast gluons and light quarks in quark-gluon plasma produced in central (Au+Au) collisions at at energies currently available at the BNL Relativistic Heavy Ion Collider (RHIC) ({radical}(s{sub NN})=200 GeV). We use the effective quasiparticle model for investigation of physical characteristic of expanding plasma. We take into account the possibility of hot glue production at the first stage. We calculate these energy losses and compare them with radiative energy losses of gluons and quarks in an analogous model. We show that radiative energy losses exceed considerably the collisional energy losses.

  8. Magnetic circular dichroism in electron energy loss spectrometry.

    PubMed

    Hébert, C; Schattschneider, P; Rubino, S; Novak, P; Rusz, J; Stöger-Pollach, M

    2008-02-01

    The measurement of circular dichroism in the electron microscope is a new, emerging method and, as such, it is subject to constant refinement and improvement. Different ways can be envisaged to record the signal. We present an overview of the key steps in the energy-loss magnetic chiral dichroism (EMCD) experiment as well as a detailed review of the methods used in the intrinsic way where the specimen is used as a beam splitter. Lateral resolution up to 20-30 nm can be achieved, and the use of convergent beam techniques leads to an improved S/N ratio. Dichroic effects are shown for Ni and Co single crystal; as a counterexample, measurements were carried also for a non-magnetic (Ti) sample, where no dichroic effect was found.

  9. Electron-Energy-Loss Spectra of Free-Standing Silicene

    NASA Astrophysics Data System (ADS)

    Priede, Luis; Meza-Montes, Lilia; Gomez-Barojas, E.

    2013-03-01

    Silicene, the silicon-based counterpart of graphene, is increasingly getting attention because it is a semi-metal material with Dirac cones and thus, in principle, has similar electronic properties. In this work we calculated the Electron Energy Loss Spectrum (EELS) of ideal free-standing silicene. Dielectric function is obtained by using a discretization method as suggested by Delerue, et al.. Tight-binding method is applied considering 2nd Nearest Neighbors with sp2 orbitals, the Slater-Koster parameterization and the Harrison's rule. This has been done for plane and buckled silicon sheets, in the latter case with a structure based on DFT calculations. The resulting dielectric function is compared to those of bulk silicon and graphene. Spectra of EEELS are contrasted for plane and buckled silicene, particularly the plasmon frequency as a function of the z displacement of buckled silicene. Partially supported by Grant CB/2009/133516 CONACyT, Mexico.

  10. Jet energy loss and fragmentation in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Kharzeev, Dmitri E.; Loshaj, Frashër

    2013-04-01

    Recent LHC results indicate a suppression of jet fragmentation functions in Pb-Pb collisions at intermediate values of ξ=ln⁡(1/z). This seems to contradict the picture of energy loss based on the induced QCD radiation that is expected to lead to the enhancement of in-medium fragmentation functions. We use an effective 1+1 dimensional quasi-Abelian model to describe the dynamical modification of jet fragmentation in the medium. We find that this approach describes the data, and argue that there is no contradiction between the LHC results and the picture of QCD radiation induced by the in-medium scattering of the jet. The physics that underlies the suppression of the in-medium fragmentation function at intermediate values of ξ=ln⁡(1/z) is the partial screening of the color charge of the jet by the comoving medium-induced gluon.

  11. Energy summation method for energy loss computation in radial distribution networks

    SciTech Connect

    Taleski, R.; Rajicic, D.

    1996-05-01

    A method for energy loss calculation in radial distribution networks is presented. It is based on the statistical representation of the influence of different load curves in the network upon element power flows and on the oriented ordering of the network elements. Also, the paper proposes the use of different, but constant, voltages at each node, instead of nominal voltage at all nodes. The procedure is very simple, and it involves four steps: element ordering, calculation of second moments, power flow calculation with average loads at nodes, and energy calculation in network elements. The presented results illustrate that the algorithm has advantages over methods that use nominal voltage at each node for accuracy, and advantages over methods that calculate accurate energy losses for speed.

  12. Energy loss mechanics in the erosion of cemented tungsten carbide

    SciTech Connect

    Freinkel, D.M. ); Luyckx, S.B. )

    1989-05-01

    The erosion of tungsten carbide has been studied by several researchers under various conditions: the cobalt content of the cemented carbide has been varied from 4.5 to 11.3 wt % Co, the size of the WC grains varied from 0.9 to 5.1 {mu}m, the size of the erodant particles varied from 30 to 630 {mu}m, the velocity of the particles varied from 30 to 507 m/s, and particle incidence angle varied from 15{degrees} to 90{degrees}. While it is generally agreed that with increasing cobalt content and increasing particle velocity the erosion rate of WC-Co increases, there is disagreement on the effect of grain size and angle of incidence. More work was clearly required to explain this disagreement, thus the present investigation was undertaken. The present work differs from previous experimental work in that the erodant particles are 4 mm average diameter and that the present investigation does not neglect the role of plastic deformation in the erosion process and the energy lost in damage to the erodant particles. These two additional energy loss mechanisms have been found to contribute significantly to the interpretation of the present results and of the results previously reported in the literature.

  13. Rotational Spectroscopy of the Lowest Energy Conformer of 2-Cyanobutane.

    PubMed

    Müller, Holger S P; Zingsheim, Oliver; Wehres, Nadine; Grabow, Jens-Uwe; Lewen, Frank; Schlemmer, Stephan

    2017-09-28

    Isopropyl cyanide was recently detected in space as the first branched alkyl compound. Its abundance with respect to n-propyl cyanide in the Galactic center source Sagittarius B2(N2) is about 0.4. Astrochemical model calculations suggest that for the heavier homologue butyl cyanide the branched isomers dominate over the unbranched n-butyl cyanide and that 2-cyanobutane is the most abundant isomer. We have studied the rotational spectrum of 2-cyanobutane between 2 and 24 GHz using Fourier transform microwave spectroscopy and between 36 and 402 GHz employing (sub)millimeter absorption spectroscopy. Transitions of the lowest energy conformer were identified easily. Its rotational spectrum is very rich, and the quantum numbers J and Ka reach values of 111 and 73, respectively. This wealth of data yielded rotational and centrifugal distortion parameters up to tenth order, diagonal and one off-diagonal (14)N nuclear quadrupole coupling parameters, and one nuclear spin-rotation coupling parameter. We have also carried out quantum chemical calculations in part to facilitate the assignments. The molecule 2-cyanobutane was not found in the present ALMA data of Sagittarius B2(N2), but it may be found in the more sensitive data that have been completed very recently in the ALMA Cycle 4.

  14. High energy resolution off-resonant spectroscopy: A review

    NASA Astrophysics Data System (ADS)

    Błachucki, Wojciech; Hoszowska, Joanna; Dousse, Jean-Claude; Kayser, Yves; Stachura, Regina; Tyrała, Krzysztof; Wojtaszek, Klaudia; Sá, Jacinto; Szlachetko, Jakub

    2017-10-01

    We review the high energy resolution off-resonant spectroscopy (HEROS) technique. HEROS probes the unoccupied electronic states of matter in a single-shot manner thanks to the combination of off-resonant excitation around atomic core states using wavelength dispersive X-ray detection setups. In this review we provide a general introduction to the field of X-ray spectroscopy together with the specification of the available X-ray techniques and X-ray methodologies. Next, the theoretical description of the HEROS approach is introduced with a special focus on the derivation of the X-ray emission and X-ray absorption correspondence relation at off-resonant excitation conditions. Finally, a number of experimental HEROS reports are reviewed in the field of chemistry and material science. We emphasize the applicability of HEROS to pulsed X-ray sources, like X-ray free electron lasers, and support the review with experimental examples. The review is complemented with perspectives on and possible further applications of the HEROS technique to the field of X-ray science.

  15. Spectroscopy of low energy solar neutrinos by MOON

    NASA Astrophysics Data System (ADS)

    Hazama, R.; Doe, P.; Ejiri, H.; Elliott, S. R.; Engel, J.; Finger, M.; Formaggio, J. A.; Fushimi, K.; Gehman, V.; Gorin, A.; Greenfield, M.; Ichihara, K.; Ikegami, Y.; Ishii, H.; Itahashi, T.; Kavitov, P.; Kekelidze, V.; Kuroda, K.; Kutsalo, V.; Manouilov, I.; Matsuoka, K.; Nakamura, H.; Nomachi, M.; Para, A.; Rielage, K.; Rjazantsev, A.; Robertson, R. G. H.; Shichijo, Y.; Shima, T.; Shimada, Y.; Shirkov, G.; Sissakian, A.; Sugaya, Y.; Titov, A.; Vatulin, V.; Vilches, O. E.; Voronov, V.; Wilkerson, J. F.; Will, D. I.; Yoshida, S.

    2005-01-01

    The MOON (Molybdenum Observatory Of Neutrinos) project aims at high sensitive studies of the double beta (ββ) decays with sensitivity to Majorana ν mass of the order of ˜0.03 eV and the charged-current (CC) neutrino spectroscopy of the major components of the pp and 7Be solar ν's. The present status of MOON for the low energy solar ν experiment is briefly discussed. The inverse β rays from solar-ν captures of 100Mo are measured in delayed coincidence with the subsequent β decay of 100Tc. MOON's exclusive CC value by 7Be solar ν, together with the GNO CC data, will provide the pp solar ν flux with good accuracy.

  16. Constraints on dark energy with the LOSS SN Ia sample

    NASA Astrophysics Data System (ADS)

    Ganeshalingam, Mohan; Li, Weidong; Filippenko, Alexei V.

    2013-08-01

    We present a cosmological analysis of the Lick Observatory Supernova Search (LOSS) Type Ia supernova (SN Ia) photometry sample introduced by Ganeshalingam et al. These supernovae (SNe) provide an effective anchor point to estimate cosmological parameters when combined with data sets at higher redshift. The data presented by Ganeshalingam et al. have been rereduced in the natural system of the Katzman Automatic Imaging Telescope (KAIT) and Nickel telescopes to minimize systematic uncertainties. We have run the light-curve-fitting software SALT2 on our natural-system light curves to measure light-curve parameters for LOSS light curves and available SN Ia data sets in the literature. We present a Hubble diagram of 586 SNe in the redshift range z = 0.01-1.4 with a residual scatter of 0.176 mag. Of the 226 low-z SNe Ia in our sample, 91 objects are from LOSS, including 45 without previously published distances. Assuming a flat Universe, we find that the best fit for the dark energy equation-of-state parameter w = -0.86^{+0.13}_{-0.16} (stat) ±0.11 (sys) from SNe alone, consistent with a cosmological constant. Our data prefer a Universe with an accelerating rate of expansion with 99.999 per cent confidence. When looking at Hubble residuals as a function of host-galaxy morphology, we do not see evidence for a significant trend, although we find a somewhat reduced scatter in Hubble residuals from SNe residing within a projected distance <10 kpc of the host-galaxy nucleus (σ = 0.156 mag). Similar to the results of Blondin, Mandel and Kirshner and Silverman et al., we find that Hubble residuals do not correlate with the expansion velocity of Si II λ6355 measured in optical spectra near maximum light. Our data are consistent with no presence of a local `Hubble bubble.' Improvements in cosmological analyses within low-z samples can be achieved by better constraining calibration uncertainties in the zero-points of photometric systems.

  17. Elemental electron energy loss mapping of a precipitate in a multi-component aluminium alloy.

    PubMed

    Mørtsell, Eva A; Wenner, Sigurd; Longo, Paolo; Andersen, Sigmund J; Marioara, Calin D; Holmestad, Randi

    2016-07-01

    The elemental distribution of a precipitate cross section, situated in a lean Al-Mg-Si-Cu-Ag-Ge alloy, has been investigated in detail by electron energy loss spectroscopy (EELS) and aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). A correlative analysis of the EELS data is connected to the results and discussed in detail. The energy loss maps for all relevant elements were recorded simultaneously. The good spatial resolution allows elemental distribution to be evaluated, such as by correlation functions, in addition to being compared with the HAADF image. The fcc-Al lattice and the hexagonal Si-network within the precipitates were resolved by EELS. The combination of EELS and HAADF-STEM demonstrated that some atomic columns consist of mixed elements, a result that would be very uncertain based on one of the techniques alone. EELS elemental mapping combined with a correlative analysis have great potential for identification and quantification of small amounts of elements at the atomic scale.

  18. Detection of photosynthetic energy storage in a photosystem I reaction center preparation by photoacoustic spectroscopy.

    PubMed

    Owens, T G; Carpentier, R; Leblanc, R M

    1990-06-01

    Thermal emission and photochemical energy storage were examined in photosystem I reaction center/core antenna complexes (about 40 Chl a/P700) using photoacoustic spectroscopy. Satisfactory signals could only be obtained from samples bound to hydroxyapatite and all samples had a low signal-to-noise ratio compared to either PS I or PS II in thylakoid membranes. The energy storage signal was saturated at low intensity (half saturation at 1.5 W m(-2)) and predicted a photochemical quantum yield of >90%. Exogenous donors and acceptors had no effect on the signal amplitudes indicating that energy storage is the result of charge separation between endogenous components. Fe(CN)6 (-3) oxidation of P700 and dithionite-induced reduction of acceptors FA-FB inhibited energy storage. These data are compatible with the hypothesis that energy storage in PS I arises from charge separation between P700 and Fe-S centers FA-FB that is stable on the time scale of the photoacoustic modulation. High intensity background light (160 W m(-2)) caused an irreversible loss of energy storage and correlated with a decrease in oxidizable P700; both are probably the result of high light-induced photoinhibition. By analogy to the low fluorescence yield of PS I, the low signal-to-noise ratio in these preparations is attributed to the short lifetime of Chl singlet excited states in PS I-40 and its indirect effect on the yield of thermal emission.

  19. Daily energy expenditure, physical activity, and weight loss in Parkinson's disease patients

    USDA-ARS?s Scientific Manuscript database

    Patients with Parkinson's disease (PD) commonly exhibit weight loss (WL) which investigators attribute to various factors, including elevated energy expenditure. We tested the hypothesis that daily energy expenditure (DEE) and its components, resting energy expenditure (REE) and physical activity (P...

  20. Daily energy expenditure and physical activity measured in Parkinson's disease patients with and without weight loss

    USDA-ARS?s Scientific Manuscript database

    Patients with Parkinson's disease (PD) commonly exhibit weight loss, which investigators attribute to various factors, including elevated resting energy expenditure. We tested the hypothesis that daily energy expenditure (DEE) and its components, resting energy expenditure (REF) and physical activit...

  1. Parametric study of minimum converter loss in an energy-storage dc-to-dc converter

    NASA Technical Reports Server (NTRS)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

    1982-01-01

    Through a combination of analytical and numerical minimization procedures, a converter design that results in the minimum total converter loss (including core loss, winding loss, capacitor and energy-storage-reactor loss, and various losses in the semiconductor switches) is obtained. Because the initial phase involves analytical minimization, the computation time required by the subsequent phase of numerical minimization is considerably reduced in this combination approach. The effects of various loss parameters on the optimum values of the design variables are also examined.

  2. EMPIRICAL DETERMINATION OF THE ENERGY LOSS RATE OF ACCELERATED ELECTRONS IN A WELL-OBSERVED SOLAR FLARE

    SciTech Connect

    Torre, Gabriele; Pinamonti, Nicola; Guo, Jingnan; Piana, Michele; Emslie, A. Gordon; Massone, Anna Maria E-mail: pinamont@dima.unige.it E-mail: piana@dima.unige.it E-mail: annamaria.massone@cnr.it

    2012-06-01

    We present electron images of an extended solar flare source, deduced from RHESSI hard X-ray imaging spectroscopy data. We apply the electron continuity equation to these maps in order to determine empirically the form of the energy loss rate for the bremsstrahlung-emitting electrons. We show that this form is consistent with an energy transport model involving Coulomb collisions in a target with a temperature of about 2 Multiplication-Sign 10{sup 7} K, with a continuous injection of fresh deka-keV electrons at a rate of approximately 10{sup -2} electrons s{sup -1} per ambient electron.

  3. Comparing the rates of absorption and weight loss during a desorption test using near infrared spectroscopy.

    PubMed

    Qassem, M; Kyriacou, P A

    2013-05-01

    The importance of determining skin hydration has over the years prompt the development of many instruments and methods, specifically designed to assess this parameter or water contents especially in the stratum corneum, and have greatly matured to suit different anatomical sites and measure multiple attributes. Of those, Near Infrared Spectroscopy (NIRS) has gained wide interest as a precise, safe, fast and noninvasive technique for determining skin hydration due to its high sensitivity to hydrogen bonding and ability to measure the amount of water in skin directly using the intensities of overtone and combination bands of OH and HOH water bonds occurring in the NIR region, that are good indicators of the state of skin hydration. This paper reports near infrared spectrophotometric measurements using a highly sophisticated spectrophotometer in the region of 1000-2500 nm to study the water uptake and dehydration properties of skin in vitro using samples of porcine skin. Initial results of pure liquid water and skin samples have clearly displayed the prominent bands associated with water content, and desorption tests have been able to verify changes in these bands associated with water content, although a clear correlation between the rates of weight loss and absorbance loss at various hydration periods has not yet been established. These preliminary results are expected to further explain the relationship between water and skin, and its role within, in hope to aid the future development of a portable instrument based on near infrared spectroscopy that would be capable of directly measuring skin hydration and/or water content in a fast and noninvasive manner.

  4. High energy cosmic ray spectroscopy. I. Status and prospects

    NASA Astrophysics Data System (ADS)

    Erlykin, A. D.; Wolfendale, A. W.

    1997-06-01

    In a recent paper ( Nature, 1996, submitted) we claimed that the 'bump' in the extensive air shower size spectrum near 10 6 particles is due to heavy nuclei from a comparatively local 'source'. The energy spectrum of this single source is of the shape advocated by Berezhko et al. (JETP 82 (1996) 1) for supernova remnants (SNR) and is characterized by, approximately, an E-2 spectrum up to an energy Emax followed by a rapid fall above. The SNR model makes specific predictions for Emax as a function of nuclear charge. If, as is likely, the CR nuclei are fully ionized, we must identify the 'bump' in the paper submitted to Nature with the CNO group of nuclei. We have, accordingly, searched for the corresponding bump due to iron at a bigger shower size. Analysis of the world's data so far leads us to claim its detection, although not, yet, at as high a level of significance as the first bump. Prospects for augmenting the size spectrum technique, for studying what we call this new branch of spectroscopy, are examined.

  5. High energy resolution bandpass photon detector for inverse photoemission spectroscopy.

    PubMed

    Maniraj, M; D'Souza, S W; Nayak, J; Rai, Abhishek; Singh, Sanjay; Sekhar, B N Raja; Barman, S R

    2011-09-01

    We report a bandpass ultraviolet photon detector for inverse photoemission spectroscopy with energy resolution of 82 ± 2 meV. The detector (Sr(0.7)Ca(0.3)F(2)/acetone) consists of Sr(0.7)Ca(0.3)F(2) entrance window with energy transmission cutoff of 9.85 eV and acetone as detection gas with 9.7 eV photoionization threshold. The response function of the detector, measured using synchrotron radiation, has a nearly Gaussian shape. The n = 1 image potential state of Cu(100) and the Fermi edge of silver have been measured to demonstrate the improvement in resolution compared to the CaF(2)/acetone detector. To show the advantage of improved resolution of the Sr(0.7)Ca(0.3)F(2)/acetone detector, the metal to semiconductor transition in Sn has been studied. The pseudogap in the semiconducting phase of Sn could be identified, which is not possible with the CaF(2)/acetone detector because of its worse resolution. © 2011 American Institute of Physics

  6. Modeling heavy ion ionization energy loss at low and intermediate energies

    SciTech Connect

    Rakhno, I.L.; /Fermilab

    2009-11-01

    The needs of contemporary accelerator and space projects led to significant efforts made to include description of heavy ion interactions with matter in general-purpose Monte Carlo codes. This paper deals with an updated model of heavy ion ionization energy loss developed previously for the MARS code. The model agrees well with experimental data for various projectiles and targets including super-heavy ions in low-Z media.

  7. Adriatic seiche decay and energy loss to the Mediterranean

    NASA Astrophysics Data System (ADS)

    Cerovečki, Ivana; Orlić, Mirko; Hendershott, Myrl C.

    1997-12-01

    work are as follows. (1) Exponential decay of seiche amplitude with time does not necessarily guarantee that the observed decay is free of wind influence. (2) Winds blowing across the Adriatic may be of comparable importance to winds blowing along the Adriatic in influencing apparent decay of seiches; across-basin winds are probably coupled to the longitudinal seiche on account of the strong along-basin variability of across-basin winds forced by Croatian coastal orography. (3) The free decay time of the 21.2 h Adriatic seiche is 3.2±0.5 d. (4) A one dimensional shallow water model of the seiche damped by bottom stress represented by Godin's (1988) approximation to the quadratic bottom friction law ρ0CDu| u| using the commonly accepted drag coefficient CD = 0.0015 and quantitative estimates of bottom currents associated with wind driven currents, tides and wind waves, as well as with the seiche itself with no radiation gives a damping time of 9.46 d; radiation sufficient to give the observed damping time must then account for 66% of the energy loss per period. But independent estimates of bottom friction for Adriatic wind driven currents and inertial oscillations, as well as comparisons between quadratic law bottom stress and directly measured bottom stress, all suggest that the quadratic law with CD=0.0015 substantially underestimates the bottom stress. Based on these studies, a more appropriate value of the drag coefficient is at least CD=0. In this case, bottom friction with no radiation leads to a damping time of 4.73 d, radiation sufficient to give the observed damping time then accounts for 32% of the energy loss per period.

  8. Energy loss of heavy quarks and B and D meson spectra in PbPb collisions at LHC energies

    NASA Astrophysics Data System (ADS)

    Saraswat, Kapil; Shukla, Prashant; Kumar, Vineet; Singh, Venktesh

    2017-05-01

    We study the production and evolution of charm and bottom quarks in hot partonic medium produced in heavy ion collisions. The heavy quarks loose energy in the medium which is reflected in the transverse momentum spectra of heavy mesons. The collisional energy loss of heavy quarks has been calculated using QCD calculations. The radiative energy loss is obtained using two models namely reaction operator formalism and generalized dead cone approach. The nuclear modification factors, RAA as a function of transverse momentum by including shadowing and energy loss are calculated for D0 and B+ mesons in PbPb collisions at √{sNN} = 5.02 TeV and for D0 mesons at √{sNN} = 2.76 TeV and are compared with the recent measurements. The radiative energy loss from generalized dead cone approach alone is sufficient to produce measured D0 meson RAA at both the LHC energies. The radiative energy loss from reaction operator formalism plus collisional energy loss gives good description of D0 meson RAA. For the case of B+ meson, the radiative energy loss from generalized dead cone approach plus collisional energy loss gives good description of the CMS data. The radiative process is dominant for charm quarks while for the bottom, both the radiative process and the elastic collisions are important.

  9. Optical spectroscopy and energy-filtered transmission electron microscopy of surface plasmons in core-shell nanoparticles.

    SciTech Connect

    Eggeman, A. S.; Dobson, P. J.; Petford-Long, A. K.; Materials Science Division; Oxford Univ.

    2007-01-01

    Silica-silver core-shell nanoparticles were produced using colloidal chemistry methods. Surface plasmon resonances in the silver shells were investigated using optical absorption measurements in ultraviolet-to-visible (UV-vis) spectroscopy and the effect of shell thickness on the wavelength of the resonance was noted. Further studies of the resonances were performed using electron-energy-loss spectroscopy (EELS) and energy-filtered transmission electron microscope (EFTEM) imaging. The plasmon resonance was seen in an EELS spectrum at an energy corresponding to the wavelengths measured in an UV-vis spectrophotometer, and EFTEM images confirmed that the resonance was indeed localized at the surface of the silver shell. Further features were seen in the EELS spectrum and confirmed as bulk-plasmon features of silica and the carbon support film in the TEM specimen.

  10. Bipolar energy-loss measurements on cryostable, low-loss conductors

    NASA Astrophysics Data System (ADS)

    Wollan, J. J.

    1981-11-01

    Losses have been measured on a prototype conductor for the 20 MJ coil for conditions which simulate closely the actual coil field sweep. The data on the prototype II conductor indicates coil losses which exceed the coil specification. The application of certain correction factors reduces the projected losses within the specification for a 2 s reversal but not for a 1 s reversal. Verification of these corrections await measurements on the actual strand and completion of coil construction and testing.

  11. Electron structure of excited configurations in Ca2V2O7 studied by electron-induced core-ionization loss spectroscopy, appearance-potential spectroscopy, and x-ray-photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Curelaru, I. M.; Strid, K.-G.; Suoninen, E.; Minni, E.; Rönnhult, T.

    1981-04-01

    We have measured the electron-induced core-ionization loss (CILS) spectra, the appearance-potential (APS) spectra, and the x-ray-photoelectron (XPS) spectra of Ca2V2O7, that is a prototype for a series of luminescent materials with general formula M2V2O7(M=Mg, Ca, Sr, Ba, Zn, Cd, Hg). From the analysis of the data provided by the edge spectroscopies (CILS and APS) and their comparison with the XPS binding energies, we deduced the electronic structure of the outer orbitals (occupied and empty) involved in these processes. Our data illustrate the strong many-body effects that occur in the excitation and decay of localized atomiclike configurations within the big ionic cluster V2O4-7. Excitation of core levels in calcium, outside the V2O4-7 ion, seems to involve more extended orbitals, since the screening is more efficient. Usefulness of complementary studies by x-ray emission and Auger electron spectroscopy is anticipated.

  12. Charge exchange and energy loss of slow highly charged ions in 1 nm thick carbon nanomembranes.

    PubMed

    Wilhelm, Richard A; Gruber, Elisabeth; Ritter, Robert; Heller, René; Facsko, Stefan; Aumayr, Friedrich

    2014-04-18

    Experimental charge exchange and energy loss data for the transmission of slow highly charged Xe ions through ultrathin polymeric carbon membranes are presented. Surprisingly, two distinct exit charge state distributions accompanied by charge exchange dependent energy losses are observed. The energy loss for ions exhibiting large charge loss shows a quadratic dependency on the incident charge state indicating that equilibrium stopping force values do not apply in this case. Additional angle resolved transmission measurements point on a significant contribution of elastic energy loss. The observations show that regimes of different impact parameters can be separated and thus a particle's energy deposition in an ultrathin solid target may not be described in terms of an averaged energy loss per unit length.

  13. Oxygen-induced changes in electron-energy-loss spectra for Al, Be and Ni. [Al; Be; Ni

    SciTech Connect

    Madden, H.H.; Landers, R.; Kleiman, G.G. , 13081-970 Campinas, Sao Paulo, Brasil); Zehner, D.M. )

    1999-09-01

    Electron-energy-loss spectroscopy (EELS) data are presented to illustrate line shape changes that occur as a result of oxygen interaction with metal surfaces. The metals were aluminum, beryllium and nickel. Core-level EELS data were taken for excitations from Al(2p), Be(1s), Ni(3p/3s) and O(1s) levels to the conduction band (CB) density of states (DOS) of the materials. The primary beam energies for the spectra were 300, 450, 300, and 1135 eV, respectively. The data are presented in both the (as measured) first-derivative and the integral forms. The integral spectra were corrected for coherent background losses and analyzed for CB DOS information. These spectra were found to be in qualitative agreement with published experimental and theoretical studies of these materials. One peak in the spectra for Al oxide is analyzed for its correlation with excitonic screening of the Al(2p) core hole. Similar evidence for exciton formation is found in the Ni(3p) spectra for Ni oxide. Data are also presented showing oxygen-induced changes in the lower-loss-energy EELS curves that, in the pure metal, are dominated by plasmon-loss and interband-transition signals. Single-scattering loss profiles in the integral form of the data were calculated using a procedure of Tougaard and Chorkendorff [S. Tougaard and I. Chorkendorff, Phys. Rev. B. [bold 35], 6570 (1987)]. For all three oxides these profiles are dominated by a feature with a loss energy of around 20[endash]25 eV. Although this feature has been ascribed by other researchers as due to bulk plasmon losses in the oxide, an alternative explanation is that the feature is simply due to O(2s)-to-CB-level excitations. An even stronger feature is found at 7 eV loss energy for Ni oxide. Speculation is given as to its source. The line shapes in both the core-level and noncore-level spectra can also be used simply as [open quotes]fingerprints[close quotes] of the surface chemistry of the materials. Our data were taken using commercially

  14. Stellar energy loss rates in the pair-annihilation process beyond the standard model

    NASA Astrophysics Data System (ADS)

    Hernández-Ruíz, M. A.; Gutiérrez-Rodríguez, A.; González-Sánchez, A.

    2017-01-01

    We calculate the stellar energy loss due to neutrino-pair production in e+e- annihilation in the context of a 331 model, a left-right symmetric model and a simplest little Higgs model in a way that can be used in supernova calculations. We also present some simple estimates which show that such process can act as an efficient energy loss mechanism in the shocked supernova core. We find that the stellar energy loss is almost independent of the parameters of the models in the allowed range for these parameters. This work complements other studies on the stellar energy loss rate in e+e- annihilation.

  15. Nonlinear effects in the energy loss of a slow dipole in a free-electron gas

    SciTech Connect

    Alducin, M.; Juaristi, J.I.

    2002-11-01

    We analyze beyond linear-response theory the energy loss of a slow dipole moving inside a free-electron gas. The energy loss is obtained from a nonlinear treatment of the scattering of electrons at the dipole-induced potential. This potential and the total electronic density are calculated with density-functional theory. We focus on the interference effects, i.e., the difference between the energy loss of a dipole and that of the isolated charges forming it. Comparison of our results to those obtained in linear-response theory shows that a nonlinear treatment of the screening is required to accurately describe the energy loss of slow dipoles.

  16. Derivation of dielectric function and inelastic mean free path from photoelectron energy-loss spectra of amorphous carbon surfaces

    NASA Astrophysics Data System (ADS)

    David, Denis; Godet, Christian

    2016-11-01

    Photoelectron Energy Loss Spectroscopy (PEELS) is a highly valuable non destructive tool in applied surface science because it gives access to both chemical composition and electronic properties of surfaces, including the near-surface dielectric function. An algorithm is proposed for real materials to make full use of experimental X-ray photoelectron spectra (XPS). To illustrate the capabilities and limitations of this algorithm, the near-surface dielectric function ε(ℏω) of a wide range of amorphous carbon (a-C) thin films is derived from energy losses measured in XPS, using a dielectric response theory which relates ε(ℏω) and the bulk plasmon (BP) loss distribution. Self-consistent separation of bulk vs surface plasmon excitations, deconvolution of multiple BP losses and evaluation of Bethe-Born sensitivity factors for bulk and surface loss distributions are crucial to obtain several material parameters: (1) energy loss function for BP excitation, (2) dielectric function of the near-surface material (3-5 nm depth sensitivity), (3) inelastic mean free path, λP (E0), for plasmon excitation, (4) surface excitation parameter, (5) effective number NEFF of valence electrons participating in the plasma oscillation. This photoelectron energy loss spectra analysis has been applied to a-C and a-C:H films grown by physical and chemical methods with a wide range of (sp3/sp2 + sp3) hybridization, optical gap and average plasmon energy values. Different methods are assessed to accurately remove the photoemission peak tail at low loss energy (0-10 eV) due to many-body interactions during the photo-ionization process. The σ + π plasmon excitation represents the main energy-loss channel in a-C; as the C atom density decreases, λP (970 eV) increases from 1.22 nm to 1.6 nm, assuming a cutoff plasmon wavenumber given by a free electron model. The π-π* and σ-σ* transitions observed in the retrieved dielectric function are discussed as a function of the average (sp3/sp

  17. Self-Directed Weight Loss Strategies: Energy Expenditure Due to Physical Activity Is Not Increased to Achieve Intended Weight Loss.

    PubMed

    Elbelt, Ulf; Schuetz, Tatjana; Knoll, Nina; Burkert, Silke

    2015-07-16

    Reduced physical activity and almost unlimited availability of food are major contributors to the development of obesity. With the decline of strenuous work, energy expenditure due to spontaneous physical activity has attracted increasing attention. Our aim was to assess changes in energy expenditure, physical activity patterns and nutritional habits in obese subjects aiming at self-directed weight loss. Energy expenditure and physical activity patterns were measured with a portable armband device. Nutritional habits were assessed with a food frequency questionnaire. Data on weight development, energy expenditure, physical activity patterns and nutritional habits were obtained for 105 patients over a six-month period from an initial cohort of 160 outpatients aiming at weight loss. Mean weight loss was -1.5 ± 7.0 kg (p = 0.028). Patients with weight maintenance (n = 75), with substantial weight loss (>5% body weight, n = 20) and with substantial weight gain (>5% body weight, n = 10) did not differ in regard to changes of body weight adjusted energy expenditure components (total energy expenditure: -0.2 kcal/kg/day; non-exercise activity thermogenesis: -0.3 kcal/kg/day; exercise-related activity thermogenesis (EAT): -0.2 kcal/kg/day) or patterns of physical activity (duration of EAT: -2 min/day; steps/day: -156; metabolic equivalent unchanged) measured objectively with a portable armband device. Self-reported consumption frequency of unfavorable food decreased significantly (p = 0.019) over the six-month period. An increase in energy expenditure or changes of physical activity patterns (objectively assessed with a portable armband device) are not employed by obese subjects to achieve self-directed weight loss. However, modified nutritional habits could be detected with the use of a food frequency questionnaire.

  18. Self-Directed Weight Loss Strategies: Energy Expenditure Due to Physical Activity Is Not Increased to Achieve Intended Weight Loss

    PubMed Central

    Elbelt, Ulf; Schuetz, Tatjana; Knoll, Nina; Burkert, Silke

    2015-01-01

    Reduced physical activity and almost unlimited availability of food are major contributors to the development of obesity. With the decline of strenuous work, energy expenditure due to spontaneous physical activity has attracted increasing attention. Our aim was to assess changes in energy expenditure, physical activity patterns and nutritional habits in obese subjects aiming at self-directed weight loss. Methods: Energy expenditure and physical activity patterns were measured with a portable armband device. Nutritional habits were assessed with a food frequency questionnaire. Results: Data on weight development, energy expenditure, physical activity patterns and nutritional habits were obtained for 105 patients over a six-month period from an initial cohort of 160 outpatients aiming at weight loss. Mean weight loss was −1.5 ± 7.0 kg (p = 0.028). Patients with weight maintenance (n = 75), with substantial weight loss (>5% body weight, n = 20) and with substantial weight gain (>5% body weight, n = 10) did not differ in regard to changes of body weight adjusted energy expenditure components (total energy expenditure: −0.2 kcal/kg/day; non-exercise activity thermogenesis: −0.3 kcal/kg/day; exercise-related activity thermogenesis (EAT): −0.2 kcal/kg/day) or patterns of physical activity (duration of EAT: −2 min/day; steps/day: −156; metabolic equivalent unchanged) measured objectively with a portable armband device. Self-reported consumption frequency of unfavorable food decreased significantly (p = 0.019) over the six-month period. Conclusions: An increase in energy expenditure or changes of physical activity patterns (objectively assessed with a portable armband device) are not employed by obese subjects to achieve self-directed weight loss. However, modified nutritional habits could be detected with the use of a food frequency questionnaire. PMID:26193310

  19. Theory of highly charged ion energy gain spectroscopy of molecular collective excitations

    NASA Astrophysics Data System (ADS)

    Lucas, A. A.; Benedek, G.; Sunjic, M.; Echenique, P. M.

    2011-01-01

    This paper discusses the physical mechanism by which a highly charged, energetic ion partly neutralized by electron transfers from a target—a large molecule, a cluster or a solid surface—can create target collective excitations in the process. We develop an analysis for the system of a highly charged ion flying by a fullerene molecule. Our analysis offers a new explanation for the periodic oscillations observed in the high-resolution energy gain spectra of energetic Arq+ ions (q=8, 13, 14, 15) flying by C60 molecules. For the Arq+→Ar(q-s)+ spectra with q=13-15 and s=1 or 2, the observed oscillations of 6 eV periodicity are assigned to energy losses due to multiple, Poissonian excitations of C60 π-plasmons (6 eV quantum). The excitation energy quanta are subtracted from the kinetic energy gained by the ion when one or at most two electrons are transferred to increasingly deep Rydberg states of the ion. The observed 3 eV periodicity for q=8 arises from the specific Rydberg energy levels of ArVIII (Ar7+). The first few shallow levels of this ion are separated by about 3 eV, while some of the pairs of adjacent, deeper levels are also separated by 3 eV. Each deep-level pair produces two interdigitated, Poissonian series of 6 eV π-plasmon excitation peaks resulting in an apparent periodicity of 3 eV throughout the spectra. The broad σ-plasmons (25 eV quantum) are found to contribute a background continuum to the medium- and high-energy regions of the observed spectra. The physical model analyzed here indicates that electronic collective excitations in several other systems could be studied by highly charged ion energy gain spectroscopy at sufficient resolution.

  20. Collisional Diffusion and Thick-Target Energy Losses in Solar Flares -- Death to the "Low-Energy Cufoff"

    NASA Astrophysics Data System (ADS)

    Emslie, Gordon; Bian, Nicolas; Jeffrey, Natasha; Kontar, Eduard

    2015-04-01

    We extend previous studies of nonthermal electron transport in solar flares by including the effects of collisional diffusion on the energy loss rate of the electron distribution as a whole. We conclude that previous estimates of electron energy loss, particularly at energies E ~ 10kT or less, have been greatly overestimated. Consequently the required number of electrons at the low-energy end of the accelerated electron spectrum, and concomitantly the overall energy content in the accelerated electrons, are significantly reduced. Use of an artificially-imposed ``low-energy cutoff'' in the accelerated spectrum is therefore not only unwarranted, but also unnecessary.

  1. Exploring energy loss by vector flow mapping in children with ventricular septal defect: Pathophysiologic significance.

    PubMed

    Honda, Takashi; Itatani, Keiichi; Takanashi, Manabu; Kitagawa, Atsushi; Ando, Hisashi; Kimura, Sumito; Oka, Norihiko; Miyaji, Kagami; Ishii, Masahiro

    2017-10-01

    Vector flow mapping is a novel echocardiographic flow visualization method, and it has enabled us to quantitatively evaluate the energy loss in the left ventricle (intraventricular energy loss). Although intraventricular energy loss is assumed to be a part of left ventricular workload itself, it is unclear what this parameter actually represents. The aim of the present study was to elucidate the characteristics of intraventricular energy loss. We enrolled 26 consecutive children with ventricular septal defect (VSD). On echocardiography vector flow mapping, intraventricular energy loss was measured in the apical 3-chamber view. We measured peak energy loss and averaged energy loss in the diastolic and systolic phases, and subsequently compared these parameters with catheterization parameters and serum brain natrium peptide (BNP) level. Diastolic, peak, and systolic energy loss were strongly and positively correlated with right ventricular systolic pressure (r=0.76, 0.68, and 0.56, p<0.0001, = 0.0001, and 0.0029, respectively) and right ventricular end diastolic pressure (r=0.55, 0.49, and 0.49, p=0.0038, 0.0120, and 0.0111, respectively). In addition, diastolic, peak, and systolic energy loss were significantly correlated with BNP (r=0.75, 0.69 and 0.49, p<0.0001, < 0.0001, and=0.0116, respectively). In children with VSD, elevated right ventricular pressure is one of the factors that increase energy loss in the left ventricle. The results of the present study encourage further studies in other study populations to elucidate the characteristics of intraventricular energy loss for its possible clinical application. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Probing the electronic and spintronic properties of buried interfaces by extremely low energy photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Fetzer, Roman; Stadtmüller, Benjamin; Ohdaira, Yusuke; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Aeschlimann, Martin; Cinchetti, Mirko

    2015-02-01

    Ultraviolet photoemission spectroscopy (UPS) is a powerful tool to study the electronic spin and symmetry features at both surfaces and interfaces to ultrathin top layers. However, the very low mean free path of the photoelectrons usually prevents a direct access to the properties of buried interfaces. The latter are of particular interest since they crucially influence the performance of spintronic devices like magnetic tunnel junctions (MTJs). Here, we introduce spin-resolved extremely low energy photoemission spectroscopy (ELEPS) to provide a powerful way for overcoming this limitation. We apply ELEPS to the interface formed between the half-metallic Heusler compound Co2MnSi and the insulator MgO, prepared as in state-of-the-art Co2MnSi/MgO-based MTJs. The high accordance between the spintronic fingerprint of the free Co2MnSi surface and the Co2MnSi/MgO interface buried below up to 4 nm MgO provides clear evidence for the high interface sensitivity of ELEPS to buried interfaces. Although the absolute values of the interface spin polarization are well below 100%, the now accessible spin- and symmetry-resolved wave functions are in line with the predicted existence of non-collinear spin moments at the Co2MnSi/MgO interface, one of the mechanisms evoked to explain the controversially discussed performance loss of Heusler-based MTJs at room temperature.

  3. Probing the electronic and spintronic properties of buried interfaces by extremely low energy photoemission spectroscopy

    PubMed Central

    Fetzer, Roman; Stadtmüller, Benjamin; Ohdaira, Yusuke; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Aeschlimann, Martin; Cinchetti, Mirko

    2015-01-01

    Ultraviolet photoemission spectroscopy (UPS) is a powerful tool to study the electronic spin and symmetry features at both surfaces and interfaces to ultrathin top layers. However, the very low mean free path of the photoelectrons usually prevents a direct access to the properties of buried interfaces. The latter are of particular interest since they crucially influence the performance of spintronic devices like magnetic tunnel junctions (MTJs). Here, we introduce spin-resolved extremely low energy photoemission spectroscopy (ELEPS) to provide a powerful way for overcoming this limitation. We apply ELEPS to the interface formed between the half-metallic Heusler compound Co2MnSi and the insulator MgO, prepared as in state-of-the-art Co2MnSi/MgO-based MTJs. The high accordance between the spintronic fingerprint of the free Co2MnSi surface and the Co2MnSi/MgO interface buried below up to 4 nm MgO provides clear evidence for the high interface sensitivity of ELEPS to buried interfaces. Although the absolute values of the interface spin polarization are well below 100%, the now accessible spin- and symmetry-resolved wave functions are in line with the predicted existence of non-collinear spin moments at the Co2MnSi/MgO interface, one of the mechanisms evoked to explain the controversially discussed performance loss of Heusler-based MTJs at room temperature. PMID:25702631

  4. Probing the electronic and spintronic properties of buried interfaces by extremely low energy photoemission spectroscopy.

    PubMed

    Fetzer, Roman; Stadtmüller, Benjamin; Ohdaira, Yusuke; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Aeschlimann, Martin; Cinchetti, Mirko

    2015-02-23

    Ultraviolet photoemission spectroscopy (UPS) is a powerful tool to study the electronic spin and symmetry features at both surfaces and interfaces to ultrathin top layers. However, the very low mean free path of the photoelectrons usually prevents a direct access to the properties of buried interfaces. The latter are of particular interest since they crucially influence the performance of spintronic devices like magnetic tunnel junctions (MTJs). Here, we introduce spin-resolved extremely low energy photoemission spectroscopy (ELEPS) to provide a powerful way for overcoming this limitation. We apply ELEPS to the interface formed between the half-metallic Heusler compound Co2MnSi and the insulator MgO, prepared as in state-of-the-art Co2MnSi/MgO-based MTJs. The high accordance between the spintronic fingerprint of the free Co2MnSi surface and the Co2MnSi/MgO interface buried below up to 4 nm MgO provides clear evidence for the high interface sensitivity of ELEPS to buried interfaces. Although the absolute values of the interface spin polarization are well below 100%, the now accessible spin- and symmetry-resolved wave functions are in line with the predicted existence of non-collinear spin moments at the Co2MnSi/MgO interface, one of the mechanisms evoked to explain the controversially discussed performance loss of Heusler-based MTJs at room temperature.

  5. Evaluation of economic loss from energy-related environmental pollution: a case study of Beijing

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Su, Meirong; Liu, Gengyuan; Yang, Zhifeng

    2013-09-01

    With the growth of energy consumption, energy-related environmental pollution has become increasingly serious, which in turn causes enormous economic loss because of public health damage, corrosion of materials, crop yield reduction, and other factors. Evaluating economic loss caused by energy-related environmental pollution can contribute to decision making in energy management. A framework for evaluating economic loss from environmental pollution produced during energy production, transportation, and consumption is proposed in this paper. Regarding SO2, PM10, and solid waste as the main pollutants, economic losses from health damage, materials corrosion, crop yield reduction, and solid waste pollution are estimated based on multiple concentration-response relationships and dose-response functions. The proposed framework and evaluation methods are applied to Beijing, China. It is evident that total economic loss attributable to energy-related environmental pollution fluctuated during 2000-2011 but had a general growth trend, with the highest value reaching 2.3 × 108 CNY (China Yuan) in 2006. Economic loss caused by health damage contributes most to the total loss among the four measured damage types. The total economic loss strongly correlates with the amount of energy consumption, especially for oil and electricity. Our evaluation framework and methods can be used widely to measure the potential impact of environmental pollution in the energy lifecycle.

  6. Energy loss of a heavy particle near 3D charged rotating hairy black hole

    NASA Astrophysics Data System (ADS)

    Naji, Jalil

    2014-01-01

    In this paper we consider a charged rotating black hole in three dimensions with a scalar charge and discuss the energy loss of a heavy particle moving near the black-hole horizon. We also study quasi-normal modes and find the dispersion relations. We find that the effect of scalar charge and electric charge increases the energy loss.

  7. Feasibility of investigating Smith-Purcell free-electron laser configurations by electron energy loss studies

    NASA Astrophysics Data System (ADS)

    Speller, L. C.; Thorpe, A. N.

    1986-06-01

    An electron beam of energies 20 - 25 KeV was passed over an optical metallic grating (600 lines/mm) and the energy loss spectrum was obtained. The loss peak values, determined to be between approx. (1.8 - 1.9eV), were in fair agreement with the predicted values. However, these results could not be reproduced.

  8. Effects of dietary composition of energy expenditure during weight-loss maintenance

    USDA-ARS?s Scientific Manuscript database

    Reduced energy expenditure following weight loss is thought to contribute to weight gain. However, the effect of dietary composition on energy expenditure during weight-loss maintenance has not been studied. To examine the effects of 3 diets differing widely in macronutrient composition and glycemic...

  9. Lifestyle modification to promote weight loss in the absence of energy restriction

    USDA-ARS?s Scientific Manuscript database

    With the obesity epidemic showing no signs of abating, there is ongoing interest in altering energy balance (i.e., decreasing energy intake and/or increasing energy expenditure) to promote weight, specifically fat, loss. However, short- and long-term outcomes of, and adherence to, decreasing energy ...

  10. Skipping meals and alcohol consumption. The regulation of energy intake and expenditure among weight loss participants.

    PubMed

    Carels, Robert A; Young, Kathleen M; Coit, Carissa; Clayton, Anna Marie; Spencer, Alexis; Wagner, Marissa

    2008-11-01

    Research suggests that specific eating patterns (e.g., eating breakfast) may be related to favorable weight status. This investigation examined the relationship between eating patterns (i.e., skipping meals; consuming alcohol) and weight loss treatment outcomes (weight loss, energy intake, energy expenditure, and duration of exercise). Fifty-four overweight or obese adults (BMI> or =27 kg/m(2)) participated in a self-help or therapist-assisted weight loss program. Daily energy intake from breakfast, lunch, dinner, and alcoholic beverages, total daily energy intake, total daily energy expenditure, physical activity, and weekly weight loss were assessed. On days that breakfast or dinner was skipped, or alcoholic beverages were not consumed, less total daily energy was consumed compared to days that breakfast, dinner, or alcoholic beverages were consumed. On days that breakfast or alcohol was consumed, daily energy expenditure (breakfast only) and duration of exercise were higher compared to days that breakfast or alcohol was not consumed. Individuals who skipped dinner or lunch more often had lower energy expenditure and exercise duration than individuals who skipped dinner or lunch less often. Individuals who consumed alcohol more often had high daily energy expenditure than individuals who consumed alcohol less often. Skipping meals or consuming alcoholic beverages was not associated with weekly weight loss. In this investigation, weight loss program participants may have compensated for excess energy intake from alcoholic beverages and meals with greater daily energy expenditure and longer exercise duration.

  11. The role of electronic energy loss in ion beam modification of materials

    DOE PAGES

    Weber, William J.; Duffy, Dorothy M.; Thome, Lionel; ...

    2014-10-05

    The interaction of energetic ions with solids results in energy loss to both atomic nuclei and electrons in the solid. In this article, recent advances in understanding and modeling the additive and competitive effects of nuclear and electronic energy loss on the response of materials to ion irradiation are reviewed. Experimental methods and large-scale atomistic simulations are used to study the separate and combined effects of nuclear and electronic energy loss on ion beam modification of materials. The results demonstrate that nuclear and electronic energy loss can lead to additive effects on irradiation damage production in some materials; while inmore » other materials, the competitive effects of electronic energy loss leads to recovery of damage induced by elastic collision cascades. Lastly, these results have significant implications for ion beam modification of materials, non-thermal recovery of ion implantation damage, and the response of materials to extreme radiation environments.« less

  12. The role of electronic energy loss in ion beam modification of materials

    SciTech Connect

    Weber, William J.; Duffy, Dorothy M.; Thome, Lionel; Zhang, Yanwen

    2014-10-05

    The interaction of energetic ions with solids results in energy loss to both atomic nuclei and electrons in the solid. In this article, recent advances in understanding and modeling the additive and competitive effects of nuclear and electronic energy loss on the response of materials to ion irradiation are reviewed. Experimental methods and large-scale atomistic simulations are used to study the separate and combined effects of nuclear and electronic energy loss on ion beam modification of materials. The results demonstrate that nuclear and electronic energy loss can lead to additive effects on irradiation damage production in some materials; while in other materials, the competitive effects of electronic energy loss leads to recovery of damage induced by elastic collision cascades. Lastly, these results have significant implications for ion beam modification of materials, non-thermal recovery of ion implantation damage, and the response of materials to extreme radiation environments.

  13. Resistant starch and energy balance: impact on weight loss and maintenance

    PubMed Central

    Higgins, Janine A.

    2013-01-01

    The obesity epidemic has prompted researchers to find effective weight loss and maintenance tools. Weight loss and subsequent maintenance are reliant on energy balance; the net difference between energy intake and energy expenditure. Negative energy balance, lower intake than expenditure, results in weight loss whereas positive energy balance, greater intake than expenditure, results in weight gain. Resistant starch has many attributes which could promote weight loss and/or maintenance including reduced prostprandial insulinemia, increased release of gut satiety peptides, increased fat oxidation, lower fat storage in adipocytes, and preservation of lean body mass. Retention of lean body mass during weight loss or maintenance would prevent the decrease in basal metabolic rate and, therefore, the decrease in total energy expenditure, that occurs with weight loss. In addition, the fiber-like properties of resistant starch may increase the thermic effect of food thereby increasing total energy expenditure. Due its ability to increase fat oxidation and reduce fat storage in adipocytes, resistant starch has recently been promoted in the popular press as a “weight loss wonder food”. This review focuses on data describing the effects of resistant starch on body weight, energy intake, energy expenditure, and body composition to determine if there is sufficient evidence to warrant these claims. PMID:24499148

  14. Resistant starch and energy balance: impact on weight loss and maintenance.

    PubMed

    Higgins, Janine A

    2014-01-01

    The obesity epidemic has prompted researchers to find effective weight-loss and maintenance tools. Weight loss and subsequent maintenance are reliant on energy balance--the net difference between energy intake and energy expenditure. Negative energy balance, lower intake than expenditure, results in weight loss whereas positive energy balance, greater intake than expenditure, results in weight gain. Resistant starch has many attributes, which could promote weight loss and/or maintenance including reduced postprandial insulinemia, increased release of gut satiety peptides, increased fat oxidation, lower fat storage in adipocytes, and preservation of lean body mass. Retention of lean body mass during weight loss or maintenance would prevent the decrease in basal metabolic rate and, therefore, the decrease in total energy expenditure, that occurs with weight loss. In addition, the fiber-like properties of resistant starch may increase the thermic effect of food, thereby increasing total energy expenditure. Due to its ability to increase fat oxidation and reduce fat storage in adipocytes, resistant starch has recently been promoted in the popular press as a "weight loss wonder food". This review focuses on data describing the effects of resistant starch on body weight, energy intake, energy expenditure, and body composition to determine if there is sufficient evidence to warrant these claims.

  15. Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Roy, Khokan; Kayal, Surajit; Ariese, Freek; Beeby, Andrew; Umapathy, Siva

    2017-02-01

    Femtosecond transient absorption (fs-TA) and Ultrafast Raman Loss Spectroscopy (URLS) have been applied to reveal the excited state dynamics of bis(phenylethynyl)benzene (BPEB), a model system for one-dimensional molecular wires that have numerous applications in opto-electronics. It is known from the literature that in the ground state BPEB has a low torsional barrier, resulting in a mixed population of rotamers in solution at room temperature. For the excited state this torsional barrier had been calculated to be much higher. Our femtosecond TA measurements show a multi-exponential behaviour, related to the complex structural dynamics in the excited electronic state. Time-resolved, excited state URLS studies in different solvents reveal mode-dependent kinetics and picosecond vibrational relaxation dynamics of high frequency vibrations. After excitation, a gradual increase in intensity is observed for all Raman bands, which reflects the structural reorganization of Franck-Condon excited, non-planar rotamers to a planar conformation. It is argued that this excited state planarization is also responsible for its high fluorescence quantum yield. The time dependent peak positions of high frequency vibrations provide additional information: a rapid, sub-picosecond decrease in peak frequency, followed by a slower increase, indicates the extent of conjugation during different phases of excited state relaxation. The CC triple (-C≡C-) bond responds somewhat faster to structural reorganization than the CC double (>C=C<) bonds. This study deepens our understanding of the excited state of BPEB and analogous linear pi-conjugated systems and may thus contribute to the advancement of polymeric "molecular wires."

  16. Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy.

    PubMed

    Roy, Khokan; Kayal, Surajit; Ariese, Freek; Beeby, Andrew; Umapathy, Siva

    2017-02-14

    Femtosecond transient absorption (fs-TA) and Ultrafast Raman Loss Spectroscopy (URLS) have been applied to reveal the excited state dynamics of bis(phenylethynyl)benzene (BPEB), a model system for one-dimensional molecular wires that have numerous applications in opto-electronics. It is known from the literature that in the ground state BPEB has a low torsional barrier, resulting in a mixed population of rotamers in solution at room temperature. For the excited state this torsional barrier had been calculated to be much higher. Our femtosecond TA measurements show a multi-exponential behaviour, related to the complex structural dynamics in the excited electronic state. Time-resolved, excited state URLS studies in different solvents reveal mode-dependent kinetics and picosecond vibrational relaxation dynamics of high frequency vibrations. After excitation, a gradual increase in intensity is observed for all Raman bands, which reflects the structural reorganization of Franck-Condon excited, non-planar rotamers to a planar conformation. It is argued that this excited state planarization is also responsible for its high fluorescence quantum yield. The time dependent peak positions of high frequency vibrations provide additional information: a rapid, sub-picosecond decrease in peak frequency, followed by a slower increase, indicates the extent of conjugation during different phases of excited state relaxation. The CC triple (-C≡C-) bond responds somewhat faster to structural reorganization than the CC double (>C=C<) bonds. This study deepens our understanding of the excited state of BPEB and analogous linear pi-conjugated systems and may thus contribute to the advancement of polymeric "molecular wires."

  17. Energy loss and straggling of MeV ions through biological samples

    SciTech Connect

    Ma Lei; Wang Yugang; Xue Jianming; Chen Qizhong; Zhang Weiming; Zhang Yanwen

    2007-10-15

    Energy loss and energy straggling of energetic ions through natural dehydrated biological samples were investigated using transmission technique. Biological samples (onion membrane, egg coat, and tomato coat) with different mass thickness were studied, together with Mylar for comparison. The energy loss and energy straggling of MeV H and He ions after penetrating the biological and Mylar samples were measured. The experimental results show that the average energy losses of MeV ions through the biological samples are consistent with SRIM predictions; however, large deviation in energy straggling is observed between the measured results and the SRIM predictions. Taking into account inhomogeneity in mass density and structure of the biological sample, an energy straggling formula is suggested, and the experimental energy straggling values are well predicted by the proposed formula.

  18. Energy loss and straggling of MeV ions through biological samples

    SciTech Connect

    Ma, Lie; Wang, Yugang; Xue, Jianming; Chen, Qizhong; Zhang, Weiming; Zhang, Yanwen

    2007-10-15

    Energy loss and energy straggling of energetic ions through natural dehydrated biological samples were investigated using transmission technique. Biological samples (onion membrane, egg coat and tomato coat) with different mass thickness were studied, together with mylar for comparison, in this work. The energy loss and energy straggling of MeV H and He ions after penetrating from the biological and mylar samples were measured. The experimental results show that the average energy losses of MeV ions through the biological samples are consistent with SRIM predictions, however, large deviation in energy straggling is observed between the measured result and the SRIM predictions. Taking into account inhomogeneity in mass density and structure of the biological sample, an energy straggling formula is suggested, and the experimental energy straggling values are well predicated by the proposed formula.

  19. Energy Density and Weight Loss: Feel Full on Fewer Calories

    MedlinePlus

    ... Fat. Fat is high in energy density. One pat of butter, for example, contains almost the same ... choosing whole-wheat bread, whole-wheat pasta, oatmeal, brown rice and whole-grain cereal instead of refined ...

  20. A coupled effect of nuclear and electronic energy loss on ion irradiation damage in lithium niobate

    DOE PAGES

    Liu, Peng; Zhang, Yanwen; Xue, Haizhou; ...

    2016-01-09

    Understanding irradiation effects induced by elastic energy loss to atomic nuclei and inelastic energy loss to electrons in a crystal, as well as the coupled effect between them, is a scientific challenge. Damage evolution in LiNbO3 irradiated by 0.9 and 21 MeV Si ions at 300 K has been studied utilizing Rutherford backscattering spectrometry in channeling mode. During the low-energy ion irradiation process, damage accumulation produced due to elastic collisions is described utilizing a disorder accumulation model. Moreover, low electronic energy loss is shown to induce observable damage that increases with ion fluence. For the same electronic energy loss, themore » velocity of the incident ion could affect the energy and spatial distribution of excited electrons, and therefore effectively modify the diameter of the ion track. Furthermore, nonlinear additive phenomenon of irradiation damage induced by high electronic energy loss in pre-damaged LiNbO3 has been observed. The result indicates that pre-existing damage induced from nuclear energy loss interacts synergistically with inelastic electronic energy loss to promote the formation of amorphous tracks and lead to rapid phase transformation, much more efficient than what is observed in pristine crystal solely induced by electronic energy loss. As a result, this synergistic effect is attributed to the fundamental mechanism that the defects produced by the elastic collisions result in a decrease in thermal conductivity, increase in the electron-phonon coupling, and further lead to higher intensity in thermal spike from intense electronic energy deposition along high-energy ion trajectory.« less

  1. A coupled effect of nuclear and electronic energy loss on ion irradiation damage in lithium niobate

    SciTech Connect

    Liu, Peng; Zhang, Yanwen; Xue, Haizhou; Jin, Ke; Crespillo, Miguel L.; Wang, Xuelin; Weber, William J.

    2016-01-09

    Understanding irradiation effects induced by elastic energy loss to atomic nuclei and inelastic energy loss to electrons in a crystal, as well as the coupled effect between them, is a scientific challenge. Damage evolution in LiNbO3 irradiated by 0.9 and 21 MeV Si ions at 300 K has been studied utilizing Rutherford backscattering spectrometry in channeling mode. During the low-energy ion irradiation process, damage accumulation produced due to elastic collisions is described utilizing a disorder accumulation model. Moreover, low electronic energy loss is shown to induce observable damage that increases with ion fluence. For the same electronic energy loss, the velocity of the incident ion could affect the energy and spatial distribution of excited electrons, and therefore effectively modify the diameter of the ion track. Furthermore, nonlinear additive phenomenon of irradiation damage induced by high electronic energy loss in pre-damaged LiNbO3 has been observed. The result indicates that pre-existing damage induced from nuclear energy loss interacts synergistically with inelastic electronic energy loss to promote the formation of amorphous tracks and lead to rapid phase transformation, much more efficient than what is observed in pristine crystal solely induced by electronic energy loss. As a result, this synergistic effect is attributed to the fundamental mechanism that the defects produced by the elastic collisions result in a decrease in thermal conductivity, increase in the electron-phonon coupling, and further lead to higher intensity in thermal spike from intense electronic energy deposition along high-energy ion trajectory.

  2. Energy loss partitioning during ballistic impact of polymer composites

    NASA Technical Reports Server (NTRS)

    Zee, Ralph H.; Hsieh, Chung Y.

    1993-01-01

    The objective of this study is to determine the energy dissipation processes in polymer-matrix composites during impact of ballistic projectiles. These processes include heat, fiber deformation and breakage, matrix deformation and fracture, and interfacial delamination. In this study, experimental measurements were made, using specialized specimen designs and test methods, to isolate the energy consumed by each of these processes during impact in the ballistic range. Using these experiments, relationships between material parameters and energy dissipation were examined. Composites with the same matrix but reinforced with Kevlar, PE, and graphite fabric were included in this study. These fibers were selected based on the differences in their intrinsic properties. Matrix cracking was found to be one of the most important energy absorption mechanisms during impact, especially in ductile samples such as Spectra-900 PE and Kevlar-49 reinforced polymer. On the contrary, delamination dominated the energy dissipation in brittle composites such as graphite reinforced materials. The contribution from frictional forces was also investigated and the energy partitioning among the different processes evaluated.

  3. CEBAF at higher energies: Working group report on hadron spectroscopy and production

    SciTech Connect

    Barnes, T. |; Napolitano, J.

    1994-04-01

    This report summarizes topics in hadron spectroscopy and production which could be addressed at CEBAF with an energy upgrade to E{sub {gamma}} = 8 GeV and beyond. The topics discussed include conventional meson and baryon spectrocopy, spectroscopy of exotica (especially molecules and hybrids), CP and CPT tests using {phi} mesons, and new detector and accelerator options.

  4. Effects of rapid weight loss and regain on body composition and energy expenditure.

    PubMed

    Sagayama, Hiroyuki; Yoshimura, Eiichi; Yamada, Yosuke; Ichikawa, Mamiko; Ebine, Naoyuki; Higaki, Yasuki; Kiyonaga, Akira; Tanaka, Hiroaki

    2014-01-01

    Weight-classified athletes need an energy intake plan to accomplish target weight reduction. They have to consider body composition and energy metabolism during rapid weight loss followed by rapid weight regain to achieve their energy intake plan. We investigated the effects of rapid weight loss, followed by weight regain, on body composition and energy expenditure. Ten weight-classified athletes were instructed to reduce their body weight by 5% in 7 days. Following the weight loss, they were asked to try to regain all of their lost weight with an ad libitum diet for 12 h. Food intake was recorded during the baseline, weight loss, and regain periods. Fat mass, total body water, and fat-free dry solids were estimated by underwater weighing and stable isotope dilution methods. A three-component model was calculated using Siri's equation. Basal and sleeping metabolic rates were measured by indirect calorimetry. Body composition and energy expenditure were measured before and after weight loss and after weight regain. Body weight, total body water, and fat-free dry solids were decreased after the weight loss period but recovered after weight regain (p < 0.05). Basal metabolic rate did not change throughout the study. Sleeping metabolic rate decreased significantly during weight loss but recovered after weight regain. Changes in total body water greatly affect body weight during rapid weight loss and regain. In addition, rapid weight loss and regain did not greatly affect the basal metabolic rate in weight-classified athletes.

  5. Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

    SciTech Connect

    Vos, M.; Marmitt, G. G.; Finkelstein, Y.; Moreh, R.

    2015-09-14

    Reflection electron energy loss spectra from some insulating materials (CaCO{sub 3}, Li{sub 2}CO{sub 3}, and SiO{sub 2}) taken at relatively high incoming electron energies (5–40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO{sub 2}, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E − E{sub gap}){sup 1.5}. For CaCO{sub 3}, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li{sub 2}CO{sub 3} (7.5 eV) is the first experimental estimate.

  6. Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

    NASA Astrophysics Data System (ADS)

    Vos, M.; Marmitt, G. G.; Finkelstein, Y.; Moreh, R.

    2015-09-01

    Reflection electron energy loss spectra from some insulating materials (CaCO3, Li2CO3, and SiO2) taken at relatively high incoming electron energies (5-40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO2, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E - Egap)1.5. For CaCO3, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li2CO3 (7.5 eV) is the first experimental estimate.

  7. Energy losses and transition radiation produced by the interaction of charged particles with a graphene sheet

    NASA Astrophysics Data System (ADS)

    Mišković, Zoran L.; Segui, Silvina; Gervasoni, Juana L.; Arista, Néstor R.

    2016-09-01

    We present a fully relativistic formulation of the energy loss of a charged particle traversing a conductive monoatomic layer and apply it to the case of graphene in a transmission electron microscope (TEM). We use two models of conductivity appropriate for different frequency regimes: (a) THz (terahertz) frequency range and (b) optical range. In each range we distinguish two types of contributions to the electron energy loss: the energy deposited in graphene in the form of electronic excitations (Ohm losses), and the energy that is emitted in the form of radiation. We find strong relativistic effects in the electron energy loss spectra, which are manifested, e.g., in the increased heights of the principal π and σ +π peaks that may be observed in TEM in the optical range. While the radiative energy losses are suppressed in the optical range in comparison to the Ohmic losses, we find that these two contributions are comparable in magnitude in the THz range, where the response of doped graphene is dominated by the Dirac plasmon polariton (DPP). In particular, relative contributions of the Ohmic and radiative energy losses are strongly affected by the damping of DPP. In the case of a clean graphene with low damping, the angular distribution of the radiated spectra at the sub-THz frequencies exhibit strong and possibly observable skewing towards graphene.

  8. Magnetostrictive and Kinematic Model Considering the Dynamic Hysteresis and Energy Loss for GMA

    NASA Astrophysics Data System (ADS)

    LIU, Huifang; SUN, Xingwei; GAO, Yifei; WANG, Hanyu; GAO, Zijin

    2017-03-01

    Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials (GMM), output displacement accuracy of giant magnetostrictive actuator (GMA) can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D'Alembert's principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.

  9. Laser spectroscopy applied to energy, environmental and medical research

    NASA Astrophysics Data System (ADS)

    Svanberg, S.

    1988-01-01

    Applications of laser spectroscopy to the fields of combustion diagnostics, environmental remote sensing, and medicine are discussed. The techniques emphasized are CARS and laser-induced fluorescence. The monitoring of atmospheric trace gases, the treatment of tumors, and the detection and characterization of atherosclerotic plaques are addressed.

  10. Energy loss straggling in collisions of fast finite-size ions with atoms

    NASA Astrophysics Data System (ADS)

    Makarov, D. N.; Matveev, V. I.

    2013-03-01

    The influence of ion size on straggling of energy losses by fast partially stripped ions is studied using the nonperturbative approach based on the eikonal approximation. It is shown that such a consideration of collisions of ions with complex atoms can lead to considerable corrections in calculating root-mean-square straggling of energy losses by fast ions compared to the results obtained for point ions. The root-mean-square straggling of energy losses are calculated for bromide and iodine ions in collisions with copper, silver, and aluminum atoms. It is shown that allowance for the size of the electron "coat" of an ion noticeably improves the agreement with experimental data.

  11. Energy loss straggling in collisions of fast finite-size ions with atoms

    SciTech Connect

    Makarov, D. N. Matveev, V. I.

    2013-03-15

    The influence of ion size on straggling of energy losses by fast partially stripped ions is studied using the nonperturbative approach based on the eikonal approximation. It is shown that such a consideration of collisions of ions with complex atoms can lead to considerable corrections in calculating root-mean-square straggling of energy losses by fast ions compared to the results obtained for point ions. The root-mean-square straggling of energy losses are calculated for bromide and iodine ions in collisions with copper, silver, and aluminum atoms. It is shown that allowance for the size of the electron 'coat' of an ion noticeably improves the agreement with experimental data.

  12. Phase effect in the energy loss of hydrogen projectiles in zinc targets

    SciTech Connect

    Arnau, A.; Bauer, P.; Kastner, F.; Salin, A.; Ponce, V.H.; Fainstein, P.D.; Echenique, P.M.

    1994-03-01

    We present an experimental and theoretical study of the phase effect in the energy loss of fast hydrogen beams colliding with gas and solid zinc targets. The experiments show a maximum phase effect of 50% around 50 keV/u, the energy loss per atom in the solid target being smaller than in the gas target. An extensive theoretical study of all the processes contributing to the energy loss in the two phases shows that the experimental findings can be explained primarily by the screening of the projectile field by the valence electrons in the solid.

  13. Synergy of inelastic and elastic energy loss. Temperature effects and electronic stopping power dependence

    DOE PAGES

    Zarkadoula, Eva; Xue, Haizhou; Zhang, Yanwen; ...

    2015-06-16

    A combination of an inelastic thermal spike model suitable for insulators and molecular dynamics simulations is used to study the effects of temperature and electronic energy loss on ion track formation, size and morphology in SrTiO3 systems with pre-existing disorder. We find temperature dependence of the ion track size. In addition, we find a threshold in the electronic energy loss for a given pre-existing defect concentration, which indicates a threshold in the synergy between the inelastic and elastic energy loss.

  14. Synergy of inelastic and elastic energy loss. Temperature effects and electronic stopping power dependence

    SciTech Connect

    Zarkadoula, Eva; Xue, Haizhou; Zhang, Yanwen; Weber, William J.

    2015-06-16

    A combination of an inelastic thermal spike model suitable for insulators and molecular dynamics simulations is used to study the effects of temperature and electronic energy loss on ion track formation, size and morphology in SrTiO3 systems with pre-existing disorder. We find temperature dependence of the ion track size. In addition, we find a threshold in the electronic energy loss for a given pre-existing defect concentration, which indicates a threshold in the synergy between the inelastic and elastic energy loss.

  15. Measurement of Quark Energy Loss in Cold Nuclear Matter at Fermilab E906/SeaQuest

    SciTech Connect

    Lin, Po-Ju

    2017-01-01

    Parton energy loss is a process within QCD that draws considerable interest. The measurement of parton energy loss can provide valuable information for other hard-scattering processes in nuclei, and also serves as an important tool for exploring the properties of the quark-gluon plasma (QGP). Quantifying the energy loss in cold nuclear matter will help to set a baseline relative to energy loss in the QGP. With the Drell-Yan process, the energy loss of incoming quarks in cold nuclear matter can be ideally investigated since the final state interaction is expected to be minimal. E906/SeaQuest is a fixed-target experiment using the 120 GeV proton beam from the Fermilab Main Injector and has been collecting data from p+p, p+d, p+C, p+Fe, and p+W collisions. Within the E906 kinematic coverage of Drell-Yan production via the dimuon channel, the quark energy loss can be measured in a regime where other nuclear effects are expected to be small. In this thesis, the study of quark ener gy loss from different cold nuclear targets is presented.

  16. Energy loss effect of incoming gluons from J/ψ production in p-A collisions

    NASA Astrophysics Data System (ADS)

    Song, Li-Hua; Yan, Lin-Wan; Duan, Chun-Gui

    2017-02-01

    The energy loss effect of incoming gluons from J/ψ production in p-A (or d-A) collisions is investigated by means of the E866, RHIC and LHC experimental data. The gluon mean energy loss per unit path length dE/dL = 2.18 ± 0.14 GeV/fm is extracted by fitting the E866 experimental data for J/ψ production cross section ratios R W(Fe)/Be(x F). The obtained result indicates that the incoming gluons lose more energy than the incident quarks. By comparing the theoretical results with E866, RHIC, and LHC experimental data, it is found that the nuclear suppression due to the incident gluon (quark) energy loss reduces (increases) with the increase of the kinematic variable x F (or y). The energy loss effect of incoming gluons plays an important role in the suppression of J/ψ production in a wide energy range from to , and the influence of incident quark energy loss can be ignored for high energies (such as at RHIC and LHC energy). Supported by National Natural Science Foundation of China (11405043, 11575052)

  17. The effects on γ-LiAlO2 induced by nuclear energy losses during Ga ions implantation

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Song, Hong-Lian; Qiao, Mei; Yu, Xiao-Fei; Wang, Tie-Jun; Wang, Xue-Lin

    2017-09-01

    To explore the evolution of γ-LiAlO2 under ion irradiation at low energy, we implanted Ga ions of 30, 80 and 150 keV at fluences of 1 × 1014 and 1 × 1015 ions/cm2 in z-cut γ-LiAlO2 samples, respectively. The implantation resulted in damage regions dominated by nuclear energy losses at depth of 232 Å, 514 Å, and 911 Å beneath the surface, respectively, which was simulated by the Stopping and Range of Ions in Matter program. The irradiated γ-LiAlO2 were characterized with atomic force microscope, Raman spectroscopy, X-ray diffraction and Rutherford backscattering in a channeling mode for morphology evolution, structure information and damage profiles. The interesting and partly abnormal results showed the various behaviors in modification of surface by Ga ions implantation.

  18. Hydrodynamic evolution and jet energy loss in Cu + Cu collisions

    SciTech Connect

    Schenke, Bjoern; Jeon, Sangyong; Gale, Charles

    2011-04-15

    We present results from a hybrid description of Cu + Cu collisions using (3 + 1)-dimensional hydrodynamics (music) for the bulk evolution and a Monte Carlo simulation (martini) for the evolution of high-momentum partons in the hydrodynamical background. We explore the limits of this description by going to small system sizes and determine the dependence on different fractions of wounded nucleon and binary collisions scaling of the initial energy density. We find that Cu + Cu collisions are well described by the hybrid description at least up to 20% central collisions.

  19. Reflection electron energy loss spectrum of single layer graphene measured on a graphite substrate

    NASA Astrophysics Data System (ADS)

    Werner, Wolfgang S. M.; Bellissimo, Alessandra; Leber, Roland; Ashraf, Afshan; Segui, Silvina

    2015-05-01

    Reflection electron energy loss spectra (REELS) have been measured on a highly oriented pyrolytic graphite (HOPG) sample. Two spectra were measured for different energies, 1600 eV, being more sensitive to the bulk and 500 eV being more sensitive to the surface. The energy loss distributions for a single surface and bulk excitation were extracted from the two spectra using a simple decomposition procedure. These single scattering loss distributions correspond to electron trajectories with significantly different penetration depths and agree with energy loss spectra measured on free standing single layer graphene and multilayer graphene (i.e. graphite). This result implies that for a layered electron gas (LEG) material, the number of layers which responds in a correlated fashion to an external perturbation is determined by the depth range penetrated by the external perturbation, and not by the number of layers actually present in the specimen.

  20. Energy losses from fast structured heavy ions in multiple collisions with molecules and nanoparticles

    SciTech Connect

    Matveev, V. I. Gusarevich, E. S.; Makarov, D. N.

    2009-11-15

    A nonperturbative method is developed to calculate the energy losses from fast, highly charged, heavy ions in collisions with complex molecules and nanoparticles. All possible processes of excitation and ionization of both projectile and target are taken into account. The contributions to energy losses due to multiple collisions are calculated, and the effect of target orientation with respect to the direction of projectile motion is examined. As examples, the energy losses in collisions with the XeF{sub 4} molecule and a C{sub 300} nanotube are determined. It is shown that the effect of multiple collisions leads to significant change in energy loss with target orientation, being insignificant for randomly oriented targets.

  1. Fast ion surface energy loss and straggling in the surface wake fields.

    PubMed

    Nandi, T; Haris, K; Hala; Singh, Gurjeet; Kumar, Pankaj; Kumar, Rajesh; Saini, S K; Khan, S A; Jhingan, Akhil; Verma, P; Tauheed, A; Mehta, D; Berry, H G

    2013-04-19

    We have measured the stopping powers and straggling of fast, highly ionized atoms passing through thin bilayer targets made up of metals and insulators. We were surprised to find that the energy losses as well as the straggling depend on the ordering of the target and have small but significantly different values on bilayer reversal. We ascribe this newly found difference in energy loss to the surface energy loss field effect due to the differing surface wake fields as the beam exits the target in the two cases. This finding is validated with experiments using several different projectiles, velocities, and bilayer targets. Both partners of the diatomic molecular ions also display similar results. A comparison of the energy loss results with those of previous theoretical predictions for the surface wake potential for fast ions in solids supports the existence of a self-wake.

  2. Understanding energy loss in parallelly connected microbial fuel cells: Non-Faradaic current.

    PubMed

    An, Junyeong; Sim, Junyoung; Feng, Yujie; Lee, Hyung-Sool

    2016-03-01

    In this work, the mechanisms of energy loss in parallel connection of microbial fuel cells (MFCs) is explored using two MFC units producing different open circuit voltage (OCV) and current. In open circuit mode, non-Faradaic current flows in low OCV unit, implying energy loss caused by different OCVs in parallelly stacked MFCs. In a stacked MFC in parallel under close circuit mode, it is confirmed that energy loss occurs until the working voltage in high OCV unit becomes identical to the other unit having low OCV. This result indicates that different voltage between individual MFC units can cause energy loss due to both non-Faradic and Faradaic current that flow from high voltage unit to low voltage unit even in parallelly stacked MFCs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Energy balance and the composition of weight loss during prolonged space flight

    NASA Technical Reports Server (NTRS)

    Leonard, J. I.

    1982-01-01

    Integrated metabolic balance analysis, Skylab integrated metabolic balance analysis and computer simulation of fluid-electrolyte responses to zero-g, overall mission weight and tissue losses, energy balance, diet and exercise, continuous changes, electrolyte losses, caloric and exercise requirements, and body composition are discussed.

  4. Reducing heat loss from the energy absorber of a solar collector

    DOEpatents

    Chao, Bei Tse; Rabl, Ari

    1976-01-01

    A device is provided for reducing convective heat loss in a cylindrical radiant energy collector. It includes a curved reflective wall in the shape of the arc of a circle positioned on the opposite side of the exit aperture from the reflective side walls of the collector. Radiant energy exiting the exit aperture is directed by the curved wall onto an energy absorber such that the portion of the absorber upon which the energy is directed faces downward to reduce convective heat loss from the absorber.

  5. Energy loss of ions by electric-field fluctuations in a magnetized plasma

    SciTech Connect

    Nersisyan, Hrachya B.; Deutsch, Claude

    2011-06-15

    The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

  6. Energy loss of ions by electric-field fluctuations in a magnetized plasma.

    PubMed

    Nersisyan, Hrachya B; Deutsch, Claude

    2011-06-01

    The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

  7. Calculation of the energy loss for an electron passing near giant fullerenes

    NASA Astrophysics Data System (ADS)

    Henrard, L.; Lambin, Ph

    1996-11-01

    We present a theoretical analysis of the electron energy-loss spectra of isolated giant fullerenes. We use a macroscopic dielectric description of spherical onion-like fullerenes and a discrete dipole approximation (DDA) framework for tubular fullerenes. In the DDA model, an anisotropic dynamical polarizability is assigned to each carbon site. We stress the fundamental importance of the hollow character of giant fullerenes in the electron energy-loss resonances.

  8. Energy losses of positive and negative charged particles in electron gas

    NASA Astrophysics Data System (ADS)

    Diachenko, M. M.; Kholodov, R. I.

    2017-02-01

    A heavy charged particle propagation through electron gas has been studied using combination of non-relativistic quantum mechanics and the Green’s functions method. The energy loss of a charged particle has been found in the case of large transferred momentum taking into account the interference term in the expression for the rate. The dependence of the energy loss of a charged particles in electron gas with nonzero temperature on the sign of the charge has been obtained.

  9. Energy dependent 3-body loss in out-of-equilibrium 1D Bose gases

    NASA Astrophysics Data System (ADS)

    Zundel, Laura; Xia, Lin; Wilson, Joshua; Riou, Jean-Felix; Weiss, David

    2015-05-01

    We measure the three-body loss of out-of-equilibrium one-dimensional (1D) Bose gases and find that it depends strongly on the average energy of the distribution. The theory of three-body loss in 1D gas experiments is incomplete due to the challenge of calculating how correlations evolve. We present an empirical model based on energy dependent correlations and show that it reproduces the data.

  10. Energy losses at three-way circular drop manholes under surcharged conditions.

    PubMed

    Arao, Shinji; Kusuda, Tetsuya; Moriyama, Katsumi; Hiratsuka, Shunsuke; Asada, Jyunsaku; Hirose, Nozomu

    2012-01-01

    Energy loss at manholes is of importance in the design of storm sewer networks and in flood-analysis. Some researchers have already investigated the energy loss at three-way manholes under surcharged conditions. However, formulation to calculate the energy loss at manholes, including all variables of structural elements of the pipes and of the manhole has not yet been accomplished. Therefore, more study to formulate the energy loss at three-way drop manholes is needed. In this study, the ratio of the diameter between inflow pipes and an outflow pipe, the ratio of flow rates between those pipes, water depth in a manhole and the drop gaps between those pipes are considered and the energy loss at three-way circular drop manholes is examined. Finally, a modified formula, more accurate than that in the U.S. Federal Highway Administration's 2001 Urban Drainage Design Manual is proposed. The proposed formula takes the influence of the ratio of the diameter between inflow pipes and outflow pipe and drop gaps between those pipes into consideration. The calculated energy loss coefficients in both straight-through and lateral pipes successfully reproduce the measured values.

  11. Effect of self-gravitation on the energy loss of pair of projectiles in dusty plasma

    SciTech Connect

    Mirza, Arshad M.; Sarwar, M. Adnan; Qaisar, M.S.

    2006-05-15

    The effect of self-gravitation of massive dust grains is investigated on the shielded potential and the energy loss of pair of charged projectiles passing through a dust-contaminated plasma. Analytical general expressions are derived for the shielded potential and for the energy loss by incorporating two-body correlation effects. An interference contribution of these projectiles to the shielded potential and energy loss is observed that depends upon their orientation and separation distance. It is found that for two collinear projectiles the potential is enhanced by increasing dust Jeans frequency for separation less than Debye length and the energy loss versus projectile velocity decreases with the increase of Jeans frequency for arbitrary separation. The effect of inclination of two noncollinear projectiles on energy loss is also investigated for a fixed value of Jeans frequency {omega}{sub jd}=4x10{sup -4}{omega}{sub pd}. The contribution to the energy loss due to the interference term has been separately calculated for a typical Jeans frequency. The present investigation would be useful to explain the coagulation of dust particles in the molecular clouds and in the ion-beam-driven inertial confinement fusion approach.

  12. Electrochemistry and spectroscopy of energy conversion and polynuclear aromatic materials

    NASA Astrophysics Data System (ADS)

    Nazri, Maryam

    The field of materials chemistry is becoming increasingly important in many technological disciplines, including batteries, fuel cells, hydrogen storage materials, and application of poly-nuclear aromatic compounds in solar cells, color copiers, sensors, and catalysis. This multidisciplinary research work focuses on the development, understanding, and characterization of novel materials for advanced lithium batteries and a unique series of polyaromatic compounds for application in solar cells and color copiers. A general overview of materials and techniques used in this work is presented, including the electrochemistry, spectroscopy, thermal analysis, and x-ray diffraction. A unique electrochemical procedure based on carbon paste microelectrode was applied to study the electrochemistry of novel poly-nuclear aromatic compounds. X-ray diffraction and vibrational spectroscopy are also used to gain further information about their molecular organization in solid-state. Conductivity of a novel electrolyte based on a multi-blend of organic carbonate solvents, has been studied over a wide range of temperatures (-40 to 70°C). An optimized electrolyte for an advanced lithium battery based on ternary solvent blend of linear and cyclic organic carbonates has been developed. The nature of ion-association and ion-solvent interactions in complex electrolytes are studied using infrared spectroscopy. We have found a strong preferred solvation of lithium ion in electrolyte containing multi-blend solvent molecules. The advanced lithium battery uses intercalation compounds with layered structure such as LiCoO2 cathode, and lithiated graphite, (LiC 6), anode. In this work, we have studied the reactivity of Li-C anode materials in contact with organic carbonate-based electrolyte, and have investigated the nature of the decomposition products formed on the electrode surface. A significant reactivity between the LiC6 and organic electrolytes is observed, and is a major safety concern. A

  13. Energy loss and straggling of MeV Si ions in gases

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Arstila, K.; Jensen, J.; Julin, J.; Kettunen, H.; Laitinen, M.; Rossi, M.; Sajavaara, T.; Thöni, M.; Whitlow, H. J.

    2017-01-01

    We present measurements of energy loss and straggling of Si ions in gases. An energy range from 0.5 to 12 MeV/u was covered using the 6 MV EN tandem accelerator at ETH Zurich, Switzerland, and the K130 cyclotron accelerator facility at the University of Jyväskylä, Finland. Our energy-loss data compare well with calculation based on the SRIM and PASS code. The new straggling measurements support a pronounced peak in He gas at around 4 MeV/u predicted by recent theoretical calculations. The straggling curve structure in the other gases (N2, Ne, Ar, Kr) is relatively flat in the covered energy range. Although there is a general agreement between the straggling data and the theoretical calculations, the experimental uncertainties are too large to confirm or exclude the predicted weak multi-peak structure in the energy-loss straggling.

  14. Electronic energy-loss mechanisms for H, He, and Ne in TiN

    NASA Astrophysics Data System (ADS)

    Sortica, M. A.; Paneta, V.; Bruckner, B.; Lohmann, S.; Hans, M.; Nyberg, T.; Bauer, P.; Primetzhofer, D.

    2017-09-01

    The specific energy loss of medium-energy hydrogen, helium, and neon ions in titanium nitride is studied. Electronic stopping cross sections of ions in the energy range of 3-140 keV/amu were measured in backscattering geometry using time-of-flight medium-energy ion scattering, from the energy loss experienced in TiN thin films on Si. For the lowest energies, data for H show a strong deviation from Bragg's rule. For hydrogen and Ne ions, electronic stopping exhibits velocity proportionality at ion velocities below 1 a.u. Comparison to density functional theory calculations of the stopping power yields very good agreement for H, while for He and Ne, the experimentally observed electronic stopping power is considerably higher than predicted. For He the extrapolation of the stopping power at low energies points to a nonvanishing energy loss at vanishing ion velocity. The present data can thus be taken as an indication of additional energy-loss processes different from direct electron-hole pair excitation. Furthermore, the results provide reference values for ion-beam-based analysis of TiN, a material with huge technological relevance.

  15. Biomedical and agricultural applications of energy dispersive X-ray spectroscopy in electron microscopy.

    PubMed

    Wyroba, Elżbieta; Suski, Szymon; Miller, Karolina; Bartosiewicz, Rafał

    2015-09-01

    Energy dispersive X-ray spectroscopy (EDS) in electron microscopy has been widely used in many research areas since it provides precise information on the chemical composition of subcellular structures that may be correlated with their high resolution images. In EDS the characteristic X-rays typical of each element are analyzed and the new detectors - an example of which we describe - allow for setting precisely the area of measurements and acquiring signals as a point analysis, as a linescan or in the image format of the desired area. Mapping of the elements requires stringent methods of sample preparation to prevent redistribution/loss of the elements as well as elimination of the risk of overlapping spectra. Both qualitative and quantitative analyses may be performed at a low probe current suitable for thin biological samples. Descriptions of preparation techniques, drawbacks and precautions necessary to obtain reliable results are provided, including data on standards, effects of specimen roughness and quantification. Data on EPMA application in different fields of biomedical and agricultural studies are reviewed. In this review we refer to recent EDS/EPMA applications in medical diagnostics, studies on air pollution and agrochemicals as well as on plant models used to monitor the environment.

  16. Thickness uniformity of beryllium foils derived from energy loss broadening of transmitted MeV protons

    NASA Astrophysics Data System (ADS)

    Hietel, B.; Wittmaack, K.

    2000-03-01

    The thickness uniformity of beryllium foils commonly in use as entrance windows of Si(Li) detectors has been determined by measuring the broadening in energy loss of 1.5-2.5 MeV protons transmitted through such foils. The energy loss spectra were measured after backscattering of the transmitted protons from a thin layer of gold on a polypropylene film. The contribution due to energy loss straggling was assessed in transmission studies on uniform films of polypropylene and polyester (Mylar). The full width at half maximum (FWHM) of the loss peaks for the polymer films increased with the square root of the energy loss Δ E, in accordance with theory. By contrast, the FWHM of the energy loss in Be increased linearly with increasing Δ E, with a maximum FWHM=0.21Δ E at 2.5 MeV. After correcting for the straggling contribution in quadrature, the net excess broadening was found to range from 18% to 20%, for Be foils with a nominal thickness between 12.5 and 37.5 μm. The excess broadening is attributed to a corresponding variation in thickness across the foils, probably due to a significant porosity generated during the fabrication process (sintering). This result supports previous indirect evidence derived from studies on background generation in proton-induced X-ray emission spectrometry (PIXE).

  17. Hysteresis model and statistical interpretation of energy losses in non-oriented steels

    NASA Astrophysics Data System (ADS)

    Mănescu (Păltânea), Veronica; Păltânea, Gheorghe; Gavrilă, Horia

    2016-04-01

    In this paper the hysteresis energy losses in two non-oriented industrial steels (M400-65A and M800-65A) were determined, by means of an efficient classical Preisach model, which is based on the Pescetti-Biorci method for the identification of the Preisach density. The excess and the total energy losses were also determined, using a statistical framework, based on magnetic object theory. The hysteresis energy losses, in a non-oriented steel alloy, depend on the peak magnetic polarization and they can be computed using a Preisach model, due to the fact that in these materials there is a direct link between the elementary rectangular loops and the discontinuous character of the magnetization process (Barkhausen jumps). To determine the Preisach density it was necessary to measure the normal magnetization curve and the saturation hysteresis cycle. A system of equations was deduced and the Preisach density was calculated for a magnetic polarization of 1.5 T; then the hysteresis cycle was reconstructed. Using the same pattern for the Preisach distribution, it was computed the hysteresis cycle for 1 T. The classical losses were calculated using a well known formula and the excess energy losses were determined by means of the magnetic object theory. The total energy losses were mathematically reconstructed and compared with those, measured experimentally.

  18. Gas Phase Molecular Spectroscopy: Electronic Spectroscopy of Combustion Intermediates, Chlorine Azide kinetics, and Rovibrational Energy Transfer in Acetylene

    NASA Astrophysics Data System (ADS)

    Freel, Keith A.

    This dissertation is composed of three sections. The first deals with the electronic spectroscopy of combustion intermediates that are related to the formation of polycyclic aromatic hydrocarbons. Absorption spectra for phenyl, phenoxy, benzyl, and phenyl peroxy radicals were recorded using the technique of cavity ring-down spectroscopy. When possible, molecular constants, vibrational frequencies, and excited state lifetimes for these radicals were derived from these data. The results were supported by theoretical predictions. The second section presents a study of electron attachment to chlorine azide (ClN3) using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10-8 and 4.5x10-8 cm3s-1 at 298 and 400 K respectively. The reactions of ClN3 with eighteen cations and seventeen anions were characterized. Rate constants were measured using a selected ion flow tube. The ionization energy (>9.6eV), proton affinity (713+/-41 kJ mol-1), and electron affinity (2.48+/-0.2 eV) for ClN 3 were determined from these data. The third section demonstrates the use of double resonance spectroscopy to observe state-selected rovibrational energy transfer from the first overtone asymmetric stretch of acetylene. The total population removal rate constants from various rotational levels of the (1,0,1,00,00) vibrational state were determined to be in the range of (9-17) x 10 -10 cm3s-1. Rotational energy transfer accounted for approximately 90% of the total removal rate from each state. Therefore, the upper limit of vibrational energy transfer from the (1,0,1,0 0,00) state was 10%.

  19. Elemental profiling of laser cladded multilayer coatings by laser induced breakdown spectroscopy and energy dispersive X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Lednev, V. N.; Sdvizhenskii, P. A.; Filippov, M. N.; Grishin, M. Ya.; Filichkina, V. A.; Stavertiy, A. Ya.; Tretyakov, R. S.; Bunkin, A. F.; Pershin, S. M.

    2017-09-01

    Multilayer tungsten carbide wear resistant coatings were analyzed by laser induced breakdown spectroscopy (LIBS) and energy dispersive X-ray (EDX) spectroscopy. Coaxial laser cladding technique was utilized to produce tungsten carbide coating deposited on low alloy steel substrate with additional inconel 625 interlayer. EDX and LIBS techniques were used for elemental profiling of major components (Ni, W, C, Fe, etc.) in the coating. A good correlation between EDX and LIBS data was observed while LIBS provided additional information on light element distribution (carbon). A non-uniform distribution of tungsten carbide grains along coating depth was detected by both LIBS and EDX. In contrast, horizontal elemental profiling showed a uniform tungsten carbide particles distribution. Depth elemental profiling by layer-by-layer LIBS analysis was demonstrated to be an effective method for studying tungsten carbide grains distribution in wear resistant coating without any sample preparation.

  20. Low or moderate dietary energy restriction for long-term weight loss: what works best?

    USDA-ARS?s Scientific Manuscript database

    Theoretical calculations suggest that small daily reductions in energy intake can cumulatively lead to substantial weight loss, but experimental data to support these calculations are lacking. We conducted a 1-year randomized controlled pilot study of low (10%) or moderate (30%) energy restriction (...

  1. Impact-parameter dependence of the energy loss of fast molecular clusters in hydrogen

    NASA Astrophysics Data System (ADS)

    Fadanelli, R. C.; Grande, P. L.; Schiwietz, G.

    2008-03-01

    The electronic energy loss of molecular clusters as a function of impact parameter is far less understood than atomic energy losses. For instance, there are no analytical expressions for the energy loss as a function of impact parameter for cluster ions. In this work, we describe two procedures to evaluate the combined energy loss of molecules: Ab initio calculations within the semiclassical approximation and the coupled-channels method using atomic orbitals; and simplified models for the electronic cluster energy loss as a function of the impact parameter, namely the molecular perturbative convolution approximation (MPCA, an extension of the corresponding atomic model PCA) and the molecular unitary convolution approximation (MUCA, a molecular extension of the previous unitary convolution approximation UCA). In this work, an improved ansatz for MPCA is proposed, extending its validity for very compact clusters. For the simplified models, the physical inputs are the oscillators strengths of the target atoms and the target-electron density. The results from these models applied to an atomic hydrogen target yield remarkable agreement with their corresponding ab initio counterparts for different angles between cluster axis and velocity direction at specific energies of 150 and 300 keV/u.

  2. A new beam loss detector for low-energy proton and heavy-ion accelerators

    NASA Astrophysics Data System (ADS)

    Liu, Zhengzheng; Crisp, Jenna; Russo, Tom; Webber, Robert; Zhang, Yan

    2014-12-01

    The Facility for Rare Isotope Beams (FRIB) to be constructed at Michigan State University shall deliver a continuous, 400 kW heavy ion beam to the isotope production target. This beam is capable of inflicting serious damage on accelerator components, e.g. superconducting RF accelerating cavities. A Beam Loss Monitoring (BLM) System is essential for detecting beam loss with sufficient sensitivity and promptness to inform the machine protection system (MPS) and operations personnel of impending dangerous losses. Radiation transport simulations reveal shortcomings in the use of ionization chambers for the detection of beam losses in low-energy, heavy-ion accelerators. Radiation cross-talk effects due to the folded geometry of the FRIB LINAC pose further complications to locating specific points of beam loss. We propose a newly developed device, named the Loss Monitor Ring (LMR1

  3. [Calculation of energy losses in the participants of the skiing expedition to the North Pole].

    PubMed

    Efremov, V V; Ushakov, A S; Khmelevskiĭ, Iu I

    1983-01-01

    During the expedition to the North Pole, the food consumption rates were calculated on a regular basis. The mean daily energy losses of the participants of the expedition, the energy losses during skiing with a rucksack across the drifting ice were estimated and the energy metabolism curve by days was built up. The body weight of the participants averaged 78 +/- 5 kg. This made it possible to perform an overall calculation per whole group. The total energy supply with food was appraised from the total amount of the food consumed during the expedition. The total body weight loss of the participants was 11.5 kg, the energy consumption being 100.000 kkal. The total (for 7 men) energy consumption during skiing without a rucksack was calculated according to the formula: [(2,770 kkal X 28.5 days)]+ +[(2,385 kkal X 35.5 days)]. It was thus found to be equal to 1.145.300 kkal. The total energy consumption during skiing with a rucksack was calculated according to the formula: (7 men X X 449 h) and was found to be equal to 1.883.200 kkal. The total energy consumption during the expedition amounted to 3.237.500 kkal. During the expedition, the daily energy deficiency per man was 1.300-1.500 kkal. This deficiency was compensated for during rest. The maintenance of such an energy supply pattern made it possible to preserve a high level of work fitness.

  4. Energy loss to intravalley acoustic modes in nano-dimensional wire structures at low temperatures

    NASA Astrophysics Data System (ADS)

    Nag, S.; Das, B.; Basu, A.; Das, J.; Bhattacharya, D. P.; Sarkar, C. K.

    2017-03-01

    The theory of rate of loss of energy of non-equilibrium electrons due to inelastic interaction with the intravalley acoustic phonons in a nano-dimensional semiconductor wire has been developed under the condition of low lattice temperature, when the approximations of the well known traditional theory are not valid. Numerical results are obtained for narrow-channel GaAs-GaAlAs wires structures. On comparison with other available results it is revealed that the finite energy of the intravalley acoustic phonons and, the use of the full form of the phonon distribution without truncation to the equipartition law, produce significant changes in the energy loss characteristics at low temperatures.

  5. Ab initio research of energy loss for energetic protons in solid-density Be

    NASA Astrophysics Data System (ADS)

    He, Bin; Meng, Xu-Jun; Wang, Zhi-Gang; Wang, Jian-Guo

    2017-03-01

    Ab initio research of energy loss for energetic protons in solid-density Be is made based on the average atom model. Our results are found in good agreement with the recent experiment for both warm and cool matter. Our results are compared with the local density approximation model and the reason for their difference is also explored. The energy loss at smaller projectile energies is predicted by our model and local density approximation, which helps probe the higher reliability of the proving model and judge the existence of the non-Fermi-Dirac velocity distribution for free electrons exists in dense plasmas in future.

  6. Hybrid superconducting magnetic bearing and its frictional energy loss and dynamics

    SciTech Connect

    Xia, Z.; Ma, K.B.; Chen, Q.Y.; Cooley, R.R.

    1995-12-31

    A hybrid superconducting magnetic bearing (SMB) has been designed and tested. A flywheel energy storage (FES) prototype has been constructed for testing bearing friction loss and characterizing the dynamics of the rotor. The hybrid SMB design uses magnetic forces from permanent magnets for levitation and high temperature superconductor YBCO in between the magnets for stabilization. A 42 lb. flywheel currently can rotate up to 6,000 RPM with kinetic energy of 8 Wh stored. The result from the recent rotor spin-down experiment indicates an average frictional energy loss <2% per hour in a vacuum of 10 {sup {minus}5} torr, with imperfect system alignment and balance of rotor. The system dynamics has been conducted to improve upon the energy loss and rotor-bearing modeling.

  7. High-energy resolution X-ray, gamma and electron spectroscopy with cryogenic detectors.

    PubMed

    Loidl, M; Leblanc, E; Bouchard, J; Branger, T; Coron, N; Leblanc, J; de Marcillac, P; Rotzinger, H; Daniyarov, T; Linck, M; Fleischmann, A; Enss, C

    2004-01-01

    Cryogenic detectors offer remarkably better energy resolutions than those achievable with conventional semiconductor or scintillation detectors. With the additional asset of a detection efficiency close to unity for low-energy X-ray photons and electrons, these detectors have the potential to perform X-ray, gamma and electron spectroscopy of a hitherto unknown quality, in particular at low energies. Two types of cryogenic detectors are described and the results of prototype detectors are presented.

  8. Theoretical Basis and Application for Measuring Pork Loin Drip Loss Using Microwave Spectroscopy.

    PubMed

    Mason, Alex; Abdullah, Badr; Muradov, Magomed; Korostynska, Olga; Al-Shamma'a, Ahmed; Bjarnadottir, Stefania Gudrun; Lunde, Kathrine; Alvseike, Ole

    2016-02-02

    During cutting and processing of meat, the loss of water is critical in determining both product quality and value. From the point of slaughter until packaging, water is lost due to the hanging, movement, handling, and cutting of the carcass, with every 1% of lost water having the potential to cost a large meat processing plant somewhere in the region of €50,000 per day. Currently the options for monitoring the loss of water from meat, or determining its drip loss, are limited to destructive tests which take 24-72 h to complete. This paper presents results from work which has led to the development of a novel microwave cavity sensor capable of providing an indication of drip loss within 6 min, while demonstrating good correlation with the well-known EZ-Driploss method (R² = 0.896).

  9. Theoretical Basis and Application for Measuring Pork Loin Drip Loss Using Microwave Spectroscopy

    PubMed Central

    Mason, Alex; Abdullah, Badr; Muradov, Magomed; Korostynska, Olga; Al-Shamma’a, Ahmed; Bjarnadottir, Stefania Gudrun; Lunde, Kathrine; Alvseike, Ole

    2016-01-01

    During cutting and processing of meat, the loss of water is critical in determining both product quality and value. From the point of slaughter until packaging, water is lost due to the hanging, movement, handling, and cutting of the carcass, with every 1% of lost water having the potential to cost a large meat processing plant somewhere in the region of €50,000 per day. Currently the options for monitoring the loss of water from meat, or determining its drip loss, are limited to destructive tests which take 24–72 h to complete. This paper presents results from work which has led to the development of a novel microwave cavity sensor capable of providing an indication of drip loss within 6 min, while demonstrating good correlation with the well-known EZ-Driploss method (R2 = 0.896). PMID:26848661

  10. Argon hydrochloride, Ar.HCl, bond energy by infrared spectroscopy

    NASA Technical Reports Server (NTRS)

    Miziolek, A. W.; Pimentel, G. C.

    1976-01-01

    The infrared absorption of argon (200 to 760 torr) and hydrogen chloride (2 to 6 torr) mixtures is reexamined in the missing Q branch region (spectral region between 2860 and 3010 wavelength/cm) at temperatures ranging from 195 to 298 K. The temperature dependence of two absorption features of the argon hydrogen chloride complex, at 2887 and 2879 wavelength/cm, leads to a bond energy estimate that depends on the assumptions made about the internal degrees of freedom of the complex. It is shown that agreement with experiment can be reached for well depths near 1.2 kcal/mole. This result is relatively insensitive to the choice of the vibrational frequencies and anharmonicities, but does depend on the extent to which the energy level manifolds are truncated to avoid molecular excitation in excess of the bond energy. The bond energy is found to deviate from the commonly accepted value of 0.4 kcal/mole. Possible causes for the discrepancy are considered.

  11. Signaling proteins that influence energy intake may affect unintentional weight loss in elderly persons.

    PubMed

    Wernette, Catherine M; White, B Douglas; Zizza, Claire A

    2011-06-01

    After age 70 to 75 years, average body weight decreases both in ailing and healthy people because of a loss of appetite that results in reduced energy intake and the loss of body fat and lean muscle tissue. This so-called anorexia of aging predisposes elderly people to continued pathologic weight loss and malnutrition-major causes of morbidity and mortality. Health care professionals must understand the many factors involved in the anorexia of aging to help older adults prevent unintentional weight loss. Psychological, social, and cultural factors are important effectors; however, physiological factors are emphasized here because they are not thoroughly understood and they make it inherently difficult for most people to alter their body weight. Monoamines, steroid hormones (glucocorticoids and mineralocorticoids), endocannabinoids, and proteins all influence body weight. This review is an analysis of proteins from the brain, pancreas, adipose tissue, and gastrointestinal tract that are known to affect energy intake and energy balance, with an attempt to identify those factors that may change with aging. The articles included in this review were obtained by a PubMed database search using the keywords mouse OR rat OR human AND aged OR aging OR older OR elderly AND adult AND anorexia OR "unintentional weight loss," and each of the individual proteins discussed, as well as from the reference lists of those articles. The results reveal that some proteins may be important in the development of unintentional weight loss in elderly persons, whereas others may not have a significant role. However, many of the proteins that could conceivably have a role in unintentional weight loss have not yet been studied with that question in mind. Preventing unintentional weight loss in older adults is an important goal and further research on the role of proteins important for the maintenance of energy balance and the development of unintentional weight loss in elderly persons is

  12. Energy loss straggling in Aluminium foils for Li and C ions in fractional energy loss limits (ΔE/E) ∼10-60%

    NASA Astrophysics Data System (ADS)

    Diwan, P. K.; Kumar, Sunil; Kumar, Shyam; Sharma, V.; Khan, S. A.; Avasthi, D. K.

    2016-02-01

    The energy loss straggling of Li and C ions in Al foils of various thicknesses has been measured, within the fractional energy loss limit (∆E/E) ∼ 10-60%. These measurements have been performed using the 15UD Pelletron accelerator facility available at Inter University Accelerator Centre (IUAC), New Delhi, India. The measured straggling values have been compared with the corresponding predicted values adopting popularly used collisional straggling formulations viz Bohr, Lindhard and Scharff, Bethe-Livingston, Titeica. In addition, the experimental data has been compared to the Yang et al. empirical formula and Close Form Model, recently proposed by Montanari et al. The straggling values derived by Titeica theory were found to be in better agreement with the measured values as compared to other straggling formulations. The charge-exchange straggling component has been estimated from the measured data based on Titeica's theory. Finally, a function of the ion effective charge and the energy loss fraction within the target has been fitted to the latter straggling component.

  13. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans.

    PubMed

    Müller, Manfred J; Enderle, Janna; Bosy-Westphal, Anja

    2016-12-01

    Metabolic adaptation to weight changes relates to body weight control, obesity and malnutrition. Adaptive thermogenesis (AT) refers to changes in resting and non-resting energy expenditure (REE and nREE) which are independent from changes in fat-free mass (FFM) and FFM composition. AT differs in response to changes in energy balance. With negative energy balance, AT is directed towards energy sparing. It relates to a reset of biological defence of body weight and mainly refers to REE. After weight loss, AT of nREE adds to weight maintenance. During overfeeding, energy dissipation is explained by AT of the nREE component only. As to body weight regulation during weight loss, AT relates to two different set points with a settling between them. During early weight loss, the first set is related to depleted glycogen stores associated with the fall in insulin secretion where AT adds to meet brain's energy needs. During maintenance of reduced weight, the second set is related to low leptin levels keeping energy expenditure low to prevent triglyceride stores getting too low which is a risk for some basic biological functions (e.g., reproduction). Innovative topics of AT in humans are on its definition and assessment, its dynamics related to weight loss and its constitutional and neuro-endocrine determinants.

  14. Studies of Photosynthetic Energy and Charge Transfer by Two-dimensional Fourier transform electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Ogilvie, Jennifer

    2010-03-01

    Two-dimensional (2D) Fourier transform electronic spectroscopy has recently emerged as a powerful tool for the study of energy transfer in complex condensed-phase systems. Its experimental implementation is challenging but can be greatly simplified by implementing a pump-probe geometry, where the two phase-stable collinear pump pulses are created with an acousto-optic pulse-shaper. This approach also allows the use of a continuum probe pulse, expanding the available frequency range of the detection axis and allowing studies of energy transfer and electronic coupling over a broad range of frequencies. We discuss several benefits of 2D electronic spectroscopy and present 2D data on the D1-D2 reaction center complex of Photosystem II from spinach. We discuss the ability of 2D spectroscopy to distinguish between current models of energy and charge transfer in this system.

  15. Entropy Generation/Availability Energy Loss Analysis Inside MIT Gas Spring and "Two Space" Test Rigs

    NASA Technical Reports Server (NTRS)

    Ebiana, Asuquo B.; Savadekar, Rupesh T.; Patel, Kaushal V.

    2006-01-01

    The results of the entropy generation and availability energy loss analysis under conditions of oscillating pressure and oscillating helium gas flow in two Massachusetts Institute of Technology (MIT) test rigs piston-cylinder and piston-cylinder-heat exchanger are presented. Two solution domains, the gas spring (single-space) in the piston-cylinder test rig and the gas spring + heat exchanger (two-space) in the piston-cylinder-heat exchanger test rig are of interest. Sage and CFD-ACE+ commercial numerical codes are used to obtain 1-D and 2-D computer models, respectively, of each of the two solution domains and to simulate the oscillating gas flow and heat transfer effects in these domains. Second law analysis is used to characterize the entropy generation and availability energy losses inside the two solution domains. Internal and external entropy generation and availability energy loss results predicted by Sage and CFD-ACE+ are compared. Thermodynamic loss analysis of simple systems such as the MIT test rigs are often useful to understand some important features of complex pattern forming processes in more complex systems like the Stirling engine. This study is aimed at improving numerical codes for the prediction of thermodynamic losses via the development of a loss post-processor. The incorporation of loss post-processors in Stirling engine numerical codes will facilitate Stirling engine performance optimization. Loss analysis using entropy-generation rates due to heat and fluid flow is a relatively new technique for assessing component performance. It offers a deep insight into the flow phenomena, allows a more exact calculation of losses than is possible with traditional means involving the application of loss correlations and provides an effective tool for improving component and overall system performance.

  16. Athermal Energy Loss from X-rays Deposited in Thin Superconducting Films on Solid Substrates

    NASA Technical Reports Server (NTRS)

    Kozorezov, Alexander G.; Lambert, Colin J.; Bandler, Simon R.; Balvin, Manuel A.; Busch, Sarah E.; Sagler, Peter N.; Porst, Jan-Patrick; Smith, Stephen J.; Stevenson, Thomas R.; Sadleir, John E.

    2013-01-01

    When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an X-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position-dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low temperature detector. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various di.erent processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal di.usivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral line-shapes, and shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with di.erent geometries, where good agreement is also found.

  17. A low energy ion source for electron capture spectroscopy.

    PubMed

    Tusche, C; Kirschner, J

    2014-06-01

    We report on the design of an ion source for the production of single and double charged Helium ions with kinetic energies in the range from 300 eV down to 5 eV. The construction is based on a commercial sputter ion gun equipped with a Wien-filter for mass/charge separation. Retardation of the ions from the ionizer potential (2 keV) takes place completely within the lens system of the sputter gun, without modification of original parts. For 15 eV He(+) ions, the design allows for beam currents up to 30 nA, limited by the space charge repulsion in the beam. For He(2 +) operation, we obtain a beam current of 320 pA at 30 eV, and 46 pA at 5 eV beam energy, respectively. In addition, operating parameters can be optimized for a significant contribution of metastable He*(+) (2s) ions.

  18. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Győző; Tan, Howe-Siang

    2015-07-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems.

  19. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    PubMed Central

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Győző; Tan, Howe-Siang

    2015-01-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems. PMID:26228055

  20. Proton MR spectroscopy in herpes simplex encephalitis: Assessment of neuronal loss

    SciTech Connect

    Menon, D.K.; Sargentoni, J.; Peden, C.J.; Bell, J.D.; Cox, I.J.; Coutts, G.A.; Baudouin, C.; Newman, C.G. )

    1990-05-01

    We present here the case of an 11-year-old boy with herpes simplex encephalitis diagnosed on the basis of clinical features, serology, and response to acyclovir, who relapsed after 3 weeks of therapy. In vivo proton magnetic resonance spectroscopy (1H MRS) of the brain, at 8 and 16 weeks after the onset of symptoms, showed abnormalities, most prominently a reduction in the N-acetylaspartate/choline ratio. The role of 1H MRS in assessing disease activity is discussed.

  1. Revisiting the Characterization of the Losses in Piezoelectric Materials from Impedance Spectroscopy at Resonance.

    PubMed

    González, Amador M; García, Álvaro; Benavente-Peces, César; Pardo, Lorena

    2016-01-26

    Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics), polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we made simulations of the effect of the three types of losses in piezoelectric materials on the impedance spectrum at the resonance. We analyze independently each type of loss and show the differences among them. On the other hand, electrical and electronic engineers include piezoelectric sensors in electrical circuits to build devices and need electrical models of the sensor element. Frequently, material scientists and engineers use different languages, and the characteristic material coefficients do not have a straightforward translation to those specific electrical circuit components. To connect both fields of study, we propose the use of accurate methods of characterization from impedance measurements at electromechanical resonance that lead to determination of all types of losses, as an alternative to current standards. We introduce a simplified equivalent circuit model with electrical parameters that account for piezoceramic losses needed for the modeling and design of industrial applications.

  2. Revisiting the Characterization of the Losses in Piezoelectric Materials from Impedance Spectroscopy at Resonance

    PubMed Central

    González, Amador M.; García, Álvaro; Benavente-Peces, César; Pardo, Lorena

    2016-01-01

    Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics), polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we made simulations of the effect of the three types of losses in piezoelectric materials on the impedance spectrum at the resonance. We analyze independently each type of loss and show the differences among them. On the other hand, electrical and electronic engineers include piezoelectric sensors in electrical circuits to build devices and need electrical models of the sensor element. Frequently, material scientists and engineers use different languages, and the characteristic material coefficients do not have a straightforward translation to those specific electrical circuit components. To connect both fields of study, we propose the use of accurate methods of characterization from impedance measurements at electromechanical resonance that lead to determination of all types of losses, as an alternative to current standards. We introduce a simplified equivalent circuit model with electrical parameters that account for piezoceramic losses needed for the modeling and design of industrial applications. PMID:28787872

  3. Using high energy angle resolved photoelectron spectroscopy to reveal the charge density in solids.

    PubMed

    Månsson, M; Claesson, T; Finazzi, M; Dallera, C; Brookes, N B; Tjernberg, O

    2008-11-28

    The charge density in solids is a fundamental parameter. Here we demonstrate that the charge density can be determined by the use of angle resolved photoelectron spectroscopy. The method, which involves a Fourier-like transform from momentum space to real space, is demonstrated by utilizing soft x-ray angle resolved photoelectron spectroscopy to sample the complete three-dimensional Brillouin zone of copper. It is also shown that this can be done in an energy resolved way as to extract the charge density contribution from states of a particular energy.

  4. Low-loss and energy efficient modulation in silicon photonic waveguides by adiabatic elimination scheme

    NASA Astrophysics Data System (ADS)

    Mrejen, Michael; Suchowski, Haim; Bachelard, Nicolas; Wang, Yuan; Zhang, Xiang

    2017-07-01

    High-speed Silicon Photonics calls for solutions providing a small footprint, high density, and minimum crosstalk, as exemplified by the recent development of integrated optical modulators. Yet, the performances of such modulators are hindered by intrinsic material losses, which results in low energy efficiency. Using the concept of Adiabatic Elimination, here, we introduce a scheme allowing for the low-loss modulation in densely packed waveguides. Our system is composed of two waveguides, whose coupling is mediated by an intermediate third waveguide. The signal is carried by the two outer modes, while the active control of their coupling is achieved via the intermediate dark mode. The modulation is performed by the manipulation of the central-waveguide mode index, leaving the signal-carrying waveguides unaffected by the loss. We discuss how Adiabatic Elimination provides a solution for mitigating signal losses and designing relatively compact, broadband, and energy-efficient integrated optical modulators.

  5. Impact of potassium doping on the electronic structure of tetracene and pentacene: An electron energy-loss study

    SciTech Connect

    Roth, Friedrich

    2015-10-21

    We report the doping induced changes of the electronic structure of tetracene and pentacene probed by electron energy-loss spectroscopy in transmission. A comparison between the dynamic response of undoped and potassium-intercalated tetracene and pentacene emphasizes the appearance of a new excitation feature in the former gap upon potassium addition. Interestingly, the momentum dependency of this new excitation shows a negative dispersion. Moreover, the analysis of the C 1s and K 2p core-level excitation results in a significantly lower doping level compared to potassium doped picene, a recently discovered superconductor. Therefore, the present electronic structure investigations open a new pathway to better understand the exceptional differences between acenes and phenacene and their divergent behavior upon alkali doping.

  6. Low Energy Solar Neutrino Spectroscopy:. Results from the Borexino Experiment

    NASA Astrophysics Data System (ADS)

    D'Angelo, D.

    2011-03-01

    Till very recent the real-time solar neutrino experiments were detecting the tiny fraction of about 0.01% of the total neutrino flux above some MeV energy, the sub-MeV region remained explored only by radiochemical experiments without spectroscopical capabilities. The Borexino experiment, an unsegmented large volume liquid scintillator detector located in the Gran Sasso National Laboratory in central Italy, is at present the only experiment in the world acquiring the real-time solar neutrino data in the low-energy region, via the elastic scattering on electrons in the target mass. The data taking campaign started in 2007 and rapidly lead to the first independent measurement of the mono-cromatic line of 7Be of the solar neutrino spectrum at 862keV, which is of special interest because of the very loose limits coming from existing experiments. The latest measurement, after 41.3t · yr of exposure, is (49 ± 3stat ± 4syst)c/(day · 100t) and leaves the hypothesis of no oscillation inconsistent with data at 4σ level. It also represents the first direct measurement of the survival probability for solar ν e (P{7 Be}ee = 0.56 ± 0.10) in the vacuum-dominates oscillation regime. Recently Borexino was also able to measure of the 8B solar neutrinos interaction rate down to the threshold energy of 3 MeV, the lowest achieved so far. The inferred electron neutrino flux is Φ {8 B}ES = (2.7 ± 0.4stat ± 0.1syst ) × 106 cm{ - 2} s{ - 1} . The corresponding mean electron neutrino survival probability, is P{8 B}ee = 0.29 ± 0.10 at the effective energy of 8.9 MeV. Both measurements are in good agreement with other existing measurements and with predictions from the SSM in the hypothesis of MSW-LMA oscillation scenario. For the first time, thanks to the unprecedented radio-purity of the Borexino target and construction materials, we confirm with a single detector, the presence of a transition between the low energy vacuum-dominated and the high-energy matter-enhanced solar

  7. Heavy quark energy loss in high multiplicity proton-proton collisions at the LHC.

    PubMed

    Vogel, Sascha; Gossiaux, Pol Bernard; Werner, Klaus; Aichelin, Jörg

    2011-07-15

    One of the most promising probes to study deconfined matter created in high energy nuclear collisions is the energy loss of (heavy) quarks. It has been shown in experiments at the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass, experience a remarkable medium suppression in the quark gluon plasma. In this exploratory investigation we study the energy loss of heavy quarks in high multiplicity proton-proton collisions at LHC energies. Although the colliding systems are smaller than compared to those at the Relativistic Heavy Ion Collider (p+p vs Au+Au), the higher energy might lead to multiplicities comparable to Cu+Cu collisions at the Relativistic Heavy Ion Collider. The interaction of charm quarks with this environment gives rise to a non-negligible suppression of high momentum heavy quarks in elementary collisions.

  8. Energy loss of ions at metal surfaces: Band-structure effects

    SciTech Connect

    Alducin, M.; Silkin, V.M.; Juaristi, J.I.; Chulkov, E.V.

    2003-03-01

    We study band-structure effects on the energy loss of protons scattered off the Cu (111) surface. The distance dependent stopping power for a projectile traveling parallel to the surface is calculated within the linear response theory. The self-consistent electronic response of the system is evaluated within the random-phase approximation. In order to characterize the surface band structure, the electronic single-particle wave functions and energies are obtained by solving the Schroedinger equation with a realistic one-dimensional model potential. This potential reproduces the main features of the Cu (111) surface: the energy band gap for electron motion along the surface normal, as well as the binding energy of the occupied surface state and the first image state. Comparison of our results with those obtained within the jellium model allows us to characterize the band-structure effects in the energy loss of protons interacting with the Cu (111) surface.

  9. The energy cost of walking before and after significant weight loss.

    PubMed

    Foster, G D; Wadden, T A; Kendrick, Z V; Letizia, K A; Lander, D P; Conill, A M

    1995-06-01

    The purpose of this study was to determine whether significant weight loss reduced the energy cost of activity more than that expected based on decreased body weight. Standing energy expenditure was measured and subtracted from the total energy cost of walking to determine ambulatory energy expenditure (AEE). The energy cost of walking was determined in 11 obese women at baseline, week 9 [after 8 wk of a 1758-3349 kJ.d-1 diet], and week 22 (after 2 wk of weight stability). AEE accounted for 80% of the energy cost of walking. Body weight was the principal determinant of AEE, but the relationship was not 1:1. Subjects reduced body weight by 13% at week 9 and 21% at week 22. Analyses which controlled for the relationship between AEE and weight at baseline, showed no change in AEE at week 9. By contrast, at week 22, AEE was reduced more than expected based on a lower body weight. These findings suggest that after significant weight loss, reduced-obese persons will expend less energy for the same activity, even after accounting for the decrease in body weight. These data also suggest that weight-based estimates of exercise energy expenditure may be inappropriate after significant weight loss.

  10. Spectroscopy and Chemistry of Molecules with High Vibrational Energy Content.

    DTIC Science & Technology

    1982-10-15

    dissociation channels, viz., HC elimination, ring scission, and C=Cl homolysis. (Francisco and Steinfeld, 1981; Lawrance et al., 1981). The species CF300CF 3...Trifluoromethyl) peroxide", Intl. J. Chem. Kinetics, 13, 627 (1981). W.D. Lawrance , J. Silberstein, Zhang Fu-min, Zhu Qing-shi, J.S. Francisco, and J...75, 3153 (1981). J.S. Francisco, W.D. Lawrance , J.I. Steinfeld, and R.G. Gilbert, "Infrared Multiphoton Decomposition and Energy-Dependent

  11. Energy loss of MeV protons specularly reflected from metal surfaces

    SciTech Connect

    Juaristi, J.I.

    1996-05-01

    A parameter-free model is presented to study the energy loss of fast protons specularly reflected from metal surfaces. The contributions to the energy loss from excitation of valence-band electrons and ionization of localized target-atom electronic states are calculated separately. The former is calculated from the induced surface wake potential using linear response theory and the specular-reflection model, while the latter is calculated in the first Born approximation. The results obtained are in good agreement with available experimental data. However, the experimental qualitative trend of the energy loss as a function of the angle of incidence is obtained when the valence-band electron model is replaced by localized target atom electron states, though with a worse quantitative agreement. {copyright} {ital 1996 The American Physical Society.}

  12. Jet suppression and the flavor dependence of partonic energy loss with ATLAS

    NASA Astrophysics Data System (ADS)

    Kosek, Tomas

    2016-12-01

    In relativistic heavy ion collisions, a hot medium with a high density of unscreened color charges is produced. One manifestation of the energy loss of jets propagating through the medium is a lower yield of jets and hadrons emerging from this medium than expected in the absence of medium effects. Therefore modifications of the jet yield are directly sensitive to the energy loss mechanism. Furthermore, jets with different flavor content are expected to be affected by the medium in different ways. In this publication, the latest ATLAS results on single hadron suppression along with the complementary measurements of single jet suppression are presented. Rapidity dependence, which is sensitive to the relative energy loss between quark and gluon jets, is discussed. Finally, a new measurement of jet fragmentation functions is presented.

  13. Additive effects of electronic and nuclear energy loss in irradiation-induced amorphization of zircon

    DOE PAGES

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-29

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. As a result, we found that taking the electronic energy loss out as a frictionmore » term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.« less

  14. Additive effects of electronic and nuclear energy loss in irradiation-induced amorphization of zircon

    SciTech Connect

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-29

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. As a result, we found that taking the electronic energy loss out as a friction term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.

  15. Technical and Economic Assessment of the Implementation of Measures for Reducing Energy Losses in Distribution Systems

    NASA Astrophysics Data System (ADS)

    Aguila, Alexander; Wilson, Jorge

    2017-07-01

    This paper develops a methodology to assess a group of measures of electrical improvements in distribution systems, starting from the complementation of technical and economic criteria. In order to solve the problem of energy losses in distribution systems, technical and economic analysis was performed based on a mathematical model to establish a direct relationship between the energy saved by way of minimized losses and the costs of implementing the proposed measures. This paper aims at analysing the feasibility of reducing energy losses in distribution systems, by changing existing network conductors by larger crosssection conductors and distribution voltage change at higher levels. The impact of this methodology provides a highly efficient mathematical tool for analysing the feasibility of implementing improvement projects based on their costs which is a very useful tool for the distribution companies that will serve as a starting point to the analysis for this type of projects in distribution systems.

  16. Additive effects of electronic and nuclear energy losses in irradiation-induced amorphization of zircon

    SciTech Connect

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-28

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. We found that taking the electronic energy loss out as a friction term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.

  17. Energetics and optimum motion of oscillating lifting surfaces. [energy losses of rigid wings

    NASA Technical Reports Server (NTRS)

    Ahmadi, A. R.; Widnall, S. E.

    1983-01-01

    Low-frequency, unsteady, lifting-line theory is used to characterize the energetics and optimum motion of an unswept rigid wing oscillating harmonically in an inviscid, incompressible flow. The energetics calculations account for the leading edge suction force, the power absorbed in the wing oscillations, and the energy loss rate produced by vortex shedding. Optimization is achieved by minimizing the average energy loss rate in relation to a given thrust, and a unique solution is found in the three dimensional case for low, reduced frequencies. The two-dimensional solution is nonunique, a condition which is examined in terms of the normal modes of the energy loss rate matrix. An invisible mode with a hydrodynamic efficiency of 100 pct is obtained in the two-dimensional case, causing the nonuniqueness of the solution by yielding no fixed positive thrust through perfect unsteady feathering.

  18. Hypochlorous acid-promoted loss of metabolic energy in Escherichia coli.

    PubMed Central

    Barrette, W C; Albrich, J M; Hurst, J K

    1987-01-01

    Oxidation of Escherichia coli by hypochlorous acid (HOCl) or chloramine (NH2Cl) gives rise to massive hydrolysis of cytosolic nucleotide phosphoanhydride bonds, although no immediate change occurs in either the nucleotide pool size or the concentrations of extracellular end products of AMP catabolism. Titrimetric curves of the extent of hydrolysis coincide with curves for loss of cell viability, e.g., reduction in the adenylate energy charge from 0.8 to 0.1-0.2 accompanies loss of 99% of the bacterial CFU. The oxidative damage caused by HOCl is irreversible within 100 ms of exposure of the organism, although nucleotide phosphate bond hydrolysis requires several minutes to reach completion. Neither HOCl nor NH2Cl reacts directly with nucleotides to hydrolyze phosphoanhydride bonds. Loss of viability is also accompanied by inhibition of induction of beta-galactosidase. The proton motive force, determined from the distribution of 14C-radiolabeled lipophilic ions, declines with incremental addition of HOCl after loss of respiratory function; severalfold more oxidant is required for the dissipation of the proton motive force than for loss of viability. These observations establish a causal link between loss of metabolic energy and cellular death and indicate that the mechanisms of oxidant-induced nucleotide phosphate bond hydrolysis are indirect and that they probably involve damage to the energy-transducing and transport proteins located in the bacterial plasma membrane. PMID:2820883

  19. Hypochlorous acid-promoted loss of metabolic energy in Escherichia coli

    SciTech Connect

    Barrette, W.C. Jr.; Albrich, J.M.; Hurst, J.K.

    1987-10-01

    Oxidation of Escherichia coli by hypochlorous acid (HOCl) or chloramine (NH/sub 2/Cl) gives rise to massive hydrolysis of cytosolic nucleotide phosphoanhydride bonds, although no immediate change occurs in either the nucleotide pool size or the concentrations of extracellular end products of AMP catabolism. Titrimetric curves of the extent of hydrolysis coincide with curves for loss of cell viability, e.g., reduction in the adenylate energy charge from 0.8 to 0.1-0.2 accompanies loss of 99% of the bacterial CFU. The oxidative damage caused by HOCl is irreversible within 100 ms of exposure of the organism, although nucleotide phosphate bond hydrolysis requires several minutes to reach completion. Neither HOCl nor NH/sub 2/Cl reacts directly with nucleotides to hydrolyze phosphoanhydride bonds. Loss of viability is also accompanied by inhibition of induction of beta-galactosidase. The proton motive force, determined from the distribution of /sup 14/C-radiolabeled lipophilic ions, declines with incremental addition of HOCl after loss of respiratory function; severalfold more oxidant is required for the dissipation of the proton motive force than for loss of viability. These observations establish a causal link between loss of metabolic energy and cellular death and indicate that the mechanisms of oxidant-induced nucleotide phosphate bond hydrolysis are indirect and that they probably involve damage to the energy-transducing and transport proteins located in the bacterial plasma membrane.

  20. Quantitative analysis of electron energy loss spectra and modelling of optical properties of multilayer systems for extreme ultraviolet radiation regime

    SciTech Connect

    Gusenleitner, S.; Hauschild, D.; Reinert, F.; Handick, E.

    2014-03-28

    Ruthenium capped multilayer coatings for use in the extreme ultraviolet (EUV) radiation regime have manifold applications in science and industry. Although the Ru cap shall protect the reflecting multilayers, the surface of the heterostructures suffers from contamination issues and surface degradation. In order to get a better understanding of the effects of these impurities on the optical parameters, reflection electron energy loss spectroscopy (REELS) measurements of contaminated and H cleaned Ru multilayer coatings were taken at various primary electron beam energies. Experiments conducted at low primary beam energies between 100 eV and 1000 eV are very surface sensitive due to the short inelastic mean free path of the electrons in this energy range. Therefore, influences of the surface condition on the above mentioned characteristics can be appraised. In this paper, it can be shown that carbon and oxide impurities on the mirror surface decrease the transmission of the Ru cap by about 0.75% and the overall reflectance of the device is impaired as the main share of the non-transmitted EUV light is absorbed in the contamination layer.

  1. Measurement of optical constants of Si and SiO2 from reflection electron energy loss spectra using factor analysis method

    NASA Astrophysics Data System (ADS)

    Jin, H.; Shinotsuka, H.; Yoshikawa, H.; Iwai, H.; Tanuma, S.; Tougaard, S.

    2010-04-01

    The energy loss functions (ELFs) and optical constants of Si and SiO2 were obtained from quantitative analysis of reflection electron energy loss spectroscopy (REELS) by a new approach. In order to obtain the ELF, which is directly related to the optical constants, we measured series of angular and energy dependent REELS spectra for Si and SiO2. The λ(E )K(ΔE) spectra, which are the product of the inelastic mean free path (IMFP) and the differential inverse IMFP, were obtained from the measured REELS spectra. We used the factor analysis (FA) method to analyze series of λ(E )K(ΔE) spectra for various emission angles at fixed primary beam energy to separate the surface-loss and bulk-loss components. The extracted bulk-loss components enable to obtain the ELFs of Si and SiO2, which are checked by oscillator strength-sum and perfect-screening-sum rules. The real part of the reciprocal of the complex dielectric function was determined by Kramers-Kronig analysis of the ELFs. Subsequently, the optical constants of Si and SiO2 were calculated. The resulting optical constants in terms of the refractive index and the extinction coefficient for Si and SiO2 are in good agreement with Palik's reference data. The results demonstrate the general applicability of FA as an efficient method to obtain the bulk ELF and to determine the optical properties from REELS measurements.

  2. Multi-excitation Raman difference spectroscopy based on modified multi-energy constrained iterative deconvolution algorithm

    NASA Astrophysics Data System (ADS)

    Zou, Wenlong; Cai, Zhijian; Zhou, Hongwu; Wu, Jianhong

    2013-12-01

    Raman spectroscopy is fast and nondestructive, and it is widely used in chemistry, biomedicine, food safety and other areas. However, Raman spectroscopy is often hampered by strong fluorescence background, especially in food additives detection and biomedicine researching. In this paper, one efficient technique was the multi-excitation Raman difference spectroscopy (MERDS) which incorporated a series of small wavelength-shift wavelengths as excitation sources. A modified multi-energy constrained iterative deconvolution (MMECID) algorithm was proposed to reconstruct the Raman Spectroscopy. Computer simulation and experiments both demonstrated that the Raman spectrum can be well reconstructed from large fluorescence background. The more excitation sources used, the better signal to noise ratio got. However, many excitation sources were equipped on the Raman spectrometer, which increased the complexity of the experimental system. Thus, a trade-off should be made between the number of excitation frequencies and experimental complexity.

  3. Non-equilibrium energy loss for very highly charged ions in insulators

    SciTech Connect

    Briere, M.A.; Schenkel, T.; Bauer, P.; Amau, A.

    1996-12-31

    The energy loss of 144 keV Ar{sup +16} ions on a bilayer structure of C-CaF{sub 2} has been measured. An asymmetry in the results is found depending on which layer is passed by the ion first: the energy loss is about four times larger when the CaF{sub 2} layer is traversed by the ion first. We interpret this as an indication of the existence of a nonequilibrium charge state of the Ar ions inside the solid in the case of the insulator.

  4. Negative electron energy loss and second-harmonic emission of nonlinear nanoparticles.

    PubMed

    Xu, Jinying; Zhang, Xiangdong

    2011-11-07

    A fast and general technique to investigation the interaction between a fast electron and nonlinear materials consisting of centrosymmetric spheres is presented by means of multiple scattering of electromagnetic multipole fields. Two kinds of new effect, the negative electron energy loss caused by the second-harmonic field and the second-harmonic Smith-Purcell radiation using finite chain of nonlinear spheres, are predicted for the first time. It is shown that these new effects can be probed by the electron energy loss spectrum, suggesting their possible applications in tunable light sources for the second-harmonic generation.

  5. Synergistic effects of nuclear and electronic energy loss in KTaO3 under ion irradiation

    DOE PAGES

    Zarkadoula, Eva; Jin, Ke; Zhang, Yanwen; ...

    2017-01-09

    In this paper, we use the inelastic thermal spike model for insulators and molecular dynamic simulations to investigate the effects of pre-existing damage on the energy dissipation and structural alterations in KTaO3 under irradiation with 21 MeV Ni ions. Our results reveal a synergy between the pre-existing defects and the electronic energy loss, indicating that the defects play an important role on the energy deposition in the system. Our findings highlight the need for better understanding on the role of defects in electronic energy dissipation and the coupling of the electronic and atomic subsystems.

  6. Energy-loss of He ions in carbon allotropes studied by elastic resonance in backscattering spectra

    NASA Astrophysics Data System (ADS)

    Tosaki, Mitsuo; Rauhala, Eero

    2015-10-01

    Backscattering spectra for 4He ions incident on carbon allotropes have been measured in the energy range from 4.30 to 4.95 MeV in steps of 50-100 keV at scattering angles of 106° and 170°. We used three carbon allotropes: graphite, diamond and amorphous carbon. For all these allotropes, we can observe the sharp (4He, 12C) elastic nuclear resonance at the He ion energy of 4.265 MeV in the backscattering spectra. By varying the incident He energy, we have systematically analyzed the profiles of the resonance peaks to study the energy-loss processes: stopping cross-sections and energy-loss straggling around the interesting region of the stopping maximum at about 500 keV. We focus on the resonance profiles and investigate an allotropic effect concerning the energy-loss. Furthermore, an energy bunching effect on the straggling is presented and the mechanism is discussed.

  7. Intermittent Moderate Energy Restriction Improves Weight Loss Efficiency in Diet-Induced Obese Mice.

    PubMed

    Seimon, Radhika V; Shi, Yan-Chuan; Slack, Katy; Lee, Kailun; Fernando, Hamish A; Nguyen, Amy D; Zhang, Lei; Lin, Shu; Enriquez, Ronaldo F; Lau, Jackie; Herzog, Herbert; Sainsbury, Amanda

    2016-01-01

    Intermittent severe energy restriction is popular for weight management. To investigate whether intermittent moderate energy restriction may improve this approach by enhancing weight loss efficiency, we conducted a study in mice, where energy intake can be controlled. Male C57/Bl6 mice that had been rendered obese by an ad libitum diet high in fat and sugar for 22 weeks were then fed one of two energy-restricted normal chow diets for a 12-week weight loss phase. The continuous diet (CD) provided 82% of the energy intake of age-matched ad libitum chow-fed controls. The intermittent diet (ID) provided cycles of 82% of control intake for 5-6 consecutive days, and ad libitum intake for 1-3 days. Weight loss efficiency during this phase was calculated as (total weight change) ÷ [(total energy intake of mice on CD or ID)-(total average energy intake of controls)]. Subsets of mice then underwent a 3-week weight regain phase involving ad libitum re-feeding. Mice on the ID showed transient hyperphagia relative to controls during each 1-3-day ad libitum feeding period, and overall ate significantly more than CD mice (91.1±1.0 versus 82.2±0.5% of control intake respectively, n = 10, P<0.05). There were no significant differences between CD and ID groups at the end of the weight loss or weight regain phases with respect to body weight, fat mass, circulating glucose or insulin concentrations, or the insulin resistance index. Weight loss efficiency was significantly greater with ID than with CD (0.042±0.007 versus 0.018±0.001 g/kJ, n = 10, P<0.01). Mice on the CD exhibited significantly greater hypothalamic mRNA expression of proopiomelanocortin (POMC) relative to ID and control mice, with no differences in neuropeptide Y or agouti-related peptide mRNA expression between energy-restricted groups. Intermittent moderate energy restriction may offer an advantage over continuous moderate energy restriction, because it induces significantly greater weight loss relative to energy

  8. Intermittent Moderate Energy Restriction Improves Weight Loss Efficiency in Diet-Induced Obese Mice

    PubMed Central

    Seimon, Radhika V.; Shi, Yan-Chuan; Slack, Katy; Lee, Kailun; Fernando, Hamish A.; Nguyen, Amy D.; Zhang, Lei; Lin, Shu; Enriquez, Ronaldo F.; Lau, Jackie

    2016-01-01

    Background Intermittent severe energy restriction is popular for weight management. To investigate whether intermittent moderate energy restriction may improve this approach by enhancing weight loss efficiency, we conducted a study in mice, where energy intake can be controlled. Methods Male C57/Bl6 mice that had been rendered obese by an ad libitum diet high in fat and sugar for 22 weeks were then fed one of two energy-restricted normal chow diets for a 12-week weight loss phase. The continuous diet (CD) provided 82% of the energy intake of age-matched ad libitum chow-fed controls. The intermittent diet (ID) provided cycles of 82% of control intake for 5–6 consecutive days, and ad libitum intake for 1–3 days. Weight loss efficiency during this phase was calculated as (total weight change) ÷ [(total energy intake of mice on CD or ID)–(total average energy intake of controls)]. Subsets of mice then underwent a 3-week weight regain phase involving ad libitum re-feeding. Results Mice on the ID showed transient hyperphagia relative to controls during each 1–3-day ad libitum feeding period, and overall ate significantly more than CD mice (91.1±1.0 versus 82.2±0.5% of control intake respectively, n = 10, P<0.05). There were no significant differences between CD and ID groups at the end of the weight loss or weight regain phases with respect to body weight, fat mass, circulating glucose or insulin concentrations, or the insulin resistance index. Weight loss efficiency was significantly greater with ID than with CD (0.042±0.007 versus 0.018±0.001 g/kJ, n = 10, P<0.01). Mice on the CD exhibited significantly greater hypothalamic mRNA expression of proopiomelanocortin (POMC) relative to ID and control mice, with no differences in neuropeptide Y or agouti-related peptide mRNA expression between energy-restricted groups. Conclusion Intermittent moderate energy restriction may offer an advantage over continuous moderate energy restriction, because it induces

  9. Band structure effects in the energy loss of low-energy protons and deuterons in thin films of Pt

    NASA Astrophysics Data System (ADS)

    Celedón, C. E.; Sánchez, E. A.; Salazar Alarcón, L.; Guimpel, J.; Cortés, A.; Vargas, P.; Arista, N. R.

    2015-10-01

    We have investigated experimentally and by computer simulations the energy-loss and angular distribution of low energy (E < 10 keV) protons and deuterons transmitted through thin polycrystalline platinum films. The experimental results show significant deviations from the expected velocity dependence of the stopping power in the range of very low energies with respect to the predictions of the Density Functional Theory for a jellium model. This behavior is similar to those observed in other transition metals such as Cu, Ag and Au, but different from the linear dependence recently observed in another transition metal, Pd, which belongs to the same Group of Pt in the Periodic Table. These differences are analyzed in term of the properties of the electronic bands corresponding to Pt and Pd, represented in terms of the corresponding density of states. The present experiments include also a detailed study of the angular dependence of the energy loss and the angular distributions of transmitted protons and deuterons. The results are compared with computer simulations based on the Monte Carlo method and with a theoretical model that evaluates the contributions of elastic collisions, path length effects in the inelastic energy losses, and the effects of the foil roughness. The results of the analysis obtained from these various approaches provide a consistent and comprehensive description of the experimental findings.

  10. Vibrational energy transport in molecules studied by relaxation-assisted two-dimensional infrared spectroscopy.

    PubMed

    Rubtsova, Natalia I; Rubtsov, Igor V

    2015-04-01

    This review presents an overview of the relaxation-assisted two-dimensional infrared (RA 2DIR) spectroscopy method for measuring structures and energy transport dynamics in molecules. The method strongly enhances the range of accessible distances compared to traditional 2DIR and offers new structural reporters, such as the energy transport time, cross-peak amplification factors, and connectivity patterns. The use of the method for assigning vibrational modes with various levels of delocalization is illustrated. RA 2DIR relies on vibrational energy transport in molecules; as such, the transport mechanism can be conveniently studied by the method. Applications to identify diffusive and ballistic energy transport are demonstrated.

  11. Simulating Energy Relaxation in Pump-Probe Vibrational Spectroscopy of Hydrogen-Bonded Liquids.

    PubMed

    Dettori, Riccardo; Ceriotti, Michele; Hunger, Johannes; Melis, Claudio; Colombo, Luciano; Donadio, Davide

    2017-03-14

    We introduce a nonequilibrium molecular dynamics simulation approach, based on the generalized Langevin equation, to study vibrational energy relaxation in pump-probe spectroscopy. A colored noise thermostat is used to selectively excite a set of vibrational modes, leaving the other modes nearly unperturbed, to mimic the effect of a monochromatic laser pump. Energy relaxation is probed by analyzing the evolution of the system after excitation in the microcanonical ensemble, thus providing direct information about the energy redistribution paths at the molecular level and their time scale. The method is applied to hydrogen-bonded molecular liquids, specifically deuterated methanol and water, providing a robust picture of energy relaxation at the molecular scale.

  12. Determination of molecular spectroscopic parameters and energy-transfer rates by double-resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Steinfeld, J. I.; Foy, B.; Hetzler, J.; Flannery, C.; Klaassen, J.; Mizugai, Y.; Coy, S.

    1990-05-01

    The spectroscopy of small to medium-size polyatomic molecules can be extremely complex, especially in higher-lying overtone and combination vibrational levels. The high density of levels also complicates the understanding of inelastic collision processes, which is required to model energy transfer and collision broadening of spectral lines. Both of these problems can be addressed by double-resonance spectroscopy, i.e., time-resolved pump-probe measurements using microwave, infrared, near-infrared, and visible-wavelength sources. Information on excited-state spectroscopy, transition moments, inelastic energy transfer rates and propensity rules, and pressure-broadening parameters may be obtained from such experiments. Examples are given for several species of importance in planetary atmospheres, including ozone, silane, ethane, and ammonia.

  13. Determination of molecular spectroscopic parameters and energy-transfer rates by double-resonance spectroscopy

    NASA Technical Reports Server (NTRS)

    Steinfeld, J. I.; Foy, B.; Hetzler, J.; Flannery, C.; Klaassen, J.; Mizugai, Y.; Coy, S.

    1990-01-01

    The spectroscopy of small to medium-size polyatomic molecules can be extremely complex, especially in higher-lying overtone and combination vibrational levels. The high density of levels also complicates the understanding of inelastic collision processes, which is required to model energy transfer and collision broadening of spectral lines. Both of these problems can be addressed by double-resonance spectroscopy, i.e., time-resolved pump-probe measurements using microwave, infrared, near-infrared, and visible-wavelength sources. Information on excited-state spectroscopy, transition moments, inelastic energy transfer rates and propensity rules, and pressure-broadening parameters may be obtained from such experiments. Examples are given for several species of importance in planetary atmospheres, including ozone, silane, ethane, and ammonia.

  14. Energy loss distributions of relativistic protons axially channeled in a bent silicon crystal

    NASA Astrophysics Data System (ADS)

    Stojanov, Nace; Petrović, Srdjan; Nešković, Nebojša

    2013-05-01

    A detailed study of the energy loss distributions of the relativistic protons axially channeled in the bent < 100 > Si crystals is presented in this work. The bending angle was varied from 0 to 20 μrad, while the crystal thickness was equal to 1 mm. The proton energy was chosen to be 7 TeV in accordance with the Large Hadron Collider (LHC) project, at the European Organization for Nuclear Research (CERN), in Geneva, Switzerland. The energy loss distributions of the channeled protons were generated using the numerical solution of the proton equations of motion in the transverse plane and the computer simulation method. An accurate energy loss model was used, which takes into account the trajectory dependence of the energy loss of protons during their motion through the crystal channels. Further, the dispersion of the proton's scattering angle caused by its collisions with the electrons of the crystal and the divergence of the proton beam were taken into account. The calculated dependence of the number of dechanneled protons on the bending angle was excellently fitted by the Gompertz type dechanneling function.

  15. The energy loss straggling of low Z ions in solids and gases

    NASA Astrophysics Data System (ADS)

    Montanari, C. C.; Miraglia, J. E.

    2013-04-01

    We present a study on the energy loss straggling of low Z ions (H up to B) in different solid (Al, Ti, Cu, Zn, Ge, Au) and gaseous targets (Ne, Ar, Kr, Xe). This work includes on one side, a critical analysis of the available experimental data and possible non-statistical (rugosity and inhomogeneity) contributions. On the other side, theoretical calculations performed by using the shell-wise local plasma approximation and the comparison of these results with the experimental data and with other theoretical curves available in the literature. We find that for the ions here considered, the square of the energy loss straggling normalized to Bohr limit is independent of the ion nuclear charge and of the ion charge state, in the case of electrons bound to the projectile. This shows a clear Z2 dependence of the square energy loss straggling, with Z being the ion nuclear charge. The tendency to Bohr limit at high energies, and the inconvenience of using Yang formula (Q. Yang etal, Nucl. Instrum. Meth. Phys. Res B 61, 149-155 (1991)) are also mentioned. The bases for the future development of a general formula for the energy loss straggling are introduced.

  16. Collisional vibrational relaxation of a triplet state: Energy-dependent energy loss from [ital T][sub 1] pyrazine

    SciTech Connect

    Bevilacqua, T.J.; Weisman, R.B. )

    1993-04-15

    The loss of vibrational energy from gas phase [ital T][sub 1] pyrazine molecules has been measured for thermal collisions with helium, argon, H[sub 2], SF[sub 6], and ground state pyrazine. Triplet pyrazine was prepared with a well defined vibrational energy of 5433 cm[sup [minus]1] through [ital S][sub 1][r arrow][ital T][sub 1] intersystem crossing following optical excitation to the 8[ital a][sup 1] level of [ital S][sub 1]. The time-dependent vibrational energy content of the excited pyrazine molecules was then deduced using a recently developed direct'' method involving the kinetics of subsequent [ital T][sub 1][r arrow][ital S][sub 0] intersystem crossing. For each of the collision partners studied, it was possible to find the average energy lost per gas kinetic collision for donor energies ranging from ca. 2000 to 5433 cm[sup [minus]1]. The magnitudes of these energy losses generally increased with the mass and vibrational complexity of the relaxing collision partner. For vibrational energy contents near 5000 cm[sup [minus]1], relaxation of the triplet pyrazine was enhanced by factors of as much as 24 relative to [ital S][sub 0] benzene at a similar vibrational energy. In addition, with all collision partners studied the average energy lost per collision showed appparent threshold behavior near 3000 cm[sup [minus]1], increasing by approximately an order of magnitude as the donor's energy increased from 2500 to 5000 cm[sup [minus]1]. The findings of this first quantitative study of triplet relaxation suggest that collisional vibrational energy transfer from organic triplet states may proceed by mechanisms different from those that dominate ground state relaxation.

  17. Energy homeostasis and appetite regulating hormones as predictors of weight loss in men and women.

    PubMed

    Williams, Rebecca L; Wood, Lisa G; Collins, Clare E; Morgan, Philip J; Callister, Robin

    2016-06-01

    Sex differences in weight loss are often seen despite using the same weight loss program. There has been relatively little investigation of physiological influences on weight loss success in males and females, such as energy homeostasis and appetite regulating hormones. The aims were to 1) characterise baseline plasma leptin, ghrelin and adiponectin concentrations in overweight and obese males and females, and 2) determine whether baseline concentrations of these hormones predict weight loss in males and females. Subjects were overweight or obese (BMI 25-40 kg/m(2)) adults aged 18-60 years. Weight was measured at baseline, and after three and six months participation in a weight loss program. Baseline concentrations of leptin, adiponectin and ghrelin were determined by enzyme-linked immunosorbent assay (ELISA). An independent t-test or non-parametric equivalent was used to determine any differences between sex. Linear regression determined whether baseline hormone concentrations were predictors of six-month weight change. Females had significantly higher baseline concentrations of leptin, adiponectin and unacylated ghrelin as well as ratios of leptin:adiponectin and leptin:ghrelin. The ratio of acylated:unacylated ghrelin was significantly higher in males. In males and females, a higher baseline concentration of unacylated ghrelin predicted greater weight loss at six months. Additionally in females, higher baseline total ghrelin predicted greater weight loss and a higher ratio of leptin:ghrelin predicted weight gain at six months. A higher pre-weight-loss plasma concentration of unacylated ghrelin is a modest predictor of weight loss success in males and females, while a higher leptin:ghrelin ratio is a predictor of weight loss failure in females. Further investigation is required into what combinations and concentrations of these hormones are optimal for weight loss success. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Precise measurements of energy loss straggling for swift heavy ions in polymers

    NASA Astrophysics Data System (ADS)

    Rani, Bindu; Neetu; Sharma, Kalpana; Diwan, P. K.; Kumar, Shyam

    2016-11-01

    The energy loss straggling measurements for heavy ions with Z = 3-22 (∼0.2-2.5 MeV/u) in PEN (C7H5O2) and PET (C10H8O4) polymers have been carried out utilizing the swift heavy ion beam facility from 15UD Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi, India. The recorded spectra are analyzed in such a way that the Straggling associated with energy loss process could be measured in a systematic manner at any selected value of energy, in terms of per unit thickness of the absorber, at any desired energy intervals. The measured values have been compared with the calculated values obtained from the most commonly used Bethe-Livingston formulations applicable for collisional straggling. The results are tried to be understood in terms of the effective charge on the impinging ion within the absorber. Some interesting trends are observed.

  19. X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium

    SciTech Connect

    Drummond, J.L.; Steinberg, A.D.; Krauss, A.R.

    1997-08-01

    The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

  20. Changes of pH and energy state in subacute human ischemia assessed by multinuclear magnetic resonance spectroscopy.

    PubMed

    Zöllner, Johann Philipp; Hattingen, Elke; Singer, Oliver C; Pilatus, Ulrich

    2015-02-01

    In vivo changes in tissue pH and energy metabolism are key to understanding stroke pathophysiology. Our goal was to study pH changes in subacute ischemic stroke and their relation to energy metabolism, which, unlike acidosis in acute stroke, are not yet well understood. We measured tissue pH and phospholipid as well as cell energy markers, including creatine, phosphocreatine, and N-acetyl-aspartate in subacute stroke with combined (1)H and (31)P magnetic resonance spectroscopy. We included 19 patients with first-ever ischemic stroke (mean time after stroke, 6 days). We then compared metabolite concentrations in the ischemic tissue to contralateral (healthy) tissue using multivariate ANOVA to assess significant differences in metabolite levels between both tissue compartments. In subacute stroke, a tissue fraction with significantly increased tissue pH was observed as compared with healthy contralateral tissue (pH, 7.09 versus 7.03; P=0.002) concurrent with splitting of the pH signal with 1 peak being more alkalotic. Furthermore, only a moderate decrease of energy-rich metabolites (phosphocreatine reduced by 17%, ATP reduced by 19%) was present, whereas total creatine was reduced by 51%. The finding of an alkalotic pH split in subacute ischemia is unprecedented. The pH split and only incomplete energy loss in subacute stroke suggest 2 differently viable cellular moieties, best explained by active compensatory mechanisms after acute cerebral ischemia. © 2014 American Heart Association, Inc.

  1. Energy losses of charged particles in a finite layer of substance

    NASA Astrophysics Data System (ADS)

    Chechin, V. A.

    1985-04-01

    The energy lost by a charged particle as it crosses a plane-parallel plate with dielectric permittivity in a vacuum is calculated theoretically, applying the intermediate transition to the Heaviside transformation and considering various combinations of particle Lorentz factor and plate thickness. The problems encountered in comparing the theoretical predictions with experimental data are examined, and the application of the model of energy loss in very thin layers of Ermilova et al. (1974) is found to explain the observed anomalies.

  2. Antiferroelectric Thin-Film Capacitors with High Energy-Storage Densities, Low Energy Losses, and Fast Discharge Times.

    PubMed

    Ahn, Chang Won; Amarsanaa, Gantsooj; Won, Sung Sik; Chae, Song A; Lee, Dae Su; Kim, Ill Won

    2015-12-09

    We demonstrate a capacitor with high energy densities, low energy losses, fast discharge times, and high temperature stabilities, based on Pb(0.97)Y(0.02)[(Zr(0.6)Sn(0.4))(0.925)Ti(0.075)]O3 (PYZST) antiferroelectric thin-films. PYZST thin-films exhibited a high recoverable energy density of U(reco) = 21.0 J/cm(3) with a high energy-storage efficiency of η = 91.9% under an electric field of 1300 kV/cm, providing faster microsecond discharge times than those of commercial polypropylene capacitors. Moreover, PYZST thin-films exhibited high temperature stabilities with regard to their energy-storage properties over temperatures ranging from room temperature to 100 °C and also exhibited strong charge-discharge fatigue endurance up to 1 × 10(7) cycles.

  3. Resolving Losses at the Negative Electrode in All-Vanadium Redox Flow Batteries Using Electrochemical Impedance Spectroscopy

    SciTech Connect

    Sun, Che Nan; Delnick, Frank M; Aaron, D; Mench, Matthew M; Zawodzinski, Thomas A

    2014-01-01

    We present an in situ electrochemical technique for the quantitative measurement and resolution of the ohmic, charge transfer and diffusion overvoltages at the negative electrode of an all-vanadium redox flow battery (VRFB) using electrochemical impedance spectroscopy (EIS). The mathematics describing the complex impedance of the V+2/V+3 redox reaction is derived and matches the experimental data. The voltage losses contributed by each process have been resolved and quantified at various flow rates and electrode thicknesses as a function of current density during anodic and cathodic polarization. The diffusion overvoltage was affected strongly by flow rate while the charge transfer and ohmic losses were invariant. On the other hand, adopting a thicker electrode significantly changed both the charge transfer and diffusion losses due to increased surface area. Furthermore, the Tafel plot obtained from the impedance resolved charge transfer overvoltage yielded the geometric exchange current density, anodic and cathodic Tafel slopes (135 5 and 121 5 mV/decade respectively) and corresponding transfer coefficients = 0.45 0.02 and = 0.50 0.02 in an operating cell.

  4. Characterizing the weathering induced haze formation and gloss loss of poly(ethylene-terephthalate) via MaPd:RTS spectroscopy

    NASA Astrophysics Data System (ADS)

    Gordon, Devin A.; Gok, Abdulkerim; Meyer, Corey W.; Fagerholm, Cara L.; Sweet, Noah W.; DeNoyer, Lin; Bruckman, Laura S.; French, Roger H.

    2016-09-01

    Poly(ethylene-terephthalate) (PET) film is a widely used material in photovoltaic module backsheets, for its dielectric breakdown strength, and in optical displays for its excellent combination of properties, notably optical clarity. However, PET degrades and loses optical clarity under environmental stressors of heat, moisture, and ultraviolet irradiance. Stabilizers are often included in PET formulation to increase its longevity; however, even these are subject to degradation and further reduce optical clarity. In a previous study, it was found that material yellowing is dominant with UV light exposures while moisture mostly causes hazing of the samples. Lifetime service prediction models were developed for PET from yellowing and hazing responses. To study the loss of optical clarity in PET films, samples of a UV-stabilized grade of PET were exposed to heat, moisture, and UV irradiance as prescribed by ASTM-G154 Cycle 4 and their optical properties were studied over time. Surface gloss loss and bulk haze formation were observed as primary material responses to degradation; after the first 168 hour exposure step an initial three-fold increase in bulk haze and a two-fold reduction in gloss were observed. Multi-Angle, Polarization-Dependent, Reflection, Transmission, and Scattering (MaPd:RTS) spectroscopy was employed to fully characterize the haze formation and gloss loss of the PET films under exposure.

  5. Total light loss optic spectroscopy. Progress towards a fiber optic Raman organic vapor sensor

    SciTech Connect

    Kyle, K.R.; Vess, T.M.; Angel, S.M.

    1993-09-01

    A Raman probe has been developed utilizing a single optical fiber as both a light pipe and an active sensing element. By coating a small segment of the surface of an exposed glass fiber core with a thin polymer film, an inverted waveguide is formed where light transmitted down the fiber is stripped out of the core and into the polymer film. The polymer coating is used both as a waveguide and as a medium for concentrating small organic molecules to be interrogated by Raman spectroscopy. The ability of the fiber optic thin film waveguide probe to detect organic vapors is demonstrated. The utility of the probe in the detection of nonaqueous phase liquids (NAPLs) is also described.

  6. Competing Effects Of Electronic And Nuclear Energy Loss On Microstructural Evolution In Ionic-covalent Materials

    SciTech Connect

    Zhang, Yanwen; Varga, Tamas; Ishimaru, Manabu; Edmondson, P. D.; Xue, H.; Liu, Peng; Moll, Sandra; Hardiman, Christopher M.; Shannon, Steven; Weber, William J.

    2014-05-01

    Ever increasing energy needs have raised the demands for advanced fuels and cladding materials that withstand the extreme radiation environments with improved accident tolerance over a long period of time. Ceria (CeO2) is a well known ionic conductor that is isostructural with urania and plutonia-based nuclear fuels. In the context of nuclear fuels, immobilization and transmutation of actinides, CeO2 is a model system for radiation effect studies. Covalent silicon carbide (SiC) is a candidate for use as structural material in fusion, cladding material for fission reactors, and an inert matrix for the transmutation of plutonium and other radioactive actinides. Understanding microstructural change of these ionic-covalent materials to irradiation is important for advanced nuclear energy systems. While displacements from nuclear energy loss may be the primary contribution to damage accumulation in a crystalline matrix and a driving force for the grain boundary evolution in nanostructured materials, local non-equilibrium disorder and excitation through electronic While displacements from nuclear energy loss may be the primary contribution to damage accumulation in a crystalline matrix and a driving force for the grain boundary evolution in nanostructured materials, local non-equilibrium disorder and excitation through electronic energy loss may, however, produce additional damage or anneal pre-existing defect. At intermediate transit energies where electronic and nuclear energy losses are both significant, synergistic, additive or competitive processes may evolve that affect the dynamic response of materials to irradiation. The response of crystalline and nanostructured CeO2 and SiC to ion irradiation are studied under different nuclear and electronic stopping powers to describe some general material response in this transit energy regime. Although fast radiation-induced grain growth in CeO2 is evident with no phase transformation, different fluence and dose dependence

  7. Model for Calculating Electrolytic Shunt Path Losses in Large Electrochemical Energy Conversion Systems

    NASA Technical Reports Server (NTRS)

    Prokopius, P. R.

    1976-01-01

    Generalized analysis and solution techniques were developed to evaluate the shunt power losses in electrochemical systems designed with a common or circulating electrolyte supply. Sample data are presented for a hypothetical bulk energy storage redox system, and the general applicability of the analysis technique is discussed.

  8. Fast-ion Energy Loss During TAE Avalanches in the National Spherical Torus Experiment

    SciTech Connect

    Fredrickson, E D; Darrow, D S; Gorelenkov, N N; Kramer, G J; Kubota, S; Podesta, M; White, R B; Bortolon, A; Gerhardt, S P; Bell, R E; Diallo, A; LeBlanc, B; Levinton, F M

    2012-07-11

    Strong TAE avalanches on NSTX, the National Spherical Torus Experiment [M. Ono, et al., Nucl. Fusion 40 (2000) 557] are typically correlated with drops in the neutron rate in the range of 5% - 15%. In previous studies of avalanches in L-mode plasmas, these neutron drops were found to be consistent with modeled losses of fast ions. Here we expand the study to TAE avalanches in NSTX H-mode plasmas with improved analysis techniques. At the measured TAE mode amplitudes, simulations with the ORBIT code predict that fast ion losses are negligible. However, the simulations predict that the TAE scatter the fast ions in energy, resulting in a small (≈ 6%) drop in fast ion β. The net decrease in energy of the fast ions is sufficient to account for the bulk of the drop in neutron rate, even in the absence of fast ion losses. This loss of energy from the fast ion population is comparable to the estimated energy lost by damping from the Alfven wave during the burst. The previously studied TAE avalanches in L-mode are re-evaluated using an improved calculation of the potential fluctuations in the ORBIT code.

  9. Energy loss in gas lasers operating in hollow-core optical fibers

    NASA Astrophysics Data System (ADS)

    Lane, Ryan A.; Madden, Timothy J.

    2017-03-01

    The output of solid core fiber lasers is constrained in the mid-infrared due to the absorption properties of silica. Optically pumped gas lasers can reach the mid-infrared but require long path lengths for interaction between the pump light and gain medium. Optically pumped gas lasers where the gain medium is contained in a hollow-core optical fiber may provide a robust and compact platform that combines advantages of fiber and optically-pumped gas lasers. Experimental demonstrations of gas-filled-fiber lasers have been reported. The energy output of a molecular gas laser operating in a hollow-core optical fiber is computationally modeled using rate equations. The rate equations include terms for various physical processes including molecular self-collisions, molecular collisions with the fiber walls, and fiber attenuation. The rate equations are solved for a time-dependent, one-dimensional fiber model with an acetylene gain medium that lases along rotation-vibrational transitions. The energy output and losses are computed for multiple configurations. Model correspondence with reported experiments is shown. The computed energy losses due to backwards propagating light, fiber losses, and molecular collisions are applied to pulsed, continuous wave, and synchronously pumped gas lasers operating in hollow-core optical fibers. Energy losses due to molecular collisions are used to estimate heating in the gain medium.

  10. Polarization correction in the theory of energy losses by charged particles

    SciTech Connect

    Makarov, D. N. Matveev, V. I.

    2015-05-15

    A method for finding the polarization (Barkas) correction in the theory of energy losses by charged particles in collisions with multielectron atoms is proposed. The Barkas correction is presented in a simple analytical form. We make comparisons with experimental data and show that applying the Barkas correction improves the agreement between theory and experiment.

  11. A Bench Measurement of the Energy Loss of a Stored Beam to a Cavity

    SciTech Connect

    Sands, M.; Rees, John R.; /SLAC

    2005-08-08

    A rather simple electronic bench experiment is proposed for obtaining a measure of the impulse energy loss of a stored particle bunch to an rf cavity or other vacuum-chamber structure--the so-called ''cavity radiation''. The proposed method is analyzed in some detail.

  12. Surface and bulk-loss reduction research by low-energy hydrogen doping

    NASA Technical Reports Server (NTRS)

    Fonash, S.

    1985-01-01

    Surface and bulk loss reduction by low energy hydrogen doping of silicon solar cells was examined. Hydrogen ions provided a suppression of space charge recombination currents. Implantation of hydrogen followed by the anneal cycle caused more redistribution of boron than the anneal which could complicate processing. It was demonstrated that passivation leads to space charge current reduction.

  13. A Bench Measurement of the Energy Loss of a Stored Beam to a Cavity

    SciTech Connect

    Sands, M.; Rees, J.

    2016-12-19

    A rather simple electronic bench experiment is proposed for obtaining a measure of the impulse energy loss of a stored particle bunch to an rf cavity or other vacuum-chamber structure--the so-called "cavity radiation". The proposed method is analyzed in some detail.

  14. Electron beam guiding by grooved SiO{sub 2} parallel plates without energy loss

    SciTech Connect

    Xue, Yingli; Yu, Deyang Liu, Junliang; Zhang, Mingwu; Yang, Bian; Zhang, Yuezhao; Cai, Xiaohong

    2015-12-21

    Using a pair of grooved SiO{sub 2} parallel plates, stably guided electron beams were obtained without energy loss at 800–2000 eV. This shows that the transmitted electrons are guided by a self-organized repulsive electric field, paving the way for a self-adaptive manipulation of electron beams.

  15. Determination of Mass-Loss Rates of PG 1159 Stars from Far-Ultraviolet Spectroscopy

    NASA Astrophysics Data System (ADS)

    Koesterke, Lars; Werner, Klaus

    1998-06-01

    We determine the mass-loss rates of four hot, low-gravity PG 1159 stars that are regarded as immediate descendants of Wolf-Rayet central stars of planetary nebulae (i.e., early spectral type [WCE]). The sample consists of classical hydrogen-deficient PG 1159 stars (K1-16, NGC 246, and RX J2117.1+3412) as well as one object of the very rare ``hybrid'' subtype, which also exhibits hydrogen lines (NGC 7094). The sample is complemented by the famous [WC]-PG 1159 transition object Abell 78. Our analysis is based on the O VI λλ1032, 1038 resonance line, which is the strongest wind feature in these objects. Far-UV observations were performed with the Berkeley spectrograph during the ORFEUS-SPAS II mission. One spectrum is taken from archive data of the ORFEUS-SPAS I mission, and another one was obtained with the Hopkins Ultraviolet Telescope during the Astro-2 mission. We find mass-loss rates in the range log(Ṁ/Msolar yr-1)=-8,...,-7, as compared to the [WCE] stars that have mass-loss rates of about log(Ṁ/Msolar yr-1)=-5.5,...,-6.5. By comparing with theory, we conclude that the wind of PG 1159 stars is driven by radiation pressure. Based on the development and utilization of ORFEUS (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometers), a collaboration of the Institute for Astronomy and Astrophysics at the University of Tübingen, the Space Astrophysics Group of the University of California at Berkeley, and the Landessternwarte Heidelberg.

  16. Tagging of Isobars Using Energy Loss and Time-of-flight Measurements

    SciTech Connect

    Shapira, D.

    2001-11-02

    The technique for tagging isobars in a mixed beam by measuring energy loss by time-of-flight has been tested. With this method, isobar separation should improve by allowing more energy loss (thicker absorber), but only if one can control absorber homogeneity. Measurements of beam energy toss and energy spread obtained under such conditions were shown to be close to predicted values using both collisional and charge exchange contributions to energy straggling. The calculation of energy straggling allows us to study the efficacy of this method for isobar separation when applied to different mass ranges and beam energies. Separation in a most difficult case, an analyzed beam of A = 132 isobars at energies near 3 MeV/A has been demonstrated. The time-of-flight information can be added on line as an additional tag to the data stream for events of interest. Such event by event tagging enables one to study the effect of differences in isobaric mixture in the beam on the reaction outcome even when isobar separation is not complete.

  17. Measurement of Absolute Excitation Cross Sections in Highly-Charged Ions Using Electron Energy Loss and Merged Beams

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Smith, Steven J.; Lozano, J.

    2002-01-01

    There is increasing emphasis during this decade on understanding energy balance and phenomena observed in high electron temperature plasmas. The UV spectral return from FUSE, the X-ray spectral return from the HETG on Chandra and the LETGS 011 XMM-Newton are just beginning. Line emissions are almost entirely from highly-charged ions (HCIs) of C, N, 0, Ne, Mg, S, Si, Ca, and Fe. The Constellation-X mission will provide X-ray spectroscopy up to photon energies of 0.12 nm (10 keV) where primary line emitters will be HCIs. A variety of atomic parameters are required to model the stellar and solar plasma. These include cross sections for excitation, ionization, charge-exchange, X-ray emission, direct and indirect recombination, lifetimes and branching ratios, and dependences on l, m mixing by external E and B fields. In almost all cases the atomic quantities are calculated, and few comparisons to experiment have been carried out. Collision strengths and Einstein A-values are required to convert the observed spectral intensities to electron temperatures and densities in the stellar plasma. The JPL electron energy-loss and merged beam approach has been used to measure absolute collision strengths in a number of ions, with critical comparison made to the best available theories.

  18. IMPLICATIONS OF MASS AND ENERGY LOSS DUE TO CORONAL MASS EJECTIONS ON MAGNETICALLY ACTIVE STARS

    SciTech Connect

    Drake, Jeremy J.; Cohen, Ofer; Yashiro, Seiji; Gopalswamy, Nat

    2013-02-20

    Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power-law relationships between the 1-8 A flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE = kE {sup -{alpha}}. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of {alpha} and are very large: M-dot {approx}5 Multiplication-Sign 10{sup -10} M{sub sun} yr{sup -1} and E-dot {approx}0.1 L{sub sun}. In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence {approx}> 10{sup 31} erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10{sup -3} L {sub bol} X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L {sub bol}, the CME mass loss rate is about 5 Multiplication-Sign 10{sup -11} M {sub Sun} yr{sup -1}.

  19. Energy Dispersive X-Ray and Electrochemical Impedance Spectroscopies for Performance and Corrosion Analysis of PEMWEs

    NASA Astrophysics Data System (ADS)

    Steen, S. M., Iii; Zhang, F.-Y.

    2014-11-01

    Proton exchange membrane water electrolyzers (PEMWEs) are a promising energy storage technology due to their high efficiency, compact design, and ability to be used in a renewable energy system. Before they are able to make a large commercial impact, there are several hurdles facing the technology today. Two powerful techniques for both in-situ and ex- situ characterizations to improve upon their performance and better understand their corrosion are electrochemical impedance spectroscopy and energy dispersive x-ray spectroscopy, respectively. In this paper, the authors use both methods in order to characterize the anode gas diffusion layer (GDL) in a PEMWE cell and better understand the corrosion that occurs in the oxygen electrode during electrolysis.

  20. Effect of Diet Composition on Energy Expenditure during Weight Loss: The POUNDS LOST Study

    PubMed Central

    Bray, George A.; Smith, Steven R.; DeJonge, Lilian; de Souza, Russell; Rood, Jennifer; Champagne, Catherine M.; Laranjo, Nancy; Carey, Vincent; Obarzanek, Eva; Loria, Catherine M.; Anton, Stephen D.; Ryan, Donna H.; Greenway, Frank L.; Williamson, Donald; Sacks, Frank M.

    2011-01-01

    Background Weight loss reduces energy expenditure, but the contribution of different macronutrients to this change is unclear. Hypothesis We tested the hypothesis that macronutrient composition of the diet might affect the partitioning of energy expenditure during weight loss. Design A sub-study of 99 participants from the POUNDS LOST trial had total energy expenditure (TEE) measured by doubly labeled water and resting energy expenditure (REE) measured by indirect calorimetry at baseline and repeated at 6 months in 89 participants. Participants were randomly assigned to one of 4 diets with either 15% or 25% protein and 20% or 40% fat. Results TEE and REE were positively correlated with each other and with fat free mass and body fat, at baseline and 6 months. The average weight loss of 8.1±0.65 kg (LSmean±SE) reduced TEE by 120±56 kcal/d and REE by 136±18 kcal/d. A greater weight loss at 6 months was associated with a greater decrease in TEE and REE. Participants eating the high fat diet lost significantly more fat free mass (1.52±0.55 kg) than the low fat diet group (p<0.05). Participants eating the low fat diet had significantly higher measures of physical activity than the high fat group. Conclusion A greater weight loss was associated with a larger decrease in both TEE and REE. The low fat diet was associated with significant changes in fat free body mass and energy expenditure from physical activity compared to the high fat diet. PMID:21946707